From cb2d884d7d2b5fe83aba42f1387542b50d5f06b1 Mon Sep 17 00:00:00 2001 From: Arnaud Charlet Date: Fri, 20 Feb 2015 10:11:44 +0100 Subject: [PATCH] gnat_rm.texi, [...]: Now automatically generated from sphinx in the doc directory. 2015-02-20 Arnaud Charlet * gnat_rm.texi, gnat_ugn.texi: Now automatically generated from sphinx in the doc directory. * doc: New directory containing sphinx versions of gnat_rm and gnat_ugn From-SVN: r220837 --- gcc/ada/doc/Makefile | 79 + gcc/ada/doc/gnat_rm.rst | 66 + gcc/ada/doc/gnat_rm/about_this_guide.rst | 185 + .../compatibility_and_porting_guide.rst | 661 + gcc/ada/doc/gnat_rm/implementation_advice.rst | 1395 + .../implementation_defined_aspects.rst | 520 + .../implementation_defined_attributes.rst | 1589 + ...implementation_defined_characteristics.rst | 1295 + .../implementation_defined_pragmas.rst | 6887 ++ .../implementation_of_ada_2012_features.rst | 1328 + ...mplementation_of_specific_ada_features.rst | 671 + 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gcc/ada/doc/share/gnu_free_documentation_license.rst create mode 100644 gcc/ada/doc/share/latex_elements.py create mode 100644 gcc/ada/doc/share/sphinx.sty diff --git a/gcc/ada/doc/Makefile b/gcc/ada/doc/Makefile new file mode 100644 index 00000000000..9a8070ce612 --- /dev/null +++ b/gcc/ada/doc/Makefile @@ -0,0 +1,79 @@ +# Makefile for Sphinx documentation + +# You can set these variables from the command line. +SPHINXOPTS = +SPHINXBUILD = DOC_NAME=$* sphinx-build +PAPER = +BUILDDIR = build +SOURCEDIR = . + +# Internal variables. +PAPEROPT_a4 = -D latex_paper_size=a4 +PAPEROPT_letter = -D latex_paper_size=letter +ALLSPHINXOPTS = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) \ + -c $(SOURCEDIR)/share \ + -d $(BUILDDIR)/$*/doctrees \ + $(SOURCEDIR) +DOC_LIST=gnat_rm gnat_ugn +FMT_LIST=html pdf txt info + +.PHONY: help clean + +help: + @echo "Please use \`make ' where is one of" + @echo " DOC_NAME.html to make standalone HTML files" + @echo " DOC_NAME.pdf to make LaTeX files and run them through pdflatex" + @echo " DOC_NAME.txt to make text files" + @echo " DOC_NAME.texinfo to make Texinfo files" + @echo " DOC_NAME.info to make info files" + @echo " DOC_NAME.all to build DOC_NAME for all previous formats" + @echo " all to build all documentations in all formats" + @echo " html-all same as previous rule but only for HTML format" + @echo " pdf-all same as previous rule but only for PDF format" + @echo " txt-all same as previous rule but only for text format" + @echo " texinfo-all same as previous rule but only for texinfo format" + @echo " info-all same as previous rule but only for info format" + @echo "" + @echo "DOC_NAME should be a documentation name in the following list:" + @echo " $(DOC_LIST)" + @echo "" + @echo "source and location can be overriden using SOURCEDIR and BUILDDIR variables" + +clean: + -rm -rf $(BUILDDIR)/*/html \ + $(BUILDDIR)/*/pdf \ + $(BUILDDIR)/*/txt \ + $(BUILDDIR)/*/info + +%.html: + $(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/$*/html + +%.pdf: + $(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/$*/pdf + cp $(SOURCEDIR)/share/sphinx.sty $(BUILDDIR)/$*/pdf + $(MAKE) -C $(BUILDDIR)/$*/pdf all-pdf LATEXOPTS="-interaction=nonstopmode" + +%.txt: + $(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/$*/txt + $(MAKE) -C $(BUILDDIR)/$*/txt plaintext + +%.info: + $(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/$*/info + $(MAKE) -C $(BUILDDIR)/$*/info info + +%.texinfo: + $(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/$*/texinfo + +html-all: $(foreach doc, $(DOC_LIST), $(doc).html) + +pdf-all: $(foreach doc, $(DOC_LIST), $(doc).pdf) + +txt-all: $(foreach doc, $(DOC_LIST), $(doc).txt) + +texinfo-all: $(foreach doc, $(DOC_LIST), $(doc).texinfo) + +%.all: + $(MAKE) $(foreach fmt, $(FMT_LIST), $*.$(fmt)) + +all: $(foreach fmt, $(FMT_LIST), $(fmt).all) + diff --git a/gcc/ada/doc/gnat_rm.rst b/gcc/ada/doc/gnat_rm.rst new file mode 100644 index 00000000000..a9ea40d679e --- /dev/null +++ b/gcc/ada/doc/gnat_rm.rst @@ -0,0 +1,66 @@ +GNAT Reference Manual +===================== + +*GNAT, The GNU Ada Development Environment* + +.. only:: PRO + + *GNAT Pro Edition* + + | Version |version| + | Date: |today| + +.. only:: GPL + + *GNAT GPL Edition* + + | Version |version| + | Date: |today| + +.. only:: FSF + + .. raw:: texinfo + + @include gcc-common.texi + GCC version @value{version-GCC}@* + +AdaCore + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with the Front-Cover Texts being "GNAT Reference +Manual", and with no Back-Cover Texts. A copy of the license is +included in the section entitled :ref:`gnu_fdl`. + +.. toctree:: + :numbered: + :maxdepth: 3 + + gnat_rm/about_this_guide + gnat_rm/implementation_defined_pragmas + gnat_rm/implementation_defined_aspects + gnat_rm/implementation_defined_attributes + gnat_rm/standard_and_implementation_defined_restrictions + gnat_rm/implementation_advice + gnat_rm/implementation_defined_characteristics + gnat_rm/intrinsic_subprograms + gnat_rm/representation_clauses_and_pragmas + gnat_rm/standard_library_routines + gnat_rm/the_implementation_of_standard_i_o + gnat_rm/the_gnat_library + gnat_rm/interfacing_to_other_languages + gnat_rm/specialized_needs_annexes + gnat_rm/implementation_of_specific_ada_features + gnat_rm/implementation_of_ada_2012_features + gnat_rm/obsolescent_features + gnat_rm/compatibility_and_porting_guide + +.. raw:: latex + + \appendix + +.. toctree:: + :maxdepth: 3 + + share/gnu_free_documentation_license diff --git a/gcc/ada/doc/gnat_rm/about_this_guide.rst b/gcc/ada/doc/gnat_rm/about_this_guide.rst new file mode 100644 index 00000000000..ad3ca5f460a --- /dev/null +++ b/gcc/ada/doc/gnat_rm/about_this_guide.rst @@ -0,0 +1,185 @@ +.. _About_This_Guide: + +**************** +About This Guide +**************** + +.. only:: PRO + + For ease of exposition, 'GNAT Pro' will be referred to simply as + 'GNAT' in the remainder of this document. + +This manual contains useful information in writing programs using the +GNAT compiler. It includes information on implementation dependent +characteristics of GNAT, including all the information required by +Annex M of the Ada language standard. + +GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be +invoked in Ada 83 compatibility mode. +By default, GNAT assumes Ada 2012, +but you can override with a compiler switch +to explicitly specify the language version. +(Please refer to the *GNAT User's Guide* for details on these switches.) +Throughout this manual, references to 'Ada' without a year suffix +apply to all the Ada versions of the language. + +Ada is designed to be highly portable. +In general, a program will have the same effect even when compiled by +different compilers on different platforms. +However, since Ada is designed to be used in a +wide variety of applications, it also contains a number of system +dependent features to be used in interfacing to the external world. +.. index:: Implementation-dependent features + +.. index:: Portability + +Note: Any program that makes use of implementation-dependent features +may be non-portable. You should follow good programming practice and +isolate and clearly document any sections of your program that make use +of these features in a non-portable manner. + +What This Reference Manual Contains +=================================== + +This reference manual contains the following chapters: + +* :ref:`Implementation_Defined_Pragmas`, lists GNAT implementation-dependent + pragmas, which can be used to extend and enhance the functionality of the + compiler. + +* :ref:`Implementation_Defined_Attributes`, lists GNAT + implementation-dependent attributes, which can be used to extend and + enhance the functionality of the compiler. + +* :ref:`Standard_and_Implementation_Defined_Restrictions`, lists GNAT + implementation-dependent restrictions, which can be used to extend and + enhance the functionality of the compiler. + +* :ref:`Implementation_Advice`, provides information on generally + desirable behavior which are not requirements that all compilers must + follow since it cannot be provided on all systems, or which may be + undesirable on some systems. + +* :ref:`Implementation_Defined_Characteristics`, provides a guide to + minimizing implementation dependent features. + +* :ref:`Intrinsic_Subprograms`, describes the intrinsic subprograms + implemented by GNAT, and how they can be imported into user + application programs. + +* :ref:`Representation_Clauses_and_Pragmas`, describes in detail the + way that GNAT represents data, and in particular the exact set + of representation clauses and pragmas that is accepted. + +* :ref:`Standard_Library_Routines`, provides a listing of packages and a + brief description of the functionality that is provided by Ada's + extensive set of standard library routines as implemented by GNAT. + +* :ref:`The_Implementation_of_Standard_I/O`, details how the GNAT + implementation of the input-output facilities. + +* :ref:`The_GNAT_Library`, is a catalog of packages that complement + the Ada predefined library. + +* :ref:`Interfacing_to_Other_Languages`, describes how programs + written in Ada using GNAT can be interfaced to other programming + languages. + +* :ref:`Specialized_Needs_Annexes`, describes the GNAT implementation of all + of the specialized needs annexes. + +* :ref:`Implementation_of_Specific_Ada_Features`, discusses issues related + to GNAT's implementation of machine code insertions, tasking, and several + other features. + +* :ref:`Implementation_of_Ada_2012_Features`, describes the status of the + GNAT implementation of the Ada 2012 language standard. + +* :ref:`Obsolescent_Features` documents implementation dependent features, + including pragmas and attributes, which are considered obsolescent, since + there are other preferred ways of achieving the same results. These + obsolescent forms are retained for backwards compatibility. + +* :ref:`Compatibility_and_Porting_Guide` presents some guidelines for + developing portable Ada code, describes the compatibility issues that + may arise between GNAT and other Ada compilation systems (including those + for Ada 83), and shows how GNAT can expedite porting applications + developed in other Ada environments. + +* :ref:`gnu_fdl` contains the license for this document. + +.. index:: Ada 95 Language Reference Manual + +.. index:: Ada 2005 Language Reference Manual + +This reference manual assumes a basic familiarity with the Ada 95 language, as +described in the +:title:`International Standard ANSI/ISO/IEC-8652:1995`. +It does not require knowledge of the new features introduced by Ada 2005, +(officially known as `ISO/IEC 8652:1995 with Technical Corrigendum 1 +and Amendment 1`). +Both reference manuals are included in the GNAT documentation +package. + +Conventions +=========== +.. index:: Conventions, typographical + +.. index:: Typographical conventions + +Following are examples of the typographical and graphic conventions used +in this guide: + +* `Functions`, `utility program names`, `standard names`, + and `classes`. + +* `Option flags` + +* :file:`File names` + +* `Variables` + +* *Emphasis* + +* [optional information or parameters] + +* Examples are described by text + + :: + + and then shown this way. + +* Commands that are entered by the user are shown as preceded by a prompt string + comprising the ``$`` character followed by a space. + +Related Information +=================== + +See the following documents for further information on GNAT: + +* :title:`GNAT User's Guide for Native Platforms`, + which provides information on how to use the + GNAT development environment. + +* :title:`Ada 95 Reference Manual`, the Ada 95 programming language standard. + +* :title:`Ada 95 Annotated Reference Manual`, which is an annotated version + of the Ada 95 standard. The annotations describe + detailed aspects of the design decision, and in particular contain useful + sections on Ada 83 compatibility. + +* :title:`Ada 2005 Reference Manual`, the Ada 2005 programming language standard. + +* :title:`Ada 2005 Annotated Reference Manual`, which is an annotated version + of the Ada 2005 standard. The annotations describe + detailed aspects of the design decision. + +* :title:`Ada 2012 Reference Manual`, the Ada 2012 programming language standard. + +* :title:`DEC Ada, Technical Overview and Comparison on DIGITAL Platforms`, + which contains specific information on compatibility between GNAT and + DEC Ada 83 systems. + +* :title:`DEC Ada, Language Reference Manual`, part number AA-PYZAB-TK, which + describes in detail the pragmas and attributes provided by the DEC Ada 83 + compiler system. diff --git a/gcc/ada/doc/gnat_rm/compatibility_and_porting_guide.rst b/gcc/ada/doc/gnat_rm/compatibility_and_porting_guide.rst new file mode 100644 index 00000000000..153d585b547 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/compatibility_and_porting_guide.rst @@ -0,0 +1,661 @@ +.. _Compatibility_and_Porting_Guide: + +******************************* +Compatibility and Porting Guide +******************************* + +This chapter presents some guidelines for developing portable Ada code, +describes the compatibility issues that may arise between +GNAT and other Ada compilation systems (including those for Ada 83), +and shows how GNAT can expedite porting +applications developed in other Ada environments. + +.. _Writing_Portable_Fixed-Point_Declarations: + +Writing Portable Fixed-Point Declarations +========================================= + +The Ada Reference Manual gives an implementation freedom to choose bounds +that are narrower by `Small` from the given bounds. +For example, if we write + +.. code-block:: ada + + type F1 is delta 1.0 range -128.0 .. +128.0; + +then the implementation is allowed to choose -128.0 .. +127.0 if it +likes, but is not required to do so. + +This leads to possible portability problems, so let's have a closer +look at this, and figure out how to avoid these problems. + +First, why does this freedom exist, and why would an implementation +take advantage of it? To answer this, take a closer look at the type +declaration for `F1` above. If the compiler uses the given bounds, +it would need 9 bits to hold the largest positive value (and typically +that means 16 bits on all machines). But if the implementation chooses +the +127.0 bound then it can fit values of the type in 8 bits. + +Why not make the user write +127.0 if that's what is wanted? +The rationale is that if you are thinking of fixed point +as a kind of 'poor man's floating-point', then you don't want +to be thinking about the scaled integers that are used in its +representation. Let's take another example: + +.. code-block:: ada + + type F2 is delta 2.0**(-15) range -1.0 .. +1.0; + +Looking at this declaration, it seems casually as though +it should fit in 16 bits, but again that extra positive value ++1.0 has the scaled integer equivalent of 2**15 which is one too +big for signed 16 bits. The implementation can treat this as: + +.. code-block:: ada + + type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15)); + +and the Ada language design team felt that this was too annoying +to require. We don't need to debate this decision at this point, +since it is well established (the rule about narrowing the ranges +dates to Ada 83). + +But the important point is that an implementation is not required +to do this narrowing, so we have a potential portability problem. +We could imagine three types of implementation: + +(a) those that narrow the range automatically if they can figure + out that the narrower range will allow storage in a smaller machine unit, + +(b) those that will narrow only if forced to by a `'Size` clause, and + +(c) those that will never narrow. + +Now if we are language theoreticians, we can imagine a fourth +approach: to narrow all the time, e.g. to treat + +.. code-block:: ada + + type F3 is delta 1.0 range -10.0 .. +23.0; + +as though it had been written: + + +.. code-block:: ada + + type F3 is delta 1.0 range -9.0 .. +22.0; + +But although technically allowed, such a behavior would be hostile and silly, +and no real compiler would do this. All real compilers will fall into one of +the categories (a), (b) or (c) above. + +So, how do you get the compiler to do what you want? The answer is give the +actual bounds you want, and then use a `'Small` clause and a +`'Size` clause to absolutely pin down what the compiler does. +E.g., for `F2` above, we will write: + +.. code-block:: ada + + My_Small : constant := 2.0**(-15); + My_First : constant := -1.0; + My_Last : constant := +1.0 - My_Small; + + type F2 is delta My_Small range My_First .. My_Last; + +and then add + +.. code-block:: ada + + for F2'Small use my_Small; + for F2'Size use 16; + +In practice all compilers will do the same thing here and will give you +what you want, so the above declarations are fully portable. If you really +want to play language lawyer and guard against ludicrous behavior by the +compiler you could add + +.. code-block:: ada + + Test1 : constant := 1 / Boolean'Pos (F2'First = My_First); + Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last); + +One or other or both are allowed to be illegal if the compiler is +behaving in a silly manner, but at least the silly compiler will not +get away with silently messing with your (very clear) intentions. + +If you follow this scheme you will be guaranteed that your fixed-point +types will be portable. + + + + +.. _Compatibility_with_Ada_83: + +Compatibility with Ada 83 +========================= + +.. index:: Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012) + +Ada 95 and the subsequent revisions Ada 2005 and Ada 2012 +are highly upwards compatible with Ada 83. In +particular, the design intention was that the difficulties associated +with moving from Ada 83 to later versions of the standard should be no greater +than those that occur when moving from one Ada 83 system to another. + +However, there are a number of points at which there are minor +incompatibilities. The :title:`Ada 95 Annotated Reference Manual` contains +full details of these issues as they relate to Ada 95, +and should be consulted for a complete treatment. +In practice the +following subsections treat the most likely issues to be encountered. + +.. _Legal_Ada_83_programs_that_are_illegal_in_Ada_95: + +Legal Ada 83 programs that are illegal in Ada 95 +------------------------------------------------ + +Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in +Ada 95 and later versions of the standard: + + +* *Character literals* + + Some uses of character literals are ambiguous. Since Ada 95 has introduced + `Wide_Character` as a new predefined character type, some uses of + character literals that were legal in Ada 83 are illegal in Ada 95. + For example: + + .. code-block:: ada + + for Char in 'A' .. 'Z' loop ... end loop; + + The problem is that 'A' and 'Z' could be from either + `Character` or `Wide_Character`. The simplest correction + is to make the type explicit; e.g.: + + .. code-block:: ada + + for Char in Character range 'A' .. 'Z' loop ... end loop; + +* *New reserved words* + + The identifiers `abstract`, `aliased`, `protected`, + `requeue`, `tagged`, and `until` are reserved in Ada 95. + Existing Ada 83 code using any of these identifiers must be edited to + use some alternative name. + +* *Freezing rules* + + The rules in Ada 95 are slightly different with regard to the point at + which entities are frozen, and representation pragmas and clauses are + not permitted past the freeze point. This shows up most typically in + the form of an error message complaining that a representation item + appears too late, and the appropriate corrective action is to move + the item nearer to the declaration of the entity to which it refers. + + A particular case is that representation pragmas + cannot be applied to a subprogram body. If necessary, a separate subprogram + declaration must be introduced to which the pragma can be applied. + +* *Optional bodies for library packages* + + In Ada 83, a package that did not require a package body was nevertheless + allowed to have one. This lead to certain surprises in compiling large + systems (situations in which the body could be unexpectedly ignored by the + binder). In Ada 95, if a package does not require a body then it is not + permitted to have a body. To fix this problem, simply remove a redundant + body if it is empty, or, if it is non-empty, introduce a dummy declaration + into the spec that makes the body required. One approach is to add a private + part to the package declaration (if necessary), and define a parameterless + procedure called `Requires_Body`, which must then be given a dummy + procedure body in the package body, which then becomes required. + Another approach (assuming that this does not introduce elaboration + circularities) is to add an `Elaborate_Body` pragma to the package spec, + since one effect of this pragma is to require the presence of a package body. + +* *Numeric_Error is the same exception as Constraint_Error* + + In Ada 95, the exception `Numeric_Error` is a renaming of `Constraint_Error`. + This means that it is illegal to have separate exception handlers for + the two exceptions. The fix is simply to remove the handler for the + `Numeric_Error` case (since even in Ada 83, a compiler was free to raise + `Constraint_Error` in place of `Numeric_Error` in all cases). + +* *Indefinite subtypes in generics* + + In Ada 83, it was permissible to pass an indefinite type (e.g, `String`) + as the actual for a generic formal private type, but then the instantiation + would be illegal if there were any instances of declarations of variables + of this type in the generic body. In Ada 95, to avoid this clear violation + of the methodological principle known as the 'contract model', + the generic declaration explicitly indicates whether + or not such instantiations are permitted. If a generic formal parameter + has explicit unknown discriminants, indicated by using `(<>)` after the + subtype name, then it can be instantiated with indefinite types, but no + stand-alone variables can be declared of this type. Any attempt to declare + such a variable will result in an illegality at the time the generic is + declared. If the `(<>)` notation is not used, then it is illegal + to instantiate the generic with an indefinite type. + This is the potential incompatibility issue when porting Ada 83 code to Ada 95. + It will show up as a compile time error, and + the fix is usually simply to add the `(<>)` to the generic declaration. + + +.. _More_deterministic_semantics: + +More deterministic semantics +---------------------------- + +* *Conversions* + + Conversions from real types to integer types round away from 0. In Ada 83 + the conversion Integer(2.5) could deliver either 2 or 3 as its value. This + implementation freedom was intended to support unbiased rounding in + statistical applications, but in practice it interfered with portability. + In Ada 95 the conversion semantics are unambiguous, and rounding away from 0 + is required. Numeric code may be affected by this change in semantics. + Note, though, that this issue is no worse than already existed in Ada 83 + when porting code from one vendor to another. + +* *Tasking* + + The Real-Time Annex introduces a set of policies that define the behavior of + features that were implementation dependent in Ada 83, such as the order in + which open select branches are executed. + + +.. _Changed_semantics: + +Changed semantics +----------------- + +The worst kind of incompatibility is one where a program that is legal in +Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not +possible in Ada 83. Fortunately this is extremely rare, but the one +situation that you should be alert to is the change in the predefined type +`Character` from 7-bit ASCII to 8-bit Latin-1. + + .. index:: Latin-1 + +* *Range of type `Character`* + + The range of `Standard.Character` is now the full 256 characters + of Latin-1, whereas in most Ada 83 implementations it was restricted + to 128 characters. Although some of the effects of + this change will be manifest in compile-time rejection of legal + Ada 83 programs it is possible for a working Ada 83 program to have + a different effect in Ada 95, one that was not permitted in Ada 83. + As an example, the expression + `Character'Pos(Character'Last)` returned `127` in Ada 83 and now + delivers `255` as its value. + In general, you should look at the logic of any + character-processing Ada 83 program and see whether it needs to be adapted + to work correctly with Latin-1. Note that the predefined Ada 95 API has a + character handling package that may be relevant if code needs to be adapted + to account for the additional Latin-1 elements. + The desirable fix is to + modify the program to accommodate the full character set, but in some cases + it may be convenient to define a subtype or derived type of Character that + covers only the restricted range. + + +.. _Other_language_compatibility_issues: + +Other language compatibility issues +----------------------------------- + +* *-gnat83* switch + + All implementations of GNAT provide a switch that causes GNAT to operate + in Ada 83 mode. In this mode, some but not all compatibility problems + of the type described above are handled automatically. For example, the + new reserved words introduced in Ada 95 and Ada 2005 are treated simply + as identifiers as in Ada 83. However, + in practice, it is usually advisable to make the necessary modifications + to the program to remove the need for using this switch. + See the `Compiling Different Versions of Ada` section in + the :title:`GNAT User's Guide`. + + +* Support for removed Ada 83 pragmas and attributes + + A number of pragmas and attributes from Ada 83 were removed from Ada 95, + generally because they were replaced by other mechanisms. Ada 95 and Ada 2005 + compilers are allowed, but not required, to implement these missing + elements. In contrast with some other compilers, GNAT implements all + such pragmas and attributes, eliminating this compatibility concern. These + include `pragma Interface` and the floating point type attributes + (`Emax`, `Mantissa`, etc.), among other items. + + +.. _Compatibility_between_Ada_95_and_Ada_2005: + +Compatibility between Ada 95 and Ada 2005 +========================================= + +.. index:: Compatibility between Ada 95 and Ada 2005 + +Although Ada 2005 was designed to be upwards compatible with Ada 95, there are +a number of incompatibilities. Several are enumerated below; +for a complete description please see the +:title:`Annotated Ada 2005 Reference Manual`, or section 9.1.1 in +:title:`Rationale for Ada 2005`. + +* *New reserved words.* + + The words `interface`, `overriding` and `synchronized` are + reserved in Ada 2005. + A pre-Ada 2005 program that uses any of these as an identifier will be + illegal. + +* *New declarations in predefined packages.* + + A number of packages in the predefined environment contain new declarations: + `Ada.Exceptions`, `Ada.Real_Time`, `Ada.Strings`, + `Ada.Strings.Fixed`, `Ada.Strings.Bounded`, + `Ada.Strings.Unbounded`, `Ada.Strings.Wide_Fixed`, + `Ada.Strings.Wide_Bounded`, `Ada.Strings.Wide_Unbounded`, + `Ada.Tags`, `Ada.Text_IO`, and `Interfaces.C`. + If an Ada 95 program does a `with` and `use` of any of these + packages, the new declarations may cause name clashes. + +* *Access parameters.* + + A nondispatching subprogram with an access parameter cannot be renamed + as a dispatching operation. This was permitted in Ada 95. + +* *Access types, discriminants, and constraints.* + + Rule changes in this area have led to some incompatibilities; for example, + constrained subtypes of some access types are not permitted in Ada 2005. + +* *Aggregates for limited types.* + + The allowance of aggregates for limited types in Ada 2005 raises the + possibility of ambiguities in legal Ada 95 programs, since additional types + now need to be considered in expression resolution. + +* *Fixed-point multiplication and division.* + + Certain expressions involving '*' or '/' for a fixed-point type, which + were legal in Ada 95 and invoked the predefined versions of these operations, + are now ambiguous. + The ambiguity may be resolved either by applying a type conversion to the + expression, or by explicitly invoking the operation from package + `Standard`. + +* *Return-by-reference types.* + + The Ada 95 return-by-reference mechanism has been removed. Instead, the user + can declare a function returning a value from an anonymous access type. + + +.. _Implementation-dependent_characteristics: + +Implementation-dependent characteristics +======================================== + +Although the Ada language defines the semantics of each construct as +precisely as practical, in some situations (for example for reasons of +efficiency, or where the effect is heavily dependent on the host or target +platform) the implementation is allowed some freedom. In porting Ada 83 +code to GNAT, you need to be aware of whether / how the existing code +exercised such implementation dependencies. Such characteristics fall into +several categories, and GNAT offers specific support in assisting the +transition from certain Ada 83 compilers. + +.. _Implementation-defined_pragmas: + +Implementation-defined pragmas +------------------------------ + +Ada compilers are allowed to supplement the language-defined pragmas, and +these are a potential source of non-portability. All GNAT-defined pragmas +are described in the `Implementation Defined Pragmas` chapter of the +:title:`GNAT Reference Manual`, and these include several that are specifically +intended to correspond to other vendors' Ada 83 pragmas. +For migrating from VADS, the pragma `Use_VADS_Size` may be useful. +For compatibility with HP Ada 83, GNAT supplies the pragmas +`Extend_System`, `Ident`, `Inline_Generic`, +`Interface_Name`, `Passive`, `Suppress_All`, +and `Volatile`. +Other relevant pragmas include `External` and `Link_With`. +Some vendor-specific +Ada 83 pragmas (`Share_Generic`, `Subtitle`, and `Title`) are +recognized, thus +avoiding compiler rejection of units that contain such pragmas; they are not +relevant in a GNAT context and hence are not otherwise implemented. + + +.. _Implementation-defined_attributes: + +Implementation-defined attributes +--------------------------------- + +Analogous to pragmas, the set of attributes may be extended by an +implementation. All GNAT-defined attributes are described in +`Implementation Defined Attributes` section of the +:title:`GNAT Reference Manual`, and these include several that are specifically intended +to correspond to other vendors' Ada 83 attributes. For migrating from VADS, +the attribute `VADS_Size` may be useful. For compatibility with HP +Ada 83, GNAT supplies the attributes `Bit`, `Machine_Size` and +`Type_Class`. + +.. _Libraries: + +Libraries +--------- + +Vendors may supply libraries to supplement the standard Ada API. If Ada 83 +code uses vendor-specific libraries then there are several ways to manage +this in Ada 95 and later versions of the standard: + +* If the source code for the libraries (specs and bodies) are + available, then the libraries can be migrated in the same way as the + application. + +* If the source code for the specs but not the bodies are + available, then you can reimplement the bodies. + +* Some features introduced by Ada 95 obviate the need for library support. For + example most Ada 83 vendors supplied a package for unsigned integers. The + Ada 95 modular type feature is the preferred way to handle this need, so + instead of migrating or reimplementing the unsigned integer package it may + be preferable to retrofit the application using modular types. + + +.. _Elaboration_order: + +Elaboration order +----------------- +The implementation can choose any elaboration order consistent with the unit +dependency relationship. This freedom means that some orders can result in +Program_Error being raised due to an 'Access Before Elaboration': an attempt +to invoke a subprogram its body has been elaborated, or to instantiate a +generic before the generic body has been elaborated. By default GNAT +attempts to choose a safe order (one that will not encounter access before +elaboration problems) by implicitly inserting `Elaborate` or +`Elaborate_All` pragmas where +needed. However, this can lead to the creation of elaboration circularities +and a resulting rejection of the program by gnatbind. This issue is +thoroughly described in the `Elaboration Order Handling in GNAT` appendix +in the :title:`GNAT User's Guide`. +In brief, there are several +ways to deal with this situation: + +* Modify the program to eliminate the circularities, e.g., by moving + elaboration-time code into explicitly-invoked procedures + +* Constrain the elaboration order by including explicit `Elaborate_Body` or + `Elaborate` pragmas, and then inhibit the generation of implicit + `Elaborate_All` + pragmas either globally (as an effect of the *-gnatE* switch) or locally + (by selectively suppressing elaboration checks via pragma + `Suppress(Elaboration_Check)` when it is safe to do so). + + +.. _Target-specific_aspects: + +Target-specific aspects +----------------------- + +Low-level applications need to deal with machine addresses, data +representations, interfacing with assembler code, and similar issues. If +such an Ada 83 application is being ported to different target hardware (for +example where the byte endianness has changed) then you will need to +carefully examine the program logic; the porting effort will heavily depend +on the robustness of the original design. Moreover, Ada 95 (and thus +Ada 2005 and Ada 2012) are sometimes +incompatible with typical Ada 83 compiler practices regarding implicit +packing, the meaning of the Size attribute, and the size of access values. +GNAT's approach to these issues is described in :ref:`Representation_Clauses`. + + +.. _Compatibility_with_Other_Ada_Systems: + +Compatibility with Other Ada Systems +==================================== + +If programs avoid the use of implementation dependent and +implementation defined features, as documented in the +:title:`Ada Reference Manual`, there should be a high degree of portability between +GNAT and other Ada systems. The following are specific items which +have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95 +compilers, but do not affect porting code to GNAT. +(As of January 2007, GNAT is the only compiler available for Ada 2005; +the following issues may or may not arise for Ada 2005 programs +when other compilers appear.) + +* *Ada 83 Pragmas and Attributes* + + Ada 95 compilers are allowed, but not required, to implement the missing + Ada 83 pragmas and attributes that are no longer defined in Ada 95. + GNAT implements all such pragmas and attributes, eliminating this as + a compatibility concern, but some other Ada 95 compilers reject these + pragmas and attributes. + +* *Specialized Needs Annexes* + + GNAT implements the full set of special needs annexes. At the + current time, it is the only Ada 95 compiler to do so. This means that + programs making use of these features may not be portable to other Ada + 95 compilation systems. + +* *Representation Clauses* + + Some other Ada 95 compilers implement only the minimal set of + representation clauses required by the Ada 95 reference manual. GNAT goes + far beyond this minimal set, as described in the next section. + + +.. _Representation_Clauses: + +Representation Clauses +====================== + +The Ada 83 reference manual was quite vague in describing both the minimal +required implementation of representation clauses, and also their precise +effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the +minimal set of capabilities required is still quite limited. + +GNAT implements the full required set of capabilities in +Ada 95 and Ada 2005, but also goes much further, and in particular +an effort has been made to be compatible with existing Ada 83 usage to the +greatest extent possible. + +A few cases exist in which Ada 83 compiler behavior is incompatible with +the requirements in Ada 95 (and thus also Ada 2005). These are instances of +intentional or accidental dependence on specific implementation dependent +characteristics of these Ada 83 compilers. The following is a list of +the cases most likely to arise in existing Ada 83 code. + +* *Implicit Packing* + + Some Ada 83 compilers allowed a Size specification to cause implicit + packing of an array or record. This could cause expensive implicit + conversions for change of representation in the presence of derived + types, and the Ada design intends to avoid this possibility. + Subsequent AI's were issued to make it clear that such implicit + change of representation in response to a Size clause is inadvisable, + and this recommendation is represented explicitly in the Ada 95 (and Ada 2005) + Reference Manuals as implementation advice that is followed by GNAT. + The problem will show up as an error + message rejecting the size clause. The fix is simply to provide + the explicit pragma `Pack`, or for more fine tuned control, provide + a Component_Size clause. + +* *Meaning of Size Attribute* + + The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as + the minimal number of bits required to hold values of the type. For example, + on a 32-bit machine, the size of `Natural` will typically be 31 and not + 32 (since no sign bit is required). Some Ada 83 compilers gave 31, and + some 32 in this situation. This problem will usually show up as a compile + time error, but not always. It is a good idea to check all uses of the + 'Size attribute when porting Ada 83 code. The GNAT specific attribute + Object_Size can provide a useful way of duplicating the behavior of + some Ada 83 compiler systems. + +* *Size of Access Types* + + A common assumption in Ada 83 code is that an access type is in fact a pointer, + and that therefore it will be the same size as a System.Address value. This + assumption is true for GNAT in most cases with one exception. For the case of + a pointer to an unconstrained array type (where the bounds may vary from one + value of the access type to another), the default is to use a 'fat pointer', + which is represented as two separate pointers, one to the bounds, and one to + the array. This representation has a number of advantages, including improved + efficiency. However, it may cause some difficulties in porting existing Ada 83 + code which makes the assumption that, for example, pointers fit in 32 bits on + a machine with 32-bit addressing. + + To get around this problem, GNAT also permits the use of 'thin pointers' for + access types in this case (where the designated type is an unconstrained array + type). These thin pointers are indeed the same size as a System.Address value. + To specify a thin pointer, use a size clause for the type, for example: + + .. code-block:: ada + + type X is access all String; + for X'Size use Standard'Address_Size; + + which will cause the type X to be represented using a single pointer. + When using this representation, the bounds are right behind the array. + This representation is slightly less efficient, and does not allow quite + such flexibility in the use of foreign pointers or in using the + Unrestricted_Access attribute to create pointers to non-aliased objects. + But for any standard portable use of the access type it will work in + a functionally correct manner and allow porting of existing code. + Note that another way of forcing a thin pointer representation + is to use a component size clause for the element size in an array, + or a record representation clause for an access field in a record. + + See the documentation of Unrestricted_Access in the GNAT RM for a + full discussion of possible problems using this attribute in conjunction + with thin pointers. + + +.. _Compatibility_with_HP_Ada_83: + +Compatibility with HP Ada 83 +============================ + +All the HP Ada 83 pragmas and attributes are recognized, although only a subset +of them can sensibly be implemented. The description of pragmas in +:ref:`Implementation_Defined_Pragmas` indicates whether or not they are +applicable to GNAT. + +* *Default floating-point representation* + + In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83, + it is VMS format. + +* *System* + + the package System in GNAT exactly corresponds to the definition in the + Ada 95 reference manual, which means that it excludes many of the + HP Ada 83 extensions. However, a separate package Aux_DEC is provided + that contains the additional definitions, and a special pragma, + Extend_System allows this package to be treated transparently as an + extension of package System. + diff --git a/gcc/ada/doc/gnat_rm/implementation_advice.rst b/gcc/ada/doc/gnat_rm/implementation_advice.rst new file mode 100644 index 00000000000..2ccb4e40172 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_advice.rst @@ -0,0 +1,1395 @@ +.. _Implementation_Advice: + +********************* +Implementation Advice +********************* + +The main text of the Ada Reference Manual describes the required +behavior of all Ada compilers, and the GNAT compiler conforms to +these requirements. + +In addition, there are sections throughout the Ada Reference Manual headed +by the phrase 'Implementation advice'. These sections are not normative, +i.e., they do not specify requirements that all compilers must +follow. Rather they provide advice on generally desirable behavior. +They are not requirements, because they describe behavior that cannot +be provided on all systems, or may be undesirable on some systems. + +As far as practical, GNAT follows the implementation advice in +the Ada Reference Manual. Each such RM section corresponds to a section +in this chapter whose title specifies the +RM section number and paragraph number and the subject of +the advice. The contents of each section consists of the RM text within +quotation marks, +followed by the GNAT interpretation of the advice. Most often, this simply says +'followed', which means that GNAT follows the advice. However, in a +number of cases, GNAT deliberately deviates from this advice, in which +case the text describes what GNAT does and why. + +.. index:: Error detection + +RM 1.1.3(20): Error Detection +============================= + + "If an implementation detects the use of an unsupported Specialized Needs + Annex feature at run time, it should raise `Program_Error` if + feasible." + +Not relevant. All specialized needs annex features are either supported, +or diagnosed at compile time. + +.. index:: Child Units + +RM 1.1.3(31): Child Units +========================= + + + "If an implementation wishes to provide implementation-defined + extensions to the functionality of a language-defined library unit, it + should normally do so by adding children to the library unit." + +Followed. + +.. index:: Bounded errors + +RM 1.1.5(12): Bounded Errors +============================ + + "If an implementation detects a bounded error or erroneous + execution, it should raise `Program_Error`." + +Followed in all cases in which the implementation detects a bounded +error or erroneous execution. Not all such situations are detected at +runtime. + +.. index:: Pragmas + +.. _RM_2_8_16_Pragmas: + +RM 2.8(16): Pragmas +=================== + + "Normally, implementation-defined pragmas should have no semantic effect + for error-free programs; that is, if the implementation-defined pragmas + are removed from a working program, the program should still be legal, + and should still have the same semantics." + +The following implementation defined pragmas are exceptions to this +rule: + ++--------------------+-------------------+ +| Pragma | Explanation | ++====================+===================+ +| *Abort_Defer* | Affects semantics | ++--------------------+-------------------+ +|*Ada_83* | Affects legality | ++--------------------+-------------------+ +|*Assert* | Affects semantics | ++--------------------+-------------------+ +|*CPP_Class* | Affects semantics | ++--------------------+-------------------+ +|*CPP_Constructor* | Affects semantics | ++--------------------+-------------------+ +|*Debug* | Affects semantics | ++--------------------+-------------------+ +|*Interface_Name* | Affects semantics | ++--------------------+-------------------+ +|*Machine_Attribute* | Affects semantics | ++--------------------+-------------------+ +|*Unimplemented_Unit*| Affects legality | ++--------------------+-------------------+ +|*Unchecked_Union* | Affects semantics | ++--------------------+-------------------+ + +In each of the above cases, it is essential to the purpose of the pragma +that this advice not be followed. For details see +:ref:`Implementation_Defined_Pragmas`. + +RM 2.8(17-19): Pragmas +====================== + + "Normally, an implementation should not define pragmas that can + make an illegal program legal, except as follows: + + * A pragma used to complete a declaration, such as a pragma `Import`; + + * A pragma used to configure the environment by adding, removing, or + replacing `library_items`." + +See :ref:`RM_2_8_16_Pragmas`. + +.. index:: Character Sets + +.. index:: Alternative Character Sets + +RM 3.5.2(5): Alternative Character Sets +======================================= + + "If an implementation supports a mode with alternative interpretations + for `Character` and `Wide_Character`, the set of graphic + characters of `Character` should nevertheless remain a proper + subset of the set of graphic characters of `Wide_Character`. Any + character set 'localizations' should be reflected in the results of + the subprograms defined in the language-defined package + `Characters.Handling` (see A.3) available in such a mode. In a mode with + an alternative interpretation of `Character`, the implementation should + also support a corresponding change in what is a legal + `identifier_letter`." + +Not all wide character modes follow this advice, in particular the JIS +and IEC modes reflect standard usage in Japan, and in these encoding, +the upper half of the Latin-1 set is not part of the wide-character +subset, since the most significant bit is used for wide character +encoding. However, this only applies to the external forms. Internally +there is no such restriction. + +.. index:: Integer types + +RM 3.5.4(28): Integer Types +=========================== + + "An implementation should support `Long_Integer` in addition to + `Integer` if the target machine supports 32-bit (or longer) + arithmetic. No other named integer subtypes are recommended for package + `Standard`. Instead, appropriate named integer subtypes should be + provided in the library package `Interfaces` (see B.2)." + +`Long_Integer` is supported. Other standard integer types are supported +so this advice is not fully followed. These types +are supported for convenient interface to C, and so that all hardware +types of the machine are easily available. + +RM 3.5.4(29): Integer Types +=========================== + + "An implementation for a two's complement machine should support + modular types with a binary modulus up to ``System.Max_Int*2+2``. An + implementation should support a non-binary modules up to `Integer'Last`." + +Followed. + +.. index:: Enumeration values + +RM 3.5.5(8): Enumeration Values +=============================== + + "For the evaluation of a call on ``S'Pos`` for an enumeration + subtype, if the value of the operand does not correspond to the internal + code for any enumeration literal of its type (perhaps due to an + un-initialized variable), then the implementation should raise + `Program_Error`. This is particularly important for enumeration + types with noncontiguous internal codes specified by an + enumeration_representation_clause." + +Followed. + +.. index:: Float types + +RM 3.5.7(17): Float Types +========================= + + "An implementation should support `Long_Float` in addition to + `Float` if the target machine supports 11 or more digits of + precision. No other named floating point subtypes are recommended for + package `Standard`. Instead, appropriate named floating point subtypes + should be provided in the library package `Interfaces` (see B.2)." + +`Short_Float` and `Long_Long_Float` are also provided. The +former provides improved compatibility with other implementations +supporting this type. The latter corresponds to the highest precision +floating-point type supported by the hardware. On most machines, this +will be the same as `Long_Float`, but on some machines, it will +correspond to the IEEE extended form. The notable case is all ia32 +(x86) implementations, where `Long_Long_Float` corresponds to +the 80-bit extended precision format supported in hardware on this +processor. Note that the 128-bit format on SPARC is not supported, +since this is a software rather than a hardware format. + +.. index:: Multidimensional arrays + +.. index:: Arrays, multidimensional + +RM 3.6.2(11): Multidimensional Arrays +===================================== + + "An implementation should normally represent multidimensional arrays in + row-major order, consistent with the notation used for multidimensional + array aggregates (see 4.3.3). However, if a pragma `Convention` + (`Fortran`, ...) applies to a multidimensional array type, then + column-major order should be used instead (see B.5, `Interfacing with Fortran`)." + +Followed. + +.. index:: Duration'Small + +RM 9.6(30-31): Duration'Small +============================= + + "Whenever possible in an implementation, the value of `Duration'Small` + should be no greater than 100 microseconds." + +Followed. (`Duration'Small` = 10**(-9)). + + "The time base for `delay_relative_statements` should be monotonic; + it need not be the same time base as used for `Calendar.Clock`." + +Followed. + +RM 10.2.1(12): Consistent Representation +======================================== + + "In an implementation, a type declared in a pre-elaborated package should + have the same representation in every elaboration of a given version of + the package, whether the elaborations occur in distinct executions of + the same program, or in executions of distinct programs or partitions + that include the given version." + +Followed, except in the case of tagged types. Tagged types involve +implicit pointers to a local copy of a dispatch table, and these pointers +have representations which thus depend on a particular elaboration of the +package. It is not easy to see how it would be possible to follow this +advice without severely impacting efficiency of execution. + +.. index:: Exception information + +RM 11.4.1(19): Exception Information +==================================== + + "`Exception_Message` by default and `Exception_Information` + should produce information useful for + debugging. `Exception_Message` should be short, about one + line. `Exception_Information` can be long. `Exception_Message` + should not include the + `Exception_Name`. `Exception_Information` should include both + the `Exception_Name` and the `Exception_Message`." + +Followed. For each exception that doesn't have a specified +`Exception_Message`, the compiler generates one containing the location +of the raise statement. This location has the form 'file_name:line', where +file_name is the short file name (without path information) and line is the line +number in the file. Note that in the case of the Zero Cost Exception +mechanism, these messages become redundant with the Exception_Information that +contains a full backtrace of the calling sequence, so they are disabled. +To disable explicitly the generation of the source location message, use the +Pragma `Discard_Names`. + +.. index:: Suppression of checks + +.. index:: Checks, suppression of + +RM 11.5(28): Suppression of Checks +================================== + + "The implementation should minimize the code executed for checks that + have been suppressed." + +Followed. + +.. index:: Representation clauses + +RM 13.1 (21-24): Representation Clauses +======================================= + + "The recommended level of support for all representation items is + qualified as follows: + + An implementation need not support representation items containing + non-static expressions, except that an implementation should support a + representation item for a given entity if each non-static expression in + the representation item is a name that statically denotes a constant + declared before the entity." + +Followed. In fact, GNAT goes beyond the recommended level of support +by allowing nonstatic expressions in some representation clauses even +without the need to declare constants initialized with the values of +such expressions. +For example: + +.. code-block:: ada + + X : Integer; + Y : Float; + for Y'Address use X'Address;>> + + + "An implementation need not support a specification for the `Size` + for a given composite subtype, nor the size or storage place for an + object (including a component) of a given composite subtype, unless the + constraints on the subtype and its composite subcomponents (if any) are + all static constraints." + +Followed. Size Clauses are not permitted on non-static components, as +described above. + + + "An aliased component, or a component whose type is by-reference, should + always be allocated at an addressable location." + +Followed. + +.. index:: Packed types + +RM 13.2(6-8): Packed Types +========================== + + "If a type is packed, then the implementation should try to minimize + storage allocated to objects of the type, possibly at the expense of + speed of accessing components, subject to reasonable complexity in + addressing calculations. + + The recommended level of support pragma `Pack` is: + + For a packed record type, the components should be packed as tightly as + possible subject to the Sizes of the component subtypes, and subject to + any `record_representation_clause` that applies to the type; the + implementation may, but need not, reorder components or cross aligned + word boundaries to improve the packing. A component whose `Size` is + greater than the word size may be allocated an integral number of words." + +Followed. Tight packing of arrays is supported for all component sizes +up to 64-bits. If the array component size is 1 (that is to say, if +the component is a boolean type or an enumeration type with two values) +then values of the type are implicitly initialized to zero. This +happens both for objects of the packed type, and for objects that have a +subcomponent of the packed type. + + + "An implementation should support Address clauses for imported + subprograms." + +Followed. + +.. index:: Address clauses + +RM 13.3(14-19): Address Clauses +=============================== + + "For an array `X`, ``X'Address`` should point at the first + component of the array, and not at the array bounds." + +Followed. + + "The recommended level of support for the `Address` attribute is: + + ``X'Address`` should produce a useful result if `X` is an + object that is aliased or of a by-reference type, or is an entity whose + `Address` has been specified." + +Followed. A valid address will be produced even if none of those +conditions have been met. If necessary, the object is forced into +memory to ensure the address is valid. + + "An implementation should support `Address` clauses for imported + subprograms." + +Followed. + + "Objects (including subcomponents) that are aliased or of a by-reference + type should be allocated on storage element boundaries." + +Followed. + + "If the `Address` of an object is specified, or it is imported or exported, + then the implementation should not perform optimizations based on + assumptions of no aliases." + +Followed. + +.. index:: Alignment clauses + +RM 13.3(29-35): Alignment Clauses +================================= + + "The recommended level of support for the `Alignment` attribute for + subtypes is: + + An implementation should support specified Alignments that are factors + and multiples of the number of storage elements per word, subject to the + following:" + +Followed. + + "An implementation need not support specified Alignments for + combinations of Sizes and Alignments that cannot be easily + loaded and stored by available machine instructions." + +Followed. + + "An implementation need not support specified Alignments that are + greater than the maximum `Alignment` the implementation ever returns by + default." + +Followed. + + "The recommended level of support for the `Alignment` attribute for + objects is: + + Same as above, for subtypes, but in addition:" + +Followed. + + "For stand-alone library-level objects of statically constrained + subtypes, the implementation should support all alignments + supported by the target linker. For example, page alignment is likely to + be supported for such objects, but not for subtypes." + +Followed. + +.. index:: Size clauses + +RM 13.3(42-43): Size Clauses +============================ + + "The recommended level of support for the `Size` attribute of + objects is: + + A `Size` clause should be supported for an object if the specified + `Size` is at least as large as its subtype's `Size`, and + corresponds to a size in storage elements that is a multiple of the + object's `Alignment` (if the `Alignment` is nonzero)." + +Followed. + +RM 13.3(50-56): Size Clauses +============================ + + "If the `Size` of a subtype is specified, and allows for efficient + independent addressability (see 9.10) on the target architecture, then + the `Size` of the following objects of the subtype should equal the + `Size` of the subtype: + + Aliased objects (including components)." + +Followed. + + "`Size` clause on a composite subtype should not affect the + internal layout of components." + +Followed. But note that this can be overridden by use of the implementation +pragma Implicit_Packing in the case of packed arrays. + + "The recommended level of support for the `Size` attribute of subtypes is: + + The `Size` (if not specified) of a static discrete or fixed point + subtype should be the number of bits needed to represent each value + belonging to the subtype using an unbiased representation, leaving space + for a sign bit only if the subtype contains negative values. If such a + subtype is a first subtype, then an implementation should support a + specified `Size` for it that reflects this representation." + +Followed. + + "For a subtype implemented with levels of indirection, the `Size` + should include the size of the pointers, but not the size of what they + point at." + +Followed. + +.. index:: Component_Size clauses + +RM 13.3(71-73): Component Size Clauses +====================================== + + "The recommended level of support for the `Component_Size` + attribute is: + + An implementation need not support specified `Component_Sizes` that are + less than the `Size` of the component subtype." + +Followed. + + "An implementation should support specified Component_Sizes that + are factors and multiples of the word size. For such + Component_Sizes, the array should contain no gaps between + components. For other Component_Sizes (if supported), the array + should contain no gaps between components when packing is also + specified; the implementation should forbid this combination in cases + where it cannot support a no-gaps representation." + +Followed. + +.. index:: Enumeration representation clauses + +.. index:: Representation clauses, enumeration + +RM 13.4(9-10): Enumeration Representation Clauses +================================================= + + "The recommended level of support for enumeration representation clauses + is: + + An implementation need not support enumeration representation clauses + for boolean types, but should at minimum support the internal codes in + the range `System.Min_Int .. System.Max_Int`." + +Followed. + +.. index:: Record representation clauses + +.. index:: Representation clauses, records + +RM 13.5.1(17-22): Record Representation Clauses +=============================================== + + "The recommended level of support for + `record_representation_clauses` is: + + An implementation should support storage places that can be extracted + with a load, mask, shift sequence of machine code, and set with a load, + shift, mask, store sequence, given the available machine instructions + and run-time model." + +Followed. + + "A storage place should be supported if its size is equal to the + `Size` of the component subtype, and it starts and ends on a + boundary that obeys the `Alignment` of the component subtype." + +Followed. + + "If the default bit ordering applies to the declaration of a given type, + then for a component whose subtype's `Size` is less than the word + size, any storage place that does not cross an aligned word boundary + should be supported." + +Followed. + + "An implementation may reserve a storage place for the tag field of a + tagged type, and disallow other components from overlapping that place." + +Followed. The storage place for the tag field is the beginning of the tagged +record, and its size is Address'Size. GNAT will reject an explicit component +clause for the tag field. + + "An implementation need not support a `component_clause` for a + component of an extension part if the storage place is not after the + storage places of all components of the parent type, whether or not + those storage places had been specified." + +Followed. The above advice on record representation clauses is followed, +and all mentioned features are implemented. + +.. index:: Storage place attributes + +RM 13.5.2(5): Storage Place Attributes +====================================== + + "If a component is represented using some form of pointer (such as an + offset) to the actual data of the component, and this data is contiguous + with the rest of the object, then the storage place attributes should + reflect the place of the actual data, not the pointer. If a component is + allocated discontinuously from the rest of the object, then a warning + should be generated upon reference to one of its storage place + attributes." + +Followed. There are no such components in GNAT. + +.. index:: Bit ordering + +RM 13.5.3(7-8): Bit Ordering +============================ + + "The recommended level of support for the non-default bit ordering is: + + If `Word_Size` = `Storage_Unit`, then the implementation + should support the non-default bit ordering in addition to the default + bit ordering." + +Followed. Word size does not equal storage size in this implementation. +Thus non-default bit ordering is not supported. + +.. index:: Address, as private type + +RM 13.7(37): Address as Private +=============================== + + "`Address` should be of a private type." + +Followed. + +.. index:: Operations, on `Address` + +.. index:: Address, operations of + +RM 13.7.1(16): Address Operations +================================= + + "Operations in `System` and its children should reflect the target + environment semantics as closely as is reasonable. For example, on most + machines, it makes sense for address arithmetic to 'wrap around'. + Operations that do not make sense should raise `Program_Error`." + +Followed. Address arithmetic is modular arithmetic that wraps around. No +operation raises `Program_Error`, since all operations make sense. + +.. index:: Unchecked conversion + +RM 13.9(14-17): Unchecked Conversion +==================================== + + "The `Size` of an array object should not include its bounds; hence, + the bounds should not be part of the converted data." + +Followed. + + "The implementation should not generate unnecessary run-time checks to + ensure that the representation of `S` is a representation of the + target type. It should take advantage of the permission to return by + reference when possible. Restrictions on unchecked conversions should be + avoided unless required by the target environment." + +Followed. There are no restrictions on unchecked conversion. A warning is +generated if the source and target types do not have the same size since +the semantics in this case may be target dependent. + + "The recommended level of support for unchecked conversions is: + + Unchecked conversions should be supported and should be reversible in + the cases where this clause defines the result. To enable meaningful use + of unchecked conversion, a contiguous representation should be used for + elementary subtypes, for statically constrained array subtypes whose + component subtype is one of the subtypes described in this paragraph, + and for record subtypes without discriminants whose component subtypes + are described in this paragraph." + +Followed. + +.. index:: Heap usage, implicit + +RM 13.11(23-25): Implicit Heap Usage +==================================== + + "An implementation should document any cases in which it dynamically + allocates heap storage for a purpose other than the evaluation of an + allocator." + +Followed, the only other points at which heap storage is dynamically +allocated are as follows: + +* + At initial elaboration time, to allocate dynamically sized global + objects. + +* + To allocate space for a task when a task is created. + +* + To extend the secondary stack dynamically when needed. The secondary + stack is used for returning variable length results. + +.. + + "A default (implementation-provided) storage pool for an + access-to-constant type should not have overhead to support deallocation of + individual objects." + +Followed. + + "A storage pool for an anonymous access type should be created at the + point of an allocator for the type, and be reclaimed when the designated + object becomes inaccessible." + +Followed. + +.. index:: Unchecked deallocation + +RM 13.11.2(17): Unchecked Deallocation +====================================== + + "For a standard storage pool, `Free` should actually reclaim the + storage." + +Followed. + +.. index:: Stream oriented attributes + +RM 13.13.2(17): Stream Oriented Attributes +========================================== + + "If a stream element is the same size as a storage element, then the + normal in-memory representation should be used by `Read` and + `Write` for scalar objects. Otherwise, `Read` and `Write` + should use the smallest number of stream elements needed to represent + all values in the base range of the scalar type." + +Followed. By default, GNAT uses the interpretation suggested by AI-195, +which specifies using the size of the first subtype. +However, such an implementation is based on direct binary +representations and is therefore target- and endianness-dependent. +To address this issue, GNAT also supplies an alternate implementation +of the stream attributes `Read` and `Write`, +which uses the target-independent XDR standard representation +for scalar types. + +.. index:: XDR representation + +.. index:: Read attribute + +.. index:: Write attribute + +.. index:: Stream oriented attributes + +The XDR implementation is provided as an alternative body of the +`System.Stream_Attributes` package, in the file +:file:`s-stratt-xdr.adb` in the GNAT library. +There is no :file:`s-stratt-xdr.ads` file. +In order to install the XDR implementation, do the following: + +* Replace the default implementation of the + `System.Stream_Attributes` package with the XDR implementation. + For example on a Unix platform issue the commands: + + .. code-block:: sh + + $ mv s-stratt.adb s-stratt-default.adb + $ mv s-stratt-xdr.adb s-stratt.adb + + +* + Rebuild the GNAT run-time library as documented in + the `GNAT and Libraries` section of the :title:`GNAT User's Guide`. + +RM A.1(52): Names of Predefined Numeric Types +============================================= + + "If an implementation provides additional named predefined integer types, + then the names should end with ``Integer`` as in + ``Long_Integer``. If an implementation provides additional named + predefined floating point types, then the names should end with + ``Float`` as in ``Long_Float``." + +Followed. + +.. index:: Ada.Characters.Handling + +RM A.3.2(49): `Ada.Characters.Handling` +======================================= + + "If an implementation provides a localized definition of `Character` + or `Wide_Character`, then the effects of the subprograms in + `Characters.Handling` should reflect the localizations. + See also 3.5.2." + +Followed. GNAT provides no such localized definitions. + +.. index:: Bounded-length strings + +RM A.4.4(106): Bounded-Length String Handling +============================================= + + "Bounded string objects should not be implemented by implicit pointers + and dynamic allocation." + +Followed. No implicit pointers or dynamic allocation are used. + +.. index:: Random number generation + +RM A.5.2(46-47): Random Number Generation +========================================= + + "Any storage associated with an object of type `Generator` should be + reclaimed on exit from the scope of the object." + +Followed. + + "If the generator period is sufficiently long in relation to the number + of distinct initiator values, then each possible value of + `Initiator` passed to `Reset` should initiate a sequence of + random numbers that does not, in a practical sense, overlap the sequence + initiated by any other value. If this is not possible, then the mapping + between initiator values and generator states should be a rapidly + varying function of the initiator value." + +Followed. The generator period is sufficiently long for the first +condition here to hold true. + +.. index:: Get_Immediate + +RM A.10.7(23): `Get_Immediate` +============================== + + "The `Get_Immediate` procedures should be implemented with + unbuffered input. For a device such as a keyboard, input should be + available if a key has already been typed, whereas for a disk + file, input should always be available except at end of file. For a file + associated with a keyboard-like device, any line-editing features of the + underlying operating system should be disabled during the execution of + `Get_Immediate`." + +Followed on all targets except VxWorks. For VxWorks, there is no way to +provide this functionality that does not result in the input buffer being +flushed before the `Get_Immediate` call. A special unit +`Interfaces.Vxworks.IO` is provided that contains routines to enable +this functionality. + +.. index:: Export + +RM B.1(39-41): Pragma `Export` +============================== + + "If an implementation supports pragma `Export` to a given language, + then it should also allow the main subprogram to be written in that + language. It should support some mechanism for invoking the elaboration + of the Ada library units included in the system, and for invoking the + finalization of the environment task. On typical systems, the + recommended mechanism is to provide two subprograms whose link names are + `adainit` and `adafinal`. `adainit` should contain the + elaboration code for library units. `adafinal` should contain the + finalization code. These subprograms should have no effect the second + and subsequent time they are called." + +Followed. + + "Automatic elaboration of pre-elaborated packages should be + provided when pragma `Export` is supported." + +Followed when the main program is in Ada. If the main program is in a +foreign language, then +`adainit` must be called to elaborate pre-elaborated +packages. + + "For each supported convention `L` other than `Intrinsic`, an + implementation should support `Import` and `Export` pragmas + for objects of `L`-compatible types and for subprograms, and pragma + `Convention` for `L`-eligible types and for subprograms, + presuming the other language has corresponding features. Pragma + `Convention` need not be supported for scalar types." + +Followed. + +.. index:: Package Interfaces + +.. index:: Interfaces + +RM B.2(12-13): Package `Interfaces` +=================================== + + "For each implementation-defined convention identifier, there should be a + child package of package Interfaces with the corresponding name. This + package should contain any declarations that would be useful for + interfacing to the language (implementation) represented by the + convention. Any declarations useful for interfacing to any language on + the given hardware architecture should be provided directly in + `Interfaces`." + +Followed. + + "An implementation supporting an interface to C, COBOL, or Fortran should + provide the corresponding package or packages described in the following + clauses." + +Followed. GNAT provides all the packages described in this section. + +.. index:: C, interfacing with + +RM B.3(63-71): Interfacing with C +================================= + + "An implementation should support the following interface correspondences + between Ada and C." + +Followed. + + "An Ada procedure corresponds to a void-returning C function." + +Followed. + + "An Ada function corresponds to a non-void C function." + +Followed. + + "An Ada `in` scalar parameter is passed as a scalar argument to a C + function." + +Followed. + + "An Ada `in` parameter of an access-to-object type with designated + type `T` is passed as a ``t*`` argument to a C function, + where ``t`` is the C type corresponding to the Ada type `T`." + +Followed. + + "An Ada access `T` parameter, or an Ada `out` or `in out` + parameter of an elementary type `T`, is passed as a ``t*`` + argument to a C function, where ``t`` is the C type corresponding to + the Ada type `T`. In the case of an elementary `out` or + `in out` parameter, a pointer to a temporary copy is used to + preserve by-copy semantics." + +Followed. + + "An Ada parameter of a record type `T`, of any mode, is passed as a + ``t*`` argument to a C function, where ``t`` is the C + structure corresponding to the Ada type `T`." + +Followed. This convention may be overridden by the use of the C_Pass_By_Copy +pragma, or Convention, or by explicitly specifying the mechanism for a given +call using an extended import or export pragma. + + "An Ada parameter of an array type with component type `T`, of any + mode, is passed as a ``t*`` argument to a C function, where + ``t`` is the C type corresponding to the Ada type `T`." + +Followed. + + "An Ada parameter of an access-to-subprogram type is passed as a pointer + to a C function whose prototype corresponds to the designated + subprogram's specification." + +Followed. + +.. index:: COBOL, interfacing with + +RM B.4(95-98): Interfacing with COBOL +===================================== + + "An Ada implementation should support the following interface + correspondences between Ada and COBOL." + +Followed. + + "An Ada access `T` parameter is passed as a ``BY REFERENCE`` data item of + the COBOL type corresponding to `T`." + +Followed. + + "An Ada in scalar parameter is passed as a ``BY CONTENT`` data item of + the corresponding COBOL type." + +Followed. + + "Any other Ada parameter is passed as a ``BY REFERENCE`` data item of the + COBOL type corresponding to the Ada parameter type; for scalars, a local + copy is used if necessary to ensure by-copy semantics." + +Followed. + +.. index:: Fortran, interfacing with + +RM B.5(22-26): Interfacing with Fortran +======================================= + + "An Ada implementation should support the following interface + correspondences between Ada and Fortran:" + +Followed. + + "An Ada procedure corresponds to a Fortran subroutine." + +Followed. + + "An Ada function corresponds to a Fortran function." + +Followed. + + "An Ada parameter of an elementary, array, or record type `T` is + passed as a `T` argument to a Fortran procedure, where `T` is + the Fortran type corresponding to the Ada type `T`, and where the + INTENT attribute of the corresponding dummy argument matches the Ada + formal parameter mode; the Fortran implementation's parameter passing + conventions are used. For elementary types, a local copy is used if + necessary to ensure by-copy semantics." + +Followed. + + "An Ada parameter of an access-to-subprogram type is passed as a + reference to a Fortran procedure whose interface corresponds to the + designated subprogram's specification." + +Followed. + +.. index:: Machine operations + +RM C.1(3-5): Access to Machine Operations +========================================= + + "The machine code or intrinsic support should allow access to all + operations normally available to assembly language programmers for the + target environment, including privileged instructions, if any." + +Followed. + + "The interfacing pragmas (see Annex B) should support interface to + assembler; the default assembler should be associated with the + convention identifier `Assembler`." + +Followed. + + "If an entity is exported to assembly language, then the implementation + should allocate it at an addressable location, and should ensure that it + is retained by the linking process, even if not otherwise referenced + from the Ada code. The implementation should assume that any call to a + machine code or assembler subprogram is allowed to read or update every + object that is specified as exported." + +Followed. + +RM C.1(10-16): Access to Machine Operations +=========================================== + + "The implementation should ensure that little or no overhead is + associated with calling intrinsic and machine-code subprograms." + +Followed for both intrinsics and machine-code subprograms. + + "It is recommended that intrinsic subprograms be provided for convenient + access to any machine operations that provide special capabilities or + efficiency and that are not otherwise available through the language + constructs." + +Followed. A full set of machine operation intrinsic subprograms is provided. + + "Atomic read-modify-write operations---e.g., test and set, compare and + swap, decrement and test, enqueue/dequeue." + +Followed on any target supporting such operations. + + "Standard numeric functions---e.g.:, sin, log." + +Followed on any target supporting such operations. + + "String manipulation operations---e.g.:, translate and test." + +Followed on any target supporting such operations. + + "Vector operations---e.g.:, compare vector against thresholds." + +Followed on any target supporting such operations. + + "Direct operations on I/O ports." + +Followed on any target supporting such operations. + +.. index:: Interrupt support + +RM C.3(28): Interrupt Support +============================= + + "If the `Ceiling_Locking` policy is not in effect, the + implementation should provide means for the application to specify which + interrupts are to be blocked during protected actions, if the underlying + system allows for a finer-grain control of interrupt blocking." + +Followed. The underlying system does not allow for finer-grain control +of interrupt blocking. + +.. index:: Protected procedure handlers + +RM C.3.1(20-21): Protected Procedure Handlers +============================================= + + "Whenever possible, the implementation should allow interrupt handlers to + be called directly by the hardware." + +Followed on any target where the underlying operating system permits +such direct calls. + + "Whenever practical, violations of any + implementation-defined restrictions should be detected before run time." + +Followed. Compile time warnings are given when possible. + +.. index:: Package `Interrupts` + +.. index:: Interrupts + +RM C.3.2(25): Package `Interrupts` +================================== + + "If implementation-defined forms of interrupt handler procedures are + supported, such as protected procedures with parameters, then for each + such form of a handler, a type analogous to `Parameterless_Handler` + should be specified in a child package of `Interrupts`, with the + same operations as in the predefined package Interrupts." + +Followed. + +.. index:: Pre-elaboration requirements + +RM C.4(14): Pre-elaboration Requirements +======================================== + + "It is recommended that pre-elaborated packages be implemented in such a + way that there should be little or no code executed at run time for the + elaboration of entities not already covered by the Implementation + Requirements." + +Followed. Executable code is generated in some cases, e.g., loops +to initialize large arrays. + +RM C.5(8): Pragma `Discard_Names` +================================= + + "If the pragma applies to an entity, then the implementation should + reduce the amount of storage used for storing names associated with that + entity." + +Followed. + +.. index:: Package Task_Attributes + +.. index:: Task_Attributes + +RM C.7.2(30): The Package Task_Attributes +========================================= + + "Some implementations are targeted to domains in which memory use at run + time must be completely deterministic. For such implementations, it is + recommended that the storage for task attributes will be pre-allocated + statically and not from the heap. This can be accomplished by either + placing restrictions on the number and the size of the task's + attributes, or by using the pre-allocated storage for the first `N` + attribute objects, and the heap for the others. In the latter case, + `N` should be documented." + +Not followed. This implementation is not targeted to such a domain. + +.. index:: Locking Policies + +RM D.3(17): Locking Policies +============================ + + "The implementation should use names that end with ``_Locking`` for + locking policies defined by the implementation." + +Followed. Two implementation-defined locking policies are defined, +whose names (`Inheritance_Locking` and +`Concurrent_Readers_Locking`) follow this suggestion. + +.. index:: Entry queuing policies + +RM D.4(16): Entry Queuing Policies +================================== + + "Names that end with ``_Queuing`` should be used + for all implementation-defined queuing policies." + +Followed. No such implementation-defined queuing policies exist. + +.. index:: Preemptive abort + +RM D.6(9-10): Preemptive Abort +============================== + + "Even though the `abort_statement` is included in the list of + potentially blocking operations (see 9.5.1), it is recommended that this + statement be implemented in a way that never requires the task executing + the `abort_statement` to block." + +Followed. + + "On a multi-processor, the delay associated with aborting a task on + another processor should be bounded; the implementation should use + periodic polling, if necessary, to achieve this." + +Followed. + +.. index:: Tasking restrictions + +RM D.7(21): Tasking Restrictions +================================ + + "When feasible, the implementation should take advantage of the specified + restrictions to produce a more efficient implementation." + +GNAT currently takes advantage of these restrictions by providing an optimized +run time when the Ravenscar profile and the GNAT restricted run time set +of restrictions are specified. See pragma `Profile (Ravenscar)` and +pragma `Profile (Restricted)` for more details. + +.. index:: Time, monotonic + +RM D.8(47-49): Monotonic Time +============================= + + "When appropriate, implementations should provide configuration + mechanisms to change the value of `Tick`." + +Such configuration mechanisms are not appropriate to this implementation +and are thus not supported. + + "It is recommended that `Calendar.Clock` and `Real_Time.Clock` + be implemented as transformations of the same time base." + +Followed. + + + "It is recommended that the best time base which exists in + the underlying system be available to the application through + `Clock`. `Best` may mean highest accuracy or largest range." + +Followed. + +.. index:: Partition communication subsystem + +.. index:: PCS + +RM E.5(28-29): Partition Communication Subsystem +================================================ + + "Whenever possible, the PCS on the called partition should allow for + multiple tasks to call the RPC-receiver with different messages and + should allow them to block until the corresponding subprogram body + returns." + +Followed by GLADE, a separately supplied PCS that can be used with +GNAT. + + "The `Write` operation on a stream of type `Params_Stream_Type` + should raise `Storage_Error` if it runs out of space trying to + write the `Item` into the stream." + +Followed by GLADE, a separately supplied PCS that can be used with +GNAT. + +.. index:: COBOL support + +RM F(7): COBOL Support +====================== + + "If COBOL (respectively, C) is widely supported in the target + environment, implementations supporting the Information Systems Annex + should provide the child package `Interfaces.COBOL` (respectively, + `Interfaces.C`) specified in Annex B and should support a + `convention_identifier` of COBOL (respectively, C) in the interfacing + pragmas (see Annex B), thus allowing Ada programs to interface with + programs written in that language." + +Followed. + +.. index:: Decimal radix support + +RM F.1(2): Decimal Radix Support +================================ + + "Packed decimal should be used as the internal representation for objects + of subtype `S` when `S`'Machine_Radix = 10." + +Not followed. GNAT ignores `S`'Machine_Radix and always uses binary +representations. + +.. index:: Numerics + +RM G: Numerics +============== + + "If Fortran (respectively, C) is widely supported in the target + environment, implementations supporting the Numerics Annex + should provide the child package `Interfaces.Fortran` (respectively, + `Interfaces.C`) specified in Annex B and should support a + `convention_identifier` of Fortran (respectively, C) in the interfacing + pragmas (see Annex B), thus allowing Ada programs to interface with + programs written in that language." + +Followed. + +.. index:: Complex types + +RM G.1.1(56-58): Complex Types +============================== + + "Because the usual mathematical meaning of multiplication of a complex + operand and a real operand is that of the scaling of both components of + the former by the latter, an implementation should not perform this + operation by first promoting the real operand to complex type and then + performing a full complex multiplication. In systems that, in the + future, support an Ada binding to IEC 559:1989, the latter technique + will not generate the required result when one of the components of the + complex operand is infinite. (Explicit multiplication of the infinite + component by the zero component obtained during promotion yields a NaN + that propagates into the final result.) Analogous advice applies in the + case of multiplication of a complex operand and a pure-imaginary + operand, and in the case of division of a complex operand by a real or + pure-imaginary operand." + +Not followed. + + "Similarly, because the usual mathematical meaning of addition of a + complex operand and a real operand is that the imaginary operand remains + unchanged, an implementation should not perform this operation by first + promoting the real operand to complex type and then performing a full + complex addition. In implementations in which the `Signed_Zeros` + attribute of the component type is `True` (and which therefore + conform to IEC 559:1989 in regard to the handling of the sign of zero in + predefined arithmetic operations), the latter technique will not + generate the required result when the imaginary component of the complex + operand is a negatively signed zero. (Explicit addition of the negative + zero to the zero obtained during promotion yields a positive zero.) + Analogous advice applies in the case of addition of a complex operand + and a pure-imaginary operand, and in the case of subtraction of a + complex operand and a real or pure-imaginary operand." + +Not followed. + + "Implementations in which `Real'Signed_Zeros` is `True` should + attempt to provide a rational treatment of the signs of zero results and + result components. As one example, the result of the `Argument` + function should have the sign of the imaginary component of the + parameter `X` when the point represented by that parameter lies on + the positive real axis; as another, the sign of the imaginary component + of the `Compose_From_Polar` function should be the same as + (respectively, the opposite of) that of the `Argument` parameter when that + parameter has a value of zero and the `Modulus` parameter has a + nonnegative (respectively, negative) value." + +Followed. + +.. index:: Complex elementary functions + +RM G.1.2(49): Complex Elementary Functions +========================================== + + "Implementations in which `Complex_Types.Real'Signed_Zeros` is + `True` should attempt to provide a rational treatment of the signs + of zero results and result components. For example, many of the complex + elementary functions have components that are odd functions of one of + the parameter components; in these cases, the result component should + have the sign of the parameter component at the origin. Other complex + elementary functions have zero components whose sign is opposite that of + a parameter component at the origin, or is always positive or always + negative." + +Followed. + +.. index:: Accuracy requirements + +RM G.2.4(19): Accuracy Requirements +=================================== + + "The versions of the forward trigonometric functions without a + `Cycle` parameter should not be implemented by calling the + corresponding version with a `Cycle` parameter of + `2.0*Numerics.Pi`, since this will not provide the required + accuracy in some portions of the domain. For the same reason, the + version of `Log` without a `Base` parameter should not be + implemented by calling the corresponding version with a `Base` + parameter of `Numerics.e`." + +Followed. + +.. index:: Complex arithmetic accuracy + +.. index:: Accuracy, complex arithmetic + +RM G.2.6(15): Complex Arithmetic Accuracy +========================================= + + "The version of the `Compose_From_Polar` function without a + `Cycle` parameter should not be implemented by calling the + corresponding version with a `Cycle` parameter of + `2.0*Numerics.Pi`, since this will not provide the required + accuracy in some portions of the domain." + +Followed. + +.. index:: Sequential elaboration policy + +RM H.6(15/2): Pragma Partition_Elaboration_Policy +================================================= + + "If the partition elaboration policy is `Sequential` and the + Environment task becomes permanently blocked during elaboration then the + partition is deadlocked and it is recommended that the partition be + immediately terminated." + +Not followed. diff --git a/gcc/ada/doc/gnat_rm/implementation_defined_aspects.rst b/gcc/ada/doc/gnat_rm/implementation_defined_aspects.rst new file mode 100644 index 00000000000..9b9fd11442a --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_defined_aspects.rst @@ -0,0 +1,520 @@ +.. _Implementation_Defined_Aspects: + +****************************** +Implementation Defined Aspects +****************************** + +Ada defines (throughout the Ada 2012 reference manual, summarized +in Annex K) a set of aspects that can be specified for certain entities. +These language defined aspects are implemented in GNAT in Ada 2012 mode +and work as described in the Ada 2012 Reference Manual. + +In addition, Ada 2012 allows implementations to define additional aspects +whose meaning is defined by the implementation. GNAT provides +a number of these implementation-defined aspects which can be used +to extend and enhance the functionality of the compiler. This section of +the GNAT reference manual describes these additional aspects. + +Note that any program using these aspects may not be portable to +other compilers (although GNAT implements this set of aspects on all +platforms). Therefore if portability to other compilers is an important +consideration, you should minimize the use of these aspects. + +Note that for many of these aspects, the effect is essentially similar +to the use of a pragma or attribute specification with the same name +applied to the entity. For example, if we write: + + +.. code-block:: ada + + type R is range 1 .. 100 + with Value_Size => 10; + + +then the effect is the same as: + +.. code-block:: ada + + type R is range 1 .. 100; + for R'Value_Size use 10; + + +and if we write: + +.. code-block:: ada + + type R is new Integer + with Shared => True; + + +then the effect is the same as: + +.. code-block:: ada + + type R is new Integer; + pragma Shared (R); + + +In the documentation below, such cases are simply marked +as being boolean aspects equivalent to the corresponding pragma +or attribute definition clause. + +Aspect Abstract_State +===================== + +.. index:: Abstract_State + +This aspect is equivalent to pragma `Abstract_State`. + +Annotate +======== +.. index:: Annotate + +There are three forms of this aspect (where ID is an identifier, +and ARG is a general expression). + + + +*Annotate => ID* + Equivalent to `pragma Annotate (ID, Entity => Name);` + + +*Annotate => (ID)* + Equivalent to `pragma Annotate (ID, Entity => Name);` + + +*Annotate => (ID ,ID {, ARG})* + Equivalent to `pragma Annotate (ID, ID {, ARG}, Entity => Name);` + +Aspect Async_Readers +==================== +.. index:: Async_Readers + +This boolean aspect is equivalent to pragma `Async_Readers`. + +Aspect Async_Writers +==================== +.. index:: Async_Writers + +This boolean aspect is equivalent to pragma `Async_Writers`. + +Aspect Contract_Cases +===================== +.. index:: Contract_Cases + +This aspect is equivalent to pragma `Contract_Cases`, the sequence +of clauses being enclosed in parentheses so that syntactically it is an +aggregate. + +Aspect Depends +============== +.. index:: Depends + +This aspect is equivalent to pragma `Depends`. + +Aspect Dimension +================ +.. index:: Dimension + +The `Dimension` aspect is used to specify the dimensions of a given +subtype of a dimensioned numeric type. The aspect also specifies a symbol +used when doing formatted output of dimensioned quantities. The syntax is:: + + with Dimension => + ([Symbol =>] SYMBOL, DIMENSION_VALUE {, DIMENSION_Value}) + + SYMBOL ::= STRING_LITERAL | CHARACTER_LITERAL + + DIMENSION_VALUE ::= + RATIONAL + | others => RATIONAL + | DISCRETE_CHOICE_LIST => RATIONAL + + RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL] + + +This aspect can only be applied to a subtype whose parent type has +a `Dimension_Systen` aspect. The aspect must specify values for +all dimensions of the system. The rational values are the powers of the +corresponding dimensions that are used by the compiler to verify that +physical (numeric) computations are dimensionally consistent. For example, +the computation of a force must result in dimensions (L => 1, M => 1, T => -2). +For further examples of the usage +of this aspect, see package `System.Dim.Mks`. +Note that when the dimensioned type is an integer type, then any +dimension value must be an integer literal. + +Aspect Dimension_System +======================= +.. index:: Dimension_System + +The `Dimension_System` aspect is used to define a system of +dimensions that will be used in subsequent subtype declarations with +`Dimension` aspects that reference this system. The syntax is:: + + with Dimension_System => (DIMENSION {, DIMENSION}); + + DIMENSION ::= ([Unit_Name =>] IDENTIFIER, + [Unit_Symbol =>] SYMBOL, + [Dim_Symbol =>] SYMBOL) + + SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL + + +This aspect is applied to a type, which must be a numeric derived type +(typically a floating-point type), that +will represent values within the dimension system. Each `DIMENSION` +corresponds to one particular dimension. A maximum of 7 dimensions may +be specified. `Unit_Name` is the name of the dimension (for example +`Meter`). `Unit_Symbol` is the shorthand used for quantities +of this dimension (for example `m` for `Meter`). +`Dim_Symbol` gives +the identification within the dimension system (typically this is a +single letter, e.g. `L` standing for length for unit name `Meter`). +The `Unit_Symbol` is used in formatted output of dimensioned quantities. +The `Dim_Symbol` is used in error messages when numeric operations have +inconsistent dimensions. + +GNAT provides the standard definition of the International MKS system in +the run-time package `System.Dim.Mks`. You can easily define +similar packages for cgs units or British units, and define conversion factors +between values in different systems. The MKS system is characterized by the +following aspect: + +.. code-block:: ada + + type Mks_Type is new Long_Long_Float with + Dimension_System => ( + (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), + (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), + (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), + (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), + (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@'), + (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), + (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); + + +Note that in the above type definition, we use the `at` symbol (``@``) to +represent a theta character (avoiding the use of extended Latin-1 +characters in this context). + +See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users +Guide for detailed examples of use of the dimension system. + +Aspect Effective_Reads +====================== +.. index:: Effective_Reads + +This aspect is equivalent to pragma `Effective_Reads`. + +Aspect Effective_Writes +======================= +.. index:: Effective_Writes + +This aspect is equivalent to pragma `Effective_Writes`. + +Aspect Favor_Top_Level +====================== +.. index:: Favor_Top_Level + +This boolean aspect is equivalent to pragma `Favor_Top_Level`. + +Aspect Global +============= +.. index:: Global + +This aspect is equivalent to pragma `Global`. + +Aspect Initial_Condition +======================== +.. index:: Initial_Condition + +This aspect is equivalent to pragma `Initial_Condition`. + +Aspect Initializes +================== +.. index:: Initializes + +This aspect is equivalent to pragma `Initializes`. + +Aspect Inline_Always +==================== +.. index:: Inline_Always + +This boolean aspect is equivalent to pragma `Inline_Always`. + +Aspect Invariant +================ +.. index:: Invariant + +This aspect is equivalent to pragma `Invariant`. It is a +synonym for the language defined aspect `Type_Invariant` except +that it is separately controllable using pragma `Assertion_Policy`. + +Aspect Invariant'Class +====================== +.. index:: Invariant'Class + +This aspect is equivalent to pragma `Type_Invariant_Class`. It is a +synonym for the language defined aspect `Type_Invariant'Class` except +that it is separately controllable using pragma `Assertion_Policy`. + +Aspect Iterable +=============== +.. index:: Iterable + +This aspect provides a light-weight mechanism for loops and quantified +expressions over container types, without the overhead imposed by the tampering +checks of standard Ada 2012 iterators. The value of the aspect is an aggregate +with four named components: `First`, `Next`, `Has_Element`, and `Element` (the +last one being optional). When only 3 components are specified, only the +`for .. in` form of iteration over cursors is available. When all 4 components +are specified, both this form and the `for .. of` form of iteration over +elements are available. The following is a typical example of use: + +.. code-block:: ada + + type List is private with + Iterable => (First => First_Cursor, + Next => Advance, + Has_Element => Cursor_Has_Element, + [Element => Get_Element]); + +* The value denoted by `First` must denote a primitive operation of the + container type that returns a `Cursor`, which must a be a type declared in + the container package or visible from it. For example: + +.. code-block:: ada + + function First_Cursor (Cont : Container) return Cursor; + +* The value of `Next` is a primitive operation of the container type that takes + both a container and a cursor and yields a cursor. For example: + +.. code-block:: ada + + function Advance (Cont : Container; Position : Cursor) return Cursor; + +* The value of `Has_Element` is a primitive operation of the container type + that takes both a container and a cursor and yields a boolean. For example: + +.. code-block:: ada + + function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean; + +* The value of `Element` is a primitive operation of the container type that + takes both a container and a cursor and yields an `Element_Type`, which must + be a type declared in the container package or visible from it. For example: + +.. code-block:: ada + + function Get_Element (Cont : Container; Position : Cursor) return Element_Type; + +This aspect is used in the GNAT-defined formal container packages. + +Aspect Linker_Section +===================== +.. index:: Linker_Section + +This aspect is equivalent to an `Linker_Section` pragma. + +Aspect Lock_Free +================ +.. index:: Lock_Free + +This boolean aspect is equivalent to pragma `Lock_Free`. + +Aspect No_Elaboration_Code_All +============================== +.. index:: No_Elaboration_Code_All + +This aspect is equivalent to a `pragma No_Elaboration_Code_All` +statement for a program unit. + +Aspect No_Tagged_Streams +======================== +.. index:: No_Tagged_Streams + +This aspect is equivalent to a `pragma No_Tagged_Streams` with an +argument specifying a root tagged type (thus this aspect can only be +applied to such a type). + +Aspect Object_Size +================== +.. index:: Object_Size + +This aspect is equivalent to an `Object_Size` attribute definition +clause. + +Aspect Obsolescent +================== +.. index:: Obsolsecent + +This aspect is equivalent to an `Obsolescent` pragma. Note that the +evaluation of this aspect happens at the point of occurrence, it is not +delayed until the freeze point. + +Aspect Part_Of +============== +.. index:: Part_Of + +This aspect is equivalent to pragma `Part_Of`. + +Aspect Persistent_BSS +===================== +.. index:: Persistent_BSS + +This boolean aspect is equivalent to pragma `Persistent_BSS`. + +Aspect Predicate +================ +.. index:: Predicate + +This aspect is equivalent to pragma `Predicate`. It is thus +similar to the language defined aspects `Dynamic_Predicate` +and `Static_Predicate` except that whether the resulting +predicate is static or dynamic is controlled by the form of the +expression. It is also separately controllable using pragma +`Assertion_Policy`. + +Aspect Pure_Function +==================== +.. index:: Pure_Function + +This boolean aspect is equivalent to pragma `Pure_Function`. + +Aspect Refined_Depends +====================== +.. index:: Refined_Depends + +This aspect is equivalent to pragma `Refined_Depends`. + +Aspect Refined_Global +===================== +.. index:: Refined_Global + +This aspect is equivalent to pragma `Refined_Global`. + +Aspect Refined_Post +=================== +.. index:: Refined_Post + +This aspect is equivalent to pragma `Refined_Post`. + +Aspect Refined_State +==================== +.. index:: Refined_State + +This aspect is equivalent to pragma `Refined_State`. + +Aspect Remote_Access_Type +========================= +.. index:: Remote_Access_Type + +This aspect is equivalent to pragma `Remote_Access_Type`. + +Aspect Scalar_Storage_Order +=========================== +.. index:: Scalar_Storage_Order + +This aspect is equivalent to a `Scalar_Storage_Order` +attribute definition clause. + +Aspect Shared +============= +.. index:: Shared + +This boolean aspect is equivalent to pragma `Shared`, +and is thus a synonym for aspect `Atomic`. + +Aspect Simple_Storage_Pool +========================== +.. index:: Simple_Storage_Pool + +This aspect is equivalent to a `Simple_Storage_Pool` +attribute definition clause. + +Aspect Simple_Storage_Pool_Type +=============================== +.. index:: Simple_Storage_Pool_Type + +This boolean aspect is equivalent to pragma `Simple_Storage_Pool_Type`. + +Aspect SPARK_Mode +================= +.. index:: SPARK_Mode + +This aspect is equivalent to pragma `SPARK_Mode` and +may be specified for either or both of the specification and body +of a subprogram or package. + +Aspect Suppress_Debug_Info +========================== +.. index:: Suppress_Debug_Info + +This boolean aspect is equivalent to pragma `Suppress_Debug_Info`. + +Aspect Suppress_Initialization +============================== +.. index:: Suppress_Initialization + +This boolean aspect is equivalent to pragma `Suppress_Initialization`. + +Aspect Test_Case +================ +.. index:: Test_Case + +This aspect is equivalent to pragma `Test_Case`. + +Aspect Thread_Local_Storage +=========================== +.. index:: Thread_Local_Storage + +This boolean aspect is equivalent to pragma `Thread_Local_Storage`. + +Aspect Universal_Aliasing +========================= +.. index:: Universal_Aliasing + +This boolean aspect is equivalent to pragma `Universal_Aliasing`. + +Aspect Universal_Data +===================== +.. index:: Universal_Data + +This aspect is equivalent to pragma `Universal_Data`. + +Aspect Unmodified +================= +.. index:: Unmodified + +This boolean aspect is equivalent to pragma `Unmodified`. + +Aspect Unreferenced +=================== +.. index:: Unreferenced + +This boolean aspect is equivalent to pragma `Unreferenced`. Note that +in the case of formal parameters, it is not permitted to have aspects for +a formal parameter, so in this case the pragma form must be used. + +Aspect Unreferenced_Objects +=========================== +.. index:: Unreferenced_Objects + +This boolean aspect is equivalent to pragma `Unreferenced_Objects`. + +Aspect Value_Size +================= +.. index:: Value_Size + +This aspect is equivalent to a `Value_Size` +attribute definition clause. + +Aspect Warnings +=============== +.. index:: Warnings + +This aspect is equivalent to the two argument form of pragma `Warnings`, +where the first argument is `ON` or `OFF` and the second argument +is the entity. diff --git a/gcc/ada/doc/gnat_rm/implementation_defined_attributes.rst b/gcc/ada/doc/gnat_rm/implementation_defined_attributes.rst new file mode 100644 index 00000000000..b25f9c996a6 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_defined_attributes.rst @@ -0,0 +1,1589 @@ +.. _Implementation_Defined_Attributes: + +********************************* +Implementation Defined Attributes +********************************* + +Ada defines (throughout the Ada reference manual, +summarized in Annex K), +a set of attributes that provide useful additional functionality in all +areas of the language. These language defined attributes are implemented +in GNAT and work as described in the Ada Reference Manual. + +In addition, Ada allows implementations to define additional +attributes whose meaning is defined by the implementation. GNAT provides +a number of these implementation-dependent attributes which can be used +to extend and enhance the functionality of the compiler. This section of +the GNAT reference manual describes these additional attributes. It also +describes additional implementation-dependent features of standard +language-defined attributes. + +Note that any program using these attributes may not be portable to +other compilers (although GNAT implements this set of attributes on all +platforms). Therefore if portability to other compilers is an important +consideration, you should minimize the use of these attributes. + +Attribute Abort_Signal +====================== +.. index:: Abort_Signal + +`Standard'Abort_Signal` (`Standard` is the only allowed +prefix) provides the entity for the special exception used to signal +task abort or asynchronous transfer of control. Normally this attribute +should only be used in the tasking runtime (it is highly peculiar, and +completely outside the normal semantics of Ada, for a user program to +intercept the abort exception). + +Attribute Address_Size +====================== +.. index:: Size of `Address` + +.. index:: Address_Size + +`Standard'Address_Size` (`Standard` is the only allowed +prefix) is a static constant giving the number of bits in an +`Address`. It is the same value as System.Address'Size, +but has the advantage of being static, while a direct +reference to System.Address'Size is non-static because Address +is a private type. + +Attribute Asm_Input +=================== +.. index:: Asm_Input + +The `Asm_Input` attribute denotes a function that takes two +parameters. The first is a string, the second is an expression of the +type designated by the prefix. The first (string) argument is required +to be a static expression, and is the constraint for the parameter, +(e.g., what kind of register is required). The second argument is the +value to be used as the input argument. The possible values for the +constant are the same as those used in the RTL, and are dependent on +the configuration file used to built the GCC back end. +:ref:`Machine_Code_Insertions` + +Attribute Asm_Output +==================== +.. index:: Asm_Output + +The `Asm_Output` attribute denotes a function that takes two +parameters. The first is a string, the second is the name of a variable +of the type designated by the attribute prefix. The first (string) +argument is required to be a static expression and designates the +constraint for the parameter (e.g., what kind of register is +required). The second argument is the variable to be updated with the +result. The possible values for constraint are the same as those used in +the RTL, and are dependent on the configuration file used to build the +GCC back end. If there are no output operands, then this argument may +either be omitted, or explicitly given as `No_Output_Operands`. +:ref:`Machine_Code_Insertions` + +Attribute Atomic_Always_Lock_Free +================================= +.. index:: Atomic_Always_Lock_Free + +The prefix of the `Atomic_Always_Lock_Free` attribute is a type. +The result is a Boolean value which is True if the type has discriminants, +and False otherwise. The result indicate whether atomic operations are +supported by the target for the given type. + +Attribute Bit +============= +.. index:: Bit + +``obj'Bit``, where `obj` is any object, yields the bit +offset within the storage unit (byte) that contains the first bit of +storage allocated for the object. The value of this attribute is of the +type `Universal_Integer`, and is always a non-negative number not +exceeding the value of `System.Storage_Unit`. + +For an object that is a variable or a constant allocated in a register, +the value is zero. (The use of this attribute does not force the +allocation of a variable to memory). + +For an object that is a formal parameter, this attribute applies +to either the matching actual parameter or to a copy of the +matching actual parameter. + +For an access object the value is zero. Note that +``obj.all'Bit`` is subject to an `Access_Check` for the +designated object. Similarly for a record component +``X.C'Bit`` is subject to a discriminant check and +``X(I).Bit`` and ``X(I1..I2)'Bit`` +are subject to index checks. + +This attribute is designed to be compatible with the DEC Ada 83 definition +and implementation of the `Bit` attribute. + +Attribute Bit_Position +====================== +.. index:: Bit_Position + +``R.C'Bit_Position``, where `R` is a record object and `C` is one +of the fields of the record type, yields the bit +offset within the record contains the first bit of +storage allocated for the object. The value of this attribute is of the +type `Universal_Integer`. The value depends only on the field +`C` and is independent of the alignment of +the containing record `R`. + +Attribute Code_Address +====================== +.. index:: Code_Address +.. index:: Subprogram address + +.. index:: Address of subprogram code + +The `'Address` +attribute may be applied to subprograms in Ada 95 and Ada 2005, but the +intended effect seems to be to provide +an address value which can be used to call the subprogram by means of +an address clause as in the following example: + +.. code-block:: ada + + procedure K is ... + + procedure L; + for L'Address use K'Address; + pragma Import (Ada, L); + + +A call to `L` is then expected to result in a call to `K`. +In Ada 83, where there were no access-to-subprogram values, this was +a common work-around for getting the effect of an indirect call. +GNAT implements the above use of `Address` and the technique +illustrated by the example code works correctly. + +However, for some purposes, it is useful to have the address of the start +of the generated code for the subprogram. On some architectures, this is +not necessarily the same as the `Address` value described above. +For example, the `Address` value may reference a subprogram +descriptor rather than the subprogram itself. + +The `'Code_Address` attribute, which can only be applied to +subprogram entities, always returns the address of the start of the +generated code of the specified subprogram, which may or may not be +the same value as is returned by the corresponding `'Address` +attribute. + +Attribute Compiler_Version +========================== +.. index:: Compiler_Version + +`Standard'Compiler_Version` (`Standard` is the only allowed +prefix) yields a static string identifying the version of the compiler +being used to compile the unit containing the attribute reference. + +Attribute Constrained +===================== +.. index:: Constrained + +In addition to the usage of this attribute in the Ada RM, `GNAT` +also permits the use of the `'Constrained` attribute +in a generic template +for any type, including types without discriminants. The value of this +attribute in the generic instance when applied to a scalar type or a +record type without discriminants is always `True`. This usage is +compatible with older Ada compilers, including notably DEC Ada. + +Attribute Default_Bit_Order +=========================== +.. index:: Big endian + +.. index:: Little endian + +.. index:: Default_Bit_Order + +`Standard'Default_Bit_Order` (`Standard` is the only +permissible prefix), provides the value `System.Default_Bit_Order` +as a `Pos` value (0 for `High_Order_First`, 1 for +`Low_Order_First`). This is used to construct the definition of +`Default_Bit_Order` in package `System`. + +Attribute Default_Scalar_Storage_Order +====================================== +.. index:: Big endian + +.. index:: Little endian + +.. index:: Default_Scalar_Storage_Order + +`Standard'Default_Scalar_Storage_Order` (`Standard` is the only +permissible prefix), provides the current value of the default scalar storage +order (as specified using pragma `Default_Scalar_Storage_Order`, or +equal to `Default_Bit_Order` if unspecified) as a +`System.Bit_Order` value. This is a static attribute. + +Attribute Descriptor_Size +========================= +.. index:: Descriptor + +.. index:: Dope vector + +.. index:: Descriptor_Size + +Non-static attribute `Descriptor_Size` returns the size in bits of the +descriptor allocated for a type. The result is non-zero only for unconstrained +array types and the returned value is of type universal integer. In GNAT, an +array descriptor contains bounds information and is located immediately before +the first element of the array. + +.. code-block:: ada + + type Unconstr_Array is array (Positive range <>) of Boolean; + Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img); + + +The attribute takes into account any additional padding due to type alignment. +In the example above, the descriptor contains two values of type +`Positive` representing the low and high bound. Since `Positive` has +a size of 31 bits and an alignment of 4, the descriptor size is `2 * Positive'Size + 2` or 64 bits. + +Attribute Elaborated +==================== +.. index:: Elaborated + +The prefix of the `'Elaborated` attribute must be a unit name. The +value is a Boolean which indicates whether or not the given unit has been +elaborated. This attribute is primarily intended for internal use by the +generated code for dynamic elaboration checking, but it can also be used +in user programs. The value will always be True once elaboration of all +units has been completed. An exception is for units which need no +elaboration, the value is always False for such units. + +Attribute Elab_Body +=================== +.. index:: Elab_Body + +This attribute can only be applied to a program unit name. It returns +the entity for the corresponding elaboration procedure for elaborating +the body of the referenced unit. This is used in the main generated +elaboration procedure by the binder and is not normally used in any +other context. However, there may be specialized situations in which it +is useful to be able to call this elaboration procedure from Ada code, +e.g., if it is necessary to do selective re-elaboration to fix some +error. + +Attribute Elab_Spec +=================== +.. index:: Elab_Spec + +This attribute can only be applied to a program unit name. It returns +the entity for the corresponding elaboration procedure for elaborating +the spec of the referenced unit. This is used in the main +generated elaboration procedure by the binder and is not normally used +in any other context. However, there may be specialized situations in +which it is useful to be able to call this elaboration procedure from +Ada code, e.g., if it is necessary to do selective re-elaboration to fix +some error. + +Attribute Elab_Subp_Body +======================== +.. index:: Elab_Subp_Body + +This attribute can only be applied to a library level subprogram +name and is only allowed in CodePeer mode. It returns the entity +for the corresponding elaboration procedure for elaborating the body +of the referenced subprogram unit. This is used in the main generated +elaboration procedure by the binder in CodePeer mode only and is unrecognized +otherwise. + +Attribute Emax +============== +.. index:: Ada 83 attributes + +.. index:: Emax + +The `Emax` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Enabled +================= +.. index:: Enabled + +The `Enabled` attribute allows an application program to check at compile +time to see if the designated check is currently enabled. The prefix is a +simple identifier, referencing any predefined check name (other than +`All_Checks`) or a check name introduced by pragma Check_Name. If +no argument is given for the attribute, the check is for the general state +of the check, if an argument is given, then it is an entity name, and the +check indicates whether an `Suppress` or `Unsuppress` has been +given naming the entity (if not, then the argument is ignored). + +Note that instantiations inherit the check status at the point of the +instantiation, so a useful idiom is to have a library package that +introduces a check name with `pragma Check_Name`, and then contains +generic packages or subprograms which use the `Enabled` attribute +to see if the check is enabled. A user of this package can then issue +a `pragma Suppress` or `pragma Unsuppress` before instantiating +the package or subprogram, controlling whether the check will be present. + +Attribute Enum_Rep +================== +.. index:: Representation of enums + +.. index:: Enum_Rep + +For every enumeration subtype `S`, ``S'Enum_Rep`` denotes a +function with the following spec: + +.. code-block:: ada + + function S'Enum_Rep (Arg : S'Base) return ; + + +It is also allowable to apply `Enum_Rep` directly to an object of an +enumeration type or to a non-overloaded enumeration +literal. In this case ``S'Enum_Rep`` is equivalent to +``typ'Enum_Rep(S)`` where `typ` is the type of the +enumeration literal or object. + +The function returns the representation value for the given enumeration +value. This will be equal to value of the `Pos` attribute in the +absence of an enumeration representation clause. This is a static +attribute (i.e.,:the result is static if the argument is static). + +``S'Enum_Rep`` can also be used with integer types and objects, +in which case it simply returns the integer value. The reason for this +is to allow it to be used for `(<>)` discrete formal arguments in +a generic unit that can be instantiated with either enumeration types +or integer types. Note that if `Enum_Rep` is used on a modular +type whose upper bound exceeds the upper bound of the largest signed +integer type, and the argument is a variable, so that the universal +integer calculation is done at run time, then the call to `Enum_Rep` +may raise `Constraint_Error`. + +Attribute Enum_Val +================== +.. index:: Representation of enums + +.. index:: Enum_Val + +For every enumeration subtype `S`, ``S'Enum_Val`` denotes a +function with the following spec: + +.. code-block:: ada + + function S'Enum_Val (Arg : ) return S'Base; + + +The function returns the enumeration value whose representation matches the +argument, or raises Constraint_Error if no enumeration literal of the type +has the matching value. +This will be equal to value of the `Val` attribute in the +absence of an enumeration representation clause. This is a static +attribute (i.e., the result is static if the argument is static). + +Attribute Epsilon +================= +.. index:: Ada 83 attributes + +.. index:: Epsilon + +The `Epsilon` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Fast_Math +=================== +.. index:: Fast_Math + +`Standard'Fast_Math` (`Standard` is the only allowed +prefix) yields a static Boolean value that is True if pragma +`Fast_Math` is active, and False otherwise. + +Attribute Fixed_Value +===================== +.. index:: Fixed_Value + +For every fixed-point type `S`, ``S'Fixed_Value`` denotes a +function with the following specification: + +.. code-block:: ada + + function S'Fixed_Value (Arg : ) return S; + +The value returned is the fixed-point value `V` such that:: + + V = Arg * S'Small + + +The effect is thus similar to first converting the argument to the +integer type used to represent `S`, and then doing an unchecked +conversion to the fixed-point type. The difference is +that there are full range checks, to ensure that the result is in range. +This attribute is primarily intended for use in implementation of the +input-output functions for fixed-point values. + +Attribute From_Any +================== +.. index:: From_Any + +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. + +Attribute Has_Access_Values +=========================== +.. index:: Access values, testing for + +.. index:: Has_Access_Values + +The prefix of the `Has_Access_Values` attribute is a type. The result +is a Boolean value which is True if the is an access type, or is a composite +type with a component (at any nesting depth) that is an access type, and is +False otherwise. +The intended use of this attribute is in conjunction with generic +definitions. If the attribute is applied to a generic private type, it +indicates whether or not the corresponding actual type has access values. + +Attribute Has_Discriminants +=========================== +.. index:: Discriminants, testing for + +.. index:: Has_Discriminants + +The prefix of the `Has_Discriminants` attribute is a type. The result +is a Boolean value which is True if the type has discriminants, and False +otherwise. The intended use of this attribute is in conjunction with generic +definitions. If the attribute is applied to a generic private type, it +indicates whether or not the corresponding actual type has discriminants. + +Attribute Img +============= +.. index:: Img + +The `Img` attribute differs from `Image` in that it is applied +directly to an object, and yields the same result as +`Image` for the subtype of the object. This is convenient for +debugging: + +.. code-block:: ada + + Put_Line ("X = " & X'Img); + + +has the same meaning as the more verbose: + +.. code-block:: ada + + Put_Line ("X = " & T'Image (X)); + +where `T` is the (sub)type of the object `X`. + +Note that technically, in analogy to `Image`, +`X'Img` returns a parameterless function +that returns the appropriate string when called. This means that +`X'Img` can be renamed as a function-returning-string, or used +in an instantiation as a function parameter. + +Attribute Integer_Value +======================= +.. index:: Integer_Value + +For every integer type `S`, ``S'Integer_Value`` denotes a +function with the following spec: + +.. code-block:: ada + + function S'Integer_Value (Arg : ) return S; + +The value returned is the integer value `V`, such that:: + + Arg = V * T'Small + + +where `T` is the type of `Arg`. +The effect is thus similar to first doing an unchecked conversion from +the fixed-point type to its corresponding implementation type, and then +converting the result to the target integer type. The difference is +that there are full range checks, to ensure that the result is in range. +This attribute is primarily intended for use in implementation of the +standard input-output functions for fixed-point values. + +Attribute Invalid_Value +======================= +.. index:: Invalid_Value + +For every scalar type S, S'Invalid_Value returns an undefined value of the +type. If possible this value is an invalid representation for the type. The +value returned is identical to the value used to initialize an otherwise +uninitialized value of the type if pragma Initialize_Scalars is used, +including the ability to modify the value with the binder -Sxx flag and +relevant environment variables at run time. + +Attribute Iterable +================== +.. index:: Iterable + +Equivalent to Aspect Iterable. + +Attribute Large +=============== +.. index:: Ada 83 attributes + +.. index:: Large + +The `Large` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Library_Level +======================= +.. index:: Library_Level + +`P'Library_Level`, where P is an entity name, +returns a Boolean value which is True if the entity is declared +at the library level, and False otherwise. Note that within a +generic instantition, the name of the generic unit denotes the +instance, which means that this attribute can be used to test +if a generic is instantiated at the library level, as shown +in this example: + +.. code-block:: ada + + generic + ... + package Gen is + pragma Compile_Time_Error + (not Gen'Library_Level, + "Gen can only be instantiated at library level"); + ... + end Gen; + + +Attribute Lock_Free +=================== +.. index:: Lock_Free + +`P'Lock_Free`, where P is a protected object, returns True if a +pragma `Lock_Free` applies to P. + +Attribute Loop_Entry +==================== +.. index:: Loop_Entry + +Syntax:: + + X'Loop_Entry [(loop_name)] + + +The `Loop_Entry` attribute is used to refer to the value that an +expression had upon entry to a given loop in much the same way that the +`Old` attribute in a subprogram postcondition can be used to refer +to the value an expression had upon entry to the subprogram. The +relevant loop is either identified by the given loop name, or it is the +innermost enclosing loop when no loop name is given. + +A `Loop_Entry` attribute can only occur within a +`Loop_Variant` or `Loop_Invariant` pragma. A common use of +`Loop_Entry` is to compare the current value of objects with their +initial value at loop entry, in a `Loop_Invariant` pragma. + +The effect of using `X'Loop_Entry` is the same as declaring +a constant initialized with the initial value of `X` at loop +entry. This copy is not performed if the loop is not entered, or if the +corresponding pragmas are ignored or disabled. + +Attribute Machine_Size +====================== +.. index:: Machine_Size + +This attribute is identical to the `Object_Size` attribute. It is +provided for compatibility with the DEC Ada 83 attribute of this name. + +Attribute Mantissa +================== +.. index:: Ada 83 attributes + +.. index:: Mantissa + +The `Mantissa` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +.. _Attribute_Maximum_Alignment: + +Attribute Maximum_Alignment +=========================== +.. index:: Alignment, maximum + +.. index:: Maximum_Alignment + +`Standard'Maximum_Alignment` (`Standard` is the only +permissible prefix) provides the maximum useful alignment value for the +target. This is a static value that can be used to specify the alignment +for an object, guaranteeing that it is properly aligned in all +cases. + +Attribute Mechanism_Code +======================== +.. index:: Return values, passing mechanism + +.. index:: Parameters, passing mechanism + +.. index:: Mechanism_Code + +``function'Mechanism_Code`` yields an integer code for the +mechanism used for the result of function, and +``subprogram'Mechanism_Code (n)`` yields the mechanism +used for formal parameter number `n` (a static integer value with 1 +meaning the first parameter) of `subprogram`. The code returned is: + + + +*1* + by copy (value) + +*2* + by reference + +Attribute Null_Parameter +======================== +.. index:: Zero address, passing + +.. index:: Null_Parameter + +A reference ``T'Null_Parameter`` denotes an imaginary object of +type or subtype `T` allocated at machine address zero. The attribute +is allowed only as the default expression of a formal parameter, or as +an actual expression of a subprogram call. In either case, the +subprogram must be imported. + +The identity of the object is represented by the address zero in the +argument list, independent of the passing mechanism (explicit or +default). + +This capability is needed to specify that a zero address should be +passed for a record or other composite object passed by reference. +There is no way of indicating this without the `Null_Parameter` +attribute. + +Attribute Object_Size +===================== +.. index:: Size, used for objects + +.. index:: Object_Size + +The size of an object is not necessarily the same as the size of the type +of an object. This is because by default object sizes are increased to be +a multiple of the alignment of the object. For example, +`Natural'Size` is +31, but by default objects of type `Natural` will have a size of 32 bits. +Similarly, a record containing an integer and a character: + +.. code-block:: ada + + type Rec is record + I : Integer; + C : Character; + end record; + + +will have a size of 40 (that is `Rec'Size` will be 40). The +alignment will be 4, because of the +integer field, and so the default size of record objects for this type +will be 64 (8 bytes). + +If the alignment of the above record is specified to be 1, then the +object size will be 40 (5 bytes). This is true by default, and also +an object size of 40 can be explicitly specified in this case. + +A consequence of this capability is that different object sizes can be +given to subtypes that would otherwise be considered in Ada to be +statically matching. But it makes no sense to consider such subtypes +as statically matching. Consequently, in `GNAT` we add a rule +to the static matching rules that requires object sizes to match. +Consider this example: + +.. code-block:: ada + + 1. procedure BadAVConvert is + 2. type R is new Integer; + 3. subtype R1 is R range 1 .. 10; + 4. subtype R2 is R range 1 .. 10; + 5. for R1'Object_Size use 8; + 6. for R2'Object_Size use 16; + 7. type R1P is access all R1; + 8. type R2P is access all R2; + 9. R1PV : R1P := new R1'(4); + 10. R2PV : R2P; + 11. begin + 12. R2PV := R2P (R1PV); + | + >>> target designated subtype not compatible with + type "R1" defined at line 3 + + 13. end; + + +In the absence of lines 5 and 6, +types `R1` and `R2` statically match and +hence the conversion on line 12 is legal. But since lines 5 and 6 +cause the object sizes to differ, `GNAT` considers that types +`R1` and `R2` are not statically matching, and line 12 +generates the diagnostic shown above. + +Similar additional checks are performed in other contexts requiring +statically matching subtypes. + +Attribute Old +============= +.. index:: Old + +In addition to the usage of `Old` defined in the Ada 2012 RM (usage +within `Post` aspect), GNAT also permits the use of this attribute +in implementation defined pragmas `Postcondition`, +`Contract_Cases` and `Test_Case`. Also usages of +`Old` which would be illegal according to the Ada 2012 RM +definition are allowed under control of +implementation defined pragma `Unevaluated_Use_Of_Old`. + +Attribute Passed_By_Reference +============================= +.. index:: Parameters, when passed by reference + +.. index:: Passed_By_Reference + +``type'Passed_By_Reference`` for any subtype `type` returns +a value of type `Boolean` value that is `True` if the type is +normally passed by reference and `False` if the type is normally +passed by copy in calls. For scalar types, the result is always `False` +and is static. For non-scalar types, the result is non-static. + +Attribute Pool_Address +====================== +.. index:: Parameters, when passed by reference + +.. index:: Pool_Address + +``X'Pool_Address`` for any object `X` returns the address +of X within its storage pool. This is the same as +``X'Address``, except that for an unconstrained array whose +bounds are allocated just before the first component, +``X'Pool_Address`` returns the address of those bounds, +whereas ``X'Address`` returns the address of the first +component. + +Here, we are interpreting 'storage pool' broadly to mean +``wherever the object is allocated``, which could be a +user-defined storage pool, +the global heap, on the stack, or in a static memory area. +For an object created by `new`, ``Ptr.all'Pool_Address`` is +what is passed to `Allocate` and returned from `Deallocate`. + +Attribute Range_Length +====================== +.. index:: Range_Length + +``type'Range_Length`` for any discrete type `type` yields +the number of values represented by the subtype (zero for a null +range). The result is static for static subtypes. `Range_Length` +applied to the index subtype of a one dimensional array always gives the +same result as `Length` applied to the array itself. + +Attribute Ref +============= +.. index:: Ref + +Attribute Restriction_Set +========================= +.. index:: Restriction_Set +.. index:: Restrictions + +This attribute allows compile time testing of restrictions that +are currently in effect. It is primarily intended for specializing +code in the run-time based on restrictions that are active (e.g. +don't need to save fpt registers if restriction No_Floating_Point +is known to be in effect), but can be used anywhere. + +There are two forms: + +.. code-block:: ada + + System'Restriction_Set (partition_boolean_restriction_NAME) + System'Restriction_Set (No_Dependence => library_unit_NAME); + + +In the case of the first form, the only restriction names +allowed are parameterless restrictions that are checked +for consistency at bind time. For a complete list see the +subtype `System.Rident.Partition_Boolean_Restrictions`. + +The result returned is True if the restriction is known to +be in effect, and False if the restriction is known not to +be in effect. An important guarantee is that the value of +a Restriction_Set attribute is known to be consistent throughout +all the code of a partition. + +This is trivially achieved if the entire partition is compiled +with a consistent set of restriction pragmas. However, the +compilation model does not require this. It is possible to +compile one set of units with one set of pragmas, and another +set of units with another set of pragmas. It is even possible +to compile a spec with one set of pragmas, and then WITH the +same spec with a different set of pragmas. Inconsistencies +in the actual use of the restriction are checked at bind time. + +In order to achieve the guarantee of consistency for the +Restriction_Set pragma, we consider that a use of the pragma +that yields False is equivalent to a violation of the +restriction. + +So for example if you write + +.. code-block:: ada + + if System'Restriction_Set (No_Floating_Point) then + ... + else + ... + end if; + + +And the result is False, so that the else branch is executed, +you can assume that this restriction is not set for any unit +in the partition. This is checked by considering this use of +the restriction pragma to be a violation of the restriction +No_Floating_Point. This means that no other unit can attempt +to set this restriction (if some unit does attempt to set it, +the binder will refuse to bind the partition). + +Technical note: The restriction name and the unit name are +intepreted entirely syntactically, as in the corresponding +Restrictions pragma, they are not analyzed semantically, +so they do not have a type. + +Attribute Result +================ +.. index:: Result + +``function'Result`` can only be used with in a Postcondition pragma +for a function. The prefix must be the name of the corresponding function. This +is used to refer to the result of the function in the postcondition expression. +For a further discussion of the use of this attribute and examples of its use, +see the description of pragma Postcondition. + +Attribute Safe_Emax +=================== +.. index:: Ada 83 attributes + +.. index:: Safe_Emax + +The `Safe_Emax` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Safe_Large +==================== +.. index:: Ada 83 attributes + +.. index:: Safe_Large + +The `Safe_Large` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Safe_Small +==================== +.. index:: Ada 83 attributes + +.. index:: Safe_Small + +The `Safe_Small` attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. + +Attribute Scalar_Storage_Order +============================== +.. index:: Endianness + +.. index:: Scalar storage order + +.. index:: Scalar_Storage_Order + +For every array or record type `S`, the representation attribute +`Scalar_Storage_Order` denotes the order in which storage elements +that make up scalar components are ordered within S. The value given must +be a static expression of type System.Bit_Order. The following is an example +of the use of this feature: + +.. code-block:: ada + + -- Component type definitions + + subtype Yr_Type is Natural range 0 .. 127; + subtype Mo_Type is Natural range 1 .. 12; + subtype Da_Type is Natural range 1 .. 31; + + -- Record declaration + + type Date is record + Years_Since_1980 : Yr_Type; + Month : Mo_Type; + Day_Of_Month : Da_Type; + end record; + + -- Record representation clause + + for Date use record + Years_Since_1980 at 0 range 0 .. 6; + Month at 0 range 7 .. 10; + Day_Of_Month at 0 range 11 .. 15; + end record; + + -- Attribute definition clauses + + for Date'Bit_Order use System.High_Order_First; + for Date'Scalar_Storage_Order use System.High_Order_First; + -- If Scalar_Storage_Order is specified, it must be consistent with + -- Bit_Order, so it's best to always define the latter explicitly if + -- the former is used. + + +Other properties are as for standard representation attribute `Bit_Order`, +as defined by Ada RM 13.5.3(4). The default is `System.Default_Bit_Order`. + +For a record type `T`, if ``T'Scalar_Storage_Order`` is +specified explicitly, it shall be equal to ``T'Bit_Order``. Note: +this means that if a `Scalar_Storage_Order` attribute definition +clause is not confirming, then the type's `Bit_Order` shall be +specified explicitly and set to the same value. + +Derived types inherit an explicitly set scalar storage order from their parent +types. This may be overridden for the derived type by giving an explicit scalar +storage order for the derived type. For a record extension, the derived type +must have the same scalar storage order as the parent type. + +If a component of `T` is of a record or array type, then that type must +also have a `Scalar_Storage_Order` attribute definition clause. + +A component of a record or array type that is a packed array, or that +does not start on a byte boundary, must have the same scalar storage order +as the enclosing record or array type. + +No component of a type that has an explicit `Scalar_Storage_Order` +attribute definition may be aliased. + +A confirming `Scalar_Storage_Order` attribute definition clause (i.e. +with a value equal to `System.Default_Bit_Order`) has no effect. + +If the opposite storage order is specified, then whenever the value of +a scalar component of an object of type `S` is read, the storage +elements of the enclosing machine scalar are first reversed (before +retrieving the component value, possibly applying some shift and mask +operatings on the enclosing machine scalar), and the opposite operation +is done for writes. + +In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components +are relaxed. Instead, the following rules apply: + +* the underlying storage elements are those at positions + `(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)` +* the sequence of underlying storage elements shall have + a size no greater than the largest machine scalar +* the enclosing machine scalar is defined as the smallest machine + scalar starting at a position no greater than + `position + first_bit / storage_element_size` and covering + storage elements at least up to `position + (last_bit + storage_element_size - 1) / storage_element_size` +* the position of the component is interpreted relative to that machine + scalar. + +If no scalar storage order is specified for a type (either directly, or by +inheritance in the case of a derived type), then the default is normally +the native ordering of the target, but this default can be overridden using +pragma `Default_Scalar_Storage_Order`. + +Note that the scalar storage order only affects the in-memory data +representation. It has no effect on the representation used by stream +attributes. + +.. _Attribute_Simple_Storage_Pool: + +Attribute Simple_Storage_Pool +============================= +.. index:: Storage pool, simple + +.. index:: Simple storage pool + +.. index:: Simple_Storage_Pool + +For every nonformal, nonderived access-to-object type `Acc`, the +representation attribute `Simple_Storage_Pool` may be specified +via an attribute_definition_clause (or by specifying the equivalent aspect): + +.. code-block:: ada + + My_Pool : My_Simple_Storage_Pool_Type; + + type Acc is access My_Data_Type; + + for Acc'Simple_Storage_Pool use My_Pool; + + + +The name given in an attribute_definition_clause for the +`Simple_Storage_Pool` attribute shall denote a variable of +a 'simple storage pool type' (see pragma `Simple_Storage_Pool_Type`). + +The use of this attribute is only allowed for a prefix denoting a type +for which it has been specified. The type of the attribute is the type +of the variable specified as the simple storage pool of the access type, +and the attribute denotes that variable. + +It is illegal to specify both `Storage_Pool` and `Simple_Storage_Pool` +for the same access type. + +If the `Simple_Storage_Pool` attribute has been specified for an access +type, then applying the `Storage_Pool` attribute to the type is flagged +with a warning and its evaluation raises the exception `Program_Error`. + +If the Simple_Storage_Pool attribute has been specified for an access +type `S`, then the evaluation of the attribute ``S'Storage_Size`` +returns the result of calling ``Storage_Size (S'Simple_Storage_Pool)``, +which is intended to indicate the number of storage elements reserved for +the simple storage pool. If the Storage_Size function has not been defined +for the simple storage pool type, then this attribute returns zero. + +If an access type `S` has a specified simple storage pool of type +`SSP`, then the evaluation of an allocator for that access type calls +the primitive `Allocate` procedure for type `SSP`, passing +``S'Simple_Storage_Pool`` as the pool parameter. The detailed +semantics of such allocators is the same as those defined for allocators +in section 13.11 of the :title:`Ada Reference Manual`, with the term +`simple storage pool` substituted for `storage pool`. + +If an access type `S` has a specified simple storage pool of type +`SSP`, then a call to an instance of the `Ada.Unchecked_Deallocation` +for that access type invokes the primitive `Deallocate` procedure +for type `SSP`, passing ``S'Simple_Storage_Pool`` as the pool +parameter. The detailed semantics of such unchecked deallocations is the same +as defined in section 13.11.2 of the Ada Reference Manual, except that the +term 'simple storage pool' is substituted for 'storage pool'. + +Attribute Small +=============== +.. index:: Ada 83 attributes + +.. index:: Small + +The `Small` attribute is defined in Ada 95 (and Ada 2005) only for +fixed-point types. +GNAT also allows this attribute to be applied to floating-point types +for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute when applied to floating-point types. + +Attribute Storage_Unit +====================== +.. index:: Storage_Unit + +`Standard'Storage_Unit` (`Standard` is the only permissible +prefix) provides the same value as `System.Storage_Unit`. + +Attribute Stub_Type +=================== +.. index:: Stub_Type + +The GNAT implementation of remote access-to-classwide types is +organized as described in AARM section E.4 (20.t): a value of an RACW type +(designating a remote object) is represented as a normal access +value, pointing to a "stub" object which in turn contains the +necessary information to contact the designated remote object. A +call on any dispatching operation of such a stub object does the +remote call, if necessary, using the information in the stub object +to locate the target partition, etc. + +For a prefix `T` that denotes a remote access-to-classwide type, +`T'Stub_Type` denotes the type of the corresponding stub objects. + +By construction, the layout of `T'Stub_Type` is identical to that of +type `RACW_Stub_Type` declared in the internal implementation-defined +unit `System.Partition_Interface`. Use of this attribute will create +an implicit dependency on this unit. + +Attribute System_Allocator_Alignment +==================================== +.. index:: Alignment, allocator + +.. index:: System_Allocator_Alignment + +`Standard'System_Allocator_Alignment` (`Standard` is the only +permissible prefix) provides the observable guaranted to be honored by +the system allocator (malloc). This is a static value that can be used +in user storage pools based on malloc either to reject allocation +with alignment too large or to enable a realignment circuitry if the +alignment request is larger than this value. + +Attribute Target_Name +===================== +.. index:: Target_Name + +`Standard'Target_Name` (`Standard` is the only permissible +prefix) provides a static string value that identifies the target +for the current compilation. For GCC implementations, this is the +standard gcc target name without the terminating slash (for +example, GNAT 5.0 on windows yields "i586-pc-mingw32msv"). + +Attribute To_Address +==================== +.. index:: To_Address + +The `System'To_Address` +(`System` is the only permissible prefix) +denotes a function identical to +`System.Storage_Elements.To_Address` except that +it is a static attribute. This means that if its argument is +a static expression, then the result of the attribute is a +static expression. This means that such an expression can be +used in contexts (e.g., preelaborable packages) which require a +static expression and where the function call could not be used +(since the function call is always non-static, even if its +argument is static). The argument must be in the range +-(2**(m-1) .. 2**m-1, where m is the memory size +(typically 32 or 64). Negative values are intepreted in a +modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on +a 32 bits machine). + +Attribute To_Any +================ +.. index:: To_Any + +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. + +Attribute Type_Class +==================== +.. index:: Type_Class + +``type'Type_Class`` for any type or subtype `type` yields +the value of the type class for the full type of `type`. If +`type` is a generic formal type, the value is the value for the +corresponding actual subtype. The value of this attribute is of type +``System.Aux_DEC.Type_Class``, which has the following definition: + +.. code-block:: ada + + type Type_Class is + (Type_Class_Enumeration, + Type_Class_Integer, + Type_Class_Fixed_Point, + Type_Class_Floating_Point, + Type_Class_Array, + Type_Class_Record, + Type_Class_Access, + Type_Class_Task, + Type_Class_Address); + + +Protected types yield the value `Type_Class_Task`, which thus +applies to all concurrent types. This attribute is designed to +be compatible with the DEC Ada 83 attribute of the same name. + +Attribute Type_Key +================== +.. index:: Type_Key + +The `Type_Key` attribute is applicable to a type or subtype and +yields a value of type Standard.String containing encoded information +about the type or subtype. This provides improved compatibility with +other implementations that support this attribute. + +Attribute TypeCode +================== +.. index:: TypeCode + +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. + +Attribute UET_Address +===================== +.. index:: UET_Address + +The `UET_Address` attribute can only be used for a prefix which +denotes a library package. It yields the address of the unit exception +table when zero cost exception handling is used. This attribute is +intended only for use within the GNAT implementation. See the unit +`Ada.Exceptions` in files :file:`a-except.ads` and :file:`a-except.adb` +for details on how this attribute is used in the implementation. + +Attribute Unconstrained_Array +============================= +.. index:: Unconstrained_Array + +The `Unconstrained_Array` attribute can be used with a prefix that +denotes any type or subtype. It is a static attribute that yields +`True` if the prefix designates an unconstrained array, +and `False` otherwise. In a generic instance, the result is +still static, and yields the result of applying this test to the +generic actual. + +Attribute Universal_Literal_String +================================== +.. index:: Named numbers, representation of + +.. index:: Universal_Literal_String + +The prefix of `Universal_Literal_String` must be a named +number. The static result is the string consisting of the characters of +the number as defined in the original source. This allows the user +program to access the actual text of named numbers without intermediate +conversions and without the need to enclose the strings in quotes (which +would preclude their use as numbers). + +For example, the following program prints the first 50 digits of pi: + +.. code-block:: ada + + with Text_IO; use Text_IO; + with Ada.Numerics; + procedure Pi is + begin + Put (Ada.Numerics.Pi'Universal_Literal_String); + end; + + +Attribute Unrestricted_Access +============================= +.. index:: Access, unrestricted + +.. index:: Unrestricted_Access + +The `Unrestricted_Access` attribute is similar to `Access` +except that all accessibility and aliased view checks are omitted. This +is a user-beware attribute. + +For objects, it is similar to `Address`, for which it is a +desirable replacement where the value desired is an access type. +In other words, its effect is similar to first applying the +`Address` attribute and then doing an unchecked conversion to a +desired access type. + +For subprograms, `P'Unrestricted_Access` may be used where +`P'Access` would be illegal, to construct a value of a +less-nested named access type that designates a more-nested +subprogram. This value may be used in indirect calls, so long as the +more-nested subprogram still exists; once the subprogram containing it +has returned, such calls are erroneous. For example: + +.. code-block:: ada + + package body P is + + type Less_Nested is not null access procedure; + Global : Less_Nested; + + procedure P1 is + begin + Global.all; + end P1; + + procedure P2 is + Local_Var : Integer; + + procedure More_Nested is + begin + ... Local_Var ... + end More_Nested; + begin + Global := More_Nested'Unrestricted_Access; + P1; + end P2; + + end P; + + +When P1 is called from P2, the call via Global is OK, but if P1 were +called after P2 returns, it would be an erroneous use of a dangling +pointer. + +For objects, it is possible to use `Unrestricted_Access` for any +type. However, if the result is of an access-to-unconstrained array +subtype, then the resulting pointer has the same scope as the context +of the attribute, and must not be returned to some enclosing scope. +For instance, if a function uses `Unrestricted_Access` to create +an access-to-unconstrained-array and returns that value to the caller, +the result will involve dangling pointers. In addition, it is only +valid to create pointers to unconstrained arrays using this attribute +if the pointer has the normal default 'fat' representation where a +pointer has two components, one points to the array and one points to +the bounds. If a size clause is used to force 'thin' representation +for a pointer to unconstrained where there is only space for a single +pointer, then the resulting pointer is not usable. + +In the simple case where a direct use of Unrestricted_Access attempts +to make a thin pointer for a non-aliased object, the compiler will +reject the use as illegal, as shown in the following example: + +.. code-block:: ada + + with System; use System; + procedure SliceUA2 is + type A is access all String; + for A'Size use Standard'Address_Size; + + procedure P (Arg : A) is + begin + null; + end P; + + X : String := "hello world!"; + X2 : aliased String := "hello world!"; + + AV : A := X'Unrestricted_Access; -- ERROR + | + >>> illegal use of Unrestricted_Access attribute + >>> attempt to generate thin pointer to unaliased object + + begin + P (X'Unrestricted_Access); -- ERROR + | + >>> illegal use of Unrestricted_Access attribute + >>> attempt to generate thin pointer to unaliased object + + P (X(7 .. 12)'Unrestricted_Access); -- ERROR + | + >>> illegal use of Unrestricted_Access attribute + >>> attempt to generate thin pointer to unaliased object + + P (X2'Unrestricted_Access); -- OK + end; + + +but other cases cannot be detected by the compiler, and are +considered to be erroneous. Consider the following example: + +.. code-block:: ada + + with System; use System; + with System; use System; + procedure SliceUA is + type AF is access all String; + + type A is access all String; + for A'Size use Standard'Address_Size; + + procedure P (Arg : A) is + begin + if Arg'Length /= 6 then + raise Program_Error; + end if; + end P; + + X : String := "hello world!"; + Y : AF := X (7 .. 12)'Unrestricted_Access; + + begin + P (A (Y)); + end; + + +A normal unconstrained array value +or a constrained array object marked as aliased has the bounds in memory +just before the array, so a thin pointer can retrieve both the data and +the bounds. But in this case, the non-aliased object `X` does not have the +bounds before the string. If the size clause for type `A` +were not present, then the pointer +would be a fat pointer, where one component is a pointer to the bounds, +and all would be well. But with the size clause present, the conversion from +fat pointer to thin pointer in the call loses the bounds, and so this +is erroneous, and the program likely raises a `Program_Error` exception. + +In general, it is advisable to completely +avoid mixing the use of thin pointers and the use of +`Unrestricted_Access` where the designated type is an +unconstrained array. The use of thin pointers should be restricted to +cases of porting legacy code that implicitly assumes the size of pointers, +and such code should not in any case be using this attribute. + +Another erroneous situation arises if the attribute is +applied to a constant. The resulting pointer can be used to access the +constant, but the effect of trying to modify a constant in this manner +is not well-defined. Consider this example: + +.. code-block:: ada + + P : constant Integer := 4; + type R is access all Integer; + RV : R := P'Unrestricted_Access; + .. + RV.all := 3; + + +Here we attempt to modify the constant P from 4 to 3, but the compiler may +or may not notice this attempt, and subsequent references to P may yield +either the value 3 or the value 4 or the assignment may blow up if the +compiler decides to put P in read-only memory. One particular case where +`Unrestricted_Access` can be used in this way is to modify the +value of an `IN` parameter: + +.. code-block:: ada + + procedure K (S : in String) is + type R is access all Character; + RV : R := S (3)'Unrestricted_Access; + begin + RV.all := 'a'; + end; + + +In general this is a risky approach. It may appear to "work" but such uses of +`Unrestricted_Access` are potentially non-portable, even from one version +of `GNAT` to another, so are best avoided if possible. + +Attribute Update +================ +.. index:: Update + +The `Update` attribute creates a copy of an array or record value +with one or more modified components. The syntax is:: + + PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST ) + PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION {, ARRAY_COMPONENT_ASSOCIATION } ) + PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION + {, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION } ) + + MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION + INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST {| INDEX_EXPRESSION_LIST } + INDEX_EXPRESSION_LIST ::= ( EXPRESSION {, EXPRESSION } ) + + +where `PREFIX` is the name of an array or record object, the +association list in parentheses does not contain an `others` +choice and the box symbol `<>` may not appear in any +expression. The effect is to yield a copy of the array or record value +which is unchanged apart from the components mentioned in the +association list, which are changed to the indicated value. The +original value of the array or record value is not affected. For +example: + +.. code-block:: ada + + type Arr is Array (1 .. 5) of Integer; + ... + Avar1 : Arr := (1,2,3,4,5); + Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20); + + +yields a value for `Avar2` of 1,10,20,20,5 with `Avar1` +begin unmodified. Similarly: + +.. code-block:: ada + + type Rec is A, B, C : Integer; + ... + Rvar1 : Rec := (A => 1, B => 2, C => 3); + Rvar2 : Rec := Rvar1'Update (B => 20); + + +yields a value for `Rvar2` of (A => 1, B => 20, C => 3), +with `Rvar1` being unmodifed. +Note that the value of the attribute reference is computed +completely before it is used. This means that if you write: + +.. code-block:: ada + + Avar1 := Avar1'Update (1 => 10, 2 => Function_Call); + + +then the value of `Avar1` is not modified if `Function_Call` +raises an exception, unlike the effect of a series of direct assignments +to elements of `Avar1`. In general this requires that +two extra complete copies of the object are required, which should be +kept in mind when considering efficiency. + +The `Update` attribute cannot be applied to prefixes of a limited +type, and cannot reference discriminants in the case of a record type. +The accessibility level of an Update attribute result object is defined +as for an aggregate. + +In the record case, no component can be mentioned more than once. In +the array case, two overlapping ranges can appear in the association list, +in which case the modifications are processed left to right. + +Multi-dimensional arrays can be modified, as shown by this example: + +.. code-block:: ada + + A : array (1 .. 10, 1 .. 10) of Integer; + .. + A := A'Update ((1, 2) => 20, (3, 4) => 30); + + +which changes element (1,2) to 20 and (3,4) to 30. + +Attribute Valid_Scalars +======================= +.. index:: Valid_Scalars + +The `'Valid_Scalars` attribute is intended to make it easier to +check the validity of scalar subcomponents of composite objects. It +is defined for any prefix `X` that denotes an object. +The value of this attribute is of the predefined type Boolean. +`X'Valid_Scalars` yields True if and only if evaluation of +`P'Valid` yields True for every scalar part P of X or if X has +no scalar parts. It is not specified in what order the scalar parts +are checked, nor whether any more are checked after any one of them +is determined to be invalid. If the prefix `X` is of a class-wide +type `T'Class` (where `T` is the associated specific type), +or if the prefix `X` is of a specific tagged type `T`, then +only the scalar parts of components of `T` are traversed; in other +words, components of extensions of `T` are not traversed even if +`T'Class (X)'Tag /= T'Tag` . The compiler will issue a warning if it can +be determined at compile time that the prefix of the attribute has no +scalar parts (e.g., if the prefix is of an access type, an interface type, +an undiscriminated task type, or an undiscriminated protected type). + +For scalar types, `Valid_Scalars` is equivalent to `Valid`. The use +of this attribute is not permitted for `Unchecked_Union` types for which +in general it is not possible to determine the values of the discriminants. + +Note: `Valid_Scalars` can generate a lot of code, especially in the case +of a large variant record. If the attribute is called in many places in the +same program applied to objects of the same type, it can reduce program size +to write a function with a single use of the attribute, and then call that +function from multiple places. + +Attribute VADS_Size +=================== +.. index:: Size, VADS compatibility + +.. index:: VADS_Size + +The `'VADS_Size` attribute is intended to make it easier to port +legacy code which relies on the semantics of `'Size` as implemented +by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the +same semantic interpretation. In particular, `'VADS_Size` applied +to a predefined or other primitive type with no Size clause yields the +Object_Size (for example, `Natural'Size` is 32 rather than 31 on +typical machines). In addition `'VADS_Size` applied to an object +gives the result that would be obtained by applying the attribute to +the corresponding type. + +Attribute Value_Size +==================== +.. index:: Size, setting for not-first subtype + +.. index:: Value_Size + +``type'Value_Size`` is the number of bits required to represent +a value of the given subtype. It is the same as ``type'Size``, +but, unlike `Size`, may be set for non-first subtypes. + +Attribute Wchar_T_Size +====================== +.. index:: Wchar_T_Size + +`Standard'Wchar_T_Size` (`Standard` is the only permissible +prefix) provides the size in bits of the C `wchar_t` type +primarily for constructing the definition of this type in +package `Interfaces.C`. The result is a static constant. + +Attribute Word_Size +=================== +.. index:: Word_Size + +`Standard'Word_Size` (`Standard` is the only permissible +prefix) provides the value `System.Word_Size`. The result is +a static constant. + diff --git a/gcc/ada/doc/gnat_rm/implementation_defined_characteristics.rst b/gcc/ada/doc/gnat_rm/implementation_defined_characteristics.rst new file mode 100644 index 00000000000..f26dd912998 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_defined_characteristics.rst @@ -0,0 +1,1295 @@ +.. _Implementation_Defined_Characteristics: + +************************************** +Implementation Defined Characteristics +************************************** + +In addition to the implementation dependent pragmas and attributes, and the +implementation advice, there are a number of other Ada features that are +potentially implementation dependent and are designated as +implementation-defined. These are mentioned throughout the Ada Reference +Manual, and are summarized in Annex M. + +A requirement for conforming Ada compilers is that they provide +documentation describing how the implementation deals with each of these +issues. In this chapter you will find each point in Annex M listed, +followed by a description of how GNAT +handles the implementation dependence. + +You can use this chapter as a guide to minimizing implementation +dependent features in your programs if portability to other compilers +and other operating systems is an important consideration. The numbers +in each entry below correspond to the paragraph numbers in the Ada +Reference Manual. + +* + "Whether or not each recommendation given in Implementation + Advice is followed. See 1.1.2(37)." + +See :ref:`Implementation_Advice`. + +* + "Capacity limitations of the implementation. See 1.1.3(3)." + +The complexity of programs that can be processed is limited only by the +total amount of available virtual memory, and disk space for the +generated object files. + +* + "Variations from the standard that are impractical to avoid + given the implementation's execution environment. See 1.1.3(6)." + +There are no variations from the standard. + +* + "Which code_statements cause external + interactions. See 1.1.3(10)." + +Any `code_statement` can potentially cause external interactions. + +* + "The coded representation for the text of an Ada + program. See 2.1(4)." + +See separate section on source representation. + +* + "The control functions allowed in comments. See 2.1(14)." + +See separate section on source representation. + +* + "The representation for an end of line. See 2.2(2)." + +See separate section on source representation. + +* + "Maximum supported line length and lexical element + length. See 2.2(15)." + +The maximum line length is 255 characters and the maximum length of +a lexical element is also 255 characters. This is the default setting +if not overridden by the use of compiler switch *-gnaty* (which +sets the maximum to 79) or *-gnatyMnn* which allows the maximum +line length to be specified to be any value up to 32767. The maximum +length of a lexical element is the same as the maximum line length. + +* + "Implementation defined pragmas. See 2.8(14)." + +See :ref:`Implementation_Defined_Pragmas`. + +* + "Effect of pragma `Optimize`. See 2.8(27)." + +Pragma `Optimize`, if given with a `Time` or `Space` +parameter, checks that the optimization flag is set, and aborts if it is +not. + +* + "The sequence of characters of the value returned by + ``S'Image`` when some of the graphic characters of + ``S'Wide_Image`` are not defined in `Character`. See + 3.5(37)." + +The sequence of characters is as defined by the wide character encoding +method used for the source. See section on source representation for +further details. + +* + "The predefined integer types declared in + `Standard`. See 3.5.4(25)." + +====================== ======================================= +Type Representation +====================== ======================================= +*Short_Short_Integer* 8 bit signed +*Short_Integer* (Short) 16 bit signed +*Integer* 32 bit signed +*Long_Integer* 64 bit signed (on most 64 bit targets, + depending on the C definition of long). + 32 bit signed (all other targets) +*Long_Long_Integer* 64 bit signed +====================== ======================================= + +* + "Any nonstandard integer types and the operators defined + for them. See 3.5.4(26)." + +There are no nonstandard integer types. + +* + "Any nonstandard real types and the operators defined for + them. See 3.5.6(8)." + +There are no nonstandard real types. + +* + "What combinations of requested decimal precision and range + are supported for floating point types. See 3.5.7(7)." + +The precision and range is as defined by the IEEE standard. + +* + "The predefined floating point types declared in + `Standard`. See 3.5.7(16)." + +====================== ==================================================== +Type Representation +====================== ==================================================== +*Short_Float* 32 bit IEEE short +*Float* (Short) 32 bit IEEE short +*Long_Float* 64 bit IEEE long +*Long_Long_Float* 64 bit IEEE long (80 bit IEEE long on x86 processors) +====================== ==================================================== + +* + "The small of an ordinary fixed point type. See 3.5.9(8)." + +`Fine_Delta` is 2**(-63) + +* + "What combinations of small, range, and digits are + supported for fixed point types. See 3.5.9(10)." + +Any combinations are permitted that do not result in a small less than +`Fine_Delta` and do not result in a mantissa larger than 63 bits. +If the mantissa is larger than 53 bits on machines where Long_Long_Float +is 64 bits (true of all architectures except ia32), then the output from +Text_IO is accurate to only 53 bits, rather than the full mantissa. This +is because floating-point conversions are used to convert fixed point. + + +* + "The result of `Tags.Expanded_Name` for types declared + within an unnamed `block_statement`. See 3.9(10)." + +Block numbers of the form `B`nnn``, where `nnn` is a +decimal integer are allocated. + +* + "Implementation-defined attributes. See 4.1.4(12)." + +See :ref:`Implementation_Defined_Attributes`. + +* + "Any implementation-defined time types. See 9.6(6)." + +There are no implementation-defined time types. + +* + "The time base associated with relative delays." + +See 9.6(20). The time base used is that provided by the C library +function `gettimeofday`. + +* + "The time base of the type `Calendar.Time`. See + 9.6(23)." + +The time base used is that provided by the C library function +`gettimeofday`. + +* + "The time zone used for package `Calendar` + operations. See 9.6(24)." + +The time zone used by package `Calendar` is the current system time zone +setting for local time, as accessed by the C library function +`localtime`. + +* + "Any limit on `delay_until_statements` of + `select_statements`. See 9.6(29)." + +There are no such limits. + +* + "Whether or not two non-overlapping parts of a composite + object are independently addressable, in the case where packing, record + layout, or `Component_Size` is specified for the object. See + 9.10(1)." + +Separate components are independently addressable if they do not share +overlapping storage units. + +* + "The representation for a compilation. See 10.1(2)." + +A compilation is represented by a sequence of files presented to the +compiler in a single invocation of the *gcc* command. + +* + "Any restrictions on compilations that contain multiple + compilation_units. See 10.1(4)." + +No single file can contain more than one compilation unit, but any +sequence of files can be presented to the compiler as a single +compilation. + +* + "The mechanisms for creating an environment and for adding + and replacing compilation units. See 10.1.4(3)." + +See separate section on compilation model. + +* + "The manner of explicitly assigning library units to a + partition. See 10.2(2)." + +If a unit contains an Ada main program, then the Ada units for the partition +are determined by recursive application of the rules in the Ada Reference +Manual section 10.2(2-6). In other words, the Ada units will be those that +are needed by the main program, and then this definition of need is applied +recursively to those units, and the partition contains the transitive +closure determined by this relationship. In short, all the necessary units +are included, with no need to explicitly specify the list. If additional +units are required, e.g., by foreign language units, then all units must be +mentioned in the context clause of one of the needed Ada units. + +If the partition contains no main program, or if the main program is in +a language other than Ada, then GNAT +provides the binder options *-z* and *-n* respectively, and in +this case a list of units can be explicitly supplied to the binder for +inclusion in the partition (all units needed by these units will also +be included automatically). For full details on the use of these +options, refer to the `GNAT Make Program gnatmake` in the +:title:`GNAT User's Guide`. + +* + "The implementation-defined means, if any, of specifying + which compilation units are needed by a given compilation unit. See + 10.2(2)." + +The units needed by a given compilation unit are as defined in +the Ada Reference Manual section 10.2(2-6). There are no +implementation-defined pragmas or other implementation-defined +means for specifying needed units. + +* + "The manner of designating the main subprogram of a + partition. See 10.2(7)." + +The main program is designated by providing the name of the +corresponding :file:`ALI` file as the input parameter to the binder. + +* + "The order of elaboration of `library_items`. See + 10.2(18)." + +The first constraint on ordering is that it meets the requirements of +Chapter 10 of the Ada Reference Manual. This still leaves some +implementation dependent choices, which are resolved by first +elaborating bodies as early as possible (i.e., in preference to specs +where there is a choice), and second by evaluating the immediate with +clauses of a unit to determine the probably best choice, and +third by elaborating in alphabetical order of unit names +where a choice still remains. + +* + "Parameter passing and function return for the main + subprogram. See 10.2(21)." + +The main program has no parameters. It may be a procedure, or a function +returning an integer type. In the latter case, the returned integer +value is the return code of the program (overriding any value that +may have been set by a call to `Ada.Command_Line.Set_Exit_Status`). + +* + "The mechanisms for building and running partitions. See + 10.2(24)." + +GNAT itself supports programs with only a single partition. The GNATDIST +tool provided with the GLADE package (which also includes an implementation +of the PCS) provides a completely flexible method for building and running +programs consisting of multiple partitions. See the separate GLADE manual +for details. + +* + "The details of program execution, including program + termination. See 10.2(25)." + +See separate section on compilation model. + +* + "The semantics of any non-active partitions supported by the + implementation. See 10.2(28)." + +Passive partitions are supported on targets where shared memory is +provided by the operating system. See the GLADE reference manual for +further details. + +* + "The information returned by `Exception_Message`. See + 11.4.1(10)." + +Exception message returns the null string unless a specific message has +been passed by the program. + +* + "The result of `Exceptions.Exception_Name` for types + declared within an unnamed `block_statement`. See 11.4.1(12)." + +Blocks have implementation defined names of the form `B`nnn`` +where `nnn` is an integer. + +* + "The information returned by + `Exception_Information`. See 11.4.1(13)." + +`Exception_Information` returns a string in the following format:: + + *Exception_Name:* nnnnn + *Message:* mmmmm + *PID:* ppp + *Load address:* 0xhhhh + *Call stack traceback locations:* + 0xhhhh 0xhhhh 0xhhhh ... 0xhhh + +where + + * `nnnn` is the fully qualified name of the exception in all upper + case letters. This line is always present. + + * `mmmm` is the message (this line present only if message is non-null) + + * `ppp` is the Process Id value as a decimal integer (this line is + present only if the Process Id is nonzero). Currently we are + not making use of this field. + + * The Load address line, the Call stack traceback locations line and the + following values are present only if at least one traceback location was + recorded. The Load address indicates the address at which the main executable + was loaded; this line may not be present if operating system hasn't relocated + the main executable. The values are given in C style format, with lower case + letters for a-f, and only as many digits present as are necessary. + The line terminator sequence at the end of each line, including + the last line is a single `LF` character (`16#0A#`). + +* + "Implementation-defined check names. See 11.5(27)." + +The implementation defined check name Alignment_Check controls checking of +address clause values for proper alignment (that is, the address supplied +must be consistent with the alignment of the type). + +The implementation defined check name Predicate_Check controls whether +predicate checks are generated. + +The implementation defined check name Validity_Check controls whether +validity checks are generated. + +In addition, a user program can add implementation-defined check names +by means of the pragma Check_Name. + +* + "The interpretation of each aspect of representation. See + 13.1(20)." + +See separate section on data representations. + +* + "Any restrictions placed upon representation items. See + 13.1(20)." + +See separate section on data representations. + +* + "The meaning of `Size` for indefinite subtypes. See + 13.3(48)." + +Size for an indefinite subtype is the maximum possible size, except that +for the case of a subprogram parameter, the size of the parameter object +is the actual size. + +* + "The default external representation for a type tag. See + 13.3(75)." + +The default external representation for a type tag is the fully expanded +name of the type in upper case letters. + +* + "What determines whether a compilation unit is the same in + two different partitions. See 13.3(76)." + +A compilation unit is the same in two different partitions if and only +if it derives from the same source file. + +* + "Implementation-defined components. See 13.5.1(15)." + +The only implementation defined component is the tag for a tagged type, +which contains a pointer to the dispatching table. + +* + "If `Word_Size` = `Storage_Unit`, the default bit + ordering. See 13.5.3(5)." + +`Word_Size` (32) is not the same as `Storage_Unit` (8) for this +implementation, so no non-default bit ordering is supported. The default +bit ordering corresponds to the natural endianness of the target architecture. + +* + "The contents of the visible part of package `System` + and its language-defined children. See 13.7(2)." + +See the definition of these packages in files :file:`system.ads` and +:file:`s-stoele.ads`. Note that two declarations are added to package +System. + +.. code-block:: ada + + Max_Priority : constant Positive := Priority'Last; + Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last; + +* + "The contents of the visible part of package + `System.Machine_Code`, and the meaning of + `code_statements`. See 13.8(7)." + +See the definition and documentation in file :file:`s-maccod.ads`. + +* + "The effect of unchecked conversion. See 13.9(11)." + +Unchecked conversion between types of the same size +results in an uninterpreted transmission of the bits from one type +to the other. If the types are of unequal sizes, then in the case of +discrete types, a shorter source is first zero or sign extended as +necessary, and a shorter target is simply truncated on the left. +For all non-discrete types, the source is first copied if necessary +to ensure that the alignment requirements of the target are met, then +a pointer is constructed to the source value, and the result is obtained +by dereferencing this pointer after converting it to be a pointer to the +target type. Unchecked conversions where the target subtype is an +unconstrained array are not permitted. If the target alignment is +greater than the source alignment, then a copy of the result is +made with appropriate alignment + +* + "The semantics of operations on invalid representations. + See 13.9.2(10-11)." + +For assignments and other operations where the use of invalid values cannot +result in erroneous behavior, the compiler ignores the possibility of invalid +values. An exception is raised at the point where an invalid value would +result in erroneous behavior. For example executing: + +.. code-block:: ada + + procedure invalidvals is + X : Integer := -1; + Y : Natural range 1 .. 10; + for Y'Address use X'Address; + Z : Natural range 1 .. 10; + A : array (Natural range 1 .. 10) of Integer; + begin + Z := Y; -- no exception + A (Z) := 3; -- exception raised; + end; + +As indicated, an exception is raised on the array assignment, but not +on the simple assignment of the invalid negative value from Y to Z. + +* + "The manner of choosing a storage pool for an access type + when `Storage_Pool` is not specified for the type. See 13.11(17)." + +There are 3 different standard pools used by the compiler when +`Storage_Pool` is not specified depending whether the type is local +to a subprogram or defined at the library level and whether +`Storage_Size`is specified or not. See documentation in the runtime +library units `System.Pool_Global`, `System.Pool_Size` and +`System.Pool_Local` in files :file:`s-poosiz.ads`, +:file:`s-pooglo.ads` and :file:`s-pooloc.ads` for full details on the +default pools used. + +* + "Whether or not the implementation provides user-accessible + names for the standard pool type(s). See 13.11(17)." + +See documentation in the sources of the run time mentioned in the previous +paragraph. All these pools are accessible by means of `with`'ing +these units. + +* + "The meaning of `Storage_Size`. See 13.11(18)." + +`Storage_Size` is measured in storage units, and refers to the +total space available for an access type collection, or to the primary +stack space for a task. + +* + "Implementation-defined aspects of storage pools. See + 13.11(22)." + +See documentation in the sources of the run time mentioned in the +paragraph about standard storage pools above +for details on GNAT-defined aspects of storage pools. + +* + "The set of restrictions allowed in a pragma + `Restrictions`. See 13.12(7)." + +See :ref:`Standard_and_Implementation_Defined_Restrictions`. + +* + "The consequences of violating limitations on + `Restrictions` pragmas. See 13.12(9)." + +Restrictions that can be checked at compile time result in illegalities +if violated. Currently there are no other consequences of violating +restrictions. + +* + "The representation used by the `Read` and + `Write` attributes of elementary types in terms of stream + elements. See 13.13.2(9)." + +The representation is the in-memory representation of the base type of +the type, using the number of bits corresponding to the +``type'Size`` value, and the natural ordering of the machine. + +* + "The names and characteristics of the numeric subtypes + declared in the visible part of package `Standard`. See A.1(3)." + +See items describing the integer and floating-point types supported. + +* + "The string returned by `Character_Set_Version`. + See A.3.5(3)." + +`Ada.Wide_Characters.Handling.Character_Set_Version` returns +the string "Unicode 4.0", referring to version 4.0 of the +Unicode specification. + +* + "The accuracy actually achieved by the elementary + functions. See A.5.1(1)." + +The elementary functions correspond to the functions available in the C +library. Only fast math mode is implemented. + +* + "The sign of a zero result from some of the operators or + functions in `Numerics.Generic_Elementary_Functions`, when + `Float_Type'Signed_Zeros` is `True`. See A.5.1(46)." + +The sign of zeroes follows the requirements of the IEEE 754 standard on +floating-point. + +* + "The value of + `Numerics.Float_Random.Max_Image_Width`. See A.5.2(27)." + +Maximum image width is 6864, see library file :file:`s-rannum.ads`. + +* + "The value of + `Numerics.Discrete_Random.Max_Image_Width`. See A.5.2(27)." + +Maximum image width is 6864, see library file :file:`s-rannum.ads`. + +* + "The algorithms for random number generation. See + A.5.2(32)." + +The algorithm is the Mersenne Twister, as documented in the source file +:file:`s-rannum.adb`. This version of the algorithm has a period of +2**19937-1. + +* + "The string representation of a random number generator's + state. See A.5.2(38)." + +The value returned by the Image function is the concatenation of +the fixed-width decimal representations of the 624 32-bit integers +of the state vector. + +* + "The minimum time interval between calls to the + time-dependent Reset procedure that are guaranteed to initiate different + random number sequences. See A.5.2(45)." + +The minimum period between reset calls to guarantee distinct series of +random numbers is one microsecond. + +* + "The values of the `Model_Mantissa`, + `Model_Emin`, `Model_Epsilon`, `Model`, + `Safe_First`, and `Safe_Last` attributes, if the Numerics + Annex is not supported. See A.5.3(72)." + +Run the compiler with *-gnatS* to produce a listing of package +`Standard`, has the values of all numeric attributes. + +* + "Any implementation-defined characteristics of the + input-output packages. See A.7(14)." + +There are no special implementation defined characteristics for these +packages. + +* + "The value of `Buffer_Size` in `Storage_IO`. See + A.9(10)." + +All type representations are contiguous, and the `Buffer_Size` is +the value of ``type'Size`` rounded up to the next storage unit +boundary. + +* + "External files for standard input, standard output, and + standard error See A.10(5)." + +These files are mapped onto the files provided by the C streams +libraries. See source file :file:`i-cstrea.ads` for further details. + +* + "The accuracy of the value produced by `Put`. See + A.10.9(36)." + +If more digits are requested in the output than are represented by the +precision of the value, zeroes are output in the corresponding least +significant digit positions. + +* + "The meaning of `Argument_Count`, `Argument`, and + `Command_Name`. See A.15(1)." + +These are mapped onto the `argv` and `argc` parameters of the +main program in the natural manner. + +* + "The interpretation of the `Form` parameter in procedure + `Create_Directory`. See A.16(56)." + +The `Form` parameter is not used. + +* + "The interpretation of the `Form` parameter in procedure + `Create_Path`. See A.16(60)." + +The `Form` parameter is not used. + +* + "The interpretation of the `Form` parameter in procedure + `Copy_File`. See A.16(68)." + +The `Form` parameter is case-insensitive. +Two fields are recognized in the `Form` parameter:: + + *preserve=* + *mode=* + + starts immediately after the character '=' and ends with the +character immediately preceding the next comma (',') or with the last +character of the parameter. + +The only possible values for preserve= are: + +================== =================================================================== +Value Meaning +================== =================================================================== +*no_attributes* Do not try to preserve any file attributes. This is the + default if no preserve= is found in Form. +*all_attributes* Try to preserve all file attributes (timestamps, access rights). +*timestamps* Preserve the timestamp of the copied file, but not the other + file attributes. +================== =================================================================== + +The only possible values for mode= are: + +============== =============================================================================== +Value Meaning +============== =============================================================================== +*copy* Only do the copy if the destination file does not already exist. + If it already exists, Copy_File fails. +*overwrite* Copy the file in all cases. Overwrite an already existing destination file. +*append* Append the original file to the destination file. If the destination file + does not exist, the destination file is a copy of the source file. + When mode=append, the field preserve=, if it exists, is not taken into account. +============== =============================================================================== + +If the Form parameter includes one or both of the fields and the value or +values are incorrect, Copy_file fails with Use_Error. + +Examples of correct Forms:: + + Form => "preserve=no_attributes,mode=overwrite" (the default) + Form => "mode=append" + Form => "mode=copy, preserve=all_attributes" + +Examples of incorrect Forms:: + + Form => "preserve=junk" + Form => "mode=internal, preserve=timestamps" + +* + "The interpretation of the `Pattern` parameter, when not the null string, + in the `Start_Search` and `Search` procedures. + See A.16(104) and A.16(112)." + +When the `Pattern` parameter is not the null string, it is interpreted +according to the syntax of regular expressions as defined in the +`GNAT.Regexp` package. + +See :ref:`GNAT.Regexp_(g-regexp.ads)`. + +* + "Implementation-defined convention names. See B.1(11)." + +The following convention names are supported + +======================= ============================================================================== +Convention Name Interpretation +======================= ============================================================================== +*Ada* Ada +*Ada_Pass_By_Copy* Allowed for any types except by-reference types such as limited + records. Compatible with convention Ada, but causes any parameters + with this convention to be passed by copy. +*Ada_Pass_By_Reference* Allowed for any types except by-copy types such as scalars. + Compatible with convention Ada, but causes any parameters + with this convention to be passed by reference. +*Assembler* Assembly language +*Asm* Synonym for Assembler +*Assembly* Synonym for Assembler +*C* C +*C_Pass_By_Copy* Allowed only for record types, like C, but also notes that record + is to be passed by copy rather than reference. +*COBOL* COBOL +*C_Plus_Plus (or CPP)* C++ +*Default* Treated the same as C +*External* Treated the same as C +*Fortran* Fortran +*Intrinsic* For support of pragma `Import` with convention Intrinsic, see + separate section on Intrinsic Subprograms. +*Stdcall* Stdcall (used for Windows implementations only). This convention correspond + to the WINAPI (previously called Pascal convention) C/C++ convention under + Windows. A routine with this convention cleans the stack before + exit. This pragma cannot be applied to a dispatching call. +*DLL* Synonym for Stdcall +*Win32* Synonym for Stdcall +*Stubbed* Stubbed is a special convention used to indicate that the body of the + subprogram will be entirely ignored. Any call to the subprogram + is converted into a raise of the `Program_Error` exception. If a + pragma `Import` specifies convention `stubbed` then no body need + be present at all. This convention is useful during development for the + inclusion of subprograms whose body has not yet been written. + In addition, all otherwise unrecognized convention names are also + treated as being synonymous with convention C. In all implementations + except for VMS, use of such other names results in a warning. In VMS + implementations, these names are accepted silently. +======================= ============================================================================== + +* + "The meaning of link names. See B.1(36)." + +Link names are the actual names used by the linker. + +* + "The manner of choosing link names when neither the link + name nor the address of an imported or exported entity is specified. See + B.1(36)." + +The default linker name is that which would be assigned by the relevant +external language, interpreting the Ada name as being in all lower case +letters. + +* + "The effect of pragma `Linker_Options`. See B.1(37)." + +The string passed to `Linker_Options` is presented uninterpreted as +an argument to the link command, unless it contains ASCII.NUL characters. +NUL characters if they appear act as argument separators, so for example + +.. code-block:: ada + + pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef"); + +causes two separate arguments `-labc` and `-ldef` to be passed to the +linker. The order of linker options is preserved for a given unit. The final +list of options passed to the linker is in reverse order of the elaboration +order. For example, linker options for a body always appear before the options +from the corresponding package spec. + +* + "The contents of the visible part of package + `Interfaces` and its language-defined descendants. See B.2(1)." + +See files with prefix :file:`i-` in the distributed library. + +* + "Implementation-defined children of package + `Interfaces`. The contents of the visible part of package + `Interfaces`. See B.2(11)." + +See files with prefix :file:`i-` in the distributed library. + +* + "The types `Floating`, `Long_Floating`, + `Binary`, `Long_Binary`, `Decimal_ Element`, and + `COBOL_Character`; and the initialization of the variables + `Ada_To_COBOL` and `COBOL_To_Ada`, in + `Interfaces.COBOL`. See B.4(50)." + +===================== ==================================== +COBOL Ada +===================== ==================================== +*Floating* Float +*Long_Floating* (Floating) Long_Float +*Binary* Integer +*Long_Binary* Long_Long_Integer +*Decimal_Element* Character +*COBOL_Character* Character +===================== ==================================== + +For initialization, see the file :file:`i-cobol.ads` in the distributed library. + +* + "Support for access to machine instructions. See C.1(1)." + +See documentation in file :file:`s-maccod.ads` in the distributed library. + +* + "Implementation-defined aspects of access to machine + operations. See C.1(9)." + +See documentation in file :file:`s-maccod.ads` in the distributed library. + +* + "Implementation-defined aspects of interrupts. See C.3(2)." + +Interrupts are mapped to signals or conditions as appropriate. See +definition of unit +`Ada.Interrupt_Names` in source file :file:`a-intnam.ads` for details +on the interrupts supported on a particular target. + +* + "Implementation-defined aspects of pre-elaboration. See + C.4(13)." + +GNAT does not permit a partition to be restarted without reloading, +except under control of the debugger. + +* + "The semantics of pragma `Discard_Names`. See C.5(7)." + +Pragma `Discard_Names` causes names of enumeration literals to +be suppressed. In the presence of this pragma, the Image attribute +provides the image of the Pos of the literal, and Value accepts +Pos values. + +* + "The result of the `Task_Identification.Image` + attribute. See C.7.1(7)." + +The result of this attribute is a string that identifies +the object or component that denotes a given task. If a variable `Var` +has a task type, the image for this task will have the form `Var_`XXXXXXXX``, +where the suffix +is the hexadecimal representation of the virtual address of the corresponding +task control block. If the variable is an array of tasks, the image of each +task will have the form of an indexed component indicating the position of a +given task in the array, e.g., `Group(5)_`XXXXXXX``. If the task is a +component of a record, the image of the task will have the form of a selected +component. These rules are fully recursive, so that the image of a task that +is a subcomponent of a composite object corresponds to the expression that +designates this task. + +If a task is created by an allocator, its image depends on the context. If the +allocator is part of an object declaration, the rules described above are used +to construct its image, and this image is not affected by subsequent +assignments. If the allocator appears within an expression, the image +includes only the name of the task type. + +If the configuration pragma Discard_Names is present, or if the restriction +No_Implicit_Heap_Allocation is in effect, the image reduces to +the numeric suffix, that is to say the hexadecimal representation of the +virtual address of the control block of the task. + +* + "The value of `Current_Task` when in a protected entry + or interrupt handler. See C.7.1(17)." + +Protected entries or interrupt handlers can be executed by any +convenient thread, so the value of `Current_Task` is undefined. + +* + "The effect of calling `Current_Task` from an entry + body or interrupt handler. See C.7.1(19)." + +The effect of calling `Current_Task` from an entry body or +interrupt handler is to return the identification of the task currently +executing the code. + +* + "Implementation-defined aspects of + `Task_Attributes`. See C.7.2(19)." + +There are no implementation-defined aspects of `Task_Attributes`. + +* + "Values of all `Metrics`. See D(2)." + +The metrics information for GNAT depends on the performance of the +underlying operating system. The sources of the run-time for tasking +implementation, together with the output from *-gnatG* can be +used to determine the exact sequence of operating systems calls made +to implement various tasking constructs. Together with appropriate +information on the performance of the underlying operating system, +on the exact target in use, this information can be used to determine +the required metrics. + +* + "The declarations of `Any_Priority` and + `Priority`. See D.1(11)." + +See declarations in file :file:`system.ads`. + +* + "Implementation-defined execution resources. See D.1(15)." + +There are no implementation-defined execution resources. + +* + "Whether, on a multiprocessor, a task that is waiting for + access to a protected object keeps its processor busy. See D.2.1(3)." + +On a multi-processor, a task that is waiting for access to a protected +object does not keep its processor busy. + +* + "The affect of implementation defined execution resources + on task dispatching. See D.2.1(9)." + +Tasks map to threads in the threads package used by GNAT. Where possible +and appropriate, these threads correspond to native threads of the +underlying operating system. + +* + "Implementation-defined `policy_identifiers` allowed + in a pragma `Task_Dispatching_Policy`. See D.2.2(3)." + +There are no implementation-defined policy-identifiers allowed in this +pragma. + +* + "Implementation-defined aspects of priority inversion. See + D.2.2(16)." + +Execution of a task cannot be preempted by the implementation processing +of delay expirations for lower priority tasks. + +* + "Implementation-defined task dispatching. See D.2.2(18)." + +The policy is the same as that of the underlying threads implementation. + +* + "Implementation-defined `policy_identifiers` allowed + in a pragma `Locking_Policy`. See D.3(4)." + +The two implementation defined policies permitted in GNAT are +`Inheritance_Locking` and `Conccurent_Readers_Locking`. On +targets that support the `Inheritance_Locking` policy, locking is +implemented by inheritance, i.e., the task owning the lock operates +at a priority equal to the highest priority of any task currently +requesting the lock. On targets that support the +`Conccurent_Readers_Locking` policy, locking is implemented with a +read/write lock allowing multiple propected object functions to enter +concurrently. + +* + "Default ceiling priorities. See D.3(10)." + +The ceiling priority of protected objects of the type +`System.Interrupt_Priority'Last` as described in the Ada +Reference Manual D.3(10), + +* + "The ceiling of any protected object used internally by + the implementation. See D.3(16)." + +The ceiling priority of internal protected objects is +`System.Priority'Last`. + +* + "Implementation-defined queuing policies. See D.4(1)." + +There are no implementation-defined queuing policies. + +* + "On a multiprocessor, any conditions that cause the + completion of an aborted construct to be delayed later than what is + specified for a single processor. See D.6(3)." + +The semantics for abort on a multi-processor is the same as on a single +processor, there are no further delays. + +* + "Any operations that implicitly require heap storage + allocation. See D.7(8)." + +The only operation that implicitly requires heap storage allocation is +task creation. + +* + "What happens when a task terminates in the presence of + pragma `No_Task_Termination`. See D.7(15)." + +Execution is erroneous in that case. + +* + "Implementation-defined aspects of pragma + `Restrictions`. See D.7(20)." + +There are no such implementation-defined aspects. + +* + "Implementation-defined aspects of package + `Real_Time`. See D.8(17)." + +There are no implementation defined aspects of package `Real_Time`. + +* + "Implementation-defined aspects of + `delay_statements`. See D.9(8)." + +Any difference greater than one microsecond will cause the task to be +delayed (see D.9(7)). + +* + "The upper bound on the duration of interrupt blocking + caused by the implementation. See D.12(5)." + +The upper bound is determined by the underlying operating system. In +no cases is it more than 10 milliseconds. + +* + "The means for creating and executing distributed + programs. See E(5)." + +The GLADE package provides a utility GNATDIST for creating and executing +distributed programs. See the GLADE reference manual for further details. + +* + "Any events that can result in a partition becoming + inaccessible. See E.1(7)." + +See the GLADE reference manual for full details on such events. + +* + "The scheduling policies, treatment of priorities, and + management of shared resources between partitions in certain cases. See + E.1(11)." + +See the GLADE reference manual for full details on these aspects of +multi-partition execution. + +* + "Events that cause the version of a compilation unit to + change. See E.3(5)." + +Editing the source file of a compilation unit, or the source files of +any units on which it is dependent in a significant way cause the version +to change. No other actions cause the version number to change. All changes +are significant except those which affect only layout, capitalization or +comments. + +* + "Whether the execution of the remote subprogram is + immediately aborted as a result of cancellation. See E.4(13)." + +See the GLADE reference manual for details on the effect of abort in +a distributed application. + +* + "Implementation-defined aspects of the PCS. See E.5(25)." + +See the GLADE reference manual for a full description of all implementation +defined aspects of the PCS. + +* + "Implementation-defined interfaces in the PCS. See + E.5(26)." + +See the GLADE reference manual for a full description of all +implementation defined interfaces. + +* + "The values of named numbers in the package + `Decimal`. See F.2(7)." + +==================== ========== +Named Number Value +==================== ========== +*Max_Scale* +18 +*Min_Scale* -18 +*Min_Delta* 1.0E-18 +*Max_Delta* 1.0E+18 +*Max_Decimal_Digits* 18 +==================== ========== + +* + "The value of `Max_Picture_Length` in the package + `Text_IO.Editing`. See F.3.3(16)." + +64 + +* + "The value of `Max_Picture_Length` in the package + `Wide_Text_IO.Editing`. See F.3.4(5)." + +64 + +* + "The accuracy actually achieved by the complex elementary + functions and by other complex arithmetic operations. See G.1(1)." + +Standard library functions are used for the complex arithmetic +operations. Only fast math mode is currently supported. + +* + "The sign of a zero result (or a component thereof) from + any operator or function in `Numerics.Generic_Complex_Types`, when + `Real'Signed_Zeros` is True. See G.1.1(53)." + +The signs of zero values are as recommended by the relevant +implementation advice. + +* + "The sign of a zero result (or a component thereof) from + any operator or function in + `Numerics.Generic_Complex_Elementary_Functions`, when + `Real'Signed_Zeros` is `True`. See G.1.2(45)." + +The signs of zero values are as recommended by the relevant +implementation advice. + +* + "Whether the strict mode or the relaxed mode is the + default. See G.2(2)." + +The strict mode is the default. There is no separate relaxed mode. GNAT +provides a highly efficient implementation of strict mode. + +* + "The result interval in certain cases of fixed-to-float + conversion. See G.2.1(10)." + +For cases where the result interval is implementation dependent, the +accuracy is that provided by performing all operations in 64-bit IEEE +floating-point format. + +* + "The result of a floating point arithmetic operation in + overflow situations, when the `Machine_Overflows` attribute of the + result type is `False`. See G.2.1(13)." + +Infinite and NaN values are produced as dictated by the IEEE +floating-point standard. +Note that on machines that are not fully compliant with the IEEE +floating-point standard, such as Alpha, the *-mieee* compiler flag +must be used for achieving IEEE conforming behavior (although at the cost +of a significant performance penalty), so infinite and NaN values are +properly generated. + +* + "The result interval for division (or exponentiation by a + negative exponent), when the floating point hardware implements division + as multiplication by a reciprocal. See G.2.1(16)." + +Not relevant, division is IEEE exact. + +* + "The definition of close result set, which determines the + accuracy of certain fixed point multiplications and divisions. See + G.2.3(5)." + +Operations in the close result set are performed using IEEE long format +floating-point arithmetic. The input operands are converted to +floating-point, the operation is done in floating-point, and the result +is converted to the target type. + +* + "Conditions on a `universal_real` operand of a fixed + point multiplication or division for which the result shall be in the + perfect result set. See G.2.3(22)." + +The result is only defined to be in the perfect result set if the result +can be computed by a single scaling operation involving a scale factor +representable in 64-bits. + +* + "The result of a fixed point arithmetic operation in + overflow situations, when the `Machine_Overflows` attribute of the + result type is `False`. See G.2.3(27)." + +Not relevant, `Machine_Overflows` is `True` for fixed-point +types. + +* + "The result of an elementary function reference in + overflow situations, when the `Machine_Overflows` attribute of the + result type is `False`. See G.2.4(4)." + +IEEE infinite and Nan values are produced as appropriate. + +* + "The value of the angle threshold, within which certain + elementary functions, complex arithmetic operations, and complex + elementary functions yield results conforming to a maximum relative + error bound. See G.2.4(10)." + +Information on this subject is not yet available. + +* + "The accuracy of certain elementary functions for + parameters beyond the angle threshold. See G.2.4(10)." + +Information on this subject is not yet available. + +* + "The result of a complex arithmetic operation or complex + elementary function reference in overflow situations, when the + `Machine_Overflows` attribute of the corresponding real type is + `False`. See G.2.6(5)." + +IEEE infinite and Nan values are produced as appropriate. + +* + "The accuracy of certain complex arithmetic operations and + certain complex elementary functions for parameters (or components + thereof) beyond the angle threshold. See G.2.6(8)." + +Information on those subjects is not yet available. + +* + "Information regarding bounded errors and erroneous + execution. See H.2(1)." + +Information on this subject is not yet available. + +* + "Implementation-defined aspects of pragma + `Inspection_Point`. See H.3.2(8)." + +Pragma `Inspection_Point` ensures that the variable is live and can +be examined by the debugger at the inspection point. + +* + "Implementation-defined aspects of pragma + `Restrictions`. See H.4(25)." + +There are no implementation-defined aspects of pragma `Restrictions`. The +use of pragma `Restrictions [No_Exceptions]` has no effect on the +generated code. Checks must suppressed by use of pragma `Suppress`. + +* + "Any restrictions on pragma `Restrictions`. See + H.4(27)." + +There are no restrictions on pragma `Restrictions`. diff --git a/gcc/ada/doc/gnat_rm/implementation_defined_pragmas.rst b/gcc/ada/doc/gnat_rm/implementation_defined_pragmas.rst new file mode 100644 index 00000000000..a1147adca1c --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_defined_pragmas.rst @@ -0,0 +1,6887 @@ +.. _Implementation_Defined_Pragmas: + +****************************** +Implementation Defined Pragmas +****************************** + +Ada defines a set of pragmas that can be used to supply additional +information to the compiler. These language defined pragmas are +implemented in GNAT and work as described in the Ada Reference Manual. + +In addition, Ada allows implementations to define additional pragmas +whose meaning is defined by the implementation. GNAT provides a number +of these implementation-defined pragmas, which can be used to extend +and enhance the functionality of the compiler. This section of the GNAT +Reference Manual describes these additional pragmas. + +Note that any program using these pragmas might not be portable to other +compilers (although GNAT implements this set of pragmas on all +platforms). Therefore if portability to other compilers is an important +consideration, the use of these pragmas should be minimized. + +Pragma Abort_Defer +================== + +.. index:: Deferring aborts + +Syntax: + +.. code-block:: ada + + pragma Abort_Defer; + + +This pragma must appear at the start of the statement sequence of a +handled sequence of statements (right after the `begin`). It has +the effect of deferring aborts for the sequence of statements (but not +for the declarations or handlers, if any, associated with this statement +sequence). + +Pragma Abstract_State +===================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.4. + +Pragma Ada_83 +============= + +Syntax: + +.. code-block:: ada + + pragma Ada_83; + + +A configuration pragma that establishes Ada 83 mode for the unit to +which it applies, regardless of the mode set by the command line +switches. In Ada 83 mode, GNAT attempts to be as compatible with +the syntax and semantics of Ada 83, as defined in the original Ada +83 Reference Manual as possible. In particular, the keywords added by Ada 95 +and Ada 2005 are not recognized, optional package bodies are allowed, +and generics may name types with unknown discriminants without using +the `(<>)` notation. In addition, some but not all of the additional +restrictions of Ada 83 are enforced. + +Ada 83 mode is intended for two purposes. Firstly, it allows existing +Ada 83 code to be compiled and adapted to GNAT with less effort. +Secondly, it aids in keeping code backwards compatible with Ada 83. +However, there is no guarantee that code that is processed correctly +by GNAT in Ada 83 mode will in fact compile and execute with an Ada +83 compiler, since GNAT does not enforce all the additional checks +required by Ada 83. + +Pragma Ada_95 +============= + +Syntax: + +.. code-block:: ada + + pragma Ada_95; + + +A configuration pragma that establishes Ada 95 mode for the unit to which +it applies, regardless of the mode set by the command line switches. +This mode is set automatically for the `Ada` and `System` +packages and their children, so you need not specify it in these +contexts. This pragma is useful when writing a reusable component that +itself uses Ada 95 features, but which is intended to be usable from +either Ada 83 or Ada 95 programs. + +Pragma Ada_05 +============= + +Syntax: + +.. code-block:: ada + + pragma Ada_05; + pragma Ada_05 (local_NAME); + + +A configuration pragma that establishes Ada 2005 mode for the unit to which +it applies, regardless of the mode set by the command line switches. +This pragma is useful when writing a reusable component that +itself uses Ada 2005 features, but which is intended to be usable from +either Ada 83 or Ada 95 programs. + +The one argument form (which is not a configuration pragma) +is used for managing the transition from +Ada 95 to Ada 2005 in the run-time library. If an entity is marked +as Ada_2005 only, then referencing the entity in Ada_83 or Ada_95 +mode will generate a warning. In addition, in Ada_83 or Ada_95 +mode, a preference rule is established which does not choose +such an entity unless it is unambiguously specified. This avoids +extra subprograms marked this way from generating ambiguities in +otherwise legal pre-Ada_2005 programs. The one argument form is +intended for exclusive use in the GNAT run-time library. + +Pragma Ada_2005 +=============== + +Syntax: + +.. code-block:: ada + + pragma Ada_2005; + + +This configuration pragma is a synonym for pragma Ada_05 and has the +same syntax and effect. + +Pragma Ada_12 +============= + +Syntax: + +.. code-block:: ada + + pragma Ada_12; + pragma Ada_12 (local_NAME); + + +A configuration pragma that establishes Ada 2012 mode for the unit to which +it applies, regardless of the mode set by the command line switches. +This mode is set automatically for the `Ada` and `System` +packages and their children, so you need not specify it in these +contexts. This pragma is useful when writing a reusable component that +itself uses Ada 2012 features, but which is intended to be usable from +Ada 83, Ada 95, or Ada 2005 programs. + +The one argument form, which is not a configuration pragma, +is used for managing the transition from Ada +2005 to Ada 2012 in the run-time library. If an entity is marked +as Ada_201 only, then referencing the entity in any pre-Ada_2012 +mode will generate a warning. In addition, in any pre-Ada_2012 +mode, a preference rule is established which does not choose +such an entity unless it is unambiguously specified. This avoids +extra subprograms marked this way from generating ambiguities in +otherwise legal pre-Ada_2012 programs. The one argument form is +intended for exclusive use in the GNAT run-time library. + +Pragma Ada_2012 +=============== + +Syntax: + +.. code-block:: ada + + pragma Ada_2012; + + +This configuration pragma is a synonym for pragma Ada_12 and has the +same syntax and effect. + +Pragma Allow_Integer_Address +============================ + +Syntax: + +.. code-block:: ada + + pragma Allow_Integer_Address; + + +In almost all versions of GNAT, `System.Address` is a private +type in accordance with the implementation advice in the RM. This +means that integer values, +in particular integer literals, are not allowed as address values. +If the configuration pragma +`Allow_Integer_Address` is given, then integer expressions may +be used anywhere a value of type `System.Address` is required. +The effect is to introduce an implicit unchecked conversion from the +integer value to type `System.Address`. The reverse case of using +an address where an integer type is required is handled analogously. +The following example compiles without errors: + + +.. code-block:: ada + + pragma Allow_Integer_Address; + with System; use System; + package AddrAsInt is + X : Integer; + Y : Integer; + for X'Address use 16#1240#; + for Y use at 16#3230#; + m : Address := 16#4000#; + n : constant Address := 4000; + p : constant Address := Address (X + Y); + v : Integer := y'Address; + w : constant Integer := Integer (Y'Address); + type R is new integer; + RR : R := 1000; + Z : Integer; + for Z'Address use RR; + end AddrAsInt; + + +Note that pragma `Allow_Integer_Address` is ignored if `System.Address` +is not a private type. In implementations of `GNAT` where +System.Address is a visible integer type, +this pragma serves no purpose but is ignored +rather than rejected to allow common sets of sources to be used +in the two situations. + +Pragma Annotate +=============== + +Syntax:: + + pragma Annotate (IDENTIFIER [, IDENTIFIER {, ARG}] [, entity => local_NAME]); + + ARG ::= NAME | EXPRESSION + + +This pragma is used to annotate programs. `identifier` identifies +the type of annotation. GNAT verifies that it is an identifier, but does +not otherwise analyze it. The second optional identifier is also left +unanalyzed, and by convention is used to control the action of the tool to +which the annotation is addressed. The remaining `arg` arguments +can be either string literals or more generally expressions. +String literals are assumed to be either of type +`Standard.String` or else `Wide_String` or `Wide_Wide_String` +depending on the character literals they contain. +All other kinds of arguments are analyzed as expressions, and must be +unambiguous. The last argument if present must have the identifier +`Entity` and GNAT verifies that a local name is given. + +The analyzed pragma is retained in the tree, but not otherwise processed +by any part of the GNAT compiler, except to generate corresponding note +lines in the generated ALI file. For the format of these note lines, see +the compiler source file lib-writ.ads. This pragma is intended for use by +external tools, including ASIS. The use of pragma Annotate does not +affect the compilation process in any way. This pragma may be used as +a configuration pragma. + +Pragma Assert +============= + +Syntax:: + + pragma Assert ( + boolean_EXPRESSION + [, string_EXPRESSION]); + + +The effect of this pragma depends on whether the corresponding command +line switch is set to activate assertions. The pragma expands into code +equivalent to the following: + +.. code-block:: ada + + if assertions-enabled then + if not boolean_EXPRESSION then + System.Assertions.Raise_Assert_Failure + (string_EXPRESSION); + end if; + end if; + + +The string argument, if given, is the message that will be associated +with the exception occurrence if the exception is raised. If no second +argument is given, the default message is `file`:`nnn`, +where `file` is the name of the source file containing the assert, +and `nnn` is the line number of the assert. A pragma is not a +statement, so if a statement sequence contains nothing but a pragma +assert, then a null statement is required in addition, as in: + +.. code-block:: ada + + ... + if J > 3 then + pragma Assert (K > 3, "Bad value for K"); + null; + end if; + + +Note that, as with the `if` statement to which it is equivalent, the +type of the expression is either `Standard.Boolean`, or any type derived +from this standard type. + +Assert checks can be either checked or ignored. By default they are ignored. +They will be checked if either the command line switch *-gnata* is +used, or if an `Assertion_Policy` or `Check_Policy` pragma is used +to enable `Assert_Checks`. + +If assertions are ignored, then there +is no run-time effect (and in particular, any side effects from the +expression will not occur at run time). (The expression is still +analyzed at compile time, and may cause types to be frozen if they are +mentioned here for the first time). + +If assertions are checked, then the given expression is tested, and if +it is `False` then `System.Assertions.Raise_Assert_Failure` is called +which results in the raising of `Assert_Failure` with the given message. + +You should generally avoid side effects in the expression arguments of +this pragma, because these side effects will turn on and off with the +setting of the assertions mode, resulting in assertions that have an +effect on the program. However, the expressions are analyzed for +semantic correctness whether or not assertions are enabled, so turning +assertions on and off cannot affect the legality of a program. + +Note that the implementation defined policy `DISABLE`, given in a +pragma `Assertion_Policy`, can be used to suppress this semantic analysis. + +Note: this is a standard language-defined pragma in versions +of Ada from 2005 on. In GNAT, it is implemented in all versions +of Ada, and the DISABLE policy is an implementation-defined +addition. + +Pragma Assert_And_Cut +===================== + +Syntax:: + + pragma Assert_And_Cut ( + boolean_EXPRESSION + [, string_EXPRESSION]); + + +The effect of this pragma is identical to that of pragma `Assert`, +except that in an `Assertion_Policy` pragma, the identifier +`Assert_And_Cut` is used to control whether it is ignored or checked +(or disabled). + +The intention is that this be used within a subprogram when the +given test expresion sums up all the work done so far in the +subprogram, so that the rest of the subprogram can be verified +(informally or formally) using only the entry preconditions, +and the expression in this pragma. This allows dividing up +a subprogram into sections for the purposes of testing or +formal verification. The pragma also serves as useful +documentation. + +Pragma Assertion_Policy +======================= + +Syntax:: + + pragma Assertion_Policy (CHECK | DISABLE | IGNORE); + + pragma Assertion_Policy ( + ASSERTION_KIND => POLICY_IDENTIFIER + {, ASSERTION_KIND => POLICY_IDENTIFIER}); + + ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND + + RM_ASSERTION_KIND ::= Assert | + Static_Predicate | + Dynamic_Predicate | + Pre | + Pre'Class | + Post | + Post'Class | + Type_Invariant | + Type_Invariant'Class + + ID_ASSERTION_KIND ::= Assertions | + Assert_And_Cut | + Assume | + Contract_Cases | + Debug | + Invariant | + Invariant'Class | + Loop_Invariant | + Loop_Variant | + Postcondition | + Precondition | + Predicate | + Refined_Post | + Statement_Assertions + + POLICY_IDENTIFIER ::= Check | Disable | Ignore + + +This is a standard Ada 2012 pragma that is available as an +implementation-defined pragma in earlier versions of Ada. +The assertion kinds `RM_ASSERTION_KIND` are those defined in +the Ada standard. The assertion kinds `ID_ASSERTION_KIND` +are implementation defined additions recognized by the GNAT compiler. + +The pragma applies in both cases to pragmas and aspects with matching +names, e.g. `Pre` applies to the Pre aspect, and `Precondition` +applies to both the `Precondition` pragma +and the aspect `Precondition`. Note that the identifiers for +pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not +Pre_Class and Post_Class), since these pragmas are intended to be +identical to the corresponding aspects). + +If the policy is `CHECK`, then assertions are enabled, i.e. +the corresponding pragma or aspect is activated. +If the policy is `IGNORE`, then assertions are ignored, i.e. +the corresponding pragma or aspect is deactivated. +This pragma overrides the effect of the *-gnata* switch on the +command line. + +The implementation defined policy `DISABLE` is like +`IGNORE` except that it completely disables semantic +checking of the corresponding pragma or aspect. This is +useful when the pragma or aspect argument references subprograms +in a with'ed package which is replaced by a dummy package +for the final build. + +The implementation defined assertion kind `Assertions` applies to all +assertion kinds. The form with no assertion kind given implies this +choice, so it applies to all assertion kinds (RM defined, and +implementation defined). + +The implementation defined assertion kind `Statement_Assertions` +applies to `Assert`, `Assert_And_Cut`, +`Assume`, `Loop_Invariant`, and `Loop_Variant`. + +Pragma Assume +============= + +Syntax: + +:: + + pragma Assume ( + boolean_EXPRESSION + [, string_EXPRESSION]); + + +The effect of this pragma is identical to that of pragma `Assert`, +except that in an `Assertion_Policy` pragma, the identifier +`Assume` is used to control whether it is ignored or checked +(or disabled). + +The intention is that this be used for assumptions about the +external environment. So you cannot expect to verify formally +or informally that the condition is met, this must be +established by examining things outside the program itself. +For example, we may have code that depends on the size of +`Long_Long_Integer` being at least 64. So we could write: + +.. code-block:: ada + + pragma Assume (Long_Long_Integer'Size >= 64); + + +This assumption cannot be proved from the program itself, +but it acts as a useful run-time check that the assumption +is met, and documents the need to ensure that it is met by +reference to information outside the program. + +Pragma Assume_No_Invalid_Values +=============================== +.. index:: Invalid representations + +.. index:: Invalid values + +Syntax: + +.. code-block:: ada + + pragma Assume_No_Invalid_Values (On | Off); + + +This is a configuration pragma that controls the assumptions made by the +compiler about the occurrence of invalid representations (invalid values) +in the code. + +The default behavior (corresponding to an Off argument for this pragma), is +to assume that values may in general be invalid unless the compiler can +prove they are valid. Consider the following example: + +.. code-block:: ada + + V1 : Integer range 1 .. 10; + V2 : Integer range 11 .. 20; + ... + for J in V2 .. V1 loop + ... + end loop; + + +if V1 and V2 have valid values, then the loop is known at compile +time not to execute since the lower bound must be greater than the +upper bound. However in default mode, no such assumption is made, +and the loop may execute. If `Assume_No_Invalid_Values (On)` +is given, the compiler will assume that any occurrence of a variable +other than in an explicit `'Valid` test always has a valid +value, and the loop above will be optimized away. + +The use of `Assume_No_Invalid_Values (On)` is appropriate if +you know your code is free of uninitialized variables and other +possible sources of invalid representations, and may result in +more efficient code. A program that accesses an invalid representation +with this pragma in effect is erroneous, so no guarantees can be made +about its behavior. + +It is peculiar though permissible to use this pragma in conjunction +with validity checking (-gnatVa). In such cases, accessing invalid +values will generally give an exception, though formally the program +is erroneous so there are no guarantees that this will always be the +case, and it is recommended that these two options not be used together. + +Pragma Async_Readers +==================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.2. + +Pragma Async_Writers +==================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.2. + +Pragma Attribute_Definition +=========================== + +Syntax: + +:: + + pragma Attribute_Definition + ([Attribute =>] ATTRIBUTE_DESIGNATOR, + [Entity =>] LOCAL_NAME, + [Expression =>] EXPRESSION | NAME); + + +If `Attribute` is a known attribute name, this pragma is equivalent to +the attribute definition clause: + + +.. code-block:: ada + + for Entity'Attribute use Expression; + + +If `Attribute` is not a recognized attribute name, the pragma is +ignored, and a warning is emitted. This allows source +code to be written that takes advantage of some new attribute, while remaining +compilable with earlier compilers. + +Pragma C_Pass_By_Copy +===================== +.. index:: Passing by copy + + +Syntax: + +:: + + pragma C_Pass_By_Copy + ([Max_Size =>] static_integer_EXPRESSION); + + +Normally the default mechanism for passing C convention records to C +convention subprograms is to pass them by reference, as suggested by RM +B.3(69). Use the configuration pragma `C_Pass_By_Copy` to change +this default, by requiring that record formal parameters be passed by +copy if all of the following conditions are met: + +* + The size of the record type does not exceed the value specified for + `Max_Size`. +* + The record type has `Convention C`. +* + The formal parameter has this record type, and the subprogram has a + foreign (non-Ada) convention. + +If these conditions are met the argument is passed by copy; i.e., in a +manner consistent with what C expects if the corresponding formal in the +C prototype is a struct (rather than a pointer to a struct). + +You can also pass records by copy by specifying the convention +`C_Pass_By_Copy` for the record type, or by using the extended +`Import` and `Export` pragmas, which allow specification of +passing mechanisms on a parameter by parameter basis. + +Pragma Check +============ +.. index:: Assertions + +.. index:: Named assertions + + +Syntax: + +:: + + pragma Check ( + [Name =>] CHECK_KIND, + [Check =>] Boolean_EXPRESSION + [, [Message =>] string_EXPRESSION] ); + + CHECK_KIND ::= IDENTIFIER | + Pre'Class | + Post'Class | + Type_Invariant'Class | + Invariant'Class + + +This pragma is similar to the predefined pragma `Assert` except that an +extra identifier argument is present. In conjunction with pragma +`Check_Policy`, this can be used to define groups of assertions that can +be independently controlled. The identifier `Assertion` is special, it +refers to the normal set of pragma `Assert` statements. + +Checks introduced by this pragma are normally deactivated by default. They can +be activated either by the command line option *-gnata*, which turns on +all checks, or individually controlled using pragma `Check_Policy`. + +The identifiers `Assertions` and `Statement_Assertions` are not +permitted as check kinds, since this would cause confusion with the use +of these identifiers in `Assertion_Policy` and `Check_Policy` +pragmas, where they are used to refer to sets of assertions. + +Pragma Check_Float_Overflow +=========================== +.. index:: Floating-point overflow + + +Syntax: + +.. code-block:: ada + + pragma Check_Float_Overflow; + + +In Ada, the predefined floating-point types (`Short_Float`, +`Float`, `Long_Float`, `Long_Long_Float`) are +defined to be *unconstrained*. This means that even though each +has a well-defined base range, an operation that delivers a result +outside this base range is not required to raise an exception. +This implementation permission accommodates the notion +of infinities in IEEE floating-point, and corresponds to the +efficient execution mode on most machines. GNAT will not raise +overflow exceptions on these machines; instead it will generate +infinities and NaN's as defined in the IEEE standard. + +Generating infinities, although efficient, is not always desirable. +Often the preferable approach is to check for overflow, even at the +(perhaps considerable) expense of run-time performance. +This can be accomplished by defining your own constrained floating-point subtypes -- i.e., by supplying explicit +range constraints -- and indeed such a subtype +can have the same base range as its base type. For example: + + +.. code-block:: ada + + subtype My_Float is Float range Float'Range; + + +Here `My_Float` has the same range as +`Float` but is constrained, so operations on +`My_Float` values will be checked for overflow +against this range. + +This style will achieve the desired goal, but +it is often more convenient to be able to simply use +the standard predefined floating-point types as long +as overflow checking could be guaranteed. +The `Check_Float_Overflow` +configuration pragma achieves this effect. If a unit is compiled +subject to this configuration pragma, then all operations +on predefined floating-point types including operations on +base types of these floating-point types will be treated as +though those types were constrained, and overflow checks +will be generated. The `Constraint_Error` +exception is raised if the result is out of range. + +This mode can also be set by use of the compiler +switch *-gnateF*. + +Pragma Check_Name +================= +.. index:: Defining check names + +.. index:: Check names, defining + + +Syntax: + +.. code-block:: ada + + pragma Check_Name (check_name_IDENTIFIER); + + +This is a configuration pragma that defines a new implementation +defined check name (unless IDENTIFIER matches one of the predefined +check names, in which case the pragma has no effect). Check names +are global to a partition, so if two or more configuration pragmas +are present in a partition mentioning the same name, only one new +check name is introduced. + +An implementation defined check name introduced with this pragma may +be used in only three contexts: `pragma Suppress`, +`pragma Unsuppress`, +and as the prefix of a `Check_Name'Enabled` attribute reference. For +any of these three cases, the check name must be visible. A check +name is visible if it is in the configuration pragmas applying to +the current unit, or if it appears at the start of any unit that +is part of the dependency set of the current unit (e.g., units that +are mentioned in `with` clauses). + +Check names introduced by this pragma are subject to control by compiler +switches (in particular -gnatp) in the usual manner. + +Pragma Check_Policy +=================== +.. index:: Controlling assertions + +.. index:: Assertions, control + +.. index:: Check pragma control + +.. index:: Named assertions + + +Syntax: + +:: + + pragma Check_Policy + ([Name =>] CHECK_KIND, + [Policy =>] POLICY_IDENTIFIER); + + pragma Check_Policy ( + CHECK_KIND => POLICY_IDENTIFIER + {, CHECK_KIND => POLICY_IDENTIFIER}); + + ASSERTION_KIND ::= RM_ASSERTION_KIND | ID_ASSERTION_KIND + + CHECK_KIND ::= IDENTIFIER | + Pre'Class | + Post'Class | + Type_Invariant'Class | + Invariant'Class + + The identifiers Name and Policy are not allowed as CHECK_KIND values. This + avoids confusion between the two possible syntax forms for this pragma. + + POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE + + +This pragma is used to set the checking policy for assertions (specified +by aspects or pragmas), the `Debug` pragma, or additional checks +to be checked using the `Check` pragma. It may appear either as +a configuration pragma, or within a declarative part of package. In the +latter case, it applies from the point where it appears to the end of +the declarative region (like pragma `Suppress`). + +The `Check_Policy` pragma is similar to the +predefined `Assertion_Policy` pragma, +and if the check kind corresponds to one of the assertion kinds that +are allowed by `Assertion_Policy`, then the effect is identical. + +If the first argument is Debug, then the policy applies to Debug pragmas, +disabling their effect if the policy is `OFF`, `DISABLE`, or +`IGNORE`, and allowing them to execute with normal semantics if +the policy is `ON` or `CHECK`. In addition if the policy is +`DISABLE`, then the procedure call in `Debug` pragmas will +be totally ignored and not analyzed semantically. + +Finally the first argument may be some other identifier than the above +possibilities, in which case it controls a set of named assertions +that can be checked using pragma `Check`. For example, if the pragma: + + +.. code-block:: ada + + pragma Check_Policy (Critical_Error, OFF); + + +is given, then subsequent `Check` pragmas whose first argument is also +`Critical_Error` will be disabled. + +The check policy is `OFF` to turn off corresponding checks, and `ON` +to turn on corresponding checks. The default for a set of checks for which no +`Check_Policy` is given is `OFF` unless the compiler switch +*-gnata* is given, which turns on all checks by default. + +The check policy settings `CHECK` and `IGNORE` are recognized +as synonyms for `ON` and `OFF`. These synonyms are provided for +compatibility with the standard `Assertion_Policy` pragma. The check +policy setting `DISABLE` causes the second argument of a corresponding +`Check` pragma to be completely ignored and not analyzed. + +Pragma CIL_Constructor +====================== + +Syntax: + + +:: + + pragma CIL_Constructor ([Entity =>] function_LOCAL_NAME); + + +This pragma is used to assert that the specified Ada function should be +mapped to the .NET constructor for some Ada tagged record type. + +See section 4.1 of the +`GNAT User's Guide: Supplement for the .NET Platform.` +for related information. + +Pragma Comment +============== + +Syntax: + + +.. code-block:: ada + + pragma Comment (static_string_EXPRESSION); + + +This is almost identical in effect to pragma `Ident`. It allows the +placement of a comment into the object file and hence into the +executable file if the operating system permits such usage. The +difference is that `Comment`, unlike `Ident`, has +no limitations on placement of the pragma (it can be placed +anywhere in the main source unit), and if more than one pragma +is used, all comments are retained. + +Pragma Common_Object +==================== + +Syntax: + + +:: + + pragma Common_Object ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Size =>] EXTERNAL_SYMBOL] ); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + +This pragma enables the shared use of variables stored in overlaid +linker areas corresponding to the use of `COMMON` +in Fortran. The single +object `LOCAL_NAME` is assigned to the area designated by +the `External` argument. +You may define a record to correspond to a series +of fields. The `Size` argument +is syntax checked in GNAT, but otherwise ignored. + +`Common_Object` is not supported on all platforms. If no +support is available, then the code generator will issue a message +indicating that the necessary attribute for implementation of this +pragma is not available. + +Pragma Compile_Time_Error +========================= + +Syntax: + + +.. code-block:: ada + + pragma Compile_Time_Error + (boolean_EXPRESSION, static_string_EXPRESSION); + + +This pragma can be used to generate additional compile time +error messages. It +is particularly useful in generics, where errors can be issued for +specific problematic instantiations. The first parameter is a boolean +expression. The pragma is effective only if the value of this expression +is known at compile time, and has the value True. The set of expressions +whose values are known at compile time includes all static boolean +expressions, and also other values which the compiler can determine +at compile time (e.g., the size of a record type set by an explicit +size representation clause, or the value of a variable which was +initialized to a constant and is known not to have been modified). +If these conditions are met, an error message is generated using +the value given as the second argument. This string value may contain +embedded ASCII.LF characters to break the message into multiple lines. + +Pragma Compile_Time_Warning +=========================== + +Syntax: + + +.. code-block:: ada + + pragma Compile_Time_Warning + (boolean_EXPRESSION, static_string_EXPRESSION); + + +Same as pragma Compile_Time_Error, except a warning is issued instead +of an error message. Note that if this pragma is used in a package that +is with'ed by a client, the client will get the warning even though it +is issued by a with'ed package (normally warnings in with'ed units are +suppressed, but this is a special exception to that rule). + +One typical use is within a generic where compile time known characteristics +of formal parameters are tested, and warnings given appropriately. Another use +with a first parameter of True is to warn a client about use of a package, +for example that it is not fully implemented. + +Pragma Compiler_Unit +==================== + +Syntax: + + +.. code-block:: ada + + pragma Compiler_Unit; + + +This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is +retained so that old versions of the GNAT run-time that use this pragma can +be compiled with newer versions of the compiler. + +Pragma Compiler_Unit_Warning +============================ + +Syntax: + + +.. code-block:: ada + + pragma Compiler_Unit_Warning; + + +This pragma is intended only for internal use in the GNAT run-time library. +It indicates that the unit is used as part of the compiler build. The effect +is to generate warnings for the use of constructs (for example, conditional +expressions) that would cause trouble when bootstrapping using an older +version of GNAT. For the exact list of restrictions, see the compiler sources +and references to Check_Compiler_Unit. + +Pragma Complete_Representation +============================== + +Syntax: + + +.. code-block:: ada + + pragma Complete_Representation; + + +This pragma must appear immediately within a record representation +clause. Typical placements are before the first component clause +or after the last component clause. The effect is to give an error +message if any component is missing a component clause. This pragma +may be used to ensure that a record representation clause is +complete, and that this invariant is maintained if fields are +added to the record in the future. + +Pragma Complex_Representation +============================= + +Syntax: + + +:: + + pragma Complex_Representation + ([Entity =>] LOCAL_NAME); + + +The `Entity` argument must be the name of a record type which has +two fields of the same floating-point type. The effect of this pragma is +to force gcc to use the special internal complex representation form for +this record, which may be more efficient. Note that this may result in +the code for this type not conforming to standard ABI (application +binary interface) requirements for the handling of record types. For +example, in some environments, there is a requirement for passing +records by pointer, and the use of this pragma may result in passing +this type in floating-point registers. + +Pragma Component_Alignment +========================== +.. index:: Alignments of components +.. index:: Pragma Component_Alignment + + +Syntax: + +:: + + pragma Component_Alignment ( + [Form =>] ALIGNMENT_CHOICE + [, [Name =>] type_LOCAL_NAME]); + + ALIGNMENT_CHOICE ::= + Component_Size + | Component_Size_4 + | Storage_Unit + | Default + + +Specifies the alignment of components in array or record types. +The meaning of the `Form` argument is as follows: + + + .. index:: Component_Size (in pragma Component_Alignment) + +*Component_Size* + Aligns scalar components and subcomponents of the array or record type + on boundaries appropriate to their inherent size (naturally + aligned). For example, 1-byte components are aligned on byte boundaries, + 2-byte integer components are aligned on 2-byte boundaries, 4-byte + integer components are aligned on 4-byte boundaries and so on. These + alignment rules correspond to the normal rules for C compilers on all + machines except the VAX. + + .. index:: Component_Size_4 (in pragma Component_Alignment) + +*Component_Size_4* + Naturally aligns components with a size of four or fewer + bytes. Components that are larger than 4 bytes are placed on the next + 4-byte boundary. + + .. index:: Storage_Unit (in pragma Component_Alignment) + +*Storage_Unit* + Specifies that array or record components are byte aligned, i.e., + aligned on boundaries determined by the value of the constant + `System.Storage_Unit`. + + .. index:: Default (in pragma Component_Alignment) + +*Default* + Specifies that array or record components are aligned on default + boundaries, appropriate to the underlying hardware or operating system or + both. The `Default` choice is the same as `Component_Size` (natural + alignment). + +If the `Name` parameter is present, `type_LOCAL_NAME` must +refer to a local record or array type, and the specified alignment +choice applies to the specified type. The use of +`Component_Alignment` together with a pragma `Pack` causes the +`Component_Alignment` pragma to be ignored. The use of +`Component_Alignment` together with a record representation clause +is only effective for fields not specified by the representation clause. + +If the `Name` parameter is absent, the pragma can be used as either +a configuration pragma, in which case it applies to one or more units in +accordance with the normal rules for configuration pragmas, or it can be +used within a declarative part, in which case it applies to types that +are declared within this declarative part, or within any nested scope +within this declarative part. In either case it specifies the alignment +to be applied to any record or array type which has otherwise standard +representation. + +If the alignment for a record or array type is not specified (using +pragma `Pack`, pragma `Component_Alignment`, or a record rep +clause), the GNAT uses the default alignment as described previously. + +Pragma Contract_Cases +===================== +.. index:: Contract cases + + +Syntax: + + +:: + + pragma Contract_Cases ( + Condition => Consequence + {,Condition => Consequence}); + + +The `Contract_Cases` pragma allows defining fine-grain specifications +that can complement or replace the contract given by a precondition and a +postcondition. Additionally, the `Contract_Cases` pragma can be used +by testing and formal verification tools. The compiler checks its validity and, +depending on the assertion policy at the point of declaration of the pragma, +it may insert a check in the executable. For code generation, the contract +cases + + +.. code-block:: ada + + pragma Contract_Cases ( + Cond1 => Pred1, + Cond2 => Pred2); + + +are equivalent to + + +.. code-block:: ada + + C1 : constant Boolean := Cond1; -- evaluated at subprogram entry + C2 : constant Boolean := Cond2; -- evaluated at subprogram entry + pragma Precondition ((C1 and not C2) or (C2 and not C1)); + pragma Postcondition (if C1 then Pred1); + pragma Postcondition (if C2 then Pred2); + + +The precondition ensures that one and only one of the conditions is +satisfied on entry to the subprogram. +The postcondition ensures that for the condition that was True on entry, +the corrresponding consequence is True on exit. Other consequence expressions +are not evaluated. + +A precondition `P` and postcondition `Q` can also be +expressed as contract cases: + +.. code-block:: ada + + pragma Contract_Cases (P => Q); + + +The placement and visibility rules for `Contract_Cases` pragmas are +identical to those described for preconditions and postconditions. + +The compiler checks that boolean expressions given in conditions and +consequences are valid, where the rules for conditions are the same as +the rule for an expression in `Precondition` and the rules for +consequences are the same as the rule for an expression in +`Postcondition`. In particular, attributes `'Old` and +`'Result` can only be used within consequence expressions. +The condition for the last contract case may be `others`, to denote +any case not captured by the previous cases. The +following is an example of use within a package spec: + + +.. code-block:: ada + + package Math_Functions is + ... + function Sqrt (Arg : Float) return Float; + pragma Contract_Cases ((Arg in 0 .. 99) => Sqrt'Result < 10, + Arg >= 100 => Sqrt'Result >= 10, + others => Sqrt'Result = 0); + ... + end Math_Functions; + + +The meaning of contract cases is that only one case should apply at each +call, as determined by the corresponding condition evaluating to True, +and that the consequence for this case should hold when the subprogram +returns. + +Pragma Convention_Identifier +============================ +.. index:: Conventions, synonyms + +Syntax: + + +:: + + pragma Convention_Identifier ( + [Name =>] IDENTIFIER, + [Convention =>] convention_IDENTIFIER); + + +This pragma provides a mechanism for supplying synonyms for existing +convention identifiers. The `Name` identifier can subsequently +be used as a synonym for the given convention in other pragmas (including +for example pragma `Import` or another `Convention_Identifier` +pragma). As an example of the use of this, suppose you had legacy code +which used Fortran77 as the identifier for Fortran. Then the pragma: + + +.. code-block:: ada + + pragma Convention_Identifier (Fortran77, Fortran); + + +would allow the use of the convention identifier `Fortran77` in +subsequent code, avoiding the need to modify the sources. As another +example, you could use this to parameterize convention requirements +according to systems. Suppose you needed to use `Stdcall` on +windows systems, and `C` on some other system, then you could +define a convention identifier `Library` and use a single +`Convention_Identifier` pragma to specify which convention +would be used system-wide. + +Pragma CPP_Class +================ +.. index:: Interfacing with C++ + +Syntax: + + +:: + + pragma CPP_Class ([Entity =>] LOCAL_NAME); + + +The argument denotes an entity in the current declarative region that is +declared as a record type. It indicates that the type corresponds to an +externally declared C++ class type, and is to be laid out the same way +that C++ would lay out the type. If the C++ class has virtual primitives +then the record must be declared as a tagged record type. + +Types for which `CPP_Class` is specified do not have assignment or +equality operators defined (such operations can be imported or declared +as subprograms as required). Initialization is allowed only by constructor +functions (see pragma `CPP_Constructor`). Such types are implicitly +limited if not explicitly declared as limited or derived from a limited +type, and an error is issued in that case. + +See :ref:`Interfacing_to_C++` for related information. + +Note: Pragma `CPP_Class` is currently obsolete. It is supported +for backward compatibility but its functionality is available +using pragma `Import` with `Convention` = `CPP`. + +Pragma CPP_Constructor +====================== +.. index:: Interfacing with C++ + + +Syntax: + + +:: + + pragma CPP_Constructor ([Entity =>] LOCAL_NAME + [, [External_Name =>] static_string_EXPRESSION ] + [, [Link_Name =>] static_string_EXPRESSION ]); + + +This pragma identifies an imported function (imported in the usual way +with pragma `Import`) as corresponding to a C++ constructor. If +`External_Name` and `Link_Name` are not specified then the +`Entity` argument is a name that must have been previously mentioned +in a pragma `Import` with `Convention` = `CPP`. Such name +must be of one of the following forms: + +* + **function** `Fname` **return** T` + +* + **function** `Fname` **return** T'Class + +* + **function** `Fname` (...) **return** T` + +* + **function** `Fname` (...) **return** T'Class + +where `T` is a limited record type imported from C++ with pragma +`Import` and `Convention` = `CPP`. + +The first two forms import the default constructor, used when an object +of type `T` is created on the Ada side with no explicit constructor. +The latter two forms cover all the non-default constructors of the type. +See the GNAT User's Guide for details. + +If no constructors are imported, it is impossible to create any objects +on the Ada side and the type is implicitly declared abstract. + +Pragma `CPP_Constructor` is intended primarily for automatic generation +using an automatic binding generator tool (such as the `-fdump-ada-spec` +GCC switch). +See :ref:`Interfacing_to_C++` for more related information. + +Note: The use of functions returning class-wide types for constructors is +currently obsolete. They are supported for backward compatibility. The +use of functions returning the type T leave the Ada sources more clear +because the imported C++ constructors always return an object of type T; +that is, they never return an object whose type is a descendant of type T. + +Pragma CPP_Virtual +================== +.. index:: Interfacing to C++ + + +This pragma is now obsolete and, other than generating a warning if warnings +on obsolescent features are enabled, is completely ignored. +It is retained for compatibility +purposes. It used to be required to ensure compoatibility with C++, but +is no longer required for that purpose because GNAT generates +the same object layout as the G++ compiler by default. + +See :ref:`Interfacing_to_C++` for related information. + +Pragma CPP_Vtable +================= +.. index:: Interfacing with C++ + + +This pragma is now obsolete and, other than generating a warning if warnings +on obsolescent features are enabled, is completely ignored. +It used to be required to ensure compatibility with C++, but +is no longer required for that purpose because GNAT generates +the same object layout as the G++ compiler by default. + +See :ref:`Interfacing_to_C++` for related information. + +Pragma CPU +========== + +Syntax: + + +.. code-block:: ada + + pragma CPU (EXPRESSION); + + +This pragma is standard in Ada 2012, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Debug +============ + +Syntax: + + +:: + + pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON); + + PROCEDURE_CALL_WITHOUT_SEMICOLON ::= + PROCEDURE_NAME + | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART + + +The procedure call argument has the syntactic form of an expression, meeting +the syntactic requirements for pragmas. + +If debug pragmas are not enabled or if the condition is present and evaluates +to False, this pragma has no effect. If debug pragmas are enabled, the +semantics of the pragma is exactly equivalent to the procedure call statement +corresponding to the argument with a terminating semicolon. Pragmas are +permitted in sequences of declarations, so you can use pragma `Debug` to +intersperse calls to debug procedures in the middle of declarations. Debug +pragmas can be enabled either by use of the command line switch *-gnata* +or by use of the pragma `Check_Policy` with a first argument of +`Debug`. + +Pragma Debug_Policy +=================== + +Syntax: + + +.. code-block:: ada + + pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF); + + +This pragma is equivalent to a corresponding `Check_Policy` pragma +with a first argument of `Debug`. It is retained for historical +compatibility reasons. + +Pragma Default_Scalar_Storage_Order +=================================== +.. index:: Default_Scalar_Storage_Order + +.. index:: Scalar_Storage_Order + + +Syntax: + + +.. code-block:: ada + + pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First); + + +Normally if no explicit `Scalar_Storage_Order` is given for a record +type or array type, then the scalar storage order defaults to the ordinary +default for the target. But this default may be overridden using this pragma. +The pragma may appear as a configuration pragma, or locally within a package +spec or declarative part. In the latter case, it applies to all subsequent +types declared within that package spec or declarative part. + +The following example shows the use of this pragma: + + +.. code-block:: ada + + pragma Default_Scalar_Storage_Order (High_Order_First); + with System; use System; + package DSSO1 is + type H1 is record + a : Integer; + end record; + + type L2 is record + a : Integer; + end record; + for L2'Scalar_Storage_Order use Low_Order_First; + + type L2a is new L2; + + package Inner is + type H3 is record + a : Integer; + end record; + + pragma Default_Scalar_Storage_Order (Low_Order_First); + + type L4 is record + a : Integer; + end record; + end Inner; + + type H4a is new Inner.L4; + + type H5 is record + a : Integer; + end record; + end DSSO1; + + +In this example record types L.. have `Low_Order_First` scalar +storage order, and record types H.. have `High_Order_First`. +Note that in the case of `H4a`, the order is not inherited +from the parent type. Only an explicitly set `Scalar_Storage_Order` +gets inherited on type derivation. + +If this pragma is used as a configuration pragma which appears within a +configuration pragma file (as opposed to appearing explicitly at the start +of a single unit), then the binder will require that all units in a partition +be compiled in a similar manner, other than run-time units, which are not +affected by this pragma. Note that the use of this form is discouraged because +it may significantly degrade the run-time performance of the software, instead +the default scalar storage order ought to be changed only on a local basis. + +Pragma Default_Storage_Pool +=========================== +.. index:: Default_Storage_Pool + + +Syntax: + + +.. code-block:: ada + + pragma Default_Storage_Pool (storage_pool_NAME | null); + + +This pragma is standard in Ada 2012, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Depends +============== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 6.1.5. + +Pragma Detect_Blocking +====================== + +Syntax: + +.. code-block:: ada + + pragma Detect_Blocking; + + +This is a standard pragma in Ada 2005, that is available in all earlier +versions of Ada as an implementation-defined pragma. + +This is a configuration pragma that forces the detection of potentially +blocking operations within a protected operation, and to raise Program_Error +if that happens. + +Pragma Disable_Atomic_Synchronization +===================================== + +.. index:: Atomic Synchronization + +Syntax: + +:: + + pragma Disable_Atomic_Synchronization [(Entity)]; + + +Ada requires that accesses (reads or writes) of an atomic variable be +regarded as synchronization points in the case of multiple tasks. +Particularly in the case of multi-processors this may require special +handling, e.g. the generation of memory barriers. This capability may +be turned off using this pragma in cases where it is known not to be +required. + +The placement and scope rules for this pragma are the same as those +for `pragma Suppress`. In particular it can be used as a +configuration pragma, or in a declaration sequence where it applies +till the end of the scope. If an `Entity` argument is present, +the action applies only to that entity. + +Pragma Dispatching_Domain +========================= + +Syntax: + + +.. code-block:: ada + + pragma Dispatching_Domain (EXPRESSION); + + +This pragma is standard in Ada 2012, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Effective_Reads +====================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.2. + +Pragma Effective_Writes +======================= + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.2. + +Pragma Elaboration_Checks +========================= +.. index:: Elaboration control + + +Syntax: + + +.. code-block:: ada + + pragma Elaboration_Checks (Dynamic | Static); + + +This is a configuration pragma that provides control over the +elaboration model used by the compilation affected by the +pragma. If the parameter is `Dynamic`, +then the dynamic elaboration +model described in the Ada Reference Manual is used, as though +the *-gnatE* switch had been specified on the command +line. If the parameter is `Static`, then the default GNAT static +model is used. This configuration pragma overrides the setting +of the command line. For full details on the elaboration models +used by the GNAT compiler, see the chapter on elaboration order handling +in the *GNAT User's Guide*. + +Pragma Eliminate +================ +.. index:: Elimination of unused subprograms + + +Syntax: + + +:: + + pragma Eliminate ([Entity =>] DEFINING_DESIGNATOR, + [Source_Location =>] STRING_LITERAL); + + +The string literal given for the source location is a string which +specifies the line number of the occurrence of the entity, using +the syntax for SOURCE_TRACE given below: + + +:: + + SOURCE_TRACE ::= SOURCE_REFERENCE [LBRACKET SOURCE_TRACE RBRACKET] + + LBRACKET ::= [ + RBRACKET ::= ] + + SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER + + LINE_NUMBER ::= DIGIT {DIGIT} + + +Spaces around the colon in a `Source_Reference` are optional. + +The `DEFINING_DESIGNATOR` matches the defining designator used in an +explicit subprogram declaration, where the `entity` name in this +designator appears on the source line specified by the source location. + +The source trace that is given as the `Source_Location` shall obey the +following rules. The `FILE_NAME` is the short name (with no directory +information) of an Ada source file, given using exactly the required syntax +for the underlying file system (e.g. case is important if the underlying +operating system is case sensitive). `LINE_NUMBER` gives the line +number of the occurrence of the `entity` +as a decimal literal without an exponent or point. If an `entity` is not +declared in a generic instantiation (this includes generic subprogram +instances), the source trace includes only one source reference. If an entity +is declared inside a generic instantiation, its source trace (when parsing +from left to right) starts with the source location of the declaration of the +entity in the generic unit and ends with the source location of the +instantiation (it is given in square brackets). This approach is recursively +used in case of nested instantiations: the rightmost (nested most deeply in +square brackets) element of the source trace is the location of the outermost +instantiation, the next to left element is the location of the next (first +nested) instantiation in the code of the corresponding generic unit, and so +on, and the leftmost element (that is out of any square brackets) is the +location of the declaration of the entity to eliminate in a generic unit. + +Note that the `Source_Location` argument specifies which of a set of +similarly named entities is being eliminated, dealing both with overloading, +and also appearance of the same entity name in different scopes. + +This pragma indicates that the given entity is not used in the program to be +compiled and built. The effect of the pragma is to allow the compiler to +eliminate the code or data associated with the named entity. Any reference to +an eliminated entity causes a compile-time or link-time error. + +The intention of pragma `Eliminate` is to allow a program to be compiled +in a system-independent manner, with unused entities eliminated, without +needing to modify the source text. Normally the required set of +`Eliminate` pragmas is constructed automatically using the gnatelim tool. + +Any source file change that removes, splits, or +adds lines may make the set of Eliminate pragmas invalid because their +`Source_Location` argument values may get out of date. + +Pragma `Eliminate` may be used where the referenced entity is a dispatching +operation. In this case all the subprograms to which the given operation can +dispatch are considered to be unused (are never called as a result of a direct +or a dispatching call). + +Pragma Enable_Atomic_Synchronization +==================================== +.. index:: Atomic Synchronization + + +Syntax: + + +:: + + pragma Enable_Atomic_Synchronization [(Entity)]; + + +Ada requires that accesses (reads or writes) of an atomic variable be +regarded as synchronization points in the case of multiple tasks. +Particularly in the case of multi-processors this may require special +handling, e.g. the generation of memory barriers. This synchronization +is performed by default, but can be turned off using +`pragma Disable_Atomic_Synchronization`. The +`Enable_Atomic_Synchronization` pragma can be used to turn +it back on. + +The placement and scope rules for this pragma are the same as those +for `pragma Unsuppress`. In particular it can be used as a +configuration pragma, or in a declaration sequence where it applies +till the end of the scope. If an `Entity` argument is present, +the action applies only to that entity. + +Pragma Export_Function +====================== +.. index:: Argument passing mechanisms + + +Syntax: + + +:: + + pragma Export_Function ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Result_Type =>] result_SUBTYPE_MARK] + [, [Mechanism =>] MECHANISM] + [, [Result_Mechanism =>] MECHANISM_NAME]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + | "" + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= Value | Reference + + +Use this pragma to make a function externally callable and optionally +provide information on mechanisms to be used for passing parameter and +result values. We recommend, for the purposes of improving portability, +this pragma always be used in conjunction with a separate pragma +`Export`, which must precede the pragma `Export_Function`. +GNAT does not require a separate pragma `Export`, but if none is +present, `Convention Ada` is assumed, which is usually +not what is wanted, so it is usually appropriate to use this +pragma in conjunction with a `Export` or `Convention` +pragma that specifies the desired foreign convention. +Pragma `Export_Function` +(and `Export`, if present) must appear in the same declarative +region as the function to which they apply. + +`internal_name` must uniquely designate the function to which the +pragma applies. If more than one function name exists of this name in +the declarative part you must use the `Parameter_Types` and +`Result_Type` parameters is mandatory to achieve the required +unique designation. `subtype_mark`s in these parameters must +exactly match the subtypes in the corresponding function specification, +using positional notation to match parameters with subtype marks. +The form with an `'Access` attribute can be used to match an +anonymous access parameter. + +.. index:: Suppressing external name + +Special treatment is given if the EXTERNAL is an explicit null +string or a static string expressions that evaluates to the null +string. In this case, no external name is generated. This form +still allows the specification of parameter mechanisms. + +Pragma Export_Object +==================== + +Syntax: + + +:: + + pragma Export_Object + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Size =>] EXTERNAL_SYMBOL] + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + +This pragma designates an object as exported, and apart from the +extended rules for external symbols, is identical in effect to the use of +the normal `Export` pragma applied to an object. You may use a +separate Export pragma (and you probably should from the point of view +of portability), but it is not required. `Size` is syntax checked, +but otherwise ignored by GNAT. + +Pragma Export_Procedure +======================= + +Syntax: + + +:: + + pragma Export_Procedure ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Mechanism =>] MECHANISM]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + | "" + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= Value | Reference + + +This pragma is identical to `Export_Function` except that it +applies to a procedure rather than a function and the parameters +`Result_Type` and `Result_Mechanism` are not permitted. +GNAT does not require a separate pragma `Export`, but if none is +present, `Convention Ada` is assumed, which is usually +not what is wanted, so it is usually appropriate to use this +pragma in conjunction with a `Export` or `Convention` +pragma that specifies the desired foreign convention. + +.. index:: Suppressing external name + +Special treatment is given if the EXTERNAL is an explicit null +string or a static string expressions that evaluates to the null +string. In this case, no external name is generated. This form +still allows the specification of parameter mechanisms. + +Pragma Export_Value +=================== + +Syntax: + + +:: + + pragma Export_Value ( + [Value =>] static_integer_EXPRESSION, + [Link_Name =>] static_string_EXPRESSION); + + +This pragma serves to export a static integer value for external use. +The first argument specifies the value to be exported. The Link_Name +argument specifies the symbolic name to be associated with the integer +value. This pragma is useful for defining a named static value in Ada +that can be referenced in assembly language units to be linked with +the application. This pragma is currently supported only for the +AAMP target and is ignored for other targets. + +Pragma Export_Valued_Procedure +============================== + +Syntax: + + +:: + + pragma Export_Valued_Procedure ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Mechanism =>] MECHANISM]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + | "" + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= Value | Reference + + +This pragma is identical to `Export_Procedure` except that the +first parameter of `LOCAL_NAME`, which must be present, must be of +mode `OUT`, and externally the subprogram is treated as a function +with this parameter as the result of the function. GNAT provides for +this capability to allow the use of `OUT` and `IN OUT` +parameters in interfacing to external functions (which are not permitted +in Ada functions). +GNAT does not require a separate pragma `Export`, but if none is +present, `Convention Ada` is assumed, which is almost certainly +not what is wanted since the whole point of this pragma is to interface +with foreign language functions, so it is usually appropriate to use this +pragma in conjunction with a `Export` or `Convention` +pragma that specifies the desired foreign convention. + +.. index:: Suppressing external name + +Special treatment is given if the EXTERNAL is an explicit null +string or a static string expressions that evaluates to the null +string. In this case, no external name is generated. This form +still allows the specification of parameter mechanisms. + +Pragma Extend_System +==================== +.. index:: System, extending + +.. index:: DEC Ada 83 + + +Syntax: + + +:: + + pragma Extend_System ([Name =>] IDENTIFIER); + + +This pragma is used to provide backwards compatibility with other +implementations that extend the facilities of package `System`. In +GNAT, `System` contains only the definitions that are present in +the Ada RM. However, other implementations, notably the DEC Ada 83 +implementation, provide many extensions to package `System`. + +For each such implementation accommodated by this pragma, GNAT provides a +package `Aux_`xxx``, e.g., `Aux_DEC` for the DEC Ada 83 +implementation, which provides the required additional definitions. You +can use this package in two ways. You can `with` it in the normal +way and access entities either by selection or using a `use` +clause. In this case no special processing is required. + +However, if existing code contains references such as +`System.`xxx`` where `xxx` is an entity in the extended +definitions provided in package `System`, you may use this pragma +to extend visibility in `System` in a non-standard way that +provides greater compatibility with the existing code. Pragma +`Extend_System` is a configuration pragma whose single argument is +the name of the package containing the extended definition +(e.g., `Aux_DEC` for the DEC Ada case). A unit compiled under +control of this pragma will be processed using special visibility +processing that looks in package `System.Aux_`xxx`` where +`Aux_`xxx`` is the pragma argument for any entity referenced in +package `System`, but not found in package `System`. + +You can use this pragma either to access a predefined `System` +extension supplied with the compiler, for example `Aux_DEC` or +you can construct your own extension unit following the above +definition. Note that such a package is a child of `System` +and thus is considered part of the implementation. +To compile it you will have to use the *-gnatg* switch +for compiling System units, as explained in the +GNAT User's Guide. + +Pragma Extensions_Allowed +========================= +.. index:: Ada Extensions + +.. index:: GNAT Extensions + + +Syntax: + +.. code-block:: ada + + pragma Extensions_Allowed (On | Off); + + +This configuration pragma enables or disables the implementation +extension mode (the use of Off as a parameter cancels the effect +of the *-gnatX* command switch). + +In extension mode, the latest version of the Ada language is +implemented (currently Ada 2012), and in addition a small number +of GNAT specific extensions are recognized as follows: + + + +*Constrained attribute for generic objects* + The `Constrained` attribute is permitted for objects of + generic types. The result indicates if the corresponding actual + is constrained. + + +Pragma External +=============== + +Syntax: + + +:: + + pragma External ( + [ Convention =>] convention_IDENTIFIER, + [ Entity =>] LOCAL_NAME + [, [External_Name =>] static_string_EXPRESSION ] + [, [Link_Name =>] static_string_EXPRESSION ]); + + +This pragma is identical in syntax and semantics to pragma +`Export` as defined in the Ada Reference Manual. It is +provided for compatibility with some Ada 83 compilers that +used this pragma for exactly the same purposes as pragma +`Export` before the latter was standardized. + +Pragma External_Name_Casing +=========================== +.. index:: Dec Ada 83 casing compatibility + +.. index:: External Names, casing + +.. index:: Casing of External names + + +Syntax: + + +:: + + pragma External_Name_Casing ( + Uppercase | Lowercase + [, Uppercase | Lowercase | As_Is]); + + +This pragma provides control over the casing of external names associated +with Import and Export pragmas. There are two cases to consider: + + + +* Implicit external names + + Implicit external names are derived from identifiers. The most common case + arises when a standard Ada Import or Export pragma is used with only two + arguments, as in: + + .. code-block:: ada + + pragma Import (C, C_Routine); + + Since Ada is a case-insensitive language, the spelling of the identifier in + the Ada source program does not provide any information on the desired + casing of the external name, and so a convention is needed. In GNAT the + default treatment is that such names are converted to all lower case + letters. This corresponds to the normal C style in many environments. + The first argument of pragma `External_Name_Casing` can be used to + control this treatment. If `Uppercase` is specified, then the name + will be forced to all uppercase letters. If `Lowercase` is specified, + then the normal default of all lower case letters will be used. + + This same implicit treatment is also used in the case of extended DEC Ada 83 + compatible Import and Export pragmas where an external name is explicitly + specified using an identifier rather than a string. + + +* Explicit external names + + Explicit external names are given as string literals. The most common case + arises when a standard Ada Import or Export pragma is used with three + arguments, as in: + + .. code-block:: ada + + pragma Import (C, C_Routine, "C_routine"); + + In this case, the string literal normally provides the exact casing required + for the external name. The second argument of pragma + `External_Name_Casing` may be used to modify this behavior. + If `Uppercase` is specified, then the name + will be forced to all uppercase letters. If `Lowercase` is specified, + then the name will be forced to all lowercase letters. A specification of + `As_Is` provides the normal default behavior in which the casing is + taken from the string provided. + +This pragma may appear anywhere that a pragma is valid. In particular, it +can be used as a configuration pragma in the :file:`gnat.adc` file, in which +case it applies to all subsequent compilations, or it can be used as a program +unit pragma, in which case it only applies to the current unit, or it can +be used more locally to control individual Import/Export pragmas. + +It was primarily intended for use with OpenVMS systems, where many +compilers convert all symbols to upper case by default. For interfacing to +such compilers (e.g., the DEC C compiler), it may be convenient to use +the pragma: + +.. code-block:: ada + + pragma External_Name_Casing (Uppercase, Uppercase); + + +to enforce the upper casing of all external symbols. + +Pragma Fast_Math +================ + +Syntax: + + +.. code-block:: ada + + pragma Fast_Math; + + +This is a configuration pragma which activates a mode in which speed is +considered more important for floating-point operations than absolutely +accurate adherence to the requirements of the standard. Currently the +following operations are affected: + + + +*Complex Multiplication* + The normal simple formula for complex multiplication can result in intermediate + overflows for numbers near the end of the range. The Ada standard requires that + this situation be detected and corrected by scaling, but in Fast_Math mode such + cases will simply result in overflow. Note that to take advantage of this you + must instantiate your own version of `Ada.Numerics.Generic_Complex_Types` + under control of the pragma, rather than use the preinstantiated versions. + +Pragma Favor_Top_Level +====================== + +Syntax: + + +.. code-block:: ada + + pragma Favor_Top_Level (type_NAME); + + +The named type must be an access-to-subprogram type. This pragma is an +efficiency hint to the compiler, regarding the use of 'Access or +'Unrestricted_Access on nested (non-library-level) subprograms. The +pragma means that nested subprograms are not used with this type, or +are rare, so that the generated code should be efficient in the +top-level case. When this pragma is used, dynamically generated +trampolines may be used on some targets for nested subprograms. +See also the No_Implicit_Dynamic_Code restriction. + +Pragma Finalize_Storage_Only +============================ + +Syntax: + + +.. code-block:: ada + + pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME); + + +This pragma allows the compiler not to emit a Finalize call for objects +defined at the library level. This is mostly useful for types where +finalization is only used to deal with storage reclamation since in most +environments it is not necessary to reclaim memory just before terminating +execution, hence the name. + +Pragma Float_Representation +=========================== + +Syntax:: + + pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]); + + FLOAT_REP ::= VAX_Float | IEEE_Float + + +In the one argument form, this pragma is a configuration pragma which +allows control over the internal representation chosen for the predefined +floating point types declared in the packages `Standard` and +`System`. This pragma is only provided for compatibility and has no effect. + +The two argument form specifies the representation to be used for +the specified floating-point type. The argument must +be `IEEE_Float` to specify the use of IEEE format, as follows: + +* + For a digits value of 6, 32-bit IEEE short format will be used. +* + For a digits value of 15, 64-bit IEEE long format will be used. +* + No other value of digits is permitted. + +Pragma Global +============= + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 6.1.4. + +Pragma Ident +============ + +Syntax: + + +.. code-block:: ada + + pragma Ident (static_string_EXPRESSION); + + +This pragma is identical in effect to pragma `Comment`. It is provided +for compatibility with other Ada compilers providing this pragma. + +Pragma Implementation_Defined +============================= + +Syntax: + + +.. code-block:: ada + + pragma Implementation_Defined (local_NAME); + + +This pragma marks a previously declared entioty as implementation-defined. +For an overloaded entity, applies to the most recent homonym. + + +.. code-block:: ada + + pragma Implementation_Defined; + + +The form with no arguments appears anywhere within a scope, most +typically a package spec, and indicates that all entities that are +defined within the package spec are Implementation_Defined. + +This pragma is used within the GNAT runtime library to identify +implementation-defined entities introduced in language-defined units, +for the purpose of implementing the No_Implementation_Identifiers +restriction. + +Pragma Implemented +================== + +Syntax: + + +:: + + pragma Implemented (procedure_LOCAL_NAME, implementation_kind); + + implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any + + +This is an Ada 2012 representation pragma which applies to protected, task +and synchronized interface primitives. The use of pragma Implemented provides +a way to impose a static requirement on the overriding operation by adhering +to one of the three implementation kinds: entry, protected procedure or any of +the above. This pragma is available in all earlier versions of Ada as an +implementation-defined pragma. + + +.. code-block:: ada + + type Synch_Iface is synchronized interface; + procedure Prim_Op (Obj : in out Iface) is abstract; + pragma Implemented (Prim_Op, By_Protected_Procedure); + + protected type Prot_1 is new Synch_Iface with + procedure Prim_Op; -- Legal + end Prot_1; + + protected type Prot_2 is new Synch_Iface with + entry Prim_Op; -- Illegal + end Prot_2; + + task type Task_Typ is new Synch_Iface with + entry Prim_Op; -- Illegal + end Task_Typ; + + +When applied to the procedure_or_entry_NAME of a requeue statement, pragma +Implemented determines the runtime behavior of the requeue. Implementation kind +By_Entry guarantees that the action of requeueing will proceed from an entry to +another entry. Implementation kind By_Protected_Procedure transforms the +requeue into a dispatching call, thus eliminating the chance of blocking. Kind +By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on +the target's overriding subprogram kind. + +Pragma Implicit_Packing +======================= +.. index:: Rational Profile + +Syntax: + + +.. code-block:: ada + + pragma Implicit_Packing; + + +This is a configuration pragma that requests implicit packing for packed +arrays for which a size clause is given but no explicit pragma Pack or +specification of Component_Size is present. It also applies to records +where no record representation clause is present. Consider this example: + + +.. code-block:: ada + + type R is array (0 .. 7) of Boolean; + for R'Size use 8; + + +In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause +does not change the layout of a composite object. So the Size clause in the +above example is normally rejected, since the default layout of the array uses +8-bit components, and thus the array requires a minimum of 64 bits. + +If this declaration is compiled in a region of code covered by an occurrence +of the configuration pragma Implicit_Packing, then the Size clause in this +and similar examples will cause implicit packing and thus be accepted. For +this implicit packing to occur, the type in question must be an array of small +components whose size is known at compile time, and the Size clause must +specify the exact size that corresponds to the number of elements in the array +multiplied by the size in bits of the component type (both single and +multi-dimensioned arrays can be controlled with this pragma). + +.. index:: Array packing + +Similarly, the following example shows the use in the record case + + +.. code-block:: ada + + type r is record + a, b, c, d, e, f, g, h : boolean; + chr : character; + end record; + for r'size use 16; + + +Without a pragma Pack, each Boolean field requires 8 bits, so the +minimum size is 72 bits, but with a pragma Pack, 16 bits would be +sufficient. The use of pragma Implicit_Packing allows this record +declaration to compile without an explicit pragma Pack. + +Pragma Import_Function +====================== + +Syntax: + + +:: + + pragma Import_Function ( + [Internal =>] LOCAL_NAME, + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Result_Type =>] SUBTYPE_MARK] + [, [Mechanism =>] MECHANISM] + [, [Result_Mechanism =>] MECHANISM_NAME]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= + Value + | Reference + + +This pragma is used in conjunction with a pragma `Import` to +specify additional information for an imported function. The pragma +`Import` (or equivalent pragma `Interface`) must precede the +`Import_Function` pragma and both must appear in the same +declarative part as the function specification. + +The `Internal` argument must uniquely designate +the function to which the +pragma applies. If more than one function name exists of this name in +the declarative part you must use the `Parameter_Types` and +`Result_Type` parameters to achieve the required unique +designation. Subtype marks in these parameters must exactly match the +subtypes in the corresponding function specification, using positional +notation to match parameters with subtype marks. +The form with an `'Access` attribute can be used to match an +anonymous access parameter. + +You may optionally use the `Mechanism` and `Result_Mechanism` +parameters to specify passing mechanisms for the +parameters and result. If you specify a single mechanism name, it +applies to all parameters. Otherwise you may specify a mechanism on a +parameter by parameter basis using either positional or named +notation. If the mechanism is not specified, the default mechanism +is used. + +Pragma Import_Object +==================== + +Syntax: + + +:: + + pragma Import_Object + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Size =>] EXTERNAL_SYMBOL]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + +This pragma designates an object as imported, and apart from the +extended rules for external symbols, is identical in effect to the use of +the normal `Import` pragma applied to an object. Unlike the +subprogram case, you need not use a separate `Import` pragma, +although you may do so (and probably should do so from a portability +point of view). `size` is syntax checked, but otherwise ignored by +GNAT. + +Pragma Import_Procedure +======================= + +Syntax: + + +:: + + pragma Import_Procedure ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Mechanism =>] MECHANISM]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= Value | Reference + + +This pragma is identical to `Import_Function` except that it +applies to a procedure rather than a function and the parameters +`Result_Type` and `Result_Mechanism` are not permitted. + +Pragma Import_Valued_Procedure +============================== + +Syntax: + + +:: + + pragma Import_Valued_Procedure ( + [Internal =>] LOCAL_NAME + [, [External =>] EXTERNAL_SYMBOL] + [, [Parameter_Types =>] PARAMETER_TYPES] + [, [Mechanism =>] MECHANISM]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + PARAMETER_TYPES ::= + null + | TYPE_DESIGNATOR {, TYPE_DESIGNATOR} + + TYPE_DESIGNATOR ::= + subtype_NAME + | subtype_Name ' Access + + MECHANISM ::= + MECHANISM_NAME + | (MECHANISM_ASSOCIATION {, MECHANISM_ASSOCIATION}) + + MECHANISM_ASSOCIATION ::= + [formal_parameter_NAME =>] MECHANISM_NAME + + MECHANISM_NAME ::= Value | Reference + + +This pragma is identical to `Import_Procedure` except that the +first parameter of `LOCAL_NAME`, which must be present, must be of +mode `OUT`, and externally the subprogram is treated as a function +with this parameter as the result of the function. The purpose of this +capability is to allow the use of `OUT` and `IN OUT` +parameters in interfacing to external functions (which are not permitted +in Ada functions). You may optionally use the `Mechanism` +parameters to specify passing mechanisms for the parameters. +If you specify a single mechanism name, it applies to all parameters. +Otherwise you may specify a mechanism on a parameter by parameter +basis using either positional or named notation. If the mechanism is not +specified, the default mechanism is used. + +Note that it is important to use this pragma in conjunction with a separate +pragma Import that specifies the desired convention, since otherwise the +default convention is Ada, which is almost certainly not what is required. + +Pragma Independent +================== + +Syntax: + + +.. code-block:: ada + + pragma Independent (Local_NAME); + + +This pragma is standard in Ada 2012 mode (which also provides an aspect +of the same name). It is also available as an implementation-defined +pragma in all earlier versions. It specifies that the +designated object or all objects of the designated type must be +independently addressable. This means that separate tasks can safely +manipulate such objects. For example, if two components of a record are +independent, then two separate tasks may access these two components. +This may place +constraints on the representation of the object (for instance prohibiting +tight packing). + +Pragma Independent_Components +============================= + +Syntax: + + +.. code-block:: ada + + pragma Independent_Components (Local_NAME); + + +This pragma is standard in Ada 2012 mode (which also provides an aspect +of the same name). It is also available as an implementation-defined +pragma in all earlier versions. It specifies that the components of the +designated object, or the components of each object of the designated +type, must be +independently addressable. This means that separate tasks can safely +manipulate separate components in the composite object. This may place +constraints on the representation of the object (for instance prohibiting +tight packing). + +Pragma Initial_Condition +======================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.6. + +Pragma Initialize_Scalars +========================= +.. index:: debugging with Initialize_Scalars + +Syntax: + + +.. code-block:: ada + + pragma Initialize_Scalars; + + +This pragma is similar to `Normalize_Scalars` conceptually but has +two important differences. First, there is no requirement for the pragma +to be used uniformly in all units of a partition, in particular, it is fine +to use this just for some or all of the application units of a partition, +without needing to recompile the run-time library. + +In the case where some units are compiled with the pragma, and some without, +then a declaration of a variable where the type is defined in package +Standard or is locally declared will always be subject to initialization, +as will any declaration of a scalar variable. For composite variables, +whether the variable is initialized may also depend on whether the package +in which the type of the variable is declared is compiled with the pragma. + +The other important difference is that you can control the value used +for initializing scalar objects. At bind time, you can select several +options for initialization. You can +initialize with invalid values (similar to Normalize_Scalars, though for +Initialize_Scalars it is not always possible to determine the invalid +values in complex cases like signed component fields with non-standard +sizes). You can also initialize with high or +low values, or with a specified bit pattern. See the GNAT +User's Guide for binder options for specifying these cases. + +This means that you can compile a program, and then without having to +recompile the program, you can run it with different values being used +for initializing otherwise uninitialized values, to test if your program +behavior depends on the choice. Of course the behavior should not change, +and if it does, then most likely you have an incorrect reference to an +uninitialized value. + +It is even possible to change the value at execution time eliminating even +the need to rebind with a different switch using an environment variable. +See the GNAT User's Guide for details. + +Note that pragma `Initialize_Scalars` is particularly useful in +conjunction with the enhanced validity checking that is now provided +in GNAT, which checks for invalid values under more conditions. +Using this feature (see description of the *-gnatV* flag in the +GNAT User's Guide) in conjunction with +pragma `Initialize_Scalars` +provides a powerful new tool to assist in the detection of problems +caused by uninitialized variables. + +Note: the use of `Initialize_Scalars` has a fairly extensive +effect on the generated code. This may cause your code to be +substantially larger. It may also cause an increase in the amount +of stack required, so it is probably a good idea to turn on stack +checking (see description of stack checking in the GNAT +User's Guide) when using this pragma. + +Pragma Initializes +================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.1.5. + +Pragma Inline_Always +==================== + +Syntax: + + +:: + + pragma Inline_Always (NAME [, NAME]); + + +Similar to pragma `Inline` except that inlining is not subject to +the use of option *-gnatn* or *-gnatN* and the inlining +happens regardless of whether these options are used. + +Pragma Inline_Generic +===================== + +Syntax: + + +:: + + pragma Inline_Generic (GNAME {, GNAME}); + + GNAME ::= generic_unit_NAME | generic_instance_NAME + + +This pragma is provided for compatibility with Dec Ada 83. It has +no effect in `GNAT` (which always inlines generics), other +than to check that the given names are all names of generic units or +generic instances. + +Pragma Interface +================ + +Syntax: + + +:: + + pragma Interface ( + [Convention =>] convention_identifier, + [Entity =>] local_NAME + [, [External_Name =>] static_string_expression] + [, [Link_Name =>] static_string_expression]); + + +This pragma is identical in syntax and semantics to +the standard Ada pragma `Import`. It is provided for compatibility +with Ada 83. The definition is upwards compatible both with pragma +`Interface` as defined in the Ada 83 Reference Manual, and also +with some extended implementations of this pragma in certain Ada 83 +implementations. The only difference between pragma `Interface` +and pragma `Import` is that there is special circuitry to allow +both pragmas to appear for the same subprogram entity (normally it +is illegal to have multiple `Import` pragmas. This is useful in +maintaining Ada 83/Ada 95 compatibility and is compatible with other +Ada 83 compilers. + +Pragma Interface_Name +===================== + +Syntax: + + +:: + + pragma Interface_Name ( + [Entity =>] LOCAL_NAME + [, [External_Name =>] static_string_EXPRESSION] + [, [Link_Name =>] static_string_EXPRESSION]); + + +This pragma provides an alternative way of specifying the interface name +for an interfaced subprogram, and is provided for compatibility with Ada +83 compilers that use the pragma for this purpose. You must provide at +least one of `External_Name` or `Link_Name`. + +Pragma Interrupt_Handler +======================== + +Syntax: + + +.. code-block:: ada + + pragma Interrupt_Handler (procedure_LOCAL_NAME); + + +This program unit pragma is supported for parameterless protected procedures +as described in Annex C of the Ada Reference Manual. On the AAMP target +the pragma can also be specified for nonprotected parameterless procedures +that are declared at the library level (which includes procedures +declared at the top level of a library package). In the case of AAMP, +when this pragma is applied to a nonprotected procedure, the instruction +`IERET` is generated for returns from the procedure, enabling +maskable interrupts, in place of the normal return instruction. + +Pragma Interrupt_State +====================== + +Syntax: + + +:: + + pragma Interrupt_State + ([Name =>] value, + [State =>] SYSTEM | RUNTIME | USER); + + +Normally certain interrupts are reserved to the implementation. Any attempt +to attach an interrupt causes Program_Error to be raised, as described in +RM C.3.2(22). A typical example is the `SIGINT` interrupt used in +many systems for an :kbd:`Ctrl-C` interrupt. Normally this interrupt is +reserved to the implementation, so that :kbd:`Ctrl-C` can be used to +interrupt execution. Additionally, signals such as `SIGSEGV`, +`SIGABRT`, `SIGFPE` and `SIGILL` are often mapped to specific +Ada exceptions, or used to implement run-time functions such as the +`abort` statement and stack overflow checking. + +Pragma `Interrupt_State` provides a general mechanism for overriding +such uses of interrupts. It subsumes the functionality of pragma +`Unreserve_All_Interrupts`. Pragma `Interrupt_State` is not +available on Windows or VMS. On all other platforms than VxWorks, +it applies to signals; on VxWorks, it applies to vectored hardware interrupts +and may be used to mark interrupts required by the board support package +as reserved. + +Interrupts can be in one of three states: + +* System + + The interrupt is reserved (no Ada handler can be installed), and the + Ada run-time may not install a handler. As a result you are guaranteed + standard system default action if this interrupt is raised. + +* Runtime + + The interrupt is reserved (no Ada handler can be installed). The run time + is allowed to install a handler for internal control purposes, but is + not required to do so. + +* User + + The interrupt is unreserved. The user may install a handler to provide + some other action. + +These states are the allowed values of the `State` parameter of the +pragma. The `Name` parameter is a value of the type +`Ada.Interrupts.Interrupt_ID`. Typically, it is a name declared in +`Ada.Interrupts.Names`. + +This is a configuration pragma, and the binder will check that there +are no inconsistencies between different units in a partition in how a +given interrupt is specified. It may appear anywhere a pragma is legal. + +The effect is to move the interrupt to the specified state. + +By declaring interrupts to be SYSTEM, you guarantee the standard system +action, such as a core dump. + +By declaring interrupts to be USER, you guarantee that you can install +a handler. + +Note that certain signals on many operating systems cannot be caught and +handled by applications. In such cases, the pragma is ignored. See the +operating system documentation, or the value of the array `Reserved` +declared in the spec of package `System.OS_Interface`. + +Overriding the default state of signals used by the Ada runtime may interfere +with an application's runtime behavior in the cases of the synchronous signals, +and in the case of the signal used to implement the `abort` statement. + +Pragma Invariant +================ + +Syntax: + + +:: + + pragma Invariant + ([Entity =>] private_type_LOCAL_NAME, + [Check =>] EXPRESSION + [,[Message =>] String_Expression]); + + +This pragma provides exactly the same capabilities as the Type_Invariant aspect +defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The +Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it +requires the use of the aspect syntax, which is not available except in 2012 +mode, it is not possible to use the Type_Invariant aspect in earlier versions +of Ada. However the Invariant pragma may be used in any version of Ada. Also +note that the aspect Invariant is a synonym in GNAT for the aspect +Type_Invariant, but there is no pragma Type_Invariant. + +The pragma must appear within the visible part of the package specification, +after the type to which its Entity argument appears. As with the Invariant +aspect, the Check expression is not analyzed until the end of the visible +part of the package, so it may contain forward references. The Message +argument, if present, provides the exception message used if the invariant +is violated. If no Message parameter is provided, a default message that +identifies the line on which the pragma appears is used. + +It is permissible to have multiple Invariants for the same type entity, in +which case they are and'ed together. It is permissible to use this pragma +in Ada 2012 mode, but you cannot have both an invariant aspect and an +invariant pragma for the same entity. + +For further details on the use of this pragma, see the Ada 2012 documentation +of the Type_Invariant aspect. + +Pragma Java_Constructor +======================= + +Syntax: + + +:: + + pragma Java_Constructor ([Entity =>] function_LOCAL_NAME); + + +This pragma is used to assert that the specified Ada function should be +mapped to the Java constructor for some Ada tagged record type. + +See section 7.3.2 of the +`GNAT User's Guide: Supplement for the JVM Platform.` +for related information. + +Pragma Java_Interface +===================== + +Syntax: + + +:: + + pragma Java_Interface ([Entity =>] abstract_tagged_type_LOCAL_NAME); + + +This pragma is used to assert that the specified Ada abstract tagged type +is to be mapped to a Java interface name. + +See sections 7.1 and 7.2 of the +`GNAT User's Guide: Supplement for the JVM Platform.` +for related information. + +Pragma Keep_Names +================= + +Syntax: + + +:: + + pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME); + + +The `LOCAL_NAME` argument +must refer to an enumeration first subtype +in the current declarative part. The effect is to retain the enumeration +literal names for use by `Image` and `Value` even if a global +`Discard_Names` pragma applies. This is useful when you want to +generally suppress enumeration literal names and for example you therefore +use a `Discard_Names` pragma in the :file:`gnat.adc` file, but you +want to retain the names for specific enumeration types. + +Pragma License +============== +.. index:: License checking + +Syntax: + + +.. code-block:: ada + + pragma License (Unrestricted | GPL | Modified_GPL | Restricted); + + +This pragma is provided to allow automated checking for appropriate license +conditions with respect to the standard and modified GPL. A pragma +`License`, which is a configuration pragma that typically appears at +the start of a source file or in a separate :file:`gnat.adc` file, specifies +the licensing conditions of a unit as follows: + +* Unrestricted + This is used for a unit that can be freely used with no license restrictions. + Examples of such units are public domain units, and units from the Ada + Reference Manual. + +* GPL + This is used for a unit that is licensed under the unmodified GPL, and which + therefore cannot be `with`'ed by a restricted unit. + +* Modified_GPL + This is used for a unit licensed under the GNAT modified GPL that includes + a special exception paragraph that specifically permits the inclusion of + the unit in programs without requiring the entire program to be released + under the GPL. + +* Restricted + This is used for a unit that is restricted in that it is not permitted to + depend on units that are licensed under the GPL. Typical examples are + proprietary code that is to be released under more restrictive license + conditions. Note that restricted units are permitted to `with` units + which are licensed under the modified GPL (this is the whole point of the + modified GPL). + + +Normally a unit with no `License` pragma is considered to have an +unknown license, and no checking is done. However, standard GNAT headers +are recognized, and license information is derived from them as follows. + +A GNAT license header starts with a line containing 78 hyphens. The following +comment text is searched for the appearance of any of the following strings. + +If the string 'GNU General Public License' is found, then the unit is assumed +to have GPL license, unless the string 'As a special exception' follows, in +which case the license is assumed to be modified GPL. + +If one of the strings +'This specification is adapted from the Ada Semantic Interface' or +'This specification is derived from the Ada Reference Manual' is found +then the unit is assumed to be unrestricted. + +These default actions means that a program with a restricted license pragma +will automatically get warnings if a GPL unit is inappropriately +`with`'ed. For example, the program: + +.. code-block:: ada + + with Sem_Ch3; + with GNAT.Sockets; + procedure Secret_Stuff is + ... + end Secret_Stuff + + +if compiled with pragma `License` (`Restricted`) in a +:file:`gnat.adc` file will generate the warning:: + + 1. with Sem_Ch3; + | + >>> license of withed unit "Sem_Ch3" is incompatible + + 2. with GNAT.Sockets; + 3. procedure Secret_Stuff is + + +Here we get a warning on `Sem_Ch3` since it is part of the GNAT +compiler and is licensed under the +GPL, but no warning for `GNAT.Sockets` which is part of the GNAT +run time, and is therefore licensed under the modified GPL. + +Pragma Link_With +================ + +Syntax: + + +:: + + pragma Link_With (static_string_EXPRESSION {,static_string_EXPRESSION}); + + +This pragma is provided for compatibility with certain Ada 83 compilers. +It has exactly the same effect as pragma `Linker_Options` except +that spaces occurring within one of the string expressions are treated +as separators. For example, in the following case: + +.. code-block:: ada + + pragma Link_With ("-labc -ldef"); + + +results in passing the strings `-labc` and `-ldef` as two +separate arguments to the linker. In addition pragma Link_With allows +multiple arguments, with the same effect as successive pragmas. + +Pragma Linker_Alias +=================== + +Syntax: + + +:: + + pragma Linker_Alias ( + [Entity =>] LOCAL_NAME, + [Target =>] static_string_EXPRESSION); + + +`LOCAL_NAME` must refer to an object that is declared at the library +level. This pragma establishes the given entity as a linker alias for the +given target. It is equivalent to `__attribute__((alias))` in GNU C +and causes `LOCAL_NAME` to be emitted as an alias for the symbol +`static_string_EXPRESSION` in the object file, that is to say no space +is reserved for `LOCAL_NAME` by the assembler and it will be resolved +to the same address as `static_string_EXPRESSION` by the linker. + +The actual linker name for the target must be used (e.g., the fully +encoded name with qualification in Ada, or the mangled name in C++), +or it must be declared using the C convention with `pragma Import` +or `pragma Export`. + +Not all target machines support this pragma. On some of them it is accepted +only if `pragma Weak_External` has been applied to `LOCAL_NAME`. + + +.. code-block:: ada + + -- Example of the use of pragma Linker_Alias + + package p is + i : Integer := 1; + pragma Export (C, i); + + new_name_for_i : Integer; + pragma Linker_Alias (new_name_for_i, "i"); + end p; + + +Pragma Linker_Constructor +========================= + +Syntax: + + +.. code-block:: ada + + pragma Linker_Constructor (procedure_LOCAL_NAME); + + +`procedure_LOCAL_NAME` must refer to a parameterless procedure that +is declared at the library level. A procedure to which this pragma is +applied will be treated as an initialization routine by the linker. +It is equivalent to `__attribute__((constructor))` in GNU C and +causes `procedure_LOCAL_NAME` to be invoked before the entry point +of the executable is called (or immediately after the shared library is +loaded if the procedure is linked in a shared library), in particular +before the Ada run-time environment is set up. + +Because of these specific contexts, the set of operations such a procedure +can perform is very limited and the type of objects it can manipulate is +essentially restricted to the elementary types. In particular, it must only +contain code to which pragma Restrictions (No_Elaboration_Code) applies. + +This pragma is used by GNAT to implement auto-initialization of shared Stand +Alone Libraries, which provides a related capability without the restrictions +listed above. Where possible, the use of Stand Alone Libraries is preferable +to the use of this pragma. + +Pragma Linker_Destructor +======================== + +Syntax: + + +.. code-block:: ada + + pragma Linker_Destructor (procedure_LOCAL_NAME); + + +`procedure_LOCAL_NAME` must refer to a parameterless procedure that +is declared at the library level. A procedure to which this pragma is +applied will be treated as a finalization routine by the linker. +It is equivalent to `__attribute__((destructor))` in GNU C and +causes `procedure_LOCAL_NAME` to be invoked after the entry point +of the executable has exited (or immediately before the shared library +is unloaded if the procedure is linked in a shared library), in particular +after the Ada run-time environment is shut down. + +See `pragma Linker_Constructor` for the set of restrictions that apply +because of these specific contexts. + +Pragma Linker_Section +===================== + +Syntax: + + +:: + + pragma Linker_Section ( + [Entity =>] LOCAL_NAME, + [Section =>] static_string_EXPRESSION); + + +`LOCAL_NAME` must refer to an object, type, or subprogram that is +declared at the library level. This pragma specifies the name of the +linker section for the given entity. It is equivalent to +`__attribute__((section))` in GNU C and causes `LOCAL_NAME` to +be placed in the `static_string_EXPRESSION` section of the +executable (assuming the linker doesn't rename the section). +GNAT also provides an implementation defined aspect of the same name. + +In the case of specifying this aspect for a type, the effect is to +specify the corresponding for all library level objects of the type which +do not have an explicit linker section set. Note that this only applies to +whole objects, not to components of composite objects. + +In the case of a subprogram, the linker section applies to all previously +declared matching overloaded subprograms in the current declarative part +which do not already have a linker section assigned. The linker section +aspect is useful in this case for specifying different linker sections +for different elements of such an overloaded set. + +Note that an empty string specifies that no linker section is specified. +This is not quite the same as omitting the pragma or aspect, since it +can be used to specify that one element of an overloaded set of subprograms +has the default linker section, or that one object of a type for which a +linker section is specified should has the default linker section. + +The compiler normally places library-level entities in standard sections +depending on the class: procedures and functions generally go in the +`.text` section, initialized variables in the `.data` section +and uninitialized variables in the `.bss` section. + +Other, special sections may exist on given target machines to map special +hardware, for example I/O ports or flash memory. This pragma is a means to +defer the final layout of the executable to the linker, thus fully working +at the symbolic level with the compiler. + +Some file formats do not support arbitrary sections so not all target +machines support this pragma. The use of this pragma may cause a program +execution to be erroneous if it is used to place an entity into an +inappropriate section (e.g., a modified variable into the `.text` +section). See also `pragma Persistent_BSS`. + + +.. code-block:: ada + + -- Example of the use of pragma Linker_Section + + package IO_Card is + Port_A : Integer; + pragma Volatile (Port_A); + pragma Linker_Section (Port_A, ".bss.port_a"); + + Port_B : Integer; + pragma Volatile (Port_B); + pragma Linker_Section (Port_B, ".bss.port_b"); + + type Port_Type is new Integer with Linker_Section => ".bss"; + PA : Port_Type with Linker_Section => ".bss.PA"; + PB : Port_Type; -- ends up in linker section ".bss" + + procedure Q with Linker_Section => "Qsection"; + end IO_Card; + + +Pragma Lock_Free +================ + +Syntax: +This pragma may be specified for protected types or objects. It specifies that +the implementation of protected operations must be implemented without locks. +Compilation fails if the compiler cannot generate lock-free code for the +operations. + +Pragma Loop_Invariant +===================== + +Syntax: + + +.. code-block:: ada + + pragma Loop_Invariant ( boolean_EXPRESSION ); + + +The effect of this pragma is similar to that of pragma `Assert`, +except that in an `Assertion_Policy` pragma, the identifier +`Loop_Invariant` is used to control whether it is ignored or checked +(or disabled). + +`Loop_Invariant` can only appear as one of the items in the sequence +of statements of a loop body, or nested inside block statements that +appear in the sequence of statements of a loop body. +The intention is that it be used to +represent a "loop invariant" assertion, i.e. something that is true each +time through the loop, and which can be used to show that the loop is +achieving its purpose. + +Multiple `Loop_Invariant` and `Loop_Variant` pragmas that +apply to the same loop should be grouped in the same sequence of +statements. + +To aid in writing such invariants, the special attribute `Loop_Entry` +may be used to refer to the value of an expression on entry to the loop. This +attribute can only be used within the expression of a `Loop_Invariant` +pragma. For full details, see documentation of attribute `Loop_Entry`. + +Pragma Loop_Optimize +==================== + +Syntax: + + +:: + + pragma Loop_Optimize (OPTIMIZATION_HINT {, OPTIMIZATION_HINT}); + + OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector + + +This pragma must appear immediately within a loop statement. It allows the +programmer to specify optimization hints for the enclosing loop. The hints +are not mutually exclusive and can be freely mixed, but not all combinations +will yield a sensible outcome. + +There are five supported optimization hints for a loop: + +* Ivdep + + The programmer asserts that there are no loop-carried dependencies + which would prevent consecutive iterations of the loop from being + executed simultaneously. + +* No_Unroll + + The loop must not be unrolled. This is a strong hint: the compiler will not + unroll a loop marked with this hint. + +* Unroll + + The loop should be unrolled. This is a weak hint: the compiler will try to + apply unrolling to this loop preferably to other optimizations, notably + vectorization, but there is no guarantee that the loop will be unrolled. + +* No_Vector + + The loop must not be vectorized. This is a strong hint: the compiler will not + vectorize a loop marked with this hint. + +* Vector + + The loop should be vectorized. This is a weak hint: the compiler will try to + apply vectorization to this loop preferably to other optimizations, notably + unrolling, but there is no guarantee that the loop will be vectorized. + + +These hints do not remove the need to pass the appropriate switches to the +compiler in order to enable the relevant optimizations, that is to say +*-funroll-loops* for unrolling and *-ftree-vectorize* for +vectorization. + +Pragma Loop_Variant +=================== + +Syntax: + + +:: + + pragma Loop_Variant ( LOOP_VARIANT_ITEM {, LOOP_VARIANT_ITEM } ); + LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION + CHANGE_DIRECTION ::= Increases | Decreases + + +`Loop_Variant` can only appear as one of the items in the sequence +of statements of a loop body, or nested inside block statements that +appear in the sequence of statements of a loop body. +It allows the specification of quantities which must always +decrease or increase in successive iterations of the loop. In its simplest +form, just one expression is specified, whose value must increase or decrease +on each iteration of the loop. + +In a more complex form, multiple arguments can be given which are intepreted +in a nesting lexicographic manner. For example: + +.. code-block:: ada + + pragma Loop_Variant (Increases => X, Decreases => Y); + + +specifies that each time through the loop either X increases, or X stays +the same and Y decreases. A `Loop_Variant` pragma ensures that the +loop is making progress. It can be useful in helping to show informally +or prove formally that the loop always terminates. + +`Loop_Variant` is an assertion whose effect can be controlled using +an `Assertion_Policy` with a check name of `Loop_Variant`. The +policy can be `Check` to enable the loop variant check, `Ignore` +to ignore the check (in which case the pragma has no effect on the program), +or `Disable` in which case the pragma is not even checked for correct +syntax. + +Multiple `Loop_Invariant` and `Loop_Variant` pragmas that +apply to the same loop should be grouped in the same sequence of +statements. + +The `Loop_Entry` attribute may be used within the expressions of the +`Loop_Variant` pragma to refer to values on entry to the loop. + +Pragma Machine_Attribute +======================== + +Syntax: + + +:: + + pragma Machine_Attribute ( + [Entity =>] LOCAL_NAME, + [Attribute_Name =>] static_string_EXPRESSION + [, [Info =>] static_EXPRESSION] ); + + +Machine-dependent attributes can be specified for types and/or +declarations. This pragma is semantically equivalent to +`__attribute__((`attribute_name`))` (if `info` is not +specified) or `__attribute__((`attribute_name`(`info`))) +in GNU C, where ``attribute_name`` is recognized by the +compiler middle-end or the `TARGET_ATTRIBUTE_TABLE` machine +specific macro. A string literal for the optional parameter `info` +is transformed into an identifier, which may make this pragma unusable +for some attributes. +For further information see :title:`GNU Compiler Collection (GCC) Internals`. + +Pragma Main +=========== + +Syntax:: + + pragma Main + (MAIN_OPTION [, MAIN_OPTION]); + + MAIN_OPTION ::= + [Stack_Size =>] static_integer_EXPRESSION + | [Task_Stack_Size_Default =>] static_integer_EXPRESSION + | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION + + +This pragma is provided for compatibility with OpenVMS VAX Systems. It has +no effect in GNAT, other than being syntax checked. + +Pragma Main_Storage +=================== + +Syntax:: + + pragma Main_Storage + (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]); + + MAIN_STORAGE_OPTION ::= + [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION + | [TOP_GUARD =>] static_SIMPLE_EXPRESSION + + +This pragma is provided for compatibility with OpenVMS VAX Systems. It has +no effect in GNAT, other than being syntax checked. + +Pragma No_Body +============== + +Syntax: + + +.. code-block:: ada + + pragma No_Body; + + +There are a number of cases in which a package spec does not require a body, +and in fact a body is not permitted. GNAT will not permit the spec to be +compiled if there is a body around. The pragma No_Body allows you to provide +a body file, even in a case where no body is allowed. The body file must +contain only comments and a single No_Body pragma. This is recognized by +the compiler as indicating that no body is logically present. + +This is particularly useful during maintenance when a package is modified in +such a way that a body needed before is no longer needed. The provision of a +dummy body with a No_Body pragma ensures that there is no interference from +earlier versions of the package body. + +Pragma No_Elaboration_Code_All +============================== + +Syntax: + + +:: + + pragma No_Elaboration_Code_All [(program_unit_NAME)]; + + +This is a program unit pragma (there is also an equivalent aspect of the +same name) that establishes the restriction `No_Elaboration_Code` for +the current unit and any extended main source units (body and subunits. +It also has has the effect of enforcing a transitive application of this +aspect, so that if any unit is implicitly or explicitly WITH'ed by the +current unit, it must also have the No_Elaboration_Code_All aspect set. +It may be applied to package or subprogram specs or their generic versions. + +Pragma No_Inline +================ + +Syntax: + + +:: + + pragma No_Inline (NAME {, NAME}); + + +This pragma suppresses inlining for the callable entity or the instances of +the generic subprogram designated by `NAME`, including inlining that +results from the use of pragma `Inline`. This pragma is always active, +in particular it is not subject to the use of option *-gnatn* or +*-gnatN*. It is illegal to specify both pragma `No_Inline` and +pragma `Inline_Always` for the same `NAME`. + +Pragma No_Return +================ + +Syntax: + + +:: + + pragma No_Return (procedure_LOCAL_NAME {, procedure_LOCAL_NAME}); + + +Each `procedure_LOCAL_NAME` argument must refer to one or more procedure +declarations in the current declarative part. A procedure to which this +pragma is applied may not contain any explicit `return` statements. +In addition, if the procedure contains any implicit returns from falling +off the end of a statement sequence, then execution of that implicit +return will cause Program_Error to be raised. + +One use of this pragma is to identify procedures whose only purpose is to raise +an exception. Another use of this pragma is to suppress incorrect warnings +about missing returns in functions, where the last statement of a function +statement sequence is a call to such a procedure. + +Note that in Ada 2005 mode, this pragma is part of the language. It is +available in all earlier versions of Ada as an implementation-defined +pragma. + +Pragma No_Run_Time +================== + +Syntax: + + +.. code-block:: ada + + pragma No_Run_Time; + + +This is an obsolete configuration pragma that historically was used to +set up a runtime library with no object code. It is now used only for +internal testing. The pragma has been superseded by the reconfigurable +runtime capability of `GNAT`. + +Pragma No_Strict_Aliasing +========================= + +Syntax: + + +:: + + pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)]; + + +`type_LOCAL_NAME` must refer to an access type +declaration in the current declarative part. The effect is to inhibit +strict aliasing optimization for the given type. The form with no +arguments is a configuration pragma which applies to all access types +declared in units to which the pragma applies. For a detailed +description of the strict aliasing optimization, and the situations +in which it must be suppressed, see the section on Optimization and Strict Aliasing +in the :title:`GNAT User's Guide`. + +This pragma currently has no effects on access to unconstrained array types. + +Pragma No_Tagged_Streams +======================== + +Syntax: + + +:: + + pragma No_Tagged_Streams; + pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)]; + + +Normally when a tagged type is introduced using a full type declaration, +part of the processing includes generating stream access routines to be +used by stream attributes referencing the type (or one of its subtypes +or derived types). This can involve the generation of significant amounts +of code which is wasted space if stream routines are not needed for the +type in question. + +The `No_Tagged_Streams` pragma causes the generation of these stream +routines to be skipped, and any attempt to use stream operations on +types subject to this pragma will be statically rejected as illegal. + +There are two forms of the pragma. The form with no arguments must appear +in a declarative sequence or in the declarations of a package spec. This +pragma affects all subsequent root tagged types declared in the declaration +sequence, and specifies that no stream routines be generated. The form with +an argument (for which there is also a corresponding aspect) specifies a +single root tagged type for which stream routines are not to be generated. + +Once the pragma has been given for a particular root tagged type, all subtypes +and derived types of this type inherit the pragma automatically, so the effect +applies to a complete hierarchy (this is necessary to deal with the class-wide +dispatching versions of the stream routines). + +Pragma Normalize_Scalars +======================== + +Syntax: + + +.. code-block:: ada + + pragma Normalize_Scalars; + + +This is a language defined pragma which is fully implemented in GNAT. The +effect is to cause all scalar objects that are not otherwise initialized +to be initialized. The initial values are implementation dependent and +are as follows: + + + +*Standard.Character* + Objects whose root type is Standard.Character are initialized to + Character'Last unless the subtype range excludes NUL (in which case + NUL is used). This choice will always generate an invalid value if + one exists. + + +*Standard.Wide_Character* + Objects whose root type is Standard.Wide_Character are initialized to + Wide_Character'Last unless the subtype range excludes NUL (in which case + NUL is used). This choice will always generate an invalid value if + one exists. + + +*Standard.Wide_Wide_Character* + Objects whose root type is Standard.Wide_Wide_Character are initialized to + the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in + which case NUL is used). This choice will always generate an invalid value if + one exists. + + +*Integer types* + Objects of an integer type are treated differently depending on whether + negative values are present in the subtype. If no negative values are + present, then all one bits is used as the initial value except in the + special case where zero is excluded from the subtype, in which case + all zero bits are used. This choice will always generate an invalid + value if one exists. + + For subtypes with negative values present, the largest negative number + is used, except in the unusual case where this largest negative number + is in the subtype, and the largest positive number is not, in which case + the largest positive value is used. This choice will always generate + an invalid value if one exists. + + +*Floating-Point Types* + Objects of all floating-point types are initialized to all 1-bits. For + standard IEEE format, this corresponds to a NaN (not a number) which is + indeed an invalid value. + + +*Fixed-Point Types* + Objects of all fixed-point types are treated as described above for integers, + with the rules applying to the underlying integer value used to represent + the fixed-point value. + + +*Modular types* + Objects of a modular type are initialized to all one bits, except in + the special case where zero is excluded from the subtype, in which + case all zero bits are used. This choice will always generate an + invalid value if one exists. + + +*Enumeration types* + Objects of an enumeration type are initialized to all one-bits, i.e., to + the value `2 ** typ'Size - 1` unless the subtype excludes the literal + whose Pos value is zero, in which case a code of zero is used. This choice + will always generate an invalid value if one exists. + +.. _Pragma_Obsolescent: + +Pragma Obsolescent +================== + +Syntax: + + +:: + + pragma Obsolescent; + + pragma Obsolescent ( + [Message =>] static_string_EXPRESSION + [,[Version =>] Ada_05]]); + + pragma Obsolescent ( + [Entity =>] NAME + [,[Message =>] static_string_EXPRESSION + [,[Version =>] Ada_05]] ); + + +This pragma can occur immediately following a declaration of an entity, +including the case of a record component. If no Entity argument is present, +then this declaration is the one to which the pragma applies. If an Entity +parameter is present, it must either match the name of the entity in this +declaration, or alternatively, the pragma can immediately follow an enumeration +type declaration, where the Entity argument names one of the enumeration +literals. + +This pragma is used to indicate that the named entity +is considered obsolescent and should not be used. Typically this is +used when an API must be modified by eventually removing or modifying +existing subprograms or other entities. The pragma can be used at an +intermediate stage when the entity is still present, but will be +removed later. + +The effect of this pragma is to output a warning message on a reference to +an entity thus marked that the subprogram is obsolescent if the appropriate +warning option in the compiler is activated. If the Message parameter is +present, then a second warning message is given containing this text. In +addition, a reference to the entity is considered to be a violation of pragma +Restrictions (No_Obsolescent_Features). + +This pragma can also be used as a program unit pragma for a package, +in which case the entity name is the name of the package, and the +pragma indicates that the entire package is considered +obsolescent. In this case a client `with`'ing such a package +violates the restriction, and the `with` statement is +flagged with warnings if the warning option is set. + +If the Version parameter is present (which must be exactly +the identifier Ada_05, no other argument is allowed), then the +indication of obsolescence applies only when compiling in Ada 2005 +mode. This is primarily intended for dealing with the situations +in the predefined library where subprograms or packages +have become defined as obsolescent in Ada 2005 +(e.g., in Ada.Characters.Handling), but may be used anywhere. + +The following examples show typical uses of this pragma: + + +.. code-block:: ada + + package p is + pragma Obsolescent (p, Message => "use pp instead of p"); + end p; + + package q is + procedure q2; + pragma Obsolescent ("use q2new instead"); + + type R is new integer; + pragma Obsolescent + (Entity => R, + Message => "use RR in Ada 2005", + Version => Ada_05); + + type M is record + F1 : Integer; + F2 : Integer; + pragma Obsolescent; + F3 : Integer; + end record; + + type E is (a, bc, 'd', quack); + pragma Obsolescent (Entity => bc) + pragma Obsolescent (Entity => 'd') + + function "+" + (a, b : character) return character; + pragma Obsolescent (Entity => "+"); + end; + + +Note that, as for all pragmas, if you use a pragma argument identifier, +then all subsequent parameters must also use a pragma argument identifier. +So if you specify "Entity =>" for the Entity argument, and a Message +argument is present, it must be preceded by "Message =>". + +Pragma Optimize_Alignment +========================= +.. index:: Alignment, default settings + +Syntax: + + +.. code-block:: ada + + pragma Optimize_Alignment (TIME | SPACE | OFF); + + +This is a configuration pragma which affects the choice of default alignments +for types and objects where no alignment is explicitly specified. There is a +time/space trade-off in the selection of these values. Large alignments result +in more efficient code, at the expense of larger data space, since sizes have +to be increased to match these alignments. Smaller alignments save space, but +the access code is slower. The normal choice of default alignments for types +and individual alignment promotions for objects (which is what you get if you +do not use this pragma, or if you use an argument of OFF), tries to balance +these two requirements. + +Specifying SPACE causes smaller default alignments to be chosen in two cases. +First any packed record is given an alignment of 1. Second, if a size is given +for the type, then the alignment is chosen to avoid increasing this size. For +example, consider: + + +.. code-block:: ada + + type R is record + X : Integer; + Y : Character; + end record; + + for R'Size use 5*8; + + +In the default mode, this type gets an alignment of 4, so that access to the +Integer field X are efficient. But this means that objects of the type end up +with a size of 8 bytes. This is a valid choice, since sizes of objects are +allowed to be bigger than the size of the type, but it can waste space if for +example fields of type R appear in an enclosing record. If the above type is +compiled in `Optimize_Alignment (Space)` mode, the alignment is set to 1. + +However, there is one case in which SPACE is ignored. If a variable length +record (that is a discriminated record with a component which is an array +whose length depends on a discriminant), has a pragma Pack, then it is not +in general possible to set the alignment of such a record to one, so the +pragma is ignored in this case (with a warning). + +Specifying SPACE also disables alignment promotions for standalone objects, +which occur when the compiler increases the alignment of a specific object +without changing the alignment of its type. + +Specifying TIME causes larger default alignments to be chosen in the case of +small types with sizes that are not a power of 2. For example, consider: + + +.. code-block:: ada + + type R is record + A : Character; + B : Character; + C : Boolean; + end record; + + pragma Pack (R); + for R'Size use 17; + + +The default alignment for this record is normally 1, but if this type is +compiled in `Optimize_Alignment (Time)` mode, then the alignment is set +to 4, which wastes space for objects of the type, since they are now 4 bytes +long, but results in more efficient access when the whole record is referenced. + +As noted above, this is a configuration pragma, and there is a requirement +that all units in a partition be compiled with a consistent setting of the +optimization setting. This would normally be achieved by use of a configuration +pragma file containing the appropriate setting. The exception to this rule is +that units with an explicit configuration pragma in the same file as the source +unit are excluded from the consistency check, as are all predefined units. The +latter are compiled by default in pragma Optimize_Alignment (Off) mode if no +pragma appears at the start of the file. + +Pragma Ordered +============== + +Syntax: + + +.. code-block:: ada + + pragma Ordered (enumeration_first_subtype_LOCAL_NAME); + + +Most enumeration types are from a conceptual point of view unordered. +For example, consider: + + +.. code-block:: ada + + type Color is (Red, Blue, Green, Yellow); + + +By Ada semantics `Blue > Red` and `Green > Blue`, +but really these relations make no sense; the enumeration type merely +specifies a set of possible colors, and the order is unimportant. + +For unordered enumeration types, it is generally a good idea if +clients avoid comparisons (other than equality or inequality) and +explicit ranges. (A *client* is a unit where the type is referenced, +other than the unit where the type is declared, its body, and its subunits.) +For example, if code buried in some client says: + + +.. code-block:: ada + + if Current_Color < Yellow then ... + if Current_Color in Blue .. Green then ... + + +then the client code is relying on the order, which is undesirable. +It makes the code hard to read and creates maintenance difficulties if +entries have to be added to the enumeration type. Instead, +the code in the client should list the possibilities, or an +appropriate subtype should be declared in the unit that declares +the original enumeration type. E.g., the following subtype could +be declared along with the type `Color`: + + +.. code-block:: ada + + subtype RBG is Color range Red .. Green; + + +and then the client could write: + + +.. code-block:: ada + + if Current_Color in RBG then ... + if Current_Color = Blue or Current_Color = Green then ... + + +However, some enumeration types are legitimately ordered from a conceptual +point of view. For example, if you declare: + + +.. code-block:: ada + + type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun); + + +then the ordering imposed by the language is reasonable, and +clients can depend on it, writing for example: + + +.. code-block:: ada + + if D in Mon .. Fri then ... + if D < Wed then ... + + +The pragma *Ordered* is provided to mark enumeration types that +are conceptually ordered, alerting the reader that clients may depend +on the ordering. GNAT provides a pragma to mark enumerations as ordered +rather than one to mark them as unordered, since in our experience, +the great majority of enumeration types are conceptually unordered. + +The types `Boolean`, `Character`, `Wide_Character`, +and `Wide_Wide_Character` +are considered to be ordered types, so each is declared with a +pragma `Ordered` in package `Standard`. + +Normally pragma `Ordered` serves only as documentation and a guide for +coding standards, but GNAT provides a warning switch *-gnatw.u* that +requests warnings for inappropriate uses (comparisons and explicit +subranges) for unordered types. If this switch is used, then any +enumeration type not marked with pragma `Ordered` will be considered +as unordered, and will generate warnings for inappropriate uses. + +Note that generic types are not considered ordered or unordered (since the +template can be instantiated for both cases), so we never generate warnings +for the case of generic enumerated types. + +For additional information please refer to the description of the +*-gnatw.u* switch in the GNAT User's Guide. + +Pragma Overflow_Mode +==================== + +Syntax: + + +:: + + pragma Overflow_Mode + ( [General =>] MODE + [,[Assertions =>] MODE]); + + MODE ::= STRICT | MINIMIZED | ELIMINATED + + +This pragma sets the current overflow mode to the given setting. For details +of the meaning of these modes, please refer to the +'Overflow Check Handling in GNAT' appendix in the +GNAT User's Guide. If only the `General` parameter is present, +the given mode applies to all expressions. If both parameters are present, +the `General` mode applies to expressions outside assertions, and +the `Eliminated` mode applies to expressions within assertions. + +The case of the `MODE` parameter is ignored, +so `MINIMIZED`, `Minimized` and +`minimized` all have the same effect. + +The `Overflow_Mode` pragma has the same scoping and placement +rules as pragma `Suppress`, so it can occur either as a +configuration pragma, specifying a default for the whole +program, or in a declarative scope, where it applies to the +remaining declarations and statements in that scope. + +The pragma `Suppress (Overflow_Check)` suppresses +overflow checking, but does not affect the overflow mode. + +The pragma `Unsuppress (Overflow_Check)` unsuppresses (enables) +overflow checking, but does not affect the overflow mode. + +Pragma Overriding_Renamings +=========================== +.. index:: Rational profile + +.. index:: Rational compatibility + +Syntax: + + +.. code-block:: ada + + pragma Overriding_Renamings; + + +This is a GNAT configuration pragma to simplify porting +legacy code accepted by the Rational +Ada compiler. In the presence of this pragma, a renaming declaration that +renames an inherited operation declared in the same scope is legal if selected +notation is used as in: + + +.. code-block:: ada + + pragma Overriding_Renamings; + ... + package R is + function F (..); + ... + function F (..) renames R.F; + end R; + + +even though +RM 8.3 (15) stipulates that an overridden operation is not visible within the +declaration of the overriding operation. + +Pragma Partition_Elaboration_Policy +=================================== + +Syntax: + + +:: + + pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER); + + POLICY_IDENTIFIER ::= Concurrent | Sequential + + +This pragma is standard in Ada 2005, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Part_Of +============== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.2.6. + +Pragma Passive +============== + +Syntax: + + +:: + + pragma Passive [(Semaphore | No)]; + + +Syntax checked, but otherwise ignored by GNAT. This is recognized for +compatibility with DEC Ada 83 implementations, where it is used within a +task definition to request that a task be made passive. If the argument +`Semaphore` is present, or the argument is omitted, then DEC Ada 83 +treats the pragma as an assertion that the containing task is passive +and that optimization of context switch with this task is permitted and +desired. If the argument `No` is present, the task must not be +optimized. GNAT does not attempt to optimize any tasks in this manner +(since protected objects are available in place of passive tasks). + +For more information on the subject of passive tasks, see the section +'Passive Task Optimization' in the GNAT Users Guide. + +Pragma Persistent_BSS +===================== + +Syntax: + + +:: + + pragma Persistent_BSS [(LOCAL_NAME)] + + +This pragma allows selected objects to be placed in the `.persistent_bss` +section. On some targets the linker and loader provide for special +treatment of this section, allowing a program to be reloaded without +affecting the contents of this data (hence the name persistent). + +There are two forms of usage. If an argument is given, it must be the +local name of a library level object, with no explicit initialization +and whose type is potentially persistent. If no argument is given, then +the pragma is a configuration pragma, and applies to all library level +objects with no explicit initialization of potentially persistent types. + +A potentially persistent type is a scalar type, or an untagged, +non-discriminated record, all of whose components have no explicit +initialization and are themselves of a potentially persistent type, +or an array, all of whose constraints are static, and whose component +type is potentially persistent. + +If this pragma is used on a target where this feature is not supported, +then the pragma will be ignored. See also `pragma Linker_Section`. + +Pragma Polling +============== + +Syntax: + + +.. code-block:: ada + + pragma Polling (ON | OFF); + + +This pragma controls the generation of polling code. This is normally off. +If `pragma Polling (ON)` is used then periodic calls are generated to +the routine `Ada.Exceptions.Poll`. This routine is a separate unit in the +runtime library, and can be found in file :file:`a-excpol.adb`. + +Pragma `Polling` can appear as a configuration pragma (for example it +can be placed in the :file:`gnat.adc` file) to enable polling globally, or it +can be used in the statement or declaration sequence to control polling +more locally. + +A call to the polling routine is generated at the start of every loop and +at the start of every subprogram call. This guarantees that the `Poll` +routine is called frequently, and places an upper bound (determined by +the complexity of the code) on the period between two `Poll` calls. + +The primary purpose of the polling interface is to enable asynchronous +aborts on targets that cannot otherwise support it (for example Windows +NT), but it may be used for any other purpose requiring periodic polling. +The standard version is null, and can be replaced by a user program. This +will require re-compilation of the `Ada.Exceptions` package that can +be found in files :file:`a-except.ads` and :file:`a-except.adb`. + +A standard alternative unit (in file :file:`4wexcpol.adb` in the standard GNAT +distribution) is used to enable the asynchronous abort capability on +targets that do not normally support the capability. The version of +`Poll` in this file makes a call to the appropriate runtime routine +to test for an abort condition. + +Note that polling can also be enabled by use of the *-gnatP* switch. +See the section on switches for gcc in the :title:`GNAT User's Guide`. + +Pragma Post +=========== +.. index:: Post + +.. index:: Checks, postconditions + + +Syntax: + + +.. code-block:: ada + + pragma Post (Boolean_Expression); + + +The `Post` pragma is intended to be an exact replacement for +the language-defined +`Post` aspect, and shares its restrictions and semantics. +It must appear either immediately following the corresponding +subprogram declaration (only other pragmas may intervene), or +if there is no separate subprogram declaration, then it can +appear at the start of the declarations in a subprogram body +(preceded only by other pragmas). + +Pragma Postcondition +==================== +.. index:: Postcondition + +.. index:: Checks, postconditions + + +Syntax: + + +:: + + pragma Postcondition ( + [Check =>] Boolean_Expression + [,[Message =>] String_Expression]); + + +The `Postcondition` pragma allows specification of automatic +postcondition checks for subprograms. These checks are similar to +assertions, but are automatically inserted just prior to the return +statements of the subprogram with which they are associated (including +implicit returns at the end of procedure bodies and associated +exception handlers). + +In addition, the boolean expression which is the condition which +must be true may contain references to function'Result in the case +of a function to refer to the returned value. + +`Postcondition` pragmas may appear either immediately following the +(separate) declaration of a subprogram, or at the start of the +declarations of a subprogram body. Only other pragmas may intervene +(that is appear between the subprogram declaration and its +postconditions, or appear before the postcondition in the +declaration sequence in a subprogram body). In the case of a +postcondition appearing after a subprogram declaration, the +formal arguments of the subprogram are visible, and can be +referenced in the postcondition expressions. + +The postconditions are collected and automatically tested just +before any return (implicit or explicit) in the subprogram body. +A postcondition is only recognized if postconditions are active +at the time the pragma is encountered. The compiler switch *gnata* +turns on all postconditions by default, and pragma `Check_Policy` +with an identifier of `Postcondition` can also be used to +control whether postconditions are active. + +The general approach is that postconditions are placed in the spec +if they represent functional aspects which make sense to the client. +For example we might have: + + +.. code-block:: ada + + function Direction return Integer; + pragma Postcondition + (Direction'Result = +1 + or else + Direction'Result = -1); + + +which serves to document that the result must be +1 or -1, and +will test that this is the case at run time if postcondition +checking is active. + +Postconditions within the subprogram body can be used to +check that some internal aspect of the implementation, +not visible to the client, is operating as expected. +For instance if a square root routine keeps an internal +counter of the number of times it is called, then we +might have the following postcondition: + + +.. code-block:: ada + + Sqrt_Calls : Natural := 0; + + function Sqrt (Arg : Float) return Float is + pragma Postcondition + (Sqrt_Calls = Sqrt_Calls'Old + 1); + ... + end Sqrt + + +As this example, shows, the use of the `Old` attribute +is often useful in postconditions to refer to the state on +entry to the subprogram. + +Note that postconditions are only checked on normal returns +from the subprogram. If an abnormal return results from +raising an exception, then the postconditions are not checked. + +If a postcondition fails, then the exception +`System.Assertions.Assert_Failure` is raised. If +a message argument was supplied, then the given string +will be used as the exception message. If no message +argument was supplied, then the default message has +the form "Postcondition failed at file_name:line". The +exception is raised in the context of the subprogram +body, so it is possible to catch postcondition failures +within the subprogram body itself. + +Within a package spec, normal visibility rules +in Ada would prevent forward references within a +postcondition pragma to functions defined later in +the same package. This would introduce undesirable +ordering constraints. To avoid this problem, all +postcondition pragmas are analyzed at the end of +the package spec, allowing forward references. + +The following example shows that this even allows +mutually recursive postconditions as in: + + +.. code-block:: ada + + package Parity_Functions is + function Odd (X : Natural) return Boolean; + pragma Postcondition + (Odd'Result = + (x = 1 + or else + (x /= 0 and then Even (X - 1)))); + + function Even (X : Natural) return Boolean; + pragma Postcondition + (Even'Result = + (x = 0 + or else + (x /= 1 and then Odd (X - 1)))); + + end Parity_Functions; + + +There are no restrictions on the complexity or form of +conditions used within `Postcondition` pragmas. +The following example shows that it is even possible +to verify performance behavior. + + +.. code-block:: ada + + package Sort is + + Performance : constant Float; + -- Performance constant set by implementation + -- to match target architecture behavior. + + procedure Treesort (Arg : String); + -- Sorts characters of argument using N*logN sort + pragma Postcondition + (Float (Clock - Clock'Old) <= + Float (Arg'Length) * + log (Float (Arg'Length)) * + Performance); + end Sort; + + +Note: postcondition pragmas associated with subprograms that are +marked as Inline_Always, or those marked as Inline with front-end +inlining (-gnatN option set) are accepted and legality-checked +by the compiler, but are ignored at run-time even if postcondition +checking is enabled. + +Note that pragma `Postcondition` differs from the language-defined +`Post` aspect (and corresponding `Post` pragma) in allowing +multiple occurrences, allowing occurences in the body even if there +is a separate spec, and allowing a second string parameter, and the +use of the pragma identifier `Check`. Historically, pragma +`Postcondition` was implemented prior to the development of +Ada 2012, and has been retained in its original form for +compatibility purposes. + +Pragma Post_Class +================= +.. index:: Post + +.. index:: Checks, postconditions + + +Syntax: + + +.. code-block:: ada + + pragma Post_Class (Boolean_Expression); + + +The `Post_Class` pragma is intended to be an exact replacement for +the language-defined +`Post'Class` aspect, and shares its restrictions and semantics. +It must appear either immediately following the corresponding +subprogram declaration (only other pragmas may intervene), or +if there is no separate subprogram declaration, then it can +appear at the start of the declarations in a subprogram body +(preceded only by other pragmas). + +Note: This pragma is called `Post_Class` rather than +`Post'Class` because the latter would not be strictly +conforming to the allowed syntax for pragmas. The motivation +for provinding pragmas equivalent to the aspects is to allow a program +to be written using the pragmas, and then compiled if necessary +using an Ada compiler that does not recognize the pragmas or +aspects, but is prepared to ignore the pragmas. The assertion +policy that controls this pragma is `Post'Class`, not +`Post_Class`. + +Pragma Pre +========== +.. index:: Pre + +.. index:: Checks, preconditions + + +Syntax: + + +.. code-block:: ada + + pragma Pre (Boolean_Expression); + + +The `Pre` pragma is intended to be an exact replacement for +the language-defined +`Pre` aspect, and shares its restrictions and semantics. +It must appear either immediately following the corresponding +subprogram declaration (only other pragmas may intervene), or +if there is no separate subprogram declaration, then it can +appear at the start of the declarations in a subprogram body +(preceded only by other pragmas). + +Pragma Precondition +=================== +.. index:: Preconditions + +.. index:: Checks, preconditions + + +Syntax: + + +:: + + pragma Precondition ( + [Check =>] Boolean_Expression + [,[Message =>] String_Expression]); + + +The `Precondition` pragma is similar to `Postcondition` +except that the corresponding checks take place immediately upon +entry to the subprogram, and if a precondition fails, the exception +is raised in the context of the caller, and the attribute 'Result +cannot be used within the precondition expression. + +Otherwise, the placement and visibility rules are identical to those +described for postconditions. The following is an example of use +within a package spec: + + +.. code-block:: ada + + package Math_Functions is + ... + function Sqrt (Arg : Float) return Float; + pragma Precondition (Arg >= 0.0) + ... + end Math_Functions; + + +`Precondition` pragmas may appear either immediately following the +(separate) declaration of a subprogram, or at the start of the +declarations of a subprogram body. Only other pragmas may intervene +(that is appear between the subprogram declaration and its +postconditions, or appear before the postcondition in the +declaration sequence in a subprogram body). + +Note: precondition pragmas associated with subprograms that are +marked as Inline_Always, or those marked as Inline with front-end +inlining (-gnatN option set) are accepted and legality-checked +by the compiler, but are ignored at run-time even if precondition +checking is enabled. + +Note that pragma `Precondition` differs from the language-defined +`Pre` aspect (and corresponding `Pre` pragma) in allowing +multiple occurrences, allowing occurences in the body even if there +is a separate spec, and allowing a second string parameter, and the +use of the pragma identifier `Check`. Historically, pragma +`Precondition` was implemented prior to the development of +Ada 2012, and has been retained in its original form for +compatibility purposes. + +Pragma Predicate +================ + +Syntax: + + +:: + + pragma Predicate + ([Entity =>] type_LOCAL_NAME, + [Check =>] EXPRESSION); + + +This pragma (available in all versions of Ada in GNAT) encompasses both +the `Static_Predicate` and `Dynamic_Predicate` aspects in +Ada 2012. A predicate is regarded as static if it has an allowed form +for `Static_Predicate` and is otherwise treated as a +`Dynamic_Predicate`. Otherwise, predicates specified by this +pragma behave exactly as described in the Ada 2012 reference manual. +For example, if we have + + +.. code-block:: ada + + type R is range 1 .. 10; + subtype S is R; + pragma Predicate (Entity => S, Check => S not in 4 .. 6); + subtype Q is R + pragma Predicate (Entity => Q, Check => F(Q) or G(Q)); + + +the effect is identical to the following Ada 2012 code: + + +.. code-block:: ada + + type R is range 1 .. 10; + subtype S is R with + Static_Predicate => S not in 4 .. 6; + subtype Q is R with + Dynamic_Predicate => F(Q) or G(Q); + + +Note that there is are no pragmas `Dynamic_Predicate` +or `Static_Predicate`. That is +because these pragmas would affect legality and semantics of +the program and thus do not have a neutral effect if ignored. +The motivation behind providing pragmas equivalent to +corresponding aspects is to allow a program to be written +using the pragmas, and then compiled with a compiler that +will ignore the pragmas. That doesn't work in the case of +static and dynamic predicates, since if the corresponding +pragmas are ignored, then the behavior of the program is +fundamentally changed (for example a membership test +`A in B` would not take into account a predicate +defined for subtype B). When following this approach, the +use of predicates should be avoided. + +Pragma Preelaborable_Initialization +=================================== + +Syntax: + + +.. code-block:: ada + + pragma Preelaborable_Initialization (DIRECT_NAME); + + +This pragma is standard in Ada 2005, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Prefix_Exception_Messages +================================ +.. index:: Prefix_Exception_Messages + +.. index:: exception + +.. index:: Exception_Message + + +Syntax: + + +.. code-block:: ada + + pragma Prefix_Exception_Messages; + + +This is an implementation-defined configuration pragma that affects the +behavior of raise statements with a message given as a static string +constant (typically a string literal). In such cases, the string will +be automatically prefixed by the name of the enclosing entity (giving +the package and subprogram containing the raise statement). This helps +to identify where messages are coming from, and this mode is automatic +for the run-time library. + +The pragma has no effect if the message is computed with an expression other +than a static string constant, since the assumption in this case is that +the program computes exactly the string it wants. If you still want the +prefixing in this case, you can always call +`GNAT.Source_Info.Enclosing_Entity` and prepend the string manually. + +Pragma Pre_Class +================ +.. index:: Pre_Class + +.. index:: Checks, preconditions + + +Syntax: + + +.. code-block:: ada + + pragma Pre_Class (Boolean_Expression); + + +The `Pre_Class` pragma is intended to be an exact replacement for +the language-defined +`Pre'Class` aspect, and shares its restrictions and semantics. +It must appear either immediately following the corresponding +subprogram declaration (only other pragmas may intervene), or +if there is no separate subprogram declaration, then it can +appear at the start of the declarations in a subprogram body +(preceded only by other pragmas). + +Note: This pragma is called `Pre_Class` rather than +`Pre'Class` because the latter would not be strictly +conforming to the allowed syntax for pragmas. The motivation +for providing pragmas equivalent to the aspects is to allow a program +to be written using the pragmas, and then compiled if necessary +using an Ada compiler that does not recognize the pragmas or +aspects, but is prepared to ignore the pragmas. The assertion +policy that controls this pragma is `Pre'Class`, not +`Pre_Class`. + +Pragma Priority_Specific_Dispatching +==================================== + +Syntax: + + +:: + + pragma Priority_Specific_Dispatching ( + POLICY_IDENTIFIER, + first_priority_EXPRESSION, + last_priority_EXPRESSION) + + POLICY_IDENTIFIER ::= + EDF_Across_Priorities | + FIFO_Within_Priorities | + Non_Preemptive_Within_Priorities | + Round_Robin_Within_Priorities + + +This pragma is standard in Ada 2005, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Profile +============== + +Syntax: + + +.. code-block:: ada + + pragma Profile (Ravenscar | Restricted | Rational); + + +This pragma is standard in Ada 2005, but is available in all earlier +versions of Ada as an implementation-defined pragma. This is a +configuration pragma that establishes a set of configuration pragmas +that depend on the argument. `Ravenscar` is standard in Ada 2005. +The other two possibilities (`Restricted` or `Rational`) +are implementation-defined. The set of configuration pragmas +is defined in the following sections. + + +* Pragma Profile (Ravenscar) + + The `Ravenscar` profile is standard in Ada 2005, + but is available in all earlier + versions of Ada as an implementation-defined pragma. This profile + establishes the following set of configuration pragmas: + + * ``Task_Dispatching_Policy (FIFO_Within_Priorities)`` + + [RM D.2.2] Tasks are dispatched following a preemptive + priority-ordered scheduling policy. + + + * ``Locking_Policy (Ceiling_Locking)`` + + [RM D.3] While tasks and interrupts execute a protected action, they inherit + the ceiling priority of the corresponding protected object. + + + * ``Detect_Blocking`` + + This pragma forces the detection of potentially blocking operations within a + protected operation, and to raise Program_Error if that happens. + + plus the following set of restrictions: + + * ``Max_Entry_Queue_Length => 1`` + + No task can be queued on a protected entry. + + * ``Max_Protected_Entries => 1`` + + * ``Max_Task_Entries => 0`` + + No rendezvous statements are allowed. + + * ``No_Abort_Statements`` + + * ``No_Dynamic_Attachment`` + + * ``No_Dynamic_Priorities`` + + * ``No_Implicit_Heap_Allocations`` + + * ``No_Local_Protected_Objects`` + + * ``No_Local_Timing_Events`` + + * ``No_Protected_Type_Allocators`` + + * ``No_Relative_Delay`` + + * ``No_Requeue_Statements`` + + * ``No_Select_Statements`` + + * ``No_Specific_Termination_Handlers`` + + * ``No_Task_Allocators`` + + * ``No_Task_Hierarchy`` + + * ``No_Task_Termination`` + + * ``Simple_Barriers`` + + The Ravenscar profile also includes the following restrictions that specify + that there are no semantic dependences on the corresponding predefined + packages: + + * ``No_Dependence => Ada.Asynchronous_Task_Control`` + + * ``No_Dependence => Ada.Calendar`` + + * ``No_Dependence => Ada.Execution_Time.Group_Budget`` + + * ``No_Dependence => Ada.Execution_Time.Timers`` + + * ``No_Dependence => Ada.Task_Attributes`` + + * ``No_Dependence => System.Multiprocessors.Dispatching_Domains`` + + This set of configuration pragmas and restrictions correspond to the + definition of the 'Ravenscar Profile' for limited tasking, devised and + published by the :title:`International Real-Time Ada Workshop, 1997`. + A description is also available at + `http://www-users.cs.york.ac.uk/~burns/ravenscar.ps `_. + + The original definition of the profile was revised at subsequent IRTAW + meetings. It has been included in the ISO + :title:`Guide for the Use of the Ada Programming Language in High Integrity Systems`, + and was made part of the Ada 2005 standard. + The formal definition given by + the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and + AI-305) available at + `http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt `_ and + `http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt `_. + + The above set is a superset of the restrictions provided by pragma + ``Profile (Restricted)``, it includes six additional restrictions + (``Simple_Barriers``, ``No_Select_Statements``, + ``No_Calendar``, ``No_Implicit_Heap_Allocations``, + ``No_Relative_Delay`` and ``No_Task_Termination``). This means + that pragma ``Profile (Ravenscar)``, like the pragma + ``Profile (Restricted)``, + automatically causes the use of a simplified, + more efficient version of the tasking run-time library. + +* Pragma Profile (Restricted) + + This profile corresponds to the GNAT restricted run time. It + establishes the following set of restrictions: + + * ``No_Abort_Statements`` + * ``No_Entry_Queue`` + * ``No_Task_Hierarchy`` + * ``No_Task_Allocators`` + * ``No_Dynamic_Priorities`` + * ``No_Terminate_Alternatives`` + * ``No_Dynamic_Attachment`` + * ``No_Protected_Type_Allocators`` + * ``No_Local_Protected_Objects`` + * ``No_Requeue_Statements`` + * ``No_Task_Attributes_Package`` + * ``Max_Asynchronous_Select_Nesting = 0`` + * ``Max_Task_Entries = 0`` + * ``Max_Protected_Entries = 1`` + * ``Max_Select_Alternatives = 0`` + + This set of restrictions causes the automatic selection of a simplified + version of the run time that provides improved performance for the + limited set of tasking functionality permitted by this set of restrictions. + +* Pragma Profile (Rational) + + The Rational profile is intended to facilitate porting legacy code that + compiles with the Rational APEX compiler, even when the code includes non- + conforming Ada constructs. The profile enables the following three pragmas: + + * ``pragma Implicit_Packing`` + * ``pragma Overriding_Renamings`` + * ``pragma Use_VADS_Size`` + + +Pragma Profile_Warnings +======================= + +Syntax: + + +.. code-block:: ada + + pragma Profile_Warnings (Ravenscar | Restricted | Rational); + + +This is an implementation-defined pragma that is similar in +effect to `pragma Profile` except that instead of +generating `Restrictions` pragmas, it generates +`Restriction_Warnings` pragmas. The result is that +violations of the profile generate warning messages instead +of error messages. + +Pragma Propagate_Exceptions +=========================== +.. index:: Interfacing to C++ + + +Syntax: + + +.. code-block:: ada + + pragma Propagate_Exceptions; + + +This pragma is now obsolete and, other than generating a warning if warnings +on obsolescent features are enabled, is ignored. +It is retained for compatibility +purposes. It used to be used in connection with optimization of +a now-obsolete mechanism for implementation of exceptions. + +Pragma Provide_Shift_Operators +============================== +.. index:: Shift operators + + +Syntax: + + +.. code-block:: ada + + pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME); + + +This pragma can be applied to a first subtype local name that specifies +either an unsigned or signed type. It has the effect of providing the +five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic, +Rotate_Left and Rotate_Right) for the given type. It is similar to +including the function declarations for these five operators, together +with the pragma Import (Intrinsic, ...) statements. + +Pragma Psect_Object +=================== + +Syntax: + + +:: + + pragma Psect_Object ( + [Internal =>] LOCAL_NAME, + [, [External =>] EXTERNAL_SYMBOL] + [, [Size =>] EXTERNAL_SYMBOL]); + + EXTERNAL_SYMBOL ::= + IDENTIFIER + | static_string_EXPRESSION + + +This pragma is identical in effect to pragma `Common_Object`. + +Pragma Pure_Function +==================== + +Syntax: + + +:: + + pragma Pure_Function ([Entity =>] function_LOCAL_NAME); + + +This pragma appears in the same declarative part as a function +declaration (or a set of function declarations if more than one +overloaded declaration exists, in which case the pragma applies +to all entities). It specifies that the function `Entity` is +to be considered pure for the purposes of code generation. This means +that the compiler can assume that there are no side effects, and +in particular that two calls with identical arguments produce the +same result. It also means that the function can be used in an +address clause. + +Note that, quite deliberately, there are no static checks to try +to ensure that this promise is met, so `Pure_Function` can be used +with functions that are conceptually pure, even if they do modify +global variables. For example, a square root function that is +instrumented to count the number of times it is called is still +conceptually pure, and can still be optimized, even though it +modifies a global variable (the count). Memo functions are another +example (where a table of previous calls is kept and consulted to +avoid re-computation). + +Note also that the normal rules excluding optimization of subprograms +in pure units (when parameter types are descended from System.Address, +or when the full view of a parameter type is limited), do not apply +for the Pure_Function case. If you explicitly specify Pure_Function, +the compiler may optimize away calls with identical arguments, and +if that results in unexpected behavior, the proper action is not to +use the pragma for subprograms that are not (conceptually) pure. + +Note: Most functions in a `Pure` package are automatically pure, and +there is no need to use pragma `Pure_Function` for such functions. One +exception is any function that has at least one formal of type +`System.Address` or a type derived from it. Such functions are not +considered pure by default, since the compiler assumes that the +`Address` parameter may be functioning as a pointer and that the +referenced data may change even if the address value does not. +Similarly, imported functions are not considered to be pure by default, +since there is no way of checking that they are in fact pure. The use +of pragma `Pure_Function` for such a function will override these default +assumption, and cause the compiler to treat a designated subprogram as pure +in these cases. + +Note: If pragma `Pure_Function` is applied to a renamed function, it +applies to the underlying renamed function. This can be used to +disambiguate cases of overloading where some but not all functions +in a set of overloaded functions are to be designated as pure. + +If pragma `Pure_Function` is applied to a library level function, the +function is also considered pure from an optimization point of view, but the +unit is not a Pure unit in the categorization sense. So for example, a function +thus marked is free to `with` non-pure units. + +Pragma Rational +=============== + +Syntax: + + +.. code-block:: ada + + pragma Rational; + + +This pragma is considered obsolescent, but is retained for +compatibility purposes. It is equivalent to: + + +.. code-block:: ada + + pragma Profile (Rational); + + +Pragma Ravenscar +================ + +Syntax: + + +.. code-block:: ada + + pragma Ravenscar; + + +This pragma is considered obsolescent, but is retained for +compatibility purposes. It is equivalent to: + + +.. code-block:: ada + + pragma Profile (Ravenscar); + + +which is the preferred method of setting the `Ravenscar` profile. + +Pragma Refined_Depends +====================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 6.1.5. + +Pragma Refined_Global +===================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 6.1.4. + +Pragma Refined_Post +=================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.2.7. + +Pragma Refined_State +==================== + +For the description of this pragma, see SPARK 2014 Reference Manual, +section 7.2.2. + +Pragma Relative_Deadline +======================== + +Syntax: + + +.. code-block:: ada + + pragma Relative_Deadline (time_span_EXPRESSION); + + +This pragma is standard in Ada 2005, but is available in all earlier +versions of Ada as an implementation-defined pragma. +See Ada 2012 Reference Manual for details. + +Pragma Remote_Access_Type +========================= + +Syntax: + + +:: + + pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME); + + +This pragma appears in the formal part of a generic declaration. +It specifies an exception to the RM rule from E.2.2(17/2), which forbids +the use of a remote access to class-wide type as actual for a formal +access type. + +When this pragma applies to a formal access type `Entity`, that +type is treated as a remote access to class-wide type in the generic. +It must be a formal general access type, and its designated type must +be the class-wide type of a formal tagged limited private type from the +same generic declaration. + +In the generic unit, the formal type is subject to all restrictions +pertaining to remote access to class-wide types. At instantiation, the +actual type must be a remote access to class-wide type. + +Pragma Restricted_Run_Time +========================== + +Syntax: + + +.. code-block:: ada + + pragma Restricted_Run_Time; + + +This pragma is considered obsolescent, but is retained for +compatibility purposes. It is equivalent to: + + +.. code-block:: ada + + pragma Profile (Restricted); + + +which is the preferred method of setting the restricted run time +profile. + +Pragma Restriction_Warnings +=========================== + +Syntax: + + +:: + + pragma Restriction_Warnings + (restriction_IDENTIFIER {, restriction_IDENTIFIER}); + + +This pragma allows a series of restriction identifiers to be +specified (the list of allowed identifiers is the same as for +pragma `Restrictions`). For each of these identifiers +the compiler checks for violations of the restriction, but +generates a warning message rather than an error message +if the restriction is violated. + +One use of this is in situations where you want to know +about violations of a restriction, but you want to ignore some of +these violations. Consider this example, where you want to set +Ada_95 mode and enable style checks, but you want to know about +any other use of implementation pragmas: + + +.. code-block:: ada + + pragma Restriction_Warnings (No_Implementation_Pragmas); + pragma Warnings (Off, "violation of No_Implementation_Pragmas"); + pragma Ada_95; + pragma Style_Checks ("2bfhkM160"); + pragma Warnings (On, "violation of No_Implementation_Pragmas"); + + +By including the above lines in a configuration pragmas file, +the Ada_95 and Style_Checks pragmas are accepted without +generating a warning, but any other use of implementation +defined pragmas will cause a warning to be generated. + +Pragma Reviewable +================= + +Syntax: + + +.. code-block:: ada + + pragma Reviewable; + + +This pragma is an RM-defined standard pragma, but has no effect on the +program being compiled, or on the code generated for the program. + +To obtain the required output specified in RM H.3.1, the compiler must be +run with various special switches as follows: + +* *Where compiler-generated run-time checks remain* + + The switch *-gnatGL* + may be used to list the expanded code in pseudo-Ada form. + Runtime checks show up in the listing either as explicit + checks or operators marked with {} to indicate a check is present. + + +* *An identification of known exceptions at compile time* + + If the program is compiled with *-gnatwa*, + the compiler warning messages will indicate all cases where the compiler + detects that an exception is certain to occur at run time. + + +* *Possible reads of uninitialized variables* + + The compiler warns of many such cases, but its output is incomplete. + +.. only:: PRO or GPL + + The CodePeer analysis tool + may be used to obtain a comprehensive list of all + possible points at which uninitialized data may be read. + +.. only:: FSF + + A supplemental static analysis tool + may be used to obtain a comprehensive list of all + possible points at which uninitialized data may be read. + + +* *Where run-time support routines are implicitly invoked* + + In the output from *-gnatGL*, + run-time calls are explicitly listed as calls to the relevant + run-time routine. + + +* *Object code listing* + + This may be obtained either by using the *-S* switch, + or the objdump utility. + + +* *Constructs known to be erroneous at compile time* + + These are identified by warnings issued by the compiler (use *-gnatwa*). + + +* *Stack usage information* + + Static stack usage data (maximum per-subprogram) can be obtained via the + *-fstack-usage* switch to the compiler. + Dynamic stack usage data (per task) can be obtained via the *-u* switch + to gnatbind + +.. only:: PRO or GPL + + The gnatstack utility + can be used to provide additional information on stack usage. + + +* *Object code listing of entire partition* + + This can be obtained by compiling the partition with *-S*, + or by applying objdump + to all the object files that are part of the partition. + + +* *A description of the run-time model* + + The full sources of the run-time are available, and the documentation of + these routines describes how these run-time routines interface to the + underlying operating system facilities. + + +* *Control and data-flow information* + +.. only:: PRO or GPL + + The CodePeer tool + may be used to obtain complete control and data-flow information, as well as + comprehensive messages identifying possible problems based on this + information. + +.. only:: FSF + + A supplemental static analysis tool + may be used to obtain complete control and data-flow information, as well as + comprehensive messages identifying possible problems based on this + information. + + +Pragma Share_Generic +==================== + +Syntax: + + +:: + + pragma Share_Generic (GNAME {, GNAME}); + + GNAME ::= generic_unit_NAME | generic_instance_NAME + + +This pragma is provided for compatibility with Dec Ada 83. It has +no effect in `GNAT` (which does not implement shared generics), other +than to check that the given names are all names of generic units or +generic instances. + +Pragma Shared +============= + +This pragma is provided for compatibility with Ada 83. The syntax and +semantics are identical to pragma Atomic. + +Pragma Short_Circuit_And_Or +=========================== + +Syntax: + + +.. code-block:: ada + + pragma Short_Circuit_And_Or; + + +This configuration pragma causes any occurrence of the AND operator applied to +operands of type Standard.Boolean to be short-circuited (i.e. the AND operator +is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This +may be useful in the context of certification protocols requiring the use of +short-circuited logical operators. If this configuration pragma occurs locally +within the file being compiled, it applies only to the file being compiled. +There is no requirement that all units in a partition use this option. + +Pragma Short_Descriptors +======================== + +Syntax: + + +.. code-block:: ada + + pragma Short_Descriptors + + +This pragma is provided for compatibility with other Ada implementations. It +is recognized but ignored by all current versions of GNAT. + +Pragma Simple_Storage_Pool_Type +=============================== +.. index:: Storage pool, simple + +.. index:: Simple storage pool + +Syntax: + + +.. code-block:: ada + + pragma Simple_Storage_Pool_Type (type_LOCAL_NAME); + + +A type can be established as a 'simple storage pool type' by applying +the representation pragma `Simple_Storage_Pool_Type` to the type. +A type named in the pragma must be a library-level immutably limited record +type or limited tagged type declared immediately within a package declaration. +The type can also be a limited private type whose full type is allowed as +a simple storage pool type. + +For a simple storage pool type `SSP`, nonabstract primitive subprograms +`Allocate`, `Deallocate`, and `Storage_Size` can be declared that +are subtype conformant with the following subprogram declarations: + + +.. code-block:: ada + + procedure Allocate + (Pool : in out SSP; + Storage_Address : out System.Address; + Size_In_Storage_Elements : System.Storage_Elements.Storage_Count; + Alignment : System.Storage_Elements.Storage_Count); + + procedure Deallocate + (Pool : in out SSP; + Storage_Address : System.Address; + Size_In_Storage_Elements : System.Storage_Elements.Storage_Count; + Alignment : System.Storage_Elements.Storage_Count); + + function Storage_Size (Pool : SSP) + return System.Storage_Elements.Storage_Count; + + +Procedure `Allocate` must be declared, whereas `Deallocate` and +`Storage_Size` are optional. If `Deallocate` is not declared, then +applying an unchecked deallocation has no effect other than to set its actual +parameter to null. If `Storage_Size` is not declared, then the +`Storage_Size` attribute applied to an access type associated with +a pool object of type SSP returns zero. Additional operations can be declared +for a simple storage pool type (such as for supporting a mark/release +storage-management discipline). + +An object of a simple storage pool type can be associated with an access +type by specifying the attribute +:ref:`Simple_Storage_Pool `. For example: + + +.. code-block:: ada + + My_Pool : My_Simple_Storage_Pool_Type; + + type Acc is access My_Data_Type; + + for Acc'Simple_Storage_Pool use My_Pool; + + + +See attribute :ref:`Simple_Storage_Pool ` +for further details. + +.. _Pragma_Source_File_Name: + +Pragma Source_File_Name +======================= + +Syntax: + + +:: + + pragma Source_File_Name ( + [Unit_Name =>] unit_NAME, + Spec_File_Name => STRING_LITERAL, + [Index => INTEGER_LITERAL]); + + pragma Source_File_Name ( + [Unit_Name =>] unit_NAME, + Body_File_Name => STRING_LITERAL, + [Index => INTEGER_LITERAL]); + + +Use this to override the normal naming convention. It is a configuration +pragma, and so has the usual applicability of configuration pragmas +(i.e., it applies to either an entire partition, or to all units in a +compilation, or to a single unit, depending on how it is used. +`unit_name` is mapped to `file_name_literal`. The identifier for +the second argument is required, and indicates whether this is the file +name for the spec or for the body. + +The optional Index argument should be used when a file contains multiple +units, and when you do not want to use `gnatchop` to separate then +into multiple files (which is the recommended procedure to limit the +number of recompilations that are needed when some sources change). +For instance, if the source file :file:`source.ada` contains + + +.. code-block:: ada + + package B is + ... + end B; + + with B; + procedure A is + begin + .. + end A; + + +you could use the following configuration pragmas: + + +.. code-block:: ada + + pragma Source_File_Name + (B, Spec_File_Name => "source.ada", Index => 1); + pragma Source_File_Name + (A, Body_File_Name => "source.ada", Index => 2); + + +Note that the `gnatname` utility can also be used to generate those +configuration pragmas. + +Another form of the `Source_File_Name` pragma allows +the specification of patterns defining alternative file naming schemes +to apply to all files. + + +:: + + pragma Source_File_Name + ( [Spec_File_Name =>] STRING_LITERAL + [,[Casing =>] CASING_SPEC] + [,[Dot_Replacement =>] STRING_LITERAL]); + + pragma Source_File_Name + ( [Body_File_Name =>] STRING_LITERAL + [,[Casing =>] CASING_SPEC] + [,[Dot_Replacement =>] STRING_LITERAL]); + + pragma Source_File_Name + ( [Subunit_File_Name =>] STRING_LITERAL + [,[Casing =>] CASING_SPEC] + [,[Dot_Replacement =>] STRING_LITERAL]); + + CASING_SPEC ::= Lowercase | Uppercase | Mixedcase + + +The first argument is a pattern that contains a single asterisk indicating +the point at which the unit name is to be inserted in the pattern string +to form the file name. The second argument is optional. If present it +specifies the casing of the unit name in the resulting file name string. +The default is lower case. Finally the third argument allows for systematic +replacement of any dots in the unit name by the specified string literal. + +Note that Source_File_Name pragmas should not be used if you are using +project files. The reason for this rule is that the project manager is not +aware of these pragmas, and so other tools that use the projet file would not +be aware of the intended naming conventions. If you are using project files, +file naming is controlled by Source_File_Name_Project pragmas, which are +usually supplied automatically by the project manager. A pragma +Source_File_Name cannot appear after a :ref:`Pragma_Source_File_Name_Project`. + +For more details on the use of the `Source_File_Name` pragma, see the +sections on `Using Other File Names` and `Alternative File Naming Schemes' +in the :title:`GNAT User's Guide`. + +.. _Pragma_Source_File_Name_Project: + +Pragma Source_File_Name_Project +=============================== + +This pragma has the same syntax and semantics as pragma Source_File_Name. +It is only allowed as a stand alone configuration pragma. +It cannot appear after a :ref:`Pragma_Source_File_Name`, and +most importantly, once pragma Source_File_Name_Project appears, +no further Source_File_Name pragmas are allowed. + +The intention is that Source_File_Name_Project pragmas are always +generated by the Project Manager in a manner consistent with the naming +specified in a project file, and when naming is controlled in this manner, +it is not permissible to attempt to modify this naming scheme using +Source_File_Name or Source_File_Name_Project pragmas (which would not be +known to the project manager). + +Pragma Source_Reference +======================= + +Syntax: + + +.. code-block:: ada + + pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL); + + +This pragma must appear as the first line of a source file. +`integer_literal` is the logical line number of the line following +the pragma line (for use in error messages and debugging +information). `string_literal` is a static string constant that +specifies the file name to be used in error messages and debugging +information. This is most notably used for the output of `gnatchop` +with the *-r* switch, to make sure that the original unchopped +source file is the one referred to. + +The second argument must be a string literal, it cannot be a static +string expression other than a string literal. This is because its value +is needed for error messages issued by all phases of the compiler. + +Pragma SPARK_Mode +================= + +Syntax: + + +:: + + pragma SPARK_Mode [(On | Off)] ; + + +In general a program can have some parts that are in SPARK 2014 (and +follow all the rules in the SPARK Reference Manual), and some parts +that are full Ada 2012. + +The SPARK_Mode pragma is used to identify which parts are in SPARK +2014 (by default programs are in full Ada). The SPARK_Mode pragma can +be used in the following places: + + +* + As a configuration pragma, in which case it sets the default mode for + all units compiled with this pragma. + +* + Immediately following a library-level subprogram spec + +* + Immediately within a library-level package body + +* + Immediately following the `private` keyword of a library-level + package spec + +* + Immediately following the `begin` keyword of a library-level + package body + +* + Immediately within a library-level subprogram body + + +Normally a subprogram or package spec/body inherits the current mode +that is active at the point it is declared. But this can be overridden +by pragma within the spec or body as above. + +The basic consistency rule is that you can't turn SPARK_Mode back +`On`, once you have explicitly (with a pragma) turned if +`Off`. So the following rules apply: + +If a subprogram spec has SPARK_Mode `Off`, then the body must +also have SPARK_Mode `Off`. + +For a package, we have four parts: + +* + the package public declarations +* + the package private part +* + the body of the package +* + the elaboration code after `begin` + +For a package, the rule is that if you explicitly turn SPARK_Mode +`Off` for any part, then all the following parts must have +SPARK_Mode `Off`. Note that this may require repeating a pragma +SPARK_Mode (`Off`) in the body. For example, if we have a +configuration pragma SPARK_Mode (`On`) that turns the mode on by +default everywhere, and one particular package spec has pragma +SPARK_Mode (`Off`), then that pragma will need to be repeated in +the package body. + +Pragma Static_Elaboration_Desired +================================= + +Syntax: + + +.. code-block:: ada + + pragma Static_Elaboration_Desired; + + +This pragma is used to indicate that the compiler should attempt to initialize +statically the objects declared in the library unit to which the pragma applies, +when these objects are initialized (explicitly or implicitly) by an aggregate. +In the absence of this pragma, aggregates in object declarations are expanded +into assignments and loops, even when the aggregate components are static +constants. When the aggregate is present the compiler builds a static expression +that requires no run-time code, so that the initialized object can be placed in +read-only data space. If the components are not static, or the aggregate has +more that 100 components, the compiler emits a warning that the pragma cannot +be obeyed. (See also the restriction No_Implicit_Loops, which supports static +construction of larger aggregates with static components that include an others +choice.) + +Pragma Stream_Convert +===================== + +Syntax: + + +:: + + pragma Stream_Convert ( + [Entity =>] type_LOCAL_NAME, + [Read =>] function_NAME, + [Write =>] function_NAME); + + +This pragma provides an efficient way of providing user-defined stream +attributes. Not only is it simpler to use than specifying the attributes +directly, but more importantly, it allows the specification to be made in such +a way that the predefined unit Ada.Streams is not loaded unless it is actually +needed (i.e. unless the stream attributes are actually used); the use of +the Stream_Convert pragma adds no overhead at all, unless the stream +attributes are actually used on the designated type. + +The first argument specifies the type for which stream functions are +provided. The second parameter provides a function used to read values +of this type. It must name a function whose argument type may be any +subtype, and whose returned type must be the type given as the first +argument to the pragma. + +The meaning of the `Read` parameter is that if a stream attribute directly +or indirectly specifies reading of the type given as the first parameter, +then a value of the type given as the argument to the Read function is +read from the stream, and then the Read function is used to convert this +to the required target type. + +Similarly the `Write` parameter specifies how to treat write attributes +that directly or indirectly apply to the type given as the first parameter. +It must have an input parameter of the type specified by the first parameter, +and the return type must be the same as the input type of the Read function. +The effect is to first call the Write function to convert to the given stream +type, and then write the result type to the stream. + +The Read and Write functions must not be overloaded subprograms. If necessary +renamings can be supplied to meet this requirement. +The usage of this attribute is best illustrated by a simple example, taken +from the GNAT implementation of package Ada.Strings.Unbounded: + + +.. code-block:: ada + + function To_Unbounded (S : String) return Unbounded_String + renames To_Unbounded_String; + + pragma Stream_Convert + (Unbounded_String, To_Unbounded, To_String); + + +The specifications of the referenced functions, as given in the Ada +Reference Manual are: + + +.. code-block:: ada + + function To_Unbounded_String (Source : String) + return Unbounded_String; + + function To_String (Source : Unbounded_String) + return String; + + +The effect is that if the value of an unbounded string is written to a stream, +then the representation of the item in the stream is in the same format that +would be used for `Standard.String'Output`, and this same representation +is expected when a value of this type is read from the stream. Note that the +value written always includes the bounds, even for Unbounded_String'Write, +since Unbounded_String is not an array type. + +Note that the `Stream_Convert` pragma is not effective in the case of +a derived type of a non-limited tagged type. If such a type is specified then +the pragma is silently ignored, and the default implementation of the stream +attributes is used instead. + +Pragma Style_Checks +=================== + +Syntax: + + +:: + + pragma Style_Checks (string_LITERAL | ALL_CHECKS | + On | Off [, LOCAL_NAME]); + + +This pragma is used in conjunction with compiler switches to control the +built in style checking provided by GNAT. The compiler switches, if set, +provide an initial setting for the switches, and this pragma may be used +to modify these settings, or the settings may be provided entirely by +the use of the pragma. This pragma can be used anywhere that a pragma +is legal, including use as a configuration pragma (including use in +the :file:`gnat.adc` file). + +The form with a string literal specifies which style options are to be +activated. These are additive, so they apply in addition to any previously +set style check options. The codes for the options are the same as those +used in the *-gnaty* switch to *gcc* or *gnatmake*. +For example the following two methods can be used to enable +layout checking: + +* + + :: + + pragma Style_Checks ("l"); + + +* + + :: + + gcc -c -gnatyl ... + + +The form ALL_CHECKS activates all standard checks (its use is equivalent +to the use of the `gnaty` switch with no options. +See the :title:`GNAT User's Guide` for details.) + +Note: the behavior is slightly different in GNAT mode (*-gnatg* used). +In this case, ALL_CHECKS implies the standard set of GNAT mode style check +options (i.e. equivalent to *-gnatyg*). + +The forms with `Off` and `On` +can be used to temporarily disable style checks +as shown in the following example: + + +.. code-block:: ada + + pragma Style_Checks ("k"); -- requires keywords in lower case + pragma Style_Checks (Off); -- turn off style checks + NULL; -- this will not generate an error message + pragma Style_Checks (On); -- turn style checks back on + NULL; -- this will generate an error message + + +Finally the two argument form is allowed only if the first argument is +`On` or `Off`. The effect is to turn of semantic style checks +for the specified entity, as shown in the following example: + + +.. code-block:: ada + + pragma Style_Checks ("r"); -- require consistency of identifier casing + Arg : Integer; + Rf1 : Integer := ARG; -- incorrect, wrong case + pragma Style_Checks (Off, Arg); + Rf2 : Integer := ARG; -- OK, no error + + +Pragma Subtitle +=============== + +Syntax: + + +:: + + pragma Subtitle ([Subtitle =>] STRING_LITERAL); + + +This pragma is recognized for compatibility with other Ada compilers +but is ignored by GNAT. + +Pragma Suppress +=============== + +Syntax: + + +:: + + pragma Suppress (Identifier [, [On =>] Name]); + + +This is a standard pragma, and supports all the check names required in +the RM. It is included here because GNAT recognizes some additional check +names that are implementation defined (as permitted by the RM): + + +* + `Alignment_Check` can be used to suppress alignment checks + on addresses used in address clauses. Such checks can also be suppressed + by suppressing range checks, but the specific use of `Alignment_Check` + allows suppression of alignment checks without suppressing other range checks. + +* + `Atomic_Synchronization` can be used to suppress the special memory + synchronization instructions that are normally generated for access to + `Atomic` variables to ensure correct synchronization between tasks + that use such variables for synchronization purposes. + +* + `Duplicated_Tag_Check` Can be used to suppress the check that is generated + for a duplicated tag value when a tagged type is declared. + +* + `Predicate_Check` can be used to control whether predicate checks are + active. It is applicable only to predicates for which the policy is + `Check`. Unlike `Assertion_Policy`, which determines if a given + predicate is ignored or checked for the whole program, the use of + `Suppress` and `Unsuppress` with this check name allows a given + predicate to be turned on and off at specific points in the program. + +* + `Validity_Check` can be used specifically to control validity checks. + If `Suppress` is used to suppress validity checks, then no validity + checks are performed, including those specified by the appropriate compiler + switch or the `Validity_Checks` pragma. + +* + Additional check names previously introduced by use of the `Check_Name` + pragma are also allowed. + + +Note that pragma Suppress gives the compiler permission to omit +checks, but does not require the compiler to omit checks. The compiler +will generate checks if they are essentially free, even when they are +suppressed. In particular, if the compiler can prove that a certain +check will necessarily fail, it will generate code to do an +unconditional 'raise', even if checks are suppressed. The compiler +warns in this case. + +Of course, run-time checks are omitted whenever the compiler can prove +that they will not fail, whether or not checks are suppressed. + +Pragma Suppress_All +=================== + +Syntax: + + +.. code-block:: ada + + pragma Suppress_All; + + +This pragma can appear anywhere within a unit. +The effect is to apply `Suppress (All_Checks)` to the unit +in which it appears. This pragma is implemented for compatibility with DEC +Ada 83 usage where it appears at the end of a unit, and for compatibility +with Rational Ada, where it appears as a program unit pragma. +The use of the standard Ada pragma `Suppress (All_Checks)` +as a normal configuration pragma is the preferred usage in GNAT. + +Pragma Suppress_Debug_Info +========================== + +Syntax: + + +:: + + pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME); + + +This pragma can be used to suppress generation of debug information +for the specified entity. It is intended primarily for use in debugging +the debugger, and navigating around debugger problems. + +Pragma Suppress_Exception_Locations +=================================== + +Syntax: + + +.. code-block:: ada + + pragma Suppress_Exception_Locations; + + +In normal mode, a raise statement for an exception by default generates +an exception message giving the file name and line number for the location +of the raise. This is useful for debugging and logging purposes, but this +entails extra space for the strings for the messages. The configuration +pragma `Suppress_Exception_Locations` can be used to suppress the +generation of these strings, with the result that space is saved, but the +exception message for such raises is null. This configuration pragma may +appear in a global configuration pragma file, or in a specific unit as +usual. It is not required that this pragma be used consistently within +a partition, so it is fine to have some units within a partition compiled +with this pragma and others compiled in normal mode without it. + +Pragma Suppress_Initialization +============================== +.. index:: Suppressing initialization + +.. index:: Initialization, suppression of + +Syntax: + + +:: + + pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name); + + +Here variable_or_subtype_Name is the name introduced by a type declaration +or subtype declaration or the name of a variable introduced by an +object declaration. + +In the case of a type or subtype +this pragma suppresses any implicit or explicit initialization +for all variables of the given type or subtype, +including initialization resulting from the use of pragmas +Normalize_Scalars or Initialize_Scalars. + +This is considered a representation item, so it cannot be given after +the type is frozen. It applies to all subsequent object declarations, +and also any allocator that creates objects of the type. + +If the pragma is given for the first subtype, then it is considered +to apply to the base type and all its subtypes. If the pragma is given +for other than a first subtype, then it applies only to the given subtype. +The pragma may not be given after the type is frozen. + +Note that this includes eliminating initialization of discriminants +for discriminated types, and tags for tagged types. In these cases, +you will have to use some non-portable mechanism (e.g. address +overlays or unchecked conversion) to achieve required initialization +of these fields before accessing any object of the corresponding type. + +For the variable case, implicit initialization for the named variable +is suppressed, just as though its subtype had been given in a pragma +Suppress_Initialization, as described above. + +Pragma Task_Name +================ + +Syntax + + +.. code-block:: ada + + pragma Task_Name (string_EXPRESSION); + + +This pragma appears within a task definition (like pragma +`Priority`) and applies to the task in which it appears. The +argument must be of type String, and provides a name to be used for +the task instance when the task is created. Note that this expression +is not required to be static, and in particular, it can contain +references to task discriminants. This facility can be used to +provide different names for different tasks as they are created, +as illustrated in the example below. + +The task name is recorded internally in the run-time structures +and is accessible to tools like the debugger. In addition the +routine `Ada.Task_Identification.Image` will return this +string, with a unique task address appended. + + +.. code-block:: ada + + -- Example of the use of pragma Task_Name + + with Ada.Task_Identification; + use Ada.Task_Identification; + with Text_IO; use Text_IO; + procedure t3 is + + type Astring is access String; + + task type Task_Typ (Name : access String) is + pragma Task_Name (Name.all); + end Task_Typ; + + task body Task_Typ is + Nam : constant String := Image (Current_Task); + begin + Put_Line ("-->" & Nam (1 .. 14) & "<--"); + end Task_Typ; + + type Ptr_Task is access Task_Typ; + Task_Var : Ptr_Task; + + begin + Task_Var := + new Task_Typ (new String'("This is task 1")); + Task_Var := + new Task_Typ (new String'("This is task 2")); + end; + + +Pragma Task_Storage +=================== +Syntax: + + +:: + + pragma Task_Storage ( + [Task_Type =>] LOCAL_NAME, + [Top_Guard =>] static_integer_EXPRESSION); + + +This pragma specifies the length of the guard area for tasks. The guard +area is an additional storage area allocated to a task. A value of zero +means that either no guard area is created or a minimal guard area is +created, depending on the target. This pragma can appear anywhere a +`Storage_Size` attribute definition clause is allowed for a task +type. + +Pragma Test_Case +================ +.. index:: Test cases + + +Syntax: + + +:: + + pragma Test_Case ( + [Name =>] static_string_Expression + ,[Mode =>] (Nominal | Robustness) + [, Requires => Boolean_Expression] + [, Ensures => Boolean_Expression]); + + +The `Test_Case` pragma allows defining fine-grain specifications +for use by testing tools. +The compiler checks the validity of the `Test_Case` pragma, but its +presence does not lead to any modification of the code generated by the +compiler. + +`Test_Case` pragmas may only appear immediately following the +(separate) declaration of a subprogram in a package declaration, inside +a package spec unit. Only other pragmas may intervene (that is appear +between the subprogram declaration and a test case). + +The compiler checks that boolean expressions given in `Requires` and +`Ensures` are valid, where the rules for `Requires` are the +same as the rule for an expression in `Precondition` and the rules +for `Ensures` are the same as the rule for an expression in +`Postcondition`. In particular, attributes `'Old` and +`'Result` can only be used within the `Ensures` +expression. The following is an example of use within a package spec: + + +.. code-block:: ada + + package Math_Functions is + ... + function Sqrt (Arg : Float) return Float; + pragma Test_Case (Name => "Test 1", + Mode => Nominal, + Requires => Arg < 10000, + Ensures => Sqrt'Result < 10); + ... + end Math_Functions; + + +The meaning of a test case is that there is at least one context where +`Requires` holds such that, if the associated subprogram is executed in +that context, then `Ensures` holds when the subprogram returns. +Mode `Nominal` indicates that the input context should also satisfy the +precondition of the subprogram, and the output context should also satisfy its +postcondition. Mode `Robustness` indicates that the precondition and +postcondition of the subprogram should be ignored for this test case. + +Pragma Thread_Local_Storage +=========================== +.. index:: Task specific storage + +.. index:: TLS (Thread Local Storage) + +.. index:: Task_Attributes + +Syntax: + + +:: + + pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME); + + +This pragma specifies that the specified entity, which must be +a variable declared in a library level package, is to be marked as +"Thread Local Storage" (`TLS`). On systems supporting this (which +include Solaris, GNU/Linux and VxWorks 6), this causes each thread +(and hence each Ada task) to see a distinct copy of the variable. + +The variable may not have default initialization, and if there is +an explicit initialization, it must be either `null` for an +access variable, or a static expression for a scalar variable. +This provides a low level mechanism similar to that provided by +the `Ada.Task_Attributes` package, but much more efficient +and is also useful in writing interface code that will interact +with foreign threads. + +If this pragma is used on a system where `TLS` is not supported, +then an error message will be generated and the program will be rejected. + +Pragma Time_Slice +================= + +Syntax: + + +.. code-block:: ada + + pragma Time_Slice (static_duration_EXPRESSION); + + +For implementations of GNAT on operating systems where it is possible +to supply a time slice value, this pragma may be used for this purpose. +It is ignored if it is used in a system that does not allow this control, +or if it appears in other than the main program unit. + +Pragma Title +============ + +Syntax: + + +:: + + pragma Title (TITLING_OPTION [, TITLING OPTION]); + + TITLING_OPTION ::= + [Title =>] STRING_LITERAL, + | [Subtitle =>] STRING_LITERAL + + +Syntax checked but otherwise ignored by GNAT. This is a listing control +pragma used in DEC Ada 83 implementations to provide a title and/or +subtitle for the program listing. The program listing generated by GNAT +does not have titles or subtitles. + +Unlike other pragmas, the full flexibility of named notation is allowed +for this pragma, i.e., the parameters may be given in any order if named +notation is used, and named and positional notation can be mixed +following the normal rules for procedure calls in Ada. + +Pragma Type_Invariant +===================== + +Syntax: + + +:: + + pragma Type_Invariant + ([Entity =>] type_LOCAL_NAME, + [Check =>] EXPRESSION); + + +The `Type_Invariant` pragma is intended to be an exact +replacement for the language-defined `Type_Invariant` +aspect, and shares its restrictions and semantics. It differs +from the language defined `Invariant` pragma in that it +does not permit a string parameter, and it is +controlled by the assertion identifier `Type_Invariant` +rather than `Invariant`. + +Pragma Type_Invariant_Class +=========================== + +Syntax: + + +:: + + pragma Type_Invariant_Class + ([Entity =>] type_LOCAL_NAME, + [Check =>] EXPRESSION); + + +The `Type_Invariant_Class` pragma is intended to be an exact +replacement for the language-defined `Type_Invariant'Class` +aspect, and shares its restrictions and semantics. + +Note: This pragma is called `Type_Invariant_Class` rather than +`Type_Invariant'Class` because the latter would not be strictly +conforming to the allowed syntax for pragmas. The motivation +for providing pragmas equivalent to the aspects is to allow a program +to be written using the pragmas, and then compiled if necessary +using an Ada compiler that does not recognize the pragmas or +aspects, but is prepared to ignore the pragmas. The assertion +policy that controls this pragma is `Type_Invariant'Class`, +not `Type_Invariant_Class`. + +Pragma Unchecked_Union +====================== +.. index:: Unions in C + + +Syntax: + + +.. code-block:: ada + + pragma Unchecked_Union (first_subtype_LOCAL_NAME); + + +This pragma is used to specify a representation of a record type that is +equivalent to a C union. It was introduced as a GNAT implementation defined +pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this +pragma, making it language defined, and GNAT fully implements this extended +version in all language modes (Ada 83, Ada 95, and Ada 2005). For full +details, consult the Ada 2012 Reference Manual, section B.3.3. + +Pragma Unevaluated_Use_Of_Old +============================= +.. index:: Attribute Old + +.. index:: Attribute Loop_Entry + +.. index:: Unevaluated_Use_Of_Old + + +Syntax: + + +.. code-block:: ada + + pragma Unevaluated_Use_Of_Old (Error | Warn | Allow); + + +This pragma controls the processing of attributes Old and Loop_Entry. +If either of these attributes is used in a potentially unevaluated +expression (e.g. the then or else parts of an if expression), then +normally this usage is considered illegal if the prefix of the attribute +is other than an entity name. The language requires this +behavior for Old, and GNAT copies the same rule for Loop_Entry. + +The reason for this rule is that otherwise, we can have a situation +where we save the Old value, and this results in an exception, even +though we might not evaluate the attribute. Consider this example: + + +.. code-block:: ada + + package UnevalOld is + K : Character; + procedure U (A : String; C : Boolean) -- ERROR + with Post => (if C then A(1)'Old = K else True); + end; + + +If procedure U is called with a string with a lower bound of 2, and +C false, then an exception would be raised trying to evaluate A(1) +on entry even though the value would not be actually used. + +Although the rule guarantees against this possibility, it is sometimes +too restrictive. For example if we know that the string has a lower +bound of 1, then we will never raise an exception. +The pragma `Unevaluated_Use_Of_Old` can be +used to modify this behavior. If the argument is `Error` then an +error is given (this is the default RM behavior). If the argument is +`Warn` then the usage is allowed as legal but with a warning +that an exception might be raised. If the argument is `Allow` +then the usage is allowed as legal without generating a warning. + +This pragma may appear as a configuration pragma, or in a declarative +part or package specification. In the latter case it applies to +uses up to the end of the corresponding statement sequence or +sequence of package declarations. + +Pragma Unimplemented_Unit +========================= + +Syntax: + + +.. code-block:: ada + + pragma Unimplemented_Unit; + + +If this pragma occurs in a unit that is processed by the compiler, GNAT +aborts with the message :samp:`xxx not implemented`, where +`xxx` is the name of the current compilation unit. This pragma is +intended to allow the compiler to handle unimplemented library units in +a clean manner. + +The abort only happens if code is being generated. Thus you can use +specs of unimplemented packages in syntax or semantic checking mode. + +Pragma Universal_Aliasing +========================= + +Syntax: + + +:: + + pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)]; + + +`type_LOCAL_NAME` must refer to a type declaration in the current +declarative part. The effect is to inhibit strict type-based aliasing +optimization for the given type. In other words, the effect is as though +access types designating this type were subject to pragma No_Strict_Aliasing. +For a detailed description of the strict aliasing optimization, and the +situations in which it must be suppressed, see the section on +`Optimization and Strict Aliasing` in the :title:`GNAT User's Guide`. + +Pragma Universal_Data +===================== + +Syntax: + + +:: + + pragma Universal_Data [(library_unit_Name)]; + + +This pragma is supported only for the AAMP target and is ignored for +other targets. The pragma specifies that all library-level objects +(Counter 0 data) associated with the library unit are to be accessed +and updated using universal addressing (24-bit addresses for AAMP5) +rather than the default of 16-bit Data Environment (DENV) addressing. +Use of this pragma will generally result in less efficient code for +references to global data associated with the library unit, but +allows such data to be located anywhere in memory. This pragma is +a library unit pragma, but can also be used as a configuration pragma +(including use in the :file:`gnat.adc` file). The functionality +of this pragma is also available by applying the -univ switch on the +compilations of units where universal addressing of the data is desired. + +Pragma Unmodified +================= +.. index:: Warnings, unmodified + +Syntax: + + +:: + + pragma Unmodified (LOCAL_NAME {, LOCAL_NAME}); + + +This pragma signals that the assignable entities (variables, +`out` parameters, `in out` parameters) whose names are listed are +deliberately not assigned in the current source unit. This +suppresses warnings about the +entities being referenced but not assigned, and in addition a warning will be +generated if one of these entities is in fact assigned in the +same unit as the pragma (or in the corresponding body, or one +of its subunits). + +This is particularly useful for clearly signaling that a particular +parameter is not modified, even though the spec suggests that it might +be. + +For the variable case, warnings are never given for unreferenced variables +whose name contains one of the substrings +`DISCARD, DUMMY, IGNORE, JUNK, UNUSED` in any casing. Such names +are typically to be used in cases where such warnings are expected. +Thus it is never necessary to use `pragma Unmodified` for such +variables, though it is harmless to do so. + +Pragma Unreferenced +=================== +.. index:: Warnings, unreferenced + +Syntax: + + +:: + + pragma Unreferenced (LOCAL_NAME {, LOCAL_NAME}); + pragma Unreferenced (library_unit_NAME {, library_unit_NAME}); + + +This pragma signals that the entities whose names are listed are +deliberately not referenced in the current source unit after the +occurrence of the pragma. This +suppresses warnings about the +entities being unreferenced, and in addition a warning will be +generated if one of these entities is in fact subsequently referenced in the +same unit as the pragma (or in the corresponding body, or one +of its subunits). + +This is particularly useful for clearly signaling that a particular +parameter is not referenced in some particular subprogram implementation +and that this is deliberate. It can also be useful in the case of +objects declared only for their initialization or finalization side +effects. + +If `LOCAL_NAME` identifies more than one matching homonym in the +current scope, then the entity most recently declared is the one to which +the pragma applies. Note that in the case of accept formals, the pragma +Unreferenced may appear immediately after the keyword `do` which +allows the indication of whether or not accept formals are referenced +or not to be given individually for each accept statement. + +The left hand side of an assignment does not count as a reference for the +purpose of this pragma. Thus it is fine to assign to an entity for which +pragma Unreferenced is given. + +Note that if a warning is desired for all calls to a given subprogram, +regardless of whether they occur in the same unit as the subprogram +declaration, then this pragma should not be used (calls from another +unit would not be flagged); pragma Obsolescent can be used instead +for this purpose, see :ref:`Pragma_Obsolescent`. + +The second form of pragma `Unreferenced` is used within a context +clause. In this case the arguments must be unit names of units previously +mentioned in `with` clauses (similar to the usage of pragma +`Elaborate_All`. The effect is to suppress warnings about unreferenced +units and unreferenced entities within these units. + +For the variable case, warnings are never given for unreferenced variables +whose name contains one of the substrings +`DISCARD, DUMMY, IGNORE, JUNK, UNUSED` in any casing. Such names +are typically to be used in cases where such warnings are expected. +Thus it is never necessary to use `pragma Unreferenced` for such +variables, though it is harmless to do so. + +Pragma Unreferenced_Objects +=========================== +.. index:: Warnings, unreferenced + +Syntax: + + +:: + + pragma Unreferenced_Objects (local_subtype_NAME {, local_subtype_NAME}); + + +This pragma signals that for the types or subtypes whose names are +listed, objects which are declared with one of these types or subtypes may +not be referenced, and if no references appear, no warnings are given. + +This is particularly useful for objects which are declared solely for their +initialization and finalization effect. Such variables are sometimes referred +to as RAII variables (Resource Acquisition Is Initialization). Using this +pragma on the relevant type (most typically a limited controlled type), the +compiler will automatically suppress unwanted warnings about these variables +not being referenced. + +Pragma Unreserve_All_Interrupts +=============================== + +Syntax: + + +.. code-block:: ada + + pragma Unreserve_All_Interrupts; + + +Normally certain interrupts are reserved to the implementation. Any attempt +to attach an interrupt causes Program_Error to be raised, as described in +RM C.3.2(22). A typical example is the `SIGINT` interrupt used in +many systems for a :kbd:`Ctrl-C` interrupt. Normally this interrupt is +reserved to the implementation, so that :kbd:`Ctrl-C` can be used to +interrupt execution. + +If the pragma `Unreserve_All_Interrupts` appears anywhere in any unit in +a program, then all such interrupts are unreserved. This allows the +program to handle these interrupts, but disables their standard +functions. For example, if this pragma is used, then pressing +:kbd:`Ctrl-C` will not automatically interrupt execution. However, +a program can then handle the `SIGINT` interrupt as it chooses. + +For a full list of the interrupts handled in a specific implementation, +see the source code for the spec of `Ada.Interrupts.Names` in +file :file:`a-intnam.ads`. This is a target dependent file that contains the +list of interrupts recognized for a given target. The documentation in +this file also specifies what interrupts are affected by the use of +the `Unreserve_All_Interrupts` pragma. + +For a more general facility for controlling what interrupts can be +handled, see pragma `Interrupt_State`, which subsumes the functionality +of the `Unreserve_All_Interrupts` pragma. + +Pragma Unsuppress +================= + +Syntax: + + +:: + + pragma Unsuppress (IDENTIFIER [, [On =>] NAME]); + + +This pragma undoes the effect of a previous pragma `Suppress`. If +there is no corresponding pragma `Suppress` in effect, it has no +effect. The range of the effect is the same as for pragma +`Suppress`. The meaning of the arguments is identical to that used +in pragma `Suppress`. + +One important application is to ensure that checks are on in cases where +code depends on the checks for its correct functioning, so that the code +will compile correctly even if the compiler switches are set to suppress +checks. For example, in a program that depends on external names of tagged +types and wants to ensure that the duplicated tag check occurs even if all +run-time checks are suppressed by a compiler switch, the following +configuration pragma will ensure this test is not suppressed: + + +.. code-block:: ada + + pragma Unsuppress (Duplicated_Tag_Check); + + +This pragma is standard in Ada 2005. It is available in all earlier versions +of Ada as an implementation-defined pragma. + +Note that in addition to the checks defined in the Ada RM, GNAT recogizes +a number of implementation-defined check names. See description of pragma +`Suppress` for full details. + +Pragma Use_VADS_Size +==================== +.. index:: Size, VADS compatibility + +.. index:: Rational profile + + +Syntax: + + +.. code-block:: ada + + pragma Use_VADS_Size; + + +This is a configuration pragma. In a unit to which it applies, any use +of the 'Size attribute is automatically interpreted as a use of the +'VADS_Size attribute. Note that this may result in incorrect semantic +processing of valid Ada 95 or Ada 2005 programs. This is intended to aid in +the handling of existing code which depends on the interpretation of Size +as implemented in the VADS compiler. See description of the VADS_Size +attribute for further details. + +Pragma Validity_Checks +====================== + +Syntax: + + +.. code-block:: ada + + pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off); + + +This pragma is used in conjunction with compiler switches to control the +built-in validity checking provided by GNAT. The compiler switches, if set +provide an initial setting for the switches, and this pragma may be used +to modify these settings, or the settings may be provided entirely by +the use of the pragma. This pragma can be used anywhere that a pragma +is legal, including use as a configuration pragma (including use in +the :file:`gnat.adc` file). + +The form with a string literal specifies which validity options are to be +activated. The validity checks are first set to include only the default +reference manual settings, and then a string of letters in the string +specifies the exact set of options required. The form of this string +is exactly as described for the *-gnatVx* compiler switch (see the +GNAT User's Guide for details). For example the following two +methods can be used to enable validity checking for mode `in` and +`in out` subprogram parameters: + +* + + .. code-block:: ada + + pragma Validity_Checks ("im"); + + +* + + .. code-block:: sh + + $ gcc -c -gnatVim ... + + +The form ALL_CHECKS activates all standard checks (its use is equivalent +to the use of the `gnatva` switch. + +The forms with `Off` and `On` +can be used to temporarily disable validity checks +as shown in the following example: + + +.. code-block:: ada + + pragma Validity_Checks ("c"); -- validity checks for copies + pragma Validity_Checks (Off); -- turn off validity checks + A := B; -- B will not be validity checked + pragma Validity_Checks (On); -- turn validity checks back on + A := C; -- C will be validity checked + + +Pragma Volatile +=============== + +Syntax: + + +.. code-block:: ada + + pragma Volatile (LOCAL_NAME); + + +This pragma is defined by the Ada Reference Manual, and the GNAT +implementation is fully conformant with this definition. The reason it +is mentioned in this section is that a pragma of the same name was supplied +in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005 +implementation of pragma Volatile is upwards compatible with the +implementation in DEC Ada 83. + +Pragma Warning_As_Error +======================= + +Syntax: + + +.. code-block:: ada + + pragma Warning_As_Error (static_string_EXPRESSION); + + +This configuration pragma allows the programmer to specify a set +of warnings that will be treated as errors. Any warning which +matches the pattern given by the pragma argument will be treated +as an error. This gives much more precise control that -gnatwe +which treats all warnings as errors. + +The pattern may contain asterisks, which match zero or more characters in +the message. For example, you can use +`pragma Warning_As_Error ("bits of*unused")` to treat the warning +message `warning: 960 bits of "a" unused` as an error. No other regular +expression notations are permitted. All characters other than asterisk in +these three specific cases are treated as literal characters in the match. +The match is case insensitive, for example XYZ matches xyz. + +Note that the pattern matches if it occurs anywhere within the warning +message string (it is not necessary to put an asterisk at the start and +the end of the message, since this is implied). + +Another possibility for the static_string_EXPRESSION which works whether +or not error tags are enabled (*-gnatw.d*) is to use the +*-gnatw* tag string, enclosed in brackets, +as shown in the example below, to treat a class of warnings as errors. + +The above use of patterns to match the message applies only to warning +messages generated by the front end. This pragma can also be applied to +warnings provided by the back end and mentioned in :ref:`Pragma_Warnings`. +By using a single full *-Wxxx* switch in the pragma, such warnings +can also be treated as errors. + +The pragma can appear either in a global configuration pragma file +(e.g. :file:`gnat.adc`), or at the start of a file. Given a global +configuration pragma file containing: + + +.. code-block:: ada + + pragma Warning_As_Error ("[-gnatwj]"); + + +which will treat all obsolescent feature warnings as errors, the +following program compiles as shown (compile options here are +*-gnatwa.d -gnatl -gnatj55*). + + +:: + + 1. pragma Warning_As_Error ("*never assigned*"); + 2. function Warnerr return String is + 3. X : Integer; + | + >>> error: variable "X" is never read and + never assigned [-gnatwv] [warning-as-error] + + 4. Y : Integer; + | + >>> warning: variable "Y" is assigned but + never read [-gnatwu] + + 5. begin + 6. Y := 0; + 7. return %ABC%; + | + >>> error: use of "%" is an obsolescent + feature (RM J.2(4)), use """ instead + [-gnatwj] [warning-as-error] + + 8. end; + + 8 lines: No errors, 3 warnings (2 treated as errors) + + +Note that this pragma does not affect the set of warnings issued in +any way, it merely changes the effect of a matching warning if one +is produced as a result of other warnings options. As shown in this +example, if the pragma results in a warning being treated as an error, +the tag is changed from "warning:" to "error:" and the string +"[warning-as-error]" is appended to the end of the message. + +.. _Pragma_Warnings: + +Pragma Warnings +=============== + +Syntax: + + +.. code-block:: ada + + pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]); + + DETAILS ::= On | Off + DETAILS ::= On | Off, local_NAME + DETAILS ::= static_string_EXPRESSION + DETAILS ::= On | Off, static_string_EXPRESSION + + TOOL_NAME ::= GNAT | GNATProve + + REASON ::= Reason => STRING_LITERAL {& STRING_LITERAL} + +Note: in Ada 83 mode, a string literal may be used in place of a static string +expression (which does not exist in Ada 83). + +Note if the second argument of `DETAILS` is a `local_NAME` then the +second form is always understood. If the intention is to use +the fourth form, then you can write `NAME & ""` to force the +intepretation as a `static_string_EXPRESSION`. + +Note: if the first argument is a valid `TOOL_NAME`, it will be interpreted +that way. The use of the `TOOL_NAME` argument is relevant only to users +of SPARK and GNATprove, see last part of this section for details. + +Normally warnings are enabled, with the output being controlled by +the command line switch. Warnings (`Off`) turns off generation of +warnings until a Warnings (`On`) is encountered or the end of the +current unit. If generation of warnings is turned off using this +pragma, then some or all of the warning messages are suppressed, +regardless of the setting of the command line switches. + +The `Reason` parameter may optionally appear as the last argument +in any of the forms of this pragma. It is intended purely for the +purposes of documenting the reason for the `Warnings` pragma. +The compiler will check that the argument is a static string but +otherwise ignore this argument. Other tools may provide specialized +processing for this string. + +The form with a single argument (or two arguments if Reason present), +where the first argument is `ON` or `OFF` +may be used as a configuration pragma. + +If the `LOCAL_NAME` parameter is present, warnings are suppressed for +the specified entity. This suppression is effective from the point where +it occurs till the end of the extended scope of the variable (similar to +the scope of `Suppress`). This form cannot be used as a configuration +pragma. + +In the case where the first argument is other than `ON` or +`OFF`, +the third form with a single static_string_EXPRESSION argument (and possible +reason) provides more precise +control over which warnings are active. The string is a list of letters +specifying which warnings are to be activated and which deactivated. The +code for these letters is the same as the string used in the command +line switch controlling warnings. For a brief summary, use the gnatmake +command with no arguments, which will generate usage information containing +the list of warnings switches supported. For +full details see the section on `Warning Message Control` in the +:title:`GNAT User's Guide`. +This form can also be used as a configuration pragma. + +The warnings controlled by the *-gnatw* switch are generated by the +front end of the compiler. The GCC back end can provide additional warnings +and they are controlled by the *-W* switch. Such warnings can be +identified by the appearance of a string of the form `[-Wxxx]` in the +message which designates the *-Wxxx* switch that controls the message. +The form with a single static_string_EXPRESSION argument also works for these +warnings, but the string must be a single full *-Wxxx* switch in this +case. The above reference lists a few examples of these additional warnings. + +The specified warnings will be in effect until the end of the program +or another pragma Warnings is encountered. The effect of the pragma is +cumulative. Initially the set of warnings is the standard default set +as possibly modified by compiler switches. Then each pragma Warning +modifies this set of warnings as specified. This form of the pragma may +also be used as a configuration pragma. + +The fourth form, with an `On|Off` parameter and a string, is used to +control individual messages, based on their text. The string argument +is a pattern that is used to match against the text of individual +warning messages (not including the initial "warning: " tag). + +The pattern may contain asterisks, which match zero or more characters in +the message. For example, you can use +`pragma Warnings (Off, "bits of*unused")` to suppress the warning +message `warning: 960 bits of "a" unused`. No other regular +expression notations are permitted. All characters other than asterisk in +these three specific cases are treated as literal characters in the match. +The match is case insensitive, for example XYZ matches xyz. + +Note that the pattern matches if it occurs anywhere within the warning +message string (it is not necessary to put an asterisk at the start and +the end of the message, since this is implied). + +The above use of patterns to match the message applies only to warning +messages generated by the front end. This form of the pragma with a string +argument can also be used to control warnings provided by the back end and +mentioned above. By using a single full *-Wxxx* switch in the pragma, +such warnings can be turned on and off. + +There are two ways to use the pragma in this form. The OFF form can be used +as a configuration pragma. The effect is to suppress all warnings (if any) +that match the pattern string throughout the compilation (or match the +-W switch in the back end case). + +The second usage is to suppress a warning locally, and in this case, two +pragmas must appear in sequence: + + +.. code-block:: ada + + pragma Warnings (Off, Pattern); + ... code where given warning is to be suppressed + pragma Warnings (On, Pattern); + + +In this usage, the pattern string must match in the Off and On +pragmas, and (if *-gnatw.w* is given) at least one matching +warning must be suppressed. + +Note: to write a string that will match any warning, use the string +`"***"`. It will not work to use a single asterisk or two +asterisks since this looks like an operator name. This form with three +asterisks is similar in effect to specifying `pragma Warnings (Off)` except (if *-gnatw.w* is given) that a matching +`pragma Warnings (On, "***")` will be required. This can be +helpful in avoiding forgetting to turn warnings back on. + +Note: the debug flag -gnatd.i (`/NOWARNINGS_PRAGMAS` in VMS) can be +used to cause the compiler to entirely ignore all WARNINGS pragmas. This can +be useful in checking whether obsolete pragmas in existing programs are hiding +real problems. + +Note: pragma Warnings does not affect the processing of style messages. See +separate entry for pragma Style_Checks for control of style messages. + +Users of the formal verification tool GNATprove for the SPARK subset of Ada may +use the version of the pragma with a `TOOL_NAME` parameter. + +If present, `TOOL_NAME` is the name of a tool, currently either `GNAT` for the +compiler or `GNATprove` for the formal verification tool. A given tool only +takes into account pragma Warnings that do not specify a tool name, or that +specify the matching tool name. This makes it possible to disable warnings +selectively for each tool, and as a consequence to detect useless pragma +Warnings with switch `-gnatw.w`. + +Pragma Weak_External +==================== + +Syntax: + + +.. code-block:: ada + + pragma Weak_External ([Entity =>] LOCAL_NAME); + + +`LOCAL_NAME` must refer to an object that is declared at the library +level. This pragma specifies that the given entity should be marked as a +weak symbol for the linker. It is equivalent to `__attribute__((weak))` +in GNU C and causes `LOCAL_NAME` to be emitted as a weak symbol instead +of a regular symbol, that is to say a symbol that does not have to be +resolved by the linker if used in conjunction with a pragma Import. + +When a weak symbol is not resolved by the linker, its address is set to +zero. This is useful in writing interfaces to external modules that may +or may not be linked in the final executable, for example depending on +configuration settings. + +If a program references at run time an entity to which this pragma has been +applied, and the corresponding symbol was not resolved at link time, then +the execution of the program is erroneous. It is not erroneous to take the +Address of such an entity, for example to guard potential references, +as shown in the example below. + +Some file formats do not support weak symbols so not all target machines +support this pragma. + + +.. code-block:: ada + + -- Example of the use of pragma Weak_External + + package External_Module is + key : Integer; + pragma Import (C, key); + pragma Weak_External (key); + function Present return boolean; + end External_Module; + + with System; use System; + package body External_Module is + function Present return boolean is + begin + return key'Address /= System.Null_Address; + end Present; + end External_Module; + + +Pragma Wide_Character_Encoding +============================== + +Syntax: + + +.. code-block:: ada + + pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL); + + +This pragma specifies the wide character encoding to be used in program +source text appearing subsequently. It is a configuration pragma, but may +also be used at any point that a pragma is allowed, and it is permissible +to have more than one such pragma in a file, allowing multiple encodings +to appear within the same file. + +The argument can be an identifier or a character literal. In the identifier +case, it is one of `HEX`, `UPPER`, `SHIFT_JIS`, +`EUC`, `UTF8`, or `BRACKETS`. In the character literal +case it is correspondingly one of the characters :kbd:`h`, :kbd:`u`, +:kbd:`s`, :kbd:`e`, :kbd:`8`, or :kbd:`b`. + +Note that when the pragma is used within a file, it affects only the +encoding within that file, and does not affect withed units, specs, +or subunits. diff --git a/gcc/ada/doc/gnat_rm/implementation_of_ada_2012_features.rst b/gcc/ada/doc/gnat_rm/implementation_of_ada_2012_features.rst new file mode 100644 index 00000000000..5ae5faca67f --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_of_ada_2012_features.rst @@ -0,0 +1,1328 @@ +.. _Implementation_of_Ada_2012_Features: + +*********************************** +Implementation of Ada 2012 Features +*********************************** + +.. index:: Ada 2012 implementation status + +.. index:: -gnat12 option (gcc) + +.. index:: pragma Ada_2012 + +.. index:: configuration pragma Ada_2012 + +.. index:: Ada_2012 configuration pragma + +This chapter contains a complete list of Ada 2012 features that have been +implemented as of GNAT version 6.4. Generally, these features are only +available if the *-gnat12* (Ada 2012 features enabled) flag is set +or if the configuration pragma `Ada_2012` is used. + +However, new pragmas, attributes, and restrictions are +unconditionally available, since the Ada 95 standard allows the addition of +new pragmas, attributes, and restrictions (there are exceptions, which are +documented in the individual descriptions), and also certain packages +were made available in earlier versions of Ada. + +An ISO date (YYYY-MM-DD) appears in parentheses on the description line. +This date shows the implementation date of the feature. Any wavefront +subsequent to this date will contain the indicated feature, as will any +subsequent releases. A date of 0000-00-00 means that GNAT has always +implemented the feature, or implemented it as soon as it appeared as a +binding interpretation. + +Each feature corresponds to an Ada Issue ('AI') approved by the Ada +standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012. +The features are ordered based on the relevant sections of the Ada +Reference Manual ("RM"). When a given AI relates to multiple points +in the RM, the earliest is used. + +A complete description of the AIs may be found in +http://www.ada-auth.org/ai05-summary.html. + +.. index:: AI-0176 (Ada 2012 feature) + +* *AI-0176 Quantified expressions (2010-09-29)* + + Both universally and existentially quantified expressions are implemented. + They use the new syntax for iterators proposed in AI05-139-2, as well as + the standard Ada loop syntax. + + RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0) + +.. index:: AI-0079 (Ada 2012 feature) + +* *AI-0079 Allow other_format characters in source (2010-07-10)* + + Wide characters in the unicode category *other_format* are now allowed in + source programs between tokens, but not within a token such as an identifier. + + RM References: 2.01 (4/2) 2.02 (7) + +.. index:: AI-0091 (Ada 2012 feature) + +* *AI-0091 Do not allow other_format in identifiers (0000-00-00)* + + Wide characters in the unicode category *other_format* are not permitted + within an identifier, since this can be a security problem. The error + message for this case has been improved to be more specific, but GNAT has + never allowed such characters to appear in identifiers. + + RM References: 2.03 (3.1/2) 2.03 (4/2) 2.03 (5/2) 2.03 (5.1/2) 2.03 (5.2/2) 2.03 (5.3/2) 2.09 (2/2) + +.. index:: AI-0100 (Ada 2012 feature) + +* *AI-0100 Placement of pragmas (2010-07-01)* + + This AI is an earlier version of AI-163. It simplifies the rules + for legal placement of pragmas. In the case of lists that allow pragmas, if + the list may have no elements, then the list may consist solely of pragmas. + + RM References: 2.08 (7) + +.. index:: AI-0163 (Ada 2012 feature) + +* *AI-0163 Pragmas in place of null (2010-07-01)* + + A statement sequence may be composed entirely of pragmas. It is no longer + necessary to add a dummy `null` statement to make the sequence legal. + + RM References: 2.08 (7) 2.08 (16) + +.. index:: AI-0080 (Ada 2012 feature) + +* *AI-0080 'View of' not needed if clear from context (0000-00-00)* + + This is an editorial change only, described as non-testable in the AI. + + RM References: 3.01 (7) + +.. index:: AI-0183 (Ada 2012 feature) + +* *AI-0183 Aspect specifications (2010-08-16)* + + Aspect specifications have been fully implemented except for pre and post- + conditions, and type invariants, which have their own separate AI's. All + forms of declarations listed in the AI are supported. The following is a + list of the aspects supported (with GNAT implementation aspects marked) + +================================== =========== +Supported Aspect Source +================================== =========== + `Ada_2005` -- GNAT + `Ada_2012` -- GNAT + `Address` + `Alignment` + `Atomic` + `Atomic_Components` + `Bit_Order` + `Component_Size` + `Contract_Cases` -- GNAT + `Discard_Names` + `External_Tag` + `Favor_Top_Level` -- GNAT + `Inline` + `Inline_Always` -- GNAT + `Invariant` -- GNAT + `Machine_Radix` + `No_Return` + `Object_Size` -- GNAT + `Pack` + `Persistent_BSS` -- GNAT + `Post` + `Pre` + `Predicate` + `Preelaborable_Initialization` + `Pure_Function` -- GNAT + `Remote_Access_Type` -- GNAT + `Shared` -- GNAT + `Size` + `Storage_Pool` + `Storage_Size` + `Stream_Size` + `Suppress` + `Suppress_Debug_Info` -- GNAT + `Test_Case` -- GNAT + `Thread_Local_Storage` -- GNAT + `Type_Invariant` + `Unchecked_Union` + `Universal_Aliasing` -- GNAT + `Unmodified` -- GNAT + `Unreferenced` -- GNAT + `Unreferenced_Objects` -- GNAT + `Unsuppress` + `Value_Size` -- GNAT + `Volatile` + `Volatile_Components` + `Warnings` -- GNAT +================================== =========== + + Note that for aspects with an expression, e.g. `Size`, the expression is + treated like a default expression (visibility is analyzed at the point of + occurrence of the aspect, but evaluation of the expression occurs at the + freeze point of the entity involved). + + RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6) + 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03 + (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2) + 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2) + 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1) + 13.03.01 (0) + +.. index:: AI-0128 (Ada 2012 feature) + +* *AI-0128 Inequality is a primitive operation (0000-00-00)* + + If an equality operator ("=") is declared for a type, then the implicitly + declared inequality operator ("/=") is a primitive operation of the type. + This is the only reasonable interpretation, and is the one always implemented + by GNAT, but the RM was not entirely clear in making this point. + + RM References: 3.02.03 (6) 6.06 (6) + +.. index:: AI-0003 (Ada 2012 feature) + +* *AI-0003 Qualified expressions as names (2010-07-11)* + + In Ada 2012, a qualified expression is considered to be syntactically a name, + meaning that constructs such as `A'(F(X)).B` are now legal. This is + useful in disambiguating some cases of overloading. + + RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3) + 5.04 (7) + +.. index:: AI-0120 (Ada 2012 feature) + +* *AI-0120 Constant instance of protected object (0000-00-00)* + + This is an RM editorial change only. The section that lists objects that are + constant failed to include the current instance of a protected object + within a protected function. This has always been treated as a constant + in GNAT. + + RM References: 3.03 (21) + +.. index:: AI-0008 (Ada 2012 feature) + +* *AI-0008 General access to constrained objects (0000-00-00)* + + The wording in the RM implied that if you have a general access to a + constrained object, it could be used to modify the discriminants. This was + obviously not intended. `Constraint_Error` should be raised, and GNAT + has always done so in this situation. + + RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2) + +.. index:: AI-0093 (Ada 2012 feature) + +* *AI-0093 Additional rules use immutably limited (0000-00-00)* + + This is an editorial change only, to make more widespread use of the Ada 2012 + 'immutably limited'. + + RM References: 3.03 (23.4/3) + +.. index:: AI-0096 (Ada 2012 feature) + +* *AI-0096 Deriving from formal private types (2010-07-20)* + + In general it is illegal for a type derived from a formal limited type to be + nonlimited. This AI makes an exception to this rule: derivation is legal + if it appears in the private part of the generic, and the formal type is not + tagged. If the type is tagged, the legality check must be applied to the + private part of the package. + + RM References: 3.04 (5.1/2) 6.02 (7) + +.. index:: AI-0181 (Ada 2012 feature) + +* *AI-0181 Soft hyphen is a non-graphic character (2010-07-23)* + + From Ada 2005 on, soft hyphen is considered a non-graphic character, which + means that it has a special name (`SOFT_HYPHEN`) in conjunction with the + `Image` and `Value` attributes for the character types. Strictly + speaking this is an inconsistency with Ada 95, but in practice the use of + these attributes is so obscure that it will not cause problems. + + RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21) + +.. index:: AI-0182 (Ada 2012 feature) + +* *AI-0182 Additional forms for `Character'Value* (0000-00-00)` + + This AI allows `Character'Value` to accept the string `'?'` where + `?` is any character including non-graphic control characters. GNAT has + always accepted such strings. It also allows strings such as + `HEX_00000041` to be accepted, but GNAT does not take advantage of this + permission and raises `Constraint_Error`, as is certainly still + permitted. + + RM References: 3.05 (56/2) + +.. index:: AI-0214 (Ada 2012 feature) + +* *AI-0214 Defaulted discriminants for limited tagged (2010-10-01)* + + Ada 2012 relaxes the restriction that forbids discriminants of tagged types + to have default expressions by allowing them when the type is limited. It + is often useful to define a default value for a discriminant even though + it can't be changed by assignment. + + RM References: 3.07 (9.1/2) 3.07.02 (3) + +.. index:: AI-0102 (Ada 2012 feature) + +* *AI-0102 Some implicit conversions are illegal (0000-00-00)* + + It is illegal to assign an anonymous access constant to an anonymous access + variable. The RM did not have a clear rule to prevent this, but GNAT has + always generated an error for this usage. + + RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2) + +.. index:: AI-0158 (Ada 2012 feature) + +* *AI-0158 Generalizing membership tests (2010-09-16)* + + This AI extends the syntax of membership tests to simplify complex conditions + that can be expressed as membership in a subset of values of any type. It + introduces syntax for a list of expressions that may be used in loop contexts + as well. + + RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27) + +.. index:: AI-0173 (Ada 2012 feature) + +* *AI-0173 Testing if tags represent abstract types (2010-07-03)* + + The function `Ada.Tags.Type_Is_Abstract` returns `True` if invoked + with the tag of an abstract type, and `False` otherwise. + + RM References: 3.09 (7.4/2) 3.09 (12.4/2) + +.. index:: AI-0076 (Ada 2012 feature) + +* *AI-0076 function with controlling result (0000-00-00)* + + This is an editorial change only. The RM defines calls with controlling + results, but uses the term 'function with controlling result' without an + explicit definition. + + RM References: 3.09.02 (2/2) + +.. index:: AI-0126 (Ada 2012 feature) + +* *AI-0126 Dispatching with no declared operation (0000-00-00)* + + This AI clarifies dispatching rules, and simply confirms that dispatching + executes the operation of the parent type when there is no explicitly or + implicitly declared operation for the descendant type. This has always been + the case in all versions of GNAT. + + RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2) + +.. index:: AI-0097 (Ada 2012 feature) + +* *AI-0097 Treatment of abstract null extension (2010-07-19)* + + The RM as written implied that in some cases it was possible to create an + object of an abstract type, by having an abstract extension inherit a non- + abstract constructor from its parent type. This mistake has been corrected + in GNAT and in the RM, and this construct is now illegal. + + RM References: 3.09.03 (4/2) + +.. index:: AI-0203 (Ada 2012 feature) + +* *AI-0203 Extended return cannot be abstract (0000-00-00)* + + A return_subtype_indication cannot denote an abstract subtype. GNAT has never + permitted such usage. + + RM References: 3.09.03 (8/3) + +.. index:: AI-0198 (Ada 2012 feature) + +* *AI-0198 Inheriting abstract operators (0000-00-00)* + + This AI resolves a conflict between two rules involving inherited abstract + operations and predefined operators. If a derived numeric type inherits + an abstract operator, it overrides the predefined one. This interpretation + was always the one implemented in GNAT. + + RM References: 3.09.03 (4/3) + +.. index:: AI-0073 (Ada 2012 feature) + +* *AI-0073 Functions returning abstract types (2010-07-10)* + + This AI covers a number of issues regarding returning abstract types. In + particular generic functions cannot have abstract result types or access + result types designated an abstract type. There are some other cases which + are detailed in the AI. Note that this binding interpretation has not been + retrofitted to operate before Ada 2012 mode, since it caused a significant + number of regressions. + + RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2) + +.. index:: AI-0070 (Ada 2012 feature) + +* *AI-0070 Elaboration of interface types (0000-00-00)* + + This is an editorial change only, there are no testable consequences short of + checking for the absence of generated code for an interface declaration. + + RM References: 3.09.04 (18/2) + +.. index:: AI-0208 (Ada 2012 feature) + +* *AI-0208 Characteristics of incomplete views (0000-00-00)* + + The wording in the Ada 2005 RM concerning characteristics of incomplete views + was incorrect and implied that some programs intended to be legal were now + illegal. GNAT had never considered such programs illegal, so it has always + implemented the intent of this AI. + + RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2) + +.. index:: AI-0162 (Ada 2012 feature) + +* *AI-0162 Incomplete type completed by partial view (2010-09-15)* + + Incomplete types are made more useful by allowing them to be completed by + private types and private extensions. + + RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2) + +.. index:: AI-0098 (Ada 2012 feature) + +* *AI-0098 Anonymous subprogram access restrictions (0000-00-00)* + + An unintentional omission in the RM implied some inconsistent restrictions on + the use of anonymous access to subprogram values. These restrictions were not + intentional, and have never been enforced by GNAT. + + RM References: 3.10.01 (6) 3.10.01 (9.2/2) + +.. index:: AI-0199 (Ada 2012 feature) + +* *AI-0199 Aggregate with anonymous access components (2010-07-14)* + + A choice list in a record aggregate can include several components of + (distinct) anonymous access types as long as they have matching designated + subtypes. + + RM References: 4.03.01 (16) + +.. index:: AI-0220 (Ada 2012 feature) + +* *AI-0220 Needed components for aggregates (0000-00-00)* + + This AI addresses a wording problem in the RM that appears to permit some + complex cases of aggregates with non-static discriminants. GNAT has always + implemented the intended semantics. + + RM References: 4.03.01 (17) + +.. index:: AI-0147 (Ada 2012 feature) + +* *AI-0147 Conditional expressions (2009-03-29)* + + Conditional expressions are permitted. The form of such an expression is: + + :: + + (if expr then expr {elsif expr then expr} [else expr]) + + The parentheses can be omitted in contexts where parentheses are present + anyway, such as subprogram arguments and pragma arguments. If the **else** + clause is omitted, **else** *True* is assumed; + thus ``(if A then B)`` is a way to conveniently represent + *(A implies B)* in standard logic. + + RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2) + 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2) + +.. index:: AI-0037 (Ada 2012 feature) + +* *AI-0037 Out-of-range box associations in aggregate (0000-00-00)* + + This AI confirms that an association of the form `Indx => <>` in an + array aggregate must raise `Constraint_Error` if `Indx` + is out of range. The RM specified a range check on other associations, but + not when the value of the association was defaulted. GNAT has always inserted + a constraint check on the index value. + + RM References: 4.03.03 (29) + +.. index:: AI-0123 (Ada 2012 feature) + +* *AI-0123 Composability of equality (2010-04-13)* + + Equality of untagged record composes, so that the predefined equality for a + composite type that includes a component of some untagged record type + `R` uses the equality operation of `R` (which may be user-defined + or predefined). This makes the behavior of untagged records identical to that + of tagged types in this respect. + + This change is an incompatibility with previous versions of Ada, but it + corrects a non-uniformity that was often a source of confusion. Analysis of + a large number of industrial programs indicates that in those rare cases + where a composite type had an untagged record component with a user-defined + equality, either there was no use of the composite equality, or else the code + expected the same composability as for tagged types, and thus had a bug that + would be fixed by this change. + + RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24) + 8.05.04 (8) + +.. index:: AI-0088 (Ada 2012 feature) + +* *AI-0088 The value of exponentiation (0000-00-00)* + + This AI clarifies the equivalence rule given for the dynamic semantics of + exponentiation: the value of the operation can be obtained by repeated + multiplication, but the operation can be implemented otherwise (for example + using the familiar divide-by-two-and-square algorithm, even if this is less + accurate), and does not imply repeated reads of a volatile base. + + RM References: 4.05.06 (11) + +.. index:: AI-0188 (Ada 2012 feature) + +* *AI-0188 Case expressions (2010-01-09)* + + Case expressions are permitted. This allows use of constructs such as: + + .. code-block:: ada + + X := (case Y is when 1 => 2, when 2 => 3, when others => 31) + + RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33) + +.. index:: AI-0104 (Ada 2012 feature) + +* *AI-0104 Null exclusion and uninitialized allocator (2010-07-15)* + + The assignment ``Ptr := new not null Some_Ptr;`` will raise + ``Constraint_Error`` because the default value of the allocated object is + **null**. This useless construct is illegal in Ada 2012. + + RM References: 4.08 (2) + +.. index:: AI-0157 (Ada 2012 feature) + +* *AI-0157 Allocation/Deallocation from empty pool (2010-07-11)* + + Allocation and Deallocation from an empty storage pool (i.e. allocation or + deallocation of a pointer for which a static storage size clause of zero + has been given) is now illegal and is detected as such. GNAT + previously gave a warning but not an error. + + RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17) + +.. index:: AI-0179 (Ada 2012 feature) + +* *AI-0179 Statement not required after label (2010-04-10)* + + It is not necessary to have a statement following a label, so a label + can appear at the end of a statement sequence without the need for putting a + null statement afterwards, but it is not allowable to have only labels and + no real statements in a statement sequence. + + RM References: 5.01 (2) + +.. index:: AI-0139-2 (Ada 2012 feature) + +* *AI-0139-2 Syntactic sugar for iterators (2010-09-29)* + + The new syntax for iterating over arrays and containers is now implemented. + Iteration over containers is for now limited to read-only iterators. Only + default iterators are supported, with the syntax: `for Elem of C`. + + RM References: 5.05 + +.. index:: AI-0134 (Ada 2012 feature) + +* *AI-0134 Profiles must match for full conformance (0000-00-00)* + + For full conformance, the profiles of anonymous-access-to-subprogram + parameters must match. GNAT has always enforced this rule. + + RM References: 6.03.01 (18) + +.. index:: AI-0207 (Ada 2012 feature) + +* *AI-0207 Mode conformance and access constant (0000-00-00)* + + This AI confirms that access_to_constant indication must match for mode + conformance. This was implemented in GNAT when the qualifier was originally + introduced in Ada 2005. + + RM References: 6.03.01 (16/2) + +.. index:: AI-0046 (Ada 2012 feature) + +* *AI-0046 Null exclusion match for full conformance (2010-07-17)* + + For full conformance, in the case of access parameters, the null exclusion + must match (either both or neither must have ``not null``). + + RM References: 6.03.02 (18) + +.. index:: AI-0118 (Ada 2012 feature) + +* *AI-0118 The association of parameter associations (0000-00-00)* + + This AI clarifies the rules for named associations in subprogram calls and + generic instantiations. The rules have been in place since Ada 83. + + RM References: 6.04.01 (2) 12.03 (9) + +.. index:: AI-0196 (Ada 2012 feature) + +* *AI-0196 Null exclusion tests for out parameters (0000-00-00)* + + Null exclusion checks are not made for `**out**` parameters when + evaluating the actual parameters. GNAT has never generated these checks. + + RM References: 6.04.01 (13) + +.. index:: AI-0015 (Ada 2012 feature) + +* *AI-0015 Constant return objects (0000-00-00)* + + The return object declared in an *extended_return_statement* may be + declared constant. This was always intended, and GNAT has always allowed it. + + RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2) + 6.05 (5.7/2) + +.. index:: AI-0032 (Ada 2012 feature) + +* *AI-0032 Extended return for class-wide functions (0000-00-00)* + + If a function returns a class-wide type, the object of an extended return + statement can be declared with a specific type that is covered by the class- + wide type. This has been implemented in GNAT since the introduction of + extended returns. Note AI-0103 complements this AI by imposing matching + rules for constrained return types. + + RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2) + 6.05 (8/2) + +.. index:: AI-0103 (Ada 2012 feature) + +* *AI-0103 Static matching for extended return (2010-07-23)* + + If the return subtype of a function is an elementary type or a constrained + type, the subtype indication in an extended return statement must match + statically this return subtype. + + RM References: 6.05 (5.2/2) + +.. index:: AI-0058 (Ada 2012 feature) + +* *AI-0058 Abnormal completion of an extended return (0000-00-00)* + + The RM had some incorrect wording implying wrong treatment of abnormal + completion in an extended return. GNAT has always implemented the intended + correct semantics as described by this AI. + + RM References: 6.05 (22/2) + +.. index:: AI-0050 (Ada 2012 feature) + +* *AI-0050 Raising Constraint_Error early for function call (0000-00-00)* + + The implementation permissions for raising `Constraint_Error` early on a function call + when it was clear an exception would be raised were over-permissive and allowed + mishandling of discriminants in some cases. GNAT did + not take advantage of these incorrect permissions in any case. + + RM References: 6.05 (24/2) + +.. index:: AI-0125 (Ada 2012 feature) + +* *AI-0125 Nonoverridable operations of an ancestor (2010-09-28)* + + In Ada 2012, the declaration of a primitive operation of a type extension + or private extension can also override an inherited primitive that is not + visible at the point of this declaration. + + RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2) + +.. index:: AI-0062 (Ada 2012 feature) + +* *AI-0062 Null exclusions and deferred constants (0000-00-00)* + + A full constant may have a null exclusion even if its associated deferred + constant does not. GNAT has always allowed this. + + RM References: 7.04 (6/2) 7.04 (7.1/2) + +.. index:: AI-0178 (Ada 2012 feature) + +* *AI-0178 Incomplete views are limited (0000-00-00)* + + This AI clarifies the role of incomplete views and plugs an omission in the + RM. GNAT always correctly restricted the use of incomplete views and types. + + RM References: 7.05 (3/2) 7.05 (6/2) + +.. index:: AI-0087 (Ada 2012 feature) + +* *AI-0087 Actual for formal nonlimited derived type (2010-07-15)* + + The actual for a formal nonlimited derived type cannot be limited. In + particular, a formal derived type that extends a limited interface but which + is not explicitly limited cannot be instantiated with a limited type. + + RM References: 7.05 (5/2) 12.05.01 (5.1/2) + +.. index:: AI-0099 (Ada 2012 feature) + +* *AI-0099 Tag determines whether finalization needed (0000-00-00)* + + This AI clarifies that 'needs finalization' is part of dynamic semantics, + and therefore depends on the run-time characteristics of an object (i.e. its + tag) and not on its nominal type. As the AI indicates: "we do not expect + this to affect any implementation''. + + RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2) + +.. index:: AI-0064 (Ada 2012 feature) + +* *AI-0064 Redundant finalization rule (0000-00-00)* + + This is an editorial change only. The intended behavior is already checked + by an existing ACATS test, which GNAT has always executed correctly. + + RM References: 7.06.01 (17.1/1) + +.. index:: AI-0026 (Ada 2012 feature) + +* *AI-0026 Missing rules for Unchecked_Union (2010-07-07)* + + Record representation clauses concerning Unchecked_Union types cannot mention + the discriminant of the type. The type of a component declared in the variant + part of an Unchecked_Union cannot be controlled, have controlled components, + nor have protected or task parts. If an Unchecked_Union type is declared + within the body of a generic unit or its descendants, then the type of a + component declared in the variant part cannot be a formal private type or a + formal private extension declared within the same generic unit. + + RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2) + +.. index:: AI-0205 (Ada 2012 feature) + +* *AI-0205 Extended return declares visible name (0000-00-00)* + + This AI corrects a simple omission in the RM. Return objects have always + been visible within an extended return statement. + + RM References: 8.03 (17) + +.. index:: AI-0042 (Ada 2012 feature) + +* *AI-0042 Overriding versus implemented-by (0000-00-00)* + + This AI fixes a wording gap in the RM. An operation of a synchronized + interface can be implemented by a protected or task entry, but the abstract + operation is not being overridden in the usual sense, and it must be stated + separately that this implementation is legal. This has always been the case + in GNAT. + + RM References: 9.01 (9.2/2) 9.04 (11.1/2) + +.. index:: AI-0030 (Ada 2012 feature) + +* *AI-0030 Requeue on synchronized interfaces (2010-07-19)* + + Requeue is permitted to a protected, synchronized or task interface primitive + providing it is known that the overriding operation is an entry. Otherwise + the requeue statement has the same effect as a procedure call. Use of pragma + `Implemented` provides a way to impose a static requirement on the + overriding operation by adhering to one of the implementation kinds: entry, + protected procedure or any of the above. + + RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5) + 9.05.04 (6) 9.05.04 (7) 9.05.04 (12) + +.. index:: AI-0201 (Ada 2012 feature) + +* *AI-0201 Independence of atomic object components (2010-07-22)* + + If an Atomic object has a pragma `Pack` or a `Component_Size` + attribute, then individual components may not be addressable by independent + tasks. However, if the representation clause has no effect (is confirming), + then independence is not compromised. Furthermore, in GNAT, specification of + other appropriately addressable component sizes (e.g. 16 for 8-bit + characters) also preserves independence. GNAT now gives very clear warnings + both for the declaration of such a type, and for any assignment to its components. + + RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2) + +.. index:: AI-0009 (Ada 2012 feature) + +* *AI-0009 Pragma Independent[_Components] (2010-07-23)* + + This AI introduces the new pragmas `Independent` and + `Independent_Components`, + which control guaranteeing independence of access to objects and components. + The AI also requires independence not unaffected by confirming rep clauses. + + RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2) + C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14) + +.. index:: AI-0072 (Ada 2012 feature) + +* *AI-0072 Task signalling using 'Terminated (0000-00-00)* + + This AI clarifies that task signalling for reading `'Terminated` only + occurs if the result is True. GNAT semantics has always been consistent with + this notion of task signalling. + + RM References: 9.10 (6.1/1) + +.. index:: AI-0108 (Ada 2012 feature) + +* *AI-0108 Limited incomplete view and discriminants (0000-00-00)* + + This AI confirms that an incomplete type from a limited view does not have + discriminants. This has always been the case in GNAT. + + RM References: 10.01.01 (12.3/2) + +.. index:: AI-0129 (Ada 2012 feature) + +* *AI-0129 Limited views and incomplete types (0000-00-00)* + + This AI clarifies the description of limited views: a limited view of a + package includes only one view of a type that has an incomplete declaration + and a full declaration (there is no possible ambiguity in a client package). + This AI also fixes an omission: a nested package in the private part has no + limited view. GNAT always implemented this correctly. + + RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2) + +.. index:: AI-0077 (Ada 2012 feature) + +* *AI-0077 Limited withs and scope of declarations (0000-00-00)* + + This AI clarifies that a declaration does not include a context clause, + and confirms that it is illegal to have a context in which both a limited + and a nonlimited view of a package are accessible. Such double visibility + was always rejected by GNAT. + + RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2) + +.. index:: AI-0122 (Ada 2012 feature) + +* *AI-0122 Private with and children of generics (0000-00-00)* + + This AI clarifies the visibility of private children of generic units within + instantiations of a parent. GNAT has always handled this correctly. + + RM References: 10.01.02 (12/2) + +.. index:: AI-0040 (Ada 2012 feature) + +* *AI-0040 Limited with clauses on descendant (0000-00-00)* + + This AI confirms that a limited with clause in a child unit cannot name + an ancestor of the unit. This has always been checked in GNAT. + + RM References: 10.01.02 (20/2) + +.. index:: AI-0132 (Ada 2012 feature) + +* *AI-0132 Placement of library unit pragmas (0000-00-00)* + + This AI fills a gap in the description of library unit pragmas. The pragma + clearly must apply to a library unit, even if it does not carry the name + of the enclosing unit. GNAT has always enforced the required check. + + RM References: 10.01.05 (7) + +.. index:: AI-0034 (Ada 2012 feature) + +* *AI-0034 Categorization of limited views (0000-00-00)* + + The RM makes certain limited with clauses illegal because of categorization + considerations, when the corresponding normal with would be legal. This is + not intended, and GNAT has always implemented the recommended behavior. + + RM References: 10.02.01 (11/1) 10.02.01 (17/2) + +.. index:: AI-0035 (Ada 2012 feature) + +* *AI-0035 Inconsistencies with Pure units (0000-00-00)* + + This AI remedies some inconsistencies in the legality rules for Pure units. + Derived access types are legal in a pure unit (on the assumption that the + rule for a zero storage pool size has been enforced on the ancestor type). + The rules are enforced in generic instances and in subunits. GNAT has always + implemented the recommended behavior. + + RM References: 10.02.01 (15.1/2) 10.02.01 (15.4/2) 10.02.01 (15.5/2) 10.02.01 (17/2) + +.. index:: AI-0219 (Ada 2012 feature) + +* *AI-0219 Pure permissions and limited parameters (2010-05-25)* + + This AI refines the rules for the cases with limited parameters which do not + allow the implementations to omit 'redundant'. GNAT now properly conforms + to the requirements of this binding interpretation. + + RM References: 10.02.01 (18/2) + +.. index:: AI-0043 (Ada 2012 feature) + +* *AI-0043 Rules about raising exceptions (0000-00-00)* + + This AI covers various omissions in the RM regarding the raising of + exceptions. GNAT has always implemented the intended semantics. + + RM References: 11.04.01 (10.1/2) 11 (2) + +.. index:: AI-0200 (Ada 2012 feature) + +* *AI-0200 Mismatches in formal package declarations (0000-00-00)* + + This AI plugs a gap in the RM which appeared to allow some obviously intended + illegal instantiations. GNAT has never allowed these instantiations. + + RM References: 12.07 (16) + +.. index:: AI-0112 (Ada 2012 feature) + +* *AI-0112 Detection of duplicate pragmas (2010-07-24)* + + This AI concerns giving names to various representation aspects, but the + practical effect is simply to make the use of duplicate + `Atomic[_Components]`, + `Volatile[_Components]`, and + `Independent[_Components]` pragmas illegal, and GNAT + now performs this required check. + + RM References: 13.01 (8) + +.. index:: AI-0106 (Ada 2012 feature) + +* *AI-0106 No representation pragmas on generic formals (0000-00-00)* + + The RM appeared to allow representation pragmas on generic formal parameters, + but this was not intended, and GNAT has never permitted this usage. + + RM References: 13.01 (9.1/1) + +.. index:: AI-0012 (Ada 2012 feature) + +* *AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)* + + It is now illegal to give an inappropriate component size or a pragma + `Pack` that attempts to change the component size in the case of atomic + or aliased components. Previously GNAT ignored such an attempt with a + warning. + + RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21) + +.. index:: AI-0039 (Ada 2012 feature) + +* *AI-0039 Stream attributes cannot be dynamic (0000-00-00)* + + The RM permitted the use of dynamic expressions (such as ``ptr.all``)` + for stream attributes, but these were never useful and are now illegal. GNAT + has always regarded such expressions as illegal. + + RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2) + +.. index:: AI-0095 (Ada 2012 feature) + +* *AI-0095 Address of intrinsic subprograms (0000-00-00)* + + The prefix of `'Address` cannot statically denote a subprogram with + convention `Intrinsic`. The use of the `Address` attribute raises + `Program_Error` if the prefix denotes a subprogram with convention + `Intrinsic`. + + RM References: 13.03 (11/1) + +.. index:: AI-0116 (Ada 2012 feature) + +* *AI-0116 Alignment of class-wide objects (0000-00-00)* + + This AI requires that the alignment of a class-wide object be no greater + than the alignment of any type in the class. GNAT has always followed this + recommendation. + + RM References: 13.03 (29) 13.11 (16) + +.. index:: AI-0146 (Ada 2012 feature) + +* *AI-0146 Type invariants (2009-09-21)* + + Type invariants may be specified for private types using the aspect notation. + Aspect `Type_Invariant` may be specified for any private type, + `Type_Invariant'Class` can + only be specified for tagged types, and is inherited by any descendent of the + tagged types. The invariant is a boolean expression that is tested for being + true in the following situations: conversions to the private type, object + declarations for the private type that are default initialized, and + [**in**] **out** + parameters and returned result on return from any primitive operation for + the type that is visible to a client. + GNAT defines the synonyms `Invariant` for `Type_Invariant` and + `Invariant'Class` for `Type_Invariant'Class`. + + RM References: 13.03.03 (00) + +.. index:: AI-0078 (Ada 2012 feature) + +* *AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)* + + In Ada 2012, compilers are required to support unchecked conversion where the + target alignment is a multiple of the source alignment. GNAT always supported + this case (and indeed all cases of differing alignments, doing copies where + required if the alignment was reduced). + + RM References: 13.09 (7) + +.. index:: AI-0195 (Ada 2012 feature) + +* *AI-0195 Invalid value handling is implementation defined (2010-07-03)* + + The handling of invalid values is now designated to be implementation + defined. This is a documentation change only, requiring Annex M in the GNAT + Reference Manual to document this handling. + In GNAT, checks for invalid values are made + only when necessary to avoid erroneous behavior. Operations like assignments + which cannot cause erroneous behavior ignore the possibility of invalid + values and do not do a check. The date given above applies only to the + documentation change, this behavior has always been implemented by GNAT. + + RM References: 13.09.01 (10) + +.. index:: AI-0193 (Ada 2012 feature) + +* *AI-0193 Alignment of allocators (2010-09-16)* + + This AI introduces a new attribute `Max_Alignment_For_Allocation`, + analogous to `Max_Size_In_Storage_Elements`, but for alignment instead + of size. + + RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1) + 13.11.01 (2) 13.11.01 (3) + +.. index:: AI-0177 (Ada 2012 feature) + +* *AI-0177 Parameterized expressions (2010-07-10)* + + The new Ada 2012 notion of parameterized expressions is implemented. The form + is: + + .. code-block:: ada + + function-specification is (expression) + + This is exactly equivalent to the + corresponding function body that returns the expression, but it can appear + in a package spec. Note that the expression must be parenthesized. + + RM References: 13.11.01 (3/2) + +.. index:: AI-0033 (Ada 2012 feature) + +* *AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)* + + Neither of these two pragmas may appear within a generic template, because + the generic might be instantiated at other than the library level. + + RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2) + +.. index:: AI-0161 (Ada 2012 feature) + +* *AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)* + + A new restriction `No_Default_Stream_Attributes` prevents the use of any + of the default stream attributes for elementary types. If this restriction is + in force, then it is necessary to provide explicit subprograms for any + stream attributes used. + + RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2) + +.. index:: AI-0194 (Ada 2012 feature) + +* *AI-0194 Value of Stream_Size attribute (0000-00-00)* + + The `Stream_Size` attribute returns the default number of bits in the + stream representation of the given type. + This value is not affected by the presence + of stream subprogram attributes for the type. GNAT has always implemented + this interpretation. + + RM References: 13.13.02 (1.2/2) + +.. index:: AI-0109 (Ada 2012 feature) + +* *AI-0109 Redundant check in S'Class'Input (0000-00-00)* + + This AI is an editorial change only. It removes the need for a tag check + that can never fail. + + RM References: 13.13.02 (34/2) + +.. index:: AI-0007 (Ada 2012 feature) + +* *AI-0007 Stream read and private scalar types (0000-00-00)* + + The RM as written appeared to limit the possibilities of declaring read + attribute procedures for private scalar types. This limitation was not + intended, and has never been enforced by GNAT. + + RM References: 13.13.02 (50/2) 13.13.02 (51/2) + +.. index:: AI-0065 (Ada 2012 feature) + +* *AI-0065 Remote access types and external streaming (0000-00-00)* + + This AI clarifies the fact that all remote access types support external + streaming. This fixes an obvious oversight in the definition of the + language, and GNAT always implemented the intended correct rules. + + RM References: 13.13.02 (52/2) + +.. index:: AI-0019 (Ada 2012 feature) + +* *AI-0019 Freezing of primitives for tagged types (0000-00-00)* + + The RM suggests that primitive subprograms of a specific tagged type are + frozen when the tagged type is frozen. This would be an incompatible change + and is not intended. GNAT has never attempted this kind of freezing and its + behavior is consistent with the recommendation of this AI. + + RM References: 13.14 (2) 13.14 (3/1) 13.14 (8.1/1) 13.14 (10) 13.14 (14) 13.14 (15.1/2) + +.. index:: AI-0017 (Ada 2012 feature) + +* *AI-0017 Freezing and incomplete types (0000-00-00)* + + So-called 'Taft-amendment types' (i.e., types that are completed in package + bodies) are not frozen by the occurrence of bodies in the + enclosing declarative part. GNAT always implemented this properly. + + RM References: 13.14 (3/1) + +.. index:: AI-0060 (Ada 2012 feature) + +* *AI-0060 Extended definition of remote access types (0000-00-00)* + + This AI extends the definition of remote access types to include access + to limited, synchronized, protected or task class-wide interface types. + GNAT already implemented this extension. + + RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18) + +.. index:: AI-0114 (Ada 2012 feature) + +* *AI-0114 Classification of letters (0000-00-00)* + + The code points 170 (`FEMININE ORDINAL INDICATOR`), + 181 (`MICRO SIGN`), and + 186 (`MASCULINE ORDINAL INDICATOR`) are technically considered + lower case letters by Unicode. + However, they are not allowed in identifiers, and they + return `False` to `Ada.Characters.Handling.Is_Letter/Is_Lower`. + This behavior is consistent with that defined in Ada 95. + + RM References: A.03.02 (59) A.04.06 (7) + +.. index:: AI-0185 (Ada 2012 feature) + +* *AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)* + + Two new packages `Ada.Wide_[Wide_]Characters.Handling` provide + classification functions for `Wide_Character` and + `Wide_Wide_Character`, as well as providing + case folding routines for `Wide_[Wide_]Character` and + `Wide_[Wide_]String`. + + RM References: A.03.05 (0) A.03.06 (0) + +.. index:: AI-0031 (Ada 2012 feature) + +* *AI-0031 Add From parameter to Find_Token (2010-07-25)* + + A new version of `Find_Token` is added to all relevant string packages, + with an extra parameter `From`. Instead of starting at the first + character of the string, the search for a matching Token starts at the + character indexed by the value of `From`. + These procedures are available in all versions of Ada + but if used in versions earlier than Ada 2012 they will generate a warning + that an Ada 2012 subprogram is being used. + + RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51) + A.04.05 (46) + +.. index:: AI-0056 (Ada 2012 feature) + +* *AI-0056 Index on null string returns zero (0000-00-00)* + + The wording in the Ada 2005 RM implied an incompatible handling of the + `Index` functions, resulting in raising an exception instead of + returning zero in some situations. + This was not intended and has been corrected. + GNAT always returned zero, and is thus consistent with this AI. + + RM References: A.04.03 (56.2/2) A.04.03 (58.5/2) + +.. index:: AI-0137 (Ada 2012 feature) + +* *AI-0137 String encoding package (2010-03-25)* + + The packages `Ada.Strings.UTF_Encoding`, together with its child + packages, `Conversions`, `Strings`, `Wide_Strings`, + and `Wide_Wide_Strings` have been + implemented. These packages (whose documentation can be found in the spec + files :file:`a-stuten.ads`, :file:`a-suenco.ads`, :file:`a-suenst.ads`, + :file:`a-suewst.ads`, :file:`a-suezst.ads`) allow encoding and decoding of + `String`, `Wide_String`, and `Wide_Wide_String` + values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and + UTF-16), as well as conversions between the different UTF encodings. With + the exception of `Wide_Wide_Strings`, these packages are available in + Ada 95 and Ada 2005 mode as well as Ada 2012 mode. + The `Wide_Wide_Strings package` + is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95 + mode since it uses `Wide_Wide_Character`). + + RM References: A.04.11 + +.. index:: AI-0038 (Ada 2012 feature) + +* *AI-0038 Minor errors in Text_IO (0000-00-00)* + + These are minor errors in the description on three points. The intent on + all these points has always been clear, and GNAT has always implemented the + correct intended semantics. + + RM References: A.10.05 (37) A.10.07 (8/1) A.10.07 (10) A.10.07 (12) A.10.08 (10) A.10.08 (24) + +.. index:: AI-0044 (Ada 2012 feature) + +* *AI-0044 Restrictions on container instantiations (0000-00-00)* + + This AI places restrictions on allowed instantiations of generic containers. + These restrictions are not checked by the compiler, so there is nothing to + change in the implementation. This affects only the RM documentation. + + RM References: A.18 (4/2) A.18.02 (231/2) A.18.03 (145/2) A.18.06 (56/2) A.18.08 (66/2) A.18.09 (79/2) A.18.26 (5/2) A.18.26 (9/2) + +.. index:: AI-0127 (Ada 2012 feature) + +* *AI-0127 Adding Locale Capabilities (2010-09-29)* + + This package provides an interface for identifying the current locale. + + RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06 + A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13 + +.. index:: AI-0002 (Ada 2012 feature) + +* *AI-0002 Export C with unconstrained arrays (0000-00-00)* + + The compiler is not required to support exporting an Ada subprogram with + convention C if there are parameters or a return type of an unconstrained + array type (such as `String`). GNAT allows such declarations but + generates warnings. It is possible, but complicated, to write the + corresponding C code and certainly such code would be specific to GNAT and + non-portable. + + RM References: B.01 (17) B.03 (62) B.03 (71.1/2) + +.. index:: AI05-0216 (Ada 2012 feature) + +* *AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)* + + It is clearly the intention that `No_Task_Hierarchy` is intended to + forbid tasks declared locally within subprograms, or functions returning task + objects, and that is the implementation that GNAT has always provided. + However the language in the RM was not sufficiently clear on this point. + Thus this is a documentation change in the RM only. + + RM References: D.07 (3/3) + +.. index:: AI-0211 (Ada 2012 feature) + +* *AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)* + + The restriction `No_Relative_Delays` forbids any calls to the subprogram + `Ada.Real_Time.Timing_Events.Set_Handler`. + + RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2) + +.. index:: AI-0190 (Ada 2012 feature) + +* *AI-0190 pragma Default_Storage_Pool (2010-09-15)* + + This AI introduces a new pragma `Default_Storage_Pool`, which can be + used to control storage pools globally. + In particular, you can force every access + type that is used for allocation (**new**) to have an explicit storage pool, + or you can declare a pool globally to be used for all access types that lack + an explicit one. + + RM References: D.07 (8) + +.. index:: AI-0189 (Ada 2012 feature) + +* *AI-0189 No_Allocators_After_Elaboration (2010-01-23)* + + This AI introduces a new restriction `No_Allocators_After_Elaboration`, + which says that no dynamic allocation will occur once elaboration is + completed. + In general this requires a run-time check, which is not required, and which + GNAT does not attempt. But the static cases of allocators in a task body or + in the body of the main program are detected and flagged at compile or bind + time. + + RM References: D.07 (19.1/2) H.04 (23.3/2) + +.. index:: AI-0171 (Ada 2012 feature) + +* *AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)* + + A new package `System.Multiprocessors` is added, together with the + definition of pragma `CPU` for controlling task affinity. A new no + dependence restriction, on `System.Multiprocessors.Dispatching_Domains`, + is added to the Ravenscar profile. + + RM References: D.13.01 (4/2) D.16 + +.. index:: AI-0210 (Ada 2012 feature) + +* *AI-0210 Correct Timing_Events metric (0000-00-00)* + + This is a documentation only issue regarding wording of metric requirements, + that does not affect the implementation of the compiler. + + RM References: D.15 (24/2) + +.. index:: AI-0206 (Ada 2012 feature) + +* *AI-0206 Remote types packages and preelaborate (2010-07-24)* + + Remote types packages are now allowed to depend on preelaborated packages. + This was formerly considered illegal. + + RM References: E.02.02 (6) + +.. index:: AI-0152 (Ada 2012 feature) + +* *AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)* + + Restriction `No_Anonymous_Allocators` prevents the use of allocators + where the type of the returned value is an anonymous access type. + + RM References: H.04 (8/1) diff --git a/gcc/ada/doc/gnat_rm/implementation_of_specific_ada_features.rst b/gcc/ada/doc/gnat_rm/implementation_of_specific_ada_features.rst new file mode 100644 index 00000000000..5788929bedc --- /dev/null +++ b/gcc/ada/doc/gnat_rm/implementation_of_specific_ada_features.rst @@ -0,0 +1,671 @@ +.. _Implementation_of_Specific_Ada_Features: + +*************************************** +Implementation of Specific Ada Features +*************************************** + +This chapter describes the GNAT implementation of several Ada language +facilities. + +.. _Machine_Code_Insertions: + +Machine Code Insertions +======================= + +.. index:: Machine Code insertions + +Package `Machine_Code` provides machine code support as described +in the Ada Reference Manual in two separate forms: + +* + Machine code statements, consisting of qualified expressions that + fit the requirements of RM section 13.8. +* + An intrinsic callable procedure, providing an alternative mechanism of + including machine instructions in a subprogram. + +The two features are similar, and both are closely related to the mechanism +provided by the asm instruction in the GNU C compiler. Full understanding +and use of the facilities in this package requires understanding the asm +instruction, see the section on Extended Asm in +:title:`Using_the_GNU_Compiler_Collection_(GCC)`. + +Calls to the function `Asm` and the procedure `Asm` have identical +semantic restrictions and effects as described below. Both are provided so +that the procedure call can be used as a statement, and the function call +can be used to form a code_statement. + +Consider this C `asm` instruction: + +:: + + asm ("fsinx %1 %0" : "=f" (result) : "f" (angle)); + + +The equivalent can be written for GNAT as: + +.. code-block:: ada + + Asm ("fsinx %1 %0", + My_Float'Asm_Output ("=f", result), + My_Float'Asm_Input ("f", angle)); + + +The first argument to `Asm` is the assembler template, and is +identical to what is used in GNU C. This string must be a static +expression. The second argument is the output operand list. It is +either a single `Asm_Output` attribute reference, or a list of such +references enclosed in parentheses (technically an array aggregate of +such references). + +The `Asm_Output` attribute denotes a function that takes two +parameters. The first is a string, the second is the name of a variable +of the type designated by the attribute prefix. The first (string) +argument is required to be a static expression and designates the +constraint (see the section on Constraints in +:title:`Using_the_GNU_Compiler_Collection_(GCC)`) +for the parameter; e.g., what kind of register is required. The second +argument is the variable to be written or updated with the +result. The possible values for constraint are the same as those used in +the RTL, and are dependent on the configuration file used to build the +GCC back end. If there are no output operands, then this argument may +either be omitted, or explicitly given as `No_Output_Operands`. +No support is provided for GNU C's symbolic names for output parameters. + +The second argument of ``my_float'Asm_Output`` functions as +though it were an `out` parameter, which is a little curious, but +all names have the form of expressions, so there is no syntactic +irregularity, even though normally functions would not be permitted +`out` parameters. The third argument is the list of input +operands. It is either a single `Asm_Input` attribute reference, or +a list of such references enclosed in parentheses (technically an array +aggregate of such references). + +The `Asm_Input` attribute denotes a function that takes two +parameters. The first is a string, the second is an expression of the +type designated by the prefix. The first (string) argument is required +to be a static expression, and is the constraint for the parameter, +(e.g., what kind of register is required). The second argument is the +value to be used as the input argument. The possible values for the +constraint are the same as those used in the RTL, and are dependent on +the configuration file used to built the GCC back end. +No support is provided for GNU C's symbolic names for input parameters. + +If there are no input operands, this argument may either be omitted, or +explicitly given as `No_Input_Operands`. The fourth argument, not +present in the above example, is a list of register names, called the +*clobber* argument. This argument, if given, must be a static string +expression, and is a space or comma separated list of names of registers +that must be considered destroyed as a result of the `Asm` call. If +this argument is the null string (the default value), then the code +generator assumes that no additional registers are destroyed. +In addition to registers, the special clobbers `memory` and +`cc` as described in the GNU C docs are both supported. + +The fifth argument, not present in the above example, called the +*volatile* argument, is by default `False`. It can be set to +the literal value `True` to indicate to the code generator that all +optimizations with respect to the instruction specified should be +suppressed, and in particular an instruction that has outputs +will still be generated, even if none of the outputs are +used. See :title:`Using_the_GNU_Compiler_Collection_(GCC)` +for the full description. +Generally it is strongly advisable to use Volatile for any ASM statement +that is missing either input or output operands or to avoid unwanted +optimizations. A warning is generated if this advice is not followed. + +No support is provided for GNU C's `asm goto` feature. + +The `Asm` subprograms may be used in two ways. First the procedure +forms can be used anywhere a procedure call would be valid, and +correspond to what the RM calls 'intrinsic' routines. Such calls can +be used to intersperse machine instructions with other Ada statements. +Second, the function forms, which return a dummy value of the limited +private type `Asm_Insn`, can be used in code statements, and indeed +this is the only context where such calls are allowed. Code statements +appear as aggregates of the form: + +.. code-block:: ada + + Asm_Insn'(Asm (...)); + Asm_Insn'(Asm_Volatile (...)); + +In accordance with RM rules, such code statements are allowed only +within subprograms whose entire body consists of such statements. It is +not permissible to intermix such statements with other Ada statements. + +Typically the form using intrinsic procedure calls is more convenient +and more flexible. The code statement form is provided to meet the RM +suggestion that such a facility should be made available. The following +is the exact syntax of the call to `Asm`. As usual, if named notation +is used, the arguments may be given in arbitrary order, following the +normal rules for use of positional and named arguments: + +:: + + ASM_CALL ::= Asm ( + [Template =>] static_string_EXPRESSION + [,[Outputs =>] OUTPUT_OPERAND_LIST ] + [,[Inputs =>] INPUT_OPERAND_LIST ] + [,[Clobber =>] static_string_EXPRESSION ] + [,[Volatile =>] static_boolean_EXPRESSION] ) + + OUTPUT_OPERAND_LIST ::= + [PREFIX.]No_Output_Operands + | OUTPUT_OPERAND_ATTRIBUTE + | (OUTPUT_OPERAND_ATTRIBUTE {,OUTPUT_OPERAND_ATTRIBUTE}) + + OUTPUT_OPERAND_ATTRIBUTE ::= + SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME) + + INPUT_OPERAND_LIST ::= + [PREFIX.]No_Input_Operands + | INPUT_OPERAND_ATTRIBUTE + | (INPUT_OPERAND_ATTRIBUTE {,INPUT_OPERAND_ATTRIBUTE}) + + INPUT_OPERAND_ATTRIBUTE ::= + SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION) + +The identifiers `No_Input_Operands` and `No_Output_Operands` +are declared in the package `Machine_Code` and must be referenced +according to normal visibility rules. In particular if there is no +`use` clause for this package, then appropriate package name +qualification is required. + +.. _GNAT_Implementation_of_Tasking: + +GNAT Implementation of Tasking +============================== + +This chapter outlines the basic GNAT approach to tasking (in particular, +a multi-layered library for portability) and discusses issues related +to compliance with the Real-Time Systems Annex. + +.. _Mapping_Ada_Tasks_onto_the_Underlying_Kernel_Threads: + +Mapping Ada Tasks onto the Underlying Kernel Threads +---------------------------------------------------- + +GNAT's run-time support comprises two layers: + +* GNARL (GNAT Run-time Layer) +* GNULL (GNAT Low-level Library) + +In GNAT, Ada's tasking services rely on a platform and OS independent +layer known as GNARL. This code is responsible for implementing the +correct semantics of Ada's task creation, rendezvous, protected +operations etc. + +GNARL decomposes Ada's tasking semantics into simpler lower level +operations such as create a thread, set the priority of a thread, +yield, create a lock, lock/unlock, etc. The spec for these low-level +operations constitutes GNULLI, the GNULL Interface. This interface is +directly inspired from the POSIX real-time API. + +If the underlying executive or OS implements the POSIX standard +faithfully, the GNULL Interface maps as is to the services offered by +the underlying kernel. Otherwise, some target dependent glue code maps +the services offered by the underlying kernel to the semantics expected +by GNARL. + +Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the +key point is that each Ada task is mapped on a thread in the underlying +kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task. + +In addition Ada task priorities map onto the underlying thread priorities. +Mapping Ada tasks onto the underlying kernel threads has several advantages: + +* + The underlying scheduler is used to schedule the Ada tasks. This + makes Ada tasks as efficient as kernel threads from a scheduling + standpoint. + +* + Interaction with code written in C containing threads is eased + since at the lowest level Ada tasks and C threads map onto the same + underlying kernel concept. + +* + When an Ada task is blocked during I/O the remaining Ada tasks are + able to proceed. + +* + On multiprocessor systems Ada tasks can execute in parallel. + +Some threads libraries offer a mechanism to fork a new process, with the +child process duplicating the threads from the parent. +GNAT does not +support this functionality when the parent contains more than one task. +.. index:: Forking a new process + +.. _Ensuring_Compliance_with_the_Real-Time_Annex: + +Ensuring Compliance with the Real-Time Annex +-------------------------------------------- + +.. index:: Real-Time Systems Annex compliance + +Although mapping Ada tasks onto +the underlying threads has significant advantages, it does create some +complications when it comes to respecting the scheduling semantics +specified in the real-time annex (Annex D). + +For instance the Annex D requirement for the `FIFO_Within_Priorities` +scheduling policy states: + + *When the active priority of a ready task that is not running + changes, or the setting of its base priority takes effect, the + task is removed from the ready queue for its old active priority + and is added at the tail of the ready queue for its new active + priority, except in the case where the active priority is lowered + due to the loss of inherited priority, in which case the task is + added at the head of the ready queue for its new active priority.* + +While most kernels do put tasks at the end of the priority queue when +a task changes its priority, (which respects the main +FIFO_Within_Priorities requirement), almost none keep a thread at the +beginning of its priority queue when its priority drops from the loss +of inherited priority. + +As a result most vendors have provided incomplete Annex D implementations. + +The GNAT run-time, has a nice cooperative solution to this problem +which ensures that accurate FIFO_Within_Priorities semantics are +respected. + +The principle is as follows. When an Ada task T is about to start +running, it checks whether some other Ada task R with the same +priority as T has been suspended due to the loss of priority +inheritance. If this is the case, T yields and is placed at the end of +its priority queue. When R arrives at the front of the queue it +executes. + +Note that this simple scheme preserves the relative order of the tasks +that were ready to execute in the priority queue where R has been +placed at the end. + +.. _GNAT_Implementation_of_Shared_Passive_Packages: + +GNAT Implementation of Shared Passive Packages +============================================== + +.. index:: Shared passive packages + +GNAT fully implements the pragma `Shared_Passive` for +.. index:: pragma `Shared_Passive` + +the purpose of designating shared passive packages. +This allows the use of passive partitions in the +context described in the Ada Reference Manual; i.e., for communication +between separate partitions of a distributed application using the +features in Annex E. +.. index:: Annex E + +.. index:: Distribution Systems Annex + +However, the implementation approach used by GNAT provides for more +extensive usage as follows: + +*Communication between separate programs* + This allows separate programs to access the data in passive + partitions, using protected objects for synchronization where + needed. The only requirement is that the two programs have a + common shared file system. It is even possible for programs + running on different machines with different architectures + (e.g., different endianness) to communicate via the data in + a passive partition. + +*Persistence between program runs* + The data in a passive package can persist from one run of a + program to another, so that a later program sees the final + values stored by a previous run of the same program. + +The implementation approach used is to store the data in files. A +separate stream file is created for each object in the package, and +an access to an object causes the corresponding file to be read or +written. + +.. index:: SHARED_MEMORY_DIRECTORY environment variable + +The environment variable `SHARED_MEMORY_DIRECTORY` should be +set to the directory to be used for these files. +The files in this directory +have names that correspond to their fully qualified names. For +example, if we have the package + +.. code-block:: ada + + package X is + pragma Shared_Passive (X); + Y : Integer; + Z : Float; + end X; + +and the environment variable is set to `/stemp/`, then the files created +will have the names: + +:: + + /stemp/x.y + /stemp/x.z + + +These files are created when a value is initially written to the object, and +the files are retained until manually deleted. This provides the persistence +semantics. If no file exists, it means that no partition has assigned a value +to the variable; in this case the initial value declared in the package +will be used. This model ensures that there are no issues in synchronizing +the elaboration process, since elaboration of passive packages elaborates the +initial values, but does not create the files. + +The files are written using normal `Stream_IO` access. +If you want to be able +to communicate between programs or partitions running on different +architectures, then you should use the XDR versions of the stream attribute +routines, since these are architecture independent. + +If active synchronization is required for access to the variables in the +shared passive package, then as described in the Ada Reference Manual, the +package may contain protected objects used for this purpose. In this case +a lock file (whose name is :file:`___lock` (three underscores) +is created in the shared memory directory. + +.. index:: ___lock file (for shared passive packages) + +This is used to provide the required locking +semantics for proper protected object synchronization. + +GNAT supports shared passive packages on all platforms +except for OpenVMS. + +.. _Code_Generation_for_Array_Aggregates: + +Code Generation for Array Aggregates +==================================== + +Aggregates have a rich syntax and allow the user to specify the values of +complex data structures by means of a single construct. As a result, the +code generated for aggregates can be quite complex and involve loops, case +statements and multiple assignments. In the simplest cases, however, the +compiler will recognize aggregates whose components and constraints are +fully static, and in those cases the compiler will generate little or no +executable code. The following is an outline of the code that GNAT generates +for various aggregate constructs. For further details, you will find it +useful to examine the output produced by the -gnatG flag to see the expanded +source that is input to the code generator. You may also want to examine +the assembly code generated at various levels of optimization. + +The code generated for aggregates depends on the context, the component values, +and the type. In the context of an object declaration the code generated is +generally simpler than in the case of an assignment. As a general rule, static +component values and static subtypes also lead to simpler code. + +.. _Static_constant_aggregates_with_static_bounds: + +Static constant aggregates with static bounds +--------------------------------------------- + +For the declarations: + +.. code-block:: ada + + type One_Dim is array (1..10) of integer; + ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0); + + +GNAT generates no executable code: the constant ar0 is placed in static memory. +The same is true for constant aggregates with named associations: + + +.. code-block:: ada + + Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0); + Cr3 : constant One_Dim := (others => 7777); + + +The same is true for multidimensional constant arrays such as: + +.. code-block:: ada + + type two_dim is array (1..3, 1..3) of integer; + Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1)); + + +The same is true for arrays of one-dimensional arrays: the following are +static: + + +.. code-block:: ada + + type ar1b is array (1..3) of boolean; + type ar_ar is array (1..3) of ar1b; + None : constant ar1b := (others => false); -- fully static + None2 : constant ar_ar := (1..3 => None); -- fully static + + +However, for multidimensional aggregates with named associations, GNAT will +generate assignments and loops, even if all associations are static. The +following two declarations generate a loop for the first dimension, and +individual component assignments for the second dimension: + + +.. code-block:: ada + + Zero1: constant two_dim := (1..3 => (1..3 => 0)); + Zero2: constant two_dim := (others => (others => 0)); + + +.. _Constant_aggregates_with_unconstrained_nominal_types: + +Constant aggregates with unconstrained nominal types +---------------------------------------------------- + +In such cases the aggregate itself establishes the subtype, so that +associations with `others` cannot be used. GNAT determines the +bounds for the actual subtype of the aggregate, and allocates the +aggregate statically as well. No code is generated for the following: + + +.. code-block:: ada + + type One_Unc is array (natural range <>) of integer; + Cr_Unc : constant One_Unc := (12,24,36); + + +.. _Aggregates_with_static_bounds: + +Aggregates with static bounds +----------------------------- + +In all previous examples the aggregate was the initial (and immutable) value +of a constant. If the aggregate initializes a variable, then code is generated +for it as a combination of individual assignments and loops over the target +object. The declarations + + +.. code-block:: ada + + Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0); + Cr_Var2 : One_Dim := (others > -1); + + +generate the equivalent of + + +.. code-block:: ada + + Cr_Var1 (1) := 2; + Cr_Var1 (2) := 3; + Cr_Var1 (3) := 5; + Cr_Var1 (4) := 11; + + for I in Cr_Var2'range loop + Cr_Var2 (I) := -1; + end loop; + + +.. _Aggregates_with_non-static_bounds: + +Aggregates with non-static bounds +--------------------------------- + +If the bounds of the aggregate are not statically compatible with the bounds +of the nominal subtype of the target, then constraint checks have to be +generated on the bounds. For a multidimensional array, constraint checks may +have to be applied to sub-arrays individually, if they do not have statically +compatible subtypes. + +.. _Aggregates_in_assignment_statements: + +Aggregates in assignment statements +----------------------------------- + +In general, aggregate assignment requires the construction of a temporary, +and a copy from the temporary to the target of the assignment. This is because +it is not always possible to convert the assignment into a series of individual +component assignments. For example, consider the simple case: + + +.. code-block:: ada + + A := (A(2), A(1)); + + +This cannot be converted into: + + +.. code-block:: ada + + A(1) := A(2); + A(2) := A(1); + + +So the aggregate has to be built first in a separate location, and then +copied into the target. GNAT recognizes simple cases where this intermediate +step is not required, and the assignments can be performed in place, directly +into the target. The following sufficient criteria are applied: + +* + The bounds of the aggregate are static, and the associations are static. +* + The components of the aggregate are static constants, names of + simple variables that are not renamings, or expressions not involving + indexed components whose operands obey these rules. + +If any of these conditions are violated, the aggregate will be built in +a temporary (created either by the front-end or the code generator) and then +that temporary will be copied onto the target. + +.. _The_Size_of_Discriminated_Records_with_Default_Discriminants: + +The Size of Discriminated Records with Default Discriminants +============================================================ + +If a discriminated type `T` has discriminants with default values, it is +possible to declare an object of this type without providing an explicit +constraint: + + +.. code-block:: ada + + type Size is range 1..100; + + type Rec (D : Size := 15) is record + Name : String (1..D); + end T; + + Word : Rec; + + +Such an object is said to be *unconstrained*. +The discriminant of the object +can be modified by a full assignment to the object, as long as it preserves the +relation between the value of the discriminant, and the value of the components +that depend on it: + + +.. code-block:: ada + + Word := (3, "yes"); + + Word := (5, "maybe"); + + Word := (5, "no"); -- raises Constraint_Error + +In order to support this behavior efficiently, an unconstrained object is +given the maximum size that any value of the type requires. In the case +above, `Word` has storage for the discriminant and for +a `String` of length 100. +It is important to note that unconstrained objects do not require dynamic +allocation. It would be an improper implementation to place on the heap those +components whose size depends on discriminants. (This improper implementation +was used by some Ada83 compilers, where the `Name` component above +would have +been stored as a pointer to a dynamic string). Following the principle that +dynamic storage management should never be introduced implicitly, +an Ada compiler should reserve the full size for an unconstrained declared +object, and place it on the stack. + +This maximum size approach +has been a source of surprise to some users, who expect the default +values of the discriminants to determine the size reserved for an +unconstrained object: "If the default is 15, why should the object occupy +a larger size?" +The answer, of course, is that the discriminant may be later modified, +and its full range of values must be taken into account. This is why the +declaration: + + +.. code-block:: ada + + type Rec (D : Positive := 15) is record + Name : String (1..D); + end record; + + Too_Large : Rec; + +is flagged by the compiler with a warning: +an attempt to create `Too_Large` will raise `Storage_Error`, +because the required size includes `Positive'Last` +bytes. As the first example indicates, the proper approach is to declare an +index type of 'reasonable' range so that unconstrained objects are not too +large. + +One final wrinkle: if the object is declared to be `aliased`, or if it is +created in the heap by means of an allocator, then it is *not* +unconstrained: +it is constrained by the default values of the discriminants, and those values +cannot be modified by full assignment. This is because in the presence of +aliasing all views of the object (which may be manipulated by different tasks, +say) must be consistent, so it is imperative that the object, once created, +remain invariant. + +.. _Strict_Conformance_to_the_Ada_Reference_Manual: + +Strict Conformance to the Ada Reference Manual +============================================== + +The dynamic semantics defined by the Ada Reference Manual impose a set of +run-time checks to be generated. By default, the GNAT compiler will insert many +run-time checks into the compiled code, including most of those required by the +Ada Reference Manual. However, there are three checks that are not enabled +in the default mode for efficiency reasons: arithmetic overflow checking for +integer operations (including division by zero), checks for access before +elaboration on subprogram calls, and stack overflow checking (most operating +systems do not perform this check by default). + +Strict conformance to the Ada Reference Manual can be achieved by adding +three compiler options for overflow checking for integer operations +(*-gnato*), dynamic checks for access-before-elaboration on subprogram +calls and generic instantiations (*-gnatE*), and stack overflow +checking (*-fstack-check*). + +Note that the result of a floating point arithmetic operation in overflow and +invalid situations, when the `Machine_Overflows` attribute of the result +type is `False`, is to generate IEEE NaN and infinite values. This is the +case for machines compliant with the IEEE floating-point standard, but on +machines that are not fully compliant with this standard, such as Alpha, the +*-mieee* compiler flag must be used for achieving IEEE confirming +behavior (although at the cost of a significant performance penalty), so +infinite and NaN values are properly generated. + diff --git a/gcc/ada/doc/gnat_rm/interfacing_to_other_languages.rst b/gcc/ada/doc/gnat_rm/interfacing_to_other_languages.rst new file mode 100644 index 00000000000..32403e19903 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/interfacing_to_other_languages.rst @@ -0,0 +1,165 @@ +.. _Interfacing_to_Other_Languages: + +****************************** +Interfacing to Other Languages +****************************** + +The facilities in Annex B of the Ada Reference Manual are fully +implemented in GNAT, and in addition, a full interface to C++ is +provided. + +.. _Interfacing_to_C: + +Interfacing to C +================ + +Interfacing to C with GNAT can use one of two approaches: + +* + The types in the package `Interfaces.C` may be used. +* + Standard Ada types may be used directly. This may be less portable to + other compilers, but will work on all GNAT compilers, which guarantee + correspondence between the C and Ada types. + +Pragma `Convention C` may be applied to Ada types, but mostly has no +effect, since this is the default. The following table shows the +correspondence between Ada scalar types and the corresponding C types. + + +======================== ================================================================== +Ada Type C Type +======================== ================================================================== +``Integer`` ``int`` +``Short_Integer`` ``short`` +``Short_Short_Integer`` ``signed char`` +``Long_Integer`` ``long`` +``Long_Long_Integer`` ``long long`` +``Short_Float`` ``float`` +``Float`` ``float`` +``Long_Float`` ``double`` +``Long_Long_Float`` This is the longest floating-point type supported by the hardware. +======================== ================================================================== + +Additionally, there are the following general correspondences between Ada +and C types: + +* + Ada enumeration types map to C enumeration types directly if pragma + `Convention C` is specified, which causes them to have int + length. Without pragma `Convention C`, Ada enumeration types map to + 8, 16, or 32 bits (i.e., C types `signed char`, `short`, + `int`, respectively) depending on the number of values passed. + This is the only case in which pragma `Convention C` affects the + representation of an Ada type. + +* + Ada access types map to C pointers, except for the case of pointers to + unconstrained types in Ada, which have no direct C equivalent. + +* + Ada arrays map directly to C arrays. + +* + Ada records map directly to C structures. + +* + Packed Ada records map to C structures where all members are bit fields + of the length corresponding to the ``type'Size`` value in Ada. + +.. _Interfacing_to_C++: + +Interfacing to C++ +================== + +The interface to C++ makes use of the following pragmas, which are +primarily intended to be constructed automatically using a binding generator +tool, although it is possible to construct them by hand. + +Using these pragmas it is possible to achieve complete +inter-operability between Ada tagged types and C++ class definitions. +See :ref:`Implementation_Defined_Pragmas`, for more details. + +*pragma CPP_Class ([Entity =>] `LOCAL_NAME`)* + The argument denotes an entity in the current declarative region that is + declared as a tagged or untagged record type. It indicates that the type + corresponds to an externally declared C++ class type, and is to be laid + out the same way that C++ would lay out the type. + + Note: Pragma `CPP_Class` is currently obsolete. It is supported + for backward compatibility but its functionality is available + using pragma `Import` with `Convention` = `CPP`. + + +*pragma CPP_Constructor ([Entity =>] `LOCAL_NAME`)* + This pragma identifies an imported function (imported in the usual way + with pragma `Import`) as corresponding to a C++ constructor. + +A few restrictions are placed on the use of the `Access` attribute +in conjunction with subprograms subject to convention `CPP`: the +attribute may be used neither on primitive operations of a tagged +record type with convention `CPP`, imported or not, nor on +subprograms imported with pragma `CPP_Constructor`. + +In addition, C++ exceptions are propagated and can be handled in an +`others` choice of an exception handler. The corresponding Ada +occurrence has no message, and the simple name of the exception identity +contains ``Foreign_Exception``. Finalization and awaiting dependent +tasks works properly when such foreign exceptions are propagated. + +It is also possible to import a C++ exception using the following syntax: + + +:: + + LOCAL_NAME : exception; + pragma Import (Cpp, + [Entity =>] LOCAL_NAME, + [External_Name =>] static_string_EXPRESSION); + + +The `External_Name` is the name of the C++ RTTI symbol. You can then +cover a specific C++ exception in an exception handler. + +.. _Interfacing_to_COBOL: + +Interfacing to COBOL +==================== + +Interfacing to COBOL is achieved as described in section B.4 of +the Ada Reference Manual. + +.. _Interfacing_to_Fortran: + +Interfacing to Fortran +====================== + +Interfacing to Fortran is achieved as described in section B.5 of the +Ada Reference Manual. The pragma `Convention Fortran`, applied to a +multi-dimensional array causes the array to be stored in column-major +order as required for convenient interface to Fortran. + +.. _Interfacing_to_non-GNAT_Ada_code: + +Interfacing to non-GNAT Ada code +================================ + +It is possible to specify the convention `Ada` in a pragma +`Import` or pragma `Export`. However this refers to +the calling conventions used by GNAT, which may or may not be +similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005 +compiler to allow interoperation. + +If arguments types are kept simple, and if the foreign compiler generally +follows system calling conventions, then it may be possible to integrate +files compiled by other Ada compilers, provided that the elaboration +issues are adequately addressed (for example by eliminating the +need for any load time elaboration). + +In particular, GNAT running on VMS is designed to +be highly compatible with the DEC Ada 83 compiler, so this is one +case in which it is possible to import foreign units of this type, +provided that the data items passed are restricted to simple scalar +values or simple record types without variants, or simple array +types with fixed bounds. + diff --git a/gcc/ada/doc/gnat_rm/intrinsic_subprograms.rst b/gcc/ada/doc/gnat_rm/intrinsic_subprograms.rst new file mode 100644 index 00000000000..1558d06bef1 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/intrinsic_subprograms.rst @@ -0,0 +1,225 @@ +.. _Intrinsic_Subprograms: + +********************* +Intrinsic Subprograms +********************* + +.. index:: Intrinsic Subprograms + +GNAT allows a user application program to write the declaration: + + +.. code-block:: ada + + pragma Import (Intrinsic, name); + + +providing that the name corresponds to one of the implemented intrinsic +subprograms in GNAT, and that the parameter profile of the referenced +subprogram meets the requirements. This chapter describes the set of +implemented intrinsic subprograms, and the requirements on parameter profiles. +Note that no body is supplied; as with other uses of pragma Import, the +body is supplied elsewhere (in this case by the compiler itself). Note +that any use of this feature is potentially non-portable, since the +Ada standard does not require Ada compilers to implement this feature. + +.. _Intrinsic_Operators: + +Intrinsic Operators +=================== + +.. index:: Intrinsic operator + +All the predefined numeric operators in package Standard +in `pragma Import (Intrinsic,..)` +declarations. In the binary operator case, the operands must have the same +size. The operand or operands must also be appropriate for +the operator. For example, for addition, the operands must +both be floating-point or both be fixed-point, and the +right operand for `"**"` must have a root type of +`Standard.Integer'Base`. +You can use an intrinsic operator declaration as in the following example: + + +.. code-block:: ada + + type Int1 is new Integer; + type Int2 is new Integer; + + function "+" (X1 : Int1; X2 : Int2) return Int1; + function "+" (X1 : Int1; X2 : Int2) return Int2; + pragma Import (Intrinsic, "+"); + + +This declaration would permit 'mixed mode' arithmetic on items +of the differing types `Int1` and `Int2`. +It is also possible to specify such operators for private types, if the +full views are appropriate arithmetic types. + +.. _Compilation_Date: + +Compilation_Date +================ + +.. index:: Compilation_Date + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.Compilation_Date` to obtain the date of +the current compilation (in local time format MMM DD YYYY). + +.. _Compilation_Time: + +Compilation_Time +================ + +.. index:: Compilation_Time + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.Compilation_Time` to obtain the time of +the current compilation (in local time format HH:MM:SS). + +.. _Enclosing_Entity: + +Enclosing_Entity +================ + +.. index:: Enclosing_Entity + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.Enclosing_Entity` to obtain the name of +the current subprogram, package, task, entry, or protected subprogram. + +.. _Exception_Information: + +Exception_Information +===================== + +.. index:: Exception_Information' + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Current_Exception`. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +`GNAT.Current_Exception.Exception_Information` to obtain +the exception information associated with the current exception. + +.. _Exception_Message: + +Exception_Message +================= + +.. index:: Exception_Message + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Current_Exception`. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +`GNAT.Current_Exception.Exception_Message` to obtain +the message associated with the current exception. + +.. _Exception_Name: + +Exception_Name +============== + +.. index:: Exception_Name + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Current_Exception`. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +`GNAT.Current_Exception.Exception_Name` to obtain +the name of the current exception. + +.. _File: + +File +==== + +.. index:: File + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.File` to obtain the name of the current +file. + +.. _Line: + +Line +==== + +.. index:: Line + +This intrinsic subprogram is used in the implementation of the +library package `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.Line` to obtain the number of the current +source line. + +.. _Shifts_and_Rotates: + +Shifts and Rotates +================== + +.. index:: Shift_Left + +.. index:: Shift_Right + +.. index:: Shift_Right_Arithmetic + +.. index:: Rotate_Left + +.. index:: Rotate_Right + +In standard Ada, the shift and rotate functions are available only +for the predefined modular types in package `Interfaces`. However, in +GNAT it is possible to define these functions for any integer +type (signed or modular), as in this example: + + +.. code-block:: ada + + function Shift_Left + (Value : T; + Amount : Natural) return T; + + +The function name must be one of +Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or +Rotate_Right. T must be an integer type. T'Size must be +8, 16, 32 or 64 bits; if T is modular, the modulus +must be 2**8, 2**16, 2**32 or 2**64. +The result type must be the same as the type of `Value`. +The shift amount must be Natural. +The formal parameter names can be anything. + +A more convenient way of providing these shift operators is to use +the Provide_Shift_Operators pragma, which provides the function declarations +and corresponding pragma Import's for all five shift functions. + +.. _Source_Location: + +Source_Location +=============== + +.. index:: Source_Location + +This intrinsic subprogram is used in the implementation of the +library routine `GNAT.Source_Info`. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +`GNAT.Source_Info.Source_Location` to obtain the current +source file location. + diff --git a/gcc/ada/doc/gnat_rm/obsolescent_features.rst b/gcc/ada/doc/gnat_rm/obsolescent_features.rst new file mode 100644 index 00000000000..f5ea188a34d --- /dev/null +++ b/gcc/ada/doc/gnat_rm/obsolescent_features.rst @@ -0,0 +1,82 @@ +.. _Obsolescent_Features: + +******************** +Obsolescent Features +******************** + +This chapter describes features that are provided by GNAT, but are +considered obsolescent since there are preferred ways of achieving +the same effect. These features are provided solely for historical +compatibility purposes. + +.. _pragma_No_Run_Time: + +pragma No_Run_Time +================== + +The pragma `No_Run_Time` is used to achieve an affect similar +to the use of the "Zero Foot Print" configurable run time, but without +requiring a specially configured run time. The result of using this +pragma, which must be used for all units in a partition, is to restrict +the use of any language features requiring run-time support code. The +preferred usage is to use an appropriately configured run-time that +includes just those features that are to be made accessible. + +.. _pragma_Ravenscar: + +pragma Ravenscar +================ + +The pragma `Ravenscar` has exactly the same effect as pragma +`Profile (Ravenscar)`. The latter usage is preferred since it +is part of the new Ada 2005 standard. + +.. _pragma_Restricted_Run_Time: + +pragma Restricted_Run_Time +========================== + +The pragma `Restricted_Run_Time` has exactly the same effect as +pragma `Profile (Restricted)`. The latter usage is +preferred since the Ada 2005 pragma `Profile` is intended for +this kind of implementation dependent addition. + +.. _pragma_Task_Info: + +pragma Task_Info +================ + +The functionality provided by pragma `Task_Info` is now part of the +Ada language. The `CPU` aspect and the package +`System.Multiprocessors` offer a less system-dependent way to specify +task affinity or to query the number of processsors. + +Syntax + +.. code-block:: ada + + pragma Task_Info (EXPRESSION); + +This pragma appears within a task definition (like pragma +`Priority`) and applies to the task in which it appears. The +argument must be of type `System.Task_Info.Task_Info_Type`. +The `Task_Info` pragma provides system dependent control over +aspects of tasking implementation, for example, the ability to map +tasks to specific processors. For details on the facilities available +for the version of GNAT that you are using, see the documentation +in the spec of package System.Task_Info in the runtime +library. + +.. _package_System_Task_Info: + +package System.Task_Info (:file:`s-tasinf.ads`) +=============================================== + +This package provides target dependent functionality that is used +to support the `Task_Info` pragma. The predefined Ada package +`System.Multiprocessors` and the `CPU` aspect now provide a +standard replacement for GNAT's `Task_Info` functionality. + +.. raw:: latex + + \appendix diff --git a/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst b/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst new file mode 100644 index 00000000000..d2a19877fcc --- /dev/null +++ b/gcc/ada/doc/gnat_rm/representation_clauses_and_pragmas.rst @@ -0,0 +1,2138 @@ +.. _Representation_Clauses_and_Pragmas: + +********************************** +Representation Clauses and Pragmas +********************************** + +.. index:: Representation Clauses + +.. index:: Representation Clause + +.. index:: Representation Pragma + +.. index:: Pragma, representation + +This section describes the representation clauses accepted by GNAT, and +their effect on the representation of corresponding data objects. + +GNAT fully implements Annex C (Systems Programming). This means that all +the implementation advice sections in chapter 13 are fully implemented. +However, these sections only require a minimal level of support for +representation clauses. GNAT provides much more extensive capabilities, +and this section describes the additional capabilities provided. + +.. _Alignment_Clauses: + +Alignment Clauses +================= + +.. index:: Alignment Clause + +GNAT requires that all alignment clauses specify a power of 2, and all +default alignments are always a power of 2. The default alignment +values are as follows: + +* *Primitive Types*. + + For primitive types, the alignment is the minimum of the actual size of + objects of the type divided by `Storage_Unit`, + and the maximum alignment supported by the target. + (This maximum alignment is given by the GNAT-specific attribute + `Standard'Maximum_Alignment`; see :ref:`Attribute_Maximum_Alignment`.) + + .. index:: Maximum_Alignment attribute + + For example, for type `Long_Float`, the object size is 8 bytes, and the + default alignment will be 8 on any target that supports alignments + this large, but on some targets, the maximum alignment may be smaller + than 8, in which case objects of type `Long_Float` will be maximally + aligned. + +* *Arrays*. + + For arrays, the alignment is equal to the alignment of the component type + for the normal case where no packing or component size is given. If the + array is packed, and the packing is effective (see separate section on + packed arrays), then the alignment will be one for long packed arrays, + or arrays whose length is not known at compile time. For short packed + arrays, which are handled internally as modular types, the alignment + will be as described for primitive types, e.g., a packed array of length + 31 bits will have an object size of four bytes, and an alignment of 4. + +* *Records*. + + For the normal non-packed case, the alignment of a record is equal to + the maximum alignment of any of its components. For tagged records, this + includes the implicit access type used for the tag. If a pragma `Pack` + is used and all components are packable (see separate section on pragma + `Pack`), then the resulting alignment is 1, unless the layout of the + record makes it profitable to increase it. + + A special case is when: + + * the size of the record is given explicitly, or a + full record representation clause is given, and + + * the size of the record is 2, 4, or 8 bytes. + + In this case, an alignment is chosen to match the + size of the record. For example, if we have: + + .. code-block:: ada + + type Small is record + A, B : Character; + end record; + for Small'Size use 16; + + then the default alignment of the record type `Small` is 2, not 1. This + leads to more efficient code when the record is treated as a unit, and also + allows the type to specified as `Atomic` on architectures requiring + strict alignment. + +An alignment clause may specify a larger alignment than the default value +up to some maximum value dependent on the target (obtainable by using the +attribute reference `Standard'Maximum_Alignment`). It may also specify +a smaller alignment than the default value for enumeration, integer and +fixed point types, as well as for record types, for example + +.. code-block:: ada + + type V is record + A : Integer; + end record; + + for V'alignment use 1; + +.. index:: Alignment, default + +The default alignment for the type `V` is 4, as a result of the +Integer field in the record, but it is permissible, as shown, to +override the default alignment of the record with a smaller value. + +.. index:: Alignment, subtypes + +Note that according to the Ada standard, an alignment clause applies only +to the first named subtype. If additional subtypes are declared, then the +compiler is allowed to choose any alignment it likes, and there is no way +to control this choice. Consider: + +.. code-block:: ada + + type R is range 1 .. 10_000; + for R'Alignment use 1; + subtype RS is R range 1 .. 1000; + +The alignment clause specifies an alignment of 1 for the first named subtype +`R` but this does not necessarily apply to `RS`. When writing +portable Ada code, you should avoid writing code that explicitly or +implicitly relies on the alignment of such subtypes. + +For the GNAT compiler, if an explicit alignment clause is given, this +value is also used for any subsequent subtypes. So for GNAT, in the +above example, you can count on the alignment of `RS` being 1. But this +assumption is non-portable, and other compilers may choose different +alignments for the subtype `RS`. + +.. _Size_Clauses: + +Size Clauses +============ + +.. index:: Size Clause + +The default size for a type `T` is obtainable through the +language-defined attribute `T'Size` and also through the +equivalent GNAT-defined attribute `T'Value_Size`. +For objects of type `T`, GNAT will generally increase the type size +so that the object size (obtainable through the GNAT-defined attribute +`T'Object_Size`) +is a multiple of `T'Alignment * Storage_Unit`. + +For example: + +.. code-block:: ada + + type Smallint is range 1 .. 6; + + type Rec is record + Y1 : integer; + Y2 : boolean; + end record; + +In this example, `Smallint'Size` = `Smallint'Value_Size` = 3, +as specified by the RM rules, +but objects of this type will have a size of 8 +(`Smallint'Object_Size` = 8), +since objects by default occupy an integral number +of storage units. On some targets, notably older +versions of the Digital Alpha, the size of stand +alone objects of this type may be 32, reflecting +the inability of the hardware to do byte load/stores. + +Similarly, the size of type `Rec` is 40 bits +(`Rec'Size` = `Rec'Value_Size` = 40), but +the alignment is 4, so objects of this type will have +their size increased to 64 bits so that it is a multiple +of the alignment (in bits). This decision is +in accordance with the specific Implementation Advice in RM 13.3(43): + + "A `Size` clause should be supported for an object if the specified + `Size` is at least as large as its subtype's `Size`, and corresponds + to a size in storage elements that is a multiple of the object's + `Alignment` (if the `Alignment` is nonzero)." + +An explicit size clause may be used to override the default size by +increasing it. For example, if we have: + +.. code-block:: ada + + type My_Boolean is new Boolean; + for My_Boolean'Size use 32; + +then values of this type will always be 32 bits long. In the case of +discrete types, the size can be increased up to 64 bits, with the effect +that the entire specified field is used to hold the value, sign- or +zero-extended as appropriate. If more than 64 bits is specified, then +padding space is allocated after the value, and a warning is issued that +there are unused bits. + +Similarly the size of records and arrays may be increased, and the effect +is to add padding bits after the value. This also causes a warning message +to be generated. + +The largest Size value permitted in GNAT is 2**31-1. Since this is a +Size in bits, this corresponds to an object of size 256 megabytes (minus +one). This limitation is true on all targets. The reason for this +limitation is that it improves the quality of the code in many cases +if it is known that a Size value can be accommodated in an object of +type Integer. + + +.. _Storage_Size_Clauses: + +Storage_Size Clauses +==================== + +.. index:: Storage_Size Clause + +For tasks, the `Storage_Size` clause specifies the amount of space +to be allocated for the task stack. This cannot be extended, and if the +stack is exhausted, then `Storage_Error` will be raised (if stack +checking is enabled). Use a `Storage_Size` attribute definition clause, +or a `Storage_Size` pragma in the task definition to set the +appropriate required size. A useful technique is to include in every +task definition a pragma of the form: + +.. code-block:: ada + + pragma Storage_Size (Default_Stack_Size); + +Then `Default_Stack_Size` can be defined in a global package, and +modified as required. Any tasks requiring stack sizes different from the +default can have an appropriate alternative reference in the pragma. + +You can also use the *-d* binder switch to modify the default stack +size. + +For access types, the `Storage_Size` clause specifies the maximum +space available for allocation of objects of the type. If this space is +exceeded then `Storage_Error` will be raised by an allocation attempt. +In the case where the access type is declared local to a subprogram, the +use of a `Storage_Size` clause triggers automatic use of a special +predefined storage pool (`System.Pool_Size`) that ensures that all +space for the pool is automatically reclaimed on exit from the scope in +which the type is declared. + +A special case recognized by the compiler is the specification of a +`Storage_Size` of zero for an access type. This means that no +items can be allocated from the pool, and this is recognized at compile +time, and all the overhead normally associated with maintaining a fixed +size storage pool is eliminated. Consider the following example: + +.. code-block:: ada + + procedure p is + type R is array (Natural) of Character; + type P is access all R; + for P'Storage_Size use 0; + -- Above access type intended only for interfacing purposes + + y : P; + + procedure g (m : P); + pragma Import (C, g); + + -- ... + + begin + -- ... + y := new R; + end; + +As indicated in this example, these dummy storage pools are often useful in +connection with interfacing where no object will ever be allocated. If you +compile the above example, you get the warning: + +:: + + p.adb:16:09: warning: allocation from empty storage pool + p.adb:16:09: warning: Storage_Error will be raised at run time + + +Of course in practice, there will not be any explicit allocators in the +case of such an access declaration. + +.. _Size_of_Variant_Record_Objects: + +Size of Variant Record Objects +============================== + +.. index:: Size, variant record objects + +.. index:: Variant record objects, size + +In the case of variant record objects, there is a question whether Size gives +information about a particular variant, or the maximum size required +for any variant. Consider the following program + +.. code-block:: ada + + with Text_IO; use Text_IO; + procedure q is + type R1 (A : Boolean := False) is record + case A is + when True => X : Character; + when False => null; + end case; + end record; + + V1 : R1 (False); + V2 : R1; + + begin + Put_Line (Integer'Image (V1'Size)); + Put_Line (Integer'Image (V2'Size)); + end q; + +Here we are dealing with a variant record, where the True variant +requires 16 bits, and the False variant requires 8 bits. +In the above example, both V1 and V2 contain the False variant, +which is only 8 bits long. However, the result of running the +program is: + +:: + + 8 + 16 + +The reason for the difference here is that the discriminant value of +V1 is fixed, and will always be False. It is not possible to assign +a True variant value to V1, therefore 8 bits is sufficient. On the +other hand, in the case of V2, the initial discriminant value is +False (from the default), but it is possible to assign a True +variant value to V2, therefore 16 bits must be allocated for V2 +in the general case, even fewer bits may be needed at any particular +point during the program execution. + +As can be seen from the output of this program, the `'Size` +attribute applied to such an object in GNAT gives the actual allocated +size of the variable, which is the largest size of any of the variants. +The Ada Reference Manual is not completely clear on what choice should +be made here, but the GNAT behavior seems most consistent with the +language in the RM. + +In some cases, it may be desirable to obtain the size of the current +variant, rather than the size of the largest variant. This can be +achieved in GNAT by making use of the fact that in the case of a +subprogram parameter, GNAT does indeed return the size of the current +variant (because a subprogram has no way of knowing how much space +is actually allocated for the actual). + +Consider the following modified version of the above program: + +.. code-block:: ada + + with Text_IO; use Text_IO; + procedure q is + type R1 (A : Boolean := False) is record + case A is + when True => X : Character; + when False => null; + end case; + end record; + + V2 : R1; + + function Size (V : R1) return Integer is + begin + return V'Size; + end Size; + + begin + Put_Line (Integer'Image (V2'Size)); + Put_Line (Integer'IMage (Size (V2))); + V2 := (True, 'x'); + Put_Line (Integer'Image (V2'Size)); + Put_Line (Integer'IMage (Size (V2))); + end q; + +The output from this program is + +:: + + 16 + 8 + 16 + 16 + +Here we see that while the `'Size` attribute always returns +the maximum size, regardless of the current variant value, the +`Size` function does indeed return the size of the current +variant value. + + +.. _Biased_Representation: + +Biased Representation +===================== + +.. index:: Size for biased representation + +.. index:: Biased representation + +In the case of scalars with a range starting at other than zero, it is +possible in some cases to specify a size smaller than the default minimum +value, and in such cases, GNAT uses an unsigned biased representation, +in which zero is used to represent the lower bound, and successive values +represent successive values of the type. + +For example, suppose we have the declaration: + +.. code-block:: ada + + type Small is range -7 .. -4; + for Small'Size use 2; + +Although the default size of type `Small` is 4, the `Size` +clause is accepted by GNAT and results in the following representation +scheme: + +:: + + -7 is represented as 2#00# + -6 is represented as 2#01# + -5 is represented as 2#10# + -4 is represented as 2#11# + +Biased representation is only used if the specified `Size` clause +cannot be accepted in any other manner. These reduced sizes that force +biased representation can be used for all discrete types except for +enumeration types for which a representation clause is given. + + +.. _Value_Size_and_Object_Size_Clauses: + +Value_Size and Object_Size Clauses +================================== + +.. index:: Value_Size +.. index:: Object_Size +.. index:: Size, of objects + +In Ada 95 and Ada 2005, `T'Size` for a type `T` is the minimum +number of bits required to hold values of type `T`. +Although this interpretation was allowed in Ada 83, it was not required, +and this requirement in practice can cause some significant difficulties. +For example, in most Ada 83 compilers, `Natural'Size` was 32. +However, in Ada 95 and Ada 2005, +`Natural'Size` is +typically 31. This means that code may change in behavior when moving +from Ada 83 to Ada 95 or Ada 2005. For example, consider: + +.. code-block:: ada + + type Rec is record; + A : Natural; + B : Natural; + end record; + + for Rec use record + at 0 range 0 .. Natural'Size - 1; + at 0 range Natural'Size .. 2 * Natural'Size - 1; + end record; + +In the above code, since the typical size of `Natural` objects +is 32 bits and `Natural'Size` is 31, the above code can cause +unexpected inefficient packing in Ada 95 and Ada 2005, and in general +there are cases where the fact that the object size can exceed the +size of the type causes surprises. + +To help get around this problem GNAT provides two implementation +defined attributes, `Value_Size` and `Object_Size`. When +applied to a type, these attributes yield the size of the type +(corresponding to the RM defined size attribute), and the size of +objects of the type respectively. + +The `Object_Size` is used for determining the default size of +objects and components. This size value can be referred to using the +`Object_Size` attribute. The phrase 'is used' here means that it is +the basis of the determination of the size. The backend is free to +pad this up if necessary for efficiency, e.g., an 8-bit stand-alone +character might be stored in 32 bits on a machine with no efficient +byte access instructions such as the Alpha. + +The default rules for the value of `Object_Size` for +discrete types are as follows: + +* + The `Object_Size` for base subtypes reflect the natural hardware + size in bits (run the compiler with *-gnatS* to find those values + for numeric types). Enumeration types and fixed-point base subtypes have + 8, 16, 32 or 64 bits for this size, depending on the range of values + to be stored. + +* + The `Object_Size` of a subtype is the same as the + `Object_Size` of + the type from which it is obtained. + +* + The `Object_Size` of a derived base type is copied from the parent + base type, and the `Object_Size` of a derived first subtype is copied + from the parent first subtype. + +The `Value_Size` attribute +is the (minimum) number of bits required to store a value +of the type. +This value is used to determine how tightly to pack +records or arrays with components of this type, and also affects +the semantics of unchecked conversion (unchecked conversions where +the `Value_Size` values differ generate a warning, and are potentially +target dependent). + +The default rules for the value of `Value_Size` are as follows: + +* + The `Value_Size` for a base subtype is the minimum number of bits + required to store all values of the type (including the sign bit + only if negative values are possible). + +* + If a subtype statically matches the first subtype of a given type, then it has + by default the same `Value_Size` as the first subtype. This is a + consequence of RM 13.1(14): "if two subtypes statically match, + then their subtype-specific aspects are the same".) + +* + All other subtypes have a `Value_Size` corresponding to the minimum + number of bits required to store all values of the subtype. For + dynamic bounds, it is assumed that the value can range down or up + to the corresponding bound of the ancestor + +The RM defined attribute `Size` corresponds to the +`Value_Size` attribute. + +The `Size` attribute may be defined for a first-named subtype. This sets +the `Value_Size` of +the first-named subtype to the given value, and the +`Object_Size` of this first-named subtype to the given value padded up +to an appropriate boundary. It is a consequence of the default rules +above that this `Object_Size` will apply to all further subtypes. On the +other hand, `Value_Size` is affected only for the first subtype, any +dynamic subtypes obtained from it directly, and any statically matching +subtypes. The `Value_Size` of any other static subtypes is not affected. + +`Value_Size` and +`Object_Size` may be explicitly set for any subtype using +an attribute definition clause. Note that the use of these attributes +can cause the RM 13.1(14) rule to be violated. If two access types +reference aliased objects whose subtypes have differing `Object_Size` +values as a result of explicit attribute definition clauses, then it +is illegal to convert from one access subtype to the other. For a more +complete description of this additional legality rule, see the +description of the `Object_Size` attribute. + +At the implementation level, Esize stores the Object_Size and the +RM_Size field stores the `Value_Size` (and hence the value of the +`Size` attribute, +which, as noted above, is equivalent to `Value_Size`). + +To get a feel for the difference, consider the following examples (note +that in each case the base is `Short_Short_Integer` with a size of 8): + ++---------------------------------------------+-------------+-------------+ +|Type or subtype declaration | Object_Size | Value_Size| ++=============================================+=============+=============+ +|``type x1 is range 0 .. 5;`` | 8 | 3 | ++---------------------------------------------+-------------+-------------+ +|``type x2 is range 0 .. 5;`` | 16 | 12 | +|``for x2'size use 12;`` | | | ++---------------------------------------------+-------------+-------------+ +|``subtype x3 is x2 range 0 .. 3;`` | 16 | 2 | ++---------------------------------------------+-------------+-------------+ +|``subtype x4 is x2'base range 0 .. 10;`` | 8 | 4 | ++---------------------------------------------+-------------+-------------+ +|``subtype x5 is x2 range 0 .. dynamic;`` | 16 | 3* | ++---------------------------------------------+-------------+-------------+ +|``subtype x6 is x2'base range 0 .. dynamic;``| 8 | 3* | ++---------------------------------------------+-------------+-------------+ + +Note: the entries marked '3*' are not actually specified by the Ada +Reference Manual, but it seems in the spirit of the RM rules to allocate +the minimum number of bits (here 3, given the range for `x2`) +known to be large enough to hold the given range of values. + +So far, so good, but GNAT has to obey the RM rules, so the question is +under what conditions must the RM `Size` be used. +The following is a list +of the occasions on which the RM `Size` must be used: + +* + Component size for packed arrays or records + +* + Value of the attribute `Size` for a type + +* + Warning about sizes not matching for unchecked conversion + +For record types, the `Object_Size` is always a multiple of the +alignment of the type (this is true for all types). In some cases the +`Value_Size` can be smaller. Consider: + + +.. code-block:: ada + + type R is record + X : Integer; + Y : Character; + end record; + + +On a typical 32-bit architecture, the X component will be four bytes, and +require four-byte alignment, and the Y component will be one byte. In this +case `R'Value_Size` will be 40 (bits) since this is the minimum size +required to store a value of this type, and for example, it is permissible +to have a component of type R in an outer array whose component size is +specified to be 48 bits. However, `R'Object_Size` will be 64 (bits), +since it must be rounded up so that this value is a multiple of the +alignment (4 bytes = 32 bits). + +For all other types, the `Object_Size` +and Value_Size are the same (and equivalent to the RM attribute `Size`). +Only `Size` may be specified for such types. + +Note that `Value_Size` can be used to force biased representation +for a particular subtype. Consider this example: + + +.. code-block:: ada + + type R is (A, B, C, D, E, F); + subtype RAB is R range A .. B; + subtype REF is R range E .. F; + + +By default, `RAB` +has a size of 1 (sufficient to accommodate the representation +of `A` and `B`, 0 and 1), and `REF` +has a size of 3 (sufficient to accommodate the representation +of `E` and `F`, 4 and 5). But if we add the +following `Value_Size` attribute definition clause: + + +.. code-block:: ada + + for REF'Value_Size use 1; + + +then biased representation is forced for `REF`, +and 0 will represent `E` and 1 will represent `F`. +A warning is issued when a `Value_Size` attribute +definition clause forces biased representation. This +warning can be turned off using `-gnatw.B`. + +.. _Component_Size_Clauses: + +Component_Size Clauses +====================== + +.. index:: Component_Size Clause + +Normally, the value specified in a component size clause must be consistent +with the subtype of the array component with regard to size and alignment. +In other words, the value specified must be at least equal to the size +of this subtype, and must be a multiple of the alignment value. + +In addition, component size clauses are allowed which cause the array +to be packed, by specifying a smaller value. A first case is for +component size values in the range 1 through 63. The value specified +must not be smaller than the Size of the subtype. GNAT will accurately +honor all packing requests in this range. For example, if we have: + + +.. code-block:: ada + + type r is array (1 .. 8) of Natural; + for r'Component_Size use 31; + + +then the resulting array has a length of 31 bytes (248 bits = 8 * 31). +Of course access to the components of such an array is considerably +less efficient than if the natural component size of 32 is used. +A second case is when the subtype of the component is a record type +padded because of its default alignment. For example, if we have: + + +.. code-block:: ada + + type r is record + i : Integer; + j : Integer; + b : Boolean; + end record; + + type a is array (1 .. 8) of r; + for a'Component_Size use 72; + + +then the resulting array has a length of 72 bytes, instead of 96 bytes +if the alignment of the record (4) was obeyed. + +Note that there is no point in giving both a component size clause +and a pragma Pack for the same array type. if such duplicate +clauses are given, the pragma Pack will be ignored. + +.. _Bit_Order_Clauses: + +Bit_Order Clauses +================= + +.. index:: Bit_Order Clause + +.. index:: bit ordering + +.. index:: ordering, of bits + +For record subtypes, GNAT permits the specification of the `Bit_Order` +attribute. The specification may either correspond to the default bit +order for the target, in which case the specification has no effect and +places no additional restrictions, or it may be for the non-standard +setting (that is the opposite of the default). + +In the case where the non-standard value is specified, the effect is +to renumber bits within each byte, but the ordering of bytes is not +affected. There are certain +restrictions placed on component clauses as follows: + + +* Components fitting within a single storage unit. + + These are unrestricted, and the effect is merely to renumber bits. For + example if we are on a little-endian machine with `Low_Order_First` + being the default, then the following two declarations have exactly + the same effect: + + + :: + + type R1 is record + A : Boolean; + B : Integer range 1 .. 120; + end record; + + for R1 use record + A at 0 range 0 .. 0; + B at 0 range 1 .. 7; + end record; + + type R2 is record + A : Boolean; + B : Integer range 1 .. 120; + end record; + + for R2'Bit_Order use High_Order_First; + + for R2 use record + A at 0 range 7 .. 7; + B at 0 range 0 .. 6; + end record; + + + The useful application here is to write the second declaration with the + `Bit_Order` attribute definition clause, and know that it will be treated + the same, regardless of whether the target is little-endian or big-endian. + +* Components occupying an integral number of bytes. + + These are components that exactly fit in two or more bytes. Such component + declarations are allowed, but have no effect, since it is important to realize + that the `Bit_Order` specification does not affect the ordering of bytes. + In particular, the following attempt at getting an endian-independent integer + does not work: + + + :: + + type R2 is record + A : Integer; + end record; + + for R2'Bit_Order use High_Order_First; + + for R2 use record + A at 0 range 0 .. 31; + end record; + + + This declaration will result in a little-endian integer on a + little-endian machine, and a big-endian integer on a big-endian machine. + If byte flipping is required for interoperability between big- and + little-endian machines, this must be explicitly programmed. This capability + is not provided by `Bit_Order`. + +* Components that are positioned across byte boundaries + + but do not occupy an integral number of bytes. Given that bytes are not + reordered, such fields would occupy a non-contiguous sequence of bits + in memory, requiring non-trivial code to reassemble. They are for this + reason not permitted, and any component clause specifying such a layout + will be flagged as illegal by GNAT. + + +Since the misconception that Bit_Order automatically deals with all +endian-related incompatibilities is a common one, the specification of +a component field that is an integral number of bytes will always +generate a warning. This warning may be suppressed using `pragma Warnings (Off)` +if desired. The following section contains additional +details regarding the issue of byte ordering. + +.. _Effect_of_Bit_Order_on_Byte_Ordering: + +Effect of Bit_Order on Byte Ordering +==================================== + +.. index:: byte ordering + +.. index:: ordering, of bytes + +In this section we will review the effect of the `Bit_Order` attribute +definition clause on byte ordering. Briefly, it has no effect at all, but +a detailed example will be helpful. Before giving this +example, let us review the precise +definition of the effect of defining `Bit_Order`. The effect of a +non-standard bit order is described in section 15.5.3 of the Ada +Reference Manual: + + "2 A bit ordering is a method of interpreting the meaning of + the storage place attributes." + +To understand the precise definition of storage place attributes in +this context, we visit section 13.5.1 of the manual: + + "13 A record_representation_clause (without the mod_clause) + specifies the layout. The storage place attributes (see 13.5.2) + are taken from the values of the position, first_bit, and last_bit + expressions after normalizing those values so that first_bit is + less than Storage_Unit." + +The critical point here is that storage places are taken from +the values after normalization, not before. So the `Bit_Order` +interpretation applies to normalized values. The interpretation +is described in the later part of the 15.5.3 paragraph: + + "2 A bit ordering is a method of interpreting the meaning of + the storage place attributes. High_Order_First (known in the + vernacular as 'big endian') means that the first bit of a + storage element (bit 0) is the most significant bit (interpreting + the sequence of bits that represent a component as an unsigned + integer value). Low_Order_First (known in the vernacular as + 'little endian') means the opposite: the first bit is the + least significant." + +Note that the numbering is with respect to the bits of a storage +unit. In other words, the specification affects only the numbering +of bits within a single storage unit. + +We can make the effect clearer by giving an example. + +Suppose that we have an external device which presents two bytes, the first +byte presented, which is the first (low addressed byte) of the two byte +record is called Master, and the second byte is called Slave. + +The left most (most significant bit is called Control for each byte, and +the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost +(least significant) bit. + +On a big-endian machine, we can write the following representation clause + + +.. code-block:: ada + + type Data is record + Master_Control : Bit; + Master_V1 : Bit; + Master_V2 : Bit; + Master_V3 : Bit; + Master_V4 : Bit; + Master_V5 : Bit; + Master_V6 : Bit; + Master_V7 : Bit; + Slave_Control : Bit; + Slave_V1 : Bit; + Slave_V2 : Bit; + Slave_V3 : Bit; + Slave_V4 : Bit; + Slave_V5 : Bit; + Slave_V6 : Bit; + Slave_V7 : Bit; + end record; + + for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 1 range 0 .. 0; + Slave_V1 at 1 range 1 .. 1; + Slave_V2 at 1 range 2 .. 2; + Slave_V3 at 1 range 3 .. 3; + Slave_V4 at 1 range 4 .. 4; + Slave_V5 at 1 range 5 .. 5; + Slave_V6 at 1 range 6 .. 6; + Slave_V7 at 1 range 7 .. 7; + end record; + + +Now if we move this to a little endian machine, then the bit ordering within +the byte is backwards, so we have to rewrite the record rep clause as: + + +.. code-block:: ada + + for Data use record + Master_Control at 0 range 7 .. 7; + Master_V1 at 0 range 6 .. 6; + Master_V2 at 0 range 5 .. 5; + Master_V3 at 0 range 4 .. 4; + Master_V4 at 0 range 3 .. 3; + Master_V5 at 0 range 2 .. 2; + Master_V6 at 0 range 1 .. 1; + Master_V7 at 0 range 0 .. 0; + Slave_Control at 1 range 7 .. 7; + Slave_V1 at 1 range 6 .. 6; + Slave_V2 at 1 range 5 .. 5; + Slave_V3 at 1 range 4 .. 4; + Slave_V4 at 1 range 3 .. 3; + Slave_V5 at 1 range 2 .. 2; + Slave_V6 at 1 range 1 .. 1; + Slave_V7 at 1 range 0 .. 0; + end record; + + +It is a nuisance to have to rewrite the clause, especially if +the code has to be maintained on both machines. However, +this is a case that we can handle with the +`Bit_Order` attribute if it is implemented. +Note that the implementation is not required on byte addressed +machines, but it is indeed implemented in GNAT. +This means that we can simply use the +first record clause, together with the declaration + + +.. code-block:: ada + + for Data'Bit_Order use High_Order_First; + + +and the effect is what is desired, namely the layout is exactly the same, +independent of whether the code is compiled on a big-endian or little-endian +machine. + +The important point to understand is that byte ordering is not affected. +A `Bit_Order` attribute definition never affects which byte a field +ends up in, only where it ends up in that byte. +To make this clear, let us rewrite the record rep clause of the previous +example as: + + +.. code-block:: ada + + for Data'Bit_Order use High_Order_First; + for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 0 range 8 .. 8; + Slave_V1 at 0 range 9 .. 9; + Slave_V2 at 0 range 10 .. 10; + Slave_V3 at 0 range 11 .. 11; + Slave_V4 at 0 range 12 .. 12; + Slave_V5 at 0 range 13 .. 13; + Slave_V6 at 0 range 14 .. 14; + Slave_V7 at 0 range 15 .. 15; + end record; + + +This is exactly equivalent to saying (a repeat of the first example): + + +.. code-block:: ada + + for Data'Bit_Order use High_Order_First; + for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 1 range 0 .. 0; + Slave_V1 at 1 range 1 .. 1; + Slave_V2 at 1 range 2 .. 2; + Slave_V3 at 1 range 3 .. 3; + Slave_V4 at 1 range 4 .. 4; + Slave_V5 at 1 range 5 .. 5; + Slave_V6 at 1 range 6 .. 6; + Slave_V7 at 1 range 7 .. 7; + end record; + + +Why are they equivalent? Well take a specific field, the `Slave_V2` +field. The storage place attributes are obtained by normalizing the +values given so that the `First_Bit` value is less than 8. After +normalizing the values (0,10,10) we get (1,2,2) which is exactly what +we specified in the other case. + +Now one might expect that the `Bit_Order` attribute might affect +bit numbering within the entire record component (two bytes in this +case, thus affecting which byte fields end up in), but that is not +the way this feature is defined, it only affects numbering of bits, +not which byte they end up in. + +Consequently it never makes sense to specify a starting bit number +greater than 7 (for a byte addressable field) if an attribute +definition for `Bit_Order` has been given, and indeed it +may be actively confusing to specify such a value, so the compiler +generates a warning for such usage. + +If you do need to control byte ordering then appropriate conditional +values must be used. If in our example, the slave byte came first on +some machines we might write: + +.. code-block:: ada + + Master_Byte_First constant Boolean := ...; + + Master_Byte : constant Natural := + 1 - Boolean'Pos (Master_Byte_First); + Slave_Byte : constant Natural := + Boolean'Pos (Master_Byte_First); + + for Data'Bit_Order use High_Order_First; + for Data use record + Master_Control at Master_Byte range 0 .. 0; + Master_V1 at Master_Byte range 1 .. 1; + Master_V2 at Master_Byte range 2 .. 2; + Master_V3 at Master_Byte range 3 .. 3; + Master_V4 at Master_Byte range 4 .. 4; + Master_V5 at Master_Byte range 5 .. 5; + Master_V6 at Master_Byte range 6 .. 6; + Master_V7 at Master_Byte range 7 .. 7; + Slave_Control at Slave_Byte range 0 .. 0; + Slave_V1 at Slave_Byte range 1 .. 1; + Slave_V2 at Slave_Byte range 2 .. 2; + Slave_V3 at Slave_Byte range 3 .. 3; + Slave_V4 at Slave_Byte range 4 .. 4; + Slave_V5 at Slave_Byte range 5 .. 5; + Slave_V6 at Slave_Byte range 6 .. 6; + Slave_V7 at Slave_Byte range 7 .. 7; + end record; + +Now to switch between machines, all that is necessary is +to set the boolean constant `Master_Byte_First` in +an appropriate manner. + +.. _Pragma_Pack_for_Arrays: + +Pragma Pack for Arrays +====================== + +.. index:: Pragma Pack (for arrays) + +Pragma `Pack` applied to an array has no effect unless the component type +is packable. For a component type to be packable, it must be one of the +following cases: + +* + Any scalar type +* + Any type whose size is specified with a size clause +* + Any packed array type with a static size +* + Any record type padded because of its default alignment + +For all these cases, if the component subtype size is in the range +1 through 63, then the effect of the pragma `Pack` is exactly as though a +component size were specified giving the component subtype size. +For example if we have: + +.. code-block:: ada + + type r is range 0 .. 17; + + type ar is array (1 .. 8) of r; + pragma Pack (ar); + +Then the component size of `ar` will be set to 5 (i.e., to `r'size`, +and the size of the array `ar` will be exactly 40 bits. + +Note that in some cases this rather fierce approach to packing can produce +unexpected effects. For example, in Ada 95 and Ada 2005, +subtype `Natural` typically has a size of 31, meaning that if you +pack an array of `Natural`, you get 31-bit +close packing, which saves a few bits, but results in far less efficient +access. Since many other Ada compilers will ignore such a packing request, +GNAT will generate a warning on some uses of pragma `Pack` that it guesses +might not be what is intended. You can easily remove this warning by +using an explicit `Component_Size` setting instead, which never generates +a warning, since the intention of the programmer is clear in this case. + +GNAT treats packed arrays in one of two ways. If the size of the array is +known at compile time and is less than 64 bits, then internally the array +is represented as a single modular type, of exactly the appropriate number +of bits. If the length is greater than 63 bits, or is not known at compile +time, then the packed array is represented as an array of bytes, and the +length is always a multiple of 8 bits. + +Note that to represent a packed array as a modular type, the alignment must +be suitable for the modular type involved. For example, on typical machines +a 32-bit packed array will be represented by a 32-bit modular integer with +an alignment of four bytes. If you explicitly override the default alignment +with an alignment clause that is too small, the modular representation +cannot be used. For example, consider the following set of declarations: + +.. code-block:: ada + + type R is range 1 .. 3; + type S is array (1 .. 31) of R; + for S'Component_Size use 2; + for S'Size use 62; + for S'Alignment use 1; + +If the alignment clause were not present, then a 62-bit modular +representation would be chosen (typically with an alignment of 4 or 8 +bytes depending on the target). But the default alignment is overridden +with the explicit alignment clause. This means that the modular +representation cannot be used, and instead the array of bytes +representation must be used, meaning that the length must be a multiple +of 8. Thus the above set of declarations will result in a diagnostic +rejecting the size clause and noting that the minimum size allowed is 64. + +.. index:: Pragma Pack (for type Natural) + +.. index:: Pragma Pack warning + +One special case that is worth noting occurs when the base type of the +component size is 8/16/32 and the subtype is one bit less. Notably this +occurs with subtype `Natural`. Consider: + +.. code-block:: ada + + type Arr is array (1 .. 32) of Natural; + pragma Pack (Arr); + +In all commonly used Ada 83 compilers, this pragma Pack would be ignored, +since typically `Natural'Size` is 32 in Ada 83, and in any case most +Ada 83 compilers did not attempt 31 bit packing. + +In Ada 95 and Ada 2005, `Natural'Size` is required to be 31. Furthermore, +GNAT really does pack 31-bit subtype to 31 bits. This may result in a +substantial unintended performance penalty when porting legacy Ada 83 code. +To help prevent this, GNAT generates a warning in such cases. If you really +want 31 bit packing in a case like this, you can set the component size +explicitly: + +.. code-block:: ada + + type Arr is array (1 .. 32) of Natural; + for Arr'Component_Size use 31; + +Here 31-bit packing is achieved as required, and no warning is generated, +since in this case the programmer intention is clear. + +.. _Pragma_Pack_for_Records: + +Pragma Pack for Records +======================= + +.. index:: Pragma Pack (for records) + +Pragma `Pack` applied to a record will pack the components to reduce +wasted space from alignment gaps and by reducing the amount of space +taken by components. We distinguish between *packable* components and +*non-packable* components. +Components of the following types are considered packable: + +* + Components of a primitive type are packable unless they are aliased + or of an atomic type. + +* + Small packed arrays, whose size does not exceed 64 bits, and where the + size is statically known at compile time, are represented internally + as modular integers, and so they are also packable. + + +All packable components occupy the exact number of bits corresponding to +their `Size` value, and are packed with no padding bits, i.e., they +can start on an arbitrary bit boundary. + +All other types are non-packable, they occupy an integral number of +storage units, and +are placed at a boundary corresponding to their alignment requirements. + +For example, consider the record + +.. code-block:: ada + + type Rb1 is array (1 .. 13) of Boolean; + pragma Pack (Rb1); + + type Rb2 is array (1 .. 65) of Boolean; + pragma Pack (Rb2); + + type AF is new Float with Atomic; + + type X2 is record + L1 : Boolean; + L2 : Duration; + L3 : AF; + L4 : Boolean; + L5 : Rb1; + L6 : Rb2; + end record; + pragma Pack (X2); + +The representation for the record X2 is as follows: + +.. code-block:: ada + + for X2'Size use 224; + for X2 use record + L1 at 0 range 0 .. 0; + L2 at 0 range 1 .. 64; + L3 at 12 range 0 .. 31; + L4 at 16 range 0 .. 0; + L5 at 16 range 1 .. 13; + L6 at 18 range 0 .. 71; + end record; + +Studying this example, we see that the packable fields `L1` +and `L2` are +of length equal to their sizes, and placed at specific bit boundaries (and +not byte boundaries) to +eliminate padding. But `L3` is of a non-packable float type (because +it is aliased), so it is on the next appropriate alignment boundary. + +The next two fields are fully packable, so `L4` and `L5` are +minimally packed with no gaps. However, type `Rb2` is a packed +array that is longer than 64 bits, so it is itself non-packable. Thus +the `L6` field is aligned to the next byte boundary, and takes an +integral number of bytes, i.e., 72 bits. + +.. _Record_Representation_Clauses: + +Record Representation Clauses +============================= + +.. index:: Record Representation Clause + +Record representation clauses may be given for all record types, including +types obtained by record extension. Component clauses are allowed for any +static component. The restrictions on component clauses depend on the type +of the component. + +.. index:: Component Clause + +For all components of an elementary type, the only restriction on component +clauses is that the size must be at least the 'Size value of the type +(actually the Value_Size). There are no restrictions due to alignment, +and such components may freely cross storage boundaries. + +Packed arrays with a size up to and including 64 bits are represented +internally using a modular type with the appropriate number of bits, and +thus the same lack of restriction applies. For example, if you declare: + +.. code-block:: ada + + type R is array (1 .. 49) of Boolean; + pragma Pack (R); + for R'Size use 49; + +then a component clause for a component of type R may start on any +specified bit boundary, and may specify a value of 49 bits or greater. + +For packed bit arrays that are longer than 64 bits, there are two +cases. If the component size is a power of 2 (1,2,4,8,16,32 bits), +including the important case of single bits or boolean values, then +there are no limitations on placement of such components, and they +may start and end at arbitrary bit boundaries. + +If the component size is not a power of 2 (e.g., 3 or 5), then +an array of this type longer than 64 bits must always be placed on +on a storage unit (byte) boundary and occupy an integral number +of storage units (bytes). Any component clause that does not +meet this requirement will be rejected. + +Any aliased component, or component of an aliased type, must +have its normal alignment and size. A component clause that +does not meet this requirement will be rejected. + +The tag field of a tagged type always occupies an address sized field at +the start of the record. No component clause may attempt to overlay this +tag. When a tagged type appears as a component, the tag field must have +proper alignment + +In the case of a record extension T1, of a type T, no component clause applied +to the type T1 can specify a storage location that would overlap the first +T'Size bytes of the record. + +For all other component types, including non-bit-packed arrays, +the component can be placed at an arbitrary bit boundary, +so for example, the following is permitted: + +.. code-block:: ada + + type R is array (1 .. 10) of Boolean; + for R'Size use 80; + + type Q is record + G, H : Boolean; + L, M : R; + end record; + + for Q use record + G at 0 range 0 .. 0; + H at 0 range 1 .. 1; + L at 0 range 2 .. 81; + R at 0 range 82 .. 161; + end record; + +Note: the above rules apply to recent releases of GNAT 5. +In GNAT 3, there are more severe restrictions on larger components. +For non-primitive types, including packed arrays with a size greater than +64 bits, component clauses must respect the alignment requirement of the +type, in particular, always starting on a byte boundary, and the length +must be a multiple of the storage unit. + +.. _Handling_of_Records_with_Holes: + +Handling of Records with Holes +============================== + +.. index:: Handling of Records with Holes + +As a result of alignment considerations, records may contain "holes" +or gaps +which do not correspond to the data bits of any of the components. +Record representation clauses can also result in holes in records. + +GNAT does not attempt to clear these holes, so in record objects, +they should be considered to hold undefined rubbish. The generated +equality routine just tests components so does not access these +undefined bits, and assignment and copy operations may or may not +preserve the contents of these holes (for assignments, the holes +in the target will in practice contain either the bits that are +present in the holes in the source, or the bits that were present +in the target before the assignment). + +If it is necessary to ensure that holes in records have all zero +bits, then record objects for which this initialization is desired +should be explicitly set to all zero values using Unchecked_Conversion +or address overlays. For example + +.. code-block:: ada + + type HRec is record + C : Character; + I : Integer; + end record; + +On typical machines, integers need to be aligned on a four-byte +boundary, resulting in three bytes of undefined rubbish following +the 8-bit field for C. To ensure that the hole in a variable of +type HRec is set to all zero bits, +you could for example do: + +.. code-block:: ada + + type Base is record + Dummy1, Dummy2 : Integer := 0; + end record; + + BaseVar : Base; + RealVar : Hrec; + for RealVar'Address use BaseVar'Address; + + +Now the 8-bytes of the value of RealVar start out containing all zero +bits. A safer approach is to just define dummy fields, avoiding the +holes, as in: + +.. code-block:: ada + + type HRec is record + C : Character; + Dummy1 : Short_Short_Integer := 0; + Dummy2 : Short_Short_Integer := 0; + Dummy3 : Short_Short_Integer := 0; + I : Integer; + end record; + +And to make absolutely sure that the intent of this is followed, you +can use representation clauses: + +.. code-block:: ada + + for Hrec use record + C at 0 range 0 .. 7; + Dummy1 at 1 range 0 .. 7; + Dummy2 at 2 range 0 .. 7; + Dummy3 at 3 range 0 .. 7; + I at 4 range 0 .. 31; + end record; + for Hrec'Size use 64; + + +.. _Enumeration_Clauses: + +Enumeration Clauses +=================== + +The only restriction on enumeration clauses is that the range of values +must be representable. For the signed case, if one or more of the +representation values are negative, all values must be in the range: + +.. code-block:: ada + + System.Min_Int .. System.Max_Int + +For the unsigned case, where all values are nonnegative, the values must +be in the range: + +.. code-block:: ada + + 0 .. System.Max_Binary_Modulus; + + +A *confirming* representation clause is one in which the values range +from 0 in sequence, i.e., a clause that confirms the default representation +for an enumeration type. +Such a confirming representation +is permitted by these rules, and is specially recognized by the compiler so +that no extra overhead results from the use of such a clause. + +If an array has an index type which is an enumeration type to which an +enumeration clause has been applied, then the array is stored in a compact +manner. Consider the declarations: + +.. code-block:: ada + + type r is (A, B, C); + for r use (A => 1, B => 5, C => 10); + type t is array (r) of Character; + +The array type t corresponds to a vector with exactly three elements and +has a default size equal to `3*Character'Size`. This ensures efficient +use of space, but means that accesses to elements of the array will incur +the overhead of converting representation values to the corresponding +positional values, (i.e., the value delivered by the `Pos` attribute). + + +.. _Address_Clauses: + +Address Clauses +=============== +.. index:: Address Clause + +The reference manual allows a general restriction on representation clauses, +as found in RM 13.1(22): + + "An implementation need not support representation + items containing nonstatic expressions, except that + an implementation should support a representation item + for a given entity if each nonstatic expression in the + representation item is a name that statically denotes + a constant declared before the entity." + +In practice this is applicable only to address clauses, since this is the +only case in which a non-static expression is permitted by the syntax. As +the AARM notes in sections 13.1 (22.a-22.h): + + 22.a Reason: This is to avoid the following sort of thing: + + 22.b X : Integer := F(...); + Y : Address := G(...); + for X'Address use Y; + + 22.c In the above, we have to evaluate the + initialization expression for X before we + know where to put the result. This seems + like an unreasonable implementation burden. + + 22.d The above code should instead be written + like this: + + 22.e Y : constant Address := G(...); + X : Integer := F(...); + for X'Address use Y; + + 22.f This allows the expression 'Y' to be safely + evaluated before X is created. + + 22.g The constant could be a formal parameter of mode in. + + 22.h An implementation can support other nonstatic + expressions if it wants to. Expressions of type + Address are hardly ever static, but their value + might be known at compile time anyway in many + cases. + +GNAT does indeed permit many additional cases of non-static expressions. In +particular, if the type involved is elementary there are no restrictions +(since in this case, holding a temporary copy of the initialization value, +if one is present, is inexpensive). In addition, if there is no implicit or +explicit initialization, then there are no restrictions. GNAT will reject +only the case where all three of these conditions hold: + +* + The type of the item is non-elementary (e.g., a record or array). + +* + There is explicit or implicit initialization required for the object. + Note that access values are always implicitly initialized. + +* + The address value is non-static. Here GNAT is more permissive than the + RM, and allows the address value to be the address of a previously declared + stand-alone variable, as long as it does not itself have an address clause. + + :: + + Anchor : Some_Initialized_Type; + Overlay : Some_Initialized_Type; + for Overlay'Address use Anchor'Address; + + However, the prefix of the address clause cannot be an array component, or + a component of a discriminated record. + +As noted above in section 22.h, address values are typically non-static. In +particular the To_Address function, even if applied to a literal value, is +a non-static function call. To avoid this minor annoyance, GNAT provides +the implementation defined attribute 'To_Address. The following two +expressions have identical values: + +.. index:: Attribute +.. index:: To_Address + +.. code-block:: ada + + To_Address (16#1234_0000#) + System'To_Address (16#1234_0000#); + +except that the second form is considered to be a static expression, and +thus when used as an address clause value is always permitted. + +Additionally, GNAT treats as static an address clause that is an +unchecked_conversion of a static integer value. This simplifies the porting +of legacy code, and provides a portable equivalent to the GNAT attribute +`To_Address`. + +Another issue with address clauses is the interaction with alignment +requirements. When an address clause is given for an object, the address +value must be consistent with the alignment of the object (which is usually +the same as the alignment of the type of the object). If an address clause +is given that specifies an inappropriately aligned address value, then the +program execution is erroneous. + +Since this source of erroneous behavior can have unfortunate effects, GNAT +checks (at compile time if possible, generating a warning, or at execution +time with a run-time check) that the alignment is appropriate. If the +run-time check fails, then `Program_Error` is raised. This run-time +check is suppressed if range checks are suppressed, or if the special GNAT +check Alignment_Check is suppressed, or if +`pragma Restrictions (No_Elaboration_Code)` is in effect. + +Finally, GNAT does not permit overlaying of objects of controlled types or +composite types containing a controlled component. In most cases, the compiler +can detect an attempt at such overlays and will generate a warning at compile +time and a Program_Error exception at run time. + +.. index:: Export + +An address clause cannot be given for an exported object. More +understandably the real restriction is that objects with an address +clause cannot be exported. This is because such variables are not +defined by the Ada program, so there is no external object to export. + +.. index:: Import + +It is permissible to give an address clause and a pragma Import for the +same object. In this case, the variable is not really defined by the +Ada program, so there is no external symbol to be linked. The link name +and the external name are ignored in this case. The reason that we allow this +combination is that it provides a useful idiom to avoid unwanted +initializations on objects with address clauses. + +When an address clause is given for an object that has implicit or +explicit initialization, then by default initialization takes place. This +means that the effect of the object declaration is to overwrite the +memory at the specified address. This is almost always not what the +programmer wants, so GNAT will output a warning: + +:: + + with System; + package G is + type R is record + M : Integer := 0; + end record; + + Ext : R; + for Ext'Address use System'To_Address (16#1234_1234#); + | + >>> warning: implicit initialization of "Ext" may + modify overlaid storage + >>> warning: use pragma Import for "Ext" to suppress + initialization (RM B(24)) + + end G; + +As indicated by the warning message, the solution is to use a (dummy) pragma +Import to suppress this initialization. The pragma tell the compiler that the +object is declared and initialized elsewhere. The following package compiles +without warnings (and the initialization is suppressed): + +.. code-block:: ada + + with System; + package G is + type R is record + M : Integer := 0; + end record; + + Ext : R; + for Ext'Address use System'To_Address (16#1234_1234#); + pragma Import (Ada, Ext); + end G; + + +A final issue with address clauses involves their use for overlaying +variables, as in the following example: + +.. index:: Overlaying of objects + +.. code-block:: ada + + A : Integer; + B : Integer; + for B'Address use A'Address; + + +or alternatively, using the form recommended by the RM: + +.. code-block:: ada + + A : Integer; + Addr : constant Address := A'Address; + B : Integer; + for B'Address use Addr; + + +In both of these cases, `A` +and `B` become aliased to one another via the +address clause. This use of address clauses to overlay +variables, achieving an effect similar to unchecked +conversion was erroneous in Ada 83, but in Ada 95 and Ada 2005 +the effect is implementation defined. Furthermore, the +Ada RM specifically recommends that in a situation +like this, `B` should be subject to the following +implementation advice (RM 13.3(19)): + + "19 If the Address of an object is specified, or it is imported + or exported, then the implementation should not perform + optimizations based on assumptions of no aliases." + +GNAT follows this recommendation, and goes further by also applying +this recommendation to the overlaid variable (`A` +in the above example) in this case. This means that the overlay +works "as expected", in that a modification to one of the variables +will affect the value of the other. + +Note that when address clause overlays are used in this way, there is an +issue of unintentional initialization, as shown by this example: + +:: + + package Overwrite_Record is + type R is record + A : Character := 'C'; + B : Character := 'A'; + end record; + X : Short_Integer := 3; + Y : R; + for Y'Address use X'Address; + | + >>> warning: default initialization of "Y" may + modify "X", use pragma Import for "Y" to + suppress initialization (RM B.1(24)) + + end Overwrite_Record; + +Here the default initialization of `Y` will clobber the value +of `X`, which justifies the warning. The warning notes that +this effect can be eliminated by adding a `pragma Import` +which suppresses the initialization: + +.. code-block:: ada + + package Overwrite_Record is + type R is record + A : Character := 'C'; + B : Character := 'A'; + end record; + X : Short_Integer := 3; + Y : R; + for Y'Address use X'Address; + pragma Import (Ada, Y); + end Overwrite_Record; + + +Note that the use of `pragma Initialize_Scalars` may cause variables to +be initialized when they would not otherwise have been in the absence +of the use of this pragma. This may cause an overlay to have this +unintended clobbering effect. The compiler avoids this for scalar +types, but not for composite objects (where in general the effect +of `Initialize_Scalars` is part of the initialization routine +for the composite object: + +:: + + pragma Initialize_Scalars; + with Ada.Text_IO; use Ada.Text_IO; + procedure Overwrite_Array is + type Arr is array (1 .. 5) of Integer; + X : Arr := (others => 1); + A : Arr; + for A'Address use X'Address; + | + >>> warning: default initialization of "A" may + modify "X", use pragma Import for "A" to + suppress initialization (RM B.1(24)) + + begin + if X /= Arr'(others => 1) then + Put_Line ("X was clobbered"); + else + Put_Line ("X was not clobbered"); + end if; + end Overwrite_Array; + +The above program generates the warning as shown, and at execution +time, prints `X was clobbered`. If the `pragma Import` is +added as suggested: + +.. code-block:: ada + + pragma Initialize_Scalars; + with Ada.Text_IO; use Ada.Text_IO; + procedure Overwrite_Array is + type Arr is array (1 .. 5) of Integer; + X : Arr := (others => 1); + A : Arr; + for A'Address use X'Address; + pragma Import (Ada, A); + begin + if X /= Arr'(others => 1) then + Put_Line ("X was clobbered"); + else + Put_Line ("X was not clobbered"); + end if; + end Overwrite_Array; + +then the program compiles without the warning and when run will generate +the output `X was not clobbered`. + + +.. _Use_of_Address_Clauses_for_Memory-Mapped_I/O: + +Use of Address Clauses for Memory-Mapped I/O +============================================ + +.. index:: Memory-mapped I/O + +A common pattern is to use an address clause to map an atomic variable to +a location in memory that corresponds to a memory-mapped I/O operation or +operations, for example: + +.. code-block:: ada + + type Mem_Word is record + A,B,C,D : Byte; + end record; + pragma Atomic (Mem_Word); + for Mem_Word_Size use 32; + + Mem : Mem_Word; + for Mem'Address use some-address; + ... + Temp := Mem; + Temp.A := 32; + Mem := Temp; + +For a full access (reference or modification) of the variable (Mem) in +this case, as in the above examples, GNAT guarantees that the entire atomic +word will be accessed. It is not clear whether the RM requires this. For +example in the above, can the compiler reference only the Mem.A field as +an optimization? Whatever the answer to this question is, GNAT makes the +guarantee that for such a reference, the entire word is read or written. + +A problem arises with a component access such as: + +.. code-block:: ada + + Mem.A := 32; + +Note that the component A is not declared as atomic. This means that it is +not clear what this assignment means. It could correspond to full word read +and write as given in the first example, or on architectures that supported +such an operation it might be a single byte store instruction. The RM does +not have anything to say in this situation, and GNAT does not make any +guarantee. The code generated may vary from target to target. GNAT will issue +a warning in such a case: + +:: + + Mem.A := 32; + | + >>> warning: access to non-atomic component of atomic array, + may cause unexpected accesses to atomic object + +It is best to be explicit in this situation, by either declaring the +components to be atomic if you want the byte store, or explicitly writing +the full word access sequence if that is what the hardware requires. + + +.. _Effect_of_Convention_on_Representation: + +Effect of Convention on Representation +====================================== + +.. index:: Convention, effect on representation + +Normally the specification of a foreign language convention for a type or +an object has no effect on the chosen representation. In particular, the +representation chosen for data in GNAT generally meets the standard system +conventions, and for example records are laid out in a manner that is +consistent with C. This means that specifying convention C (for example) +has no effect. + +There are four exceptions to this general rule: + +* *Convention Fortran and array subtypes*. + + If pragma Convention Fortran is specified for an array subtype, then in + accordance with the implementation advice in section 3.6.2(11) of the + Ada Reference Manual, the array will be stored in a Fortran-compatible + column-major manner, instead of the normal default row-major order. + +* *Convention C and enumeration types* + + GNAT normally stores enumeration types in 8, 16, or 32 bits as required + to accommodate all values of the type. For example, for the enumeration + type declared by: + + :: + + type Color is (Red, Green, Blue); + + 8 bits is sufficient to store all values of the type, so by default, objects + of type `Color` will be represented using 8 bits. However, normal C + convention is to use 32 bits for all enum values in C, since enum values + are essentially of type int. If pragma `Convention C` is specified for an + Ada enumeration type, then the size is modified as necessary (usually to + 32 bits) to be consistent with the C convention for enum values. + + Note that this treatment applies only to types. If Convention C is given for + an enumeration object, where the enumeration type is not Convention C, then + Object_Size bits are allocated. For example, for a normal enumeration type, + with less than 256 elements, only 8 bits will be allocated for the object. + Since this may be a surprise in terms of what C expects, GNAT will issue a + warning in this situation. The warning can be suppressed by giving an explicit + size clause specifying the desired size. + +* *Convention C/Fortran and Boolean types* + + In C, the usual convention for boolean values, that is values used for + conditions, is that zero represents false, and nonzero values represent + true. In Ada, the normal convention is that two specific values, typically + 0/1, are used to represent false/true respectively. + + Fortran has a similar convention for `LOGICAL` values (any nonzero + value represents true). + + To accommodate the Fortran and C conventions, if a pragma Convention specifies + C or Fortran convention for a derived Boolean, as in the following example: + + :: + + type C_Switch is new Boolean; + pragma Convention (C, C_Switch); + + + then the GNAT generated code will treat any nonzero value as true. For truth + values generated by GNAT, the conventional value 1 will be used for True, but + when one of these values is read, any nonzero value is treated as True. + + +.. _Conventions_and_Anonymous_Access_Types: + +Conventions and Anonymous Access Types +====================================== + +.. index:: Anonymous access types + +.. index:: Convention for anonymous access types + +The RM is not entirely clear on convention handling in a number of cases, +and in particular, it is not clear on the convention to be given to +anonymous access types in general, and in particular what is to be +done for the case of anonymous access-to-subprogram. + +In GNAT, we decide that if an explicit Convention is applied +to an object or component, and its type is such an anonymous type, +then the convention will apply to this anonymous type as well. This +seems to make sense since it is anomolous in any case to have a +different convention for an object and its type, and there is clearly +no way to explicitly specify a convention for an anonymous type, since +it doesn't have a name to specify! + +Furthermore, we decide that if a convention is applied to a record type, +then this convention is inherited by any of its components that are of an +anonymous access type which do not have an explicitly specified convention. + +The following program shows these conventions in action: + +:: + + package ConvComp is + type Foo is range 1 .. 10; + type T1 is record + A : access function (X : Foo) return Integer; + B : Integer; + end record; + pragma Convention (C, T1); + + type T2 is record + A : access function (X : Foo) return Integer; + pragma Convention (C, A); + B : Integer; + end record; + pragma Convention (COBOL, T2); + + type T3 is record + A : access function (X : Foo) return Integer; + pragma Convention (COBOL, A); + B : Integer; + end record; + pragma Convention (C, T3); + + type T4 is record + A : access function (X : Foo) return Integer; + B : Integer; + end record; + pragma Convention (COBOL, T4); + + function F (X : Foo) return Integer; + pragma Convention (C, F); + + function F (X : Foo) return Integer is (13); + + TV1 : T1 := (F'Access, 12); -- OK + TV2 : T2 := (F'Access, 13); -- OK + + TV3 : T3 := (F'Access, 13); -- ERROR + | + >>> subprogram "F" has wrong convention + >>> does not match access to subprogram declared at line 17 + 38. TV4 : T4 := (F'Access, 13); -- ERROR + | + >>> subprogram "F" has wrong convention + >>> does not match access to subprogram declared at line 24 + 39. end ConvComp; + + +.. _Determining_the_Representations_chosen_by_GNAT: + +Determining the Representations chosen by GNAT +============================================== + +.. index:: Representation, determination of + +.. index:: -gnatR (gcc) + +Although the descriptions in this section are intended to be complete, it is +often easier to simply experiment to see what GNAT accepts and what the +effect is on the layout of types and objects. + +As required by the Ada RM, if a representation clause is not accepted, then +it must be rejected as illegal by the compiler. However, when a +representation clause or pragma is accepted, there can still be questions +of what the compiler actually does. For example, if a partial record +representation clause specifies the location of some components and not +others, then where are the non-specified components placed? Or if pragma +`Pack` is used on a record, then exactly where are the resulting +fields placed? The section on pragma `Pack` in this chapter can be +used to answer the second question, but it is often easier to just see +what the compiler does. + +For this purpose, GNAT provides the option *-gnatR*. If you compile +with this option, then the compiler will output information on the actual +representations chosen, in a format similar to source representation +clauses. For example, if we compile the package: + +.. code-block:: ada + + package q is + type r (x : boolean) is tagged record + case x is + when True => S : String (1 .. 100); + when False => null; + end case; + end record; + + type r2 is new r (false) with record + y2 : integer; + end record; + + for r2 use record + y2 at 16 range 0 .. 31; + end record; + + type x is record + y : character; + end record; + + type x1 is array (1 .. 10) of x; + for x1'component_size use 11; + + type ia is access integer; + + type Rb1 is array (1 .. 13) of Boolean; + pragma Pack (rb1); + + type Rb2 is array (1 .. 65) of Boolean; + pragma Pack (rb2); + + type x2 is record + l1 : Boolean; + l2 : Duration; + l3 : Float; + l4 : Boolean; + l5 : Rb1; + l6 : Rb2; + end record; + pragma Pack (x2); + end q; + +using the switch *-gnatR* we obtain the following output: + +.. code-block:: ada + + Representation information for unit q + ------------------------------------- + + for r'Size use ??; + for r'Alignment use 4; + for r use record + x at 4 range 0 .. 7; + _tag at 0 range 0 .. 31; + s at 5 range 0 .. 799; + end record; + + for r2'Size use 160; + for r2'Alignment use 4; + for r2 use record + x at 4 range 0 .. 7; + _tag at 0 range 0 .. 31; + _parent at 0 range 0 .. 63; + y2 at 16 range 0 .. 31; + end record; + + for x'Size use 8; + for x'Alignment use 1; + for x use record + y at 0 range 0 .. 7; + end record; + + for x1'Size use 112; + for x1'Alignment use 1; + for x1'Component_Size use 11; + + for rb1'Size use 13; + for rb1'Alignment use 2; + for rb1'Component_Size use 1; + + for rb2'Size use 72; + for rb2'Alignment use 1; + for rb2'Component_Size use 1; + + for x2'Size use 224; + for x2'Alignment use 4; + for x2 use record + l1 at 0 range 0 .. 0; + l2 at 0 range 1 .. 64; + l3 at 12 range 0 .. 31; + l4 at 16 range 0 .. 0; + l5 at 16 range 1 .. 13; + l6 at 18 range 0 .. 71; + end record; + +The Size values are actually the Object_Size, i.e., the default size that +will be allocated for objects of the type. +The ``??`` size for type r indicates that we have a variant record, and the +actual size of objects will depend on the discriminant value. + +The Alignment values show the actual alignment chosen by the compiler +for each record or array type. + +The record representation clause for type r shows where all fields +are placed, including the compiler generated tag field (whose location +cannot be controlled by the programmer). + +The record representation clause for the type extension r2 shows all the +fields present, including the parent field, which is a copy of the fields +of the parent type of r2, i.e., r1. + +The component size and size clauses for types rb1 and rb2 show +the exact effect of pragma `Pack` on these arrays, and the record +representation clause for type x2 shows how pragma `Pack` affects +this record type. + +In some cases, it may be useful to cut and paste the representation clauses +generated by the compiler into the original source to fix and guarantee +the actual representation to be used. diff --git a/gcc/ada/doc/gnat_rm/specialized_needs_annexes.rst b/gcc/ada/doc/gnat_rm/specialized_needs_annexes.rst new file mode 100644 index 00000000000..15b4a9483d0 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/specialized_needs_annexes.rst @@ -0,0 +1,37 @@ +.. _Specialized_Needs_Annexes: + +************************* +Specialized Needs Annexes +************************* + +Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not +required in all implementations. However, as described in this chapter, +GNAT implements all of these annexes: + +*Systems Programming (Annex C)* + The Systems Programming Annex is fully implemented. + + +*Real-Time Systems (Annex D)* + The Real-Time Systems Annex is fully implemented. + + +*Distributed Systems (Annex E)* + Stub generation is fully implemented in the GNAT compiler. In addition, + a complete compatible PCS is available as part of the GLADE system, + a separate product. When the two + products are used in conjunction, this annex is fully implemented. + + +*Information Systems (Annex F)* + The Information Systems annex is fully implemented. + + +*Numerics (Annex G)* + The Numerics Annex is fully implemented. + + +*Safety and Security / High-Integrity Systems (Annex H)* + The Safety and Security Annex (termed the High-Integrity Systems Annex + in Ada 2005) is fully implemented. + diff --git a/gcc/ada/doc/gnat_rm/standard_and_implementation_defined_restrictions.rst b/gcc/ada/doc/gnat_rm/standard_and_implementation_defined_restrictions.rst new file mode 100644 index 00000000000..c5cabb98af4 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/standard_and_implementation_defined_restrictions.rst @@ -0,0 +1,1057 @@ +.. _Standard_and_Implementation_Defined_Restrictions: + +************************************************ +Standard and Implementation Defined Restrictions +************************************************ + +All Ada Reference Manual-defined Restriction identifiers are implemented: + +* language-defined restrictions (see 13.12.1) +* tasking restrictions (see D.7) +* high integrity restrictions (see H.4) + +GNAT implements additional restriction identifiers. All restrictions, whether +language defined or GNAT-specific, are listed in the following. + +.. _Partition-Wide_Restrictions: + +Partition-Wide Restrictions +=========================== + +There are two separate lists of restriction identifiers. The first +set requires consistency throughout a partition (in other words, if the +restriction identifier is used for any compilation unit in the partition, +then all compilation units in the partition must obey the restriction). + +Immediate_Reclamation +--------------------- +.. index:: Immediate_Reclamation + +[RM H.4] This restriction ensures that, except for storage occupied by +objects created by allocators and not deallocated via unchecked +deallocation, any storage reserved at run time for an object is +immediately reclaimed when the object no longer exists. + +Max_Asynchronous_Select_Nesting +------------------------------- +.. index:: Max_Asynchronous_Select_Nesting + +[RM D.7] Specifies the maximum dynamic nesting level of asynchronous +selects. Violations of this restriction with a value of zero are +detected at compile time. Violations of this restriction with values +other than zero cause Storage_Error to be raised. + +Max_Entry_Queue_Length +---------------------- +.. index:: Max_Entry_Queue_Length + +[RM D.7] This restriction is a declaration that any protected entry compiled in +the scope of the restriction has at most the specified number of +tasks waiting on the entry at any one time, and so no queue is required. +Note that this restriction is checked at run time. Violation of this +restriction results in the raising of Program_Error exception at the point of +the call. + +.. index:: Max_Entry_Queue_Depth + +The restriction `Max_Entry_Queue_Depth` is recognized as a +synonym for `Max_Entry_Queue_Length`. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +Max_Protected_Entries +--------------------- +.. index:: Max_Protected_Entries + +[RM D.7] Specifies the maximum number of entries per protected type. The +bounds of every entry family of a protected unit shall be static, or shall be +defined by a discriminant of a subtype whose corresponding bound is static. + +Max_Select_Alternatives +----------------------- +.. index:: Max_Select_Alternatives + +[RM D.7] Specifies the maximum number of alternatives in a selective accept. + +Max_Storage_At_Blocking +----------------------- +.. index:: Max_Storage_At_Blocking + +[RM D.7] Specifies the maximum portion (in storage elements) of a task's +Storage_Size that can be retained by a blocked task. A violation of this +restriction causes Storage_Error to be raised. + +Max_Task_Entries +---------------- +.. index:: Max_Task_Entries + +[RM D.7] Specifies the maximum number of entries +per task. The bounds of every entry family +of a task unit shall be static, or shall be +defined by a discriminant of a subtype whose +corresponding bound is static. + +Max_Tasks +--------- +.. index:: Max_Tasks + +[RM D.7] Specifies the maximum number of task that may be created, not +counting the creation of the environment task. Violations of this +restriction with a value of zero are detected at compile +time. Violations of this restriction with values other than zero cause +Storage_Error to be raised. + +No_Abort_Statements +------------------- +.. index:: No_Abort_Statements + +[RM D.7] There are no abort_statements, and there are +no calls to Task_Identification.Abort_Task. + +No_Access_Parameter_Allocators +------------------------------ +.. index:: No_Access_Parameter_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator as the actual parameter to an access +parameter. + +No_Access_Subprograms +--------------------- +.. index:: No_Access_Subprograms + +[RM H.4] This restriction ensures at compile time that there are no +declarations of access-to-subprogram types. + +No_Allocators +------------- +.. index:: No_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator. + +No_Anonymous_Allocators +----------------------- +.. index:: No_Anonymous_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator of anonymous access type. + +No_Calendar +----------- +.. index:: No_Calendar + +[GNAT] This restriction ensures at compile time that there is no implicit or +explicit dependence on the package `Ada.Calendar`. + +No_Coextensions +--------------- +.. index:: No_Coextensions + +[RM H.4] This restriction ensures at compile time that there are no +coextensions. See 3.10.2. + +No_Default_Initialization +------------------------- +.. index:: No_Default_Initialization + +[GNAT] This restriction prohibits any instance of default initialization +of variables. The binder implements a consistency rule which prevents +any unit compiled without the restriction from with'ing a unit with the +restriction (this allows the generation of initialization procedures to +be skipped, since you can be sure that no call is ever generated to an +initialization procedure in a unit with the restriction active). If used +in conjunction with Initialize_Scalars or Normalize_Scalars, the effect +is to prohibit all cases of variables declared without a specific +initializer (including the case of OUT scalar parameters). + +No_Delay +-------- +.. index:: No_Delay + +[RM H.4] This restriction ensures at compile time that there are no +delay statements and no dependences on package Calendar. + +No_Dependence +------------- +.. index:: No_Dependence + +[RM 13.12.1] This restriction checks at compile time that there are no +dependence on a library unit. + +No_Direct_Boolean_Operators +--------------------------- +.. index:: No_Direct_Boolean_Operators + +[GNAT] This restriction ensures that no logical operators (and/or/xor) +are used on operands of type Boolean (or any type derived from Boolean). +This is intended for use in safety critical programs where the certification +protocol requires the use of short-circuit (and then, or else) forms for all +composite boolean operations. + +No_Dispatch +----------- +.. index:: No_Dispatch + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of `T'Class`, for any (tagged) subtype `T`. + +No_Dispatching_Calls +-------------------- +.. index:: No_Dispatching_Calls + +[GNAT] This restriction ensures at compile time that the code generated by the +compiler involves no dispatching calls. The use of this restriction allows the +safe use of record extensions, classwide membership tests and other classwide +features not involving implicit dispatching. This restriction ensures that +the code contains no indirect calls through a dispatching mechanism. Note that +this includes internally-generated calls created by the compiler, for example +in the implementation of class-wide objects assignments. The +membership test is allowed in the presence of this restriction, because its +implementation requires no dispatching. +This restriction is comparable to the official Ada restriction +`No_Dispatch` except that it is a bit less restrictive in that it allows +all classwide constructs that do not imply dispatching. +The following example indicates constructs that violate this restriction. + + +.. code-block:: ada + + package Pkg is + type T is tagged record + Data : Natural; + end record; + procedure P (X : T); + + type DT is new T with record + More_Data : Natural; + end record; + procedure Q (X : DT); + end Pkg; + + with Pkg; use Pkg; + procedure Example is + procedure Test (O : T'Class) is + N : Natural := O'Size;-- Error: Dispatching call + C : T'Class := O; -- Error: implicit Dispatching Call + begin + if O in DT'Class then -- OK : Membership test + Q (DT (O)); -- OK : Type conversion plus direct call + else + P (O); -- Error: Dispatching call + end if; + end Test; + + Obj : DT; + begin + P (Obj); -- OK : Direct call + P (T (Obj)); -- OK : Type conversion plus direct call + P (T'Class (Obj)); -- Error: Dispatching call + + Test (Obj); -- OK : Type conversion + + if Obj in T'Class then -- OK : Membership test + null; + end if; + end Example; + + +No_Dynamic_Attachment +--------------------- +.. index:: No_Dynamic_Attachment + +[RM D.7] This restriction ensures that there is no call to any of the +operations defined in package Ada.Interrupts +(Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler, +Detach_Handler, and Reference). + +.. index:: No_Dynamic_Interrupts + +The restriction `No_Dynamic_Interrupts` is recognized as a +synonym for `No_Dynamic_Attachment`. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +No_Dynamic_Priorities +--------------------- +.. index:: No_Dynamic_Priorities + +[RM D.7] There are no semantic dependencies on the package Dynamic_Priorities. + +No_Entry_Calls_In_Elaboration_Code +---------------------------------- +.. index:: No_Entry_Calls_In_Elaboration_Code + +[GNAT] This restriction ensures at compile time that no task or protected entry +calls are made during elaboration code. As a result of the use of this +restriction, the compiler can assume that no code past an accept statement +in a task can be executed at elaboration time. + +No_Enumeration_Maps +------------------- +.. index:: No_Enumeration_Maps + +[GNAT] This restriction ensures at compile time that no operations requiring +enumeration maps are used (that is Image and Value attributes applied +to enumeration types). + +No_Exception_Handlers +--------------------- +.. index:: No_Exception_Handlers + +[GNAT] This restriction ensures at compile time that there are no explicit +exception handlers. It also indicates that no exception propagation will +be provided. In this mode, exceptions may be raised but will result in +an immediate call to the last chance handler, a routine that the user +must define with the following profile: + + +.. code-block:: ada + + procedure Last_Chance_Handler + (Source_Location : System.Address; Line : Integer); + pragma Export (C, Last_Chance_Handler, + "__gnat_last_chance_handler"); + + +The parameter is a C null-terminated string representing a message to be +associated with the exception (typically the source location of the raise +statement generated by the compiler). The Line parameter when nonzero +represents the line number in the source program where the raise occurs. + +No_Exception_Propagation +------------------------ +.. index:: No_Exception_Propagation + +[GNAT] This restriction guarantees that exceptions are never propagated +to an outer subprogram scope. The only case in which an exception may +be raised is when the handler is statically in the same subprogram, so +that the effect of a raise is essentially like a goto statement. Any +other raise statement (implicit or explicit) will be considered +unhandled. Exception handlers are allowed, but may not contain an +exception occurrence identifier (exception choice). In addition, use of +the package GNAT.Current_Exception is not permitted, and reraise +statements (raise with no operand) are not permitted. + +No_Exception_Registration +------------------------- +.. index:: No_Exception_Registration + +[GNAT] This restriction ensures at compile time that no stream operations for +types Exception_Id or Exception_Occurrence are used. This also makes it +impossible to pass exceptions to or from a partition with this restriction +in a distributed environment. If this restriction is active, the generated +code is simplified by omitting the otherwise-required global registration +of exceptions when they are declared. + +No_Exceptions +------------- +.. index:: No_Exceptions + +[RM H.4] This restriction ensures at compile time that there are no +raise statements and no exception handlers. + +No_Finalization +--------------- +.. index:: No_Finalization + +[GNAT] This restriction disables the language features described in +chapter 7.6 of the Ada 2005 RM as well as all form of code generation +performed by the compiler to support these features. The following types +are no longer considered controlled when this restriction is in effect: + +* + `Ada.Finalization.Controlled` +* + `Ada.Finalization.Limited_Controlled` +* + Derivations from `Controlled` or `Limited_Controlled` +* + Class-wide types +* + Protected types +* + Task types +* + Array and record types with controlled components + +The compiler no longer generates code to initialize, finalize or adjust an +object or a nested component, either declared on the stack or on the heap. The +deallocation of a controlled object no longer finalizes its contents. + +No_Fixed_Point +-------------- +.. index:: No_Fixed_Point + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of fixed point types and operations. + +No_Floating_Point +----------------- +.. index:: No_Floating_Point + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of floating point types and operations. + +No_Implicit_Conditionals +------------------------ +.. index:: No_Implicit_Conditionals + +[GNAT] This restriction ensures that the generated code does not contain any +implicit conditionals, either by modifying the generated code where possible, +or by rejecting any construct that would otherwise generate an implicit +conditional. Note that this check does not include run time constraint +checks, which on some targets may generate implicit conditionals as +well. To control the latter, constraint checks can be suppressed in the +normal manner. Constructs generating implicit conditionals include comparisons +of composite objects and the Max/Min attributes. + +No_Implicit_Dynamic_Code +------------------------ +.. index:: No_Implicit_Dynamic_Code +.. index:: trampoline + +[GNAT] This restriction prevents the compiler from building 'trampolines'. +This is a structure that is built on the stack and contains dynamic +code to be executed at run time. On some targets, a trampoline is +built for the following features: `Access`, +`Unrestricted_Access`, or `Address` of a nested subprogram; +nested task bodies; primitive operations of nested tagged types. +Trampolines do not work on machines that prevent execution of stack +data. For example, on windows systems, enabling DEP (data execution +protection) will cause trampolines to raise an exception. +Trampolines are also quite slow at run time. + +On many targets, trampolines have been largely eliminated. Look at the +version of system.ads for your target --- if it has +Always_Compatible_Rep equal to False, then trampolines are largely +eliminated. In particular, a trampoline is built for the following +features: `Address` of a nested subprogram; +`Access` or `Unrestricted_Access` of a nested subprogram, +but only if pragma Favor_Top_Level applies, or the access type has a +foreign-language convention; primitive operations of nested tagged +types. + +No_Implicit_Heap_Allocations +---------------------------- +.. index:: No_Implicit_Heap_Allocations + +[RM D.7] No constructs are allowed to cause implicit heap allocation. + +No_Implicit_Loops +----------------- +.. index:: No_Implicit_Loops + +[GNAT] This restriction ensures that the generated code does not contain any +implicit `for` loops, either by modifying +the generated code where possible, +or by rejecting any construct that would otherwise generate an implicit +`for` loop. If this restriction is active, it is possible to build +large array aggregates with all static components without generating an +intermediate temporary, and without generating a loop to initialize individual +components. Otherwise, a loop is created for arrays larger than about 5000 +scalar components. + +No_Initialize_Scalars +--------------------- +.. index:: No_Initialize_Scalars + +[GNAT] This restriction ensures that no unit in the partition is compiled with +pragma Initialize_Scalars. This allows the generation of more efficient +code, and in particular eliminates dummy null initialization routines that +are otherwise generated for some record and array types. + +No_IO +----- +.. index:: No_IO + +[RM H.4] This restriction ensures at compile time that there are no +dependences on any of the library units Sequential_IO, Direct_IO, +Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO. + +No_Local_Allocators +------------------- +.. index:: No_Local_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator in subprograms, generic subprograms, tasks, +and entry bodies. + +No_Local_Protected_Objects +-------------------------- +.. index:: No_Local_Protected_Objects + +[RM D.7] This restriction ensures at compile time that protected objects are +only declared at the library level. + +No_Local_Timing_Events +---------------------- +.. index:: No_Local_Timing_Events + +[RM D.7] All objects of type Ada.Timing_Events.Timing_Event are +declared at the library level. + +No_Long_Long_Integers +--------------------- +.. index:: No_Long_Long_Integers + +[GNAT] This partition-wide restriction forbids any explicit reference to +type Standard.Long_Long_Integer, and also forbids declaring range types whose +implicit base type is Long_Long_Integer, and modular types whose size exceeds +Long_Integer'Size. + +No_Multiple_Elaboration +----------------------- +.. index:: No_Multiple_Elaboration + +[GNAT] Normally each package contains a 16-bit counter used to check for access +before elaboration, and to control multiple elaboration attempts. +This counter is eliminated for units compiled with the static model +of elaboration if restriction `No_Elaboration_Code` +is active but because of +the need to check for multiple elaboration in the general case, these +counters cannot be eliminated if elaboration code may be present. The +restriction `No_Multiple_Elaboration` +allows suppression of these counters +in static elaboration units even if they do have elaboration code. If this +restriction is used, then the situations in which multiple elaboration is +possible, including non-Ada main programs, and Stand Alone libraries, are not +permitted, and will be diagnosed by the binder. + +No_Nested_Finalization +---------------------- +.. index:: No_Nested_Finalization + +[RM D.7] All objects requiring finalization are declared at the library level. + +No_Protected_Type_Allocators +---------------------------- +.. index:: No_Protected_Type_Allocators + +[RM D.7] This restriction ensures at compile time that there are no allocator +expressions that attempt to allocate protected objects. + +No_Protected_Types +------------------ +.. index:: No_Protected_Types + +[RM H.4] This restriction ensures at compile time that there are no +declarations of protected types or protected objects. + +No_Recursion +------------ +.. index:: No_Recursion + +[RM H.4] A program execution is erroneous if a subprogram is invoked as +part of its execution. + +No_Reentrancy +------------- +.. index:: No_Reentrancy + +[RM H.4] A program execution is erroneous if a subprogram is executed by +two tasks at the same time. + +No_Relative_Delay +----------------- +.. index:: No_Relative_Delay + +[RM D.7] This restriction ensures at compile time that there are no delay +relative statements and prevents expressions such as `delay 1.23;` from +appearing in source code. + +No_Requeue_Statements +--------------------- +.. index:: No_Requeue_Statements + +[RM D.7] This restriction ensures at compile time that no requeue statements +are permitted and prevents keyword `requeue` from being used in source +code. + +.. index:: No_Requeue + +The restriction `No_Requeue` is recognized as a +synonym for `No_Requeue_Statements`. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on oNobsolescent features are activated). + +No_Secondary_Stack +------------------ +.. index:: No_Secondary_Stack + +[GNAT] This restriction ensures at compile time that the generated code +does not contain any reference to the secondary stack. The secondary +stack is used to implement functions returning unconstrained objects +(arrays or records) on some targets. + +No_Select_Statements +-------------------- +.. index:: No_Select_Statements + +[RM D.7] This restriction ensures at compile time no select statements of any +kind are permitted, that is the keyword `select` may not appear. + +No_Specific_Termination_Handlers +-------------------------------- +.. index:: No_Specific_Termination_Handlers + +[RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler +or to Ada.Task_Termination.Specific_Handler. + +No_Specification_of_Aspect +-------------------------- +.. index:: No_Specification_of_Aspect + +[RM 13.12.1] This restriction checks at compile time that no aspect +specification, attribute definition clause, or pragma is given for a +given aspect. + +No_Standard_Allocators_After_Elaboration +---------------------------------------- +.. index:: No_Standard_Allocators_After_Elaboration + +[RM D.7] Specifies that an allocator using a standard storage pool +should never be evaluated at run time after the elaboration of the +library items of the partition has completed. Otherwise, Storage_Error +is raised. + +No_Standard_Storage_Pools +------------------------- +.. index:: No_Standard_Storage_Pools + +[GNAT] This restriction ensures at compile time that no access types +use the standard default storage pool. Any access type declared must +have an explicit Storage_Pool attribute defined specifying a +user-defined storage pool. + +No_Stream_Optimizations +----------------------- +.. index:: No_Stream_Optimizations + +[GNAT] This restriction affects the performance of stream operations on types +`String`, `Wide_String` and `Wide_Wide_String`. By default, the +compiler uses block reads and writes when manipulating `String` objects +due to their supperior performance. When this restriction is in effect, the +compiler performs all IO operations on a per-character basis. + +No_Streams +---------- +.. index:: No_Streams + +[GNAT] This restriction ensures at compile/bind time that there are no +stream objects created and no use of stream attributes. +This restriction does not forbid dependences on the package +`Ada.Streams`. So it is permissible to with +`Ada.Streams` (or another package that does so itself) +as long as no actual stream objects are created and no +stream attributes are used. + +Note that the use of restriction allows optimization of tagged types, +since they do not need to worry about dispatching stream operations. +To take maximum advantage of this space-saving optimization, any +unit declaring a tagged type should be compiled with the restriction, +though this is not required. + +No_Task_Allocators +------------------ +.. index:: No_Task_Allocators + +[RM D.7] There are no allocators for task types +or types containing task subcomponents. + +No_Task_Attributes_Package +-------------------------- +.. index:: No_Task_Attributes_Package + +[GNAT] This restriction ensures at compile time that there are no implicit or +explicit dependencies on the package `Ada.Task_Attributes`. + +.. index:: No_Task_Attributes + +The restriction `No_Task_Attributes` is recognized as a synonym +for `No_Task_Attributes_Package`. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +No_Task_Hierarchy +----------------- +.. index:: No_Task_Hierarchy + +[RM D.7] All (non-environment) tasks depend +directly on the environment task of the partition. + +No_Task_Termination +------------------- +.. index:: No_Task_Termination + +[RM D.7] Tasks that terminate are erroneous. + +No_Tasking +---------- +.. index:: No_Tasking + +[GNAT] This restriction prevents the declaration of tasks or task types +throughout the partition. It is similar in effect to the use of +`Max_Tasks => 0` except that violations are caught at compile time +and cause an error message to be output either by the compiler or +binder. + +No_Terminate_Alternatives +------------------------- +.. index:: No_Terminate_Alternatives + +[RM D.7] There are no selective accepts with terminate alternatives. + +No_Unchecked_Access +------------------- +.. index:: No_Unchecked_Access + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of the Unchecked_Access attribute. + +No_Use_Of_Entity +---------------- +.. index:: No_Use_Of_Entity + +[GNAT] This restriction ensures at compile time that there are no references +to the entity given in the form :: + + No_Use_Of_Entity => Name + +where ``Name`` is the fully qualified entity, for example :: + + No_Use_Of_Entity => Ada.Text_IO.Put_Line + +Simple_Barriers +--------------- +.. index:: Simple_Barriers + +[RM D.7] This restriction ensures at compile time that barriers in entry +declarations for protected types are restricted to either static boolean +expressions or references to simple boolean variables defined in the private +part of the protected type. No other form of entry barriers is permitted. + +.. index:: Boolean_Entry_Barriers + +The restriction `Boolean_Entry_Barriers` is recognized as a +synonym for `Simple_Barriers`. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +Static_Priorities +----------------- +.. index:: Static_Priorities + +[GNAT] This restriction ensures at compile time that all priority expressions +are static, and that there are no dependences on the package +`Ada.Dynamic_Priorities`. + +Static_Storage_Size +------------------- +.. index:: Static_Storage_Size + +[GNAT] This restriction ensures at compile time that any expression appearing +in a Storage_Size pragma or attribute definition clause is static. + +.. _Program_Unit_Level_Restrictions: + + +Program Unit Level Restrictions +=============================== + +The second set of restriction identifiers +does not require partition-wide consistency. +The restriction may be enforced for a single +compilation unit without any effect on any of the +other compilation units in the partition. + +No_Elaboration_Code +------------------- +.. index:: No_Elaboration_Code + +[GNAT] This restriction ensures at compile time that no elaboration code is +generated. Note that this is not the same condition as is enforced +by pragma `Preelaborate`. There are cases in which pragma +`Preelaborate` still permits code to be generated (e.g., code +to initialize a large array to all zeroes), and there are cases of units +which do not meet the requirements for pragma `Preelaborate`, +but for which no elaboration code is generated. Generally, it is +the case that preelaborable units will meet the restrictions, with +the exception of large aggregates initialized with an others_clause, +and exception declarations (which generate calls to a run-time +registry procedure). This restriction is enforced on +a unit by unit basis, it need not be obeyed consistently +throughout a partition. + +In the case of aggregates with others, if the aggregate has a dynamic +size, there is no way to eliminate the elaboration code (such dynamic +bounds would be incompatible with `Preelaborate` in any case). If +the bounds are static, then use of this restriction actually modifies +the code choice of the compiler to avoid generating a loop, and instead +generate the aggregate statically if possible, no matter how many times +the data for the others clause must be repeatedly generated. + +It is not possible to precisely document +the constructs which are compatible with this restriction, since, +unlike most other restrictions, this is not a restriction on the +source code, but a restriction on the generated object code. For +example, if the source contains a declaration: + + +.. code-block:: ada + + Val : constant Integer := X; + + +where X is not a static constant, it may be possible, depending +on complex optimization circuitry, for the compiler to figure +out the value of X at compile time, in which case this initialization +can be done by the loader, and requires no initialization code. It +is not possible to document the precise conditions under which the +optimizer can figure this out. + +Note that this the implementation of this restriction requires full +code generation. If it is used in conjunction with "semantics only" +checking, then some cases of violations may be missed. + +No_Entry_Queue +-------------- +.. index:: No_Entry_Queue + +[GNAT] This restriction is a declaration that any protected entry compiled in +the scope of the restriction has at most one task waiting on the entry +at any one time, and so no queue is required. This restriction is not +checked at compile time. A program execution is erroneous if an attempt +is made to queue a second task on such an entry. + +No_Implementation_Aspect_Specifications +--------------------------------------- +.. index:: No_Implementation_Aspect_Specifications + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined aspects are present. With this restriction, the only +aspects that can be used are those defined in the Ada Reference Manual. + +No_Implementation_Attributes +---------------------------- +.. index:: No_Implementation_Attributes + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined attributes are present. With this restriction, the only +attributes that can be used are those defined in the Ada Reference +Manual. + +No_Implementation_Identifiers +----------------------------- +.. index:: No_Implementation_Identifiers + +[RM 13.12.1] This restriction checks at compile time that no +implementation-defined identifiers (marked with pragma Implementation_Defined) +occur within language-defined packages. + +No_Implementation_Pragmas +------------------------- +.. index:: No_Implementation_Pragmas + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined pragmas are present. With this restriction, the only +pragmas that can be used are those defined in the Ada Reference Manual. + +No_Implementation_Restrictions +------------------------------ +.. index:: No_Implementation_Restrictions + +[GNAT] This restriction checks at compile time that no GNAT-defined restriction +identifiers (other than `No_Implementation_Restrictions` itself) +are present. With this restriction, the only other restriction identifiers +that can be used are those defined in the Ada Reference Manual. + +No_Implementation_Units +----------------------- +.. index:: No_Implementation_Units + +[RM 13.12.1] This restriction checks at compile time that there is no +mention in the context clause of any implementation-defined descendants +of packages Ada, Interfaces, or System. + +No_Implicit_Aliasing +-------------------- +.. index:: No_Implicit_Aliasing + +[GNAT] This restriction, which is not required to be partition-wide consistent, +requires an explicit aliased keyword for an object to which 'Access, +'Unchecked_Access, or 'Address is applied, and forbids entirely the use of +the 'Unrestricted_Access attribute for objects. Note: the reason that +Unrestricted_Access is forbidden is that it would require the prefix +to be aliased, and in such cases, it can always be replaced by +the standard attribute Unchecked_Access which is preferable. + +No_Obsolescent_Features +----------------------- +.. index:: No_Obsolescent_Features + +[RM 13.12.1] This restriction checks at compile time that no obsolescent +features are used, as defined in Annex J of the Ada Reference Manual. + +No_Wide_Characters +------------------ +.. index:: No_Wide_Characters + +[GNAT] This restriction ensures at compile time that no uses of the types +`Wide_Character` or `Wide_String` or corresponding wide +wide types +appear, and that no wide or wide wide string or character literals +appear in the program (that is literals representing characters not in +type `Character`). + +SPARK_05 +-------- +.. index:: SPARK_05 + +[GNAT] This restriction checks at compile time that some constructs +forbidden in SPARK 2005 are not present. Error messages related to +SPARK restriction have the form: + + +:: + + violation of restriction "SPARK_05" at + + + +.. index:: SPARK + +The restriction `SPARK` is recognized as a +synonym for `SPARK_05`. This is retained for historical +compatibility purposes (and an unconditional warning will be generated +for its use, advising replacement by `SPARK`). + +This is not a replacement for the semantic checks performed by the +SPARK Examiner tool, as the compiler currently only deals with code, +not SPARK 2005 annotations, and does not guarantee catching all +cases of constructs forbidden by SPARK 2005. + +Thus it may well be the case that code which passes the compiler with +the SPARK restriction is rejected by the SPARK Examiner, e.g. due to +the different visibility rules of the Examiner based on SPARK 2005 +`inherit` annotations. + +This restriction can be useful in providing an initial filter for code +developed using SPARK 2005, or in examining legacy code to see how far +it is from meeting SPARK restrictions. + +The list below summarizes the checks that are performed when this +restriction is in force: + +* No block statements +* No case statements with only an others clause +* Exit statements in loops must respect the SPARK 2005 language restrictions +* No goto statements +* Return can only appear as last statement in function +* Function must have return statement +* Loop parameter specification must include subtype mark +* Prefix of expanded name cannot be a loop statement +* Abstract subprogram not allowed +* User-defined operators not allowed +* Access type parameters not allowed +* Default expressions for parameters not allowed +* Default expressions for record fields not allowed +* No tasking constructs allowed +* Label needed at end of subprograms and packages +* No mixing of positional and named parameter association +* No access types as result type +* No unconstrained arrays as result types +* No null procedures +* Initial and later declarations must be in correct order (declaration can't come after body) +* No attributes on private types if full declaration not visible +* No package declaration within package specification +* No controlled types +* No discriminant types +* No overloading +* Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed) +* Access attribute not allowed +* Allocator not allowed +* Result of catenation must be String +* Operands of catenation must be string literal, static char or another catenation +* No conditional expressions +* No explicit dereference +* Quantified expression not allowed +* Slicing not allowed +* No exception renaming +* No generic renaming +* No object renaming +* No use clause +* Aggregates must be qualified +* Non-static choice in array aggregates not allowed +* The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type +* No mixing of positional and named association in aggregate, no multi choice +* AND, OR and XOR for arrays only allowed when operands have same static bounds +* Fixed point operands to * or / must be qualified or converted +* Comparison operators not allowed for Booleans or arrays (except strings) +* Equality not allowed for arrays with non-matching static bounds (except strings) +* Conversion / qualification not allowed for arrays with non-matching static bounds +* Subprogram declaration only allowed in package spec (unless followed by import) +* Access types not allowed +* Incomplete type declaration not allowed +* Object and subtype declarations must respect SPARK restrictions +* Digits or delta constraint not allowed +* Decimal fixed point type not allowed +* Aliasing of objects not allowed +* Modular type modulus must be power of 2 +* Base not allowed on subtype mark +* Unary operators not allowed on modular types (except not) +* Untagged record cannot be null +* No class-wide operations +* Initialization expressions must respect SPARK restrictions +* Non-static ranges not allowed except in iteration schemes +* String subtypes must have lower bound of 1 +* Subtype of Boolean cannot have constraint +* At most one tagged type or extension per package +* Interface is not allowed +* Character literal cannot be prefixed (selector name cannot be character literal) +* Record aggregate cannot contain 'others' +* Component association in record aggregate must contain a single choice +* Ancestor part cannot be a type mark +* Attributes 'Image, 'Width and 'Value not allowed +* Functions may not update globals +* Subprograms may not contain direct calls to themselves (prevents recursion within unit) +* Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit) + +The following restrictions are enforced, but note that they are actually more +strict that the latest SPARK 2005 language definition: + +* No derived types other than tagged type extensions +* Subtype of unconstrained array must have constraint + +This list summarises the main SPARK 2005 language rules that are not +currently checked by the SPARK_05 restriction: + +* SPARK annotations are treated as comments so are not checked at all +* Based real literals not allowed +* Objects cannot be initialized at declaration by calls to user-defined functions +* Objects cannot be initialized at declaration by assignments from variables +* Objects cannot be initialized at declaration by assignments from indexed/selected components +* Ranges shall not be null +* A fixed point delta expression must be a simple expression +* Restrictions on where renaming declarations may be placed +* Externals of mode 'out' cannot be referenced +* Externals of mode 'in' cannot be updated +* Loop with no iteration scheme or exits only allowed as last statement in main program or task +* Subprogram cannot have parent unit name +* SPARK 2005 inherited subprogram must be prefixed with overriding +* External variables (or functions that reference them) may not be passed as actual parameters +* Globals must be explicitly mentioned in contract +* Deferred constants cannot be completed by pragma Import +* Package initialization cannot read/write variables from other packages +* Prefix not allowed for entities that are directly visible +* Identifier declaration can't override inherited package name +* Cannot use Standard or other predefined packages as identifiers +* After renaming, cannot use the original name +* Subprograms can only be renamed to remove package prefix +* Pragma import must be immediately after entity it names +* No mutual recursion between multiple units (this can be checked with gnatcheck) + +Note that if a unit is compiled in Ada 95 mode with the SPARK restriction, +violations will be reported for constructs forbidden in SPARK 95, +instead of SPARK 2005. + diff --git a/gcc/ada/doc/gnat_rm/standard_library_routines.rst b/gcc/ada/doc/gnat_rm/standard_library_routines.rst new file mode 100644 index 00000000000..8b8d3c27987 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/standard_library_routines.rst @@ -0,0 +1,709 @@ +.. _Standard_Library_Routines: + +************************* +Standard Library Routines +************************* + +The Ada Reference Manual contains in Annex A a full description of an +extensive set of standard library routines that can be used in any Ada +program, and which must be provided by all Ada compilers. They are +analogous to the standard C library used by C programs. + +GNAT implements all of the facilities described in annex A, and for most +purposes the description in the Ada Reference Manual, or appropriate Ada +text book, will be sufficient for making use of these facilities. + +In the case of the input-output facilities, +:ref:`The_Implementation_of_Standard_I/O`, +gives details on exactly how GNAT interfaces to the +file system. For the remaining packages, the Ada Reference Manual +should be sufficient. The following is a list of the packages included, +together with a brief description of the functionality that is provided. + +For completeness, references are included to other predefined library +routines defined in other sections of the Ada Reference Manual (these are +cross-indexed from Annex A). For further details see the relevant +package declarations in the run-time library. In particular, a few units +are not implemented, as marked by the presence of pragma Unimplemented_Unit, +and in this case the package declaration contains comments explaining why +the unit is not implemented. + + + +``Ada`` *(A.2)* + This is a parent package for all the standard library packages. It is + usually included implicitly in your program, and itself contains no + useful data or routines. + + +``Ada.Assertions`` *(11.4.2)* + `Assertions` provides the `Assert` subprograms, and also + the declaration of the `Assertion_Error` exception. + + +``Ada.Asynchronous_Task_Control`` *(D.11)* + `Asynchronous_Task_Control` provides low level facilities for task + synchronization. It is typically not implemented. See package spec for details. + + +``Ada.Calendar`` *(9.6)* + `Calendar` provides time of day access, and routines for + manipulating times and durations. + + +``Ada.Calendar.Arithmetic`` *(9.6.1)* + This package provides additional arithmetic + operations for `Calendar`. + + +``Ada.Calendar.Formatting`` *(9.6.1)* + This package provides formatting operations for `Calendar`. + + +``Ada.Calendar.Time_Zones`` *(9.6.1)* + This package provides additional `Calendar` facilities + for handling time zones. + + +``Ada.Characters`` *(A.3.1)* + This is a dummy parent package that contains no useful entities + + +``Ada.Characters.Conversions`` *(A.3.2)* + This package provides character conversion functions. + + +``Ada.Characters.Handling`` *(A.3.2)* + This package provides some basic character handling capabilities, + including classification functions for classes of characters (e.g., test + for letters, or digits). + + +``Ada.Characters.Latin_1`` *(A.3.3)* + This package includes a complete set of definitions of the characters + that appear in type CHARACTER. It is useful for writing programs that + will run in international environments. For example, if you want an + upper case E with an acute accent in a string, it is often better to use + the definition of `UC_E_Acute` in this package. Then your program + will print in an understandable manner even if your environment does not + support these extended characters. + + +``Ada.Command_Line`` *(A.15)* + This package provides access to the command line parameters and the name + of the current program (analogous to the use of `argc` and `argv` + in C), and also allows the exit status for the program to be set in a + system-independent manner. + + +``Ada.Complex_Text_IO`` *(G.1.3)* + This package provides text input and output of complex numbers. + + +``Ada.Containers`` *(A.18.1)* + A top level package providing a few basic definitions used by all the + following specific child packages that provide specific kinds of + containers. + +``Ada.Containers.Bounded_Priority_Queues`` *(A.18.31)* + +``Ada.Containers.Bounded_Synchronized_Queues`` *(A.18.29)* + +``Ada.Containers.Doubly_Linked_Lists`` *(A.18.3)* + +``Ada.Containers.Generic_Array_Sort`` *(A.18.26)* + +``Ada.Containers.Generic_Constrained_Array_Sort`` *(A.18.26)* + +``Ada.Containers.Generic_Sort`` *(A.18.26)* + +``Ada.Containers.Hashed_Maps`` *(A.18.5)* + +``Ada.Containers.Hashed_Sets`` *(A.18.8)* + +``Ada.Containers.Indefinite_Doubly_Linked_Lists`` *(A.18.12)* + +``Ada.Containers.Indefinite_Hashed_Maps`` *(A.18.13)* + +``Ada.Containers.Indefinite_Hashed_Sets`` *(A.18.15)* + +``Ada.Containers.Indefinite_Holders`` *(A.18.18)* + +``Ada.Containers.Indefinite_Multiway_Trees`` *(A.18.17)* + +``Ada.Containers.Indefinite_Ordered_Maps`` *(A.18.14)* + +``Ada.Containers.Indefinite_Ordered_Sets`` *(A.18.16)* + +``Ada.Containers.Indefinite_Vectors`` *(A.18.11)* + +``Ada.Containers.Multiway_Trees`` *(A.18.10)* + +``Ada.Containers.Ordered_Maps`` *(A.18.6)* + +``Ada.Containers.Ordered_Sets`` *(A.18.9)* + +``Ada.Containers.Synchronized_Queue_Interfaces`` *(A.18.27)* + +``Ada.Containers.Unbounded_Priority_Queues`` *(A.18.30)* + +``Ada.Containers.Unbounded_Synchronized_Queues`` *(A.18.28)* + +``Ada.Containers.Vectors`` *(A.18.2)* + +``Ada.Directories`` *(A.16)* + This package provides operations on directories. + + +``Ada.Directories.Hierarchical_File_Names`` *(A.16.1)* + This package provides additional directory operations handling + hiearchical file names. + + +``Ada.Directories.Information`` *(A.16)* + This is an implementation defined package for additional directory + operations, which is not implemented in GNAT. + + +``Ada.Decimal`` *(F.2)* + This package provides constants describing the range of decimal numbers + implemented, and also a decimal divide routine (analogous to the COBOL + verb DIVIDE ... GIVING ... REMAINDER ...) + + +``Ada.Direct_IO`` *(A.8.4)* + This package provides input-output using a model of a set of records of + fixed-length, containing an arbitrary definite Ada type, indexed by an + integer record number. + + +``Ada.Dispatching`` *(D.2.1)* + A parent package containing definitions for task dispatching operations. + + +``Ada.Dispatching.EDF`` *(D.2.6)* + Not implemented in GNAT. + + +``Ada.Dispatching.Non_Preemptive`` *(D.2.4)* + Not implemented in GNAT. + + +``Ada.Dispatching.Round_Robin`` *(D.2.5)* + Not implemented in GNAT. + + +``Ada.Dynamic_Priorities`` *(D.5)* + This package allows the priorities of a task to be adjusted dynamically + as the task is running. + + +``Ada.Environment_Variables`` *(A.17)* + This package provides facilities for accessing environment variables. + + +``Ada.Exceptions`` *(11.4.1)* + This package provides additional information on exceptions, and also + contains facilities for treating exceptions as data objects, and raising + exceptions with associated messages. + + +``Ada.Execution_Time`` *(D.14)* + Not implemented in GNAT. + + +``Ada.Execution_Time.Group_Budgets`` *(D.14.2)* + Not implemented in GNAT. + + +``Ada.Execution_Time.Timers`` *(D.14.1)'* + Not implemented in GNAT. + + +``Ada.Finalization`` *(7.6)* + This package contains the declarations and subprograms to support the + use of controlled types, providing for automatic initialization and + finalization (analogous to the constructors and destructors of C++). + + +``Ada.Float_Text_IO`` *(A.10.9)* + A library level instantiation of Text_IO.Float_IO for type Float. + + +``Ada.Float_Wide_Text_IO`` *(A.10.9)* + A library level instantiation of Wide_Text_IO.Float_IO for type Float. + + +``Ada.Float_Wide_Wide_Text_IO`` *(A.10.9)* + A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float. + + +``Ada.Integer_Text_IO`` *(A.10.9)* + A library level instantiation of Text_IO.Integer_IO for type Integer. + + +``Ada.Integer_Wide_Text_IO`` *(A.10.9)* + A library level instantiation of Wide_Text_IO.Integer_IO for type Integer. + + +``Ada.Integer_Wide_Wide_Text_IO`` *(A.10.9)* + A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer. + + +``Ada.Interrupts`` *(C.3.2)* + This package provides facilities for interfacing to interrupts, which + includes the set of signals or conditions that can be raised and + recognized as interrupts. + + +``Ada.Interrupts.Names`` *(C.3.2)* + This package provides the set of interrupt names (actually signal + or condition names) that can be handled by GNAT. + + +``Ada.IO_Exceptions`` *(A.13)* + This package defines the set of exceptions that can be raised by use of + the standard IO packages. + + +``Ada.Iterator_Interfaces`` *(5.5.1)* + This package provides a generic interface to generalized iterators. + + +``Ada.Locales`` *(A.19)* + This package provides declarations providing information (Language + and Country) about the current locale. + + +``Ada.Numerics`` + This package contains some standard constants and exceptions used + throughout the numerics packages. Note that the constants pi and e are + defined here, and it is better to use these definitions than rolling + your own. + + +``Ada.Numerics.Complex_Arrays`` *(G.3.2)* + Provides operations on arrays of complex numbers. + + +``Ada.Numerics.Complex_Elementary_Functions`` + Provides the implementation of standard elementary functions (such as + log and trigonometric functions) operating on complex numbers using the + standard `Float` and the `Complex` and `Imaginary` types + created by the package `Numerics.Complex_Types`. + + +``Ada.Numerics.Complex_Types`` + This is a predefined instantiation of + `Numerics.Generic_Complex_Types` using `Standard.Float` to + build the type `Complex` and `Imaginary`. + + +``Ada.Numerics.Discrete_Random`` + This generic package provides a random number generator suitable for generating + uniformly distributed values of a specified discrete subtype. + + +``Ada.Numerics.Float_Random`` + This package provides a random number generator suitable for generating + uniformly distributed floating point values in the unit interval. + + +``Ada.Numerics.Generic_Complex_Elementary_Functions`` + This is a generic version of the package that provides the + implementation of standard elementary functions (such as log and + trigonometric functions) for an arbitrary complex type. + + The following predefined instantiations of this package are provided: + + * ``Short_Float`` + + `Ada.Numerics.Short_Complex_Elementary_Functions` + + * ``Float`` + + `Ada.Numerics.Complex_Elementary_Functions` + + * ``Long_Float`` + + `Ada.Numerics.Long_Complex_Elementary_Functions` + +``Ada.Numerics.Generic_Complex_Types`` + This is a generic package that allows the creation of complex types, + with associated complex arithmetic operations. + + The following predefined instantiations of this package exist + + * ``Short_Float`` + + `Ada.Numerics.Short_Complex_Complex_Types` + + * ``Float`` + + `Ada.Numerics.Complex_Complex_Types` + + * ``Long_Float`` + + `Ada.Numerics.Long_Complex_Complex_Types` + +``Ada.Numerics.Generic_Elementary_Functions`` + This is a generic package that provides the implementation of standard + elementary functions (such as log an trigonometric functions) for an + arbitrary float type. + + The following predefined instantiations of this package exist + + * ``Short_Float`` + + `Ada.Numerics.Short_Elementary_Functions` + + * ``Float`` + + `Ada.Numerics.Elementary_Functions` + + * ``Long_Float`` + + `Ada.Numerics.Long_Elementary_Functions` + +``Ada.Numerics.Generic_Real_Arrays`` *(G.3.1)* + Generic operations on arrays of reals + +``Ada.Numerics.Real_Arrays`` *(G.3.1)* + Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float). + +``Ada.Real_Time`` *(D.8)* + This package provides facilities similar to those of `Calendar`, but + operating with a finer clock suitable for real time control. Note that + annex D requires that there be no backward clock jumps, and GNAT generally + guarantees this behavior, but of course if the external clock on which + the GNAT runtime depends is deliberately reset by some external event, + then such a backward jump may occur. + +``Ada.Real_Time.Timing_Events`` *(D.15)* + Not implemented in GNAT. + +``Ada.Sequential_IO`` *(A.8.1)* + This package provides input-output facilities for sequential files, + which can contain a sequence of values of a single type, which can be + any Ada type, including indefinite (unconstrained) types. + +``Ada.Storage_IO`` *(A.9)* + This package provides a facility for mapping arbitrary Ada types to and + from a storage buffer. It is primarily intended for the creation of new + IO packages. + +``Ada.Streams`` *(13.13.1)* + This is a generic package that provides the basic support for the + concept of streams as used by the stream attributes (`Input`, + `Output`, `Read` and `Write`). + +``Ada.Streams.Stream_IO`` *(A.12.1)* + This package is a specialization of the type `Streams` defined in + package `Streams` together with a set of operations providing + Stream_IO capability. The Stream_IO model permits both random and + sequential access to a file which can contain an arbitrary set of values + of one or more Ada types. + +``Ada.Strings`` *(A.4.1)* + This package provides some basic constants used by the string handling + packages. + + +``Ada.Strings.Bounded`` *(A.4.4)* + This package provides facilities for handling variable length + strings. The bounded model requires a maximum length. It is thus + somewhat more limited than the unbounded model, but avoids the use of + dynamic allocation or finalization. + +``Ada.Strings.Bounded.Equal_Case_Insensitive`` *(A.4.10)* + Provides case-insensitive comparisons of bounded strings + +``Ada.Strings.Bounded.Hash`` *(A.4.9)* + This package provides a generic hash function for bounded strings + +``Ada.Strings.Bounded.Hash_Case_Insensitive`` *(A.4.9)* + This package provides a generic hash function for bounded strings that + converts the string to be hashed to lower case. + +``Ada.Strings.Bounded.Less_Case_Insensitive`` *(A.4.10)* + This package provides a comparison function for bounded strings that works + in a case insensitive manner by converting to lower case before the comparison. + +``Ada.Strings.Fixed`` *(A.4.3)* + This package provides facilities for handling fixed length strings. + +``Ada.Strings.Fixed.Equal_Case_Insensitive`` *(A.4.10)* + This package provides an equality function for fixed strings that compares + the strings after converting both to lower case. + +``Ada.Strings.Fixed.Hash_Case_Insensitive`` *(A.4.9)* + This package provides a case insensitive hash function for fixed strings that + converts the string to lower case before computing the hash. + +``Ada.Strings.Fixed.Less_Case_Insensitive`` *(A.4.10)* + This package provides a comparison function for fixed strings that works + in a case insensitive manner by converting to lower case before the comparison. + +``Ada.Strings.Hash`` *(A.4.9)* + This package provides a hash function for strings. + +``Ada.Strings.Hash_Case_Insensitive`` *(A.4.9)* + This package provides a hash function for strings that is case insensitive. + The string is converted to lower case before computing the hash. + +``Ada.Strings.Less_Case_Insensitive`` *(A.4.10)* + This package provides a comparison function for\\strings that works + in a case insensitive manner by converting to lower case before the comparison. + +``Ada.Strings.Maps`` *(A.4.2)* + This package provides facilities for handling character mappings and + arbitrarily defined subsets of characters. For instance it is useful in + defining specialized translation tables. + +``Ada.Strings.Maps.Constants`` *(A.4.6)* + This package provides a standard set of predefined mappings and + predefined character sets. For example, the standard upper to lower case + conversion table is found in this package. Note that upper to lower case + conversion is non-trivial if you want to take the entire set of + characters, including extended characters like E with an acute accent, + into account. You should use the mappings in this package (rather than + adding 32 yourself) to do case mappings. + +``Ada.Strings.Unbounded`` *(A.4.5)* + This package provides facilities for handling variable length + strings. The unbounded model allows arbitrary length strings, but + requires the use of dynamic allocation and finalization. + +``Ada.Strings.Unbounded.Equal_Case_Insensitive`` *(A.4.10)* + Provides case-insensitive comparisons of unbounded strings + +``Ada.Strings.Unbounded.Hash`` *(A.4.9)* + This package provides a generic hash function for unbounded strings + +``Ada.Strings.Unbounded.Hash_Case_Insensitive`` *(A.4.9)* + This package provides a generic hash function for unbounded strings that + converts the string to be hashed to lower case. + +``Ada.Strings.Unbounded.Less_Case_Insensitive`` *(A.4.10)* + This package provides a comparison function for unbounded strings that works + in a case insensitive manner by converting to lower case before the comparison. + +``Ada.Strings.UTF_Encoding`` *(A.4.11)* + This package provides basic definitions for dealing with UTF-encoded strings. + +``Ada.Strings.UTF_Encoding.Conversions`` *(A.4.11)* + This package provides conversion functions for UTF-encoded strings. + +``Ada.Strings.UTF_Encoding.Strings`` *(A.4.11)* + +``Ada.Strings.UTF_Encoding.Wide_Strings`` *(A.4.11)* + +``Ada.Strings.UTF_Encoding.Wide_Wide_Strings`` *(A.4.11)* + These packages provide facilities for handling UTF encodings for + Strings, Wide_Strings and Wide_Wide_Strings. + +``Ada.Strings.Wide_Bounded`` *(A.4.7)* + +``Ada.Strings.Wide_Fixed`` *(A.4.7)* + +``Ada.Strings.Wide_Maps`` *(A.4.7)* + +``Ada.Strings.Wide_Unbounded`` *(A.4.7)* + These packages provide analogous capabilities to the corresponding + packages without ``Wide_`` in the name, but operate with the types + `Wide_String` and `Wide_Character` instead of `String` + and `Character`. Versions of all the child packages are available. + +``Ada.Strings.Wide_Wide_Bounded`` *(A.4.7)* + +``Ada.Strings.Wide_Wide_Fixed`` *(A.4.7)* + +``Ada.Strings.Wide_Wide_Maps`` *(A.4.7)* + +``Ada.Strings.Wide_Wide_Unbounded`` *(A.4.7)* + These packages provide analogous capabilities to the corresponding + packages without ``Wide_`` in the name, but operate with the types + `Wide_Wide_String` and `Wide_Wide_Character` instead + of `String` and `Character`. + +``Ada.Synchronous_Barriers`` *(D.10.1)* + This package provides facilities for synchronizing tasks at a low level + with barriers. + +``Ada.Synchronous_Task_Control`` *(D.10)* + This package provides some standard facilities for controlling task + communication in a synchronous manner. + +``Ada.Synchronous_Task_Control.EDF`` *(D.10)* + Not implemented in GNAT. + +``Ada.Tags`` + This package contains definitions for manipulation of the tags of tagged + values. + +``Ada.Tags.Generic_Dispatching_Constructor`` *(3.9)* + This package provides a way of constructing tagged class-wide values given + only the tag value. + +``Ada.Task_Attributes`` *(C.7.2)* + This package provides the capability of associating arbitrary + task-specific data with separate tasks. + +``Ada.Task_Identifification`` *(C.7.1)* + This package provides capabilities for task identification. + +``Ada.Task_Termination`` *(C.7.3)* + This package provides control over task termination. + +``Ada.Text_IO`` + This package provides basic text input-output capabilities for + character, string and numeric data. The subpackages of this + package are listed next. Note that although these are defined + as subpackages in the RM, they are actually transparently + implemented as child packages in GNAT, meaning that they + are only loaded if needed. + +``Ada.Text_IO.Decimal_IO`` + Provides input-output facilities for decimal fixed-point types + +``Ada.Text_IO.Enumeration_IO`` + Provides input-output facilities for enumeration types. + +``Ada.Text_IO.Fixed_IO`` + Provides input-output facilities for ordinary fixed-point types. + +``Ada.Text_IO.Float_IO`` + Provides input-output facilities for float types. The following + predefined instantiations of this generic package are available: + + * ``Short_Float`` + + `Short_Float_Text_IO` + + * ``Float`` + + `Float_Text_IO` + + * ``Long_Float`` + + `Long_Float_Text_IO` + +``Ada.Text_IO.Integer_IO`` + Provides input-output facilities for integer types. The following + predefined instantiations of this generic package are available: + + * ``Short_Short_Integer`` + + `Ada.Short_Short_Integer_Text_IO` + + * ``Short_Integer`` + + `Ada.Short_Integer_Text_IO` + + * ``Integer`` + + `Ada.Integer_Text_IO` + + * ``Long_Integer`` + + `Ada.Long_Integer_Text_IO` + + * ``Long_Long_Integer`` + + `Ada.Long_Long_Integer_Text_IO` + +``Ada.Text_IO.Modular_IO`` + Provides input-output facilities for modular (unsigned) types. + +``Ada.Text_IO.Bounded_IO (A.10.11)`` + Provides input-output facilities for bounded strings. + +``Ada.Text_IO.Complex_IO (G.1.3)`` + This package provides basic text input-output capabilities for complex + data. + +``Ada.Text_IO.Editing (F.3.3)`` + This package contains routines for edited output, analogous to the use + of pictures in COBOL. The picture formats used by this package are a + close copy of the facility in COBOL. + +``Ada.Text_IO.Text_Streams (A.12.2)`` + This package provides a facility that allows Text_IO files to be treated + as streams, so that the stream attributes can be used for writing + arbitrary data, including binary data, to Text_IO files. + +``Ada.Text_IO.Unbounded_IO (A.10.12)`` + This package provides input-output facilities for unbounded strings. + +``Ada.Unchecked_Conversion (13.9)`` + This generic package allows arbitrary conversion from one type to + another of the same size, providing for breaking the type safety in + special circumstances. + + If the types have the same Size (more accurately the same Value_Size), + then the effect is simply to transfer the bits from the source to the + target type without any modification. This usage is well defined, and + for simple types whose representation is typically the same across + all implementations, gives a portable method of performing such + conversions. + + If the types do not have the same size, then the result is implementation + defined, and thus may be non-portable. The following describes how GNAT + handles such unchecked conversion cases. + + If the types are of different sizes, and are both discrete types, then + the effect is of a normal type conversion without any constraint checking. + In particular if the result type has a larger size, the result will be + zero or sign extended. If the result type has a smaller size, the result + will be truncated by ignoring high order bits. + + If the types are of different sizes, and are not both discrete types, + then the conversion works as though pointers were created to the source + and target, and the pointer value is converted. The effect is that bits + are copied from successive low order storage units and bits of the source + up to the length of the target type. + + A warning is issued if the lengths differ, since the effect in this + case is implementation dependent, and the above behavior may not match + that of some other compiler. + + A pointer to one type may be converted to a pointer to another type using + unchecked conversion. The only case in which the effect is undefined is + when one or both pointers are pointers to unconstrained array types. In + this case, the bounds information may get incorrectly transferred, and in + particular, GNAT uses double size pointers for such types, and it is + meaningless to convert between such pointer types. GNAT will issue a + warning if the alignment of the target designated type is more strict + than the alignment of the source designated type (since the result may + be unaligned in this case). + + A pointer other than a pointer to an unconstrained array type may be + converted to and from System.Address. Such usage is common in Ada 83 + programs, but note that Ada.Address_To_Access_Conversions is the + preferred method of performing such conversions in Ada 95 and Ada 2005. + Neither + unchecked conversion nor Ada.Address_To_Access_Conversions should be + used in conjunction with pointers to unconstrained objects, since + the bounds information cannot be handled correctly in this case. + +``Ada.Unchecked_Deallocation`` *(13.11.2)* + This generic package allows explicit freeing of storage previously + allocated by use of an allocator. + +``Ada.Wide_Text_IO`` *(A.11)* + This package is similar to `Ada.Text_IO`, except that the external + file supports wide character representations, and the internal types are + `Wide_Character` and `Wide_String` instead of `Character` + and `String`. The corresponding set of nested packages and child + packages are defined. + +``Ada.Wide_Wide_Text_IO`` *(A.11)* + This package is similar to `Ada.Text_IO`, except that the external + file supports wide character representations, and the internal types are + `Wide_Character` and `Wide_String` instead of `Character` + and `String`. The corresponding set of nested packages and child + packages are defined. + +For packages in Interfaces and System, all the RM defined packages are +available in GNAT, see the Ada 2012 RM for full details. + diff --git a/gcc/ada/doc/gnat_rm/the_gnat_library.rst b/gcc/ada/doc/gnat_rm/the_gnat_library.rst new file mode 100644 index 00000000000..a5f0aa210e6 --- /dev/null +++ b/gcc/ada/doc/gnat_rm/the_gnat_library.rst @@ -0,0 +1,2218 @@ +.. _The_GNAT_Library: + +**************** +The GNAT Library +**************** + +The GNAT library contains a number of general and special purpose packages. +It represents functionality that the GNAT developers have found useful, and +which is made available to GNAT users. The packages described here are fully +supported, and upwards compatibility will be maintained in future releases, +so you can use these facilities with the confidence that the same functionality +will be available in future releases. + +The chapter here simply gives a brief summary of the facilities available. +The full documentation is found in the spec file for the package. The full +sources of these library packages, including both spec and body, are provided +with all GNAT releases. For example, to find out the full specifications of +the SPITBOL pattern matching capability, including a full tutorial and +extensive examples, look in the :file:`g-spipat.ads` file in the library. + +For each entry here, the package name (as it would appear in a `with` +clause) is given, followed by the name of the corresponding spec file in +parentheses. The packages are children in four hierarchies, `Ada`, +`Interfaces`, `System`, and `GNAT`, the latter being a +GNAT-specific hierarchy. + +Note that an application program should only use packages in one of these +four hierarchies if the package is defined in the Ada Reference Manual, +or is listed in this section of the GNAT Programmers Reference Manual. +All other units should be considered internal implementation units and +should not be directly `with`'ed by application code. The use of +a `with` statement that references one of these internal implementation +units makes an application potentially dependent on changes in versions +of GNAT, and will generate a warning message. + +.. _`Ada.Characters.Latin_9_(a-chlat9.ads)`: + +`Ada.Characters.Latin_9` (:file:`a-chlat9.ads`) +=============================================== + +.. index:: Ada.Characters.Latin_9 (a-chlat9.ads) + +.. index:: Latin_9 constants for Character + +This child of `Ada.Characters` +provides a set of definitions corresponding to those in the +RM-defined package `Ada.Characters.Latin_1` but with the +few modifications required for `Latin-9` +The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +.. _`Ada.Characters.Wide_Latin_1_(a-cwila1.ads)`: + +`Ada.Characters.Wide_Latin_1` (:file:`a-cwila1.ads`) +==================================================== + +.. index:: Ada.Characters.Wide_Latin_1 (a-cwila1.ads) + +.. index:: Latin_1 constants for Wide_Character + +This child of `Ada.Characters` +provides a set of definitions corresponding to those in the +RM-defined package `Ada.Characters.Latin_1` but with the +types of the constants being `Wide_Character` +instead of `Character`. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +.. _`Ada.Characters.Wide_Latin_9_(a-cwila1.ads)`: + +`Ada.Characters.Wide_Latin_9` (:file:`a-cwila1.ads`) +==================================================== + +.. index:: Ada.Characters.Wide_Latin_9 (a-cwila1.ads) + +.. index:: Latin_9 constants for Wide_Character + +This child of `Ada.Characters` +provides a set of definitions corresponding to those in the +GNAT defined package `Ada.Characters.Latin_9` but with the +types of the constants being `Wide_Character` +instead of `Character`. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +.. _`Ada.Characters.Wide_Wide_Latin_1_(a-chzla1.ads)`: + +`Ada.Characters.Wide_Wide_Latin_1` (:file:`a-chzla1.ads`) +========================================================= + +.. index:: Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads) + +.. index:: Latin_1 constants for Wide_Wide_Character + +This child of `Ada.Characters` +provides a set of definitions corresponding to those in the +RM-defined package `Ada.Characters.Latin_1` but with the +types of the constants being `Wide_Wide_Character` +instead of `Character`. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +.. _`Ada.Characters.Wide_Wide_Latin_9_(a-chzla9.ads)`: + +`Ada.Characters.Wide_Wide_Latin_9` (:file:`a-chzla9.ads`) +========================================================= + +.. index:: Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads) + +.. index:: Latin_9 constants for Wide_Wide_Character + +This child of `Ada.Characters` +provides a set of definitions corresponding to those in the +GNAT defined package `Ada.Characters.Latin_9` but with the +types of the constants being `Wide_Wide_Character` +instead of `Character`. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +.. _`Ada.Containers.Formal_Doubly_Linked_Lists_(a-cfdlli.ads)`: + +`Ada.Containers.Formal_Doubly_Linked_Lists` (:file:`a-cfdlli.ads`) +================================================================== + +.. index:: Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads) + +.. index:: Formal container for doubly linked lists + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for doubly linked lists, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Hashed_Maps_(a-cfhama.ads)`: + +`Ada.Containers.Formal_Hashed_Maps` (:file:`a-cfhama.ads`) +========================================================== + +.. index:: Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads) + +.. index:: Formal container for hashed maps + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for hashed maps, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Hashed_Sets_(a-cfhase.ads)`: + +`Ada.Containers.Formal_Hashed_Sets` (:file:`a-cfhase.ads`) +========================================================== + +.. index:: Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads) + +.. index:: Formal container for hashed sets + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for hashed sets, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Ordered_Maps_(a-cforma.ads)`: + +`Ada.Containers.Formal_Ordered_Maps` (:file:`a-cforma.ads`) +=========================================================== + +.. index:: Ada.Containers.Formal_Ordered_Maps (a-cforma.ads) + +.. index:: Formal container for ordered maps + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for ordered maps, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Ordered_Sets_(a-cforse.ads)`: + +`Ada.Containers.Formal_Ordered_Sets` (:file:`a-cforse.ads`) +=========================================================== + +.. index:: Ada.Containers.Formal_Ordered_Sets (a-cforse.ads) + +.. index:: Formal container for ordered sets + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for ordered sets, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Vectors_(a-cofove.ads)`: + +`Ada.Containers.Formal_Vectors` (:file:`a-cofove.ads`) +====================================================== + +.. index:: Ada.Containers.Formal_Vectors (a-cofove.ads) + +.. index:: Formal container for vectors + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for vectors, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Formal_Indefinite_Vectors_(a-cfinve.ads)`: + +`Ada.Containers.Formal_Indefinite_Vectors` (:file:`a-cfinve.ads`) +================================================================= + +.. index:: Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads) + +.. index:: Formal container for vectors + +This child of `Ada.Containers` defines a modified version of the +Ada 2005 container for vectors of indefinite elements, meant to +facilitate formal verification of code using such containers. The +specification of this unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +.. _`Ada.Containers.Bounded_Holders_(a-coboho.ads)`: + +`Ada.Containers.Bounded_Holders` (:file:`a-coboho.ads`) +======================================================= + +.. index:: Ada.Containers.Bounded_Holders (a-coboho.ads) + +.. index:: Formal container for vectors + +This child of `Ada.Containers` defines a modified version of +Indefinite_Holders that avoids heap allocation. + +.. _`Ada.Command_Line.Environment_(a-colien.ads)`: + +`Ada.Command_Line.Environment` (:file:`a-colien.ads`) +===================================================== + +.. index:: Ada.Command_Line.Environment (a-colien.ads) + +.. index:: Environment entries + +This child of `Ada.Command_Line` +provides a mechanism for obtaining environment values on systems +where this concept makes sense. + +.. _`Ada.Command_Line.Remove_(a-colire.ads)`: + +`Ada.Command_Line.Remove` (:file:`a-colire.ads`) +================================================ + +.. index:: Ada.Command_Line.Remove (a-colire.ads) + +.. index:: Removing command line arguments + +.. index:: Command line, argument removal + +This child of `Ada.Command_Line` +provides a mechanism for logically removing +arguments from the argument list. Once removed, an argument is not visible +to further calls on the subprograms in `Ada.Command_Line` will not +see the removed argument. + +.. _`Ada.Command_Line.Response_File_(a-clrefi.ads)`: + +`Ada.Command_Line.Response_File` (:file:`a-clrefi.ads`) +======================================================= + +.. index:: Ada.Command_Line.Response_File (a-clrefi.ads) + +.. index:: Response file for command line + +.. index:: Command line, response file + +.. index:: Command line, handling long command lines + +This child of `Ada.Command_Line` provides a mechanism facilities for +getting command line arguments from a text file, called a "response file". +Using a response file allow passing a set of arguments to an executable longer +than the maximum allowed by the system on the command line. + +.. _`Ada.Direct_IO.C_Streams_(a-diocst.ads)`: + +`Ada.Direct_IO.C_Streams` (:file:`a-diocst.ads`) +================================================ + +.. index:: Ada.Direct_IO.C_Streams (a-diocst.ads) + +.. index:: C Streams, Interfacing with Direct_IO + +This package provides subprograms that allow interfacing between +C streams and `Direct_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Exceptions.Is_Null_Occurrence_(a-einuoc.ads)`: + +`Ada.Exceptions.Is_Null_Occurrence` (:file:`a-einuoc.ads`) +========================================================== + +.. index:: Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads) + +.. index:: Null_Occurrence, testing for + +This child subprogram provides a way of testing for the null +exception occurrence (`Null_Occurrence`) without raising +an exception. + +.. _`Ada.Exceptions.Last_Chance_Handler_(a-elchha.ads)`: + +`Ada.Exceptions.Last_Chance_Handler` (:file:`a-elchha.ads`) +=========================================================== + +.. index:: Ada.Exceptions.Last_Chance_Handler (a-elchha.ads) + +.. index:: Null_Occurrence, testing for + +This child subprogram is used for handling otherwise unhandled +exceptions (hence the name last chance), and perform clean ups before +terminating the program. Note that this subprogram never returns. + +.. _`Ada.Exceptions.Traceback_(a-exctra.ads)`: + +`Ada.Exceptions.Traceback` (:file:`a-exctra.ads`) +================================================= + +.. index:: Ada.Exceptions.Traceback (a-exctra.ads) + +.. index:: Traceback for Exception Occurrence + +This child package provides the subprogram (`Tracebacks`) to +give a traceback array of addresses based on an exception +occurrence. + +.. _`Ada.Sequential_IO.C_Streams_(a-siocst.ads)`: + +`Ada.Sequential_IO.C_Streams` (:file:`a-siocst.ads`) +==================================================== + +.. index:: Ada.Sequential_IO.C_Streams (a-siocst.ads) + +.. index:: C Streams, Interfacing with Sequential_IO + +This package provides subprograms that allow interfacing between +C streams and `Sequential_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Streams.Stream_IO.C_Streams_(a-ssicst.ads)`: + +`Ada.Streams.Stream_IO.C_Streams` (:file:`a-ssicst.ads`) +======================================================== + +.. index:: Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads) + +.. index:: C Streams, Interfacing with Stream_IO + +This package provides subprograms that allow interfacing between +C streams and `Stream_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Strings.Unbounded.Text_IO_(a-suteio.ads)`: + +`Ada.Strings.Unbounded.Text_IO` (:file:`a-suteio.ads`) +====================================================== + +.. index:: Ada.Strings.Unbounded.Text_IO (a-suteio.ads) + +.. index:: Unbounded_String, IO support + +.. index:: Text_IO, extensions for unbounded strings + +This package provides subprograms for Text_IO for unbounded +strings, avoiding the necessity for an intermediate operation +with ordinary strings. + +.. _`Ada.Strings.Wide_Unbounded.Wide_Text_IO_(a-swuwti.ads)`: + +`Ada.Strings.Wide_Unbounded.Wide_Text_IO` (:file:`a-swuwti.ads`) +================================================================ + +.. index:: Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads) + +.. index:: Unbounded_Wide_String, IO support + +.. index:: Text_IO, extensions for unbounded wide strings + +This package provides subprograms for Text_IO for unbounded +wide strings, avoiding the necessity for an intermediate operation +with ordinary wide strings. + +.. _`Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO_(a-szuzti.ads)`: + +`Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO` (:file:`a-szuzti.ads`) +========================================================================== + +.. index:: Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads) + +.. index:: Unbounded_Wide_Wide_String, IO support + +.. index:: Text_IO, extensions for unbounded wide wide strings + +This package provides subprograms for Text_IO for unbounded +wide wide strings, avoiding the necessity for an intermediate operation +with ordinary wide wide strings. + +.. _`Ada.Text_IO.C_Streams_(a-tiocst.ads)`: + +`Ada.Text_IO.C_Streams` (:file:`a-tiocst.ads`) +============================================== + +.. index:: Ada.Text_IO.C_Streams (a-tiocst.ads) + +.. index:: C Streams, Interfacing with `Text_IO` + +This package provides subprograms that allow interfacing between +C streams and `Text_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Text_IO.Reset_Standard_Files_(a-tirsfi.ads)`: + +`Ada.Text_IO.Reset_Standard_Files` (:file:`a-tirsfi.ads`) +========================================================= + +.. index:: Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads) + +.. index:: Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Text_IO. This is useful in a situation (such as a restart in an +embedded application) where the status of the files may change during +execution (for example a standard input file may be redefined to be +interactive). + +.. _`Ada.Wide_Characters.Unicode_(a-wichun.ads)`: + +`Ada.Wide_Characters.Unicode` (:file:`a-wichun.ads`) +==================================================== + +.. index:: Ada.Wide_Characters.Unicode (a-wichun.ads) + +.. index:: Unicode categorization, Wide_Character + +This package provides subprograms that allow categorization of +Wide_Character values according to Unicode categories. + +.. _`Ada.Wide_Text_IO.C_Streams_(a-wtcstr.ads)`: + +`Ada.Wide_Text_IO.C_Streams` (:file:`a-wtcstr.ads`) +=================================================== + +.. index:: Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads) + +.. index:: C Streams, Interfacing with `Wide_Text_IO` + +This package provides subprograms that allow interfacing between +C streams and `Wide_Text_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Wide_Text_IO.Reset_Standard_Files_(a-wrstfi.ads)`: + +`Ada.Wide_Text_IO.Reset_Standard_Files` (:file:`a-wrstfi.ads`) +============================================================== + +.. index:: Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads) + +.. index:: Wide_Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an +embedded application) where the status of the files may change during +execution (for example a standard input file may be redefined to be +interactive). + +.. _`Ada.Wide_Wide_Characters.Unicode_(a-zchuni.ads)`: + +`Ada.Wide_Wide_Characters.Unicode` (:file:`a-zchuni.ads`) +========================================================= + +.. index:: Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads) + +.. index:: Unicode categorization, Wide_Wide_Character + +This package provides subprograms that allow categorization of +Wide_Wide_Character values according to Unicode categories. + +.. _`Ada.Wide_Wide_Text_IO.C_Streams_(a-ztcstr.ads)`: + +`Ada.Wide_Wide_Text_IO.C_Streams` (:file:`a-ztcstr.ads`) +======================================================== + +.. index:: Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads) + +.. index:: C Streams, Interfacing with `Wide_Wide_Text_IO` + +This package provides subprograms that allow interfacing between +C streams and `Wide_Wide_Text_IO`. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +.. _`Ada.Wide_Wide_Text_IO.Reset_Standard_Files_(a-zrstfi.ads)`: + +`Ada.Wide_Wide_Text_IO.Reset_Standard_Files` (:file:`a-zrstfi.ads`) +=================================================================== + +.. index:: Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads) + +.. index:: Wide_Wide_Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a +restart in an embedded application) where the status of the files may +change during execution (for example a standard input file may be +redefined to be interactive). + +.. _`GNAT.Altivec_(g-altive.ads)`: + +`GNAT.Altivec` (:file:`g-altive.ads`) +===================================== + +.. index:: GNAT.Altivec (g-altive.ads) + +.. index:: AltiVec + +This is the root package of the GNAT AltiVec binding. It provides +definitions of constants and types common to all the versions of the +binding. + +.. _`GNAT.Altivec.Conversions_(g-altcon.ads)`: + +`GNAT.Altivec.Conversions` (:file:`g-altcon.ads`) +================================================= + +.. index:: GNAT.Altivec.Conversions (g-altcon.ads) + +.. index:: AltiVec + +This package provides the Vector/View conversion routines. + +.. _`GNAT.Altivec.Vector_Operations_(g-alveop.ads)`: + +`GNAT.Altivec.Vector_Operations` (:file:`g-alveop.ads`) +======================================================= + +.. index:: GNAT.Altivec.Vector_Operations (g-alveop.ads) + +.. index:: AltiVec + +This package exposes the Ada interface to the AltiVec operations on +vector objects. A soft emulation is included by default in the GNAT +library. The hard binding is provided as a separate package. This unit +is common to both bindings. + +.. _`GNAT.Altivec.Vector_Types_(g-alvety.ads)`: + +`GNAT.Altivec.Vector_Types` (:file:`g-alvety.ads`) +================================================== + +.. index:: GNAT.Altivec.Vector_Types (g-alvety.ads) + +.. index:: AltiVec + +This package exposes the various vector types part of the Ada binding +to AltiVec facilities. + +.. _`GNAT.Altivec.Vector_Views_(g-alvevi.ads)`: + +`GNAT.Altivec.Vector_Views` (:file:`g-alvevi.ads`) +================================================== + +.. index:: GNAT.Altivec.Vector_Views (g-alvevi.ads) + +.. index:: AltiVec + +This package provides public 'View' data types from/to which private +vector representations can be converted via +GNAT.Altivec.Conversions. This allows convenient access to individual +vector elements and provides a simple way to initialize vector +objects. + +.. _`GNAT.Array_Split_(g-arrspl.ads)`: + +`GNAT.Array_Split` (:file:`g-arrspl.ads`) +========================================= + +.. index:: GNAT.Array_Split (g-arrspl.ads) + +.. index:: Array splitter + +Useful array-manipulation routines: given a set of separators, split +an array wherever the separators appear, and provide direct access +to the resulting slices. + +.. _`GNAT.AWK_(g-awk.ads)`: + +`GNAT.AWK` (:file:`g-awk.ads`) +============================== + +.. index:: GNAT.AWK (g-awk.ads) + +.. index:: Parsing + +.. index:: AWK + +Provides AWK-like parsing functions, with an easy interface for parsing one +or more files containing formatted data. The file is viewed as a database +where each record is a line and a field is a data element in this line. + +.. _`GNAT.Bounded_Buffers_(g-boubuf.ads)`: + +`GNAT.Bounded_Buffers` (:file:`g-boubuf.ads`) +============================================= + +.. index:: GNAT.Bounded_Buffers (g-boubuf.ads) + +.. index:: Parsing + +.. index:: Bounded Buffers + +Provides a concurrent generic bounded buffer abstraction. Instances are +useful directly or as parts of the implementations of other abstractions, +such as mailboxes. + +.. _`GNAT.Bounded_Mailboxes_(g-boumai.ads)`: + +`GNAT.Bounded_Mailboxes` (:file:`g-boumai.ads`) +=============================================== + +.. index:: GNAT.Bounded_Mailboxes (g-boumai.ads) + +.. index:: Parsing + +.. index:: Mailboxes + +Provides a thread-safe asynchronous intertask mailbox communication facility. + +.. _`GNAT.Bubble_Sort_(g-bubsor.ads)`: + +`GNAT.Bubble_Sort` (:file:`g-bubsor.ads`) +========================================= + +.. index:: GNAT.Bubble_Sort (g-bubsor.ads) + +.. index:: Sorting + +.. index:: Bubble sort + +Provides a general implementation of bubble sort usable for sorting arbitrary +data items. Exchange and comparison procedures are provided by passing +access-to-procedure values. + +.. _`GNAT.Bubble_Sort_A_(g-busora.ads)`: + +`GNAT.Bubble_Sort_A` (:file:`g-busora.ads`) +=========================================== + +.. index:: GNAT.Bubble_Sort_A (g-busora.ads) + +.. index:: Sorting + +.. index:: Bubble sort + +Provides a general implementation of bubble sort usable for sorting arbitrary +data items. Move and comparison procedures are provided by passing +access-to-procedure values. This is an older version, retained for +compatibility. Usually `GNAT.Bubble_Sort` will be preferable. + +.. _`GNAT.Bubble_Sort_G_(g-busorg.ads)`: + +`GNAT.Bubble_Sort_G` (:file:`g-busorg.ads`) +=========================================== + +.. index:: GNAT.Bubble_Sort_G (g-busorg.ads) + +.. index:: Sorting + +.. index:: Bubble sort + +Similar to `Bubble_Sort_A` except that the move and sorting procedures +are provided as generic parameters, this improves efficiency, especially +if the procedures can be inlined, at the expense of duplicating code for +multiple instantiations. + +.. _`GNAT.Byte_Order_Mark_(g-byorma.ads)`: + +`GNAT.Byte_Order_Mark` (:file:`g-byorma.ads`) +============================================= + +.. index:: GNAT.Byte_Order_Mark (g-byorma.ads) + +.. index:: UTF-8 representation + +.. index:: Wide characte representations + +Provides a routine which given a string, reads the start of the string to +see whether it is one of the standard byte order marks (BOM's) which signal +the encoding of the string. The routine includes detection of special XML +sequences for various UCS input formats. + +.. _`GNAT.Byte_Swapping_(g-bytswa.ads)`: + +`GNAT.Byte_Swapping` (:file:`g-bytswa.ads`) +=========================================== + +.. index:: GNAT.Byte_Swapping (g-bytswa.ads) + +.. index:: Byte swapping + +.. index:: Endianness + +General routines for swapping the bytes in 2-, 4-, and 8-byte quantities. +Machine-specific implementations are available in some cases. + +.. _`GNAT.Calendar_(g-calend.ads)`: + +`GNAT.Calendar` (:file:`g-calend.ads`) +====================================== + +.. index:: GNAT.Calendar (g-calend.ads) + +.. index:: Calendar + +Extends the facilities provided by `Ada.Calendar` to include handling +of days of the week, an extended `Split` and `Time_Of` capability. +Also provides conversion of `Ada.Calendar.Time` values to and from the +C `timeval` format. + +.. _`GNAT.Calendar.Time_IO_(g-catiio.ads)`: + +`GNAT.Calendar.Time_IO` (:file:`g-catiio.ads`) +============================================== + +.. index:: Calendar + +.. index:: Time + +.. index:: GNAT.Calendar.Time_IO (g-catiio.ads) + +.. _`GNAT.CRC32_(g-crc32.ads)`: + +`GNAT.CRC32` (:file:`g-crc32.ads`) +================================== + +.. index:: GNAT.CRC32 (g-crc32.ads) + +.. index:: CRC32 + +.. index:: Cyclic Redundancy Check + +This package implements the CRC-32 algorithm. For a full description +of this algorithm see +*Computation of Cyclic Redundancy Checks via Table Look-Up*, +:title:`Communications of the ACM`, Vol. 31 No. 8, pp. 1008-1013, +Aug. 1988. Sarwate, D.V. + +.. _`GNAT.Case_Util_(g-casuti.ads)`: + +`GNAT.Case_Util` (:file:`g-casuti.ads`) +======================================= + +.. index:: GNAT.Case_Util (g-casuti.ads) + +.. index:: Casing utilities + +.. index:: Character handling (`GNAT.Case_Util`) + +A set of simple routines for handling upper and lower casing of strings +without the overhead of the full casing tables +in `Ada.Characters.Handling`. + +.. _`GNAT.CGI_(g-cgi.ads)`: + +`GNAT.CGI` (:file:`g-cgi.ads`) +============================== + +.. index:: GNAT.CGI (g-cgi.ads) + +.. index:: CGI (Common Gateway Interface) + +This is a package for interfacing a GNAT program with a Web server via the +Common Gateway Interface (CGI). Basically this package parses the CGI +parameters, which are a set of key/value pairs sent by the Web server. It +builds a table whose index is the key and provides some services to deal +with this table. + +.. _`GNAT.CGI.Cookie_(g-cgicoo.ads)`: + +`GNAT.CGI.Cookie` (:file:`g-cgicoo.ads`) +======================================== + +.. index:: GNAT.CGI.Cookie (g-cgicoo.ads) + +.. index:: CGI (Common Gateway Interface) cookie support + +.. index:: Cookie support in CGI + +This is a package to interface a GNAT program with a Web server via the +Common Gateway Interface (CGI). It exports services to deal with Web +cookies (piece of information kept in the Web client software). + +.. _`GNAT.CGI.Debug_(g-cgideb.ads)`: + +`GNAT.CGI.Debug` (:file:`g-cgideb.ads`) +======================================= + +.. index:: GNAT.CGI.Debug (g-cgideb.ads) + +.. index:: CGI (Common Gateway Interface) debugging + +This is a package to help debugging CGI (Common Gateway Interface) +programs written in Ada. + +.. _`GNAT.Command_Line_(g-comlin.ads)`: + +`GNAT.Command_Line` (:file:`g-comlin.ads`) +========================================== + +.. index:: GNAT.Command_Line (g-comlin.ads) + +.. index:: Command line + +Provides a high level interface to `Ada.Command_Line` facilities, +including the ability to scan for named switches with optional parameters +and expand file names using wild card notations. + +.. _`GNAT.Compiler_Version_(g-comver.ads)`: + +`GNAT.Compiler_Version` (:file:`g-comver.ads`) +============================================== + +.. index:: GNAT.Compiler_Version (g-comver.ads) + +.. index:: Compiler Version + +.. index:: Version, of compiler + +Provides a routine for obtaining the version of the compiler used to +compile the program. More accurately this is the version of the binder +used to bind the program (this will normally be the same as the version +of the compiler if a consistent tool set is used to compile all units +of a partition). + +.. _`GNAT.Ctrl_C_(g-ctrl_c.ads)`: + +`GNAT.Ctrl_C` (:file:`g-ctrl_c.ads`) +==================================== + +.. index:: GNAT.Ctrl_C (g-ctrl_c.ads) + +.. index:: Interrupt + +Provides a simple interface to handle Ctrl-C keyboard events. + +.. _`GNAT.Current_Exception_(g-curexc.ads)`: + +`GNAT.Current_Exception` (:file:`g-curexc.ads`) +=============================================== + +.. index:: GNAT.Current_Exception (g-curexc.ads) + +.. index:: Current exception + +.. index:: Exception retrieval + +Provides access to information on the current exception that has been raised +without the need for using the Ada 95 / Ada 2005 exception choice parameter +specification syntax. +This is particularly useful in simulating typical facilities for +obtaining information about exceptions provided by Ada 83 compilers. + +.. _`GNAT.Debug_Pools_(g-debpoo.ads)`: + +`GNAT.Debug_Pools` (:file:`g-debpoo.ads`) +========================================= + +.. index:: GNAT.Debug_Pools (g-debpoo.ads) + +.. index:: Debugging + +.. index:: Debug pools + +.. index:: Memory corruption debugging + +Provide a debugging storage pools that helps tracking memory corruption +problems. +See `The GNAT Debug_Pool Facility` section in the :title:`GNAT User's Guide`. + +.. _`GNAT.Debug_Utilities_(g-debuti.ads)`: + +`GNAT.Debug_Utilities` (:file:`g-debuti.ads`) +============================================= + +.. index:: GNAT.Debug_Utilities (g-debuti.ads) + +.. index:: Debugging + +Provides a few useful utilities for debugging purposes, including conversion +to and from string images of address values. Supports both C and Ada formats +for hexadecimal literals. + +.. _`GNAT.Decode_String_(g-decstr.ads)`: + +`GNAT.Decode_String` (:file:`g-decstr.ads`) +=========================================== + +.. index:: GNAT.Decode_String (g-decstr.ads) + +.. index:: Decoding strings + +.. index:: String decoding + +.. index:: Wide character encoding + +.. index:: UTF-8 + +.. index:: Unicode + +A generic package providing routines for decoding wide character and wide wide +character strings encoded as sequences of 8-bit characters using a specified +encoding method. Includes validation routines, and also routines for stepping +to next or previous encoded character in an encoded string. +Useful in conjunction with Unicode character coding. Note there is a +preinstantiation for UTF-8. See next entry. + +.. _`GNAT.Decode_UTF8_String_(g-deutst.ads)`: + +`GNAT.Decode_UTF8_String` (:file:`g-deutst.ads`) +================================================ + +.. index:: GNAT.Decode_UTF8_String (g-deutst.ads) + +.. index:: Decoding strings + +.. index:: Decoding UTF-8 strings + +.. index:: UTF-8 string decoding + +.. index:: Wide character decoding + +.. index:: UTF-8 + +.. index:: Unicode + +A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding. + +.. _`GNAT.Directory_Operations_(g-dirope.ads)`: + +`GNAT.Directory_Operations` (:file:`g-dirope.ads`) +================================================== + +.. index:: GNAT.Directory_Operations (g-dirope.ads) + +.. index:: Directory operations + +Provides a set of routines for manipulating directories, including changing +the current directory, making new directories, and scanning the files in a +directory. + +.. _`GNAT.Directory_Operations.Iteration_(g-diopit.ads)`: + +`GNAT.Directory_Operations.Iteration` (:file:`g-diopit.ads`) +============================================================ + +.. index:: GNAT.Directory_Operations.Iteration (g-diopit.ads) + +.. index:: Directory operations iteration + +A child unit of GNAT.Directory_Operations providing additional operations +for iterating through directories. + +.. _`GNAT.Dynamic_HTables_(g-dynhta.ads)`: + +`GNAT.Dynamic_HTables` (:file:`g-dynhta.ads`) +============================================= + +.. index:: GNAT.Dynamic_HTables (g-dynhta.ads) + +.. index:: Hash tables + +A generic implementation of hash tables that can be used to hash arbitrary +data. Provided in two forms, a simple form with built in hash functions, +and a more complex form in which the hash function is supplied. + +This package provides a facility similar to that of `GNAT.HTable`, +except that this package declares a type that can be used to define +dynamic instances of the hash table, while an instantiation of +`GNAT.HTable` creates a single instance of the hash table. + +.. _`GNAT.Dynamic_Tables_(g-dyntab.ads)`: + +`GNAT.Dynamic_Tables` (:file:`g-dyntab.ads`) +============================================ + +.. index:: GNAT.Dynamic_Tables (g-dyntab.ads) + +.. index:: Table implementation + +.. index:: Arrays, extendable + +A generic package providing a single dimension array abstraction where the +length of the array can be dynamically modified. + +This package provides a facility similar to that of `GNAT.Table`, +except that this package declares a type that can be used to define +dynamic instances of the table, while an instantiation of +`GNAT.Table` creates a single instance of the table type. + +.. _`GNAT.Encode_String_(g-encstr.ads)`: + +`GNAT.Encode_String` (:file:`g-encstr.ads`) +=========================================== + +.. index:: GNAT.Encode_String (g-encstr.ads) + +.. index:: Encoding strings + +.. index:: String encoding + +.. index:: Wide character encoding + +.. index:: UTF-8 + +.. index:: Unicode + +A generic package providing routines for encoding wide character and wide +wide character strings as sequences of 8-bit characters using a specified +encoding method. Useful in conjunction with Unicode character coding. +Note there is a preinstantiation for UTF-8. See next entry. + +.. _`GNAT.Encode_UTF8_String_(g-enutst.ads)`: + +`GNAT.Encode_UTF8_String` (:file:`g-enutst.ads`) +================================================ + +.. index:: GNAT.Encode_UTF8_String (g-enutst.ads) + +.. index:: Encoding strings + +.. index:: Encoding UTF-8 strings + +.. index:: UTF-8 string encoding + +.. index:: Wide character encoding + +.. index:: UTF-8 + +.. index:: Unicode + +A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding. + +.. _`GNAT.Exception_Actions_(g-excact.ads)`: + +`GNAT.Exception_Actions` (:file:`g-excact.ads`) +=============================================== + +.. index:: GNAT.Exception_Actions (g-excact.ads) + +.. index:: Exception actions + +Provides callbacks when an exception is raised. Callbacks can be registered +for specific exceptions, or when any exception is raised. This +can be used for instance to force a core dump to ease debugging. + +.. _`GNAT.Exception_Traces_(g-exctra.ads)`: + +`GNAT.Exception_Traces` (:file:`g-exctra.ads`) +============================================== + +.. index:: GNAT.Exception_Traces (g-exctra.ads) + +.. index:: Exception traces + +.. index:: Debugging + +Provides an interface allowing to control automatic output upon exception +occurrences. + +.. _`GNAT.Exceptions_(g-expect.ads)`: + +`GNAT.Exceptions` (:file:`g-expect.ads`) +======================================== + +.. index:: GNAT.Exceptions (g-expect.ads) + +.. index:: Exceptions, Pure + +.. index:: Pure packages, exceptions + +Normally it is not possible to raise an exception with +a message from a subprogram in a pure package, since the +necessary types and subprograms are in `Ada.Exceptions` +which is not a pure unit. `GNAT.Exceptions` provides a +facility for getting around this limitation for a few +predefined exceptions, and for example allow raising +`Constraint_Error` with a message from a pure subprogram. + +.. _`GNAT.Expect_(g-expect.ads)`: + +`GNAT.Expect` (:file:`g-expect.ads`) +==================================== + +.. index:: GNAT.Expect (g-expect.ads) + +Provides a set of subprograms similar to what is available +with the standard Tcl Expect tool. +It allows you to easily spawn and communicate with an external process. +You can send commands or inputs to the process, and compare the output +with some expected regular expression. Currently `GNAT.Expect` +is implemented on all native GNAT ports. +It is not implemented for cross ports, and in particular is not +implemented for VxWorks or LynxOS. + +.. _`GNAT.Expect.TTY_(g-exptty.ads)`: + +`GNAT.Expect.TTY` (:file:`g-exptty.ads`) +======================================== + +.. index:: GNAT.Expect.TTY (g-exptty.ads) + +As GNAT.Expect but using pseudo-terminal. +Currently `GNAT.Expect.TTY` is implemented on all native GNAT +ports. It is not implemented for cross ports, and +in particular is not implemented for VxWorks or LynxOS. + +.. _`GNAT.Float_Control_(g-flocon.ads)`: + +`GNAT.Float_Control` (:file:`g-flocon.ads`) +=========================================== + +.. index:: GNAT.Float_Control (g-flocon.ads) + +.. index:: Floating-Point Processor + +Provides an interface for resetting the floating-point processor into the +mode required for correct semantic operation in Ada. Some third party +library calls may cause this mode to be modified, and the Reset procedure +in this package can be used to reestablish the required mode. + +.. _`GNAT.Formatted_String_(g-forstr.ads)`: + +`GNAT.Formatted_String` (:file:`g-forstr.ads`) +============================================== + +.. index:: GNAT.Formatted_String (g-forstr.ads) + +.. index:: Formatted String + +Provides support for C/C++ printf() formatted strings. The format is +copied from the printf() routine and should therefore gives identical +output. Some generic routines are provided to be able to use types +derived from Integer, Float or enumerations as values for the +formatted string. + +.. _`GNAT.Heap_Sort_(g-heasor.ads)`: + +`GNAT.Heap_Sort` (:file:`g-heasor.ads`) +======================================= + +.. index:: GNAT.Heap_Sort (g-heasor.ads) + +.. index:: Sorting + +Provides a general implementation of heap sort usable for sorting arbitrary +data items. Exchange and comparison procedures are provided by passing +access-to-procedure values. The algorithm used is a modified heap sort +that performs approximately N*log(N) comparisons in the worst case. + +.. _`GNAT.Heap_Sort_A_(g-hesora.ads)`: + +`GNAT.Heap_Sort_A` (:file:`g-hesora.ads`) +========================================= + +.. index:: GNAT.Heap_Sort_A (g-hesora.ads) + +.. index:: Sorting + +Provides a general implementation of heap sort usable for sorting arbitrary +data items. Move and comparison procedures are provided by passing +access-to-procedure values. The algorithm used is a modified heap sort +that performs approximately N*log(N) comparisons in the worst case. +This differs from `GNAT.Heap_Sort` in having a less convenient +interface, but may be slightly more efficient. + +.. _`GNAT.Heap_Sort_G_(g-hesorg.ads)`: + +`GNAT.Heap_Sort_G` (:file:`g-hesorg.ads`) +========================================= + +.. index:: GNAT.Heap_Sort_G (g-hesorg.ads) + +.. index:: Sorting + +Similar to `Heap_Sort_A` except that the move and sorting procedures +are provided as generic parameters, this improves efficiency, especially +if the procedures can be inlined, at the expense of duplicating code for +multiple instantiations. + +.. _`GNAT.HTable_(g-htable.ads)`: + +`GNAT.HTable` (:file:`g-htable.ads`) +==================================== + +.. index:: GNAT.HTable (g-htable.ads) + +.. index:: Hash tables + +A generic implementation of hash tables that can be used to hash arbitrary +data. Provides two approaches, one a simple static approach, and the other +allowing arbitrary dynamic hash tables. + +.. _`GNAT.IO_(g-io.ads)`: + +`GNAT.IO` (:file:`g-io.ads`) +============================ + +.. index:: GNAT.IO (g-io.ads) + +.. index:: Simple I/O + +.. index:: Input/Output facilities + +A simple preelaborable input-output package that provides a subset of +simple Text_IO functions for reading characters and strings from +Standard_Input, and writing characters, strings and integers to either +Standard_Output or Standard_Error. + +.. _`GNAT.IO_Aux_(g-io_aux.ads)`: + +`GNAT.IO_Aux` (:file:`g-io_aux.ads`) +==================================== + +.. index:: GNAT.IO_Aux (g-io_aux.ads) + +.. index:: Text_IO + +.. index:: Input/Output facilities + +Provides some auxiliary functions for use with Text_IO, including a test +for whether a file exists, and functions for reading a line of text. + +.. _`GNAT.Lock_Files_(g-locfil.ads)`: + +`GNAT.Lock_Files` (:file:`g-locfil.ads`) +======================================== + +.. index:: GNAT.Lock_Files (g-locfil.ads) + +.. index:: File locking + +.. index:: Locking using files + +Provides a general interface for using files as locks. Can be used for +providing program level synchronization. + +.. _`GNAT.MBBS_Discrete_Random_(g-mbdira.ads)`: + +`GNAT.MBBS_Discrete_Random` (:file:`g-mbdira.ads`) +================================================== + +.. index:: GNAT.MBBS_Discrete_Random (g-mbdira.ads) + +.. index:: Random number generation + +The original implementation of `Ada.Numerics.Discrete_Random`. Uses +a modified version of the Blum-Blum-Shub generator. + +.. _`GNAT.MBBS_Float_Random_(g-mbflra.ads)`: + +`GNAT.MBBS_Float_Random` (:file:`g-mbflra.ads`) +=============================================== + +.. index:: GNAT.MBBS_Float_Random (g-mbflra.ads) + +.. index:: Random number generation + +The original implementation of `Ada.Numerics.Float_Random`. Uses +a modified version of the Blum-Blum-Shub generator. + +.. _`GNAT.MD5_(g-md5.ads)`: + +`GNAT.MD5` (:file:`g-md5.ads`) +============================== + +.. index:: GNAT.MD5 (g-md5.ads) + +.. index:: Message Digest MD5 + +Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and +the HMAC-MD5 message authentication function as described in RFC 2104 and +FIPS PUB 198. + +.. _`GNAT.Memory_Dump_(g-memdum.ads)`: + +`GNAT.Memory_Dump` (:file:`g-memdum.ads`) +========================================= + +.. index:: GNAT.Memory_Dump (g-memdum.ads) + +.. index:: Dump Memory + +Provides a convenient routine for dumping raw memory to either the +standard output or standard error files. Uses GNAT.IO for actual +output. + +.. _`GNAT.Most_Recent_Exception_(g-moreex.ads)`: + +`GNAT.Most_Recent_Exception` (:file:`g-moreex.ads`) +=================================================== + +.. index:: GNAT.Most_Recent_Exception (g-moreex.ads) + +.. index:: Exception, obtaining most recent + +Provides access to the most recently raised exception. Can be used for +various logging purposes, including duplicating functionality of some +Ada 83 implementation dependent extensions. + +.. _`GNAT.OS_Lib_(g-os_lib.ads)`: + +`GNAT.OS_Lib` (:file:`g-os_lib.ads`) +==================================== + +.. index:: GNAT.OS_Lib (g-os_lib.ads) + +.. index:: Operating System interface + +.. index:: Spawn capability + +Provides a range of target independent operating system interface functions, +including time/date management, file operations, subprocess management, +including a portable spawn procedure, and access to environment variables +and error return codes. + +.. _`GNAT.Perfect_Hash_Generators_(g-pehage.ads)`: + +`GNAT.Perfect_Hash_Generators` (:file:`g-pehage.ads`) +===================================================== + +.. index:: GNAT.Perfect_Hash_Generators (g-pehage.ads) + +.. index:: Hash functions + +Provides a generator of static minimal perfect hash functions. No +collisions occur and each item can be retrieved from the table in one +probe (perfect property). The hash table size corresponds to the exact +size of the key set and no larger (minimal property). The key set has to +be know in advance (static property). The hash functions are also order +preserving. If w2 is inserted after w1 in the generator, their +hashcode are in the same order. These hashing functions are very +convenient for use with realtime applications. + +.. _`GNAT.Random_Numbers_(g-rannum.ads)`: + +`GNAT.Random_Numbers` (:file:`g-rannum.ads`) +============================================ + +.. index:: GNAT.Random_Numbers (g-rannum.ads) + +.. index:: Random number generation + +Provides random number capabilities which extend those available in the +standard Ada library and are more convenient to use. + +.. _`GNAT.Regexp_(g-regexp.ads)`: + +`GNAT.Regexp` (:file:`g-regexp.ads`) +==================================== + +.. index:: GNAT.Regexp (g-regexp.ads) + +.. index:: Regular expressions + +.. index:: Pattern matching + +A simple implementation of regular expressions, using a subset of regular +expression syntax copied from familiar Unix style utilities. This is the +simplest of the three pattern matching packages provided, and is particularly +suitable for 'file globbing' applications. + +.. _`GNAT.Registry_(g-regist.ads)`: + +`GNAT.Registry` (:file:`g-regist.ads`) +====================================== + +.. index:: GNAT.Registry (g-regist.ads) + +.. index:: Windows Registry + +This is a high level binding to the Windows registry. It is possible to +do simple things like reading a key value, creating a new key. For full +registry API, but at a lower level of abstraction, refer to the Win32.Winreg +package provided with the Win32Ada binding + +.. _`GNAT.Regpat_(g-regpat.ads)`: + +`GNAT.Regpat` (:file:`g-regpat.ads`) +==================================== + +.. index:: GNAT.Regpat (g-regpat.ads) + +.. index:: Regular expressions + +.. index:: Pattern matching + +A complete implementation of Unix-style regular expression matching, copied +from the original V7 style regular expression library written in C by +Henry Spencer (and binary compatible with this C library). + +.. _`GNAT.Rewrite_Data_(g-rewdat.ads)`: + +`GNAT.Rewrite_Data` (:file:`g-rewdat.ads`) +========================================== + +.. index:: GNAT.Rewrite_Data (g-rewdat.ads) + +.. index:: Rewrite data + +A unit to rewrite on-the-fly string occurrences in a stream of +data. The implementation has a very minimal memory footprint as the +full content to be processed is not loaded into memory all at once. This makes +this interface usable for large files or socket streams. + +.. _`GNAT.Secondary_Stack_Info_(g-sestin.ads)`: + +`GNAT.Secondary_Stack_Info` (:file:`g-sestin.ads`) +================================================== + +.. index:: GNAT.Secondary_Stack_Info (g-sestin.ads) + +.. index:: Secondary Stack Info + +Provide the capability to query the high water mark of the current task's +secondary stack. + +.. _`GNAT.Semaphores_(g-semaph.ads)`: + +`GNAT.Semaphores` (:file:`g-semaph.ads`) +======================================== + +.. index:: GNAT.Semaphores (g-semaph.ads) + +.. index:: Semaphores + +Provides classic counting and binary semaphores using protected types. + +.. _`GNAT.Serial_Communications_(g-sercom.ads)`: + +`GNAT.Serial_Communications` (:file:`g-sercom.ads`) +=================================================== + +.. index:: GNAT.Serial_Communications (g-sercom.ads) + +.. index:: Serial_Communications + +Provides a simple interface to send and receive data over a serial +port. This is only supported on GNU/Linux and Windows. + +.. _`GNAT.SHA1_(g-sha1.ads)`: + +`GNAT.SHA1` (:file:`g-sha1.ads`) +================================ + +.. index:: GNAT.SHA1 (g-sha1.ads) + +.. index:: Secure Hash Algorithm SHA-1 + +Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3 +and RFC 3174, and the HMAC-SHA1 message authentication function as described +in RFC 2104 and FIPS PUB 198. + +.. _`GNAT.SHA224_(g-sha224.ads)`: + +`GNAT.SHA224` (:file:`g-sha224.ads`) +==================================== + +.. index:: GNAT.SHA224 (g-sha224.ads) + +.. index:: Secure Hash Algorithm SHA-224 + +Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA224 message authentication function as described +in RFC 2104 and FIPS PUB 198. + +.. _`GNAT.SHA256_(g-sha256.ads)`: + +`GNAT.SHA256` (:file:`g-sha256.ads`) +==================================== + +.. index:: GNAT.SHA256 (g-sha256.ads) + +.. index:: Secure Hash Algorithm SHA-256 + +Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA256 message authentication function as described +in RFC 2104 and FIPS PUB 198. + +.. _`GNAT.SHA384_(g-sha384.ads)`: + +`GNAT.SHA384` (:file:`g-sha384.ads`) +==================================== + +.. index:: GNAT.SHA384 (g-sha384.ads) + +.. index:: Secure Hash Algorithm SHA-384 + +Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA384 message authentication function as described +in RFC 2104 and FIPS PUB 198. + +.. _`GNAT.SHA512_(g-sha512.ads)`: + +`GNAT.SHA512` (:file:`g-sha512.ads`) +==================================== + +.. index:: GNAT.SHA512 (g-sha512.ads) + +.. index:: Secure Hash Algorithm SHA-512 + +Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA512 message authentication function as described +in RFC 2104 and FIPS PUB 198. + +.. _`GNAT.Signals_(g-signal.ads)`: + +`GNAT.Signals` (:file:`g-signal.ads`) +===================================== + +.. index:: GNAT.Signals (g-signal.ads) + +.. index:: Signals + +Provides the ability to manipulate the blocked status of signals on supported +targets. + +.. _`GNAT.Sockets_(g-socket.ads)`: + +`GNAT.Sockets` (:file:`g-socket.ads`) +===================================== + +.. index:: GNAT.Sockets (g-socket.ads) + +.. index:: Sockets + +A high level and portable interface to develop sockets based applications. +This package is based on the sockets thin binding found in +`GNAT.Sockets.Thin`. Currently `GNAT.Sockets` is implemented +on all native GNAT ports and on VxWorks cross prots. It is not implemented for +the LynxOS cross port. + +.. _`GNAT.Source_Info_(g-souinf.ads)`: + +`GNAT.Source_Info` (:file:`g-souinf.ads`) +========================================= + +.. index:: GNAT.Source_Info (g-souinf.ads) + +.. index:: Source Information + +Provides subprograms that give access to source code information known at +compile time, such as the current file name and line number. Also provides +subprograms yielding the date and time of the current compilation (like the +C macros `__DATE__` and `__TIME__`) + +.. _`GNAT.Spelling_Checker_(g-speche.ads)`: + +`GNAT.Spelling_Checker` (:file:`g-speche.ads`) +============================================== + +.. index:: GNAT.Spelling_Checker (g-speche.ads) + +.. index:: Spell checking + +Provides a function for determining whether one string is a plausible +near misspelling of another string. + +.. _`GNAT.Spelling_Checker_Generic_(g-spchge.ads)`: + +`GNAT.Spelling_Checker_Generic` (:file:`g-spchge.ads`) +====================================================== + +.. index:: GNAT.Spelling_Checker_Generic (g-spchge.ads) + +.. index:: Spell checking + +Provides a generic function that can be instantiated with a string type for +determining whether one string is a plausible near misspelling of another +string. + +.. _`GNAT.Spitbol.Patterns_(g-spipat.ads)`: + +`GNAT.Spitbol.Patterns` (:file:`g-spipat.ads`) +============================================== + +.. index:: GNAT.Spitbol.Patterns (g-spipat.ads) + +.. index:: SPITBOL pattern matching + +.. index:: Pattern matching + +A complete implementation of SNOBOL4 style pattern matching. This is the +most elaborate of the pattern matching packages provided. It fully duplicates +the SNOBOL4 dynamic pattern construction and matching capabilities, using the +efficient algorithm developed by Robert Dewar for the SPITBOL system. + +.. _`GNAT.Spitbol_(g-spitbo.ads)`: + +`GNAT.Spitbol` (:file:`g-spitbo.ads`) +===================================== + +.. index:: GNAT.Spitbol (g-spitbo.ads) + +.. index:: SPITBOL interface + +The top level package of the collection of SPITBOL-style functionality, this +package provides basic SNOBOL4 string manipulation functions, such as +Pad, Reverse, Trim, Substr capability, as well as a generic table function +useful for constructing arbitrary mappings from strings in the style of +the SNOBOL4 TABLE function. + +.. _`GNAT.Spitbol.Table_Boolean_(g-sptabo.ads)`: + +`GNAT.Spitbol.Table_Boolean` (:file:`g-sptabo.ads`) +=================================================== + +.. index:: GNAT.Spitbol.Table_Boolean (g-sptabo.ads) + +.. index:: Sets of strings + +.. index:: SPITBOL Tables + +A library level of instantiation of `GNAT.Spitbol.Patterns.Table` +for type `Standard.Boolean`, giving an implementation of sets of +string values. + +.. _`GNAT.Spitbol.Table_Integer_(g-sptain.ads)`: + +`GNAT.Spitbol.Table_Integer` (:file:`g-sptain.ads`) +=================================================== + +.. index:: GNAT.Spitbol.Table_Integer (g-sptain.ads) + +.. index:: Integer maps + +.. index:: Maps + +.. index:: SPITBOL Tables + +A library level of instantiation of `GNAT.Spitbol.Patterns.Table` +for type `Standard.Integer`, giving an implementation of maps +from string to integer values. + +.. _`GNAT.Spitbol.Table_VString_(g-sptavs.ads)`: + +`GNAT.Spitbol.Table_VString` (:file:`g-sptavs.ads`) +=================================================== + +.. index:: GNAT.Spitbol.Table_VString (g-sptavs.ads) + +.. index:: String maps + +.. index:: Maps + +.. index:: SPITBOL Tables + +A library level of instantiation of `GNAT.Spitbol.Patterns.Table` for +a variable length string type, giving an implementation of general +maps from strings to strings. + +.. _`GNAT.SSE_(g-sse.ads)`: + +`GNAT.SSE` (:file:`g-sse.ads`) +============================== + +.. index:: GNAT.SSE (g-sse.ads) + +Root of a set of units aimed at offering Ada bindings to a subset of +the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of +targets. It exposes vector component types together with a general +introduction to the binding contents and use. + +.. _`GNAT.SSE.Vector_Types_(g-ssvety.ads)`: + +`GNAT.SSE.Vector_Types` (:file:`g-ssvety.ads`) +============================================== + +.. index:: GNAT.SSE.Vector_Types (g-ssvety.ads) + +SSE vector types for use with SSE related intrinsics. + +.. _`GNAT.Strings_(g-string.ads)`: + +`GNAT.Strings` (:file:`g-string.ads`) +===================================== + +.. index:: GNAT.Strings (g-string.ads) + +Common String access types and related subprograms. Basically it +defines a string access and an array of string access types. + +.. _`GNAT.String_Split_(g-strspl.ads)`: + +`GNAT.String_Split` (:file:`g-strspl.ads`) +========================================== + +.. index:: GNAT.String_Split (g-strspl.ads) + +.. index:: String splitter + +Useful string manipulation routines: given a set of separators, split +a string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +`GNAT.Array_Split`. + +.. _`GNAT.Table_(g-table.ads)`: + +`GNAT.Table` (:file:`g-table.ads`) +================================== + +.. index:: GNAT.Table (g-table.ads) + +.. index:: Table implementation + +.. index:: Arrays, extendable + +A generic package providing a single dimension array abstraction where the +length of the array can be dynamically modified. + +This package provides a facility similar to that of `GNAT.Dynamic_Tables`, +except that this package declares a single instance of the table type, +while an instantiation of `GNAT.Dynamic_Tables` creates a type that can be +used to define dynamic instances of the table. + +.. _`GNAT.Task_Lock_(g-tasloc.ads)`: + +`GNAT.Task_Lock` (:file:`g-tasloc.ads`) +======================================= + +.. index:: GNAT.Task_Lock (g-tasloc.ads) + +.. index:: Task synchronization + +.. index:: Task locking + +.. index:: Locking + +A very simple facility for locking and unlocking sections of code using a +single global task lock. Appropriate for use in situations where contention +between tasks is very rarely expected. + +.. _`GNAT.Time_Stamp_(g-timsta.ads)`: + +`GNAT.Time_Stamp` (:file:`g-timsta.ads`) +======================================== + +.. index:: GNAT.Time_Stamp (g-timsta.ads) + +.. index:: Time stamp + +.. index:: Current time + +Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that +represents the current date and time in ISO 8601 format. This is a very simple +routine with minimal code and there are no dependencies on any other unit. + +.. _`GNAT.Threads_(g-thread.ads)`: + +`GNAT.Threads` (:file:`g-thread.ads`) +===================================== + +.. index:: GNAT.Threads (g-thread.ads) + +.. index:: Foreign threads + +.. index:: Threads, foreign + +Provides facilities for dealing with foreign threads which need to be known +by the GNAT run-time system. Consult the documentation of this package for +further details if your program has threads that are created by a non-Ada +environment which then accesses Ada code. + +.. _`GNAT.Traceback_(g-traceb.ads)`: + +`GNAT.Traceback` (:file:`g-traceb.ads`) +======================================= + +.. index:: GNAT.Traceback (g-traceb.ads) + +.. index:: Trace back facilities + +Provides a facility for obtaining non-symbolic traceback information, useful +in various debugging situations. + +.. _`GNAT.Traceback.Symbolic_(g-trasym.ads)`: + +`GNAT.Traceback.Symbolic` (:file:`g-trasym.ads`) +================================================ + +.. index:: GNAT.Traceback.Symbolic (g-trasym.ads) + +.. index:: Trace back facilities + +.. _`GNAT.UTF_32_(g-table.ads)`: + +`GNAT.UTF_32` (:file:`g-table.ads`) +=================================== + +.. index:: GNAT.UTF_32 (g-table.ads) + +.. index:: Wide character codes + +This is a package intended to be used in conjunction with the +`Wide_Character` type in Ada 95 and the +`Wide_Wide_Character` type in Ada 2005 (available +in `GNAT` in Ada 2005 mode). This package contains +Unicode categorization routines, as well as lexical +categorization routines corresponding to the Ada 2005 +lexical rules for identifiers and strings, and also a +lower case to upper case fold routine corresponding to +the Ada 2005 rules for identifier equivalence. + +.. _`GNAT.Wide_Spelling_Checker_(g-u3spch.ads)`: + +`GNAT.Wide_Spelling_Checker` (:file:`g-u3spch.ads`) +=================================================== + +.. index:: GNAT.Wide_Spelling_Checker (g-u3spch.ads) + +.. index:: Spell checking + +Provides a function for determining whether one wide wide string is a plausible +near misspelling of another wide wide string, where the strings are represented +using the UTF_32_String type defined in System.Wch_Cnv. + +.. _`GNAT.Wide_Spelling_Checker_(g-wispch.ads)`: + +`GNAT.Wide_Spelling_Checker` (:file:`g-wispch.ads`) +=================================================== + +.. index:: GNAT.Wide_Spelling_Checker (g-wispch.ads) + +.. index:: Spell checking + +Provides a function for determining whether one wide string is a plausible +near misspelling of another wide string. + +.. _`GNAT.Wide_String_Split_(g-wistsp.ads)`: + +`GNAT.Wide_String_Split` (:file:`g-wistsp.ads`) +=============================================== + +.. index:: GNAT.Wide_String_Split (g-wistsp.ads) + +.. index:: Wide_String splitter + +Useful wide string manipulation routines: given a set of separators, split +a wide string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +`GNAT.Array_Split`. + +.. _`GNAT.Wide_Wide_Spelling_Checker_(g-zspche.ads)`: + +`GNAT.Wide_Wide_Spelling_Checker` (:file:`g-zspche.ads`) +======================================================== + +.. index:: GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads) + +.. index:: Spell checking + +Provides a function for determining whether one wide wide string is a plausible +near misspelling of another wide wide string. + +.. _`GNAT.Wide_Wide_String_Split_(g-zistsp.ads)`: + +`GNAT.Wide_Wide_String_Split` (:file:`g-zistsp.ads`) +==================================================== + +.. index:: GNAT.Wide_Wide_String_Split (g-zistsp.ads) + +.. index:: Wide_Wide_String splitter + +Useful wide wide string manipulation routines: given a set of separators, split +a wide wide string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +`GNAT.Array_Split`. + +.. _`Interfaces.C.Extensions_(i-cexten.ads)`: + +`Interfaces.C.Extensions` (:file:`i-cexten.ads`) +================================================ + +.. index:: Interfaces.C.Extensions (i-cexten.ads) + +This package contains additional C-related definitions, intended +for use with either manually or automatically generated bindings +to C libraries. + +.. _`Interfaces.C.Streams_(i-cstrea.ads)`: + +`Interfaces.C.Streams` (:file:`i-cstrea.ads`) +============================================= + +.. index:: Interfaces.C.Streams (i-cstrea.ads) + +.. index:: C streams, interfacing + +This package is a binding for the most commonly used operations +on C streams. + +.. _`Interfaces.Packed_Decimal_(i-pacdec.ads)`: + +`Interfaces.Packed_Decimal` (:file:`i-pacdec.ads`) +================================================== + +.. index:: Interfaces.Packed_Decimal (i-pacdec.ads) + +.. index:: IBM Packed Format + +.. index:: Packed Decimal + +This package provides a set of routines for conversions to and +from a packed decimal format compatible with that used on IBM +mainframes. + +.. _`Interfaces.VxWorks_(i-vxwork.ads)`: + +`Interfaces.VxWorks` (:file:`i-vxwork.ads`) +=========================================== + +.. index:: Interfaces.VxWorks (i-vxwork.ads) + +.. index:: Interfacing to VxWorks + +.. index:: VxWorks, interfacing + +This package provides a limited binding to the VxWorks API. +In particular, it interfaces with the +VxWorks hardware interrupt facilities. + +.. _`Interfaces.VxWorks.IO_(i-vxwoio.ads)`: + +`Interfaces.VxWorks.IO` (:file:`i-vxwoio.ads`) +============================================== + +.. index:: Interfaces.VxWorks.IO (i-vxwoio.ads) + +.. index:: Interfacing to VxWorks' I/O + +.. index:: VxWorks, I/O interfacing + +.. index:: VxWorks, Get_Immediate + +.. index:: Get_Immediate, VxWorks + +This package provides a binding to the ioctl (IO/Control) +function of VxWorks, defining a set of option values and +function codes. A particular use of this package is +to enable the use of Get_Immediate under VxWorks. + +.. _`System.Address_Image_(s-addima.ads)`: + +`System.Address_Image` (:file:`s-addima.ads`) +============================================= + +.. index:: System.Address_Image (s-addima.ads) + +.. index:: Address image + +.. index:: Image, of an address + +This function provides a useful debugging +function that gives an (implementation dependent) +string which identifies an address. + +.. _`System.Assertions_(s-assert.ads)`: + +`System.Assertions` (:file:`s-assert.ads`) +========================================== + +.. index:: System.Assertions (s-assert.ads) + +.. index:: Assertions + +.. index:: Assert_Failure, exception + +This package provides the declaration of the exception raised +by an run-time assertion failure, as well as the routine that +is used internally to raise this assertion. + +.. _`System.Atomic_Counters_(s-atocou.ads)`: + +`System.Atomic_Counters` (:file:`s-atocou.ads`) +=============================================== + +.. index:: System.Atomic_Counters (s-atocou.ads) + +This package provides the declaration of an atomic counter type, +together with efficient routines (using hardware +synchronization primitives) for incrementing, decrementing, +and testing of these counters. This package is implemented +on most targets, including all Alpha, ia64, PowerPC, SPARC V9, +x86, and x86_64 platforms. + +.. _`System.Memory_(s-memory.ads)`: + +`System.Memory` (:file:`s-memory.ads`) +====================================== + +.. index:: System.Memory (s-memory.ads) + +.. index:: Memory allocation + +This package provides the interface to the low level routines used +by the generated code for allocation and freeing storage for the +default storage pool (analogous to the C routines malloc and free. +It also provides a reallocation interface analogous to the C routine +realloc. The body of this unit may be modified to provide alternative +allocation mechanisms for the default pool, and in addition, direct +calls to this unit may be made for low level allocation uses (for +example see the body of `GNAT.Tables`). + +.. _`System.Multiprocessors_(s-multip.ads)`: + +`System.Multiprocessors` (:file:`s-multip.ads`) +=============================================== + +.. index:: System.Multiprocessors (s-multip.ads) + +.. index:: Multiprocessor interface + +This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but +in GNAT we also make it available in Ada 95 and Ada 2005 (where it is +technically an implementation-defined addition). + +.. _`System.Multiprocessors.Dispatching_Domains_(s-mudido.ads)`: + +`System.Multiprocessors.Dispatching_Domains` (:file:`s-mudido.ads`) +=================================================================== + +.. index:: System.Multiprocessors.Dispatching_Domains (s-mudido.ads) + +.. index:: Multiprocessor interface + +This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but +in GNAT we also make it available in Ada 95 and Ada 2005 (where it is +technically an implementation-defined addition). + +.. _`System.Partition_Interface_(s-parint.ads)`: + +`System.Partition_Interface` (:file:`s-parint.ads`) +=================================================== + +.. index:: System.Partition_Interface (s-parint.ads) + +.. index:: Partition interfacing functions + +This package provides facilities for partition interfacing. It +is used primarily in a distribution context when using Annex E +with `GLADE`. + +.. _`System.Pool_Global_(s-pooglo.ads)`: + +`System.Pool_Global` (:file:`s-pooglo.ads`) +=========================================== + +.. index:: System.Pool_Global (s-pooglo.ads) + +.. index:: Storage pool, global + +.. index:: Global storage pool + +This package provides a storage pool that is equivalent to the default +storage pool used for access types for which no pool is specifically +declared. It uses malloc/free to allocate/free and does not attempt to +do any automatic reclamation. + +.. _`System.Pool_Local_(s-pooloc.ads)`: + +`System.Pool_Local` (:file:`s-pooloc.ads`) +========================================== + +.. index:: System.Pool_Local (s-pooloc.ads) + +.. index:: Storage pool, local + +.. index:: Local storage pool + +This package provides a storage pool that is intended for use with locally +defined access types. It uses malloc/free for allocate/free, and maintains +a list of allocated blocks, so that all storage allocated for the pool can +be freed automatically when the pool is finalized. + +.. _`System.Restrictions_(s-restri.ads)`: + +`System.Restrictions` (:file:`s-restri.ads`) +============================================ + +.. index:: System.Restrictions (s-restri.ads) + +.. index:: Run-time restrictions access + +This package provides facilities for accessing at run time +the status of restrictions specified at compile time for +the partition. Information is available both with regard +to actual restrictions specified, and with regard to +compiler determined information on which restrictions +are violated by one or more packages in the partition. + +.. _`System.Rident_(s-rident.ads)`: + +`System.Rident` (:file:`s-rident.ads`) +====================================== + +.. index:: System.Rident (s-rident.ads) + +.. index:: Restrictions definitions + +This package provides definitions of the restrictions +identifiers supported by GNAT, and also the format of +the restrictions provided in package System.Restrictions. +It is not normally necessary to `with` this generic package +since the necessary instantiation is included in +package System.Restrictions. + +.. _`System.Strings.Stream_Ops_(s-ststop.ads)`: + +`System.Strings.Stream_Ops` (:file:`s-ststop.ads`) +================================================== + +.. index:: System.Strings.Stream_Ops (s-ststop.ads) + +.. index:: Stream operations + +.. index:: String stream operations + +This package provides a set of stream subprograms for standard string types. +It is intended primarily to support implicit use of such subprograms when +stream attributes are applied to string types, but the subprograms in this +package can be used directly by application programs. + +.. _`System.Unsigned_Types_(s-unstyp.ads)`: + +`System.Unsigned_Types` (:file:`s-unstyp.ads`) +============================================== + +.. index:: System.Unsigned_Types (s-unstyp.ads) + +This package contains definitions of standard unsigned types that +correspond in size to the standard signed types declared in Standard, +and (unlike the types in Interfaces) have corresponding names. It +also contains some related definitions for other specialized types +used by the compiler in connection with packed array types. + +.. _`System.Wch_Cnv_(s-wchcnv.ads)`: + +`System.Wch_Cnv` (:file:`s-wchcnv.ads`) +======================================= + +.. index:: System.Wch_Cnv (s-wchcnv.ads) + +.. index:: Wide Character, Representation + +.. index:: Wide String, Conversion + +.. index:: Representation of wide characters + +This package provides routines for converting between +wide and wide wide characters and a representation as a value of type +`Standard.String`, using a specified wide character +encoding method. It uses definitions in +package `System.Wch_Con`. + +.. _`System.Wch_Con_(s-wchcon.ads)`: + +`System.Wch_Con` (:file:`s-wchcon.ads`) +======================================= + +.. index:: System.Wch_Con (s-wchcon.ads) + +This package provides definitions and descriptions of +the various methods used for encoding wide characters +in ordinary strings. These definitions are used by +the package `System.Wch_Cnv`. + diff --git a/gcc/ada/doc/gnat_rm/the_implementation_of_standard_i_o.rst b/gcc/ada/doc/gnat_rm/the_implementation_of_standard_i_o.rst new file mode 100644 index 00000000000..3d39876c2dd --- /dev/null +++ b/gcc/ada/doc/gnat_rm/the_implementation_of_standard_i_o.rst @@ -0,0 +1,1252 @@ +.. _The_Implementation_of_Standard_I/O: + +********************************** +The Implementation of Standard I/O +********************************** + +GNAT implements all the required input-output facilities described in +A.6 through A.14. These sections of the Ada Reference Manual describe the +required behavior of these packages from the Ada point of view, and if +you are writing a portable Ada program that does not need to know the +exact manner in which Ada maps to the outside world when it comes to +reading or writing external files, then you do not need to read this +chapter. As long as your files are all regular files (not pipes or +devices), and as long as you write and read the files only from Ada, the +description in the Ada Reference Manual is sufficient. + +However, if you want to do input-output to pipes or other devices, such +as the keyboard or screen, or if the files you are dealing with are +either generated by some other language, or to be read by some other +language, then you need to know more about the details of how the GNAT +implementation of these input-output facilities behaves. + +In this chapter we give a detailed description of exactly how GNAT +interfaces to the file system. As always, the sources of the system are +available to you for answering questions at an even more detailed level, +but for most purposes the information in this chapter will suffice. + +Another reason that you may need to know more about how input-output is +implemented arises when you have a program written in mixed languages +where, for example, files are shared between the C and Ada sections of +the same program. GNAT provides some additional facilities, in the form +of additional child library packages, that facilitate this sharing, and +these additional facilities are also described in this chapter. + +.. _Standard_I/O_Packages: + +Standard I/O Packages +===================== + +The Standard I/O packages described in Annex A for + +* + Ada.Text_IO +* + Ada.Text_IO.Complex_IO +* + Ada.Text_IO.Text_Streams +* + Ada.Wide_Text_IO +* + Ada.Wide_Text_IO.Complex_IO +* + Ada.Wide_Text_IO.Text_Streams +* + Ada.Wide_Wide_Text_IO +* + Ada.Wide_Wide_Text_IO.Complex_IO +* + Ada.Wide_Wide_Text_IO.Text_Streams +* + Ada.Stream_IO +* + Ada.Sequential_IO +* + Ada.Direct_IO + +are implemented using the C +library streams facility; where + +* + All files are opened using `fopen`. +* + All input/output operations use `fread`/`fwrite`. + +There is no internal buffering of any kind at the Ada library level. The only +buffering is that provided at the system level in the implementation of the +library routines that support streams. This facilitates shared use of these +streams by mixed language programs. Note though that system level buffering is +explicitly enabled at elaboration of the standard I/O packages and that can +have an impact on mixed language programs, in particular those using I/O before +calling the Ada elaboration routine (e.g., adainit). It is recommended to call +the Ada elaboration routine before performing any I/O or when impractical, +flush the common I/O streams and in particular Standard_Output before +elaborating the Ada code. + +.. _FORM_Strings: + +FORM Strings +============ + +The format of a FORM string in GNAT is: + + +:: + + "keyword=value,keyword=value,...,keyword=value" + + +where letters may be in upper or lower case, and there are no spaces +between values. The order of the entries is not important. Currently +the following keywords defined. + + +:: + + TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT] + SHARED=[YES|NO] + WCEM=[n|h|u|s|e|8|b] + ENCODING=[UTF8|8BITS] + + +The use of these parameters is described later in this section. If an +unrecognized keyword appears in a form string, it is silently ignored +and not considered invalid. + +.. _Direct_IO: + +Direct_IO +========= + +Direct_IO can only be instantiated for definite types. This is a +restriction of the Ada language, which means that the records are fixed +length (the length being determined by ``type'Size``, rounded +up to the next storage unit boundary if necessary). + +The records of a Direct_IO file are simply written to the file in index +sequence, with the first record starting at offset zero, and subsequent +records following. There is no control information of any kind. For +example, if 32-bit integers are being written, each record takes +4-bytes, so the record at index `K` starts at offset +(`K`-1)*4. + +There is no limit on the size of Direct_IO files, they are expanded as +necessary to accommodate whatever records are written to the file. + +.. _Sequential_IO: + +Sequential_IO +============= + +Sequential_IO may be instantiated with either a definite (constrained) +or indefinite (unconstrained) type. + +For the definite type case, the elements written to the file are simply +the memory images of the data values with no control information of any +kind. The resulting file should be read using the same type, no validity +checking is performed on input. + +For the indefinite type case, the elements written consist of two +parts. First is the size of the data item, written as the memory image +of a `Interfaces.C.size_t` value, followed by the memory image of +the data value. The resulting file can only be read using the same +(unconstrained) type. Normal assignment checks are performed on these +read operations, and if these checks fail, `Data_Error` is +raised. In particular, in the array case, the lengths must match, and in +the variant record case, if the variable for a particular read operation +is constrained, the discriminants must match. + +Note that it is not possible to use Sequential_IO to write variable +length array items, and then read the data back into different length +arrays. For example, the following will raise `Data_Error`: + + +.. code-block:: ada + + package IO is new Sequential_IO (String); + F : IO.File_Type; + S : String (1..4); + ... + IO.Create (F) + IO.Write (F, "hello!") + IO.Reset (F, Mode=>In_File); + IO.Read (F, S); + Put_Line (S); + + + +On some Ada implementations, this will print `hell`, but the program is +clearly incorrect, since there is only one element in the file, and that +element is the string `hello!`. + +In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved +using Stream_IO, and this is the preferred mechanism. In particular, the +above program fragment rewritten to use Stream_IO will work correctly. + +.. _Text_IO: + +Text_IO +======= + +Text_IO files consist of a stream of characters containing the following +special control characters: + + +:: + + LF (line feed, 16#0A#) Line Mark + FF (form feed, 16#0C#) Page Mark + + +A canonical Text_IO file is defined as one in which the following +conditions are met: + +* + The character `LF` is used only as a line mark, i.e., to mark the end + of the line. + +* + The character `FF` is used only as a page mark, i.e., to mark the + end of a page and consequently can appear only immediately following a + `LF` (line mark) character. + +* + The file ends with either `LF` (line mark) or `LF`-`FF` + (line mark, page mark). In the former case, the page mark is implicitly + assumed to be present. + +A file written using Text_IO will be in canonical form provided that no +explicit `LF` or `FF` characters are written using `Put` +or `Put_Line`. There will be no `FF` character at the end of +the file unless an explicit `New_Page` operation was performed +before closing the file. + +A canonical Text_IO file that is a regular file (i.e., not a device or a +pipe) can be read using any of the routines in Text_IO. The +semantics in this case will be exactly as defined in the Ada Reference +Manual, and all the routines in Text_IO are fully implemented. + +A text file that does not meet the requirements for a canonical Text_IO +file has one of the following: + +* + The file contains `FF` characters not immediately following a + `LF` character. + +* + The file contains `LF` or `FF` characters written by + `Put` or `Put_Line`, which are not logically considered to be + line marks or page marks. + +* + The file ends in a character other than `LF` or `FF`, + i.e., there is no explicit line mark or page mark at the end of the file. + +Text_IO can be used to read such non-standard text files but subprograms +to do with line or page numbers do not have defined meanings. In +particular, a `FF` character that does not follow a `LF` +character may or may not be treated as a page mark from the point of +view of page and line numbering. Every `LF` character is considered +to end a line, and there is an implied `LF` character at the end of +the file. + +.. _Stream_Pointer_Positioning: + +Stream Pointer Positioning +-------------------------- + +`Ada.Text_IO` has a definition of current position for a file that +is being read. No internal buffering occurs in Text_IO, and usually the +physical position in the stream used to implement the file corresponds +to this logical position defined by Text_IO. There are two exceptions: + +* + After a call to `End_Of_Page` that returns `True`, the stream + is positioned past the `LF` (line mark) that precedes the page + mark. Text_IO maintains an internal flag so that subsequent read + operations properly handle the logical position which is unchanged by + the `End_Of_Page` call. + +* + After a call to `End_Of_File` that returns `True`, if the + Text_IO file was positioned before the line mark at the end of file + before the call, then the logical position is unchanged, but the stream + is physically positioned right at the end of file (past the line mark, + and past a possible page mark following the line mark. Again Text_IO + maintains internal flags so that subsequent read operations properly + handle the logical position. + +These discrepancies have no effect on the observable behavior of +Text_IO, but if a single Ada stream is shared between a C program and +Ada program, or shared (using ``shared=yes`` in the form string) +between two Ada files, then the difference may be observable in some +situations. + +.. _Reading_and_Writing_Non-Regular_Files: + +Reading and Writing Non-Regular Files +------------------------------------- + +A non-regular file is a device (such as a keyboard), or a pipe. Text_IO +can be used for reading and writing. Writing is not affected and the +sequence of characters output is identical to the normal file case, but +for reading, the behavior of Text_IO is modified to avoid undesirable +look-ahead as follows: + +An input file that is not a regular file is considered to have no page +marks. Any `Ascii.FF` characters (the character normally used for a +page mark) appearing in the file are considered to be data +characters. In particular: + +* + `Get_Line` and `Skip_Line` do not test for a page mark + following a line mark. If a page mark appears, it will be treated as a + data character. + +* + This avoids the need to wait for an extra character to be typed or + entered from the pipe to complete one of these operations. + +* + `End_Of_Page` always returns `False` + +* + `End_Of_File` will return `False` if there is a page mark at + the end of the file. + +Output to non-regular files is the same as for regular files. Page marks +may be written to non-regular files using `New_Page`, but as noted +above they will not be treated as page marks on input if the output is +piped to another Ada program. + +Another important discrepancy when reading non-regular files is that the end +of file indication is not 'sticky'. If an end of file is entered, e.g., by +pressing the :kbd:`EOT` key, +then end of file +is signaled once (i.e., the test `End_Of_File` +will yield `True`, or a read will +raise `End_Error`), but then reading can resume +to read data past that end of +file indication, until another end of file indication is entered. + +.. _Get_Immediate: + +Get_Immediate +------------- + +.. index:: Get_Immediate + +Get_Immediate returns the next character (including control characters) +from the input file. In particular, Get_Immediate will return LF or FF +characters used as line marks or page marks. Such operations leave the +file positioned past the control character, and it is thus not treated +as having its normal function. This means that page, line and column +counts after this kind of Get_Immediate call are set as though the mark +did not occur. In the case where a Get_Immediate leaves the file +positioned between the line mark and page mark (which is not normally +possible), it is undefined whether the FF character will be treated as a +page mark. + +.. _Treating_Text_IO_Files_as_Streams: + +Treating Text_IO Files as Streams +--------------------------------- + +.. index:: Stream files + +The package `Text_IO.Streams` allows a Text_IO file to be treated +as a stream. Data written to a Text_IO file in this stream mode is +binary data. If this binary data contains bytes 16#0A# (`LF`) or +16#0C# (`FF`), the resulting file may have non-standard +format. Similarly if read operations are used to read from a Text_IO +file treated as a stream, then `LF` and `FF` characters may be +skipped and the effect is similar to that described above for +`Get_Immediate`. + +.. _Text_IO_Extensions: + +Text_IO Extensions +------------------ + +.. index:: Text_IO extensions + +A package GNAT.IO_Aux in the GNAT library provides some useful extensions +to the standard `Text_IO` package: + +* function File_Exists (Name : String) return Boolean; + Determines if a file of the given name exists. + +* function Get_Line return String; + Reads a string from the standard input file. The value returned is exactly + the length of the line that was read. + +* function Get_Line (File : Ada.Text_IO.File_Type) return String; + Similar, except that the parameter File specifies the file from which + the string is to be read. + + +.. _Text_IO_Facilities_for_Unbounded_Strings: + +Text_IO Facilities for Unbounded Strings +---------------------------------------- + +.. index:: Text_IO for unbounded strings + +.. index:: Unbounded_String, Text_IO operations + +The package `Ada.Strings.Unbounded.Text_IO` +in library files `a-suteio.ads/adb` contains some GNAT-specific +subprograms useful for Text_IO operations on unbounded strings: + + +* function Get_Line (File : File_Type) return Unbounded_String; + Reads a line from the specified file + and returns the result as an unbounded string. + +* procedure Put (File : File_Type; U : Unbounded_String); + Writes the value of the given unbounded string to the specified file + Similar to the effect of + `Put (To_String (U))` except that an extra copy is avoided. + +* procedure Put_Line (File : File_Type; U : Unbounded_String); + Writes the value of the given unbounded string to the specified file, + followed by a `New_Line`. + Similar to the effect of `Put_Line (To_String (U))` except + that an extra copy is avoided. + +In the above procedures, `File` is of type `Ada.Text_IO.File_Type` +and is optional. If the parameter is omitted, then the standard input or +output file is referenced as appropriate. + +The package `Ada.Strings.Wide_Unbounded.Wide_Text_IO` in library +files :file:`a-swuwti.ads` and :file:`a-swuwti.adb` provides similar extended +`Wide_Text_IO` functionality for unbounded wide strings. + +The package `Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO` in library +files :file:`a-szuzti.ads` and :file:`a-szuzti.adb` provides similar extended +`Wide_Wide_Text_IO` functionality for unbounded wide wide strings. + +.. _Wide_Text_IO: + +Wide_Text_IO +============ + +`Wide_Text_IO` is similar in most respects to Text_IO, except that +both input and output files may contain special sequences that represent +wide character values. The encoding scheme for a given file may be +specified using a FORM parameter: + + +:: + + WCEM=`x` + + +as part of the FORM string (WCEM = wide character encoding method), +where `x` is one of the following characters + +========== ==================== +Character Encoding +========== ==================== +*h* Hex ESC encoding +*u* Upper half encoding +*s* Shift-JIS encoding +*e* EUC Encoding +*8* UTF-8 encoding +*b* Brackets encoding +========== ==================== + +The encoding methods match those that +can be used in a source +program, but there is no requirement that the encoding method used for +the source program be the same as the encoding method used for files, +and different files may use different encoding methods. + +The default encoding method for the standard files, and for opened files +for which no WCEM parameter is given in the FORM string matches the +wide character encoding specified for the main program (the default +being brackets encoding if no coding method was specified with -gnatW). + + + +*Hex Coding* + In this encoding, a wide character is represented by a five character + sequence: + + +:: + + ESC a b c d + +.. + + where `a`, `b`, `c`, `d` are the four hexadecimal + characters (using upper case letters) of the wide character code. For + example, ESC A345 is used to represent the wide character with code + 16#A345#. This scheme is compatible with use of the full + `Wide_Character` set. + + +*Upper Half Coding* + The wide character with encoding 16#abcd#, where the upper bit is on + (i.e., a is in the range 8-F) is represented as two bytes 16#ab# and + 16#cd#. The second byte may never be a format control character, but is + not required to be in the upper half. This method can be also used for + shift-JIS or EUC where the internal coding matches the external coding. + + +*Shift JIS Coding* + A wide character is represented by a two character sequence 16#ab# and + 16#cd#, with the restrictions described for upper half encoding as + described above. The internal character code is the corresponding JIS + character according to the standard algorithm for Shift-JIS + conversion. Only characters defined in the JIS code set table can be + used with this encoding method. + + +*EUC Coding* + A wide character is represented by a two character sequence 16#ab# and + 16#cd#, with both characters being in the upper half. The internal + character code is the corresponding JIS character according to the EUC + encoding algorithm. Only characters defined in the JIS code set table + can be used with this encoding method. + + +*UTF-8 Coding* + A wide character is represented using + UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO + 10646-1/Am.2. Depending on the character value, the representation + is a one, two, or three byte sequence: + + +:: + + 16#0000#-16#007f#: 2#0xxxxxxx# + 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx# + 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# + +.. + + where the `xxx` bits correspond to the left-padded bits of the + 16-bit character value. Note that all lower half ASCII characters + are represented as ASCII bytes and all upper half characters and + other wide characters are represented as sequences of upper-half + (The full UTF-8 scheme allows for encoding 31-bit characters as + 6-byte sequences, but in this implementation, all UTF-8 sequences + of four or more bytes length will raise a Constraint_Error, as + will all invalid UTF-8 sequences.) + + +*Brackets Coding* + In this encoding, a wide character is represented by the following eight + character sequence: + + +:: + + [ " a b c d " ] + +.. + + where `a`, `b`, `c`, `d` are the four hexadecimal + characters (using uppercase letters) of the wide character code. For + example, `["A345"]` is used to represent the wide character with code + `16#A345#`. + This scheme is compatible with use of the full Wide_Character set. + On input, brackets coding can also be used for upper half characters, + e.g., `["C1"]` for lower case a. However, on output, brackets notation + is only used for wide characters with a code greater than `16#FF#`. + + Note that brackets coding is not normally used in the context of + Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as + a portable way of encoding source files. In the context of Wide_Text_IO + or Wide_Wide_Text_IO, it can only be used if the file does not contain + any instance of the left bracket character other than to encode wide + character values using the brackets encoding method. In practice it is + expected that some standard wide character encoding method such + as UTF-8 will be used for text input output. + + If brackets notation is used, then any occurrence of a left bracket + in the input file which is not the start of a valid wide character + sequence will cause Constraint_Error to be raised. It is possible to + encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO + input will interpret this as a left bracket. + + However, when a left bracket is output, it will be output as a left bracket + and not as ["5B"]. We make this decision because for normal use of + Wide_Text_IO for outputting messages, it is unpleasant to clobber left + brackets. For example, if we write: + + + .. code-block:: ada + + Put_Line ("Start of output [first run]"); + + + we really do not want to have the left bracket in this message clobbered so + that the output reads: + + +:: + + Start of output ["5B"]first run] + +.. + + In practice brackets encoding is reasonably useful for normal Put_Line use + since we won't get confused between left brackets and wide character + sequences in the output. But for input, or when files are written out + and read back in, it really makes better sense to use one of the standard + encoding methods such as UTF-8. + + +For the coding schemes other than UTF-8, Hex, or Brackets encoding, +not all wide character +values can be represented. An attempt to output a character that cannot +be represented using the encoding scheme for the file causes +Constraint_Error to be raised. An invalid wide character sequence on +input also causes Constraint_Error to be raised. + +.. _Stream_Pointer_Positioning_1: + +Stream Pointer Positioning +-------------------------- + +`Ada.Wide_Text_IO` is similar to `Ada.Text_IO` in its handling +of stream pointer positioning (:ref:`Text_IO`). There is one additional +case: + +If `Ada.Wide_Text_IO.Look_Ahead` reads a character outside the +normal lower ASCII set (i.e., a character in the range: + + +.. code-block:: ada + + Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#) + + +then although the logical position of the file pointer is unchanged by +the `Look_Ahead` call, the stream is physically positioned past the +wide character sequence. Again this is to avoid the need for buffering +or backup, and all `Wide_Text_IO` routines check the internal +indication that this situation has occurred so that this is not visible +to a normal program using `Wide_Text_IO`. However, this discrepancy +can be observed if the wide text file shares a stream with another file. + +.. _Reading_and_Writing_Non-Regular_Files_1: + +Reading and Writing Non-Regular Files +------------------------------------- + +As in the case of Text_IO, when a non-regular file is read, it is +assumed that the file contains no page marks (any form characters are +treated as data characters), and `End_Of_Page` always returns +`False`. Similarly, the end of file indication is not sticky, so +it is possible to read beyond an end of file. + +.. _Wide_Wide_Text_IO: + +Wide_Wide_Text_IO +================= + +`Wide_Wide_Text_IO` is similar in most respects to Text_IO, except that +both input and output files may contain special sequences that represent +wide wide character values. The encoding scheme for a given file may be +specified using a FORM parameter: + + +:: + + WCEM=`x` + + +as part of the FORM string (WCEM = wide character encoding method), +where `x` is one of the following characters + +========== ==================== +Character Encoding +========== ==================== +*h* Hex ESC encoding +*u* Upper half encoding +*s* Shift-JIS encoding +*e* EUC Encoding +*8* UTF-8 encoding +*b* Brackets encoding +========== ==================== + + +The encoding methods match those that +can be used in a source +program, but there is no requirement that the encoding method used for +the source program be the same as the encoding method used for files, +and different files may use different encoding methods. + +The default encoding method for the standard files, and for opened files +for which no WCEM parameter is given in the FORM string matches the +wide character encoding specified for the main program (the default +being brackets encoding if no coding method was specified with -gnatW). + + + +*UTF-8 Coding* + A wide character is represented using + UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO + 10646-1/Am.2. Depending on the character value, the representation + is a one, two, three, or four byte sequence: + + +:: + + 16#000000#-16#00007f#: 2#0xxxxxxx# + 16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx# + 16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# + 16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx# + +.. + + where the `xxx` bits correspond to the left-padded bits of the + 21-bit character value. Note that all lower half ASCII characters + are represented as ASCII bytes and all upper half characters and + other wide characters are represented as sequences of upper-half + characters. + + +*Brackets Coding* + In this encoding, a wide wide character is represented by the following eight + character sequence if is in wide character range + + +:: + + [ " a b c d " ] + +.. + + and by the following ten character sequence if not + + +:: + + [ " a b c d e f " ] + +.. + + where `a`, `b`, `c`, `d`, `e`, and `f` + are the four or six hexadecimal + characters (using uppercase letters) of the wide wide character code. For + example, `["01A345"]` is used to represent the wide wide character + with code `16#01A345#`. + + This scheme is compatible with use of the full Wide_Wide_Character set. + On input, brackets coding can also be used for upper half characters, + e.g., `["C1"]` for lower case a. However, on output, brackets notation + is only used for wide characters with a code greater than `16#FF#`. + + +If is also possible to use the other Wide_Character encoding methods, +such as Shift-JIS, but the other schemes cannot support the full range +of wide wide characters. +An attempt to output a character that cannot +be represented using the encoding scheme for the file causes +Constraint_Error to be raised. An invalid wide character sequence on +input also causes Constraint_Error to be raised. + +.. _Stream_Pointer_Positioning_2: + +Stream Pointer Positioning +-------------------------- + +`Ada.Wide_Wide_Text_IO` is similar to `Ada.Text_IO` in its handling +of stream pointer positioning (:ref:`Text_IO`). There is one additional +case: + +If `Ada.Wide_Wide_Text_IO.Look_Ahead` reads a character outside the +normal lower ASCII set (i.e., a character in the range: + + +.. code-block:: ada + + Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#) + + +then although the logical position of the file pointer is unchanged by +the `Look_Ahead` call, the stream is physically positioned past the +wide character sequence. Again this is to avoid the need for buffering +or backup, and all `Wide_Wide_Text_IO` routines check the internal +indication that this situation has occurred so that this is not visible +to a normal program using `Wide_Wide_Text_IO`. However, this discrepancy +can be observed if the wide text file shares a stream with another file. + +.. _Reading_and_Writing_Non-Regular_Files_2: + +Reading and Writing Non-Regular Files +------------------------------------- + +As in the case of Text_IO, when a non-regular file is read, it is +assumed that the file contains no page marks (any form characters are +treated as data characters), and `End_Of_Page` always returns +`False`. Similarly, the end of file indication is not sticky, so +it is possible to read beyond an end of file. + +.. _Stream_IO: + +Stream_IO +========= + +A stream file is a sequence of bytes, where individual elements are +written to the file as described in the Ada Reference Manual. The type +`Stream_Element` is simply a byte. There are two ways to read or +write a stream file. + +* + The operations `Read` and `Write` directly read or write a + sequence of stream elements with no control information. + +* + The stream attributes applied to a stream file transfer data in the + manner described for stream attributes. + +.. _Text_Translation: + +Text Translation +================ + +``Text_Translation=xxx`` may be used as the Form parameter +passed to Text_IO.Create and Text_IO.Open. ``Text_Translation=xxx`` +has no effect on Unix systems. Possible values are: + + +* + ``Yes`` or ``Text`` is the default, which means to + translate LF to/from CR/LF on Windows systems. + + ``No`` disables this translation; i.e. it + uses binary mode. For output files, ``Text_Translation=No`` + may be used to create Unix-style files on + Windows. + +* + ``wtext`` translation enabled in Unicode mode. + (corresponds to _O_WTEXT). + +* + ``u8text`` translation enabled in Unicode UTF-8 mode. + (corresponds to O_U8TEXT). + +* + ``u16text`` translation enabled in Unicode UTF-16 + mode. (corresponds to_O_U16TEXT). + + +.. _Shared_Files: + +Shared Files +============ + +Section A.14 of the Ada Reference Manual allows implementations to +provide a wide variety of behavior if an attempt is made to access the +same external file with two or more internal files. + +To provide a full range of functionality, while at the same time +minimizing the problems of portability caused by this implementation +dependence, GNAT handles file sharing as follows: + +* + In the absence of a ``shared=xxx`` form parameter, an attempt + to open two or more files with the same full name is considered an error + and is not supported. The exception `Use_Error` will be + raised. Note that a file that is not explicitly closed by the program + remains open until the program terminates. + +* + If the form parameter ``shared=no`` appears in the form string, the + file can be opened or created with its own separate stream identifier, + regardless of whether other files sharing the same external file are + opened. The exact effect depends on how the C stream routines handle + multiple accesses to the same external files using separate streams. + +* + If the form parameter ``shared=yes`` appears in the form string for + each of two or more files opened using the same full name, the same + stream is shared between these files, and the semantics are as described + in Ada Reference Manual, Section A.14. + +When a program that opens multiple files with the same name is ported +from another Ada compiler to GNAT, the effect will be that +`Use_Error` is raised. + +The documentation of the original compiler and the documentation of the +program should then be examined to determine if file sharing was +expected, and ``shared=xxx`` parameters added to `Open` +and `Create` calls as required. + +When a program is ported from GNAT to some other Ada compiler, no +special attention is required unless the ``shared=xxx`` form +parameter is used in the program. In this case, you must examine the +documentation of the new compiler to see if it supports the required +file sharing semantics, and form strings modified appropriately. Of +course it may be the case that the program cannot be ported if the +target compiler does not support the required functionality. The best +approach in writing portable code is to avoid file sharing (and hence +the use of the ``shared=xxx`` parameter in the form string) +completely. + +One common use of file sharing in Ada 83 is the use of instantiations of +Sequential_IO on the same file with different types, to achieve +heterogeneous input-output. Although this approach will work in GNAT if +``shared=yes`` is specified, it is preferable in Ada to use Stream_IO +for this purpose (using the stream attributes) + +.. _Filenames_encoding: + +Filenames encoding +================== + +An encoding form parameter can be used to specify the filename +encoding ``encoding=xxx``. + +* + If the form parameter ``encoding=utf8`` appears in the form string, the + filename must be encoded in UTF-8. + +* + If the form parameter ``encoding=8bits`` appears in the form + string, the filename must be a standard 8bits string. + +In the absence of a ``encoding=xxx`` form parameter, the +encoding is controlled by the ``GNAT_CODE_PAGE`` environment +variable. And if not set ``utf8`` is assumed. + + + +*CP_ACP* + The current system Windows ANSI code page. + +*CP_UTF8* + UTF-8 encoding + +This encoding form parameter is only supported on the Windows +platform. On the other Operating Systems the run-time is supporting +UTF-8 natively. + +.. _File_content_encoding: + +File content encoding +===================== + +For text files it is possible to specify the encoding to use. This is +controlled by the by the ``GNAT_CCS_ENCODING`` environment +variable. And if not set ``TEXT`` is assumed. + +The possible values are those supported on Windows: + + + +*TEXT* + Translated text mode + +*WTEXT* + Translated unicode encoding + +*U16TEXT* + Unicode 16-bit encoding + +*U8TEXT* + Unicode 8-bit encoding + +This encoding is only supported on the Windows platform. + +.. _Open_Modes: + +Open Modes +========== + +`Open` and `Create` calls result in a call to `fopen` +using the mode shown in the following table: + ++----------------------------+---------------+------------------+ +| `Open` and `Create` Call Modes | ++----------------------------+---------------+------------------+ +| | **OPEN** | **CREATE** | ++============================+===============+==================+ +| Append_File | "r+" | "w+" | ++----------------------------+---------------+------------------+ +| In_File | "r" | "w+" | ++----------------------------+---------------+------------------+ +| Out_File (Direct_IO) | "r+" | "w" | ++----------------------------+---------------+------------------+ +| Out_File (all other cases) | "w" | "w" | ++----------------------------+---------------+------------------+ +| Inout_File | "r+" | "w+" | ++----------------------------+---------------+------------------+ + + +If text file translation is required, then either ``b`` or ``t`` +is added to the mode, depending on the setting of Text. Text file +translation refers to the mapping of CR/LF sequences in an external file +to LF characters internally. This mapping only occurs in DOS and +DOS-like systems, and is not relevant to other systems. + +A special case occurs with Stream_IO. As shown in the above table, the +file is initially opened in ``r`` or ``w`` mode for the +`In_File` and `Out_File` cases. If a `Set_Mode` operation +subsequently requires switching from reading to writing or vice-versa, +then the file is reopened in ``r+`` mode to permit the required operation. + +.. _Operations_on_C_Streams: + +Operations on C Streams +======================= + +The package `Interfaces.C_Streams` provides an Ada program with direct +access to the C library functions for operations on C streams: + + +.. code-block:: ada + + package Interfaces.C_Streams is + -- Note: the reason we do not use the types that are in + -- Interfaces.C is that we want to avoid dragging in the + -- code in this unit if possible. + subtype chars is System.Address; + -- Pointer to null-terminated array of characters + subtype FILEs is System.Address; + -- Corresponds to the C type FILE* + subtype voids is System.Address; + -- Corresponds to the C type void* + subtype int is Integer; + subtype long is Long_Integer; + -- Note: the above types are subtypes deliberately, and it + -- is part of this spec that the above correspondences are + -- guaranteed. This means that it is legitimate to, for + -- example, use Integer instead of int. We provide these + -- synonyms for clarity, but in some cases it may be + -- convenient to use the underlying types (for example to + -- avoid an unnecessary dependency of a spec on the spec + -- of this unit). + type size_t is mod 2 ** Standard'Address_Size; + NULL_Stream : constant FILEs; + -- Value returned (NULL in C) to indicate an + -- fdopen/fopen/tmpfile error + ---------------------------------- + -- Constants Defined in stdio.h -- + ---------------------------------- + EOF : constant int; + -- Used by a number of routines to indicate error or + -- end of file + IOFBF : constant int; + IOLBF : constant int; + IONBF : constant int; + -- Used to indicate buffering mode for setvbuf call + SEEK_CUR : constant int; + SEEK_END : constant int; + SEEK_SET : constant int; + -- Used to indicate origin for fseek call + function stdin return FILEs; + function stdout return FILEs; + function stderr return FILEs; + -- Streams associated with standard files + -------------------------- + -- Standard C functions -- + -------------------------- + -- The functions selected below are ones that are + -- available in UNIX (but not necessarily in ANSI C). + -- These are very thin interfaces + -- which copy exactly the C headers. For more + -- documentation on these functions, see the Microsoft C + -- "Run-Time Library Reference" (Microsoft Press, 1990, + -- ISBN 1-55615-225-6), which includes useful information + -- on system compatibility. + procedure clearerr (stream : FILEs); + function fclose (stream : FILEs) return int; + function fdopen (handle : int; mode : chars) return FILEs; + function feof (stream : FILEs) return int; + function ferror (stream : FILEs) return int; + function fflush (stream : FILEs) return int; + function fgetc (stream : FILEs) return int; + function fgets (strng : chars; n : int; stream : FILEs) + return chars; + function fileno (stream : FILEs) return int; + function fopen (filename : chars; Mode : chars) + return FILEs; + -- Note: to maintain target independence, use + -- text_translation_required, a boolean variable defined in + -- a-sysdep.c to deal with the target dependent text + -- translation requirement. If this variable is set, + -- then b/t should be appended to the standard mode + -- argument to set the text translation mode off or on + -- as required. + function fputc (C : int; stream : FILEs) return int; + function fputs (Strng : chars; Stream : FILEs) return int; + function fread + (buffer : voids; + size : size_t; + count : size_t; + stream : FILEs) + return size_t; + function freopen + (filename : chars; + mode : chars; + stream : FILEs) + return FILEs; + function fseek + (stream : FILEs; + offset : long; + origin : int) + return int; + function ftell (stream : FILEs) return long; + function fwrite + (buffer : voids; + size : size_t; + count : size_t; + stream : FILEs) + return size_t; + function isatty (handle : int) return int; + procedure mktemp (template : chars); + -- The return value (which is just a pointer to template) + -- is discarded + procedure rewind (stream : FILEs); + function rmtmp return int; + function setvbuf + (stream : FILEs; + buffer : chars; + mode : int; + size : size_t) + return int; + + function tmpfile return FILEs; + function ungetc (c : int; stream : FILEs) return int; + function unlink (filename : chars) return int; + --------------------- + -- Extra functions -- + --------------------- + -- These functions supply slightly thicker bindings than + -- those above. They are derived from functions in the + -- C Run-Time Library, but may do a bit more work than + -- just directly calling one of the Library functions. + function is_regular_file (handle : int) return int; + -- Tests if given handle is for a regular file (result 1) + -- or for a non-regular file (pipe or device, result 0). + --------------------------------- + -- Control of Text/Binary Mode -- + --------------------------------- + -- If text_translation_required is true, then the following + -- functions may be used to dynamically switch a file from + -- binary to text mode or vice versa. These functions have + -- no effect if text_translation_required is false (i.e., in + -- normal UNIX mode). Use fileno to get a stream handle. + procedure set_binary_mode (handle : int); + procedure set_text_mode (handle : int); + ---------------------------- + -- Full Path Name support -- + ---------------------------- + procedure full_name (nam : chars; buffer : chars); + -- Given a NUL terminated string representing a file + -- name, returns in buffer a NUL terminated string + -- representing the full path name for the file name. + -- On systems where it is relevant the drive is also + -- part of the full path name. It is the responsibility + -- of the caller to pass an actual parameter for buffer + -- that is big enough for any full path name. Use + -- max_path_len given below as the size of buffer. + max_path_len : integer; + -- Maximum length of an allowable full path name on the + -- system, including a terminating NUL character. + end Interfaces.C_Streams; + + +.. _Interfacing_to_C_Streams: + +Interfacing to C Streams +======================== + +The packages in this section permit interfacing Ada files to C Stream +operations. + + +.. code-block:: ada + + with Interfaces.C_Streams; + package Ada.Sequential_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Sequential_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Direct_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Direct_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Text_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Wide_Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Wide_Text_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Wide_Wide_Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Wide_Wide_Text_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Stream_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Stream_IO.C_Streams; + + +In each of these six packages, the `C_Stream` function obtains the +`FILE` pointer from a currently opened Ada file. It is then +possible to use the `Interfaces.C_Streams` package to operate on +this stream, or the stream can be passed to a C program which can +operate on it directly. Of course the program is responsible for +ensuring that only appropriate sequences of operations are executed. + +One particular use of relevance to an Ada program is that the +`setvbuf` function can be used to control the buffering of the +stream used by an Ada file. In the absence of such a call the standard +default buffering is used. + +The `Open` procedures in these packages open a file giving an +existing C Stream instead of a file name. Typically this stream is +imported from a C program, allowing an Ada file to operate on an +existing C file. + diff --git a/gcc/ada/doc/gnat_ugn.rst b/gcc/ada/doc/gnat_ugn.rst new file mode 100644 index 00000000000..7892160b477 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn.rst @@ -0,0 +1,63 @@ +GNAT User's Guide for Native Platforms +====================================== + +*GNAT, The GNU Ada Development Environment* + +.. only:: PRO + + *GNAT Pro Edition* + + | Version |version| + | Date: |today| + +.. only:: GPL + + *GNAT GPL Edition* + + | Version |version| + | Date: |today| + +.. only:: FSF + + .. raw:: texinfo + + @include gcc-common.texi + GCC version @value{version-GCC}@* + +AdaCore + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with the Front-Cover Texts being +"GNAT User's Guide for Native Platforms", +and with no Back-Cover Texts. A copy of the license is +included in the section entitled :ref:`gnu_fdl`. + +.. toctree:: + :maxdepth: 3 + :numbered: + + gnat_ugn/about_this_guide + gnat_ugn/getting_started_with_gnat + gnat_ugn/the_gnat_compilation_model + gnat_ugn/building_executable_programs_with_gnat + gnat_ugn/gnat_project_manager + gnat_ugn/tools_supporting_project_files + gnat_ugn/gnat_utility_programs + gnat_ugn/gnat_and_program_execution + +.. raw:: latex + + \appendix + +.. toctree:: + :maxdepth: 3 + + A. Platform-Specific Information + B. Example of Binder Output + C. Elaboration Order Handling in GNAT + D. Inline Assembler + E. GNU Free Documentation License + + diff --git a/gcc/ada/doc/gnat_ugn/about_this_guide.rst b/gcc/ada/doc/gnat_ugn/about_this_guide.rst new file mode 100644 index 00000000000..467d3366b66 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/about_this_guide.rst @@ -0,0 +1,223 @@ +.. _About_This_Guide: + +About This Guide +~~~~~~~~~~~~~~~~ + +.. only:: PRO + + For ease of exposition, 'GNAT Pro' will be referred to simply as + 'GNAT' in the remainder of this document. + +This guide describes the use of GNAT, +a compiler and software development +toolset for the full Ada programming language. +It documents the features of the compiler and tools, and explains +how to use them to build Ada applications. + +GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be +invoked in Ada 83 compatibility mode. +By default, GNAT assumes Ada 2012, but you can override with a +compiler switch (:ref:`Compiling_Different_Versions_of_Ada`) +to explicitly specify the language version. +Throughout this manual, references to 'Ada' without a year suffix +apply to all Ada 95/2005/2012 versions of the language. + +What This Guide Contains +======================== + +This guide contains the following chapters: + +* :ref:`Getting_Started_with_GNAT` describes how to get started compiling + and running Ada programs with the GNAT Ada programming environment. + +* :ref:`The_GNAT_Compilation_Model` describes the compilation model used + by GNAT. + +* :ref:`Building_Executable_Programs_With_GNAT` describes how to use the + main GNAT tools to build executable programs, and it also gives examples of + using the GNU make utility with GNAT. + +* :ref:`GNAT_Project_Manager` describes how to use project files + to organize large projects. + +* :ref:`Tools_Supporting_Project_Files` described how to use the project + facility in conjunction with various GNAT tools. + +* :ref:`GNAT_Utility_Programs` explains the various utility programs that + are included in the GNAT environment + +* :ref:`GNAT_and_Program_Execution` covers a number of topics related to + running, debugging, and tuning the performace of programs developed + with GNAT + +Appendices cover several additional topics: + +* :ref:`Platform_Specific_Information` describes the different run-time + library implementations and also presents information on how to use + GNAT on several specific platforms + +* :ref:`Example_of_Binder_Output_File` shows the source code for the binder + output file for a sample program. + +* :ref:`Elaboration_Order_Handling_in_GNAT` describes how GNAT helps + you deal with elaboration order issues. + +* :ref:`Inline_Assembler` shows how to use the inline assembly facility + in an Ada program. + + + +What You Should Know before Reading This Guide +============================================== + +.. index:: Ada 95 Language Reference Manual + +.. index:: Ada 2005 Language Reference Manual + +This guide assumes a basic familiarity with the Ada 95 language, as +described in the International Standard ANSI/ISO/IEC-8652:1995, January +1995. +It does not require knowledge of the features introduced by Ada 2005 +or Ada 2012. +Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in +the GNAT documentation package. + + +Related Information +=================== + +For further information about Ada and related tools, please refer to the +following documents: + +* :title:`Ada 95 Reference Manual`, :title:`Ada 2005 Reference Manual`, and + :title:`Ada 2012 Reference Manual`, which contain reference + material for the several revisions of the Ada language standard. + +* :title:`GNAT Reference_Manual`, which contains all reference material for the GNAT + implementation of Ada. + +* :title:`Using the GNAT Programming Studio`, which describes the GPS + Integrated Development Environment. + +* :title:`GNAT Programming Studio Tutorial`, which introduces the + main GPS features through examples. + +* :title:`Debugging with GDB`, + for all details on the use of the GNU source-level debugger. + +* :title:`GNU Emacs Manual`, + for full information on the extensible editor and programming + environment Emacs. + + +A Note to Readers of Previous Versions of the Manual +==================================================== + +In early 2015 the GNAT manuals were transitioned to the +reStructuredText (rst) / Sphinx documentation generator technology. +During that process the :title:`GNAT User's Guide` was reorganized +so that related topics would be described together in the same chapter +or appendix. Here's a summary of the major changes realized in +the new document structure. + +* :ref:`The_GNAT_Compilation_Model` has been extended so that it now covers + the following material: + + - The `gnatname`, `gnatkr`, and `gnatchop` tools + - :ref:`Configuration_Pragmas` + - :ref:`GNAT_and_Libraries` + - :ref:`Conditional_Compilation` including :ref:`Preprocessing_with_gnatprep` + and :ref:`Integrated_Preprocessing` + - :ref:`Generating_Ada_Bindings_for_C_and_C++_headers` + - :ref:`Using_GNAT_Files_with_External_Tools` + +* :ref:`Building_Executable_Programs_With_GNAT` is a new chapter consolidating + the following content: + + - :ref:`The_GNAT_Make_Program_gnatmake` + - :ref:`Compiling_with_GCC` + - :ref:`Binding_with_gnatbind` + - :ref:`Linking_with_gnatlink` + - :ref:`Using_the_GNU_make_Utility` + +* :ref:`GNAT_Utility_Programs` is a new chapter consolidating the information about several + GNAT tools: + + .. only:: PRO or GPL + + - :ref:`The_File_Cleanup_Utility_gnatclean` + - :ref:`The_GNAT_Library_Browser_gnatls` + - :ref:`The_Cross-Referencing_Tools_gnatxref_and_gnatfind` + - :ref:`The_Ada_to_HTML_Converter_gnathtml` + - :ref:`The_Ada-to-XML_Converter_gnat2xml` + - :ref:`The_Program_Property_Verifier_gnatcheck` + - :ref:`The_GNAT_Metrics_Tool_gnatmetric` + - :ref:`The_GNAT_Pretty-Printer_gnatpp` + - :ref:`The_Body_Stub_Generator_gnatstub` + - :ref:`The_Unit_Test_Generator_gnattest` + + .. only:: FSF + + - :ref:`The_File_Cleanup_Utility_gnatclean` + - :ref:`The_GNAT_Library_Browser_gnatls` + - :ref:`The_Cross-Referencing_Tools_gnatxref_and_gnatfind` + - :ref:`The_Ada_to_HTML_Converter_gnathtml` + +* :ref:`GNAT_and_Program_Execution` is a new chapter consolidating the following: + + - :ref:`Running_and_Debugging_Ada_Programs` + - :ref:`Code_Coverage_and_Profiling` + - :ref:`Improving_Performance` + - :ref:`Overflow Check Handling in GNAT ` + - :ref:`Performing Dimensionality Analysis in GNAT ` + - :ref:`Stack_Related_Facilities` + - :ref:`Memory_Management_Issues` + +* :ref:`Platform_Specific_Information` is a new appendix consolidating the following: + + - :ref:`Run_Time_Libraries` + - :ref:`Microsoft_Windows_Topics` + - :ref:`Mac_OS_Topics` + +* The `Compatibility and Porting Guide` appendix has been moved to the + :title:`GNAT Reference Manual`. It now includes a section + `Writing Portable Fixed-Point Declarations` which was previously + a separate chapter in the :title:`GNAT User's Guide`. + + +Conventions +=========== +.. index:: Conventions, typographical + +.. index:: Typographical conventions + +Following are examples of the typographical and graphic conventions used +in this guide: + +* `Functions`, `utility program names`, `standard names`, + and `classes`. + +* `Option flags` + +* :file:`File names` + +* `Variables` + +* *Emphasis* + +* [optional information or parameters] + +* Examples are described by text + + :: + + and then shown this way. + +* Commands that are entered by the user are shown as preceded by a prompt string + comprising the ``$`` character followed by a space. + +* Full file names are shown with the '/' character + as the directory separator; e.g., :file:`parent-dir/subdir/myfile.adb`. + If you are using GNAT on a Windows platform, please note that + the '\\' character should be used instead. + diff --git a/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst new file mode 100644 index 00000000000..495e9fa4578 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst @@ -0,0 +1,7381 @@ +.. |with| replace:: *with* +.. |withs| replace:: *with*\ s +.. |withed| replace:: *with*\ ed +.. |withing| replace:: *with*\ ing + +.. -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + + + +.. _Building_Executable_Programs_With_GNAT: + +************************************** +Building Executable Programs with GNAT +************************************** + +This chapter describes first the gnatmake tool +(:ref:`The_GNAT_Make_Program_gnatmake`), +which automatically determines the set of sources +needed by an Ada compilation unit and executes the necessary +(re)compilations, binding and linking. +It also explains how to use each tool individually: the +compiler (gcc, see :ref:`Compiling_with_gcc`), +binder (gnatbind, see :ref:`Binding_with_gnatbind`), +and linker (gnatlink, see :ref:`Linking_with_gnatlink`) +to build executable programs. +Finally, this chapter provides examples of +how to make use of the general GNU make mechanism +in a GNAT context (see :ref:`Using_the_GNU_make_Utility`). + + +.. _The_GNAT_Make_Program_gnatmake: + +Building with *gnatmake* +======================== + +.. index:: gnatmake + +A typical development cycle when working on an Ada program consists of +the following steps: + +#. Edit some sources to fix bugs; + +#. Add enhancements; + +#. Compile all sources affected; + +#. Rebind and relink; and + +#. Test. + +.. index:: Dependency rules (compilation) + +The third step in particular can be tricky, because not only do the modified +files have to be compiled, but any files depending on these files must also be +recompiled. The dependency rules in Ada can be quite complex, especially +in the presence of overloading, `use` clauses, generics and inlined +subprograms. + +*gnatmake* automatically takes care of the third and fourth steps +of this process. It determines which sources need to be compiled, +compiles them, and binds and links the resulting object files. + +Unlike some other Ada make programs, the dependencies are always +accurately recomputed from the new sources. The source based approach of +the GNAT compilation model makes this possible. This means that if +changes to the source program cause corresponding changes in +dependencies, they will always be tracked exactly correctly by +*gnatmake*. + +Note that for advanced description of project structure, we recommend creating +a project file as explained in :ref:`GNAT_Project_Manager` and use the +*gprbuild* tool which supports building with project files and works similarly +to *gnatmake*. + +.. _Running_gnatmake: + +Running *gnatmake* +------------------ + +The usual form of the *gnatmake* command is + +.. code-block:: sh + + $ gnatmake [] [] [] + +The only required argument is one `file_name`, which specifies +a compilation unit that is a main program. Several `file_names` can be +specified: this will result in several executables being built. +If `switches` are present, they can be placed before the first +`file_name`, between `file_names` or after the last `file_name`. +If `mode_switches` are present, they must always be placed after +the last `file_name` and all `switches`. + +If you are using standard file extensions (:file:`.adb` and +:file:`.ads`), then the +extension may be omitted from the `file_name` arguments. However, if +you are using non-standard extensions, then it is required that the +extension be given. A relative or absolute directory path can be +specified in a `file_name`, in which case, the input source file will +be searched for in the specified directory only. Otherwise, the input +source file will first be searched in the directory where +*gnatmake* was invoked and if it is not found, it will be search on +the source path of the compiler as described in +:ref:`Search_Paths_and_the_Run-Time_Library_RTL`. + +All *gnatmake* output (except when you specify *-M*) is sent to +:file:`stderr`. The output produced by the +*-M* switch is sent to :file:`stdout`. + + +.. _Switches_for_gnatmake: + +Switches for *gnatmake* +----------------------- + +You may specify any of the following switches to *gnatmake*: + + +.. index:: --version (gnatmake) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatmake) + +:samp:`--help` + If ``--version`` was not used, display usage, then exit disregarding + all other options. + + +.. index:: --GCC=compiler_name (gnatmake) + +:samp:`--GCC={compiler_name}` + Program used for compiling. The default is ``gcc``. You need to use + quotes around `compiler_name` if `compiler_name` contains + spaces or other separator characters. + As an example ``--GCC="foo -x -y"`` + will instruct *gnatmake* to use ``foo -x -y`` as your + compiler. A limitation of this syntax is that the name and path name of + the executable itself must not include any embedded spaces. Note that + switch ``-c`` is always inserted after your command name. Thus in the + above example the compiler command that will be used by *gnatmake* + will be ``foo -c -x -y``. If several ``--GCC=compiler_name`` are + used, only the last `compiler_name` is taken into account. However, + all the additional switches are also taken into account. Thus, + ``--GCC="foo -x -y" --GCC="bar -z -t"`` is equivalent to + ``--GCC="bar -x -y -z -t"``. + + +.. index:: --GNATBIND=binder_name (gnatmake) + +:samp:`--GNATBIND={binder_name}` + Program used for binding. The default is ``gnatbind``. You need to + use quotes around `binder_name` if `binder_name` contains spaces + or other separator characters. + As an example ``--GNATBIND="bar -x -y"`` + will instruct *gnatmake* to use `bar -x -y` as your + binder. Binder switches that are normally appended by *gnatmake* + to ``gnatbind`` are now appended to the end of `bar -x -y`. + A limitation of this syntax is that the name and path name of the executable + itself must not include any embedded spaces. + +.. index:: --GNATLINK=linker_name (gnatmake) + +:samp:`--GNATLINK={linker_name}` + Program used for linking. The default is ``gnatlink``. You need to + use quotes around `linker_name` if `linker_name` contains spaces + or other separator characters. + As an example ``--GNATLINK="lan -x -y"`` + will instruct *gnatmake* to use ``lan -x -y`` as your + linker. Linker switches that are normally appended by ``gnatmake`` to + ``gnatlink`` are now appended to the end of ``lan -x -y``. + A limitation of this syntax is that the name and path name of the executable + itself must not include any embedded spaces. + +:samp:`--create-map-file` + When linking an executable, create a map file. The name of the map file + has the same name as the executable with extension ".map". + +:samp:`--create-map-file={mapfile}` + When linking an executable, create a map file with the specified name. + +.. index:: --create-missing-dirs (gnatmake) + +:samp:`--create-missing-dirs` + When using project files (:samp:`-P{project}`), automatically create + missing object directories, library directories and exec + directories. + +:samp:`--single-compile-per-obj-dir` + Disallow simultaneous compilations in the same object directory when + project files are used. + +:samp:`--subdirs={subdir}` + Actual object directory of each project file is the subdirectory subdir of the + object directory specified or defaulted in the project file. + +:samp:`--unchecked-shared-lib-imports` + By default, shared library projects are not allowed to import static library + projects. When this switch is used on the command line, this restriction is + relaxed. + +:samp:`--source-info={source info file}` + Specify a source info file. This switch is active only when project files + are used. If the source info file is specified as a relative path, then it is + relative to the object directory of the main project. If the source info file + does not exist, then after the Project Manager has successfully parsed and + processed the project files and found the sources, it creates the source info + file. If the source info file already exists and can be read successfully, + then the Project Manager will get all the needed information about the sources + from the source info file and will not look for them. This reduces the time + to process the project files, especially when looking for sources that take a + long time. If the source info file exists but cannot be parsed successfully, + the Project Manager will attempt to recreate it. If the Project Manager fails + to create the source info file, a message is issued, but gnatmake does not + fail. *gnatmake* "trusts" the source info file. This means that + if the source files have changed (addition, deletion, moving to a different + source directory), then the source info file need to be deleted and recreated. + + +.. index:: -a (gnatmake) + +:samp:`-a` + Consider all files in the make process, even the GNAT internal system + files (for example, the predefined Ada library files), as well as any + locked files. Locked files are files whose ALI file is write-protected. + By default, + *gnatmake* does not check these files, + because the assumption is that the GNAT internal files are properly up + to date, and also that any write protected ALI files have been properly + installed. Note that if there is an installation problem, such that one + of these files is not up to date, it will be properly caught by the + binder. + You may have to specify this switch if you are working on GNAT + itself. The switch ``-a`` is also useful + in conjunction with ``-f`` + if you need to recompile an entire application, + including run-time files, using special configuration pragmas, + such as a `Normalize_Scalars` pragma. + + By default + ``gnatmake -a`` compiles all GNAT + internal files with + ``gcc -c -gnatpg`` rather than ``gcc -c``. + + +.. index:: -b (gnatmake) + +:samp:`-b` + Bind only. Can be combined with *-c* to do + compilation and binding, but no link. + Can be combined with *-l* + to do binding and linking. When not combined with + *-c* + all the units in the closure of the main program must have been previously + compiled and must be up to date. The root unit specified by `file_name` + may be given without extension, with the source extension or, if no GNAT + Project File is specified, with the ALI file extension. + + +.. index:: -c (gnatmake) + +:samp:`-c` + Compile only. Do not perform binding, except when *-b* + is also specified. Do not perform linking, except if both + *-b* and + *-l* are also specified. + If the root unit specified by `file_name` is not a main unit, this is the + default. Otherwise *gnatmake* will attempt binding and linking + unless all objects are up to date and the executable is more recent than + the objects. + + +.. index:: -C (gnatmake) + +:samp:`-C` + Use a temporary mapping file. A mapping file is a way to communicate + to the compiler two mappings: from unit names to file names (without + any directory information) and from file names to path names (with + full directory information). A mapping file can make the compiler's + file searches faster, especially if there are many source directories, + or the sources are read over a slow network connection. If + *-P* is used, a mapping file is always used, so + *-C* is unnecessary; in this case the mapping file + is initially populated based on the project file. If + *-C* is used without + *-P*, + the mapping file is initially empty. Each invocation of the compiler + will add any newly accessed sources to the mapping file. + + +.. index:: -C= (gnatmake) + +:samp:`-C={file}` + Use a specific mapping file. The file, specified as a path name (absolute or + relative) by this switch, should already exist, otherwise the switch is + ineffective. The specified mapping file will be communicated to the compiler. + This switch is not compatible with a project file + (-P`file`) or with multiple compiling processes + (-jnnn, when nnn is greater than 1). + + +.. index:: -d (gnatmake) + +:samp:`-d` + Display progress for each source, up to date or not, as a single line: + + :: + + completed x out of y (zz%) + + If the file needs to be compiled this is displayed after the invocation of + the compiler. These lines are displayed even in quiet output mode. + + +.. index:: -D (gnatmake) + +:samp:`-D {dir}` + Put all object files and ALI file in directory `dir`. + If the *-D* switch is not used, all object files + and ALI files go in the current working directory. + + This switch cannot be used when using a project file. + + +.. index:: -eI (gnatmake) + +:samp:`-eI{nnn}` + Indicates that the main source is a multi-unit source and the rank of the unit + in the source file is nnn. nnn needs to be a positive number and a valid + index in the source. This switch cannot be used when *gnatmake* is + invoked for several mains. + + +.. index:: -eL (gnatmake) +.. index:: symbolic links + +:samp:`-eL` + Follow all symbolic links when processing project files. + This should be used if your project uses symbolic links for files or + directories, but is not needed in other cases. + + .. index:: naming scheme + + This also assumes that no directory matches the naming scheme for files (for + instance that you do not have a directory called "sources.ads" when using the + default GNAT naming scheme). + + When you do not have to use this switch (i.e., by default), gnatmake is able to + save a lot of system calls (several per source file and object file), which + can result in a significant speed up to load and manipulate a project file, + especially when using source files from a remote system. + + +.. index:: -eS (gnatmake) + +:samp:`-eS` + Output the commands for the compiler, the binder and the linker + on standard output, + instead of standard error. + + +.. index:: -f (gnatmake) + +:samp:`-f` + Force recompilations. Recompile all sources, even though some object + files may be up to date, but don't recompile predefined or GNAT internal + files or locked files (files with a write-protected ALI file), + unless the *-a* switch is also specified. + + +.. index:: -F (gnatmake) + +:samp:`-F` + When using project files, if some errors or warnings are detected during + parsing and verbose mode is not in effect (no use of switch + -v), then error lines start with the full path name of the project + file, rather than its simple file name. + + +.. index:: -g (gnatmake) + +:samp:`-g` + Enable debugging. This switch is simply passed to the compiler and to the + linker. + + +.. index:: -i (gnatmake) + +:samp:`-i` + In normal mode, *gnatmake* compiles all object files and ALI files + into the current directory. If the *-i* switch is used, + then instead object files and ALI files that already exist are overwritten + in place. This means that once a large project is organized into separate + directories in the desired manner, then *gnatmake* will automatically + maintain and update this organization. If no ALI files are found on the + Ada object path (see :ref:`Search_Paths_and_the_Run-Time_Library_RTL`), + the new object and ALI files are created in the + directory containing the source being compiled. If another organization + is desired, where objects and sources are kept in different directories, + a useful technique is to create dummy ALI files in the desired directories. + When detecting such a dummy file, *gnatmake* will be forced to + recompile the corresponding source file, and it will be put the resulting + object and ALI files in the directory where it found the dummy file. + + +.. index:: -j (gnatmake) +.. index:: Parallel make + +:samp:`-j{n}` + Use `n` processes to carry out the (re)compilations. On a multiprocessor + machine compilations will occur in parallel. If `n` is 0, then the + maximum number of parallel compilations is the number of core processors + on the platform. In the event of compilation errors, messages from various + compilations might get interspersed (but *gnatmake* will give you the + full ordered list of failing compiles at the end). If this is problematic, + rerun the make process with n set to 1 to get a clean list of messages. + + +.. index:: -k (gnatmake) + +:samp:`-k` + Keep going. Continue as much as possible after a compilation error. To + ease the programmer's task in case of compilation errors, the list of + sources for which the compile fails is given when *gnatmake* + terminates. + + If *gnatmake* is invoked with several :file:`file_names` and with this + switch, if there are compilation errors when building an executable, + *gnatmake* will not attempt to build the following executables. + + +.. index:: -l (gnatmake) + +:samp:`-l` + Link only. Can be combined with *-b* to binding + and linking. Linking will not be performed if combined with + *-c* + but not with *-b*. + When not combined with *-b* + all the units in the closure of the main program must have been previously + compiled and must be up to date, and the main program needs to have been bound. + The root unit specified by `file_name` + may be given without extension, with the source extension or, if no GNAT + Project File is specified, with the ALI file extension. + + +.. index:: -m (gnatmake) + +:samp:`-m` + Specify that the minimum necessary amount of recompilations + be performed. In this mode *gnatmake* ignores time + stamp differences when the only + modifications to a source file consist in adding/removing comments, + empty lines, spaces or tabs. This means that if you have changed the + comments in a source file or have simply reformatted it, using this + switch will tell *gnatmake* not to recompile files that depend on it + (provided other sources on which these files depend have undergone no + semantic modifications). Note that the debugging information may be + out of date with respect to the sources if the *-m* switch causes + a compilation to be switched, so the use of this switch represents a + trade-off between compilation time and accurate debugging information. + + +.. index:: Dependencies, producing list +.. index:: -M (gnatmake) + +:samp:`-M` + Check if all objects are up to date. If they are, output the object + dependences to :file:`stdout` in a form that can be directly exploited in + a :file:`Makefile`. By default, each source file is prefixed with its + (relative or absolute) directory name. This name is whatever you + specified in the various *-aI* + and *-I* switches. If you use + `gnatmake -M` *-q* + (see below), only the source file names, + without relative paths, are output. If you just specify the *-M* + switch, dependencies of the GNAT internal system files are omitted. This + is typically what you want. If you also specify + the *-a* switch, + dependencies of the GNAT internal files are also listed. Note that + dependencies of the objects in external Ada libraries (see + switch :samp:`-aL{dir}` in the following list) + are never reported. + + +.. index:: -n (gnatmake) + +:samp:`-n` + Don't compile, bind, or link. Checks if all objects are up to date. + If they are not, the full name of the first file that needs to be + recompiled is printed. + Repeated use of this option, followed by compiling the indicated source + file, will eventually result in recompiling all required units. + + +.. index:: -o (gnatmake) + +:samp:`-o {exec_name}` + Output executable name. The name of the final executable program will be + `exec_name`. If the *-o* switch is omitted the default + name for the executable will be the name of the input file in appropriate form + for an executable file on the host system. + + This switch cannot be used when invoking *gnatmake* with several + :file:`file_names`. + + +.. index:: -p (gnatmake) + +:samp:`-p` + Same as :samp:`--create-missing-dirs` + +.. index:: -P (gnatmake) + +:samp:`-P{project}` + Use project file `project`. Only one such switch can be used. + :ref:`gnatmake_and_Project_Files`. + + +.. index:: -q (gnatmake) + +:samp:`-q` + Quiet. When this flag is not set, the commands carried out by + *gnatmake* are displayed. + + +.. index:: -s (gnatmake) + +:samp:`-s` + Recompile if compiler switches have changed since last compilation. + All compiler switches but -I and -o are taken into account in the + following way: + orders between different 'first letter' switches are ignored, but + orders between same switches are taken into account. For example, + *-O -O2* is different than *-O2 -O*, but *-g -O* + is equivalent to *-O -g*. + + This switch is recommended when Integrated Preprocessing is used. + + +.. index:: -u (gnatmake) + +:samp:`-u` + Unique. Recompile at most the main files. It implies -c. Combined with + -f, it is equivalent to calling the compiler directly. Note that using + -u with a project file and no main has a special meaning + (:ref:`Project_Files_and_Main_Subprograms`). + + +.. index:: -U (gnatmake) + +:samp:`-U` + When used without a project file or with one or several mains on the command + line, is equivalent to -u. When used with a project file and no main + on the command line, all sources of all project files are checked and compiled + if not up to date, and libraries are rebuilt, if necessary. + + +.. index:: -v (gnatmake) + +:samp:`-v` + Verbose. Display the reason for all recompilations *gnatmake* + decides are necessary, with the highest verbosity level. + + +.. index:: -vl (gnatmake) + +:samp:`-vl` + Verbosity level Low. Display fewer lines than in verbosity Medium. + + +.. index:: -vm (gnatmake) + +:samp:`-vm` + Verbosity level Medium. Potentially display fewer lines than in verbosity High. + + +.. index:: -vm (gnatmake) + +:samp:`-vh` + Verbosity level High. Equivalent to -v. + + +:samp:`-vP{x}` + Indicate the verbosity of the parsing of GNAT project files. + See :ref:`Switches_Related_to_Project_Files`. + + +.. index:: -x (gnatmake) + +:samp:`-x` + Indicate that sources that are not part of any Project File may be compiled. + Normally, when using Project Files, only sources that are part of a Project + File may be compile. When this switch is used, a source outside of all Project + Files may be compiled. The ALI file and the object file will be put in the + object directory of the main Project. The compilation switches used will only + be those specified on the command line. Even when + *-x* is used, mains specified on the + command line need to be sources of a project file. + + +:samp:`-X{name}={value}` + Indicate that external variable `name` has the value `value`. + The Project Manager will use this value for occurrences of + `external(name)` when parsing the project file. + :ref:`Switches_Related_to_Project_Files`. + + +.. index:: -z (gnatmake) + +:samp:`-z` + No main subprogram. Bind and link the program even if the unit name + given on the command line is a package name. The resulting executable + will execute the elaboration routines of the package and its closure, + then the finalization routines. + + +.. rubric:: GCC switches + +Any uppercase or multi-character switch that is not a *gnatmake* switch +is passed to *gcc* (e.g., *-O*, *-gnato,* etc.) + + +.. rubric:: Source and library search path switches + +.. index:: -aI (gnatmake) + +:samp:`-aI{dir}` + When looking for source files also look in directory `dir`. + The order in which source files search is undertaken is + described in :ref:`Search_Paths_and_the_Run-Time_Library_RTL`. + + +.. index:: -aL (gnatmake) + +:samp:`-aL{dir}` + Consider `dir` as being an externally provided Ada library. + Instructs *gnatmake* to skip compilation units whose :file:`.ALI` + files have been located in directory `dir`. This allows you to have + missing bodies for the units in `dir` and to ignore out of date bodies + for the same units. You still need to specify + the location of the specs for these units by using the switches + :samp:`-aI{dir}` or :samp:`-I{dir}`. + Note: this switch is provided for compatibility with previous versions + of *gnatmake*. The easier method of causing standard libraries + to be excluded from consideration is to write-protect the corresponding + ALI files. + + +.. index:: -aO (gnatmake) + +:samp:`-aO{dir}` + When searching for library and object files, look in directory + `dir`. The order in which library files are searched is described in + :ref:`Search_Paths_for_gnatbind`. + + +.. index:: Search paths, for gnatmake +.. index:: -A (gnatmake) + +:samp:`-A{dir}` + Equivalent to :samp:`-aL{dir}` :samp:`-aI{dir}`. + + + .. index:: -I (gnatmake) + +:samp:`-I{dir}` + Equivalent to :samp:`-aO{dir} -aI{dir}`. + + +.. index:: -I- (gnatmake) +.. index:: Source files, suppressing search + +:samp:`-I-` + Do not look for source files in the directory containing the source + file named in the command line. + Do not look for ALI or object files in the directory + where *gnatmake* was invoked. + + +.. index:: -L (gnatmake) +.. index:: Linker libraries + +:samp:`-L{dir}` + Add directory `dir` to the list of directories in which the linker + will search for libraries. This is equivalent to + :samp:`-largs` :samp:`-L{dir}`. + Furthermore, under Windows, the sources pointed to by the libraries path + set in the registry are not searched for. + + +.. index:: -nostdinc (gnatmake) + +:samp:`-nostdinc` + Do not look for source files in the system default directory. + + +.. index:: -nostdlib (gnatmake) + +:samp:`-nostdlib` + Do not look for library files in the system default directory. + + +.. index:: --RTS (gnatmake) + +:samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. GNAT looks for the + runtime + in the following directories, and stops as soon as a valid runtime is found + (:file:`adainclude` or :file:`ada_source_path`, and :file:`adalib` or + :file:`ada_object_path` present): + + * */$rts_path* + + * */$rts_path* + + * */rts-$rts_path* + + * The selected path is handled like a normal RTS path. + + +.. _Mode_Switches_for_gnatmake: + +Mode Switches for *gnatmake* +---------------------------- + +The mode switches (referred to as `mode_switches`) allow the +inclusion of switches that are to be passed to the compiler itself, the +binder or the linker. The effect of a mode switch is to cause all +subsequent switches up to the end of the switch list, or up to the next +mode switch, to be interpreted as switches to be passed on to the +designated component of GNAT. + +.. index:: -cargs (gnatmake) + +:samp:`-cargs {switches}` + Compiler switches. Here `switches` is a list of switches + that are valid switches for *gcc*. They will be passed on to + all compile steps performed by *gnatmake*. + + +.. index:: -bargs (gnatmake) + +:samp:`-bargs {switches}` + Binder switches. Here `switches` is a list of switches + that are valid switches for `gnatbind`. They will be passed on to + all bind steps performed by *gnatmake*. + + +.. index:: -largs (gnatmake) + +:samp:`-largs {switches}` + Linker switches. Here `switches` is a list of switches + that are valid switches for *gnatlink*. They will be passed on to + all link steps performed by *gnatmake*. + + +.. index:: -margs (gnatmake) + +:samp:`-margs {switches}` + Make switches. The switches are directly interpreted by *gnatmake*, + regardless of any previous occurrence of *-cargs*, *-bargs* + or *-largs*. + + +.. _Notes_on_the_Command_Line: + +Notes on the Command Line +------------------------- + +This section contains some additional useful notes on the operation +of the *gnatmake* command. + +.. index:: Recompilation (by gnatmake) + +* If *gnatmake* finds no ALI files, it recompiles the main program + and all other units required by the main program. + This means that *gnatmake* + can be used for the initial compile, as well as during subsequent steps of + the development cycle. + +* If you enter ``gnatmake foo.adb``, where ``foo`` + is a subunit or body of a generic unit, *gnatmake* recompiles + :file:`foo.adb` (because it finds no ALI) and stops, issuing a + warning. + +* In *gnatmake* the switch *-I* + is used to specify both source and + library file paths. Use *-aI* + instead if you just want to specify + source paths only and *-aO* + if you want to specify library paths + only. + +* *gnatmake* will ignore any files whose ALI file is write-protected. + This may conveniently be used to exclude standard libraries from + consideration and in particular it means that the use of the + *-f* switch will not recompile these files + unless *-a* is also specified. + +* *gnatmake* has been designed to make the use of Ada libraries + particularly convenient. Assume you have an Ada library organized + as follows: *obj-dir* contains the objects and ALI files for + of your Ada compilation units, + whereas *include-dir* contains the + specs of these units, but no bodies. Then to compile a unit + stored in `main.adb`, which uses this Ada library you would just type: + + .. code-block:: sh + + $ gnatmake -aI`include-dir` -aL`obj-dir` main + +* Using *gnatmake* along with the *-m (minimal recompilation)* + switch provides a mechanism for avoiding unnecessary recompilations. Using + this switch, + you can update the comments/format of your + source files without having to recompile everything. Note, however, that + adding or deleting lines in a source files may render its debugging + info obsolete. If the file in question is a spec, the impact is rather + limited, as that debugging info will only be useful during the + elaboration phase of your program. For bodies the impact can be more + significant. In all events, your debugger will warn you if a source file + is more recent than the corresponding object, and alert you to the fact + that the debugging information may be out of date. + + +.. _How_gnatmake_Works: + +How *gnatmake* Works +-------------------- + +Generally *gnatmake* automatically performs all necessary +recompilations and you don't need to worry about how it works. However, +it may be useful to have some basic understanding of the *gnatmake* +approach and in particular to understand how it uses the results of +previous compilations without incorrectly depending on them. + +First a definition: an object file is considered *up to date* if the +corresponding ALI file exists and if all the source files listed in the +dependency section of this ALI file have time stamps matching those in +the ALI file. This means that neither the source file itself nor any +files that it depends on have been modified, and hence there is no need +to recompile this file. + +*gnatmake* works by first checking if the specified main unit is up +to date. If so, no compilations are required for the main unit. If not, +*gnatmake* compiles the main program to build a new ALI file that +reflects the latest sources. Then the ALI file of the main unit is +examined to find all the source files on which the main program depends, +and *gnatmake* recursively applies the above procedure on all these +files. + +This process ensures that *gnatmake* only trusts the dependencies +in an existing ALI file if they are known to be correct. Otherwise it +always recompiles to determine a new, guaranteed accurate set of +dependencies. As a result the program is compiled 'upside down' from what may +be more familiar as the required order of compilation in some other Ada +systems. In particular, clients are compiled before the units on which +they depend. The ability of GNAT to compile in any order is critical in +allowing an order of compilation to be chosen that guarantees that +*gnatmake* will recompute a correct set of new dependencies if +necessary. + +When invoking *gnatmake* with several `file_names`, if a unit is +imported by several of the executables, it will be recompiled at most once. + +Note: when using non-standard naming conventions +(:ref:`Using_Other_File_Names`), changing through a configuration pragmas +file the version of a source and invoking *gnatmake* to recompile may +have no effect, if the previous version of the source is still accessible +by *gnatmake*. It may be necessary to use the switch +-f. + + +.. _Examples_of_gnatmake_Usage: + +Examples of *gnatmake* Usage +---------------------------- + +*gnatmake hello.adb* + Compile all files necessary to bind and link the main program + :file:`hello.adb` (containing unit `Hello`) and bind and link the + resulting object files to generate an executable file :file:`hello`. + +*gnatmake main1 main2 main3* + Compile all files necessary to bind and link the main programs + :file:`main1.adb` (containing unit `Main1`), :file:`main2.adb` + (containing unit `Main2`) and :file:`main3.adb` + (containing unit `Main3`) and bind and link the resulting object files + to generate three executable files :file:`main1`, + :file:`main2` and :file:`main3`. + +*gnatmake -q Main_Unit -cargs -O2 -bargs -l* + Compile all files necessary to bind and link the main program unit + `Main_Unit` (from file :file:`main_unit.adb`). All compilations will + be done with optimization level 2 and the order of elaboration will be + listed by the binder. *gnatmake* will operate in quiet mode, not + displaying commands it is executing. + + +.. _Compiling_with_gcc: + +Compiling with *gcc* +==================== + +This section discusses how to compile Ada programs using the *gcc* +command. It also describes the set of switches +that can be used to control the behavior of the compiler. + +.. _Compiling_Programs: + +Compiling Programs +------------------ + +The first step in creating an executable program is to compile the units +of the program using the *gcc* command. You must compile the +following files: + +* the body file (:file:`.adb`) for a library level subprogram or generic + subprogram + +* the spec file (:file:`.ads`) for a library level package or generic + package that has no body + +* the body file (:file:`.adb`) for a library level package + or generic package that has a body + +You need *not* compile the following files + +* the spec of a library unit which has a body + +* subunits + +because they are compiled as part of compiling related units. GNAT +package specs +when the corresponding body is compiled, and subunits when the parent is +compiled. + +.. index:: cannot generate code + +If you attempt to compile any of these files, you will get one of the +following error messages (where `fff` is the name of the file you +compiled): + + :: + + cannot generate code for file `fff` (package spec) + to check package spec, use -gnatc + + cannot generate code for file `fff` (missing subunits) + to check parent unit, use -gnatc + + cannot generate code for file `fff` (subprogram spec) + to check subprogram spec, use -gnatc + + cannot generate code for file `fff` (subunit) + to check subunit, use -gnatc + + +As indicated by the above error messages, if you want to submit +one of these files to the compiler to check for correct semantics +without generating code, then use the *-gnatc* switch. + +The basic command for compiling a file containing an Ada unit is: + +.. code-block:: sh + + $ gcc -c [switches] + +where `file name` is the name of the Ada file (usually +having an extension :file:`.ads` for a spec or :file:`.adb` for a body). +You specify the +:option:`-c` switch to tell *gcc* to compile, but not link, the file. +The result of a successful compilation is an object file, which has the +same name as the source file but an extension of :file:`.o` and an Ada +Library Information (ALI) file, which also has the same name as the +source file, but with :file:`.ali` as the extension. GNAT creates these +two output files in the current directory, but you may specify a source +file in any directory using an absolute or relative path specification +containing the directory information. + +.. index:: gnat1 + +*gcc* is actually a driver program that looks at the extensions of +the file arguments and loads the appropriate compiler. For example, the +GNU C compiler is :file:`cc1`, and the Ada compiler is :file:`gnat1`. +These programs are in directories known to the driver program (in some +configurations via environment variables you set), but need not be in +your path. The *gcc* driver also calls the assembler and any other +utilities needed to complete the generation of the required object +files. + +It is possible to supply several file names on the same *gcc* +command. This causes *gcc* to call the appropriate compiler for +each file. For example, the following command lists two separate +files to be compiled: + +.. code-block:: sh + + $ gcc -c x.adb y.adb + + +calls `gnat1` (the Ada compiler) twice to compile :file:`x.adb` and +:file:`y.adb`. +The compiler generates two object files :file:`x.o` and :file:`y.o` +and the two ALI files :file:`x.ali` and :file:`y.ali`. + +Any switches apply to all the files listed, see :ref:`Switches_for_gcc` for a +list of available *gcc* switches. + +.. _Search_Paths_and_the_Run-Time_Library_RTL: + +Search Paths and the Run-Time Library (RTL) +------------------------------------------- + +With the GNAT source-based library system, the compiler must be able to +find source files for units that are needed by the unit being compiled. +Search paths are used to guide this process. + +The compiler compiles one source file whose name must be given +explicitly on the command line. In other words, no searching is done +for this file. To find all other source files that are needed (the most +common being the specs of units), the compiler examines the following +directories, in the following order: + +* The directory containing the source file of the main unit being compiled + (the file name on the command line). + +* Each directory named by an *-I* switch given on the *gcc* + command line, in the order given. + + .. index:: ADA_PRJ_INCLUDE_FILE + +* Each of the directories listed in the text file whose name is given + by the :envvar:`ADA_PRJ_INCLUDE_FILE` environment variable. + :envvar:`ADA_PRJ_INCLUDE_FILE` is normally set by gnatmake or by the gnat + driver when project files are used. It should not normally be set + by other means. + + .. index:: ADA_INCLUDE_PATH + +* Each of the directories listed in the value of the + :envvar:`ADA_INCLUDE_PATH` environment variable. + Construct this value + exactly as the :envvar:`PATH` environment variable: a list of directory + names separated by colons (semicolons when working with the NT version). + +* The content of the :file:`ada_source_path` file which is part of the GNAT + installation tree and is used to store standard libraries such as the + GNAT Run Time Library (RTL) source files. + :ref:`Installing_a_library` + +Specifying the switch *-I-* +inhibits the use of the directory +containing the source file named in the command line. You can still +have this directory on your search path, but in this case it must be +explicitly requested with a *-I* switch. + +Specifying the switch *-nostdinc* +inhibits the search of the default location for the GNAT Run Time +Library (RTL) source files. + +The compiler outputs its object files and ALI files in the current +working directory. +Caution: The object file can be redirected with the *-o* switch; +however, *gcc* and `gnat1` have not been coordinated on this +so the :file:`ALI` file will not go to the right place. Therefore, you should +avoid using the *-o* switch. + +.. index:: System.IO + +The packages `Ada`, `System`, and `Interfaces` and their +children make up the GNAT RTL, together with the simple `System.IO` +package used in the `"Hello World"` example. The sources for these units +are needed by the compiler and are kept together in one directory. Not +all of the bodies are needed, but all of the sources are kept together +anyway. In a normal installation, you need not specify these directory +names when compiling or binding. Either the environment variables or +the built-in defaults cause these files to be found. + +In addition to the language-defined hierarchies (`System`, `Ada` and +`Interfaces`), the GNAT distribution provides a fourth hierarchy, +consisting of child units of `GNAT`. This is a collection of generally +useful types, subprograms, etc. See the :title:`GNAT_Reference_Manual` +for further details. + +Besides simplifying access to the RTL, a major use of search paths is +in compiling sources from multiple directories. This can make +development environments much more flexible. + +.. _Order_of_Compilation_Issues: + +Order of Compilation Issues +--------------------------- + +If, in our earlier example, there was a spec for the `hello` +procedure, it would be contained in the file :file:`hello.ads`; yet this +file would not have to be explicitly compiled. This is the result of the +model we chose to implement library management. Some of the consequences +of this model are as follows: + +* There is no point in compiling specs (except for package + specs with no bodies) because these are compiled as needed by clients. If + you attempt a useless compilation, you will receive an error message. + It is also useless to compile subunits because they are compiled as needed + by the parent. + +* There are no order of compilation requirements: performing a + compilation never obsoletes anything. The only way you can obsolete + something and require recompilations is to modify one of the + source files on which it depends. + +* There is no library as such, apart from the ALI files + (:ref:`The_Ada_Library_Information_Files`, for information on the format + of these files). For now we find it convenient to create separate ALI files, + but eventually the information therein may be incorporated into the object + file directly. + +* When you compile a unit, the source files for the specs of all units + that it |withs|, all its subunits, and the bodies of any generics it + instantiates must be available (reachable by the search-paths mechanism + described above), or you will receive a fatal error message. + +.. _Examples: + +Examples +-------- + +The following are some typical Ada compilation command line examples: + +.. code-block:: sh + + $ gcc -c xyz.adb + +Compile body in file :file:`xyz.adb` with all default options. + +.. code-block:: sh + + $ gcc -c -O2 -gnata xyz-def.adb + +Compile the child unit package in file :file:`xyz-def.adb` with extensive +optimizations, and pragma `Assert`/`Debug` statements +enabled. + +.. code-block:: sh + + $ gcc -c -gnatc abc-def.adb + +Compile the subunit in file :file:`abc-def.adb` in semantic-checking-only +mode. + + +.. _Switches_for_gcc: + +Compiler Switches +================= + +The *gcc* command accepts switches that control the +compilation process. These switches are fully described in this section: +first an alphabetical listing of all switches with a brief description, +and then functionally grouped sets of switches with more detailed +information. + +More switches exist for GCC than those documented here, especially +for specific targets. However, their use is not recommended as +they may change code generation in ways that are incompatible with +the Ada run-time library, or can cause inconsistencies between +compilation units. + +.. _Alphabetical_List_of_All_Switches: + +Alphabetical List of All Switches +--------------------------------- + +.. index:: -b (gcc) + +:samp:`-b {target}` + Compile your program to run on `target`, which is the name of a + system configuration. You must have a GNAT cross-compiler built if + `target` is not the same as your host system. + + +.. index:: -B (gcc) + +:samp:`-B{dir}` + Load compiler executables (for example, `gnat1`, the Ada compiler) + from `dir` instead of the default location. Only use this switch + when multiple versions of the GNAT compiler are available. + See the "Options for Directory Search" section in the + :title:`Using the GNU Compiler Collection (GCC)` manual for further details. + You would normally use the *-b* or *-V* switch instead. + +.. index:: -c (gcc) + +:samp:`-c` + Compile. Always use this switch when compiling Ada programs. + + Note: for some other languages when using *gcc*, notably in + the case of C and C++, it is possible to use + use *gcc* without a *-c* switch to + compile and link in one step. In the case of GNAT, you + cannot use this approach, because the binder must be run + and *gcc* cannot be used to run the GNAT binder. + + +.. index:: -fcallgraph-info (gcc) + +:samp:`-fcallgraph-info[=su,da]` + Makes the compiler output callgraph information for the program, on a + per-file basis. The information is generated in the VCG format. It can + be decorated with additional, per-node and/or per-edge information, if a + list of comma-separated markers is additionally specified. When the + `su` marker is specified, the callgraph is decorated with stack usage + information; it is equivalent to *-fstack-usage*. When the `da` + marker is specified, the callgraph is decorated with information about + dynamically allocated objects. + + +.. index:: -fdump-scos (gcc) + +:samp:`-fdump-scos` + Generates SCO (Source Coverage Obligation) information in the ALI file. + This information is used by advanced coverage tools. See unit :file:`SCOs` + in the compiler sources for details in files :file:`scos.ads` and + :file:`scos.adb`. + + +.. index:: -fdump-xref (gcc) + +:samp:`-fdump-xref` + Generates cross reference information in GLI files for C and C++ sources. + The GLI files have the same syntax as the ALI files for Ada, and can be used + for source navigation in IDEs and on the command line using e.g. gnatxref + and the *--ext=gli* switch. + + +.. index:: -flto (gcc) + +:samp:`-flto[={n}]` + Enables Link Time Optimization. This switch must be used in conjunction + with the traditional *-Ox* switches and instructs the compiler to + defer most optimizations until the link stage. The advantage of this + approach is that the compiler can do a whole-program analysis and choose + the best interprocedural optimization strategy based on a complete view + of the program, instead of a fragmentary view with the usual approach. + This can also speed up the compilation of big programs and reduce the + size of the executable, compared with a traditional per-unit compilation + with inlining across modules enabled by the *-gnatn* switch. + The drawback of this approach is that it may require more memory and that + the debugging information generated by -g with it might be hardly usable. + The switch, as well as the accompanying *-Ox* switches, must be + specified both for the compilation and the link phases. + If the `n` parameter is specified, the optimization and final code + generation at link time are executed using `n` parallel jobs by + means of an installed *make* program. + + +.. index:: -fno-inline (gcc) + +:samp:`-fno-inline` + Suppresses all inlining, unless requested with pragma `Inline_Always`. The + effect is enforced regardless of other optimization or inlining switches. + Note that inlining can also be suppressed on a finer-grained basis with + pragma `No_Inline`. + + +.. index:: -fno-inline-functions (gcc) + +:samp:`-fno-inline-functions` + Suppresses automatic inlining of subprograms, which is enabled + if *-O3* is used. + + +.. index:: -fno-inline-small-functions (gcc) + +:samp:`-fno-inline-small-functions` + Suppresses automatic inlining of small subprograms, which is enabled + if *-O2* is used. + + +.. index:: -fno-inline-functions-called-once (gcc) + +:samp:`-fno-inline-functions-called-once` + Suppresses inlining of subprograms local to the unit and called once + from within it, which is enabled if *-O1* is used. + + +.. index:: -fno-ivopts (gcc) + +:samp:`-fno-ivopts` + Suppresses high-level loop induction variable optimizations, which are + enabled if *-O1* is used. These optimizations are generally + profitable but, for some specific cases of loops with numerous uses + of the iteration variable that follow a common pattern, they may end + up destroying the regularity that could be exploited at a lower level + and thus producing inferior code. + + +.. index:: -fno-strict-aliasing (gcc) + +:samp:`-fno-strict-aliasing` + Causes the compiler to avoid assumptions regarding non-aliasing + of objects of different types. See + :ref:`Optimization_and_Strict_Aliasing` for details. + + +.. index:: -fstack-check (gcc) + +:samp:`-fstack-check` + Activates stack checking. + See :ref:`Stack_Overflow_Checking` for details. + + +.. index:: -fstack-usage (gcc) + +:samp:`-fstack-usage` + Makes the compiler output stack usage information for the program, on a + per-subprogram basis. See :ref:`Static_Stack_Usage_Analysis` for details. + + +.. index:: -g (gcc) + +:samp:`-g` + Generate debugging information. This information is stored in the object + file and copied from there to the final executable file by the linker, + where it can be read by the debugger. You must use the + *-g* switch if you plan on using the debugger. + + +.. index:: -gnat05 (gcc) + +:samp:`-gnat05` + Allow full Ada 2005 features. + + +.. index:: -gnat12 (gcc) + +:samp:`-gnat12` + Allow full Ada 2012 features. + +.. index:: -gnat83 (gcc) + +.. index:: -gnat2005 (gcc) + +:samp:`-gnat2005` + Allow full Ada 2005 features (same as *-gnat05*) + + +.. index:: -gnat2012 (gcc) + +:samp:`-gnat2012` + Allow full Ada 2012 features (same as *-gnat12*) + + +:samp:`-gnat83` + Enforce Ada 83 restrictions. + + +.. index:: -gnat95 (gcc) + +:samp:`-gnat95` + Enforce Ada 95 restrictions. + + Note: for compatibility with some Ada 95 compilers which support only + the `overriding` keyword of Ada 2005, the *-gnatd.D* switch can + be used along with *-gnat95* to achieve a similar effect with GNAT. + + *-gnatd.D* instructs GNAT to consider `overriding` as a keyword + and handle its associated semantic checks, even in Ada 95 mode. + + +.. index:: -gnata (gcc) + +:samp:`-gnata` + Assertions enabled. `Pragma Assert` and `pragma Debug` to be + activated. Note that these pragmas can also be controlled using the + configuration pragmas `Assertion_Policy` and `Debug_Policy`. + It also activates pragmas `Check`, `Precondition`, and + `Postcondition`. Note that these pragmas can also be controlled + using the configuration pragma `Check_Policy`. In Ada 2012, it + also activates all assertions defined in the RM as aspects: preconditions, + postconditions, type invariants and (sub)type predicates. In all Ada modes, + corresponding pragmas for type invariants and (sub)type predicates are + also activated. The default is that all these assertions are disabled, + and have no effect, other than being checked for syntactic validity, and + in the case of subtype predicates, constructions such as membership tests + still test predicates even if assertions are turned off. + + +.. index:: -gnatA (gcc) + +:samp:`-gnatA` + Avoid processing :file:`gnat.adc`. If a :file:`gnat.adc` file is present, + it will be ignored. + + +.. index:: -gnatb (gcc) + +:samp:`-gnatb` + Generate brief messages to :file:`stderr` even if verbose mode set. + + +.. index:: -gnatB (gcc) + +:samp:`-gnatB` + Assume no invalid (bad) values except for 'Valid attribute use + (:ref:`Validity_Checking`). + + +.. index:: -gnatc (gcc) + +:samp:`-gnatc` + Check syntax and semantics only (no code generation attempted). When the + compiler is invoked by *gnatmake*, if the switch *-gnatc* is + only given to the compiler (after *-cargs* or in package Compiler of + the project file, *gnatmake* will fail because it will not find the + object file after compilation. If *gnatmake* is called with + *-gnatc* as a builder switch (before *-cargs* or in package + Builder of the project file) then *gnatmake* will not fail because + it will not look for the object files after compilation, and it will not try + to build and link. This switch may not be given if a previous `-gnatR` + switch has been given, since `-gnatR` requires that the code generator + be called to complete determination of representation information. + + +.. index:: -gnatC (gcc) + +:samp:`-gnatC` + Generate CodePeer intermediate format (no code generation attempted). + This switch will generate an intermediate representation suitable for + use by CodePeer (:file:`.scil` files). This switch is not compatible with + code generation (it will, among other things, disable some switches such + as -gnatn, and enable others such as -gnata). + + +.. index:: -gnatd (gcc) + +:samp:`-gnatd` + Specify debug options for the compiler. The string of characters after + the *-gnatd* specify the specific debug options. The possible + characters are 0-9, a-z, A-Z, optionally preceded by a dot. See + compiler source file :file:`debug.adb` for details of the implemented + debug options. Certain debug options are relevant to applications + programmers, and these are documented at appropriate points in this + users guide. + + +.. index:: -gnatD[nn] (gcc) + +:samp:`-gnatD` + Create expanded source files for source level debugging. This switch + also suppress generation of cross-reference information + (see *-gnatx*). Note that this switch is not allowed if a previous + -gnatR switch has been given, since these two switches are not compatible. + + +.. index:: -gnateA (gcc) + +:samp:`-gnateA` + Check that the actual parameters of a subprogram call are not aliases of one + another. To qualify as aliasing, the actuals must denote objects of a composite + type, their memory locations must be identical or overlapping, and at least one + of the corresponding formal parameters must be of mode OUT or IN OUT. + + + .. code-block:: ada + + type Rec_Typ is record + Data : Integer := 0; + end record; + + function Self (Val : Rec_Typ) return Rec_Typ is + begin + return Val; + end Self; + + procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is + begin + null; + end Detect_Aliasing; + + Obj : Rec_Typ; + + Detect_Aliasing (Obj, Obj); + Detect_Aliasing (Obj, Self (Obj)); + + + In the example above, the first call to `Detect_Aliasing` fails with a + `Program_Error` at runtime because the actuals for `Val_1` and + `Val_2` denote the same object. The second call executes without raising + an exception because `Self(Obj)` produces an anonymous object which does + not share the memory location of `Obj`. + + +.. index:: -gnatec (gcc) + +:samp:`-gnatec={path}` + Specify a configuration pragma file + (the equal sign is optional) + (:ref:`The_Configuration_Pragmas_Files`). + + +.. index:: -gnateC (gcc) + +:samp:`-gnateC` + Generate CodePeer messages in a compiler-like format. This switch is only + effective if *-gnatcC* is also specified and requires an installation + of CodePeer. + + +.. index:: -gnated (gcc) + +:samp:`-gnated` + Disable atomic synchronization + + +.. index:: -gnateD (gcc) + +:samp:`-gnateDsymbol[={value}]` + Defines a symbol, associated with `value`, for preprocessing. + (:ref:`Integrated_Preprocessing`). + + +.. index:: -gnateE (gcc) + +:samp:`-gnateE` + Generate extra information in exception messages. In particular, display + extra column information and the value and range associated with index and + range check failures, and extra column information for access checks. + In cases where the compiler is able to determine at compile time that + a check will fail, it gives a warning, and the extra information is not + produced at run time. + + +.. index:: -gnatef (gcc) + +:samp:`-gnatef` + Display full source path name in brief error messages. + + +.. index:: -gnateF (gcc) + +:samp:`-gnateF` + Check for overflow on all floating-point operations, including those + for unconstrained predefined types. See description of pragma + `Check_Float_Overflow` in GNAT RM. + + +.. index:: -gnateG (gcc) + +:samp:`-gnateG` + Save result of preprocessing in a text file. + + +.. index:: -gnatei (gcc) + +:samp:`-gnatei{nnn}` + Set maximum number of instantiations during compilation of a single unit to + `nnn`. This may be useful in increasing the default maximum of 8000 for + the rare case when a single unit legitimately exceeds this limit. + + +.. index:: -gnateI (gcc) + +:samp:`-gnateI{nnn}` + Indicates that the source is a multi-unit source and that the index of the + unit to compile is `nnn`. `nnn` needs to be a positive number and need + to be a valid index in the multi-unit source. + + +.. index:: -gnatel (gcc) + +:samp:`-gnatel` + This switch can be used with the static elaboration model to issue info + messages showing + where implicit `pragma Elaborate` and `pragma Elaborate_All` + are generated. This is useful in diagnosing elaboration circularities + caused by these implicit pragmas when using the static elaboration + model. See See the section in this guide on elaboration checking for + further details. These messages are not generated by default, and are + intended only for temporary use when debugging circularity problems. + + +.. index:: -gnatel (gcc) + +:samp:`-gnateL` + This switch turns off the info messages about implicit elaboration pragmas. + + +.. index:: -gnatem (gcc) + +:samp:`-gnatem={path}` + Specify a mapping file + (the equal sign is optional) + (:ref:`Units_to_Sources_Mapping_Files`). + + +.. index:: -gnatep (gcc) + +:samp:`-gnatep={file}` + Specify a preprocessing data file + (the equal sign is optional) + (:ref:`Integrated_Preprocessing`). + + +.. index:: -gnateP (gcc) + +:samp:`-gnateP` + Turn categorization dependency errors into warnings. + Ada requires that units that WITH one another have compatible categories, for + example a Pure unit cannot WITH a Preelaborate unit. If this switch is used, + these errors become warnings (which can be ignored, or suppressed in the usual + manner). This can be useful in some specialized circumstances such as the + temporary use of special test software. + + +.. index:: -gnateS (gcc) + +:samp:`-gnateS` + Synonym of *-fdump-scos*, kept for backwards compatibility. + + +.. index:: -gnatet=file (gcc) + +:samp:`-gnatet={path}` + Generate target dependent information. The format of the output file is + described in the section about switch *-gnateT*. + + +.. index:: -gnateT (gcc) + +:samp:`-gnateT={path}` + Read target dependent information, such as endianness or sizes and alignments + of base type. If this switch is passed, the default target dependent + information of the compiler is replaced by the one read from the input file. + This is used by tools other than the compiler, e.g. to do + semantic analysis of programs that will run on some other target than + the machine on which the tool is run. + + The following target dependent values should be defined, + where `Nat` denotes a natural integer value, `Pos` denotes a + positive integer value, and fields marked with a question mark are + boolean fields, where a value of 0 is False, and a value of 1 is True: + + + :: + + Bits_BE : Nat; -- Bits stored big-endian? + Bits_Per_Unit : Pos; -- Bits in a storage unit + Bits_Per_Word : Pos; -- Bits in a word + Bytes_BE : Nat; -- Bytes stored big-endian? + Char_Size : Pos; -- Standard.Character'Size + Double_Float_Alignment : Nat; -- Alignment of double float + Double_Scalar_Alignment : Nat; -- Alignment of double length scalar + Double_Size : Pos; -- Standard.Long_Float'Size + Float_Size : Pos; -- Standard.Float'Size + Float_Words_BE : Nat; -- Float words stored big-endian? + Int_Size : Pos; -- Standard.Integer'Size + Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size + Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size + Long_Size : Pos; -- Standard.Long_Integer'Size + Maximum_Alignment : Pos; -- Maximum permitted alignment + Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field + Pointer_Size : Pos; -- System.Address'Size + Short_Enums : Nat; -- Short foreign convention enums? + Short_Size : Pos; -- Standard.Short_Integer'Size + Strict_Alignment : Nat; -- Strict alignment? + System_Allocator_Alignment : Nat; -- Alignment for malloc calls + Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size + Words_BE : Nat; -- Words stored big-endian? + + + The format of the input file is as follows. First come the values of + the variables defined above, with one line per value: + + + :: + + name value + + where `name` is the name of the parameter, spelled out in full, + and cased as in the above list, and `value` is an unsigned decimal + integer. Two or more blanks separates the name from the value. + + All the variables must be present, in alphabetical order (i.e. the + same order as the list above). + + Then there is a blank line to separate the two parts of the file. Then + come the lines showing the floating-point types to be registered, with + one line per registered mode: + + + :: + + name digs float_rep size alignment + + + where `name` is the string name of the type (which can have + single spaces embedded in the name (e.g. long double), `digs` is + the number of digits for the floating-point type, `float_rep` is + the float representation (I/V/A for IEEE-754-Binary, Vax_Native, + AAMP), `size` is the size in bits, `alignment` is the + alignment in bits. The name is followed by at least two blanks, fields + are separated by at least one blank, and a LF character immediately + follows the alignment field. + + Here is an example of a target parameterization file: + + + :: + + Bits_BE 0 + Bits_Per_Unit 8 + Bits_Per_Word 64 + Bytes_BE 0 + Char_Size 8 + Double_Float_Alignment 0 + Double_Scalar_Alignment 0 + Double_Size 64 + Float_Size 32 + Float_Words_BE 0 + Int_Size 64 + Long_Double_Size 128 + Long_Long_Size 64 + Long_Size 64 + Maximum_Alignment 16 + Max_Unaligned_Field 64 + Pointer_Size 64 + Short_Size 16 + Strict_Alignment 0 + System_Allocator_Alignment 16 + Wchar_T_Size 32 + Words_BE 0 + + float 15 I 64 64 + double 15 I 64 64 + long double 18 I 80 128 + TF 33 I 128 128 + + + +.. index:: -gnateu (gcc) + +:samp:`-gnateu` + Ignore unrecognized validity, warning, and style switches that + appear after this switch is given. This may be useful when + compiling sources developed on a later version of the compiler + with an earlier version. Of course the earlier version must + support this switch. + + +.. index:: -gnateV (gcc) + +:samp:`-gnateV` + Check that all actual parameters of a subprogram call are valid according to + the rules of validity checking (:ref:`Validity_Checking`). + + +.. index:: -gnateY (gcc) + +:samp:`-gnateY` + Ignore all STYLE_CHECKS pragmas. Full legality checks + are still carried out, but the pragmas have no effect + on what style checks are active. This allows all style + checking options to be controlled from the command line. + + +.. index:: -gnatE (gcc) + +:samp:`-gnatE` + Full dynamic elaboration checks. + + +.. index:: -gnatf (gcc) + +:samp:`-gnatf` + Full errors. Multiple errors per line, all undefined references, do not + attempt to suppress cascaded errors. + + +.. index:: -gnatF (gcc) + +:samp:`-gnatF` + Externals names are folded to all uppercase. + + +.. index:: -gnatg (gcc) + +:samp:`-gnatg` + Internal GNAT implementation mode. This should not be used for + applications programs, it is intended only for use by the compiler + and its run-time library. For documentation, see the GNAT sources. + Note that *-gnatg* implies + *-gnatw.ge* and + *-gnatyg* + so that all standard warnings and all standard style options are turned on. + All warnings and style messages are treated as errors. + + +.. index:: -gnatG[nn] (gcc) + +:samp:`-gnatG=nn` + List generated expanded code in source form. + + +.. index:: -gnath (gcc) + +:samp:`-gnath` + Output usage information. The output is written to :file:`stdout`. + + +.. index:: -gnati (gcc) + +:samp:`-gnati{c}` + Identifier character set (`c` = 1/2/3/4/8/9/p/f/n/w). + For details of the possible selections for `c`, + see :ref:`Character_Set_Control`. + + +.. index:: -gnatI (gcc) + +:samp:`-gnatI` + Ignore representation clauses. When this switch is used, + representation clauses are treated as comments. This is useful + when initially porting code where you want to ignore rep clause + problems, and also for compiling foreign code (particularly + for use with ASIS). The representation clauses that are ignored + are: enumeration_representation_clause, record_representation_clause, + and attribute_definition_clause for the following attributes: + Address, Alignment, Bit_Order, Component_Size, Machine_Radix, + Object_Size, Size, Small, Stream_Size, and Value_Size. + Note that this option should be used only for compiling -- the + code is likely to malfunction at run time. + + Note that when `-gnatct` is used to generate trees for input + into `ASIS` tools, these representation clauses are removed + from the tree and ignored. This means that the tool will not see them. + + +.. index:: -gnatjnn (gcc) + +:samp:`-gnatj{nn}` + Reformat error messages to fit on `nn` character lines + + +.. index:: -gnatk (gcc) + +:samp:`-gnatk={n}` + Limit file names to `n` (1-999) characters (`k` = krunch). + + +.. index:: -gnatl (gcc) + +:samp:`-gnatl` + Output full source listing with embedded error messages. + + +.. index:: -gnatL (gcc) + +:samp:`-gnatL` + Used in conjunction with -gnatG or -gnatD to intersperse original + source lines (as comment lines with line numbers) in the expanded + source output. + + +.. index:: -gnatm (gcc) + +:samp:`-gnatm={n}` + Limit number of detected error or warning messages to `n` + where `n` is in the range 1..999999. The default setting if + no switch is given is 9999. If the number of warnings reaches this + limit, then a message is output and further warnings are suppressed, + but the compilation is continued. If the number of error messages + reaches this limit, then a message is output and the compilation + is abandoned. The equal sign here is optional. A value of zero + means that no limit applies. + + +.. index:: -gnatn (gcc) + +:samp:`-gnatn[12]` + Activate inlining for subprograms for which pragma `Inline` is + specified. This inlining is performed by the GCC back-end. An optional + digit sets the inlining level: 1 for moderate inlining across modules + or 2 for full inlining across modules. If no inlining level is specified, + the compiler will pick it based on the optimization level. + + +.. index:: -gnatN (gcc) + +:samp:`-gnatN` + Activate front end inlining for subprograms for which + pragma `Inline` is specified. This inlining is performed + by the front end and will be visible in the + *-gnatG* output. + + When using a gcc-based back end (in practice this means using any version + of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of + *-gnatN* is deprecated, and the use of *-gnatn* is preferred. + Historically front end inlining was more extensive than the gcc back end + inlining, but that is no longer the case. + + +.. index:: -gnato0 (gcc) + +:samp:`-gnato0` + Suppresses overflow checking. This causes the behavior of the compiler to + match the default for older versions where overflow checking was suppressed + by default. This is equivalent to having + `pragma Suppress (Overflow_Mode)` in a configuration pragma file. + + +.. index:: -gnato?? (gcc) + +:samp:`-gnato??` + Set default mode for handling generation of code to avoid intermediate + arithmetic overflow. Here `??` is two digits, a + single digit, or nothing. Each digit is one of the digits `1` + through `3`: + + ===== =============================================================== + Digit Interpretation + ----- --------------------------------------------------------------- + *1* All intermediate overflows checked against base type (`STRICT`) + *2* Minimize intermediate overflows (`MINIMIZED`) + *3* Eliminate intermediate overflows (`ELIMINATED`) + ===== =============================================================== + + If only one digit appears then it applies to all + cases; if two digits are given, then the first applies outside + assertions, and the second within assertions. + + If no digits follow the *-gnato*, then it is equivalent to + *-gnato11*, + causing all intermediate overflows to be handled in strict mode. + + This switch also causes arithmetic overflow checking to be performed + (as though `pragma Unsuppress (Overflow_Mode)` had been specified. + + The default if no option *-gnato* is given is that overflow handling + is in `STRICT` mode (computations done using the base type), and that + overflow checking is enabled. + + Note that division by zero is a separate check that is not + controlled by this switch (division by zero checking is on by default). + + See also :ref:`Specifying_the_Desired_Mode`. + + +.. index:: -gnatp (gcc) + +:samp:`-gnatp` + Suppress all checks. See :ref:`Run-Time_Checks` for details. This switch + has no effect if cancelled by a subsequent *-gnat-p* switch. + + +.. index:: -gnat-p (gcc) + +:samp:`-gnat-p` + Cancel effect of previous *-gnatp* switch. + + +.. index:: -gnatP (gcc) + +:samp:`-gnatP` + Enable polling. This is required on some systems (notably Windows NT) to + obtain asynchronous abort and asynchronous transfer of control capability. + See `Pragma_Polling` in the :title:`GNAT_Reference_Manual` for full + details. + + +.. index:: -gnatq (gcc) + +:samp:`-gnatq` + Don't quit. Try semantics, even if parse errors. + + +.. index:: -gnatQ (gcc) + +:samp:`-gnatQ` + Don't quit. Generate :file:`ALI` and tree files even if illegalities. + Note that code generation is still suppressed in the presence of any + errors, so even with *-gnatQ* no object file is generated. + + +.. index:: -gnatr (gcc) + +:samp:`-gnatr` + Treat pragma Restrictions as Restriction_Warnings. + + +.. index:: -gnatR (gcc) + +:samp:`-gnatR[0/1/2/3[s]]` + Output representation information for declared types and objects. + Note that this switch is not allowed if a previous `-gnatD` switch has + been given, since these two switches are not compatible. + + +:samp:`-gnatRm[s]` + Output convention and parameter passing mechanisms for all subprograms. + + +.. index:: -gnats (gcc) + +:samp:`-gnats` + Syntax check only. + + +.. index:: -gnatS (gcc) + +:samp:`-gnatS` + Print package Standard. + + +.. index:: -gnatt (gcc) + +:samp:`-gnatt` + Generate tree output file. + + +.. index:: -gnatT (gcc) + +:samp:`-gnatT{nnn}` + All compiler tables start at `nnn` times usual starting size. + + +.. index:: -gnatu (gcc) + +:samp:`-gnatu` + List units for this compilation. + + +.. index:: -gnatU (gcc) + +:samp:`-gnatU` + Tag all error messages with the unique string 'error:' + + +.. index:: -gnatv (gcc) + +:samp:`-gnatv` + Verbose mode. Full error output with source lines to :file:`stdout`. + + +.. index:: -gnatV (gcc) + +:samp:`-gnatV` + Control level of validity checking (:ref:`Validity_Checking`). + + +.. index:: -gnatw (gcc) + +:samp:`-gnatw{xxx}` + Warning mode where + `xxx` is a string of option letters that denotes + the exact warnings that + are enabled or disabled (:ref:`Warning_Message_Control`). + + +.. index:: -gnatW (gcc) + +:samp:`-gnatW{e}` + Wide character encoding method + (`e`\ =n/h/u/s/e/8). + + +.. index:: -gnatx (gcc) + +:samp:`-gnatx` + Suppress generation of cross-reference information. + + +.. index:: -gnatX (gcc) + +:samp:`-gnatX` + Enable GNAT implementation extensions and latest Ada version. + + +.. index:: -gnaty (gcc) + +:samp:`-gnaty` + Enable built-in style checks (:ref:`Style_Checking`). + + +.. index:: -gnatz (gcc) + +:samp:`-gnatz{m}` + Distribution stub generation and compilation + (`m`\ =r/c for receiver/caller stubs). + + +.. index:: -I (gcc) + +:samp:`-I{dir}` + .. index:: RTL + + Direct GNAT to search the `dir` directory for source files needed by + the current compilation + (see :ref:`Search_Paths_and_the_Run-Time_Library_RTL`). + + +.. index:: -I- (gcc) + +:samp:`-I-` + .. index:: RTL + + Except for the source file named in the command line, do not look for source + files in the directory containing the source file named in the command line + (see :ref:`Search_Paths_and_the_Run-Time_Library_RTL`). + + +.. index:: -o (gcc) + +:samp:`-o {file}` + This switch is used in *gcc* to redirect the generated object file + and its associated ALI file. Beware of this switch with GNAT, because it may + cause the object file and ALI file to have different names which in turn + may confuse the binder and the linker. + + +.. index:: -nostdinc (gcc) + +:samp:`-nostdinc` + Inhibit the search of the default location for the GNAT Run Time + Library (RTL) source files. + + +.. index:: -nostdlib (gcc) + +:samp:`-nostdlib` + Inhibit the search of the default location for the GNAT Run Time + Library (RTL) ALI files. + + +.. index:: -O (gcc) + +:samp:`-O[{n}]` + `n` controls the optimization level: + + ======= ================================================================== + *n* Effect + ------- ------------------------------------------------------------------ + *0* No optimization, the default setting if no *-O* appears + *1* Normal optimization, the default if you specify *-O* without an + operand. A good compromise between code quality and compilation + time. + *2* Extensive optimization, may improve execution time, possibly at + the cost of substantially increased compilation time. + *3* Same as *-O2*, and also includes inline expansion for small + subprograms in the same unit. + *s* Optimize space usage + ======= ================================================================== + + See also :ref:`Optimization_Levels`. + + +.. index:: -pass-exit-codes (gcc) + +:samp:`-pass-exit-codes` + Catch exit codes from the compiler and use the most meaningful as + exit status. + + +.. index:: --RTS (gcc) + +:samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + +.. index:: -S (gcc) + +:samp:`-S` + Used in place of *-c* to + cause the assembler source file to be + generated, using :file:`.s` as the extension, + instead of the object file. + This may be useful if you need to examine the generated assembly code. + + +.. index:: -fverbose-asm (gcc) + +:samp:`-fverbose-asm` + Used in conjunction with *-S* + to cause the generated assembly code file to be annotated with variable + names, making it significantly easier to follow. + + +.. index:: -v (gcc) + +:samp:`-v` + Show commands generated by the *gcc* driver. Normally used only for + debugging purposes or if you need to be sure what version of the + compiler you are executing. + + +.. index:: -V (gcc) + +:samp:`-V {ver}` + Execute `ver` version of the compiler. This is the *gcc* + version, not the GNAT version. + + +.. index:: -w (gcc) + +:samp:`-w` + Turn off warnings generated by the back end of the compiler. Use of + this switch also causes the default for front end warnings to be set + to suppress (as though *-gnatws* had appeared at the start of + the options). + + +.. index:: Combining GNAT switches + +You may combine a sequence of GNAT switches into a single switch. For +example, the combined switch + + :: + + -gnatofi3 + +is equivalent to specifying the following sequence of switches: + + :: + + -gnato -gnatf -gnati3 + +The following restrictions apply to the combination of switches +in this manner: + +* The switch *-gnatc* if combined with other switches must come + first in the string. + +* The switch *-gnats* if combined with other switches must come + first in the string. + +* The switches + *-gnatzc* and *-gnatzr* may not be combined with any other + switches, and only one of them may appear in the command line. + +* The switch *-gnat-p* may not be combined with any other switch. + +* Once a 'y' appears in the string (that is a use of the *-gnaty* + switch), then all further characters in the switch are interpreted + as style modifiers (see description of *-gnaty*). + +* Once a 'd' appears in the string (that is a use of the *-gnatd* + switch), then all further characters in the switch are interpreted + as debug flags (see description of *-gnatd*). + +* Once a 'w' appears in the string (that is a use of the *-gnatw* + switch), then all further characters in the switch are interpreted + as warning mode modifiers (see description of *-gnatw*). + +* Once a 'V' appears in the string (that is a use of the *-gnatV* + switch), then all further characters in the switch are interpreted + as validity checking options (:ref:`Validity_Checking`). + +* Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in + a combined list of options. + +.. _Output_and_Error_Message_Control: + +Output and Error Message Control +-------------------------------- + +.. index:: stderr + +The standard default format for error messages is called 'brief format'. +Brief format messages are written to :file:`stderr` (the standard error +file) and have the following form: + +:: + + e.adb:3:04: Incorrect spelling of keyword "function" + e.adb:4:20: ";" should be "is" + +The first integer after the file name is the line number in the file, +and the second integer is the column number within the line. +`GPS` can parse the error messages +and point to the referenced character. +The following switches provide control over the error message +format: + + +.. index:: -gnatv (gcc) + +:samp:`-gnatv` + The `v` stands for verbose. + The effect of this setting is to write long-format error + messages to :file:`stdout` (the standard output file. + The same program compiled with the + *-gnatv* switch would generate: + + :: + + 3. funcion X (Q : Integer) + | + >>> Incorrect spelling of keyword "function" + 4. return Integer; + | + >>> ";" should be "is" + + + The vertical bar indicates the location of the error, and the :samp:`>>>` + prefix can be used to search for error messages. When this switch is + used the only source lines output are those with errors. + + +.. index:: -gnatl (gcc) + +:samp:`-gnatl` + The `l` stands for list. + This switch causes a full listing of + the file to be generated. In the case where a body is + compiled, the corresponding spec is also listed, along + with any subunits. Typical output from compiling a package + body :file:`p.adb` might look like:: + + Compiling: p.adb + + 1. package body p is + 2. procedure a; + 3. procedure a is separate; + 4. begin + 5. null + | + >>> missing ";" + + 6. end; + + Compiling: p.ads + + 1. package p is + 2. pragma Elaborate_Body + | + >>> missing ";" + + 3. end p; + + Compiling: p-a.adb + + 1. separate p + | + >>> missing "(" + + 2. procedure a is + 3. begin + 4. null + | + >>> missing ";" + + 5. end; + + + When you specify the *-gnatv* or *-gnatl* switches and + standard output is redirected, a brief summary is written to + :file:`stderr` (standard error) giving the number of error messages and + warning messages generated. + + +.. index:: -gnatl=fname (gcc) + +:samp:`-gnatl={fname}` + This has the same effect as *-gnatl* except that the output is + written to a file instead of to standard output. If the given name + :file:`fname` does not start with a period, then it is the full name + of the file to be written. If :file:`fname` is an extension, it is + appended to the name of the file being compiled. For example, if + file :file:`xyz.adb` is compiled with *-gnatl=.lst*, + then the output is written to file xyz.adb.lst. + + +.. index:: -gnatU (gcc) + +:samp:`-gnatU` + This switch forces all error messages to be preceded by the unique + string 'error:'. This means that error messages take a few more + characters in space, but allows easy searching for and identification + of error messages. + + +.. index:: -gnatb (gcc) + +:samp:`-gnatb` + The `b` stands for brief. + This switch causes GNAT to generate the + brief format error messages to :file:`stderr` (the standard error + file) as well as the verbose + format message or full listing (which as usual is written to + :file:`stdout` (the standard output file). + + +.. index:: -gnatm (gcc) + +:samp:`-gnatm={n}` + The `m` stands for maximum. + `n` is a decimal integer in the + range of 1 to 999999 and limits the number of error or warning + messages to be generated. For example, using + *-gnatm2* might yield + + :: + + e.adb:3:04: Incorrect spelling of keyword "function" + e.adb:5:35: missing ".." + fatal error: maximum number of errors detected + compilation abandoned + + + The default setting if + no switch is given is 9999. If the number of warnings reaches this + limit, then a message is output and further warnings are suppressed, + but the compilation is continued. If the number of error messages + reaches this limit, then a message is output and the compilation + is abandoned. A value of zero means that no limit applies. + + Note that the equal sign is optional, so the switches + *-gnatm2* and *-gnatm=2* are equivalent. + + +.. index:: -gnatf (gcc) + +:samp:`-gnatf` + .. index:: Error messages, suppressing + + The `f` stands for full. + Normally, the compiler suppresses error messages that are likely to be + redundant. This switch causes all error + messages to be generated. In particular, in the case of + references to undefined variables. If a given variable is referenced + several times, the normal format of messages is + + :: + + e.adb:7:07: "V" is undefined (more references follow) + + where the parenthetical comment warns that there are additional + references to the variable `V`. Compiling the same program with the + *-gnatf* switch yields + + :: + + e.adb:7:07: "V" is undefined + e.adb:8:07: "V" is undefined + e.adb:8:12: "V" is undefined + e.adb:8:16: "V" is undefined + e.adb:9:07: "V" is undefined + e.adb:9:12: "V" is undefined + + The *-gnatf* switch also generates additional information for + some error messages. Some examples are: + + * Details on possibly non-portable unchecked conversion + + * List possible interpretations for ambiguous calls + + * Additional details on incorrect parameters + + +.. index:: -gnatjnn (gcc) + +:samp:`-gnatjnn` + In normal operation mode (or if *-gnatj0* is used), then error messages + with continuation lines are treated as though the continuation lines were + separate messages (and so a warning with two continuation lines counts as + three warnings, and is listed as three separate messages). + + If the *-gnatjnn* switch is used with a positive value for nn, then + messages are output in a different manner. A message and all its continuation + lines are treated as a unit, and count as only one warning or message in the + statistics totals. Furthermore, the message is reformatted so that no line + is longer than nn characters. + + +.. index:: -gnatq (gcc) + +:samp:`-gnatq` + The `q` stands for quit (really 'don't quit'). + In normal operation mode, the compiler first parses the program and + determines if there are any syntax errors. If there are, appropriate + error messages are generated and compilation is immediately terminated. + This switch tells + GNAT to continue with semantic analysis even if syntax errors have been + found. This may enable the detection of more errors in a single run. On + the other hand, the semantic analyzer is more likely to encounter some + internal fatal error when given a syntactically invalid tree. + + +.. index:: -gnatQ (gcc) + +:samp:`-gnatQ` + In normal operation mode, the :file:`ALI` file is not generated if any + illegalities are detected in the program. The use of *-gnatQ* forces + generation of the :file:`ALI` file. This file is marked as being in + error, so it cannot be used for binding purposes, but it does contain + reasonably complete cross-reference information, and thus may be useful + for use by tools (e.g., semantic browsing tools or integrated development + environments) that are driven from the :file:`ALI` file. This switch + implies *-gnatq*, since the semantic phase must be run to get a + meaningful ALI file. + + In addition, if *-gnatt* is also specified, then the tree file is + generated even if there are illegalities. It may be useful in this case + to also specify *-gnatq* to ensure that full semantic processing + occurs. The resulting tree file can be processed by ASIS, for the purpose + of providing partial information about illegal units, but if the error + causes the tree to be badly malformed, then ASIS may crash during the + analysis. + + When *-gnatQ* is used and the generated :file:`ALI` file is marked as + being in error, *gnatmake* will attempt to recompile the source when it + finds such an :file:`ALI` file, including with switch *-gnatc*. + + Note that *-gnatQ* has no effect if *-gnats* is specified, + since ALI files are never generated if *-gnats* is set. + + +.. _Warning_Message_Control: + +Warning Message Control +----------------------- + +.. index:: Warning messages + +In addition to error messages, which correspond to illegalities as defined +in the Ada Reference Manual, the compiler detects two kinds of warning +situations. + +First, the compiler considers some constructs suspicious and generates a +warning message to alert you to a possible error. Second, if the +compiler detects a situation that is sure to raise an exception at +run time, it generates a warning message. The following shows an example +of warning messages: + +:: + + e.adb:4:24: warning: creation of object may raise Storage_Error + e.adb:10:17: warning: static value out of range + e.adb:10:17: warning: "Constraint_Error" will be raised at run time + + +GNAT considers a large number of situations as appropriate +for the generation of warning messages. As always, warnings are not +definite indications of errors. For example, if you do an out-of-range +assignment with the deliberate intention of raising a +`Constraint_Error` exception, then the warning that may be +issued does not indicate an error. Some of the situations for which GNAT +issues warnings (at least some of the time) are given in the following +list. This list is not complete, and new warnings are often added to +subsequent versions of GNAT. The list is intended to give a general idea +of the kinds of warnings that are generated. + +* Possible infinitely recursive calls + +* Out-of-range values being assigned + +* Possible order of elaboration problems + +* Size not a multiple of alignment for a record type + +* Assertions (pragma Assert) that are sure to fail + +* Unreachable code + +* Address clauses with possibly unaligned values, or where an attempt is + made to overlay a smaller variable with a larger one. + +* Fixed-point type declarations with a null range + +* Direct_IO or Sequential_IO instantiated with a type that has access values + +* Variables that are never assigned a value + +* Variables that are referenced before being initialized + +* Task entries with no corresponding `accept` statement + +* Duplicate accepts for the same task entry in a `select` + +* Objects that take too much storage + +* Unchecked conversion between types of differing sizes + +* Missing `return` statement along some execution path in a function + +* Incorrect (unrecognized) pragmas + +* Incorrect external names + +* Allocation from empty storage pool + +* Potentially blocking operation in protected type + +* Suspicious parenthesization of expressions + +* Mismatching bounds in an aggregate + +* Attempt to return local value by reference + +* Premature instantiation of a generic body + +* Attempt to pack aliased components + +* Out of bounds array subscripts + +* Wrong length on string assignment + +* Violations of style rules if style checking is enabled + +* Unused |with| clauses + +* `Bit_Order` usage that does not have any effect + +* `Standard.Duration` used to resolve universal fixed expression + +* Dereference of possibly null value + +* Declaration that is likely to cause storage error + +* Internal GNAT unit |withed| by application unit + +* Values known to be out of range at compile time + +* Unreferenced or unmodified variables. Note that a special + exemption applies to variables which contain any of the substrings + `DISCARD, DUMMY, IGNORE, JUNK, UNUSED`, in any casing. Such variables + are considered likely to be intentionally used in a situation where + otherwise a warning would be given, so warnings of this kind are + always suppressed for such variables. + +* Address overlays that could clobber memory + +* Unexpected initialization when address clause present + +* Bad alignment for address clause + +* Useless type conversions + +* Redundant assignment statements and other redundant constructs + +* Useless exception handlers + +* Accidental hiding of name by child unit + +* Access before elaboration detected at compile time + +* A range in a `for` loop that is known to be null or might be null + + +The following section lists compiler switches that are available +to control the handling of warning messages. It is also possible +to exercise much finer control over what warnings are issued and +suppressed using the GNAT pragma Warnings (see the description +of the pragma in the :title:`GNAT_Reference_manual`). + + +.. index:: -gnatwa (gcc) + +:samp:`-gnatwa` + *Activate most optional warnings.* + + This switch activates most optional warning messages. See the remaining list + in this section for details on optional warning messages that can be + individually controlled. The warnings that are not turned on by this + switch are: + + + * :samp:`-gnatwd` (implicit dereferencing) + + * :samp:`-gnatw.d` (tag warnings with -gnatw switch) + + * :samp:`-gnatwh` (hiding) + + * :samp:`-gnatw.h` (holes in record layouts) + + * :samp:`-gnatw.k` (redefinition of names in standard) + + * :samp:`-gnatwl` (elaboration warnings) + + * :samp:`-gnatw.l` (inherited aspects) + + * :samp:`-gnatw.n` (atomic synchronization) + + * :samp:`-gnatwo` (address clause overlay) + + * :samp:`-gnatw.o` (values set by out parameters ignored) + + * :samp:`-gnatw.s` (overridden size clause) + + * :samp:`-gnatwt` (tracking of deleted conditional code) + + * :samp:`-gnatw.u` (unordered enumeration) + + * :samp:`-gnatw.w` (use of Warnings Off) + + * :samp:`-gnatw.y` (reasons for package needing body) + + All other optional warnings are turned on. + + +.. index:: -gnatwA (gcc) + +:samp:`-gnatwA` + *Suppress all optional errors.* + + This switch suppresses all optional warning messages, see remaining list + in this section for details on optional warning messages that can be + individually controlled. Note that unlike switch *-gnatws*, the + use of switch *-gnatwA* does not suppress warnings that are + normally given unconditionally and cannot be individually controlled + (for example, the warning about a missing exit path in a function). + Also, again unlike switch *-gnatws*, warnings suppressed by + the use of switch *-gnatwA* can be individually turned back + on. For example the use of switch *-gnatwA* followed by + switch *-gnatwd* will suppress all optional warnings except + the warnings for implicit dereferencing. + +.. index:: -gnatw.a (gcc) + +:samp:`-gnatw.a` + *Activate warnings on failing assertions.* + + .. index:: Assert failures + + This switch activates warnings for assertions where the compiler can tell at + compile time that the assertion will fail. Note that this warning is given + even if assertions are disabled. The default is that such warnings are + generated. + + +.. index:: -gnatw.A (gcc) + +:samp:`-gnatw.A` + *Suppress warnings on failing assertions.* + + .. index:: Assert failures + + This switch suppresses warnings for assertions where the compiler can tell at + compile time that the assertion will fail. + + +.. index:: -gnatwb (gcc) + +:samp:`-gnatwb` + *Activate warnings on bad fixed values.* + + .. index:: Bad fixed values + + .. index:: Fixed-point Small value + + .. index:: Small value + + This switch activates warnings for static fixed-point expressions whose + value is not an exact multiple of Small. Such values are implementation + dependent, since an implementation is free to choose either of the multiples + that surround the value. GNAT always chooses the closer one, but this is not + required behavior, and it is better to specify a value that is an exact + multiple, ensuring predictable execution. The default is that such warnings + are not generated. + + +.. index:: -gnatwB (gcc) + +:samp:`-gnatwB` + *Suppress warnings on bad fixed values.* + + This switch suppresses warnings for static fixed-point expressions whose + value is not an exact multiple of Small. + + +.. index:: -gnatw.b (gcc) + +:samp:`-gnatw.b` + *Activate warnings on biased representation.* + + .. index:: Biased representation + + This switch activates warnings when a size clause, value size clause, component + clause, or component size clause forces the use of biased representation for an + integer type (e.g. representing a range of 10..11 in a single bit by using 0/1 + to represent 10/11). The default is that such warnings are generated. + + +.. index:: -gnatwB (gcc) + +:samp:`-gnatw.B` + *Suppress warnings on biased representation.* + + This switch suppresses warnings for representation clauses that force the use + of biased representation. + + +.. index:: -gnatwc (gcc) + +:samp:`-gnatwc` + *Activate warnings on conditionals.* + + .. index:: Conditionals, constant + + This switch activates warnings for conditional expressions used in + tests that are known to be True or False at compile time. The default + is that such warnings are not generated. + Note that this warning does + not get issued for the use of boolean variables or constants whose + values are known at compile time, since this is a standard technique + for conditional compilation in Ada, and this would generate too many + false positive warnings. + + This warning option also activates a special test for comparisons using + the operators '>=' and' <='. + If the compiler can tell that only the equality condition is possible, + then it will warn that the '>' or '<' part of the test + is useless and that the operator could be replaced by '='. + An example would be comparing a `Natural` variable <= 0. + + This warning option also generates warnings if + one or both tests is optimized away in a membership test for integer + values if the result can be determined at compile time. Range tests on + enumeration types are not included, since it is common for such tests + to include an end point. + + This warning can also be turned on using *-gnatwa*. + + +.. index:: -gnatwC (gcc) + +:samp:`-gnatwC` + *Suppress warnings on conditionals.* + + This switch suppresses warnings for conditional expressions used in + tests that are known to be True or False at compile time. + + +.. index:: -gnatw.c (gcc) + +:samp:`-gnatw.c` + *Activate warnings on missing component clauses.* + + .. index:: Component clause, missing + + This switch activates warnings for record components where a record + representation clause is present and has component clauses for the + majority, but not all, of the components. A warning is given for each + component for which no component clause is present. + + +.. index:: -gnatwC (gcc) + +:samp:`-gnatw.C` + *Suppress warnings on missing component clauses.* + + This switch suppresses warnings for record components that are + missing a component clause in the situation described above. + + +.. index:: -gnatwd (gcc) + +:samp:`-gnatwd` + *Activate warnings on implicit dereferencing.* + + If this switch is set, then the use of a prefix of an access type + in an indexed component, slice, or selected component without an + explicit `.all` will generate a warning. With this warning + enabled, access checks occur only at points where an explicit + `.all` appears in the source code (assuming no warnings are + generated as a result of this switch). The default is that such + warnings are not generated. + + +.. index:: -gnatwD (gcc) + +:samp:`-gnatwD` + *Suppress warnings on implicit dereferencing.* + + .. index:: Implicit dereferencing + + .. index:: Dereferencing, implicit + + This switch suppresses warnings for implicit dereferences in + indexed components, slices, and selected components. + + +.. index:: -gnatw.d (gcc) + +:samp:`-gnatw.d` + *Activate tagging of warning and info messages.* + + If this switch is set, then warning messages are tagged, with one of the + following strings: + + - *[-gnatw?]* + Used to tag warnings controlled by the switch *-gnatwx* where x + is a letter a-z. + + + - *[-gnatw.?]* + Used to tag warnings controlled by the switch *-gnatw.x* where x + is a letter a-z. + + + - *[-gnatel]* + Used to tag elaboration information (info) messages generated when the + static model of elaboration is used and the *-gnatel* switch is set. + + + - *[restriction warning]* + Used to tag warning messages for restriction violations, activated by use + of the pragma *Restriction_Warnings*. + + + - *[warning-as-error]* + Used to tag warning messages that have been converted to error messages by + use of the pragma Warning_As_Error. Note that such warnings are prefixed by + the string "error: " rather than "warning: ". + + + - *[enabled by default]* + Used to tag all other warnings that are always given by default, unless + warnings are completely suppressed using pragma *Warnings(Off)* or + the switch *-gnatws*. + + + +.. index:: -gnatw.d (gcc) + +:samp:`-gnatw.D` + *Deactivate tagging of warning and info messages messages.* + + If this switch is set, then warning messages return to the default + mode in which warnings and info messages are not tagged as described above for + `-gnatw.d`. + + +.. index:: -gnatwe (gcc) +.. index:: Warnings, treat as error + +:samp:`-gnatwe` + *Treat warnings and style checks as errors.* + + This switch causes warning messages and style check messages to be + treated as errors. + The warning string still appears, but the warning messages are counted + as errors, and prevent the generation of an object file. Note that this + is the only -gnatw switch that affects the handling of style check messages. + Note also that this switch has no effect on info (information) messages, which + are not treated as errors if this switch is present. + + +.. index:: -gnatw.e (gcc) + +:samp:`-gnatw.e` + *Activate every optional warning* + + .. index:: Warnings, activate every optional warning + + This switch activates all optional warnings, including those which + are not activated by `-gnatwa`. The use of this switch is not + recommended for normal use. If you turn this switch on, it is almost + certain that you will get large numbers of useless warnings. The + warnings that are excluded from `-gnatwa` are typically highly + specialized warnings that are suitable for use only in code that has + been specifically designed according to specialized coding rules. + + +.. index:: -gnatwf (gcc) + +:samp:`-gnatwf` + *Activate warnings on unreferenced formals.* + + .. index:: Formals, unreferenced + + This switch causes a warning to be generated if a formal parameter + is not referenced in the body of the subprogram. This warning can + also be turned on using *-gnatwu*. The + default is that these warnings are not generated. + + +.. index:: -gnatwF (gcc) + +:samp:`-gnatwF` + *Suppress warnings on unreferenced formals.* + + This switch suppresses warnings for unreferenced formal + parameters. Note that the + combination *-gnatwu* followed by *-gnatwF* has the + effect of warning on unreferenced entities other than subprogram + formals. + + +.. index:: -gnatwg (gcc) + +:samp:`-gnatwg` + *Activate warnings on unrecognized pragmas.* + + .. index:: Pragmas, unrecognized + + This switch causes a warning to be generated if an unrecognized + pragma is encountered. Apart from issuing this warning, the + pragma is ignored and has no effect. The default + is that such warnings are issued (satisfying the Ada Reference + Manual requirement that such warnings appear). + + +.. index:: -gnatwG (gcc) + +:samp:`-gnatwG` + *Suppress warnings on unrecognized pragmas.* + + This switch suppresses warnings for unrecognized pragmas. + + +.. index:: -gnatw.g (gcc) + +:samp:`-gnatw.g` + *Warnings used for GNAT sources* + + This switch sets the warning categories that are used by the standard + GNAT style. Currently this is equivalent to + *-gnatwAao.sI.C.V.X* + but more warnings may be added in the future without advanced notice. + + +.. index:: -gnatwh (gcc) + +:samp:`-gnatwh` + *Activate warnings on hiding.* + + .. index:: Hiding of Declarations + + This switch activates warnings on hiding declarations. + A declaration is considered hiding + if it is for a non-overloadable entity, and it declares an entity with the + same name as some other entity that is directly or use-visible. The default + is that such warnings are not generated. + + +.. index:: -gnatwH (gcc) + +:samp:`-gnatwH` + *Suppress warnings on hiding.* + + This switch suppresses warnings on hiding declarations. + + +.. index:: -gnatw.h (gcc) + +:samp:`-gnatw.h` + *Activate warnings on holes/gaps in records.* + + .. index:: Record Representation (gaps) + + This switch activates warnings on component clauses in record + representation clauses that leave holes (gaps) in the record layout. + If this warning option is active, then record representation clauses + should specify a contiguous layout, adding unused fill fields if needed. + + +.. index:: -gnatw.H (gcc) + +:samp:`-gnatw.H` + *Suppress warnings on holes/gaps in records.* + + This switch suppresses warnings on component clauses in record + representation clauses that leave holes (haps) in the record layout. + + +.. index:: -gnatwi (gcc) + +:samp:`-gnatwi` + *Activate warnings on implementation units.* + + This switch activates warnings for a |with| of an internal GNAT + implementation unit, defined as any unit from the `Ada`, + `Interfaces`, `GNAT`, + or `System` + hierarchies that is not + documented in either the Ada Reference Manual or the GNAT + Programmer's Reference Manual. Such units are intended only + for internal implementation purposes and should not be |withed| + by user programs. The default is that such warnings are generated + + +.. index:: -gnatwI (gcc) + +:samp:`-gnatwI` + *Disable warnings on implementation units.* + + This switch disables warnings for a |with| of an internal GNAT + implementation unit. + + +.. index:: -gnatw.i (gcc) + +:samp:`-gnatw.i` + *Activate warnings on overlapping actuals.* + + This switch enables a warning on statically detectable overlapping actuals in + a subprogram call, when one of the actuals is an in-out parameter, and the + types of the actuals are not by-copy types. This warning is off by default. + + +.. index:: -gnatw.I (gcc) + +:samp:`-gnatw.I` + *Disable warnings on overlapping actuals.* + + This switch disables warnings on overlapping actuals in a call.. + + +.. index:: -gnatwj (gcc) + +:samp:`-gnatwj` + *Activate warnings on obsolescent features (Annex J).* + + .. index:: Features, obsolescent + + .. index:: Obsolescent features + + If this warning option is activated, then warnings are generated for + calls to subprograms marked with `pragma Obsolescent` and + for use of features in Annex J of the Ada Reference Manual. In the + case of Annex J, not all features are flagged. In particular use + of the renamed packages (like `Text_IO`) and use of package + `ASCII` are not flagged, since these are very common and + would generate many annoying positive warnings. The default is that + such warnings are not generated. + + In addition to the above cases, warnings are also generated for + GNAT features that have been provided in past versions but which + have been superseded (typically by features in the new Ada standard). + For example, `pragma Ravenscar` will be flagged since its + function is replaced by `pragma Profile(Ravenscar)`, and + `pragma Interface_Name` will be flagged since its function + is replaced by `pragma Import`. + + Note that this warning option functions differently from the + restriction `No_Obsolescent_Features` in two respects. + First, the restriction applies only to annex J features. + Second, the restriction does flag uses of package `ASCII`. + + +:samp:`-gnatwJ` + *Suppress warnings on obsolescent features (Annex J).* + .. index:: -gnatwJ (gcc) + + This switch disables warnings on use of obsolescent features. + + +:samp:`-gnatwk` + *Activate warnings on variables that could be constants.* + .. index:: -gnatwk (gcc) + + This switch activates warnings for variables that are initialized but + never modified, and then could be declared constants. The default is that + such warnings are not given. + + +.. index:: -gnatwK (gcc) + +:samp:`-gnatwK` + *Suppress warnings on variables that could be constants.* + + This switch disables warnings on variables that could be declared constants. + + +.. index:: -gnatw.k (gcc) + +:samp:`-gnatw.k` + *Activate warnings on redefinition of names in standard.* + + This switch activates warnings for declarations that declare a name that + is defined in package Standard. Such declarations can be confusing, + especially since the names in package Standard continue to be directly + visible, meaning that use visibiliy on such redeclared names does not + work as expected. Names of discriminants and components in records are + not included in this check. + + +.. index:: -gnatwK (gcc) + +:samp:`-gnatw.K` + *Suppress warnings on redefinition of names in standard.* + + This switch activates warnings for declarations that declare a name that + is defined in package Standard. + + +.. index:: -gnatwl (gcc) + +:samp:`-gnatwl` + *Activate warnings for elaboration pragmas.* + + .. index:: Elaboration, warnings + + This switch activates warnings for possible elaboration problems, + including suspicious use + of `Elaborate` pragmas, when using the static elaboration model, and + possible situations that may raise `Program_Error` when using the + dynamic elaboration model. + See the section in this guide on elaboration checking for further details. + The default is that such warnings + are not generated. + + +.. index:: -gnatwL (gcc) + +:samp:`-gnatwL` + *Suppress warnings for elaboration pragmas.* + + This switch suppresses warnings for possible elaboration problems. + + +.. index:: -gnatw.l (gcc) + +:samp:`-gnatw.l` + *List inherited aspects.* + + This switch causes the compiler to list inherited invariants, + preconditions, and postconditions from Type_Invariant'Class, Invariant'Class, + Pre'Class, and Post'Class aspects. Also list inherited subtype predicates. + + +.. index:: -gnatw.L (gcc) + +:samp:`-gnatw.L` + *Suppress listing of inherited aspects.* + + This switch suppresses listing of inherited aspects. + + +.. index:: -gnatwm (gcc) + +:samp:`-gnatwm` + *Activate warnings on modified but unreferenced variables.* + + This switch activates warnings for variables that are assigned (using + an initialization value or with one or more assignment statements) but + whose value is never read. The warning is suppressed for volatile + variables and also for variables that are renamings of other variables + or for which an address clause is given. + The default is that these warnings are not given. + + +.. index:: -gnatwM (gcc) + +:samp:`-gnatwM` + *Disable warnings on modified but unreferenced variables.* + + This switch disables warnings for variables that are assigned or + initialized, but never read. + + +.. index:: -gnatw.m (gcc) + +:samp:`-gnatw.m` + *Activate warnings on suspicious modulus values.* + + This switch activates warnings for modulus values that seem suspicious. + The cases caught are where the size is the same as the modulus (e.g. + a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64 + with no size clause. The guess in both cases is that 2**x was intended + rather than x. In addition expressions of the form 2*x for small x + generate a warning (the almost certainly accurate guess being that + 2**x was intended). The default is that these warnings are given. + + +.. index:: -gnatw.M (gcc) + +:samp:`-gnatw.M` + *Disable warnings on suspicious modulus values.* + + This switch disables warnings for suspicious modulus values. + + +.. index:: -gnatwn (gcc) + +:samp:`-gnatwn` + *Set normal warnings mode.* + + This switch sets normal warning mode, in which enabled warnings are + issued and treated as warnings rather than errors. This is the default + mode. the switch *-gnatwn* can be used to cancel the effect of + an explicit *-gnatws* or + *-gnatwe*. It also cancels the effect of the + implicit *-gnatwe* that is activated by the + use of *-gnatg*. + + +.. index:: -gnatw.n (gcc) +.. index:: Atomic Synchronization, warnings + +:samp:`-gnatw.n` + *Activate warnings on atomic synchronization.* + + This switch actives warnings when an access to an atomic variable + requires the generation of atomic synchronization code. These + warnings are off by default. + +.. index:: -gnatw.N (gcc) + +:samp:`-gnatw.N` + *Suppress warnings on atomic synchronization.* + + .. index:: Atomic Synchronization, warnings + + This switch suppresses warnings when an access to an atomic variable + requires the generation of atomic synchronization code. + + +.. index:: -gnatwo (gcc) +.. index:: Address Clauses, warnings + +:samp:`-gnatwo` + *Activate warnings on address clause overlays.* + + This switch activates warnings for possibly unintended initialization + effects of defining address clauses that cause one variable to overlap + another. The default is that such warnings are generated. + + +.. index:: -gnatwO (gcc) + +:samp:`-gnatwO` + *Suppress warnings on address clause overlays.* + + This switch suppresses warnings on possibly unintended initialization + effects of defining address clauses that cause one variable to overlap + another. + + +.. index:: -gnatw.o (gcc) + +:samp:`-gnatw.o` + *Activate warnings on modified but unreferenced out parameters.* + + This switch activates warnings for variables that are modified by using + them as actuals for a call to a procedure with an out mode formal, where + the resulting assigned value is never read. It is applicable in the case + where there is more than one out mode formal. If there is only one out + mode formal, the warning is issued by default (controlled by -gnatwu). + The warning is suppressed for volatile + variables and also for variables that are renamings of other variables + or for which an address clause is given. + The default is that these warnings are not given. + + +.. index:: -gnatw.O (gcc) + +:samp:`-gnatw.O` + *Disable warnings on modified but unreferenced out parameters.* + + This switch suppresses warnings for variables that are modified by using + them as actuals for a call to a procedure with an out mode formal, where + the resulting assigned value is never read. + + +.. index:: -gnatwp (gcc) +.. index:: Inlining, warnings + +:samp:`-gnatwp` + *Activate warnings on ineffective pragma Inlines.* + + This switch activates warnings for failure of front end inlining + (activated by *-gnatN*) to inline a particular call. There are + many reasons for not being able to inline a call, including most + commonly that the call is too complex to inline. The default is + that such warnings are not given. + Warnings on ineffective inlining by the gcc back-end can be activated + separately, using the gcc switch -Winline. + + +.. index:: -gnatwP (gcc) + +:samp:`-gnatwP` + *Suppress warnings on ineffective pragma Inlines.* + + This switch suppresses warnings on ineffective pragma Inlines. If the + inlining mechanism cannot inline a call, it will simply ignore the + request silently. + + +.. index:: -gnatw.p (gcc) +.. index:: Parameter order, warnings + +:samp:`-gnatw.p` + *Activate warnings on parameter ordering.* + + This switch activates warnings for cases of suspicious parameter + ordering when the list of arguments are all simple identifiers that + match the names of the formals, but are in a different order. The + warning is suppressed if any use of named parameter notation is used, + so this is the appropriate way to suppress a false positive (and + serves to emphasize that the "misordering" is deliberate). The + default is that such warnings are not given. + + +.. index:: -gnatw.P (gcc) + +:samp:`-gnatw.P` + *Suppress warnings on parameter ordering.* + + This switch suppresses warnings on cases of suspicious parameter + ordering. + + +.. index:: -gnatwq (gcc) +.. index:: Parentheses, warnings + +:samp:`-gnatwq` + *Activate warnings on questionable missing parentheses.* + + This switch activates warnings for cases where parentheses are not used and + the result is potential ambiguity from a readers point of view. For example + (not a > b) when a and b are modular means ((not a) > b) and very likely the + programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and + quite likely ((-x) mod 5) was intended. In such situations it seems best to + follow the rule of always parenthesizing to make the association clear, and + this warning switch warns if such parentheses are not present. The default + is that these warnings are given. + + +.. index:: -gnatwQ (gcc) + +:samp:`-gnatwQ` + *Suppress warnings on questionable missing parentheses.* + + This switch suppresses warnings for cases where the association is not + clear and the use of parentheses is preferred. + + +.. index:: -gnatwr (gcc) + +:samp:`-gnatwr` + *Activate warnings on redundant constructs.* + + This switch activates warnings for redundant constructs. The following + is the current list of constructs regarded as redundant: + + * Assignment of an item to itself. + + * Type conversion that converts an expression to its own type. + + * Use of the attribute `Base` where `typ'Base` is the same + as `typ`. + + * Use of pragma `Pack` when all components are placed by a record + representation clause. + + * Exception handler containing only a reraise statement (raise with no + operand) which has no effect. + + * Use of the operator abs on an operand that is known at compile time + to be non-negative + + * Comparison of boolean expressions to an explicit True value. + + The default is that warnings for redundant constructs are not given. + + +.. index:: -gnatwR (gcc) + +:samp:`-gnatwR` + *Suppress warnings on redundant constructs.* + + This switch suppresses warnings for redundant constructs. + + +.. index:: -gnatw.r (gcc) + +:samp:`-gnatw.r` + *Activate warnings for object renaming function.* + + This switch activates warnings for an object renaming that renames a + function call, which is equivalent to a constant declaration (as + opposed to renaming the function itself). The default is that these + warnings are given. + + +.. index:: -gnatwT (gcc) + +:samp:`-gnatw.R` + *Suppress warnings for object renaming function.* + + This switch suppresses warnings for object renaming function. + + +.. index:: -gnatws (gcc) + +:samp:`-gnatws` + *Suppress all warnings.* + + This switch completely suppresses the + output of all warning messages from the GNAT front end, including + both warnings that can be controlled by switches described in this + section, and those that are normally given unconditionally. The + effect of this suppress action can only be cancelled by a subsequent + use of the switch *-gnatwn*. + + Note that switch *-gnatws* does not suppress + warnings from the *gcc* back end. + To suppress these back end warnings as well, use the switch *-w* + in addition to *-gnatws*. Also this switch has no effect on the + handling of style check messages. + + +.. index:: -gnatw.s (gcc) +.. index:: Record Representation (component sizes) + +:samp:`-gnatw.s` + *Activate warnings on overridden size clauses.* + + This switch activates warnings on component clauses in record + representation clauses where the length given overrides that + specified by an explicit size clause for the component type. A + warning is similarly given in the array case if a specified + component size overrides an explicit size clause for the array + component type. + + +.. index:: -gnatw.S (gcc) + +:samp:`-gnatw.S` + *Suppress warnings on overridden size clauses.* + + This switch suppresses warnings on component clauses in record + representation clauses that override size clauses, and similar + warnings when an array component size overrides a size clause. + + +.. index:: -gnatwt (gcc) +.. index:: Deactivated code, warnings +.. index:: Deleted code, warnings + +:samp:`-gnatwt` + *Activate warnings for tracking of deleted conditional code.* + + This switch activates warnings for tracking of code in conditionals (IF and + CASE statements) that is detected to be dead code which cannot be executed, and + which is removed by the front end. This warning is off by default. This may be + useful for detecting deactivated code in certified applications. + + +.. index:: -gnatwT (gcc) + +:samp:`-gnatwT` + *Suppress warnings for tracking of deleted conditional code.* + + This switch suppresses warnings for tracking of deleted conditional code. + + +.. index:: -gnatw.t (gcc) + +:samp:`-gnatw.t` + *Activate warnings on suspicious contracts.* + + This switch activates warnings on suspicious contracts. This includes + warnings on suspicious postconditions (whether a pragma `Postcondition` or a + `Post` aspect in Ada 2012) and suspicious contract cases (pragma or aspect + `Contract_Cases`). A function postcondition or contract case is suspicious + when no postcondition or contract case for this function mentions the result + of the function. A procedure postcondition or contract case is suspicious + when it only refers to the pre-state of the procedure, because in that case + it should rather be expressed as a precondition. This switch also controls + warnings on suspicious cases of expressions typically found in contracts like + quantified expressions and uses of Update attribute. The default is that such + warnings are generated. + + +.. index:: -gnatw.T (gcc) + +:samp:`-gnatw.T` + *Suppress warnings on suspicious contracts.* + + This switch suppresses warnings on suspicious contracts. + + +.. index:: -gnatwu (gcc) + +:samp:`-gnatwu` + *Activate warnings on unused entities.* + + This switch activates warnings to be generated for entities that + are declared but not referenced, and for units that are |withed| + and not + referenced. In the case of packages, a warning is also generated if + no entities in the package are referenced. This means that if a with'ed + package is referenced but the only references are in `use` + clauses or `renames` + declarations, a warning is still generated. A warning is also generated + for a generic package that is |withed| but never instantiated. + In the case where a package or subprogram body is compiled, and there + is a |with| on the corresponding spec + that is only referenced in the body, + a warning is also generated, noting that the + |with| can be moved to the body. The default is that + such warnings are not generated. + This switch also activates warnings on unreferenced formals + (it includes the effect of *-gnatwf*). + + +.. index:: -gnatwU (gcc) + +:samp:`-gnatwU` + *Suppress warnings on unused entities.* + + This switch suppresses warnings for unused entities and packages. + It also turns off warnings on unreferenced formals (and thus includes + the effect of *-gnatwF*). + + +.. index:: -gnatw.u (gcc) + +:samp:`-gnatw.u` + *Activate warnings on unordered enumeration types.* + + This switch causes enumeration types to be considered as conceptually + unordered, unless an explicit pragma `Ordered` is given for the type. + The effect is to generate warnings in clients that use explicit comparisons + or subranges, since these constructs both treat objects of the type as + ordered. (A *client* is defined as a unit that is other than the unit in + which the type is declared, or its body or subunits.) Please refer to + the description of pragma `Ordered` in the + :title:`GNAT Reference Manual` for further details. + The default is that such warnings are not generated. + + +.. index:: -gnatw.U (gcc) + +:samp:`-gnatw.U` + *Deactivate warnings on unordered enumeration types.* + + This switch causes all enumeration types to be considered as ordered, so + that no warnings are given for comparisons or subranges for any type. + + +.. index:: -gnatwv (gcc) +.. index:: Unassigned variable warnings + +:samp:`-gnatwv` + *Activate warnings on unassigned variables.* + + This switch activates warnings for access to variables which + may not be properly initialized. The default is that + such warnings are generated. + + +.. index:: -gnatwV (gcc) + +:samp:`-gnatwV` + *Suppress warnings on unassigned variables.* + + This switch suppresses warnings for access to variables which + may not be properly initialized. + For variables of a composite type, the warning can also be suppressed in + Ada 2005 by using a default initialization with a box. For example, if + Table is an array of records whose components are only partially uninitialized, + then the following code: + + .. code-block:: ada + + Tab : Table := (others => <>); + + will suppress warnings on subsequent statements that access components + of variable Tab. + + +.. index:: -gnatw.v (gcc) +.. index:: bit order warnings + +:samp:`-gnatw.v` + *Activate info messages for non-default bit order.* + + This switch activates messages (labeled "info", they are not warnings, + just informational messages) about the effects of non-default bit-order + on records to which a component clause is applied. The effect of specifying + non-default bit ordering is a bit subtle (and changed with Ada 2005), so + these messages, which are given by default, are useful in understanding the + exact consequences of using this feature. + + +.. index:: -gnatw.V (gcc) + +:samp:`-gnatw.V` + *Suppress info messages for non-default bit order.* + + This switch suppresses information messages for the effects of specifying + non-default bit order on record components with component clauses. + + +.. index:: -gnatww (gcc) +.. index:: String indexing warnings + +:samp:`-gnatww` + *Activate warnings on wrong low bound assumption.* + + This switch activates warnings for indexing an unconstrained string parameter + with a literal or S'Length. This is a case where the code is assuming that the + low bound is one, which is in general not true (for example when a slice is + passed). The default is that such warnings are generated. + + +.. index:: -gnatwW (gcc) + +:samp:`-gnatwW` + *Suppress warnings on wrong low bound assumption.* + + This switch suppresses warnings for indexing an unconstrained string parameter + with a literal or S'Length. Note that this warning can also be suppressed + in a particular case by adding an assertion that the lower bound is 1, + as shown in the following example: + + .. code-block:: ada + + procedure K (S : String) is + pragma Assert (S'First = 1); + ... + + +.. index:: -gnatw.w (gcc) +.. index:: Warnings Off control + +:samp:`-gnatw.w` + *Activate warnings on Warnings Off pragmas* + + This switch activates warnings for use of `pragma Warnings (Off, entity)` + where either the pragma is entirely useless (because it suppresses no + warnings), or it could be replaced by `pragma Unreferenced` or + `pragma Unmodified`. + Also activates warnings for the case of + Warnings (Off, String), where either there is no matching + Warnings (On, String), or the Warnings (Off) did not suppress any warning. + The default is that these warnings are not given. + + +.. index:: -gnatw.W (gcc) + +:samp:`-gnatw.W` + *Suppress warnings on unnecessary Warnings Off pragmas* + + This switch suppresses warnings for use of `pragma Warnings (Off, ...)`. + + +.. index:: -gnatwx (gcc) +.. index:: Export/Import pragma warnings + +:samp:`-gnatwx` + *Activate warnings on Export/Import pragmas.* + + This switch activates warnings on Export/Import pragmas when + the compiler detects a possible conflict between the Ada and + foreign language calling sequences. For example, the use of + default parameters in a convention C procedure is dubious + because the C compiler cannot supply the proper default, so + a warning is issued. The default is that such warnings are + generated. + + +.. index:: -gnatwX (gcc) + +:samp:`-gnatwX` + *Suppress warnings on Export/Import pragmas.* + + This switch suppresses warnings on Export/Import pragmas. + The sense of this is that you are telling the compiler that + you know what you are doing in writing the pragma, and it + should not complain at you. + + +.. index:: -gnatwm (gcc) + +:samp:`-gnatw.x` + *Activate warnings for No_Exception_Propagation mode.* + + This switch activates warnings for exception usage when pragma Restrictions + (No_Exception_Propagation) is in effect. Warnings are given for implicit or + explicit exception raises which are not covered by a local handler, and for + exception handlers which do not cover a local raise. The default is that these + warnings are not given. + + +:samp:`-gnatw.X` + *Disable warnings for No_Exception_Propagation mode.* + + This switch disables warnings for exception usage when pragma Restrictions + (No_Exception_Propagation) is in effect. + + +.. index:: -gnatwy (gcc) +.. index:: Ada compatibility issues warnings + +:samp:`-gnatwy` + *Activate warnings for Ada compatibility issues.* + + For the most part, newer versions of Ada are upwards compatible + with older versions. For example, Ada 2005 programs will almost + always work when compiled as Ada 2012. + However there are some exceptions (for example the fact that + `some` is now a reserved word in Ada 2012). This + switch activates several warnings to help in identifying + and correcting such incompatibilities. The default is that + these warnings are generated. Note that at one point Ada 2005 + was called Ada 0Y, hence the choice of character. + + +.. index:: -gnatwY (gcc) +.. index:: Ada compatibility issues warnings + +:samp:`-gnatwY` + *Disable warnings for Ada compatibility issues.* + + This switch suppresses the warnings intended to help in identifying + incompatibilities between Ada language versions. + + +.. index:: -gnatw.y (gcc) +.. index:: Package spec needing body + +:samp:`-gnatw.y` + *Activate information messages for why package spec needs body* + + There are a number of cases in which a package spec needs a body. + For example, the use of pragma Elaborate_Body, or the declaration + of a procedure specification requiring a completion. This switch + causes information messages to be output showing why a package + specification requires a body. This can be useful in the case of + a large package specification which is unexpectedly requiring a + body. The default is that such information messages are not output. + + +.. index:: -gnatw.Y (gcc) +.. index:: No information messages for why package spec needs body + +:samp:`-gnatw.Y` + *Disable information messages for why package spec needs body* + + This switch suppresses the output of information messages showing why + a package specification needs a body. + + +.. index:: -gnatwz (gcc) +.. index:: Unchecked_Conversion warnings + +:samp:`-gnatwz` + *Activate warnings on unchecked conversions.* + + This switch activates warnings for unchecked conversions + where the types are known at compile time to have different + sizes. The default is that such warnings are generated. Warnings are also + generated for subprogram pointers with different conventions. + + +.. index:: -gnatwZ (gcc) + +:samp:`-gnatwZ` + *Suppress warnings on unchecked conversions.* + + This switch suppresses warnings for unchecked conversions + where the types are known at compile time to have different + sizes or conventions. + + +.. index:: -gnatw.z (gcc) +.. index:: Size/Alignment warnings + +:samp:`-gnatw.z` + *Activate warnings for size not a multiple of alignment.* + + This switch activates warnings for cases of record types with + specified `Size` and `Alignment` attributes where the + size is not a multiple of the alignment, resulting in an object + size that is greater than the specified size. The default + is that such warnings are generated. + + +.. index:: -gnatw.Z (gcc) +.. index:: Size/Alignment warnings + +:samp:`-gnatw.Z` + *Suppress warnings for size not a multiple of alignment.* + + This switch suppresses warnings for cases of record types with + specified `Size` and `Alignment` attributes where the + size is not a multiple of the alignment, resulting in an object + size that is greater than the specified size. + The warning can also be + suppressed by giving an explicit `Object_Size` value. + + +.. index:: -Wunused (gcc) + +:samp:`-Wunused` + The warnings controlled by the *-gnatw* switch are generated by + the front end of the compiler. The *GCC* back end can provide + additional warnings and they are controlled by the *-W* switch. + For example, *-Wunused* activates back end + warnings for entities that are declared but not referenced. + + +.. index:: -Wuninitialized (gcc) + +:samp:`-Wuninitialized` + Similarly, *-Wuninitialized* activates + the back end warning for uninitialized variables. This switch must be + used in conjunction with an optimization level greater than zero. + + +.. index:: -Wstack-usage (gcc) + +:samp:`-Wstack-usage={len}` + Warn if the stack usage of a subprogram might be larger than `len` bytes. + See :ref:`Static_Stack_Usage_Analysis` for details. + + +.. index:: -Wall (gcc) + +:samp:`-Wall` + This switch enables most warnings from the *GCC* back end. + The code generator detects a number of warning situations that are missed + by the *GNAT* front end, and this switch can be used to activate them. + The use of this switch also sets the default front end warning mode to + *-gnatwa*, that is, most front end warnings activated as well. + + +.. index:: -w (gcc) + +:samp:`-w` + Conversely, this switch suppresses warnings from the *GCC* back end. + The use of this switch also sets the default front end warning mode to + *-gnatws*, that is, front end warnings suppressed as well. + + +.. index:: -Werror (gcc) + +:samp:`-Werror` + This switch causes warnings from the *GCC* back end to be treated as + errors. The warning string still appears, but the warning messages are + counted as errors, and prevent the generation of an object file. + + +A string of warning parameters can be used in the same parameter. For example:: + + -gnatwaGe + + +will turn on all optional warnings except for unrecognized pragma warnings, +and also specify that warnings should be treated as errors. + +When no switch *-gnatw* is used, this is equivalent to: + + * :samp:`-gnatw.a` + + * :samp:`-gnatwB` + + * :samp:`-gnatw.b` + + * :samp:`-gnatwC` + + * :samp:`-gnatw.C` + + * :samp:`-gnatwD` + + * :samp:`-gnatwF` + + * :samp:`-gnatwg` + + * :samp:`-gnatwH` + + * :samp:`-gnatwi` + + * :samp:`-gnatw.I` + + * :samp:`-gnatwJ` + + * :samp:`-gnatwK` + + * :samp:`-gnatwL` + + * :samp:`-gnatw.L` + + * :samp:`-gnatwM` + + * :samp:`-gnatw.m` + + * :samp:`-gnatwn` + + * :samp:`-gnatwo` + + * :samp:`-gnatw.O` + + * :samp:`-gnatwP` + + * :samp:`-gnatw.P` + + * :samp:`-gnatwq` + + * :samp:`-gnatwR` + + * :samp:`-gnatw.R` + + * :samp:`-gnatw.S` + + * :samp:`-gnatwT` + + * :samp:`-gnatw.T` + + * :samp:`-gnatwU` + + * :samp:`-gnatwv` + + * :samp:`-gnatww` + + * :samp:`-gnatw.W` + + * :samp:`-gnatwx` + + * :samp:`-gnatw.X` + + * :samp:`-gnatwy` + + * :samp:`-gnatwz` + +.. _Debugging_and_Assertion_Control: + +Debugging and Assertion Control +------------------------------- + + + +.. index:: -gnata (gcc) + +:samp:`-gnata` + .. index:: Assert + .. index:: Debug + .. index:: Assertions + + The pragmas `Assert` and `Debug` normally have no effect and + are ignored. This switch, where :samp:`a` stands for assert, causes + `Assert` and `Debug` pragmas to be activated. + + The pragmas have the form:: + + pragma Assert ( [, ]) + pragma Debug () + + + The `Assert` pragma causes `Boolean-expression` to be tested. + If the result is `True`, the pragma has no effect (other than + possible side effects from evaluating the expression). If the result is + `False`, the exception `Assert_Failure` declared in the package + `System.Assertions` is + raised (passing `static-string-expression`, if present, as the + message associated with the exception). If no string expression is + given the default is a string giving the file name and line number + of the pragma. + + The `Debug` pragma causes `procedure` to be called. Note that + `pragma Debug` may appear within a declaration sequence, allowing + debugging procedures to be called between declarations. + + +.. _Validity_Checking: + +Validity Checking +----------------- + +.. index:: Validity Checking + +The Ada Reference Manual defines the concept of invalid values (see +RM 13.9.1). The primary source of invalid values is uninitialized +variables. A scalar variable that is left uninitialized may contain +an invalid value; the concept of invalid does not apply to access or +composite types. + +It is an error to read an invalid value, but the RM does not require +run-time checks to detect such errors, except for some minimal +checking to prevent erroneous execution (i.e. unpredictable +behavior). This corresponds to the *-gnatVd* switch below, +which is the default. For example, by default, if the expression of a +case statement is invalid, it will raise Constraint_Error rather than +causing a wild jump, and if an array index on the left-hand side of an +assignment is invalid, it will raise Constraint_Error rather than +overwriting an arbitrary memory location. + +The *-gnatVa* may be used to enable additional validity checks, +which are not required by the RM. These checks are often very +expensive (which is why the RM does not require them). These checks +are useful in tracking down uninitialized variables, but they are +not usually recommended for production builds, and in particular +we do not recommend using these extra validity checking options in +combination with optimization, since this can confuse the optimizer. +If performance is a consideration, leading to the need to optimize, +then the validity checking options should not be used. + +The other *-gnatV*\ ``x`` switches below allow finer-grained +control; you can enable whichever validity checks you desire. However, +for most debugging purposes, *-gnatVa* is sufficient, and the +default *-gnatVd* (i.e. standard Ada behavior) is usually +sufficient for non-debugging use. + +The *-gnatB* switch tells the compiler to assume that all +values are valid (that is, within their declared subtype range) +except in the context of a use of the Valid attribute. This means +the compiler can generate more efficient code, since the range +of values is better known at compile time. However, an uninitialized +variable can cause wild jumps and memory corruption in this mode. + +The *-gnatV*\ ``x`` switch allows control over the validity +checking mode as described below. +The ``x`` argument is a string of letters that +indicate validity checks that are performed or not performed in addition +to the default checks required by Ada as described above. + + +.. index:: -gnatVa (gcc) + +:samp:`-gnatVa` + *All validity checks.* + + All validity checks are turned on. + That is, *-gnatVa* is + equivalent to *gnatVcdfimorst*. + + +.. index:: -gnatVc (gcc) + +:samp:`-gnatVc` + *Validity checks for copies.* + + The right hand side of assignments, and the initializing values of + object declarations are validity checked. + + +.. index:: -gnatVd (gcc) + +:samp:`-gnatVd` + *Default (RM) validity checks.* + + Some validity checks are done by default following normal Ada semantics + (RM 13.9.1 (9-11)). + A check is done in case statements that the expression is within the range + of the subtype. If it is not, Constraint_Error is raised. + For assignments to array components, a check is done that the expression used + as index is within the range. If it is not, Constraint_Error is raised. + Both these validity checks may be turned off using switch *-gnatVD*. + They are turned on by default. If *-gnatVD* is specified, a subsequent + switch *-gnatVd* will leave the checks turned on. + Switch *-gnatVD* should be used only if you are sure that all such + expressions have valid values. If you use this switch and invalid values + are present, then the program is erroneous, and wild jumps or memory + overwriting may occur. + + +.. index:: -gnatVe (gcc) + +:samp:`-gnatVe` + *Validity checks for elementary components.* + + In the absence of this switch, assignments to record or array components are + not validity checked, even if validity checks for assignments generally + (*-gnatVc*) are turned on. In Ada, assignment of composite values do not + require valid data, but assignment of individual components does. So for + example, there is a difference between copying the elements of an array with a + slice assignment, compared to assigning element by element in a loop. This + switch allows you to turn off validity checking for components, even when they + are assigned component by component. + + +.. index:: -gnatVf (gcc) + +:samp:`-gnatVf` + *Validity checks for floating-point values.* + + In the absence of this switch, validity checking occurs only for discrete + values. If *-gnatVf* is specified, then validity checking also applies + for floating-point values, and NaNs and infinities are considered invalid, + as well as out of range values for constrained types. Note that this means + that standard IEEE infinity mode is not allowed. The exact contexts + in which floating-point values are checked depends on the setting of other + options. For example, *-gnatVif* or *-gnatVfi* + (the order does not matter) specifies that floating-point parameters of mode + `in` should be validity checked. + + +.. index:: -gnatVi (gcc) + +:samp:`-gnatVi` + *Validity checks for `in* mode parameters` + + Arguments for parameters of mode `in` are validity checked in function + and procedure calls at the point of call. + + +.. index:: -gnatVm (gcc) + +:samp:`-gnatVm` + *Validity checks for `in out* mode parameters.` + + Arguments for parameters of mode `in out` are validity checked in + procedure calls at the point of call. The `'m'` here stands for + modify, since this concerns parameters that can be modified by the call. + Note that there is no specific option to test `out` parameters, + but any reference within the subprogram will be tested in the usual + manner, and if an invalid value is copied back, any reference to it + will be subject to validity checking. + + +.. index:: -gnatVn (gcc) + +:samp:`-gnatVn` + *No validity checks.* + + This switch turns off all validity checking, including the default checking + for case statements and left hand side subscripts. Note that the use of + the switch *-gnatp* suppresses all run-time checks, including + validity checks, and thus implies *-gnatVn*. When this switch + is used, it cancels any other *-gnatV* previously issued. + + +:samp:`-gnatVo` + *Validity checks for operator and attribute operands.* + .. index:: -gnatVo (gcc) + + Arguments for predefined operators and attributes are validity checked. + This includes all operators in package `Standard`, + the shift operators defined as intrinsic in package `Interfaces` + and operands for attributes such as `Pos`. Checks are also made + on individual component values for composite comparisons, and on the + expressions in type conversions and qualified expressions. Checks are + also made on explicit ranges using :samp:`..` (e.g., slices, loops etc). + + +.. index:: -gnatVp (gcc) + +:samp:`-gnatVp` + *Validity checks for parameters.* + + This controls the treatment of parameters within a subprogram (as opposed + to *-gnatVi* and *-gnatVm* which control validity testing + of parameters on a call. If either of these call options is used, then + normally an assumption is made within a subprogram that the input arguments + have been validity checking at the point of call, and do not need checking + again within a subprogram). If *-gnatVp* is set, then this assumption + is not made, and parameters are not assumed to be valid, so their validity + will be checked (or rechecked) within the subprogram. + + +.. index:: -gnatVr (gcc) + +:samp:`-gnatVr` + *Validity checks for function returns.* + + The expression in `return` statements in functions is validity + checked. + + +.. index:: -gnatVs (gcc) + +:samp:`-gnatVs` + *Validity checks for subscripts.* + + All subscripts expressions are checked for validity, whether they appear + on the right side or left side (in default mode only left side subscripts + are validity checked). + + +.. index:: -gnatVt (gcc) + +:samp:`-gnatVt` + *Validity checks for tests.* + + Expressions used as conditions in `if`, `while` or `exit` + statements are checked, as well as guard expressions in entry calls. + + +The *-gnatV* switch may be followed by a string of letters +to turn on a series of validity checking options. +For example, :samp:`-gnatVcr` +specifies that in addition to the default validity checking, copies and +function return expressions are to be validity checked. +In order to make it easier to specify the desired combination of effects, +the upper case letters `CDFIMORST` may +be used to turn off the corresponding lower case option. +Thus :samp:`-gnatVaM` turns on all validity checking options except for +checking of `**in out**` procedure arguments. + +The specification of additional validity checking generates extra code (and +in the case of *-gnatVa* the code expansion can be substantial). +However, these additional checks can be very useful in detecting +uninitialized variables, incorrect use of unchecked conversion, and other +errors leading to invalid values. The use of pragma `Initialize_Scalars` +is useful in conjunction with the extra validity checking, since this +ensures that wherever possible uninitialized variables have invalid values. + +See also the pragma `Validity_Checks` which allows modification of +the validity checking mode at the program source level, and also allows for +temporary disabling of validity checks. + +.. _Style_Checking: + +Style Checking +-------------- + +.. index:: Style checking + +.. index:: -gnaty (gcc) + +The *-gnatyx* switch causes the compiler to +enforce specified style rules. A limited set of style rules has been used +in writing the GNAT sources themselves. This switch allows user programs +to activate all or some of these checks. If the source program fails a +specified style check, an appropriate message is given, preceded by +the character sequence '(style)'. This message does not prevent +successful compilation (unless the *-gnatwe* switch is used). + +Note that this is by no means intended to be a general facility for +checking arbitrary coding standards. It is simply an embedding of the +style rules we have chosen for the GNAT sources. If you are starting +a project which does not have established style standards, you may +find it useful to adopt the entire set of GNAT coding standards, or +some subset of them. + +.. only:: PRO or GPL + + If you already have an established set of coding + standards, then the selected style checking options may + indeed correspond to choices you have made, but for general checking + of an existing set of coding rules, you should look to the gnatcheck + tool, which is designed for that purpose. + +The string `x` is a sequence of letters or digits +indicating the particular style +checks to be performed. The following checks are defined: + + +.. index:: -gnaty[0-9] (gcc) + +:samp:`-gnaty0` + *Specify indentation level.* + + If a digit from 1-9 appears + in the string after *-gnaty* + then proper indentation is checked, with the digit indicating the + indentation level required. A value of zero turns off this style check. + The general style of required indentation is as specified by + the examples in the Ada Reference Manual. Full line comments must be + aligned with the `--` starting on a column that is a multiple of + the alignment level, or they may be aligned the same way as the following + non-blank line (this is useful when full line comments appear in the middle + of a statement, or they may be aligned with the source line on the previous + non-blank line. + +.. index:: -gnatya (gcc) + +:samp:`-gnatya` + *Check attribute casing.* + + Attribute names, including the case of keywords such as `digits` + used as attributes names, must be written in mixed case, that is, the + initial letter and any letter following an underscore must be uppercase. + All other letters must be lowercase. + + +.. index:: -gnatyA (gcc) + +:samp:`-gnatyA` + *Use of array index numbers in array attributes.* + + When using the array attributes First, Last, Range, + or Length, the index number must be omitted for one-dimensional arrays + and is required for multi-dimensional arrays. + + +.. index:: -gnatyb (gcc) + +:samp:`-gnatyb` + *Blanks not allowed at statement end.* + + Trailing blanks are not allowed at the end of statements. The purpose of this + rule, together with h (no horizontal tabs), is to enforce a canonical format + for the use of blanks to separate source tokens. + + +.. index:: -gnatyB (gcc) + +:samp:`-gnatyB` + *Check Boolean operators.* + + The use of AND/OR operators is not permitted except in the cases of modular + operands, array operands, and simple stand-alone boolean variables or + boolean constants. In all other cases `and then`/`or else` are + required. + + +.. index:: -gnatyc (gcc) + +:samp:`-gnatyc` + *Check comments, double space.* + + Comments must meet the following set of rules: + + * The '`--`' that starts the column must either start in column one, + or else at least one blank must precede this sequence. + + * Comments that follow other tokens on a line must have at least one blank + following the '`--`' at the start of the comment. + + * Full line comments must have at least two blanks following the + '`--`' that starts the comment, with the following exceptions. + + * A line consisting only of the '`--`' characters, possibly preceded + by blanks is permitted. + + * A comment starting with '`--x`' where `x` is a special character + is permitted. + This allows proper processing of the output generated by specialized tools + including *gnatprep* (where '`--!`' is used) and the SPARK + annotation + language (where '`--#`' is used). For the purposes of this rule, a + special character is defined as being in one of the ASCII ranges + `16#21#...16#2F#` or `16#3A#...16#3F#`. + Note that this usage is not permitted + in GNAT implementation units (i.e., when *-gnatg* is used). + + * A line consisting entirely of minus signs, possibly preceded by blanks, is + permitted. This allows the construction of box comments where lines of minus + signs are used to form the top and bottom of the box. + + * A comment that starts and ends with '`--`' is permitted as long as at + least one blank follows the initial '`--`'. Together with the preceding + rule, this allows the construction of box comments, as shown in the following + example: + + .. code-block:: ada + + --------------------------- + -- This is a box comment -- + -- with two text lines. -- + --------------------------- + + +.. index:: -gnatyC (gcc) + +:samp:`-gnatyC` + *Check comments, single space.* + + This is identical to `c` except that only one space + is required following the `--` of a comment instead of two. + + +.. index:: -gnatyd (gcc) + +:samp:`-gnatyd` + *Check no DOS line terminators present.* + + All lines must be terminated by a single ASCII.LF + character (in particular the DOS line terminator sequence CR/LF is not + allowed). + + +.. index:: -gnatye (gcc) + +:samp:`-gnatye` + *Check end/exit labels.* + + Optional labels on `end` statements ending subprograms and on + `exit` statements exiting named loops, are required to be present. + + +.. index:: -gnatyf (gcc) + +:samp:`-gnatyf` + *No form feeds or vertical tabs.* + + Neither form feeds nor vertical tab characters are permitted + in the source text. + + +.. index:: -gnatyg (gcc) + +:samp:`-gnatyg` + *GNAT style mode.* + + The set of style check switches is set to match that used by the GNAT sources. + This may be useful when developing code that is eventually intended to be + incorporated into GNAT. Currently this is equivalent to *-gnatwydISux*) + but additional style switches may be added to this set in the future without + advance notice. + + +.. index:: -gnatyh (gcc) + +:samp:`-gnatyh` + *No horizontal tabs.* + + Horizontal tab characters are not permitted in the source text. + Together with the b (no blanks at end of line) check, this + enforces a canonical form for the use of blanks to separate + source tokens. + + +.. index:: -gnatyi (gcc) + +:samp:`-gnatyi` + *Check if-then layout.* + + The keyword `then` must appear either on the same + line as corresponding `if`, or on a line on its own, lined + up under the `if`. + + +.. index:: -gnatyI (gcc) + +:samp:`-gnatyI` + *check mode IN keywords.* + + Mode `in` (the default mode) is not + allowed to be given explicitly. `in out` is fine, + but not `in` on its own. + + +.. index:: -gnatyk (gcc) + +:samp:`-gnatyk` + *Check keyword casing.* + + All keywords must be in lower case (with the exception of keywords + such as `digits` used as attribute names to which this check + does not apply). + + +.. index:: -gnatyl (gcc) + +:samp:`-gnatyl` + *Check layout.* + + Layout of statement and declaration constructs must follow the + recommendations in the Ada Reference Manual, as indicated by the + form of the syntax rules. For example an `else` keyword must + be lined up with the corresponding `if` keyword. + + There are two respects in which the style rule enforced by this check + option are more liberal than those in the Ada Reference Manual. First + in the case of record declarations, it is permissible to put the + `record` keyword on the same line as the `type` keyword, and + then the `end` in `end record` must line up under `type`. + This is also permitted when the type declaration is split on two lines. + For example, any of the following three layouts is acceptable: + + .. code-block:: ada + + type q is record + a : integer; + b : integer; + end record; + + type q is + record + a : integer; + b : integer; + end record; + + type q is + record + a : integer; + b : integer; + end record; + + Second, in the case of a block statement, a permitted alternative + is to put the block label on the same line as the `declare` or + `begin` keyword, and then line the `end` keyword up under + the block label. For example both the following are permitted: + + .. code-block:: ada + + Block : declare + A : Integer := 3; + begin + Proc (A, A); + end Block; + + Block : + declare + A : Integer := 3; + begin + Proc (A, A); + end Block; + + The same alternative format is allowed for loops. For example, both of + the following are permitted: + + .. code-block:: ada + + Clear : while J < 10 loop + A (J) := 0; + end loop Clear; + + Clear : + while J < 10 loop + A (J) := 0; + end loop Clear; + + +.. index:: -gnatyLnnn (gcc) + +:samp:`-gnatyL` + *Set maximum nesting level.* + + The maximum level of nesting of constructs (including subprograms, loops, + blocks, packages, and conditionals) may not exceed the given value + *nnn*. A value of zero disconnects this style check. + + +.. index:: -gnatym (gcc) + +:samp:`-gnatym` + *Check maximum line length.* + + The length of source lines must not exceed 79 characters, including + any trailing blanks. The value of 79 allows convenient display on an + 80 character wide device or window, allowing for possible special + treatment of 80 character lines. Note that this count is of + characters in the source text. This means that a tab character counts + as one character in this count and a wide character sequence counts as + a single character (however many bytes are needed in the encoding). + + +.. index:: -gnatyMnnn (gcc) + +:samp:`-gnatyM` + *Set maximum line length.* + + The length of lines must not exceed the + given value *nnn*. The maximum value that can be specified is 32767. + If neither style option for setting the line length is used, then the + default is 255. This also controls the maximum length of lexical elements, + where the only restriction is that they must fit on a single line. + + +.. index:: -gnatyn (gcc) + +:samp:`-gnatyn` + *Check casing of entities in Standard.* + + Any identifier from Standard must be cased + to match the presentation in the Ada Reference Manual (for example, + `Integer` and `ASCII.NUL`). + + +.. index:: -gnatyN (gcc) + +:samp:`-gnatyN` + *Turn off all style checks.* + + All style check options are turned off. + + +.. index:: -gnatyo (gcc) + +:samp:`-gnatyo` + *Check order of subprogram bodies.* + + All subprogram bodies in a given scope + (e.g., a package body) must be in alphabetical order. The ordering + rule uses normal Ada rules for comparing strings, ignoring casing + of letters, except that if there is a trailing numeric suffix, then + the value of this suffix is used in the ordering (e.g., Junk2 comes + before Junk10). + + +.. index:: -gnatyO (gcc) + +:samp:`-gnatyO` + *Check that overriding subprograms are explicitly marked as such.* + + The declaration of a primitive operation of a type extension that overrides + an inherited operation must carry an overriding indicator. + + +.. index:: -gnatyp (gcc) + +:samp:`-gnatyp` + *Check pragma casing.* + + Pragma names must be written in mixed case, that is, the + initial letter and any letter following an underscore must be uppercase. + All other letters must be lowercase. An exception is that SPARK_Mode is + allowed as an alternative for Spark_Mode. + + +.. index:: -gnatyr (gcc) + +:samp:`-gnatyr` + *Check references.* + + All identifier references must be cased in the same way as the + corresponding declaration. No specific casing style is imposed on + identifiers. The only requirement is for consistency of references + with declarations. + + +.. index:: -gnatys (gcc) + +:samp:`-gnatys` + *Check separate specs.* + + Separate declarations ('specs') are required for subprograms (a + body is not allowed to serve as its own declaration). The only + exception is that parameterless library level procedures are + not required to have a separate declaration. This exception covers + the most frequent form of main program procedures. + + +.. index:: -gnatyS (gcc) + +:samp:`-gnatyS` + *Check no statements after then/else.* + + No statements are allowed + on the same line as a `then` or `else` keyword following the + keyword in an `if` statement. `or else` and `and then` are not + affected, and a special exception allows a pragma to appear after `else`. + + +.. index:: -gnatyt (gcc) + +:samp:`-gnatyt` + *Check token spacing.* + + The following token spacing rules are enforced: + + * The keywords `abs` and `not` must be followed by a space. + + * The token `=>` must be surrounded by spaces. + + * The token `<>` must be preceded by a space or a left parenthesis. + + * Binary operators other than `**` must be surrounded by spaces. + There is no restriction on the layout of the `**` binary operator. + + * Colon must be surrounded by spaces. + + * Colon-equal (assignment, initialization) must be surrounded by spaces. + + * Comma must be the first non-blank character on the line, or be + immediately preceded by a non-blank character, and must be followed + by a space. + + * If the token preceding a left parenthesis ends with a letter or digit, then + a space must separate the two tokens. + + * If the token following a right parenthesis starts with a letter or digit, then + a space must separate the two tokens. + + * A right parenthesis must either be the first non-blank character on + a line, or it must be preceded by a non-blank character. + + * A semicolon must not be preceded by a space, and must not be followed by + a non-blank character. + + * A unary plus or minus may not be followed by a space. + + * A vertical bar must be surrounded by spaces. + + Exactly one blank (and no other white space) must appear between + a `not` token and a following `in` token. + + +.. index:: -gnatyu (gcc) + +:samp:`-gnatyu` + *Check unnecessary blank lines.* + + Unnecessary blank lines are not allowed. A blank line is considered + unnecessary if it appears at the end of the file, or if more than + one blank line occurs in sequence. + + +.. index:: -gnatyx (gcc) + +:samp:`-gnatyx` + *Check extra parentheses.* + + Unnecessary extra level of parentheses (C-style) are not allowed + around conditions in `if` statements, `while` statements and + `exit` statements. + + +.. index:: -gnatyy (gcc) + +:samp:`-gnatyy` + *Set all standard style check options* + + This is equivalent to `gnaty3aAbcefhiklmnprst`, that is all checking + options enabled with the exception of *-gnatyB*, *-gnatyd*, + *-gnatyI*, *-gnatyLnnn*, *-gnatyo*, *-gnatyO*, + *-gnatyS*, *-gnatyu*, and *-gnatyx*. + + +.. index:: -gnaty- (gcc) + +:samp:`-gnaty-` + *Remove style check options* + + This causes any subsequent options in the string to act as canceling the + corresponding style check option. To cancel maximum nesting level control, + use *L* parameter witout any integer value after that, because any + digit following *-* in the parameter string of the *-gnaty* + option will be threated as canceling indentation check. The same is true + for *M* parameter. *y* and *N* parameters are not + allowed after *-*. + + +.. index:: -gnaty+ (gcc) + +:samp:`-gnaty+` + *Enable style check options* + + This causes any subsequent options in the string to enable the corresponding + style check option. That is, it cancels the effect of a previous -, + if any. + + +.. end of switch description (leave this comment to ease automatic parsing for +.. GPS + +In the above rules, appearing in column one is always permitted, that is, +counts as meeting either a requirement for a required preceding space, +or as meeting a requirement for no preceding space. + +Appearing at the end of a line is also always permitted, that is, counts +as meeting either a requirement for a following space, or as meeting +a requirement for no following space. + +If any of these style rules is violated, a message is generated giving +details on the violation. The initial characters of such messages are +always '`(style)`'. Note that these messages are treated as warning +messages, so they normally do not prevent the generation of an object +file. The *-gnatwe* switch can be used to treat warning messages, +including style messages, as fatal errors. + +The switch :samp:`-gnaty` on its own (that is not +followed by any letters or digits) is equivalent +to the use of *-gnatyy* as described above, that is all +built-in standard style check options are enabled. + +The switch :samp:`-gnatyN` clears any previously set style checks. + +.. _Run-Time_Checks: + +Run-Time Checks +--------------- + +.. index:: Division by zero + +.. index:: Access before elaboration + +.. index:: Checks, division by zero + +.. index:: Checks, access before elaboration + +.. index:: Checks, stack overflow checking + +By default, the following checks are suppressed: integer overflow +checks, stack overflow checks, and checks for access before +elaboration on subprogram calls. All other checks, including range +checks and array bounds checks, are turned on by default. The +following *gcc* switches refine this default behavior. + +.. index:: -gnatp (gcc) + +:samp:`-gnatp` + .. index:: Suppressing checks + + .. index:: Checks, suppressing + + This switch causes the unit to be compiled + as though `pragma Suppress (All_checks)` + had been present in the source. Validity checks are also eliminated (in + other words *-gnatp* also implies *-gnatVn*. + Use this switch to improve the performance + of the code at the expense of safety in the presence of invalid data or + program bugs. + + Note that when checks are suppressed, the compiler is allowed, but not + required, to omit the checking code. If the run-time cost of the + checking code is zero or near-zero, the compiler will generate it even + if checks are suppressed. In particular, if the compiler can prove + that a certain check will necessarily fail, it will generate code to + do an unconditional 'raise', even if checks are suppressed. The + compiler warns in this case. Another case in which checks may not be + eliminated is when they are embedded in certain run time routines such + as math library routines. + + Of course, run-time checks are omitted whenever the compiler can prove + that they will not fail, whether or not checks are suppressed. + + Note that if you suppress a check that would have failed, program + execution is erroneous, which means the behavior is totally + unpredictable. The program might crash, or print wrong answers, or + do anything else. It might even do exactly what you wanted it to do + (and then it might start failing mysteriously next week or next + year). The compiler will generate code based on the assumption that + the condition being checked is true, which can result in erroneous + execution if that assumption is wrong. + + The checks subject to suppression include all the checks defined by + the Ada standard, the additional implementation defined checks + `Alignment_Check`, + `Duplicated_Tag_Check`, `Predicate_Check`, and + `Validity_Check`, as well as any checks introduced using + `pragma Check_Name`. Note that `Atomic_Synchronization` + is not automatically suppressed by use of this option. + + If the code depends on certain checks being active, you can use + pragma `Unsuppress` either as a configuration pragma or as + a local pragma to make sure that a specified check is performed + even if *gnatp* is specified. + + The *-gnatp* switch has no effect if a subsequent + *-gnat-p* switch appears. + + +.. index:: -gnat-p (gcc) +.. index:: Suppressing checks +.. index:: Checks, suppressing +.. index:: Suppress + +:samp:`-gnat-p` + This switch cancels the effect of a previous *gnatp* switch. + + +.. index:: -gnato?? (gcc) +.. index:: Overflow checks +.. index:: Overflow mode +.. index:: Check, overflow + +:samp:`-gnato??` + This switch controls the mode used for computing intermediate + arithmetic integer operations, and also enables overflow checking. + For a full description of overflow mode and checking control, see + the 'Overflow Check Handling in GNAT' appendix in this + User's Guide. + + Overflow checks are always enabled by this switch. The argument + controls the mode, using the codes + + + *1 = STRICT* + In STRICT mode, intermediate operations are always done using the + base type, and overflow checking ensures that the result is within + the base type range. + + + *2 = MINIMIZED* + In MINIMIZED mode, overflows in intermediate operations are avoided + where possible by using a larger integer type for the computation + (typically `Long_Long_Integer`). Overflow checking ensures that + the result fits in this larger integer type. + + + *3 = ELIMINATED* + In ELIMINATED mode, overflows in intermediate operations are avoided + by using multi-precision arithmetic. In this case, overflow checking + has no effect on intermediate operations (since overflow is impossible). + + If two digits are present after *-gnato* then the first digit + sets the mode for expressions outside assertions, and the second digit + sets the mode for expressions within assertions. Here assertions is used + in the technical sense (which includes for example precondition and + postcondition expressions). + + If one digit is present, the corresponding mode is applicable to both + expressions within and outside assertion expressions. + + If no digits are present, the default is to enable overflow checks + and set STRICT mode for both kinds of expressions. This is compatible + with the use of *-gnato* in previous versions of GNAT. + + .. index:: Machine_Overflows + + Note that the *-gnato??* switch does not affect the code generated + for any floating-point operations; it applies only to integer semantics. + For floating-point, GNAT has the `Machine_Overflows` + attribute set to `False` and the normal mode of operation is to + generate IEEE NaN and infinite values on overflow or invalid operations + (such as dividing 0.0 by 0.0). + + The reason that we distinguish overflow checking from other kinds of + range constraint checking is that a failure of an overflow check, unlike + for example the failure of a range check, can result in an incorrect + value, but cannot cause random memory destruction (like an out of range + subscript), or a wild jump (from an out of range case value). Overflow + checking is also quite expensive in time and space, since in general it + requires the use of double length arithmetic. + + Note again that the default is *-gnato00*, + so overflow checking is not performed in default mode. This means that out of + the box, with the default settings, GNAT does not do all the checks + expected from the language description in the Ada Reference Manual. + If you want all constraint checks to be performed, as described in this Manual, + then you must explicitly use the *-gnato??* + switch either on the *gnatmake* or *gcc* command. + + +.. index:: -gnatE (gcc) +.. index:: Elaboration checks +.. index:: Check, elaboration + +:samp:`-gnatE` + Enables dynamic checks for access-before-elaboration + on subprogram calls and generic instantiations. + Note that *-gnatE* is not necessary for safety, because in the + default mode, GNAT ensures statically that the checks would not fail. + For full details of the effect and use of this switch, + :ref:`Compiling_with_gcc`. + + +.. index:: -fstack-check (gcc) +.. index:: Stack Overflow Checking +.. index:: Checks, stack overflow checking + +:samp:`-fstack-check` + Activates stack overflow checking. For full details of the effect and use of + this switch see :ref:`Stack_Overflow_Checking`. + +.. index:: Unsuppress + +The setting of these switches only controls the default setting of the +checks. You may modify them using either `Suppress` (to remove +checks) or `Unsuppress` (to add back suppressed checks) pragmas in +the program source. + + +.. _Using_gcc_for_Syntax_Checking: + +Using *gcc* for Syntax Checking +------------------------------- + +.. index:: -gnats (gcc) + +:samp:`-gnats` + The `s` stands for 'syntax'. + + Run GNAT in syntax checking only mode. For + example, the command + + :: + + $ gcc -c -gnats x.adb + + compiles file :file:`x.adb` in syntax-check-only mode. You can check a + series of files in a single command + , and can use wild cards to specify such a group of files. + Note that you must specify the *-c* (compile + only) flag in addition to the *-gnats* flag. + + You may use other switches in conjunction with *-gnats*. In + particular, *-gnatl* and *-gnatv* are useful to control the + format of any generated error messages. + + When the source file is empty or contains only empty lines and/or comments, + the output is a warning: + + + :: + + $ gcc -c -gnats -x ada toto.txt + toto.txt:1:01: warning: empty file, contains no compilation units + $ + + + Otherwise, the output is simply the error messages, if any. No object file or + ALI file is generated by a syntax-only compilation. Also, no units other + than the one specified are accessed. For example, if a unit `X` + |withs| a unit `Y`, compiling unit `X` in syntax + check only mode does not access the source file containing unit + `Y`. + + .. index:: Multiple units, syntax checking + + Normally, GNAT allows only a single unit in a source file. However, this + restriction does not apply in syntax-check-only mode, and it is possible + to check a file containing multiple compilation units concatenated + together. This is primarily used by the `gnatchop` utility + (:ref:`Renaming_Files_with_gnatchop`). + +.. _Using_gcc_for_Semantic_Checking: + +Using *gcc* for Semantic Checking +--------------------------------- + + + +.. index:: -gnatc (gcc) + +:samp:`-gnatc` + The `c` stands for 'check'. + Causes the compiler to operate in semantic check mode, + with full checking for all illegalities specified in the + Ada Reference Manual, but without generation of any object code + (no object file is generated). + + Because dependent files must be accessed, you must follow the GNAT + semantic restrictions on file structuring to operate in this mode: + + * The needed source files must be accessible + (see :ref:`Search_Paths_and_the_Run-Time_Library_RTL`). + + * Each file must contain only one compilation unit. + + * The file name and unit name must match (:ref:`File_Naming_Rules`). + + The output consists of error messages as appropriate. No object file is + generated. An :file:`ALI` file is generated for use in the context of + cross-reference tools, but this file is marked as not being suitable + for binding (since no object file is generated). + The checking corresponds exactly to the notion of + legality in the Ada Reference Manual. + + Any unit can be compiled in semantics-checking-only mode, including + units that would not normally be compiled (subunits, + and specifications where a separate body is present). + +.. _Compiling_Different_Versions_of_Ada: + +Compiling Different Versions of Ada +----------------------------------- + +The switches described in this section allow you to explicitly specify +the version of the Ada language that your programs are written in. +The default mode is Ada 2012, +but you can also specify Ada 95, Ada 2005 mode, or +indicate Ada 83 compatibility mode. + + +.. index:: Compatibility with Ada 83 +.. index:: -gnat83 (gcc) +.. index:: ACVC, Ada 83 tests +.. index:: Ada 83 mode + +:samp:`-gnat83 (Ada 83 Compatibility Mode)` + Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch + specifies that the program is to be compiled in Ada 83 mode. With + *-gnat83*, GNAT rejects most post-Ada 83 extensions and applies Ada 83 + semantics where this can be done easily. + It is not possible to guarantee this switch does a perfect + job; some subtle tests, such as are + found in earlier ACVC tests (and that have been removed from the ACATS suite + for Ada 95), might not compile correctly. + Nevertheless, this switch may be useful in some circumstances, for example + where, due to contractual reasons, existing code needs to be maintained + using only Ada 83 features. + + With few exceptions (most notably the need to use `<>` on + .. index:: Generic formal parameters + + unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005 + reserved words, and the use of packages + with optional bodies), it is not necessary to specify the + *-gnat83* switch when compiling Ada 83 programs, because, with rare + exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus + a correct Ada 83 program is usually also a correct program + in these later versions of the language standard. For further information + please refer to the `Compatibility_and_Porting_Guide` chapter in the + :title:`GNAT Reference Manual`. + + +.. index:: -gnat95 (gcc) +.. index:: Ada 95 mode + +:samp:`-gnat95` (Ada 95 mode) + This switch directs the compiler to implement the Ada 95 version of the + language. + Since Ada 95 is almost completely upwards + compatible with Ada 83, Ada 83 programs may generally be compiled using + this switch (see the description of the *-gnat83* switch for further + information about Ada 83 mode). + If an Ada 2005 program is compiled in Ada 95 mode, + uses of the new Ada 2005 features will cause error + messages or warnings. + + This switch also can be used to cancel the effect of a previous + *-gnat83*, *-gnat05/2005*, or *-gnat12/2012* + switch earlier in the command line. + + +.. index:: -gnat05 (gcc) +.. index:: -gnat2005 (gcc) +.. index:: Ada 2005 mode + +:samp:`-gnat05` or :samp:`-gnat2005` (Ada 2005 mode) + This switch directs the compiler to implement the Ada 2005 version of the + language, as documented in the official Ada standards document. + Since Ada 2005 is almost completely upwards + compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs + may generally be compiled using this switch (see the description of the + *-gnat83* and *-gnat95* switches for further + information). + + +.. index:: -gnat12 (gcc) +.. index:: -gnat2012 (gcc) +.. index:: Ada 2012 mode + +:samp:`-gnat12` or :samp:`-gnat2012` (Ada 2012 mode) + This switch directs the compiler to implement the Ada 2012 version of the + language (also the default). + Since Ada 2012 is almost completely upwards + compatible with Ada 2005 (and thus also with Ada 83, and Ada 95), + Ada 83 and Ada 95 programs + may generally be compiled using this switch (see the description of the + *-gnat83*, *-gnat95*, and *-gnat05/2005* switches + for further information). + + +.. index:: -gnatX (gcc) +.. index:: Ada language extensions +.. index:: GNAT extensions + +:samp:`-gnatX` (Enable GNAT Extensions) + This switch directs the compiler to implement the latest version of the + language (currently Ada 2012) and also to enable certain GNAT implementation + extensions that are not part of any Ada standard. For a full list of these + extensions, see the GNAT reference manual. + + +.. _Character_Set_Control: + +Character Set Control +--------------------- + +.. index:: -gnati (gcc) + +:samp:`-gnati{c}` + Normally GNAT recognizes the Latin-1 character set in source program + identifiers, as described in the Ada Reference Manual. + This switch causes + GNAT to recognize alternate character sets in identifiers. `c` is a + single character indicating the character set, as follows: + + ========== ====================================================== + *1* ISO 8859-1 (Latin-1) identifiers + *2* ISO 8859-2 (Latin-2) letters allowed in identifiers + *3* ISO 8859-3 (Latin-3) letters allowed in identifiers + *4* ISO 8859-4 (Latin-4) letters allowed in identifiers + *5* ISO 8859-5 (Cyrillic) letters allowed in identifiers + *9* ISO 8859-15 (Latin-9) letters allowed in identifiers + *p* IBM PC letters (code page 437) allowed in identifiers + *8* IBM PC letters (code page 850) allowed in identifiers + *f* Full upper-half codes allowed in identifiers + *n* No upper-half codes allowed in identifiers + *w* Wide-character codes (that is, codes greater than 255) + allowed in identifiers + ========== ====================================================== + + See :ref:`Foreign_Language_Representation` for full details on the + implementation of these character sets. + + +.. index:: -gnatW (gcc) + +:samp:`-gnatW{e}` + Specify the method of encoding for wide characters. + `e` is one of the following: + + ========== ====================================================== + *h* Hex encoding (brackets coding also recognized) + *u* Upper half encoding (brackets encoding also recognized) + *s* Shift/JIS encoding (brackets encoding also recognized) + *e* EUC encoding (brackets encoding also recognized) + *8* UTF-8 encoding (brackets encoding also recognized) + *b* Brackets encoding only (default value) + ========== ====================================================== + + For full details on these encoding + methods see :ref:`Wide_Character_Encodings`. + Note that brackets coding is always accepted, even if one of the other + options is specified, so for example *-gnatW8* specifies that both + brackets and UTF-8 encodings will be recognized. The units that are + with'ed directly or indirectly will be scanned using the specified + representation scheme, and so if one of the non-brackets scheme is + used, it must be used consistently throughout the program. However, + since brackets encoding is always recognized, it may be conveniently + used in standard libraries, allowing these libraries to be used with + any of the available coding schemes. + + Note that brackets encoding only applies to program text. Within comments, + brackets are considered to be normal graphic characters, and bracket sequences + are never recognized as wide characters. + + If no *-gnatW?* parameter is present, then the default + representation is normally Brackets encoding only. However, if the + first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard + byte order mark or BOM for UTF-8), then these three characters are + skipped and the default representation for the file is set to UTF-8. + + Note that the wide character representation that is specified (explicitly + or by default) for the main program also acts as the default encoding used + for Wide_Text_IO files if not specifically overridden by a WCEM form + parameter. + + +When no *-gnatW?* is specified, then characters (other than wide +characters represented using brackets notation) are treated as 8-bit +Latin-1 codes. The codes recognized are the Latin-1 graphic characters, +and ASCII format effectors (CR, LF, HT, VT). Other lower half control +characters in the range 16#00#..16#1F# are not accepted in program text +or in comments. Upper half control characters (16#80#..16#9F#) are rejected +in program text, but allowed and ignored in comments. Note in particular +that the Next Line (NEL) character whose encoding is 16#85# is not recognized +as an end of line in this default mode. If your source program contains +instances of the NEL character used as a line terminator, +you must use UTF-8 encoding for the whole +source program. In default mode, all lines must be ended by a standard +end of line sequence (CR, CR/LF, or LF). + +Note that the convention of simply accepting all upper half characters in +comments means that programs that use standard ASCII for program text, but +UTF-8 encoding for comments are accepted in default mode, providing that the +comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator. +This is a common mode for many programs with foreign language comments. + +.. _File_Naming_Control: + +File Naming Control +------------------- + +.. index:: -gnatk (gcc) + +:samp:`-gnatk{n}` + Activates file name 'krunching'. `n`, a decimal integer in the range + 1-999, indicates the maximum allowable length of a file name (not + including the :file:`.ads` or :file:`.adb` extension). The default is not + to enable file name krunching. + + For the source file naming rules, :ref:`File_Naming_Rules`. + +.. _Subprogram_Inlining_Control: + +Subprogram Inlining Control +--------------------------- + +.. index:: -gnatn (gcc) + +:samp:`-gnatn[12]` + The `n` here is intended to suggest the first syllable of the + word 'inline'. + GNAT recognizes and processes `Inline` pragmas. However, for the + inlining to actually occur, optimization must be enabled and, in order + to enable inlining of subprograms specified by pragma `Inline`, + you must also specify this switch. + In the absence of this switch, GNAT does not attempt + inlining and does not need to access the bodies of + subprograms for which `pragma Inline` is specified if they are not + in the current unit. + + You can optionally specify the inlining level: 1 for moderate inlining across + modules, which is a good compromise between compilation times and performances + at run time, or 2 for full inlining across modules, which may bring about + longer compilation times. If no inlining level is specified, the compiler will + pick it based on the optimization level: 1 for *-O1*, *-O2* or + *-Os* and 2 for *-O3*. + + If you specify this switch the compiler will access these bodies, + creating an extra source dependency for the resulting object file, and + where possible, the call will be inlined. + For further details on when inlining is possible + see :ref:`Inlining_of_Subprograms`. + + +.. index:: -gnatN (gcc) + +:samp:`-gnatN` + This switch activates front-end inlining which also + generates additional dependencies. + + When using a gcc-based back end (in practice this means using any version + of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of + *-gnatN* is deprecated, and the use of *-gnatn* is preferred. + Historically front end inlining was more extensive than the gcc back end + inlining, but that is no longer the case. + +.. _Auxiliary_Output_Control: + +Auxiliary Output Control +------------------------ + +.. index:: -gnatt (gcc) +.. index:: Writing internal trees +.. index:: Internal trees, writing to file + +:samp:`-gnatt` + Causes GNAT to write the internal tree for a unit to a file (with the + extension :file:`.adt`. + This not normally required, but is used by separate analysis tools. + Typically + these tools do the necessary compilations automatically, so you should + not have to specify this switch in normal operation. + Note that the combination of switches *-gnatct* + generates a tree in the form required by ASIS applications. + + +.. index:: -gnatu (gcc) + +:samp:`-gnatu` + Print a list of units required by this compilation on :file:`stdout`. + The listing includes all units on which the unit being compiled depends + either directly or indirectly. + + +.. index:: -pass-exit-codes (gcc) + +:samp:`-pass-exit-codes` + If this switch is not used, the exit code returned by *gcc* when + compiling multiple files indicates whether all source files have + been successfully used to generate object files or not. + + When *-pass-exit-codes* is used, *gcc* exits with an extended + exit status and allows an integrated development environment to better + react to a compilation failure. Those exit status are: + + ========== ====================================================== + *5* There was an error in at least one source file. + *3* At least one source file did not generate an object file. + *2* The compiler died unexpectedly (internal error for example). + *0* An object file has been generated for every source file. + ========== ====================================================== + +.. _Debugging_Control: + +Debugging Control +----------------- + + .. index:: Debugging options + + +.. index:: -gnatd (gcc) + +:samp:`-gnatd{x}` + Activate internal debugging switches. `x` is a letter or digit, or + string of letters or digits, which specifies the type of debugging + outputs desired. Normally these are used only for internal development + or system debugging purposes. You can find full documentation for these + switches in the body of the `Debug` unit in the compiler source + file :file:`debug.adb`. + + +.. index:: -gnatG (gcc) + +:samp:`-gnatG[={nn}]` + This switch causes the compiler to generate auxiliary output containing + a pseudo-source listing of the generated expanded code. Like most Ada + compilers, GNAT works by first transforming the high level Ada code into + lower level constructs. For example, tasking operations are transformed + into calls to the tasking run-time routines. A unique capability of GNAT + is to list this expanded code in a form very close to normal Ada source. + This is very useful in understanding the implications of various Ada + usage on the efficiency of the generated code. There are many cases in + Ada (e.g., the use of controlled types), where simple Ada statements can + generate a lot of run-time code. By using *-gnatG* you can identify + these cases, and consider whether it may be desirable to modify the coding + approach to improve efficiency. + + The optional parameter `nn` if present after -gnatG specifies an + alternative maximum line length that overrides the normal default of 72. + This value is in the range 40-999999, values less than 40 being silently + reset to 40. The equal sign is optional. + + The format of the output is very similar to standard Ada source, and is + easily understood by an Ada programmer. The following special syntactic + additions correspond to low level features used in the generated code that + do not have any exact analogies in pure Ada source form. The following + is a partial list of these special constructions. See the spec + of package `Sprint` in file :file:`sprint.ads` for a full list. + + .. index:: -gnatL (gcc) + + If the switch *-gnatL* is used in conjunction with + *-gnatG*, then the original source lines are interspersed + in the expanded source (as comment lines with the original line number). + + :samp:`new {xxx} [storage_pool = {yyy}]` + Shows the storage pool being used for an allocator. + + + :samp:`at end {procedure-name};` + Shows the finalization (cleanup) procedure for a scope. + + + :samp:`(if {expr} then {expr} else {expr})` + Conditional expression equivalent to the `x?y:z` construction in C. + + + :samp:`{target}^({source})` + A conversion with floating-point truncation instead of rounding. + + + :samp:`{target}?({source})` + A conversion that bypasses normal Ada semantic checking. In particular + enumeration types and fixed-point types are treated simply as integers. + + + :samp:`{target}?^({source})` + Combines the above two cases. + + + :samp:`{x} #/ {y}` + + :samp:`{x} #mod {y}` + + :samp:`{x} # {y}` + + :samp:`{x} #rem {y}` + A division or multiplication of fixed-point values which are treated as + integers without any kind of scaling. + + + :samp:`free {expr} [storage_pool = {xxx}]` + Shows the storage pool associated with a `free` statement. + + + :samp:`[subtype or type declaration]` + Used to list an equivalent declaration for an internally generated + type that is referenced elsewhere in the listing. + + + :samp:`freeze {type-name} [{actions}]` + Shows the point at which `type-name` is frozen, with possible + associated actions to be performed at the freeze point. + + + :samp:`reference {itype}` + Reference (and hence definition) to internal type `itype`. + + + :samp:`{function-name}! ({arg}, {arg}, {arg})` + Intrinsic function call. + + + :samp:`{label-name} : label` + Declaration of label `labelname`. + + + :samp:`#$ {subprogram-name}` + An implicit call to a run-time support routine + (to meet the requirement of H.3.1(9) in a + convenient manner). + + + :samp:`{expr} && {expr} && {expr} ... && {expr}` + A multiple concatenation (same effect as `expr` & `expr` & + `expr`, but handled more efficiently). + + + :samp:`[constraint_error]` + Raise the `Constraint_Error` exception. + + + :samp:`{expression}'reference` + A pointer to the result of evaluating {expression}. + + + :samp:`{target-type}!({source-expression})` + An unchecked conversion of `source-expression` to `target-type`. + + + :samp:`[{numerator}/{denominator}]` + Used to represent internal real literals (that) have no exact + representation in base 2-16 (for example, the result of compile time + evaluation of the expression 1.0/27.0). + + +.. index:: -gnatD (gcc) + +:samp:`-gnatD[=nn]` + When used in conjunction with *-gnatG*, this switch causes + the expanded source, as described above for + *-gnatG* to be written to files with names + :file:`xxx.dg`, where :file:`xxx` is the normal file name, + instead of to the standard output file. For + example, if the source file name is :file:`hello.adb`, then a file + :file:`hello.adb.dg` will be written. The debugging + information generated by the *gcc* *-g* switch + will refer to the generated :file:`xxx.dg` file. This allows + you to do source level debugging using the generated code which is + sometimes useful for complex code, for example to find out exactly + which part of a complex construction raised an exception. This switch + also suppress generation of cross-reference information (see + *-gnatx*) since otherwise the cross-reference information + would refer to the :file:`.dg` file, which would cause + confusion since this is not the original source file. + + Note that *-gnatD* actually implies *-gnatG* + automatically, so it is not necessary to give both options. + In other words *-gnatD* is equivalent to *-gnatDG*). + + .. index:: -gnatL (gcc) + + If the switch *-gnatL* is used in conjunction with + *-gnatDG*, then the original source lines are interspersed + in the expanded source (as comment lines with the original line number). + + The optional parameter `nn` if present after -gnatD specifies an + alternative maximum line length that overrides the normal default of 72. + This value is in the range 40-999999, values less than 40 being silently + reset to 40. The equal sign is optional. + + +.. index:: -gnatr (gcc) +.. index:: pragma Restrictions + +:samp:`-gnatr` + This switch causes pragma Restrictions to be treated as Restriction_Warnings + so that violation of restrictions causes warnings rather than illegalities. + This is useful during the development process when new restrictions are added + or investigated. The switch also causes pragma Profile to be treated as + Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set + restriction warnings rather than restrictions. + + +.. index:: -gnatR (gcc) + +:samp:`-gnatR[0|1|2|3[s]]` + This switch controls output from the compiler of a listing showing + representation information for declared types and objects. For + *-gnatR0*, no information is output (equivalent to omitting + the *-gnatR* switch). For *-gnatR1* (which is the default, + so *-gnatR* with no parameter has the same effect), size and alignment + information is listed for declared array and record types. For + *-gnatR2*, size and alignment information is listed for all + declared types and objects. The `Linker_Section` is also listed for any + entity for which the `Linker_Section` is set explicitly or implicitly (the + latter case occurs for objects of a type for which a `Linker_Section` + is set). + + Finally *-gnatR3* includes symbolic + expressions for values that are computed at run time for + variant records. These symbolic expressions have a mostly obvious + format with #n being used to represent the value of the n'th + discriminant. See source files :file:`repinfo.ads/adb` in the + `GNAT` sources for full details on the format of *-gnatR3* + output. If the switch is followed by an s (e.g., *-gnatR2s*), then + the output is to a file with the name :file:`file.rep` where + file is the name of the corresponding source file. + + +:samp:`-gnatRm[s]` + This form of the switch controls output of subprogram conventions + and parameter passing mechanisms for all subprograms. A following + `s` means output to a file as described above. + + Note that it is possible for record components to have zero size. In + this case, the component clause uses an obvious extension of permitted + Ada syntax, for example `at 0 range 0 .. -1`. + + Representation information requires that code be generated (since it is the + code generator that lays out complex data structures). If an attempt is made + to output representation information when no code is generated, for example + when a subunit is compiled on its own, then no information can be generated + and the compiler outputs a message to this effect. + + +.. index:: -gnatS (gcc) + +:samp:`-gnatS` + The use of the switch *-gnatS* for an + Ada compilation will cause the compiler to output a + representation of package Standard in a form very + close to standard Ada. It is not quite possible to + do this entirely in standard Ada (since new + numeric base types cannot be created in standard + Ada), but the output is easily + readable to any Ada programmer, and is useful to + determine the characteristics of target dependent + types in package Standard. + + +.. index:: -gnatx (gcc) + +:samp:`-gnatx` + Normally the compiler generates full cross-referencing information in + the :file:`ALI` file. This information is used by a number of tools, + including `gnatfind` and `gnatxref`. The *-gnatx* switch + suppresses this information. This saves some space and may slightly + speed up compilation, but means that these tools cannot be used. + +.. _Exception_Handling_Control: + +Exception Handling Control +-------------------------- + +GNAT uses two methods for handling exceptions at run-time. The +`setjmp/longjmp` method saves the context when entering +a frame with an exception handler. Then when an exception is +raised, the context can be restored immediately, without the +need for tracing stack frames. This method provides very fast +exception propagation, but introduces significant overhead for +the use of exception handlers, even if no exception is raised. + +The other approach is called 'zero cost' exception handling. +With this method, the compiler builds static tables to describe +the exception ranges. No dynamic code is required when entering +a frame containing an exception handler. When an exception is +raised, the tables are used to control a back trace of the +subprogram invocation stack to locate the required exception +handler. This method has considerably poorer performance for +the propagation of exceptions, but there is no overhead for +exception handlers if no exception is raised. Note that in this +mode and in the context of mixed Ada and C/C++ programming, +to propagate an exception through a C/C++ code, the C/C++ code +must be compiled with the *-funwind-tables* GCC's +option. + +The following switches may be used to control which of the +two exception handling methods is used. + + + +.. index:: --RTS=sjlj (gnatmake) + +:samp:`--RTS=sjlj` + This switch causes the setjmp/longjmp run-time (when available) to be used + for exception handling. If the default + mechanism for the target is zero cost exceptions, then + this switch can be used to modify this default, and must be + used for all units in the partition. + This option is rarely used. One case in which it may be + advantageous is if you have an application where exception + raising is common and the overall performance of the + application is improved by favoring exception propagation. + + +.. index:: --RTS=zcx (gnatmake) +.. index:: Zero Cost Exceptions + +:samp:`--RTS=zcx` + This switch causes the zero cost approach to be used + for exception handling. If this is the default mechanism for the + target (see below), then this switch is unneeded. If the default + mechanism for the target is setjmp/longjmp exceptions, then + this switch can be used to modify this default, and must be + used for all units in the partition. + This option can only be used if the zero cost approach + is available for the target in use, otherwise it will generate an error. + +The same option *--RTS* must be used both for *gcc* +and *gnatbind*. Passing this option to *gnatmake* +(:ref:`Switches_for_gnatmake`) will ensure the required consistency +through the compilation and binding steps. + +.. _Units_to_Sources_Mapping_Files: + +Units to Sources Mapping Files +------------------------------ + + + +.. index:: -gnatem (gcc) + +:samp:`-gnatem={path}` + A mapping file is a way to communicate to the compiler two mappings: + from unit names to file names (without any directory information) and from + file names to path names (with full directory information). These mappings + are used by the compiler to short-circuit the path search. + + The use of mapping files is not required for correct operation of the + compiler, but mapping files can improve efficiency, particularly when + sources are read over a slow network connection. In normal operation, + you need not be concerned with the format or use of mapping files, + and the *-gnatem* switch is not a switch that you would use + explicitly. It is intended primarily for use by automatic tools such as + *gnatmake* running under the project file facility. The + description here of the format of mapping files is provided + for completeness and for possible use by other tools. + + A mapping file is a sequence of sets of three lines. In each set, the + first line is the unit name, in lower case, with `%s` appended + for specs and `%b` appended for bodies; the second line is the + file name; and the third line is the path name. + + Example:: + + main%b + main.2.ada + /gnat/project1/sources/main.2.ada + + + When the switch *-gnatem* is specified, the compiler will + create in memory the two mappings from the specified file. If there is + any problem (nonexistent file, truncated file or duplicate entries), + no mapping will be created. + + Several *-gnatem* switches may be specified; however, only the + last one on the command line will be taken into account. + + When using a project file, *gnatmake* creates a temporary + mapping file and communicates it to the compiler using this switch. + + +.. _Code_Generation_Control: + +Code Generation Control +----------------------- + +The GCC technology provides a wide range of target dependent +:samp:`-m` switches for controlling +details of code generation with respect to different versions of +architectures. This includes variations in instruction sets (e.g., +different members of the power pc family), and different requirements +for optimal arrangement of instructions (e.g., different members of +the x86 family). The list of available *-m* switches may be +found in the GCC documentation. + +Use of these *-m* switches may in some cases result in improved +code performance. + +The GNAT technology is tested and qualified without any +:samp:`-m` switches, +so generally the most reliable approach is to avoid the use of these +switches. However, we generally expect most of these switches to work +successfully with GNAT, and many customers have reported successful +use of these options. + +Our general advice is to avoid the use of *-m* switches unless +special needs lead to requirements in this area. In particular, +there is no point in using *-m* switches to improve performance +unless you actually see a performance improvement. + + +.. _Binding_with_gnatbind: + +Binding with `gnatbind` +======================= + +.. index:: ! gnatbind + +This chapter describes the GNAT binder, `gnatbind`, which is used +to bind compiled GNAT objects. + +Note: to invoke `gnatbind` with a project file, use the `gnat` +driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + +The `gnatbind` program performs four separate functions: + +* Checks that a program is consistent, in accordance with the rules in + Chapter 10 of the Ada Reference Manual. In particular, error + messages are generated if a program uses inconsistent versions of a + given unit. + +* Checks that an acceptable order of elaboration exists for the program + and issues an error message if it cannot find an order of elaboration + that satisfies the rules in Chapter 10 of the Ada Language Manual. + +* Generates a main program incorporating the given elaboration order. + This program is a small Ada package (body and spec) that + must be subsequently compiled + using the GNAT compiler. The necessary compilation step is usually + performed automatically by *gnatlink*. The two most important + functions of this program + are to call the elaboration routines of units in an appropriate order + and to call the main program. + +* Determines the set of object files required by the given main program. + This information is output in the forms of comments in the generated program, + to be read by the *gnatlink* utility used to link the Ada application. + +.. _Running_gnatbind: + +Running `gnatbind` +------------------ + +The form of the `gnatbind` command is + +.. code-block:: sh + + $ gnatbind [`switches`] `mainprog`[.ali] [`switches`] + + +where :file:`mainprog.adb` is the Ada file containing the main program +unit body. `gnatbind` constructs an Ada +package in two files whose names are +:file:`b~mainprog.ads`, and :file:`b~mainprog.adb`. +For example, if given the +parameter :file:`hello.ali`, for a main program contained in file +:file:`hello.adb`, the binder output files would be :file:`b~hello.ads` +and :file:`b~hello.adb`. + +When doing consistency checking, the binder takes into consideration +any source files it can locate. For example, if the binder determines +that the given main program requires the package `Pack`, whose +:file:`.ALI` +file is :file:`pack.ali` and whose corresponding source spec file is +:file:`pack.ads`, it attempts to locate the source file :file:`pack.ads` +(using the same search path conventions as previously described for the +*gcc* command). If it can locate this source file, it checks that +the time stamps +or source checksums of the source and its references to in :file:`ALI` files +match. In other words, any :file:`ALI` files that mentions this spec must have +resulted from compiling this version of the source file (or in the case +where the source checksums match, a version close enough that the +difference does not matter). + +.. index:: Source files, use by binder + +The effect of this consistency checking, which includes source files, is +that the binder ensures that the program is consistent with the latest +version of the source files that can be located at bind time. Editing a +source file without compiling files that depend on the source file cause +error messages to be generated by the binder. + +For example, suppose you have a main program :file:`hello.adb` and a +package `P`, from file :file:`p.ads` and you perform the following +steps: + +* Enter `gcc -c hello.adb` to compile the main program. + +* Enter `gcc -c p.ads` to compile package `P`. + +* Edit file :file:`p.ads`. + +* Enter `gnatbind hello`. + +At this point, the file :file:`p.ali` contains an out-of-date time stamp +because the file :file:`p.ads` has been edited. The attempt at binding +fails, and the binder generates the following error messages: + + +:: + + error: "hello.adb" must be recompiled ("p.ads" has been modified) + error: "p.ads" has been modified and must be recompiled + + +Now both files must be recompiled as indicated, and then the bind can +succeed, generating a main program. You need not normally be concerned +with the contents of this file, but for reference purposes a sample +binder output file is given in :ref:`Example_of_Binder_Output_File`. + +In most normal usage, the default mode of *gnatbind* which is to +generate the main package in Ada, as described in the previous section. +In particular, this means that any Ada programmer can read and understand +the generated main program. It can also be debugged just like any other +Ada code provided the *-g* switch is used for +*gnatbind* and *gnatlink*. + +.. _Switches_for_gnatbind: + +Switches for *gnatbind* +----------------------- + +The following switches are available with `gnatbind`; details will +be presented in subsequent sections. + + +.. index:: --version (gnatbind) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatbind) + +:samp:`--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + + +.. index:: -a (gnatbind) + +:samp:`-a` + Indicates that, if supported by the platform, the adainit procedure should + be treated as an initialisation routine by the linker (a constructor). This + is intended to be used by the Project Manager to automatically initialize + shared Stand-Alone Libraries. + + +.. index:: -aO (gnatbind) + +:samp:`-aO` + Specify directory to be searched for ALI files. + + +.. index:: -aI (gnatbind) + +:samp:`-aI` + Specify directory to be searched for source file. + + +.. index:: -A (gnatbind) + +:samp:`-A[={filename}]` + Output ALI list (to standard output or to the named file). + + +.. index:: -b (gnatbind) + +:samp:`-b` + Generate brief messages to :file:`stderr` even if verbose mode set. + + +.. index:: -c (gnatbind) + +:samp:`-c` + Check only, no generation of binder output file. + + +.. index:: -dnn[k|m] (gnatbind) + +:samp:`-d{nn}[k|m]` + This switch can be used to change the default task stack size value + to a specified size `nn`, which is expressed in bytes by default, or + in kilobytes when suffixed with `k` or in megabytes when suffixed + with `m`. + In the absence of a :samp:`[k|m]` suffix, this switch is equivalent, + in effect, to completing all task specs with + + .. code-block:: ada + + pragma Storage_Size (nn); + + When they do not already have such a pragma. + + +.. index:: -D (gnatbind) + +:samp:`-D{nn}[k|m]` + This switch can be used to change the default secondary stack size value + to a specified size `nn`, which is expressed in bytes by default, or + in kilobytes when suffixed with `k` or in megabytes when suffixed + with `m`. + + The secondary stack is used to deal with functions that return a variable + sized result, for example a function returning an unconstrained + String. There are two ways in which this secondary stack is allocated. + + For most targets, the secondary stack is growing on demand and is allocated + as a chain of blocks in the heap. The -D option is not very + relevant. It only give some control over the size of the allocated + blocks (whose size is the minimum of the default secondary stack size value, + and the actual size needed for the current allocation request). + + For certain targets, notably VxWorks 653, + the secondary stack is allocated by carving off a fixed ratio chunk of the + primary task stack. The -D option is used to define the + size of the environment task's secondary stack. + + +.. index:: -e (gnatbind) + +:samp:`-e` + Output complete list of elaboration-order dependencies. + + +.. index:: -E (gnatbind) + +:samp:`-E` + Store tracebacks in exception occurrences when the target supports it. + + See also the packages `GNAT.Traceback` and + `GNAT.Traceback.Symbolic` for more information. + Note that on x86 ports, you must not use *-fomit-frame-pointer* + *gcc* option. + + +.. index:: -F (gnatbind) + +:samp:`-F` + Force the checks of elaboration flags. *gnatbind* does not normally + generate checks of elaboration flags for the main executable, except when + a Stand-Alone Library is used. However, there are cases when this cannot be + detected by gnatbind. An example is importing an interface of a Stand-Alone + Library through a pragma Import and only specifying through a linker switch + this Stand-Alone Library. This switch is used to guarantee that elaboration + flag checks are generated. + + +.. index:: -h (gnatbind) + +:samp:`-h` + Output usage (help) information + + + .. index:: -H32 (gnatbind) + +:samp:`-H32` + Use 32-bit allocations for `__gnat_malloc` (and thus for access types). + For further details see :ref:`Dynamic_Allocation_Control`. + + + .. index:: -H64 (gnatbind) + .. index:: __gnat_malloc + +:samp:`-H64` + Use 64-bit allocations for `__gnat_malloc` (and thus for access types). + For further details see :ref:`Dynamic_Allocation_Control`. + + + .. index:: -I (gnatbind) + +:samp:`-I` + Specify directory to be searched for source and ALI files. + + + .. index:: -I- (gnatbind) + +:samp:`-I-` + Do not look for sources in the current directory where `gnatbind` was + invoked, and do not look for ALI files in the directory containing the + ALI file named in the `gnatbind` command line. + + + .. index:: -l (gnatbind) + +:samp:`-l` + Output chosen elaboration order. + + + .. index:: -L (gnatbind) + +:samp:`-L{xxx}` + Bind the units for library building. In this case the adainit and + adafinal procedures (:ref:`Binding_with_Non-Ada_Main_Programs`) + are renamed to `xxx`init and + `xxx`final. + Implies -n. + (:ref:`GNAT_and_Libraries`, for more details.) + + + .. index:: -M (gnatbind) + +:samp:`-M{xyz}` + Rename generated main program from main to xyz. This option is + supported on cross environments only. + + + .. index:: -m (gnatbind) + +:samp:`-m{n}` + Limit number of detected errors or warnings to `n`, where `n` is + in the range 1..999999. The default value if no switch is + given is 9999. If the number of warnings reaches this limit, then a + message is output and further warnings are suppressed, the bind + continues in this case. If the number of errors reaches this + limit, then a message is output and the bind is abandoned. + A value of zero means that no limit is enforced. The equal + sign is optional. + + + .. index:: -n (gnatbind) + +:samp:`-n` + No main program. + + + .. index:: -nostdinc (gnatbind) + +:samp:`-nostdinc` + Do not look for sources in the system default directory. + + + .. index:: -nostdlib (gnatbind) + +:samp:`-nostdlib` + Do not look for library files in the system default directory. + + + .. index:: --RTS (gnatbind) + +:samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + .. index:: -o (gnatbind) + +:samp:`-o {file}` + Name the output file `file` (default is :file:`b~`xxx`.adb`). + Note that if this option is used, then linking must be done manually, + gnatlink cannot be used. + + + .. index:: -O (gnatbind) + +:samp:`-O[={filename}]` + Output object list (to standard output or to the named file). + + + .. index:: -p (gnatbind) + +:samp:`-p` + Pessimistic (worst-case) elaboration order + + + .. index:: -P (gnatbind) + +:samp:`-P` + Generate binder file suitable for CodePeer. + + + .. index:: -R (gnatbind) + +:samp:`-R` + Output closure source list, which includes all non-run-time units that are + included in the bind. + + + .. index:: -Ra (gnatbind) + +:samp:`-Ra` + Like *-R* but the list includes run-time units. + + + .. index:: -s (gnatbind) + +:samp:`-s` + Require all source files to be present. + + + .. index:: -S (gnatbind) + +:samp:`-S{xxx}` + Specifies the value to be used when detecting uninitialized scalar + objects with pragma Initialize_Scalars. + The `xxx` string specified with the switch is one of: + + * ``in`` for an invalid value*. + + If zero is invalid for the discrete type in question, + then the scalar value is set to all zero bits. + For signed discrete types, the largest possible negative value of + the underlying scalar is set (i.e. a one bit followed by all zero bits). + For unsigned discrete types, the underlying scalar value is set to all + one bits. For floating-point types, a NaN value is set + (see body of package System.Scalar_Values for exact values). + + * ``lo`` for low value. + + If zero is invalid for the discrete type in question, + then the scalar value is set to all zero bits. + For signed discrete types, the largest possible negative value of + the underlying scalar is set (i.e. a one bit followed by all zero bits). + For unsigned discrete types, the underlying scalar value is set to all + zero bits. For floating-point, a small value is set + (see body of package System.Scalar_Values for exact values). + + * ``hi`` for high value. + + If zero is invalid for the discrete type in question, + then the scalar value is set to all one bits. + For signed discrete types, the largest possible positive value of + the underlying scalar is set (i.e. a zero bit followed by all one bits). + For unsigned discrete types, the underlying scalar value is set to all + one bits. For floating-point, a large value is set + (see body of package System.Scalar_Values for exact values). + + * `xx` for hex value (two hex digits). + + The underlying scalar is set to a value consisting of repeated bytes, whose + value corresponds to the given value. For example if ``BF`` is given, + then a 32-bit scalar value will be set to the bit patterm ``16#BFBFBFBF#``. + + .. index:: GNAT_INIT_SCALARS + + In addition, you can specify *-Sev* to indicate that the value is + to be set at run time. In this case, the program will look for an environment + variable of the form :samp:`GNAT_INIT_SCALARS={yy}`, where `yy` is one + of *in/lo/hi/`xx*` with the same meanings as above. + If no environment variable is found, or if it does not have a valid value, + then the default is *in* (invalid values). + +.. index:: -static (gnatbind) + +:samp:`-static` + Link against a static GNAT run time. + + + .. index:: -shared (gnatbind) + +:samp:`-shared` + Link against a shared GNAT run time when available. + + + .. index:: -t (gnatbind) + +:samp:`-t` + Tolerate time stamp and other consistency errors + + + .. index:: -T (gnatbind) + +:samp:`-T{n}` + Set the time slice value to `n` milliseconds. If the system supports + the specification of a specific time slice value, then the indicated value + is used. If the system does not support specific time slice values, but + does support some general notion of round-robin scheduling, then any + nonzero value will activate round-robin scheduling. + + A value of zero is treated specially. It turns off time + slicing, and in addition, indicates to the tasking run time that the + semantics should match as closely as possible the Annex D + requirements of the Ada RM, and in particular sets the default + scheduling policy to `FIFO_Within_Priorities`. + + + .. index:: -u (gnatbind) + +:samp:`-u{n}` + Enable dynamic stack usage, with `n` results stored and displayed + at program termination. A result is generated when a task + terminates. Results that can't be stored are displayed on the fly, at + task termination. This option is currently not supported on Itanium + platforms. (See :ref:`Dynamic_Stack_Usage_Analysis` for details.) + + + .. index:: -v (gnatbind) + +:samp:`-v` + Verbose mode. Write error messages, header, summary output to + :file:`stdout`. + + + .. index:: -w (gnatbind) + +:samp:`-w{x}` + Warning mode; `x` = s/e for suppress/treat as error + + + .. index:: -Wx (gnatbind) + +:samp:`-Wx{e}` + Override default wide character encoding for standard Text_IO files. + + + .. index:: -x (gnatbind) + +:samp:`-x` + Exclude source files (check object consistency only). + + + .. index:: -Xnnn (gnatbind) + +:samp:`-X{nnn}` + Set default exit status value, normally 0 for POSIX compliance. + + + .. index:: -y (gnatbind) + +:samp:`-y` + Enable leap seconds support in `Ada.Calendar` and its children. + + + .. index:: -z (gnatbind) + +:samp:`-z` + No main subprogram. + +You may obtain this listing of switches by running `gnatbind` with +no arguments. + + +.. _Consistency-Checking_Modes: + +Consistency-Checking Modes +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +As described earlier, by default `gnatbind` checks +that object files are consistent with one another and are consistent +with any source files it can locate. The following switches control binder +access to sources. + + + .. index:: -s (gnatbind) + +:samp:`-s` + Require source files to be present. In this mode, the binder must be + able to locate all source files that are referenced, in order to check + their consistency. In normal mode, if a source file cannot be located it + is simply ignored. If you specify this switch, a missing source + file is an error. + + + .. index:: -Wx (gnatbind) + +:samp:`-Wx{e}` + Override default wide character encoding for standard Text_IO files. + Normally the default wide character encoding method used for standard + [Wide\_[Wide\_]]Text_IO files is taken from the encoding specified for + the main source input (see description of switch + *-gnatWx* for the compiler). The + use of this switch for the binder (which has the same set of + possible arguments) overrides this default as specified. + + + .. index:: -x (gnatbind) + +:samp:`-x` + Exclude source files. In this mode, the binder only checks that ALI + files are consistent with one another. Source files are not accessed. + The binder runs faster in this mode, and there is still a guarantee that + the resulting program is self-consistent. + If a source file has been edited since it was last compiled, and you + specify this switch, the binder will not detect that the object + file is out of date with respect to the source file. Note that this is the + mode that is automatically used by *gnatmake* because in this + case the checking against sources has already been performed by + *gnatmake* in the course of compilation (i.e., before binding). + + +.. _Binder_Error_Message_Control: + +Binder Error Message Control +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The following switches provide control over the generation of error +messages from the binder: + + + + .. index:: -v (gnatbind) + +:samp:`-v` + Verbose mode. In the normal mode, brief error messages are generated to + :file:`stderr`. If this switch is present, a header is written + to :file:`stdout` and any error messages are directed to :file:`stdout`. + All that is written to :file:`stderr` is a brief summary message. + + + .. index:: -b (gnatbind) + +:samp:`-b` + Generate brief error messages to :file:`stderr` even if verbose mode is + specified. This is relevant only when used with the + *-v* switch. + + + .. index:: -m (gnatbind) + +:samp:`-m{n}` + Limits the number of error messages to `n`, a decimal integer in the + range 1-999. The binder terminates immediately if this limit is reached. + + + .. index:: -M (gnatbind) + +:samp:`-M{xxx}` + Renames the generated main program from `main` to `xxx`. + This is useful in the case of some cross-building environments, where + the actual main program is separate from the one generated + by `gnatbind`. + + + .. index:: -ws (gnatbind) + .. index:: Warnings + +:samp:`-ws` + Suppress all warning messages. + + + .. index:: -we (gnatbind) + +:samp:`-we` + Treat any warning messages as fatal errors. + + + .. index:: -t (gnatbind) + .. index:: Time stamp checks, in binder + .. index:: Binder consistency checks + .. index:: Consistency checks, in binder + +:samp:`-t` + The binder performs a number of consistency checks including: + + + * Check that time stamps of a given source unit are consistent + + * Check that checksums of a given source unit are consistent + + * Check that consistent versions of `GNAT` were used for compilation + + * Check consistency of configuration pragmas as required + + Normally failure of such checks, in accordance with the consistency + requirements of the Ada Reference Manual, causes error messages to be + generated which abort the binder and prevent the output of a binder + file and subsequent link to obtain an executable. + + The *-t* switch converts these error messages + into warnings, so that + binding and linking can continue to completion even in the presence of such + errors. The result may be a failed link (due to missing symbols), or a + non-functional executable which has undefined semantics. + + .. note:: + + This means that *-t* should be used only in unusual situations, + with extreme care. + +.. _Elaboration_Control: + +Elaboration Control +^^^^^^^^^^^^^^^^^^^ + +The following switches provide additional control over the elaboration +order. For full details see :ref:`Elaboration_Order_Handling_in_GNAT`. + + + .. index:: -p (gnatbind) + +:samp:`-p` + Normally the binder attempts to choose an elaboration order that is + likely to minimize the likelihood of an elaboration order error resulting + in raising a `Program_Error` exception. This switch reverses the + action of the binder, and requests that it deliberately choose an order + that is likely to maximize the likelihood of an elaboration error. + This is useful in ensuring portability and avoiding dependence on + accidental fortuitous elaboration ordering. + + Normally it only makes sense to use the *-p* + switch if dynamic + elaboration checking is used (*-gnatE* switch used for compilation). + This is because in the default static elaboration mode, all necessary + `Elaborate` and `Elaborate_All` pragmas are implicitly inserted. + These implicit pragmas are still respected by the binder in + *-p* mode, so a + safe elaboration order is assured. + + Note that *-p* is not intended for + production use; it is more for debugging/experimental use. + +.. _Output_Control: + +Output Control +^^^^^^^^^^^^^^ + +The following switches allow additional control over the output +generated by the binder. + + + .. index:: -c (gnatbind) + +:samp:`-c` + Check only. Do not generate the binder output file. In this mode the + binder performs all error checks but does not generate an output file. + + + .. index:: -e (gnatbind) + +:samp:`-e` + Output complete list of elaboration-order dependencies, showing the + reason for each dependency. This output can be rather extensive but may + be useful in diagnosing problems with elaboration order. The output is + written to :file:`stdout`. + + + .. index:: -h (gnatbind) + +:samp:`-h` + Output usage information. The output is written to :file:`stdout`. + + + .. index:: -K (gnatbind) + +:samp:`-K` + Output linker options to :file:`stdout`. Includes library search paths, + contents of pragmas Ident and Linker_Options, and libraries added + by `gnatbind`. + + + .. index:: -l (gnatbind) + +:samp:`-l` + Output chosen elaboration order. The output is written to :file:`stdout`. + + + .. index:: -O (gnatbind) + +:samp:`-O` + Output full names of all the object files that must be linked to provide + the Ada component of the program. The output is written to :file:`stdout`. + This list includes the files explicitly supplied and referenced by the user + as well as implicitly referenced run-time unit files. The latter are + omitted if the corresponding units reside in shared libraries. The + directory names for the run-time units depend on the system configuration. + + + .. index:: -o (gnatbind) + +:samp:`-o {file}` + Set name of output file to `file` instead of the normal + :file:`b~`mainprog`.adb` default. Note that `file` denote the Ada + binder generated body filename. + Note that if this option is used, then linking must be done manually. + It is not possible to use gnatlink in this case, since it cannot locate + the binder file. + + + .. index:: -r (gnatbind) + +:samp:`-r` + Generate list of `pragma Restrictions` that could be applied to + the current unit. This is useful for code audit purposes, and also may + be used to improve code generation in some cases. + + +.. _Dynamic_Allocation_Control: + +Dynamic Allocation Control +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The heap control switches -- *-H32* and *-H64* -- +determine whether dynamic allocation uses 32-bit or 64-bit memory. +They only affect compiler-generated allocations via `__gnat_malloc`; +explicit calls to `malloc` and related functions from the C +run-time library are unaffected. + +:samp:`-H32` + Allocate memory on 32-bit heap + + +:samp:`-H64` + Allocate memory on 64-bit heap. This is the default + unless explicitly overridden by a `'Size` clause on the access type. + +These switches are only effective on VMS platforms. + + +.. _Binding_with_Non-Ada_Main_Programs: + +Binding with Non-Ada Main Programs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The description so far has assumed that the main +program is in Ada, and that the task of the binder is to generate a +corresponding function `main` that invokes this Ada main +program. GNAT also supports the building of executable programs where +the main program is not in Ada, but some of the called routines are +written in Ada and compiled using GNAT (:ref:`Mixed_Language_Programming`). +The following switch is used in this situation: + + + .. index:: -n (gnatbind) + +:samp:`-n` + No main program. The main program is not in Ada. + +In this case, most of the functions of the binder are still required, +but instead of generating a main program, the binder generates a file +containing the following callable routines: + + .. index:: adainit + + *adainit* + You must call this routine to initialize the Ada part of the program by + calling the necessary elaboration routines. A call to `adainit` is + required before the first call to an Ada subprogram. + + Note that it is assumed that the basic execution environment must be setup + to be appropriate for Ada execution at the point where the first Ada + subprogram is called. In particular, if the Ada code will do any + floating-point operations, then the FPU must be setup in an appropriate + manner. For the case of the x86, for example, full precision mode is + required. The procedure GNAT.Float_Control.Reset may be used to ensure + that the FPU is in the right state. + + .. index:: adafinal + + *adafinal* + You must call this routine to perform any library-level finalization + required by the Ada subprograms. A call to `adafinal` is required + after the last call to an Ada subprogram, and before the program + terminates. + +.. index:: -n (gnatbind) +.. index:: Binder, multiple input files + +If the *-n* switch +is given, more than one ALI file may appear on +the command line for `gnatbind`. The normal *closure* +calculation is performed for each of the specified units. Calculating +the closure means finding out the set of units involved by tracing +|with| references. The reason it is necessary to be able to +specify more than one ALI file is that a given program may invoke two or +more quite separate groups of Ada units. + +The binder takes the name of its output file from the last specified ALI +file, unless overridden by the use of the *-o file*. + +.. index:: -o (gnatbind) + +The output is an Ada unit in source form that can be compiled with GNAT. +This compilation occurs automatically as part of the *gnatlink* +processing. + +Currently the GNAT run time requires a FPU using 80 bits mode +precision. Under targets where this is not the default it is required to +call GNAT.Float_Control.Reset before using floating point numbers (this +include float computation, float input and output) in the Ada code. A +side effect is that this could be the wrong mode for the foreign code +where floating point computation could be broken after this call. + + +.. _Binding_Programs_with_No_Main_Subprogram: + +Binding Programs with No Main Subprogram +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +It is possible to have an Ada program which does not have a main +subprogram. This program will call the elaboration routines of all the +packages, then the finalization routines. + +The following switch is used to bind programs organized in this manner: + + .. index:: -z (gnatbind) + +:samp:`-z` + Normally the binder checks that the unit name given on the command line + corresponds to a suitable main subprogram. When this switch is used, + a list of ALI files can be given, and the execution of the program + consists of elaboration of these units in an appropriate order. Note + that the default wide character encoding method for standard Text_IO + files is always set to Brackets if this switch is set (you can use + the binder switch + *-Wx* to override this default). + + +.. _Command-Line_Access: + +Command-Line Access +------------------- + +The package `Ada.Command_Line` provides access to the command-line +arguments and program name. In order for this interface to operate +correctly, the two variables + +.. code-block:: c + + int gnat_argc; + char **gnat_argv; + +.. index:: gnat_argv +.. index:: gnat_argc + +are declared in one of the GNAT library routines. These variables must +be set from the actual `argc` and `argv` values passed to the +main program. With no *n* present, `gnatbind` +generates the C main program to automatically set these variables. +If the *n* switch is used, there is no automatic way to +set these variables. If they are not set, the procedures in +`Ada.Command_Line` will not be available, and any attempt to use +them will raise `Constraint_Error`. If command line access is +required, your main program must set `gnat_argc` and +`gnat_argv` from the `argc` and `argv` values passed to +it. + + +.. _Search_Paths_for_gnatbind: + +Search Paths for `gnatbind` +--------------------------- + +The binder takes the name of an ALI file as its argument and needs to +locate source files as well as other ALI files to verify object consistency. + +For source files, it follows exactly the same search rules as *gcc* +(see :ref:`Search_Paths_and_the_Run-Time_Library_RTL`). For ALI files the +directories searched are: + +* The directory containing the ALI file named in the command line, unless + the switch *-I-* is specified. + +* All directories specified by *-I* + switches on the `gnatbind` + command line, in the order given. + + .. index:: ADA_PRJ_OBJECTS_FILE + +* Each of the directories listed in the text file whose name is given + by the :envvar:`ADA_PRJ_OBJECTS_FILE` environment variable. + + :envvar:`ADA_PRJ_OBJECTS_FILE` is normally set by gnatmake or by the gnat + driver when project files are used. It should not normally be set + by other means. + + .. index:: ADA_OBJECTS_PATH + +* Each of the directories listed in the value of the + :envvar:`ADA_OBJECTS_PATH` environment variable. + Construct this value + exactly as the :envvar:`PATH` environment variable: a list of directory + names separated by colons (semicolons when working with the NT version + of GNAT). + +* The content of the :file:`ada_object_path` file which is part of the GNAT + installation tree and is used to store standard libraries such as the + GNAT Run Time Library (RTL) unless the switch *-nostdlib* is + specified. See :ref:`Installing_a_library` + +.. index:: -I (gnatbind) +.. index:: -aI (gnatbind) +.. index:: -aO (gnatbind) + +In the binder the switch *-I* +is used to specify both source and +library file paths. Use *-aI* +instead if you want to specify +source paths only, and *-aO* +if you want to specify library paths +only. This means that for the binder +:samp:`-I{dir}` is equivalent to +:samp:`-aI{dir}` +:samp:`-aO`{dir}`. +The binder generates the bind file (a C language source file) in the +current working directory. + +.. index:: Ada +.. index:: System +.. index:: Interfaces +.. index:: GNAT + +The packages `Ada`, `System`, and `Interfaces` and their +children make up the GNAT Run-Time Library, together with the package +GNAT and its children, which contain a set of useful additional +library functions provided by GNAT. The sources for these units are +needed by the compiler and are kept together in one directory. The ALI +files and object files generated by compiling the RTL are needed by the +binder and the linker and are kept together in one directory, typically +different from the directory containing the sources. In a normal +installation, you need not specify these directory names when compiling +or binding. Either the environment variables or the built-in defaults +cause these files to be found. + +Besides simplifying access to the RTL, a major use of search paths is +in compiling sources from multiple directories. This can make +development environments much more flexible. + + +.. _Examples_of_gnatbind_Usage: + +Examples of `gnatbind` Usage +---------------------------- + +Here are some examples of `gnatbind` invovations: + + :: + + gnatbind hello + + The main program `Hello` (source program in :file:`hello.adb`) is + bound using the standard switch settings. The generated main program is + :file:`b~hello.adb`. This is the normal, default use of the binder. + + :: + + gnatbind hello -o mainprog.adb + + The main program `Hello` (source program in :file:`hello.adb`) is + bound using the standard switch settings. The generated main program is + :file:`mainprog.adb` with the associated spec in + :file:`mainprog.ads`. Note that you must specify the body here not the + spec. Note that if this option is used, then linking must be done manually, + since gnatlink will not be able to find the generated file. + + +.. _Linking_with_gnatlink: + +Linking with *gnatlink* +======================= + +.. index: ! gnatlink + +This chapter discusses *gnatlink*, a tool that links +an Ada program and builds an executable file. This utility +invokes the system linker (via the *gcc* command) +with a correct list of object files and library references. +*gnatlink* automatically determines the list of files and +references for the Ada part of a program. It uses the binder file +generated by the *gnatbind* to determine this list. + +Note: to invoke `gnatlink` with a project file, use the `gnat` +driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + +.. _Running_gnatlink: + +Running *gnatlink* +------------------ + +The form of the *gnatlink* command is + + +.. code-block:: sh + + $ gnatlink [`switches`] `mainprog`[.ali] + [`non-Ada objects`] [`linker options`] + + + +The arguments of *gnatlink* (switches, main :file:`ALI` file, +non-Ada objects +or linker options) may be in any order, provided that no non-Ada object may +be mistaken for a main :file:`ALI` file. +Any file name :file:`F` without the :file:`.ali` +extension will be taken as the main :file:`ALI` file if a file exists +whose name is the concatenation of :file:`F` and :file:`.ali`. + +:file:`mainprog.ali` references the ALI file of the main program. +The :file:`.ali` extension of this file can be omitted. From this +reference, *gnatlink* locates the corresponding binder file +:file:`b~mainprog.adb` and, using the information in this file along +with the list of non-Ada objects and linker options, constructs a +linker command file to create the executable. + +The arguments other than the *gnatlink* switches and the main +:file:`ALI` file are passed to the linker uninterpreted. +They typically include the names of +object files for units written in other languages than Ada and any library +references required to resolve references in any of these foreign language +units, or in `Import` pragmas in any Ada units. + +`linker options` is an optional list of linker specific +switches. +The default linker called by gnatlink is *gcc* which in +turn calls the appropriate system linker. + +One useful option for the linker is *-s*: it reduces the size of the +executable by removing all symbol table and relocation information from the +executable. + +Standard options for the linker such as *-lmy_lib* or +*-Ldir* can be added as is. +For options that are not recognized by +*gcc* as linker options, use the *gcc* switches +*-Xlinker* or *-Wl,*. + +Refer to the GCC documentation for +details. + +Here is an example showing how to generate a linker map: + +.. code-block:: sh + + $ gnatlink my_prog -Wl,-Map,MAPFILE + + +Using `linker options` it is possible to set the program stack and +heap size. +See :ref:`Setting_Stack_Size_from_gnatlink` and +:ref:`Setting_Heap_Size_from_gnatlink`. + +*gnatlink* determines the list of objects required by the Ada +program and prepends them to the list of objects passed to the linker. +*gnatlink* also gathers any arguments set by the use of +`pragma Linker_Options` and adds them to the list of arguments +presented to the linker. + + +.. _Switches_for_gnatlink: + +Switches for *gnatlink* +----------------------- + +The following switches are available with the *gnatlink* utility: + +.. index:: --version (gnatlink) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatlink) + +:samp:`--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + + +.. index:: Command line length +.. index:: -f (gnatlink) + +:samp:`-f` + On some targets, the command line length is limited, and *gnatlink* + will generate a separate file for the linker if the list of object files + is too long. + The *-f* switch forces this file + to be generated even if + the limit is not exceeded. This is useful in some cases to deal with + special situations where the command line length is exceeded. + + +.. index:: Debugging information, including +.. index:: -g (gnatlink) + +:samp:`-g` + The option to include debugging information causes the Ada bind file (in + other words, :file:`b~mainprog.adb`) to be compiled with *-g*. + In addition, the binder does not delete the :file:`b~mainprog.adb`, + :file:`b~mainprog.o` and :file:`b~mainprog.ali` files. + Without *-g*, the binder removes these files by default. + +.. index:: -n (gnatlink) + +:samp:`-n` + Do not compile the file generated by the binder. This may be used when + a link is rerun with different options, but there is no need to recompile + the binder file. + + +.. index:: -v (gnatlink) + +:samp:`-v` + Verbose mode. Causes additional information to be output, including a full + list of the included object files. + This switch option is most useful when you want + to see what set of object files are being used in the link step. + + +.. index:: -v -v (gnatlink) + +:samp:`-v -v` + Very verbose mode. Requests that the compiler operate in verbose mode when + it compiles the binder file, and that the system linker run in verbose mode. + + +.. index:: -o (gnatlink) + +:samp:`-o {exec-name}` + `exec-name` specifies an alternate name for the generated + executable program. If this switch is omitted, the executable has the same + name as the main unit. For example, `gnatlink try.ali` creates + an executable called :file:`try`. + + +.. index:: -b (gnatlink) + +:samp:`-b {target}` + Compile your program to run on `target`, which is the name of a + system configuration. You must have a GNAT cross-compiler built if + `target` is not the same as your host system. + + +.. index:: -B (gnatlink) + +:samp:`-B{dir}` + Load compiler executables (for example, `gnat1`, the Ada compiler) + from `dir` instead of the default location. Only use this switch + when multiple versions of the GNAT compiler are available. + See the `Directory Options` section in :title:`The_GNU_Compiler_Collection` + for further details. You would normally use the *-b* or + *-V* switch instead. + + +.. index:: -M (gnatlink) + +:samp:`-M` + When linking an executable, create a map file. The name of the map file + has the same name as the executable with extension ".map". + + +.. index:: -M= (gnatlink) + +:samp:`-M={mapfile}` + When linking an executable, create a map file. The name of the map file is + `mapfile`. + + +.. index:: --GCC=compiler_name (gnatlink) + +:samp:`--GCC={compiler_name}` + Program used for compiling the binder file. The default is + ``gcc``. You need to use quotes around `compiler_name` if + `compiler_name` contains spaces or other separator characters. + As an example ``--GCC="foo -x -y"`` will instruct *gnatlink* to + use ``foo -x -y`` as your compiler. Note that switch ``-c`` is always + inserted after your command name. Thus in the above example the compiler + command that will be used by *gnatlink* will be ``foo -c -x -y``. + A limitation of this syntax is that the name and path name of the executable + itself must not include any embedded spaces. If the compiler executable is + different from the default one (gcc or -gcc), then the back-end + switches in the ALI file are not used to compile the binder generated source. + For example, this is the case with ``--GCC="foo -x -y"``. But the back end + switches will be used for ``--GCC="gcc -gnatv"``. If several + ``--GCC=compiler_name`` are used, only the last `compiler_name` + is taken into account. However, all the additional switches are also taken + into account. Thus, + ``--GCC="foo -x -y" --GCC="bar -z -t"`` is equivalent to + ``--GCC="bar -x -y -z -t"``. + + +.. index:: --LINK= (gnatlink) + +:samp:`--LINK={name}` + `name` is the name of the linker to be invoked. This is especially + useful in mixed language programs since languages such as C++ require + their own linker to be used. When this switch is omitted, the default + name for the linker is *gcc*. When this switch is used, the + specified linker is called instead of *gcc* with exactly the same + parameters that would have been passed to *gcc* so if the desired + linker requires different parameters it is necessary to use a wrapper + script that massages the parameters before invoking the real linker. It + may be useful to control the exact invocation by using the verbose + switch. + + +.. _Using_the_GNU_make_Utility: + +Using the GNU `make` Utility +============================ + +.. index:: make (GNU), GNU make + +This chapter offers some examples of makefiles that solve specific +problems. It does not explain how to write a makefile, nor does it try to replace the +*gnatmake* utility (:ref:`The_GNAT_Make_Program_gnatmake`). + +All the examples in this section are specific to the GNU version of +make. Although *make* is a standard utility, and the basic language +is the same, these examples use some advanced features found only in +`GNU make`. + +.. _Using_gnatmake_in_a_Makefile: + +Using gnatmake in a Makefile +---------------------------- + +.. index makefile (GNU make) + +Complex project organizations can be handled in a very powerful way by +using GNU make combined with gnatmake. For instance, here is a Makefile +which allows you to build each subsystem of a big project into a separate +shared library. Such a makefile allows you to significantly reduce the link +time of very big applications while maintaining full coherence at +each step of the build process. + +The list of dependencies are handled automatically by +*gnatmake*. The Makefile is simply used to call gnatmake in each of +the appropriate directories. + +Note that you should also read the example on how to automatically +create the list of directories +(:ref:`Automatically_Creating_a_List_of_Directories`) +which might help you in case your project has a lot of subdirectories. + + +.. code-block:: makefile + + ## This Makefile is intended to be used with the following directory + ## configuration: + ## - The sources are split into a series of csc (computer software components) + ## Each of these csc is put in its own directory. + ## Their name are referenced by the directory names. + ## They will be compiled into shared library (although this would also work + ## with static libraries + ## - The main program (and possibly other packages that do not belong to any + ## csc is put in the top level directory (where the Makefile is). + ## toplevel_dir __ first_csc (sources) __ lib (will contain the library) + ## \\_ second_csc (sources) __ lib (will contain the library) + ## \\_ ... + ## Although this Makefile is build for shared library, it is easy to modify + ## to build partial link objects instead (modify the lines with -shared and + ## gnatlink below) + ## + ## With this makefile, you can change any file in the system or add any new + ## file, and everything will be recompiled correctly (only the relevant shared + ## objects will be recompiled, and the main program will be re-linked). + + # The list of computer software component for your project. This might be + # generated automatically. + CSC_LIST=aa bb cc + + # Name of the main program (no extension) + MAIN=main + + # If we need to build objects with -fPIC, uncomment the following line + #NEED_FPIC=-fPIC + + # The following variable should give the directory containing libgnat.so + # You can get this directory through 'gnatls -v'. This is usually the last + # directory in the Object_Path. + GLIB=... + + # The directories for the libraries + # (This macro expands the list of CSC to the list of shared libraries, you + # could simply use the expanded form: + # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so + LIB_DIR=${foreach dir,${CSC_LIST},${dir}/lib/lib${dir}.so} + + ${MAIN}: objects ${LIB_DIR} + gnatbind ${MAIN} ${CSC_LIST:%=-aO%/lib} -shared + gnatlink ${MAIN} ${CSC_LIST:%=-l%} + + objects:: + # recompile the sources + gnatmake -c -i ${MAIN}.adb ${NEED_FPIC} ${CSC_LIST:%=-I%} + + # Note: In a future version of GNAT, the following commands will be simplified + # by a new tool, gnatmlib + ${LIB_DIR}: + mkdir -p ${dir $@ } + cd ${dir $@ } && gcc -shared -o ${notdir $@ } ../*.o -L${GLIB} -lgnat + cd ${dir $@ } && cp -f ../*.ali . + + # The dependencies for the modules + # Note that we have to force the expansion of *.o, since in some cases + # make won't be able to do it itself. + aa/lib/libaa.so: ${wildcard aa/*.o} + bb/lib/libbb.so: ${wildcard bb/*.o} + cc/lib/libcc.so: ${wildcard cc/*.o} + + # Make sure all of the shared libraries are in the path before starting the + # program + run:: + LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./${MAIN} + + clean:: + ${RM} -rf ${CSC_LIST:%=%/lib} + ${RM} ${CSC_LIST:%=%/*.ali} + ${RM} ${CSC_LIST:%=%/*.o} + ${RM} *.o *.ali ${MAIN} + + +.. _Automatically_Creating_a_List_of_Directories: + +Automatically Creating a List of Directories +-------------------------------------------- + +In most makefiles, you will have to specify a list of directories, and +store it in a variable. For small projects, it is often easier to +specify each of them by hand, since you then have full control over what +is the proper order for these directories, which ones should be +included. + +However, in larger projects, which might involve hundreds of +subdirectories, it might be more convenient to generate this list +automatically. + +The example below presents two methods. The first one, although less +general, gives you more control over the list. It involves wildcard +characters, that are automatically expanded by *make*. Its +shortcoming is that you need to explicitly specify some of the +organization of your project, such as for instance the directory tree +depth, whether some directories are found in a separate tree, etc. + +The second method is the most general one. It requires an external +program, called *find*, which is standard on all Unix systems. All +the directories found under a given root directory will be added to the +list. + +.. code-block:: makefile + + # The examples below are based on the following directory hierarchy: + # All the directories can contain any number of files + # ROOT_DIRECTORY -> a -> aa -> aaa + # -> ab + # -> ac + # -> b -> ba -> baa + # -> bb + # -> bc + # This Makefile creates a variable called DIRS, that can be reused any time + # you need this list (see the other examples in this section) + + # The root of your project's directory hierarchy + ROOT_DIRECTORY=. + + #### + # First method: specify explicitly the list of directories + # This allows you to specify any subset of all the directories you need. + #### + + DIRS := a/aa/ a/ab/ b/ba/ + + #### + # Second method: use wildcards + # Note that the argument(s) to wildcard below should end with a '/'. + # Since wildcards also return file names, we have to filter them out + # to avoid duplicate directory names. + # We thus use make's `dir` and `sort` functions. + # It sets DIRs to the following value (note that the directories aaa and baa + # are not given, unless you change the arguments to wildcard). + # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/ + #### + + DIRS := ${sort ${dir ${wildcard ${ROOT_DIRECTORY}/*/ + ${ROOT_DIRECTORY}/*/*/}}} + + #### + # Third method: use an external program + # This command is much faster if run on local disks, avoiding NFS slowdowns. + # This is the most complete command: it sets DIRs to the following value: + # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc + #### + + DIRS := ${shell find ${ROOT_DIRECTORY} -type d -print} + + + +.. _Generating_the_Command_Line_Switches: + +Generating the Command Line Switches +------------------------------------ + +Once you have created the list of directories as explained in the +previous section (:ref:`Automatically_Creating_a_List_of_Directories`), +you can easily generate the command line arguments to pass to gnatmake. + +For the sake of completeness, this example assumes that the source path +is not the same as the object path, and that you have two separate lists +of directories. + +.. code-block:: makefile + + # see "Automatically creating a list of directories" to create + # these variables + SOURCE_DIRS= + OBJECT_DIRS= + + GNATMAKE_SWITCHES := ${patsubst %,-aI%,${SOURCE_DIRS}} + GNATMAKE_SWITCHES += ${patsubst %,-aO%,${OBJECT_DIRS}} + + all: + gnatmake ${GNATMAKE_SWITCHES} main_unit + + +.. _Overcoming_Command_Line_Length_Limits: + +Overcoming Command Line Length Limits +------------------------------------- + +One problem that might be encountered on big projects is that many +operating systems limit the length of the command line. It is thus hard to give +gnatmake the list of source and object directories. + +This example shows how you can set up environment variables, which will +make *gnatmake* behave exactly as if the directories had been +specified on the command line, but have a much higher length limit (or +even none on most systems). + +It assumes that you have created a list of directories in your Makefile, +using one of the methods presented in +:ref:`Automatically_Creating_a_List_of_Directories`. +For the sake of completeness, we assume that the object +path (where the ALI files are found) is different from the sources patch. + +Note a small trick in the Makefile below: for efficiency reasons, we +create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are +expanded immediately by `make`. This way we overcome the standard +make behavior which is to expand the variables only when they are +actually used. + +On Windows, if you are using the standard Windows command shell, you must +replace colons with semicolons in the assignments to these variables. + +.. code-block:: makefile + + # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH. + # This is the same thing as putting the -I arguments on the command line. + # (the equivalent of using -aI on the command line would be to define + # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH). + # You can of course have different values for these variables. + # + # Note also that we need to keep the previous values of these variables, since + # they might have been set before running 'make' to specify where the GNAT + # library is installed. + + # see "Automatically creating a list of directories" to create these + # variables + SOURCE_DIRS= + OBJECT_DIRS= + + empty:= + space:=${empty} ${empty} + SOURCE_LIST := ${subst ${space},:,${SOURCE_DIRS}} + OBJECT_LIST := ${subst ${space},:,${OBJECT_DIRS}} + ADA_INCLUDE_PATH += ${SOURCE_LIST} + ADA_OBJECTS_PATH += ${OBJECT_LIST} + export ADA_INCLUDE_PATH + export ADA_OBJECTS_PATH + + all: + gnatmake main_unit diff --git a/gcc/ada/doc/gnat_ugn/elaboration_order_handling_in_gnat.rst b/gcc/ada/doc/gnat_ugn/elaboration_order_handling_in_gnat.rst new file mode 100644 index 00000000000..90b64a7f17a --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/elaboration_order_handling_in_gnat.rst @@ -0,0 +1,1864 @@ +.. |with| replace:: *with* +.. |withs| replace:: *with*\ s +.. |withed| replace:: *with*\ ed +.. |withing| replace:: *with*\ ing + +.. -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + + +.. _Elaboration_Order_Handling_in_GNAT: + +********************************** +Elaboration Order Handling in GNAT +********************************** + +.. index:: Order of elaboration +.. index:: Elaboration control + +This appendix describes the handling of elaboration code in Ada and +in GNAT, and discusses how the order of elaboration of program units can +be controlled in GNAT, either automatically or with explicit programming +features. + +.. _Elaboration_Code: + +Elaboration Code +================ + +Ada provides rather general mechanisms for executing code at elaboration +time, that is to say before the main program starts executing. Such code arises +in three contexts: + +* *Initializers for variables* + + Variables declared at the library level, in package specs or bodies, can + require initialization that is performed at elaboration time, as in: + + .. code-block:: ada + + Sqrt_Half : Float := Sqrt (0.5); + +* *Package initialization code* + + Code in a `BEGIN-END` section at the outer level of a package body is + executed as part of the package body elaboration code. + +* *Library level task allocators* + + Tasks that are declared using task allocators at the library level + start executing immediately and hence can execute at elaboration time. + +Subprogram calls are possible in any of these contexts, which means that +any arbitrary part of the program may be executed as part of the elaboration +code. It is even possible to write a program which does all its work at +elaboration time, with a null main program, although stylistically this +would usually be considered an inappropriate way to structure +a program. + +An important concern arises in the context of elaboration code: +we have to be sure that it is executed in an appropriate order. What we +have is a series of elaboration code sections, potentially one section +for each unit in the program. It is important that these execute +in the correct order. Correctness here means that, taking the above +example of the declaration of `Sqrt_Half`, +if some other piece of +elaboration code references `Sqrt_Half`, +then it must run after the +section of elaboration code that contains the declaration of +`Sqrt_Half`. + +There would never be any order of elaboration problem if we made a rule +that whenever you |with| a unit, you must elaborate both the spec and body +of that unit before elaborating the unit doing the |withing|: + +.. code-block:: ada + + with Unit_1; + package Unit_2 is ... + +would require that both the body and spec of `Unit_1` be elaborated +before the spec of `Unit_2`. However, a rule like that would be far too +restrictive. In particular, it would make it impossible to have routines +in separate packages that were mutually recursive. + +You might think that a clever enough compiler could look at the actual +elaboration code and determine an appropriate correct order of elaboration, +but in the general case, this is not possible. Consider the following +example. + +In the body of `Unit_1`, we have a procedure `Func_1` +that references +the variable `Sqrt_1`, which is declared in the elaboration code +of the body of `Unit_1`: + +.. code-block:: ada + + Sqrt_1 : Float := Sqrt (0.1); + +The elaboration code of the body of `Unit_1` also contains: + +.. code-block:: ada + + if expression_1 = 1 then + Q := Unit_2.Func_2; + end if; + +`Unit_2` is exactly parallel, +it has a procedure `Func_2` that references +the variable `Sqrt_2`, which is declared in the elaboration code of +the body `Unit_2`: + +.. code-block:: ada + + Sqrt_2 : Float := Sqrt (0.1); + +The elaboration code of the body of `Unit_2` also contains: + +.. code-block:: ada + + if expression_2 = 2 then + Q := Unit_1.Func_1; + end if; + +Now the question is, which of the following orders of elaboration is +acceptable: + +:: + + Spec of Unit_1 + Spec of Unit_2 + Body of Unit_1 + Body of Unit_2 + +or + +:: + + Spec of Unit_2 + Spec of Unit_1 + Body of Unit_2 + Body of Unit_1 + +If you carefully analyze the flow here, you will see that you cannot tell +at compile time the answer to this question. +If `expression_1` is not equal to 1, +and `expression_2` is not equal to 2, +then either order is acceptable, because neither of the function calls is +executed. If both tests evaluate to true, then neither order is acceptable +and in fact there is no correct order. + +If one of the two expressions is true, and the other is false, then one +of the above orders is correct, and the other is incorrect. For example, +if `expression_1` /= 1 and `expression_2` = 2, +then the call to `Func_1` +will occur, but not the call to `Func_2.` +This means that it is essential +to elaborate the body of `Unit_1` before +the body of `Unit_2`, so the first +order of elaboration is correct and the second is wrong. + +By making `expression_1` and `expression_2` +depend on input data, or perhaps +the time of day, we can make it impossible for the compiler or binder +to figure out which of these expressions will be true, and hence it +is impossible to guarantee a safe order of elaboration at run time. + +.. _Checking_the_Elaboration_Order: + +Checking the Elaboration Order +============================== + +In some languages that involve the same kind of elaboration problems, +e.g., Java and C++, the programmer needs to take these +ordering problems into account, and it is common to +write a program in which an incorrect elaboration order gives +surprising results, because it references variables before they +are initialized. +Ada is designed to be a safe language, and a programmer-beware approach is +clearly not sufficient. Consequently, the language provides three lines +of defense: + +* *Standard rules* + + Some standard rules restrict the possible choice of elaboration + order. In particular, if you |with| a unit, then its spec is always + elaborated before the unit doing the |with|. Similarly, a parent + spec is always elaborated before the child spec, and finally + a spec is always elaborated before its corresponding body. + +.. index:: Elaboration checks +.. index:: Checks, elaboration + +* *Dynamic elaboration checks* + + Dynamic checks are made at run time, so that if some entity is accessed + before it is elaborated (typically by means of a subprogram call) + then the exception (`Program_Error`) is raised. + +* *Elaboration control* + + Facilities are provided for the programmer to specify the desired order + of elaboration. + +Let's look at these facilities in more detail. First, the rules for +dynamic checking. One possible rule would be simply to say that the +exception is raised if you access a variable which has not yet been +elaborated. The trouble with this approach is that it could require +expensive checks on every variable reference. Instead Ada has two +rules which are a little more restrictive, but easier to check, and +easier to state: + +* *Restrictions on calls* + + A subprogram can only be called at elaboration time if its body + has been elaborated. The rules for elaboration given above guarantee + that the spec of the subprogram has been elaborated before the + call, but not the body. If this rule is violated, then the + exception `Program_Error` is raised. + +* *Restrictions on instantiations* + + A generic unit can only be instantiated if the body of the generic + unit has been elaborated. Again, the rules for elaboration given above + guarantee that the spec of the generic unit has been elaborated + before the instantiation, but not the body. If this rule is + violated, then the exception `Program_Error` is raised. + +The idea is that if the body has been elaborated, then any variables +it references must have been elaborated; by checking for the body being +elaborated we guarantee that none of its references causes any +trouble. As we noted above, this is a little too restrictive, because a +subprogram that has no non-local references in its body may in fact be safe +to call. However, it really would be unsafe to rely on this, because +it would mean that the caller was aware of details of the implementation +in the body. This goes against the basic tenets of Ada. + +A plausible implementation can be described as follows. +A Boolean variable is associated with each subprogram +and each generic unit. This variable is initialized to False, and is set to +True at the point body is elaborated. Every call or instantiation checks the +variable, and raises `Program_Error` if the variable is False. + +Note that one might think that it would be good enough to have one Boolean +variable for each package, but that would not deal with cases of trying +to call a body in the same package as the call +that has not been elaborated yet. +Of course a compiler may be able to do enough analysis to optimize away +some of the Boolean variables as unnecessary, and `GNAT` indeed +does such optimizations, but still the easiest conceptual model is to +think of there being one variable per subprogram. + +.. _Controlling_the_Elaboration_Order: + +Controlling the Elaboration Order +================================= + +In the previous section we discussed the rules in Ada which ensure +that `Program_Error` is raised if an incorrect elaboration order is +chosen. This prevents erroneous executions, but we need mechanisms to +specify a correct execution and avoid the exception altogether. +To achieve this, Ada provides a number of features for controlling +the order of elaboration. We discuss these features in this section. + +First, there are several ways of indicating to the compiler that a given +unit has no elaboration problems: + +* *packages that do not require a body* + + A library package that does not require a body does not permit + a body (this rule was introduced in Ada 95). + Thus if we have a such a package, as in: + + .. code-block:: ada + + package Definitions is + generic + type m is new integer; + package Subp is + type a is array (1 .. 10) of m; + type b is array (1 .. 20) of m; + end Subp; + end Definitions; + + A package that |withs| `Definitions` may safely instantiate + `Definitions.Subp` because the compiler can determine that there + definitely is no package body to worry about in this case + +.. index:: pragma Pure + +* *pragma Pure* + + This pragma places sufficient restrictions on a unit to guarantee that + no call to any subprogram in the unit can result in an + elaboration problem. This means that the compiler does not need + to worry about the point of elaboration of such units, and in + particular, does not need to check any calls to any subprograms + in this unit. + +.. index:: pragma Preelaborate + +* *pragma Preelaborate* + + This pragma places slightly less stringent restrictions on a unit than + does pragma Pure, + but these restrictions are still sufficient to ensure that there + are no elaboration problems with any calls to the unit. + +.. index:: pragma Elaborate_Body + +* *pragma Elaborate_Body* + + This pragma requires that the body of a unit be elaborated immediately + after its spec. Suppose a unit `A` has such a pragma, + and unit `B` does + a |with| of unit `A`. Recall that the standard rules require + the spec of unit `A` + to be elaborated before the |withing| unit; given the pragma in + `A`, we also know that the body of `A` + will be elaborated before `B`, so + that calls to `A` are safe and do not need a check. + + Note that, unlike pragma `Pure` and pragma `Preelaborate`, + the use of `Elaborate_Body` does not guarantee that the program is + free of elaboration problems, because it may not be possible + to satisfy the requested elaboration order. + Let's go back to the example with `Unit_1` and `Unit_2`. + If a programmer marks `Unit_1` as `Elaborate_Body`, + and not `Unit_2,` then the order of + elaboration will be:: + + Spec of Unit_2 + Spec of Unit_1 + Body of Unit_1 + Body of Unit_2 + + Now that means that the call to `Func_1` in `Unit_2` + need not be checked, + it must be safe. But the call to `Func_2` in + `Unit_1` may still fail if + `Expression_1` is equal to 1, + and the programmer must still take + responsibility for this not being the case. + + If all units carry a pragma `Elaborate_Body`, then all problems are + eliminated, except for calls entirely within a body, which are + in any case fully under programmer control. However, using the pragma + everywhere is not always possible. + In particular, for our `Unit_1`/`Unit_2` example, if + we marked both of them as having pragma `Elaborate_Body`, then + clearly there would be no possible elaboration order. + +The above pragmas allow a server to guarantee safe use by clients, and +clearly this is the preferable approach. Consequently a good rule +is to mark units as `Pure` or `Preelaborate` if possible, +and if this is not possible, +mark them as `Elaborate_Body` if possible. +As we have seen, there are situations where neither of these +three pragmas can be used. +So we also provide methods for clients to control the +order of elaboration of the servers on which they depend: + +.. index:: pragma Elaborate + +* *pragma Elaborate (unit)* + + This pragma is placed in the context clause, after a |with| clause, + and it requires that the body of the named unit be elaborated before + the unit in which the pragma occurs. The idea is to use this pragma + if the current unit calls at elaboration time, directly or indirectly, + some subprogram in the named unit. + + +.. index:: pragma Elaborate_All + +* *pragma Elaborate_All (unit)* + + This is a stronger version of the Elaborate pragma. Consider the + following example:: + + Unit A |withs| unit B and calls B.Func in elab code + Unit B |withs| unit C, and B.Func calls C.Func + + + Now if we put a pragma `Elaborate (B)` + in unit `A`, this ensures that the + body of `B` is elaborated before the call, but not the + body of `C`, so + the call to `C.Func` could still cause `Program_Error` to + be raised. + + The effect of a pragma `Elaborate_All` is stronger, it requires + not only that the body of the named unit be elaborated before the + unit doing the |with|, but also the bodies of all units that the + named unit uses, following |with| links transitively. For example, + if we put a pragma `Elaborate_All (B)` in unit `A`, + then it requires not only that the body of `B` be elaborated before `A`, + but also the body of `C`, because `B` |withs| `C`. + +We are now in a position to give a usage rule in Ada for avoiding +elaboration problems, at least if dynamic dispatching and access to +subprogram values are not used. We will handle these cases separately +later. + +The rule is simple: + +*If a unit has elaboration code that can directly or +indirectly make a call to a subprogram in a |withed| unit, or instantiate +a generic package in a |withed| unit, +then if the |withed| unit does not have +pragma `Pure` or `Preelaborate`, then the client should have +a pragma `Elaborate_All`for the |withed| unit.** + +By following this rule a client is +assured that calls can be made without risk of an exception. + +For generic subprogram instantiations, the rule can be relaxed to +require only a pragma `Elaborate` since elaborating the body +of a subprogram cannot cause any transitive elaboration (we are +not calling the subprogram in this case, just elaborating its +declaration). + +If this rule is not followed, then a program may be in one of four +states: + +* *No order exists* + + No order of elaboration exists which follows the rules, taking into + account any `Elaborate`, `Elaborate_All`, + or `Elaborate_Body` pragmas. In + this case, an Ada compiler must diagnose the situation at bind + time, and refuse to build an executable program. + +* *One or more orders exist, all incorrect* + + One or more acceptable elaboration orders exist, and all of them + generate an elaboration order problem. In this case, the binder + can build an executable program, but `Program_Error` will be raised + when the program is run. + +* *Several orders exist, some right, some incorrect* + + One or more acceptable elaboration orders exists, and some of them + work, and some do not. The programmer has not controlled + the order of elaboration, so the binder may or may not pick one of + the correct orders, and the program may or may not raise an + exception when it is run. This is the worst case, because it means + that the program may fail when moved to another compiler, or even + another version of the same compiler. + +* *One or more orders exists, all correct* + + One ore more acceptable elaboration orders exist, and all of them + work. In this case the program runs successfully. This state of + affairs can be guaranteed by following the rule we gave above, but + may be true even if the rule is not followed. + +Note that one additional advantage of following our rules on the use +of `Elaborate` and `Elaborate_All` +is that the program continues to stay in the ideal (all orders OK) state +even if maintenance +changes some bodies of some units. Conversely, if a program that does +not follow this rule happens to be safe at some point, this state of affairs +may deteriorate silently as a result of maintenance changes. + +You may have noticed that the above discussion did not mention +the use of `Elaborate_Body`. This was a deliberate omission. If you +|with| an `Elaborate_Body` unit, it still may be the case that +code in the body makes calls to some other unit, so it is still necessary +to use `Elaborate_All` on such units. + + +.. _Controlling_Elaboration_in_GNAT_-_Internal_Calls: + +Controlling Elaboration in GNAT - Internal Calls +================================================ + +In the case of internal calls, i.e., calls within a single package, the +programmer has full control over the order of elaboration, and it is up +to the programmer to elaborate declarations in an appropriate order. For +example writing: + +.. code-block:: ada + + function One return Float; + + Q : Float := One; + + function One return Float is + begin + return 1.0; + end One; + +will obviously raise `Program_Error` at run time, because function +One will be called before its body is elaborated. In this case GNAT will +generate a warning that the call will raise `Program_Error`:: + + 1. procedure y is + 2. function One return Float; + 3. + 4. Q : Float := One; + | + >>> warning: cannot call "One" before body is elaborated + >>> warning: Program_Error will be raised at run time + + 5. + 6. function One return Float is + 7. begin + 8. return 1.0; + 9. end One; + 10. + 11. begin + 12. null; + 13. end; + + +Note that in this particular case, it is likely that the call is safe, because +the function `One` does not access any global variables. +Nevertheless in Ada, we do not want the validity of the check to depend on +the contents of the body (think about the separate compilation case), so this +is still wrong, as we discussed in the previous sections. + +The error is easily corrected by rearranging the declarations so that the +body of `One` appears before the declaration containing the call +(note that in Ada 95 as well as later versions of the Ada standard, +declarations can appear in any order, so there is no restriction that +would prevent this reordering, and if we write: + +.. code-block:: ada + + function One return Float; + + function One return Float is + begin + return 1.0; + end One; + + Q : Float := One; + +then all is well, no warning is generated, and no +`Program_Error` exception +will be raised. +Things are more complicated when a chain of subprograms is executed: + +.. code-block:: ada + + function A return Integer; + function B return Integer; + function C return Integer; + + function B return Integer is begin return A; end; + function C return Integer is begin return B; end; + + X : Integer := C; + + function A return Integer is begin return 1; end; + +Now the call to `C` +at elaboration time in the declaration of `X` is correct, because +the body of `C` is already elaborated, +and the call to `B` within the body of +`C` is correct, but the call +to `A` within the body of `B` is incorrect, because the body +of `A` has not been elaborated, so `Program_Error` +will be raised on the call to `A`. +In this case GNAT will generate a +warning that `Program_Error` may be +raised at the point of the call. Let's look at the warning:: + + 1. procedure x is + 2. function A return Integer; + 3. function B return Integer; + 4. function C return Integer; + 5. + 6. function B return Integer is begin return A; end; + | + >>> warning: call to "A" before body is elaborated may + raise Program_Error + >>> warning: "B" called at line 7 + >>> warning: "C" called at line 9 + + 7. function C return Integer is begin return B; end; + 8. + 9. X : Integer := C; + 10. + 11. function A return Integer is begin return 1; end; + 12. + 13. begin + 14. null; + 15. end; + + +Note that the message here says 'may raise', instead of the direct case, +where the message says 'will be raised'. That's because whether +`A` is +actually called depends in general on run-time flow of control. +For example, if the body of `B` said + +.. code-block:: ada + + function B return Integer is + begin + if some-condition-depending-on-input-data then + return A; + else + return 1; + end if; + end B; + +then we could not know until run time whether the incorrect call to A would +actually occur, so `Program_Error` might +or might not be raised. It is possible for a compiler to +do a better job of analyzing bodies, to +determine whether or not `Program_Error` +might be raised, but it certainly +couldn't do a perfect job (that would require solving the halting problem +and is provably impossible), and because this is a warning anyway, it does +not seem worth the effort to do the analysis. Cases in which it +would be relevant are rare. + +In practice, warnings of either of the forms given +above will usually correspond to +real errors, and should be examined carefully and eliminated. +In the rare case where a warning is bogus, it can be suppressed by any of +the following methods: + +* Compile with the *-gnatws* switch set + +* Suppress `Elaboration_Check` for the called subprogram + +* Use pragma `Warnings_Off` to turn warnings off for the call + +For the internal elaboration check case, +GNAT by default generates the +necessary run-time checks to ensure +that `Program_Error` is raised if any +call fails an elaboration check. Of course this can only happen if a +warning has been issued as described above. The use of pragma +`Suppress (Elaboration_Check)` may (but is not guaranteed to) suppress +some of these checks, meaning that it may be possible (but is not +guaranteed) for a program to be able to call a subprogram whose body +is not yet elaborated, without raising a `Program_Error` exception. + + +.. _Controlling_Elaboration_in_GNAT_-_External_Calls: + +Controlling Elaboration in GNAT - External Calls +================================================ + +The previous section discussed the case in which the execution of a +particular thread of elaboration code occurred entirely within a +single unit. This is the easy case to handle, because a programmer +has direct and total control over the order of elaboration, and +furthermore, checks need only be generated in cases which are rare +and which the compiler can easily detect. +The situation is more complex when separate compilation is taken into account. +Consider the following: + +.. code-block:: ada + + package Math is + function Sqrt (Arg : Float) return Float; + end Math; + + package body Math is + function Sqrt (Arg : Float) return Float is + begin + ... + end Sqrt; + end Math; + + with Math; + package Stuff is + X : Float := Math.Sqrt (0.5); + end Stuff; + + with Stuff; + procedure Main is + begin + ... + end Main; + +where `Main` is the main program. When this program is executed, the +elaboration code must first be executed, and one of the jobs of the +binder is to determine the order in which the units of a program are +to be elaborated. In this case we have four units: the spec and body +of `Math`, +the spec of `Stuff` and the body of `Main`). +In what order should the four separate sections of elaboration code +be executed? + +There are some restrictions in the order of elaboration that the binder +can choose. In particular, if unit U has a |with| +for a package `X`, then you +are assured that the spec of `X` +is elaborated before U , but you are +not assured that the body of `X` +is elaborated before U. +This means that in the above case, the binder is allowed to choose the +order:: + + spec of Math + spec of Stuff + body of Math + body of Main + +but that's not good, because now the call to `Math.Sqrt` +that happens during +the elaboration of the `Stuff` +spec happens before the body of `Math.Sqrt` is +elaborated, and hence causes `Program_Error` exception to be raised. +At first glance, one might say that the binder is misbehaving, because +obviously you want to elaborate the body of something you |with| first, but +that is not a general rule that can be followed in all cases. Consider + +.. code-block:: ada + + package X is ... + + package Y is ... + + with X; + package body Y is ... + + with Y; + package body X is ... + +This is a common arrangement, and, apart from the order of elaboration +problems that might arise in connection with elaboration code, this works fine. +A rule that says that you must first elaborate the body of anything you +|with| cannot work in this case: +the body of `X` |withs| `Y`, +which means you would have to +elaborate the body of `Y` first, but that |withs| `X`, +which means +you have to elaborate the body of `X` first, but ... and we have a +loop that cannot be broken. + +It is true that the binder can in many cases guess an order of elaboration +that is unlikely to cause a `Program_Error` +exception to be raised, and it tries to do so (in the +above example of `Math/Stuff/Spec`, the GNAT binder will +by default +elaborate the body of `Math` right after its spec, so all will be well). + +However, a program that blindly relies on the binder to be helpful can +get into trouble, as we discussed in the previous sections, so GNAT +provides a number of facilities for assisting the programmer in +developing programs that are robust with respect to elaboration order. + + +.. _Default_Behavior_in_GNAT_-_Ensuring_Safety: + +Default Behavior in GNAT - Ensuring Safety +========================================== + +The default behavior in GNAT ensures elaboration safety. In its +default mode GNAT implements the +rule we previously described as the right approach. Let's restate it: + +*If a unit has elaboration code that can directly or indirectly make a +call to a subprogram in a |withed| unit, or instantiate a generic +package in a |withed| unit, then if the |withed| unit +does not have pragma `Pure` or `Preelaborate`, then the client should have an +`Elaborate_All` pragma for the |withed| unit.* + +*In the case of instantiating a generic subprogram, it is always +sufficient to have only an `Elaborate` pragma for the +|withed| unit.* + +By following this rule a client is assured that calls and instantiations +can be made without risk of an exception. + +In this mode GNAT traces all calls that are potentially made from +elaboration code, and puts in any missing implicit `Elaborate` +and `Elaborate_All` pragmas. +The advantage of this approach is that no elaboration problems +are possible if the binder can find an elaboration order that is +consistent with these implicit `Elaborate` and +`Elaborate_All` pragmas. The +disadvantage of this approach is that no such order may exist. + +If the binder does not generate any diagnostics, then it means that it has +found an elaboration order that is guaranteed to be safe. However, the binder +may still be relying on implicitly generated `Elaborate` and +`Elaborate_All` pragmas so portability to other compilers than GNAT is not +guaranteed. + +If it is important to guarantee portability, then the compilations should +use the *-gnatel* +(info messages for elaboration pragmas) switch. This will cause info messages +to be generated indicating the missing `Elaborate` and +`Elaborate_All` pragmas. +Consider the following source program: + +.. code-block:: ada + + with k; + package j is + m : integer := k.r; + end; + +where it is clear that there +should be a pragma `Elaborate_All` +for unit `k`. An implicit pragma will be generated, and it is +likely that the binder will be able to honor it. However, if you want +to port this program to some other Ada compiler than GNAT. +it is safer to include the pragma explicitly in the source. If this +unit is compiled with the *-gnatel* +switch, then the compiler outputs an information message:: + + 1. with k; + 2. package j is + 3. m : integer := k.r; + | + >>> info: call to "r" may raise Program_Error + >>> info: missing pragma Elaborate_All for "k" + + 4. end; + +and these messages can be used as a guide for supplying manually +the missing pragmas. It is usually a bad idea to use this +option during development. That's because it will tell you when +you need to put in a pragma, but cannot tell you when it is time +to take it out. So the use of pragma `Elaborate_All` may lead to +unnecessary dependencies and even false circularities. + +This default mode is more restrictive than the Ada Reference +Manual, and it is possible to construct programs which will compile +using the dynamic model described there, but will run into a +circularity using the safer static model we have described. + +Of course any Ada compiler must be able to operate in a mode +consistent with the requirements of the Ada Reference Manual, +and in particular must have the capability of implementing the +standard dynamic model of elaboration with run-time checks. + +In GNAT, this standard mode can be achieved either by the use of +the *-gnatE* switch on the compiler (*gcc* or +*gnatmake*) command, or by the use of the configuration pragma: + +.. code-block:: ada + + pragma Elaboration_Checks (DYNAMIC); + +Either approach will cause the unit affected to be compiled using the +standard dynamic run-time elaboration checks described in the Ada +Reference Manual. The static model is generally preferable, since it +is clearly safer to rely on compile and link time checks rather than +run-time checks. However, in the case of legacy code, it may be +difficult to meet the requirements of the static model. This +issue is further discussed in +:ref:`What_to_Do_If_the_Default_Elaboration_Behavior_Fails`. + +Note that the static model provides a strict subset of the allowed +behavior and programs of the Ada Reference Manual, so if you do +adhere to the static model and no circularities exist, +then you are assured that your program will +work using the dynamic model, providing that you remove any +pragma Elaborate statements from the source. + + +.. _Treatment_of_Pragma_Elaborate: + +Treatment of Pragma Elaborate +============================= + +.. index:: Pragma Elaborate + +The use of `pragma Elaborate` +should generally be avoided in Ada 95 and Ada 2005 programs, +since there is no guarantee that transitive calls +will be properly handled. Indeed at one point, this pragma was placed +in Annex J (Obsolescent Features), on the grounds that it is never useful. + +Now that's a bit restrictive. In practice, the case in which +`pragma Elaborate` is useful is when the caller knows that there +are no transitive calls, or that the called unit contains all necessary +transitive `pragma Elaborate` statements, and legacy code often +contains such uses. + +Strictly speaking the static mode in GNAT should ignore such pragmas, +since there is no assurance at compile time that the necessary safety +conditions are met. In practice, this would cause GNAT to be incompatible +with correctly written Ada 83 code that had all necessary +`pragma Elaborate` statements in place. Consequently, we made the +decision that GNAT in its default mode will believe that if it encounters +a `pragma Elaborate` then the programmer knows what they are doing, +and it will trust that no elaboration errors can occur. + +The result of this decision is two-fold. First to be safe using the +static mode, you should remove all `pragma Elaborate` statements. +Second, when fixing circularities in existing code, you can selectively +use `pragma Elaborate` statements to convince the static mode of +GNAT that it need not generate an implicit `pragma Elaborate_All` +statement. + +When using the static mode with *-gnatwl*, any use of +`pragma Elaborate` will generate a warning about possible +problems. + + +.. _Elaboration_Issues_for_Library_Tasks: + +Elaboration Issues for Library Tasks +==================================== + +.. index:: Library tasks, elaboration issues + +.. index:: Elaboration of library tasks + +In this section we examine special elaboration issues that arise for +programs that declare library level tasks. + +Generally the model of execution of an Ada program is that all units are +elaborated, and then execution of the program starts. However, the +declaration of library tasks definitely does not fit this model. The +reason for this is that library tasks start as soon as they are declared +(more precisely, as soon as the statement part of the enclosing package +body is reached), that is to say before elaboration +of the program is complete. This means that if such a task calls a +subprogram, or an entry in another task, the callee may or may not be +elaborated yet, and in the standard +Reference Manual model of dynamic elaboration checks, you can even +get timing dependent Program_Error exceptions, since there can be +a race between the elaboration code and the task code. + +The static model of elaboration in GNAT seeks to avoid all such +dynamic behavior, by being conservative, and the conservative +approach in this particular case is to assume that all the code +in a task body is potentially executed at elaboration time if +a task is declared at the library level. + +This can definitely result in unexpected circularities. Consider +the following example + +.. code-block:: ada + + package Decls is + task Lib_Task is + entry Start; + end Lib_Task; + + type My_Int is new Integer; + + function Ident (M : My_Int) return My_Int; + end Decls; + + with Utils; + package body Decls is + task body Lib_Task is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task; + + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; + end Decls; + + with Decls; + package Utils is + procedure Put_Val (Arg : Decls.My_Int); + end Utils; + + with Text_IO; + package body Utils is + procedure Put_Val (Arg : Decls.My_Int) is + begin + Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); + end Put_Val; + end Utils; + + with Decls; + procedure Main is + begin + Decls.Lib_Task.Start; + end; + +If the above example is compiled in the default static elaboration +mode, then a circularity occurs. The circularity comes from the call +`Utils.Put_Val` in the task body of `Decls.Lib_Task`. Since +this call occurs in elaboration code, we need an implicit pragma +`Elaborate_All` for `Utils`. This means that not only must +the spec and body of `Utils` be elaborated before the body +of `Decls`, but also the spec and body of any unit that is +|withed| by the body of `Utils` must also be elaborated before +the body of `Decls`. This is the transitive implication of +pragma `Elaborate_All` and it makes sense, because in general +the body of `Put_Val` might have a call to something in a +|withed| unit. + +In this case, the body of Utils (actually its spec) |withs| +`Decls`. Unfortunately this means that the body of `Decls` +must be elaborated before itself, in case there is a call from the +body of `Utils`. + +Here is the exact chain of events we are worrying about: + +* In the body of `Decls` a call is made from within the body of a library + task to a subprogram in the package `Utils`. Since this call may + occur at elaboration time (given that the task is activated at elaboration + time), we have to assume the worst, i.e., that the + call does happen at elaboration time. + +* This means that the body and spec of `Util` must be elaborated before + the body of `Decls` so that this call does not cause an access before + elaboration. + +* Within the body of `Util`, specifically within the body of + `Util.Put_Val` there may be calls to any unit |withed| + by this package. + +* One such |withed| package is package `Decls`, so there + might be a call to a subprogram in `Decls` in `Put_Val`. + In fact there is such a call in this example, but we would have to + assume that there was such a call even if it were not there, since + we are not supposed to write the body of `Decls` knowing what + is in the body of `Utils`; certainly in the case of the + static elaboration model, the compiler does not know what is in + other bodies and must assume the worst. + +* This means that the spec and body of `Decls` must also be + elaborated before we elaborate the unit containing the call, but + that unit is `Decls`! This means that the body of `Decls` + must be elaborated before itself, and that's a circularity. + +Indeed, if you add an explicit pragma `Elaborate_All` for `Utils` in +the body of `Decls` you will get a true Ada Reference Manual +circularity that makes the program illegal. + +In practice, we have found that problems with the static model of +elaboration in existing code often arise from library tasks, so +we must address this particular situation. + +Note that if we compile and run the program above, using the dynamic model of +elaboration (that is to say use the *-gnatE* switch), +then it compiles, binds, +links, and runs, printing the expected result of 2. Therefore in some sense +the circularity here is only apparent, and we need to capture +the properties of this program that distinguish it from other library-level +tasks that have real elaboration problems. + +We have four possible answers to this question: + + +* Use the dynamic model of elaboration. + + If we use the *-gnatE* switch, then as noted above, the program works. + Why is this? If we examine the task body, it is apparent that the task cannot + proceed past the + `accept` statement until after elaboration has been completed, because + the corresponding entry call comes from the main program, not earlier. + This is why the dynamic model works here. But that's really giving + up on a precise analysis, and we prefer to take this approach only if we cannot + solve the + problem in any other manner. So let us examine two ways to reorganize + the program to avoid the potential elaboration problem. + +* Split library tasks into separate packages. + + Write separate packages, so that library tasks are isolated from + other declarations as much as possible. Let us look at a variation on + the above program. + + + .. code-block:: ada + + package Decls1 is + task Lib_Task is + entry Start; + end Lib_Task; + end Decls1; + + with Utils; + package body Decls1 is + task body Lib_Task is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task; + end Decls1; + + package Decls2 is + type My_Int is new Integer; + function Ident (M : My_Int) return My_Int; + end Decls2; + + with Utils; + package body Decls2 is + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; + end Decls2; + + with Decls2; + package Utils is + procedure Put_Val (Arg : Decls2.My_Int); + end Utils; + + with Text_IO; + package body Utils is + procedure Put_Val (Arg : Decls2.My_Int) is + begin + Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg))); + end Put_Val; + end Utils; + + with Decls1; + procedure Main is + begin + Decls1.Lib_Task.Start; + end; + + + All we have done is to split `Decls` into two packages, one + containing the library task, and one containing everything else. Now + there is no cycle, and the program compiles, binds, links and executes + using the default static model of elaboration. + +* Declare separate task types. + + A significant part of the problem arises because of the use of the + single task declaration form. This means that the elaboration of + the task type, and the elaboration of the task itself (i.e., the + creation of the task) happen at the same time. A good rule + of style in Ada is to always create explicit task types. By + following the additional step of placing task objects in separate + packages from the task type declaration, many elaboration problems + are avoided. Here is another modified example of the example program: + + .. code-block:: ada + + package Decls is + task type Lib_Task_Type is + entry Start; + end Lib_Task_Type; + + type My_Int is new Integer; + + function Ident (M : My_Int) return My_Int; + end Decls; + + with Utils; + package body Decls is + task body Lib_Task_Type is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task_Type; + + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; + end Decls; + + with Decls; + package Utils is + procedure Put_Val (Arg : Decls.My_Int); + end Utils; + + with Text_IO; + package body Utils is + procedure Put_Val (Arg : Decls.My_Int) is + begin + Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); + end Put_Val; + end Utils; + + with Decls; + package Declst is + Lib_Task : Decls.Lib_Task_Type; + end Declst; + + with Declst; + procedure Main is + begin + Declst.Lib_Task.Start; + end; + + + What we have done here is to replace the `task` declaration in + package `Decls` with a `task type` declaration. Then we + introduce a separate package `Declst` to contain the actual + task object. This separates the elaboration issues for + the `task type` + declaration, which causes no trouble, from the elaboration issues + of the task object, which is also unproblematic, since it is now independent + of the elaboration of `Utils`. + This separation of concerns also corresponds to + a generally sound engineering principle of separating declarations + from instances. This version of the program also compiles, binds, links, + and executes, generating the expected output. + +.. index:: No_Entry_Calls_In_Elaboration_Code restriction + +* Use No_Entry_Calls_In_Elaboration_Code restriction. + + The previous two approaches described how a program can be restructured + to avoid the special problems caused by library task bodies. in practice, + however, such restructuring may be difficult to apply to existing legacy code, + so we must consider solutions that do not require massive rewriting. + + Let us consider more carefully why our original sample program works + under the dynamic model of elaboration. The reason is that the code + in the task body blocks immediately on the `accept` + statement. Now of course there is nothing to prohibit elaboration + code from making entry calls (for example from another library level task), + so we cannot tell in isolation that + the task will not execute the accept statement during elaboration. + + However, in practice it is very unusual to see elaboration code + make any entry calls, and the pattern of tasks starting + at elaboration time and then immediately blocking on `accept` or + `select` statements is very common. What this means is that + the compiler is being too pessimistic when it analyzes the + whole package body as though it might be executed at elaboration + time. + + If we know that the elaboration code contains no entry calls, (a very safe + assumption most of the time, that could almost be made the default + behavior), then we can compile all units of the program under control + of the following configuration pragma: + + .. code-block:: ada + + pragma Restrictions (No_Entry_Calls_In_Elaboration_Code); + + This pragma can be placed in the :file:`gnat.adc` file in the usual + manner. If we take our original unmodified program and compile it + in the presence of a :file:`gnat.adc` containing the above pragma, + then once again, we can compile, bind, link, and execute, obtaining + the expected result. In the presence of this pragma, the compiler does + not trace calls in a task body, that appear after the first `accept` + or `select` statement, and therefore does not report a potential + circularity in the original program. + + The compiler will check to the extent it can that the above + restriction is not violated, but it is not always possible to do a + complete check at compile time, so it is important to use this + pragma only if the stated restriction is in fact met, that is to say + no task receives an entry call before elaboration of all units is completed. + + +.. _Mixing_Elaboration_Models: + +Mixing Elaboration Models +========================= + +So far, we have assumed that the entire program is either compiled +using the dynamic model or static model, ensuring consistency. It +is possible to mix the two models, but rules have to be followed +if this mixing is done to ensure that elaboration checks are not +omitted. + +The basic rule is that +**a unit compiled with the static model cannot +be |withed| by a unit compiled with the dynamic model**. +The reason for this is that in the static model, a unit assumes that +its clients guarantee to use (the equivalent of) pragma +`Elaborate_All` so that no elaboration checks are required +in inner subprograms, and this assumption is violated if the +client is compiled with dynamic checks. + +The precise rule is as follows. A unit that is compiled with dynamic +checks can only |with| a unit that meets at least one of the +following criteria: + + +* The |withed| unit is itself compiled with dynamic elaboration + checks (that is with the *-gnatE* switch. + +* The |withed| unit is an internal GNAT implementation unit from + the System, Interfaces, Ada, or GNAT hierarchies. + +* The |withed| unit has pragma Preelaborate or pragma Pure. + +* The |withing| unit (that is the client) has an explicit pragma + `Elaborate_All` for the |withed| unit. + + +If this rule is violated, that is if a unit with dynamic elaboration +checks |withs| a unit that does not meet one of the above four +criteria, then the binder (`gnatbind`) will issue a warning +similar to that in the following example:: + + warning: "x.ads" has dynamic elaboration checks and with's + warning: "y.ads" which has static elaboration checks + +These warnings indicate that the rule has been violated, and that as a result +elaboration checks may be missed in the resulting executable file. +This warning may be suppressed using the *-ws* binder switch +in the usual manner. + +One useful application of this mixing rule is in the case of a subsystem +which does not itself |with| units from the remainder of the +application. In this case, the entire subsystem can be compiled with +dynamic checks to resolve a circularity in the subsystem, while +allowing the main application that uses this subsystem to be compiled +using the more reliable default static model. + + +.. _What_to_Do_If_the_Default_Elaboration_Behavior_Fails: + +What to Do If the Default Elaboration Behavior Fails +==================================================== + +If the binder cannot find an acceptable order, it outputs detailed +diagnostics. For example:: + + error: elaboration circularity detected + info: "proc (body)" must be elaborated before "pack (body)" + info: reason: Elaborate_All probably needed in unit "pack (body)" + info: recompile "pack (body)" with -gnatel + info: for full details + info: "proc (body)" + info: is needed by its spec: + info: "proc (spec)" + info: which is withed by: + info: "pack (body)" + info: "pack (body)" must be elaborated before "proc (body)" + info: reason: pragma Elaborate in unit "proc (body)" + +In this case we have a cycle that the binder cannot break. On the one +hand, there is an explicit pragma Elaborate in `proc` for +`pack`. This means that the body of `pack` must be elaborated +before the body of `proc`. On the other hand, there is elaboration +code in `pack` that calls a subprogram in `proc`. This means +that for maximum safety, there should really be a pragma +Elaborate_All in `pack` for `proc` which would require that +the body of `proc` be elaborated before the body of +`pack`. Clearly both requirements cannot be satisfied. +Faced with a circularity of this kind, you have three different options. + + +* *Fix the program* + + The most desirable option from the point of view of long-term maintenance + is to rearrange the program so that the elaboration problems are avoided. + One useful technique is to place the elaboration code into separate + child packages. Another is to move some of the initialization code to + explicitly called subprograms, where the program controls the order + of initialization explicitly. Although this is the most desirable option, + it may be impractical and involve too much modification, especially in + the case of complex legacy code. + +* *Perform dynamic checks* + + If the compilations are done using the *-gnatE* + (dynamic elaboration check) switch, then GNAT behaves in a quite different + manner. Dynamic checks are generated for all calls that could possibly result + in raising an exception. With this switch, the compiler does not generate + implicit `Elaborate` or `Elaborate_All` pragmas. The behavior then is + exactly as specified in the :title:`Ada Reference Manual`. + The binder will generate + an executable program that may or may not raise `Program_Error`, and then + it is the programmer's job to ensure that it does not raise an exception. Note + that it is important to compile all units with the switch, it cannot be used + selectively. + +* *Suppress checks* + + The drawback of dynamic checks is that they generate a + significant overhead at run time, both in space and time. If you + are absolutely sure that your program cannot raise any elaboration + exceptions, and you still want to use the dynamic elaboration model, + then you can use the configuration pragma + `Suppress (Elaboration_Check)` to suppress all such checks. For + example this pragma could be placed in the :file:`gnat.adc` file. + +* *Suppress checks selectively* + + When you know that certain calls or instantiations in elaboration code cannot + possibly lead to an elaboration error, and the binder nevertheless complains + about implicit `Elaborate` and `Elaborate_All` pragmas that lead to + elaboration circularities, it is possible to remove those warnings locally and + obtain a program that will bind. Clearly this can be unsafe, and it is the + responsibility of the programmer to make sure that the resulting program has no + elaboration anomalies. The pragma `Suppress (Elaboration_Check)` can be + used with different granularity to suppress warnings and break elaboration + circularities: + + * Place the pragma that names the called subprogram in the declarative part + that contains the call. + + * Place the pragma in the declarative part, without naming an entity. This + disables warnings on all calls in the corresponding declarative region. + + * Place the pragma in the package spec that declares the called subprogram, + and name the subprogram. This disables warnings on all elaboration calls to + that subprogram. + + * Place the pragma in the package spec that declares the called subprogram, + without naming any entity. This disables warnings on all elaboration calls to + all subprograms declared in this spec. + + * Use Pragma Elaborate. + + As previously described in section :ref:`Treatment_of_Pragma_Elaborate`, + GNAT in static mode assumes that a `pragma` Elaborate indicates correctly + that no elaboration checks are required on calls to the designated unit. + There may be cases in which the caller knows that no transitive calls + can occur, so that a `pragma Elaborate` will be sufficient in a + case where `pragma Elaborate_All` would cause a circularity. + + These five cases are listed in order of decreasing safety, and therefore + require increasing programmer care in their application. Consider the + following program: + + .. code-block:: ada + + package Pack1 is + function F1 return Integer; + X1 : Integer; + end Pack1; + + package Pack2 is + function F2 return Integer; + function Pure (x : integer) return integer; + -- pragma Suppress (Elaboration_Check, On => Pure); -- (3) + -- pragma Suppress (Elaboration_Check); -- (4) + end Pack2; + + with Pack2; + package body Pack1 is + function F1 return Integer is + begin + return 100; + end F1; + Val : integer := Pack2.Pure (11); -- Elab. call (1) + begin + declare + -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1) + -- pragma Suppress(Elaboration_Check); -- (2) + begin + X1 := Pack2.F2 + 1; -- Elab. call (2) + end; + end Pack1; + + with Pack1; + package body Pack2 is + function F2 return Integer is + begin + return Pack1.F1; + end F2; + function Pure (x : integer) return integer is + begin + return x ** 3 - 3 * x; + end; + end Pack2; + + with Pack1, Ada.Text_IO; + procedure Proc3 is + begin + Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101 + end Proc3; + + In the absence of any pragmas, an attempt to bind this program produces + the following diagnostics:: + + error: elaboration circularity detected + info: "pack1 (body)" must be elaborated before "pack1 (body)" + info: reason: Elaborate_All probably needed in unit "pack1 (body)" + info: recompile "pack1 (body)" with -gnatel for full details + info: "pack1 (body)" + info: must be elaborated along with its spec: + info: "pack1 (spec)" + info: which is withed by: + info: "pack2 (body)" + info: which must be elaborated along with its spec: + info: "pack2 (spec)" + info: which is withed by: + info: "pack1 (body)" + + The sources of the circularity are the two calls to `Pack2.Pure` and + `Pack2.F2` in the body of `Pack1`. We can see that the call to + F2 is safe, even though F2 calls F1, because the call appears after the + elaboration of the body of F1. Therefore the pragma (1) is safe, and will + remove the warning on the call. It is also possible to use pragma (2) + because there are no other potentially unsafe calls in the block. + + The call to `Pure` is safe because this function does not depend on the + state of `Pack2`. Therefore any call to this function is safe, and it + is correct to place pragma (3) in the corresponding package spec. + + Finally, we could place pragma (4) in the spec of `Pack2` to disable + warnings on all calls to functions declared therein. Note that this is not + necessarily safe, and requires more detailed examination of the subprogram + bodies involved. In particular, a call to `F2` requires that `F1` + be already elaborated. + +It is hard to generalize on which of these four approaches should be +taken. Obviously if it is possible to fix the program so that the default +treatment works, this is preferable, but this may not always be practical. +It is certainly simple enough to use *-gnatE* +but the danger in this case is that, even if the GNAT binder +finds a correct elaboration order, it may not always do so, +and certainly a binder from another Ada compiler might not. A +combination of testing and analysis (for which the +information messages generated with the *-gnatel* +switch can be useful) must be used to ensure that the program is free +of errors. One switch that is useful in this testing is the +*-p (pessimistic elaboration order)* switch for `gnatbind`. +Normally the binder tries to find an order that has the best chance +of avoiding elaboration problems. However, if this switch is used, the binder +plays a devil's advocate role, and tries to choose the order that +has the best chance of failing. If your program works even with this +switch, then it has a better chance of being error free, but this is still +not a guarantee. + +For an example of this approach in action, consider the C-tests (executable +tests) from the ACATS suite. If these are compiled and run with the default +treatment, then all but one of them succeed without generating any error +diagnostics from the binder. However, there is one test that fails, and +this is not surprising, because the whole point of this test is to ensure +that the compiler can handle cases where it is impossible to determine +a correct order statically, and it checks that an exception is indeed +raised at run time. + +This one test must be compiled and run using the *-gnatE* +switch, and then it passes. Alternatively, the entire suite can +be run using this switch. It is never wrong to run with the dynamic +elaboration switch if your code is correct, and we assume that the +C-tests are indeed correct (it is less efficient, but efficiency is +not a factor in running the ACATS tests.) + + +.. _Elaboration_for_Indirect_Calls: + +Elaboration for Indirect Calls +============================== + +.. index:: Dispatching calls +.. index:: Indirect calls + +In rare cases, the static elaboration model fails to prevent +dispatching calls to not-yet-elaborated subprograms. In such cases, we +fall back to run-time checks; premature calls to any primitive +operation of a tagged type before the body of the operation has been +elaborated will raise `Program_Error`. + +Access-to-subprogram types, however, are handled conservatively, and +do not require run-time checks. This was not true in earlier versions +of the compiler; you can use the *-gnatd.U* debug switch to +revert to the old behavior if the new conservative behavior causes +elaboration cycles. Here, 'conservative' means that if you do +`P'Access` during elaboration, the compiler will assume that you +might call `P` indirectly during elaboration, so it adds an +implicit `pragma Elaborate_All` on the library unit containing +`P`. The *-gnatd.U* switch is safe if you know there are +no such calls. If the program worked before, it will continue to work +with *-gnatd.U*. But beware that code modifications such as +adding an indirect call can cause erroneous behavior in the presence +of *-gnatd.U*. + + +.. _Summary_of_Procedures_for_Elaboration_Control: + +Summary of Procedures for Elaboration Control +============================================= + +.. index:: Elaboration control + +First, compile your program with the default options, using none of +the special elaboration control switches. If the binder successfully +binds your program, then you can be confident that, apart from issues +raised by the use of access-to-subprogram types and dynamic dispatching, +the program is free of elaboration errors. If it is important that the +program be portable to other compilers than GNAT, then use the +*-gnatel* +switch to generate messages about missing `Elaborate` or +`Elaborate_All` pragmas, and supply the missing pragmas. + +If the program fails to bind using the default static elaboration +handling, then you can fix the program to eliminate the binder +message, or recompile the entire program with the +*-gnatE* switch to generate dynamic elaboration checks, +and, if you are sure there really are no elaboration problems, +use a global pragma `Suppress (Elaboration_Check)`. + + +.. _Other_Elaboration_Order_Considerations: + +Other Elaboration Order Considerations +====================================== + +This section has been entirely concerned with the issue of finding a valid +elaboration order, as defined by the Ada Reference Manual. In a case +where several elaboration orders are valid, the task is to find one +of the possible valid elaboration orders (and the static model in GNAT +will ensure that this is achieved). + +The purpose of the elaboration rules in the Ada Reference Manual is to +make sure that no entity is accessed before it has been elaborated. For +a subprogram, this means that the spec and body must have been elaborated +before the subprogram is called. For an object, this means that the object +must have been elaborated before its value is read or written. A violation +of either of these two requirements is an access before elaboration order, +and this section has been all about avoiding such errors. + +In the case where more than one order of elaboration is possible, in the +sense that access before elaboration errors are avoided, then any one of +the orders is 'correct' in the sense that it meets the requirements of +the Ada Reference Manual, and no such error occurs. + +However, it may be the case for a given program, that there are +constraints on the order of elaboration that come not from consideration +of avoiding elaboration errors, but rather from extra-lingual logic +requirements. Consider this example: + +.. code-block:: ada + + with Init_Constants; + package Constants is + X : Integer := 0; + Y : Integer := 0; + end Constants; + + package Init_Constants is + procedure P; --* require a body* + end Init_Constants; + + with Constants; + package body Init_Constants is + procedure P is begin null; end; + begin + Constants.X := 3; + Constants.Y := 4; + end Init_Constants; + + with Constants; + package Calc is + Z : Integer := Constants.X + Constants.Y; + end Calc; + + with Calc; + with Text_IO; use Text_IO; + procedure Main is + begin + Put_Line (Calc.Z'Img); + end Main; + +In this example, there is more than one valid order of elaboration. For +example both the following are correct orders:: + + Init_Constants spec + Constants spec + Calc spec + Init_Constants body + Main body + +and + +:: + + Init_Constants spec + Init_Constants body + Constants spec + Calc spec + Main body + +There is no language rule to prefer one or the other, both are correct +from an order of elaboration point of view. But the programmatic effects +of the two orders are very different. In the first, the elaboration routine +of `Calc` initializes `Z` to zero, and then the main program +runs with this value of zero. But in the second order, the elaboration +routine of `Calc` runs after the body of Init_Constants has set +`X` and `Y` and thus `Z` is set to 7 before `Main` runs. + +One could perhaps by applying pretty clever non-artificial intelligence +to the situation guess that it is more likely that the second order of +elaboration is the one desired, but there is no formal linguistic reason +to prefer one over the other. In fact in this particular case, GNAT will +prefer the second order, because of the rule that bodies are elaborated +as soon as possible, but it's just luck that this is what was wanted +(if indeed the second order was preferred). + +If the program cares about the order of elaboration routines in a case like +this, it is important to specify the order required. In this particular +case, that could have been achieved by adding to the spec of Calc: + +.. code-block:: ada + + pragma Elaborate_All (Constants); + +which requires that the body (if any) and spec of `Constants`, +as well as the body and spec of any unit |withed| by +`Constants` be elaborated before `Calc` is elaborated. + +Clearly no automatic method can always guess which alternative you require, +and if you are working with legacy code that had constraints of this kind +which were not properly specified by adding `Elaborate` or +`Elaborate_All` pragmas, then indeed it is possible that two different +compilers can choose different orders. + +However, GNAT does attempt to diagnose the common situation where there +are uninitialized variables in the visible part of a package spec, and the +corresponding package body has an elaboration block that directly or +indirectly initialized one or more of these variables. This is the situation +in which a pragma Elaborate_Body is usually desirable, and GNAT will generate +a warning that suggests this addition if it detects this situation. + +The `gnatbind` *-p* switch may be useful in smoking +out problems. This switch causes bodies to be elaborated as late as possible +instead of as early as possible. In the example above, it would have forced +the choice of the first elaboration order. If you get different results +when using this switch, and particularly if one set of results is right, +and one is wrong as far as you are concerned, it shows that you have some +missing `Elaborate` pragmas. For the example above, we have the +following output: + +.. code-block:: sh + + $ gnatmake -f -q main + $ main + 7 + $ gnatmake -f -q main -bargs -p + $ main + 0 + +It is of course quite unlikely that both these results are correct, so +it is up to you in a case like this to investigate the source of the +difference, by looking at the two elaboration orders that are chosen, +and figuring out which is correct, and then adding the necessary +`Elaborate` or `Elaborate_All` pragmas to ensure the desired order. + + +.. _Determining_the_Chosen_Elaboration_Order: + +Determining the Chosen Elaboration Order +======================================== + +To see the elaboration order that the binder chooses, you can look at +the last part of the file:`b~xxx.adb` binder output file. Here is an example:: + + System.Soft_Links'Elab_Body; + E14 := True; + System.Secondary_Stack'Elab_Body; + E18 := True; + System.Exception_Table'Elab_Body; + E24 := True; + Ada.Io_Exceptions'Elab_Spec; + E67 := True; + Ada.Tags'Elab_Spec; + Ada.Streams'Elab_Spec; + E43 := True; + Interfaces.C'Elab_Spec; + E69 := True; + System.Finalization_Root'Elab_Spec; + E60 := True; + System.Os_Lib'Elab_Body; + E71 := True; + System.Finalization_Implementation'Elab_Spec; + System.Finalization_Implementation'Elab_Body; + E62 := True; + Ada.Finalization'Elab_Spec; + E58 := True; + Ada.Finalization.List_Controller'Elab_Spec; + E76 := True; + System.File_Control_Block'Elab_Spec; + E74 := True; + System.File_Io'Elab_Body; + E56 := True; + Ada.Tags'Elab_Body; + E45 := True; + Ada.Text_Io'Elab_Spec; + Ada.Text_Io'Elab_Body; + E07 := True; + +Here Elab_Spec elaborates the spec +and Elab_Body elaborates the body. The assignments to the :samp:`E{xx}` flags +flag that the corresponding body is now elaborated. + +You can also ask the binder to generate a more +readable list of the elaboration order using the +`-l` switch when invoking the binder. Here is +an example of the output generated by this switch:: + + ada (spec) + interfaces (spec) + system (spec) + system.case_util (spec) + system.case_util (body) + system.concat_2 (spec) + system.concat_2 (body) + system.concat_3 (spec) + system.concat_3 (body) + system.htable (spec) + system.parameters (spec) + system.parameters (body) + system.crtl (spec) + interfaces.c_streams (spec) + interfaces.c_streams (body) + system.restrictions (spec) + system.restrictions (body) + system.standard_library (spec) + system.exceptions (spec) + system.exceptions (body) + system.storage_elements (spec) + system.storage_elements (body) + system.secondary_stack (spec) + system.stack_checking (spec) + system.stack_checking (body) + system.string_hash (spec) + system.string_hash (body) + system.htable (body) + system.strings (spec) + system.strings (body) + system.traceback (spec) + system.traceback (body) + system.traceback_entries (spec) + system.traceback_entries (body) + ada.exceptions (spec) + ada.exceptions.last_chance_handler (spec) + system.soft_links (spec) + system.soft_links (body) + ada.exceptions.last_chance_handler (body) + system.secondary_stack (body) + system.exception_table (spec) + system.exception_table (body) + ada.io_exceptions (spec) + ada.tags (spec) + ada.streams (spec) + interfaces.c (spec) + interfaces.c (body) + system.finalization_root (spec) + system.finalization_root (body) + system.memory (spec) + system.memory (body) + system.standard_library (body) + system.os_lib (spec) + system.os_lib (body) + system.unsigned_types (spec) + system.stream_attributes (spec) + system.stream_attributes (body) + system.finalization_implementation (spec) + system.finalization_implementation (body) + ada.finalization (spec) + ada.finalization (body) + ada.finalization.list_controller (spec) + ada.finalization.list_controller (body) + system.file_control_block (spec) + system.file_io (spec) + system.file_io (body) + system.val_uns (spec) + system.val_util (spec) + system.val_util (body) + system.val_uns (body) + system.wch_con (spec) + system.wch_con (body) + system.wch_cnv (spec) + system.wch_jis (spec) + system.wch_jis (body) + system.wch_cnv (body) + system.wch_stw (spec) + system.wch_stw (body) + ada.tags (body) + ada.exceptions (body) + ada.text_io (spec) + ada.text_io (body) + text_io (spec) + gdbstr (body) diff --git a/gcc/ada/doc/gnat_ugn/example_of_binder_output.rst b/gcc/ada/doc/gnat_ugn/example_of_binder_output.rst new file mode 100644 index 00000000000..b2c34c0b820 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/example_of_binder_output.rst @@ -0,0 +1,750 @@ +.. _Example_of_Binder_Output_File: + +***************************** +Example of Binder Output File +***************************** + +.. index:: Binder output (example) + +This Appendix displays the source code for the output file +generated by *gnatbind* for a simple 'Hello World' program. +Comments have been added for clarification purposes. + + +.. code-block:: ada + + -- The package is called Ada_Main unless this name is actually used + -- as a unit name in the partition, in which case some other unique + -- name is used. + + pragma Ada_95; + with System; + package ada_main is + pragma Warnings (Off); + + -- The main program saves the parameters (argument count, + -- argument values, environment pointer) in global variables + -- for later access by other units including + -- Ada.Command_Line. + + gnat_argc : Integer; + gnat_argv : System.Address; + gnat_envp : System.Address; + + -- The actual variables are stored in a library routine. This + -- is useful for some shared library situations, where there + -- are problems if variables are not in the library. + + pragma Import (C, gnat_argc); + pragma Import (C, gnat_argv); + pragma Import (C, gnat_envp); + + -- The exit status is similarly an external location + + gnat_exit_status : Integer; + pragma Import (C, gnat_exit_status); + + GNAT_Version : constant String := + "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL; + pragma Export (C, GNAT_Version, "__gnat_version"); + + Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL; + pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name"); + + -- This is the generated adainit routine that performs + -- initialization at the start of execution. In the case + -- where Ada is the main program, this main program makes + -- a call to adainit at program startup. + + procedure adainit; + pragma Export (C, adainit, "adainit"); + + -- This is the generated adafinal routine that performs + -- finalization at the end of execution. In the case where + -- Ada is the main program, this main program makes a call + -- to adafinal at program termination. + + procedure adafinal; + pragma Export (C, adafinal, "adafinal"); + + -- This routine is called at the start of execution. It is + -- a dummy routine that is used by the debugger to breakpoint + -- at the start of execution. + + -- This is the actual generated main program (it would be + -- suppressed if the no main program switch were used). As + -- required by standard system conventions, this program has + -- the external name main. + + function main + (argc : Integer; + argv : System.Address; + envp : System.Address) + return Integer; + pragma Export (C, main, "main"); + + -- The following set of constants give the version + -- identification values for every unit in the bound + -- partition. This identification is computed from all + -- dependent semantic units, and corresponds to the + -- string that would be returned by use of the + -- Body_Version or Version attributes. + + -- The following Export pragmas export the version numbers + -- with symbolic names ending in B (for body) or S + -- (for spec) so that they can be located in a link. The + -- information provided here is sufficient to track down + -- the exact versions of units used in a given build. + + type Version_32 is mod 2 ** 32; + u00001 : constant Version_32 := 16#8ad6e54a#; + pragma Export (C, u00001, "helloB"); + u00002 : constant Version_32 := 16#fbff4c67#; + pragma Export (C, u00002, "system__standard_libraryB"); + u00003 : constant Version_32 := 16#1ec6fd90#; + pragma Export (C, u00003, "system__standard_libraryS"); + u00004 : constant Version_32 := 16#3ffc8e18#; + pragma Export (C, u00004, "adaS"); + u00005 : constant Version_32 := 16#28f088c2#; + pragma Export (C, u00005, "ada__text_ioB"); + u00006 : constant Version_32 := 16#f372c8ac#; + pragma Export (C, u00006, "ada__text_ioS"); + u00007 : constant Version_32 := 16#2c143749#; + pragma Export (C, u00007, "ada__exceptionsB"); + u00008 : constant Version_32 := 16#f4f0cce8#; + pragma Export (C, u00008, "ada__exceptionsS"); + u00009 : constant Version_32 := 16#a46739c0#; + pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB"); + u00010 : constant Version_32 := 16#3aac8c92#; + pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS"); + u00011 : constant Version_32 := 16#1d274481#; + pragma Export (C, u00011, "systemS"); + u00012 : constant Version_32 := 16#a207fefe#; + pragma Export (C, u00012, "system__soft_linksB"); + u00013 : constant Version_32 := 16#467d9556#; + pragma Export (C, u00013, "system__soft_linksS"); + u00014 : constant Version_32 := 16#b01dad17#; + pragma Export (C, u00014, "system__parametersB"); + u00015 : constant Version_32 := 16#630d49fe#; + pragma Export (C, u00015, "system__parametersS"); + u00016 : constant Version_32 := 16#b19b6653#; + pragma Export (C, u00016, "system__secondary_stackB"); + u00017 : constant Version_32 := 16#b6468be8#; + pragma Export (C, u00017, "system__secondary_stackS"); + u00018 : constant Version_32 := 16#39a03df9#; + pragma Export (C, u00018, "system__storage_elementsB"); + u00019 : constant Version_32 := 16#30e40e85#; + pragma Export (C, u00019, "system__storage_elementsS"); + u00020 : constant Version_32 := 16#41837d1e#; + pragma Export (C, u00020, "system__stack_checkingB"); + u00021 : constant Version_32 := 16#93982f69#; + pragma Export (C, u00021, "system__stack_checkingS"); + u00022 : constant Version_32 := 16#393398c1#; + pragma Export (C, u00022, "system__exception_tableB"); + u00023 : constant Version_32 := 16#b33e2294#; + pragma Export (C, u00023, "system__exception_tableS"); + u00024 : constant Version_32 := 16#ce4af020#; + pragma Export (C, u00024, "system__exceptionsB"); + u00025 : constant Version_32 := 16#75442977#; + pragma Export (C, u00025, "system__exceptionsS"); + u00026 : constant Version_32 := 16#37d758f1#; + pragma Export (C, u00026, "system__exceptions__machineS"); + u00027 : constant Version_32 := 16#b895431d#; + pragma Export (C, u00027, "system__exceptions_debugB"); + u00028 : constant Version_32 := 16#aec55d3f#; + pragma Export (C, u00028, "system__exceptions_debugS"); + u00029 : constant Version_32 := 16#570325c8#; + pragma Export (C, u00029, "system__img_intB"); + u00030 : constant Version_32 := 16#1ffca443#; + pragma Export (C, u00030, "system__img_intS"); + u00031 : constant Version_32 := 16#b98c3e16#; + pragma Export (C, u00031, "system__tracebackB"); + u00032 : constant Version_32 := 16#831a9d5a#; + pragma Export (C, u00032, "system__tracebackS"); + u00033 : constant Version_32 := 16#9ed49525#; + pragma Export (C, u00033, "system__traceback_entriesB"); + u00034 : constant Version_32 := 16#1d7cb2f1#; + pragma Export (C, u00034, "system__traceback_entriesS"); + u00035 : constant Version_32 := 16#8c33a517#; + pragma Export (C, u00035, "system__wch_conB"); + u00036 : constant Version_32 := 16#065a6653#; + pragma Export (C, u00036, "system__wch_conS"); + u00037 : constant Version_32 := 16#9721e840#; + pragma Export (C, u00037, "system__wch_stwB"); + u00038 : constant Version_32 := 16#2b4b4a52#; + pragma Export (C, u00038, "system__wch_stwS"); + u00039 : constant Version_32 := 16#92b797cb#; + pragma Export (C, u00039, "system__wch_cnvB"); + u00040 : constant Version_32 := 16#09eddca0#; + pragma Export (C, u00040, "system__wch_cnvS"); + u00041 : constant Version_32 := 16#6033a23f#; + pragma Export (C, u00041, "interfacesS"); + u00042 : constant Version_32 := 16#ece6fdb6#; + pragma Export (C, u00042, "system__wch_jisB"); + u00043 : constant Version_32 := 16#899dc581#; + pragma Export (C, u00043, "system__wch_jisS"); + u00044 : constant Version_32 := 16#10558b11#; + pragma Export (C, u00044, "ada__streamsB"); + u00045 : constant Version_32 := 16#2e6701ab#; + pragma Export (C, u00045, "ada__streamsS"); + u00046 : constant Version_32 := 16#db5c917c#; + pragma Export (C, u00046, "ada__io_exceptionsS"); + u00047 : constant Version_32 := 16#12c8cd7d#; + pragma Export (C, u00047, "ada__tagsB"); + u00048 : constant Version_32 := 16#ce72c228#; + pragma Export (C, u00048, "ada__tagsS"); + u00049 : constant Version_32 := 16#c3335bfd#; + pragma Export (C, u00049, "system__htableB"); + u00050 : constant Version_32 := 16#99e5f76b#; + pragma Export (C, u00050, "system__htableS"); + u00051 : constant Version_32 := 16#089f5cd0#; + pragma Export (C, u00051, "system__string_hashB"); + u00052 : constant Version_32 := 16#3bbb9c15#; + pragma Export (C, u00052, "system__string_hashS"); + u00053 : constant Version_32 := 16#807fe041#; + pragma Export (C, u00053, "system__unsigned_typesS"); + u00054 : constant Version_32 := 16#d27be59e#; + pragma Export (C, u00054, "system__val_lluB"); + u00055 : constant Version_32 := 16#fa8db733#; + pragma Export (C, u00055, "system__val_lluS"); + u00056 : constant Version_32 := 16#27b600b2#; + pragma Export (C, u00056, "system__val_utilB"); + u00057 : constant Version_32 := 16#b187f27f#; + pragma Export (C, u00057, "system__val_utilS"); + u00058 : constant Version_32 := 16#d1060688#; + pragma Export (C, u00058, "system__case_utilB"); + u00059 : constant Version_32 := 16#392e2d56#; + pragma Export (C, u00059, "system__case_utilS"); + u00060 : constant Version_32 := 16#84a27f0d#; + pragma Export (C, u00060, "interfaces__c_streamsB"); + u00061 : constant Version_32 := 16#8bb5f2c0#; + pragma Export (C, u00061, "interfaces__c_streamsS"); + u00062 : constant Version_32 := 16#6db6928f#; + pragma Export (C, u00062, "system__crtlS"); + u00063 : constant Version_32 := 16#4e6a342b#; + pragma Export (C, u00063, "system__file_ioB"); + u00064 : constant Version_32 := 16#ba56a5e4#; + pragma Export (C, u00064, "system__file_ioS"); + u00065 : constant Version_32 := 16#b7ab275c#; + pragma Export (C, u00065, "ada__finalizationB"); + u00066 : constant Version_32 := 16#19f764ca#; + pragma Export (C, u00066, "ada__finalizationS"); + u00067 : constant Version_32 := 16#95817ed8#; + pragma Export (C, u00067, "system__finalization_rootB"); + u00068 : constant Version_32 := 16#52d53711#; + pragma Export (C, u00068, "system__finalization_rootS"); + u00069 : constant Version_32 := 16#769e25e6#; + pragma Export (C, u00069, "interfaces__cB"); + u00070 : constant Version_32 := 16#4a38bedb#; + pragma Export (C, u00070, "interfaces__cS"); + u00071 : constant Version_32 := 16#07e6ee66#; + pragma Export (C, u00071, "system__os_libB"); + u00072 : constant Version_32 := 16#d7b69782#; + pragma Export (C, u00072, "system__os_libS"); + u00073 : constant Version_32 := 16#1a817b8e#; + pragma Export (C, u00073, "system__stringsB"); + u00074 : constant Version_32 := 16#639855e7#; + pragma Export (C, u00074, "system__stringsS"); + u00075 : constant Version_32 := 16#e0b8de29#; + pragma Export (C, u00075, "system__file_control_blockS"); + u00076 : constant Version_32 := 16#b5b2aca1#; + pragma Export (C, u00076, "system__finalization_mastersB"); + u00077 : constant Version_32 := 16#69316dc1#; + pragma Export (C, u00077, "system__finalization_mastersS"); + u00078 : constant Version_32 := 16#57a37a42#; + pragma Export (C, u00078, "system__address_imageB"); + u00079 : constant Version_32 := 16#bccbd9bb#; + pragma Export (C, u00079, "system__address_imageS"); + u00080 : constant Version_32 := 16#7268f812#; + pragma Export (C, u00080, "system__img_boolB"); + u00081 : constant Version_32 := 16#e8fe356a#; + pragma Export (C, u00081, "system__img_boolS"); + u00082 : constant Version_32 := 16#d7aac20c#; + pragma Export (C, u00082, "system__ioB"); + u00083 : constant Version_32 := 16#8365b3ce#; + pragma Export (C, u00083, "system__ioS"); + u00084 : constant Version_32 := 16#6d4d969a#; + pragma Export (C, u00084, "system__storage_poolsB"); + u00085 : constant Version_32 := 16#e87cc305#; + pragma Export (C, u00085, "system__storage_poolsS"); + u00086 : constant Version_32 := 16#e34550ca#; + pragma Export (C, u00086, "system__pool_globalB"); + u00087 : constant Version_32 := 16#c88d2d16#; + pragma Export (C, u00087, "system__pool_globalS"); + u00088 : constant Version_32 := 16#9d39c675#; + pragma Export (C, u00088, "system__memoryB"); + u00089 : constant Version_32 := 16#445a22b5#; + pragma Export (C, u00089, "system__memoryS"); + u00090 : constant Version_32 := 16#6a859064#; + pragma Export (C, u00090, "system__storage_pools__subpoolsB"); + u00091 : constant Version_32 := 16#e3b008dc#; + pragma Export (C, u00091, "system__storage_pools__subpoolsS"); + u00092 : constant Version_32 := 16#63f11652#; + pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB"); + u00093 : constant Version_32 := 16#fe2f4b3a#; + pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS"); + + -- BEGIN ELABORATION ORDER + -- ada%s + -- interfaces%s + -- system%s + -- system.case_util%s + -- system.case_util%b + -- system.htable%s + -- system.img_bool%s + -- system.img_bool%b + -- system.img_int%s + -- system.img_int%b + -- system.io%s + -- system.io%b + -- system.parameters%s + -- system.parameters%b + -- system.crtl%s + -- interfaces.c_streams%s + -- interfaces.c_streams%b + -- system.standard_library%s + -- system.exceptions_debug%s + -- system.exceptions_debug%b + -- system.storage_elements%s + -- system.storage_elements%b + -- system.stack_checking%s + -- system.stack_checking%b + -- system.string_hash%s + -- system.string_hash%b + -- system.htable%b + -- system.strings%s + -- system.strings%b + -- system.os_lib%s + -- system.traceback_entries%s + -- system.traceback_entries%b + -- ada.exceptions%s + -- system.soft_links%s + -- system.unsigned_types%s + -- system.val_llu%s + -- system.val_util%s + -- system.val_util%b + -- system.val_llu%b + -- system.wch_con%s + -- system.wch_con%b + -- system.wch_cnv%s + -- system.wch_jis%s + -- system.wch_jis%b + -- system.wch_cnv%b + -- system.wch_stw%s + -- system.wch_stw%b + -- ada.exceptions.last_chance_handler%s + -- ada.exceptions.last_chance_handler%b + -- system.address_image%s + -- system.exception_table%s + -- system.exception_table%b + -- ada.io_exceptions%s + -- ada.tags%s + -- ada.streams%s + -- ada.streams%b + -- interfaces.c%s + -- system.exceptions%s + -- system.exceptions%b + -- system.exceptions.machine%s + -- system.finalization_root%s + -- system.finalization_root%b + -- ada.finalization%s + -- ada.finalization%b + -- system.storage_pools%s + -- system.storage_pools%b + -- system.finalization_masters%s + -- system.storage_pools.subpools%s + -- system.storage_pools.subpools.finalization%s + -- system.storage_pools.subpools.finalization%b + -- system.memory%s + -- system.memory%b + -- system.standard_library%b + -- system.pool_global%s + -- system.pool_global%b + -- system.file_control_block%s + -- system.file_io%s + -- system.secondary_stack%s + -- system.file_io%b + -- system.storage_pools.subpools%b + -- system.finalization_masters%b + -- interfaces.c%b + -- ada.tags%b + -- system.soft_links%b + -- system.os_lib%b + -- system.secondary_stack%b + -- system.address_image%b + -- system.traceback%s + -- ada.exceptions%b + -- system.traceback%b + -- ada.text_io%s + -- ada.text_io%b + -- hello%b + -- END ELABORATION ORDER + + end ada_main; + +.. code-block:: ada + + pragma Ada_95; + -- The following source file name pragmas allow the generated file + -- names to be unique for different main programs. They are needed + -- since the package name will always be Ada_Main. + + pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads"); + pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb"); + + pragma Suppress (Overflow_Check); + with Ada.Exceptions; + + -- Generated package body for Ada_Main starts here + + package body ada_main is + pragma Warnings (Off); + + -- These values are reference counter associated to units which have + -- been elaborated. It is also used to avoid elaborating the + -- same unit twice. + + E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E"); + E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E"); + E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E"); + E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E"); + E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E"); + E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E"); + E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E"); + E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E"); + E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E"); + E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E"); + E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E"); + E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E"); + E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E"); + E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E"); + E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E"); + E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E"); + E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E"); + E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E"); + + Local_Priority_Specific_Dispatching : constant String := ""; + Local_Interrupt_States : constant String := ""; + + Is_Elaborated : Boolean := False; + + procedure finalize_library is + begin + E06 := E06 - 1; + declare + procedure F1; + pragma Import (Ada, F1, "ada__text_io__finalize_spec"); + begin + F1; + end; + E77 := E77 - 1; + E91 := E91 - 1; + declare + procedure F2; + pragma Import (Ada, F2, "system__file_io__finalize_body"); + begin + E64 := E64 - 1; + F2; + end; + declare + procedure F3; + pragma Import (Ada, F3, "system__file_control_block__finalize_spec"); + begin + E75 := E75 - 1; + F3; + end; + E87 := E87 - 1; + declare + procedure F4; + pragma Import (Ada, F4, "system__pool_global__finalize_spec"); + begin + F4; + end; + declare + procedure F5; + pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec"); + begin + F5; + end; + declare + procedure F6; + pragma Import (Ada, F6, "system__finalization_masters__finalize_spec"); + begin + F6; + end; + declare + procedure Reraise_Library_Exception_If_Any; + pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any"); + begin + Reraise_Library_Exception_If_Any; + end; + end finalize_library; + + ------------- + -- adainit -- + ------------- + + procedure adainit is + + Main_Priority : Integer; + pragma Import (C, Main_Priority, "__gl_main_priority"); + Time_Slice_Value : Integer; + pragma Import (C, Time_Slice_Value, "__gl_time_slice_val"); + WC_Encoding : Character; + pragma Import (C, WC_Encoding, "__gl_wc_encoding"); + Locking_Policy : Character; + pragma Import (C, Locking_Policy, "__gl_locking_policy"); + Queuing_Policy : Character; + pragma Import (C, Queuing_Policy, "__gl_queuing_policy"); + Task_Dispatching_Policy : Character; + pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy"); + Priority_Specific_Dispatching : System.Address; + pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching"); + Num_Specific_Dispatching : Integer; + pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching"); + Main_CPU : Integer; + pragma Import (C, Main_CPU, "__gl_main_cpu"); + Interrupt_States : System.Address; + pragma Import (C, Interrupt_States, "__gl_interrupt_states"); + Num_Interrupt_States : Integer; + pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states"); + Unreserve_All_Interrupts : Integer; + pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts"); + Detect_Blocking : Integer; + pragma Import (C, Detect_Blocking, "__gl_detect_blocking"); + Default_Stack_Size : Integer; + pragma Import (C, Default_Stack_Size, "__gl_default_stack_size"); + Leap_Seconds_Support : Integer; + pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support"); + + procedure Runtime_Initialize; + pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize"); + + Finalize_Library_Objects : No_Param_Proc; + pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects"); + + -- Start of processing for adainit + + begin + + -- Record various information for this partition. The values + -- are derived by the binder from information stored in the ali + -- files by the compiler. + + if Is_Elaborated then + return; + end if; + Is_Elaborated := True; + Main_Priority := -1; + Time_Slice_Value := -1; + WC_Encoding := 'b'; + Locking_Policy := ' '; + Queuing_Policy := ' '; + Task_Dispatching_Policy := ' '; + Priority_Specific_Dispatching := + Local_Priority_Specific_Dispatching'Address; + Num_Specific_Dispatching := 0; + Main_CPU := -1; + Interrupt_States := Local_Interrupt_States'Address; + Num_Interrupt_States := 0; + Unreserve_All_Interrupts := 0; + Detect_Blocking := 0; + Default_Stack_Size := -1; + Leap_Seconds_Support := 0; + + Runtime_Initialize; + + Finalize_Library_Objects := finalize_library'access; + + -- Now we have the elaboration calls for all units in the partition. + -- The Elab_Spec and Elab_Body attributes generate references to the + -- implicit elaboration procedures generated by the compiler for + -- each unit that requires elaboration. Increment a counter of + -- reference for each unit. + + System.Soft_Links'Elab_Spec; + System.Exception_Table'Elab_Body; + E23 := E23 + 1; + Ada.Io_Exceptions'Elab_Spec; + E46 := E46 + 1; + Ada.Tags'Elab_Spec; + Ada.Streams'Elab_Spec; + E45 := E45 + 1; + Interfaces.C'Elab_Spec; + System.Exceptions'Elab_Spec; + E25 := E25 + 1; + System.Finalization_Root'Elab_Spec; + E68 := E68 + 1; + Ada.Finalization'Elab_Spec; + E66 := E66 + 1; + System.Storage_Pools'Elab_Spec; + E85 := E85 + 1; + System.Finalization_Masters'Elab_Spec; + System.Storage_Pools.Subpools'Elab_Spec; + System.Pool_Global'Elab_Spec; + E87 := E87 + 1; + System.File_Control_Block'Elab_Spec; + E75 := E75 + 1; + System.File_Io'Elab_Body; + E64 := E64 + 1; + E91 := E91 + 1; + System.Finalization_Masters'Elab_Body; + E77 := E77 + 1; + E70 := E70 + 1; + Ada.Tags'Elab_Body; + E48 := E48 + 1; + System.Soft_Links'Elab_Body; + E13 := E13 + 1; + System.Os_Lib'Elab_Body; + E72 := E72 + 1; + System.Secondary_Stack'Elab_Body; + E17 := E17 + 1; + Ada.Text_Io'Elab_Spec; + Ada.Text_Io'Elab_Body; + E06 := E06 + 1; + end adainit; + + -------------- + -- adafinal -- + -------------- + + procedure adafinal is + procedure s_stalib_adafinal; + pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal"); + + procedure Runtime_Finalize; + pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize"); + + begin + if not Is_Elaborated then + return; + end if; + Is_Elaborated := False; + Runtime_Finalize; + s_stalib_adafinal; + end adafinal; + + -- We get to the main program of the partition by using + -- pragma Import because if we try to with the unit and + -- call it Ada style, then not only do we waste time + -- recompiling it, but also, we don't really know the right + -- switches (e.g.@: identifier character set) to be used + -- to compile it. + + procedure Ada_Main_Program; + pragma Import (Ada, Ada_Main_Program, "_ada_hello"); + + ---------- + -- main -- + ---------- + + -- main is actually a function, as in the ANSI C standard, + -- defined to return the exit status. The three parameters + -- are the argument count, argument values and environment + -- pointer. + + function main + (argc : Integer; + argv : System.Address; + envp : System.Address) + return Integer + is + -- The initialize routine performs low level system + -- initialization using a standard library routine which + -- sets up signal handling and performs any other + -- required setup. The routine can be found in file + -- a-init.c. + + procedure initialize; + pragma Import (C, initialize, "__gnat_initialize"); + + -- The finalize routine performs low level system + -- finalization using a standard library routine. The + -- routine is found in file a-final.c and in the standard + -- distribution is a dummy routine that does nothing, so + -- really this is a hook for special user finalization. + + procedure finalize; + pragma Import (C, finalize, "__gnat_finalize"); + + -- The following is to initialize the SEH exceptions + + SEH : aliased array (1 .. 2) of Integer; + + Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address; + pragma Volatile (Ensure_Reference); + + -- Start of processing for main + + begin + -- Save global variables + + gnat_argc := argc; + gnat_argv := argv; + gnat_envp := envp; + + -- Call low level system initialization + + Initialize (SEH'Address); + + -- Call our generated Ada initialization routine + + adainit; + + -- Now we call the main program of the partition + + Ada_Main_Program; + + -- Perform Ada finalization + + adafinal; + + -- Perform low level system finalization + + Finalize; + + -- Return the proper exit status + return (gnat_exit_status); + end; + + -- This section is entirely comments, so it has no effect on the + -- compilation of the Ada_Main package. It provides the list of + -- object files and linker options, as well as some standard + -- libraries needed for the link. The gnatlink utility parses + -- this b~hello.adb file to read these comment lines to generate + -- the appropriate command line arguments for the call to the + -- system linker. The BEGIN/END lines are used for sentinels for + -- this parsing operation. + + -- The exact file names will of course depend on the environment, + -- host/target and location of files on the host system. + + -- BEGIN Object file/option list + -- ./hello.o + -- -L./ + -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/ + -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a + -- END Object file/option list + + end ada_main; + + +The Ada code in the above example is exactly what is generated by the +binder. We have added comments to more clearly indicate the function +of each part of the generated `Ada_Main` package. + +The code is standard Ada in all respects, and can be processed by any +tools that handle Ada. In particular, it is possible to use the debugger +in Ada mode to debug the generated `Ada_Main` package. For example, +suppose that for reasons that you do not understand, your program is crashing +during elaboration of the body of `Ada.Text_IO`. To locate this bug, +you can place a breakpoint on the call: + + .. code-block:: ada + + Ada.Text_Io'Elab_Body; + +and trace the elaboration routine for this package to find out where +the problem might be (more usually of course you would be debugging +elaboration code in your own application). + diff --git a/gcc/ada/doc/gnat_ugn/getting_started_with_gnat.rst b/gcc/ada/doc/gnat_ugn/getting_started_with_gnat.rst new file mode 100644 index 00000000000..fcfb07875e4 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/getting_started_with_gnat.rst @@ -0,0 +1,276 @@ +.. _Getting_Started_with_GNAT: + +************************* +Getting Started with GNAT +************************* + +This chapter describes how to use GNAT's command line interface to build +executable Ada programs. +On most platforms a visually oriented Integrated Development Environment +is also available, the GNAT Programming Studio (GPS). +GPS offers a graphical "look and feel", support for development in +other programming languages, comprehensive browsing features, and +many other capabilities. +For information on GPS please refer to +:title:`Using the GNAT Programming Studio`. + + +.. _Running_GNAT: + +Running GNAT +============ + +Three steps are needed to create an executable file from an Ada source +file: + +* The source file(s) must be compiled. +* The file(s) must be bound using the GNAT binder. +* All appropriate object files must be linked to produce an executable. + +All three steps are most commonly handled by using the *gnatmake* +utility program that, given the name of the main program, automatically +performs the necessary compilation, binding and linking steps. + +.. _Running_a_Simple_Ada_Program: + +Running a Simple Ada Program +============================ + +Any text editor may be used to prepare an Ada program. +(If Emacs is used, the optional Ada mode may be helpful in laying out the +program.) +The program text is a normal text file. We will assume in our initial +example that you have used your editor to prepare the following +standard format text file: + + +.. code-block:: ada + + with Ada.Text_IO; use Ada.Text_IO; + procedure Hello is + begin + Put_Line ("Hello WORLD!"); + end Hello; + +This file should be named :file:`hello.adb`. +With the normal default file naming conventions, GNAT requires +that each file +contain a single compilation unit whose file name is the +unit name, +with periods replaced by hyphens; the +extension is :file:`ads` for a +spec and :file:`adb` for a body. +You can override this default file naming convention by use of the +special pragma `Source_File_Name` (for further information please +see :ref:`Using_Other_File_Names`). +Alternatively, if you want to rename your files according to this default +convention, which is probably more convenient if you will be using GNAT +for all your compilations, then the `gnatchop` utility +can be used to generate correctly-named source files +(see :ref:`Renaming_Files_with_gnatchop`). + +You can compile the program using the following command (`$` is used +as the command prompt in the examples in this document): + +.. code-block:: sh + + $ gcc -c hello.adb + + +*gcc* is the command used to run the compiler. This compiler is +capable of compiling programs in several languages, including Ada and +C. It assumes that you have given it an Ada program if the file extension is +either :file:`.ads` or :file:`.adb`, and it will then call +the GNAT compiler to compile the specified file. + +The :option:`-c` switch is required. It tells *gcc* to only do a +compilation. (For C programs, *gcc* can also do linking, but this +capability is not used directly for Ada programs, so the :option:`-c` +switch must always be present.) + +This compile command generates a file +:file:`hello.o`, which is the object +file corresponding to your Ada program. It also generates +an 'Ada Library Information' file :file:`hello.ali`, +which contains additional information used to check +that an Ada program is consistent. +To build an executable file, +use `gnatbind` to bind the program +and *gnatlink* to link it. The +argument to both `gnatbind` and *gnatlink* is the name of the +:file:`ALI` file, but the default extension of :file:`.ali` can +be omitted. This means that in the most common case, the argument +is simply the name of the main program: + +.. code-block:: sh + + $ gnatbind hello + $ gnatlink hello + +A simpler method of carrying out these steps is to use *gnatmake*, +a master program that invokes all the required +compilation, binding and linking tools in the correct order. In particular, +*gnatmake* automatically recompiles any sources that have been +modified since they were last compiled, or sources that depend +on such modified sources, so that 'version skew' is avoided. + +.. index:: Version skew (avoided by *gnatmake*) + +.. code-block:: sh + + $ gnatmake hello.adb + +The result is an executable program called :file:`hello`, which can be +run by entering: + +.. code-block:: sh + + $ hello + +assuming that the current directory is on the search path +for executable programs. + +and, if all has gone well, you will see:: + + Hello WORLD! + +appear in response to this command. + +.. _Running_a_Program_with_Multiple_Units: + +Running a Program with Multiple Units +===================================== + +Consider a slightly more complicated example that has three files: a +main program, and the spec and body of a package: + + +.. code-block:: ada + + package Greetings is + procedure Hello; + procedure Goodbye; + end Greetings; + + with Ada.Text_IO; use Ada.Text_IO; + package body Greetings is + procedure Hello is + begin + Put_Line ("Hello WORLD!"); + end Hello; + + procedure Goodbye is + begin + Put_Line ("Goodbye WORLD!"); + end Goodbye; + end Greetings; + + with Greetings; + procedure Gmain is + begin + Greetings.Hello; + Greetings.Goodbye; + end Gmain; + +Following the one-unit-per-file rule, place this program in the +following three separate files: + + + +*greetings.ads* + spec of package `Greetings` + + +*greetings.adb* + body of package `Greetings` + + +*gmain.adb* + body of main program + +To build an executable version of +this program, we could use four separate steps to compile, bind, and link +the program, as follows: + +.. code-block:: sh + + $ gcc -c gmain.adb + $ gcc -c greetings.adb + $ gnatbind gmain + $ gnatlink gmain + +Note that there is no required order of compilation when using GNAT. +In particular it is perfectly fine to compile the main program first. +Also, it is not necessary to compile package specs in the case where +there is an accompanying body; you only need to compile the body. If you want +to submit these files to the compiler for semantic checking and not code +generation, then use the :option:`-gnatc` switch: + +.. code-block:: sh + + $ gcc -c greetings.ads -gnatc + +Although the compilation can be done in separate steps as in the +above example, in practice it is almost always more convenient +to use the *gnatmake* tool. All you need to know in this case +is the name of the main program's source file. The effect of the above four +commands can be achieved with a single one: + +.. code-block:: sh + + $ gnatmake gmain.adb + +In the next section we discuss the advantages of using *gnatmake* in +more detail. + +.. _Using_the_gnatmake_Utility: + +Using the *gnatmake* Utility +============================ + +If you work on a program by compiling single components at a time using +*gcc*, you typically keep track of the units you modify. In order to +build a consistent system, you compile not only these units, but also any +units that depend on the units you have modified. +For example, in the preceding case, +if you edit :file:`gmain.adb`, you only need to recompile that file. But if +you edit :file:`greetings.ads`, you must recompile both +:file:`greetings.adb` and :file:`gmain.adb`, because both files contain +units that depend on :file:`greetings.ads`. + +*gnatbind* will warn you if you forget one of these compilation +steps, so that it is impossible to generate an inconsistent program as a +result of forgetting to do a compilation. Nevertheless it is tedious and +error-prone to keep track of dependencies among units. +One approach to handle the dependency-bookkeeping is to use a +makefile. However, makefiles present maintenance problems of their own: +if the dependencies change as you change the program, you must make +sure that the makefile is kept up-to-date manually, which is also an +error-prone process. + +The *gnatmake* utility takes care of these details automatically. +Invoke it using either one of the following forms: + +.. code-block:: sh + + $ gnatmake gmain.adb + $ gnatmake gmain + +The argument is the name of the file containing the main program; +you may omit the extension. *gnatmake* +examines the environment, automatically recompiles any files that need +recompiling, and binds and links the resulting set of object files, +generating the executable file, :file:`gmain`. +In a large program, it +can be extremely helpful to use *gnatmake*, because working out by hand +what needs to be recompiled can be difficult. + +Note that *gnatmake* takes into account all the Ada rules that +establish dependencies among units. These include dependencies that result +from inlining subprogram bodies, and from +generic instantiation. Unlike some other +Ada make tools, *gnatmake* does not rely on the dependencies that were +found by the compiler on a previous compilation, which may possibly +be wrong when sources change. *gnatmake* determines the exact set of +dependencies from scratch each time it is run. + diff --git a/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst b/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst new file mode 100644 index 00000000000..9e332d9d076 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/gnat_and_program_execution.rst @@ -0,0 +1,4190 @@ +.. |with| replace:: *with* +.. |withs| replace:: *with*\ s +.. |withed| replace:: *with*\ ed +.. |withing| replace:: *with*\ ing + +.. -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + + +.. _GNAT_and_Program_Execution: + +************************** +GNAT and Program Execution +************************** + +This chapter covers several topics: + +* `Running and Debugging Ada Programs`_ +* `Code Coverage and Profiling`_ +* `Improving Performance`_ +* `Overflow Check Handling in GNAT`_ +* `Performing Dimensionality Analysis in GNAT`_ +* `Stack Related Facilities`_ +* `Memory Management Issues`_ + +.. _Running_and_Debugging_Ada_Programs: + +Running and Debugging Ada Programs +================================== + +.. index:: Debugging + +This section discusses how to debug Ada programs. + +An incorrect Ada program may be handled in three ways by the GNAT compiler: + +* The illegality may be a violation of the static semantics of Ada. In + that case GNAT diagnoses the constructs in the program that are illegal. + It is then a straightforward matter for the user to modify those parts of + the program. + +* The illegality may be a violation of the dynamic semantics of Ada. In + that case the program compiles and executes, but may generate incorrect + results, or may terminate abnormally with some exception. + +* When presented with a program that contains convoluted errors, GNAT + itself may terminate abnormally without providing full diagnostics on + the incorrect user program. + +.. index:: Debugger + +.. index:: ! gdb + +.. _The_GNAT_Debugger_GDB: + +The GNAT Debugger GDB +--------------------- + +`GDB` is a general purpose, platform-independent debugger that +can be used to debug mixed-language programs compiled with *gcc*, +and in particular is capable of debugging Ada programs compiled with +GNAT. The latest versions of `GDB` are Ada-aware and can handle +complex Ada data structures. + +See :title:`Debugging with GDB`, +for full details on the usage of `GDB`, including a section on +its usage on programs. This manual should be consulted for full +details. The section that follows is a brief introduction to the +philosophy and use of `GDB`. + +When GNAT programs are compiled, the compiler optionally writes debugging +information into the generated object file, including information on +line numbers, and on declared types and variables. This information is +separate from the generated code. It makes the object files considerably +larger, but it does not add to the size of the actual executable that +will be loaded into memory, and has no impact on run-time performance. The +generation of debug information is triggered by the use of the +-g switch in the *gcc* or *gnatmake* command +used to carry out the compilations. It is important to emphasize that +the use of these options does not change the generated code. + +The debugging information is written in standard system formats that +are used by many tools, including debuggers and profilers. The format +of the information is typically designed to describe C types and +semantics, but GNAT implements a translation scheme which allows full +details about Ada types and variables to be encoded into these +standard C formats. Details of this encoding scheme may be found in +the file exp_dbug.ads in the GNAT source distribution. However, the +details of this encoding are, in general, of no interest to a user, +since `GDB` automatically performs the necessary decoding. + +When a program is bound and linked, the debugging information is +collected from the object files, and stored in the executable image of +the program. Again, this process significantly increases the size of +the generated executable file, but it does not increase the size of +the executable program itself. Furthermore, if this program is run in +the normal manner, it runs exactly as if the debug information were +not present, and takes no more actual memory. + +However, if the program is run under control of `GDB`, the +debugger is activated. The image of the program is loaded, at which +point it is ready to run. If a run command is given, then the program +will run exactly as it would have if `GDB` were not present. This +is a crucial part of the `GDB` design philosophy. `GDB` is +entirely non-intrusive until a breakpoint is encountered. If no +breakpoint is ever hit, the program will run exactly as it would if no +debugger were present. When a breakpoint is hit, `GDB` accesses +the debugging information and can respond to user commands to inspect +variables, and more generally to report on the state of execution. + +.. _Running_GDB: + +Running GDB +----------- + +This section describes how to initiate the debugger. + +The debugger can be launched from a `GPS` menu or +directly from the command line. The description below covers the latter use. +All the commands shown can be used in the `GPS` debug console window, +but there are usually more GUI-based ways to achieve the same effect. + +The command to run `GDB` is + + :: + + $ gdb program + +where `program` is the name of the executable file. This +activates the debugger and results in a prompt for debugger commands. +The simplest command is simply `run`, which causes the program to run +exactly as if the debugger were not present. The following section +describes some of the additional commands that can be given to `GDB`. + + +.. _Introduction_to_GDB_Commands: + +Introduction to GDB Commands +---------------------------- + +`GDB` contains a large repertoire of commands. +See :title:`Debugging with GDB` for extensive documentation on the use +of these commands, together with examples of their use. Furthermore, +the command *help* invoked from within GDB activates a simple help +facility which summarizes the available commands and their options. +In this section we summarize a few of the most commonly +used commands to give an idea of what `GDB` is about. You should create +a simple program with debugging information and experiment with the use of +these `GDB` commands on the program as you read through the +following section. + +* *set args `arguments`* + The `arguments` list above is a list of arguments to be passed to + the program on a subsequent run command, just as though the arguments + had been entered on a normal invocation of the program. The `set args` + command is not needed if the program does not require arguments. + + +* *run* + The `run` command causes execution of the program to start from + the beginning. If the program is already running, that is to say if + you are currently positioned at a breakpoint, then a prompt will ask + for confirmation that you want to abandon the current execution and + restart. + + +* *breakpoint `location`* + The breakpoint command sets a breakpoint, that is to say a point at which + execution will halt and `GDB` will await further + commands. `location` is + either a line number within a file, given in the format `file:linenumber`, + or it is the name of a subprogram. If you request that a breakpoint be set on + a subprogram that is overloaded, a prompt will ask you to specify on which of + those subprograms you want to breakpoint. You can also + specify that all of them should be breakpointed. If the program is run + and execution encounters the breakpoint, then the program + stops and `GDB` signals that the breakpoint was encountered by + printing the line of code before which the program is halted. + + +* *catch exception `name`* + This command causes the program execution to stop whenever exception + `name` is raised. If `name` is omitted, then the execution is + suspended when any exception is raised. + + +* *print `expression`* + This will print the value of the given expression. Most simple + Ada expression formats are properly handled by `GDB`, so the expression + can contain function calls, variables, operators, and attribute references. + + +* *continue* + Continues execution following a breakpoint, until the next breakpoint or the + termination of the program. + + +* *step* + Executes a single line after a breakpoint. If the next statement + is a subprogram call, execution continues into (the first statement of) + the called subprogram. + + +* *next* + Executes a single line. If this line is a subprogram call, executes and + returns from the call. + + +* *list* + Lists a few lines around the current source location. In practice, it + is usually more convenient to have a separate edit window open with the + relevant source file displayed. Successive applications of this command + print subsequent lines. The command can be given an argument which is a + line number, in which case it displays a few lines around the specified one. + + +* *backtrace* + Displays a backtrace of the call chain. This command is typically + used after a breakpoint has occurred, to examine the sequence of calls that + leads to the current breakpoint. The display includes one line for each + activation record (frame) corresponding to an active subprogram. + + +* *up* + At a breakpoint, `GDB` can display the values of variables local + to the current frame. The command `up` can be used to + examine the contents of other active frames, by moving the focus up + the stack, that is to say from callee to caller, one frame at a time. + + +* *down* + Moves the focus of `GDB` down from the frame currently being + examined to the frame of its callee (the reverse of the previous command), + + +* *frame `n`* + Inspect the frame with the given number. The value 0 denotes the frame + of the current breakpoint, that is to say the top of the call stack. + + +* *kill* + Kills the child process in which the program is running under GDB. + This may be useful for several purposes: + + * It allows you to recompile and relink your program, since on many systems + you cannot regenerate an executable file while it is running in a process. + + * You can run your program outside the debugger, on systems that do not + permit executing a program outside GDB while breakpoints are set + within GDB. + + * It allows you to debug a core dump rather than a running process. + +The above list is a very short introduction to the commands that +`GDB` provides. Important additional capabilities, including conditional +breakpoints, the ability to execute command sequences on a breakpoint, +the ability to debug at the machine instruction level and many other +features are described in detail in :title:`Debugging with GDB`. +Note that most commands can be abbreviated +(for example, c for continue, bt for backtrace). + + +.. _Using_Ada_Expressions: + +Using Ada Expressions +--------------------- + +.. index:: Ada expressions (in gdb) + +`GDB` supports a fairly large subset of Ada expression syntax, with some +extensions. The philosophy behind the design of this subset is + + * That `GDB` should provide basic literals and access to operations for + arithmetic, dereferencing, field selection, indexing, and subprogram calls, + leaving more sophisticated computations to subprograms written into the + program (which therefore may be called from `GDB`). + + * That type safety and strict adherence to Ada language restrictions + are not particularly relevant in a debugging context. + + * That brevity is important to the `GDB` user. + +Thus, for brevity, the debugger acts as if there were +implicit `with` and `use` clauses in effect for all user-written +packages, thus making it unnecessary to fully qualify most names with +their packages, regardless of context. Where this causes ambiguity, +`GDB` asks the user's intent. + +For details on the supported Ada syntax, see :title:`Debugging with GDB`. + + +.. _Calling_User-Defined_Subprograms: + +Calling User-Defined Subprograms +-------------------------------- + +An important capability of `GDB` is the ability to call user-defined +subprograms while debugging. This is achieved simply by entering +a subprogram call statement in the form: + + :: + + call subprogram-name (parameters) + +The keyword `call` can be omitted in the normal case where the +`subprogram-name` does not coincide with any of the predefined +`GDB` commands. + +The effect is to invoke the given subprogram, passing it the +list of parameters that is supplied. The parameters can be expressions and +can include variables from the program being debugged. The +subprogram must be defined +at the library level within your program, and `GDB` will call the +subprogram within the environment of your program execution (which +means that the subprogram is free to access or even modify variables +within your program). + +The most important use of this facility is in allowing the inclusion of +debugging routines that are tailored to particular data structures +in your program. Such debugging routines can be written to provide a suitably +high-level description of an abstract type, rather than a low-level dump +of its physical layout. After all, the standard +`GDB print` command only knows the physical layout of your +types, not their abstract meaning. Debugging routines can provide information +at the desired semantic level and are thus enormously useful. + +For example, when debugging GNAT itself, it is crucial to have access to +the contents of the tree nodes used to represent the program internally. +But tree nodes are represented simply by an integer value (which in turn +is an index into a table of nodes). +Using the `print` command on a tree node would simply print this integer +value, which is not very useful. But the PN routine (defined in file +treepr.adb in the GNAT sources) takes a tree node as input, and displays +a useful high level representation of the tree node, which includes the +syntactic category of the node, its position in the source, the integers +that denote descendant nodes and parent node, as well as varied +semantic information. To study this example in more detail, you might want to +look at the body of the PN procedure in the stated file. + +Another useful application of this capability is to deal with situations of +complex data which are not handled suitably by GDB. For example, if you specify +Convention Fortran for a multi-dimensional array, GDB does not know that +the ordering of array elements has been switched and will not properly +address the array elements. In such a case, instead of trying to print the +elements directly from GDB, you can write a callable procedure that prints +the elements in the desired format. + + +.. _Using_the_Next_Command_in_a_Function: + +Using the *next* Command in a Function +-------------------------------------- + +When you use the `next` command in a function, the current source +location will advance to the next statement as usual. A special case +arises in the case of a `return` statement. + +Part of the code for a return statement is the 'epilogue' of the function. +This is the code that returns to the caller. There is only one copy of +this epilogue code, and it is typically associated with the last return +statement in the function if there is more than one return. In some +implementations, this epilogue is associated with the first statement +of the function. + +The result is that if you use the `next` command from a return +statement that is not the last return statement of the function you +may see a strange apparent jump to the last return statement or to +the start of the function. You should simply ignore this odd jump. +The value returned is always that from the first return statement +that was stepped through. + + +.. _Stopping_When_Ada_Exceptions_Are_Raised: + +Stopping When Ada Exceptions Are Raised +--------------------------------------- + +.. index:: Exceptions (in gdb) + +You can set catchpoints that stop the program execution when your program +raises selected exceptions. + + +* *catch exception* + Set a catchpoint that stops execution whenever (any task in the) program + raises any exception. + + +* *catch exception `name`* + Set a catchpoint that stops execution whenever (any task in the) program + raises the exception `name`. + + +* *catch exception unhandled* + Set a catchpoint that stops executing whenever (any task in the) program + raises an exception for which there is no handler. + + +* *info exceptions*, *info exceptions `regexp`* + The `info exceptions` command permits the user to examine all defined + exceptions within Ada programs. With a regular expression, `regexp`, as + argument, prints out only those exceptions whose name matches `regexp`. + + +.. index:: Tasks (in gdb) + +.. _Ada_Tasks: + +Ada Tasks +--------- + +`GDB` allows the following task-related commands: + + +* *info tasks* + This command shows a list of current Ada tasks, as in the following example: + + :: + + (gdb) info tasks + ID TID P-ID Thread Pri State Name + 1 8088000 0 807e000 15 Child Activation Wait main_task + 2 80a4000 1 80ae000 15 Accept/Select Wait b + 3 809a800 1 80a4800 15 Child Activation Wait a + * 4 80ae800 3 80b8000 15 Running c + + + In this listing, the asterisk before the first task indicates it to be the + currently running task. The first column lists the task ID that is used + to refer to tasks in the following commands. + + +.. index:: Breakpoints and tasks + +* *break `linespec` task `taskid`*, *break `linespec` task `taskid` if ...* + + These commands are like the `break ... thread ...`. + `linespec` specifies source lines. + + Use the qualifier :samp:`task {taskid}` with a breakpoint command + to specify that you only want `GDB` to stop the program when a + particular Ada task reaches this breakpoint. `taskid` is one of the + numeric task identifiers assigned by `GDB`, shown in the first + column of the ``info tasks`` display. + + If you do not specify :samp:`task {taskid}` when you set a + breakpoint, the breakpoint applies to *all* tasks of your + program. + + You can use the `task` qualifier on conditional breakpoints as + well; in this case, place :samp:`task {taskid}` before the + breakpoint condition (before the `if`). + +.. index:: Task switching (in gdb) + +* *task `taskno`* + + This command allows switching to the task referred by `taskno`. In + particular, this allows browsing of the backtrace of the specified + task. It is advisable to switch back to the original task before + continuing execution otherwise the scheduling of the program may be + perturbed. + +For more detailed information on the tasking support, +see :title:`Debugging with GDB`. + + +.. index:: Debugging Generic Units +.. index:: Generics + +.. _Debugging_Generic_Units: + +Debugging Generic Units +----------------------- + +GNAT always uses code expansion for generic instantiation. This means that +each time an instantiation occurs, a complete copy of the original code is +made, with appropriate substitutions of formals by actuals. + +It is not possible to refer to the original generic entities in +`GDB`, but it is always possible to debug a particular instance of +a generic, by using the appropriate expanded names. For example, if we have + + .. code-block:: ada + + procedure g is + + generic package k is + procedure kp (v1 : in out integer); + end k; + + package body k is + procedure kp (v1 : in out integer) is + begin + v1 := v1 + 1; + end kp; + end k; + + package k1 is new k; + package k2 is new k; + + var : integer := 1; + + begin + k1.kp (var); + k2.kp (var); + k1.kp (var); + k2.kp (var); + end; + +Then to break on a call to procedure kp in the k2 instance, simply +use the command: + + :: + + (gdb) break g.k2.kp + +When the breakpoint occurs, you can step through the code of the +instance in the normal manner and examine the values of local variables, as for +other units. + + +.. index:: Remote Debugging with gdbserver + +.. _Remote_Debugging_with_gdbserver: + +Remote Debugging with gdbserver +------------------------------- + +On platforms where gdbserver is supported, it is possible to use this tool +to debug your application remotely. This can be useful in situations +where the program needs to be run on a target host that is different +from the host used for development, particularly when the target has +a limited amount of resources (either CPU and/or memory). + +To do so, start your program using gdbserver on the target machine. +gdbserver then automatically suspends the execution of your program +at its entry point, waiting for a debugger to connect to it. The +following commands starts an application and tells gdbserver to +wait for a connection with the debugger on localhost port 4444. + + + :: + + $ gdbserver localhost:4444 program + Process program created; pid = 5685 + Listening on port 4444 + +Once gdbserver has started listening, we can tell the debugger to establish +a connection with this gdbserver, and then start the same debugging session +as if the program was being debugged on the same host, directly under +the control of GDB. + + :: + + $ gdb program + (gdb) target remote targethost:4444 + Remote debugging using targethost:4444 + 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so. + (gdb) b foo.adb:3 + Breakpoint 1 at 0x401f0c: file foo.adb, line 3. + (gdb) continue + Continuing. + + Breakpoint 1, foo () at foo.adb:4 + 4 end foo; + +It is also possible to use gdbserver to attach to an already running +program, in which case the execution of that program is simply suspended +until the connection between the debugger and gdbserver is established. + +For more information on how to use gdbserver, see the *Using the gdbserver Program* +section in :title:`Debugging with GDB`. +GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux. + + +.. index:: Abnormal Termination or Failure to Terminate + +.. _GNAT_Abnormal_Termination_or_Failure_to_Terminate: + +GNAT Abnormal Termination or Failure to Terminate +------------------------------------------------- + +When presented with programs that contain serious errors in syntax +or semantics, +GNAT may on rare occasions experience problems in operation, such +as aborting with a +segmentation fault or illegal memory access, raising an internal +exception, terminating abnormally, or failing to terminate at all. +In such cases, you can activate +various features of GNAT that can help you pinpoint the construct in your +program that is the likely source of the problem. + +The following strategies are presented in increasing order of +difficulty, corresponding to your experience in using GNAT and your +familiarity with compiler internals. + +* Run *gcc* with the *-gnatf*. This first + switch causes all errors on a given line to be reported. In its absence, + only the first error on a line is displayed. + + The *-gnatdO* switch causes errors to be displayed as soon as they + are encountered, rather than after compilation is terminated. If GNAT + terminates prematurely or goes into an infinite loop, the last error + message displayed may help to pinpoint the culprit. + +* Run *gcc* with the *-v (verbose)* switch. In this + mode, *gcc* produces ongoing information about the progress of the + compilation and provides the name of each procedure as code is + generated. This switch allows you to find which Ada procedure was being + compiled when it encountered a code generation problem. + +.. index:: -gnatdc switch + +* Run *gcc* with the *-gnatdc* switch. This is a GNAT specific + switch that does for the front-end what *-v* does + for the back end. The system prints the name of each unit, + either a compilation unit or nested unit, as it is being analyzed. + +* Finally, you can start + `gdb` directly on the `gnat1` executable. `gnat1` is the + front-end of GNAT, and can be run independently (normally it is just + called from *gcc*). You can use `gdb` on `gnat1` as you + would on a C program (but :ref:`The_GNAT_Debugger_GDB` for caveats). The + `where` command is the first line of attack; the variable + `lineno` (seen by `print lineno`), used by the second phase of + `gnat1` and by the *gcc* backend, indicates the source line at + which the execution stopped, and `input_file name` indicates the name of + the source file. + + +.. _Naming_Conventions_for_GNAT_Source_Files: + +Naming Conventions for GNAT Source Files +---------------------------------------- + +In order to examine the workings of the GNAT system, the following +brief description of its organization may be helpful: + +* Files with prefix :file:`sc` contain the lexical scanner. + +* All files prefixed with :file:`par` are components of the parser. The + numbers correspond to chapters of the Ada Reference Manual. For example, + parsing of select statements can be found in :file:`par-ch9.adb`. + +* All files prefixed with :file:`sem` perform semantic analysis. The + numbers correspond to chapters of the Ada standard. For example, all + issues involving context clauses can be found in :file:`sem_ch10.adb`. In + addition, some features of the language require sufficient special processing + to justify their own semantic files: sem_aggr for aggregates, sem_disp for + dynamic dispatching, etc. + +* All files prefixed with :file:`exp` perform normalization and + expansion of the intermediate representation (abstract syntax tree, or AST). + these files use the same numbering scheme as the parser and semantics files. + For example, the construction of record initialization procedures is done in + :file:`exp_ch3.adb`. + +* The files prefixed with :file:`bind` implement the binder, which + verifies the consistency of the compilation, determines an order of + elaboration, and generates the bind file. + +* The files :file:`atree.ads` and :file:`atree.adb` detail the low-level + data structures used by the front-end. + +* The files :file:`sinfo.ads` and :file:`sinfo.adb` detail the structure of + the abstract syntax tree as produced by the parser. + +* The files :file:`einfo.ads` and :file:`einfo.adb` detail the attributes of + all entities, computed during semantic analysis. + +* Library management issues are dealt with in files with prefix + :file:`lib`. + + .. index:: Annex A (in Ada Reference Manual) + +* Ada files with the prefix :file:`a-` are children of `Ada`, as + defined in Annex A. + + .. index:: Annex B (in Ada reference Manual) + +* Files with prefix :file:`i-` are children of `Interfaces`, as + defined in Annex B. + + .. index:: System (package in Ada Reference Manual) + +* Files with prefix :file:`s-` are children of `System`. This includes + both language-defined children and GNAT run-time routines. + + .. index:: GNAT (package) + +* Files with prefix :file:`g-` are children of `GNAT`. These are useful + general-purpose packages, fully documented in their specs. All + the other :file:`.c` files are modifications of common *gcc* files. + + +.. _Getting_Internal_Debugging_Information: + +Getting Internal Debugging Information +-------------------------------------- + +Most compilers have internal debugging switches and modes. GNAT +does also, except GNAT internal debugging switches and modes are not +secret. A summary and full description of all the compiler and binder +debug flags are in the file :file:`debug.adb`. You must obtain the +sources of the compiler to see the full detailed effects of these flags. + +The switches that print the source of the program (reconstructed from +the internal tree) are of general interest for user programs, as are the +options to print +the full internal tree, and the entity table (the symbol table +information). The reconstructed source provides a readable version of the +program after the front-end has completed analysis and expansion, +and is useful when studying the performance of specific constructs. +For example, constraint checks are indicated, complex aggregates +are replaced with loops and assignments, and tasking primitives +are replaced with run-time calls. + + +.. index:: traceback +.. index:: stack traceback +.. index:: stack unwinding + +.. _Stack_Traceback: + +Stack Traceback +--------------- + +Traceback is a mechanism to display the sequence of subprogram calls that +leads to a specified execution point in a program. Often (but not always) +the execution point is an instruction at which an exception has been raised. +This mechanism is also known as *stack unwinding* because it obtains +its information by scanning the run-time stack and recovering the activation +records of all active subprograms. Stack unwinding is one of the most +important tools for program debugging. + +The first entry stored in traceback corresponds to the deepest calling level, +that is to say the subprogram currently executing the instruction +from which we want to obtain the traceback. + +Note that there is no runtime performance penalty when stack traceback +is enabled, and no exception is raised during program execution. + +.. index:: traceback, non-symbolic + +.. _Non-Symbolic_Traceback: + +Non-Symbolic Traceback +^^^^^^^^^^^^^^^^^^^^^^ + +Note: this feature is not supported on all platforms. See +:samp:`GNAT.Traceback` spec in :file:`g-traceb.ads` +for a complete list of supported platforms. + +.. rubric:: Tracebacks From an Unhandled Exception + +A runtime non-symbolic traceback is a list of addresses of call instructions. +To enable this feature you must use the *-E* +`gnatbind`'s option. With this option a stack traceback is stored as part +of exception information. You can retrieve this information using the +`addr2line` tool. + +Here is a simple example: + + .. code-block:: ada + + procedure STB is + + procedure P1 is + begin + raise Constraint_Error; + end P1; + + procedure P2 is + begin + P1; + end P2; + + begin + P2; + end STB; + + :: + + $ gnatmake stb -bargs -E + $ stb + + Execution terminated by unhandled exception + Exception name: CONSTRAINT_ERROR + Message: stb.adb:5 + Call stack traceback locations: + 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 + +As we see the traceback lists a sequence of addresses for the unhandled +exception `CONSTRAINT_ERROR` raised in procedure P1. It is easy to +guess that this exception come from procedure P1. To translate these +addresses into the source lines where the calls appear, the +`addr2line` tool, described below, is invaluable. The use of this tool +requires the program to be compiled with debug information. + + :: + + $ gnatmake -g stb -bargs -E + $ stb + + Execution terminated by unhandled exception + Exception name: CONSTRAINT_ERROR + Message: stb.adb:5 + Call stack traceback locations: + 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 + + $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 + 0x4011f1 0x77e892a4 + + 00401373 at d:/stb/stb.adb:5 + 0040138B at d:/stb/stb.adb:10 + 0040139C at d:/stb/stb.adb:14 + 00401335 at d:/stb/b~stb.adb:104 + 004011C4 at /build/.../crt1.c:200 + 004011F1 at /build/.../crt1.c:222 + 77E892A4 in ?? at ??:0 + +The `addr2line` tool has several other useful options: + + ======================== ======================================================== + :samp:`--functions` to get the function name corresponding to any location + :samp:`--demangle=gnat` to use the gnat decoding mode for the function names. + Note that for binutils version 2.9.x the option is + simply :samp:`--demangle`. + ======================== ======================================================== + + :: + + $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b + 0x40139c 0x401335 0x4011c4 0x4011f1 + + 00401373 in stb.p1 at d:/stb/stb.adb:5 + 0040138B in stb.p2 at d:/stb/stb.adb:10 + 0040139C in stb at d:/stb/stb.adb:14 + 00401335 in main at d:/stb/b~stb.adb:104 + 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200 + 004011F1 in at /build/.../crt1.c:222 + +From this traceback we can see that the exception was raised in +:file:`stb.adb` at line 5, which was reached from a procedure call in +:file:`stb.adb` at line 10, and so on. The :file:`b~std.adb` is the binder file, +which contains the call to the main program. +:ref:`Running_gnatbind`. The remaining entries are assorted runtime routines, +and the output will vary from platform to platform. + +It is also possible to use `GDB` with these traceback addresses to debug +the program. For example, we can break at a given code location, as reported +in the stack traceback: + + :: + + $ gdb -nw stb + +Furthermore, this feature is not implemented inside Windows DLL. Only +the non-symbolic traceback is reported in this case. + + :: + + (gdb) break *0x401373 + Breakpoint 1 at 0x401373: file stb.adb, line 5. + +It is important to note that the stack traceback addresses +do not change when debug information is included. This is particularly useful +because it makes it possible to release software without debug information (to +minimize object size), get a field report that includes a stack traceback +whenever an internal bug occurs, and then be able to retrieve the sequence +of calls with the same program compiled with debug information. + + +.. rubric:: Tracebacks From Exception Occurrences + +Non-symbolic tracebacks are obtained by using the *-E* binder argument. +The stack traceback is attached to the exception information string, and can +be retrieved in an exception handler within the Ada program, by means of the +Ada facilities defined in `Ada.Exceptions`. Here is a simple example: + + .. code-block:: ada + + with Ada.Text_IO; + with Ada.Exceptions; + + procedure STB is + + use Ada; + use Ada.Exceptions; + + procedure P1 is + K : Positive := 1; + begin + K := K - 1; + exception + when E : others => + Text_IO.Put_Line (Exception_Information (E)); + end P1; + + procedure P2 is + begin + P1; + end P2; + + begin + P2; + end STB; + +This program will output: + + :: + + $ stb + + Exception name: CONSTRAINT_ERROR + Message: stb.adb:12 + Call stack traceback locations: + 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4 + + +.. rubric:: Tracebacks From Anywhere in a Program + +It is also possible to retrieve a stack traceback from anywhere in a +program. For this you need to +use the `GNAT.Traceback` API. This package includes a procedure called +`Call_Chain` that computes a complete stack traceback, as well as useful +display procedures described below. It is not necessary to use the +*-E gnatbind* option in this case, because the stack traceback mechanism +is invoked explicitly. + +In the following example we compute a traceback at a specific location in +the program, and we display it using `GNAT.Debug_Utilities.Image` to +convert addresses to strings: + + + .. code-block:: ada + + with Ada.Text_IO; + with GNAT.Traceback; + with GNAT.Debug_Utilities; + + procedure STB is + + use Ada; + use GNAT; + use GNAT.Traceback; + + procedure P1 is + TB : Tracebacks_Array (1 .. 10); + -- We are asking for a maximum of 10 stack frames. + Len : Natural; + -- Len will receive the actual number of stack frames returned. + begin + Call_Chain (TB, Len); + + Text_IO.Put ("In STB.P1 : "); + + for K in 1 .. Len loop + Text_IO.Put (Debug_Utilities.Image (TB (K))); + Text_IO.Put (' '); + end loop; + + Text_IO.New_Line; + end P1; + + procedure P2 is + begin + P1; + end P2; + + begin + P2; + end STB; + + :: + + $ gnatmake -g stb + $ stb + + In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C# + 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4# + + +You can then get further information by invoking the `addr2line` +tool as described earlier (note that the hexadecimal addresses +need to be specified in C format, with a leading '0x'). + +.. index:: traceback, symbolic + +.. _Symbolic_Traceback: + +Symbolic Traceback +^^^^^^^^^^^^^^^^^^ + +A symbolic traceback is a stack traceback in which procedure names are +associated with each code location. + +Note that this feature is not supported on all platforms. See +:samp:`GNAT.Traceback.Symbolic` spec in :file:`g-trasym.ads` for a complete +list of currently supported platforms. + +Note that the symbolic traceback requires that the program be compiled +with debug information. If it is not compiled with debug information +only the non-symbolic information will be valid. + + +.. rubric:: Tracebacks From Exception Occurrences + +Here is an example: + + .. code-block:: ada + + with Ada.Text_IO; + with GNAT.Traceback.Symbolic; + + procedure STB is + + procedure P1 is + begin + raise Constraint_Error; + end P1; + + procedure P2 is + begin + P1; + end P2; + + procedure P3 is + begin + P2; + end P3; + + begin + P3; + exception + when E : others => + Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E)); + end STB; + + :: + + $ gnatmake -g .\stb -bargs -E + $ stb + + 0040149F in stb.p1 at stb.adb:8 + 004014B7 in stb.p2 at stb.adb:13 + 004014CF in stb.p3 at stb.adb:18 + 004015DD in ada.stb at stb.adb:22 + 00401461 in main at b~stb.adb:168 + 004011C4 in __mingw_CRTStartup at crt1.c:200 + 004011F1 in mainCRTStartup at crt1.c:222 + 77E892A4 in ?? at ??:0 + +In the above example the ``.\`` syntax in the *gnatmake* command +is currently required by *addr2line* for files that are in +the current working directory. +Moreover, the exact sequence of linker options may vary from platform +to platform. +The above *-largs* section is for Windows platforms. By contrast, +under Unix there is no need for the *-largs* section. +Differences across platforms are due to details of linker implementation. + + +.. rubric:: Tracebacks From Anywhere in a Program + +It is possible to get a symbolic stack traceback +from anywhere in a program, just as for non-symbolic tracebacks. +The first step is to obtain a non-symbolic +traceback, and then call `Symbolic_Traceback` to compute the symbolic +information. Here is an example: + + .. code-block:: ada + + with Ada.Text_IO; + with GNAT.Traceback; + with GNAT.Traceback.Symbolic; + + procedure STB is + + use Ada; + use GNAT.Traceback; + use GNAT.Traceback.Symbolic; + + procedure P1 is + TB : Tracebacks_Array (1 .. 10); + -- We are asking for a maximum of 10 stack frames. + Len : Natural; + -- Len will receive the actual number of stack frames returned. + begin + Call_Chain (TB, Len); + Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len))); + end P1; + + procedure P2 is + begin + P1; + end P2; + + begin + P2; + end STB; + + +.. index:: Code Coverage +.. index:: Profiling + + +.. _Code_Coverage_and_Profiling: + +Code Coverage and Profiling +=========================== + +This section describes how to use the `gcov` coverage testing tool and +the `gprof` profiler tool on Ada programs. + +.. index:: ! gcov + +.. _Code_Coverage_of_Ada_Programs_with_gcov: + +Code Coverage of Ada Programs with gcov +--------------------------------------- + +`gcov` is a test coverage program: it analyzes the execution of a given +program on selected tests, to help you determine the portions of the program +that are still untested. + +`gcov` is part of the GCC suite, and is described in detail in the GCC +User's Guide. You can refer to this documentation for a more complete +description. + +This chapter provides a quick startup guide, and +details some GNAT-specific features. + +.. _Quick_startup_guide: + +Quick startup guide +^^^^^^^^^^^^^^^^^^^ + +In order to perform coverage analysis of a program using `gcov`, several +steps are needed: + +#. Instrument the code during the compilation process, +#. Execute the instrumented program, and +#. Invoke the `gcov` tool to generate the coverage results. + +.. index:: -fprofile-arcs (gcc) +.. index:: -ftest-coverage (gcc +.. index:: -fprofile-arcs (gnatbind) + +The code instrumentation needed by gcov is created at the object level. +The source code is not modified in any way, because the instrumentation code is +inserted by gcc during the compilation process. To compile your code with code +coverage activated, you need to recompile your whole project using the +switches +`-fprofile-arcs` and `-ftest-coverage`, and link it using +`-fprofile-arcs`. + + :: + + $ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \\ + -largs -fprofile-arcs + +This compilation process will create :file:`.gcno` files together with +the usual object files. + +Once the program is compiled with coverage instrumentation, you can +run it as many times as needed -- on portions of a test suite for +example. The first execution will produce :file:`.gcda` files at the +same location as the :file:`.gcno` files. Subsequent executions +will update those files, so that a cumulative result of the covered +portions of the program is generated. + +Finally, you need to call the `gcov` tool. The different options of +`gcov` are described in the GCC User's Guide, section 'Invoking gcov'. + +This will create annotated source files with a :file:`.gcov` extension: +:file:`my_main.adb` file will be analyzed in :file:`my_main.adb.gcov`. + + +.. _GNAT_specifics: + +GNAT specifics +^^^^^^^^^^^^^^ + +Because of Ada semantics, portions of the source code may be shared among +several object files. This is the case for example when generics are +involved, when inlining is active or when declarations generate initialisation +calls. In order to take +into account this shared code, you need to call `gcov` on all +source files of the tested program at once. + +The list of source files might exceed the system's maximum command line +length. In order to bypass this limitation, a new mechanism has been +implemented in `gcov`: you can now list all your project's files into a +text file, and provide this file to gcov as a parameter, preceded by a ``@`` +(e.g. :samp:`gcov @mysrclist.txt`). + +Note that on AIX compiling a static library with `-fprofile-arcs` is +not supported as there can be unresolved symbols during the final link. + + +.. index:: ! gprof +.. index:: Profiling + +.. _Profiling_an_Ada_Program_with_gprof: + +Profiling an Ada Program with gprof +----------------------------------- + +This section is not meant to be an exhaustive documentation of `gprof`. +Full documentation for it can be found in the :title:`GNU Profiler User's Guide` +documentation that is part of this GNAT distribution. + +Profiling a program helps determine the parts of a program that are executed +most often, and are therefore the most time-consuming. + +`gprof` is the standard GNU profiling tool; it has been enhanced to +better handle Ada programs and multitasking. +It is currently supported on the following platforms + +* linux x86/x86_64 +* solaris sparc/sparc64/x86 +* windows x86 + +In order to profile a program using `gprof`, several steps are needed: + +#. Instrument the code, which requires a full recompilation of the project with the + proper switches. + +#. Execute the program under the analysis conditions, i.e. with the desired + input. + +#. Analyze the results using the `gprof` tool. + +The following sections detail the different steps, and indicate how +to interpret the results. + + +.. _Compilation_for_profiling: + +Compilation for profiling +^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: -pg (gcc), for profiling +.. index:: -pg (gnatlink), for profiling + +In order to profile a program the first step is to tell the compiler +to generate the necessary profiling information. The compiler switch to be used +is ``-pg``, which must be added to other compilation switches. This +switch needs to be specified both during compilation and link stages, and can +be specified once when using gnatmake: + + :: + + $ gnatmake -f -pg -P my_project + +Note that only the objects that were compiled with the ``-pg`` switch will +be profiled; if you need to profile your whole project, use the ``-f`` +gnatmake switch to force full recompilation. + +.. _Program_execution: + + +Program execution +^^^^^^^^^^^^^^^^^ + +Once the program has been compiled for profiling, you can run it as usual. + +The only constraint imposed by profiling is that the program must terminate +normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be +properly analyzed. + +Once the program completes execution, a data file called :file:`gmon.out` is +generated in the directory where the program was launched from. If this file +already exists, it will be overwritten. + + +.. _Running_gprof: + +Running gprof +^^^^^^^^^^^^^ + +The `gprof` tool is called as follow: + + :: + + $ gprof my_prog gmon.out + +or simply: + + :: + + $ gprof my_prog + +The complete form of the gprof command line is the following: + + :: + + $ gprof [switches] [executable [data-file]] + +`gprof` supports numerous switches. The order of these +switch does not matter. The full list of options can be found in +the GNU Profiler User's Guide documentation that comes with this documentation. + +The following is the subset of those switches that is most relevant: + +.. index:: --demangle (gprof) + +:samp:`--demangle[={style}]`, :samp:`--no-demangle` + These options control whether symbol names should be demangled when + printing output. The default is to demangle C++ symbols. The + ``--no-demangle`` option may be used to turn off demangling. Different + compilers have different mangling styles. The optional demangling style + argument can be used to choose an appropriate demangling style for your + compiler, in particular Ada symbols generated by GNAT can be demangled using + ``--demangle=gnat``. + + +.. index:: -e (gprof) + +:samp:`-e {function_name}` + The :samp:`-e {function}` option tells `gprof` not to print + information about the function `function_name` (and its + children...) in the call graph. The function will still be listed + as a child of any functions that call it, but its index number will be + shown as ``[not printed]``. More than one ``-e`` option may be + given; only one `function_name` may be indicated with each ``-e`` + option. + + +.. index:: -E (gprof) + +:samp:`-E {function_name}` + The :samp:`-E {function}` option works like the ``-e`` option, but + execution time spent in the function (and children who were not called from + anywhere else), will not be used to compute the percentages-of-time for + the call graph. More than one ``-E`` option may be given; only one + `function_name` may be indicated with each ``-E`` option. + + +.. index:: -f (gprof) + +:samp:`-f {function_name}` + The :samp:`-f {function}` option causes `gprof` to limit the + call graph to the function `function_name` and its children (and + their children...). More than one ``-f`` option may be given; + only one `function_name` may be indicated with each ``-f`` + option. + + +.. index:: -F (gprof) + +:samp:`-F {function_name}` + The :samp:`-F {function}` option works like the ``-f`` option, but + only time spent in the function and its children (and their + children...) will be used to determine total-time and + percentages-of-time for the call graph. More than one ``-F`` option + may be given; only one `function_name` may be indicated with each + ``-F`` option. The ``-F`` option overrides the ``-E`` option. + + +.. _Interpretation_of_profiling_results: + +Interpretation of profiling results +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The results of the profiling analysis are represented by two arrays: the +'flat profile' and the 'call graph'. Full documentation of those outputs +can be found in the GNU Profiler User's Guide. + +The flat profile shows the time spent in each function of the program, and how +many time it has been called. This allows you to locate easily the most +time-consuming functions. + +The call graph shows, for each subprogram, the subprograms that call it, +and the subprograms that it calls. It also provides an estimate of the time +spent in each of those callers/called subprograms. + + + +.. _Improving_Performance: + +Improving Performance +===================== + +.. index:: Improving performance + +This section presents several topics related to program performance. +It first describes some of the tradeoffs that need to be considered +and some of the techniques for making your program run faster. + +.. only:: PRO or GPL + + It then documents the unused subprogram/data elimination feature + and the *gnatelim* tool, + which can reduce the size of program executables. + + +.. only:: FSF + + It then documents the unused subprogram/data elimination feature, + which can reduce the size of program executables. + + +.. _Performance_Considerations: + +Performance Considerations +-------------------------- + +The GNAT system provides a number of options that allow a trade-off +between + +* performance of the generated code + +* speed of compilation + +* minimization of dependences and recompilation + +* the degree of run-time checking. + +The defaults (if no options are selected) aim at improving the speed +of compilation and minimizing dependences, at the expense of performance +of the generated code: + +* no optimization + +* no inlining of subprogram calls + +* all run-time checks enabled except overflow and elaboration checks + +These options are suitable for most program development purposes. This +section describes how you can modify these choices, and also provides +some guidelines on debugging optimized code. + + +.. _Controlling_Run-Time_Checks: + +Controlling Run-Time Checks +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +By default, GNAT generates all run-time checks, except integer overflow +checks, stack overflow checks, and checks for access before elaboration on +subprogram calls. The latter are not required in default mode, because all +necessary checking is done at compile time. + +.. index:: -gnatp (gcc) +.. index:: -gnato (gcc) + +Two gnat switches, *-gnatp* and *-gnato* allow this default to +be modified. See :ref:`Run-Time_Checks`. + +Our experience is that the default is suitable for most development +purposes. + +We treat integer overflow specially because these +are quite expensive and in our experience are not as important as other +run-time checks in the development process. Note that division by zero +is not considered an overflow check, and divide by zero checks are +generated where required by default. + +Elaboration checks are off by default, and also not needed by default, since +GNAT uses a static elaboration analysis approach that avoids the need for +run-time checking. This manual contains a full chapter discussing the issue +of elaboration checks, and if the default is not satisfactory for your use, +you should read this chapter. + +For validity checks, the minimal checks required by the Ada Reference +Manual (for case statements and assignments to array elements) are on +by default. These can be suppressed by use of the *-gnatVn* switch. +Note that in Ada 83, there were no validity checks, so if the Ada 83 mode +is acceptable (or when comparing GNAT performance with an Ada 83 compiler), +it may be reasonable to routinely use *-gnatVn*. Validity checks +are also suppressed entirely if *-gnatp* is used. + +.. index:: Overflow checks +.. index:: Checks, overflow + +.. index:: Suppress +.. index:: Unsuppress +.. index:: pragma Suppress +.. index:: pragma Unsuppress + +Note that the setting of the switches controls the default setting of +the checks. They may be modified using either `pragma Suppress` (to +remove checks) or `pragma Unsuppress` (to add back suppressed +checks) in the program source. + + +.. _Use_of_Restrictions: + +Use of Restrictions +^^^^^^^^^^^^^^^^^^^ + +The use of pragma Restrictions allows you to control which features are +permitted in your program. Apart from the obvious point that if you avoid +relatively expensive features like finalization (enforceable by the use +of pragma Restrictions (No_Finalization), the use of this pragma does not +affect the generated code in most cases. + +One notable exception to this rule is that the possibility of task abort +results in some distributed overhead, particularly if finalization or +exception handlers are used. The reason is that certain sections of code +have to be marked as non-abortable. + +If you use neither the `abort` statement, nor asynchronous transfer +of control (`select ... then abort`), then this distributed overhead +is removed, which may have a general positive effect in improving +overall performance. Especially code involving frequent use of tasking +constructs and controlled types will show much improved performance. +The relevant restrictions pragmas are + + .. code-block:: ada + + pragma Restrictions (No_Abort_Statements); + pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); + +It is recommended that these restriction pragmas be used if possible. Note +that this also means that you can write code without worrying about the +possibility of an immediate abort at any point. + + +.. _Optimization_Levels: + +Optimization Levels +^^^^^^^^^^^^^^^^^^^ + +.. index:: -O (gcc) + +Without any optimization option, +the compiler's goal is to reduce the cost of +compilation and to make debugging produce the expected results. +Statements are independent: if you stop the program with a breakpoint between +statements, you can then assign a new value to any variable or change +the program counter to any other statement in the subprogram and get exactly +the results you would expect from the source code. + +Turning on optimization makes the compiler attempt to improve the +performance and/or code size at the expense of compilation time and +possibly the ability to debug the program. + +If you use multiple +-O options, with or without level numbers, +the last such option is the one that is effective. + +The default is optimization off. This results in the fastest compile +times, but GNAT makes absolutely no attempt to optimize, and the +generated programs are considerably larger and slower than when +optimization is enabled. You can use the +*-O* switch (the permitted forms are *-O0*, *-O1* +*-O2*, *-O3*, and *-Os*) +to *gcc* to control the optimization level: + + +* *-O0* + No optimization (the default); + generates unoptimized code but has + the fastest compilation time. + + Note that many other compilers do fairly extensive optimization + even if 'no optimization' is specified. With gcc, it is + very unusual to use -O0 for production if + execution time is of any concern, since -O0 + really does mean no optimization at all. This difference between + gcc and other compilers should be kept in mind when doing + performance comparisons. + +* *-O1* + Moderate optimization; + optimizes reasonably well but does not + degrade compilation time significantly. + +* *-O2* + Full optimization; + generates highly optimized code and has + the slowest compilation time. + +* *-O3* + Full optimization as in *-O2*; + also uses more aggressive automatic inlining of subprograms within a unit + (:ref:`Inlining_of_Subprograms`) and attempts to vectorize loops. + + +* *-Os* + Optimize space usage (code and data) of resulting program. + +Higher optimization levels perform more global transformations on the +program and apply more expensive analysis algorithms in order to generate +faster and more compact code. The price in compilation time, and the +resulting improvement in execution time, +both depend on the particular application and the hardware environment. +You should experiment to find the best level for your application. + +Since the precise set of optimizations done at each level will vary from +release to release (and sometime from target to target), it is best to think +of the optimization settings in general terms. +See the *Options That Control Optimization* section in +:title:`Using the GNU Compiler Collection (GCC)` +for details about +the *-O* settings and a number of *-f* options that +individually enable or disable specific optimizations. + +Unlike some other compilation systems, *gcc* has +been tested extensively at all optimization levels. There are some bugs +which appear only with optimization turned on, but there have also been +bugs which show up only in *unoptimized* code. Selecting a lower +level of optimization does not improve the reliability of the code +generator, which in practice is highly reliable at all optimization +levels. + +Note regarding the use of *-O3*: The use of this optimization level +is generally discouraged with GNAT, since it often results in larger +executables which may run more slowly. See further discussion of this point +in :ref:`Inlining_of_Subprograms`. + + +.. _Debugging_Optimized_Code: + +Debugging Optimized Code +^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Debugging optimized code +.. index:: Optimization and debugging + +Although it is possible to do a reasonable amount of debugging at +nonzero optimization levels, +the higher the level the more likely that +source-level constructs will have been eliminated by optimization. +For example, if a loop is strength-reduced, the loop +control variable may be completely eliminated and thus cannot be +displayed in the debugger. +This can only happen at *-O2* or *-O3*. +Explicit temporary variables that you code might be eliminated at +level *-O1* or higher. + +.. index:: -g (gcc) + +The use of the *-g* switch, +which is needed for source-level debugging, +affects the size of the program executable on disk, +and indeed the debugging information can be quite large. +However, it has no effect on the generated code (and thus does not +degrade performance) + +Since the compiler generates debugging tables for a compilation unit before +it performs optimizations, the optimizing transformations may invalidate some +of the debugging data. You therefore need to anticipate certain +anomalous situations that may arise while debugging optimized code. +These are the most common cases: + +* *The 'hopping Program Counter':* Repeated `step` or `next` + commands show + the PC bouncing back and forth in the code. This may result from any of + the following optimizations: + + - *Common subexpression elimination:* using a single instance of code for a + quantity that the source computes several times. As a result you + may not be able to stop on what looks like a statement. + + - *Invariant code motion:* moving an expression that does not change within a + loop, to the beginning of the loop. + + - *Instruction scheduling:* moving instructions so as to + overlap loads and stores (typically) with other code, or in + general to move computations of values closer to their uses. Often + this causes you to pass an assignment statement without the assignment + happening and then later bounce back to the statement when the + value is actually needed. Placing a breakpoint on a line of code + and then stepping over it may, therefore, not always cause all the + expected side-effects. + +* *The 'big leap':* More commonly known as *cross-jumping*, in which + two identical pieces of code are merged and the program counter suddenly + jumps to a statement that is not supposed to be executed, simply because + it (and the code following) translates to the same thing as the code + that *was* supposed to be executed. This effect is typically seen in + sequences that end in a jump, such as a `goto`, a `return`, or + a `break` in a C `switch` statement. + +* *The 'roving variable':* The symptom is an unexpected value in a variable. + There are various reasons for this effect: + + - In a subprogram prologue, a parameter may not yet have been moved to its + 'home'. + + - A variable may be dead, and its register re-used. This is + probably the most common cause. + + - As mentioned above, the assignment of a value to a variable may + have been moved. + + - A variable may be eliminated entirely by value propagation or + other means. In this case, GCC may incorrectly generate debugging + information for the variable + + In general, when an unexpected value appears for a local variable or parameter + you should first ascertain if that value was actually computed by + your program, as opposed to being incorrectly reported by the debugger. + Record fields or + array elements in an object designated by an access value + are generally less of a problem, once you have ascertained that the access + value is sensible. + Typically, this means checking variables in the preceding code and in the + calling subprogram to verify that the value observed is explainable from other + values (one must apply the procedure recursively to those + other values); or re-running the code and stopping a little earlier + (perhaps before the call) and stepping to better see how the variable obtained + the value in question; or continuing to step *from* the point of the + strange value to see if code motion had simply moved the variable's + assignments later. + +In light of such anomalies, a recommended technique is to use *-O0* +early in the software development cycle, when extensive debugging capabilities +are most needed, and then move to *-O1* and later *-O2* as +the debugger becomes less critical. +Whether to use the *-g* switch in the release version is +a release management issue. +Note that if you use *-g* you can then use the *strip* program +on the resulting executable, +which removes both debugging information and global symbols. + + +.. _Inlining_of_Subprograms: + +Inlining of Subprograms +^^^^^^^^^^^^^^^^^^^^^^^ + +A call to a subprogram in the current unit is inlined if all the +following conditions are met: + +* The optimization level is at least *-O1*. + +* The called subprogram is suitable for inlining: It must be small enough + and not contain something that *gcc* cannot support in inlined + subprograms. + + .. index:: pragma Inline + .. index:: Inline + +* Any one of the following applies: `pragma Inline` is applied to the + subprogram and the *-gnatn* switch is specified; the + subprogram is local to the unit and called once from within it; the + subprogram is small and optimization level *-O2* is specified; + optimization level *-O3* is specified. + +Calls to subprograms in |withed| units are normally not inlined. +To achieve actual inlining (that is, replacement of the call by the code +in the body of the subprogram), the following conditions must all be true: + +* The optimization level is at least *-O1*. + +* The called subprogram is suitable for inlining: It must be small enough + and not contain something that *gcc* cannot support in inlined + subprograms. + +* The call appears in a body (not in a package spec). + +* There is a `pragma Inline` for the subprogram. + +* The *-gnatn* switch is used on the command line. + +Even if all these conditions are met, it may not be possible for +the compiler to inline the call, due to the length of the body, +or features in the body that make it impossible for the compiler +to do the inlining. + +Note that specifying the *-gnatn* switch causes additional +compilation dependencies. Consider the following: + + .. code-block:: ada + + package R is + procedure Q; + pragma Inline (Q); + end R; + package body R is + ... + end R; + + with R; + procedure Main is + begin + ... + R.Q; + end Main; + +With the default behavior (no *-gnatn* switch specified), the +compilation of the `Main` procedure depends only on its own source, +:file:`main.adb`, and the spec of the package in file :file:`r.ads`. This +means that editing the body of `R` does not require recompiling +`Main`. + +On the other hand, the call `R.Q` is not inlined under these +circumstances. If the *-gnatn* switch is present when `Main` +is compiled, the call will be inlined if the body of `Q` is small +enough, but now `Main` depends on the body of `R` in +:file:`r.adb` as well as on the spec. This means that if this body is edited, +the main program must be recompiled. Note that this extra dependency +occurs whether or not the call is in fact inlined by *gcc*. + +The use of front end inlining with *-gnatN* generates similar +additional dependencies. + +.. index:: -fno-inline (gcc) + +Note: The *-fno-inline* switch overrides all other conditions and ensures that +no inlining occurs, unless requested with pragma Inline_Always for gcc +back-ends. The extra dependences resulting from *-gnatn* will still be active, +even if this switch is used to suppress the resulting inlining actions. + +.. index:: -fno-inline-functions (gcc) + +Note: The *-fno-inline-functions* switch can be used to prevent +automatic inlining of subprograms if *-O3* is used. + +.. index:: -fno-inline-small-functions (gcc) + +Note: The *-fno-inline-small-functions* switch can be used to prevent +automatic inlining of small subprograms if *-O2* is used. + +.. index:: -fno-inline-functions-called-once (gcc) + +Note: The *-fno-inline-functions-called-once* switch +can be used to prevent inlining of subprograms local to the unit +and called once from within it if *-O1* is used. + +Note regarding the use of *-O3*: *-gnatn* is made up of two +sub-switches *-gnatn1* and *-gnatn2* that can be directly +specified in lieu of it, *-gnatn* being translated into one of them +based on the optimization level. With *-O2* or below, *-gnatn* +is equivalent to *-gnatn1* which activates pragma `Inline` with +moderate inlining across modules. With *-O3*, *-gnatn* is +equivalent to *-gnatn2* which activates pragma `Inline` with +full inlining across modules. If you have used pragma `Inline` in +appropriate cases, then it is usually much better to use *-O2* +and *-gnatn* and avoid the use of *-O3* which has the additional +effect of inlining subprograms you did not think should be inlined. We have +found that the use of *-O3* may slow down the compilation and increase +the code size by performing excessive inlining, leading to increased +instruction cache pressure from the increased code size and thus minor +performance improvements. So the bottom line here is that you should not +automatically assume that *-O3* is better than *-O2*, and +indeed you should use *-O3* only if tests show that it actually +improves performance for your program. + +.. _Floating_Point_Operations: + +Floating_Point_Operations +^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Floating-Point Operations + +On almost all targets, GNAT maps Float and Long_Float to the 32-bit and +64-bit standard IEEE floating-point representations, and operations will +use standard IEEE arithmetic as provided by the processor. On most, but +not all, architectures, the attribute Machine_Overflows is False for these +types, meaning that the semantics of overflow is implementation-defined. +In the case of GNAT, these semantics correspond to the normal IEEE +treatment of infinities and NaN (not a number) values. For example, +1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By +avoiding explicit overflow checks, the performance is greatly improved +on many targets. However, if required, floating-point overflow can be +enabled by the use of the pragma Check_Float_Overflow. + +Another consideration that applies specifically to x86 32-bit +architectures is which form of floating-point arithmetic is used. +By default the operations use the old style x86 floating-point, +which implements an 80-bit extended precision form (on these +architectures the type Long_Long_Float corresponds to that form). +In addition, generation of efficient code in this mode means that +the extended precision form will be used for intermediate results. +This may be helpful in improving the final precision of a complex +expression. However it means that the results obtained on the x86 +will be different from those on other architectures, and for some +algorithms, the extra intermediate precision can be detrimental. + +In addition to this old-style floating-point, all modern x86 chips +implement an alternative floating-point operation model referred +to as SSE2. In this model there is no extended form, and furthermore +execution performance is significantly enhanced. To force GNAT to use +this more modern form, use both of the switches: + + -msse2 -mfpmath=sse + +A unit compiled with these switches will automatically use the more +efficient SSE2 instruction set for Float and Long_Float operations. +Note that the ABI has the same form for both floating-point models, +so it is permissible to mix units compiled with and without these +switches. + + + + + +.. _Vectorization_of_loops: + +Vectorization of loops +^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Optimization Switches + +You can take advantage of the auto-vectorizer present in the *gcc* +back end to vectorize loops with GNAT. The corresponding command line switch +is *-ftree-vectorize* but, as it is enabled by default at *-O3* +and other aggressive optimizations helpful for vectorization also are enabled +by default at this level, using *-O3* directly is recommended. + +You also need to make sure that the target architecture features a supported +SIMD instruction set. For example, for the x86 architecture, you should at +least specify *-msse2* to get significant vectorization (but you don't +need to specify it for x86-64 as it is part of the base 64-bit architecture). +Similarly, for the PowerPC architecture, you should specify *-maltivec*. + +The preferred loop form for vectorization is the `for` iteration scheme. +Loops with a `while` iteration scheme can also be vectorized if they are +very simple, but the vectorizer will quickly give up otherwise. With either +iteration scheme, the flow of control must be straight, in particular no +`exit` statement may appear in the loop body. The loop may however +contain a single nested loop, if it can be vectorized when considered alone: + + .. code-block:: ada + + A : array (1..4, 1..4) of Long_Float; + S : array (1..4) of Long_Float; + + procedure Sum is + begin + for I in A'Range(1) loop + for J in A'Range(2) loop + S (I) := S (I) + A (I, J); + end loop; + end loop; + end Sum; + +The vectorizable operations depend on the targeted SIMD instruction set, but +the adding and some of the multiplying operators are generally supported, as +well as the logical operators for modular types. Note that, in the former +case, enabling overflow checks, for example with *-gnato*, totally +disables vectorization. The other checks are not supposed to have the same +definitive effect, although compiling with *-gnatp* might well reveal +cases where some checks do thwart vectorization. + +Type conversions may also prevent vectorization if they involve semantics that +are not directly supported by the code generator or the SIMD instruction set. +A typical example is direct conversion from floating-point to integer types. +The solution in this case is to use the following idiom: + + .. code-block:: ada + + Integer (S'Truncation (F)) + +if `S` is the subtype of floating-point object `F`. + +In most cases, the vectorizable loops are loops that iterate over arrays. +All kinds of array types are supported, i.e. constrained array types with +static bounds: + + .. code-block:: ada + + type Array_Type is array (1 .. 4) of Long_Float; + +constrained array types with dynamic bounds: + + + .. code-block:: ada + + type Array_Type is array (1 .. Q.N) of Long_Float; + + type Array_Type is array (Q.K .. 4) of Long_Float; + + type Array_Type is array (Q.K .. Q.N) of Long_Float; + +or unconstrained array types: + + .. code-block:: ada + + type Array_Type is array (Positive range <>) of Long_Float; + +The quality of the generated code decreases when the dynamic aspect of the +array type increases, the worst code being generated for unconstrained array +types. This is so because, the less information the compiler has about the +bounds of the array, the more fallback code it needs to generate in order to +fix things up at run time. + +It is possible to specify that a given loop should be subject to vectorization +preferably to other optimizations by means of pragma `Loop_Optimize`: + + .. code-block:: ada + + pragma Loop_Optimize (Vector); + +placed immediately within the loop will convey the appropriate hint to the +compiler for this loop. + +It is also possible to help the compiler generate better vectorized code +for a given loop by asserting that there are no loop-carried dependencies +in the loop. Consider for example the procedure: + + .. code-block:: ada + + type Arr is array (1 .. 4) of Long_Float; + + procedure Add (X, Y : not null access Arr; R : not null access Arr) is + begin + for I in Arr'Range loop + R(I) := X(I) + Y(I); + end loop; + end; + +By default, the compiler cannot unconditionally vectorize the loop because +assigning to a component of the array designated by R in one iteration could +change the value read from the components of the array designated by X or Y +in a later iteration. As a result, the compiler will generate two versions +of the loop in the object code, one vectorized and the other not vectorized, +as well as a test to select the appropriate version at run time. This can +be overcome by another hint: + + .. code-block:: ada + + pragma Loop_Optimize (Ivdep); + +placed immediately within the loop will tell the compiler that it can safely +omit the non-vectorized version of the loop as well as the run-time test. + + +.. _Other_Optimization_Switches: + +Other Optimization Switches +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Optimization Switches + +Since `GNAT` uses the *gcc* back end, all the specialized +*gcc* optimization switches are potentially usable. These switches +have not been extensively tested with GNAT but can generally be expected +to work. Examples of switches in this category are *-funroll-loops* +and the various target-specific *-m* options (in particular, it has +been observed that *-march=xxx* can significantly improve performance +on appropriate machines). For full details of these switches, see +the `Submodel Options` section in the `Hardware Models and Configurations` +chapter of :title:`Using the GNU Compiler Collection (GCC)`. + + +.. _Optimization_and_Strict_Aliasing: + +Optimization and Strict Aliasing +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Aliasing +.. index:: Strict Aliasing +.. index:: No_Strict_Aliasing + +The strong typing capabilities of Ada allow an optimizer to generate +efficient code in situations where other languages would be forced to +make worst case assumptions preventing such optimizations. Consider +the following example: + + .. code-block:: ada + + procedure R is + type Int1 is new Integer; + type Int2 is new Integer; + type Int1A is access Int1; + type Int2A is access Int2; + Int1V : Int1A; + Int2V : Int2A; + ... + + begin + ... + for J in Data'Range loop + if Data (J) = Int1V.all then + Int2V.all := Int2V.all + 1; + end if; + end loop; + ... + end R; + +In this example, since the variable `Int1V` can only access objects +of type `Int1`, and `Int2V` can only access objects of type +`Int2`, there is no possibility that the assignment to +`Int2V.all` affects the value of `Int1V.all`. This means that +the compiler optimizer can "know" that the value `Int1V.all` is constant +for all iterations of the loop and avoid the extra memory reference +required to dereference it each time through the loop. + +This kind of optimization, called strict aliasing analysis, is +triggered by specifying an optimization level of *-O2* or +higher or *-Os* and allows `GNAT` to generate more efficient code +when access values are involved. + +However, although this optimization is always correct in terms of +the formal semantics of the Ada Reference Manual, difficulties can +arise if features like `Unchecked_Conversion` are used to break +the typing system. Consider the following complete program example: + + .. code-block:: ada + + package p1 is + type int1 is new integer; + type int2 is new integer; + type a1 is access int1; + type a2 is access int2; + end p1; + + with p1; use p1; + package p2 is + function to_a2 (Input : a1) return a2; + end p2; + + with Unchecked_Conversion; + package body p2 is + function to_a2 (Input : a1) return a2 is + function to_a2u is + new Unchecked_Conversion (a1, a2); + begin + return to_a2u (Input); + end to_a2; + end p2; + + with p2; use p2; + with p1; use p1; + with Text_IO; use Text_IO; + procedure m is + v1 : a1 := new int1; + v2 : a2 := to_a2 (v1); + begin + v1.all := 1; + v2.all := 0; + put_line (int1'image (v1.all)); + end; + +This program prints out 0 in *-O0* or *-O1* +mode, but it prints out 1 in *-O2* mode. That's +because in strict aliasing mode, the compiler can and +does assume that the assignment to `v2.all` could not +affect the value of `v1.all`, since different types +are involved. + +This behavior is not a case of non-conformance with the standard, since +the Ada RM specifies that an unchecked conversion where the resulting +bit pattern is not a correct value of the target type can result in an +abnormal value and attempting to reference an abnormal value makes the +execution of a program erroneous. That's the case here since the result +does not point to an object of type `int2`. This means that the +effect is entirely unpredictable. + +However, although that explanation may satisfy a language +lawyer, in practice an applications programmer expects an +unchecked conversion involving pointers to create true +aliases and the behavior of printing 1 seems plain wrong. +In this case, the strict aliasing optimization is unwelcome. + +Indeed the compiler recognizes this possibility, and the +unchecked conversion generates a warning: + + :: + + p2.adb:5:07: warning: possible aliasing problem with type "a2" + p2.adb:5:07: warning: use -fno-strict-aliasing switch for references + p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);" + +Unfortunately the problem is recognized when compiling the body of +package `p2`, but the actual "bad" code is generated while +compiling the body of `m` and this latter compilation does not see +the suspicious `Unchecked_Conversion`. + +As implied by the warning message, there are approaches you can use to +avoid the unwanted strict aliasing optimization in a case like this. + +One possibility is to simply avoid the use of *-O2*, but +that is a bit drastic, since it throws away a number of useful +optimizations that do not involve strict aliasing assumptions. + +A less drastic approach is to compile the program using the +option *-fno-strict-aliasing*. Actually it is only the +unit containing the dereferencing of the suspicious pointer +that needs to be compiled. So in this case, if we compile +unit `m` with this switch, then we get the expected +value of zero printed. Analyzing which units might need +the switch can be painful, so a more reasonable approach +is to compile the entire program with options *-O2* +and *-fno-strict-aliasing*. If the performance is +satisfactory with this combination of options, then the +advantage is that the entire issue of possible "wrong" +optimization due to strict aliasing is avoided. + +To avoid the use of compiler switches, the configuration +pragma `No_Strict_Aliasing` with no parameters may be +used to specify that for all access types, the strict +aliasing optimization should be suppressed. + +However, these approaches are still overkill, in that they causes +all manipulations of all access values to be deoptimized. A more +refined approach is to concentrate attention on the specific +access type identified as problematic. + +First, if a careful analysis of uses of the pointer shows +that there are no possible problematic references, then +the warning can be suppressed by bracketing the +instantiation of `Unchecked_Conversion` to turn +the warning off: + + .. code-block:: ada + + pragma Warnings (Off); + function to_a2u is + new Unchecked_Conversion (a1, a2); + pragma Warnings (On); + +Of course that approach is not appropriate for this particular +example, since indeed there is a problematic reference. In this +case we can take one of two other approaches. + +The first possibility is to move the instantiation of unchecked +conversion to the unit in which the type is declared. In +this example, we would move the instantiation of +`Unchecked_Conversion` from the body of package +`p2` to the spec of package `p1`. Now the +warning disappears. That's because any use of the +access type knows there is a suspicious unchecked +conversion, and the strict aliasing optimization +is automatically suppressed for the type. + +If it is not practical to move the unchecked conversion to the same unit +in which the destination access type is declared (perhaps because the +source type is not visible in that unit), you may use pragma +`No_Strict_Aliasing` for the type. This pragma must occur in the +same declarative sequence as the declaration of the access type: + + .. code-block:: ada + + type a2 is access int2; + pragma No_Strict_Aliasing (a2); + +Here again, the compiler now knows that the strict aliasing optimization +should be suppressed for any reference to type `a2` and the +expected behavior is obtained. + +Finally, note that although the compiler can generate warnings for +simple cases of unchecked conversions, there are tricker and more +indirect ways of creating type incorrect aliases which the compiler +cannot detect. Examples are the use of address overlays and unchecked +conversions involving composite types containing access types as +components. In such cases, no warnings are generated, but there can +still be aliasing problems. One safe coding practice is to forbid the +use of address clauses for type overlaying, and to allow unchecked +conversion only for primitive types. This is not really a significant +restriction since any possible desired effect can be achieved by +unchecked conversion of access values. + +The aliasing analysis done in strict aliasing mode can certainly +have significant benefits. We have seen cases of large scale +application code where the time is increased by up to 5% by turning +this optimization off. If you have code that includes significant +usage of unchecked conversion, you might want to just stick with +*-O1* and avoid the entire issue. If you get adequate +performance at this level of optimization level, that's probably +the safest approach. If tests show that you really need higher +levels of optimization, then you can experiment with *-O2* +and *-O2 -fno-strict-aliasing* to see how much effect this +has on size and speed of the code. If you really need to use +*-O2* with strict aliasing in effect, then you should +review any uses of unchecked conversion of access types, +particularly if you are getting the warnings described above. + + +.. _Aliased_Variables_and_Optimization: + +Aliased Variables and Optimization +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Aliasing + +There are scenarios in which programs may +use low level techniques to modify variables +that otherwise might be considered to be unassigned. For example, +a variable can be passed to a procedure by reference, which takes +the address of the parameter and uses the address to modify the +variable's value, even though it is passed as an IN parameter. +Consider the following example: + + .. code-block:: ada + + procedure P is + Max_Length : constant Natural := 16; + type Char_Ptr is access all Character; + + procedure Get_String(Buffer: Char_Ptr; Size : Integer); + pragma Import (C, Get_String, "get_string"); + + Name : aliased String (1 .. Max_Length) := (others => ' '); + Temp : Char_Ptr; + + function Addr (S : String) return Char_Ptr is + function To_Char_Ptr is + new Ada.Unchecked_Conversion (System.Address, Char_Ptr); + begin + return To_Char_Ptr (S (S'First)'Address); + end; + + begin + Temp := Addr (Name); + Get_String (Temp, Max_Length); + end; + +where Get_String is a C function that uses the address in Temp to +modify the variable `Name`. This code is dubious, and arguably +erroneous, and the compiler would be entitled to assume that +`Name` is never modified, and generate code accordingly. + +However, in practice, this would cause some existing code that +seems to work with no optimization to start failing at high +levels of optimzization. + +What the compiler does for such cases is to assume that marking +a variable as aliased indicates that some "funny business" may +be going on. The optimizer recognizes the aliased keyword and +inhibits optimizations that assume the value cannot be assigned. +This means that the above example will in fact "work" reliably, +that is, it will produce the expected results. + + +.. _Atomic_Variables_and_Optimization: + +Atomic Variables and Optimization +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Atomic + +There are two considerations with regard to performance when +atomic variables are used. + +First, the RM only guarantees that access to atomic variables +be atomic, it has nothing to say about how this is achieved, +though there is a strong implication that this should not be +achieved by explicit locking code. Indeed GNAT will never +generate any locking code for atomic variable access (it will +simply reject any attempt to make a variable or type atomic +if the atomic access cannot be achieved without such locking code). + +That being said, it is important to understand that you cannot +assume that the entire variable will always be accessed. Consider +this example: + + .. code-block:: ada + + type R is record + A,B,C,D : Character; + end record; + for R'Size use 32; + for R'Alignment use 4; + + RV : R; + pragma Atomic (RV); + X : Character; + ... + X := RV.B; + +You cannot assume that the reference to `RV.B` +will read the entire 32-bit +variable with a single load instruction. It is perfectly legitimate if +the hardware allows it to do a byte read of just the B field. This read +is still atomic, which is all the RM requires. GNAT can and does take +advantage of this, depending on the architecture and optimization level. +Any assumption to the contrary is non-portable and risky. Even if you +examine the assembly language and see a full 32-bit load, this might +change in a future version of the compiler. + +If your application requires that all accesses to `RV` in this +example be full 32-bit loads, you need to make a copy for the access +as in: + + .. code-block:: ada + + declare + RV_Copy : constant R := RV; + begin + X := RV_Copy.B; + end; + +Now the reference to RV must read the whole variable. +Actually one can imagine some compiler which figures +out that the whole copy is not required (because only +the B field is actually accessed), but GNAT +certainly won't do that, and we don't know of any +compiler that would not handle this right, and the +above code will in practice work portably across +all architectures (that permit the Atomic declaration). + +The second issue with atomic variables has to do with +the possible requirement of generating synchronization +code. For more details on this, consult the sections on +the pragmas Enable/Disable_Atomic_Synchronization in the +GNAT Reference Manual. If performance is critical, and +such synchronization code is not required, it may be +useful to disable it. + + +.. _Passive_Task_Optimization: + +Passive Task Optimization +^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Passive Task + +A passive task is one which is sufficiently simple that +in theory a compiler could recognize it an implement it +efficiently without creating a new thread. The original design +of Ada 83 had in mind this kind of passive task optimization, but +only a few Ada 83 compilers attempted it. The problem was that +it was difficult to determine the exact conditions under which +the optimization was possible. The result is a very fragile +optimization where a very minor change in the program can +suddenly silently make a task non-optimizable. + +With the revisiting of this issue in Ada 95, there was general +agreement that this approach was fundamentally flawed, and the +notion of protected types was introduced. When using protected +types, the restrictions are well defined, and you KNOW that the +operations will be optimized, and furthermore this optimized +performance is fully portable. + +Although it would theoretically be possible for GNAT to attempt to +do this optimization, but it really doesn't make sense in the +context of Ada 95, and none of the Ada 95 compilers implement +this optimization as far as we know. In particular GNAT never +attempts to perform this optimization. + +In any new Ada 95 code that is written, you should always +use protected types in place of tasks that might be able to +be optimized in this manner. +Of course this does not help if you have legacy Ada 83 code +that depends on this optimization, but it is unusual to encounter +a case where the performance gains from this optimization +are significant. + +Your program should work correctly without this optimization. If +you have performance problems, then the most practical +approach is to figure out exactly where these performance problems +arise, and update those particular tasks to be protected types. Note +that typically clients of the tasks who call entries, will not have +to be modified, only the task definition itself. + + +.. _Text_IO_Suggestions: + +`Text_IO` Suggestions +--------------------- + +.. index:: Text_IO and performance + +The `Ada.Text_IO` package has fairly high overheads due in part to +the requirement of maintaining page and line counts. If performance +is critical, a recommendation is to use `Stream_IO` instead of +`Text_IO` for volume output, since this package has less overhead. + +If `Text_IO` must be used, note that by default output to the standard +output and standard error files is unbuffered (this provides better +behavior when output statements are used for debugging, or if the +progress of a program is observed by tracking the output, e.g. by +using the Unix *tail -f* command to watch redirected output. + +If you are generating large volumes of output with `Text_IO` and +performance is an important factor, use a designated file instead +of the standard output file, or change the standard output file to +be buffered using `Interfaces.C_Streams.setvbuf`. + + +.. _Reducing_Size_of_Executables_with_Unused_Subprogram/Data_Elimination: + +Reducing Size of Executables with Unused Subprogram/Data Elimination +-------------------------------------------------------------------- + +.. index:: Uunused subprogram/data elimination + +This section describes how you can eliminate unused subprograms and data from +your executable just by setting options at compilation time. + +.. _About_unused_subprogram/data_elimination: + +About unused subprogram/data elimination +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +By default, an executable contains all code and data of its composing objects +(directly linked or coming from statically linked libraries), even data or code +never used by this executable. + +This feature will allow you to eliminate such unused code from your +executable, making it smaller (in disk and in memory). + +This functionality is available on all Linux platforms except for the IA-64 +architecture and on all cross platforms using the ELF binary file format. +In both cases GNU binutils version 2.16 or later are required to enable it. + +.. _Compilation_options: + +Compilation options +^^^^^^^^^^^^^^^^^^^ + +The operation of eliminating the unused code and data from the final executable +is directly performed by the linker. + +.. index:: -ffunction-sections (gcc) +.. index:: -fdata-sections (gcc) + +In order to do this, it has to work with objects compiled with the +following options: +*-ffunction-sections* *-fdata-sections*. + +These options are usable with C and Ada files. +They will place respectively each +function or data in a separate section in the resulting object file. + +Once the objects and static libraries are created with these options, the +linker can perform the dead code elimination. You can do this by setting +the *-Wl,--gc-sections* option to gcc command or in the +*-largs* section of *gnatmake*. This will perform a +garbage collection of code and data never referenced. + +If the linker performs a partial link (*-r* linker option), then you +will need to provide the entry point using the *-e* / *--entry* +linker option. + +Note that objects compiled without the *-ffunction-sections* and +*-fdata-sections* options can still be linked with the executable. +However, no dead code elimination will be performed on those objects (they will +be linked as is). + +The GNAT static library is now compiled with -ffunction-sections and +-fdata-sections on some platforms. This allows you to eliminate the unused code +and data of the GNAT library from your executable. + + +.. _Example_of_unused_subprogram/data_elimination: + +Example of unused subprogram/data elimination +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Here is a simple example: + + .. code-block:: ada + + with Aux; + + procedure Test is + begin + Aux.Used (10); + end Test; + + package Aux is + Used_Data : Integer; + Unused_Data : Integer; + + procedure Used (Data : Integer); + procedure Unused (Data : Integer); + end Aux; + + package body Aux is + procedure Used (Data : Integer) is + begin + Used_Data := Data; + end Used; + + procedure Unused (Data : Integer) is + begin + Unused_Data := Data; + end Unused; + end Aux; + +`Unused` and `Unused_Data` are never referenced in this code +excerpt, and hence they may be safely removed from the final executable. + + :: + + $ gnatmake test + + $ nm test | grep used + 020015f0 T aux__unused + 02005d88 B aux__unused_data + 020015cc T aux__used + 02005d84 B aux__used_data + + $ gnatmake test -cargs -fdata-sections -ffunction-sections \\ + -largs -Wl,--gc-sections + + $ nm test | grep used + 02005350 T aux__used + 0201ffe0 B aux__used_data + +It can be observed that the procedure `Unused` and the object +`Unused_Data` are removed by the linker when using the +appropriate options. + +.. only:: PRO or GPL + + .. _Reducing_Size_of_Ada_Executables_with_gnatelim: + + Reducing Size of Ada Executables with `gnatelim` + ------------------------------------------------ + + .. index:: gnatelim + + This section describes *gnatelim*, a tool which detects unused + subprograms and helps the compiler to create a smaller executable for your + program. + + .. _About_gnatelim: + + About `gnatelim` + ^^^^^^^^^^^^^^^^ + + When a program shares a set of Ada + packages with other programs, it may happen that this program uses + only a fraction of the subprograms defined in these packages. The code + created for these unused subprograms increases the size of the executable. + + `gnatelim` tracks unused subprograms in an Ada program and + outputs a list of GNAT-specific pragmas `Eliminate` marking all the + subprograms that are declared but never called. By placing the list of + `Eliminate` pragmas in the GNAT configuration file :file:`gnat.adc` and + recompiling your program, you may decrease the size of its executable, + because the compiler will not generate the code for 'eliminated' subprograms. + See `Pragma_Eliminate` in the :title:`GNAT_Reference_Manual` for more + information about this pragma. + + `gnatelim` needs as its input data the name of the main subprogram. + + If a set of source files is specified as `gnatelim` arguments, it + treats these files as a complete set of sources making up a program to + analyse, and analyses only these sources. + + After a full successful build of the main subprogram `gnatelim` can be + called without specifying sources to analyse, in this case it computes + the source closure of the main unit from the :file:`ALI` files. + + If the set of sources to be processed by `gnatelim` contains sources with + preprocessing directives + then the needed options should be provided to run preprocessor as a part of + the *gnatelim* call, and the generated set of pragmas `Eliminate` + will correspond to preprocessed sources. + + The following command will create the set of :file:`ALI` files needed for + `gnatelim`: + + :: + + $ gnatmake -c Main_Prog + + Note that `gnatelim` does not need object files. + + + .. _Running_gnatelim: + + Running `gnatelim` + ^^^^^^^^^^^^^^^^^^ + + `gnatelim` has the following command-line interface: + + + :: + + $ gnatelim [`switches`] -main=`main_unit_name` {`filename`} [-cargs `gcc_switches`] + + `main_unit_name` should be a name of a source file that contains the main + subprogram of a program (partition). + + Each `filename` is the name (including the extension) of a source + file to process. 'Wildcards' are allowed, and + the file name may contain path information. + + `gcc_switches` is a list of switches for + *gcc*. They will be passed on to all compiler invocations made by + *gnatelim* to generate the ASIS trees. Here you can provide + *-I* switches to form the source search path, + use the *-gnatec* switch to set the configuration file, + use the *-gnat05* switch if sources should be compiled in + Ada 2005 mode etc. + + `gnatelim` has the following switches: + + + .. index:: --version (gnatelim) + + :samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + + .. index:: --help (gnatelim) + + :samp:`--help` + Display usage, then exit disregarding all other options. + + + .. index:: -P (gnatelim) + + :samp:`-P {file}` + Indicates the name of the project file that describes the set of sources + to be processed. + + + .. index:: -X (gnatelim) + + :samp:`-X{name}={value}` + Indicates that external variable `name` in the argument project + has the value `value`. Has no effect if no project is specified as + tool argument. + + + .. index:: --RTS (gnatelim) + + :samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + + .. index:: -files (gnatelim) + + :samp:`-files={filename}` + Take the argument source files from the specified file. This file should be an + ordinary text file containing file names separated by spaces or + line breaks. You can use this switch more than once in the same call to + *gnatelim*. You also can combine this switch with + an explicit list of files. + + + .. index:: -log (gnatelim) + + :samp:`-log` + Duplicate all the output sent to :file:`stderr` into a log file. The log file + is named :file:`gnatelim.log` and is located in the current directory. + + .. index:: --no-elim-dispatch (gnatelim) + + :samp:`--no-elim-dispatch` + Do not generate pragmas for dispatching operations. + + + .. index:: --ignore (gnatelim) + + :samp:`--ignore={filename}` + Do not generate pragmas for subprograms declared in the sources + listed in a specified file + + .. index:: -o (gnatelim) + + + :samp:`-o={report_file}` + Put *gnatelim* output into a specified file. If this file already exists, + it is overridden. If this switch is not used, *gnatelim* outputs its results + into :file:`stderr` + + + .. index:: -j (gnatelim) + + :samp:`-j{n}` + Use `n` processes to carry out the tree creations (internal representations + of the argument sources). On a multiprocessor machine this speeds up processing + of big sets of argument sources. If `n` is 0, then the maximum number of + parallel tree creations is the number of core processors on the platform. + + + .. index:: -q (gnatelim) + + :samp:`-q` + Quiet mode: by default `gnatelim` outputs to the standard error + stream the number of program units left to be processed. This option turns + this trace off. + + .. index:: -t (gnatelim) + + + :samp:`-t` + Print out execution time. + + + .. index:: -v (gnatelim) + + :samp:`-v` + Verbose mode: `gnatelim` version information is printed as Ada + comments to the standard output stream. Also, in addition to the number of + program units left `gnatelim` will output the name of the current unit + being processed. + + + .. index:: -wq (gnatelim) + + :samp:`-wq` + Quiet warning mode - some warnings are suppressed. In particular warnings that + indicate that the analysed set of sources is incomplete to make up a + partition and that some subprogram bodies are missing are not generated. + + Note: to invoke *gnatelim* with a project file, use the `gnat` + driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + + + .. _Processing_Precompiled_Libraries: + + Processing Precompiled Libraries + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + If some program uses a precompiled Ada library, it can be processed by + `gnatelim` in a usual way. `gnatelim` will newer generate an + Eliminate pragma for a subprogram if the body of this subprogram has not + been analysed, this is a typical case for subprograms from precompiled + libraries. Switch *-wq* may be used to suppress + warnings about missing source files and non-analyzed subprogram bodies + that can be generated when processing precompiled Ada libraries. + + + .. _Correcting_the_List_of_Eliminate_Pragmas: + + Correcting the List of Eliminate Pragmas + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + In some rare cases `gnatelim` may try to eliminate + subprograms that are actually called in the program. In this case, the + compiler will generate an error message of the form: + + :: + + main.adb:4:08: cannot reference subprogram "P" eliminated at elim.out:5 + + You will need to manually remove the wrong `Eliminate` pragmas from + the configuration file indicated in the error message. You should recompile + your program from scratch after that, because you need a consistent + configuration file(s) during the entire compilation. + + + .. _Making_Your_Executables_Smaller: + + Making Your Executables Smaller + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + In order to get a smaller executable for your program you now have to + recompile the program completely with the configuration file containing + pragmas Eliminate generated by gnatelim. If these pragmas are placed in + :file:`gnat.adc` file located in your current directory, just do: + + :: + + $ gnatmake -f main_prog + + (Use the *-f* option for *gnatmake* to + recompile everything + with the set of pragmas `Eliminate` that you have obtained with + *gnatelim*). + + Be aware that the set of `Eliminate` pragmas is specific to each + program. It is not recommended to merge sets of `Eliminate` + pragmas created for different programs in one configuration file. + + + .. _Summary_of_the_gnatelim_Usage_Cycle: + + Summary of the `gnatelim` Usage Cycle + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + Here is a quick summary of the steps to be taken in order to reduce + the size of your executables with `gnatelim`. You may use + other GNAT options to control the optimization level, + to produce the debugging information, to set search path, etc. + + * Create a complete set of :file:`ALI` files (if the program has not been + built already) + + :: + + $ gnatmake -c main_prog + + * Generate a list of `Eliminate` pragmas in default configuration file + :file:`gnat.adc` in the current directory + + :: + + $ gnatelim main_prog >[>] gnat.adc + + * Recompile the application + + :: + + $ gnatmake -f main_prog + + + +.. index:: Overflow checks +.. index:: Checks (overflow) + +.. _Overflow_Check_Handling_in_GNAT: + +Overflow Check Handling in GNAT +=============================== + +This section explains how to control the handling of overflow checks. + +.. _Background: + +Background +---------- + +Overflow checks are checks that the compiler may make to ensure +that intermediate results are not out of range. For example: + + .. code-block:: ada + + A : Integer; + ... + A := A + 1; + +If `A` has the value `Integer'Last`, then the addition may cause +overflow since the result is out of range of the type `Integer`. +In this case `Constraint_Error` will be raised if checks are +enabled. + +A trickier situation arises in examples like the following: + + .. code-block:: ada + + A, C : Integer; + ... + A := (A + 1) + C; + +where `A` is `Integer'Last` and `C` is `-1`. +Now the final result of the expression on the right hand side is +`Integer'Last` which is in range, but the question arises whether the +intermediate addition of `(A + 1)` raises an overflow error. + +The (perhaps surprising) answer is that the Ada language +definition does not answer this question. Instead it leaves +it up to the implementation to do one of two things if overflow +checks are enabled. + +* raise an exception (`Constraint_Error`), or + +* yield the correct mathematical result which is then used in + subsequent operations. + +If the compiler chooses the first approach, then the assignment of this +example will indeed raise `Constraint_Error` if overflow checking is +enabled, or result in erroneous execution if overflow checks are suppressed. + +But if the compiler +chooses the second approach, then it can perform both additions yielding +the correct mathematical result, which is in range, so no exception +will be raised, and the right result is obtained, regardless of whether +overflow checks are suppressed. + +Note that in the first example an +exception will be raised in either case, since if the compiler +gives the correct mathematical result for the addition, it will +be out of range of the target type of the assignment, and thus +fails the range check. + +This lack of specified behavior in the handling of overflow for +intermediate results is a source of non-portability, and can thus +be problematic when programs are ported. Most typically this arises +in a situation where the original compiler did not raise an exception, +and then the application is moved to a compiler where the check is +performed on the intermediate result and an unexpected exception is +raised. + +Furthermore, when using Ada 2012's preconditions and other +assertion forms, another issue arises. Consider: + + .. code-block:: ada + + procedure P (A, B : Integer) with + Pre => A + B <= Integer'Last; + +One often wants to regard arithmetic in a context like this from +a mathematical point of view. So for example, if the two actual parameters +for a call to `P` are both `Integer'Last`, then +the precondition should be regarded as False. If we are executing +in a mode with run-time checks enabled for preconditions, then we would +like this precondition to fail, rather than raising an exception +because of the intermediate overflow. + +However, the language definition leaves the specification of +whether the above condition fails (raising `Assert_Error`) or +causes an intermediate overflow (raising `Constraint_Error`) +up to the implementation. + +The situation is worse in a case such as the following: + + .. code-block:: ada + + procedure Q (A, B, C : Integer) with + Pre => A + B + C <= Integer'Last; + +Consider the call + + .. code-block:: ada + + Q (A => Integer'Last, B => 1, C => -1); + +From a mathematical point of view the precondition +is True, but at run time we may (but are not guaranteed to) get an +exception raised because of the intermediate overflow (and we really +would prefer this precondition to be considered True at run time). + + +.. _Overflow_Checking_Modes_in_GNAT: + +Overflow Checking Modes in GNAT +------------------------------- + +To deal with the portability issue, and with the problem of +mathematical versus run-time interpretation of the expressions in +assertions, GNAT provides comprehensive control over the handling +of intermediate overflow. GNAT can operate in three modes, and +furthemore, permits separate selection of operating modes for +the expressions within assertions (here the term 'assertions' +is used in the technical sense, which includes preconditions and so forth) +and for expressions appearing outside assertions. + +The three modes are: + +* *Use base type for intermediate operations* (`STRICT`) + + In this mode, all intermediate results for predefined arithmetic + operators are computed using the base type, and the result must + be in range of the base type. If this is not the + case then either an exception is raised (if overflow checks are + enabled) or the execution is erroneous (if overflow checks are suppressed). + This is the normal default mode. + +* *Most intermediate overflows avoided* (`MINIMIZED`) + + In this mode, the compiler attempts to avoid intermediate overflows by + using a larger integer type, typically `Long_Long_Integer`, + as the type in which arithmetic is + performed for predefined arithmetic operators. This may be slightly more + expensive at + run time (compared to suppressing intermediate overflow checks), though + the cost is negligible on modern 64-bit machines. For the examples given + earlier, no intermediate overflows would have resulted in exceptions, + since the intermediate results are all in the range of + `Long_Long_Integer` (typically 64-bits on nearly all implementations + of GNAT). In addition, if checks are enabled, this reduces the number of + checks that must be made, so this choice may actually result in an + improvement in space and time behavior. + + However, there are cases where `Long_Long_Integer` is not large + enough, consider the following example: + + .. code-block:: ada + + procedure R (A, B, C, D : Integer) with + Pre => (A**2 * B**2) / (C**2 * D**2) <= 10; + + where `A` = `B` = `C` = `D` = `Integer'Last`. + Now the intermediate results are + out of the range of `Long_Long_Integer` even though the final result + is in range and the precondition is True (from a mathematical point + of view). In such a case, operating in this mode, an overflow occurs + for the intermediate computation (which is why this mode + says *most* intermediate overflows are avoided). In this case, + an exception is raised if overflow checks are enabled, and the + execution is erroneous if overflow checks are suppressed. + +* *All intermediate overflows avoided* (`ELIMINATED`) + + In this mode, the compiler avoids all intermediate overflows + by using arbitrary precision arithmetic as required. In this + mode, the above example with `A**2 * B**2` would + not cause intermediate overflow, because the intermediate result + would be evaluated using sufficient precision, and the result + of evaluating the precondition would be True. + + This mode has the advantage of avoiding any intermediate + overflows, but at the expense of significant run-time overhead, + including the use of a library (included automatically in this + mode) for multiple-precision arithmetic. + + This mode provides cleaner semantics for assertions, since now + the run-time behavior emulates true arithmetic behavior for the + predefined arithmetic operators, meaning that there is never a + conflict between the mathematical view of the assertion, and its + run-time behavior. + + Note that in this mode, the behavior is unaffected by whether or + not overflow checks are suppressed, since overflow does not occur. + It is possible for gigantic intermediate expressions to raise + `Storage_Error` as a result of attempting to compute the + results of such expressions (e.g. `Integer'Last ** Integer'Last`) + but overflow is impossible. + + +Note that these modes apply only to the evaluation of predefined +arithmetic, membership, and comparison operators for signed integer +aritmetic. + +For fixed-point arithmetic, checks can be suppressed. But if checks +are enabled +then fixed-point values are always checked for overflow against the +base type for intermediate expressions (that is such checks always +operate in the equivalent of `STRICT` mode). + +For floating-point, on nearly all architectures, `Machine_Overflows` +is False, and IEEE infinities are generated, so overflow exceptions +are never raised. If you want to avoid infinities, and check that +final results of expressions are in range, then you can declare a +constrained floating-point type, and range checks will be carried +out in the normal manner (with infinite values always failing all +range checks). + + +.. _Specifying_the_Desired_Mode: + +Specifying the Desired Mode +--------------------------- + +.. index:: pragma Overflow_Mode + +The desired mode of for handling intermediate overflow can be specified using +either the `Overflow_Mode` pragma or an equivalent compiler switch. +The pragma has the form + + .. code-block:: ada + + pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]); + +where `MODE` is one of + +* `STRICT`: intermediate overflows checked (using base type) +* `MINIMIZED`: minimize intermediate overflows +* `ELIMINATED`: eliminate intermediate overflows + +The case is ignored, so `MINIMIZED`, `Minimized` and +`minimized` all have the same effect. + +If only the `General` parameter is present, then the given `MODE` +applies +to expressions both within and outside assertions. If both arguments +are present, then `General` applies to expressions outside assertions, +and `Assertions` applies to expressions within assertions. For example: + + .. code-block:: ada + + pragma Overflow_Mode + (General => Minimized, Assertions => Eliminated); + +specifies that general expressions outside assertions be evaluated +in 'minimize intermediate overflows' mode, and expressions within +assertions be evaluated in 'eliminate intermediate overflows' mode. +This is often a reasonable choice, avoiding excessive overhead +outside assertions, but assuring a high degree of portability +when importing code from another compiler, while incurring +the extra overhead for assertion expressions to ensure that +the behavior at run time matches the expected mathematical +behavior. + +The `Overflow_Mode` pragma has the same scoping and placement +rules as pragma `Suppress`, so it can occur either as a +configuration pragma, specifying a default for the whole +program, or in a declarative scope, where it applies to the +remaining declarations and statements in that scope. + +Note that pragma `Overflow_Mode` does not affect whether +overflow checks are enabled or suppressed. It only controls the +method used to compute intermediate values. To control whether +overflow checking is enabled or suppressed, use pragma `Suppress` +or `Unsuppress` in the usual manner + + +.. index:: -gnato? (gcc) +.. index:: -gnato?? (gcc) + +Additionally, a compiler switch *-gnato?* or *-gnato??* +can be used to control the checking mode default (which can be subsequently +overridden using pragmas). + +Here ``?`` is one of the digits ``1`` through ``3``: + + ====== ===================================================== + ``1`` use base type for intermediate operations (`STRICT`) + ``2`` minimize intermediate overflows (`MINIMIZED`) + ``3`` eliminate intermediate overflows (`ELIMINATED`) + ====== ===================================================== + +As with the pragma, if only one digit appears then it applies to all +cases; if two digits are given, then the first applies outside +assertions, and the second within assertions. Thus the equivalent +of the example pragma above would be +*-gnato23*. + +If no digits follow the *-gnato*, then it is equivalent to +*-gnato11*, +causing all intermediate operations to be computed using the base +type (`STRICT` mode). + +In addition to setting the mode used for computation of intermediate +results, the `-gnato` switch also enables overflow checking (which +is suppressed by default). It thus combines the effect of using +a pragma `Overflow_Mode` and pragma `Unsuppress`. + +.. _Default_Settings: + +Default Settings +---------------- + +The default mode for overflow checks is + + :: + + General => Strict + +which causes all computations both inside and outside assertions to use +the base type. In addition overflow checks are suppressed. + +This retains compatibility with previous versions of +GNAT which suppressed overflow checks by default and always +used the base type for computation of intermediate results. + +The switch *-gnato* (with no digits following) is equivalent to +.. index:: -gnato (gcc) + + :: + + General => Strict + +which causes overflow checking of all intermediate overflows +both inside and outside assertions against the base type. +This provides compatibility +with this switch as implemented in previous versions of GNAT. + +The pragma `Suppress (Overflow_Check)` disables overflow +checking, but it has no effect on the method used for computing +intermediate results. + +The pragma `Unsuppress (Overflow_Check)` enables overflow +checking, but it has no effect on the method used for computing +intermediate results. + + +.. _Implementation_Notes: + +Implementation Notes +-------------------- + +In practice on typical 64-bit machines, the `MINIMIZED` mode is +reasonably efficient, and can be generally used. It also helps +to ensure compatibility with code imported from some other +compiler to GNAT. + +Setting all intermediate overflows checking (`CHECKED` mode) +makes sense if you want to +make sure that your code is compatible with any other possible +Ada implementation. This may be useful in ensuring portability +for code that is to be exported to some other compiler than GNAT. + +The Ada standard allows the reassociation of expressions at +the same precedence level if no parentheses are present. For +example, `A+B+C` parses as though it were `(A+B)+C`, but +the compiler can reintepret this as `A+(B+C)`, possibly +introducing or eliminating an overflow exception. The GNAT +compiler never takes advantage of this freedom, and the +expression `A+B+C` will be evaluated as `(A+B)+C`. +If you need the other order, you can write the parentheses +explicitly `A+(B+C)` and GNAT will respect this order. + +The use of `ELIMINATED` mode will cause the compiler to +automatically include an appropriate arbitrary precision +integer arithmetic package. The compiler will make calls +to this package, though only in cases where it cannot be +sure that `Long_Long_Integer` is sufficient to guard against +intermediate overflows. This package does not use dynamic +alllocation, but it does use the secondary stack, so an +appropriate secondary stack package must be present (this +is always true for standard full Ada, but may require +specific steps for restricted run times such as ZFP). + +Although `ELIMINATED` mode causes expressions to use arbitrary +precision arithmetic, avoiding overflow, the final result +must be in an appropriate range. This is true even if the +final result is of type `[Long_[Long_]]Integer'Base`, which +still has the same bounds as its associated constrained +type at run-time. + +Currently, the `ELIMINATED` mode is only available on target +platforms for which `Long_Long_Integer` is 64-bits (nearly all GNAT +platforms). + + + +.. _Performing_Dimensionality_Analysis_in_GNAT: + +Performing Dimensionality Analysis in GNAT +========================================== + +.. index:: Dimensionality analysis + +The GNAT compiler supports dimensionality checking. The user can +specify physical units for objects, and the compiler will verify that uses +of these objects are compatible with their dimensions, in a fashion that is +familiar to engineering practice. The dimensions of algebraic expressions +(including powers with static exponents) are computed from their constituents. + +.. index:: Dimension_System aspect +.. index:: Dimension aspect + +This feature depends on Ada 2012 aspect specifications, and is available from +version 7.0.1 of GNAT onwards. +The GNAT-specific aspect `Dimension_System` +allows you to define a system of units; the aspect `Dimension` +then allows the user to declare dimensioned quantities within a given system. +(These aspects are described in the *Implementation Defined Aspects* +chapter of the *GNAT Reference Manual*). + +The major advantage of this model is that it does not require the declaration of +multiple operators for all possible combinations of types: it is only necessary +to use the proper subtypes in object declarations. + +.. index:: System.Dim.Mks package (GNAT library) +.. index:: MKS_Type type + +The simplest way to impose dimensionality checking on a computation is to make +use of the package `System.Dim.Mks`, +which is part of the GNAT library. This +package defines a floating-point type `MKS_Type`, +for which a sequence of +dimension names are specified, together with their conventional abbreviations. +The following should be read together with the full specification of the +package, in file :file:`s-dimmks.ads`. + + .. index:: s-dimmks.ads file + + .. code-block:: ada + + type Mks_Type is new Long_Long_Float + with + Dimension_System => ( + (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), + (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), + (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), + (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), + (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"), + (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), + (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); + +The package then defines a series of subtypes that correspond to these +conventional units. For example: + + .. code-block:: ada + + subtype Length is Mks_Type + with + Dimension => (Symbol => 'm', Meter => 1, others => 0); + +and similarly for `Mass`, `Time`, `Electric_Current`, +`Thermodynamic_Temperature`, `Amount_Of_Substance`, and +`Luminous_Intensity` (the standard set of units of the SI system). + +The package also defines conventional names for values of each unit, for +example: + + .. code-block":: ada + + m : constant Length := 1.0; + kg : constant Mass := 1.0; + s : constant Time := 1.0; + A : constant Electric_Current := 1.0; + +as well as useful multiples of these units: + + .. code-block:: ada + + cm : constant Length := 1.0E-02; + g : constant Mass := 1.0E-03; + min : constant Time := 60.0; + day : constant Time := 60.0 * 24.0 * min; + ... + +Using this package, you can then define a derived unit by +providing the aspect that +specifies its dimensions within the MKS system, as well as the string to +be used for output of a value of that unit: + + .. code-block:: ada + + subtype Acceleration is Mks_Type + with Dimension => ("m/sec^2", + Meter => 1, + Second => -2, + others => 0); + +Here is a complete example of use: + + .. code-block:: ada + + with System.Dim.MKS; use System.Dim.Mks; + with System.Dim.Mks_IO; use System.Dim.Mks_IO; + with Text_IO; use Text_IO; + procedure Free_Fall is + subtype Acceleration is Mks_Type + with Dimension => ("m/sec^2", 1, 0, -2, others => 0); + G : constant acceleration := 9.81 * m / (s ** 2); + T : Time := 10.0*s; + Distance : Length; + + begin + Put ("Gravitational constant: "); + Put (G, Aft => 2, Exp => 0); Put_Line (""); + Distance := 0.5 * G * T ** 2; + Put ("distance travelled in 10 seconds of free fall "); + Put (Distance, Aft => 2, Exp => 0); + Put_Line (""); + end Free_Fall; + +Execution of this program yields: + + :: + + Gravitational constant: 9.81 m/sec^2 + distance travelled in 10 seconds of free fall 490.50 m + +However, incorrect assignments such as: + + .. code-block:: ada + + Distance := 5.0; + Distance := 5.0 * kg: + +are rejected with the following diagnoses: + + :: + + Distance := 5.0; + >>> dimensions mismatch in assignment + >>> left-hand side has dimension [L] + >>> right-hand side is dimensionless + + Distance := 5.0 * kg: + >>> dimensions mismatch in assignment + >>> left-hand side has dimension [L] + >>> right-hand side has dimension [M] + +The dimensions of an expression are properly displayed, even if there is +no explicit subtype for it. If we add to the program: + + .. code-block:: ada + + Put ("Final velocity: "); + Put (G * T, Aft =>2, Exp =>0); + Put_Line (""); + +then the output includes: + + :: + + Final velocity: 98.10 m.s**(-1) + + + +.. _Stack_Related_Facilities: + +Stack Related Facilities +======================== + +This section describes some useful tools associated with stack +checking and analysis. In +particular, it deals with dynamic and static stack usage measurements. + +.. _Stack_Overflow_Checking: + +Stack Overflow Checking +----------------------- + +.. index:: Stack Overflow Checking + +.. index:: -fstack-check (gcc) + +For most operating systems, *gcc* does not perform stack overflow +checking by default. This means that if the main environment task or +some other task exceeds the available stack space, then unpredictable +behavior will occur. Most native systems offer some level of protection by +adding a guard page at the end of each task stack. This mechanism is usually +not enough for dealing properly with stack overflow situations because +a large local variable could "jump" above the guard page. +Furthermore, when the +guard page is hit, there may not be any space left on the stack for executing +the exception propagation code. Enabling stack checking avoids +such situations. + +To activate stack checking, compile all units with the gcc option +`-fstack-check`. For example: + + :: + + $ gcc -c -fstack-check package1.adb + +Units compiled with this option will generate extra instructions to check +that any use of the stack (for procedure calls or for declaring local +variables in declare blocks) does not exceed the available stack space. +If the space is exceeded, then a `Storage_Error` exception is raised. + +For declared tasks, the stack size is controlled by the size +given in an applicable `Storage_Size` pragma or by the value specified +at bind time with ``-d`` (:ref:`Switches_for_gnatbind`) or is set to +the default size as defined in the GNAT runtime otherwise. + +.. index:: GNAT_STACK_LIMIT + +For the environment task, the stack size depends on +system defaults and is unknown to the compiler. Stack checking +may still work correctly if a fixed +size stack is allocated, but this cannot be guaranteed. +To ensure that a clean exception is signalled for stack +overflow, set the environment variable +:envvar:`GNAT_STACK_LIMIT` to indicate the maximum +stack area that can be used, as in: + + :: + + $ SET GNAT_STACK_LIMIT 1600 + +The limit is given in kilobytes, so the above declaration would +set the stack limit of the environment task to 1.6 megabytes. +Note that the only purpose of this usage is to limit the amount +of stack used by the environment task. If it is necessary to +increase the amount of stack for the environment task, then this +is an operating systems issue, and must be addressed with the +appropriate operating systems commands. + + +.. _Static_Stack_Usage_Analysis: + +Static Stack Usage Analysis +--------------------------- + +.. index:: Static Stack Usage Analysis + +.. index:: -fstack-usage + +A unit compiled with ``-fstack-usage`` will generate an extra file +that specifies +the maximum amount of stack used, on a per-function basis. +The file has the same +basename as the target object file with a :file:`.su` extension. +Each line of this file is made up of three fields: + +* The name of the function. +* A number of bytes. +* One or more qualifiers: `static`, `dynamic`, `bounded`. + +The second field corresponds to the size of the known part of the function +frame. + +The qualifier `static` means that the function frame size +is purely static. +It usually means that all local variables have a static size. +In this case, the second field is a reliable measure of the function stack +utilization. + +The qualifier `dynamic` means that the function frame size is not static. +It happens mainly when some local variables have a dynamic size. When this +qualifier appears alone, the second field is not a reliable measure +of the function stack analysis. When it is qualified with `bounded`, it +means that the second field is a reliable maximum of the function stack +utilization. + +A unit compiled with ``-Wstack-usage`` will issue a warning for each +subprogram whose stack usage might be larger than the specified amount of +bytes. The wording is in keeping with the qualifier documented above. + + +.. _Dynamic_Stack_Usage_Analysis: + +Dynamic Stack Usage Analysis +---------------------------- + +It is possible to measure the maximum amount of stack used by a task, by +adding a switch to *gnatbind*, as: + + :: + + $ gnatbind -u0 file + +With this option, at each task termination, its stack usage is output on +:file:`stderr`. +It is not always convenient to output the stack usage when the program +is still running. Hence, it is possible to delay this output until program +termination. for a given number of tasks specified as the argument of the +``-u`` option. For instance: + + :: + + $ gnatbind -u100 file + +will buffer the stack usage information of the first 100 tasks to terminate and +output this info at program termination. Results are displayed in four +columns: + + :: + + Index | Task Name | Stack Size | Stack Usage + +where: + +* *Index* is a number associated with each task. + +* *Task Name* is the name of the task analyzed. + +* *Stack Size* is the maximum size for the stack. + +* *Stack Usage* is the measure done by the stack analyzer. + In order to prevent overflow, the stack + is not entirely analyzed, and it's not possible to know exactly how + much has actually been used. + +The environment task stack, e.g., the stack that contains the main unit, is +only processed when the environment variable GNAT_STACK_LIMIT is set. + +The package `GNAT.Task_Stack_Usage` provides facilities to get +stack usage reports at run-time. See its body for the details. + + + +.. _Memory_Management_Issues: + +Memory Management Issues +======================== + +This section describes some useful memory pools provided in the GNAT library +and in particular the GNAT Debug Pool facility, which can be used to detect +incorrect uses of access values (including 'dangling references'). + +.. only:: PRO or GPL + + It also describes the *gnatmem* tool, which can be used to track down + "memory leaks". + +.. _Some_Useful_Memory_Pools: + +Some Useful Memory Pools +------------------------ + +.. index:: Memory Pool +.. index:: storage, pool + +The `System.Pool_Global` package offers the Unbounded_No_Reclaim_Pool +storage pool. Allocations use the standard system call `malloc` while +deallocations use the standard system call `free`. No reclamation is +performed when the pool goes out of scope. For performance reasons, the +standard default Ada allocators/deallocators do not use any explicit storage +pools but if they did, they could use this storage pool without any change in +behavior. That is why this storage pool is used when the user +manages to make the default implicit allocator explicit as in this example: + + .. code-block:: ada + + type T1 is access Something; + -- no Storage pool is defined for T2 + + type T2 is access Something_Else; + for T2'Storage_Pool use T1'Storage_Pool; + -- the above is equivalent to + for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object; + +The `System.Pool_Local` package offers the Unbounded_Reclaim_Pool storage +pool. The allocation strategy is similar to `Pool_Local`'s +except that the all +storage allocated with this pool is reclaimed when the pool object goes out of +scope. This pool provides a explicit mechanism similar to the implicit one +provided by several Ada 83 compilers for allocations performed through a local +access type and whose purpose was to reclaim memory when exiting the +scope of a given local access. As an example, the following program does not +leak memory even though it does not perform explicit deallocation: + + .. code-block:: ada + + with System.Pool_Local; + procedure Pooloc1 is + procedure Internal is + type A is access Integer; + X : System.Pool_Local.Unbounded_Reclaim_Pool; + for A'Storage_Pool use X; + v : A; + begin + for I in 1 .. 50 loop + v := new Integer; + end loop; + end Internal; + begin + for I in 1 .. 100 loop + Internal; + end loop; + end Pooloc1; + +The `System.Pool_Size` package implements the Stack_Bounded_Pool used when +`Storage_Size` is specified for an access type. +The whole storage for the pool is +allocated at once, usually on the stack at the point where the access type is +elaborated. It is automatically reclaimed when exiting the scope where the +access type is defined. This package is not intended to be used directly by the +user and it is implicitly used for each such declaration: + + .. code-block:: ada + + type T1 is access Something; + for T1'Storage_Size use 10_000; + + +.. _The_GNAT_Debug_Pool_Facility: + +The GNAT Debug Pool Facility +---------------------------- + +.. index:: Debug Pool +.. index:: storage, pool, memory corruption + +The use of unchecked deallocation and unchecked conversion can easily +lead to incorrect memory references. The problems generated by such +references are usually difficult to tackle because the symptoms can be +very remote from the origin of the problem. In such cases, it is +very helpful to detect the problem as early as possible. This is the +purpose of the Storage Pool provided by `GNAT.Debug_Pools`. + +In order to use the GNAT specific debugging pool, the user must +associate a debug pool object with each of the access types that may be +related to suspected memory problems. See Ada Reference Manual 13.11. + + .. code-block:: ada + + type Ptr is access Some_Type; + Pool : GNAT.Debug_Pools.Debug_Pool; + for Ptr'Storage_Pool use Pool; + +`GNAT.Debug_Pools` is derived from a GNAT-specific kind of +pool: the `Checked_Pool`. Such pools, like standard Ada storage pools, +allow the user to redefine allocation and deallocation strategies. They +also provide a checkpoint for each dereference, through the use of +the primitive operation `Dereference` which is implicitly called at +each dereference of an access value. + +Once an access type has been associated with a debug pool, operations on +values of the type may raise four distinct exceptions, +which correspond to four potential kinds of memory corruption: + +* `GNAT.Debug_Pools.Accessing_Not_Allocated_Storage` +* `GNAT.Debug_Pools.Accessing_Deallocated_Storage` +* `GNAT.Debug_Pools.Freeing_Not_Allocated_Storage` +* `GNAT.Debug_Pools.Freeing_Deallocated_Storage` + +For types associated with a Debug_Pool, dynamic allocation is performed using +the standard GNAT allocation routine. References to all allocated chunks of +memory are kept in an internal dictionary. Several deallocation strategies are +provided, whereupon the user can choose to release the memory to the system, +keep it allocated for further invalid access checks, or fill it with an easily +recognizable pattern for debug sessions. The memory pattern is the old IBM +hexadecimal convention: `16#DEADBEEF#`. + +See the documentation in the file g-debpoo.ads for more information on the +various strategies. + +Upon each dereference, a check is made that the access value denotes a +properly allocated memory location. Here is a complete example of use of +`Debug_Pools`, that includes typical instances of memory corruption: + + .. code-block:: ada + + with Gnat.Io; use Gnat.Io; + with Unchecked_Deallocation; + with Unchecked_Conversion; + with GNAT.Debug_Pools; + with System.Storage_Elements; + with Ada.Exceptions; use Ada.Exceptions; + procedure Debug_Pool_Test is + + type T is access Integer; + type U is access all T; + + P : GNAT.Debug_Pools.Debug_Pool; + for T'Storage_Pool use P; + + procedure Free is new Unchecked_Deallocation (Integer, T); + function UC is new Unchecked_Conversion (U, T); + A, B : aliased T; + + procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line); + + begin + Info (P); + A := new Integer; + B := new Integer; + B := A; + Info (P); + Free (A); + begin + Put_Line (Integer'Image(B.all)); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + begin + Free (B); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + B := UC(A'Access); + begin + Put_Line (Integer'Image(B.all)); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + begin + Free (B); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + Info (P); + end Debug_Pool_Test; + +The debug pool mechanism provides the following precise diagnostics on the +execution of this erroneous program: + + :: + + Debug Pool info: + Total allocated bytes : 0 + Total deallocated bytes : 0 + Current Water Mark: 0 + High Water Mark: 0 + + Debug Pool info: + Total allocated bytes : 8 + Total deallocated bytes : 0 + Current Water Mark: 8 + High Water Mark: 8 + + raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE + raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE + raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE + raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE + Debug Pool info: + Total allocated bytes : 8 + Total deallocated bytes : 4 + Current Water Mark: 4 + High Water Mark: 8 + +.. only:: PRO or GPL + + .. _The_gnatmem_Tool: + + The *gnatmem* Tool + ------------------ + + .. index:: ! gnatmem + + The `gnatmem` utility monitors dynamic allocation and + deallocation activity in a program, and displays information about + incorrect deallocations and possible sources of memory leaks. + It is designed to work in association with a static runtime library + only and in this context provides three types of information: + + * General information concerning memory management, such as the total + number of allocations and deallocations, the amount of allocated + memory and the high water mark, i.e., the largest amount of allocated + memory in the course of program execution. + + * Backtraces for all incorrect deallocations, that is to say deallocations + which do not correspond to a valid allocation. + + * Information on each allocation that is potentially the origin of a memory + leak. + + .. _Running_gnatmem: + + Running `gnatmem` + ^^^^^^^^^^^^^^^^^ + + `gnatmem` makes use of the output created by the special version of + allocation and deallocation routines that record call information. This allows + it to obtain accurate dynamic memory usage history at a minimal cost to the + execution speed. Note however, that `gnatmem` is not supported on all + platforms (currently, it is supported on AIX, HP-UX, GNU/Linux, Solaris and + Windows NT/2000/XP (x86). + + The `gnatmem` command has the form + + :: + + $ gnatmem [`switches`] `user_program` + + The program must have been linked with the instrumented version of the + allocation and deallocation routines. This is done by linking with the + :file:`libgmem.a` library. For correct symbolic backtrace information, + the user program should be compiled with debugging options + (see :ref:`Switches_for_gcc`). For example to build :file:`my_program`: + + :: + + $ gnatmake -g my_program -largs -lgmem + + As library :file:`libgmem.a` contains an alternate body for package + `System.Memory`, :file:`s-memory.adb` should not be compiled and linked + when an executable is linked with library :file:`libgmem.a`. It is then not + recommended to use *gnatmake* with switch *-a*. + + When :file:`my_program` is executed, the file :file:`gmem.out` is produced. + This file contains information about all allocations and deallocations + performed by the program. It is produced by the instrumented allocations and + deallocations routines and will be used by `gnatmem`. + + In order to produce symbolic backtrace information for allocations and + deallocations performed by the GNAT run-time library, you need to use a + version of that library that has been compiled with the *-g* switch + (see :ref:`Rebuilding_the_GNAT_Run-Time_Library`). + + *gnatmem* must be supplied with the :file:`gmem.out` file and the executable to + examine. If the location of :file:`gmem.out` file was not explicitly supplied by + *-i* switch, gnatmem will assume that this file can be found in the + current directory. For example, after you have executed :file:`my_program`, + :file:`gmem.out` can be analyzed by `gnatmem` using the command: + + :: + + $ gnatmem my_program + + This will produce the output with the following format: + + :: + + $ gnatmem my_program + + Global information + ------------------ + Total number of allocations : 45 + Total number of deallocations : 6 + Final Water Mark (non freed mem) : 11.29 Kilobytes + High Water Mark : 11.40 Kilobytes + + . + . + . + Allocation Root # 2 + ------------------- + Number of non freed allocations : 11 + Final Water Mark (non freed mem) : 1.16 Kilobytes + High Water Mark : 1.27 Kilobytes + Backtrace : + my_program.adb:23 my_program.alloc + . + . + . + + The first block of output gives general information. In this case, the + Ada construct **new** was executed 45 times, and only 6 calls to an + Unchecked_Deallocation routine occurred. + + Subsequent paragraphs display information on all allocation roots. + An allocation root is a specific point in the execution of the program + that generates some dynamic allocation, such as a **new** + construct. This root is represented by an execution backtrace (or subprogram + call stack). By default the backtrace depth for allocations roots is 1, so + that a root corresponds exactly to a source location. The backtrace can + be made deeper, to make the root more specific. + + .. _Switches_for_gnatmem: + + Switches for `gnatmem` + ^^^^^^^^^^^^^^^^^^^^^^ + + `gnatmem` recognizes the following switches: + + .. index:: -q (gnatmem) + + :samp:`-q` + Quiet. Gives the minimum output needed to identify the origin of the + memory leaks. Omits statistical information. + + + .. index:: N switch (gnatmem) + + :samp:`{N}` + `N` is an integer literal (usually between 1 and 10) which controls the + depth of the backtraces defining allocation root. The default value for + N is 1. The deeper the backtrace, the more precise the localization of + the root. Note that the total number of roots can depend on this + parameter. This parameter must be specified *before* the name of the + executable to be analyzed, to avoid ambiguity. + + + .. index:: -b (gnatmem) + + :samp:`-b {N}` + This switch has the same effect as just a depth parameter `N`. + + + .. index:: -i (gnatmem) + + :samp:`-i {file}` + Do the `gnatmem` processing starting from :file:`file`, rather than + :file:`gmem.out` in the current directory. + + + .. index:: -m (gnatmem) + + :samp:`-m {n}` + This switch causes `gnatmem` to mask the allocation roots that have less + than n leaks. The default value is 1. Specifying the value of 0 will allow + examination of even the roots that did not result in leaks. + + + .. index:: -s (gnatmem) + + :samp:`-s {order}` + This switch causes `gnatmem` to sort the allocation roots according to the + specified order of sort criteria, each identified by a single letter. The + currently supported criteria are `n`, `h`, and `w` standing respectively for + number of unfreed allocations, high watermark, and final watermark + corresponding to a specific root. The default order is `nwh`. + + + .. index:: -t (gnatmem) + + :samp:`-t` + This switch causes memory allocated size to be always output in bytes. + Default `gnatmem` behavior is to show memory sizes less then 1 kilobyte + in bytes, from 1 kilobyte till 1 megabyte in kilobytes and the rest in + megabytes. + + + .. _Example_of_gnatmem_Usage: + + Example of `gnatmem` Usage + ^^^^^^^^^^^^^^^^^^^^^^^^^^ + + The following example shows the use of `gnatmem` + on a simple memory-leaking program. + Suppose that we have the following Ada program: + + .. code-block:: ada + + with Unchecked_Deallocation; + procedure Test_Gm is + + type T is array (1..1000) of Integer; + type Ptr is access T; + procedure Free is new Unchecked_Deallocation (T, Ptr); + A : Ptr; + + procedure My_Alloc is + begin + A := new T; + end My_Alloc; + + procedure My_DeAlloc is + B : Ptr := A; + begin + Free (B); + end My_DeAlloc; + + begin + My_Alloc; + for I in 1 .. 5 loop + for J in I .. 5 loop + My_Alloc; + end loop; + My_Dealloc; + end loop; + end; + + The program needs to be compiled with the debugging option and linked with + the `gmem` library: + + :: + + $ gnatmake -g test_gm -largs -lgmem + + Then we execute the program as usual: + + :: + + $ test_gm + + Then `gnatmem` is invoked simply with + + :: + + $ gnatmem test_gm + + which produces the following output (result may vary on different platforms): + + :: + + Global information + ------------------ + Total number of allocations : 18 + Total number of deallocations : 5 + Final Water Mark (non freed mem) : 53.00 Kilobytes + High Water Mark : 56.90 Kilobytes + + Allocation Root # 1 + ------------------- + Number of non freed allocations : 11 + Final Water Mark (non freed mem) : 42.97 Kilobytes + High Water Mark : 46.88 Kilobytes + Backtrace : + test_gm.adb:11 test_gm.my_alloc + + Allocation Root # 2 + ------------------- + Number of non freed allocations : 1 + Final Water Mark (non freed mem) : 10.02 Kilobytes + High Water Mark : 10.02 Kilobytes + Backtrace : + s-secsta.adb:81 system.secondary_stack.ss_init + + Allocation Root # 3 + ------------------- + Number of non freed allocations : 1 + Final Water Mark (non freed mem) : 12 Bytes + High Water Mark : 12 Bytes + Backtrace : + s-secsta.adb:181 system.secondary_stack.ss_init + + + Note that the GNAT runtime contains itself a certain number of + allocations that have no corresponding deallocation, + as shown here for root #2 and root #3. + This is a normal behavior when the number of non-freed allocations + is one, it allocates dynamic data structures that the run time needs for + the complete lifetime of the program. Note also that there is only one + allocation root in the user program with a single line back trace: + test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the + program shows that 'My_Alloc' is called at 2 different points in the + source (line 21 and line 24). If those two allocation roots need to be + distinguished, the backtrace depth parameter can be used: + + :: + + $ gnatmem 3 test_gm + + which will give the following output: + + + :: + + Global information + ------------------ + Total number of allocations : 18 + Total number of deallocations : 5 + Final Water Mark (non freed mem) : 53.00 Kilobytes + High Water Mark : 56.90 Kilobytes + + Allocation Root # 1 + ------------------- + Number of non freed allocations : 10 + Final Water Mark (non freed mem) : 39.06 Kilobytes + High Water Mark : 42.97 Kilobytes + Backtrace : + test_gm.adb:11 test_gm.my_alloc + test_gm.adb:24 test_gm + b_test_gm.c:52 main + + Allocation Root # 2 + ------------------- + Number of non freed allocations : 1 + Final Water Mark (non freed mem) : 10.02 Kilobytes + High Water Mark : 10.02 Kilobytes + Backtrace : + s-secsta.adb:81 system.secondary_stack.ss_init + s-secsta.adb:283 + b_test_gm.c:33 adainit + + Allocation Root # 3 + ------------------- + Number of non freed allocations : 1 + Final Water Mark (non freed mem) : 3.91 Kilobytes + High Water Mark : 3.91 Kilobytes + Backtrace : + test_gm.adb:11 test_gm.my_alloc + test_gm.adb:21 test_gm + b_test_gm.c:52 main + + Allocation Root # 4 + ------------------- + Number of non freed allocations : 1 + Final Water Mark (non freed mem) : 12 Bytes + High Water Mark : 12 Bytes + Backtrace : + s-secsta.adb:181 system.secondary_stack.ss_init + s-secsta.adb:283 + b_test_gm.c:33 adainit + + The allocation root #1 of the first example has been split in 2 roots #1 + and #3, thanks to the more precise associated backtrace. + + + + diff --git a/gcc/ada/doc/gnat_ugn/gnat_project_manager.rst b/gcc/ada/doc/gnat_ugn/gnat_project_manager.rst new file mode 100644 index 00000000000..70d3c284276 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/gnat_project_manager.rst @@ -0,0 +1,4907 @@ +.. |with| replace:: *with* +.. |withs| replace:: *with*\ s +.. |withed| replace:: *with*\ ed +.. |withing| replace:: *with*\ ing + +.. -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + + +.. _GNAT_Project_Manager: + +******************** +GNAT Project Manager +******************** + + +.. _GNAT_Project_Manager_Introduction: + +Introduction +============ + +This chapter describes GNAT's *Project Manager*, a facility that allows +you to manage complex builds involving a number of source files, directories, +and options for different system configurations. In particular, +project files allow you to specify: + +* The directory or set of directories containing the source files, and/or the + names of the specific source files themselves +* The directory in which the compiler's output + (:file:`ALI` files, object files, tree files, etc.) is to be placed +* The directory in which the executable programs are to be placed +* Switch settings for any of the project-enabled tools; + you can apply these settings either globally or to individual compilation units. +* The source files containing the main subprogram(s) to be built +* The source programming language(s) +* Source file naming conventions; you can specify these either globally or for + individual compilation units (see :ref:`Naming_Schemes`). +* Change any of the above settings depending on external values, thus enabling + the reuse of the projects in various **scenarios** (see :ref:`Scenarios_in_Projects`). +* Automatically build libraries as part of the build process + (see :ref:`Library_Projects`). + + +Project files are written in a syntax close to that of Ada, using familiar +notions such as packages, context clauses, declarations, default values, +assignments, and inheritance (see :ref:`Project_File_Reference`). + +Project files can be built hierarchically from other project files, simplifying +complex system integration and project reuse (see :ref:`Organizing_Projects_into_Subsystems`). + +* One project can import other projects containing needed source files. + More generally, the Project Manager lets you structure large development + efforts into hierarchical subsystems, where build decisions are delegated + to the subsystem level, and thus different compilation environments + (switch settings) used for different subsystems. +* You can organize GNAT projects in a hierarchy: a child project + can extend a parent project, inheriting the parent's source files and + optionally overriding any of them with alternative versions + (see :ref:`Project_Extension`). + + +Several tools support project files, generally in addition to specifying +the information on the command line itself). They share common switches +to control the loading of the project (in particular +:samp:`-P{projectfile}` and +:samp:`-X{vbl}={value}`). + +The Project Manager supports a wide range of development strategies, +for systems of all sizes. Here are some typical practices that are +easily handled: + +* Using a common set of source files and generating object files in different + directories via different switch settings. It can be used for instance, for + generating separate sets of object files for debugging and for production. +* Using a mostly-shared set of source files with different versions of + some units or subunits. It can be used for instance, for grouping and hiding + all OS dependencies in a small number of implementation units. + +Project files can be used to achieve some of the effects of a source +versioning system (for example, defining separate projects for +the different sets of sources that comprise different releases) but the +Project Manager is independent of any source configuration management tool +that might be used by the developers. + +The various sections below introduce the different concepts related to +projects. Each section starts with examples and use cases, and then goes into +the details of related project file capabilities. + +.. _Building_With_Projects: + +Building With Projects +====================== + +In its simplest form, a unique project is used to build a single executable. +This section concentrates on such a simple setup. Later sections will extend +this basic model to more complex setups. + +The following concepts are the foundation of project files, and will be further +detailed later in this documentation. They are summarized here as a reference. + +**Project file**: + A text file using an Ada-like syntax, generally using the :file:`.gpr` + extension. It defines build-related characteristics of an application. + The characteristics include the list of sources, the location of those + sources, the location for the generated object files, the name of + the main program, and the options for the various tools involved in the + build process. + + +**Project attribute**: + A specific project characteristic is defined by an attribute clause. Its + value is a string or a sequence of strings. All settings in a project + are defined through a list of predefined attributes with precise + semantics. See :ref:`Attributes`. + + +**Package in a project**: + Global attributes are defined at the top level of a project. + Attributes affecting specific tools are grouped in a + package whose name is related to tool's function. The most common + packages are `Builder`, `Compiler`, `Binder`, + and `Linker`. See :ref:`Packages`. + + +**Project variables**: + In addition to attributes, a project can use variables to store intermediate + values and avoid duplication in complex expressions. It can be initialized + with a value coming from the environment. + A frequent use of variables is to define scenarios. + See :ref:`External_Values`, :ref:`Scenarios_in_Projects`, and :ref:`Variables`. + + +**Source files** and **source directories**: + A source file is associated with a language through a naming convention. For + instance, `foo.c` is typically the name of a C source file; + `bar.ads` or `bar.1.ada` are two common naming conventions for a + file containing an Ada spec. A compilation unit is often composed of a main + source file and potentially several auxiliary ones, such as header files in C. + The naming conventions can be user defined :ref:`Naming_Schemes`, and will + drive the builder to call the appropriate compiler for the given source file. + Source files are searched for in the source directories associated with the + project through the **Source_Dirs** attribute. By default, all the files (in + these source directories) following the naming conventions associated with the + declared languages are considered to be part of the project. It is also + possible to limit the list of source files using the **Source_Files** or + **Source_List_File** attributes. Note that those last two attributes only + accept basenames with no directory information. + + +**Object files** and **object directory**: + An object file is an intermediate file produced by the compiler from a + compilation unit. It is used by post-compilation tools to produce + final executables or libraries. Object files produced in the context of + a given project are stored in a single directory that can be specified by the + **Object_Dir** attribute. In order to store objects in + two or more object directories, the system must be split into + distinct subsystems with their own project file. + + +The following subsections introduce gradually all the attributes of interest +for simple build needs. Here is the simple setup that will be used in the +following examples. + +The Ada source files :file:`pack.ads`, :file:`pack.adb`, and :file:`proc.adb` are in +the :file:`common/` directory. The file :file:`proc.adb` contains an Ada main +subprogram `Proc` that |withs| package `Pack`. We want to compile +these source files with the switch +*-O2*, and put the resulting files in +the directory :file:`obj/`. + +:: + + common/ + pack.ads + pack.adb + proc.adb + common/obj/ + proc.ali, proc.o pack.ali, pack.o + + +Our project is to be called *Build*. The name of the +file is the name of the project (case-insensitive) with the +:file:`.gpr` extension, therefore the project file name is :file:`build.gpr`. This +is not mandatory, but a warning is issued when this convention is not followed. + +This is a very simple example, and as stated above, a single project +file is enough for it. We will thus create a new file, that for now +should contain the following code: + +.. code-block:: gpr + + project Build is + end Build; + + +.. _Source_Files_and_Directories: + +Source Files and Directories +---------------------------- + +When you create a new project, the first thing to describe is how to find the +corresponding source files. These are the only settings that are needed by all +the tools that will use this project (builder, compiler, binder and linker for +the compilation, IDEs to edit the source files,...). + +.. index:: Source directories (GNAT Project Manager) + +The first step is to declare the source directories, which are the directories +to be searched to find source files. In the case of the example, +the :file:`common` directory is the only source directory. + +.. index:: Source_Dirs (GNAT Project Manager) + +There are several ways of defining source directories: + +* When the attribute **Source_Dirs** is not used, a project contains a + single source directory which is the one where the project file itself + resides. In our example, if :file:`build.gpr` is placed in the :file:`common` + directory, the project has the needed implicit source directory. + +* The attribute **Source_Dirs** can be set to a list of path names, one + for each of the source directories. Such paths can either be absolute + names (for instance :file:`"/usr/local/common/"` on UNIX), or relative to the + directory in which the project file resides (for instance "." if + :file:`build.gpr` is inside :file:`common/`, or "common" if it is one level up). + Each of the source directories must exist and be readable. + + .. index:: portability of path names (GNAT Project Manager) + + The syntax for directories is platform specific. For portability, however, + the project manager will always properly translate UNIX-like path names to + the native format of the specific platform. For instance, when the same + project file is to be used both on Unix and Windows, "/" should be used as + the directory separator rather than "\\". + +* The attribute **Source_Dirs** can automatically include subdirectories + using a special syntax inspired by some UNIX shells. If any of the paths in + the list ends with ":file:`**`", then that path and all its subdirectories + (recursively) are included in the list of source directories. For instance, + :file:`**` and :file:`./**` represent the complete directory tree rooted at + the directory in which the project file resides. + + .. index:: Source directories (GNAT Project Manager) + + .. index:: Excluded_Source_Dirs (GNAT Project Manager) + + When using that construct, it can sometimes be convenient to also use the + attribute **Excluded_Source_Dirs**, which is also a list of paths. Each entry + specifies a directory whose immediate content, not including subdirs, is to + be excluded. It is also possible to exclude a complete directory subtree + using the "**" notation. + + .. index:: Ignore_Source_Sub_Dirs (GNAT Project Manager) + + It is often desirable to remove, from the source directories, directory + subtrees rooted at some subdirectories. An example is the subdirectories + created by a Version Control System such as Subversion that creates directory + subtrees rooted at subdirectories ".svn". To do that, attribute + **Ignore_Source_Sub_Dirs** can be used. It specifies the list of simple + file names for the roots of these undesirable directory subtrees. + + + .. code-block: ada-project + + for Source_Dirs use ("./**"); + for Ignore_Source_Sub_Dirs use (".svn"); + + +When applied to the simple example, and because we generally prefer to have +the project file at the toplevel directory rather than mixed with the sources, +we will create the following file + + +.. code-block: ada-project + + build.gpr + project Build is + for Source_Dirs use ("common"); -- <<<< + end Build; + + +Once source directories have been specified, one may need to indicate +source files of interest. By default, all source files present in the source +directories are considered by the project manager. When this is not desired, +it is possible to specify the list of sources to consider explicitly. +In such a case, only source file base names are indicated and not +their absolute or relative path names. The project manager is in charge of +locating the specified source files in the specified source directories. + +* By default, the project manager searches for all source files of all + specified languages in all the source directories. + + Since the project manager was initially developed for Ada environments, the + default language is usually Ada and the above project file is complete: it + defines without ambiguity the sources composing the project: that is to say, + all the sources in subdirectory "common" for the default language (Ada) using + the default naming convention. + + .. index:: Languages (GNAT Project Manager) + + However, when compiling a multi-language application, or a pure C + application, the project manager must be told which languages are of + interest, which is done by setting the **Languages** attribute to a list of + strings, each of which is the name of a language. Tools like + *gnatmake* only know about Ada, while other tools like + *gprbuild* know about many more languages such as C, C++, Fortran, + assembly and others can be added dynamically. + + .. index:: Naming scheme (GNAT Project Manager) + + Even when using only Ada, the default naming might not be suitable. Indeed, + how does the project manager recognizes an "Ada file" from any other + file? Project files can describe the naming scheme used for source files, + and override the default (see :ref:`Naming_Schemes`). The default is the + standard GNAT extension (:file:`.adb` for bodies and :file:`.ads` for + specs), which is what is used in our example, explaining why no naming scheme + is explicitly specified. + See :ref:`Naming_Schemes`. + + .. index:: Source_Files (GNAT Project Manager) + +* `Source_Files`. + In some cases, source directories might contain files that should not be + included in a project. One can specify the explicit list of file names to + be considered through the **Source_Files** attribute. + When this attribute is defined, instead of looking at every file in the + source directories, the project manager takes only those names into + consideration reports errors if they cannot be found in the source + directories or does not correspond to the naming scheme. + +* For various reasons, it is sometimes useful to have a project with no + sources (most of the time because the attributes defined in the project + file will be reused in other projects, as explained in + :ref:`Organizing_Projects_into_Subsystems`. To do this, the attribute + *Source_Files* is set to the empty list, i.e. `()`. Alternatively, + *Source_Dirs* can be set to the empty list, with the same + result. + + .. index:: Source_List_File (GNAT Project Manager) + +* `Source_List_File`. + If there is a great number of files, it might be more convenient to use + the attribute **Source_List_File**, which specifies the full path of a file. + This file must contain a list of source file names (one per line, no + directory information) that are searched as if they had been defined + through *Source_Files*. Such a file can easily be created through + external tools. + + A warning is issued if both attributes `Source_Files` and + `Source_List_File` are given explicit values. In this case, the + attribute `Source_Files` prevails. + + .. index:: Excluded_Source_Files (GNAT Project Manager) + .. index:: Locally_Removed_Files (GNAT Project Manager) + .. index:: Excluded_Source_List_File (GNAT Project Manager) + +* `Excluded_Source_Files`. + Specifying an explicit list of files is not always convenient.It might be + more convenient to use the default search rules with specific exceptions. + This can be done thanks to the attribute **Excluded_Source_Files** + (or its synonym **Locally_Removed_Files**). + Its value is the list of file names that should not be taken into account. + This attribute is often used when extending a project, + see :ref:`Project_Extension`. A similar attribute + **Excluded_Source_List_File** plays the same + role but takes the name of file containing file names similarly to + `Source_List_File`. + + +In most simple cases, such as the above example, the default source file search +behavior provides the expected result, and we do not need to add anything after +setting `Source_Dirs`. The project manager automatically finds +:file:`pack.ads`, :file:`pack.adb`, and :file:`proc.adb` as source files of the +project. + +Note that by default a warning is issued when a project has no sources attached +to it and this is not explicitly indicated in the project file. + +.. _Duplicate_Sources_in_Projects: + +Duplicate Sources in Projects +----------------------------- + +If the order of the source directories is known statically, that is if +`"/**"` is not used in the string list `Source_Dirs`, then there may +be several files with the same name sitting in different directories of the +project. In this case, only the file in the first directory is considered as a +source of the project and the others are hidden. If `"/**"` is used in the +string list `Source_Dirs`, it is an error to have several files with the +same name in the same directory `"/**"` subtree, since there would be an +ambiguity as to which one should be used. However, two files with the same name +may exist in two single directories or directory subtrees. In this case, the +one in the first directory or directory subtree is a source of the project. + +If there are two sources in different directories of the same `"/**"` +subtree, one way to resolve the problem is to exclude the directory of the +file that should not be used as a source of the project. + +.. _Object_and_Exec_Directory: + +Object and Exec Directory +------------------------- + +The next step when writing a project is to indicate where the compiler should +put the object files. In fact, the compiler and other tools might create +several different kind of files (for GNAT, there is the object file and the ALI +file for instance). One of the important concepts in projects is that most +tools may consider source directories as read-only and do not attempt to create +new or temporary files there. Instead, all files are created in the object +directory. It is of course not true for project-aware IDEs, whose purpose it is +to create the source files. + +.. index:: Object_Dir (GNAT Project Manager) + +The object directory is specified through the **Object_Dir** attribute. +Its value is the path to the object directory, either absolute or +relative to the directory containing the project file. This +directory must already exist and be readable and writable, although +some tools have a switch to create the directory if needed (See +the switch `-p` for *gnatmake* +and *gprbuild*). + +If the attribute `Object_Dir` is not specified, it defaults to +the project directory, that is the directory containing the project file. + +For our example, we can specify the object dir in this way: + +.. code-block: ada-project + + project Build is + for Source_Dirs use ("common"); + for Object_Dir use "obj"; -- <<<< + end Build; + +As mentioned earlier, there is a single object directory per project. As a +result, if you have an existing system where the object files are spread across +several directories, you can either move all of them into the same directory if +you want to build it with a single project file, or study the section on +subsystems (see :ref:`Organizing_Projects_into_Subsystems`) to see how each +separate object directory can be associated with one of the subsystems +constituting the application. + +When the *linker* is called, it usually creates an executable. By +default, this executable is placed in the object directory of the project. It +might be convenient to store it in its own directory. + +.. index:: Exec_Dir (GNAT Project Manager) + +This can be done through the `Exec_Dir` attribute, which, like +*Object_Dir* contains a single absolute or relative path and must point to +an existing and writable directory, unless you ask the tool to create it on +your behalf. When not specified, It defaults to the object directory and +therefore to the project file's directory if neither *Object_Dir* nor +*Exec_Dir* was specified. + +In the case of the example, let's place the executable in the root +of the hierarchy, ie the same directory as :file:`build.gpr`. Hence +the project file is now + +.. code-block: ada-project + + project Build is + for Source_Dirs use ("common"); + for Object_Dir use "obj"; + for Exec_Dir use "."; -- <<<< + end Build; + + +.. _Main_Subprograms: + +Main Subprograms +---------------- + +In the previous section, executables were mentioned. The project manager needs +to be taught what they are. In a project file, an executable is indicated by +pointing to the source file of a main subprogram. In C this is the file that +contains the `main` function, and in Ada the file that contains the main +unit. + +There can be any number of such main files within a given project, and thus +several executables can be built in the context of a single project file. Of +course, one given executable might not (and in fact will not) need all the +source files referenced by the project. As opposed to other build environments +such as *makefile*, one does not need to specify the list of +dependencies of each executable, the project-aware builder knows enough of the +semantics of the languages to build and link only the necessary elements. + +.. index:: Main (GNAT Project Manager) + +The list of main files is specified via the **Main** attribute. It contains +a list of file names (no directories). If a project defines this +attribute, it is not necessary to identify main files on the +command line when invoking a builder, and editors like +*GPS* will be able to create extra menus to spawn or debug the +corresponding executables. + +.. code-block: ada-project + + project Build is + for Source_Dirs use ("common"); + for Object_Dir use "obj"; + for Exec_Dir use "."; + for Main use ("proc.adb"); -- <<<< + end Build; + + +If this attribute is defined in the project, then spawning the builder +with a command such as + +.. code-block:: sh + + gprbuild -Pbuild + + +automatically builds all the executables corresponding to the files +listed in the *Main* attribute. It is possible to specify one +or more executables on the command line to build a subset of them. + +.. _Tools_Options_in_Project_Files: + +Tools Options in Project Files +------------------------------ + +We now have a project file that fully describes our environment, and can be +used to build the application with a simple *gprbuild* command as seen +in the previous section. In fact, the empty project we showed immediately at +the beginning (with no attribute at all) could already fulfill that need if it +was put in the :file:`common` directory. + +Of course, we might want more control. This section shows you how to specify +the compilation switches that the various tools involved in the building of the +executable should use. + +.. index:: command line length (GNAT Project Manager) + +Since source names and locations are described in the project file, it is not +necessary to use switches on the command line for this purpose (switches such +as -I for gcc). This removes a major source of command line length overflow. +Clearly, the builders will have to communicate this information one way or +another to the underlying compilers and tools they call but they usually use +response files for this and thus are not subject to command line overflows. + +Several tools participate to the creation of an executable: the compiler +produces object files from the source files; the binder (in the Ada case) +creates a "source" file that takes care, among other things, of elaboration +issues and global variable initialization; and the linker gathers everything +into a single executable that users can execute. All these tools are known to +the project manager and will be called with user defined switches from the +project files. However, we need to introduce a new project file concept to +express the switches to be used for any of the tools involved in the build. + +.. index:: project file packages (GNAT Project Manager) + +A project file is subdivided into zero or more **packages**, each of which +contains the attributes specific to one tool (or one set of tools). Project +files use an Ada-like syntax for packages. Package names permitted in project +files are restricted to a predefined set (see :ref:`Packages`), and the contents +of packages are limited to a small set of constructs and attributes +(see :ref:`Attributes`). + +Our example project file can be extended with the following empty packages. At +this stage, they could all be omitted since they are empty, but they show which +packages would be involved in the build process. + +.. code-block: ada-project + + project Build is + for Source_Dirs use ("common"); + for Object_Dir use "obj"; + for Exec_Dir use "."; + for Main use ("proc.adb"); + + package Builder is --<<< for gnatmake and gprbuild + end Builder; + + package Compiler is --<<< for the compiler + end Compiler; + + package Binder is --<<< for the binder + end Binder; + + package Linker is --<<< for the linker + end Linker; + end Build; + +Let's first examine the compiler switches. As stated in the initial description +of the example, we want to compile all files with *-O2*. This is a +compiler switch, although it is usual, on the command line, to pass it to the +builder which then passes it to the compiler. It is recommended to use directly +the right package, which will make the setup easier to understand for other +people. + +Several attributes can be used to specify the switches: + +.. index:: Default_Switches (GNAT Project Manager) + +**Default_Switches**: + + This is the first mention in this manual of an **indexed attribute**. When + this attribute is defined, one must supply an *index* in the form of a + literal string. + In the case of *Default_Switches*, the index is the name of the + language to which the switches apply (since a different compiler will + likely be used for each language, and each compiler has its own set of + switches). The value of the attribute is a list of switches. + + In this example, we want to compile all Ada source files with the switch + *-O2*, and the resulting project file is as follows + (only the `Compiler` package is shown): + + .. code-block: ada-project + + package Compiler is + for Default_Switches ("Ada") use ("-O2"); + end Compiler; + +.. index:: Switches (GNAT Project Manager) + +**Switches**: + + In some cases, we might want to use specific switches + for one or more files. For instance, compiling :file:`proc.adb` might not be + possible at high level of optimization because of a compiler issue. + In such a case, the *Switches* + attribute (indexed on the file name) can be used and will override the + switches defined by *Default_Switches*. Our project file would + become: + + .. code-block: ada-project + + + package Compiler is + for Default_Switches ("Ada") + use ("-O2"); + for Switches ("proc.adb") + use ("-O0"); + end Compiler; + + + `Switches` may take a pattern as an index, such as in: + + .. code-block: ada-project + + package Compiler is + for Default_Switches ("Ada") + use ("-O2"); + for Switches ("pkg*") + use ("-O0"); + end Compiler; + + Sources :file:`pkg.adb` and :file:`pkg-child.adb` would be compiled with -O0, + not -O2. + + `Switches` can also be given a language name as index instead of a file + name in which case it has the same semantics as *Default_Switches*. + However, indexes with wild cards are never valid for language name. + + +.. index:: Local_Configuration_Pragmas (GNAT Project Manager) + +**Local_Configuration_Pragmas**: + + This attribute may specify the path + of a file containing configuration pragmas for use by the Ada compiler, + such as `pragma Restrictions (No_Tasking)`. These pragmas will be + used for all the sources of the project. + + +The switches for the other tools are defined in a similar manner through the +**Default_Switches** and **Switches** attributes, respectively in the +*Builder* package (for *gnatmake* and *gprbuild*), +the *Binder* package (binding Ada executables) and the *Linker* +package (for linking executables). + + +.. _Compiling_with_Project_Files: + +Compiling with Project Files +---------------------------- + +Now that our project files are written, let's build our executable. +Here is the command we would use from the command line: + +.. code-block:: sh + + gnatmake -Pbuild + +This will automatically build the executables specified through the +*Main* attribute: for each, it will compile or recompile the +sources for which the object file does not exist or is not up-to-date; it +will then run the binder; and finally run the linker to create the +executable itself. + +*gnatmake* only knows how to handle Ada files. By using +*gprbuild* as a builder, you could automatically manage C files the +same way: create the file :file:`utils.c` in the :file:`common` directory, +set the attribute *Languages* to `"(Ada, C)"`, and run + +.. code-block:: sh + + gprbuild -Pbuild + +Gprbuild knows how to recompile the C files and will +recompile them only if one of their dependencies has changed. No direct +indication on how to build the various elements is given in the +project file, which describes the project properties rather than a +set of actions to be executed. Here is the invocation of +*gprbuild* when building a multi-language program: + +.. code-block:: sh + + $ gprbuild -Pbuild + gcc -c proc.adb + gcc -c pack.adb + gcc -c utils.c + gprbind proc + ... + gcc proc.o -o proc + +Notice the three steps described earlier: + +* The first three gcc commands correspond to the compilation phase. +* The gprbind command corresponds to the post-compilation phase. +* The last gcc command corresponds to the final link. + + +.. index:: -v option (for GPRbuild) + +The default output of GPRbuild's execution is kept reasonably simple and easy +to understand. In particular, some of the less frequently used commands are not +shown, and some parameters are abbreviated. So it is not possible to rerun the +effect of the *gprbuild* command by cut-and-pasting its output. +GPRbuild's option `-v` provides a much more verbose output which includes, +among other information, more complete compilation, post-compilation and link +commands. + + +.. _Executable_File_Names: + +Executable File Names +--------------------- + +.. index:: Executable (GNAT Project Manager) + +By default, the executable name corresponding to a main file is +computed from the main source file name. Through the attribute +**Builder.Executable**, it is possible to change this default. + +For instance, instead of building *proc* (or *proc.exe* +on Windows), we could configure our project file to build "proc1" +(resp proc1.exe) with the following addition: + +.. code-block:: gpr + + project Build is + ... -- same as before + package Builder is + for Executable ("proc.adb") use "proc1"; + end Builder + end Build; + +.. index:: Executable_Suffix (GNAT Project Manager) + +Attribute **Executable_Suffix**, when specified, may change the suffix +of the executable files, when no attribute `Executable` applies: +its value replaces the platform-specific executable suffix. +The default executable suffix is empty on UNIX and ".exe" on Windows. + +It is also possible to change the name of the produced executable by using the +command line switch *-o*. When several mains are defined in the project, +it is not possible to use the *-o* switch and the only way to change the +names of the executable is provided by Attributes `Executable` and +`Executable_Suffix`. + + +.. _Avoid_Duplication_With_Variables: + +Avoid Duplication With Variables +-------------------------------- + +To illustrate some other project capabilities, here is a slightly more complex +project using similar sources and a main program in C: + + +.. code-block:: gpr + + project C_Main is + for Languages use ("Ada", "C"); + for Source_Dirs use ("common"); + for Object_Dir use "obj"; + for Main use ("main.c"); + package Compiler is + C_Switches := ("-pedantic"); + for Default_Switches ("C") use C_Switches; + for Default_Switches ("Ada") use ("-gnaty"); + for Switches ("main.c") use C_Switches & ("-g"); + end Compiler; + end C_Main; + +This project has many similarities with the previous one. +As expected, its `Main` attribute now refers to a C source. +The attribute *Exec_Dir* is now omitted, thus the resulting +executable will be put in the directory :file:`obj`. + +The most noticeable difference is the use of a variable in the +*Compiler* package to store settings used in several attributes. +This avoids text duplication, and eases maintenance (a single place to +modify if we want to add new switches for C files). We will revisit +the use of variables in the context of scenarios (see :ref:`Scenarios_in_Projects`). + +In this example, we see how the file :file:`main.c` can be compiled with +the switches used for all the other C files, plus *-g*. +In this specific situation the use of a variable could have been +replaced by a reference to the `Default_Switches` attribute: + +.. code-block:: gpr + + for Switches ("c_main.c") use Compiler'Default_Switches ("C") & ("-g"); + +Note the tick (*'*) used to refer to attributes defined in a package. + +Here is the output of the GPRbuild command using this project: + +.. code-block:: sh + + $ gprbuild -Pc_main + gcc -c -pedantic -g main.c + gcc -c -gnaty proc.adb + gcc -c -gnaty pack.adb + gcc -c -pedantic utils.c + gprbind main.bexch + ... + gcc main.o -o main + +The default switches for Ada sources, +the default switches for C sources (in the compilation of :file:`lib.c`), +and the specific switches for :file:`main.c` have all been taken into +account. + + +.. _Naming_Schemes: + +Naming Schemes +-------------- + +Sometimes an Ada software system is ported from one compilation environment to +another (say GNAT), and the file are not named using the default GNAT +conventions. Instead of changing all the file names, which for a variety of +reasons might not be possible, you can define the relevant file naming scheme +in the **Naming** package of your project file. + +The naming scheme has two distinct goals for the project manager: it +allows finding of source files when searching in the source +directories, and given a source file name it makes it possible to guess +the associated language, and thus the compiler to use. + +Note that the use by the Ada compiler of pragmas Source_File_Name is not +supported when using project files. You must use the features described in this +paragraph. You can however specify other configuration pragmas. + +The following attributes can be defined in package `Naming`: + +.. index:: Casing (GNAT Project Manager) + +**Casing**: + + Its value must be one of `"lowercase"` (the default if + unspecified), `"uppercase"` or `"mixedcase"`. It describes the + casing of file names with regards to the Ada unit name. Given an Ada unit + My_Unit, the file name will respectively be :file:`my_unit.adb` (lowercase), + :file:`MY_UNIT.ADB` (uppercase) or :file:`My_Unit.adb` (mixedcase). + On Windows, file names are case insensitive, so this attribute is + irrelevant. + + +.. index:: Dot_Replacement (GNAT Project Manager) + +**Dot_Replacement**: + + This attribute specifies the string that should replace the "." in unit + names. Its default value is `"-"` so that a unit + `Parent.Child` is expected to be found in the file + :file:`parent-child.adb`. The replacement string must satisfy the following + requirements to avoid ambiguities in the naming scheme: + + * It must not be empty + + * It cannot start or end with an alphanumeric character + + * It cannot be a single underscore + + * It cannot start with an underscore followed by an alphanumeric + + * It cannot contain a dot `'.'` except if the entire string is `"."` + +.. index:: Spec_Suffix (GNAT Project Manager) +.. index:: Specification_Suffix (GNAT Project Manager) + +**Spec_Suffix** and **Specification_Suffix**: + + For Ada, these attributes give the suffix used in file names that contain + specifications. For other languages, they give the extension for files + that contain declaration (header files in C for instance). The attribute + is indexed on the language. + The two attributes are equivalent, but the latter is obsolescent. + + If the value of the attribute is the empty string, it indicates to the + Project Manager that the only specifications/header files for the language + are those specified with attributes `Spec` or + `Specification_Exceptions`. + + If `Spec_Suffix ("Ada")` is not specified, then the default is + `".ads"`. + + A non empty value must satisfy the following requirements: + + * It must include at least one dot + + * If `Dot_Replacement` is a single dot, then it cannot include + more than one dot. + +.. index:: Body_Suffix (GNAT Project Manager) +.. index:: Implementation_Suffix (GNAT Project Manager) + +**Body_Suffix** and **Implementation_Suffix**: + + These attributes give the extension used for file names that contain + code (bodies in Ada). They are indexed on the language. The second + version is obsolescent and fully replaced by the first attribute. + + For each language of a project, one of these two attributes need to be + specified, either in the project itself or in the configuration project file. + + If the value of the attribute is the empty string, it indicates to the + Project Manager that the only source files for the language + are those specified with attributes `Body` or + `Implementation_Exceptions`. + + These attributes must satisfy the same requirements as `Spec_Suffix`. + In addition, they must be different from any of the values in + `Spec_Suffix`. + If `Body_Suffix ("Ada")` is not specified, then the default is + `".adb"`. + + If `Body_Suffix ("Ada")` and `Spec_Suffix ("Ada")` end with the + same string, then a file name that ends with the longest of these two + suffixes will be a body if the longest suffix is `Body_Suffix ("Ada")` + or a spec if the longest suffix is `Spec_Suffix ("Ada")`. + + If the suffix does not start with a '.', a file with a name exactly equal to + the suffix will also be part of the project (for instance if you define the + suffix as `Makefile.in`, a file called :file:`Makefile.in` will be part + of the project. This capability is usually not interesting when building. + However, it might become useful when a project is also used to + find the list of source files in an editor, like the GNAT Programming System + (GPS). + +.. index:: Separate_Suffix (GNAT Project Manager) + +**Separate_Suffix**: + + This attribute is specific to Ada. It denotes the suffix used in file names + that contain separate bodies. If it is not specified, then it defaults to + same value as `Body_Suffix ("Ada")`. + + The value of this attribute cannot be the empty string. + + Otherwise, the same rules apply as for the + `Body_Suffix` attribute. The only accepted index is "Ada". + + +**Spec** or **Specification**: + + .. index:: Spec (GNAT Project Manager) + + .. index:: Specification (GNAT Project Manager) + + This attribute `Spec` can be used to define the source file name for a + given Ada compilation unit's spec. The index is the literal name of the Ada + unit (case insensitive). The value is the literal base name of the file that + contains this unit's spec (case sensitive or insensitive depending on the + operating system). This attribute allows the definition of exceptions to the + general naming scheme, in case some files do not follow the usual + convention. + + When a source file contains several units, the relative position of the unit + can be indicated. The first unit in the file is at position 1 + + + .. code-block:: gpr + + for Spec ("MyPack.MyChild") use "mypack.mychild.spec"; + for Spec ("top") use "foo.a" at 1; + for Spec ("foo") use "foo.a" at 2; + + +.. index:: Body (GNAT Project Manager) + +.. index:: Implementation (GNAT Project Manager) + +**Body** or **Implementation**: + + These attribute play the same role as *Spec* for Ada bodies. + + +.. index:: Specification_Exceptions (GNAT Project Manager) + +.. index:: Implementation_Exceptions (GNAT Project Manager) + +**Specification_Exceptions** and **Implementation_Exceptions**: + + These attributes define exceptions to the naming scheme for languages + other than Ada. They are indexed on the language name, and contain + a list of file names respectively for headers and source code. + + +For example, the following package models the Apex file naming rules: + +.. code-block:: gpr + + package Naming is + for Casing use "lowercase"; + for Dot_Replacement use "."; + for Spec_Suffix ("Ada") use ".1.ada"; + for Body_Suffix ("Ada") use ".2.ada"; + end Naming; + + +.. _Installation: + +Installation +------------ + +After building an application or a library it is often required to +install it into the development environment. For instance this step is +required if the library is to be used by another application. +The *gprinstall* tool provides an easy way to install +libraries, executable or object code generated during the build. The +**Install** package can be used to change the default locations. + +The following attributes can be defined in package `Install`: + +.. index:: Active (GNAT Project Manager) + +**Active** + Whether the project is to be installed, values are `true` + (default) or `false`. + + +.. index:: Artifacts (GNAT Project Manager) + +**Artifacts** + + An array attribute to declare a set of files not part of the sources + to be installed. The array discriminant is the directory where the + file is to be installed. If a relative directory then Prefix (see + below) is prepended. + + +.. index:: Prefix (GNAT Project Manager) + +**Prefix**: + + Root directory for the installation. + + +**Exec_Subdir** + + Subdirectory of **Prefix** where executables are to be + installed. Default is **bin**. + + +**Lib_Subdir** + + Subdirectory of **Prefix** where directory with the library or object + files is to be installed. Default is **lib**. + + +**Sources_Subdir** + + Subdirectory of **Prefix** where directory with sources is to be + installed. Default is **include**. + + +**Project_Subdir** + + Subdirectory of **Prefix** where the generated project file is to be + installed. Default is **share/gpr**. + + +**Mode** + + The installation mode, it is either **dev** (default) or **usage**. + See **gprbuild** user's guide for details. + + +**Install_Name** + + Specify the name to use for recording the installation. The default is + the project name without the extension. + + +.. _Distributed_support: + +Distributed support +------------------- + +For large projects the compilation time can become a limitation in +the development cycle. To cope with that, GPRbuild supports +distributed compilation. + +The following attributes can be defined in package `Remote`: + +.. index:: Root_Dir (GNAT Project Manager) + +**Root_Dir**: + + Root directory of the project's sources. The default value is the + project's directory. + + +.. _Organizing_Projects_into_Subsystems: + +Organizing Projects into Subsystems +=================================== + +A **subsystem** is a coherent part of the complete system to be built. It is +represented by a set of sources and one single object directory. A system can +be composed of a single subsystem when it is simple as we have seen in the +first section. Complex systems are usually composed of several interdependent +subsystems. A subsystem is dependent on another subsystem if knowledge of the +other one is required to build it, and in particular if visibility on some of +the sources of this other subsystem is required. Each subsystem is usually +represented by its own project file. + +In this section, the previous example is being extended. Let's assume some +sources of our `Build` project depend on other sources. +For instance, when building a graphical interface, it is usual to depend upon +a graphical library toolkit such as GtkAda. Furthermore, we also need +sources from a logging module we had previously written. + +.. _Project_Dependencies: + +Project Dependencies +-------------------- + +GtkAda comes with its own project file (appropriately called +:file:`gtkada.gpr`), and we will assume we have already built a project +called :file:`logging.gpr` for the logging module. With the information provided +so far in :file:`build.gpr`, building the application would fail with an error +indicating that the gtkada and logging units that are relied upon by the sources +of this project cannot be found. + +This is solved by adding the following **with** clauses at the beginning of our +project: + +.. code-block:: gpr + + with "gtkada.gpr"; + with "a/b/logging.gpr"; + project Build is + ... -- as before + end Build; + + +.. index:: Externally_Built (GNAT Project Manager) + +When such a project is compiled, *gprbuild* will automatically check +the other projects and recompile their sources when needed. It will also +recompile the sources from `Build` when needed, and finally create the +executable. In some cases, the implementation units needed to recompile a +project are not available, or come from some third party and you do not want to +recompile it yourself. In this case, set the attribute **Externally_Built** to +"true", indicating to the builder that this project can be assumed to be +up-to-date, and should not be considered for recompilation. In Ada, if the +sources of this externally built project were compiled with another version of +the compiler or with incompatible options, the binder will issue an error. + +The project's |with| clause has several effects. It provides source +visibility between projects during the compilation process. It also guarantees +that the necessary object files from `Logging` and `GtkAda` are +available when linking `Build`. + +As can be seen in this example, the syntax for importing projects is similar +to the syntax for importing compilation units in Ada. However, project files +use literal strings instead of names, and the |with| clause identifies +project files rather than packages. + +Each literal string after |with| is the path +(absolute or relative) to a project file. The `.gpr` extension is +optional, although we recommend adding it. If no extension is specified, +and no project file with the :file:`.gpr` extension is found, then +the file is searched for exactly as written in the |with| clause, +that is with no extension. + +As mentioned above, the path after a |with| has to be a literal +string, and you cannot use concatenation, or lookup the value of external +variables to change the directories from which a project is loaded. +A solution if you need something like this is to use aggregate projects +(see :ref:`Aggregate_Projects`). + +.. index:: project path (GNAT Project Manager) + +When a relative path or a base name is used, the +project files are searched relative to each of the directories in the +**project path**. This path includes all the directories found with the +following algorithm, in this order; the first matching file is used: + +* First, the file is searched relative to the directory that contains the + current project file. + + .. index:: GPR_PROJECT_PATH_FILE (GNAT Project Manager) + .. index:: GPR_PROJECT_PATH (GNAT Project Manager) + .. index:: ADA_PROJECT_PATH (GNAT Project Manager) + +* Then it is searched relative to all the directories specified in the + environment variables **GPR_PROJECT_PATH_FILE**, + **GPR_PROJECT_PATH** and **ADA_PROJECT_PATH** (in that order) if they exist. + The value of **GPR_PROJECT_PATH_FILE**, when defined, is the path name of + a text file that contains project directory path names, one per line. + **GPR_PROJECT_PATH** and **ADA_PROJECT_PATH**, when defined, contain + project directory path names separated by directory separators. + **ADA_PROJECT_PATH** is used for compatibility, it is recommended to + use **GPR_PROJECT_PATH_FILE** or **GPR_PROJECT_PATH**. + +* Finally, it is searched relative to the default project directories. + Such directories depend on the tool used. The locations searched in the + specified order are: + + * :file:`//lib/gnat` + (for *gnatmake* in all cases, and for *gprbuild* if option + *--target* is specified) + * :file:`//share/gpr` + (for *gnatmake* in all cases, and for *gprbuild* if option + *--target* is specified) + * :file:`/share/gpr/` + (for *gnatmake* and *gprbuild*) + * :file:`/lib/gnat/` + (for *gnatmake* and *gprbuild*) + + In our example, :file:`gtkada.gpr` is found in the predefined directory if + it was installed at the same root as GNAT. + +Some tools also support extending the project path from the command line, +generally through the *-aP*. You can see the value of the project +path by using the *gnatls -v* command. + +Any symbolic link will be fully resolved in the directory of the +importing project file before the imported project file is examined. + +Any source file in the imported project can be used by the sources of the +importing project, transitively. +Thus if `A` imports `B`, which imports `C`, the sources of +`A` may depend on the sources of `C`, even if `A` does not +import `C` explicitly. However, this is not recommended, because if +and when `B` ceases to import `C`, some sources in `A` will +no longer compile. *gprbuild* has a switch *--no-indirect-imports* +that will report such indirect dependencies. + +.. note:: + + One very important aspect of a project hierarchy is that + **a given source can only belong to one project** (otherwise the project manager + would not know which settings apply to it and when to recompile it). It means + that different project files do not usually share source directories or + when they do, they need to specify precisely which project owns which sources + using attribute `Source_Files` or equivalent. By contrast, 2 projects + can each own a source with the same base file name as long as they live in + different directories. The latter is not true for Ada Sources because of the + correlation between source files and Ada units. + +.. _Cyclic_Project_Dependencies: + +Cyclic Project Dependencies +--------------------------- + +Cyclic dependencies are mostly forbidden: +if `A` imports `B` (directly or indirectly) then `B` +is not allowed to import `A`. However, there are cases when cyclic +dependencies would be beneficial. For these cases, another form of import +between projects exists: the **limited with**. A project `A` that +imports a project `B` with a straight |with| may also be imported, +directly or indirectly, by `B` through a `limited with`. + +The difference between straight |with| and `limited with` is that +the name of a project imported with a `limited with` cannot be used in the +project importing it. In particular, its packages cannot be renamed and +its variables cannot be referred to. + +.. code-block:: gpr + + with "b.gpr"; + with "c.gpr"; + project A is + for Exec_Dir use B'Exec_Dir; -- ok + end A; + + limited with "a.gpr"; -- Cyclic dependency: A -> B -> A + project B is + for Exec_Dir use A'Exec_Dir; -- not ok + end B; + + with "d.gpr"; + project C is + end C; + + limited with "a.gpr"; -- Cyclic dependency: A -> C -> D -> A + project D is + for Exec_Dir use A'Exec_Dir; -- not ok + end D; + + +.. _Sharing_Between_Projects: + +Sharing Between Projects +------------------------ + +When building an application, it is common to have similar needs in several of +the projects corresponding to the subsystems under construction. For instance, +they will all have the same compilation switches. + +As seen before (see :ref:`Tools_Options_in_Project_Files`), setting compilation +switches for all sources of a subsystem is simple: it is just a matter of +adding a `Compiler.Default_Switches` attribute to each project files with +the same value. Of course, that means duplication of data, and both places need +to be changed in order to recompile the whole application with different +switches. It can become a real problem if there are many subsystems and thus +many project files to edit. + +There are two main approaches to avoiding this duplication: + +* Since :file:`build.gpr` imports :file:`logging.gpr`, we could change it + to reference the attribute in Logging, either through a package renaming, + or by referencing the attribute. The following example shows both cases: + + .. code-block:: gpr + + project Logging is + package Compiler is + for Switches ("Ada") + use ("-O2"); + end Compiler; + package Binder is + for Switches ("Ada") + use ("-E"); + end Binder; + end Logging; + + with "logging.gpr"; + project Build is + package Compiler renames Logging.Compiler; + package Binder is + for Switches ("Ada") use Logging.Binder'Switches ("Ada"); + end Binder; + end Build; + + The solution used for `Compiler` gets the same value for all + attributes of the package, but you cannot modify anything from the + package (adding extra switches or some exceptions). The second + version is more flexible, but more verbose. + + If you need to refer to the value of a variable in an imported + project, rather than an attribute, the syntax is similar but uses + a "." rather than an apostrophe. For instance: + + .. code-block:: gpr + + with "imported"; + project Main is + Var1 := Imported.Var; + end Main; + +* The second approach is to define the switches in a third project. + That project is set up without any sources (so that, as opposed to + the first example, none of the project plays a special role), and + will only be used to define the attributes. Such a project is + typically called :file:`shared.gpr`. + + .. code-block:: gpr + + abstract project Shared is + for Source_Files use (); -- no sources + package Compiler is + for Switches ("Ada") + use ("-O2"); + end Compiler; + end Shared; + + with "shared.gpr"; + project Logging is + package Compiler renames Shared.Compiler; + end Logging; + + with "shared.gpr"; + project Build is + package Compiler renames Shared.Compiler; + end Build; + + As for the first example, we could have chosen to set the attributes + one by one rather than to rename a package. The reason we explicitly + indicate that `Shared` has no sources is so that it can be created + in any directory and we are sure it shares no sources with `Build` + or `Logging`, which of course would be invalid. + + .. index:: project qualifier (GNAT Project Manager) + + Note the additional use of the **abstract** qualifier in :file:`shared.gpr`. + This qualifier is optional, but helps convey the message that we do not + intend this project to have sources (see :ref:`Qualified_Projects` for + more qualifiers). + + +.. _Global_Attributes: + +Global Attributes +----------------- + +We have already seen many examples of attributes used to specify a special +option of one of the tools involved in the build process. Most of those +attributes are project specific. That it to say, they only affect the invocation +of tools on the sources of the project where they are defined. + +There are a few additional attributes that apply to all projects in a +hierarchy as long as they are defined on the "main" project. +The main project is the project explicitly mentioned on the command-line. +The project hierarchy is the "with"-closure of the main project. + +Here is a list of commonly used global attributes: + +.. index:: Global_Configuration_Pragmas (GNAT Project Manager) + +**Builder.Global_Configuration_Pragmas**: + + This attribute points to a file that contains configuration pragmas + to use when building executables. These pragmas apply for all + executables built from this project hierarchy. As we have seen before, + additional pragmas can be specified on a per-project basis by setting the + `Compiler.Local_Configuration_Pragmas` attribute. + +.. index:: Global_Compilation_Switches (GNAT Project Manager) + +**Builder.Global_Compilation_Switches**: + + This attribute is a list of compiler switches to use when compiling any + source file in the project hierarchy. These switches are used in addition + to the ones defined in the `Compiler` package, which only apply to + the sources of the corresponding project. This attribute is indexed on + the name of the language. + +Using such global capabilities is convenient. It can also lead to unexpected +behavior. Especially when several subsystems are shared among different main +projects and the different global attributes are not +compatible. Note that using aggregate projects can be a safer and more powerful +replacement to global attributes. + +.. _Scenarios_in_Projects: + +Scenarios in Projects +===================== + +Various aspects of the projects can be modified based on **scenarios**. These +are user-defined modes that change the behavior of a project. Typical +examples are the setup of platform-specific compiler options, or the use of +a debug and a release mode (the former would activate the generation of debug +information, while the second will focus on improving code optimization). + +Let's enhance our example to support debug and release modes. The issue is to +let the user choose what kind of system he is building: use *-g* as +compiler switches in debug mode and *-O2* in release mode. We will also +set up the projects so that we do not share the same object directory in both +modes; otherwise switching from one to the other might trigger more +recompilations than needed or mix objects from the two modes. + +One naive approach is to create two different project files, say +:file:`build_debug.gpr` and :file:`build_release.gpr`, that set the appropriate +attributes as explained in previous sections. This solution does not scale +well, because in the presence of multiple projects depending on each other, you +will also have to duplicate the complete hierarchy and adapt the project files +to point to the right copies. + +.. index:: scenarios (GNAT Project Manager) + +Instead, project files support the notion of scenarios controlled +by external values. Such values can come from several sources (in decreasing +order of priority): + +.. index:: -X (usage with GNAT Project Manager) + +**Command line**: + When launching *gnatmake* or *gprbuild*, the user can pass + extra *-X* switches to define the external value. In + our case, the command line might look like + + :: + + gnatmake -Pbuild.gpr -Xmode=debug + + or + + :: + + gnatmake -Pbuild.gpr -Xmode=release + + +**Environment variables**: + When the external value does not come from the command line, it can come from + the value of environment variables of the appropriate name. + In our case, if an environment variable called "mode" + exists, its value will be taken into account. + + + +.. index:: external (GNAT Project Manager) + +**External function second parameter**. + +We now need to get that value in the project. The general form is to use +the predefined function **external** which returns the current value of +the external. For instance, we could set up the object directory to point to +either :file:`obj/debug` or :file:`obj/release` by changing our project to + +.. code-block:: gpr + + project Build is + for Object_Dir use "obj/" & external ("mode", "debug"); + ... -- as before + end Build; + +The second parameter to `external` is optional, and is the default +value to use if "mode" is not set from the command line or the environment. + +In order to set the switches according to the different scenarios, other +constructs have to be introduced such as typed variables and case constructions. + +.. index:: typed variable (GNAT Project Manager) +.. index:: case construction (GNAT Project Manager) + +A **typed variable** is a variable that +can take only a limited number of values, similar to an enumeration in Ada. +Such a variable can then be used in a **case construction** and create conditional +sections in the project. The following example shows how this can be done: + +.. code-block:: gpr + + project Build is + type Mode_Type is ("debug", "release"); -- all possible values + Mode : Mode_Type := external ("mode", "debug"); -- a typed variable + + package Compiler is + case Mode is + when "debug" => + for Switches ("Ada") + use ("-g"); + when "release" => + for Switches ("Ada") + use ("-O2"); + end case; + end Compiler; + end Build; + +The project has suddenly grown in size, but has become much more flexible. +`Mode_Type` defines the only valid values for the `mode` variable. If +any other value is read from the environment, an error is reported and the +project is considered as invalid. + +The `Mode` variable is initialized with an external value +defaulting to `"debug"`. This default could be omitted and that would +force the user to define the value. Finally, we can use a case construction to set the +switches depending on the scenario the user has chosen. + +Most aspects of the projects can depend on scenarios. The notable exception +are project dependencies (|with| clauses), which cannot depend on a scenario. + +Scenarios work the same way with **project hierarchies**: you can either +duplicate a variable similar to `Mode` in each of the project (as long +as the first argument to `external` is always the same and the type is +the same), or simply set the variable in the :file:`shared.gpr` project +(see :ref:`Sharing_Between_Projects`). + + +.. _Library_Projects: + +Library Projects +================ + +So far, we have seen examples of projects that create executables. However, +it is also possible to create libraries instead. A **library** is a specific +type of subsystem where, for convenience, objects are grouped together +using system-specific means such as archives or windows DLLs. + +Library projects provide a system- and language-independent way of building +both **static** and **dynamic** libraries. They also support the concept of +**standalone libraries** (SAL) which offer two significant properties: the +elaboration (e.g. initialization) of the library is either automatic or +very simple; a change in the +implementation part of the library implies minimal post-compilation actions on +the complete system and potentially no action at all for the rest of the +system in the case of dynamic SALs. + +There is a restriction on shared library projects: by default, they are only +allowed to import other shared library projects. They are not allowed to +import non library projects or static library projects. + +The GNAT Project Manager takes complete care of the library build, rebuild and +installation tasks, including recompilation of the source files for which +objects do not exist or are not up to date, assembly of the library archive, and +installation of the library (i.e., copying associated source, object and +:file:`ALI` files to the specified location). + + +.. _Building_Libraries: + +Building Libraries +------------------ + +Let's enhance our example and transform the `logging` subsystem into a +library. In order to do so, a few changes need to be made to +:file:`logging.gpr`. Some attributes need to be defined: at least +`Library_Name` and `Library_Dir`; in addition, some other attributes +can be used to specify specific aspects of the library. For readability, it is +also recommended (although not mandatory), to use the qualifier `library` +in front of the `project` keyword. + +.. index:: Library_Name (GNAT Project Manager) + +**Library_Name**: + + This attribute is the name of the library to be built. There is no + restriction on the name of a library imposed by the project manager, except + for stand-alone libraries whose names must follow the syntax of Ada + identifiers; however, there may be system-specific restrictions on the name. + In general, it is recommended to stick to alphanumeric characters (and + possibly single underscores) to help portability. + +.. index:: Library_Dir (GNAT Project Manager) + +**Library_Dir**: + + This attribute is the path (absolute or relative) of the directory where + the library is to be installed. In the process of building a library, + the sources are compiled, the object files end up in the explicit or + implicit `Object_Dir` directory. When all sources of a library + are compiled, some of the compilation artifacts, including the library itself, + are copied to the library_dir directory. This directory must exist and be + writable. It must also be different from the object directory so that cleanup + activities in the Library_Dir do not affect recompilation needs. + +Here is the new version of :file:`logging.gpr` that makes it a library: + +.. code-block:: gpr + + library project Logging is -- "library" is optional + for Library_Name use "logging"; -- will create "liblogging.a" on Unix + for Object_Dir use "obj"; + for Library_Dir use "lib"; -- different from object_dir + end Logging; + +Once the above two attributes are defined, the library project is valid and +is enough for building a library with default characteristics. +Other library-related attributes can be used to change the defaults: + +.. index:: Library_Kind (GNAT Project Manager) + +**Library_Kind**: + + The value of this attribute must be either `"static"`, `"dynamic"` or + `"relocatable"` (the latter is a synonym for dynamic). It indicates + which kind of library should be built (the default is to build a + static library, that is an archive of object files that can potentially + be linked into a static executable). When the library is set to be dynamic, + a separate image is created that will be loaded independently, usually + at the start of the main program execution. Support for dynamic libraries is + very platform specific, for instance on Windows it takes the form of a DLL + while on GNU/Linux, it is a dynamic elf image whose suffix is usually + :file:`.so`. Library project files, on the other hand, can be written in + a platform independent way so that the same project file can be used to build + a library on different operating systems. + + If you need to build both a static and a dynamic library, it is recommended + to use two different object directories, since in some cases some extra code + needs to be generated for the latter. For such cases, one can either define + two different project files, or a single one that uses scenarios to indicate + the various kinds of library to be built and their corresponding object_dir. + +.. index:: Library_ALI_Dir (GNAT Project Manager) + +**Library_ALI_Dir**: + + This attribute may be specified to indicate the directory where the ALI + files of the library are installed. By default, they are copied into the + `Library_Dir` directory, but as for the executables where we have a + separate `Exec_Dir` attribute, you might want to put them in a separate + directory since there can be hundreds of them. The same restrictions as for + the `Library_Dir` attribute apply. + +.. index:: Library_Version (GNAT Project Manager) + +**Library_Version**: + + This attribute is platform dependent, and has no effect on Windows. + On Unix, it is used only for dynamic libraries as the internal + name of the library (the `"soname"`). If the library file name (built + from the `Library_Name`) is different from the `Library_Version`, + then the library file will be a symbolic link to the actual file whose name + will be `Library_Version`. This follows the usual installation schemes + for dynamic libraries on many Unix systems. + + .. code-block:: gpr + + project Logging is + Version := "1"; + for Library_Dir use "lib"; + for Library_Name use "logging"; + for Library_Kind use "dynamic"; + for Library_Version use "liblogging.so." & Version; + end Logging; + + + After the compilation, the directory :file:`lib` will contain both a + :file:`libdummy.so.1` library and a symbolic link to it called + :file:`libdummy.so`. + +.. index:: Library_GCC (GNAT Project Manager) + +**Library_GCC**: + + This attribute is the name of the tool to use instead of "gcc" to link shared + libraries. A common use of this attribute is to define a wrapper script that + accomplishes specific actions before calling gcc (which itself calls the + linker to build the library image). + +.. index:: Library_Options (GNAT Project Manager) + +**Library_Options**: + + This attribute may be used to specify additional switches (last switches) + when linking a shared library. + + It may also be used to add foreign object files to a static library. + Each string in Library_Options is an absolute or relative path of an object + file. When a relative path, it is relative to the object directory. + +.. index:: Leading_Library_Options (GNAT Project Manager) + +**Leading_Library_Options**: + + This attribute, that is taken into account only by *gprbuild*, may be + used to specified leading options (first switches) when linking a shared + library. + +.. index:: Linker_Options (GNAT Project Manager) + +**Linker.Linker_Options**: + + This attribute specifies additional switches to be given to the linker when + linking an executable. It is ignored when defined in the main project and + taken into account in all other projects that are imported directly or + indirectly. These switches complement the `Linker.Switches` + defined in the main project. This is useful when a particular subsystem + depends on an external library: adding this dependency as a + `Linker_Options` in the project of the subsystem is more convenient than + adding it to all the `Linker.Switches` of the main projects that depend + upon this subsystem. + + +.. _Using_Library_Projects: + +Using Library Projects +---------------------- + +When the builder detects that a project file is a library project file, it +recompiles all sources of the project that need recompilation and rebuild the +library if any of the sources have been recompiled. It then groups all object +files into a single file, which is a shared or a static library. This library +can later on be linked with multiple executables. Note that the use +of shard libraries reduces the size of the final executable and can also reduce +the memory footprint at execution time when the library is shared among several +executables. + +It is also possible to build **multi-language libraries**. When using +*gprbuild* as a builder, multi-language library projects allow naturally +the creation of multi-language libraries . *gnatmake*, does not try to +compile non Ada sources. However, when the project is multi-language, it will +automatically link all object files found in the object directory, whether or +not they were compiled from an Ada source file. This specific behavior does not +apply to Ada-only projects which only take into account the objects +corresponding to the sources of the project. + +A non-library project can import a library project. When the builder is invoked +on the former, the library of the latter is only rebuilt when absolutely +necessary. For instance, if a unit of the library is not up-to-date but none of +the executables need this unit, then the unit is not recompiled and the library +is not reassembled. For instance, let's assume in our example that logging has +the following sources: :file:`log1.ads`, :file:`log1.adb`, :file:`log2.ads` and +:file:`log2.adb`. If :file:`log1.adb` has been modified, then the library +:file:`liblogging` will be rebuilt when compiling all the sources of +`Build` only if :file:`proc.ads`, :file:`pack.ads` or :file:`pack.adb` +include a `"with Log1"`. + +To ensure that all the sources in the `Logging` library are +up to date, and that all the sources of `Build` are also up to date, +the following two commands need to be used: + +.. code-block:: sh + + gnatmake -Plogging.gpr + gnatmake -Pbuild.gpr + +All :file:`ALI` files will also be copied from the object directory to the +library directory. To build executables, *gnatmake* will use the +library rather than the individual object files. + +Library projects can also be useful to describe a library that needs to be used +but, for some reason, cannot be rebuilt. For instance, it is the case when some +of the library sources are not available. Such library projects need to use the +`Externally_Built` attribute as in the example below: + +.. code-block: ada-project + + library project Extern_Lib is + for Languages use ("Ada", "C"); + for Source_Dirs use ("lib_src"); + for Library_Dir use "lib2"; + for Library_Kind use "dynamic"; + for Library_Name use "l2"; + for Externally_Built use "true"; -- <<<< + end Extern_Lib; + +In the case of externally built libraries, the `Object_Dir` +attribute does not need to be specified because it will never be +used. + +The main effect of using such an externally built library project is mostly to +affect the linker command in order to reference the desired library. It can +also be achieved by using `Linker.Linker_Options` or `Linker.Switches` +in the project corresponding to the subsystem needing this external library. +This latter method is more straightforward in simple cases but when several +subsystems depend upon the same external library, finding the proper place +for the `Linker.Linker_Options` might not be easy and if it is +not placed properly, the final link command is likely to present ordering issues. +In such a situation, it is better to use the externally built library project +so that all other subsystems depending on it can declare this dependency thanks +to a project |with| clause, which in turn will trigger the builder to find +the proper order of libraries in the final link command. + + +.. _Stand-alone_Library_Projects: + +Stand-alone Library Projects +---------------------------- + +.. index:: standalone libraries (usage with GNAT Project Manager) + +A **stand-alone library** is a library that contains the necessary code to +elaborate the Ada units that are included in the library. A stand-alone +library is a convenient way to add an Ada subsystem to a more global system +whose main is not in Ada since it makes the elaboration of the Ada part mostly +transparent. However, stand-alone libraries are also useful when the main is in +Ada: they provide a means for minimizing relinking & redeployment of complex +systems when localized changes are made. + +The name of a stand-alone library, specified with attribute +`Library_Name`, must have the syntax of an Ada identifier. + +The most prominent characteristic of a stand-alone library is that it offers a +distinction between interface units and implementation units. Only the former +are visible to units outside the library. A stand-alone library project is thus +characterised by a third attribute, usually **Library_Interface**, in addition +to the two attributes that make a project a Library Project +(`Library_Name` and `Library_Dir`). This third attribute may also be +**Interfaces**. **Library_Interface** only works when the interface is in Ada +and takes a list of units as parameter. **Interfaces** works for any supported +language and takes a list of sources as parameter. + +.. index:: Library_Interface (GNAT Project Manager) + +**Library_Interface**: + + This attribute defines an explicit subset of the units of the project. Units + from projects importing this library project may only "with" units whose + sources are listed in the `Library_Interface`. Other sources are + considered implementation units. + + .. code-block:: gpr + + for Library_Dir use "lib"; + for Library_Name use "logging"; + for Library_Interface use ("lib1", "lib2"); -- unit names + +**Interfaces** + + This attribute defines an explicit subset of the source files of a project. + Sources from projects importing this project, can only depend on sources from + this subset. This attribute can be used on non library projects. It can also + be used as a replacement for attribute `Library_Interface`, in which + case, units have to be replaced by source files. For multi-language library + projects, it is the only way to make the project a Stand-Alone Library project + whose interface is not purely Ada. + + +.. index:: Library_Standalone (GNAT Project Manager) + +**Library_Standalone**: + + This attribute defines the kind of standalone library to + build. Values are either `standard` (the default), `no` or + `encapsulated`. When `standard` is used the code to elaborate and + finalize the library is embedded, when `encapsulated` is used the + library can furthermore depend only on static libraries (including + the GNAT runtime). This attribute can be set to `no` to make it clear + that the library should not be standalone in which case the + `Library_Interface` should not defined. Note that this attribute + only applies to shared libraries, so `Library_Kind` must be set + to `dynamic`. + + .. code-block:: gpr + + for Library_Dir use "lib"; + for Library_Name use "logging"; + for Library_Kind use "dynamic"; + for Library_Interface use ("lib1", "lib2"); -- unit names + for Library_Standalone use "encapsulated"; + +In order to include the elaboration code in the stand-alone library, the binder +is invoked on the closure of the library units creating a package whose name +depends on the library name (b~logging.ads/b in the example). +This binder-generated package includes **initialization** and **finalization** +procedures whose names depend on the library name (`logginginit` and +`loggingfinal` in the example). The object corresponding to this package is +included in the library. + +.. index:: Library_Auto_Init (GNAT Project Manager) + +**Library_Auto_Init**: + + A dynamic stand-alone Library is automatically initialized + if automatic initialization of Stand-alone Libraries is supported on the + platform and if attribute **Library_Auto_Init** is not specified or + is specified with the value "true". A static Stand-alone Library is never + automatically initialized. Specifying "false" for this attribute + prevents automatic initialization. + + When a non-automatically initialized stand-alone library is used in an + executable, its initialization procedure must be called before any service of + the library is used. When the main subprogram is in Ada, it may mean that the + initialization procedure has to be called during elaboration of another + package. + + +.. index:: Library_Dir (GNAT Project Manager) + +**Library_Dir**: + + For a stand-alone library, only the :file:`ALI` files of the interface units + (those that are listed in attribute `Library_Interface`) are copied to + the library directory. As a consequence, only the interface units may be + imported from Ada units outside of the library. If other units are imported, + the binding phase will fail. + + +**Binder.Default_Switches**: + + When a stand-alone library is bound, the switches that are specified in + the attribute **Binder.Default_Switches ("Ada")** are + used in the call to *gnatbind*. + + +.. index:: Library_Src_Dir (GNAT Project Manager) + +**Library_Src_Dir**: + + This attribute defines the location (absolute or relative to the project + directory) where the sources of the interface units are copied at + installation time. + These sources includes the specs of the interface units along with the + closure of sources necessary to compile them successfully. That may include + bodies and subunits, when pragmas `Inline` are used, or when there are + generic units in specs. This directory cannot point to the object directory + or one of the source directories, but it can point to the library directory, + which is the default value for this attribute. + + +.. index:: Library_Symbol_Policy (GNAT Project Manager) + +**Library_Symbol_Policy**: + + This attribute controls the export of symbols and, on some platforms (like + VMS) that have the notions of major and minor IDs built in the library + files, it controls the setting of these IDs. It is not supported on all + platforms (where it will just have no effect). It may have one of the + following values: + + * `"autonomous"` or `"default"`: exported symbols are not controlled + + * `"compliant"`: if attribute **Library_Reference_Symbol_File** + is not defined, then it is equivalent to policy "autonomous". If there + are exported symbols in the reference symbol file that are not in the + object files of the interfaces, the major ID of the library is increased. + If there are symbols in the object files of the interfaces that are not + in the reference symbol file, these symbols are put at the end of the list + in the newly created symbol file and the minor ID is increased. + + * `"controlled"`: the attribute **Library_Reference_Symbol_File** must be + defined. The library will fail to build if the exported symbols in the + object files of the interfaces do not match exactly the symbol in the + symbol file. + + * `"restricted"`: The attribute **Library_Symbol_File** must be defined. + The library will fail to build if there are symbols in the symbol file that + are not in the exported symbols of the object files of the interfaces. + Additional symbols in the object files are not added to the symbol file. + + * `"direct"`: The attribute **Library_Symbol_File** must be defined and + must designate an existing file in the object directory. This symbol file + is passed directly to the underlying linker without any symbol processing. + + +.. index:: Library_Reference_Symbol_File (GNAT Project Manager) + +**Library_Reference_Symbol_File** + + This attribute may define the path name of a reference symbol file that is + read when the symbol policy is either "compliant" or "controlled", on + platforms that support symbol control, such as VMS, when building a + stand-alone library. The path may be an absolute path or a path relative + to the project directory. + + +.. index:: Library_Symbol_File (GNAT Project Manager) + +**Library_Symbol_File** + + This attribute may define the name of the symbol file to be created when + building a stand-alone library when the symbol policy is either "compliant", + "controlled" or "restricted", on platforms that support symbol control, + such as VMS. When symbol policy is "direct", then a file with this name + must exist in the object directory. + + +.. _Installing_a_library_with_project_files: + +Installing a library with project files +--------------------------------------- + +When using project files, a usable version of the library is created in the +directory specified by the `Library_Dir` attribute of the library +project file. Thus no further action is needed in order to make use of +the libraries that are built as part of the general application build. + +You may want to install a library in a context different from where the library +is built. This situation arises with third party suppliers, who may want +to distribute a library in binary form where the user is not expected to be +able to recompile the library. The simplest option in this case is to provide +a project file slightly different from the one used to build the library, by +using the `externally_built` attribute. See :ref:`Using_Library_Projects` + +Another option is to use *gprinstall* to install the library in a +different context than the build location. *gprinstall* automatically +generates a project to use this library, and also copies the minimum set of +sources needed to use the library to the install location. +:ref:`Installation` + + +.. _Project_Extension: + +Project Extension +================= + +During development of a large system, it is sometimes necessary to use +modified versions of some of the source files, without changing the original +sources. This can be achieved through the **project extension** facility. + +Suppose for instance that our example `Build` project is built every night +for the whole team, in some shared directory. A developer usually needs to work +on a small part of the system, and might not want to have a copy of all the +sources and all the object files (mostly because that would require too much +disk space, time to recompile everything). He prefers to be able to override +some of the source files in his directory, while taking advantage of all the +object files generated at night. + +Another example can be taken from large software systems, where it is common to have +multiple implementations of a common interface; in Ada terms, multiple +versions of a package body for the same spec. For example, one implementation +might be safe for use in tasking programs, while another might be used only +in sequential applications. This can be modeled in GNAT using the concept +of *project extension*. If one project (the 'child') *extends* +another project (the 'parent') then by default all source files of the +parent project are inherited by the child, but the child project can +override any of the parent's source files with new versions, and can also +add new files or remove unnecessary ones. +This facility is the project analog of a type extension in +object-oriented programming. Project hierarchies are permitted (an extending +project may itself be extended), and a project that +extends a project can also import other projects. + +A third example is that of using project extensions to provide different +versions of the same system. For instance, assume that a `Common` +project is used by two development branches. One of the branches has now +been frozen, and no further change can be done to it or to `Common`. +However, the other development branch still needs evolution of `Common`. +Project extensions provide a flexible solution to create a new version +of a subsystem while sharing and reusing as much as possible from the original +one. + +A project extension implicitly inherits all the sources and objects from the +project it extends. It is possible to create a new version of some of the +sources in one of the additional source directories of the extending +project. Those new versions hide the original versions. Adding new sources or +removing existing ones is also possible. Here is an example on how to extend +the project `Build` from previous examples: + +.. code-block:: gpr + + project Work extends "../bld/build.gpr" is + end Work; + +The project after **extends** is the one being extended. As usual, it can be +specified using an absolute path, or a path relative to any of the directories +in the project path (see :ref:`Project_Dependencies`). This project does not +specify source or object directories, so the default values for these +attributes will be used that is to say the current directory (where project +`Work` is placed). We can compile that project with + +.. code-block:: sh + + gprbuild -Pwork + +If no sources have been placed in the current directory, this command +won't do anything, since this project does not change the +sources it inherited from `Build`, therefore all the object files +in `Build` and its dependencies are still valid and are reused +automatically. + +Suppose we now want to supply an alternate version of :file:`pack.adb` but use +the existing versions of :file:`pack.ads` and :file:`proc.adb`. We can create +the new file in Work's current directory (likely by copying the one from the +`Build` project and making changes to it. If new packages are needed at +the same time, we simply create new files in the source directory of the +extending project. + +When we recompile, *gprbuild* will now automatically recompile +this file (thus creating :file:`pack.o` in the current directory) and +any file that depends on it (thus creating :file:`proc.o`). Finally, the +executable is also linked locally. + +Note that we could have obtained the desired behavior using project import +rather than project inheritance. A `base` project would contain the +sources for :file:`pack.ads` and :file:`proc.adb`, and `Work` would +import `base` and add :file:`pack.adb`. In this scenario, `base` +cannot contain the original version of :file:`pack.adb` otherwise there would be +2 versions of the same unit in the closure of the project and this is not +allowed. Generally speaking, it is not recommended to put the spec and the +body of a unit in different projects since this affects their autonomy and +reusability. + +In a project file that extends another project, it is possible to +indicate that an inherited source is **not part** of the sources of the +extending project. This is necessary sometimes when a package spec has +been overridden and no longer requires a body: in this case, it is +necessary to indicate that the inherited body is not part of the sources +of the project, otherwise there will be a compilation error +when compiling the spec. + +.. index:: Excluded_Source_Files (GNAT Project Manager) + +.. index:: Excluded_Source_List_File (GNAT Project Manager) + +For that purpose, the attribute **Excluded_Source_Files** is used. +Its value is a list of file names. +It is also possible to use attribute `Excluded_Source_List_File`. +Its value is the path of a text file containing one file name per +line. + +.. code-block:: gpr + + project Work extends "../bld/build.gpr" is + for Source_Files use ("pack.ads"); + -- New spec of Pkg does not need a completion + for Excluded_Source_Files use ("pack.adb"); + end Work; + + +All packages that are not declared in the extending project are inherited from +the project being extended, with their attributes, with the exception of +`Linker'Linker_Options` which is never inherited. In particular, an +extending project retains all the switches specified in the project being +extended. + +At the project level, if they are not declared in the extending project, some +attributes are inherited from the project being extended. They are: +`Languages`, `Main` (for a root non library project) and +`Library_Name` (for a project extending a library project). + +.. _Project_Hierarchy_Extension: + +Project Hierarchy Extension +--------------------------- + +One of the fundamental restrictions in project extension is the following: +**A project is not allowed to import directly or indirectly at the same time an extending project and one of its ancestors**. + +For example, consider the following hierarchy of projects. + +:: + + a.gpr contains package A1 + b.gpr, imports a.gpr and contains B1, which depends on A1 + c.gpr, imports b.gpr and contains C1, which depends on B1 + +If we want to locally extend the packages `A1` and `C1`, we need to +create several extending projects: + +:: + + a_ext.gpr which extends a.gpr, and overrides A1 + b_ext.gpr which extends b.gpr and imports a_ext.gpr + c_ext.gpr which extends c.gpr, imports b_ext.gpr and overrides C1 + +.. code-block:: gpr + + project A_Ext extends "a.gpr" is + for Source_Files use ("a1.adb", "a1.ads"); + end A_Ext; + + with "a_ext.gpr"; + project B_Ext extends "b.gpr" is + end B_Ext; + + with "b_ext.gpr"; + project C_Ext extends "c.gpr" is + for Source_Files use ("c1.adb"); + end C_Ext; + +The extension :file:`b_ext.gpr` is required, even though we are not overriding +any of the sources of :file:`b.gpr` because otherwise :file:`c_expr.gpr` would +import :file:`b.gpr` which itself knows nothing about :file:`a_ext.gpr`. + +.. index:: extends all (GNAT Project Manager) + +When extending a large system spanning multiple projects, it is often +inconvenient to extend every project in the hierarchy that is impacted by a +small change introduced in a low layer. In such cases, it is possible to create +an **implicit extension** of an entire hierarchy using **extends all** +relationship. + +When the project is extended using `extends all` inheritance, all projects +that are imported by it, both directly and indirectly, are considered virtually +extended. That is, the project manager creates implicit projects +that extend every project in the hierarchy; all these implicit projects do not +control sources on their own and use the object directory of +the "extending all" project. + +It is possible to explicitly extend one or more projects in the hierarchy +in order to modify the sources. These extending projects must be imported by +the "extending all" project, which will replace the corresponding virtual +projects with the explicit ones. + +When building such a project hierarchy extension, the project manager will +ensure that both modified sources and sources in implicit extending projects +that depend on them are recompiled. + +Thus, in our example we could create the following projects instead: + +:: + + a_ext.gpr, extends a.gpr and overrides A1 + c_ext.gpr, "extends all" c.gpr, imports a_ext.gpr and overrides C1 + +.. code-block:: gpr + + project A_Ext extends "a.gpr" is + for Source_Files use ("a1.adb", "a1.ads"); + end A_Ext; + + with "a_ext.gpr"; + project C_Ext extends all "c.gpr" is + for Source_Files use ("c1.adb"); + end C_Ext; + + +When building project :file:`c_ext.gpr`, the entire modified project space is +considered for recompilation, including the sources of :file:`b.gpr` that are +impacted by the changes in `A1` and `C1`. + + +.. _Aggregate_Projects: + +Aggregate Projects +================== + +Aggregate projects are an extension of the project paradigm, and are +meant to solve a few specific use cases that cannot be solved directly +using standard projects. This section will go over a few of these use +cases to try to explain what you can use aggregate projects for. + + +.. _Building_all_main_programs_from_a_single_project_tree: + +Building all main programs from a single project tree +----------------------------------------------------- + +Most often, an application is organized into modules and submodules, +which are very conveniently represented as a project tree or graph +(the root project A |withs| the projects for each modules (say B and C), +which in turn |with| projects for submodules. + +Very often, modules will build their own executables (for testing +purposes for instance), or libraries (for easier reuse in various +contexts). + +However, if you build your project through *gnatmake* or +*gprbuild*, using a syntax similar to + +:: + + gprbuild -PA.gpr + +this will only rebuild the main programs of project A, not those of the +imported projects B and C. Therefore you have to spawn several +*gnatmake* commands, one per project, to build all executables. +This is a little inconvenient, but more importantly is inefficient +because *gnatmake* needs to do duplicate work to ensure that sources are +up-to-date, and cannot easily compile things in parallel when using +the -j switch. + +Also libraries are always rebuilt when building a project. + +You could therefore define an aggregate project Agg that groups A, B +and C. Then, when you build with + +:: + + gprbuild -PAgg.gpr + +this will build all mains from A, B and C. + +.. code-block:: gpr + + aggregate project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); + end Agg; + +If B or C do not define any main program (through their Main +attribute), all their sources are built. When you do not group them +in the aggregate project, only those sources that are needed by A +will be built. + +If you add a main to a project P not already explicitly referenced in the +aggregate project, you will need to add "p.gpr" in the list of project +files for the aggregate project, or the main will not be built when +building the aggregate project. + +Aggregate projects are supported only with *gprbuild*, not with +*gnatmake*. + + +.. _Building_a_set_of_projects_with_a_single_command: + +Building a set of projects with a single command +------------------------------------------------ + +One other case is when you have multiple applications and libraries +that are built independently from each other (but can be built in +parallel). For instance, you have a project tree rooted at A, and +another one (which might share some subprojects) rooted at B. + +Using only *gprbuild*, you could do + +.. code-block:: sh + + gprbuild -PA.gpr + gprbuild -PB.gpr + +to build both. But again, *gprbuild* has to do some duplicate work for +those files that are shared between the two, and cannot truly build +things in parallel efficiently. + +If the two projects are really independent, share no sources other +than through a common subproject, and have no source files with a +common basename, you could create a project C that imports A and +B. But these restrictions are often too strong, and one has to build +them independently. An aggregate project does not have these +limitations and can aggregate two project trees that have common +sources. + +This scenario is particularly useful in environments like VxWorks 653 +where the applications running in the multiple partitions can be built +in parallel through a single *gprbuild* command. This also works nicely +with Annex E. + + +.. _Define_a_build_environment: + +Define a build environment +-------------------------- + +The environment variables at the time you launch *gprbuild* +will influence the view these tools have of the project +(PATH to find the compiler, ADA_PROJECT_PATH or GPR_PROJECT_PATH to find the +projects, environment variables that are referenced in project files +through the "external" built-in function, ...). Several command line switches +can be used to override those (-X or -aP), but on some systems and +with some projects, this might make the command line too long, and on +all systems often make it hard to read. + +An aggregate project can be used to set the environment for all +projects built through that aggregate. One of the nice aspects is that +you can put the aggregate project under configuration management, and +make sure all your user have a consistent environment when +building. The syntax looks like + +.. code-block:: gpr + + aggregate project Agg is + for Project_Files use ("A.gpr", "B.gpr"); + for Project_Path use ("../dir1", "../dir1/dir2"); + for External ("BUILD") use "PRODUCTION"; + + package Builder is + for Switches ("Ada") use ("-q"); + end Builder; + end Agg; + +One of the often requested features in projects is to be able to +reference external variables in |with| declarations, as in + +.. code-block:: gpr + + with external("SETUP") & "path/prj.gpr"; -- ILLEGAL + project MyProject is + ... + end MyProject; + +For various reasons, this is not allowed. But using aggregate projects provide +an elegant solution. For instance, you could use a project file like: + +.. code-block:: gpr + + aggregate project Agg is + for Project_Path use (external("SETUP") & "path"); + for Project_Files use ("myproject.gpr"); + end Agg; + + with "prj.gpr"; -- searched on Agg'Project_Path + project MyProject is + ... + end MyProject; + + +.. _Performance_improvements_in_builder: + +Performance improvements in builder +----------------------------------- + +The loading of aggregate projects is optimized in *gprbuild*, +so that all files are searched for only once on the disk +(thus reducing the number of system calls and contributing to faster +compilation times, especially on systems with sources on remote +servers). As part of the loading, *gprbuild* +computes how and where a source file should be compiled, and even if it is +found several times in the aggregated projects it will be compiled only +once. + +Since there is no ambiguity as to which switches should be used, files +can be compiled in parallel (through the usual -j switch) and this can +be done while maximizing the use of CPUs (compared to launching +multiple *gprbuild* and *gnatmake* commands in parallel). + + +.. _Syntax_of_aggregate_projects: + +Syntax of aggregate projects +---------------------------- + +An aggregate project follows the general syntax of project files. The +recommended extension is still :file:`.gpr`. However, a special +`aggregate` qualifier must be put before the keyword +`project`. + +An aggregate project cannot |with| any other project (standard or +aggregate), except an abstract project which can be used to share attribute +values. Also, aggregate projects cannot be extended or imported though a +|with| clause by any other project. Building other aggregate projects from +an aggregate project is done through the Project_Files attribute (see below). + +An aggregate project does not have any source files directly (only +through other standard projects). Therefore a number of the standard +attributes and packages are forbidden in an aggregate project. Here is the +(non exhaustive) list: + +* Languages +* Source_Files, Source_List_File and other attributes dealing with + list of sources. +* Source_Dirs, Exec_Dir and Object_Dir +* Library_Dir, Library_Name and other library-related attributes +* Main +* Roots +* Externally_Built +* Inherit_Source_Path +* Excluded_Source_Dirs +* Locally_Removed_Files +* Excluded_Source_Files +* Excluded_Source_List_File +* Interfaces + +The only package that is authorized (albeit optional) is +Builder. Other packages (in particular Compiler, Binder and Linker) +are forbidden. + +The following three attributes can be used only in an aggregate project: + +.. index:: Project_Files (GNAT Project Manager) + +**Project_Files**: + + This attribute is compulsory (or else we are not aggregating any project, + and thus not doing anything). It specifies a list of :file:`.gpr` files + that are grouped in the aggregate. The list may be empty. The project + files can be either other aggregate projects, or standard projects. When + grouping standard projects, you can have both the root of a project tree + (and you do not need to specify all its imported projects), and any project + within the tree. + + Basically, the idea is to specify all those projects that have + main programs you want to build and link, or libraries you want to + build. You can even specify projects that do not use the Main + attribute nor the `Library_*` attributes, and the result will be to + build all their source files (not just the ones needed by other + projects). + + The file can include paths (absolute or relative). Paths are relative to + the location of the aggregate project file itself (if you use a base name, + we expect to find the .gpr file in the same directory as the aggregate + project file). The environment variables `ADA_PROJECT_PATH`, + `GPR_PROJECT_PATH` and `GPR_PROJECT_PATH_FILE` are not used to find + the project files. The extension :file:`.gpr` is mandatory, since this attribute + contains file names, not project names. + + Paths can also include the `"*"` and `"**"` globbing patterns. The + latter indicates that any subdirectory (recursively) will be + searched for matching files. The latter (`"**"`) can only occur at the + last position in the directory part (ie `"a/**/*.gpr"` is supported, but + not `"**/a/*.gpr"`). Starting the pattern with `"**"` is equivalent + to starting with `"./**"`. + + For now, the pattern `"*"` is only allowed in the filename part, not + in the directory part. This is mostly for efficiency reasons to limit the + number of system calls that are needed. + + Here are a few valid examples: + + .. code-block:: gpr + + for Project_Files use ("a.gpr", "subdir/b.gpr"); + -- two specific projects relative to the directory of agg.gpr + + for Project_Files use ("/.gpr"); + -- all projects recursively + + +.. index:: Project_Path (GNAT Project Manager) + +**Project_Path**: + + This attribute can be used to specify a list of directories in + which to look for project files in |with| declarations. + + When you specify a project in Project_Files (say `x/y/a.gpr`), and + `a.gpr` imports a project `b.gpr`, only `b.gpr` is searched in + the project path. `a.gpr` must be exactly at + `/x/y/a.gpr`. + + This attribute, however, does not affect the search for the aggregated + project files specified with `Project_Files`. + + Each aggregate project has its own `Project_Path` (that is if + `agg1.gpr` includes `agg2.gpr`, they can potentially both have a + different `Project_Path`). + + This project path is defined as the concatenation, in that order, of: + + * the current directory; + + * followed by the command line -aP switches; + + * then the directories from the GPR_PROJECT_PATH and ADA_PROJECT_PATH environment + variables; + + * then the directories from the Project_Path attribute; + + * and finally the predefined directories. + + In the example above, agg2.gpr's project path is not influenced by + the attribute agg1'Project_Path, nor is agg1 influenced by + agg2'Project_Path. + + This can potentially lead to errors. Consider the following example: + + .. -- + -- +---------------+ +----------------+ + -- | Agg1.gpr |-=--includes--=-->| Agg2.gpr | + -- | 'project_path| | 'project_path | + -- | | | | + -- +---------------+ +----------------+ + -- : : + -- includes includes + -- : : + -- v v + -- +-------+ +---------+ + -- | P.gpr |<---------- withs --------| Q.gpr | + -- +-------+---------\ +---------+ + -- | | + -- withs | + -- | | + -- v v + -- +-------+ +---------+ + -- | R.gpr | | R'.gpr | + -- +-------+ +---------+ + + .. image:: project-manager-figure.png + + When looking for p.gpr, both aggregates find the same physical file on + the disk. However, it might happen that with their different project + paths, both aggregate projects would in fact find a different r.gpr. + Since we have a common project (p.gpr) "with"ing two different r.gpr, + this will be reported as an error by the builder. + + Directories are relative to the location of the aggregate project file. + + Example: + + .. code-block:: gpr + + for Project_Path use ("/usr/local/gpr", "gpr/"); + +.. index:: External (GNAT Project Manager) + +**External**: + + This attribute can be used to set the value of environment + variables as retrieved through the `external` function + in projects. It does not affect the environment variables + themselves (so for instance you cannot use it to change the value + of your PATH as seen from the spawned compiler). + + This attribute affects the external values as seen in the rest of + the aggregate project, and in the aggregated projects. + + The exact value of external a variable comes from one of three + sources (each level overrides the previous levels): + + * An External attribute in aggregate project, for instance + `for External ("BUILD_MODE") use "DEBUG"`; + + * Environment variables. + These override the value given by the attribute, so that + users can override the value set in the (presumably shared + with others team members) aggregate project. + + * The -X command line switch to *gprbuild*. + This always takes precedence. + + This attribute is only taken into account in the main aggregate + project (i.e. the one specified on the command line to *gprbuild*), + and ignored in other aggregate projects. It is invalid + in standard projects. + The goal is to have a consistent value in all + projects that are built through the aggregate, which would not + be the case in the diamond case: A groups the aggregate + projects B and C, which both (either directly or indirectly) + build the project P. If B and C could set different values for + the environment variables, we would have two different views of + P, which in particular might impact the list of source files in P. + + +.. _package_Builder_in_aggregate_projects: + +package Builder in aggregate projects +------------------------------------- + +As mentioned above, only the package Builder can be specified in +an aggregate project. In this package, only the following attributes +are valid: + +.. index:: Switches (GNAT Project Manager) + +**Switches**: + + This attribute gives the list of switches to use for *gprbuild*. + Because no mains can be specified for aggregate projects, the only possible + index for attribute `Switches` is `others`. All other indexes will + be ignored. + + Example: + + .. code-block:: gpr + + for Switches (others) use ("-v", "-k", "-j8"); + + These switches are only read from the main aggregate project (the + one passed on the command line), and ignored in all other aggregate + projects or projects. + + It can only contain builder switches, not compiler switches. + +.. index:: Global_Compilation_Switches (GNAT Project Manager) + +**Global_Compilation_Switches** + + This attribute gives the list of compiler switches for the various + languages. For instance, + + .. code-block:: gpr + + for Global_Compilation_Switches ("Ada") use ("O1", "-g"); + for Global_Compilation_Switches ("C") use ("-O2"); + + This attribute is only taken into account in the aggregate project + specified on the command line, not in other aggregate projects. + + In the projects grouped by that aggregate, the attribute + Builder.Global_Compilation_Switches is also ignored. However, the + attribute Compiler.Default_Switches will be taken into account (but + that of the aggregate have higher priority). The attribute + Compiler.Switches is also taken into account and can be used to + override the switches for a specific file. As a result, it always + has priority. + + The rules are meant to avoid ambiguities when compiling. For + instance, aggregate project Agg groups the projects A and B, that + both depend on C. Here is an extra for all of these projects: + + + .. code-block:: gpr + + aggregate project Agg is + for Project_Files use ("a.gpr", "b.gpr"); + package Builder is + for Global_Compilation_Switches ("Ada") use ("-O2"); + end Builder; + end Agg; + + with "c.gpr"; + project A is + package Builder is + for Global_Compilation_Switches ("Ada") use ("-O1"); + -- ignored + end Builder; + + package Compiler is + for Default_Switches ("Ada") + use ("-O1", "-g"); + for Switches ("a_file1.adb") + use ("-O0"); + end Compiler; + end A; + + with "c.gpr"; + project B is + package Compiler is + for Default_Switches ("Ada") use ("-O0"); + end Compiler; + end B; + + project C is + package Compiler is + for Default_Switches ("Ada") + use ("-O3", + "-gnatn"); + for Switches ("c_file1.adb") + use ("-O0", "-g"); + end Compiler; + end C; + + + then the following switches are used: + + * all files from project A except a_file1.adb are compiled + with "-O2 -g", since the aggregate project has priority. + + * the file a_file1.adb is compiled with + "-O0", since the Compiler.Switches has priority + + * all files from project B are compiled with + "-O2", since the aggregate project has priority + + * all files from C are compiled with "-O2 -gnatn", except for + c_file1.adb which is compiled with "-O0 -g" + + Even though C is seen through two paths (through A and through + B), the switches used by the compiler are unambiguous. + + +.. index:: Global_Configuration_Pragmas (GNAT Project Manager) + +**Global_Configuration_Pragmas** + + This attribute can be used to specify a file containing + configuration pragmas, to be passed to the Ada compiler. Since we + ignore the package Builder in other aggregate projects and projects, + only those pragmas defined in the main aggregate project will be + taken into account. + + Projects can locally add to those by using the + `Compiler.Local_Configuration_Pragmas` attribute if they need. + + +.. index:: Global_Config_File (GNAT Project Manager) + +**Global_Config_File** + + This attribute, indexed with a language name, can be used to specify a config + when compiling sources of the language. For Ada, these files are configuration + pragmas files. + +For projects that are built through the aggregate, the package Builder +is ignored, except for the Executable attribute which specifies the +name of the executables resulting from the link of the main programs, and +for the Executable_Suffix. + + +.. _Aggregate_Library_Projects: + +Aggregate Library Projects +========================== + +Aggregate library projects make it possible to build a single library +using object files built using other standard or library +projects. This gives the flexibility to describe an application as +having multiple modules (a GUI, database access, ...) using different +project files (so possibly built with different compiler options) and +yet create a single library (static or relocatable) out of the +corresponding object files. + +.. _Building_aggregate_library_projects: + +Building aggregate library projects +----------------------------------- + +For example, we can define an aggregate project Agg that groups A, B +and C: + +.. code-block:: gpr + + aggregate library project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); + for Library_Name use ("agg"); + for Library_Dir use ("lagg"); + end Agg; + +Then, when you build with: + +.. code-block:: sh + + gprbuild agg.gpr + +This will build all units from projects A, B and C and will create a +static library named :file:`libagg.a` in the :file:`lagg` +directory. An aggregate library project has the same set of +restriction as a standard library project. + +Note that a shared aggregate library project cannot aggregate a +static library project. In platforms where a compiler option is +required to create relocatable object files, a Builder package in the +aggregate library project may be used: + +.. code-block:: gpr + + aggregate library project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); + for Library_Name use ("agg"); + for Library_Dir use ("lagg"); + for Library_Kind use "relocatable"; + + package Builder is + for Global_Compilation_Switches ("Ada") use ("-fPIC"); + end Builder; + end Agg; + +With the above aggregate library Builder package, the `-fPIC` +option will be passed to the compiler when building any source code +from projects :file:`a.gpr`, :file:`b.gpr` and :file:`c.gpr`. + + +.. _Syntax_of_aggregate_library_projects: + +Syntax of aggregate library projects +------------------------------------ + +An aggregate library project follows the general syntax of project +files. The recommended extension is still :file:`.gpr`. However, a special +`aggregate library` qualifier must be put before the keyword +`project`. + +An aggregate library project cannot |with| any other project +(standard or aggregate), except an abstract project which can be used +to share attribute values. + +An aggregate library project does not have any source files directly (only +through other standard projects). Therefore a number of the standard +attributes and packages are forbidden in an aggregate library +project. Here is the (non exhaustive) list: + +* Languages +* Source_Files, Source_List_File and other attributes dealing with + list of sources. +* Source_Dirs, Exec_Dir and Object_Dir +* Main +* Roots +* Externally_Built +* Inherit_Source_Path +* Excluded_Source_Dirs +* Locally_Removed_Files +* Excluded_Source_Files +* Excluded_Source_List_File +* Interfaces + +The only package that is authorized (albeit optional) is Builder. + +The Project_Files attribute (See :ref:`Aggregate_Projects`) is used to +described the aggregated projects whose object files have to be +included into the aggregate library. The environment variables +`ADA_PROJECT_PATH`, `GPR_PROJECT_PATH` and +`GPR_PROJECT_PATH_FILE` are not used to find the project files. + + +.. _Project_File_Reference: + +Project File Reference +====================== + +This section describes the syntactic structure of project files, the various +constructs that can be used. Finally, it ends with a summary of all available +attributes. + + +.. _Project_Declaration: + +Project Declaration +------------------- + +Project files have an Ada-like syntax. The minimal project file is: + +.. code-block:: gpr + + project Empty is + end Empty; + +The identifier `Empty` is the name of the project. +This project name must be present after the reserved +word `end` at the end of the project file, followed by a semi-colon. + +**Identifiers** (i.e., the user-defined names such as project or variable names) +have the same syntax as Ada identifiers: they must start with a letter, +and be followed by zero or more letters, digits or underscore characters; +it is also illegal to have two underscores next to each other. Identifiers +are always case-insensitive ("Name" is the same as "name"). + +:: + + simple_name ::= identifier + name ::= simple_name { . simple_name } + +**Strings** are used for values of attributes or as indexes for these +attributes. They are in general case sensitive, except when noted +otherwise (in particular, strings representing file names will be case +insensitive on some systems, so that "file.adb" and "File.adb" both +represent the same file). + +**Reserved words** are the same as for standard Ada 95, and cannot +be used for identifiers. In particular, the following words are currently +used in project files, but others could be added later on. In bold are the +extra reserved words in project files: +``all``, ``at``, ``case``, ``end``, ``for``, ``is``, ``limited``, +``null``, ``others``, ``package``, ``renames``, ``type``, ``use``, ``when``, +``with``, **extends**, **external**, **project**. + +**Comments** in project files have the same syntax as in Ada, two consecutive +hyphens through the end of the line. + +A project may be an **independent project**, entirely defined by a single +project file. Any source file in an independent project depends only +on the predefined library and other source files in the same project. +But a project may also depend on other projects, either by importing them +through **with clauses**, or by **extending** at most one other project. Both +types of dependency can be used in the same project. + +A path name denotes a project file. It can be absolute or relative. +An absolute path name includes a sequence of directories, in the syntax of +the host operating system, that identifies uniquely the project file in the +file system. A relative path name identifies the project file, relative +to the directory that contains the current project, or relative to a +directory listed in the environment variables ADA_PROJECT_PATH and +GPR_PROJECT_PATH. Path names are case sensitive if file names in the host +operating system are case sensitive. As a special case, the directory +separator can always be "/" even on Windows systems, so that project files +can be made portable across architectures. +The syntax of the environment variables ADA_PROJECT_PATH and +GPR_PROJECT_PATH is a list of directory names separated by colons on UNIX and +semicolons on Windows. + +A given project name can appear only once in a context clause. + +It is illegal for a project imported by a context clause to refer, directly +or indirectly, to the project in which this context clause appears (the +dependency graph cannot contain cycles), except when one of the with clauses +in the cycle is a **limited with**. + +.. code-block:: gpr + + with "other_project.gpr"; + project My_Project extends "extended.gpr" is + end My_Project; + +These dependencies form a **directed graph**, potentially cyclic when using +**limited with**. The subgraph reflecting the **extends** relations is a tree. + +A project's **immediate sources** are the source files directly defined by +that project, either implicitly by residing in the project source directories, +or explicitly through any of the source-related attributes. +More generally, a project's **sources** are the immediate sources of the +project together with the immediate sources (unless overridden) of any project +on which it depends directly or indirectly. + +A **project hierarchy** can be created, where projects are children of +other projects. The name of such a child project must be `Parent.Child`, +where `Parent` is the name of the parent project. In particular, this +makes all |with| clauses of the parent project automatically visible +in the child project. + +:: + + project ::= context_clause project_declaration + + context_clause ::= {with_clause} + with_clause ::= *with* path_name { , path_name } ; + path_name ::= string_literal + + project_declaration ::= simple_project_declaration | project_extension + simple_project_declaration ::= + project name is + {declarative_item} + end simple_name; + + +.. _Qualified_Projects: + +Qualified Projects +------------------ + +Before the reserved `project`, there may be one or two **qualifiers**, that +is identifiers or reserved words, to qualify the project. +The current list of qualifiers is: + +**abstract**: + Qualifies a project with no sources. + Such a project must either have no declaration of attributes `Source_Dirs`, + `Source_Files`, `Languages` or `Source_List_File`, or one of + `Source_Dirs`, `Source_Files`, or `Languages` must be declared + as empty. If it extends another project, the project it extends must also be a + qualified abstract project. + +**standard**: + A standard project is a non library project with sources. + This is the default (implicit) qualifier. + +**aggregate**: + A project whose sources are aggregated from other project files. + +**aggregate library**: + A library whose sources are aggregated from other project + or library project files. + +**library**: + A library project must declare both attributes + Library_Name` and `Library_Dir`. + +**configuration**: + A configuration project cannot be in a project tree. + It describes compilers and other tools to *gprbuild*. + + +.. _Declarations: + +Declarations +------------ + +Declarations introduce new entities that denote types, variables, attributes, +and packages. Some declarations can only appear immediately within a project +declaration. Others can appear within a project or within a package. + +:: + + declarative_item ::= simple_declarative_item + | typed_string_declaration + | package_declaration + + simple_declarative_item ::= variable_declaration + | typed_variable_declaration + | attribute_declaration + | case_construction + | empty_declaration + + empty_declaration ::= *null* ; + +An empty declaration is allowed anywhere a declaration is allowed. It has +no effect. + + +.. _Packages: + +Packages +-------- + +A project file may contain **packages**, that group attributes (typically +all the attributes that are used by one of the GNAT tools). + +A package with a given name may only appear once in a project file. +The following packages are currently supported in project files +(See :ref:`Attributes` for the list of attributes that each can contain). + +*Binder* + This package specifies characteristics useful when invoking the binder either + directly via the *gnat* driver or when using a builder such as + *gnatmake* or *gprbuild*. See :ref:`Main_Subprograms`. + +*Builder* + This package specifies the compilation options used when building an + executable or a library for a project. Most of the options should be + set in one of `Compiler`, `Binder` or `Linker` packages, + but there are some general options that should be defined in this + package. See :ref:`Main_Subprograms`, and :ref:`Executable_File_Names` in + particular. + +.. only:: PRO or GPL + + *Check* + This package specifies the options used when calling the checking tool + *gnatcheck* via the *gnat* driver. Its attribute + **Default_Switches** has the same semantics as for the package + `Builder`. The first string should always be `-rules` to specify + that all the other options belong to the `-rules` section of the + parameters to *gnatcheck*. + +*Clean* + This package specifies the options used when cleaning a project or a project + tree using the tools *gnatclean* or *gprclean*. + +*Compiler* + This package specifies the compilation options used by the compiler for + each languages. See :ref:`Tools_Options_in_Project_Files`. + +*Cross_Reference* + This package specifies the options used when calling the library tool + *gnatxref* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +.. only:: PRO or GPL + + *Eliminate* + This package specifies the options used when calling the tool + *gnatelim* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*Finder* + This package specifies the options used when calling the search tool + *gnatfind* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*Gnatls* + This package specifies the options to use when invoking *gnatls* + via the *gnat* driver. + +.. only:: PRO or GPL + + *Gnatstub* + This package specifies the options used when calling the tool + *gnatstub* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*IDE* + This package specifies the options used when starting an integrated + development environment, for instance *GPS* or *Gnatbench*. + +*Install* + This package specifies the options used when installing a project + with *gprinstall*. See :ref:`Installation`. + +*Linker* + This package specifies the options used by the linker. + See :ref:`Main_Subprograms`. + +.. only:: PRO or GPL + + *Metrics* + This package specifies the options used when calling the tool + *gnatmetric* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*Naming* + This package specifies the naming conventions that apply + to the source files in a project. In particular, these conventions are + used to automatically find all source files in the source directories, + or given a file name to find out its language for proper processing. + See :ref:`Naming_Schemes`. + + .. only: PRO or GPL + + *Pretty_Printer* + This package specifies the options used when calling the formatting tool + *gnatpp* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*Remote* + This package is used by *gprbuild* to describe how distributed + compilation should be done. + +*Stack* + This package specifies the options used when calling the tool + *gnatstack* via the *gnat* driver. Its attributes + **Default_Switches** and **Switches** have the same semantics as for the + package `Builder`. + +*Synchronize* + This package specifies the options used when calling the tool + *gnatsync* via the *gnat* driver. + +In its simplest form, a package may be empty: + +.. code-block:: gpr + + project Simple is + package Builder is + end Builder; + end Simple; + +A package may contain **attribute declarations**, +**variable declarations** and **case constructions**, as will be +described below. + +When there is ambiguity between a project name and a package name, +the name always designates the project. To avoid possible confusion, it is +always a good idea to avoid naming a project with one of the +names allowed for packages or any name that starts with `gnat`. + +A package can also be defined by a **renaming declaration**. The new package +renames a package declared in a different project file, and has the same +attributes as the package it renames. The name of the renamed package +must be the same as the name of the renaming package. The project must +contain a package declaration with this name, and the project +must appear in the context clause of the current project, or be its parent +project. It is not possible to add or override attributes to the renaming +project. If you need to do so, you should use an **extending declaration** +(see below). + +Packages that are renamed in other project files often come from project files +that have no sources: they are just used as templates. Any modification in the +template will be reflected automatically in all the project files that rename +a package from the template. This is a very common way to share settings +between projects. + +Finally, a package can also be defined by an **extending declaration**. This is +similar to a **renaming declaration**, except that it is possible to add or +override attributes. + +:: + + package_declaration ::= package_spec | package_renaming | package_extension + package_spec ::= + package simple_name is + {simple_declarative_item} + end package_identifier ; + package_renaming ::== + package simple_name renames simple_name.package_identifier ; + package_extension ::== + package simple_name extends simple_name.package_identifier is + {simple_declarative_item} + end package_identifier ; + + +.. _Expressions: + +Expressions +----------- + +An expression is any value that can be assigned to an attribute or a +variable. It is either a literal value, or a construct requiring runtime +computation by the project manager. In a project file, the computed value of +an expression is either a string or a list of strings. + +A string value is one of: + +* A literal string, for instance `"comm/my_proj.gpr"` +* The name of a variable that evaluates to a string (see :ref:`Variables`) +* The name of an attribute that evaluates to a string (see :ref:`Attributes`) +* An external reference (see :ref:`External_Values`) +* A concatenation of the above, as in `"prefix_" & Var`. + +A list of strings is one of the following: + +* A parenthesized comma-separated list of zero or more string expressions, for + instance `(File_Name, "gnat.adc", File_Name & ".orig")` or `()`. +* The name of a variable that evaluates to a list of strings +* The name of an attribute that evaluates to a list of strings +* A concatenation of a list of strings and a string (as defined above), for + instance `("A", "B") & "C"` +* A concatenation of two lists of strings + +The following is the grammar for expressions + +:: + + string_literal ::= "{string_element}" -- Same as Ada + string_expression ::= string_literal + | *variable_*name + | external_value + | attribute_reference + | ( string_expression { & string_expression } ) + string_list ::= ( string_expression { , string_expression } ) + | *string_variable*_name + | *string_*attribute_reference + term ::= string_expression | string_list + expression ::= term { & term } -- Concatenation + +Concatenation involves strings and list of strings. As soon as a list of +strings is involved, the result of the concatenation is a list of strings. The +following Ada declarations show the existing operators: + +.. code-block:: ada + + function "&" (X : String; Y : String) return String; + function "&" (X : String_List; Y : String) return String_List; + function "&" (X : String_List; Y : String_List) return String_List; + + +Here are some specific examples: + +.. code-block:: ada + + List := () & File_Name; -- One string in this list + List2 := List & (File_Name & ".orig"); -- Two strings + Big_List := List & Lists2; -- Three strings + Illegal := "gnat.adc" & List2; -- Illegal, must start with list + + +.. _External_Values: + +External Values +--------------- + +An external value is an expression whose value is obtained from the command +that invoked the processing of the current project file (typically a +*gnatmake* or *gprbuild* command). + +There are two kinds of external values, one that returns a single string, and +one that returns a string list. + +The syntax of a single string external value is:: + + external_value ::= *external* ( string_literal [, string_literal] ) + + +The first string_literal is the string to be used on the command line or +in the environment to specify the external value. The second string_literal, +if present, is the default to use if there is no specification for this +external value either on the command line or in the environment. + +Typically, the external value will either exist in the +environment variables +or be specified on the command line through the +:samp:`-X{vbl}={value}` switch. If both +are specified, then the command line value is used, so that a user can more +easily override the value. + +The function `external` always returns a string. It is an error if the +value was not found in the environment and no default was specified in the +call to `external`. + +An external reference may be part of a string expression or of a string +list expression, and can therefore appear in a variable declaration or +an attribute declaration. + +Most of the time, this construct is used to initialize typed variables, which +are then used in **case** constructions to control the value assigned to +attributes in various scenarios. Thus such variables are often called +**scenario variables**. + +The syntax for a string list external value is:: + + external_value ::= *external_as_list* ( string_literal , string_literal ) + + +The first string_literal is the string to be used on the command line or +in the environment to specify the external value. The second string_literal is +the separator between each component of the string list. + +If the external value does not exist in the environment or on the command line, +the result is an empty list. This is also the case, if the separator is an +empty string or if the external value is only one separator. + +Any separator at the beginning or at the end of the external value is +discarded. Then, if there is no separator in the external value, the result is +a string list with only one string. Otherwise, any string between the beginning +and the first separator, between two consecutive separators and between the +last separator and the end are components of the string list. + +:: + + *external_as_list* ("SWITCHES", ",") + +If the external value is "-O2,-g", +the result is ("-O2", "-g"). + +If the external value is ",-O2,-g,", +the result is also ("-O2", "-g"). + +if the external value is "-gnatv", +the result is ("-gnatv"). + +If the external value is ",,", the result is (""). + +If the external value is ",", the result is (), the empty string list. + + +.. _Typed_String_Declaration: + +Typed String Declaration +------------------------ + +A **type declaration** introduces a discrete set of string literals. +If a string variable is declared to have this type, its value +is restricted to the given set of literals. These are the only named +types in project files. A string type may only be declared at the project +level, not inside a package. + +:: + + typed_string_declaration ::= + *type* **_simple_name *is* ( string_literal {, string_literal} ); + +The string literals in the list are case sensitive and must all be different. +They may include any graphic characters allowed in Ada, including spaces. +Here is an example of a string type declaration: + +.. code-block:: ada + + type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS"); + +Variables of a string type are called **typed variables**; all other +variables are called **untyped variables**. Typed variables are +particularly useful in `case` constructions, to support conditional +attribute declarations. (See :ref:`Case_Constructions`). + +A string type may be referenced by its name if it has been declared in the same +project file, or by an expanded name whose prefix is the name of the project +in which it is declared. + + +.. _Variables: + +Variables +--------- + +**Variables** store values (strings or list of strings) and can appear +as part of an expression. The declaration of a variable creates the +variable and assigns the value of the expression to it. The name of the +variable is available immediately after the assignment symbol, if you +need to reuse its old value to compute the new value. Before the completion +of its first declaration, the value of a variable defaults to the empty +string (""). + +A **typed** variable can be used as part of a **case** expression to +compute the value, but it can only be declared once in the project file, +so that all case constructions see the same value for the variable. This +provides more consistency and makes the project easier to understand. +The syntax for its declaration is identical to the Ada syntax for an +object declaration. In effect, a typed variable acts as a constant. + +An **untyped** variable can be declared and overridden multiple times +within the same project. It is declared implicitly through an Ada +assignment. The first declaration establishes the kind of the variable +(string or list of strings) and successive declarations must respect +the initial kind. Assignments are executed in the order in which they +appear, so the new value replaces the old one and any subsequent reference +to the variable uses the new value. + +A variable may be declared at the project file level, or within a package. + +:: + + typed_variable_declaration ::= + **simple_name : **name := string_expression; + + variable_declaration ::= **simple_name := expression; + +Here are some examples of variable declarations: + +.. code-block:: gpr + + This_OS : OS := external ("OS"); -- a typed variable declaration + That_OS := "GNU/Linux"; -- an untyped variable declaration + + Name := "readme.txt"; + Save_Name := Name & ".saved"; + + Empty_List := (); + List_With_One_Element := ("-gnaty"); + List_With_Two_Elements := List_With_One_Element & "-gnatg"; + Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"); + +A **variable reference** may take several forms: + +* The simple variable name, for a variable in the current package (if any) + or in the current project +* An expanded name, whose prefix is a context name. + +A **context** may be one of the following: + +* The name of an existing package in the current project +* The name of an imported project of the current project +* The name of an ancestor project (i.e., a project extended by the current + project, either directly or indirectly) +* An expanded name whose prefix is an imported/parent project name, and + whose selector is a package name in that project. + + +.. _Case_Constructions: + +Case Constructions +------------------ + +A **case** construction is used in a project file to effect conditional +behavior. Through this construction, you can set the value of attributes +and variables depending on the value previously assigned to a typed +variable. + +All choices in a choice list must be distinct. Unlike Ada, the choice +lists of all alternatives do not need to include all values of the type. +An `others` choice must appear last in the list of alternatives. + +The syntax of a `case` construction is based on the Ada case construction +(although the `null` declaration for empty alternatives is optional). + +The case expression must be a string variable, either typed or not, whose value +is often given by an external reference (see :ref:`External_Values`). + +Each alternative starts with the reserved word `when`, either a list of +literal strings separated by the `"|"` character or the reserved word +`others`, and the `"=>"` token. +When the case expression is a typed string variable, each literal string must +belong to the string type that is the type of the case variable. +After each `=>`, there are zero or more declarations. The only +declarations allowed in a case construction are other case constructions, +attribute declarations and variable declarations. String type declarations and +package declarations are not allowed. Variable declarations are restricted to +variables that have already been declared before the case construction. + +:: + + case_construction ::= + *case* **name *is* {case_item} *end case* ; + + case_item ::= + *when* discrete_choice_list => + {case_declaration + | attribute_declaration + | variable_declaration + | empty_declaration} + + discrete_choice_list ::= string_literal {| string_literal} | *others* + +Here is a typical example, with a typed string variable: + +.. code-block:: gpr + + project MyProj is + type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS"); + OS : OS_Type := external ("OS", "GNU/Linux"); + + package Compiler is + case OS is + when "GNU/Linux" | "Unix" => + for Switches ("Ada") + use ("-gnath"); + when "NT" => + for Switches ("Ada") + use ("-gnatP"); + when others => + null; + end case; + end Compiler; + end MyProj; + + +.. _Attributes: + +Attributes +---------- + +A project (and its packages) may have **attributes** that define +the project's properties. Some attributes have values that are strings; +others have values that are string lists. + +:: + + attribute_declaration ::= + simple_attribute_declaration | indexed_attribute_declaration + + simple_attribute_declaration ::= *for* attribute_designator *use* expression ; + + indexed_attribute_declaration ::= + *for* **simple_name ( string_literal) *use* expression ; + + attribute_designator ::= + **simple_name + | **simple_name ( string_literal ) + +There are two categories of attributes: **simple attributes** +and **indexed attributes**. +Each simple attribute has a default value: the empty string (for string +attributes) and the empty list (for string list attributes). +An attribute declaration defines a new value for an attribute, and overrides +the previous value. The syntax of a simple attribute declaration is similar to +that of an attribute definition clause in Ada. + +Some attributes are indexed. These attributes are mappings whose +domain is a set of strings. They are declared one association +at a time, by specifying a point in the domain and the corresponding image +of the attribute. +Like untyped variables and simple attributes, indexed attributes +may be declared several times. Each declaration supplies a new value for the +attribute, and replaces the previous setting. + +Here are some examples of attribute declarations: + +.. code-block:: gpr + + -- simple attributes + for Object_Dir use "objects"; + for Source_Dirs use ("units", "test/drivers"); + + -- indexed attributes + for Body ("main") use "Main.ada"; + for Switches ("main.ada") + use ("-v", "-gnatv"); + for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g"; + + -- indexed attributes copy (from package Builder in project Default) + -- The package name must always be specified, even if it is the current + -- package. + for Default_Switches use Default.Builder'Default_Switches; + +Attributes references may appear anywhere in expressions, and are used +to retrieve the value previously assigned to the attribute. If an attribute +has not been set in a given package or project, its value defaults to the +empty string or the empty list, with some exceptions. + +:: + + attribute_reference ::= + attribute_prefix ' *_*simple_name [ (string_literal) ] + attribute_prefix ::= *project* + | **simple_name + | package_identifier + | **simple_name . package_identifier + +Examples are:: + + 'Object_Dir + Naming'Dot_Replacement + Imported_Project'Source_Dirs + Imported_Project.Naming'Casing + Builder'Default_Switches ("Ada") + +The exceptions to the empty defaults are: + +* Object_Dir: default is "." +* Exec_Dir: default is 'Object_Dir, that is the value of attribute + Object_Dir in the same project, declared or defaulted. +* Source_Dirs: default is (".") + +The prefix of an attribute may be: + +* `project` for an attribute of the current project +* The name of an existing package of the current project +* The name of an imported project +* The name of a parent project that is extended by the current project +* An expanded name whose prefix is imported/parent project name, + and whose selector is a package name + +In the following sections, all predefined attributes are succinctly described, +first the project level attributes, that is those attributes that are not in a +package, then the attributes in the different packages. + +It is possible for different tools to dynamically create new packages with +attributes, or new attributes in predefined packages. These attributes are +not documented here. + +The attributes under Configuration headings are usually found only in +configuration project files. + +The characteristics of each attribute are indicated as follows: + +* **Type of value** + + The value of an attribute may be a single string, indicated by the word + "single", or a string list, indicated by the word "list". + +* **Read-only** + + When the attribute is read-only, that is when it is not allowed to declare + the attribute, this is indicated by the words "read-only". + +* **Optional index** + + If it is allowed in the value of the attribute (both single and list) to have + an optional index, this is indicated by the words "optional index". + +* **Indexed attribute** + + When it is an indexed attribute, this is indicated by the word "indexed". + +* **Case-sensitivity of the index** + + For an indexed attribute, if the index is case-insensitive, this is indicated + by the words "case-insensitive index". + +* **File name index** + + For an indexed attribute, when the index is a file name, this is indicated by + the words "file name index". The index may or may not be case-sensitive, + depending on the platform. + +* **others allowed in index** + + For an indexed attribute, if it is allowed to use **others** as the index, + this is indicated by the words "others allowed". + + When **others** is used as the index of an indexed attribute, the value of + the attribute indexed by **others** is used when no other index would apply. + + +.. _Project_Level_Attributes: + +Project Level Attributes +^^^^^^^^^^^^^^^^^^^^^^^^ + + +* **General** + + * **Name**: single, read-only + + The name of the project. + + * **Project_Dir**: single, read-only + + The path name of the project directory. + + * **Main**: list, optional index + + The list of main sources for the executables. + + * **Languages**: list + + The list of languages of the sources of the project. + + * **Roots**: list, indexed, file name index + + The index is the file name of an executable source. Indicates the list of units + from the main project that need to be bound and linked with their closures + with the executable. The index is either a file name, a language name or "*". + The roots for an executable source are those in **Roots** with an index that + is the executable source file name, if declared. Otherwise, they are those in + **Roots** with an index that is the language name of the executable source, + if present. Otherwise, they are those in **Roots ("*")**, if declared. If none + of these three possibilities are declared, then there are no roots for the + executable source. + + * **Externally_Built**: single + + Indicates if the project is externally built. + Only case-insensitive values allowed are "true" and "false", the default. + +* **Directories** + + * **Object_Dir**: single + + Indicates the object directory for the project. + + * **Exec_Dir**: single + + Indicates the exec directory for the project, that is the directory where the + executables are. + + * **Source_Dirs**: list + + The list of source directories of the project. + + * **Inherit_Source_Path**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of language names. Indicates that + in the source search path of the index language the source directories of + the languages in the list should be included. + + Example: + + .. code-block:: gpr + + for Inherit_Source_Path ("C++") use ("C"); + + * **Exclude_Source_Dirs**: list + + The list of directories that are included in Source_Dirs but are not source + directories of the project. + + * **Ignore_Source_Sub_Dirs**: list + + Value is a list of simple names for subdirectories that are removed from the + list of source directories, including theur subdirectories. + +* **Source Files** + + * **Source_Files**: list + + Value is a list of source file simple names. + + * **Locally_Removed_Files**: list + + Obsolescent. Equivalent to Excluded_Source_Files. + + * **Excluded_Source_Files**: list + + Value is a list of simple file names that are not sources of the project. + Allows to remove sources that are inherited or found in the source directories + and that match the naming scheme. + + * **Source_List_File**: single + + Value is a text file name that contains a list of source file simple names, + one on each line. + + * **Excluded_Source_List_File**: single + + Value is a text file name that contains a list of file simple names that + are not sources of the project. + + * **Interfaces**: list + + Value is a list of file names that constitutes the interfaces of the project. + +* **Aggregate Projects** + + * **Project_Files**: list + + Value is the list of aggregated projects. + + * **Project_Path**: list + + Value is a list of directories that are added to the project search path when + looking for the aggregated projects. + + * **External**: single, indexed + + Index is the name of an external reference. Value is the value of the + external reference to be used when parsing the aggregated projects. + +* **Libraries** + + * **Library_Dir**: single + + Value is the name of the library directory. This attribute needs to be + declared for each library project. + + * **Library_Name**: single + + Value is the name of the library. This attribute needs to be declared or + inherited for each library project. + + * **Library_Kind**: single + + Specifies the kind of library: static library (archive) or shared library. + Case-insensitive values must be one of "static" for archives (the default) or + "dynamic" or "relocatable" for shared libraries. + + * **Library_Version**: single + + Value is the name of the library file. + + * **Library_Interface**: list + + Value is the list of unit names that constitutes the interfaces + of a Stand-Alone Library project. + + * **Library_Standalone**: single + + Specifies if a Stand-Alone Library (SAL) is encapsulated or not. + Only authorized case-insensitive values are "standard" for non encapsulated + SALs, "encapsulated" for encapsulated SALs or "no" for non SAL library project. + + * **Library_Encapsulated_Options**: list + + Value is a list of options that need to be used when linking an encapsulated + Stand-Alone Library. + + * **Library_Encapsulated_Supported**: single + + Indicates if encapsulated Stand-Alone Libraries are supported. Only + authorized case-insensitive values are "true" and "false" (the default). + + * **Library_Auto_Init**: single + + Indicates if a Stand-Alone Library is auto-initialized. Only authorized + case-insentive values are "true" and "false". + + * **Leading_Library_Options**: list + + Value is a list of options that are to be used at the beginning of + the command line when linking a shared library. + + * **Library_Options**: list + + Value is a list of options that are to be used when linking a shared library. + + * **Library_Rpath_Options**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of options for an invocation of the + compiler of the language. This invocation is done for a shared library project + with sources of the language. The output of the invocation is the path name + of a shared library file. The directory name is to be put in the run path + option switch when linking the shared library for the project. + + * **Library_Src_Dir**: single + + Value is the name of the directory where copies of the sources of the + interfaces of a Stand-Alone Library are to be copied. + + * **Library_ALI_Dir**: single + + Value is the name of the directory where the ALI files of the interfaces + of a Stand-Alone Library are to be copied. When this attribute is not declared, + the directory is the library directory. + + * **Library_gcc**: single + + Obsolescent attribute. Specify the linker driver used to link a shared library. + Use instead attribute Linker'Driver. + + * **Library_Symbol_File**: single + + Value is the name of the library symbol file. + + * **Library_Symbol_Policy**: single + + Indicates the symbol policy kind. Only authorized case-insensitive values are + "autonomous", "default", "compliant", "controlled" or "direct". + + * **Library_Reference_Symbol_File**: single + + Value is the name of the reference symbol file. + +* **Configuration - General** + + * **Default_Language**: single + + Value is the case-insensitive name of the language of a project when attribute + Languages is not specified. + + * **Run_Path_Option**: list + + Value is the list of switches to be used when specifying the run path option + in an executable. + + * **Run_Path_Origin**: single + + Value is the the string that may replace the path name of the executable + directory in the run path options. + + * **Separate_Run_Path_Options**: single + + Indicates if there may be several run path options specified when linking an + executable. Only authorized case-insensitive values are "true" or "false" (the + default). + + * **Toolchain_Version**: single, indexed, case-insensitive index + + Index is a language name. Specify the version of a toolchain for a language. + + * **Toolchain_Description**: single, indexed, case-insensitive index + + Obsolescent. No longer used. + + * **Object_Generated**: single, indexed, case-insensitive index + + Index is a language name. Indicates if invoking the compiler for a language + produces an object file. Only authorized case-insensitive values are "false" + and "true" (the default). + + * **Objects_Linked**: single, indexed, case-insensitive index + + Index is a language name. Indicates if the object files created by the compiler + for a language need to be linked in the executable. Only authorized + case-insensitive values are "false" and "true" (the default). + + * **Target**: single + + Value is the name of the target platform. Taken into account only in the main + project. + + * **Runtime**: single, indexed, case-insensitive index + + Index is a language name. Indicates the runtime directory that is to be used + when using the compiler of the language. Taken into account only in the main + project. + +* **Configuration - Libraries** + + * **Library_Builder**: single + + Value is the path name of the application that is to be used to build + libraries. Usually the path name of "gprlib". + + * **Library_Support**: single + + Indicates the level of support of libraries. Only authorized case-insensitive + values are "static_only", "full" or "none" (the default). + +* **Configuration - Archives** + + * **Archive_Builder**: list + + Value is the name of the application to be used to create a static library + (archive), followed by the options to be used. + + * **Archive_Builder_Append_Option**: list + + Value is the list of options to be used when invoking the archive builder + to add project files into an archive. + + * **Archive_Indexer**: list + + Value is the name of the archive indexer, followed by the required options. + + * **Archive_Suffix**: single + + Value is the extension of archives. When not declared, the extension is ".a". + + * **Library_Partial_Linker**: list + + Value is the name of the partial linker executable, followed by the required + options. + +* **Configuration - Shared Libraries** + + * **Shared_Library_Prefix**: single + + Value is the prefix in the name of shared library files. When not declared, + the prefix is "lib". + + * **Shared_Library_Suffix**: single + + Value is the the extension of the name of shared library files. When not + declared, the extension is ".so". + + * **Symbolic_Link_Supported**: single + + Indicates if symbolic links are supported on the platform. Only authorized + case-insensitive values are "true" and "false" (the default). + + * **Library_Major_Minor_Id_Supported**: single + + Indicates if major and minor ids for shared library names are supported on + the platform. Only authorized case-insensitive values are "true" and "false" + (the default). + + * **Library_Auto_Init_Supported**: single + + Indicates if auto-initialization of Stand-Alone Libraries is supported. Only + authorized case-insensitive values are "true" and "false" (the default). + + * **Shared_Library_Minimum_Switches**: list + + Value is the list of required switches when linking a shared library. + + * **Library_Version_Switches**: list + + Value is the list of switches to specify a internal name for a shared library. + + * **Library_Install_Name_Option**: single + + Value is the name of the option that needs to be used, concatenated with the + path name of the library file, when linking a shared library. + + * **Runtime_Library_Dir**: single, indexed, case-insensitive index + + Index is a language name. Value is the path name of the directory where the + runtime libraries are located. + + * **Runtime_Source_Dir**: single, indexed, case-insensitive index + + Index is a language name. Value is the path name of the directory where the + sources of runtime libraries are located. + + +.. _Package_Binder_Attributes: + +Package Binder Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **General** + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used when binding + code of the language, if there is no applicable attribute Switches. + + * **Switches**: list, optional index, indexed, + case-insensitive index, others allowed + + Index is either a language name or a source file name. Value is the list of + switches to be used when binding code. Index is either the source file name + of the executable to be bound or the language name of the code to be bound. + +* **Configuration - Binding** + + * **Driver**: single, indexed, case-insensitive index + + Index is a language name. Value is the name of the application to be used when + binding code of the language. + + * **Required_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of the required switches to be + used when binding code of the language. + + * **Prefix**: single, indexed, case-insensitive index + + Index is a language name. Value is a prefix to be used for the binder exchange + file name for the language. Used to have different binder exchange file names + when binding different languages. + + * **Objects_Path**: single,indexed, case-insensitive index + + Index is a language name. Value is the name of the environment variable that + contains the path for the object directories. + + * **Object_Path_File**: single,indexed, case-insensitive index + + Index is a language name. Value is the name of the environment variable. The + value of the environment variable is the path name of a text file that + contains the list of object directories. + + +.. _Package_Builder_Attributes: + +Package Builder Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of builder switches to be used when + building an executable of the language, if there is no applicable attribute + Switches. + +* **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is either a language name or a source file name. Value is the list of + builder switches to be used when building an executable. Index is either the + source file name of the executable to be built or its language name. + +* **Global_Compilation_Switches**: list, optional index, indexed, + case-insensitive index + + Index is either a language name or a source file name. Value is the list of + compilation switches to be used when building an executable. Index is either + the source file name of the executable to be built or its language name. + +* **Executable**: single, indexed, case-insensitive index + + Index is an executable source file name. Value is the simple file name of the + executable to be built. + +* **Executable_Suffix**: single + + Value is the extension of the file names of executable. When not specified, + the extension is the default extension of executables on the platform. + +* **Global_Configuration_Pragmas**: single + + Value is the file name of a configuration pragmas file that is specified to + the Ada compiler when compiling any Ada source in the project tree. + +* **Global_Config_File**: single, indexed, case-insensitive index + + Index is a language name. Value is the file name of a configuration file that + is specified to the compiler when compiling any source of the language in the + project tree. + + +.. only:: PRO and GPL + + .. _Package_Check_Attributes: + + Package Check Attributes + ^^^^^^^^^^^^^^^^^^^^^^^^ + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatcheck` for a source of the language, if there is no applicable + attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatcheck` for the source. + +.. _Package_Clean_Attributes: + +Package Clean Attributes +^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Switches**: list + + Value is a list of switches to be used by the cleaning application. + +* **Source_Artifact_Extensions**: list, indexed, case-insensitive index + + Index is a language names. Value is the list of extensions for file names + derived from object file names that need to be cleaned in the object + directory of the project. + +* **Object_Artifact_Extensions**: list, indexed, case-insensitive index + + Index is a language names. Value is the list of extensions for file names + derived from source file names that need to be cleaned in the object + directory of the project. + +* **Artifacts_In_Object_Dir**: single + + Value is a list of file names expressed as regular expressions that are to be + deleted by gprclean in the object directory of the project. + +* **Artifacts_In_Exec_Dir**: single + + Value is list of file names expressed as regular expressions that are to be + deleted by gprclean in the exec directory of the main project. + +.. _Package_Compiler_Attributes: + +Package Compiler Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **General** + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + the compiler for the language for a source of the project, if there is no + applicable attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name or a language name. Value is the list of switches + to be used when invoking the compiler for the source or for its language. + + * **Local_Configuration_Pragmas**: single + + Value is the file name of a configuration pragmas file that is specified to + the Ada compiler when compiling any Ada source in the project. + + * **Local_Config_File**: single, indexed, case-insensitive index + + Index is a language name. Value is the file name of a configuration file that + is specified to the compiler when compiling any source of the language in the + project. + +* **Configuration - Compiling** + + * **Driver**: single, indexed, case-insensitive index + + Index is a language name. Value is the name of the executable for the compiler + of the language. + + * **Language_Kind**: single, indexed, case-insensitive index + + Index is a language name. Indicates the kind of the language, either file based + or unit based. Only authorized case-insensitive values are "unit_based" and + "file_based" (the default). + + * **Dependency_Kind**: single, indexed, case-insensitive index + + Index is a language name. Indicates how the dependencies are handled for the + language. Only authorized case-insensitive values are "makefile", "ali_file", + "ali_closure" or "none" (the default). + + * **Required_Switches**: list, indexed, case-insensitive index + + Equivalent to attribute Leading_Required_Switches. + + * **Leading_Required_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of the minimum switches to be used + at the beginning of the command line when invoking the compiler for the + language. + + * **Trailing_Required_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of the minimum switches to be used + at the end of the command line when invoking the compiler for the language. + + * **PIC_Option**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used when + compiling a source of the language when the project is a shared library + project. + + * **Path_Syntax**: single, indexed, case-insensitive index + + Index is a language name. Value is the kind of path syntax to be used when + invoking the compiler for the language. Only authorized case-insensitive + values are "canonical" and "host" (the default). + + * **Source_File_Switches**: single, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used just before + the path name of the source to compile when invoking the compiler for a source + of the language. + + * **Object_File_Suffix**: single, indexed, case-insensitive index + + Index is a language name. Value is the extension of the object files created + by the compiler of the language. When not specified, the extension is the + default one for the platform. + + * **Object_File_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used by the + compiler of the language to specify the path name of the object file. When not + specified, the switch used is "-o". + + * **Multi_Unit_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used to compile + a unit in a multi unit source of the language. The index of the unit in the + source is concatenated with the last switches in the list. + + * **Multi_Unit_Object_Separator**: single, indexed, case-insensitive index + + Index is a language name. Value is the string to be used in the object file + name before the index of the unit, when compiling a unit in a multi unit source + of the language. + +* **Configuration - Mapping Files** + + * **Mapping_File_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used to specify + a mapping file when invoking the compiler for a source of the language. + + * **Mapping_Spec_Suffix**: single, indexed, case-insensitive index + + Index is a language name. Value is the suffix to be used in a mapping file + to indicate that the source is a spec. + + * **Mapping_Body_Suffix**: single, indexed, case-insensitive index + + Index is a language name. Value is the suffix to be used in a mapping file + to indicate that the source is a body. + +* **Configuration - Config Files** + + * **Config_File_Switches**: list: single, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to specify to the + compiler of the language a configuration file. + + * **Config_Body_File_Name**: single, indexed, case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration specific to a body of the language in a configuration + file. + + * **Config_Body_File_Name_Index**: single, indexed, case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration specific to the body a unit in a multi unit source of the + language in a configuration file. + + * **Config_Body_File_Name_Pattern**: single, indexed, + case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration for all bodies of the languages in a configuration file. + + * **Config_Spec_File_Name**: single, indexed, case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration specific to a spec of the language in a configuration + file. + + * **Config_Spec_File_Name_Index**: single, indexed, case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration specific to the spec a unit in a multi unit source of the + language in a configuration file. + + * **Config_Spec_File_Name_Pattern**: single, indexed, + case-insensitive index + + Index is a language name. Value is the template to be used to indicate a + configuration for all specs of the languages in a configuration file. + + * **Config_File_Unique**: single, indexed, case-insensitive index + + Index is a language name. Indicates if there should be only one configuration + file specified to the compiler of the language. Only authorized + case-insensitive values are "true" and "false" (the default). + +* **Configuration - Dependencies** + + * **Dependency_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to be used to specify + to the compiler the dependency file when the dependency kind of the language is + file based, and when Dependency_Driver is not specified for the language. + + * **Dependency_Driver**: list, indexed, case-insensitive index + + Index is a language name. Value is the name of the executable to be used to + create the dependency file for a source of the language, followed by the + required switches. + +* **Configuration - Search Paths** + + * **Include_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to specify to the + compiler of the language to indicate a directory to look for sources. + + * **Include_Path**: single, indexed, case-insensitive index + + Index is a language name. Value is the name of an environment variable that + contains the path of all the directories that the compiler of the language + may search for sources. + + * **Include_Path_File**: single, indexed, case-insensitive index + + Index is a language name. Value is the name of an environment variable the + value of which is the path name of a text file that contains the directories + that the compiler of the language may search for sources. + + * **Object_Path_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is the list of switches to specify to the + compiler of the language the name of a text file that contains the list of + object directories. When this attribute is not declared, the text file is + not created. + + +.. _Package_Cross_Reference_Attributes: + +Package Cross_Reference Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatxref` for a source of the language, if there is no applicable + attribute Switches. + +* **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatxref` for the source. + + +.. only:: PRO or GPL + + .. _Package_Eliminate_Attributes: + + Package Eliminate Attributes + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatelim` for a source of the language, if there is no applicable + attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatelim` for the source. + +.. _Package_Finder_Attributes: + +Package Finder Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatfind` for a source of the language, if there is no applicable + attribute Switches. + +* **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatfind` for the source. + + +.. _Package_gnatls_Attributes: + +Package gnatls Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Switches**: list + + Value is a list of switches to be used when invoking `gnatls`. + + +.. only:: PRO or GPL + + Package gnatstub Attributes + ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatstub` for a source of the language, if there is no applicable + attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatstub` for the source. + + +.. _Package_IDE_Attributes: + +Package IDE Attributes +^^^^^^^^^^^^^^^^^^^^^^ + +* **Default_Switches**: list, indexed + + Index is the name of an external tool that the GNAT Programming System (GPS) + is supporting. Value is a list of switches to use when invoking that tool. + +* **Remote_Host**: single + + Value is a string that designates the remote host in a cross-compilation + environment, to be used for remote compilation and debugging. This attribute + should not be specified when running on the local machine. + +* **Program_Host**: single + + Value is a string that specifies the name of IP address of the embedded target + in a cross-compilation environment, on which the program should execute. + +* **Communication_Protocol**: single + + Value is the name of the protocol to use to communicate with the target + in a cross-compilation environment, for example `"wtx"` or + `"vxworks"`. + +* **Compiler_Command**: single, indexed, case-insensitive index + + Index is a language Name. Value is a string that denotes the command to be + used to invoke the compiler. The value of `Compiler_Command ("Ada")` is + expected to be compatible with *gnatmake*, in particular in + the handling of switches. + +* **Debugger_Command**: single + + Value is a string that specifies the name of the debugger to be used, such as + gdb, powerpc-wrs-vxworks-gdb or gdb-4. + +* **gnatlist**: single + + Value is a string that specifies the name of the *gnatls* utility + to be used to retrieve information about the predefined path; for example, + `"gnatls"`, `"powerpc-wrs-vxworks-gnatls"`. + +* **VCS_Kind**: single + + Value is a string used to specify the Version Control System (VCS) to be used + for this project, for example "Subversion", "ClearCase". If the + value is set to "Auto", the IDE will try to detect the actual VCS used + on the list of supported ones. + +* **VCS_File_Check**: single + + Value is a string that specifies the command used by the VCS to check + the validity of a file, either when the user explicitly asks for a check, + or as a sanity check before doing the check-in. + +* **VCS_Log_Check**: single + + Value is a string that specifies the command used by the VCS to check + the validity of a log file. + +* **Documentation_Dir**: single + + Value is the directory used to generate the documentation of source code. + + +.. _Package_Install_Attributes: + +Package Install Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Artifacts**: list, indexed + + An array attribute to declare a set of files not part of the sources + to be installed. The array discriminant is the directory where the + file is to be installed. If a relative directory then Prefix (see + below) is prepended. + +* **Prefix**: single + + Value is the install destination directory. + +* **Sources_Subdir**: single + + Value is the sources directory or subdirectory of Prefix. + +* **Exec_Subdir**: single + + Value is the executables directory or subdirectory of Prefix. + +* **Lib_Subdir**: single + + Value is library directory or subdirectory of Prefix. + +* **Project_Subdir**: single + + Value is the project directory or subdirectory of Prefix. + +* **Active**: single + + Indicates that the project is to be installed or not. Case-insensitive value + "false" means that the project is not to be installed, all other values mean + that the project is to be installed. + +* **Mode**: single + + Value is the installation mode, it is either **dev** (default) or **usage**. + +* **Install_Name**: single + + Specify the name to use for recording the installation. The default is + the project name without the extension. + + +.. _Package_Linker_Attributes: + +Package Linker Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **General** + + * **Required_Switches**: list + + Value is a list of switches that are required when invoking the linker to link + an executable. + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches for the linker when + linking an executable for a main source of the language, when there is no + applicable Switches. + + * **Leading_Switches**: list, optional index, indexed, + case-insensitive index, others allowed + + Index is a source file name or a language name. Value is the list of switches + to be used at the beginning of the command line when invoking the linker to + build an executable for the source or for its language. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name or a language name. Value is the list of switches + to be used when invoking the linker to build an executable for the source or + for its language. + + * **Trailing_Switches**: list, optional index, indexed, + case-insensitive index, others allowed + + Index is a source file name or a language name. Value is the list of switches + to be used at the end of the command line when invoking the linker to + build an executable for the source or for its language. These switches may + override the Required_Switches. + + * **Linker_Options**: list + + Value is a list of switches/options that are to be added when linking an + executable from a project importing the current project directly or indirectly. + Linker_Options are not used when linking an executable from the current + project. + + * **Map_File_Option**: single + + Value is the switch to specify the map file name that the linker needs to + create. + +* **Configuration - Linking** + + * **Driver**: single + + Value is the name of the linker executable. + +* **Configuration - Response Files** + + * **Max_Command_Line_Length**: single + + Value is the maximum number of character in the command line when invoking + the linker to link an executable. + + * **Response_File_Format**: single + + Indicates the kind of response file to create when the length of the linking + command line is too large. Only authorized case-insensitive values are "none", + "gnu", "object_list", "gcc_gnu", "gcc_option_list" and "gcc_object_list". + + * **Response_File_Switches**: list + + Value is the list of switches to specify a response file to the linker. + + + +.. only PRO or GPL + + .. _Package_Metrics_Attribute: + + Package Metrics Attribute + ^^^^^^^^^^^^^^^^^^^^^^^^^ + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatmetric` for a source of the language, if there is no applicable + attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatmetric` for the source. + + +.. _Package_Naming_Attributes: + +Package Naming Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Specification_Suffix**: single, indexed, case-insensitive index + + Equivalent to attribute Spec_Suffix. + +* **Spec_Suffix**: single, indexed, case-insensitive index + + Index is a language name. Value is the extension of file names for specs of + the language. + +* **Implementation_Suffix**: single, indexed, case-insensitive index + + Equivalent to attribute Body_Suffix. + +* **Body_Suffix**: single, indexed, case-insensitive index + + Index is a language name. Value is the extension of file names for bodies of + the language. + +* **Separate_Suffix**: single + + Value is the extension of file names for subunits of Ada. + +* **Casing**: single + + Indicates the casing of sources of the Ada language. Only authorized + case-insensitive values are "lowercase", "uppercase" and "mixedcase". + +* **Dot_Replacement**: single + + Value is the string that replace the dot of unit names in the source file names + of the Ada language. + +* **Specification**: single, optional index, indexed, + case-insensitive index + + Equivalent to attribute Spec. + +* **Spec**: single, optional index, indexed, case-insensitive index + + Index is a unit name. Value is the file name of the spec of the unit. + +* **Implementation**: single, optional index, indexed, + case-insensitive index + + Equivalent to attribute Body. + +* **Body**: single, optional index, indexed, case-insensitive index + + Index is a unit name. Value is the file name of the body of the unit. + +* **Specification_Exceptions**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of specs for the language that do not + necessarily follow the naming scheme for the language and that may or may not + be found in the source directories of the project. + +* **Implementation_Exceptions**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of bodies for the language that do not + necessarily follow the naming scheme for the language and that may or may not + be found in the source directories of the project. + + +.. only:: PRO or GPL + + .. _Package_Pretty_Printer_Attributes: + + Package Pretty_Printer Attributes + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + * **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatpp` for a source of the language, if there is no applicable + attribute Switches. + + * **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatpp` for the source. + + +.. _Package_Remote_Attributes: + +Package Remote Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Included_Patterns**: list + + If this attribute is defined it sets the patterns to + synchronized from the master to the slaves. It is exclusive + with Excluded_Patterns, that is it is an error to define + both. + +* **Included_Artifact_Patterns**: list + + If this attribute is defined it sets the patterns of compilation + artifacts to synchronized from the slaves to the build master. + This attribute replace the default hard-coded patterns. + +* **Excluded_Patterns**: list + + Set of patterns to ignore when synchronizing sources from the build + master to the slaves. A set of predefined patterns are supported + (e.g. \*.o, \*.ali, \*.exe, etc.), this attributes make it possible to + add some more patterns. + +* **Root_Dir**: single + + Value is the root directory used by the slave machines. + + +.. _Package_Stack_Attributes: + +Package Stack Attributes +^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Switches**: list + + Value is the list of switches to be used when invoking `gnatstack`. + + +Package Synchronize Attributes +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +* **Default_Switches**: list, indexed, case-insensitive index + + Index is a language name. Value is a list of switches to be used when invoking + `gnatsync` for a source of the language, if there is no applicable + attribute Switches. + +* **Switches**: list, optional index, indexed, case-insensitive index, + others allowed + + Index is a source file name. Value is the list of switches to be used when + invoking `gnatsync` for the source. + + diff --git a/gcc/ada/doc/gnat_ugn/gnat_utility_programs.rst b/gcc/ada/doc/gnat_ugn/gnat_utility_programs.rst new file mode 100644 index 00000000000..f3af60c25ea --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/gnat_utility_programs.rst @@ -0,0 +1,4997 @@ +.. _GNAT_Utility_Programs: + +********************* +GNAT Utility Programs +********************* + +This chapter describes a number of utility programs: + +.. only:: PRO or GPL + + * :ref:`The_File_Cleanup_Utility_gnatclean` + * :ref:`The_GNAT_Library_Browser_gnatls` + * :ref:`The_Cross-Referencing_Tools_gnatxref_and_gnatfind` + * :ref:`The_Ada_to_HTML_Converter_gnathtml` + * :ref:`The_Ada-to-XML_Converter_gnat2xml` + * :ref:`The_Program_Property_Verifier_gnatcheck` + * :ref:`The_GNAT_Metrics_Tool_gnatmetric` + * :ref:`The_GNAT_Pretty-Printer_gnatpp` + * :ref:`The_Body_Stub_Generator_gnatstub` + * :ref:`The_Unit_Test_Generator_gnattest` + +.. only:: FSF + + * :ref:`The_File_Cleanup_Utility_gnatclean` + * :ref:`The_GNAT_Library_Browser_gnatls` + * :ref:`The_Cross-Referencing_Tools_gnatxref_and_gnatfind` + * :ref:`The_Ada_to_HTML_Converter_gnathtml` + +Other GNAT utilities are described elsewhere in this manual: + +* :ref:`Handling_Arbitrary_File_Naming_Conventions_with_gnatname` +* :ref:`File_Name_Krunching_with_gnatkr` +* :ref:`Renaming_Files_with_gnatchop` +* :ref:`Preprocessing_with_gnatprep` + + +.. _The_File_Cleanup_Utility_gnatclean: + +The File Cleanup Utility *gnatclean* +==================================== + +.. index:: File cleanup tool +.. index:: gnatclean + +`gnatclean` is a tool that allows the deletion of files produced by the +compiler, binder and linker, including ALI files, object files, tree files, +expanded source files, library files, interface copy source files, binder +generated files and executable files. + +.. _Running_gnatclean: + +Running `gnatclean` +------------------- + +The `gnatclean` command has the form: + + :: + + $ gnatclean switches `names` + +where `names` is a list of source file names. Suffixes :file:`.ads` and +:file:`adb` may be omitted. If a project file is specified using switch +:samp:`-P`, then `names` may be completely omitted. + +In normal mode, `gnatclean` delete the files produced by the compiler and, +if switch `-c` is not specified, by the binder and +the linker. In informative-only mode, specified by switch +`-n`, the list of files that would have been deleted in +normal mode is listed, but no file is actually deleted. + + +.. _Switches_for_gnatclean: + +Switches for `gnatclean` +------------------------ + +`gnatclean` recognizes the following switches: + +.. index:: --version (gnatclean) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + +.. index:: --help (gnatclean) + +:samp:`--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + +:samp:`--subdirs={subdir}` + Actual object directory of each project file is the subdirectory subdir of the + object directory specified or defaulted in the project file. + +:samp:`--unchecked-shared-lib-imports` + By default, shared library projects are not allowed to import static library + projects. When this switch is used on the command line, this restriction is + relaxed. + +.. index:: -c (gnatclean) + +:samp:`-c` + Only attempt to delete the files produced by the compiler, not those produced + by the binder or the linker. The files that are not to be deleted are library + files, interface copy files, binder generated files and executable files. + +.. index:: -D (gnatclean) + +:samp:`-D {dir}` + Indicate that ALI and object files should normally be found in directory `dir`. + +.. index:: -F (gnatclean) + +:samp:`-F` + When using project files, if some errors or warnings are detected during + parsing and verbose mode is not in effect (no use of switch + -v), then error lines start with the full path name of the project + file, rather than its simple file name. + +.. index:: -h (gnatclean) + +:samp:`-h` + Output a message explaining the usage of `gnatclean`. + +.. index:: -n (gnatclean) + +:samp:`-n` + Informative-only mode. Do not delete any files. Output the list of the files + that would have been deleted if this switch was not specified. + +.. index:: -P (gnatclean) + +:samp:`-P{project}` + Use project file `project`. Only one such switch can be used. + When cleaning a project file, the files produced by the compilation of the + immediate sources or inherited sources of the project files are to be + deleted. This is not depending on the presence or not of executable names + on the command line. + +.. index:: -q (gnatclean) + +:samp:`-q` + Quiet output. If there are no errors, do not output anything, except in + verbose mode (switch -v) or in informative-only mode + (switch -n). + +.. index:: -r (gnatclean) + +:samp:`-r` + When a project file is specified (using switch -P), + clean all imported and extended project files, recursively. If this switch + is not specified, only the files related to the main project file are to be + deleted. This switch has no effect if no project file is specified. + +.. index:: -v (gnatclean) + +:samp:`-v` + Verbose mode. + +.. index:: -vP (gnatclean) + +:samp:`-vP{x}` + Indicates the verbosity of the parsing of GNAT project files. + :ref:`Switches_Related_to_Project_Files`. + +.. index:: -X (gnatclean) + +:samp:`-X{name}={value}` + Indicates that external variable `name` has the value `value`. + The Project Manager will use this value for occurrences of + `external(name)` when parsing the project file. + :ref:`Switches_Related_to_Project_Files`. + +.. index:: -aO (gnatclean) + +:samp:`-aO{dir}` + When searching for ALI and object files, look in directory `dir`. + +.. index:: -I (gnatclean) + +:samp:`-I{dir}` + Equivalent to :samp:`-aO{dir}`. + +.. index:: -I- (gnatclean) + +.. index:: Source files, suppressing search + +:samp:`-I-` + Do not look for ALI or object files in the directory + where `gnatclean` was invoked. + + + +.. _The_GNAT_Library_Browser_gnatls: + +The GNAT Library Browser `gnatls` +================================= + +.. index:: Library browser +.. index: ! gnatls + +`gnatls` is a tool that outputs information about compiled +units. It gives the relationship between objects, unit names and source +files. It can also be used to check the source dependencies of a unit +as well as various characteristics. + +Note: to invoke `gnatls` with a project file, use the `gnat` +driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + +.. _Running_gnatls: + +Running `gnatls` +---------------- + +The `gnatls` command has the form + + :: + + $ gnatls switches `object_or_ali_file` + +The main argument is the list of object or :file:`ali` files +(see :ref:`The_Ada_Library_Information_Files`) +for which information is requested. + +In normal mode, without additional option, `gnatls` produces a +four-column listing. Each line represents information for a specific +object. The first column gives the full path of the object, the second +column gives the name of the principal unit in this object, the third +column gives the status of the source and the fourth column gives the +full path of the source representing this unit. +Here is a simple example of use: + + + :: + + $ gnatls *.o + ./demo1.o demo1 DIF demo1.adb + ./demo2.o demo2 OK demo2.adb + ./hello.o h1 OK hello.adb + ./instr-child.o instr.child MOK instr-child.adb + ./instr.o instr OK instr.adb + ./tef.o tef DIF tef.adb + ./text_io_example.o text_io_example OK text_io_example.adb + ./tgef.o tgef DIF tgef.adb + +The first line can be interpreted as follows: the main unit which is +contained in +object file :file:`demo1.o` is demo1, whose main source is in +:file:`demo1.adb`. Furthermore, the version of the source used for the +compilation of demo1 has been modified (DIF). Each source file has a status +qualifier which can be: + +*OK (unchanged)* + The version of the source file used for the compilation of the + specified unit corresponds exactly to the actual source file. + +*MOK (slightly modified)* + The version of the source file used for the compilation of the + specified unit differs from the actual source file but not enough to + require recompilation. If you use gnatmake with the qualifier + *-m (minimal recompilation)*, a file marked + MOK will not be recompiled. + +*DIF (modified)* + No version of the source found on the path corresponds to the source + used to build this object. + +*??? (file not found)* + No source file was found for this unit. + +*HID (hidden, unchanged version not first on PATH)* + The version of the source that corresponds exactly to the source used + for compilation has been found on the path but it is hidden by another + version of the same source that has been modified. + + +.. _Switches_for_gnatls: + +Switches for `gnatls` +--------------------- + +`gnatls` recognizes the following switches: + + +.. index:: --version (gnatls) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatls) + +:samp:`*--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + + +.. index:: -a (gnatls) + +:samp:`-a` + Consider all units, including those of the predefined Ada library. + Especially useful with *-d*. + + +.. index:: -d (gnatls) + +:samp:`-d` + List sources from which specified units depend on. + + +.. index:: -h (gnatls) + +:samp:`-h` + Output the list of options. + + +.. index:: -o (gnatls) + +:samp:`-o` + Only output information about object files. + + +.. index:: -s (gnatls) + +:samp:`-s` + Only output information about source files. + + +.. index:: -u (gnatls) + +:samp:`-u` + Only output information about compilation units. + + +.. index:: -files (gnatls) + +:samp:`-files={file}` + Take as arguments the files listed in text file `file`. + Text file `file` may contain empty lines that are ignored. + Each nonempty line should contain the name of an existing file. + Several such switches may be specified simultaneously. + + +.. index:: -aO (gnatls) + +.. index:: -aI (gnatls) + +.. index:: -I (gnatls) + +.. index:: -I- (gnatls) + +:samp:`-aO{dir}`, :samp:`-aI{dir}`, :samp:`-I{dir}`, :samp:`-I-`, :samp:`-nostdinc` + Source path manipulation. Same meaning as the equivalent *gnatmake* + flags (:ref:`Switches_for_gnatmake`). + + +.. index:: -aP (gnatls) + +:samp:`-aP{dir}` + Add `dir` at the beginning of the project search dir. + + +.. index:: --RTS (gnatls) + +:samp:`--RTS={rts-path}`` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + +.. index:: -v (gnatls) + +:samp:`-v` + Verbose mode. Output the complete source, object and project paths. Do not use + the default column layout but instead use long format giving as much as + information possible on each requested units, including special + characteristics such as: + + * *Preelaborable*: The unit is preelaborable in the Ada sense. + + * *No_Elab_Code*: No elaboration code has been produced by the compiler for this unit. + + * *Pure*: The unit is pure in the Ada sense. + + * *Elaborate_Body*: The unit contains a pragma Elaborate_Body. + + * *Remote_Types*: The unit contains a pragma Remote_Types. + + * *Shared_Passive*: The unit contains a pragma Shared_Passive. + + * *Predefined*: This unit is part of the predefined environment and cannot be modified + by the user. + + * *Remote_Call_Interface*: The unit contains a pragma Remote_Call_Interface. + + +.. _Example_of_gnatls_Usage: + +Example of `gnatls` Usage +------------------------- + +Example of using the verbose switch. Note how the source and +object paths are affected by the -I switch. + + :: + + $ gnatls -v -I.. demo1.o + + GNATLS 5.03w (20041123-34) + Copyright 1997-2004 Free Software Foundation, Inc. + + Source Search Path: + + ../ + /home/comar/local/adainclude/ + + Object Search Path: + + ../ + /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/ + + Project Search Path: + + /home/comar/local/lib/gnat/ + + ./demo1.o + Unit => + Name => demo1 + Kind => subprogram body + Flags => No_Elab_Code + Source => demo1.adb modified + +The following is an example of use of the dependency list. +Note the use of the -s switch +which gives a straight list of source files. This can be useful for +building specialized scripts. + + :: + + $ gnatls -d demo2.o + ./demo2.o demo2 OK demo2.adb + OK gen_list.ads + OK gen_list.adb + OK instr.ads + OK instr-child.ads + + $ gnatls -d -s -a demo1.o + demo1.adb + /home/comar/local/adainclude/ada.ads + /home/comar/local/adainclude/a-finali.ads + /home/comar/local/adainclude/a-filico.ads + /home/comar/local/adainclude/a-stream.ads + /home/comar/local/adainclude/a-tags.ads + gen_list.ads + gen_list.adb + /home/comar/local/adainclude/gnat.ads + /home/comar/local/adainclude/g-io.ads + instr.ads + /home/comar/local/adainclude/system.ads + /home/comar/local/adainclude/s-exctab.ads + /home/comar/local/adainclude/s-finimp.ads + /home/comar/local/adainclude/s-finroo.ads + /home/comar/local/adainclude/s-secsta.ads + /home/comar/local/adainclude/s-stalib.ads + /home/comar/local/adainclude/s-stoele.ads + /home/comar/local/adainclude/s-stratt.ads + /home/comar/local/adainclude/s-tasoli.ads + /home/comar/local/adainclude/s-unstyp.ads + /home/comar/local/adainclude/unchconv.ads + + +.. _The_Cross-Referencing_Tools_gnatxref_and_gnatfind: + +The Cross-Referencing Tools `gnatxref` and `gnatfind` +===================================================== + +.. index:: ! gnatxref +.. index:: ! gnatfind + +The compiler generates cross-referencing information (unless +you set the :samp:`-gnatx` switch), which are saved in the :file:`.ali` files. +This information indicates where in the source each entity is declared and +referenced. Note that entities in package Standard are not included, but +entities in all other predefined units are included in the output. + +Before using any of these two tools, you need to compile successfully your +application, so that GNAT gets a chance to generate the cross-referencing +information. + +The two tools `gnatxref` and `gnatfind` take advantage of this +information to provide the user with the capability to easily locate the +declaration and references to an entity. These tools are quite similar, +the difference being that `gnatfind` is intended for locating +definitions and/or references to a specified entity or entities, whereas +`gnatxref` is oriented to generating a full report of all +cross-references. + +To use these tools, you must not compile your application using the +*-gnatx* switch on the *gnatmake* command line +(see :ref:`The_GNAT_Make_Program_gnatmake`). Otherwise, cross-referencing +information will not be generated. + +Note: to invoke `gnatxref` or `gnatfind` with a project file, +use the `gnat` driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + +.. _gnatxref_Switches: + +`gnatxref` Switches +------------------- + +The command invocation for `gnatxref` is: + + :: + + $ gnatxref [`switches`] `sourcefile1` [`sourcefile2` ...] + +where + +*sourcefile1* [, *sourcefile2* ...] + identify the source files for which a report is to be generated. The + 'with'ed units will be processed too. You must provide at least one file. + + These file names are considered to be regular expressions, so for instance + specifying :file:`source\*.adb` is the same as giving every file in the current + directory whose name starts with :file:`source` and whose extension is + :file:`adb`. + + You shouldn't specify any directory name, just base names. *gnatxref* + and *gnatfind* will be able to locate these files by themselves using + the source path. If you specify directories, no result is produced. + +The following switches are available for *gnatxref*: + + +.. index:: --version (gnatxref) + +:samp:`-version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatxref) + +:samp:`-help` + If *--version* was not used, display usage, then exit disregarding + all other options. + + +.. index:: -a (gnatxref) + +:samp:`a` + If this switch is present, `gnatfind` and `gnatxref` will parse + the read-only files found in the library search path. Otherwise, these files + will be ignored. This option can be used to protect Gnat sources or your own + libraries from being parsed, thus making `gnatfind` and `gnatxref` + much faster, and their output much smaller. Read-only here refers to access + or permissions status in the file system for the current user. + + +.. index:: -aIDIR (gnatxref) + +:samp:`aI{DIR}` + When looking for source files also look in directory DIR. The order in which + source file search is undertaken is the same as for *gnatmake*. + + +.. index:: -aODIR (gnatxref) + +:samp:`aO{DIR}` + When searching for library and object files, look in directory + DIR. The order in which library files are searched is the same as for + *gnatmake*. + + +.. index:: -nostdinc (gnatxref) + +:samp:`nostdinc` + Do not look for sources in the system default directory. + + +.. index:: -nostdlib (gnatxref) + +:samp:`nostdlib` + Do not look for library files in the system default directory. + + +.. index:: --ext (gnatxref) + +:samp:`-ext={extension}` + Specify an alternate ali file extension. The default is `ali` and other + extensions (e.g. `gli` for C/C++ sources when using *-fdump-xref*) + may be specified via this switch. Note that if this switch overrides the + default, which means that only the new extension will be considered. + + +.. index:: --RTS (gnatxref) + +:samp:`-RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + +.. index:: -d (gnatxref) + +:samp:`d` + If this switch is set `gnatxref` will output the parent type + reference for each matching derived types. + + +.. index:: -f (gnatxref) + +:samp:`f` + If this switch is set, the output file names will be preceded by their + directory (if the file was found in the search path). If this switch is + not set, the directory will not be printed. + + +.. index:: -g (gnatxref) + +:samp:`g` + If this switch is set, information is output only for library-level + entities, ignoring local entities. The use of this switch may accelerate + `gnatfind` and `gnatxref`. + + +.. index:: -IDIR (gnatxref) + +:samp:`I{DIR}` + Equivalent to :samp:`-aODIR -aIDIR`. + + +.. index:: -pFILE (gnatxref) + +:samp:`p{FILE}` + Specify a project file to use :ref:`GNAT_Project_Manager`. + If you need to use the :file:`.gpr` + project files, you should use gnatxref through the GNAT driver + (*gnat xref -Pproject*). + + By default, `gnatxref` and `gnatfind` will try to locate a + project file in the current directory. + + If a project file is either specified or found by the tools, then the content + of the source directory and object directory lines are added as if they + had been specified respectively by :samp:`-aI` + and :samp:`-aO`. + +:samp:`u` + Output only unused symbols. This may be really useful if you give your + main compilation unit on the command line, as `gnatxref` will then + display every unused entity and 'with'ed package. + + +:samp:`v` + Instead of producing the default output, `gnatxref` will generate a + :file:`tags` file that can be used by vi. For examples how to use this + feature, see :ref:`Examples_of_gnatxref_Usage`. The tags file is output + to the standard output, thus you will have to redirect it to a file. + +All these switches may be in any order on the command line, and may even +appear after the file names. They need not be separated by spaces, thus +you can say :samp:`gnatxref -ag` instead of :samp:`gnatxref -a -g`. + +.. _gnatfind_Switches: + +`gnatfind` Switches +------------------- + +The command invocation for `gnatfind` is: + + :: + + $ gnatfind [`switches`] `pattern`[:`sourcefile`[:`line`[:`column`]]] + [`file1` `file2` ...] + +with the following iterpretation of the command arguments: + +*pattern* + An entity will be output only if it matches the regular expression found + in `pattern`, see :ref:`Regular_Expressions_in_gnatfind_and_gnatxref`. + + Omitting the pattern is equivalent to specifying ``*``, which + will match any entity. Note that if you do not provide a pattern, you + have to provide both a sourcefile and a line. + + Entity names are given in Latin-1, with uppercase/lowercase equivalence + for matching purposes. At the current time there is no support for + 8-bit codes other than Latin-1, or for wide characters in identifiers. + +*sourcefile* + `gnatfind` will look for references, bodies or declarations + of symbols referenced in :file:`sourcefile`, at line `line` + and column `column`. See :ref:`Examples_of_gnatfind_Usage` + for syntax examples. + +*line* + A decimal integer identifying the line number containing + the reference to the entity (or entities) to be located. + + +*column* + A decimal integer identifying the exact location on the + line of the first character of the identifier for the + entity reference. Columns are numbered from 1. + + +*file1 file2 ...* + The search will be restricted to these source files. If none are given, then + the search will be conducted for every library file in the search path. + These files must appear only after the pattern or sourcefile. + + These file names are considered to be regular expressions, so for instance + specifying :file:`source\*.adb` is the same as giving every file in the current + directory whose name starts with :file:`source` and whose extension is + :file:`adb`. + + The location of the spec of the entity will always be displayed, even if it + isn't in one of :file:`file1`, :file:`file2`, ... The + occurrences of the entity in the separate units of the ones given on the + command line will also be displayed. + + Note that if you specify at least one file in this part, `gnatfind` may + sometimes not be able to find the body of the subprograms. + + +At least one of 'sourcefile' or 'pattern' has to be present on +the command line. + +The following switches are available: + +.. index:: --version (gnatfind) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + +.. index:: --help (gnatfind) + +:samp:`-help` + If *--version* was not used, display usage, then exit disregarding + all other options. + + +.. index:: -a (gnatfind) + +:samp:`a` + If this switch is present, `gnatfind` and `gnatxref` will parse + the read-only files found in the library search path. Otherwise, these files + will be ignored. This option can be used to protect Gnat sources or your own + libraries from being parsed, thus making `gnatfind` and `gnatxref` + much faster, and their output much smaller. Read-only here refers to access + or permission status in the file system for the current user. + + +.. index:: -aIDIR (gnatfind) + +:samp:`aI{DIR}` + When looking for source files also look in directory DIR. The order in which + source file search is undertaken is the same as for *gnatmake*. + + +.. index:: -aODIR (gnatfind) + +:samp:`aO{DIR}` + When searching for library and object files, look in directory + DIR. The order in which library files are searched is the same as for + *gnatmake*. + + +.. index:: -nostdinc (gnatfind) + +:samp:`nostdinc` + Do not look for sources in the system default directory. + + +.. index:: -nostdlib (gnatfind) + +:samp:`nostdlib` + Do not look for library files in the system default directory. + + +.. index:: --ext (gnatfind) + +:samp:`-ext={extension}` + Specify an alternate ali file extension. The default is `ali` and other + extensions (e.g. `gli` for C/C++ sources when using *-fdump-xref*) + may be specified via this switch. Note that if this switch overrides the + default, which means that only the new extension will be considered. + + +.. index:: --RTS (gnatfind) + +:samp:`-RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + +.. index:: -d (gnatfind) + +:samp:`d` + If this switch is set, then `gnatfind` will output the parent type + reference for each matching derived types. + + +.. index:: -e (gnatfind) + +:samp:`e` + By default, `gnatfind` accept the simple regular expression set for + `pattern`. If this switch is set, then the pattern will be + considered as full Unix-style regular expression. + + +.. index:: -f (gnatfind) + +:samp:`f` + If this switch is set, the output file names will be preceded by their + directory (if the file was found in the search path). If this switch is + not set, the directory will not be printed. + + +.. index:: -g (gnatfind) + +:samp:`g` + If this switch is set, information is output only for library-level + entities, ignoring local entities. The use of this switch may accelerate + `gnatfind` and `gnatxref`. + + +.. index:: -IDIR (gnatfind) + +:samp:`I{DIR}` + Equivalent to :samp:`-aODIR -aIDIR`. + + +.. index:: -pFILE (gnatfind) + +:samp:`p{FILE}` + Specify a project file (:ref:`GNAT_Project_Manager`) to use. + By default, `gnatxref` and `gnatfind` will try to locate a + project file in the current directory. + + If a project file is either specified or found by the tools, then the content + of the source directory and object directory lines are added as if they + had been specified respectively by :samp:`-aI` and + :samp:`-aO`. + + +.. index:: -r (gnatfind) + +:samp:`r` + By default, `gnatfind` will output only the information about the + declaration, body or type completion of the entities. If this switch is + set, the `gnatfind` will locate every reference to the entities in + the files specified on the command line (or in every file in the search + path if no file is given on the command line). + + +.. index:: -s (gnatfind) + +:samp:`s` + If this switch is set, then `gnatfind` will output the content + of the Ada source file lines were the entity was found. + + +.. index:: -t (gnatfind) + +:samp:`t` + If this switch is set, then `gnatfind` will output the type hierarchy for + the specified type. It act like -d option but recursively from parent + type to parent type. When this switch is set it is not possible to + specify more than one file. + + +All these switches may be in any order on the command line, and may even +appear after the file names. They need not be separated by spaces, thus +you can say :samp:`gnatxref -ag` instead of +:samp:`gnatxref -a -g`. + +As stated previously, gnatfind will search in every directory in the +search path. You can force it to look only in the current directory if +you specify `*` at the end of the command line. + +.. _Project_Files_for_gnatxref_and_gnatfind: + +Project Files for *gnatxref* and *gnatfind* +------------------------------------------- + +Project files allow a programmer to specify how to compile its +application, where to find sources, etc. These files are used +primarily by GPS, but they can also be used +by the two tools `gnatxref` and `gnatfind`. + +A project file name must end with :file:`.gpr`. If a single one is +present in the current directory, then `gnatxref` and `gnatfind` will +extract the information from it. If multiple project files are found, none of +them is read, and you have to use the :samp:`-p` switch to specify the one +you want to use. + +The following lines can be included, even though most of them have default +values which can be used in most cases. +The lines can be entered in any order in the file. +Except for :file:`src_dir` and :file:`obj_dir`, you can only have one instance of +each line. If you have multiple instances, only the last one is taken into +account. + +* *src_dir=DIR* + [default: `"./"`]. + Specifies a directory where to look for source files. Multiple `src_dir` + lines can be specified and they will be searched in the order they + are specified. + + +* *obj_dir=DIR* + [default: `"./"`]. + Specifies a directory where to look for object and library files. Multiple + `obj_dir` lines can be specified, and they will be searched in the order + they are specified + + +* *comp_opt=SWITCHES* + [default: `""`]. + Creates a variable which can be referred to subsequently by using + the `${comp_opt}` notation. This is intended to store the default + switches given to *gnatmake* and *gcc*. + + +* *bind_opt=SWITCHES* + [default: `""`]. + Creates a variable which can be referred to subsequently by using + the :samp:`${bind_opt}` notation. This is intended to store the default + switches given to *gnatbind*. + + +* *link_opt=SWITCHES* + [default: `""`]. + Creates a variable which can be referred to subsequently by using + the :samp:`${link_opt}` notation. This is intended to store the default + switches given to *gnatlink*. + + +* *main=EXECUTABLE* + [default: `""`]. + Specifies the name of the executable for the application. This variable can + be referred to in the following lines by using the :samp:`{${main}` notation. + + +* *comp_cmd=COMMAND* + [default: `"gcc -c -I${src_dir} -g -gnatq"`]. + Specifies the command used to compile a single file in the application. + + +* *make_cmd=COMMAND* + [default: `"gnatmake ${main} -aI${src_dir} + -aO${obj_dir} -g -gnatq -cargs ${comp_opt} + -bargs ${bind_opt} -largs ${link_opt}"`]. + Specifies the command used to recompile the whole application. + + +* *run_cmd=COMMAND* + [default: `"${main}"`]. + Specifies the command used to run the application. + + +* *debug_cmd=COMMAND* + [default: `"gdb ${main}"`]. + Specifies the command used to debug the application + + +*gnatxref* and *gnatfind* only take into account the +`src_dir` and `obj_dir` lines, and ignore the others. + + +.. _Regular_Expressions_in_gnatfind_and_gnatxref: + +Regular Expressions in `gnatfind` and `gnatxref` +------------------------------------------------ + +As specified in the section about *gnatfind*, the pattern can be a +regular expression. Two kinds of regular expressions +are recognized: + +* *Globbing pattern* + These are the most common regular expression. They are the same as are + generally used in a Unix shell command line, or in a DOS session. + + Here is a more formal grammar: + + :: + + regexp ::= term + term ::= elmt -- matches elmt + term ::= elmt elmt -- concatenation (elmt then elmt) + term ::= * -- any string of 0 or more characters + term ::= ? -- matches any character + term ::= [char {char}] -- matches any character listed + term ::= [char - char] -- matches any character in range + +* *Full regular expression* + The second set of regular expressions is much more powerful. This is the + type of regular expressions recognized by utilities such as :samp:`grep`. + + The following is the form of a regular expression, expressed in same BNF + style as is found in the Ada Reference Manual: + + :: + + regexp ::= term {| term} -- alternation (term or term ...) + + term ::= item {item} -- concatenation (item then item) + + item ::= elmt -- match elmt + item ::= elmt * -- zero or more elmt's + item ::= elmt + -- one or more elmt's + item ::= elmt ? -- matches elmt or nothing + + elmt ::= nschar -- matches given character + elmt ::= [nschar {nschar}] -- matches any character listed + elmt ::= [^ nschar {nschar}] -- matches any character not listed + elmt ::= [char - char] -- matches chars in given range + elmt ::= \\ char -- matches given character + elmt ::= . -- matches any single character + elmt ::= ( regexp ) -- parens used for grouping + + char ::= any character, including special characters + nschar ::= any character except ()[].*+?^ + + Here are a few examples: + + ``abcde|fghi`` + will match any of the two strings :samp:`abcde` and :samp:`fghi`, + + ``abc*d`` + will match any string like ``abd``, ``abcd``, ``abccd``, + ``abcccd``, and so on, + + ``[a-z]+`` + will match any string which has only lowercase characters in it (and at + least one character. + + +.. _Examples_of_gnatxref_Usage: + +Examples of `gnatxref` Usage +---------------------------- + +General Usage +^^^^^^^^^^^^^ + +For the following examples, we will consider the following units: + + .. code-block:: ada + + main.ads: + 1: with Bar; + 2: package Main is + 3: procedure Foo (B : in Integer); + 4: C : Integer; + 5: private + 6: D : Integer; + 7: end Main; + + main.adb: + 1: package body Main is + 2: procedure Foo (B : in Integer) is + 3: begin + 4: C := B; + 5: D := B; + 6: Bar.Print (B); + 7: Bar.Print (C); + 8: end Foo; + 9: end Main; + + bar.ads: + 1: package Bar is + 2: procedure Print (B : Integer); + 3: end bar; + +The first thing to do is to recompile your application (for instance, in +that case just by doing a ``gnatmake main``, so that GNAT generates +the cross-referencing information. +You can then issue any of the following commands: + + * ``gnatxref main.adb`` + `gnatxref` generates cross-reference information for main.adb + and every unit 'with'ed by main.adb. + + The output would be: + + :: + + B Type: Integer + Decl: bar.ads 2:22 + B Type: Integer + Decl: main.ads 3:20 + Body: main.adb 2:20 + Ref: main.adb 4:13 5:13 6:19 + Bar Type: Unit + Decl: bar.ads 1:9 + Ref: main.adb 6:8 7:8 + main.ads 1:6 + C Type: Integer + Decl: main.ads 4:5 + Modi: main.adb 4:8 + Ref: main.adb 7:19 + D Type: Integer + Decl: main.ads 6:5 + Modi: main.adb 5:8 + Foo Type: Unit + Decl: main.ads 3:15 + Body: main.adb 2:15 + Main Type: Unit + Decl: main.ads 2:9 + Body: main.adb 1:14 + Print Type: Unit + Decl: bar.ads 2:15 + Ref: main.adb 6:12 7:12 + + + This shows that the entity `Main` is declared in main.ads, line 2, column 9, + its body is in main.adb, line 1, column 14 and is not referenced any where. + + The entity `Print` is declared in bar.ads, line 2, column 15 and it + is referenced in main.adb, line 6 column 12 and line 7 column 12. + + + * ``gnatxref package1.adb package2.ads`` + `gnatxref` will generates cross-reference information for + package1.adb, package2.ads and any other package 'with'ed by any + of these. + + +Using gnatxref with vi +^^^^^^^^^^^^^^^^^^^^^^ + +`gnatxref` can generate a tags file output, which can be used +directly from *vi*. Note that the standard version of *vi* +will not work properly with overloaded symbols. Consider using another +free implementation of *vi*, such as *vim*. + + :: + + $ gnatxref -v gnatfind.adb > tags + + +The following command will generate the tags file for `gnatfind` itself +(if the sources are in the search path!): + + :: + + $ gnatxref -v gnatfind.adb > tags + +From *vi*, you can then use the command :samp:`:tag {entity}` +(replacing `entity` by whatever you are looking for), and vi will +display a new file with the corresponding declaration of entity. + + +.. _Examples_of_gnatfind_Usage: + +Examples of `gnatfind` Usage +---------------------------- + +* ``gnatfind -f xyz:main.adb`` + Find declarations for all entities xyz referenced at least once in + main.adb. The references are search in every library file in the search + path. + + The directories will be printed as well (as the ``-f`` + switch is set) + + The output will look like: + + :: + + directory/main.ads:106:14: xyz <= declaration + directory/main.adb:24:10: xyz <= body + directory/foo.ads:45:23: xyz <= declaration + + I.e., one of the entities xyz found in main.adb is declared at + line 12 of main.ads (and its body is in main.adb), and another one is + declared at line 45 of foo.ads + +* ``gnatfind -fs xyz:main.adb`` + This is the same command as the previous one, but `gnatfind` will + display the content of the Ada source file lines. + + The output will look like: + + :: + + directory/main.ads:106:14: xyz <= declaration + procedure xyz; + directory/main.adb:24:10: xyz <= body + procedure xyz is + directory/foo.ads:45:23: xyz <= declaration + xyz : Integer; + + This can make it easier to find exactly the location your are looking + for. + + +* ``gnatfind -r "*x*":main.ads:123 foo.adb`` + Find references to all entities containing an x that are + referenced on line 123 of main.ads. + The references will be searched only in main.ads and foo.adb. + + +* ``gnatfind main.ads:123`` + Find declarations and bodies for all entities that are referenced on + line 123 of main.ads. + + This is the same as ``gnatfind "*":main.adb:123``` + +* ``gnatfind mydir/main.adb:123:45`` + Find the declaration for the entity referenced at column 45 in + line 123 of file main.adb in directory mydir. Note that it + is usual to omit the identifier name when the column is given, + since the column position identifies a unique reference. + + The column has to be the beginning of the identifier, and should not + point to any character in the middle of the identifier. + + +.. _The_Ada_to_HTML_Converter_gnathtml: + +The Ada to HTML Converter `gnathtml` +==================================== + +.. index:: ! gnathtml + +*gnathtml* is a Perl script that allows Ada source files to be browsed using +standard Web browsers. For installation information, see :ref:`Installing_gnathtml`. + +Ada reserved keywords are highlighted in a bold font and Ada comments in +a blue font. Unless your program was compiled with the gcc *-gnatx* +switch to suppress the generation of cross-referencing information, user +defined variables and types will appear in a different color; you will +be able to click on any identifier and go to its declaration. + +.. _Invoking_gnathtml: + +Invoking *gnathtml* +------------------- + +The command line is as follows: + + :: + + $ perl gnathtml.pl [`switches`] `ada-files` + +You can specify as many Ada files as you want. `gnathtml` will generate +an html file for every ada file, and a global file called :file:`index.htm`. +This file is an index of every identifier defined in the files. + +The following switches are available: + +.. index:: -83 (gnathtml) + +:samp:`83` + Only the Ada 83 subset of keywords will be highlighted. + +.. index:: -cc (gnathtml) + +:samp:`cc {color}` + This option allows you to change the color used for comments. The default + value is green. The color argument can be any name accepted by html. + +.. index:: -d (gnathtml) + +:samp:`d` + If the Ada files depend on some other files (for instance through + `with` clauses, the latter files will also be converted to html. + Only the files in the user project will be converted to html, not the files + in the run-time library itself. + +.. index:: -D (gnathtml) + +:samp:`D` + This command is the same as *-d* above, but *gnathtml* will + also look for files in the run-time library, and generate html files for them. + +.. index:: -ext (gnathtml) + +:samp:`ext {extension}` + This option allows you to change the extension of the generated HTML files. + If you do not specify an extension, it will default to :file:`htm`. + +.. index:: -f (gnathtml) + +:samp:`f` + By default, gnathtml will generate html links only for global entities + ('with'ed units, global variables and types,...). If you specify + *-f* on the command line, then links will be generated for local + entities too. + +.. index:: -l (gnathtml) + +:samp:`l {number}` + If this switch is provided and `number` is not 0, then + `gnathtml` will number the html files every `number` line. + +.. index:: -I (gnathtml) + +:samp:`I {dir}` + Specify a directory to search for library files (:file:`.ALI` files) and + source files. You can provide several -I switches on the command line, + and the directories will be parsed in the order of the command line. + +.. index:: -o (gnathtml) + +:samp:`o {dir}` + Specify the output directory for html files. By default, gnathtml will + saved the generated html files in a subdirectory named :file:`html/`. + +.. index:: -p (gnathtml) + +:samp:`p {file}` + If you are using Emacs and the most recent Emacs Ada mode, which provides + a full Integrated Development Environment for compiling, checking, + running and debugging applications, you may use :file:`.gpr` files + to give the directories where Emacs can find sources and object files. + + Using this switch, you can tell gnathtml to use these files. + This allows you to get an html version of your application, even if it + is spread over multiple directories. + +.. index:: -sc (gnathtml) + +:samp:`sc {color}` + This switch allows you to change the color used for symbol + definitions. + The default value is red. The color argument can be any name accepted by html. + +.. index:: -t (gnathtml) + +:samp:`t {file}` + This switch provides the name of a file. This file contains a list of + file names to be converted, and the effect is exactly as though they had + appeared explicitly on the command line. This + is the recommended way to work around the command line length limit on some + systems. + +.. _Installing_gnathtml: + +Installing `gnathtml` +--------------------- + +`Perl` needs to be installed on your machine to run this script. +`Perl` is freely available for almost every architecture and +operating system via the Internet. + +On Unix systems, you may want to modify the first line of the script +`gnathtml`, to explicitly specify where Perl +is located. The syntax of this line is: + + :: + + #!full_path_name_to_perl + +Alternatively, you may run the script using the following command line: + + :: + + $ perl gnathtml.pl [`switches`] `files` + + + + +.. -- +---------------------------------------------------------------------+ +.. -- | The following sections are present only in the PRO and GPL editions | +.. -- +---------------------------------------------------------------------+ + +.. only:: PRO or GPL + + .. _The_Ada-to-XML_converter_gnat2xml: + + The Ada-to-XML converter *gnat2xml* + =================================== + + .. index: ! gnat2xml + .. index:: XML generation + + The *gnat2xml* tool is an ASIS-based utility that converts + Ada source code into XML. + + .. _Switches_for_*gnat2xml*: + + Switches for *gnat2xml* + ----------------------- + + *gnat2xml* takes Ada source code as input, and produces XML + that conforms to the schema. + + Usage: + + :: + + $ gnat2xml [options] filenames [-files filename] [-cargs gcc_switches] + + Options: + + :samp:`--help` + Generate usage information and quit, ignoring all other options + + :samp:`-h` + Same as ``--help`` + + :samp:`--version` + Print version and quit, ignoring all other options + + :samp:`-P{file}` + indicates the name of the project file that describes + the set of sources to be processed. The exact set of argument + sources depends on other options specified, see below. + + :samp:`-U` + If a project file is specified and no argument source is explicitly + specified, process all the units of the closure of the argument project. + Otherwise this option has no effect. + + :samp:`-U {main_unit}` + If a project file is specified and no argument source + is explicitly specified (either directly or by means of *-files* + option), process the closure of units rooted at `main_unit`. + Otherwise this option has no effect. + + :samp:`-X{name}={value}` + Indicates that external variable `name` in + the argument project has the value `value`. Has no effect if no + project is specified as tool argument. + + :samp:`--RTS={rts-path}` + Specifies the default location of the runtime + library. Same meaning as the equivalent *gnatmake* flag + (:ref:`Switches_for_gnatmake`). + + :samp:`--incremental` + Incremental processing on a per-file basis. Source files are + only processed if they have been modified, or if files they depend + on have been modified. This is similar to the way gnatmake/gprbuild + only compiles files that need to be recompiled. A project file + is required in this mode. + + :samp:`-j{n}` + In *--incremental* mode, use `n` *gnat2xml* + processes to perform XML generation in parallel. If `n` is 0, then + the maximum number of parallel tree creations is the number of core + processors on the platform. + + :samp:`--output-dir={dir}` + Generate one .xml file for each Ada source file, in + directory :file:`dir`. (Default is to generate the XML to standard + output.) + + :samp:`-I{include-dir}` + Directories to search for dependencies. + You can also set the ADA_INCLUDE_PATH environment variable for this. + + :samp:`--compact` + Debugging version, with interspersed source, and a more + compact representation of "sloc". This version does not conform + to any schema. + + :samp:`--rep-clauses` + generate representation clauses (see :ref:`Generating_Representation_Clauses`). + + :samp:`-files={filename}` + The name of a text file containing a list of Ada source files to process + + :samp:`-q` + Quiet + + :samp:`-v` + Verbose + + :samp:`-cargs` ... + Options to pass to gcc + + If a project file is specified and no argument source is explicitly + specified, and no *-U* is specified, then the set of processed + sources is all the immediate units of the argument project. + + Example: + + :: + + $ gnat2xml -v -output-dir=xml-files *.ad[sb] + + The above will create \*.xml files in the :file:`xml-files` subdirectory. + For example, if there is an Ada package Mumble.Dumble, whose spec and + body source code lives in mumble-dumble.ads and mumble-dumble.adb, + the above will produce xml-files/mumble-dumble.ads.xml and + xml-files/mumble-dumble.adb.xml. + + .. _Other_Programs: + + Other Programs + -------------- + + The distribution includes two other programs that are related to + *gnat2xml*: + + *gnat2xsd* is the schema generator, which generates the schema + to standard output, based on the structure of Ada as encoded by + ASIS. You don't need to run *gnat2xsd* in order to use + *gnat2xml*. To generate the schema, type: + + + :: + + $ gnat2xsd > ada-schema.xsd + + + *gnat2xml* generates XML files that will validate against + :file:`ada-schema.xsd`. + + *xml2gnat* is a back-translator that translates the XML back + into Ada source code. The Ada generated by *xml2gnat* has + identical semantics to the original Ada code passed to + *gnat2xml*. It is not textually identical, however --- for + example, no attempt is made to preserve the original indentation. + + .. _Structure_of_the_XML: + + Structure of the XML + -------------------- + + The primary documentation for the structure of the XML generated by + *gnat2xml* is the schema (see *gnat2xsd* above). The + following documentation gives additional details needed to understand + the schema and therefore the XML. + + The elements listed under Defining Occurrences, Usage Occurrences, and + Other Elements represent the syntactic structure of the Ada program. + Element names are given in lower case, with the corresponding element + type Capitalized_Like_This. The element and element type names are + derived directly from the ASIS enumeration type Flat_Element_Kinds, + declared in Asis.Extensions.Flat_Kinds, with the leading ``An_`` or ``A_`` + removed. For example, the ASIS enumeration literal + An_Assignment_Statement corresponds to the XML element + assignment_statement of XML type Assignment_Statement. + + To understand the details of the schema and the corresponding XML, it is + necessary to understand the ASIS standard, as well as the GNAT-specific + extension to ASIS. + + A defining occurrence is an identifier (or character literal or operator + symbol) declared by a declaration. A usage occurrence is an identifier + (or ...) that references such a declared entity. For example, in: + + + .. code-block:: ada + + type T is range 1..10; + X, Y : constant T := 1; + + + The first 'T' is the defining occurrence of a type. The 'X' is the + defining occurrence of a constant, as is the 'Y', and the second 'T' is + a usage occurrence referring to the defining occurrence of T. + + Each element has a 'sloc' (source location), and subelements for each + syntactic subtree, reflecting the Ada grammar as implemented by ASIS. + The types of subelements are as defined in the ASIS standard. For + example, for the right-hand side of an assignment_statement we have + the following comment in asis-statements.ads: + + .. code-block:: ada + + ------------------------------------------------------------------------------ + -- 18.3 function Assignment_Expression + ------------------------------------------------------------------------------ + + function Assignment_Expression + (Statement : Asis.Statement) + return Asis.Expression; + + ------------------------------------------------------------------------------ + ... + -- Returns the expression from the right hand side of the assignment. + ... + -- Returns Element_Kinds: + -- An_Expression + + + The corresponding sub-element of type Assignment_Statement is: + + :: + + + + where Expression_Class is defined by an xsd:choice of all the + various kinds of expression. + + The 'sloc' of each element indicates the starting and ending line and + column numbers. Column numbers are character counts; that is, a tab + counts as 1, not as however many spaces it might expand to. + + Subelements of type Element have names ending in '_q' (for ASIS + "Query"), and those of type Element_List end in '_ql' + ("Query returning List"). + + Some subelements are 'Boolean'. For example, Private_Type_Definition + has has_abstract_q and has_limited_q, to indicate whether those + keywords are present, as in `type T is abstract limited private;`. + False is represented by a Nil_Element. True is represented + by an element type specific to that query (for example, Abstract and + Limited). + + The root of the tree is a Compilation_Unit, with attributes: + + * unit_kind, unit_class, and unit_origin. These are strings that match the + enumeration literals of types Unit_Kinds, Unit_Classes, and Unit_Origins + in package Asis. + + * unit_full_name is the full expanded name of the unit, starting from a + root library unit. So for `package P.Q.R is ...`, + `unit_full_name="P.Q.R"`. Same for `separate (P.Q) package R is ...`. + + * def_name is the same as unit_full_name for library units; for subunits, + it is just the simple name. + + * source_file is the name of the Ada source file. For example, for + the spec of `P.Q.R`, `source_file="p-q-r.ads"`. This allows one to + interpret the source locations --- the 'sloc' of all elements + within this Compilation_Unit refers to line and column numbers + within the named file. + + Defining occurrences have these attributes: + + * def_name is the simple name of the declared entity, as written in the Ada + source code. + + * def is a unique URI of the form: + + :: + + ada://kind/fully/qualified/name + + where: + + * kind indicates the kind of Ada entity being declared (see below), and + + * fully/qualified/name, is the fully qualified name of the Ada + entity, with each of 'fully', 'qualified', and 'name' being + mangled for uniqueness. We do not document the mangling + algorithm, which is subject to change; we just guarantee that the + names are unique in the face of overloading. + + * type is the type of the declared object, or `null` for + declarations of things other than objects. + + Usage occurrences have these attributes: + + * ref_name is the same as the def_name of the corresponding defining + occurrence. This attribute is not of much use, because of + overloading; use ref for lookups, instead. + + * ref is the same as the def of the corresponding defining + occurrence. + + In summary, `def_name` and `ref_name` are as in the source + code of the declaration, possibly overloaded, whereas `def` and + `ref` are unique-ified. + + Literal elements have this attribute: + + * lit_val is the value of the literal as written in the source text, + appropriately escaped (e.g. `"` ---> `"`). This applies + only to numeric and string literals. Enumeration literals in Ada are + not really "literals" in the usual sense; they are usage occurrences, + and have ref_name and ref as described above. Note also that string + literals used as operator symbols are treated as defining or usage + occurrences, not as literals. + + Elements that can syntactically represent names and expressions (which + includes usage occurrences, plus function calls and so forth) have this + attribute: + + * type. If the element represents an expression or the name of an object, + 'type' is the 'def' for the defining occurrence of the type of that + expression or name. Names of other kinds of entities, such as package + names and type names, do not have a type in Ada; these have type="null" + in the XML. + + Pragma elements have this attribute: + + * pragma_name is the name of the pragma. For language-defined pragmas, the + pragma name is redundant with the element kind (for example, an + assert_pragma element necessarily has pragma_name="Assert"). However, all + implementation-defined pragmas are lumped together in ASIS as a single + element kind (for example, the GNAT-specific pragma Unreferenced is + represented by an implementation_defined_pragma element with + pragma_name="Unreferenced"). + + Defining occurrences of formal parameters and generic formal objects have this + attribute: + + * mode indicates that the parameter is of mode 'in', 'in out', or 'out'. + + All elements other than Not_An_Element have this attribute: + + * checks is a comma-separated list of run-time checks that are needed + for that element. The possible checks are: do_accessibility_check, + do_discriminant_check,do_division_check,do_length_check, + do_overflow_check,do_range_check,do_storage_check,do_tag_check. + + The "kind" part of the "def" and "ref" attributes is taken from the ASIS + enumeration type Flat_Declaration_Kinds, declared in + Asis.Extensions.Flat_Kinds, with the leading ``An_`` or ``A_`` removed, and + any trailing ``_Declaration`` or ``_Specification`` removed. Thus, the + possible kinds are as follows: + + :: + + ordinary_type + task_type + protected_type + incomplete_type + tagged_incomplete_type + private_type + private_extension + subtype + variable + constant + deferred_constant + single_task + single_protected + integer_number + real_number + enumeration_literal + discriminant + component + loop_parameter + generalized_iterator + element_iterator + procedure + function + parameter + procedure_body + function_body + return_variable + return_constant + null_procedure + expression_function + package + package_body + object_renaming + exception_renaming + package_renaming + procedure_renaming + function_renaming + generic_package_renaming + generic_procedure_renaming + generic_function_renaming + task_body + protected_body + entry + entry_body + entry_index + procedure_body_stub + function_body_stub + package_body_stub + task_body_stub + protected_body_stub + exception + choice_parameter + generic_procedure + generic_function + generic_package + package_instantiation + procedure_instantiation + function_instantiation + formal_object + formal_type + formal_incomplete_type + formal_procedure + formal_function + formal_package + formal_package_declaration_with_box + + .. _Generating_Representation_Clauses: + + Generating Representation Clauses + --------------------------------- + + If the *--rep-clauses* switch is given, *gnat2xml* will + generate representation clauses for certain types showing the + representation chosen by the compiler. The information is produced by + the ASIS 'Data Decomposition' facility --- see the + `Asis.Data_Decomposition` package for details. + + Not all types are supported. For example, `Type_Model_Kind` must + be `A_Simple_Static_Model`. Types declared within generic units + have no representation. The clauses that are generated include + `attribute_definition_clauses` for `Size` and + `Component_Size`, as well as + `record_representation_clauses`. + + There is no guarantee that the generated representation clauses could + have actually come from legal Ada code; Ada has some restrictions that + are not necessarily obeyed by the generated clauses. + + The representation clauses are surrounded by comment elements to + indicate that they are automatically generated, something like this: + + :: + + + ... + + ... + + ... + + +.. only:: PRO or GPL + + .. _The_Program_Property_Verifier_gnatcheck: + + The Program Property Verifier *gnatcheck* + ========================================= + + .. index:: ! gnatcheck + .. index:: ASIS + + The *gnatcheck* tool is an ASIS-based utility that checks properties + of Ada source files according to a given set of semantic rules. + + In order to check compliance with a given rule, *gnatcheck* has to + semantically analyze the Ada sources. + Therefore, checks can only be performed on + legal Ada units. Moreover, when a unit depends semantically upon units located + outside the current directory, the source search path has to be provided when + calling *gnatcheck*, either through a specified project file or + through *gnatcheck* switches. + + For full details, refer to :title:`GNATcheck Reference Manual`. + + + +.. only:: PRO or GPL + + .. _The_GNAT_Metrics_Tool_gnatmetric: + + The GNAT Metrics Tool *gnatmetric* + ================================== + + .. index:: ! gnatmetric + .. index:: Metric tool + + The *gnatmetric* tool is an ASIS-based utility + for computing various program metrics. + It takes an Ada source file as input and generates a file containing the + metrics data as output. Various switches control which + metrics are computed and output. + + To compute program metrics, *gnatmetric* invokes the Ada + compiler and generates and uses the ASIS tree for the input source; + thus the input must be legal Ada code, and the tool should have all the + information needed to compile the input source. To provide this information, + you may specify as a tool parameter the project file the input source belongs to + (or you may call *gnatmetric* + through the *gnat* driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + Another possibility is to specify the source search + path and needed configuration files in *-cargs* section of *gnatmetric* + call, see the description of the *gnatmetric* switches below. + + If the set of sources to be processed by `gnatmetric` contains sources with + preprocessing directives + then the needed options should be provided to run preprocessor as a part of + the *gnatmetric* call, and the computed metrics + will correspond to preprocessed sources. + + The *gnatmetric* command has the form + + :: + + $ gnatmetric [`switches`] {`filename`} [-cargs `gcc_switches`] + + where: + + * `switches` specify the metrics to compute and define the destination for + the output + + * Each `filename` is the name (including the extension) of a source + file to process. 'Wildcards' are allowed, and + the file name may contain path information. + If no `filename` is supplied, then the `switches` list must contain + at least one + *-files* switch (see :ref:`Other_gnatmetric_Switches`). + Including both a *-files* switch and one or more + `filename` arguments is permitted. + + * `gcc_switches` is a list of switches for + *gcc*. They will be passed on to all compiler invocations made by + *gnatmetric* to generate the ASIS trees. Here you can provide + *-I* switches to form the source search path, + and use the *-gnatec* switch to set the configuration file, + use the *-gnat05* switch if sources should be compiled in + Ada 2005 mode etc. + + The following subsections describe the various switches accepted by + *gnatmetric*, organized by category. + + .. _Output_File_Control-gnatmetric: + + Output File Control + ------------------- + + .. index:: Output file control in gnatmetric + + *gnatmetric* has two output formats. It can generate a + textual (human-readable) form, and also XML. By default only textual + output is generated. + + When generating the output in textual form, *gnatmetric* creates + for each Ada source file a corresponding text file + containing the computed metrics, except for the case when the set of metrics + specified by gnatmetric parameters consists only of metrics that are computed + for the whole set of analyzed sources, but not for each Ada source. + By default, the name of the file containing metric information for a source + is obtained by appending the :file:`.metrix` suffix to the + name of the input source file. If not otherwise specified and no project file + is specified as *gnatmetric* option this file is placed in the same + directory as where the source file is located. If *gnatmetric* has a + project file as its parameter, it places all the generated files in the + object directory of the project (or in the project source directory if the + project does not define an objects directory), if *--subdirs* option + is specified, the files are placed in the subrirectory of this directory + specified by this option. + + All the output information generated in XML format is placed in a single + file. By default the name of this file is :file:`metrix.xml`. + If not otherwise specified and if no project file is specified + as *gnatmetric* option this file is placed in the + current directory. + + Some of the computed metrics are summed over the units passed to + *gnatmetric*; for example, the total number of lines of code. + By default this information is sent to :file:`stdout`, but a file + can be specified with the *-og* switch. + + The following switches control the *gnatmetric* output: + + .. index:: -x (gnatmetric) + + :samp:`-x` + Generate the XML output + + .. index:: -xs (gnatmetric) + + :samp:`-xs` + Generate the XML output and the XML schema file that describes the structure + of the XML metric report, this schema is assigned to the XML file. The schema + file has the same name as the XML output file with :file:`.xml` suffix replaced + with :file:`.xsd` + + .. index:: -nt (gnatmetric) + + + :samp:`-nt` + Do not generate the output in text form (implies *-x*) + + .. index:: -d (gnatmetric) + + + :samp:`-d {output_dir}` + Put text files with detailed metrics into `output_dir` + + .. index:: -o (gnatmetric) + + + :samp:`-o {file_suffix}` + Use `file_suffix`, instead of :file:`.metrix` + in the name of the output file. + + .. index:: -og (gnatmetric) + + + :samp:`-og {file_name}` + Put global metrics into `file_name` + + .. index:: -ox (gnatmetric) + + + :samp:`-ox {file_name}` + Put the XML output into `file_name` (also implies *-x*) + + .. index:: -sfn (gnatmetric) + + + :samp:`-sfn` + Use 'short' source file names in the output. (The *gnatmetric* + output includes the name(s) of the Ada source file(s) from which the metrics + are computed. By default each name includes the absolute path. The + *-sfn* switch causes *gnatmetric* + to exclude all directory information from the file names that are output.) + + + .. index:: Disable Metrics For Local Units in gnatmetric + + .. _Disable_Metrics_For_Local_Units: + + Disable Metrics For Local Units + ------------------------------- + + *gnatmetric* relies on the GNAT compilation model -- + one compilation + unit per one source file. It computes line metrics for the whole source + file, and it also computes syntax + and complexity metrics for the file's outermost unit. + + By default, *gnatmetric* will also compute all metrics for certain + kinds of locally declared program units: + + * subprogram (and generic subprogram) bodies; + + * package (and generic package) specs and bodies; + + * task object and type specifications and bodies; + + * protected object and type specifications and bodies. + + .. index:: Eligible local unit (for gnatmetric) + + These kinds of entities will be referred to as + *eligible local program units*, or simply *eligible local units*, + in the discussion below. + + Note that a subprogram declaration, generic instantiation, + or renaming declaration only receives metrics + computation when it appear as the outermost entity + in a source file. + + Suppression of metrics computation for eligible local units can be + obtained via the following switch: + + + .. index:: -nolocal (gnatmetric) + + + :samp:`-nolocal` + Do not compute detailed metrics for eligible local program units + + + .. _Specifying_a_set_of_metrics_to_compute: + + Specifying a set of metrics to compute + -------------------------------------- + + By default all the metrics are computed and reported. The switches + described in this subsection allow you to control, on an individual + basis, whether metrics are computed and + reported. If at least one positive metric + switch is specified (that is, a switch that defines that a given + metric or set of metrics is to be computed), then only + explicitly specified metrics are reported. + + .. _Line_Metrics_Control: + + Line Metrics Control + ^^^^^^^^^^^^^^^^^^^^ + + .. index:: Line metrics control in gnatmetric + + For any (legal) source file, and for each of its + eligible local program units, *gnatmetric* computes the following + metrics: + + * the total number of lines; + + * the total number of code lines (i.e., non-blank lines that are not comments) + + * the number of comment lines + + * the number of code lines containing end-of-line comments; + + * the comment percentage: the ratio between the number of lines that contain + comments and the number of all non-blank lines, expressed as a percentage; + + * the number of empty lines and lines containing only space characters and/or + format effectors (blank lines) + + * the average number of code lines in subprogram bodies, task bodies, entry + bodies and statement sequences in package bodies (this metric is only computed + across the whole set of the analyzed units) + + *gnatmetric* sums the values of the line metrics for all the + files being processed and then generates the cumulative results. The tool + also computes for all the files being processed the average number of code + lines in bodies. + + You can use the following switches to select the specific line metrics + to be computed and reported. + + + .. index:: --lines (gnatmetric) + .. index:: --no-lines (gnatmetric) + + + :samp:`-lines-all` + Report all the line metrics + + + :samp:`-no-lines-all` + Do not report any of line metrics + + + :samp:`-lines` + Report the number of all lines + + + :samp:`-no-lines` + Do not report the number of all lines + + + :samp:`-lines-code` + Report the number of code lines + + + :samp:`-no-lines-code` + Do not report the number of code lines + + + :samp:`-lines-comment` + Report the number of comment lines + + + :samp:`-no-lines-comment` + Do not report the number of comment lines + + + :samp:`-lines-eol-comment` + Report the number of code lines containing + end-of-line comments + + + :samp:`-no-lines-eol-comment` + Do not report the number of code lines containing + end-of-line comments + + + :samp:`-lines-ratio` + Report the comment percentage in the program text + + + :samp:`-no-lines-ratio` + Do not report the comment percentage in the program text + + + :samp:`-lines-blank` + Report the number of blank lines + + + :samp:`-no-lines-blank` + Do not report the number of blank lines + + + :samp:`-lines-average` + Report the average number of code lines in subprogram bodies, task bodies, + entry bodies and statement sequences in package bodies. The metric is computed + and reported for the whole set of processed Ada sources only. + + + :samp:`-no-lines-average` + Do not report the average number of code lines in subprogram bodies, + task bodies, entry bodies and statement sequences in package bodies. + + + .. _Syntax_Metrics_Control: + + Syntax Metrics Control + ^^^^^^^^^^^^^^^^^^^^^^ + + .. index:: Syntax metrics control in gnatmetric + + *gnatmetric* computes various syntactic metrics for the + outermost unit and for each eligible local unit: + + * *LSLOC ('Logical Source Lines Of Code')* + The total number of declarations and the total number of statements. Note + that the definition of declarations is the one given in the reference + manual: + + "Each of the following is defined to be a declaration: any basic_declaration; + an enumeration_literal_specification; a discriminant_specification; + a component_declaration; a loop_parameter_specification; a + parameter_specification; a subprogram_body; an entry_declaration; + an entry_index_specification; a choice_parameter_specification; + a generic_formal_parameter_declaration." + + This means for example that each enumeration literal adds one to the count, + as well as each subprogram parameter. + + Thus the results from this metric will be significantly greater than might + be expected from a naive view of counting semicolons. + + * *Maximal static nesting level of inner program units* + According to :title:`Ada Reference Manual`, 10.1(1): + + "A program unit is either a package, a task unit, a protected unit, a + protected entry, a generic unit, or an explicitly declared subprogram other + than an enumeration literal." + + * *Maximal nesting level of composite syntactic constructs* + This corresponds to the notion of the + maximum nesting level in the GNAT built-in style checks + (see :ref:`Style_Checking`) + + For the outermost unit in the file, *gnatmetric* additionally computes + the following metrics: + + * *Public subprograms* + This metric is computed for package specs. It is the + number of subprograms and generic subprograms declared in the visible + part (including the visible part of nested packages, protected objects, and + protected types). + + + * *All subprograms* + This metric is computed for bodies and subunits. The + metric is equal to a total number of subprogram bodies in the compilation + unit. + Neither generic instantiations nor renamings-as-a-body nor body stubs + are counted. Any subprogram body is counted, independently of its nesting + level and enclosing constructs. Generic bodies and bodies of protected + subprograms are counted in the same way as 'usual' subprogram bodies. + + + * *Public types* + This metric is computed for package specs and + generic package declarations. It is the total number of types + that can be referenced from outside this compilation unit, plus the + number of types from all the visible parts of all the visible generic + packages. Generic formal types are not counted. Only types, not subtypes, + are included. + + Along with the total number of public types, the following + types are counted and reported separately: + + * *Abstract types* + + * *Root tagged types^ (abstract, non-abstract, private, non-private). Type + extensions are *not* counted + + * *Private types* (including private extensions) + + * *Task types* + + * *Protected types* + + * *All types* + This metric is computed for any compilation unit. It is equal to the total + number of the declarations of different types given in the compilation unit. + The private and the corresponding full type declaration are counted as one + type declaration. Incomplete type declarations and generic formal types + are not counted. + No distinction is made among different kinds of types (abstract, + private etc.); the total number of types is computed and reported. + + By default, all the syntax metrics are computed and reported. You can use the + following switches to select specific syntax metrics. + + + .. index:: --syntax (gnatmetric) + .. index:: --no-syntax (gnatmetric) + + + :samp:`-syntax-all` + Report all the syntax metrics + + + :samp:`-no-syntax-all` + Do not report any of syntax metrics + + + :samp:`-declarations` + Report the total number of declarations + + + :samp:`-no-declarations` + Do not report the total number of declarations + + + :samp:`-statements` + Report the total number of statements + + + :samp:`-no-statements` + Do not report the total number of statements + + + :samp:`-public-subprograms` + Report the number of public subprograms in a compilation unit + + + :samp:`-no-public-subprograms` + Do not report the number of public subprograms in a compilation unit + + + :samp:`-all-subprograms` + Report the number of all the subprograms in a compilation unit + + + :samp:`-no-all-subprograms` + Do not report the number of all the subprograms in a compilation unit + + + :samp:`-public-types` + Report the number of public types in a compilation unit + + + :samp:`-no-public-types` + Do not report the number of public types in a compilation unit + + + :samp:`-all-types` + Report the number of all the types in a compilation unit + + + :samp:`-no-all-types` + Do not report the number of all the types in a compilation unit + + + :samp:`-unit-nesting` + Report the maximal program unit nesting level + + + :samp:`-no-unit-nesting` + Do not report the maximal program unit nesting level + + + :samp:`-construct-nesting` + Report the maximal construct nesting level + + + :samp:`-no-construct-nesting` + Do not report the maximal construct nesting level + + + .. _Complexity_Metrics_Control: + + Complexity Metrics Control + ^^^^^^^^^^^^^^^^^^^^^^^^^^ + + .. index:: Complexity metrics control in gnatmetric + + For a program unit that is an executable body (a subprogram body (including + generic bodies), task body, entry body or a package body containing + its own statement sequence) *gnatmetric* computes the following + complexity metrics: + + * McCabe cyclomatic complexity; + + * McCabe essential complexity; + + * maximal loop nesting level; + + * extra exit points (for subprograms); + + The McCabe cyclomatic complexity metric is defined + in `http://www.mccabe.com/pdf/mccabe-nist235r.pdf `_ + + According to McCabe, both control statements and short-circuit control forms + should be taken into account when computing cyclomatic complexity. + For Ada 2012 we have also take into account conditional expressions + and quantified expressions. For each body, we compute three metric values: + + * the complexity introduced by control + statements only, without taking into account short-circuit forms + (referred as `statement complexity` in *gnatmetric* output), + + * the complexity introduced by short-circuit control forms only + (referred as `expression complexity` in *gnatmetric* output), and + + * the total + cyclomatic complexity, which is the sum of these two values + (referred as `cyclomatic complexity` in *gnatmetric* output). + + The cyclomatic complexity is also computed for Ada 2012 expression functions. + An expression function cannot have statements as its components, so only one + metric value is computed as a cyclomatic complexity of an expression function. + + The origin of cyclomatic complexity metric is the need to estimate the number + of independent paths in the control flow graph that in turn gives the number + of tests needed to satisfy paths coverage testing completeness criterion. + Considered from the testing point of view, a static Ada `loop` (that is, + the `loop` statement having static subtype in loop parameter + specification) does not add to cyclomatic complexity. By providing + *--no-static-loop* option a user + may specify that such loops should not be counted when computing the + cyclomatic complexity metric + + The Ada essential complexity metric is a McCabe cyclomatic complexity metric + counted for the code that is reduced by excluding all the pure structural Ada + control statements. An compound statement is considered as a non-structural + if it contains a `raise` or `return` statement as it subcomponent, + or if it contains a `goto` statement that transfers the control outside + the operator. A selective accept statement with `terminate` alternative + is considered as non-structural statement. When computing this metric, + `exit` statements are treated in the same way as `goto` + statements unless *-ne* option is specified. + + The Ada essential complexity metric defined here is intended to quantify + the extent to which the software is unstructured. It is adapted from + the McCabe essential complexity metric defined in + http://www.mccabe.com/pdf/mccabe-nist235r.pdf + but is modified to be more + suitable for typical Ada usage. For example, short circuit forms + are not penalized as unstructured in the Ada essential complexity metric. + + When computing cyclomatic and essential complexity, *gnatmetric* skips + the code in the exception handlers and in all the nested program units. The + code of assertions and predicates (that is, subprogram preconditions and + postconditions, subtype predicates and type invariants) is also skipped. + + By default, all the complexity metrics are computed and reported. + For more fine-grained control you can use + the following switches: + + + .. index:: -complexity (gnatmetric) + .. index:: --no-complexity (gnatmetric) + + + :samp:`-complexity-all` + Report all the complexity metrics + + + :samp:`-no-complexity-all` + Do not report any of complexity metrics + + + :samp:`-complexity-cyclomatic` + Report the McCabe Cyclomatic Complexity + + + :samp:`-no-complexity-cyclomatic` + Do not report the McCabe Cyclomatic Complexity + + + :samp:`-complexity-essential` + Report the Essential Complexity + + + :samp:`-no-complexity-essential` + Do not report the Essential Complexity + + + :samp:`-loop-nesting` + Report maximal loop nesting level + + + :samp:`-no-loop-nesting` + Do not report maximal loop nesting level + + + :samp:`-complexity-average` + Report the average McCabe Cyclomatic Complexity for all the subprogram bodies, + task bodies, entry bodies and statement sequences in package bodies. + The metric is computed and reported for whole set of processed Ada sources + only. + + + :samp:`-no-complexity-average` + Do not report the average McCabe Cyclomatic Complexity for all the subprogram + bodies, task bodies, entry bodies and statement sequences in package bodies + + .. index:: -ne (gnatmetric) + + + :samp:`-ne` + Do not consider `exit` statements as `goto`\ s when + computing Essential Complexity + + .. index:: --no-static-loop (gnatmetric) + + + :samp:`-no-static-loop` + Do not consider static loops when computing cyclomatic complexity + + + :samp:`-extra-exit-points` + Report the extra exit points for subprogram bodies. As an exit point, this + metric counts `return` statements and raise statements in case when the + raised exception is not handled in the same body. In case of a function this + metric subtracts 1 from the number of exit points, because a function body + must contain at least one `return` statement. + + + :samp:`-no-extra-exit-points` + Do not report the extra exit points for subprogram bodies + + + .. _Coupling_Metrics_Control: + + Coupling Metrics Control + ^^^^^^^^^^^^^^^^^^^^^^^^ + + .. index:: Coupling metrics control in gnatmetric + + .. index:: Coupling metrics (in gnatmetric) + + Coupling metrics measure the dependencies between a given entity and other + entities in the program. This information is useful since high coupling + may signal potential issues with maintainability as the program evolves. + + *gnatmetric* computes the following coupling metrics: + + + * *object-oriented coupling*, for classes in traditional object-oriented + sense; + + * *unit coupling*, for all the program units making up a program; + + * *control coupling*, reflecting dependencies between a unit and + other units that contain subprograms. + + .. index:: fan-out coupling + .. index:: efferent coupling + + Two kinds of coupling metrics are computed: + + * fan-out coupling ('efferent coupling'): + the number of entities the given entity depends upon. This metric + reflects how the given entity depends on the changes in the + 'external world'. + + .. index:: fan-in coupling + .. index:: afferent coupling + + * fan-in coupling ('afferent' coupling): + the number of entities that depend on a given entity. + This metric reflects how the 'external world' depends on the changes in a + given entity. + + Object-oriented coupling metrics measure the dependencies + between a given class (or a group of classes) and the other classes in the + program. In this subsection the term 'class' is used in its traditional + object-oriented programming sense (an instantiable module that contains data + and/or method members). A *category* (of classes) is a group of closely + related classes that are reused and/or modified together. + + A class `K`'s fan-out coupling is the number of classes + that `K` depends upon. + A category's fan-out coupling is the number of classes outside the + category that the classes inside the category depend upon. + + A class `K`'s fan-in coupling is the number of classes + that depend upon `K`. + A category's fan-in coupling is the number of classes outside the + category that depend on classes belonging to the category. + + Ada's object-oriented paradigm separates the instantiable entity + (type) from the module (package), so the definition of the coupling + metrics for Ada maps the class and class category notions + onto Ada constructs. + + For the coupling metrics, several kinds of modules that define a tagged type + or an interface type -- library packages, library generic packages, and + library generic package instantiations -- are considered to be classes. + A category consists of a library package (or + a library generic package) that defines a tagged or an interface type, + together with all its descendant (generic) packages that define tagged + or interface types. Thus a + category is an Ada hierarchy of library-level program units. Class + coupling in Ada is referred to as 'tagged coupling', and category coupling + is referred to as 'hierarchy coupling'. + + For any package serving as a class, its body and subunits (if any) are + considered together with its spec when computing dependencies, and coupling + metrics are reported for spec units only. Dependencies between classes + mean Ada semantic dependencies. For object-oriented coupling + metrics, only dependencies on units treated as classes are + considered. + + Similarly, for unit and control coupling an entity is considered to be the + conceptual construct consisting of the entity's specification, body, and + any subunits (transitively). + *gnatmetric* computes + the dependencies of all these units as a whole, but + metrics are only reported for spec + units (or for a subprogram body unit in case if there is no + separate spec for the given subprogram). + + For unit coupling, dependencies are computed between all kinds of program + units. For control coupling, the dependencies of a given unit are limited to + those units that define subprograms. Thus control fan-out coupling is reported + for all units, but control fan-in coupling is only reported for units + that define subprograms. + + The following simple example illustrates the difference between unit coupling + and control coupling metrics: + + .. code-block:: ada + + package Lib_1 is + function F_1 (I : Integer) return Integer; + end Lib_1; + + package Lib_2 is + type T_2 is new Integer; + end Lib_2; + + package body Lib_1 is + function F_1 (I : Integer) return Integer is + begin + return I + 1; + end F_1; + end Lib_1; + + with Lib_2; use Lib_2; + package Pack is + Var : T_2; + function Fun (I : Integer) return Integer; + end Pack; + + with Lib_1; use Lib_1; + package body Pack is + function Fun (I : Integer) return Integer is + begin + return F_1 (I); + end Fun; + end Pack; + + If we apply *gnatmetric* with the *--coupling-all* option to + these units, the result will be: + + :: + + Coupling metrics: + ================= + Unit Lib_1 (C:\\customers\\662\\L406-007\\lib_1.ads) + control fan-out coupling : 0 + control fan-in coupling : 1 + unit fan-out coupling : 0 + unit fan-in coupling : 1 + + Unit Pack (C:\\customers\\662\\L406-007\\pack.ads) + control fan-out coupling : 1 + control fan-in coupling : 0 + unit fan-out coupling : 2 + unit fan-in coupling : 0 + + Unit Lib_2 (C:\\customers\\662\\L406-007\\lib_2.ads) + control fan-out coupling : 0 + unit fan-out coupling : 0 + unit fan-in coupling : 1 + + The result does not contain values for object-oriented + coupling because none of the argument units contains a tagged type and + therefore none of these units can be treated as a class. + + The `Pack` package (spec and body) depends on two + units -- `Lib_1` `and Lib_2` -- and so its unit fan-out coupling + is 2. Since nothing depends on it, its unit fan-in coupling is 0, as + is its control fan-in coupling. Only one of the units `Pack` depends + upon defines a subprogram, so its control fan-out coupling is 1. + + `Lib_2` depends on nothing, so its fan-out metrics are 0. It does + not define any subprograms, so it has no control fan-in metric. + One unit (`Pack`) depends on it , so its unit fan-in coupling is 1. + + `Lib_1` is similar to `Lib_2`, but it does define a subprogram. + Its control fan-in coupling is 1 (because there is one unit + depending on it). + + When computing coupling metrics, *gnatmetric* counts only + dependencies between units that are arguments of the *gnatmetric* + invocation. Coupling metrics are program-wide (or project-wide) metrics, so + you should invoke *gnatmetric* for + the complete set of sources comprising your program. This can be done + by invoking *gnatmetric* with the corresponding project file + and with the *-U* option. + + By default, all the coupling metrics are disabled. You can use the following + switches to specify the coupling metrics to be computed and reported: + + .. index:: --tagged-coupling (gnatmetric) + .. index:: --hierarchy-coupling (gnatmetric) + .. index:: --unit-coupling (gnatmetric) + .. index:: --control-coupling (gnatmetric) + + :samp:`-coupling-all` + Report all the coupling metrics + + + :samp:`-tagged-coupling-out` + Report tagged (class) fan-out coupling + + + :samp:`-tagged-coupling-in` + Report tagged (class) fan-in coupling + + + :samp:`-hierarchy-coupling-out` + Report hierarchy (category) fan-out coupling + + + :samp:`-hierarchy-coupling-in` + Report hierarchy (category) fan-in coupling + + + :samp:`-unit-coupling-out` + Report unit fan-out coupling + + + :samp:`-unit-coupling-in` + Report unit fan-in coupling + + + :samp:`-control-coupling-out` + Report control fan-out coupling + + + :samp:`-control-coupling-in` + Report control fan-in coupling + + + .. _Other_gnatmetric_Switches: + + Other `gnatmetric` Switches + --------------------------- + + Additional *gnatmetric* switches are as follows: + + + .. index:: --version (gnatmetric) + + :samp:`-version` + Display Copyright and version, then exit disregarding all other options. + + + .. index:: --help (gnatmetric) + + :samp:`-help` + Display usage, then exit disregarding all other options. + + + .. index:: -P (gnatmetric) + + :samp:`-P {file}` + Indicates the name of the project file that describes the set of sources + to be processed. The exact set of argument sources depends on other options + specified, see below. + + + .. index:: -U (gnatmetric) + + :samp:`-U` + If a project file is specified and no argument source is explicitly + specified (either directly or by means of *-files* option), process + all the units of the closure of the argument project. Otherwise this option + has no effect. + + + :samp:`-U {main_unit}` + If a project file is specified and no argument source is explicitly + specified (either directly or by means of *-files* option), process + the closure of units rooted at `main_unit`. Otherwise this option + has no effect. + + + .. index:: -X (gnatmetric) + + :samp:`-X{name}={value}` + Indicates that external variable `name` in the argument project + has the value `value`. Has no effect if no project is specified as + tool argument. + + + .. index:: --RTS (gnatmetric) + + :samp:`-RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (see :ref:`Switches_for_gnatmake`). + + + .. index:: --subdirs=dir (gnatmetric) + + :samp:`-subdirs={dir}` + Use the specified subdirectory of the project objects file (or of the + project file directory if the project does not specify an object directory) + for tool output files. Has no effect if no project is specified as + tool argument r if *--no_objects_dir* is specified. + + + .. index:: --no_objects_dir (gnatmetric) + + :samp:`-no_objects_dir` + Place all the result files into the current directory instead of + project objects directory. This corresponds to the *gnatcheck* + behavior when it is called with the project file from the + GNAT driver. Has no effect if no project is specified. + + + .. index:: -files (gnatmetric) + + :samp:`-files {filename}` + Take the argument source files from the specified file. This file should be an + ordinary text file containing file names separated by spaces or + line breaks. You can use this switch more than once in the same call to + *gnatmetric*. You also can combine this switch with + an explicit list of files. + + + .. index:: -j (gnatmetric) + + :samp:`-j{n}` + Use `n` processes to carry out the tree creations (internal representations + of the argument sources). On a multiprocessor machine this speeds up processing + of big sets of argument sources. If `n` is 0, then the maximum number of + parallel tree creations is the number of core processors on the platform. + + .. index:: -t (gnatmetric) + + + :samp:`-t` + Print out execution time. + + + .. index:: -v (gnatmetric) + + :samp:`-v` + Verbose mode; + *gnatmetric* generates version information and then + a trace of sources being processed. + + + .. index:: -q (gnatmetric) + + :samp:`-q` + Quiet mode. + + If a project file is specified and no argument source is explicitly + specified (either directly or by means of *-files* option), and no + *-U* is specified, then the set of processed sources is + all the immediate units of the argument project. + + +.. only:: PRO or GPL + + .. _The_GNAT_Pretty-Printer_gnatpp: + + The GNAT Pretty-Printer *gnatpp* + ================================ + + .. index:: ! gnatpp + .. index:: Pretty-Printer + + The *gnatpp* tool is an ASIS-based utility + for source reformatting / pretty-printing. + It takes an Ada source file as input and generates a reformatted + version as output. + You can specify various style directives via switches; e.g., + identifier case conventions, rules of indentation, and comment layout. + + Note: A newly-redesigned set of formatting algorithms used by gnatpp + is now available. + To invoke the old formatting algorithms, use the ``--pp-old`` switch. + Support for ``--pp-old`` will be removed in some future version. + + To produce a reformatted file, *gnatpp* invokes the Ada + compiler and generates and uses the ASIS tree for the input source; + thus the input must be legal Ada code, and the tool should have all the + information needed to compile the input source. To provide this information, + you may specify as a tool parameter the project file the input source belongs to + (or you may call *gnatpp* + through the *gnat* driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + Another possibility is to specify the source search + path and needed configuration files in ``-cargs`` section of *gnatpp* + call, see the description of the *gnatpp* switches below. + + *gnatpp* cannot process sources that contain preprocessing directives. + + The *gnatpp* command has the form + + :: + + $ gnatpp [`switches`] `filename` [-cargs `gcc_switches`] + + where + + * `switches` is an optional sequence of switches defining such properties as + the formatting rules, the source search path, and the destination for the + output source file + + * `filename` is the name (including the extension) of the source file to + reformat; wildcards or several file names on the same gnatpp command are + allowed. The file name may contain path information; it does not have to + follow the GNAT file naming rules + + * `gcc_switches` is a list of switches for + *gcc*. They will be passed on to all compiler invocations made by + *gnatpp* to generate the ASIS trees. Here you can provide + ``-I`` switches to form the source search path, + use the ``-gnatec`` switch to set the configuration file, etc. + + + .. _Switches_for_gnatpp: + + Switches for *gnatpp* + --------------------- + + The following subsections describe the various switches accepted by + *gnatpp*, organized by category. + + You specify a switch by supplying a name and generally also a value. + In many cases the values for a switch with a given name are incompatible with + each other + (for example the switch that controls the casing of a reserved word may have + exactly one value: upper case, lower case, or + mixed case) and thus exactly one such switch can be in effect for an + invocation of *gnatpp*. + If more than one is supplied, the last one is used. + However, some values for the same switch are mutually compatible. + You may supply several such switches to *gnatpp*, but then + each must be specified in full, with both the name and the value. + Abbreviated forms (the name appearing once, followed by each value) are + not permitted. + + .. _Alignment_Control: + + Alignment Control + ^^^^^^^^^^^^^^^^^ + + .. index:: Alignment control in gnatpp + + Programs can be easier to read if certain constructs are vertically aligned. + By default, alignment of the following constructs is set ON: + + * ``:`` in declarations, + * ``:=`` in initializations in declarations, + * ``:=`` in assignment statements, + * ``=>`` in associations, and + * ``at`` keywords in the component clauses in record representation clauses. + + + .. index:: -A0 (gnatpp) + .. index:: -A1 (gnatpp) + + + :samp:`-A0` + Set alignment to OFF + + + :samp:`-A1` + Set alignment to ON + + .. _Casing_Control: + + + Casing Control + ^^^^^^^^^^^^^^ + + .. index:: Casing control in gnatpp + + *gnatpp* allows you to specify the casing for reserved words, + pragma names, attribute designators and identifiers. + For identifiers you may define a + general rule for name casing but also override this rule + via a set of dictionary files. + + Three types of casing are supported: lower case, upper case, and mixed case. + 'Mixed case' means that the first letter, and also each letter immediately + following an underscore, are converted to their uppercase forms; + all the other letters are converted to their lowercase forms. + + .. index:: -a (gnatpp) + + + :samp:`-aL` + Attribute designators are lower case + + + :samp:`-aU` + Attribute designators are upper case + + + :samp:`-aM` + Attribute designators are mixed case (this is the default) + + .. index:: -k (gnatpp) + + + :samp:`-kL` + Keywords (technically, these are known in Ada as *reserved words*) are + lower case (this is the default) + + + :samp:`-kU` + Keywords are upper case + + .. index:: -n (gnatpp) + + + :samp:`-nD` + Name casing for defining occurrences are as they appear in the source file + (this is the default) + + + :samp:`-nU` + Names are in upper case + + + :samp:`-nL` + Names are in lower case + + + :samp:`-nM` + Names are in mixed case + + .. index:: -ne (gnatpp) + + + :samp:`-neD` + Enumeration literal casing for defining occurrences are as they appear in the + source file. Overrides -n casing setting. + + + :samp:`-neU` + Enumeration literals are in upper case. Overrides -n casing + setting. + + + :samp:`-neL` + Enumeration literals are in lower case. Overrides -n casing + setting. + + + :samp:`-neM` + Enumeration literals are in mixed case. Overrides -n casing + setting. + + .. index:: -nt (gnatpp) + + + :samp:`-neD` + Names introduced by type and subtype declarations are always + cased as they appear in the declaration in the source file. + Overrides -n casing setting. + + + :samp:`-ntU` + Names introduced by type and subtype declarations are always in + upper case. Overrides -n casing setting. + + + :samp:`-ntL` + Names introduced by type and subtype declarations are always in + lower case. Overrides -n casing setting. + + + :samp:`-ntM` + Names introduced by type and subtype declarations are always in + mixed case. Overrides -n casing setting. + + + :samp:`-nnU` + Names introduced by number declarations are always in + upper case. Overrides -n casing setting. + + + :samp:`-nnL` + Names introduced by number declarations are always in + lower case. Overrides -n casing setting. + + + :samp:`-nnM` + Names introduced by number declarations are always in + mixed case. Overrides -n casing setting. + + .. index:: -p (gnatpp) + + + :samp:`-pL` + Pragma names are lower case + + + :samp:`-pU` + Pragma names are upper case + + + :samp:`-pM` + Pragma names are mixed case (this is the default) + + + .. index:: -D (gnatpp) + + :samp:`-D{file}` + Use `file` as a *dictionary file* that defines + the casing for a set of specified names, + thereby overriding the effect on these names by + any explicit or implicit + -n switch. + To supply more than one dictionary file, + use several ``-D`` switches. + + *gnatpp* implicitly uses a *default dictionary file* + to define the casing for the Ada predefined names and + the names declared in the GNAT libraries. + + + .. index:: -D- (gnatpp) + + :samp:`-D-` + Do not use the default dictionary file; + instead, use the casing + defined by a ``-n`` switch and any explicit + dictionary file(s) + + The structure of a dictionary file, and details on the conventions + used in the default dictionary file, are defined in :ref:`Name_Casing`. + + The ``-D-`` and + ``-D-``\ `file` switches are mutually + compatible. + + This group of *gnatpp* switches controls the layout of comments and + complex syntactic constructs. See :ref:`Formatting_Comments` for details + on their effect. + + + .. index:: -c (gnatpp) + + + :samp:`-c0` + All comments remain unchanged. + + + :samp:`-c1` + GNAT-style comment line indentation. + This is the default. + + + :samp:`-c3` + GNAT-style comment beginning. + + + :samp:`-c4` + Fill comment blocks. + + + :samp:`-c5` + Keep unchanged special form comments. + This is the default. + + + .. index:: --comments-only (gnatpp) + + :samp:`--comments-only` + Format just the comments. + + .. index:: --no-separate-is (gnatpp) + + + :samp:`--no-separate-is` + Do not place the keyword `is` on a separate line in a subprogram body in + case if the spec occupies more than one line. + + .. index:: --separate-loop-then (gnatpp) + + + :samp:`--separate-loop-then` + Place the keyword `loop` in FOR and WHILE loop statements and the + keyword `then` in IF statements on a separate line. + + .. index:: --no-separate-loop-then (gnatpp) + + + :samp:`--no-separate-loop-then` + Do not place the keyword `loop` in FOR and WHILE loop statements and the + keyword `then` in IF statements on a separate line. This option is + incompatible with ``--separate-loop-then`` option. + + .. index:: --use-on-new-line (gnatpp) + + + :samp:`--use-on-new-line` + Start each USE clause in a context clause from a separate line. + + .. index:: --insert-blank-lines (gnatpp) + + + :samp:`--insert-blank-lines` + Insert blank lines where appropriate (between bodies and other large + constructs). + + .. index:: --preserve-blank-lines (gnatpp) + + + :samp:`--preserve-blank-lines` + Preserve blank lines in the input. By default, gnatpp will squeeze + multiple blank lines down to one. + + + The ``-c`` switches are compatible with one another, except that + the ``-c0`` switch disables all other comment formatting + switches. + + + .. _General_Text_Layout_Control: + + General Text Layout Control + ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + These switches allow control over line length and indentation. + + .. index:: -M (gnatpp) + + :samp:`-M{nnn}` + Maximum line length, `nnn` from 32...256, the default value is 79 + + + .. index:: -i (gnatpp) + + :samp:`-i{nnn}` + Indentation level, `nnn` from 1...9, the default value is 3 + + + .. index:: -cl (gnatpp) + + :samp:`-cl{nnn}` + Indentation level for continuation lines (relative to the line being + continued), `nnn` from 1...9. + The default + value is one less than the (normal) indentation level, unless the + indentation is set to 1 (in which case the default value for continuation + line indentation is also 1) + + + .. _Other_Formatting_Options: + + Other Formatting Options + ^^^^^^^^^^^^^^^^^^^^^^^^ + + These switches control other formatting not listed above. + + .. index:: --decimal-grouping (gnatpp) + + :samp:`--decimal-grouping={n}` + Put underscores in decimal literals (numeric literals without a base) + every `n` characters. If a literal already has one or more + underscores, it is not modified. For example, with + `--decimal-grouping=3`, `1000000` will be changed to + `1_000_000`. + + + .. index:: --based-grouping (gnatpp) + + :samp:`--based-grouping={n}` + Same as `--decimal-grouping`, but for based literals. For + example, with `--based-grouping=4`, `16#0001FFFE#` will be + changed to `16#0001_FFFE#`. + + + .. index:: --split-line-before-op (gnatpp) + + :samp:`--split-line-before-op` + If it is necessary to split a line at a binary operator, by default + the line is split after the operator. With this option, it is split + before the operator. + + + .. index:: --RM-style-spacing (gnatpp) + + :samp:`--RM-style-spacing` + Do not insert an extra blank before various occurrences of + '(' and ':'. This also turns off alignment. + + + .. index:: -ff (gnatpp) + + :samp:`-ff` + Insert a Form Feed character after a pragma Page. + + + .. index:: --call_threshold (gnatpp) + + :samp:`--call_threshold={nnn}` + If the number of parameter associations is greater than `nnn` and if at + least one association uses named notation, start each association from + a new line. If `nnn` is 0, no check for the number of associations + is made; this is the default. + + + .. index:: --par_threshold (gnatpp) + + :samp:`--par_threshold={nnn}` + If the number of parameter specifications is greater than `nnn` + (or equal to `nnn` in case of a function), start each specification from + a new line. This feature is disabled by default. + + + .. _Setting_the_Source_Search_Path: + + Setting the Source Search Path + ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + To define the search path for the input source file, *gnatpp* + uses the same switches as the GNAT compiler, with the same effects: + + .. index:: -I (gnatpp) + + + :samp:`-I{dir}` + + .. index:: -I- (gnatpp) + + :samp:`-I-` + + .. index:: -gnatec (gnatpp) + + :samp:`-gnatec={path}` + + + .. _Output_File_Control-gnatpp: + + Output File Control + ^^^^^^^^^^^^^^^^^^^ + + By default the output is sent to a file whose name is obtained by appending + the :file:`.pp` suffix to the name of the input file. + If the file with this name already exists, it is overwritten. + Thus if the input file is :file:`my_ada_proc.adb` then + *gnatpp* will produce :file:`my_ada_proc.adb.pp` + as output file. + The output may be redirected by the following switches: + + + .. index:: --output-dir (gnatpp) + + :samp:`--output-dir={dir}` + Generate output file in directory :file:`dir` with the same name as the input + file. If :file:`dir` is the same as the directory containing the input file, + the input file is not processed; use ``-rnb`` + if you want to update the input file in place. + + + .. index:: -pipe (gnatpp) + + :samp:`-pipe` + Send the output to `Standard_Output` + + + .. index:: -o (gnatpp) + + :samp:`-o {output_file}` + Write the output into `output_file`. + If `output_file` already exists, *gnatpp* terminates without + reading or processing the input file. + + + .. index:: -of (gnatpp) + + :samp:`-of {output_file}` + Write the output into `output_file`, overwriting the existing file + (if one is present). + + + .. index:: -r (gnatpp) + + :samp:`-r` + Replace the input source file with the reformatted output, and copy the + original input source into the file whose name is obtained by appending the + :file:`.npp` suffix to the name of the input file. + If a file with this name already exists, *gnatpp* terminates without + reading or processing the input file. + + + .. index:: -rf (gnatpp) + + :samp:`-rf` + Like ``-r`` except that if the file with the specified name + already exists, it is overwritten. + + + .. index:: -rnb (gnatpp) + + :samp:`-rnb` + Replace the input source file with the reformatted output without + creating any backup copy of the input source. + + + .. index:: --eol (gnatpp) + + :samp:`--eol={xxx}` + Specifies the line-ending style of the reformatted output file. The `xxx` + string specified with the switch may be: + + * *dos* - MS DOS style, lines end with CR LF characters* + * *crlf* - the same as *dos* + * *unix* - UNIX style, lines end with LF character* + * *lf* - the same as *unix* + + .. index:: -W (gnatpp) + + :samp:`-W{e}` + Specify the wide character encoding method for the input and output files. + `e` is one of the following: + + * *h* - Hex encoding + + * *u* - Upper half encoding + + * *s* - Shift/JIS encoding + + * *e* - EUC encoding + + * *8* - UTF-8 encoding + + * *b* - Brackets encoding (default value) + + Options ``-o`` and ``-of`` are allowed only if the call to gnatpp + contains only one file to reformat. + + Option ``--eol`` and ``-W`` cannot be used together + with the ``-pipe`` option. + + + .. _Other_gnatpp_Switches: + + Other `gnatpp` Switches + ^^^^^^^^^^^^^^^^^^^^^^^ + + The additional *gnatpp* switches are defined in this subsection. + + + .. index:: --version (gnatpp) + + :samp:`--version` + Display copyright and version, then exit disregarding all other options. + + + .. index:: --help (gnatpp) + + :samp:`--help` + Display usage, then exit disregarding all other options. + + + .. index:: -P (gnatpp) + + :samp:`-P {file}` + Indicates the name of the project file that describes the set of sources + to be processed. The exact set of argument sources depends on other options + specified; see below. + + + .. index:: -U (gnatpp) + + :samp:`-U` + If a project file is specified and no argument source is explicitly + specified (either directly or by means of ``-files`` option), process + all the units of the closure of the argument project. Otherwise this option + has no effect. + + + :samp:`-U {main_unit}` + If a project file is specified and no argument source is explicitly + specified (either directly or by means of ``-files`` option), process + the closure of units rooted at `main_unit`. Otherwise this option + has no effect. + + + .. index:: -X (gnatpp) + + :samp:`-X{name}={value}` + Indicates that external variable `name` in the argument project + has the value `value`. Has no effect if no project is specified as + tool argument. + + + .. index:: --RTS (gnatpp) + + :samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + + .. index:: --incremental (gnatpp) + + :samp:`--incremental` + Incremental processing on a per-file basis. Source files are only + processed if they have been modified, or if files they depend on have + been modified. This is similar to the way gnatmake/gprbuild only + compiles files that need to be recompiled. A project file is required + in this mode, and the gnat driver (as in *gnat pretty*) is not + supported. + + + .. index:: --pp-off (gnatpp) + + :samp:`--pp-off={xxx}` + Use `--xxx` as the command to turn off pretty printing, instead + of the default `--!pp off`. + + + .. index:: --pp-on (gnatpp) + + :samp:`--pp-on={xxx}` + Use `--xxx` as the command to turn pretty printing back on, instead + of the default `--!pp on`. + + + .. index:: --pp-old (gnatpp) + + :samp:`--pp-old` + Use the old formatting algorithms. + + + .. index:: -files (gnatpp) + + :samp:`-files {filename}` + Take the argument source files from the specified file. This file should be an + ordinary text file containing file names separated by spaces or + line breaks. You can use this switch more than once in the same call to + *gnatpp*. You also can combine this switch with an explicit list of + files. + + + .. index:: -j (gnatpp) + + :samp:`-j{n}` + Without ``--incremental``, use `n` processes to carry out the + tree creations (internal representations of the argument sources). On + a multiprocessor machine this speeds up processing of big sets of + argument sources. If `n` is 0, then the maximum number of parallel + tree creations is the number of core processors on the platform. This + option cannot be used together with ``-r``, + ``-rf`` or + ``-rnb`` option. + + With ``--incremental``, use `n` *gnatpp* processes to + perform pretty-printing in parallel. `n` = 0 means the same as + above. In this case, ``-r``, + ``-rf`` or + ``-rnb`` options are allowed. + + .. index:: -t (gnatpp) + + + :samp:`-t` + Print out execution time. + + + .. index:: -v (gnatpp) + + :samp:`-v` + Verbose mode + + + .. index:: -q (gnatpp) + + :samp:`-q` + Quiet mode + + If a project file is specified and no argument source is explicitly + specified (either directly or by means of ``-files`` option), and no + ``-U`` is specified, then the set of processed sources is + all the immediate units of the argument project. + + + .. _Formatting_Rules: + + Formatting Rules + ---------------- + + The following subsections show how *gnatpp* treats white space, + comments, program layout, and name casing. + They provide detailed descriptions of the switches shown above. + + + .. _Disabling_Pretty_Printing: + + Disabling Pretty Printing + ^^^^^^^^^^^^^^^^^^^^^^^^^ + + Pretty printing is highly heuristic in nature, and sometimes doesn't + do exactly what you want. If you wish to format a certain region of + code by hand, you can turn off pretty printing in that region by + surrounding it with special comments that start with ``--!pp off`` + and ``--!pp on``. The text in that region will then be reproduced + verbatim in the output with no formatting. + + To disable pretty printing for the whole file, put ``--!pp off`` at + the top, with no following ``--!pp on``. + + The comments must appear on a line by themselves, with nothing + preceding except spaces. The initial text of the comment must be + exactly ``--!pp off`` or ``--!pp on`` (case sensitive), but may + be followed by arbitrary additional text. For example: + + .. code-block:: ada + + package Interrupts is + --!pp off -- turn off pretty printing so "Interrupt_Kind" lines up + type Interrupt_Kind is + (Asynchronous_Interrupt_Kind, + Synchronous_Interrupt_Kind, + Green_Interrupt_Kind); + --!pp on -- reenable pretty printing + ... + + You can specify different comment strings using the ``--pp-off`` + and ``--pp-on`` switches. For example, if you say: + + :: + + $ gnatpp --pp-off=' pp-' *.ad? + + then gnatpp will recognize comments of the form + ``-- pp-`` instead of ``--!pp off`` for disabling pretty + printing. Note that the leading ``--`` of the comment is not + included in the argument to these switches. + + + .. _White_Space_and_Empty_Lines: + + White Space and Empty Lines + ^^^^^^^^^^^^^^^^^^^^^^^^^^^ + + *gnatpp* does not have an option to control space characters. + It will add or remove spaces according to the style illustrated by the + examples in the :title:`Ada Reference Manual`. + The output file will contain no lines with trailing white space. + + By default, a sequence of one or more blank lines in the input is + converted to a single blank line in the output; multiple blank lines + are squeezed down to one. + The ``--preserve-blank-lines`` option + turns off the squeezing; each blank line in the input is copied + to the output. + The ``--insert-blank-lines`` option + causes additional blank lines to be inserted if not already + present in the input (e.g. between bodies). + + + .. _Formatting_Comments: + + Formatting Comments + ^^^^^^^^^^^^^^^^^^^ + + Comments in Ada code are of two kinds: + + * a *whole-line comment*, which appears by itself (possibly preceded by + white space) on a line + + * an *end-of-line comment*, which follows some other Ada code on + the same line. + + A whole-line comment is indented according to the surrounding code, + with some exceptions. + Comments that start in column 1 are kept there. + If possible, comments are not moved so far to the right that the maximum + line length is exceeded. + The ``-c0`` option + turns off comment formatting. + Special-form comments such as SPARK-style ``--#...`` are left alone. + + For an end-of-line comment, *gnatpp* tries to leave the same + number of spaces between the end of the preceding Ada code and the + beginning of the comment as appear in the original source. + + The ``-c3`` switch + (GNAT style comment beginning) has the following + effect: + + * For each whole-line comment that does not end with two hyphens, + *gnatpp* inserts spaces if necessary after the starting two hyphens + to ensure that there are at least two spaces between these hyphens and the + first non-blank character of the comment. + + The ``-c4`` switch specifies that + whole-line comments that form a paragraph will be filled in typical + word processor style (that is, moving words between lines to make the + lines other than the last similar in length ). + + The ``--comments-only`` switch specifies that only the comments + are formatted; the rest of the program text is left alone. The + comments are formatted according to the -c3 and -c4 switches; other + formatting switches are ignored. For example, + ``--comments-only -c4`` means to fill comment paragraphs, and do nothing else. + Likewise, + ``--comments-only -c3`` ensures comments start with at least two + spaces after `--`, and ``--comments-only -c3 -c4`` does + both. If ``--comments-only`` is given without ``-c3`` or + ``-c4``, then gnatpp doesn't format anything. + + + .. _Name_Casing: + + Name Casing + ^^^^^^^^^^^ + + *gnatpp* always converts the usage occurrence of a (simple) name to + the same casing as the corresponding defining identifier. + + You control the casing for defining occurrences via the + ``-n`` switch. + With ``-nD`` ('as declared', which is the default), + defining occurrences appear exactly as in the source file + where they are declared. + The other values for this switch -- + ``-nU``, + ``-nL``, + ``-nM`` -- + result in + upper, lower, or mixed case, respectively. + If *gnatpp* changes the casing of a defining + occurrence, it analogously changes the casing of all the + usage occurrences of this name. + + If the defining occurrence of a name is not in the source compilation unit + currently being processed by *gnatpp*, the casing of each reference to + this name is changed according to the value of the ``-n`` + switch (subject to the dictionary file mechanism described below). + Thus *gnatpp* acts as though the ``-n`` switch + had affected the + casing for the defining occurrence of the name. + + The options + :samp:`-a{x}`, + :samp:`-k{x}`, + :samp:`-ne{x}`, + :samp:`-nt{x}`, + :samp:`-nn{x}`, and + :samp:`-p{x}` + allow finer-grained control over casing for + attributes, keywords, enumeration literals, + types, named numbers and pragmas, respectively. + :samp:`-nt{x}` covers subtypes and + task and protected bodies as well. + + Some names may need to be spelled with casing conventions that are not + covered by the upper-, lower-, and mixed-case transformations. + You can arrange correct casing by placing such names in a + *dictionary file*, + and then supplying a ``-D`` switch. + The casing of names from dictionary files overrides + any ``-n`` switch. + + To handle the casing of Ada predefined names and the names from GNAT libraries, + *gnatpp* assumes a default dictionary file. + The name of each predefined entity is spelled with the same casing as is used + for the entity in the :title:`Ada Reference Manual` (usually mixed case). + The name of each entity in the GNAT libraries is spelled with the same casing + as is used in the declaration of that entity. + + The ``-D-`` switch suppresses the use of + the default dictionary file. Instead, the casing for predefined and + GNAT-defined names will be established by the + ``-n`` switch or explicit dictionary files. For + example, by default the names `Ada.Text_IO` and + `GNAT.OS_Lib` will appear as just shown, even in the presence of + a ``-nU`` switch. To ensure that even + such names are rendered in uppercase, additionally supply the + -D- switch (or else place these names + in upper case in a dictionary file). + + A dictionary file is a plain text file; each line in this file can be + either a blank line (containing only space characters), an Ada comment + line, or the specification of exactly one *casing schema*. + + A casing schema is a string that has the following syntax: + + :: + + `casing_schema` ::= `identifier` | `simple_identifier` + + `simple_identifier` ::= `letter`{`letter_or_digit`} + + + (See :title:`Ada Reference Manual`, Section 2.3) for the definition of the + `identifier` lexical element and the `letter_or_digit` category.) + + The casing schema string can be followed by white space and/or an Ada-style + comment; any amount of white space is allowed before the string. + + If a dictionary file is passed as + the value of a :samp:`-D{file}` switch + then for every + simple name and every identifier, *gnatpp* checks if the dictionary + defines the casing for the name or for some of its parts (the term 'subword' + is used below to denote the part of a name which is delimited by '_' or by + the beginning or end of the word and which does not contain any '_' inside): + + * if the whole name is in the dictionary, *gnatpp* uses for this name + the casing defined by the dictionary; no subwords are checked for this word + + * for every subword *gnatpp* checks if the dictionary contains the + corresponding string of the form `*`simple_identifier`*`, + and if it does, the casing of this `simple_identifier` is used + for this subword + + * if the whole name does not contain any '_' inside, and if for this name + the dictionary contains two entries - one of the form `identifier`, + and another - of the form *`simple_identifier`*, then the first one + is applied to define the casing of this name + + * if more than one dictionary file is passed as *gnatpp* switches, each + dictionary adds new casing exceptions and overrides all the existing casing + exceptions set by the previous dictionaries + + * when *gnatpp* checks if the word or subword is in the dictionary, + this check is not case sensitive + + For example, suppose we have the following source to reformat: + + .. code-block:: ada + + procedure test is + name1 : integer := 1; + name4_name3_name2 : integer := 2; + name2_name3_name4 : Boolean; + name1_var : Float; + begin + name2_name3_name4 := name4_name3_name2 > name1; + end; + + And suppose we have two dictionaries: + + :: + + *dict1:* + NAME1 + *NaMe3* + *Name1* + + *dict2:* + *NAME3* + + If *gnatpp* is called with the following switches: + + :: + + $ gnatpp -nM -D dict1 -D dict2 test.adb + + then we will get the following name casing in the *gnatpp* output: + + + .. code-block:: ada + + procedure Test is + NAME1 : Integer := 1; + Name4_NAME3_Name2 : Integer := 2; + Name2_NAME3_Name4 : Boolean; + Name1_Var : Float; + begin + Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1; + end Test; + + +.. only:: PRO or GPL + + .. _The_Body_Stub_Generator_gnatstub: + + The Body Stub Generator *gnatstub* + ================================== + + .. index:: ! gnatstub + + *gnatstub* creates empty but compilable bodies + for library unit declarations, and empty but compilable + subunit for body stubs. + + To create a body or a subunit, *gnatstub* invokes the Ada + compiler and generates and uses the ASIS tree for the input source; + thus the input must be legal Ada code, and the tool should have all the + information needed to compile the input source. To provide this information, + you may specify as a tool parameter the project file the input source belongs to + (or you may call *gnatstub* + through the *gnat* driver (see :ref:`The_GNAT_Driver_and_Project_Files`). + Another possibility is to specify the source search + path and needed configuration files in ``-cargs`` section of *gnatstub* + call, see the description of the *gnatstub* switches below. + + If the *gnatstub* argument source contains preprocessing directives + then the needed options should be provided to run preprocessor as a part of + the *gnatstub* call, and the generated body stub will correspond to + the preprocessed source. + + By default, all the program unit bodies generated by `gnatstub` + raise the predefined `Program_Error` exception, which will catch + accidental calls of generated stubs. This behavior can be changed with + option ``--no-exception`` (see below). + + .. _Running_gnatstub: + + Running *gnatstub* + ------------------ + + *gnatstub* invocation has the following form: + + :: + + $ gnatstub [`switches`] `filename` [-cargs `gcc_switches`] + + where + + * *filename* + is the name of the source file that contains a library unit declaration + for which a body must be created or a library unit body for which subunits + must be created for the body stubs declared in this body. + The file name may contain the path information. + If the name does not follow GNAT file naming conventions and a set + of seitches does not contain a project file that defines naming + conventions, the name of the body file must + be provided + explicitly as the value of the :samp:`-o{body-name}` option. + If the file name follows the GNAT file naming + conventions and the name of the body file is not provided, + *gnatstub* + takes the naming conventions for the generated source from the + project file provided as a parameter of ``-P`` switch if any, + or creates the name file to generate using the standard GNAT + naming conventions. + + * *gcc_switches* is a list of switches for *gcc*. + They will be passed on to all compiler invocations made by + *gnatstub* to generate the ASIS trees. Here you can provide + ``-I`` switches to form the source search path, + use the ``-gnatec`` switch to set the configuration file, + use the ``-gnat05`` switch if sources should be compiled in + Ada 2005 mode etc. + + * *switches* + is an optional sequence of switches as described in the next section + + + .. _Switches_for_gnatstub: + + Switches for *gnatstub* + ----------------------- + + .. index:: --version (gnatstub) + + :samp:`--version` + Display Copyright and version, then exit disregarding all other options. + + + .. index:: --help (gnatstub) + + :samp:`--help` + Display usage, then exit disregarding all other options. + + + .. index:: -P (gnatstub) + + :samp:`-P {file}` + Indicates the name of the project file that describes the set of sources + to be processed. + + + .. index:: -X (gnatstub) + + :samp:`-X{name}={value}` + Indicates that external variable `name` in the argument project + has the value `value`. Has no effect if no project is specified as + tool argument. + + + .. index:: --RTS (gnatstub) + + :samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + + .. index:: --subunits (gnatstub) + + :samp:`--subunits` + Generate subunits for body stubs. If this switch is specified, + *gnatstub* expects a library unit body as an agrument file, + otherwise a library unit declaration is expected. If a body stub + already has a corresponding subunit, *gnatstub* does not + generate anything for it. + + + .. index:: -f (gnatstub) + + :samp:`-f` + If the destination directory already contains a file with the name of the + body file + for the argument spec file, replace it with the generated body stub. + This switch cannot be used together with ``--subunits``. + + + .. index:: -hs (gnatstub) + + :samp:`-hs` + Put the comment header (i.e., all the comments preceding the + compilation unit) from the source of the library unit declaration + into the body stub. + + + .. index:: -hg (gnatstub) + + :samp:`-hg` + Put a sample comment header into the body stub. + + + .. index:: --header-file (gnatstub) + + :samp:`--header-file={filename}` + Use the content of the file as the comment header for a generated body stub. + + + .. index:: -IDIR (gnatstub) + .. index:: -I- (gnatstub) + + :samp:`-I{DIR}`, :samp:`-I-` + These switches have the same meaning as in calls to + *gcc*. + They define the source search path in the call to + *gcc* issued + by *gnatstub* to compile an argument source file. + + + .. index:: -gnatec (gnatstub) + + :samp:`-gnatec{PATH}` + This switch has the same meaning as in calls to *gcc*. + It defines the additional configuration file to be passed to the call to + *gcc* issued + by *gnatstub* to compile an argument source file. + + + .. index:: -gnatyM (gnatstub) + + :samp:`-gnatyM{n}` + (`n` is a non-negative integer). Set the maximum line length that is + allowed in a source file. The default is 79. The maximum value that can be + specified is 32767. Note that in the special case of configuration + pragma files, the maximum is always 32767 regardless of whether or + not this switch appears. + + + .. index:: -gnaty (gnatstub) + + :samp:`-gnaty{n}` + (`n` is a non-negative integer from 1 to 9). Set the indentation level in + the generated body sample to `n`. + The default indentation is 3. + + + .. index:: -gnatyo (gnatstub) + + :samp:`-gnatyo` + Order local bodies alphabetically. (By default local bodies are ordered + in the same way as the corresponding local specs in the argument spec file.) + + + .. index:: -i (gnatstub) + + :samp:`-i{n}` + Same as :samp:`-gnaty{n}`` + + + .. index:: -k (gnatstub) + + :samp:`-k` + Do not remove the tree file (i.e., the snapshot of the compiler internal + structures used by *gnatstub*) after creating the body stub. + + + .. index:: -l (gnatstub) + + :samp:`-l{n}` + Same as ``-gnatyM`n``` + + + .. index:: --no-exception (gnatstub) + + :samp:`--no-exception` + Avoid raising PROGRAM_ERROR in the generated bodies of program unit stubs. + This is not always possible for function stubs. + + + .. index:: --no-local-header (gnatstub) + + :samp:`--no-local-header` + Do not place local comment header with unit name before body stub for a + unit. + + + .. index:: -o (gnatstub) + + :samp:`-o {body-name}` + Body file name. This should be set if the argument file name does not + follow + the GNAT file naming + conventions. If this switch is omitted the default name for the body will be + obtained + from the argument file name according to the GNAT file naming conventions. + + + .. index:: --dir (gnatstub) + + :samp:`--dir={dir-name}` + The path to the directory to place the generated files into. + If this switch is not set, the generated library unit body is + placed in the current directory, and generated sununits - + in the directory where the argument body is located. + + + .. index:: -W (gnatstub) + + :samp:`-W{e}` + Specify the wide character encoding method for the output body file. + `e` is one of the following: + + ==== ================================== + *h* Hex encoding + *u* Upper half encoding + *s* Shift/JIS encoding + *e* EUC encoding + *8* UTF-8 encoding + *b* Brackets encoding (default value) + ==== ================================== + + + .. index:: -q (gnatstub) + + :samp:`-q` + Quiet mode: do not generate a confirmation when a body is + successfully created, and do not generate a message when a body is not + required for an + argument unit. + + + .. index:: -r (gnatstub) + + :samp:`-r` + Reuse the tree file (if it exists) instead of creating it. Instead of + creating the tree file for the library unit declaration, *gnatstub* + tries to find it in the current directory and use it for creating + a body. If the tree file is not found, no body is created. This option + also implies ``-k``, whether or not + the latter is set explicitly. + + + .. index:: -t (gnatstub) + + :samp:`-t` + Overwrite the existing tree file. If the current directory already + contains the file which, according to the GNAT file naming rules should + be considered as a tree file for the argument source file, + *gnatstub* + will refuse to create the tree file needed to create a sample body + unless this option is set. + + + .. index:: -v (gnatstub) + + :samp:`-v` + Verbose mode: generate version information. + + + +.. only:: PRO or GPL + + .. _The_Unit_Test_Generator_gnattest: + + The Unit Test Generator *gnattest* + ================================== + + .. index:: ! gnattest + + *gnattest* is an ASIS-based utility that creates unit-test skeletons + as well as a test driver infrastructure (harness). *gnattest* creates + a skeleton for each visible subprogram in the packages under consideration when + they do not exist already. + + The user can choose to generate a single test driver + that will run all individual tests, or separate test drivers for each test. The + second option allows much greater flexibility in test execution environment, + allows to benefit from parallel tests execution to increase performance, and + provides stubbing support. + + *gnattest* also has a mode of operation where it acts as the test + aggregator when multiple test executables must be run, in particular when + the separate test drivers were generated. In this mode it handles individual + tests execution and upon completion reports the summary results of the test + run. + + In order to process source files from a project, *gnattest* has to + semantically analyze the sources. Therefore, test skeletons can only be + generated for legal Ada units. If a unit is dependent on other units, + those units should be among the source files of the project or of other projects + imported by this one. + + Generated skeletons and harnesses are based on the AUnit testing framework. + AUnit is an Ada adaptation of the xxxUnit testing frameworks, similar to JUnit + for Java or CppUnit for C++. While it is advised that gnattest users read + the AUnit manual, deep knowledge of AUnit is not necessary for using gnattest. + For correct operation of *gnattest*, AUnit should be installed and + aunit.gpr must be on the project path. This happens automatically when Aunit + is installed at its default location. + + + .. _Running_gnattest: + + Running *gnattest* + ------------------ + + There are two ways of running *gnattest*. + + .. _Framework_Generation_Mode: + + Framework Generation Mode + ^^^^^^^^^^^^^^^^^^^^^^^^^ + + In this mode *gnattest* has the following command-line interface: + + :: + + $ gnattest `-Pprojname` [`--harness-dir=dirname`] [`switches`] [`filename`] [-cargs `gcc_switches`] + + where + + * :samp:`-P{projname}` + specifies the project defining the location of source files. When no + file names are provided on the command line, all sources in the project + are used as input. This switch is required. + + * :samp:`{filename}` + is the name of the source file containing the library unit package declaration + for which a test package will be created. The file name may be given with a + path. + + * :samp:`{gcc_switches}` + is a list of switches for + *gcc*. These switches will be passed on to all compiler invocations + made by *gnattest* to generate a set of ASIS trees. Here you can provide + ``-I`` switches to form the source search path, + use the ``-gnatec`` switch to set the configuration file, + use the ``-gnat05`` switch if sources should be compiled in + Ada 2005 mode, etc. + + + * :samp:`{switches}` + is an optional sequence of switches as described below. + + + *gnattest* results can be found in two different places. + + * *automatic harness*: + This is the harness code, which is located by default in "gnattest/harness" directory + that is created in the object directory of corresponding project file. All of + this code is generated completely automatically and can be destroyed and + regenerated at will. It is not recommended to modify this code manually, since + it could easily be overridden by mistake. The entry point in the harness code is + the project file named *test_driver.gpr*. Tests can be compiled and run + using a command such as: + + :: + + $ gnatmake -P/test_driver test_runner + + Note that you might need to specify the necessary values of scenario variables + when you are not using the AUnit defaults. + + * *actual unit test skeletons*: + A test skeleton for each visible subprogram is created in a separate file, if it + doesn't exist already. By default, those separate test files are located in a + "gnattest/tests" directory that is created in the object directory of + corresponding project file. For example, if a source file my_unit.ads in + directory src contains a visible subprogram Proc, then the corresponding unit + test will be found in file src/tests/my_unit-test_data-tests.adb and will be + called Test_Proc_. is a signature encoding used to differentiate + test names in case of overloading. + + Note that if the project already has both my_unit.ads and my_unit-test_data.ads, + this will cause a name conflict with the generated test package. + + + .. _Test_Execution_Mode: + + Test Execution Mode + ^^^^^^^^^^^^^^^^^^^ + + In this mode *gnattest* has a the following command-line interface: + + :: + + $ gnattest `test_drivers.list` [`switches`] + + where + + * :samp:`{test_drivers.list}` + is the name of the text file containing the list of executables to treat as + test drivers. This file is automatically generated by gnattest, but can be + hand-edited to add or remove tests. This switch is required. + + + * :samp:`{switches}` + is an optional sequence of switches as described below. + + + .. _Switches_for_gnattest_in_framework_generation_mode: + + Switches for *gnattest* in framework generation mode + ---------------------------------------------------- + + .. index:: -q (gnattest) + + :samp:`-q` + Quiet mode: suppresses noncritical output messages. + + + .. index:: -v (gnattest) + + :samp:`-v` + Verbose mode: generates version information if specified by itself on the + command line. If specified via GNATtest_Switches, produces output + about the execution of the tool. + + + .. index:: -r (gnattest) + + :samp:`-r` + Recursively considers all sources from all projects. + + + .. index:: -X (gnattest) + + :samp:`-X{name}={value}` + Indicate that external variable `name` has the value `value`. + + + .. index:: --RTS (gnattest) + + :samp:`--RTS={rts-path}` + Specifies the default location of the runtime library. Same meaning as the + equivalent *gnatmake* flag (:ref:`Switches_for_gnatmake`). + + + .. index:: --additional-tests (gnattest) + + :samp:`--additional-tests={projname}` + Sources described in `projname` are considered potential additional + manual tests to be added to the test suite. + + + .. index:: --harness-only (gnattest) + + :samp:`--harness-only` + When this option is given, *gnattest* creates a harness for all + sources, treating them as test packages. + + + .. index:: --separate-drivers (gnattest) + + :samp:`--separate-drivers` + Generates a separate test driver for each test, rather than a single + executable incorporating all tests. + + + .. index:: --stub (gnattest) + + :samp:`--stub` + Generates the testing framework that uses subsystem stubbing to isolate the + code under test. + + + .. index:: --harness-dir (gnattest) + + :samp:`--harness-dir={dirname}` + Specifies the directory that will hold the harness packages and project file + for the test driver. If the `dirname` is a relative path, it is considered + relative to the object directory of the project file. + + + .. index:: --tests-dir (gnattest) + + :samp:`--tests-dir={dirname}` + All test packages are placed in the `dirname` directory. + If the `dirname` is a relative path, it is considered relative to the object + directory of the project file. When all sources from all projects are taken + recursively from all projects, `dirname` directories are created for each + project in their object directories and test packages are placed accordingly. + + + .. index:: --subdir (gnattest) + + :samp:`--subdir={dirname}` + Test packages are placed in a subdirectory of the corresponding source + directory, with the name `dirname`. Thus, each set of unit tests is located + in a subdirectory of the code under test. If the sources are in separate + directories, each source directory has a test subdirectory named `dirname`. + + + .. index:: --tests-root (gnattest) + + :samp:`--tests-root={dirname}` + The hierarchy of source directories, if any, is recreated in the `dirname` + directory, with test packages placed in directories corresponding to those + of the sources. + If the `dirname` is a relative path, it is considered relative to the object + directory of the project file. When projects are considered recursively, + directory hierarchies of tested sources are + recreated for each project in their object directories and test packages are + placed accordingly. + + + .. index:: --stubs-dir (gnattest) + + :samp:`--stubs-dir={dirname}` + The hierarchy of directories containing stubbed units is recreated in + the `dirname` directory, with stubs placed in directories corresponding to + projects they are derived from. + If the `dirname` is a relative path, it is considered relative to the object + directory of the project file. When projects are considered recursively, + directory hierarchies of stubs are + recreated for each project in their object directories and test packages are + placed accordingly. + + + .. index:: --validate-type-extensions (gnattest) + + :samp:`--validate-type-extensions` + Enables substitution check: run all tests from all parents in order + to check substitutability in accordance with LSP. + + + .. index:: --skeleton-default (gnattest) + + :samp:`--skeleton-default={val}` + Specifies the default behavior of generated skeletons. `val` can be either + "fail" or "pass", "fail" being the default. + + + .. index:: --passed-tests (gnattest) + + :samp:`--passed-tests={val}` + Specifies whether or not passed tests should be shown. `val` can be either + "show" or "hide", "show" being the default. + + + .. index:: --exit-status (gnattest) + + :samp:`--exit-status={val}` + Specifies whether or not generated test driver should return failure exit + status if at least one test fails or crashes. `val` can be either + "on" or "off", "off" being the default. + + + .. index:: --omit-sloc (gnattest) + + :samp:`--omit-sloc` + Suppresses comment line containing file name and line number of corresponding + subprograms in test skeletons. + + + .. index:: --no-command-line (gnattest) + + :samp:`--no-command-line` + Don't add command line support to test driver. Note that regardless of this + switch, *gnattest* will automatically refrain from adding command + line support if it detects that the selected run-time doesn't provide + this capability. + + + .. index:: --separates (gnattest) + + :samp:`--separates` + Bodies of all test routines are generated as separates. Note that this mode is + kept for compatibility reasons only and it is not advised to use it due to + possible problems with hash in names of test skeletons when using an + inconsistent casing. Separate test skeletons can be incorporated to monolith + test package with improved hash being used by using ``--transition`` + switch. + + + .. index:: --transition (gnattest) + + :samp:`--transition` + This allows transition from separate test routines to monolith test packages. + All matching test routines are overwritten with contents of corresponding + separates. Note that if separate test routines had any manually added with + clauses they will be moved to the test package body as is and have to be moved + by hand. + + + .. index:: --test-duration (gnattest) + + :samp:`--test-duration` + Adds time measurements for each test in generated test driver. + + + :samp:`--tests_root`, ``--subdir`` and ``--tests-dir`` switches are mutually exclusive. + + + .. _Switches_for_gnattest_in_test_execution_mode: + + Switches for *gnattest* in test execution mode + ---------------------------------------------- + + + .. index:: --passed-tests (gnattest) + + :samp:`--passed-tests={val}` + Specifies whether or not passed tests should be shown. `val` can be either + "show" or "hide", "show" being the default. + + + .. index:: --queues (gnattest) + .. index:: -j (gnattest) + + :samp:`--queues={n}`, :samp:`-j{n}` + Runs `n` tests in parallel (default is 1). + + + .. _Project_Attributes_for_gnattest: + + Project Attributes for *gnattest* + --------------------------------- + + Most of the command-line options can also be passed to the tool by adding + special attributes to the project file. Those attributes should be put in + package gnattest. Here is the list of attributes: + + + * ``Tests_Root`` + is used to select the same output mode as with the ``--tests-root`` option. + This attribute cannot be used together with Subdir or Tests_Dir. + + * ``Subdir`` + is used to select the same output mode as with the ``--subdir`` option. + This attribute cannot be used together with ``Tests_Root`` or ``Tests_Dir``. + + * ``Tests_Dir`` + is used to select the same output mode as with the ``--tests-dir`` option. + This attribute cannot be used together with ``Subdir`` or ``Tests_Root``. + + * ``Harness_Dir`` + is used to specify the directory in which to place harness packages and project + file for the test driver, otherwise specified by ``--harness-dir``. + + * ``Additional_Tests`` + is used to specify the project file, otherwise given by + ``--additional-tests`` switch. + + * ``Skeletons_Default`` + is used to specify the default behaviour of test skeletons, otherwise + specified by ``--skeleton-default`` option. The value of this attribute + should be either ``pass`` or ``fail``. + + Each of those attributes can be overridden from the command line if needed. + Other *gnattest* switches can also be passed via the project + file as an attribute list called GNATtest_Switches. + + + .. _Simple_gnattest_Example: + + Simple Example + -------------- + + Let's take a very simple example using the first *gnattest* example + located in: + + :: + + /share/examples/gnattest/simple + + This project contains a simple package containing one subprogram. By running gnattest: + + :: + + $ gnattest --harness-dir=driver -Psimple.gpr + + a test driver is created in directory ``driver``. It can be compiled and run: + + :: + + $ cd obj/driver + $ gnatmake -Ptest_driver + $ test_runner + + One failed test with diagnosis ``test not implemented`` is reported. + Since no special output option was specified, the test package ``Simple.Tests`` + is located in: + + :: + + /share/examples/gnattest/simple/obj/gnattest/tests + + + For each package containing visible subprograms, a child test package is + generated. It contains one test routine per tested subprogram. Each + declaration of a test subprogram has a comment specifying which tested + subprogram it corresponds to. Bodies of test routines are placed in test package + bodies and are surrounded by special comment sections. Those comment sections + should not be removed or modified in order for gnattest to be able to regenerate + test packages and keep already written tests in place. + The test routine Test_Inc_5eaee3 located at simple-test_data-tests.adb contains + a single statement: a call to procedure Assert. It has two arguments: + the Boolean expression we want to check and the diagnosis message to display if + the condition is false. + + That is where actual testing code should be written after a proper setup. + An actual check can be performed by replacing the Assert call with: + + :: + + Assert (Inc (1) = 2, "wrong incrementation"); + + After recompiling and running the test driver, one successfully passed test + is reported. + + + .. _Setting_Up_and_Tearing_Down_the_Testing_Environment: + + Setting Up and Tearing Down the Testing Environment + --------------------------------------------------- + + Besides test routines themselves, each test package has a parent package + Test_Data that has two procedures: Set_Up and Tear_Down. This package is never + overwritten by the tool. Set_Up is called before each test routine of the + package and Tear_Down is called after each test routine. Those two procedures + can be used to perform necessary initialization and finalization, + memory allocation, etc. Test type declared in Test_Data package is parent type + for the test type of test package and can have user-defined components whose + values can be set by Set_Up routine and used in test routines afterwards. + + + .. _Regenerating_Tests: + + Regenerating Tests + ------------------ + + Bodies of test routines and test_data packages are never overridden after they + have been created once. As long as the name of the subprogram, full expanded Ada + names, and the order of its parameters is the same, and comment sections are + intact the old test routine will fit in its place and no test skeleton will be + generated for the subprogram. + + This can be demonstrated with the previous example. By uncommenting declaration + and body of function Dec in simple.ads and simple.adb, running + *gnattest* on the project, and then running the test driver: + + :: + + $ gnattest --harness-dir=driver -Psimple.gpr + $ cd obj/driver + $ gnatmake -Ptest_driver + $ test_runner + + The old test is not replaced with a stub, nor is it lost, but a new test + skeleton is created for function Dec. + + The only way of regenerating tests skeletons is to remove the previously created + tests together with corresponding comment sections. + + + .. _Default_Test_Behavior: + + Default Test Behavior + --------------------- + + The generated test driver can treat unimplemented tests in two ways: + either count them all as failed (this is useful to see which tests are still + left to implement) or as passed (to sort out unimplemented ones from those + actually failing). + + The test driver accepts a switch to specify this behavior: + :samp:`--skeleton-default={val}`, where ``val`` is either ``pass`` or ``fail`` (exactly as for + *gnattest*). + + The default behavior of the test driver is set with the same switch + as passed to gnattest when generating the test driver. + + Passing it to the driver generated on the first example: + + :: + + $ test_runner --skeleton-default=pass + + makes both tests pass, even the unimplemented one. + + + .. _Testing_Primitive_Operations_of_Tagged_Types: + + Testing Primitive Operations of Tagged Types + -------------------------------------------- + + Creation of test skeletons for primitive operations of tagged types entails + a number of features. Test routines for all primitives of a given tagged type + are placed in a separate child package named according to the tagged type. For + example, if you have tagged type T in package P, all tests for primitives + of T will be in P.T_Test_Data.T_Tests. + + Consider running gnattest on the second example (note: actual tests for this + example already exist, so there's no need to worry if the tool reports that + no new stubs were generated): + + :: + + $ cd /share/examples/gnattest/tagged_rec + $ gnattest --harness-dir=driver -Ptagged_rec.gpr + + Taking a closer look at the test type declared in the test package + Speed1.Controller_Test_Data is necessary. It is declared in: + + :: + + /share/examples/gnattest/tagged_rec/obj/gnattest/tests + + Test types are direct or indirect descendants of + AUnit.Test_Fixtures.Test_Fixture type. In the case of nonprimitive tested + subprograms, the user doesn't need to be concerned with them. However, + when generating test packages for primitive operations, there are some things + the user needs to know. + + Type Test_Controller has components that allow assignment of various + derivations of type Controller. And if you look at the specification of + package Speed2.Auto_Controller, you will see that Test_Auto_Controller + actually derives from Test_Controller rather than AUnit type Test_Fixture. + Thus, test types mirror the hierarchy of tested types. + + The Set_Up procedure of Test_Data package corresponding to a test package + of primitive operations of type T assigns to Fixture a reference to an + object of that exact type T. Notice, however, that if the tagged type has + discriminants, the Set_Up only has a commented template for setting + up the fixture, since filling the discriminant with actual value is up + to the user. + + The knowledge of the structure of test types allows additional testing + without additional effort. Those possibilities are described below. + + + .. _Testing_Inheritance: + + Testing Inheritance + ------------------- + + Since the test type hierarchy mimics the hierarchy of tested types, the + inheritance of tests takes place. An example of such inheritance can be + seen by running the test driver generated for the second example. As previously + mentioned, actual tests are already written for this example. + + :: + + $ cd obj/driver + $ gnatmake -Ptest_driver + $ test_runner + + There are 6 passed tests while there are only 5 testable subprograms. The test + routine for function Speed has been inherited and run against objects of the + derived type. + + + .. _Tagged_Type_Substitutability_Testing: + + Tagged Type Substitutability Testing + ------------------------------------- + + *Tagged Type Substitutability Testing* is a way of verifying the global type + consistency by testing. Global type consistency is a principle stating that if + S is a subtype of T (in Ada, S is a derived type of tagged type T), + then objects of type T may be replaced with objects of type S (that is, + objects of type S may be substituted for objects of type T), without + altering any of the desirable properties of the program. When the properties + of the program are expressed in the form of subprogram preconditions and + postconditions (let's call them pre and post), the principle is formulated as + relations between the pre and post of primitive operations and the pre and post + of their derived operations. The pre of a derived operation should not be + stronger than the original pre, and the post of the derived operation should + not be weaker than the original post. Those relations ensure that verifying if + a dispatching call is safe can be done just by using the pre and post of the + root operation. + + Verifying global type consistency by testing consists of running all the unit + tests associated with the primitives of a given tagged type with objects of its + derived types. + + In the example used in the previous section, there was clearly a violation of + type consistency. The overriding primitive Adjust_Speed in package Speed2 + removes the functionality of the overridden primitive and thus doesn't respect + the consistency principle. + Gnattest has a special option to run overridden parent tests against objects + of the type which have overriding primitives: + + :: + + $ gnattest --harness-dir=driver --validate-type-extensions -Ptagged_rec.gpr + $ cd obj/driver + $ gnatmake -Ptest_driver + $ test_runner + + While all the tests pass by themselves, the parent test for Adjust_Speed fails + against objects of the derived type. + + Non-overridden tests are already inherited for derived test types, so the + ``--validate-type-extensions`` enables the application of overriden tests to objects + of derived types. + + + .. _Testing_with_Contracts: + + Testing with Contracts + ---------------------- + + *gnattest* supports pragmas Precondition, Postcondition, and Test_Case, + as well as the corresponding Ada 2012 aspects. + Test routines are generated, one per each Test_Case associated with a tested + subprogram. Those test routines have special wrappers for tested functions + that have composition of pre- and postcondition of the subprogram with + "requires" and "ensures" of the Test_Case (depending on the mode, pre and post + either count for Nominal mode or do not count for Robustness mode). + + The third example demonstrates how this works: + + :: + + $ cd /share/examples/gnattest/contracts + $ gnattest --harness-dir=driver -Pcontracts.gpr + + Putting actual checks within the range of the contract does not cause any + error reports. For example, for the test routine which corresponds to + test case 1: + + :: + + Assert (Sqrt (9.0) = 3.0, "wrong sqrt"); + + and for the test routine corresponding to test case 2: + + :: + + Assert (Sqrt (-5.0) = -1.0, "wrong error indication"); + + are acceptable: + + :: + + $ cd obj/driver + $ gnatmake -Ptest_driver + $ test_runner + + However, by changing 9.0 to 25.0 and 3.0 to 5.0, for example, you can get + a precondition violation for test case one. Also, by using any otherwise + correct but positive pair of numbers in the second test routine, you can also + get a precondition violation. Postconditions are checked and reported + the same way. + + + .. _Additional_Tests: + + Additional Tests + ---------------- + + *gnattest* can add user-written tests to the main suite of the test + driver. *gnattest* traverses the given packages and searches for test + routines. All procedures with a single in out parameter of a type which is + derived from AUnit.Test_Fixtures.Test_Fixture and that are declared in package + specifications are added to the suites and are then executed by the test driver. + (Set_Up and Tear_Down are filtered out.) + + An example illustrates two ways of creating test harnesses for user-written + tests. Directory additional_tests contains an AUnit-based test driver written + by hand. + + :: + + /share/examples/gnattest/additional_tests/ + + To create a test driver for already-written tests, use the ``--harness-only`` + option: + + :: + + gnattest -Padditional/harness/harness.gpr --harness-dir=harness_only \\ + --harness-only + gnatmake -Pharness_only/test_driver.gpr + harness_only/test_runner + + Additional tests can also be executed together with generated tests: + + :: + + gnattest -Psimple.gpr --additional-tests=additional/harness/harness.gpr \\ + --harness-dir=mixing + gnatmake -Pmixing/test_driver.gpr + mixing/test_runner + + + .. _Individual_Test_Drivers: + + Individual Test Drivers + ----------------------- + + By default, *gnattest* generates a monolithic test driver that + aggregates the individual tests into a single executable. It is also possible + to generate separate executables for each test, by passing the switch + ``--separate-drivers``. This approach scales better for large testing + campaigns, especially involving target architectures with limited resources + typical for embedded development. It can also provide a major performance + benefit on multi-core systems by allowing simultaneous execution of multiple + tests. + + *gnattest* can take charge of executing the individual tests; for this, + instead of passing a project file, a text file containing the list of + executables can be passed. Such a file is automatically generated by gnattest + under the name :file:`test_drivers.list`, but it can be + hand-edited to add or remove tests, or replaced. The individual tests can + also be executed standalone, or from any user-defined scripted framework. + + + .. _Stubbing: + + Stubbing + -------- + + Depending on the testing campaign, it is sometimes necessary to isolate the + part of the algorithm under test from its dependencies. This is accomplished + via *stubbing*, i.e. replacing the subprograms that are called from the + subprogram under test by stand-in subprograms that match the profiles of the + original ones, but simply return predetermined values required by the test + scenario. + + This mode of test harness generation is activated by the switch ``--stub``. + + The implementation approach chosen by *gnattest* is as follows. + For each package under consideration all the packages it is directly depending + on are stubbed, excluding the generic packages and package instantiations. + The stubs are shared for each package under test. The specs of packages to stub + remain intact, while their bodies are replaced, and hide the original bodies by + means of extending projects. Also, for each stubbed + package, a child package with setter routines for each subprogram declaration + is created. These setters are meant to be used to set the behaviour of + stubbed subprograms from within test cases. + + Note that subprograms belonging to the same package as the subprogram under + test are not stubbed. This guarantees that the sources being tested are + exactly the sources used for production, which is an important property for + establishing the traceability between the testing campaign and production code. + + Due to the nature of stubbing process, this mode implies the switch + ``--separate-drivers``, i.e. an individual test driver (with the + corresponding hierarchy of extending projects) is generated for each test. + + .. note:: + + Developing a stubs-based testing campaign requires + good understanding of the infrastructure created by *gnattest* for + this purpose. We recommend following the stubbing tutorials provided + under :file:`/share/examples/gnattest/stubbing*` before + attempting to use this powerful feature. + + + .. _Putting_Tests_under_Version_Control: + + Putting Tests under Version Control + ----------------------------------- + + As has been stated earlier, *gnattest* generates two different types + of code, test skeletons and harness. The harness is generated completely + automatically each time, does not require manual changes and therefore should + not be put under version control. + It makes sense to put under version control files containing test data packages, + both specs and bodies, and files containing bodies of test packages. Note that + test package specs are also generated automatically each time and should not be + put under version control. + Option ``--omit-sloc`` may be useful when putting test packages under version control. + + + .. _Support_for_other_platforms/run-times: + + Support for other platforms/run-times + ------------------------------------- + + *gnattest* can be used to generate the test harness for platforms + and run-time libraries others than the default native target with the + default full run-time. For example, when using a limited run-time library + such as Zero FootPrint (ZFP), a simplified harness is generated. + + Two variables are used to tell the underlying AUnit framework how to generate + the test harness: `PLATFORM`, which identifies the target, and + `RUNTIME`, used to determine the run-time library for which the harness + is generated. Corresponding prefix should also be used when calling + *gnattest* for non-native targets. For example, the following options + are used to generate the AUnit test harness for a PowerPC ELF target using + the ZFP run-time library: + + :: + + $ powerpc-elf-gnattest -Psimple.gpr -XPLATFORM=powerpc-elf -XRUNTIME=zfp + + + .. _Current_Limitations: + + Current Limitations + ------------------- + + The tool currently does not support following features: + + * generic tests for nested generic packages and their instantiations + * tests for protected subprograms and entries + diff --git a/gcc/ada/doc/gnat_ugn/inline_assembler.rst b/gcc/ada/doc/gnat_ugn/inline_assembler.rst new file mode 100644 index 00000000000..d79b70b0814 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/inline_assembler.rst @@ -0,0 +1,668 @@ +.. _Inline_Assembler: + +**************** +Inline Assembler +**************** + +.. index:: Inline Assembler + +If you need to write low-level software that interacts directly +with the hardware, Ada provides two ways to incorporate assembly +language code into your program. First, you can import and invoke +external routines written in assembly language, an Ada feature fully +supported by GNAT. However, for small sections of code it may be simpler +or more efficient to include assembly language statements directly +in your Ada source program, using the facilities of the implementation-defined +package `System.Machine_Code`, which incorporates the gcc +Inline Assembler. The Inline Assembler approach offers a number of advantages, +including the following: + +* No need to use non-Ada tools +* Consistent interface over different targets +* Automatic usage of the proper calling conventions +* Access to Ada constants and variables +* Definition of intrinsic routines +* Possibility of inlining a subprogram comprising assembler code +* Code optimizer can take Inline Assembler code into account + +This appendix presents a series of examples to show you how to use +the Inline Assembler. Although it focuses on the Intel x86, +the general approach applies also to other processors. +It is assumed that you are familiar with Ada +and with assembly language programming. + +.. _Basic_Assembler_Syntax: + +Basic Assembler Syntax +====================== + +The assembler used by GNAT and gcc is based not on the Intel assembly +language, but rather on a language that descends from the AT&T Unix +assembler *as* (and which is often referred to as 'AT&T syntax'). +The following table summarizes the main features of *as* syntax +and points out the differences from the Intel conventions. +See the gcc *as* and *gas* (an *as* macro +pre-processor) documentation for further information. + + +| *Register names* +| gcc / *as*: Prefix with '%'; for example `%eax` +| Intel: No extra punctuation; for example `eax` + + +| *Immediate operand* +| gcc / *as*: Prefix with '$'; for example `$4` +| Intel: No extra punctuation; for example `4` + + +| *Address* +| gcc / *as*: Prefix with '$'; for example `$loc` +| Intel: No extra punctuation; for example `loc` + + +| *Memory contents* +| gcc / *as*: No extra punctuation; for example `loc` +| Intel: Square brackets; for example `[loc]` + + +| *Register contents* +| gcc / *as*: Parentheses; for example `(%eax)` +| Intel: Square brackets; for example `[eax]` + + +| *Hexadecimal numbers* +| gcc / *as*: Leading '0x' (C language syntax); for example `0xA0` +| Intel: Trailing 'h'; for example `A0h` + + +| *Operand size* +| gcc / *as*: Explicit in op code; for example `movw` to move a 16-bit word +| Intel: Implicit, deduced by assembler; for example `mov` + + +| *Instruction repetition* +| gcc / *as*: Split into two lines; for example +| `rep` +| `stosl` +| Intel: Keep on one line; for example `rep stosl` + + +| *Order of operands* +| gcc / *as*: Source first; for example `movw $4, %eax` +| Intel: Destination first; for example `mov eax, 4` + + +.. _A_Simple_Example_of_Inline_Assembler: + +A Simple Example of Inline Assembler +==================================== + +The following example will generate a single assembly language statement, +`nop`, which does nothing. Despite its lack of run-time effect, +the example will be useful in illustrating the basics of +the Inline Assembler facility. + + .. code-block:: ada + + with System.Machine_Code; use System.Machine_Code; + procedure Nothing is + begin + Asm ("nop"); + end Nothing; + +`Asm` is a procedure declared in package `System.Machine_Code`; +here it takes one parameter, a *template string* that must be a static +expression and that will form the generated instruction. +`Asm` may be regarded as a compile-time procedure that parses +the template string and additional parameters (none here), +from which it generates a sequence of assembly language instructions. + +The examples in this chapter will illustrate several of the forms +for invoking `Asm`; a complete specification of the syntax +is found in the `Machine_Code_Insertions` section of the +:title:`GNAT Reference Manual`. + +Under the standard GNAT conventions, the `Nothing` procedure +should be in a file named :file:`nothing.adb`. +You can build the executable in the usual way: + + :: + + $ gnatmake nothing + +However, the interesting aspect of this example is not its run-time behavior +but rather the generated assembly code. +To see this output, invoke the compiler as follows: + + :: + + $ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb + +where the options are: + +* :samp:`-c` + compile only (no bind or link) + +* :samp:`-S` + generate assembler listing + +* :samp:`-fomit-frame-pointer` + do not set up separate stack frames + +* :samp:`-gnatp` + do not add runtime checks + +This gives a human-readable assembler version of the code. The resulting +file will have the same name as the Ada source file, but with a `.s` +extension. In our example, the file :file:`nothing.s` has the following +contents: + + :: + + .file "nothing.adb" + gcc2_compiled.: + ___gnu_compiled_ada: + .text + .align 4 + .globl __ada_nothing + __ada_nothing: + #APP + nop + #NO_APP + jmp L1 + .align 2,0x90 + L1: + ret + +The assembly code you included is clearly indicated by +the compiler, between the `#APP` and `#NO_APP` +delimiters. The character before the 'APP' and 'NOAPP' +can differ on different targets. For example, GNU/Linux uses '#APP' while +on NT you will see '/APP'. + +If you make a mistake in your assembler code (such as using the +wrong size modifier, or using a wrong operand for the instruction) GNAT +will report this error in a temporary file, which will be deleted when +the compilation is finished. Generating an assembler file will help +in such cases, since you can assemble this file separately using the +*as* assembler that comes with gcc. + +Assembling the file using the command + + :: + + $ as nothing.s + +will give you error messages whose lines correspond to the assembler +input file, so you can easily find and correct any mistakes you made. +If there are no errors, *as* will generate an object file +:file:`nothing.out`. + + +.. _Output_Variables_in_Inline_Assembler: + +Output Variables in Inline Assembler +==================================== + +The examples in this section, showing how to access the processor flags, +illustrate how to specify the destination operands for assembly language +statements. + + + .. code-block:: ada + + with Interfaces; use Interfaces; + with Ada.Text_IO; use Ada.Text_IO; + with System.Machine_Code; use System.Machine_Code; + procedure Get_Flags is + Flags : Unsigned_32; + use ASCII; + begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax" & LF & HT & -- load eax with flags + "movl %%eax, %0", -- store flags in variable + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + Put_Line ("Flags register:" & Flags'Img); + end Get_Flags; + +In order to have a nicely aligned assembly listing, we have separated +multiple assembler statements in the Asm template string with linefeed +(ASCII.LF) and horizontal tab (ASCII.HT) characters. +The resulting section of the assembly output file is: + + :: + + #APP + pushfl + popl %eax + movl %eax, -40(%ebp) + #NO_APP + +It would have been legal to write the Asm invocation as: + + .. code-block:: ada + + Asm ("pushfl popl %%eax movl %%eax, %0") + +but in the generated assembler file, this would come out as: + + :: + + #APP + pushfl popl %eax movl %eax, -40(%ebp) + #NO_APP + +which is not so convenient for the human reader. + +We use Ada comments +at the end of each line to explain what the assembler instructions +actually do. This is a useful convention. + +When writing Inline Assembler instructions, you need to precede each register +and variable name with a percent sign. Since the assembler already requires +a percent sign at the beginning of a register name, you need two consecutive +percent signs for such names in the Asm template string, thus `%%eax`. +In the generated assembly code, one of the percent signs will be stripped off. + +Names such as `%0`, `%1`, `%2`, etc., denote input or output +variables: operands you later define using `Input` or `Output` +parameters to `Asm`. +An output variable is illustrated in +the third statement in the Asm template string: + + :: + + movl %%eax, %0 + +The intent is to store the contents of the eax register in a variable that can +be accessed in Ada. Simply writing `movl %%eax, Flags` would not +necessarily work, since the compiler might optimize by using a register +to hold Flags, and the expansion of the `movl` instruction would not be +aware of this optimization. The solution is not to store the result directly +but rather to advise the compiler to choose the correct operand form; +that is the purpose of the `%0` output variable. + +Information about the output variable is supplied in the `Outputs` +parameter to `Asm`: + + .. code-block:: ada + + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + +The output is defined by the `Asm_Output` attribute of the target type; +the general format is + + .. code-block:: ada + + Type'Asm_Output (constraint_string, variable_name) + +The constraint string directs the compiler how +to store/access the associated variable. In the example + + .. code-block:: ada + + Unsigned_32'Asm_Output ("=m", Flags); + +the `"m"` (memory) constraint tells the compiler that the variable +`Flags` should be stored in a memory variable, thus preventing +the optimizer from keeping it in a register. In contrast, + + .. code-block:: ada + + Unsigned_32'Asm_Output ("=r", Flags); + +uses the `"r"` (register) constraint, telling the compiler to +store the variable in a register. + +If the constraint is preceded by the equal character '=', it tells +the compiler that the variable will be used to store data into it. + +In the `Get_Flags` example, we used the `"g"` (global) constraint, +allowing the optimizer to choose whatever it deems best. + +There are a fairly large number of constraints, but the ones that are +most useful (for the Intel x86 processor) are the following: + + ====== ========================================== + *=* output constraint + *g* global (i.e., can be stored anywhere) + *m* in memory + *I* a constant + *a* use eax + *b* use ebx + *c* use ecx + *d* use edx + *S* use esi + *D* use edi + *r* use one of eax, ebx, ecx or edx + *q* use one of eax, ebx, ecx, edx, esi or edi + ====== ========================================== + +The full set of constraints is described in the gcc and *as* +documentation; note that it is possible to combine certain constraints +in one constraint string. + +You specify the association of an output variable with an assembler operand +through the :samp:`%{n}` notation, where *n* is a non-negative +integer. Thus in + + .. code-block:: ada + + Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax" & LF & HT & -- load eax with flags + "movl %%eax, %0", -- store flags in variable + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + + +`%0` will be replaced in the expanded code by the appropriate operand, +whatever +the compiler decided for the `Flags` variable. + +In general, you may have any number of output variables: + +* Count the operands starting at 0; thus `%0`, `%1`, etc. + +* Specify the `Outputs` parameter as a parenthesized comma-separated list + of `Asm_Output` attributes + +For example: + + .. code-block:: ada + + Asm ("movl %%eax, %0" & LF & HT & + "movl %%ebx, %1" & LF & HT & + "movl %%ecx, %2", + Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A + Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B + Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C + +where `Var_A`, `Var_B`, and `Var_C` are variables +in the Ada program. + +As a variation on the `Get_Flags` example, we can use the constraints +string to direct the compiler to store the eax register into the `Flags` +variable, instead of including the store instruction explicitly in the +`Asm` template string: + + .. code-block:: ada + + with Interfaces; use Interfaces; + with Ada.Text_IO; use Ada.Text_IO; + with System.Machine_Code; use System.Machine_Code; + procedure Get_Flags_2 is + Flags : Unsigned_32; + use ASCII; + begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax", -- save flags in eax + Outputs => Unsigned_32'Asm_Output ("=a", Flags)); + Put_Line ("Flags register:" & Flags'Img); + end Get_Flags_2; + +The `"a"` constraint tells the compiler that the `Flags` +variable will come from the eax register. Here is the resulting code: + + :: + + #APP + pushfl + popl %eax + #NO_APP + movl %eax,-40(%ebp) + +The compiler generated the store of eax into Flags after +expanding the assembler code. + +Actually, there was no need to pop the flags into the eax register; +more simply, we could just pop the flags directly into the program variable: + + .. code-block:: ada + + with Interfaces; use Interfaces; + with Ada.Text_IO; use Ada.Text_IO; + with System.Machine_Code; use System.Machine_Code; + procedure Get_Flags_3 is + Flags : Unsigned_32; + use ASCII; + begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "pop %0", -- save flags in Flags + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + Put_Line ("Flags register:" & Flags'Img); + end Get_Flags_3; + + +.. _Input_Variables_in_Inline_Assembler: + +Input Variables in Inline Assembler +=================================== + +The example in this section illustrates how to specify the source operands +for assembly language statements. +The program simply increments its input value by 1: + + .. code-block:: ada + + with Interfaces; use Interfaces; + with Ada.Text_IO; use Ada.Text_IO; + with System.Machine_Code; use System.Machine_Code; + procedure Increment is + + function Incr (Value : Unsigned_32) return Unsigned_32 is + Result : Unsigned_32; + begin + Asm ("incl %0", + Outputs => Unsigned_32'Asm_Output ("=a", Result), + Inputs => Unsigned_32'Asm_Input ("a", Value)); + return Result; + end Incr; + + Value : Unsigned_32; + + begin + Value := 5; + Put_Line ("Value before is" & Value'Img); + Value := Incr (Value); + Put_Line ("Value after is" & Value'Img); + end Increment; + +The `Outputs` parameter to `Asm` specifies +that the result will be in the eax register and that it is to be stored +in the `Result` variable. + +The `Inputs` parameter looks much like the `Outputs` parameter, +but with an `Asm_Input` attribute. +The `"="` constraint, indicating an output value, is not present. + +You can have multiple input variables, in the same way that you can have more +than one output variable. + +The parameter count (%0, %1) etc, still starts at the first output statement, +and continues with the input statements. + +Just as the `Outputs` parameter causes the register to be stored into the +target variable after execution of the assembler statements, so does the +`Inputs` parameter cause its variable to be loaded into the register +before execution of the assembler statements. + +Thus the effect of the `Asm` invocation is: + +* load the 32-bit value of `Value` into eax +* execute the `incl %eax` instruction +* store the contents of eax into the `Result` variable + +The resulting assembler file (with *-O2* optimization) contains: + + :: + + _increment__incr.1: + subl $4,%esp + movl 8(%esp),%eax + #APP + incl %eax + #NO_APP + movl %eax,%edx + movl %ecx,(%esp) + addl $4,%esp + ret + + +.. _Inlining_Inline_Assembler_Code: + +Inlining Inline Assembler Code +============================== + +For a short subprogram such as the `Incr` function in the previous +section, the overhead of the call and return (creating / deleting the stack +frame) can be significant, compared to the amount of code in the subprogram +body. A solution is to apply Ada's `Inline` pragma to the subprogram, +which directs the compiler to expand invocations of the subprogram at the +point(s) of call, instead of setting up a stack frame for out-of-line calls. +Here is the resulting program: + + .. code-block:: ada + + with Interfaces; use Interfaces; + with Ada.Text_IO; use Ada.Text_IO; + with System.Machine_Code; use System.Machine_Code; + procedure Increment_2 is + + function Incr (Value : Unsigned_32) return Unsigned_32 is + Result : Unsigned_32; + begin + Asm ("incl %0", + Outputs => Unsigned_32'Asm_Output ("=a", Result), + Inputs => Unsigned_32'Asm_Input ("a", Value)); + return Result; + end Incr; + pragma Inline (Increment); + + Value : Unsigned_32; + + begin + Value := 5; + Put_Line ("Value before is" & Value'Img); + Value := Increment (Value); + Put_Line ("Value after is" & Value'Img); + end Increment_2; + +Compile the program with both optimization (*-O2*) and inlining +(*-gnatn*) enabled. + +The `Incr` function is still compiled as usual, but at the +point in `Increment` where our function used to be called: + + + :: + + pushl %edi + call _increment__incr.1 + +the code for the function body directly appears: + + + :: + + movl %esi,%eax + #APP + incl %eax + #NO_APP + movl %eax,%edx + +thus saving the overhead of stack frame setup and an out-of-line call. + + +.. _Other_`Asm`_Functionality: + +Other `Asm` Functionality +========================= + +This section describes two important parameters to the `Asm` +procedure: `Clobber`, which identifies register usage; +and `Volatile`, which inhibits unwanted optimizations. + +.. _The_`Clobber`_Parameter: + +The `Clobber` Parameter +----------------------- + +One of the dangers of intermixing assembly language and a compiled language +such as Ada is that the compiler needs to be aware of which registers are +being used by the assembly code. In some cases, such as the earlier examples, +the constraint string is sufficient to indicate register usage (e.g., +`"a"` for +the eax register). But more generally, the compiler needs an explicit +identification of the registers that are used by the Inline Assembly +statements. + +Using a register that the compiler doesn't know about +could be a side effect of an instruction (like `mull` +storing its result in both eax and edx). +It can also arise from explicit register usage in your +assembly code; for example: + + .. code-block:: ada + + Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In)); + +where the compiler (since it does not analyze the `Asm` template string) +does not know you are using the ebx register. + +In such cases you need to supply the `Clobber` parameter to `Asm`, +to identify the registers that will be used by your assembly code: + + + .. code-block:: ada + + Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In), + Clobber => "ebx"); + +The Clobber parameter is a static string expression specifying the +register(s) you are using. Note that register names are *not* prefixed +by a percent sign. Also, if more than one register is used then their names +are separated by commas; e.g., `"eax, ebx"` + +The `Clobber` parameter has several additional uses: + +* Use 'register' name `cc` to indicate that flags might have changed +* Use 'register' name `memory` if you changed a memory location + + +.. _The_`Volatile`_Parameter: + +The `Volatile` Parameter +------------------------ + +.. index:: Volatile parameter + +Compiler optimizations in the presence of Inline Assembler may sometimes have +unwanted effects. For example, when an `Asm` invocation with an input +variable is inside a loop, the compiler might move the loading of the input +variable outside the loop, regarding it as a one-time initialization. + +If this effect is not desired, you can disable such optimizations by setting +the `Volatile` parameter to `True`; for example: + + .. code-block:: ada + + Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In), + Clobber => "ebx", + Volatile => True); + +By default, `Volatile` is set to `False` unless there is no +`Outputs` parameter. + +Although setting `Volatile` to `True` prevents unwanted +optimizations, it will also disable other optimizations that might be +important for efficiency. In general, you should set `Volatile` +to `True` only if the compiler's optimizations have created +problems. diff --git a/gcc/ada/doc/gnat_ugn/platform_specific_information.rst b/gcc/ada/doc/gnat_ugn/platform_specific_information.rst new file mode 100644 index 00000000000..dc3dfec22c8 --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/platform_specific_information.rst @@ -0,0 +1,2191 @@ +.. -- Non-breaking space in running text + -- E.g. Ada |nbsp| 95 + +.. |nbsp| unicode:: 0xA0 + :trim: + +.. _Platform_Specific_Information: + +***************************** +Platform-Specific Information +***************************** + +This appendix contains information relating to the implementation +of run-time libraries on various platforms and also covers +topics related to the GNAT implementation on Windows and Mac OS. + +.. _`Run_Time_Libraries`: + +Run-Time Libraries +================== + +.. index:: Tasking and threads libraries +.. index:: Threads libraries and tasking +.. index:: Run-time libraries (platform-specific information) + +The GNAT run-time implementation may vary with respect to both the +underlying threads library and the exception handling scheme. +For threads support, one or more of the following are supplied: + +* **native threads library**, a binding to the thread package from + the underlying operating system + +* **pthreads library** (Sparc Solaris only), a binding to the Solaris + POSIX thread package + +For exception handling, either or both of two models are supplied: + + .. index:: Zero-Cost Exceptions + .. index:: ZCX (Zero-Cost Exceptions) + +* **Zero-Cost Exceptions** ("ZCX"), + which uses binder-generated tables that + are interrogated at run time to locate a handler. + + .. index:: setjmp/longjmp Exception Model + .. index:: SJLJ (setjmp/longjmp Exception Model) + +* **setjmp / longjmp** ('SJLJ'), + which uses dynamically-set data to establish + the set of handlers + +Most programs should experience a substantial speed improvement by +being compiled with a ZCX run-time. +This is especially true for +tasking applications or applications with many exception handlers.} + +This section summarizes which combinations of threads and exception support +are supplied on various GNAT platforms. +It then shows how to select a particular library either +permanently or temporarily, +explains the properties of (and tradeoffs among) the various threads +libraries, and provides some additional +information about several specific platforms. + +.. _Summary_of_Run-Time_Configurations: + +Summary of Run-Time Configurations +---------------------------------- + ++-----------------+--------------+-------------------------+------------+ +| Platform | Run-Time | Tasking | Exceptions | ++=================+==============+=========================+============+ +| ppc-aix | rts-native | native AIX threads | ZCX | +| | (default) | | | +| +--------------+-------------------------+------------+ +| | rts-sjlj | native AIX threads | SJLJ | ++-----------------+--------------+-------------------------+------------+ +| sparc-solaris | rts-native | native Solaris | ZCX | +| | (default) | threads library | | +| +--------------+-------------------------+------------+ +| | rts-pthread | pthread library | ZCX | +| +--------------+-------------------------+------------+ +| | rts-sjlj | native Solaris | SJLJ | +| | | threads library | | ++-----------------+--------------+-------------------------+------------+ +| sparc64-solaris | rts-native | native Solaris | ZCX | +| | (default) | threads library | | ++-----------------+--------------+-------------------------+------------+ +| x86-linux | rts-native | pthread library | ZCX | +| | (default) | | | +| +--------------+-------------------------+------------+ +| | rts-sjlj | pthread library | SJLJ | ++-----------------+--------------+-------------------------+------------+ +| x86-lynx | rts-native | native LynxOS threads | SJLJ | +| | (default) | | | ++-----------------+--------------+-------------------------+------------+ +| x86-solaris | rts-native | native Solaris | ZCX | +| | (default) | threads library | | +| +--------------+-------------------------+------------+ +| | rts-sjlj | native Solaris | SJLJ | +| | | threads library | | ++-----------------+--------------+-------------------------+------------+ +| x86-windows | rts-native | native Win32 threads | ZCX | +| | (default) | | | +| +--------------+-------------------------+------------+ +| | rts-sjlj | native Win32 threads | SJLJ | ++-----------------+--------------+-------------------------+------------+ +| x86_64-linux | rts-native | pthread library | ZCX | +| | (default) | | | +| +--------------+-------------------------+------------+ +| | rts-sjlj | pthread library | SJLJ | ++-----------------+--------------+-------------------------+------------+ + + +.. _Specifying_a_Run-Time_Library: + +Specifying a Run-Time Library +============================= + +The :file:`adainclude` subdirectory containing the sources of the GNAT +run-time library, and the :file:`adalib` subdirectory containing the +:file:`ALI` files and the static and/or shared GNAT library, are located +in the gcc target-dependent area: + + + :: + + target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/ + +As indicated above, on some platforms several run-time libraries are supplied. +These libraries are installed in the target dependent area and +contain a complete source and binary subdirectory. The detailed description +below explains the differences between the different libraries in terms of +their thread support. + +The default run-time library (when GNAT is installed) is *rts-native*. +This default run time is selected by the means of soft links. +For example on x86-linux: + + .. image:: rtlibrary-structure.png + +.. -- + -- $(target-dir) + -- | + -- +--- adainclude----------+ + -- | | + -- +--- adalib-----------+ | + -- | | | + -- +--- rts-native | | + -- | | | | + -- | +--- adainclude <---+ + -- | | | + -- | +--- adalib <----+ + -- | + -- +--- rts-sjlj + -- | + -- +--- adainclude + -- | + -- +--- adalib + + +If the *rts-sjlj* library is to be selected on a permanent basis, +these soft links can be modified with the following commands: + + :: + + $ cd $target + $ rm -f adainclude adalib + $ ln -s rts-sjlj/adainclude adainclude + $ ln -s rts-sjlj/adalib adalib + +Alternatively, you can specify :file:`rts-sjlj/adainclude` in the file +:file:`$target/ada_source_path` and :file:`rts-sjlj/adalib` in +:file:`$target/ada_object_path`. + +.. index:: --RTS option + +Selecting another run-time library temporarily can be +achieved by using the *--RTS* switch, e.g., *--RTS=sjlj* + + +.. _Choosing_the_Scheduling_Policy: + +.. index:: SCHED_FIFO scheduling policy +.. index:: SCHED_RR scheduling policy +.. index:: SCHED_OTHER scheduling policy + +Choosing the Scheduling Policy +------------------------------ + +When using a POSIX threads implementation, you have a choice of several +scheduling policies: `SCHED_FIFO`, `SCHED_RR` and `SCHED_OTHER`. + +Typically, the default is `SCHED_OTHER`, while using `SCHED_FIFO` +or `SCHED_RR` requires special (e.g., root) privileges. + +.. index:: pragma Time_Slice +.. index:: -T0 option +.. index:: pragma Task_Dispatching_Policy + + +By default, GNAT uses the `SCHED_OTHER` policy. To specify +`SCHED_FIFO`, +you can use one of the following: + +* `pragma Time_Slice (0.0)` +* the corresponding binder option *-T0* +* `pragma Task_Dispatching_Policy (FIFO_Within_Priorities)` + + +To specify `SCHED_RR`, +you should use `pragma Time_Slice` with a +value greater than 0.0, or else use the corresponding *-T* +binder option. + + +.. index:: Solaris Sparc threads libraries + +.. _Solaris-Specific_Considerations: + +Solaris-Specific Considerations +------------------------------- + +This section addresses some topics related to the various threads libraries +on Sparc Solaris. + +.. index:: rts-pthread threads library + +.. _Solaris_Threads_Issues: + +Solaris Threads Issues +---------------------- + +GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time +library based on POSIX threads --- *rts-pthread*. + +.. index:: PTHREAD_PRIO_INHERIT policy (under rts-pthread) +.. index:: PTHREAD_PRIO_PROTECT policy (under rts-pthread) +.. index:: pragma Locking_Policy (under rts-pthread) +.. index:: Inheritance_Locking (under rts-pthread) +.. index:: Ceiling_Locking (under rts-pthread) + +This run-time library has the advantage of being mostly shared across all +POSIX-compliant thread implementations, and it also provides under +Solaris |nbsp| 8 the `PTHREAD_PRIO_INHERIT` +and `PTHREAD_PRIO_PROTECT` +semantics that can be selected using the predefined pragma +`Locking_Policy` +with respectively +`Inheritance_Locking` and `Ceiling_Locking` as the policy. + +As explained above, the native run-time library is based on the Solaris thread +library (`libthread`) and is the default library. + +.. index:: GNAT_PROCESSOR environment variable (on Sparc Solaris) + +When the Solaris threads library is used (this is the default), programs +compiled with GNAT can automatically take advantage of +and can thus execute on multiple processors. +The user can alternatively specify a processor on which the program should run +to emulate a single-processor system. The multiprocessor / uniprocessor choice +is made by +setting the environment variable :envvar:`GNAT_PROCESSOR` +to one of the following: + + ========================= =================================================================== + ``GNAT_PROCESSOR`` Value Effect + ========================= =================================================================== + *-2* Use the default configuration (run the program on all + available processors) - this is the same as having `GNAT_PROCESSOR` + unset + *-1* Let the run-time implementation choose one processor and run the + program on that processor + *0 .. Last_Proc* Run the program on the specified processor. + `Last_Proc` is equal to `_SC_NPROCESSORS_CONF - 1` + (where `_SC_NPROCESSORS_CONF` is a system variable). + ========================= =================================================================== + + +.. _AIX-Specific_Considerations: + +AIX-Specific Considerations +--------------------------- + +.. index:: AIX resolver library + +On AIX, the resolver library initializes some internal structure on +the first call to `get*by*` functions, which are used to implement +`GNAT.Sockets.Get_Host_By_Name` and +`GNAT.Sockets.Get_Host_By_Address`. +If such initialization occurs within an Ada task, and the stack size for +the task is the default size, a stack overflow may occur. + +To avoid this overflow, the user should either ensure that the first call +to `GNAT.Sockets.Get_Host_By_Name` or +`GNAT.Sockets.Get_Host_By_Addrss` +occurs in the environment task, or use `pragma Storage_Size` to +specify a sufficiently large size for the stack of the task that contains +this call. + + +.. index:: Windows NT +.. index:: Windows 95 +.. index:: Windows 98 + +.. _Microsoft_Windows_Topics: + +Microsoft Windows Topics +======================== + +This section describes topics that are specific to the Microsoft Windows +platforms. + + +.. only:: PRO or GPL + + .. rubric:: Installing from the Command Line + + By default the GNAT installers display a GUI that prompts you to enter + the installation path and similar information, and then guides you through the + installation process. It is also possible to perform silent installations + using the command-line interface. + + In order to install one of the GNAT installers from the command + line you should pass parameter `/S` (and, optionally, + `/D=`) as command-line arguments. + +.. only:: PRO + + For example, for an unattended installation of + GNAT 7.0.2 into the default directory + `C:\\GNATPRO\\7.0.2` you would run: + + :: + + gnatpro-7.0.2-i686-pc-mingw32-bin.exe /S + + To install into a custom directory, say, `C:\\TOOLS\\GNATPRO\\7.0.2`: + + :: + + gnatpro-7.0.2-i686-pc-mingw32-bin /S /D=C:\TOOLS\GNATPRO\7.0.2 + +.. only:: GPL + + For example, for an unattended installation of + GNAT 2012 into `C:\\GNAT\\2012`: + + :: + + gnat-gpl-2012-i686-pc-mingw32-bin /S /D=C:\GNAT\2012 + +.. only:: PRO or GPL + + You can use the same syntax for all installers. + + Note that unattended installations don't modify system path, nor create file + associations, so such activities need to be done by hand. + + + +.. _Using_GNAT_on_Windows: + +Using GNAT on Windows +--------------------- + +One of the strengths of the GNAT technology is that its tool set +(*gcc*, *gnatbind*, *gnatlink*, *gnatmake*, the +`gdb` debugger, etc.) is used in the same way regardless of the +platform. + +On Windows this tool set is complemented by a number of Microsoft-specific +tools that have been provided to facilitate interoperability with Windows +when this is required. With these tools: + + +* You can build applications using the `CONSOLE` or `WINDOWS` + subsystems. + +* You can use any Dynamically Linked Library (DLL) in your Ada code (both + relocatable and non-relocatable DLLs are supported). + +* You can build Ada DLLs for use in other applications. These applications + can be written in a language other than Ada (e.g., C, C++, etc). Again both + relocatable and non-relocatable Ada DLLs are supported. + +* You can include Windows resources in your Ada application. + +* You can use or create COM/DCOM objects. + +Immediately below are listed all known general GNAT-for-Windows restrictions. +Other restrictions about specific features like Windows Resources and DLLs +are listed in separate sections below. + + +* It is not possible to use `GetLastError` and `SetLastError` + when tasking, protected records, or exceptions are used. In these + cases, in order to implement Ada semantics, the GNAT run-time system + calls certain Win32 routines that set the last error variable to 0 upon + success. It should be possible to use `GetLastError` and + `SetLastError` when tasking, protected record, and exception + features are not used, but it is not guaranteed to work. + +* It is not possible to link against Microsoft C++ libraries except for + import libraries. Interfacing must be done by the mean of DLLs. + +* It is possible to link against Microsoft C libraries. Yet the preferred + solution is to use C/C++ compiler that comes with GNAT, since it + doesn't require having two different development environments and makes the + inter-language debugging experience smoother. + +* When the compilation environment is located on FAT32 drives, users may + experience recompilations of the source files that have not changed if + Daylight Saving Time (DST) state has changed since the last time files + were compiled. NTFS drives do not have this problem. + +* No components of the GNAT toolset use any entries in the Windows + registry. The only entries that can be created are file associations and + PATH settings, provided the user has chosen to create them at installation + time, as well as some minimal book-keeping information needed to correctly + uninstall or integrate different GNAT products. + + +.. _Using_a_network_installation_of_GNAT: + +Using a network installation of GNAT +------------------------------------ + +Make sure the system on which GNAT is installed is accessible from the +current machine, i.e., the install location is shared over the network. +Shared resources are accessed on Windows by means of UNC paths, which +have the format `\\\\server\\sharename\\path` + +In order to use such a network installation, simply add the UNC path of the +:file:`bin` directory of your GNAT installation in front of your PATH. For +example, if GNAT is installed in :file:`\\GNAT` directory of a share location +called :file:`c-drive` on a machine :file:`LOKI`, the following command will +make it available: + + :: + + $ path \\loki\c-drive\gnat\bin;%path%` + +Be aware that every compilation using the network installation results in the +transfer of large amounts of data across the network and will likely cause +serious performance penalty. + +.. _CONSOLE_and_WINDOWS_subsystems: + +CONSOLE and WINDOWS subsystems +------------------------------ + +.. index:: CONSOLE Subsystem +.. index:: WINDOWS Subsystem +.. index:: -mwindows + +There are two main subsystems under Windows. The `CONSOLE` subsystem +(which is the default subsystem) will always create a console when +launching the application. This is not something desirable when the +application has a Windows GUI. To get rid of this console the +application must be using the `WINDOWS` subsystem. To do so +the *-mwindows* linker option must be specified. + + :: + + $ gnatmake winprog -largs -mwindows + +.. _Temporary_Files: + +Temporary Files +--------------- + +.. index:: Temporary files + +It is possible to control where temporary files gets created by setting +the :envvar:`TMP` environment variable. The file will be created: + +* Under the directory pointed to by the :envvar:`TMP` environment variable if + this directory exists. + +* Under :file:`c:\\temp`, if the :envvar:`TMP` environment variable is not + set (or not pointing to a directory) and if this directory exists. + +* Under the current working directory otherwise. + +This allows you to determine exactly where the temporary +file will be created. This is particularly useful in networked +environments where you may not have write access to some +directories. + + +.. _Mixed-Language_Programming_on_Windows: + +Mixed-Language Programming on Windows +------------------------------------- + +Developing pure Ada applications on Windows is no different than on +other GNAT-supported platforms. However, when developing or porting an +application that contains a mix of Ada and C/C++, the choice of your +Windows C/C++ development environment conditions your overall +interoperability strategy. + +If you use *gcc* or Microsoft C to compile the non-Ada part of +your application, there are no Windows-specific restrictions that +affect the overall interoperability with your Ada code. If you do want +to use the Microsoft tools for your C++ code, you have two choices: + +* Encapsulate your C++ code in a DLL to be linked with your Ada + application. In this case, use the Microsoft or whatever environment to + build the DLL and use GNAT to build your executable + (:ref:`Using_DLLs_with_GNAT`). + +* Or you can encapsulate your Ada code in a DLL to be linked with the + other part of your application. In this case, use GNAT to build the DLL + (:ref:`Building_DLLs_with_GNAT_Project_files`) and use the Microsoft + or whatever environment to build your executable. + +In addition to the description about C main in +:ref:`Mixed_Language_Programming` section, if the C main uses a +stand-alone library it is required on x86-windows to +setup the SEH context. For this the C main must looks like this: + + + .. code-block:: c + + /* main.c */ + extern void adainit (void); + extern void adafinal (void); + extern void __gnat_initialize(void*); + extern void call_to_ada (void); + + int main (int argc, char *argv[]) + { + int SEH [2]; + + /* Initialize the SEH context */ + __gnat_initialize (&SEH); + + adainit(); + + /* Then call Ada services in the stand-alone library */ + + call_to_ada(); + + adafinal(); + } + +Note that this is not needed on x86_64-windows where the Windows +native SEH support is used. + + +.. _Windows_Calling_Conventions: + +Windows Calling Conventions +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Stdcall +.. index:: APIENTRY + +This section pertain only to Win32. On Win64 there is a single native +calling convention. All convention specifiers are ignored on this +platform. + +When a subprogram `F` (caller) calls a subprogram `G` +(callee), there are several ways to push `G`'s parameters on the +stack and there are several possible scenarios to clean up the stack +upon `G`'s return. A calling convention is an agreed upon software +protocol whereby the responsibilities between the caller (`F`) and +the callee (`G`) are clearly defined. Several calling conventions +are available for Windows: + +* `C` (Microsoft defined) + +* `Stdcall` (Microsoft defined) + +* `Win32` (GNAT specific) + +* `DLL` (GNAT specific) + + +.. _C_Calling_Convention: + +`C` Calling Convention +"""""""""""""""""""""" + +This is the default calling convention used when interfacing to C/C++ +routines compiled with either *gcc* or Microsoft Visual C++. + +In the `C` calling convention subprogram parameters are pushed on the +stack by the caller from right to left. The caller itself is in charge of +cleaning up the stack after the call. In addition, the name of a routine +with `C` calling convention is mangled by adding a leading underscore. + +The name to use on the Ada side when importing (or exporting) a routine +with `C` calling convention is the name of the routine. For +instance the C function: + + :: + + int get_val (long); + +should be imported from Ada as follows: + + .. code-block:: ada + + function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; + pragma Import (C, Get_Val, External_Name => "get_val"); + +Note that in this particular case the `External_Name` parameter could +have been omitted since, when missing, this parameter is taken to be the +name of the Ada entity in lower case. When the `Link_Name` parameter +is missing, as in the above example, this parameter is set to be the +`External_Name` with a leading underscore. + +When importing a variable defined in C, you should always use the `C` +calling convention unless the object containing the variable is part of a +DLL (in which case you should use the `Stdcall` calling +convention, :ref:`Stdcall_Calling_Convention`). + + +.. _Stdcall_Calling_Convention: + +`Stdcall` Calling Convention +"""""""""""""""""""""""""""" + +This convention, which was the calling convention used for Pascal +programs, is used by Microsoft for all the routines in the Win32 API for +efficiency reasons. It must be used to import any routine for which this +convention was specified. + +In the `Stdcall` calling convention subprogram parameters are pushed +on the stack by the caller from right to left. The callee (and not the +caller) is in charge of cleaning the stack on routine exit. In addition, +the name of a routine with `Stdcall` calling convention is mangled by +adding a leading underscore (as for the `C` calling convention) and a +trailing :samp:`@{nn}`, where `nn` is the overall size (in +bytes) of the parameters passed to the routine. + +The name to use on the Ada side when importing a C routine with a +`Stdcall` calling convention is the name of the C routine. The leading +underscore and trailing :samp:`@{nn}` are added automatically by +the compiler. For instance the Win32 function: + + :: + + APIENTRY int get_val (long); + +should be imported from Ada as follows: + + .. code-block:: ada + + function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; + pragma Import (Stdcall, Get_Val); + -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@4" + +As for the `C` calling convention, when the `External_Name` +parameter is missing, it is taken to be the name of the Ada entity in lower +case. If instead of writing the above import pragma you write: + + .. code-block:: ada + + function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; + pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val"); + +then the imported routine is `_retrieve_val@4`. However, if instead +of specifying the `External_Name` parameter you specify the +`Link_Name` as in the following example: + + .. code-block:: ada + + function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; + pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val"); + +then the imported routine is `retrieve_val`, that is, there is no +decoration at all. No leading underscore and no Stdcall suffix +:samp:`@{nn}`. + +This is especially important as in some special cases a DLL's entry +point name lacks a trailing :samp:`@{nn}` while the exported +name generated for a call has it. + +It is also possible to import variables defined in a DLL by using an +import pragma for a variable. As an example, if a DLL contains a +variable defined as: + + .. code-block:: c + + int my_var; + +then, to access this variable from Ada you should write: + + .. code-block:: ada + + My_Var : Interfaces.C.int; + pragma Import (Stdcall, My_Var); + +Note that to ease building cross-platform bindings this convention +will be handled as a `C` calling convention on non-Windows platforms. + + +.. _Win32_Calling_Convention: + +`Win32` Calling Convention +"""""""""""""""""""""""""" + +This convention, which is GNAT-specific is fully equivalent to the +`Stdcall` calling convention described above. + + +.. _DLL_Calling_Convention: + +`DLL` Calling Convention +"""""""""""""""""""""""" + +This convention, which is GNAT-specific is fully equivalent to the +`Stdcall` calling convention described above. + + +.. _Introduction_to_Dynamic_Link_Libraries_DLLs: + +Introduction to Dynamic Link Libraries (DLLs) +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: DLL + +A Dynamically Linked Library (DLL) is a library that can be shared by +several applications running under Windows. A DLL can contain any number of +routines and variables. + +One advantage of DLLs is that you can change and enhance them without +forcing all the applications that depend on them to be relinked or +recompiled. However, you should be aware than all calls to DLL routines are +slower since, as you will understand below, such calls are indirect. + +To illustrate the remainder of this section, suppose that an application +wants to use the services of a DLL :file:`API.dll`. To use the services +provided by :file:`API.dll` you must statically link against the DLL or +an import library which contains a jump table with an entry for each +routine and variable exported by the DLL. In the Microsoft world this +import library is called :file:`API.lib`. When using GNAT this import +library is called either :file:`libAPI.dll.a`, :file:`libapi.dll.a`, +:file:`libAPI.a` or :file:`libapi.a` (names are case insensitive). + +After you have linked your application with the DLL or the import library +and you run your application, here is what happens: + +* Your application is loaded into memory. + +* The DLL :file:`API.dll` is mapped into the address space of your + application. This means that: + + - The DLL will use the stack of the calling thread. + + - The DLL will use the virtual address space of the calling process. + + - The DLL will allocate memory from the virtual address space of the calling + process. + + - Handles (pointers) can be safely exchanged between routines in the DLL + routines and routines in the application using the DLL. + +* The entries in the jump table (from the import library :file:`libAPI.dll.a` + or :file:`API.lib` or automatically created when linking against a DLL) + which is part of your application are initialized with the addresses + of the routines and variables in :file:`API.dll`. + +* If present in :file:`API.dll`, routines `DllMain` or + `DllMainCRTStartup` are invoked. These routines typically contain + the initialization code needed for the well-being of the routines and + variables exported by the DLL. + +There is an additional point which is worth mentioning. In the Windows +world there are two kind of DLLs: relocatable and non-relocatable +DLLs. Non-relocatable DLLs can only be loaded at a very specific address +in the target application address space. If the addresses of two +non-relocatable DLLs overlap and these happen to be used by the same +application, a conflict will occur and the application will run +incorrectly. Hence, when possible, it is always preferable to use and +build relocatable DLLs. Both relocatable and non-relocatable DLLs are +supported by GNAT. Note that the *-s* linker option (see GNU Linker +User's Guide) removes the debugging symbols from the DLL but the DLL can +still be relocated. + +As a side note, an interesting difference between Microsoft DLLs and +Unix shared libraries, is the fact that on most Unix systems all public +routines are exported by default in a Unix shared library, while under +Windows it is possible (but not required) to list exported routines in +a definition file (see :ref:`The Definition File `). + + +.. _Using_DLLs_with_GNAT: + +Using DLLs with GNAT +^^^^^^^^^^^^^^^^^^^^ + +To use the services of a DLL, say :file:`API.dll`, in your Ada application +you must have: + +* The Ada spec for the routines and/or variables you want to access in + :file:`API.dll`. If not available this Ada spec must be built from the C/C++ + header files provided with the DLL. + +* The import library (:file:`libAPI.dll.a` or :file:`API.lib`). As previously + mentioned an import library is a statically linked library containing the + import table which will be filled at load time to point to the actual + :file:`API.dll` routines. Sometimes you don't have an import library for the + DLL you want to use. The following sections will explain how to build + one. Note that this is optional. + +* The actual DLL, :file:`API.dll`. + +Once you have all the above, to compile an Ada application that uses the +services of :file:`API.dll` and whose main subprogram is `My_Ada_App`, +you simply issue the command + + :: + + $ gnatmake my_ada_app -largs -lAPI + +The argument *-largs -lAPI* at the end of the *gnatmake* command +tells the GNAT linker to look for an import library. The linker will +look for a library name in this specific order: + +* :file:`libAPI.dll.a` +* :file:`API.dll.a` +* :file:`libAPI.a` +* :file:`API.lib` +* :file:`libAPI.dll` +* :file:`API.dll` + +The first three are the GNU style import libraries. The third is the +Microsoft style import libraries. The last two are the actual DLL names. + +Note that if the Ada package spec for :file:`API.dll` contains the +following pragma + + .. code-block:: ada + + pragma Linker_Options ("-lAPI"); + +you do not have to add *-largs -lAPI* at the end of the +*gnatmake* command. + +If any one of the items above is missing you will have to create it +yourself. The following sections explain how to do so using as an +example a fictitious DLL called :file:`API.dll`. + + +.. _Creating_an_Ada_Spec_for_the_DLL_Services: + +Creating an Ada Spec for the DLL Services +""""""""""""""""""""""""""""""""""""""""" + +A DLL typically comes with a C/C++ header file which provides the +definitions of the routines and variables exported by the DLL. The Ada +equivalent of this header file is a package spec that contains definitions +for the imported entities. If the DLL you intend to use does not come with +an Ada spec you have to generate one such spec yourself. For example if +the header file of :file:`API.dll` is a file :file:`api.h` containing the +following two definitions: + + .. code-block:: c + + int some_var; + int get (char *); + +then the equivalent Ada spec could be: + + .. code-block:: ada + + with Interfaces.C.Strings; + package API is + use Interfaces; + + Some_Var : C.int; + function Get (Str : C.Strings.Chars_Ptr) return C.int; + + private + pragma Import (C, Get); + pragma Import (DLL, Some_Var); + end API; + + +.. _Creating_an_Import_Library: + +Creating an Import Library +"""""""""""""""""""""""""" + +.. index:: Import library + +If a Microsoft-style import library :file:`API.lib` or a GNAT-style +import library :file:`libAPI.dll.a` or :file:`libAPI.a` is available +with :file:`API.dll` you can skip this section. You can also skip this +section if :file:`API.dll` or :file:`libAPI.dll` is built with GNU tools +as in this case it is possible to link directly against the +DLL. Otherwise read on. + + +.. index:: Definition file + +.. _The_Definition_File: + +.. rubric:: The Definition File + +As previously mentioned, and unlike Unix systems, the list of symbols +that are exported from a DLL must be provided explicitly in Windows. +The main goal of a definition file is precisely that: list the symbols +exported by a DLL. A definition file (usually a file with a `.def` +suffix) has the following structure: + + :: + + [LIBRARY `name`] + [DESCRIPTION `string`] + EXPORTS + `symbol1` + `symbol2` + ... + +*LIBRARY `name`* + This section, which is optional, gives the name of the DLL. + + +*DESCRIPTION `string`* + This section, which is optional, gives a description string that will be + embedded in the import library. + + +*EXPORTS* + This section gives the list of exported symbols (procedures, functions or + variables). For instance in the case of :file:`API.dll` the `EXPORTS` + section of :file:`API.def` looks like: + + :: + + EXPORTS + some_var + get + +Note that you must specify the correct suffix (:samp:`@{nn}`) +(see :ref:`Windows_Calling_Conventions`) for a Stdcall +calling convention function in the exported symbols list. + +There can actually be other sections in a definition file, but these +sections are not relevant to the discussion at hand. + + +.. rubric:: GNAT-Style Import Library + +.. _GNAT-Style_Import_Library: + +To create a static import library from :file:`API.dll` with the GNAT tools +you should proceed as follows: + +* Create the definition file :file:`API.def` + (see :ref:`The Definition File `). + For that use the `dll2def` tool as follows: + + :: + + $ dll2def API.dll > API.def + + `dll2def` is a very simple tool: it takes as input a DLL and prints + to standard output the list of entry points in the DLL. Note that if + some routines in the DLL have the `Stdcall` convention + (:ref:`Windows_Calling_Conventions`) with stripped :samp:`@{nn}` + suffix then you'll have to edit :file:`api.def` to add it, and specify + *-k* to *gnatdll* when creating the import library. + + Here are some hints to find the right :samp:`@{nn}` suffix. + + - If you have the Microsoft import library (.lib), it is possible to get + the right symbols by using Microsoft `dumpbin` tool (see the + corresponding Microsoft documentation for further details). + + :: + + $ dumpbin /exports api.lib + + - If you have a message about a missing symbol at link time the compiler + tells you what symbol is expected. You just have to go back to the + definition file and add the right suffix. + +* Build the import library `libAPI.dll.a`, using `gnatdll` + (see :ref:`Using_gnatdll`) as follows: + + :: + + $ gnatdll -e API.def -d API.dll + + `gnatdll` takes as input a definition file :file:`API.def` and the + name of the DLL containing the services listed in the definition file + :file:`API.dll`. The name of the static import library generated is + computed from the name of the definition file as follows: if the + definition file name is `xyz``.def`, the import library name will + be `lib``xyz``.a`. Note that in the previous example option + *-e* could have been removed because the name of the definition + file (before the '`.def`' suffix) is the same as the name of the + DLL (:ref:`Using_gnatdll` for more information about `gnatdll`). + + +.. rubric:: Microsoft-Style Import Library + +With GNAT you can either use a GNAT-style or Microsoft-style import +library. A Microsoft import library is needed only if you plan to make an +Ada DLL available to applications developed with Microsoft +tools (:ref:`Mixed-Language_Programming_on_Windows`). + +To create a Microsoft-style import library for :file:`API.dll` you +should proceed as follows: + +* Create the definition file :file:`API.def` from the DLL. For this use either + the `dll2def` tool as described above or the Microsoft `dumpbin` + tool (see the corresponding Microsoft documentation for further details). + +* Build the actual import library using Microsoft's `lib` utility: + + :: + + $ lib -machine:IX86 -def:API.def -out:API.lib + + If you use the above command the definition file :file:`API.def` must + contain a line giving the name of the DLL: + + :: + + LIBRARY "API" + + See the Microsoft documentation for further details about the usage of + `lib`. + + +.. _Building_DLLs_with_GNAT_Project_files: + +Building DLLs with GNAT Project files +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: DLLs, building + +There is nothing specific to Windows in the build process. +:ref:`Library_Projects`. + +Due to a system limitation, it is not possible under Windows to create threads +when inside the `DllMain` routine which is used for auto-initialization +of shared libraries, so it is not possible to have library level tasks in SALs. + + +.. _Building_DLLs_with_GNAT: + +Building DLLs with GNAT +^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: DLLs, building + +This section explain how to build DLLs using the GNAT built-in DLL +support. With the following procedure it is straight forward to build +and use DLLs with GNAT. + + +* Building object files. + The first step is to build all objects files that are to be included + into the DLL. This is done by using the standard *gnatmake* tool. + +* Building the DLL. + To build the DLL you must use *gcc*'s *-shared* and + *-shared-libgcc* options. It is quite simple to use this method: + + :: + + $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ... + + It is important to note that in this case all symbols found in the + object files are automatically exported. It is possible to restrict + the set of symbols to export by passing to *gcc* a definition + file (see :ref:`The Definition File `). + For example: + + :: + + $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ... + + If you use a definition file you must export the elaboration procedures + for every package that required one. Elaboration procedures are named + using the package name followed by "_E". + +* Preparing DLL to be used. + For the DLL to be used by client programs the bodies must be hidden + from it and the .ali set with read-only attribute. This is very important + otherwise GNAT will recompile all packages and will not actually use + the code in the DLL. For example: + + :: + + $ mkdir apilib + $ copy *.ads *.ali api.dll apilib + $ attrib +R apilib\\*.ali + +At this point it is possible to use the DLL by directly linking +against it. Note that you must use the GNAT shared runtime when using +GNAT shared libraries. This is achieved by using *-shared* binder's +option. + + :: + + $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI + + +.. _Building_DLLs_with_gnatdll: + +Building DLLs with gnatdll +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: DLLs, building + +Note that it is preferred to use GNAT Project files +(:ref:`Building_DLLs_with_GNAT_Project_files`) or the built-in GNAT +DLL support (:ref:`Building_DLLs_with_GNAT`) or to build DLLs. + +This section explains how to build DLLs containing Ada code using +`gnatdll`. These DLLs will be referred to as Ada DLLs in the +remainder of this section. + +The steps required to build an Ada DLL that is to be used by Ada as well as +non-Ada applications are as follows: + +* You need to mark each Ada *entity* exported by the DLL with a `C` or + `Stdcall` calling convention to avoid any Ada name mangling for the + entities exported by the DLL + (see :ref:`Exporting Ada Entities `). You can + skip this step if you plan to use the Ada DLL only from Ada applications. + +* Your Ada code must export an initialization routine which calls the routine + `adainit` generated by *gnatbind* to perform the elaboration of + the Ada code in the DLL (:ref:`Ada_DLLs_and_Elaboration`). The initialization + routine exported by the Ada DLL must be invoked by the clients of the DLL + to initialize the DLL. + +* When useful, the DLL should also export a finalization routine which calls + routine `adafinal` generated by *gnatbind* to perform the + finalization of the Ada code in the DLL (:ref:`Ada_DLLs_and_Finalization`). + The finalization routine exported by the Ada DLL must be invoked by the + clients of the DLL when the DLL services are no further needed. + +* You must provide a spec for the services exported by the Ada DLL in each + of the programming languages to which you plan to make the DLL available. + +* You must provide a definition file listing the exported entities + (:ref:`The Definition File `). + +* Finally you must use `gnatdll` to produce the DLL and the import + library (:ref:`Using_gnatdll`). + +Note that a relocatable DLL stripped using the `strip` +binutils tool will not be relocatable anymore. To build a DLL without +debug information pass `-largs -s` to `gnatdll`. This +restriction does not apply to a DLL built using a Library Project. +See :ref:`Library_Projects`. + +.. Limitations_When_Using_Ada_DLLs_from Ada: + +Limitations When Using Ada DLLs from Ada +"""""""""""""""""""""""""""""""""""""""" + +When using Ada DLLs from Ada applications there is a limitation users +should be aware of. Because on Windows the GNAT run time is not in a DLL of +its own, each Ada DLL includes a part of the GNAT run time. Specifically, +each Ada DLL includes the services of the GNAT run time that are necessary +to the Ada code inside the DLL. As a result, when an Ada program uses an +Ada DLL there are two independent GNAT run times: one in the Ada DLL and +one in the main program. + +It is therefore not possible to exchange GNAT run-time objects between the +Ada DLL and the main Ada program. Example of GNAT run-time objects are file +handles (e.g., `Text_IO.File_Type`), tasks types, protected objects +types, etc. + +It is completely safe to exchange plain elementary, array or record types, +Windows object handles, etc. + + +.. _Exporting_Ada_Entities: + +Exporting Ada Entities +"""""""""""""""""""""" + +.. index:: Export table + +Building a DLL is a way to encapsulate a set of services usable from any +application. As a result, the Ada entities exported by a DLL should be +exported with the `C` or `Stdcall` calling conventions to avoid +any Ada name mangling. As an example here is an Ada package +`API`, spec and body, exporting two procedures, a function, and a +variable: + + + .. code-block:: ada + + with Interfaces.C; use Interfaces; + package API is + Count : C.int := 0; + function Factorial (Val : C.int) return C.int; + + procedure Initialize_API; + procedure Finalize_API; + -- Initialization & Finalization routines. More in the next section. + private + pragma Export (C, Initialize_API); + pragma Export (C, Finalize_API); + pragma Export (C, Count); + pragma Export (C, Factorial); + end API; + + .. code-block:: ada + + package body API is + function Factorial (Val : C.int) return C.int is + Fact : C.int := 1; + begin + Count := Count + 1; + for K in 1 .. Val loop + Fact := Fact * K; + end loop; + return Fact; + end Factorial; + + procedure Initialize_API is + procedure Adainit; + pragma Import (C, Adainit); + begin + Adainit; + end Initialize_API; + + procedure Finalize_API is + procedure Adafinal; + pragma Import (C, Adafinal); + begin + Adafinal; + end Finalize_API; + end API; + +If the Ada DLL you are building will only be used by Ada applications +you do not have to export Ada entities with a `C` or `Stdcall` +convention. As an example, the previous package could be written as +follows: + + .. code-block:: ada + + package API is + Count : Integer := 0; + function Factorial (Val : Integer) return Integer; + + procedure Initialize_API; + procedure Finalize_API; + -- Initialization and Finalization routines. + end API; + + .. code-block:: ada + + package body API is + function Factorial (Val : Integer) return Integer is + Fact : Integer := 1; + begin + Count := Count + 1; + for K in 1 .. Val loop + Fact := Fact * K; + end loop; + return Fact; + end Factorial; + + ... + -- The remainder of this package body is unchanged. + end API; + +Note that if you do not export the Ada entities with a `C` or +`Stdcall` convention you will have to provide the mangled Ada names +in the definition file of the Ada DLL +(:ref:`Creating_the_Definition_File`). + + +.. _Ada_DLLs_and_Elaboration: + +Ada DLLs and Elaboration +"""""""""""""""""""""""" + +.. index:: DLLs and elaboration + +The DLL that you are building contains your Ada code as well as all the +routines in the Ada library that are needed by it. The first thing a +user of your DLL must do is elaborate the Ada code +(:ref:`Elaboration_Order_Handling_in_GNAT`). + +To achieve this you must export an initialization routine +(`Initialize_API` in the previous example), which must be invoked +before using any of the DLL services. This elaboration routine must call +the Ada elaboration routine `adainit` generated by the GNAT binder +(:ref:`Binding_with_Non-Ada_Main_Programs`). See the body of +`Initialize_Api` for an example. Note that the GNAT binder is +automatically invoked during the DLL build process by the `gnatdll` +tool (:ref:`Using_gnatdll`). + +When a DLL is loaded, Windows systematically invokes a routine called +`DllMain`. It would therefore be possible to call `adainit` +directly from `DllMain` without having to provide an explicit +initialization routine. Unfortunately, it is not possible to call +`adainit` from the `DllMain` if your program has library level +tasks because access to the `DllMain` entry point is serialized by +the system (that is, only a single thread can execute 'through' it at a +time), which means that the GNAT run time will deadlock waiting for the +newly created task to complete its initialization. + + +.. _Ada_DLLs_and_Finalization: + +Ada DLLs and Finalization +^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: DLLs and finalization + +When the services of an Ada DLL are no longer needed, the client code should +invoke the DLL finalization routine, if available. The DLL finalization +routine is in charge of releasing all resources acquired by the DLL. In the +case of the Ada code contained in the DLL, this is achieved by calling +routine `adafinal` generated by the GNAT binder +(:ref:`Binding_with_Non-Ada_Main_Programs`). +See the body of `Finalize_Api` for an +example. As already pointed out the GNAT binder is automatically invoked +during the DLL build process by the `gnatdll` tool +(:ref:`Using_gnatdll`). + + +.. _Creating_a_Spec_for_Ada_DLLs: + +Creating a Spec for Ada DLLs +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +To use the services exported by the Ada DLL from another programming +language (e.g., C), you have to translate the specs of the exported Ada +entities in that language. For instance in the case of `API.dll`, +the corresponding C header file could look like: + + .. code-block:: c + + extern int *_imp__count; + #define count (*_imp__count) + int factorial (int); + +It is important to understand that when building an Ada DLL to be used by +other Ada applications, you need two different specs for the packages +contained in the DLL: one for building the DLL and the other for using +the DLL. This is because the `DLL` calling convention is needed to +use a variable defined in a DLL, but when building the DLL, the variable +must have either the `Ada` or `C` calling convention. As an +example consider a DLL comprising the following package `API`: + + .. code-block:: ada + + package API is + Count : Integer := 0; + ... + -- Remainder of the package omitted. + end API; + +After producing a DLL containing package `API`, the spec that +must be used to import `API.Count` from Ada code outside of the +DLL is: + + .. code-block:: ada + + package API is + Count : Integer; + pragma Import (DLL, Count); + end API; + + +.. _Creating_the_Definition_File: + +Creating the Definition File +"""""""""""""""""""""""""""" + +The definition file is the last file needed to build the DLL. It lists +the exported symbols. As an example, the definition file for a DLL +containing only package `API` (where all the entities are exported +with a `C` calling convention) is: + + :: + + EXPORTS + count + factorial + finalize_api + initialize_api + +If the `C` calling convention is missing from package `API`, +then the definition file contains the mangled Ada names of the above +entities, which in this case are: + + :: + + EXPORTS + api__count + api__factorial + api__finalize_api + api__initialize_api + + +.. _Using_gnatdll: + +Using `gnatdll` +""""""""""""""" + +.. index:: gnatdll + +`gnatdll` is a tool to automate the DLL build process once all the Ada +and non-Ada sources that make up your DLL have been compiled. +`gnatdll` is actually in charge of two distinct tasks: build the +static import library for the DLL and the actual DLL. The form of the +`gnatdll` command is + + :: + + $ gnatdll [`switches`] `list-of-files` [-largs `opts`] + +where `list-of-files` is a list of ALI and object files. The object +file list must be the exact list of objects corresponding to the non-Ada +sources whose services are to be included in the DLL. The ALI file list +must be the exact list of ALI files for the corresponding Ada sources +whose services are to be included in the DLL. If `list-of-files` is +missing, only the static import library is generated. + +You may specify any of the following switches to `gnatdll`: + + + .. index:: -a (gnatdll) + +:samp:`-a[{address}]` + Build a non-relocatable DLL at `address`. If `address` is not + specified the default address `0x11000000` will be used. By default, + when this switch is missing, `gnatdll` builds relocatable DLL. We + advise the reader to build relocatable DLL. + + + .. index:: -b (gnatdll) + +:samp:`-b {address}` + Set the relocatable DLL base address. By default the address is + `0x11000000`. + + + .. index:: -bargs (gnatdll) + +:samp:`-bargs {opts}` + Binder options. Pass `opts` to the binder. + + + .. index:: -d (gnatdll) + +:samp:`-d {dllfile}` + `dllfile` is the name of the DLL. This switch must be present for + `gnatdll` to do anything. The name of the generated import library is + obtained algorithmically from `dllfile` as shown in the following + example: if `dllfile` is `xyz.dll`, the import library name is + `libxyz.dll.a`. The name of the definition file to use (if not specified + by option *-e*) is obtained algorithmically from `dllfile` + as shown in the following example: + if `dllfile` is `xyz.dll`, the definition + file used is `xyz.def`. + + + .. index:: -e (gnatdll) + +:samp:`-e {deffile}` + `deffile` is the name of the definition file. + + + .. index:: -g (gnatdll) + +:samp:`-g` + Generate debugging information. This information is stored in the object + file and copied from there to the final DLL file by the linker, + where it can be read by the debugger. You must use the + *-g* switch if you plan on using the debugger or the symbolic + stack traceback. + + + .. index:: -h (gnatdll) + +:samp:`-h` + Help mode. Displays `gnatdll` switch usage information. + + + .. index:: -I (gnatdll) + +:samp:`-I{dir}` + Direct `gnatdll` to search the `dir` directory for source and + object files needed to build the DLL. + (:ref:`Search_Paths_and_the_Run-Time_Library_RTL`). + + + .. index:: -k (gnatdll) + +:samp:`-k` + Removes the :samp:`@{nn}` suffix from the import library's exported + names, but keeps them for the link names. You must specify this + option if you want to use a `Stdcall` function in a DLL for which + the :samp:`@{nn}` suffix has been removed. This is the case for most + of the Windows NT DLL for example. This option has no effect when + *-n* option is specified. + + + .. index:: -l (gnatdll) + +:samp:`-l {file}` + The list of ALI and object files used to build the DLL are listed in + `file`, instead of being given in the command line. Each line in + `file` contains the name of an ALI or object file. + + + .. index:: -n (gnatdll) + +:samp:`-n` + No Import. Do not create the import library. + + + .. index:: -q (gnatdll) + +:samp:`-q` + Quiet mode. Do not display unnecessary messages. + + + .. index:: -v (gnatdll) + +:samp:`-v` + Verbose mode. Display extra information. + + + .. index:: -largs (gnatdll) + +:samp:`-largs {opts}` + Linker options. Pass `opts` to the linker. + + +.. rubric:: `gnatdll` Example + +As an example the command to build a relocatable DLL from :file:`api.adb` +once :file:`api.adb` has been compiled and :file:`api.def` created is + + :: + + $ gnatdll -d api.dll api.ali + +The above command creates two files: :file:`libapi.dll.a` (the import +library) and :file:`api.dll` (the actual DLL). If you want to create +only the DLL, just type: + + :: + + $ gnatdll -d api.dll -n api.ali + +Alternatively if you want to create just the import library, type: + + :: + + $ gnatdll -d api.dll + + +.. rubric:: `gnatdll` behind the Scenes + +This section details the steps involved in creating a DLL. `gnatdll` +does these steps for you. Unless you are interested in understanding what +goes on behind the scenes, you should skip this section. + +We use the previous example of a DLL containing the Ada package `API`, +to illustrate the steps necessary to build a DLL. The starting point is a +set of objects that will make up the DLL and the corresponding ALI +files. In the case of this example this means that :file:`api.o` and +:file:`api.ali` are available. To build a relocatable DLL, `gnatdll` does +the following: + +* `gnatdll` builds the base file (:file:`api.base`). A base file gives + the information necessary to generate relocation information for the + DLL. + + :: + + $ gnatbind -n api + $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base + + In addition to the base file, the *gnatlink* command generates an + output file :file:`api.jnk` which can be discarded. The *-mdll* switch + asks *gnatlink* to generate the routines `DllMain` and + `DllMainCRTStartup` that are called by the Windows loader when the DLL + is loaded into memory. + +* `gnatdll` uses `dlltool` (see :ref:`Using dlltool `) to build the + export table (:file:`api.exp`). The export table contains the relocation + information in a form which can be used during the final link to ensure + that the Windows loader is able to place the DLL anywhere in memory. + + :: + + $ dlltool --dllname api.dll --def api.def --base-file api.base \\ + --output-exp api.exp + +* `gnatdll` builds the base file using the new export table. Note that + *gnatbind* must be called once again since the binder generated file + has been deleted during the previous call to *gnatlink*. + + :: + + $ gnatbind -n api + $ gnatlink api -o api.jnk api.exp -mdll + -Wl,--base-file,api.base + + +* `gnatdll` builds the new export table using the new base file and + generates the DLL import library :file:`libAPI.dll.a`. + + + :: + + $ dlltool --dllname api.dll --def api.def --base-file api.base \\ + --output-exp api.exp --output-lib libAPI.a + +* Finally `gnatdll` builds the relocatable DLL using the final export + table. + + :: + + $ gnatbind -n api + $ gnatlink api api.exp -o api.dll -mdll + + +.. _Using_dlltool: + +.. rubric:: Using `dlltool` + +`dlltool` is the low-level tool used by `gnatdll` to build +DLLs and static import libraries. This section summarizes the most +common `dlltool` switches. The form of the `dlltool` command +is + + :: + + $ dlltool [`switches`] + +`dlltool` switches include: + + +.. index:: --base-file (dlltool) + +:samp:`--base-file {basefile}` + Read the base file `basefile` generated by the linker. This switch + is used to create a relocatable DLL. + + +.. index:: --def (dlltool) + +:samp:`--def {deffile}` + Read the definition file. + + +.. index:: --dllname (dlltool) + +:samp:`--dllname {name}` + Gives the name of the DLL. This switch is used to embed the name of the + DLL in the static import library generated by `dlltool` with switch + *--output-lib*. + + +.. index:: -k (dlltool) + +:samp:`-k` + Kill :samp:`@{nn}` from exported names + (:ref:`Windows_Calling_Conventions` + for a discussion about `Stdcall`-style symbols. + + +.. index:: --help (dlltool) + +:samp:`--help` + Prints the `dlltool` switches with a concise description. + + +.. index:: --output-exp (dlltool) + +:samp:`--output-exp {exportfile}` + Generate an export file `exportfile`. The export file contains the + export table (list of symbols in the DLL) and is used to create the DLL. + + +.. index:: --output-lib (dlltool) + +:samp:`--output-lib {libfile}` + Generate a static import library `libfile`. + + +.. index:: -v (dlltool) + +:samp:`-v` + Verbose mode. + + +.. index:: --as (dlltool) + +:samp:`--as {assembler-name}` + Use `assembler-name` as the assembler. The default is `as`. + + +.. _GNAT_and_Windows_Resources: + +GNAT and Windows Resources +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: Resources, windows + +Resources are an easy way to add Windows specific objects to your +application. The objects that can be added as resources include: + +* menus + +* accelerators + +* dialog boxes + +* string tables + +* bitmaps + +* cursors + +* icons + +* fonts + +* version information + +For example, a version information resource can be defined as follow and +embedded into an executable or DLL: + +A version information resource can be used to embed information into an +executable or a DLL. These information can be viewed using the file properties +from the Windows Explorer. Here is an example of a version information +resource: + + :: + + 1 VERSIONINFO + FILEVERSION 1,0,0,0 + PRODUCTVERSION 1,0,0,0 + BEGIN + BLOCK "StringFileInfo" + BEGIN + BLOCK "080904E4" + BEGIN + VALUE "CompanyName", "My Company Name" + VALUE "FileDescription", "My application" + VALUE "FileVersion", "1.0" + VALUE "InternalName", "my_app" + VALUE "LegalCopyright", "My Name" + VALUE "OriginalFilename", "my_app.exe" + VALUE "ProductName", "My App" + VALUE "ProductVersion", "1.0" + END + END + + BLOCK "VarFileInfo" + BEGIN + VALUE "Translation", 0x809, 1252 + END + END + +The value `0809` (langID) is for the U.K English language and +`04E4` (charsetID), which is equal to `1252` decimal, for +multilingual. + +This section explains how to build, compile and use resources. Note that this +section does not cover all resource objects, for a complete description see +the corresponding Microsoft documentation. + + +.. _Building_Resources: + +Building Resources +"""""""""""""""""" + +.. index:: Resources, building + +A resource file is an ASCII file. By convention resource files have an +:file:`.rc` extension. +The easiest way to build a resource file is to use Microsoft tools +such as `imagedit.exe` to build bitmaps, icons and cursors and +`dlgedit.exe` to build dialogs. +It is always possible to build an :file:`.rc` file yourself by writing a +resource script. + +It is not our objective to explain how to write a resource file. A +complete description of the resource script language can be found in the +Microsoft documentation. + + +.. _Compiling_Resources: + +Compiling Resources +""""""""""""""""""" + +.. index:: rc +.. index:: windres +.. index:: Resources, compiling + +This section describes how to build a GNAT-compatible (COFF) object file +containing the resources. This is done using the Resource Compiler +`windres` as follows: + + :: + + $ windres -i myres.rc -o myres.o + +By default `windres` will run *gcc* to preprocess the :file:`.rc` +file. You can specify an alternate preprocessor (usually named +:file:`cpp.exe`) using the `windres` *--preprocessor* +parameter. A list of all possible options may be obtained by entering +the command `windres` *--help*. + +It is also possible to use the Microsoft resource compiler `rc.exe` +to produce a :file:`.res` file (binary resource file). See the +corresponding Microsoft documentation for further details. In this case +you need to use `windres` to translate the :file:`.res` file to a +GNAT-compatible object file as follows: + + :: + + $ windres -i myres.res -o myres.o + + +.. _Using_Resources: + +Using Resources +""""""""""""""" + +.. index:: Resources, using + +To include the resource file in your program just add the +GNAT-compatible object file for the resource(s) to the linker +arguments. With *gnatmake* this is done by using the *-largs* +option: + + :: + + $ gnatmake myprog -largs myres.o + + +.. _Debugging_a_DLL: + +Debugging a DLL +^^^^^^^^^^^^^^^ + +.. index:: DLL debugging + +Debugging a DLL is similar to debugging a standard program. But +we have to deal with two different executable parts: the DLL and the +program that uses it. We have the following four possibilities: + +* The program and the DLL are built with `GCC/GNAT`. +* The program is built with foreign tools and the DLL is built with + `GCC/GNAT`. +* The program is built with `GCC/GNAT` and the DLL is built with + foreign tools. + +In this section we address only cases one and two above. +There is no point in trying to debug +a DLL with `GNU/GDB`, if there is no GDB-compatible debugging +information in it. To do so you must use a debugger compatible with the +tools suite used to build the DLL. + +.. _Program_and_DLL_Both_Built_with_GCC/GNAT: + +Program and DLL Both Built with GCC/GNAT +"""""""""""""""""""""""""""""""""""""""" + +This is the simplest case. Both the DLL and the program have `GDB` +compatible debugging information. It is then possible to break anywhere in +the process. Let's suppose here that the main procedure is named +`ada_main` and that in the DLL there is an entry point named +`ada_dll`. + +The DLL (:ref:`Introduction_to_Dynamic_Link_Libraries_DLLs`) and +program must have been built with the debugging information (see GNAT -g +switch). Here are the step-by-step instructions for debugging it: + +* Launch `GDB` on the main program. + + :: + + $ gdb -nw ada_main + +* Start the program and stop at the beginning of the main procedure + + :: + + (gdb) start + + This step is required to be able to set a breakpoint inside the DLL. As long + as the program is not run, the DLL is not loaded. This has the + consequence that the DLL debugging information is also not loaded, so it is not + possible to set a breakpoint in the DLL. + +* Set a breakpoint inside the DLL + + :: + + (gdb) break ada_dll + (gdb) cont + +At this stage a breakpoint is set inside the DLL. From there on +you can use the standard approach to debug the whole program +(:ref:`Running_and_Debugging_Ada_Programs`). + + +.. _Program_Built_with_Foreign_Tools_and_DLL_Built_with_GCC/GNAT: + +Program Built with Foreign Tools and DLL Built with GCC/GNAT +"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" + +In this case things are slightly more complex because it is not possible to +start the main program and then break at the beginning to load the DLL and the +associated DLL debugging information. It is not possible to break at the +beginning of the program because there is no `GDB` debugging information, +and therefore there is no direct way of getting initial control. This +section addresses this issue by describing some methods that can be used +to break somewhere in the DLL to debug it. + +First suppose that the main procedure is named `main` (this is for +example some C code built with Microsoft Visual C) and that there is a +DLL named `test.dll` containing an Ada entry point named +`ada_dll`. + +The DLL (see :ref:`Introduction_to_Dynamic_Link_Libraries_DLLs`) must have +been built with debugging information (see GNAT `-g` option). + + +.. rubric:: Debugging the DLL Directly + +* Find out the executable starting address + + :: + + $ objdump --file-header main.exe + + The starting address is reported on the last line. For example: + + :: + + main.exe: file format pei-i386 + architecture: i386, flags 0x0000010a: + EXEC_P, HAS_DEBUG, D_PAGED + start address 0x00401010 + +* Launch the debugger on the executable. + + :: + + $ gdb main.exe + +* Set a breakpoint at the starting address, and launch the program. + + :: + + $ (gdb) break *0x00401010 + $ (gdb) run + + The program will stop at the given address. + +* Set a breakpoint on a DLL subroutine. + + :: + + (gdb) break ada_dll.adb:45 + + Or if you want to break using a symbol on the DLL, you need first to + select the Ada language (language used by the DLL). + + :: + + (gdb) set language ada + (gdb) break ada_dll + +* Continue the program. + + :: + + (gdb) cont + + This will run the program until it reaches the breakpoint that has been + set. From that point you can use the standard way to debug a program + as described in (:ref:`Running_and_Debugging_Ada_Programs`). + +It is also possible to debug the DLL by attaching to a running process. + + +.. rubric:: Attaching to a Running Process + +.. index:: DLL debugging, attach to process + +With `GDB` it is always possible to debug a running process by +attaching to it. It is possible to debug a DLL this way. The limitation +of this approach is that the DLL must run long enough to perform the +attach operation. It may be useful for instance to insert a time wasting +loop in the code of the DLL to meet this criterion. + +* Launch the main program :file:`main.exe`. + + :: + + $ main + +* Use the Windows *Task Manager* to find the process ID. Let's say + that the process PID for :file:`main.exe` is 208. + +* Launch gdb. + + :: + + $ gdb + +* Attach to the running process to be debugged. + + :: + + (gdb) attach 208 + +* Load the process debugging information. + + :: + + (gdb) symbol-file main.exe + +* Break somewhere in the DLL. + + :: + + (gdb) break ada_dll + +* Continue process execution. + + :: + + (gdb) cont + +This last step will resume the process execution, and stop at +the breakpoint we have set. From there you can use the standard +approach to debug a program as described in +:ref:`Running_and_Debugging_Ada_Programs`. + + +.. _Setting_Stack_Size_from_gnatlink: + +Setting Stack Size from *gnatlink* +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +It is possible to specify the program stack size at link time. On modern +versions of Windows, starting with XP, this is mostly useful to set the size of +the main stack (environment task). The other task stacks are set with pragma +Storage_Size or with the *gnatbind -d* command. + +Since older versions of Windows (2000, NT4, etc.) do not allow setting the +reserve size of individual tasks, the link-time stack size applies to all +tasks, and pragma Storage_Size has no effect. +In particular, Stack Overflow checks are made against this +link-time specified size. + +This setting can be done with *gnatlink* using either of the following: + + +* *-Xlinker* linker option + + :: + + $ gnatlink hello -Xlinker --stack=0x10000,0x1000 + + + This sets the stack reserve size to 0x10000 bytes and the stack commit + size to 0x1000 bytes. + +* *-Wl* linker option + + :: + + $ gnatlink hello -Wl,--stack=0x1000000 + + This sets the stack reserve size to 0x1000000 bytes. Note that with + *-Wl* option it is not possible to set the stack commit size + because the coma is a separator for this option. + + +.. _Setting_Heap_Size_from_gnatlink: + +Setting Heap Size from *gnatlink* +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Under Windows systems, it is possible to specify the program heap size from +*gnatlink* using either of the following: + +* *-Xlinker* linker option + + :: + + $ gnatlink hello -Xlinker --heap=0x10000,0x1000 + + This sets the heap reserve size to 0x10000 bytes and the heap commit + size to 0x1000 bytes. + +* *-Wl* linker option + + :: + + $ gnatlink hello -Wl,--heap=0x1000000 + + + This sets the heap reserve size to 0x1000000 bytes. Note that with + *-Wl* option it is not possible to set the heap commit size + because the coma is a separator for this option. + + +.. _Mac_OS_Topics: + +Mac OS Topics +============= + +.. index:: OS X + +This section describes topics that are specific to Apple's OS X +platform. + +Codesigning the Debugger +------------------------ + +The Darwin Kernel requires the debugger to have special permissions +before it is allowed to control other processes. These permissions +are granted by codesigning the GDB executable. Without these +permissions, the debugger will report error messages such as:: + + Starting program: /x/y/foo + Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5). + (please check gdb is codesigned - see taskgated(8)) + +Codesigning requires a certificate. The following procedure explains +how to create one: + +* Start the Keychain Access application (in + /Applications/Utilities/Keychain Access.app) + +* Select the Keychain Access -> Certificate Assistant -> + Create a Certificate... menu + +* Then: + + * Choose a name for the new certificate (this procedure will use + "gdb-cert" as an example) + + * Set "Identity Type" to "Self Signed Root" + + * Set "Certificate Type" to "Code Signing" + + * Activate the "Let me override defaults" option + + +* Click several times on "Continue" until the "Specify a Location + For The Certificate" screen appears, then set "Keychain" to "System" + +* Click on "Continue" until the certificate is created + +* Finally, in the view, double-click on the new certificate, + and set "When using this certificate" to "Always Trust" + +* Exit the Keychain Access application and restart the computer + (this is unfortunately required) + + +Once a certificate has been created, the debugger can be codesigned +as follow. In a Terminal, run the following command: + + :: + + $ codesign -f -s "gdb-cert" /bin/gdb + +where "gdb-cert" should be replaced by the actual certificate +name chosen above, and should be replaced by +the location where you installed GNAT. Also, be sure that users are +in the Unix group ``_developer``. + + diff --git a/gcc/ada/doc/gnat_ugn/the_gnat_compilation_model.rst b/gcc/ada/doc/gnat_ugn/the_gnat_compilation_model.rst new file mode 100644 index 00000000000..30eb860789e --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/the_gnat_compilation_model.rst @@ -0,0 +1,4846 @@ +.. |with| replace:: *with* +.. |withs| replace:: *with*\ s +.. |withed| replace:: *with*\ ed +.. |withing| replace:: *with*\ ing + +.. -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + + +.. _The_GNAT_Compilation_Model: + +************************** +The GNAT Compilation Model +************************** + +.. index:: ! GNAT compilation model + +.. index:: Compilation model + +This chapter describes the compilation model used by GNAT. Although +similar to that used by other languages such as C and C++, this model +is substantially different from the traditional Ada compilation models, +which are based on a centralized program library. The chapter covers +the following material: + +* Topics related to source file makeup and naming + + * :ref:`Source_Representation` + * :ref:`Foreign_Language_Representation` + * :ref:`File_Naming_Topics_and_Utilities` + +* :ref:`Configuration_Pragmas` +* :ref:`Generating_Object_Files` +* :ref:`Source_Dependencies` +* :ref:`The_Ada_Library_Information_Files` +* :ref:`Binding_an_Ada_Program` +* :ref:`GNAT_and_Libraries` +* :ref:`Conditional_Compilation` +* :ref:`Mixed_Language_Programming` +* :ref:`GNAT_and_Other_Compilation_Models` +* :ref:`Using_GNAT_Files_with_External_Tools` + + +.. _Source_Representation: + +Source Representation +===================== + +.. index:: Latin-1 + +.. index:: VT, HT, CR, LF, FF + +Ada source programs are represented in standard text files, using +Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar +7-bit ASCII set, plus additional characters used for +representing foreign languages (see :ref:`Foreign_Language_Representation` +for support of non-USA character sets). The format effector characters +are represented using their standard ASCII encodings, as follows: + + =========== ======================= ========= + Character Effect Code + ----------- ----------------------- --------- + :kbd:`VT` Vertical tab `16#0B#` + :kbd:`HT` Horizontal tab `16#09#` + :kbd:`CR` Carriage return `16#0D#` + :kbd:`LF` Line feed `16#0A#` + :kbd:`FF` Form feed `16#0C#` + =========== ======================= ========= + +Source files are in standard text file format. In addition, GNAT will +recognize a wide variety of stream formats, in which the end of +physical lines is marked by any of the following sequences: +`LF`, `CR`, `CR-LF`, or `LF-CR`. This is useful +in accommodating files that are imported from other operating systems. + +.. index:: pair: End of source file; Source file, end + +.. index:: SUB (control character) + +The end of a source file is normally represented by the physical end of +file. However, the control character `16#1A#` (:kbd:`SUB`) is also +recognized as signalling the end of the source file. Again, this is +provided for compatibility with other operating systems where this +code is used to represent the end of file. + +.. index:: spec (definition), compilation (definition) + +Each file contains a single Ada compilation unit, including any pragmas +associated with the unit. For example, this means you must place a +package declaration (a package `spec`) and the corresponding body in +separate files. An Ada `compilation` (which is a sequence of +compilation units) is represented using a sequence of files. Similarly, +you will place each subunit or child unit in a separate file. + +.. _Foreign_Language_Representation: + +Foreign Language Representation +=============================== + +GNAT supports the standard character sets defined in Ada as well as +several other non-standard character sets for use in localized versions +of the compiler (:ref:`Character_Set_Control`). + +.. _Latin-1: + +Latin-1 +------- + +.. index:: Latin-1 + +The basic character set is Latin-1. This character set is defined by ISO +standard 8859, part 1. The lower half (character codes `16#00#` +... `16#7F#)` is identical to standard ASCII coding, but the upper +half is used to represent additional characters. These include extended letters +used by European languages, such as French accents, the vowels with umlauts +used in German, and the extra letter A-ring used in Swedish. + +.. index:: Ada.Characters.Latin_1 + +For a complete list of Latin-1 codes and their encodings, see the source +file of library unit `Ada.Characters.Latin_1` in file +:file:`a-chlat1.ads`. +You may use any of these extended characters freely in character or +string literals. In addition, the extended characters that represent +letters can be used in identifiers. + +.. _Other_8-Bit_Codes: + +Other 8-Bit Codes +----------------- + +GNAT also supports several other 8-bit coding schemes: + + +.. index:: Latin-2 +.. index:: ISO 8859-2 + +*ISO 8859-2 (Latin-2)* + Latin-2 letters allowed in identifiers, with uppercase and lowercase + equivalence. + +.. index:: Latin-3 +.. index:: ISO 8859-3 + +*ISO 8859-3 (Latin-3)* + Latin-3 letters allowed in identifiers, with uppercase and lowercase + equivalence. + + +.. index:: Latin-4 +.. index:: ISO 8859-4 + +*ISO 8859-4 (Latin-4)* + Latin-4 letters allowed in identifiers, with uppercase and lowercase + equivalence. + + +.. index:: ISO 8859-5 +.. index:: Cyrillic + +*ISO 8859-5 (Cyrillic)* + ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and + lowercase equivalence. + +.. index:: ISO 8859-15 +.. index:: Latin-9 + +*ISO 8859-15 (Latin-9)* + ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and + lowercase equivalence + +.. index:: code page 437 (IBM PC) + +*IBM PC (code page 437)* + This code page is the normal default for PCs in the U.S. It corresponds + to the original IBM PC character set. This set has some, but not all, of + the extended Latin-1 letters, but these letters do not have the same + encoding as Latin-1. In this mode, these letters are allowed in + identifiers with uppercase and lowercase equivalence. + +.. index:: code page 850 (IBM PC) + +*IBM PC (code page 850)* + This code page is a modification of 437 extended to include all the + Latin-1 letters, but still not with the usual Latin-1 encoding. In this + mode, all these letters are allowed in identifiers with uppercase and + lowercase equivalence. + + +*Full Upper 8-bit* + Any character in the range 80-FF allowed in identifiers, and all are + considered distinct. In other words, there are no uppercase and lowercase + equivalences in this range. This is useful in conjunction with + certain encoding schemes used for some foreign character sets (e.g., + the typical method of representing Chinese characters on the PC). + + +*No Upper-Half* + No upper-half characters in the range 80-FF are allowed in identifiers. + This gives Ada 83 compatibility for identifier names. + +For precise data on the encodings permitted, and the uppercase and lowercase +equivalences that are recognized, see the file :file:`csets.adb` in +the GNAT compiler sources. You will need to obtain a full source release +of GNAT to obtain this file. + +.. _Wide_Character_Encodings: + +Wide_Character Encodings +------------------------ + +GNAT allows wide character codes to appear in character and string +literals, and also optionally in identifiers, by means of the following +possible encoding schemes: + +*Hex Coding* + In this encoding, a wide character is represented by the following five + character sequence:: + + ESC a b c d + + where `a`, `b`, `c`, `d` are the four hexadecimal + characters (using uppercase letters) of the wide character code. For + example, ESC A345 is used to represent the wide character with code + `16#A345#`. + This scheme is compatible with use of the full Wide_Character set. + +*Upper-Half Coding* + .. index:: Upper-Half Coding + + The wide character with encoding `16#abcd#` where the upper bit is on + (in other words, 'a' is in the range 8-F) is represented as two bytes, + `16#ab#` and `16#cd#`. The second byte cannot be a format control + character, but is not required to be in the upper half. This method can + be also used for shift-JIS or EUC, where the internal coding matches the + external coding. + +*Shift JIS Coding* + .. index:: Shift JIS Coding + + A wide character is represented by a two-character sequence, + `16#ab#` and + `16#cd#`, with the restrictions described for upper-half encoding as + described above. The internal character code is the corresponding JIS + character according to the standard algorithm for Shift-JIS + conversion. Only characters defined in the JIS code set table can be + used with this encoding method. + + +*EUC Coding* + .. index:: EUC Coding + + A wide character is represented by a two-character sequence + `16#ab#` and + `16#cd#`, with both characters being in the upper half. The internal + character code is the corresponding JIS character according to the EUC + encoding algorithm. Only characters defined in the JIS code set table + can be used with this encoding method. + + +*UTF-8 Coding* + A wide character is represented using + UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO + 10646-1/Am.2. Depending on the character value, the representation + is a one, two, or three byte sequence:: + + 16#0000#-16#007f#: 2#0`xxxxxxx`# + 16#0080#-16#07ff#: 2#110`xxxxx`# 2#10`xxxxxx`# + 16#0800#-16#ffff#: 2#1110`xxxx`# 2#10`xxxxxx`# 2#10`xxxxxx`# + + where the `xxx` bits correspond to the left-padded bits of the + 16-bit character value. Note that all lower half ASCII characters + are represented as ASCII bytes and all upper half characters and + other wide characters are represented as sequences of upper-half + (The full UTF-8 scheme allows for encoding 31-bit characters as + 6-byte sequences, and in the following section on wide wide + characters, the use of these sequences is documented). + + +*Brackets Coding* + In this encoding, a wide character is represented by the following eight + character sequence:: + + [ " a b c d " ] + + where `a`, `b`, `c`, `d` are the four hexadecimal + characters (using uppercase letters) of the wide character code. For + example, ['A345'] is used to represent the wide character with code + `16#A345#`. It is also possible (though not required) to use the + Brackets coding for upper half characters. For example, the code + `16#A3#` can be represented as `['A3']`. + + This scheme is compatible with use of the full Wide_Character set, + and is also the method used for wide character encoding in some standard + ACATS (Ada Conformity Assessment Test Suite) test suite distributions. + +.. note:: + + Some of these coding schemes do not permit the full use of the + Ada character set. For example, neither Shift JIS nor EUC allow the + use of the upper half of the Latin-1 set. + +.. _Wide_Wide_Character_Encodings: + +Wide_Wide_Character Encodings +----------------------------- + +GNAT allows wide wide character codes to appear in character and string +literals, and also optionally in identifiers, by means of the following +possible encoding schemes: + +*UTF-8 Coding* + A wide character is represented using + UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO + 10646-1/Am.2. Depending on the character value, the representation + of character codes with values greater than 16#FFFF# is a + is a four, five, or six byte sequence:: + + 16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx + 10xxxxxx + 16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx + 10xxxxxx 10xxxxxx + 16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx + 10xxxxxx 10xxxxxx 10xxxxxx + + + where the `xxx` bits correspond to the left-padded bits of the + 32-bit character value. + +*Brackets Coding* + In this encoding, a wide wide character is represented by the following ten or + twelve byte character sequence:: + + [ " a b c d e f " ] + [ " a b c d e f g h " ] + + where `a-h` are the six or eight hexadecimal + characters (using uppercase letters) of the wide wide character code. For + example, ["1F4567"] is used to represent the wide wide character with code + `16#001F_4567#`. + + This scheme is compatible with use of the full Wide_Wide_Character set, + and is also the method used for wide wide character encoding in some standard + ACATS (Ada Conformity Assessment Test Suite) test suite distributions. + + +.. _File_Naming_Topics_and_Utilities: + +File Naming Topics and Utilities +================================ + +GNAT has a default file naming scheme and also provides the user with +a high degree of control over how the names and extensions of the +source files correspond to the Ada compilation units that they contain. + + +.. _File_Naming_Rules: + +File Naming Rules +----------------- + +The default file name is determined by the name of the unit that the +file contains. The name is formed by taking the full expanded name of +the unit and replacing the separating dots with hyphens and using +lowercase for all letters. + +An exception arises if the file name generated by the above rules starts +with one of the characters +`a`, `g`, `i`, or `s`, and the second character is a +minus. In this case, the character tilde is used in place +of the minus. The reason for this special rule is to avoid clashes with +the standard names for child units of the packages System, Ada, +Interfaces, and GNAT, which use the prefixes +`s-`, `a-`, `i-`, and `g-`, +respectively. + +The file extension is :file:`.ads` for a spec and +:file:`.adb` for a body. The following table shows some +examples of these rules. + + ============================ =============================== + Source File Ada Compilation Unit + ---------------------------- ------------------------------- + :file:`main.ads` Main (spec) + :file:`main.adb` Main (body) + :file:`arith_functions.ads` Arith_Functions (package spec) + :file:`arith_functions.adb` Arith_Functions (package body) + :file:`func-spec.ads` Func.Spec (child package spec) + :file:`func-spec.adb` Func.Spec (child package body) + :file:`main-sub.adb` Sub (subunit of Main) + :file:`a~bad.adb` A.Bad (child package body) + ============================ =============================== + +Following these rules can result in excessively long +file names if corresponding +unit names are long (for example, if child units or subunits are +heavily nested). An option is available to shorten such long file names +(called file name 'krunching'). This may be particularly useful when +programs being developed with GNAT are to be used on operating systems +with limited file name lengths. :ref:`Using_gnatkr`. + +Of course, no file shortening algorithm can guarantee uniqueness over +all possible unit names; if file name krunching is used, it is your +responsibility to ensure no name clashes occur. Alternatively you +can specify the exact file names that you want used, as described +in the next section. Finally, if your Ada programs are migrating from a +compiler with a different naming convention, you can use the gnatchop +utility to produce source files that follow the GNAT naming conventions. +(For details see :ref:`Renaming_Files_with_gnatchop`.) + +Note: in the case of Windows or Mac OS operating systems, case is not +significant. So for example on `Windows` if the canonical name is +`main-sub.adb`, you can use the file name :file:`Main-Sub.adb` instead. +However, case is significant for other operating systems, so for example, +if you want to use other than canonically cased file names on a Unix system, +you need to follow the procedures described in the next section. + +.. _Using_Other_File_Names: + +Using Other File Names +---------------------- + +.. index:: File names + +In the previous section, we have described the default rules used by +GNAT to determine the file name in which a given unit resides. It is +often convenient to follow these default rules, and if you follow them, +the compiler knows without being explicitly told where to find all +the files it needs. + +.. index:: Source_File_Name pragma + +However, in some cases, particularly when a program is imported from +another Ada compiler environment, it may be more convenient for the +programmer to specify which file names contain which units. GNAT allows +arbitrary file names to be used by means of the Source_File_Name pragma. +The form of this pragma is as shown in the following examples: + +.. code-block:: ada + + pragma Source_File_Name (My_Utilities.Stacks, + Spec_File_Name => "myutilst_a.ada"); + pragma Source_File_name (My_Utilities.Stacks, + Body_File_Name => "myutilst.ada"); + +As shown in this example, the first argument for the pragma is the unit +name (in this example a child unit). The second argument has the form +of a named association. The identifier +indicates whether the file name is for a spec or a body; +the file name itself is given by a string literal. + +The source file name pragma is a configuration pragma, which means that +normally it will be placed in the :file:`gnat.adc` +file used to hold configuration +pragmas that apply to a complete compilation environment. +For more details on how the :file:`gnat.adc` file is created and used +see :ref:`Handling_of_Configuration_Pragmas`. + +.. index:: gnat.adc + +GNAT allows completely arbitrary file names to be specified using the +source file name pragma. However, if the file name specified has an +extension other than :file:`.ads` or :file:`.adb` it is necessary to use +a special syntax when compiling the file. The name in this case must be +preceded by the special sequence *-x* followed by a space and the name +of the language, here `ada`, as in: + +.. code-block:: sh + + $ gcc -c -x ada peculiar_file_name.sim + +`gnatmake` handles non-standard file names in the usual manner (the +non-standard file name for the main program is simply used as the +argument to gnatmake). Note that if the extension is also non-standard, +then it must be included in the `gnatmake` command, it may not +be omitted. + +.. _Alternative_File_Naming_Schemes: + +Alternative File Naming Schemes +------------------------------- + +.. index:: File naming schemes, alternative + +.. index:: File names + +The previous section described the use of the `Source_File_Name` +pragma to allow arbitrary names to be assigned to individual source files. +However, this approach requires one pragma for each file, and especially in +large systems can result in very long :file:`gnat.adc` files, and also create +a maintenance problem. + +.. index:: Source_File_Name pragma + +GNAT also provides a facility for specifying systematic file naming schemes +other than the standard default naming scheme previously described. An +alternative scheme for naming is specified by the use of +`Source_File_Name` pragmas having the following format: + +.. code-block:: ada + + pragma Source_File_Name ( + Spec_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC] + [ , Dot_Replacement => STRING_LITERAL ] ); + + pragma Source_File_Name ( + Body_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC ] + [ , Dot_Replacement => STRING_LITERAL ] ) ; + + pragma Source_File_Name ( + Subunit_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC ] + [ , Dot_Replacement => STRING_LITERAL ] ) ; + + FILE_NAME_PATTERN ::= STRING_LITERAL + CASING_SPEC ::= Lowercase | Uppercase | Mixedcase + +The `FILE_NAME_PATTERN` string shows how the file name is constructed. +It contains a single asterisk character, and the unit name is substituted +systematically for this asterisk. The optional parameter +`Casing` indicates +whether the unit name is to be all upper-case letters, all lower-case letters, +or mixed-case. If no +`Casing` parameter is used, then the default is all +lower-case. + +The optional `Dot_Replacement` string is used to replace any periods +that occur in subunit or child unit names. If no `Dot_Replacement` +argument is used then separating dots appear unchanged in the resulting +file name. +Although the above syntax indicates that the +`Casing` argument must appear +before the `Dot_Replacement` argument, but it +is also permissible to write these arguments in the opposite order. + +As indicated, it is possible to specify different naming schemes for +bodies, specs, and subunits. Quite often the rule for subunits is the +same as the rule for bodies, in which case, there is no need to give +a separate `Subunit_File_Name` rule, and in this case the +`Body_File_name` rule is used for subunits as well. + +The separate rule for subunits can also be used to implement the rather +unusual case of a compilation environment (e.g., a single directory) which +contains a subunit and a child unit with the same unit name. Although +both units cannot appear in the same partition, the Ada Reference Manual +allows (but does not require) the possibility of the two units coexisting +in the same environment. + +The file name translation works in the following steps: + +* If there is a specific `Source_File_Name` pragma for the given unit, + then this is always used, and any general pattern rules are ignored. + +* If there is a pattern type `Source_File_Name` pragma that applies to + the unit, then the resulting file name will be used if the file exists. If + more than one pattern matches, the latest one will be tried first, and the + first attempt resulting in a reference to a file that exists will be used. + +* If no pattern type `Source_File_Name` pragma that applies to the unit + for which the corresponding file exists, then the standard GNAT default + naming rules are used. + +As an example of the use of this mechanism, consider a commonly used scheme +in which file names are all lower case, with separating periods copied +unchanged to the resulting file name, and specs end with :file:`.1.ada`, and +bodies end with :file:`.2.ada`. GNAT will follow this scheme if the following +two pragmas appear: + +.. code-block:: ada + + pragma Source_File_Name + (Spec_File_Name => ".1.ada"); + pragma Source_File_Name + (Body_File_Name => ".2.ada"); + +The default GNAT scheme is actually implemented by providing the following +default pragmas internally: + +.. code-block:: ada + + pragma Source_File_Name + (Spec_File_Name => ".ads", Dot_Replacement => "-"); + pragma Source_File_Name + (Body_File_Name => ".adb", Dot_Replacement => "-"); + +Our final example implements a scheme typically used with one of the +Ada 83 compilers, where the separator character for subunits was '__' +(two underscores), specs were identified by adding :file:`_.ADA`, bodies +by adding :file:`.ADA`, and subunits by +adding :file:`.SEP`. All file names were +upper case. Child units were not present of course since this was an +Ada 83 compiler, but it seems reasonable to extend this scheme to use +the same double underscore separator for child units. + +.. code-block:: ada + + pragma Source_File_Name + (Spec_File_Name => "_.ADA", + Dot_Replacement => "__", + Casing = Uppercase); + pragma Source_File_Name + (Body_File_Name => ".ADA", + Dot_Replacement => "__", + Casing = Uppercase); + pragma Source_File_Name + (Subunit_File_Name => ".SEP", + Dot_Replacement => "__", + Casing = Uppercase); + + +.. index:: ! gnatname + +.. _Handling_Arbitrary_File_Naming_Conventions_with_gnatname: + +Handling Arbitrary File Naming Conventions with `gnatname` +---------------------------------------------------------- + +.. index:: File Naming Conventions + +.. _Arbitrary_File_Naming_Conventions: + +Arbitrary File Naming Conventions +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The GNAT compiler must be able to know the source file name of a compilation +unit. When using the standard GNAT default file naming conventions +(`.ads` for specs, `.adb` for bodies), the GNAT compiler +does not need additional information. + +When the source file names do not follow the standard GNAT default file naming +conventions, the GNAT compiler must be given additional information through +a configuration pragmas file (:ref:`Configuration_Pragmas`) +or a project file. +When the non-standard file naming conventions are well-defined, +a small number of pragmas `Source_File_Name` specifying a naming pattern +(:ref:`Alternative_File_Naming_Schemes`) may be sufficient. However, +if the file naming conventions are irregular or arbitrary, a number +of pragma `Source_File_Name` for individual compilation units +must be defined. +To help maintain the correspondence between compilation unit names and +source file names within the compiler, +GNAT provides a tool `gnatname` to generate the required pragmas for a +set of files. + +.. _Running_gnatname: + +Running `gnatname` +^^^^^^^^^^^^^^^^^^ + +The usual form of the `gnatname` command is: + +.. code-block:: sh + + $ gnatname [`switches`] `naming_pattern` [`naming_patterns`] + [--and [`switches`] `naming_pattern` [`naming_patterns`]] + + +All of the arguments are optional. If invoked without any argument, +`gnatname` will display its usage. + +When used with at least one naming pattern, `gnatname` will attempt to +find all the compilation units in files that follow at least one of the +naming patterns. To find these compilation units, +`gnatname` will use the GNAT compiler in syntax-check-only mode on all +regular files. + +One or several Naming Patterns may be given as arguments to `gnatname`. +Each Naming Pattern is enclosed between double quotes (or single +quotes on Windows). +A Naming Pattern is a regular expression similar to the wildcard patterns +used in file names by the Unix shells or the DOS prompt. + +`gnatname` may be called with several sections of directories/patterns. +Sections are separated by switch `--and`. In each section, there must be +at least one pattern. If no directory is specified in a section, the current +directory (or the project directory is `-P` is used) is implied. +The options other that the directory switches and the patterns apply globally +even if they are in different sections. + +Examples of Naming Patterns are:: + + "*.[12].ada" + "*.ad[sb]*" + "body_*" "spec_*" + +For a more complete description of the syntax of Naming Patterns, +see the second kind of regular expressions described in :file:`g-regexp.ads` +(the 'Glob' regular expressions). + +When invoked with no switch `-P`, `gnatname` will create a +configuration pragmas file :file:`gnat.adc` in the current working directory, +with pragmas `Source_File_Name` for each file that contains a valid Ada +unit. + +.. _Switches_for_gnatname: + +Switches for `gnatname` +^^^^^^^^^^^^^^^^^^^^^^^ + +Switches for `gnatname` must precede any specified Naming Pattern. + +You may specify any of the following switches to `gnatname`: + +.. index:: --version (gnatname) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + +.. index:: --help (gnatname) + +:samp:`--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + +:samp:`--subdirs={dir}` + Real object, library or exec directories are subdirectories of the + specified ones. + +:samp:`--no-backup` + Do not create a backup copy of an existing project file. + +:samp:`--and` + Start another section of directories/patterns. + +.. index:: -c (gnatname) + +:samp:`-c{filename}` + Create a configuration pragmas file :file:`filename` (instead of the default + :file:`gnat.adc`). + There may be zero, one or more space between *-c* and + :file:`filename`. + :file:`filename` may include directory information. :file:`filename` must be + writable. There may be only one switch *-c*. + When a switch *-c* is + specified, no switch *-P* may be specified (see below). + +.. index:: -d (gnatname) + +:samp:`-d{dir}` + Look for source files in directory :file:`dir`. There may be zero, one or more + spaces between *-d* and :file:`dir`. + :file:`dir` may end with `/**`, that is it may be of the form + `root_dir/**`. In this case, the directory `root_dir` and all of its + subdirectories, recursively, have to be searched for sources. + When a switch *-d* + is specified, the current working directory will not be searched for source + files, unless it is explicitly specified with a *-d* + or *-D* switch. + Several switches *-d* may be specified. + If :file:`dir` is a relative path, it is relative to the directory of + the configuration pragmas file specified with switch + *-c*, + or to the directory of the project file specified with switch + *-P* or, + if neither switch *-c* + nor switch *-P* are specified, it is relative to the + current working directory. The directory + specified with switch *-d* must exist and be readable. + +.. index:: -D (gnatname) + +:samp:`-D{filename}` + Look for source files in all directories listed in text file :file:`filename`. + There may be zero, one or more spaces between *-D* + and :file:`filename`. + :file:`filename` must be an existing, readable text file. + Each nonempty line in :file:`filename` must be a directory. + Specifying switch *-D* is equivalent to specifying as many + switches *-d* as there are nonempty lines in + :file:`file`. + +:samp:`-eL` + Follow symbolic links when processing project files. + + .. index:: -f (gnatname) + +:samp:`-f{pattern}` + Foreign patterns. Using this switch, it is possible to add sources of languages + other than Ada to the list of sources of a project file. + It is only useful if a -P switch is used. + For example, + + .. code-block:: sh + + gnatname -Pprj -f"*.c" "*.ada" + + will look for Ada units in all files with the :file:`.ada` extension, + and will add to the list of file for project :file:`prj.gpr` the C files + with extension :file:`.c`. + + .. index:: -h (gnatname) + +:samp:`-h` + Output usage (help) information. The output is written to :file:`stdout`. + + .. index:: -P (gnatname) + +:samp:`-P{proj}` + Create or update project file :file:`proj`. There may be zero, one or more space + between *-P* and :file:`proj`. :file:`proj` may include directory + information. :file:`proj` must be writable. + There may be only one switch *-P*. + When a switch *-P* is specified, + no switch *-c* may be specified. + On all platforms, except on VMS, when `gnatname` is invoked for an + existing project file .gpr, a backup copy of the project file is created + in the project directory with file name .gpr.saved_x. 'x' is the first + non negative number that makes this backup copy a new file. + + .. index:: -v (gnatname) + +:samp:`-v` + Verbose mode. Output detailed explanation of behavior to :file:`stdout`. + This includes name of the file written, the name of the directories to search + and, for each file in those directories whose name matches at least one of + the Naming Patterns, an indication of whether the file contains a unit, + and if so the name of the unit. + +.. index:: -v -v (gnatname) + +:samp:`-v -v` + Very Verbose mode. In addition to the output produced in verbose mode, + for each file in the searched directories whose name matches none of + the Naming Patterns, an indication is given that there is no match. + + .. index:: -x (gnatname) + +:samp:`-x{pattern}` + Excluded patterns. Using this switch, it is possible to exclude some files + that would match the name patterns. For example, + + .. code-block:: sh + + gnatname -x "*_nt.ada" "*.ada" + + will look for Ada units in all files with the :file:`.ada` extension, + except those whose names end with :file:`_nt.ada`. + + +.. _Examples_of_gnatname_Usage: + +Examples of `gnatname` Usage +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: sh + + $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*" + +In this example, the directory :file:`/home/me` must already exist +and be writable. In addition, the directory +:file:`/home/me/sources` (specified by +*-d sources*) must exist and be readable. + +Note the optional spaces after *-c* and *-d*. + +.. code-block:: sh + + $ gnatname -P/home/me/proj -x "*_nt_body.ada" + -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*" + +Note that several switches *-d* may be used, +even in conjunction with one or several switches +*-D*. Several Naming Patterns and one excluded pattern +are used in this example. + + +.. _File_Name_Krunching_with_gnatkr: + +File Name Krunching with `gnatkr` +--------------------------------- + +.. index:: ! gnatkr + +This chapter discusses the method used by the compiler to shorten +the default file names chosen for Ada units so that they do not +exceed the maximum length permitted. It also describes the +`gnatkr` utility that can be used to determine the result of +applying this shortening. + +.. _About_gnatkr: + +About `gnatkr` +^^^^^^^^^^^^^^ + +The default file naming rule in GNAT +is that the file name must be derived from +the unit name. The exact default rule is as follows: + +* Take the unit name and replace all dots by hyphens. + +* If such a replacement occurs in the + second character position of a name, and the first character is + :samp:`a`, :samp:`g`, :samp:`s`, or :samp:`i`, + then replace the dot by the character + :samp:`~` (tilde) + instead of a minus. + + The reason for this exception is to avoid clashes + with the standard names for children of System, Ada, Interfaces, + and GNAT, which use the prefixes + :samp:`s-`, :samp:`a-`, :samp:`i-`, and :samp:`g-`, + respectively. + +The :samp:`-gnatk{nn}` +switch of the compiler activates a 'krunching' +circuit that limits file names to nn characters (where nn is a decimal +integer). + +The `gnatkr` utility can be used to determine the krunched name for +a given file, when krunched to a specified maximum length. + +.. _Using_gnatkr: + +Using `gnatkr` +^^^^^^^^^^^^^^ + +The `gnatkr` command has the form: + +.. code-block:: sh + + $ gnatkr `name` [`length`] + +`name` is the uncrunched file name, derived from the name of the unit +in the standard manner described in the previous section (i.e., in particular +all dots are replaced by hyphens). The file name may or may not have an +extension (defined as a suffix of the form period followed by arbitrary +characters other than period). If an extension is present then it will +be preserved in the output. For example, when krunching :file:`hellofile.ads` +to eight characters, the result will be hellofil.ads. + +Note: for compatibility with previous versions of `gnatkr` dots may +appear in the name instead of hyphens, but the last dot will always be +taken as the start of an extension. So if `gnatkr` is given an argument +such as :file:`Hello.World.adb` it will be treated exactly as if the first +period had been a hyphen, and for example krunching to eight characters +gives the result :file:`hellworl.adb`. + +Note that the result is always all lower case. +Characters of the other case are folded as required. + +`length` represents the length of the krunched name. The default +when no argument is given is 8 characters. A length of zero stands for +unlimited, in other words do not chop except for system files where the +implied crunching length is always eight characters. + +The output is the krunched name. The output has an extension only if the +original argument was a file name with an extension. + +.. _Krunching_Method: + +Krunching Method +^^^^^^^^^^^^^^^^ + +The initial file name is determined by the name of the unit that the file +contains. The name is formed by taking the full expanded name of the +unit and replacing the separating dots with hyphens and +using lowercase +for all letters, except that a hyphen in the second character position is +replaced by a tilde if the first character is +:samp:`a`, :samp:`i`, :samp:`g`, or :samp:`s`. +The extension is `.ads` for a +spec and `.adb` for a body. +Krunching does not affect the extension, but the file name is shortened to +the specified length by following these rules: + +* The name is divided into segments separated by hyphens, tildes or + underscores and all hyphens, tildes, and underscores are + eliminated. If this leaves the name short enough, we are done. + +* If the name is too long, the longest segment is located (left-most + if there are two of equal length), and shortened by dropping + its last character. This is repeated until the name is short enough. + + As an example, consider the krunching of :file:`our-strings-wide_fixed.adb` + to fit the name into 8 characters as required by some operating systems:: + + our-strings-wide_fixed 22 + our strings wide fixed 19 + our string wide fixed 18 + our strin wide fixed 17 + our stri wide fixed 16 + our stri wide fixe 15 + our str wide fixe 14 + our str wid fixe 13 + our str wid fix 12 + ou str wid fix 11 + ou st wid fix 10 + ou st wi fix 9 + ou st wi fi 8 + Final file name: oustwifi.adb + +* The file names for all predefined units are always krunched to eight + characters. The krunching of these predefined units uses the following + special prefix replacements: + + ===================== ============== + Prefix Replacement + --------------------- -------------- + :file:`ada-` :file:`a-` + :file:`gnat-` :file:`g-` + :file:`interfac es-` :file:`i-` + :file:`system-` :file:`s-` + ===================== ============== + + These system files have a hyphen in the second character position. That + is why normal user files replace such a character with a + tilde, to avoid confusion with system file names. + + As an example of this special rule, consider + :file:`ada-strings-wide_fixed.adb`, which gets krunched as follows:: + + ada-strings-wide_fixed 22 + a- strings wide fixed 18 + a- string wide fixed 17 + a- strin wide fixed 16 + a- stri wide fixed 15 + a- stri wide fixe 14 + a- str wide fixe 13 + a- str wid fixe 12 + a- str wid fix 11 + a- st wid fix 10 + a- st wi fix 9 + a- st wi fi 8 + Final file name: a-stwifi.adb + +Of course no file shortening algorithm can guarantee uniqueness over all +possible unit names, and if file name krunching is used then it is your +responsibility to ensure that no name clashes occur. The utility +program `gnatkr` is supplied for conveniently determining the +krunched name of a file. + +.. _Examples_of_gnatkr_Usage: + +Examples of `gnatkr` Usage +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +:: + + $ gnatkr very_long_unit_name.ads --> velounna.ads + $ gnatkr grandparent-parent-child.ads --> grparchi.ads + $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads + $ gnatkr grandparent-parent-child --> grparchi + $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads + $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads + + +.. _Renaming_Files_with_gnatchop: + +Renaming Files with `gnatchop` +------------------------------ + +.. index:: ! gnatchop + +This chapter discusses how to handle files with multiple units by using +the `gnatchop` utility. This utility is also useful in renaming +files to meet the standard GNAT default file naming conventions. + +.. _Handling_Files_with_Multiple_Units: + +Handling Files with Multiple Units +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The basic compilation model of GNAT requires that a file submitted to the +compiler have only one unit and there be a strict correspondence +between the file name and the unit name. + +The `gnatchop` utility allows both of these rules to be relaxed, +allowing GNAT to process files which contain multiple compilation units +and files with arbitrary file names. `gnatchop` +reads the specified file and generates one or more output files, +containing one unit per file. The unit and the file name correspond, +as required by GNAT. + +If you want to permanently restructure a set of 'foreign' files so that +they match the GNAT rules, and do the remaining development using the +GNAT structure, you can simply use *gnatchop* once, generate the +new set of files and work with them from that point on. + +Alternatively, if you want to keep your files in the 'foreign' format, +perhaps to maintain compatibility with some other Ada compilation +system, you can set up a procedure where you use *gnatchop* each +time you compile, regarding the source files that it writes as temporary +files that you throw away. + +Note that if your file containing multiple units starts with a byte order +mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop +will each start with a copy of this BOM, meaning that they can be compiled +automatically in UTF-8 mode without needing to specify an explicit encoding. + +.. _Operating_gnatchop_in_Compilation_Mode: + +Operating gnatchop in Compilation Mode +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The basic function of `gnatchop` is to take a file with multiple units +and split it into separate files. The boundary between files is reasonably +clear, except for the issue of comments and pragmas. In default mode, the +rule is that any pragmas between units belong to the previous unit, except +that configuration pragmas always belong to the following unit. Any comments +belong to the following unit. These rules +almost always result in the right choice of +the split point without needing to mark it explicitly and most users will +find this default to be what they want. In this default mode it is incorrect to +submit a file containing only configuration pragmas, or one that ends in +configuration pragmas, to `gnatchop`. + +However, using a special option to activate 'compilation mode', +`gnatchop` +can perform another function, which is to provide exactly the semantics +required by the RM for handling of configuration pragmas in a compilation. +In the absence of configuration pragmas (at the main file level), this +option has no effect, but it causes such configuration pragmas to be handled +in a quite different manner. + +First, in compilation mode, if `gnatchop` is given a file that consists of +only configuration pragmas, then this file is appended to the +:file:`gnat.adc` file in the current directory. This behavior provides +the required behavior described in the RM for the actions to be taken +on submitting such a file to the compiler, namely that these pragmas +should apply to all subsequent compilations in the same compilation +environment. Using GNAT, the current directory, possibly containing a +:file:`gnat.adc` file is the representation +of a compilation environment. For more information on the +:file:`gnat.adc` file, see :ref:`Handling_of_Configuration_Pragmas`. + +Second, in compilation mode, if `gnatchop` +is given a file that starts with +configuration pragmas, and contains one or more units, then these +configuration pragmas are prepended to each of the chopped files. This +behavior provides the required behavior described in the RM for the +actions to be taken on compiling such a file, namely that the pragmas +apply to all units in the compilation, but not to subsequently compiled +units. + +Finally, if configuration pragmas appear between units, they are appended +to the previous unit. This results in the previous unit being illegal, +since the compiler does not accept configuration pragmas that follow +a unit. This provides the required RM behavior that forbids configuration +pragmas other than those preceding the first compilation unit of a +compilation. + +For most purposes, `gnatchop` will be used in default mode. The +compilation mode described above is used only if you need exactly +accurate behavior with respect to compilations, and you have files +that contain multiple units and configuration pragmas. In this +circumstance the use of `gnatchop` with the compilation mode +switch provides the required behavior, and is for example the mode +in which GNAT processes the ACVC tests. + + +.. _Command_Line_for_gnatchop: + +Command Line for `gnatchop` +^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The `gnatchop` command has the form: + +.. code-block:: sh + + $ gnatchop switches file_name [file_name ...] + [directory] + +The only required argument is the file name of the file to be chopped. +There are no restrictions on the form of this file name. The file itself +contains one or more Ada units, in normal GNAT format, concatenated +together. As shown, more than one file may be presented to be chopped. + +When run in default mode, `gnatchop` generates one output file in +the current directory for each unit in each of the files. + +`directory`, if specified, gives the name of the directory to which +the output files will be written. If it is not specified, all files are +written to the current directory. + +For example, given a +file called :file:`hellofiles` containing + +.. code-block:: ada + + procedure Hello; + + with Ada.Text_IO; use Ada.Text_IO; + procedure Hello is + begin + Put_Line ("Hello"); + end Hello; + +the command + +.. code-block:: sh + + $ gnatchop hellofiles + +generates two files in the current directory, one called +:file:`hello.ads` containing the single line that is the procedure spec, +and the other called :file:`hello.adb` containing the remaining text. The +original file is not affected. The generated files can be compiled in +the normal manner. + +When gnatchop is invoked on a file that is empty or that contains only empty +lines and/or comments, gnatchop will not fail, but will not produce any +new sources. + +For example, given a +file called :file:`toto.txt` containing + +.. code-block:: ada + + -- Just a comment + +the command + +.. code-block:: sh + + $ gnatchop toto.txt + +will not produce any new file and will result in the following warnings:: + + toto.txt:1:01: warning: empty file, contains no compilation units + no compilation units found + no source files written + + +.. _Switches_for_gnatchop: + +Switches for `gnatchop` +^^^^^^^^^^^^^^^^^^^^^^^ + +*gnatchop* recognizes the following switches: + + +.. index:: --version (gnatchop) + +:samp:`--version` + Display Copyright and version, then exit disregarding all other options. + +.. index:: --help (gnatchop) + +:samp:`--help` + If *--version* was not used, display usage, then exit disregarding + all other options. + +.. index:: -c (gnatchop) + +:samp:`-c` + Causes `gnatchop` to operate in compilation mode, in which + configuration pragmas are handled according to strict RM rules. See + previous section for a full description of this mode. + +:samp:`-gnat{xxx}` + This passes the given *-gnat`xxx*` switch to `gnat` which is + used to parse the given file. Not all `xxx` options make sense, + but for example, the use of *-gnati2* allows `gnatchop` to + process a source file that uses Latin-2 coding for identifiers. + +:samp:`-h` + Causes `gnatchop` to generate a brief help summary to the standard + output file showing usage information. + +.. index:: -k (gnatchop) + +:samp:`-k{mm}` + Limit generated file names to the specified number `mm` + of characters. + This is useful if the + resulting set of files is required to be interoperable with systems + which limit the length of file names. + No space is allowed between the *-k* and the numeric value. The numeric + value may be omitted in which case a default of *-k8*, + suitable for use + with DOS-like file systems, is used. If no *-k* switch + is present then + there is no limit on the length of file names. + +.. index:: -p (gnatchop) + +:samp:`-p` + Causes the file modification time stamp of the input file to be + preserved and used for the time stamp of the output file(s). This may be + useful for preserving coherency of time stamps in an environment where + `gnatchop` is used as part of a standard build process. + +.. index:: -q (gnatchop) + +:samp:`-q` + Causes output of informational messages indicating the set of generated + files to be suppressed. Warnings and error messages are unaffected. + +.. index:: -r (gnatchop) +.. index:: Source_Reference pragmas + +:samp:`-r` + Generate `Source_Reference` pragmas. Use this switch if the output + files are regarded as temporary and development is to be done in terms + of the original unchopped file. This switch causes + `Source_Reference` pragmas to be inserted into each of the + generated files to refers back to the original file name and line number. + The result is that all error messages refer back to the original + unchopped file. + In addition, the debugging information placed into the object file (when + the *-g* switch of *gcc* or *gnatmake* is + specified) + also refers back to this original file so that tools like profilers and + debuggers will give information in terms of the original unchopped file. + + If the original file to be chopped itself contains + a `Source_Reference` + pragma referencing a third file, then gnatchop respects + this pragma, and the generated `Source_Reference` pragmas + in the chopped file refer to the original file, with appropriate + line numbers. This is particularly useful when `gnatchop` + is used in conjunction with `gnatprep` to compile files that + contain preprocessing statements and multiple units. + +.. index:: -v (gnatchop) + +:samp:`-v` + Causes `gnatchop` to operate in verbose mode. The version + number and copyright notice are output, as well as exact copies of + the gnat1 commands spawned to obtain the chop control information. + +.. index:: -w (gnatchop) + +:samp:`-w` + Overwrite existing file names. Normally `gnatchop` regards it as a + fatal error if there is already a file with the same name as a + file it would otherwise output, in other words if the files to be + chopped contain duplicated units. This switch bypasses this + check, and causes all but the last instance of such duplicated + units to be skipped. + +.. index:: --GCC= (gnatchop) + +:samp:`--GCC={xxxx}` + Specify the path of the GNAT parser to be used. When this switch is used, + no attempt is made to add the prefix to the GNAT parser executable. + + +.. _Examples_of_gnatchop_Usage: + +Examples of `gnatchop` Usage +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +.. code-block:: sh + + $ gnatchop -w hello_s.ada prerelease/files + +Chops the source file :file:`hello_s.ada`. The output files will be +placed in the directory :file:`prerelease/files`, +overwriting any +files with matching names in that directory (no files in the current +directory are modified). + +.. code-block:: sh + + $ gnatchop archive + +Chops the source file :file:`archive` +into the current directory. One +useful application of `gnatchop` is in sending sets of sources +around, for example in email messages. The required sources are simply +concatenated (for example, using a Unix `cat` +command), and then +*gnatchop* is used at the other end to reconstitute the original +file names. + +.. code-block:: sh + + $ gnatchop file1 file2 file3 direc + +Chops all units in files :file:`file1`, :file:`file2`, :file:`file3`, placing +the resulting files in the directory :file:`direc`. Note that if any units +occur more than once anywhere within this set of files, an error message +is generated, and no files are written. To override this check, use the +*-w* switch, +in which case the last occurrence in the last file will +be the one that is output, and earlier duplicate occurrences for a given +unit will be skipped. + +.. _Configuration_Pragmas: + +Configuration Pragmas +===================== + +.. index:: Configuration pragmas + +.. index:: Pragmas, configuration + +Configuration pragmas include those pragmas described as +such in the Ada Reference Manual, as well as +implementation-dependent pragmas that are configuration pragmas. +See the `Implementation_Defined_Pragmas` chapter in the +:title:`GNAT_Reference_Manual` for details on these +additional GNAT-specific configuration pragmas. +Most notably, the pragma `Source_File_Name`, which allows +specifying non-default names for source files, is a configuration +pragma. The following is a complete list of configuration pragmas +recognized by GNAT:: + + Ada_83 + Ada_95 + Ada_05 + Ada_2005 + Ada_12 + Ada_2012 + Allow_Integer_Address + Annotate + Assertion_Policy + Assume_No_Invalid_Values + C_Pass_By_Copy + Check_Name + Check_Policy + Compile_Time_Error + Compile_Time_Warning + Compiler_Unit + Component_Alignment + Convention_Identifier + Debug_Policy + Detect_Blocking + Default_Storage_Pool + Discard_Names + Elaboration_Checks + Eliminate + Extend_System + Extensions_Allowed + External_Name_Casing + Fast_Math + Favor_Top_Level + Float_Representation + Implicit_Packing + Initialize_Scalars + Interrupt_State + License + Locking_Policy + Long_Float + No_Run_Time + No_Strict_Aliasing + Normalize_Scalars + Optimize_Alignment + Persistent_BSS + Polling + Priority_Specific_Dispatching + Profile + Profile_Warnings + Propagate_Exceptions + Queuing_Policy + Ravenscar + Restricted_Run_Time + Restrictions + Restrictions_Warnings + Reviewable + Short_Circuit_And_Or + Source_File_Name + Source_File_Name_Project + SPARK_Mode + Style_Checks + Suppress + Suppress_Exception_Locations + Task_Dispatching_Policy + Universal_Data + Unsuppress + Use_VADS_Size + Validity_Checks + Warnings + Wide_Character_Encoding + + +.. _Handling_of_Configuration_Pragmas: + +Handling of Configuration Pragmas +--------------------------------- + +Configuration pragmas may either appear at the start of a compilation +unit, or they can appear in a configuration pragma file to apply to +all compilations performed in a given compilation environment. + +GNAT also provides the `gnatchop` utility to provide an automatic +way to handle configuration pragmas following the semantics for +compilations (that is, files with multiple units), described in the RM. +See :ref:`Operating_gnatchop_in_Compilation_Mode` for details. +However, for most purposes, it will be more convenient to edit the +:file:`gnat.adc` file that contains configuration pragmas directly, +as described in the following section. + +In the case of `Restrictions` pragmas appearing as configuration +pragmas in individual compilation units, the exact handling depends on +the type of restriction. + +Restrictions that require partition-wide consistency (like +`No_Tasking`) are +recognized wherever they appear +and can be freely inherited, e.g. from a |withed| unit to the |withing| +unit. This makes sense since the binder will in any case insist on seeing +consistent use, so any unit not conforming to any restrictions that are +anywhere in the partition will be rejected, and you might as well find +that out at compile time rather than at bind time. + +For restrictions that do not require partition-wide consistency, e.g. +SPARK or No_Implementation_Attributes, in general the restriction applies +only to the unit in which the pragma appears, and not to any other units. + +The exception is No_Elaboration_Code which always applies to the entire +object file from a compilation, i.e. to the body, spec, and all subunits. +This restriction can be specified in a configuration pragma file, or it +can be on the body and/or the spec (in eithe case it applies to all the +relevant units). It can appear on a subunit only if it has previously +appeared in the body of spec. + + +.. _The_Configuration_Pragmas_Files: + +The Configuration Pragmas Files +------------------------------- + +.. index:: gnat.adc + +In GNAT a compilation environment is defined by the current +directory at the time that a compile command is given. This current +directory is searched for a file whose name is :file:`gnat.adc`. If +this file is present, it is expected to contain one or more +configuration pragmas that will be applied to the current compilation. +However, if the switch *-gnatA* is used, :file:`gnat.adc` is not +considered. When taken into account, :file:`gnat.adc` is added to the +dependencies, so that if :file:`gnat.adc` is modified later, an invocation of +*gnatmake* will recompile the source. + +Configuration pragmas may be entered into the :file:`gnat.adc` file +either by running `gnatchop` on a source file that consists only of +configuration pragmas, or more conveniently by direct editing of the +:file:`gnat.adc` file, which is a standard format source file. + +Besides :file:`gnat.adc`, additional files containing configuration +pragmas may be applied to the current compilation using the switch +:samp:`-gnatec={path}` where `path` must designate an existing file that +contains only configuration pragmas. These configuration pragmas are +in addition to those found in :file:`gnat.adc` (provided :file:`gnat.adc` +is present and switch *-gnatA* is not used). + +It is allowable to specify several switches *-gnatec=*, all of which +will be taken into account. + +Files containing configuration pragmas specified with switches +*-gnatec=* are added to the dependencies, unless they are +temporary files. A file is considered temporary if its name ends in +:file:`.tmp` or :file:`.TMP`. Certain tools follow this naming +convention because they pass information to *gcc* via +temporary files that are immediately deleted; it doesn't make sense to +depend on a file that no longer exists. Such tools include +*gprbuild*, *gnatmake*, and *gnatcheck*. + +If you are using project file, a separate mechanism is provided using +project attributes, see :ref:`Specifying_Configuration_Pragmas` for more +details. + + +.. _Generating_Object_Files: + +Generating Object Files +======================= + +An Ada program consists of a set of source files, and the first step in +compiling the program is to generate the corresponding object files. +These are generated by compiling a subset of these source files. +The files you need to compile are the following: + +* If a package spec has no body, compile the package spec to produce the + object file for the package. + +* If a package has both a spec and a body, compile the body to produce the + object file for the package. The source file for the package spec need + not be compiled in this case because there is only one object file, which + contains the code for both the spec and body of the package. + +* For a subprogram, compile the subprogram body to produce the object file + for the subprogram. The spec, if one is present, is as usual in a + separate file, and need not be compiled. + +.. index:: Subunits + +* In the case of subunits, only compile the parent unit. A single object + file is generated for the entire subunit tree, which includes all the + subunits. + +* Compile child units independently of their parent units + (though, of course, the spec of all the ancestor unit must be present in order + to compile a child unit). + + .. index:: Generics + +* Compile generic units in the same manner as any other units. The object + files in this case are small dummy files that contain at most the + flag used for elaboration checking. This is because GNAT always handles generic + instantiation by means of macro expansion. However, it is still necessary to + compile generic units, for dependency checking and elaboration purposes. + +The preceding rules describe the set of files that must be compiled to +generate the object files for a program. Each object file has the same +name as the corresponding source file, except that the extension is +:file:`.o` as usual. + +You may wish to compile other files for the purpose of checking their +syntactic and semantic correctness. For example, in the case where a +package has a separate spec and body, you would not normally compile the +spec. However, it is convenient in practice to compile the spec to make +sure it is error-free before compiling clients of this spec, because such +compilations will fail if there is an error in the spec. + +GNAT provides an option for compiling such files purely for the +purposes of checking correctness; such compilations are not required as +part of the process of building a program. To compile a file in this +checking mode, use the *-gnatc* switch. + +.. _Source_Dependencies: + +Source Dependencies +=================== + +A given object file clearly depends on the source file which is compiled +to produce it. Here we are using "depends" in the sense of a typical +`make` utility; in other words, an object file depends on a source +file if changes to the source file require the object file to be +recompiled. +In addition to this basic dependency, a given object may depend on +additional source files as follows: + +* If a file being compiled |withs| a unit `X`, the object file + depends on the file containing the spec of unit `X`. This includes + files that are |withed| implicitly either because they are parents + of |withed| child units or they are run-time units required by the + language constructs used in a particular unit. + +* If a file being compiled instantiates a library level generic unit, the + object file depends on both the spec and body files for this generic + unit. + +* If a file being compiled instantiates a generic unit defined within a + package, the object file depends on the body file for the package as + well as the spec file. + +.. index:: Inline +.. index:: -gnatn switch + +* If a file being compiled contains a call to a subprogram for which + pragma `Inline` applies and inlining is activated with the + *-gnatn* switch, the object file depends on the file containing the + body of this subprogram as well as on the file containing the spec. Note + that for inlining to actually occur as a result of the use of this switch, + it is necessary to compile in optimizing mode. + + .. index:: -gnatN switch + + The use of *-gnatN* activates inlining optimization + that is performed by the front end of the compiler. This inlining does + not require that the code generation be optimized. Like *-gnatn*, + the use of this switch generates additional dependencies. + + When using a gcc-based back end (in practice this means using any version + of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of + *-gnatN* is deprecated, and the use of *-gnatn* is preferred. + Historically front end inlining was more extensive than the gcc back end + inlining, but that is no longer the case. + +* If an object file :file:`O` depends on the proper body of a subunit through + inlining or instantiation, it depends on the parent unit of the subunit. + This means that any modification of the parent unit or one of its subunits + affects the compilation of :file:`O`. + +* The object file for a parent unit depends on all its subunit body files. + +* The previous two rules meant that for purposes of computing dependencies and + recompilation, a body and all its subunits are treated as an indivisible whole. + + These rules are applied transitively: if unit `A` |withs| + unit `B`, whose elaboration calls an inlined procedure in package + `C`, the object file for unit `A` will depend on the body of + `C`, in file :file:`c.adb`. + + The set of dependent files described by these rules includes all the + files on which the unit is semantically dependent, as dictated by the + Ada language standard. However, it is a superset of what the + standard describes, because it includes generic, inline, and subunit + dependencies. + + An object file must be recreated by recompiling the corresponding source + file if any of the source files on which it depends are modified. For + example, if the `make` utility is used to control compilation, + the rule for an Ada object file must mention all the source files on + which the object file depends, according to the above definition. + The determination of the necessary + recompilations is done automatically when one uses *gnatmake*. + +.. _The_Ada_Library_Information_Files: + +The Ada Library Information Files +================================= + +.. index:: Ada Library Information files + +.. index:: ALI files + +Each compilation actually generates two output files. The first of these +is the normal object file that has a :file:`.o` extension. The second is a +text file containing full dependency information. It has the same +name as the source file, but an :file:`.ali` extension. +This file is known as the Ada Library Information (:file:`ALI`) file. +The following information is contained in the :file:`ALI` file. + +* Version information (indicates which version of GNAT was used to compile + the unit(s) in question) + +* Main program information (including priority and time slice settings, + as well as the wide character encoding used during compilation). + +* List of arguments used in the *gcc* command for the compilation + +* Attributes of the unit, including configuration pragmas used, an indication + of whether the compilation was successful, exception model used etc. + +* A list of relevant restrictions applying to the unit (used for consistency) + checking. + +* Categorization information (e.g., use of pragma `Pure`). + +* Information on all |withed| units, including presence of + Elaborate` or `Elaborate_All` pragmas. + +* Information from any `Linker_Options` pragmas used in the unit + +* Information on the use of `Body_Version` or `Version` + attributes in the unit. + +* Dependency information. This is a list of files, together with + time stamp and checksum information. These are files on which + the unit depends in the sense that recompilation is required + if any of these units are modified. + +* Cross-reference data. Contains information on all entities referenced + in the unit. Used by tools like `gnatxref` and `gnatfind` to + provide cross-reference information. + +For a full detailed description of the format of the :file:`ALI` file, +see the source of the body of unit `Lib.Writ`, contained in file +:file:`lib-writ.adb` in the GNAT compiler sources. + + +.. _Binding_an_Ada_Program: + +Binding an Ada Program +====================== + +When using languages such as C and C++, once the source files have been +compiled the only remaining step in building an executable program +is linking the object modules together. This means that it is possible to +link an inconsistent version of a program, in which two units have +included different versions of the same header. + +The rules of Ada do not permit such an inconsistent program to be built. +For example, if two clients have different versions of the same package, +it is illegal to build a program containing these two clients. +These rules are enforced by the GNAT binder, which also determines an +elaboration order consistent with the Ada rules. + +The GNAT binder is run after all the object files for a program have +been created. It is given the name of the main program unit, and from +this it determines the set of units required by the program, by reading the +corresponding ALI files. It generates error messages if the program is +inconsistent or if no valid order of elaboration exists. + +If no errors are detected, the binder produces a main program, in Ada by +default, that contains calls to the elaboration procedures of those +compilation unit that require them, followed by +a call to the main program. This Ada program is compiled to generate the +object file for the main program. The name of +the Ada file is :file:`b~xxx`.adb` (with the corresponding spec +:file:`b~xxx`.ads`) where `xxx` is the name of the +main program unit. + +Finally, the linker is used to build the resulting executable program, +using the object from the main program from the bind step as well as the +object files for the Ada units of the program. + + +.. _GNAT_and_Libraries: + +GNAT and Libraries +================== + +.. index:: Library building and using + +This chapter describes how to build and use libraries with GNAT, and also shows +how to recompile the GNAT run-time library. You should be familiar with the +Project Manager facility (:ref:`GNAT_Project_Manager`) before reading this +chapter. + +.. _Introduction_to_Libraries_in_GNAT: + +Introduction to Libraries in GNAT +--------------------------------- + +A library is, conceptually, a collection of objects which does not have its +own main thread of execution, but rather provides certain services to the +applications that use it. A library can be either statically linked with the +application, in which case its code is directly included in the application, +or, on platforms that support it, be dynamically linked, in which case +its code is shared by all applications making use of this library. + +GNAT supports both types of libraries. +In the static case, the compiled code can be provided in different ways. The +simplest approach is to provide directly the set of objects resulting from +compilation of the library source files. Alternatively, you can group the +objects into an archive using whatever commands are provided by the operating +system. For the latter case, the objects are grouped into a shared library. + +In the GNAT environment, a library has three types of components: + +* Source files, + +* :file:`ALI` files (see :ref:`The_Ada_Library_Information_Files`), and + +* Object files, an archive or a shared library. + +A GNAT library may expose all its source files, which is useful for +documentation purposes. Alternatively, it may expose only the units needed by +an external user to make use of the library. That is to say, the specs +reflecting the library services along with all the units needed to compile +those specs, which can include generic bodies or any body implementing an +inlined routine. In the case of *stand-alone libraries* those exposed +units are called *interface units* (:ref:`Stand-alone_Ada_Libraries`). + +All compilation units comprising an application, including those in a library, +need to be elaborated in an order partially defined by Ada's semantics. GNAT +computes the elaboration order from the :file:`ALI` files and this is why they +constitute a mandatory part of GNAT libraries. +*Stand-alone libraries* are the exception to this rule because a specific +library elaboration routine is produced independently of the application(s) +using the library. + +.. _General_Ada_Libraries: + +General Ada Libraries +--------------------- + + +.. _Building_a_library: + +Building a library +^^^^^^^^^^^^^^^^^^ + +The easiest way to build a library is to use the Project Manager, +which supports a special type of project called a *Library Project* +(see :ref:`Library_Projects`). + +A project is considered a library project, when two project-level attributes +are defined in it: `Library_Name` and `Library_Dir`. In order to +control different aspects of library configuration, additional optional +project-level attributes can be specified: + +* *Library_Kind* + This attribute controls whether the library is to be static or dynamic + + +* *Library_Version* + This attribute specifies the library version; this value is used + during dynamic linking of shared libraries to determine if the currently + installed versions of the binaries are compatible. + +* *Library_Options* + +* *Library_GCC* + These attributes specify additional low-level options to be used during + library generation, and redefine the actual application used to generate + library. + +The GNAT Project Manager takes full care of the library maintenance task, +including recompilation of the source files for which objects do not exist +or are not up to date, assembly of the library archive, and installation of +the library (i.e., copying associated source, object and :file:`ALI` files +to the specified location). + +Here is a simple library project file: + +.. code-block:: gpr + + project My_Lib is + for Source_Dirs use ("src1", "src2"); + for Object_Dir use "obj"; + for Library_Name use "mylib"; + for Library_Dir use "lib"; + for Library_Kind use "dynamic"; + end My_lib; + +and the compilation command to build and install the library: + +.. code-block:: sh + + $ gnatmake -Pmy_lib + +It is not entirely trivial to perform manually all the steps required to +produce a library. We recommend that you use the GNAT Project Manager +for this task. In special cases where this is not desired, the necessary +steps are discussed below. + +There are various possibilities for compiling the units that make up the +library: for example with a Makefile (:ref:`Using_the_GNU_make_Utility`) or +with a conventional script. For simple libraries, it is also possible to create +a dummy main program which depends upon all the packages that comprise the +interface of the library. This dummy main program can then be given to +*gnatmake*, which will ensure that all necessary objects are built. + +After this task is accomplished, you should follow the standard procedure +of the underlying operating system to produce the static or shared library. + +Here is an example of such a dummy program: + +.. code-block:: ada + + with My_Lib.Service1; + with My_Lib.Service2; + with My_Lib.Service3; + procedure My_Lib_Dummy is + begin + null; + end; + +Here are the generic commands that will build an archive or a shared library. + +.. code-block:: sh + + # compiling the library + $ gnatmake -c my_lib_dummy.adb + + # we don't need the dummy object itself + $ rm my_lib_dummy.o my_lib_dummy.ali + + # create an archive with the remaining objects + $ ar rc libmy_lib.a *.o + # some systems may require "ranlib" to be run as well + + # or create a shared library + $ gcc -shared -o libmy_lib.so *.o + # some systems may require the code to have been compiled with -fPIC + + # remove the object files that are now in the library + $ rm *.o + + # Make the ALI files read-only so that gnatmake will not try to + # regenerate the objects that are in the library + $ chmod -w *.ali + +Please note that the library must have a name of the form :file:`lib{xxx}.a` +or :file:`lib{xxx}.so` (or :file:`lib{xxx}.dll` on Windows) in order to +be accessed by the directive :samp:`-l{xxx}` at link time. + +.. _Installing_a_library: + +Installing a library +^^^^^^^^^^^^^^^^^^^^ + +.. index:: ADA_PROJECT_PATH +.. index:: GPR_PROJECT_PATH + +If you use project files, library installation is part of the library build +process (:ref:`Installing_a_library_with_project_files`). + +When project files are not an option, it is also possible, but not recommended, +to install the library so that the sources needed to use the library are on the +Ada source path and the ALI files & libraries be on the Ada Object path (see +:ref:`Search_Paths_and_the_Run-Time_Library_RTL`. Alternatively, the system +administrator can place general-purpose libraries in the default compiler +paths, by specifying the libraries' location in the configuration files +:file:`ada_source_path` and :file:`ada_object_path`. These configuration files +must be located in the GNAT installation tree at the same place as the gcc spec +file. The location of the gcc spec file can be determined as follows: + +.. code-block:: sh + + $ gcc -v + + +The configuration files mentioned above have a simple format: each line +must contain one unique directory name. +Those names are added to the corresponding path +in their order of appearance in the file. The names can be either absolute +or relative; in the latter case, they are relative to where theses files +are located. + +The files :file:`ada_source_path` and :file:`ada_object_path` might not be +present in a +GNAT installation, in which case, GNAT will look for its run-time library in +the directories :file:`adainclude` (for the sources) and :file:`adalib` (for the +objects and :file:`ALI` files). When the files exist, the compiler does not +look in :file:`adainclude` and :file:`adalib`, and thus the +:file:`ada_source_path` file +must contain the location for the GNAT run-time sources (which can simply +be :file:`adainclude`). In the same way, the :file:`ada_object_path` file must +contain the location for the GNAT run-time objects (which can simply +be :file:`adalib`). + +You can also specify a new default path to the run-time library at compilation +time with the switch *--RTS=rts-path*. You can thus choose / change +the run-time library you want your program to be compiled with. This switch is +recognized by *gcc*, *gnatmake*, *gnatbind*, +*gnatls*, *gnatfind* and *gnatxref*. + +It is possible to install a library before or after the standard GNAT +library, by reordering the lines in the configuration files. In general, a +library must be installed before the GNAT library if it redefines +any part of it. + +.. _Using_a_library: + +Using a library +^^^^^^^^^^^^^^^ + +Once again, the project facility greatly simplifies the use of +libraries. In this context, using a library is just a matter of adding a +|with| clause in the user project. For instance, to make use of the +library `My_Lib` shown in examples in earlier sections, you can +write: + +.. code-block:: gpr + + with "my_lib"; + project My_Proj is + ... + end My_Proj; + +Even if you have a third-party, non-Ada library, you can still use GNAT's +Project Manager facility to provide a wrapper for it. For example, the +following project, when |withed| by your main project, will link with the +third-party library :file:`liba.a`: + +.. code-block:: gpr + + project Liba is + for Externally_Built use "true"; + for Source_Files use (); + for Library_Dir use "lib"; + for Library_Name use "a"; + for Library_Kind use "static"; + end Liba; + +This is an alternative to the use of `pragma Linker_Options`. It is +especially interesting in the context of systems with several interdependent +static libraries where finding a proper linker order is not easy and best be +left to the tools having visibility over project dependence information. + +In order to use an Ada library manually, you need to make sure that this +library is on both your source and object path +(see :ref:`Search_Paths_and_the_Run-Time_Library_RTL` +and :ref:`Search_Paths_for_gnatbind`). Furthermore, when the objects are grouped +in an archive or a shared library, you need to specify the desired +library at link time. + +For example, you can use the library :file:`mylib` installed in +:file:`/dir/my_lib_src` and :file:`/dir/my_lib_obj` with the following commands: + +.. code-block:: sh + + $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\ + -largs -lmy_lib + +This can be expressed more simply: + +.. code-block:: sh + + $ gnatmake my_appl + +when the following conditions are met: + +* :file:`/dir/my_lib_src` has been added by the user to the environment + variable :envvar:`ADA_INCLUDE_PATH`, or by the administrator to the file + :file:`ada_source_path` + +* :file:`/dir/my_lib_obj` has been added by the user to the environment + variable :envvar:`ADA_OBJECTS_PATH`, or by the administrator to the file + :file:`ada_object_path` + +* a pragma `Linker_Options` has been added to one of the sources. + For example: + + .. code-block:: ada + + pragma Linker_Options ("-lmy_lib"); + +Note that you may also load a library dynamically at +run time given its filename, as illustrated in the GNAT :file:`plugins` example +in the directory :file:`share/examples/gnat/plugins` within the GNAT +install area. + +.. _Stand-alone_Ada_Libraries: + +Stand-alone Ada Libraries +------------------------- + +.. index:: ! Stand-alone libraries + +.. _Introduction_to_Stand-alone_Libraries: + +Introduction to Stand-alone Libraries +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A Stand-alone Library (abbreviated 'SAL') is a library that contains the +necessary code to +elaborate the Ada units that are included in the library. In contrast with +an ordinary library, which consists of all sources, objects and :file:`ALI` +files of the +library, a SAL may specify a restricted subset of compilation units +to serve as a library interface. In this case, the fully +self-sufficient set of files will normally consist of an objects +archive, the sources of interface units' specs, and the :file:`ALI` +files of interface units. +If an interface spec contains a generic unit or an inlined subprogram, +the body's +source must also be provided; if the units that must be provided in the source +form depend on other units, the source and :file:`ALI` files of those must +also be provided. + +The main purpose of a SAL is to minimize the recompilation overhead of client +applications when a new version of the library is installed. Specifically, +if the interface sources have not changed, client applications do not need to +be recompiled. If, furthermore, a SAL is provided in the shared form and its +version, controlled by `Library_Version` attribute, is not changed, +then the clients do not need to be relinked. + +SALs also allow the library providers to minimize the amount of library source +text exposed to the clients. Such 'information hiding' might be useful or +necessary for various reasons. + +Stand-alone libraries are also well suited to be used in an executable whose +main routine is not written in Ada. + +.. _Building_a_Stand-alone_Library: + +Building a Stand-alone Library +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +GNAT's Project facility provides a simple way of building and installing +stand-alone libraries; see :ref:`Stand-alone_Library_Projects`. +To be a Stand-alone Library Project, in addition to the two attributes +that make a project a Library Project (`Library_Name` and +`Library_Dir`; see :ref:`Library_Projects`), the attribute +`Library_Interface` must be defined. For example: + +.. code-block:: gpr + + for Library_Dir use "lib_dir"; + for Library_Name use "dummy"; + for Library_Interface use ("int1", "int1.child"); + +Attribute `Library_Interface` has a non-empty string list value, +each string in the list designating a unit contained in an immediate source +of the project file. + +When a Stand-alone Library is built, first the binder is invoked to build +a package whose name depends on the library name +(:file:`b~dummy.ads/b` in the example above). +This binder-generated package includes initialization and +finalization procedures whose +names depend on the library name (`dummyinit` and `dummyfinal` +in the example +above). The object corresponding to this package is included in the library. + +You must ensure timely (e.g., prior to any use of interfaces in the SAL) +calling of these procedures if a static SAL is built, or if a shared SAL +is built +with the project-level attribute `Library_Auto_Init` set to +`"false"`. + +For a Stand-Alone Library, only the :file:`ALI` files of the Interface Units +(those that are listed in attribute `Library_Interface`) are copied to +the Library Directory. As a consequence, only the Interface Units may be +imported from Ada units outside of the library. If other units are imported, +the binding phase will fail. + +It is also possible to build an encapsulated library where not only +the code to elaborate and finalize the library is embedded but also +ensuring that the library is linked only against static +libraries. So an encapsulated library only depends on system +libraries, all other code, including the GNAT runtime, is embedded. To +build an encapsulated library the attribute +`Library_Standalone` must be set to `encapsulated`: + +.. code-block:: gpr + + for Library_Dir use "lib_dir"; + for Library_Name use "dummy"; + for Library_Kind use "dynamic"; + for Library_Interface use ("int1", "int1.child"); + for Library_Standalone use "encapsulated"; + +The default value for this attribute is `standard` in which case +a stand-alone library is built. + +The attribute `Library_Src_Dir` may be specified for a +Stand-Alone Library. `Library_Src_Dir` is a simple attribute that has a +single string value. Its value must be the path (absolute or relative to the +project directory) of an existing directory. This directory cannot be the +object directory or one of the source directories, but it can be the same as +the library directory. The sources of the Interface +Units of the library that are needed by an Ada client of the library will be +copied to the designated directory, called the Interface Copy directory. +These sources include the specs of the Interface Units, but they may also +include bodies and subunits, when pragmas `Inline` or `Inline_Always` +are used, or when there is a generic unit in the spec. Before the sources +are copied to the Interface Copy directory, an attempt is made to delete all +files in the Interface Copy directory. + +Building stand-alone libraries by hand is somewhat tedious, but for those +occasions when it is necessary here are the steps that you need to perform: + +* Compile all library sources. + +* Invoke the binder with the switch *-n* (No Ada main program), + with all the :file:`ALI` files of the interfaces, and + with the switch *-L* to give specific names to the `init` + and `final` procedures. For example: + + .. code-block:: sh + + $ gnatbind -n int1.ali int2.ali -Lsal1 + +* Compile the binder generated file: + + .. code-block:: sh + + $ gcc -c b~int2.adb + +* Link the dynamic library with all the necessary object files, + indicating to the linker the names of the `init` (and possibly + `final`) procedures for automatic initialization (and finalization). + The built library should be placed in a directory different from + the object directory. + +* Copy the `ALI` files of the interface to the library directory, + add in this copy an indication that it is an interface to a SAL + (i.e., add a word *SL* on the line in the :file:`ALI` file that starts + with letter 'P') and make the modified copy of the :file:`ALI` file + read-only. + +Using SALs is not different from using other libraries +(see :ref:`Using_a_library`). + +.. _Creating_a_Stand-alone_Library_to_be_used_in_a_non-Ada_context: + +Creating a Stand-alone Library to be used in a non-Ada context +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +It is easy to adapt the SAL build procedure discussed above for use of a SAL in +a non-Ada context. + +The only extra step required is to ensure that library interface subprograms +are compatible with the main program, by means of `pragma Export` +or `pragma Convention`. + +Here is an example of simple library interface for use with C main program: + +.. code-block:: ada + + package My_Package is + + procedure Do_Something; + pragma Export (C, Do_Something, "do_something"); + + procedure Do_Something_Else; + pragma Export (C, Do_Something_Else, "do_something_else"); + + end My_Package; + +On the foreign language side, you must provide a 'foreign' view of the +library interface; remember that it should contain elaboration routines in +addition to interface subprograms. + +The example below shows the content of `mylib_interface.h` (note +that there is no rule for the naming of this file, any name can be used) + +.. code-block:: c + + /* the library elaboration procedure */ + extern void mylibinit (void); + + /* the library finalization procedure */ + extern void mylibfinal (void); + + /* the interface exported by the library */ + extern void do_something (void); + extern void do_something_else (void); + +Libraries built as explained above can be used from any program, provided +that the elaboration procedures (named `mylibinit` in the previous +example) are called before the library services are used. Any number of +libraries can be used simultaneously, as long as the elaboration +procedure of each library is called. + +Below is an example of a C program that uses the `mylib` library. + +.. code-block:: c + + #include "mylib_interface.h" + + int + main (void) + { + /* First, elaborate the library before using it */ + mylibinit (); + + /* Main program, using the library exported entities */ + do_something (); + do_something_else (); + + /* Library finalization at the end of the program */ + mylibfinal (); + return 0; + } + +Note that invoking any library finalization procedure generated by +`gnatbind` shuts down the Ada run-time environment. +Consequently, the +finalization of all Ada libraries must be performed at the end of the program. +No call to these libraries or to the Ada run-time library should be made +after the finalization phase. + +Note also that special care must be taken with multi-tasks +applications. The initialization and finalization routines are not +protected against concurrent access. If such requirement is needed it +must be ensured at the application level using a specific operating +system services like a mutex or a critical-section. + +.. _Restrictions_in_Stand-alone_Libraries: + +Restrictions in Stand-alone Libraries +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The pragmas listed below should be used with caution inside libraries, +as they can create incompatibilities with other Ada libraries: + +* pragma `Locking_Policy` +* pragma `Partition_Elaboration_Policy` +* pragma `Queuing_Policy` +* pragma `Task_Dispatching_Policy` +* pragma `Unreserve_All_Interrupts` + +When using a library that contains such pragmas, the user must make sure +that all libraries use the same pragmas with the same values. Otherwise, +`Program_Error` will +be raised during the elaboration of the conflicting +libraries. The usage of these pragmas and its consequences for the user +should therefore be well documented. + +Similarly, the traceback in the exception occurrence mechanism should be +enabled or disabled in a consistent manner across all libraries. +Otherwise, Program_Error will be raised during the elaboration of the +conflicting libraries. + +If the `Version` or `Body_Version` +attributes are used inside a library, then you need to +perform a `gnatbind` step that specifies all :file:`ALI` files in all +libraries, so that version identifiers can be properly computed. +In practice these attributes are rarely used, so this is unlikely +to be a consideration. + +.. _Rebuilding_the_GNAT_Run-Time_Library: + +Rebuilding the GNAT Run-Time Library +------------------------------------ + +.. index:: GNAT Run-Time Library, rebuilding +.. index:: Building the GNAT Run-Time Library +.. index:: Rebuilding the GNAT Run-Time Library +.. index:: Run-Time Library, rebuilding + +It may be useful to recompile the GNAT library in various contexts, the +most important one being the use of partition-wide configuration pragmas +such as `Normalize_Scalars`. A special Makefile called +`Makefile.adalib` is provided to that effect and can be found in +the directory containing the GNAT library. The location of this +directory depends on the way the GNAT environment has been installed and can +be determined by means of the command: + +.. code-block:: sh + + $ gnatls -v + +The last entry in the object search path usually contains the +gnat library. This Makefile contains its own documentation and in +particular the set of instructions needed to rebuild a new library and +to use it. + + +.. index:: ! Conditional compilation + +.. _Conditional_Compilation: + +Conditional Compilation +======================= + +This section presents some guidelines for modeling conditional compilation in Ada and describes the +gnatprep preprocessor utility. + +.. index:: ! Conditional compilation + +.. _Modeling_Conditional_Compilation_in_Ada: + +Modeling Conditional Compilation in Ada +--------------------------------------- + +It is often necessary to arrange for a single source program +to serve multiple purposes, where it is compiled in different +ways to achieve these different goals. Some examples of the +need for this feature are + +* Adapting a program to a different hardware environment +* Adapting a program to a different target architecture +* Turning debugging features on and off +* Arranging for a program to compile with different compilers + +In C, or C++, the typical approach would be to use the preprocessor +that is defined as part of the language. The Ada language does not +contain such a feature. This is not an oversight, but rather a very +deliberate design decision, based on the experience that overuse of +the preprocessing features in C and C++ can result in programs that +are extremely difficult to maintain. For example, if we have ten +switches that can be on or off, this means that there are a thousand +separate programs, any one of which might not even be syntactically +correct, and even if syntactically correct, the resulting program +might not work correctly. Testing all combinations can quickly become +impossible. + +Nevertheless, the need to tailor programs certainly exists, and in +this section we will discuss how this can +be achieved using Ada in general, and GNAT in particular. + +.. _Use_of_Boolean_Constants: + +Use of Boolean Constants +^^^^^^^^^^^^^^^^^^^^^^^^ + +In the case where the difference is simply which code +sequence is executed, the cleanest solution is to use Boolean +constants to control which code is executed. + +.. code-block:: ada + + FP_Initialize_Required : constant Boolean := True; + ... + if FP_Initialize_Required then + ... + end if; + +Not only will the code inside the `if` statement not be executed if +the constant Boolean is `False`, but it will also be completely +deleted from the program. +However, the code is only deleted after the `if` statement +has been checked for syntactic and semantic correctness. +(In contrast, with preprocessors the code is deleted before the +compiler ever gets to see it, so it is not checked until the switch +is turned on.) + +.. index:: Preprocessors (contrasted with conditional compilation) + +Typically the Boolean constants will be in a separate package, +something like: + +.. code-block:: ada + + package Config is + FP_Initialize_Required : constant Boolean := True; + Reset_Available : constant Boolean := False; + ... + end Config; + +The `Config` package exists in multiple forms for the various targets, +with an appropriate script selecting the version of `Config` needed. +Then any other unit requiring conditional compilation can do a |with| +of `Config` to make the constants visible. + +.. _Debugging_-_A_Special_Case: + +Debugging - A Special Case +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +A common use of conditional code is to execute statements (for example +dynamic checks, or output of intermediate results) under control of a +debug switch, so that the debugging behavior can be turned on and off. +This can be done using a Boolean constant to control whether the code +is active: + +.. code-block:: ada + + if Debugging then + Put_Line ("got to the first stage!"); + end if; + +or + +.. code-block:: ada + + if Debugging and then Temperature > 999.0 then + raise Temperature_Crazy; + end if; + +.. index:: pragma Assert + +Since this is a common case, there are special features to deal with +this in a convenient manner. For the case of tests, Ada 2005 has added +a pragma `Assert` that can be used for such tests. This pragma is modeled +on the `Assert` pragma that has always been available in GNAT, so this +feature may be used with GNAT even if you are not using Ada 2005 features. +The use of pragma `Assert` is described in the +:title:`GNAT_Reference_Manual`, but as an +example, the last test could be written: + +.. code-block:: ada + + pragma Assert (Temperature <= 999.0, "Temperature Crazy"); + +or simply + +.. code-block:: ada + + pragma Assert (Temperature <= 999.0); + +In both cases, if assertions are active and the temperature is excessive, +the exception `Assert_Failure` will be raised, with the given string in +the first case or a string indicating the location of the pragma in the second +case used as the exception message. + +.. index:: pragma Assertion_Policy + +You can turn assertions on and off by using the `Assertion_Policy` +pragma. + +.. index:: -gnata switch + +This is an Ada 2005 pragma which is implemented in all modes by +GNAT. Alternatively, you can use the *-gnata* switch +to enable assertions from the command line, which applies to +all versions of Ada. + +.. index:: pragma Debug + +For the example above with the `Put_Line`, the GNAT-specific pragma +`Debug` can be used: + +.. code-block:: ada + + pragma Debug (Put_Line ("got to the first stage!")); + +If debug pragmas are enabled, the argument, which must be of the form of +a procedure call, is executed (in this case, `Put_Line` will be called). +Only one call can be present, but of course a special debugging procedure +containing any code you like can be included in the program and then +called in a pragma `Debug` argument as needed. + +One advantage of pragma `Debug` over the `if Debugging then` +construct is that pragma `Debug` can appear in declarative contexts, +such as at the very beginning of a procedure, before local declarations have +been elaborated. + +.. index:: pragma Debug_Policy + +Debug pragmas are enabled using either the *-gnata* switch that also +controls assertions, or with a separate Debug_Policy pragma. + +The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used +in Ada 95 and Ada 83 programs as well), and is analogous to +pragma `Assertion_Policy` to control assertions. + +`Assertion_Policy` and `Debug_Policy` are configuration pragmas, +and thus they can appear in :file:`gnat.adc` if you are not using a +project file, or in the file designated to contain configuration pragmas +in a project file. +They then apply to all subsequent compilations. In practice the use of +the *-gnata* switch is often the most convenient method of controlling +the status of these pragmas. + +Note that a pragma is not a statement, so in contexts where a statement +sequence is required, you can't just write a pragma on its own. You have +to add a `null` statement. + +.. code-block:: ada + + if ... then + ... -- some statements + else + pragma Assert (Num_Cases < 10); + null; + end if; + +.. _Conditionalizing_Declarations: + +Conditionalizing Declarations +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In some cases it may be necessary to conditionalize declarations to meet +different requirements. For example we might want a bit string whose length +is set to meet some hardware message requirement. + +This may be possible using declare blocks controlled +by conditional constants: + +.. code-block:: ada + + if Small_Machine then + declare + X : Bit_String (1 .. 10); + begin + ... + end; + else + declare + X : Large_Bit_String (1 .. 1000); + begin + ... + end; + end if; + +Note that in this approach, both declarations are analyzed by the +compiler so this can only be used where both declarations are legal, +even though one of them will not be used. + +Another approach is to define integer constants, e.g., `Bits_Per_Word`, +or Boolean constants, e.g., `Little_Endian`, and then write declarations +that are parameterized by these constants. For example + +.. code-block:: ada + + for Rec use + Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word; + end record; + +If `Bits_Per_Word` is set to 32, this generates either + +.. code-block:: ada + + for Rec use + Field1 at 0 range 0 .. 32; + end record; + +for the big endian case, or + +.. code-block:: ada + + for Rec use record + Field1 at 0 range 10 .. 32; + end record; + +for the little endian case. Since a powerful subset of Ada expression +notation is usable for creating static constants, clever use of this +feature can often solve quite difficult problems in conditionalizing +compilation (note incidentally that in Ada 95, the little endian +constant was introduced as `System.Default_Bit_Order`, so you do not +need to define this one yourself). + +.. _Use_of_Alternative_Implementations: + +Use of Alternative Implementations +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In some cases, none of the approaches described above are adequate. This +can occur for example if the set of declarations required is radically +different for two different configurations. + +In this situation, the official Ada way of dealing with conditionalizing +such code is to write separate units for the different cases. As long as +this does not result in excessive duplication of code, this can be done +without creating maintenance problems. The approach is to share common +code as far as possible, and then isolate the code and declarations +that are different. Subunits are often a convenient method for breaking +out a piece of a unit that is to be conditionalized, with separate files +for different versions of the subunit for different targets, where the +build script selects the right one to give to the compiler. + +.. index:: Subunits (and conditional compilation) + +As an example, consider a situation where a new feature in Ada 2005 +allows something to be done in a really nice way. But your code must be able +to compile with an Ada 95 compiler. Conceptually you want to say: + +.. code-block:: ada + + if Ada_2005 then + ... neat Ada 2005 code + else + ... not quite as neat Ada 95 code + end if; + +where `Ada_2005` is a Boolean constant. + +But this won't work when `Ada_2005` is set to `False`, +since the `then` clause will be illegal for an Ada 95 compiler. +(Recall that although such unreachable code would eventually be deleted +by the compiler, it still needs to be legal. If it uses features +introduced in Ada 2005, it will be illegal in Ada 95.) + +So instead we write + +.. code-block:: ada + + procedure Insert is separate; + +Then we have two files for the subunit `Insert`, with the two sets of +code. +If the package containing this is called `File_Queries`, then we might +have two files + +* :file:`file_queries-insert-2005.adb` +* :file:`file_queries-insert-95.adb` + +and the build script renames the appropriate file to :file:`file_queries-insert.adb` and then carries out the compilation. + +This can also be done with project files' naming schemes. For example: + +.. code-block:: gpr + + for body ("File_Queries.Insert") use "file_queries-insert-2005.ada"; + +Note also that with project files it is desirable to use a different extension +than :file:`ads` / :file:`adb` for alternative versions. Otherwise a naming +conflict may arise through another commonly used feature: to declare as part +of the project a set of directories containing all the sources obeying the +default naming scheme. + +The use of alternative units is certainly feasible in all situations, +and for example the Ada part of the GNAT run-time is conditionalized +based on the target architecture using this approach. As a specific example, +consider the implementation of the AST feature in VMS. There is one +spec: :file:`s-asthan.ads` which is the same for all architectures, and three +bodies: + +* :file:`s-asthan.adb` + used for all non-VMS operating systems + +* :file:`s-asthan-vms-alpha.adb` + used for VMS on the Alpha + +* :file:`s-asthan-vms-ia64.adb` + used for VMS on the ia64 + +The dummy version :file:`s-asthan.adb` simply raises exceptions noting that +this operating system feature is not available, and the two remaining +versions interface with the corresponding versions of VMS to provide +VMS-compatible AST handling. The GNAT build script knows the architecture +and operating system, and automatically selects the right version, +renaming it if necessary to :file:`s-asthan.adb` before the run-time build. + +Another style for arranging alternative implementations is through Ada's +access-to-subprogram facility. +In case some functionality is to be conditionally included, +you can declare an access-to-procedure variable `Ref` that is initialized +to designate a 'do nothing' procedure, and then invoke `Ref.all` +when appropriate. +In some library package, set `Ref` to `Proc'Access` for some +procedure `Proc` that performs the relevant processing. +The initialization only occurs if the library package is included in the +program. +The same idea can also be implemented using tagged types and dispatching +calls. + +.. _Preprocessing: + +Preprocessing +^^^^^^^^^^^^^ + +.. index:: Preprocessing + +Although it is quite possible to conditionalize code without the use of +C-style preprocessing, as described earlier in this section, it is +nevertheless convenient in some cases to use the C approach. Moreover, +older Ada compilers have often provided some preprocessing capability, +so legacy code may depend on this approach, even though it is not +standard. + +To accommodate such use, GNAT provides a preprocessor (modeled to a large +extent on the various preprocessors that have been used +with legacy code on other compilers, to enable easier transition). + +.. index:: gnatprep + +The preprocessor may be used in two separate modes. It can be used quite +separately from the compiler, to generate a separate output source file +that is then fed to the compiler as a separate step. This is the +`gnatprep` utility, whose use is fully described in +:ref:`Preprocessing_with_gnatprep`. + +The preprocessing language allows such constructs as + +.. code-block:: c + + #if DEBUG or else (PRIORITY > 4) then + bunch of declarations + #else + completely different bunch of declarations + #end if; + +The values of the symbols `DEBUG` and `PRIORITY` can be +defined either on the command line or in a separate file. + +The other way of running the preprocessor is even closer to the C style and +often more convenient. In this approach the preprocessing is integrated into +the compilation process. The compiler is fed the preprocessor input which +includes `#if` lines etc, and then the compiler carries out the +preprocessing internally and processes the resulting output. +For more details on this approach, see :ref:`Integrated_Preprocessing`. + +.. _Preprocessing_with_gnatprep: + +Preprocessing with `gnatprep` +----------------------------- + +.. index:: ! gnatprep +.. index:: Preprocessing (gnatprep) + +This section discusses how to use GNAT's `gnatprep` utility for simple +preprocessing. +Although designed for use with GNAT, `gnatprep` does not depend on any +special GNAT features. +For further discussion of conditional compilation in general, see +:ref:`Conditional_Compilation`. + +.. _Preprocessing_Symbols: + +Preprocessing Symbols +^^^^^^^^^^^^^^^^^^^^^ + +Preprocessing symbols are defined in definition files and referred to in +sources to be preprocessed. A Preprocessing symbol is an identifier, following +normal Ada (case-insensitive) rules for its syntax, with the restriction that +all characters need to be in the ASCII set (no accented letters). + +.. _Using_gnatprep: + +Using `gnatprep` +^^^^^^^^^^^^^^^^ + +To call `gnatprep` use: + +.. code-block:: sh + + $ gnatprep [`switches`] `infile` `outfile` [`deffile`] + +where + +* *switches* + is an optional sequence of switches as described in the next section. + +* *infile* + is the full name of the input file, which is an Ada source + file containing preprocessor directives. + +* *outfile* + is the full name of the output file, which is an Ada source + in standard Ada form. When used with GNAT, this file name will + normally have an ads or adb suffix. + +* *deffile* + is the full name of a text file containing definitions of + preprocessing symbols to be referenced by the preprocessor. This argument is + optional, and can be replaced by the use of the *-D* switch. + + +.. _Switches_for_gnatprep: + +Switches for `gnatprep` +^^^^^^^^^^^^^^^^^^^^^^^ + +.. index:: -b (gnatprep) + +:samp:`-b` + Causes both preprocessor lines and the lines deleted by + preprocessing to be replaced by blank lines in the output source file, + preserving line numbers in the output file. + +.. index:: -c (gnatprep) + +:samp:`-c` + Causes both preprocessor lines and the lines deleted + by preprocessing to be retained in the output source as comments marked + with the special string `"--! "`. This option will result in line numbers + being preserved in the output file. + +.. index:: -C (gnatprep) + +:samp:`-C` + Causes comments to be scanned. Normally comments are ignored by gnatprep. + If this option is specified, then comments are scanned and any $symbol + substitutions performed as in program text. This is particularly useful + when structured comments are used (e.g., when writing programs in the + SPARK dialect of Ada). Note that this switch is not available when + doing integrated preprocessing (it would be useless in this context + since comments are ignored by the compiler in any case). + +.. index:: -D (gnatprep) + +:samp:`-D{symbol}={value}` + Defines a new preprocessing symbol, associated with value. If no value is given + on the command line, then symbol is considered to be `True`. This switch + can be used in place of a definition file. + +.. index:: -r (gnatprep) + +:samp:`-r` + Causes a `Source_Reference` pragma to be generated that + references the original input file, so that error messages will use + the file name of this original file. The use of this switch implies + that preprocessor lines are not to be removed from the file, so its + use will force *-b* mode if *-c* + has not been specified explicitly. + + Note that if the file to be preprocessed contains multiple units, then + it will be necessary to `gnatchop` the output file from + `gnatprep`. If a `Source_Reference` pragma is present + in the preprocessed file, it will be respected by + `gnatchop -r` + so that the final chopped files will correctly refer to the original + input source file for `gnatprep`. + +.. index:: -s (gnatprep) + +:samp:`-s` + Causes a sorted list of symbol names and values to be + listed on the standard output file. + +.. index:: -u (gnatprep) + +:samp:`-u` + Causes undefined symbols to be treated as having the value FALSE in the context + of a preprocessor test. In the absence of this option, an undefined symbol in + a `#if` or `#elsif` test will be treated as an error. + + +Note: if neither *-b* nor *-c* is present, +then preprocessor lines and +deleted lines are completely removed from the output, unless -r is +specified, in which case -b is assumed. + + +.. _Form_of_Definitions_File: + +Form of Definitions File +^^^^^^^^^^^^^^^^^^^^^^^^ + +The definitions file contains lines of the form:: + + symbol := value + +where `symbol` is a preprocessing symbol, and `value` is one of the following: + +* Empty, corresponding to a null substitution, +* A string literal using normal Ada syntax, or +* Any sequence of characters from the set {letters, digits, period, underline}. + +Comment lines may also appear in the definitions file, starting with +the usual ``--``, +and comments may be added to the definitions lines. + + +.. _Form_of_Input_Text_for_gnatprep: + +Form of Input Text for `gnatprep` +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The input text may contain preprocessor conditional inclusion lines, +as well as general symbol substitution sequences. + +The preprocessor conditional inclusion commands have the form: + +.. code-block:: c + + #if [then] + lines + #elsif [then] + lines + #elsif [then] + lines + ... + #else + lines + #end if; + +In this example, is defined by the following grammar:: + + ::= + ::= = "" + ::= = + ::= = + ::= > + ::= >= + ::= < + ::= <= + ::= 'Defined + ::= not + ::= and + ::= or + ::= and then + ::= or else + ::= ( ) + +Note the following restriction: it is not allowed to have "and" or "or" +following "not" in the same expression without parentheses. For example, this +is not allowed: + +.. code-block:: ada + + not X or Y + +This can be expressed instead as one of the following forms: + +.. code-block:: ada + + (not X) or Y + not (X or Y) + +For the first test ( ::= ) the symbol must have +either the value true or false, that is to say the right-hand of the +symbol definition must be one of the (case-insensitive) literals +`True` or `False`. If the value is true, then the +corresponding lines are included, and if the value is false, they are +excluded. + +When comparing a symbol to an integer, the integer is any non negative +literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or +2#11#. The symbol value must also be a non negative integer. Integer values +in the range 0 .. 2**31-1 are supported. + +The test ( ::= 'Defined) is true only if +the symbol has been defined in the definition file or by a *-D* +switch on the command line. Otherwise, the test is false. + +The equality tests are case insensitive, as are all the preprocessor lines. + +If the symbol referenced is not defined in the symbol definitions file, +then the effect depends on whether or not switch *-u* +is specified. If so, then the symbol is treated as if it had the value +false and the test fails. If this switch is not specified, then +it is an error to reference an undefined symbol. It is also an error to +reference a symbol that is defined with a value other than `True` +or `False`. + +The use of the `not` operator inverts the sense of this logical test. +The `not` operator cannot be combined with the `or` or `and` +operators, without parentheses. For example, "if not X or Y then" is not +allowed, but "if (not X) or Y then" and "if not (X or Y) then" are. + +The `then` keyword is optional as shown + +The `#` must be the first non-blank character on a line, but +otherwise the format is free form. Spaces or tabs may appear between +the `#` and the keyword. The keywords and the symbols are case +insensitive as in normal Ada code. Comments may be used on a +preprocessor line, but other than that, no other tokens may appear on a +preprocessor line. Any number of `elsif` clauses can be present, +including none at all. The `else` is optional, as in Ada. + +The `#` marking the start of a preprocessor line must be the first +non-blank character on the line, i.e., it must be preceded only by +spaces or horizontal tabs. + +Symbol substitution outside of preprocessor lines is obtained by using +the sequence:: + + $symbol + +anywhere within a source line, except in a comment or within a +string literal. The identifier +following the `$` must match one of the symbols defined in the symbol +definition file, and the result is to substitute the value of the +symbol in place of `$symbol` in the output file. + +Note that although the substitution of strings within a string literal +is not possible, it is possible to have a symbol whose defined value is +a string literal. So instead of setting XYZ to `hello` and writing: + +.. code-block:: c + + Header : String := "$XYZ"; + +you should set XYZ to `"hello"` and write: + +.. code-block:: c + + Header : String := $XYZ; + +and then the substitution will occur as desired. + + +.. _Integrated_Preprocessing: + +Integrated Preprocessing +------------------------ + +GNAT sources may be preprocessed immediately before compilation. +In this case, the actual +text of the source is not the text of the source file, but is derived from it +through a process called preprocessing. Integrated preprocessing is specified +through switches *-gnatep* and/or *-gnateD*. *-gnatep* +indicates, through a text file, the preprocessing data to be used. +:samp:`-gnateD` specifies or modifies the values of preprocessing symbol. +Note that integrated preprocessing applies only to Ada source files, it is +not available for configuration pragma files. + +Note that when integrated preprocessing is used, the output from the +preprocessor is not written to any external file. Instead it is passed +internally to the compiler. If you need to preserve the result of +preprocessing in a file, then you should use *gnatprep* +to perform the desired preprocessing in stand-alone mode. + +It is recommended that *gnatmake* switch -s should be +used when Integrated Preprocessing is used. The reason is that preprocessing +with another Preprocessing Data file without changing the sources will +not trigger recompilation without this switch. + +Note that *gnatmake* switch -m will almost +always trigger recompilation for sources that are preprocessed, +because *gnatmake* cannot compute the checksum of the source after +preprocessing. + +The actual preprocessing function is described in detail in section +:ref:`Preprocessing_with_gnatprep`. This section only describes how integrated +preprocessing is triggered and parameterized. + + +.. index:: -gnatep (gcc) + +:samp:`-gnatep={file}` + This switch indicates to the compiler the file name (without directory + information) of the preprocessor data file to use. The preprocessor data file + should be found in the source directories. Note that when the compiler is + called by a builder such as (*gnatmake* with a project + file, if the object directory is not also a source directory, the builder needs + to be called with *-x*. + + A preprocessing data file is a text file with significant lines indicating + how should be preprocessed either a specific source or all sources not + mentioned in other lines. A significant line is a nonempty, non-comment line. + Comments are similar to Ada comments. + + Each significant line starts with either a literal string or the character '*'. + A literal string is the file name (without directory information) of the source + to preprocess. A character '*' indicates the preprocessing for all the sources + that are not specified explicitly on other lines (order of the lines is not + significant). It is an error to have two lines with the same file name or two + lines starting with the character '*'. + + After the file name or the character '*', another optional literal string + indicating the file name of the definition file to be used for preprocessing + (:ref:`Form_of_Definitions_File`). The definition files are found by the + compiler in one of the source directories. In some cases, when compiling + a source in a directory other than the current directory, if the definition + file is in the current directory, it may be necessary to add the current + directory as a source directory through switch -I., otherwise + the compiler would not find the definition file. + + Then, optionally, switches similar to those of `gnatprep` may + be found. Those switches are: + + :samp:`-b` + Causes both preprocessor lines and the lines deleted by + preprocessing to be replaced by blank lines, preserving the line number. + This switch is always implied; however, if specified after *-c* + it cancels the effect of *-c*. + + + :samp:`-c` + Causes both preprocessor lines and the lines deleted + by preprocessing to be retained as comments marked + with the special string '`--!`'. + + + :samp:`-Dsymbol={value}` + Define or redefine a symbol, associated with value. A symbol is an Ada + identifier, or an Ada reserved word, with the exception of `if`, + `else`, `elsif`, `end`, `and`, `or` and `then`. + `value` is either a literal string, an Ada identifier or any Ada reserved + word. A symbol declared with this switch replaces a symbol with the + same name defined in a definition file. + + + :samp:`-s` + Causes a sorted list of symbol names and values to be + listed on the standard output file. + + + :samp:`-u` + Causes undefined symbols to be treated as having the value `FALSE` + in the context + of a preprocessor test. In the absence of this option, an undefined symbol in + a `#if` or `#elsif` test will be treated as an error. + + + Examples of valid lines in a preprocessor data file: + + .. code-block:: ada + + "toto.adb" "prep.def" -u + -- preprocess "toto.adb", using definition file "prep.def", + -- undefined symbol are False. + + * -c -DVERSION=V101 + -- preprocess all other sources without a definition file; + -- suppressed lined are commented; symbol VERSION has the value V101. + + "titi.adb" "prep2.def" -s + -- preprocess "titi.adb", using definition file "prep2.def"; + -- list all symbols with their values. + +.. index:: -gnateD (gcc) + +:samp:`-gnateDsymbol[=value]` + Define or redefine a preprocessing symbol, associated with value. If no value + is given on the command line, then the value of the symbol is `True`. + A symbol is an identifier, following normal Ada (case-insensitive) + rules for its syntax, and value is either an arbitrary string between double + quotes or any sequence (including an empty sequence) of characters from the + set (letters, digits, period, underline). + Ada reserved words may be used as symbols, with the exceptions of `if`, + `else`, `elsif`, `end`, `and`, `or` and `then`. + + Examples:: + + -gnateDToto=Titi + -gnateDFoo + -gnateDFoo=\"Foo-Bar\" + + A symbol declared with this switch on the command line replaces a + symbol with the same name either in a definition file or specified with a + switch -D in the preprocessor data file. + + This switch is similar to switch *-D* of `gnatprep`. + + +:samp:`-gnateG` + When integrated preprocessing is performed and the preprocessor modifies + the source text, write the result of this preprocessing into a file + .prep. + + +.. _Mixed_Language_Programming: + +Mixed Language Programming +========================== + +.. index:: Mixed Language Programming + +This section describes how to develop a mixed-language program, +with a focus on combining Ada with C or C++. + +.. _Interfacing_to_C: + +Interfacing to C +---------------- + +Interfacing Ada with a foreign language such as C involves using +compiler directives to import and/or export entity definitions in each +language -- using `extern` statements in C, for instance, and the +`Import`, `Export`, and `Convention` pragmas in Ada. +A full treatment of these topics is provided in Appendix B, section 1 +of the Ada Reference Manual. + +There are two ways to build a program using GNAT that contains some Ada +sources and some foreign language sources, depending on whether or not +the main subprogram is written in Ada. Here is a source example with +the main subprogram in Ada: + +.. code-block:: c + + /* file1.c */ + #include + + void print_num (int num) + { + printf ("num is %d.\\n", num); + return; + } + +.. code-block:: c + + /* file2.c */ + + /* num_from_Ada is declared in my_main.adb */ + extern int num_from_Ada; + + int get_num (void) + { + return num_from_Ada; + } + +.. code-block:: ada + + -- my_main.adb + procedure My_Main is + + -- Declare then export an Integer entity called num_from_Ada + My_Num : Integer := 10; + pragma Export (C, My_Num, "num_from_Ada"); + + -- Declare an Ada function spec for Get_Num, then use + -- C function get_num for the implementation. + function Get_Num return Integer; + pragma Import (C, Get_Num, "get_num"); + + -- Declare an Ada procedure spec for Print_Num, then use + -- C function print_num for the implementation. + procedure Print_Num (Num : Integer); + pragma Import (C, Print_Num, "print_num"; + + begin + Print_Num (Get_Num); + end My_Main; + +To build this example: + +* First compile the foreign language files to + generate object files: + + .. code-block:: sh + + $ gcc -c file1.c + $ gcc -c file2.c + +* Then, compile the Ada units to produce a set of object files and ALI + files: + + .. code-block:: sh + + $ gnatmake -c my_main.adb + +* Run the Ada binder on the Ada main program: + + .. code-block:: sh + + $ gnatbind my_main.ali + +* Link the Ada main program, the Ada objects and the other language + objects: + + .. code-block:: sh + + $ gnatlink my_main.ali file1.o file2.o + +The last three steps can be grouped in a single command: + +.. code-block:: sh + + $ gnatmake my_main.adb -largs file1.o file2.o + + +.. index:: Binder output file + +If the main program is in a language other than Ada, then you may have +more than one entry point into the Ada subsystem. You must use a special +binder option to generate callable routines that initialize and +finalize the Ada units (:ref:`Binding_with_Non-Ada_Main_Programs`). +Calls to the initialization and finalization routines must be inserted +in the main program, or some other appropriate point in the code. The +call to initialize the Ada units must occur before the first Ada +subprogram is called, and the call to finalize the Ada units must occur +after the last Ada subprogram returns. The binder will place the +initialization and finalization subprograms into the +:file:`b~xxx.adb` file where they can be accessed by your C +sources. To illustrate, we have the following example: + +.. code-block:: c + + /* main.c */ + extern void adainit (void); + extern void adafinal (void); + extern int add (int, int); + extern int sub (int, int); + + int main (int argc, char *argv[]) + { + int a = 21, b = 7; + + adainit(); + + /* Should print "21 + 7 = 28" */ + printf ("%d + %d = %d\\n", a, b, add (a, b)); + + /* Should print "21 - 7 = 14" */ + printf ("%d - %d = %d\\n", a, b, sub (a, b)); + + adafinal(); + } + +.. code-block:: ada + + -- unit1.ads + package Unit1 is + function Add (A, B : Integer) return Integer; + pragma Export (C, Add, "add"); + end Unit1; + +.. code-block:: ada + + -- unit1.adb + package body Unit1 is + function Add (A, B : Integer) return Integer is + begin + return A + B; + end Add; + end Unit1; + +.. code-block:: ada + + -- unit2.ads + package Unit2 is + function Sub (A, B : Integer) return Integer; + pragma Export (C, Sub, "sub"); + end Unit2; + +.. code-block:: ada + + -- unit2.adb + package body Unit2 is + function Sub (A, B : Integer) return Integer is + begin + return A - B; + end Sub; + end Unit2; + +The build procedure for this application is similar to the last +example's: + +* First, compile the foreign language files to generate object files: + + .. code-block:: sh + + $ gcc -c main.c + + +* Next, compile the Ada units to produce a set of object files and ALI + files: + + .. code-block:: sh + + $ gnatmake -c unit1.adb + $ gnatmake -c unit2.adb + +* Run the Ada binder on every generated ALI file. Make sure to use the + :option:`-n` option to specify a foreign main program: + + .. code-block:: sh + + $ gnatbind -n unit1.ali unit2.ali + +* Link the Ada main program, the Ada objects and the foreign language + objects. You need only list the last ALI file here: + + .. code-block:: sh + + $ gnatlink unit2.ali main.o -o exec_file + + This procedure yields a binary executable called :file:`exec_file`. + +Depending on the circumstances (for example when your non-Ada main object +does not provide symbol `main`), you may also need to instruct the +GNAT linker not to include the standard startup objects by passing the +:option:`-nostartfiles` switch to `gnatlink`. + +.. _Calling_Conventions: + +Calling Conventions +------------------- + +.. index:: Foreign Languages + +.. index:: Calling Conventions + +GNAT follows standard calling sequence conventions and will thus interface +to any other language that also follows these conventions. The following +Convention identifiers are recognized by GNAT: + + +.. index:: Interfacing to Ada + +.. index:: Other Ada compilers + +.. index:: Convention Ada + +*Ada* + This indicates that the standard Ada calling sequence will be + used and all Ada data items may be passed without any limitations in the + case where GNAT is used to generate both the caller and callee. It is also + possible to mix GNAT generated code and code generated by another Ada + compiler. In this case, the data types should be restricted to simple + cases, including primitive types. Whether complex data types can be passed + depends on the situation. Probably it is safe to pass simple arrays, such + as arrays of integers or floats. Records may or may not work, depending + on whether both compilers lay them out identically. Complex structures + involving variant records, access parameters, tasks, or protected types, + are unlikely to be able to be passed. + + Note that in the case of GNAT running + on a platform that supports HP Ada 83, a higher degree of compatibility + can be guaranteed, and in particular records are laid out in an identical + manner in the two compilers. Note also that if output from two different + compilers is mixed, the program is responsible for dealing with elaboration + issues. Probably the safest approach is to write the main program in the + version of Ada other than GNAT, so that it takes care of its own elaboration + requirements, and then call the GNAT-generated adainit procedure to ensure + elaboration of the GNAT components. Consult the documentation of the other + Ada compiler for further details on elaboration. + + However, it is not possible to mix the tasking run time of GNAT and + HP Ada 83, All the tasking operations must either be entirely within + GNAT compiled sections of the program, or entirely within HP Ada 83 + compiled sections of the program. + +.. index:: Interfacing to Assembly + +.. index:: Convention Assembler + + +*Assembler* + Specifies assembler as the convention. In practice this has the + same effect as convention Ada (but is not equivalent in the sense of being + considered the same convention). + +.. index:: Convention Asm + +.. index:: Asm + +*Asm* + Equivalent to Assembler. + + .. index:: Interfacing to COBOL + + .. index:: Convention COBOL + +.. index:: COBOL + +*COBOL* + Data will be passed according to the conventions described + in section B.4 of the Ada Reference Manual. + +.. index:: C +.. index:: Interfacing to C + +.. index:: Convention C + + +*C* + Data will be passed according to the conventions described + in section B.3 of the Ada Reference Manual. + + A note on interfacing to a C 'varargs' function: + + .. index:: C varargs function + .. index:: Interfacing to C varargs function + .. index:: varargs function interfaces + + In C, `varargs` allows a function to take a variable number of + arguments. There is no direct equivalent in this to Ada. One + approach that can be used is to create a C wrapper for each + different profile and then interface to this C wrapper. For + example, to print an `int` value using `printf`, + create a C function `printfi` that takes two arguments, a + pointer to a string and an int, and calls `printf`. + Then in the Ada program, use pragma `Import` to + interface to `printfi`. + + It may work on some platforms to directly interface to + a `varargs` function by providing a specific Ada profile + for a particular call. However, this does not work on + all platforms, since there is no guarantee that the + calling sequence for a two argument normal C function + is the same as for calling a `varargs` C function with + the same two arguments. + +.. index:: Convention Default + +.. index:: Default + +*Default* + Equivalent to C. + +.. index:: Convention External + +.. index:: External + +*External* + Equivalent to C. + +.. index:: C++ +.. index:: Interfacing to C++ + +.. index:: Convention C++ + + +*C_Plus_Plus (or CPP)* + This stands for C++. For most purposes this is identical to C. + See the separate description of the specialized GNAT pragmas relating to + C++ interfacing for further details. + +.. index:: Fortran +.. index:: Interfacing to Fortran +.. index:: Convention Fortran + + +*Fortran* + Data will be passed according to the conventions described + in section B.5 of the Ada Reference Manual. + + +*Intrinsic* + This applies to an intrinsic operation, as defined in the Ada + Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram, + this means that the body of the subprogram is provided by the compiler itself, + usually by means of an efficient code sequence, and that the user does not + supply an explicit body for it. In an application program, the pragma may + be applied to the following sets of names: + + + * Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic. + The corresponding subprogram declaration must have + two formal parameters. The + first one must be a signed integer type or a modular type with a binary + modulus, and the second parameter must be of type Natural. + The return type must be the same as the type of the first argument. The size + of this type can only be 8, 16, 32, or 64. + + + * Binary arithmetic operators: '+', '-', '*', '/'. + The corresponding operator declaration must have parameters and result type + that have the same root numeric type (for example, all three are long_float + types). This simplifies the definition of operations that use type checking + to perform dimensional checks: + + + .. code-block: ada + + type Distance is new Long_Float; + type Time is new Long_Float; + type Velocity is new Long_Float; + function "/" (D : Distance; T : Time) + return Velocity; + pragma Import (Intrinsic, "/"); + + This common idiom is often programmed with a generic definition and an + explicit body. The pragma makes it simpler to introduce such declarations. + It incurs no overhead in compilation time or code size, because it is + implemented as a single machine instruction. + + + * General subprogram entities. This is used to bind an Ada subprogram + declaration to + a compiler builtin by name with back-ends where such interfaces are + available. A typical example is the set of `__builtin` functions + exposed by the GCC back-end, as in the following example: + + + .. code-block:: ada + + function builtin_sqrt (F : Float) return Float; + pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf"); + + Most of the GCC builtins are accessible this way, and as for other + import conventions (e.g. C), it is the user's responsibility to ensure + that the Ada subprogram profile matches the underlying builtin + expectations. + +.. index:: Stdcall +.. index:: Convention Stdcall + +*Stdcall* + This is relevant only to Windows XP/2000/NT implementations of GNAT, + and specifies that the `Stdcall` calling sequence will be used, + as defined by the NT API. Nevertheless, to ease building + cross-platform bindings this convention will be handled as a `C` calling + convention on non-Windows platforms. + +.. index:: DLL +.. index:: Convention DLL + + +*DLL* + This is equivalent to `Stdcall`. + +.. index:: Win32 +.. index:: Convention Win32 + + +*Win32* + This is equivalent to `Stdcall`. + +.. index:: Stubbed +.. index:: Convention Stubbed + + +*Stubbed* + This is a special convention that indicates that the compiler + should provide a stub body that raises `Program_Error`. + +GNAT additionally provides a useful pragma `Convention_Identifier` +that can be used to parameterize conventions and allow additional synonyms +to be specified. For example if you have legacy code in which the convention +identifier Fortran77 was used for Fortran, you can use the configuration +pragma: + +.. code-block:: ada + + pragma Convention_Identifier (Fortran77, Fortran); + +And from now on the identifier Fortran77 may be used as a convention +identifier (for example in an `Import` pragma) with the same +meaning as Fortran. + + +.. _Building_Mixed_Ada_and_C++_Programs: + +Building Mixed Ada and C++ Programs +----------------------------------- + +A programmer inexperienced with mixed-language development may find that +building an application containing both Ada and C++ code can be a +challenge. This section gives a few hints that should make this task easier. + +.. _Interfacing_to_C++: + +Interfacing to C++ +^^^^^^^^^^^^^^^^^^ + +GNAT supports interfacing with the G++ compiler (or any C++ compiler +generating code that is compatible with the G++ Application Binary +Interface ---see http://www.codesourcery.com/archives/cxx-abi). + +Interfacing can be done at 3 levels: simple data, subprograms, and +classes. In the first two cases, GNAT offers a specific `Convention C_Plus_Plus` +(or `CPP`) that behaves exactly like `Convention C`. +Usually, C++ mangles the names of subprograms. To generate proper mangled +names automatically, see :ref:`Generating_Ada_Bindings_for_C_and_C++_headers`). +This problem can also be addressed manually in two ways: + +* by modifying the C++ code in order to force a C convention using + the `extern "C"` syntax. + +* by figuring out the mangled name (using e.g. *nm*) and using it as the + Link_Name argument of the pragma import. + +Interfacing at the class level can be achieved by using the GNAT specific +pragmas such as `CPP_Constructor`. See the :title:`GNAT_Reference_Manual` for additional information. + +.. _Linking_a_Mixed_C++_and_Ada_Program: + +Linking a Mixed C++ & Ada Program +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Usually the linker of the C++ development system must be used to link +mixed applications because most C++ systems will resolve elaboration +issues (such as calling constructors on global class instances) +transparently during the link phase. GNAT has been adapted to ease the +use of a foreign linker for the last phase. Three cases can be +considered: + + +* Using GNAT and G++ (GNU C++ compiler) from the same GCC installation: + The C++ linker can simply be called by using the C++ specific driver + called `g++`. + + Note that if the C++ code uses inline functions, you will need to + compile your C++ code with the `-fkeep-inline-functions` switch in + order to provide an existing function implementation that the Ada code can + link with. + + .. code-block:: sh + + $ g++ -c -fkeep-inline-functions file1.C + $ g++ -c -fkeep-inline-functions file2.C + $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++ + + +* Using GNAT and G++ from two different GCC installations: If both + compilers are on the :envvar`PATH`, the previous method may be used. It is + important to note that environment variables such as + :envvar:`C_INCLUDE_PATH`, :envvar:`GCC_EXEC_PREFIX`, + :envvar:`BINUTILS_ROOT`, and + :envvar:`GCC_ROOT` will affect both compilers + at the same time and may make one of the two compilers operate + improperly if set during invocation of the wrong compiler. It is also + very important that the linker uses the proper :file:`libgcc.a` GCC + library -- that is, the one from the C++ compiler installation. The + implicit link command as suggested in the `gnatmake` command + from the former example can be replaced by an explicit link command with + the full-verbosity option in order to verify which library is used: + + .. code-block:: sh + + $ gnatbind ada_unit + $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++ + + If there is a problem due to interfering environment variables, it can + be worked around by using an intermediate script. The following example + shows the proper script to use when GNAT has not been installed at its + default location and g++ has been installed at its default location: + + .. code-block:: sh + + $ cat ./my_script + #!/bin/sh + unset BINUTILS_ROOT + unset GCC_ROOT + c++ $* + $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script + + +* Using a non-GNU C++ compiler: The commands previously described can be + used to insure that the C++ linker is used. Nonetheless, you need to add + a few more parameters to the link command line, depending on the exception + mechanism used. + + If the `setjmp/longjmp` exception mechanism is used, only the paths + to the libgcc libraries are required: + + .. code-block:: sh + + $ cat ./my_script + #!/bin/sh + CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` + $ gnatlink ada_unit file1.o file2.o --LINK=./my_script + + + where CC is the name of the non-GNU C++ compiler. + + If the `zero cost` exception mechanism is used, and the platform + supports automatic registration of exception tables (e.g., Solaris), + paths to more objects are required: + + .. code-block:: sh + + $ cat ./my_script + #!/bin/sh + CC `gcc -print-file-name=crtbegin.o` $* \\ + `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \\ + `gcc -print-file-name=crtend.o` + $ gnatlink ada_unit file1.o file2.o --LINK=./my_script + + + If the "zero cost exception" mechanism is used, and the platform + doesn't support automatic registration of exception tables (e.g., HP-UX + or AIX), the simple approach described above will not work and + a pre-linking phase using GNAT will be necessary. + + +Another alternative is to use the :command:`gprbuild` multi-language builder +which has a large knowledge base and knows how to link Ada and C++ code +together automatically in most cases. + +.. _A_Simple_Example: + +A Simple Example +^^^^^^^^^^^^^^^^ + +The following example, provided as part of the GNAT examples, shows how +to achieve procedural interfacing between Ada and C++ in both +directions. The C++ class A has two methods. The first method is exported +to Ada by the means of an extern C wrapper function. The second method +calls an Ada subprogram. On the Ada side, The C++ calls are modelled by +a limited record with a layout comparable to the C++ class. The Ada +subprogram, in turn, calls the C++ method. So, starting from the C++ +main program, the process passes back and forth between the two +languages. + +Here are the compilation commands: + +.. code-block:: sh + + $ gnatmake -c simple_cpp_interface + $ g++ -c cpp_main.C + $ g++ -c ex7.C + $ gnatbind -n simple_cpp_interface + $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o + +Here are the corresponding sources: + +.. code-block:: cpp + + //cpp_main.C + + #include "ex7.h" + + extern "C" { + void adainit (void); + void adafinal (void); + void method1 (A *t); + } + + void method1 (A *t) + { + t->method1 (); + } + + int main () + { + A obj; + adainit (); + obj.method2 (3030); + adafinal (); + } + +.. code-block:: cpp + + //ex7.h + + class Origin { + public: + int o_value; + }; + class A : public Origin { + public: + void method1 (void); + void method2 (int v); + A(); + int a_value; + }; + +.. code-block:: cpp + + //ex7.C + + #include "ex7.h" + #include + + extern "C" { void ada_method2 (A *t, int v);} + + void A::method1 (void) + { + a_value = 2020; + printf ("in A::method1, a_value = %d \\n",a_value); + } + + void A::method2 (int v) + { + ada_method2 (this, v); + printf ("in A::method2, a_value = %d \\n",a_value); + } + + A::A(void) + { + a_value = 1010; + printf ("in A::A, a_value = %d \\n",a_value); + } + +.. code-block:: ada + + -- simple_cpp_interface.ads + with System; + package Simple_Cpp_Interface is + type A is limited + record + Vptr : System.Address; + O_Value : Integer; + A_Value : Integer; + end record; + pragma Convention (C, A); + + procedure Method1 (This : in out A); + pragma Import (C, Method1); + + procedure Ada_Method2 (This : in out A; V : Integer); + pragma Export (C, Ada_Method2); + + end Simple_Cpp_Interface; + +.. code-block:: ada + + -- simple_cpp_interface.adb + package body Simple_Cpp_Interface is + + procedure Ada_Method2 (This : in out A; V : Integer) is + begin + Method1 (This); + This.A_Value := V; + end Ada_Method2; + + end Simple_Cpp_Interface; + + +.. _Interfacing_with_C++_constructors: + +Interfacing with C++ constructors +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In order to interface with C++ constructors GNAT provides the +`pragma CPP_Constructor` (see the :title:`GNAT_Reference_Manual` +for additional information). +In this section we present some common uses of C++ constructors +in mixed-languages programs in GNAT. + +Let us assume that we need to interface with the following +C++ class: + +.. code-block:: cpp + + class Root { + public: + int a_value; + int b_value; + virtual int Get_Value (); + Root(); // Default constructor + Root(int v); // 1st non-default constructor + Root(int v, int w); // 2nd non-default constructor + }; + +For this purpose we can write the following package spec (further +information on how to build this spec is available in +:ref:`Interfacing_with_C++_at_the_Class_Level` and +:ref:`Generating_Ada_Bindings_for_C_and_C++_headers`). + +.. code-block:: ada + + with Interfaces.C; use Interfaces.C; + package Pkg_Root is + type Root is tagged limited record + A_Value : int; + B_Value : int; + end record; + pragma Import (CPP, Root); + + function Get_Value (Obj : Root) return int; + pragma Import (CPP, Get_Value); + + function Constructor return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev"); + + function Constructor (v : Integer) return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei"); + + function Constructor (v, w : Integer) return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii"); + end Pkg_Root; + +On the Ada side the constructor is represented by a function (whose +name is arbitrary) that returns the classwide type corresponding to +the imported C++ class. Although the constructor is described as a +function, it is typically a procedure with an extra implicit argument +(the object being initialized) at the implementation level. GNAT +issues the appropriate call, whatever it is, to get the object +properly initialized. + +Constructors can only appear in the following contexts: + +* On the right side of an initialization of an object of type `T`. +* On the right side of an initialization of a record component of type `T`. +* In an Ada 2005 limited aggregate. +* In an Ada 2005 nested limited aggregate. +* In an Ada 2005 limited aggregate that initializes an object built in + place by an extended return statement. + +In a declaration of an object whose type is a class imported from C++, +either the default C++ constructor is implicitly called by GNAT, or +else the required C++ constructor must be explicitly called in the +expression that initializes the object. For example: + +.. code-block:: ada + + Obj1 : Root; + Obj2 : Root := Constructor; + Obj3 : Root := Constructor (v => 10); + Obj4 : Root := Constructor (30, 40); + +The first two declarations are equivalent: in both cases the default C++ +constructor is invoked (in the former case the call to the constructor is +implicit, and in the latter case the call is explicit in the object +declaration). `Obj3` is initialized by the C++ non-default constructor +that takes an integer argument, and `Obj4` is initialized by the +non-default C++ constructor that takes two integers. + +Let us derive the imported C++ class in the Ada side. For example: + +.. code-block:: ada + + type DT is new Root with record + C_Value : Natural := 2009; + end record; + +In this case the components DT inherited from the C++ side must be +initialized by a C++ constructor, and the additional Ada components +of type DT are initialized by GNAT. The initialization of such an +object is done either by default, or by means of a function returning +an aggregate of type DT, or by means of an extension aggregate. + +.. code-block:: ada + + Obj5 : DT; + Obj6 : DT := Function_Returning_DT (50); + Obj7 : DT := (Constructor (30,40) with C_Value => 50); + +The declaration of `Obj5` invokes the default constructors: the +C++ default constructor of the parent type takes care of the initialization +of the components inherited from Root, and GNAT takes care of the default +initialization of the additional Ada components of type DT (that is, +`C_Value` is initialized to value 2009). The order of invocation of +the constructors is consistent with the order of elaboration required by +Ada and C++. That is, the constructor of the parent type is always called +before the constructor of the derived type. + +Let us now consider a record that has components whose type is imported +from C++. For example: + +.. code-block:: ada + + type Rec1 is limited record + Data1 : Root := Constructor (10); + Value : Natural := 1000; + end record; + + type Rec2 (D : Integer := 20) is limited record + Rec : Rec1; + Data2 : Root := Constructor (D, 30); + end record; + +The initialization of an object of type `Rec2` will call the +non-default C++ constructors specified for the imported components. +For example: + +.. code-block:: ada + + Obj8 : Rec2 (40); + +Using Ada 2005 we can use limited aggregates to initialize an object +invoking C++ constructors that differ from those specified in the type +declarations. For example: + +.. code-block:: ada + + Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16), + others => <>), + others => <>); + +The above declaration uses an Ada 2005 limited aggregate to +initialize `Obj9`, and the C++ constructor that has two integer +arguments is invoked to initialize the `Data1` component instead +of the constructor specified in the declaration of type `Rec1`. In +Ada 2005 the box in the aggregate indicates that unspecified components +are initialized using the expression (if any) available in the component +declaration. That is, in this case discriminant `D` is initialized +to value `20`, `Value` is initialized to value 1000, and the +non-default C++ constructor that handles two integers takes care of +initializing component `Data2` with values `20,30`. + +In Ada 2005 we can use the extended return statement to build the Ada +equivalent to C++ non-default constructors. For example: + +.. code-block:: ada + + function Constructor (V : Integer) return Rec2 is + begin + return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20), + others => <>), + others => <>) do + -- Further actions required for construction of + -- objects of type Rec2 + ... + end record; + end Constructor; + +In this example the extended return statement construct is used to +build in place the returned object whose components are initialized +by means of a limited aggregate. Any further action associated with +the constructor can be placed inside the construct. + +.. _Interfacing_with_C++_at_the_Class_Level: + +Interfacing with C++ at the Class Level +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In this section we demonstrate the GNAT features for interfacing with +C++ by means of an example making use of Ada 2005 abstract interface +types. This example consists of a classification of animals; classes +have been used to model our main classification of animals, and +interfaces provide support for the management of secondary +classifications. We first demonstrate a case in which the types and +constructors are defined on the C++ side and imported from the Ada +side, and latter the reverse case. + +The root of our derivation will be the `Animal` class, with a +single private attribute (the `Age` of the animal), a constructor, +and two public primitives to set and get the value of this attribute. + +.. code-block:: cpp + + class Animal { + public: + virtual void Set_Age (int New_Age); + virtual int Age (); + Animal() {Age_Count = 0;}; + private: + int Age_Count; + }; + +Abstract interface types are defined in C++ by means of classes with pure +virtual functions and no data members. In our example we will use two +interfaces that provide support for the common management of `Carnivore` +and `Domestic` animals: + +.. code-block:: cpp + + class Carnivore { + public: + virtual int Number_Of_Teeth () = 0; + }; + + class Domestic { + public: + virtual void Set_Owner (char* Name) = 0; + }; + +Using these declarations, we can now say that a `Dog` is an animal that is +both Carnivore and Domestic, that is: + +.. code-block:: cpp + + class Dog : Animal, Carnivore, Domestic { + public: + virtual int Number_Of_Teeth (); + virtual void Set_Owner (char* Name); + + Dog(); // Constructor + private: + int Tooth_Count; + char *Owner; + }; + +In the following examples we will assume that the previous declarations are +located in a file named `animals.h`. The following package demonstrates +how to import these C++ declarations from the Ada side: + +.. code-block:: ada + + with Interfaces.C.Strings; use Interfaces.C.Strings; + package Animals is + type Carnivore is limited interface; + pragma Convention (C_Plus_Plus, Carnivore); + function Number_Of_Teeth (X : Carnivore) + return Natural is abstract; + + type Domestic is limited interface; + pragma Convention (C_Plus_Plus, Domestic); + procedure Set_Owner + (X : in out Domestic; + Name : Chars_Ptr) is abstract; + + type Animal is tagged limited record + Age : Natural; + end record; + pragma Import (C_Plus_Plus, Animal); + + procedure Set_Age (X : in out Animal; Age : Integer); + pragma Import (C_Plus_Plus, Set_Age); + + function Age (X : Animal) return Integer; + pragma Import (C_Plus_Plus, Age); + + function New_Animal return Animal; + pragma CPP_Constructor (New_Animal); + pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev"); + + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : Natural; + Owner : String (1 .. 30); + end record; + pragma Import (C_Plus_Plus, Dog); + + function Number_Of_Teeth (A : Dog) return Natural; + pragma Import (C_Plus_Plus, Number_Of_Teeth); + + procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); + pragma Import (C_Plus_Plus, Set_Owner); + + function New_Dog return Dog; + pragma CPP_Constructor (New_Dog); + pragma Import (CPP, New_Dog, "_ZN3DogC2Ev"); + end Animals; + +Thanks to the compatibility between GNAT run-time structures and the C++ ABI, +interfacing with these C++ classes is easy. The only requirement is that all +the primitives and components must be declared exactly in the same order in +the two languages. + +Regarding the abstract interfaces, we must indicate to the GNAT compiler by +means of a `pragma Convention (C_Plus_Plus)`, the convention used to pass +the arguments to the called primitives will be the same as for C++. For the +imported classes we use `pragma Import` with convention `C_Plus_Plus` +to indicate that they have been defined on the C++ side; this is required +because the dispatch table associated with these tagged types will be built +in the C++ side and therefore will not contain the predefined Ada primitives +which Ada would otherwise expect. + +As the reader can see there is no need to indicate the C++ mangled names +associated with each subprogram because it is assumed that all the calls to +these primitives will be dispatching calls. The only exception is the +constructor, which must be registered with the compiler by means of +`pragma CPP_Constructor` and needs to provide its associated C++ +mangled name because the Ada compiler generates direct calls to it. + +With the above packages we can now declare objects of type Dog on the Ada side +and dispatch calls to the corresponding subprograms on the C++ side. We can +also extend the tagged type Dog with further fields and primitives, and +override some of its C++ primitives on the Ada side. For example, here we have +a type derivation defined on the Ada side that inherits all the dispatching +primitives of the ancestor from the C++ side. + +.. code-block:: ada + + with Animals; use Animals; + package Vaccinated_Animals is + type Vaccinated_Dog is new Dog with null record; + function Vaccination_Expired (A : Vaccinated_Dog) return Boolean; + end Vaccinated_Animals; + +It is important to note that, because of the ABI compatibility, the programmer +does not need to add any further information to indicate either the object +layout or the dispatch table entry associated with each dispatching operation. + +Now let us define all the types and constructors on the Ada side and export +them to C++, using the same hierarchy of our previous example: + +.. code-block:: ada + + with Interfaces.C.Strings; + use Interfaces.C.Strings; + package Animals is + type Carnivore is limited interface; + pragma Convention (C_Plus_Plus, Carnivore); + function Number_Of_Teeth (X : Carnivore) + return Natural is abstract; + + type Domestic is limited interface; + pragma Convention (C_Plus_Plus, Domestic); + procedure Set_Owner + (X : in out Domestic; + Name : Chars_Ptr) is abstract; + + type Animal is tagged record + Age : Natural; + end record; + pragma Convention (C_Plus_Plus, Animal); + + procedure Set_Age (X : in out Animal; Age : Integer); + pragma Export (C_Plus_Plus, Set_Age); + + function Age (X : Animal) return Integer; + pragma Export (C_Plus_Plus, Age); + + function New_Animal return Animal'Class; + pragma Export (C_Plus_Plus, New_Animal); + + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : Natural; + Owner : String (1 .. 30); + end record; + pragma Convention (C_Plus_Plus, Dog); + + function Number_Of_Teeth (A : Dog) return Natural; + pragma Export (C_Plus_Plus, Number_Of_Teeth); + + procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); + pragma Export (C_Plus_Plus, Set_Owner); + + function New_Dog return Dog'Class; + pragma Export (C_Plus_Plus, New_Dog); + end Animals; + +Compared with our previous example the only differences are the use of +`pragma Convention` (instead of `pragma Import`), and the use of +`pragma Export` to indicate to the GNAT compiler that the primitives will +be available to C++. Thanks to the ABI compatibility, on the C++ side there is +nothing else to be done; as explained above, the only requirement is that all +the primitives and components are declared in exactly the same order. + +For completeness, let us see a brief C++ main program that uses the +declarations available in `animals.h` (presented in our first example) to +import and use the declarations from the Ada side, properly initializing and +finalizing the Ada run-time system along the way: + +.. code-block:: cpp + + #include "animals.h" + #include + using namespace std; + + void Check_Carnivore (Carnivore *obj) {...} + void Check_Domestic (Domestic *obj) {...} + void Check_Animal (Animal *obj) {...} + void Check_Dog (Dog *obj) {...} + + extern "C" { + void adainit (void); + void adafinal (void); + Dog* new_dog (); + } + + void test () + { + Dog *obj = new_dog(); // Ada constructor + Check_Carnivore (obj); // Check secondary DT + Check_Domestic (obj); // Check secondary DT + Check_Animal (obj); // Check primary DT + Check_Dog (obj); // Check primary DT + } + + int main () + { + adainit (); test(); adafinal (); + return 0; + } + +.. _Generating_Ada_Bindings_for_C_and_C++_headers: + +Generating Ada Bindings for C and C++ headers +--------------------------------------------- + +.. index:: Binding generation (for C and C++ headers) +.. index:: C headers (binding generation) +.. index:: C++ headers (binding generation) + +GNAT includes a binding generator for C and C++ headers which is +intended to do 95% of the tedious work of generating Ada specs from C +or C++ header files. + +Note that this capability is not intended to generate 100% correct Ada specs, +and will is some cases require manual adjustments, although it can often +be used out of the box in practice. + +Some of the known limitations include: + +* only very simple character constant macros are translated into Ada + constants. Function macros (macros with arguments) are partially translated + as comments, to be completed manually if needed. +* some extensions (e.g. vector types) are not supported +* pointers to pointers or complex structures are mapped to System.Address +* identifiers with identical name (except casing) will generate compilation + errors (e.g. `shm_get` vs `SHM_GET`). + +The code generated is using the Ada 2005 syntax, which makes it +easier to interface with other languages than previous versions of Ada. + +.. _Running_the_binding_generator: + +Running the binding generator +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The binding generator is part of the *gcc* compiler and can be +invoked via the *-fdump-ada-spec* switch, which will generate Ada +spec files for the header files specified on the command line, and all +header files needed by these files transitively. For example: + +.. code-block:: sh + + $ g++ -c -fdump-ada-spec -C /usr/include/time.h + $ gcc -c -gnat05 *.ads + +will generate, under GNU/Linux, the following files: :file:`time_h.ads`, +:file:`bits_time_h.ads`, :file:`stddef_h.ads`, :file:`bits_types_h.ads` which +correspond to the files :file:`/usr/include/time.h`, +:file:`/usr/include/bits/time.h`, etc..., and will then compile in Ada 2005 +mode these Ada specs. + +The `-C` switch tells *gcc* to extract comments from headers, +and will attempt to generate corresponding Ada comments. + +If you want to generate a single Ada file and not the transitive closure, you +can use instead the *-fdump-ada-spec-slim* switch. + +You can optionally specify a parent unit, of which all generated units will +be children, using `-fada-spec-parent=``unit`. + +Note that we recommend when possible to use the *g++* driver to +generate bindings, even for most C headers, since this will in general +generate better Ada specs. For generating bindings for C++ headers, it is +mandatory to use the *g++* command, or *gcc -x c++* which +is equivalent in this case. If *g++* cannot work on your C headers +because of incompatibilities between C and C++, then you can fallback to +*gcc* instead. + +For an example of better bindings generated from the C++ front-end, +the name of the parameters (when available) are actually ignored by the C +front-end. Consider the following C header: + +.. code-block:: c + + extern void foo (int variable); + +with the C front-end, `variable` is ignored, and the above is handled as: + +.. code-block:: c + + extern void foo (int); + +generating a generic: + +.. code-block:: ada + + procedure foo (param1 : int); + +with the C++ front-end, the name is available, and we generate: + +.. code-block:: ada + + procedure foo (variable : int); + +In some cases, the generated bindings will be more complete or more meaningful +when defining some macros, which you can do via the *-D* switch. This +is for example the case with :file:`Xlib.h` under GNU/Linux: + +.. code-block:: sh + + $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h + +The above will generate more complete bindings than a straight call without +the *-DXLIB_ILLEGAL_ACCESS* switch. + +In other cases, it is not possible to parse a header file in a stand-alone +manner, because other include files need to be included first. In this +case, the solution is to create a small header file including the needed +`#include` and possible `#define` directives. For example, to +generate Ada bindings for :file:`readline/readline.h`, you need to first +include :file:`stdio.h`, so you can create a file with the following two +lines in e.g. :file:`readline1.h`: + +.. code-block:: cpp + + #include + #include + +and then generate Ada bindings from this file: + +.. code-block:: sh + + $ g++ -c -fdump-ada-spec readline1.h + + +.. _Generating_bindings_for_C++_headers: + +Generating bindings for C++ headers +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +Generating bindings for C++ headers is done using the same options, always +with the *g++* compiler. Note that generating Ada spec from C++ headers is a +much more complex job and support for C++ headers is much more limited that +support for C headers. As a result, you will need to modify the resulting +bindings by hand more extensively when using C++ headers. + +In this mode, C++ classes will be mapped to Ada tagged types, constructors +will be mapped using the `CPP_Constructor` pragma, and when possible, +multiple inheritance of abstract classes will be mapped to Ada interfaces +(see the *Interfacing to C++* section in the :title:`GNAT Reference Manual` +for additional information on interfacing to C++). + +For example, given the following C++ header file: + +.. code-block:: cpp + + class Carnivore { + public: + virtual int Number_Of_Teeth () = 0; + }; + + class Domestic { + public: + virtual void Set_Owner (char* Name) = 0; + }; + + class Animal { + public: + int Age_Count; + virtual void Set_Age (int New_Age); + }; + + class Dog : Animal, Carnivore, Domestic { + public: + int Tooth_Count; + char *Owner; + + virtual int Number_Of_Teeth (); + virtual void Set_Owner (char* Name); + + Dog(); + }; + +The corresponding Ada code is generated: + +.. code-block:: ada + + package Class_Carnivore is + type Carnivore is limited interface; + pragma Import (CPP, Carnivore); + + function Number_Of_Teeth (this : access Carnivore) return int is abstract; + end; + use Class_Carnivore; + + package Class_Domestic is + type Domestic is limited interface; + pragma Import (CPP, Domestic); + + procedure Set_Owner + (this : access Domestic; + Name : Interfaces.C.Strings.chars_ptr) is abstract; + end; + use Class_Domestic; + + package Class_Animal is + type Animal is tagged limited record + Age_Count : aliased int; + end record; + pragma Import (CPP, Animal); + + procedure Set_Age (this : access Animal; New_Age : int); + pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi"); + end; + use Class_Animal; + + package Class_Dog is + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : aliased int; + Owner : Interfaces.C.Strings.chars_ptr; + end record; + pragma Import (CPP, Dog); + + function Number_Of_Teeth (this : access Dog) return int; + pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv"); + + procedure Set_Owner + (this : access Dog; Name : Interfaces.C.Strings.chars_ptr); + pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc"); + + function New_Dog return Dog; + pragma CPP_Constructor (New_Dog); + pragma Import (CPP, New_Dog, "_ZN3DogC1Ev"); + end; + use Class_Dog; + + +.. _Switches_for_Ada_Binding_Generation: + +Switches +^^^^^^^^ + +.. index:: -fdump-ada-spec (gcc) + +:samp:`-fdump-ada-spec` + Generate Ada spec files for the given header files transitively (including + all header files that these headers depend upon). + +.. index:: -fdump-ada-spec-slim (gcc) + +:samp:`-fdump-ada-spec-slim` + Generate Ada spec files for the header files specified on the command line + only. + +.. index:: -fada-spec-parent (gcc) + +:samp:`-fada-spec-parent={unit}` + Specifies that all files generated by *-fdump-ada-spec** are + to be child units of the specified parent unit. + +.. index:: -C (gcc) + +:samp:`-C` + Extract comments from headers and generate Ada comments in the Ada spec files. + + +.. _GNAT_and_Other_Compilation_Models: + +GNAT and Other Compilation Models +================================= + +This section compares the GNAT model with the approaches taken in +other environents, first the C/C++ model and then the mechanism that +has been used in other Ada systems, in particular those traditionally +used for Ada 83. + +.. _Comparison_between_GNAT_and_C/C++_Compilation_Models: + +Comparison between GNAT and C/C++ Compilation Models +---------------------------------------------------- + +The GNAT model of compilation is close to the C and C++ models. You can +think of Ada specs as corresponding to header files in C. As in C, you +don't need to compile specs; they are compiled when they are used. The +Ada |with| is similar in effect to the `#include` of a C +header. + +One notable difference is that, in Ada, you may compile specs separately +to check them for semantic and syntactic accuracy. This is not always +possible with C headers because they are fragments of programs that have +less specific syntactic or semantic rules. + +The other major difference is the requirement for running the binder, +which performs two important functions. First, it checks for +consistency. In C or C++, the only defense against assembling +inconsistent programs lies outside the compiler, in a makefile, for +example. The binder satisfies the Ada requirement that it be impossible +to construct an inconsistent program when the compiler is used in normal +mode. + +.. index:: Elaboration order control + +The other important function of the binder is to deal with elaboration +issues. There are also elaboration issues in C++ that are handled +automatically. This automatic handling has the advantage of being +simpler to use, but the C++ programmer has no control over elaboration. +Where `gnatbind` might complain there was no valid order of +elaboration, a C++ compiler would simply construct a program that +malfunctioned at run time. + +.. _Comparison_between_GNAT_and_Conventional_Ada_Library_Models: + +Comparison between GNAT and Conventional Ada Library Models +----------------------------------------------------------- + +This section is intended for Ada programmers who have +used an Ada compiler implementing the traditional Ada library +model, as described in the Ada Reference Manual. + +.. index:: GNAT library + +In GNAT, there is no 'library' in the normal sense. Instead, the set of +source files themselves acts as the library. Compiling Ada programs does +not generate any centralized information, but rather an object file and +a ALI file, which are of interest only to the binder and linker. +In a traditional system, the compiler reads information not only from +the source file being compiled, but also from the centralized library. +This means that the effect of a compilation depends on what has been +previously compiled. In particular: + +* When a unit is |withed|, the unit seen by the compiler corresponds + to the version of the unit most recently compiled into the library. + +* Inlining is effective only if the necessary body has already been + compiled into the library. + +* Compiling a unit may obsolete other units in the library. + +In GNAT, compiling one unit never affects the compilation of any other +units because the compiler reads only source files. Only changes to source +files can affect the results of a compilation. In particular: + +* When a unit is |withed|, the unit seen by the compiler corresponds + to the source version of the unit that is currently accessible to the + compiler. + + .. index:: Inlining + +* Inlining requires the appropriate source files for the package or + subprogram bodies to be available to the compiler. Inlining is always + effective, independent of the order in which units are compiled. + +* Compiling a unit never affects any other compilations. The editing of + sources may cause previous compilations to be out of date if they + depended on the source file being modified. + +The most important result of these differences is that order of compilation +is never significant in GNAT. There is no situation in which one is +required to do one compilation before another. What shows up as order of +compilation requirements in the traditional Ada library becomes, in +GNAT, simple source dependencies; in other words, there is only a set +of rules saying what source files must be present when a file is +compiled. + + +.. _Using_GNAT_Files_with_External_Tools: + +Using GNAT Files with External Tools +==================================== + +This section explains how files that are produced by GNAT may be +used with tools designed for other languages. + + +.. _Using_Other_Utility_Programs_with_GNAT: + +Using Other Utility Programs with GNAT +-------------------------------------- + +The object files generated by GNAT are in standard system format and in +particular the debugging information uses this format. This means +programs generated by GNAT can be used with existing utilities that +depend on these formats. + +In general, any utility program that works with C will also often work with +Ada programs generated by GNAT. This includes software utilities such as +gprof (a profiling program), gdb (the FSF debugger), and utilities such +as Purify. + + +.. _The_External_Symbol_Naming_Scheme_of_GNAT: + +The External Symbol Naming Scheme of GNAT +----------------------------------------- + +In order to interpret the output from GNAT, when using tools that are +originally intended for use with other languages, it is useful to +understand the conventions used to generate link names from the Ada +entity names. + +All link names are in all lowercase letters. With the exception of library +procedure names, the mechanism used is simply to use the full expanded +Ada name with dots replaced by double underscores. For example, suppose +we have the following package spec: + +.. code-block:: ada + + package QRS is + MN : Integer; + end QRS; + +.. index:: pragma Export + +The variable `MN` has a full expanded Ada name of `QRS.MN`, so +the corresponding link name is `qrs__mn`. +Of course if a `pragma Export` is used this may be overridden: + +.. code-block:: ada + + package Exports is + Var1 : Integer; + pragma Export (Var1, C, External_Name => "var1_name"); + Var2 : Integer; + pragma Export (Var2, C, Link_Name => "var2_link_name"); + end Exports; + +In this case, the link name for `Var1` is whatever link name the +C compiler would assign for the C function `var1_name`. This typically +would be either `var1_name` or `_var1_name`, depending on operating +system conventions, but other possibilities exist. The link name for +`Var2` is `var2_link_name`, and this is not operating system +dependent. + +One exception occurs for library level procedures. A potential ambiguity +arises between the required name `_main` for the C main program, +and the name we would otherwise assign to an Ada library level procedure +called `Main` (which might well not be the main program). + +To avoid this ambiguity, we attach the prefix `_ada_` to such +names. So if we have a library level procedure such as: + +.. code-block:: ada + + procedure Hello (S : String); + +the external name of this procedure will be `_ada_hello`. + diff --git a/gcc/ada/doc/gnat_ugn/tools_supporting_project_files.rst b/gcc/ada/doc/gnat_ugn/tools_supporting_project_files.rst new file mode 100644 index 00000000000..7360acb0b8a --- /dev/null +++ b/gcc/ada/doc/gnat_ugn/tools_supporting_project_files.rst @@ -0,0 +1,745 @@ +.. _Tools_Supporting_Project_Files: + +Tools Supporting Project Files +============================== + +This section describes how project files can be used in conjunction with a number of +GNAT tools. + +.. _gnatmake_and_Project_Files: + +gnatmake and Project Files +-------------------------- + +This section covers several topics related to *gnatmake* and +project files: defining switches for *gnatmake* +and for the tools that it invokes; specifying configuration pragmas; +the use of the `Main` attribute; building and rebuilding library project +files. + +.. _Switches_Related_to_Project_Files: + +Switches Related to Project Files +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +The following switches are used by GNAT tools that support project files: + + + .. index:: -P (any project-aware tool) + +:samp:`-P{project}` + Indicates the name of a project file. This project file will be parsed with + the verbosity indicated by *-vP*x**, + if any, and using the external references indicated + by *-X* switches, if any. + There may zero, one or more spaces between *-P* and `project`. + + There must be only one *-P* switch on the command line. + + Since the Project Manager parses the project file only after all the switches + on the command line are checked, the order of the switches + *-P*, + *-vP*x** + or *-X* is not significant. + + + .. index:: -X (any project-aware tool) + +:samp:`-X{name}={value}` + Indicates that external variable `name` has the value `value`. + The Project Manager will use this value for occurrences of + `external(name)` when parsing the project file. + + If `name` or `value` includes a space, then `name=value` should be + put between quotes. + + :: + + -XOS=NT + -X"user=John Doe" + + Several *-X* switches can be used simultaneously. + If several *-X* switches specify the same + `name`, only the last one is used. + + An external variable specified with a *-X* switch + takes precedence over the value of the same name in the environment. + + + .. index:: -vP (any project-aware tool) + +:samp:`-vP{x}` + Indicates the verbosity of the parsing of GNAT project files. + + *-vP0* means Default; + *-vP1* means Medium; + *-vP2* means High. + + The default is Default: no output for syntactically correct + project files. + If several *-vP*x** switches are present, + only the last one is used. + + + .. index:: -aP (any project-aware tool) + +:samp:`-aP{dir}` + Add directory `dir` at the beginning of the project search path, in order, + after the current working directory. + + + .. index:: -eL (any project-aware tool) + +:samp:`-eL` + Follow all symbolic links when processing project files. + + + .. index:: --subdirs= (gnatmake and gnatclean) + +:samp:`--subdirs={subdir}` + This switch is recognized by *gnatmake* and *gnatclean*. It + indicate that the real directories (except the source directories) are the + subdirectories `subdir` of the directories specified in the project files. + This applies in particular to object directories, library directories and + exec directories. If the subdirectories do not exist, they are created + automatically. + + +.. _Switches_and_Project_Files: + +Switches and Project Files +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +For each of the packages `Builder`, `Compiler`, `Binder`, and +`Linker`, you can specify a `Default_Switches` +attribute, a `Switches` attribute, or both; +as their names imply, these switch-related +attributes affect the switches that are used for each of these GNAT +components when +*gnatmake* is invoked. As will be explained below, these +component-specific switches precede +the switches provided on the *gnatmake* command line. + +The `Default_Switches` attribute is an attribute +indexed by language name (case insensitive) whose value is a string list. +For example: + + .. code-block:: gpr + + package Compiler is + for Default_Switches ("Ada") + use ("-gnaty", + "-v"); + end Compiler; + +The `Switches` attribute is indexed on a file name (which may or may +not be case sensitive, depending +on the operating system) whose value is a string list. For example: + + .. code-block:: gpr + + package Builder is + for Switches ("main1.adb") + use ("-O2"); + for Switches ("main2.adb") + use ("-g"); + end Builder; + +For the `Builder` package, the file names must designate source files +for main subprograms. For the `Binder` and `Linker` packages, the +file names must designate :file:`ALI` or source files for main subprograms. +In each case just the file name without an explicit extension is acceptable. + +For each tool used in a program build (*gnatmake*, the compiler, the +binder, and the linker), the corresponding package @dfn{contributes} a set of +switches for each file on which the tool is invoked, based on the +switch-related attributes defined in the package. +In particular, the switches +that each of these packages contributes for a given file `f` comprise: + +* the value of attribute `Switches (`f`)`, + if it is specified in the package for the given file, +* otherwise, the value of `Default_Switches ("Ada")`, + if it is specified in the package. + +If neither of these attributes is defined in the package, then the package does +not contribute any switches for the given file. + +When *gnatmake* is invoked on a file, the switches comprise +two sets, in the following order: those contributed for the file +by the `Builder` package; +and the switches passed on the command line. + +When *gnatmake* invokes a tool (compiler, binder, linker) on a file, +the switches passed to the tool comprise three sets, +in the following order: + +* the applicable switches contributed for the file + by the `Builder` package in the project file supplied on the command line; + +* those contributed for the file by the package (in the relevant project file -- + see below) corresponding to the tool; and + +* the applicable switches passed on the command line. + +The term *applicable switches* reflects the fact that +*gnatmake* switches may or may not be passed to individual +tools, depending on the individual switch. + +*gnatmake* may invoke the compiler on source files from different +projects. The Project Manager will use the appropriate project file to +determine the `Compiler` package for each source file being compiled. +Likewise for the `Binder` and `Linker` packages. + +As an example, consider the following package in a project file: + + + .. code-block:: gpr + + project Proj1 is + package Compiler is + for Default_Switches ("Ada") + use ("-g"); + for Switches ("a.adb") + use ("-O1"); + for Switches ("b.adb") + use ("-O2", + "-gnaty"); + end Compiler; + end Proj1; + +If *gnatmake* is invoked with this project file, and it needs to +compile, say, the files :file:`a.adb`, :file:`b.adb`, and :file:`c.adb`, then +:file:`a.adb` will be compiled with the switch *-O1*, +:file:`b.adb` with switches *-O2* and *-gnaty*, +and :file:`c.adb` with *-g*. + +The following example illustrates the ordering of the switches +contributed by different packages: + + .. code-block:: gpr + + project Proj2 is + package Builder is + for Switches ("main.adb") + use ("-g", + "-O1", + "-f"); + end Builder; + + package Compiler is + for Switches ("main.adb") + use ("-O2"); + end Compiler; + end Proj2; + +If you issue the command: + + :: + + $ gnatmake -Pproj2 -O0 main + +then the compiler will be invoked on :file:`main.adb` with the following +sequence of switches + + :: + + -g -O1 -O2 -O0 + +with the last *-O* +switch having precedence over the earlier ones; +several other switches +(such as *-c*) are added implicitly. + +The switches *-g* +and *-O1* are contributed by package +`Builder`, *-O2* is contributed +by the package `Compiler` +and *-O0* comes from the command line. + +The *-g* switch will also be passed in the invocation of +*Gnatlink.* + +A final example illustrates switch contributions from packages in different +project files: + + .. code-block:: gpr + + project Proj3 is + for Source_Files use ("pack.ads", "pack.adb"); + package Compiler is + for Default_Switches ("Ada") + use ("-gnata"); + end Compiler; + end Proj3; + + with "Proj3"; + project Proj4 is + for Source_Files use ("foo_main.adb", "bar_main.adb"); + package Builder is + for Switches ("foo_main.adb") + use ("-s", + "-g"); + end Builder; + end Proj4; + + .. code-block:: ada + + -- Ada source file: + with Pack; + procedure Foo_Main is + ... + end Foo_Main; + +If the command is + + :: + + $ gnatmake -PProj4 foo_main.adb -cargs -gnato + +then the switches passed to the compiler for :file:`foo_main.adb` are +*-g* (contributed by the package `Proj4.Builder`) and +*-gnato* (passed on the command line). +When the imported package `Pack` is compiled, the switches used +are *-g* from `Proj4.Builder`, +*-gnata* (contributed from package `Proj3.Compiler`, +and *-gnato* from the command line. + +When using *gnatmake* with project files, some switches or +arguments may be expressed as relative paths. As the working directory where +compilation occurs may change, these relative paths are converted to absolute +paths. For the switches found in a project file, the relative paths +are relative to the project file directory, for the switches on the command +line, they are relative to the directory where *gnatmake* is invoked. +The switches for which this occurs are: +-I, +-A, +-L, +-aO, +-aL, +-aI, as well as all arguments that are not switches (arguments to +switch +-o, object files specified in package `Linker` or after +-largs on the command line). The exception to this rule is the switch +--RTS= for which a relative path argument is never converted. + +.. _Specifying_Configuration_Pragmas: + +Specifying Configuration Pragmas +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When using *gnatmake* with project files, if there exists a file +:file:`gnat.adc` that contains configuration pragmas, this file will be +ignored. + +Configuration pragmas can be defined by means of the following attributes in +project files: `Global_Configuration_Pragmas` in package `Builder` +and `Local_Configuration_Pragmas` in package `Compiler`. + +Both these attributes are single string attributes. Their values is the path +name of a file containing configuration pragmas. If a path name is relative, +then it is relative to the project directory of the project file where the +attribute is defined. + +When compiling a source, the configuration pragmas used are, in order, +those listed in the file designated by attribute +`Global_Configuration_Pragmas` in package `Builder` of the main +project file, if it is specified, and those listed in the file designated by +attribute `Local_Configuration_Pragmas` in package `Compiler` of +the project file of the source, if it exists. + +.. _Project_Files_and_Main_Subprograms: + +Project Files and Main Subprograms +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When using a project file, you can invoke *gnatmake* +with one or several main subprograms, by specifying their source files on the +command line. + + :: + + $ gnatmake -Pprj main1.adb main2.adb main3.adb + +Each of these needs to be a source file of the same project, except +when the switch `-u` is used. + +When `-u` is not used, all the mains need to be sources of the +same project, one of the project in the tree rooted at the project specified +on the command line. The package `Builder` of this common project, the +"main project" is the one that is considered by *gnatmake*. + +When `-u` is used, the specified source files may be in projects +imported directly or indirectly by the project specified on the command line. +Note that if such a source file is not part of the project specified on the +command line, the switches found in package `Builder` of the +project specified on the command line, if any, that are transmitted +to the compiler will still be used, not those found in the project file of +the source file. + +When using a project file, you can also invoke *gnatmake* without +explicitly specifying any main, and the effect depends on whether you have +defined the `Main` attribute. This attribute has a string list value, +where each element in the list is the name of a source file (the file +extension is optional) that contains a unit that can be a main subprogram. + +If the `Main` attribute is defined in a project file as a non-empty +string list and the switch *-u* is not used on the command +line, then invoking *gnatmake* with this project file but without any +main on the command line is equivalent to invoking *gnatmake* with all +the file names in the `Main` attribute on the command line. + +Example: + + .. code-block:: gpr + + project Prj is + for Main use ("main1.adb", "main2.adb", "main3.adb"); + end Prj; + +With this project file, `"gnatmake -Pprj"` +is equivalent to +`"gnatmake -Pprj main1.adb main2.adb main3.adb"`. + +When the project attribute `Main` is not specified, or is specified +as an empty string list, or when the switch *-u* is used on the command +line, then invoking *gnatmake* with no main on the command line will +result in all immediate sources of the project file being checked, and +potentially recompiled. Depending on the presence of the switch *-u*, +sources from other project files on which the immediate sources of the main +project file depend are also checked and potentially recompiled. In other +words, the *-u* switch is applied to all of the immediate sources of the +main project file. + +When no main is specified on the command line and attribute `Main` exists +and includes several mains, or when several mains are specified on the +command line, the default switches in package `Builder` will +be used for all mains, even if there are specific switches +specified for one or several mains. + +But the switches from package `Binder` or `Linker` will be +the specific switches for each main, if they are specified. + +.. _Library_Project_Files: + +Library Project Files +^^^^^^^^^^^^^^^^^^^^^ + +When *gnatmake* is invoked with a main project file that is a library +project file, it is not allowed to specify one or more mains on the command +line. + +When a library project file is specified, switches `-b` and +`-l` have special meanings. + +* `-b` is only allowed for stand-alone libraries. It indicates + to *gnatmake* that *gnatbind* should be invoked for the + library. + +* `-l` may be used for all library projects. It indicates + to *gnatmake* that the binder generated file should be compiled + (in the case of a stand-alone library) and that the library should be built. + + +.. _The_GNAT_Driver_and_Project_Files: + +The GNAT Driver and Project Files +--------------------------------- + +A number of GNAT tools beyond *gnatmake* +can benefit from project files: + +.. only:: PRO or GPL + + * *gnatbind* + * *gnatcheck* + * *gnatclean* + * *gnatelim* + * *gnatfind* + * *gnatlink* + * *gnatls* + * *gnatmetric* + * *gnatpp* + * *gnatstub* + * *gnatxref* + +.. only:: FSF + + * *gnatbind* + * *gnatclean* + * *gnatfind* + * *gnatlink* + * *gnatls* + * *gnatxref* + +However, none of these tools can be invoked +directly with a project file switch (*-P*). +They must be invoked through the *gnat* driver. + +The *gnat* driver is a wrapper that accepts a number of commands and +calls the corresponding tool. It was designed initially for VMS platforms (to +convert VMS qualifiers to Unix-style switches), but it is now available on all +GNAT platforms. + +On non-VMS platforms, the *gnat* driver accepts the following commands +(case insensitive): + +.. only:: PRO or GPL + + * BIND to invoke *gnatbind* + * CHOP to invoke *gnatchop* + * CLEAN to invoke *gnatclean* + * COMP or COMPILE to invoke the compiler + * ELIM to invoke *gnatelim* + * FIND to invoke *gnatfind* + * KR or KRUNCH to invoke *gnatkr* + * LINK to invoke *gnatlink* + * LS or LIST to invoke *gnatls* + * MAKE to invoke *gnatmake* + * METRIC to invoke *gnatmetric* + * NAME to invoke *gnatname* + * PP or PRETTY to invoke *gnatpp* + * PREP or PREPROCESS to invoke *gnatprep* + * STUB to invoke *gnatstub* + * XREF to invoke *gnatxref* + +.. only:: FSF + + * BIND to invoke *gnatbind* + * CHOP to invoke *gnatchop* + * CLEAN to invoke *gnatclean* + * COMP or COMPILE to invoke the compiler + * FIND to invoke *gnatfind* + * KR or KRUNCH to invoke *gnatkr* + * LINK to invoke *gnatlink* + * LS or LIST to invoke *gnatls* + * MAKE to invoke *gnatmake* + * NAME to invoke *gnatname* + * PREP or PREPROCESS to invoke *gnatprep* + * XREF to invoke *gnatxref* + +Note that the command +*gnatmake -c -f -u* is used to invoke the compiler. + +On non-VMS platforms, between *gnat* and the command, two +special switches may be used: + +* *-v* to display the invocation of the tool. +* *-dn* to prevent the *gnat* driver from removing + the temporary files it has created. These temporary files are + configuration files and temporary file list files. + +The command may be followed by switches and arguments for the invoked +tool. + + :: + + $ gnat bind -C main.ali + $ gnat ls -a main + $ gnat chop foo.txt + +Switches may also be put in text files, one switch per line, and the text +files may be specified with their path name preceded by '@'. + + :: + + $ gnat bind @args.txt main.ali + +In addition, for the following commands the project file related switches +(*-P*, *-X* and *-vPx*) may be used in addition to +the switches of the invoking tool: + +.. only:: PRO or GPL + + * BIND + * COMP or COMPILE + * FIND + * ELIM + * LS or LIST + * LINK + * METRIC + * PP or PRETTY + * STUB + * XREF + +.. only:: FSF + + * BIND + * COMP or COMPILE + * FIND + * LS or LIST + * LINK + * XREF + +.. only:: PRO or GPL + + When GNAT PP or GNAT PRETTY is used with a project file, but with no source + specified on the command line, it invokes *gnatpp* with all + the immediate sources of the specified project file. + + When GNAT METRIC is used with a project file, but with no source + specified on the command line, it invokes *gnatmetric* + with all the immediate sources of the specified project file and with + *-d* with the parameter pointing to the object directory + of the project. + + In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with + a project file, no source is specified on the command line and + switch -U is specified on the command line, then + the underlying tool (gnatpp or + gnatmetric) is invoked for all sources of all projects, + not only for the immediate sources of the main project. + (-U stands for Universal or Union of the project files of the project tree) + +For each of the following commands, there is optionally a corresponding +package in the main project. + +.. only:: PRO or GPL + + * package `Binder` for command BIND (invoking `gnatbind`) + * package `Check` for command CHECK (invoking `gnatcheck`) + * package `Compiler` for command COMP or COMPILE (invoking the compiler) + * package `Cross_Reference` for command XREF (invoking `gnatxref`) + * package `Eliminate` for command ELIM (invoking `gnatelim`) + * package `Finder` for command FIND (invoking `gnatfind`) + * package `Gnatls` for command LS or LIST (invoking `gnatls`) + * package `Gnatstub` for command STUB (invoking `gnatstub`) + * package `Linker` for command LINK (invoking `gnatlink`) + * package `Metrics` for command METRIC (invoking `gnatmetric`) + * package `Pretty_Printer` for command PP or PRETTY (invoking `gnatpp`) + +.. only:: FSF + + * package `Binder` for command BIND (invoking `gnatbind`) + * package `Compiler` for command COMP or COMPILE (invoking the compiler) + * package `Cross_Reference` for command XREF (invoking `gnatxref`) + * package `Finder` for command FIND (invoking `gnatfind`) + * package `Gnatls` for command LS or LIST (invoking `gnatls`) + * package `Linker` for command LINK (invoking `gnatlink`) + +Package `Gnatls` has a unique attribute `Switches`, +a simple variable with a string list value. It contains switches +for the invocation of `gnatls`. + + .. code-block:: gpr + + project Proj1 is + package gnatls is + for Switches + use ("-a", + "-v"); + end gnatls; + end Proj1; + +All other packages have two attribute `Switches` and +`Default_Switches`. + +`Switches` is an indexed attribute, indexed by the +source file name, that has a string list value: the switches to be +used when the tool corresponding to the package is invoked for the specific +source file. + +`Default_Switches` is an attribute, +indexed by the programming language that has a string list value. +`Default_Switches ("Ada")` contains the +switches for the invocation of the tool corresponding +to the package, except if a specific `Switches` attribute +is specified for the source file. + + .. code-block:: gpr + + project Proj is + + for Source_Dirs use (""); + + package gnatls is + for Switches use + ("-a", + "-v"); + end gnatls; + + package Compiler is + for Default_Switches ("Ada") + use ("-gnatv", + "-gnatwa"); + end Binder; + + package Binder is + for Default_Switches ("Ada") + use ("-C", + "-e"); + end Binder; + + package Linker is + for Default_Switches ("Ada") + use ("-C"); + for Switches ("main.adb") + use ("-C", + "-v", + "-v"); + end Linker; + + package Finder is + for Default_Switches ("Ada") + use ("-a", + "-f"); + end Finder; + + package Cross_Reference is + for Default_Switches ("Ada") + use ("-a", + "-f", + "-d", + "-u"); + end Cross_Reference; + end Proj; + +With the above project file, commands such as + + :: + + $ gnat comp -Pproj main + $ gnat ls -Pproj main + $ gnat xref -Pproj main + $ gnat bind -Pproj main.ali + $ gnat link -Pproj main.ali + +will set up the environment properly and invoke the tool with the switches +found in the package corresponding to the tool: +`Default_Switches ("Ada")` for all tools, +except `Switches ("main.adb")` +for `gnatlink`. + +.. only:: PRO or GPL + + It is also possible to invoke some of the tools, + (`gnatcheck`, + `gnatmetric`, + and `gnatpp`) + on a set of project units thanks to the combination of the switches + *-P*, *-U* and possibly the main unit when one is interested + in its closure. For instance, + + :: + + $ gnat metric -Pproj + + will compute the metrics for all the immediate units of project `proj`. + + :: + + $ gnat metric -Pproj -U + + will compute the metrics for all the units of the closure of projects + rooted at `proj`. + + :: + + $ gnat metric -Pproj -U main_unit + + will compute the metrics for the closure of units rooted at + `main_unit`. This last possibility relies implicitly + on *gnatbind*'s option *-R*. But if the argument files for the + tool invoked by the *gnat* driver are explicitly specified + either directly or through the tool *-files* option, then the tool + is called only for these explicitly specified files. diff --git a/gcc/ada/doc/share/ada_pygments.py b/gcc/ada/doc/share/ada_pygments.py new file mode 100644 index 00000000000..27462a3226d --- /dev/null +++ b/gcc/ada/doc/share/ada_pygments.py @@ -0,0 +1,180 @@ +"""Alternate Ada and Project Files parsers for Sphinx/Rest""" + +import re +from pygments.lexer import RegexLexer, bygroups +from pygments.token import Text, Comment, Operator, Keyword, Name, String, \ + Number, Punctuation + + +def get_lexer_tokens(tag_highlighting=False, project_support=False): + """Return the tokens needed for RegexLexer + + :param tag_highlighting: if True we support tag highlighting. See + AdaLexerWithTags documentation + :type tag_highlighting: bool + :param project_support: if True support additional keywors associated + with project files. + :type project_support: bool + + :return: a dictionary following the structure required by RegexLexer + :rtype: dict + """ + if project_support: + project_pattern = r'project\s+|' + project_pattern2 = r'project|' + else: + project_pattern = r'' + project_pattern2 = r'' + + result = { + 'root': [ + # Comments + (r'--.*$', Comment), + # Character literal + (r"'.'", String.Char), + # Strings + (r'"[^"]*"', String), + # Numeric + # Based literal + (r'[0-9][0-9_]*#[0-9a-f][0-9a-f_]*#(E[\+-]?[0-9][0-9_]*)?', + Number.Integer), + (r'[0-9][0-9_]*#[0-9a-f][0-9a-f_]*' + r'\.[0-9a-f][0-9a-f_]*#(E[\+-]?[0-9][0-9_]*)?', Number.Float), + # Decimal literal + (r'[0-9][0-9_]*\.[0-9][0-9_](E[\+-]?[0-9][0-9_]*)?', Number.Float), + (r'[0-9][0-9_]*(E[\+-]?[0-9][0-9_]*)?', Number.Integer), + # Match use and with statements + # The first part of the pattern is be sure we don't match + # for/use constructs. + (r'(\n\s*|;\s*)(with|use)(\s+[\w\.]+)', + bygroups(Punctuation, Keyword.Reserved, Name.Namespace)), + # Match procedure, package and function declarations + (r'end\s+(if|loop|record)', Keyword), + (r'(package(?:\s+body)?\s+|' + project_pattern + + r'function\s+|end\s+|procedure\s+)([\w\.]+)', + bygroups(Keyword, Name.Function)), + # Ada 2012 standard attributes, GNAT specific ones and + # Spark 2014 ones ('Update and 'Loop_Entry) + # (reversed order to avoid having for + # example Max before Max_Alignment_For_Allocation). + (r'\'(Write|Width|Wide_Width|Wide_Wide_Width|Wide_Wide_Value|' + r'Wide_Wide_Image|Wide_Value|Wide_Image|Word_Size|Wchar_T_Size|' + r'Version|Value_Size|Value|Valid_Scalars|VADS_Size|Valid|Val|' + r'Update|Unrestricted_Access|Universal_Literal_String|' + r'Unconstrained_Array|Unchecked_Access|Unbiased_Rounding|' + r'UET_Address|Truncation|Type_Class|To_Address|Tick|Terminated|' + r'Target_Name|Tag|System_Allocator_Alignment|Succ|Stub_Type|' + r'Stream_Size|Storage_Unit|Storage_Size|Storage_Pool|Small|Size|' + r'Simple_Storage_Pool|Signed_Zeros|Scaling|Scale|' + r'Scalar_Storage_Order|Safe_Last|Safe_Large|Safe_First|' + r'Safe_Emax|Rounding|Round|Result|Remainder|Ref|Read|' + r'Range_Length|Range|Priority|Pred|' + r'Position|Pos|Pool_Address|Passed_By_Reference|Partition_Id|' + r'Overlaps_Storage|Output|Old|Object_Size|Null_Parameter|Modulus|' + r'Model_Small|Model_Mantissa|Model_Epsilon|Model_Emin|Model|Mod|' + r'Min|Mechanism_Code|Maximum_Alignment|' + r'Max_Size_In_Storage_Elements|Max_Priority|' + r'Max_Interrupt_Priority|Max_Alignment_For_Allocation|' + r'Max|Mantissa|Machine_Size|Machine_Rounds|Machine_Rounding|' + r'Machine_Radix|Machine_Overflows|Machine_Mantissa|Machine_Emin|' + r'Machine_Emax|Machine|Loop_Entry|Length|Length|Leading_Part|' + r'Last_Valid|Last_Bit|Last|Large|Invalid_Value|Integer_Value|' + r'Input|Image|Img|Identity|Has_Same_Storage|Has_Discriminants|' + r'Has_Access_Values|Fraction|Fore|Floor|Fixed_Value|First_Valid|' + r'First_Bit|First|External_Tag|Exponent|Epsilon|Enum_Val|' + r'Enum_Rep|Enabled|Emax|Elaborated|Elab_Subp_Body|Elab_Spec|' + r'Elab_Body|Descriptor_Size|Digits|Denorm|Delta|Definite|' + r'Default_Bit_Order|Count|Copy_Sign|Constrained|' + r'Compose|Component_Size|Compiler_Version|Code_Address|Class|' + r'Ceiling|Caller|Callable|Body_Version|Bit_Order|Bit_Position|' + r'Bit|Base|Asm_Output|Asm_Input|Alignment|Aft|Adjacent|' + r'Address_Size|Address|Access|Abort_Signal|AST_Entry)', + Name.Attribute), + # All Ada2012 reserved words + (r'(abort|abstract|abs|accept|access|aliased|all|and|array|at|' + r'begin|body|case|constant|declare|delay|delta|digits|do|' + r'else|elsif|end|entry|exception|exit|for|function|generic|goto|' + r'if|interface|in|is|limited|loop|mod|new|not|null|' + r'of|or|others|out|overriding|' + project_pattern2 + + r'package|pragma|private|procedure|protected|' + r'raise|range|record|rem|renames|requeue|return|reverse|' + r'select|separate|some|subtype|synchronized|' + r'tagged|task|terminate|then|type|until|use|when|while|with|xor' + r')([\s;,])', + bygroups(Keyword.Reserved, Punctuation)), + # Two characters operators + (r'=>|\.\.|\*\*|:=|/=|>=|<=|<<|>>|<>', Operator), + # One character operators + (r'&|\'|\(|\)|\*|\+|-|\.|/|:|<|=|>|\|', Operator), + (r',|;', Punctuation), + # Spaces + (r'\s+', Text), + # Builtin values + (r'False|True', Keyword.Constant), + # Identifiers + (r'[\w\.]+', Name)], } + + # Insert tag highlighting before identifiers + if tag_highlighting: + result['root'].insert(-1, (r'\[[\w ]*\]', Name.Tag)) + + return result + + +class AdaLexer(RegexLexer): + """Alternate Pygments lexer for Ada source code and project files + + The default pygments lexer always fails causing disabling of syntax + highlighting in Sphinx. This lexer is simpler but safer. + + In order to use this lexer in your Sphinx project add the following + code at the end of your conf.py + + .. code-block:: python + + import gnatpython.ada_pygments + + def setup(app): + app.add_lexer('ada', gnatpython.ada_pygments.AdaLexer()) + + """ + name = 'Ada' + aliases = ['ada', 'ada83', 'ada95', 'ada2005', 'ada2012'] + filenames = ['*.adb', '*.ads', '*.ada'] + mimetypes = ['text/x-ada'] + + flags = re.MULTILINE | re.I # Ignore case + + tokens = get_lexer_tokens() + + +class TaggedAdaLexer(AdaLexer): + """Alternate Pygments lexer for Ada source code with tags + + A tag is a string of the form:: + + [MY STRING] + + Only alphanumerical characters and spaces are considered inside the + brackets. + """ + + name = 'TaggedAda' + aliases = ['tagged_ada'] + tokens = get_lexer_tokens(True) + + +class GNATProjectLexer(RegexLexer): + """Pygment lexer for project files + + This is the same as the AdaLexer but with support of ``project`` + keyword. + """ + name = 'GPR' + aliases = ['gpr'] + filenames = ['*.gpr'] + mimetypes = ['text/x-gpr'] + + flags = re.MULTILINE | re.I # Ignore case + + tokens = get_lexer_tokens(project_support=True) diff --git a/gcc/ada/doc/share/conf.py b/gcc/ada/doc/share/conf.py new file mode 100644 index 00000000000..c6c45b08aa8 --- /dev/null +++ b/gcc/ada/doc/share/conf.py @@ -0,0 +1,134 @@ +# -*- coding: utf-8 -*- +# +# GNAT build configuration file + +import sys +import os +import time +import re + +sys.path.append('.') + +import ada_pygments +import latex_elements + +# Some configuration values for the various documentation handled by +# this conf.py + +DOCS = { + 'gnat_rm': { + 'title': u'GNAT Reference Manual'}, + 'gnat_ugn': { + 'title': u'GNAT User\'s Guide for Native Platforms'}} + +# Then retrieve the source directory +root_source_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__))) +gnatvsn_spec = os.path.join(root_source_dir, '..', 'gnatvsn.ads') +basever = os.path.join(root_source_dir, '..', '..', 'BASE-VER') +texi_fsf = True # Set to False when FSF doc is switched to sphinx by default + +with open(gnatvsn_spec, 'rb') as fd: + gnatvsn_content = fd.read() + + +def get_copyright(): + return u'2008-%s, Free Software Foundation' % time.strftime('%Y') + + +def get_gnat_version(): + m = re.search(r'Gnat_Static_Version_String : ' + + r'constant String := "([^\(\)]+)\(.*\)?";', + gnatvsn_content) + if m: + return m.group(1).strip() + else: + if texi_fsf and os.path.exists(basever): + return '' + + try: + with open(basever, 'rb') as fd: + return fd.read() + except: + pass + + print 'cannot find GNAT version in gnatvsn.ads or in ' + basever + sys.exit(1) + + +def get_gnat_build_type(): + m = re.search(r'Build_Type : constant Gnat_Build_Type := (.+);', + gnatvsn_content) + if m: + return {'Gnatpro': 'PRO', + 'FSF': 'FSF', + 'GPL': 'GPL'}[m.group(1).strip()] + else: + print 'cannot compute GNAT build type' + sys.exit(1) + + +# First retrieve the name of the documentation we are building +doc_name = os.environ.get('DOC_NAME', None) +if doc_name is None: + print 'DOC_NAME environment variable should be set' + sys.exit(1) + +if doc_name not in DOCS: + print '%s is not a valid documentation name' % doc_name + sys.exit(1) + + +# Exclude sources that are not part of the current documentation +exclude_patterns = [] +for d in os.listdir(root_source_dir): + if d not in ('share', doc_name, doc_name + '.rst'): + exclude_patterns.append(d) + print 'ignoring %s' % d + +if doc_name == 'gnat_rm': + exclude_patterns.append('share/gnat_project_manager.rst') + print 'ignoring share/gnat_project_manager.rst' + +extensions = [] +templates_path = ['_templates'] +source_suffix = '.rst' +master_doc = doc_name + +# General information about the project. +project = DOCS[doc_name]['title'] + +copyright = get_copyright() + +version = get_gnat_version() +release = get_gnat_version() + +pygments_style = 'sphinx' +tags.add(get_gnat_build_type()) +html_theme = 'sphinxdoc' +if os.path.isfile('adacore_transparent.png'): + html_logo = 'adacore_transparent.png' +if os.path.isfile('favicon.ico'): + html_favicon = 'favicon.ico' + +html_static_path = ['_static'] + +latex_elements = { + 'preamble': latex_elements.TOC_DEPTH + + latex_elements.PAGE_BLANK + + latex_elements.TOC_CMD + + latex_elements.LATEX_HYPHEN + + latex_elements.doc_settings(DOCS[doc_name]['title'], + get_gnat_version()), + 'tableofcontents': latex_elements.TOC} + +latex_documents = [ + (master_doc, '%s.tex' % doc_name, project, u'AdaCore', 'manual')] + +texinfo_documents = [ + (master_doc, doc_name, project, + u'AdaCore', doc_name, doc_name, '')] + + +def setup(app): + app.add_lexer('ada', ada_pygments.AdaLexer()) + app.add_lexer('gpr', ada_pygments.GNATProjectLexer()) diff --git a/gcc/ada/doc/share/gnu_free_documentation_license.rst b/gcc/ada/doc/share/gnu_free_documentation_license.rst new file mode 100644 index 00000000000..c18cf6673c5 --- /dev/null +++ b/gcc/ada/doc/share/gnu_free_documentation_license.rst @@ -0,0 +1,458 @@ +.. _gnu_fdl: + +****************************** +GNU Free Documentation License +****************************** + +Version 1.3, 3 November 2008 + +Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc +http://fsf.org/ + +Everyone is permitted to copy and distribute verbatim copies of this +license document, but changing it is not allowed. + +**Preamble** + +The purpose of this License is to make a manual, textbook, or other +functional and useful document "free" in the sense of freedom: to +assure everyone the effective freedom to copy and redistribute it, +with or without modifying it, either commercially or noncommercially. +Secondarily, this License preserves for the author and publisher a way +to get credit for their work, while not being considered responsible +for modifications made by others. + +This License is a kind of "copyleft", which means that derivative +works of the document must themselves be free in the same sense. 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A +"Massive Multiauthor Collaboration" (or "MMC") contained in the +site means any set of copyrightable works thus published on the MMC +site. + +"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 +license published by Creative Commons Corporation, a not-for-profit +corporation with a principal place of business in San Francisco, +California, as well as future copyleft versions of that license +published by that same organization. + +"Incorporate" means to publish or republish a Document, in whole or +in part, as part of another Document. + +An MMC is "eligible for relicensing" if it is licensed under this +License, and if all works that were first published under this License +somewhere other than this MMC, and subsequently incorporated in whole +or in part into the MMC, (1) had no cover texts or invariant sections, +and (2) were thus incorporated prior to November 1, 2008. + +The operator of an MMC Site may republish an MMC contained in the site +under CC-BY-SA on the same site at any time before August 1, 2009, +provided the MMC is eligible for relicensing. + +**ADDENDUM: How to use this License for your documents** + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and +license notices just after the title page: + + Copyright © YEAR YOUR NAME. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.3 + or any later version published by the Free Software Foundation; + with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. + A copy of the license is included in the section entitled "GNU + Free Documentation License". + + +If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, +replace the "with ... Texts." line with this: + + with the Invariant Sections being LIST THEIR TITLES, with the + Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. + +If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. + +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. diff --git a/gcc/ada/doc/share/latex_elements.py b/gcc/ada/doc/share/latex_elements.py new file mode 100644 index 00000000000..cf8fbe1a949 --- /dev/null +++ b/gcc/ada/doc/share/latex_elements.py @@ -0,0 +1,64 @@ +# define some latex elements to be used for PDF output + +PAGE_BLANK = r''' +\makeatletter +\def\cleartooddpage{%% + \cleardoublepage%% +} +\def\cleardoublepage{%% +\clearpage%% + \if@twoside%% + \ifodd\c@page%% + %% nothing to do + \else%% + \hbox{}%% + \thispagestyle{plain}%% + \vspace*{\fill}%% + \begin{center}%% + \textbf{\em This page is intentionally left blank.}%% + \end{center}%% + \vspace{\fill}%% + \newpage%% + \if@twocolumn%% + \hbox{}%% + \newpage%% + \fi%% + \fi%% + \fi%% +} +\makeatother +''' + +TOC_DEPTH = r''' +\pagenumbering{arabic} +\setcounter{tocdepth}{3} +''' + +TOC_CMD = r''' +\makeatletter +\def\tableofcontents{%% + \pagestyle{plain}%% + \chapter*{\contentsname}%% + \@mkboth{\MakeUppercase{\contentsname}}%% + {\MakeUppercase{\contentsname}}%% + \@starttoc{toc}%% +} +\makeatother +''' + +TOC = r''' +\cleardoublepage +\tableofcontents +\cleardoublepage\pagestyle{plain} +''' + +LATEX_HYPHEN = r''' +\hyphenpenalty=5000 +\tolerance=1000 +''' + + +def doc_settings(full_document_name, version): + return '\n'.join([ + r'\newcommand*{\GNATFullDocumentName}[0]{' + full_document_name + r'}', + r'\newcommand*{\GNATVersion}[0]{' + version + r'}']) diff --git a/gcc/ada/doc/share/sphinx.sty b/gcc/ada/doc/share/sphinx.sty new file mode 100644 index 00000000000..2af577a3b3e --- /dev/null +++ b/gcc/ada/doc/share/sphinx.sty @@ -0,0 +1,570 @@ +% +% sphinx.sty +% +% Adapted from the old python.sty, mostly written by Fred Drake, +% by Georg Brandl. +% + +\NeedsTeXFormat{LaTeX2e}[1995/12/01] +\ProvidesPackage{sphinx}[2010/01/15 LaTeX package (Sphinx markup)] + +\@ifclassloaded{memoir}{}{\RequirePackage{fancyhdr}} + +\RequirePackage{textcomp} +\RequirePackage{fancybox} +\RequirePackage{titlesec} +\RequirePackage{tabulary} +\RequirePackage{amsmath} % for \text +\RequirePackage{makeidx} +\RequirePackage{framed} +\RequirePackage{ifthen} +\RequirePackage{color} +% For highlighted code. +\RequirePackage{fancyvrb} +% For table captions. +\RequirePackage{threeparttable} +% Handle footnotes in tables. +\RequirePackage{footnote} +\makesavenoteenv{tabulary} +% For floating figures in the text. +\RequirePackage{wrapfig} +% Separate paragraphs by space by default. +\RequirePackage{parskip} +\RequirePackage{lastpage} +% Redefine these colors to your liking in the preamble. +\definecolor{TitleColor}{rgb}{0.126,0.263,0.361} +\definecolor{InnerLinkColor}{rgb}{0.208,0.374,0.486} +\definecolor{OuterLinkColor}{rgb}{0.216,0.439,0.388} + +% Required to preserve indentation settings in minipage constructs +% (otherwise parskip is set to 0 by default. minipagerestore is called +% each time we enter a minipage environment) +\newcommand{\@minipagerestore}{\setlength{\parskip}{\medskipamount}} + +% Redefine these colors to something not white if you want to have colored +% background and border for code examples. +\definecolor{VerbatimColor}{rgb}{1,1,1} +\definecolor{VerbatimBorderColor}{rgb}{1,1,1} + +% Uncomment these two lines to ignore the paper size and make the page +% size more like a typical published manual. +%\renewcommand{\paperheight}{9in} +%\renewcommand{\paperwidth}{8.5in} % typical squarish manual +%\renewcommand{\paperwidth}{7in} % O'Reilly ``Programmming Python'' + +% use pdfoutput for pTeX and dvipdfmx +\ifx\kanjiskip\undefined\else + \ifx\Gin@driver{dvipdfmx.def}\undefined\else + \newcount\pdfoutput\pdfoutput=0 + \fi +\fi + +% For graphicx, check if we are compiling under latex or pdflatex. +\ifx\pdftexversion\undefined + \usepackage{graphicx} +\else + \usepackage[pdftex]{graphicx} +\fi + +% for PDF output, use colors and maximal compression +\newif\ifsphinxpdfoutput\sphinxpdfoutputfalse +\ifx\pdfoutput\undefined\else\ifcase\pdfoutput + \let\py@NormalColor\relax + \let\py@TitleColor\relax +\else + \sphinxpdfoutputtrue + \input{pdfcolor} + \def\py@NormalColor{\color[rgb]{0.0,0.0,0.0}} + \def\py@TitleColor{\color{TitleColor}} + \pdfcompresslevel=9 +\fi\fi + +% XeLaTeX can do colors, too +\ifx\XeTeXrevision\undefined\else + \def\py@NormalColor{\color[rgb]{0.0,0.0,0.0}} + \def\py@TitleColor{\color{TitleColor}} +\fi + +% Increase printable page size (copied from fullpage.sty) +\topmargin 0pt +\advance \topmargin by -\headheight +\advance \topmargin by -\headsep + +% attempt to work a little better for A4 users +\textheight \paperheight +\advance\textheight by -2in + +\oddsidemargin 0pt +\evensidemargin 0pt +%\evensidemargin -.25in % for ``manual size'' documents +\marginparwidth 0.5in + +\textwidth \paperwidth +\advance\textwidth by -2in + + +% Style parameters and macros used by most documents here +\raggedbottom +\sloppy +\hbadness = 5000 % don't print trivial gripes + +\pagestyle{empty} % start this way + +\renewcommand{\maketitle}{% + \begin{titlepage}% + \let\footnotesize\small + \let\footnoterule\relax + \rule{\textwidth}{1pt}% + \ifsphinxpdfoutput + \begingroup + % These \defs are required to deal with multi-line authors; it + % changes \\ to ', ' (comma-space), making it pass muster for + % generating document info in the PDF file. + \def\\{, } + \def\and{and } + \pdfinfo{ + /Author (\@author) + /Title (\@title) + } + \endgroup + \fi + \begin{flushright}% + \sphinxlogo% + {\rm\Huge \@title \par}% + {\em\LARGE\py@HeaderFamily \py@release\releaseinfo \par} + \vfill + {\LARGE\py@HeaderFamily + \par} + \vfill\vfill + {\large + \@date \par + \vfill + \py@authoraddress \par + }% + \end{flushright}%\par + \@thanks + \end{titlepage}% + \cleardoublepage% + \setcounter{footnote}{0}% + \let\thanks\relax\let\maketitle\relax +} + + +% Use this to set the font family for headers and other decor: +\newcommand{\py@HeaderFamily}{\sffamily\bfseries} + +% Redefine the 'normal' header/footer style when using "fancyhdr" package: +\@ifundefined{fancyhf}{}{ + % Use \pagestyle{normal} as the primary pagestyle for text. + \fancypagestyle{normal}{ + \fancyhf{} + \fancyfoot[LE,RO]{{\py@HeaderFamily\thepage\ of \pageref*{LastPage}}} + \fancyfoot[LO]{{\py@HeaderFamily\nouppercase{\rightmark}}} + \fancyfoot[RE]{{\py@HeaderFamily\nouppercase{\leftmark}}} + \fancyhead[LE,RO]{{\py@HeaderFamily \@title, \py@release}} + \renewcommand{\headrulewidth}{0.4pt} + \renewcommand{\footrulewidth}{0.4pt} + % define chaptermark with \@chappos when \@chappos is available for Japanese + \ifx\@chappos\undefined\else + \def\chaptermark##1{\markboth{\@chapapp\space\thechapter\space\@chappos\space ##1}{}} + \fi + } + % Update the plain style so we get the page number & footer line, + % but not a chapter or section title. This is to keep the first + % page of a chapter and the blank page between chapters `clean.' + \fancypagestyle{plain}{ + \fancyhf{} + \fancyfoot[LE,RO]{{\py@HeaderFamily\thepage\ of \pageref*{LastPage}}} + \fancyfoot[LO,RE]{{\py@HeaderFamily \GNATFullDocumentName}} + \fancyhead[LE,RO]{{\py@HeaderFamily \@title\ \GNATVersion}} + \renewcommand{\headrulewidth}{0.0pt} + \renewcommand{\footrulewidth}{0.4pt} + } +} + +% Some custom font markup commands. +% +\newcommand{\strong}[1]{{\textbf{#1}}} +\newcommand{\code}[1]{\texttt{#1}} +\newcommand{\bfcode}[1]{\code{\bfseries#1}} +\newcommand{\email}[1]{\textsf{#1}} + +% Redefine the Verbatim environment to allow border and background colors. +% The original environment is still used for verbatims within tables. +\let\OriginalVerbatim=\Verbatim +\let\endOriginalVerbatim=\endVerbatim + +% Play with vspace to be able to keep the indentation. +\newlength\distancetoright +\def\mycolorbox#1{% + \setlength\distancetoright{\linewidth}% + \advance\distancetoright -\@totalleftmargin % + \fcolorbox{VerbatimBorderColor}{VerbatimColor}{% + \begin{minipage}{\distancetoright}% + #1 + \end{minipage}% + }% +} +\def\FrameCommand{\mycolorbox} + +\renewcommand{\Verbatim}[1][1]{% + % list starts new par, but we don't want it to be set apart vertically + \bgroup\parskip=0pt% + \smallskip% + % The list environement is needed to control perfectly the vertical + % space. + \list{}{% + \setlength\parskip{0pt}% + \setlength\itemsep{0ex}% + \setlength\topsep{0ex}% + \setlength\partopsep{0pt}% + \setlength\leftmargin{0pt}% + }% + \item\MakeFramed {\FrameRestore}% + \small% + \OriginalVerbatim[#1]% +} +\renewcommand{\endVerbatim}{% + \endOriginalVerbatim% + \endMakeFramed% + \endlist% + % close group to restore \parskip + \egroup% +} + + +% \moduleauthor{name}{email} +\newcommand{\moduleauthor}[2]{} + +% \sectionauthor{name}{email} +\newcommand{\sectionauthor}[2]{} + +% Augment the sectioning commands used to get our own font family in place, +% and reset some internal data items: +\titleformat{\section}{\Large\py@HeaderFamily}% + {\py@TitleColor\thesection}{0.5em}{\py@TitleColor}{\py@NormalColor} +\titleformat{\subsection}{\large\py@HeaderFamily}% + {\py@TitleColor\thesubsection}{0.5em}{\py@TitleColor}{\py@NormalColor} +\titleformat{\subsubsection}{\py@HeaderFamily}% + {\py@TitleColor\thesubsubsection}{0.5em}{\py@TitleColor}{\py@NormalColor} +\titleformat{\paragraph}{\small\py@HeaderFamily}% + {\py@TitleColor}{0em}{\py@TitleColor}{\py@NormalColor} + +% {fulllineitems} is the main environment for object descriptions. +% +\newcommand{\py@itemnewline}[1]{% + \@tempdima\linewidth% + \advance\@tempdima \leftmargin\makebox[\@tempdima][l]{#1}% +} + +\newenvironment{fulllineitems}{ + \begin{list}{}{\labelwidth \leftmargin \labelsep 0pt + \rightmargin 0pt \topsep -\parskip \partopsep \parskip + \itemsep -\parsep + \let\makelabel=\py@itemnewline} +}{\end{list}} + +% \optional is used for ``[, arg]``, i.e. desc_optional nodes. +\newcommand{\optional}[1]{% + {\textnormal{\Large[}}{#1}\hspace{0.5mm}{\textnormal{\Large]}}} + +\newlength{\py@argswidth} +\newcommand{\py@sigparams}[2]{% + \parbox[t]{\py@argswidth}{#1\code{)}#2}} +\newcommand{\pysigline}[1]{\item[#1]\nopagebreak} +\newcommand{\pysiglinewithargsret}[3]{% + \settowidth{\py@argswidth}{#1\code{(}}% + \addtolength{\py@argswidth}{-2\py@argswidth}% + \addtolength{\py@argswidth}{\linewidth}% + \item[#1\code{(}\py@sigparams{#2}{#3}]} + +% Production lists +% +\newenvironment{productionlist}{ +% \def\optional##1{{\Large[}##1{\Large]}} + \def\production##1##2{\\\code{##1}&::=&\code{##2}} + \def\productioncont##1{\\& &\code{##1}} + \parindent=2em + \indent + \begin{tabular}{lcl} +}{% + \end{tabular} +} + +% Notices / Admonitions +% +\newlength{\py@noticelength} + +\newcommand{\py@heavybox}{ + \setlength{\fboxrule}{1pt} + \setlength{\fboxsep}{6pt} + \setlength{\py@noticelength}{\linewidth} + \addtolength{\py@noticelength}{-2\fboxsep} + \addtolength{\py@noticelength}{-2\fboxrule} + %\setlength{\shadowsize}{3pt} + \noindent\Sbox + \minipage{\py@noticelength} +} +\newcommand{\py@endheavybox}{ + \endminipage + \endSbox + \fbox{\TheSbox} +} + +\newcommand{\py@lightbox}{{% + \setlength\parskip{0pt}\par + \noindent\rule[0ex]{\linewidth}{0.5pt}% + \par\noindent\vspace{-0.5ex}% + }} +\newcommand{\py@endlightbox}{{% + \setlength{\parskip}{0pt}% + \par\noindent\rule[0.5ex]{\linewidth}{0.5pt}% + \par\vspace{-0.5ex}% + }} + + + +% Some are quite plain: +\newcommand{\py@noticestart@note}{\py@lightbox} +\newcommand{\py@noticeend@note}{\py@endlightbox} +\newcommand{\py@noticestart@hint}{\py@lightbox} +\newcommand{\py@noticeend@hint}{\py@endlightbox} +\newcommand{\py@noticestart@important}{\py@lightbox} +\newcommand{\py@noticeend@important}{\py@endlightbox} +\newcommand{\py@noticestart@tip}{\py@lightbox} +\newcommand{\py@noticeend@tip}{\py@endlightbox} + +% Others gets more visible distinction: +\newcommand{\py@noticestart@warning}{\py@heavybox} +\newcommand{\py@noticeend@warning}{\py@endheavybox} +\newcommand{\py@noticestart@caution}{\py@heavybox} +\newcommand{\py@noticeend@caution}{\py@endheavybox} +\newcommand{\py@noticestart@attention}{\py@heavybox} +\newcommand{\py@noticeend@attention}{\py@endheavybox} +\newcommand{\py@noticestart@danger}{\py@heavybox} +\newcommand{\py@noticeend@danger}{\py@endheavybox} +\newcommand{\py@noticestart@error}{\py@heavybox} +\newcommand{\py@noticeend@error}{\py@endheavybox} + +\newenvironment{notice}[2]{ + \def\py@noticetype{#1} + \csname py@noticestart@#1\endcsname + \strong{#2} +}{\csname py@noticeend@\py@noticetype\endcsname} + +% Allow the release number to be specified independently of the +% \date{}. This allows the date to reflect the document's date and +% release to specify the release that is documented. +% +\newcommand{\py@release}{} +\newcommand{\version}{} +\newcommand{\shortversion}{} +\newcommand{\releaseinfo}{} +\newcommand{\releasename}{GNAT} +\newcommand{\release}[1]{% + \renewcommand{\py@release}{\releasename\space\version}% + \renewcommand{\version}{#1}} +\newcommand{\setshortversion}[1]{% + \renewcommand{\shortversion}{#1}} +\newcommand{\setreleaseinfo}[1]{% + \renewcommand{\releaseinfo}{#1}} + +% Allow specification of the author's address separately from the +% author's name. This can be used to format them differently, which +% is a good thing. +% +\newcommand{\py@authoraddress}{} +\newcommand{\authoraddress}[1]{\renewcommand{\py@authoraddress}{#1}} + +% This sets up the fancy chapter headings that make the documents look +% at least a little better than the usual LaTeX output. +% +\@ifundefined{ChTitleVar}{}{ + \ChNameVar{\raggedleft\normalsize\py@HeaderFamily} + \ChNumVar{\raggedleft \bfseries\Large\py@HeaderFamily} + \ChTitleVar{\raggedleft \textrm{\Huge\py@HeaderFamily}} + % This creates chapter heads without the leading \vspace*{}: + \def\@makechapterhead#1{% + {\parindent \z@ \raggedright \normalfont + \ifnum \c@secnumdepth >\m@ne + \DOCH + \fi + \interlinepenalty\@M + \DOTI{#1} + } + } +} + +% Redefine description environment so that it is usable inside fulllineitems. +% +\renewcommand{\description}{% + \list{}{\labelwidth\z@% + \itemindent-\leftmargin% + \labelsep5pt% + \let\makelabel=\descriptionlabel}} + +% Definition lists; requested by AMK for HOWTO documents. Probably useful +% elsewhere as well, so keep in in the general style support. +% +\newenvironment{definitions}{% + \begin{description}% + \def\term##1{\item[##1]\mbox{}\\*[0mm]} +}{% + \end{description}% +} + +% Tell TeX about pathological hyphenation cases: +\hyphenation{Base-HTTP-Re-quest-Hand-ler} + + +% The following is stuff copied from docutils' latex writer. +% +\newcommand{\optionlistlabel}[1]{\bf #1 \hfill} +\newenvironment{optionlist}[1] +{\begin{list}{} + {\setlength{\labelwidth}{#1} + \setlength{\rightmargin}{1cm} + \setlength{\leftmargin}{\rightmargin} + \addtolength{\leftmargin}{\labelwidth} + \addtolength{\leftmargin}{\labelsep} + \renewcommand{\makelabel}{\optionlistlabel}} +}{\end{list}} + +\newlength{\lineblockindentation} +\setlength{\lineblockindentation}{2.5em} +\newenvironment{lineblock}[1] +{\begin{list}{} + {\setlength{\partopsep}{\parskip} + \addtolength{\partopsep}{\baselineskip} + \topsep0pt\itemsep0.15\baselineskip\parsep0pt + \leftmargin#1} + \raggedright} +{\end{list}} + +% Redefine includgraphics for avoiding images larger than the screen size +% If the size is not specified. +\let\py@Oldincludegraphics\includegraphics + +\newbox\image@box% +\newdimen\image@width% +\renewcommand\includegraphics[2][\@empty]{% + \ifx#1\@empty% + \setbox\image@box=\hbox{\py@Oldincludegraphics{#2}}% + \image@width\wd\image@box% + \ifdim \image@width>\linewidth% + \setbox\image@box=\hbox{\py@Oldincludegraphics[width=\linewidth]{#2}}% + \box\image@box% + \else% + \py@Oldincludegraphics{#2}% + \fi% + \else% + \py@Oldincludegraphics[#1]{#2}% + \fi% +} + +% to make pdf with correct encoded bookmarks in Japanese +% this should precede the hyperref package +\ifx\kanjiskip\undefined\else + \usepackage{atbegshi} + \ifx\ucs\undefined + \ifnum 42146=\euc"A4A2 + \AtBeginShipoutFirst{\special{pdf:tounicode EUC-UCS2}} + \else + \AtBeginShipoutFirst{\special{pdf:tounicode 90ms-RKSJ-UCS2}} + \fi + \else + \AtBeginShipoutFirst{\special{pdf:tounicode UTF8-UCS2}} + \fi +\fi + +% Include hyperref last. +\RequirePackage[colorlinks,breaklinks,destlabel, + linkcolor=InnerLinkColor,filecolor=OuterLinkColor, + menucolor=OuterLinkColor,urlcolor=OuterLinkColor, + citecolor=InnerLinkColor]{hyperref} +% Fix anchor placement for figures with captions. +% (Note: we don't use a package option here; instead, we give an explicit +% \capstart for figures that actually have a caption.) +\RequirePackage{hypcap} + +% From docutils.writers.latex2e +\providecommand{\DUspan}[2]{% + {% group ("span") to limit the scope of styling commands + \@for\node@class@name:=#1\do{% + \ifcsname docutilsrole\node@class@name\endcsname% + \csname docutilsrole\node@class@name\endcsname% + \fi% + }% + {#2}% node content + }% close "span" +} + +\providecommand*{\DUprovidelength}[2]{ + \ifthenelse{\isundefined{#1}}{\newlength{#1}\setlength{#1}{#2}}{} +} + +\DUprovidelength{\DUlineblockindent}{2.5em} +\ifthenelse{\isundefined{\DUlineblock}}{ + \newenvironment{DUlineblock}[1]{% + \list{}{\setlength{\partopsep}{\parskip} + \addtolength{\partopsep}{\baselineskip} + \setlength{\topsep}{0pt} + \setlength{\itemsep}{0.15\baselineskip} + \setlength{\parsep}{0pt} + \setlength{\leftmargin}{#1}} + \raggedright + } + {\endlist} +}{} + + +% From footmisc.sty: allows footnotes in titles +\let\FN@sf@@footnote\footnote +\def\footnote{\ifx\protect\@typeset@protect + \expandafter\FN@sf@@footnote + \else + \expandafter\FN@sf@gobble@opt + \fi +} +\edef\FN@sf@gobble@opt{\noexpand\protect + \expandafter\noexpand\csname FN@sf@gobble@opt \endcsname} +\expandafter\def\csname FN@sf@gobble@opt \endcsname{% + \@ifnextchar[%] + \FN@sf@gobble@twobracket + \@gobble +} +\def\FN@sf@gobble@twobracket[#1]#2{} + +% adjust the margins for footer, +% this works with the jsclasses only (Japanese standard document classes) +\ifx\@jsc@uplatextrue\undefined\else + \hypersetup{setpagesize=false} + \setlength\footskip{2\baselineskip} + \addtolength{\textheight}{-2\baselineskip} +\fi + +% fix the double index and bibliography on the table of contents +% in jsclasses (Japanese standard document classes) +\ifx\@jsc@uplatextrue\undefined\else + \renewcommand{\theindex}{ + \cleardoublepage + \phantomsection + \py@OldTheindex + } + \renewcommand{\thebibliography}[1]{ + \cleardoublepage + \phantomsection + \py@OldThebibliography{1} + } +\fi + +% do not use \@chappos in Appendix in pTeX +\ifx\kanjiskip\undefined\else + \renewcommand{\appendix}{\par + \setcounter{chapter}{0} + \setcounter{section}{0} + \gdef\@chapapp{\appendixname} + \gdef\@chappos{} + \gdef\thechapter{\@Alph\c@chapter} + } +\fi diff --git a/gcc/ada/gnat_rm.texi b/gcc/ada/gnat_rm.texi index b78bc51206f..bcf9b3c69b8 100644 --- a/gcc/ada/gnat_rm.texi +++ b/gcc/ada/gnat_rm.texi @@ -1,751 +1,887 @@ \input texinfo @c -*-texinfo-*- - @c %**start of header - -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo -@c o -@c GNAT DOCUMENTATION o -@c o -@c G N A T _ RM o -@c o -@c GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com). o -@c o -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo - @setfilename gnat_rm.info +@documentencoding UTF-8 +@ifinfo +@*Generated by Sphinx 1.2.2.@* +@end ifinfo +@settitle GNAT Reference Manual +@defindex ge +@paragraphindent 0 +@exampleindent 4 +@finalout +@dircategory +@direntry +* gnat_rm: (gnat_rm.info). gnat_rm +@end direntry -@copying -Copyright @copyright{} 1995-2012, Free Software Foundation, Inc. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, with the Front-Cover Texts being ``GNAT Reference -Manual'', and with no Back-Cover Texts. A copy of the license is -included in the section entitled ``GNU Free Documentation License''. -@end copying - -@set EDITION GNAT +@definfoenclose strong,`,' +@definfoenclose emph,`,' +@c %**end of header -@settitle GNAT Reference Manual +@copying +@quotation +GNAT Reference Manual , February 20, 2015 -@setchapternewpage odd -@syncodeindex fn cp +AdaCore -@include gcc-common.texi +Copyright @copyright{} 2008-2015, Free Software Foundation +@end quotation -@dircategory GNU Ada tools -@direntry -* GNAT Reference Manual: (gnat_rm). Reference Manual for GNU Ada tools. -@end direntry +@end copying @titlepage @title GNAT Reference Manual -@subtitle GNAT, The GNU Ada Development Environment -@versionsubtitle -@author AdaCore -@page -@vskip 0pt plus 1filll - @insertcopying - @end titlepage +@contents + +@c %** start of user preamble + +@c %** end of user preamble @ifnottex -@node Top, About This Guide, (dir), (dir) +@node Top @top GNAT Reference Manual +@insertcopying +@end ifnottex -@noindent -GNAT Reference Manual +@c %**start of body +@anchor{gnat_rm doc}@anchor{0} +@emph{GNAT, The GNU Ada Development Environment} -@noindent -GNAT, The GNU Ada Development Environment@* -GCC version @value{version-GCC}@* -@noindent +@include gcc-common.texi +GCC version @value{version-GCC}@* AdaCore +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with the Front-Cover Texts being "GNAT Reference +Manual", and with no Back-Cover Texts. A copy of the license is +included in the section entitled @ref{1,,GNU Free Documentation License}. + @menu -* About This Guide:: -* Implementation Defined Pragmas:: -* Implementation Defined Aspects:: -* Implementation Defined Attributes:: -* Standard and Implementation Defined Restrictions:: -* Implementation Advice:: -* Implementation Defined Characteristics:: -* Intrinsic Subprograms:: -* Representation Clauses and Pragmas:: -* Standard Library Routines:: -* The Implementation of Standard I/O:: -* The GNAT Library:: -* Interfacing to Other Languages:: -* Specialized Needs Annexes:: -* Implementation of Specific Ada Features:: -* Implementation of Ada 2012 Features:: -* Obsolescent Features:: -* GNU Free Documentation License:: -* Index:Concept Index. +* About This Guide:: +* Implementation Defined Pragmas:: +* Implementation Defined Aspects:: +* Implementation Defined Attributes:: +* Standard and Implementation Defined Restrictions:: +* Implementation Advice:: +* Implementation Defined Characteristics:: +* Intrinsic Subprograms:: +* Representation Clauses and Pragmas:: +* Standard Library Routines:: +* The Implementation of Standard I/O:: +* The GNAT Library:: +* Interfacing to Other Languages:: +* Specialized Needs Annexes:: +* Implementation of Specific Ada Features:: +* Implementation of Ada 2012 Features:: +* Obsolescent Features:: +* Compatibility and Porting Guide:: +* GNU Free Documentation License:: +* Index:: @detailmenu --- The Detailed Node Listing --- About This Guide -* What This Reference Manual Contains:: -* Related Information:: +* What This Reference Manual Contains:: +* Conventions:: +* Related Information:: Implementation Defined Pragmas -* Pragma Abort_Defer:: -* Pragma Abstract_State:: -* Pragma Ada_83:: -* Pragma Ada_95:: -* Pragma Ada_05:: -* Pragma Ada_2005:: -* Pragma Ada_12:: -* Pragma Ada_2012:: -* Pragma Allow_Integer_Address:: -* Pragma Annotate:: -* Pragma Assert:: -* Pragma Assert_And_Cut:: -* Pragma Assertion_Policy:: -* Pragma Assume:: -* Pragma Assume_No_Invalid_Values:: -* Pragma AST_Entry:: -* Pragma Async_Readers:: -* Pragma Async_Writers:: -* Pragma Attribute_Definition:: -* Pragma C_Pass_By_Copy:: -* Pragma Check:: -* Pragma Check_Float_Overflow:: -* Pragma Check_Name:: -* Pragma Check_Policy:: -* Pragma CIL_Constructor:: -* Pragma Comment:: -* Pragma Common_Object:: -* Pragma Compile_Time_Error:: -* Pragma Compile_Time_Warning:: -* Pragma Compiler_Unit:: -* Pragma Compiler_Unit_Warning:: -* Pragma Complete_Representation:: -* Pragma Complex_Representation:: -* Pragma Component_Alignment:: -* Pragma Contract_Cases:: -* Pragma Convention_Identifier:: -* Pragma CPP_Class:: -* Pragma CPP_Constructor:: -* Pragma CPP_Virtual:: -* Pragma CPP_Vtable:: -* Pragma CPU:: -* Pragma Debug:: -* Pragma Debug_Policy:: -* Pragma Default_Scalar_Storage_Order:: -* Pragma Default_Storage_Pool:: -* Pragma Depends:: -* Pragma Detect_Blocking:: -* Pragma Disable_Atomic_Synchronization:: -* Pragma Dispatching_Domain:: -* Pragma Effective_Reads:: -* Pragma Effective_Writes:: -* Pragma Elaboration_Checks:: -* Pragma Eliminate:: -* Pragma Enable_Atomic_Synchronization:: -* Pragma Export_Exception:: -* Pragma Export_Function:: -* Pragma Export_Object:: -* Pragma Export_Procedure:: -* Pragma Export_Value:: -* Pragma Export_Valued_Procedure:: -* Pragma Extend_System:: -* Pragma Extensions_Allowed:: -* Pragma External:: -* Pragma External_Name_Casing:: -* Pragma Fast_Math:: -* Pragma Favor_Top_Level:: -* Pragma Finalize_Storage_Only:: -* Pragma Float_Representation:: -* Pragma Global:: -* Pragma Ident:: -* Pragma Implementation_Defined:: -* Pragma Implemented:: -* Pragma Implicit_Packing:: -* Pragma Import_Exception:: -* Pragma Import_Function:: -* Pragma Import_Object:: -* Pragma Import_Procedure:: -* Pragma Import_Valued_Procedure:: -* Pragma Independent:: -* Pragma Independent_Components:: -* Pragma Initial_Condition:: -* Pragma Initialize_Scalars:: -* Pragma Initializes:: -* Pragma Inline_Always:: -* Pragma Inline_Generic:: -* Pragma Interface:: -* Pragma Interface_Name:: -* Pragma Interrupt_Handler:: -* Pragma Interrupt_State:: -* Pragma Invariant:: -* Pragma Java_Constructor:: -* Pragma Java_Interface:: -* Pragma Keep_Names:: -* Pragma License:: -* Pragma Link_With:: -* Pragma Linker_Alias:: -* Pragma Linker_Constructor:: -* Pragma Linker_Destructor:: -* Pragma Linker_Section:: -* Pragma Lock_Free:: -* Pragma Long_Float:: -* Pragma Loop_Invariant:: -* Pragma Loop_Optimize:: -* Pragma Loop_Variant:: -* Pragma Machine_Attribute:: -* Pragma Main:: -* Pragma Main_Storage:: -* Pragma No_Body:: -* Pragma No_Elaboration_Code_All:: -* Pragma No_Inline:: -* Pragma No_Return:: -* Pragma No_Run_Time:: -* Pragma No_Strict_Aliasing :: -* Pragma No_Tagged_Streams:: -* Pragma Normalize_Scalars:: -* Pragma Obsolescent:: -* Pragma Optimize_Alignment:: -* Pragma Ordered:: -* Pragma Overflow_Mode:: -* Pragma Overriding_Renamings:: -* Pragma Partition_Elaboration_Policy:: -* Pragma Part_Of:: -* Pragma Passive:: -* Pragma Persistent_BSS:: -* Pragma Polling:: -* Pragma Post:: -* Pragma Postcondition:: -* Pragma Post_Class:: -* Pragma Pre:: -* Pragma Precondition:: -* Pragma Predicate:: -* Pragma Preelaborable_Initialization:: -* Pragma Prefix_Exception_Messages:: -* Pragma Pre_Class:: -* Pragma Priority_Specific_Dispatching:: -* Pragma Profile:: -* Pragma Profile_Warnings:: -* Pragma Propagate_Exceptions:: -* Pragma Provide_Shift_Operators:: -* Pragma Psect_Object:: -* Pragma Pure_Function:: -* Pragma Rational:: -* Pragma Ravenscar:: -* Pragma Refined_Depends:: -* Pragma Refined_Global:: -* Pragma Refined_Post:: -* Pragma Refined_State:: -* Pragma Relative_Deadline:: -* Pragma Remote_Access_Type:: -* Pragma Restricted_Run_Time:: -* Pragma Restriction_Warnings:: -* Pragma Reviewable:: -* Pragma Share_Generic:: -* Pragma Shared:: -* Pragma Short_Circuit_And_Or:: -* Pragma Short_Descriptors:: -* Pragma Simple_Storage_Pool_Type:: -* Pragma Source_File_Name:: -* Pragma Source_File_Name_Project:: -* Pragma Source_Reference:: -* Pragma SPARK_Mode:: -* Pragma Static_Elaboration_Desired:: -* Pragma Stream_Convert:: -* Pragma Style_Checks:: -* Pragma Subtitle:: -* Pragma Suppress:: -* Pragma Suppress_All:: -* Pragma Suppress_Debug_Info:: -* Pragma Suppress_Exception_Locations:: -* Pragma Suppress_Initialization:: -* Pragma Task_Name:: -* Pragma Task_Storage:: -* Pragma Test_Case:: -* Pragma Thread_Local_Storage:: -* Pragma Time_Slice:: -* Pragma Title:: -* Pragma Type_Invariant:: -* Pragma Type_Invariant_Class:: -* Pragma Unchecked_Union:: -* Pragma Unevaluated_Use_Of_Old:: -* Pragma Unimplemented_Unit:: -* Pragma Universal_Aliasing :: -* Pragma Universal_Data:: -* Pragma Unmodified:: -* Pragma Unreferenced:: -* Pragma Unreferenced_Objects:: -* Pragma Unreserve_All_Interrupts:: -* Pragma Unsuppress:: -* Pragma Use_VADS_Size:: -* Pragma Validity_Checks:: -* Pragma Volatile:: -* Pragma Warning_As_Error:: -* Pragma Warnings:: -* Pragma Weak_External:: -* Pragma Wide_Character_Encoding:: +* Pragma Abort_Defer:: +* Pragma Abstract_State:: +* Pragma Ada_83:: +* Pragma Ada_95:: +* Pragma Ada_05:: +* Pragma Ada_2005:: +* Pragma Ada_12:: +* Pragma Ada_2012:: +* Pragma Allow_Integer_Address:: +* Pragma Annotate:: +* Pragma Assert:: +* Pragma Assert_And_Cut:: +* Pragma Assertion_Policy:: +* Pragma Assume:: +* Pragma Assume_No_Invalid_Values:: +* Pragma Async_Readers:: +* Pragma Async_Writers:: +* Pragma Attribute_Definition:: +* Pragma C_Pass_By_Copy:: +* Pragma Check:: +* Pragma Check_Float_Overflow:: +* Pragma Check_Name:: +* Pragma Check_Policy:: +* Pragma CIL_Constructor:: +* Pragma Comment:: +* Pragma Common_Object:: +* Pragma Compile_Time_Error:: +* Pragma Compile_Time_Warning:: +* Pragma Compiler_Unit:: +* Pragma Compiler_Unit_Warning:: +* Pragma Complete_Representation:: +* Pragma Complex_Representation:: +* Pragma Component_Alignment:: +* Pragma Contract_Cases:: +* Pragma Convention_Identifier:: +* Pragma CPP_Class:: +* Pragma CPP_Constructor:: +* Pragma CPP_Virtual:: +* Pragma CPP_Vtable:: +* Pragma CPU:: +* Pragma Debug:: +* Pragma Debug_Policy:: +* Pragma Default_Scalar_Storage_Order:: +* Pragma Default_Storage_Pool:: +* Pragma Depends:: +* Pragma Detect_Blocking:: +* Pragma Disable_Atomic_Synchronization:: +* Pragma Dispatching_Domain:: +* Pragma Effective_Reads:: +* Pragma Effective_Writes:: +* Pragma Elaboration_Checks:: +* Pragma Eliminate:: +* Pragma Enable_Atomic_Synchronization:: +* Pragma Export_Function:: +* Pragma Export_Object:: +* Pragma Export_Procedure:: +* Pragma Export_Value:: +* Pragma Export_Valued_Procedure:: +* Pragma Extend_System:: +* Pragma Extensions_Allowed:: +* Pragma External:: +* Pragma External_Name_Casing:: +* Pragma Fast_Math:: +* Pragma Favor_Top_Level:: +* Pragma Finalize_Storage_Only:: +* Pragma Float_Representation:: +* Pragma Global:: +* Pragma Ident:: +* Pragma Implementation_Defined:: +* Pragma Implemented:: +* Pragma Implicit_Packing:: +* Pragma Import_Function:: +* Pragma Import_Object:: +* Pragma Import_Procedure:: +* Pragma Import_Valued_Procedure:: +* Pragma Independent:: +* Pragma Independent_Components:: +* Pragma Initial_Condition:: +* Pragma Initialize_Scalars:: +* Pragma Initializes:: +* Pragma Inline_Always:: +* Pragma Inline_Generic:: +* Pragma Interface:: +* Pragma Interface_Name:: +* Pragma Interrupt_Handler:: +* Pragma Interrupt_State:: +* Pragma Invariant:: +* Pragma Java_Constructor:: +* Pragma Java_Interface:: +* Pragma Keep_Names:: +* Pragma License:: +* Pragma Link_With:: +* Pragma Linker_Alias:: +* Pragma Linker_Constructor:: +* Pragma Linker_Destructor:: +* Pragma Linker_Section:: +* Pragma Lock_Free:: +* Pragma Loop_Invariant:: +* Pragma Loop_Optimize:: +* Pragma Loop_Variant:: +* Pragma Machine_Attribute:: +* Pragma Main:: +* Pragma Main_Storage:: +* Pragma No_Body:: +* Pragma No_Elaboration_Code_All:: +* Pragma No_Inline:: +* Pragma No_Return:: +* Pragma No_Run_Time:: +* Pragma No_Strict_Aliasing:: +* Pragma No_Tagged_Streams:: +* Pragma Normalize_Scalars:: +* Pragma Obsolescent:: +* Pragma Optimize_Alignment:: +* Pragma Ordered:: +* Pragma Overflow_Mode:: +* Pragma Overriding_Renamings:: +* Pragma Partition_Elaboration_Policy:: +* Pragma Part_Of:: +* Pragma Passive:: +* Pragma Persistent_BSS:: +* Pragma Polling:: +* Pragma Post:: +* Pragma Postcondition:: +* Pragma Post_Class:: +* Pragma Pre:: +* Pragma Precondition:: +* Pragma Predicate:: +* Pragma Preelaborable_Initialization:: +* Pragma Prefix_Exception_Messages:: +* Pragma Pre_Class:: +* Pragma Priority_Specific_Dispatching:: +* Pragma Profile:: +* Pragma Profile_Warnings:: +* Pragma Propagate_Exceptions:: +* Pragma Provide_Shift_Operators:: +* Pragma Psect_Object:: +* Pragma Pure_Function:: +* Pragma Rational:: +* Pragma Ravenscar:: +* Pragma Refined_Depends:: +* Pragma Refined_Global:: +* Pragma Refined_Post:: +* Pragma Refined_State:: +* Pragma Relative_Deadline:: +* Pragma Remote_Access_Type:: +* Pragma Restricted_Run_Time:: +* Pragma Restriction_Warnings:: +* Pragma Reviewable:: +* Pragma Share_Generic:: +* Pragma Shared:: +* Pragma Short_Circuit_And_Or:: +* Pragma Short_Descriptors:: +* Pragma Simple_Storage_Pool_Type:: +* Pragma Source_File_Name:: +* Pragma Source_File_Name_Project:: +* Pragma Source_Reference:: +* Pragma SPARK_Mode:: +* Pragma Static_Elaboration_Desired:: +* Pragma Stream_Convert:: +* Pragma Style_Checks:: +* Pragma Subtitle:: +* Pragma Suppress:: +* Pragma Suppress_All:: +* Pragma Suppress_Debug_Info:: +* Pragma Suppress_Exception_Locations:: +* Pragma Suppress_Initialization:: +* Pragma Task_Name:: +* Pragma Task_Storage:: +* Pragma Test_Case:: +* Pragma Thread_Local_Storage:: +* Pragma Time_Slice:: +* Pragma Title:: +* Pragma Type_Invariant:: +* Pragma Type_Invariant_Class:: +* Pragma Unchecked_Union:: +* Pragma Unevaluated_Use_Of_Old:: +* Pragma Unimplemented_Unit:: +* Pragma Universal_Aliasing:: +* Pragma Universal_Data:: +* Pragma Unmodified:: +* Pragma Unreferenced:: +* Pragma Unreferenced_Objects:: +* Pragma Unreserve_All_Interrupts:: +* Pragma Unsuppress:: +* Pragma Use_VADS_Size:: +* Pragma Validity_Checks:: +* Pragma Volatile:: +* Pragma Warning_As_Error:: +* Pragma Warnings:: +* Pragma Weak_External:: +* Pragma Wide_Character_Encoding:: Implementation Defined Aspects -* Aspect Abstract_State:: -* Aspect Annotate:: -* Aspect Async_Readers:: -* Aspect Async_Writers:: -* Aspect Contract_Cases:: -* Aspect Depends:: -* Aspect Dimension:: -* Aspect Dimension_System:: -* Aspect Effective_Reads:: -* Aspect Effective_Writes:: -* Aspect Favor_Top_Level:: -* Aspect Global:: -* Aspect Initial_Condition:: -* Aspect Initializes:: -* Aspect Inline_Always:: -* Aspect Invariant:: -* Aspect Invariant'Class:: -* Aspect Iterable:: -* Aspect Linker_Section:: -* Aspect No_Elaboration_Code_All:: -* Aspect No_Tagged_Streams:: -* Aspect Object_Size:: -* Aspect Obsolescent:: -* Aspect Part_Of:: -* Aspect Persistent_BSS:: -* Aspect Predicate:: -* Aspect Pure_Function:: -* Aspect Refined_Depends:: -* Aspect Refined_Global:: -* Aspect Refined_Post:: -* Aspect Refined_State:: -* Aspect Remote_Access_Type:: -* Aspect Scalar_Storage_Order:: -* Aspect Shared:: -* Aspect Simple_Storage_Pool:: -* Aspect Simple_Storage_Pool_Type:: -* Aspect SPARK_Mode:: -* Aspect Suppress_Debug_Info:: -* Aspect Suppress_Initialization:: -* Aspect Test_Case:: -* Aspect Thread_Local_Storage:: -* Aspect Universal_Aliasing:: -* Aspect Universal_Data:: -* Aspect Unmodified:: -* Aspect Unreferenced:: -* Aspect Unreferenced_Objects:: -* Aspect Value_Size:: -* Aspect Warnings:: +* Aspect Abstract_State:: +* Annotate:: +* Aspect Async_Readers:: +* Aspect Async_Writers:: +* Aspect Contract_Cases:: +* Aspect Depends:: +* Aspect Dimension:: +* Aspect Dimension_System:: +* Aspect Effective_Reads:: +* Aspect Effective_Writes:: +* Aspect Favor_Top_Level:: +* Aspect Global:: +* Aspect Initial_Condition:: +* Aspect Initializes:: +* Aspect Inline_Always:: +* Aspect Invariant:: +* Aspect Invariant'Class:: +* Aspect Iterable:: +* Aspect Linker_Section:: +* Aspect Lock_Free:: +* Aspect No_Elaboration_Code_All:: +* Aspect No_Tagged_Streams:: +* Aspect Object_Size:: +* Aspect Obsolescent:: +* Aspect Part_Of:: +* Aspect Persistent_BSS:: +* Aspect Predicate:: +* Aspect Pure_Function:: +* Aspect Refined_Depends:: +* Aspect Refined_Global:: +* Aspect Refined_Post:: +* Aspect Refined_State:: +* Aspect Remote_Access_Type:: +* Aspect Scalar_Storage_Order:: +* Aspect Shared:: +* Aspect Simple_Storage_Pool:: +* Aspect Simple_Storage_Pool_Type:: +* Aspect SPARK_Mode:: +* Aspect Suppress_Debug_Info:: +* Aspect Suppress_Initialization:: +* Aspect Test_Case:: +* Aspect Thread_Local_Storage:: +* Aspect Universal_Aliasing:: +* Aspect Universal_Data:: +* Aspect Unmodified:: +* Aspect Unreferenced:: +* Aspect Unreferenced_Objects:: +* Aspect Value_Size:: +* Aspect Warnings:: Implementation Defined Attributes -* Attribute Abort_Signal:: -* Attribute Address_Size:: -* Attribute Asm_Input:: -* Attribute Asm_Output:: -* Attribute AST_Entry:: -* Attribute Atomic_Always_Lock_Free:: -* Attribute Bit:: -* Attribute Bit_Position:: -* Attribute Code_Address:: -* Attribute Compiler_Version:: -* Attribute Constrained:: -* Attribute Default_Bit_Order:: -* Attribute Default_Scalar_Storage_Order:: -* Attribute Descriptor_Size:: -* Attribute Elaborated:: -* Attribute Elab_Body:: -* Attribute Elab_Spec:: -* Attribute Elab_Subp_Body:: -* Attribute Emax:: -* Attribute Enabled:: -* Attribute Enum_Rep:: -* Attribute Enum_Val:: -* Attribute Epsilon:: -* Attribute Fast_Math:: -* Attribute Fixed_Value:: -* Attribute From_Any:: -* Attribute Has_Access_Values:: -* Attribute Has_Discriminants:: -* Attribute Img:: -* Attribute Integer_Value:: -* Attribute Invalid_Value:: -* Attribute Iterable:: -* Attribute Large:: -* Attribute Library_Level:: -* Attribute Lock_Free:: -* Attribute Loop_Entry:: -* Attribute Machine_Size:: -* Attribute Mantissa:: -* Attribute Maximum_Alignment:: -* Attribute Mechanism_Code:: -* Attribute Null_Parameter:: -* Attribute Object_Size:: -* Attribute Old:: -* Attribute Passed_By_Reference:: -* Attribute Pool_Address:: -* Attribute Range_Length:: -* Attribute Ref:: -* Attribute Restriction_Set:: -* Attribute Result:: -* Attribute Safe_Emax:: -* Attribute Safe_Large:: -* Attribute Safe_Small:: -* Attribute Scalar_Storage_Order:: -* Attribute Simple_Storage_Pool:: -* Attribute Small:: -* Attribute Storage_Unit:: -* Attribute Stub_Type:: -* Attribute System_Allocator_Alignment:: -* Attribute Target_Name:: -* Attribute To_Address:: -* Attribute To_Any:: -* Attribute Type_Class:: -* Attribute Type_Key:: -* Attribute TypeCode:: -* Attribute UET_Address:: -* Attribute Unconstrained_Array:: -* Attribute Universal_Literal_String:: -* Attribute Unrestricted_Access:: -* Attribute Update:: -* Attribute VADS_Size:: -* Attribute Valid_Scalars:: -* Attribute Value_Size:: -* Attribute Wchar_T_Size:: -* Attribute Word_Size:: +* Attribute Abort_Signal:: +* Attribute Address_Size:: +* Attribute Asm_Input:: +* Attribute Asm_Output:: +* Attribute Atomic_Always_Lock_Free:: +* Attribute Bit:: +* Attribute Bit_Position:: +* Attribute Code_Address:: +* Attribute Compiler_Version:: +* Attribute Constrained:: +* Attribute Default_Bit_Order:: +* Attribute Default_Scalar_Storage_Order:: +* Attribute Descriptor_Size:: +* Attribute Elaborated:: +* Attribute Elab_Body:: +* Attribute Elab_Spec:: +* Attribute Elab_Subp_Body:: +* Attribute Emax:: +* Attribute Enabled:: +* Attribute Enum_Rep:: +* Attribute Enum_Val:: +* Attribute Epsilon:: +* Attribute Fast_Math:: +* Attribute Fixed_Value:: +* Attribute From_Any:: +* Attribute Has_Access_Values:: +* Attribute Has_Discriminants:: +* Attribute Img:: +* Attribute Integer_Value:: +* Attribute Invalid_Value:: +* Attribute Iterable:: +* Attribute Large:: +* Attribute Library_Level:: +* Attribute Lock_Free:: +* Attribute Loop_Entry:: +* Attribute Machine_Size:: +* Attribute Mantissa:: +* Attribute Maximum_Alignment:: +* Attribute Mechanism_Code:: +* Attribute Null_Parameter:: +* Attribute Object_Size:: +* Attribute Old:: +* Attribute Passed_By_Reference:: +* Attribute Pool_Address:: +* Attribute Range_Length:: +* Attribute Ref:: +* Attribute Restriction_Set:: +* Attribute Result:: +* Attribute Safe_Emax:: +* Attribute Safe_Large:: +* Attribute Safe_Small:: +* Attribute Scalar_Storage_Order:: +* Attribute Simple_Storage_Pool:: +* Attribute Small:: +* Attribute Storage_Unit:: +* Attribute Stub_Type:: +* Attribute System_Allocator_Alignment:: +* Attribute Target_Name:: +* Attribute To_Address:: +* Attribute To_Any:: +* Attribute Type_Class:: +* Attribute Type_Key:: +* Attribute TypeCode:: +* Attribute UET_Address:: +* Attribute Unconstrained_Array:: +* Attribute Universal_Literal_String:: +* Attribute Unrestricted_Access:: +* Attribute Update:: +* Attribute Valid_Scalars:: +* Attribute VADS_Size:: +* Attribute Value_Size:: +* Attribute Wchar_T_Size:: +* Attribute Word_Size:: Standard and Implementation Defined Restrictions -* Partition-Wide Restrictions:: -* Program Unit Level Restrictions:: +* Partition-Wide Restrictions:: +* Program Unit Level Restrictions:: Partition-Wide Restrictions -* Immediate_Reclamation:: -* Max_Asynchronous_Select_Nesting:: -* Max_Entry_Queue_Length:: -* Max_Protected_Entries:: -* Max_Select_Alternatives:: -* Max_Storage_At_Blocking:: -* Max_Task_Entries:: -* Max_Tasks:: -* No_Abort_Statements:: -* No_Access_Parameter_Allocators:: -* No_Access_Subprograms:: -* No_Allocators:: -* No_Anonymous_Allocators:: -* No_Calendar:: -* No_Coextensions:: -* No_Default_Initialization:: -* No_Delay:: -* No_Dependence:: -* No_Direct_Boolean_Operators:: -* No_Dispatch:: -* No_Dispatching_Calls:: -* No_Dynamic_Attachment:: -* No_Dynamic_Priorities:: -* No_Entry_Calls_In_Elaboration_Code:: -* No_Enumeration_Maps:: -* No_Exception_Handlers:: -* No_Exception_Propagation:: -* No_Exception_Registration:: -* No_Exceptions:: -* No_Finalization:: -* No_Fixed_Point:: -* No_Floating_Point:: -* No_Implicit_Conditionals:: -* No_Implicit_Dynamic_Code:: -* No_Implicit_Heap_Allocations:: -* No_Implicit_Loops:: -* No_Initialize_Scalars:: -* No_IO:: -* No_Local_Allocators:: -* No_Local_Protected_Objects:: -* No_Local_Timing_Events:: -* No_Long_Long_Integers:: -* No_Multiple_Elaboration:: -* No_Nested_Finalization:: -* No_Protected_Type_Allocators:: -* No_Protected_Types:: -* No_Recursion:: -* No_Reentrancy:: -* No_Relative_Delay:: -* No_Requeue_Statements:: -* No_Secondary_Stack:: -* No_Select_Statements:: -* No_Specific_Termination_Handlers:: -* No_Specification_of_Aspect:: -* No_Standard_Allocators_After_Elaboration:: -* No_Standard_Storage_Pools:: -* No_Stream_Optimizations:: -* No_Streams:: -* No_Task_Allocators:: -* No_Task_Attributes_Package:: -* No_Task_Hierarchy:: -* No_Task_Termination:: -* No_Tasking:: -* No_Terminate_Alternatives:: -* No_Unchecked_Access:: -* Simple_Barriers:: -* Static_Priorities:: -* Static_Storage_Size:: +* Immediate_Reclamation:: +* Max_Asynchronous_Select_Nesting:: +* Max_Entry_Queue_Length:: +* Max_Protected_Entries:: +* Max_Select_Alternatives:: +* Max_Storage_At_Blocking:: +* Max_Task_Entries:: +* Max_Tasks:: +* No_Abort_Statements:: +* No_Access_Parameter_Allocators:: +* No_Access_Subprograms:: +* No_Allocators:: +* No_Anonymous_Allocators:: +* No_Calendar:: +* No_Coextensions:: +* No_Default_Initialization:: +* No_Delay:: +* No_Dependence:: +* No_Direct_Boolean_Operators:: +* No_Dispatch:: +* No_Dispatching_Calls:: +* No_Dynamic_Attachment:: +* No_Dynamic_Priorities:: +* No_Entry_Calls_In_Elaboration_Code:: +* No_Enumeration_Maps:: +* No_Exception_Handlers:: +* No_Exception_Propagation:: +* No_Exception_Registration:: +* No_Exceptions:: +* No_Finalization:: +* No_Fixed_Point:: +* No_Floating_Point:: +* No_Implicit_Conditionals:: +* No_Implicit_Dynamic_Code:: +* No_Implicit_Heap_Allocations:: +* No_Implicit_Loops:: +* No_Initialize_Scalars:: +* No_IO:: +* No_Local_Allocators:: +* No_Local_Protected_Objects:: +* No_Local_Timing_Events:: +* No_Long_Long_Integers:: +* No_Multiple_Elaboration:: +* No_Nested_Finalization:: +* No_Protected_Type_Allocators:: +* No_Protected_Types:: +* No_Recursion:: +* No_Reentrancy:: +* No_Relative_Delay:: +* No_Requeue_Statements:: +* No_Secondary_Stack:: +* No_Select_Statements:: +* No_Specific_Termination_Handlers:: +* No_Specification_of_Aspect:: +* No_Standard_Allocators_After_Elaboration:: +* No_Standard_Storage_Pools:: +* No_Stream_Optimizations:: +* No_Streams:: +* No_Task_Allocators:: +* No_Task_Attributes_Package:: +* No_Task_Hierarchy:: +* No_Task_Termination:: +* No_Tasking:: +* No_Terminate_Alternatives:: +* No_Unchecked_Access:: +* No_Use_Of_Entity:: +* Simple_Barriers:: +* Static_Priorities:: +* Static_Storage_Size:: Program Unit Level Restrictions -* No_Elaboration_Code:: -* No_Entry_Queue:: -* No_Implementation_Aspect_Specifications:: -* No_Implementation_Attributes:: -* No_Implementation_Identifiers:: -* No_Implementation_Pragmas:: -* No_Implementation_Restrictions:: -* No_Implementation_Units:: -* No_Implicit_Aliasing:: -* No_Obsolescent_Features:: -* No_Wide_Characters:: -* SPARK_05:: +* No_Elaboration_Code:: +* No_Entry_Queue:: +* No_Implementation_Aspect_Specifications:: +* No_Implementation_Attributes:: +* No_Implementation_Identifiers:: +* No_Implementation_Pragmas:: +* No_Implementation_Restrictions:: +* No_Implementation_Units:: +* No_Implicit_Aliasing:: +* No_Obsolescent_Features:: +* No_Wide_Characters:: +* SPARK_05:: + +Implementation Advice + +* RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection. +* RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units. +* RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors. +* RM 2.8(16); Pragmas: RM 2 8 16 Pragmas. +* RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas. +* RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets. +* RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types. +* RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types. +* RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values. +* RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types. +* RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays. +* RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small. +* RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation. +* RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information. +* RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks. +* RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses. +* RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types. +* RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses. +* RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses. +* RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses. +* RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses. +* RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses. +* RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses. +* RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses. +* RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes. +* RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering. +* RM 13.7(37); Address as Private: RM 13 7 37 Address as Private. +* RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations. +* RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion. +* RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage. +* RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation. +* RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes. +* RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types. +* RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling. +* RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling. +* RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation. +* RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate. +* RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export. +* RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces. +* RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C. +* RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL. +* RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran. +* RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations. +* RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations. +* RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support. +* RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers. +* RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts. +* RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements. +* RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names. +* RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes. +* RM D.3(17); Locking Policies: RM D 3 17 Locking Policies. +* RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies. +* RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort. +* RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions. +* RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time. +* RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem. +* RM F(7); COBOL Support: RM F 7 COBOL Support. +* RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support. +* RM G; Numerics: RM G Numerics. +* RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types. +* RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions. +* RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements. +* RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy. +* RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy. + +Intrinsic Subprograms + +* Intrinsic Operators:: +* Compilation_Date:: +* Compilation_Time:: +* Enclosing_Entity:: +* Exception_Information:: +* Exception_Message:: +* Exception_Name:: +* File:: +* Line:: +* Shifts and Rotates:: +* Source_Location:: + +Representation Clauses and Pragmas + +* Alignment Clauses:: +* Size Clauses:: +* Storage_Size Clauses:: +* Size of Variant Record Objects:: +* Biased Representation:: +* Value_Size and Object_Size Clauses:: +* Component_Size Clauses:: +* Bit_Order Clauses:: +* Effect of Bit_Order on Byte Ordering:: +* Pragma Pack for Arrays:: +* Pragma Pack for Records:: +* Record Representation Clauses:: +* Handling of Records with Holes:: +* Enumeration Clauses:: +* Address Clauses:: +* Use of Address Clauses for Memory-Mapped I/O:: +* Effect of Convention on Representation:: +* Conventions and Anonymous Access Types:: +* Determining the Representations chosen by GNAT:: The Implementation of Standard I/O -* Standard I/O Packages:: -* FORM Strings:: -* Direct_IO:: -* Sequential_IO:: -* Text_IO:: -* Wide_Text_IO:: -* Wide_Wide_Text_IO:: -* Stream_IO:: -* Text Translation:: -* Shared Files:: -* Filenames encoding:: -* File content encoding:: -* Open Modes:: -* Operations on C Streams:: -* Interfacing to C Streams:: - -The GNAT Library - -* Ada.Characters.Latin_9 (a-chlat9.ads):: -* Ada.Characters.Wide_Latin_1 (a-cwila1.ads):: -* Ada.Characters.Wide_Latin_9 (a-cwila9.ads):: -* Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads):: -* Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads):: -* Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads):: -* Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads):: -* Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads):: -* Ada.Containers.Formal_Ordered_Maps (a-cforma.ads):: -* Ada.Containers.Formal_Ordered_Sets (a-cforse.ads):: -* Ada.Containers.Formal_Vectors (a-cofove.ads):: -* Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads):: -* Ada.Containers.Bounded_Holders (a-coboho.ads):: -* Ada.Command_Line.Environment (a-colien.ads):: -* Ada.Command_Line.Remove (a-colire.ads):: -* Ada.Command_Line.Response_File (a-clrefi.ads):: -* Ada.Direct_IO.C_Streams (a-diocst.ads):: -* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads):: -* Ada.Exceptions.Last_Chance_Handler (a-elchha.ads):: -* Ada.Exceptions.Traceback (a-exctra.ads):: -* Ada.Sequential_IO.C_Streams (a-siocst.ads):: -* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads):: -* Ada.Strings.Unbounded.Text_IO (a-suteio.ads):: -* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads):: -* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads):: -* Ada.Text_IO.C_Streams (a-tiocst.ads):: -* Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads):: -* Ada.Wide_Characters.Unicode (a-wichun.ads):: -* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads):: -* Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads):: -* Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads):: -* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads):: -* Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads):: -* GNAT.Altivec (g-altive.ads):: -* GNAT.Altivec.Conversions (g-altcon.ads):: -* GNAT.Altivec.Vector_Operations (g-alveop.ads):: -* GNAT.Altivec.Vector_Types (g-alvety.ads):: -* GNAT.Altivec.Vector_Views (g-alvevi.ads):: -* GNAT.Array_Split (g-arrspl.ads):: -* GNAT.AWK (g-awk.ads):: -* GNAT.Bounded_Buffers (g-boubuf.ads):: -* GNAT.Bounded_Mailboxes (g-boumai.ads):: -* GNAT.Bubble_Sort (g-bubsor.ads):: -* GNAT.Bubble_Sort_A (g-busora.ads):: -* GNAT.Bubble_Sort_G (g-busorg.ads):: -* GNAT.Byte_Order_Mark (g-byorma.ads):: -* GNAT.Byte_Swapping (g-bytswa.ads):: -* GNAT.Calendar (g-calend.ads):: -* GNAT.Calendar.Time_IO (g-catiio.ads):: -* GNAT.Case_Util (g-casuti.ads):: -* GNAT.CGI (g-cgi.ads):: -* GNAT.CGI.Cookie (g-cgicoo.ads):: -* GNAT.CGI.Debug (g-cgideb.ads):: -* GNAT.Command_Line (g-comlin.ads):: -* GNAT.Compiler_Version (g-comver.ads):: -* GNAT.Ctrl_C (g-ctrl_c.ads):: -* GNAT.CRC32 (g-crc32.ads):: -* GNAT.Current_Exception (g-curexc.ads):: -* GNAT.Debug_Pools (g-debpoo.ads):: -* GNAT.Debug_Utilities (g-debuti.ads):: -* GNAT.Decode_String (g-decstr.ads):: -* GNAT.Decode_UTF8_String (g-deutst.ads):: -* GNAT.Directory_Operations (g-dirope.ads):: -* GNAT.Directory_Operations.Iteration (g-diopit.ads):: -* GNAT.Dynamic_HTables (g-dynhta.ads):: -* GNAT.Dynamic_Tables (g-dyntab.ads):: -* GNAT.Encode_String (g-encstr.ads):: -* GNAT.Encode_UTF8_String (g-enutst.ads):: -* GNAT.Exception_Actions (g-excact.ads):: -* GNAT.Exception_Traces (g-exctra.ads):: -* GNAT.Exceptions (g-except.ads):: -* GNAT.Expect (g-expect.ads):: -* GNAT.Expect.TTY (g-exptty.ads):: -* GNAT.Float_Control (g-flocon.ads):: -* GNAT.Formatted_String (g-forstr.ads):: -* GNAT.Heap_Sort (g-heasor.ads):: -* GNAT.Heap_Sort_A (g-hesora.ads):: -* GNAT.Heap_Sort_G (g-hesorg.ads):: -* GNAT.HTable (g-htable.ads):: -* GNAT.IO (g-io.ads):: -* GNAT.IO_Aux (g-io_aux.ads):: -* GNAT.Lock_Files (g-locfil.ads):: -* GNAT.MBBS_Discrete_Random (g-mbdira.ads):: -* GNAT.MBBS_Float_Random (g-mbflra.ads):: -* GNAT.MD5 (g-md5.ads):: -* GNAT.Memory_Dump (g-memdum.ads):: -* GNAT.Most_Recent_Exception (g-moreex.ads):: -* GNAT.OS_Lib (g-os_lib.ads):: -* GNAT.Perfect_Hash_Generators (g-pehage.ads):: -* GNAT.Random_Numbers (g-rannum.ads):: -* GNAT.Regexp (g-regexp.ads):: -* GNAT.Registry (g-regist.ads):: -* GNAT.Regpat (g-regpat.ads):: -* GNAT.Rewrite_Data (g-rewdat.ads):: -* GNAT.Secondary_Stack_Info (g-sestin.ads):: -* GNAT.Semaphores (g-semaph.ads):: -* GNAT.Serial_Communications (g-sercom.ads):: -* GNAT.SHA1 (g-sha1.ads):: -* GNAT.SHA224 (g-sha224.ads):: -* GNAT.SHA256 (g-sha256.ads):: -* GNAT.SHA384 (g-sha384.ads):: -* GNAT.SHA512 (g-sha512.ads):: -* GNAT.Signals (g-signal.ads):: -* GNAT.Sockets (g-socket.ads):: -* GNAT.Source_Info (g-souinf.ads):: -* GNAT.Spelling_Checker (g-speche.ads):: -* GNAT.Spelling_Checker_Generic (g-spchge.ads):: -* GNAT.Spitbol.Patterns (g-spipat.ads):: -* GNAT.Spitbol (g-spitbo.ads):: -* GNAT.Spitbol.Table_Boolean (g-sptabo.ads):: -* GNAT.Spitbol.Table_Integer (g-sptain.ads):: -* GNAT.Spitbol.Table_VString (g-sptavs.ads):: -* GNAT.SSE (g-sse.ads):: -* GNAT.SSE.Vector_Types (g-ssvety.ads):: -* GNAT.Strings (g-string.ads):: -* GNAT.String_Split (g-strspl.ads):: -* GNAT.Table (g-table.ads):: -* GNAT.Task_Lock (g-tasloc.ads):: -* GNAT.Threads (g-thread.ads):: -* GNAT.Time_Stamp (g-timsta.ads):: -* GNAT.Traceback (g-traceb.ads):: -* GNAT.Traceback.Symbolic (g-trasym.ads):: -* GNAT.UTF_32 (g-utf_32.ads):: -* GNAT.UTF_32_Spelling_Checker (g-u3spch.ads):: -* GNAT.Wide_Spelling_Checker (g-wispch.ads):: -* GNAT.Wide_String_Split (g-wistsp.ads):: -* GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads):: -* GNAT.Wide_Wide_String_Split (g-zistsp.ads):: -* Interfaces.C.Extensions (i-cexten.ads):: -* Interfaces.C.Streams (i-cstrea.ads):: -* Interfaces.Packed_Decimal (i-pacdec.ads):: -* Interfaces.VxWorks (i-vxwork.ads):: -* Interfaces.VxWorks.IO (i-vxwoio.ads):: -* System.Address_Image (s-addima.ads):: -* System.Assertions (s-assert.ads):: -* System.Atomic_Counters (s-atocou.ads):: -* System.Memory (s-memory.ads):: -* System.Multiprocessors (s-multip.ads):: -* System.Multiprocessors.Dispatching_Domains (s-mudido.ads):: -* System.Partition_Interface (s-parint.ads):: -* System.Pool_Global (s-pooglo.ads):: -* System.Pool_Local (s-pooloc.ads):: -* System.Restrictions (s-restri.ads):: -* System.Rident (s-rident.ads):: -* System.Strings.Stream_Ops (s-ststop.ads):: -* System.Unsigned_Types (s-unstyp.ads):: -* System.Wch_Cnv (s-wchcnv.ads):: -* System.Wch_Con (s-wchcon.ads):: +* Standard I/O Packages:: +* FORM Strings:: +* Direct_IO:: +* Sequential_IO:: +* Text_IO:: +* Wide_Text_IO:: +* Wide_Wide_Text_IO:: +* Stream_IO:: +* Text Translation:: +* Shared Files:: +* Filenames encoding:: +* File content encoding:: +* Open Modes:: +* Operations on C Streams:: +* Interfacing to C Streams:: Text_IO -* Text_IO Stream Pointer Positioning:: -* Text_IO Reading and Writing Non-Regular Files:: -* Get_Immediate:: -* Treating Text_IO Files as Streams:: -* Text_IO Extensions:: -* Text_IO Facilities for Unbounded Strings:: +* Stream Pointer Positioning:: +* Reading and Writing Non-Regular Files:: +* Get_Immediate:: +* Treating Text_IO Files as Streams:: +* Text_IO Extensions:: +* Text_IO Facilities for Unbounded Strings:: Wide_Text_IO -* Wide_Text_IO Stream Pointer Positioning:: -* Wide_Text_IO Reading and Writing Non-Regular Files:: +* Stream Pointer Positioning: Stream Pointer Positioning<2>. +* Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>. Wide_Wide_Text_IO -* Wide_Wide_Text_IO Stream Pointer Positioning:: -* Wide_Wide_Text_IO Reading and Writing Non-Regular Files:: +* Stream Pointer Positioning: Stream Pointer Positioning<3>. +* Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>. -Interfacing to Other Languages +The GNAT Library + +* Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads. +* Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads. +* Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads. +* Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads. +* Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads. +* Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads. +* Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads. +* Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads. +* Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads. +* Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads. +* Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads. +* Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads. +* Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads. +* Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads. +* Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads. +* Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads. +* Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads. +* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads. +* Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads. +* Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads. +* Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads. +* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads. +* Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads. +* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads. +* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads. +* Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads. +* Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads. +* Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads. +* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads. +* Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads. +* Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads. +* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads. +* Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads. +* GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads. +* GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads. +* GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads. +* GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads. +* GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads. +* GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads. +* GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads. +* GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads. +* GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads. +* GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads. +* GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads. +* GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads. +* GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads. +* GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads. +* GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads. +* GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads. +* GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads. +* GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads. +* GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads. +* GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads. +* GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads. +* GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads. +* GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads. +* GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads. +* GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads. +* GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads. +* GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads. +* GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads. +* GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads. +* GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads. +* GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads. +* GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads. +* GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads. +* GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads. +* GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads. +* GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads. +* GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads. +* GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads. +* GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads. +* GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads. +* GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads. +* GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads. +* GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads. +* GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads. +* GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads. +* GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads. +* GNAT.IO (g-io.ads): GNAT IO g-io ads. +* GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads. +* GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads. +* GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads. +* GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads. +* GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads. +* GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads. +* GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads. +* GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads. +* GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads. +* GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads. +* GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads. +* GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads. +* GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads. +* GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads. +* GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads. +* GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads. +* GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads. +* GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads. +* GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads. +* GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads. +* GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads. +* GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads. +* GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads. +* GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads. +* GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads. +* GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads. +* GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads. +* GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads. +* GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads. +* GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads. +* GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads. +* GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads. +* GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads. +* GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads. +* GNAT.Strings (g-string.ads): GNAT Strings g-string ads. +* GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads. +* GNAT.Table (g-table.ads): GNAT Table g-table ads. +* GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads. +* GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads. +* GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads. +* GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads. +* GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads. +* GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads. +* GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads. +* GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads. +* GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads. +* GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads. +* GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads. +* Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads. +* Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads. +* Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads. +* Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads. +* Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads. +* System.Address_Image (s-addima.ads): System Address_Image s-addima ads. +* System.Assertions (s-assert.ads): System Assertions s-assert ads. +* System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads. +* System.Memory (s-memory.ads): System Memory s-memory ads. +* System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads. +* System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads. +* System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads. +* System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads. +* System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads. +* System.Restrictions (s-restri.ads): System Restrictions s-restri ads. +* System.Rident (s-rident.ads): System Rident s-rident ads. +* System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads. +* System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads. +* System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads. +* System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads. -* Interfacing to C:: -* Interfacing to C++:: -* Interfacing to COBOL:: -* Interfacing to Fortran:: -* Interfacing to non-GNAT Ada code:: +Interfacing to Other Languages -Specialized Needs Annexes +* Interfacing to C:: +* Interfacing to C++:: +* Interfacing to COBOL:: +* Interfacing to Fortran:: +* Interfacing to non-GNAT Ada code:: Implementation of Specific Ada Features -* Machine Code Insertions:: -* GNAT Implementation of Tasking:: -* GNAT Implementation of Shared Passive Packages:: -* Code Generation for Array Aggregates:: -* The Size of Discriminated Records with Default Discriminants:: -* Strict Conformance to the Ada Reference Manual:: -Implementation of Ada 2012 Features +* Machine Code Insertions:: +* GNAT Implementation of Tasking:: +* GNAT Implementation of Shared Passive Packages:: +* Code Generation for Array Aggregates:: +* The Size of Discriminated Records with Default Discriminants:: +* Strict Conformance to the Ada Reference Manual:: + +GNAT Implementation of Tasking + +* Mapping Ada Tasks onto the Underlying Kernel Threads:: +* Ensuring Compliance with the Real-Time Annex:: + +Code Generation for Array Aggregates + +* Static constant aggregates with static bounds:: +* Constant aggregates with unconstrained nominal types:: +* Aggregates with static bounds:: +* Aggregates with non-static bounds:: +* Aggregates in assignment statements:: Obsolescent Features -GNU Free Documentation License +* pragma No_Run_Time:: +* pragma Ravenscar:: +* pragma Restricted_Run_Time:: +* pragma Task_Info:: +* package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads. + +Compatibility and Porting Guide + +* Writing Portable Fixed-Point Declarations:: +* Compatibility with Ada 83:: +* Compatibility between Ada 95 and Ada 2005:: +* Implementation-dependent characteristics:: +* Compatibility with Other Ada Systems:: +* Representation Clauses:: +* Compatibility with HP Ada 83:: + +Compatibility with Ada 83 + +* Legal Ada 83 programs that are illegal in Ada 95:: +* More deterministic semantics:: +* Changed semantics:: +* Other language compatibility issues:: + +Implementation-dependent characteristics + +* Implementation-defined pragmas:: +* Implementation-defined attributes:: +* Libraries:: +* Elaboration order:: +* Target-specific aspects:: -Index @end detailmenu @end menu -@end ifnottex +@node About This Guide,Implementation Defined Pragmas,Top,Top +@anchor{gnat_rm/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_rm/about_this_guide doc}@anchor{3}@anchor{gnat_rm/about_this_guide gnat-reference-manual}@anchor{4}@anchor{gnat_rm/about_this_guide id1}@anchor{5} +@chapter About This Guide + -@node About This Guide -@unnumbered About This Guide -@noindent This manual contains useful information in writing programs using the -@value{EDITION} compiler. It includes information on implementation dependent -characteristics of @value{EDITION}, including all the information required by +GNAT compiler. It includes information on implementation dependent +characteristics of GNAT, including all the information required by Annex M of the Ada language standard. -@value{EDITION} implements Ada 95, Ada 2005 and Ada 2012, and it may also be +GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be invoked in Ada 83 compatibility mode. -By default, @value{EDITION} assumes Ada 2012, +By default, GNAT assumes Ada 2012, but you can override with a compiler switch to explicitly specify the language version. -(Please refer to @ref{Compiling Different Versions of Ada,,, gnat_ugn, -@value{EDITION} User's Guide}, for details on these switches.) -Throughout this manual, references to ``Ada'' without a year suffix +(Please refer to the @emph{GNAT User's Guide} for details on these switches.) +Throughout this manual, references to 'Ada' without a year suffix apply to all the Ada versions of the language. Ada is designed to be highly portable. @@ -754,208 +890,225 @@ different compilers on different platforms. However, since Ada is designed to be used in a wide variety of applications, it also contains a number of system dependent features to be used in interfacing to the external world. -@cindex Implementation-dependent features -@cindex Portability +.. index:: Implementation-dependent features + +@geindex Portability Note: Any program that makes use of implementation-dependent features may be non-portable. You should follow good programming practice and isolate and clearly document any sections of your program that make use of these features in a non-portable manner. -@ifset PROEDITION -For ease of exposition, ``@value{EDITION}'' will be referred to simply as -``GNAT'' in the remainder of this document. -@end ifset - @menu -* What This Reference Manual Contains:: -* Conventions:: -* Related Information:: +* What This Reference Manual Contains:: +* Conventions:: +* Related Information:: + @end menu -@node What This Reference Manual Contains -@unnumberedsec What This Reference Manual Contains +@node What This Reference Manual Contains,Conventions,,About This Guide +@anchor{gnat_rm/about_this_guide what-this-reference-manual-contains}@anchor{6} +@section What This Reference Manual Contains + -@noindent This reference manual contains the following chapters: -@itemize @bullet -@item -@ref{Implementation Defined Pragmas}, lists GNAT implementation-dependent + +@itemize * + +@item +@ref{7,,Implementation Defined Pragmas}, lists GNAT implementation-dependent pragmas, which can be used to extend and enhance the functionality of the compiler. -@item -@ref{Implementation Defined Attributes}, lists GNAT +@item +@ref{8,,Implementation Defined Attributes}, lists GNAT implementation-dependent attributes, which can be used to extend and enhance the functionality of the compiler. -@item -@ref{Standard and Implementation Defined Restrictions}, lists GNAT +@item +@ref{9,,Standard and Implementation Defined Restrictions}, lists GNAT implementation-dependent restrictions, which can be used to extend and enhance the functionality of the compiler. -@item -@ref{Implementation Advice}, provides information on generally +@item +@ref{a,,Implementation Advice}, provides information on generally desirable behavior which are not requirements that all compilers must follow since it cannot be provided on all systems, or which may be undesirable on some systems. -@item -@ref{Implementation Defined Characteristics}, provides a guide to +@item +@ref{b,,Implementation Defined Characteristics}, provides a guide to minimizing implementation dependent features. -@item -@ref{Intrinsic Subprograms}, describes the intrinsic subprograms +@item +@ref{c,,Intrinsic Subprograms}, describes the intrinsic subprograms implemented by GNAT, and how they can be imported into user application programs. -@item -@ref{Representation Clauses and Pragmas}, describes in detail the +@item +@ref{d,,Representation Clauses and Pragmas}, describes in detail the way that GNAT represents data, and in particular the exact set of representation clauses and pragmas that is accepted. -@item -@ref{Standard Library Routines}, provides a listing of packages and a +@item +@ref{e,,Standard Library Routines}, provides a listing of packages and a brief description of the functionality that is provided by Ada's -extensive set of standard library routines as implemented by GNAT@. +extensive set of standard library routines as implemented by GNAT. -@item -@ref{The Implementation of Standard I/O}, details how the GNAT +@item +@ref{f,,The Implementation of Standard I/O}, details how the GNAT implementation of the input-output facilities. -@item -@ref{The GNAT Library}, is a catalog of packages that complement +@item +@ref{10,,The GNAT Library}, is a catalog of packages that complement the Ada predefined library. -@item -@ref{Interfacing to Other Languages}, describes how programs +@item +@ref{11,,Interfacing to Other Languages}, describes how programs written in Ada using GNAT can be interfaced to other programming languages. -@ref{Specialized Needs Annexes}, describes the GNAT implementation of all +@item +@ref{12,,Specialized Needs Annexes}, describes the GNAT implementation of all of the specialized needs annexes. -@item -@ref{Implementation of Specific Ada Features}, discusses issues related +@item +@ref{13,,Implementation of Specific Ada Features}, discusses issues related to GNAT's implementation of machine code insertions, tasking, and several other features. -@item -@ref{Implementation of Ada 2012 Features}, describes the status of the +@item +@ref{14,,Implementation of Ada 2012 Features}, describes the status of the GNAT implementation of the Ada 2012 language standard. -@item -@ref{Obsolescent Features} documents implementation dependent features, +@item +@ref{15,,Obsolescent Features} documents implementation dependent features, including pragmas and attributes, which are considered obsolescent, since there are other preferred ways of achieving the same results. These obsolescent forms are retained for backwards compatibility. +@item +@ref{16,,Compatibility and Porting Guide} presents some guidelines for +developing portable Ada code, describes the compatibility issues that +may arise between GNAT and other Ada compilation systems (including those +for Ada 83), and shows how GNAT can expedite porting applications +developed in other Ada environments. + +@item +@ref{1,,GNU Free Documentation License} contains the license for this document. @end itemize -@cindex Ada 95 Language Reference Manual -@cindex Ada 2005 Language Reference Manual -@noindent +@geindex Ada 95 Language Reference Manual + +@geindex Ada 2005 Language Reference Manual + This reference manual assumes a basic familiarity with the Ada 95 language, as -described in the International Standard ANSI/ISO/IEC-8652:1995, -January 1995. +described in the +@cite{International Standard ANSI/ISO/IEC-8652:1995}. It does not require knowledge of the new features introduced by Ada 2005, -(officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1 -and Amendment 1). +(officially known as @cite{ISO/IEC 8652:1995 with Technical Corrigendum 1 and Amendment 1}). Both reference manuals are included in the GNAT documentation package. -@node Conventions -@unnumberedsec Conventions -@cindex Conventions, typographical -@cindex Typographical conventions +@node Conventions,Related Information,What This Reference Manual Contains,About This Guide +@anchor{gnat_rm/about_this_guide conventions}@anchor{17} +@section Conventions + + +@geindex Conventions +@geindex typographical + +@geindex Typographical conventions -@noindent Following are examples of the typographical and graphic conventions used in this guide: -@itemize @bullet -@item -@code{Functions}, @code{utility program names}, @code{standard names}, -and @code{classes}. -@item -@code{Option flags} +@itemize * -@item -@file{File names}, @samp{button names}, and @samp{field names}. +@item +@cite{Functions}, @cite{utility program names}, @cite{standard names}, +and @cite{classes}. -@item -@code{Variables}, @env{environment variables}, and @var{metasyntactic -variables}. +@item +@cite{Option flags} -@item -@emph{Emphasis}. +@item +@code{File names} -@item +@item +@cite{Variables} + +@item +@emph{Emphasis} + +@item [optional information or parameters] -@item +@item Examples are described by text -@smallexample + +@example and then shown this way. -@end smallexample +@end example + +@item +Commands that are entered by the user are shown as preceded by a prompt string +comprising the @code{$} character followed by a space. @end itemize -@noindent -Commands that are entered by the user are preceded in this manual by the -characters @samp{$ } (dollar sign followed by space). If your system uses this -sequence as a prompt, then the commands will appear exactly as you see them -in the manual. If your system uses some other prompt, then the command will -appear with the @samp{$} replaced by whatever prompt character you are using. +@node Related Information,,Conventions,About This Guide +@anchor{gnat_rm/about_this_guide related-information}@anchor{18} +@section Related Information + -@node Related Information -@unnumberedsec Related Information -@noindent See the following documents for further information on GNAT: -@itemize @bullet -@item -@xref{Top, @value{EDITION} User's Guide, About This Guide, gnat_ugn, -@value{EDITION} User's Guide}, which provides information on how to use the -GNAT compiler system. -@item -@cite{Ada 95 Reference Manual}, which contains all reference -material for the Ada 95 programming language. +@itemize * -@item +@item +@cite{GNAT User's Guide for Native Platforms}, +which provides information on how to use the +GNAT development environment. + +@item +@cite{Ada 95 Reference Manual}, the Ada 95 programming language standard. + +@item @cite{Ada 95 Annotated Reference Manual}, which is an annotated version of the Ada 95 standard. The annotations describe detailed aspects of the design decision, and in particular contain useful sections on Ada 83 compatibility. -@item -@cite{Ada 2005 Reference Manual}, which contains all reference -material for the Ada 2005 programming language. +@item +@cite{Ada 2005 Reference Manual}, the Ada 2005 programming language standard. -@item +@item @cite{Ada 2005 Annotated Reference Manual}, which is an annotated version of the Ada 2005 standard. The annotations describe -detailed aspects of the design decision, and in particular contain useful -sections on Ada 83 and Ada 95 compatibility. +detailed aspects of the design decision. -@item -@cite{DEC Ada, Technical Overview and Comparison on DIGITAL Platforms}, +@item +@cite{Ada 2012 Reference Manual}, the Ada 2012 programming language standard. + +@item +@cite{DEC Ada@comma{} Technical Overview and Comparison on DIGITAL Platforms}, which contains specific information on compatibility between GNAT and DEC Ada 83 systems. -@item -@cite{DEC Ada, Language Reference Manual, part number AA-PYZAB-TK} which +@item +@cite{DEC Ada@comma{} Language Reference Manual}, part number AA-PYZAB-TK, which describes in detail the pragmas and attributes provided by the DEC Ada 83 compiler system. - @end itemize -@node Implementation Defined Pragmas +@node Implementation Defined Pragmas,Implementation Defined Aspects,About This Guide,Top +@anchor{gnat_rm/implementation_defined_pragmas implementation-defined-pragmas}@anchor{7}@anchor{gnat_rm/implementation_defined_pragmas doc}@anchor{19}@anchor{gnat_rm/implementation_defined_pragmas id1}@anchor{1a} @chapter Implementation Defined Pragmas -@noindent + Ada defines a set of pragmas that can be used to supply additional information to the compiler. These language defined pragmas are implemented in GNAT and work as described in the Ada Reference Manual. @@ -972,237 +1125,238 @@ platforms). Therefore if portability to other compilers is an important consideration, the use of these pragmas should be minimized. @menu -* Pragma Abort_Defer:: -* Pragma Abstract_State:: -* Pragma Ada_83:: -* Pragma Ada_95:: -* Pragma Ada_05:: -* Pragma Ada_2005:: -* Pragma Ada_12:: -* Pragma Ada_2012:: -* Pragma Allow_Integer_Address:: -* Pragma Annotate:: -* Pragma Assert:: -* Pragma Assert_And_Cut:: -* Pragma Assertion_Policy:: -* Pragma Assume:: -* Pragma Assume_No_Invalid_Values:: -* Pragma AST_Entry:: -* Pragma Async_Readers:: -* Pragma Async_Writers:: -* Pragma Attribute_Definition:: -* Pragma C_Pass_By_Copy:: -* Pragma Check:: -* Pragma Check_Float_Overflow:: -* Pragma Check_Name:: -* Pragma Check_Policy:: -* Pragma CIL_Constructor:: -* Pragma Comment:: -* Pragma Common_Object:: -* Pragma Compile_Time_Error:: -* Pragma Compile_Time_Warning:: -* Pragma Compiler_Unit:: -* Pragma Compiler_Unit_Warning:: -* Pragma Complete_Representation:: -* Pragma Complex_Representation:: -* Pragma Component_Alignment:: -* Pragma Contract_Cases:: -* Pragma Convention_Identifier:: -* Pragma CPP_Class:: -* Pragma CPP_Constructor:: -* Pragma CPP_Virtual:: -* Pragma CPP_Vtable:: -* Pragma CPU:: -* Pragma Debug:: -* Pragma Debug_Policy:: -* Pragma Default_Scalar_Storage_Order:: -* Pragma Default_Storage_Pool:: -* Pragma Depends:: -* Pragma Detect_Blocking:: -* Pragma Disable_Atomic_Synchronization:: -* Pragma Dispatching_Domain:: -* Pragma Effective_Reads:: -* Pragma Effective_Writes:: -* Pragma Elaboration_Checks:: -* Pragma Eliminate:: -* Pragma Enable_Atomic_Synchronization:: -* Pragma Export_Exception:: -* Pragma Export_Function:: -* Pragma Export_Object:: -* Pragma Export_Procedure:: -* Pragma Export_Value:: -* Pragma Export_Valued_Procedure:: -* Pragma Extend_System:: -* Pragma Extensions_Allowed:: -* Pragma External:: -* Pragma External_Name_Casing:: -* Pragma Fast_Math:: -* Pragma Favor_Top_Level:: -* Pragma Finalize_Storage_Only:: -* Pragma Float_Representation:: -* Pragma Global:: -* Pragma Ident:: -* Pragma Implementation_Defined:: -* Pragma Implemented:: -* Pragma Implicit_Packing:: -* Pragma Import_Exception:: -* Pragma Import_Function:: -* Pragma Import_Object:: -* Pragma Import_Procedure:: -* Pragma Import_Valued_Procedure:: -* Pragma Independent:: -* Pragma Independent_Components:: -* Pragma Initial_Condition:: -* Pragma Initialize_Scalars:: -* Pragma Initializes:: -* Pragma Inline_Always:: -* Pragma Inline_Generic:: -* Pragma Interface:: -* Pragma Interface_Name:: -* Pragma Interrupt_Handler:: -* Pragma Interrupt_State:: -* Pragma Invariant:: -* Pragma Java_Constructor:: -* Pragma Java_Interface:: -* Pragma Keep_Names:: -* Pragma License:: -* Pragma Link_With:: -* Pragma Linker_Alias:: -* Pragma Linker_Constructor:: -* Pragma Linker_Destructor:: -* Pragma Linker_Section:: -* Pragma Lock_Free:: -* Pragma Long_Float:: -* Pragma Loop_Invariant:: -* Pragma Loop_Optimize:: -* Pragma Loop_Variant:: -* Pragma Machine_Attribute:: -* Pragma Main:: -* Pragma Main_Storage:: -* Pragma No_Body:: -* Pragma No_Elaboration_Code_All:: -* Pragma No_Inline:: -* Pragma No_Return:: -* Pragma No_Run_Time:: -* Pragma No_Strict_Aliasing:: -* Pragma No_Tagged_Streams:: -* Pragma Normalize_Scalars:: -* Pragma Obsolescent:: -* Pragma Optimize_Alignment:: -* Pragma Ordered:: -* Pragma Overflow_Mode:: -* Pragma Overriding_Renamings:: -* Pragma Partition_Elaboration_Policy:: -* Pragma Part_Of:: -* Pragma Passive:: -* Pragma Persistent_BSS:: -* Pragma Polling:: -* Pragma Post:: -* Pragma Postcondition:: -* Pragma Post_Class:: -* Pragma Pre:: -* Pragma Precondition:: -* Pragma Predicate:: -* Pragma Preelaborable_Initialization:: -* Pragma Prefix_Exception_Messages:: -* Pragma Pre_Class:: -* Pragma Priority_Specific_Dispatching:: -* Pragma Profile:: -* Pragma Profile_Warnings:: -* Pragma Propagate_Exceptions:: -* Pragma Provide_Shift_Operators:: -* Pragma Psect_Object:: -* Pragma Pure_Function:: -* Pragma Rational:: -* Pragma Ravenscar:: -* Pragma Refined_Depends:: -* Pragma Refined_Global:: -* Pragma Refined_Post:: -* Pragma Refined_State:: -* Pragma Relative_Deadline:: -* Pragma Remote_Access_Type:: -* Pragma Restricted_Run_Time:: -* Pragma Restriction_Warnings:: -* Pragma Reviewable:: -* Pragma Share_Generic:: -* Pragma Shared:: -* Pragma Short_Circuit_And_Or:: -* Pragma Short_Descriptors:: -* Pragma Simple_Storage_Pool_Type:: -* Pragma Source_File_Name:: -* Pragma Source_File_Name_Project:: -* Pragma Source_Reference:: -* Pragma SPARK_Mode:: -* Pragma Static_Elaboration_Desired:: -* Pragma Stream_Convert:: -* Pragma Style_Checks:: -* Pragma Subtitle:: -* Pragma Suppress:: -* Pragma Suppress_All:: -* Pragma Suppress_Debug_Info:: -* Pragma Suppress_Exception_Locations:: -* Pragma Suppress_Initialization:: -* Pragma Task_Name:: -* Pragma Task_Storage:: -* Pragma Test_Case:: -* Pragma Thread_Local_Storage:: -* Pragma Time_Slice:: -* Pragma Title:: -* Pragma Type_Invariant:: -* Pragma Type_Invariant_Class:: -* Pragma Unchecked_Union:: -* Pragma Unevaluated_Use_Of_Old:: -* Pragma Unimplemented_Unit:: -* Pragma Universal_Aliasing :: -* Pragma Universal_Data:: -* Pragma Unmodified:: -* Pragma Unreferenced:: -* Pragma Unreferenced_Objects:: -* Pragma Unreserve_All_Interrupts:: -* Pragma Unsuppress:: -* Pragma Use_VADS_Size:: -* Pragma Validity_Checks:: -* Pragma Volatile:: -* Pragma Warning_As_Error:: -* Pragma Warnings:: -* Pragma Weak_External:: -* Pragma Wide_Character_Encoding:: +* Pragma Abort_Defer:: +* Pragma Abstract_State:: +* Pragma Ada_83:: +* Pragma Ada_95:: +* Pragma Ada_05:: +* Pragma Ada_2005:: +* Pragma Ada_12:: +* Pragma Ada_2012:: +* Pragma Allow_Integer_Address:: +* Pragma Annotate:: +* Pragma Assert:: +* Pragma Assert_And_Cut:: +* Pragma Assertion_Policy:: +* Pragma Assume:: +* Pragma Assume_No_Invalid_Values:: +* Pragma Async_Readers:: +* Pragma Async_Writers:: +* Pragma Attribute_Definition:: +* Pragma C_Pass_By_Copy:: +* Pragma Check:: +* Pragma Check_Float_Overflow:: +* Pragma Check_Name:: +* Pragma Check_Policy:: +* Pragma CIL_Constructor:: +* Pragma Comment:: +* Pragma Common_Object:: +* Pragma Compile_Time_Error:: +* Pragma Compile_Time_Warning:: +* Pragma Compiler_Unit:: +* Pragma Compiler_Unit_Warning:: +* Pragma Complete_Representation:: +* Pragma Complex_Representation:: +* Pragma Component_Alignment:: +* Pragma Contract_Cases:: +* Pragma Convention_Identifier:: +* Pragma CPP_Class:: +* Pragma CPP_Constructor:: +* Pragma CPP_Virtual:: +* Pragma CPP_Vtable:: +* Pragma CPU:: +* Pragma Debug:: +* Pragma Debug_Policy:: +* Pragma Default_Scalar_Storage_Order:: +* Pragma Default_Storage_Pool:: +* Pragma Depends:: +* Pragma Detect_Blocking:: +* Pragma Disable_Atomic_Synchronization:: +* Pragma Dispatching_Domain:: +* Pragma Effective_Reads:: +* Pragma Effective_Writes:: +* Pragma Elaboration_Checks:: +* Pragma Eliminate:: +* Pragma Enable_Atomic_Synchronization:: +* Pragma Export_Function:: +* Pragma Export_Object:: +* Pragma Export_Procedure:: +* Pragma Export_Value:: +* Pragma Export_Valued_Procedure:: +* Pragma Extend_System:: +* Pragma Extensions_Allowed:: +* Pragma External:: +* Pragma External_Name_Casing:: +* Pragma Fast_Math:: +* Pragma Favor_Top_Level:: +* Pragma Finalize_Storage_Only:: +* Pragma Float_Representation:: +* Pragma Global:: +* Pragma Ident:: +* Pragma Implementation_Defined:: +* Pragma Implemented:: +* Pragma Implicit_Packing:: +* Pragma Import_Function:: +* Pragma Import_Object:: +* Pragma Import_Procedure:: +* Pragma Import_Valued_Procedure:: +* Pragma Independent:: +* Pragma Independent_Components:: +* Pragma Initial_Condition:: +* Pragma Initialize_Scalars:: +* Pragma Initializes:: +* Pragma Inline_Always:: +* Pragma Inline_Generic:: +* Pragma Interface:: +* Pragma Interface_Name:: +* Pragma Interrupt_Handler:: +* Pragma Interrupt_State:: +* Pragma Invariant:: +* Pragma Java_Constructor:: +* Pragma Java_Interface:: +* Pragma Keep_Names:: +* Pragma License:: +* Pragma Link_With:: +* Pragma Linker_Alias:: +* Pragma Linker_Constructor:: +* Pragma Linker_Destructor:: +* Pragma Linker_Section:: +* Pragma Lock_Free:: +* Pragma Loop_Invariant:: +* Pragma Loop_Optimize:: +* Pragma Loop_Variant:: +* Pragma Machine_Attribute:: +* Pragma Main:: +* Pragma Main_Storage:: +* Pragma No_Body:: +* Pragma No_Elaboration_Code_All:: +* Pragma No_Inline:: +* Pragma No_Return:: +* Pragma No_Run_Time:: +* Pragma No_Strict_Aliasing:: +* Pragma No_Tagged_Streams:: +* Pragma Normalize_Scalars:: +* Pragma Obsolescent:: +* Pragma Optimize_Alignment:: +* Pragma Ordered:: +* Pragma Overflow_Mode:: +* Pragma Overriding_Renamings:: +* Pragma Partition_Elaboration_Policy:: +* Pragma Part_Of:: +* Pragma Passive:: +* Pragma Persistent_BSS:: +* Pragma Polling:: +* Pragma Post:: +* Pragma Postcondition:: +* Pragma Post_Class:: +* Pragma Pre:: +* Pragma Precondition:: +* Pragma Predicate:: +* Pragma Preelaborable_Initialization:: +* Pragma Prefix_Exception_Messages:: +* Pragma Pre_Class:: +* Pragma Priority_Specific_Dispatching:: +* Pragma Profile:: +* Pragma Profile_Warnings:: +* Pragma Propagate_Exceptions:: +* Pragma Provide_Shift_Operators:: +* Pragma Psect_Object:: +* Pragma Pure_Function:: +* Pragma Rational:: +* Pragma Ravenscar:: +* Pragma Refined_Depends:: +* Pragma Refined_Global:: +* Pragma Refined_Post:: +* Pragma Refined_State:: +* Pragma Relative_Deadline:: +* Pragma Remote_Access_Type:: +* Pragma Restricted_Run_Time:: +* Pragma Restriction_Warnings:: +* Pragma Reviewable:: +* Pragma Share_Generic:: +* Pragma Shared:: +* Pragma Short_Circuit_And_Or:: +* Pragma Short_Descriptors:: +* Pragma Simple_Storage_Pool_Type:: +* Pragma Source_File_Name:: +* Pragma Source_File_Name_Project:: +* Pragma Source_Reference:: +* Pragma SPARK_Mode:: +* Pragma Static_Elaboration_Desired:: +* Pragma Stream_Convert:: +* Pragma Style_Checks:: +* Pragma Subtitle:: +* Pragma Suppress:: +* Pragma Suppress_All:: +* Pragma Suppress_Debug_Info:: +* Pragma Suppress_Exception_Locations:: +* Pragma Suppress_Initialization:: +* Pragma Task_Name:: +* Pragma Task_Storage:: +* Pragma Test_Case:: +* Pragma Thread_Local_Storage:: +* Pragma Time_Slice:: +* Pragma Title:: +* Pragma Type_Invariant:: +* Pragma Type_Invariant_Class:: +* Pragma Unchecked_Union:: +* Pragma Unevaluated_Use_Of_Old:: +* Pragma Unimplemented_Unit:: +* Pragma Universal_Aliasing:: +* Pragma Universal_Data:: +* Pragma Unmodified:: +* Pragma Unreferenced:: +* Pragma Unreferenced_Objects:: +* Pragma Unreserve_All_Interrupts:: +* Pragma Unsuppress:: +* Pragma Use_VADS_Size:: +* Pragma Validity_Checks:: +* Pragma Volatile:: +* Pragma Warning_As_Error:: +* Pragma Warnings:: +* Pragma Weak_External:: +* Pragma Wide_Character_Encoding:: + @end menu -@node Pragma Abort_Defer -@unnumberedsec Pragma Abort_Defer -@findex Abort_Defer -@cindex Deferring aborts -@noindent +@node Pragma Abort_Defer,Pragma Abstract_State,,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-abort-defer}@anchor{1b} +@section Pragma Abort_Defer + + +@geindex Deferring aborts + Syntax: -@smallexample + +@example pragma Abort_Defer; -@end smallexample +@end example -@noindent This pragma must appear at the start of the statement sequence of a -handled sequence of statements (right after the @code{begin}). It has +handled sequence of statements (right after the @cite{begin}). It has the effect of deferring aborts for the sequence of statements (but not for the declarations or handlers, if any, associated with this statement sequence). -@node Pragma Abstract_State -@unnumberedsec Pragma Abstract_State -@findex Abstract_State -@noindent +@node Pragma Abstract_State,Pragma Ada_83,Pragma Abort_Defer,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-abstract-state}@anchor{1c} +@section Pragma Abstract_State + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.4. -@node Pragma Ada_83 -@unnumberedsec Pragma Ada_83 -@findex Ada_83 -@noindent +@node Pragma Ada_83,Pragma Ada_95,Pragma Abstract_State,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-83}@anchor{1d} +@section Pragma Ada_83 + + Syntax: -@smallexample @c ada + +@example pragma Ada_83; -@end smallexample +@end example -@noindent A configuration pragma that establishes Ada 83 mode for the unit to which it applies, regardless of the mode set by the command line switches. In Ada 83 mode, GNAT attempts to be as compatible with @@ -1210,7 +1364,7 @@ the syntax and semantics of Ada 83, as defined in the original Ada 83 Reference Manual as possible. In particular, the keywords added by Ada 95 and Ada 2005 are not recognized, optional package bodies are allowed, and generics may name types with unknown discriminants without using -the @code{(<>)} notation. In addition, some but not all of the additional +the @cite{(<>)} notation. In addition, some but not all of the additional restrictions of Ada 83 are enforced. Ada 83 mode is intended for two purposes. Firstly, it allows existing @@ -1221,35 +1375,37 @@ by GNAT in Ada 83 mode will in fact compile and execute with an Ada 83 compiler, since GNAT does not enforce all the additional checks required by Ada 83. -@node Pragma Ada_95 -@unnumberedsec Pragma Ada_95 -@findex Ada_95 -@noindent +@node Pragma Ada_95,Pragma Ada_05,Pragma Ada_83,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-95}@anchor{1e} +@section Pragma Ada_95 + + Syntax: -@smallexample @c ada + +@example pragma Ada_95; -@end smallexample +@end example -@noindent A configuration pragma that establishes Ada 95 mode for the unit to which it applies, regardless of the mode set by the command line switches. -This mode is set automatically for the @code{Ada} and @code{System} +This mode is set automatically for the @cite{Ada} and @cite{System} packages and their children, so you need not specify it in these contexts. This pragma is useful when writing a reusable component that itself uses Ada 95 features, but which is intended to be usable from either Ada 83 or Ada 95 programs. -@node Pragma Ada_05 -@unnumberedsec Pragma Ada_05 -@findex Ada_05 -@noindent +@node Pragma Ada_05,Pragma Ada_2005,Pragma Ada_95,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-05}@anchor{1f} +@section Pragma Ada_05 + + Syntax: -@smallexample @c ada + +@example pragma Ada_05; pragma Ada_05 (local_NAME); -@end smallexample +@end example -@noindent A configuration pragma that establishes Ada 2005 mode for the unit to which it applies, regardless of the mode set by the command line switches. This pragma is useful when writing a reusable component that @@ -1267,33 +1423,35 @@ extra subprograms marked this way from generating ambiguities in otherwise legal pre-Ada_2005 programs. The one argument form is intended for exclusive use in the GNAT run-time library. -@node Pragma Ada_2005 -@unnumberedsec Pragma Ada_2005 -@findex Ada_2005 -@noindent +@node Pragma Ada_2005,Pragma Ada_12,Pragma Ada_05,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2005}@anchor{20} +@section Pragma Ada_2005 + + Syntax: -@smallexample @c ada + +@example pragma Ada_2005; -@end smallexample +@end example -@noindent This configuration pragma is a synonym for pragma Ada_05 and has the same syntax and effect. -@node Pragma Ada_12 -@unnumberedsec Pragma Ada_12 -@findex Ada_12 -@noindent +@node Pragma Ada_12,Pragma Ada_2012,Pragma Ada_2005,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-12}@anchor{21} +@section Pragma Ada_12 + + Syntax: -@smallexample @c ada + +@example pragma Ada_12; pragma Ada_12 (local_NAME); -@end smallexample +@end example -@noindent A configuration pragma that establishes Ada 2012 mode for the unit to which it applies, regardless of the mode set by the command line switches. -This mode is set automatically for the @code{Ada} and @code{System} +This mode is set automatically for the @cite{Ada} and @cite{System} packages and their children, so you need not specify it in these contexts. This pragma is useful when writing a reusable component that itself uses Ada 2012 features, but which is intended to be usable from @@ -1310,42 +1468,44 @@ extra subprograms marked this way from generating ambiguities in otherwise legal pre-Ada_2012 programs. The one argument form is intended for exclusive use in the GNAT run-time library. -@node Pragma Ada_2012 -@unnumberedsec Pragma Ada_2012 -@findex Ada_2005 -@noindent +@node Pragma Ada_2012,Pragma Allow_Integer_Address,Pragma Ada_12,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ada-2012}@anchor{22} +@section Pragma Ada_2012 + + Syntax: -@smallexample @c ada + +@example pragma Ada_2012; -@end smallexample +@end example -@noindent This configuration pragma is a synonym for pragma Ada_12 and has the same syntax and effect. -@node Pragma Allow_Integer_Address -@unnumberedsec Pragma Allow_Integer_Address -@findex Allow_Integer_Address -@noindent +@node Pragma Allow_Integer_Address,Pragma Annotate,Pragma Ada_2012,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-allow-integer-address}@anchor{23} +@section Pragma Allow_Integer_Address + + Syntax: -@smallexample @c ada + +@example pragma Allow_Integer_Address; -@end smallexample +@end example -@noindent -In almost all versions of GNAT, @code{System.Address} is a private +In almost all versions of GNAT, @cite{System.Address} is a private type in accordance with the implementation advice in the RM. This means that integer values, in particular integer literals, are not allowed as address values. If the configuration pragma -@code{Allow_Integer_Address} is given, then integer expressions may -be used anywhere a value of type @code{System.Address} is required. +@cite{Allow_Integer_Address} is given, then integer expressions may +be used anywhere a value of type @cite{System.Address} is required. The effect is to introduce an implicit unchecked conversion from the -integer value to type @code{System.Address}. The reverse case of using +integer value to type @cite{System.Address}. The reverse case of using an address where an integer type is required is handled analogously. The following example compiles without errors: -@smallexample @c ada +@example pragma Allow_Integer_Address; with System; use System; package AddrAsInt is @@ -1363,101 +1523,99 @@ package AddrAsInt is Z : Integer; for Z'Address use RR; end AddrAsInt; -@end smallexample - -@noindent -Note that pragma @code{Allow_Integer_Address} is ignored if -@code{System.Address} -is not a private type. In implementations of @code{GNAT} where -System.Address is a visible integer type (notably the implementations -for @code{OpenVMS}), this pragma serves no purpose but is ignored +@end example + +Note that pragma @cite{Allow_Integer_Address} is ignored if @cite{System.Address} +is not a private type. In implementations of @cite{GNAT} where +System.Address is a visible integer type, +this pragma serves no purpose but is ignored rather than rejected to allow common sets of sources to be used in the two situations. -@node Pragma Annotate -@unnumberedsec Pragma Annotate -@findex Annotate -@noindent +@node Pragma Annotate,Pragma Assert,Pragma Allow_Integer_Address,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-annotate}@anchor{24} +@section Pragma Annotate + + Syntax: -@smallexample @c ada + +@example pragma Annotate (IDENTIFIER [, IDENTIFIER @{, ARG@}] [, entity => local_NAME]); ARG ::= NAME | EXPRESSION -@end smallexample +@end example -@noindent -This pragma is used to annotate programs. @var{identifier} identifies +This pragma is used to annotate programs. @cite{identifier} identifies the type of annotation. GNAT verifies that it is an identifier, but does not otherwise analyze it. The second optional identifier is also left unanalyzed, and by convention is used to control the action of the tool to -which the annotation is addressed. The remaining @var{arg} arguments +which the annotation is addressed. The remaining @cite{arg} arguments can be either string literals or more generally expressions. String literals are assumed to be either of type -@code{Standard.String} or else @code{Wide_String} or @code{Wide_Wide_String} +@cite{Standard.String} or else @cite{Wide_String} or @cite{Wide_Wide_String} depending on the character literals they contain. All other kinds of arguments are analyzed as expressions, and must be unambiguous. The last argument if present must have the identifier -@code{Entity} and GNAT verifies that a local name is given. +@cite{Entity} and GNAT verifies that a local name is given. The analyzed pragma is retained in the tree, but not otherwise processed by any part of the GNAT compiler, except to generate corresponding note lines in the generated ALI file. For the format of these note lines, see the compiler source file lib-writ.ads. This pragma is intended for use by -external tools, including ASIS@. The use of pragma Annotate does not +external tools, including ASIS. The use of pragma Annotate does not affect the compilation process in any way. This pragma may be used as a configuration pragma. -@node Pragma Assert -@unnumberedsec Pragma Assert -@findex Assert -@noindent +@node Pragma Assert,Pragma Assert_And_Cut,Pragma Annotate,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-assert}@anchor{25} +@section Pragma Assert + + Syntax: -@smallexample @c ada + +@example pragma Assert ( boolean_EXPRESSION [, string_EXPRESSION]); -@end smallexample +@end example -@noindent The effect of this pragma depends on whether the corresponding command line switch is set to activate assertions. The pragma expands into code equivalent to the following: -@smallexample @c ada +@example if assertions-enabled then if not boolean_EXPRESSION then System.Assertions.Raise_Assert_Failure (string_EXPRESSION); end if; end if; -@end smallexample +@end example -@noindent The string argument, if given, is the message that will be associated with the exception occurrence if the exception is raised. If no second -argument is given, the default message is @samp{@var{file}:@var{nnn}}, -where @var{file} is the name of the source file containing the assert, -and @var{nnn} is the line number of the assert. A pragma is not a +argument is given, the default message is @cite{file}:@cite{nnn}, +where @cite{file} is the name of the source file containing the assert, +and @cite{nnn} is the line number of the assert. A pragma is not a statement, so if a statement sequence contains nothing but a pragma assert, then a null statement is required in addition, as in: -@smallexample @c ada -@dots{} +@example +... if J > 3 then pragma Assert (K > 3, "Bad value for K"); null; end if; -@end smallexample +@end example -@noindent -Note that, as with the @code{if} statement to which it is equivalent, the -type of the expression is either @code{Standard.Boolean}, or any type derived +Note that, as with the @cite{if} statement to which it is equivalent, the +type of the expression is either @cite{Standard.Boolean}, or any type derived from this standard type. Assert checks can be either checked or ignored. By default they are ignored. -They will be checked if either the command line switch @option{-gnata} is -used, or if an @code{Assertion_Policy} or @code{Check_Policy} pragma is used -to enable @code{Assert_Checks}. +They will be checked if either the command line switch @emph{-gnata} is +used, or if an @cite{Assertion_Policy} or @cite{Check_Policy} pragma is used +to enable @cite{Assert_Checks}. If assertions are ignored, then there is no run-time effect (and in particular, any side effects from the @@ -1466,8 +1624,8 @@ analyzed at compile time, and may cause types to be frozen if they are mentioned here for the first time). If assertions are checked, then the given expression is tested, and if -it is @code{False} then @code{System.Assertions.Raise_Assert_Failure} is called -which results in the raising of @code{Assert_Failure} with the given message. +it is @cite{False} then @cite{System.Assertions.Raise_Assert_Failure} is called +which results in the raising of @cite{Assert_Failure} with the given message. You should generally avoid side effects in the expression arguments of this pragma, because these side effects will turn on and off with the @@ -1476,29 +1634,30 @@ effect on the program. However, the expressions are analyzed for semantic correctness whether or not assertions are enabled, so turning assertions on and off cannot affect the legality of a program. -Note that the implementation defined policy @code{DISABLE}, given in a -pragma @code{Assertion_Policy}, can be used to suppress this semantic analysis. +Note that the implementation defined policy @cite{DISABLE}, given in a +pragma @cite{Assertion_Policy}, can be used to suppress this semantic analysis. Note: this is a standard language-defined pragma in versions of Ada from 2005 on. In GNAT, it is implemented in all versions of Ada, and the DISABLE policy is an implementation-defined addition. -@node Pragma Assert_And_Cut -@unnumberedsec Pragma Assert_And_Cut -@findex Assert_And_Cut -@noindent +@node Pragma Assert_And_Cut,Pragma Assertion_Policy,Pragma Assert,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-assert-and-cut}@anchor{26} +@section Pragma Assert_And_Cut + + Syntax: -@smallexample @c ada + +@example pragma Assert_And_Cut ( boolean_EXPRESSION [, string_EXPRESSION]); -@end smallexample +@end example -@noindent -The effect of this pragma is identical to that of pragma @code{Assert}, -except that in an @code{Assertion_Policy} pragma, the identifier -@code{Assert_And_Cut} is used to control whether it is ignored or checked +The effect of this pragma is identical to that of pragma @cite{Assert}, +except that in an @cite{Assertion_Policy} pragma, the identifier +@cite{Assert_And_Cut} is used to control whether it is ignored or checked (or disabled). The intention is that this be used within a subprogram when the @@ -1510,12 +1669,14 @@ a subprogram into sections for the purposes of testing or formal verification. The pragma also serves as useful documentation. -@node Pragma Assertion_Policy -@unnumberedsec Pragma Assertion_Policy -@findex Assertion_Policy -@noindent +@node Pragma Assertion_Policy,Pragma Assume,Pragma Assert_And_Cut,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-assertion-policy}@anchor{27} +@section Pragma Assertion_Policy + + Syntax: -@smallexample @c ada + +@example pragma Assertion_Policy (CHECK | DISABLE | IGNORE); pragma Assertion_Policy ( @@ -1550,61 +1711,61 @@ ID_ASSERTION_KIND ::= Assertions | Statement_Assertions POLICY_IDENTIFIER ::= Check | Disable | Ignore -@end smallexample +@end example -@noindent This is a standard Ada 2012 pragma that is available as an implementation-defined pragma in earlier versions of Ada. -The assertion kinds @code{RM_ASSERTION_KIND} are those defined in -the Ada standard. The assertion kinds @code{ID_ASSERTION_KIND} +The assertion kinds @cite{RM_ASSERTION_KIND} are those defined in +the Ada standard. The assertion kinds @cite{ID_ASSERTION_KIND} are implementation defined additions recognized by the GNAT compiler. The pragma applies in both cases to pragmas and aspects with matching -names, e.g. @code{Pre} applies to the Pre aspect, and @code{Precondition} -applies to both the @code{Precondition} pragma -and the aspect @code{Precondition}. Note that the identifiers for +names, e.g. @cite{Pre} applies to the Pre aspect, and @cite{Precondition} +applies to both the @cite{Precondition} pragma +and the aspect @cite{Precondition}. Note that the identifiers for pragmas Pre_Class and Post_Class are Pre'Class and Post'Class (not Pre_Class and Post_Class), since these pragmas are intended to be identical to the corresponding aspects). -If the policy is @code{CHECK}, then assertions are enabled, i.e. +If the policy is @cite{CHECK}, then assertions are enabled, i.e. the corresponding pragma or aspect is activated. -If the policy is @code{IGNORE}, then assertions are ignored, i.e. +If the policy is @cite{IGNORE}, then assertions are ignored, i.e. the corresponding pragma or aspect is deactivated. -This pragma overrides the effect of the @option{-gnata} switch on the +This pragma overrides the effect of the @emph{-gnata} switch on the command line. -The implementation defined policy @code{DISABLE} is like -@code{IGNORE} except that it completely disables semantic +The implementation defined policy @cite{DISABLE} is like +@cite{IGNORE} except that it completely disables semantic checking of the corresponding pragma or aspect. This is useful when the pragma or aspect argument references subprograms in a with'ed package which is replaced by a dummy package for the final build. -The implementation defined assertion kind @code{Assertions} applies to all +The implementation defined assertion kind @cite{Assertions} applies to all assertion kinds. The form with no assertion kind given implies this choice, so it applies to all assertion kinds (RM defined, and implementation defined). -The implementation defined assertion kind @code{Statement_Assertions} -applies to @code{Assert}, @code{Assert_And_Cut}, -@code{Assume}, @code{Loop_Invariant}, and @code{Loop_Variant}. +The implementation defined assertion kind @cite{Statement_Assertions} +applies to @cite{Assert}, @cite{Assert_And_Cut}, +@cite{Assume}, @cite{Loop_Invariant}, and @cite{Loop_Variant}. + +@node Pragma Assume,Pragma Assume_No_Invalid_Values,Pragma Assertion_Policy,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-assume}@anchor{28} +@section Pragma Assume + -@node Pragma Assume -@unnumberedsec Pragma Assume -@findex Assume -@noindent Syntax: -@smallexample @c ada + +@example pragma Assume ( boolean_EXPRESSION [, string_EXPRESSION]); -@end smallexample +@end example -@noindent -The effect of this pragma is identical to that of pragma @code{Assert}, -except that in an @code{Assertion_Policy} pragma, the identifier -@code{Assume} is used to control whether it is ignored or checked +The effect of this pragma is identical to that of pragma @cite{Assert}, +except that in an @cite{Assertion_Policy} pragma, the identifier +@cite{Assume} is used to control whether it is ignored or checked (or disabled). The intention is that this be used for assumptions about the @@ -1612,30 +1773,32 @@ external environment. So you cannot expect to verify formally or informally that the condition is met, this must be established by examining things outside the program itself. For example, we may have code that depends on the size of -@code{Long_Long_Integer} being at least 64. So we could write: +@cite{Long_Long_Integer} being at least 64. So we could write: -@smallexample @c ada +@example pragma Assume (Long_Long_Integer'Size >= 64); -@end smallexample +@end example -@noindent This assumption cannot be proved from the program itself, but it acts as a useful run-time check that the assumption is met, and documents the need to ensure that it is met by reference to information outside the program. -@node Pragma Assume_No_Invalid_Values -@unnumberedsec Pragma Assume_No_Invalid_Values -@findex Assume_No_Invalid_Values -@cindex Invalid representations -@cindex Invalid values -@noindent +@node Pragma Assume_No_Invalid_Values,Pragma Async_Readers,Pragma Assume,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-assume-no-invalid-values}@anchor{29} +@section Pragma Assume_No_Invalid_Values + + +@geindex Invalid representations + +@geindex Invalid values + Syntax: -@smallexample @c ada + +@example pragma Assume_No_Invalid_Values (On | Off); -@end smallexample +@end example -@noindent This is a configuration pragma that controls the assumptions made by the compiler about the occurrence of invalid representations (invalid values) in the code. @@ -1644,25 +1807,24 @@ The default behavior (corresponding to an Off argument for this pragma), is to assume that values may in general be invalid unless the compiler can prove they are valid. Consider the following example: -@smallexample @c ada +@example V1 : Integer range 1 .. 10; V2 : Integer range 11 .. 20; ... for J in V2 .. V1 loop ... end loop; -@end smallexample +@end example -@noindent if V1 and V2 have valid values, then the loop is known at compile time not to execute since the lower bound must be greater than the upper bound. However in default mode, no such assumption is made, -and the loop may execute. If @code{Assume_No_Invalid_Values (On)} +and the loop may execute. If @cite{Assume_No_Invalid_Values (On)} is given, the compiler will assume that any occurrence of a variable -other than in an explicit @code{'Valid} test always has a valid +other than in an explicit @cite{'Valid} test always has a valid value, and the loop above will be optimized away. -The use of @code{Assume_No_Invalid_Values (On)} is appropriate if +The use of @cite{Assume_No_Invalid_Values (On)} is appropriate if you know your code is free of uninitialized variables and other possible sources of invalid representations, and may result in more efficient code. A program that accesses an invalid representation @@ -1675,114 +1837,104 @@ values will generally give an exception, though formally the program is erroneous so there are no guarantees that this will always be the case, and it is recommended that these two options not be used together. -@node Pragma Async_Readers -@unnumberedsec Pragma Async_Readers -@findex Async_Readers -@noindent +@node Pragma Async_Readers,Pragma Async_Writers,Pragma Assume_No_Invalid_Values,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-async-readers}@anchor{2a} +@section Pragma Async_Readers + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.2. -@node Pragma Async_Writers -@unnumberedsec Pragma Async_Writers -@findex Async_Writers -@noindent +@node Pragma Async_Writers,Pragma Attribute_Definition,Pragma Async_Readers,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-async-writers}@anchor{2b} +@section Pragma Async_Writers + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.2. -@node Pragma AST_Entry -@unnumberedsec Pragma AST_Entry -@cindex OpenVMS -@findex AST_Entry -@noindent -Syntax: -@smallexample @c ada -pragma AST_Entry (entry_IDENTIFIER); -@end smallexample - -@noindent -This pragma is implemented only in the OpenVMS implementation of GNAT@. The -argument is the simple name of a single entry; at most one @code{AST_Entry} -pragma is allowed for any given entry. This pragma must be used in -conjunction with the @code{AST_Entry} attribute, and is only allowed after -the entry declaration and in the same task type specification or single task -as the entry to which it applies. This pragma specifies that the given entry -may be used to handle an OpenVMS asynchronous system trap (@code{AST}) -resulting from an OpenVMS system service call. The pragma does not affect -normal use of the entry. For further details on this pragma, see the -DEC Ada Language Reference Manual, section 9.12a. - -@node Pragma Attribute_Definition -@unnumberedsec Pragma Attribute_Definition -@findex Attribute_Definition -@noindent +@node Pragma Attribute_Definition,Pragma C_Pass_By_Copy,Pragma Async_Writers,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-attribute-definition}@anchor{2c} +@section Pragma Attribute_Definition + + Syntax: -@smallexample @c ada + +@example pragma Attribute_Definition ([Attribute =>] ATTRIBUTE_DESIGNATOR, [Entity =>] LOCAL_NAME, [Expression =>] EXPRESSION | NAME); -@end smallexample +@end example -@noindent -If @code{Attribute} is a known attribute name, this pragma is equivalent to +If @cite{Attribute} is a known attribute name, this pragma is equivalent to the attribute definition clause: -@smallexample @c ada - for Entity'Attribute use Expression; -@end smallexample +@example +for Entity'Attribute use Expression; +@end example -If @code{Attribute} is not a recognized attribute name, the pragma is +If @cite{Attribute} is not a recognized attribute name, the pragma is ignored, and a warning is emitted. This allows source code to be written that takes advantage of some new attribute, while remaining compilable with earlier compilers. -@node Pragma C_Pass_By_Copy -@unnumberedsec Pragma C_Pass_By_Copy -@cindex Passing by copy -@findex C_Pass_By_Copy -@noindent +@node Pragma C_Pass_By_Copy,Pragma Check,Pragma Attribute_Definition,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-c-pass-by-copy}@anchor{2d} +@section Pragma C_Pass_By_Copy + + +@geindex Passing by copy + Syntax: -@smallexample @c ada + +@example pragma C_Pass_By_Copy ([Max_Size =>] static_integer_EXPRESSION); -@end smallexample +@end example -@noindent Normally the default mechanism for passing C convention records to C convention subprograms is to pass them by reference, as suggested by RM -B.3(69). Use the configuration pragma @code{C_Pass_By_Copy} to change +B.3(69). Use the configuration pragma @cite{C_Pass_By_Copy} to change this default, by requiring that record formal parameters be passed by copy if all of the following conditions are met: -@itemize @bullet -@item + +@itemize * + +@item The size of the record type does not exceed the value specified for -@code{Max_Size}. -@item -The record type has @code{Convention C}. -@item +@cite{Max_Size}. + +@item +The record type has @cite{Convention C}. + +@item The formal parameter has this record type, and the subprogram has a foreign (non-Ada) convention. @end itemize -@noindent -If these conditions are met the argument is passed by copy, i.e.@: in a +If these conditions are met the argument is passed by copy; i.e., in a manner consistent with what C expects if the corresponding formal in the C prototype is a struct (rather than a pointer to a struct). You can also pass records by copy by specifying the convention -@code{C_Pass_By_Copy} for the record type, or by using the extended -@code{Import} and @code{Export} pragmas, which allow specification of +@cite{C_Pass_By_Copy} for the record type, or by using the extended +@cite{Import} and @cite{Export} pragmas, which allow specification of passing mechanisms on a parameter by parameter basis. -@node Pragma Check -@unnumberedsec Pragma Check -@cindex Assertions -@cindex Named assertions -@findex Check -@noindent +@node Pragma Check,Pragma Check_Float_Overflow,Pragma C_Pass_By_Copy,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-check}@anchor{2e} +@section Pragma Check + + +@geindex Assertions + +@geindex Named assertions + Syntax: -@smallexample @c ada + +@example pragma Check ( [Name =>] CHECK_KIND, [Check =>] Boolean_EXPRESSION @@ -1793,37 +1945,38 @@ CHECK_KIND ::= IDENTIFIER | Post'Class | Type_Invariant'Class | Invariant'Class -@end smallexample +@end example -@noindent -This pragma is similar to the predefined pragma @code{Assert} except that an +This pragma is similar to the predefined pragma @cite{Assert} except that an extra identifier argument is present. In conjunction with pragma -@code{Check_Policy}, this can be used to define groups of assertions that can -be independently controlled. The identifier @code{Assertion} is special, it -refers to the normal set of pragma @code{Assert} statements. +@cite{Check_Policy}, this can be used to define groups of assertions that can +be independently controlled. The identifier @cite{Assertion} is special, it +refers to the normal set of pragma @cite{Assert} statements. Checks introduced by this pragma are normally deactivated by default. They can -be activated either by the command line option @option{-gnata}, which turns on -all checks, or individually controlled using pragma @code{Check_Policy}. +be activated either by the command line option @emph{-gnata}, which turns on +all checks, or individually controlled using pragma @cite{Check_Policy}. -The identifiers @code{Assertions} and @code{Statement_Assertions} are not +The identifiers @cite{Assertions} and @cite{Statement_Assertions} are not permitted as check kinds, since this would cause confusion with the use -of these identifiers in @code{Assertion_Policy} and @code{Check_Policy} +of these identifiers in @cite{Assertion_Policy} and @cite{Check_Policy} pragmas, where they are used to refer to sets of assertions. -@node Pragma Check_Float_Overflow -@unnumberedsec Pragma Check_Float_Overflow -@cindex Floating-point overflow -@findex Check_Float_Overflow -@noindent +@node Pragma Check_Float_Overflow,Pragma Check_Name,Pragma Check,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-check-float-overflow}@anchor{2f} +@section Pragma Check_Float_Overflow + + +@geindex Floating-point overflow + Syntax: -@smallexample @c ada + +@example pragma Check_Float_Overflow; -@end smallexample +@end example -@noindent -In Ada, the predefined floating-point types (@code{Short_Float}, -@code{Float}, @code{Long_Float}, @code{Long_Long_Float}) are +In Ada, the predefined floating-point types (@cite{Short_Float}, +@cite{Float}, @cite{Long_Float}, @cite{Long_Long_Float}) are defined to be @emph{unconstrained}. This means that even though each has a well-defined base range, an operation that delivers a result outside this base range is not required to raise an exception. @@ -1840,44 +1993,47 @@ This can be accomplished by defining your own constrained floating-point subtype range constraints -- and indeed such a subtype can have the same base range as its base type. For example: -@smallexample @c ada +@example subtype My_Float is Float range Float'Range; -@end smallexample +@end example -@noindent -Here @code{My_Float} has the same range as -@code{Float} but is constrained, so operations on -@code{My_Float} values will be checked for overflow +Here @cite{My_Float} has the same range as +@cite{Float} but is constrained, so operations on +@cite{My_Float} values will be checked for overflow against this range. This style will achieve the desired goal, but it is often more convenient to be able to simply use the standard predefined floating-point types as long as overflow checking could be guaranteed. -The @code{Check_Float_Overflow} +The @cite{Check_Float_Overflow} configuration pragma achieves this effect. If a unit is compiled subject to this configuration pragma, then all operations on predefined floating-point types including operations on base types of these floating-point types will be treated as though those types were constrained, and overflow checks -will be generated. The @code{Constraint_Error} +will be generated. The @cite{Constraint_Error} exception is raised if the result is out of range. This mode can also be set by use of the compiler -switch @option{-gnateF}. - -@node Pragma Check_Name -@unnumberedsec Pragma Check_Name -@cindex Defining check names -@cindex Check names, defining -@findex Check_Name -@noindent +switch @emph{-gnateF}. + +@node Pragma Check_Name,Pragma Check_Policy,Pragma Check_Float_Overflow,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-check-name}@anchor{30} +@section Pragma Check_Name + + +@geindex Defining check names + +@geindex Check names +@geindex defining + Syntax: -@smallexample @c ada + +@example pragma Check_Name (check_name_IDENTIFIER); -@end smallexample +@end example -@noindent This is a configuration pragma that defines a new implementation defined check name (unless IDENTIFIER matches one of the predefined check names, in which case the pragma has no effect). Check names @@ -1886,28 +2042,35 @@ are present in a partition mentioning the same name, only one new check name is introduced. An implementation defined check name introduced with this pragma may -be used in only three contexts: @code{pragma Suppress}, -@code{pragma Unsuppress}, -and as the prefix of a @code{Check_Name'Enabled} attribute reference. For +be used in only three contexts: @cite{pragma Suppress}, +@cite{pragma Unsuppress}, +and as the prefix of a @cite{Check_Name'Enabled} attribute reference. For any of these three cases, the check name must be visible. A check name is visible if it is in the configuration pragmas applying to the current unit, or if it appears at the start of any unit that is part of the dependency set of the current unit (e.g., units that -are mentioned in @code{with} clauses). +are mentioned in @cite{with} clauses). Check names introduced by this pragma are subject to control by compiler switches (in particular -gnatp) in the usual manner. -@node Pragma Check_Policy -@unnumberedsec Pragma Check_Policy -@cindex Controlling assertions -@cindex Assertions, control -@cindex Check pragma control -@cindex Named assertions -@findex Check -@noindent +@node Pragma Check_Policy,Pragma CIL_Constructor,Pragma Check_Name,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-check-policy}@anchor{31} +@section Pragma Check_Policy + + +@geindex Controlling assertions + +@geindex Assertions +@geindex control + +@geindex Check pragma control + +@geindex Named assertions + Syntax: -@smallexample @c ada + +@example pragma Check_Policy ([Name =>] CHECK_KIND, [Policy =>] POLICY_IDENTIFIER); @@ -1928,95 +2091,94 @@ The identifiers Name and Policy are not allowed as CHECK_KIND values. This avoids confusion between the two possible syntax forms for this pragma. POLICY_IDENTIFIER ::= ON | OFF | CHECK | DISABLE | IGNORE -@end smallexample +@end example -@noindent This pragma is used to set the checking policy for assertions (specified -by aspects or pragmas), the @code{Debug} pragma, or additional checks -to be checked using the @code{Check} pragma. It may appear either as +by aspects or pragmas), the @cite{Debug} pragma, or additional checks +to be checked using the @cite{Check} pragma. It may appear either as a configuration pragma, or within a declarative part of package. In the latter case, it applies from the point where it appears to the end of -the declarative region (like pragma @code{Suppress}). +the declarative region (like pragma @cite{Suppress}). -The @code{Check_Policy} pragma is similar to the -predefined @code{Assertion_Policy} pragma, +The @cite{Check_Policy} pragma is similar to the +predefined @cite{Assertion_Policy} pragma, and if the check kind corresponds to one of the assertion kinds that -are allowed by @code{Assertion_Policy}, then the effect is identical. +are allowed by @cite{Assertion_Policy}, then the effect is identical. If the first argument is Debug, then the policy applies to Debug pragmas, -disabling their effect if the policy is @code{OFF}, @code{DISABLE}, or -@code{IGNORE}, and allowing them to execute with normal semantics if -the policy is @code{ON} or @code{CHECK}. In addition if the policy is -@code{DISABLE}, then the procedure call in @code{Debug} pragmas will +disabling their effect if the policy is @cite{OFF}, @cite{DISABLE}, or +@cite{IGNORE}, and allowing them to execute with normal semantics if +the policy is @cite{ON} or @cite{CHECK}. In addition if the policy is +@cite{DISABLE}, then the procedure call in @cite{Debug} pragmas will be totally ignored and not analyzed semantically. Finally the first argument may be some other identifier than the above possibilities, in which case it controls a set of named assertions -that can be checked using pragma @code{Check}. For example, if the pragma: +that can be checked using pragma @cite{Check}. For example, if the pragma: -@smallexample @c ada +@example pragma Check_Policy (Critical_Error, OFF); -@end smallexample +@end example -@noindent -is given, then subsequent @code{Check} pragmas whose first argument is also -@code{Critical_Error} will be disabled. +is given, then subsequent @cite{Check} pragmas whose first argument is also +@cite{Critical_Error} will be disabled. -The check policy is @code{OFF} to turn off corresponding checks, and @code{ON} +The check policy is @cite{OFF} to turn off corresponding checks, and @cite{ON} to turn on corresponding checks. The default for a set of checks for which no -@code{Check_Policy} is given is @code{OFF} unless the compiler switch -@option{-gnata} is given, which turns on all checks by default. - -The check policy settings @code{CHECK} and @code{IGNORE} are recognized -as synonyms for @code{ON} and @code{OFF}. These synonyms are provided for -compatibility with the standard @code{Assertion_Policy} pragma. The check -policy setting @code{DISABLE} causes the second argument of a corresponding -@code{Check} pragma to be completely ignored and not analyzed. - -@node Pragma CIL_Constructor -@unnumberedsec Pragma CIL_Constructor -@findex CIL_Constructor -@noindent +@cite{Check_Policy} is given is @cite{OFF} unless the compiler switch +@emph{-gnata} is given, which turns on all checks by default. + +The check policy settings @cite{CHECK} and @cite{IGNORE} are recognized +as synonyms for @cite{ON} and @cite{OFF}. These synonyms are provided for +compatibility with the standard @cite{Assertion_Policy} pragma. The check +policy setting @cite{DISABLE} causes the second argument of a corresponding +@cite{Check} pragma to be completely ignored and not analyzed. + +@node Pragma CIL_Constructor,Pragma Comment,Pragma Check_Policy,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cil-constructor}@anchor{32} +@section Pragma CIL_Constructor + + Syntax: -@smallexample @c ada +@example pragma CIL_Constructor ([Entity =>] function_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma is used to assert that the specified Ada function should be mapped to the .NET constructor for some Ada tagged record type. See section 4.1 of the -@code{GNAT User's Guide: Supplement for the .NET Platform.} +@cite{GNAT User's Guide: Supplement for the .NET Platform.} for related information. -@node Pragma Comment -@unnumberedsec Pragma Comment -@findex Comment -@noindent +@node Pragma Comment,Pragma Common_Object,Pragma CIL_Constructor,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-comment}@anchor{33} +@section Pragma Comment + + Syntax: -@smallexample @c ada +@example pragma Comment (static_string_EXPRESSION); -@end smallexample +@end example -@noindent -This is almost identical in effect to pragma @code{Ident}. It allows the +This is almost identical in effect to pragma @cite{Ident}. It allows the placement of a comment into the object file and hence into the executable file if the operating system permits such usage. The -difference is that @code{Comment}, unlike @code{Ident}, has +difference is that @cite{Comment}, unlike @cite{Ident}, has no limitations on placement of the pragma (it can be placed anywhere in the main source unit), and if more than one pragma is used, all comments are retained. -@node Pragma Common_Object -@unnumberedsec Pragma Common_Object -@findex Common_Object -@noindent +@node Pragma Common_Object,Pragma Compile_Time_Error,Pragma Comment,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-common-object}@anchor{34} +@section Pragma Common_Object + + Syntax: -@smallexample @c ada +@example pragma Common_Object ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -2025,35 +2187,34 @@ pragma Common_Object ( EXTERNAL_SYMBOL ::= IDENTIFIER | static_string_EXPRESSION -@end smallexample +@end example -@noindent This pragma enables the shared use of variables stored in overlaid -linker areas corresponding to the use of @code{COMMON} +linker areas corresponding to the use of @cite{COMMON} in Fortran. The single -object @var{LOCAL_NAME} is assigned to the area designated by -the @var{External} argument. +object @cite{LOCAL_NAME} is assigned to the area designated by +the @cite{External} argument. You may define a record to correspond to a series -of fields. The @var{Size} argument +of fields. The @cite{Size} argument is syntax checked in GNAT, but otherwise ignored. -@code{Common_Object} is not supported on all platforms. If no +@cite{Common_Object} is not supported on all platforms. If no support is available, then the code generator will issue a message indicating that the necessary attribute for implementation of this pragma is not available. -@node Pragma Compile_Time_Error -@unnumberedsec Pragma Compile_Time_Error -@findex Compile_Time_Error -@noindent +@node Pragma Compile_Time_Error,Pragma Compile_Time_Warning,Pragma Common_Object,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-error}@anchor{35} +@section Pragma Compile_Time_Error + + Syntax: -@smallexample @c ada +@example pragma Compile_Time_Error (boolean_EXPRESSION, static_string_EXPRESSION); -@end smallexample +@end example -@noindent This pragma can be used to generate additional compile time error messages. It is particularly useful in generics, where errors can be issued for @@ -2069,18 +2230,18 @@ If these conditions are met, an error message is generated using the value given as the second argument. This string value may contain embedded ASCII.LF characters to break the message into multiple lines. -@node Pragma Compile_Time_Warning -@unnumberedsec Pragma Compile_Time_Warning -@findex Compile_Time_Warning -@noindent +@node Pragma Compile_Time_Warning,Pragma Compiler_Unit,Pragma Compile_Time_Error,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-compile-time-warning}@anchor{36} +@section Pragma Compile_Time_Warning + + Syntax: -@smallexample @c ada +@example pragma Compile_Time_Warning (boolean_EXPRESSION, static_string_EXPRESSION); -@end smallexample +@end example -@noindent Same as pragma Compile_Time_Error, except a warning is issued instead of an error message. Note that if this pragma is used in a package that is with'ed by a client, the client will get the warning even though it @@ -2092,32 +2253,32 @@ of formal parameters are tested, and warnings given appropriately. Another use with a first parameter of True is to warn a client about use of a package, for example that it is not fully implemented. -@node Pragma Compiler_Unit -@unnumberedsec Pragma Compiler_Unit -@findex Compiler_Unit -@noindent +@node Pragma Compiler_Unit,Pragma Compiler_Unit_Warning,Pragma Compile_Time_Warning,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit}@anchor{37} +@section Pragma Compiler_Unit + + Syntax: -@smallexample @c ada +@example pragma Compiler_Unit; -@end smallexample +@end example -@noindent This pragma is obsolete. It is equivalent to Compiler_Unit_Warning. It is retained so that old versions of the GNAT run-time that use this pragma can be compiled with newer versions of the compiler. -@node Pragma Compiler_Unit_Warning -@unnumberedsec Pragma Compiler_Unit_Warning -@findex Compiler_Unit_Warning -@noindent +@node Pragma Compiler_Unit_Warning,Pragma Complete_Representation,Pragma Compiler_Unit,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-compiler-unit-warning}@anchor{38} +@section Pragma Compiler_Unit_Warning + + Syntax: -@smallexample @c ada +@example pragma Compiler_Unit_Warning; -@end smallexample +@end example -@noindent This pragma is intended only for internal use in the GNAT run-time library. It indicates that the unit is used as part of the compiler build. The effect is to generate warnings for the use of constructs (for example, conditional @@ -2125,17 +2286,17 @@ expressions) that would cause trouble when bootstrapping using an older version of GNAT. For the exact list of restrictions, see the compiler sources and references to Check_Compiler_Unit. -@node Pragma Complete_Representation -@unnumberedsec Pragma Complete_Representation -@findex Complete_Representation -@noindent +@node Pragma Complete_Representation,Pragma Complex_Representation,Pragma Compiler_Unit_Warning,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-complete-representation}@anchor{39} +@section Pragma Complete_Representation + + Syntax: -@smallexample @c ada +@example pragma Complete_Representation; -@end smallexample +@end example -@noindent This pragma must appear immediately within a record representation clause. Typical placements are before the first component clause or after the last component clause. The effect is to give an error @@ -2144,19 +2305,19 @@ may be used to ensure that a record representation clause is complete, and that this invariant is maintained if fields are added to the record in the future. -@node Pragma Complex_Representation -@unnumberedsec Pragma Complex_Representation -@findex Complex_Representation -@noindent +@node Pragma Complex_Representation,Pragma Component_Alignment,Pragma Complete_Representation,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-complex-representation}@anchor{3a} +@section Pragma Complex_Representation + + Syntax: -@smallexample @c ada +@example pragma Complex_Representation ([Entity =>] LOCAL_NAME); -@end smallexample +@end example -@noindent -The @var{Entity} argument must be the name of a record type which has +The @cite{Entity} argument must be the name of a record type which has two fields of the same floating-point type. The effect of this pragma is to force gcc to use the special internal complex representation form for this record, which may be more efficient. Note that this may result in @@ -2166,14 +2327,18 @@ example, in some environments, there is a requirement for passing records by pointer, and the use of this pragma may result in passing this type in floating-point registers. -@node Pragma Component_Alignment -@unnumberedsec Pragma Component_Alignment -@cindex Alignments of components -@findex Component_Alignment -@noindent +@node Pragma Component_Alignment,Pragma Contract_Cases,Pragma Complex_Representation,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-component-alignment}@anchor{3b} +@section Pragma Component_Alignment + + +@geindex Alignments of components + +@geindex Pragma Component_Alignment + Syntax: -@smallexample @c ada +@example pragma Component_Alignment ( [Form =>] ALIGNMENT_CHOICE [, [Name =>] type_LOCAL_NAME]); @@ -2183,55 +2348,64 @@ ALIGNMENT_CHOICE ::= | Component_Size_4 | Storage_Unit | Default -@end smallexample +@end example -@noindent Specifies the alignment of components in array or record types. -The meaning of the @var{Form} argument is as follows: +The meaning of the @cite{Form} argument is as follows: + +@quotation + +@geindex Component_Size (in pragma Component_Alignment) +@end quotation + + +@table @asis + +@item @emph{Component_Size} -@table @code -@findex Component_Size -@item Component_Size Aligns scalar components and subcomponents of the array or record type on boundaries appropriate to their inherent size (naturally aligned). For example, 1-byte components are aligned on byte boundaries, 2-byte integer components are aligned on 2-byte boundaries, 4-byte integer components are aligned on 4-byte boundaries and so on. These alignment rules correspond to the normal rules for C compilers on all -machines except the VAX@. +machines except the VAX. + +@geindex Component_Size_4 (in pragma Component_Alignment) + +@item @emph{Component_Size_4} -@findex Component_Size_4 -@item Component_Size_4 Naturally aligns components with a size of four or fewer bytes. Components that are larger than 4 bytes are placed on the next 4-byte boundary. -@findex Storage_Unit -@item Storage_Unit -Specifies that array or record components are byte aligned, i.e.@: +@geindex Storage_Unit (in pragma Component_Alignment) + +@item @emph{Storage_Unit} + +Specifies that array or record components are byte aligned, i.e., aligned on boundaries determined by the value of the constant -@code{System.Storage_Unit}. +@cite{System.Storage_Unit}. + +@geindex Default (in pragma Component_Alignment) + +@item @emph{Default} -@cindex OpenVMS -@item Default Specifies that array or record components are aligned on default boundaries, appropriate to the underlying hardware or operating system or -both. For OpenVMS VAX systems, the @code{Default} choice is the same as -the @code{Storage_Unit} choice (byte alignment). For all other systems, -the @code{Default} choice is the same as @code{Component_Size} (natural +both. The @cite{Default} choice is the same as @cite{Component_Size} (natural alignment). @end table -@noindent -If the @code{Name} parameter is present, @var{type_LOCAL_NAME} must +If the @cite{Name} parameter is present, @cite{type_LOCAL_NAME} must refer to a local record or array type, and the specified alignment choice applies to the specified type. The use of -@code{Component_Alignment} together with a pragma @code{Pack} causes the -@code{Component_Alignment} pragma to be ignored. The use of -@code{Component_Alignment} together with a record representation clause +@cite{Component_Alignment} together with a pragma @cite{Pack} causes the +@cite{Component_Alignment} pragma to be ignored. The use of +@cite{Component_Alignment} together with a record representation clause is only effective for fields not specified by the representation clause. -If the @code{Name} parameter is absent, the pragma can be used as either +If the @cite{Name} parameter is absent, the pragma can be used as either a configuration pragma, in which case it applies to one or more units in accordance with the normal rules for configuration pragmas, or it can be used within a declarative part, in which case it applies to types that @@ -2241,76 +2415,75 @@ to be applied to any record or array type which has otherwise standard representation. If the alignment for a record or array type is not specified (using -pragma @code{Pack}, pragma @code{Component_Alignment}, or a record rep +pragma @cite{Pack}, pragma @cite{Component_Alignment}, or a record rep clause), the GNAT uses the default alignment as described previously. -@node Pragma Contract_Cases -@unnumberedsec Pragma Contract_Cases -@cindex Contract cases -@findex Contract_Cases -@noindent +@node Pragma Contract_Cases,Pragma Convention_Identifier,Pragma Component_Alignment,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-contract-cases}@anchor{3c} +@section Pragma Contract_Cases + + +@geindex Contract cases + Syntax: -@smallexample @c ada +@example pragma Contract_Cases ( Condition => Consequence @{,Condition => Consequence@}); -@end smallexample +@end example -@noindent -The @code{Contract_Cases} pragma allows defining fine-grain specifications +The @cite{Contract_Cases} pragma allows defining fine-grain specifications that can complement or replace the contract given by a precondition and a -postcondition. Additionally, the @code{Contract_Cases} pragma can be used +postcondition. Additionally, the @cite{Contract_Cases} pragma can be used by testing and formal verification tools. The compiler checks its validity and, depending on the assertion policy at the point of declaration of the pragma, it may insert a check in the executable. For code generation, the contract cases -@smallexample @c ada +@example pragma Contract_Cases ( Cond1 => Pred1, Cond2 => Pred2); -@end smallexample +@end example -@noindent are equivalent to -@smallexample @c ada +@example C1 : constant Boolean := Cond1; -- evaluated at subprogram entry C2 : constant Boolean := Cond2; -- evaluated at subprogram entry pragma Precondition ((C1 and not C2) or (C2 and not C1)); pragma Postcondition (if C1 then Pred1); pragma Postcondition (if C2 then Pred2); -@end smallexample +@end example -@noindent The precondition ensures that one and only one of the conditions is satisfied on entry to the subprogram. The postcondition ensures that for the condition that was True on entry, the corrresponding consequence is True on exit. Other consequence expressions are not evaluated. -A precondition @code{P} and postcondition @code{Q} can also be +A precondition @cite{P} and postcondition @cite{Q} can also be expressed as contract cases: -@smallexample @c ada +@example pragma Contract_Cases (P => Q); -@end smallexample +@end example -The placement and visibility rules for @code{Contract_Cases} pragmas are +The placement and visibility rules for @cite{Contract_Cases} pragmas are identical to those described for preconditions and postconditions. The compiler checks that boolean expressions given in conditions and consequences are valid, where the rules for conditions are the same as -the rule for an expression in @code{Precondition} and the rules for +the rule for an expression in @cite{Precondition} and the rules for consequences are the same as the rule for an expression in -@code{Postcondition}. In particular, attributes @code{'Old} and -@code{'Result} can only be used within consequence expressions. -The condition for the last contract case may be @code{others}, to denote +@cite{Postcondition}. In particular, attributes @cite{'Old} and +@cite{'Result} can only be used within consequence expressions. +The condition for the last contract case may be @cite{others}, to denote any case not captured by the previous cases. The following is an example of use within a package spec: -@smallexample @c ada +@example package Math_Functions is ... function Sqrt (Arg : Float) return Float; @@ -2319,133 +2492,134 @@ package Math_Functions is others => Sqrt'Result = 0); ... end Math_Functions; -@end smallexample +@end example -@noindent The meaning of contract cases is that only one case should apply at each call, as determined by the corresponding condition evaluating to True, and that the consequence for this case should hold when the subprogram returns. -@node Pragma Convention_Identifier -@unnumberedsec Pragma Convention_Identifier -@findex Convention_Identifier -@cindex Conventions, synonyms -@noindent +@node Pragma Convention_Identifier,Pragma CPP_Class,Pragma Contract_Cases,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-convention-identifier}@anchor{3d} +@section Pragma Convention_Identifier + + +@geindex Conventions +@geindex synonyms + Syntax: -@smallexample @c ada +@example pragma Convention_Identifier ( [Name =>] IDENTIFIER, [Convention =>] convention_IDENTIFIER); -@end smallexample +@end example -@noindent This pragma provides a mechanism for supplying synonyms for existing -convention identifiers. The @code{Name} identifier can subsequently +convention identifiers. The @cite{Name} identifier can subsequently be used as a synonym for the given convention in other pragmas (including -for example pragma @code{Import} or another @code{Convention_Identifier} +for example pragma @cite{Import} or another @cite{Convention_Identifier} pragma). As an example of the use of this, suppose you had legacy code which used Fortran77 as the identifier for Fortran. Then the pragma: -@smallexample @c ada +@example pragma Convention_Identifier (Fortran77, Fortran); -@end smallexample +@end example -@noindent -would allow the use of the convention identifier @code{Fortran77} in +would allow the use of the convention identifier @cite{Fortran77} in subsequent code, avoiding the need to modify the sources. As another example, you could use this to parameterize convention requirements -according to systems. Suppose you needed to use @code{Stdcall} on -windows systems, and @code{C} on some other system, then you could -define a convention identifier @code{Library} and use a single -@code{Convention_Identifier} pragma to specify which convention +according to systems. Suppose you needed to use @cite{Stdcall} on +windows systems, and @cite{C} on some other system, then you could +define a convention identifier @cite{Library} and use a single +@cite{Convention_Identifier} pragma to specify which convention would be used system-wide. -@node Pragma CPP_Class -@unnumberedsec Pragma CPP_Class -@findex CPP_Class -@cindex Interfacing with C++ -@noindent +@node Pragma CPP_Class,Pragma CPP_Constructor,Pragma Convention_Identifier,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-class}@anchor{3e} +@section Pragma CPP_Class + + +@geindex Interfacing with C++ + Syntax: -@smallexample @c ada +@example pragma CPP_Class ([Entity =>] LOCAL_NAME); -@end smallexample +@end example -@noindent The argument denotes an entity in the current declarative region that is declared as a record type. It indicates that the type corresponds to an externally declared C++ class type, and is to be laid out the same way that C++ would lay out the type. If the C++ class has virtual primitives then the record must be declared as a tagged record type. -Types for which @code{CPP_Class} is specified do not have assignment or +Types for which @cite{CPP_Class} is specified do not have assignment or equality operators defined (such operations can be imported or declared as subprograms as required). Initialization is allowed only by constructor -functions (see pragma @code{CPP_Constructor}). Such types are implicitly +functions (see pragma @cite{CPP_Constructor}). Such types are implicitly limited if not explicitly declared as limited or derived from a limited type, and an error is issued in that case. -See @ref{Interfacing to C++} for related information. +See @ref{3f,,Interfacing to C++} for related information. -Note: Pragma @code{CPP_Class} is currently obsolete. It is supported +Note: Pragma @cite{CPP_Class} is currently obsolete. It is supported for backward compatibility but its functionality is available -using pragma @code{Import} with @code{Convention} = @code{CPP}. +using pragma @cite{Import} with @cite{Convention} = @cite{CPP}. + +@node Pragma CPP_Constructor,Pragma CPP_Virtual,Pragma CPP_Class,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-constructor}@anchor{40} +@section Pragma CPP_Constructor + + +@geindex Interfacing with C++ -@node Pragma CPP_Constructor -@unnumberedsec Pragma CPP_Constructor -@cindex Interfacing with C++ -@findex CPP_Constructor -@noindent Syntax: -@smallexample @c ada +@example pragma CPP_Constructor ([Entity =>] LOCAL_NAME [, [External_Name =>] static_string_EXPRESSION ] [, [Link_Name =>] static_string_EXPRESSION ]); -@end smallexample +@end example -@noindent This pragma identifies an imported function (imported in the usual way -with pragma @code{Import}) as corresponding to a C++ constructor. If -@code{External_Name} and @code{Link_Name} are not specified then the -@code{Entity} argument is a name that must have been previously mentioned -in a pragma @code{Import} with @code{Convention} = @code{CPP}. Such name +with pragma @cite{Import}) as corresponding to a C++ constructor. If +@cite{External_Name} and @cite{Link_Name} are not specified then the +@cite{Entity} argument is a name that must have been previously mentioned +in a pragma @cite{Import} with @cite{Convention} = @cite{CPP}. Such name must be of one of the following forms: -@itemize @bullet -@item -@code{function @var{Fname} return @var{T}} -@itemize @bullet -@item -@code{function @var{Fname} return @var{T}'Class} +@itemize * -@item -@code{function @var{Fname} (@dots{}) return @var{T}} -@end itemize +@item +@strong{function} @cite{Fname} @strong{return} T` -@item -@code{function @var{Fname} (@dots{}) return @var{T}'Class} +@item +@strong{function} @cite{Fname} @strong{return} T'Class + +@item +@strong{function} @cite{Fname} (...) @strong{return} T` + +@item +@strong{function} @cite{Fname} (...) @strong{return} T'Class @end itemize -@noindent -where @var{T} is a limited record type imported from C++ with pragma -@code{Import} and @code{Convention} = @code{CPP}. +where @cite{T} is a limited record type imported from C++ with pragma +@cite{Import} and @cite{Convention} = @cite{CPP}. The first two forms import the default constructor, used when an object -of type @var{T} is created on the Ada side with no explicit constructor. +of type @cite{T} is created on the Ada side with no explicit constructor. The latter two forms cover all the non-default constructors of the type. -See the @value{EDITION} User's Guide for details. +See the GNAT User's Guide for details. If no constructors are imported, it is impossible to create any objects on the Ada side and the type is implicitly declared abstract. -Pragma @code{CPP_Constructor} is intended primarily for automatic generation -using an automatic binding generator tool (such as the @code{-fdump-ada-spec} +Pragma @cite{CPP_Constructor} is intended primarily for automatic generation +using an automatic binding generator tool (such as the @cite{-fdump-ada-spec} GCC switch). -See @ref{Interfacing to C++} for more related information. +See @ref{3f,,Interfacing to C++} for more related information. Note: The use of functions returning class-wide types for constructors is currently obsolete. They are supported for backward compatibility. The @@ -2453,63 +2627,67 @@ use of functions returning the type T leave the Ada sources more clear because the imported C++ constructors always return an object of type T; that is, they never return an object whose type is a descendant of type T. -@node Pragma CPP_Virtual -@unnumberedsec Pragma CPP_Virtual -@cindex Interfacing to C++ -@findex CPP_Virtual -@noindent -This pragma is now obsolete and, other than generating a warning if warnings -on obsolescent features are enabled, is completely ignored. +@node Pragma CPP_Virtual,Pragma CPP_Vtable,Pragma CPP_Constructor,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-virtual}@anchor{41} +@section Pragma CPP_Virtual + + +@geindex Interfacing to C++ + +This pragma is now obsolete and, other than generating a warning if warnings +on obsolescent features are enabled, is completely ignored. It is retained for compatibility purposes. It used to be required to ensure compoatibility with C++, but is no longer required for that purpose because GNAT generates the same object layout as the G++ compiler by default. -See @ref{Interfacing to C++} for related information. +See @ref{3f,,Interfacing to C++} for related information. + +@node Pragma CPP_Vtable,Pragma CPU,Pragma CPP_Virtual,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cpp-vtable}@anchor{42} +@section Pragma CPP_Vtable + + +@geindex Interfacing with C++ -@node Pragma CPP_Vtable -@unnumberedsec Pragma CPP_Vtable -@cindex Interfacing with C++ -@findex CPP_Vtable -@noindent This pragma is now obsolete and, other than generating a warning if warnings on obsolescent features are enabled, is completely ignored. It used to be required to ensure compatibility with C++, but is no longer required for that purpose because GNAT generates the same object layout as the G++ compiler by default. -See @ref{Interfacing to C++} for related information. +See @ref{3f,,Interfacing to C++} for related information. + +@node Pragma CPU,Pragma Debug,Pragma CPP_Vtable,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-cpu}@anchor{43} +@section Pragma CPU + -@node Pragma CPU -@unnumberedsec Pragma CPU -@findex CPU -@noindent Syntax: -@smallexample @c ada +@example pragma CPU (EXPRESSION); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2012, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Debug -@unnumberedsec Pragma Debug -@findex Debug -@noindent +@node Pragma Debug,Pragma Debug_Policy,Pragma CPU,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-debug}@anchor{44} +@section Pragma Debug + + Syntax: -@smallexample @c ada +@example pragma Debug ([CONDITION, ]PROCEDURE_CALL_WITHOUT_SEMICOLON); PROCEDURE_CALL_WITHOUT_SEMICOLON ::= PROCEDURE_NAME | PROCEDURE_PREFIX ACTUAL_PARAMETER_PART -@end smallexample +@end example -@noindent The procedure call argument has the syntactic form of an expression, meeting the syntactic requirements for pragmas. @@ -2517,58 +2695,52 @@ If debug pragmas are not enabled or if the condition is present and evaluates to False, this pragma has no effect. If debug pragmas are enabled, the semantics of the pragma is exactly equivalent to the procedure call statement corresponding to the argument with a terminating semicolon. Pragmas are -permitted in sequences of declarations, so you can use pragma @code{Debug} to +permitted in sequences of declarations, so you can use pragma @cite{Debug} to intersperse calls to debug procedures in the middle of declarations. Debug -pragmas can be enabled either by use of the command line switch @option{-gnata} -or by use of the pragma @code{Check_Policy} with a first argument of -@code{Debug}. - -@node Pragma Debug_Policy -@unnumberedsec Pragma Debug_Policy -@findex Debug_Policy -@noindent +pragmas can be enabled either by use of the command line switch @emph{-gnata} +or by use of the pragma @cite{Check_Policy} with a first argument of +@cite{Debug}. + +@node Pragma Debug_Policy,Pragma Default_Scalar_Storage_Order,Pragma Debug,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-debug-policy}@anchor{45} +@section Pragma Debug_Policy + + Syntax: -@smallexample @c ada +@example pragma Debug_Policy (CHECK | DISABLE | IGNORE | ON | OFF); -@end smallexample +@end example -@noindent -This pragma is equivalent to a corresponding @code{Check_Policy} pragma -with a first argument of @code{Debug}. It is retained for historical +This pragma is equivalent to a corresponding @cite{Check_Policy} pragma +with a first argument of @cite{Debug}. It is retained for historical compatibility reasons. -@node Pragma Default_Scalar_Storage_Order -@unnumberedsec Pragma Default_Scalar_Storage_Order -@cindex Default_Scalar_Storage_Order -@cindex Scalar_Storage_Order -@findex Default_Scalar_Storage_Order -@noindent +@node Pragma Default_Scalar_Storage_Order,Pragma Default_Storage_Pool,Pragma Debug_Policy,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-default-scalar-storage-order}@anchor{46} +@section Pragma Default_Scalar_Storage_Order + + +@geindex Default_Scalar_Storage_Order + +@geindex Scalar_Storage_Order + Syntax: -@smallexample @c ada +@example pragma Default_Scalar_Storage_Order (High_Order_First | Low_Order_First); -@end smallexample - -@noindent -Normally if no explicit @code{Scalar_Storage_Order} is given for a record -type or array type, then the scalar storage order defaults to the native -order for the target. However, this default may be overridden using -this pragma (except for derived tagged types, which always default to -inheriting the scalar storage order of their parent). The pragma may -appear as a configuration pragma, or locally within a package spec or -declarative part. In the latter case, it applies to all subsequent -types declared within that package spec or declarative part. +@end example -If this pragma is used as a configuration pragma which appears within a -configuration pragma file (as opposed to appearing explicitly at the start -of a single unit), then the binder will require that all units in a partition -be compiled in a similar manner, other than run-time units, which are not -affected by this pragma. +Normally if no explicit @cite{Scalar_Storage_Order} is given for a record +type or array type, then the scalar storage order defaults to the ordinary +default for the target. But this default may be overridden using this pragma. +The pragma may appear as a configuration pragma, or locally within a package +spec or declarative part. In the latter case, it applies to all subsequent +types declared within that package spec or declarative part. The following example shows the use of this pragma: -@smallexample @c ada +@example pragma Default_Scalar_Storage_Order (High_Order_First); with System; use System; package DSSO1 is @@ -2601,49 +2773,58 @@ package DSSO1 is a : Integer; end record; end DSSO1; -@end smallexample +@end example -@noindent -In this example record types L.. have @code{Low_Order_First} scalar -storage order, and record types H.. have @code{High_Order_First}. -Note that in the case of @code{H4a}, the order is not inherited -from the parent type. Only an explicitly set @code{Scalar_Storage_Order} +In this example record types L.. have @cite{Low_Order_First} scalar +storage order, and record types H.. have @cite{High_Order_First}. +Note that in the case of @cite{H4a}, the order is not inherited +from the parent type. Only an explicitly set @cite{Scalar_Storage_Order} gets inherited on type derivation. -@node Pragma Default_Storage_Pool -@unnumberedsec Pragma Default_Storage_Pool -@cindex Default_Storage_Pool -@findex Default_Storage_Pool -@noindent +If this pragma is used as a configuration pragma which appears within a +configuration pragma file (as opposed to appearing explicitly at the start +of a single unit), then the binder will require that all units in a partition +be compiled in a similar manner, other than run-time units, which are not +affected by this pragma. Note that the use of this form is discouraged because +it may significantly degrade the run-time performance of the software, instead +the default scalar storage order ought to be changed only on a local basis. + +@node Pragma Default_Storage_Pool,Pragma Depends,Pragma Default_Scalar_Storage_Order,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-default-storage-pool}@anchor{47} +@section Pragma Default_Storage_Pool + + +@geindex Default_Storage_Pool + Syntax: -@smallexample @c ada +@example pragma Default_Storage_Pool (storage_pool_NAME | null); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2012, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Depends -@unnumberedsec Pragma Depends -@findex Depends -@noindent +@node Pragma Depends,Pragma Detect_Blocking,Pragma Default_Storage_Pool,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-depends}@anchor{48} +@section Pragma Depends + + For the description of this pragma, see SPARK 2014 Reference Manual, section 6.1.5. -@node Pragma Detect_Blocking -@unnumberedsec Pragma Detect_Blocking -@findex Detect_Blocking -@noindent +@node Pragma Detect_Blocking,Pragma Disable_Atomic_Synchronization,Pragma Depends,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-detect-blocking}@anchor{49} +@section Pragma Detect_Blocking + + Syntax: -@smallexample @c ada +@example pragma Detect_Blocking; -@end smallexample +@end example -@noindent This is a standard pragma in Ada 2005, that is available in all earlier versions of Ada as an implementation-defined pragma. @@ -2651,18 +2832,19 @@ This is a configuration pragma that forces the detection of potentially blocking operations within a protected operation, and to raise Program_Error if that happens. -@node Pragma Disable_Atomic_Synchronization -@unnumberedsec Pragma Disable_Atomic_Synchronization -@cindex Atomic Synchronization -@findex Disable_Atomic_Synchronization -@noindent +@node Pragma Disable_Atomic_Synchronization,Pragma Dispatching_Domain,Pragma Detect_Blocking,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-disable-atomic-synchronization}@anchor{4a} +@section Pragma Disable_Atomic_Synchronization + + +@geindex Atomic Synchronization + Syntax: -@smallexample @c ada +@example pragma Disable_Atomic_Synchronization [(Entity)]; -@end smallexample +@end example -@noindent Ada requires that accesses (reads or writes) of an atomic variable be regarded as synchronization points in the case of multiple tasks. Particularly in the case of multi-processors this may require special @@ -2671,106 +2853,109 @@ be turned off using this pragma in cases where it is known not to be required. The placement and scope rules for this pragma are the same as those -for @code{pragma Suppress}. In particular it can be used as a +for @cite{pragma Suppress}. In particular it can be used as a configuration pragma, or in a declaration sequence where it applies -till the end of the scope. If an @code{Entity} argument is present, +till the end of the scope. If an @cite{Entity} argument is present, the action applies only to that entity. -@node Pragma Dispatching_Domain -@unnumberedsec Pragma Dispatching_Domain -@findex Dispatching_Domain -@noindent +@node Pragma Dispatching_Domain,Pragma Effective_Reads,Pragma Disable_Atomic_Synchronization,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-dispatching-domain}@anchor{4b} +@section Pragma Dispatching_Domain + + Syntax: -@smallexample @c ada +@example pragma Dispatching_Domain (EXPRESSION); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2012, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Effective_Reads -@unnumberedsec Pragma Effective_Reads -@findex Effective_Reads -@noindent +@node Pragma Effective_Reads,Pragma Effective_Writes,Pragma Dispatching_Domain,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-reads}@anchor{4c} +@section Pragma Effective_Reads + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.2. -@node Pragma Effective_Writes -@unnumberedsec Pragma Effective_Writes -@findex Effective_Writes -@noindent +@node Pragma Effective_Writes,Pragma Elaboration_Checks,Pragma Effective_Reads,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-effective-writes}@anchor{4d} +@section Pragma Effective_Writes + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.2. -@node Pragma Elaboration_Checks -@unnumberedsec Pragma Elaboration_Checks -@cindex Elaboration control -@findex Elaboration_Checks -@noindent +@node Pragma Elaboration_Checks,Pragma Eliminate,Pragma Effective_Writes,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-elaboration-checks}@anchor{4e} +@section Pragma Elaboration_Checks + + +@geindex Elaboration control + Syntax: -@smallexample @c ada +@example pragma Elaboration_Checks (Dynamic | Static); -@end smallexample +@end example -@noindent This is a configuration pragma that provides control over the elaboration model used by the compilation affected by the -pragma. If the parameter is @code{Dynamic}, +pragma. If the parameter is @cite{Dynamic}, then the dynamic elaboration model described in the Ada Reference Manual is used, as though -the @option{-gnatE} switch had been specified on the command -line. If the parameter is @code{Static}, then the default GNAT static +the @emph{-gnatE} switch had been specified on the command +line. If the parameter is @cite{Static}, then the default GNAT static model is used. This configuration pragma overrides the setting of the command line. For full details on the elaboration models -used by the GNAT compiler, see @ref{Elaboration Order Handling in GNAT,,, -gnat_ugn, @value{EDITION} User's Guide}. - -@node Pragma Eliminate -@unnumberedsec Pragma Eliminate -@cindex Elimination of unused subprograms -@findex Eliminate -@noindent +used by the GNAT compiler, see the chapter on elaboration order handling +in the @emph{GNAT User's Guide}. + +@node Pragma Eliminate,Pragma Enable_Atomic_Synchronization,Pragma Elaboration_Checks,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-eliminate}@anchor{4f} +@section Pragma Eliminate + + +@geindex Elimination of unused subprograms + Syntax: -@smallexample @c ada +@example pragma Eliminate ([Entity =>] DEFINING_DESIGNATOR, [Source_Location =>] STRING_LITERAL); -@end smallexample +@end example -@noindent The string literal given for the source location is a string which specifies the line number of the occurrence of the entity, using the syntax for SOURCE_TRACE given below: -@smallexample @c ada - SOURCE_TRACE ::= SOURCE_REFERENCE [LBRACKET SOURCE_TRACE RBRACKET] +@example +SOURCE_TRACE ::= SOURCE_REFERENCE [LBRACKET SOURCE_TRACE RBRACKET] - LBRACKET ::= [ - RBRACKET ::= ] +LBRACKET ::= [ +RBRACKET ::= ] - SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER +SOURCE_REFERENCE ::= FILE_NAME : LINE_NUMBER - LINE_NUMBER ::= DIGIT @{DIGIT@} -@end smallexample +LINE_NUMBER ::= DIGIT @{DIGIT@} +@end example -@noindent -Spaces around the colon in a @code{Source_Reference} are optional. +Spaces around the colon in a @cite{Source_Reference} are optional. -The @code{DEFINING_DESIGNATOR} matches the defining designator used in an -explicit subprogram declaration, where the @code{entity} name in this +The @cite{DEFINING_DESIGNATOR} matches the defining designator used in an +explicit subprogram declaration, where the @cite{entity} name in this designator appears on the source line specified by the source location. -The source trace that is given as the @code{Source_Location} shall obey the -following rules. The @code{FILE_NAME} is the short name (with no directory +The source trace that is given as the @cite{Source_Location} shall obey the +following rules. The @cite{FILE_NAME} is the short name (with no directory information) of an Ada source file, given using exactly the required syntax for the underlying file system (e.g. case is important if the underlying -operating system is case sensitive). @code{LINE_NUMBER} gives the line -number of the occurrence of the @code{entity} -as a decimal literal without an exponent or point. If an @code{entity} is not +operating system is case sensitive). @cite{LINE_NUMBER} gives the line +number of the occurrence of the @cite{entity} +as a decimal literal without an exponent or point. If an @cite{entity} is not declared in a generic instantiation (this includes generic subprogram instances), the source trace includes only one source reference. If an entity is declared inside a generic instantiation, its source trace (when parsing @@ -2784,7 +2969,7 @@ nested) instantiation in the code of the corresponding generic unit, and so on, and the leftmost element (that is out of any square brackets) is the location of the declaration of the entity to eliminate in a generic unit. -Note that the @code{Source_Location} argument specifies which of a set of +Note that the @cite{Source_Location} argument specifies which of a set of similarly named entities is being eliminated, dealing both with overloading, and also appearance of the same entity name in different scopes. @@ -2793,84 +2978,58 @@ compiled and built. The effect of the pragma is to allow the compiler to eliminate the code or data associated with the named entity. Any reference to an eliminated entity causes a compile-time or link-time error. -The intention of pragma @code{Eliminate} is to allow a program to be compiled +The intention of pragma @cite{Eliminate} is to allow a program to be compiled in a system-independent manner, with unused entities eliminated, without needing to modify the source text. Normally the required set of -@code{Eliminate} pragmas is constructed automatically using the gnatelim tool. +@cite{Eliminate} pragmas is constructed automatically using the gnatelim tool. Any source file change that removes, splits, or adds lines may make the set of Eliminate pragmas invalid because their -@code{Source_Location} argument values may get out of date. +@cite{Source_Location} argument values may get out of date. -Pragma @code{Eliminate} may be used where the referenced entity is a dispatching +Pragma @cite{Eliminate} may be used where the referenced entity is a dispatching operation. In this case all the subprograms to which the given operation can dispatch are considered to be unused (are never called as a result of a direct or a dispatching call). -@node Pragma Enable_Atomic_Synchronization -@unnumberedsec Pragma Enable_Atomic_Synchronization -@cindex Atomic Synchronization -@findex Enable_Atomic_Synchronization -@noindent +@node Pragma Enable_Atomic_Synchronization,Pragma Export_Function,Pragma Eliminate,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-enable-atomic-synchronization}@anchor{50} +@section Pragma Enable_Atomic_Synchronization + + +@geindex Atomic Synchronization + Syntax: -@smallexample @c ada +@example pragma Enable_Atomic_Synchronization [(Entity)]; -@end smallexample +@end example -@noindent Ada requires that accesses (reads or writes) of an atomic variable be regarded as synchronization points in the case of multiple tasks. Particularly in the case of multi-processors this may require special handling, e.g. the generation of memory barriers. This synchronization is performed by default, but can be turned off using -@code{pragma Disable_Atomic_Synchronization}. The -@code{Enable_Atomic_Synchronization} pragma can be used to turn +@cite{pragma Disable_Atomic_Synchronization}. The +@cite{Enable_Atomic_Synchronization} pragma can be used to turn it back on. The placement and scope rules for this pragma are the same as those -for @code{pragma Unsuppress}. In particular it can be used as a +for @cite{pragma Unsuppress}. In particular it can be used as a configuration pragma, or in a declaration sequence where it applies -till the end of the scope. If an @code{Entity} argument is present, +till the end of the scope. If an @cite{Entity} argument is present, the action applies only to that entity. -@node Pragma Export_Exception -@unnumberedsec Pragma Export_Exception -@cindex OpenVMS -@findex Export_Exception -@noindent -Syntax: +@node Pragma Export_Function,Pragma Export_Object,Pragma Enable_Atomic_Synchronization,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-export-function}@anchor{51} +@section Pragma Export_Function -@smallexample @c ada -pragma Export_Exception ( - [Internal =>] LOCAL_NAME - [, [External =>] EXTERNAL_SYMBOL] - [, [Form =>] Ada | VMS] - [, [Code =>] static_integer_EXPRESSION]); -EXTERNAL_SYMBOL ::= - IDENTIFIER -| static_string_EXPRESSION -@end smallexample - -@noindent -This pragma is implemented only in the OpenVMS implementation of GNAT@. It -causes the specified exception to be propagated outside of the Ada program, -so that it can be handled by programs written in other OpenVMS languages. -This pragma establishes an external name for an Ada exception and makes the -name available to the OpenVMS Linker as a global symbol. For further details -on this pragma, see the -DEC Ada Language Reference Manual, section 13.9a3.2. - -@node Pragma Export_Function -@unnumberedsec Pragma Export_Function -@cindex Argument passing mechanisms -@findex Export_Function - -@noindent +@geindex Argument passing mechanisms + Syntax: -@smallexample @c ada +@example pragma Export_Function ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -2900,46 +3059,44 @@ MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent Use this pragma to make a function externally callable and optionally provide information on mechanisms to be used for passing parameter and result values. We recommend, for the purposes of improving portability, this pragma always be used in conjunction with a separate pragma -@code{Export}, which must precede the pragma @code{Export_Function}. -GNAT does not require a separate pragma @code{Export}, but if none is -present, @code{Convention Ada} is assumed, which is usually +@cite{Export}, which must precede the pragma @cite{Export_Function}. +GNAT does not require a separate pragma @cite{Export}, but if none is +present, @cite{Convention Ada} is assumed, which is usually not what is wanted, so it is usually appropriate to use this -pragma in conjunction with a @code{Export} or @code{Convention} +pragma in conjunction with a @cite{Export} or @cite{Convention} pragma that specifies the desired foreign convention. -Pragma @code{Export_Function} -(and @code{Export}, if present) must appear in the same declarative +Pragma @cite{Export_Function} +(and @cite{Export}, if present) must appear in the same declarative region as the function to which they apply. -@var{internal_name} must uniquely designate the function to which the +@cite{internal_name} must uniquely designate the function to which the pragma applies. If more than one function name exists of this name in -the declarative part you must use the @code{Parameter_Types} and -@code{Result_Type} parameters is mandatory to achieve the required -unique designation. @var{subtype_mark}s in these parameters must -exactly match the subtypes in the corresponding function specification, -using positional notation to match parameters with subtype marks. -The form with an @code{'Access} attribute can be used to match an +the declarative part you must use the @cite{Parameter_Types} and +@cite{Result_Type} parameters is mandatory to achieve the required +unique designation. @cite{subtype_mark`s in these parameters must exactly match the subtypes in the corresponding function specification@comma{} using positional notation to match parameters with subtype marks. The form with an `'Access} attribute can be used to match an anonymous access parameter. -@cindex Suppressing external name +@geindex Suppressing external name + Special treatment is given if the EXTERNAL is an explicit null string or a static string expressions that evaluates to the null string. In this case, no external name is generated. This form still allows the specification of parameter mechanisms. -@node Pragma Export_Object -@unnumberedsec Pragma Export_Object -@findex Export_Object -@noindent +@node Pragma Export_Object,Pragma Export_Procedure,Pragma Export_Function,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-export-object}@anchor{52} +@section Pragma Export_Object + + Syntax: -@smallexample @c ada +@example pragma Export_Object [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -2948,23 +3105,23 @@ pragma Export_Object EXTERNAL_SYMBOL ::= IDENTIFIER | static_string_EXPRESSION -@end smallexample +@end example -@noindent This pragma designates an object as exported, and apart from the extended rules for external symbols, is identical in effect to the use of -the normal @code{Export} pragma applied to an object. You may use a +the normal @cite{Export} pragma applied to an object. You may use a separate Export pragma (and you probably should from the point of view -of portability), but it is not required. @var{Size} is syntax checked, -but otherwise ignored by GNAT@. +of portability), but it is not required. @cite{Size} is syntax checked, +but otherwise ignored by GNAT. + +@node Pragma Export_Procedure,Pragma Export_Value,Pragma Export_Object,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-export-procedure}@anchor{53} +@section Pragma Export_Procedure + -@node Pragma Export_Procedure -@unnumberedsec Pragma Export_Procedure -@findex Export_Procedure -@noindent Syntax: -@smallexample @c ada +@example pragma Export_Procedure ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -2992,37 +3149,37 @@ MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent -This pragma is identical to @code{Export_Function} except that it +This pragma is identical to @cite{Export_Function} except that it applies to a procedure rather than a function and the parameters -@code{Result_Type} and @code{Result_Mechanism} are not permitted. -GNAT does not require a separate pragma @code{Export}, but if none is -present, @code{Convention Ada} is assumed, which is usually +@cite{Result_Type} and @cite{Result_Mechanism} are not permitted. +GNAT does not require a separate pragma @cite{Export}, but if none is +present, @cite{Convention Ada} is assumed, which is usually not what is wanted, so it is usually appropriate to use this -pragma in conjunction with a @code{Export} or @code{Convention} +pragma in conjunction with a @cite{Export} or @cite{Convention} pragma that specifies the desired foreign convention. -@cindex Suppressing external name +@geindex Suppressing external name + Special treatment is given if the EXTERNAL is an explicit null string or a static string expressions that evaluates to the null string. In this case, no external name is generated. This form still allows the specification of parameter mechanisms. -@node Pragma Export_Value -@unnumberedsec Pragma Export_Value -@findex Export_Value -@noindent +@node Pragma Export_Value,Pragma Export_Valued_Procedure,Pragma Export_Procedure,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-export-value}@anchor{54} +@section Pragma Export_Value + + Syntax: -@smallexample @c ada +@example pragma Export_Value ( [Value =>] static_integer_EXPRESSION, [Link_Name =>] static_string_EXPRESSION); -@end smallexample +@end example -@noindent This pragma serves to export a static integer value for external use. The first argument specifies the value to be exported. The Link_Name argument specifies the symbolic name to be associated with the integer @@ -3031,13 +3188,14 @@ that can be referenced in assembly language units to be linked with the application. This pragma is currently supported only for the AAMP target and is ignored for other targets. -@node Pragma Export_Valued_Procedure -@unnumberedsec Pragma Export_Valued_Procedure -@findex Export_Valued_Procedure -@noindent +@node Pragma Export_Valued_Procedure,Pragma Extend_System,Pragma Export_Value,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-export-valued-procedure}@anchor{55} +@section Pragma Export_Valued_Procedure + + Syntax: -@smallexample @c ada +@example pragma Export_Valued_Procedure ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -3065,248 +3223,263 @@ MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent -This pragma is identical to @code{Export_Procedure} except that the -first parameter of @var{LOCAL_NAME}, which must be present, must be of -mode @code{OUT}, and externally the subprogram is treated as a function +This pragma is identical to @cite{Export_Procedure} except that the +first parameter of @cite{LOCAL_NAME}, which must be present, must be of +mode @cite{OUT}, and externally the subprogram is treated as a function with this parameter as the result of the function. GNAT provides for -this capability to allow the use of @code{OUT} and @code{IN OUT} +this capability to allow the use of @cite{OUT} and @cite{IN OUT} parameters in interfacing to external functions (which are not permitted in Ada functions). -GNAT does not require a separate pragma @code{Export}, but if none is -present, @code{Convention Ada} is assumed, which is almost certainly +GNAT does not require a separate pragma @cite{Export}, but if none is +present, @cite{Convention Ada} is assumed, which is almost certainly not what is wanted since the whole point of this pragma is to interface with foreign language functions, so it is usually appropriate to use this -pragma in conjunction with a @code{Export} or @code{Convention} +pragma in conjunction with a @cite{Export} or @cite{Convention} pragma that specifies the desired foreign convention. -@cindex Suppressing external name +@geindex Suppressing external name + Special treatment is given if the EXTERNAL is an explicit null string or a static string expressions that evaluates to the null string. In this case, no external name is generated. This form still allows the specification of parameter mechanisms. -@node Pragma Extend_System -@unnumberedsec Pragma Extend_System -@cindex @code{system}, extending -@cindex Dec Ada 83 -@findex Extend_System -@noindent +@node Pragma Extend_System,Pragma Extensions_Allowed,Pragma Export_Valued_Procedure,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-extend-system}@anchor{56} +@section Pragma Extend_System + + +@geindex System +@geindex extending + +@geindex DEC Ada 83 + Syntax: -@smallexample @c ada +@example pragma Extend_System ([Name =>] IDENTIFIER); -@end smallexample +@end example -@noindent This pragma is used to provide backwards compatibility with other -implementations that extend the facilities of package @code{System}. In -GNAT, @code{System} contains only the definitions that are present in -the Ada RM@. However, other implementations, notably the DEC Ada 83 -implementation, provide many extensions to package @code{System}. +implementations that extend the facilities of package @cite{System}. In +GNAT, @cite{System} contains only the definitions that are present in +the Ada RM. However, other implementations, notably the DEC Ada 83 +implementation, provide many extensions to package @cite{System}. For each such implementation accommodated by this pragma, GNAT provides a -package @code{Aux_@var{xxx}}, e.g.@: @code{Aux_DEC} for the DEC Ada 83 +package @cite{Aux_`xxx`}, e.g., @cite{Aux_DEC} for the DEC Ada 83 implementation, which provides the required additional definitions. You -can use this package in two ways. You can @code{with} it in the normal -way and access entities either by selection or using a @code{use} +can use this package in two ways. You can @cite{with} it in the normal +way and access entities either by selection or using a @cite{use} clause. In this case no special processing is required. However, if existing code contains references such as -@code{System.@var{xxx}} where @var{xxx} is an entity in the extended -definitions provided in package @code{System}, you may use this pragma -to extend visibility in @code{System} in a non-standard way that +@cite{System.`xxx`} where @cite{xxx} is an entity in the extended +definitions provided in package @cite{System}, you may use this pragma +to extend visibility in @cite{System} in a non-standard way that provides greater compatibility with the existing code. Pragma -@code{Extend_System} is a configuration pragma whose single argument is +@cite{Extend_System} is a configuration pragma whose single argument is the name of the package containing the extended definition -(e.g.@: @code{Aux_DEC} for the DEC Ada case). A unit compiled under +(e.g., @cite{Aux_DEC} for the DEC Ada case). A unit compiled under control of this pragma will be processed using special visibility -processing that looks in package @code{System.Aux_@var{xxx}} where -@code{Aux_@var{xxx}} is the pragma argument for any entity referenced in -package @code{System}, but not found in package @code{System}. +processing that looks in package @cite{System.Aux_`xxx`} where +@cite{Aux_`xxx`} is the pragma argument for any entity referenced in +package @cite{System}, but not found in package @cite{System}. -You can use this pragma either to access a predefined @code{System} -extension supplied with the compiler, for example @code{Aux_DEC} or +You can use this pragma either to access a predefined @cite{System} +extension supplied with the compiler, for example @cite{Aux_DEC} or you can construct your own extension unit following the above -definition. Note that such a package is a child of @code{System} +definition. Note that such a package is a child of @cite{System} and thus is considered part of the implementation. -To compile it you will have to use the @option{-gnatg} switch, -or the @option{/GNAT_INTERNAL} qualifier on OpenVMS, +To compile it you will have to use the @emph{-gnatg} switch for compiling System units, as explained in the -@value{EDITION} User's Guide. - -@node Pragma Extensions_Allowed -@unnumberedsec Pragma Extensions_Allowed -@cindex Ada Extensions -@cindex GNAT Extensions -@findex Extensions_Allowed -@noindent +GNAT User's Guide. + +@node Pragma Extensions_Allowed,Pragma External,Pragma Extend_System,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-extensions-allowed}@anchor{57} +@section Pragma Extensions_Allowed + + +@geindex Ada Extensions + +@geindex GNAT Extensions + Syntax: -@smallexample @c ada +@example pragma Extensions_Allowed (On | Off); -@end smallexample +@end example -@noindent This configuration pragma enables or disables the implementation extension mode (the use of Off as a parameter cancels the effect -of the @option{-gnatX} command switch). +of the @emph{-gnatX} command switch). In extension mode, the latest version of the Ada language is implemented (currently Ada 2012), and in addition a small number of GNAT specific extensions are recognized as follows: + @table @asis -@item Constrained attribute for generic objects -The @code{Constrained} attribute is permitted for objects of + +@item @emph{Constrained attribute for generic objects} + +The @cite{Constrained} attribute is permitted for objects of generic types. The result indicates if the corresponding actual is constrained. - @end table -@node Pragma External -@unnumberedsec Pragma External -@findex External -@noindent +@node Pragma External,Pragma External_Name_Casing,Pragma Extensions_Allowed,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-external}@anchor{58} +@section Pragma External + + Syntax: -@smallexample @c ada +@example pragma External ( [ Convention =>] convention_IDENTIFIER, [ Entity =>] LOCAL_NAME [, [External_Name =>] static_string_EXPRESSION ] [, [Link_Name =>] static_string_EXPRESSION ]); -@end smallexample +@end example -@noindent This pragma is identical in syntax and semantics to pragma -@code{Export} as defined in the Ada Reference Manual. It is +@cite{Export} as defined in the Ada Reference Manual. It is provided for compatibility with some Ada 83 compilers that used this pragma for exactly the same purposes as pragma -@code{Export} before the latter was standardized. - -@node Pragma External_Name_Casing -@unnumberedsec Pragma External_Name_Casing -@cindex Dec Ada 83 casing compatibility -@cindex External Names, casing -@cindex Casing of External names -@findex External_Name_Casing -@noindent +@cite{Export} before the latter was standardized. + +@node Pragma External_Name_Casing,Pragma Fast_Math,Pragma External,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-external-name-casing}@anchor{59} +@section Pragma External_Name_Casing + + +@geindex Dec Ada 83 casing compatibility + +@geindex External Names +@geindex casing + +@geindex Casing of External names + Syntax: -@smallexample @c ada +@example pragma External_Name_Casing ( Uppercase | Lowercase [, Uppercase | Lowercase | As_Is]); -@end smallexample +@end example -@noindent This pragma provides control over the casing of external names associated with Import and Export pragmas. There are two cases to consider: -@table @asis -@item Implicit external names + +@itemize * + +@item +Implicit external names + Implicit external names are derived from identifiers. The most common case arises when a standard Ada Import or Export pragma is used with only two arguments, as in: -@smallexample @c ada - pragma Import (C, C_Routine); -@end smallexample +@example +pragma Import (C, C_Routine); +@end example -@noindent Since Ada is a case-insensitive language, the spelling of the identifier in the Ada source program does not provide any information on the desired casing of the external name, and so a convention is needed. In GNAT the default treatment is that such names are converted to all lower case letters. This corresponds to the normal C style in many environments. -The first argument of pragma @code{External_Name_Casing} can be used to -control this treatment. If @code{Uppercase} is specified, then the name -will be forced to all uppercase letters. If @code{Lowercase} is specified, +The first argument of pragma @cite{External_Name_Casing} can be used to +control this treatment. If @cite{Uppercase} is specified, then the name +will be forced to all uppercase letters. If @cite{Lowercase} is specified, then the normal default of all lower case letters will be used. This same implicit treatment is also used in the case of extended DEC Ada 83 compatible Import and Export pragmas where an external name is explicitly specified using an identifier rather than a string. -@item Explicit external names +@item +Explicit external names + Explicit external names are given as string literals. The most common case arises when a standard Ada Import or Export pragma is used with three arguments, as in: -@smallexample @c ada +@example pragma Import (C, C_Routine, "C_routine"); -@end smallexample +@end example -@noindent In this case, the string literal normally provides the exact casing required for the external name. The second argument of pragma -@code{External_Name_Casing} may be used to modify this behavior. -If @code{Uppercase} is specified, then the name -will be forced to all uppercase letters. If @code{Lowercase} is specified, +@cite{External_Name_Casing} may be used to modify this behavior. +If @cite{Uppercase} is specified, then the name +will be forced to all uppercase letters. If @cite{Lowercase} is specified, then the name will be forced to all lowercase letters. A specification of -@code{As_Is} provides the normal default behavior in which the casing is +@cite{As_Is} provides the normal default behavior in which the casing is taken from the string provided. -@end table +@end itemize -@noindent This pragma may appear anywhere that a pragma is valid. In particular, it -can be used as a configuration pragma in the @file{gnat.adc} file, in which +can be used as a configuration pragma in the @code{gnat.adc} file, in which case it applies to all subsequent compilations, or it can be used as a program unit pragma, in which case it only applies to the current unit, or it can be used more locally to control individual Import/Export pragmas. -It is primarily intended for use with OpenVMS systems, where many +It was primarily intended for use with OpenVMS systems, where many compilers convert all symbols to upper case by default. For interfacing to -such compilers (e.g.@: the DEC C compiler), it may be convenient to use +such compilers (e.g., the DEC C compiler), it may be convenient to use the pragma: -@smallexample @c ada +@example pragma External_Name_Casing (Uppercase, Uppercase); -@end smallexample +@end example -@noindent to enforce the upper casing of all external symbols. -@node Pragma Fast_Math -@unnumberedsec Pragma Fast_Math -@findex Fast_Math -@noindent +@node Pragma Fast_Math,Pragma Favor_Top_Level,Pragma External_Name_Casing,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-fast-math}@anchor{5a} +@section Pragma Fast_Math + + Syntax: -@smallexample @c ada +@example pragma Fast_Math; -@end smallexample +@end example -@noindent This is a configuration pragma which activates a mode in which speed is considered more important for floating-point operations than absolutely accurate adherence to the requirements of the standard. Currently the following operations are affected: + @table @asis -@item Complex Multiplication + +@item @emph{Complex Multiplication} + The normal simple formula for complex multiplication can result in intermediate overflows for numbers near the end of the range. The Ada standard requires that this situation be detected and corrected by scaling, but in Fast_Math mode such cases will simply result in overflow. Note that to take advantage of this you -must instantiate your own version of @code{Ada.Numerics.Generic_Complex_Types} +must instantiate your own version of @cite{Ada.Numerics.Generic_Complex_Types} under control of the pragma, rather than use the preinstantiated versions. @end table -@node Pragma Favor_Top_Level -@unnumberedsec Pragma Favor_Top_Level -@findex Favor_Top_Level -@noindent +@node Pragma Favor_Top_Level,Pragma Finalize_Storage_Only,Pragma Fast_Math,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-favor-top-level}@anchor{5b} +@section Pragma Favor_Top_Level + + Syntax: -@smallexample @c ada +@example pragma Favor_Top_Level (type_NAME); -@end smallexample +@end example -@noindent The named type must be an access-to-subprogram type. This pragma is an efficiency hint to the compiler, regarding the use of 'Access or 'Unrestricted_Access on nested (non-library-level) subprograms. The @@ -3316,115 +3489,98 @@ top-level case. When this pragma is used, dynamically generated trampolines may be used on some targets for nested subprograms. See also the No_Implicit_Dynamic_Code restriction. -@node Pragma Finalize_Storage_Only -@unnumberedsec Pragma Finalize_Storage_Only -@findex Finalize_Storage_Only -@noindent +@node Pragma Finalize_Storage_Only,Pragma Float_Representation,Pragma Favor_Top_Level,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-finalize-storage-only}@anchor{5c} +@section Pragma Finalize_Storage_Only + + Syntax: -@smallexample @c ada +@example pragma Finalize_Storage_Only (first_subtype_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma allows the compiler not to emit a Finalize call for objects defined at the library level. This is mostly useful for types where finalization is only used to deal with storage reclamation since in most environments it is not necessary to reclaim memory just before terminating execution, hence the name. -@node Pragma Float_Representation -@unnumberedsec Pragma Float_Representation -@cindex OpenVMS -@findex Float_Representation -@noindent +@node Pragma Float_Representation,Pragma Global,Pragma Finalize_Storage_Only,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-float-representation}@anchor{5d} +@section Pragma Float_Representation + + Syntax: -@smallexample @c ada +@example pragma Float_Representation (FLOAT_REP[, float_type_LOCAL_NAME]); FLOAT_REP ::= VAX_Float | IEEE_Float -@end smallexample +@end example -@noindent In the one argument form, this pragma is a configuration pragma which allows control over the internal representation chosen for the predefined -floating point types declared in the packages @code{Standard} and -@code{System}. On all systems other than OpenVMS, the argument must -be @code{IEEE_Float} and the pragma has no effect. On OpenVMS, the -argument may be @code{VAX_Float} to specify the use of the VAX float -format for the floating-point types in Standard. This requires that -the standard runtime libraries be recompiled. +floating point types declared in the packages @cite{Standard} and +@cite{System}. This pragma is only provided for compatibility and has no effect. The two argument form specifies the representation to be used for -the specified floating-point type. On all systems other than OpenVMS, -the argument must -be @code{IEEE_Float} to specify the use of IEEE format, as follows: +the specified floating-point type. The argument must +be @cite{IEEE_Float} to specify the use of IEEE format, as follows: -@itemize @bullet -@item + +@itemize * + +@item For a digits value of 6, 32-bit IEEE short format will be used. -@item + +@item For a digits value of 15, 64-bit IEEE long format will be used. -@item + +@item No other value of digits is permitted. @end itemize -On OpenVMS, the -argument may be @code{VAX_Float} to specify the use of the VAX float -format, as follows: +@node Pragma Global,Pragma Ident,Pragma Float_Representation,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-global}@anchor{5e} +@section Pragma Global -@itemize @bullet -@item -For digits values up to 6, F float format will be used. -@item -For digits values from 7 to 9, D float format will be used. -@item -For digits values from 10 to 15, G float format will be used. -@item -Digits values above 15 are not allowed. -@end itemize -@node Pragma Global -@unnumberedsec Pragma Global -@findex Global -@noindent For the description of this pragma, see SPARK 2014 Reference Manual, section 6.1.4. -@node Pragma Ident -@unnumberedsec Pragma Ident -@findex Ident -@noindent +@node Pragma Ident,Pragma Implementation_Defined,Pragma Global,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ident}@anchor{5f} +@section Pragma Ident + + Syntax: -@smallexample @c ada +@example pragma Ident (static_string_EXPRESSION); -@end smallexample +@end example -@noindent -This pragma is identical in effect to pragma @code{Comment}. It is provided +This pragma is identical in effect to pragma @cite{Comment}. It is provided for compatibility with other Ada compilers providing this pragma. -@node Pragma Implementation_Defined -@unnumberedsec Pragma Implementation_Defined -@findex Implementation_Defined -@noindent +@node Pragma Implementation_Defined,Pragma Implemented,Pragma Ident,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-implementation-defined}@anchor{60} +@section Pragma Implementation_Defined + + Syntax: -@smallexample @c ada +@example pragma Implementation_Defined (local_NAME); -@end smallexample +@end example -@noindent This pragma marks a previously declared entioty as implementation-defined. For an overloaded entity, applies to the most recent homonym. -@smallexample @c ada +@example pragma Implementation_Defined; -@end smallexample +@end example -@noindent The form with no arguments appears anywhere within a scope, most typically a package spec, and indicates that all entities that are defined within the package spec are Implementation_Defined. @@ -3434,19 +3590,19 @@ implementation-defined entities introduced in language-defined units, for the purpose of implementing the No_Implementation_Identifiers restriction. -@node Pragma Implemented -@unnumberedsec Pragma Implemented -@findex Implemented -@noindent +@node Pragma Implemented,Pragma Implicit_Packing,Pragma Implementation_Defined,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-implemented}@anchor{61} +@section Pragma Implemented + + Syntax: -@smallexample @c ada +@example pragma Implemented (procedure_LOCAL_NAME, implementation_kind); implementation_kind ::= By_Entry | By_Protected_Procedure | By_Any -@end smallexample +@end example -@noindent This is an Ada 2012 representation pragma which applies to protected, task and synchronized interface primitives. The use of pragma Implemented provides a way to impose a static requirement on the overriding operation by adhering @@ -3454,7 +3610,7 @@ to one of the three implementation kinds: entry, protected procedure or any of the above. This pragma is available in all earlier versions of Ada as an implementation-defined pragma. -@smallexample @c ada +@example type Synch_Iface is synchronized interface; procedure Prim_Op (Obj : in out Iface) is abstract; pragma Implemented (Prim_Op, By_Protected_Procedure); @@ -3470,9 +3626,8 @@ end Prot_2; task type Task_Typ is new Synch_Iface with entry Prim_Op; -- Illegal end Task_Typ; -@end smallexample +@end example -@noindent When applied to the procedure_or_entry_NAME of a requeue statement, pragma Implemented determines the runtime behavior of the requeue. Implementation kind By_Entry guarantees that the action of requeueing will proceed from an entry to @@ -3481,29 +3636,29 @@ requeue into a dispatching call, thus eliminating the chance of blocking. Kind By_Any shares the behavior of By_Entry and By_Protected_Procedure depending on the target's overriding subprogram kind. -@node Pragma Implicit_Packing -@unnumberedsec Pragma Implicit_Packing -@findex Implicit_Packing -@cindex Rational Profile -@noindent +@node Pragma Implicit_Packing,Pragma Import_Function,Pragma Implemented,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-implicit-packing}@anchor{62} +@section Pragma Implicit_Packing + + +@geindex Rational Profile + Syntax: -@smallexample @c ada +@example pragma Implicit_Packing; -@end smallexample +@end example -@noindent This is a configuration pragma that requests implicit packing for packed arrays for which a size clause is given but no explicit pragma Pack or specification of Component_Size is present. It also applies to records where no record representation clause is present. Consider this example: -@smallexample @c ada +@example type R is array (0 .. 7) of Boolean; for R'Size use 8; -@end smallexample +@end example -@noindent In accordance with the recommendation in the RM (RM 13.3(53)), a Size clause does not change the layout of a composite object. So the Size clause in the above example is normally rejected, since the default layout of the array uses @@ -3518,58 +3673,31 @@ specify the exact size that corresponds to the number of elements in the array multiplied by the size in bits of the component type (both single and multi-dimensioned arrays can be controlled with this pragma). -@cindex Array packing +@geindex Array packing Similarly, the following example shows the use in the record case -@smallexample @c ada +@example type r is record a, b, c, d, e, f, g, h : boolean; chr : character; end record; for r'size use 16; -@end smallexample +@end example -@noindent Without a pragma Pack, each Boolean field requires 8 bits, so the minimum size is 72 bits, but with a pragma Pack, 16 bits would be sufficient. The use of pragma Implicit_Packing allows this record declaration to compile without an explicit pragma Pack. -@node Pragma Import_Exception -@unnumberedsec Pragma Import_Exception -@cindex OpenVMS -@findex Import_Exception -@noindent -Syntax: -@smallexample @c ada -pragma Import_Exception ( - [Internal =>] LOCAL_NAME - [, [External =>] EXTERNAL_SYMBOL] - [, [Form =>] Ada | VMS] - [, [Code =>] static_integer_EXPRESSION]); +@node Pragma Import_Function,Pragma Import_Object,Pragma Implicit_Packing,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-import-function}@anchor{63} +@section Pragma Import_Function + -EXTERNAL_SYMBOL ::= - IDENTIFIER -| static_string_EXPRESSION -@end smallexample - -@noindent -This pragma is implemented only in the OpenVMS implementation of GNAT@. -It allows OpenVMS conditions (for example, from OpenVMS system services or -other OpenVMS languages) to be propagated to Ada programs as Ada exceptions. -The pragma specifies that the exception associated with an exception -declaration in an Ada program be defined externally (in non-Ada code). -For further details on this pragma, see the -DEC Ada Language Reference Manual, section 13.9a.3.1. - -@node Pragma Import_Function -@unnumberedsec Pragma Import_Function -@findex Import_Function -@noindent Syntax: -@smallexample @c ada +@example pragma Import_Function ( [Internal =>] LOCAL_NAME, [, [External =>] EXTERNAL_SYMBOL] @@ -3600,27 +3728,26 @@ MECHANISM_ASSOCIATION ::= MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent -This pragma is used in conjunction with a pragma @code{Import} to +This pragma is used in conjunction with a pragma @cite{Import} to specify additional information for an imported function. The pragma -@code{Import} (or equivalent pragma @code{Interface}) must precede the -@code{Import_Function} pragma and both must appear in the same +@cite{Import} (or equivalent pragma @cite{Interface}) must precede the +@cite{Import_Function} pragma and both must appear in the same declarative part as the function specification. -The @var{Internal} argument must uniquely designate +The @cite{Internal} argument must uniquely designate the function to which the pragma applies. If more than one function name exists of this name in -the declarative part you must use the @code{Parameter_Types} and -@var{Result_Type} parameters to achieve the required unique +the declarative part you must use the @cite{Parameter_Types} and +@cite{Result_Type} parameters to achieve the required unique designation. Subtype marks in these parameters must exactly match the subtypes in the corresponding function specification, using positional notation to match parameters with subtype marks. -The form with an @code{'Access} attribute can be used to match an +The form with an @cite{'Access} attribute can be used to match an anonymous access parameter. -You may optionally use the @var{Mechanism} and @var{Result_Mechanism} +You may optionally use the @cite{Mechanism} and @cite{Result_Mechanism} parameters to specify passing mechanisms for the parameters and result. If you specify a single mechanism name, it applies to all parameters. Otherwise you may specify a mechanism on a @@ -3628,13 +3755,14 @@ parameter by parameter basis using either positional or named notation. If the mechanism is not specified, the default mechanism is used. -@node Pragma Import_Object -@unnumberedsec Pragma Import_Object -@findex Import_Object -@noindent +@node Pragma Import_Object,Pragma Import_Procedure,Pragma Import_Function,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-import-object}@anchor{64} +@section Pragma Import_Object + + Syntax: -@smallexample @c ada +@example pragma Import_Object [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -3643,24 +3771,24 @@ pragma Import_Object EXTERNAL_SYMBOL ::= IDENTIFIER | static_string_EXPRESSION -@end smallexample +@end example -@noindent This pragma designates an object as imported, and apart from the extended rules for external symbols, is identical in effect to the use of -the normal @code{Import} pragma applied to an object. Unlike the -subprogram case, you need not use a separate @code{Import} pragma, +the normal @cite{Import} pragma applied to an object. Unlike the +subprogram case, you need not use a separate @cite{Import} pragma, although you may do so (and probably should do so from a portability -point of view). @var{size} is syntax checked, but otherwise ignored by -GNAT@. +point of view). @cite{size} is syntax checked, but otherwise ignored by +GNAT. + +@node Pragma Import_Procedure,Pragma Import_Valued_Procedure,Pragma Import_Object,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-import-procedure}@anchor{65} +@section Pragma Import_Procedure + -@node Pragma Import_Procedure -@unnumberedsec Pragma Import_Procedure -@findex Import_Procedure -@noindent Syntax: -@smallexample @c ada +@example pragma Import_Procedure ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -3687,20 +3815,20 @@ MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent -This pragma is identical to @code{Import_Function} except that it +This pragma is identical to @cite{Import_Function} except that it applies to a procedure rather than a function and the parameters -@code{Result_Type} and @code{Result_Mechanism} are not permitted. +@cite{Result_Type} and @cite{Result_Mechanism} are not permitted. + +@node Pragma Import_Valued_Procedure,Pragma Independent,Pragma Import_Procedure,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-import-valued-procedure}@anchor{66} +@section Pragma Import_Valued_Procedure + -@node Pragma Import_Valued_Procedure -@unnumberedsec Pragma Import_Valued_Procedure -@findex Import_Valued_Procedure -@noindent Syntax: -@smallexample @c ada +@example pragma Import_Valued_Procedure ( [Internal =>] LOCAL_NAME [, [External =>] EXTERNAL_SYMBOL] @@ -3727,16 +3855,15 @@ MECHANISM_ASSOCIATION ::= [formal_parameter_NAME =>] MECHANISM_NAME MECHANISM_NAME ::= Value | Reference -@end smallexample +@end example -@noindent -This pragma is identical to @code{Import_Procedure} except that the -first parameter of @var{LOCAL_NAME}, which must be present, must be of -mode @code{OUT}, and externally the subprogram is treated as a function +This pragma is identical to @cite{Import_Procedure} except that the +first parameter of @cite{LOCAL_NAME}, which must be present, must be of +mode @cite{OUT}, and externally the subprogram is treated as a function with this parameter as the result of the function. The purpose of this -capability is to allow the use of @code{OUT} and @code{IN OUT} +capability is to allow the use of @cite{OUT} and @cite{IN OUT} parameters in interfacing to external functions (which are not permitted -in Ada functions). You may optionally use the @code{Mechanism} +in Ada functions). You may optionally use the @cite{Mechanism} parameters to specify passing mechanisms for the parameters. If you specify a single mechanism name, it applies to all parameters. Otherwise you may specify a mechanism on a parameter by parameter @@ -3747,17 +3874,17 @@ Note that it is important to use this pragma in conjunction with a separate pragma Import that specifies the desired convention, since otherwise the default convention is Ada, which is almost certainly not what is required. -@node Pragma Independent -@unnumberedsec Pragma Independent -@findex Independent -@noindent +@node Pragma Independent,Pragma Independent_Components,Pragma Import_Valued_Procedure,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-independent}@anchor{67} +@section Pragma Independent + + Syntax: -@smallexample @c ada +@example pragma Independent (Local_NAME); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2012 mode (which also provides an aspect of the same name). It is also available as an implementation-defined pragma in all earlier versions. It specifies that the @@ -3769,17 +3896,17 @@ This may place constraints on the representation of the object (for instance prohibiting tight packing). -@node Pragma Independent_Components -@unnumberedsec Pragma Independent_Components -@findex Independent_Components -@noindent +@node Pragma Independent_Components,Pragma Initial_Condition,Pragma Independent,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-independent-components}@anchor{68} +@section Pragma Independent_Components + + Syntax: -@smallexample @c ada +@example pragma Independent_Components (Local_NAME); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2012 mode (which also provides an aspect of the same name). It is also available as an implementation-defined pragma in all earlier versions. It specifies that the components of the @@ -3790,26 +3917,28 @@ manipulate separate components in the composite object. This may place constraints on the representation of the object (for instance prohibiting tight packing). -@node Pragma Initial_Condition -@unnumberedsec Pragma Initial_Condition -@findex Initial_Condition -@noindent +@node Pragma Initial_Condition,Pragma Initialize_Scalars,Pragma Independent_Components,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-initial-condition}@anchor{69} +@section Pragma Initial_Condition + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.6. -@node Pragma Initialize_Scalars -@unnumberedsec Pragma Initialize_Scalars -@findex Initialize_Scalars -@cindex debugging with Initialize_Scalars -@noindent +@node Pragma Initialize_Scalars,Pragma Initializes,Pragma Initial_Condition,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-initialize-scalars}@anchor{6a} +@section Pragma Initialize_Scalars + + +@geindex debugging with Initialize_Scalars + Syntax: -@smallexample @c ada +@example pragma Initialize_Scalars; -@end smallexample +@end example -@noindent -This pragma is similar to @code{Normalize_Scalars} conceptually but has +This pragma is similar to @cite{Normalize_Scalars} conceptually but has two important differences. First, there is no requirement for the pragma to be used uniformly in all units of a partition, in particular, it is fine to use this just for some or all of the application units of a partition, @@ -3829,7 +3958,7 @@ initialize with invalid values (similar to Normalize_Scalars, though for Initialize_Scalars it is not always possible to determine the invalid values in complex cases like signed component fields with non-standard sizes). You can also initialize with high or -low values, or with a specified bit pattern. See the @value{EDITION} +low values, or with a specified bit pattern. See the GNAT User's Guide for binder options for specifying these cases. This means that you can compile a program, and then without having to @@ -3841,186 +3970,192 @@ uninitialized value. It is even possible to change the value at execution time eliminating even the need to rebind with a different switch using an environment variable. -See the @value{EDITION} User's Guide for details. +See the GNAT User's Guide for details. -Note that pragma @code{Initialize_Scalars} is particularly useful in +Note that pragma @cite{Initialize_Scalars} is particularly useful in conjunction with the enhanced validity checking that is now provided in GNAT, which checks for invalid values under more conditions. -Using this feature (see description of the @option{-gnatV} flag in the -@value{EDITION} User's Guide) in conjunction with -pragma @code{Initialize_Scalars} +Using this feature (see description of the @emph{-gnatV} flag in the +GNAT User's Guide) in conjunction with +pragma @cite{Initialize_Scalars} provides a powerful new tool to assist in the detection of problems caused by uninitialized variables. -Note: the use of @code{Initialize_Scalars} has a fairly extensive +Note: the use of @cite{Initialize_Scalars} has a fairly extensive effect on the generated code. This may cause your code to be substantially larger. It may also cause an increase in the amount of stack required, so it is probably a good idea to turn on stack -checking (see description of stack checking in the @value{EDITION} +checking (see description of stack checking in the GNAT User's Guide) when using this pragma. -@node Pragma Initializes -@unnumberedsec Pragma Initializes -@findex Initializes -@noindent +@node Pragma Initializes,Pragma Inline_Always,Pragma Initialize_Scalars,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-initializes}@anchor{6b} +@section Pragma Initializes + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.1.5. -@node Pragma Inline_Always -@unnumberedsec Pragma Inline_Always -@findex Inline_Always -@noindent +@node Pragma Inline_Always,Pragma Inline_Generic,Pragma Initializes,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-always}@anchor{6c} +@section Pragma Inline_Always + + Syntax: -@smallexample @c ada +@example pragma Inline_Always (NAME [, NAME]); -@end smallexample +@end example -@noindent -Similar to pragma @code{Inline} except that inlining is not subject to -the use of option @option{-gnatn} or @option{-gnatN} and the inlining +Similar to pragma @cite{Inline} except that inlining is not subject to +the use of option @emph{-gnatn} or @emph{-gnatN} and the inlining happens regardless of whether these options are used. -@node Pragma Inline_Generic -@unnumberedsec Pragma Inline_Generic -@findex Inline_Generic -@noindent +@node Pragma Inline_Generic,Pragma Interface,Pragma Inline_Always,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-inline-generic}@anchor{6d} +@section Pragma Inline_Generic + + Syntax: -@smallexample @c ada +@example pragma Inline_Generic (GNAME @{, GNAME@}); GNAME ::= generic_unit_NAME | generic_instance_NAME -@end smallexample +@end example -@noindent This pragma is provided for compatibility with Dec Ada 83. It has -no effect in @code{GNAT} (which always inlines generics), other +no effect in @cite{GNAT} (which always inlines generics), other than to check that the given names are all names of generic units or generic instances. -@node Pragma Interface -@unnumberedsec Pragma Interface -@findex Interface -@noindent +@node Pragma Interface,Pragma Interface_Name,Pragma Inline_Generic,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-interface}@anchor{6e} +@section Pragma Interface + + Syntax: -@smallexample @c ada +@example pragma Interface ( [Convention =>] convention_identifier, [Entity =>] local_NAME [, [External_Name =>] static_string_expression] [, [Link_Name =>] static_string_expression]); -@end smallexample +@end example -@noindent This pragma is identical in syntax and semantics to -the standard Ada pragma @code{Import}. It is provided for compatibility +the standard Ada pragma @cite{Import}. It is provided for compatibility with Ada 83. The definition is upwards compatible both with pragma -@code{Interface} as defined in the Ada 83 Reference Manual, and also +@cite{Interface} as defined in the Ada 83 Reference Manual, and also with some extended implementations of this pragma in certain Ada 83 -implementations. The only difference between pragma @code{Interface} -and pragma @code{Import} is that there is special circuitry to allow +implementations. The only difference between pragma @cite{Interface} +and pragma @cite{Import} is that there is special circuitry to allow both pragmas to appear for the same subprogram entity (normally it -is illegal to have multiple @code{Import} pragmas. This is useful in +is illegal to have multiple @cite{Import} pragmas. This is useful in maintaining Ada 83/Ada 95 compatibility and is compatible with other Ada 83 compilers. -@node Pragma Interface_Name -@unnumberedsec Pragma Interface_Name -@findex Interface_Name -@noindent +@node Pragma Interface_Name,Pragma Interrupt_Handler,Pragma Interface,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-interface-name}@anchor{6f} +@section Pragma Interface_Name + + Syntax: -@smallexample @c ada +@example pragma Interface_Name ( [Entity =>] LOCAL_NAME [, [External_Name =>] static_string_EXPRESSION] [, [Link_Name =>] static_string_EXPRESSION]); -@end smallexample +@end example -@noindent This pragma provides an alternative way of specifying the interface name for an interfaced subprogram, and is provided for compatibility with Ada 83 compilers that use the pragma for this purpose. You must provide at -least one of @var{External_Name} or @var{Link_Name}. +least one of @cite{External_Name} or @cite{Link_Name}. + +@node Pragma Interrupt_Handler,Pragma Interrupt_State,Pragma Interface_Name,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-handler}@anchor{70} +@section Pragma Interrupt_Handler + -@node Pragma Interrupt_Handler -@unnumberedsec Pragma Interrupt_Handler -@findex Interrupt_Handler -@noindent Syntax: -@smallexample @c ada +@example pragma Interrupt_Handler (procedure_LOCAL_NAME); -@end smallexample +@end example -@noindent This program unit pragma is supported for parameterless protected procedures as described in Annex C of the Ada Reference Manual. On the AAMP target the pragma can also be specified for nonprotected parameterless procedures that are declared at the library level (which includes procedures declared at the top level of a library package). In the case of AAMP, when this pragma is applied to a nonprotected procedure, the instruction -@code{IERET} is generated for returns from the procedure, enabling +@cite{IERET} is generated for returns from the procedure, enabling maskable interrupts, in place of the normal return instruction. -@node Pragma Interrupt_State -@unnumberedsec Pragma Interrupt_State -@findex Interrupt_State -@noindent +@node Pragma Interrupt_State,Pragma Invariant,Pragma Interrupt_Handler,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-interrupt-state}@anchor{71} +@section Pragma Interrupt_State + + Syntax: -@smallexample @c ada +@example pragma Interrupt_State ([Name =>] value, [State =>] SYSTEM | RUNTIME | USER); -@end smallexample +@end example -@noindent Normally certain interrupts are reserved to the implementation. Any attempt to attach an interrupt causes Program_Error to be raised, as described in -RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in -many systems for an @kbd{Ctrl-C} interrupt. Normally this interrupt is -reserved to the implementation, so that @kbd{Ctrl-C} can be used to -interrupt execution. Additionally, signals such as @code{SIGSEGV}, -@code{SIGABRT}, @code{SIGFPE} and @code{SIGILL} are often mapped to specific +RM C.3.2(22). A typical example is the @cite{SIGINT} interrupt used in +many systems for an @code{Ctrl-C} interrupt. Normally this interrupt is +reserved to the implementation, so that @code{Ctrl-C} can be used to +interrupt execution. Additionally, signals such as @cite{SIGSEGV}, +@cite{SIGABRT}, @cite{SIGFPE} and @cite{SIGILL} are often mapped to specific Ada exceptions, or used to implement run-time functions such as the -@code{abort} statement and stack overflow checking. +@cite{abort} statement and stack overflow checking. -Pragma @code{Interrupt_State} provides a general mechanism for overriding +Pragma @cite{Interrupt_State} provides a general mechanism for overriding such uses of interrupts. It subsumes the functionality of pragma -@code{Unreserve_All_Interrupts}. Pragma @code{Interrupt_State} is not +@cite{Unreserve_All_Interrupts}. Pragma @cite{Interrupt_State} is not available on Windows or VMS. On all other platforms than VxWorks, it applies to signals; on VxWorks, it applies to vectored hardware interrupts and may be used to mark interrupts required by the board support package as reserved. Interrupts can be in one of three states: -@itemize @bullet -@item System + + +@itemize * + +@item +System The interrupt is reserved (no Ada handler can be installed), and the Ada run-time may not install a handler. As a result you are guaranteed standard system default action if this interrupt is raised. -@item Runtime +@item +Runtime The interrupt is reserved (no Ada handler can be installed). The run time is allowed to install a handler for internal control purposes, but is not required to do so. -@item User +@item +User The interrupt is unreserved. The user may install a handler to provide some other action. @end itemize -@noindent -These states are the allowed values of the @code{State} parameter of the -pragma. The @code{Name} parameter is a value of the type -@code{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in -@code{Ada.Interrupts.Names}. +These states are the allowed values of the @cite{State} parameter of the +pragma. The @cite{Name} parameter is a value of the type +@cite{Ada.Interrupts.Interrupt_ID}. Typically, it is a name declared in +@cite{Ada.Interrupts.Names}. This is a configuration pragma, and the binder will check that there are no inconsistencies between different units in a partition in how a @@ -4036,27 +4171,27 @@ a handler. Note that certain signals on many operating systems cannot be caught and handled by applications. In such cases, the pragma is ignored. See the -operating system documentation, or the value of the array @code{Reserved} -declared in the spec of package @code{System.OS_Interface}. +operating system documentation, or the value of the array @cite{Reserved} +declared in the spec of package @cite{System.OS_Interface}. Overriding the default state of signals used by the Ada runtime may interfere with an application's runtime behavior in the cases of the synchronous signals, -and in the case of the signal used to implement the @code{abort} statement. +and in the case of the signal used to implement the @cite{abort} statement. + +@node Pragma Invariant,Pragma Java_Constructor,Pragma Interrupt_State,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-invariant}@anchor{72} +@section Pragma Invariant + -@node Pragma Invariant -@unnumberedsec Pragma Invariant -@findex Invariant -@noindent Syntax: -@smallexample @c ada +@example pragma Invariant ([Entity =>] private_type_LOCAL_NAME, [Check =>] EXPRESSION [,[Message =>] String_Expression]); -@end smallexample +@end example -@noindent This pragma provides exactly the same capabilities as the Type_Invariant aspect defined in AI05-0146-1, and in the Ada 2012 Reference Manual. The Type_Invariant aspect is fully implemented in Ada 2012 mode, but since it @@ -4082,210 +4217,211 @@ invariant pragma for the same entity. For further details on the use of this pragma, see the Ada 2012 documentation of the Type_Invariant aspect. -@node Pragma Java_Constructor -@unnumberedsec Pragma Java_Constructor -@findex Java_Constructor -@noindent +@node Pragma Java_Constructor,Pragma Java_Interface,Pragma Invariant,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-java-constructor}@anchor{73} +@section Pragma Java_Constructor + + Syntax: -@smallexample @c ada +@example pragma Java_Constructor ([Entity =>] function_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma is used to assert that the specified Ada function should be mapped to the Java constructor for some Ada tagged record type. See section 7.3.2 of the -@code{GNAT User's Guide: Supplement for the JVM Platform.} +@cite{GNAT User's Guide: Supplement for the JVM Platform.} for related information. -@node Pragma Java_Interface -@unnumberedsec Pragma Java_Interface -@findex Java_Interface -@noindent +@node Pragma Java_Interface,Pragma Keep_Names,Pragma Java_Constructor,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-java-interface}@anchor{74} +@section Pragma Java_Interface + + Syntax: -@smallexample @c ada +@example pragma Java_Interface ([Entity =>] abstract_tagged_type_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma is used to assert that the specified Ada abstract tagged type is to be mapped to a Java interface name. See sections 7.1 and 7.2 of the -@code{GNAT User's Guide: Supplement for the JVM Platform.} +@cite{GNAT User's Guide: Supplement for the JVM Platform.} for related information. -@node Pragma Keep_Names -@unnumberedsec Pragma Keep_Names -@findex Keep_Names -@noindent +@node Pragma Keep_Names,Pragma License,Pragma Java_Interface,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-keep-names}@anchor{75} +@section Pragma Keep_Names + + Syntax: -@smallexample @c ada +@example pragma Keep_Names ([On =>] enumeration_first_subtype_LOCAL_NAME); -@end smallexample +@end example -@noindent -The @var{LOCAL_NAME} argument +The @cite{LOCAL_NAME} argument must refer to an enumeration first subtype in the current declarative part. The effect is to retain the enumeration -literal names for use by @code{Image} and @code{Value} even if a global -@code{Discard_Names} pragma applies. This is useful when you want to +literal names for use by @cite{Image} and @cite{Value} even if a global +@cite{Discard_Names} pragma applies. This is useful when you want to generally suppress enumeration literal names and for example you therefore -use a @code{Discard_Names} pragma in the @file{gnat.adc} file, but you +use a @cite{Discard_Names} pragma in the @code{gnat.adc} file, but you want to retain the names for specific enumeration types. -@node Pragma License -@unnumberedsec Pragma License -@findex License -@cindex License checking -@noindent +@node Pragma License,Pragma Link_With,Pragma Keep_Names,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-license}@anchor{76} +@section Pragma License + + +@geindex License checking + Syntax: -@smallexample @c ada +@example pragma License (Unrestricted | GPL | Modified_GPL | Restricted); -@end smallexample +@end example -@noindent This pragma is provided to allow automated checking for appropriate license -conditions with respect to the standard and modified GPL@. A pragma -@code{License}, which is a configuration pragma that typically appears at -the start of a source file or in a separate @file{gnat.adc} file, specifies +conditions with respect to the standard and modified GPL. A pragma +@cite{License}, which is a configuration pragma that typically appears at +the start of a source file or in a separate @code{gnat.adc} file, specifies the licensing conditions of a unit as follows: -@itemize @bullet -@item Unrestricted + +@itemize * + +@item +Unrestricted This is used for a unit that can be freely used with no license restrictions. Examples of such units are public domain units, and units from the Ada Reference Manual. -@item GPL +@item +GPL This is used for a unit that is licensed under the unmodified GPL, and which -therefore cannot be @code{with}'ed by a restricted unit. +therefore cannot be @cite{with}'ed by a restricted unit. -@item Modified_GPL +@item +Modified_GPL This is used for a unit licensed under the GNAT modified GPL that includes a special exception paragraph that specifically permits the inclusion of the unit in programs without requiring the entire program to be released -under the GPL@. +under the GPL. -@item Restricted +@item +Restricted This is used for a unit that is restricted in that it is not permitted to -depend on units that are licensed under the GPL@. Typical examples are +depend on units that are licensed under the GPL. Typical examples are proprietary code that is to be released under more restrictive license -conditions. Note that restricted units are permitted to @code{with} units +conditions. Note that restricted units are permitted to @cite{with} units which are licensed under the modified GPL (this is the whole point of the modified GPL). - @end itemize -@noindent -Normally a unit with no @code{License} pragma is considered to have an +Normally a unit with no @cite{License} pragma is considered to have an unknown license, and no checking is done. However, standard GNAT headers are recognized, and license information is derived from them as follows. A GNAT license header starts with a line containing 78 hyphens. The following comment text is searched for the appearance of any of the following strings. -If the string ``GNU General Public License'' is found, then the unit is assumed -to have GPL license, unless the string ``As a special exception'' follows, in -which case the license is assumed to be modified GPL@. +If the string 'GNU General Public License' is found, then the unit is assumed +to have GPL license, unless the string 'As a special exception' follows, in +which case the license is assumed to be modified GPL. If one of the strings -``This specification is adapted from the Ada Semantic Interface'' or -``This specification is derived from the Ada Reference Manual'' is found +'This specification is adapted from the Ada Semantic Interface' or +'This specification is derived from the Ada Reference Manual' is found then the unit is assumed to be unrestricted. -@noindent These default actions means that a program with a restricted license pragma will automatically get warnings if a GPL unit is inappropriately -@code{with}'ed. For example, the program: +@cite{with}'ed. For example, the program: -@smallexample @c ada +@example with Sem_Ch3; with GNAT.Sockets; procedure Secret_Stuff is - @dots{} + ... end Secret_Stuff -@end smallexample +@end example -@noindent -if compiled with pragma @code{License} (@code{Restricted}) in a -@file{gnat.adc} file will generate the warning: +if compiled with pragma @cite{License} (@cite{Restricted}) in a +@code{gnat.adc} file will generate the warning: -@smallexample +@example 1. with Sem_Ch3; | >>> license of withed unit "Sem_Ch3" is incompatible 2. with GNAT.Sockets; 3. procedure Secret_Stuff is -@end smallexample +@end example -@noindent -Here we get a warning on @code{Sem_Ch3} since it is part of the GNAT +Here we get a warning on @cite{Sem_Ch3} since it is part of the GNAT compiler and is licensed under the -GPL, but no warning for @code{GNAT.Sockets} which is part of the GNAT -run time, and is therefore licensed under the modified GPL@. +GPL, but no warning for @cite{GNAT.Sockets} which is part of the GNAT +run time, and is therefore licensed under the modified GPL. + +@node Pragma Link_With,Pragma Linker_Alias,Pragma License,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-link-with}@anchor{77} +@section Pragma Link_With + -@node Pragma Link_With -@unnumberedsec Pragma Link_With -@findex Link_With -@noindent Syntax: -@smallexample @c ada +@example pragma Link_With (static_string_EXPRESSION @{,static_string_EXPRESSION@}); -@end smallexample +@end example -@noindent This pragma is provided for compatibility with certain Ada 83 compilers. -It has exactly the same effect as pragma @code{Linker_Options} except +It has exactly the same effect as pragma @cite{Linker_Options} except that spaces occurring within one of the string expressions are treated as separators. For example, in the following case: -@smallexample @c ada +@example pragma Link_With ("-labc -ldef"); -@end smallexample +@end example -@noindent -results in passing the strings @code{-labc} and @code{-ldef} as two +results in passing the strings @cite{-labc} and @cite{-ldef} as two separate arguments to the linker. In addition pragma Link_With allows multiple arguments, with the same effect as successive pragmas. -@node Pragma Linker_Alias -@unnumberedsec Pragma Linker_Alias -@findex Linker_Alias -@noindent +@node Pragma Linker_Alias,Pragma Linker_Constructor,Pragma Link_With,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-alias}@anchor{78} +@section Pragma Linker_Alias + + Syntax: -@smallexample @c ada +@example pragma Linker_Alias ( [Entity =>] LOCAL_NAME, [Target =>] static_string_EXPRESSION); -@end smallexample +@end example -@noindent -@var{LOCAL_NAME} must refer to an object that is declared at the library +@cite{LOCAL_NAME} must refer to an object that is declared at the library level. This pragma establishes the given entity as a linker alias for the -given target. It is equivalent to @code{__attribute__((alias))} in GNU C -and causes @var{LOCAL_NAME} to be emitted as an alias for the symbol -@var{static_string_EXPRESSION} in the object file, that is to say no space -is reserved for @var{LOCAL_NAME} by the assembler and it will be resolved -to the same address as @var{static_string_EXPRESSION} by the linker. +given target. It is equivalent to @cite{__attribute__((alias))} in GNU C +and causes @cite{LOCAL_NAME} to be emitted as an alias for the symbol +@cite{static_string_EXPRESSION} in the object file, that is to say no space +is reserved for @cite{LOCAL_NAME} by the assembler and it will be resolved +to the same address as @cite{static_string_EXPRESSION} by the linker. -The actual linker name for the target must be used (e.g.@: the fully +The actual linker name for the target must be used (e.g., the fully encoded name with qualification in Ada, or the mangled name in C++), -or it must be declared using the C convention with @code{pragma Import} -or @code{pragma Export}. +or it must be declared using the C convention with @cite{pragma Import} +or @cite{pragma Export}. Not all target machines support this pragma. On some of them it is accepted -only if @code{pragma Weak_External} has been applied to @var{LOCAL_NAME}. +only if @cite{pragma Weak_External} has been applied to @cite{LOCAL_NAME}. -@smallexample @c ada +@example -- Example of the use of pragma Linker_Alias package p is @@ -4295,24 +4431,24 @@ package p is new_name_for_i : Integer; pragma Linker_Alias (new_name_for_i, "i"); end p; -@end smallexample +@end example + +@node Pragma Linker_Constructor,Pragma Linker_Destructor,Pragma Linker_Alias,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-constructor}@anchor{79} +@section Pragma Linker_Constructor + -@node Pragma Linker_Constructor -@unnumberedsec Pragma Linker_Constructor -@findex Linker_Constructor -@noindent Syntax: -@smallexample @c ada +@example pragma Linker_Constructor (procedure_LOCAL_NAME); -@end smallexample +@end example -@noindent -@var{procedure_LOCAL_NAME} must refer to a parameterless procedure that +@cite{procedure_LOCAL_NAME} must refer to a parameterless procedure that is declared at the library level. A procedure to which this pragma is applied will be treated as an initialization routine by the linker. -It is equivalent to @code{__attribute__((constructor))} in GNU C and -causes @var{procedure_LOCAL_NAME} to be invoked before the entry point +It is equivalent to @cite{__attribute__((constructor))} in GNU C and +causes @cite{procedure_LOCAL_NAME} to be invoked before the entry point of the executable is called (or immediately after the shared library is loaded if the procedure is linked in a shared library), in particular before the Ada run-time environment is set up. @@ -4327,47 +4463,47 @@ Alone Libraries, which provides a related capability without the restrictions listed above. Where possible, the use of Stand Alone Libraries is preferable to the use of this pragma. -@node Pragma Linker_Destructor -@unnumberedsec Pragma Linker_Destructor -@findex Linker_Destructor -@noindent +@node Pragma Linker_Destructor,Pragma Linker_Section,Pragma Linker_Constructor,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-destructor}@anchor{7a} +@section Pragma Linker_Destructor + + Syntax: -@smallexample @c ada +@example pragma Linker_Destructor (procedure_LOCAL_NAME); -@end smallexample +@end example -@noindent -@var{procedure_LOCAL_NAME} must refer to a parameterless procedure that +@cite{procedure_LOCAL_NAME} must refer to a parameterless procedure that is declared at the library level. A procedure to which this pragma is applied will be treated as a finalization routine by the linker. -It is equivalent to @code{__attribute__((destructor))} in GNU C and -causes @var{procedure_LOCAL_NAME} to be invoked after the entry point +It is equivalent to @cite{__attribute__((destructor))} in GNU C and +causes @cite{procedure_LOCAL_NAME} to be invoked after the entry point of the executable has exited (or immediately before the shared library is unloaded if the procedure is linked in a shared library), in particular after the Ada run-time environment is shut down. -See @code{pragma Linker_Constructor} for the set of restrictions that apply +See @cite{pragma Linker_Constructor} for the set of restrictions that apply because of these specific contexts. -@node Pragma Linker_Section -@unnumberedsec Pragma Linker_Section -@findex Linker_Section -@noindent +@node Pragma Linker_Section,Pragma Lock_Free,Pragma Linker_Destructor,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-linker-section}@anchor{7b} +@section Pragma Linker_Section + + Syntax: -@smallexample @c ada +@example pragma Linker_Section ( [Entity =>] LOCAL_NAME, [Section =>] static_string_EXPRESSION); -@end smallexample +@end example -@noindent -@var{LOCAL_NAME} must refer to an object, type, or subprogram that is +@cite{LOCAL_NAME} must refer to an object, type, or subprogram that is declared at the library level. This pragma specifies the name of the linker section for the given entity. It is equivalent to -@code{__attribute__((section))} in GNU C and causes @var{LOCAL_NAME} to -be placed in the @var{static_string_EXPRESSION} section of the +@cite{__attribute__((section))} in GNU C and causes @cite{LOCAL_NAME} to +be placed in the @cite{static_string_EXPRESSION} section of the executable (assuming the linker doesn't rename the section). GNAT also provides an implementation defined aspect of the same name. @@ -4390,8 +4526,8 @@ linker section is specified should has the default linker section. The compiler normally places library-level entities in standard sections depending on the class: procedures and functions generally go in the -@code{.text} section, initialized variables in the @code{.data} section -and uninitialized variables in the @code{.bss} section. +@cite{.text} section, initialized variables in the @cite{.data} section +and uninitialized variables in the @cite{.bss} section. Other, special sections may exist on given target machines to map special hardware, for example I/O ports or flash memory. This pragma is a means to @@ -4401,10 +4537,10 @@ at the symbolic level with the compiler. Some file formats do not support arbitrary sections so not all target machines support this pragma. The use of this pragma may cause a program execution to be erroneous if it is used to place an entity into an -inappropriate section (e.g.@: a modified variable into the @code{.text} -section). See also @code{pragma Persistent_BSS}. +inappropriate section (e.g., a modified variable into the @cite{.text} +section). See also @cite{pragma Persistent_BSS}. -@smallexample @c ada +@example -- Example of the use of pragma Linker_Section package IO_Card is @@ -4422,57 +4558,36 @@ package IO_Card is procedure Q with Linker_Section => "Qsection"; end IO_Card; -@end smallexample +@end example + +@node Pragma Lock_Free,Pragma Loop_Invariant,Pragma Linker_Section,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-lock-free}@anchor{7c} +@section Pragma Lock_Free + -@node Pragma Lock_Free -@unnumberedsec Pragma Lock_Free -@findex Lock_Free -@noindent Syntax: This pragma may be specified for protected types or objects. It specifies that the implementation of protected operations must be implemented without locks. Compilation fails if the compiler cannot generate lock-free code for the operations. -@node Pragma Long_Float -@unnumberedsec Pragma Long_Float -@cindex OpenVMS -@findex Long_Float -@noindent -Syntax: +@node Pragma Loop_Invariant,Pragma Loop_Optimize,Pragma Lock_Free,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-loop-invariant}@anchor{7d} +@section Pragma Loop_Invariant + -@smallexample @c ada -pragma Long_Float (FLOAT_FORMAT); - -FLOAT_FORMAT ::= D_Float | G_Float -@end smallexample - -@noindent -This pragma is implemented only in the OpenVMS implementation of GNAT@. -It allows control over the internal representation chosen for the predefined -type @code{Long_Float} and for floating point type representations with -@code{digits} specified in the range 7 through 15. -For further details on this pragma, see the -@cite{DEC Ada Language Reference Manual}, section 3.5.7b. Note that to use -this pragma, the standard runtime libraries must be recompiled. - -@node Pragma Loop_Invariant -@unnumberedsec Pragma Loop_Invariant -@findex Loop_Invariant -@noindent Syntax: -@smallexample @c ada +@example pragma Loop_Invariant ( boolean_EXPRESSION ); -@end smallexample +@end example -@noindent -The effect of this pragma is similar to that of pragma @code{Assert}, -except that in an @code{Assertion_Policy} pragma, the identifier -@code{Loop_Invariant} is used to control whether it is ignored or checked +The effect of this pragma is similar to that of pragma @cite{Assert}, +except that in an @cite{Assertion_Policy} pragma, the identifier +@cite{Loop_Invariant} is used to control whether it is ignored or checked (or disabled). -@code{Loop_Invariant} can only appear as one of the items in the sequence +@cite{Loop_Invariant} can only appear as one of the items in the sequence of statements of a loop body, or nested inside block statements that appear in the sequence of statements of a loop body. The intention is that it be used to @@ -4480,28 +4595,28 @@ represent a "loop invariant" assertion, i.e. something that is true each time through the loop, and which can be used to show that the loop is achieving its purpose. -Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that +Multiple @cite{Loop_Invariant} and @cite{Loop_Variant} pragmas that apply to the same loop should be grouped in the same sequence of statements. -To aid in writing such invariants, the special attribute @code{Loop_Entry} +To aid in writing such invariants, the special attribute @cite{Loop_Entry} may be used to refer to the value of an expression on entry to the loop. This -attribute can only be used within the expression of a @code{Loop_Invariant} -pragma. For full details, see documentation of attribute @code{Loop_Entry}. +attribute can only be used within the expression of a @cite{Loop_Invariant} +pragma. For full details, see documentation of attribute @cite{Loop_Entry}. + +@node Pragma Loop_Optimize,Pragma Loop_Variant,Pragma Loop_Invariant,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-loop-optimize}@anchor{7e} +@section Pragma Loop_Optimize + -@node Pragma Loop_Optimize -@unnumberedsec Pragma Loop_Optimize -@findex Loop_Optimize -@noindent Syntax: -@smallexample @c ada +@example pragma Loop_Optimize (OPTIMIZATION_HINT @{, OPTIMIZATION_HINT@}); OPTIMIZATION_HINT ::= Ivdep | No_Unroll | Unroll | No_Vector | Vector -@end smallexample +@end example -@noindent This pragma must appear immediately within a loop statement. It allows the programmer to specify optimization hints for the enclosing loop. The hints are not mutually exclusive and can be freely mixed, but not all combinations @@ -4509,56 +4624,62 @@ will yield a sensible outcome. There are five supported optimization hints for a loop: -@itemize @bullet -@item Ivdep + +@itemize * + +@item +Ivdep The programmer asserts that there are no loop-carried dependencies which would prevent consecutive iterations of the loop from being executed simultaneously. -@item No_Unroll +@item +No_Unroll The loop must not be unrolled. This is a strong hint: the compiler will not unroll a loop marked with this hint. -@item Unroll +@item +Unroll The loop should be unrolled. This is a weak hint: the compiler will try to apply unrolling to this loop preferably to other optimizations, notably vectorization, but there is no guarantee that the loop will be unrolled. -@item No_Vector +@item +No_Vector The loop must not be vectorized. This is a strong hint: the compiler will not vectorize a loop marked with this hint. -@item Vector +@item +Vector The loop should be vectorized. This is a weak hint: the compiler will try to apply vectorization to this loop preferably to other optimizations, notably unrolling, but there is no guarantee that the loop will be vectorized. - @end itemize These hints do not remove the need to pass the appropriate switches to the compiler in order to enable the relevant optimizations, that is to say -@option{-funroll-loops} for unrolling and @option{-ftree-vectorize} for +@emph{-funroll-loops} for unrolling and @emph{-ftree-vectorize} for vectorization. -@node Pragma Loop_Variant -@unnumberedsec Pragma Loop_Variant -@findex Loop_Variant -@noindent +@node Pragma Loop_Variant,Pragma Machine_Attribute,Pragma Loop_Optimize,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-loop-variant}@anchor{7f} +@section Pragma Loop_Variant + + Syntax: -@smallexample @c ada +@example pragma Loop_Variant ( LOOP_VARIANT_ITEM @{, LOOP_VARIANT_ITEM @} ); LOOP_VARIANT_ITEM ::= CHANGE_DIRECTION => discrete_EXPRESSION CHANGE_DIRECTION ::= Increases | Decreases -@end smallexample +@end example -@noindent -@code{Loop_Variant} can only appear as one of the items in the sequence +@cite{Loop_Variant} can only appear as one of the items in the sequence of statements of a loop body, or nested inside block statements that appear in the sequence of statements of a loop body. It allows the specification of quantities which must always @@ -4569,64 +4690,62 @@ on each iteration of the loop. In a more complex form, multiple arguments can be given which are intepreted in a nesting lexicographic manner. For example: -@smallexample @c ada +@example pragma Loop_Variant (Increases => X, Decreases => Y); -@end smallexample +@end example -@noindent specifies that each time through the loop either X increases, or X stays -the same and Y decreases. A @code{Loop_Variant} pragma ensures that the +the same and Y decreases. A @cite{Loop_Variant} pragma ensures that the loop is making progress. It can be useful in helping to show informally or prove formally that the loop always terminates. -@code{Loop_Variant} is an assertion whose effect can be controlled using -an @code{Assertion_Policy} with a check name of @code{Loop_Variant}. The -policy can be @code{Check} to enable the loop variant check, @code{Ignore} +@cite{Loop_Variant} is an assertion whose effect can be controlled using +an @cite{Assertion_Policy} with a check name of @cite{Loop_Variant}. The +policy can be @cite{Check} to enable the loop variant check, @cite{Ignore} to ignore the check (in which case the pragma has no effect on the program), -or @code{Disable} in which case the pragma is not even checked for correct +or @cite{Disable} in which case the pragma is not even checked for correct syntax. -Multiple @code{Loop_Invariant} and @code{Loop_Variant} pragmas that +Multiple @cite{Loop_Invariant} and @cite{Loop_Variant} pragmas that apply to the same loop should be grouped in the same sequence of statements. -The @code{Loop_Entry} attribute may be used within the expressions of the -@code{Loop_Variant} pragma to refer to values on entry to the loop. +The @cite{Loop_Entry} attribute may be used within the expressions of the +@cite{Loop_Variant} pragma to refer to values on entry to the loop. + +@node Pragma Machine_Attribute,Pragma Main,Pragma Loop_Variant,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-machine-attribute}@anchor{80} +@section Pragma Machine_Attribute + -@node Pragma Machine_Attribute -@unnumberedsec Pragma Machine_Attribute -@findex Machine_Attribute -@noindent Syntax: -@smallexample @c ada +@example pragma Machine_Attribute ( [Entity =>] LOCAL_NAME, [Attribute_Name =>] static_string_EXPRESSION [, [Info =>] static_EXPRESSION] ); -@end smallexample +@end example -@noindent Machine-dependent attributes can be specified for types and/or declarations. This pragma is semantically equivalent to -@code{__attribute__((@var{attribute_name}))} (if @var{info} is not -specified) or @code{__attribute__((@var{attribute_name}(@var{info})))} -in GNU C, where @code{@var{attribute_name}} is recognized by the -compiler middle-end or the @code{TARGET_ATTRIBUTE_TABLE} machine -specific macro. A string literal for the optional parameter @var{info} +@cite{__attribute__((`attribute_name}))` (if @cite{info} is not +specified) or @cite{__attribute__((`attribute_name`(`info}))) +in GNU C, where @code{attribute_name} is recognized by the +compiler middle-end or the @cite{TARGET_ATTRIBUTE_TABLE} machine +specific macro. A string literal for the optional parameter @cite{info} is transformed into an identifier, which may make this pragma unusable -for some attributes. @xref{Target Attributes,, Defining target-specific -uses of @code{__attribute__}, gccint, GNU Compiler Collection (GCC) -Internals}, further information. - -@node Pragma Main -@unnumberedsec Pragma Main -@cindex OpenVMS -@findex Main -@noindent +for some attributes. +For further information see @cite{GNU Compiler Collection (GCC) Internals}. + +@node Pragma Main,Pragma Main_Storage,Pragma Machine_Attribute,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-main}@anchor{81} +@section Pragma Main + + Syntax: -@smallexample @c ada +@example pragma Main (MAIN_OPTION [, MAIN_OPTION]); @@ -4634,44 +4753,41 @@ MAIN_OPTION ::= [Stack_Size =>] static_integer_EXPRESSION | [Task_Stack_Size_Default =>] static_integer_EXPRESSION | [Time_Slicing_Enabled =>] static_boolean_EXPRESSION -@end smallexample +@end example -@noindent This pragma is provided for compatibility with OpenVMS VAX Systems. It has no effect in GNAT, other than being syntax checked. -@node Pragma Main_Storage -@unnumberedsec Pragma Main_Storage -@cindex OpenVMS -@findex Main_Storage -@noindent +@node Pragma Main_Storage,Pragma No_Body,Pragma Main,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-main-storage}@anchor{82} +@section Pragma Main_Storage + + Syntax: -@smallexample @c ada +@example pragma Main_Storage (MAIN_STORAGE_OPTION [, MAIN_STORAGE_OPTION]); MAIN_STORAGE_OPTION ::= [WORKING_STORAGE =>] static_SIMPLE_EXPRESSION | [TOP_GUARD =>] static_SIMPLE_EXPRESSION -@end smallexample +@end example -@noindent This pragma is provided for compatibility with OpenVMS VAX Systems. It has -no effect in GNAT, other than being syntax checked. Note that the pragma -also has no effect in DEC Ada 83 for OpenVMS Alpha Systems. +no effect in GNAT, other than being syntax checked. + +@node Pragma No_Body,Pragma No_Elaboration_Code_All,Pragma Main_Storage,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-body}@anchor{83} +@section Pragma No_Body + -@node Pragma No_Body -@unnumberedsec Pragma No_Body -@findex No_Body -@noindent Syntax: -@smallexample @c ada +@example pragma No_Body; -@end smallexample +@end example -@noindent There are a number of cases in which a package spec does not require a body, and in fact a body is not permitted. GNAT will not permit the spec to be compiled if there is a body around. The pragma No_Body allows you to provide @@ -4684,57 +4800,57 @@ such a way that a body needed before is no longer needed. The provision of a dummy body with a No_Body pragma ensures that there is no interference from earlier versions of the package body. -@node Pragma No_Elaboration_Code_All -@unnumberedsec Pragma No_Elaboration_Code_All -@findex No_Elaboration_Code_All -@noindent +@node Pragma No_Elaboration_Code_All,Pragma No_Inline,Pragma No_Body,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-elaboration-code-all}@anchor{84} +@section Pragma No_Elaboration_Code_All + + Syntax: -@smallexample @c ada +@example pragma No_Elaboration_Code_All [(program_unit_NAME)]; -@end smallexample +@end example -@noindent This is a program unit pragma (there is also an equivalent aspect of the -same name) that establishes the restriction @code{No_Elaboration_Code} for +same name) that establishes the restriction @cite{No_Elaboration_Code} for the current unit and any extended main source units (body and subunits. It also has has the effect of enforcing a transitive application of this aspect, so that if any unit is implicitly or explicitly WITH'ed by the current unit, it must also have the No_Elaboration_Code_All aspect set. It may be applied to package or subprogram specs or their generic versions. -@node Pragma No_Inline -@unnumberedsec Pragma No_Inline -@findex No_Inline -@noindent +@node Pragma No_Inline,Pragma No_Return,Pragma No_Elaboration_Code_All,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-inline}@anchor{85} +@section Pragma No_Inline + + Syntax: -@smallexample @c ada +@example pragma No_Inline (NAME @{, NAME@}); -@end smallexample +@end example -@noindent This pragma suppresses inlining for the callable entity or the instances of -the generic subprogram designated by @var{NAME}, including inlining that -results from the use of pragma @code{Inline}. This pragma is always active, -in particular it is not subject to the use of option @option{-gnatn} or -@option{-gnatN}. It is illegal to specify both pragma @code{No_Inline} and -pragma @code{Inline_Always} for the same @var{NAME}. - -@node Pragma No_Return -@unnumberedsec Pragma No_Return -@findex No_Return -@noindent +the generic subprogram designated by @cite{NAME}, including inlining that +results from the use of pragma @cite{Inline}. This pragma is always active, +in particular it is not subject to the use of option @emph{-gnatn} or +@emph{-gnatN}. It is illegal to specify both pragma @cite{No_Inline} and +pragma @cite{Inline_Always} for the same @cite{NAME}. + +@node Pragma No_Return,Pragma No_Run_Time,Pragma No_Inline,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-return}@anchor{86} +@section Pragma No_Return + + Syntax: -@smallexample @c ada +@example pragma No_Return (procedure_LOCAL_NAME @{, procedure_LOCAL_NAME@}); -@end smallexample +@end example -@noindent -Each @var{procedure_LOCAL_NAME} argument must refer to one or more procedure +Each @cite{procedure_LOCAL_NAME} argument must refer to one or more procedure declarations in the current declarative part. A procedure to which this -pragma is applied may not contain any explicit @code{return} statements. +pragma is applied may not contain any explicit @cite{return} statements. In addition, if the procedure contains any implicit returns from falling off the end of a statement sequence, then execution of that implicit return will cause Program_Error to be raised. @@ -4748,56 +4864,56 @@ Note that in Ada 2005 mode, this pragma is part of the language. It is available in all earlier versions of Ada as an implementation-defined pragma. -@node Pragma No_Run_Time -@unnumberedsec Pragma No_Run_Time -@findex No_Run_Time -@noindent +@node Pragma No_Run_Time,Pragma No_Strict_Aliasing,Pragma No_Return,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-run-time}@anchor{87} +@section Pragma No_Run_Time + + Syntax: -@smallexample @c ada +@example pragma No_Run_Time; -@end smallexample +@end example -@noindent This is an obsolete configuration pragma that historically was used to set up a runtime library with no object code. It is now used only for internal testing. The pragma has been superseded by the reconfigurable -runtime capability of @code{GNAT}. +runtime capability of @cite{GNAT}. + +@node Pragma No_Strict_Aliasing,Pragma No_Tagged_Streams,Pragma No_Run_Time,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-strict-aliasing}@anchor{88} +@section Pragma No_Strict_Aliasing + -@node Pragma No_Strict_Aliasing -@unnumberedsec Pragma No_Strict_Aliasing -@findex No_Strict_Aliasing -@noindent Syntax: -@smallexample @c ada +@example pragma No_Strict_Aliasing [([Entity =>] type_LOCAL_NAME)]; -@end smallexample +@end example -@noindent -@var{type_LOCAL_NAME} must refer to an access type +@cite{type_LOCAL_NAME} must refer to an access type declaration in the current declarative part. The effect is to inhibit strict aliasing optimization for the given type. The form with no arguments is a configuration pragma which applies to all access types declared in units to which the pragma applies. For a detailed description of the strict aliasing optimization, and the situations -in which it must be suppressed, see @ref{Optimization and Strict -Aliasing,,, gnat_ugn, @value{EDITION} User's Guide}. +in which it must be suppressed, see the section on Optimization and Strict Aliasing +in the @cite{GNAT User's Guide}. This pragma currently has no effects on access to unconstrained array types. -@node Pragma No_Tagged_Streams -@unnumberedsec Pragma No_Tagged_Streams -@findex No_Tagged_Streams -@noindent +@node Pragma No_Tagged_Streams,Pragma Normalize_Scalars,Pragma No_Strict_Aliasing,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-no-tagged-streams}@anchor{89} +@section Pragma No_Tagged_Streams + + Syntax: -@smallexample @c ada +@example pragma No_Tagged_Streams; pragma No_Tagged_Streams [([Entity =>] tagged_type_LOCAL_NAME)]; -@end smallexample +@end example -@noindent Normally when a tagged type is introduced using a full type declaration, part of the processing includes generating stream access routines to be used by stream attributes referencing the type (or one of its subtypes @@ -4805,7 +4921,7 @@ or derived types). This can involve the generation of significant amounts of code which is wasted space if stream routines are not needed for the type in question. -The @code{No_Tagged_Streams} pragma causes the generation of these stream +The @cite{No_Tagged_Streams} pragma causes the generation of these stream routines to be skipped, and any attempt to use stream operations on types subject to this pragma will be statically rejected as illegal. @@ -4821,46 +4937,48 @@ and derived types of this type inherit the pragma automatically, so the effect applies to a complete hierarchy (this is necessary to deal with the class-wide dispatching versions of the stream routines). -@node Pragma Normalize_Scalars -@unnumberedsec Pragma Normalize_Scalars -@findex Normalize_Scalars -@noindent +@node Pragma Normalize_Scalars,Pragma Obsolescent,Pragma No_Tagged_Streams,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-normalize-scalars}@anchor{8a} +@section Pragma Normalize_Scalars + + Syntax: -@smallexample @c ada +@example pragma Normalize_Scalars; -@end smallexample +@end example -@noindent -This is a language defined pragma which is fully implemented in GNAT@. The +This is a language defined pragma which is fully implemented in GNAT. The effect is to cause all scalar objects that are not otherwise initialized to be initialized. The initial values are implementation dependent and are as follows: -@table @code -@item Standard.Character -@noindent + +@table @asis + +@item @emph{Standard.Character} + Objects whose root type is Standard.Character are initialized to Character'Last unless the subtype range excludes NUL (in which case NUL is used). This choice will always generate an invalid value if one exists. -@item Standard.Wide_Character -@noindent +@item @emph{Standard.Wide_Character} + Objects whose root type is Standard.Wide_Character are initialized to Wide_Character'Last unless the subtype range excludes NUL (in which case NUL is used). This choice will always generate an invalid value if one exists. -@item Standard.Wide_Wide_Character -@noindent +@item @emph{Standard.Wide_Wide_Character} + Objects whose root type is Standard.Wide_Wide_Character are initialized to the invalid value 16#FFFF_FFFF# unless the subtype range excludes NUL (in which case NUL is used). This choice will always generate an invalid value if one exists. -@item Integer types -@noindent +@item @emph{Integer types} + Objects of an integer type are treated differently depending on whether negative values are present in the subtype. If no negative values are present, then all one bits is used as the initial value except in the @@ -4874,37 +4992,41 @@ is in the subtype, and the largest positive number is not, in which case the largest positive value is used. This choice will always generate an invalid value if one exists. -@item Floating-Point Types +@item @emph{Floating-Point Types} + Objects of all floating-point types are initialized to all 1-bits. For standard IEEE format, this corresponds to a NaN (not a number) which is indeed an invalid value. -@item Fixed-Point Types +@item @emph{Fixed-Point Types} + Objects of all fixed-point types are treated as described above for integers, with the rules applying to the underlying integer value used to represent the fixed-point value. -@item Modular types +@item @emph{Modular types} + Objects of a modular type are initialized to all one bits, except in the special case where zero is excluded from the subtype, in which case all zero bits are used. This choice will always generate an invalid value if one exists. -@item Enumeration types -Objects of an enumeration type are initialized to all one-bits, i.e.@: to -the value @code{2 ** typ'Size - 1} unless the subtype excludes the literal +@item @emph{Enumeration types} + +Objects of an enumeration type are initialized to all one-bits, i.e., to +the value @cite{2 ** typ'Size - 1} unless the subtype excludes the literal whose Pos value is zero, in which case a code of zero is used. This choice will always generate an invalid value if one exists. - @end table -@node Pragma Obsolescent -@unnumberedsec Pragma Obsolescent -@findex Obsolescent -@noindent +@node Pragma Obsolescent,Pragma Optimize_Alignment,Pragma Normalize_Scalars,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-obsolescent}@anchor{8b}@anchor{gnat_rm/implementation_defined_pragmas id2}@anchor{8c} +@section Pragma Obsolescent + + Syntax: -@smallexample @c ada +@example pragma Obsolescent; pragma Obsolescent ( @@ -4915,9 +5037,8 @@ pragma Obsolescent ( [Entity =>] NAME [,[Message =>] static_string_EXPRESSION [,[Version =>] Ada_05]] ); -@end smallexample +@end example -@noindent This pragma can occur immediately following a declaration of an entity, including the case of a record component. If no Entity argument is present, then this declaration is the one to which the pragma applies. If an Entity @@ -4943,8 +5064,8 @@ Restrictions (No_Obsolescent_Features). This pragma can also be used as a program unit pragma for a package, in which case the entity name is the name of the package, and the pragma indicates that the entire package is considered -obsolescent. In this case a client @code{with}'ing such a package -violates the restriction, and the @code{with} statement is +obsolescent. In this case a client @cite{with}'ing such a package +violates the restriction, and the @cite{with} statement is flagged with warnings if the warning option is set. If the Version parameter is present (which must be exactly @@ -4953,11 +5074,11 @@ indication of obsolescence applies only when compiling in Ada 2005 mode. This is primarily intended for dealing with the situations in the predefined library where subprograms or packages have become defined as obsolescent in Ada 2005 -(e.g.@: in Ada.Characters.Handling), but may be used anywhere. +(e.g., in Ada.Characters.Handling), but may be used anywhere. The following examples show typical uses of this pragma: -@smallexample @c ada +@example package p is pragma Obsolescent (p, Message => "use pp instead of p"); end p; @@ -4987,26 +5108,27 @@ package q is (a, b : character) return character; pragma Obsolescent (Entity => "+"); end; -@end smallexample +@end example -@noindent Note that, as for all pragmas, if you use a pragma argument identifier, then all subsequent parameters must also use a pragma argument identifier. So if you specify "Entity =>" for the Entity argument, and a Message argument is present, it must be preceded by "Message =>". -@node Pragma Optimize_Alignment -@unnumberedsec Pragma Optimize_Alignment -@findex Optimize_Alignment -@cindex Alignment, default settings -@noindent +@node Pragma Optimize_Alignment,Pragma Ordered,Pragma Obsolescent,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-optimize-alignment}@anchor{8d} +@section Pragma Optimize_Alignment + + +@geindex Alignment +@geindex default settings + Syntax: -@smallexample @c ada +@example pragma Optimize_Alignment (TIME | SPACE | OFF); -@end smallexample +@end example -@noindent This is a configuration pragma which affects the choice of default alignments for types and objects where no alignment is explicitly specified. There is a time/space trade-off in the selection of these values. Large alignments result @@ -5022,22 +5144,21 @@ First any packed record is given an alignment of 1. Second, if a size is given for the type, then the alignment is chosen to avoid increasing this size. For example, consider: -@smallexample @c ada - type R is record - X : Integer; - Y : Character; - end record; +@example +type R is record + X : Integer; + Y : Character; +end record; - for R'Size use 5*8; -@end smallexample +for R'Size use 5*8; +@end example -@noindent In the default mode, this type gets an alignment of 4, so that access to the Integer field X are efficient. But this means that objects of the type end up with a size of 8 bytes. This is a valid choice, since sizes of objects are allowed to be bigger than the size of the type, but it can waste space if for example fields of type R appear in an enclosing record. If the above type is -compiled in @code{Optimize_Alignment (Space)} mode, the alignment is set to 1. +compiled in @cite{Optimize_Alignment (Space)} mode, the alignment is set to 1. However, there is one case in which SPACE is ignored. If a variable length record (that is a discriminated record with a component which is an array @@ -5052,20 +5173,19 @@ without changing the alignment of its type. Specifying TIME causes larger default alignments to be chosen in the case of small types with sizes that are not a power of 2. For example, consider: -@smallexample @c ada - type R is record - A : Character; - B : Character; - C : Boolean; - end record; +@example +type R is record + A : Character; + B : Character; + C : Boolean; +end record; - pragma Pack (R); - for R'Size use 17; -@end smallexample +pragma Pack (R); +for R'Size use 17; +@end example -@noindent The default alignment for this record is normally 1, but if this type is -compiled in @code{Optimize_Alignment (Time)} mode, then the alignment is set +compiled in @cite{Optimize_Alignment (Time)} mode, then the alignment is set to 4, which wastes space for objects of the type, since they are now 4 bytes long, but results in more efficient access when the whole record is referenced. @@ -5078,27 +5198,25 @@ unit are excluded from the consistency check, as are all predefined units. The latter are compiled by default in pragma Optimize_Alignment (Off) mode if no pragma appears at the start of the file. -@node Pragma Ordered -@unnumberedsec Pragma Ordered -@findex Ordered -@findex pragma @code{Ordered} -@noindent +@node Pragma Ordered,Pragma Overflow_Mode,Pragma Optimize_Alignment,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ordered}@anchor{8e} +@section Pragma Ordered + + Syntax: -@smallexample @c ada +@example pragma Ordered (enumeration_first_subtype_LOCAL_NAME); -@end smallexample +@end example -@noindent Most enumeration types are from a conceptual point of view unordered. For example, consider: -@smallexample @c ada +@example type Color is (Red, Blue, Green, Yellow); -@end smallexample +@end example -@noindent -By Ada semantics @code{Blue > Red} and @code{Green > Blue}, +By Ada semantics @cite{Blue > Red} and @cite{Green > Blue}, but really these relations make no sense; the enumeration type merely specifies a set of possible colors, and the order is unimportant. @@ -5108,66 +5226,61 @@ explicit ranges. (A @emph{client} is a unit where the type is referenced, other than the unit where the type is declared, its body, and its subunits.) For example, if code buried in some client says: -@smallexample @c ada +@example if Current_Color < Yellow then ... if Current_Color in Blue .. Green then ... -@end smallexample +@end example -@noindent then the client code is relying on the order, which is undesirable. It makes the code hard to read and creates maintenance difficulties if entries have to be added to the enumeration type. Instead, the code in the client should list the possibilities, or an appropriate subtype should be declared in the unit that declares the original enumeration type. E.g., the following subtype could -be declared along with the type @code{Color}: +be declared along with the type @cite{Color}: -@smallexample @c ada +@example subtype RBG is Color range Red .. Green; -@end smallexample +@end example -@noindent and then the client could write: -@smallexample @c ada +@example if Current_Color in RBG then ... if Current_Color = Blue or Current_Color = Green then ... -@end smallexample +@end example -@noindent However, some enumeration types are legitimately ordered from a conceptual point of view. For example, if you declare: -@smallexample @c ada +@example type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun); -@end smallexample +@end example -@noindent then the ordering imposed by the language is reasonable, and clients can depend on it, writing for example: -@smallexample @c ada +@example if D in Mon .. Fri then ... if D < Wed then ... -@end smallexample +@end example -@noindent -The pragma @option{Ordered} is provided to mark enumeration types that +The pragma @emph{Ordered} is provided to mark enumeration types that are conceptually ordered, alerting the reader that clients may depend on the ordering. GNAT provides a pragma to mark enumerations as ordered rather than one to mark them as unordered, since in our experience, the great majority of enumeration types are conceptually unordered. -The types @code{Boolean}, @code{Character}, @code{Wide_Character}, -and @code{Wide_Wide_Character} +The types @cite{Boolean}, @cite{Character}, @cite{Wide_Character}, +and @cite{Wide_Wide_Character} are considered to be ordered types, so each is declared with a -pragma @code{Ordered} in package @code{Standard}. +pragma @cite{Ordered} in package @cite{Standard}. -Normally pragma @code{Ordered} serves only as documentation and a guide for -coding standards, but GNAT provides a warning switch @option{-gnatw.u} that +Normally pragma @cite{Ordered} serves only as documentation and a guide for +coding standards, but GNAT provides a warning switch @emph{-gnatw.u} that requests warnings for inappropriate uses (comparisons and explicit subranges) for unordered types. If this switch is used, then any -enumeration type not marked with pragma @code{Ordered} will be considered +enumeration type not marked with pragma @cite{Ordered} will be considered as unordered, and will generate warnings for inappropriate uses. Note that generic types are not considered ordered or unordered (since the @@ -5175,69 +5288,69 @@ template can be instantiated for both cases), so we never generate warnings for the case of generic enumerated types. For additional information please refer to the description of the -@option{-gnatw.u} switch in the @value{EDITION} User's Guide. - -@node Pragma Overflow_Mode -@unnumberedsec Pragma Overflow_Mode -@findex Overflow checks -@findex Overflow mode -@findex pragma @code{Overflow_Mode} -@noindent +@emph{-gnatw.u} switch in the GNAT User's Guide. + +@node Pragma Overflow_Mode,Pragma Overriding_Renamings,Pragma Ordered,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-overflow-mode}@anchor{8f} +@section Pragma Overflow_Mode + + Syntax: -@smallexample @c ada +@example pragma Overflow_Mode ( [General =>] MODE [,[Assertions =>] MODE]); MODE ::= STRICT | MINIMIZED | ELIMINATED -@end smallexample +@end example -@noindent This pragma sets the current overflow mode to the given setting. For details of the meaning of these modes, please refer to the -``Overflow Check Handling in GNAT'' appendix in the -@value{EDITION} User's Guide. If only the @code{General} parameter is present, +'Overflow Check Handling in GNAT' appendix in the +GNAT User's Guide. If only the @cite{General} parameter is present, the given mode applies to all expressions. If both parameters are present, -the @code{General} mode applies to expressions outside assertions, and -the @code{Eliminated} mode applies to expressions within assertions. +the @cite{General} mode applies to expressions outside assertions, and +the @cite{Eliminated} mode applies to expressions within assertions. -The case of the @code{MODE} parameter is ignored, -so @code{MINIMIZED}, @code{Minimized} and -@code{minimized} all have the same effect. +The case of the @cite{MODE} parameter is ignored, +so @cite{MINIMIZED}, @cite{Minimized} and +@cite{minimized} all have the same effect. -The @code{Overflow_Mode} pragma has the same scoping and placement -rules as pragma @code{Suppress}, so it can occur either as a +The @cite{Overflow_Mode} pragma has the same scoping and placement +rules as pragma @cite{Suppress}, so it can occur either as a configuration pragma, specifying a default for the whole program, or in a declarative scope, where it applies to the remaining declarations and statements in that scope. -The pragma @code{Suppress (Overflow_Check)} suppresses +The pragma @cite{Suppress (Overflow_Check)} suppresses overflow checking, but does not affect the overflow mode. -The pragma @code{Unsuppress (Overflow_Check)} unsuppresses (enables) +The pragma @cite{Unsuppress (Overflow_Check)} unsuppresses (enables) overflow checking, but does not affect the overflow mode. -@node Pragma Overriding_Renamings -@unnumberedsec Pragma Overriding_Renamings -@findex Overriding_Renamings -@cindex Rational profile -@cindex Rational compatibility -@noindent +@node Pragma Overriding_Renamings,Pragma Partition_Elaboration_Policy,Pragma Overflow_Mode,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-overriding-renamings}@anchor{90} +@section Pragma Overriding_Renamings + + +@geindex Rational profile + +@geindex Rational compatibility + Syntax: -@smallexample @c ada +@example pragma Overriding_Renamings; -@end smallexample +@end example -@noindent This is a GNAT configuration pragma to simplify porting legacy code accepted by the Rational Ada compiler. In the presence of this pragma, a renaming declaration that renames an inherited operation declared in the same scope is legal if selected notation is used as in: -@smallexample @c ada +@example pragma Overriding_Renamings; ... package R is @@ -5245,72 +5358,73 @@ package R is ... function F (..) renames R.F; end R; -@end smallexample +@end example even though RM 8.3 (15) stipulates that an overridden operation is not visible within the declaration of the overriding operation. -@node Pragma Partition_Elaboration_Policy -@unnumberedsec Pragma Partition_Elaboration_Policy -@findex Partition_Elaboration_Policy -@noindent +@node Pragma Partition_Elaboration_Policy,Pragma Part_Of,Pragma Overriding_Renamings,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-partition-elaboration-policy}@anchor{91} +@section Pragma Partition_Elaboration_Policy + + Syntax: -@smallexample @c ada +@example pragma Partition_Elaboration_Policy (POLICY_IDENTIFIER); POLICY_IDENTIFIER ::= Concurrent | Sequential -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Part_Of -@unnumberedsec Pragma Part_Of -@findex Part_Of -@noindent +@node Pragma Part_Of,Pragma Passive,Pragma Partition_Elaboration_Policy,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-part-of}@anchor{92} +@section Pragma Part_Of + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.2.6. -@node Pragma Passive -@unnumberedsec Pragma Passive -@findex Passive -@noindent +@node Pragma Passive,Pragma Persistent_BSS,Pragma Part_Of,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-passive}@anchor{93} +@section Pragma Passive + + Syntax: -@smallexample @c ada +@example pragma Passive [(Semaphore | No)]; -@end smallexample +@end example -@noindent -Syntax checked, but otherwise ignored by GNAT@. This is recognized for +Syntax checked, but otherwise ignored by GNAT. This is recognized for compatibility with DEC Ada 83 implementations, where it is used within a task definition to request that a task be made passive. If the argument -@code{Semaphore} is present, or the argument is omitted, then DEC Ada 83 +@cite{Semaphore} is present, or the argument is omitted, then DEC Ada 83 treats the pragma as an assertion that the containing task is passive and that optimization of context switch with this task is permitted and -desired. If the argument @code{No} is present, the task must not be +desired. If the argument @cite{No} is present, the task must not be optimized. GNAT does not attempt to optimize any tasks in this manner (since protected objects are available in place of passive tasks). For more information on the subject of passive tasks, see the section -``Passive Task Optimization'' in the GNAT Users Guide. +'Passive Task Optimization' in the GNAT Users Guide. + +@node Pragma Persistent_BSS,Pragma Polling,Pragma Passive,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-persistent-bss}@anchor{94} +@section Pragma Persistent_BSS + -@node Pragma Persistent_BSS -@unnumberedsec Pragma Persistent_BSS -@findex Persistent_BSS -@noindent Syntax: -@smallexample @c ada +@example pragma Persistent_BSS [(LOCAL_NAME)] -@end smallexample +@end example -@noindent -This pragma allows selected objects to be placed in the @code{.persistent_bss} +This pragma allows selected objects to be placed in the @cite{.persistent_bss} section. On some targets the linker and loader provide for special treatment of this section, allowing a program to be reloaded without affecting the contents of this data (hence the name persistent). @@ -5328,89 +5442,94 @@ or an array, all of whose constraints are static, and whose component type is potentially persistent. If this pragma is used on a target where this feature is not supported, -then the pragma will be ignored. See also @code{pragma Linker_Section}. +then the pragma will be ignored. See also @cite{pragma Linker_Section}. + +@node Pragma Polling,Pragma Post,Pragma Persistent_BSS,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-polling}@anchor{95} +@section Pragma Polling + -@node Pragma Polling -@unnumberedsec Pragma Polling -@findex Polling -@noindent Syntax: -@smallexample @c ada +@example pragma Polling (ON | OFF); -@end smallexample +@end example -@noindent This pragma controls the generation of polling code. This is normally off. -If @code{pragma Polling (ON)} is used then periodic calls are generated to -the routine @code{Ada.Exceptions.Poll}. This routine is a separate unit in the -runtime library, and can be found in file @file{a-excpol.adb}. +If @cite{pragma Polling (ON)} is used then periodic calls are generated to +the routine @cite{Ada.Exceptions.Poll}. This routine is a separate unit in the +runtime library, and can be found in file @code{a-excpol.adb}. -Pragma @code{Polling} can appear as a configuration pragma (for example it -can be placed in the @file{gnat.adc} file) to enable polling globally, or it +Pragma @cite{Polling} can appear as a configuration pragma (for example it +can be placed in the @code{gnat.adc} file) to enable polling globally, or it can be used in the statement or declaration sequence to control polling more locally. A call to the polling routine is generated at the start of every loop and -at the start of every subprogram call. This guarantees that the @code{Poll} +at the start of every subprogram call. This guarantees that the @cite{Poll} routine is called frequently, and places an upper bound (determined by -the complexity of the code) on the period between two @code{Poll} calls. +the complexity of the code) on the period between two @cite{Poll} calls. The primary purpose of the polling interface is to enable asynchronous aborts on targets that cannot otherwise support it (for example Windows NT), but it may be used for any other purpose requiring periodic polling. The standard version is null, and can be replaced by a user program. This -will require re-compilation of the @code{Ada.Exceptions} package that can -be found in files @file{a-except.ads} and @file{a-except.adb}. +will require re-compilation of the @cite{Ada.Exceptions} package that can +be found in files @code{a-except.ads} and @code{a-except.adb}. -A standard alternative unit (in file @file{4wexcpol.adb} in the standard GNAT +A standard alternative unit (in file @code{4wexcpol.adb} in the standard GNAT distribution) is used to enable the asynchronous abort capability on targets that do not normally support the capability. The version of -@code{Poll} in this file makes a call to the appropriate runtime routine +@cite{Poll} in this file makes a call to the appropriate runtime routine to test for an abort condition. -Note that polling can also be enabled by use of the @option{-gnatP} switch. -@xref{Switches for gcc,,, gnat_ugn, @value{EDITION} User's Guide}, for -details. +Note that polling can also be enabled by use of the @emph{-gnatP} switch. +See the section on switches for gcc in the @cite{GNAT User's Guide}. + +@node Pragma Post,Pragma Postcondition,Pragma Polling,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-post}@anchor{96} +@section Pragma Post + + +@geindex Post + +@geindex Checks +@geindex postconditions -@node Pragma Post -@unnumberedsec Pragma Post -@cindex Post -@cindex Checks, postconditions -@findex Postconditions -@noindent Syntax: -@smallexample @c ada +@example pragma Post (Boolean_Expression); -@end smallexample +@end example -@noindent -The @code{Post} pragma is intended to be an exact replacement for +The @cite{Post} pragma is intended to be an exact replacement for the language-defined -@code{Post} aspect, and shares its restrictions and semantics. +@cite{Post} aspect, and shares its restrictions and semantics. It must appear either immediately following the corresponding subprogram declaration (only other pragmas may intervene), or if there is no separate subprogram declaration, then it can appear at the start of the declarations in a subprogram body (preceded only by other pragmas). -@node Pragma Postcondition -@unnumberedsec Pragma Postcondition -@cindex Postcondition -@cindex Checks, postconditions -@findex Postconditions -@noindent +@node Pragma Postcondition,Pragma Post_Class,Pragma Post,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-postcondition}@anchor{97} +@section Pragma Postcondition + + +@geindex Postcondition + +@geindex Checks +@geindex postconditions + Syntax: -@smallexample @c ada +@example pragma Postcondition ( [Check =>] Boolean_Expression [,[Message =>] String_Expression]); -@end smallexample +@end example -@noindent -The @code{Postcondition} pragma allows specification of automatic +The @cite{Postcondition} pragma allows specification of automatic postcondition checks for subprograms. These checks are similar to assertions, but are automatically inserted just prior to the return statements of the subprogram with which they are associated (including @@ -5421,7 +5540,7 @@ In addition, the boolean expression which is the condition which must be true may contain references to function'Result in the case of a function to refer to the returned value. -@code{Postcondition} pragmas may appear either immediately following the +@cite{Postcondition} pragmas may appear either immediately following the (separate) declaration of a subprogram, or at the start of the declarations of a subprogram body. Only other pragmas may intervene (that is appear between the subprogram declaration and its @@ -5434,24 +5553,23 @@ referenced in the postcondition expressions. The postconditions are collected and automatically tested just before any return (implicit or explicit) in the subprogram body. A postcondition is only recognized if postconditions are active -at the time the pragma is encountered. The compiler switch @option{gnata} -turns on all postconditions by default, and pragma @code{Check_Policy} -with an identifier of @code{Postcondition} can also be used to +at the time the pragma is encountered. The compiler switch @emph{gnata} +turns on all postconditions by default, and pragma @cite{Check_Policy} +with an identifier of @cite{Postcondition} can also be used to control whether postconditions are active. The general approach is that postconditions are placed in the spec if they represent functional aspects which make sense to the client. For example we might have: -@smallexample @c ada - function Direction return Integer; - pragma Postcondition - (Direction'Result = +1 - or else - Direction'Result = -1); -@end smallexample +@example +function Direction return Integer; +pragma Postcondition + (Direction'Result = +1 + or else + Direction'Result = -1); +@end example -@noindent which serves to document that the result must be +1 or -1, and will test that this is the case at run time if postcondition checking is active. @@ -5463,18 +5581,17 @@ For instance if a square root routine keeps an internal counter of the number of times it is called, then we might have the following postcondition: -@smallexample @c ada - Sqrt_Calls : Natural := 0; +@example +Sqrt_Calls : Natural := 0; - function Sqrt (Arg : Float) return Float is - pragma Postcondition - (Sqrt_Calls = Sqrt_Calls'Old + 1); - ... - end Sqrt -@end smallexample +function Sqrt (Arg : Float) return Float is + pragma Postcondition + (Sqrt_Calls = Sqrt_Calls'Old + 1); + ... +end Sqrt +@end example -@noindent -As this example, shows, the use of the @code{Old} attribute +As this example, shows, the use of the @cite{Old} attribute is often useful in postconditions to refer to the state on entry to the subprogram. @@ -5483,11 +5600,11 @@ from the subprogram. If an abnormal return results from raising an exception, then the postconditions are not checked. If a postcondition fails, then the exception -@code{System.Assertions.Assert_Failure} is raised. If +@cite{System.Assertions.Assert_Failure} is raised. If a message argument was supplied, then the given string will be used as the exception message. If no message argument was supplied, then the default message has -the form "Postcondition failed at file:line". The +the form "Postcondition failed at file_name:line". The exception is raised in the context of the subprogram body, so it is possible to catch postcondition failures within the subprogram body itself. @@ -5503,7 +5620,7 @@ the package spec, allowing forward references. The following example shows that this even allows mutually recursive postconditions as in: -@smallexample @c ada +@example package Parity_Functions is function Odd (X : Natural) return Boolean; pragma Postcondition @@ -5520,15 +5637,14 @@ package Parity_Functions is (x /= 1 and then Odd (X - 1)))); end Parity_Functions; -@end smallexample +@end example -@noindent There are no restrictions on the complexity or form of -conditions used within @code{Postcondition} pragmas. +conditions used within @cite{Postcondition} pragmas. The following example shows that it is even possible to verify performance behavior. -@smallexample @c ada +@example package Sort is Performance : constant Float; @@ -5543,94 +5659,102 @@ package Sort is log (Float (Arg'Length)) * Performance); end Sort; -@end smallexample +@end example -@noindent Note: postcondition pragmas associated with subprograms that are marked as Inline_Always, or those marked as Inline with front-end inlining (-gnatN option set) are accepted and legality-checked by the compiler, but are ignored at run-time even if postcondition checking is enabled. -Note that pragma @code{Postcondition} differs from the language-defined -@code{Post} aspect (and corresponding @code{Post} pragma) in allowing +Note that pragma @cite{Postcondition} differs from the language-defined +@cite{Post} aspect (and corresponding @cite{Post} pragma) in allowing multiple occurrences, allowing occurences in the body even if there is a separate spec, and allowing a second string parameter, and the -use of the pragma identifier @code{Check}. Historically, pragma -@code{Postcondition} was implemented prior to the development of +use of the pragma identifier @cite{Check}. Historically, pragma +@cite{Postcondition} was implemented prior to the development of Ada 2012, and has been retained in its original form for compatibility purposes. -@node Pragma Post_Class -@unnumberedsec Pragma Post_Class -@cindex Post -@cindex Checks, postconditions -@findex Postconditions -@noindent +@node Pragma Post_Class,Pragma Pre,Pragma Postcondition,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-post-class}@anchor{98} +@section Pragma Post_Class + + +@geindex Post + +@geindex Checks +@geindex postconditions + Syntax: -@smallexample @c ada +@example pragma Post_Class (Boolean_Expression); -@end smallexample +@end example -@noindent -The @code{Post_Class} pragma is intended to be an exact replacement for +The @cite{Post_Class} pragma is intended to be an exact replacement for the language-defined -@code{Post'Class} aspect, and shares its restrictions and semantics. +@cite{Post'Class} aspect, and shares its restrictions and semantics. It must appear either immediately following the corresponding subprogram declaration (only other pragmas may intervene), or if there is no separate subprogram declaration, then it can appear at the start of the declarations in a subprogram body (preceded only by other pragmas). -Note: This pragma is called @code{Post_Class} rather than -@code{Post'Class} because the latter would not be strictly +Note: This pragma is called @cite{Post_Class} rather than +@cite{Post'Class} because the latter would not be strictly conforming to the allowed syntax for pragmas. The motivation for provinding pragmas equivalent to the aspects is to allow a program to be written using the pragmas, and then compiled if necessary using an Ada compiler that does not recognize the pragmas or aspects, but is prepared to ignore the pragmas. The assertion -policy that controls this pragma is @code{Post'Class}, not -@code{Post_Class}. - -@node Pragma Pre -@unnumberedsec Pragma Pre -@cindex Pre -@cindex Checks, preconditions -@findex Preconditions -@noindent +policy that controls this pragma is @cite{Post'Class}, not +@cite{Post_Class}. + +@node Pragma Pre,Pragma Precondition,Pragma Post_Class,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-pre}@anchor{99} +@section Pragma Pre + + +@geindex Pre + +@geindex Checks +@geindex preconditions + Syntax: -@smallexample @c ada +@example pragma Pre (Boolean_Expression); -@end smallexample +@end example -@noindent -The @code{Pre} pragma is intended to be an exact replacement for +The @cite{Pre} pragma is intended to be an exact replacement for the language-defined -@code{Pre} aspect, and shares its restrictions and semantics. +@cite{Pre} aspect, and shares its restrictions and semantics. It must appear either immediately following the corresponding subprogram declaration (only other pragmas may intervene), or if there is no separate subprogram declaration, then it can appear at the start of the declarations in a subprogram body (preceded only by other pragmas). -@node Pragma Precondition -@unnumberedsec Pragma Precondition -@cindex Preconditions -@cindex Checks, preconditions -@findex Preconditions -@noindent +@node Pragma Precondition,Pragma Predicate,Pragma Pre,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-precondition}@anchor{9a} +@section Pragma Precondition + + +@geindex Preconditions + +@geindex Checks +@geindex preconditions + Syntax: -@smallexample @c ada +@example pragma Precondition ( [Check =>] Boolean_Expression [,[Message =>] String_Expression]); -@end smallexample +@end example -@noindent -The @code{Precondition} pragma is similar to @code{Postcondition} +The @cite{Precondition} pragma is similar to @cite{Postcondition} except that the corresponding checks take place immediately upon entry to the subprogram, and if a precondition fails, the exception is raised in the context of the caller, and the attribute 'Result @@ -5640,17 +5764,16 @@ Otherwise, the placement and visibility rules are identical to those described for postconditions. The following is an example of use within a package spec: -@smallexample @c ada +@example package Math_Functions is ... function Sqrt (Arg : Float) return Float; pragma Precondition (Arg >= 0.0) ... end Math_Functions; -@end smallexample +@end example -@noindent -@code{Precondition} pragmas may appear either immediately following the +@cite{Precondition} pragmas may appear either immediately following the (separate) declaration of a subprogram, or at the start of the declarations of a subprogram body. Only other pragmas may intervene (that is appear between the subprogram declaration and its @@ -5663,58 +5786,56 @@ inlining (-gnatN option set) are accepted and legality-checked by the compiler, but are ignored at run-time even if precondition checking is enabled. -Note that pragma @code{Precondition} differs from the language-defined -@code{Pre} aspect (and corresponding @code{Pre} pragma) in allowing +Note that pragma @cite{Precondition} differs from the language-defined +@cite{Pre} aspect (and corresponding @cite{Pre} pragma) in allowing multiple occurrences, allowing occurences in the body even if there is a separate spec, and allowing a second string parameter, and the -use of the pragma identifier @code{Check}. Historically, pragma -@code{Precondition} was implemented prior to the development of +use of the pragma identifier @cite{Check}. Historically, pragma +@cite{Precondition} was implemented prior to the development of Ada 2012, and has been retained in its original form for compatibility purposes. -@node Pragma Predicate -@unnumberedsec Pragma Predicate -@findex Predicate -@findex Predicate pragma -@noindent +@node Pragma Predicate,Pragma Preelaborable_Initialization,Pragma Precondition,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-predicate}@anchor{9b} +@section Pragma Predicate + + Syntax: -@smallexample @c ada +@example pragma Predicate ([Entity =>] type_LOCAL_NAME, [Check =>] EXPRESSION); -@end smallexample +@end example -@noindent This pragma (available in all versions of Ada in GNAT) encompasses both -the @code{Static_Predicate} and @code{Dynamic_Predicate} aspects in +the @cite{Static_Predicate} and @cite{Dynamic_Predicate} aspects in Ada 2012. A predicate is regarded as static if it has an allowed form -for @code{Static_Predicate} and is otherwise treated as a -@code{Dynamic_Predicate}. Otherwise, predicates specified by this +for @cite{Static_Predicate} and is otherwise treated as a +@cite{Dynamic_Predicate}. Otherwise, predicates specified by this pragma behave exactly as described in the Ada 2012 reference manual. For example, if we have -@smallexample @c ada +@example type R is range 1 .. 10; subtype S is R; pragma Predicate (Entity => S, Check => S not in 4 .. 6); subtype Q is R pragma Predicate (Entity => Q, Check => F(Q) or G(Q)); -@end smallexample +@end example -@noindent the effect is identical to the following Ada 2012 code: -@smallexample @c ada +@example type R is range 1 .. 10; subtype S is R with Static_Predicate => S not in 4 .. 6; subtype Q is R with Dynamic_Predicate => F(Q) or G(Q); -@end smallexample +@end example -Note that there is are no pragmas @code{Dynamic_Predicate} -or @code{Static_Predicate}. That is +Note that there is are no pragmas @cite{Dynamic_Predicate} +or @cite{Static_Predicate}. That is because these pragmas would affect legality and semantics of the program and thus do not have a neutral effect if ignored. The motivation behind providing pragmas equivalent to @@ -5724,39 +5845,42 @@ will ignore the pragmas. That doesn't work in the case of static and dynamic predicates, since if the corresponding pragmas are ignored, then the behavior of the program is fundamentally changed (for example a membership test -@code{A in B} would not take into account a predicate +@cite{A in B} would not take into account a predicate defined for subtype B). When following this approach, the use of predicates should be avoided. -@node Pragma Preelaborable_Initialization -@unnumberedsec Pragma Preelaborable_Initialization -@findex Preelaborable_Initialization -@noindent +@node Pragma Preelaborable_Initialization,Pragma Prefix_Exception_Messages,Pragma Predicate,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-preelaborable-initialization}@anchor{9c} +@section Pragma Preelaborable_Initialization + + Syntax: -@smallexample @c ada +@example pragma Preelaborable_Initialization (DIRECT_NAME); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Prefix_Exception_Messages -@unnumberedsec Pragma Prefix_Exception_Messages -@cindex Prefix_Exception_Messages -@cindex exception -@cindex Exception_Message -@findex Exceptions -@noindent +@node Pragma Prefix_Exception_Messages,Pragma Pre_Class,Pragma Preelaborable_Initialization,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-prefix-exception-messages}@anchor{9d} +@section Pragma Prefix_Exception_Messages + + +@geindex Prefix_Exception_Messages + +@geindex exception + +@geindex Exception_Message + Syntax: -@smallexample @c ada +@example pragma Prefix_Exception_Messages; -@end smallexample +@end example -@noindent This is an implementation-defined configuration pragma that affects the behavior of raise statements with a message given as a static string constant (typically a string literal). In such cases, the string will @@ -5769,47 +5893,51 @@ The pragma has no effect if the message is computed with an expression other than a static string constant, since the assumption in this case is that the program computes exactly the string it wants. If you still want the prefixing in this case, you can always call -@code{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually. - -@node Pragma Pre_Class -@unnumberedsec Pragma Pre_Class -@cindex Pre_Class -@cindex Checks, preconditions -@findex Preconditions -@noindent +@cite{GNAT.Source_Info.Enclosing_Entity} and prepend the string manually. + +@node Pragma Pre_Class,Pragma Priority_Specific_Dispatching,Pragma Prefix_Exception_Messages,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-pre-class}@anchor{9e} +@section Pragma Pre_Class + + +@geindex Pre_Class + +@geindex Checks +@geindex preconditions + Syntax: -@smallexample @c ada +@example pragma Pre_Class (Boolean_Expression); -@end smallexample +@end example -@noindent -The @code{Pre_Class} pragma is intended to be an exact replacement for +The @cite{Pre_Class} pragma is intended to be an exact replacement for the language-defined -@code{Pre'Class} aspect, and shares its restrictions and semantics. +@cite{Pre'Class} aspect, and shares its restrictions and semantics. It must appear either immediately following the corresponding subprogram declaration (only other pragmas may intervene), or if there is no separate subprogram declaration, then it can appear at the start of the declarations in a subprogram body (preceded only by other pragmas). -Note: This pragma is called @code{Pre_Class} rather than -@code{Pre'Class} because the latter would not be strictly +Note: This pragma is called @cite{Pre_Class} rather than +@cite{Pre'Class} because the latter would not be strictly conforming to the allowed syntax for pragmas. The motivation for providing pragmas equivalent to the aspects is to allow a program to be written using the pragmas, and then compiled if necessary using an Ada compiler that does not recognize the pragmas or aspects, but is prepared to ignore the pragmas. The assertion -policy that controls this pragma is @code{Pre'Class}, not -@code{Pre_Class}. +policy that controls this pragma is @cite{Pre'Class}, not +@cite{Pre_Class}. + +@node Pragma Priority_Specific_Dispatching,Pragma Profile,Pragma Pre_Class,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-priority-specific-dispatching}@anchor{9f} +@section Pragma Priority_Specific_Dispatching + -@node Pragma Priority_Specific_Dispatching -@unnumberedsec Pragma Priority_Specific_Dispatching -@findex Priority_Specific_Dispatching -@noindent Syntax: -@smallexample @c ada +@example pragma Priority_Specific_Dispatching ( POLICY_IDENTIFIER, first_priority_EXPRESSION, @@ -5820,114 +5948,169 @@ POLICY_IDENTIFIER ::= FIFO_Within_Priorities | Non_Preemptive_Within_Priorities | Round_Robin_Within_Priorities -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Profile -@unnumberedsec Pragma Profile -@findex Profile -@noindent +@node Pragma Profile,Pragma Profile_Warnings,Pragma Priority_Specific_Dispatching,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-profile}@anchor{a0} +@section Pragma Profile + + Syntax: -@smallexample @c ada +@example pragma Profile (Ravenscar | Restricted | Rational); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. This is a -configuration pragma that establishes a set of configiuration pragmas -that depend on the argument. @code{Ravenscar} is standard in Ada 2005. -The other two possibilities (@code{Restricted} or @code{Rational}) +configuration pragma that establishes a set of configuration pragmas +that depend on the argument. @cite{Ravenscar} is standard in Ada 2005. +The other two possibilities (@cite{Restricted} or @cite{Rational}) are implementation-defined. The set of configuration pragmas is defined in the following sections. -@itemize -@item Pragma Profile (Ravenscar) -@findex Ravenscar -@noindent +@itemize * + +@item +Pragma Profile (Ravenscar) -The @code{Ravenscar} profile is standard in Ada 2005, +The @cite{Ravenscar} profile is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. This profile establishes the following set of configuration pragmas: -@table @code -@item Task_Dispatching_Policy (FIFO_Within_Priorities) + +@itemize * + +@item +@code{Task_Dispatching_Policy (FIFO_Within_Priorities)} + [RM D.2.2] Tasks are dispatched following a preemptive priority-ordered scheduling policy. -@item Locking_Policy (Ceiling_Locking) +@item +@code{Locking_Policy (Ceiling_Locking)} + [RM D.3] While tasks and interrupts execute a protected action, they inherit the ceiling priority of the corresponding protected object. -@item Detect_Blocking +@item +@code{Detect_Blocking} + This pragma forces the detection of potentially blocking operations within a protected operation, and to raise Program_Error if that happens. -@end table -@noindent +@end itemize plus the following set of restrictions: -@table @code -@item Max_Entry_Queue_Length => 1 + +@itemize * + +@item +@code{Max_Entry_Queue_Length => 1} + No task can be queued on a protected entry. -@item Max_Protected_Entries => 1 -@item Max_Task_Entries => 0 + +@item +@code{Max_Protected_Entries => 1} + +@item +@code{Max_Task_Entries => 0} + No rendezvous statements are allowed. -@item No_Abort_Statements -@item No_Dynamic_Attachment -@item No_Dynamic_Priorities -@item No_Implicit_Heap_Allocations -@item No_Local_Protected_Objects -@item No_Local_Timing_Events -@item No_Protected_Type_Allocators -@item No_Relative_Delay -@item No_Requeue_Statements -@item No_Select_Statements -@item No_Specific_Termination_Handlers -@item No_Task_Allocators -@item No_Task_Hierarchy -@item No_Task_Termination -@item Simple_Barriers -@end table -@noindent + +@item +@code{No_Abort_Statements} + +@item +@code{No_Dynamic_Attachment} + +@item +@code{No_Dynamic_Priorities} + +@item +@code{No_Implicit_Heap_Allocations} + +@item +@code{No_Local_Protected_Objects} + +@item +@code{No_Local_Timing_Events} + +@item +@code{No_Protected_Type_Allocators} + +@item +@code{No_Relative_Delay} + +@item +@code{No_Requeue_Statements} + +@item +@code{No_Select_Statements} + +@item +@code{No_Specific_Termination_Handlers} + +@item +@code{No_Task_Allocators} + +@item +@code{No_Task_Hierarchy} + +@item +@code{No_Task_Termination} + +@item +@code{Simple_Barriers} +@end itemize The Ravenscar profile also includes the following restrictions that specify that there are no semantic dependences on the corresponding predefined packages: -@table @code -@item No_Dependence => Ada.Asynchronous_Task_Control -@item No_Dependence => Ada.Calendar -@item No_Dependence => Ada.Execution_Time.Group_Budget -@item No_Dependence => Ada.Execution_Time.Timers -@item No_Dependence => Ada.Task_Attributes -@item No_Dependence => System.Multiprocessors.Dispatching_Domains -@end table -@noindent +@itemize * + +@item +@code{No_Dependence => Ada.Asynchronous_Task_Control} + +@item +@code{No_Dependence => Ada.Calendar} + +@item +@code{No_Dependence => Ada.Execution_Time.Group_Budget} + +@item +@code{No_Dependence => Ada.Execution_Time.Timers} + +@item +@code{No_Dependence => Ada.Task_Attributes} + +@item +@code{No_Dependence => System.Multiprocessors.Dispatching_Domains} +@end itemize This set of configuration pragmas and restrictions correspond to the -definition of the ``Ravenscar Profile'' for limited tasking, devised and -published by the @cite{International Real-Time Ada Workshop}, 1997, -and whose most recent description is available at -@url{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}. +definition of the 'Ravenscar Profile' for limited tasking, devised and +published by the @cite{International Real-Time Ada Workshop@comma{} 1997}. +A description is also available at +@indicateurl{http://www-users.cs.york.ac.uk/~burns/ravenscar.ps}. The original definition of the profile was revised at subsequent IRTAW meetings. It has been included in the ISO -@cite{Guide for the Use of the Ada Programming Language in High -Integrity Systems}, and has been approved by ISO/IEC/SC22/WG9 for inclusion in -the next revision of the standard. The formal definition given by +@cite{Guide for the Use of the Ada Programming Language in High Integrity Systems}, +and was made part of the Ada 2005 standard. +The formal definition given by the Ada Rapporteur Group (ARG) can be found in two Ada Issues (AI-249 and AI-305) available at -@url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and -@url{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}. +@indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00249.txt} and +@indicateurl{http://www.ada-auth.org/cgi-bin/cvsweb.cgi/ais/ai-00305.txt}. The above set is a superset of the restrictions provided by pragma @code{Profile (Restricted)}, it includes six additional restrictions @@ -5937,100 +6120,138 @@ The above set is a superset of the restrictions provided by pragma that pragma @code{Profile (Ravenscar)}, like the pragma @code{Profile (Restricted)}, automatically causes the use of a simplified, -more efficient version of the tasking run-time system. +more efficient version of the tasking run-time library. + +@item +Pragma Profile (Restricted) -@item Pragma Profile (Restricted) -@findex Restricted Run Time -@noindent This profile corresponds to the GNAT restricted run time. It establishes the following set of restrictions: -@itemize @bullet -@item No_Abort_Statements -@item No_Entry_Queue -@item No_Task_Hierarchy -@item No_Task_Allocators -@item No_Dynamic_Priorities -@item No_Terminate_Alternatives -@item No_Dynamic_Attachment -@item No_Protected_Type_Allocators -@item No_Local_Protected_Objects -@item No_Requeue_Statements -@item No_Task_Attributes_Package -@item Max_Asynchronous_Select_Nesting = 0 -@item Max_Task_Entries = 0 -@item Max_Protected_Entries = 1 -@item Max_Select_Alternatives = 0 -@end itemize - -@noindent + +@itemize * + +@item +@code{No_Abort_Statements} + +@item +@code{No_Entry_Queue} + +@item +@code{No_Task_Hierarchy} + +@item +@code{No_Task_Allocators} + +@item +@code{No_Dynamic_Priorities} + +@item +@code{No_Terminate_Alternatives} + +@item +@code{No_Dynamic_Attachment} + +@item +@code{No_Protected_Type_Allocators} + +@item +@code{No_Local_Protected_Objects} + +@item +@code{No_Requeue_Statements} + +@item +@code{No_Task_Attributes_Package} + +@item +@code{Max_Asynchronous_Select_Nesting = 0} + +@item +@code{Max_Task_Entries = 0} + +@item +@code{Max_Protected_Entries = 1} + +@item +@code{Max_Select_Alternatives = 0} +@end itemize + This set of restrictions causes the automatic selection of a simplified version of the run time that provides improved performance for the limited set of tasking functionality permitted by this set of restrictions. -@item Pragma Profile (Rational) -@findex Rational compatibility mode -@noindent +@item +Pragma Profile (Rational) + The Rational profile is intended to facilitate porting legacy code that compiles with the Rational APEX compiler, even when the code includes non- conforming Ada constructs. The profile enables the following three pragmas: -@itemize @bullet -@item pragma Implicit_Packing -@item pragma Overriding_Renamings -@item pragma Use_VADS_Size -@end itemize +@itemize * + +@item +@code{pragma Implicit_Packing} + +@item +@code{pragma Overriding_Renamings} + +@item +@code{pragma Use_VADS_Size} @end itemize +@end itemize + +@node Pragma Profile_Warnings,Pragma Propagate_Exceptions,Pragma Profile,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-profile-warnings}@anchor{a1} +@section Pragma Profile_Warnings + -@node Pragma Profile_Warnings -@unnumberedsec Pragma Profile_Warnings -@findex Profile_Warnings -@noindent Syntax: -@smallexample @c ada +@example pragma Profile_Warnings (Ravenscar | Restricted | Rational); -@end smallexample +@end example -@noindent This is an implementation-defined pragma that is similar in -effect to @code{pragma Profile} except that instead of -generating @code{Restrictions} pragmas, it generates -@code{Restriction_Warnings} pragmas. The result is that +effect to @cite{pragma Profile} except that instead of +generating @cite{Restrictions} pragmas, it generates +@cite{Restriction_Warnings} pragmas. The result is that violations of the profile generate warning messages instead of error messages. -@node Pragma Propagate_Exceptions -@unnumberedsec Pragma Propagate_Exceptions -@cindex Interfacing to C++ -@findex Propagate_Exceptions -@noindent +@node Pragma Propagate_Exceptions,Pragma Provide_Shift_Operators,Pragma Profile_Warnings,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-propagate-exceptions}@anchor{a2} +@section Pragma Propagate_Exceptions + + +@geindex Interfacing to C++ + Syntax: -@smallexample @c ada +@example pragma Propagate_Exceptions; -@end smallexample +@end example -@noindent This pragma is now obsolete and, other than generating a warning if warnings on obsolescent features are enabled, is ignored. It is retained for compatibility purposes. It used to be used in connection with optimization of a now-obsolete mechanism for implementation of exceptions. -@node Pragma Provide_Shift_Operators -@unnumberedsec Pragma Provide_Shift_Operators -@cindex Shift operators -@findex Provide_Shift_Operators -@noindent +@node Pragma Provide_Shift_Operators,Pragma Psect_Object,Pragma Propagate_Exceptions,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-provide-shift-operators}@anchor{a3} +@section Pragma Provide_Shift_Operators + + +@geindex Shift operators + Syntax: -@smallexample @c ada +@example pragma Provide_Shift_Operators (integer_first_subtype_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma can be applied to a first subtype local name that specifies either an unsigned or signed type. It has the effect of providing the five shift operators (Shift_Left, Shift_Right, Shift_Right_Arithmetic, @@ -6038,13 +6259,14 @@ Rotate_Left and Rotate_Right) for the given type. It is similar to including the function declarations for these five operators, together with the pragma Import (Intrinsic, ...) statements. -@node Pragma Psect_Object -@unnumberedsec Pragma Psect_Object -@findex Psect_Object -@noindent +@node Pragma Psect_Object,Pragma Pure_Function,Pragma Provide_Shift_Operators,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-psect-object}@anchor{a4} +@section Pragma Psect_Object + + Syntax: -@smallexample @c ada +@example pragma Psect_Object ( [Internal =>] LOCAL_NAME, [, [External =>] EXTERNAL_SYMBOL] @@ -6053,26 +6275,25 @@ pragma Psect_Object ( EXTERNAL_SYMBOL ::= IDENTIFIER | static_string_EXPRESSION -@end smallexample +@end example + +This pragma is identical in effect to pragma @cite{Common_Object}. + +@node Pragma Pure_Function,Pragma Rational,Pragma Psect_Object,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-pure-function}@anchor{a5} +@section Pragma Pure_Function -@noindent -This pragma is identical in effect to pragma @code{Common_Object}. -@node Pragma Pure_Function -@unnumberedsec Pragma Pure_Function -@findex Pure_Function -@noindent Syntax: -@smallexample @c ada +@example pragma Pure_Function ([Entity =>] function_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma appears in the same declarative part as a function declaration (or a set of function declarations if more than one overloaded declaration exists, in which case the pragma applies -to all entities). It specifies that the function @code{Entity} is +to all entities). It specifies that the function @cite{Entity} is to be considered pure for the purposes of code generation. This means that the compiler can assume that there are no side effects, and in particular that two calls with identical arguments produce the @@ -6080,7 +6301,7 @@ same result. It also means that the function can be used in an address clause. Note that, quite deliberately, there are no static checks to try -to ensure that this promise is met, so @code{Pure_Function} can be used +to ensure that this promise is met, so @cite{Pure_Function} can be used with functions that are conceptually pure, even if they do modify global variables. For example, a square root function that is instrumented to count the number of times it is called is still @@ -6097,129 +6318,131 @@ the compiler may optimize away calls with identical arguments, and if that results in unexpected behavior, the proper action is not to use the pragma for subprograms that are not (conceptually) pure. -@findex Pure -Note: Most functions in a @code{Pure} package are automatically pure, and -there is no need to use pragma @code{Pure_Function} for such functions. One +Note: Most functions in a @cite{Pure} package are automatically pure, and +there is no need to use pragma @cite{Pure_Function} for such functions. One exception is any function that has at least one formal of type -@code{System.Address} or a type derived from it. Such functions are not +@cite{System.Address} or a type derived from it. Such functions are not considered pure by default, since the compiler assumes that the -@code{Address} parameter may be functioning as a pointer and that the +@cite{Address} parameter may be functioning as a pointer and that the referenced data may change even if the address value does not. Similarly, imported functions are not considered to be pure by default, since there is no way of checking that they are in fact pure. The use -of pragma @code{Pure_Function} for such a function will override these default +of pragma @cite{Pure_Function} for such a function will override these default assumption, and cause the compiler to treat a designated subprogram as pure in these cases. -Note: If pragma @code{Pure_Function} is applied to a renamed function, it +Note: If pragma @cite{Pure_Function} is applied to a renamed function, it applies to the underlying renamed function. This can be used to disambiguate cases of overloading where some but not all functions in a set of overloaded functions are to be designated as pure. -If pragma @code{Pure_Function} is applied to a library level function, the +If pragma @cite{Pure_Function} is applied to a library level function, the function is also considered pure from an optimization point of view, but the unit is not a Pure unit in the categorization sense. So for example, a function -thus marked is free to @code{with} non-pure units. +thus marked is free to @cite{with} non-pure units. + +@node Pragma Rational,Pragma Ravenscar,Pragma Pure_Function,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-rational}@anchor{a6} +@section Pragma Rational + -@node Pragma Rational -@unnumberedsec Pragma Rational -@findex Rational -@noindent Syntax: -@smallexample @c ada +@example pragma Rational; -@end smallexample +@end example -@noindent This pragma is considered obsolescent, but is retained for compatibility purposes. It is equivalent to: -@smallexample @c ada +@example pragma Profile (Rational); -@end smallexample +@end example + +@node Pragma Ravenscar,Pragma Refined_Depends,Pragma Rational,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-ravenscar}@anchor{a7} +@section Pragma Ravenscar + -@node Pragma Ravenscar -@unnumberedsec Pragma Ravenscar -@findex Pragma Ravenscar -@noindent Syntax: -@smallexample @c ada +@example pragma Ravenscar; -@end smallexample +@end example -@noindent This pragma is considered obsolescent, but is retained for compatibility purposes. It is equivalent to: -@smallexample @c ada +@example pragma Profile (Ravenscar); -@end smallexample +@end example + +which is the preferred method of setting the @cite{Ravenscar} profile. + +@node Pragma Refined_Depends,Pragma Refined_Global,Pragma Ravenscar,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-refined-depends}@anchor{a8} +@section Pragma Refined_Depends -@noindent -which is the preferred method of setting the @code{Ravenscar} profile. -@node Pragma Refined_Depends -@unnumberedsec Pragma Refined_Depends -@findex Refined_Depends -@noindent For the description of this pragma, see SPARK 2014 Reference Manual, section 6.1.5. -@node Pragma Refined_Global -@unnumberedsec Pragma Refined_Global -@findex Refined_Global -@noindent +@node Pragma Refined_Global,Pragma Refined_Post,Pragma Refined_Depends,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-refined-global}@anchor{a9} +@section Pragma Refined_Global + + For the description of this pragma, see SPARK 2014 Reference Manual, section 6.1.4. -@node Pragma Refined_Post -@unnumberedsec Pragma Refined_Post -@findex Refined_Post -@noindent +@node Pragma Refined_Post,Pragma Refined_State,Pragma Refined_Global,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-refined-post}@anchor{aa} +@section Pragma Refined_Post + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.2.7. -@node Pragma Refined_State -@unnumberedsec Pragma Refined_State -@findex Refined_State -@noindent +@node Pragma Refined_State,Pragma Relative_Deadline,Pragma Refined_Post,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-refined-state}@anchor{ab} +@section Pragma Refined_State + + For the description of this pragma, see SPARK 2014 Reference Manual, section 7.2.2. -@node Pragma Relative_Deadline -@unnumberedsec Pragma Relative_Deadline -@findex Relative_Deadline -@noindent +@node Pragma Relative_Deadline,Pragma Remote_Access_Type,Pragma Refined_State,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-relative-deadline}@anchor{ac} +@section Pragma Relative_Deadline + + Syntax: -@smallexample @c ada +@example pragma Relative_Deadline (time_span_EXPRESSION); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005, but is available in all earlier versions of Ada as an implementation-defined pragma. See Ada 2012 Reference Manual for details. -@node Pragma Remote_Access_Type -@unnumberedsec Pragma Remote_Access_Type -@findex Remote_Access_Type -@noindent +@node Pragma Remote_Access_Type,Pragma Restricted_Run_Time,Pragma Relative_Deadline,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-remote-access-type}@anchor{ad} +@section Pragma Remote_Access_Type + + Syntax: -@smallexample @c ada +@example pragma Remote_Access_Type ([Entity =>] formal_access_type_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma appears in the formal part of a generic declaration. It specifies an exception to the RM rule from E.2.2(17/2), which forbids the use of a remote access to class-wide type as actual for a formal access type. -When this pragma applies to a formal access type @code{Entity}, that +When this pragma applies to a formal access type @cite{Entity}, that type is treated as a remote access to class-wide type in the generic. It must be a formal general access type, and its designated type must be the class-wide type of a formal tagged limited private type from the @@ -6229,43 +6452,42 @@ In the generic unit, the formal type is subject to all restrictions pertaining to remote access to class-wide types. At instantiation, the actual type must be a remote access to class-wide type. -@node Pragma Restricted_Run_Time -@unnumberedsec Pragma Restricted_Run_Time -@findex Pragma Restricted_Run_Time -@noindent +@node Pragma Restricted_Run_Time,Pragma Restriction_Warnings,Pragma Remote_Access_Type,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-restricted-run-time}@anchor{ae} +@section Pragma Restricted_Run_Time + + Syntax: -@smallexample @c ada +@example pragma Restricted_Run_Time; -@end smallexample +@end example -@noindent This pragma is considered obsolescent, but is retained for compatibility purposes. It is equivalent to: -@smallexample @c ada +@example pragma Profile (Restricted); -@end smallexample +@end example -@noindent which is the preferred method of setting the restricted run time profile. -@node Pragma Restriction_Warnings -@unnumberedsec Pragma Restriction_Warnings -@findex Restriction_Warnings -@noindent +@node Pragma Restriction_Warnings,Pragma Reviewable,Pragma Restricted_Run_Time,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-restriction-warnings}@anchor{af} +@section Pragma Restriction_Warnings + + Syntax: -@smallexample @c ada +@example pragma Restriction_Warnings (restriction_IDENTIFIER @{, restriction_IDENTIFIER@}); -@end smallexample +@end example -@noindent This pragma allows a series of restriction identifiers to be specified (the list of allowed identifiers is the same as for -pragma @code{Restrictions}). For each of these identifiers +pragma @cite{Restrictions}). For each of these identifiers the compiler checks for violations of the restriction, but generates a warning message rather than an error message if the restriction is violated. @@ -6276,165 +6498,160 @@ these violations. Consider this example, where you want to set Ada_95 mode and enable style checks, but you want to know about any other use of implementation pragmas: -@smallexample @c ada +@example pragma Restriction_Warnings (No_Implementation_Pragmas); -7 (Off, "violation of*No_Implementation_Pragmas*"); +pragma Warnings (Off, "violation of No_Implementation_Pragmas"); pragma Ada_95; pragma Style_Checks ("2bfhkM160"); -pragma Warnings (On, "violation of*No_Implementation_Pragmas*"); -@end smallexample +pragma Warnings (On, "violation of No_Implementation_Pragmas"); +@end example -@noindent By including the above lines in a configuration pragmas file, the Ada_95 and Style_Checks pragmas are accepted without generating a warning, but any other use of implementation defined pragmas will cause a warning to be generated. -@node Pragma Reviewable -@unnumberedsec Pragma Reviewable -@findex Reviewable -@noindent +@node Pragma Reviewable,Pragma Share_Generic,Pragma Restriction_Warnings,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-reviewable}@anchor{b0} +@section Pragma Reviewable + + Syntax: -@smallexample @c ada +@example pragma Reviewable; -@end smallexample +@end example -@noindent This pragma is an RM-defined standard pragma, but has no effect on the program being compiled, or on the code generated for the program. To obtain the required output specified in RM H.3.1, the compiler must be run with various special switches as follows: -@table @i -@item Where compiler-generated run-time checks remain +@itemize * + +@item +@emph{Where compiler-generated run-time checks remain} -The switch @option{-gnatGL} -@findex @option{-gnatGL} +The switch @emph{-gnatGL} may be used to list the expanded code in pseudo-Ada form. Runtime checks show up in the listing either as explicit checks or operators marked with @{@} to indicate a check is present. -@item An identification of known exceptions at compile time +@item +@emph{An identification of known exceptions at compile time} -If the program is compiled with @option{-gnatwa}, -@findex @option{-gnatwa} +If the program is compiled with @emph{-gnatwa}, the compiler warning messages will indicate all cases where the compiler detects that an exception is certain to occur at run time. -@item Possible reads of uninitialized variables +@item +@emph{Possible reads of uninitialized variables} The compiler warns of many such cases, but its output is incomplete. -@ifclear FSFEDITION -The CodePeer analysis tool -@findex CodePeer static analysis tool -@end ifclear -@ifset FSFEDITION +@end itemize + + A supplemental static analysis tool -@end ifset may be used to obtain a comprehensive list of all possible points at which uninitialized data may be read. -@item Where run-time support routines are implicitly invoked -In the output from @option{-gnatGL}, -@findex @option{-gnatGL} +@itemize * + +@item +@emph{Where run-time support routines are implicitly invoked} + +In the output from @emph{-gnatGL}, run-time calls are explicitly listed as calls to the relevant run-time routine. -@item Object code listing +@item +@emph{Object code listing} -This may be obtained either by using the @option{-S} switch, -@findex @option{-S} +This may be obtained either by using the @emph{-S} switch, or the objdump utility. -@findex objdump -@item Constructs known to be erroneous at compile time +@item +@emph{Constructs known to be erroneous at compile time} -These are identified by warnings issued by the compiler (use @option{-gnatwa}). -@findex @option{-gnatwa} +These are identified by warnings issued by the compiler (use @emph{-gnatwa}). -@item Stack usage information +@item +@emph{Stack usage information} Static stack usage data (maximum per-subprogram) can be obtained via the -@option{-fstack-usage} switch to the compiler. -@findex @option{-fstack-usage} -Dynamic stack usage data (per task) can be obtained via the @option{-u} switch +@emph{-fstack-usage} switch to the compiler. +Dynamic stack usage data (per task) can be obtained via the @emph{-u} switch to gnatbind -@findex @option{-u} -@ifclear FSFEDITION -The gnatstack utility -@findex gnatstack -can be used to provide additional information on stack usage. -@end ifclear +@end itemize -@item Object code listing of entire partition -This can be obtained by compiling the partition with @option{-S}, -@findex @option{-S} + +@itemize * + +@item +@emph{Object code listing of entire partition} + +This can be obtained by compiling the partition with @emph{-S}, or by applying objdump -@findex objdump to all the object files that are part of the partition. -@item A description of the run-time model +@item +@emph{A description of the run-time model} The full sources of the run-time are available, and the documentation of these routines describes how these run-time routines interface to the underlying operating system facilities. -@item Control and data-flow information +@item +@emph{Control and data-flow information} +@end itemize + -@ifclear FSFEDITION -The CodePeer tool -@findex CodePeer static analysis tool -@end ifclear -@ifset FSFEDITION A supplemental static analysis tool -@end ifset may be used to obtain complete control and data-flow information, as well as comprehensive messages identifying possible problems based on this information. -@end table -@node Pragma Share_Generic -@unnumberedsec Pragma Share_Generic -@findex Share_Generic -@noindent +@node Pragma Share_Generic,Pragma Shared,Pragma Reviewable,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-share-generic}@anchor{b1} +@section Pragma Share_Generic + + Syntax: -@smallexample @c ada +@example pragma Share_Generic (GNAME @{, GNAME@}); GNAME ::= generic_unit_NAME | generic_instance_NAME -@end smallexample +@end example -@noindent This pragma is provided for compatibility with Dec Ada 83. It has -no effect in @code{GNAT} (which does not implement shared generics), other +no effect in @cite{GNAT} (which does not implement shared generics), other than to check that the given names are all names of generic units or generic instances. -@node Pragma Shared -@unnumberedsec Pragma Shared -@findex Shared +@node Pragma Shared,Pragma Short_Circuit_And_Or,Pragma Share_Generic,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-shared}@anchor{b2} +@section Pragma Shared + -@noindent This pragma is provided for compatibility with Ada 83. The syntax and semantics are identical to pragma Atomic. -@node Pragma Short_Circuit_And_Or -@unnumberedsec Pragma Short_Circuit_And_Or -@findex Short_Circuit_And_Or -@noindent +@node Pragma Short_Circuit_And_Or,Pragma Short_Descriptors,Pragma Shared,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-short-circuit-and-or}@anchor{b3} +@section Pragma Short_Circuit_And_Or + + Syntax: -@smallexample @c ada +@example pragma Short_Circuit_And_Or; -@end smallexample +@end example -@noindent This configuration pragma causes any occurrence of the AND operator applied to operands of type Standard.Boolean to be short-circuited (i.e. the AND operator is treated as if it were AND THEN). Or is similarly treated as OR ELSE. This @@ -6443,45 +6660,48 @@ short-circuited logical operators. If this configuration pragma occurs locally within the file being compiled, it applies only to the file being compiled. There is no requirement that all units in a partition use this option. -@node Pragma Short_Descriptors -@unnumberedsec Pragma Short_Descriptors -@findex Short_Descriptors -@noindent +@node Pragma Short_Descriptors,Pragma Simple_Storage_Pool_Type,Pragma Short_Circuit_And_Or,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-short-descriptors}@anchor{b4} +@section Pragma Short_Descriptors + + Syntax: -@smallexample @c ada +@example pragma Short_Descriptors -@end smallexample +@end example -@noindent This pragma is provided for compatibility with other Ada implementations. It is recognized but ignored by all current versions of GNAT. -@node Pragma Simple_Storage_Pool_Type -@unnumberedsec Pragma Simple_Storage_Pool_Type -@findex Simple_Storage_Pool_Type -@cindex Storage pool, simple -@cindex Simple storage pool -@noindent +@node Pragma Simple_Storage_Pool_Type,Pragma Source_File_Name,Pragma Short_Descriptors,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-simple-storage-pool-type}@anchor{b5} +@section Pragma Simple_Storage_Pool_Type + + +@geindex Storage pool +@geindex simple + +@geindex Simple storage pool + Syntax: -@smallexample @c ada +@example pragma Simple_Storage_Pool_Type (type_LOCAL_NAME); -@end smallexample +@end example -@noindent -A type can be established as a ``simple storage pool type'' by applying -the representation pragma @code{Simple_Storage_Pool_Type} to the type. +A type can be established as a 'simple storage pool type' by applying +the representation pragma @cite{Simple_Storage_Pool_Type} to the type. A type named in the pragma must be a library-level immutably limited record type or limited tagged type declared immediately within a package declaration. The type can also be a limited private type whose full type is allowed as a simple storage pool type. -For a simple storage pool type @var{SSP}, nonabstract primitive subprograms -@code{Allocate}, @code{Deallocate}, and @code{Storage_Size} can be declared that +For a simple storage pool type @cite{SSP}, nonabstract primitive subprograms +@cite{Allocate}, @cite{Deallocate}, and @cite{Storage_Size} can be declared that are subtype conformant with the following subprogram declarations: -@smallexample @c ada +@example procedure Allocate (Pool : in out SSP; Storage_Address : out System.Address; @@ -6496,41 +6716,40 @@ procedure Deallocate function Storage_Size (Pool : SSP) return System.Storage_Elements.Storage_Count; -@end smallexample +@end example -@noindent -Procedure @code{Allocate} must be declared, whereas @code{Deallocate} and -@code{Storage_Size} are optional. If @code{Deallocate} is not declared, then +Procedure @cite{Allocate} must be declared, whereas @cite{Deallocate} and +@cite{Storage_Size} are optional. If @cite{Deallocate} is not declared, then applying an unchecked deallocation has no effect other than to set its actual -parameter to null. If @code{Storage_Size} is not declared, then the -@code{Storage_Size} attribute applied to an access type associated with +parameter to null. If @cite{Storage_Size} is not declared, then the +@cite{Storage_Size} attribute applied to an access type associated with a pool object of type SSP returns zero. Additional operations can be declared for a simple storage pool type (such as for supporting a mark/release storage-management discipline). An object of a simple storage pool type can be associated with an access -type by specifying the attribute @code{Simple_Storage_Pool}. For example: - -@smallexample @c ada +type by specifying the attribute +@ref{b6,,Simple_Storage_Pool}. For example: +@example My_Pool : My_Simple_Storage_Pool_Type; type Acc is access My_Data_Type; for Acc'Simple_Storage_Pool use My_Pool; +@end example -@end smallexample +See attribute @ref{b6,,Simple_Storage_Pool} +for further details. + +@node Pragma Source_File_Name,Pragma Source_File_Name_Project,Pragma Simple_Storage_Pool_Type,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name}@anchor{b7}@anchor{gnat_rm/implementation_defined_pragmas id3}@anchor{b8} +@section Pragma Source_File_Name -@noindent -See attribute @code{Simple_Storage_Pool} for further details. -@node Pragma Source_File_Name -@unnumberedsec Pragma Source_File_Name -@findex Source_File_Name -@noindent Syntax: -@smallexample @c ada +@example pragma Source_File_Name ( [Unit_Name =>] unit_NAME, Spec_File_Name => STRING_LITERAL, @@ -6540,24 +6759,23 @@ pragma Source_File_Name ( [Unit_Name =>] unit_NAME, Body_File_Name => STRING_LITERAL, [Index => INTEGER_LITERAL]); -@end smallexample +@end example -@noindent Use this to override the normal naming convention. It is a configuration pragma, and so has the usual applicability of configuration pragmas -(i.e.@: it applies to either an entire partition, or to all units in a +(i.e., it applies to either an entire partition, or to all units in a compilation, or to a single unit, depending on how it is used. -@var{unit_name} is mapped to @var{file_name_literal}. The identifier for +@cite{unit_name} is mapped to @cite{file_name_literal}. The identifier for the second argument is required, and indicates whether this is the file name for the spec or for the body. The optional Index argument should be used when a file contains multiple -units, and when you do not want to use @code{gnatchop} to separate then +units, and when you do not want to use @cite{gnatchop} to separate then into multiple files (which is the recommended procedure to limit the number of recompilations that are needed when some sources change). -For instance, if the source file @file{source.ada} contains +For instance, if the source file @code{source.ada} contains -@smallexample @c ada +@example package B is ... end B; @@ -6567,25 +6785,25 @@ procedure A is begin .. end A; -@end smallexample +@end example you could use the following configuration pragmas: -@smallexample @c ada +@example pragma Source_File_Name (B, Spec_File_Name => "source.ada", Index => 1); pragma Source_File_Name (A, Body_File_Name => "source.ada", Index => 2); -@end smallexample +@end example -Note that the @code{gnatname} utility can also be used to generate those +Note that the @cite{gnatname} utility can also be used to generate those configuration pragmas. -Another form of the @code{Source_File_Name} pragma allows +Another form of the @cite{Source_File_Name} pragma allows the specification of patterns defining alternative file naming schemes to apply to all files. -@smallexample @c ada +@example pragma Source_File_Name ( [Spec_File_Name =>] STRING_LITERAL [,[Casing =>] CASING_SPEC] @@ -6602,9 +6820,8 @@ pragma Source_File_Name [,[Dot_Replacement =>] STRING_LITERAL]); CASING_SPEC ::= Lowercase | Uppercase | Mixedcase -@end smallexample +@end example -@noindent The first argument is a pattern that contains a single asterisk indicating the point at which the unit name is to be inserted in the pattern string to form the file name. The second argument is optional. If present it @@ -6618,21 +6835,19 @@ aware of these pragmas, and so other tools that use the projet file would not be aware of the intended naming conventions. If you are using project files, file naming is controlled by Source_File_Name_Project pragmas, which are usually supplied automatically by the project manager. A pragma -Source_File_Name cannot appear after a @ref{Pragma Source_File_Name_Project}. +Source_File_Name cannot appear after a @ref{b9,,Pragma Source_File_Name_Project}. + +For more details on the use of the @cite{Source_File_Name} pragma, see the +sections on @cite{Using Other File Names} and @cite{Alternative File Naming Schemes' in the :title:`GNAT User's Guide}. -For more details on the use of the @code{Source_File_Name} pragma, -@xref{Using Other File Names,,, gnat_ugn, @value{EDITION} User's Guide}, -and @ref{Alternative File Naming Schemes,,, gnat_ugn, @value{EDITION} -User's Guide}. +@node Pragma Source_File_Name_Project,Pragma Source_Reference,Pragma Source_File_Name,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas id4}@anchor{ba}@anchor{gnat_rm/implementation_defined_pragmas pragma-source-file-name-project}@anchor{b9} +@section Pragma Source_File_Name_Project -@node Pragma Source_File_Name_Project -@unnumberedsec Pragma Source_File_Name_Project -@findex Source_File_Name_Project -@noindent This pragma has the same syntax and semantics as pragma Source_File_Name. It is only allowed as a stand alone configuration pragma. -It cannot appear after a @ref{Pragma Source_File_Name}, and +It cannot appear after a @ref{b7,,Pragma Source_File_Name}, and most importantly, once pragma Source_File_Name_Project appears, no further Source_File_Name pragmas are allowed. @@ -6643,41 +6858,41 @@ it is not permissible to attempt to modify this naming scheme using Source_File_Name or Source_File_Name_Project pragmas (which would not be known to the project manager). -@node Pragma Source_Reference -@unnumberedsec Pragma Source_Reference -@findex Source_Reference -@noindent +@node Pragma Source_Reference,Pragma SPARK_Mode,Pragma Source_File_Name_Project,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-source-reference}@anchor{bb} +@section Pragma Source_Reference + + Syntax: -@smallexample @c ada +@example pragma Source_Reference (INTEGER_LITERAL, STRING_LITERAL); -@end smallexample +@end example -@noindent This pragma must appear as the first line of a source file. -@var{integer_literal} is the logical line number of the line following +@cite{integer_literal} is the logical line number of the line following the pragma line (for use in error messages and debugging -information). @var{string_literal} is a static string constant that +information). @cite{string_literal} is a static string constant that specifies the file name to be used in error messages and debugging -information. This is most notably used for the output of @code{gnatchop} -with the @option{-r} switch, to make sure that the original unchopped +information. This is most notably used for the output of @cite{gnatchop} +with the @emph{-r} switch, to make sure that the original unchopped source file is the one referred to. The second argument must be a string literal, it cannot be a static string expression other than a string literal. This is because its value is needed for error messages issued by all phases of the compiler. -@node Pragma SPARK_Mode -@unnumberedsec Pragma SPARK_Mode -@findex SPARK_Mode -@noindent +@node Pragma SPARK_Mode,Pragma Static_Elaboration_Desired,Pragma Source_Reference,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-spark-mode}@anchor{bc} +@section Pragma SPARK_Mode + + Syntax: -@smallexample @c ada +@example pragma SPARK_Mode [(On | Off)] ; -@end smallexample +@end example -@noindent In general a program can have some parts that are in SPARK 2014 (and follow all the rules in the SPARK Reference Manual), and some parts that are full Ada 2012. @@ -6686,79 +6901,80 @@ The SPARK_Mode pragma is used to identify which parts are in SPARK 2014 (by default programs are in full Ada). The SPARK_Mode pragma can be used in the following places: -@itemize @bullet -@item +@itemize * + +@item As a configuration pragma, in which case it sets the default mode for all units compiled with this pragma. -@item +@item Immediately following a library-level subprogram spec -@item +@item Immediately within a library-level package body -@item -Immediately following the @code{private} keyword of a library-level +@item +Immediately following the @cite{private} keyword of a library-level package spec -@item -Immediately following the @code{begin} keyword of a library-level +@item +Immediately following the @cite{begin} keyword of a library-level package body -@item +@item Immediately within a library-level subprogram body - @end itemize -@noindent Normally a subprogram or package spec/body inherits the current mode that is active at the point it is declared. But this can be overridden by pragma within the spec or body as above. The basic consistency rule is that you can't turn SPARK_Mode back -@code{On}, once you have explicitly (with a pragma) turned if -@code{Off}. So the following rules apply: +@cite{On}, once you have explicitly (with a pragma) turned if +@cite{Off}. So the following rules apply: -@noindent -If a subprogram spec has SPARK_Mode @code{Off}, then the body must -also have SPARK_Mode @code{Off}. +If a subprogram spec has SPARK_Mode @cite{Off}, then the body must +also have SPARK_Mode @cite{Off}. -@noindent For a package, we have four parts: -@itemize -@item + +@itemize * + +@item the package public declarations -@item + +@item the package private part -@item + +@item the body of the package -@item -the elaboration code after @code{begin} + +@item +the elaboration code after @cite{begin} @end itemize -@noindent For a package, the rule is that if you explicitly turn SPARK_Mode -@code{Off} for any part, then all the following parts must have -SPARK_Mode @code{Off}. Note that this may require repeating a pragma -SPARK_Mode (@code{Off}) in the body. For example, if we have a -configuration pragma SPARK_Mode (@code{On}) that turns the mode on by +@cite{Off} for any part, then all the following parts must have +SPARK_Mode @cite{Off}. Note that this may require repeating a pragma +SPARK_Mode (@cite{Off}) in the body. For example, if we have a +configuration pragma SPARK_Mode (@cite{On}) that turns the mode on by default everywhere, and one particular package spec has pragma -SPARK_Mode (@code{Off}), then that pragma will need to be repeated in +SPARK_Mode (@cite{Off}), then that pragma will need to be repeated in the package body. -@node Pragma Static_Elaboration_Desired -@unnumberedsec Pragma Static_Elaboration_Desired -@findex Static_Elaboration_Desired -@noindent +@node Pragma Static_Elaboration_Desired,Pragma Stream_Convert,Pragma SPARK_Mode,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-static-elaboration-desired}@anchor{bd} +@section Pragma Static_Elaboration_Desired + + Syntax: -@smallexample @c ada +@example pragma Static_Elaboration_Desired; -@end smallexample +@end example -@noindent This pragma is used to indicate that the compiler should attempt to initialize statically the objects declared in the library unit to which the pragma applies, when these objects are initialized (explicitly or implicitly) by an aggregate. @@ -6772,20 +6988,20 @@ be obeyed. (See also the restriction No_Implicit_Loops, which supports static construction of larger aggregates with static components that include an others choice.) -@node Pragma Stream_Convert -@unnumberedsec Pragma Stream_Convert -@findex Stream_Convert -@noindent +@node Pragma Stream_Convert,Pragma Style_Checks,Pragma Static_Elaboration_Desired,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-stream-convert}@anchor{be} +@section Pragma Stream_Convert + + Syntax: -@smallexample @c ada +@example pragma Stream_Convert ( [Entity =>] type_LOCAL_NAME, [Read =>] function_NAME, [Write =>] function_NAME); -@end smallexample +@end example -@noindent This pragma provides an efficient way of providing user-defined stream attributes. Not only is it simpler to use than specifying the attributes directly, but more importantly, it allows the specification to be made in such @@ -6800,13 +7016,13 @@ of this type. It must name a function whose argument type may be any subtype, and whose returned type must be the type given as the first argument to the pragma. -The meaning of the @var{Read} parameter is that if a stream attribute directly +The meaning of the @cite{Read} parameter is that if a stream attribute directly or indirectly specifies reading of the type given as the first parameter, then a value of the type given as the argument to the Read function is read from the stream, and then the Read function is used to convert this to the required target type. -Similarly the @var{Write} parameter specifies how to treat write attributes +Similarly the @cite{Write} parameter specifies how to treat write attributes that directly or indirectly apply to the type given as the first parameter. It must have an input parameter of the type specified by the first parameter, and the return type must be the same as the input type of the Read function. @@ -6818,249 +7034,238 @@ renamings can be supplied to meet this requirement. The usage of this attribute is best illustrated by a simple example, taken from the GNAT implementation of package Ada.Strings.Unbounded: -@smallexample @c ada -function To_Unbounded (S : String) - return Unbounded_String +@example +function To_Unbounded (S : String) return Unbounded_String renames To_Unbounded_String; pragma Stream_Convert (Unbounded_String, To_Unbounded, To_String); -@end smallexample +@end example -@noindent The specifications of the referenced functions, as given in the Ada Reference Manual are: -@smallexample @c ada +@example function To_Unbounded_String (Source : String) return Unbounded_String; function To_String (Source : Unbounded_String) return String; -@end smallexample +@end example -@noindent The effect is that if the value of an unbounded string is written to a stream, then the representation of the item in the stream is in the same format that -would be used for @code{Standard.String'Output}, and this same representation +would be used for @cite{Standard.String'Output}, and this same representation is expected when a value of this type is read from the stream. Note that the value written always includes the bounds, even for Unbounded_String'Write, since Unbounded_String is not an array type. -Note that the @code{Stream_Convert} pragma is not effective in the case of +Note that the @cite{Stream_Convert} pragma is not effective in the case of a derived type of a non-limited tagged type. If such a type is specified then the pragma is silently ignored, and the default implementation of the stream attributes is used instead. -@node Pragma Style_Checks -@unnumberedsec Pragma Style_Checks -@findex Style_Checks -@noindent +@node Pragma Style_Checks,Pragma Subtitle,Pragma Stream_Convert,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-style-checks}@anchor{bf} +@section Pragma Style_Checks + + Syntax: -@smallexample @c ada +@example pragma Style_Checks (string_LITERAL | ALL_CHECKS | On | Off [, LOCAL_NAME]); -@end smallexample +@end example -@noindent This pragma is used in conjunction with compiler switches to control the -built in style checking provided by GNAT@. The compiler switches, if set, +built in style checking provided by GNAT. The compiler switches, if set, provide an initial setting for the switches, and this pragma may be used to modify these settings, or the settings may be provided entirely by the use of the pragma. This pragma can be used anywhere that a pragma is legal, including use as a configuration pragma (including use in -the @file{gnat.adc} file). +the @code{gnat.adc} file). The form with a string literal specifies which style options are to be activated. These are additive, so they apply in addition to any previously set style check options. The codes for the options are the same as those -used in the @option{-gnaty} switch to @command{gcc} or @command{gnatmake}. +used in the @emph{-gnaty} switch to @emph{gcc} or @emph{gnatmake}. For example the following two methods can be used to enable layout checking: -@itemize @bullet -@item -@smallexample @c ada + +@itemize * + +@item +@example pragma Style_Checks ("l"); -@end smallexample +@end example -@item -@smallexample -gcc -c -gnatyl @dots{} -@end smallexample +@item +@example +gcc -c -gnatyl ... +@end example @end itemize -@noindent The form ALL_CHECKS activates all standard checks (its use is equivalent -to the use of the @code{gnaty} switch with no options. @xref{Top, -@value{EDITION} User's Guide, About This Guide, gnat_ugn, -@value{EDITION} User's Guide}, for details.) +to the use of the @cite{gnaty} switch with no options. +See the @cite{GNAT User's Guide} for details.) -Note: the behavior is slightly different in GNAT mode (@option{-gnatg} used). +Note: the behavior is slightly different in GNAT mode (@emph{-gnatg} used). In this case, ALL_CHECKS implies the standard set of GNAT mode style check -options (i.e. equivalent to -gnatyg). +options (i.e. equivalent to @emph{-gnatyg}). -The forms with @code{Off} and @code{On} +The forms with @cite{Off} and @cite{On} can be used to temporarily disable style checks as shown in the following example: -@smallexample @c ada -@iftex -@leftskip=0cm -@end iftex +@example pragma Style_Checks ("k"); -- requires keywords in lower case pragma Style_Checks (Off); -- turn off style checks NULL; -- this will not generate an error message pragma Style_Checks (On); -- turn style checks back on NULL; -- this will generate an error message -@end smallexample +@end example -@noindent Finally the two argument form is allowed only if the first argument is -@code{On} or @code{Off}. The effect is to turn of semantic style checks +@cite{On} or @cite{Off}. The effect is to turn of semantic style checks for the specified entity, as shown in the following example: -@smallexample @c ada -@iftex -@leftskip=0cm -@end iftex +@example pragma Style_Checks ("r"); -- require consistency of identifier casing Arg : Integer; Rf1 : Integer := ARG; -- incorrect, wrong case pragma Style_Checks (Off, Arg); Rf2 : Integer := ARG; -- OK, no error -@end smallexample +@end example + +@node Pragma Subtitle,Pragma Suppress,Pragma Style_Checks,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-subtitle}@anchor{c0} +@section Pragma Subtitle + -@node Pragma Subtitle -@unnumberedsec Pragma Subtitle -@findex Subtitle -@noindent Syntax: -@smallexample @c ada +@example pragma Subtitle ([Subtitle =>] STRING_LITERAL); -@end smallexample +@end example -@noindent This pragma is recognized for compatibility with other Ada compilers -but is ignored by GNAT@. +but is ignored by GNAT. + +@node Pragma Suppress,Pragma Suppress_All,Pragma Subtitle,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress}@anchor{c1} +@section Pragma Suppress + -@node Pragma Suppress -@unnumberedsec Pragma Suppress -@findex Suppress -@noindent Syntax: -@smallexample @c ada +@example pragma Suppress (Identifier [, [On =>] Name]); -@end smallexample +@end example -@noindent This is a standard pragma, and supports all the check names required in the RM. It is included here because GNAT recognizes some additional check names that are implementation defined (as permitted by the RM): -@itemize @bullet -@item -@code{Alignment_Check} can be used to suppress alignment checks +@itemize * + +@item +@cite{Alignment_Check} can be used to suppress alignment checks on addresses used in address clauses. Such checks can also be suppressed -by suppressing range checks, but the specific use of @code{Alignment_Check} +by suppressing range checks, but the specific use of @cite{Alignment_Check} allows suppression of alignment checks without suppressing other range checks. -@item -@code{Atomic_Synchronization} can be used to suppress the special memory +@item +@cite{Atomic_Synchronization} can be used to suppress the special memory synchronization instructions that are normally generated for access to -@code{Atomic} variables to ensure correct synchronization between tasks +@cite{Atomic} variables to ensure correct synchronization between tasks that use such variables for synchronization purposes. -@item -@code{Duplicated_Tag_Check} Can be used to suppress the check that is generated +@item +@cite{Duplicated_Tag_Check} Can be used to suppress the check that is generated for a duplicated tag value when a tagged type is declared. -@item -@code{Predicate_Check} can be used to control whether predicate checks are +@item +@cite{Predicate_Check} can be used to control whether predicate checks are active. It is applicable only to predicates for which the policy is -@code{Check}. Unlike @code{Assertion_Policy}, which determines if a given +@cite{Check}. Unlike @cite{Assertion_Policy}, which determines if a given predicate is ignored or checked for the whole program, the use of -@code{Suppress} and @code{Unsuppress} with this check name allows a given +@cite{Suppress} and @cite{Unsuppress} with this check name allows a given predicate to be turned on and off at specific points in the program. -@item -@code{Validity_Check} can be used specifically to control validity checks. -If @code{Suppress} is used to suppress validity checks, then no validity +@item +@cite{Validity_Check} can be used specifically to control validity checks. +If @cite{Suppress} is used to suppress validity checks, then no validity checks are performed, including those specified by the appropriate compiler -switch or the @code{Validity_Checks} pragma. +switch or the @cite{Validity_Checks} pragma. -@item -Additional check names previously introduced by use of the @code{Check_Name} +@item +Additional check names previously introduced by use of the @cite{Check_Name} pragma are also allowed. - @end itemize -@noindent Note that pragma Suppress gives the compiler permission to omit checks, but does not require the compiler to omit checks. The compiler will generate checks if they are essentially free, even when they are suppressed. In particular, if the compiler can prove that a certain check will necessarily fail, it will generate code to do an -unconditional ``raise'', even if checks are suppressed. The compiler +unconditional 'raise', even if checks are suppressed. The compiler warns in this case. Of course, run-time checks are omitted whenever the compiler can prove that they will not fail, whether or not checks are suppressed. -@node Pragma Suppress_All -@unnumberedsec Pragma Suppress_All -@findex Suppress_All -@noindent +@node Pragma Suppress_All,Pragma Suppress_Debug_Info,Pragma Suppress,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-all}@anchor{c2} +@section Pragma Suppress_All + + Syntax: -@smallexample @c ada +@example pragma Suppress_All; -@end smallexample +@end example -@noindent This pragma can appear anywhere within a unit. -The effect is to apply @code{Suppress (All_Checks)} to the unit +The effect is to apply @cite{Suppress (All_Checks)} to the unit in which it appears. This pragma is implemented for compatibility with DEC Ada 83 usage where it appears at the end of a unit, and for compatibility with Rational Ada, where it appears as a program unit pragma. -The use of the standard Ada pragma @code{Suppress (All_Checks)} -as a normal configuration pragma is the preferred usage in GNAT@. +The use of the standard Ada pragma @cite{Suppress (All_Checks)} +as a normal configuration pragma is the preferred usage in GNAT. + +@node Pragma Suppress_Debug_Info,Pragma Suppress_Exception_Locations,Pragma Suppress_All,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-debug-info}@anchor{c3} +@section Pragma Suppress_Debug_Info + -@node Pragma Suppress_Debug_Info -@unnumberedsec Pragma Suppress_Debug_Info -@findex Suppress_Debug_Info -@noindent Syntax: -@smallexample @c ada -Suppress_Debug_Info ([Entity =>] LOCAL_NAME); -@end smallexample +@example +pragma Suppress_Debug_Info ([Entity =>] LOCAL_NAME); +@end example -@noindent This pragma can be used to suppress generation of debug information for the specified entity. It is intended primarily for use in debugging the debugger, and navigating around debugger problems. -@node Pragma Suppress_Exception_Locations -@unnumberedsec Pragma Suppress_Exception_Locations -@findex Suppress_Exception_Locations -@noindent +@node Pragma Suppress_Exception_Locations,Pragma Suppress_Initialization,Pragma Suppress_Debug_Info,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-exception-locations}@anchor{c4} +@section Pragma Suppress_Exception_Locations + + Syntax: -@smallexample @c ada +@example pragma Suppress_Exception_Locations; -@end smallexample +@end example -@noindent In normal mode, a raise statement for an exception by default generates an exception message giving the file name and line number for the location of the raise. This is useful for debugging and logging purposes, but this entails extra space for the strings for the messages. The configuration -pragma @code{Suppress_Exception_Locations} can be used to suppress the +pragma @cite{Suppress_Exception_Locations} can be used to suppress the generation of these strings, with the result that space is saved, but the exception message for such raises is null. This configuration pragma may appear in a global configuration pragma file, or in a specific unit as @@ -7068,19 +7273,22 @@ usual. It is not required that this pragma be used consistently within a partition, so it is fine to have some units within a partition compiled with this pragma and others compiled in normal mode without it. -@node Pragma Suppress_Initialization -@unnumberedsec Pragma Suppress_Initialization -@findex Suppress_Initialization -@cindex Suppressing initialization -@cindex Initialization, suppression of -@noindent +@node Pragma Suppress_Initialization,Pragma Task_Name,Pragma Suppress_Exception_Locations,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-suppress-initialization}@anchor{c5} +@section Pragma Suppress_Initialization + + +@geindex Suppressing initialization + +@geindex Initialization +@geindex suppression of + Syntax: -@smallexample @c ada +@example pragma Suppress_Initialization ([Entity =>] variable_or_subtype_Name); -@end smallexample +@end example -@noindent Here variable_or_subtype_Name is the name introduced by a type declaration or subtype declaration or the name of a variable introduced by an object declaration. @@ -7110,19 +7318,19 @@ For the variable case, implicit initialization for the named variable is suppressed, just as though its subtype had been given in a pragma Suppress_Initialization, as described above. -@node Pragma Task_Name -@unnumberedsec Pragma Task_Name -@findex Task_Name -@noindent +@node Pragma Task_Name,Pragma Task_Storage,Pragma Suppress_Initialization,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-task-name}@anchor{c6} +@section Pragma Task_Name + + Syntax -@smallexample @c ada +@example pragma Task_Name (string_EXPRESSION); -@end smallexample +@end example -@noindent This pragma appears within a task definition (like pragma -@code{Priority}) and applies to the task in which it appears. The +@cite{Priority}) and applies to the task in which it appears. The argument must be of type String, and provides a name to be used for the task instance when the task is created. Note that this expression is not required to be static, and in particular, it can contain @@ -7132,10 +7340,10 @@ as illustrated in the example below. The task name is recorded internally in the run-time structures and is accessible to tools like the debugger. In addition the -routine @code{Ada.Task_Identification.Image} will return this +routine @cite{Ada.Task_Identification.Image} will return this string, with a unique task address appended. -@smallexample @c ada +@example -- Example of the use of pragma Task_Name with Ada.Task_Identification; @@ -7164,63 +7372,65 @@ begin Task_Var := new Task_Typ (new String'("This is task 2")); end; -@end smallexample +@end example + +@node Pragma Task_Storage,Pragma Test_Case,Pragma Task_Name,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-task-storage}@anchor{c7} +@section Pragma Task_Storage + -@node Pragma Task_Storage -@unnumberedsec Pragma Task_Storage -@findex Task_Storage Syntax: -@smallexample @c ada +@example pragma Task_Storage ( [Task_Type =>] LOCAL_NAME, [Top_Guard =>] static_integer_EXPRESSION); -@end smallexample +@end example -@noindent This pragma specifies the length of the guard area for tasks. The guard area is an additional storage area allocated to a task. A value of zero means that either no guard area is created or a minimal guard area is created, depending on the target. This pragma can appear anywhere a -@code{Storage_Size} attribute definition clause is allowed for a task +@cite{Storage_Size} attribute definition clause is allowed for a task type. -@node Pragma Test_Case -@unnumberedsec Pragma Test_Case -@cindex Test cases -@findex Test_Case -@noindent +@node Pragma Test_Case,Pragma Thread_Local_Storage,Pragma Task_Storage,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-test-case}@anchor{c8} +@section Pragma Test_Case + + +@geindex Test cases + Syntax: -@smallexample @c ada +@example pragma Test_Case ( [Name =>] static_string_Expression ,[Mode =>] (Nominal | Robustness) [, Requires => Boolean_Expression] [, Ensures => Boolean_Expression]); -@end smallexample +@end example -@noindent -The @code{Test_Case} pragma allows defining fine-grain specifications +The @cite{Test_Case} pragma allows defining fine-grain specifications for use by testing tools. -The compiler checks the validity of the @code{Test_Case} pragma, but its +The compiler checks the validity of the @cite{Test_Case} pragma, but its presence does not lead to any modification of the code generated by the compiler. -@code{Test_Case} pragmas may only appear immediately following the +@cite{Test_Case} pragmas may only appear immediately following the (separate) declaration of a subprogram in a package declaration, inside a package spec unit. Only other pragmas may intervene (that is appear between the subprogram declaration and a test case). -The compiler checks that boolean expressions given in @code{Requires} and -@code{Ensures} are valid, where the rules for @code{Requires} are the -same as the rule for an expression in @code{Precondition} and the rules -for @code{Ensures} are the same as the rule for an expression in -@code{Postcondition}. In particular, attributes @code{'Old} and -@code{'Result} can only be used within the @code{Ensures} +The compiler checks that boolean expressions given in @cite{Requires} and +@cite{Ensures} are valid, where the rules for @cite{Requires} are the +same as the rule for an expression in @cite{Precondition} and the rules +for @cite{Ensures} are the same as the rule for an expression in +@cite{Postcondition}. In particular, attributes @cite{'Old} and +@cite{'Result} can only be used within the @cite{Ensures} expression. The following is an example of use within a package spec: -@smallexample @c ada +@example package Math_Functions is ... function Sqrt (Arg : Float) return Float; @@ -7230,153 +7440,152 @@ package Math_Functions is Ensures => Sqrt'Result < 10); ... end Math_Functions; -@end smallexample +@end example -@noindent The meaning of a test case is that there is at least one context where -@code{Requires} holds such that, if the associated subprogram is executed in -that context, then @code{Ensures} holds when the subprogram returns. -Mode @code{Nominal} indicates that the input context should also satisfy the +@cite{Requires} holds such that, if the associated subprogram is executed in +that context, then @cite{Ensures} holds when the subprogram returns. +Mode @cite{Nominal} indicates that the input context should also satisfy the precondition of the subprogram, and the output context should also satisfy its -postcondition. Mode @code{Robustness} indicates that the precondition and +postcondition. Mode @cite{Robustness} indicates that the precondition and postcondition of the subprogram should be ignored for this test case. -@node Pragma Thread_Local_Storage -@unnumberedsec Pragma Thread_Local_Storage -@findex Thread_Local_Storage -@cindex Task specific storage -@cindex TLS (Thread Local Storage) -@cindex Task_Attributes +@node Pragma Thread_Local_Storage,Pragma Time_Slice,Pragma Test_Case,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-thread-local-storage}@anchor{c9} +@section Pragma Thread_Local_Storage + + +@geindex Task specific storage + +@geindex TLS (Thread Local Storage) + +@geindex Task_Attributes + Syntax: -@smallexample @c ada +@example pragma Thread_Local_Storage ([Entity =>] LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma specifies that the specified entity, which must be a variable declared in a library level package, is to be marked as -"Thread Local Storage" (@code{TLS}). On systems supporting this (which +"Thread Local Storage" (@cite{TLS}). On systems supporting this (which include Solaris, GNU/Linux and VxWorks 6), this causes each thread (and hence each Ada task) to see a distinct copy of the variable. The variable may not have default initialization, and if there is -an explicit initialization, it must be either @code{null} for an +an explicit initialization, it must be either @cite{null} for an access variable, or a static expression for a scalar variable. This provides a low level mechanism similar to that provided by -the @code{Ada.Task_Attributes} package, but much more efficient +the @cite{Ada.Task_Attributes} package, but much more efficient and is also useful in writing interface code that will interact with foreign threads. -If this pragma is used on a system where @code{TLS} is not supported, +If this pragma is used on a system where @cite{TLS} is not supported, then an error message will be generated and the program will be rejected. -@node Pragma Time_Slice -@unnumberedsec Pragma Time_Slice -@findex Time_Slice -@noindent +@node Pragma Time_Slice,Pragma Title,Pragma Thread_Local_Storage,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-time-slice}@anchor{ca} +@section Pragma Time_Slice + + Syntax: -@smallexample @c ada +@example pragma Time_Slice (static_duration_EXPRESSION); -@end smallexample +@end example -@noindent For implementations of GNAT on operating systems where it is possible to supply a time slice value, this pragma may be used for this purpose. It is ignored if it is used in a system that does not allow this control, or if it appears in other than the main program unit. -@cindex OpenVMS -Note that the effect of this pragma is identical to the effect of the -DEC Ada 83 pragma of the same name when operating under OpenVMS systems. - -@node Pragma Title -@unnumberedsec Pragma Title -@findex Title -@noindent -Syntax: -@smallexample @c ada +@node Pragma Title,Pragma Type_Invariant,Pragma Time_Slice,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-title}@anchor{cb} +@section Pragma Title + + +Syntax: + +@example pragma Title (TITLING_OPTION [, TITLING OPTION]); TITLING_OPTION ::= [Title =>] STRING_LITERAL, | [Subtitle =>] STRING_LITERAL -@end smallexample +@end example -@noindent -Syntax checked but otherwise ignored by GNAT@. This is a listing control +Syntax checked but otherwise ignored by GNAT. This is a listing control pragma used in DEC Ada 83 implementations to provide a title and/or subtitle for the program listing. The program listing generated by GNAT does not have titles or subtitles. Unlike other pragmas, the full flexibility of named notation is allowed -for this pragma, i.e.@: the parameters may be given in any order if named +for this pragma, i.e., the parameters may be given in any order if named notation is used, and named and positional notation can be mixed following the normal rules for procedure calls in Ada. -@node Pragma Type_Invariant -@unnumberedsec Pragma Type_Invariant -@findex Invariant -@findex Type_Invariant pragma -@noindent +@node Pragma Type_Invariant,Pragma Type_Invariant_Class,Pragma Title,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant}@anchor{cc} +@section Pragma Type_Invariant + + Syntax: -@smallexample @c ada +@example pragma Type_Invariant ([Entity =>] type_LOCAL_NAME, [Check =>] EXPRESSION); -@end smallexample +@end example -@noindent -The @code{Type_Invariant} pragma is intended to be an exact -replacement for the language-defined @code{Type_Invariant} +The @cite{Type_Invariant} pragma is intended to be an exact +replacement for the language-defined @cite{Type_Invariant} aspect, and shares its restrictions and semantics. It differs -from the language defined @code{Invariant} pragma in that it +from the language defined @cite{Invariant} pragma in that it does not permit a string parameter, and it is -controlled by the assertion identifier @code{Type_Invariant} -rather than @code{Invariant}. - -@node Pragma Type_Invariant_Class -@unnumberedsec Pragma Type_Invariant_Class -@findex Invariant -@findex Type_Invariant_Class pragma -@noindent +controlled by the assertion identifier @cite{Type_Invariant} +rather than @cite{Invariant}. + +@node Pragma Type_Invariant_Class,Pragma Unchecked_Union,Pragma Type_Invariant,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-type-invariant-class}@anchor{cd} +@section Pragma Type_Invariant_Class + + Syntax: -@smallexample @c ada +@example pragma Type_Invariant_Class ([Entity =>] type_LOCAL_NAME, [Check =>] EXPRESSION); -@end smallexample +@end example -@noindent -The @code{Type_Invariant_Class} pragma is intended to be an exact -replacement for the language-defined @code{Type_Invariant'Class} +The @cite{Type_Invariant_Class} pragma is intended to be an exact +replacement for the language-defined @cite{Type_Invariant'Class} aspect, and shares its restrictions and semantics. -Note: This pragma is called @code{Type_Invariant_Class} rather than -@code{Type_Invariant'Class} because the latter would not be strictly +Note: This pragma is called @cite{Type_Invariant_Class} rather than +@cite{Type_Invariant'Class} because the latter would not be strictly conforming to the allowed syntax for pragmas. The motivation for providing pragmas equivalent to the aspects is to allow a program to be written using the pragmas, and then compiled if necessary using an Ada compiler that does not recognize the pragmas or aspects, but is prepared to ignore the pragmas. The assertion -policy that controls this pragma is @code{Type_Invariant'Class}, -not @code{Type_Invariant_Class}. - -@node Pragma Unchecked_Union -@unnumberedsec Pragma Unchecked_Union -@cindex Unions in C -@findex Unchecked_Union -@noindent +policy that controls this pragma is @cite{Type_Invariant'Class}, +not @cite{Type_Invariant_Class}. + +@node Pragma Unchecked_Union,Pragma Unevaluated_Use_Of_Old,Pragma Type_Invariant_Class,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unchecked-union}@anchor{ce} +@section Pragma Unchecked_Union + + +@geindex Unions in C + Syntax: -@smallexample @c ada +@example pragma Unchecked_Union (first_subtype_LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma is used to specify a representation of a record type that is equivalent to a C union. It was introduced as a GNAT implementation defined pragma in the GNAT Ada 95 mode. Ada 2005 includes an extended version of this @@ -7384,20 +7593,23 @@ pragma, making it language defined, and GNAT fully implements this extended version in all language modes (Ada 83, Ada 95, and Ada 2005). For full details, consult the Ada 2012 Reference Manual, section B.3.3. -@node Pragma Unevaluated_Use_Of_Old -@unnumberedsec Pragma Unevaluated_Use_Of_Old -@cindex Attribute Old -@cindex Attribute Loop_Entry -@cindex Unevaluated_Use_Of_Old -@findex Unevaluated_Use_Of_Old -@noindent +@node Pragma Unevaluated_Use_Of_Old,Pragma Unimplemented_Unit,Pragma Unchecked_Union,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unevaluated-use-of-old}@anchor{cf} +@section Pragma Unevaluated_Use_Of_Old + + +@geindex Attribute Old + +@geindex Attribute Loop_Entry + +@geindex Unevaluated_Use_Of_Old + Syntax: -@smallexample @c ada +@example pragma Unevaluated_Use_Of_Old (Error | Warn | Allow); -@end smallexample +@end example -@noindent This pragma controls the processing of attributes Old and Loop_Entry. If either of these attributes is used in a potentially unevaluated expression (e.g. the then or else parts of an if expression), then @@ -7409,15 +7621,14 @@ The reason for this rule is that otherwise, we can have a situation where we save the Old value, and this results in an exception, even though we might not evaluate the attribute. Consider this example: -@smallexample @c ada +@example package UnevalOld is K : Character; procedure U (A : String; C : Boolean) -- ERROR with Post => (if C then A(1)'Old = K else True); end; -@end smallexample +@end example -@noindent If procedure U is called with a string with a lower bound of 2, and C false, then an exception would be raised trying to evaluate A(1) on entry even though the value would not be actually used. @@ -7425,11 +7636,11 @@ on entry even though the value would not be actually used. Although the rule guarantees against this possibility, it is sometimes too restrictive. For example if we know that the string has a lower bound of 1, then we will never raise an exception. -The pragma @code{Unevaluated_Use_Of_Old} can be -used to modify this behavior. If the argument is @code{Error} then an +The pragma @cite{Unevaluated_Use_Of_Old} can be +used to modify this behavior. If the argument is @cite{Error} then an error is given (this is the default RM behavior). If the argument is -@code{Warn} then the usage is allowed as legal but with a warning -that an exception might be raised. If the argument is @code{Allow} +@cite{Warn} then the usage is allowed as legal but with a warning +that an exception might be raised. If the argument is @cite{Allow} then the usage is allowed as legal without generating a warning. This pragma may appear as a configuration pragma, or in a declarative @@ -7437,56 +7648,56 @@ part or package specification. In the latter case it applies to uses up to the end of the corresponding statement sequence or sequence of package declarations. -@node Pragma Unimplemented_Unit -@unnumberedsec Pragma Unimplemented_Unit -@findex Unimplemented_Unit -@noindent +@node Pragma Unimplemented_Unit,Pragma Universal_Aliasing,Pragma Unevaluated_Use_Of_Old,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unimplemented-unit}@anchor{d0} +@section Pragma Unimplemented_Unit + + Syntax: -@smallexample @c ada +@example pragma Unimplemented_Unit; -@end smallexample +@end example -@noindent If this pragma occurs in a unit that is processed by the compiler, GNAT -aborts with the message @samp{@var{xxx} not implemented}, where -@var{xxx} is the name of the current compilation unit. This pragma is +aborts with the message @code{xxx not implemented}, where +@cite{xxx} is the name of the current compilation unit. This pragma is intended to allow the compiler to handle unimplemented library units in a clean manner. The abort only happens if code is being generated. Thus you can use specs of unimplemented packages in syntax or semantic checking mode. -@node Pragma Universal_Aliasing -@unnumberedsec Pragma Universal_Aliasing -@findex Universal_Aliasing -@noindent +@node Pragma Universal_Aliasing,Pragma Universal_Data,Pragma Unimplemented_Unit,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-universal-aliasing}@anchor{d1} +@section Pragma Universal_Aliasing + + Syntax: -@smallexample @c ada +@example pragma Universal_Aliasing [([Entity =>] type_LOCAL_NAME)]; -@end smallexample +@end example -@noindent -@var{type_LOCAL_NAME} must refer to a type declaration in the current +@cite{type_LOCAL_NAME} must refer to a type declaration in the current declarative part. The effect is to inhibit strict type-based aliasing optimization for the given type. In other words, the effect is as though access types designating this type were subject to pragma No_Strict_Aliasing. For a detailed description of the strict aliasing optimization, and the -situations in which it must be suppressed, @xref{Optimization and Strict -Aliasing,,, gnat_ugn, @value{EDITION} User's Guide}. +situations in which it must be suppressed, see the section on +@cite{Optimization and Strict Aliasing} in the @cite{GNAT User's Guide}. + +@node Pragma Universal_Data,Pragma Unmodified,Pragma Universal_Aliasing,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-universal-data}@anchor{d2} +@section Pragma Universal_Data + -@node Pragma Universal_Data -@unnumberedsec Pragma Universal_Data -@findex Universal_Data -@noindent Syntax: -@smallexample @c ada +@example pragma Universal_Data [(library_unit_Name)]; -@end smallexample +@end example -@noindent This pragma is supported only for the AAMP target and is ignored for other targets. The pragma specifies that all library-level objects (Counter 0 data) associated with the library unit are to be accessed @@ -7496,24 +7707,26 @@ Use of this pragma will generally result in less efficient code for references to global data associated with the library unit, but allows such data to be located anywhere in memory. This pragma is a library unit pragma, but can also be used as a configuration pragma -(including use in the @file{gnat.adc} file). The functionality +(including use in the @code{gnat.adc} file). The functionality of this pragma is also available by applying the -univ switch on the compilations of units where universal addressing of the data is desired. -@node Pragma Unmodified -@unnumberedsec Pragma Unmodified -@findex Unmodified -@cindex Warnings, unmodified -@noindent +@node Pragma Unmodified,Pragma Unreferenced,Pragma Universal_Data,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unmodified}@anchor{d3} +@section Pragma Unmodified + + +@geindex Warnings +@geindex unmodified + Syntax: -@smallexample @c ada +@example pragma Unmodified (LOCAL_NAME @{, LOCAL_NAME@}); -@end smallexample +@end example -@noindent This pragma signals that the assignable entities (variables, -@code{out} parameters, @code{in out} parameters) whose names are listed are +@cite{out} parameters, @cite{in out} parameters) whose names are listed are deliberately not assigned in the current source unit. This suppresses warnings about the entities being referenced but not assigned, and in addition a warning will be @@ -7527,24 +7740,26 @@ be. For the variable case, warnings are never given for unreferenced variables whose name contains one of the substrings -@code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names +@cite{DISCARD@comma{} DUMMY@comma{} IGNORE@comma{} JUNK@comma{} UNUSED} in any casing. Such names are typically to be used in cases where such warnings are expected. -Thus it is never necessary to use @code{pragma Unmodified} for such +Thus it is never necessary to use @cite{pragma Unmodified} for such variables, though it is harmless to do so. -@node Pragma Unreferenced -@unnumberedsec Pragma Unreferenced -@findex Unreferenced -@cindex Warnings, unreferenced -@noindent +@node Pragma Unreferenced,Pragma Unreferenced_Objects,Pragma Unmodified,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced}@anchor{d4} +@section Pragma Unreferenced + + +@geindex Warnings +@geindex unreferenced + Syntax: -@smallexample @c ada +@example pragma Unreferenced (LOCAL_NAME @{, LOCAL_NAME@}); pragma Unreferenced (library_unit_NAME @{, library_unit_NAME@}); -@end smallexample +@end example -@noindent This pragma signals that the entities whose names are listed are deliberately not referenced in the current source unit after the occurrence of the pragma. This @@ -7560,10 +7775,10 @@ and that this is deliberate. It can also be useful in the case of objects declared only for their initialization or finalization side effects. -If @code{LOCAL_NAME} identifies more than one matching homonym in the +If @cite{LOCAL_NAME} identifies more than one matching homonym in the current scope, then the entity most recently declared is the one to which the pragma applies. Note that in the case of accept formals, the pragma -Unreferenced may appear immediately after the keyword @code{do} which +Unreferenced may appear immediately after the keyword @cite{do} which allows the indication of whether or not accept formals are referenced or not to be given individually for each accept statement. @@ -7575,33 +7790,35 @@ Note that if a warning is desired for all calls to a given subprogram, regardless of whether they occur in the same unit as the subprogram declaration, then this pragma should not be used (calls from another unit would not be flagged); pragma Obsolescent can be used instead -for this purpose, see @xref{Pragma Obsolescent}. +for this purpose, see @ref{8b,,Pragma Obsolescent}. -The second form of pragma @code{Unreferenced} is used within a context +The second form of pragma @cite{Unreferenced} is used within a context clause. In this case the arguments must be unit names of units previously -mentioned in @code{with} clauses (similar to the usage of pragma -@code{Elaborate_All}. The effect is to suppress warnings about unreferenced +mentioned in @cite{with} clauses (similar to the usage of pragma +@cite{Elaborate_All}. The effect is to suppress warnings about unreferenced units and unreferenced entities within these units. For the variable case, warnings are never given for unreferenced variables whose name contains one of the substrings -@code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED} in any casing. Such names +@cite{DISCARD@comma{} DUMMY@comma{} IGNORE@comma{} JUNK@comma{} UNUSED} in any casing. Such names are typically to be used in cases where such warnings are expected. -Thus it is never necessary to use @code{pragma Unreferenced} for such +Thus it is never necessary to use @cite{pragma Unreferenced} for such variables, though it is harmless to do so. -@node Pragma Unreferenced_Objects -@unnumberedsec Pragma Unreferenced_Objects -@findex Unreferenced_Objects -@cindex Warnings, unreferenced -@noindent +@node Pragma Unreferenced_Objects,Pragma Unreserve_All_Interrupts,Pragma Unreferenced,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unreferenced-objects}@anchor{d5} +@section Pragma Unreferenced_Objects + + +@geindex Warnings +@geindex unreferenced + Syntax: -@smallexample @c ada +@example pragma Unreferenced_Objects (local_subtype_NAME @{, local_subtype_NAME@}); -@end smallexample +@end example -@noindent This pragma signals that for the types or subtypes whose names are listed, objects which are declared with one of these types or subtypes may not be referenced, and if no references appear, no warnings are given. @@ -7613,58 +7830,58 @@ pragma on the relevant type (most typically a limited controlled type), the compiler will automatically suppress unwanted warnings about these variables not being referenced. -@node Pragma Unreserve_All_Interrupts -@unnumberedsec Pragma Unreserve_All_Interrupts -@findex Unreserve_All_Interrupts -@noindent +@node Pragma Unreserve_All_Interrupts,Pragma Unsuppress,Pragma Unreferenced_Objects,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unreserve-all-interrupts}@anchor{d6} +@section Pragma Unreserve_All_Interrupts + + Syntax: -@smallexample @c ada +@example pragma Unreserve_All_Interrupts; -@end smallexample +@end example -@noindent Normally certain interrupts are reserved to the implementation. Any attempt to attach an interrupt causes Program_Error to be raised, as described in -RM C.3.2(22). A typical example is the @code{SIGINT} interrupt used in -many systems for a @kbd{Ctrl-C} interrupt. Normally this interrupt is -reserved to the implementation, so that @kbd{Ctrl-C} can be used to +RM C.3.2(22). A typical example is the @cite{SIGINT} interrupt used in +many systems for a @code{Ctrl-C} interrupt. Normally this interrupt is +reserved to the implementation, so that @code{Ctrl-C} can be used to interrupt execution. -If the pragma @code{Unreserve_All_Interrupts} appears anywhere in any unit in +If the pragma @cite{Unreserve_All_Interrupts} appears anywhere in any unit in a program, then all such interrupts are unreserved. This allows the program to handle these interrupts, but disables their standard functions. For example, if this pragma is used, then pressing -@kbd{Ctrl-C} will not automatically interrupt execution. However, -a program can then handle the @code{SIGINT} interrupt as it chooses. +@code{Ctrl-C} will not automatically interrupt execution. However, +a program can then handle the @cite{SIGINT} interrupt as it chooses. For a full list of the interrupts handled in a specific implementation, -see the source code for the spec of @code{Ada.Interrupts.Names} in -file @file{a-intnam.ads}. This is a target dependent file that contains the +see the source code for the spec of @cite{Ada.Interrupts.Names} in +file @code{a-intnam.ads}. This is a target dependent file that contains the list of interrupts recognized for a given target. The documentation in this file also specifies what interrupts are affected by the use of -the @code{Unreserve_All_Interrupts} pragma. +the @cite{Unreserve_All_Interrupts} pragma. For a more general facility for controlling what interrupts can be -handled, see pragma @code{Interrupt_State}, which subsumes the functionality -of the @code{Unreserve_All_Interrupts} pragma. +handled, see pragma @cite{Interrupt_State}, which subsumes the functionality +of the @cite{Unreserve_All_Interrupts} pragma. + +@node Pragma Unsuppress,Pragma Use_VADS_Size,Pragma Unreserve_All_Interrupts,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-unsuppress}@anchor{d7} +@section Pragma Unsuppress + -@node Pragma Unsuppress -@unnumberedsec Pragma Unsuppress -@findex Unsuppress -@noindent Syntax: -@smallexample @c ada +@example pragma Unsuppress (IDENTIFIER [, [On =>] NAME]); -@end smallexample +@end example -@noindent -This pragma undoes the effect of a previous pragma @code{Suppress}. If -there is no corresponding pragma @code{Suppress} in effect, it has no +This pragma undoes the effect of a previous pragma @cite{Suppress}. If +there is no corresponding pragma @cite{Suppress} in effect, it has no effect. The range of the effect is the same as for pragma -@code{Suppress}. The meaning of the arguments is identical to that used -in pragma @code{Suppress}. +@cite{Suppress}. The meaning of the arguments is identical to that used +in pragma @cite{Suppress}. One important application is to ensure that checks are on in cases where code depends on the checks for its correct functioning, so that the code @@ -7674,31 +7891,33 @@ types and wants to ensure that the duplicated tag check occurs even if all run-time checks are suppressed by a compiler switch, the following configuration pragma will ensure this test is not suppressed: -@smallexample @c ada +@example pragma Unsuppress (Duplicated_Tag_Check); -@end smallexample +@end example -@noindent This pragma is standard in Ada 2005. It is available in all earlier versions of Ada as an implementation-defined pragma. Note that in addition to the checks defined in the Ada RM, GNAT recogizes a number of implementation-defined check names. See description of pragma -@code{Suppress} for full details. - -@node Pragma Use_VADS_Size -@unnumberedsec Pragma Use_VADS_Size -@cindex @code{Size}, VADS compatibility -@cindex Rational profile -@findex Use_VADS_Size -@noindent +@cite{Suppress} for full details. + +@node Pragma Use_VADS_Size,Pragma Validity_Checks,Pragma Unsuppress,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-use-vads-size}@anchor{d8} +@section Pragma Use_VADS_Size + + +@geindex Size +@geindex VADS compatibility + +@geindex Rational profile + Syntax: -@smallexample @c ada +@example pragma Use_VADS_Size; -@end smallexample +@end example -@noindent This is a configuration pragma. In a unit to which it applies, any use of the 'Size attribute is automatically interpreted as a use of the 'VADS_Size attribute. Note that this may result in incorrect semantic @@ -7707,76 +7926,74 @@ the handling of existing code which depends on the interpretation of Size as implemented in the VADS compiler. See description of the VADS_Size attribute for further details. -@node Pragma Validity_Checks -@unnumberedsec Pragma Validity_Checks -@findex Validity_Checks -@noindent +@node Pragma Validity_Checks,Pragma Volatile,Pragma Use_VADS_Size,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-validity-checks}@anchor{d9} +@section Pragma Validity_Checks + + Syntax: -@smallexample @c ada +@example pragma Validity_Checks (string_LITERAL | ALL_CHECKS | On | Off); -@end smallexample +@end example -@noindent This pragma is used in conjunction with compiler switches to control the -built-in validity checking provided by GNAT@. The compiler switches, if set +built-in validity checking provided by GNAT. The compiler switches, if set provide an initial setting for the switches, and this pragma may be used to modify these settings, or the settings may be provided entirely by the use of the pragma. This pragma can be used anywhere that a pragma is legal, including use as a configuration pragma (including use in -the @file{gnat.adc} file). +the @code{gnat.adc} file). The form with a string literal specifies which validity options are to be activated. The validity checks are first set to include only the default reference manual settings, and then a string of letters in the string specifies the exact set of options required. The form of this string -is exactly as described for the @option{-gnatVx} compiler switch (see the -@value{EDITION} User's Guide for details). For example the following two -methods can be used to enable validity checking for mode @code{in} and -@code{in out} subprogram parameters: +is exactly as described for the @emph{-gnatVx} compiler switch (see the +GNAT User's Guide for details). For example the following two +methods can be used to enable validity checking for mode @cite{in} and +@cite{in out} subprogram parameters: -@itemize @bullet -@item -@smallexample @c ada + +@itemize * + +@item +@example pragma Validity_Checks ("im"); -@end smallexample +@end example -@item -@smallexample -gcc -c -gnatVim @dots{} -@end smallexample +@item +@example +$ gcc -c -gnatVim ... +@end example @end itemize -@noindent The form ALL_CHECKS activates all standard checks (its use is equivalent -to the use of the @code{gnatva} switch. +to the use of the @cite{gnatva} switch. -The forms with @code{Off} and @code{On} +The forms with @cite{Off} and @cite{On} can be used to temporarily disable validity checks as shown in the following example: -@smallexample @c ada -@iftex -@leftskip=0cm -@end iftex +@example pragma Validity_Checks ("c"); -- validity checks for copies pragma Validity_Checks (Off); -- turn off validity checks A := B; -- B will not be validity checked pragma Validity_Checks (On); -- turn validity checks back on A := C; -- C will be validity checked -@end smallexample +@end example + +@node Pragma Volatile,Pragma Warning_As_Error,Pragma Validity_Checks,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-volatile}@anchor{da} +@section Pragma Volatile + -@node Pragma Volatile -@unnumberedsec Pragma Volatile -@findex Volatile -@noindent Syntax: -@smallexample @c ada +@example pragma Volatile (LOCAL_NAME); -@end smallexample +@end example -@noindent This pragma is defined by the Ada Reference Manual, and the GNAT implementation is fully conformant with this definition. The reason it is mentioned in this section is that a pragma of the same name was supplied @@ -7784,17 +8001,17 @@ in some Ada 83 compilers, including DEC Ada 83. The Ada 95 / Ada 2005 implementation of pragma Volatile is upwards compatible with the implementation in DEC Ada 83. -@node Pragma Warning_As_Error -@unnumberedsec Pragma Warning_As_Error -@findex Warning_As_Error -@noindent +@node Pragma Warning_As_Error,Pragma Warnings,Pragma Volatile,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-warning-as-error}@anchor{db} +@section Pragma Warning_As_Error + + Syntax: -@smallexample @c ada +@example pragma Warning_As_Error (static_string_EXPRESSION); -@end smallexample +@end example -@noindent This configuration pragma allows the programmer to specify a set of warnings that will be treated as errors. Any warning which matches the pattern given by the pragma argument will be treated @@ -7803,8 +8020,8 @@ which treats all warnings as errors. The pattern may contain asterisks, which match zero or more characters in the message. For example, you can use -@code{pragma Warning_As_Error ("bits of*unused")} to treat the warning -message @code{warning: 960 bits of "a" unused} as an error. No other regular +@cite{pragma Warning_As_Error ("bits of*unused")} to treat the warning +message @cite{warning: 960 bits of "a" unused} as an error. No other regular expression notations are permitted. All characters other than asterisk in these three specific cases are treated as literal characters in the match. The match is case insensitive, for example XYZ matches xyz. @@ -7814,56 +8031,54 @@ message string (it is not necessary to put an asterisk at the start and the end of the message, since this is implied). Another possibility for the static_string_EXPRESSION which works whether -or not error tags are enabled (@option{-gnatw.d}) is to use the -@option{-gnatw} tag string, enclosed in brackets, +or not error tags are enabled (@emph{-gnatw.d}) is to use the +@emph{-gnatw} tag string, enclosed in brackets, as shown in the example below, to treat a class of warnings as errors. The above use of patterns to match the message applies only to warning messages generated by the front end. This pragma can also be applied to -warnings provided by the back end and mentioned in @ref{Pragma Warnings}. -By using a single full @option{-Wxxx} switch in the pragma, such warnings +warnings provided by the back end and mentioned in @ref{dc,,Pragma Warnings}. +By using a single full @emph{-Wxxx} switch in the pragma, such warnings can also be treated as errors. The pragma can appear either in a global configuration pragma file -(e.g. @file{gnat.adc}), or at the start of a file. Given a global +(e.g. @code{gnat.adc}), or at the start of a file. Given a global configuration pragma file containing: -@smallexample @c ada +@example pragma Warning_As_Error ("[-gnatwj]"); -@end smallexample +@end example -@noindent which will treat all obsolescent feature warnings as errors, the following program compiles as shown (compile options here are -@option{-gnatwa.d -gnatl -gnatj55}). - -@smallexample @c ada - 1. pragma Warning_As_Error ("*never assigned*"); - 2. function Warnerr return String is - 3. X : Integer; - | - >>> error: variable "X" is never read and - never assigned [-gnatwv] [warning-as-error] - - 4. Y : Integer; - | - >>> warning: variable "Y" is assigned but - never read [-gnatwu] - - 5. begin - 6. Y := 0; - 7. return %ABC%; - | - >>> error: use of "%" is an obsolescent - feature (RM J.2(4)), use """ instead - [-gnatwj] [warning-as-error] - - 8. end; - - 8 lines: No errors, 3 warnings (2 treated as errors) -@end smallexample - -@noindent +@emph{-gnatwa.d -gnatl -gnatj55}). + +@example + 1. pragma Warning_As_Error ("*never assigned*"); + 2. function Warnerr return String is + 3. X : Integer; + | + >>> error: variable "X" is never read and + never assigned [-gnatwv] [warning-as-error] + + 4. Y : Integer; + | + >>> warning: variable "Y" is assigned but + never read [-gnatwu] + + 5. begin + 6. Y := 0; + 7. return %ABC%; + | + >>> error: use of "%" is an obsolescent + feature (RM J.2(4)), use """ instead + [-gnatwj] [warning-as-error] + + 8. end; + +8 lines: No errors, 3 warnings (2 treated as errors) +@end example + Note that this pragma does not affect the set of warnings issued in any way, it merely changes the effect of a matching warning if one is produced as a result of other warnings options. As shown in this @@ -7871,51 +8086,64 @@ example, if the pragma results in a warning being treated as an error, the tag is changed from "warning:" to "error:" and the string "[warning-as-error]" is appended to the end of the message. -@node Pragma Warnings -@unnumberedsec Pragma Warnings -@findex Warnings -@noindent +@node Pragma Warnings,Pragma Weak_External,Pragma Warning_As_Error,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas id5}@anchor{dd}@anchor{gnat_rm/implementation_defined_pragmas pragma-warnings}@anchor{dc} +@section Pragma Warnings + + Syntax: -@smallexample @c ada -pragma Warnings (On | Off [,REASON]); -pragma Warnings (On | Off, LOCAL_NAME [,REASON]); -pragma Warnings (static_string_EXPRESSION [,REASON]); -pragma Warnings (On | Off, static_string_EXPRESSION [,REASON]); +@example +pragma Warnings ([TOOL_NAME,] DETAILS [, REASON]); + +DETAILS ::= On | Off +DETAILS ::= On | Off, local_NAME +DETAILS ::= static_string_EXPRESSION +DETAILS ::= On | Off, static_string_EXPRESSION + +TOOL_NAME ::= GNAT | GNATProve REASON ::= Reason => STRING_LITERAL @{& STRING_LITERAL@} +@end example + +Note: in Ada 83 mode, a string literal may be used in place of a static string +expression (which does not exist in Ada 83). -Note: in Ada 83 mode, a string literal may be used in place of -a static string expression (which does not exist in Ada 83). -@end smallexample +Note if the second argument of @cite{DETAILS} is a @cite{local_NAME} then the +second form is always understood. If the intention is to use +the fourth form, then you can write @cite{NAME & ""} to force the +intepretation as a @cite{static_string_EXPRESSION}. + +Note: if the first argument is a valid @cite{TOOL_NAME}, it will be interpreted +that way. The use of the @cite{TOOL_NAME} argument is relevant only to users +of SPARK and GNATprove, see last part of this section for details. -@noindent Normally warnings are enabled, with the output being controlled by -the command line switch. Warnings (@code{Off}) turns off generation of -warnings until a Warnings (@code{On}) is encountered or the end of the +the command line switch. Warnings (@cite{Off}) turns off generation of +warnings until a Warnings (@cite{On}) is encountered or the end of the current unit. If generation of warnings is turned off using this pragma, then some or all of the warning messages are suppressed, regardless of the setting of the command line switches. -The @code{Reason} parameter may optionally appear as the last argument +The @cite{Reason} parameter may optionally appear as the last argument in any of the forms of this pragma. It is intended purely for the -purposes of documenting the reason for the @code{Warnings} pragma. +purposes of documenting the reason for the @cite{Warnings} pragma. The compiler will check that the argument is a static string but otherwise ignore this argument. Other tools may provide specialized processing for this string. The form with a single argument (or two arguments if Reason present), -where the first argument is @code{ON} or @code{OFF} +where the first argument is @cite{ON} or @cite{OFF} may be used as a configuration pragma. -If the @var{LOCAL_NAME} parameter is present, warnings are suppressed for +If the @cite{LOCAL_NAME} parameter is present, warnings are suppressed for the specified entity. This suppression is effective from the point where it occurs till the end of the extended scope of the variable (similar to -the scope of @code{Suppress}). This form cannot be used as a configuration +the scope of @cite{Suppress}). This form cannot be used as a configuration pragma. -In the case where the first argument is other than @code{ON} or -@code{OFF}, +In the case where the first argument is other than @cite{ON} or +@cite{OFF}, the third form with a single static_string_EXPRESSION argument (and possible reason) provides more precise control over which warnings are active. The string is a list of letters @@ -7924,20 +8152,19 @@ code for these letters is the same as the string used in the command line switch controlling warnings. For a brief summary, use the gnatmake command with no arguments, which will generate usage information containing the list of warnings switches supported. For -full details see @ref{Warning Message Control,,, gnat_ugn, @value{EDITION} -User's Guide}. This form can also be used as a configuration pragma. +full details see the section on @cite{Warning Message Control} in the +@cite{GNAT User's Guide}. +This form can also be used as a configuration pragma. -@noindent -The warnings controlled by the @option{-gnatw} switch are generated by the +The warnings controlled by the @emph{-gnatw} switch are generated by the front end of the compiler. The GCC back end can provide additional warnings -and they are controlled by the @option{-W} switch. Such warnings can be -identified by the appearance of a string of the form @code{[-Wxxx]} in the -message which designates the @option{-Wxxx} switch that controls the message. +and they are controlled by the @emph{-W} switch. Such warnings can be +identified by the appearance of a string of the form @cite{[-Wxxx]} in the +message which designates the @emph{-Wxxx} switch that controls the message. The form with a single static_string_EXPRESSION argument also works for these -warnings, but the string must be a single full @option{-Wxxx} switch in this +warnings, but the string must be a single full @emph{-Wxxx} switch in this case. The above reference lists a few examples of these additional warnings. -@noindent The specified warnings will be in effect until the end of the program or another pragma Warnings is encountered. The effect of the pragma is cumulative. Initially the set of warnings is the standard default set @@ -7945,15 +8172,15 @@ as possibly modified by compiler switches. Then each pragma Warning modifies this set of warnings as specified. This form of the pragma may also be used as a configuration pragma. -The fourth form, with an @code{On|Off} parameter and a string, is used to +The fourth form, with an @cite{On|Off} parameter and a string, is used to control individual messages, based on their text. The string argument is a pattern that is used to match against the text of individual warning messages (not including the initial "warning: " tag). The pattern may contain asterisks, which match zero or more characters in the message. For example, you can use -@code{pragma Warnings (Off, "bits of*unused")} to suppress the warning -message @code{warning: 960 bits of "a" unused}. No other regular +@cite{pragma Warnings (Off@comma{} "bits of*unused")} to suppress the warning +message @cite{warning: 960 bits of "a" unused}. No other regular expression notations are permitted. All characters other than asterisk in these three specific cases are treated as literal characters in the match. The match is case insensitive, for example XYZ matches xyz. @@ -7965,7 +8192,7 @@ the end of the message, since this is implied). The above use of patterns to match the message applies only to warning messages generated by the front end. This form of the pragma with a string argument can also be used to control warnings provided by the back end and -mentioned above. By using a single full @option{-Wxxx} switch in the pragma, +mentioned above. By using a single full @emph{-Wxxx} switch in the pragma, such warnings can be turned on and off. There are two ways to use the pragma in this form. The OFF form can be used @@ -7976,26 +8203,24 @@ that match the pattern string throughout the compilation (or match the The second usage is to suppress a warning locally, and in this case, two pragmas must appear in sequence: -@smallexample @c ada +@example pragma Warnings (Off, Pattern); -@dots{} code where given warning is to be suppressed +... code where given warning is to be suppressed pragma Warnings (On, Pattern); -@end smallexample +@end example -@noindent In this usage, the pattern string must match in the Off and On -pragmas, and (if @option{-gnatw.w} is given) at least one matching +pragmas, and (if @emph{-gnatw.w} is given) at least one matching warning must be suppressed. Note: to write a string that will match any warning, use the string -@code{"***"}. It will not work to use a single asterisk or two +@cite{"***"}. It will not work to use a single asterisk or two asterisks since this looks like an operator name. This form with three -asterisks is similar in effect to specifying @code{pragma Warnings -(Off)} except (if @option{-gnatw.w} is given) that a matching -@code{pragma Warnings (On, "***")} will be required. This can be +asterisks is similar in effect to specifying @cite{pragma Warnings (Off)} except (if @emph{-gnatw.w} is given) that a matching +@cite{pragma Warnings (On@comma{} "***")} will be required. This can be helpful in avoiding forgetting to turn warnings back on. -Note: the debug flag -gnatd.i (@code{/NOWARNINGS_PRAGMAS} in VMS) can be +Note: the debug flag -gnatd.i (@cite{/NOWARNINGS_PRAGMAS} in VMS) can be used to cause the compiler to entirely ignore all WARNINGS pragmas. This can be useful in checking whether obsolete pragmas in existing programs are hiding real problems. @@ -8003,21 +8228,31 @@ real problems. Note: pragma Warnings does not affect the processing of style messages. See separate entry for pragma Style_Checks for control of style messages. -@node Pragma Weak_External -@unnumberedsec Pragma Weak_External -@findex Weak_External -@noindent +Users of the formal verification tool GNATprove for the SPARK subset of Ada may +use the version of the pragma with a @cite{TOOL_NAME} parameter. + +If present, @cite{TOOL_NAME} is the name of a tool, currently either @cite{GNAT} for the +compiler or @cite{GNATprove} for the formal verification tool. A given tool only +takes into account pragma Warnings that do not specify a tool name, or that +specify the matching tool name. This makes it possible to disable warnings +selectively for each tool, and as a consequence to detect useless pragma +Warnings with switch @cite{-gnatw.w}. + +@node Pragma Weak_External,Pragma Wide_Character_Encoding,Pragma Warnings,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-weak-external}@anchor{de} +@section Pragma Weak_External + + Syntax: -@smallexample @c ada +@example pragma Weak_External ([Entity =>] LOCAL_NAME); -@end smallexample +@end example -@noindent -@var{LOCAL_NAME} must refer to an object that is declared at the library +@cite{LOCAL_NAME} must refer to an object that is declared at the library level. This pragma specifies that the given entity should be marked as a -weak symbol for the linker. It is equivalent to @code{__attribute__((weak))} -in GNU C and causes @var{LOCAL_NAME} to be emitted as a weak symbol instead +weak symbol for the linker. It is equivalent to @cite{__attribute__((weak))} +in GNU C and causes @cite{LOCAL_NAME} to be emitted as a weak symbol instead of a regular symbol, that is to say a symbol that does not have to be resolved by the linker if used in conjunction with a pragma Import. @@ -8035,7 +8270,7 @@ as shown in the example below. Some file formats do not support weak symbols so not all target machines support this pragma. -@smallexample @c ada +@example -- Example of the use of pragma Weak_External package External_Module is @@ -8052,19 +8287,19 @@ package body External_Module is return key'Address /= System.Null_Address; end Present; end External_Module; -@end smallexample +@end example + +@node Pragma Wide_Character_Encoding,,Pragma Weak_External,Implementation Defined Pragmas +@anchor{gnat_rm/implementation_defined_pragmas pragma-wide-character-encoding}@anchor{df} +@section Pragma Wide_Character_Encoding + -@node Pragma Wide_Character_Encoding -@unnumberedsec Pragma Wide_Character_Encoding -@findex Wide_Character_Encoding -@noindent Syntax: -@smallexample @c ada +@example pragma Wide_Character_Encoding (IDENTIFIER | CHARACTER_LITERAL); -@end smallexample +@end example -@noindent This pragma specifies the wide character encoding to be used in program source text appearing subsequently. It is a configuration pragma, but may also be used at any point that a pragma is allowed, and it is permissible @@ -8072,17 +8307,20 @@ to have more than one such pragma in a file, allowing multiple encodings to appear within the same file. The argument can be an identifier or a character literal. In the identifier -case, it is one of @code{HEX}, @code{UPPER}, @code{SHIFT_JIS}, -@code{EUC}, @code{UTF8}, or @code{BRACKETS}. In the character literal -case it is correspondingly one of the characters @samp{h}, @samp{u}, -@samp{s}, @samp{e}, @samp{8}, or @samp{b}. +case, it is one of @cite{HEX}, @cite{UPPER}, @cite{SHIFT_JIS}, +@cite{EUC}, @cite{UTF8}, or @cite{BRACKETS}. In the character literal +case it is correspondingly one of the characters @code{h}, @code{u}, +@code{s}, @code{e}, @code{8}, or @code{b}. Note that when the pragma is used within a file, it affects only the encoding within that file, and does not affect withed units, specs, or subunits. -@node Implementation Defined Aspects +@node Implementation Defined Aspects,Implementation Defined Attributes,Implementation Defined Pragmas,Top +@anchor{gnat_rm/implementation_defined_aspects implementation-defined-aspects}@anchor{e0}@anchor{gnat_rm/implementation_defined_aspects doc}@anchor{e1}@anchor{gnat_rm/implementation_defined_aspects id1}@anchor{e2} @chapter Implementation Defined Aspects + + Ada defines (throughout the Ada 2012 reference manual, summarized in Annex K) a set of aspects that can be specified for certain entities. These language defined aspects are implemented in GNAT in Ada 2012 mode @@ -8103,151 +8341,174 @@ Note that for many of these aspects, the effect is essentially similar to the use of a pragma or attribute specification with the same name applied to the entity. For example, if we write: -@smallexample @c ada +@example type R is range 1 .. 100 with Value_Size => 10; -@end smallexample +@end example -@noindent then the effect is the same as: -@smallexample @c ada +@example type R is range 1 .. 100; for R'Value_Size use 10; -@end smallexample +@end example -@noindent and if we write: -@smallexample @c ada +@example type R is new Integer with Shared => True; -@end smallexample +@end example -@noindent then the effect is the same as: -@smallexample @c ada +@example type R is new Integer; pragma Shared (R); -@end smallexample +@end example -@noindent In the documentation below, such cases are simply marked as being boolean aspects equivalent to the corresponding pragma or attribute definition clause. @menu -* Aspect Abstract_State:: -* Aspect Annotate:: -* Aspect Async_Readers:: -* Aspect Async_Writers:: -* Aspect Contract_Cases:: -* Aspect Depends:: -* Aspect Dimension:: -* Aspect Dimension_System:: -* Aspect Effective_Reads:: -* Aspect Effective_Writes:: -* Aspect Favor_Top_Level:: -* Aspect Global:: -* Aspect Initial_Condition:: -* Aspect Initializes:: -* Aspect Inline_Always:: -* Aspect Invariant:: -* Aspect Invariant'Class:: -* Aspect Iterable:: -* Aspect Linker_Section:: -* Aspect Lock_Free:: -* Aspect No_Elaboration_Code_All:: -* Aspect No_Tagged_Streams:: -* Aspect Object_Size:: -* Aspect Obsolescent:: -* Aspect Part_Of:: -* Aspect Persistent_BSS:: -* Aspect Predicate:: -* Aspect Pure_Function:: -* Aspect Refined_Depends:: -* Aspect Refined_Global:: -* Aspect Refined_Post:: -* Aspect Refined_State:: -* Aspect Remote_Access_Type:: -* Aspect Scalar_Storage_Order:: -* Aspect Shared:: -* Aspect Simple_Storage_Pool:: -* Aspect Simple_Storage_Pool_Type:: -* Aspect SPARK_Mode:: -* Aspect Suppress_Debug_Info:: -* Aspect Suppress_Initialization:: -* Aspect Test_Case:: -* Aspect Thread_Local_Storage:: -* Aspect Universal_Aliasing:: -* Aspect Universal_Data:: -* Aspect Unmodified:: -* Aspect Unreferenced:: -* Aspect Unreferenced_Objects:: -* Aspect Value_Size:: -* Aspect Warnings:: +* Aspect Abstract_State:: +* Annotate:: +* Aspect Async_Readers:: +* Aspect Async_Writers:: +* Aspect Contract_Cases:: +* Aspect Depends:: +* Aspect Dimension:: +* Aspect Dimension_System:: +* Aspect Effective_Reads:: +* Aspect Effective_Writes:: +* Aspect Favor_Top_Level:: +* Aspect Global:: +* Aspect Initial_Condition:: +* Aspect Initializes:: +* Aspect Inline_Always:: +* Aspect Invariant:: +* Aspect Invariant'Class:: +* Aspect Iterable:: +* Aspect Linker_Section:: +* Aspect Lock_Free:: +* Aspect No_Elaboration_Code_All:: +* Aspect No_Tagged_Streams:: +* Aspect Object_Size:: +* Aspect Obsolescent:: +* Aspect Part_Of:: +* Aspect Persistent_BSS:: +* Aspect Predicate:: +* Aspect Pure_Function:: +* Aspect Refined_Depends:: +* Aspect Refined_Global:: +* Aspect Refined_Post:: +* Aspect Refined_State:: +* Aspect Remote_Access_Type:: +* Aspect Scalar_Storage_Order:: +* Aspect Shared:: +* Aspect Simple_Storage_Pool:: +* Aspect Simple_Storage_Pool_Type:: +* Aspect SPARK_Mode:: +* Aspect Suppress_Debug_Info:: +* Aspect Suppress_Initialization:: +* Aspect Test_Case:: +* Aspect Thread_Local_Storage:: +* Aspect Universal_Aliasing:: +* Aspect Universal_Data:: +* Aspect Unmodified:: +* Aspect Unreferenced:: +* Aspect Unreferenced_Objects:: +* Aspect Value_Size:: +* Aspect Warnings:: + @end menu -@node Aspect Abstract_State -@unnumberedsec Aspect Abstract_State -@findex Abstract_State -@noindent -This aspect is equivalent to pragma @code{Abstract_State}. +@node Aspect Abstract_State,Annotate,,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-abstract-state}@anchor{e3} +@section Aspect Abstract_State + + +@geindex Abstract_State + +This aspect is equivalent to pragma @cite{Abstract_State}. + +@node Annotate,Aspect Async_Readers,Aspect Abstract_State,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects annotate}@anchor{e4} +@section Annotate + + +@geindex Annotate -@node Aspect Annotate -@unnumberedsec Annotate -@findex Annotate -@noindent There are three forms of this aspect (where ID is an identifier, and ARG is a general expression). -@table @code -@item Annotate => ID -Equivalent to @code{pragma Annotate (ID, Entity => Name);} -@item Annotate => (ID) -Equivalent to @code{pragma Annotate (ID, Entity => Name);} +@table @asis + +@item @emph{Annotate => ID} + +Equivalent to @cite{pragma Annotate (ID@comma{} Entity => Name);} + +@item @emph{Annotate => (ID)} + +Equivalent to @cite{pragma Annotate (ID@comma{} Entity => Name);} + +@item @emph{Annotate => (ID ,ID @{, ARG@})} -@item Annotate => (ID ,ID @{, ARG@}) -Equivalent to @code{pragma Annotate (ID, ID @{, ARG@}, Entity => Name);} +Equivalent to @cite{pragma Annotate (ID@comma{} ID @{@comma{} ARG@}@comma{} Entity => Name);} @end table -@node Aspect Async_Readers -@unnumberedsec Aspect Async_Readers -@findex Async_Readers -@noindent -This boolean aspect is equivalent to pragma @code{Async_Readers}. - -@node Aspect Async_Writers -@unnumberedsec Aspect Async_Writers -@findex Async_Writers -@noindent -This boolean aspect is equivalent to pragma @code{Async_Writers}. - -@node Aspect Contract_Cases -@unnumberedsec Aspect Contract_Cases -@findex Contract_Cases -@noindent -This aspect is equivalent to pragma @code{Contract_Cases}, the sequence +@node Aspect Async_Readers,Aspect Async_Writers,Annotate,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-async-readers}@anchor{e5} +@section Aspect Async_Readers + + +@geindex Async_Readers + +This boolean aspect is equivalent to pragma @cite{Async_Readers}. + +@node Aspect Async_Writers,Aspect Contract_Cases,Aspect Async_Readers,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-async-writers}@anchor{e6} +@section Aspect Async_Writers + + +@geindex Async_Writers + +This boolean aspect is equivalent to pragma @cite{Async_Writers}. + +@node Aspect Contract_Cases,Aspect Depends,Aspect Async_Writers,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-contract-cases}@anchor{e7} +@section Aspect Contract_Cases + + +@geindex Contract_Cases + +This aspect is equivalent to pragma @cite{Contract_Cases}, the sequence of clauses being enclosed in parentheses so that syntactically it is an aggregate. -@node Aspect Depends -@unnumberedsec Aspect Depends -@findex Depends -@noindent -This aspect is equivalent to pragma @code{Depends}. - -@node Aspect Dimension -@unnumberedsec Aspect Dimension -@findex Dimension -@noindent -The @code{Dimension} aspect is used to specify the dimensions of a given +@node Aspect Depends,Aspect Dimension,Aspect Contract_Cases,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-depends}@anchor{e8} +@section Aspect Depends + + +@geindex Depends + +This aspect is equivalent to pragma @cite{Depends}. + +@node Aspect Dimension,Aspect Dimension_System,Aspect Depends,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-dimension}@anchor{e9} +@section Aspect Dimension + + +@geindex Dimension + +The @cite{Dimension} aspect is used to specify the dimensions of a given subtype of a dimensioned numeric type. The aspect also specifies a symbol used when doing formatted output of dimensioned quantities. The syntax is: -@smallexample @c ada +@example with Dimension => ([Symbol =>] SYMBOL, DIMENSION_VALUE @{, DIMENSION_Value@}) @@ -8259,29 +8520,31 @@ DIMENSION_VALUE ::= | DISCRETE_CHOICE_LIST => RATIONAL RATIONAL ::= [-] NUMERIC_LITERAL [/ NUMERIC_LITERAL] -@end smallexample +@end example -@noindent This aspect can only be applied to a subtype whose parent type has -a @code{Dimension_Systen} aspect. The aspect must specify values for +a @cite{Dimension_Systen} aspect. The aspect must specify values for all dimensions of the system. The rational values are the powers of the corresponding dimensions that are used by the compiler to verify that physical (numeric) computations are dimensionally consistent. For example, the computation of a force must result in dimensions (L => 1, M => 1, T => -2). For further examples of the usage -of this aspect, see package @code{System.Dim.Mks}. +of this aspect, see package @cite{System.Dim.Mks}. Note that when the dimensioned type is an integer type, then any dimension value must be an integer literal. -@node Aspect Dimension_System -@unnumberedsec Aspect Dimension_System -@findex Dimension_System -@noindent -The @code{Dimension_System} aspect is used to define a system of +@node Aspect Dimension_System,Aspect Effective_Reads,Aspect Dimension,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-dimension-system}@anchor{ea} +@section Aspect Dimension_System + + +@geindex Dimension_System + +The @cite{Dimension_System} aspect is used to define a system of dimensions that will be used in subsequent subtype declarations with -@code{Dimension} aspects that reference this system. The syntax is: +@cite{Dimension} aspects that reference this system. The syntax is: -@smallexample @c ada +@example with Dimension_System => (DIMENSION @{, DIMENSION@}); DIMENSION ::= ([Unit_Name =>] IDENTIFIER, @@ -8289,15165 +8552,20063 @@ DIMENSION ::= ([Unit_Name =>] IDENTIFIER, [Dim_Symbol =>] SYMBOL) SYMBOL ::= CHARACTER_LITERAL | STRING_LITERAL -@end smallexample +@end example -@noindent This aspect is applied to a type, which must be a numeric derived type (typically a floating-point type), that -will represent values within the dimension system. Each @code{DIMENSION} +will represent values within the dimension system. Each @cite{DIMENSION} corresponds to one particular dimension. A maximum of 7 dimensions may -be specified. @code{Unit_Name} is the name of the dimension (for example -@code{Meter}). @code{Unit_Symbol} is the shorthand used for quantities -of this dimension (for example @code{m} for @code{Meter}). -@code{Dim_Symbol} gives +be specified. @cite{Unit_Name} is the name of the dimension (for example +@cite{Meter}). @cite{Unit_Symbol} is the shorthand used for quantities +of this dimension (for example @cite{m} for @cite{Meter}). +@cite{Dim_Symbol} gives the identification within the dimension system (typically this is a -single letter, e.g. @code{L} standing for length for unit name @code{Meter}). -The @code{Unit_Symbol} is used in formatted output of dimensioned quantities. -The @code{Dim_Symbol} is used in error messages when numeric operations have +single letter, e.g. @cite{L} standing for length for unit name @cite{Meter}). +The @cite{Unit_Symbol} is used in formatted output of dimensioned quantities. +The @cite{Dim_Symbol} is used in error messages when numeric operations have inconsistent dimensions. GNAT provides the standard definition of the International MKS system in -the run-time package @code{System.Dim.Mks}. You can easily define +the run-time package @cite{System.Dim.Mks}. You can easily define similar packages for cgs units or British units, and define conversion factors between values in different systems. The MKS system is characterized by the following aspect: -@smallexample @c ada - type Mks_Type is new Long_Long_Float with - Dimension_System => ( - (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), - (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), - (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), - (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), - (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@'), - (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), - (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); -@end smallexample - -@noindent -Note that in the above type definition, we use the symbol @code{@@} to +@example +type Mks_Type is new Long_Long_Float with + Dimension_System => ( + (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), + (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), + (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), + (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), + (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => '@@'), + (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), + (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); +@end example + +Note that in the above type definition, we use the @cite{at} symbol (@code{@@}) to represent a theta character (avoiding the use of extended Latin-1 characters in this context). -See section ``Performing Dimensionality Analysis in GNAT'' in the GNAT Users +See section 'Performing Dimensionality Analysis in GNAT' in the GNAT Users Guide for detailed examples of use of the dimension system. -@node Aspect Effective_Reads -@unnumberedsec Aspect Effective_Reads -@findex Effective_Reads -@noindent -This aspect is equivalent to pragma @code{Effective_Reads}. - -@node Aspect Effective_Writes -@unnumberedsec Aspect Effective_Writes -@findex Effective_Writes -@noindent -This aspect is equivalent to pragma @code{Effective_Writes}. - -@node Aspect Favor_Top_Level -@unnumberedsec Aspect Favor_Top_Level -@findex Favor_Top_Level -@noindent -This boolean aspect is equivalent to pragma @code{Favor_Top_Level}. - -@node Aspect Global -@unnumberedsec Aspect Global -@findex Global -@noindent -This aspect is equivalent to pragma @code{Global}. - -@node Aspect Initial_Condition -@unnumberedsec Aspect Initial_Condition -@findex Initial_Condition -@noindent -This aspect is equivalent to pragma @code{Initial_Condition}. - -@node Aspect Initializes -@unnumberedsec Aspect Initializes -@findex Initializes -@noindent -This aspect is equivalent to pragma @code{Initializes}. - -@node Aspect Inline_Always -@unnumberedsec Aspect Inline_Always -@findex Inline_Always -@noindent -This boolean aspect is equivalent to pragma @code{Inline_Always}. - -@node Aspect Invariant -@unnumberedsec Aspect Invariant -@findex Invariant -@noindent -This aspect is equivalent to pragma @code{Invariant}. It is a -synonym for the language defined aspect @code{Type_Invariant} except -that it is separately controllable using pragma @code{Assertion_Policy}. - -@node Aspect Invariant'Class -@unnumberedsec Aspect Invariant'Class -@findex Invariant'Class -@noindent -This aspect is equivalent to pragma @code{Type_Invariant_Class}. It is a -synonym for the language defined aspect @code{Type_Invariant'Class} except -that it is separately controllable using pragma @code{Assertion_Policy}. - -@node Aspect Iterable -@unnumberedsec Aspect Iterable -@findex Iterable -@noindent -This aspect is used in the GNAT-defined formal container packages, to provide -a light-weight mechanism for loops over such containers, without the overhead -imposed by the tampering checks of standard Ada2012 iterators. The value of the -aspect is a aggregate with four named components: First, Next, Has_Element, -and Element. The following is a typical example of use: - -@smallexample @c ada -type List is private with - Iterable => (First => First_Element, - Next => Advance, - Has_Element => Get_Element, - Element => List_Element); -@end smallexample -@itemize @bullet -@item The value denoted by @code{First} must denote a primitive operation of -the container type that returns a Cursor, which must a be a type declared in -the container package. -@item The value of @code{Next} is a primitive operation of the container type -that takes a cursor and yields a cursor. -@item @code{Has_Element} is an operation that applies to a cursor a yields an -element of the container. -@item @code{Element} is the type of the elements of the container type, and -thus the result of the function denoted by Has_Element. -@end itemize - -@node Aspect Linker_Section -@unnumberedsec Aspect Linker_Section -@findex Linker_Section -@noindent -This aspect is equivalent to an @code{Linker_Section} pragma. - -@node Aspect Lock_Free -@unnumberedsec Aspect Lock_Free -@findex Lock_Free -@noindent -This boolean aspect is equivalent to pragma @code{Lock_Free}. - -@node Aspect No_Elaboration_Code_All -@unnumberedsec Aspect No_Elaboration_Code_All -@findex No_Elaboration_Code_All -@noindent -This aspect is equivalent to a @code{pragma No_Elaboration_Code_All} -statement for a program unit. +@node Aspect Effective_Reads,Aspect Effective_Writes,Aspect Dimension_System,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-effective-reads}@anchor{eb} +@section Aspect Effective_Reads -@node Aspect No_Tagged_Streams -@unnumberedsec Aspect No_Tagged_Streams -@findex No_Tagged_Streams -@noindent -This aspect is equivalent to a @code{pragma No_Tagged_Streams} with an -argument specifying a root tagged type (thus this aspect can only be -applied to such a type). -@node Aspect Object_Size -@unnumberedsec Aspect Object_Size -@findex Object_Size -@noindent -This aspect is equivalent to an @code{Object_Size} attribute definition -clause. +@geindex Effective_Reads -@node Aspect Obsolescent -@unnumberedsec Aspect Obsolescent -@findex Obsolsecent -@noindent -This aspect is equivalent to an @code{Obsolescent} pragma. Note that the -evaluation of this aspect happens at the point of occurrence, it is not -delayed until the freeze point. +This aspect is equivalent to pragma @cite{Effective_Reads}. -@node Aspect Part_Of -@unnumberedsec Aspect Part_Of -@findex Part_Of -@noindent -This aspect is equivalent to pragma @code{Part_Of}. - -@node Aspect Persistent_BSS -@unnumberedsec Aspect Persistent_BSS -@findex Persistent_BSS -@noindent -This boolean aspect is equivalent to pragma @code{Persistent_BSS}. - -@node Aspect Predicate -@unnumberedsec Aspect Predicate -@findex Predicate -@noindent -This aspect is equivalent to pragma @code{Predicate}. It is thus -similar to the language defined aspects @code{Dynamic_Predicate} -and @code{Static_Predicate} except that whether the resulting -predicate is static or dynamic is controlled by the form of the -expression. It is also separately controllable using pragma -@code{Assertion_Policy}. - -@node Aspect Pure_Function -@unnumberedsec Aspect Pure_Function -@findex Pure_Function -@noindent -This boolean aspect is equivalent to pragma @code{Pure_Function}. - -@node Aspect Refined_Depends -@unnumberedsec Aspect Refined_Depends -@findex Refined_Depends -@noindent -This aspect is equivalent to pragma @code{Refined_Depends}. - -@node Aspect Refined_Global -@unnumberedsec Aspect Refined_Global -@findex Refined_Global -@noindent -This aspect is equivalent to pragma @code{Refined_Global}. - -@node Aspect Refined_Post -@unnumberedsec Aspect Refined_Post -@findex Refined_Post -@noindent -This aspect is equivalent to pragma @code{Refined_Post}. - -@node Aspect Refined_State -@unnumberedsec Aspect Refined_State -@findex Refined_State -@noindent -This aspect is equivalent to pragma @code{Refined_State}. - -@node Aspect Remote_Access_Type -@unnumberedsec Aspect Remote_Access_Type -@findex Remote_Access_Type -@noindent -This aspect is equivalent to pragma @code{Remote_Access_Type}. - -@node Aspect Scalar_Storage_Order -@unnumberedsec Aspect Scalar_Storage_Order -@findex Scalar_Storage_Order -@noindent -This aspect is equivalent to a @code{Scalar_Storage_Order} -attribute definition clause. +@node Aspect Effective_Writes,Aspect Favor_Top_Level,Aspect Effective_Reads,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-effective-writes}@anchor{ec} +@section Aspect Effective_Writes -@node Aspect Shared -@unnumberedsec Aspect Shared -@findex Shared -@noindent -This booleanaspect is equivalent to pragma @code{Shared}, -and is thus a synonym for aspect @code{Atomic}. - -@node Aspect Simple_Storage_Pool -@unnumberedsec Aspect Simple_Storage_Pool -@findex Simple_Storage_Pool -@noindent -This aspect is equivalent to a @code{Simple_Storage_Pool} -attribute definition clause. -@node Aspect Simple_Storage_Pool_Type -@unnumberedsec Aspect Simple_Storage_Pool_Type -@findex Simple_Storage_Pool_Type -@noindent -This boolean aspect is equivalent to pragma @code{Simple_Storage_Pool_Type}. - -@node Aspect SPARK_Mode -@unnumberedsec Aspect SPARK_Mode -@findex SPARK_Mode -@noindent -This aspect is equivalent to pragma @code{SPARK_Mode} and -may be specified for either or both of the specification and body -of a subprogram or package. +@geindex Effective_Writes -@node Aspect Suppress_Debug_Info -@unnumberedsec Aspect Suppress_Debug_Info -@findex Suppress_Debug_Info -@noindent -This boolean aspect is equivalent to pragma @code{Suppress_Debug_Info}. - -@node Aspect Suppress_Initialization -@unnumberedsec Aspect Suppress_Initialization -@findex Suppress_Initialization -@noindent -This boolean aspect is equivalent to pragma @code{Suppress_Initialization}. - -@node Aspect Test_Case -@unnumberedsec Aspect Test_Case -@findex Test_Case -@noindent -This aspect is equivalent to pragma @code{Test_Case}. - -@node Aspect Thread_Local_Storage -@unnumberedsec Aspect Thread_Local_Storage -@findex Thread_Local_Storage -@noindent -This boolean aspect is equivalent to pragma @code{Thread_Local_Storage}. - -@node Aspect Universal_Aliasing -@unnumberedsec Aspect Universal_Aliasing -@findex Universal_Aliasing -@noindent -This boolean aspect is equivalent to pragma @code{Universal_Aliasing}. - -@node Aspect Universal_Data -@unnumberedsec Aspect Universal_Data -@findex Universal_Data -@noindent -This aspect is equivalent to pragma @code{Universal_Data}. - -@node Aspect Unmodified -@unnumberedsec Aspect Unmodified -@findex Unmodified -@noindent -This boolean aspect is equivalent to pragma @code{Unmodified}. - -@node Aspect Unreferenced -@unnumberedsec Aspect Unreferenced -@findex Unreferenced -@noindent -This boolean aspect is equivalent to pragma @code{Unreferenced}. Note that -in the case of formal parameters, it is not permitted to have aspects for -a formal parameter, so in this case the pragma form must be used. +This aspect is equivalent to pragma @cite{Effective_Writes}. -@node Aspect Unreferenced_Objects -@unnumberedsec Aspect Unreferenced_Objects -@findex Unreferenced_Objects -@noindent -This boolean aspect is equivalent to pragma @code{Unreferenced_Objects}. - -@node Aspect Value_Size -@unnumberedsec Aspect Value_Size -@findex Value_Size -@noindent -This aspect is equivalent to a @code{Value_Size} -attribute definition clause. +@node Aspect Favor_Top_Level,Aspect Global,Aspect Effective_Writes,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-favor-top-level}@anchor{ed} +@section Aspect Favor_Top_Level -@node Aspect Warnings -@unnumberedsec Aspect Warnings -@findex Warnings -@noindent -This aspect is equivalent to the two argument form of pragma @code{Warnings}, -where the first argument is @code{ON} or @code{OFF} and the second argument -is the entity. +@geindex Favor_Top_Level -@node Implementation Defined Attributes -@chapter Implementation Defined Attributes -Ada defines (throughout the Ada reference manual, -summarized in Annex K), -a set of attributes that provide useful additional functionality in all -areas of the language. These language defined attributes are implemented -in GNAT and work as described in the Ada Reference Manual. +This boolean aspect is equivalent to pragma @cite{Favor_Top_Level}. -In addition, Ada allows implementations to define additional -attributes whose meaning is defined by the implementation. GNAT provides -a number of these implementation-dependent attributes which can be used -to extend and enhance the functionality of the compiler. This section of -the GNAT reference manual describes these additional attributes. It also -describes additional implementation-dependent features of standard -language-defined attributes. +@node Aspect Global,Aspect Initial_Condition,Aspect Favor_Top_Level,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-global}@anchor{ee} +@section Aspect Global -Note that any program using these attributes may not be portable to -other compilers (although GNAT implements this set of attributes on all -platforms). Therefore if portability to other compilers is an important -consideration, you should minimize the use of these attributes. -@menu -* Attribute Abort_Signal:: -* Attribute Address_Size:: -* Attribute Asm_Input:: -* Attribute Asm_Output:: -* Attribute AST_Entry:: -* Attribute Atomic_Always_Lock_Free:: -* Attribute Bit:: -* Attribute Bit_Position:: -* Attribute Code_Address:: -* Attribute Compiler_Version:: -* Attribute Constrained:: -* Attribute Default_Bit_Order:: -* Attribute Default_Scalar_Storage_Order:: -* Attribute Descriptor_Size:: -* Attribute Elaborated:: -* Attribute Elab_Body:: -* Attribute Elab_Spec:: -* Attribute Elab_Subp_Body:: -* Attribute Emax:: -* Attribute Enabled:: -* Attribute Enum_Rep:: -* Attribute Enum_Val:: -* Attribute Epsilon:: -* Attribute Fast_Math:: -* Attribute Fixed_Value:: -* Attribute From_Any:: -* Attribute Has_Access_Values:: -* Attribute Has_Discriminants:: -* Attribute Img:: -* Attribute Integer_Value:: -* Attribute Invalid_Value:: -* Attribute Iterable:: -* Attribute Large:: -* Attribute Library_Level:: -* Attribute Lock_Free:: -* Attribute Loop_Entry:: -* Attribute Machine_Size:: -* Attribute Mantissa:: -* Attribute Maximum_Alignment:: -* Attribute Mechanism_Code:: -* Attribute Null_Parameter:: -* Attribute Object_Size:: -* Attribute Old:: -* Attribute Passed_By_Reference:: -* Attribute Pool_Address:: -* Attribute Range_Length:: -* Attribute Ref:: -* Attribute Restriction_Set:: -* Attribute Result:: -* Attribute Safe_Emax:: -* Attribute Safe_Large:: -* Attribute Safe_Small:: -* Attribute Scalar_Storage_Order:: -* Attribute Simple_Storage_Pool:: -* Attribute Small:: -* Attribute Storage_Unit:: -* Attribute Stub_Type:: -* Attribute System_Allocator_Alignment:: -* Attribute Target_Name:: -* Attribute To_Address:: -* Attribute To_Any:: -* Attribute Type_Class:: -* Attribute Type_Key:: -* Attribute TypeCode:: -* Attribute UET_Address:: -* Attribute Unconstrained_Array:: -* Attribute Universal_Literal_String:: -* Attribute Unrestricted_Access:: -* Attribute Update:: -* Attribute VADS_Size:: -* Attribute Valid_Scalars:: -* Attribute Value_Size:: -* Attribute Wchar_T_Size:: -* Attribute Word_Size:: -@end menu +@geindex Global -@node Attribute Abort_Signal -@unnumberedsec Attribute Abort_Signal -@findex Abort_Signal -@noindent -@code{Standard'Abort_Signal} (@code{Standard} is the only allowed -prefix) provides the entity for the special exception used to signal -task abort or asynchronous transfer of control. Normally this attribute -should only be used in the tasking runtime (it is highly peculiar, and -completely outside the normal semantics of Ada, for a user program to -intercept the abort exception). +This aspect is equivalent to pragma @cite{Global}. -@node Attribute Address_Size -@unnumberedsec Attribute Address_Size -@cindex Size of @code{Address} -@findex Address_Size -@noindent -@code{Standard'Address_Size} (@code{Standard} is the only allowed -prefix) is a static constant giving the number of bits in an -@code{Address}. It is the same value as System.Address'Size, -but has the advantage of being static, while a direct -reference to System.Address'Size is non-static because Address -is a private type. +@node Aspect Initial_Condition,Aspect Initializes,Aspect Global,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-initial-condition}@anchor{ef} +@section Aspect Initial_Condition -@node Attribute Asm_Input -@unnumberedsec Attribute Asm_Input -@findex Asm_Input -@noindent -The @code{Asm_Input} attribute denotes a function that takes two -parameters. The first is a string, the second is an expression of the -type designated by the prefix. The first (string) argument is required -to be a static expression, and is the constraint for the parameter, -(e.g.@: what kind of register is required). The second argument is the -value to be used as the input argument. The possible values for the -constant are the same as those used in the RTL, and are dependent on -the configuration file used to built the GCC back end. -@ref{Machine Code Insertions} -@node Attribute Asm_Output -@unnumberedsec Attribute Asm_Output -@findex Asm_Output -@noindent -The @code{Asm_Output} attribute denotes a function that takes two -parameters. The first is a string, the second is the name of a variable -of the type designated by the attribute prefix. The first (string) -argument is required to be a static expression and designates the -constraint for the parameter (e.g.@: what kind of register is -required). The second argument is the variable to be updated with the -result. The possible values for constraint are the same as those used in -the RTL, and are dependent on the configuration file used to build the -GCC back end. If there are no output operands, then this argument may -either be omitted, or explicitly given as @code{No_Output_Operands}. -@ref{Machine Code Insertions} - -@node Attribute AST_Entry -@unnumberedsec Attribute AST_Entry -@cindex OpenVMS -@findex AST_Entry -@noindent -This attribute is implemented only in OpenVMS versions of GNAT@. Applied to -the name of an entry, it yields a value of the predefined type AST_Handler -(declared in the predefined package System, as extended by the use of -pragma @code{Extend_System (Aux_DEC)}). This value enables the given entry to -be called when an AST occurs. For further details, refer to the @cite{DEC Ada -Language Reference Manual}, section 9.12a. - -@node Attribute Atomic_Always_Lock_Free -@unnumberedsec Attribute Atomic_Always_Lock_Free -@findex Atomic_Always_Lock_Free -@noindent - -The prefix of the @code{Atomic_Always_Lock_Free} attribute is a type. -The result is a Boolean value which is True if the type has discriminants, -and False otherwise. The result indicate whether atomic operations are -supported by the target for the given type. +@geindex Initial_Condition -@node Attribute Bit -@unnumberedsec Attribute Bit -@findex Bit -@code{@var{obj}'Bit}, where @var{obj} is any object, yields the bit -offset within the storage unit (byte) that contains the first bit of -storage allocated for the object. The value of this attribute is of the -type @code{Universal_Integer}, and is always a non-negative number not -exceeding the value of @code{System.Storage_Unit}. +This aspect is equivalent to pragma @cite{Initial_Condition}. -For an object that is a variable or a constant allocated in a register, -the value is zero. (The use of this attribute does not force the -allocation of a variable to memory). +@node Aspect Initializes,Aspect Inline_Always,Aspect Initial_Condition,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-initializes}@anchor{f0} +@section Aspect Initializes -For an object that is a formal parameter, this attribute applies -to either the matching actual parameter or to a copy of the -matching actual parameter. -For an access object the value is zero. Note that -@code{@var{obj}.all'Bit} is subject to an @code{Access_Check} for the -designated object. Similarly for a record component -@code{@var{X}.@var{C}'Bit} is subject to a discriminant check and -@code{@var{X}(@var{I}).Bit} and @code{@var{X}(@var{I1}..@var{I2})'Bit} -are subject to index checks. +@geindex Initializes -This attribute is designed to be compatible with the DEC Ada 83 definition -and implementation of the @code{Bit} attribute. +This aspect is equivalent to pragma @cite{Initializes}. -@node Attribute Bit_Position -@unnumberedsec Attribute Bit_Position -@findex Bit_Position -@noindent -@code{@var{R.C}'Bit_Position}, where @var{R} is a record object and C is one -of the fields of the record type, yields the bit -offset within the record contains the first bit of -storage allocated for the object. The value of this attribute is of the -type @code{Universal_Integer}. The value depends only on the field -@var{C} and is independent of the alignment of -the containing record @var{R}. - -@node Attribute Code_Address -@unnumberedsec Attribute Code_Address -@findex Code_Address -@cindex Subprogram address -@cindex Address of subprogram code -@noindent -The @code{'Address} -attribute may be applied to subprograms in Ada 95 and Ada 2005, but the -intended effect seems to be to provide -an address value which can be used to call the subprogram by means of -an address clause as in the following example: +@node Aspect Inline_Always,Aspect Invariant,Aspect Initializes,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-inline-always}@anchor{f1} +@section Aspect Inline_Always -@smallexample @c ada -procedure K is @dots{} -procedure L; -for L'Address use K'Address; -pragma Import (Ada, L); -@end smallexample +@geindex Inline_Always -@noindent -A call to @code{L} is then expected to result in a call to @code{K}@. -In Ada 83, where there were no access-to-subprogram values, this was -a common work-around for getting the effect of an indirect call. -GNAT implements the above use of @code{Address} and the technique -illustrated by the example code works correctly. +This boolean aspect is equivalent to pragma @cite{Inline_Always}. -However, for some purposes, it is useful to have the address of the start -of the generated code for the subprogram. On some architectures, this is -not necessarily the same as the @code{Address} value described above. -For example, the @code{Address} value may reference a subprogram -descriptor rather than the subprogram itself. +@node Aspect Invariant,Aspect Invariant'Class,Aspect Inline_Always,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-invariant}@anchor{f2} +@section Aspect Invariant -The @code{'Code_Address} attribute, which can only be applied to -subprogram entities, always returns the address of the start of the -generated code of the specified subprogram, which may or may not be -the same value as is returned by the corresponding @code{'Address} -attribute. -@node Attribute Compiler_Version -@unnumberedsec Attribute Compiler_Version -@findex Compiler_Version -@noindent -@code{Standard'Compiler_Version} (@code{Standard} is the only allowed -prefix) yields a static string identifying the version of the compiler -being used to compile the unit containing the attribute reference. A -typical result would be something like -"@value{EDITION} @value{gnat_version} (20090221)". - -@node Attribute Constrained -@unnumberedsec Attribute Constrained -@findex Constrained -@noindent -In addition to the usage of this attribute in the Ada RM, @code{GNAT} -also permits the use of the @code{'Constrained} attribute -in a generic template -for any type, including types without discriminants. The value of this -attribute in the generic instance when applied to a scalar type or a -record type without discriminants is always @code{True}. This usage is -compatible with older Ada compilers, including notably DEC Ada. +@geindex Invariant -@node Attribute Default_Bit_Order -@unnumberedsec Attribute Default_Bit_Order -@cindex Big endian -@cindex Little endian -@findex Default_Bit_Order -@noindent -@code{Standard'Default_Bit_Order} (@code{Standard} is the only -permissible prefix), provides the value @code{System.Default_Bit_Order} -as a @code{Pos} value (0 for @code{High_Order_First}, 1 for -@code{Low_Order_First}). This is used to construct the definition of -@code{Default_Bit_Order} in package @code{System}. - -@node Attribute Default_Scalar_Storage_Order -@unnumberedsec Attribute Default_Scalar_Storage_Order -@cindex Big endian -@cindex Little endian -@findex Default_Scalar_Storage_Order -@noindent -@code{Standard'Default_Scalar_Storage_Order} (@code{Standard} is the only -permissible prefix), provides the current value of the default scalar storage -order (as specified using pragma @code{Default_Scalar_Storage_Order}, or -equal to @code{Default_Bit_Order} if unspecified) as a -@code{System.Bit_Order} value. This is a static attribute. - -@node Attribute Descriptor_Size -@unnumberedsec Attribute Descriptor_Size -@cindex Descriptor -@cindex Dope vector -@findex Descriptor_Size -@noindent -Non-static attribute @code{Descriptor_Size} returns the size in bits of the -descriptor allocated for a type. The result is non-zero only for unconstrained -array types and the returned value is of type universal integer. In GNAT, an -array descriptor contains bounds information and is located immediately before -the first element of the array. +This aspect is equivalent to pragma @cite{Invariant}. It is a +synonym for the language defined aspect @cite{Type_Invariant} except +that it is separately controllable using pragma @cite{Assertion_Policy}. -@smallexample @c ada -type Unconstr_Array is array (Positive range <>) of Boolean; -Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img); -@end smallexample +@node Aspect Invariant'Class,Aspect Iterable,Aspect Invariant,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-invariant-class}@anchor{f3} +@section Aspect Invariant'Class -@noindent -The attribute takes into account any additional padding due to type alignment. -In the example above, the descriptor contains two values of type -@code{Positive} representing the low and high bound. Since @code{Positive} has -a size of 31 bits and an alignment of 4, the descriptor size is @code{2 * -Positive'Size + 2} or 64 bits. - -@node Attribute Elaborated -@unnumberedsec Attribute Elaborated -@findex Elaborated -@noindent -The prefix of the @code{'Elaborated} attribute must be a unit name. The -value is a Boolean which indicates whether or not the given unit has been -elaborated. This attribute is primarily intended for internal use by the -generated code for dynamic elaboration checking, but it can also be used -in user programs. The value will always be True once elaboration of all -units has been completed. An exception is for units which need no -elaboration, the value is always False for such units. -@node Attribute Elab_Body -@unnumberedsec Attribute Elab_Body -@findex Elab_Body -@noindent -This attribute can only be applied to a program unit name. It returns -the entity for the corresponding elaboration procedure for elaborating -the body of the referenced unit. This is used in the main generated -elaboration procedure by the binder and is not normally used in any -other context. However, there may be specialized situations in which it -is useful to be able to call this elaboration procedure from Ada code, -e.g.@: if it is necessary to do selective re-elaboration to fix some -error. +@geindex Invariant'Class -@node Attribute Elab_Spec -@unnumberedsec Attribute Elab_Spec -@findex Elab_Spec -@noindent -This attribute can only be applied to a program unit name. It returns -the entity for the corresponding elaboration procedure for elaborating -the spec of the referenced unit. This is used in the main -generated elaboration procedure by the binder and is not normally used -in any other context. However, there may be specialized situations in -which it is useful to be able to call this elaboration procedure from -Ada code, e.g.@: if it is necessary to do selective re-elaboration to fix -some error. +This aspect is equivalent to pragma @cite{Type_Invariant_Class}. It is a +synonym for the language defined aspect @cite{Type_Invariant'Class} except +that it is separately controllable using pragma @cite{Assertion_Policy}. -@node Attribute Elab_Subp_Body -@unnumberedsec Attribute Elab_Subp_Body -@findex Elab_Subp_Body -@noindent -This attribute can only be applied to a library level subprogram -name and is only allowed in CodePeer mode. It returns the entity -for the corresponding elaboration procedure for elaborating the body -of the referenced subprogram unit. This is used in the main generated -elaboration procedure by the binder in CodePeer mode only and is unrecognized -otherwise. +@node Aspect Iterable,Aspect Linker_Section,Aspect Invariant'Class,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-iterable}@anchor{f4} +@section Aspect Iterable -@node Attribute Emax -@unnumberedsec Attribute Emax -@cindex Ada 83 attributes -@findex Emax -@noindent -The @code{Emax} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. -@node Attribute Enabled -@unnumberedsec Attribute Enabled -@findex Enabled -@noindent -The @code{Enabled} attribute allows an application program to check at compile -time to see if the designated check is currently enabled. The prefix is a -simple identifier, referencing any predefined check name (other than -@code{All_Checks}) or a check name introduced by pragma Check_Name. If -no argument is given for the attribute, the check is for the general state -of the check, if an argument is given, then it is an entity name, and the -check indicates whether an @code{Suppress} or @code{Unsuppress} has been -given naming the entity (if not, then the argument is ignored). +@geindex Iterable -Note that instantiations inherit the check status at the point of the -instantiation, so a useful idiom is to have a library package that -introduces a check name with @code{pragma Check_Name}, and then contains -generic packages or subprograms which use the @code{Enabled} attribute -to see if the check is enabled. A user of this package can then issue -a @code{pragma Suppress} or @code{pragma Unsuppress} before instantiating -the package or subprogram, controlling whether the check will be present. +This aspect provides a light-weight mechanism for loops and quantified +expressions over container types, without the overhead imposed by the tampering +checks of standard Ada 2012 iterators. The value of the aspect is an aggregate +with four named components: @cite{First}, @cite{Next}, @cite{Has_Element}, and @cite{Element} (the +last one being optional). When only 3 components are specified, only the +@cite{for .. in} form of iteration over cursors is available. When all 4 components +are specified, both this form and the @cite{for .. of} form of iteration over +elements are available. The following is a typical example of use: -@node Attribute Enum_Rep -@unnumberedsec Attribute Enum_Rep -@cindex Representation of enums -@findex Enum_Rep -@noindent -For every enumeration subtype @var{S}, @code{@var{S}'Enum_Rep} denotes a -function with the following spec: +@example +type List is private with + Iterable => (First => First_Cursor, + Next => Advance, + Has_Element => Cursor_Has_Element, + [Element => Get_Element]); +@end example -@smallexample @c ada -function @var{S}'Enum_Rep (Arg : @var{S}'Base) - return @i{Universal_Integer}; -@end smallexample -@noindent -It is also allowable to apply @code{Enum_Rep} directly to an object of an -enumeration type or to a non-overloaded enumeration -literal. In this case @code{@var{S}'Enum_Rep} is equivalent to -@code{@var{typ}'Enum_Rep(@var{S})} where @var{typ} is the type of the -enumeration literal or object. +@itemize * -The function returns the representation value for the given enumeration -value. This will be equal to value of the @code{Pos} attribute in the -absence of an enumeration representation clause. This is a static -attribute (i.e.@: the result is static if the argument is static). +@item +The value denoted by @cite{First} must denote a primitive operation of the +container type that returns a @cite{Cursor}, which must a be a type declared in +the container package or visible from it. For example: +@end itemize -@code{@var{S}'Enum_Rep} can also be used with integer types and objects, -in which case it simply returns the integer value. The reason for this -is to allow it to be used for @code{(<>)} discrete formal arguments in -a generic unit that can be instantiated with either enumeration types -or integer types. Note that if @code{Enum_Rep} is used on a modular -type whose upper bound exceeds the upper bound of the largest signed -integer type, and the argument is a variable, so that the universal -integer calculation is done at run time, then the call to @code{Enum_Rep} -may raise @code{Constraint_Error}. - -@node Attribute Enum_Val -@unnumberedsec Attribute Enum_Val -@cindex Representation of enums -@findex Enum_Val -@noindent -For every enumeration subtype @var{S}, @code{@var{S}'Enum_Val} denotes a -function with the following spec: +@example +function First_Cursor (Cont : Container) return Cursor; +@end example -@smallexample @c ada -function @var{S}'Enum_Val (Arg : @i{Universal_Integer) - return @var{S}'Base}; -@end smallexample -@noindent -The function returns the enumeration value whose representation matches the -argument, or raises Constraint_Error if no enumeration literal of the type -has the matching value. -This will be equal to value of the @code{Val} attribute in the -absence of an enumeration representation clause. This is a static -attribute (i.e.@: the result is static if the argument is static). - -@node Attribute Epsilon -@unnumberedsec Attribute Epsilon -@cindex Ada 83 attributes -@findex Epsilon -@noindent -The @code{Epsilon} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. +@itemize * -@node Attribute Fast_Math -@unnumberedsec Attribute Fast_Math -@findex Fast_Math -@noindent -@code{Standard'Fast_Math} (@code{Standard} is the only allowed -prefix) yields a static Boolean value that is True if pragma -@code{Fast_Math} is active, and False otherwise. +@item +The value of @cite{Next} is a primitive operation of the container type that takes +both a container and a cursor and yields a cursor. For example: +@end itemize -@node Attribute Fixed_Value -@unnumberedsec Attribute Fixed_Value -@findex Fixed_Value -@noindent -For every fixed-point type @var{S}, @code{@var{S}'Fixed_Value} denotes a -function with the following specification: +@example +function Advance (Cont : Container; Position : Cursor) return Cursor; +@end example -@smallexample @c ada -function @var{S}'Fixed_Value (Arg : @i{Universal_Integer}) - return @var{S}; -@end smallexample -@noindent -The value returned is the fixed-point value @var{V} such that +@itemize * -@smallexample @c ada -@var{V} = Arg * @var{S}'Small -@end smallexample +@item +The value of @cite{Has_Element} is a primitive operation of the container type +that takes both a container and a cursor and yields a boolean. For example: +@end itemize -@noindent -The effect is thus similar to first converting the argument to the -integer type used to represent @var{S}, and then doing an unchecked -conversion to the fixed-point type. The difference is -that there are full range checks, to ensure that the result is in range. -This attribute is primarily intended for use in implementation of the -input-output functions for fixed-point values. +@example +function Cursor_Has_Element (Cont : Container; Position : Cursor) return Boolean; +@end example -@node Attribute From_Any -@unnumberedsec Attribute From_Any -@findex From_Any -@noindent -This internal attribute is used for the generation of remote subprogram -stubs in the context of the Distributed Systems Annex. -@node Attribute Has_Access_Values -@unnumberedsec Attribute Has_Access_Values -@cindex Access values, testing for -@findex Has_Access_Values -@noindent -The prefix of the @code{Has_Access_Values} attribute is a type. The result -is a Boolean value which is True if the is an access type, or is a composite -type with a component (at any nesting depth) that is an access type, and is -False otherwise. -The intended use of this attribute is in conjunction with generic -definitions. If the attribute is applied to a generic private type, it -indicates whether or not the corresponding actual type has access values. +@itemize * -@node Attribute Has_Discriminants -@unnumberedsec Attribute Has_Discriminants -@cindex Discriminants, testing for -@findex Has_Discriminants -@noindent -The prefix of the @code{Has_Discriminants} attribute is a type. The result -is a Boolean value which is True if the type has discriminants, and False -otherwise. The intended use of this attribute is in conjunction with generic -definitions. If the attribute is applied to a generic private type, it -indicates whether or not the corresponding actual type has discriminants. +@item +The value of @cite{Element} is a primitive operation of the container type that +takes both a container and a cursor and yields an @cite{Element_Type}, which must +be a type declared in the container package or visible from it. For example: +@end itemize -@node Attribute Img -@unnumberedsec Attribute Img -@findex Img -@noindent -The @code{Img} attribute differs from @code{Image} in that it is applied -directly to an object, and yields the same result as -@code{Image} for the subtype of the object. This is convenient for -debugging: +@example +function Get_Element (Cont : Container; Position : Cursor) return Element_Type; +@end example -@smallexample @c ada -Put_Line ("X = " & X'Img); -@end smallexample +This aspect is used in the GNAT-defined formal container packages. -@noindent -has the same meaning as the more verbose: +@node Aspect Linker_Section,Aspect Lock_Free,Aspect Iterable,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-linker-section}@anchor{f5} +@section Aspect Linker_Section -@smallexample @c ada -Put_Line ("X = " & @var{T}'Image (X)); -@end smallexample -@noindent -where @var{T} is the (sub)type of the object @code{X}. +@geindex Linker_Section -Note that technically, in analogy to @code{Image}, -@code{X'Img} returns a parameterless function -that returns the appropriate string when called. This means that -@code{X'Img} can be renamed as a function-returning-string, or used -in an instantiation as a function parameter. +This aspect is equivalent to an @cite{Linker_Section} pragma. -@node Attribute Integer_Value -@unnumberedsec Attribute Integer_Value -@findex Integer_Value -@noindent -For every integer type @var{S}, @code{@var{S}'Integer_Value} denotes a -function with the following spec: +@node Aspect Lock_Free,Aspect No_Elaboration_Code_All,Aspect Linker_Section,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-lock-free}@anchor{f6} +@section Aspect Lock_Free -@smallexample @c ada -function @var{S}'Integer_Value (Arg : @i{Universal_Fixed}) - return @var{S}; -@end smallexample -@noindent -The value returned is the integer value @var{V}, such that +@geindex Lock_Free -@smallexample @c ada -Arg = @var{V} * @var{T}'Small -@end smallexample +This boolean aspect is equivalent to pragma @cite{Lock_Free}. -@noindent -where @var{T} is the type of @code{Arg}. -The effect is thus similar to first doing an unchecked conversion from -the fixed-point type to its corresponding implementation type, and then -converting the result to the target integer type. The difference is -that there are full range checks, to ensure that the result is in range. -This attribute is primarily intended for use in implementation of the -standard input-output functions for fixed-point values. +@node Aspect No_Elaboration_Code_All,Aspect No_Tagged_Streams,Aspect Lock_Free,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-no-elaboration-code-all}@anchor{f7} +@section Aspect No_Elaboration_Code_All -@node Attribute Invalid_Value -@unnumberedsec Attribute Invalid_Value -@findex Invalid_Value -@noindent -For every scalar type S, S'Invalid_Value returns an undefined value of the -type. If possible this value is an invalid representation for the type. The -value returned is identical to the value used to initialize an otherwise -uninitialized value of the type if pragma Initialize_Scalars is used, -including the ability to modify the value with the binder -Sxx flag and -relevant environment variables at run time. -@node Attribute Iterable -@unnumberedsec Attribute Iterable -@findex Iterable -@noindent -Equivalent to Aspect Iterable. +@geindex No_Elaboration_Code_All -@node Attribute Large -@unnumberedsec Attribute Large -@cindex Ada 83 attributes -@findex Large -@noindent -The @code{Large} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. +This aspect is equivalent to a @cite{pragma No_Elaboration_Code_All} +statement for a program unit. -@node Attribute Library_Level -@unnumberedsec Attribute Library_Level -@findex Library_Level -@noindent -@noindent -@code{P'Library_Level}, where P is an entity name, -returns a Boolean value which is True if the entity is declared -at the library level, and False otherwise. Note that within a -generic instantition, the name of the generic unit denotes the -instance, which means that this attribute can be used to test -if a generic is instantiated at the library level, as shown -in this example: +@node Aspect No_Tagged_Streams,Aspect Object_Size,Aspect No_Elaboration_Code_All,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-no-tagged-streams}@anchor{f8} +@section Aspect No_Tagged_Streams -@smallexample @c ada -generic - ... -package Gen is - pragma Compile_Time_Error - (not Gen'Library_Level, - "Gen can only be instantiated at library level"); - ... -end Gen; -@end smallexample - -@node Attribute Lock_Free -@unnumberedsec Attribute Lock_Free -@findex Lock_Free -@noindent -@code{P'Lock_Free}, where P is a protected object, returns True if a -pragma @code{Lock_Free} applies to P. - -@node Attribute Loop_Entry -@unnumberedsec Attribute Loop_Entry -@findex Loop_Entry -@noindent -Syntax: -@smallexample @c ada -X'Loop_Entry [(loop_name)] -@end smallexample +@geindex No_Tagged_Streams -@noindent -The @code{Loop_Entry} attribute is used to refer to the value that an -expression had upon entry to a given loop in much the same way that the -@code{Old} attribute in a subprogram postcondition can be used to refer -to the value an expression had upon entry to the subprogram. The -relevant loop is either identified by the given loop name, or it is the -innermost enclosing loop when no loop name is given. +This aspect is equivalent to a @cite{pragma No_Tagged_Streams} with an +argument specifying a root tagged type (thus this aspect can only be +applied to such a type). -@noindent -A @code{Loop_Entry} attribute can only occur within a -@code{Loop_Variant} or @code{Loop_Invariant} pragma. A common use of -@code{Loop_Entry} is to compare the current value of objects with their -initial value at loop entry, in a @code{Loop_Invariant} pragma. +@node Aspect Object_Size,Aspect Obsolescent,Aspect No_Tagged_Streams,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-object-size}@anchor{f9} +@section Aspect Object_Size -@noindent -The effect of using @code{X'Loop_Entry} is the same as declaring -a constant initialized with the initial value of @code{X} at loop -entry. This copy is not performed if the loop is not entered, or if the -corresponding pragmas are ignored or disabled. -@node Attribute Machine_Size -@unnumberedsec Attribute Machine_Size -@findex Machine_Size -@noindent -This attribute is identical to the @code{Object_Size} attribute. It is -provided for compatibility with the DEC Ada 83 attribute of this name. +@geindex Object_Size -@node Attribute Mantissa -@unnumberedsec Attribute Mantissa -@cindex Ada 83 attributes -@findex Mantissa -@noindent -The @code{Mantissa} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. +This aspect is equivalent to an @cite{Object_Size} attribute definition +clause. -@node Attribute Maximum_Alignment -@unnumberedsec Attribute Maximum_Alignment -@cindex Alignment, maximum -@findex Maximum_Alignment -@noindent -@code{Standard'Maximum_Alignment} (@code{Standard} is the only -permissible prefix) provides the maximum useful alignment value for the -target. This is a static value that can be used to specify the alignment -for an object, guaranteeing that it is properly aligned in all -cases. +@node Aspect Obsolescent,Aspect Part_Of,Aspect Object_Size,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-obsolescent}@anchor{fa} +@section Aspect Obsolescent -@node Attribute Mechanism_Code -@unnumberedsec Attribute Mechanism_Code -@cindex Return values, passing mechanism -@cindex Parameters, passing mechanism -@findex Mechanism_Code -@noindent -@code{@var{function}'Mechanism_Code} yields an integer code for the -mechanism used for the result of function, and -@code{@var{subprogram}'Mechanism_Code (@var{n})} yields the mechanism -used for formal parameter number @var{n} (a static integer value with 1 -meaning the first parameter) of @var{subprogram}. The code returned is: -@table @asis -@item 1 -by copy (value) -@item 2 -by reference -@end table +@geindex Obsolsecent -@node Attribute Null_Parameter -@unnumberedsec Attribute Null_Parameter -@cindex Zero address, passing -@findex Null_Parameter -@noindent -A reference @code{@var{T}'Null_Parameter} denotes an imaginary object of -type or subtype @var{T} allocated at machine address zero. The attribute -is allowed only as the default expression of a formal parameter, or as -an actual expression of a subprogram call. In either case, the -subprogram must be imported. +This aspect is equivalent to an @cite{Obsolescent} pragma. Note that the +evaluation of this aspect happens at the point of occurrence, it is not +delayed until the freeze point. -The identity of the object is represented by the address zero in the -argument list, independent of the passing mechanism (explicit or -default). +@node Aspect Part_Of,Aspect Persistent_BSS,Aspect Obsolescent,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-part-of}@anchor{fb} +@section Aspect Part_Of -This capability is needed to specify that a zero address should be -passed for a record or other composite object passed by reference. -There is no way of indicating this without the @code{Null_Parameter} -attribute. -@node Attribute Object_Size -@unnumberedsec Attribute Object_Size -@cindex Size, used for objects -@findex Object_Size -@noindent -The size of an object is not necessarily the same as the size of the type -of an object. This is because by default object sizes are increased to be -a multiple of the alignment of the object. For example, -@code{Natural'Size} is -31, but by default objects of type @code{Natural} will have a size of 32 bits. -Similarly, a record containing an integer and a character: +@geindex Part_Of -@smallexample @c ada -type Rec is record - I : Integer; - C : Character; -end record; -@end smallexample +This aspect is equivalent to pragma @cite{Part_Of}. -@noindent -will have a size of 40 (that is @code{Rec'Size} will be 40). The -alignment will be 4, because of the -integer field, and so the default size of record objects for this type -will be 64 (8 bytes). +@node Aspect Persistent_BSS,Aspect Predicate,Aspect Part_Of,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-persistent-bss}@anchor{fc} +@section Aspect Persistent_BSS -If the alignment of the above record is specified to be 1, then the -object size will be 40 (5 bytes). This is true by default, and also -an object size of 40 can be explicitly specified in this case. -A consequence of this capability is that different object sizes can be -given to subtypes that would otherwise be considered in Ada to be -statically matching. But it makes no sense to consider such subtypes -as statically matching. Consequently, in @code{GNAT} we add a rule -to the static matching rules that requires object sizes to match. -Consider this example: +@geindex Persistent_BSS -@smallexample @c ada - 1. procedure BadAVConvert is - 2. type R is new Integer; - 3. subtype R1 is R range 1 .. 10; - 4. subtype R2 is R range 1 .. 10; - 5. for R1'Object_Size use 8; - 6. for R2'Object_Size use 16; - 7. type R1P is access all R1; - 8. type R2P is access all R2; - 9. R1PV : R1P := new R1'(4); -10. R2PV : R2P; -11. begin -12. R2PV := R2P (R1PV); - | - >>> target designated subtype not compatible with - type "R1" defined at line 3 +This boolean aspect is equivalent to pragma @cite{Persistent_BSS}. -13. end; -@end smallexample +@node Aspect Predicate,Aspect Pure_Function,Aspect Persistent_BSS,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-predicate}@anchor{fd} +@section Aspect Predicate -@noindent -In the absence of lines 5 and 6, -types @code{R1} and @code{R2} statically match and -hence the conversion on line 12 is legal. But since lines 5 and 6 -cause the object sizes to differ, @code{GNAT} considers that types -@code{R1} and @code{R2} are not statically matching, and line 12 -generates the diagnostic shown above. -@noindent -Similar additional checks are performed in other contexts requiring -statically matching subtypes. +@geindex Predicate -@node Attribute Old -@unnumberedsec Attribute Old -@findex Old -@noindent -In addition to the usage of @code{Old} defined in the Ada 2012 RM (usage -within @code{Post} aspect), GNAT also permits the use of this attribute -in implementation defined pragmas @code{Postcondition}, -@code{Contract_Cases} and @code{Test_Case}. Also usages of -@code{Old} which would be illegal according to the Ada 2012 RM -definition are allowed under control of -implementation defined pragma @code{Unevaluated_Use_Of_Old}. - -@node Attribute Passed_By_Reference -@unnumberedsec Attribute Passed_By_Reference -@cindex Parameters, when passed by reference -@findex Passed_By_Reference -@noindent -@code{@var{type}'Passed_By_Reference} for any subtype @var{type} returns -a value of type @code{Boolean} value that is @code{True} if the type is -normally passed by reference and @code{False} if the type is normally -passed by copy in calls. For scalar types, the result is always @code{False} -and is static. For non-scalar types, the result is non-static. +This aspect is equivalent to pragma @cite{Predicate}. It is thus +similar to the language defined aspects @cite{Dynamic_Predicate} +and @cite{Static_Predicate} except that whether the resulting +predicate is static or dynamic is controlled by the form of the +expression. It is also separately controllable using pragma +@cite{Assertion_Policy}. -@node Attribute Pool_Address -@unnumberedsec Attribute Pool_Address -@cindex Parameters, when passed by reference -@findex Pool_Address -@noindent -@code{@var{X}'Pool_Address} for any object @var{X} returns the address -of X within its storage pool. This is the same as -@code{@var{X}'Address}, except that for an unconstrained array whose -bounds are allocated just before the first component, -@code{@var{X}'Pool_Address} returns the address of those bounds, -whereas @code{@var{X}'Address} returns the address of the first -component. +@node Aspect Pure_Function,Aspect Refined_Depends,Aspect Predicate,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-pure-function}@anchor{fe} +@section Aspect Pure_Function -Here, we are interpreting ``storage pool'' broadly to mean ``wherever -the object is allocated'', which could be a user-defined storage pool, -the global heap, on the stack, or in a static memory area. For an -object created by @code{new}, @code{@var{Ptr.all}'Pool_Address} is -what is passed to @code{Allocate} and returned from @code{Deallocate}. - -@node Attribute Range_Length -@unnumberedsec Attribute Range_Length -@findex Range_Length -@noindent -@code{@var{type}'Range_Length} for any discrete type @var{type} yields -the number of values represented by the subtype (zero for a null -range). The result is static for static subtypes. @code{Range_Length} -applied to the index subtype of a one dimensional array always gives the -same result as @code{Length} applied to the array itself. -@node Attribute Ref -@unnumberedsec Attribute Ref -@findex Ref -@noindent +@geindex Pure_Function +This boolean aspect is equivalent to pragma @cite{Pure_Function}. -@node Attribute Restriction_Set -@unnumberedsec Attribute Restriction_Set -@findex Restriction_Set -@cindex Restrictions -@noindent -This attribute allows compile time testing of restrictions that -are currently in effect. It is primarily intended for specializing -code in the run-time based on restrictions that are active (e.g. -don't need to save fpt registers if restriction No_Floating_Point -is known to be in effect), but can be used anywhere. +@node Aspect Refined_Depends,Aspect Refined_Global,Aspect Pure_Function,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-refined-depends}@anchor{ff} +@section Aspect Refined_Depends -There are two forms: -@smallexample @c ada -System'Restriction_Set (partition_boolean_restriction_NAME) -System'Restriction_Set (No_Dependence => library_unit_NAME); -@end smallexample +@geindex Refined_Depends -@noindent -In the case of the first form, the only restriction names -allowed are parameterless restrictions that are checked -for consistency at bind time. For a complete list see the -subtype @code{System.Rident.Partition_Boolean_Restrictions}. +This aspect is equivalent to pragma @cite{Refined_Depends}. -The result returned is True if the restriction is known to -be in effect, and False if the restriction is known not to -be in effect. An important guarantee is that the value of -a Restriction_Set attribute is known to be consistent throughout -all the code of a partition. +@node Aspect Refined_Global,Aspect Refined_Post,Aspect Refined_Depends,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-refined-global}@anchor{100} +@section Aspect Refined_Global -This is trivially achieved if the entire partition is compiled -with a consistent set of restriction pragmas. However, the -compilation model does not require this. It is possible to -compile one set of units with one set of pragmas, and another -set of units with another set of pragmas. It is even possible -to compile a spec with one set of pragmas, and then WITH the -same spec with a different set of pragmas. Inconsistencies -in the actual use of the restriction are checked at bind time. -In order to achieve the guarantee of consistency for the -Restriction_Set pragma, we consider that a use of the pragma -that yields False is equivalent to a violation of the -restriction. +@geindex Refined_Global -So for example if you write +This aspect is equivalent to pragma @cite{Refined_Global}. -@smallexample @c ada -if System'Restriction_Set (No_Floating_Point) then - ... -else - ... -end if; -@end smallexample +@node Aspect Refined_Post,Aspect Refined_State,Aspect Refined_Global,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-refined-post}@anchor{101} +@section Aspect Refined_Post -@noindent -And the result is False, so that the else branch is executed, -you can assume that this restriction is not set for any unit -in the partition. This is checked by considering this use of -the restriction pragma to be a violation of the restriction -No_Floating_Point. This means that no other unit can attempt -to set this restriction (if some unit does attempt to set it, -the binder will refuse to bind the partition). -Technical note: The restriction name and the unit name are -intepreted entirely syntactically, as in the corresponding -Restrictions pragma, they are not analyzed semantically, -so they do not have a type. +@geindex Refined_Post -@node Attribute Result -@unnumberedsec Attribute Result -@findex Result -@noindent -@code{@var{function}'Result} can only be used with in a Postcondition pragma -for a function. The prefix must be the name of the corresponding function. This -is used to refer to the result of the function in the postcondition expression. -For a further discussion of the use of this attribute and examples of its use, -see the description of pragma Postcondition. +This aspect is equivalent to pragma @cite{Refined_Post}. -@node Attribute Safe_Emax -@unnumberedsec Attribute Safe_Emax -@cindex Ada 83 attributes -@findex Safe_Emax -@noindent -The @code{Safe_Emax} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. +@node Aspect Refined_State,Aspect Remote_Access_Type,Aspect Refined_Post,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-refined-state}@anchor{102} +@section Aspect Refined_State -@node Attribute Safe_Large -@unnumberedsec Attribute Safe_Large -@cindex Ada 83 attributes -@findex Safe_Large -@noindent -The @code{Safe_Large} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. -@node Attribute Safe_Small -@unnumberedsec Attribute Safe_Small -@cindex Ada 83 attributes -@findex Safe_Small -@noindent -The @code{Safe_Small} attribute is provided for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute. +@geindex Refined_State -@node Attribute Scalar_Storage_Order -@unnumberedsec Attribute Scalar_Storage_Order -@cindex Endianness -@cindex Scalar storage order -@findex Scalar_Storage_Order -@noindent -For every array or record type @var{S}, the representation attribute -@code{Scalar_Storage_Order} denotes the order in which storage elements -that make up scalar components are ordered within S. The value given must -be a static expression of type System.Bit_Order. The following is an example -of the use of this feature: +This aspect is equivalent to pragma @cite{Refined_State}. -@smallexample @c ada - -- Component type definitions +@node Aspect Remote_Access_Type,Aspect Scalar_Storage_Order,Aspect Refined_State,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-remote-access-type}@anchor{103} +@section Aspect Remote_Access_Type - subtype Yr_Type is Natural range 0 .. 127; - subtype Mo_Type is Natural range 1 .. 12; - subtype Da_Type is Natural range 1 .. 31; - -- Record declaration +@geindex Remote_Access_Type - type Date is record - Years_Since_1980 : Yr_Type; - Month : Mo_Type; - Day_Of_Month : Da_Type; - end record; +This aspect is equivalent to pragma @cite{Remote_Access_Type}. - -- Record representation clause +@node Aspect Scalar_Storage_Order,Aspect Shared,Aspect Remote_Access_Type,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-scalar-storage-order}@anchor{104} +@section Aspect Scalar_Storage_Order - for Date use record - Years_Since_1980 at 0 range 0 .. 6; - Month at 0 range 7 .. 10; - Day_Of_Month at 0 range 11 .. 15; - end record; - -- Attribute definition clauses +@geindex Scalar_Storage_Order - for Date'Bit_Order use System.High_Order_First; - for Date'Scalar_Storage_Order use System.High_Order_First; - -- If Scalar_Storage_Order is specified, it must be consistent with - -- Bit_Order, so it's best to always define the latter explicitly if - -- the former is used. -@end smallexample +This aspect is equivalent to a @cite{Scalar_Storage_Order} +attribute definition clause. -@noindent -Other properties are as for standard representation attribute @code{Bit_Order}, -as defined by Ada RM 13.5.3(4). The default is @code{System.Default_Bit_Order}. +@node Aspect Shared,Aspect Simple_Storage_Pool,Aspect Scalar_Storage_Order,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-shared}@anchor{105} +@section Aspect Shared -For a record type @var{T}, if @code{@var{T}'Scalar_Storage_Order} is -specified explicitly, it shall be equal to @code{@var{T}'Bit_Order}. Note: -this means that if a @code{Scalar_Storage_Order} attribute definition -clause is not confirming, then the type's @code{Bit_Order} shall be -specified explicitly and set to the same value. -Derived types inherit an explicitly set scalar storage order from their parent -types. This may be overridden for the derived type by giving an explicit scalar -storage order for the derived type. For a record extension, the derived type -must have the same scalar storage order as the parent type. +@geindex Shared -If a component of @var{T} is of a record or array type, then that type must -also have a @code{Scalar_Storage_Order} attribute definition clause. +This boolean aspect is equivalent to pragma @cite{Shared}, +and is thus a synonym for aspect @cite{Atomic}. -A component of a record or array type that is a packed array, or that -does not start on a byte boundary, must have the same scalar storage order -as the enclosing record or array type. +@node Aspect Simple_Storage_Pool,Aspect Simple_Storage_Pool_Type,Aspect Shared,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool}@anchor{106} +@section Aspect Simple_Storage_Pool -No component of a type that has an explicit @code{Scalar_Storage_Order} -attribute definition may be aliased. -A confirming @code{Scalar_Storage_Order} attribute definition clause (i.e. -with a value equal to @code{System.Default_Bit_Order}) has no effect. +@geindex Simple_Storage_Pool -If the opposite storage order is specified, then whenever the value of -a scalar component of an object of type @var{S} is read, the storage -elements of the enclosing machine scalar are first reversed (before -retrieving the component value, possibly applying some shift and mask -operatings on the enclosing machine scalar), and the opposite operation -is done for writes. +This aspect is equivalent to a @cite{Simple_Storage_Pool} +attribute definition clause. -In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components -are relaxed. Instead, the following rules apply: +@node Aspect Simple_Storage_Pool_Type,Aspect SPARK_Mode,Aspect Simple_Storage_Pool,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-simple-storage-pool-type}@anchor{107} +@section Aspect Simple_Storage_Pool_Type -@itemize @bullet -@item the underlying storage elements are those at positions - @code{(position + first_bit / storage_element_size) .. - (position + (last_bit + storage_element_size - 1) / - storage_element_size)} -@item the sequence of underlying storage elements shall have - a size no greater than the largest machine scalar -@item the enclosing machine scalar is defined as the smallest machine - scalar starting at a position no greater than - @code{position + first_bit / storage_element_size} and covering - storage elements at least up to @code{position + (last_bit + - storage_element_size - 1) / storage_element_size} -@item the position of the component is interpreted relative to that machine - scalar. -@end itemize +@geindex Simple_Storage_Pool_Type -If no scalar storage order is specified for a type (either directly, or by -inheritance in the case of a derived type), then the default is normally -the native ordering of the target, but this default can be overridden using -pragma @code{Default_Scalar_Storage_Order}. - -@node Attribute Simple_Storage_Pool -@unnumberedsec Attribute Simple_Storage_Pool -@cindex Storage pool, simple -@cindex Simple storage pool -@findex Simple_Storage_Pool -@noindent -For every nonformal, nonderived access-to-object type @var{Acc}, the -representation attribute @code{Simple_Storage_Pool} may be specified -via an attribute_definition_clause (or by specifying the equivalent aspect): +This boolean aspect is equivalent to pragma @cite{Simple_Storage_Pool_Type}. -@smallexample @c ada +@node Aspect SPARK_Mode,Aspect Suppress_Debug_Info,Aspect Simple_Storage_Pool_Type,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-spark-mode}@anchor{108} +@section Aspect SPARK_Mode -My_Pool : My_Simple_Storage_Pool_Type; -type Acc is access My_Data_Type; +@geindex SPARK_Mode -for Acc'Simple_Storage_Pool use My_Pool; +This aspect is equivalent to pragma @cite{SPARK_Mode} and +may be specified for either or both of the specification and body +of a subprogram or package. -@end smallexample +@node Aspect Suppress_Debug_Info,Aspect Suppress_Initialization,Aspect SPARK_Mode,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-suppress-debug-info}@anchor{109} +@section Aspect Suppress_Debug_Info -@noindent -The name given in an attribute_definition_clause for the -@code{Simple_Storage_Pool} attribute shall denote a variable of -a ``simple storage pool type'' (see pragma @code{Simple_Storage_Pool_Type}). -The use of this attribute is only allowed for a prefix denoting a type -for which it has been specified. The type of the attribute is the type -of the variable specified as the simple storage pool of the access type, -and the attribute denotes that variable. +@geindex Suppress_Debug_Info -It is illegal to specify both @code{Storage_Pool} and @code{Simple_Storage_Pool} -for the same access type. +This boolean aspect is equivalent to pragma @cite{Suppress_Debug_Info}. -If the @code{Simple_Storage_Pool} attribute has been specified for an access -type, then applying the @code{Storage_Pool} attribute to the type is flagged -with a warning and its evaluation raises the exception @code{Program_Error}. +@node Aspect Suppress_Initialization,Aspect Test_Case,Aspect Suppress_Debug_Info,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-suppress-initialization}@anchor{10a} +@section Aspect Suppress_Initialization -If the Simple_Storage_Pool attribute has been specified for an access -type @var{S}, then the evaluation of the attribute @code{@var{S}'Storage_Size} -returns the result of calling @code{Storage_Size (@var{S}'Simple_Storage_Pool)}, -which is intended to indicate the number of storage elements reserved for -the simple storage pool. If the Storage_Size function has not been defined -for the simple storage pool type, then this attribute returns zero. -If an access type @var{S} has a specified simple storage pool of type -@var{SSP}, then the evaluation of an allocator for that access type calls -the primitive @code{Allocate} procedure for type @var{SSP}, passing -@code{@var{S}'Simple_Storage_Pool} as the pool parameter. The detailed -semantics of such allocators is the same as those defined for allocators -in section 13.11 of the Ada Reference Manual, with the term -``simple storage pool'' substituted for ``storage pool''. +@geindex Suppress_Initialization -If an access type @var{S} has a specified simple storage pool of type -@var{SSP}, then a call to an instance of the @code{Ada.Unchecked_Deallocation} -for that access type invokes the primitive @code{Deallocate} procedure -for type @var{SSP}, passing @code{@var{S}'Simple_Storage_Pool} as the pool -parameter. The detailed semantics of such unchecked deallocations is the same -as defined in section 13.11.2 of the Ada Reference Manual, except that the -term ``simple storage pool'' is substituted for ``storage pool''. - -@node Attribute Small -@unnumberedsec Attribute Small -@cindex Ada 83 attributes -@findex Small -@noindent -The @code{Small} attribute is defined in Ada 95 (and Ada 2005) only for -fixed-point types. -GNAT also allows this attribute to be applied to floating-point types -for compatibility with Ada 83. See -the Ada 83 reference manual for an exact description of the semantics of -this attribute when applied to floating-point types. +This boolean aspect is equivalent to pragma @cite{Suppress_Initialization}. -@node Attribute Storage_Unit -@unnumberedsec Attribute Storage_Unit -@findex Storage_Unit -@noindent -@code{Standard'Storage_Unit} (@code{Standard} is the only permissible -prefix) provides the same value as @code{System.Storage_Unit}. - -@node Attribute Stub_Type -@unnumberedsec Attribute Stub_Type -@findex Stub_Type -@noindent -The GNAT implementation of remote access-to-classwide types is -organized as described in AARM section E.4 (20.t): a value of an RACW type -(designating a remote object) is represented as a normal access -value, pointing to a "stub" object which in turn contains the -necessary information to contact the designated remote object. A -call on any dispatching operation of such a stub object does the -remote call, if necessary, using the information in the stub object -to locate the target partition, etc. +@node Aspect Test_Case,Aspect Thread_Local_Storage,Aspect Suppress_Initialization,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-test-case}@anchor{10b} +@section Aspect Test_Case -For a prefix @code{T} that denotes a remote access-to-classwide type, -@code{T'Stub_Type} denotes the type of the corresponding stub objects. -By construction, the layout of @code{T'Stub_Type} is identical to that of -type @code{RACW_Stub_Type} declared in the internal implementation-defined -unit @code{System.Partition_Interface}. Use of this attribute will create -an implicit dependency on this unit. +@geindex Test_Case -@node Attribute System_Allocator_Alignment -@unnumberedsec Attribute System_Allocator_Alignment -@cindex Alignment, allocator -@findex System_Allocator_Alignment -@noindent -@code{Standard'System_Allocator_Alignment} (@code{Standard} is the only -permissible prefix) provides the observable guaranted to be honored by -the system allocator (malloc). This is a static value that can be used -in user storage pools based on malloc either to reject allocation -with alignment too large or to enable a realignment circuitry if the -alignment request is larger than this value. +This aspect is equivalent to pragma @cite{Test_Case}. -@node Attribute Target_Name -@unnumberedsec Attribute Target_Name -@findex Target_Name -@noindent -@code{Standard'Target_Name} (@code{Standard} is the only permissible -prefix) provides a static string value that identifies the target -for the current compilation. For GCC implementations, this is the -standard gcc target name without the terminating slash (for -example, GNAT 5.0 on windows yields "i586-pc-mingw32msv"). +@node Aspect Thread_Local_Storage,Aspect Universal_Aliasing,Aspect Test_Case,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-thread-local-storage}@anchor{10c} +@section Aspect Thread_Local_Storage -@node Attribute To_Address -@unnumberedsec Attribute To_Address -@findex To_Address -@noindent -The @code{System'To_Address} -(@code{System} is the only permissible prefix) -denotes a function identical to -@code{System.Storage_Elements.To_Address} except that -it is a static attribute. This means that if its argument is -a static expression, then the result of the attribute is a -static expression. This means that such an expression can be -used in contexts (e.g.@: preelaborable packages) which require a -static expression and where the function call could not be used -(since the function call is always non-static, even if its -argument is static). The argument must be in the range --(2**(m-1) .. 2**m-1, where m is the memory size -(typically 32 or 64). Negative values are intepreted in a -modular manner (e.g. -1 means the same as 16#FFFF_FFFF# on -a 32 bits machine). -@node Attribute To_Any -@unnumberedsec Attribute To_Any -@findex To_Any -@noindent -This internal attribute is used for the generation of remote subprogram -stubs in the context of the Distributed Systems Annex. +@geindex Thread_Local_Storage -@node Attribute Type_Class -@unnumberedsec Attribute Type_Class -@findex Type_Class -@noindent -@code{@var{type}'Type_Class} for any type or subtype @var{type} yields -the value of the type class for the full type of @var{type}. If -@var{type} is a generic formal type, the value is the value for the -corresponding actual subtype. The value of this attribute is of type -@code{System.Aux_DEC.Type_Class}, which has the following definition: +This boolean aspect is equivalent to pragma @cite{Thread_Local_Storage}. -@smallexample @c ada -type Type_Class is - (Type_Class_Enumeration, - Type_Class_Integer, - Type_Class_Fixed_Point, - Type_Class_Floating_Point, - Type_Class_Array, - Type_Class_Record, - Type_Class_Access, - Type_Class_Task, - Type_Class_Address); -@end smallexample +@node Aspect Universal_Aliasing,Aspect Universal_Data,Aspect Thread_Local_Storage,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-universal-aliasing}@anchor{10d} +@section Aspect Universal_Aliasing -@noindent -Protected types yield the value @code{Type_Class_Task}, which thus -applies to all concurrent types. This attribute is designed to -be compatible with the DEC Ada 83 attribute of the same name. -@node Attribute Type_Key -@unnumberedsec Attribute Type_Key -@findex Type_Key -@noindent -The @code{Type_Key} attribute is applicable to a type or subtype and -yields a value of type Standard.String containing encoded information -about the type or subtype. This provides improved compatibility with -other implementations that support this attribute. +@geindex Universal_Aliasing -@node Attribute TypeCode -@unnumberedsec Attribute TypeCode -@findex TypeCode -@noindent -This internal attribute is used for the generation of remote subprogram -stubs in the context of the Distributed Systems Annex. +This boolean aspect is equivalent to pragma @cite{Universal_Aliasing}. -@node Attribute UET_Address -@unnumberedsec Attribute UET_Address -@findex UET_Address -@noindent -The @code{UET_Address} attribute can only be used for a prefix which -denotes a library package. It yields the address of the unit exception -table when zero cost exception handling is used. This attribute is -intended only for use within the GNAT implementation. See the unit -@code{Ada.Exceptions} in files @file{a-except.ads} and @file{a-except.adb} -for details on how this attribute is used in the implementation. +@node Aspect Universal_Data,Aspect Unmodified,Aspect Universal_Aliasing,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-universal-data}@anchor{10e} +@section Aspect Universal_Data -@node Attribute Unconstrained_Array -@unnumberedsec Attribute Unconstrained_Array -@findex Unconstrained_Array -@noindent -The @code{Unconstrained_Array} attribute can be used with a prefix that -denotes any type or subtype. It is a static attribute that yields -@code{True} if the prefix designates an unconstrained array, -and @code{False} otherwise. In a generic instance, the result is -still static, and yields the result of applying this test to the -generic actual. -@node Attribute Universal_Literal_String -@unnumberedsec Attribute Universal_Literal_String -@cindex Named numbers, representation of -@findex Universal_Literal_String -@noindent -The prefix of @code{Universal_Literal_String} must be a named -number. The static result is the string consisting of the characters of -the number as defined in the original source. This allows the user -program to access the actual text of named numbers without intermediate -conversions and without the need to enclose the strings in quotes (which -would preclude their use as numbers). +@geindex Universal_Data -For example, the following program prints the first 50 digits of pi: +This aspect is equivalent to pragma @cite{Universal_Data}. -@smallexample @c ada -with Text_IO; use Text_IO; -with Ada.Numerics; -procedure Pi is -begin - Put (Ada.Numerics.Pi'Universal_Literal_String); -end; -@end smallexample - -@node Attribute Unrestricted_Access -@unnumberedsec Attribute Unrestricted_Access -@cindex @code{Access}, unrestricted -@findex Unrestricted_Access -@noindent -The @code{Unrestricted_Access} attribute is similar to @code{Access} -except that all accessibility and aliased view checks are omitted. This -is a user-beware attribute. +@node Aspect Unmodified,Aspect Unreferenced,Aspect Universal_Data,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-unmodified}@anchor{10f} +@section Aspect Unmodified -For objects, it is similar to @code{Address}, for which it is a -desirable replacement where the value desired is an access type. -In other words, its effect is similar to first applying the -@code{Address} attribute and then doing an unchecked conversion to a -desired access type. -For subprograms, @code{P'Unrestricted_Access} may be used where -@code{P'Access} would be illegal, to construct a value of a -less-nested named access type that designates a more-nested -subprogram. This value may be used in indirect calls, so long as the -more-nested subprogram still exists; once the subprogram containing it -has returned, such calls are erroneous. For example: +@geindex Unmodified -@smallexample @c ada -package body P is +This boolean aspect is equivalent to pragma @cite{Unmodified}. - type Less_Nested is not null access procedure; - Global : Less_Nested; +@node Aspect Unreferenced,Aspect Unreferenced_Objects,Aspect Unmodified,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced}@anchor{110} +@section Aspect Unreferenced - procedure P1 is - begin - Global.all; - end P1; - procedure P2 is - Local_Var : Integer; +@geindex Unreferenced - procedure More_Nested is - begin - ... Local_Var ... - end More_Nested; - begin - Global := More_Nested'Unrestricted_Access; - P1; - end P2; +This boolean aspect is equivalent to pragma @cite{Unreferenced}. Note that +in the case of formal parameters, it is not permitted to have aspects for +a formal parameter, so in this case the pragma form must be used. -end P; -@end smallexample +@node Aspect Unreferenced_Objects,Aspect Value_Size,Aspect Unreferenced,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-unreferenced-objects}@anchor{111} +@section Aspect Unreferenced_Objects -When P1 is called from P2, the call via Global is OK, but if P1 were -called after P2 returns, it would be an erroneous use of a dangling -pointer. -For objects, it is possible to use @code{Unrestricted_Access} for any -type. However, if the result is of an access-to-unconstrained array -subtype, then the resulting pointer has the same scope as the context -of the attribute, and must not be returned to some enclosing scope. -For instance, if a function uses @code{Unrestricted_Access} to create -an access-to-unconstrained-array and returns that value to the caller, -the result will involve dangling pointers. In addition, it is only -valid to create pointers to unconstrained arrays using this attribute -if the pointer has the normal default ``fat'' representation where a -pointer has two components, one points to the array and one points to -the bounds. If a size clause is used to force ``thin'' representation -for a pointer to unconstrained where there is only space for a single -pointer, then the resulting pointer is not usable. +@geindex Unreferenced_Objects -In the simple case where a direct use of Unrestricted_Access attempts -to make a thin pointer for a non-aliased object, the compiler will -reject the use as illegal, as shown in the following example: +This boolean aspect is equivalent to pragma @cite{Unreferenced_Objects}. -@smallexample @c ada -with System; use System; -procedure SliceUA2 is - type A is access all String; - for A'Size use Standard'Address_Size; +@node Aspect Value_Size,Aspect Warnings,Aspect Unreferenced_Objects,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-value-size}@anchor{112} +@section Aspect Value_Size - procedure P (Arg : A) is - begin - null; - end P; - X : String := "hello world!"; - X2 : aliased String := "hello world!"; +@geindex Value_Size - AV : A := X'Unrestricted_Access; -- ERROR - | ->>> illegal use of Unrestricted_Access attribute ->>> attempt to generate thin pointer to unaliased object +This aspect is equivalent to a @cite{Value_Size} +attribute definition clause. -begin - P (X'Unrestricted_Access); -- ERROR - | ->>> illegal use of Unrestricted_Access attribute ->>> attempt to generate thin pointer to unaliased object +@node Aspect Warnings,,Aspect Value_Size,Implementation Defined Aspects +@anchor{gnat_rm/implementation_defined_aspects aspect-warnings}@anchor{113} +@section Aspect Warnings - P (X(7 .. 12)'Unrestricted_Access); -- ERROR - | ->>> illegal use of Unrestricted_Access attribute ->>> attempt to generate thin pointer to unaliased object - P (X2'Unrestricted_Access); -- OK -end; -@end smallexample +@geindex Warnings -@noindent -but other cases cannot be detected by the compiler, and are -considered to be erroneous. Consider the following example: +This aspect is equivalent to the two argument form of pragma @cite{Warnings}, +where the first argument is @cite{ON} or @cite{OFF} and the second argument +is the entity. -@smallexample @c ada -with System; use System; -with System; use System; -procedure SliceUA is - type AF is access all String; +@node Implementation Defined Attributes,Standard and Implementation Defined Restrictions,Implementation Defined Aspects,Top +@anchor{gnat_rm/implementation_defined_attributes doc}@anchor{114}@anchor{gnat_rm/implementation_defined_attributes implementation-defined-attributes}@anchor{8}@anchor{gnat_rm/implementation_defined_attributes id1}@anchor{115} +@chapter Implementation Defined Attributes - type A is access all String; - for A'Size use Standard'Address_Size; - procedure P (Arg : A) is - begin - if Arg'Length /= 6 then - raise Program_Error; - end if; - end P; +Ada defines (throughout the Ada reference manual, +summarized in Annex K), +a set of attributes that provide useful additional functionality in all +areas of the language. These language defined attributes are implemented +in GNAT and work as described in the Ada Reference Manual. - X : String := "hello world!"; - Y : AF := X (7 .. 12)'Unrestricted_Access; +In addition, Ada allows implementations to define additional +attributes whose meaning is defined by the implementation. GNAT provides +a number of these implementation-dependent attributes which can be used +to extend and enhance the functionality of the compiler. This section of +the GNAT reference manual describes these additional attributes. It also +describes additional implementation-dependent features of standard +language-defined attributes. -begin - P (A (Y)); -end; -@end smallexample +Note that any program using these attributes may not be portable to +other compilers (although GNAT implements this set of attributes on all +platforms). Therefore if portability to other compilers is an important +consideration, you should minimize the use of these attributes. -@noindent -A normal unconstrained array value -or a constrained array object marked as aliased has the bounds in memory -just before the array, so a thin pointer can retrieve both the data and -the bounds. But in this case, the non-aliased object @code{X} does not have the -bounds before the string. If the size clause for type @code{A} -were not present, then the pointer -would be a fat pointer, where one component is a pointer to the bounds, -and all would be well. But with the size clause present, the conversion from -fat pointer to thin pointer in the call loses the bounds, and so this -is erroneous, and the program likely raises a @code{Program_Error} exception. +@menu +* Attribute Abort_Signal:: +* Attribute Address_Size:: +* Attribute Asm_Input:: +* Attribute Asm_Output:: +* Attribute Atomic_Always_Lock_Free:: +* Attribute Bit:: +* Attribute Bit_Position:: +* Attribute Code_Address:: +* Attribute Compiler_Version:: +* Attribute Constrained:: +* Attribute Default_Bit_Order:: +* Attribute Default_Scalar_Storage_Order:: +* Attribute Descriptor_Size:: +* Attribute Elaborated:: +* Attribute Elab_Body:: +* Attribute Elab_Spec:: +* Attribute Elab_Subp_Body:: +* Attribute Emax:: +* Attribute Enabled:: +* Attribute Enum_Rep:: +* Attribute Enum_Val:: +* Attribute Epsilon:: +* Attribute Fast_Math:: +* Attribute Fixed_Value:: +* Attribute From_Any:: +* Attribute Has_Access_Values:: +* Attribute Has_Discriminants:: +* Attribute Img:: +* Attribute Integer_Value:: +* Attribute Invalid_Value:: +* Attribute Iterable:: +* Attribute Large:: +* Attribute Library_Level:: +* Attribute Lock_Free:: +* Attribute Loop_Entry:: +* Attribute Machine_Size:: +* Attribute Mantissa:: +* Attribute Maximum_Alignment:: +* Attribute Mechanism_Code:: +* Attribute Null_Parameter:: +* Attribute Object_Size:: +* Attribute Old:: +* Attribute Passed_By_Reference:: +* Attribute Pool_Address:: +* Attribute Range_Length:: +* Attribute Ref:: +* Attribute Restriction_Set:: +* Attribute Result:: +* Attribute Safe_Emax:: +* Attribute Safe_Large:: +* Attribute Safe_Small:: +* Attribute Scalar_Storage_Order:: +* Attribute Simple_Storage_Pool:: +* Attribute Small:: +* Attribute Storage_Unit:: +* Attribute Stub_Type:: +* Attribute System_Allocator_Alignment:: +* Attribute Target_Name:: +* Attribute To_Address:: +* Attribute To_Any:: +* Attribute Type_Class:: +* Attribute Type_Key:: +* Attribute TypeCode:: +* Attribute UET_Address:: +* Attribute Unconstrained_Array:: +* Attribute Universal_Literal_String:: +* Attribute Unrestricted_Access:: +* Attribute Update:: +* Attribute Valid_Scalars:: +* Attribute VADS_Size:: +* Attribute Value_Size:: +* Attribute Wchar_T_Size:: +* Attribute Word_Size:: -In general, it is advisable to completely -avoid mixing the use of thin pointers and the use of -@code{Unrestricted_Access} where the designated type is an -unconstrained array. The use of thin pointers should be restricted to -cases of porting legacy code that implicitly assumes the size of pointers, -and such code should not in any case be using this attribute. +@end menu -Another erroneous situation arises if the attribute is -applied to a constant. The resulting pointer can be used to access the -constant, but the effect of trying to modify a constant in this manner -is not well-defined. Consider this example: +@node Attribute Abort_Signal,Attribute Address_Size,,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-abort-signal}@anchor{116} +@section Attribute Abort_Signal -@smallexample @c ada -P : constant Integer := 4; -type R is access all Integer; -RV : R := P'Unrestricted_Access; -.. -RV.all := 3; -@end smallexample -@noindent -Here we attempt to modify the constant P from 4 to 3, but the compiler may -or may not notice this attempt, and subsequent references to P may yield -either the value 3 or the value 4 or the assignment may blow up if the -compiler decides to put P in read-only memory. One particular case where -@code{Unrestricted_Access} can be used in this way is to modify the -value of an @code{IN} parameter: +@geindex Abort_Signal -@smallexample @c ada -procedure K (S : in String) is - type R is access all Character; - RV : R := S (3)'Unrestricted_Access; -begin - RV.all := 'a'; -end; -@end smallexample +@cite{Standard'Abort_Signal} (@cite{Standard} is the only allowed +prefix) provides the entity for the special exception used to signal +task abort or asynchronous transfer of control. Normally this attribute +should only be used in the tasking runtime (it is highly peculiar, and +completely outside the normal semantics of Ada, for a user program to +intercept the abort exception). -@noindent -In general this is a risky approach. It may appear to "work" but such uses of -@code{Unrestricted_Access} are potentially non-portable, even from one version -of @code{GNAT} to another, so are best avoided if possible. - -@node Attribute Update -@unnumberedsec Attribute Update -@findex Update -@noindent -The @code{Update} attribute creates a copy of an array or record value -with one or more modified components. The syntax is: +@node Attribute Address_Size,Attribute Asm_Input,Attribute Abort_Signal,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-address-size}@anchor{117} +@section Attribute Address_Size -@smallexample @c ada -PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST ) -PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} ) -PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION - @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} ) -MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION -INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @} -INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} ) -@end smallexample +@geindex Size of `Address` -@noindent -where @code{PREFIX} is the name of an array or record object, the -association list in parentheses does not contain an @code{others} -choice and the box symbol @code{<>} may not appear in any -expression. The effect is to yield a copy of the array or record value -which is unchanged apart from the components mentioned in the -association list, which are changed to the indicated value. The -original value of the array or record value is not affected. For -example: +@geindex Address_Size -@smallexample @c ada -type Arr is Array (1 .. 5) of Integer; -... -Avar1 : Arr := (1,2,3,4,5); -Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20); -@end smallexample +@cite{Standard'Address_Size} (@cite{Standard} is the only allowed +prefix) is a static constant giving the number of bits in an +@cite{Address}. It is the same value as System.Address'Size, +but has the advantage of being static, while a direct +reference to System.Address'Size is non-static because Address +is a private type. -@noindent -yields a value for @code{Avar2} of 1,10,20,20,5 with @code{Avar1} -begin unmodified. Similarly: +@node Attribute Asm_Input,Attribute Asm_Output,Attribute Address_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-asm-input}@anchor{118} +@section Attribute Asm_Input -@smallexample @c ada -type Rec is A, B, C : Integer; -... -Rvar1 : Rec := (A => 1, B => 2, C => 3); -Rvar2 : Rec := Rvar1'Update (B => 20); -@end smallexample -@noindent -yields a value for @code{Rvar2} of (A => 1, B => 20, C => 3), -with @code{Rvar1} being unmodifed. -Note that the value of the attribute reference is computed -completely before it is used. This means that if you write: +@geindex Asm_Input -@smallexample @c ada -Avar1 := Avar1'Update (1 => 10, 2 => Function_Call); -@end smallexample +The @cite{Asm_Input} attribute denotes a function that takes two +parameters. The first is a string, the second is an expression of the +type designated by the prefix. The first (string) argument is required +to be a static expression, and is the constraint for the parameter, +(e.g., what kind of register is required). The second argument is the +value to be used as the input argument. The possible values for the +constant are the same as those used in the RTL, and are dependent on +the configuration file used to built the GCC back end. +@ref{119,,Machine Code Insertions} -@noindent -then the value of @code{Avar1} is not modified if @code{Function_Call} -raises an exception, unlike the effect of a series of direct assignments -to elements of @code{Avar1}. In general this requires that -two extra complete copies of the object are required, which should be -kept in mind when considering efficiency. +@node Attribute Asm_Output,Attribute Atomic_Always_Lock_Free,Attribute Asm_Input,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-asm-output}@anchor{11a} +@section Attribute Asm_Output -The @code{Update} attribute cannot be applied to prefixes of a limited -type, and cannot reference discriminants in the case of a record type. -The accessibility level of an Update attribute result object is defined -as for an aggregate. -In the record case, no component can be mentioned more than once. In -the array case, two overlapping ranges can appear in the association list, -in which case the modifications are processed left to right. +@geindex Asm_Output -Multi-dimensional arrays can be modified, as shown by this example: +The @cite{Asm_Output} attribute denotes a function that takes two +parameters. The first is a string, the second is the name of a variable +of the type designated by the attribute prefix. The first (string) +argument is required to be a static expression and designates the +constraint for the parameter (e.g., what kind of register is +required). The second argument is the variable to be updated with the +result. The possible values for constraint are the same as those used in +the RTL, and are dependent on the configuration file used to build the +GCC back end. If there are no output operands, then this argument may +either be omitted, or explicitly given as @cite{No_Output_Operands}. +@ref{119,,Machine Code Insertions} -@smallexample @c ada -A : array (1 .. 10, 1 .. 10) of Integer; -.. -A := A'Update ((1, 2) => 20, (3, 4) => 30); -@end smallexample +@node Attribute Atomic_Always_Lock_Free,Attribute Bit,Attribute Asm_Output,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-atomic-always-lock-free}@anchor{11b} +@section Attribute Atomic_Always_Lock_Free -@noindent -which changes element (1,2) to 20 and (3,4) to 30. -@node Attribute Valid_Scalars -@unnumberedsec Attribute Valid_Scalars -@findex Valid_Scalars -@noindent -The @code{'Valid_Scalars} attribute is intended to make it easier to -check the validity of scalar subcomponents of composite objects. It -is defined for any prefix @code{X} that denotes an object. -The value of this attribute is of the predefined type Boolean. -@code{X'Valid_Scalars} yields True if and only if evaluation of -@code{P'Valid} yields True for every scalar part P of X or if X has -no scalar parts. It is not specified in what order the scalar parts -are checked, nor whether any more are checked after any one of them -is determined to be invalid. If the prefix @code{X} is of a class-wide -type @code{T'Class} (where @code{T} is the associated specific type), -or if the prefix @code{X} is of a specific tagged type @code{T}, then -only the scalar parts of components of @code{T} are traversed; in other -words, components of extensions of @code{T} are not traversed even if -@code{T'Class (X)'Tag /= T'Tag} . The compiler will issue a warning if it can -be determined at compile time that the prefix of the attribute has no -scalar parts (e.g., if the prefix is of an access type, an interface type, -an undiscriminated task type, or an undiscriminated protected type). +@geindex Atomic_Always_Lock_Free -For scalar types, @code{Valid_Scalars} is equivalent to @code{Valid}. The use -of this attribute is not permitted for @code{Unchecked_Union} types for which -in general it is not possible to determine the values of the discriminants. +The prefix of the @cite{Atomic_Always_Lock_Free} attribute is a type. +The result is a Boolean value which is True if the type has discriminants, +and False otherwise. The result indicate whether atomic operations are +supported by the target for the given type. -Note: @code{Valid_Scalars} can generate a lot of code, especially in the case -of a large variant record. If the attribute is called in many places in the -same program applied to objects of the same type, it can reduce program size -to write a function with a single use of the attribute, and then call that -function from multiple places. +@node Attribute Bit,Attribute Bit_Position,Attribute Atomic_Always_Lock_Free,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-bit}@anchor{11c} +@section Attribute Bit -@node Attribute VADS_Size -@unnumberedsec Attribute VADS_Size -@cindex @code{Size}, VADS compatibility -@findex VADS_Size -@noindent -The @code{'VADS_Size} attribute is intended to make it easier to port -legacy code which relies on the semantics of @code{'Size} as implemented -by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the -same semantic interpretation. In particular, @code{'VADS_Size} applied -to a predefined or other primitive type with no Size clause yields the -Object_Size (for example, @code{Natural'Size} is 32 rather than 31 on -typical machines). In addition @code{'VADS_Size} applied to an object -gives the result that would be obtained by applying the attribute to -the corresponding type. -@node Attribute Value_Size -@unnumberedsec Attribute Value_Size -@cindex @code{Size}, setting for not-first subtype -@findex Value_Size -@code{@var{type}'Value_Size} is the number of bits required to represent -a value of the given subtype. It is the same as @code{@var{type}'Size}, -but, unlike @code{Size}, may be set for non-first subtypes. - -@node Attribute Wchar_T_Size -@unnumberedsec Attribute Wchar_T_Size -@findex Wchar_T_Size -@code{Standard'Wchar_T_Size} (@code{Standard} is the only permissible -prefix) provides the size in bits of the C @code{wchar_t} type -primarily for constructing the definition of this type in -package @code{Interfaces.C}. The result is a static constant. +@geindex Bit -@node Attribute Word_Size -@unnumberedsec Attribute Word_Size -@findex Word_Size -@code{Standard'Word_Size} (@code{Standard} is the only permissible -prefix) provides the value @code{System.Word_Size}. The result is -a static constant. +@code{obj'Bit}, where @cite{obj} is any object, yields the bit +offset within the storage unit (byte) that contains the first bit of +storage allocated for the object. The value of this attribute is of the +type @cite{Universal_Integer}, and is always a non-negative number not +exceeding the value of @cite{System.Storage_Unit}. -@node Standard and Implementation Defined Restrictions -@chapter Standard and Implementation Defined Restrictions +For an object that is a variable or a constant allocated in a register, +the value is zero. (The use of this attribute does not force the +allocation of a variable to memory). -@noindent -All RM defined Restriction identifiers are implemented: +For an object that is a formal parameter, this attribute applies +to either the matching actual parameter or to a copy of the +matching actual parameter. -@itemize @bullet -@item language-defined restrictions (see 13.12.1) -@item tasking restrictions (see D.7) -@item high integrity restrictions (see H.4) -@end itemize +For an access object the value is zero. Note that +@code{obj.all'Bit} is subject to an @cite{Access_Check} for the +designated object. Similarly for a record component +@code{X.C'Bit} is subject to a discriminant check and +@code{X(I).Bit} and @code{X(I1..I2)'Bit} +are subject to index checks. -@noindent -GNAT implements additional restriction identifiers. All restrictions, whether -language defined or GNAT-specific, are listed in the following. +This attribute is designed to be compatible with the DEC Ada 83 definition +and implementation of the @cite{Bit} attribute. -@menu -* Partition-Wide Restrictions:: -* Program Unit Level Restrictions:: -@end menu +@node Attribute Bit_Position,Attribute Code_Address,Attribute Bit,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-bit-position}@anchor{11d} +@section Attribute Bit_Position -@node Partition-Wide Restrictions -@section Partition-Wide Restrictions -There are two separate lists of restriction identifiers. The first -set requires consistency throughout a partition (in other words, if the -restriction identifier is used for any compilation unit in the partition, -then all compilation units in the partition must obey the restriction). +@geindex Bit_Position -@menu -* Immediate_Reclamation:: -* Max_Asynchronous_Select_Nesting:: -* Max_Entry_Queue_Length:: -* Max_Protected_Entries:: -* Max_Select_Alternatives:: -* Max_Storage_At_Blocking:: -* Max_Task_Entries:: -* Max_Tasks:: -* No_Abort_Statements:: -* No_Access_Parameter_Allocators:: -* No_Access_Subprograms:: -* No_Allocators:: -* No_Anonymous_Allocators:: -* No_Calendar:: -* No_Coextensions:: -* No_Default_Initialization:: -* No_Delay:: -* No_Dependence:: -* No_Direct_Boolean_Operators:: -* No_Dispatch:: -* No_Dispatching_Calls:: -* No_Dynamic_Attachment:: -* No_Dynamic_Priorities:: -* No_Entry_Calls_In_Elaboration_Code:: -* No_Enumeration_Maps:: -* No_Exception_Handlers:: -* No_Exception_Propagation:: -* No_Exception_Registration:: -* No_Exceptions:: -* No_Finalization:: -* No_Fixed_Point:: -* No_Floating_Point:: -* No_Implicit_Conditionals:: -* No_Implicit_Dynamic_Code:: -* No_Implicit_Heap_Allocations:: -* No_Implicit_Loops:: -* No_Initialize_Scalars:: -* No_IO:: -* No_Local_Allocators:: -* No_Local_Protected_Objects:: -* No_Local_Timing_Events:: -* No_Long_Long_Integers:: -* No_Multiple_Elaboration:: -* No_Nested_Finalization:: -* No_Protected_Type_Allocators:: -* No_Protected_Types:: -* No_Recursion:: -* No_Reentrancy:: -* No_Relative_Delay:: -* No_Requeue_Statements:: -* No_Secondary_Stack:: -* No_Select_Statements:: -* No_Specific_Termination_Handlers:: -* No_Specification_of_Aspect:: -* No_Standard_Allocators_After_Elaboration:: -* No_Standard_Storage_Pools:: -* No_Stream_Optimizations:: -* No_Streams:: -* No_Task_Allocators:: -* No_Task_Attributes_Package:: -* No_Task_Hierarchy:: -* No_Task_Termination:: -* No_Tasking:: -* No_Terminate_Alternatives:: -* No_Unchecked_Access:: -* Simple_Barriers:: -* Static_Priorities:: -* Static_Storage_Size:: -@end menu +@code{R.C'Bit_Position}, where @cite{R} is a record object and @cite{C} is one +of the fields of the record type, yields the bit +offset within the record contains the first bit of +storage allocated for the object. The value of this attribute is of the +type @cite{Universal_Integer}. The value depends only on the field +@cite{C} and is independent of the alignment of +the containing record @cite{R}. -@node Immediate_Reclamation -@unnumberedsubsec Immediate_Reclamation -@findex Immediate_Reclamation -[RM H.4] This restriction ensures that, except for storage occupied by -objects created by allocators and not deallocated via unchecked -deallocation, any storage reserved at run time for an object is -immediately reclaimed when the object no longer exists. +@node Attribute Code_Address,Attribute Compiler_Version,Attribute Bit_Position,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-code-address}@anchor{11e} +@section Attribute Code_Address -@node Max_Asynchronous_Select_Nesting -@unnumberedsubsec Max_Asynchronous_Select_Nesting -@findex Max_Asynchronous_Select_Nesting -[RM D.7] Specifies the maximum dynamic nesting level of asynchronous -selects. Violations of this restriction with a value of zero are -detected at compile time. Violations of this restriction with values -other than zero cause Storage_Error to be raised. -@node Max_Entry_Queue_Length -@unnumberedsubsec Max_Entry_Queue_Length -@findex Max_Entry_Queue_Length -[RM D.7] This restriction is a declaration that any protected entry compiled in -the scope of the restriction has at most the specified number of -tasks waiting on the entry at any one time, and so no queue is required. -Note that this restriction is checked at run time. Violation of this -restriction results in the raising of Program_Error exception at the point of -the call. +@geindex Code_Address -@findex Max_Entry_Queue_Depth -The restriction @code{Max_Entry_Queue_Depth} is recognized as a -synonym for @code{Max_Entry_Queue_Length}. This is retained for historical -compatibility purposes (and a warning will be generated for its use if -warnings on obsolescent features are activated). +@geindex Subprogram address -@node Max_Protected_Entries -@unnumberedsubsec Max_Protected_Entries -@findex Max_Protected_Entries -[RM D.7] Specifies the maximum number of entries per protected type. The -bounds of every entry family of a protected unit shall be static, or shall be -defined by a discriminant of a subtype whose corresponding bound is static. +@geindex Address of subprogram code -@node Max_Select_Alternatives -@unnumberedsubsec Max_Select_Alternatives -@findex Max_Select_Alternatives -[RM D.7] Specifies the maximum number of alternatives in a selective accept. +The @cite{'Address} +attribute may be applied to subprograms in Ada 95 and Ada 2005, but the +intended effect seems to be to provide +an address value which can be used to call the subprogram by means of +an address clause as in the following example: -@node Max_Storage_At_Blocking -@unnumberedsubsec Max_Storage_At_Blocking -@findex Max_Storage_At_Blocking -[RM D.7] Specifies the maximum portion (in storage elements) of a task's -Storage_Size that can be retained by a blocked task. A violation of this -restriction causes Storage_Error to be raised. +@example +procedure K is ... -@node Max_Task_Entries -@unnumberedsubsec Max_Task_Entries -@findex Max_Task_Entries -[RM D.7] Specifies the maximum number of entries -per task. The bounds of every entry family -of a task unit shall be static, or shall be -defined by a discriminant of a subtype whose -corresponding bound is static. +procedure L; +for L'Address use K'Address; +pragma Import (Ada, L); +@end example -@node Max_Tasks -@unnumberedsubsec Max_Tasks -@findex Max_Tasks -[RM D.7] Specifies the maximum number of task that may be created, not -counting the creation of the environment task. Violations of this -restriction with a value of zero are detected at compile -time. Violations of this restriction with values other than zero cause -Storage_Error to be raised. +A call to @cite{L} is then expected to result in a call to @cite{K}. +In Ada 83, where there were no access-to-subprogram values, this was +a common work-around for getting the effect of an indirect call. +GNAT implements the above use of @cite{Address} and the technique +illustrated by the example code works correctly. -@node No_Abort_Statements -@unnumberedsubsec No_Abort_Statements -@findex No_Abort_Statements -[RM D.7] There are no abort_statements, and there are -no calls to Task_Identification.Abort_Task. +However, for some purposes, it is useful to have the address of the start +of the generated code for the subprogram. On some architectures, this is +not necessarily the same as the @cite{Address} value described above. +For example, the @cite{Address} value may reference a subprogram +descriptor rather than the subprogram itself. -@node No_Access_Parameter_Allocators -@unnumberedsubsec No_Access_Parameter_Allocators -@findex No_Access_Parameter_Allocators -[RM H.4] This restriction ensures at compile time that there are no -occurrences of an allocator as the actual parameter to an access -parameter. +The @cite{'Code_Address} attribute, which can only be applied to +subprogram entities, always returns the address of the start of the +generated code of the specified subprogram, which may or may not be +the same value as is returned by the corresponding @cite{'Address} +attribute. -@node No_Access_Subprograms -@unnumberedsubsec No_Access_Subprograms -@findex No_Access_Subprograms -[RM H.4] This restriction ensures at compile time that there are no -declarations of access-to-subprogram types. +@node Attribute Compiler_Version,Attribute Constrained,Attribute Code_Address,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-compiler-version}@anchor{11f} +@section Attribute Compiler_Version -@node No_Allocators -@unnumberedsubsec No_Allocators -@findex No_Allocators -[RM H.4] This restriction ensures at compile time that there are no -occurrences of an allocator. -@node No_Anonymous_Allocators -@unnumberedsubsec No_Anonymous_Allocators -@findex No_Anonymous_Allocators -[RM H.4] This restriction ensures at compile time that there are no -occurrences of an allocator of anonymous access type. +@geindex Compiler_Version -@node No_Calendar -@unnumberedsubsec No_Calendar -@findex No_Calendar -[GNAT] This restriction ensures at compile time that there is no implicit or -explicit dependence on the package @code{Ada.Calendar}. +@cite{Standard'Compiler_Version} (@cite{Standard} is the only allowed +prefix) yields a static string identifying the version of the compiler +being used to compile the unit containing the attribute reference. -@node No_Coextensions -@unnumberedsubsec No_Coextensions -@findex No_Coextensions -[RM H.4] This restriction ensures at compile time that there are no -coextensions. See 3.10.2. +@node Attribute Constrained,Attribute Default_Bit_Order,Attribute Compiler_Version,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-constrained}@anchor{120} +@section Attribute Constrained -@node No_Default_Initialization -@unnumberedsubsec No_Default_Initialization -@findex No_Default_Initialization -[GNAT] This restriction prohibits any instance of default initialization -of variables. The binder implements a consistency rule which prevents -any unit compiled without the restriction from with'ing a unit with the -restriction (this allows the generation of initialization procedures to -be skipped, since you can be sure that no call is ever generated to an -initialization procedure in a unit with the restriction active). If used -in conjunction with Initialize_Scalars or Normalize_Scalars, the effect -is to prohibit all cases of variables declared without a specific -initializer (including the case of OUT scalar parameters). +@geindex Constrained -@node No_Delay -@unnumberedsubsec No_Delay -@findex No_Delay -[RM H.4] This restriction ensures at compile time that there are no -delay statements and no dependences on package Calendar. +In addition to the usage of this attribute in the Ada RM, @cite{GNAT} +also permits the use of the @cite{'Constrained} attribute +in a generic template +for any type, including types without discriminants. The value of this +attribute in the generic instance when applied to a scalar type or a +record type without discriminants is always @cite{True}. This usage is +compatible with older Ada compilers, including notably DEC Ada. -@node No_Dependence -@unnumberedsubsec No_Dependence -@findex No_Dependence -[RM 13.12.1] This restriction checks at compile time that there are no -dependence on a library unit. +@node Attribute Default_Bit_Order,Attribute Default_Scalar_Storage_Order,Attribute Constrained,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-default-bit-order}@anchor{121} +@section Attribute Default_Bit_Order -@node No_Direct_Boolean_Operators -@unnumberedsubsec No_Direct_Boolean_Operators -@findex No_Direct_Boolean_Operators -[GNAT] This restriction ensures that no logical operators (and/or/xor) -are used on operands of type Boolean (or any type derived from Boolean). -This is intended for use in safety critical programs where the certification -protocol requires the use of short-circuit (and then, or else) forms for all -composite boolean operations. -@node No_Dispatch -@unnumberedsubsec No_Dispatch -@findex No_Dispatch -[RM H.4] This restriction ensures at compile time that there are no -occurrences of @code{T'Class}, for any (tagged) subtype @code{T}. +@geindex Big endian -@node No_Dispatching_Calls -@unnumberedsubsec No_Dispatching_Calls -@findex No_Dispatching_Calls -[GNAT] This restriction ensures at compile time that the code generated by the -compiler involves no dispatching calls. The use of this restriction allows the -safe use of record extensions, classwide membership tests and other classwide -features not involving implicit dispatching. This restriction ensures that -the code contains no indirect calls through a dispatching mechanism. Note that -this includes internally-generated calls created by the compiler, for example -in the implementation of class-wide objects assignments. The -membership test is allowed in the presence of this restriction, because its -implementation requires no dispatching. -This restriction is comparable to the official Ada restriction -@code{No_Dispatch} except that it is a bit less restrictive in that it allows -all classwide constructs that do not imply dispatching. -The following example indicates constructs that violate this restriction. +@geindex Little endian -@smallexample -package Pkg is - type T is tagged record - Data : Natural; - end record; - procedure P (X : T); +@geindex Default_Bit_Order - type DT is new T with record - More_Data : Natural; - end record; - procedure Q (X : DT); -end Pkg; +@cite{Standard'Default_Bit_Order} (@cite{Standard} is the only +permissible prefix), provides the value @cite{System.Default_Bit_Order} +as a @cite{Pos} value (0 for @cite{High_Order_First}, 1 for +@cite{Low_Order_First}). This is used to construct the definition of +@cite{Default_Bit_Order} in package @cite{System}. -with Pkg; use Pkg; -procedure Example is - procedure Test (O : T'Class) is - N : Natural := O'Size;-- Error: Dispatching call - C : T'Class := O; -- Error: implicit Dispatching Call - begin - if O in DT'Class then -- OK : Membership test - Q (DT (O)); -- OK : Type conversion plus direct call - else - P (O); -- Error: Dispatching call - end if; - end Test; +@node Attribute Default_Scalar_Storage_Order,Attribute Descriptor_Size,Attribute Default_Bit_Order,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-default-scalar-storage-order}@anchor{122} +@section Attribute Default_Scalar_Storage_Order - Obj : DT; -begin - P (Obj); -- OK : Direct call - P (T (Obj)); -- OK : Type conversion plus direct call - P (T'Class (Obj)); -- Error: Dispatching call - Test (Obj); -- OK : Type conversion +@geindex Big endian - if Obj in T'Class then -- OK : Membership test - null; - end if; -end Example; -@end smallexample +@geindex Little endian -@node No_Dynamic_Attachment -@unnumberedsubsec No_Dynamic_Attachment -@findex No_Dynamic_Attachment -[RM D.7] This restriction ensures that there is no call to any of the -operations defined in package Ada.Interrupts -(Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler, -Detach_Handler, and Reference). +@geindex Default_Scalar_Storage_Order -@findex No_Dynamic_Interrupts -The restriction @code{No_Dynamic_Interrupts} is recognized as a -synonym for @code{No_Dynamic_Attachment}. This is retained for historical -compatibility purposes (and a warning will be generated for its use if -warnings on obsolescent features are activated). +@cite{Standard'Default_Scalar_Storage_Order} (@cite{Standard} is the only +permissible prefix), provides the current value of the default scalar storage +order (as specified using pragma @cite{Default_Scalar_Storage_Order}, or +equal to @cite{Default_Bit_Order} if unspecified) as a +@cite{System.Bit_Order} value. This is a static attribute. -@node No_Dynamic_Priorities -@unnumberedsubsec No_Dynamic_Priorities -@findex No_Dynamic_Priorities -[RM D.7] There are no semantic dependencies on the package Dynamic_Priorities. +@node Attribute Descriptor_Size,Attribute Elaborated,Attribute Default_Scalar_Storage_Order,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-descriptor-size}@anchor{123} +@section Attribute Descriptor_Size -@node No_Entry_Calls_In_Elaboration_Code -@unnumberedsubsec No_Entry_Calls_In_Elaboration_Code -@findex No_Entry_Calls_In_Elaboration_Code -[GNAT] This restriction ensures at compile time that no task or protected entry -calls are made during elaboration code. As a result of the use of this -restriction, the compiler can assume that no code past an accept statement -in a task can be executed at elaboration time. -@node No_Enumeration_Maps -@unnumberedsubsec No_Enumeration_Maps -@findex No_Enumeration_Maps -[GNAT] This restriction ensures at compile time that no operations requiring -enumeration maps are used (that is Image and Value attributes applied -to enumeration types). +@geindex Descriptor -@node No_Exception_Handlers -@unnumberedsubsec No_Exception_Handlers -@findex No_Exception_Handlers -[GNAT] This restriction ensures at compile time that there are no explicit -exception handlers. It also indicates that no exception propagation will -be provided. In this mode, exceptions may be raised but will result in -an immediate call to the last chance handler, a routine that the user -must define with the following profile: +@geindex Dope vector -@smallexample @c ada -procedure Last_Chance_Handler - (Source_Location : System.Address; Line : Integer); -pragma Export (C, Last_Chance_Handler, - "__gnat_last_chance_handler"); -@end smallexample +@geindex Descriptor_Size -The parameter is a C null-terminated string representing a message to be -associated with the exception (typically the source location of the raise -statement generated by the compiler). The Line parameter when nonzero -represents the line number in the source program where the raise occurs. +Non-static attribute @cite{Descriptor_Size} returns the size in bits of the +descriptor allocated for a type. The result is non-zero only for unconstrained +array types and the returned value is of type universal integer. In GNAT, an +array descriptor contains bounds information and is located immediately before +the first element of the array. -@node No_Exception_Propagation -@unnumberedsubsec No_Exception_Propagation -@findex No_Exception_Propagation -[GNAT] This restriction guarantees that exceptions are never propagated -to an outer subprogram scope. The only case in which an exception may -be raised is when the handler is statically in the same subprogram, so -that the effect of a raise is essentially like a goto statement. Any -other raise statement (implicit or explicit) will be considered -unhandled. Exception handlers are allowed, but may not contain an -exception occurrence identifier (exception choice). In addition, use of -the package GNAT.Current_Exception is not permitted, and reraise -statements (raise with no operand) are not permitted. +@example +type Unconstr_Array is array (Positive range <>) of Boolean; +Put_Line ("Descriptor size = " & Unconstr_Array'Descriptor_Size'Img); +@end example -@node No_Exception_Registration -@unnumberedsubsec No_Exception_Registration -@findex No_Exception_Registration -[GNAT] This restriction ensures at compile time that no stream operations for -types Exception_Id or Exception_Occurrence are used. This also makes it -impossible to pass exceptions to or from a partition with this restriction -in a distributed environment. If this restriction is active, the generated -code is simplified by omitting the otherwise-required global registration -of exceptions when they are declared. +The attribute takes into account any additional padding due to type alignment. +In the example above, the descriptor contains two values of type +@cite{Positive} representing the low and high bound. Since @cite{Positive} has +a size of 31 bits and an alignment of 4, the descriptor size is @cite{2 * Positive'Size + 2} or 64 bits. -@node No_Exceptions -@unnumberedsubsec No_Exceptions -@findex No_Exceptions -[RM H.4] This restriction ensures at compile time that there are no -raise statements and no exception handlers. +@node Attribute Elaborated,Attribute Elab_Body,Attribute Descriptor_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-elaborated}@anchor{124} +@section Attribute Elaborated -@node No_Finalization -@unnumberedsubsec No_Finalization -@findex No_Finalization -[GNAT] This restriction disables the language features described in -chapter 7.6 of the Ada 2005 RM as well as all form of code generation -performed by the compiler to support these features. The following types -are no longer considered controlled when this restriction is in effect: -@itemize @bullet -@item -@code{Ada.Finalization.Controlled} -@item -@code{Ada.Finalization.Limited_Controlled} -@item -Derivations from @code{Controlled} or @code{Limited_Controlled} -@item -Class-wide types -@item -Protected types -@item -Task types -@item -Array and record types with controlled components -@end itemize -The compiler no longer generates code to initialize, finalize or adjust an -object or a nested component, either declared on the stack or on the heap. The -deallocation of a controlled object no longer finalizes its contents. - -@node No_Fixed_Point -@unnumberedsubsec No_Fixed_Point -@findex No_Fixed_Point -[RM H.4] This restriction ensures at compile time that there are no -occurrences of fixed point types and operations. -@node No_Floating_Point -@unnumberedsubsec No_Floating_Point -@findex No_Floating_Point -[RM H.4] This restriction ensures at compile time that there are no -occurrences of floating point types and operations. +@geindex Elaborated -@node No_Implicit_Conditionals -@unnumberedsubsec No_Implicit_Conditionals -@findex No_Implicit_Conditionals -[GNAT] This restriction ensures that the generated code does not contain any -implicit conditionals, either by modifying the generated code where possible, -or by rejecting any construct that would otherwise generate an implicit -conditional. Note that this check does not include run time constraint -checks, which on some targets may generate implicit conditionals as -well. To control the latter, constraint checks can be suppressed in the -normal manner. Constructs generating implicit conditionals include comparisons -of composite objects and the Max/Min attributes. +The prefix of the @cite{'Elaborated} attribute must be a unit name. The +value is a Boolean which indicates whether or not the given unit has been +elaborated. This attribute is primarily intended for internal use by the +generated code for dynamic elaboration checking, but it can also be used +in user programs. The value will always be True once elaboration of all +units has been completed. An exception is for units which need no +elaboration, the value is always False for such units. -@node No_Implicit_Dynamic_Code -@unnumberedsubsec No_Implicit_Dynamic_Code -@findex No_Implicit_Dynamic_Code -@cindex trampoline -[GNAT] This restriction prevents the compiler from building ``trampolines''. -This is a structure that is built on the stack and contains dynamic -code to be executed at run time. On some targets, a trampoline is -built for the following features: @code{Access}, -@code{Unrestricted_Access}, or @code{Address} of a nested subprogram; -nested task bodies; primitive operations of nested tagged types. -Trampolines do not work on machines that prevent execution of stack -data. For example, on windows systems, enabling DEP (data execution -protection) will cause trampolines to raise an exception. -Trampolines are also quite slow at run time. +@node Attribute Elab_Body,Attribute Elab_Spec,Attribute Elaborated,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-elab-body}@anchor{125} +@section Attribute Elab_Body -On many targets, trampolines have been largely eliminated. Look at the -version of system.ads for your target --- if it has -Always_Compatible_Rep equal to False, then trampolines are largely -eliminated. In particular, a trampoline is built for the following -features: @code{Address} of a nested subprogram; -@code{Access} or @code{Unrestricted_Access} of a nested subprogram, -but only if pragma Favor_Top_Level applies, or the access type has a -foreign-language convention; primitive operations of nested tagged -types. -@node No_Implicit_Heap_Allocations -@unnumberedsubsec No_Implicit_Heap_Allocations -@findex No_Implicit_Heap_Allocations -[RM D.7] No constructs are allowed to cause implicit heap allocation. +@geindex Elab_Body -@node No_Implicit_Loops -@unnumberedsubsec No_Implicit_Loops -@findex No_Implicit_Loops -[GNAT] This restriction ensures that the generated code does not contain any -implicit @code{for} loops, either by modifying -the generated code where possible, -or by rejecting any construct that would otherwise generate an implicit -@code{for} loop. If this restriction is active, it is possible to build -large array aggregates with all static components without generating an -intermediate temporary, and without generating a loop to initialize individual -components. Otherwise, a loop is created for arrays larger than about 5000 -scalar components. +This attribute can only be applied to a program unit name. It returns +the entity for the corresponding elaboration procedure for elaborating +the body of the referenced unit. This is used in the main generated +elaboration procedure by the binder and is not normally used in any +other context. However, there may be specialized situations in which it +is useful to be able to call this elaboration procedure from Ada code, +e.g., if it is necessary to do selective re-elaboration to fix some +error. -@node No_Initialize_Scalars -@unnumberedsubsec No_Initialize_Scalars -@findex No_Initialize_Scalars -[GNAT] This restriction ensures that no unit in the partition is compiled with -pragma Initialize_Scalars. This allows the generation of more efficient -code, and in particular eliminates dummy null initialization routines that -are otherwise generated for some record and array types. +@node Attribute Elab_Spec,Attribute Elab_Subp_Body,Attribute Elab_Body,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-elab-spec}@anchor{126} +@section Attribute Elab_Spec -@node No_IO -@unnumberedsubsec No_IO -@findex No_IO -[RM H.4] This restriction ensures at compile time that there are no -dependences on any of the library units Sequential_IO, Direct_IO, -Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO. -@node No_Local_Allocators -@unnumberedsubsec No_Local_Allocators -@findex No_Local_Allocators -[RM H.4] This restriction ensures at compile time that there are no -occurrences of an allocator in subprograms, generic subprograms, tasks, -and entry bodies. +@geindex Elab_Spec -@node No_Local_Protected_Objects -@unnumberedsubsec No_Local_Protected_Objects -@findex No_Local_Protected_Objects -[RM D.7] This restriction ensures at compile time that protected objects are -only declared at the library level. +This attribute can only be applied to a program unit name. It returns +the entity for the corresponding elaboration procedure for elaborating +the spec of the referenced unit. This is used in the main +generated elaboration procedure by the binder and is not normally used +in any other context. However, there may be specialized situations in +which it is useful to be able to call this elaboration procedure from +Ada code, e.g., if it is necessary to do selective re-elaboration to fix +some error. -@node No_Local_Timing_Events -@unnumberedsubsec No_Local_Timing_Events -@findex No_Local_Timing_Events -[RM D.7] All objects of type Ada.Timing_Events.Timing_Event are -declared at the library level. +@node Attribute Elab_Subp_Body,Attribute Emax,Attribute Elab_Spec,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-elab-subp-body}@anchor{127} +@section Attribute Elab_Subp_Body -@node No_Long_Long_Integers -@unnumberedsubsec No_Long_Long_Integers -@findex No_Long_Long_Integers -[GNAT] This partition-wide restriction forbids any explicit reference to -type Standard.Long_Long_Integer, and also forbids declaring range types whose -implicit base type is Long_Long_Integer, and modular types whose size exceeds -Long_Integer'Size. -@node No_Multiple_Elaboration -@unnumberedsubsec No_Multiple_Elaboration -@findex No_Multiple_Elaboration -[GNAT] Normally each package contains a 16-bit counter used to check for access -before elaboration, and to control multiple elaboration attempts. -This counter is eliminated for units compiled with the static model -of elaboration if restriction @code{No_Elaboration_Code} -is active but because of -the need to check for multiple elaboration in the general case, these -counters cannot be eliminated if elaboration code may be present. The -restriction @code{No_Multiple_Elaboration} -allows suppression of these counters -in static elaboration units even if they do have elaboration code. If this -restriction is used, then the situations in which multiple elaboration is -possible, including non-Ada main programs, and Stand Alone libraries, are not -permitted, and will be diagnosed by the binder. +@geindex Elab_Subp_Body -@node No_Nested_Finalization -@unnumberedsubsec No_Nested_Finalization -@findex No_Nested_Finalization -[RM D.7] All objects requiring finalization are declared at the library level. +This attribute can only be applied to a library level subprogram +name and is only allowed in CodePeer mode. It returns the entity +for the corresponding elaboration procedure for elaborating the body +of the referenced subprogram unit. This is used in the main generated +elaboration procedure by the binder in CodePeer mode only and is unrecognized +otherwise. -@node No_Protected_Type_Allocators -@unnumberedsubsec No_Protected_Type_Allocators -@findex No_Protected_Type_Allocators -[RM D.7] This restriction ensures at compile time that there are no allocator -expressions that attempt to allocate protected objects. +@node Attribute Emax,Attribute Enabled,Attribute Elab_Subp_Body,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-emax}@anchor{128} +@section Attribute Emax -@node No_Protected_Types -@unnumberedsubsec No_Protected_Types -@findex No_Protected_Types -[RM H.4] This restriction ensures at compile time that there are no -declarations of protected types or protected objects. -@node No_Recursion -@unnumberedsubsec No_Recursion -@findex No_Recursion -[RM H.4] A program execution is erroneous if a subprogram is invoked as -part of its execution. +@geindex Ada 83 attributes -@node No_Reentrancy -@unnumberedsubsec No_Reentrancy -@findex No_Reentrancy -[RM H.4] A program execution is erroneous if a subprogram is executed by -two tasks at the same time. +@geindex Emax -@node No_Relative_Delay -@unnumberedsubsec No_Relative_Delay -@findex No_Relative_Delay -[RM D.7] This restriction ensures at compile time that there are no delay -relative statements and prevents expressions such as @code{delay 1.23;} from -appearing in source code. +The @cite{Emax} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@node No_Requeue_Statements -@unnumberedsubsec No_Requeue_Statements -@findex No_Requeue_Statements -[RM D.7] This restriction ensures at compile time that no requeue statements -are permitted and prevents keyword @code{requeue} from being used in source -code. +@node Attribute Enabled,Attribute Enum_Rep,Attribute Emax,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-enabled}@anchor{129} +@section Attribute Enabled -@findex No_Requeue -The restriction @code{No_Requeue} is recognized as a -synonym for @code{No_Requeue_Statements}. This is retained for historical -compatibility purposes (and a warning will be generated for its use if -warnings on oNobsolescent features are activated). -@node No_Secondary_Stack -@unnumberedsubsec No_Secondary_Stack -@findex No_Secondary_Stack -[GNAT] This restriction ensures at compile time that the generated code -does not contain any reference to the secondary stack. The secondary -stack is used to implement functions returning unconstrained objects -(arrays or records) on some targets. +@geindex Enabled -@node No_Select_Statements -@unnumberedsubsec No_Select_Statements -@findex No_Select_Statements -[RM D.7] This restriction ensures at compile time no select statements of any -kind are permitted, that is the keyword @code{select} may not appear. +The @cite{Enabled} attribute allows an application program to check at compile +time to see if the designated check is currently enabled. The prefix is a +simple identifier, referencing any predefined check name (other than +@cite{All_Checks}) or a check name introduced by pragma Check_Name. If +no argument is given for the attribute, the check is for the general state +of the check, if an argument is given, then it is an entity name, and the +check indicates whether an @cite{Suppress} or @cite{Unsuppress} has been +given naming the entity (if not, then the argument is ignored). -@node No_Specific_Termination_Handlers -@unnumberedsubsec No_Specific_Termination_Handlers -@findex No_Specific_Termination_Handlers -[RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler -or to Ada.Task_Termination.Specific_Handler. +Note that instantiations inherit the check status at the point of the +instantiation, so a useful idiom is to have a library package that +introduces a check name with @cite{pragma Check_Name}, and then contains +generic packages or subprograms which use the @cite{Enabled} attribute +to see if the check is enabled. A user of this package can then issue +a @cite{pragma Suppress} or @cite{pragma Unsuppress} before instantiating +the package or subprogram, controlling whether the check will be present. -@node No_Specification_of_Aspect -@unnumberedsubsec No_Specification_of_Aspect -@findex No_Specification_of_Aspect -[RM 13.12.1] This restriction checks at compile time that no aspect -specification, attribute definition clause, or pragma is given for a -given aspect. +@node Attribute Enum_Rep,Attribute Enum_Val,Attribute Enabled,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-enum-rep}@anchor{12a} +@section Attribute Enum_Rep -@node No_Standard_Allocators_After_Elaboration -@unnumberedsubsec No_Standard_Allocators_After_Elaboration -@findex No_Standard_Allocators_After_Elaboration -[RM D.7] Specifies that an allocator using a standard storage pool -should never be evaluated at run time after the elaboration of the -library items of the partition has completed. Otherwise, Storage_Error -is raised. -@node No_Standard_Storage_Pools -@unnumberedsubsec No_Standard_Storage_Pools -@findex No_Standard_Storage_Pools -[GNAT] This restriction ensures at compile time that no access types -use the standard default storage pool. Any access type declared must -have an explicit Storage_Pool attribute defined specifying a -user-defined storage pool. +@geindex Representation of enums -@node No_Stream_Optimizations -@unnumberedsubsec No_Stream_Optimizations -@findex No_Stream_Optimizations -[GNAT] This restriction affects the performance of stream operations on types -@code{String}, @code{Wide_String} and @code{Wide_Wide_String}. By default, the -compiler uses block reads and writes when manipulating @code{String} objects -due to their supperior performance. When this restriction is in effect, the -compiler performs all IO operations on a per-character basis. +@geindex Enum_Rep -@node No_Streams -@unnumberedsubsec No_Streams -@findex No_Streams -[GNAT] This restriction ensures at compile/bind time that there are no -stream objects created and no use of stream attributes. -This restriction does not forbid dependences on the package -@code{Ada.Streams}. So it is permissible to with -@code{Ada.Streams} (or another package that does so itself) -as long as no actual stream objects are created and no -stream attributes are used. +For every enumeration subtype @cite{S}, @code{S'Enum_Rep} denotes a +function with the following spec: -Note that the use of restriction allows optimization of tagged types, -since they do not need to worry about dispatching stream operations. -To take maximum advantage of this space-saving optimization, any -unit declaring a tagged type should be compiled with the restriction, -though this is not required. +@example +function S'Enum_Rep (Arg : S'Base) return ; +@end example -@node No_Task_Allocators -@unnumberedsubsec No_Task_Allocators -@findex No_Task_Allocators -[RM D.7] There are no allocators for task types -or types containing task subcomponents. +It is also allowable to apply @cite{Enum_Rep} directly to an object of an +enumeration type or to a non-overloaded enumeration +literal. In this case @code{S'Enum_Rep} is equivalent to +@code{typ'Enum_Rep(S)} where @cite{typ} is the type of the +enumeration literal or object. -@node No_Task_Attributes_Package -@unnumberedsubsec No_Task_Attributes_Package -@findex No_Task_Attributes_Package -[GNAT] This restriction ensures at compile time that there are no implicit or -explicit dependencies on the package @code{Ada.Task_Attributes}. +The function returns the representation value for the given enumeration +value. This will be equal to value of the @cite{Pos} attribute in the +absence of an enumeration representation clause. This is a static +attribute (i.e.,:the result is static if the argument is static). -@findex No_Task_Attributes -The restriction @code{No_Task_Attributes} is recognized as a synonym -for @code{No_Task_Attributes_Package}. This is retained for historical -compatibility purposes (and a warning will be generated for its use if -warnings on obsolescent features are activated). +@code{S'Enum_Rep} can also be used with integer types and objects, +in which case it simply returns the integer value. The reason for this +is to allow it to be used for @cite{(<>)} discrete formal arguments in +a generic unit that can be instantiated with either enumeration types +or integer types. Note that if @cite{Enum_Rep} is used on a modular +type whose upper bound exceeds the upper bound of the largest signed +integer type, and the argument is a variable, so that the universal +integer calculation is done at run time, then the call to @cite{Enum_Rep} +may raise @cite{Constraint_Error}. -@node No_Task_Hierarchy -@unnumberedsubsec No_Task_Hierarchy -@findex No_Task_Hierarchy -[RM D.7] All (non-environment) tasks depend -directly on the environment task of the partition. +@node Attribute Enum_Val,Attribute Epsilon,Attribute Enum_Rep,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-enum-val}@anchor{12b} +@section Attribute Enum_Val -@node No_Task_Termination -@unnumberedsubsec No_Task_Termination -@findex No_Task_Termination -[RM D.7] Tasks that terminate are erroneous. -@node No_Tasking -@unnumberedsubsec No_Tasking -@findex No_Tasking -[GNAT] This restriction prevents the declaration of tasks or task types -throughout the partition. It is similar in effect to the use of -@code{Max_Tasks => 0} except that violations are caught at compile time -and cause an error message to be output either by the compiler or -binder. +@geindex Representation of enums -@node No_Terminate_Alternatives -@unnumberedsubsec No_Terminate_Alternatives -@findex No_Terminate_Alternatives -[RM D.7] There are no selective accepts with terminate alternatives. +@geindex Enum_Val -@node No_Unchecked_Access -@unnumberedsubsec No_Unchecked_Access -@findex No_Unchecked_Access -[RM H.4] This restriction ensures at compile time that there are no -occurrences of the Unchecked_Access attribute. +For every enumeration subtype @cite{S}, @code{S'Enum_Val} denotes a +function with the following spec: -@node Simple_Barriers -@unnumberedsubsec Simple_Barriers -@findex Simple_Barriers -[RM D.7] This restriction ensures at compile time that barriers in entry -declarations for protected types are restricted to either static boolean -expressions or references to simple boolean variables defined in the private -part of the protected type. No other form of entry barriers is permitted. +@example +function S'Enum_Val (Arg : ) return S'Base; +@end example -@findex Boolean_Entry_Barriers -The restriction @code{Boolean_Entry_Barriers} is recognized as a -synonym for @code{Simple_Barriers}. This is retained for historical -compatibility purposes (and a warning will be generated for its use if -warnings on obsolescent features are activated). +The function returns the enumeration value whose representation matches the +argument, or raises Constraint_Error if no enumeration literal of the type +has the matching value. +This will be equal to value of the @cite{Val} attribute in the +absence of an enumeration representation clause. This is a static +attribute (i.e., the result is static if the argument is static). -@node Static_Priorities -@unnumberedsubsec Static_Priorities -@findex Static_Priorities -[GNAT] This restriction ensures at compile time that all priority expressions -are static, and that there are no dependences on the package -@code{Ada.Dynamic_Priorities}. +@node Attribute Epsilon,Attribute Fast_Math,Attribute Enum_Val,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-epsilon}@anchor{12c} +@section Attribute Epsilon -@node Static_Storage_Size -@unnumberedsubsec Static_Storage_Size -@findex Static_Storage_Size -[GNAT] This restriction ensures at compile time that any expression appearing -in a Storage_Size pragma or attribute definition clause is static. -@node Program Unit Level Restrictions -@section Program Unit Level Restrictions +@geindex Ada 83 attributes -@noindent -The second set of restriction identifiers -does not require partition-wide consistency. -The restriction may be enforced for a single -compilation unit without any effect on any of the -other compilation units in the partition. +@geindex Epsilon -@menu -* No_Elaboration_Code:: -* No_Entry_Queue:: -* No_Implementation_Aspect_Specifications:: -* No_Implementation_Attributes:: -* No_Implementation_Identifiers:: -* No_Implementation_Pragmas:: -* No_Implementation_Restrictions:: -* No_Implementation_Units:: -* No_Implicit_Aliasing:: -* No_Obsolescent_Features:: -* No_Wide_Characters:: -* SPARK_05:: -@end menu +The @cite{Epsilon} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@node No_Elaboration_Code -@unnumberedsubsec No_Elaboration_Code -@findex No_Elaboration_Code -[GNAT] This restriction ensures at compile time that no elaboration code is -generated. Note that this is not the same condition as is enforced -by pragma @code{Preelaborate}. There are cases in which pragma -@code{Preelaborate} still permits code to be generated (e.g.@: code -to initialize a large array to all zeroes), and there are cases of units -which do not meet the requirements for pragma @code{Preelaborate}, -but for which no elaboration code is generated. Generally, it is -the case that preelaborable units will meet the restrictions, with -the exception of large aggregates initialized with an others_clause, -and exception declarations (which generate calls to a run-time -registry procedure). This restriction is enforced on -a unit by unit basis, it need not be obeyed consistently -throughout a partition. +@node Attribute Fast_Math,Attribute Fixed_Value,Attribute Epsilon,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-fast-math}@anchor{12d} +@section Attribute Fast_Math -In the case of aggregates with others, if the aggregate has a dynamic -size, there is no way to eliminate the elaboration code (such dynamic -bounds would be incompatible with @code{Preelaborate} in any case). If -the bounds are static, then use of this restriction actually modifies -the code choice of the compiler to avoid generating a loop, and instead -generate the aggregate statically if possible, no matter how many times -the data for the others clause must be repeatedly generated. -It is not possible to precisely document -the constructs which are compatible with this restriction, since, -unlike most other restrictions, this is not a restriction on the -source code, but a restriction on the generated object code. For -example, if the source contains a declaration: +@geindex Fast_Math -@smallexample - Val : constant Integer := X; -@end smallexample +@cite{Standard'Fast_Math} (@cite{Standard} is the only allowed +prefix) yields a static Boolean value that is True if pragma +@cite{Fast_Math} is active, and False otherwise. -@noindent -where X is not a static constant, it may be possible, depending -on complex optimization circuitry, for the compiler to figure -out the value of X at compile time, in which case this initialization -can be done by the loader, and requires no initialization code. It -is not possible to document the precise conditions under which the -optimizer can figure this out. +@node Attribute Fixed_Value,Attribute From_Any,Attribute Fast_Math,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-fixed-value}@anchor{12e} +@section Attribute Fixed_Value -Note that this the implementation of this restriction requires full -code generation. If it is used in conjunction with "semantics only" -checking, then some cases of violations may be missed. -@node No_Entry_Queue -@unnumberedsubsec No_Entry_Queue -@findex No_Entry_Queue -[GNAT] This restriction is a declaration that any protected entry compiled in -the scope of the restriction has at most one task waiting on the entry -at any one time, and so no queue is required. This restriction is not -checked at compile time. A program execution is erroneous if an attempt -is made to queue a second task on such an entry. +@geindex Fixed_Value -@node No_Implementation_Aspect_Specifications -@unnumberedsubsec No_Implementation_Aspect_Specifications -@findex No_Implementation_Aspect_Specifications -[RM 13.12.1] This restriction checks at compile time that no -GNAT-defined aspects are present. With this restriction, the only -aspects that can be used are those defined in the Ada Reference Manual. +For every fixed-point type @cite{S}, @code{S'Fixed_Value} denotes a +function with the following specification: -@node No_Implementation_Attributes -@unnumberedsubsec No_Implementation_Attributes -@findex No_Implementation_Attributes -[RM 13.12.1] This restriction checks at compile time that no -GNAT-defined attributes are present. With this restriction, the only -attributes that can be used are those defined in the Ada Reference -Manual. +@example +function S'Fixed_Value (Arg : ) return S; +@end example -@node No_Implementation_Identifiers -@unnumberedsubsec No_Implementation_Identifiers -@findex No_Implementation_Identifiers -[RM 13.12.1] This restriction checks at compile time that no -implementation-defined identifiers (marked with pragma Implementation_Defined) -occur within language-defined packages. +The value returned is the fixed-point value @cite{V} such that: -@node No_Implementation_Pragmas -@unnumberedsubsec No_Implementation_Pragmas -@findex No_Implementation_Pragmas -[RM 13.12.1] This restriction checks at compile time that no -GNAT-defined pragmas are present. With this restriction, the only -pragmas that can be used are those defined in the Ada Reference Manual. +@example +V = Arg * S'Small +@end example -@node No_Implementation_Restrictions -@unnumberedsubsec No_Implementation_Restrictions -@findex No_Implementation_Restrictions -[GNAT] This restriction checks at compile time that no GNAT-defined restriction -identifiers (other than @code{No_Implementation_Restrictions} itself) -are present. With this restriction, the only other restriction identifiers -that can be used are those defined in the Ada Reference Manual. +The effect is thus similar to first converting the argument to the +integer type used to represent @cite{S}, and then doing an unchecked +conversion to the fixed-point type. The difference is +that there are full range checks, to ensure that the result is in range. +This attribute is primarily intended for use in implementation of the +input-output functions for fixed-point values. -@node No_Implementation_Units -@unnumberedsubsec No_Implementation_Units -@findex No_Implementation_Units -[RM 13.12.1] This restriction checks at compile time that there is no -mention in the context clause of any implementation-defined descendants -of packages Ada, Interfaces, or System. +@node Attribute From_Any,Attribute Has_Access_Values,Attribute Fixed_Value,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-from-any}@anchor{12f} +@section Attribute From_Any -@node No_Implicit_Aliasing -@unnumberedsubsec No_Implicit_Aliasing -@findex No_Implicit_Aliasing -[GNAT] This restriction, which is not required to be partition-wide consistent, -requires an explicit aliased keyword for an object to which 'Access, -'Unchecked_Access, or 'Address is applied, and forbids entirely the use of -the 'Unrestricted_Access attribute for objects. Note: the reason that -Unrestricted_Access is forbidden is that it would require the prefix -to be aliased, and in such cases, it can always be replaced by -the standard attribute Unchecked_Access which is preferable. -@node No_Obsolescent_Features -@unnumberedsubsec No_Obsolescent_Features -@findex No_Obsolescent_Features -[RM 13.12.1] This restriction checks at compile time that no obsolescent -features are used, as defined in Annex J of the Ada Reference Manual. +@geindex From_Any -@node No_Wide_Characters -@unnumberedsubsec No_Wide_Characters -@findex No_Wide_Characters -[GNAT] This restriction ensures at compile time that no uses of the types -@code{Wide_Character} or @code{Wide_String} or corresponding wide -wide types -appear, and that no wide or wide wide string or character literals -appear in the program (that is literals representing characters not in -type @code{Character}). +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. -@node SPARK_05 -@unnumberedsubsec SPARK_05 -@findex SPARK_05 -[GNAT] This restriction checks at compile time that some constructs -forbidden in SPARK 2005 are not present. Error messages related to -SPARK restriction have the form: +@node Attribute Has_Access_Values,Attribute Has_Discriminants,Attribute From_Any,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-has-access-values}@anchor{130} +@section Attribute Has_Access_Values -@smallexample -violation of restriction "SPARK_05" at - -@end smallexample -@findex SPARK -The restriction @code{SPARK} is recognized as a -synonym for @code{SPARK_05}. This is retained for historical -compatibility purposes (and an unconditional warning will be generated -for its use, advising replacement by @code{SPARK}). +@geindex Access values +@geindex testing for -This is not a replacement for the semantic checks performed by the -SPARK Examiner tool, as the compiler currently only deals with code, -not SPARK 2005 annotations, and does not guarantee catching all -cases of constructs forbidden by SPARK 2005. +@geindex Has_Access_Values -Thus it may well be the case that code which passes the compiler with -the SPARK restriction is rejected by the SPARK Examiner, e.g. due to -the different visibility rules of the Examiner based on SPARK 2005 -@code{inherit} annotations. +The prefix of the @cite{Has_Access_Values} attribute is a type. The result +is a Boolean value which is True if the is an access type, or is a composite +type with a component (at any nesting depth) that is an access type, and is +False otherwise. +The intended use of this attribute is in conjunction with generic +definitions. If the attribute is applied to a generic private type, it +indicates whether or not the corresponding actual type has access values. -This restriction can be useful in providing an initial filter for code -developed using SPARK 2005, or in examining legacy code to see how far -it is from meeting SPARK restrictions. +@node Attribute Has_Discriminants,Attribute Img,Attribute Has_Access_Values,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-has-discriminants}@anchor{131} +@section Attribute Has_Discriminants -The list below summarizes the checks that are performed when this -restriction is in force: -@itemize @bullet -@item No block statements -@item No case statements with only an others clause -@item Exit statements in loops must respect the SPARK 2005 language restrictions -@item No goto statements -@item Return can only appear as last statement in function -@item Function must have return statement -@item Loop parameter specification must include subtype mark -@item Prefix of expanded name cannot be a loop statement -@item Abstract subprogram not allowed -@item User-defined operators not allowed -@item Access type parameters not allowed -@item Default expressions for parameters not allowed -@item Default expressions for record fields not allowed -@item No tasking constructs allowed -@item Label needed at end of subprograms and packages -@item No mixing of positional and named parameter association -@item No access types as result type -@item No unconstrained arrays as result types -@item No null procedures -@item Initial and later declarations must be in correct order (declaration can't come after body) -@item No attributes on private types if full declaration not visible -@item No package declaration within package specification -@item No controlled types -@item No discriminant types -@item No overloading -@item Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed) -@item Access attribute not allowed -@item Allocator not allowed -@item Result of catenation must be String -@item Operands of catenation must be string literal, static char or another catenation -@item No conditional expressions -@item No explicit dereference -@item Quantified expression not allowed -@item Slicing not allowed -@item No exception renaming -@item No generic renaming -@item No object renaming -@item No use clause -@item Aggregates must be qualified -@item Non-static choice in array aggregates not allowed -@item The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type -@item No mixing of positional and named association in aggregate, no multi choice -@item AND, OR and XOR for arrays only allowed when operands have same static bounds -@item Fixed point operands to * or / must be qualified or converted -@item Comparison operators not allowed for Booleans or arrays (except strings) -@item Equality not allowed for arrays with non-matching static bounds (except strings) -@item Conversion / qualification not allowed for arrays with non-matching static bounds -@item Subprogram declaration only allowed in package spec (unless followed by import) -@item Access types not allowed -@item Incomplete type declaration not allowed -@item Object and subtype declarations must respect SPARK restrictions -@item Digits or delta constraint not allowed -@item Decimal fixed point type not allowed -@item Aliasing of objects not allowed -@item Modular type modulus must be power of 2 -@item Base not allowed on subtype mark -@item Unary operators not allowed on modular types (except not) -@item Untagged record cannot be null -@item No class-wide operations -@item Initialization expressions must respect SPARK restrictions -@item Non-static ranges not allowed except in iteration schemes -@item String subtypes must have lower bound of 1 -@item Subtype of Boolean cannot have constraint -@item At most one tagged type or extension per package -@item Interface is not allowed -@item Character literal cannot be prefixed (selector name cannot be character literal) -@item Record aggregate cannot contain 'others' -@item Component association in record aggregate must contain a single choice -@item Ancestor part cannot be a type mark -@item Attributes 'Image, 'Width and 'Value not allowed -@item Functions may not update globals -@item Subprograms may not contain direct calls to themselves (prevents recursion within unit) -@item Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit) -@end itemize -The following restrictions are enforced, but note that they are actually more -strict that the latest SPARK 2005 language definition: +@geindex Discriminants +@geindex testing for -@itemize @bullet -@item No derived types other than tagged type extensions -@item Subtype of unconstrained array must have constraint -@end itemize +@geindex Has_Discriminants -This list summarises the main SPARK 2005 language rules that are not -currently checked by the SPARK_05 restriction: +The prefix of the @cite{Has_Discriminants} attribute is a type. The result +is a Boolean value which is True if the type has discriminants, and False +otherwise. The intended use of this attribute is in conjunction with generic +definitions. If the attribute is applied to a generic private type, it +indicates whether or not the corresponding actual type has discriminants. -@itemize @bullet -@item SPARK annotations are treated as comments so are not checked at all -@item Based real literals not allowed -@item Objects cannot be initialized at declaration by calls to user-defined functions -@item Objects cannot be initialized at declaration by assignments from variables -@item Objects cannot be initialized at declaration by assignments from indexed/selected components -@item Ranges shall not be null -@item A fixed point delta expression must be a simple expression -@item Restrictions on where renaming declarations may be placed -@item Externals of mode 'out' cannot be referenced -@item Externals of mode 'in' cannot be updated -@item Loop with no iteration scheme or exits only allowed as last statement in main program or task -@item Subprogram cannot have parent unit name -@item SPARK 2005 inherited subprogram must be prefixed with overriding -@item External variables (or functions that reference them) may not be passed as actual parameters -@item Globals must be explicitly mentioned in contract -@item Deferred constants cannot be completed by pragma Import -@item Package initialization cannot read/write variables from other packages -@item Prefix not allowed for entities that are directly visible -@item Identifier declaration can't override inherited package name -@item Cannot use Standard or other predefined packages as identifiers -@item After renaming, cannot use the original name -@item Subprograms can only be renamed to remove package prefix -@item Pragma import must be immediately after entity it names -@item No mutual recursion between multiple units (this can be checked with gnatcheck) -@end itemize +@node Attribute Img,Attribute Integer_Value,Attribute Has_Discriminants,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-img}@anchor{132} +@section Attribute Img -Note that if a unit is compiled in Ada 95 mode with the SPARK restriction, -violations will be reported for constructs forbidden in SPARK 95, -instead of SPARK 2005. -@c ------------------------ -@node Implementation Advice -@chapter Implementation Advice -@noindent -The main text of the Ada Reference Manual describes the required -behavior of all Ada compilers, and the GNAT compiler conforms to -these requirements. +@geindex Img -In addition, there are sections throughout the Ada Reference Manual headed -by the phrase ``Implementation advice''. These sections are not normative, -i.e., they do not specify requirements that all compilers must -follow. Rather they provide advice on generally desirable behavior. You -may wonder why they are not requirements. The most typical answer is -that they describe behavior that seems generally desirable, but cannot -be provided on all systems, or which may be undesirable on some systems. - -As far as practical, GNAT follows the implementation advice sections in -the Ada Reference Manual. This chapter contains a table giving the -reference manual section number, paragraph number and several keywords -for each advice. Each entry consists of the text of the advice followed -by the GNAT interpretation of this advice. Most often, this simply says -``followed'', which means that GNAT follows the advice. However, in a -number of cases, GNAT deliberately deviates from this advice, in which -case the text describes what GNAT does and why. +The @cite{Img} attribute differs from @cite{Image} in that it is applied +directly to an object, and yields the same result as +@cite{Image} for the subtype of the object. This is convenient for +debugging: -@cindex Error detection -@unnumberedsec 1.1.3(20): Error Detection -@sp 1 -@cartouche -If an implementation detects the use of an unsupported Specialized Needs -Annex feature at run time, it should raise @code{Program_Error} if -feasible. -@end cartouche -Not relevant. All specialized needs annex features are either supported, -or diagnosed at compile time. +@example +Put_Line ("X = " & X'Img); +@end example -@cindex Child Units -@unnumberedsec 1.1.3(31): Child Units -@sp 1 -@cartouche -If an implementation wishes to provide implementation-defined -extensions to the functionality of a language-defined library unit, it -should normally do so by adding children to the library unit. -@end cartouche -Followed. +has the same meaning as the more verbose: -@cindex Bounded errors -@unnumberedsec 1.1.5(12): Bounded Errors -@sp 1 -@cartouche -If an implementation detects a bounded error or erroneous -execution, it should raise @code{Program_Error}. -@end cartouche -Followed in all cases in which the implementation detects a bounded -error or erroneous execution. Not all such situations are detected at -runtime. +@example +Put_Line ("X = " & T'Image (X)); +@end example -@cindex Pragmas -@unnumberedsec 2.8(16): Pragmas -@sp 1 -@cartouche -Normally, implementation-defined pragmas should have no semantic effect -for error-free programs; that is, if the implementation-defined pragmas -are removed from a working program, the program should still be legal, -and should still have the same semantics. -@end cartouche -The following implementation defined pragmas are exceptions to this -rule: +where @cite{T} is the (sub)type of the object @cite{X}. -@table @code -@item Abort_Defer -Affects semantics -@item Ada_83 -Affects legality -@item Assert -Affects semantics -@item CPP_Class -Affects semantics -@item CPP_Constructor -Affects semantics -@item Debug -Affects semantics -@item Interface_Name -Affects semantics -@item Machine_Attribute -Affects semantics -@item Unimplemented_Unit -Affects legality -@item Unchecked_Union -Affects semantics -@end table +Note that technically, in analogy to @cite{Image}, +@cite{X'Img} returns a parameterless function +that returns the appropriate string when called. This means that +@cite{X'Img} can be renamed as a function-returning-string, or used +in an instantiation as a function parameter. -@noindent -In each of the above cases, it is essential to the purpose of the pragma -that this advice not be followed. For details see the separate section -on implementation defined pragmas. +@node Attribute Integer_Value,Attribute Invalid_Value,Attribute Img,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-integer-value}@anchor{133} +@section Attribute Integer_Value -@unnumberedsec 2.8(17-19): Pragmas -@sp 1 -@cartouche -Normally, an implementation should not define pragmas that can -make an illegal program legal, except as follows: -@end cartouche -@sp 1 -@cartouche -A pragma used to complete a declaration, such as a pragma @code{Import}; -@end cartouche -@sp 1 -@cartouche -A pragma used to configure the environment by adding, removing, or -replacing @code{library_items}. -@end cartouche -See response to paragraph 16 of this same section. - -@cindex Character Sets -@cindex Alternative Character Sets -@unnumberedsec 3.5.2(5): Alternative Character Sets -@sp 1 -@cartouche -If an implementation supports a mode with alternative interpretations -for @code{Character} and @code{Wide_Character}, the set of graphic -characters of @code{Character} should nevertheless remain a proper -subset of the set of graphic characters of @code{Wide_Character}. Any -character set ``localizations'' should be reflected in the results of -the subprograms defined in the language-defined package -@code{Characters.Handling} (see A.3) available in such a mode. In a mode with -an alternative interpretation of @code{Character}, the implementation should -also support a corresponding change in what is a legal -@code{identifier_letter}. -@end cartouche -Not all wide character modes follow this advice, in particular the JIS -and IEC modes reflect standard usage in Japan, and in these encoding, -the upper half of the Latin-1 set is not part of the wide-character -subset, since the most significant bit is used for wide character -encoding. However, this only applies to the external forms. Internally -there is no such restriction. -@cindex Integer types -@unnumberedsec 3.5.4(28): Integer Types +@geindex Integer_Value -@sp 1 -@cartouche -An implementation should support @code{Long_Integer} in addition to -@code{Integer} if the target machine supports 32-bit (or longer) -arithmetic. No other named integer subtypes are recommended for package -@code{Standard}. Instead, appropriate named integer subtypes should be -provided in the library package @code{Interfaces} (see B.2). -@end cartouche -@code{Long_Integer} is supported. Other standard integer types are supported -so this advice is not fully followed. These types -are supported for convenient interface to C, and so that all hardware -types of the machine are easily available. -@unnumberedsec 3.5.4(29): Integer Types +For every integer type @cite{S}, @code{S'Integer_Value} denotes a +function with the following spec: -@sp 1 -@cartouche -An implementation for a two's complement machine should support -modular types with a binary modulus up to @code{System.Max_Int*2+2}. An -implementation should support a non-binary modules up to @code{Integer'Last}. -@end cartouche -Followed. +@example +function S'Integer_Value (Arg : ) return S; +@end example -@cindex Enumeration values -@unnumberedsec 3.5.5(8): Enumeration Values -@sp 1 -@cartouche -For the evaluation of a call on @code{@var{S}'Pos} for an enumeration -subtype, if the value of the operand does not correspond to the internal -code for any enumeration literal of its type (perhaps due to an -un-initialized variable), then the implementation should raise -@code{Program_Error}. This is particularly important for enumeration -types with noncontiguous internal codes specified by an -enumeration_representation_clause. -@end cartouche -Followed. +The value returned is the integer value @cite{V}, such that: -@cindex Float types -@unnumberedsec 3.5.7(17): Float Types -@sp 1 -@cartouche -An implementation should support @code{Long_Float} in addition to -@code{Float} if the target machine supports 11 or more digits of -precision. No other named floating point subtypes are recommended for -package @code{Standard}. Instead, appropriate named floating point subtypes -should be provided in the library package @code{Interfaces} (see B.2). -@end cartouche -@code{Short_Float} and @code{Long_Long_Float} are also provided. The -former provides improved compatibility with other implementations -supporting this type. The latter corresponds to the highest precision -floating-point type supported by the hardware. On most machines, this -will be the same as @code{Long_Float}, but on some machines, it will -correspond to the IEEE extended form. The notable case is all ia32 -(x86) implementations, where @code{Long_Long_Float} corresponds to -the 80-bit extended precision format supported in hardware on this -processor. Note that the 128-bit format on SPARC is not supported, -since this is a software rather than a hardware format. +@example +Arg = V * T'Small +@end example -@cindex Multidimensional arrays -@cindex Arrays, multidimensional -@unnumberedsec 3.6.2(11): Multidimensional Arrays -@sp 1 -@cartouche -An implementation should normally represent multidimensional arrays in -row-major order, consistent with the notation used for multidimensional -array aggregates (see 4.3.3). However, if a pragma @code{Convention} -(@code{Fortran}, @dots{}) applies to a multidimensional array type, then -column-major order should be used instead (see B.5, ``Interfacing with -Fortran''). -@end cartouche -Followed. +where @cite{T} is the type of @cite{Arg}. +The effect is thus similar to first doing an unchecked conversion from +the fixed-point type to its corresponding implementation type, and then +converting the result to the target integer type. The difference is +that there are full range checks, to ensure that the result is in range. +This attribute is primarily intended for use in implementation of the +standard input-output functions for fixed-point values. -@findex Duration'Small -@unnumberedsec 9.6(30-31): Duration'Small -@sp 1 -@cartouche -Whenever possible in an implementation, the value of @code{Duration'Small} -should be no greater than 100 microseconds. -@end cartouche -Followed. (@code{Duration'Small} = 10**(@minus{}9)). - -@sp 1 -@cartouche -The time base for @code{delay_relative_statements} should be monotonic; -it need not be the same time base as used for @code{Calendar.Clock}. -@end cartouche -Followed. +@node Attribute Invalid_Value,Attribute Iterable,Attribute Integer_Value,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-invalid-value}@anchor{134} +@section Attribute Invalid_Value -@unnumberedsec 10.2.1(12): Consistent Representation -@sp 1 -@cartouche -In an implementation, a type declared in a pre-elaborated package should -have the same representation in every elaboration of a given version of -the package, whether the elaborations occur in distinct executions of -the same program, or in executions of distinct programs or partitions -that include the given version. -@end cartouche -Followed, except in the case of tagged types. Tagged types involve -implicit pointers to a local copy of a dispatch table, and these pointers -have representations which thus depend on a particular elaboration of the -package. It is not easy to see how it would be possible to follow this -advice without severely impacting efficiency of execution. -@cindex Exception information -@unnumberedsec 11.4.1(19): Exception Information -@sp 1 -@cartouche -@code{Exception_Message} by default and @code{Exception_Information} -should produce information useful for -debugging. @code{Exception_Message} should be short, about one -line. @code{Exception_Information} can be long. @code{Exception_Message} -should not include the -@code{Exception_Name}. @code{Exception_Information} should include both -the @code{Exception_Name} and the @code{Exception_Message}. -@end cartouche -Followed. For each exception that doesn't have a specified -@code{Exception_Message}, the compiler generates one containing the location -of the raise statement. This location has the form ``file:line'', where -file is the short file name (without path information) and line is the line -number in the file. Note that in the case of the Zero Cost Exception -mechanism, these messages become redundant with the Exception_Information that -contains a full backtrace of the calling sequence, so they are disabled. -To disable explicitly the generation of the source location message, use the -Pragma @code{Discard_Names}. - -@cindex Suppression of checks -@cindex Checks, suppression of -@unnumberedsec 11.5(28): Suppression of Checks -@sp 1 -@cartouche -The implementation should minimize the code executed for checks that -have been suppressed. -@end cartouche -Followed. +@geindex Invalid_Value -@cindex Representation clauses -@unnumberedsec 13.1 (21-24): Representation Clauses -@sp 1 -@cartouche -The recommended level of support for all representation items is -qualified as follows: -@end cartouche -@sp 1 -@cartouche -An implementation need not support representation items containing -non-static expressions, except that an implementation should support a -representation item for a given entity if each non-static expression in -the representation item is a name that statically denotes a constant -declared before the entity. -@end cartouche -Followed. In fact, GNAT goes beyond the recommended level of support -by allowing nonstatic expressions in some representation clauses even -without the need to declare constants initialized with the values of -such expressions. -For example: +For every scalar type S, S'Invalid_Value returns an undefined value of the +type. If possible this value is an invalid representation for the type. The +value returned is identical to the value used to initialize an otherwise +uninitialized value of the type if pragma Initialize_Scalars is used, +including the ability to modify the value with the binder -Sxx flag and +relevant environment variables at run time. -@smallexample @c ada - X : Integer; - Y : Float; - for Y'Address use X'Address;>> -@end smallexample +@node Attribute Iterable,Attribute Large,Attribute Invalid_Value,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-iterable}@anchor{135} +@section Attribute Iterable -@sp 1 -@cartouche -An implementation need not support a specification for the @code{Size} -for a given composite subtype, nor the size or storage place for an -object (including a component) of a given composite subtype, unless the -constraints on the subtype and its composite subcomponents (if any) are -all static constraints. -@end cartouche -Followed. Size Clauses are not permitted on non-static components, as -described above. -@sp 1 -@cartouche -An aliased component, or a component whose type is by-reference, should -always be allocated at an addressable location. -@end cartouche -Followed. +@geindex Iterable -@cindex Packed types -@unnumberedsec 13.2(6-8): Packed Types -@sp 1 -@cartouche -If a type is packed, then the implementation should try to minimize -storage allocated to objects of the type, possibly at the expense of -speed of accessing components, subject to reasonable complexity in -addressing calculations. -@end cartouche -@sp 1 -@cartouche -The recommended level of support pragma @code{Pack} is: +Equivalent to Aspect Iterable. -For a packed record type, the components should be packed as tightly as -possible subject to the Sizes of the component subtypes, and subject to -any @code{record_representation_clause} that applies to the type; the -implementation may, but need not, reorder components or cross aligned -word boundaries to improve the packing. A component whose @code{Size} is -greater than the word size may be allocated an integral number of words. -@end cartouche -Followed. Tight packing of arrays is supported for all component sizes -up to 64-bits. If the array component size is 1 (that is to say, if -the component is a boolean type or an enumeration type with two values) -then values of the type are implicitly initialized to zero. This -happens both for objects of the packed type, and for objects that have a -subcomponent of the packed type. +@node Attribute Large,Attribute Library_Level,Attribute Iterable,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-large}@anchor{136} +@section Attribute Large -@sp 1 -@cartouche -An implementation should support Address clauses for imported -subprograms. -@end cartouche -Followed. -@cindex @code{Address} clauses -@unnumberedsec 13.3(14-19): Address Clauses - -@sp 1 -@cartouche -For an array @var{X}, @code{@var{X}'Address} should point at the first -component of the array, and not at the array bounds. -@end cartouche -Followed. -@sp 1 -@cartouche -The recommended level of support for the @code{Address} attribute is: +@geindex Ada 83 attributes -@code{@var{X}'Address} should produce a useful result if @var{X} is an -object that is aliased or of a by-reference type, or is an entity whose -@code{Address} has been specified. -@end cartouche -Followed. A valid address will be produced even if none of those -conditions have been met. If necessary, the object is forced into -memory to ensure the address is valid. +@geindex Large -@sp 1 -@cartouche -An implementation should support @code{Address} clauses for imported -subprograms. -@end cartouche -Followed. +The @cite{Large} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@sp 1 -@cartouche -Objects (including subcomponents) that are aliased or of a by-reference -type should be allocated on storage element boundaries. -@end cartouche -Followed. +@node Attribute Library_Level,Attribute Lock_Free,Attribute Large,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-library-level}@anchor{137} +@section Attribute Library_Level -@sp 1 -@cartouche -If the @code{Address} of an object is specified, or it is imported or exported, -then the implementation should not perform optimizations based on -assumptions of no aliases. -@end cartouche -Followed. -@cindex @code{Alignment} clauses -@unnumberedsec 13.3(29-35): Alignment Clauses -@sp 1 -@cartouche -The recommended level of support for the @code{Alignment} attribute for -subtypes is: +@geindex Library_Level -An implementation should support specified Alignments that are factors -and multiples of the number of storage elements per word, subject to the -following: -@end cartouche -Followed. +@cite{P'Library_Level}, where P is an entity name, +returns a Boolean value which is True if the entity is declared +at the library level, and False otherwise. Note that within a +generic instantition, the name of the generic unit denotes the +instance, which means that this attribute can be used to test +if a generic is instantiated at the library level, as shown +in this example: -@sp 1 -@cartouche -An implementation need not support specified @code{Alignment}s for -combinations of @code{Size}s and @code{Alignment}s that cannot be easily -loaded and stored by available machine instructions. -@end cartouche -Followed. +@example +generic + ... +package Gen is + pragma Compile_Time_Error + (not Gen'Library_Level, + "Gen can only be instantiated at library level"); + ... +end Gen; +@end example -@sp 1 -@cartouche -An implementation need not support specified @code{Alignment}s that are -greater than the maximum @code{Alignment} the implementation ever returns by -default. -@end cartouche -Followed. +@node Attribute Lock_Free,Attribute Loop_Entry,Attribute Library_Level,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-lock-free}@anchor{138} +@section Attribute Lock_Free -@sp 1 -@cartouche -The recommended level of support for the @code{Alignment} attribute for -objects is: -Same as above, for subtypes, but in addition: -@end cartouche -Followed. +@geindex Lock_Free -@sp 1 -@cartouche -For stand-alone library-level objects of statically constrained -subtypes, the implementation should support all @code{Alignment}s -supported by the target linker. For example, page alignment is likely to -be supported for such objects, but not for subtypes. -@end cartouche -Followed. +@cite{P'Lock_Free}, where P is a protected object, returns True if a +pragma @cite{Lock_Free} applies to P. -@cindex @code{Size} clauses -@unnumberedsec 13.3(42-43): Size Clauses -@sp 1 -@cartouche -The recommended level of support for the @code{Size} attribute of -objects is: +@node Attribute Loop_Entry,Attribute Machine_Size,Attribute Lock_Free,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-loop-entry}@anchor{139} +@section Attribute Loop_Entry -A @code{Size} clause should be supported for an object if the specified -@code{Size} is at least as large as its subtype's @code{Size}, and -corresponds to a size in storage elements that is a multiple of the -object's @code{Alignment} (if the @code{Alignment} is nonzero). -@end cartouche -Followed. -@unnumberedsec 13.3(50-56): Size Clauses -@sp 1 -@cartouche -If the @code{Size} of a subtype is specified, and allows for efficient -independent addressability (see 9.10) on the target architecture, then -the @code{Size} of the following objects of the subtype should equal the -@code{Size} of the subtype: +@geindex Loop_Entry -Aliased objects (including components). -@end cartouche -Followed. +Syntax: -@sp 1 -@cartouche -@code{Size} clause on a composite subtype should not affect the -internal layout of components. -@end cartouche -Followed. But note that this can be overridden by use of the implementation -pragma Implicit_Packing in the case of packed arrays. +@example +X'Loop_Entry [(loop_name)] +@end example -@sp 1 -@cartouche -The recommended level of support for the @code{Size} attribute of subtypes is: -@end cartouche -@sp 1 -@cartouche -The @code{Size} (if not specified) of a static discrete or fixed point -subtype should be the number of bits needed to represent each value -belonging to the subtype using an unbiased representation, leaving space -for a sign bit only if the subtype contains negative values. If such a -subtype is a first subtype, then an implementation should support a -specified @code{Size} for it that reflects this representation. -@end cartouche -Followed. +The @cite{Loop_Entry} attribute is used to refer to the value that an +expression had upon entry to a given loop in much the same way that the +@cite{Old} attribute in a subprogram postcondition can be used to refer +to the value an expression had upon entry to the subprogram. The +relevant loop is either identified by the given loop name, or it is the +innermost enclosing loop when no loop name is given. -@sp 1 -@cartouche -For a subtype implemented with levels of indirection, the @code{Size} -should include the size of the pointers, but not the size of what they -point at. -@end cartouche -Followed. +A @cite{Loop_Entry} attribute can only occur within a +@cite{Loop_Variant} or @cite{Loop_Invariant} pragma. A common use of +@cite{Loop_Entry} is to compare the current value of objects with their +initial value at loop entry, in a @cite{Loop_Invariant} pragma. -@cindex @code{Component_Size} clauses -@unnumberedsec 13.3(71-73): Component Size Clauses -@sp 1 -@cartouche -The recommended level of support for the @code{Component_Size} -attribute is: -@end cartouche -@sp 1 -@cartouche -An implementation need not support specified @code{Component_Sizes} that are -less than the @code{Size} of the component subtype. -@end cartouche -Followed. +The effect of using @cite{X'Loop_Entry} is the same as declaring +a constant initialized with the initial value of @cite{X} at loop +entry. This copy is not performed if the loop is not entered, or if the +corresponding pragmas are ignored or disabled. -@sp 1 -@cartouche -An implementation should support specified @code{Component_Size}s that -are factors and multiples of the word size. For such -@code{Component_Size}s, the array should contain no gaps between -components. For other @code{Component_Size}s (if supported), the array -should contain no gaps between components when packing is also -specified; the implementation should forbid this combination in cases -where it cannot support a no-gaps representation. -@end cartouche -Followed. +@node Attribute Machine_Size,Attribute Mantissa,Attribute Loop_Entry,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-machine-size}@anchor{13a} +@section Attribute Machine_Size -@cindex Enumeration representation clauses -@cindex Representation clauses, enumeration -@unnumberedsec 13.4(9-10): Enumeration Representation Clauses -@sp 1 -@cartouche -The recommended level of support for enumeration representation clauses -is: -An implementation need not support enumeration representation clauses -for boolean types, but should at minimum support the internal codes in -the range @code{System.Min_Int.System.Max_Int}. -@end cartouche -Followed. +@geindex Machine_Size -@cindex Record representation clauses -@cindex Representation clauses, records -@unnumberedsec 13.5.1(17-22): Record Representation Clauses -@sp 1 -@cartouche -The recommended level of support for -@*@code{record_representation_clauses} is: +This attribute is identical to the @cite{Object_Size} attribute. It is +provided for compatibility with the DEC Ada 83 attribute of this name. -An implementation should support storage places that can be extracted -with a load, mask, shift sequence of machine code, and set with a load, -shift, mask, store sequence, given the available machine instructions -and run-time model. -@end cartouche -Followed. +@node Attribute Mantissa,Attribute Maximum_Alignment,Attribute Machine_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-mantissa}@anchor{13b} +@section Attribute Mantissa -@sp 1 -@cartouche -A storage place should be supported if its size is equal to the -@code{Size} of the component subtype, and it starts and ends on a -boundary that obeys the @code{Alignment} of the component subtype. -@end cartouche -Followed. -@sp 1 -@cartouche -If the default bit ordering applies to the declaration of a given type, -then for a component whose subtype's @code{Size} is less than the word -size, any storage place that does not cross an aligned word boundary -should be supported. -@end cartouche -Followed. +@geindex Ada 83 attributes -@sp 1 -@cartouche -An implementation may reserve a storage place for the tag field of a -tagged type, and disallow other components from overlapping that place. -@end cartouche -Followed. The storage place for the tag field is the beginning of the tagged -record, and its size is Address'Size. GNAT will reject an explicit component -clause for the tag field. +@geindex Mantissa -@sp 1 -@cartouche -An implementation need not support a @code{component_clause} for a -component of an extension part if the storage place is not after the -storage places of all components of the parent type, whether or not -those storage places had been specified. -@end cartouche -Followed. The above advice on record representation clauses is followed, -and all mentioned features are implemented. +The @cite{Mantissa} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@cindex Storage place attributes -@unnumberedsec 13.5.2(5): Storage Place Attributes -@sp 1 -@cartouche -If a component is represented using some form of pointer (such as an -offset) to the actual data of the component, and this data is contiguous -with the rest of the object, then the storage place attributes should -reflect the place of the actual data, not the pointer. If a component is -allocated discontinuously from the rest of the object, then a warning -should be generated upon reference to one of its storage place -attributes. -@end cartouche -Followed. There are no such components in GNAT@. - -@cindex Bit ordering -@unnumberedsec 13.5.3(7-8): Bit Ordering -@sp 1 -@cartouche -The recommended level of support for the non-default bit ordering is: -@end cartouche -@sp 1 -@cartouche -If @code{Word_Size} = @code{Storage_Unit}, then the implementation -should support the non-default bit ordering in addition to the default -bit ordering. -@end cartouche -Followed. Word size does not equal storage size in this implementation. -Thus non-default bit ordering is not supported. +@node Attribute Maximum_Alignment,Attribute Mechanism_Code,Attribute Mantissa,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-maximum-alignment}@anchor{13c}@anchor{gnat_rm/implementation_defined_attributes id2}@anchor{13d} +@section Attribute Maximum_Alignment -@cindex @code{Address}, as private type -@unnumberedsec 13.7(37): Address as Private -@sp 1 -@cartouche -@code{Address} should be of a private type. -@end cartouche -Followed. -@cindex Operations, on @code{Address} -@cindex @code{Address}, operations of -@unnumberedsec 13.7.1(16): Address Operations -@sp 1 -@cartouche -Operations in @code{System} and its children should reflect the target -environment semantics as closely as is reasonable. For example, on most -machines, it makes sense for address arithmetic to ``wrap around''. -Operations that do not make sense should raise @code{Program_Error}. -@end cartouche -Followed. Address arithmetic is modular arithmetic that wraps around. No -operation raises @code{Program_Error}, since all operations make sense. - -@cindex Unchecked conversion -@unnumberedsec 13.9(14-17): Unchecked Conversion -@sp 1 -@cartouche -The @code{Size} of an array object should not include its bounds; hence, -the bounds should not be part of the converted data. -@end cartouche -Followed. +@geindex Alignment +@geindex maximum -@sp 1 -@cartouche -The implementation should not generate unnecessary run-time checks to -ensure that the representation of @var{S} is a representation of the -target type. It should take advantage of the permission to return by -reference when possible. Restrictions on unchecked conversions should be -avoided unless required by the target environment. -@end cartouche -Followed. There are no restrictions on unchecked conversion. A warning is -generated if the source and target types do not have the same size since -the semantics in this case may be target dependent. +@geindex Maximum_Alignment -@sp 1 -@cartouche -The recommended level of support for unchecked conversions is: -@end cartouche -@sp 1 -@cartouche -Unchecked conversions should be supported and should be reversible in -the cases where this clause defines the result. To enable meaningful use -of unchecked conversion, a contiguous representation should be used for -elementary subtypes, for statically constrained array subtypes whose -component subtype is one of the subtypes described in this paragraph, -and for record subtypes without discriminants whose component subtypes -are described in this paragraph. -@end cartouche -Followed. +@cite{Standard'Maximum_Alignment} (@cite{Standard} is the only +permissible prefix) provides the maximum useful alignment value for the +target. This is a static value that can be used to specify the alignment +for an object, guaranteeing that it is properly aligned in all +cases. -@cindex Heap usage, implicit -@unnumberedsec 13.11(23-25): Implicit Heap Usage -@sp 1 -@cartouche -An implementation should document any cases in which it dynamically -allocates heap storage for a purpose other than the evaluation of an -allocator. -@end cartouche -Followed, the only other points at which heap storage is dynamically -allocated are as follows: +@node Attribute Mechanism_Code,Attribute Null_Parameter,Attribute Maximum_Alignment,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-mechanism-code}@anchor{13e} +@section Attribute Mechanism_Code -@itemize @bullet -@item -At initial elaboration time, to allocate dynamically sized global -objects. -@item -To allocate space for a task when a task is created. +@geindex Return values +@geindex passing mechanism -@item -To extend the secondary stack dynamically when needed. The secondary -stack is used for returning variable length results. -@end itemize +@geindex Parameters +@geindex passing mechanism -@sp 1 -@cartouche -A default (implementation-provided) storage pool for an -access-to-constant type should not have overhead to support deallocation of -individual objects. -@end cartouche -Followed. +@geindex Mechanism_Code -@sp 1 -@cartouche -A storage pool for an anonymous access type should be created at the -point of an allocator for the type, and be reclaimed when the designated -object becomes inaccessible. -@end cartouche -Followed. +@code{function'Mechanism_Code} yields an integer code for the +mechanism used for the result of function, and +@code{subprogram'Mechanism_Code (n)} yields the mechanism +used for formal parameter number @cite{n} (a static integer value with 1 +meaning the first parameter) of @cite{subprogram}. The code returned is: -@cindex Unchecked deallocation -@unnumberedsec 13.11.2(17): Unchecked De-allocation -@sp 1 -@cartouche -For a standard storage pool, @code{Free} should actually reclaim the -storage. -@end cartouche -Followed. -@cindex Stream oriented attributes -@unnumberedsec 13.13.2(17): Stream Oriented Attributes -@sp 1 -@cartouche -If a stream element is the same size as a storage element, then the -normal in-memory representation should be used by @code{Read} and -@code{Write} for scalar objects. Otherwise, @code{Read} and @code{Write} -should use the smallest number of stream elements needed to represent -all values in the base range of the scalar type. -@end cartouche +@table @asis -Followed. By default, GNAT uses the interpretation suggested by AI-195, -which specifies using the size of the first subtype. -However, such an implementation is based on direct binary -representations and is therefore target- and endianness-dependent. -To address this issue, GNAT also supplies an alternate implementation -of the stream attributes @code{Read} and @code{Write}, -which uses the target-independent XDR standard representation -for scalar types. -@cindex XDR representation -@cindex @code{Read} attribute -@cindex @code{Write} attribute -@cindex Stream oriented attributes -The XDR implementation is provided as an alternative body of the -@code{System.Stream_Attributes} package, in the file -@file{s-stratt-xdr.adb} in the GNAT library. -There is no @file{s-stratt-xdr.ads} file. -In order to install the XDR implementation, do the following: -@enumerate -@item Replace the default implementation of the -@code{System.Stream_Attributes} package with the XDR implementation. -For example on a Unix platform issue the commands: -@smallexample -$ mv s-stratt.adb s-stratt-default.adb -$ mv s-stratt-xdr.adb s-stratt.adb -@end smallexample +@item @emph{1} -@item -Rebuild the GNAT run-time library as documented in -@ref{GNAT and Libraries,,, gnat_ugn, @value{EDITION} User's Guide}. -@end enumerate +by copy (value) -@unnumberedsec A.1(52): Names of Predefined Numeric Types -@sp 1 -@cartouche -If an implementation provides additional named predefined integer types, -then the names should end with @samp{Integer} as in -@samp{Long_Integer}. If an implementation provides additional named -predefined floating point types, then the names should end with -@samp{Float} as in @samp{Long_Float}. -@end cartouche -Followed. +@item @emph{2} -@findex Ada.Characters.Handling -@unnumberedsec A.3.2(49): @code{Ada.Characters.Handling} -@sp 1 -@cartouche -If an implementation provides a localized definition of @code{Character} -or @code{Wide_Character}, then the effects of the subprograms in -@code{Characters.Handling} should reflect the localizations. See also -3.5.2. -@end cartouche -Followed. GNAT provides no such localized definitions. +by reference +@end table -@cindex Bounded-length strings -@unnumberedsec A.4.4(106): Bounded-Length String Handling -@sp 1 -@cartouche -Bounded string objects should not be implemented by implicit pointers -and dynamic allocation. -@end cartouche -Followed. No implicit pointers or dynamic allocation are used. +@node Attribute Null_Parameter,Attribute Object_Size,Attribute Mechanism_Code,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-null-parameter}@anchor{13f} +@section Attribute Null_Parameter -@cindex Random number generation -@unnumberedsec A.5.2(46-47): Random Number Generation -@sp 1 -@cartouche -Any storage associated with an object of type @code{Generator} should be -reclaimed on exit from the scope of the object. -@end cartouche -Followed. -@sp 1 -@cartouche -If the generator period is sufficiently long in relation to the number -of distinct initiator values, then each possible value of -@code{Initiator} passed to @code{Reset} should initiate a sequence of -random numbers that does not, in a practical sense, overlap the sequence -initiated by any other value. If this is not possible, then the mapping -between initiator values and generator states should be a rapidly -varying function of the initiator value. -@end cartouche -Followed. The generator period is sufficiently long for the first -condition here to hold true. +@geindex Zero address +@geindex passing -@findex Get_Immediate -@unnumberedsec A.10.7(23): @code{Get_Immediate} -@sp 1 -@cartouche -The @code{Get_Immediate} procedures should be implemented with -unbuffered input. For a device such as a keyboard, input should be -@dfn{available} if a key has already been typed, whereas for a disk -file, input should always be available except at end of file. For a file -associated with a keyboard-like device, any line-editing features of the -underlying operating system should be disabled during the execution of -@code{Get_Immediate}. -@end cartouche -Followed on all targets except VxWorks. For VxWorks, there is no way to -provide this functionality that does not result in the input buffer being -flushed before the @code{Get_Immediate} call. A special unit -@code{Interfaces.Vxworks.IO} is provided that contains routines to enable -this functionality. +@geindex Null_Parameter -@findex Export -@unnumberedsec B.1(39-41): Pragma @code{Export} -@sp 1 -@cartouche -If an implementation supports pragma @code{Export} to a given language, -then it should also allow the main subprogram to be written in that -language. It should support some mechanism for invoking the elaboration -of the Ada library units included in the system, and for invoking the -finalization of the environment task. On typical systems, the -recommended mechanism is to provide two subprograms whose link names are -@code{adainit} and @code{adafinal}. @code{adainit} should contain the -elaboration code for library units. @code{adafinal} should contain the -finalization code. These subprograms should have no effect the second -and subsequent time they are called. -@end cartouche -Followed. +A reference @code{T'Null_Parameter} denotes an imaginary object of +type or subtype @cite{T} allocated at machine address zero. The attribute +is allowed only as the default expression of a formal parameter, or as +an actual expression of a subprogram call. In either case, the +subprogram must be imported. -@sp 1 -@cartouche -Automatic elaboration of pre-elaborated packages should be -provided when pragma @code{Export} is supported. -@end cartouche -Followed when the main program is in Ada. If the main program is in a -foreign language, then -@code{adainit} must be called to elaborate pre-elaborated -packages. +The identity of the object is represented by the address zero in the +argument list, independent of the passing mechanism (explicit or +default). -@sp 1 -@cartouche -For each supported convention @var{L} other than @code{Intrinsic}, an -implementation should support @code{Import} and @code{Export} pragmas -for objects of @var{L}-compatible types and for subprograms, and pragma -@code{Convention} for @var{L}-eligible types and for subprograms, -presuming the other language has corresponding features. Pragma -@code{Convention} need not be supported for scalar types. -@end cartouche -Followed. +This capability is needed to specify that a zero address should be +passed for a record or other composite object passed by reference. +There is no way of indicating this without the @cite{Null_Parameter} +attribute. -@cindex Package @code{Interfaces} -@findex Interfaces -@unnumberedsec B.2(12-13): Package @code{Interfaces} -@sp 1 -@cartouche -For each implementation-defined convention identifier, there should be a -child package of package Interfaces with the corresponding name. This -package should contain any declarations that would be useful for -interfacing to the language (implementation) represented by the -convention. Any declarations useful for interfacing to any language on -the given hardware architecture should be provided directly in -@code{Interfaces}. -@end cartouche -Followed. +@node Attribute Object_Size,Attribute Old,Attribute Null_Parameter,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-object-size}@anchor{140} +@section Attribute Object_Size -@sp 1 -@cartouche -An implementation supporting an interface to C, COBOL, or Fortran should -provide the corresponding package or packages described in the following -clauses. -@end cartouche -Followed. GNAT provides all the packages described in this section. -@cindex C, interfacing with -@unnumberedsec B.3(63-71): Interfacing with C -@sp 1 -@cartouche -An implementation should support the following interface correspondences -between Ada and C@. -@end cartouche -Followed. +@geindex Size +@geindex used for objects -@sp 1 -@cartouche -An Ada procedure corresponds to a void-returning C function. -@end cartouche -Followed. +@geindex Object_Size -@sp 1 -@cartouche -An Ada function corresponds to a non-void C function. -@end cartouche -Followed. +The size of an object is not necessarily the same as the size of the type +of an object. This is because by default object sizes are increased to be +a multiple of the alignment of the object. For example, +@cite{Natural'Size} is +31, but by default objects of type @cite{Natural} will have a size of 32 bits. +Similarly, a record containing an integer and a character: -@sp 1 -@cartouche -An Ada @code{in} scalar parameter is passed as a scalar argument to a C -function. -@end cartouche -Followed. +@example +type Rec is record + I : Integer; + C : Character; +end record; +@end example -@sp 1 -@cartouche -An Ada @code{in} parameter of an access-to-object type with designated -type @var{T} is passed as a @code{@var{t}*} argument to a C function, -where @var{t} is the C type corresponding to the Ada type @var{T}. -@end cartouche -Followed. +will have a size of 40 (that is @cite{Rec'Size} will be 40). The +alignment will be 4, because of the +integer field, and so the default size of record objects for this type +will be 64 (8 bytes). -@sp 1 -@cartouche -An Ada access @var{T} parameter, or an Ada @code{out} or @code{in out} -parameter of an elementary type @var{T}, is passed as a @code{@var{t}*} -argument to a C function, where @var{t} is the C type corresponding to -the Ada type @var{T}. In the case of an elementary @code{out} or -@code{in out} parameter, a pointer to a temporary copy is used to -preserve by-copy semantics. -@end cartouche -Followed. +If the alignment of the above record is specified to be 1, then the +object size will be 40 (5 bytes). This is true by default, and also +an object size of 40 can be explicitly specified in this case. -@sp 1 -@cartouche -An Ada parameter of a record type @var{T}, of any mode, is passed as a -@code{@var{t}*} argument to a C function, where @var{t} is the C -structure corresponding to the Ada type @var{T}. -@end cartouche -Followed. This convention may be overridden by the use of the C_Pass_By_Copy -pragma, or Convention, or by explicitly specifying the mechanism for a given -call using an extended import or export pragma. +A consequence of this capability is that different object sizes can be +given to subtypes that would otherwise be considered in Ada to be +statically matching. But it makes no sense to consider such subtypes +as statically matching. Consequently, in @cite{GNAT} we add a rule +to the static matching rules that requires object sizes to match. +Consider this example: -@sp 1 -@cartouche -An Ada parameter of an array type with component type @var{T}, of any -mode, is passed as a @code{@var{t}*} argument to a C function, where -@var{t} is the C type corresponding to the Ada type @var{T}. -@end cartouche -Followed. +@example + 1. procedure BadAVConvert is + 2. type R is new Integer; + 3. subtype R1 is R range 1 .. 10; + 4. subtype R2 is R range 1 .. 10; + 5. for R1'Object_Size use 8; + 6. for R2'Object_Size use 16; + 7. type R1P is access all R1; + 8. type R2P is access all R2; + 9. R1PV : R1P := new R1'(4); +10. R2PV : R2P; +11. begin +12. R2PV := R2P (R1PV); + | + >>> target designated subtype not compatible with + type "R1" defined at line 3 -@sp 1 -@cartouche -An Ada parameter of an access-to-subprogram type is passed as a pointer -to a C function whose prototype corresponds to the designated -subprogram's specification. -@end cartouche -Followed. +13. end; +@end example -@cindex COBOL, interfacing with -@unnumberedsec B.4(95-98): Interfacing with COBOL -@sp 1 -@cartouche -An Ada implementation should support the following interface -correspondences between Ada and COBOL@. -@end cartouche -Followed. +In the absence of lines 5 and 6, +types @cite{R1} and @cite{R2} statically match and +hence the conversion on line 12 is legal. But since lines 5 and 6 +cause the object sizes to differ, @cite{GNAT} considers that types +@cite{R1} and @cite{R2} are not statically matching, and line 12 +generates the diagnostic shown above. -@sp 1 -@cartouche -An Ada access @var{T} parameter is passed as a @samp{BY REFERENCE} data item of -the COBOL type corresponding to @var{T}. -@end cartouche -Followed. +Similar additional checks are performed in other contexts requiring +statically matching subtypes. -@sp 1 -@cartouche -An Ada in scalar parameter is passed as a @samp{BY CONTENT} data item of -the corresponding COBOL type. -@end cartouche -Followed. +@node Attribute Old,Attribute Passed_By_Reference,Attribute Object_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-old}@anchor{141} +@section Attribute Old -@sp 1 -@cartouche -Any other Ada parameter is passed as a @samp{BY REFERENCE} data item of the -COBOL type corresponding to the Ada parameter type; for scalars, a local -copy is used if necessary to ensure by-copy semantics. -@end cartouche -Followed. -@cindex Fortran, interfacing with -@unnumberedsec B.5(22-26): Interfacing with Fortran -@sp 1 -@cartouche -An Ada implementation should support the following interface -correspondences between Ada and Fortran: -@end cartouche -Followed. +@geindex Old -@sp 1 -@cartouche -An Ada procedure corresponds to a Fortran subroutine. -@end cartouche -Followed. +In addition to the usage of @cite{Old} defined in the Ada 2012 RM (usage +within @cite{Post} aspect), GNAT also permits the use of this attribute +in implementation defined pragmas @cite{Postcondition}, +@cite{Contract_Cases} and @cite{Test_Case}. Also usages of +@cite{Old} which would be illegal according to the Ada 2012 RM +definition are allowed under control of +implementation defined pragma @cite{Unevaluated_Use_Of_Old}. -@sp 1 -@cartouche -An Ada function corresponds to a Fortran function. -@end cartouche -Followed. +@node Attribute Passed_By_Reference,Attribute Pool_Address,Attribute Old,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-passed-by-reference}@anchor{142} +@section Attribute Passed_By_Reference -@sp 1 -@cartouche -An Ada parameter of an elementary, array, or record type @var{T} is -passed as a @var{T} argument to a Fortran procedure, where @var{T} is -the Fortran type corresponding to the Ada type @var{T}, and where the -INTENT attribute of the corresponding dummy argument matches the Ada -formal parameter mode; the Fortran implementation's parameter passing -conventions are used. For elementary types, a local copy is used if -necessary to ensure by-copy semantics. -@end cartouche -Followed. -@sp 1 -@cartouche -An Ada parameter of an access-to-subprogram type is passed as a -reference to a Fortran procedure whose interface corresponds to the -designated subprogram's specification. -@end cartouche -Followed. +@geindex Parameters +@geindex when passed by reference -@cindex Machine operations -@unnumberedsec C.1(3-5): Access to Machine Operations -@sp 1 -@cartouche -The machine code or intrinsic support should allow access to all -operations normally available to assembly language programmers for the -target environment, including privileged instructions, if any. -@end cartouche -Followed. +@geindex Passed_By_Reference -@sp 1 -@cartouche -The interfacing pragmas (see Annex B) should support interface to -assembler; the default assembler should be associated with the -convention identifier @code{Assembler}. -@end cartouche -Followed. +@code{type'Passed_By_Reference} for any subtype @cite{type} returns +a value of type @cite{Boolean} value that is @cite{True} if the type is +normally passed by reference and @cite{False} if the type is normally +passed by copy in calls. For scalar types, the result is always @cite{False} +and is static. For non-scalar types, the result is non-static. -@sp 1 -@cartouche -If an entity is exported to assembly language, then the implementation -should allocate it at an addressable location, and should ensure that it -is retained by the linking process, even if not otherwise referenced -from the Ada code. The implementation should assume that any call to a -machine code or assembler subprogram is allowed to read or update every -object that is specified as exported. -@end cartouche -Followed. +@node Attribute Pool_Address,Attribute Range_Length,Attribute Passed_By_Reference,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-pool-address}@anchor{143} +@section Attribute Pool_Address -@unnumberedsec C.1(10-16): Access to Machine Operations -@sp 1 -@cartouche -The implementation should ensure that little or no overhead is -associated with calling intrinsic and machine-code subprograms. -@end cartouche -Followed for both intrinsics and machine-code subprograms. -@sp 1 -@cartouche -It is recommended that intrinsic subprograms be provided for convenient -access to any machine operations that provide special capabilities or -efficiency and that are not otherwise available through the language -constructs. -@end cartouche -Followed. A full set of machine operation intrinsic subprograms is provided. +@geindex Parameters +@geindex when passed by reference -@sp 1 -@cartouche -Atomic read-modify-write operations---e.g.@:, test and set, compare and -swap, decrement and test, enqueue/dequeue. -@end cartouche -Followed on any target supporting such operations. +@geindex Pool_Address -@sp 1 -@cartouche -Standard numeric functions---e.g.@:, sin, log. -@end cartouche -Followed on any target supporting such operations. +@code{X'Pool_Address} for any object @cite{X} returns the address +of X within its storage pool. This is the same as +@code{X'Address}, except that for an unconstrained array whose +bounds are allocated just before the first component, +@code{X'Pool_Address} returns the address of those bounds, +whereas @code{X'Address} returns the address of the first +component. -@sp 1 -@cartouche -String manipulation operations---e.g.@:, translate and test. -@end cartouche -Followed on any target supporting such operations. +Here, we are interpreting 'storage pool' broadly to mean +@code{wherever the object is allocated}, which could be a +user-defined storage pool, +the global heap, on the stack, or in a static memory area. +For an object created by @cite{new}, @code{Ptr.all'Pool_Address} is +what is passed to @cite{Allocate} and returned from @cite{Deallocate}. -@sp 1 -@cartouche -Vector operations---e.g.@:, compare vector against thresholds. -@end cartouche -Followed on any target supporting such operations. +@node Attribute Range_Length,Attribute Ref,Attribute Pool_Address,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-range-length}@anchor{144} +@section Attribute Range_Length -@sp 1 -@cartouche -Direct operations on I/O ports. -@end cartouche -Followed on any target supporting such operations. -@cindex Interrupt support -@unnumberedsec C.3(28): Interrupt Support -@sp 1 -@cartouche -If the @code{Ceiling_Locking} policy is not in effect, the -implementation should provide means for the application to specify which -interrupts are to be blocked during protected actions, if the underlying -system allows for a finer-grain control of interrupt blocking. -@end cartouche -Followed. The underlying system does not allow for finer-grain control -of interrupt blocking. +@geindex Range_Length -@cindex Protected procedure handlers -@unnumberedsec C.3.1(20-21): Protected Procedure Handlers -@sp 1 -@cartouche -Whenever possible, the implementation should allow interrupt handlers to -be called directly by the hardware. -@end cartouche -Followed on any target where the underlying operating system permits -such direct calls. +@code{type'Range_Length} for any discrete type @cite{type} yields +the number of values represented by the subtype (zero for a null +range). The result is static for static subtypes. @cite{Range_Length} +applied to the index subtype of a one dimensional array always gives the +same result as @cite{Length} applied to the array itself. -@sp 1 -@cartouche -Whenever practical, violations of any -implementation-defined restrictions should be detected before run time. -@end cartouche -Followed. Compile time warnings are given when possible. +@node Attribute Ref,Attribute Restriction_Set,Attribute Range_Length,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-ref}@anchor{145} +@section Attribute Ref -@cindex Package @code{Interrupts} -@findex Interrupts -@unnumberedsec C.3.2(25): Package @code{Interrupts} -@sp 1 -@cartouche -If implementation-defined forms of interrupt handler procedures are -supported, such as protected procedures with parameters, then for each -such form of a handler, a type analogous to @code{Parameterless_Handler} -should be specified in a child package of @code{Interrupts}, with the -same operations as in the predefined package Interrupts. -@end cartouche -Followed. +@geindex Ref -@cindex Pre-elaboration requirements -@unnumberedsec C.4(14): Pre-elaboration Requirements -@sp 1 -@cartouche -It is recommended that pre-elaborated packages be implemented in such a -way that there should be little or no code executed at run time for the -elaboration of entities not already covered by the Implementation -Requirements. -@end cartouche -Followed. Executable code is generated in some cases, e.g.@: loops -to initialize large arrays. +@node Attribute Restriction_Set,Attribute Result,Attribute Ref,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-restriction-set}@anchor{146} +@section Attribute Restriction_Set -@unnumberedsec C.5(8): Pragma @code{Discard_Names} -@sp 1 -@cartouche -If the pragma applies to an entity, then the implementation should -reduce the amount of storage used for storing names associated with that -entity. -@end cartouche -Followed. -@cindex Package @code{Task_Attributes} -@findex Task_Attributes -@unnumberedsec C.7.2(30): The Package Task_Attributes -@sp 1 -@cartouche -Some implementations are targeted to domains in which memory use at run -time must be completely deterministic. For such implementations, it is -recommended that the storage for task attributes will be pre-allocated -statically and not from the heap. This can be accomplished by either -placing restrictions on the number and the size of the task's -attributes, or by using the pre-allocated storage for the first @var{N} -attribute objects, and the heap for the others. In the latter case, -@var{N} should be documented. -@end cartouche -Not followed. This implementation is not targeted to such a domain. +@geindex Restriction_Set -@cindex Locking Policies -@unnumberedsec D.3(17): Locking Policies +@geindex Restrictions -@sp 1 -@cartouche -The implementation should use names that end with @samp{_Locking} for -locking policies defined by the implementation. -@end cartouche -Followed. Two implementation-defined locking policies are defined, -whose names (@code{Inheritance_Locking} and -@code{Concurrent_Readers_Locking}) follow this suggestion. - -@cindex Entry queuing policies -@unnumberedsec D.4(16): Entry Queuing Policies -@sp 1 -@cartouche -Names that end with @samp{_Queuing} should be used -for all implementation-defined queuing policies. -@end cartouche -Followed. No such implementation-defined queuing policies exist. +This attribute allows compile time testing of restrictions that +are currently in effect. It is primarily intended for specializing +code in the run-time based on restrictions that are active (e.g. +don't need to save fpt registers if restriction No_Floating_Point +is known to be in effect), but can be used anywhere. -@cindex Preemptive abort -@unnumberedsec D.6(9-10): Preemptive Abort -@sp 1 -@cartouche -Even though the @code{abort_statement} is included in the list of -potentially blocking operations (see 9.5.1), it is recommended that this -statement be implemented in a way that never requires the task executing -the @code{abort_statement} to block. -@end cartouche -Followed. +There are two forms: -@sp 1 -@cartouche -On a multi-processor, the delay associated with aborting a task on -another processor should be bounded; the implementation should use -periodic polling, if necessary, to achieve this. -@end cartouche -Followed. +@example +System'Restriction_Set (partition_boolean_restriction_NAME) +System'Restriction_Set (No_Dependence => library_unit_NAME); +@end example -@cindex Tasking restrictions -@unnumberedsec D.7(21): Tasking Restrictions -@sp 1 -@cartouche -When feasible, the implementation should take advantage of the specified -restrictions to produce a more efficient implementation. -@end cartouche -GNAT currently takes advantage of these restrictions by providing an optimized -run time when the Ravenscar profile and the GNAT restricted run time set -of restrictions are specified. See pragma @code{Profile (Ravenscar)} and -pragma @code{Profile (Restricted)} for more details. - -@cindex Time, monotonic -@unnumberedsec D.8(47-49): Monotonic Time -@sp 1 -@cartouche -When appropriate, implementations should provide configuration -mechanisms to change the value of @code{Tick}. -@end cartouche -Such configuration mechanisms are not appropriate to this implementation -and are thus not supported. +In the case of the first form, the only restriction names +allowed are parameterless restrictions that are checked +for consistency at bind time. For a complete list see the +subtype @cite{System.Rident.Partition_Boolean_Restrictions}. -@sp 1 -@cartouche -It is recommended that @code{Calendar.Clock} and @code{Real_Time.Clock} -be implemented as transformations of the same time base. -@end cartouche -Followed. +The result returned is True if the restriction is known to +be in effect, and False if the restriction is known not to +be in effect. An important guarantee is that the value of +a Restriction_Set attribute is known to be consistent throughout +all the code of a partition. -@sp 1 -@cartouche -It is recommended that the @dfn{best} time base which exists in -the underlying system be available to the application through -@code{Clock}. @dfn{Best} may mean highest accuracy or largest range. -@end cartouche -Followed. +This is trivially achieved if the entire partition is compiled +with a consistent set of restriction pragmas. However, the +compilation model does not require this. It is possible to +compile one set of units with one set of pragmas, and another +set of units with another set of pragmas. It is even possible +to compile a spec with one set of pragmas, and then WITH the +same spec with a different set of pragmas. Inconsistencies +in the actual use of the restriction are checked at bind time. -@cindex Partition communication subsystem -@cindex PCS -@unnumberedsec E.5(28-29): Partition Communication Subsystem -@sp 1 -@cartouche -Whenever possible, the PCS on the called partition should allow for -multiple tasks to call the RPC-receiver with different messages and -should allow them to block until the corresponding subprogram body -returns. -@end cartouche -Followed by GLADE, a separately supplied PCS that can be used with -GNAT. +In order to achieve the guarantee of consistency for the +Restriction_Set pragma, we consider that a use of the pragma +that yields False is equivalent to a violation of the +restriction. -@sp 1 -@cartouche -The @code{Write} operation on a stream of type @code{Params_Stream_Type} -should raise @code{Storage_Error} if it runs out of space trying to -write the @code{Item} into the stream. -@end cartouche -Followed by GLADE, a separately supplied PCS that can be used with -GNAT@. +So for example if you write -@cindex COBOL support -@unnumberedsec F(7): COBOL Support -@sp 1 -@cartouche -If COBOL (respectively, C) is widely supported in the target -environment, implementations supporting the Information Systems Annex -should provide the child package @code{Interfaces.COBOL} (respectively, -@code{Interfaces.C}) specified in Annex B and should support a -@code{convention_identifier} of COBOL (respectively, C) in the interfacing -pragmas (see Annex B), thus allowing Ada programs to interface with -programs written in that language. -@end cartouche -Followed. +@example +if System'Restriction_Set (No_Floating_Point) then + ... +else + ... +end if; +@end example -@cindex Decimal radix support -@unnumberedsec F.1(2): Decimal Radix Support -@sp 1 -@cartouche -Packed decimal should be used as the internal representation for objects -of subtype @var{S} when @var{S}'Machine_Radix = 10. -@end cartouche -Not followed. GNAT ignores @var{S}'Machine_Radix and always uses binary -representations. +And the result is False, so that the else branch is executed, +you can assume that this restriction is not set for any unit +in the partition. This is checked by considering this use of +the restriction pragma to be a violation of the restriction +No_Floating_Point. This means that no other unit can attempt +to set this restriction (if some unit does attempt to set it, +the binder will refuse to bind the partition). -@cindex Numerics -@unnumberedsec G: Numerics -@sp 2 -@cartouche -If Fortran (respectively, C) is widely supported in the target -environment, implementations supporting the Numerics Annex -should provide the child package @code{Interfaces.Fortran} (respectively, -@code{Interfaces.C}) specified in Annex B and should support a -@code{convention_identifier} of Fortran (respectively, C) in the interfacing -pragmas (see Annex B), thus allowing Ada programs to interface with -programs written in that language. -@end cartouche -Followed. +Technical note: The restriction name and the unit name are +intepreted entirely syntactically, as in the corresponding +Restrictions pragma, they are not analyzed semantically, +so they do not have a type. -@cindex Complex types -@unnumberedsec G.1.1(56-58): Complex Types -@sp 2 -@cartouche -Because the usual mathematical meaning of multiplication of a complex -operand and a real operand is that of the scaling of both components of -the former by the latter, an implementation should not perform this -operation by first promoting the real operand to complex type and then -performing a full complex multiplication. In systems that, in the -future, support an Ada binding to IEC 559:1989, the latter technique -will not generate the required result when one of the components of the -complex operand is infinite. (Explicit multiplication of the infinite -component by the zero component obtained during promotion yields a NaN -that propagates into the final result.) Analogous advice applies in the -case of multiplication of a complex operand and a pure-imaginary -operand, and in the case of division of a complex operand by a real or -pure-imaginary operand. -@end cartouche -Not followed. +@node Attribute Result,Attribute Safe_Emax,Attribute Restriction_Set,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-result}@anchor{147} +@section Attribute Result -@sp 1 -@cartouche -Similarly, because the usual mathematical meaning of addition of a -complex operand and a real operand is that the imaginary operand remains -unchanged, an implementation should not perform this operation by first -promoting the real operand to complex type and then performing a full -complex addition. In implementations in which the @code{Signed_Zeros} -attribute of the component type is @code{True} (and which therefore -conform to IEC 559:1989 in regard to the handling of the sign of zero in -predefined arithmetic operations), the latter technique will not -generate the required result when the imaginary component of the complex -operand is a negatively signed zero. (Explicit addition of the negative -zero to the zero obtained during promotion yields a positive zero.) -Analogous advice applies in the case of addition of a complex operand -and a pure-imaginary operand, and in the case of subtraction of a -complex operand and a real or pure-imaginary operand. -@end cartouche -Not followed. -@sp 1 -@cartouche -Implementations in which @code{Real'Signed_Zeros} is @code{True} should -attempt to provide a rational treatment of the signs of zero results and -result components. As one example, the result of the @code{Argument} -function should have the sign of the imaginary component of the -parameter @code{X} when the point represented by that parameter lies on -the positive real axis; as another, the sign of the imaginary component -of the @code{Compose_From_Polar} function should be the same as -(respectively, the opposite of) that of the @code{Argument} parameter when that -parameter has a value of zero and the @code{Modulus} parameter has a -nonnegative (respectively, negative) value. -@end cartouche -Followed. +@geindex Result -@cindex Complex elementary functions -@unnumberedsec G.1.2(49): Complex Elementary Functions -@sp 1 -@cartouche -Implementations in which @code{Complex_Types.Real'Signed_Zeros} is -@code{True} should attempt to provide a rational treatment of the signs -of zero results and result components. For example, many of the complex -elementary functions have components that are odd functions of one of -the parameter components; in these cases, the result component should -have the sign of the parameter component at the origin. Other complex -elementary functions have zero components whose sign is opposite that of -a parameter component at the origin, or is always positive or always -negative. -@end cartouche -Followed. +@code{function'Result} can only be used with in a Postcondition pragma +for a function. The prefix must be the name of the corresponding function. This +is used to refer to the result of the function in the postcondition expression. +For a further discussion of the use of this attribute and examples of its use, +see the description of pragma Postcondition. -@cindex Accuracy requirements -@unnumberedsec G.2.4(19): Accuracy Requirements -@sp 1 -@cartouche -The versions of the forward trigonometric functions without a -@code{Cycle} parameter should not be implemented by calling the -corresponding version with a @code{Cycle} parameter of -@code{2.0*Numerics.Pi}, since this will not provide the required -accuracy in some portions of the domain. For the same reason, the -version of @code{Log} without a @code{Base} parameter should not be -implemented by calling the corresponding version with a @code{Base} -parameter of @code{Numerics.e}. -@end cartouche -Followed. +@node Attribute Safe_Emax,Attribute Safe_Large,Attribute Result,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-safe-emax}@anchor{148} +@section Attribute Safe_Emax -@cindex Complex arithmetic accuracy -@cindex Accuracy, complex arithmetic -@unnumberedsec G.2.6(15): Complex Arithmetic Accuracy - -@sp 1 -@cartouche -The version of the @code{Compose_From_Polar} function without a -@code{Cycle} parameter should not be implemented by calling the -corresponding version with a @code{Cycle} parameter of -@code{2.0*Numerics.Pi}, since this will not provide the required -accuracy in some portions of the domain. -@end cartouche -Followed. -@cindex Sequential elaboration policy -@unnumberedsec H.6(15/2): Pragma Partition_Elaboration_Policy +@geindex Ada 83 attributes -@sp 1 -@cartouche -If the partition elaboration policy is @code{Sequential} and the -Environment task becomes permanently blocked during elaboration then the -partition is deadlocked and it is recommended that the partition be -immediately terminated. -@end cartouche -Not followed. +@geindex Safe_Emax -@c ----------------------------------------- -@node Implementation Defined Characteristics -@chapter Implementation Defined Characteristics +The @cite{Safe_Emax} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@noindent -In addition to the implementation dependent pragmas and attributes, and the -implementation advice, there are a number of other Ada features that are -potentially implementation dependent and are designated as -implementation-defined. These are mentioned throughout the Ada Reference -Manual, and are summarized in Annex M@. +@node Attribute Safe_Large,Attribute Safe_Small,Attribute Safe_Emax,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-safe-large}@anchor{149} +@section Attribute Safe_Large -A requirement for conforming Ada compilers is that they provide -documentation describing how the implementation deals with each of these -issues. In this chapter you will find each point in Annex M listed, -followed by a description of how GNAT -handles the implementation dependence. -You can use this chapter as a guide to minimizing implementation -dependent features in your programs if portability to other compilers -and other operating systems is an important consideration. The numbers -in each entry below correspond to the paragraph numbers in the Ada -Reference Manual. +@geindex Ada 83 attributes +@geindex Safe_Large -@itemize @bullet -@sp 1 -@item -@cartouche -@noindent -Whether or not each recommendation given in Implementation -Advice is followed. See 1.1.2(37). -@end cartouche -@noindent -@xref{Implementation Advice}. +The @cite{Safe_Large} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. +@node Attribute Safe_Small,Attribute Scalar_Storage_Order,Attribute Safe_Large,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-safe-small}@anchor{14a} +@section Attribute Safe_Small -@sp 1 -@item -@cartouche -@noindent -Capacity limitations of the implementation. See 1.1.3(3). -@end cartouche -@noindent -The complexity of programs that can be processed is limited only by the -total amount of available virtual memory, and disk space for the -generated object files. +@geindex Ada 83 attributes -@sp 1 -@item -@cartouche -@noindent -Variations from the standard that are impractical to avoid -given the implementation's execution environment. See 1.1.3(6). -@end cartouche -@noindent -There are no variations from the standard. +@geindex Safe_Small +The @cite{Safe_Small} attribute is provided for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute. -@sp 1 -@item -@cartouche -@noindent -Which @code{code_statement}s cause external -interactions. See 1.1.3(10). -@end cartouche -@noindent -Any @code{code_statement} can potentially cause external interactions. - -@sp 1 -@item -@cartouche -@noindent -The coded representation for the text of an Ada -program. See 2.1(4). -@end cartouche -@noindent -See separate section on source representation. +@node Attribute Scalar_Storage_Order,Attribute Simple_Storage_Pool,Attribute Safe_Small,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-scalar-storage-order}@anchor{14b} +@section Attribute Scalar_Storage_Order -@sp 1 -@item -@cartouche -@noindent -The control functions allowed in comments. See 2.1(14). -@end cartouche -@noindent -See separate section on source representation. +@geindex Endianness -@sp 1 -@item -@cartouche -@noindent -The representation for an end of line. See 2.2(2). -@end cartouche -@noindent -See separate section on source representation. +@geindex Scalar storage order -@sp 1 -@item -@cartouche -@noindent -Maximum supported line length and lexical element -length. See 2.2(15). -@end cartouche -@noindent -The maximum line length is 255 characters and the maximum length of -a lexical element is also 255 characters. This is the default setting -if not overridden by the use of compiler switch @option{-gnaty} (which -sets the maximum to 79) or @option{-gnatyMnn} which allows the maximum -line length to be specified to be any value up to 32767. The maximum -length of a lexical element is the same as the maximum line length. +@geindex Scalar_Storage_Order -@sp 1 -@item -@cartouche -@noindent -Implementation defined pragmas. See 2.8(14). -@end cartouche -@noindent +For every array or record type @cite{S}, the representation attribute +@cite{Scalar_Storage_Order} denotes the order in which storage elements +that make up scalar components are ordered within S. The value given must +be a static expression of type System.Bit_Order. The following is an example +of the use of this feature: -@xref{Implementation Defined Pragmas}. +@example +-- Component type definitions -@sp 1 -@item -@cartouche -@noindent -Effect of pragma @code{Optimize}. See 2.8(27). -@end cartouche -@noindent -Pragma @code{Optimize}, if given with a @code{Time} or @code{Space} -parameter, checks that the optimization flag is set, and aborts if it is -not. +subtype Yr_Type is Natural range 0 .. 127; +subtype Mo_Type is Natural range 1 .. 12; +subtype Da_Type is Natural range 1 .. 31; -@sp 1 -@item -@cartouche -@noindent -The sequence of characters of the value returned by -@code{@var{S}'Image} when some of the graphic characters of -@code{@var{S}'Wide_Image} are not defined in @code{Character}. See -3.5(37). -@end cartouche -@noindent -The sequence of characters is as defined by the wide character encoding -method used for the source. See section on source representation for -further details. +-- Record declaration -@sp 1 -@item -@cartouche -@noindent -The predefined integer types declared in -@code{Standard}. See 3.5.4(25). -@end cartouche -@noindent -@table @code -@item Short_Short_Integer -8 bit signed -@item Short_Integer -(Short) 16 bit signed -@item Integer -32 bit signed -@item Long_Integer -64 bit signed (on most 64 bit targets, depending on the C definition of long). -32 bit signed (all other targets) -@item Long_Long_Integer -64 bit signed -@end table +type Date is record + Years_Since_1980 : Yr_Type; + Month : Mo_Type; + Day_Of_Month : Da_Type; +end record; -@sp 1 -@item -@cartouche -@noindent -Any nonstandard integer types and the operators defined -for them. See 3.5.4(26). -@end cartouche -@noindent -There are no nonstandard integer types. +-- Record representation clause -@sp 1 -@item -@cartouche -@noindent -Any nonstandard real types and the operators defined for -them. See 3.5.6(8). -@end cartouche -@noindent -There are no nonstandard real types. +for Date use record + Years_Since_1980 at 0 range 0 .. 6; + Month at 0 range 7 .. 10; + Day_Of_Month at 0 range 11 .. 15; +end record; -@sp 1 -@item -@cartouche -@noindent -What combinations of requested decimal precision and range -are supported for floating point types. See 3.5.7(7). -@end cartouche -@noindent -The precision and range is as defined by the IEEE standard. +-- Attribute definition clauses -@sp 1 -@item -@cartouche -@noindent -The predefined floating point types declared in -@code{Standard}. See 3.5.7(16). -@end cartouche -@noindent -@table @code -@item Short_Float -32 bit IEEE short -@item Float -(Short) 32 bit IEEE short -@item Long_Float -64 bit IEEE long -@item Long_Long_Float -64 bit IEEE long (80 bit IEEE long on x86 processors) -@end table +for Date'Bit_Order use System.High_Order_First; +for Date'Scalar_Storage_Order use System.High_Order_First; +-- If Scalar_Storage_Order is specified, it must be consistent with +-- Bit_Order, so it's best to always define the latter explicitly if +-- the former is used. +@end example -@sp 1 -@item -@cartouche -@noindent -The small of an ordinary fixed point type. See 3.5.9(8). -@end cartouche -@noindent -@code{Fine_Delta} is 2**(@minus{}63) - -@sp 1 -@item -@cartouche -@noindent -What combinations of small, range, and digits are -supported for fixed point types. See 3.5.9(10). -@end cartouche -@noindent -Any combinations are permitted that do not result in a small less than -@code{Fine_Delta} and do not result in a mantissa larger than 63 bits. -If the mantissa is larger than 53 bits on machines where Long_Long_Float -is 64 bits (true of all architectures except ia32), then the output from -Text_IO is accurate to only 53 bits, rather than the full mantissa. This -is because floating-point conversions are used to convert fixed point. +Other properties are as for standard representation attribute @cite{Bit_Order}, +as defined by Ada RM 13.5.3(4). The default is @cite{System.Default_Bit_Order}. -@sp 1 -@item -@cartouche -@noindent -The result of @code{Tags.Expanded_Name} for types declared -within an unnamed @code{block_statement}. See 3.9(10). -@end cartouche -@noindent -Block numbers of the form @code{B@var{nnn}}, where @var{nnn} is a -decimal integer are allocated. +For a record type @cite{T}, if @code{T'Scalar_Storage_Order} is +specified explicitly, it shall be equal to @code{T'Bit_Order}. Note: +this means that if a @cite{Scalar_Storage_Order} attribute definition +clause is not confirming, then the type's @cite{Bit_Order} shall be +specified explicitly and set to the same value. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined attributes. See 4.1.4(12). -@end cartouche -@noindent -@xref{Implementation Defined Attributes}. - -@sp 1 -@item -@cartouche -@noindent -Any implementation-defined time types. See 9.6(6). -@end cartouche -@noindent -There are no implementation-defined time types. +Derived types inherit an explicitly set scalar storage order from their parent +types. This may be overridden for the derived type by giving an explicit scalar +storage order for the derived type. For a record extension, the derived type +must have the same scalar storage order as the parent type. -@sp 1 -@item -@cartouche -@noindent -The time base associated with relative delays. -@end cartouche -@noindent -See 9.6(20). The time base used is that provided by the C library -function @code{gettimeofday}. +If a component of @cite{T} is of a record or array type, then that type must +also have a @cite{Scalar_Storage_Order} attribute definition clause. -@sp 1 -@item -@cartouche -@noindent -The time base of the type @code{Calendar.Time}. See -9.6(23). -@end cartouche -@noindent -The time base used is that provided by the C library function -@code{gettimeofday}. +A component of a record or array type that is a packed array, or that +does not start on a byte boundary, must have the same scalar storage order +as the enclosing record or array type. -@sp 1 -@item -@cartouche -@noindent -The time zone used for package @code{Calendar} -operations. See 9.6(24). -@end cartouche -@noindent -The time zone used by package @code{Calendar} is the current system time zone -setting for local time, as accessed by the C library function -@code{localtime}. +No component of a type that has an explicit @cite{Scalar_Storage_Order} +attribute definition may be aliased. -@sp 1 -@item -@cartouche -@noindent -Any limit on @code{delay_until_statements} of -@code{select_statements}. See 9.6(29). -@end cartouche -@noindent -There are no such limits. +A confirming @cite{Scalar_Storage_Order} attribute definition clause (i.e. +with a value equal to @cite{System.Default_Bit_Order}) has no effect. -@sp 1 -@item -@cartouche -@noindent -Whether or not two non-overlapping parts of a composite -object are independently addressable, in the case where packing, record -layout, or @code{Component_Size} is specified for the object. See -9.10(1). -@end cartouche -@noindent -Separate components are independently addressable if they do not share -overlapping storage units. +If the opposite storage order is specified, then whenever the value of +a scalar component of an object of type @cite{S} is read, the storage +elements of the enclosing machine scalar are first reversed (before +retrieving the component value, possibly applying some shift and mask +operatings on the enclosing machine scalar), and the opposite operation +is done for writes. -@sp 1 -@item -@cartouche -@noindent -The representation for a compilation. See 10.1(2). -@end cartouche -@noindent -A compilation is represented by a sequence of files presented to the -compiler in a single invocation of the @command{gcc} command. +In that case, the restrictions set forth in 13.5.1(10.3/2) for scalar components +are relaxed. Instead, the following rules apply: -@sp 1 -@item -@cartouche -@noindent -Any restrictions on compilations that contain multiple -compilation_units. See 10.1(4). -@end cartouche -@noindent -No single file can contain more than one compilation unit, but any -sequence of files can be presented to the compiler as a single -compilation. -@sp 1 -@item -@cartouche -@noindent -The mechanisms for creating an environment and for adding -and replacing compilation units. See 10.1.4(3). -@end cartouche -@noindent -See separate section on compilation model. +@itemize * -@sp 1 -@item -@cartouche -@noindent -The manner of explicitly assigning library units to a -partition. See 10.2(2). -@end cartouche -@noindent -If a unit contains an Ada main program, then the Ada units for the partition -are determined by recursive application of the rules in the Ada Reference -Manual section 10.2(2-6). In other words, the Ada units will be those that -are needed by the main program, and then this definition of need is applied -recursively to those units, and the partition contains the transitive -closure determined by this relationship. In short, all the necessary units -are included, with no need to explicitly specify the list. If additional -units are required, e.g.@: by foreign language units, then all units must be -mentioned in the context clause of one of the needed Ada units. +@item +the underlying storage elements are those at positions +@cite{(position + first_bit / storage_element_size) .. (position + (last_bit + storage_element_size - 1) / storage_element_size)} -If the partition contains no main program, or if the main program is in -a language other than Ada, then GNAT -provides the binder options @option{-z} and @option{-n} respectively, and in -this case a list of units can be explicitly supplied to the binder for -inclusion in the partition (all units needed by these units will also -be included automatically). For full details on the use of these -options, refer to @ref{The GNAT Make Program gnatmake,,, gnat_ugn, -@value{EDITION} User's Guide}. +@item +the sequence of underlying storage elements shall have +a size no greater than the largest machine scalar -@sp 1 -@item -@cartouche -@noindent -The implementation-defined means, if any, of specifying -which compilation units are needed by a given compilation unit. See -10.2(2). -@end cartouche -@noindent -The units needed by a given compilation unit are as defined in -the Ada Reference Manual section 10.2(2-6). There are no -implementation-defined pragmas or other implementation-defined -means for specifying needed units. +@item +the enclosing machine scalar is defined as the smallest machine +scalar starting at a position no greater than +@cite{position + first_bit / storage_element_size} and covering +storage elements at least up to @cite{position + (last_bit + storage_element_size - 1) / storage_element_size} -@sp 1 -@item -@cartouche -@noindent -The manner of designating the main subprogram of a -partition. See 10.2(7). -@end cartouche -@noindent -The main program is designated by providing the name of the -corresponding @file{ALI} file as the input parameter to the binder. +@item +the position of the component is interpreted relative to that machine +scalar. +@end itemize -@sp 1 -@item -@cartouche -@noindent -The order of elaboration of @code{library_items}. See -10.2(18). -@end cartouche -@noindent -The first constraint on ordering is that it meets the requirements of -Chapter 10 of the Ada Reference Manual. This still leaves some -implementation dependent choices, which are resolved by first -elaborating bodies as early as possible (i.e., in preference to specs -where there is a choice), and second by evaluating the immediate with -clauses of a unit to determine the probably best choice, and -third by elaborating in alphabetical order of unit names -where a choice still remains. +If no scalar storage order is specified for a type (either directly, or by +inheritance in the case of a derived type), then the default is normally +the native ordering of the target, but this default can be overridden using +pragma @cite{Default_Scalar_Storage_Order}. -@sp 1 -@item -@cartouche -@noindent -Parameter passing and function return for the main -subprogram. See 10.2(21). -@end cartouche -@noindent -The main program has no parameters. It may be a procedure, or a function -returning an integer type. In the latter case, the returned integer -value is the return code of the program (overriding any value that -may have been set by a call to @code{Ada.Command_Line.Set_Exit_Status}). +Note that the scalar storage order only affects the in-memory data +representation. It has no effect on the representation used by stream +attributes. -@sp 1 -@item -@cartouche -@noindent -The mechanisms for building and running partitions. See -10.2(24). -@end cartouche -@noindent -GNAT itself supports programs with only a single partition. The GNATDIST -tool provided with the GLADE package (which also includes an implementation -of the PCS) provides a completely flexible method for building and running -programs consisting of multiple partitions. See the separate GLADE manual -for details. +@node Attribute Simple_Storage_Pool,Attribute Small,Attribute Scalar_Storage_Order,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-simple-storage-pool}@anchor{b6}@anchor{gnat_rm/implementation_defined_attributes id3}@anchor{14c} +@section Attribute Simple_Storage_Pool -@sp 1 -@item -@cartouche -@noindent -The details of program execution, including program -termination. See 10.2(25). -@end cartouche -@noindent -See separate section on compilation model. -@sp 1 -@item -@cartouche -@noindent -The semantics of any non-active partitions supported by the -implementation. See 10.2(28). -@end cartouche -@noindent -Passive partitions are supported on targets where shared memory is -provided by the operating system. See the GLADE reference manual for -further details. +@geindex Storage pool +@geindex simple -@sp 1 -@item -@cartouche -@noindent -The information returned by @code{Exception_Message}. See -11.4.1(10). -@end cartouche -@noindent -Exception message returns the null string unless a specific message has -been passed by the program. +@geindex Simple storage pool -@sp 1 -@item -@cartouche -@noindent -The result of @code{Exceptions.Exception_Name} for types -declared within an unnamed @code{block_statement}. See 11.4.1(12). -@end cartouche -@noindent -Blocks have implementation defined names of the form @code{B@var{nnn}} -where @var{nnn} is an integer. - -@sp 1 -@item -@cartouche -@noindent -The information returned by -@code{Exception_Information}. See 11.4.1(13). -@end cartouche -@noindent -@code{Exception_Information} returns a string in the following format: - -@smallexample -@emph{Exception_Name:} nnnnn -@emph{Message:} mmmmm -@emph{PID:} ppp -@emph{Load address:} 0xhhhh -@emph{Call stack traceback locations:} -0xhhhh 0xhhhh 0xhhhh ... 0xhhh -@end smallexample +@geindex Simple_Storage_Pool -@noindent -where +For every nonformal, nonderived access-to-object type @cite{Acc}, the +representation attribute @cite{Simple_Storage_Pool} may be specified +via an attribute_definition_clause (or by specifying the equivalent aspect): -@itemize @bullet -@item -@code{nnnn} is the fully qualified name of the exception in all upper -case letters. This line is always present. +@example +My_Pool : My_Simple_Storage_Pool_Type; -@item -@code{mmmm} is the message (this line present only if message is non-null) +type Acc is access My_Data_Type; -@item -@code{ppp} is the Process Id value as a decimal integer (this line is -present only if the Process Id is nonzero). Currently we are -not making use of this field. +for Acc'Simple_Storage_Pool use My_Pool; +@end example -@item -The Load address line, the Call stack traceback locations line and the -following values are present only if at least one traceback location was -recorded. The Load address indicates the address at which the main executable -was loaded; this line may not be present if operating system hasn't relocated -the main executable. The values are given in C style format, with lower case -letters for a-f, and only as many digits present as are necessary. -@end itemize +The name given in an attribute_definition_clause for the +@cite{Simple_Storage_Pool} attribute shall denote a variable of +a 'simple storage pool type' (see pragma @cite{Simple_Storage_Pool_Type}). -@noindent -The line terminator sequence at the end of each line, including -the last line is a single @code{LF} character (@code{16#0A#}). +The use of this attribute is only allowed for a prefix denoting a type +for which it has been specified. The type of the attribute is the type +of the variable specified as the simple storage pool of the access type, +and the attribute denotes that variable. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined check names. See 11.5(27). -@end cartouche -@noindent -The implementation defined check name Alignment_Check controls checking of -address clause values for proper alignment (that is, the address supplied -must be consistent with the alignment of the type). +It is illegal to specify both @cite{Storage_Pool} and @cite{Simple_Storage_Pool} +for the same access type. -The implementation defined check name Predicate_Check controls whether -predicate checks are generated. +If the @cite{Simple_Storage_Pool} attribute has been specified for an access +type, then applying the @cite{Storage_Pool} attribute to the type is flagged +with a warning and its evaluation raises the exception @cite{Program_Error}. -The implementation defined check name Validity_Check controls whether -validity checks are generated. +If the Simple_Storage_Pool attribute has been specified for an access +type @cite{S}, then the evaluation of the attribute @code{S'Storage_Size} +returns the result of calling @code{Storage_Size (S'Simple_Storage_Pool)}, +which is intended to indicate the number of storage elements reserved for +the simple storage pool. If the Storage_Size function has not been defined +for the simple storage pool type, then this attribute returns zero. -In addition, a user program can add implementation-defined check names -by means of the pragma Check_Name. +If an access type @cite{S} has a specified simple storage pool of type +@cite{SSP}, then the evaluation of an allocator for that access type calls +the primitive @cite{Allocate} procedure for type @cite{SSP}, passing +@code{S'Simple_Storage_Pool} as the pool parameter. The detailed +semantics of such allocators is the same as those defined for allocators +in section 13.11 of the @cite{Ada Reference Manual}, with the term +@cite{simple storage pool} substituted for @cite{storage pool}. -@sp 1 -@item -@cartouche -@noindent -The interpretation of each aspect of representation. See -13.1(20). -@end cartouche -@noindent -See separate section on data representations. +If an access type @cite{S} has a specified simple storage pool of type +@cite{SSP}, then a call to an instance of the @cite{Ada.Unchecked_Deallocation} +for that access type invokes the primitive @cite{Deallocate} procedure +for type @cite{SSP}, passing @code{S'Simple_Storage_Pool} as the pool +parameter. The detailed semantics of such unchecked deallocations is the same +as defined in section 13.11.2 of the Ada Reference Manual, except that the +term 'simple storage pool' is substituted for 'storage pool'. -@sp 1 -@item -@cartouche -@noindent -Any restrictions placed upon representation items. See -13.1(20). -@end cartouche -@noindent -See separate section on data representations. +@node Attribute Small,Attribute Storage_Unit,Attribute Simple_Storage_Pool,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-small}@anchor{14d} +@section Attribute Small -@sp 1 -@item -@cartouche -@noindent -The meaning of @code{Size} for indefinite subtypes. See -13.3(48). -@end cartouche -@noindent -Size for an indefinite subtype is the maximum possible size, except that -for the case of a subprogram parameter, the size of the parameter object -is the actual size. -@sp 1 -@item -@cartouche -@noindent -The default external representation for a type tag. See -13.3(75). -@end cartouche -@noindent -The default external representation for a type tag is the fully expanded -name of the type in upper case letters. +@geindex Ada 83 attributes -@sp 1 -@item -@cartouche -@noindent -What determines whether a compilation unit is the same in -two different partitions. See 13.3(76). -@end cartouche -@noindent -A compilation unit is the same in two different partitions if and only -if it derives from the same source file. +@geindex Small -@sp 1 -@item -@cartouche -@noindent -Implementation-defined components. See 13.5.1(15). -@end cartouche -@noindent -The only implementation defined component is the tag for a tagged type, -which contains a pointer to the dispatching table. +The @cite{Small} attribute is defined in Ada 95 (and Ada 2005) only for +fixed-point types. +GNAT also allows this attribute to be applied to floating-point types +for compatibility with Ada 83. See +the Ada 83 reference manual for an exact description of the semantics of +this attribute when applied to floating-point types. -@sp 1 -@item -@cartouche -@noindent -If @code{Word_Size} = @code{Storage_Unit}, the default bit -ordering. See 13.5.3(5). -@end cartouche -@noindent -@code{Word_Size} (32) is not the same as @code{Storage_Unit} (8) for this -implementation, so no non-default bit ordering is supported. The default -bit ordering corresponds to the natural endianness of the target architecture. +@node Attribute Storage_Unit,Attribute Stub_Type,Attribute Small,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-storage-unit}@anchor{14e} +@section Attribute Storage_Unit -@sp 1 -@item -@cartouche -@noindent -The contents of the visible part of package @code{System} -and its language-defined children. See 13.7(2). -@end cartouche -@noindent -See the definition of these packages in files @file{system.ads} and -@file{s-stoele.ads}. Note that two declarations are added to package -System. -@smallexample @c ada - Max_Priority : constant Positive := - Priority'Last; - Max_Interrupt_Priority : constant Positive := - Interrupt_Priority'Last; -@end smallexample +@geindex Storage_Unit -@sp 1 -@item -@cartouche -@noindent -The contents of the visible part of package -@code{System.Machine_Code}, and the meaning of -@code{code_statements}. See 13.8(7). -@end cartouche -@noindent -See the definition and documentation in file @file{s-maccod.ads}. - -@sp 1 -@item -@cartouche -@noindent -The effect of unchecked conversion. See 13.9(11). -@end cartouche -@noindent -Unchecked conversion between types of the same size -results in an uninterpreted transmission of the bits from one type -to the other. If the types are of unequal sizes, then in the case of -discrete types, a shorter source is first zero or sign extended as -necessary, and a shorter target is simply truncated on the left. -For all non-discrete types, the source is first copied if necessary -to ensure that the alignment requirements of the target are met, then -a pointer is constructed to the source value, and the result is obtained -by dereferencing this pointer after converting it to be a pointer to the -target type. Unchecked conversions where the target subtype is an -unconstrained array are not permitted. If the target alignment is -greater than the source alignment, then a copy of the result is -made with appropriate alignment +@cite{Standard'Storage_Unit} (@cite{Standard} is the only permissible +prefix) provides the same value as @cite{System.Storage_Unit}. -@sp 1 -@item -@cartouche -@noindent -The semantics of operations on invalid representations. -See 13.9.2(10-11). -@end cartouche -@noindent -For assignments and other operations where the use of invalid values cannot -result in erroneous behavior, the compiler ignores the possibility of invalid -values. An exception is raised at the point where an invalid value would -result in erroneous behavior. For example executing: +@node Attribute Stub_Type,Attribute System_Allocator_Alignment,Attribute Storage_Unit,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-stub-type}@anchor{14f} +@section Attribute Stub_Type -@smallexample @c ada -procedure invalidvals is - X : Integer := -1; - Y : Natural range 1 .. 10; - for Y'Address use X'Address; - Z : Natural range 1 .. 10; - A : array (Natural range 1 .. 10) of Integer; -begin - Z := Y; -- no exception - A (Z) := 3; -- exception raised; -end; -@end smallexample -@noindent -As indicated, an exception is raised on the array assignment, but not -on the simple assignment of the invalid negative value from Y to Z. +@geindex Stub_Type -@sp 1 -@item -@cartouche -@noindent -The manner of choosing a storage pool for an access type -when @code{Storage_Pool} is not specified for the type. See 13.11(17). -@end cartouche -@noindent -There are 3 different standard pools used by the compiler when -@code{Storage_Pool} is not specified depending whether the type is local -to a subprogram or defined at the library level and whether -@code{Storage_Size}is specified or not. See documentation in the runtime -library units @code{System.Pool_Global}, @code{System.Pool_Size} and -@code{System.Pool_Local} in files @file{s-poosiz.ads}, -@file{s-pooglo.ads} and @file{s-pooloc.ads} for full details on the -default pools used. +The GNAT implementation of remote access-to-classwide types is +organized as described in AARM section E.4 (20.t): a value of an RACW type +(designating a remote object) is represented as a normal access +value, pointing to a "stub" object which in turn contains the +necessary information to contact the designated remote object. A +call on any dispatching operation of such a stub object does the +remote call, if necessary, using the information in the stub object +to locate the target partition, etc. -@sp 1 -@item -@cartouche -@noindent -Whether or not the implementation provides user-accessible -names for the standard pool type(s). See 13.11(17). -@end cartouche -@noindent +For a prefix @cite{T} that denotes a remote access-to-classwide type, +@cite{T'Stub_Type} denotes the type of the corresponding stub objects. -See documentation in the sources of the run time mentioned in the previous -paragraph. All these pools are accessible by means of @code{with}'ing -these units. +By construction, the layout of @cite{T'Stub_Type} is identical to that of +type @cite{RACW_Stub_Type} declared in the internal implementation-defined +unit @cite{System.Partition_Interface}. Use of this attribute will create +an implicit dependency on this unit. -@sp 1 -@item -@cartouche -@noindent -The meaning of @code{Storage_Size}. See 13.11(18). -@end cartouche -@noindent -@code{Storage_Size} is measured in storage units, and refers to the -total space available for an access type collection, or to the primary -stack space for a task. +@node Attribute System_Allocator_Alignment,Attribute Target_Name,Attribute Stub_Type,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-system-allocator-alignment}@anchor{150} +@section Attribute System_Allocator_Alignment -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of storage pools. See -13.11(22). -@end cartouche -@noindent -See documentation in the sources of the run time mentioned in the -paragraph about standard storage pools above -for details on GNAT-defined aspects of storage pools. -@sp 1 -@item -@cartouche -@noindent -The set of restrictions allowed in a pragma -@code{Restrictions}. See 13.12(7). -@end cartouche -@noindent -@xref{Standard and Implementation Defined Restrictions}. - -@sp 1 -@item -@cartouche -@noindent -The consequences of violating limitations on -@code{Restrictions} pragmas. See 13.12(9). -@end cartouche -@noindent -Restrictions that can be checked at compile time result in illegalities -if violated. Currently there are no other consequences of violating -restrictions. +@geindex Alignment +@geindex allocator -@sp 1 -@item -@cartouche -@noindent -The representation used by the @code{Read} and -@code{Write} attributes of elementary types in terms of stream -elements. See 13.13.2(9). -@end cartouche -@noindent -The representation is the in-memory representation of the base type of -the type, using the number of bits corresponding to the -@code{@var{type}'Size} value, and the natural ordering of the machine. +@geindex System_Allocator_Alignment -@sp 1 -@item -@cartouche -@noindent -The names and characteristics of the numeric subtypes -declared in the visible part of package @code{Standard}. See A.1(3). -@end cartouche -@noindent -See items describing the integer and floating-point types supported. +@cite{Standard'System_Allocator_Alignment} (@cite{Standard} is the only +permissible prefix) provides the observable guaranted to be honored by +the system allocator (malloc). This is a static value that can be used +in user storage pools based on malloc either to reject allocation +with alignment too large or to enable a realignment circuitry if the +alignment request is larger than this value. -@sp 1 -@item -@cartouche -@noindent -The string returned by @code{Character_Set_Version}. -See A.3.5(3). -@end cartouche -@noindent -@code{Ada.Wide_Characters.Handling.Character_Set_Version} returns -the string "Unicode 4.0", referring to version 4.0 of the -Unicode specification. +@node Attribute Target_Name,Attribute To_Address,Attribute System_Allocator_Alignment,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-target-name}@anchor{151} +@section Attribute Target_Name -@sp 1 -@item -@cartouche -@noindent -The accuracy actually achieved by the elementary -functions. See A.5.1(1). -@end cartouche -@noindent -The elementary functions correspond to the functions available in the C -library. Only fast math mode is implemented. -@sp 1 -@item -@cartouche -@noindent -The sign of a zero result from some of the operators or -functions in @code{Numerics.Generic_Elementary_Functions}, when -@code{Float_Type'Signed_Zeros} is @code{True}. See A.5.1(46). -@end cartouche -@noindent -The sign of zeroes follows the requirements of the IEEE 754 standard on -floating-point. +@geindex Target_Name -@sp 1 -@item -@cartouche -@noindent -The value of -@code{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27). -@end cartouche -@noindent -Maximum image width is 6864, see library file @file{s-rannum.ads}. - -@sp 1 -@item -@cartouche -@noindent -The value of -@code{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27). -@end cartouche -@noindent -Maximum image width is 6864, see library file @file{s-rannum.ads}. - -@sp 1 -@item -@cartouche -@noindent -The algorithms for random number generation. See -A.5.2(32). -@end cartouche -@noindent -The algorithm is the Mersenne Twister, as documented in the source file -@file{s-rannum.adb}. This version of the algorithm has a period of -2**19937-1. +@cite{Standard'Target_Name} (@cite{Standard} is the only permissible +prefix) provides a static string value that identifies the target +for the current compilation. For GCC implementations, this is the +standard gcc target name without the terminating slash (for +example, GNAT 5.0 on windows yields "i586-pc-mingw32msv"). -@sp 1 -@item -@cartouche -@noindent -The string representation of a random number generator's -state. See A.5.2(38). -@end cartouche -@noindent -The value returned by the Image function is the concatenation of -the fixed-width decimal representations of the 624 32-bit integers -of the state vector. +@node Attribute To_Address,Attribute To_Any,Attribute Target_Name,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-to-address}@anchor{152} +@section Attribute To_Address -@sp 1 -@item -@cartouche -@noindent -The minimum time interval between calls to the -time-dependent Reset procedure that are guaranteed to initiate different -random number sequences. See A.5.2(45). -@end cartouche -@noindent -The minimum period between reset calls to guarantee distinct series of -random numbers is one microsecond. -@sp 1 -@item -@cartouche -@noindent -The values of the @code{Model_Mantissa}, -@code{Model_Emin}, @code{Model_Epsilon}, @code{Model}, -@code{Safe_First}, and @code{Safe_Last} attributes, if the Numerics -Annex is not supported. See A.5.3(72). -@end cartouche -@noindent -Run the compiler with @option{-gnatS} to produce a listing of package -@code{Standard}, has the values of all numeric attributes. - -@sp 1 -@item -@cartouche -@noindent -Any implementation-defined characteristics of the -input-output packages. See A.7(14). -@end cartouche -@noindent -There are no special implementation defined characteristics for these -packages. +@geindex To_Address -@sp 1 -@item -@cartouche -@noindent -The value of @code{Buffer_Size} in @code{Storage_IO}. See -A.9(10). -@end cartouche -@noindent -All type representations are contiguous, and the @code{Buffer_Size} is -the value of @code{@var{type}'Size} rounded up to the next storage unit -boundary. +The @cite{System'To_Address} +(@cite{System} is the only permissible prefix) +denotes a function identical to +@cite{System.Storage_Elements.To_Address} except that +it is a static attribute. This means that if its argument is +a static expression, then the result of the attribute is a +static expression. This means that such an expression can be +used in contexts (e.g., preelaborable packages) which require a +static expression and where the function call could not be used +(since the function call is always non-static, even if its +argument is static). The argument must be in the range +-(2**(m-1) .. 2**m-1, where m is the memory size +(typically 32 or 64). Negative values are intepreted in a +modular manner (e.g., -1 means the same as 16#FFFF_FFFF# on +a 32 bits machine). -@sp 1 -@item -@cartouche -@noindent -External files for standard input, standard output, and -standard error See A.10(5). -@end cartouche -@noindent -These files are mapped onto the files provided by the C streams -libraries. See source file @file{i-cstrea.ads} for further details. +@node Attribute To_Any,Attribute Type_Class,Attribute To_Address,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-to-any}@anchor{153} +@section Attribute To_Any -@sp 1 -@item -@cartouche -@noindent -The accuracy of the value produced by @code{Put}. See -A.10.9(36). -@end cartouche -@noindent -If more digits are requested in the output than are represented by the -precision of the value, zeroes are output in the corresponding least -significant digit positions. -@sp 1 -@item -@cartouche -@noindent -The meaning of @code{Argument_Count}, @code{Argument}, and -@code{Command_Name}. See A.15(1). -@end cartouche -@noindent -These are mapped onto the @code{argv} and @code{argc} parameters of the -main program in the natural manner. +@geindex To_Any -@sp 1 -@item -@cartouche -@noindent -The interpretation of the @code{Form} parameter in procedure -@code{Create_Directory}. See A.16(56). -@end cartouche -@noindent -The @code{Form} parameter is not used. - -@sp 1 -@item -@cartouche -@noindent -The interpretation of the @code{Form} parameter in procedure -@code{Create_Path}. See A.16(60). -@end cartouche -@noindent -The @code{Form} parameter is not used. - -@sp 1 -@item -@cartouche -@noindent -The interpretation of the @code{Form} parameter in procedure -@code{Copy_File}. See A.16(68). -@end cartouche -@noindent -The @code{Form} parameter is case-insensitive. +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. -Two fields are recognized in the @code{Form} parameter: +@node Attribute Type_Class,Attribute Type_Key,Attribute To_Any,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-type-class}@anchor{154} +@section Attribute Type_Class -@table @code -@item preserve= +@geindex Type_Class -@item mode= +@code{type'Type_Class} for any type or subtype @cite{type} yields +the value of the type class for the full type of @cite{type}. If +@cite{type} is a generic formal type, the value is the value for the +corresponding actual subtype. The value of this attribute is of type +@code{System.Aux_DEC.Type_Class}, which has the following definition: -@end table +@example +type Type_Class is + (Type_Class_Enumeration, + Type_Class_Integer, + Type_Class_Fixed_Point, + Type_Class_Floating_Point, + Type_Class_Array, + Type_Class_Record, + Type_Class_Access, + Type_Class_Task, + Type_Class_Address); +@end example -@noindent - starts immediately after the character '=' and ends with the -character immediately preceding the next comma (',') or with the last -character of the parameter. +Protected types yield the value @cite{Type_Class_Task}, which thus +applies to all concurrent types. This attribute is designed to +be compatible with the DEC Ada 83 attribute of the same name. -The only possible values for preserve= are: +@node Attribute Type_Key,Attribute TypeCode,Attribute Type_Class,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-type-key}@anchor{155} +@section Attribute Type_Key -@table @code -@item no_attributes -Do not try to preserve any file attributes. This is the default if no -preserve= is found in Form. +@geindex Type_Key -@item all_attributes -Try to preserve all file attributes (timestamps, access rights). +The @cite{Type_Key} attribute is applicable to a type or subtype and +yields a value of type Standard.String containing encoded information +about the type or subtype. This provides improved compatibility with +other implementations that support this attribute. -@item timestamps -Preserve the timestamp of the copied file, but not the other file attributes. +@node Attribute TypeCode,Attribute UET_Address,Attribute Type_Key,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-typecode}@anchor{156} +@section Attribute TypeCode -@end table -@noindent -The only possible values for mode= are: +@geindex TypeCode -@table @code +This internal attribute is used for the generation of remote subprogram +stubs in the context of the Distributed Systems Annex. -@item copy -Only do the copy if the destination file does not already exist. If it already -exists, Copy_File fails. +@node Attribute UET_Address,Attribute Unconstrained_Array,Attribute TypeCode,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-uet-address}@anchor{157} +@section Attribute UET_Address -@item overwrite -Copy the file in all cases. Overwrite an already existing destination file. -@item append -Append the original file to the destination file. If the destination file does -not exist, the destination file is a copy of the source file. When mode=append, -the field preserve=, if it exists, is not taken into account. +@geindex UET_Address -@end table +The @cite{UET_Address} attribute can only be used for a prefix which +denotes a library package. It yields the address of the unit exception +table when zero cost exception handling is used. This attribute is +intended only for use within the GNAT implementation. See the unit +@cite{Ada.Exceptions} in files @code{a-except.ads} and @code{a-except.adb} +for details on how this attribute is used in the implementation. -@noindent -If the Form parameter includes one or both of the fields and the value or -values are incorrect, Copy_file fails with Use_Error. +@node Attribute Unconstrained_Array,Attribute Universal_Literal_String,Attribute UET_Address,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-unconstrained-array}@anchor{158} +@section Attribute Unconstrained_Array -Examples of correct Forms: -@smallexample -Form => "preserve=no_attributes,mode=overwrite" (the default) +@geindex Unconstrained_Array + +The @cite{Unconstrained_Array} attribute can be used with a prefix that +denotes any type or subtype. It is a static attribute that yields +@cite{True} if the prefix designates an unconstrained array, +and @cite{False} otherwise. In a generic instance, the result is +still static, and yields the result of applying this test to the +generic actual. + +@node Attribute Universal_Literal_String,Attribute Unrestricted_Access,Attribute Unconstrained_Array,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-universal-literal-string}@anchor{159} +@section Attribute Universal_Literal_String + + +@geindex Named numbers +@geindex representation of + +@geindex Universal_Literal_String + +The prefix of @cite{Universal_Literal_String} must be a named +number. The static result is the string consisting of the characters of +the number as defined in the original source. This allows the user +program to access the actual text of named numbers without intermediate +conversions and without the need to enclose the strings in quotes (which +would preclude their use as numbers). + +For example, the following program prints the first 50 digits of pi: + +@example +with Text_IO; use Text_IO; +with Ada.Numerics; +procedure Pi is +begin + Put (Ada.Numerics.Pi'Universal_Literal_String); +end; +@end example + +@node Attribute Unrestricted_Access,Attribute Update,Attribute Universal_Literal_String,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-unrestricted-access}@anchor{15a} +@section Attribute Unrestricted_Access + + +@geindex Access +@geindex unrestricted + +@geindex Unrestricted_Access + +The @cite{Unrestricted_Access} attribute is similar to @cite{Access} +except that all accessibility and aliased view checks are omitted. This +is a user-beware attribute. + +For objects, it is similar to @cite{Address}, for which it is a +desirable replacement where the value desired is an access type. +In other words, its effect is similar to first applying the +@cite{Address} attribute and then doing an unchecked conversion to a +desired access type. + +For subprograms, @cite{P'Unrestricted_Access} may be used where +@cite{P'Access} would be illegal, to construct a value of a +less-nested named access type that designates a more-nested +subprogram. This value may be used in indirect calls, so long as the +more-nested subprogram still exists; once the subprogram containing it +has returned, such calls are erroneous. For example: + +@example +package body P is + + type Less_Nested is not null access procedure; + Global : Less_Nested; + + procedure P1 is + begin + Global.all; + end P1; + + procedure P2 is + Local_Var : Integer; + + procedure More_Nested is + begin + ... Local_Var ... + end More_Nested; + begin + Global := More_Nested'Unrestricted_Access; + P1; + end P2; + +end P; +@end example + +When P1 is called from P2, the call via Global is OK, but if P1 were +called after P2 returns, it would be an erroneous use of a dangling +pointer. + +For objects, it is possible to use @cite{Unrestricted_Access} for any +type. However, if the result is of an access-to-unconstrained array +subtype, then the resulting pointer has the same scope as the context +of the attribute, and must not be returned to some enclosing scope. +For instance, if a function uses @cite{Unrestricted_Access} to create +an access-to-unconstrained-array and returns that value to the caller, +the result will involve dangling pointers. In addition, it is only +valid to create pointers to unconstrained arrays using this attribute +if the pointer has the normal default 'fat' representation where a +pointer has two components, one points to the array and one points to +the bounds. If a size clause is used to force 'thin' representation +for a pointer to unconstrained where there is only space for a single +pointer, then the resulting pointer is not usable. + +In the simple case where a direct use of Unrestricted_Access attempts +to make a thin pointer for a non-aliased object, the compiler will +reject the use as illegal, as shown in the following example: + +@example +with System; use System; +procedure SliceUA2 is + type A is access all String; + for A'Size use Standard'Address_Size; + + procedure P (Arg : A) is + begin + null; + end P; + + X : String := "hello world!"; + X2 : aliased String := "hello world!"; + + AV : A := X'Unrestricted_Access; -- ERROR + | +>>> illegal use of Unrestricted_Access attribute +>>> attempt to generate thin pointer to unaliased object + +begin + P (X'Unrestricted_Access); -- ERROR + | +>>> illegal use of Unrestricted_Access attribute +>>> attempt to generate thin pointer to unaliased object + + P (X(7 .. 12)'Unrestricted_Access); -- ERROR + | +>>> illegal use of Unrestricted_Access attribute +>>> attempt to generate thin pointer to unaliased object + + P (X2'Unrestricted_Access); -- OK +end; +@end example + +but other cases cannot be detected by the compiler, and are +considered to be erroneous. Consider the following example: + +@example +with System; use System; +with System; use System; +procedure SliceUA is + type AF is access all String; + + type A is access all String; + for A'Size use Standard'Address_Size; + + procedure P (Arg : A) is + begin + if Arg'Length /= 6 then + raise Program_Error; + end if; + end P; + + X : String := "hello world!"; + Y : AF := X (7 .. 12)'Unrestricted_Access; + +begin + P (A (Y)); +end; +@end example + +A normal unconstrained array value +or a constrained array object marked as aliased has the bounds in memory +just before the array, so a thin pointer can retrieve both the data and +the bounds. But in this case, the non-aliased object @cite{X} does not have the +bounds before the string. If the size clause for type @cite{A} +were not present, then the pointer +would be a fat pointer, where one component is a pointer to the bounds, +and all would be well. But with the size clause present, the conversion from +fat pointer to thin pointer in the call loses the bounds, and so this +is erroneous, and the program likely raises a @cite{Program_Error} exception. + +In general, it is advisable to completely +avoid mixing the use of thin pointers and the use of +@cite{Unrestricted_Access} where the designated type is an +unconstrained array. The use of thin pointers should be restricted to +cases of porting legacy code that implicitly assumes the size of pointers, +and such code should not in any case be using this attribute. + +Another erroneous situation arises if the attribute is +applied to a constant. The resulting pointer can be used to access the +constant, but the effect of trying to modify a constant in this manner +is not well-defined. Consider this example: + +@example +P : constant Integer := 4; +type R is access all Integer; +RV : R := P'Unrestricted_Access; +.. +RV.all := 3; +@end example + +Here we attempt to modify the constant P from 4 to 3, but the compiler may +or may not notice this attempt, and subsequent references to P may yield +either the value 3 or the value 4 or the assignment may blow up if the +compiler decides to put P in read-only memory. One particular case where +@cite{Unrestricted_Access} can be used in this way is to modify the +value of an @cite{IN} parameter: + +@example +procedure K (S : in String) is + type R is access all Character; + RV : R := S (3)'Unrestricted_Access; +begin + RV.all := 'a'; +end; +@end example + +In general this is a risky approach. It may appear to "work" but such uses of +@cite{Unrestricted_Access} are potentially non-portable, even from one version +of @cite{GNAT} to another, so are best avoided if possible. + +@node Attribute Update,Attribute Valid_Scalars,Attribute Unrestricted_Access,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-update}@anchor{15b} +@section Attribute Update + + +@geindex Update + +The @cite{Update} attribute creates a copy of an array or record value +with one or more modified components. The syntax is: + +@example +PREFIX'Update ( RECORD_COMPONENT_ASSOCIATION_LIST ) +PREFIX'Update ( ARRAY_COMPONENT_ASSOCIATION @{, ARRAY_COMPONENT_ASSOCIATION @} ) +PREFIX'Update ( MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION + @{, MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION @} ) + +MULTIDIMENSIONAL_ARRAY_COMPONENT_ASSOCIATION ::= INDEX_EXPRESSION_LIST_LIST => EXPRESSION +INDEX_EXPRESSION_LIST_LIST ::= INDEX_EXPRESSION_LIST @{| INDEX_EXPRESSION_LIST @} +INDEX_EXPRESSION_LIST ::= ( EXPRESSION @{, EXPRESSION @} ) +@end example + +where @cite{PREFIX} is the name of an array or record object, the +association list in parentheses does not contain an @cite{others} +choice and the box symbol @cite{<>} may not appear in any +expression. The effect is to yield a copy of the array or record value +which is unchanged apart from the components mentioned in the +association list, which are changed to the indicated value. The +original value of the array or record value is not affected. For +example: + +@example +type Arr is Array (1 .. 5) of Integer; +... +Avar1 : Arr := (1,2,3,4,5); +Avar2 : Arr := Avar1'Update (2 => 10, 3 .. 4 => 20); +@end example + +yields a value for @cite{Avar2} of 1,10,20,20,5 with @cite{Avar1} +begin unmodified. Similarly: + +@example +type Rec is A, B, C : Integer; +... +Rvar1 : Rec := (A => 1, B => 2, C => 3); +Rvar2 : Rec := Rvar1'Update (B => 20); +@end example + +yields a value for @cite{Rvar2} of (A => 1, B => 20, C => 3), +with @cite{Rvar1} being unmodifed. +Note that the value of the attribute reference is computed +completely before it is used. This means that if you write: + +@example +Avar1 := Avar1'Update (1 => 10, 2 => Function_Call); +@end example + +then the value of @cite{Avar1} is not modified if @cite{Function_Call} +raises an exception, unlike the effect of a series of direct assignments +to elements of @cite{Avar1}. In general this requires that +two extra complete copies of the object are required, which should be +kept in mind when considering efficiency. + +The @cite{Update} attribute cannot be applied to prefixes of a limited +type, and cannot reference discriminants in the case of a record type. +The accessibility level of an Update attribute result object is defined +as for an aggregate. + +In the record case, no component can be mentioned more than once. In +the array case, two overlapping ranges can appear in the association list, +in which case the modifications are processed left to right. + +Multi-dimensional arrays can be modified, as shown by this example: + +@example +A : array (1 .. 10, 1 .. 10) of Integer; +.. +A := A'Update ((1, 2) => 20, (3, 4) => 30); +@end example + +which changes element (1,2) to 20 and (3,4) to 30. + +@node Attribute Valid_Scalars,Attribute VADS_Size,Attribute Update,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-valid-scalars}@anchor{15c} +@section Attribute Valid_Scalars + + +@geindex Valid_Scalars + +The @cite{'Valid_Scalars} attribute is intended to make it easier to +check the validity of scalar subcomponents of composite objects. It +is defined for any prefix @cite{X} that denotes an object. +The value of this attribute is of the predefined type Boolean. +@cite{X'Valid_Scalars} yields True if and only if evaluation of +@cite{P'Valid} yields True for every scalar part P of X or if X has +no scalar parts. It is not specified in what order the scalar parts +are checked, nor whether any more are checked after any one of them +is determined to be invalid. If the prefix @cite{X} is of a class-wide +type @cite{T'Class} (where @cite{T} is the associated specific type), +or if the prefix @cite{X} is of a specific tagged type @cite{T}, then +only the scalar parts of components of @cite{T} are traversed; in other +words, components of extensions of @cite{T} are not traversed even if +@cite{T'Class (X)'Tag /= T'Tag} . The compiler will issue a warning if it can +be determined at compile time that the prefix of the attribute has no +scalar parts (e.g., if the prefix is of an access type, an interface type, +an undiscriminated task type, or an undiscriminated protected type). + +For scalar types, @cite{Valid_Scalars} is equivalent to @cite{Valid}. The use +of this attribute is not permitted for @cite{Unchecked_Union} types for which +in general it is not possible to determine the values of the discriminants. + +Note: @cite{Valid_Scalars} can generate a lot of code, especially in the case +of a large variant record. If the attribute is called in many places in the +same program applied to objects of the same type, it can reduce program size +to write a function with a single use of the attribute, and then call that +function from multiple places. + +@node Attribute VADS_Size,Attribute Value_Size,Attribute Valid_Scalars,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-vads-size}@anchor{15d} +@section Attribute VADS_Size + + +@geindex Size +@geindex VADS compatibility + +@geindex VADS_Size + +The @cite{'VADS_Size} attribute is intended to make it easier to port +legacy code which relies on the semantics of @cite{'Size} as implemented +by the VADS Ada 83 compiler. GNAT makes a best effort at duplicating the +same semantic interpretation. In particular, @cite{'VADS_Size} applied +to a predefined or other primitive type with no Size clause yields the +Object_Size (for example, @cite{Natural'Size} is 32 rather than 31 on +typical machines). In addition @cite{'VADS_Size} applied to an object +gives the result that would be obtained by applying the attribute to +the corresponding type. + +@node Attribute Value_Size,Attribute Wchar_T_Size,Attribute VADS_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-value-size}@anchor{15e} +@section Attribute Value_Size + + +@geindex Size +@geindex setting for not-first subtype + +@geindex Value_Size + +@code{type'Value_Size} is the number of bits required to represent +a value of the given subtype. It is the same as @code{type'Size}, +but, unlike @cite{Size}, may be set for non-first subtypes. + +@node Attribute Wchar_T_Size,Attribute Word_Size,Attribute Value_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-wchar-t-size}@anchor{15f} +@section Attribute Wchar_T_Size + + +@geindex Wchar_T_Size + +@cite{Standard'Wchar_T_Size} (@cite{Standard} is the only permissible +prefix) provides the size in bits of the C @cite{wchar_t} type +primarily for constructing the definition of this type in +package @cite{Interfaces.C}. The result is a static constant. + +@node Attribute Word_Size,,Attribute Wchar_T_Size,Implementation Defined Attributes +@anchor{gnat_rm/implementation_defined_attributes attribute-word-size}@anchor{160} +@section Attribute Word_Size + + +@geindex Word_Size + +@cite{Standard'Word_Size} (@cite{Standard} is the only permissible +prefix) provides the value @cite{System.Word_Size}. The result is +a static constant. + +@node Standard and Implementation Defined Restrictions,Implementation Advice,Implementation Defined Attributes,Top +@anchor{gnat_rm/standard_and_implementation_defined_restrictions standard-and-implementation-defined-restrictions}@anchor{9}@anchor{gnat_rm/standard_and_implementation_defined_restrictions doc}@anchor{161}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id1}@anchor{162} +@chapter Standard and Implementation Defined Restrictions + + +All Ada Reference Manual-defined Restriction identifiers are implemented: + + +@itemize * + +@item +language-defined restrictions (see 13.12.1) + +@item +tasking restrictions (see D.7) + +@item +high integrity restrictions (see H.4) +@end itemize + +GNAT implements additional restriction identifiers. All restrictions, whether +language defined or GNAT-specific, are listed in the following. + +@menu +* Partition-Wide Restrictions:: +* Program Unit Level Restrictions:: + +@end menu + +@node Partition-Wide Restrictions,Program Unit Level Restrictions,,Standard and Implementation Defined Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions partition-wide-restrictions}@anchor{163}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id2}@anchor{164} +@section Partition-Wide Restrictions + + +There are two separate lists of restriction identifiers. The first +set requires consistency throughout a partition (in other words, if the +restriction identifier is used for any compilation unit in the partition, +then all compilation units in the partition must obey the restriction). + +@menu +* Immediate_Reclamation:: +* Max_Asynchronous_Select_Nesting:: +* Max_Entry_Queue_Length:: +* Max_Protected_Entries:: +* Max_Select_Alternatives:: +* Max_Storage_At_Blocking:: +* Max_Task_Entries:: +* Max_Tasks:: +* No_Abort_Statements:: +* No_Access_Parameter_Allocators:: +* No_Access_Subprograms:: +* No_Allocators:: +* No_Anonymous_Allocators:: +* No_Calendar:: +* No_Coextensions:: +* No_Default_Initialization:: +* No_Delay:: +* No_Dependence:: +* No_Direct_Boolean_Operators:: +* No_Dispatch:: +* No_Dispatching_Calls:: +* No_Dynamic_Attachment:: +* No_Dynamic_Priorities:: +* No_Entry_Calls_In_Elaboration_Code:: +* No_Enumeration_Maps:: +* No_Exception_Handlers:: +* No_Exception_Propagation:: +* No_Exception_Registration:: +* No_Exceptions:: +* No_Finalization:: +* No_Fixed_Point:: +* No_Floating_Point:: +* No_Implicit_Conditionals:: +* No_Implicit_Dynamic_Code:: +* No_Implicit_Heap_Allocations:: +* No_Implicit_Loops:: +* No_Initialize_Scalars:: +* No_IO:: +* No_Local_Allocators:: +* No_Local_Protected_Objects:: +* No_Local_Timing_Events:: +* No_Long_Long_Integers:: +* No_Multiple_Elaboration:: +* No_Nested_Finalization:: +* No_Protected_Type_Allocators:: +* No_Protected_Types:: +* No_Recursion:: +* No_Reentrancy:: +* No_Relative_Delay:: +* No_Requeue_Statements:: +* No_Secondary_Stack:: +* No_Select_Statements:: +* No_Specific_Termination_Handlers:: +* No_Specification_of_Aspect:: +* No_Standard_Allocators_After_Elaboration:: +* No_Standard_Storage_Pools:: +* No_Stream_Optimizations:: +* No_Streams:: +* No_Task_Allocators:: +* No_Task_Attributes_Package:: +* No_Task_Hierarchy:: +* No_Task_Termination:: +* No_Tasking:: +* No_Terminate_Alternatives:: +* No_Unchecked_Access:: +* No_Use_Of_Entity:: +* Simple_Barriers:: +* Static_Priorities:: +* Static_Storage_Size:: + +@end menu + +@node Immediate_Reclamation,Max_Asynchronous_Select_Nesting,,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions immediate-reclamation}@anchor{165} +@subsection Immediate_Reclamation + + +@geindex Immediate_Reclamation + +[RM H.4] This restriction ensures that, except for storage occupied by +objects created by allocators and not deallocated via unchecked +deallocation, any storage reserved at run time for an object is +immediately reclaimed when the object no longer exists. + +@node Max_Asynchronous_Select_Nesting,Max_Entry_Queue_Length,Immediate_Reclamation,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-asynchronous-select-nesting}@anchor{166} +@subsection Max_Asynchronous_Select_Nesting + + +@geindex Max_Asynchronous_Select_Nesting + +[RM D.7] Specifies the maximum dynamic nesting level of asynchronous +selects. Violations of this restriction with a value of zero are +detected at compile time. Violations of this restriction with values +other than zero cause Storage_Error to be raised. + +@node Max_Entry_Queue_Length,Max_Protected_Entries,Max_Asynchronous_Select_Nesting,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-entry-queue-length}@anchor{167} +@subsection Max_Entry_Queue_Length + + +@geindex Max_Entry_Queue_Length + +[RM D.7] This restriction is a declaration that any protected entry compiled in +the scope of the restriction has at most the specified number of +tasks waiting on the entry at any one time, and so no queue is required. +Note that this restriction is checked at run time. Violation of this +restriction results in the raising of Program_Error exception at the point of +the call. + +@geindex Max_Entry_Queue_Depth + +The restriction @cite{Max_Entry_Queue_Depth} is recognized as a +synonym for @cite{Max_Entry_Queue_Length}. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +@node Max_Protected_Entries,Max_Select_Alternatives,Max_Entry_Queue_Length,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-protected-entries}@anchor{168} +@subsection Max_Protected_Entries + + +@geindex Max_Protected_Entries + +[RM D.7] Specifies the maximum number of entries per protected type. The +bounds of every entry family of a protected unit shall be static, or shall be +defined by a discriminant of a subtype whose corresponding bound is static. + +@node Max_Select_Alternatives,Max_Storage_At_Blocking,Max_Protected_Entries,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-select-alternatives}@anchor{169} +@subsection Max_Select_Alternatives + + +@geindex Max_Select_Alternatives + +[RM D.7] Specifies the maximum number of alternatives in a selective accept. + +@node Max_Storage_At_Blocking,Max_Task_Entries,Max_Select_Alternatives,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-storage-at-blocking}@anchor{16a} +@subsection Max_Storage_At_Blocking + + +@geindex Max_Storage_At_Blocking + +[RM D.7] Specifies the maximum portion (in storage elements) of a task's +Storage_Size that can be retained by a blocked task. A violation of this +restriction causes Storage_Error to be raised. + +@node Max_Task_Entries,Max_Tasks,Max_Storage_At_Blocking,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-task-entries}@anchor{16b} +@subsection Max_Task_Entries + + +@geindex Max_Task_Entries + +[RM D.7] Specifies the maximum number of entries +per task. The bounds of every entry family +of a task unit shall be static, or shall be +defined by a discriminant of a subtype whose +corresponding bound is static. + +@node Max_Tasks,No_Abort_Statements,Max_Task_Entries,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions max-tasks}@anchor{16c} +@subsection Max_Tasks + + +@geindex Max_Tasks + +[RM D.7] Specifies the maximum number of task that may be created, not +counting the creation of the environment task. Violations of this +restriction with a value of zero are detected at compile +time. Violations of this restriction with values other than zero cause +Storage_Error to be raised. + +@node No_Abort_Statements,No_Access_Parameter_Allocators,Max_Tasks,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-abort-statements}@anchor{16d} +@subsection No_Abort_Statements + + +@geindex No_Abort_Statements + +[RM D.7] There are no abort_statements, and there are +no calls to Task_Identification.Abort_Task. + +@node No_Access_Parameter_Allocators,No_Access_Subprograms,No_Abort_Statements,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-parameter-allocators}@anchor{16e} +@subsection No_Access_Parameter_Allocators + + +@geindex No_Access_Parameter_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator as the actual parameter to an access +parameter. + +@node No_Access_Subprograms,No_Allocators,No_Access_Parameter_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-access-subprograms}@anchor{16f} +@subsection No_Access_Subprograms + + +@geindex No_Access_Subprograms + +[RM H.4] This restriction ensures at compile time that there are no +declarations of access-to-subprogram types. + +@node No_Allocators,No_Anonymous_Allocators,No_Access_Subprograms,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-allocators}@anchor{170} +@subsection No_Allocators + + +@geindex No_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator. + +@node No_Anonymous_Allocators,No_Calendar,No_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-anonymous-allocators}@anchor{171} +@subsection No_Anonymous_Allocators + + +@geindex No_Anonymous_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator of anonymous access type. + +@node No_Calendar,No_Coextensions,No_Anonymous_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-calendar}@anchor{172} +@subsection No_Calendar + + +@geindex No_Calendar + +[GNAT] This restriction ensures at compile time that there is no implicit or +explicit dependence on the package @cite{Ada.Calendar}. + +@node No_Coextensions,No_Default_Initialization,No_Calendar,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-coextensions}@anchor{173} +@subsection No_Coextensions + + +@geindex No_Coextensions + +[RM H.4] This restriction ensures at compile time that there are no +coextensions. See 3.10.2. + +@node No_Default_Initialization,No_Delay,No_Coextensions,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-default-initialization}@anchor{174} +@subsection No_Default_Initialization + + +@geindex No_Default_Initialization + +[GNAT] This restriction prohibits any instance of default initialization +of variables. The binder implements a consistency rule which prevents +any unit compiled without the restriction from with'ing a unit with the +restriction (this allows the generation of initialization procedures to +be skipped, since you can be sure that no call is ever generated to an +initialization procedure in a unit with the restriction active). If used +in conjunction with Initialize_Scalars or Normalize_Scalars, the effect +is to prohibit all cases of variables declared without a specific +initializer (including the case of OUT scalar parameters). + +@node No_Delay,No_Dependence,No_Default_Initialization,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-delay}@anchor{175} +@subsection No_Delay + + +@geindex No_Delay + +[RM H.4] This restriction ensures at compile time that there are no +delay statements and no dependences on package Calendar. + +@node No_Dependence,No_Direct_Boolean_Operators,No_Delay,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dependence}@anchor{176} +@subsection No_Dependence + + +@geindex No_Dependence + +[RM 13.12.1] This restriction checks at compile time that there are no +dependence on a library unit. + +@node No_Direct_Boolean_Operators,No_Dispatch,No_Dependence,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-direct-boolean-operators}@anchor{177} +@subsection No_Direct_Boolean_Operators + + +@geindex No_Direct_Boolean_Operators + +[GNAT] This restriction ensures that no logical operators (and/or/xor) +are used on operands of type Boolean (or any type derived from Boolean). +This is intended for use in safety critical programs where the certification +protocol requires the use of short-circuit (and then, or else) forms for all +composite boolean operations. + +@node No_Dispatch,No_Dispatching_Calls,No_Direct_Boolean_Operators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatch}@anchor{178} +@subsection No_Dispatch + + +@geindex No_Dispatch + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of @cite{T'Class}, for any (tagged) subtype @cite{T}. + +@node No_Dispatching_Calls,No_Dynamic_Attachment,No_Dispatch,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dispatching-calls}@anchor{179} +@subsection No_Dispatching_Calls + + +@geindex No_Dispatching_Calls + +[GNAT] This restriction ensures at compile time that the code generated by the +compiler involves no dispatching calls. The use of this restriction allows the +safe use of record extensions, classwide membership tests and other classwide +features not involving implicit dispatching. This restriction ensures that +the code contains no indirect calls through a dispatching mechanism. Note that +this includes internally-generated calls created by the compiler, for example +in the implementation of class-wide objects assignments. The +membership test is allowed in the presence of this restriction, because its +implementation requires no dispatching. +This restriction is comparable to the official Ada restriction +@cite{No_Dispatch} except that it is a bit less restrictive in that it allows +all classwide constructs that do not imply dispatching. +The following example indicates constructs that violate this restriction. + +@example +package Pkg is + type T is tagged record + Data : Natural; + end record; + procedure P (X : T); + + type DT is new T with record + More_Data : Natural; + end record; + procedure Q (X : DT); +end Pkg; + +with Pkg; use Pkg; +procedure Example is + procedure Test (O : T'Class) is + N : Natural := O'Size;-- Error: Dispatching call + C : T'Class := O; -- Error: implicit Dispatching Call + begin + if O in DT'Class then -- OK : Membership test + Q (DT (O)); -- OK : Type conversion plus direct call + else + P (O); -- Error: Dispatching call + end if; + end Test; + + Obj : DT; +begin + P (Obj); -- OK : Direct call + P (T (Obj)); -- OK : Type conversion plus direct call + P (T'Class (Obj)); -- Error: Dispatching call + + Test (Obj); -- OK : Type conversion + + if Obj in T'Class then -- OK : Membership test + null; + end if; +end Example; +@end example + +@node No_Dynamic_Attachment,No_Dynamic_Priorities,No_Dispatching_Calls,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-attachment}@anchor{17a} +@subsection No_Dynamic_Attachment + + +@geindex No_Dynamic_Attachment + +[RM D.7] This restriction ensures that there is no call to any of the +operations defined in package Ada.Interrupts +(Is_Reserved, Is_Attached, Current_Handler, Attach_Handler, Exchange_Handler, +Detach_Handler, and Reference). + +@geindex No_Dynamic_Interrupts + +The restriction @cite{No_Dynamic_Interrupts} is recognized as a +synonym for @cite{No_Dynamic_Attachment}. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +@node No_Dynamic_Priorities,No_Entry_Calls_In_Elaboration_Code,No_Dynamic_Attachment,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-dynamic-priorities}@anchor{17b} +@subsection No_Dynamic_Priorities + + +@geindex No_Dynamic_Priorities + +[RM D.7] There are no semantic dependencies on the package Dynamic_Priorities. + +@node No_Entry_Calls_In_Elaboration_Code,No_Enumeration_Maps,No_Dynamic_Priorities,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-calls-in-elaboration-code}@anchor{17c} +@subsection No_Entry_Calls_In_Elaboration_Code + + +@geindex No_Entry_Calls_In_Elaboration_Code + +[GNAT] This restriction ensures at compile time that no task or protected entry +calls are made during elaboration code. As a result of the use of this +restriction, the compiler can assume that no code past an accept statement +in a task can be executed at elaboration time. + +@node No_Enumeration_Maps,No_Exception_Handlers,No_Entry_Calls_In_Elaboration_Code,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-enumeration-maps}@anchor{17d} +@subsection No_Enumeration_Maps + + +@geindex No_Enumeration_Maps + +[GNAT] This restriction ensures at compile time that no operations requiring +enumeration maps are used (that is Image and Value attributes applied +to enumeration types). + +@node No_Exception_Handlers,No_Exception_Propagation,No_Enumeration_Maps,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-handlers}@anchor{17e} +@subsection No_Exception_Handlers + + +@geindex No_Exception_Handlers + +[GNAT] This restriction ensures at compile time that there are no explicit +exception handlers. It also indicates that no exception propagation will +be provided. In this mode, exceptions may be raised but will result in +an immediate call to the last chance handler, a routine that the user +must define with the following profile: + +@example +procedure Last_Chance_Handler + (Source_Location : System.Address; Line : Integer); +pragma Export (C, Last_Chance_Handler, + "__gnat_last_chance_handler"); +@end example + +The parameter is a C null-terminated string representing a message to be +associated with the exception (typically the source location of the raise +statement generated by the compiler). The Line parameter when nonzero +represents the line number in the source program where the raise occurs. + +@node No_Exception_Propagation,No_Exception_Registration,No_Exception_Handlers,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-propagation}@anchor{17f} +@subsection No_Exception_Propagation + + +@geindex No_Exception_Propagation + +[GNAT] This restriction guarantees that exceptions are never propagated +to an outer subprogram scope. The only case in which an exception may +be raised is when the handler is statically in the same subprogram, so +that the effect of a raise is essentially like a goto statement. Any +other raise statement (implicit or explicit) will be considered +unhandled. Exception handlers are allowed, but may not contain an +exception occurrence identifier (exception choice). In addition, use of +the package GNAT.Current_Exception is not permitted, and reraise +statements (raise with no operand) are not permitted. + +@node No_Exception_Registration,No_Exceptions,No_Exception_Propagation,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exception-registration}@anchor{180} +@subsection No_Exception_Registration + + +@geindex No_Exception_Registration + +[GNAT] This restriction ensures at compile time that no stream operations for +types Exception_Id or Exception_Occurrence are used. This also makes it +impossible to pass exceptions to or from a partition with this restriction +in a distributed environment. If this restriction is active, the generated +code is simplified by omitting the otherwise-required global registration +of exceptions when they are declared. + +@node No_Exceptions,No_Finalization,No_Exception_Registration,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-exceptions}@anchor{181} +@subsection No_Exceptions + + +@geindex No_Exceptions + +[RM H.4] This restriction ensures at compile time that there are no +raise statements and no exception handlers. + +@node No_Finalization,No_Fixed_Point,No_Exceptions,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-finalization}@anchor{182} +@subsection No_Finalization + + +@geindex No_Finalization + +[GNAT] This restriction disables the language features described in +chapter 7.6 of the Ada 2005 RM as well as all form of code generation +performed by the compiler to support these features. The following types +are no longer considered controlled when this restriction is in effect: + + +@itemize * + +@item +@cite{Ada.Finalization.Controlled} + +@item +@cite{Ada.Finalization.Limited_Controlled} + +@item +Derivations from @cite{Controlled} or @cite{Limited_Controlled} + +@item +Class-wide types + +@item +Protected types + +@item +Task types + +@item +Array and record types with controlled components +@end itemize + +The compiler no longer generates code to initialize, finalize or adjust an +object or a nested component, either declared on the stack or on the heap. The +deallocation of a controlled object no longer finalizes its contents. + +@node No_Fixed_Point,No_Floating_Point,No_Finalization,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-fixed-point}@anchor{183} +@subsection No_Fixed_Point + + +@geindex No_Fixed_Point + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of fixed point types and operations. + +@node No_Floating_Point,No_Implicit_Conditionals,No_Fixed_Point,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-floating-point}@anchor{184} +@subsection No_Floating_Point + + +@geindex No_Floating_Point + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of floating point types and operations. + +@node No_Implicit_Conditionals,No_Implicit_Dynamic_Code,No_Floating_Point,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-conditionals}@anchor{185} +@subsection No_Implicit_Conditionals + + +@geindex No_Implicit_Conditionals + +[GNAT] This restriction ensures that the generated code does not contain any +implicit conditionals, either by modifying the generated code where possible, +or by rejecting any construct that would otherwise generate an implicit +conditional. Note that this check does not include run time constraint +checks, which on some targets may generate implicit conditionals as +well. To control the latter, constraint checks can be suppressed in the +normal manner. Constructs generating implicit conditionals include comparisons +of composite objects and the Max/Min attributes. + +@node No_Implicit_Dynamic_Code,No_Implicit_Heap_Allocations,No_Implicit_Conditionals,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-dynamic-code}@anchor{186} +@subsection No_Implicit_Dynamic_Code + + +@geindex No_Implicit_Dynamic_Code + +@geindex trampoline + +[GNAT] This restriction prevents the compiler from building 'trampolines'. +This is a structure that is built on the stack and contains dynamic +code to be executed at run time. On some targets, a trampoline is +built for the following features: @cite{Access}, +@cite{Unrestricted_Access}, or @cite{Address} of a nested subprogram; +nested task bodies; primitive operations of nested tagged types. +Trampolines do not work on machines that prevent execution of stack +data. For example, on windows systems, enabling DEP (data execution +protection) will cause trampolines to raise an exception. +Trampolines are also quite slow at run time. + +On many targets, trampolines have been largely eliminated. Look at the +version of system.ads for your target --- if it has +Always_Compatible_Rep equal to False, then trampolines are largely +eliminated. In particular, a trampoline is built for the following +features: @cite{Address} of a nested subprogram; +@cite{Access} or @cite{Unrestricted_Access} of a nested subprogram, +but only if pragma Favor_Top_Level applies, or the access type has a +foreign-language convention; primitive operations of nested tagged +types. + +@node No_Implicit_Heap_Allocations,No_Implicit_Loops,No_Implicit_Dynamic_Code,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-heap-allocations}@anchor{187} +@subsection No_Implicit_Heap_Allocations + + +@geindex No_Implicit_Heap_Allocations + +[RM D.7] No constructs are allowed to cause implicit heap allocation. + +@node No_Implicit_Loops,No_Initialize_Scalars,No_Implicit_Heap_Allocations,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-loops}@anchor{188} +@subsection No_Implicit_Loops + + +@geindex No_Implicit_Loops + +[GNAT] This restriction ensures that the generated code does not contain any +implicit @cite{for} loops, either by modifying +the generated code where possible, +or by rejecting any construct that would otherwise generate an implicit +@cite{for} loop. If this restriction is active, it is possible to build +large array aggregates with all static components without generating an +intermediate temporary, and without generating a loop to initialize individual +components. Otherwise, a loop is created for arrays larger than about 5000 +scalar components. + +@node No_Initialize_Scalars,No_IO,No_Implicit_Loops,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-initialize-scalars}@anchor{189} +@subsection No_Initialize_Scalars + + +@geindex No_Initialize_Scalars + +[GNAT] This restriction ensures that no unit in the partition is compiled with +pragma Initialize_Scalars. This allows the generation of more efficient +code, and in particular eliminates dummy null initialization routines that +are otherwise generated for some record and array types. + +@node No_IO,No_Local_Allocators,No_Initialize_Scalars,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-io}@anchor{18a} +@subsection No_IO + + +@geindex No_IO + +[RM H.4] This restriction ensures at compile time that there are no +dependences on any of the library units Sequential_IO, Direct_IO, +Text_IO, Wide_Text_IO, Wide_Wide_Text_IO, or Stream_IO. + +@node No_Local_Allocators,No_Local_Protected_Objects,No_IO,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-allocators}@anchor{18b} +@subsection No_Local_Allocators + + +@geindex No_Local_Allocators + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of an allocator in subprograms, generic subprograms, tasks, +and entry bodies. + +@node No_Local_Protected_Objects,No_Local_Timing_Events,No_Local_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-protected-objects}@anchor{18c} +@subsection No_Local_Protected_Objects + + +@geindex No_Local_Protected_Objects + +[RM D.7] This restriction ensures at compile time that protected objects are +only declared at the library level. + +@node No_Local_Timing_Events,No_Long_Long_Integers,No_Local_Protected_Objects,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-local-timing-events}@anchor{18d} +@subsection No_Local_Timing_Events + + +@geindex No_Local_Timing_Events + +[RM D.7] All objects of type Ada.Timing_Events.Timing_Event are +declared at the library level. + +@node No_Long_Long_Integers,No_Multiple_Elaboration,No_Local_Timing_Events,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-long-long-integers}@anchor{18e} +@subsection No_Long_Long_Integers + + +@geindex No_Long_Long_Integers + +[GNAT] This partition-wide restriction forbids any explicit reference to +type Standard.Long_Long_Integer, and also forbids declaring range types whose +implicit base type is Long_Long_Integer, and modular types whose size exceeds +Long_Integer'Size. + +@node No_Multiple_Elaboration,No_Nested_Finalization,No_Long_Long_Integers,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-multiple-elaboration}@anchor{18f} +@subsection No_Multiple_Elaboration + + +@geindex No_Multiple_Elaboration + +[GNAT] Normally each package contains a 16-bit counter used to check for access +before elaboration, and to control multiple elaboration attempts. +This counter is eliminated for units compiled with the static model +of elaboration if restriction @cite{No_Elaboration_Code} +is active but because of +the need to check for multiple elaboration in the general case, these +counters cannot be eliminated if elaboration code may be present. The +restriction @cite{No_Multiple_Elaboration} +allows suppression of these counters +in static elaboration units even if they do have elaboration code. If this +restriction is used, then the situations in which multiple elaboration is +possible, including non-Ada main programs, and Stand Alone libraries, are not +permitted, and will be diagnosed by the binder. + +@node No_Nested_Finalization,No_Protected_Type_Allocators,No_Multiple_Elaboration,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-nested-finalization}@anchor{190} +@subsection No_Nested_Finalization + + +@geindex No_Nested_Finalization + +[RM D.7] All objects requiring finalization are declared at the library level. + +@node No_Protected_Type_Allocators,No_Protected_Types,No_Nested_Finalization,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-type-allocators}@anchor{191} +@subsection No_Protected_Type_Allocators + + +@geindex No_Protected_Type_Allocators + +[RM D.7] This restriction ensures at compile time that there are no allocator +expressions that attempt to allocate protected objects. + +@node No_Protected_Types,No_Recursion,No_Protected_Type_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-protected-types}@anchor{192} +@subsection No_Protected_Types + + +@geindex No_Protected_Types + +[RM H.4] This restriction ensures at compile time that there are no +declarations of protected types or protected objects. + +@node No_Recursion,No_Reentrancy,No_Protected_Types,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-recursion}@anchor{193} +@subsection No_Recursion + + +@geindex No_Recursion + +[RM H.4] A program execution is erroneous if a subprogram is invoked as +part of its execution. + +@node No_Reentrancy,No_Relative_Delay,No_Recursion,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-reentrancy}@anchor{194} +@subsection No_Reentrancy + + +@geindex No_Reentrancy + +[RM H.4] A program execution is erroneous if a subprogram is executed by +two tasks at the same time. + +@node No_Relative_Delay,No_Requeue_Statements,No_Reentrancy,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-relative-delay}@anchor{195} +@subsection No_Relative_Delay + + +@geindex No_Relative_Delay + +[RM D.7] This restriction ensures at compile time that there are no delay +relative statements and prevents expressions such as @cite{delay 1.23;} from +appearing in source code. + +@node No_Requeue_Statements,No_Secondary_Stack,No_Relative_Delay,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-requeue-statements}@anchor{196} +@subsection No_Requeue_Statements + + +@geindex No_Requeue_Statements + +[RM D.7] This restriction ensures at compile time that no requeue statements +are permitted and prevents keyword @cite{requeue} from being used in source +code. + +@geindex No_Requeue + +The restriction @cite{No_Requeue} is recognized as a +synonym for @cite{No_Requeue_Statements}. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on oNobsolescent features are activated). + +@node No_Secondary_Stack,No_Select_Statements,No_Requeue_Statements,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-secondary-stack}@anchor{197} +@subsection No_Secondary_Stack + + +@geindex No_Secondary_Stack + +[GNAT] This restriction ensures at compile time that the generated code +does not contain any reference to the secondary stack. The secondary +stack is used to implement functions returning unconstrained objects +(arrays or records) on some targets. + +@node No_Select_Statements,No_Specific_Termination_Handlers,No_Secondary_Stack,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-select-statements}@anchor{198} +@subsection No_Select_Statements + + +@geindex No_Select_Statements + +[RM D.7] This restriction ensures at compile time no select statements of any +kind are permitted, that is the keyword @cite{select} may not appear. + +@node No_Specific_Termination_Handlers,No_Specification_of_Aspect,No_Select_Statements,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specific-termination-handlers}@anchor{199} +@subsection No_Specific_Termination_Handlers + + +@geindex No_Specific_Termination_Handlers + +[RM D.7] There are no calls to Ada.Task_Termination.Set_Specific_Handler +or to Ada.Task_Termination.Specific_Handler. + +@node No_Specification_of_Aspect,No_Standard_Allocators_After_Elaboration,No_Specific_Termination_Handlers,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-specification-of-aspect}@anchor{19a} +@subsection No_Specification_of_Aspect + + +@geindex No_Specification_of_Aspect + +[RM 13.12.1] This restriction checks at compile time that no aspect +specification, attribute definition clause, or pragma is given for a +given aspect. + +@node No_Standard_Allocators_After_Elaboration,No_Standard_Storage_Pools,No_Specification_of_Aspect,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-allocators-after-elaboration}@anchor{19b} +@subsection No_Standard_Allocators_After_Elaboration + + +@geindex No_Standard_Allocators_After_Elaboration + +[RM D.7] Specifies that an allocator using a standard storage pool +should never be evaluated at run time after the elaboration of the +library items of the partition has completed. Otherwise, Storage_Error +is raised. + +@node No_Standard_Storage_Pools,No_Stream_Optimizations,No_Standard_Allocators_After_Elaboration,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-standard-storage-pools}@anchor{19c} +@subsection No_Standard_Storage_Pools + + +@geindex No_Standard_Storage_Pools + +[GNAT] This restriction ensures at compile time that no access types +use the standard default storage pool. Any access type declared must +have an explicit Storage_Pool attribute defined specifying a +user-defined storage pool. + +@node No_Stream_Optimizations,No_Streams,No_Standard_Storage_Pools,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-stream-optimizations}@anchor{19d} +@subsection No_Stream_Optimizations + + +@geindex No_Stream_Optimizations + +[GNAT] This restriction affects the performance of stream operations on types +@cite{String}, @cite{Wide_String} and @cite{Wide_Wide_String}. By default, the +compiler uses block reads and writes when manipulating @cite{String} objects +due to their supperior performance. When this restriction is in effect, the +compiler performs all IO operations on a per-character basis. + +@node No_Streams,No_Task_Allocators,No_Stream_Optimizations,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-streams}@anchor{19e} +@subsection No_Streams + + +@geindex No_Streams + +[GNAT] This restriction ensures at compile/bind time that there are no +stream objects created and no use of stream attributes. +This restriction does not forbid dependences on the package +@cite{Ada.Streams}. So it is permissible to with +@cite{Ada.Streams} (or another package that does so itself) +as long as no actual stream objects are created and no +stream attributes are used. + +Note that the use of restriction allows optimization of tagged types, +since they do not need to worry about dispatching stream operations. +To take maximum advantage of this space-saving optimization, any +unit declaring a tagged type should be compiled with the restriction, +though this is not required. + +@node No_Task_Allocators,No_Task_Attributes_Package,No_Streams,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-allocators}@anchor{19f} +@subsection No_Task_Allocators + + +@geindex No_Task_Allocators + +[RM D.7] There are no allocators for task types +or types containing task subcomponents. + +@node No_Task_Attributes_Package,No_Task_Hierarchy,No_Task_Allocators,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-attributes-package}@anchor{1a0} +@subsection No_Task_Attributes_Package + + +@geindex No_Task_Attributes_Package + +[GNAT] This restriction ensures at compile time that there are no implicit or +explicit dependencies on the package @cite{Ada.Task_Attributes}. + +@geindex No_Task_Attributes + +The restriction @cite{No_Task_Attributes} is recognized as a synonym +for @cite{No_Task_Attributes_Package}. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +@node No_Task_Hierarchy,No_Task_Termination,No_Task_Attributes_Package,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-hierarchy}@anchor{1a1} +@subsection No_Task_Hierarchy + + +@geindex No_Task_Hierarchy + +[RM D.7] All (non-environment) tasks depend +directly on the environment task of the partition. + +@node No_Task_Termination,No_Tasking,No_Task_Hierarchy,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-task-termination}@anchor{1a2} +@subsection No_Task_Termination + + +@geindex No_Task_Termination + +[RM D.7] Tasks that terminate are erroneous. + +@node No_Tasking,No_Terminate_Alternatives,No_Task_Termination,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-tasking}@anchor{1a3} +@subsection No_Tasking + + +@geindex No_Tasking + +[GNAT] This restriction prevents the declaration of tasks or task types +throughout the partition. It is similar in effect to the use of +@cite{Max_Tasks => 0} except that violations are caught at compile time +and cause an error message to be output either by the compiler or +binder. + +@node No_Terminate_Alternatives,No_Unchecked_Access,No_Tasking,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-terminate-alternatives}@anchor{1a4} +@subsection No_Terminate_Alternatives + + +@geindex No_Terminate_Alternatives + +[RM D.7] There are no selective accepts with terminate alternatives. + +@node No_Unchecked_Access,No_Use_Of_Entity,No_Terminate_Alternatives,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-unchecked-access}@anchor{1a5} +@subsection No_Unchecked_Access + + +@geindex No_Unchecked_Access + +[RM H.4] This restriction ensures at compile time that there are no +occurrences of the Unchecked_Access attribute. + +@node No_Use_Of_Entity,Simple_Barriers,No_Unchecked_Access,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-use-of-entity}@anchor{1a6} +@subsection No_Use_Of_Entity + + +@geindex No_Use_Of_Entity + +[GNAT] This restriction ensures at compile time that there are no references +to the entity given in the form + +@example +No_Use_Of_Entity => Name +@end example + +where @code{Name} is the fully qualified entity, for example + +@example +No_Use_Of_Entity => Ada.Text_IO.Put_Line +@end example + +@node Simple_Barriers,Static_Priorities,No_Use_Of_Entity,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions simple-barriers}@anchor{1a7} +@subsection Simple_Barriers + + +@geindex Simple_Barriers + +[RM D.7] This restriction ensures at compile time that barriers in entry +declarations for protected types are restricted to either static boolean +expressions or references to simple boolean variables defined in the private +part of the protected type. No other form of entry barriers is permitted. + +@geindex Boolean_Entry_Barriers + +The restriction @cite{Boolean_Entry_Barriers} is recognized as a +synonym for @cite{Simple_Barriers}. This is retained for historical +compatibility purposes (and a warning will be generated for its use if +warnings on obsolescent features are activated). + +@node Static_Priorities,Static_Storage_Size,Simple_Barriers,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions static-priorities}@anchor{1a8} +@subsection Static_Priorities + + +@geindex Static_Priorities + +[GNAT] This restriction ensures at compile time that all priority expressions +are static, and that there are no dependences on the package +@cite{Ada.Dynamic_Priorities}. + +@node Static_Storage_Size,,Static_Priorities,Partition-Wide Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions static-storage-size}@anchor{1a9} +@subsection Static_Storage_Size + + +@geindex Static_Storage_Size + +[GNAT] This restriction ensures at compile time that any expression appearing +in a Storage_Size pragma or attribute definition clause is static. + +@node Program Unit Level Restrictions,,Partition-Wide Restrictions,Standard and Implementation Defined Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions program-unit-level-restrictions}@anchor{1aa}@anchor{gnat_rm/standard_and_implementation_defined_restrictions id3}@anchor{1ab} +@section Program Unit Level Restrictions + + +The second set of restriction identifiers +does not require partition-wide consistency. +The restriction may be enforced for a single +compilation unit without any effect on any of the +other compilation units in the partition. + +@menu +* No_Elaboration_Code:: +* No_Entry_Queue:: +* No_Implementation_Aspect_Specifications:: +* No_Implementation_Attributes:: +* No_Implementation_Identifiers:: +* No_Implementation_Pragmas:: +* No_Implementation_Restrictions:: +* No_Implementation_Units:: +* No_Implicit_Aliasing:: +* No_Obsolescent_Features:: +* No_Wide_Characters:: +* SPARK_05:: + +@end menu + +@node No_Elaboration_Code,No_Entry_Queue,,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-elaboration-code}@anchor{1ac} +@subsection No_Elaboration_Code + + +@geindex No_Elaboration_Code + +[GNAT] This restriction ensures at compile time that no elaboration code is +generated. Note that this is not the same condition as is enforced +by pragma @cite{Preelaborate}. There are cases in which pragma +@cite{Preelaborate} still permits code to be generated (e.g., code +to initialize a large array to all zeroes), and there are cases of units +which do not meet the requirements for pragma @cite{Preelaborate}, +but for which no elaboration code is generated. Generally, it is +the case that preelaborable units will meet the restrictions, with +the exception of large aggregates initialized with an others_clause, +and exception declarations (which generate calls to a run-time +registry procedure). This restriction is enforced on +a unit by unit basis, it need not be obeyed consistently +throughout a partition. + +In the case of aggregates with others, if the aggregate has a dynamic +size, there is no way to eliminate the elaboration code (such dynamic +bounds would be incompatible with @cite{Preelaborate} in any case). If +the bounds are static, then use of this restriction actually modifies +the code choice of the compiler to avoid generating a loop, and instead +generate the aggregate statically if possible, no matter how many times +the data for the others clause must be repeatedly generated. + +It is not possible to precisely document +the constructs which are compatible with this restriction, since, +unlike most other restrictions, this is not a restriction on the +source code, but a restriction on the generated object code. For +example, if the source contains a declaration: + +@example +Val : constant Integer := X; +@end example + +where X is not a static constant, it may be possible, depending +on complex optimization circuitry, for the compiler to figure +out the value of X at compile time, in which case this initialization +can be done by the loader, and requires no initialization code. It +is not possible to document the precise conditions under which the +optimizer can figure this out. + +Note that this the implementation of this restriction requires full +code generation. If it is used in conjunction with "semantics only" +checking, then some cases of violations may be missed. + +@node No_Entry_Queue,No_Implementation_Aspect_Specifications,No_Elaboration_Code,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-entry-queue}@anchor{1ad} +@subsection No_Entry_Queue + + +@geindex No_Entry_Queue + +[GNAT] This restriction is a declaration that any protected entry compiled in +the scope of the restriction has at most one task waiting on the entry +at any one time, and so no queue is required. This restriction is not +checked at compile time. A program execution is erroneous if an attempt +is made to queue a second task on such an entry. + +@node No_Implementation_Aspect_Specifications,No_Implementation_Attributes,No_Entry_Queue,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-aspect-specifications}@anchor{1ae} +@subsection No_Implementation_Aspect_Specifications + + +@geindex No_Implementation_Aspect_Specifications + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined aspects are present. With this restriction, the only +aspects that can be used are those defined in the Ada Reference Manual. + +@node No_Implementation_Attributes,No_Implementation_Identifiers,No_Implementation_Aspect_Specifications,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-attributes}@anchor{1af} +@subsection No_Implementation_Attributes + + +@geindex No_Implementation_Attributes + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined attributes are present. With this restriction, the only +attributes that can be used are those defined in the Ada Reference +Manual. + +@node No_Implementation_Identifiers,No_Implementation_Pragmas,No_Implementation_Attributes,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-identifiers}@anchor{1b0} +@subsection No_Implementation_Identifiers + + +@geindex No_Implementation_Identifiers + +[RM 13.12.1] This restriction checks at compile time that no +implementation-defined identifiers (marked with pragma Implementation_Defined) +occur within language-defined packages. + +@node No_Implementation_Pragmas,No_Implementation_Restrictions,No_Implementation_Identifiers,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-pragmas}@anchor{1b1} +@subsection No_Implementation_Pragmas + + +@geindex No_Implementation_Pragmas + +[RM 13.12.1] This restriction checks at compile time that no +GNAT-defined pragmas are present. With this restriction, the only +pragmas that can be used are those defined in the Ada Reference Manual. + +@node No_Implementation_Restrictions,No_Implementation_Units,No_Implementation_Pragmas,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-restrictions}@anchor{1b2} +@subsection No_Implementation_Restrictions + + +@geindex No_Implementation_Restrictions + +[GNAT] This restriction checks at compile time that no GNAT-defined restriction +identifiers (other than @cite{No_Implementation_Restrictions} itself) +are present. With this restriction, the only other restriction identifiers +that can be used are those defined in the Ada Reference Manual. + +@node No_Implementation_Units,No_Implicit_Aliasing,No_Implementation_Restrictions,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implementation-units}@anchor{1b3} +@subsection No_Implementation_Units + + +@geindex No_Implementation_Units + +[RM 13.12.1] This restriction checks at compile time that there is no +mention in the context clause of any implementation-defined descendants +of packages Ada, Interfaces, or System. + +@node No_Implicit_Aliasing,No_Obsolescent_Features,No_Implementation_Units,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-implicit-aliasing}@anchor{1b4} +@subsection No_Implicit_Aliasing + + +@geindex No_Implicit_Aliasing + +[GNAT] This restriction, which is not required to be partition-wide consistent, +requires an explicit aliased keyword for an object to which 'Access, +'Unchecked_Access, or 'Address is applied, and forbids entirely the use of +the 'Unrestricted_Access attribute for objects. Note: the reason that +Unrestricted_Access is forbidden is that it would require the prefix +to be aliased, and in such cases, it can always be replaced by +the standard attribute Unchecked_Access which is preferable. + +@node No_Obsolescent_Features,No_Wide_Characters,No_Implicit_Aliasing,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-obsolescent-features}@anchor{1b5} +@subsection No_Obsolescent_Features + + +@geindex No_Obsolescent_Features + +[RM 13.12.1] This restriction checks at compile time that no obsolescent +features are used, as defined in Annex J of the Ada Reference Manual. + +@node No_Wide_Characters,SPARK_05,No_Obsolescent_Features,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions no-wide-characters}@anchor{1b6} +@subsection No_Wide_Characters + + +@geindex No_Wide_Characters + +[GNAT] This restriction ensures at compile time that no uses of the types +@cite{Wide_Character} or @cite{Wide_String} or corresponding wide +wide types +appear, and that no wide or wide wide string or character literals +appear in the program (that is literals representing characters not in +type @cite{Character}). + +@node SPARK_05,,No_Wide_Characters,Program Unit Level Restrictions +@anchor{gnat_rm/standard_and_implementation_defined_restrictions spark-05}@anchor{1b7} +@subsection SPARK_05 + + +@geindex SPARK_05 + +[GNAT] This restriction checks at compile time that some constructs +forbidden in SPARK 2005 are not present. Error messages related to +SPARK restriction have the form: + +@example +violation of restriction "SPARK_05" at + +@end example + +@geindex SPARK + +The restriction @cite{SPARK} is recognized as a +synonym for @cite{SPARK_05}. This is retained for historical +compatibility purposes (and an unconditional warning will be generated +for its use, advising replacement by @cite{SPARK}). + +This is not a replacement for the semantic checks performed by the +SPARK Examiner tool, as the compiler currently only deals with code, +not SPARK 2005 annotations, and does not guarantee catching all +cases of constructs forbidden by SPARK 2005. + +Thus it may well be the case that code which passes the compiler with +the SPARK restriction is rejected by the SPARK Examiner, e.g. due to +the different visibility rules of the Examiner based on SPARK 2005 +@cite{inherit} annotations. + +This restriction can be useful in providing an initial filter for code +developed using SPARK 2005, or in examining legacy code to see how far +it is from meeting SPARK restrictions. + +The list below summarizes the checks that are performed when this +restriction is in force: + + +@itemize * + +@item +No block statements + +@item +No case statements with only an others clause + +@item +Exit statements in loops must respect the SPARK 2005 language restrictions + +@item +No goto statements + +@item +Return can only appear as last statement in function + +@item +Function must have return statement + +@item +Loop parameter specification must include subtype mark + +@item +Prefix of expanded name cannot be a loop statement + +@item +Abstract subprogram not allowed + +@item +User-defined operators not allowed + +@item +Access type parameters not allowed + +@item +Default expressions for parameters not allowed + +@item +Default expressions for record fields not allowed + +@item +No tasking constructs allowed + +@item +Label needed at end of subprograms and packages + +@item +No mixing of positional and named parameter association + +@item +No access types as result type + +@item +No unconstrained arrays as result types + +@item +No null procedures + +@item +Initial and later declarations must be in correct order (declaration can't come after body) + +@item +No attributes on private types if full declaration not visible + +@item +No package declaration within package specification + +@item +No controlled types + +@item +No discriminant types + +@item +No overloading + +@item +Selector name cannot be operator symbol (i.e. operator symbol cannot be prefixed) + +@item +Access attribute not allowed + +@item +Allocator not allowed + +@item +Result of catenation must be String + +@item +Operands of catenation must be string literal, static char or another catenation + +@item +No conditional expressions + +@item +No explicit dereference + +@item +Quantified expression not allowed + +@item +Slicing not allowed + +@item +No exception renaming + +@item +No generic renaming + +@item +No object renaming + +@item +No use clause + +@item +Aggregates must be qualified + +@item +Non-static choice in array aggregates not allowed + +@item +The only view conversions which are allowed as in-out parameters are conversions of a tagged type to an ancestor type + +@item +No mixing of positional and named association in aggregate, no multi choice + +@item +AND, OR and XOR for arrays only allowed when operands have same static bounds + +@item +Fixed point operands to * or / must be qualified or converted + +@item +Comparison operators not allowed for Booleans or arrays (except strings) + +@item +Equality not allowed for arrays with non-matching static bounds (except strings) + +@item +Conversion / qualification not allowed for arrays with non-matching static bounds + +@item +Subprogram declaration only allowed in package spec (unless followed by import) + +@item +Access types not allowed + +@item +Incomplete type declaration not allowed + +@item +Object and subtype declarations must respect SPARK restrictions + +@item +Digits or delta constraint not allowed + +@item +Decimal fixed point type not allowed + +@item +Aliasing of objects not allowed + +@item +Modular type modulus must be power of 2 + +@item +Base not allowed on subtype mark + +@item +Unary operators not allowed on modular types (except not) + +@item +Untagged record cannot be null + +@item +No class-wide operations + +@item +Initialization expressions must respect SPARK restrictions + +@item +Non-static ranges not allowed except in iteration schemes + +@item +String subtypes must have lower bound of 1 + +@item +Subtype of Boolean cannot have constraint + +@item +At most one tagged type or extension per package + +@item +Interface is not allowed + +@item +Character literal cannot be prefixed (selector name cannot be character literal) + +@item +Record aggregate cannot contain 'others' + +@item +Component association in record aggregate must contain a single choice + +@item +Ancestor part cannot be a type mark + +@item +Attributes 'Image, 'Width and 'Value not allowed + +@item +Functions may not update globals + +@item +Subprograms may not contain direct calls to themselves (prevents recursion within unit) + +@item +Call to subprogram not allowed in same unit before body has been seen (prevents recursion within unit) +@end itemize + +The following restrictions are enforced, but note that they are actually more +strict that the latest SPARK 2005 language definition: + + +@itemize * + +@item +No derived types other than tagged type extensions + +@item +Subtype of unconstrained array must have constraint +@end itemize + +This list summarises the main SPARK 2005 language rules that are not +currently checked by the SPARK_05 restriction: + + +@itemize * + +@item +SPARK annotations are treated as comments so are not checked at all + +@item +Based real literals not allowed + +@item +Objects cannot be initialized at declaration by calls to user-defined functions + +@item +Objects cannot be initialized at declaration by assignments from variables + +@item +Objects cannot be initialized at declaration by assignments from indexed/selected components + +@item +Ranges shall not be null + +@item +A fixed point delta expression must be a simple expression + +@item +Restrictions on where renaming declarations may be placed + +@item +Externals of mode 'out' cannot be referenced + +@item +Externals of mode 'in' cannot be updated + +@item +Loop with no iteration scheme or exits only allowed as last statement in main program or task + +@item +Subprogram cannot have parent unit name + +@item +SPARK 2005 inherited subprogram must be prefixed with overriding + +@item +External variables (or functions that reference them) may not be passed as actual parameters + +@item +Globals must be explicitly mentioned in contract + +@item +Deferred constants cannot be completed by pragma Import + +@item +Package initialization cannot read/write variables from other packages + +@item +Prefix not allowed for entities that are directly visible + +@item +Identifier declaration can't override inherited package name + +@item +Cannot use Standard or other predefined packages as identifiers + +@item +After renaming, cannot use the original name + +@item +Subprograms can only be renamed to remove package prefix + +@item +Pragma import must be immediately after entity it names + +@item +No mutual recursion between multiple units (this can be checked with gnatcheck) +@end itemize + +Note that if a unit is compiled in Ada 95 mode with the SPARK restriction, +violations will be reported for constructs forbidden in SPARK 95, +instead of SPARK 2005. + +@node Implementation Advice,Implementation Defined Characteristics,Standard and Implementation Defined Restrictions,Top +@anchor{gnat_rm/implementation_advice doc}@anchor{1b8}@anchor{gnat_rm/implementation_advice implementation-advice}@anchor{a}@anchor{gnat_rm/implementation_advice id1}@anchor{1b9} +@chapter Implementation Advice + + +The main text of the Ada Reference Manual describes the required +behavior of all Ada compilers, and the GNAT compiler conforms to +these requirements. + +In addition, there are sections throughout the Ada Reference Manual headed +by the phrase 'Implementation advice'. These sections are not normative, +i.e., they do not specify requirements that all compilers must +follow. Rather they provide advice on generally desirable behavior. +They are not requirements, because they describe behavior that cannot +be provided on all systems, or may be undesirable on some systems. + +As far as practical, GNAT follows the implementation advice in +the Ada Reference Manual. Each such RM section corresponds to a section +in this chapter whose title specifies the +RM section number and paragraph number and the subject of +the advice. The contents of each section consists of the RM text within +quotation marks, +followed by the GNAT interpretation of the advice. Most often, this simply says +'followed', which means that GNAT follows the advice. However, in a +number of cases, GNAT deliberately deviates from this advice, in which +case the text describes what GNAT does and why. + +@geindex Error detection + +@menu +* RM 1.1.3(20); Error Detection: RM 1 1 3 20 Error Detection. +* RM 1.1.3(31); Child Units: RM 1 1 3 31 Child Units. +* RM 1.1.5(12); Bounded Errors: RM 1 1 5 12 Bounded Errors. +* RM 2.8(16); Pragmas: RM 2 8 16 Pragmas. +* RM 2.8(17-19); Pragmas: RM 2 8 17-19 Pragmas. +* RM 3.5.2(5); Alternative Character Sets: RM 3 5 2 5 Alternative Character Sets. +* RM 3.5.4(28); Integer Types: RM 3 5 4 28 Integer Types. +* RM 3.5.4(29); Integer Types: RM 3 5 4 29 Integer Types. +* RM 3.5.5(8); Enumeration Values: RM 3 5 5 8 Enumeration Values. +* RM 3.5.7(17); Float Types: RM 3 5 7 17 Float Types. +* RM 3.6.2(11); Multidimensional Arrays: RM 3 6 2 11 Multidimensional Arrays. +* RM 9.6(30-31); Duration'Small: RM 9 6 30-31 Duration'Small. +* RM 10.2.1(12); Consistent Representation: RM 10 2 1 12 Consistent Representation. +* RM 11.4.1(19); Exception Information: RM 11 4 1 19 Exception Information. +* RM 11.5(28); Suppression of Checks: RM 11 5 28 Suppression of Checks. +* RM 13.1 (21-24); Representation Clauses: RM 13 1 21-24 Representation Clauses. +* RM 13.2(6-8); Packed Types: RM 13 2 6-8 Packed Types. +* RM 13.3(14-19); Address Clauses: RM 13 3 14-19 Address Clauses. +* RM 13.3(29-35); Alignment Clauses: RM 13 3 29-35 Alignment Clauses. +* RM 13.3(42-43); Size Clauses: RM 13 3 42-43 Size Clauses. +* RM 13.3(50-56); Size Clauses: RM 13 3 50-56 Size Clauses. +* RM 13.3(71-73); Component Size Clauses: RM 13 3 71-73 Component Size Clauses. +* RM 13.4(9-10); Enumeration Representation Clauses: RM 13 4 9-10 Enumeration Representation Clauses. +* RM 13.5.1(17-22); Record Representation Clauses: RM 13 5 1 17-22 Record Representation Clauses. +* RM 13.5.2(5); Storage Place Attributes: RM 13 5 2 5 Storage Place Attributes. +* RM 13.5.3(7-8); Bit Ordering: RM 13 5 3 7-8 Bit Ordering. +* RM 13.7(37); Address as Private: RM 13 7 37 Address as Private. +* RM 13.7.1(16); Address Operations: RM 13 7 1 16 Address Operations. +* RM 13.9(14-17); Unchecked Conversion: RM 13 9 14-17 Unchecked Conversion. +* RM 13.11(23-25); Implicit Heap Usage: RM 13 11 23-25 Implicit Heap Usage. +* RM 13.11.2(17); Unchecked Deallocation: RM 13 11 2 17 Unchecked Deallocation. +* RM 13.13.2(17); Stream Oriented Attributes: RM 13 13 2 17 Stream Oriented Attributes. +* RM A.1(52); Names of Predefined Numeric Types: RM A 1 52 Names of Predefined Numeric Types. +* RM A.3.2(49); Ada.Characters.Handling: RM A 3 2 49 Ada Characters Handling. +* RM A.4.4(106); Bounded-Length String Handling: RM A 4 4 106 Bounded-Length String Handling. +* RM A.5.2(46-47); Random Number Generation: RM A 5 2 46-47 Random Number Generation. +* RM A.10.7(23); Get_Immediate: RM A 10 7 23 Get_Immediate. +* RM B.1(39-41); Pragma Export: RM B 1 39-41 Pragma Export. +* RM B.2(12-13); Package Interfaces: RM B 2 12-13 Package Interfaces. +* RM B.3(63-71); Interfacing with C: RM B 3 63-71 Interfacing with C. +* RM B.4(95-98); Interfacing with COBOL: RM B 4 95-98 Interfacing with COBOL. +* RM B.5(22-26); Interfacing with Fortran: RM B 5 22-26 Interfacing with Fortran. +* RM C.1(3-5); Access to Machine Operations: RM C 1 3-5 Access to Machine Operations. +* RM C.1(10-16); Access to Machine Operations: RM C 1 10-16 Access to Machine Operations. +* RM C.3(28); Interrupt Support: RM C 3 28 Interrupt Support. +* RM C.3.1(20-21); Protected Procedure Handlers: RM C 3 1 20-21 Protected Procedure Handlers. +* RM C.3.2(25); Package Interrupts: RM C 3 2 25 Package Interrupts. +* RM C.4(14); Pre-elaboration Requirements: RM C 4 14 Pre-elaboration Requirements. +* RM C.5(8); Pragma Discard_Names: RM C 5 8 Pragma Discard_Names. +* RM C.7.2(30); The Package Task_Attributes: RM C 7 2 30 The Package Task_Attributes. +* RM D.3(17); Locking Policies: RM D 3 17 Locking Policies. +* RM D.4(16); Entry Queuing Policies: RM D 4 16 Entry Queuing Policies. +* RM D.6(9-10); Preemptive Abort: RM D 6 9-10 Preemptive Abort. +* RM D.7(21); Tasking Restrictions: RM D 7 21 Tasking Restrictions. +* RM D.8(47-49); Monotonic Time: RM D 8 47-49 Monotonic Time. +* RM E.5(28-29); Partition Communication Subsystem: RM E 5 28-29 Partition Communication Subsystem. +* RM F(7); COBOL Support: RM F 7 COBOL Support. +* RM F.1(2); Decimal Radix Support: RM F 1 2 Decimal Radix Support. +* RM G; Numerics: RM G Numerics. +* RM G.1.1(56-58); Complex Types: RM G 1 1 56-58 Complex Types. +* RM G.1.2(49); Complex Elementary Functions: RM G 1 2 49 Complex Elementary Functions. +* RM G.2.4(19); Accuracy Requirements: RM G 2 4 19 Accuracy Requirements. +* RM G.2.6(15); Complex Arithmetic Accuracy: RM G 2 6 15 Complex Arithmetic Accuracy. +* RM H.6(15/2); Pragma Partition_Elaboration_Policy: RM H 6 15/2 Pragma Partition_Elaboration_Policy. + +@end menu + +@node RM 1 1 3 20 Error Detection,RM 1 1 3 31 Child Units,,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-1-1-3-20-error-detection}@anchor{1ba} +@section RM 1.1.3(20): Error Detection + + +@quotation + +"If an implementation detects the use of an unsupported Specialized Needs +Annex feature at run time, it should raise @cite{Program_Error} if +feasible." +@end quotation + +Not relevant. All specialized needs annex features are either supported, +or diagnosed at compile time. + +@geindex Child Units + +@node RM 1 1 3 31 Child Units,RM 1 1 5 12 Bounded Errors,RM 1 1 3 20 Error Detection,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-1-1-3-31-child-units}@anchor{1bb} +@section RM 1.1.3(31): Child Units + + +@quotation + +"If an implementation wishes to provide implementation-defined +extensions to the functionality of a language-defined library unit, it +should normally do so by adding children to the library unit." +@end quotation + +Followed. + +@geindex Bounded errors + +@node RM 1 1 5 12 Bounded Errors,RM 2 8 16 Pragmas,RM 1 1 3 31 Child Units,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-1-1-5-12-bounded-errors}@anchor{1bc} +@section RM 1.1.5(12): Bounded Errors + + +@quotation + +"If an implementation detects a bounded error or erroneous +execution, it should raise @cite{Program_Error}." +@end quotation + +Followed in all cases in which the implementation detects a bounded +error or erroneous execution. Not all such situations are detected at +runtime. + +@geindex Pragmas + +@node RM 2 8 16 Pragmas,RM 2 8 17-19 Pragmas,RM 1 1 5 12 Bounded Errors,Implementation Advice +@anchor{gnat_rm/implementation_advice id2}@anchor{1bd}@anchor{gnat_rm/implementation_advice rm-2-8-16-pragmas}@anchor{1be} +@section RM 2.8(16): Pragmas + + +@quotation + +"Normally, implementation-defined pragmas should have no semantic effect +for error-free programs; that is, if the implementation-defined pragmas +are removed from a working program, the program should still be legal, +and should still have the same semantics." +@end quotation + +The following implementation defined pragmas are exceptions to this +rule: + + +@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxx} +@headitem + +Pragma + +@tab + +Explanation + +@item + +@emph{Abort_Defer} + +@tab + +Affects semantics + +@item + +@emph{Ada_83} + +@tab + +Affects legality + +@item + +@emph{Assert} + +@tab + +Affects semantics + +@item + +@emph{CPP_Class} + +@tab + +Affects semantics + +@item + +@emph{CPP_Constructor} + +@tab + +Affects semantics + +@item + +@emph{Debug} + +@tab + +Affects semantics + +@item + +@emph{Interface_Name} + +@tab + +Affects semantics + +@item + +@emph{Machine_Attribute} + +@tab + +Affects semantics + +@item + +@emph{Unimplemented_Unit} + +@tab + +Affects legality + +@item + +@emph{Unchecked_Union} + +@tab + +Affects semantics + +@end multitable + + +In each of the above cases, it is essential to the purpose of the pragma +that this advice not be followed. For details see +@ref{7,,Implementation Defined Pragmas}. + +@node RM 2 8 17-19 Pragmas,RM 3 5 2 5 Alternative Character Sets,RM 2 8 16 Pragmas,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-2-8-17-19-pragmas}@anchor{1bf} +@section RM 2.8(17-19): Pragmas + + +@quotation + +"Normally, an implementation should not define pragmas that can +make an illegal program legal, except as follows: + + +@itemize * + +@item +A pragma used to complete a declaration, such as a pragma @cite{Import}; + +@item +A pragma used to configure the environment by adding, removing, or +replacing @cite{library_items}." +@end itemize +@end quotation + +See @ref{1be,,RM 2.8(16); Pragmas}. + +@geindex Character Sets + +@geindex Alternative Character Sets + +@node RM 3 5 2 5 Alternative Character Sets,RM 3 5 4 28 Integer Types,RM 2 8 17-19 Pragmas,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-5-2-5-alternative-character-sets}@anchor{1c0} +@section RM 3.5.2(5): Alternative Character Sets + + +@quotation + +"If an implementation supports a mode with alternative interpretations +for @cite{Character} and @cite{Wide_Character}, the set of graphic +characters of @cite{Character} should nevertheless remain a proper +subset of the set of graphic characters of @cite{Wide_Character}. Any +character set 'localizations' should be reflected in the results of +the subprograms defined in the language-defined package +@cite{Characters.Handling} (see A.3) available in such a mode. In a mode with +an alternative interpretation of @cite{Character}, the implementation should +also support a corresponding change in what is a legal +@cite{identifier_letter}." +@end quotation + +Not all wide character modes follow this advice, in particular the JIS +and IEC modes reflect standard usage in Japan, and in these encoding, +the upper half of the Latin-1 set is not part of the wide-character +subset, since the most significant bit is used for wide character +encoding. However, this only applies to the external forms. Internally +there is no such restriction. + +@geindex Integer types + +@node RM 3 5 4 28 Integer Types,RM 3 5 4 29 Integer Types,RM 3 5 2 5 Alternative Character Sets,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-5-4-28-integer-types}@anchor{1c1} +@section RM 3.5.4(28): Integer Types + + +@quotation + +"An implementation should support @cite{Long_Integer} in addition to +@cite{Integer} if the target machine supports 32-bit (or longer) +arithmetic. No other named integer subtypes are recommended for package +@cite{Standard}. Instead, appropriate named integer subtypes should be +provided in the library package @cite{Interfaces} (see B.2)." +@end quotation + +@cite{Long_Integer} is supported. Other standard integer types are supported +so this advice is not fully followed. These types +are supported for convenient interface to C, and so that all hardware +types of the machine are easily available. + +@node RM 3 5 4 29 Integer Types,RM 3 5 5 8 Enumeration Values,RM 3 5 4 28 Integer Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-5-4-29-integer-types}@anchor{1c2} +@section RM 3.5.4(29): Integer Types + + +@quotation + +"An implementation for a two's complement machine should support +modular types with a binary modulus up to @code{System.Max_Int*2+2}. An +implementation should support a non-binary modules up to @cite{Integer'Last}." +@end quotation + +Followed. + +@geindex Enumeration values + +@node RM 3 5 5 8 Enumeration Values,RM 3 5 7 17 Float Types,RM 3 5 4 29 Integer Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-5-5-8-enumeration-values}@anchor{1c3} +@section RM 3.5.5(8): Enumeration Values + + +@quotation + +"For the evaluation of a call on @code{S'Pos} for an enumeration +subtype, if the value of the operand does not correspond to the internal +code for any enumeration literal of its type (perhaps due to an +un-initialized variable), then the implementation should raise +@cite{Program_Error}. This is particularly important for enumeration +types with noncontiguous internal codes specified by an +enumeration_representation_clause." +@end quotation + +Followed. + +@geindex Float types + +@node RM 3 5 7 17 Float Types,RM 3 6 2 11 Multidimensional Arrays,RM 3 5 5 8 Enumeration Values,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-5-7-17-float-types}@anchor{1c4} +@section RM 3.5.7(17): Float Types + + +@quotation + +"An implementation should support @cite{Long_Float} in addition to +@cite{Float} if the target machine supports 11 or more digits of +precision. No other named floating point subtypes are recommended for +package @cite{Standard}. Instead, appropriate named floating point subtypes +should be provided in the library package @cite{Interfaces} (see B.2)." +@end quotation + +@cite{Short_Float} and @cite{Long_Long_Float} are also provided. The +former provides improved compatibility with other implementations +supporting this type. The latter corresponds to the highest precision +floating-point type supported by the hardware. On most machines, this +will be the same as @cite{Long_Float}, but on some machines, it will +correspond to the IEEE extended form. The notable case is all ia32 +(x86) implementations, where @cite{Long_Long_Float} corresponds to +the 80-bit extended precision format supported in hardware on this +processor. Note that the 128-bit format on SPARC is not supported, +since this is a software rather than a hardware format. + +@geindex Multidimensional arrays + +@geindex Arrays +@geindex multidimensional + +@node RM 3 6 2 11 Multidimensional Arrays,RM 9 6 30-31 Duration'Small,RM 3 5 7 17 Float Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-3-6-2-11-multidimensional-arrays}@anchor{1c5} +@section RM 3.6.2(11): Multidimensional Arrays + + +@quotation + +"An implementation should normally represent multidimensional arrays in +row-major order, consistent with the notation used for multidimensional +array aggregates (see 4.3.3). However, if a pragma @cite{Convention} +(@cite{Fortran}, ...) applies to a multidimensional array type, then +column-major order should be used instead (see B.5, @cite{Interfacing with Fortran})." +@end quotation + +Followed. + +@geindex Duration'Small + +@node RM 9 6 30-31 Duration'Small,RM 10 2 1 12 Consistent Representation,RM 3 6 2 11 Multidimensional Arrays,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-9-6-30-31-duration-small}@anchor{1c6} +@section RM 9.6(30-31): Duration'Small + + +@quotation + +"Whenever possible in an implementation, the value of @cite{Duration'Small} +should be no greater than 100 microseconds." +@end quotation + +Followed. (@cite{Duration'Small} = 10**(-9)). + +@quotation + +"The time base for @cite{delay_relative_statements} should be monotonic; +it need not be the same time base as used for @cite{Calendar.Clock}." +@end quotation + +Followed. + +@node RM 10 2 1 12 Consistent Representation,RM 11 4 1 19 Exception Information,RM 9 6 30-31 Duration'Small,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-10-2-1-12-consistent-representation}@anchor{1c7} +@section RM 10.2.1(12): Consistent Representation + + +@quotation + +"In an implementation, a type declared in a pre-elaborated package should +have the same representation in every elaboration of a given version of +the package, whether the elaborations occur in distinct executions of +the same program, or in executions of distinct programs or partitions +that include the given version." +@end quotation + +Followed, except in the case of tagged types. Tagged types involve +implicit pointers to a local copy of a dispatch table, and these pointers +have representations which thus depend on a particular elaboration of the +package. It is not easy to see how it would be possible to follow this +advice without severely impacting efficiency of execution. + +@geindex Exception information + +@node RM 11 4 1 19 Exception Information,RM 11 5 28 Suppression of Checks,RM 10 2 1 12 Consistent Representation,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-11-4-1-19-exception-information}@anchor{1c8} +@section RM 11.4.1(19): Exception Information + + +@quotation + +"@cite{Exception_Message} by default and @cite{Exception_Information} +should produce information useful for +debugging. @cite{Exception_Message} should be short, about one +line. @cite{Exception_Information} can be long. @cite{Exception_Message} +should not include the +@cite{Exception_Name}. @cite{Exception_Information} should include both +the @cite{Exception_Name} and the @cite{Exception_Message}." +@end quotation + +Followed. For each exception that doesn't have a specified +@cite{Exception_Message}, the compiler generates one containing the location +of the raise statement. This location has the form 'file_name:line', where +file_name is the short file name (without path information) and line is the line +number in the file. Note that in the case of the Zero Cost Exception +mechanism, these messages become redundant with the Exception_Information that +contains a full backtrace of the calling sequence, so they are disabled. +To disable explicitly the generation of the source location message, use the +Pragma @cite{Discard_Names}. + +@geindex Suppression of checks + +@geindex Checks +@geindex suppression of + +@node RM 11 5 28 Suppression of Checks,RM 13 1 21-24 Representation Clauses,RM 11 4 1 19 Exception Information,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-11-5-28-suppression-of-checks}@anchor{1c9} +@section RM 11.5(28): Suppression of Checks + + +@quotation + +"The implementation should minimize the code executed for checks that +have been suppressed." +@end quotation + +Followed. + +@geindex Representation clauses + +@node RM 13 1 21-24 Representation Clauses,RM 13 2 6-8 Packed Types,RM 11 5 28 Suppression of Checks,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-1-21-24-representation-clauses}@anchor{1ca} +@section RM 13.1 (21-24): Representation Clauses + + +@quotation + +"The recommended level of support for all representation items is +qualified as follows: + +An implementation need not support representation items containing +non-static expressions, except that an implementation should support a +representation item for a given entity if each non-static expression in +the representation item is a name that statically denotes a constant +declared before the entity." +@end quotation + +Followed. In fact, GNAT goes beyond the recommended level of support +by allowing nonstatic expressions in some representation clauses even +without the need to declare constants initialized with the values of +such expressions. +For example: + +@example + X : Integer; + Y : Float; + for Y'Address use X'Address;>> + + +"An implementation need not support a specification for the `Size` +for a given composite subtype, nor the size or storage place for an +object (including a component) of a given composite subtype, unless the +constraints on the subtype and its composite subcomponents (if any) are +all static constraints." +@end example + +Followed. Size Clauses are not permitted on non-static components, as +described above. + +@quotation + +"An aliased component, or a component whose type is by-reference, should +always be allocated at an addressable location." +@end quotation + +Followed. + +@geindex Packed types + +@node RM 13 2 6-8 Packed Types,RM 13 3 14-19 Address Clauses,RM 13 1 21-24 Representation Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-2-6-8-packed-types}@anchor{1cb} +@section RM 13.2(6-8): Packed Types + + +@quotation + +"If a type is packed, then the implementation should try to minimize +storage allocated to objects of the type, possibly at the expense of +speed of accessing components, subject to reasonable complexity in +addressing calculations. + +The recommended level of support pragma @cite{Pack} is: + +For a packed record type, the components should be packed as tightly as +possible subject to the Sizes of the component subtypes, and subject to +any @cite{record_representation_clause} that applies to the type; the +implementation may, but need not, reorder components or cross aligned +word boundaries to improve the packing. A component whose @cite{Size} is +greater than the word size may be allocated an integral number of words." +@end quotation + +Followed. Tight packing of arrays is supported for all component sizes +up to 64-bits. If the array component size is 1 (that is to say, if +the component is a boolean type or an enumeration type with two values) +then values of the type are implicitly initialized to zero. This +happens both for objects of the packed type, and for objects that have a +subcomponent of the packed type. + +@quotation + +"An implementation should support Address clauses for imported +subprograms." +@end quotation + +Followed. + +@geindex Address clauses + +@node RM 13 3 14-19 Address Clauses,RM 13 3 29-35 Alignment Clauses,RM 13 2 6-8 Packed Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-3-14-19-address-clauses}@anchor{1cc} +@section RM 13.3(14-19): Address Clauses + + +@quotation + +"For an array @cite{X}, @code{X'Address} should point at the first +component of the array, and not at the array bounds." +@end quotation + +Followed. + +@quotation + +"The recommended level of support for the @cite{Address} attribute is: + +@code{X'Address} should produce a useful result if @cite{X} is an +object that is aliased or of a by-reference type, or is an entity whose +@cite{Address} has been specified." +@end quotation + +Followed. A valid address will be produced even if none of those +conditions have been met. If necessary, the object is forced into +memory to ensure the address is valid. + +@quotation + +"An implementation should support @cite{Address} clauses for imported +subprograms." +@end quotation + +Followed. + +@quotation + +"Objects (including subcomponents) that are aliased or of a by-reference +type should be allocated on storage element boundaries." +@end quotation + +Followed. + +@quotation + +"If the @cite{Address} of an object is specified, or it is imported or exported, +then the implementation should not perform optimizations based on +assumptions of no aliases." +@end quotation + +Followed. + +@geindex Alignment clauses + +@node RM 13 3 29-35 Alignment Clauses,RM 13 3 42-43 Size Clauses,RM 13 3 14-19 Address Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-3-29-35-alignment-clauses}@anchor{1cd} +@section RM 13.3(29-35): Alignment Clauses + + +@quotation + +"The recommended level of support for the @cite{Alignment} attribute for +subtypes is: + +An implementation should support specified Alignments that are factors +and multiples of the number of storage elements per word, subject to the +following:" +@end quotation + +Followed. + +@quotation + +"An implementation need not support specified Alignments for +combinations of Sizes and Alignments that cannot be easily +loaded and stored by available machine instructions." +@end quotation + +Followed. + +@quotation + +"An implementation need not support specified Alignments that are +greater than the maximum @cite{Alignment} the implementation ever returns by +default." +@end quotation + +Followed. + +@quotation + +"The recommended level of support for the @cite{Alignment} attribute for +objects is: + +Same as above, for subtypes, but in addition:" +@end quotation + +Followed. + +@quotation + +"For stand-alone library-level objects of statically constrained +subtypes, the implementation should support all alignments +supported by the target linker. For example, page alignment is likely to +be supported for such objects, but not for subtypes." +@end quotation + +Followed. + +@geindex Size clauses + +@node RM 13 3 42-43 Size Clauses,RM 13 3 50-56 Size Clauses,RM 13 3 29-35 Alignment Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-3-42-43-size-clauses}@anchor{1ce} +@section RM 13.3(42-43): Size Clauses + + +@quotation + +"The recommended level of support for the @cite{Size} attribute of +objects is: + +A @cite{Size} clause should be supported for an object if the specified +@cite{Size} is at least as large as its subtype's @cite{Size}, and +corresponds to a size in storage elements that is a multiple of the +object's @cite{Alignment} (if the @cite{Alignment} is nonzero)." +@end quotation + +Followed. + +@node RM 13 3 50-56 Size Clauses,RM 13 3 71-73 Component Size Clauses,RM 13 3 42-43 Size Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-3-50-56-size-clauses}@anchor{1cf} +@section RM 13.3(50-56): Size Clauses + + +@quotation + +"If the @cite{Size} of a subtype is specified, and allows for efficient +independent addressability (see 9.10) on the target architecture, then +the @cite{Size} of the following objects of the subtype should equal the +@cite{Size} of the subtype: + +Aliased objects (including components)." +@end quotation + +Followed. + +@quotation + +"@cite{Size} clause on a composite subtype should not affect the +internal layout of components." +@end quotation + +Followed. But note that this can be overridden by use of the implementation +pragma Implicit_Packing in the case of packed arrays. + +@quotation + +"The recommended level of support for the @cite{Size} attribute of subtypes is: + +The @cite{Size} (if not specified) of a static discrete or fixed point +subtype should be the number of bits needed to represent each value +belonging to the subtype using an unbiased representation, leaving space +for a sign bit only if the subtype contains negative values. If such a +subtype is a first subtype, then an implementation should support a +specified @cite{Size} for it that reflects this representation." +@end quotation + +Followed. + +@quotation + +"For a subtype implemented with levels of indirection, the @cite{Size} +should include the size of the pointers, but not the size of what they +point at." +@end quotation + +Followed. + +@geindex Component_Size clauses + +@node RM 13 3 71-73 Component Size Clauses,RM 13 4 9-10 Enumeration Representation Clauses,RM 13 3 50-56 Size Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-3-71-73-component-size-clauses}@anchor{1d0} +@section RM 13.3(71-73): Component Size Clauses + + +@quotation + +"The recommended level of support for the @cite{Component_Size} +attribute is: + +An implementation need not support specified @cite{Component_Sizes} that are +less than the @cite{Size} of the component subtype." +@end quotation + +Followed. + +@quotation + +"An implementation should support specified Component_Sizes that +are factors and multiples of the word size. For such +Component_Sizes, the array should contain no gaps between +components. For other Component_Sizes (if supported), the array +should contain no gaps between components when packing is also +specified; the implementation should forbid this combination in cases +where it cannot support a no-gaps representation." +@end quotation + +Followed. + +@geindex Enumeration representation clauses + +@geindex Representation clauses +@geindex enumeration + +@node RM 13 4 9-10 Enumeration Representation Clauses,RM 13 5 1 17-22 Record Representation Clauses,RM 13 3 71-73 Component Size Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-4-9-10-enumeration-representation-clauses}@anchor{1d1} +@section RM 13.4(9-10): Enumeration Representation Clauses + + +@quotation + +"The recommended level of support for enumeration representation clauses +is: + +An implementation need not support enumeration representation clauses +for boolean types, but should at minimum support the internal codes in +the range @cite{System.Min_Int .. System.Max_Int}." +@end quotation + +Followed. + +@geindex Record representation clauses + +@geindex Representation clauses +@geindex records + +@node RM 13 5 1 17-22 Record Representation Clauses,RM 13 5 2 5 Storage Place Attributes,RM 13 4 9-10 Enumeration Representation Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-5-1-17-22-record-representation-clauses}@anchor{1d2} +@section RM 13.5.1(17-22): Record Representation Clauses + + +@quotation + +"The recommended level of support for +@cite{record_representation_clauses} is: + +An implementation should support storage places that can be extracted +with a load, mask, shift sequence of machine code, and set with a load, +shift, mask, store sequence, given the available machine instructions +and run-time model." +@end quotation + +Followed. + +@quotation + +"A storage place should be supported if its size is equal to the +@cite{Size} of the component subtype, and it starts and ends on a +boundary that obeys the @cite{Alignment} of the component subtype." +@end quotation + +Followed. + +@quotation + +"If the default bit ordering applies to the declaration of a given type, +then for a component whose subtype's @cite{Size} is less than the word +size, any storage place that does not cross an aligned word boundary +should be supported." +@end quotation + +Followed. + +@quotation + +"An implementation may reserve a storage place for the tag field of a +tagged type, and disallow other components from overlapping that place." +@end quotation + +Followed. The storage place for the tag field is the beginning of the tagged +record, and its size is Address'Size. GNAT will reject an explicit component +clause for the tag field. + +@quotation + +"An implementation need not support a @cite{component_clause} for a +component of an extension part if the storage place is not after the +storage places of all components of the parent type, whether or not +those storage places had been specified." +@end quotation + +Followed. The above advice on record representation clauses is followed, +and all mentioned features are implemented. + +@geindex Storage place attributes + +@node RM 13 5 2 5 Storage Place Attributes,RM 13 5 3 7-8 Bit Ordering,RM 13 5 1 17-22 Record Representation Clauses,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-5-2-5-storage-place-attributes}@anchor{1d3} +@section RM 13.5.2(5): Storage Place Attributes + + +@quotation + +"If a component is represented using some form of pointer (such as an +offset) to the actual data of the component, and this data is contiguous +with the rest of the object, then the storage place attributes should +reflect the place of the actual data, not the pointer. If a component is +allocated discontinuously from the rest of the object, then a warning +should be generated upon reference to one of its storage place +attributes." +@end quotation + +Followed. There are no such components in GNAT. + +@geindex Bit ordering + +@node RM 13 5 3 7-8 Bit Ordering,RM 13 7 37 Address as Private,RM 13 5 2 5 Storage Place Attributes,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-5-3-7-8-bit-ordering}@anchor{1d4} +@section RM 13.5.3(7-8): Bit Ordering + + +@quotation + +"The recommended level of support for the non-default bit ordering is: + +If @cite{Word_Size} = @cite{Storage_Unit}, then the implementation +should support the non-default bit ordering in addition to the default +bit ordering." +@end quotation + +Followed. Word size does not equal storage size in this implementation. +Thus non-default bit ordering is not supported. + +@geindex Address +@geindex as private type + +@node RM 13 7 37 Address as Private,RM 13 7 1 16 Address Operations,RM 13 5 3 7-8 Bit Ordering,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-7-37-address-as-private}@anchor{1d5} +@section RM 13.7(37): Address as Private + + +@quotation + +"@cite{Address} should be of a private type." +@end quotation + +Followed. + +@geindex Operations +@geindex on `Address` + +@geindex Address +@geindex operations of + +@node RM 13 7 1 16 Address Operations,RM 13 9 14-17 Unchecked Conversion,RM 13 7 37 Address as Private,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-7-1-16-address-operations}@anchor{1d6} +@section RM 13.7.1(16): Address Operations + + +@quotation + +"Operations in @cite{System} and its children should reflect the target +environment semantics as closely as is reasonable. For example, on most +machines, it makes sense for address arithmetic to 'wrap around'. +Operations that do not make sense should raise @cite{Program_Error}." +@end quotation + +Followed. Address arithmetic is modular arithmetic that wraps around. No +operation raises @cite{Program_Error}, since all operations make sense. + +@geindex Unchecked conversion + +@node RM 13 9 14-17 Unchecked Conversion,RM 13 11 23-25 Implicit Heap Usage,RM 13 7 1 16 Address Operations,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-9-14-17-unchecked-conversion}@anchor{1d7} +@section RM 13.9(14-17): Unchecked Conversion + + +@quotation + +"The @cite{Size} of an array object should not include its bounds; hence, +the bounds should not be part of the converted data." +@end quotation + +Followed. + +@quotation + +"The implementation should not generate unnecessary run-time checks to +ensure that the representation of @cite{S} is a representation of the +target type. It should take advantage of the permission to return by +reference when possible. Restrictions on unchecked conversions should be +avoided unless required by the target environment." +@end quotation + +Followed. There are no restrictions on unchecked conversion. A warning is +generated if the source and target types do not have the same size since +the semantics in this case may be target dependent. + +@quotation + +"The recommended level of support for unchecked conversions is: + +Unchecked conversions should be supported and should be reversible in +the cases where this clause defines the result. To enable meaningful use +of unchecked conversion, a contiguous representation should be used for +elementary subtypes, for statically constrained array subtypes whose +component subtype is one of the subtypes described in this paragraph, +and for record subtypes without discriminants whose component subtypes +are described in this paragraph." +@end quotation + +Followed. + +@geindex Heap usage +@geindex implicit + +@node RM 13 11 23-25 Implicit Heap Usage,RM 13 11 2 17 Unchecked Deallocation,RM 13 9 14-17 Unchecked Conversion,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-11-23-25-implicit-heap-usage}@anchor{1d8} +@section RM 13.11(23-25): Implicit Heap Usage + + +@quotation + +"An implementation should document any cases in which it dynamically +allocates heap storage for a purpose other than the evaluation of an +allocator." +@end quotation + +Followed, the only other points at which heap storage is dynamically +allocated are as follows: + + +@itemize * + +@item +At initial elaboration time, to allocate dynamically sized global +objects. + +@item +To allocate space for a task when a task is created. + +@item +To extend the secondary stack dynamically when needed. The secondary +stack is used for returning variable length results. +@end itemize + + +@quotation + +"A default (implementation-provided) storage pool for an +access-to-constant type should not have overhead to support deallocation of +individual objects." +@end quotation + +Followed. + +@quotation + +"A storage pool for an anonymous access type should be created at the +point of an allocator for the type, and be reclaimed when the designated +object becomes inaccessible." +@end quotation + +Followed. + +@geindex Unchecked deallocation + +@node RM 13 11 2 17 Unchecked Deallocation,RM 13 13 2 17 Stream Oriented Attributes,RM 13 11 23-25 Implicit Heap Usage,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-11-2-17-unchecked-deallocation}@anchor{1d9} +@section RM 13.11.2(17): Unchecked Deallocation + + +@quotation + +"For a standard storage pool, @cite{Free} should actually reclaim the +storage." +@end quotation + +Followed. + +@geindex Stream oriented attributes + +@node RM 13 13 2 17 Stream Oriented Attributes,RM A 1 52 Names of Predefined Numeric Types,RM 13 11 2 17 Unchecked Deallocation,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-13-13-2-17-stream-oriented-attributes}@anchor{1da} +@section RM 13.13.2(17): Stream Oriented Attributes + + +@quotation + +"If a stream element is the same size as a storage element, then the +normal in-memory representation should be used by @cite{Read} and +@cite{Write} for scalar objects. Otherwise, @cite{Read} and @cite{Write} +should use the smallest number of stream elements needed to represent +all values in the base range of the scalar type." +@end quotation + +Followed. By default, GNAT uses the interpretation suggested by AI-195, +which specifies using the size of the first subtype. +However, such an implementation is based on direct binary +representations and is therefore target- and endianness-dependent. +To address this issue, GNAT also supplies an alternate implementation +of the stream attributes @cite{Read} and @cite{Write}, +which uses the target-independent XDR standard representation +for scalar types. + +@geindex XDR representation + +@geindex Read attribute + +@geindex Write attribute + +@geindex Stream oriented attributes + +The XDR implementation is provided as an alternative body of the +@cite{System.Stream_Attributes} package, in the file +@code{s-stratt-xdr.adb} in the GNAT library. +There is no @code{s-stratt-xdr.ads} file. +In order to install the XDR implementation, do the following: + + +@itemize * + +@item +Replace the default implementation of the +@cite{System.Stream_Attributes} package with the XDR implementation. +For example on a Unix platform issue the commands: + +@example +$ mv s-stratt.adb s-stratt-default.adb +$ mv s-stratt-xdr.adb s-stratt.adb +@end example + +@item +Rebuild the GNAT run-time library as documented in +the @cite{GNAT and Libraries} section of the @cite{GNAT User's Guide}. +@end itemize + +@node RM A 1 52 Names of Predefined Numeric Types,RM A 3 2 49 Ada Characters Handling,RM 13 13 2 17 Stream Oriented Attributes,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-a-1-52-names-of-predefined-numeric-types}@anchor{1db} +@section RM A.1(52): Names of Predefined Numeric Types + + +@quotation + +"If an implementation provides additional named predefined integer types, +then the names should end with @code{Integer} as in +@code{Long_Integer}. If an implementation provides additional named +predefined floating point types, then the names should end with +@code{Float} as in @code{Long_Float}." +@end quotation + +Followed. + +@geindex Ada.Characters.Handling + +@node RM A 3 2 49 Ada Characters Handling,RM A 4 4 106 Bounded-Length String Handling,RM A 1 52 Names of Predefined Numeric Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-a-3-2-49-ada-characters-handling}@anchor{1dc} +@section RM A.3.2(49): @cite{Ada.Characters.Handling} + + +@quotation + +"If an implementation provides a localized definition of @cite{Character} +or @cite{Wide_Character}, then the effects of the subprograms in +@cite{Characters.Handling} should reflect the localizations. +See also 3.5.2." +@end quotation + +Followed. GNAT provides no such localized definitions. + +@geindex Bounded-length strings + +@node RM A 4 4 106 Bounded-Length String Handling,RM A 5 2 46-47 Random Number Generation,RM A 3 2 49 Ada Characters Handling,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-a-4-4-106-bounded-length-string-handling}@anchor{1dd} +@section RM A.4.4(106): Bounded-Length String Handling + + +@quotation + +"Bounded string objects should not be implemented by implicit pointers +and dynamic allocation." +@end quotation + +Followed. No implicit pointers or dynamic allocation are used. + +@geindex Random number generation + +@node RM A 5 2 46-47 Random Number Generation,RM A 10 7 23 Get_Immediate,RM A 4 4 106 Bounded-Length String Handling,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-a-5-2-46-47-random-number-generation}@anchor{1de} +@section RM A.5.2(46-47): Random Number Generation + + +@quotation + +"Any storage associated with an object of type @cite{Generator} should be +reclaimed on exit from the scope of the object." +@end quotation + +Followed. + +@quotation + +"If the generator period is sufficiently long in relation to the number +of distinct initiator values, then each possible value of +@cite{Initiator} passed to @cite{Reset} should initiate a sequence of +random numbers that does not, in a practical sense, overlap the sequence +initiated by any other value. If this is not possible, then the mapping +between initiator values and generator states should be a rapidly +varying function of the initiator value." +@end quotation + +Followed. The generator period is sufficiently long for the first +condition here to hold true. + +@geindex Get_Immediate + +@node RM A 10 7 23 Get_Immediate,RM B 1 39-41 Pragma Export,RM A 5 2 46-47 Random Number Generation,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-a-10-7-23-get-immediate}@anchor{1df} +@section RM A.10.7(23): @cite{Get_Immediate} + + +@quotation + +"The @cite{Get_Immediate} procedures should be implemented with +unbuffered input. For a device such as a keyboard, input should be +available if a key has already been typed, whereas for a disk +file, input should always be available except at end of file. For a file +associated with a keyboard-like device, any line-editing features of the +underlying operating system should be disabled during the execution of +@cite{Get_Immediate}." +@end quotation + +Followed on all targets except VxWorks. For VxWorks, there is no way to +provide this functionality that does not result in the input buffer being +flushed before the @cite{Get_Immediate} call. A special unit +@cite{Interfaces.Vxworks.IO} is provided that contains routines to enable +this functionality. + +@geindex Export + +@node RM B 1 39-41 Pragma Export,RM B 2 12-13 Package Interfaces,RM A 10 7 23 Get_Immediate,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-b-1-39-41-pragma-export}@anchor{1e0} +@section RM B.1(39-41): Pragma @cite{Export} + + +@quotation + +"If an implementation supports pragma @cite{Export} to a given language, +then it should also allow the main subprogram to be written in that +language. It should support some mechanism for invoking the elaboration +of the Ada library units included in the system, and for invoking the +finalization of the environment task. On typical systems, the +recommended mechanism is to provide two subprograms whose link names are +@cite{adainit} and @cite{adafinal}. @cite{adainit} should contain the +elaboration code for library units. @cite{adafinal} should contain the +finalization code. These subprograms should have no effect the second +and subsequent time they are called." +@end quotation + +Followed. + +@quotation + +"Automatic elaboration of pre-elaborated packages should be +provided when pragma @cite{Export} is supported." +@end quotation + +Followed when the main program is in Ada. If the main program is in a +foreign language, then +@cite{adainit} must be called to elaborate pre-elaborated +packages. + +@quotation + +"For each supported convention @cite{L} other than @cite{Intrinsic}, an +implementation should support @cite{Import} and @cite{Export} pragmas +for objects of @cite{L}-compatible types and for subprograms, and pragma +@cite{Convention} for @cite{L}-eligible types and for subprograms, +presuming the other language has corresponding features. Pragma +@cite{Convention} need not be supported for scalar types." +@end quotation + +Followed. + +@geindex Package Interfaces + +@geindex Interfaces + +@node RM B 2 12-13 Package Interfaces,RM B 3 63-71 Interfacing with C,RM B 1 39-41 Pragma Export,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-b-2-12-13-package-interfaces}@anchor{1e1} +@section RM B.2(12-13): Package @cite{Interfaces} + + +@quotation + +"For each implementation-defined convention identifier, there should be a +child package of package Interfaces with the corresponding name. This +package should contain any declarations that would be useful for +interfacing to the language (implementation) represented by the +convention. Any declarations useful for interfacing to any language on +the given hardware architecture should be provided directly in +@cite{Interfaces}." +@end quotation + +Followed. + +@quotation + +"An implementation supporting an interface to C, COBOL, or Fortran should +provide the corresponding package or packages described in the following +clauses." +@end quotation + +Followed. GNAT provides all the packages described in this section. + +@geindex C +@geindex interfacing with + +@node RM B 3 63-71 Interfacing with C,RM B 4 95-98 Interfacing with COBOL,RM B 2 12-13 Package Interfaces,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-b-3-63-71-interfacing-with-c}@anchor{1e2} +@section RM B.3(63-71): Interfacing with C + + +@quotation + +"An implementation should support the following interface correspondences +between Ada and C." +@end quotation + +Followed. + +@quotation + +"An Ada procedure corresponds to a void-returning C function." +@end quotation + +Followed. + +@quotation + +"An Ada function corresponds to a non-void C function." +@end quotation + +Followed. + +@quotation + +"An Ada @cite{in} scalar parameter is passed as a scalar argument to a C +function." +@end quotation + +Followed. + +@quotation + +"An Ada @cite{in} parameter of an access-to-object type with designated +type @cite{T} is passed as a @code{t*} argument to a C function, +where @code{t} is the C type corresponding to the Ada type @cite{T}." +@end quotation + +Followed. + +@quotation + +"An Ada access @cite{T} parameter, or an Ada @cite{out} or @cite{in out} +parameter of an elementary type @cite{T}, is passed as a @code{t*} +argument to a C function, where @code{t} is the C type corresponding to +the Ada type @cite{T}. In the case of an elementary @cite{out} or +@cite{in out} parameter, a pointer to a temporary copy is used to +preserve by-copy semantics." +@end quotation + +Followed. + +@quotation + +"An Ada parameter of a record type @cite{T}, of any mode, is passed as a +@code{t*} argument to a C function, where @code{t} is the C +structure corresponding to the Ada type @cite{T}." +@end quotation + +Followed. This convention may be overridden by the use of the C_Pass_By_Copy +pragma, or Convention, or by explicitly specifying the mechanism for a given +call using an extended import or export pragma. + +@quotation + +"An Ada parameter of an array type with component type @cite{T}, of any +mode, is passed as a @code{t*} argument to a C function, where +@code{t} is the C type corresponding to the Ada type @cite{T}." +@end quotation + +Followed. + +@quotation + +"An Ada parameter of an access-to-subprogram type is passed as a pointer +to a C function whose prototype corresponds to the designated +subprogram's specification." +@end quotation + +Followed. + +@geindex COBOL +@geindex interfacing with + +@node RM B 4 95-98 Interfacing with COBOL,RM B 5 22-26 Interfacing with Fortran,RM B 3 63-71 Interfacing with C,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-b-4-95-98-interfacing-with-cobol}@anchor{1e3} +@section RM B.4(95-98): Interfacing with COBOL + + +@quotation + +"An Ada implementation should support the following interface +correspondences between Ada and COBOL." +@end quotation + +Followed. + +@quotation + +"An Ada access @cite{T} parameter is passed as a @code{BY REFERENCE} data item of +the COBOL type corresponding to @cite{T}." +@end quotation + +Followed. + +@quotation + +"An Ada in scalar parameter is passed as a @code{BY CONTENT} data item of +the corresponding COBOL type." +@end quotation + +Followed. + +@quotation + +"Any other Ada parameter is passed as a @code{BY REFERENCE} data item of the +COBOL type corresponding to the Ada parameter type; for scalars, a local +copy is used if necessary to ensure by-copy semantics." +@end quotation + +Followed. + +@geindex Fortran +@geindex interfacing with + +@node RM B 5 22-26 Interfacing with Fortran,RM C 1 3-5 Access to Machine Operations,RM B 4 95-98 Interfacing with COBOL,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-b-5-22-26-interfacing-with-fortran}@anchor{1e4} +@section RM B.5(22-26): Interfacing with Fortran + + +@quotation + +"An Ada implementation should support the following interface +correspondences between Ada and Fortran:" +@end quotation + +Followed. + +@quotation + +"An Ada procedure corresponds to a Fortran subroutine." +@end quotation + +Followed. + +@quotation + +"An Ada function corresponds to a Fortran function." +@end quotation + +Followed. + +@quotation + +"An Ada parameter of an elementary, array, or record type @cite{T} is +passed as a @cite{T} argument to a Fortran procedure, where @cite{T} is +the Fortran type corresponding to the Ada type @cite{T}, and where the +INTENT attribute of the corresponding dummy argument matches the Ada +formal parameter mode; the Fortran implementation's parameter passing +conventions are used. For elementary types, a local copy is used if +necessary to ensure by-copy semantics." +@end quotation + +Followed. + +@quotation + +"An Ada parameter of an access-to-subprogram type is passed as a +reference to a Fortran procedure whose interface corresponds to the +designated subprogram's specification." +@end quotation + +Followed. + +@geindex Machine operations + +@node RM C 1 3-5 Access to Machine Operations,RM C 1 10-16 Access to Machine Operations,RM B 5 22-26 Interfacing with Fortran,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-1-3-5-access-to-machine-operations}@anchor{1e5} +@section RM C.1(3-5): Access to Machine Operations + + +@quotation + +"The machine code or intrinsic support should allow access to all +operations normally available to assembly language programmers for the +target environment, including privileged instructions, if any." +@end quotation + +Followed. + +@quotation + +"The interfacing pragmas (see Annex B) should support interface to +assembler; the default assembler should be associated with the +convention identifier @cite{Assembler}." +@end quotation + +Followed. + +@quotation + +"If an entity is exported to assembly language, then the implementation +should allocate it at an addressable location, and should ensure that it +is retained by the linking process, even if not otherwise referenced +from the Ada code. The implementation should assume that any call to a +machine code or assembler subprogram is allowed to read or update every +object that is specified as exported." +@end quotation + +Followed. + +@node RM C 1 10-16 Access to Machine Operations,RM C 3 28 Interrupt Support,RM C 1 3-5 Access to Machine Operations,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-1-10-16-access-to-machine-operations}@anchor{1e6} +@section RM C.1(10-16): Access to Machine Operations + + +@quotation + +"The implementation should ensure that little or no overhead is +associated with calling intrinsic and machine-code subprograms." +@end quotation + +Followed for both intrinsics and machine-code subprograms. + +@quotation + +"It is recommended that intrinsic subprograms be provided for convenient +access to any machine operations that provide special capabilities or +efficiency and that are not otherwise available through the language +constructs." +@end quotation + +Followed. A full set of machine operation intrinsic subprograms is provided. + +@quotation + +"Atomic read-modify-write operations---e.g., test and set, compare and +swap, decrement and test, enqueue/dequeue." +@end quotation + +Followed on any target supporting such operations. + +@quotation + +"Standard numeric functions---e.g.:, sin, log." +@end quotation + +Followed on any target supporting such operations. + +@quotation + +"String manipulation operations---e.g.:, translate and test." +@end quotation + +Followed on any target supporting such operations. + +@quotation + +"Vector operations---e.g.:, compare vector against thresholds." +@end quotation + +Followed on any target supporting such operations. + +@quotation + +"Direct operations on I/O ports." +@end quotation + +Followed on any target supporting such operations. + +@geindex Interrupt support + +@node RM C 3 28 Interrupt Support,RM C 3 1 20-21 Protected Procedure Handlers,RM C 1 10-16 Access to Machine Operations,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-3-28-interrupt-support}@anchor{1e7} +@section RM C.3(28): Interrupt Support + + +@quotation + +"If the @cite{Ceiling_Locking} policy is not in effect, the +implementation should provide means for the application to specify which +interrupts are to be blocked during protected actions, if the underlying +system allows for a finer-grain control of interrupt blocking." +@end quotation + +Followed. The underlying system does not allow for finer-grain control +of interrupt blocking. + +@geindex Protected procedure handlers + +@node RM C 3 1 20-21 Protected Procedure Handlers,RM C 3 2 25 Package Interrupts,RM C 3 28 Interrupt Support,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-3-1-20-21-protected-procedure-handlers}@anchor{1e8} +@section RM C.3.1(20-21): Protected Procedure Handlers + + +@quotation + +"Whenever possible, the implementation should allow interrupt handlers to +be called directly by the hardware." +@end quotation + +Followed on any target where the underlying operating system permits +such direct calls. + +@quotation + +"Whenever practical, violations of any +implementation-defined restrictions should be detected before run time." +@end quotation + +Followed. Compile time warnings are given when possible. + +@geindex Package `Interrupts` + +@geindex Interrupts + +@node RM C 3 2 25 Package Interrupts,RM C 4 14 Pre-elaboration Requirements,RM C 3 1 20-21 Protected Procedure Handlers,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-3-2-25-package-interrupts}@anchor{1e9} +@section RM C.3.2(25): Package @cite{Interrupts} + + +@quotation + +"If implementation-defined forms of interrupt handler procedures are +supported, such as protected procedures with parameters, then for each +such form of a handler, a type analogous to @cite{Parameterless_Handler} +should be specified in a child package of @cite{Interrupts}, with the +same operations as in the predefined package Interrupts." +@end quotation + +Followed. + +@geindex Pre-elaboration requirements + +@node RM C 4 14 Pre-elaboration Requirements,RM C 5 8 Pragma Discard_Names,RM C 3 2 25 Package Interrupts,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-4-14-pre-elaboration-requirements}@anchor{1ea} +@section RM C.4(14): Pre-elaboration Requirements + + +@quotation + +"It is recommended that pre-elaborated packages be implemented in such a +way that there should be little or no code executed at run time for the +elaboration of entities not already covered by the Implementation +Requirements." +@end quotation + +Followed. Executable code is generated in some cases, e.g., loops +to initialize large arrays. + +@node RM C 5 8 Pragma Discard_Names,RM C 7 2 30 The Package Task_Attributes,RM C 4 14 Pre-elaboration Requirements,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-5-8-pragma-discard-names}@anchor{1eb} +@section RM C.5(8): Pragma @cite{Discard_Names} + + +@quotation + +"If the pragma applies to an entity, then the implementation should +reduce the amount of storage used for storing names associated with that +entity." +@end quotation + +Followed. + +@geindex Package Task_Attributes + +@geindex Task_Attributes + +@node RM C 7 2 30 The Package Task_Attributes,RM D 3 17 Locking Policies,RM C 5 8 Pragma Discard_Names,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-c-7-2-30-the-package-task-attributes}@anchor{1ec} +@section RM C.7.2(30): The Package Task_Attributes + + +@quotation + +"Some implementations are targeted to domains in which memory use at run +time must be completely deterministic. For such implementations, it is +recommended that the storage for task attributes will be pre-allocated +statically and not from the heap. This can be accomplished by either +placing restrictions on the number and the size of the task's +attributes, or by using the pre-allocated storage for the first @cite{N} +attribute objects, and the heap for the others. In the latter case, +@cite{N} should be documented." +@end quotation + +Not followed. This implementation is not targeted to such a domain. + +@geindex Locking Policies + +@node RM D 3 17 Locking Policies,RM D 4 16 Entry Queuing Policies,RM C 7 2 30 The Package Task_Attributes,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-d-3-17-locking-policies}@anchor{1ed} +@section RM D.3(17): Locking Policies + + +@quotation + +"The implementation should use names that end with @code{_Locking} for +locking policies defined by the implementation." +@end quotation + +Followed. Two implementation-defined locking policies are defined, +whose names (@cite{Inheritance_Locking} and +@cite{Concurrent_Readers_Locking}) follow this suggestion. + +@geindex Entry queuing policies + +@node RM D 4 16 Entry Queuing Policies,RM D 6 9-10 Preemptive Abort,RM D 3 17 Locking Policies,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-d-4-16-entry-queuing-policies}@anchor{1ee} +@section RM D.4(16): Entry Queuing Policies + + +@quotation + +"Names that end with @code{_Queuing} should be used +for all implementation-defined queuing policies." +@end quotation + +Followed. No such implementation-defined queuing policies exist. + +@geindex Preemptive abort + +@node RM D 6 9-10 Preemptive Abort,RM D 7 21 Tasking Restrictions,RM D 4 16 Entry Queuing Policies,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-d-6-9-10-preemptive-abort}@anchor{1ef} +@section RM D.6(9-10): Preemptive Abort + + +@quotation + +"Even though the @cite{abort_statement} is included in the list of +potentially blocking operations (see 9.5.1), it is recommended that this +statement be implemented in a way that never requires the task executing +the @cite{abort_statement} to block." +@end quotation + +Followed. + +@quotation + +"On a multi-processor, the delay associated with aborting a task on +another processor should be bounded; the implementation should use +periodic polling, if necessary, to achieve this." +@end quotation + +Followed. + +@geindex Tasking restrictions + +@node RM D 7 21 Tasking Restrictions,RM D 8 47-49 Monotonic Time,RM D 6 9-10 Preemptive Abort,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-d-7-21-tasking-restrictions}@anchor{1f0} +@section RM D.7(21): Tasking Restrictions + + +@quotation + +"When feasible, the implementation should take advantage of the specified +restrictions to produce a more efficient implementation." +@end quotation + +GNAT currently takes advantage of these restrictions by providing an optimized +run time when the Ravenscar profile and the GNAT restricted run time set +of restrictions are specified. See pragma @cite{Profile (Ravenscar)} and +pragma @cite{Profile (Restricted)} for more details. + +@geindex Time +@geindex monotonic + +@node RM D 8 47-49 Monotonic Time,RM E 5 28-29 Partition Communication Subsystem,RM D 7 21 Tasking Restrictions,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-d-8-47-49-monotonic-time}@anchor{1f1} +@section RM D.8(47-49): Monotonic Time + + +@quotation + +"When appropriate, implementations should provide configuration +mechanisms to change the value of @cite{Tick}." +@end quotation + +Such configuration mechanisms are not appropriate to this implementation +and are thus not supported. + +@quotation + +"It is recommended that @cite{Calendar.Clock} and @cite{Real_Time.Clock} +be implemented as transformations of the same time base." +@end quotation + +Followed. + +@quotation + +"It is recommended that the best time base which exists in +the underlying system be available to the application through +@cite{Clock}. @cite{Best} may mean highest accuracy or largest range." +@end quotation + +Followed. + +@geindex Partition communication subsystem + +@geindex PCS + +@node RM E 5 28-29 Partition Communication Subsystem,RM F 7 COBOL Support,RM D 8 47-49 Monotonic Time,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-e-5-28-29-partition-communication-subsystem}@anchor{1f2} +@section RM E.5(28-29): Partition Communication Subsystem + + +@quotation + +"Whenever possible, the PCS on the called partition should allow for +multiple tasks to call the RPC-receiver with different messages and +should allow them to block until the corresponding subprogram body +returns." +@end quotation + +Followed by GLADE, a separately supplied PCS that can be used with +GNAT. + +@quotation + +"The @cite{Write} operation on a stream of type @cite{Params_Stream_Type} +should raise @cite{Storage_Error} if it runs out of space trying to +write the @cite{Item} into the stream." +@end quotation + +Followed by GLADE, a separately supplied PCS that can be used with +GNAT. + +@geindex COBOL support + +@node RM F 7 COBOL Support,RM F 1 2 Decimal Radix Support,RM E 5 28-29 Partition Communication Subsystem,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-f-7-cobol-support}@anchor{1f3} +@section RM F(7): COBOL Support + + +@quotation + +"If COBOL (respectively, C) is widely supported in the target +environment, implementations supporting the Information Systems Annex +should provide the child package @cite{Interfaces.COBOL} (respectively, +@cite{Interfaces.C}) specified in Annex B and should support a +@cite{convention_identifier} of COBOL (respectively, C) in the interfacing +pragmas (see Annex B), thus allowing Ada programs to interface with +programs written in that language." +@end quotation + +Followed. + +@geindex Decimal radix support + +@node RM F 1 2 Decimal Radix Support,RM G Numerics,RM F 7 COBOL Support,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-f-1-2-decimal-radix-support}@anchor{1f4} +@section RM F.1(2): Decimal Radix Support + + +@quotation + +"Packed decimal should be used as the internal representation for objects +of subtype @cite{S} when @cite{S}'Machine_Radix = 10." +@end quotation + +Not followed. GNAT ignores @cite{S}'Machine_Radix and always uses binary +representations. + +@geindex Numerics + +@node RM G Numerics,RM G 1 1 56-58 Complex Types,RM F 1 2 Decimal Radix Support,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-g-numerics}@anchor{1f5} +@section RM G: Numerics + + +@quotation + +"If Fortran (respectively, C) is widely supported in the target +environment, implementations supporting the Numerics Annex +should provide the child package @cite{Interfaces.Fortran} (respectively, +@cite{Interfaces.C}) specified in Annex B and should support a +@cite{convention_identifier} of Fortran (respectively, C) in the interfacing +pragmas (see Annex B), thus allowing Ada programs to interface with +programs written in that language." +@end quotation + +Followed. + +@geindex Complex types + +@node RM G 1 1 56-58 Complex Types,RM G 1 2 49 Complex Elementary Functions,RM G Numerics,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-g-1-1-56-58-complex-types}@anchor{1f6} +@section RM G.1.1(56-58): Complex Types + + +@quotation + +"Because the usual mathematical meaning of multiplication of a complex +operand and a real operand is that of the scaling of both components of +the former by the latter, an implementation should not perform this +operation by first promoting the real operand to complex type and then +performing a full complex multiplication. In systems that, in the +future, support an Ada binding to IEC 559:1989, the latter technique +will not generate the required result when one of the components of the +complex operand is infinite. (Explicit multiplication of the infinite +component by the zero component obtained during promotion yields a NaN +that propagates into the final result.) Analogous advice applies in the +case of multiplication of a complex operand and a pure-imaginary +operand, and in the case of division of a complex operand by a real or +pure-imaginary operand." +@end quotation + +Not followed. + +@quotation + +"Similarly, because the usual mathematical meaning of addition of a +complex operand and a real operand is that the imaginary operand remains +unchanged, an implementation should not perform this operation by first +promoting the real operand to complex type and then performing a full +complex addition. In implementations in which the @cite{Signed_Zeros} +attribute of the component type is @cite{True} (and which therefore +conform to IEC 559:1989 in regard to the handling of the sign of zero in +predefined arithmetic operations), the latter technique will not +generate the required result when the imaginary component of the complex +operand is a negatively signed zero. (Explicit addition of the negative +zero to the zero obtained during promotion yields a positive zero.) +Analogous advice applies in the case of addition of a complex operand +and a pure-imaginary operand, and in the case of subtraction of a +complex operand and a real or pure-imaginary operand." +@end quotation + +Not followed. + +@quotation + +"Implementations in which @cite{Real'Signed_Zeros} is @cite{True} should +attempt to provide a rational treatment of the signs of zero results and +result components. As one example, the result of the @cite{Argument} +function should have the sign of the imaginary component of the +parameter @cite{X} when the point represented by that parameter lies on +the positive real axis; as another, the sign of the imaginary component +of the @cite{Compose_From_Polar} function should be the same as +(respectively, the opposite of) that of the @cite{Argument} parameter when that +parameter has a value of zero and the @cite{Modulus} parameter has a +nonnegative (respectively, negative) value." +@end quotation + +Followed. + +@geindex Complex elementary functions + +@node RM G 1 2 49 Complex Elementary Functions,RM G 2 4 19 Accuracy Requirements,RM G 1 1 56-58 Complex Types,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-g-1-2-49-complex-elementary-functions}@anchor{1f7} +@section RM G.1.2(49): Complex Elementary Functions + + +@quotation + +"Implementations in which @cite{Complex_Types.Real'Signed_Zeros} is +@cite{True} should attempt to provide a rational treatment of the signs +of zero results and result components. For example, many of the complex +elementary functions have components that are odd functions of one of +the parameter components; in these cases, the result component should +have the sign of the parameter component at the origin. Other complex +elementary functions have zero components whose sign is opposite that of +a parameter component at the origin, or is always positive or always +negative." +@end quotation + +Followed. + +@geindex Accuracy requirements + +@node RM G 2 4 19 Accuracy Requirements,RM G 2 6 15 Complex Arithmetic Accuracy,RM G 1 2 49 Complex Elementary Functions,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-g-2-4-19-accuracy-requirements}@anchor{1f8} +@section RM G.2.4(19): Accuracy Requirements + + +@quotation + +"The versions of the forward trigonometric functions without a +@cite{Cycle} parameter should not be implemented by calling the +corresponding version with a @cite{Cycle} parameter of +@cite{2.0*Numerics.Pi}, since this will not provide the required +accuracy in some portions of the domain. For the same reason, the +version of @cite{Log} without a @cite{Base} parameter should not be +implemented by calling the corresponding version with a @cite{Base} +parameter of @cite{Numerics.e}." +@end quotation + +Followed. + +@geindex Complex arithmetic accuracy + +@geindex Accuracy +@geindex complex arithmetic + +@node RM G 2 6 15 Complex Arithmetic Accuracy,RM H 6 15/2 Pragma Partition_Elaboration_Policy,RM G 2 4 19 Accuracy Requirements,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-g-2-6-15-complex-arithmetic-accuracy}@anchor{1f9} +@section RM G.2.6(15): Complex Arithmetic Accuracy + + +@quotation + +"The version of the @cite{Compose_From_Polar} function without a +@cite{Cycle} parameter should not be implemented by calling the +corresponding version with a @cite{Cycle} parameter of +@cite{2.0*Numerics.Pi}, since this will not provide the required +accuracy in some portions of the domain." +@end quotation + +Followed. + +@geindex Sequential elaboration policy + +@node RM H 6 15/2 Pragma Partition_Elaboration_Policy,,RM G 2 6 15 Complex Arithmetic Accuracy,Implementation Advice +@anchor{gnat_rm/implementation_advice rm-h-6-15-2-pragma-partition-elaboration-policy}@anchor{1fa} +@section RM H.6(15/2): Pragma Partition_Elaboration_Policy + + +@quotation + +"If the partition elaboration policy is @cite{Sequential} and the +Environment task becomes permanently blocked during elaboration then the +partition is deadlocked and it is recommended that the partition be +immediately terminated." +@end quotation + +Not followed. + +@node Implementation Defined Characteristics,Intrinsic Subprograms,Implementation Advice,Top +@anchor{gnat_rm/implementation_defined_characteristics implementation-defined-characteristics}@anchor{b}@anchor{gnat_rm/implementation_defined_characteristics doc}@anchor{1fb}@anchor{gnat_rm/implementation_defined_characteristics id1}@anchor{1fc} +@chapter Implementation Defined Characteristics + + +In addition to the implementation dependent pragmas and attributes, and the +implementation advice, there are a number of other Ada features that are +potentially implementation dependent and are designated as +implementation-defined. These are mentioned throughout the Ada Reference +Manual, and are summarized in Annex M. + +A requirement for conforming Ada compilers is that they provide +documentation describing how the implementation deals with each of these +issues. In this chapter you will find each point in Annex M listed, +followed by a description of how GNAT +handles the implementation dependence. + +You can use this chapter as a guide to minimizing implementation +dependent features in your programs if portability to other compilers +and other operating systems is an important consideration. The numbers +in each entry below correspond to the paragraph numbers in the Ada +Reference Manual. + + +@itemize * + +@item +"Whether or not each recommendation given in Implementation +Advice is followed. See 1.1.2(37)." +@end itemize + +See @ref{a,,Implementation Advice}. + + +@itemize * + +@item +"Capacity limitations of the implementation. See 1.1.3(3)." +@end itemize + +The complexity of programs that can be processed is limited only by the +total amount of available virtual memory, and disk space for the +generated object files. + + +@itemize * + +@item +"Variations from the standard that are impractical to avoid +given the implementation's execution environment. See 1.1.3(6)." +@end itemize + +There are no variations from the standard. + + +@itemize * + +@item +"Which code_statements cause external +interactions. See 1.1.3(10)." +@end itemize + +Any @cite{code_statement} can potentially cause external interactions. + + +@itemize * + +@item +"The coded representation for the text of an Ada +program. See 2.1(4)." +@end itemize + +See separate section on source representation. + + +@itemize * + +@item +"The control functions allowed in comments. See 2.1(14)." +@end itemize + +See separate section on source representation. + + +@itemize * + +@item +"The representation for an end of line. See 2.2(2)." +@end itemize + +See separate section on source representation. + + +@itemize * + +@item +"Maximum supported line length and lexical element +length. See 2.2(15)." +@end itemize + +The maximum line length is 255 characters and the maximum length of +a lexical element is also 255 characters. This is the default setting +if not overridden by the use of compiler switch @emph{-gnaty} (which +sets the maximum to 79) or @emph{-gnatyMnn} which allows the maximum +line length to be specified to be any value up to 32767. The maximum +length of a lexical element is the same as the maximum line length. + + +@itemize * + +@item +"Implementation defined pragmas. See 2.8(14)." +@end itemize + +See @ref{7,,Implementation Defined Pragmas}. + + +@itemize * + +@item +"Effect of pragma @cite{Optimize}. See 2.8(27)." +@end itemize + +Pragma @cite{Optimize}, if given with a @cite{Time} or @cite{Space} +parameter, checks that the optimization flag is set, and aborts if it is +not. + + +@itemize * + +@item +"The sequence of characters of the value returned by +@code{S'Image} when some of the graphic characters of +@code{S'Wide_Image} are not defined in @cite{Character}. See +3.5(37)." +@end itemize + +The sequence of characters is as defined by the wide character encoding +method used for the source. See section on source representation for +further details. + + +@itemize * + +@item +"The predefined integer types declared in +@cite{Standard}. See 3.5.4(25)." +@end itemize + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Type + +@tab + +Representation + +@item + +@emph{Short_Short_Integer} + +@tab + +8 bit signed + +@item + +@emph{Short_Integer} + +@tab + +(Short) 16 bit signed + +@item + +@emph{Integer} + +@tab + +32 bit signed + +@item + +@emph{Long_Integer} + +@tab + +64 bit signed (on most 64 bit targets, +depending on the C definition of long). +32 bit signed (all other targets) + +@item + +@emph{Long_Long_Integer} + +@tab + +64 bit signed + +@end multitable + + + +@itemize * + +@item +"Any nonstandard integer types and the operators defined +for them. See 3.5.4(26)." +@end itemize + +There are no nonstandard integer types. + + +@itemize * + +@item +"Any nonstandard real types and the operators defined for +them. See 3.5.6(8)." +@end itemize + +There are no nonstandard real types. + + +@itemize * + +@item +"What combinations of requested decimal precision and range +are supported for floating point types. See 3.5.7(7)." +@end itemize + +The precision and range is as defined by the IEEE standard. + + +@itemize * + +@item +"The predefined floating point types declared in +@cite{Standard}. See 3.5.7(16)." +@end itemize + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Type + +@tab + +Representation + +@item + +@emph{Short_Float} + +@tab + +32 bit IEEE short + +@item + +@emph{Float} + +@tab + +(Short) 32 bit IEEE short + +@item + +@emph{Long_Float} + +@tab + +64 bit IEEE long + +@item + +@emph{Long_Long_Float} + +@tab + +64 bit IEEE long (80 bit IEEE long on x86 processors) + +@end multitable + + + +@itemize * + +@item +"The small of an ordinary fixed point type. See 3.5.9(8)." +@end itemize + +@cite{Fine_Delta} is 2**(-63) + + +@itemize * + +@item +"What combinations of small, range, and digits are +supported for fixed point types. See 3.5.9(10)." +@end itemize + +Any combinations are permitted that do not result in a small less than +@cite{Fine_Delta} and do not result in a mantissa larger than 63 bits. +If the mantissa is larger than 53 bits on machines where Long_Long_Float +is 64 bits (true of all architectures except ia32), then the output from +Text_IO is accurate to only 53 bits, rather than the full mantissa. This +is because floating-point conversions are used to convert fixed point. + + +@itemize * + +@item +"The result of @cite{Tags.Expanded_Name} for types declared +within an unnamed @cite{block_statement}. See 3.9(10)." +@end itemize + +Block numbers of the form @cite{B`nnn`}, where @cite{nnn} is a +decimal integer are allocated. + + +@itemize * + +@item +"Implementation-defined attributes. See 4.1.4(12)." +@end itemize + +See @ref{8,,Implementation Defined Attributes}. + + +@itemize * + +@item +"Any implementation-defined time types. See 9.6(6)." +@end itemize + +There are no implementation-defined time types. + + +@itemize * + +@item +"The time base associated with relative delays." +@end itemize + +See 9.6(20). The time base used is that provided by the C library +function @cite{gettimeofday}. + + +@itemize * + +@item +"The time base of the type @cite{Calendar.Time}. See +9.6(23)." +@end itemize + +The time base used is that provided by the C library function +@cite{gettimeofday}. + + +@itemize * + +@item +"The time zone used for package @cite{Calendar} +operations. See 9.6(24)." +@end itemize + +The time zone used by package @cite{Calendar} is the current system time zone +setting for local time, as accessed by the C library function +@cite{localtime}. + + +@itemize * + +@item +"Any limit on @cite{delay_until_statements} of +@cite{select_statements}. See 9.6(29)." +@end itemize + +There are no such limits. + + +@itemize * + +@item +"Whether or not two non-overlapping parts of a composite +object are independently addressable, in the case where packing, record +layout, or @cite{Component_Size} is specified for the object. See +9.10(1)." +@end itemize + +Separate components are independently addressable if they do not share +overlapping storage units. + + +@itemize * + +@item +"The representation for a compilation. See 10.1(2)." +@end itemize + +A compilation is represented by a sequence of files presented to the +compiler in a single invocation of the @emph{gcc} command. + + +@itemize * + +@item +"Any restrictions on compilations that contain multiple +compilation_units. See 10.1(4)." +@end itemize + +No single file can contain more than one compilation unit, but any +sequence of files can be presented to the compiler as a single +compilation. + + +@itemize * + +@item +"The mechanisms for creating an environment and for adding +and replacing compilation units. See 10.1.4(3)." +@end itemize + +See separate section on compilation model. + + +@itemize * + +@item +"The manner of explicitly assigning library units to a +partition. See 10.2(2)." +@end itemize + +If a unit contains an Ada main program, then the Ada units for the partition +are determined by recursive application of the rules in the Ada Reference +Manual section 10.2(2-6). In other words, the Ada units will be those that +are needed by the main program, and then this definition of need is applied +recursively to those units, and the partition contains the transitive +closure determined by this relationship. In short, all the necessary units +are included, with no need to explicitly specify the list. If additional +units are required, e.g., by foreign language units, then all units must be +mentioned in the context clause of one of the needed Ada units. + +If the partition contains no main program, or if the main program is in +a language other than Ada, then GNAT +provides the binder options @emph{-z} and @emph{-n} respectively, and in +this case a list of units can be explicitly supplied to the binder for +inclusion in the partition (all units needed by these units will also +be included automatically). For full details on the use of these +options, refer to the @cite{GNAT Make Program gnatmake} in the +@cite{GNAT User's Guide}. + + +@itemize * + +@item +"The implementation-defined means, if any, of specifying +which compilation units are needed by a given compilation unit. See +10.2(2)." +@end itemize + +The units needed by a given compilation unit are as defined in +the Ada Reference Manual section 10.2(2-6). There are no +implementation-defined pragmas or other implementation-defined +means for specifying needed units. + + +@itemize * + +@item +"The manner of designating the main subprogram of a +partition. See 10.2(7)." +@end itemize + +The main program is designated by providing the name of the +corresponding @code{ALI} file as the input parameter to the binder. + + +@itemize * + +@item +"The order of elaboration of @cite{library_items}. See +10.2(18)." +@end itemize + +The first constraint on ordering is that it meets the requirements of +Chapter 10 of the Ada Reference Manual. This still leaves some +implementation dependent choices, which are resolved by first +elaborating bodies as early as possible (i.e., in preference to specs +where there is a choice), and second by evaluating the immediate with +clauses of a unit to determine the probably best choice, and +third by elaborating in alphabetical order of unit names +where a choice still remains. + + +@itemize * + +@item +"Parameter passing and function return for the main +subprogram. See 10.2(21)." +@end itemize + +The main program has no parameters. It may be a procedure, or a function +returning an integer type. In the latter case, the returned integer +value is the return code of the program (overriding any value that +may have been set by a call to @cite{Ada.Command_Line.Set_Exit_Status}). + + +@itemize * + +@item +"The mechanisms for building and running partitions. See +10.2(24)." +@end itemize + +GNAT itself supports programs with only a single partition. The GNATDIST +tool provided with the GLADE package (which also includes an implementation +of the PCS) provides a completely flexible method for building and running +programs consisting of multiple partitions. See the separate GLADE manual +for details. + + +@itemize * + +@item +"The details of program execution, including program +termination. See 10.2(25)." +@end itemize + +See separate section on compilation model. + + +@itemize * + +@item +"The semantics of any non-active partitions supported by the +implementation. See 10.2(28)." +@end itemize + +Passive partitions are supported on targets where shared memory is +provided by the operating system. See the GLADE reference manual for +further details. + + +@itemize * + +@item +"The information returned by @cite{Exception_Message}. See +11.4.1(10)." +@end itemize + +Exception message returns the null string unless a specific message has +been passed by the program. + + +@itemize * + +@item +"The result of @cite{Exceptions.Exception_Name} for types +declared within an unnamed @cite{block_statement}. See 11.4.1(12)." +@end itemize + +Blocks have implementation defined names of the form @cite{B`nnn`} +where @cite{nnn} is an integer. + + +@itemize * + +@item +"The information returned by +@cite{Exception_Information}. See 11.4.1(13)." +@end itemize + +@cite{Exception_Information} returns a string in the following format: + +@example +*Exception_Name:* nnnnn +*Message:* mmmmm +*PID:* ppp +*Load address:* 0xhhhh +*Call stack traceback locations:* +0xhhhh 0xhhhh 0xhhhh ... 0xhhh +@end example + +where + +@quotation + + +@itemize * + +@item +@cite{nnnn} is the fully qualified name of the exception in all upper +case letters. This line is always present. + +@item +@cite{mmmm} is the message (this line present only if message is non-null) + +@item +@cite{ppp} is the Process Id value as a decimal integer (this line is +present only if the Process Id is nonzero). Currently we are +not making use of this field. + +@item +The Load address line, the Call stack traceback locations line and the +following values are present only if at least one traceback location was +recorded. The Load address indicates the address at which the main executable +was loaded; this line may not be present if operating system hasn't relocated +the main executable. The values are given in C style format, with lower case +letters for a-f, and only as many digits present as are necessary. +The line terminator sequence at the end of each line, including +the last line is a single @cite{LF} character (@cite{16#0A#}). +@end itemize +@end quotation + + +@itemize * + +@item +"Implementation-defined check names. See 11.5(27)." +@end itemize + +The implementation defined check name Alignment_Check controls checking of +address clause values for proper alignment (that is, the address supplied +must be consistent with the alignment of the type). + +The implementation defined check name Predicate_Check controls whether +predicate checks are generated. + +The implementation defined check name Validity_Check controls whether +validity checks are generated. + +In addition, a user program can add implementation-defined check names +by means of the pragma Check_Name. + + +@itemize * + +@item +"The interpretation of each aspect of representation. See +13.1(20)." +@end itemize + +See separate section on data representations. + + +@itemize * + +@item +"Any restrictions placed upon representation items. See +13.1(20)." +@end itemize + +See separate section on data representations. + + +@itemize * + +@item +"The meaning of @cite{Size} for indefinite subtypes. See +13.3(48)." +@end itemize + +Size for an indefinite subtype is the maximum possible size, except that +for the case of a subprogram parameter, the size of the parameter object +is the actual size. + + +@itemize * + +@item +"The default external representation for a type tag. See +13.3(75)." +@end itemize + +The default external representation for a type tag is the fully expanded +name of the type in upper case letters. + + +@itemize * + +@item +"What determines whether a compilation unit is the same in +two different partitions. See 13.3(76)." +@end itemize + +A compilation unit is the same in two different partitions if and only +if it derives from the same source file. + + +@itemize * + +@item +"Implementation-defined components. See 13.5.1(15)." +@end itemize + +The only implementation defined component is the tag for a tagged type, +which contains a pointer to the dispatching table. + + +@itemize * + +@item +"If @cite{Word_Size} = @cite{Storage_Unit}, the default bit +ordering. See 13.5.3(5)." +@end itemize + +@cite{Word_Size} (32) is not the same as @cite{Storage_Unit} (8) for this +implementation, so no non-default bit ordering is supported. The default +bit ordering corresponds to the natural endianness of the target architecture. + + +@itemize * + +@item +"The contents of the visible part of package @cite{System} +and its language-defined children. See 13.7(2)." +@end itemize + +See the definition of these packages in files @code{system.ads} and +@code{s-stoele.ads}. Note that two declarations are added to package +System. + +@example +Max_Priority : constant Positive := Priority'Last; +Max_Interrupt_Priority : constant Positive := Interrupt_Priority'Last; +@end example + + +@itemize * + +@item +"The contents of the visible part of package +@cite{System.Machine_Code}, and the meaning of +@cite{code_statements}. See 13.8(7)." +@end itemize + +See the definition and documentation in file @code{s-maccod.ads}. + + +@itemize * + +@item +"The effect of unchecked conversion. See 13.9(11)." +@end itemize + +Unchecked conversion between types of the same size +results in an uninterpreted transmission of the bits from one type +to the other. If the types are of unequal sizes, then in the case of +discrete types, a shorter source is first zero or sign extended as +necessary, and a shorter target is simply truncated on the left. +For all non-discrete types, the source is first copied if necessary +to ensure that the alignment requirements of the target are met, then +a pointer is constructed to the source value, and the result is obtained +by dereferencing this pointer after converting it to be a pointer to the +target type. Unchecked conversions where the target subtype is an +unconstrained array are not permitted. If the target alignment is +greater than the source alignment, then a copy of the result is +made with appropriate alignment + + +@itemize * + +@item +"The semantics of operations on invalid representations. +See 13.9.2(10-11)." +@end itemize + +For assignments and other operations where the use of invalid values cannot +result in erroneous behavior, the compiler ignores the possibility of invalid +values. An exception is raised at the point where an invalid value would +result in erroneous behavior. For example executing: + +@example +procedure invalidvals is + X : Integer := -1; + Y : Natural range 1 .. 10; + for Y'Address use X'Address; + Z : Natural range 1 .. 10; + A : array (Natural range 1 .. 10) of Integer; +begin + Z := Y; -- no exception + A (Z) := 3; -- exception raised; +end; +@end example + +As indicated, an exception is raised on the array assignment, but not +on the simple assignment of the invalid negative value from Y to Z. + + +@itemize * + +@item +"The manner of choosing a storage pool for an access type +when @cite{Storage_Pool} is not specified for the type. See 13.11(17)." +@end itemize + +There are 3 different standard pools used by the compiler when +@cite{Storage_Pool} is not specified depending whether the type is local +to a subprogram or defined at the library level and whether +@cite{Storage_Size`is specified or not. See documentation in the runtime library units `System.Pool_Global}, @cite{System.Pool_Size} and +@cite{System.Pool_Local} in files @code{s-poosiz.ads}, +@code{s-pooglo.ads} and @code{s-pooloc.ads} for full details on the +default pools used. + + +@itemize * + +@item +"Whether or not the implementation provides user-accessible +names for the standard pool type(s). See 13.11(17)." +@end itemize + +See documentation in the sources of the run time mentioned in the previous +paragraph. All these pools are accessible by means of @cite{with}'ing +these units. + + +@itemize * + +@item +"The meaning of @cite{Storage_Size}. See 13.11(18)." +@end itemize + +@cite{Storage_Size} is measured in storage units, and refers to the +total space available for an access type collection, or to the primary +stack space for a task. + + +@itemize * + +@item +"Implementation-defined aspects of storage pools. See +13.11(22)." +@end itemize + +See documentation in the sources of the run time mentioned in the +paragraph about standard storage pools above +for details on GNAT-defined aspects of storage pools. + + +@itemize * + +@item +"The set of restrictions allowed in a pragma +@cite{Restrictions}. See 13.12(7)." +@end itemize + +See @ref{9,,Standard and Implementation Defined Restrictions}. + + +@itemize * + +@item +"The consequences of violating limitations on +@cite{Restrictions} pragmas. See 13.12(9)." +@end itemize + +Restrictions that can be checked at compile time result in illegalities +if violated. Currently there are no other consequences of violating +restrictions. + + +@itemize * + +@item +"The representation used by the @cite{Read} and +@cite{Write} attributes of elementary types in terms of stream +elements. See 13.13.2(9)." +@end itemize + +The representation is the in-memory representation of the base type of +the type, using the number of bits corresponding to the +@code{type'Size} value, and the natural ordering of the machine. + + +@itemize * + +@item +"The names and characteristics of the numeric subtypes +declared in the visible part of package @cite{Standard}. See A.1(3)." +@end itemize + +See items describing the integer and floating-point types supported. + + +@itemize * + +@item +"The string returned by @cite{Character_Set_Version}. +See A.3.5(3)." +@end itemize + +@cite{Ada.Wide_Characters.Handling.Character_Set_Version} returns +the string "Unicode 4.0", referring to version 4.0 of the +Unicode specification. + + +@itemize * + +@item +"The accuracy actually achieved by the elementary +functions. See A.5.1(1)." +@end itemize + +The elementary functions correspond to the functions available in the C +library. Only fast math mode is implemented. + + +@itemize * + +@item +"The sign of a zero result from some of the operators or +functions in @cite{Numerics.Generic_Elementary_Functions}, when +@cite{Float_Type'Signed_Zeros} is @cite{True}. See A.5.1(46)." +@end itemize + +The sign of zeroes follows the requirements of the IEEE 754 standard on +floating-point. + + +@itemize * + +@item +"The value of +@cite{Numerics.Float_Random.Max_Image_Width}. See A.5.2(27)." +@end itemize + +Maximum image width is 6864, see library file @code{s-rannum.ads}. + + +@itemize * + +@item +"The value of +@cite{Numerics.Discrete_Random.Max_Image_Width}. See A.5.2(27)." +@end itemize + +Maximum image width is 6864, see library file @code{s-rannum.ads}. + + +@itemize * + +@item +"The algorithms for random number generation. See +A.5.2(32)." +@end itemize + +The algorithm is the Mersenne Twister, as documented in the source file +@code{s-rannum.adb}. This version of the algorithm has a period of +2**19937-1. + + +@itemize * + +@item +"The string representation of a random number generator's +state. See A.5.2(38)." +@end itemize + +The value returned by the Image function is the concatenation of +the fixed-width decimal representations of the 624 32-bit integers +of the state vector. + + +@itemize * + +@item +"The minimum time interval between calls to the +time-dependent Reset procedure that are guaranteed to initiate different +random number sequences. See A.5.2(45)." +@end itemize + +The minimum period between reset calls to guarantee distinct series of +random numbers is one microsecond. + + +@itemize * + +@item +"The values of the @cite{Model_Mantissa}, +@cite{Model_Emin}, @cite{Model_Epsilon}, @cite{Model}, +@cite{Safe_First}, and @cite{Safe_Last} attributes, if the Numerics +Annex is not supported. See A.5.3(72)." +@end itemize + +Run the compiler with @emph{-gnatS} to produce a listing of package +@cite{Standard}, has the values of all numeric attributes. + + +@itemize * + +@item +"Any implementation-defined characteristics of the +input-output packages. See A.7(14)." +@end itemize + +There are no special implementation defined characteristics for these +packages. + + +@itemize * + +@item +"The value of @cite{Buffer_Size} in @cite{Storage_IO}. See +A.9(10)." +@end itemize + +All type representations are contiguous, and the @cite{Buffer_Size} is +the value of @code{type'Size} rounded up to the next storage unit +boundary. + + +@itemize * + +@item +"External files for standard input, standard output, and +standard error See A.10(5)." +@end itemize + +These files are mapped onto the files provided by the C streams +libraries. See source file @code{i-cstrea.ads} for further details. + + +@itemize * + +@item +"The accuracy of the value produced by @cite{Put}. See +A.10.9(36)." +@end itemize + +If more digits are requested in the output than are represented by the +precision of the value, zeroes are output in the corresponding least +significant digit positions. + + +@itemize * + +@item +"The meaning of @cite{Argument_Count}, @cite{Argument}, and +@cite{Command_Name}. See A.15(1)." +@end itemize + +These are mapped onto the @cite{argv} and @cite{argc} parameters of the +main program in the natural manner. + + +@itemize * + +@item +"The interpretation of the @cite{Form} parameter in procedure +@cite{Create_Directory}. See A.16(56)." +@end itemize + +The @cite{Form} parameter is not used. + + +@itemize * + +@item +"The interpretation of the @cite{Form} parameter in procedure +@cite{Create_Path}. See A.16(60)." +@end itemize + +The @cite{Form} parameter is not used. + + +@itemize * + +@item +"The interpretation of the @cite{Form} parameter in procedure +@cite{Copy_File}. See A.16(68)." +@end itemize + +The @cite{Form} parameter is case-insensitive. +Two fields are recognized in the @cite{Form} parameter: + +@example +*preserve=* +*mode=* +@end example + + starts immediately after the character '=' and ends with the +character immediately preceding the next comma (',') or with the last +character of the parameter. + +The only possible values for preserve= are: + + +@multitable {xxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Value + +@tab + +Meaning + +@item + +@emph{no_attributes} + +@tab + +Do not try to preserve any file attributes. This is the +default if no preserve= is found in Form. + +@item + +@emph{all_attributes} + +@tab + +Try to preserve all file attributes (timestamps, access rights). + +@item + +@emph{timestamps} + +@tab + +Preserve the timestamp of the copied file, but not the other +file attributes. + +@end multitable + + +The only possible values for mode= are: + + +@multitable {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Value + +@tab + +Meaning + +@item + +@emph{copy} + +@tab + +Only do the copy if the destination file does not already exist. +If it already exists, Copy_File fails. + +@item + +@emph{overwrite} + +@tab + +Copy the file in all cases. Overwrite an already existing destination file. + +@item + +@emph{append} + +@tab + +Append the original file to the destination file. If the destination file +does not exist, the destination file is a copy of the source file. +When mode=append, the field preserve=, if it exists, is not taken into account. + +@end multitable + + +If the Form parameter includes one or both of the fields and the value or +values are incorrect, Copy_file fails with Use_Error. + +Examples of correct Forms: + +@example +Form => "preserve=no_attributes,mode=overwrite" (the default) Form => "mode=append" Form => "mode=copy, preserve=all_attributes" -@end smallexample +@end example + +Examples of incorrect Forms: + +@example +Form => "preserve=junk" +Form => "mode=internal, preserve=timestamps" +@end example + + +@itemize * + +@item +"The interpretation of the @cite{Pattern} parameter, when not the null string, +in the @cite{Start_Search} and @cite{Search} procedures. +See A.16(104) and A.16(112)." +@end itemize + +When the @cite{Pattern} parameter is not the null string, it is interpreted +according to the syntax of regular expressions as defined in the +@cite{GNAT.Regexp} package. + +See @ref{1fd,,GNAT.Regexp (g-regexp.ads)}. + + +@itemize * + +@item +"Implementation-defined convention names. See B.1(11)." +@end itemize + +The following convention names are supported + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Convention Name + +@tab + +Interpretation + +@item + +@emph{Ada} + +@tab + +Ada + +@item + +@emph{Ada_Pass_By_Copy} + +@tab + +Allowed for any types except by-reference types such as limited +records. Compatible with convention Ada, but causes any parameters +with this convention to be passed by copy. + +@item + +@emph{Ada_Pass_By_Reference} + +@tab + +Allowed for any types except by-copy types such as scalars. +Compatible with convention Ada, but causes any parameters +with this convention to be passed by reference. + +@item + +@emph{Assembler} + +@tab + +Assembly language + +@item + +@emph{Asm} + +@tab + +Synonym for Assembler + +@item + +@emph{Assembly} + +@tab + +Synonym for Assembler + +@item + +@emph{C} + +@tab + +C + +@item + +@emph{C_Pass_By_Copy} + +@tab + +Allowed only for record types, like C, but also notes that record +is to be passed by copy rather than reference. + +@item + +@emph{COBOL} + +@tab + +COBOL + +@item + +@emph{C_Plus_Plus (or CPP)} + +@tab + +C++ + +@item + +@emph{Default} + +@tab + +Treated the same as C + +@item + +@emph{External} + +@tab + +Treated the same as C + +@item + +@emph{Fortran} + +@tab + +Fortran + +@item + +@emph{Intrinsic} + +@tab + +For support of pragma @cite{Import} with convention Intrinsic, see +separate section on Intrinsic Subprograms. + +@item + +@emph{Stdcall} + +@tab + +Stdcall (used for Windows implementations only). This convention correspond +to the WINAPI (previously called Pascal convention) C/C++ convention under +Windows. A routine with this convention cleans the stack before +exit. This pragma cannot be applied to a dispatching call. + +@item + +@emph{DLL} + +@tab + +Synonym for Stdcall + +@item + +@emph{Win32} + +@tab + +Synonym for Stdcall + +@item + +@emph{Stubbed} + +@tab + +Stubbed is a special convention used to indicate that the body of the +subprogram will be entirely ignored. Any call to the subprogram +is converted into a raise of the @cite{Program_Error} exception. If a +pragma @cite{Import} specifies convention @cite{stubbed} then no body need +be present at all. This convention is useful during development for the +inclusion of subprograms whose body has not yet been written. +In addition, all otherwise unrecognized convention names are also +treated as being synonymous with convention C. In all implementations +except for VMS, use of such other names results in a warning. In VMS +implementations, these names are accepted silently. + +@end multitable + + + +@itemize * + +@item +"The meaning of link names. See B.1(36)." +@end itemize + +Link names are the actual names used by the linker. + + +@itemize * + +@item +"The manner of choosing link names when neither the link +name nor the address of an imported or exported entity is specified. See +B.1(36)." +@end itemize + +The default linker name is that which would be assigned by the relevant +external language, interpreting the Ada name as being in all lower case +letters. + + +@itemize * + +@item +"The effect of pragma @cite{Linker_Options}. See B.1(37)." +@end itemize + +The string passed to @cite{Linker_Options} is presented uninterpreted as +an argument to the link command, unless it contains ASCII.NUL characters. +NUL characters if they appear act as argument separators, so for example + +@example +pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef"); +@end example + +causes two separate arguments @cite{-labc} and @cite{-ldef} to be passed to the +linker. The order of linker options is preserved for a given unit. The final +list of options passed to the linker is in reverse order of the elaboration +order. For example, linker options for a body always appear before the options +from the corresponding package spec. + + +@itemize * + +@item +"The contents of the visible part of package +@cite{Interfaces} and its language-defined descendants. See B.2(1)." +@end itemize + +See files with prefix @code{i-} in the distributed library. + + +@itemize * + +@item +"Implementation-defined children of package +@cite{Interfaces}. The contents of the visible part of package +@cite{Interfaces}. See B.2(11)." +@end itemize + +See files with prefix @code{i-} in the distributed library. + + +@itemize * + +@item +"The types @cite{Floating}, @cite{Long_Floating}, +@cite{Binary}, @cite{Long_Binary}, @cite{Decimal_ Element}, and +@cite{COBOL_Character}; and the initialization of the variables +@cite{Ada_To_COBOL} and @cite{COBOL_To_Ada}, in +@cite{Interfaces.COBOL}. See B.4(50)." +@end itemize + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +COBOL + +@tab + +Ada + +@item + +@emph{Floating} + +@tab + +Float + +@item + +@emph{Long_Floating} + +@tab + +(Floating) Long_Float + +@item + +@emph{Binary} + +@tab + +Integer + +@item + +@emph{Long_Binary} + +@tab + +Long_Long_Integer + +@item + +@emph{Decimal_Element} + +@tab + +Character + +@item + +@emph{COBOL_Character} + +@tab + +Character + +@end multitable + + +For initialization, see the file @code{i-cobol.ads} in the distributed library. + + +@itemize * + +@item +"Support for access to machine instructions. See C.1(1)." +@end itemize + +See documentation in file @code{s-maccod.ads} in the distributed library. + + +@itemize * + +@item +"Implementation-defined aspects of access to machine +operations. See C.1(9)." +@end itemize + +See documentation in file @code{s-maccod.ads} in the distributed library. + + +@itemize * + +@item +"Implementation-defined aspects of interrupts. See C.3(2)." +@end itemize + +Interrupts are mapped to signals or conditions as appropriate. See +definition of unit +@cite{Ada.Interrupt_Names} in source file @code{a-intnam.ads} for details +on the interrupts supported on a particular target. + + +@itemize * + +@item +"Implementation-defined aspects of pre-elaboration. See +C.4(13)." +@end itemize + +GNAT does not permit a partition to be restarted without reloading, +except under control of the debugger. + + +@itemize * + +@item +"The semantics of pragma @cite{Discard_Names}. See C.5(7)." +@end itemize + +Pragma @cite{Discard_Names} causes names of enumeration literals to +be suppressed. In the presence of this pragma, the Image attribute +provides the image of the Pos of the literal, and Value accepts +Pos values. + + +@itemize * + +@item +"The result of the @cite{Task_Identification.Image} +attribute. See C.7.1(7)." +@end itemize + +The result of this attribute is a string that identifies +the object or component that denotes a given task. If a variable @cite{Var} +has a task type, the image for this task will have the form @cite{Var_`XXXXXXXX`}, +where the suffix +is the hexadecimal representation of the virtual address of the corresponding +task control block. If the variable is an array of tasks, the image of each +task will have the form of an indexed component indicating the position of a +given task in the array, e.g., @cite{Group(5)_`XXXXXXX`}. If the task is a +component of a record, the image of the task will have the form of a selected +component. These rules are fully recursive, so that the image of a task that +is a subcomponent of a composite object corresponds to the expression that +designates this task. + +If a task is created by an allocator, its image depends on the context. If the +allocator is part of an object declaration, the rules described above are used +to construct its image, and this image is not affected by subsequent +assignments. If the allocator appears within an expression, the image +includes only the name of the task type. + +If the configuration pragma Discard_Names is present, or if the restriction +No_Implicit_Heap_Allocation is in effect, the image reduces to +the numeric suffix, that is to say the hexadecimal representation of the +virtual address of the control block of the task. + + +@itemize * + +@item +"The value of @cite{Current_Task} when in a protected entry +or interrupt handler. See C.7.1(17)." +@end itemize + +Protected entries or interrupt handlers can be executed by any +convenient thread, so the value of @cite{Current_Task} is undefined. + + +@itemize * + +@item +"The effect of calling @cite{Current_Task} from an entry +body or interrupt handler. See C.7.1(19)." +@end itemize + +The effect of calling @cite{Current_Task} from an entry body or +interrupt handler is to return the identification of the task currently +executing the code. + + +@itemize * + +@item +"Implementation-defined aspects of +@cite{Task_Attributes}. See C.7.2(19)." +@end itemize + +There are no implementation-defined aspects of @cite{Task_Attributes}. + + +@itemize * + +@item +"Values of all @cite{Metrics}. See D(2)." +@end itemize + +The metrics information for GNAT depends on the performance of the +underlying operating system. The sources of the run-time for tasking +implementation, together with the output from @emph{-gnatG} can be +used to determine the exact sequence of operating systems calls made +to implement various tasking constructs. Together with appropriate +information on the performance of the underlying operating system, +on the exact target in use, this information can be used to determine +the required metrics. + + +@itemize * + +@item +"The declarations of @cite{Any_Priority} and +@cite{Priority}. See D.1(11)." +@end itemize + +See declarations in file @code{system.ads}. + + +@itemize * + +@item +"Implementation-defined execution resources. See D.1(15)." +@end itemize + +There are no implementation-defined execution resources. + + +@itemize * + +@item +"Whether, on a multiprocessor, a task that is waiting for +access to a protected object keeps its processor busy. See D.2.1(3)." +@end itemize + +On a multi-processor, a task that is waiting for access to a protected +object does not keep its processor busy. + + +@itemize * + +@item +"The affect of implementation defined execution resources +on task dispatching. See D.2.1(9)." +@end itemize + +Tasks map to threads in the threads package used by GNAT. Where possible +and appropriate, these threads correspond to native threads of the +underlying operating system. + + +@itemize * + +@item +"Implementation-defined @cite{policy_identifiers} allowed +in a pragma @cite{Task_Dispatching_Policy}. See D.2.2(3)." +@end itemize + +There are no implementation-defined policy-identifiers allowed in this +pragma. + + +@itemize * + +@item +"Implementation-defined aspects of priority inversion. See +D.2.2(16)." +@end itemize + +Execution of a task cannot be preempted by the implementation processing +of delay expirations for lower priority tasks. + + +@itemize * + +@item +"Implementation-defined task dispatching. See D.2.2(18)." +@end itemize + +The policy is the same as that of the underlying threads implementation. + + +@itemize * + +@item +"Implementation-defined @cite{policy_identifiers} allowed +in a pragma @cite{Locking_Policy}. See D.3(4)." +@end itemize + +The two implementation defined policies permitted in GNAT are +@cite{Inheritance_Locking} and @cite{Conccurent_Readers_Locking}. On +targets that support the @cite{Inheritance_Locking} policy, locking is +implemented by inheritance, i.e., the task owning the lock operates +at a priority equal to the highest priority of any task currently +requesting the lock. On targets that support the +@cite{Conccurent_Readers_Locking} policy, locking is implemented with a +read/write lock allowing multiple propected object functions to enter +concurrently. + + +@itemize * + +@item +"Default ceiling priorities. See D.3(10)." +@end itemize + +The ceiling priority of protected objects of the type +@cite{System.Interrupt_Priority'Last} as described in the Ada +Reference Manual D.3(10), + + +@itemize * + +@item +"The ceiling of any protected object used internally by +the implementation. See D.3(16)." +@end itemize + +The ceiling priority of internal protected objects is +@cite{System.Priority'Last}. + + +@itemize * + +@item +"Implementation-defined queuing policies. See D.4(1)." +@end itemize + +There are no implementation-defined queuing policies. + + +@itemize * + +@item +"On a multiprocessor, any conditions that cause the +completion of an aborted construct to be delayed later than what is +specified for a single processor. See D.6(3)." +@end itemize + +The semantics for abort on a multi-processor is the same as on a single +processor, there are no further delays. + + +@itemize * + +@item +"Any operations that implicitly require heap storage +allocation. See D.7(8)." +@end itemize + +The only operation that implicitly requires heap storage allocation is +task creation. + + +@itemize * + +@item +"What happens when a task terminates in the presence of +pragma @cite{No_Task_Termination}. See D.7(15)." +@end itemize + +Execution is erroneous in that case. + + +@itemize * + +@item +"Implementation-defined aspects of pragma +@cite{Restrictions}. See D.7(20)." +@end itemize + +There are no such implementation-defined aspects. + + +@itemize * + +@item +"Implementation-defined aspects of package +@cite{Real_Time}. See D.8(17)." +@end itemize + +There are no implementation defined aspects of package @cite{Real_Time}. + + +@itemize * + +@item +"Implementation-defined aspects of +@cite{delay_statements}. See D.9(8)." +@end itemize + +Any difference greater than one microsecond will cause the task to be +delayed (see D.9(7)). + + +@itemize * + +@item +"The upper bound on the duration of interrupt blocking +caused by the implementation. See D.12(5)." +@end itemize + +The upper bound is determined by the underlying operating system. In +no cases is it more than 10 milliseconds. + + +@itemize * + +@item +"The means for creating and executing distributed +programs. See E(5)." +@end itemize + +The GLADE package provides a utility GNATDIST for creating and executing +distributed programs. See the GLADE reference manual for further details. + + +@itemize * + +@item +"Any events that can result in a partition becoming +inaccessible. See E.1(7)." +@end itemize + +See the GLADE reference manual for full details on such events. + + +@itemize * + +@item +"The scheduling policies, treatment of priorities, and +management of shared resources between partitions in certain cases. See +E.1(11)." +@end itemize + +See the GLADE reference manual for full details on these aspects of +multi-partition execution. + + +@itemize * + +@item +"Events that cause the version of a compilation unit to +change. See E.3(5)." +@end itemize + +Editing the source file of a compilation unit, or the source files of +any units on which it is dependent in a significant way cause the version +to change. No other actions cause the version number to change. All changes +are significant except those which affect only layout, capitalization or +comments. + + +@itemize * + +@item +"Whether the execution of the remote subprogram is +immediately aborted as a result of cancellation. See E.4(13)." +@end itemize + +See the GLADE reference manual for details on the effect of abort in +a distributed application. + + +@itemize * + +@item +"Implementation-defined aspects of the PCS. See E.5(25)." +@end itemize + +See the GLADE reference manual for a full description of all implementation +defined aspects of the PCS. + + +@itemize * + +@item +"Implementation-defined interfaces in the PCS. See +E.5(26)." +@end itemize + +See the GLADE reference manual for a full description of all +implementation defined interfaces. + + +@itemize * + +@item +"The values of named numbers in the package +@cite{Decimal}. See F.2(7)." +@end itemize + + +@multitable {xxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxx} +@headitem + +Named Number + +@tab + +Value + +@item + +@emph{Max_Scale} + +@tab + ++18 + +@item + +@emph{Min_Scale} + +@tab + +-18 + +@item + +@emph{Min_Delta} + +@tab + +1.0E-18 + +@item + +@emph{Max_Delta} + +@tab + +1.0E+18 + +@item + +@emph{Max_Decimal_Digits} + +@tab + +18 + +@end multitable + + + +@itemize * + +@item +"The value of @cite{Max_Picture_Length} in the package +@cite{Text_IO.Editing}. See F.3.3(16)." +@end itemize + +64 + + +@itemize * + +@item +"The value of @cite{Max_Picture_Length} in the package +@cite{Wide_Text_IO.Editing}. See F.3.4(5)." +@end itemize + +64 + + +@itemize * + +@item +"The accuracy actually achieved by the complex elementary +functions and by other complex arithmetic operations. See G.1(1)." +@end itemize + +Standard library functions are used for the complex arithmetic +operations. Only fast math mode is currently supported. + + +@itemize * + +@item +"The sign of a zero result (or a component thereof) from +any operator or function in @cite{Numerics.Generic_Complex_Types}, when +@cite{Real'Signed_Zeros} is True. See G.1.1(53)." +@end itemize + +The signs of zero values are as recommended by the relevant +implementation advice. + + +@itemize * + +@item +"The sign of a zero result (or a component thereof) from +any operator or function in +@cite{Numerics.Generic_Complex_Elementary_Functions}, when +@cite{Real'Signed_Zeros} is @cite{True}. See G.1.2(45)." +@end itemize + +The signs of zero values are as recommended by the relevant +implementation advice. + + +@itemize * + +@item +"Whether the strict mode or the relaxed mode is the +default. See G.2(2)." +@end itemize + +The strict mode is the default. There is no separate relaxed mode. GNAT +provides a highly efficient implementation of strict mode. + + +@itemize * + +@item +"The result interval in certain cases of fixed-to-float +conversion. See G.2.1(10)." +@end itemize + +For cases where the result interval is implementation dependent, the +accuracy is that provided by performing all operations in 64-bit IEEE +floating-point format. + + +@itemize * + +@item +"The result of a floating point arithmetic operation in +overflow situations, when the @cite{Machine_Overflows} attribute of the +result type is @cite{False}. See G.2.1(13)." +@end itemize + +Infinite and NaN values are produced as dictated by the IEEE +floating-point standard. +Note that on machines that are not fully compliant with the IEEE +floating-point standard, such as Alpha, the @emph{-mieee} compiler flag +must be used for achieving IEEE conforming behavior (although at the cost +of a significant performance penalty), so infinite and NaN values are +properly generated. + + +@itemize * + +@item +"The result interval for division (or exponentiation by a +negative exponent), when the floating point hardware implements division +as multiplication by a reciprocal. See G.2.1(16)." +@end itemize + +Not relevant, division is IEEE exact. + + +@itemize * + +@item +"The definition of close result set, which determines the +accuracy of certain fixed point multiplications and divisions. See +G.2.3(5)." +@end itemize + +Operations in the close result set are performed using IEEE long format +floating-point arithmetic. The input operands are converted to +floating-point, the operation is done in floating-point, and the result +is converted to the target type. + + +@itemize * + +@item +"Conditions on a @cite{universal_real} operand of a fixed +point multiplication or division for which the result shall be in the +perfect result set. See G.2.3(22)." +@end itemize + +The result is only defined to be in the perfect result set if the result +can be computed by a single scaling operation involving a scale factor +representable in 64-bits. + + +@itemize * + +@item +"The result of a fixed point arithmetic operation in +overflow situations, when the @cite{Machine_Overflows} attribute of the +result type is @cite{False}. See G.2.3(27)." +@end itemize + +Not relevant, @cite{Machine_Overflows} is @cite{True} for fixed-point +types. + + +@itemize * + +@item +"The result of an elementary function reference in +overflow situations, when the @cite{Machine_Overflows} attribute of the +result type is @cite{False}. See G.2.4(4)." +@end itemize + +IEEE infinite and Nan values are produced as appropriate. + + +@itemize * + +@item +"The value of the angle threshold, within which certain +elementary functions, complex arithmetic operations, and complex +elementary functions yield results conforming to a maximum relative +error bound. See G.2.4(10)." +@end itemize + +Information on this subject is not yet available. + + +@itemize * + +@item +"The accuracy of certain elementary functions for +parameters beyond the angle threshold. See G.2.4(10)." +@end itemize + +Information on this subject is not yet available. + + +@itemize * + +@item +"The result of a complex arithmetic operation or complex +elementary function reference in overflow situations, when the +@cite{Machine_Overflows} attribute of the corresponding real type is +@cite{False}. See G.2.6(5)." +@end itemize + +IEEE infinite and Nan values are produced as appropriate. + + +@itemize * + +@item +"The accuracy of certain complex arithmetic operations and +certain complex elementary functions for parameters (or components +thereof) beyond the angle threshold. See G.2.6(8)." +@end itemize + +Information on those subjects is not yet available. + + +@itemize * + +@item +"Information regarding bounded errors and erroneous +execution. See H.2(1)." +@end itemize + +Information on this subject is not yet available. + + +@itemize * + +@item +"Implementation-defined aspects of pragma +@cite{Inspection_Point}. See H.3.2(8)." +@end itemize + +Pragma @cite{Inspection_Point} ensures that the variable is live and can +be examined by the debugger at the inspection point. + + +@itemize * + +@item +"Implementation-defined aspects of pragma +@cite{Restrictions}. See H.4(25)." +@end itemize + +There are no implementation-defined aspects of pragma @cite{Restrictions}. The +use of pragma @cite{Restrictions [No_Exceptions]} has no effect on the +generated code. Checks must suppressed by use of pragma @cite{Suppress}. + + +@itemize * + +@item +"Any restrictions on pragma @cite{Restrictions}. See +H.4(27)." +@end itemize + +There are no restrictions on pragma @cite{Restrictions}. + +@node Intrinsic Subprograms,Representation Clauses and Pragmas,Implementation Defined Characteristics,Top +@anchor{gnat_rm/intrinsic_subprograms doc}@anchor{1fe}@anchor{gnat_rm/intrinsic_subprograms intrinsic-subprograms}@anchor{c}@anchor{gnat_rm/intrinsic_subprograms id1}@anchor{1ff} +@chapter Intrinsic Subprograms + + +@geindex Intrinsic Subprograms + +GNAT allows a user application program to write the declaration: + +@example +pragma Import (Intrinsic, name); +@end example + +providing that the name corresponds to one of the implemented intrinsic +subprograms in GNAT, and that the parameter profile of the referenced +subprogram meets the requirements. This chapter describes the set of +implemented intrinsic subprograms, and the requirements on parameter profiles. +Note that no body is supplied; as with other uses of pragma Import, the +body is supplied elsewhere (in this case by the compiler itself). Note +that any use of this feature is potentially non-portable, since the +Ada standard does not require Ada compilers to implement this feature. + +@menu +* Intrinsic Operators:: +* Compilation_Date:: +* Compilation_Time:: +* Enclosing_Entity:: +* Exception_Information:: +* Exception_Message:: +* Exception_Name:: +* File:: +* Line:: +* Shifts and Rotates:: +* Source_Location:: + +@end menu + +@node Intrinsic Operators,Compilation_Date,,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms id2}@anchor{200}@anchor{gnat_rm/intrinsic_subprograms intrinsic-operators}@anchor{201} +@section Intrinsic Operators + + +@geindex Intrinsic operator + +All the predefined numeric operators in package Standard +in @cite{pragma Import (Intrinsic@comma{}..)} +declarations. In the binary operator case, the operands must have the same +size. The operand or operands must also be appropriate for +the operator. For example, for addition, the operands must +both be floating-point or both be fixed-point, and the +right operand for @cite{"**"} must have a root type of +@cite{Standard.Integer'Base}. +You can use an intrinsic operator declaration as in the following example: + +@example +type Int1 is new Integer; +type Int2 is new Integer; + +function "+" (X1 : Int1; X2 : Int2) return Int1; +function "+" (X1 : Int1; X2 : Int2) return Int2; +pragma Import (Intrinsic, "+"); +@end example + +This declaration would permit 'mixed mode' arithmetic on items +of the differing types @cite{Int1} and @cite{Int2}. +It is also possible to specify such operators for private types, if the +full views are appropriate arithmetic types. + +@node Compilation_Date,Compilation_Time,Intrinsic Operators,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms compilation-date}@anchor{202}@anchor{gnat_rm/intrinsic_subprograms id3}@anchor{203} +@section Compilation_Date + + +@geindex Compilation_Date + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.Compilation_Date} to obtain the date of +the current compilation (in local time format MMM DD YYYY). + +@node Compilation_Time,Enclosing_Entity,Compilation_Date,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms compilation-time}@anchor{204}@anchor{gnat_rm/intrinsic_subprograms id4}@anchor{205} +@section Compilation_Time + + +@geindex Compilation_Time + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.Compilation_Time} to obtain the time of +the current compilation (in local time format HH:MM:SS). + +@node Enclosing_Entity,Exception_Information,Compilation_Time,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms id5}@anchor{206}@anchor{gnat_rm/intrinsic_subprograms enclosing-entity}@anchor{207} +@section Enclosing_Entity + + +@geindex Enclosing_Entity + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.Enclosing_Entity} to obtain the name of +the current subprogram, package, task, entry, or protected subprogram. + +@node Exception_Information,Exception_Message,Enclosing_Entity,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms id6}@anchor{208}@anchor{gnat_rm/intrinsic_subprograms exception-information}@anchor{209} +@section Exception_Information + + +@geindex Exception_Information' + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Current_Exception}. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +@cite{GNAT.Current_Exception.Exception_Information} to obtain +the exception information associated with the current exception. + +@node Exception_Message,Exception_Name,Exception_Information,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms exception-message}@anchor{20a}@anchor{gnat_rm/intrinsic_subprograms id7}@anchor{20b} +@section Exception_Message + + +@geindex Exception_Message + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Current_Exception}. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +@cite{GNAT.Current_Exception.Exception_Message} to obtain +the message associated with the current exception. + +@node Exception_Name,File,Exception_Message,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms exception-name}@anchor{20c}@anchor{gnat_rm/intrinsic_subprograms id8}@anchor{20d} +@section Exception_Name + + +@geindex Exception_Name + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Current_Exception}. The only useful +use of the intrinsic import in this case is the one in this unit, +so an application program should simply call the function +@cite{GNAT.Current_Exception.Exception_Name} to obtain +the name of the current exception. + +@node File,Line,Exception_Name,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms file}@anchor{20e}@anchor{gnat_rm/intrinsic_subprograms id9}@anchor{20f} +@section File + + +@geindex File + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.File} to obtain the name of the current +file. + +@node Line,Shifts and Rotates,File,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms id10}@anchor{210}@anchor{gnat_rm/intrinsic_subprograms line}@anchor{211} +@section Line + + +@geindex Line + +This intrinsic subprogram is used in the implementation of the +library package @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.Line} to obtain the number of the current +source line. + +@node Shifts and Rotates,Source_Location,Line,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms id11}@anchor{212}@anchor{gnat_rm/intrinsic_subprograms shifts-and-rotates}@anchor{213} +@section Shifts and Rotates + + +@geindex Shift_Left + +@geindex Shift_Right + +@geindex Shift_Right_Arithmetic + +@geindex Rotate_Left + +@geindex Rotate_Right + +In standard Ada, the shift and rotate functions are available only +for the predefined modular types in package @cite{Interfaces}. However, in +GNAT it is possible to define these functions for any integer +type (signed or modular), as in this example: + +@example +function Shift_Left + (Value : T; + Amount : Natural) return T; +@end example + +The function name must be one of +Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or +Rotate_Right. T must be an integer type. T'Size must be +8, 16, 32 or 64 bits; if T is modular, the modulus +must be 2**8, 2**16, 2**32 or 2**64. +The result type must be the same as the type of @cite{Value}. +The shift amount must be Natural. +The formal parameter names can be anything. + +A more convenient way of providing these shift operators is to use +the Provide_Shift_Operators pragma, which provides the function declarations +and corresponding pragma Import's for all five shift functions. + +@node Source_Location,,Shifts and Rotates,Intrinsic Subprograms +@anchor{gnat_rm/intrinsic_subprograms source-location}@anchor{214}@anchor{gnat_rm/intrinsic_subprograms id12}@anchor{215} +@section Source_Location + + +@geindex Source_Location + +This intrinsic subprogram is used in the implementation of the +library routine @cite{GNAT.Source_Info}. The only useful use of the +intrinsic import in this case is the one in this unit, so an +application program should simply call the function +@cite{GNAT.Source_Info.Source_Location} to obtain the current +source file location. + +@node Representation Clauses and Pragmas,Standard Library Routines,Intrinsic Subprograms,Top +@anchor{gnat_rm/representation_clauses_and_pragmas representation-clauses-and-pragmas}@anchor{d}@anchor{gnat_rm/representation_clauses_and_pragmas doc}@anchor{216}@anchor{gnat_rm/representation_clauses_and_pragmas id1}@anchor{217} +@chapter Representation Clauses and Pragmas + + +@geindex Representation Clauses + +@geindex Representation Clause + +@geindex Representation Pragma + +@geindex Pragma +@geindex representation + +This section describes the representation clauses accepted by GNAT, and +their effect on the representation of corresponding data objects. + +GNAT fully implements Annex C (Systems Programming). This means that all +the implementation advice sections in chapter 13 are fully implemented. +However, these sections only require a minimal level of support for +representation clauses. GNAT provides much more extensive capabilities, +and this section describes the additional capabilities provided. + +@menu +* Alignment Clauses:: +* Size Clauses:: +* Storage_Size Clauses:: +* Size of Variant Record Objects:: +* Biased Representation:: +* Value_Size and Object_Size Clauses:: +* Component_Size Clauses:: +* Bit_Order Clauses:: +* Effect of Bit_Order on Byte Ordering:: +* Pragma Pack for Arrays:: +* Pragma Pack for Records:: +* Record Representation Clauses:: +* Handling of Records with Holes:: +* Enumeration Clauses:: +* Address Clauses:: +* Use of Address Clauses for Memory-Mapped I/O:: +* Effect of Convention on Representation:: +* Conventions and Anonymous Access Types:: +* Determining the Representations chosen by GNAT:: + +@end menu + +@node Alignment Clauses,Size Clauses,,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id2}@anchor{218}@anchor{gnat_rm/representation_clauses_and_pragmas alignment-clauses}@anchor{219} +@section Alignment Clauses + + +@geindex Alignment Clause + +GNAT requires that all alignment clauses specify a power of 2, and all +default alignments are always a power of 2. The default alignment +values are as follows: + + +@itemize * + +@item +@emph{Primitive Types}. + +For primitive types, the alignment is the minimum of the actual size of +objects of the type divided by @cite{Storage_Unit}, +and the maximum alignment supported by the target. +(This maximum alignment is given by the GNAT-specific attribute +@cite{Standard'Maximum_Alignment}; see @ref{13c,,Attribute Maximum_Alignment}.) + +@geindex Maximum_Alignment attribute + +For example, for type @cite{Long_Float}, the object size is 8 bytes, and the +default alignment will be 8 on any target that supports alignments +this large, but on some targets, the maximum alignment may be smaller +than 8, in which case objects of type @cite{Long_Float} will be maximally +aligned. + +@item +@emph{Arrays}. + +For arrays, the alignment is equal to the alignment of the component type +for the normal case where no packing or component size is given. If the +array is packed, and the packing is effective (see separate section on +packed arrays), then the alignment will be one for long packed arrays, +or arrays whose length is not known at compile time. For short packed +arrays, which are handled internally as modular types, the alignment +will be as described for primitive types, e.g., a packed array of length +31 bits will have an object size of four bytes, and an alignment of 4. + +@item +@emph{Records}. + +For the normal non-packed case, the alignment of a record is equal to +the maximum alignment of any of its components. For tagged records, this +includes the implicit access type used for the tag. If a pragma @cite{Pack} +is used and all components are packable (see separate section on pragma +@cite{Pack}), then the resulting alignment is 1, unless the layout of the +record makes it profitable to increase it. + +A special case is when: + + +@itemize * + +@item +the size of the record is given explicitly, or a +full record representation clause is given, and + +@item +the size of the record is 2, 4, or 8 bytes. +@end itemize + +In this case, an alignment is chosen to match the +size of the record. For example, if we have: + +@example +type Small is record + A, B : Character; +end record; +for Small'Size use 16; +@end example + +then the default alignment of the record type @cite{Small} is 2, not 1. This +leads to more efficient code when the record is treated as a unit, and also +allows the type to specified as @cite{Atomic} on architectures requiring +strict alignment. +@end itemize + +An alignment clause may specify a larger alignment than the default value +up to some maximum value dependent on the target (obtainable by using the +attribute reference @cite{Standard'Maximum_Alignment}). It may also specify +a smaller alignment than the default value for enumeration, integer and +fixed point types, as well as for record types, for example + +@example +type V is record + A : Integer; +end record; + +for V'alignment use 1; +@end example + +@geindex Alignment +@geindex default + +The default alignment for the type @cite{V} is 4, as a result of the +Integer field in the record, but it is permissible, as shown, to +override the default alignment of the record with a smaller value. + +@geindex Alignment +@geindex subtypes + +Note that according to the Ada standard, an alignment clause applies only +to the first named subtype. If additional subtypes are declared, then the +compiler is allowed to choose any alignment it likes, and there is no way +to control this choice. Consider: + +@example +type R is range 1 .. 10_000; +for R'Alignment use 1; +subtype RS is R range 1 .. 1000; +@end example + +The alignment clause specifies an alignment of 1 for the first named subtype +@cite{R} but this does not necessarily apply to @cite{RS}. When writing +portable Ada code, you should avoid writing code that explicitly or +implicitly relies on the alignment of such subtypes. + +For the GNAT compiler, if an explicit alignment clause is given, this +value is also used for any subsequent subtypes. So for GNAT, in the +above example, you can count on the alignment of @cite{RS} being 1. But this +assumption is non-portable, and other compilers may choose different +alignments for the subtype @cite{RS}. + +@node Size Clauses,Storage_Size Clauses,Alignment Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id3}@anchor{21a}@anchor{gnat_rm/representation_clauses_and_pragmas size-clauses}@anchor{21b} +@section Size Clauses + + +@geindex Size Clause + +The default size for a type @cite{T} is obtainable through the +language-defined attribute @cite{T'Size} and also through the +equivalent GNAT-defined attribute @cite{T'Value_Size}. +For objects of type @cite{T}, GNAT will generally increase the type size +so that the object size (obtainable through the GNAT-defined attribute +@cite{T'Object_Size}) +is a multiple of @cite{T'Alignment * Storage_Unit}. + +For example: + +@example +type Smallint is range 1 .. 6; + +type Rec is record + Y1 : integer; + Y2 : boolean; +end record; +@end example + +In this example, @cite{Smallint'Size} = @cite{Smallint'Value_Size} = 3, +as specified by the RM rules, +but objects of this type will have a size of 8 +(@cite{Smallint'Object_Size} = 8), +since objects by default occupy an integral number +of storage units. On some targets, notably older +versions of the Digital Alpha, the size of stand +alone objects of this type may be 32, reflecting +the inability of the hardware to do byte load/stores. + +Similarly, the size of type @cite{Rec} is 40 bits +(@cite{Rec'Size} = @cite{Rec'Value_Size} = 40), but +the alignment is 4, so objects of this type will have +their size increased to 64 bits so that it is a multiple +of the alignment (in bits). This decision is +in accordance with the specific Implementation Advice in RM 13.3(43): + +@quotation + +"A @cite{Size} clause should be supported for an object if the specified +@cite{Size} is at least as large as its subtype's @cite{Size}, and corresponds +to a size in storage elements that is a multiple of the object's +@cite{Alignment} (if the @cite{Alignment} is nonzero)." +@end quotation + +An explicit size clause may be used to override the default size by +increasing it. For example, if we have: + +@example +type My_Boolean is new Boolean; +for My_Boolean'Size use 32; +@end example + +then values of this type will always be 32 bits long. In the case of +discrete types, the size can be increased up to 64 bits, with the effect +that the entire specified field is used to hold the value, sign- or +zero-extended as appropriate. If more than 64 bits is specified, then +padding space is allocated after the value, and a warning is issued that +there are unused bits. + +Similarly the size of records and arrays may be increased, and the effect +is to add padding bits after the value. This also causes a warning message +to be generated. + +The largest Size value permitted in GNAT is 2**31-1. Since this is a +Size in bits, this corresponds to an object of size 256 megabytes (minus +one). This limitation is true on all targets. The reason for this +limitation is that it improves the quality of the code in many cases +if it is known that a Size value can be accommodated in an object of +type Integer. + +@node Storage_Size Clauses,Size of Variant Record Objects,Size Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas storage-size-clauses}@anchor{21c}@anchor{gnat_rm/representation_clauses_and_pragmas id4}@anchor{21d} +@section Storage_Size Clauses + + +@geindex Storage_Size Clause + +For tasks, the @cite{Storage_Size} clause specifies the amount of space +to be allocated for the task stack. This cannot be extended, and if the +stack is exhausted, then @cite{Storage_Error} will be raised (if stack +checking is enabled). Use a @cite{Storage_Size} attribute definition clause, +or a @cite{Storage_Size} pragma in the task definition to set the +appropriate required size. A useful technique is to include in every +task definition a pragma of the form: + +@example +pragma Storage_Size (Default_Stack_Size); +@end example + +Then @cite{Default_Stack_Size} can be defined in a global package, and +modified as required. Any tasks requiring stack sizes different from the +default can have an appropriate alternative reference in the pragma. + +You can also use the @emph{-d} binder switch to modify the default stack +size. + +For access types, the @cite{Storage_Size} clause specifies the maximum +space available for allocation of objects of the type. If this space is +exceeded then @cite{Storage_Error} will be raised by an allocation attempt. +In the case where the access type is declared local to a subprogram, the +use of a @cite{Storage_Size} clause triggers automatic use of a special +predefined storage pool (@cite{System.Pool_Size}) that ensures that all +space for the pool is automatically reclaimed on exit from the scope in +which the type is declared. + +A special case recognized by the compiler is the specification of a +@cite{Storage_Size} of zero for an access type. This means that no +items can be allocated from the pool, and this is recognized at compile +time, and all the overhead normally associated with maintaining a fixed +size storage pool is eliminated. Consider the following example: + +@example +procedure p is + type R is array (Natural) of Character; + type P is access all R; + for P'Storage_Size use 0; + -- Above access type intended only for interfacing purposes + + y : P; + + procedure g (m : P); + pragma Import (C, g); + + -- ... + +begin + -- ... + y := new R; +end; +@end example + +As indicated in this example, these dummy storage pools are often useful in +connection with interfacing where no object will ever be allocated. If you +compile the above example, you get the warning: + +@example +p.adb:16:09: warning: allocation from empty storage pool +p.adb:16:09: warning: Storage_Error will be raised at run time +@end example + +Of course in practice, there will not be any explicit allocators in the +case of such an access declaration. + +@node Size of Variant Record Objects,Biased Representation,Storage_Size Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id5}@anchor{21e}@anchor{gnat_rm/representation_clauses_and_pragmas size-of-variant-record-objects}@anchor{21f} +@section Size of Variant Record Objects + + +@geindex Size +@geindex variant record objects + +@geindex Variant record objects +@geindex size + +In the case of variant record objects, there is a question whether Size gives +information about a particular variant, or the maximum size required +for any variant. Consider the following program + +@example +with Text_IO; use Text_IO; +procedure q is + type R1 (A : Boolean := False) is record + case A is + when True => X : Character; + when False => null; + end case; + end record; + + V1 : R1 (False); + V2 : R1; + +begin + Put_Line (Integer'Image (V1'Size)); + Put_Line (Integer'Image (V2'Size)); +end q; +@end example + +Here we are dealing with a variant record, where the True variant +requires 16 bits, and the False variant requires 8 bits. +In the above example, both V1 and V2 contain the False variant, +which is only 8 bits long. However, the result of running the +program is: + +@example +8 +16 +@end example + +The reason for the difference here is that the discriminant value of +V1 is fixed, and will always be False. It is not possible to assign +a True variant value to V1, therefore 8 bits is sufficient. On the +other hand, in the case of V2, the initial discriminant value is +False (from the default), but it is possible to assign a True +variant value to V2, therefore 16 bits must be allocated for V2 +in the general case, even fewer bits may be needed at any particular +point during the program execution. + +As can be seen from the output of this program, the @cite{'Size} +attribute applied to such an object in GNAT gives the actual allocated +size of the variable, which is the largest size of any of the variants. +The Ada Reference Manual is not completely clear on what choice should +be made here, but the GNAT behavior seems most consistent with the +language in the RM. + +In some cases, it may be desirable to obtain the size of the current +variant, rather than the size of the largest variant. This can be +achieved in GNAT by making use of the fact that in the case of a +subprogram parameter, GNAT does indeed return the size of the current +variant (because a subprogram has no way of knowing how much space +is actually allocated for the actual). + +Consider the following modified version of the above program: + +@example +with Text_IO; use Text_IO; +procedure q is + type R1 (A : Boolean := False) is record + case A is + when True => X : Character; + when False => null; + end case; + end record; + + V2 : R1; + + function Size (V : R1) return Integer is + begin + return V'Size; + end Size; + +begin + Put_Line (Integer'Image (V2'Size)); + Put_Line (Integer'IMage (Size (V2))); + V2 := (True, 'x'); + Put_Line (Integer'Image (V2'Size)); + Put_Line (Integer'IMage (Size (V2))); +end q; +@end example + +The output from this program is + +@example +16 +8 +16 +16 +@end example + +Here we see that while the @cite{'Size} attribute always returns +the maximum size, regardless of the current variant value, the +@cite{Size} function does indeed return the size of the current +variant value. + +@node Biased Representation,Value_Size and Object_Size Clauses,Size of Variant Record Objects,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id6}@anchor{220}@anchor{gnat_rm/representation_clauses_and_pragmas biased-representation}@anchor{221} +@section Biased Representation + + +@geindex Size for biased representation + +@geindex Biased representation + +In the case of scalars with a range starting at other than zero, it is +possible in some cases to specify a size smaller than the default minimum +value, and in such cases, GNAT uses an unsigned biased representation, +in which zero is used to represent the lower bound, and successive values +represent successive values of the type. + +For example, suppose we have the declaration: + +@example +type Small is range -7 .. -4; +for Small'Size use 2; +@end example + +Although the default size of type @cite{Small} is 4, the @cite{Size} +clause is accepted by GNAT and results in the following representation +scheme: + +@example +-7 is represented as 2#00# +-6 is represented as 2#01# +-5 is represented as 2#10# +-4 is represented as 2#11# +@end example + +Biased representation is only used if the specified @cite{Size} clause +cannot be accepted in any other manner. These reduced sizes that force +biased representation can be used for all discrete types except for +enumeration types for which a representation clause is given. + +@node Value_Size and Object_Size Clauses,Component_Size Clauses,Biased Representation,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id7}@anchor{222}@anchor{gnat_rm/representation_clauses_and_pragmas value-size-and-object-size-clauses}@anchor{223} +@section Value_Size and Object_Size Clauses + + +@geindex Value_Size + +@geindex Object_Size + +@geindex Size +@geindex of objects + +In Ada 95 and Ada 2005, @cite{T'Size} for a type @cite{T} is the minimum +number of bits required to hold values of type @cite{T}. +Although this interpretation was allowed in Ada 83, it was not required, +and this requirement in practice can cause some significant difficulties. +For example, in most Ada 83 compilers, @cite{Natural'Size} was 32. +However, in Ada 95 and Ada 2005, +@cite{Natural'Size} is +typically 31. This means that code may change in behavior when moving +from Ada 83 to Ada 95 or Ada 2005. For example, consider: + +@example +type Rec is record; + A : Natural; + B : Natural; +end record; + +for Rec use record + at 0 range 0 .. Natural'Size - 1; + at 0 range Natural'Size .. 2 * Natural'Size - 1; +end record; +@end example + +In the above code, since the typical size of @cite{Natural} objects +is 32 bits and @cite{Natural'Size} is 31, the above code can cause +unexpected inefficient packing in Ada 95 and Ada 2005, and in general +there are cases where the fact that the object size can exceed the +size of the type causes surprises. + +To help get around this problem GNAT provides two implementation +defined attributes, @cite{Value_Size} and @cite{Object_Size}. When +applied to a type, these attributes yield the size of the type +(corresponding to the RM defined size attribute), and the size of +objects of the type respectively. + +The @cite{Object_Size} is used for determining the default size of +objects and components. This size value can be referred to using the +@cite{Object_Size} attribute. The phrase 'is used' here means that it is +the basis of the determination of the size. The backend is free to +pad this up if necessary for efficiency, e.g., an 8-bit stand-alone +character might be stored in 32 bits on a machine with no efficient +byte access instructions such as the Alpha. + +The default rules for the value of @cite{Object_Size} for +discrete types are as follows: + + +@itemize * + +@item +The @cite{Object_Size} for base subtypes reflect the natural hardware +size in bits (run the compiler with @emph{-gnatS} to find those values +for numeric types). Enumeration types and fixed-point base subtypes have +8, 16, 32 or 64 bits for this size, depending on the range of values +to be stored. + +@item +The @cite{Object_Size} of a subtype is the same as the +@cite{Object_Size} of +the type from which it is obtained. + +@item +The @cite{Object_Size} of a derived base type is copied from the parent +base type, and the @cite{Object_Size} of a derived first subtype is copied +from the parent first subtype. +@end itemize + +The @cite{Value_Size} attribute +is the (minimum) number of bits required to store a value +of the type. +This value is used to determine how tightly to pack +records or arrays with components of this type, and also affects +the semantics of unchecked conversion (unchecked conversions where +the @cite{Value_Size} values differ generate a warning, and are potentially +target dependent). + +The default rules for the value of @cite{Value_Size} are as follows: + + +@itemize * + +@item +The @cite{Value_Size} for a base subtype is the minimum number of bits +required to store all values of the type (including the sign bit +only if negative values are possible). + +@item +If a subtype statically matches the first subtype of a given type, then it has +by default the same @cite{Value_Size} as the first subtype. This is a +consequence of RM 13.1(14): "if two subtypes statically match, +then their subtype-specific aspects are the same".) + +@item +All other subtypes have a @cite{Value_Size} corresponding to the minimum +number of bits required to store all values of the subtype. For +dynamic bounds, it is assumed that the value can range down or up +to the corresponding bound of the ancestor +@end itemize + +The RM defined attribute @cite{Size} corresponds to the +@cite{Value_Size} attribute. + +The @cite{Size} attribute may be defined for a first-named subtype. This sets +the @cite{Value_Size} of +the first-named subtype to the given value, and the +@cite{Object_Size} of this first-named subtype to the given value padded up +to an appropriate boundary. It is a consequence of the default rules +above that this @cite{Object_Size} will apply to all further subtypes. On the +other hand, @cite{Value_Size} is affected only for the first subtype, any +dynamic subtypes obtained from it directly, and any statically matching +subtypes. The @cite{Value_Size} of any other static subtypes is not affected. + +@cite{Value_Size} and +@cite{Object_Size} may be explicitly set for any subtype using +an attribute definition clause. Note that the use of these attributes +can cause the RM 13.1(14) rule to be violated. If two access types +reference aliased objects whose subtypes have differing @cite{Object_Size} +values as a result of explicit attribute definition clauses, then it +is illegal to convert from one access subtype to the other. For a more +complete description of this additional legality rule, see the +description of the @cite{Object_Size} attribute. + +At the implementation level, Esize stores the Object_Size and the +RM_Size field stores the @cite{Value_Size} (and hence the value of the +@cite{Size} attribute, +which, as noted above, is equivalent to @cite{Value_Size}). + +To get a feel for the difference, consider the following examples (note +that in each case the base is @cite{Short_Short_Integer} with a size of 8): + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxx} +@headitem + +Type or subtype declaration + +@tab + +Object_Size + +@tab + +Value_Size + +@item + +@code{type x1 is range 0 .. 5;} + +@tab + +8 + +@tab + +3 + +@item + +@code{type x2 is range 0 .. 5;} +@code{for x2'size use 12;} + +@tab + +16 + +@tab + +12 + +@item + +@code{subtype x3 is x2 range 0 .. 3;} + +@tab + +16 + +@tab + +2 + +@item + +@code{subtype x4 is x2'base range 0 .. 10;} + +@tab + +8 + +@tab + +4 + +@item + +@code{subtype x5 is x2 range 0 .. dynamic;} + +@tab + +16 + +@tab + +3* + +@item + +@code{subtype x6 is x2'base range 0 .. dynamic;} + +@tab + +8 + +@tab + +3* + +@end multitable + + +Note: the entries marked '3*' are not actually specified by the Ada +Reference Manual, but it seems in the spirit of the RM rules to allocate +the minimum number of bits (here 3, given the range for @cite{x2}) +known to be large enough to hold the given range of values. + +So far, so good, but GNAT has to obey the RM rules, so the question is +under what conditions must the RM @cite{Size} be used. +The following is a list +of the occasions on which the RM @cite{Size} must be used: + + +@itemize * + +@item +Component size for packed arrays or records + +@item +Value of the attribute @cite{Size} for a type + +@item +Warning about sizes not matching for unchecked conversion +@end itemize + +For record types, the @cite{Object_Size} is always a multiple of the +alignment of the type (this is true for all types). In some cases the +@cite{Value_Size} can be smaller. Consider: + +@example +type R is record + X : Integer; + Y : Character; +end record; +@end example + +On a typical 32-bit architecture, the X component will be four bytes, and +require four-byte alignment, and the Y component will be one byte. In this +case @cite{R'Value_Size} will be 40 (bits) since this is the minimum size +required to store a value of this type, and for example, it is permissible +to have a component of type R in an outer array whose component size is +specified to be 48 bits. However, @cite{R'Object_Size} will be 64 (bits), +since it must be rounded up so that this value is a multiple of the +alignment (4 bytes = 32 bits). + +For all other types, the @cite{Object_Size} +and Value_Size are the same (and equivalent to the RM attribute @cite{Size}). +Only @cite{Size} may be specified for such types. + +Note that @cite{Value_Size} can be used to force biased representation +for a particular subtype. Consider this example: + +@example +type R is (A, B, C, D, E, F); +subtype RAB is R range A .. B; +subtype REF is R range E .. F; +@end example + +By default, @cite{RAB} +has a size of 1 (sufficient to accommodate the representation +of @cite{A} and @cite{B}, 0 and 1), and @cite{REF} +has a size of 3 (sufficient to accommodate the representation +of @cite{E} and @cite{F}, 4 and 5). But if we add the +following @cite{Value_Size} attribute definition clause: + +@example +for REF'Value_Size use 1; +@end example + +then biased representation is forced for @cite{REF}, +and 0 will represent @cite{E} and 1 will represent @cite{F}. +A warning is issued when a @cite{Value_Size} attribute +definition clause forces biased representation. This +warning can be turned off using @cite{-gnatw.B}. + +@node Component_Size Clauses,Bit_Order Clauses,Value_Size and Object_Size Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id8}@anchor{224}@anchor{gnat_rm/representation_clauses_and_pragmas component-size-clauses}@anchor{225} +@section Component_Size Clauses + + +@geindex Component_Size Clause + +Normally, the value specified in a component size clause must be consistent +with the subtype of the array component with regard to size and alignment. +In other words, the value specified must be at least equal to the size +of this subtype, and must be a multiple of the alignment value. + +In addition, component size clauses are allowed which cause the array +to be packed, by specifying a smaller value. A first case is for +component size values in the range 1 through 63. The value specified +must not be smaller than the Size of the subtype. GNAT will accurately +honor all packing requests in this range. For example, if we have: + +@example +type r is array (1 .. 8) of Natural; +for r'Component_Size use 31; +@end example + +then the resulting array has a length of 31 bytes (248 bits = 8 * 31). +Of course access to the components of such an array is considerably +less efficient than if the natural component size of 32 is used. +A second case is when the subtype of the component is a record type +padded because of its default alignment. For example, if we have: + +@example +type r is record + i : Integer; + j : Integer; + b : Boolean; +end record; + +type a is array (1 .. 8) of r; +for a'Component_Size use 72; +@end example + +then the resulting array has a length of 72 bytes, instead of 96 bytes +if the alignment of the record (4) was obeyed. + +Note that there is no point in giving both a component size clause +and a pragma Pack for the same array type. if such duplicate +clauses are given, the pragma Pack will be ignored. + +@node Bit_Order Clauses,Effect of Bit_Order on Byte Ordering,Component_Size Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas bit-order-clauses}@anchor{226}@anchor{gnat_rm/representation_clauses_and_pragmas id9}@anchor{227} +@section Bit_Order Clauses + + +@geindex Bit_Order Clause + +@geindex bit ordering + +@geindex ordering +@geindex of bits + +For record subtypes, GNAT permits the specification of the @cite{Bit_Order} +attribute. The specification may either correspond to the default bit +order for the target, in which case the specification has no effect and +places no additional restrictions, or it may be for the non-standard +setting (that is the opposite of the default). + +In the case where the non-standard value is specified, the effect is +to renumber bits within each byte, but the ordering of bytes is not +affected. There are certain +restrictions placed on component clauses as follows: + + +@itemize * + +@item +Components fitting within a single storage unit. + +These are unrestricted, and the effect is merely to renumber bits. For +example if we are on a little-endian machine with @cite{Low_Order_First} +being the default, then the following two declarations have exactly +the same effect: + +@example +type R1 is record + A : Boolean; + B : Integer range 1 .. 120; +end record; + +for R1 use record + A at 0 range 0 .. 0; + B at 0 range 1 .. 7; +end record; + +type R2 is record + A : Boolean; + B : Integer range 1 .. 120; +end record; + +for R2'Bit_Order use High_Order_First; + +for R2 use record + A at 0 range 7 .. 7; + B at 0 range 0 .. 6; +end record; +@end example + +The useful application here is to write the second declaration with the +@cite{Bit_Order} attribute definition clause, and know that it will be treated +the same, regardless of whether the target is little-endian or big-endian. + +@item +Components occupying an integral number of bytes. + +These are components that exactly fit in two or more bytes. Such component +declarations are allowed, but have no effect, since it is important to realize +that the @cite{Bit_Order} specification does not affect the ordering of bytes. +In particular, the following attempt at getting an endian-independent integer +does not work: + +@example +type R2 is record + A : Integer; +end record; + +for R2'Bit_Order use High_Order_First; + +for R2 use record + A at 0 range 0 .. 31; +end record; +@end example + +This declaration will result in a little-endian integer on a +little-endian machine, and a big-endian integer on a big-endian machine. +If byte flipping is required for interoperability between big- and +little-endian machines, this must be explicitly programmed. This capability +is not provided by @cite{Bit_Order}. + +@item +Components that are positioned across byte boundaries + +but do not occupy an integral number of bytes. Given that bytes are not +reordered, such fields would occupy a non-contiguous sequence of bits +in memory, requiring non-trivial code to reassemble. They are for this +reason not permitted, and any component clause specifying such a layout +will be flagged as illegal by GNAT. +@end itemize + +Since the misconception that Bit_Order automatically deals with all +endian-related incompatibilities is a common one, the specification of +a component field that is an integral number of bytes will always +generate a warning. This warning may be suppressed using @cite{pragma Warnings (Off)} +if desired. The following section contains additional +details regarding the issue of byte ordering. + +@node Effect of Bit_Order on Byte Ordering,Pragma Pack for Arrays,Bit_Order Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id10}@anchor{228}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-bit-order-on-byte-ordering}@anchor{229} +@section Effect of Bit_Order on Byte Ordering + + +@geindex byte ordering + +@geindex ordering +@geindex of bytes + +In this section we will review the effect of the @cite{Bit_Order} attribute +definition clause on byte ordering. Briefly, it has no effect at all, but +a detailed example will be helpful. Before giving this +example, let us review the precise +definition of the effect of defining @cite{Bit_Order}. The effect of a +non-standard bit order is described in section 15.5.3 of the Ada +Reference Manual: + +@quotation + +"2 A bit ordering is a method of interpreting the meaning of +the storage place attributes." +@end quotation + +To understand the precise definition of storage place attributes in +this context, we visit section 13.5.1 of the manual: + +@quotation + +"13 A record_representation_clause (without the mod_clause) +specifies the layout. The storage place attributes (see 13.5.2) +are taken from the values of the position, first_bit, and last_bit +expressions after normalizing those values so that first_bit is +less than Storage_Unit." +@end quotation + +The critical point here is that storage places are taken from +the values after normalization, not before. So the @cite{Bit_Order} +interpretation applies to normalized values. The interpretation +is described in the later part of the 15.5.3 paragraph: + +@quotation + +"2 A bit ordering is a method of interpreting the meaning of +the storage place attributes. High_Order_First (known in the +vernacular as 'big endian') means that the first bit of a +storage element (bit 0) is the most significant bit (interpreting +the sequence of bits that represent a component as an unsigned +integer value). Low_Order_First (known in the vernacular as +'little endian') means the opposite: the first bit is the +least significant." +@end quotation + +Note that the numbering is with respect to the bits of a storage +unit. In other words, the specification affects only the numbering +of bits within a single storage unit. + +We can make the effect clearer by giving an example. + +Suppose that we have an external device which presents two bytes, the first +byte presented, which is the first (low addressed byte) of the two byte +record is called Master, and the second byte is called Slave. + +The left most (most significant bit is called Control for each byte, and +the remaining 7 bits are called V1, V2, ... V7, where V7 is the rightmost +(least significant) bit. + +On a big-endian machine, we can write the following representation clause + +@example +type Data is record + Master_Control : Bit; + Master_V1 : Bit; + Master_V2 : Bit; + Master_V3 : Bit; + Master_V4 : Bit; + Master_V5 : Bit; + Master_V6 : Bit; + Master_V7 : Bit; + Slave_Control : Bit; + Slave_V1 : Bit; + Slave_V2 : Bit; + Slave_V3 : Bit; + Slave_V4 : Bit; + Slave_V5 : Bit; + Slave_V6 : Bit; + Slave_V7 : Bit; +end record; + +for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 1 range 0 .. 0; + Slave_V1 at 1 range 1 .. 1; + Slave_V2 at 1 range 2 .. 2; + Slave_V3 at 1 range 3 .. 3; + Slave_V4 at 1 range 4 .. 4; + Slave_V5 at 1 range 5 .. 5; + Slave_V6 at 1 range 6 .. 6; + Slave_V7 at 1 range 7 .. 7; +end record; +@end example + +Now if we move this to a little endian machine, then the bit ordering within +the byte is backwards, so we have to rewrite the record rep clause as: + +@example +for Data use record + Master_Control at 0 range 7 .. 7; + Master_V1 at 0 range 6 .. 6; + Master_V2 at 0 range 5 .. 5; + Master_V3 at 0 range 4 .. 4; + Master_V4 at 0 range 3 .. 3; + Master_V5 at 0 range 2 .. 2; + Master_V6 at 0 range 1 .. 1; + Master_V7 at 0 range 0 .. 0; + Slave_Control at 1 range 7 .. 7; + Slave_V1 at 1 range 6 .. 6; + Slave_V2 at 1 range 5 .. 5; + Slave_V3 at 1 range 4 .. 4; + Slave_V4 at 1 range 3 .. 3; + Slave_V5 at 1 range 2 .. 2; + Slave_V6 at 1 range 1 .. 1; + Slave_V7 at 1 range 0 .. 0; +end record; +@end example + +It is a nuisance to have to rewrite the clause, especially if +the code has to be maintained on both machines. However, +this is a case that we can handle with the +@cite{Bit_Order} attribute if it is implemented. +Note that the implementation is not required on byte addressed +machines, but it is indeed implemented in GNAT. +This means that we can simply use the +first record clause, together with the declaration + +@example +for Data'Bit_Order use High_Order_First; +@end example + +and the effect is what is desired, namely the layout is exactly the same, +independent of whether the code is compiled on a big-endian or little-endian +machine. + +The important point to understand is that byte ordering is not affected. +A @cite{Bit_Order} attribute definition never affects which byte a field +ends up in, only where it ends up in that byte. +To make this clear, let us rewrite the record rep clause of the previous +example as: + +@example +for Data'Bit_Order use High_Order_First; +for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 0 range 8 .. 8; + Slave_V1 at 0 range 9 .. 9; + Slave_V2 at 0 range 10 .. 10; + Slave_V3 at 0 range 11 .. 11; + Slave_V4 at 0 range 12 .. 12; + Slave_V5 at 0 range 13 .. 13; + Slave_V6 at 0 range 14 .. 14; + Slave_V7 at 0 range 15 .. 15; +end record; +@end example + +This is exactly equivalent to saying (a repeat of the first example): + +@example +for Data'Bit_Order use High_Order_First; +for Data use record + Master_Control at 0 range 0 .. 0; + Master_V1 at 0 range 1 .. 1; + Master_V2 at 0 range 2 .. 2; + Master_V3 at 0 range 3 .. 3; + Master_V4 at 0 range 4 .. 4; + Master_V5 at 0 range 5 .. 5; + Master_V6 at 0 range 6 .. 6; + Master_V7 at 0 range 7 .. 7; + Slave_Control at 1 range 0 .. 0; + Slave_V1 at 1 range 1 .. 1; + Slave_V2 at 1 range 2 .. 2; + Slave_V3 at 1 range 3 .. 3; + Slave_V4 at 1 range 4 .. 4; + Slave_V5 at 1 range 5 .. 5; + Slave_V6 at 1 range 6 .. 6; + Slave_V7 at 1 range 7 .. 7; +end record; +@end example + +Why are they equivalent? Well take a specific field, the @cite{Slave_V2} +field. The storage place attributes are obtained by normalizing the +values given so that the @cite{First_Bit} value is less than 8. After +normalizing the values (0,10,10) we get (1,2,2) which is exactly what +we specified in the other case. + +Now one might expect that the @cite{Bit_Order} attribute might affect +bit numbering within the entire record component (two bytes in this +case, thus affecting which byte fields end up in), but that is not +the way this feature is defined, it only affects numbering of bits, +not which byte they end up in. + +Consequently it never makes sense to specify a starting bit number +greater than 7 (for a byte addressable field) if an attribute +definition for @cite{Bit_Order} has been given, and indeed it +may be actively confusing to specify such a value, so the compiler +generates a warning for such usage. + +If you do need to control byte ordering then appropriate conditional +values must be used. If in our example, the slave byte came first on +some machines we might write: + +@example +Master_Byte_First constant Boolean := ...; + +Master_Byte : constant Natural := + 1 - Boolean'Pos (Master_Byte_First); +Slave_Byte : constant Natural := + Boolean'Pos (Master_Byte_First); + +for Data'Bit_Order use High_Order_First; +for Data use record + Master_Control at Master_Byte range 0 .. 0; + Master_V1 at Master_Byte range 1 .. 1; + Master_V2 at Master_Byte range 2 .. 2; + Master_V3 at Master_Byte range 3 .. 3; + Master_V4 at Master_Byte range 4 .. 4; + Master_V5 at Master_Byte range 5 .. 5; + Master_V6 at Master_Byte range 6 .. 6; + Master_V7 at Master_Byte range 7 .. 7; + Slave_Control at Slave_Byte range 0 .. 0; + Slave_V1 at Slave_Byte range 1 .. 1; + Slave_V2 at Slave_Byte range 2 .. 2; + Slave_V3 at Slave_Byte range 3 .. 3; + Slave_V4 at Slave_Byte range 4 .. 4; + Slave_V5 at Slave_Byte range 5 .. 5; + Slave_V6 at Slave_Byte range 6 .. 6; + Slave_V7 at Slave_Byte range 7 .. 7; +end record; +@end example + +Now to switch between machines, all that is necessary is +to set the boolean constant @cite{Master_Byte_First} in +an appropriate manner. + +@node Pragma Pack for Arrays,Pragma Pack for Records,Effect of Bit_Order on Byte Ordering,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-arrays}@anchor{22a}@anchor{gnat_rm/representation_clauses_and_pragmas id11}@anchor{22b} +@section Pragma Pack for Arrays + + +@geindex Pragma Pack (for arrays) + +Pragma @cite{Pack} applied to an array has no effect unless the component type +is packable. For a component type to be packable, it must be one of the +following cases: + + +@itemize * + +@item +Any scalar type + +@item +Any type whose size is specified with a size clause + +@item +Any packed array type with a static size + +@item +Any record type padded because of its default alignment +@end itemize + +For all these cases, if the component subtype size is in the range +1 through 63, then the effect of the pragma @cite{Pack} is exactly as though a +component size were specified giving the component subtype size. +For example if we have: + +@example +type r is range 0 .. 17; + +type ar is array (1 .. 8) of r; +pragma Pack (ar); +@end example + +Then the component size of @cite{ar} will be set to 5 (i.e., to @cite{r'size}, +and the size of the array @cite{ar} will be exactly 40 bits. + +Note that in some cases this rather fierce approach to packing can produce +unexpected effects. For example, in Ada 95 and Ada 2005, +subtype @cite{Natural} typically has a size of 31, meaning that if you +pack an array of @cite{Natural}, you get 31-bit +close packing, which saves a few bits, but results in far less efficient +access. Since many other Ada compilers will ignore such a packing request, +GNAT will generate a warning on some uses of pragma @cite{Pack} that it guesses +might not be what is intended. You can easily remove this warning by +using an explicit @cite{Component_Size} setting instead, which never generates +a warning, since the intention of the programmer is clear in this case. + +GNAT treats packed arrays in one of two ways. If the size of the array is +known at compile time and is less than 64 bits, then internally the array +is represented as a single modular type, of exactly the appropriate number +of bits. If the length is greater than 63 bits, or is not known at compile +time, then the packed array is represented as an array of bytes, and the +length is always a multiple of 8 bits. + +Note that to represent a packed array as a modular type, the alignment must +be suitable for the modular type involved. For example, on typical machines +a 32-bit packed array will be represented by a 32-bit modular integer with +an alignment of four bytes. If you explicitly override the default alignment +with an alignment clause that is too small, the modular representation +cannot be used. For example, consider the following set of declarations: + +@example +type R is range 1 .. 3; +type S is array (1 .. 31) of R; +for S'Component_Size use 2; +for S'Size use 62; +for S'Alignment use 1; +@end example + +If the alignment clause were not present, then a 62-bit modular +representation would be chosen (typically with an alignment of 4 or 8 +bytes depending on the target). But the default alignment is overridden +with the explicit alignment clause. This means that the modular +representation cannot be used, and instead the array of bytes +representation must be used, meaning that the length must be a multiple +of 8. Thus the above set of declarations will result in a diagnostic +rejecting the size clause and noting that the minimum size allowed is 64. + +@geindex Pragma Pack (for type Natural) + +@geindex Pragma Pack warning + +One special case that is worth noting occurs when the base type of the +component size is 8/16/32 and the subtype is one bit less. Notably this +occurs with subtype @cite{Natural}. Consider: + +@example +type Arr is array (1 .. 32) of Natural; +pragma Pack (Arr); +@end example + +In all commonly used Ada 83 compilers, this pragma Pack would be ignored, +since typically @cite{Natural'Size} is 32 in Ada 83, and in any case most +Ada 83 compilers did not attempt 31 bit packing. + +In Ada 95 and Ada 2005, @cite{Natural'Size} is required to be 31. Furthermore, +GNAT really does pack 31-bit subtype to 31 bits. This may result in a +substantial unintended performance penalty when porting legacy Ada 83 code. +To help prevent this, GNAT generates a warning in such cases. If you really +want 31 bit packing in a case like this, you can set the component size +explicitly: + +@example +type Arr is array (1 .. 32) of Natural; +for Arr'Component_Size use 31; +@end example + +Here 31-bit packing is achieved as required, and no warning is generated, +since in this case the programmer intention is clear. + +@node Pragma Pack for Records,Record Representation Clauses,Pragma Pack for Arrays,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas pragma-pack-for-records}@anchor{22c}@anchor{gnat_rm/representation_clauses_and_pragmas id12}@anchor{22d} +@section Pragma Pack for Records + + +@geindex Pragma Pack (for records) + +Pragma @cite{Pack} applied to a record will pack the components to reduce +wasted space from alignment gaps and by reducing the amount of space +taken by components. We distinguish between @emph{packable} components and +@emph{non-packable} components. +Components of the following types are considered packable: + + +@itemize * + +@item +Components of a primitive type are packable unless they are aliased +or of an atomic type. + +@item +Small packed arrays, whose size does not exceed 64 bits, and where the +size is statically known at compile time, are represented internally +as modular integers, and so they are also packable. +@end itemize + +All packable components occupy the exact number of bits corresponding to +their @cite{Size} value, and are packed with no padding bits, i.e., they +can start on an arbitrary bit boundary. + +All other types are non-packable, they occupy an integral number of +storage units, and +are placed at a boundary corresponding to their alignment requirements. + +For example, consider the record + +@example +type Rb1 is array (1 .. 13) of Boolean; +pragma Pack (Rb1); + +type Rb2 is array (1 .. 65) of Boolean; +pragma Pack (Rb2); + +type AF is new Float with Atomic; + +type X2 is record + L1 : Boolean; + L2 : Duration; + L3 : AF; + L4 : Boolean; + L5 : Rb1; + L6 : Rb2; +end record; +pragma Pack (X2); +@end example + +The representation for the record X2 is as follows: + +@example +for X2'Size use 224; +for X2 use record + L1 at 0 range 0 .. 0; + L2 at 0 range 1 .. 64; + L3 at 12 range 0 .. 31; + L4 at 16 range 0 .. 0; + L5 at 16 range 1 .. 13; + L6 at 18 range 0 .. 71; +end record; +@end example + +Studying this example, we see that the packable fields @cite{L1} +and @cite{L2} are +of length equal to their sizes, and placed at specific bit boundaries (and +not byte boundaries) to +eliminate padding. But @cite{L3} is of a non-packable float type (because +it is aliased), so it is on the next appropriate alignment boundary. + +The next two fields are fully packable, so @cite{L4} and @cite{L5} are +minimally packed with no gaps. However, type @cite{Rb2} is a packed +array that is longer than 64 bits, so it is itself non-packable. Thus +the @cite{L6} field is aligned to the next byte boundary, and takes an +integral number of bytes, i.e., 72 bits. + +@node Record Representation Clauses,Handling of Records with Holes,Pragma Pack for Records,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id13}@anchor{22e}@anchor{gnat_rm/representation_clauses_and_pragmas record-representation-clauses}@anchor{22f} +@section Record Representation Clauses + + +@geindex Record Representation Clause + +Record representation clauses may be given for all record types, including +types obtained by record extension. Component clauses are allowed for any +static component. The restrictions on component clauses depend on the type +of the component. + +@geindex Component Clause + +For all components of an elementary type, the only restriction on component +clauses is that the size must be at least the 'Size value of the type +(actually the Value_Size). There are no restrictions due to alignment, +and such components may freely cross storage boundaries. + +Packed arrays with a size up to and including 64 bits are represented +internally using a modular type with the appropriate number of bits, and +thus the same lack of restriction applies. For example, if you declare: + +@example +type R is array (1 .. 49) of Boolean; +pragma Pack (R); +for R'Size use 49; +@end example + +then a component clause for a component of type R may start on any +specified bit boundary, and may specify a value of 49 bits or greater. + +For packed bit arrays that are longer than 64 bits, there are two +cases. If the component size is a power of 2 (1,2,4,8,16,32 bits), +including the important case of single bits or boolean values, then +there are no limitations on placement of such components, and they +may start and end at arbitrary bit boundaries. + +If the component size is not a power of 2 (e.g., 3 or 5), then +an array of this type longer than 64 bits must always be placed on +on a storage unit (byte) boundary and occupy an integral number +of storage units (bytes). Any component clause that does not +meet this requirement will be rejected. + +Any aliased component, or component of an aliased type, must +have its normal alignment and size. A component clause that +does not meet this requirement will be rejected. + +The tag field of a tagged type always occupies an address sized field at +the start of the record. No component clause may attempt to overlay this +tag. When a tagged type appears as a component, the tag field must have +proper alignment + +In the case of a record extension T1, of a type T, no component clause applied +to the type T1 can specify a storage location that would overlap the first +T'Size bytes of the record. + +For all other component types, including non-bit-packed arrays, +the component can be placed at an arbitrary bit boundary, +so for example, the following is permitted: + +@example +type R is array (1 .. 10) of Boolean; +for R'Size use 80; + +type Q is record + G, H : Boolean; + L, M : R; +end record; + +for Q use record + G at 0 range 0 .. 0; + H at 0 range 1 .. 1; + L at 0 range 2 .. 81; + R at 0 range 82 .. 161; +end record; +@end example + +Note: the above rules apply to recent releases of GNAT 5. +In GNAT 3, there are more severe restrictions on larger components. +For non-primitive types, including packed arrays with a size greater than +64 bits, component clauses must respect the alignment requirement of the +type, in particular, always starting on a byte boundary, and the length +must be a multiple of the storage unit. + +@node Handling of Records with Holes,Enumeration Clauses,Record Representation Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas handling-of-records-with-holes}@anchor{230}@anchor{gnat_rm/representation_clauses_and_pragmas id14}@anchor{231} +@section Handling of Records with Holes + + +@geindex Handling of Records with Holes + +As a result of alignment considerations, records may contain "holes" +or gaps +which do not correspond to the data bits of any of the components. +Record representation clauses can also result in holes in records. + +GNAT does not attempt to clear these holes, so in record objects, +they should be considered to hold undefined rubbish. The generated +equality routine just tests components so does not access these +undefined bits, and assignment and copy operations may or may not +preserve the contents of these holes (for assignments, the holes +in the target will in practice contain either the bits that are +present in the holes in the source, or the bits that were present +in the target before the assignment). + +If it is necessary to ensure that holes in records have all zero +bits, then record objects for which this initialization is desired +should be explicitly set to all zero values using Unchecked_Conversion +or address overlays. For example + +@example +type HRec is record + C : Character; + I : Integer; +end record; +@end example + +On typical machines, integers need to be aligned on a four-byte +boundary, resulting in three bytes of undefined rubbish following +the 8-bit field for C. To ensure that the hole in a variable of +type HRec is set to all zero bits, +you could for example do: + +@example +type Base is record + Dummy1, Dummy2 : Integer := 0; +end record; + +BaseVar : Base; +RealVar : Hrec; +for RealVar'Address use BaseVar'Address; +@end example + +Now the 8-bytes of the value of RealVar start out containing all zero +bits. A safer approach is to just define dummy fields, avoiding the +holes, as in: + +@example +type HRec is record + C : Character; + Dummy1 : Short_Short_Integer := 0; + Dummy2 : Short_Short_Integer := 0; + Dummy3 : Short_Short_Integer := 0; + I : Integer; +end record; +@end example + +And to make absolutely sure that the intent of this is followed, you +can use representation clauses: + +@example +for Hrec use record + C at 0 range 0 .. 7; + Dummy1 at 1 range 0 .. 7; + Dummy2 at 2 range 0 .. 7; + Dummy3 at 3 range 0 .. 7; + I at 4 range 0 .. 31; +end record; +for Hrec'Size use 64; +@end example + +@node Enumeration Clauses,Address Clauses,Handling of Records with Holes,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas enumeration-clauses}@anchor{232}@anchor{gnat_rm/representation_clauses_and_pragmas id15}@anchor{233} +@section Enumeration Clauses + + +The only restriction on enumeration clauses is that the range of values +must be representable. For the signed case, if one or more of the +representation values are negative, all values must be in the range: + +@example +System.Min_Int .. System.Max_Int +@end example + +For the unsigned case, where all values are nonnegative, the values must +be in the range: + +@example +0 .. System.Max_Binary_Modulus; +@end example + +A @emph{confirming} representation clause is one in which the values range +from 0 in sequence, i.e., a clause that confirms the default representation +for an enumeration type. +Such a confirming representation +is permitted by these rules, and is specially recognized by the compiler so +that no extra overhead results from the use of such a clause. + +If an array has an index type which is an enumeration type to which an +enumeration clause has been applied, then the array is stored in a compact +manner. Consider the declarations: + +@example +type r is (A, B, C); +for r use (A => 1, B => 5, C => 10); +type t is array (r) of Character; +@end example + +The array type t corresponds to a vector with exactly three elements and +has a default size equal to @cite{3*Character'Size}. This ensures efficient +use of space, but means that accesses to elements of the array will incur +the overhead of converting representation values to the corresponding +positional values, (i.e., the value delivered by the @cite{Pos} attribute). + +@node Address Clauses,Use of Address Clauses for Memory-Mapped I/O,Enumeration Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id16}@anchor{234}@anchor{gnat_rm/representation_clauses_and_pragmas address-clauses}@anchor{235} +@section Address Clauses + + +@geindex Address Clause + +The reference manual allows a general restriction on representation clauses, +as found in RM 13.1(22): + +@quotation + +"An implementation need not support representation +items containing nonstatic expressions, except that +an implementation should support a representation item +for a given entity if each nonstatic expression in the +representation item is a name that statically denotes +a constant declared before the entity." +@end quotation + +In practice this is applicable only to address clauses, since this is the +only case in which a non-static expression is permitted by the syntax. As +the AARM notes in sections 13.1 (22.a-22.h): + +@quotation + +22.a Reason: This is to avoid the following sort of thing: + +22.b X : Integer := F(...); +Y : Address := G(...); +for X'Address use Y; + +22.c In the above, we have to evaluate the +initialization expression for X before we +know where to put the result. This seems +like an unreasonable implementation burden. + +22.d The above code should instead be written +like this: + +22.e Y : constant Address := G(...); +X : Integer := F(...); +for X'Address use Y; + +22.f This allows the expression 'Y' to be safely +evaluated before X is created. + +22.g The constant could be a formal parameter of mode in. + +22.h An implementation can support other nonstatic +expressions if it wants to. Expressions of type +Address are hardly ever static, but their value +might be known at compile time anyway in many +cases. +@end quotation + +GNAT does indeed permit many additional cases of non-static expressions. In +particular, if the type involved is elementary there are no restrictions +(since in this case, holding a temporary copy of the initialization value, +if one is present, is inexpensive). In addition, if there is no implicit or +explicit initialization, then there are no restrictions. GNAT will reject +only the case where all three of these conditions hold: + + +@itemize * + +@item +The type of the item is non-elementary (e.g., a record or array). + +@item +There is explicit or implicit initialization required for the object. +Note that access values are always implicitly initialized. + +@item +The address value is non-static. Here GNAT is more permissive than the +RM, and allows the address value to be the address of a previously declared +stand-alone variable, as long as it does not itself have an address clause. + +@example +Anchor : Some_Initialized_Type; +Overlay : Some_Initialized_Type; +for Overlay'Address use Anchor'Address; +@end example + +However, the prefix of the address clause cannot be an array component, or +a component of a discriminated record. +@end itemize + +As noted above in section 22.h, address values are typically non-static. In +particular the To_Address function, even if applied to a literal value, is +a non-static function call. To avoid this minor annoyance, GNAT provides +the implementation defined attribute 'To_Address. The following two +expressions have identical values: + +@geindex Attribute + +@geindex To_Address + +@example +To_Address (16#1234_0000#) +System'To_Address (16#1234_0000#); +@end example + +except that the second form is considered to be a static expression, and +thus when used as an address clause value is always permitted. + +Additionally, GNAT treats as static an address clause that is an +unchecked_conversion of a static integer value. This simplifies the porting +of legacy code, and provides a portable equivalent to the GNAT attribute +@cite{To_Address}. + +Another issue with address clauses is the interaction with alignment +requirements. When an address clause is given for an object, the address +value must be consistent with the alignment of the object (which is usually +the same as the alignment of the type of the object). If an address clause +is given that specifies an inappropriately aligned address value, then the +program execution is erroneous. + +Since this source of erroneous behavior can have unfortunate effects, GNAT +checks (at compile time if possible, generating a warning, or at execution +time with a run-time check) that the alignment is appropriate. If the +run-time check fails, then @cite{Program_Error} is raised. This run-time +check is suppressed if range checks are suppressed, or if the special GNAT +check Alignment_Check is suppressed, or if +@cite{pragma Restrictions (No_Elaboration_Code)} is in effect. + +Finally, GNAT does not permit overlaying of objects of controlled types or +composite types containing a controlled component. In most cases, the compiler +can detect an attempt at such overlays and will generate a warning at compile +time and a Program_Error exception at run time. + +@geindex Export + +An address clause cannot be given for an exported object. More +understandably the real restriction is that objects with an address +clause cannot be exported. This is because such variables are not +defined by the Ada program, so there is no external object to export. + +@geindex Import + +It is permissible to give an address clause and a pragma Import for the +same object. In this case, the variable is not really defined by the +Ada program, so there is no external symbol to be linked. The link name +and the external name are ignored in this case. The reason that we allow this +combination is that it provides a useful idiom to avoid unwanted +initializations on objects with address clauses. + +When an address clause is given for an object that has implicit or +explicit initialization, then by default initialization takes place. This +means that the effect of the object declaration is to overwrite the +memory at the specified address. This is almost always not what the +programmer wants, so GNAT will output a warning: + +@example +with System; +package G is + type R is record + M : Integer := 0; + end record; + + Ext : R; + for Ext'Address use System'To_Address (16#1234_1234#); + | +>>> warning: implicit initialization of "Ext" may + modify overlaid storage +>>> warning: use pragma Import for "Ext" to suppress + initialization (RM B(24)) + +end G; +@end example + +As indicated by the warning message, the solution is to use a (dummy) pragma +Import to suppress this initialization. The pragma tell the compiler that the +object is declared and initialized elsewhere. The following package compiles +without warnings (and the initialization is suppressed): + +@example +with System; +package G is + type R is record + M : Integer := 0; + end record; + + Ext : R; + for Ext'Address use System'To_Address (16#1234_1234#); + pragma Import (Ada, Ext); +end G; +@end example + +A final issue with address clauses involves their use for overlaying +variables, as in the following example: + +@geindex Overlaying of objects + +@example +A : Integer; +B : Integer; +for B'Address use A'Address; +@end example + +or alternatively, using the form recommended by the RM: + +@example +A : Integer; +Addr : constant Address := A'Address; +B : Integer; +for B'Address use Addr; +@end example + +In both of these cases, @cite{A} +and @cite{B} become aliased to one another via the +address clause. This use of address clauses to overlay +variables, achieving an effect similar to unchecked +conversion was erroneous in Ada 83, but in Ada 95 and Ada 2005 +the effect is implementation defined. Furthermore, the +Ada RM specifically recommends that in a situation +like this, @cite{B} should be subject to the following +implementation advice (RM 13.3(19)): + +@quotation + +"19 If the Address of an object is specified, or it is imported +or exported, then the implementation should not perform +optimizations based on assumptions of no aliases." +@end quotation + +GNAT follows this recommendation, and goes further by also applying +this recommendation to the overlaid variable (@cite{A} +in the above example) in this case. This means that the overlay +works "as expected", in that a modification to one of the variables +will affect the value of the other. + +Note that when address clause overlays are used in this way, there is an +issue of unintentional initialization, as shown by this example: + +@example +package Overwrite_Record is + type R is record + A : Character := 'C'; + B : Character := 'A'; + end record; + X : Short_Integer := 3; + Y : R; + for Y'Address use X'Address; + | +>>> warning: default initialization of "Y" may + modify "X", use pragma Import for "Y" to + suppress initialization (RM B.1(24)) + +end Overwrite_Record; +@end example + +Here the default initialization of @cite{Y} will clobber the value +of @cite{X}, which justifies the warning. The warning notes that +this effect can be eliminated by adding a @cite{pragma Import} +which suppresses the initialization: + +@example +package Overwrite_Record is + type R is record + A : Character := 'C'; + B : Character := 'A'; + end record; + X : Short_Integer := 3; + Y : R; + for Y'Address use X'Address; + pragma Import (Ada, Y); +end Overwrite_Record; +@end example + +Note that the use of @cite{pragma Initialize_Scalars} may cause variables to +be initialized when they would not otherwise have been in the absence +of the use of this pragma. This may cause an overlay to have this +unintended clobbering effect. The compiler avoids this for scalar +types, but not for composite objects (where in general the effect +of @cite{Initialize_Scalars} is part of the initialization routine +for the composite object: + +@example +pragma Initialize_Scalars; +with Ada.Text_IO; use Ada.Text_IO; +procedure Overwrite_Array is + type Arr is array (1 .. 5) of Integer; + X : Arr := (others => 1); + A : Arr; + for A'Address use X'Address; + | +>>> warning: default initialization of "A" may + modify "X", use pragma Import for "A" to + suppress initialization (RM B.1(24)) + +begin + if X /= Arr'(others => 1) then + Put_Line ("X was clobbered"); + else + Put_Line ("X was not clobbered"); + end if; +end Overwrite_Array; +@end example + +The above program generates the warning as shown, and at execution +time, prints @cite{X was clobbered}. If the @cite{pragma Import} is +added as suggested: + +@example +pragma Initialize_Scalars; +with Ada.Text_IO; use Ada.Text_IO; +procedure Overwrite_Array is + type Arr is array (1 .. 5) of Integer; + X : Arr := (others => 1); + A : Arr; + for A'Address use X'Address; + pragma Import (Ada, A); +begin + if X /= Arr'(others => 1) then + Put_Line ("X was clobbered"); + else + Put_Line ("X was not clobbered"); + end if; +end Overwrite_Array; +@end example + +then the program compiles without the warning and when run will generate +the output @cite{X was not clobbered}. + +@node Use of Address Clauses for Memory-Mapped I/O,Effect of Convention on Representation,Address Clauses,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id17}@anchor{236}@anchor{gnat_rm/representation_clauses_and_pragmas use-of-address-clauses-for-memory-mapped-i-o}@anchor{237} +@section Use of Address Clauses for Memory-Mapped I/O + + +@geindex Memory-mapped I/O + +A common pattern is to use an address clause to map an atomic variable to +a location in memory that corresponds to a memory-mapped I/O operation or +operations, for example: + +@example +type Mem_Word is record + A,B,C,D : Byte; +end record; +pragma Atomic (Mem_Word); +for Mem_Word_Size use 32; + +Mem : Mem_Word; +for Mem'Address use some-address; +... +Temp := Mem; +Temp.A := 32; +Mem := Temp; +@end example + +For a full access (reference or modification) of the variable (Mem) in +this case, as in the above examples, GNAT guarantees that the entire atomic +word will be accessed. It is not clear whether the RM requires this. For +example in the above, can the compiler reference only the Mem.A field as +an optimization? Whatever the answer to this question is, GNAT makes the +guarantee that for such a reference, the entire word is read or written. + +A problem arises with a component access such as: + +@example +Mem.A := 32; +@end example + +Note that the component A is not declared as atomic. This means that it is +not clear what this assignment means. It could correspond to full word read +and write as given in the first example, or on architectures that supported +such an operation it might be a single byte store instruction. The RM does +not have anything to say in this situation, and GNAT does not make any +guarantee. The code generated may vary from target to target. GNAT will issue +a warning in such a case: + +@example +Mem.A := 32; +| +>>> warning: access to non-atomic component of atomic array, + may cause unexpected accesses to atomic object +@end example + +It is best to be explicit in this situation, by either declaring the +components to be atomic if you want the byte store, or explicitly writing +the full word access sequence if that is what the hardware requires. + +@node Effect of Convention on Representation,Conventions and Anonymous Access Types,Use of Address Clauses for Memory-Mapped I/O,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id18}@anchor{238}@anchor{gnat_rm/representation_clauses_and_pragmas effect-of-convention-on-representation}@anchor{239} +@section Effect of Convention on Representation + + +@geindex Convention +@geindex effect on representation + +Normally the specification of a foreign language convention for a type or +an object has no effect on the chosen representation. In particular, the +representation chosen for data in GNAT generally meets the standard system +conventions, and for example records are laid out in a manner that is +consistent with C. This means that specifying convention C (for example) +has no effect. + +There are four exceptions to this general rule: + + +@itemize * + +@item +@emph{Convention Fortran and array subtypes}. + +If pragma Convention Fortran is specified for an array subtype, then in +accordance with the implementation advice in section 3.6.2(11) of the +Ada Reference Manual, the array will be stored in a Fortran-compatible +column-major manner, instead of the normal default row-major order. + +@item +@emph{Convention C and enumeration types} + +GNAT normally stores enumeration types in 8, 16, or 32 bits as required +to accommodate all values of the type. For example, for the enumeration +type declared by: + +@example +type Color is (Red, Green, Blue); +@end example + +8 bits is sufficient to store all values of the type, so by default, objects +of type @cite{Color} will be represented using 8 bits. However, normal C +convention is to use 32 bits for all enum values in C, since enum values +are essentially of type int. If pragma @cite{Convention C} is specified for an +Ada enumeration type, then the size is modified as necessary (usually to +32 bits) to be consistent with the C convention for enum values. + +Note that this treatment applies only to types. If Convention C is given for +an enumeration object, where the enumeration type is not Convention C, then +Object_Size bits are allocated. For example, for a normal enumeration type, +with less than 256 elements, only 8 bits will be allocated for the object. +Since this may be a surprise in terms of what C expects, GNAT will issue a +warning in this situation. The warning can be suppressed by giving an explicit +size clause specifying the desired size. + +@item +@emph{Convention C/Fortran and Boolean types} + +In C, the usual convention for boolean values, that is values used for +conditions, is that zero represents false, and nonzero values represent +true. In Ada, the normal convention is that two specific values, typically +0/1, are used to represent false/true respectively. + +Fortran has a similar convention for @cite{LOGICAL} values (any nonzero +value represents true). + +To accommodate the Fortran and C conventions, if a pragma Convention specifies +C or Fortran convention for a derived Boolean, as in the following example: + +@example +type C_Switch is new Boolean; +pragma Convention (C, C_Switch); +@end example + +then the GNAT generated code will treat any nonzero value as true. For truth +values generated by GNAT, the conventional value 1 will be used for True, but +when one of these values is read, any nonzero value is treated as True. +@end itemize + +@node Conventions and Anonymous Access Types,Determining the Representations chosen by GNAT,Effect of Convention on Representation,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas conventions-and-anonymous-access-types}@anchor{23a}@anchor{gnat_rm/representation_clauses_and_pragmas id19}@anchor{23b} +@section Conventions and Anonymous Access Types + + +@geindex Anonymous access types + +@geindex Convention for anonymous access types + +The RM is not entirely clear on convention handling in a number of cases, +and in particular, it is not clear on the convention to be given to +anonymous access types in general, and in particular what is to be +done for the case of anonymous access-to-subprogram. + +In GNAT, we decide that if an explicit Convention is applied +to an object or component, and its type is such an anonymous type, +then the convention will apply to this anonymous type as well. This +seems to make sense since it is anomolous in any case to have a +different convention for an object and its type, and there is clearly +no way to explicitly specify a convention for an anonymous type, since +it doesn't have a name to specify! + +Furthermore, we decide that if a convention is applied to a record type, +then this convention is inherited by any of its components that are of an +anonymous access type which do not have an explicitly specified convention. + +The following program shows these conventions in action: + +@example +package ConvComp is + type Foo is range 1 .. 10; + type T1 is record + A : access function (X : Foo) return Integer; + B : Integer; + end record; + pragma Convention (C, T1); + + type T2 is record + A : access function (X : Foo) return Integer; + pragma Convention (C, A); + B : Integer; + end record; + pragma Convention (COBOL, T2); + + type T3 is record + A : access function (X : Foo) return Integer; + pragma Convention (COBOL, A); + B : Integer; + end record; + pragma Convention (C, T3); + + type T4 is record + A : access function (X : Foo) return Integer; + B : Integer; + end record; + pragma Convention (COBOL, T4); + + function F (X : Foo) return Integer; + pragma Convention (C, F); + + function F (X : Foo) return Integer is (13); + + TV1 : T1 := (F'Access, 12); -- OK + TV2 : T2 := (F'Access, 13); -- OK + + TV3 : T3 := (F'Access, 13); -- ERROR + | +>>> subprogram "F" has wrong convention +>>> does not match access to subprogram declared at line 17 + 38. TV4 : T4 := (F'Access, 13); -- ERROR + | +>>> subprogram "F" has wrong convention +>>> does not match access to subprogram declared at line 24 + 39. end ConvComp; +@end example + +@node Determining the Representations chosen by GNAT,,Conventions and Anonymous Access Types,Representation Clauses and Pragmas +@anchor{gnat_rm/representation_clauses_and_pragmas id20}@anchor{23c}@anchor{gnat_rm/representation_clauses_and_pragmas determining-the-representations-chosen-by-gnat}@anchor{23d} +@section Determining the Representations chosen by GNAT + + +@geindex Representation +@geindex determination of + +@geindex -gnatR (gcc) + +Although the descriptions in this section are intended to be complete, it is +often easier to simply experiment to see what GNAT accepts and what the +effect is on the layout of types and objects. + +As required by the Ada RM, if a representation clause is not accepted, then +it must be rejected as illegal by the compiler. However, when a +representation clause or pragma is accepted, there can still be questions +of what the compiler actually does. For example, if a partial record +representation clause specifies the location of some components and not +others, then where are the non-specified components placed? Or if pragma +@cite{Pack} is used on a record, then exactly where are the resulting +fields placed? The section on pragma @cite{Pack} in this chapter can be +used to answer the second question, but it is often easier to just see +what the compiler does. + +For this purpose, GNAT provides the option @emph{-gnatR}. If you compile +with this option, then the compiler will output information on the actual +representations chosen, in a format similar to source representation +clauses. For example, if we compile the package: + +@example +package q is + type r (x : boolean) is tagged record + case x is + when True => S : String (1 .. 100); + when False => null; + end case; + end record; + + type r2 is new r (false) with record + y2 : integer; + end record; + + for r2 use record + y2 at 16 range 0 .. 31; + end record; + + type x is record + y : character; + end record; + + type x1 is array (1 .. 10) of x; + for x1'component_size use 11; + + type ia is access integer; + + type Rb1 is array (1 .. 13) of Boolean; + pragma Pack (rb1); + + type Rb2 is array (1 .. 65) of Boolean; + pragma Pack (rb2); + + type x2 is record + l1 : Boolean; + l2 : Duration; + l3 : Float; + l4 : Boolean; + l5 : Rb1; + l6 : Rb2; + end record; + pragma Pack (x2); +end q; +@end example + +using the switch @emph{-gnatR} we obtain the following output: + +@example +Representation information for unit q +------------------------------------- + +for r'Size use ??; +for r'Alignment use 4; +for r use record + x at 4 range 0 .. 7; + _tag at 0 range 0 .. 31; + s at 5 range 0 .. 799; +end record; + +for r2'Size use 160; +for r2'Alignment use 4; +for r2 use record + x at 4 range 0 .. 7; + _tag at 0 range 0 .. 31; + _parent at 0 range 0 .. 63; + y2 at 16 range 0 .. 31; +end record; + +for x'Size use 8; +for x'Alignment use 1; +for x use record + y at 0 range 0 .. 7; +end record; + +for x1'Size use 112; +for x1'Alignment use 1; +for x1'Component_Size use 11; + +for rb1'Size use 13; +for rb1'Alignment use 2; +for rb1'Component_Size use 1; + +for rb2'Size use 72; +for rb2'Alignment use 1; +for rb2'Component_Size use 1; + +for x2'Size use 224; +for x2'Alignment use 4; +for x2 use record + l1 at 0 range 0 .. 0; + l2 at 0 range 1 .. 64; + l3 at 12 range 0 .. 31; + l4 at 16 range 0 .. 0; + l5 at 16 range 1 .. 13; + l6 at 18 range 0 .. 71; +end record; +@end example + +The Size values are actually the Object_Size, i.e., the default size that +will be allocated for objects of the type. +The @code{??} size for type r indicates that we have a variant record, and the +actual size of objects will depend on the discriminant value. + +The Alignment values show the actual alignment chosen by the compiler +for each record or array type. + +The record representation clause for type r shows where all fields +are placed, including the compiler generated tag field (whose location +cannot be controlled by the programmer). + +The record representation clause for the type extension r2 shows all the +fields present, including the parent field, which is a copy of the fields +of the parent type of r2, i.e., r1. + +The component size and size clauses for types rb1 and rb2 show +the exact effect of pragma @cite{Pack} on these arrays, and the record +representation clause for type x2 shows how pragma @cite{Pack} affects +this record type. + +In some cases, it may be useful to cut and paste the representation clauses +generated by the compiler into the original source to fix and guarantee +the actual representation to be used. + +@node Standard Library Routines,The Implementation of Standard I/O,Representation Clauses and Pragmas,Top +@anchor{gnat_rm/standard_library_routines standard-library-routines}@anchor{e}@anchor{gnat_rm/standard_library_routines doc}@anchor{23e}@anchor{gnat_rm/standard_library_routines id1}@anchor{23f} +@chapter Standard Library Routines + + +The Ada Reference Manual contains in Annex A a full description of an +extensive set of standard library routines that can be used in any Ada +program, and which must be provided by all Ada compilers. They are +analogous to the standard C library used by C programs. + +GNAT implements all of the facilities described in annex A, and for most +purposes the description in the Ada Reference Manual, or appropriate Ada +text book, will be sufficient for making use of these facilities. + +In the case of the input-output facilities, +@ref{f,,The Implementation of Standard I/O}, +gives details on exactly how GNAT interfaces to the +file system. For the remaining packages, the Ada Reference Manual +should be sufficient. The following is a list of the packages included, +together with a brief description of the functionality that is provided. + +For completeness, references are included to other predefined library +routines defined in other sections of the Ada Reference Manual (these are +cross-indexed from Annex A). For further details see the relevant +package declarations in the run-time library. In particular, a few units +are not implemented, as marked by the presence of pragma Unimplemented_Unit, +and in this case the package declaration contains comments explaining why +the unit is not implemented. + + +@table @asis + +@item @code{Ada} @emph{(A.2)} + +This is a parent package for all the standard library packages. It is +usually included implicitly in your program, and itself contains no +useful data or routines. + +@item @code{Ada.Assertions} @emph{(11.4.2)} + +@cite{Assertions} provides the @cite{Assert} subprograms, and also +the declaration of the @cite{Assertion_Error} exception. + +@item @code{Ada.Asynchronous_Task_Control} @emph{(D.11)} + +@cite{Asynchronous_Task_Control} provides low level facilities for task +synchronization. It is typically not implemented. See package spec for details. + +@item @code{Ada.Calendar} @emph{(9.6)} + +@cite{Calendar} provides time of day access, and routines for +manipulating times and durations. + +@item @code{Ada.Calendar.Arithmetic} @emph{(9.6.1)} + +This package provides additional arithmetic +operations for @cite{Calendar}. + +@item @code{Ada.Calendar.Formatting} @emph{(9.6.1)} + +This package provides formatting operations for @cite{Calendar}. + +@item @code{Ada.Calendar.Time_Zones} @emph{(9.6.1)} + +This package provides additional @cite{Calendar} facilities +for handling time zones. + +@item @code{Ada.Characters} @emph{(A.3.1)} + +This is a dummy parent package that contains no useful entities + +@item @code{Ada.Characters.Conversions} @emph{(A.3.2)} + +This package provides character conversion functions. + +@item @code{Ada.Characters.Handling} @emph{(A.3.2)} + +This package provides some basic character handling capabilities, +including classification functions for classes of characters (e.g., test +for letters, or digits). + +@item @code{Ada.Characters.Latin_1} @emph{(A.3.3)} + +This package includes a complete set of definitions of the characters +that appear in type CHARACTER. It is useful for writing programs that +will run in international environments. For example, if you want an +upper case E with an acute accent in a string, it is often better to use +the definition of @cite{UC_E_Acute} in this package. Then your program +will print in an understandable manner even if your environment does not +support these extended characters. + +@item @code{Ada.Command_Line} @emph{(A.15)} + +This package provides access to the command line parameters and the name +of the current program (analogous to the use of @cite{argc} and @cite{argv} +in C), and also allows the exit status for the program to be set in a +system-independent manner. + +@item @code{Ada.Complex_Text_IO} @emph{(G.1.3)} + +This package provides text input and output of complex numbers. + +@item @code{Ada.Containers} @emph{(A.18.1)} + +A top level package providing a few basic definitions used by all the +following specific child packages that provide specific kinds of +containers. +@end table + +@code{Ada.Containers.Bounded_Priority_Queues} @emph{(A.18.31)} + +@code{Ada.Containers.Bounded_Synchronized_Queues} @emph{(A.18.29)} + +@code{Ada.Containers.Doubly_Linked_Lists} @emph{(A.18.3)} + +@code{Ada.Containers.Generic_Array_Sort} @emph{(A.18.26)} + +@code{Ada.Containers.Generic_Constrained_Array_Sort} @emph{(A.18.26)} + +@code{Ada.Containers.Generic_Sort} @emph{(A.18.26)} + +@code{Ada.Containers.Hashed_Maps} @emph{(A.18.5)} + +@code{Ada.Containers.Hashed_Sets} @emph{(A.18.8)} + +@code{Ada.Containers.Indefinite_Doubly_Linked_Lists} @emph{(A.18.12)} + +@code{Ada.Containers.Indefinite_Hashed_Maps} @emph{(A.18.13)} + +@code{Ada.Containers.Indefinite_Hashed_Sets} @emph{(A.18.15)} + +@code{Ada.Containers.Indefinite_Holders} @emph{(A.18.18)} + +@code{Ada.Containers.Indefinite_Multiway_Trees} @emph{(A.18.17)} + +@code{Ada.Containers.Indefinite_Ordered_Maps} @emph{(A.18.14)} + +@code{Ada.Containers.Indefinite_Ordered_Sets} @emph{(A.18.16)} + +@code{Ada.Containers.Indefinite_Vectors} @emph{(A.18.11)} + +@code{Ada.Containers.Multiway_Trees} @emph{(A.18.10)} + +@code{Ada.Containers.Ordered_Maps} @emph{(A.18.6)} + +@code{Ada.Containers.Ordered_Sets} @emph{(A.18.9)} + +@code{Ada.Containers.Synchronized_Queue_Interfaces} @emph{(A.18.27)} + +@code{Ada.Containers.Unbounded_Priority_Queues} @emph{(A.18.30)} + +@code{Ada.Containers.Unbounded_Synchronized_Queues} @emph{(A.18.28)} + +@code{Ada.Containers.Vectors} @emph{(A.18.2)} + + +@table @asis + +@item @code{Ada.Directories} @emph{(A.16)} + +This package provides operations on directories. + +@item @code{Ada.Directories.Hierarchical_File_Names} @emph{(A.16.1)} + +This package provides additional directory operations handling +hiearchical file names. + +@item @code{Ada.Directories.Information} @emph{(A.16)} + +This is an implementation defined package for additional directory +operations, which is not implemented in GNAT. + +@item @code{Ada.Decimal} @emph{(F.2)} + +This package provides constants describing the range of decimal numbers +implemented, and also a decimal divide routine (analogous to the COBOL +verb DIVIDE ... GIVING ... REMAINDER ...) + +@item @code{Ada.Direct_IO} @emph{(A.8.4)} + +This package provides input-output using a model of a set of records of +fixed-length, containing an arbitrary definite Ada type, indexed by an +integer record number. + +@item @code{Ada.Dispatching} @emph{(D.2.1)} + +A parent package containing definitions for task dispatching operations. + +@item @code{Ada.Dispatching.EDF} @emph{(D.2.6)} + +Not implemented in GNAT. + +@item @code{Ada.Dispatching.Non_Preemptive} @emph{(D.2.4)} + +Not implemented in GNAT. + +@item @code{Ada.Dispatching.Round_Robin} @emph{(D.2.5)} + +Not implemented in GNAT. + +@item @code{Ada.Dynamic_Priorities} @emph{(D.5)} + +This package allows the priorities of a task to be adjusted dynamically +as the task is running. + +@item @code{Ada.Environment_Variables} @emph{(A.17)} + +This package provides facilities for accessing environment variables. + +@item @code{Ada.Exceptions} @emph{(11.4.1)} + +This package provides additional information on exceptions, and also +contains facilities for treating exceptions as data objects, and raising +exceptions with associated messages. + +@item @code{Ada.Execution_Time} @emph{(D.14)} + +Not implemented in GNAT. + +@item @code{Ada.Execution_Time.Group_Budgets} @emph{(D.14.2)} + +Not implemented in GNAT. + +@item @code{Ada.Execution_Time.Timers} @emph{(D.14.1)'} + +Not implemented in GNAT. + +@item @code{Ada.Finalization} @emph{(7.6)} + +This package contains the declarations and subprograms to support the +use of controlled types, providing for automatic initialization and +finalization (analogous to the constructors and destructors of C++). + +@item @code{Ada.Float_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Text_IO.Float_IO for type Float. + +@item @code{Ada.Float_Wide_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Wide_Text_IO.Float_IO for type Float. + +@item @code{Ada.Float_Wide_Wide_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float. + +@item @code{Ada.Integer_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Text_IO.Integer_IO for type Integer. + +@item @code{Ada.Integer_Wide_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Wide_Text_IO.Integer_IO for type Integer. + +@item @code{Ada.Integer_Wide_Wide_Text_IO} @emph{(A.10.9)} + +A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer. + +@item @code{Ada.Interrupts} @emph{(C.3.2)} + +This package provides facilities for interfacing to interrupts, which +includes the set of signals or conditions that can be raised and +recognized as interrupts. + +@item @code{Ada.Interrupts.Names} @emph{(C.3.2)} + +This package provides the set of interrupt names (actually signal +or condition names) that can be handled by GNAT. + +@item @code{Ada.IO_Exceptions} @emph{(A.13)} + +This package defines the set of exceptions that can be raised by use of +the standard IO packages. + +@item @code{Ada.Iterator_Interfaces} @emph{(5.5.1)} + +This package provides a generic interface to generalized iterators. + +@item @code{Ada.Locales} @emph{(A.19)} + +This package provides declarations providing information (Language +and Country) about the current locale. + +@item @code{Ada.Numerics} + +This package contains some standard constants and exceptions used +throughout the numerics packages. Note that the constants pi and e are +defined here, and it is better to use these definitions than rolling +your own. + +@item @code{Ada.Numerics.Complex_Arrays} @emph{(G.3.2)} + +Provides operations on arrays of complex numbers. + +@item @code{Ada.Numerics.Complex_Elementary_Functions} + +Provides the implementation of standard elementary functions (such as +log and trigonometric functions) operating on complex numbers using the +standard @cite{Float} and the @cite{Complex} and @cite{Imaginary} types +created by the package @cite{Numerics.Complex_Types}. + +@item @code{Ada.Numerics.Complex_Types} + +This is a predefined instantiation of +@cite{Numerics.Generic_Complex_Types} using @cite{Standard.Float} to +build the type @cite{Complex} and @cite{Imaginary}. + +@item @code{Ada.Numerics.Discrete_Random} + +This generic package provides a random number generator suitable for generating +uniformly distributed values of a specified discrete subtype. + +@item @code{Ada.Numerics.Float_Random} + +This package provides a random number generator suitable for generating +uniformly distributed floating point values in the unit interval. + +@item @code{Ada.Numerics.Generic_Complex_Elementary_Functions} + +This is a generic version of the package that provides the +implementation of standard elementary functions (such as log and +trigonometric functions) for an arbitrary complex type. + +The following predefined instantiations of this package are provided: + + +@itemize * + +@item +@code{Short_Float} + +@cite{Ada.Numerics.Short_Complex_Elementary_Functions} + +@item +@code{Float} + +@cite{Ada.Numerics.Complex_Elementary_Functions} + +@item +@code{Long_Float} + +@cite{Ada.Numerics.Long_Complex_Elementary_Functions} +@end itemize + +@item @code{Ada.Numerics.Generic_Complex_Types} + +This is a generic package that allows the creation of complex types, +with associated complex arithmetic operations. + +The following predefined instantiations of this package exist + + +@itemize * + +@item +@code{Short_Float} + +@cite{Ada.Numerics.Short_Complex_Complex_Types} + +@item +@code{Float} + +@cite{Ada.Numerics.Complex_Complex_Types} + +@item +@code{Long_Float} + +@cite{Ada.Numerics.Long_Complex_Complex_Types} +@end itemize + +@item @code{Ada.Numerics.Generic_Elementary_Functions} + +This is a generic package that provides the implementation of standard +elementary functions (such as log an trigonometric functions) for an +arbitrary float type. + +The following predefined instantiations of this package exist + + +@itemize * + +@item +@code{Short_Float} + +@cite{Ada.Numerics.Short_Elementary_Functions} + +@item +@code{Float} + +@cite{Ada.Numerics.Elementary_Functions} + +@item +@code{Long_Float} + +@cite{Ada.Numerics.Long_Elementary_Functions} +@end itemize + +@item @code{Ada.Numerics.Generic_Real_Arrays} @emph{(G.3.1)} + +Generic operations on arrays of reals + +@item @code{Ada.Numerics.Real_Arrays} @emph{(G.3.1)} + +Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float). + +@item @code{Ada.Real_Time} @emph{(D.8)} + +This package provides facilities similar to those of @cite{Calendar}, but +operating with a finer clock suitable for real time control. Note that +annex D requires that there be no backward clock jumps, and GNAT generally +guarantees this behavior, but of course if the external clock on which +the GNAT runtime depends is deliberately reset by some external event, +then such a backward jump may occur. + +@item @code{Ada.Real_Time.Timing_Events} @emph{(D.15)} + +Not implemented in GNAT. + +@item @code{Ada.Sequential_IO} @emph{(A.8.1)} + +This package provides input-output facilities for sequential files, +which can contain a sequence of values of a single type, which can be +any Ada type, including indefinite (unconstrained) types. + +@item @code{Ada.Storage_IO} @emph{(A.9)} + +This package provides a facility for mapping arbitrary Ada types to and +from a storage buffer. It is primarily intended for the creation of new +IO packages. + +@item @code{Ada.Streams} @emph{(13.13.1)} + +This is a generic package that provides the basic support for the +concept of streams as used by the stream attributes (@cite{Input}, +@cite{Output}, @cite{Read} and @cite{Write}). + +@item @code{Ada.Streams.Stream_IO} @emph{(A.12.1)} + +This package is a specialization of the type @cite{Streams} defined in +package @cite{Streams} together with a set of operations providing +Stream_IO capability. The Stream_IO model permits both random and +sequential access to a file which can contain an arbitrary set of values +of one or more Ada types. + +@item @code{Ada.Strings} @emph{(A.4.1)} + +This package provides some basic constants used by the string handling +packages. + +@item @code{Ada.Strings.Bounded} @emph{(A.4.4)} + +This package provides facilities for handling variable length +strings. The bounded model requires a maximum length. It is thus +somewhat more limited than the unbounded model, but avoids the use of +dynamic allocation or finalization. + +@item @code{Ada.Strings.Bounded.Equal_Case_Insensitive} @emph{(A.4.10)} + +Provides case-insensitive comparisons of bounded strings + +@item @code{Ada.Strings.Bounded.Hash} @emph{(A.4.9)} + +This package provides a generic hash function for bounded strings + +@item @code{Ada.Strings.Bounded.Hash_Case_Insensitive} @emph{(A.4.9)} + +This package provides a generic hash function for bounded strings that +converts the string to be hashed to lower case. + +@item @code{Ada.Strings.Bounded.Less_Case_Insensitive} @emph{(A.4.10)} + +This package provides a comparison function for bounded strings that works +in a case insensitive manner by converting to lower case before the comparison. + +@item @code{Ada.Strings.Fixed} @emph{(A.4.3)} + +This package provides facilities for handling fixed length strings. + +@item @code{Ada.Strings.Fixed.Equal_Case_Insensitive} @emph{(A.4.10)} + +This package provides an equality function for fixed strings that compares +the strings after converting both to lower case. + +@item @code{Ada.Strings.Fixed.Hash_Case_Insensitive} @emph{(A.4.9)} + +This package provides a case insensitive hash function for fixed strings that +converts the string to lower case before computing the hash. + +@item @code{Ada.Strings.Fixed.Less_Case_Insensitive} @emph{(A.4.10)} + +This package provides a comparison function for fixed strings that works +in a case insensitive manner by converting to lower case before the comparison. + +@item @code{Ada.Strings.Hash} @emph{(A.4.9)} + +This package provides a hash function for strings. + +@item @code{Ada.Strings.Hash_Case_Insensitive} @emph{(A.4.9)} + +This package provides a hash function for strings that is case insensitive. +The string is converted to lower case before computing the hash. + +@item @code{Ada.Strings.Less_Case_Insensitive} @emph{(A.4.10)} + +This package provides a comparison function for\strings that works +in a case insensitive manner by converting to lower case before the comparison. + +@item @code{Ada.Strings.Maps} @emph{(A.4.2)} + +This package provides facilities for handling character mappings and +arbitrarily defined subsets of characters. For instance it is useful in +defining specialized translation tables. + +@item @code{Ada.Strings.Maps.Constants} @emph{(A.4.6)} + +This package provides a standard set of predefined mappings and +predefined character sets. For example, the standard upper to lower case +conversion table is found in this package. Note that upper to lower case +conversion is non-trivial if you want to take the entire set of +characters, including extended characters like E with an acute accent, +into account. You should use the mappings in this package (rather than +adding 32 yourself) to do case mappings. + +@item @code{Ada.Strings.Unbounded} @emph{(A.4.5)} + +This package provides facilities for handling variable length +strings. The unbounded model allows arbitrary length strings, but +requires the use of dynamic allocation and finalization. + +@item @code{Ada.Strings.Unbounded.Equal_Case_Insensitive} @emph{(A.4.10)} + +Provides case-insensitive comparisons of unbounded strings + +@item @code{Ada.Strings.Unbounded.Hash} @emph{(A.4.9)} + +This package provides a generic hash function for unbounded strings + +@item @code{Ada.Strings.Unbounded.Hash_Case_Insensitive} @emph{(A.4.9)} + +This package provides a generic hash function for unbounded strings that +converts the string to be hashed to lower case. + +@item @code{Ada.Strings.Unbounded.Less_Case_Insensitive} @emph{(A.4.10)} + +This package provides a comparison function for unbounded strings that works +in a case insensitive manner by converting to lower case before the comparison. + +@item @code{Ada.Strings.UTF_Encoding} @emph{(A.4.11)} + +This package provides basic definitions for dealing with UTF-encoded strings. + +@item @code{Ada.Strings.UTF_Encoding.Conversions} @emph{(A.4.11)} + +This package provides conversion functions for UTF-encoded strings. +@end table + +@code{Ada.Strings.UTF_Encoding.Strings} @emph{(A.4.11)} + +@code{Ada.Strings.UTF_Encoding.Wide_Strings} @emph{(A.4.11)} + + +@table @asis + +@item @code{Ada.Strings.UTF_Encoding.Wide_Wide_Strings} @emph{(A.4.11)} + +These packages provide facilities for handling UTF encodings for +Strings, Wide_Strings and Wide_Wide_Strings. +@end table + +@code{Ada.Strings.Wide_Bounded} @emph{(A.4.7)} + +@code{Ada.Strings.Wide_Fixed} @emph{(A.4.7)} + +@code{Ada.Strings.Wide_Maps} @emph{(A.4.7)} + + +@table @asis + +@item @code{Ada.Strings.Wide_Unbounded} @emph{(A.4.7)} + +These packages provide analogous capabilities to the corresponding +packages without @code{Wide_} in the name, but operate with the types +@cite{Wide_String} and @cite{Wide_Character} instead of @cite{String} +and @cite{Character}. Versions of all the child packages are available. +@end table + +@code{Ada.Strings.Wide_Wide_Bounded} @emph{(A.4.7)} + +@code{Ada.Strings.Wide_Wide_Fixed} @emph{(A.4.7)} + +@code{Ada.Strings.Wide_Wide_Maps} @emph{(A.4.7)} + + +@table @asis + +@item @code{Ada.Strings.Wide_Wide_Unbounded} @emph{(A.4.7)} + +These packages provide analogous capabilities to the corresponding +packages without @code{Wide_} in the name, but operate with the types +@cite{Wide_Wide_String} and @cite{Wide_Wide_Character} instead +of @cite{String} and @cite{Character}. + +@item @code{Ada.Synchronous_Barriers} @emph{(D.10.1)} + +This package provides facilities for synchronizing tasks at a low level +with barriers. + +@item @code{Ada.Synchronous_Task_Control} @emph{(D.10)} + +This package provides some standard facilities for controlling task +communication in a synchronous manner. + +@item @code{Ada.Synchronous_Task_Control.EDF} @emph{(D.10)} + +Not implemented in GNAT. + +@item @code{Ada.Tags} + +This package contains definitions for manipulation of the tags of tagged +values. + +@item @code{Ada.Tags.Generic_Dispatching_Constructor} @emph{(3.9)} + +This package provides a way of constructing tagged class-wide values given +only the tag value. + +@item @code{Ada.Task_Attributes} @emph{(C.7.2)} + +This package provides the capability of associating arbitrary +task-specific data with separate tasks. + +@item @code{Ada.Task_Identifification} @emph{(C.7.1)} + +This package provides capabilities for task identification. + +@item @code{Ada.Task_Termination} @emph{(C.7.3)} + +This package provides control over task termination. + +@item @code{Ada.Text_IO} + +This package provides basic text input-output capabilities for +character, string and numeric data. The subpackages of this +package are listed next. Note that although these are defined +as subpackages in the RM, they are actually transparently +implemented as child packages in GNAT, meaning that they +are only loaded if needed. + +@item @code{Ada.Text_IO.Decimal_IO} + +Provides input-output facilities for decimal fixed-point types + +@item @code{Ada.Text_IO.Enumeration_IO} + +Provides input-output facilities for enumeration types. + +@item @code{Ada.Text_IO.Fixed_IO} + +Provides input-output facilities for ordinary fixed-point types. + +@item @code{Ada.Text_IO.Float_IO} + +Provides input-output facilities for float types. The following +predefined instantiations of this generic package are available: + + +@itemize * + +@item +@code{Short_Float} + +@cite{Short_Float_Text_IO} + +@item +@code{Float} + +@cite{Float_Text_IO} + +@item +@code{Long_Float} + +@cite{Long_Float_Text_IO} +@end itemize + +@item @code{Ada.Text_IO.Integer_IO} + +Provides input-output facilities for integer types. The following +predefined instantiations of this generic package are available: + + +@itemize * + +@item +@code{Short_Short_Integer} + +@cite{Ada.Short_Short_Integer_Text_IO} + +@item +@code{Short_Integer} + +@cite{Ada.Short_Integer_Text_IO} + +@item +@code{Integer} + +@cite{Ada.Integer_Text_IO} + +@item +@code{Long_Integer} + +@cite{Ada.Long_Integer_Text_IO} + +@item +@code{Long_Long_Integer} + +@cite{Ada.Long_Long_Integer_Text_IO} +@end itemize + +@item @code{Ada.Text_IO.Modular_IO} + +Provides input-output facilities for modular (unsigned) types. + +@item @code{Ada.Text_IO.Bounded_IO (A.10.11)} + +Provides input-output facilities for bounded strings. + +@item @code{Ada.Text_IO.Complex_IO (G.1.3)} + +This package provides basic text input-output capabilities for complex +data. + +@item @code{Ada.Text_IO.Editing (F.3.3)} + +This package contains routines for edited output, analogous to the use +of pictures in COBOL. The picture formats used by this package are a +close copy of the facility in COBOL. + +@item @code{Ada.Text_IO.Text_Streams (A.12.2)} + +This package provides a facility that allows Text_IO files to be treated +as streams, so that the stream attributes can be used for writing +arbitrary data, including binary data, to Text_IO files. + +@item @code{Ada.Text_IO.Unbounded_IO (A.10.12)} + +This package provides input-output facilities for unbounded strings. + +@item @code{Ada.Unchecked_Conversion (13.9)} + +This generic package allows arbitrary conversion from one type to +another of the same size, providing for breaking the type safety in +special circumstances. + +If the types have the same Size (more accurately the same Value_Size), +then the effect is simply to transfer the bits from the source to the +target type without any modification. This usage is well defined, and +for simple types whose representation is typically the same across +all implementations, gives a portable method of performing such +conversions. + +If the types do not have the same size, then the result is implementation +defined, and thus may be non-portable. The following describes how GNAT +handles such unchecked conversion cases. + +If the types are of different sizes, and are both discrete types, then +the effect is of a normal type conversion without any constraint checking. +In particular if the result type has a larger size, the result will be +zero or sign extended. If the result type has a smaller size, the result +will be truncated by ignoring high order bits. + +If the types are of different sizes, and are not both discrete types, +then the conversion works as though pointers were created to the source +and target, and the pointer value is converted. The effect is that bits +are copied from successive low order storage units and bits of the source +up to the length of the target type. + +A warning is issued if the lengths differ, since the effect in this +case is implementation dependent, and the above behavior may not match +that of some other compiler. + +A pointer to one type may be converted to a pointer to another type using +unchecked conversion. The only case in which the effect is undefined is +when one or both pointers are pointers to unconstrained array types. In +this case, the bounds information may get incorrectly transferred, and in +particular, GNAT uses double size pointers for such types, and it is +meaningless to convert between such pointer types. GNAT will issue a +warning if the alignment of the target designated type is more strict +than the alignment of the source designated type (since the result may +be unaligned in this case). + +A pointer other than a pointer to an unconstrained array type may be +converted to and from System.Address. Such usage is common in Ada 83 +programs, but note that Ada.Address_To_Access_Conversions is the +preferred method of performing such conversions in Ada 95 and Ada 2005. +Neither +unchecked conversion nor Ada.Address_To_Access_Conversions should be +used in conjunction with pointers to unconstrained objects, since +the bounds information cannot be handled correctly in this case. + +@item @code{Ada.Unchecked_Deallocation} @emph{(13.11.2)} + +This generic package allows explicit freeing of storage previously +allocated by use of an allocator. + +@item @code{Ada.Wide_Text_IO} @emph{(A.11)} + +This package is similar to @cite{Ada.Text_IO}, except that the external +file supports wide character representations, and the internal types are +@cite{Wide_Character} and @cite{Wide_String} instead of @cite{Character} +and @cite{String}. The corresponding set of nested packages and child +packages are defined. + +@item @code{Ada.Wide_Wide_Text_IO} @emph{(A.11)} + +This package is similar to @cite{Ada.Text_IO}, except that the external +file supports wide character representations, and the internal types are +@cite{Wide_Character} and @cite{Wide_String} instead of @cite{Character} +and @cite{String}. The corresponding set of nested packages and child +packages are defined. +@end table + +For packages in Interfaces and System, all the RM defined packages are +available in GNAT, see the Ada 2012 RM for full details. + +@node The Implementation of Standard I/O,The GNAT Library,Standard Library Routines,Top +@anchor{gnat_rm/the_implementation_of_standard_i_o the-implementation-of-standard-i-o}@anchor{f}@anchor{gnat_rm/the_implementation_of_standard_i_o doc}@anchor{240}@anchor{gnat_rm/the_implementation_of_standard_i_o id1}@anchor{241} +@chapter The Implementation of Standard I/O + + +GNAT implements all the required input-output facilities described in +A.6 through A.14. These sections of the Ada Reference Manual describe the +required behavior of these packages from the Ada point of view, and if +you are writing a portable Ada program that does not need to know the +exact manner in which Ada maps to the outside world when it comes to +reading or writing external files, then you do not need to read this +chapter. As long as your files are all regular files (not pipes or +devices), and as long as you write and read the files only from Ada, the +description in the Ada Reference Manual is sufficient. + +However, if you want to do input-output to pipes or other devices, such +as the keyboard or screen, or if the files you are dealing with are +either generated by some other language, or to be read by some other +language, then you need to know more about the details of how the GNAT +implementation of these input-output facilities behaves. + +In this chapter we give a detailed description of exactly how GNAT +interfaces to the file system. As always, the sources of the system are +available to you for answering questions at an even more detailed level, +but for most purposes the information in this chapter will suffice. + +Another reason that you may need to know more about how input-output is +implemented arises when you have a program written in mixed languages +where, for example, files are shared between the C and Ada sections of +the same program. GNAT provides some additional facilities, in the form +of additional child library packages, that facilitate this sharing, and +these additional facilities are also described in this chapter. + +@menu +* Standard I/O Packages:: +* FORM Strings:: +* Direct_IO:: +* Sequential_IO:: +* Text_IO:: +* Wide_Text_IO:: +* Wide_Wide_Text_IO:: +* Stream_IO:: +* Text Translation:: +* Shared Files:: +* Filenames encoding:: +* File content encoding:: +* Open Modes:: +* Operations on C Streams:: +* Interfacing to C Streams:: + +@end menu + +@node Standard I/O Packages,FORM Strings,,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o standard-i-o-packages}@anchor{242}@anchor{gnat_rm/the_implementation_of_standard_i_o id2}@anchor{243} +@section Standard I/O Packages + + +The Standard I/O packages described in Annex A for + + +@itemize * + +@item +Ada.Text_IO + +@item +Ada.Text_IO.Complex_IO + +@item +Ada.Text_IO.Text_Streams + +@item +Ada.Wide_Text_IO + +@item +Ada.Wide_Text_IO.Complex_IO + +@item +Ada.Wide_Text_IO.Text_Streams + +@item +Ada.Wide_Wide_Text_IO + +@item +Ada.Wide_Wide_Text_IO.Complex_IO + +@item +Ada.Wide_Wide_Text_IO.Text_Streams + +@item +Ada.Stream_IO + +@item +Ada.Sequential_IO + +@item +Ada.Direct_IO +@end itemize + +are implemented using the C +library streams facility; where + + +@itemize * + +@item +All files are opened using @cite{fopen}. + +@item +All input/output operations use @cite{fread}/@cite{fwrite}. +@end itemize + +There is no internal buffering of any kind at the Ada library level. The only +buffering is that provided at the system level in the implementation of the +library routines that support streams. This facilitates shared use of these +streams by mixed language programs. Note though that system level buffering is +explicitly enabled at elaboration of the standard I/O packages and that can +have an impact on mixed language programs, in particular those using I/O before +calling the Ada elaboration routine (e.g., adainit). It is recommended to call +the Ada elaboration routine before performing any I/O or when impractical, +flush the common I/O streams and in particular Standard_Output before +elaborating the Ada code. + +@node FORM Strings,Direct_IO,Standard I/O Packages,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o form-strings}@anchor{244}@anchor{gnat_rm/the_implementation_of_standard_i_o id3}@anchor{245} +@section FORM Strings + + +The format of a FORM string in GNAT is: + +@example +"keyword=value,keyword=value,...,keyword=value" +@end example + +where letters may be in upper or lower case, and there are no spaces +between values. The order of the entries is not important. Currently +the following keywords defined. + +@example +TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT] +SHARED=[YES|NO] +WCEM=[n|h|u|s|e|8|b] +ENCODING=[UTF8|8BITS] +@end example + +The use of these parameters is described later in this section. If an +unrecognized keyword appears in a form string, it is silently ignored +and not considered invalid. + +@node Direct_IO,Sequential_IO,FORM Strings,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o direct-io}@anchor{246}@anchor{gnat_rm/the_implementation_of_standard_i_o id4}@anchor{247} +@section Direct_IO + + +Direct_IO can only be instantiated for definite types. This is a +restriction of the Ada language, which means that the records are fixed +length (the length being determined by @code{type'Size}, rounded +up to the next storage unit boundary if necessary). + +The records of a Direct_IO file are simply written to the file in index +sequence, with the first record starting at offset zero, and subsequent +records following. There is no control information of any kind. For +example, if 32-bit integers are being written, each record takes +4-bytes, so the record at index @cite{K} starts at offset +(@cite{K}-1)*4. + +There is no limit on the size of Direct_IO files, they are expanded as +necessary to accommodate whatever records are written to the file. + +@node Sequential_IO,Text_IO,Direct_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o sequential-io}@anchor{248}@anchor{gnat_rm/the_implementation_of_standard_i_o id5}@anchor{249} +@section Sequential_IO + + +Sequential_IO may be instantiated with either a definite (constrained) +or indefinite (unconstrained) type. + +For the definite type case, the elements written to the file are simply +the memory images of the data values with no control information of any +kind. The resulting file should be read using the same type, no validity +checking is performed on input. + +For the indefinite type case, the elements written consist of two +parts. First is the size of the data item, written as the memory image +of a @cite{Interfaces.C.size_t} value, followed by the memory image of +the data value. The resulting file can only be read using the same +(unconstrained) type. Normal assignment checks are performed on these +read operations, and if these checks fail, @cite{Data_Error} is +raised. In particular, in the array case, the lengths must match, and in +the variant record case, if the variable for a particular read operation +is constrained, the discriminants must match. + +Note that it is not possible to use Sequential_IO to write variable +length array items, and then read the data back into different length +arrays. For example, the following will raise @cite{Data_Error}: + +@example +package IO is new Sequential_IO (String); +F : IO.File_Type; +S : String (1..4); +... +IO.Create (F) +IO.Write (F, "hello!") +IO.Reset (F, Mode=>In_File); +IO.Read (F, S); +Put_Line (S); +@end example + +On some Ada implementations, this will print @cite{hell}, but the program is +clearly incorrect, since there is only one element in the file, and that +element is the string @cite{hello!}. + +In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved +using Stream_IO, and this is the preferred mechanism. In particular, the +above program fragment rewritten to use Stream_IO will work correctly. + +@node Text_IO,Wide_Text_IO,Sequential_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o id6}@anchor{24a}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io}@anchor{24b} +@section Text_IO + + +Text_IO files consist of a stream of characters containing the following +special control characters: + +@example +LF (line feed, 16#0A#) Line Mark +FF (form feed, 16#0C#) Page Mark +@end example + +A canonical Text_IO file is defined as one in which the following +conditions are met: + + +@itemize * + +@item +The character @cite{LF} is used only as a line mark, i.e., to mark the end +of the line. + +@item +The character @cite{FF} is used only as a page mark, i.e., to mark the +end of a page and consequently can appear only immediately following a +@cite{LF} (line mark) character. + +@item +The file ends with either @cite{LF} (line mark) or @cite{LF}-@cite{FF} +(line mark, page mark). In the former case, the page mark is implicitly +assumed to be present. +@end itemize + +A file written using Text_IO will be in canonical form provided that no +explicit @cite{LF} or @cite{FF} characters are written using @cite{Put} +or @cite{Put_Line}. There will be no @cite{FF} character at the end of +the file unless an explicit @cite{New_Page} operation was performed +before closing the file. + +A canonical Text_IO file that is a regular file (i.e., not a device or a +pipe) can be read using any of the routines in Text_IO. The +semantics in this case will be exactly as defined in the Ada Reference +Manual, and all the routines in Text_IO are fully implemented. + +A text file that does not meet the requirements for a canonical Text_IO +file has one of the following: + + +@itemize * + +@item +The file contains @cite{FF} characters not immediately following a +@cite{LF} character. + +@item +The file contains @cite{LF} or @cite{FF} characters written by +@cite{Put} or @cite{Put_Line}, which are not logically considered to be +line marks or page marks. + +@item +The file ends in a character other than @cite{LF} or @cite{FF}, +i.e., there is no explicit line mark or page mark at the end of the file. +@end itemize + +Text_IO can be used to read such non-standard text files but subprograms +to do with line or page numbers do not have defined meanings. In +particular, a @cite{FF} character that does not follow a @cite{LF} +character may or may not be treated as a page mark from the point of +view of page and line numbering. Every @cite{LF} character is considered +to end a line, and there is an implied @cite{LF} character at the end of +the file. + +@menu +* Stream Pointer Positioning:: +* Reading and Writing Non-Regular Files:: +* Get_Immediate:: +* Treating Text_IO Files as Streams:: +* Text_IO Extensions:: +* Text_IO Facilities for Unbounded Strings:: + +@end menu + +@node Stream Pointer Positioning,Reading and Writing Non-Regular Files,,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o id7}@anchor{24c}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning}@anchor{24d} +@subsection Stream Pointer Positioning + + +@cite{Ada.Text_IO} has a definition of current position for a file that +is being read. No internal buffering occurs in Text_IO, and usually the +physical position in the stream used to implement the file corresponds +to this logical position defined by Text_IO. There are two exceptions: + + +@itemize * + +@item +After a call to @cite{End_Of_Page} that returns @cite{True}, the stream +is positioned past the @cite{LF} (line mark) that precedes the page +mark. Text_IO maintains an internal flag so that subsequent read +operations properly handle the logical position which is unchanged by +the @cite{End_Of_Page} call. + +@item +After a call to @cite{End_Of_File} that returns @cite{True}, if the +Text_IO file was positioned before the line mark at the end of file +before the call, then the logical position is unchanged, but the stream +is physically positioned right at the end of file (past the line mark, +and past a possible page mark following the line mark. Again Text_IO +maintains internal flags so that subsequent read operations properly +handle the logical position. +@end itemize + +These discrepancies have no effect on the observable behavior of +Text_IO, but if a single Ada stream is shared between a C program and +Ada program, or shared (using @code{shared=yes} in the form string) +between two Ada files, then the difference may be observable in some +situations. + +@node Reading and Writing Non-Regular Files,Get_Immediate,Stream Pointer Positioning,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files}@anchor{24e}@anchor{gnat_rm/the_implementation_of_standard_i_o id8}@anchor{24f} +@subsection Reading and Writing Non-Regular Files + + +A non-regular file is a device (such as a keyboard), or a pipe. Text_IO +can be used for reading and writing. Writing is not affected and the +sequence of characters output is identical to the normal file case, but +for reading, the behavior of Text_IO is modified to avoid undesirable +look-ahead as follows: + +An input file that is not a regular file is considered to have no page +marks. Any @cite{Ascii.FF} characters (the character normally used for a +page mark) appearing in the file are considered to be data +characters. In particular: + + +@itemize * + +@item +@cite{Get_Line} and @cite{Skip_Line} do not test for a page mark +following a line mark. If a page mark appears, it will be treated as a +data character. + +@item +This avoids the need to wait for an extra character to be typed or +entered from the pipe to complete one of these operations. + +@item +@cite{End_Of_Page} always returns @cite{False} + +@item +@cite{End_Of_File} will return @cite{False} if there is a page mark at +the end of the file. +@end itemize + +Output to non-regular files is the same as for regular files. Page marks +may be written to non-regular files using @cite{New_Page}, but as noted +above they will not be treated as page marks on input if the output is +piped to another Ada program. + +Another important discrepancy when reading non-regular files is that the end +of file indication is not 'sticky'. If an end of file is entered, e.g., by +pressing the @code{EOT} key, +then end of file +is signaled once (i.e., the test @cite{End_Of_File} +will yield @cite{True}, or a read will +raise @cite{End_Error}), but then reading can resume +to read data past that end of +file indication, until another end of file indication is entered. + +@node Get_Immediate,Treating Text_IO Files as Streams,Reading and Writing Non-Regular Files,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o get-immediate}@anchor{250}@anchor{gnat_rm/the_implementation_of_standard_i_o id9}@anchor{251} +@subsection Get_Immediate + + +@geindex Get_Immediate + +Get_Immediate returns the next character (including control characters) +from the input file. In particular, Get_Immediate will return LF or FF +characters used as line marks or page marks. Such operations leave the +file positioned past the control character, and it is thus not treated +as having its normal function. This means that page, line and column +counts after this kind of Get_Immediate call are set as though the mark +did not occur. In the case where a Get_Immediate leaves the file +positioned between the line mark and page mark (which is not normally +possible), it is undefined whether the FF character will be treated as a +page mark. + +@node Treating Text_IO Files as Streams,Text_IO Extensions,Get_Immediate,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o id10}@anchor{252}@anchor{gnat_rm/the_implementation_of_standard_i_o treating-text-io-files-as-streams}@anchor{253} +@subsection Treating Text_IO Files as Streams + + +@geindex Stream files + +The package @cite{Text_IO.Streams} allows a Text_IO file to be treated +as a stream. Data written to a Text_IO file in this stream mode is +binary data. If this binary data contains bytes 16#0A# (@cite{LF}) or +16#0C# (@cite{FF}), the resulting file may have non-standard +format. Similarly if read operations are used to read from a Text_IO +file treated as a stream, then @cite{LF} and @cite{FF} characters may be +skipped and the effect is similar to that described above for +@cite{Get_Immediate}. + +@node Text_IO Extensions,Text_IO Facilities for Unbounded Strings,Treating Text_IO Files as Streams,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o id11}@anchor{254}@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-extensions}@anchor{255} +@subsection Text_IO Extensions + + +@geindex Text_IO extensions + +A package GNAT.IO_Aux in the GNAT library provides some useful extensions +to the standard @cite{Text_IO} package: + + +@itemize * + +@item +function File_Exists (Name : String) return Boolean; +Determines if a file of the given name exists. + +@item +function Get_Line return String; +Reads a string from the standard input file. The value returned is exactly +the length of the line that was read. + +@item +function Get_Line (File : Ada.Text_IO.File_Type) return String; +Similar, except that the parameter File specifies the file from which +the string is to be read. +@end itemize + +@node Text_IO Facilities for Unbounded Strings,,Text_IO Extensions,Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o text-io-facilities-for-unbounded-strings}@anchor{256}@anchor{gnat_rm/the_implementation_of_standard_i_o id12}@anchor{257} +@subsection Text_IO Facilities for Unbounded Strings + + +@geindex Text_IO for unbounded strings + +@geindex Unbounded_String +@geindex Text_IO operations + +The package @cite{Ada.Strings.Unbounded.Text_IO} +in library files @cite{a-suteio.ads/adb} contains some GNAT-specific +subprograms useful for Text_IO operations on unbounded strings: + + +@itemize * + +@item +function Get_Line (File : File_Type) return Unbounded_String; +Reads a line from the specified file +and returns the result as an unbounded string. + +@item +procedure Put (File : File_Type; U : Unbounded_String); +Writes the value of the given unbounded string to the specified file +Similar to the effect of +@cite{Put (To_String (U))} except that an extra copy is avoided. + +@item +procedure Put_Line (File : File_Type; U : Unbounded_String); +Writes the value of the given unbounded string to the specified file, +followed by a @cite{New_Line}. +Similar to the effect of @cite{Put_Line (To_String (U))} except +that an extra copy is avoided. +@end itemize + +In the above procedures, @cite{File} is of type @cite{Ada.Text_IO.File_Type} +and is optional. If the parameter is omitted, then the standard input or +output file is referenced as appropriate. + +The package @cite{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library +files @code{a-swuwti.ads} and @code{a-swuwti.adb} provides similar extended +@cite{Wide_Text_IO} functionality for unbounded wide strings. + +The package @cite{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library +files @code{a-szuzti.ads} and @code{a-szuzti.adb} provides similar extended +@cite{Wide_Wide_Text_IO} functionality for unbounded wide wide strings. + +@node Wide_Text_IO,Wide_Wide_Text_IO,Text_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o wide-text-io}@anchor{258}@anchor{gnat_rm/the_implementation_of_standard_i_o id13}@anchor{259} +@section Wide_Text_IO + + +@cite{Wide_Text_IO} is similar in most respects to Text_IO, except that +both input and output files may contain special sequences that represent +wide character values. The encoding scheme for a given file may be +specified using a FORM parameter: + +@example +WCEM=`x` +@end example + +as part of the FORM string (WCEM = wide character encoding method), +where @cite{x} is one of the following characters + + +@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Character + +@tab + +Encoding + +@item + +@emph{h} + +@tab + +Hex ESC encoding + +@item + +@emph{u} + +@tab + +Upper half encoding + +@item + +@emph{s} + +@tab + +Shift-JIS encoding + +@item + +@emph{e} + +@tab + +EUC Encoding + +@item + +@emph{8} + +@tab + +UTF-8 encoding + +@item + +@emph{b} + +@tab + +Brackets encoding + +@end multitable + + +The encoding methods match those that +can be used in a source +program, but there is no requirement that the encoding method used for +the source program be the same as the encoding method used for files, +and different files may use different encoding methods. + +The default encoding method for the standard files, and for opened files +for which no WCEM parameter is given in the FORM string matches the +wide character encoding specified for the main program (the default +being brackets encoding if no coding method was specified with -gnatW). + + +@table @asis + +@item @emph{Hex Coding} + +In this encoding, a wide character is represented by a five character +sequence: +@end table + +@example +ESC a b c d +@end example + + +@quotation + +where @cite{a}, @cite{b}, @cite{c}, @cite{d} are the four hexadecimal +characters (using upper case letters) of the wide character code. For +example, ESC A345 is used to represent the wide character with code +16#A345#. This scheme is compatible with use of the full +@cite{Wide_Character} set. +@end quotation + + +@table @asis + +@item @emph{Upper Half Coding} + +The wide character with encoding 16#abcd#, where the upper bit is on +(i.e., a is in the range 8-F) is represented as two bytes 16#ab# and +16#cd#. The second byte may never be a format control character, but is +not required to be in the upper half. This method can be also used for +shift-JIS or EUC where the internal coding matches the external coding. + +@item @emph{Shift JIS Coding} + +A wide character is represented by a two character sequence 16#ab# and +16#cd#, with the restrictions described for upper half encoding as +described above. The internal character code is the corresponding JIS +character according to the standard algorithm for Shift-JIS +conversion. Only characters defined in the JIS code set table can be +used with this encoding method. + +@item @emph{EUC Coding} + +A wide character is represented by a two character sequence 16#ab# and +16#cd#, with both characters being in the upper half. The internal +character code is the corresponding JIS character according to the EUC +encoding algorithm. Only characters defined in the JIS code set table +can be used with this encoding method. + +@item @emph{UTF-8 Coding} + +A wide character is represented using +UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO +10646-1/Am.2. Depending on the character value, the representation +is a one, two, or three byte sequence: +@end table + +@example +16#0000#-16#007f#: 2#0xxxxxxx# +16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx# +16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# +@end example + + +@quotation + +where the @cite{xxx} bits correspond to the left-padded bits of the +16-bit character value. Note that all lower half ASCII characters +are represented as ASCII bytes and all upper half characters and +other wide characters are represented as sequences of upper-half +(The full UTF-8 scheme allows for encoding 31-bit characters as +6-byte sequences, but in this implementation, all UTF-8 sequences +of four or more bytes length will raise a Constraint_Error, as +will all invalid UTF-8 sequences.) +@end quotation + + +@table @asis + +@item @emph{Brackets Coding} + +In this encoding, a wide character is represented by the following eight +character sequence: +@end table + +@example +[ " a b c d " ] +@end example + + +@quotation + +where @cite{a}, @cite{b}, @cite{c}, @cite{d} are the four hexadecimal +characters (using uppercase letters) of the wide character code. For +example, @cite{["A345"]} is used to represent the wide character with code +@cite{16#A345#}. +This scheme is compatible with use of the full Wide_Character set. +On input, brackets coding can also be used for upper half characters, +e.g., @cite{["C1"]} for lower case a. However, on output, brackets notation +is only used for wide characters with a code greater than @cite{16#FF#}. + +Note that brackets coding is not normally used in the context of +Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as +a portable way of encoding source files. In the context of Wide_Text_IO +or Wide_Wide_Text_IO, it can only be used if the file does not contain +any instance of the left bracket character other than to encode wide +character values using the brackets encoding method. In practice it is +expected that some standard wide character encoding method such +as UTF-8 will be used for text input output. + +If brackets notation is used, then any occurrence of a left bracket +in the input file which is not the start of a valid wide character +sequence will cause Constraint_Error to be raised. It is possible to +encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO +input will interpret this as a left bracket. + +However, when a left bracket is output, it will be output as a left bracket +and not as ["5B"]. We make this decision because for normal use of +Wide_Text_IO for outputting messages, it is unpleasant to clobber left +brackets. For example, if we write: + +@example +Put_Line ("Start of output [first run]"); +@end example + +we really do not want to have the left bracket in this message clobbered so +that the output reads: +@end quotation + +@example +Start of output ["5B"]first run] +@end example + + +@quotation + +In practice brackets encoding is reasonably useful for normal Put_Line use +since we won't get confused between left brackets and wide character +sequences in the output. But for input, or when files are written out +and read back in, it really makes better sense to use one of the standard +encoding methods such as UTF-8. +@end quotation + +For the coding schemes other than UTF-8, Hex, or Brackets encoding, +not all wide character +values can be represented. An attempt to output a character that cannot +be represented using the encoding scheme for the file causes +Constraint_Error to be raised. An invalid wide character sequence on +input also causes Constraint_Error to be raised. + +@menu +* Stream Pointer Positioning: Stream Pointer Positioning<2>. +* Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<2>. + +@end menu + +@node Stream Pointer Positioning<2>,Reading and Writing Non-Regular Files<2>,,Wide_Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-1}@anchor{25a}@anchor{gnat_rm/the_implementation_of_standard_i_o id14}@anchor{25b} +@subsection Stream Pointer Positioning + + +@cite{Ada.Wide_Text_IO} is similar to @cite{Ada.Text_IO} in its handling +of stream pointer positioning (@ref{24b,,Text_IO}). There is one additional +case: + +If @cite{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the +normal lower ASCII set (i.e., a character in the range: + +@example +Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#) +@end example + +then although the logical position of the file pointer is unchanged by +the @cite{Look_Ahead} call, the stream is physically positioned past the +wide character sequence. Again this is to avoid the need for buffering +or backup, and all @cite{Wide_Text_IO} routines check the internal +indication that this situation has occurred so that this is not visible +to a normal program using @cite{Wide_Text_IO}. However, this discrepancy +can be observed if the wide text file shares a stream with another file. + +@node Reading and Writing Non-Regular Files<2>,,Stream Pointer Positioning<2>,Wide_Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-1}@anchor{25c}@anchor{gnat_rm/the_implementation_of_standard_i_o id15}@anchor{25d} +@subsection Reading and Writing Non-Regular Files + + +As in the case of Text_IO, when a non-regular file is read, it is +assumed that the file contains no page marks (any form characters are +treated as data characters), and @cite{End_Of_Page} always returns +@cite{False}. Similarly, the end of file indication is not sticky, so +it is possible to read beyond an end of file. + +@node Wide_Wide_Text_IO,Stream_IO,Wide_Text_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o id16}@anchor{25e}@anchor{gnat_rm/the_implementation_of_standard_i_o wide-wide-text-io}@anchor{25f} +@section Wide_Wide_Text_IO + + +@cite{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that +both input and output files may contain special sequences that represent +wide wide character values. The encoding scheme for a given file may be +specified using a FORM parameter: + +@example +WCEM=`x` +@end example + +as part of the FORM string (WCEM = wide character encoding method), +where @cite{x} is one of the following characters + + +@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxx} +@headitem + +Character + +@tab + +Encoding + +@item + +@emph{h} + +@tab + +Hex ESC encoding + +@item + +@emph{u} + +@tab + +Upper half encoding + +@item + +@emph{s} + +@tab + +Shift-JIS encoding + +@item + +@emph{e} + +@tab + +EUC Encoding + +@item + +@emph{8} + +@tab + +UTF-8 encoding + +@item + +@emph{b} + +@tab + +Brackets encoding + +@end multitable + + +The encoding methods match those that +can be used in a source +program, but there is no requirement that the encoding method used for +the source program be the same as the encoding method used for files, +and different files may use different encoding methods. + +The default encoding method for the standard files, and for opened files +for which no WCEM parameter is given in the FORM string matches the +wide character encoding specified for the main program (the default +being brackets encoding if no coding method was specified with -gnatW). + + +@table @asis + +@item @emph{UTF-8 Coding} + +A wide character is represented using +UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO +10646-1/Am.2. Depending on the character value, the representation +is a one, two, three, or four byte sequence: +@end table + +@example +16#000000#-16#00007f#: 2#0xxxxxxx# +16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx# +16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# +16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx# +@end example + + +@quotation + +where the @cite{xxx} bits correspond to the left-padded bits of the +21-bit character value. Note that all lower half ASCII characters +are represented as ASCII bytes and all upper half characters and +other wide characters are represented as sequences of upper-half +characters. +@end quotation + + +@table @asis + +@item @emph{Brackets Coding} + +In this encoding, a wide wide character is represented by the following eight +character sequence if is in wide character range +@end table + +@example +[ " a b c d " ] +@end example + + +@quotation + +and by the following ten character sequence if not +@end quotation + +@example +[ " a b c d e f " ] +@end example + + +@quotation + +where @cite{a}, @cite{b}, @cite{c}, @cite{d}, @cite{e}, and @cite{f} +are the four or six hexadecimal +characters (using uppercase letters) of the wide wide character code. For +example, @cite{["01A345"]} is used to represent the wide wide character +with code @cite{16#01A345#}. + +This scheme is compatible with use of the full Wide_Wide_Character set. +On input, brackets coding can also be used for upper half characters, +e.g., @cite{["C1"]} for lower case a. However, on output, brackets notation +is only used for wide characters with a code greater than @cite{16#FF#}. +@end quotation + +If is also possible to use the other Wide_Character encoding methods, +such as Shift-JIS, but the other schemes cannot support the full range +of wide wide characters. +An attempt to output a character that cannot +be represented using the encoding scheme for the file causes +Constraint_Error to be raised. An invalid wide character sequence on +input also causes Constraint_Error to be raised. + +@menu +* Stream Pointer Positioning: Stream Pointer Positioning<3>. +* Reading and Writing Non-Regular Files: Reading and Writing Non-Regular Files<3>. + +@end menu + +@node Stream Pointer Positioning<3>,Reading and Writing Non-Regular Files<3>,,Wide_Wide_Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o stream-pointer-positioning-2}@anchor{260}@anchor{gnat_rm/the_implementation_of_standard_i_o id17}@anchor{261} +@subsection Stream Pointer Positioning + + +@cite{Ada.Wide_Wide_Text_IO} is similar to @cite{Ada.Text_IO} in its handling +of stream pointer positioning (@ref{24b,,Text_IO}). There is one additional +case: + +If @cite{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the +normal lower ASCII set (i.e., a character in the range: + +@example +Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#) +@end example + +then although the logical position of the file pointer is unchanged by +the @cite{Look_Ahead} call, the stream is physically positioned past the +wide character sequence. Again this is to avoid the need for buffering +or backup, and all @cite{Wide_Wide_Text_IO} routines check the internal +indication that this situation has occurred so that this is not visible +to a normal program using @cite{Wide_Wide_Text_IO}. However, this discrepancy +can be observed if the wide text file shares a stream with another file. + +@node Reading and Writing Non-Regular Files<3>,,Stream Pointer Positioning<3>,Wide_Wide_Text_IO +@anchor{gnat_rm/the_implementation_of_standard_i_o id18}@anchor{262}@anchor{gnat_rm/the_implementation_of_standard_i_o reading-and-writing-non-regular-files-2}@anchor{263} +@subsection Reading and Writing Non-Regular Files + + +As in the case of Text_IO, when a non-regular file is read, it is +assumed that the file contains no page marks (any form characters are +treated as data characters), and @cite{End_Of_Page} always returns +@cite{False}. Similarly, the end of file indication is not sticky, so +it is possible to read beyond an end of file. + +@node Stream_IO,Text Translation,Wide_Wide_Text_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o id19}@anchor{264}@anchor{gnat_rm/the_implementation_of_standard_i_o stream-io}@anchor{265} +@section Stream_IO + + +A stream file is a sequence of bytes, where individual elements are +written to the file as described in the Ada Reference Manual. The type +@cite{Stream_Element} is simply a byte. There are two ways to read or +write a stream file. + + +@itemize * + +@item +The operations @cite{Read} and @cite{Write} directly read or write a +sequence of stream elements with no control information. + +@item +The stream attributes applied to a stream file transfer data in the +manner described for stream attributes. +@end itemize + +@node Text Translation,Shared Files,Stream_IO,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o id20}@anchor{266}@anchor{gnat_rm/the_implementation_of_standard_i_o text-translation}@anchor{267} +@section Text Translation + + +@code{Text_Translation=xxx} may be used as the Form parameter +passed to Text_IO.Create and Text_IO.Open. @code{Text_Translation=xxx} +has no effect on Unix systems. Possible values are: + + +@itemize * + +@item +@code{Yes} or @code{Text} is the default, which means to +translate LF to/from CR/LF on Windows systems. + +@code{No} disables this translation; i.e. it +uses binary mode. For output files, @code{Text_Translation=No} +may be used to create Unix-style files on +Windows. + +@item +@code{wtext} translation enabled in Unicode mode. +(corresponds to _O_WTEXT). + +@item +@code{u8text} translation enabled in Unicode UTF-8 mode. +(corresponds to O_U8TEXT). + +@item +@code{u16text} translation enabled in Unicode UTF-16 +mode. (corresponds to_O_U16TEXT). +@end itemize + +@node Shared Files,Filenames encoding,Text Translation,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o id21}@anchor{268}@anchor{gnat_rm/the_implementation_of_standard_i_o shared-files}@anchor{269} +@section Shared Files + + +Section A.14 of the Ada Reference Manual allows implementations to +provide a wide variety of behavior if an attempt is made to access the +same external file with two or more internal files. + +To provide a full range of functionality, while at the same time +minimizing the problems of portability caused by this implementation +dependence, GNAT handles file sharing as follows: + + +@itemize * + +@item +In the absence of a @code{shared=xxx} form parameter, an attempt +to open two or more files with the same full name is considered an error +and is not supported. The exception @cite{Use_Error} will be +raised. Note that a file that is not explicitly closed by the program +remains open until the program terminates. + +@item +If the form parameter @code{shared=no} appears in the form string, the +file can be opened or created with its own separate stream identifier, +regardless of whether other files sharing the same external file are +opened. The exact effect depends on how the C stream routines handle +multiple accesses to the same external files using separate streams. + +@item +If the form parameter @code{shared=yes} appears in the form string for +each of two or more files opened using the same full name, the same +stream is shared between these files, and the semantics are as described +in Ada Reference Manual, Section A.14. +@end itemize + +When a program that opens multiple files with the same name is ported +from another Ada compiler to GNAT, the effect will be that +@cite{Use_Error} is raised. + +The documentation of the original compiler and the documentation of the +program should then be examined to determine if file sharing was +expected, and @code{shared=xxx} parameters added to @cite{Open} +and @cite{Create} calls as required. + +When a program is ported from GNAT to some other Ada compiler, no +special attention is required unless the @code{shared=xxx} form +parameter is used in the program. In this case, you must examine the +documentation of the new compiler to see if it supports the required +file sharing semantics, and form strings modified appropriately. Of +course it may be the case that the program cannot be ported if the +target compiler does not support the required functionality. The best +approach in writing portable code is to avoid file sharing (and hence +the use of the @code{shared=xxx} parameter in the form string) +completely. + +One common use of file sharing in Ada 83 is the use of instantiations of +Sequential_IO on the same file with different types, to achieve +heterogeneous input-output. Although this approach will work in GNAT if +@code{shared=yes} is specified, it is preferable in Ada to use Stream_IO +for this purpose (using the stream attributes) + +@node Filenames encoding,File content encoding,Shared Files,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o filenames-encoding}@anchor{26a}@anchor{gnat_rm/the_implementation_of_standard_i_o id22}@anchor{26b} +@section Filenames encoding + + +An encoding form parameter can be used to specify the filename +encoding @code{encoding=xxx}. + + +@itemize * + +@item +If the form parameter @code{encoding=utf8} appears in the form string, the +filename must be encoded in UTF-8. + +@item +If the form parameter @code{encoding=8bits} appears in the form +string, the filename must be a standard 8bits string. +@end itemize + +In the absence of a @code{encoding=xxx} form parameter, the +encoding is controlled by the @code{GNAT_CODE_PAGE} environment +variable. And if not set @code{utf8} is assumed. + + +@table @asis + +@item @emph{CP_ACP} + +The current system Windows ANSI code page. + +@item @emph{CP_UTF8} + +UTF-8 encoding +@end table + +This encoding form parameter is only supported on the Windows +platform. On the other Operating Systems the run-time is supporting +UTF-8 natively. + +@node File content encoding,Open Modes,Filenames encoding,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o file-content-encoding}@anchor{26c}@anchor{gnat_rm/the_implementation_of_standard_i_o id23}@anchor{26d} +@section File content encoding + + +For text files it is possible to specify the encoding to use. This is +controlled by the by the @code{GNAT_CCS_ENCODING} environment +variable. And if not set @code{TEXT} is assumed. + +The possible values are those supported on Windows: + + +@table @asis + +@item @emph{TEXT} + +Translated text mode + +@item @emph{WTEXT} + +Translated unicode encoding + +@item @emph{U16TEXT} + +Unicode 16-bit encoding + +@item @emph{U8TEXT} + +Unicode 8-bit encoding +@end table + +This encoding is only supported on the Windows platform. + +@node Open Modes,Operations on C Streams,File content encoding,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o open-modes}@anchor{26e}@anchor{gnat_rm/the_implementation_of_standard_i_o id24}@anchor{26f} +@section Open Modes + + +@cite{Open} and @cite{Create} calls result in a call to @cite{fopen} +using the mode shown in the following table: + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxx} +@headitem + +@cite{Open} and @cite{Create} Call Modes + +@tab + +@tab + +@item + +@tab + +@strong{OPEN} + +@tab + +@strong{CREATE} + +@item + +Append_File + +@tab + +"r+" + +@tab + +"w+" + +@item + +In_File + +@tab + +"r" + +@tab + +"w+" + +@item + +Out_File (Direct_IO) + +@tab + +"r+" + +@tab + +"w" + +@item + +Out_File (all other cases) + +@tab + +"w" + +@tab + +"w" + +@item + +Inout_File + +@tab + +"r+" + +@tab + +"w+" + +@end multitable + + +If text file translation is required, then either @code{b} or @code{t} +is added to the mode, depending on the setting of Text. Text file +translation refers to the mapping of CR/LF sequences in an external file +to LF characters internally. This mapping only occurs in DOS and +DOS-like systems, and is not relevant to other systems. + +A special case occurs with Stream_IO. As shown in the above table, the +file is initially opened in @code{r} or @code{w} mode for the +@cite{In_File} and @cite{Out_File} cases. If a @cite{Set_Mode} operation +subsequently requires switching from reading to writing or vice-versa, +then the file is reopened in @code{r+} mode to permit the required operation. + +@node Operations on C Streams,Interfacing to C Streams,Open Modes,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o operations-on-c-streams}@anchor{270}@anchor{gnat_rm/the_implementation_of_standard_i_o id25}@anchor{271} +@section Operations on C Streams + + +The package @cite{Interfaces.C_Streams} provides an Ada program with direct +access to the C library functions for operations on C streams: + +@example +package Interfaces.C_Streams is + -- Note: the reason we do not use the types that are in + -- Interfaces.C is that we want to avoid dragging in the + -- code in this unit if possible. + subtype chars is System.Address; + -- Pointer to null-terminated array of characters + subtype FILEs is System.Address; + -- Corresponds to the C type FILE* + subtype voids is System.Address; + -- Corresponds to the C type void* + subtype int is Integer; + subtype long is Long_Integer; + -- Note: the above types are subtypes deliberately, and it + -- is part of this spec that the above correspondences are + -- guaranteed. This means that it is legitimate to, for + -- example, use Integer instead of int. We provide these + -- synonyms for clarity, but in some cases it may be + -- convenient to use the underlying types (for example to + -- avoid an unnecessary dependency of a spec on the spec + -- of this unit). + type size_t is mod 2 ** Standard'Address_Size; + NULL_Stream : constant FILEs; + -- Value returned (NULL in C) to indicate an + -- fdopen/fopen/tmpfile error + ---------------------------------- + -- Constants Defined in stdio.h -- + ---------------------------------- + EOF : constant int; + -- Used by a number of routines to indicate error or + -- end of file + IOFBF : constant int; + IOLBF : constant int; + IONBF : constant int; + -- Used to indicate buffering mode for setvbuf call + SEEK_CUR : constant int; + SEEK_END : constant int; + SEEK_SET : constant int; + -- Used to indicate origin for fseek call + function stdin return FILEs; + function stdout return FILEs; + function stderr return FILEs; + -- Streams associated with standard files + -------------------------- + -- Standard C functions -- + -------------------------- + -- The functions selected below are ones that are + -- available in UNIX (but not necessarily in ANSI C). + -- These are very thin interfaces + -- which copy exactly the C headers. For more + -- documentation on these functions, see the Microsoft C + -- "Run-Time Library Reference" (Microsoft Press, 1990, + -- ISBN 1-55615-225-6), which includes useful information + -- on system compatibility. + procedure clearerr (stream : FILEs); + function fclose (stream : FILEs) return int; + function fdopen (handle : int; mode : chars) return FILEs; + function feof (stream : FILEs) return int; + function ferror (stream : FILEs) return int; + function fflush (stream : FILEs) return int; + function fgetc (stream : FILEs) return int; + function fgets (strng : chars; n : int; stream : FILEs) + return chars; + function fileno (stream : FILEs) return int; + function fopen (filename : chars; Mode : chars) + return FILEs; + -- Note: to maintain target independence, use + -- text_translation_required, a boolean variable defined in + -- a-sysdep.c to deal with the target dependent text + -- translation requirement. If this variable is set, + -- then b/t should be appended to the standard mode + -- argument to set the text translation mode off or on + -- as required. + function fputc (C : int; stream : FILEs) return int; + function fputs (Strng : chars; Stream : FILEs) return int; + function fread + (buffer : voids; + size : size_t; + count : size_t; + stream : FILEs) + return size_t; + function freopen + (filename : chars; + mode : chars; + stream : FILEs) + return FILEs; + function fseek + (stream : FILEs; + offset : long; + origin : int) + return int; + function ftell (stream : FILEs) return long; + function fwrite + (buffer : voids; + size : size_t; + count : size_t; + stream : FILEs) + return size_t; + function isatty (handle : int) return int; + procedure mktemp (template : chars); + -- The return value (which is just a pointer to template) + -- is discarded + procedure rewind (stream : FILEs); + function rmtmp return int; + function setvbuf + (stream : FILEs; + buffer : chars; + mode : int; + size : size_t) + return int; + + function tmpfile return FILEs; + function ungetc (c : int; stream : FILEs) return int; + function unlink (filename : chars) return int; + --------------------- + -- Extra functions -- + --------------------- + -- These functions supply slightly thicker bindings than + -- those above. They are derived from functions in the + -- C Run-Time Library, but may do a bit more work than + -- just directly calling one of the Library functions. + function is_regular_file (handle : int) return int; + -- Tests if given handle is for a regular file (result 1) + -- or for a non-regular file (pipe or device, result 0). + --------------------------------- + -- Control of Text/Binary Mode -- + --------------------------------- + -- If text_translation_required is true, then the following + -- functions may be used to dynamically switch a file from + -- binary to text mode or vice versa. These functions have + -- no effect if text_translation_required is false (i.e., in + -- normal UNIX mode). Use fileno to get a stream handle. + procedure set_binary_mode (handle : int); + procedure set_text_mode (handle : int); + ---------------------------- + -- Full Path Name support -- + ---------------------------- + procedure full_name (nam : chars; buffer : chars); + -- Given a NUL terminated string representing a file + -- name, returns in buffer a NUL terminated string + -- representing the full path name for the file name. + -- On systems where it is relevant the drive is also + -- part of the full path name. It is the responsibility + -- of the caller to pass an actual parameter for buffer + -- that is big enough for any full path name. Use + -- max_path_len given below as the size of buffer. + max_path_len : integer; + -- Maximum length of an allowable full path name on the + -- system, including a terminating NUL character. +end Interfaces.C_Streams; +@end example + +@node Interfacing to C Streams,,Operations on C Streams,The Implementation of Standard I/O +@anchor{gnat_rm/the_implementation_of_standard_i_o interfacing-to-c-streams}@anchor{272}@anchor{gnat_rm/the_implementation_of_standard_i_o id26}@anchor{273} +@section Interfacing to C Streams + + +The packages in this section permit interfacing Ada files to C Stream +operations. + +@example +with Interfaces.C_Streams; +package Ada.Sequential_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); +end Ada.Sequential_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Direct_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Direct_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); + end Ada.Text_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Wide_Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); +end Ada.Wide_Text_IO.C_Streams; + + with Interfaces.C_Streams; + package Ada.Wide_Wide_Text_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); +end Ada.Wide_Wide_Text_IO.C_Streams; + +with Interfaces.C_Streams; +package Ada.Stream_IO.C_Streams is + function C_Stream (F : File_Type) + return Interfaces.C_Streams.FILEs; + procedure Open + (File : in out File_Type; + Mode : in File_Mode; + C_Stream : in Interfaces.C_Streams.FILEs; + Form : in String := ""); +end Ada.Stream_IO.C_Streams; +@end example + +In each of these six packages, the @cite{C_Stream} function obtains the +@cite{FILE} pointer from a currently opened Ada file. It is then +possible to use the @cite{Interfaces.C_Streams} package to operate on +this stream, or the stream can be passed to a C program which can +operate on it directly. Of course the program is responsible for +ensuring that only appropriate sequences of operations are executed. + +One particular use of relevance to an Ada program is that the +@cite{setvbuf} function can be used to control the buffering of the +stream used by an Ada file. In the absence of such a call the standard +default buffering is used. + +The @cite{Open} procedures in these packages open a file giving an +existing C Stream instead of a file name. Typically this stream is +imported from a C program, allowing an Ada file to operate on an +existing C file. + +@node The GNAT Library,Interfacing to Other Languages,The Implementation of Standard I/O,Top +@anchor{gnat_rm/the_gnat_library the-gnat-library}@anchor{10}@anchor{gnat_rm/the_gnat_library doc}@anchor{274}@anchor{gnat_rm/the_gnat_library id1}@anchor{275} +@chapter The GNAT Library + + +The GNAT library contains a number of general and special purpose packages. +It represents functionality that the GNAT developers have found useful, and +which is made available to GNAT users. The packages described here are fully +supported, and upwards compatibility will be maintained in future releases, +so you can use these facilities with the confidence that the same functionality +will be available in future releases. + +The chapter here simply gives a brief summary of the facilities available. +The full documentation is found in the spec file for the package. The full +sources of these library packages, including both spec and body, are provided +with all GNAT releases. For example, to find out the full specifications of +the SPITBOL pattern matching capability, including a full tutorial and +extensive examples, look in the @code{g-spipat.ads} file in the library. + +For each entry here, the package name (as it would appear in a @cite{with} +clause) is given, followed by the name of the corresponding spec file in +parentheses. The packages are children in four hierarchies, @cite{Ada}, +@cite{Interfaces}, @cite{System}, and @cite{GNAT}, the latter being a +GNAT-specific hierarchy. + +Note that an application program should only use packages in one of these +four hierarchies if the package is defined in the Ada Reference Manual, +or is listed in this section of the GNAT Programmers Reference Manual. +All other units should be considered internal implementation units and +should not be directly @cite{with}'ed by application code. The use of +a @cite{with} statement that references one of these internal implementation +units makes an application potentially dependent on changes in versions +of GNAT, and will generate a warning message. + +@menu +* Ada.Characters.Latin_9 (a-chlat9.ads): Ada Characters Latin_9 a-chlat9 ads. +* Ada.Characters.Wide_Latin_1 (a-cwila1.ads): Ada Characters Wide_Latin_1 a-cwila1 ads. +* Ada.Characters.Wide_Latin_9 (a-cwila1.ads): Ada Characters Wide_Latin_9 a-cwila1 ads. +* Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads): Ada Characters Wide_Wide_Latin_1 a-chzla1 ads. +* Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads): Ada Characters Wide_Wide_Latin_9 a-chzla9 ads. +* Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads): Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads. +* Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads): Ada Containers Formal_Hashed_Maps a-cfhama ads. +* Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads): Ada Containers Formal_Hashed_Sets a-cfhase ads. +* Ada.Containers.Formal_Ordered_Maps (a-cforma.ads): Ada Containers Formal_Ordered_Maps a-cforma ads. +* Ada.Containers.Formal_Ordered_Sets (a-cforse.ads): Ada Containers Formal_Ordered_Sets a-cforse ads. +* Ada.Containers.Formal_Vectors (a-cofove.ads): Ada Containers Formal_Vectors a-cofove ads. +* Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads): Ada Containers Formal_Indefinite_Vectors a-cfinve ads. +* Ada.Containers.Bounded_Holders (a-coboho.ads): Ada Containers Bounded_Holders a-coboho ads. +* Ada.Command_Line.Environment (a-colien.ads): Ada Command_Line Environment a-colien ads. +* Ada.Command_Line.Remove (a-colire.ads): Ada Command_Line Remove a-colire ads. +* Ada.Command_Line.Response_File (a-clrefi.ads): Ada Command_Line Response_File a-clrefi ads. +* Ada.Direct_IO.C_Streams (a-diocst.ads): Ada Direct_IO C_Streams a-diocst ads. +* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads): Ada Exceptions Is_Null_Occurrence a-einuoc ads. +* Ada.Exceptions.Last_Chance_Handler (a-elchha.ads): Ada Exceptions Last_Chance_Handler a-elchha ads. +* Ada.Exceptions.Traceback (a-exctra.ads): Ada Exceptions Traceback a-exctra ads. +* Ada.Sequential_IO.C_Streams (a-siocst.ads): Ada Sequential_IO C_Streams a-siocst ads. +* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads): Ada Streams Stream_IO C_Streams a-ssicst ads. +* Ada.Strings.Unbounded.Text_IO (a-suteio.ads): Ada Strings Unbounded Text_IO a-suteio ads. +* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads): Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads. +* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads): Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads. +* Ada.Text_IO.C_Streams (a-tiocst.ads): Ada Text_IO C_Streams a-tiocst ads. +* Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads): Ada Text_IO Reset_Standard_Files a-tirsfi ads. +* Ada.Wide_Characters.Unicode (a-wichun.ads): Ada Wide_Characters Unicode a-wichun ads. +* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads): Ada Wide_Text_IO C_Streams a-wtcstr ads. +* Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads): Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads. +* Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads): Ada Wide_Wide_Characters Unicode a-zchuni ads. +* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads): Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads. +* Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads): Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads. +* GNAT.Altivec (g-altive.ads): GNAT Altivec g-altive ads. +* GNAT.Altivec.Conversions (g-altcon.ads): GNAT Altivec Conversions g-altcon ads. +* GNAT.Altivec.Vector_Operations (g-alveop.ads): GNAT Altivec Vector_Operations g-alveop ads. +* GNAT.Altivec.Vector_Types (g-alvety.ads): GNAT Altivec Vector_Types g-alvety ads. +* GNAT.Altivec.Vector_Views (g-alvevi.ads): GNAT Altivec Vector_Views g-alvevi ads. +* GNAT.Array_Split (g-arrspl.ads): GNAT Array_Split g-arrspl ads. +* GNAT.AWK (g-awk.ads): GNAT AWK g-awk ads. +* GNAT.Bounded_Buffers (g-boubuf.ads): GNAT Bounded_Buffers g-boubuf ads. +* GNAT.Bounded_Mailboxes (g-boumai.ads): GNAT Bounded_Mailboxes g-boumai ads. +* GNAT.Bubble_Sort (g-bubsor.ads): GNAT Bubble_Sort g-bubsor ads. +* GNAT.Bubble_Sort_A (g-busora.ads): GNAT Bubble_Sort_A g-busora ads. +* GNAT.Bubble_Sort_G (g-busorg.ads): GNAT Bubble_Sort_G g-busorg ads. +* GNAT.Byte_Order_Mark (g-byorma.ads): GNAT Byte_Order_Mark g-byorma ads. +* GNAT.Byte_Swapping (g-bytswa.ads): GNAT Byte_Swapping g-bytswa ads. +* GNAT.Calendar (g-calend.ads): GNAT Calendar g-calend ads. +* GNAT.Calendar.Time_IO (g-catiio.ads): GNAT Calendar Time_IO g-catiio ads. +* GNAT.CRC32 (g-crc32.ads): GNAT CRC32 g-crc32 ads. +* GNAT.Case_Util (g-casuti.ads): GNAT Case_Util g-casuti ads. +* GNAT.CGI (g-cgi.ads): GNAT CGI g-cgi ads. +* GNAT.CGI.Cookie (g-cgicoo.ads): GNAT CGI Cookie g-cgicoo ads. +* GNAT.CGI.Debug (g-cgideb.ads): GNAT CGI Debug g-cgideb ads. +* GNAT.Command_Line (g-comlin.ads): GNAT Command_Line g-comlin ads. +* GNAT.Compiler_Version (g-comver.ads): GNAT Compiler_Version g-comver ads. +* GNAT.Ctrl_C (g-ctrl_c.ads): GNAT Ctrl_C g-ctrl_c ads. +* GNAT.Current_Exception (g-curexc.ads): GNAT Current_Exception g-curexc ads. +* GNAT.Debug_Pools (g-debpoo.ads): GNAT Debug_Pools g-debpoo ads. +* GNAT.Debug_Utilities (g-debuti.ads): GNAT Debug_Utilities g-debuti ads. +* GNAT.Decode_String (g-decstr.ads): GNAT Decode_String g-decstr ads. +* GNAT.Decode_UTF8_String (g-deutst.ads): GNAT Decode_UTF8_String g-deutst ads. +* GNAT.Directory_Operations (g-dirope.ads): GNAT Directory_Operations g-dirope ads. +* GNAT.Directory_Operations.Iteration (g-diopit.ads): GNAT Directory_Operations Iteration g-diopit ads. +* GNAT.Dynamic_HTables (g-dynhta.ads): GNAT Dynamic_HTables g-dynhta ads. +* GNAT.Dynamic_Tables (g-dyntab.ads): GNAT Dynamic_Tables g-dyntab ads. +* GNAT.Encode_String (g-encstr.ads): GNAT Encode_String g-encstr ads. +* GNAT.Encode_UTF8_String (g-enutst.ads): GNAT Encode_UTF8_String g-enutst ads. +* GNAT.Exception_Actions (g-excact.ads): GNAT Exception_Actions g-excact ads. +* GNAT.Exception_Traces (g-exctra.ads): GNAT Exception_Traces g-exctra ads. +* GNAT.Exceptions (g-expect.ads): GNAT Exceptions g-expect ads. +* GNAT.Expect (g-expect.ads): GNAT Expect g-expect ads. +* GNAT.Expect.TTY (g-exptty.ads): GNAT Expect TTY g-exptty ads. +* GNAT.Float_Control (g-flocon.ads): GNAT Float_Control g-flocon ads. +* GNAT.Formatted_String (g-forstr.ads): GNAT Formatted_String g-forstr ads. +* GNAT.Heap_Sort (g-heasor.ads): GNAT Heap_Sort g-heasor ads. +* GNAT.Heap_Sort_A (g-hesora.ads): GNAT Heap_Sort_A g-hesora ads. +* GNAT.Heap_Sort_G (g-hesorg.ads): GNAT Heap_Sort_G g-hesorg ads. +* GNAT.HTable (g-htable.ads): GNAT HTable g-htable ads. +* GNAT.IO (g-io.ads): GNAT IO g-io ads. +* GNAT.IO_Aux (g-io_aux.ads): GNAT IO_Aux g-io_aux ads. +* GNAT.Lock_Files (g-locfil.ads): GNAT Lock_Files g-locfil ads. +* GNAT.MBBS_Discrete_Random (g-mbdira.ads): GNAT MBBS_Discrete_Random g-mbdira ads. +* GNAT.MBBS_Float_Random (g-mbflra.ads): GNAT MBBS_Float_Random g-mbflra ads. +* GNAT.MD5 (g-md5.ads): GNAT MD5 g-md5 ads. +* GNAT.Memory_Dump (g-memdum.ads): GNAT Memory_Dump g-memdum ads. +* GNAT.Most_Recent_Exception (g-moreex.ads): GNAT Most_Recent_Exception g-moreex ads. +* GNAT.OS_Lib (g-os_lib.ads): GNAT OS_Lib g-os_lib ads. +* GNAT.Perfect_Hash_Generators (g-pehage.ads): GNAT Perfect_Hash_Generators g-pehage ads. +* GNAT.Random_Numbers (g-rannum.ads): GNAT Random_Numbers g-rannum ads. +* GNAT.Regexp (g-regexp.ads): GNAT Regexp g-regexp ads. +* GNAT.Registry (g-regist.ads): GNAT Registry g-regist ads. +* GNAT.Regpat (g-regpat.ads): GNAT Regpat g-regpat ads. +* GNAT.Rewrite_Data (g-rewdat.ads): GNAT Rewrite_Data g-rewdat ads. +* GNAT.Secondary_Stack_Info (g-sestin.ads): GNAT Secondary_Stack_Info g-sestin ads. +* GNAT.Semaphores (g-semaph.ads): GNAT Semaphores g-semaph ads. +* GNAT.Serial_Communications (g-sercom.ads): GNAT Serial_Communications g-sercom ads. +* GNAT.SHA1 (g-sha1.ads): GNAT SHA1 g-sha1 ads. +* GNAT.SHA224 (g-sha224.ads): GNAT SHA224 g-sha224 ads. +* GNAT.SHA256 (g-sha256.ads): GNAT SHA256 g-sha256 ads. +* GNAT.SHA384 (g-sha384.ads): GNAT SHA384 g-sha384 ads. +* GNAT.SHA512 (g-sha512.ads): GNAT SHA512 g-sha512 ads. +* GNAT.Signals (g-signal.ads): GNAT Signals g-signal ads. +* GNAT.Sockets (g-socket.ads): GNAT Sockets g-socket ads. +* GNAT.Source_Info (g-souinf.ads): GNAT Source_Info g-souinf ads. +* GNAT.Spelling_Checker (g-speche.ads): GNAT Spelling_Checker g-speche ads. +* GNAT.Spelling_Checker_Generic (g-spchge.ads): GNAT Spelling_Checker_Generic g-spchge ads. +* GNAT.Spitbol.Patterns (g-spipat.ads): GNAT Spitbol Patterns g-spipat ads. +* GNAT.Spitbol (g-spitbo.ads): GNAT Spitbol g-spitbo ads. +* GNAT.Spitbol.Table_Boolean (g-sptabo.ads): GNAT Spitbol Table_Boolean g-sptabo ads. +* GNAT.Spitbol.Table_Integer (g-sptain.ads): GNAT Spitbol Table_Integer g-sptain ads. +* GNAT.Spitbol.Table_VString (g-sptavs.ads): GNAT Spitbol Table_VString g-sptavs ads. +* GNAT.SSE (g-sse.ads): GNAT SSE g-sse ads. +* GNAT.SSE.Vector_Types (g-ssvety.ads): GNAT SSE Vector_Types g-ssvety ads. +* GNAT.Strings (g-string.ads): GNAT Strings g-string ads. +* GNAT.String_Split (g-strspl.ads): GNAT String_Split g-strspl ads. +* GNAT.Table (g-table.ads): GNAT Table g-table ads. +* GNAT.Task_Lock (g-tasloc.ads): GNAT Task_Lock g-tasloc ads. +* GNAT.Time_Stamp (g-timsta.ads): GNAT Time_Stamp g-timsta ads. +* GNAT.Threads (g-thread.ads): GNAT Threads g-thread ads. +* GNAT.Traceback (g-traceb.ads): GNAT Traceback g-traceb ads. +* GNAT.Traceback.Symbolic (g-trasym.ads): GNAT Traceback Symbolic g-trasym ads. +* GNAT.UTF_32 (g-table.ads): GNAT UTF_32 g-table ads. +* GNAT.Wide_Spelling_Checker (g-u3spch.ads): GNAT Wide_Spelling_Checker g-u3spch ads. +* GNAT.Wide_Spelling_Checker (g-wispch.ads): GNAT Wide_Spelling_Checker g-wispch ads. +* GNAT.Wide_String_Split (g-wistsp.ads): GNAT Wide_String_Split g-wistsp ads. +* GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads): GNAT Wide_Wide_Spelling_Checker g-zspche ads. +* GNAT.Wide_Wide_String_Split (g-zistsp.ads): GNAT Wide_Wide_String_Split g-zistsp ads. +* Interfaces.C.Extensions (i-cexten.ads): Interfaces C Extensions i-cexten ads. +* Interfaces.C.Streams (i-cstrea.ads): Interfaces C Streams i-cstrea ads. +* Interfaces.Packed_Decimal (i-pacdec.ads): Interfaces Packed_Decimal i-pacdec ads. +* Interfaces.VxWorks (i-vxwork.ads): Interfaces VxWorks i-vxwork ads. +* Interfaces.VxWorks.IO (i-vxwoio.ads): Interfaces VxWorks IO i-vxwoio ads. +* System.Address_Image (s-addima.ads): System Address_Image s-addima ads. +* System.Assertions (s-assert.ads): System Assertions s-assert ads. +* System.Atomic_Counters (s-atocou.ads): System Atomic_Counters s-atocou ads. +* System.Memory (s-memory.ads): System Memory s-memory ads. +* System.Multiprocessors (s-multip.ads): System Multiprocessors s-multip ads. +* System.Multiprocessors.Dispatching_Domains (s-mudido.ads): System Multiprocessors Dispatching_Domains s-mudido ads. +* System.Partition_Interface (s-parint.ads): System Partition_Interface s-parint ads. +* System.Pool_Global (s-pooglo.ads): System Pool_Global s-pooglo ads. +* System.Pool_Local (s-pooloc.ads): System Pool_Local s-pooloc ads. +* System.Restrictions (s-restri.ads): System Restrictions s-restri ads. +* System.Rident (s-rident.ads): System Rident s-rident ads. +* System.Strings.Stream_Ops (s-ststop.ads): System Strings Stream_Ops s-ststop ads. +* System.Unsigned_Types (s-unstyp.ads): System Unsigned_Types s-unstyp ads. +* System.Wch_Cnv (s-wchcnv.ads): System Wch_Cnv s-wchcnv ads. +* System.Wch_Con (s-wchcon.ads): System Wch_Con s-wchcon ads. + +@end menu + +@node Ada Characters Latin_9 a-chlat9 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,,The GNAT Library +@anchor{gnat_rm/the_gnat_library id2}@anchor{276}@anchor{gnat_rm/the_gnat_library ada-characters-latin-9-a-chlat9-ads}@anchor{277} +@section @cite{Ada.Characters.Latin_9} (@code{a-chlat9.ads}) + + +@geindex Ada.Characters.Latin_9 (a-chlat9.ads) + +@geindex Latin_9 constants for Character + +This child of @cite{Ada.Characters} +provides a set of definitions corresponding to those in the +RM-defined package @cite{Ada.Characters.Latin_1} but with the +few modifications required for @cite{Latin-9} +The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +@node Ada Characters Wide_Latin_1 a-cwila1 ads,Ada Characters Wide_Latin_9 a-cwila1 ads,Ada Characters Latin_9 a-chlat9 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-1-a-cwila1-ads}@anchor{278}@anchor{gnat_rm/the_gnat_library id3}@anchor{279} +@section @cite{Ada.Characters.Wide_Latin_1} (@code{a-cwila1.ads}) + + +@geindex Ada.Characters.Wide_Latin_1 (a-cwila1.ads) + +@geindex Latin_1 constants for Wide_Character + +This child of @cite{Ada.Characters} +provides a set of definitions corresponding to those in the +RM-defined package @cite{Ada.Characters.Latin_1} but with the +types of the constants being @cite{Wide_Character} +instead of @cite{Character}. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +@node Ada Characters Wide_Latin_9 a-cwila1 ads,Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,Ada Characters Wide_Latin_1 a-cwila1 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id4}@anchor{27a}@anchor{gnat_rm/the_gnat_library ada-characters-wide-latin-9-a-cwila1-ads}@anchor{27b} +@section @cite{Ada.Characters.Wide_Latin_9} (@code{a-cwila1.ads}) + + +@geindex Ada.Characters.Wide_Latin_9 (a-cwila1.ads) + +@geindex Latin_9 constants for Wide_Character + +This child of @cite{Ada.Characters} +provides a set of definitions corresponding to those in the +GNAT defined package @cite{Ada.Characters.Latin_9} but with the +types of the constants being @cite{Wide_Character} +instead of @cite{Character}. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +@node Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,Ada Characters Wide_Latin_9 a-cwila1 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-1-a-chzla1-ads}@anchor{27c}@anchor{gnat_rm/the_gnat_library id5}@anchor{27d} +@section @cite{Ada.Characters.Wide_Wide_Latin_1} (@code{a-chzla1.ads}) + + +@geindex Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads) + +@geindex Latin_1 constants for Wide_Wide_Character + +This child of @cite{Ada.Characters} +provides a set of definitions corresponding to those in the +RM-defined package @cite{Ada.Characters.Latin_1} but with the +types of the constants being @cite{Wide_Wide_Character} +instead of @cite{Character}. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +@node Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,Ada Characters Wide_Wide_Latin_1 a-chzla1 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-characters-wide-wide-latin-9-a-chzla9-ads}@anchor{27e}@anchor{gnat_rm/the_gnat_library id6}@anchor{27f} +@section @cite{Ada.Characters.Wide_Wide_Latin_9} (@code{a-chzla9.ads}) + + +@geindex Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads) + +@geindex Latin_9 constants for Wide_Wide_Character + +This child of @cite{Ada.Characters} +provides a set of definitions corresponding to those in the +GNAT defined package @cite{Ada.Characters.Latin_9} but with the +types of the constants being @cite{Wide_Wide_Character} +instead of @cite{Character}. The provision of such a package +is specifically authorized by the Ada Reference Manual +(RM A.3.3(27)). + +@node Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,Ada Containers Formal_Hashed_Maps a-cfhama ads,Ada Characters Wide_Wide_Latin_9 a-chzla9 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id7}@anchor{280}@anchor{gnat_rm/the_gnat_library ada-containers-formal-doubly-linked-lists-a-cfdlli-ads}@anchor{281} +@section @cite{Ada.Containers.Formal_Doubly_Linked_Lists} (@code{a-cfdlli.ads}) + + +@geindex Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads) + +@geindex Formal container for doubly linked lists + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for doubly linked lists, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Hashed_Maps a-cfhama ads,Ada Containers Formal_Hashed_Sets a-cfhase ads,Ada Containers Formal_Doubly_Linked_Lists a-cfdlli ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id8}@anchor{282}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-maps-a-cfhama-ads}@anchor{283} +@section @cite{Ada.Containers.Formal_Hashed_Maps} (@code{a-cfhama.ads}) + + +@geindex Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads) + +@geindex Formal container for hashed maps + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for hashed maps, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Hashed_Sets a-cfhase ads,Ada Containers Formal_Ordered_Maps a-cforma ads,Ada Containers Formal_Hashed_Maps a-cfhama ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id9}@anchor{284}@anchor{gnat_rm/the_gnat_library ada-containers-formal-hashed-sets-a-cfhase-ads}@anchor{285} +@section @cite{Ada.Containers.Formal_Hashed_Sets} (@code{a-cfhase.ads}) + + +@geindex Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads) + +@geindex Formal container for hashed sets + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for hashed sets, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Ordered_Maps a-cforma ads,Ada Containers Formal_Ordered_Sets a-cforse ads,Ada Containers Formal_Hashed_Sets a-cfhase ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id10}@anchor{286}@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-maps-a-cforma-ads}@anchor{287} +@section @cite{Ada.Containers.Formal_Ordered_Maps} (@code{a-cforma.ads}) + + +@geindex Ada.Containers.Formal_Ordered_Maps (a-cforma.ads) + +@geindex Formal container for ordered maps + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for ordered maps, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Ordered_Sets a-cforse ads,Ada Containers Formal_Vectors a-cofove ads,Ada Containers Formal_Ordered_Maps a-cforma ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-containers-formal-ordered-sets-a-cforse-ads}@anchor{288}@anchor{gnat_rm/the_gnat_library id11}@anchor{289} +@section @cite{Ada.Containers.Formal_Ordered_Sets} (@code{a-cforse.ads}) + + +@geindex Ada.Containers.Formal_Ordered_Sets (a-cforse.ads) + +@geindex Formal container for ordered sets + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for ordered sets, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Vectors a-cofove ads,Ada Containers Formal_Indefinite_Vectors a-cfinve ads,Ada Containers Formal_Ordered_Sets a-cforse ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id12}@anchor{28a}@anchor{gnat_rm/the_gnat_library ada-containers-formal-vectors-a-cofove-ads}@anchor{28b} +@section @cite{Ada.Containers.Formal_Vectors} (@code{a-cofove.ads}) + + +@geindex Ada.Containers.Formal_Vectors (a-cofove.ads) + +@geindex Formal container for vectors + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for vectors, meant to facilitate formal +verification of code using such containers. The specification of this +unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Formal_Indefinite_Vectors a-cfinve ads,Ada Containers Bounded_Holders a-coboho ads,Ada Containers Formal_Vectors a-cofove ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id13}@anchor{28c}@anchor{gnat_rm/the_gnat_library ada-containers-formal-indefinite-vectors-a-cfinve-ads}@anchor{28d} +@section @cite{Ada.Containers.Formal_Indefinite_Vectors} (@code{a-cfinve.ads}) + + +@geindex Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads) + +@geindex Formal container for vectors + +This child of @cite{Ada.Containers} defines a modified version of the +Ada 2005 container for vectors of indefinite elements, meant to +facilitate formal verification of code using such containers. The +specification of this unit is compatible with SPARK 2014. + +Note that although this container was designed with formal verification +in mind, it may well be generally useful in that it is a simplified more +efficient version than the one defined in the standard. In particular it +does not have the complex overhead required to detect cursor tampering. + +@node Ada Containers Bounded_Holders a-coboho ads,Ada Command_Line Environment a-colien ads,Ada Containers Formal_Indefinite_Vectors a-cfinve ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id14}@anchor{28e}@anchor{gnat_rm/the_gnat_library ada-containers-bounded-holders-a-coboho-ads}@anchor{28f} +@section @cite{Ada.Containers.Bounded_Holders} (@code{a-coboho.ads}) + + +@geindex Ada.Containers.Bounded_Holders (a-coboho.ads) + +@geindex Formal container for vectors + +This child of @cite{Ada.Containers} defines a modified version of +Indefinite_Holders that avoids heap allocation. + +@node Ada Command_Line Environment a-colien ads,Ada Command_Line Remove a-colire ads,Ada Containers Bounded_Holders a-coboho ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-command-line-environment-a-colien-ads}@anchor{290}@anchor{gnat_rm/the_gnat_library id15}@anchor{291} +@section @cite{Ada.Command_Line.Environment} (@code{a-colien.ads}) + + +@geindex Ada.Command_Line.Environment (a-colien.ads) + +@geindex Environment entries + +This child of @cite{Ada.Command_Line} +provides a mechanism for obtaining environment values on systems +where this concept makes sense. + +@node Ada Command_Line Remove a-colire ads,Ada Command_Line Response_File a-clrefi ads,Ada Command_Line Environment a-colien ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id16}@anchor{292}@anchor{gnat_rm/the_gnat_library ada-command-line-remove-a-colire-ads}@anchor{293} +@section @cite{Ada.Command_Line.Remove} (@code{a-colire.ads}) + + +@geindex Ada.Command_Line.Remove (a-colire.ads) + +@geindex Removing command line arguments + +@geindex Command line +@geindex argument removal + +This child of @cite{Ada.Command_Line} +provides a mechanism for logically removing +arguments from the argument list. Once removed, an argument is not visible +to further calls on the subprograms in @cite{Ada.Command_Line} will not +see the removed argument. + +@node Ada Command_Line Response_File a-clrefi ads,Ada Direct_IO C_Streams a-diocst ads,Ada Command_Line Remove a-colire ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-command-line-response-file-a-clrefi-ads}@anchor{294}@anchor{gnat_rm/the_gnat_library id17}@anchor{295} +@section @cite{Ada.Command_Line.Response_File} (@code{a-clrefi.ads}) + + +@geindex Ada.Command_Line.Response_File (a-clrefi.ads) + +@geindex Response file for command line + +@geindex Command line +@geindex response file + +@geindex Command line +@geindex handling long command lines + +This child of @cite{Ada.Command_Line} provides a mechanism facilities for +getting command line arguments from a text file, called a "response file". +Using a response file allow passing a set of arguments to an executable longer +than the maximum allowed by the system on the command line. + +@node Ada Direct_IO C_Streams a-diocst ads,Ada Exceptions Is_Null_Occurrence a-einuoc ads,Ada Command_Line Response_File a-clrefi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id18}@anchor{296}@anchor{gnat_rm/the_gnat_library ada-direct-io-c-streams-a-diocst-ads}@anchor{297} +@section @cite{Ada.Direct_IO.C_Streams} (@code{a-diocst.ads}) + + +@geindex Ada.Direct_IO.C_Streams (a-diocst.ads) + +@geindex C Streams +@geindex Interfacing with Direct_IO + +This package provides subprograms that allow interfacing between +C streams and @cite{Direct_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Exceptions Is_Null_Occurrence a-einuoc ads,Ada Exceptions Last_Chance_Handler a-elchha ads,Ada Direct_IO C_Streams a-diocst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id19}@anchor{298}@anchor{gnat_rm/the_gnat_library ada-exceptions-is-null-occurrence-a-einuoc-ads}@anchor{299} +@section @cite{Ada.Exceptions.Is_Null_Occurrence} (@code{a-einuoc.ads}) + + +@geindex Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads) + +@geindex Null_Occurrence +@geindex testing for + +This child subprogram provides a way of testing for the null +exception occurrence (@cite{Null_Occurrence}) without raising +an exception. + +@node Ada Exceptions Last_Chance_Handler a-elchha ads,Ada Exceptions Traceback a-exctra ads,Ada Exceptions Is_Null_Occurrence a-einuoc ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id20}@anchor{29a}@anchor{gnat_rm/the_gnat_library ada-exceptions-last-chance-handler-a-elchha-ads}@anchor{29b} +@section @cite{Ada.Exceptions.Last_Chance_Handler} (@code{a-elchha.ads}) + + +@geindex Ada.Exceptions.Last_Chance_Handler (a-elchha.ads) + +@geindex Null_Occurrence +@geindex testing for + +This child subprogram is used for handling otherwise unhandled +exceptions (hence the name last chance), and perform clean ups before +terminating the program. Note that this subprogram never returns. + +@node Ada Exceptions Traceback a-exctra ads,Ada Sequential_IO C_Streams a-siocst ads,Ada Exceptions Last_Chance_Handler a-elchha ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-exceptions-traceback-a-exctra-ads}@anchor{29c}@anchor{gnat_rm/the_gnat_library id21}@anchor{29d} +@section @cite{Ada.Exceptions.Traceback} (@code{a-exctra.ads}) + + +@geindex Ada.Exceptions.Traceback (a-exctra.ads) + +@geindex Traceback for Exception Occurrence + +This child package provides the subprogram (@cite{Tracebacks}) to +give a traceback array of addresses based on an exception +occurrence. + +@node Ada Sequential_IO C_Streams a-siocst ads,Ada Streams Stream_IO C_Streams a-ssicst ads,Ada Exceptions Traceback a-exctra ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-sequential-io-c-streams-a-siocst-ads}@anchor{29e}@anchor{gnat_rm/the_gnat_library id22}@anchor{29f} +@section @cite{Ada.Sequential_IO.C_Streams} (@code{a-siocst.ads}) + + +@geindex Ada.Sequential_IO.C_Streams (a-siocst.ads) + +@geindex C Streams +@geindex Interfacing with Sequential_IO + +This package provides subprograms that allow interfacing between +C streams and @cite{Sequential_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Streams Stream_IO C_Streams a-ssicst ads,Ada Strings Unbounded Text_IO a-suteio ads,Ada Sequential_IO C_Streams a-siocst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id23}@anchor{2a0}@anchor{gnat_rm/the_gnat_library ada-streams-stream-io-c-streams-a-ssicst-ads}@anchor{2a1} +@section @cite{Ada.Streams.Stream_IO.C_Streams} (@code{a-ssicst.ads}) + + +@geindex Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads) + +@geindex C Streams +@geindex Interfacing with Stream_IO + +This package provides subprograms that allow interfacing between +C streams and @cite{Stream_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Strings Unbounded Text_IO a-suteio ads,Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,Ada Streams Stream_IO C_Streams a-ssicst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-strings-unbounded-text-io-a-suteio-ads}@anchor{2a2}@anchor{gnat_rm/the_gnat_library id24}@anchor{2a3} +@section @cite{Ada.Strings.Unbounded.Text_IO} (@code{a-suteio.ads}) + + +@geindex Ada.Strings.Unbounded.Text_IO (a-suteio.ads) + +@geindex Unbounded_String +@geindex IO support + +@geindex Text_IO +@geindex extensions for unbounded strings + +This package provides subprograms for Text_IO for unbounded +strings, avoiding the necessity for an intermediate operation +with ordinary strings. + +@node Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,Ada Strings Unbounded Text_IO a-suteio ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id25}@anchor{2a4}@anchor{gnat_rm/the_gnat_library ada-strings-wide-unbounded-wide-text-io-a-swuwti-ads}@anchor{2a5} +@section @cite{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@code{a-swuwti.ads}) + + +@geindex Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads) + +@geindex Unbounded_Wide_String +@geindex IO support + +@geindex Text_IO +@geindex extensions for unbounded wide strings + +This package provides subprograms for Text_IO for unbounded +wide strings, avoiding the necessity for an intermediate operation +with ordinary wide strings. + +@node Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,Ada Text_IO C_Streams a-tiocst ads,Ada Strings Wide_Unbounded Wide_Text_IO a-swuwti ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-strings-wide-wide-unbounded-wide-wide-text-io-a-szuzti-ads}@anchor{2a6}@anchor{gnat_rm/the_gnat_library id26}@anchor{2a7} +@section @cite{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@code{a-szuzti.ads}) + + +@geindex Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads) + +@geindex Unbounded_Wide_Wide_String +@geindex IO support + +@geindex Text_IO +@geindex extensions for unbounded wide wide strings + +This package provides subprograms for Text_IO for unbounded +wide wide strings, avoiding the necessity for an intermediate operation +with ordinary wide wide strings. + +@node Ada Text_IO C_Streams a-tiocst ads,Ada Text_IO Reset_Standard_Files a-tirsfi ads,Ada Strings Wide_Wide_Unbounded Wide_Wide_Text_IO a-szuzti ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-text-io-c-streams-a-tiocst-ads}@anchor{2a8}@anchor{gnat_rm/the_gnat_library id27}@anchor{2a9} +@section @cite{Ada.Text_IO.C_Streams} (@code{a-tiocst.ads}) + + +@geindex Ada.Text_IO.C_Streams (a-tiocst.ads) + +@geindex C Streams +@geindex Interfacing with `Text_IO` + +This package provides subprograms that allow interfacing between +C streams and @cite{Text_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Text_IO Reset_Standard_Files a-tirsfi ads,Ada Wide_Characters Unicode a-wichun ads,Ada Text_IO C_Streams a-tiocst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id28}@anchor{2aa}@anchor{gnat_rm/the_gnat_library ada-text-io-reset-standard-files-a-tirsfi-ads}@anchor{2ab} +@section @cite{Ada.Text_IO.Reset_Standard_Files} (@code{a-tirsfi.ads}) + + +@geindex Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads) + +@geindex Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Text_IO. This is useful in a situation (such as a restart in an +embedded application) where the status of the files may change during +execution (for example a standard input file may be redefined to be +interactive). + +@node Ada Wide_Characters Unicode a-wichun ads,Ada Wide_Text_IO C_Streams a-wtcstr ads,Ada Text_IO Reset_Standard_Files a-tirsfi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id29}@anchor{2ac}@anchor{gnat_rm/the_gnat_library ada-wide-characters-unicode-a-wichun-ads}@anchor{2ad} +@section @cite{Ada.Wide_Characters.Unicode} (@code{a-wichun.ads}) + + +@geindex Ada.Wide_Characters.Unicode (a-wichun.ads) + +@geindex Unicode categorization +@geindex Wide_Character + +This package provides subprograms that allow categorization of +Wide_Character values according to Unicode categories. + +@node Ada Wide_Text_IO C_Streams a-wtcstr ads,Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,Ada Wide_Characters Unicode a-wichun ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-wide-text-io-c-streams-a-wtcstr-ads}@anchor{2ae}@anchor{gnat_rm/the_gnat_library id30}@anchor{2af} +@section @cite{Ada.Wide_Text_IO.C_Streams} (@code{a-wtcstr.ads}) + + +@geindex Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads) + +@geindex C Streams +@geindex Interfacing with `Wide_Text_IO` + +This package provides subprograms that allow interfacing between +C streams and @cite{Wide_Text_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,Ada Wide_Wide_Characters Unicode a-zchuni ads,Ada Wide_Text_IO C_Streams a-wtcstr ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library ada-wide-text-io-reset-standard-files-a-wrstfi-ads}@anchor{2b0}@anchor{gnat_rm/the_gnat_library id31}@anchor{2b1} +@section @cite{Ada.Wide_Text_IO.Reset_Standard_Files} (@code{a-wrstfi.ads}) + + +@geindex Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads) + +@geindex Wide_Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an +embedded application) where the status of the files may change during +execution (for example a standard input file may be redefined to be +interactive). + +@node Ada Wide_Wide_Characters Unicode a-zchuni ads,Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,Ada Wide_Text_IO Reset_Standard_Files a-wrstfi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id32}@anchor{2b2}@anchor{gnat_rm/the_gnat_library ada-wide-wide-characters-unicode-a-zchuni-ads}@anchor{2b3} +@section @cite{Ada.Wide_Wide_Characters.Unicode} (@code{a-zchuni.ads}) + + +@geindex Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads) + +@geindex Unicode categorization +@geindex Wide_Wide_Character + +This package provides subprograms that allow categorization of +Wide_Wide_Character values according to Unicode categories. + +@node Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,Ada Wide_Wide_Characters Unicode a-zchuni ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id33}@anchor{2b4}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-c-streams-a-ztcstr-ads}@anchor{2b5} +@section @cite{Ada.Wide_Wide_Text_IO.C_Streams} (@code{a-ztcstr.ads}) + + +@geindex Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads) + +@geindex C Streams +@geindex Interfacing with `Wide_Wide_Text_IO` + +This package provides subprograms that allow interfacing between +C streams and @cite{Wide_Wide_Text_IO}. The stream identifier can be +extracted from a file opened on the Ada side, and an Ada file +can be constructed from a stream opened on the C side. + +@node Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,GNAT Altivec g-altive ads,Ada Wide_Wide_Text_IO C_Streams a-ztcstr ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id34}@anchor{2b6}@anchor{gnat_rm/the_gnat_library ada-wide-wide-text-io-reset-standard-files-a-zrstfi-ads}@anchor{2b7} +@section @cite{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@code{a-zrstfi.ads}) + + +@geindex Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads) + +@geindex Wide_Wide_Text_IO resetting standard files + +This procedure is used to reset the status of the standard files used +by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a +restart in an embedded application) where the status of the files may +change during execution (for example a standard input file may be +redefined to be interactive). + +@node GNAT Altivec g-altive ads,GNAT Altivec Conversions g-altcon ads,Ada Wide_Wide_Text_IO Reset_Standard_Files a-zrstfi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-altivec-g-altive-ads}@anchor{2b8}@anchor{gnat_rm/the_gnat_library id35}@anchor{2b9} +@section @cite{GNAT.Altivec} (@code{g-altive.ads}) + + +@geindex GNAT.Altivec (g-altive.ads) + +@geindex AltiVec + +This is the root package of the GNAT AltiVec binding. It provides +definitions of constants and types common to all the versions of the +binding. + +@node GNAT Altivec Conversions g-altcon ads,GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec g-altive ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id36}@anchor{2ba}@anchor{gnat_rm/the_gnat_library gnat-altivec-conversions-g-altcon-ads}@anchor{2bb} +@section @cite{GNAT.Altivec.Conversions} (@code{g-altcon.ads}) + + +@geindex GNAT.Altivec.Conversions (g-altcon.ads) + +@geindex AltiVec + +This package provides the Vector/View conversion routines. + +@node GNAT Altivec Vector_Operations g-alveop ads,GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Conversions g-altcon ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id37}@anchor{2bc}@anchor{gnat_rm/the_gnat_library gnat-altivec-vector-operations-g-alveop-ads}@anchor{2bd} +@section @cite{GNAT.Altivec.Vector_Operations} (@code{g-alveop.ads}) + + +@geindex GNAT.Altivec.Vector_Operations (g-alveop.ads) + +@geindex AltiVec + +This package exposes the Ada interface to the AltiVec operations on +vector objects. A soft emulation is included by default in the GNAT +library. The hard binding is provided as a separate package. This unit +is common to both bindings. + +@node GNAT Altivec Vector_Types g-alvety ads,GNAT Altivec Vector_Views g-alvevi ads,GNAT Altivec Vector_Operations g-alveop ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-altivec-vector-types-g-alvety-ads}@anchor{2be}@anchor{gnat_rm/the_gnat_library id38}@anchor{2bf} +@section @cite{GNAT.Altivec.Vector_Types} (@code{g-alvety.ads}) + + +@geindex GNAT.Altivec.Vector_Types (g-alvety.ads) + +@geindex AltiVec + +This package exposes the various vector types part of the Ada binding +to AltiVec facilities. + +@node GNAT Altivec Vector_Views g-alvevi ads,GNAT Array_Split g-arrspl ads,GNAT Altivec Vector_Types g-alvety ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-altivec-vector-views-g-alvevi-ads}@anchor{2c0}@anchor{gnat_rm/the_gnat_library id39}@anchor{2c1} +@section @cite{GNAT.Altivec.Vector_Views} (@code{g-alvevi.ads}) + + +@geindex GNAT.Altivec.Vector_Views (g-alvevi.ads) + +@geindex AltiVec + +This package provides public 'View' data types from/to which private +vector representations can be converted via +GNAT.Altivec.Conversions. This allows convenient access to individual +vector elements and provides a simple way to initialize vector +objects. + +@node GNAT Array_Split g-arrspl ads,GNAT AWK g-awk ads,GNAT Altivec Vector_Views g-alvevi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-array-split-g-arrspl-ads}@anchor{2c2}@anchor{gnat_rm/the_gnat_library id40}@anchor{2c3} +@section @cite{GNAT.Array_Split} (@code{g-arrspl.ads}) + + +@geindex GNAT.Array_Split (g-arrspl.ads) + +@geindex Array splitter + +Useful array-manipulation routines: given a set of separators, split +an array wherever the separators appear, and provide direct access +to the resulting slices. + +@node GNAT AWK g-awk ads,GNAT Bounded_Buffers g-boubuf ads,GNAT Array_Split g-arrspl ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id41}@anchor{2c4}@anchor{gnat_rm/the_gnat_library gnat-awk-g-awk-ads}@anchor{2c5} +@section @cite{GNAT.AWK} (@code{g-awk.ads}) + + +@geindex GNAT.AWK (g-awk.ads) + +@geindex Parsing + +@geindex AWK + +Provides AWK-like parsing functions, with an easy interface for parsing one +or more files containing formatted data. The file is viewed as a database +where each record is a line and a field is a data element in this line. + +@node GNAT Bounded_Buffers g-boubuf ads,GNAT Bounded_Mailboxes g-boumai ads,GNAT AWK g-awk ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-bounded-buffers-g-boubuf-ads}@anchor{2c6}@anchor{gnat_rm/the_gnat_library id42}@anchor{2c7} +@section @cite{GNAT.Bounded_Buffers} (@code{g-boubuf.ads}) + + +@geindex GNAT.Bounded_Buffers (g-boubuf.ads) + +@geindex Parsing + +@geindex Bounded Buffers + +Provides a concurrent generic bounded buffer abstraction. Instances are +useful directly or as parts of the implementations of other abstractions, +such as mailboxes. + +@node GNAT Bounded_Mailboxes g-boumai ads,GNAT Bubble_Sort g-bubsor ads,GNAT Bounded_Buffers g-boubuf ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-bounded-mailboxes-g-boumai-ads}@anchor{2c8}@anchor{gnat_rm/the_gnat_library id43}@anchor{2c9} +@section @cite{GNAT.Bounded_Mailboxes} (@code{g-boumai.ads}) + + +@geindex GNAT.Bounded_Mailboxes (g-boumai.ads) + +@geindex Parsing + +@geindex Mailboxes + +Provides a thread-safe asynchronous intertask mailbox communication facility. + +@node GNAT Bubble_Sort g-bubsor ads,GNAT Bubble_Sort_A g-busora ads,GNAT Bounded_Mailboxes g-boumai ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-bubsor-ads}@anchor{2ca}@anchor{gnat_rm/the_gnat_library id44}@anchor{2cb} +@section @cite{GNAT.Bubble_Sort} (@code{g-bubsor.ads}) + + +@geindex GNAT.Bubble_Sort (g-bubsor.ads) + +@geindex Sorting + +@geindex Bubble sort + +Provides a general implementation of bubble sort usable for sorting arbitrary +data items. Exchange and comparison procedures are provided by passing +access-to-procedure values. + +@node GNAT Bubble_Sort_A g-busora ads,GNAT Bubble_Sort_G g-busorg ads,GNAT Bubble_Sort g-bubsor ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id45}@anchor{2cc}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-a-g-busora-ads}@anchor{2cd} +@section @cite{GNAT.Bubble_Sort_A} (@code{g-busora.ads}) + + +@geindex GNAT.Bubble_Sort_A (g-busora.ads) + +@geindex Sorting + +@geindex Bubble sort + +Provides a general implementation of bubble sort usable for sorting arbitrary +data items. Move and comparison procedures are provided by passing +access-to-procedure values. This is an older version, retained for +compatibility. Usually @cite{GNAT.Bubble_Sort} will be preferable. + +@node GNAT Bubble_Sort_G g-busorg ads,GNAT Byte_Order_Mark g-byorma ads,GNAT Bubble_Sort_A g-busora ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id46}@anchor{2ce}@anchor{gnat_rm/the_gnat_library gnat-bubble-sort-g-g-busorg-ads}@anchor{2cf} +@section @cite{GNAT.Bubble_Sort_G} (@code{g-busorg.ads}) + + +@geindex GNAT.Bubble_Sort_G (g-busorg.ads) + +@geindex Sorting + +@geindex Bubble sort + +Similar to @cite{Bubble_Sort_A} except that the move and sorting procedures +are provided as generic parameters, this improves efficiency, especially +if the procedures can be inlined, at the expense of duplicating code for +multiple instantiations. + +@node GNAT Byte_Order_Mark g-byorma ads,GNAT Byte_Swapping g-bytswa ads,GNAT Bubble_Sort_G g-busorg ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id47}@anchor{2d0}@anchor{gnat_rm/the_gnat_library gnat-byte-order-mark-g-byorma-ads}@anchor{2d1} +@section @cite{GNAT.Byte_Order_Mark} (@code{g-byorma.ads}) + + +@geindex GNAT.Byte_Order_Mark (g-byorma.ads) + +@geindex UTF-8 representation + +@geindex Wide characte representations + +Provides a routine which given a string, reads the start of the string to +see whether it is one of the standard byte order marks (BOM's) which signal +the encoding of the string. The routine includes detection of special XML +sequences for various UCS input formats. + +@node GNAT Byte_Swapping g-bytswa ads,GNAT Calendar g-calend ads,GNAT Byte_Order_Mark g-byorma ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-byte-swapping-g-bytswa-ads}@anchor{2d2}@anchor{gnat_rm/the_gnat_library id48}@anchor{2d3} +@section @cite{GNAT.Byte_Swapping} (@code{g-bytswa.ads}) + + +@geindex GNAT.Byte_Swapping (g-bytswa.ads) + +@geindex Byte swapping + +@geindex Endianness + +General routines for swapping the bytes in 2-, 4-, and 8-byte quantities. +Machine-specific implementations are available in some cases. + +@node GNAT Calendar g-calend ads,GNAT Calendar Time_IO g-catiio ads,GNAT Byte_Swapping g-bytswa ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-calendar-g-calend-ads}@anchor{2d4}@anchor{gnat_rm/the_gnat_library id49}@anchor{2d5} +@section @cite{GNAT.Calendar} (@code{g-calend.ads}) + + +@geindex GNAT.Calendar (g-calend.ads) + +@geindex Calendar + +Extends the facilities provided by @cite{Ada.Calendar} to include handling +of days of the week, an extended @cite{Split} and @cite{Time_Of} capability. +Also provides conversion of @cite{Ada.Calendar.Time} values to and from the +C @cite{timeval} format. + +@node GNAT Calendar Time_IO g-catiio ads,GNAT CRC32 g-crc32 ads,GNAT Calendar g-calend ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-calendar-time-io-g-catiio-ads}@anchor{2d6}@anchor{gnat_rm/the_gnat_library id50}@anchor{2d7} +@section @cite{GNAT.Calendar.Time_IO} (@code{g-catiio.ads}) + + +@geindex Calendar + +@geindex Time + +@geindex GNAT.Calendar.Time_IO (g-catiio.ads) + +@node GNAT CRC32 g-crc32 ads,GNAT Case_Util g-casuti ads,GNAT Calendar Time_IO g-catiio ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id51}@anchor{2d8}@anchor{gnat_rm/the_gnat_library gnat-crc32-g-crc32-ads}@anchor{2d9} +@section @cite{GNAT.CRC32} (@code{g-crc32.ads}) + + +@geindex GNAT.CRC32 (g-crc32.ads) + +@geindex CRC32 + +@geindex Cyclic Redundancy Check + +This package implements the CRC-32 algorithm. For a full description +of this algorithm see +@emph{Computation of Cyclic Redundancy Checks via Table Look-Up}, +@cite{Communications of the ACM}, Vol. 31 No. 8, pp. 1008-1013, +Aug. 1988. Sarwate, D.V. + +@node GNAT Case_Util g-casuti ads,GNAT CGI g-cgi ads,GNAT CRC32 g-crc32 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-case-util-g-casuti-ads}@anchor{2da}@anchor{gnat_rm/the_gnat_library id52}@anchor{2db} +@section @cite{GNAT.Case_Util} (@code{g-casuti.ads}) + + +@geindex GNAT.Case_Util (g-casuti.ads) + +@geindex Casing utilities + +@geindex Character handling (`GNAT.Case_Util`) + +A set of simple routines for handling upper and lower casing of strings +without the overhead of the full casing tables +in @cite{Ada.Characters.Handling}. + +@node GNAT CGI g-cgi ads,GNAT CGI Cookie g-cgicoo ads,GNAT Case_Util g-casuti ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id53}@anchor{2dc}@anchor{gnat_rm/the_gnat_library gnat-cgi-g-cgi-ads}@anchor{2dd} +@section @cite{GNAT.CGI} (@code{g-cgi.ads}) + + +@geindex GNAT.CGI (g-cgi.ads) + +@geindex CGI (Common Gateway Interface) + +This is a package for interfacing a GNAT program with a Web server via the +Common Gateway Interface (CGI). Basically this package parses the CGI +parameters, which are a set of key/value pairs sent by the Web server. It +builds a table whose index is the key and provides some services to deal +with this table. + +@node GNAT CGI Cookie g-cgicoo ads,GNAT CGI Debug g-cgideb ads,GNAT CGI g-cgi ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id54}@anchor{2de}@anchor{gnat_rm/the_gnat_library gnat-cgi-cookie-g-cgicoo-ads}@anchor{2df} +@section @cite{GNAT.CGI.Cookie} (@code{g-cgicoo.ads}) + + +@geindex GNAT.CGI.Cookie (g-cgicoo.ads) + +@geindex CGI (Common Gateway Interface) cookie support + +@geindex Cookie support in CGI + +This is a package to interface a GNAT program with a Web server via the +Common Gateway Interface (CGI). It exports services to deal with Web +cookies (piece of information kept in the Web client software). + +@node GNAT CGI Debug g-cgideb ads,GNAT Command_Line g-comlin ads,GNAT CGI Cookie g-cgicoo ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-cgi-debug-g-cgideb-ads}@anchor{2e0}@anchor{gnat_rm/the_gnat_library id55}@anchor{2e1} +@section @cite{GNAT.CGI.Debug} (@code{g-cgideb.ads}) + + +@geindex GNAT.CGI.Debug (g-cgideb.ads) + +@geindex CGI (Common Gateway Interface) debugging + +This is a package to help debugging CGI (Common Gateway Interface) +programs written in Ada. + +@node GNAT Command_Line g-comlin ads,GNAT Compiler_Version g-comver ads,GNAT CGI Debug g-cgideb ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id56}@anchor{2e2}@anchor{gnat_rm/the_gnat_library gnat-command-line-g-comlin-ads}@anchor{2e3} +@section @cite{GNAT.Command_Line} (@code{g-comlin.ads}) + + +@geindex GNAT.Command_Line (g-comlin.ads) + +@geindex Command line + +Provides a high level interface to @cite{Ada.Command_Line} facilities, +including the ability to scan for named switches with optional parameters +and expand file names using wild card notations. + +@node GNAT Compiler_Version g-comver ads,GNAT Ctrl_C g-ctrl_c ads,GNAT Command_Line g-comlin ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-compiler-version-g-comver-ads}@anchor{2e4}@anchor{gnat_rm/the_gnat_library id57}@anchor{2e5} +@section @cite{GNAT.Compiler_Version} (@code{g-comver.ads}) + + +@geindex GNAT.Compiler_Version (g-comver.ads) + +@geindex Compiler Version + +@geindex Version +@geindex of compiler + +Provides a routine for obtaining the version of the compiler used to +compile the program. More accurately this is the version of the binder +used to bind the program (this will normally be the same as the version +of the compiler if a consistent tool set is used to compile all units +of a partition). -@noindent -Examples of incorrect Forms +@node GNAT Ctrl_C g-ctrl_c ads,GNAT Current_Exception g-curexc ads,GNAT Compiler_Version g-comver ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id58}@anchor{2e6}@anchor{gnat_rm/the_gnat_library gnat-ctrl-c-g-ctrl-c-ads}@anchor{2e7} +@section @cite{GNAT.Ctrl_C} (@code{g-ctrl_c.ads}) -@smallexample -Form => "preserve=junk" -Form => "mode=internal, preserve=timestamps" -@end smallexample -@sp 1 -@item -@cartouche -@noindent -The interpretation of the @code{Pattern} parameter, when not the null string, -in the @code{Start_Search} and @code{Search} procedures. -See A.16(104) and A.16(112). -@end cartouche -@noindent -When the @code{Pattern} parameter is not the null string, it is interpreted -according to the syntax of regular expressions as defined in the -@code{GNAT.Regexp} package. -@xref{GNAT.Regexp (g-regexp.ads)}. +@geindex GNAT.Ctrl_C (g-ctrl_c.ads) -@sp 1 -@item -@cartouche -@noindent -Implementation-defined convention names. See B.1(11). -@end cartouche -@noindent -The following convention names are supported +@geindex Interrupt -@table @code -@item Ada -Ada -@item Ada_Pass_By_Copy -Allowed for any types except by-reference types such as limited -records. Compatible with convention Ada, but causes any parameters -with this convention to be passed by copy. -@item Ada_Pass_By_Reference -Allowed for any types except by-copy types such as scalars. -Compatible with convention Ada, but causes any parameters -with this convention to be passed by reference. -@item Assembler -Assembly language -@item Asm -Synonym for Assembler -@item Assembly -Synonym for Assembler -@item C -C -@item C_Pass_By_Copy -Allowed only for record types, like C, but also notes that record -is to be passed by copy rather than reference. -@item COBOL -COBOL -@item C_Plus_Plus (or CPP) -C++ -@item Default -Treated the same as C -@item External -Treated the same as C -@item Fortran -Fortran -@item Intrinsic -For support of pragma @code{Import} with convention Intrinsic, see -separate section on Intrinsic Subprograms. -@item Stdcall -Stdcall (used for Windows implementations only). This convention correspond -to the WINAPI (previously called Pascal convention) C/C++ convention under -Windows. A routine with this convention cleans the stack before -exit. This pragma cannot be applied to a dispatching call. -@item DLL -Synonym for Stdcall -@item Win32 -Synonym for Stdcall -@item Stubbed -Stubbed is a special convention used to indicate that the body of the -subprogram will be entirely ignored. Any call to the subprogram -is converted into a raise of the @code{Program_Error} exception. If a -pragma @code{Import} specifies convention @code{stubbed} then no body need -be present at all. This convention is useful during development for the -inclusion of subprograms whose body has not yet been written. +Provides a simple interface to handle Ctrl-C keyboard events. -@end table -@noindent -In addition, all otherwise unrecognized convention names are also -treated as being synonymous with convention C@. In all implementations -except for VMS, use of such other names results in a warning. In VMS -implementations, these names are accepted silently. +@node GNAT Current_Exception g-curexc ads,GNAT Debug_Pools g-debpoo ads,GNAT Ctrl_C g-ctrl_c ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id59}@anchor{2e8}@anchor{gnat_rm/the_gnat_library gnat-current-exception-g-curexc-ads}@anchor{2e9} +@section @cite{GNAT.Current_Exception} (@code{g-curexc.ads}) -@sp 1 -@item -@cartouche -@noindent -The meaning of link names. See B.1(36). -@end cartouche -@noindent -Link names are the actual names used by the linker. -@sp 1 -@item -@cartouche -@noindent -The manner of choosing link names when neither the link -name nor the address of an imported or exported entity is specified. See -B.1(36). -@end cartouche -@noindent -The default linker name is that which would be assigned by the relevant -external language, interpreting the Ada name as being in all lower case -letters. +@geindex GNAT.Current_Exception (g-curexc.ads) -@sp 1 -@item -@cartouche -@noindent -The effect of pragma @code{Linker_Options}. See B.1(37). -@end cartouche -@noindent -The string passed to @code{Linker_Options} is presented uninterpreted as -an argument to the link command, unless it contains ASCII.NUL characters. -NUL characters if they appear act as argument separators, so for example +@geindex Current exception -@smallexample @c ada -pragma Linker_Options ("-labc" & ASCII.NUL & "-ldef"); -@end smallexample +@geindex Exception retrieval -@noindent -causes two separate arguments @code{-labc} and @code{-ldef} to be passed to the -linker. The order of linker options is preserved for a given unit. The final -list of options passed to the linker is in reverse order of the elaboration -order. For example, linker options for a body always appear before the options -from the corresponding package spec. +Provides access to information on the current exception that has been raised +without the need for using the Ada 95 / Ada 2005 exception choice parameter +specification syntax. +This is particularly useful in simulating typical facilities for +obtaining information about exceptions provided by Ada 83 compilers. -@sp 1 -@item -@cartouche -@noindent -The contents of the visible part of package -@code{Interfaces} and its language-defined descendants. See B.2(1). -@end cartouche -@noindent -See files with prefix @file{i-} in the distributed library. - -@sp 1 -@item -@cartouche -@noindent -Implementation-defined children of package -@code{Interfaces}. The contents of the visible part of package -@code{Interfaces}. See B.2(11). -@end cartouche -@noindent -See files with prefix @file{i-} in the distributed library. - -@sp 1 -@item -@cartouche -@noindent -The types @code{Floating}, @code{Long_Floating}, -@code{Binary}, @code{Long_Binary}, @code{Decimal_ Element}, and -@code{COBOL_Character}; and the initialization of the variables -@code{Ada_To_COBOL} and @code{COBOL_To_Ada}, in -@code{Interfaces.COBOL}. See B.4(50). -@end cartouche -@noindent -@table @code -@item Floating -Float -@item Long_Floating -(Floating) Long_Float -@item Binary -Integer -@item Long_Binary -Long_Long_Integer -@item Decimal_Element -Character -@item COBOL_Character -Character -@end table +@node GNAT Debug_Pools g-debpoo ads,GNAT Debug_Utilities g-debuti ads,GNAT Current_Exception g-curexc ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-debug-pools-g-debpoo-ads}@anchor{2ea}@anchor{gnat_rm/the_gnat_library id60}@anchor{2eb} +@section @cite{GNAT.Debug_Pools} (@code{g-debpoo.ads}) -@noindent -For initialization, see the file @file{i-cobol.ads} in the distributed library. -@sp 1 -@item -@cartouche -@noindent -Support for access to machine instructions. See C.1(1). -@end cartouche -@noindent -See documentation in file @file{s-maccod.ads} in the distributed library. - -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of access to machine -operations. See C.1(9). -@end cartouche -@noindent -See documentation in file @file{s-maccod.ads} in the distributed library. - -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of interrupts. See C.3(2). -@end cartouche -@noindent -Interrupts are mapped to signals or conditions as appropriate. See -definition of unit -@code{Ada.Interrupt_Names} in source file @file{a-intnam.ads} for details -on the interrupts supported on a particular target. +@geindex GNAT.Debug_Pools (g-debpoo.ads) -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of pre-elaboration. See -C.4(13). -@end cartouche -@noindent -GNAT does not permit a partition to be restarted without reloading, -except under control of the debugger. +@geindex Debugging -@sp 1 -@item -@cartouche -@noindent -The semantics of pragma @code{Discard_Names}. See C.5(7). -@end cartouche -@noindent -Pragma @code{Discard_Names} causes names of enumeration literals to -be suppressed. In the presence of this pragma, the Image attribute -provides the image of the Pos of the literal, and Value accepts -Pos values. +@geindex Debug pools -@sp 1 -@item -@cartouche -@noindent -The result of the @code{Task_Identification.Image} -attribute. See C.7.1(7). -@end cartouche -@noindent -The result of this attribute is a string that identifies -the object or component that denotes a given task. If a variable @code{Var} -has a task type, the image for this task will have the form @code{Var_@var{XXXXXXXX}}, -where the suffix -is the hexadecimal representation of the virtual address of the corresponding -task control block. If the variable is an array of tasks, the image of each -task will have the form of an indexed component indicating the position of a -given task in the array, e.g.@: @code{Group(5)_@var{XXXXXXX}}. If the task is a -component of a record, the image of the task will have the form of a selected -component. These rules are fully recursive, so that the image of a task that -is a subcomponent of a composite object corresponds to the expression that -designates this task. -@noindent -If a task is created by an allocator, its image depends on the context. If the -allocator is part of an object declaration, the rules described above are used -to construct its image, and this image is not affected by subsequent -assignments. If the allocator appears within an expression, the image -includes only the name of the task type. -@noindent -If the configuration pragma Discard_Names is present, or if the restriction -No_Implicit_Heap_Allocation is in effect, the image reduces to -the numeric suffix, that is to say the hexadecimal representation of the -virtual address of the control block of the task. -@sp 1 -@item -@cartouche -@noindent -The value of @code{Current_Task} when in a protected entry -or interrupt handler. See C.7.1(17). -@end cartouche -@noindent -Protected entries or interrupt handlers can be executed by any -convenient thread, so the value of @code{Current_Task} is undefined. +@geindex Memory corruption debugging -@sp 1 -@item -@cartouche -@noindent -The effect of calling @code{Current_Task} from an entry -body or interrupt handler. See C.7.1(19). -@end cartouche -@noindent -The effect of calling @code{Current_Task} from an entry body or -interrupt handler is to return the identification of the task currently -executing the code. +Provide a debugging storage pools that helps tracking memory corruption +problems. +See @cite{The GNAT Debug_Pool Facility} section in the @cite{GNAT User's Guide}. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of -@code{Task_Attributes}. See C.7.2(19). -@end cartouche -@noindent -There are no implementation-defined aspects of @code{Task_Attributes}. - -@sp 1 -@item -@cartouche -@noindent -Values of all @code{Metrics}. See D(2). -@end cartouche -@noindent -The metrics information for GNAT depends on the performance of the -underlying operating system. The sources of the run-time for tasking -implementation, together with the output from @option{-gnatG} can be -used to determine the exact sequence of operating systems calls made -to implement various tasking constructs. Together with appropriate -information on the performance of the underlying operating system, -on the exact target in use, this information can be used to determine -the required metrics. +@node GNAT Debug_Utilities g-debuti ads,GNAT Decode_String g-decstr ads,GNAT Debug_Pools g-debpoo ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-debug-utilities-g-debuti-ads}@anchor{2ec}@anchor{gnat_rm/the_gnat_library id61}@anchor{2ed} +@section @cite{GNAT.Debug_Utilities} (@code{g-debuti.ads}) -@sp 1 -@item -@cartouche -@noindent -The declarations of @code{Any_Priority} and -@code{Priority}. See D.1(11). -@end cartouche -@noindent -See declarations in file @file{system.ads}. - -@sp 1 -@item -@cartouche -@noindent -Implementation-defined execution resources. See D.1(15). -@end cartouche -@noindent -There are no implementation-defined execution resources. -@sp 1 -@item -@cartouche -@noindent -Whether, on a multiprocessor, a task that is waiting for -access to a protected object keeps its processor busy. See D.2.1(3). -@end cartouche -@noindent -On a multi-processor, a task that is waiting for access to a protected -object does not keep its processor busy. +@geindex GNAT.Debug_Utilities (g-debuti.ads) -@sp 1 -@item -@cartouche -@noindent -The affect of implementation defined execution resources -on task dispatching. See D.2.1(9). -@end cartouche -@noindent -Tasks map to threads in the threads package used by GNAT@. Where possible -and appropriate, these threads correspond to native threads of the -underlying operating system. +@geindex Debugging -@sp 1 -@item -@cartouche -@noindent -Implementation-defined @code{policy_identifiers} allowed -in a pragma @code{Task_Dispatching_Policy}. See D.2.2(3). -@end cartouche -@noindent -There are no implementation-defined policy-identifiers allowed in this -pragma. +Provides a few useful utilities for debugging purposes, including conversion +to and from string images of address values. Supports both C and Ada formats +for hexadecimal literals. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of priority inversion. See -D.2.2(16). -@end cartouche -@noindent -Execution of a task cannot be preempted by the implementation processing -of delay expirations for lower priority tasks. +@node GNAT Decode_String g-decstr ads,GNAT Decode_UTF8_String g-deutst ads,GNAT Debug_Utilities g-debuti ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-decode-string-g-decstr-ads}@anchor{2ee}@anchor{gnat_rm/the_gnat_library id62}@anchor{2ef} +@section @cite{GNAT.Decode_String} (@code{g-decstr.ads}) -@sp 1 -@item -@cartouche -@noindent -Implementation-defined task dispatching. See D.2.2(18). -@end cartouche -@noindent -The policy is the same as that of the underlying threads implementation. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined @code{policy_identifiers} allowed -in a pragma @code{Locking_Policy}. See D.3(4). -@end cartouche -@noindent -The two implementation defined policies permitted in GNAT are -@code{Inheritance_Locking} and @code{Conccurent_Readers_Locking}. On -targets that support the @code{Inheritance_Locking} policy, locking is -implemented by inheritance, i.e.@: the task owning the lock operates -at a priority equal to the highest priority of any task currently -requesting the lock. On targets that support the -@code{Conccurent_Readers_Locking} policy, locking is implemented with a -read/write lock allowing multiple propected object functions to enter -concurrently. +@geindex GNAT.Decode_String (g-decstr.ads) -@sp 1 -@item -@cartouche -@noindent -Default ceiling priorities. See D.3(10). -@end cartouche -@noindent -The ceiling priority of protected objects of the type -@code{System.Interrupt_Priority'Last} as described in the Ada -Reference Manual D.3(10), +@geindex Decoding strings -@sp 1 -@item -@cartouche -@noindent -The ceiling of any protected object used internally by -the implementation. See D.3(16). -@end cartouche -@noindent -The ceiling priority of internal protected objects is -@code{System.Priority'Last}. +@geindex String decoding -@sp 1 -@item -@cartouche -@noindent -Implementation-defined queuing policies. See D.4(1). -@end cartouche -@noindent -There are no implementation-defined queuing policies. +@geindex Wide character encoding -@sp 1 -@item -@cartouche -@noindent -On a multiprocessor, any conditions that cause the -completion of an aborted construct to be delayed later than what is -specified for a single processor. See D.6(3). -@end cartouche -@noindent -The semantics for abort on a multi-processor is the same as on a single -processor, there are no further delays. +@geindex UTF-8 -@sp 1 -@item -@cartouche -@noindent -Any operations that implicitly require heap storage -allocation. See D.7(8). -@end cartouche -@noindent -The only operation that implicitly requires heap storage allocation is -task creation. +@geindex Unicode -@sp 1 -@item -@cartouche -@noindent -What happens when a task terminates in the presence of -pragma @code{No_Task_Termination}. See D.7(15). -@end cartouche -@noindent -Execution is erroneous in that case. +A generic package providing routines for decoding wide character and wide wide +character strings encoded as sequences of 8-bit characters using a specified +encoding method. Includes validation routines, and also routines for stepping +to next or previous encoded character in an encoded string. +Useful in conjunction with Unicode character coding. Note there is a +preinstantiation for UTF-8. See next entry. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of pragma -@code{Restrictions}. See D.7(20). -@end cartouche -@noindent -There are no such implementation-defined aspects. +@node GNAT Decode_UTF8_String g-deutst ads,GNAT Directory_Operations g-dirope ads,GNAT Decode_String g-decstr ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-decode-utf8-string-g-deutst-ads}@anchor{2f0}@anchor{gnat_rm/the_gnat_library id63}@anchor{2f1} +@section @cite{GNAT.Decode_UTF8_String} (@code{g-deutst.ads}) + + +@geindex GNAT.Decode_UTF8_String (g-deutst.ads) + +@geindex Decoding strings + +@geindex Decoding UTF-8 strings + +@geindex UTF-8 string decoding + +@geindex Wide character decoding + +@geindex UTF-8 + +@geindex Unicode + +A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding. + +@node GNAT Directory_Operations g-dirope ads,GNAT Directory_Operations Iteration g-diopit ads,GNAT Decode_UTF8_String g-deutst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id64}@anchor{2f2}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-g-dirope-ads}@anchor{2f3} +@section @cite{GNAT.Directory_Operations} (@code{g-dirope.ads}) + + +@geindex GNAT.Directory_Operations (g-dirope.ads) + +@geindex Directory operations + +Provides a set of routines for manipulating directories, including changing +the current directory, making new directories, and scanning the files in a +directory. + +@node GNAT Directory_Operations Iteration g-diopit ads,GNAT Dynamic_HTables g-dynhta ads,GNAT Directory_Operations g-dirope ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id65}@anchor{2f4}@anchor{gnat_rm/the_gnat_library gnat-directory-operations-iteration-g-diopit-ads}@anchor{2f5} +@section @cite{GNAT.Directory_Operations.Iteration} (@code{g-diopit.ads}) + + +@geindex GNAT.Directory_Operations.Iteration (g-diopit.ads) + +@geindex Directory operations iteration + +A child unit of GNAT.Directory_Operations providing additional operations +for iterating through directories. + +@node GNAT Dynamic_HTables g-dynhta ads,GNAT Dynamic_Tables g-dyntab ads,GNAT Directory_Operations Iteration g-diopit ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-dynamic-htables-g-dynhta-ads}@anchor{2f6}@anchor{gnat_rm/the_gnat_library id66}@anchor{2f7} +@section @cite{GNAT.Dynamic_HTables} (@code{g-dynhta.ads}) + + +@geindex GNAT.Dynamic_HTables (g-dynhta.ads) + +@geindex Hash tables + +A generic implementation of hash tables that can be used to hash arbitrary +data. Provided in two forms, a simple form with built in hash functions, +and a more complex form in which the hash function is supplied. + +This package provides a facility similar to that of @cite{GNAT.HTable}, +except that this package declares a type that can be used to define +dynamic instances of the hash table, while an instantiation of +@cite{GNAT.HTable} creates a single instance of the hash table. + +@node GNAT Dynamic_Tables g-dyntab ads,GNAT Encode_String g-encstr ads,GNAT Dynamic_HTables g-dynhta ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-dynamic-tables-g-dyntab-ads}@anchor{2f8}@anchor{gnat_rm/the_gnat_library id67}@anchor{2f9} +@section @cite{GNAT.Dynamic_Tables} (@code{g-dyntab.ads}) + + +@geindex GNAT.Dynamic_Tables (g-dyntab.ads) + +@geindex Table implementation + +@geindex Arrays +@geindex extendable + +A generic package providing a single dimension array abstraction where the +length of the array can be dynamically modified. + +This package provides a facility similar to that of @cite{GNAT.Table}, +except that this package declares a type that can be used to define +dynamic instances of the table, while an instantiation of +@cite{GNAT.Table} creates a single instance of the table type. + +@node GNAT Encode_String g-encstr ads,GNAT Encode_UTF8_String g-enutst ads,GNAT Dynamic_Tables g-dyntab ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id68}@anchor{2fa}@anchor{gnat_rm/the_gnat_library gnat-encode-string-g-encstr-ads}@anchor{2fb} +@section @cite{GNAT.Encode_String} (@code{g-encstr.ads}) + + +@geindex GNAT.Encode_String (g-encstr.ads) + +@geindex Encoding strings + +@geindex String encoding + +@geindex Wide character encoding + +@geindex UTF-8 + +@geindex Unicode + +A generic package providing routines for encoding wide character and wide +wide character strings as sequences of 8-bit characters using a specified +encoding method. Useful in conjunction with Unicode character coding. +Note there is a preinstantiation for UTF-8. See next entry. + +@node GNAT Encode_UTF8_String g-enutst ads,GNAT Exception_Actions g-excact ads,GNAT Encode_String g-encstr ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-encode-utf8-string-g-enutst-ads}@anchor{2fc}@anchor{gnat_rm/the_gnat_library id69}@anchor{2fd} +@section @cite{GNAT.Encode_UTF8_String} (@code{g-enutst.ads}) + + +@geindex GNAT.Encode_UTF8_String (g-enutst.ads) + +@geindex Encoding strings + +@geindex Encoding UTF-8 strings + +@geindex UTF-8 string encoding + +@geindex Wide character encoding + +@geindex UTF-8 + +@geindex Unicode + +A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding. + +@node GNAT Exception_Actions g-excact ads,GNAT Exception_Traces g-exctra ads,GNAT Encode_UTF8_String g-enutst ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id70}@anchor{2fe}@anchor{gnat_rm/the_gnat_library gnat-exception-actions-g-excact-ads}@anchor{2ff} +@section @cite{GNAT.Exception_Actions} (@code{g-excact.ads}) + + +@geindex GNAT.Exception_Actions (g-excact.ads) + +@geindex Exception actions + +Provides callbacks when an exception is raised. Callbacks can be registered +for specific exceptions, or when any exception is raised. This +can be used for instance to force a core dump to ease debugging. + +@node GNAT Exception_Traces g-exctra ads,GNAT Exceptions g-expect ads,GNAT Exception_Actions g-excact ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-exception-traces-g-exctra-ads}@anchor{300}@anchor{gnat_rm/the_gnat_library id71}@anchor{301} +@section @cite{GNAT.Exception_Traces} (@code{g-exctra.ads}) + + +@geindex GNAT.Exception_Traces (g-exctra.ads) + +@geindex Exception traces + +@geindex Debugging + +Provides an interface allowing to control automatic output upon exception +occurrences. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of package -@code{Real_Time}. See D.8(17). -@end cartouche -@noindent -There are no implementation defined aspects of package @code{Real_Time}. - -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of -@code{delay_statements}. See D.9(8). -@end cartouche -@noindent -Any difference greater than one microsecond will cause the task to be -delayed (see D.9(7)). +@node GNAT Exceptions g-expect ads,GNAT Expect g-expect ads,GNAT Exception_Traces g-exctra ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id72}@anchor{302}@anchor{gnat_rm/the_gnat_library gnat-exceptions-g-expect-ads}@anchor{303} +@section @cite{GNAT.Exceptions} (@code{g-expect.ads}) -@sp 1 -@item -@cartouche -@noindent -The upper bound on the duration of interrupt blocking -caused by the implementation. See D.12(5). -@end cartouche -@noindent -The upper bound is determined by the underlying operating system. In -no cases is it more than 10 milliseconds. -@sp 1 -@item -@cartouche -@noindent -The means for creating and executing distributed -programs. See E(5). -@end cartouche -@noindent -The GLADE package provides a utility GNATDIST for creating and executing -distributed programs. See the GLADE reference manual for further details. +@geindex GNAT.Exceptions (g-expect.ads) -@sp 1 -@item -@cartouche -@noindent -Any events that can result in a partition becoming -inaccessible. See E.1(7). -@end cartouche -@noindent -See the GLADE reference manual for full details on such events. +@geindex Exceptions +@geindex Pure -@sp 1 -@item -@cartouche -@noindent -The scheduling policies, treatment of priorities, and -management of shared resources between partitions in certain cases. See -E.1(11). -@end cartouche -@noindent -See the GLADE reference manual for full details on these aspects of -multi-partition execution. +@geindex Pure packages +@geindex exceptions -@sp 1 -@item -@cartouche -@noindent -Events that cause the version of a compilation unit to -change. See E.3(5). -@end cartouche -@noindent -Editing the source file of a compilation unit, or the source files of -any units on which it is dependent in a significant way cause the version -to change. No other actions cause the version number to change. All changes -are significant except those which affect only layout, capitalization or -comments. +Normally it is not possible to raise an exception with +a message from a subprogram in a pure package, since the +necessary types and subprograms are in @cite{Ada.Exceptions} +which is not a pure unit. @cite{GNAT.Exceptions} provides a +facility for getting around this limitation for a few +predefined exceptions, and for example allow raising +@cite{Constraint_Error} with a message from a pure subprogram. -@sp 1 -@item -@cartouche -@noindent -Whether the execution of the remote subprogram is -immediately aborted as a result of cancellation. See E.4(13). -@end cartouche -@noindent -See the GLADE reference manual for details on the effect of abort in -a distributed application. +@node GNAT Expect g-expect ads,GNAT Expect TTY g-exptty ads,GNAT Exceptions g-expect ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id73}@anchor{304}@anchor{gnat_rm/the_gnat_library gnat-expect-g-expect-ads}@anchor{305} +@section @cite{GNAT.Expect} (@code{g-expect.ads}) -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of the PCS@. See E.5(25). -@end cartouche -@noindent -See the GLADE reference manual for a full description of all implementation -defined aspects of the PCS@. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined interfaces in the PCS@. See -E.5(26). -@end cartouche -@noindent -See the GLADE reference manual for a full description of all -implementation defined interfaces. +@geindex GNAT.Expect (g-expect.ads) -@sp 1 -@item -@cartouche -@noindent -The values of named numbers in the package -@code{Decimal}. See F.2(7). -@end cartouche -@noindent -@table @code -@item Max_Scale -+18 -@item Min_Scale --18 -@item Min_Delta -1.0E-18 -@item Max_Delta -1.0E+18 -@item Max_Decimal_Digits -18 -@end table +Provides a set of subprograms similar to what is available +with the standard Tcl Expect tool. +It allows you to easily spawn and communicate with an external process. +You can send commands or inputs to the process, and compare the output +with some expected regular expression. Currently @cite{GNAT.Expect} +is implemented on all native GNAT ports. +It is not implemented for cross ports, and in particular is not +implemented for VxWorks or LynxOS. -@sp 1 -@item -@cartouche -@noindent -The value of @code{Max_Picture_Length} in the package -@code{Text_IO.Editing}. See F.3.3(16). -@end cartouche -@noindent -64 +@node GNAT Expect TTY g-exptty ads,GNAT Float_Control g-flocon ads,GNAT Expect g-expect ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id74}@anchor{306}@anchor{gnat_rm/the_gnat_library gnat-expect-tty-g-exptty-ads}@anchor{307} +@section @cite{GNAT.Expect.TTY} (@code{g-exptty.ads}) -@sp 1 -@item -@cartouche -@noindent -The value of @code{Max_Picture_Length} in the package -@code{Wide_Text_IO.Editing}. See F.3.4(5). -@end cartouche -@noindent -64 -@sp 1 -@item -@cartouche -@noindent -The accuracy actually achieved by the complex elementary -functions and by other complex arithmetic operations. See G.1(1). -@end cartouche -@noindent -Standard library functions are used for the complex arithmetic -operations. Only fast math mode is currently supported. +@geindex GNAT.Expect.TTY (g-exptty.ads) -@sp 1 -@item -@cartouche -@noindent -The sign of a zero result (or a component thereof) from -any operator or function in @code{Numerics.Generic_Complex_Types}, when -@code{Real'Signed_Zeros} is True. See G.1.1(53). -@end cartouche -@noindent -The signs of zero values are as recommended by the relevant -implementation advice. +As GNAT.Expect but using pseudo-terminal. +Currently @cite{GNAT.Expect.TTY} is implemented on all native GNAT +ports. It is not implemented for cross ports, and +in particular is not implemented for VxWorks or LynxOS. -@sp 1 -@item -@cartouche -@noindent -The sign of a zero result (or a component thereof) from -any operator or function in -@code{Numerics.Generic_Complex_Elementary_Functions}, when -@code{Real'Signed_Zeros} is @code{True}. See G.1.2(45). -@end cartouche -@noindent -The signs of zero values are as recommended by the relevant -implementation advice. +@node GNAT Float_Control g-flocon ads,GNAT Formatted_String g-forstr ads,GNAT Expect TTY g-exptty ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id75}@anchor{308}@anchor{gnat_rm/the_gnat_library gnat-float-control-g-flocon-ads}@anchor{309} +@section @cite{GNAT.Float_Control} (@code{g-flocon.ads}) -@sp 1 -@item -@cartouche -@noindent -Whether the strict mode or the relaxed mode is the -default. See G.2(2). -@end cartouche -@noindent -The strict mode is the default. There is no separate relaxed mode. GNAT -provides a highly efficient implementation of strict mode. -@sp 1 -@item -@cartouche -@noindent -The result interval in certain cases of fixed-to-float -conversion. See G.2.1(10). -@end cartouche -@noindent -For cases where the result interval is implementation dependent, the -accuracy is that provided by performing all operations in 64-bit IEEE -floating-point format. +@geindex GNAT.Float_Control (g-flocon.ads) -@sp 1 -@item -@cartouche -@noindent -The result of a floating point arithmetic operation in -overflow situations, when the @code{Machine_Overflows} attribute of the -result type is @code{False}. See G.2.1(13). -@end cartouche -@noindent -Infinite and NaN values are produced as dictated by the IEEE -floating-point standard. +@geindex Floating-Point Processor -Note that on machines that are not fully compliant with the IEEE -floating-point standard, such as Alpha, the @option{-mieee} compiler flag -must be used for achieving IEEE conforming behavior (although at the cost -of a significant performance penalty), so infinite and NaN values are -properly generated. +Provides an interface for resetting the floating-point processor into the +mode required for correct semantic operation in Ada. Some third party +library calls may cause this mode to be modified, and the Reset procedure +in this package can be used to reestablish the required mode. -@sp 1 -@item -@cartouche -@noindent -The result interval for division (or exponentiation by a -negative exponent), when the floating point hardware implements division -as multiplication by a reciprocal. See G.2.1(16). -@end cartouche -@noindent -Not relevant, division is IEEE exact. +@node GNAT Formatted_String g-forstr ads,GNAT Heap_Sort g-heasor ads,GNAT Float_Control g-flocon ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id76}@anchor{30a}@anchor{gnat_rm/the_gnat_library gnat-formatted-string-g-forstr-ads}@anchor{30b} +@section @cite{GNAT.Formatted_String} (@code{g-forstr.ads}) -@sp 1 -@item -@cartouche -@noindent -The definition of close result set, which determines the -accuracy of certain fixed point multiplications and divisions. See -G.2.3(5). -@end cartouche -@noindent -Operations in the close result set are performed using IEEE long format -floating-point arithmetic. The input operands are converted to -floating-point, the operation is done in floating-point, and the result -is converted to the target type. -@sp 1 -@item -@cartouche -@noindent -Conditions on a @code{universal_real} operand of a fixed -point multiplication or division for which the result shall be in the -perfect result set. See G.2.3(22). -@end cartouche -@noindent -The result is only defined to be in the perfect result set if the result -can be computed by a single scaling operation involving a scale factor -representable in 64-bits. +@geindex GNAT.Formatted_String (g-forstr.ads) -@sp 1 -@item -@cartouche -@noindent -The result of a fixed point arithmetic operation in -overflow situations, when the @code{Machine_Overflows} attribute of the -result type is @code{False}. See G.2.3(27). -@end cartouche -@noindent -Not relevant, @code{Machine_Overflows} is @code{True} for fixed-point -types. +@geindex Formatted String -@sp 1 -@item -@cartouche -@noindent -The result of an elementary function reference in -overflow situations, when the @code{Machine_Overflows} attribute of the -result type is @code{False}. See G.2.4(4). -@end cartouche -@noindent -IEEE infinite and Nan values are produced as appropriate. +Provides support for C/C++ printf() formatted strings. The format is +copied from the printf() routine and should therefore gives identical +output. Some generic routines are provided to be able to use types +derived from Integer, Float or enumerations as values for the +formatted string. -@sp 1 -@item -@cartouche -@noindent -The value of the angle threshold, within which certain -elementary functions, complex arithmetic operations, and complex -elementary functions yield results conforming to a maximum relative -error bound. See G.2.4(10). -@end cartouche -@noindent -Information on this subject is not yet available. +@node GNAT Heap_Sort g-heasor ads,GNAT Heap_Sort_A g-hesora ads,GNAT Formatted_String g-forstr ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-heasor-ads}@anchor{30c}@anchor{gnat_rm/the_gnat_library id77}@anchor{30d} +@section @cite{GNAT.Heap_Sort} (@code{g-heasor.ads}) -@sp 1 -@item -@cartouche -@noindent -The accuracy of certain elementary functions for -parameters beyond the angle threshold. See G.2.4(10). -@end cartouche -@noindent -Information on this subject is not yet available. -@sp 1 -@item -@cartouche -@noindent -The result of a complex arithmetic operation or complex -elementary function reference in overflow situations, when the -@code{Machine_Overflows} attribute of the corresponding real type is -@code{False}. See G.2.6(5). -@end cartouche -@noindent -IEEE infinite and Nan values are produced as appropriate. +@geindex GNAT.Heap_Sort (g-heasor.ads) -@sp 1 -@item -@cartouche -@noindent -The accuracy of certain complex arithmetic operations and -certain complex elementary functions for parameters (or components -thereof) beyond the angle threshold. See G.2.6(8). -@end cartouche -@noindent -Information on those subjects is not yet available. +@geindex Sorting -@sp 1 -@item -@cartouche -@noindent -Information regarding bounded errors and erroneous -execution. See H.2(1). -@end cartouche -@noindent -Information on this subject is not yet available. +Provides a general implementation of heap sort usable for sorting arbitrary +data items. Exchange and comparison procedures are provided by passing +access-to-procedure values. The algorithm used is a modified heap sort +that performs approximately N*log(N) comparisons in the worst case. -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of pragma -@code{Inspection_Point}. See H.3.2(8). -@end cartouche -@noindent -Pragma @code{Inspection_Point} ensures that the variable is live and can -be examined by the debugger at the inspection point. +@node GNAT Heap_Sort_A g-hesora ads,GNAT Heap_Sort_G g-hesorg ads,GNAT Heap_Sort g-heasor ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id78}@anchor{30e}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-a-g-hesora-ads}@anchor{30f} +@section @cite{GNAT.Heap_Sort_A} (@code{g-hesora.ads}) -@sp 1 -@item -@cartouche -@noindent -Implementation-defined aspects of pragma -@code{Restrictions}. See H.4(25). -@end cartouche -@noindent -There are no implementation-defined aspects of pragma @code{Restrictions}. The -use of pragma @code{Restrictions [No_Exceptions]} has no effect on the -generated code. Checks must suppressed by use of pragma @code{Suppress}. - -@sp 1 -@item -@cartouche -@noindent -Any restrictions on pragma @code{Restrictions}. See -H.4(27). -@end cartouche -@noindent -There are no restrictions on pragma @code{Restrictions}. -@end itemize +@geindex GNAT.Heap_Sort_A (g-hesora.ads) +@geindex Sorting -@c ======================= -@node Intrinsic Subprograms -@chapter Intrinsic Subprograms -@cindex Intrinsic Subprograms +Provides a general implementation of heap sort usable for sorting arbitrary +data items. Move and comparison procedures are provided by passing +access-to-procedure values. The algorithm used is a modified heap sort +that performs approximately N*log(N) comparisons in the worst case. +This differs from @cite{GNAT.Heap_Sort} in having a less convenient +interface, but may be slightly more efficient. -@menu -* Intrinsic Operators:: -* Compilation_Date:: -* Compilation_Time:: -* Enclosing_Entity:: -* Exception_Information:: -* Exception_Message:: -* Exception_Name:: -* File:: -* Line:: -* Shifts and Rotates:: -* Source_Location:: -@end menu +@node GNAT Heap_Sort_G g-hesorg ads,GNAT HTable g-htable ads,GNAT Heap_Sort_A g-hesora ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id79}@anchor{310}@anchor{gnat_rm/the_gnat_library gnat-heap-sort-g-g-hesorg-ads}@anchor{311} +@section @cite{GNAT.Heap_Sort_G} (@code{g-hesorg.ads}) -@noindent -GNAT allows a user application program to write the declaration: -@smallexample @c ada - pragma Import (Intrinsic, name); -@end smallexample +@geindex GNAT.Heap_Sort_G (g-hesorg.ads) -@noindent -providing that the name corresponds to one of the implemented intrinsic -subprograms in GNAT, and that the parameter profile of the referenced -subprogram meets the requirements. This chapter describes the set of -implemented intrinsic subprograms, and the requirements on parameter profiles. -Note that no body is supplied; as with other uses of pragma Import, the -body is supplied elsewhere (in this case by the compiler itself). Note -that any use of this feature is potentially non-portable, since the -Ada standard does not require Ada compilers to implement this feature. +@geindex Sorting -@node Intrinsic Operators -@section Intrinsic Operators -@cindex Intrinsic operator +Similar to @cite{Heap_Sort_A} except that the move and sorting procedures +are provided as generic parameters, this improves efficiency, especially +if the procedures can be inlined, at the expense of duplicating code for +multiple instantiations. -@noindent -All the predefined numeric operators in package Standard -in @code{pragma Import (Intrinsic,..)} -declarations. In the binary operator case, the operands must have the same -size. The operand or operands must also be appropriate for -the operator. For example, for addition, the operands must -both be floating-point or both be fixed-point, and the -right operand for @code{"**"} must have a root type of -@code{Standard.Integer'Base}. -You can use an intrinsic operator declaration as in the following example: +@node GNAT HTable g-htable ads,GNAT IO g-io ads,GNAT Heap_Sort_G g-hesorg ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id80}@anchor{312}@anchor{gnat_rm/the_gnat_library gnat-htable-g-htable-ads}@anchor{313} +@section @cite{GNAT.HTable} (@code{g-htable.ads}) -@smallexample @c ada - type Int1 is new Integer; - type Int2 is new Integer; - function "+" (X1 : Int1; X2 : Int2) return Int1; - function "+" (X1 : Int1; X2 : Int2) return Int2; - pragma Import (Intrinsic, "+"); -@end smallexample +@geindex GNAT.HTable (g-htable.ads) -@noindent -This declaration would permit ``mixed mode'' arithmetic on items -of the differing types @code{Int1} and @code{Int2}. -It is also possible to specify such operators for private types, if the -full views are appropriate arithmetic types. +@geindex Hash tables -@node Compilation_Date -@section Compilation_Date -@cindex Compilation_Date -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.Compilation_Date} to obtain the date of -the current compilation (in local time format MMM DD YYYY). +A generic implementation of hash tables that can be used to hash arbitrary +data. Provides two approaches, one a simple static approach, and the other +allowing arbitrary dynamic hash tables. -@node Compilation_Time -@section Compilation_Time -@cindex Compilation_Time -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.Compilation_Time} to obtain the time of -the current compilation (in local time format HH:MM:SS). +@node GNAT IO g-io ads,GNAT IO_Aux g-io_aux ads,GNAT HTable g-htable ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id81}@anchor{314}@anchor{gnat_rm/the_gnat_library gnat-io-g-io-ads}@anchor{315} +@section @cite{GNAT.IO} (@code{g-io.ads}) -@node Enclosing_Entity -@section Enclosing_Entity -@cindex Enclosing_Entity -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.Enclosing_Entity} to obtain the name of -the current subprogram, package, task, entry, or protected subprogram. -@node Exception_Information -@section Exception_Information -@cindex Exception_Information' -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Current_Exception}. The only useful -use of the intrinsic import in this case is the one in this unit, -so an application program should simply call the function -@code{GNAT.Current_Exception.Exception_Information} to obtain -the exception information associated with the current exception. +@geindex GNAT.IO (g-io.ads) -@node Exception_Message -@section Exception_Message -@cindex Exception_Message -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Current_Exception}. The only useful -use of the intrinsic import in this case is the one in this unit, -so an application program should simply call the function -@code{GNAT.Current_Exception.Exception_Message} to obtain -the message associated with the current exception. +@geindex Simple I/O -@node Exception_Name -@section Exception_Name -@cindex Exception_Name -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Current_Exception}. The only useful -use of the intrinsic import in this case is the one in this unit, -so an application program should simply call the function -@code{GNAT.Current_Exception.Exception_Name} to obtain -the name of the current exception. +@geindex Input/Output facilities -@node File -@section File -@cindex File -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.File} to obtain the name of the current -file. +A simple preelaborable input-output package that provides a subset of +simple Text_IO functions for reading characters and strings from +Standard_Input, and writing characters, strings and integers to either +Standard_Output or Standard_Error. -@node Line -@section Line -@cindex Line -@noindent -This intrinsic subprogram is used in the implementation of the -library package @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.Line} to obtain the number of the current -source line. +@node GNAT IO_Aux g-io_aux ads,GNAT Lock_Files g-locfil ads,GNAT IO g-io ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id82}@anchor{316}@anchor{gnat_rm/the_gnat_library gnat-io-aux-g-io-aux-ads}@anchor{317} +@section @cite{GNAT.IO_Aux} (@code{g-io_aux.ads}) -@node Shifts and Rotates -@section Shifts and Rotates -@cindex Shift_Left -@cindex Shift_Right -@cindex Shift_Right_Arithmetic -@cindex Rotate_Left -@cindex Rotate_Right -@noindent -In standard Ada, the shift and rotate functions are available only -for the predefined modular types in package @code{Interfaces}. However, in -GNAT it is possible to define these functions for any integer -type (signed or modular), as in this example: -@smallexample @c ada - function Shift_Left - (Value : T; - Amount : Natural) return T; -@end smallexample +@geindex GNAT.IO_Aux (g-io_aux.ads) -@noindent -The function name must be one of -Shift_Left, Shift_Right, Shift_Right_Arithmetic, Rotate_Left, or -Rotate_Right. T must be an integer type. T'Size must be -8, 16, 32 or 64 bits; if T is modular, the modulus -must be 2**8, 2**16, 2**32 or 2**64. -The result type must be the same as the type of @code{Value}. -The shift amount must be Natural. -The formal parameter names can be anything. +@geindex Text_IO -A more convenient way of providing these shift operators is to use -the Provide_Shift_Operators pragma, which provides the function declarations -and corresponding pragma Import's for all five shift functions. +@geindex Input/Output facilities -@node Source_Location -@section Source_Location -@cindex Source_Location -@noindent -This intrinsic subprogram is used in the implementation of the -library routine @code{GNAT.Source_Info}. The only useful use of the -intrinsic import in this case is the one in this unit, so an -application program should simply call the function -@code{GNAT.Source_Info.Source_Location} to obtain the current -source file location. +Provides some auxiliary functions for use with Text_IO, including a test +for whether a file exists, and functions for reading a line of text. -@node Representation Clauses and Pragmas -@chapter Representation Clauses and Pragmas -@cindex Representation Clauses +@node GNAT Lock_Files g-locfil ads,GNAT MBBS_Discrete_Random g-mbdira ads,GNAT IO_Aux g-io_aux ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id83}@anchor{318}@anchor{gnat_rm/the_gnat_library gnat-lock-files-g-locfil-ads}@anchor{319} +@section @cite{GNAT.Lock_Files} (@code{g-locfil.ads}) -@menu -* Alignment Clauses:: -* Size Clauses:: -* Storage_Size Clauses:: -* Size of Variant Record Objects:: -* Biased Representation :: -* Value_Size and Object_Size Clauses:: -* Component_Size Clauses:: -* Bit_Order Clauses:: -* Effect of Bit_Order on Byte Ordering:: -* Pragma Pack for Arrays:: -* Pragma Pack for Records:: -* Record Representation Clauses:: -* Handling of Records with Holes:: -* Enumeration Clauses:: -* Address Clauses:: -* Use of Address Clauses for Memory-Mapped I/O:: -* Effect of Convention on Representation:: -* Conventions and Anonymous Access Types:: -* Determining the Representations chosen by GNAT:: -@end menu -@noindent -@cindex Representation Clause -@cindex Representation Pragma -@cindex Pragma, representation -This section describes the representation clauses accepted by GNAT, and -their effect on the representation of corresponding data objects. +@geindex GNAT.Lock_Files (g-locfil.ads) -GNAT fully implements Annex C (Systems Programming). This means that all -the implementation advice sections in chapter 13 are fully implemented. -However, these sections only require a minimal level of support for -representation clauses. GNAT provides much more extensive capabilities, -and this section describes the additional capabilities provided. +@geindex File locking -@node Alignment Clauses -@section Alignment Clauses -@cindex Alignment Clause +@geindex Locking using files -@noindent -GNAT requires that all alignment clauses specify a power of 2, and all -default alignments are always a power of 2. The default alignment -values are as follows: +Provides a general interface for using files as locks. Can be used for +providing program level synchronization. -@itemize @bullet -@item @emph{Primitive Types}. -For primitive types, the alignment is the minimum of the actual size of -objects of the type divided by @code{Storage_Unit}, -and the maximum alignment supported by the target. -(This maximum alignment is given by the GNAT-specific attribute -@code{Standard'Maximum_Alignment}; see @ref{Attribute Maximum_Alignment}.) -@cindex @code{Maximum_Alignment} attribute -For example, for type @code{Long_Float}, the object size is 8 bytes, and the -default alignment will be 8 on any target that supports alignments -this large, but on some targets, the maximum alignment may be smaller -than 8, in which case objects of type @code{Long_Float} will be maximally -aligned. +@node GNAT MBBS_Discrete_Random g-mbdira ads,GNAT MBBS_Float_Random g-mbflra ads,GNAT Lock_Files g-locfil ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-mbbs-discrete-random-g-mbdira-ads}@anchor{31a}@anchor{gnat_rm/the_gnat_library id84}@anchor{31b} +@section @cite{GNAT.MBBS_Discrete_Random} (@code{g-mbdira.ads}) -@item @emph{Arrays}. -For arrays, the alignment is equal to the alignment of the component type -for the normal case where no packing or component size is given. If the -array is packed, and the packing is effective (see separate section on -packed arrays), then the alignment will be one for long packed arrays, -or arrays whose length is not known at compile time. For short packed -arrays, which are handled internally as modular types, the alignment -will be as described for primitive types, e.g.@: a packed array of length -31 bits will have an object size of four bytes, and an alignment of 4. -@item @emph{Records}. -For the normal non-packed case, the alignment of a record is equal to -the maximum alignment of any of its components. For tagged records, this -includes the implicit access type used for the tag. If a pragma @code{Pack} -is used and all components are packable (see separate section on pragma -@code{Pack}), then the resulting alignment is 1, unless the layout of the -record makes it profitable to increase it. +@geindex GNAT.MBBS_Discrete_Random (g-mbdira.ads) -A special case is when: -@itemize @bullet -@item -the size of the record is given explicitly, or a -full record representation clause is given, and -@item -the size of the record is 2, 4, or 8 bytes. -@end itemize -@noindent -In this case, an alignment is chosen to match the -size of the record. For example, if we have: +@geindex Random number generation -@smallexample @c ada - type Small is record - A, B : Character; - end record; - for Small'Size use 16; -@end smallexample +The original implementation of @cite{Ada.Numerics.Discrete_Random}. Uses +a modified version of the Blum-Blum-Shub generator. -@noindent -then the default alignment of the record type @code{Small} is 2, not 1. This -leads to more efficient code when the record is treated as a unit, and also -allows the type to specified as @code{Atomic} on architectures requiring -strict alignment. +@node GNAT MBBS_Float_Random g-mbflra ads,GNAT MD5 g-md5 ads,GNAT MBBS_Discrete_Random g-mbdira ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id85}@anchor{31c}@anchor{gnat_rm/the_gnat_library gnat-mbbs-float-random-g-mbflra-ads}@anchor{31d} +@section @cite{GNAT.MBBS_Float_Random} (@code{g-mbflra.ads}) -@end itemize -@noindent -An alignment clause may specify a larger alignment than the default value -up to some maximum value dependent on the target (obtainable by using the -attribute reference @code{Standard'Maximum_Alignment}). It may also specify -a smaller alignment than the default value for enumeration, integer and -fixed point types, as well as for record types, for example +@geindex GNAT.MBBS_Float_Random (g-mbflra.ads) -@smallexample @c ada - type V is record - A : Integer; - end record; +@geindex Random number generation - for V'alignment use 1; -@end smallexample +The original implementation of @cite{Ada.Numerics.Float_Random}. Uses +a modified version of the Blum-Blum-Shub generator. -@noindent -@cindex Alignment, default -The default alignment for the type @code{V} is 4, as a result of the -Integer field in the record, but it is permissible, as shown, to -override the default alignment of the record with a smaller value. +@node GNAT MD5 g-md5 ads,GNAT Memory_Dump g-memdum ads,GNAT MBBS_Float_Random g-mbflra ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id86}@anchor{31e}@anchor{gnat_rm/the_gnat_library gnat-md5-g-md5-ads}@anchor{31f} +@section @cite{GNAT.MD5} (@code{g-md5.ads}) -@cindex Alignment, subtypes -Note that according to the Ada standard, an alignment clause applies only -to the first named subtype. If additional subtypes are declared, then the -compiler is allowed to choose any alignment it likes, and there is no way -to control this choice. Consider: -@smallexample @c ada - type R is range 1 .. 10_000; - for R'Alignment use 1; - subtype RS is R range 1 .. 1000; -@end smallexample +@geindex GNAT.MD5 (g-md5.ads) -@noindent -The alignment clause specifies an alignment of 1 for the first named subtype -@code{R} but this does not necessarily apply to @code{RS}. When writing -portable Ada code, you should avoid writing code that explicitly or -implicitly relies on the alignment of such subtypes. +@geindex Message Digest MD5 -For the GNAT compiler, if an explicit alignment clause is given, this -value is also used for any subsequent subtypes. So for GNAT, in the -above example, you can count on the alignment of @code{RS} being 1. But this -assumption is non-portable, and other compilers may choose different -alignments for the subtype @code{RS}. +Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and +the HMAC-MD5 message authentication function as described in RFC 2104 and +FIPS PUB 198. -@node Size Clauses -@section Size Clauses -@cindex Size Clause +@node GNAT Memory_Dump g-memdum ads,GNAT Most_Recent_Exception g-moreex ads,GNAT MD5 g-md5 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id87}@anchor{320}@anchor{gnat_rm/the_gnat_library gnat-memory-dump-g-memdum-ads}@anchor{321} +@section @cite{GNAT.Memory_Dump} (@code{g-memdum.ads}) -@noindent -The default size for a type @code{T} is obtainable through the -language-defined attribute @code{T'Size} and also through the -equivalent GNAT-defined attribute @code{T'Value_Size}. -For objects of type @code{T}, GNAT will generally increase the type size -so that the object size (obtainable through the GNAT-defined attribute -@code{T'Object_Size}) -is a multiple of @code{T'Alignment * Storage_Unit}. -For example -@smallexample @c ada - type Smallint is range 1 .. 6; +@geindex GNAT.Memory_Dump (g-memdum.ads) - type Rec is record - Y1 : integer; - Y2 : boolean; - end record; -@end smallexample +@geindex Dump Memory -@noindent -In this example, @code{Smallint'Size} = @code{Smallint'Value_Size} = 3, -as specified by the RM rules, -but objects of this type will have a size of 8 -(@code{Smallint'Object_Size} = 8), -since objects by default occupy an integral number -of storage units. On some targets, notably older -versions of the Digital Alpha, the size of stand -alone objects of this type may be 32, reflecting -the inability of the hardware to do byte load/stores. +Provides a convenient routine for dumping raw memory to either the +standard output or standard error files. Uses GNAT.IO for actual +output. -Similarly, the size of type @code{Rec} is 40 bits -(@code{Rec'Size} = @code{Rec'Value_Size} = 40), but -the alignment is 4, so objects of this type will have -their size increased to 64 bits so that it is a multiple -of the alignment (in bits). This decision is -in accordance with the specific Implementation Advice in RM 13.3(43): +@node GNAT Most_Recent_Exception g-moreex ads,GNAT OS_Lib g-os_lib ads,GNAT Memory_Dump g-memdum ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id88}@anchor{322}@anchor{gnat_rm/the_gnat_library gnat-most-recent-exception-g-moreex-ads}@anchor{323} +@section @cite{GNAT.Most_Recent_Exception} (@code{g-moreex.ads}) -@quotation -A @code{Size} clause should be supported for an object if the specified -@code{Size} is at least as large as its subtype's @code{Size}, and corresponds -to a size in storage elements that is a multiple of the object's -@code{Alignment} (if the @code{Alignment} is nonzero). -@end quotation -@noindent -An explicit size clause may be used to override the default size by -increasing it. For example, if we have: +@geindex GNAT.Most_Recent_Exception (g-moreex.ads) -@smallexample @c ada - type My_Boolean is new Boolean; - for My_Boolean'Size use 32; -@end smallexample +@geindex Exception +@geindex obtaining most recent -@noindent -then values of this type will always be 32 bits long. In the case of -discrete types, the size can be increased up to 64 bits, with the effect -that the entire specified field is used to hold the value, sign- or -zero-extended as appropriate. If more than 64 bits is specified, then -padding space is allocated after the value, and a warning is issued that -there are unused bits. +Provides access to the most recently raised exception. Can be used for +various logging purposes, including duplicating functionality of some +Ada 83 implementation dependent extensions. -Similarly the size of records and arrays may be increased, and the effect -is to add padding bits after the value. This also causes a warning message -to be generated. +@node GNAT OS_Lib g-os_lib ads,GNAT Perfect_Hash_Generators g-pehage ads,GNAT Most_Recent_Exception g-moreex ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id89}@anchor{324}@anchor{gnat_rm/the_gnat_library gnat-os-lib-g-os-lib-ads}@anchor{325} +@section @cite{GNAT.OS_Lib} (@code{g-os_lib.ads}) -The largest Size value permitted in GNAT is 2**31@minus{}1. Since this is a -Size in bits, this corresponds to an object of size 256 megabytes (minus -one). This limitation is true on all targets. The reason for this -limitation is that it improves the quality of the code in many cases -if it is known that a Size value can be accommodated in an object of -type Integer. -@node Storage_Size Clauses -@section Storage_Size Clauses -@cindex Storage_Size Clause +@geindex GNAT.OS_Lib (g-os_lib.ads) -@noindent -For tasks, the @code{Storage_Size} clause specifies the amount of space -to be allocated for the task stack. This cannot be extended, and if the -stack is exhausted, then @code{Storage_Error} will be raised (if stack -checking is enabled). Use a @code{Storage_Size} attribute definition clause, -or a @code{Storage_Size} pragma in the task definition to set the -appropriate required size. A useful technique is to include in every -task definition a pragma of the form: +@geindex Operating System interface -@smallexample @c ada - pragma Storage_Size (Default_Stack_Size); -@end smallexample +@geindex Spawn capability -@noindent -Then @code{Default_Stack_Size} can be defined in a global package, and -modified as required. Any tasks requiring stack sizes different from the -default can have an appropriate alternative reference in the pragma. +Provides a range of target independent operating system interface functions, +including time/date management, file operations, subprocess management, +including a portable spawn procedure, and access to environment variables +and error return codes. -You can also use the @option{-d} binder switch to modify the default stack -size. +@node GNAT Perfect_Hash_Generators g-pehage ads,GNAT Random_Numbers g-rannum ads,GNAT OS_Lib g-os_lib ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id90}@anchor{326}@anchor{gnat_rm/the_gnat_library gnat-perfect-hash-generators-g-pehage-ads}@anchor{327} +@section @cite{GNAT.Perfect_Hash_Generators} (@code{g-pehage.ads}) -For access types, the @code{Storage_Size} clause specifies the maximum -space available for allocation of objects of the type. If this space is -exceeded then @code{Storage_Error} will be raised by an allocation attempt. -In the case where the access type is declared local to a subprogram, the -use of a @code{Storage_Size} clause triggers automatic use of a special -predefined storage pool (@code{System.Pool_Size}) that ensures that all -space for the pool is automatically reclaimed on exit from the scope in -which the type is declared. -A special case recognized by the compiler is the specification of a -@code{Storage_Size} of zero for an access type. This means that no -items can be allocated from the pool, and this is recognized at compile -time, and all the overhead normally associated with maintaining a fixed -size storage pool is eliminated. Consider the following example: +@geindex GNAT.Perfect_Hash_Generators (g-pehage.ads) -@smallexample @c ada - procedure p is - type R is array (Natural) of Character; - type P is access all R; - for P'Storage_Size use 0; - -- Above access type intended only for interfacing purposes +@geindex Hash functions - y : P; +Provides a generator of static minimal perfect hash functions. No +collisions occur and each item can be retrieved from the table in one +probe (perfect property). The hash table size corresponds to the exact +size of the key set and no larger (minimal property). The key set has to +be know in advance (static property). The hash functions are also order +preserving. If w2 is inserted after w1 in the generator, their +hashcode are in the same order. These hashing functions are very +convenient for use with realtime applications. - procedure g (m : P); - pragma Import (C, g); +@node GNAT Random_Numbers g-rannum ads,GNAT Regexp g-regexp ads,GNAT Perfect_Hash_Generators g-pehage ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id91}@anchor{328}@anchor{gnat_rm/the_gnat_library gnat-random-numbers-g-rannum-ads}@anchor{329} +@section @cite{GNAT.Random_Numbers} (@code{g-rannum.ads}) - -- @dots{} - begin - -- @dots{} - y := new R; - end; -@end smallexample +@geindex GNAT.Random_Numbers (g-rannum.ads) -@noindent -As indicated in this example, these dummy storage pools are often useful in -connection with interfacing where no object will ever be allocated. If you -compile the above example, you get the warning: +@geindex Random number generation -@smallexample - p.adb:16:09: warning: allocation from empty storage pool - p.adb:16:09: warning: Storage_Error will be raised at run time -@end smallexample +Provides random number capabilities which extend those available in the +standard Ada library and are more convenient to use. -@noindent -Of course in practice, there will not be any explicit allocators in the -case of such an access declaration. +@node GNAT Regexp g-regexp ads,GNAT Registry g-regist ads,GNAT Random_Numbers g-rannum ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-regexp-g-regexp-ads}@anchor{1fd}@anchor{gnat_rm/the_gnat_library id92}@anchor{32a} +@section @cite{GNAT.Regexp} (@code{g-regexp.ads}) -@node Size of Variant Record Objects -@section Size of Variant Record Objects -@cindex Size, variant record objects -@cindex Variant record objects, size -@noindent -In the case of variant record objects, there is a question whether Size gives -information about a particular variant, or the maximum size required -for any variant. Consider the following program +@geindex GNAT.Regexp (g-regexp.ads) -@smallexample @c ada -with Text_IO; use Text_IO; -procedure q is - type R1 (A : Boolean := False) is record - case A is - when True => X : Character; - when False => null; - end case; - end record; +@geindex Regular expressions - V1 : R1 (False); - V2 : R1; +@geindex Pattern matching -begin - Put_Line (Integer'Image (V1'Size)); - Put_Line (Integer'Image (V2'Size)); -end q; -@end smallexample +A simple implementation of regular expressions, using a subset of regular +expression syntax copied from familiar Unix style utilities. This is the +simplest of the three pattern matching packages provided, and is particularly +suitable for 'file globbing' applications. -@noindent -Here we are dealing with a variant record, where the True variant -requires 16 bits, and the False variant requires 8 bits. -In the above example, both V1 and V2 contain the False variant, -which is only 8 bits long. However, the result of running the -program is: +@node GNAT Registry g-regist ads,GNAT Regpat g-regpat ads,GNAT Regexp g-regexp ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id93}@anchor{32b}@anchor{gnat_rm/the_gnat_library gnat-registry-g-regist-ads}@anchor{32c} +@section @cite{GNAT.Registry} (@code{g-regist.ads}) -@smallexample -8 -16 -@end smallexample -@noindent -The reason for the difference here is that the discriminant value of -V1 is fixed, and will always be False. It is not possible to assign -a True variant value to V1, therefore 8 bits is sufficient. On the -other hand, in the case of V2, the initial discriminant value is -False (from the default), but it is possible to assign a True -variant value to V2, therefore 16 bits must be allocated for V2 -in the general case, even fewer bits may be needed at any particular -point during the program execution. +@geindex GNAT.Registry (g-regist.ads) -As can be seen from the output of this program, the @code{'Size} -attribute applied to such an object in GNAT gives the actual allocated -size of the variable, which is the largest size of any of the variants. -The Ada Reference Manual is not completely clear on what choice should -be made here, but the GNAT behavior seems most consistent with the -language in the RM@. +@geindex Windows Registry -In some cases, it may be desirable to obtain the size of the current -variant, rather than the size of the largest variant. This can be -achieved in GNAT by making use of the fact that in the case of a -subprogram parameter, GNAT does indeed return the size of the current -variant (because a subprogram has no way of knowing how much space -is actually allocated for the actual). +This is a high level binding to the Windows registry. It is possible to +do simple things like reading a key value, creating a new key. For full +registry API, but at a lower level of abstraction, refer to the Win32.Winreg +package provided with the Win32Ada binding -Consider the following modified version of the above program: +@node GNAT Regpat g-regpat ads,GNAT Rewrite_Data g-rewdat ads,GNAT Registry g-regist ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id94}@anchor{32d}@anchor{gnat_rm/the_gnat_library gnat-regpat-g-regpat-ads}@anchor{32e} +@section @cite{GNAT.Regpat} (@code{g-regpat.ads}) -@smallexample @c ada -with Text_IO; use Text_IO; -procedure q is - type R1 (A : Boolean := False) is record - case A is - when True => X : Character; - when False => null; - end case; - end record; - V2 : R1; +@geindex GNAT.Regpat (g-regpat.ads) - function Size (V : R1) return Integer is - begin - return V'Size; - end Size; +@geindex Regular expressions -begin - Put_Line (Integer'Image (V2'Size)); - Put_Line (Integer'IMage (Size (V2))); - V2 := (True, 'x'); - Put_Line (Integer'Image (V2'Size)); - Put_Line (Integer'IMage (Size (V2))); -end q; -@end smallexample +@geindex Pattern matching -@noindent -The output from this program is +A complete implementation of Unix-style regular expression matching, copied +from the original V7 style regular expression library written in C by +Henry Spencer (and binary compatible with this C library). -@smallexample -16 -8 -16 -16 -@end smallexample +@node GNAT Rewrite_Data g-rewdat ads,GNAT Secondary_Stack_Info g-sestin ads,GNAT Regpat g-regpat ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id95}@anchor{32f}@anchor{gnat_rm/the_gnat_library gnat-rewrite-data-g-rewdat-ads}@anchor{330} +@section @cite{GNAT.Rewrite_Data} (@code{g-rewdat.ads}) -@noindent -Here we see that while the @code{'Size} attribute always returns -the maximum size, regardless of the current variant value, the -@code{Size} function does indeed return the size of the current -variant value. -@node Biased Representation -@section Biased Representation -@cindex Size for biased representation -@cindex Biased representation +@geindex GNAT.Rewrite_Data (g-rewdat.ads) -@noindent -In the case of scalars with a range starting at other than zero, it is -possible in some cases to specify a size smaller than the default minimum -value, and in such cases, GNAT uses an unsigned biased representation, -in which zero is used to represent the lower bound, and successive values -represent successive values of the type. +@geindex Rewrite data -For example, suppose we have the declaration: +A unit to rewrite on-the-fly string occurrences in a stream of +data. The implementation has a very minimal memory footprint as the +full content to be processed is not loaded into memory all at once. This makes +this interface usable for large files or socket streams. -@smallexample @c ada - type Small is range -7 .. -4; - for Small'Size use 2; -@end smallexample +@node GNAT Secondary_Stack_Info g-sestin ads,GNAT Semaphores g-semaph ads,GNAT Rewrite_Data g-rewdat ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-secondary-stack-info-g-sestin-ads}@anchor{331}@anchor{gnat_rm/the_gnat_library id96}@anchor{332} +@section @cite{GNAT.Secondary_Stack_Info} (@code{g-sestin.ads}) -@noindent -Although the default size of type @code{Small} is 4, the @code{Size} -clause is accepted by GNAT and results in the following representation -scheme: -@smallexample - -7 is represented as 2#00# - -6 is represented as 2#01# - -5 is represented as 2#10# - -4 is represented as 2#11# -@end smallexample +@geindex GNAT.Secondary_Stack_Info (g-sestin.ads) -@noindent -Biased representation is only used if the specified @code{Size} clause -cannot be accepted in any other manner. These reduced sizes that force -biased representation can be used for all discrete types except for -enumeration types for which a representation clause is given. +@geindex Secondary Stack Info -@node Value_Size and Object_Size Clauses -@section Value_Size and Object_Size Clauses -@findex Value_Size -@findex Object_Size -@cindex Size, of objects +Provide the capability to query the high water mark of the current task's +secondary stack. -@noindent -In Ada 95 and Ada 2005, @code{T'Size} for a type @code{T} is the minimum -number of bits required to hold values of type @code{T}. -Although this interpretation was allowed in Ada 83, it was not required, -and this requirement in practice can cause some significant difficulties. -For example, in most Ada 83 compilers, @code{Natural'Size} was 32. -However, in Ada 95 and Ada 2005, -@code{Natural'Size} is -typically 31. This means that code may change in behavior when moving -from Ada 83 to Ada 95 or Ada 2005. For example, consider: +@node GNAT Semaphores g-semaph ads,GNAT Serial_Communications g-sercom ads,GNAT Secondary_Stack_Info g-sestin ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-semaphores-g-semaph-ads}@anchor{333}@anchor{gnat_rm/the_gnat_library id97}@anchor{334} +@section @cite{GNAT.Semaphores} (@code{g-semaph.ads}) -@smallexample @c ada - type Rec is record; - A : Natural; - B : Natural; - end record; - for Rec use record - at 0 range 0 .. Natural'Size - 1; - at 0 range Natural'Size .. 2 * Natural'Size - 1; - end record; -@end smallexample +@geindex GNAT.Semaphores (g-semaph.ads) -@noindent -In the above code, since the typical size of @code{Natural} objects -is 32 bits and @code{Natural'Size} is 31, the above code can cause -unexpected inefficient packing in Ada 95 and Ada 2005, and in general -there are cases where the fact that the object size can exceed the -size of the type causes surprises. +@geindex Semaphores -To help get around this problem GNAT provides two implementation -defined attributes, @code{Value_Size} and @code{Object_Size}. When -applied to a type, these attributes yield the size of the type -(corresponding to the RM defined size attribute), and the size of -objects of the type respectively. +Provides classic counting and binary semaphores using protected types. -The @code{Object_Size} is used for determining the default size of -objects and components. This size value can be referred to using the -@code{Object_Size} attribute. The phrase ``is used'' here means that it is -the basis of the determination of the size. The backend is free to -pad this up if necessary for efficiency, e.g.@: an 8-bit stand-alone -character might be stored in 32 bits on a machine with no efficient -byte access instructions such as the Alpha. +@node GNAT Serial_Communications g-sercom ads,GNAT SHA1 g-sha1 ads,GNAT Semaphores g-semaph ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id98}@anchor{335}@anchor{gnat_rm/the_gnat_library gnat-serial-communications-g-sercom-ads}@anchor{336} +@section @cite{GNAT.Serial_Communications} (@code{g-sercom.ads}) -The default rules for the value of @code{Object_Size} for -discrete types are as follows: -@itemize @bullet -@item -The @code{Object_Size} for base subtypes reflect the natural hardware -size in bits (run the compiler with @option{-gnatS} to find those values -for numeric types). Enumeration types and fixed-point base subtypes have -8, 16, 32 or 64 bits for this size, depending on the range of values -to be stored. +@geindex GNAT.Serial_Communications (g-sercom.ads) -@item -The @code{Object_Size} of a subtype is the same as the -@code{Object_Size} of -the type from which it is obtained. +@geindex Serial_Communications -@item -The @code{Object_Size} of a derived base type is copied from the parent -base type, and the @code{Object_Size} of a derived first subtype is copied -from the parent first subtype. -@end itemize +Provides a simple interface to send and receive data over a serial +port. This is only supported on GNU/Linux and Windows. -@noindent -The @code{Value_Size} attribute -is the (minimum) number of bits required to store a value -of the type. -This value is used to determine how tightly to pack -records or arrays with components of this type, and also affects -the semantics of unchecked conversion (unchecked conversions where -the @code{Value_Size} values differ generate a warning, and are potentially -target dependent). +@node GNAT SHA1 g-sha1 ads,GNAT SHA224 g-sha224 ads,GNAT Serial_Communications g-sercom ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-sha1-g-sha1-ads}@anchor{337}@anchor{gnat_rm/the_gnat_library id99}@anchor{338} +@section @cite{GNAT.SHA1} (@code{g-sha1.ads}) -The default rules for the value of @code{Value_Size} are as follows: -@itemize @bullet -@item -The @code{Value_Size} for a base subtype is the minimum number of bits -required to store all values of the type (including the sign bit -only if negative values are possible). +@geindex GNAT.SHA1 (g-sha1.ads) -@item -If a subtype statically matches the first subtype of a given type, then it has -by default the same @code{Value_Size} as the first subtype. This is a -consequence of RM 13.1(14) (``if two subtypes statically match, -then their subtype-specific aspects are the same''.) +@geindex Secure Hash Algorithm SHA-1 -@item -All other subtypes have a @code{Value_Size} corresponding to the minimum -number of bits required to store all values of the subtype. For -dynamic bounds, it is assumed that the value can range down or up -to the corresponding bound of the ancestor -@end itemize +Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3 +and RFC 3174, and the HMAC-SHA1 message authentication function as described +in RFC 2104 and FIPS PUB 198. -@noindent -The RM defined attribute @code{Size} corresponds to the -@code{Value_Size} attribute. +@node GNAT SHA224 g-sha224 ads,GNAT SHA256 g-sha256 ads,GNAT SHA1 g-sha1 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id100}@anchor{339}@anchor{gnat_rm/the_gnat_library gnat-sha224-g-sha224-ads}@anchor{33a} +@section @cite{GNAT.SHA224} (@code{g-sha224.ads}) -The @code{Size} attribute may be defined for a first-named subtype. This sets -the @code{Value_Size} of -the first-named subtype to the given value, and the -@code{Object_Size} of this first-named subtype to the given value padded up -to an appropriate boundary. It is a consequence of the default rules -above that this @code{Object_Size} will apply to all further subtypes. On the -other hand, @code{Value_Size} is affected only for the first subtype, any -dynamic subtypes obtained from it directly, and any statically matching -subtypes. The @code{Value_Size} of any other static subtypes is not affected. -@code{Value_Size} and -@code{Object_Size} may be explicitly set for any subtype using -an attribute definition clause. Note that the use of these attributes -can cause the RM 13.1(14) rule to be violated. If two access types -reference aliased objects whose subtypes have differing @code{Object_Size} -values as a result of explicit attribute definition clauses, then it -is illegal to convert from one access subtype to the other. For a more -complete description of this additional legality rule, see the -description of the @code{Object_Size} attribute. +@geindex GNAT.SHA224 (g-sha224.ads) -At the implementation level, Esize stores the Object_Size and the -RM_Size field stores the @code{Value_Size} (and hence the value of the -@code{Size} attribute, -which, as noted above, is equivalent to @code{Value_Size}). +@geindex Secure Hash Algorithm SHA-224 -To get a feel for the difference, consider the following examples (note -that in each case the base is @code{Short_Short_Integer} with a size of 8): +Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA224 message authentication function as described +in RFC 2104 and FIPS PUB 198. -@smallexample - Object_Size Value_Size +@node GNAT SHA256 g-sha256 ads,GNAT SHA384 g-sha384 ads,GNAT SHA224 g-sha224 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id101}@anchor{33b}@anchor{gnat_rm/the_gnat_library gnat-sha256-g-sha256-ads}@anchor{33c} +@section @cite{GNAT.SHA256} (@code{g-sha256.ads}) -type x1 is range 0 .. 5; 8 3 -type x2 is range 0 .. 5; -for x2'size use 12; 16 12 +@geindex GNAT.SHA256 (g-sha256.ads) -subtype x3 is x2 range 0 .. 3; 16 2 +@geindex Secure Hash Algorithm SHA-256 -subtype x4 is x2'base range 0 .. 10; 8 4 +Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA256 message authentication function as described +in RFC 2104 and FIPS PUB 198. -subtype x5 is x2 range 0 .. dynamic; 16 3* +@node GNAT SHA384 g-sha384 ads,GNAT SHA512 g-sha512 ads,GNAT SHA256 g-sha256 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id102}@anchor{33d}@anchor{gnat_rm/the_gnat_library gnat-sha384-g-sha384-ads}@anchor{33e} +@section @cite{GNAT.SHA384} (@code{g-sha384.ads}) -subtype x6 is x2'base range 0 .. dynamic; 8 3* -@end smallexample +@geindex GNAT.SHA384 (g-sha384.ads) -@noindent -Note: the entries marked ``3*'' are not actually specified by the Ada -Reference Manual, but it seems in the spirit of the RM rules to allocate -the minimum number of bits (here 3, given the range for @code{x2}) -known to be large enough to hold the given range of values. +@geindex Secure Hash Algorithm SHA-384 -So far, so good, but GNAT has to obey the RM rules, so the question is -under what conditions must the RM @code{Size} be used. -The following is a list -of the occasions on which the RM @code{Size} must be used: +Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA384 message authentication function as described +in RFC 2104 and FIPS PUB 198. -@itemize @bullet -@item -Component size for packed arrays or records +@node GNAT SHA512 g-sha512 ads,GNAT Signals g-signal ads,GNAT SHA384 g-sha384 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id103}@anchor{33f}@anchor{gnat_rm/the_gnat_library gnat-sha512-g-sha512-ads}@anchor{340} +@section @cite{GNAT.SHA512} (@code{g-sha512.ads}) -@item -Value of the attribute @code{Size} for a type -@item -Warning about sizes not matching for unchecked conversion -@end itemize +@geindex GNAT.SHA512 (g-sha512.ads) -@noindent -For record types, the @code{Object_Size} is always a multiple of the -alignment of the type (this is true for all types). In some cases the -@code{Value_Size} can be smaller. Consider: +@geindex Secure Hash Algorithm SHA-512 -@smallexample - type R is record - X : Integer; - Y : Character; - end record; -@end smallexample +Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3, +and the HMAC-SHA512 message authentication function as described +in RFC 2104 and FIPS PUB 198. -@noindent -On a typical 32-bit architecture, the X component will be four bytes, and -require four-byte alignment, and the Y component will be one byte. In this -case @code{R'Value_Size} will be 40 (bits) since this is the minimum size -required to store a value of this type, and for example, it is permissible -to have a component of type R in an outer array whose component size is -specified to be 48 bits. However, @code{R'Object_Size} will be 64 (bits), -since it must be rounded up so that this value is a multiple of the -alignment (4 bytes = 32 bits). +@node GNAT Signals g-signal ads,GNAT Sockets g-socket ads,GNAT SHA512 g-sha512 ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-signals-g-signal-ads}@anchor{341}@anchor{gnat_rm/the_gnat_library id104}@anchor{342} +@section @cite{GNAT.Signals} (@code{g-signal.ads}) -@noindent -For all other types, the @code{Object_Size} -and Value_Size are the same (and equivalent to the RM attribute @code{Size}). -Only @code{Size} may be specified for such types. -Note that @code{Value_Size} can be used to force biased representation -for a particular subtype. Consider this example: +@geindex GNAT.Signals (g-signal.ads) -@smallexample - type R is (A, B, C, D, E, F); - subtype RAB is R range A .. B; - subtype REF is R range E .. F; -@end smallexample +@geindex Signals -@noindent -By default, @code{RAB} -has a size of 1 (sufficient to accommodate the representation -of @code{A} and @code{B}, 0 and 1), and @code{REF} -has a size of 3 (sufficient to accommodate the representation -of @code{E} and @code{F}, 4 and 5). But if we add the -following @code{Value_Size} attribute definition clause: +Provides the ability to manipulate the blocked status of signals on supported +targets. -@smallexample - for REF'Value_Size use 1; -@end smallexample +@node GNAT Sockets g-socket ads,GNAT Source_Info g-souinf ads,GNAT Signals g-signal ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-sockets-g-socket-ads}@anchor{343}@anchor{gnat_rm/the_gnat_library id105}@anchor{344} +@section @cite{GNAT.Sockets} (@code{g-socket.ads}) -@noindent -then biased representation is forced for @code{REF}, -and 0 will represent @code{E} and 1 will represent @code{F}. -A warning is issued when a @code{Value_Size} attribute -definition clause forces biased representation. This -warning can be turned off using @code{-gnatw.B}. -@node Component_Size Clauses -@section Component_Size Clauses -@cindex Component_Size Clause +@geindex GNAT.Sockets (g-socket.ads) -@noindent -Normally, the value specified in a component size clause must be consistent -with the subtype of the array component with regard to size and alignment. -In other words, the value specified must be at least equal to the size -of this subtype, and must be a multiple of the alignment value. +@geindex Sockets -In addition, component size clauses are allowed which cause the array -to be packed, by specifying a smaller value. A first case is for -component size values in the range 1 through 63. The value specified -must not be smaller than the Size of the subtype. GNAT will accurately -honor all packing requests in this range. For example, if we have: +A high level and portable interface to develop sockets based applications. +This package is based on the sockets thin binding found in +@cite{GNAT.Sockets.Thin}. Currently @cite{GNAT.Sockets} is implemented +on all native GNAT ports and on VxWorks cross prots. It is not implemented for +the LynxOS cross port. -@smallexample @c ada -type r is array (1 .. 8) of Natural; -for r'Component_Size use 31; -@end smallexample +@node GNAT Source_Info g-souinf ads,GNAT Spelling_Checker g-speche ads,GNAT Sockets g-socket ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-source-info-g-souinf-ads}@anchor{345}@anchor{gnat_rm/the_gnat_library id106}@anchor{346} +@section @cite{GNAT.Source_Info} (@code{g-souinf.ads}) -@noindent -then the resulting array has a length of 31 bytes (248 bits = 8 * 31). -Of course access to the components of such an array is considerably -less efficient than if the natural component size of 32 is used. -A second case is when the subtype of the component is a record type -padded because of its default alignment. For example, if we have: -@smallexample @c ada -type r is record - i : Integer; - j : Integer; - b : Boolean; -end record; +@geindex GNAT.Source_Info (g-souinf.ads) -type a is array (1 .. 8) of r; -for a'Component_Size use 72; -@end smallexample +@geindex Source Information -@noindent -then the resulting array has a length of 72 bytes, instead of 96 bytes -if the alignment of the record (4) was obeyed. +Provides subprograms that give access to source code information known at +compile time, such as the current file name and line number. Also provides +subprograms yielding the date and time of the current compilation (like the +C macros @cite{__DATE__} and @cite{__TIME__}) -Note that there is no point in giving both a component size clause -and a pragma Pack for the same array type. if such duplicate -clauses are given, the pragma Pack will be ignored. +@node GNAT Spelling_Checker g-speche ads,GNAT Spelling_Checker_Generic g-spchge ads,GNAT Source_Info g-souinf ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-g-speche-ads}@anchor{347}@anchor{gnat_rm/the_gnat_library id107}@anchor{348} +@section @cite{GNAT.Spelling_Checker} (@code{g-speche.ads}) -@node Bit_Order Clauses -@section Bit_Order Clauses -@cindex Bit_Order Clause -@cindex bit ordering -@cindex ordering, of bits -@noindent -For record subtypes, GNAT permits the specification of the @code{Bit_Order} -attribute. The specification may either correspond to the default bit -order for the target, in which case the specification has no effect and -places no additional restrictions, or it may be for the non-standard -setting (that is the opposite of the default). +@geindex GNAT.Spelling_Checker (g-speche.ads) -In the case where the non-standard value is specified, the effect is -to renumber bits within each byte, but the ordering of bytes is not -affected. There are certain -restrictions placed on component clauses as follows: +@geindex Spell checking -@itemize @bullet +Provides a function for determining whether one string is a plausible +near misspelling of another string. -@item Components fitting within a single storage unit. -@noindent -These are unrestricted, and the effect is merely to renumber bits. For -example if we are on a little-endian machine with @code{Low_Order_First} -being the default, then the following two declarations have exactly -the same effect: +@node GNAT Spelling_Checker_Generic g-spchge ads,GNAT Spitbol Patterns g-spipat ads,GNAT Spelling_Checker g-speche ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-spelling-checker-generic-g-spchge-ads}@anchor{349}@anchor{gnat_rm/the_gnat_library id108}@anchor{34a} +@section @cite{GNAT.Spelling_Checker_Generic} (@code{g-spchge.ads}) -@smallexample @c ada - type R1 is record - A : Boolean; - B : Integer range 1 .. 120; - end record; - for R1 use record - A at 0 range 0 .. 0; - B at 0 range 1 .. 7; - end record; +@geindex GNAT.Spelling_Checker_Generic (g-spchge.ads) - type R2 is record - A : Boolean; - B : Integer range 1 .. 120; - end record; +@geindex Spell checking - for R2'Bit_Order use High_Order_First; +Provides a generic function that can be instantiated with a string type for +determining whether one string is a plausible near misspelling of another +string. - for R2 use record - A at 0 range 7 .. 7; - B at 0 range 0 .. 6; - end record; -@end smallexample +@node GNAT Spitbol Patterns g-spipat ads,GNAT Spitbol g-spitbo ads,GNAT Spelling_Checker_Generic g-spchge ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id109}@anchor{34b}@anchor{gnat_rm/the_gnat_library gnat-spitbol-patterns-g-spipat-ads}@anchor{34c} +@section @cite{GNAT.Spitbol.Patterns} (@code{g-spipat.ads}) -@noindent -The useful application here is to write the second declaration with the -@code{Bit_Order} attribute definition clause, and know that it will be treated -the same, regardless of whether the target is little-endian or big-endian. -@item Components occupying an integral number of bytes. -@noindent -These are components that exactly fit in two or more bytes. Such component -declarations are allowed, but have no effect, since it is important to realize -that the @code{Bit_Order} specification does not affect the ordering of bytes. -In particular, the following attempt at getting an endian-independent integer -does not work: +@geindex GNAT.Spitbol.Patterns (g-spipat.ads) -@smallexample @c ada - type R2 is record - A : Integer; - end record; +@geindex SPITBOL pattern matching - for R2'Bit_Order use High_Order_First; +@geindex Pattern matching - for R2 use record - A at 0 range 0 .. 31; - end record; -@end smallexample +A complete implementation of SNOBOL4 style pattern matching. This is the +most elaborate of the pattern matching packages provided. It fully duplicates +the SNOBOL4 dynamic pattern construction and matching capabilities, using the +efficient algorithm developed by Robert Dewar for the SPITBOL system. -@noindent -This declaration will result in a little-endian integer on a -little-endian machine, and a big-endian integer on a big-endian machine. -If byte flipping is required for interoperability between big- and -little-endian machines, this must be explicitly programmed. This capability -is not provided by @code{Bit_Order}. +@node GNAT Spitbol g-spitbo ads,GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Patterns g-spipat ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id110}@anchor{34d}@anchor{gnat_rm/the_gnat_library gnat-spitbol-g-spitbo-ads}@anchor{34e} +@section @cite{GNAT.Spitbol} (@code{g-spitbo.ads}) -@item Components that are positioned across byte boundaries -@noindent -but do not occupy an integral number of bytes. Given that bytes are not -reordered, such fields would occupy a non-contiguous sequence of bits -in memory, requiring non-trivial code to reassemble. They are for this -reason not permitted, and any component clause specifying such a layout -will be flagged as illegal by GNAT@. -@end itemize +@geindex GNAT.Spitbol (g-spitbo.ads) -@noindent -Since the misconception that Bit_Order automatically deals with all -endian-related incompatibilities is a common one, the specification of -a component field that is an integral number of bytes will always -generate a warning. This warning may be suppressed using @code{pragma -Warnings (Off)} if desired. The following section contains additional -details regarding the issue of byte ordering. +@geindex SPITBOL interface -@node Effect of Bit_Order on Byte Ordering -@section Effect of Bit_Order on Byte Ordering -@cindex byte ordering -@cindex ordering, of bytes +The top level package of the collection of SPITBOL-style functionality, this +package provides basic SNOBOL4 string manipulation functions, such as +Pad, Reverse, Trim, Substr capability, as well as a generic table function +useful for constructing arbitrary mappings from strings in the style of +the SNOBOL4 TABLE function. -@noindent -In this section we will review the effect of the @code{Bit_Order} attribute -definition clause on byte ordering. Briefly, it has no effect at all, but -a detailed example will be helpful. Before giving this -example, let us review the precise -definition of the effect of defining @code{Bit_Order}. The effect of a -non-standard bit order is described in section 15.5.3 of the Ada -Reference Manual: +@node GNAT Spitbol Table_Boolean g-sptabo ads,GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol g-spitbo ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id111}@anchor{34f}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-boolean-g-sptabo-ads}@anchor{350} +@section @cite{GNAT.Spitbol.Table_Boolean} (@code{g-sptabo.ads}) -@quotation -2 A bit ordering is a method of interpreting the meaning of -the storage place attributes. -@end quotation -@noindent -To understand the precise definition of storage place attributes in -this context, we visit section 13.5.1 of the manual: +@geindex GNAT.Spitbol.Table_Boolean (g-sptabo.ads) -@quotation -13 A record_representation_clause (without the mod_clause) -specifies the layout. The storage place attributes (see 13.5.2) -are taken from the values of the position, first_bit, and last_bit -expressions after normalizing those values so that first_bit is -less than Storage_Unit. -@end quotation +@geindex Sets of strings -@noindent -The critical point here is that storage places are taken from -the values after normalization, not before. So the @code{Bit_Order} -interpretation applies to normalized values. The interpretation -is described in the later part of the 15.5.3 paragraph: +@geindex SPITBOL Tables -@quotation -2 A bit ordering is a method of interpreting the meaning of -the storage place attributes. High_Order_First (known in the -vernacular as ``big endian'') means that the first bit of a -storage element (bit 0) is the most significant bit (interpreting -the sequence of bits that represent a component as an unsigned -integer value). Low_Order_First (known in the vernacular as -``little endian'') means the opposite: the first bit is the -least significant. -@end quotation +A library level of instantiation of @cite{GNAT.Spitbol.Patterns.Table} +for type @cite{Standard.Boolean}, giving an implementation of sets of +string values. -@noindent -Note that the numbering is with respect to the bits of a storage -unit. In other words, the specification affects only the numbering -of bits within a single storage unit. +@node GNAT Spitbol Table_Integer g-sptain ads,GNAT Spitbol Table_VString g-sptavs ads,GNAT Spitbol Table_Boolean g-sptabo ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id112}@anchor{351}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-integer-g-sptain-ads}@anchor{352} +@section @cite{GNAT.Spitbol.Table_Integer} (@code{g-sptain.ads}) -We can make the effect clearer by giving an example. -Suppose that we have an external device which presents two bytes, the first -byte presented, which is the first (low addressed byte) of the two byte -record is called Master, and the second byte is called Slave. +@geindex GNAT.Spitbol.Table_Integer (g-sptain.ads) -The left most (most significant bit is called Control for each byte, and -the remaining 7 bits are called V1, V2, @dots{} V7, where V7 is the rightmost -(least significant) bit. +@geindex Integer maps -On a big-endian machine, we can write the following representation clause +@geindex Maps -@smallexample @c ada - type Data is record - Master_Control : Bit; - Master_V1 : Bit; - Master_V2 : Bit; - Master_V3 : Bit; - Master_V4 : Bit; - Master_V5 : Bit; - Master_V6 : Bit; - Master_V7 : Bit; - Slave_Control : Bit; - Slave_V1 : Bit; - Slave_V2 : Bit; - Slave_V3 : Bit; - Slave_V4 : Bit; - Slave_V5 : Bit; - Slave_V6 : Bit; - Slave_V7 : Bit; - end record; +@geindex SPITBOL Tables - for Data use record - Master_Control at 0 range 0 .. 0; - Master_V1 at 0 range 1 .. 1; - Master_V2 at 0 range 2 .. 2; - Master_V3 at 0 range 3 .. 3; - Master_V4 at 0 range 4 .. 4; - Master_V5 at 0 range 5 .. 5; - Master_V6 at 0 range 6 .. 6; - Master_V7 at 0 range 7 .. 7; - Slave_Control at 1 range 0 .. 0; - Slave_V1 at 1 range 1 .. 1; - Slave_V2 at 1 range 2 .. 2; - Slave_V3 at 1 range 3 .. 3; - Slave_V4 at 1 range 4 .. 4; - Slave_V5 at 1 range 5 .. 5; - Slave_V6 at 1 range 6 .. 6; - Slave_V7 at 1 range 7 .. 7; - end record; -@end smallexample +A library level of instantiation of @cite{GNAT.Spitbol.Patterns.Table} +for type @cite{Standard.Integer}, giving an implementation of maps +from string to integer values. -@noindent -Now if we move this to a little endian machine, then the bit ordering within -the byte is backwards, so we have to rewrite the record rep clause as: +@node GNAT Spitbol Table_VString g-sptavs ads,GNAT SSE g-sse ads,GNAT Spitbol Table_Integer g-sptain ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id113}@anchor{353}@anchor{gnat_rm/the_gnat_library gnat-spitbol-table-vstring-g-sptavs-ads}@anchor{354} +@section @cite{GNAT.Spitbol.Table_VString} (@code{g-sptavs.ads}) -@smallexample @c ada - for Data use record - Master_Control at 0 range 7 .. 7; - Master_V1 at 0 range 6 .. 6; - Master_V2 at 0 range 5 .. 5; - Master_V3 at 0 range 4 .. 4; - Master_V4 at 0 range 3 .. 3; - Master_V5 at 0 range 2 .. 2; - Master_V6 at 0 range 1 .. 1; - Master_V7 at 0 range 0 .. 0; - Slave_Control at 1 range 7 .. 7; - Slave_V1 at 1 range 6 .. 6; - Slave_V2 at 1 range 5 .. 5; - Slave_V3 at 1 range 4 .. 4; - Slave_V4 at 1 range 3 .. 3; - Slave_V5 at 1 range 2 .. 2; - Slave_V6 at 1 range 1 .. 1; - Slave_V7 at 1 range 0 .. 0; - end record; -@end smallexample -@noindent -It is a nuisance to have to rewrite the clause, especially if -the code has to be maintained on both machines. However, -this is a case that we can handle with the -@code{Bit_Order} attribute if it is implemented. -Note that the implementation is not required on byte addressed -machines, but it is indeed implemented in GNAT. -This means that we can simply use the -first record clause, together with the declaration +@geindex GNAT.Spitbol.Table_VString (g-sptavs.ads) -@smallexample @c ada - for Data'Bit_Order use High_Order_First; -@end smallexample +@geindex String maps -@noindent -and the effect is what is desired, namely the layout is exactly the same, -independent of whether the code is compiled on a big-endian or little-endian -machine. +@geindex Maps -The important point to understand is that byte ordering is not affected. -A @code{Bit_Order} attribute definition never affects which byte a field -ends up in, only where it ends up in that byte. -To make this clear, let us rewrite the record rep clause of the previous -example as: +@geindex SPITBOL Tables -@smallexample @c ada - for Data'Bit_Order use High_Order_First; - for Data use record - Master_Control at 0 range 0 .. 0; - Master_V1 at 0 range 1 .. 1; - Master_V2 at 0 range 2 .. 2; - Master_V3 at 0 range 3 .. 3; - Master_V4 at 0 range 4 .. 4; - Master_V5 at 0 range 5 .. 5; - Master_V6 at 0 range 6 .. 6; - Master_V7 at 0 range 7 .. 7; - Slave_Control at 0 range 8 .. 8; - Slave_V1 at 0 range 9 .. 9; - Slave_V2 at 0 range 10 .. 10; - Slave_V3 at 0 range 11 .. 11; - Slave_V4 at 0 range 12 .. 12; - Slave_V5 at 0 range 13 .. 13; - Slave_V6 at 0 range 14 .. 14; - Slave_V7 at 0 range 15 .. 15; - end record; -@end smallexample +A library level of instantiation of @cite{GNAT.Spitbol.Patterns.Table} for +a variable length string type, giving an implementation of general +maps from strings to strings. -@noindent -This is exactly equivalent to saying (a repeat of the first example): +@node GNAT SSE g-sse ads,GNAT SSE Vector_Types g-ssvety ads,GNAT Spitbol Table_VString g-sptavs ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id114}@anchor{355}@anchor{gnat_rm/the_gnat_library gnat-sse-g-sse-ads}@anchor{356} +@section @cite{GNAT.SSE} (@code{g-sse.ads}) -@smallexample @c ada - for Data'Bit_Order use High_Order_First; - for Data use record - Master_Control at 0 range 0 .. 0; - Master_V1 at 0 range 1 .. 1; - Master_V2 at 0 range 2 .. 2; - Master_V3 at 0 range 3 .. 3; - Master_V4 at 0 range 4 .. 4; - Master_V5 at 0 range 5 .. 5; - Master_V6 at 0 range 6 .. 6; - Master_V7 at 0 range 7 .. 7; - Slave_Control at 1 range 0 .. 0; - Slave_V1 at 1 range 1 .. 1; - Slave_V2 at 1 range 2 .. 2; - Slave_V3 at 1 range 3 .. 3; - Slave_V4 at 1 range 4 .. 4; - Slave_V5 at 1 range 5 .. 5; - Slave_V6 at 1 range 6 .. 6; - Slave_V7 at 1 range 7 .. 7; - end record; -@end smallexample -@noindent -Why are they equivalent? Well take a specific field, the @code{Slave_V2} -field. The storage place attributes are obtained by normalizing the -values given so that the @code{First_Bit} value is less than 8. After -normalizing the values (0,10,10) we get (1,2,2) which is exactly what -we specified in the other case. +@geindex GNAT.SSE (g-sse.ads) -Now one might expect that the @code{Bit_Order} attribute might affect -bit numbering within the entire record component (two bytes in this -case, thus affecting which byte fields end up in), but that is not -the way this feature is defined, it only affects numbering of bits, -not which byte they end up in. +Root of a set of units aimed at offering Ada bindings to a subset of +the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of +targets. It exposes vector component types together with a general +introduction to the binding contents and use. -Consequently it never makes sense to specify a starting bit number -greater than 7 (for a byte addressable field) if an attribute -definition for @code{Bit_Order} has been given, and indeed it -may be actively confusing to specify such a value, so the compiler -generates a warning for such usage. +@node GNAT SSE Vector_Types g-ssvety ads,GNAT Strings g-string ads,GNAT SSE g-sse ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-sse-vector-types-g-ssvety-ads}@anchor{357}@anchor{gnat_rm/the_gnat_library id115}@anchor{358} +@section @cite{GNAT.SSE.Vector_Types} (@code{g-ssvety.ads}) -If you do need to control byte ordering then appropriate conditional -values must be used. If in our example, the slave byte came first on -some machines we might write: -@smallexample @c ada - Master_Byte_First constant Boolean := @dots{}; - - Master_Byte : constant Natural := - 1 - Boolean'Pos (Master_Byte_First); - Slave_Byte : constant Natural := - Boolean'Pos (Master_Byte_First); - - for Data'Bit_Order use High_Order_First; - for Data use record - Master_Control at Master_Byte range 0 .. 0; - Master_V1 at Master_Byte range 1 .. 1; - Master_V2 at Master_Byte range 2 .. 2; - Master_V3 at Master_Byte range 3 .. 3; - Master_V4 at Master_Byte range 4 .. 4; - Master_V5 at Master_Byte range 5 .. 5; - Master_V6 at Master_Byte range 6 .. 6; - Master_V7 at Master_Byte range 7 .. 7; - Slave_Control at Slave_Byte range 0 .. 0; - Slave_V1 at Slave_Byte range 1 .. 1; - Slave_V2 at Slave_Byte range 2 .. 2; - Slave_V3 at Slave_Byte range 3 .. 3; - Slave_V4 at Slave_Byte range 4 .. 4; - Slave_V5 at Slave_Byte range 5 .. 5; - Slave_V6 at Slave_Byte range 6 .. 6; - Slave_V7 at Slave_Byte range 7 .. 7; - end record; -@end smallexample +@geindex GNAT.SSE.Vector_Types (g-ssvety.ads) -@noindent -Now to switch between machines, all that is necessary is -to set the boolean constant @code{Master_Byte_First} in -an appropriate manner. +SSE vector types for use with SSE related intrinsics. -@node Pragma Pack for Arrays -@section Pragma Pack for Arrays -@cindex Pragma Pack (for arrays) +@node GNAT Strings g-string ads,GNAT String_Split g-strspl ads,GNAT SSE Vector_Types g-ssvety ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id116}@anchor{359}@anchor{gnat_rm/the_gnat_library gnat-strings-g-string-ads}@anchor{35a} +@section @cite{GNAT.Strings} (@code{g-string.ads}) -@noindent -Pragma @code{Pack} applied to an array has no effect unless the component type -is packable. For a component type to be packable, it must be one of the -following cases: -@itemize @bullet -@item -Any scalar type -@item -Any type whose size is specified with a size clause -@item -Any packed array type with a static size -@item -Any record type padded because of its default alignment -@end itemize +@geindex GNAT.Strings (g-string.ads) -@noindent -For all these cases, if the component subtype size is in the range -1 through 63, then the effect of the pragma @code{Pack} is exactly as though a -component size were specified giving the component subtype size. -For example if we have: +Common String access types and related subprograms. Basically it +defines a string access and an array of string access types. -@smallexample @c ada - type r is range 0 .. 17; +@node GNAT String_Split g-strspl ads,GNAT Table g-table ads,GNAT Strings g-string ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-string-split-g-strspl-ads}@anchor{35b}@anchor{gnat_rm/the_gnat_library id117}@anchor{35c} +@section @cite{GNAT.String_Split} (@code{g-strspl.ads}) - type ar is array (1 .. 8) of r; - pragma Pack (ar); -@end smallexample -@noindent -Then the component size of @code{ar} will be set to 5 (i.e.@: to @code{r'size}, -and the size of the array @code{ar} will be exactly 40 bits. +@geindex GNAT.String_Split (g-strspl.ads) -Note that in some cases this rather fierce approach to packing can produce -unexpected effects. For example, in Ada 95 and Ada 2005, -subtype @code{Natural} typically has a size of 31, meaning that if you -pack an array of @code{Natural}, you get 31-bit -close packing, which saves a few bits, but results in far less efficient -access. Since many other Ada compilers will ignore such a packing request, -GNAT will generate a warning on some uses of pragma @code{Pack} that it guesses -might not be what is intended. You can easily remove this warning by -using an explicit @code{Component_Size} setting instead, which never generates -a warning, since the intention of the programmer is clear in this case. +@geindex String splitter -GNAT treats packed arrays in one of two ways. If the size of the array is -known at compile time and is less than 64 bits, then internally the array -is represented as a single modular type, of exactly the appropriate number -of bits. If the length is greater than 63 bits, or is not known at compile -time, then the packed array is represented as an array of bytes, and the -length is always a multiple of 8 bits. +Useful string manipulation routines: given a set of separators, split +a string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +@cite{GNAT.Array_Split}. + +@node GNAT Table g-table ads,GNAT Task_Lock g-tasloc ads,GNAT String_Split g-strspl ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id118}@anchor{35d}@anchor{gnat_rm/the_gnat_library gnat-table-g-table-ads}@anchor{35e} +@section @cite{GNAT.Table} (@code{g-table.ads}) -Note that to represent a packed array as a modular type, the alignment must -be suitable for the modular type involved. For example, on typical machines -a 32-bit packed array will be represented by a 32-bit modular integer with -an alignment of four bytes. If you explicitly override the default alignment -with an alignment clause that is too small, the modular representation -cannot be used. For example, consider the following set of declarations: -@smallexample @c ada - type R is range 1 .. 3; - type S is array (1 .. 31) of R; - for S'Component_Size use 2; - for S'Size use 62; - for S'Alignment use 1; -@end smallexample +@geindex GNAT.Table (g-table.ads) -@noindent -If the alignment clause were not present, then a 62-bit modular -representation would be chosen (typically with an alignment of 4 or 8 -bytes depending on the target). But the default alignment is overridden -with the explicit alignment clause. This means that the modular -representation cannot be used, and instead the array of bytes -representation must be used, meaning that the length must be a multiple -of 8. Thus the above set of declarations will result in a diagnostic -rejecting the size clause and noting that the minimum size allowed is 64. +@geindex Table implementation -@cindex Pragma Pack (for type Natural) -@cindex Pragma Pack warning +@geindex Arrays +@geindex extendable -One special case that is worth noting occurs when the base type of the -component size is 8/16/32 and the subtype is one bit less. Notably this -occurs with subtype @code{Natural}. Consider: +A generic package providing a single dimension array abstraction where the +length of the array can be dynamically modified. -@smallexample @c ada - type Arr is array (1 .. 32) of Natural; - pragma Pack (Arr); -@end smallexample +This package provides a facility similar to that of @cite{GNAT.Dynamic_Tables}, +except that this package declares a single instance of the table type, +while an instantiation of @cite{GNAT.Dynamic_Tables} creates a type that can be +used to define dynamic instances of the table. -@noindent -In all commonly used Ada 83 compilers, this pragma Pack would be ignored, -since typically @code{Natural'Size} is 32 in Ada 83, and in any case most -Ada 83 compilers did not attempt 31 bit packing. +@node GNAT Task_Lock g-tasloc ads,GNAT Time_Stamp g-timsta ads,GNAT Table g-table ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-task-lock-g-tasloc-ads}@anchor{35f}@anchor{gnat_rm/the_gnat_library id119}@anchor{360} +@section @cite{GNAT.Task_Lock} (@code{g-tasloc.ads}) -In Ada 95 and Ada 2005, @code{Natural'Size} is required to be 31. Furthermore, -GNAT really does pack 31-bit subtype to 31 bits. This may result in a -substantial unintended performance penalty when porting legacy Ada 83 code. -To help prevent this, GNAT generates a warning in such cases. If you really -want 31 bit packing in a case like this, you can set the component size -explicitly: -@smallexample @c ada - type Arr is array (1 .. 32) of Natural; - for Arr'Component_Size use 31; -@end smallexample +@geindex GNAT.Task_Lock (g-tasloc.ads) -@noindent -Here 31-bit packing is achieved as required, and no warning is generated, -since in this case the programmer intention is clear. +@geindex Task synchronization -@node Pragma Pack for Records -@section Pragma Pack for Records -@cindex Pragma Pack (for records) +@geindex Task locking -@noindent -Pragma @code{Pack} applied to a record will pack the components to reduce -wasted space from alignment gaps and by reducing the amount of space -taken by components. We distinguish between @emph{packable} components and -@emph{non-packable} components. -Components of the following types are considered packable: -@itemize @bullet -@item -Components of a primitive type are packable unless they are aliased -or of an atomic type. +@geindex Locking -@item -Small packed arrays, whose size does not exceed 64 bits, and where the -size is statically known at compile time, are represented internally -as modular integers, and so they are also packable. +A very simple facility for locking and unlocking sections of code using a +single global task lock. Appropriate for use in situations where contention +between tasks is very rarely expected. -@end itemize +@node GNAT Time_Stamp g-timsta ads,GNAT Threads g-thread ads,GNAT Task_Lock g-tasloc ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-time-stamp-g-timsta-ads}@anchor{361}@anchor{gnat_rm/the_gnat_library id120}@anchor{362} +@section @cite{GNAT.Time_Stamp} (@code{g-timsta.ads}) -@noindent -All packable components occupy the exact number of bits corresponding to -their @code{Size} value, and are packed with no padding bits, i.e.@: they -can start on an arbitrary bit boundary. -All other types are non-packable, they occupy an integral number of -storage units, and -are placed at a boundary corresponding to their alignment requirements. +@geindex GNAT.Time_Stamp (g-timsta.ads) -For example, consider the record +@geindex Time stamp -@smallexample @c ada - type Rb1 is array (1 .. 13) of Boolean; - pragma Pack (Rb1); +@geindex Current time - type Rb2 is array (1 .. 65) of Boolean; - pragma Pack (Rb2); +Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that +represents the current date and time in ISO 8601 format. This is a very simple +routine with minimal code and there are no dependencies on any other unit. - type AF is new Float with Atomic; +@node GNAT Threads g-thread ads,GNAT Traceback g-traceb ads,GNAT Time_Stamp g-timsta ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-threads-g-thread-ads}@anchor{363}@anchor{gnat_rm/the_gnat_library id121}@anchor{364} +@section @cite{GNAT.Threads} (@code{g-thread.ads}) - type X2 is record - L1 : Boolean; - L2 : Duration; - L3 : AF; - L4 : Boolean; - L5 : Rb1; - L6 : Rb2; - end record; - pragma Pack (X2); -@end smallexample -@noindent -The representation for the record X2 is as follows: +@geindex GNAT.Threads (g-thread.ads) -@smallexample @c ada -for X2'Size use 224; -for X2 use record - L1 at 0 range 0 .. 0; - L2 at 0 range 1 .. 64; - L3 at 12 range 0 .. 31; - L4 at 16 range 0 .. 0; - L5 at 16 range 1 .. 13; - L6 at 18 range 0 .. 71; -end record; -@end smallexample +@geindex Foreign threads -@noindent -Studying this example, we see that the packable fields @code{L1} -and @code{L2} are -of length equal to their sizes, and placed at specific bit boundaries (and -not byte boundaries) to -eliminate padding. But @code{L3} is of a non-packable float type (because -it is aliased), so it is on the next appropriate alignment boundary. +@geindex Threads +@geindex foreign -The next two fields are fully packable, so @code{L4} and @code{L5} are -minimally packed with no gaps. However, type @code{Rb2} is a packed -array that is longer than 64 bits, so it is itself non-packable. Thus -the @code{L6} field is aligned to the next byte boundary, and takes an -integral number of bytes, i.e.@: 72 bits. +Provides facilities for dealing with foreign threads which need to be known +by the GNAT run-time system. Consult the documentation of this package for +further details if your program has threads that are created by a non-Ada +environment which then accesses Ada code. -@node Record Representation Clauses -@section Record Representation Clauses -@cindex Record Representation Clause +@node GNAT Traceback g-traceb ads,GNAT Traceback Symbolic g-trasym ads,GNAT Threads g-thread ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id122}@anchor{365}@anchor{gnat_rm/the_gnat_library gnat-traceback-g-traceb-ads}@anchor{366} +@section @cite{GNAT.Traceback} (@code{g-traceb.ads}) -@noindent -Record representation clauses may be given for all record types, including -types obtained by record extension. Component clauses are allowed for any -static component. The restrictions on component clauses depend on the type -of the component. -@cindex Component Clause -For all components of an elementary type, the only restriction on component -clauses is that the size must be at least the 'Size value of the type -(actually the Value_Size). There are no restrictions due to alignment, -and such components may freely cross storage boundaries. +@geindex GNAT.Traceback (g-traceb.ads) -Packed arrays with a size up to and including 64 bits are represented -internally using a modular type with the appropriate number of bits, and -thus the same lack of restriction applies. For example, if you declare: +@geindex Trace back facilities -@smallexample @c ada - type R is array (1 .. 49) of Boolean; - pragma Pack (R); - for R'Size use 49; -@end smallexample +Provides a facility for obtaining non-symbolic traceback information, useful +in various debugging situations. -@noindent -then a component clause for a component of type R may start on any -specified bit boundary, and may specify a value of 49 bits or greater. +@node GNAT Traceback Symbolic g-trasym ads,GNAT UTF_32 g-table ads,GNAT Traceback g-traceb ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-traceback-symbolic-g-trasym-ads}@anchor{367}@anchor{gnat_rm/the_gnat_library id123}@anchor{368} +@section @cite{GNAT.Traceback.Symbolic} (@code{g-trasym.ads}) -For packed bit arrays that are longer than 64 bits, there are two -cases. If the component size is a power of 2 (1,2,4,8,16,32 bits), -including the important case of single bits or boolean values, then -there are no limitations on placement of such components, and they -may start and end at arbitrary bit boundaries. -If the component size is not a power of 2 (e.g.@: 3 or 5), then -an array of this type longer than 64 bits must always be placed on -on a storage unit (byte) boundary and occupy an integral number -of storage units (bytes). Any component clause that does not -meet this requirement will be rejected. +@geindex GNAT.Traceback.Symbolic (g-trasym.ads) -Any aliased component, or component of an aliased type, must -have its normal alignment and size. A component clause that -does not meet this requirement will be rejected. +@geindex Trace back facilities -The tag field of a tagged type always occupies an address sized field at -the start of the record. No component clause may attempt to overlay this -tag. When a tagged type appears as a component, the tag field must have -proper alignment +@node GNAT UTF_32 g-table ads,GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Traceback Symbolic g-trasym ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id124}@anchor{369}@anchor{gnat_rm/the_gnat_library gnat-utf-32-g-table-ads}@anchor{36a} +@section @cite{GNAT.UTF_32} (@code{g-table.ads}) -In the case of a record extension T1, of a type T, no component clause applied -to the type T1 can specify a storage location that would overlap the first -T'Size bytes of the record. -For all other component types, including non-bit-packed arrays, -the component can be placed at an arbitrary bit boundary, -so for example, the following is permitted: +@geindex GNAT.UTF_32 (g-table.ads) -@smallexample @c ada - type R is array (1 .. 10) of Boolean; - for R'Size use 80; +@geindex Wide character codes - type Q is record - G, H : Boolean; - L, M : R; - end record; +This is a package intended to be used in conjunction with the +@cite{Wide_Character} type in Ada 95 and the +@cite{Wide_Wide_Character} type in Ada 2005 (available +in @cite{GNAT} in Ada 2005 mode). This package contains +Unicode categorization routines, as well as lexical +categorization routines corresponding to the Ada 2005 +lexical rules for identifiers and strings, and also a +lower case to upper case fold routine corresponding to +the Ada 2005 rules for identifier equivalence. - for Q use record - G at 0 range 0 .. 0; - H at 0 range 1 .. 1; - L at 0 range 2 .. 81; - R at 0 range 82 .. 161; - end record; -@end smallexample +@node GNAT Wide_Spelling_Checker g-u3spch ads,GNAT Wide_Spelling_Checker g-wispch ads,GNAT UTF_32 g-table ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-u3spch-ads}@anchor{36b}@anchor{gnat_rm/the_gnat_library id125}@anchor{36c} +@section @cite{GNAT.Wide_Spelling_Checker} (@code{g-u3spch.ads}) -@noindent -Note: the above rules apply to recent releases of GNAT 5. -In GNAT 3, there are more severe restrictions on larger components. -For non-primitive types, including packed arrays with a size greater than -64 bits, component clauses must respect the alignment requirement of the -type, in particular, always starting on a byte boundary, and the length -must be a multiple of the storage unit. -@node Handling of Records with Holes -@section Handling of Records with Holes -@cindex Handling of Records with Holes +@geindex GNAT.Wide_Spelling_Checker (g-u3spch.ads) -As a result of alignment considerations, records may contain "holes" -or gaps -which do not correspond to the data bits of any of the components. -Record representation clauses can also result in holes in records. +@geindex Spell checking -GNAT does not attempt to clear these holes, so in record objects, -they should be considered to hold undefined rubbish. The generated -equality routine just tests components so does not access these -undefined bits, and assignment and copy operations may or may not -preserve the contents of these holes (for assignments, the holes -in the target will in practice contain either the bits that are -present in the holes in the source, or the bits that were present -in the target before the assignment). +Provides a function for determining whether one wide wide string is a plausible +near misspelling of another wide wide string, where the strings are represented +using the UTF_32_String type defined in System.Wch_Cnv. -If it is necessary to ensure that holes in records have all zero -bits, then record objects for which this initialization is desired -should be explicitly set to all zero values using Unchecked_Conversion -or address overlays. For example +@node GNAT Wide_Spelling_Checker g-wispch ads,GNAT Wide_String_Split g-wistsp ads,GNAT Wide_Spelling_Checker g-u3spch ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-wide-spelling-checker-g-wispch-ads}@anchor{36d}@anchor{gnat_rm/the_gnat_library id126}@anchor{36e} +@section @cite{GNAT.Wide_Spelling_Checker} (@code{g-wispch.ads}) -@smallexample @c ada -type HRec is record - C : Character; - I : Integer; -end record; -@end smallexample -@noindent -On typical machines, integers need to be aligned on a four-byte -boundary, resulting in three bytes of undefined rubbish following -the 8-bit field for C. To ensure that the hole in a variable of -type HRec is set to all zero bits, -you could for example do: +@geindex GNAT.Wide_Spelling_Checker (g-wispch.ads) -@smallexample @c ada -type Base is record - Dummy1, Dummy2 : Integer := 0; -end record; +@geindex Spell checking -BaseVar : Base; -RealVar : Hrec; -for RealVar'Address use BaseVar'Address; -@end smallexample +Provides a function for determining whether one wide string is a plausible +near misspelling of another wide string. -@noindent -Now the 8-bytes of the value of RealVar start out containing all zero -bits. A safer approach is to just define dummy fields, avoiding the -holes, as in: +@node GNAT Wide_String_Split g-wistsp ads,GNAT Wide_Wide_Spelling_Checker g-zspche ads,GNAT Wide_Spelling_Checker g-wispch ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id127}@anchor{36f}@anchor{gnat_rm/the_gnat_library gnat-wide-string-split-g-wistsp-ads}@anchor{370} +@section @cite{GNAT.Wide_String_Split} (@code{g-wistsp.ads}) -@smallexample @c ada -type HRec is record - C : Character; - Dummy1 : Short_Short_Integer := 0; - Dummy2 : Short_Short_Integer := 0; - Dummy3 : Short_Short_Integer := 0; - I : Integer; -end record; -@end smallexample -@noindent -And to make absolutely sure that the intent of this is followed, you -can use representation clauses: +@geindex GNAT.Wide_String_Split (g-wistsp.ads) -@smallexample @c ada -for Hrec use record - C at 0 range 0 .. 7; - Dummy1 at 1 range 0 .. 7; - Dummy2 at 2 range 0 .. 7; - Dummy3 at 3 range 0 .. 7; - I at 4 range 0 .. 31; -end record; -for Hrec'Size use 64; -@end smallexample +@geindex Wide_String splitter -@node Enumeration Clauses -@section Enumeration Clauses +Useful wide string manipulation routines: given a set of separators, split +a wide string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +@cite{GNAT.Array_Split}. -The only restriction on enumeration clauses is that the range of values -must be representable. For the signed case, if one or more of the -representation values are negative, all values must be in the range: +@node GNAT Wide_Wide_Spelling_Checker g-zspche ads,GNAT Wide_Wide_String_Split g-zistsp ads,GNAT Wide_String_Split g-wistsp ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-wide-wide-spelling-checker-g-zspche-ads}@anchor{371}@anchor{gnat_rm/the_gnat_library id128}@anchor{372} +@section @cite{GNAT.Wide_Wide_Spelling_Checker} (@code{g-zspche.ads}) -@smallexample @c ada - System.Min_Int .. System.Max_Int -@end smallexample -@noindent -For the unsigned case, where all values are nonnegative, the values must -be in the range: +@geindex GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads) -@smallexample @c ada - 0 .. System.Max_Binary_Modulus; -@end smallexample +@geindex Spell checking -@noindent -A @emph{confirming} representation clause is one in which the values range -from 0 in sequence, i.e.@: a clause that confirms the default representation -for an enumeration type. -Such a confirming representation -is permitted by these rules, and is specially recognized by the compiler so -that no extra overhead results from the use of such a clause. +Provides a function for determining whether one wide wide string is a plausible +near misspelling of another wide wide string. -If an array has an index type which is an enumeration type to which an -enumeration clause has been applied, then the array is stored in a compact -manner. Consider the declarations: +@node GNAT Wide_Wide_String_Split g-zistsp ads,Interfaces C Extensions i-cexten ads,GNAT Wide_Wide_Spelling_Checker g-zspche ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library gnat-wide-wide-string-split-g-zistsp-ads}@anchor{373}@anchor{gnat_rm/the_gnat_library id129}@anchor{374} +@section @cite{GNAT.Wide_Wide_String_Split} (@code{g-zistsp.ads}) -@smallexample @c ada - type r is (A, B, C); - for r use (A => 1, B => 5, C => 10); - type t is array (r) of Character; -@end smallexample -@noindent -The array type t corresponds to a vector with exactly three elements and -has a default size equal to @code{3*Character'Size}. This ensures efficient -use of space, but means that accesses to elements of the array will incur -the overhead of converting representation values to the corresponding -positional values, (i.e.@: the value delivered by the @code{Pos} attribute). +@geindex GNAT.Wide_Wide_String_Split (g-zistsp.ads) -@node Address Clauses -@section Address Clauses -@cindex Address Clause +@geindex Wide_Wide_String splitter -The reference manual allows a general restriction on representation clauses, -as found in RM 13.1(22): +Useful wide wide string manipulation routines: given a set of separators, split +a wide wide string wherever the separators appear, and provide direct access +to the resulting slices. This package is instantiated from +@cite{GNAT.Array_Split}. -@quotation -An implementation need not support representation -items containing nonstatic expressions, except that -an implementation should support a representation item -for a given entity if each nonstatic expression in the -representation item is a name that statically denotes -a constant declared before the entity. -@end quotation +@node Interfaces C Extensions i-cexten ads,Interfaces C Streams i-cstrea ads,GNAT Wide_Wide_String_Split g-zistsp ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id130}@anchor{375}@anchor{gnat_rm/the_gnat_library interfaces-c-extensions-i-cexten-ads}@anchor{376} +@section @cite{Interfaces.C.Extensions} (@code{i-cexten.ads}) -@noindent -In practice this is applicable only to address clauses, since this is the -only case in which a non-static expression is permitted by the syntax. As -the AARM notes in sections 13.1 (22.a-22.h): -@display - 22.a Reason: This is to avoid the following sort of thing: +@geindex Interfaces.C.Extensions (i-cexten.ads) - 22.b X : Integer := F(@dots{}); - Y : Address := G(@dots{}); - for X'Address use Y; +This package contains additional C-related definitions, intended +for use with either manually or automatically generated bindings +to C libraries. - 22.c In the above, we have to evaluate the - initialization expression for X before we - know where to put the result. This seems - like an unreasonable implementation burden. +@node Interfaces C Streams i-cstrea ads,Interfaces Packed_Decimal i-pacdec ads,Interfaces C Extensions i-cexten ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id131}@anchor{377}@anchor{gnat_rm/the_gnat_library interfaces-c-streams-i-cstrea-ads}@anchor{378} +@section @cite{Interfaces.C.Streams} (@code{i-cstrea.ads}) - 22.d The above code should instead be written - like this: - 22.e Y : constant Address := G(@dots{}); - X : Integer := F(@dots{}); - for X'Address use Y; +@geindex Interfaces.C.Streams (i-cstrea.ads) - 22.f This allows the expression ``Y'' to be safely - evaluated before X is created. +@geindex C streams +@geindex interfacing - 22.g The constant could be a formal parameter of mode in. +This package is a binding for the most commonly used operations +on C streams. - 22.h An implementation can support other nonstatic - expressions if it wants to. Expressions of type - Address are hardly ever static, but their value - might be known at compile time anyway in many - cases. -@end display +@node Interfaces Packed_Decimal i-pacdec ads,Interfaces VxWorks i-vxwork ads,Interfaces C Streams i-cstrea ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library interfaces-packed-decimal-i-pacdec-ads}@anchor{379}@anchor{gnat_rm/the_gnat_library id132}@anchor{37a} +@section @cite{Interfaces.Packed_Decimal} (@code{i-pacdec.ads}) -@noindent -GNAT does indeed permit many additional cases of non-static expressions. In -particular, if the type involved is elementary there are no restrictions -(since in this case, holding a temporary copy of the initialization value, -if one is present, is inexpensive). In addition, if there is no implicit or -explicit initialization, then there are no restrictions. GNAT will reject -only the case where all three of these conditions hold: -@itemize @bullet +@geindex Interfaces.Packed_Decimal (i-pacdec.ads) -@item -The type of the item is non-elementary (e.g.@: a record or array). +@geindex IBM Packed Format -@item -There is explicit or implicit initialization required for the object. -Note that access values are always implicitly initialized. +@geindex Packed Decimal -@item -The address value is non-static. Here GNAT is more permissive than the -RM, and allows the address value to be the address of a previously declared -stand-alone variable, as long as it does not itself have an address clause. +This package provides a set of routines for conversions to and +from a packed decimal format compatible with that used on IBM +mainframes. -@smallexample @c ada - Anchor : Some_Initialized_Type; - Overlay : Some_Initialized_Type; - for Overlay'Address use Anchor'Address; -@end smallexample +@node Interfaces VxWorks i-vxwork ads,Interfaces VxWorks IO i-vxwoio ads,Interfaces Packed_Decimal i-pacdec ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id133}@anchor{37b}@anchor{gnat_rm/the_gnat_library interfaces-vxworks-i-vxwork-ads}@anchor{37c} +@section @cite{Interfaces.VxWorks} (@code{i-vxwork.ads}) -@noindent -However, the prefix of the address clause cannot be an array component, or -a component of a discriminated record. -@end itemize +@geindex Interfaces.VxWorks (i-vxwork.ads) -@noindent -As noted above in section 22.h, address values are typically non-static. In -particular the To_Address function, even if applied to a literal value, is -a non-static function call. To avoid this minor annoyance, GNAT provides -the implementation defined attribute 'To_Address. The following two -expressions have identical values: +@geindex Interfacing to VxWorks -@findex Attribute -@findex To_Address -@smallexample @c ada - To_Address (16#1234_0000#) - System'To_Address (16#1234_0000#); -@end smallexample +@geindex VxWorks +@geindex interfacing -@noindent -except that the second form is considered to be a static expression, and -thus when used as an address clause value is always permitted. +This package provides a limited binding to the VxWorks API. +In particular, it interfaces with the +VxWorks hardware interrupt facilities. -@noindent -Additionally, GNAT treats as static an address clause that is an -unchecked_conversion of a static integer value. This simplifies the porting -of legacy code, and provides a portable equivalent to the GNAT attribute -@code{To_Address}. +@node Interfaces VxWorks IO i-vxwoio ads,System Address_Image s-addima ads,Interfaces VxWorks i-vxwork ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library interfaces-vxworks-io-i-vxwoio-ads}@anchor{37d}@anchor{gnat_rm/the_gnat_library id134}@anchor{37e} +@section @cite{Interfaces.VxWorks.IO} (@code{i-vxwoio.ads}) + + +@geindex Interfaces.VxWorks.IO (i-vxwoio.ads) + +@geindex Interfacing to VxWorks' I/O -Another issue with address clauses is the interaction with alignment -requirements. When an address clause is given for an object, the address -value must be consistent with the alignment of the object (which is usually -the same as the alignment of the type of the object). If an address clause -is given that specifies an inappropriately aligned address value, then the -program execution is erroneous. +@geindex VxWorks +@geindex I/O interfacing -Since this source of erroneous behavior can have unfortunate effects, GNAT -checks (at compile time if possible, generating a warning, or at execution -time with a run-time check) that the alignment is appropriate. If the -run-time check fails, then @code{Program_Error} is raised. This run-time -check is suppressed if range checks are suppressed, or if the special GNAT -check Alignment_Check is suppressed, or if -@code{pragma Restrictions (No_Elaboration_Code)} is in effect. +@geindex VxWorks +@geindex Get_Immediate -Finally, GNAT does not permit overlaying of objects of controlled types or -composite types containing a controlled component. In most cases, the compiler -can detect an attempt at such overlays and will generate a warning at compile -time and a Program_Error exception at run time. +@geindex Get_Immediate +@geindex VxWorks -@findex Export -An address clause cannot be given for an exported object. More -understandably the real restriction is that objects with an address -clause cannot be exported. This is because such variables are not -defined by the Ada program, so there is no external object to export. +This package provides a binding to the ioctl (IO/Control) +function of VxWorks, defining a set of option values and +function codes. A particular use of this package is +to enable the use of Get_Immediate under VxWorks. -@findex Import -It is permissible to give an address clause and a pragma Import for the -same object. In this case, the variable is not really defined by the -Ada program, so there is no external symbol to be linked. The link name -and the external name are ignored in this case. The reason that we allow this -combination is that it provides a useful idiom to avoid unwanted -initializations on objects with address clauses. +@node System Address_Image s-addima ads,System Assertions s-assert ads,Interfaces VxWorks IO i-vxwoio ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-address-image-s-addima-ads}@anchor{37f}@anchor{gnat_rm/the_gnat_library id135}@anchor{380} +@section @cite{System.Address_Image} (@code{s-addima.ads}) -When an address clause is given for an object that has implicit or -explicit initialization, then by default initialization takes place. This -means that the effect of the object declaration is to overwrite the -memory at the specified address. This is almost always not what the -programmer wants, so GNAT will output a warning: -@smallexample - with System; - package G is - type R is record - M : Integer := 0; - end record; - - Ext : R; - for Ext'Address use System'To_Address (16#1234_1234#); - | - >>> warning: implicit initialization of "Ext" may - modify overlaid storage - >>> warning: use pragma Import for "Ext" to suppress - initialization (RM B(24)) - - end G; -@end smallexample - -@noindent -As indicated by the warning message, the solution is to use a (dummy) pragma -Import to suppress this initialization. The pragma tell the compiler that the -object is declared and initialized elsewhere. The following package compiles -without warnings (and the initialization is suppressed): +@geindex System.Address_Image (s-addima.ads) -@smallexample @c ada - with System; - package G is - type R is record - M : Integer := 0; - end record; +@geindex Address image - Ext : R; - for Ext'Address use System'To_Address (16#1234_1234#); - pragma Import (Ada, Ext); - end G; -@end smallexample +@geindex Image +@geindex of an address -@noindent -A final issue with address clauses involves their use for overlaying -variables, as in the following example: -@cindex Overlaying of objects +This function provides a useful debugging +function that gives an (implementation dependent) +string which identifies an address. -@smallexample @c ada - A : Integer; - B : Integer; - for B'Address use A'Address; -@end smallexample +@node System Assertions s-assert ads,System Atomic_Counters s-atocou ads,System Address_Image s-addima ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-assertions-s-assert-ads}@anchor{381}@anchor{gnat_rm/the_gnat_library id136}@anchor{382} +@section @cite{System.Assertions} (@code{s-assert.ads}) -@noindent -or alternatively, using the form recommended by the RM: -@smallexample @c ada - A : Integer; - Addr : constant Address := A'Address; - B : Integer; - for B'Address use Addr; -@end smallexample +@geindex System.Assertions (s-assert.ads) -@noindent -In both of these cases, @code{A} -and @code{B} become aliased to one another via the -address clause. This use of address clauses to overlay -variables, achieving an effect similar to unchecked -conversion was erroneous in Ada 83, but in Ada 95 and Ada 2005 -the effect is implementation defined. Furthermore, the -Ada RM specifically recommends that in a situation -like this, @code{B} should be subject to the following -implementation advice (RM 13.3(19)): +@geindex Assertions -@quotation -19 If the Address of an object is specified, or it is imported - or exported, then the implementation should not perform - optimizations based on assumptions of no aliases. -@end quotation +@geindex Assert_Failure +@geindex exception -@noindent -GNAT follows this recommendation, and goes further by also applying -this recommendation to the overlaid variable (@code{A} -in the above example) in this case. This means that the overlay -works "as expected", in that a modification to one of the variables -will affect the value of the other. +This package provides the declaration of the exception raised +by an run-time assertion failure, as well as the routine that +is used internally to raise this assertion. -Note that when address clause overlays are used in this way, there is an -issue of unintentional initialization, as shown by this example: +@node System Atomic_Counters s-atocou ads,System Memory s-memory ads,System Assertions s-assert ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id137}@anchor{383}@anchor{gnat_rm/the_gnat_library system-atomic-counters-s-atocou-ads}@anchor{384} +@section @cite{System.Atomic_Counters} (@code{s-atocou.ads}) -@smallexample @c ada -package Overwrite_Record is - type R is record - A : Character := 'C'; - B : Character := 'A'; - end record; - X : Short_Integer := 3; - Y : R; - for Y'Address use X'Address; - | ->>> warning: default initialization of "Y" may - modify "X", use pragma Import for "Y" to - suppress initialization (RM B.1(24)) -end Overwrite_Record; -@end smallexample +@geindex System.Atomic_Counters (s-atocou.ads) -@noindent -Here the default initialization of @code{Y} will clobber the value -of @code{X}, which justifies the warning. The warning notes that -this effect can be eliminated by adding a @code{pragma Import} -which suppresses the initialization: +This package provides the declaration of an atomic counter type, +together with efficient routines (using hardware +synchronization primitives) for incrementing, decrementing, +and testing of these counters. This package is implemented +on most targets, including all Alpha, ia64, PowerPC, SPARC V9, +x86, and x86_64 platforms. -@smallexample @c ada -package Overwrite_Record is - type R is record - A : Character := 'C'; - B : Character := 'A'; - end record; - X : Short_Integer := 3; - Y : R; - for Y'Address use X'Address; - pragma Import (Ada, Y); -end Overwrite_Record; -@end smallexample +@node System Memory s-memory ads,System Multiprocessors s-multip ads,System Atomic_Counters s-atocou ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-memory-s-memory-ads}@anchor{385}@anchor{gnat_rm/the_gnat_library id138}@anchor{386} +@section @cite{System.Memory} (@code{s-memory.ads}) -@noindent -Note that the use of @code{pragma Initialize_Scalars} may cause variables to -be initialized when they would not otherwise have been in the absence -of the use of this pragma. This may cause an overlay to have this -unintended clobbering effect. The compiler avoids this for scalar -types, but not for composite objects (where in general the effect -of @code{Initialize_Scalars} is part of the initialization routine -for the composite object: -@smallexample @c ada -pragma Initialize_Scalars; -with Ada.Text_IO; use Ada.Text_IO; -procedure Overwrite_Array is - type Arr is array (1 .. 5) of Integer; - X : Arr := (others => 1); - A : Arr; - for A'Address use X'Address; - | ->>> warning: default initialization of "A" may - modify "X", use pragma Import for "A" to - suppress initialization (RM B.1(24)) +@geindex System.Memory (s-memory.ads) -begin - if X /= Arr'(others => 1) then - Put_Line ("X was clobbered"); - else - Put_Line ("X was not clobbered"); - end if; -end Overwrite_Array; -@end smallexample +@geindex Memory allocation -@noindent -The above program generates the warning as shown, and at execution -time, prints @code{X was clobbered}. If the @code{pragma Import} is -added as suggested: +This package provides the interface to the low level routines used +by the generated code for allocation and freeing storage for the +default storage pool (analogous to the C routines malloc and free. +It also provides a reallocation interface analogous to the C routine +realloc. The body of this unit may be modified to provide alternative +allocation mechanisms for the default pool, and in addition, direct +calls to this unit may be made for low level allocation uses (for +example see the body of @cite{GNAT.Tables}). -@smallexample @c ada -pragma Initialize_Scalars; -with Ada.Text_IO; use Ada.Text_IO; -procedure Overwrite_Array is - type Arr is array (1 .. 5) of Integer; - X : Arr := (others => 1); - A : Arr; - for A'Address use X'Address; - pragma Import (Ada, A); -begin - if X /= Arr'(others => 1) then - Put_Line ("X was clobbered"); - else - Put_Line ("X was not clobbered"); - end if; -end Overwrite_Array; -@end smallexample +@node System Multiprocessors s-multip ads,System Multiprocessors Dispatching_Domains s-mudido ads,System Memory s-memory ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id139}@anchor{387}@anchor{gnat_rm/the_gnat_library system-multiprocessors-s-multip-ads}@anchor{388} +@section @cite{System.Multiprocessors} (@code{s-multip.ads}) -@noindent -then the program compiles without the warning and when run will generate -the output @code{X was not clobbered}. -@node Use of Address Clauses for Memory-Mapped I/O -@section Use of Address Clauses for Memory-Mapped I/O -@cindex Memory-mapped I/O +@geindex System.Multiprocessors (s-multip.ads) -A common pattern is to use an address clause to map an atomic variable to -a location in memory that corresponds to a memory-mapped I/O operation or -operations, for example: +@geindex Multiprocessor interface -@smallexample @c ada - type Mem_Word is record - A,B,C,D : Byte; - end record; - pragma Atomic (Mem_Word); - for Mem_Word_Size use 32; - - Mem : Mem_Word; - for Mem'Address use some-address; - ... - Temp := Mem; - Temp.A := 32; - Mem := Temp; -@end smallexample - -@noindent -For a full access (reference or modification) of the variable (Mem) in -this case, as in the above examples, GNAT guarantees that the entire atomic -word will be accessed. It is not clear whether the RM requires this. For -example in the above, can the compiler reference only the Mem.A field as -an optimization? Whatever the answer to this question is, GNAT makes the -guarantee that for such a reference, the entire word is read or written. +This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but +in GNAT we also make it available in Ada 95 and Ada 2005 (where it is +technically an implementation-defined addition). -A problem arises with a component access such as: +@node System Multiprocessors Dispatching_Domains s-mudido ads,System Partition_Interface s-parint ads,System Multiprocessors s-multip ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-multiprocessors-dispatching-domains-s-mudido-ads}@anchor{389}@anchor{gnat_rm/the_gnat_library id140}@anchor{38a} +@section @cite{System.Multiprocessors.Dispatching_Domains} (@code{s-mudido.ads}) -@smallexample @c ada - Mem.A := 32; -@end smallexample -@noindent -Note that the component A is not declared as atomic. This means that it is -not clear what this assignment means. It could correspond to full word read -and write as given in the first example, or on architectures that supported -such an operation it might be a single byte store instruction. The RM does -not have anything to say in this situation, and GNAT does not make any -guarantee. The code generated may vary from target to target. GNAT will issue -a warning in such a case: +@geindex System.Multiprocessors.Dispatching_Domains (s-mudido.ads) -@smallexample @c ada - Mem.A := 32; - | - >>> warning: access to non-atomic component of atomic array, - may cause unexpected accesses to atomic object -@end smallexample +@geindex Multiprocessor interface -@noindent -It is best to be explicit in this situation, by either declaring the -components to be atomic if you want the byte store, or explicitly writing -the full word access sequence if that is what the hardware requires. +This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but +in GNAT we also make it available in Ada 95 and Ada 2005 (where it is +technically an implementation-defined addition). -@node Effect of Convention on Representation -@section Effect of Convention on Representation -@cindex Convention, effect on representation +@node System Partition_Interface s-parint ads,System Pool_Global s-pooglo ads,System Multiprocessors Dispatching_Domains s-mudido ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id141}@anchor{38b}@anchor{gnat_rm/the_gnat_library system-partition-interface-s-parint-ads}@anchor{38c} +@section @cite{System.Partition_Interface} (@code{s-parint.ads}) -@noindent -Normally the specification of a foreign language convention for a type or -an object has no effect on the chosen representation. In particular, the -representation chosen for data in GNAT generally meets the standard system -conventions, and for example records are laid out in a manner that is -consistent with C@. This means that specifying convention C (for example) -has no effect. -There are four exceptions to this general rule: +@geindex System.Partition_Interface (s-parint.ads) -@itemize @bullet +@geindex Partition interfacing functions -@item Convention Fortran and array subtypes -If pragma Convention Fortran is specified for an array subtype, then in -accordance with the implementation advice in section 3.6.2(11) of the -Ada Reference Manual, the array will be stored in a Fortran-compatible -column-major manner, instead of the normal default row-major order. +This package provides facilities for partition interfacing. It +is used primarily in a distribution context when using Annex E +with @cite{GLADE}. -@item Convention C and enumeration types -GNAT normally stores enumeration types in 8, 16, or 32 bits as required -to accommodate all values of the type. For example, for the enumeration -type declared by: +@node System Pool_Global s-pooglo ads,System Pool_Local s-pooloc ads,System Partition_Interface s-parint ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id142}@anchor{38d}@anchor{gnat_rm/the_gnat_library system-pool-global-s-pooglo-ads}@anchor{38e} +@section @cite{System.Pool_Global} (@code{s-pooglo.ads}) -@smallexample @c ada - type Color is (Red, Green, Blue); -@end smallexample -@noindent -8 bits is sufficient to store all values of the type, so by default, objects -of type @code{Color} will be represented using 8 bits. However, normal C -convention is to use 32 bits for all enum values in C, since enum values -are essentially of type int. If pragma @code{Convention C} is specified for an -Ada enumeration type, then the size is modified as necessary (usually to -32 bits) to be consistent with the C convention for enum values. +@geindex System.Pool_Global (s-pooglo.ads) -Note that this treatment applies only to types. If Convention C is given for -an enumeration object, where the enumeration type is not Convention C, then -Object_Size bits are allocated. For example, for a normal enumeration type, -with less than 256 elements, only 8 bits will be allocated for the object. -Since this may be a surprise in terms of what C expects, GNAT will issue a -warning in this situation. The warning can be suppressed by giving an explicit -size clause specifying the desired size. +@geindex Storage pool +@geindex global -@item Convention C/Fortran and Boolean types -In C, the usual convention for boolean values, that is values used for -conditions, is that zero represents false, and nonzero values represent -true. In Ada, the normal convention is that two specific values, typically -0/1, are used to represent false/true respectively. +@geindex Global storage pool -Fortran has a similar convention for @code{LOGICAL} values (any nonzero -value represents true). +This package provides a storage pool that is equivalent to the default +storage pool used for access types for which no pool is specifically +declared. It uses malloc/free to allocate/free and does not attempt to +do any automatic reclamation. -To accommodate the Fortran and C conventions, if a pragma Convention specifies -C or Fortran convention for a derived Boolean, as in the following example: +@node System Pool_Local s-pooloc ads,System Restrictions s-restri ads,System Pool_Global s-pooglo ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-pool-local-s-pooloc-ads}@anchor{38f}@anchor{gnat_rm/the_gnat_library id143}@anchor{390} +@section @cite{System.Pool_Local} (@code{s-pooloc.ads}) -@smallexample @c ada - type C_Switch is new Boolean; - pragma Convention (C, C_Switch); -@end smallexample -@noindent -then the GNAT generated code will treat any nonzero value as true. For truth -values generated by GNAT, the conventional value 1 will be used for True, but -when one of these values is read, any nonzero value is treated as True. +@geindex System.Pool_Local (s-pooloc.ads) -@item Access types on OpenVMS -For 64-bit OpenVMS systems, access types (other than those for unconstrained -arrays) are 64-bits long. An exception to this rule is for the case of -C-convention access types where there is no explicit size clause present (or -inherited for derived types). In this case, GNAT chooses to make these -pointers 32-bits, which provides an easier path for migration of 32-bit legacy -code. size clause specifying 64-bits must be used to obtain a 64-bit pointer. +@geindex Storage pool +@geindex local -@end itemize +@geindex Local storage pool -@node Conventions and Anonymous Access Types -@section Conventions and Anonymous Access Types -@cindex Anonymous access types -@cindex Convention for anonymous access types +This package provides a storage pool that is intended for use with locally +defined access types. It uses malloc/free for allocate/free, and maintains +a list of allocated blocks, so that all storage allocated for the pool can +be freed automatically when the pool is finalized. -The RM is not entirely clear on convention handling in a number of cases, -and in particular, it is not clear on the convention to be given to -anonymous access types in general, and in particular what is to be -done for the case of anonymous access-to-subprogram. +@node System Restrictions s-restri ads,System Rident s-rident ads,System Pool_Local s-pooloc ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id144}@anchor{391}@anchor{gnat_rm/the_gnat_library system-restrictions-s-restri-ads}@anchor{392} +@section @cite{System.Restrictions} (@code{s-restri.ads}) -In GNAT, we decide that if an explicit Convention is applied -to an object or component, and its type is such an anonymous type, -then the convention will apply to this anonymous type as well. This -seems to make sense since it is anomolous in any case to have a -different convention for an object and its type, and there is clearly -no way to explicitly specify a convention for an anonymous type, since -it doesn't have a name to specify! -Furthermore, we decide that if a convention is applied to a record type, -then this convention is inherited by any of its components that are of an -anonymous access type which do not have an explicitly specified convention. +@geindex System.Restrictions (s-restri.ads) -The following program shows these conventions in action: +@geindex Run-time restrictions access -@smallexample @c ada -package ConvComp is - type Foo is range 1 .. 10; - type T1 is record - A : access function (X : Foo) return Integer; - B : Integer; - end record; - pragma Convention (C, T1); +This package provides facilities for accessing at run time +the status of restrictions specified at compile time for +the partition. Information is available both with regard +to actual restrictions specified, and with regard to +compiler determined information on which restrictions +are violated by one or more packages in the partition. - type T2 is record - A : access function (X : Foo) return Integer; - pragma Convention (C, A); - B : Integer; - end record; - pragma Convention (COBOL, T2); +@node System Rident s-rident ads,System Strings Stream_Ops s-ststop ads,System Restrictions s-restri ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id145}@anchor{393}@anchor{gnat_rm/the_gnat_library system-rident-s-rident-ads}@anchor{394} +@section @cite{System.Rident} (@code{s-rident.ads}) - type T3 is record - A : access function (X : Foo) return Integer; - pragma Convention (COBOL, A); - B : Integer; - end record; - pragma Convention (C, T3); - type T4 is record - A : access function (X : Foo) return Integer; - B : Integer; - end record; - pragma Convention (COBOL, T4); +@geindex System.Rident (s-rident.ads) + +@geindex Restrictions definitions + +This package provides definitions of the restrictions +identifiers supported by GNAT, and also the format of +the restrictions provided in package System.Restrictions. +It is not normally necessary to @cite{with} this generic package +since the necessary instantiation is included in +package System.Restrictions. - function F (X : Foo) return Integer; - pragma Convention (C, F); +@node System Strings Stream_Ops s-ststop ads,System Unsigned_Types s-unstyp ads,System Rident s-rident ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library id146}@anchor{395}@anchor{gnat_rm/the_gnat_library system-strings-stream-ops-s-ststop-ads}@anchor{396} +@section @cite{System.Strings.Stream_Ops} (@code{s-ststop.ads}) - function F (X : Foo) return Integer is (13); - TV1 : T1 := (F'Access, 12); -- OK - TV2 : T2 := (F'Access, 13); -- OK +@geindex System.Strings.Stream_Ops (s-ststop.ads) - TV3 : T3 := (F'Access, 13); -- ERROR - | ->>> subprogram "F" has wrong convention ->>> does not match access to subprogram declared at line 17 - 38. TV4 : T4 := (F'Access, 13); -- ERROR - | ->>> subprogram "F" has wrong convention ->>> does not match access to subprogram declared at line 24 - 39. end ConvComp; -@end smallexample +@geindex Stream operations -@node Determining the Representations chosen by GNAT -@section Determining the Representations chosen by GNAT -@cindex Representation, determination of -@cindex @option{-gnatR} switch +@geindex String stream operations -@noindent -Although the descriptions in this section are intended to be complete, it is -often easier to simply experiment to see what GNAT accepts and what the -effect is on the layout of types and objects. +This package provides a set of stream subprograms for standard string types. +It is intended primarily to support implicit use of such subprograms when +stream attributes are applied to string types, but the subprograms in this +package can be used directly by application programs. -As required by the Ada RM, if a representation clause is not accepted, then -it must be rejected as illegal by the compiler. However, when a -representation clause or pragma is accepted, there can still be questions -of what the compiler actually does. For example, if a partial record -representation clause specifies the location of some components and not -others, then where are the non-specified components placed? Or if pragma -@code{Pack} is used on a record, then exactly where are the resulting -fields placed? The section on pragma @code{Pack} in this chapter can be -used to answer the second question, but it is often easier to just see -what the compiler does. +@node System Unsigned_Types s-unstyp ads,System Wch_Cnv s-wchcnv ads,System Strings Stream_Ops s-ststop ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-unsigned-types-s-unstyp-ads}@anchor{397}@anchor{gnat_rm/the_gnat_library id147}@anchor{398} +@section @cite{System.Unsigned_Types} (@code{s-unstyp.ads}) -For this purpose, GNAT provides the option @option{-gnatR}. If you compile -with this option, then the compiler will output information on the actual -representations chosen, in a format similar to source representation -clauses. For example, if we compile the package: -@smallexample @c ada -package q is - type r (x : boolean) is tagged record - case x is - when True => S : String (1 .. 100); - when False => null; - end case; - end record; +@geindex System.Unsigned_Types (s-unstyp.ads) - type r2 is new r (false) with record - y2 : integer; - end record; +This package contains definitions of standard unsigned types that +correspond in size to the standard signed types declared in Standard, +and (unlike the types in Interfaces) have corresponding names. It +also contains some related definitions for other specialized types +used by the compiler in connection with packed array types. - for r2 use record - y2 at 16 range 0 .. 31; - end record; +@node System Wch_Cnv s-wchcnv ads,System Wch_Con s-wchcon ads,System Unsigned_Types s-unstyp ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-wch-cnv-s-wchcnv-ads}@anchor{399}@anchor{gnat_rm/the_gnat_library id148}@anchor{39a} +@section @cite{System.Wch_Cnv} (@code{s-wchcnv.ads}) - type x is record - y : character; - end record; - type x1 is array (1 .. 10) of x; - for x1'component_size use 11; +@geindex System.Wch_Cnv (s-wchcnv.ads) - type ia is access integer; +@geindex Wide Character +@geindex Representation - type Rb1 is array (1 .. 13) of Boolean; - pragma Pack (rb1); +@geindex Wide String +@geindex Conversion - type Rb2 is array (1 .. 65) of Boolean; - pragma Pack (rb2); +@geindex Representation of wide characters - type x2 is record - l1 : Boolean; - l2 : Duration; - l3 : Float; - l4 : Boolean; - l5 : Rb1; - l6 : Rb2; - end record; - pragma Pack (x2); -end q; -@end smallexample +This package provides routines for converting between +wide and wide wide characters and a representation as a value of type +@cite{Standard.String}, using a specified wide character +encoding method. It uses definitions in +package @cite{System.Wch_Con}. -@noindent -using the switch @option{-gnatR} we obtain the following output: +@node System Wch_Con s-wchcon ads,,System Wch_Cnv s-wchcnv ads,The GNAT Library +@anchor{gnat_rm/the_gnat_library system-wch-con-s-wchcon-ads}@anchor{39b}@anchor{gnat_rm/the_gnat_library id149}@anchor{39c} +@section @cite{System.Wch_Con} (@code{s-wchcon.ads}) -@smallexample -Representation information for unit q -------------------------------------- -for r'Size use ??; -for r'Alignment use 4; -for r use record - x at 4 range 0 .. 7; - _tag at 0 range 0 .. 31; - s at 5 range 0 .. 799; -end record; +@geindex System.Wch_Con (s-wchcon.ads) -for r2'Size use 160; -for r2'Alignment use 4; -for r2 use record - x at 4 range 0 .. 7; - _tag at 0 range 0 .. 31; - _parent at 0 range 0 .. 63; - y2 at 16 range 0 .. 31; -end record; +This package provides definitions and descriptions of +the various methods used for encoding wide characters +in ordinary strings. These definitions are used by +the package @cite{System.Wch_Cnv}. -for x'Size use 8; -for x'Alignment use 1; -for x use record - y at 0 range 0 .. 7; -end record; +@node Interfacing to Other Languages,Specialized Needs Annexes,The GNAT Library,Top +@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-other-languages}@anchor{11}@anchor{gnat_rm/interfacing_to_other_languages doc}@anchor{39d}@anchor{gnat_rm/interfacing_to_other_languages id1}@anchor{39e} +@chapter Interfacing to Other Languages -for x1'Size use 112; -for x1'Alignment use 1; -for x1'Component_Size use 11; -for rb1'Size use 13; -for rb1'Alignment use 2; -for rb1'Component_Size use 1; +The facilities in Annex B of the Ada Reference Manual are fully +implemented in GNAT, and in addition, a full interface to C++ is +provided. -for rb2'Size use 72; -for rb2'Alignment use 1; -for rb2'Component_Size use 1; +@menu +* Interfacing to C:: +* Interfacing to C++:: +* Interfacing to COBOL:: +* Interfacing to Fortran:: +* Interfacing to non-GNAT Ada code:: -for x2'Size use 224; -for x2'Alignment use 4; -for x2 use record - l1 at 0 range 0 .. 0; - l2 at 0 range 1 .. 64; - l3 at 12 range 0 .. 31; - l4 at 16 range 0 .. 0; - l5 at 16 range 1 .. 13; - l6 at 18 range 0 .. 71; -end record; -@end smallexample +@end menu -@noindent -The Size values are actually the Object_Size, i.e.@: the default size that -will be allocated for objects of the type. -The ?? size for type r indicates that we have a variant record, and the -actual size of objects will depend on the discriminant value. +@node Interfacing to C,Interfacing to C++,,Interfacing to Other Languages +@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-c}@anchor{39f}@anchor{gnat_rm/interfacing_to_other_languages id2}@anchor{3a0} +@section Interfacing to C -The Alignment values show the actual alignment chosen by the compiler -for each record or array type. -The record representation clause for type r shows where all fields -are placed, including the compiler generated tag field (whose location -cannot be controlled by the programmer). +Interfacing to C with GNAT can use one of two approaches: -The record representation clause for the type extension r2 shows all the -fields present, including the parent field, which is a copy of the fields -of the parent type of r2, i.e.@: r1. -The component size and size clauses for types rb1 and rb2 show -the exact effect of pragma @code{Pack} on these arrays, and the record -representation clause for type x2 shows how pragma @code{Pack} affects -this record type. +@itemize * -In some cases, it may be useful to cut and paste the representation clauses -generated by the compiler into the original source to fix and guarantee -the actual representation to be used. +@item +The types in the package @cite{Interfaces.C} may be used. -@node Standard Library Routines -@chapter Standard Library Routines +@item +Standard Ada types may be used directly. This may be less portable to +other compilers, but will work on all GNAT compilers, which guarantee +correspondence between the C and Ada types. +@end itemize -@noindent -The Ada Reference Manual contains in Annex A a full description of an -extensive set of standard library routines that can be used in any Ada -program, and which must be provided by all Ada compilers. They are -analogous to the standard C library used by C programs. +Pragma @cite{Convention C} may be applied to Ada types, but mostly has no +effect, since this is the default. The following table shows the +correspondence between Ada scalar types and the corresponding C types. -GNAT implements all of the facilities described in annex A, and for most -purposes the description in the Ada Reference Manual, or appropriate Ada -text book, will be sufficient for making use of these facilities. -In the case of the input-output facilities, -@xref{The Implementation of Standard I/O}, -gives details on exactly how GNAT interfaces to the -file system. For the remaining packages, the Ada Reference Manual -should be sufficient. The following is a list of the packages included, -together with a brief description of the functionality that is provided. +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem -For completeness, references are included to other predefined library -routines defined in other sections of the Ada Reference Manual (these are -cross-indexed from Annex A). For further details see the relevant -package declarations in the run-time library. In particular, a few units -are not implemented, as marked by the presence of pragma Unimplemented_Unit, -and in this case the package declaration contains comments explaining why -the unit is not implemented. +Ada Type -@table @code -@item Ada (A.2) -This is a parent package for all the standard library packages. It is -usually included implicitly in your program, and itself contains no -useful data or routines. +@tab -@item Ada.Assertions (11.4.2) -@code{Assertions} provides the @code{Assert} subprograms, and also -the declaration of the @code{Assertion_Error} exception. +C Type -@item Ada.Asynchronous_Task_Control (D.11) -@code{Asynchronous_Task_Control} provides low level facilities for task -synchronization. It is typically not implemented. See package spec for details. +@item -@item Ada.Calendar (9.6) -@code{Calendar} provides time of day access, and routines for -manipulating times and durations. +@code{Integer} -@item Ada.Calendar.Arithmetic (9.6.1) -This package provides additional arithmetic -operations for @code{Calendar}. +@tab -@item Ada.Calendar.Formatting (9.6.1) -This package provides formatting operations for @code{Calendar}. +@code{int} -@item Ada.Calendar.Time_Zones (9.6.1) -This package provides additional @code{Calendar} facilities -for handling time zones. +@item -@item Ada.Characters (A.3.1) -This is a dummy parent package that contains no useful entities +@code{Short_Integer} -@item Ada.Characters.Conversions (A.3.2) -This package provides character conversion functions. +@tab -@item Ada.Characters.Handling (A.3.2) -This package provides some basic character handling capabilities, -including classification functions for classes of characters (e.g.@: test -for letters, or digits). +@code{short} -@item Ada.Characters.Latin_1 (A.3.3) -This package includes a complete set of definitions of the characters -that appear in type CHARACTER@. It is useful for writing programs that -will run in international environments. For example, if you want an -upper case E with an acute accent in a string, it is often better to use -the definition of @code{UC_E_Acute} in this package. Then your program -will print in an understandable manner even if your environment does not -support these extended characters. +@item -@item Ada.Command_Line (A.15) -This package provides access to the command line parameters and the name -of the current program (analogous to the use of @code{argc} and @code{argv} -in C), and also allows the exit status for the program to be set in a -system-independent manner. +@code{Short_Short_Integer} -@item Ada.Complex_Text_IO (G.1.3) -This package provides text input and output of complex numbers. +@tab -@item Ada.Containers (A.18.1) -A top level package providing a few basic definitions used by all the -following specific child packages that provide specific kinds of -containers. +@code{signed char} -@item Ada.Containers.Bounded_Priority_Queues (A.18.31) +@item -@item Ada.Containers.Bounded_Synchronized_Queues (A.18.29) +@code{Long_Integer} -@item Ada.Containers.Doubly_Linked_Lists (A.18.3) +@tab -@item Ada.Containers.Generic_Array_Sort (A.18.26) +@code{long} -@item Ada.Containers.Generic_Constrained_Array_Sort (A.18.26) +@item -@item Ada.Containers.Generic_Sort (A.18.26) +@code{Long_Long_Integer} -@item Ada.Containers.Hashed_Maps (A.18.5) +@tab -@item Ada.Containers.Hashed_Sets (A.18.8) +@code{long long} -@item Ada.Containers.Indefinite_Doubly_Linked_Lists (A.18.12) +@item -@item Ada.Containers.Indefinite_Hashed_Maps (A.18.13) +@code{Short_Float} -@item Ada.Containers.Indefinite_Hashed_Sets (A.18.15) +@tab -@item Ada.Containers.Indefinite_Holders (A.18.18) +@code{float} -@item Ada.Containers.Indefinite_Multiway_Trees (A.18.17) +@item -@item Ada.Containers.Indefinite_Ordered_Maps (A.18.14) +@code{Float} -@item Ada.Containers.Indefinite_Ordered_Sets (A.18.16) +@tab -@item Ada.Containers.Indefinite_Vectors (A.18.11) +@code{float} -@item Ada.Containers.Multiway_Trees (A.18.10) +@item -@item Ada.Containers.Ordered_Maps (A.18.6) +@code{Long_Float} -@item Ada.Containers.Ordered_Sets (A.18.9) +@tab -@item Ada.Containers.Synchronized_Queue_Interfaces (A.18.27) +@code{double} -@item Ada.Containers.Unbounded_Priority_Queues (A.18.30) +@item -@item Ada.Containers.Unbounded_Synchronized_Queues (A.18.28) +@code{Long_Long_Float} -@item Ada.Containers.Vectors (A.18.2) +@tab -@item Ada.Directories (A.16) -This package provides operations on directories. +This is the longest floating-point type supported by the hardware. -@item Ada.Directories.Hierarchical_File_Names (A.16.1) -This package provides additional directory operations handling -hiearchical file names. +@end multitable -@item Ada.Directories.Information (A.16) -This is an implementation defined package for additional directory -operations, which is not implemented in GNAT. -@item Ada.Decimal (F.2) -This package provides constants describing the range of decimal numbers -implemented, and also a decimal divide routine (analogous to the COBOL -verb DIVIDE @dots{} GIVING @dots{} REMAINDER @dots{}) +Additionally, there are the following general correspondences between Ada +and C types: -@item Ada.Direct_IO (A.8.4) -This package provides input-output using a model of a set of records of -fixed-length, containing an arbitrary definite Ada type, indexed by an -integer record number. -@item Ada.Dispatching (D.2.1) -A parent package containing definitions for task dispatching operations. +@itemize * -@item Ada.Dispatching.EDF (D.2.6) -Not implemented in GNAT. +@item +Ada enumeration types map to C enumeration types directly if pragma +@cite{Convention C} is specified, which causes them to have int +length. Without pragma @cite{Convention C}, Ada enumeration types map to +8, 16, or 32 bits (i.e., C types @cite{signed char}, @cite{short}, +@cite{int}, respectively) depending on the number of values passed. +This is the only case in which pragma @cite{Convention C} affects the +representation of an Ada type. -@item Ada.Dispatching.Non_Preemptive (D.2.4) -Not implemented in GNAT. +@item +Ada access types map to C pointers, except for the case of pointers to +unconstrained types in Ada, which have no direct C equivalent. -@item Ada.Dispatching.Round_Robin (D.2.5) -Not implemented in GNAT. +@item +Ada arrays map directly to C arrays. -@item Ada.Dynamic_Priorities (D.5) -This package allows the priorities of a task to be adjusted dynamically -as the task is running. +@item +Ada records map directly to C structures. -@item Ada.Environment_Variables (A.17) -This package provides facilities for accessing environment variables. +@item +Packed Ada records map to C structures where all members are bit fields +of the length corresponding to the @code{type'Size} value in Ada. +@end itemize -@item Ada.Exceptions (11.4.1) -This package provides additional information on exceptions, and also -contains facilities for treating exceptions as data objects, and raising -exceptions with associated messages. +@node Interfacing to C++,Interfacing to COBOL,Interfacing to C,Interfacing to Other Languages +@anchor{gnat_rm/interfacing_to_other_languages id4}@anchor{3a1}@anchor{gnat_rm/interfacing_to_other_languages id3}@anchor{3f} +@section Interfacing to C++ -@item Ada.Execution_Time (D.14) -Not implemented in GNAT. -@item Ada.Execution_Time.Group_Budgets (D.14.2) -Not implemented in GNAT. +The interface to C++ makes use of the following pragmas, which are +primarily intended to be constructed automatically using a binding generator +tool, although it is possible to construct them by hand. + +Using these pragmas it is possible to achieve complete +inter-operability between Ada tagged types and C++ class definitions. +See @ref{7,,Implementation Defined Pragmas}, for more details. -@item Ada.Execution_Time.Timers (D.14.1)' -Not implemented in GNAT. -@item Ada.Finalization (7.6) -This package contains the declarations and subprograms to support the -use of controlled types, providing for automatic initialization and -finalization (analogous to the constructors and destructors of C++). +@table @asis -@item Ada.Float_Text_IO (A.10.9) -A library level instantiation of Text_IO.Float_IO for type Float. +@item @emph{pragma CPP_Class ([Entity =>] `LOCAL_NAME`)} -@item Ada.Float_Wide_Text_IO (A.10.9) -A library level instantiation of Wide_Text_IO.Float_IO for type Float. +The argument denotes an entity in the current declarative region that is +declared as a tagged or untagged record type. It indicates that the type +corresponds to an externally declared C++ class type, and is to be laid +out the same way that C++ would lay out the type. -@item Ada.Float_Wide_Wide_Text_IO (A.10.9) -A library level instantiation of Wide_Wide_Text_IO.Float_IO for type Float. +Note: Pragma @cite{CPP_Class} is currently obsolete. It is supported +for backward compatibility but its functionality is available +using pragma @cite{Import} with @cite{Convention} = @cite{CPP}. -@item Ada.Integer_Text_IO (A.10.9) -A library level instantiation of Text_IO.Integer_IO for type Integer. +@item @emph{pragma CPP_Constructor ([Entity =>] `LOCAL_NAME`)} -@item Ada.Integer_Wide_Text_IO (A.10.9) -A library level instantiation of Wide_Text_IO.Integer_IO for type Integer. +This pragma identifies an imported function (imported in the usual way +with pragma @cite{Import}) as corresponding to a C++ constructor. +@end table -@item Ada.Integer_Wide_Wide_Text_IO (A.10.9) -A library level instantiation of Wide_Wide_Text_IO.Integer_IO for type Integer. +A few restrictions are placed on the use of the @cite{Access} attribute +in conjunction with subprograms subject to convention @cite{CPP}: the +attribute may be used neither on primitive operations of a tagged +record type with convention @cite{CPP}, imported or not, nor on +subprograms imported with pragma @cite{CPP_Constructor}. -@item Ada.Interrupts (C.3.2) -This package provides facilities for interfacing to interrupts, which -includes the set of signals or conditions that can be raised and -recognized as interrupts. +In addition, C++ exceptions are propagated and can be handled in an +@cite{others} choice of an exception handler. The corresponding Ada +occurrence has no message, and the simple name of the exception identity +contains @code{Foreign_Exception}. Finalization and awaiting dependent +tasks works properly when such foreign exceptions are propagated. -@item Ada.Interrupts.Names (C.3.2) -This package provides the set of interrupt names (actually signal -or condition names) that can be handled by GNAT@. +It is also possible to import a C++ exception using the following syntax: -@item Ada.IO_Exceptions (A.13) -This package defines the set of exceptions that can be raised by use of -the standard IO packages. +@example +LOCAL_NAME : exception; +pragma Import (Cpp, + [Entity =>] LOCAL_NAME, + [External_Name =>] static_string_EXPRESSION); +@end example -@item Ada.Iterator_Interfaces (5.5.1) -This package provides a generic interface to generalized iterators. +The @cite{External_Name} is the name of the C++ RTTI symbol. You can then +cover a specific C++ exception in an exception handler. -@item Ada.Locales (A.19) -This package provides declarations providing information (Language -and Country) about the current locale. +@node Interfacing to COBOL,Interfacing to Fortran,Interfacing to C++,Interfacing to Other Languages +@anchor{gnat_rm/interfacing_to_other_languages id5}@anchor{3a2}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-cobol}@anchor{3a3} +@section Interfacing to COBOL -@item Ada.Numerics -This package contains some standard constants and exceptions used -throughout the numerics packages. Note that the constants pi and e are -defined here, and it is better to use these definitions than rolling -your own. -@item Ada.Numerics.Complex_Arrays (G.3.2) -Provides operations on arrays of complex numbers. +Interfacing to COBOL is achieved as described in section B.4 of +the Ada Reference Manual. -@item Ada.Numerics.Complex_Elementary_Functions -Provides the implementation of standard elementary functions (such as -log and trigonometric functions) operating on complex numbers using the -standard @code{Float} and the @code{Complex} and @code{Imaginary} types -created by the package @code{Numerics.Complex_Types}. +@node Interfacing to Fortran,Interfacing to non-GNAT Ada code,Interfacing to COBOL,Interfacing to Other Languages +@anchor{gnat_rm/interfacing_to_other_languages id6}@anchor{3a4}@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-fortran}@anchor{3a5} +@section Interfacing to Fortran -@item Ada.Numerics.Complex_Types -This is a predefined instantiation of -@code{Numerics.Generic_Complex_Types} using @code{Standard.Float} to -build the type @code{Complex} and @code{Imaginary}. -@item Ada.Numerics.Discrete_Random -This generic package provides a random number generator suitable for generating -uniformly distributed values of a specified discrete subtype. +Interfacing to Fortran is achieved as described in section B.5 of the +Ada Reference Manual. The pragma @cite{Convention Fortran}, applied to a +multi-dimensional array causes the array to be stored in column-major +order as required for convenient interface to Fortran. -@item Ada.Numerics.Float_Random -This package provides a random number generator suitable for generating -uniformly distributed floating point values in the unit interval. +@node Interfacing to non-GNAT Ada code,,Interfacing to Fortran,Interfacing to Other Languages +@anchor{gnat_rm/interfacing_to_other_languages interfacing-to-non-gnat-ada-code}@anchor{3a6}@anchor{gnat_rm/interfacing_to_other_languages id7}@anchor{3a7} +@section Interfacing to non-GNAT Ada code -@item Ada.Numerics.Generic_Complex_Elementary_Functions -This is a generic version of the package that provides the -implementation of standard elementary functions (such as log and -trigonometric functions) for an arbitrary complex type. -The following predefined instantiations of this package are provided: +It is possible to specify the convention @cite{Ada} in a pragma +@cite{Import} or pragma @cite{Export}. However this refers to +the calling conventions used by GNAT, which may or may not be +similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005 +compiler to allow interoperation. -@table @code -@item Short_Float -@code{Ada.Numerics.Short_Complex_Elementary_Functions} -@item Float -@code{Ada.Numerics.Complex_Elementary_Functions} -@item Long_Float -@code{Ada.Numerics.Long_Complex_Elementary_Functions} -@end table +If arguments types are kept simple, and if the foreign compiler generally +follows system calling conventions, then it may be possible to integrate +files compiled by other Ada compilers, provided that the elaboration +issues are adequately addressed (for example by eliminating the +need for any load time elaboration). -@item Ada.Numerics.Generic_Complex_Types -This is a generic package that allows the creation of complex types, -with associated complex arithmetic operations. +In particular, GNAT running on VMS is designed to +be highly compatible with the DEC Ada 83 compiler, so this is one +case in which it is possible to import foreign units of this type, +provided that the data items passed are restricted to simple scalar +values or simple record types without variants, or simple array +types with fixed bounds. -The following predefined instantiations of this package exist -@table @code -@item Short_Float -@code{Ada.Numerics.Short_Complex_Complex_Types} -@item Float -@code{Ada.Numerics.Complex_Complex_Types} -@item Long_Float -@code{Ada.Numerics.Long_Complex_Complex_Types} -@end table +@node Specialized Needs Annexes,Implementation of Specific Ada Features,Interfacing to Other Languages,Top +@anchor{gnat_rm/specialized_needs_annexes specialized-needs-annexes}@anchor{12}@anchor{gnat_rm/specialized_needs_annexes doc}@anchor{3a8}@anchor{gnat_rm/specialized_needs_annexes id1}@anchor{3a9} +@chapter Specialized Needs Annexes -@item Ada.Numerics.Generic_Elementary_Functions -This is a generic package that provides the implementation of standard -elementary functions (such as log an trigonometric functions) for an -arbitrary float type. -The following predefined instantiations of this package exist +Ada 95, Ada 2005, and Ada 2012 define a number of Specialized Needs Annexes, which are not +required in all implementations. However, as described in this chapter, +GNAT implements all of these annexes: -@table @code -@item Short_Float -@code{Ada.Numerics.Short_Elementary_Functions} -@item Float -@code{Ada.Numerics.Elementary_Functions} -@item Long_Float -@code{Ada.Numerics.Long_Elementary_Functions} -@end table -@item Ada.Numerics.Generic_Real_Arrays (G.3.1) -Generic operations on arrays of reals +@table @asis -@item Ada.Numerics.Real_Arrays (G.3.1) -Preinstantiation of Ada.Numerics.Generic_Real_Arrays (Float). +@item @emph{Systems Programming (Annex C)} -@item Ada.Real_Time (D.8) -This package provides facilities similar to those of @code{Calendar}, but -operating with a finer clock suitable for real time control. Note that -annex D requires that there be no backward clock jumps, and GNAT generally -guarantees this behavior, but of course if the external clock on which -the GNAT runtime depends is deliberately reset by some external event, -then such a backward jump may occur. +The Systems Programming Annex is fully implemented. -@item Ada.Real_Time.Timing_Events (D.15) -Not implemented in GNAT. +@item @emph{Real-Time Systems (Annex D)} -@item Ada.Sequential_IO (A.8.1) -This package provides input-output facilities for sequential files, -which can contain a sequence of values of a single type, which can be -any Ada type, including indefinite (unconstrained) types. +The Real-Time Systems Annex is fully implemented. -@item Ada.Storage_IO (A.9) -This package provides a facility for mapping arbitrary Ada types to and -from a storage buffer. It is primarily intended for the creation of new -IO packages. +@item @emph{Distributed Systems (Annex E)} -@item Ada.Streams (13.13.1) -This is a generic package that provides the basic support for the -concept of streams as used by the stream attributes (@code{Input}, -@code{Output}, @code{Read} and @code{Write}). +Stub generation is fully implemented in the GNAT compiler. In addition, +a complete compatible PCS is available as part of the GLADE system, +a separate product. When the two +products are used in conjunction, this annex is fully implemented. -@item Ada.Streams.Stream_IO (A.12.1) -This package is a specialization of the type @code{Streams} defined in -package @code{Streams} together with a set of operations providing -Stream_IO capability. The Stream_IO model permits both random and -sequential access to a file which can contain an arbitrary set of values -of one or more Ada types. +@item @emph{Information Systems (Annex F)} -@item Ada.Strings (A.4.1) -This package provides some basic constants used by the string handling -packages. +The Information Systems annex is fully implemented. -@item Ada.Strings.Bounded (A.4.4) -This package provides facilities for handling variable length -strings. The bounded model requires a maximum length. It is thus -somewhat more limited than the unbounded model, but avoids the use of -dynamic allocation or finalization. +@item @emph{Numerics (Annex G)} -@item Ada.Strings.Bounded.Equal_Case_Insensitive (A.4.10) -Provides case-insensitive comparisons of bounded strings +The Numerics Annex is fully implemented. -@item Ada.Strings.Bounded.Hash (A.4.9) -This package provides a generic hash function for bounded strings +@item @emph{Safety and Security / High-Integrity Systems (Annex H)} -@item Ada.Strings.Bounded.Hash_Case_Insensitive (A.4.9) -This package provides a generic hash function for bounded strings that -converts the string to be hashed to lower case. +The Safety and Security Annex (termed the High-Integrity Systems Annex +in Ada 2005) is fully implemented. +@end table -@item Ada.Strings.Bounded.Less_Case_Insensitive (A.4.10) -This package provides a comparison function for bounded strings that works -in a case insensitive manner by converting to lower case before the comparison. +@node Implementation of Specific Ada Features,Implementation of Ada 2012 Features,Specialized Needs Annexes,Top +@anchor{gnat_rm/implementation_of_specific_ada_features implementation-of-specific-ada-features}@anchor{13}@anchor{gnat_rm/implementation_of_specific_ada_features doc}@anchor{3aa}@anchor{gnat_rm/implementation_of_specific_ada_features id1}@anchor{3ab} +@chapter Implementation of Specific Ada Features -@item Ada.Strings.Fixed (A.4.3) -This package provides facilities for handling fixed length strings. -@item Ada.Strings.Fixed.Equal_Case_Insensitive (A.4.10) -This package provides an equality function for fixed strings that compares -the strings after converting both to lower case. +This chapter describes the GNAT implementation of several Ada language +facilities. -@item Ada.Strings.Fixed.Hash_Case_Insensitive (A.4.9) -This package provides a case insensitive hash function for fixed strings that -converts the string to lower case before computing the hash. +@menu +* Machine Code Insertions:: +* GNAT Implementation of Tasking:: +* GNAT Implementation of Shared Passive Packages:: +* Code Generation for Array Aggregates:: +* The Size of Discriminated Records with Default Discriminants:: +* Strict Conformance to the Ada Reference Manual:: -@item Ada.Strings.Fixed.Less_Case_Insensitive (A.4.10) -This package provides a comparison function for fixed strings that works -in a case insensitive manner by converting to lower case before the comparison. +@end menu -Ada.Strings.Hash (A.4.9) -This package provides a hash function for strings. +@node Machine Code Insertions,GNAT Implementation of Tasking,,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features machine-code-insertions}@anchor{119}@anchor{gnat_rm/implementation_of_specific_ada_features id2}@anchor{3ac} +@section Machine Code Insertions -Ada.Strings.Hash_Case_Insensitive (A.4.9) -This package provides a hash function for strings that is case insensitive. -The string is converted to lower case before computing the hash. -@item Ada.Strings.Less_Case_Insensitive (A.4.10) -This package provides a comparison function for\strings that works -in a case insensitive manner by converting to lower case before the comparison. +@geindex Machine Code insertions -@item Ada.Strings.Maps (A.4.2) -This package provides facilities for handling character mappings and -arbitrarily defined subsets of characters. For instance it is useful in -defining specialized translation tables. +Package @cite{Machine_Code} provides machine code support as described +in the Ada Reference Manual in two separate forms: -@item Ada.Strings.Maps.Constants (A.4.6) -This package provides a standard set of predefined mappings and -predefined character sets. For example, the standard upper to lower case -conversion table is found in this package. Note that upper to lower case -conversion is non-trivial if you want to take the entire set of -characters, including extended characters like E with an acute accent, -into account. You should use the mappings in this package (rather than -adding 32 yourself) to do case mappings. -@item Ada.Strings.Unbounded (A.4.5) -This package provides facilities for handling variable length -strings. The unbounded model allows arbitrary length strings, but -requires the use of dynamic allocation and finalization. +@itemize * -@item Ada.Strings.Unbounded.Equal_Case_Insensitive (A.4.10) -Provides case-insensitive comparisons of unbounded strings +@item +Machine code statements, consisting of qualified expressions that +fit the requirements of RM section 13.8. -@item Ada.Strings.Unbounded.Hash (A.4.9) -This package provides a generic hash function for unbounded strings +@item +An intrinsic callable procedure, providing an alternative mechanism of +including machine instructions in a subprogram. +@end itemize -@item Ada.Strings.Unbounded.Hash_Case_Insensitive (A.4.9) -This package provides a generic hash function for unbounded strings that -converts the string to be hashed to lower case. +The two features are similar, and both are closely related to the mechanism +provided by the asm instruction in the GNU C compiler. Full understanding +and use of the facilities in this package requires understanding the asm +instruction, see the section on Extended Asm in +@cite{Using_the_GNU_Compiler_Collection_(GCC)}. -@item Ada.Strings.Unbounded.Less_Case_Insensitive (A.4.10) -This package provides a comparison function for unbounded strings that works -in a case insensitive manner by converting to lower case before the comparison. +Calls to the function @cite{Asm} and the procedure @cite{Asm} have identical +semantic restrictions and effects as described below. Both are provided so +that the procedure call can be used as a statement, and the function call +can be used to form a code_statement. -@item Ada.Strings.UTF_Encoding (A.4.11) -This package provides basic definitions for dealing with UTF-encoded strings. +Consider this C @cite{asm} instruction: -@item Ada.Strings.UTF_Encoding.Conversions (A.4.11) -This package provides conversion functions for UTF-encoded strings. +@example +asm ("fsinx %1 %0" : "=f" (result) : "f" (angle)); +@end example -@item Ada.Strings.UTF_Encoding.Strings (A.4.11) -@itemx Ada.Strings.UTF_Encoding.Wide_Strings (A.4.11) -@itemx Ada.Strings.UTF_Encoding.Wide_Wide_Strings (A.4.11) -These packages provide facilities for handling UTF encodings for -Strings, Wide_Strings and Wide_Wide_Strings. +The equivalent can be written for GNAT as: -@item Ada.Strings.Wide_Bounded (A.4.7) -@itemx Ada.Strings.Wide_Fixed (A.4.7) -@itemx Ada.Strings.Wide_Maps (A.4.7) -@itemx Ada.Strings.Wide_Unbounded (A.4.7) -These packages provide analogous capabilities to the corresponding -packages without @samp{Wide_} in the name, but operate with the types -@code{Wide_String} and @code{Wide_Character} instead of @code{String} -and @code{Character}. Versions of all the child packages are available. - -@item Ada.Strings.Wide_Wide_Bounded (A.4.7) -@itemx Ada.Strings.Wide_Wide_Fixed (A.4.7) -@itemx Ada.Strings.Wide_Wide_Maps (A.4.7) -@itemx Ada.Strings.Wide_Wide_Unbounded (A.4.7) -These packages provide analogous capabilities to the corresponding -packages without @samp{Wide_} in the name, but operate with the types -@code{Wide_Wide_String} and @code{Wide_Wide_Character} instead -of @code{String} and @code{Character}. +@example +Asm ("fsinx %1 %0", + My_Float'Asm_Output ("=f", result), + My_Float'Asm_Input ("f", angle)); +@end example -@item Ada.Synchronous_Barriers (D.10.1) -This package provides facilities for synchronizing tasks at a low level -with barriers. +The first argument to @cite{Asm} is the assembler template, and is +identical to what is used in GNU C. This string must be a static +expression. The second argument is the output operand list. It is +either a single @cite{Asm_Output} attribute reference, or a list of such +references enclosed in parentheses (technically an array aggregate of +such references). -@item Ada.Synchronous_Task_Control (D.10) -This package provides some standard facilities for controlling task -communication in a synchronous manner. +The @cite{Asm_Output} attribute denotes a function that takes two +parameters. The first is a string, the second is the name of a variable +of the type designated by the attribute prefix. The first (string) +argument is required to be a static expression and designates the +constraint (see the section on Constraints in +@cite{Using_the_GNU_Compiler_Collection_(GCC)}) +for the parameter; e.g., what kind of register is required. The second +argument is the variable to be written or updated with the +result. The possible values for constraint are the same as those used in +the RTL, and are dependent on the configuration file used to build the +GCC back end. If there are no output operands, then this argument may +either be omitted, or explicitly given as @cite{No_Output_Operands}. +No support is provided for GNU C's symbolic names for output parameters. -@item Ada.Synchronous_Task_Control.EDF (D.10) -Not implemented in GNAT. +The second argument of @code{my_float'Asm_Output} functions as +though it were an @cite{out} parameter, which is a little curious, but +all names have the form of expressions, so there is no syntactic +irregularity, even though normally functions would not be permitted +@cite{out} parameters. The third argument is the list of input +operands. It is either a single @cite{Asm_Input} attribute reference, or +a list of such references enclosed in parentheses (technically an array +aggregate of such references). -@item Ada.Tags -This package contains definitions for manipulation of the tags of tagged -values. +The @cite{Asm_Input} attribute denotes a function that takes two +parameters. The first is a string, the second is an expression of the +type designated by the prefix. The first (string) argument is required +to be a static expression, and is the constraint for the parameter, +(e.g., what kind of register is required). The second argument is the +value to be used as the input argument. The possible values for the +constraint are the same as those used in the RTL, and are dependent on +the configuration file used to built the GCC back end. +No support is provided for GNU C's symbolic names for input parameters. -@item Ada.Tags.Generic_Dispatching_Constructor (3.9) -This package provides a way of constructing tagged class-wide values given -only the tag value. +If there are no input operands, this argument may either be omitted, or +explicitly given as @cite{No_Input_Operands}. The fourth argument, not +present in the above example, is a list of register names, called the +@emph{clobber} argument. This argument, if given, must be a static string +expression, and is a space or comma separated list of names of registers +that must be considered destroyed as a result of the @cite{Asm} call. If +this argument is the null string (the default value), then the code +generator assumes that no additional registers are destroyed. +In addition to registers, the special clobbers @cite{memory} and +@cite{cc} as described in the GNU C docs are both supported. -@item Ada.Task_Attributes (C.7.2) -This package provides the capability of associating arbitrary -task-specific data with separate tasks. +The fifth argument, not present in the above example, called the +@emph{volatile} argument, is by default @cite{False}. It can be set to +the literal value @cite{True} to indicate to the code generator that all +optimizations with respect to the instruction specified should be +suppressed, and in particular an instruction that has outputs +will still be generated, even if none of the outputs are +used. See @cite{Using_the_GNU_Compiler_Collection_(GCC)} +for the full description. +Generally it is strongly advisable to use Volatile for any ASM statement +that is missing either input or output operands or to avoid unwanted +optimizations. A warning is generated if this advice is not followed. -@item Ada.Task_Identifification (C.7.1) -This package provides capabilities for task identification. +No support is provided for GNU C's @cite{asm goto} feature. -@item Ada.Task_Termination (C.7.3) -This package provides control over task termination. +The @cite{Asm} subprograms may be used in two ways. First the procedure +forms can be used anywhere a procedure call would be valid, and +correspond to what the RM calls 'intrinsic' routines. Such calls can +be used to intersperse machine instructions with other Ada statements. +Second, the function forms, which return a dummy value of the limited +private type @cite{Asm_Insn}, can be used in code statements, and indeed +this is the only context where such calls are allowed. Code statements +appear as aggregates of the form: -@item Ada.Text_IO -This package provides basic text input-output capabilities for -character, string and numeric data. The subpackages of this -package are listed next. Note that although these are defined -as subpackages in the RM, they are actually transparently -implemented as child packages in GNAT, meaning that they -are only loaded if needed. +@example +Asm_Insn'(Asm (...)); +Asm_Insn'(Asm_Volatile (...)); +@end example -@item Ada.Text_IO.Decimal_IO -Provides input-output facilities for decimal fixed-point types +In accordance with RM rules, such code statements are allowed only +within subprograms whose entire body consists of such statements. It is +not permissible to intermix such statements with other Ada statements. -@item Ada.Text_IO.Enumeration_IO -Provides input-output facilities for enumeration types. +Typically the form using intrinsic procedure calls is more convenient +and more flexible. The code statement form is provided to meet the RM +suggestion that such a facility should be made available. The following +is the exact syntax of the call to @cite{Asm}. As usual, if named notation +is used, the arguments may be given in arbitrary order, following the +normal rules for use of positional and named arguments: -@item Ada.Text_IO.Fixed_IO -Provides input-output facilities for ordinary fixed-point types. +@example +ASM_CALL ::= Asm ( + [Template =>] static_string_EXPRESSION + [,[Outputs =>] OUTPUT_OPERAND_LIST ] + [,[Inputs =>] INPUT_OPERAND_LIST ] + [,[Clobber =>] static_string_EXPRESSION ] + [,[Volatile =>] static_boolean_EXPRESSION] ) -@item Ada.Text_IO.Float_IO -Provides input-output facilities for float types. The following -predefined instantiations of this generic package are available: +OUTPUT_OPERAND_LIST ::= + [PREFIX.]No_Output_Operands +| OUTPUT_OPERAND_ATTRIBUTE +| (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@}) -@table @code -@item Short_Float -@code{Short_Float_Text_IO} -@item Float -@code{Float_Text_IO} -@item Long_Float -@code{Long_Float_Text_IO} -@end table +OUTPUT_OPERAND_ATTRIBUTE ::= + SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME) -@item Ada.Text_IO.Integer_IO -Provides input-output facilities for integer types. The following -predefined instantiations of this generic package are available: +INPUT_OPERAND_LIST ::= + [PREFIX.]No_Input_Operands +| INPUT_OPERAND_ATTRIBUTE +| (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@}) -@table @code -@item Short_Short_Integer -@code{Ada.Short_Short_Integer_Text_IO} -@item Short_Integer -@code{Ada.Short_Integer_Text_IO} -@item Integer -@code{Ada.Integer_Text_IO} -@item Long_Integer -@code{Ada.Long_Integer_Text_IO} -@item Long_Long_Integer -@code{Ada.Long_Long_Integer_Text_IO} -@end table +INPUT_OPERAND_ATTRIBUTE ::= + SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION) +@end example -@item Ada.Text_IO.Modular_IO -Provides input-output facilities for modular (unsigned) types. +The identifiers @cite{No_Input_Operands} and @cite{No_Output_Operands} +are declared in the package @cite{Machine_Code} and must be referenced +according to normal visibility rules. In particular if there is no +@cite{use} clause for this package, then appropriate package name +qualification is required. -@item Ada.Text_IO.Bounded_IO (A.10.11) -Provides input-output facilities for bounded strings. +@node GNAT Implementation of Tasking,GNAT Implementation of Shared Passive Packages,Machine Code Insertions,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features id3}@anchor{3ad}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-tasking}@anchor{3ae} +@section GNAT Implementation of Tasking -@item Ada.Text_IO.Complex_IO (G.1.3) -This package provides basic text input-output capabilities for complex -data. -@item Ada.Text_IO.Editing (F.3.3) -This package contains routines for edited output, analogous to the use -of pictures in COBOL@. The picture formats used by this package are a -close copy of the facility in COBOL@. +This chapter outlines the basic GNAT approach to tasking (in particular, +a multi-layered library for portability) and discusses issues related +to compliance with the Real-Time Systems Annex. -@item Ada.Text_IO.Text_Streams (A.12.2) -This package provides a facility that allows Text_IO files to be treated -as streams, so that the stream attributes can be used for writing -arbitrary data, including binary data, to Text_IO files. +@menu +* Mapping Ada Tasks onto the Underlying Kernel Threads:: +* Ensuring Compliance with the Real-Time Annex:: -@item Ada.Text_IO.Unbounded_IO (A.10.12) -This package provides input-output facilities for unbounded strings. +@end menu -@item Ada.Unchecked_Conversion (13.9) -This generic package allows arbitrary conversion from one type to -another of the same size, providing for breaking the type safety in -special circumstances. +@node Mapping Ada Tasks onto the Underlying Kernel Threads,Ensuring Compliance with the Real-Time Annex,,GNAT Implementation of Tasking +@anchor{gnat_rm/implementation_of_specific_ada_features mapping-ada-tasks-onto-the-underlying-kernel-threads}@anchor{3af}@anchor{gnat_rm/implementation_of_specific_ada_features id4}@anchor{3b0} +@subsection Mapping Ada Tasks onto the Underlying Kernel Threads -If the types have the same Size (more accurately the same Value_Size), -then the effect is simply to transfer the bits from the source to the -target type without any modification. This usage is well defined, and -for simple types whose representation is typically the same across -all implementations, gives a portable method of performing such -conversions. -If the types do not have the same size, then the result is implementation -defined, and thus may be non-portable. The following describes how GNAT -handles such unchecked conversion cases. +GNAT's run-time support comprises two layers: -If the types are of different sizes, and are both discrete types, then -the effect is of a normal type conversion without any constraint checking. -In particular if the result type has a larger size, the result will be -zero or sign extended. If the result type has a smaller size, the result -will be truncated by ignoring high order bits. -If the types are of different sizes, and are not both discrete types, -then the conversion works as though pointers were created to the source -and target, and the pointer value is converted. The effect is that bits -are copied from successive low order storage units and bits of the source -up to the length of the target type. +@itemize * -A warning is issued if the lengths differ, since the effect in this -case is implementation dependent, and the above behavior may not match -that of some other compiler. +@item +GNARL (GNAT Run-time Layer) -A pointer to one type may be converted to a pointer to another type using -unchecked conversion. The only case in which the effect is undefined is -when one or both pointers are pointers to unconstrained array types. In -this case, the bounds information may get incorrectly transferred, and in -particular, GNAT uses double size pointers for such types, and it is -meaningless to convert between such pointer types. GNAT will issue a -warning if the alignment of the target designated type is more strict -than the alignment of the source designated type (since the result may -be unaligned in this case). +@item +GNULL (GNAT Low-level Library) +@end itemize -A pointer other than a pointer to an unconstrained array type may be -converted to and from System.Address. Such usage is common in Ada 83 -programs, but note that Ada.Address_To_Access_Conversions is the -preferred method of performing such conversions in Ada 95 and Ada 2005. -Neither -unchecked conversion nor Ada.Address_To_Access_Conversions should be -used in conjunction with pointers to unconstrained objects, since -the bounds information cannot be handled correctly in this case. +In GNAT, Ada's tasking services rely on a platform and OS independent +layer known as GNARL. This code is responsible for implementing the +correct semantics of Ada's task creation, rendezvous, protected +operations etc. -@item Ada.Unchecked_Deallocation (13.11.2) -This generic package allows explicit freeing of storage previously -allocated by use of an allocator. +GNARL decomposes Ada's tasking semantics into simpler lower level +operations such as create a thread, set the priority of a thread, +yield, create a lock, lock/unlock, etc. The spec for these low-level +operations constitutes GNULLI, the GNULL Interface. This interface is +directly inspired from the POSIX real-time API. -@item Ada.Wide_Text_IO (A.11) -This package is similar to @code{Ada.Text_IO}, except that the external -file supports wide character representations, and the internal types are -@code{Wide_Character} and @code{Wide_String} instead of @code{Character} -and @code{String}. The corresponding set of nested packages and child -packages are defined. +If the underlying executive or OS implements the POSIX standard +faithfully, the GNULL Interface maps as is to the services offered by +the underlying kernel. Otherwise, some target dependent glue code maps +the services offered by the underlying kernel to the semantics expected +by GNARL. -@item Ada.Wide_Wide_Text_IO (A.11) -This package is similar to @code{Ada.Text_IO}, except that the external -file supports wide character representations, and the internal types are -@code{Wide_Character} and @code{Wide_String} instead of @code{Character} -and @code{String}. The corresponding set of nested packages and child -packages are defined. +Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the +key point is that each Ada task is mapped on a thread in the underlying +kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task. -@end table +In addition Ada task priorities map onto the underlying thread priorities. +Mapping Ada tasks onto the underlying kernel threads has several advantages: -For packages in Interfaces and System, all the RM defined packages are -available in GNAT, see the Ada 2012 RM for full details. -@node The Implementation of Standard I/O -@chapter The Implementation of Standard I/O +@itemize * -@noindent -GNAT implements all the required input-output facilities described in -A.6 through A.14. These sections of the Ada Reference Manual describe the -required behavior of these packages from the Ada point of view, and if -you are writing a portable Ada program that does not need to know the -exact manner in which Ada maps to the outside world when it comes to -reading or writing external files, then you do not need to read this -chapter. As long as your files are all regular files (not pipes or -devices), and as long as you write and read the files only from Ada, the -description in the Ada Reference Manual is sufficient. +@item +The underlying scheduler is used to schedule the Ada tasks. This +makes Ada tasks as efficient as kernel threads from a scheduling +standpoint. -However, if you want to do input-output to pipes or other devices, such -as the keyboard or screen, or if the files you are dealing with are -either generated by some other language, or to be read by some other -language, then you need to know more about the details of how the GNAT -implementation of these input-output facilities behaves. +@item +Interaction with code written in C containing threads is eased +since at the lowest level Ada tasks and C threads map onto the same +underlying kernel concept. -In this chapter we give a detailed description of exactly how GNAT -interfaces to the file system. As always, the sources of the system are -available to you for answering questions at an even more detailed level, -but for most purposes the information in this chapter will suffice. +@item +When an Ada task is blocked during I/O the remaining Ada tasks are +able to proceed. -Another reason that you may need to know more about how input-output is -implemented arises when you have a program written in mixed languages -where, for example, files are shared between the C and Ada sections of -the same program. GNAT provides some additional facilities, in the form -of additional child library packages, that facilitate this sharing, and -these additional facilities are also described in this chapter. +@item +On multiprocessor systems Ada tasks can execute in parallel. +@end itemize -@menu -* Standard I/O Packages:: -* FORM Strings:: -* Direct_IO:: -* Sequential_IO:: -* Text_IO:: -* Wide_Text_IO:: -* Wide_Wide_Text_IO:: -* Stream_IO:: -* Text Translation:: -* Shared Files:: -* Filenames encoding:: -* File content encoding:: -* Open Modes:: -* Operations on C Streams:: -* Interfacing to C Streams:: -@end menu +Some threads libraries offer a mechanism to fork a new process, with the +child process duplicating the threads from the parent. +GNAT does not +support this functionality when the parent contains more than one task. +.. index:: Forking a new process -@node Standard I/O Packages -@section Standard I/O Packages +@node Ensuring Compliance with the Real-Time Annex,,Mapping Ada Tasks onto the Underlying Kernel Threads,GNAT Implementation of Tasking +@anchor{gnat_rm/implementation_of_specific_ada_features id5}@anchor{3b1}@anchor{gnat_rm/implementation_of_specific_ada_features ensuring-compliance-with-the-real-time-annex}@anchor{3b2} +@subsection Ensuring Compliance with the Real-Time Annex -@noindent -The Standard I/O packages described in Annex A for -@itemize @bullet -@item -Ada.Text_IO -@item -Ada.Text_IO.Complex_IO -@item -Ada.Text_IO.Text_Streams -@item -Ada.Wide_Text_IO -@item -Ada.Wide_Text_IO.Complex_IO -@item -Ada.Wide_Text_IO.Text_Streams -@item -Ada.Wide_Wide_Text_IO -@item -Ada.Wide_Wide_Text_IO.Complex_IO -@item -Ada.Wide_Wide_Text_IO.Text_Streams -@item -Ada.Stream_IO -@item -Ada.Sequential_IO -@item -Ada.Direct_IO -@end itemize +@geindex Real-Time Systems Annex compliance -@noindent -are implemented using the C -library streams facility; where +Although mapping Ada tasks onto +the underlying threads has significant advantages, it does create some +complications when it comes to respecting the scheduling semantics +specified in the real-time annex (Annex D). -@itemize @bullet -@item -All files are opened using @code{fopen}. -@item -All input/output operations use @code{fread}/@code{fwrite}. -@end itemize +For instance the Annex D requirement for the @cite{FIFO_Within_Priorities} +scheduling policy states: -@noindent -There is no internal buffering of any kind at the Ada library level. The only -buffering is that provided at the system level in the implementation of the -library routines that support streams. This facilitates shared use of these -streams by mixed language programs. Note though that system level buffering is -explicitly enabled at elaboration of the standard I/O packages and that can -have an impact on mixed language programs, in particular those using I/O before -calling the Ada elaboration routine (e.g.@: adainit). It is recommended to call -the Ada elaboration routine before performing any I/O or when impractical, -flush the common I/O streams and in particular Standard_Output before -elaborating the Ada code. +@quotation -@node FORM Strings -@section FORM Strings +@emph{When the active priority of a ready task that is not running +changes, or the setting of its base priority takes effect, the +task is removed from the ready queue for its old active priority +and is added at the tail of the ready queue for its new active +priority, except in the case where the active priority is lowered +due to the loss of inherited priority, in which case the task is +added at the head of the ready queue for its new active priority.} +@end quotation -@noindent -The format of a FORM string in GNAT is: +While most kernels do put tasks at the end of the priority queue when +a task changes its priority, (which respects the main +FIFO_Within_Priorities requirement), almost none keep a thread at the +beginning of its priority queue when its priority drops from the loss +of inherited priority. -@smallexample -"keyword=value,keyword=value,@dots{},keyword=value" -@end smallexample +As a result most vendors have provided incomplete Annex D implementations. -@noindent -where letters may be in upper or lower case, and there are no spaces -between values. The order of the entries is not important. Currently -the following keywords defined. +The GNAT run-time, has a nice cooperative solution to this problem +which ensures that accurate FIFO_Within_Priorities semantics are +respected. -@smallexample -TEXT_TRANSLATION=[YES|NO|TEXT|BINARY|U8TEXT|WTEXT|U16TEXT] -SHARED=[YES|NO] -WCEM=[n|h|u|s|e|8|b] -ENCODING=[UTF8|8BITS] -@end smallexample +The principle is as follows. When an Ada task T is about to start +running, it checks whether some other Ada task R with the same +priority as T has been suspended due to the loss of priority +inheritance. If this is the case, T yields and is placed at the end of +its priority queue. When R arrives at the front of the queue it +executes. -@noindent -The use of these parameters is described later in this section. If an -unrecognized keyword appears in a form string, it is silently ignored -and not considered invalid. +Note that this simple scheme preserves the relative order of the tasks +that were ready to execute in the priority queue where R has been +placed at the end. -@noindent -For OpenVMS additional FORM string keywords are available for use with -RMS services. The syntax is: +@node GNAT Implementation of Shared Passive Packages,Code Generation for Array Aggregates,GNAT Implementation of Tasking,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features id6}@anchor{3b3}@anchor{gnat_rm/implementation_of_specific_ada_features gnat-implementation-of-shared-passive-packages}@anchor{3b4} +@section GNAT Implementation of Shared Passive Packages -@smallexample -VMS_RMS_Keys=(keyword=value,@dots{},keyword=value) -@end smallexample -@noindent -The following RMS keywords and values are currently defined: +@geindex Shared passive packages -@smallexample -Context=Force_Stream_Mode|Force_Record_Mode -@end smallexample +GNAT fully implements the pragma @cite{Shared_Passive} for +.. index:: pragma @cite{Shared_Passive} -@noindent -VMS RMS keys are silently ignored on non-VMS systems. On OpenVMS -unimplented RMS keywords, values, or invalid syntax will raise Use_Error. +the purpose of designating shared passive packages. +This allows the use of passive partitions in the +context described in the Ada Reference Manual; i.e., for communication +between separate partitions of a distributed application using the +features in Annex E. +.. index:: Annex E -@node Direct_IO -@section Direct_IO +@geindex Distribution Systems Annex -@noindent -Direct_IO can only be instantiated for definite types. This is a -restriction of the Ada language, which means that the records are fixed -length (the length being determined by @code{@var{type}'Size}, rounded -up to the next storage unit boundary if necessary). +However, the implementation approach used by GNAT provides for more +extensive usage as follows: -The records of a Direct_IO file are simply written to the file in index -sequence, with the first record starting at offset zero, and subsequent -records following. There is no control information of any kind. For -example, if 32-bit integers are being written, each record takes -4-bytes, so the record at index @var{K} starts at offset -(@var{K}@minus{}1)*4. -There is no limit on the size of Direct_IO files, they are expanded as -necessary to accommodate whatever records are written to the file. +@table @asis -@node Sequential_IO -@section Sequential_IO +@item @emph{Communication between separate programs} -@noindent -Sequential_IO may be instantiated with either a definite (constrained) -or indefinite (unconstrained) type. +This allows separate programs to access the data in passive +partitions, using protected objects for synchronization where +needed. The only requirement is that the two programs have a +common shared file system. It is even possible for programs +running on different machines with different architectures +(e.g., different endianness) to communicate via the data in +a passive partition. -For the definite type case, the elements written to the file are simply -the memory images of the data values with no control information of any -kind. The resulting file should be read using the same type, no validity -checking is performed on input. +@item @emph{Persistence between program runs} -For the indefinite type case, the elements written consist of two -parts. First is the size of the data item, written as the memory image -of a @code{Interfaces.C.size_t} value, followed by the memory image of -the data value. The resulting file can only be read using the same -(unconstrained) type. Normal assignment checks are performed on these -read operations, and if these checks fail, @code{Data_Error} is -raised. In particular, in the array case, the lengths must match, and in -the variant record case, if the variable for a particular read operation -is constrained, the discriminants must match. +The data in a passive package can persist from one run of a +program to another, so that a later program sees the final +values stored by a previous run of the same program. +@end table -Note that it is not possible to use Sequential_IO to write variable -length array items, and then read the data back into different length -arrays. For example, the following will raise @code{Data_Error}: - -@smallexample @c ada - package IO is new Sequential_IO (String); - F : IO.File_Type; - S : String (1..4); - @dots{} - IO.Create (F) - IO.Write (F, "hello!") - IO.Reset (F, Mode=>In_File); - IO.Read (F, S); - Put_Line (S); - -@end smallexample - -@noindent -On some Ada implementations, this will print @code{hell}, but the program is -clearly incorrect, since there is only one element in the file, and that -element is the string @code{hello!}. +The implementation approach used is to store the data in files. A +separate stream file is created for each object in the package, and +an access to an object causes the corresponding file to be read or +written. -In Ada 95 and Ada 2005, this kind of behavior can be legitimately achieved -using Stream_IO, and this is the preferred mechanism. In particular, the -above program fragment rewritten to use Stream_IO will work correctly. +@geindex SHARED_MEMORY_DIRECTORY environment variable -@node Text_IO -@section Text_IO +The environment variable @cite{SHARED_MEMORY_DIRECTORY} should be +set to the directory to be used for these files. +The files in this directory +have names that correspond to their fully qualified names. For +example, if we have the package -@noindent -Text_IO files consist of a stream of characters containing the following -special control characters: +@example +package X is + pragma Shared_Passive (X); + Y : Integer; + Z : Float; +end X; +@end example -@smallexample -LF (line feed, 16#0A#) Line Mark -FF (form feed, 16#0C#) Page Mark -@end smallexample +and the environment variable is set to @cite{/stemp/}, then the files created +will have the names: -@noindent -A canonical Text_IO file is defined as one in which the following -conditions are met: +@example +/stemp/x.y +/stemp/x.z +@end example -@itemize @bullet -@item -The character @code{LF} is used only as a line mark, i.e.@: to mark the end -of the line. +These files are created when a value is initially written to the object, and +the files are retained until manually deleted. This provides the persistence +semantics. If no file exists, it means that no partition has assigned a value +to the variable; in this case the initial value declared in the package +will be used. This model ensures that there are no issues in synchronizing +the elaboration process, since elaboration of passive packages elaborates the +initial values, but does not create the files. -@item -The character @code{FF} is used only as a page mark, i.e.@: to mark the -end of a page and consequently can appear only immediately following a -@code{LF} (line mark) character. +The files are written using normal @cite{Stream_IO} access. +If you want to be able +to communicate between programs or partitions running on different +architectures, then you should use the XDR versions of the stream attribute +routines, since these are architecture independent. -@item -The file ends with either @code{LF} (line mark) or @code{LF}-@code{FF} -(line mark, page mark). In the former case, the page mark is implicitly -assumed to be present. -@end itemize +If active synchronization is required for access to the variables in the +shared passive package, then as described in the Ada Reference Manual, the +package may contain protected objects used for this purpose. In this case +a lock file (whose name is @code{___lock} (three underscores) +is created in the shared memory directory. -@noindent -A file written using Text_IO will be in canonical form provided that no -explicit @code{LF} or @code{FF} characters are written using @code{Put} -or @code{Put_Line}. There will be no @code{FF} character at the end of -the file unless an explicit @code{New_Page} operation was performed -before closing the file. +@geindex ___lock file (for shared passive packages) -A canonical Text_IO file that is a regular file (i.e., not a device or a -pipe) can be read using any of the routines in Text_IO@. The -semantics in this case will be exactly as defined in the Ada Reference -Manual, and all the routines in Text_IO are fully implemented. +This is used to provide the required locking +semantics for proper protected object synchronization. -A text file that does not meet the requirements for a canonical Text_IO -file has one of the following: +GNAT supports shared passive packages on all platforms +except for OpenVMS. -@itemize @bullet -@item -The file contains @code{FF} characters not immediately following a -@code{LF} character. +@node Code Generation for Array Aggregates,The Size of Discriminated Records with Default Discriminants,GNAT Implementation of Shared Passive Packages,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features code-generation-for-array-aggregates}@anchor{3b5}@anchor{gnat_rm/implementation_of_specific_ada_features id7}@anchor{3b6} +@section Code Generation for Array Aggregates -@item -The file contains @code{LF} or @code{FF} characters written by -@code{Put} or @code{Put_Line}, which are not logically considered to be -line marks or page marks. -@item -The file ends in a character other than @code{LF} or @code{FF}, -i.e.@: there is no explicit line mark or page mark at the end of the file. -@end itemize +Aggregates have a rich syntax and allow the user to specify the values of +complex data structures by means of a single construct. As a result, the +code generated for aggregates can be quite complex and involve loops, case +statements and multiple assignments. In the simplest cases, however, the +compiler will recognize aggregates whose components and constraints are +fully static, and in those cases the compiler will generate little or no +executable code. The following is an outline of the code that GNAT generates +for various aggregate constructs. For further details, you will find it +useful to examine the output produced by the -gnatG flag to see the expanded +source that is input to the code generator. You may also want to examine +the assembly code generated at various levels of optimization. -@noindent -Text_IO can be used to read such non-standard text files but subprograms -to do with line or page numbers do not have defined meanings. In -particular, a @code{FF} character that does not follow a @code{LF} -character may or may not be treated as a page mark from the point of -view of page and line numbering. Every @code{LF} character is considered -to end a line, and there is an implied @code{LF} character at the end of -the file. +The code generated for aggregates depends on the context, the component values, +and the type. In the context of an object declaration the code generated is +generally simpler than in the case of an assignment. As a general rule, static +component values and static subtypes also lead to simpler code. @menu -* Text_IO Stream Pointer Positioning:: -* Text_IO Reading and Writing Non-Regular Files:: -* Get_Immediate:: -* Treating Text_IO Files as Streams:: -* Text_IO Extensions:: -* Text_IO Facilities for Unbounded Strings:: +* Static constant aggregates with static bounds:: +* Constant aggregates with unconstrained nominal types:: +* Aggregates with static bounds:: +* Aggregates with non-static bounds:: +* Aggregates in assignment statements:: + @end menu -@node Text_IO Stream Pointer Positioning -@subsection Stream Pointer Positioning +@node Static constant aggregates with static bounds,Constant aggregates with unconstrained nominal types,,Code Generation for Array Aggregates +@anchor{gnat_rm/implementation_of_specific_ada_features static-constant-aggregates-with-static-bounds}@anchor{3b7}@anchor{gnat_rm/implementation_of_specific_ada_features id8}@anchor{3b8} +@subsection Static constant aggregates with static bounds -@noindent -@code{Ada.Text_IO} has a definition of current position for a file that -is being read. No internal buffering occurs in Text_IO, and usually the -physical position in the stream used to implement the file corresponds -to this logical position defined by Text_IO@. There are two exceptions: -@itemize @bullet -@item -After a call to @code{End_Of_Page} that returns @code{True}, the stream -is positioned past the @code{LF} (line mark) that precedes the page -mark. Text_IO maintains an internal flag so that subsequent read -operations properly handle the logical position which is unchanged by -the @code{End_Of_Page} call. +For the declarations: -@item -After a call to @code{End_Of_File} that returns @code{True}, if the -Text_IO file was positioned before the line mark at the end of file -before the call, then the logical position is unchanged, but the stream -is physically positioned right at the end of file (past the line mark, -and past a possible page mark following the line mark. Again Text_IO -maintains internal flags so that subsequent read operations properly -handle the logical position. -@end itemize +@example +type One_Dim is array (1..10) of integer; +ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0); +@end example -@noindent -These discrepancies have no effect on the observable behavior of -Text_IO, but if a single Ada stream is shared between a C program and -Ada program, or shared (using @samp{shared=yes} in the form string) -between two Ada files, then the difference may be observable in some -situations. +GNAT generates no executable code: the constant ar0 is placed in static memory. +The same is true for constant aggregates with named associations: -@node Text_IO Reading and Writing Non-Regular Files -@subsection Reading and Writing Non-Regular Files +@example +Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0); +Cr3 : constant One_Dim := (others => 7777); +@end example -@noindent -A non-regular file is a device (such as a keyboard), or a pipe. Text_IO -can be used for reading and writing. Writing is not affected and the -sequence of characters output is identical to the normal file case, but -for reading, the behavior of Text_IO is modified to avoid undesirable -look-ahead as follows: +The same is true for multidimensional constant arrays such as: -An input file that is not a regular file is considered to have no page -marks. Any @code{Ascii.FF} characters (the character normally used for a -page mark) appearing in the file are considered to be data -characters. In particular: +@example +type two_dim is array (1..3, 1..3) of integer; +Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1)); +@end example -@itemize @bullet -@item -@code{Get_Line} and @code{Skip_Line} do not test for a page mark -following a line mark. If a page mark appears, it will be treated as a -data character. +The same is true for arrays of one-dimensional arrays: the following are +static: -@item -This avoids the need to wait for an extra character to be typed or -entered from the pipe to complete one of these operations. +@example +type ar1b is array (1..3) of boolean; +type ar_ar is array (1..3) of ar1b; +None : constant ar1b := (others => false); -- fully static +None2 : constant ar_ar := (1..3 => None); -- fully static +@end example -@item -@code{End_Of_Page} always returns @code{False} +However, for multidimensional aggregates with named associations, GNAT will +generate assignments and loops, even if all associations are static. The +following two declarations generate a loop for the first dimension, and +individual component assignments for the second dimension: -@item -@code{End_Of_File} will return @code{False} if there is a page mark at -the end of the file. -@end itemize +@example +Zero1: constant two_dim := (1..3 => (1..3 => 0)); +Zero2: constant two_dim := (others => (others => 0)); +@end example -@noindent -Output to non-regular files is the same as for regular files. Page marks -may be written to non-regular files using @code{New_Page}, but as noted -above they will not be treated as page marks on input if the output is -piped to another Ada program. +@node Constant aggregates with unconstrained nominal types,Aggregates with static bounds,Static constant aggregates with static bounds,Code Generation for Array Aggregates +@anchor{gnat_rm/implementation_of_specific_ada_features constant-aggregates-with-unconstrained-nominal-types}@anchor{3b9}@anchor{gnat_rm/implementation_of_specific_ada_features id9}@anchor{3ba} +@subsection Constant aggregates with unconstrained nominal types -Another important discrepancy when reading non-regular files is that the end -of file indication is not ``sticky''. If an end of file is entered, e.g.@: by -pressing the @key{EOT} key, -then end of file -is signaled once (i.e.@: the test @code{End_Of_File} -will yield @code{True}, or a read will -raise @code{End_Error}), but then reading can resume -to read data past that end of -file indication, until another end of file indication is entered. -@node Get_Immediate -@subsection Get_Immediate -@cindex Get_Immediate +In such cases the aggregate itself establishes the subtype, so that +associations with @cite{others} cannot be used. GNAT determines the +bounds for the actual subtype of the aggregate, and allocates the +aggregate statically as well. No code is generated for the following: -@noindent -Get_Immediate returns the next character (including control characters) -from the input file. In particular, Get_Immediate will return LF or FF -characters used as line marks or page marks. Such operations leave the -file positioned past the control character, and it is thus not treated -as having its normal function. This means that page, line and column -counts after this kind of Get_Immediate call are set as though the mark -did not occur. In the case where a Get_Immediate leaves the file -positioned between the line mark and page mark (which is not normally -possible), it is undefined whether the FF character will be treated as a -page mark. +@example +type One_Unc is array (natural range <>) of integer; +Cr_Unc : constant One_Unc := (12,24,36); +@end example -@node Treating Text_IO Files as Streams -@subsection Treating Text_IO Files as Streams -@cindex Stream files +@node Aggregates with static bounds,Aggregates with non-static bounds,Constant aggregates with unconstrained nominal types,Code Generation for Array Aggregates +@anchor{gnat_rm/implementation_of_specific_ada_features id10}@anchor{3bb}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-static-bounds}@anchor{3bc} +@subsection Aggregates with static bounds -@noindent -The package @code{Text_IO.Streams} allows a Text_IO file to be treated -as a stream. Data written to a Text_IO file in this stream mode is -binary data. If this binary data contains bytes 16#0A# (@code{LF}) or -16#0C# (@code{FF}), the resulting file may have non-standard -format. Similarly if read operations are used to read from a Text_IO -file treated as a stream, then @code{LF} and @code{FF} characters may be -skipped and the effect is similar to that described above for -@code{Get_Immediate}. -@node Text_IO Extensions -@subsection Text_IO Extensions -@cindex Text_IO extensions +In all previous examples the aggregate was the initial (and immutable) value +of a constant. If the aggregate initializes a variable, then code is generated +for it as a combination of individual assignments and loops over the target +object. The declarations -@noindent -A package GNAT.IO_Aux in the GNAT library provides some useful extensions -to the standard @code{Text_IO} package: +@example +Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0); +Cr_Var2 : One_Dim := (others > -1); +@end example -@itemize @bullet -@item function File_Exists (Name : String) return Boolean; -Determines if a file of the given name exists. +generate the equivalent of -@item function Get_Line return String; -Reads a string from the standard input file. The value returned is exactly -the length of the line that was read. +@example +Cr_Var1 (1) := 2; +Cr_Var1 (2) := 3; +Cr_Var1 (3) := 5; +Cr_Var1 (4) := 11; -@item function Get_Line (File : Ada.Text_IO.File_Type) return String; -Similar, except that the parameter File specifies the file from which -the string is to be read. +for I in Cr_Var2'range loop + Cr_Var2 (I) := -1; +end loop; +@end example -@end itemize +@node Aggregates with non-static bounds,Aggregates in assignment statements,Aggregates with static bounds,Code Generation for Array Aggregates +@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-with-non-static-bounds}@anchor{3bd}@anchor{gnat_rm/implementation_of_specific_ada_features id11}@anchor{3be} +@subsection Aggregates with non-static bounds -@node Text_IO Facilities for Unbounded Strings -@subsection Text_IO Facilities for Unbounded Strings -@cindex Text_IO for unbounded strings -@cindex Unbounded_String, Text_IO operations -@noindent -The package @code{Ada.Strings.Unbounded.Text_IO} -in library files @code{a-suteio.ads/adb} contains some GNAT-specific -subprograms useful for Text_IO operations on unbounded strings: +If the bounds of the aggregate are not statically compatible with the bounds +of the nominal subtype of the target, then constraint checks have to be +generated on the bounds. For a multidimensional array, constraint checks may +have to be applied to sub-arrays individually, if they do not have statically +compatible subtypes. -@itemize @bullet +@node Aggregates in assignment statements,,Aggregates with non-static bounds,Code Generation for Array Aggregates +@anchor{gnat_rm/implementation_of_specific_ada_features id12}@anchor{3bf}@anchor{gnat_rm/implementation_of_specific_ada_features aggregates-in-assignment-statements}@anchor{3c0} +@subsection Aggregates in assignment statements -@item function Get_Line (File : File_Type) return Unbounded_String; -Reads a line from the specified file -and returns the result as an unbounded string. -@item procedure Put (File : File_Type; U : Unbounded_String); -Writes the value of the given unbounded string to the specified file -Similar to the effect of -@code{Put (To_String (U))} except that an extra copy is avoided. +In general, aggregate assignment requires the construction of a temporary, +and a copy from the temporary to the target of the assignment. This is because +it is not always possible to convert the assignment into a series of individual +component assignments. For example, consider the simple case: -@item procedure Put_Line (File : File_Type; U : Unbounded_String); -Writes the value of the given unbounded string to the specified file, -followed by a @code{New_Line}. -Similar to the effect of @code{Put_Line (To_String (U))} except -that an extra copy is avoided. -@end itemize +@example +A := (A(2), A(1)); +@end example -@noindent -In the above procedures, @code{File} is of type @code{Ada.Text_IO.File_Type} -and is optional. If the parameter is omitted, then the standard input or -output file is referenced as appropriate. +This cannot be converted into: -The package @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} in library -files @file{a-swuwti.ads} and @file{a-swuwti.adb} provides similar extended -@code{Wide_Text_IO} functionality for unbounded wide strings. +@example +A(1) := A(2); +A(2) := A(1); +@end example -The package @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} in library -files @file{a-szuzti.ads} and @file{a-szuzti.adb} provides similar extended -@code{Wide_Wide_Text_IO} functionality for unbounded wide wide strings. +So the aggregate has to be built first in a separate location, and then +copied into the target. GNAT recognizes simple cases where this intermediate +step is not required, and the assignments can be performed in place, directly +into the target. The following sufficient criteria are applied: -@node Wide_Text_IO -@section Wide_Text_IO -@noindent -@code{Wide_Text_IO} is similar in most respects to Text_IO, except that -both input and output files may contain special sequences that represent -wide character values. The encoding scheme for a given file may be -specified using a FORM parameter: +@itemize * -@smallexample -WCEM=@var{x} -@end smallexample +@item +The bounds of the aggregate are static, and the associations are static. -@noindent -as part of the FORM string (WCEM = wide character encoding method), -where @var{x} is one of the following characters +@item +The components of the aggregate are static constants, names of +simple variables that are not renamings, or expressions not involving +indexed components whose operands obey these rules. +@end itemize -@table @samp -@item h -Hex ESC encoding -@item u -Upper half encoding -@item s -Shift-JIS encoding -@item e -EUC Encoding -@item 8 -UTF-8 encoding -@item b -Brackets encoding -@end table +If any of these conditions are violated, the aggregate will be built in +a temporary (created either by the front-end or the code generator) and then +that temporary will be copied onto the target. -@noindent -The encoding methods match those that -can be used in a source -program, but there is no requirement that the encoding method used for -the source program be the same as the encoding method used for files, -and different files may use different encoding methods. +@node The Size of Discriminated Records with Default Discriminants,Strict Conformance to the Ada Reference Manual,Code Generation for Array Aggregates,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features id13}@anchor{3c1}@anchor{gnat_rm/implementation_of_specific_ada_features the-size-of-discriminated-records-with-default-discriminants}@anchor{3c2} +@section The Size of Discriminated Records with Default Discriminants -The default encoding method for the standard files, and for opened files -for which no WCEM parameter is given in the FORM string matches the -wide character encoding specified for the main program (the default -being brackets encoding if no coding method was specified with -gnatW). -@table @asis -@item Hex Coding -In this encoding, a wide character is represented by a five character -sequence: +If a discriminated type @cite{T} has discriminants with default values, it is +possible to declare an object of this type without providing an explicit +constraint: -@smallexample -ESC a b c d -@end smallexample +@example +type Size is range 1..100; -@noindent -where @var{a}, @var{b}, @var{c}, @var{d} are the four hexadecimal -characters (using upper case letters) of the wide character code. For -example, ESC A345 is used to represent the wide character with code -16#A345#. This scheme is compatible with use of the full -@code{Wide_Character} set. +type Rec (D : Size := 15) is record + Name : String (1..D); +end T; -@item Upper Half Coding -The wide character with encoding 16#abcd#, where the upper bit is on -(i.e.@: a is in the range 8-F) is represented as two bytes 16#ab# and -16#cd#. The second byte may never be a format control character, but is -not required to be in the upper half. This method can be also used for -shift-JIS or EUC where the internal coding matches the external coding. +Word : Rec; +@end example -@item Shift JIS Coding -A wide character is represented by a two character sequence 16#ab# and -16#cd#, with the restrictions described for upper half encoding as -described above. The internal character code is the corresponding JIS -character according to the standard algorithm for Shift-JIS -conversion. Only characters defined in the JIS code set table can be -used with this encoding method. +Such an object is said to be @emph{unconstrained}. +The discriminant of the object +can be modified by a full assignment to the object, as long as it preserves the +relation between the value of the discriminant, and the value of the components +that depend on it: -@item EUC Coding -A wide character is represented by a two character sequence 16#ab# and -16#cd#, with both characters being in the upper half. The internal -character code is the corresponding JIS character according to the EUC -encoding algorithm. Only characters defined in the JIS code set table -can be used with this encoding method. +@example +Word := (3, "yes"); -@item UTF-8 Coding -A wide character is represented using -UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO -10646-1/Am.2. Depending on the character value, the representation -is a one, two, or three byte sequence: +Word := (5, "maybe"); -@smallexample -16#0000#-16#007f#: 2#0xxxxxxx# -16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx# -16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# -@end smallexample +Word := (5, "no"); -- raises Constraint_Error +@end example -@noindent -where the @var{xxx} bits correspond to the left-padded bits of the -16-bit character value. Note that all lower half ASCII characters -are represented as ASCII bytes and all upper half characters and -other wide characters are represented as sequences of upper-half -(The full UTF-8 scheme allows for encoding 31-bit characters as -6-byte sequences, but in this implementation, all UTF-8 sequences -of four or more bytes length will raise a Constraint_Error, as -will all invalid UTF-8 sequences.) +In order to support this behavior efficiently, an unconstrained object is +given the maximum size that any value of the type requires. In the case +above, @cite{Word} has storage for the discriminant and for +a @cite{String} of length 100. +It is important to note that unconstrained objects do not require dynamic +allocation. It would be an improper implementation to place on the heap those +components whose size depends on discriminants. (This improper implementation +was used by some Ada83 compilers, where the @cite{Name} component above +would have +been stored as a pointer to a dynamic string). Following the principle that +dynamic storage management should never be introduced implicitly, +an Ada compiler should reserve the full size for an unconstrained declared +object, and place it on the stack. -@item Brackets Coding -In this encoding, a wide character is represented by the following eight -character sequence: +This maximum size approach +has been a source of surprise to some users, who expect the default +values of the discriminants to determine the size reserved for an +unconstrained object: "If the default is 15, why should the object occupy +a larger size?" +The answer, of course, is that the discriminant may be later modified, +and its full range of values must be taken into account. This is why the +declaration: -@smallexample -[ " a b c d " ] -@end smallexample +@example +type Rec (D : Positive := 15) is record + Name : String (1..D); +end record; -@noindent -where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal -characters (using uppercase letters) of the wide character code. For -example, @code{["A345"]} is used to represent the wide character with code -@code{16#A345#}. -This scheme is compatible with use of the full Wide_Character set. -On input, brackets coding can also be used for upper half characters, -e.g.@: @code{["C1"]} for lower case a. However, on output, brackets notation -is only used for wide characters with a code greater than @code{16#FF#}. +Too_Large : Rec; +@end example -Note that brackets coding is not normally used in the context of -Wide_Text_IO or Wide_Wide_Text_IO, since it is really just designed as -a portable way of encoding source files. In the context of Wide_Text_IO -or Wide_Wide_Text_IO, it can only be used if the file does not contain -any instance of the left bracket character other than to encode wide -character values using the brackets encoding method. In practice it is -expected that some standard wide character encoding method such -as UTF-8 will be used for text input output. +is flagged by the compiler with a warning: +an attempt to create @cite{Too_Large} will raise @cite{Storage_Error}, +because the required size includes @cite{Positive'Last} +bytes. As the first example indicates, the proper approach is to declare an +index type of 'reasonable' range so that unconstrained objects are not too +large. -If brackets notation is used, then any occurrence of a left bracket -in the input file which is not the start of a valid wide character -sequence will cause Constraint_Error to be raised. It is possible to -encode a left bracket as ["5B"] and Wide_Text_IO and Wide_Wide_Text_IO -input will interpret this as a left bracket. +One final wrinkle: if the object is declared to be @cite{aliased}, or if it is +created in the heap by means of an allocator, then it is @emph{not} +unconstrained: +it is constrained by the default values of the discriminants, and those values +cannot be modified by full assignment. This is because in the presence of +aliasing all views of the object (which may be manipulated by different tasks, +say) must be consistent, so it is imperative that the object, once created, +remain invariant. -However, when a left bracket is output, it will be output as a left bracket -and not as ["5B"]. We make this decision because for normal use of -Wide_Text_IO for outputting messages, it is unpleasant to clobber left -brackets. For example, if we write: +@node Strict Conformance to the Ada Reference Manual,,The Size of Discriminated Records with Default Discriminants,Implementation of Specific Ada Features +@anchor{gnat_rm/implementation_of_specific_ada_features strict-conformance-to-the-ada-reference-manual}@anchor{3c3}@anchor{gnat_rm/implementation_of_specific_ada_features id14}@anchor{3c4} +@section Strict Conformance to the Ada Reference Manual -@smallexample - Put_Line ("Start of output [first run]"); -@end smallexample -@noindent -we really do not want to have the left bracket in this message clobbered so -that the output reads: +The dynamic semantics defined by the Ada Reference Manual impose a set of +run-time checks to be generated. By default, the GNAT compiler will insert many +run-time checks into the compiled code, including most of those required by the +Ada Reference Manual. However, there are three checks that are not enabled +in the default mode for efficiency reasons: arithmetic overflow checking for +integer operations (including division by zero), checks for access before +elaboration on subprogram calls, and stack overflow checking (most operating +systems do not perform this check by default). -@smallexample - Start of output ["5B"]first run] -@end smallexample +Strict conformance to the Ada Reference Manual can be achieved by adding +three compiler options for overflow checking for integer operations +(@emph{-gnato}), dynamic checks for access-before-elaboration on subprogram +calls and generic instantiations (@emph{-gnatE}), and stack overflow +checking (@emph{-fstack-check}). -@noindent -In practice brackets encoding is reasonably useful for normal Put_Line use -since we won't get confused between left brackets and wide character -sequences in the output. But for input, or when files are written out -and read back in, it really makes better sense to use one of the standard -encoding methods such as UTF-8. +Note that the result of a floating point arithmetic operation in overflow and +invalid situations, when the @cite{Machine_Overflows} attribute of the result +type is @cite{False}, is to generate IEEE NaN and infinite values. This is the +case for machines compliant with the IEEE floating-point standard, but on +machines that are not fully compliant with this standard, such as Alpha, the +@emph{-mieee} compiler flag must be used for achieving IEEE confirming +behavior (although at the cost of a significant performance penalty), so +infinite and NaN values are properly generated. -@end table +@node Implementation of Ada 2012 Features,Obsolescent Features,Implementation of Specific Ada Features,Top +@anchor{gnat_rm/implementation_of_ada_2012_features doc}@anchor{3c5}@anchor{gnat_rm/implementation_of_ada_2012_features implementation-of-ada-2012-features}@anchor{14}@anchor{gnat_rm/implementation_of_ada_2012_features id1}@anchor{3c6} +@chapter Implementation of Ada 2012 Features -@noindent -For the coding schemes other than UTF-8, Hex, or Brackets encoding, -not all wide character -values can be represented. An attempt to output a character that cannot -be represented using the encoding scheme for the file causes -Constraint_Error to be raised. An invalid wide character sequence on -input also causes Constraint_Error to be raised. -@menu -* Wide_Text_IO Stream Pointer Positioning:: -* Wide_Text_IO Reading and Writing Non-Regular Files:: -@end menu +@geindex Ada 2012 implementation status -@node Wide_Text_IO Stream Pointer Positioning -@subsection Stream Pointer Positioning +@geindex -gnat12 option (gcc) -@noindent -@code{Ada.Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling -of stream pointer positioning (@pxref{Text_IO}). There is one additional -case: +@geindex pragma Ada_2012 -If @code{Ada.Wide_Text_IO.Look_Ahead} reads a character outside the -normal lower ASCII set (i.e.@: a character in the range: +@geindex configuration pragma Ada_2012 -@smallexample @c ada -Wide_Character'Val (16#0080#) .. Wide_Character'Val (16#FFFF#) -@end smallexample +@geindex Ada_2012 configuration pragma -@noindent -then although the logical position of the file pointer is unchanged by -the @code{Look_Ahead} call, the stream is physically positioned past the -wide character sequence. Again this is to avoid the need for buffering -or backup, and all @code{Wide_Text_IO} routines check the internal -indication that this situation has occurred so that this is not visible -to a normal program using @code{Wide_Text_IO}. However, this discrepancy -can be observed if the wide text file shares a stream with another file. +This chapter contains a complete list of Ada 2012 features that have been +implemented as of GNAT version 6.4. Generally, these features are only +available if the @emph{-gnat12} (Ada 2012 features enabled) flag is set +or if the configuration pragma @cite{Ada_2012} is used. -@node Wide_Text_IO Reading and Writing Non-Regular Files -@subsection Reading and Writing Non-Regular Files +However, new pragmas, attributes, and restrictions are +unconditionally available, since the Ada 95 standard allows the addition of +new pragmas, attributes, and restrictions (there are exceptions, which are +documented in the individual descriptions), and also certain packages +were made available in earlier versions of Ada. -@noindent -As in the case of Text_IO, when a non-regular file is read, it is -assumed that the file contains no page marks (any form characters are -treated as data characters), and @code{End_Of_Page} always returns -@code{False}. Similarly, the end of file indication is not sticky, so -it is possible to read beyond an end of file. +An ISO date (YYYY-MM-DD) appears in parentheses on the description line. +This date shows the implementation date of the feature. Any wavefront +subsequent to this date will contain the indicated feature, as will any +subsequent releases. A date of 0000-00-00 means that GNAT has always +implemented the feature, or implemented it as soon as it appeared as a +binding interpretation. -@node Wide_Wide_Text_IO -@section Wide_Wide_Text_IO +Each feature corresponds to an Ada Issue ('AI') approved by the Ada +standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012. +The features are ordered based on the relevant sections of the Ada +Reference Manual ("RM"). When a given AI relates to multiple points +in the RM, the earliest is used. -@noindent -@code{Wide_Wide_Text_IO} is similar in most respects to Text_IO, except that -both input and output files may contain special sequences that represent -wide wide character values. The encoding scheme for a given file may be -specified using a FORM parameter: +A complete description of the AIs may be found in +@indicateurl{http://www.ada-auth.org/ai05-summary.html}. -@smallexample -WCEM=@var{x} -@end smallexample +@geindex AI-0176 (Ada 2012 feature) -@noindent -as part of the FORM string (WCEM = wide character encoding method), -where @var{x} is one of the following characters -@table @samp -@item h -Hex ESC encoding -@item u -Upper half encoding -@item s -Shift-JIS encoding -@item e -EUC Encoding -@item 8 -UTF-8 encoding -@item b -Brackets encoding -@end table +@itemize * -@noindent -The encoding methods match those that -can be used in a source -program, but there is no requirement that the encoding method used for -the source program be the same as the encoding method used for files, -and different files may use different encoding methods. +@item +@emph{AI-0176 Quantified expressions (2010-09-29)} -The default encoding method for the standard files, and for opened files -for which no WCEM parameter is given in the FORM string matches the -wide character encoding specified for the main program (the default -being brackets encoding if no coding method was specified with -gnatW). +Both universally and existentially quantified expressions are implemented. +They use the new syntax for iterators proposed in AI05-139-2, as well as +the standard Ada loop syntax. -@table @asis +RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0) +@end itemize -@item UTF-8 Coding -A wide character is represented using -UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO -10646-1/Am.2. Depending on the character value, the representation -is a one, two, three, or four byte sequence: +@geindex AI-0079 (Ada 2012 feature) -@smallexample -16#000000#-16#00007f#: 2#0xxxxxxx# -16#000080#-16#0007ff#: 2#110xxxxx# 2#10xxxxxx# -16#000800#-16#00ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx# -16#010000#-16#10ffff#: 2#11110xxx# 2#10xxxxxx# 2#10xxxxxx# 2#10xxxxxx# -@end smallexample -@noindent -where the @var{xxx} bits correspond to the left-padded bits of the -21-bit character value. Note that all lower half ASCII characters -are represented as ASCII bytes and all upper half characters and -other wide characters are represented as sequences of upper-half -characters. +@itemize * -@item Brackets Coding -In this encoding, a wide wide character is represented by the following eight -character sequence if is in wide character range +@item +@emph{AI-0079 Allow other_format characters in source (2010-07-10)} -@smallexample -[ " a b c d " ] -@end smallexample +Wide characters in the unicode category @emph{other_format} are now allowed in +source programs between tokens, but not within a token such as an identifier. -and by the following ten character sequence if not +RM References: 2.01 (4/2) 2.02 (7) +@end itemize -@smallexample -[ " a b c d e f " ] -@end smallexample +@geindex AI-0091 (Ada 2012 feature) -@noindent -where @code{a}, @code{b}, @code{c}, @code{d}, @code{e}, and @code{f} -are the four or six hexadecimal -characters (using uppercase letters) of the wide wide character code. For -example, @code{["01A345"]} is used to represent the wide wide character -with code @code{16#01A345#}. -This scheme is compatible with use of the full Wide_Wide_Character set. -On input, brackets coding can also be used for upper half characters, -e.g.@: @code{["C1"]} for lower case a. However, on output, brackets notation -is only used for wide characters with a code greater than @code{16#FF#}. +@itemize * -@end table +@item +@emph{AI-0091 Do not allow other_format in identifiers (0000-00-00)} -@noindent -If is also possible to use the other Wide_Character encoding methods, -such as Shift-JIS, but the other schemes cannot support the full range -of wide wide characters. -An attempt to output a character that cannot -be represented using the encoding scheme for the file causes -Constraint_Error to be raised. An invalid wide character sequence on -input also causes Constraint_Error to be raised. +Wide characters in the unicode category @emph{other_format} are not permitted +within an identifier, since this can be a security problem. The error +message for this case has been improved to be more specific, but GNAT has +never allowed such characters to appear in identifiers. -@menu -* Wide_Wide_Text_IO Stream Pointer Positioning:: -* Wide_Wide_Text_IO Reading and Writing Non-Regular Files:: -@end menu +RM References: 2.03 (3.1/2) 2.03 (4/2) 2.03 (5/2) 2.03 (5.1/2) 2.03 (5.2/2) 2.03 (5.3/2) 2.09 (2/2) +@end itemize -@node Wide_Wide_Text_IO Stream Pointer Positioning -@subsection Stream Pointer Positioning +@geindex AI-0100 (Ada 2012 feature) -@noindent -@code{Ada.Wide_Wide_Text_IO} is similar to @code{Ada.Text_IO} in its handling -of stream pointer positioning (@pxref{Text_IO}). There is one additional -case: -If @code{Ada.Wide_Wide_Text_IO.Look_Ahead} reads a character outside the -normal lower ASCII set (i.e.@: a character in the range: +@itemize * -@smallexample @c ada -Wide_Wide_Character'Val (16#0080#) .. Wide_Wide_Character'Val (16#10FFFF#) -@end smallexample +@item +@emph{AI-0100 Placement of pragmas (2010-07-01)} -@noindent -then although the logical position of the file pointer is unchanged by -the @code{Look_Ahead} call, the stream is physically positioned past the -wide character sequence. Again this is to avoid the need for buffering -or backup, and all @code{Wide_Wide_Text_IO} routines check the internal -indication that this situation has occurred so that this is not visible -to a normal program using @code{Wide_Wide_Text_IO}. However, this discrepancy -can be observed if the wide text file shares a stream with another file. +This AI is an earlier version of AI-163. It simplifies the rules +for legal placement of pragmas. In the case of lists that allow pragmas, if +the list may have no elements, then the list may consist solely of pragmas. -@node Wide_Wide_Text_IO Reading and Writing Non-Regular Files -@subsection Reading and Writing Non-Regular Files +RM References: 2.08 (7) +@end itemize -@noindent -As in the case of Text_IO, when a non-regular file is read, it is -assumed that the file contains no page marks (any form characters are -treated as data characters), and @code{End_Of_Page} always returns -@code{False}. Similarly, the end of file indication is not sticky, so -it is possible to read beyond an end of file. +@geindex AI-0163 (Ada 2012 feature) -@node Stream_IO -@section Stream_IO -@noindent -A stream file is a sequence of bytes, where individual elements are -written to the file as described in the Ada Reference Manual. The type -@code{Stream_Element} is simply a byte. There are two ways to read or -write a stream file. +@itemize * -@itemize @bullet -@item -The operations @code{Read} and @code{Write} directly read or write a -sequence of stream elements with no control information. +@item +@emph{AI-0163 Pragmas in place of null (2010-07-01)} -@item -The stream attributes applied to a stream file transfer data in the -manner described for stream attributes. +A statement sequence may be composed entirely of pragmas. It is no longer +necessary to add a dummy @cite{null} statement to make the sequence legal. + +RM References: 2.08 (7) 2.08 (16) @end itemize -@node Text Translation -@section Text Translation +@geindex AI-0080 (Ada 2012 feature) -@noindent -@samp{Text_Translation=@var{xxx}} may be used as the Form parameter -passed to Text_IO.Create and Text_IO.Open. @samp{Text_Translation=@var{xxx}} -has no effect on Unix systems. Possible values are: -@itemize @bullet +@itemize * -@item -@samp{@var{Yes} or @var{Text}} is the default, which means to -translate LF to/from CR/LF on Windows systems. +@item +@emph{AI-0080 'View of' not needed if clear from context (0000-00-00)} -@samp{@var{No}} disables this translation; i.e. it -uses binary mode. For output files, @samp{Text_Translation=@var{No}} -may be used to create Unix-style files on -Windows. +This is an editorial change only, described as non-testable in the AI. -@item -@samp{@var{wtext}} translation enabled in Unicode mode. -(corresponds to _O_WTEXT). +RM References: 3.01 (7) +@end itemize -@item -@samp{@var{u8text}} translation enabled in Unicode UTF-8 mode. -(corresponds to O_U8TEXT). +@geindex AI-0183 (Ada 2012 feature) -@item -@samp{@var{u16text}} translation enabled in Unicode UTF-16 -mode. (corresponds to_O_U16TEXT). +@itemize * + +@item +@emph{AI-0183 Aspect specifications (2010-08-16)} + +Aspect specifications have been fully implemented except for pre and post- +conditions, and type invariants, which have their own separate AI's. All +forms of declarations listed in the AI are supported. The following is a +list of the aspects supported (with GNAT implementation aspects marked) @end itemize +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx} +@headitem -@node Shared Files -@section Shared Files +Supported Aspect -@noindent -Section A.14 of the Ada Reference Manual allows implementations to -provide a wide variety of behavior if an attempt is made to access the -same external file with two or more internal files. +@tab -To provide a full range of functionality, while at the same time -minimizing the problems of portability caused by this implementation -dependence, GNAT handles file sharing as follows: +Source -@itemize @bullet @item -In the absence of a @samp{shared=@var{xxx}} form parameter, an attempt -to open two or more files with the same full name is considered an error -and is not supported. The exception @code{Use_Error} will be -raised. Note that a file that is not explicitly closed by the program -remains open until the program terminates. -@item -If the form parameter @samp{shared=no} appears in the form string, the -file can be opened or created with its own separate stream identifier, -regardless of whether other files sharing the same external file are -opened. The exact effect depends on how the C stream routines handle -multiple accesses to the same external files using separate streams. +@cite{Ada_2005} + +@tab + +-- GNAT @item -If the form parameter @samp{shared=yes} appears in the form string for -each of two or more files opened using the same full name, the same -stream is shared between these files, and the semantics are as described -in Ada Reference Manual, Section A.14. -@end itemize -@noindent -When a program that opens multiple files with the same name is ported -from another Ada compiler to GNAT, the effect will be that -@code{Use_Error} is raised. +@cite{Ada_2012} -The documentation of the original compiler and the documentation of the -program should then be examined to determine if file sharing was -expected, and @samp{shared=@var{xxx}} parameters added to @code{Open} -and @code{Create} calls as required. +@tab -When a program is ported from GNAT to some other Ada compiler, no -special attention is required unless the @samp{shared=@var{xxx}} form -parameter is used in the program. In this case, you must examine the -documentation of the new compiler to see if it supports the required -file sharing semantics, and form strings modified appropriately. Of -course it may be the case that the program cannot be ported if the -target compiler does not support the required functionality. The best -approach in writing portable code is to avoid file sharing (and hence -the use of the @samp{shared=@var{xxx}} parameter in the form string) -completely. +-- GNAT -One common use of file sharing in Ada 83 is the use of instantiations of -Sequential_IO on the same file with different types, to achieve -heterogeneous input-output. Although this approach will work in GNAT if -@samp{shared=yes} is specified, it is preferable in Ada to use Stream_IO -for this purpose (using the stream attributes) +@item -@node Filenames encoding -@section Filenames encoding +@cite{Address} -@noindent -An encoding form parameter can be used to specify the filename -encoding @samp{encoding=@var{xxx}}. +@tab -@itemize @bullet @item -If the form parameter @samp{encoding=utf8} appears in the form string, the -filename must be encoded in UTF-8. + +@cite{Alignment} + +@tab @item -If the form parameter @samp{encoding=8bits} appears in the form -string, the filename must be a standard 8bits string. -@end itemize -In the absence of a @samp{encoding=@var{xxx}} form parameter, the -encoding is controlled by the @samp{GNAT_CODE_PAGE} environment -variable. And if not set @samp{utf8} is assumed. +@cite{Atomic} -@table @samp -@item CP_ACP -The current system Windows ANSI code page. -@item CP_UTF8 -UTF-8 encoding -@end table +@tab -This encoding form parameter is only supported on the Windows -platform. On the other Operating Systems the run-time is supporting -UTF-8 natively. +@item -@node File content encoding -@section File content encoding +@cite{Atomic_Components} -@noindent -For text files it is possible to specify the encoding to use. This is -controlled by the by the @samp{GNAT_CCS_ENCODING} environment -variable. And if not set @samp{TEXT} is assumed. +@tab -The possible values are those supported on Windows: +@item -@table @samp -@item TEXT -Translated text mode -@item WTEXT -Translated unicode encoding -@item U16TEXT -Unicode 16-bit encoding -@item U8TEXT -Unicode 8-bit encoding -@end table +@cite{Bit_Order} -This encoding is only supported on the Windows platform. +@tab -@node Open Modes -@section Open Modes +@item -@noindent -@code{Open} and @code{Create} calls result in a call to @code{fopen} -using the mode shown in the following table: +@cite{Component_Size} -@sp 2 -@center @code{Open} and @code{Create} Call Modes -@smallexample - @b{OPEN } @b{CREATE} -Append_File "r+" "w+" -In_File "r" "w+" -Out_File (Direct_IO) "r+" "w" -Out_File (all other cases) "w" "w" -Inout_File "r+" "w+" -@end smallexample - -@noindent -If text file translation is required, then either @samp{b} or @samp{t} -is added to the mode, depending on the setting of Text. Text file -translation refers to the mapping of CR/LF sequences in an external file -to LF characters internally. This mapping only occurs in DOS and -DOS-like systems, and is not relevant to other systems. +@tab -A special case occurs with Stream_IO@. As shown in the above table, the -file is initially opened in @samp{r} or @samp{w} mode for the -@code{In_File} and @code{Out_File} cases. If a @code{Set_Mode} operation -subsequently requires switching from reading to writing or vice-versa, -then the file is reopened in @samp{r+} mode to permit the required operation. +@item -@node Operations on C Streams -@section Operations on C Streams -The package @code{Interfaces.C_Streams} provides an Ada program with direct -access to the C library functions for operations on C streams: +@cite{Contract_Cases} -@smallexample @c adanocomment -package Interfaces.C_Streams is - -- Note: the reason we do not use the types that are in - -- Interfaces.C is that we want to avoid dragging in the - -- code in this unit if possible. - subtype chars is System.Address; - -- Pointer to null-terminated array of characters - subtype FILEs is System.Address; - -- Corresponds to the C type FILE* - subtype voids is System.Address; - -- Corresponds to the C type void* - subtype int is Integer; - subtype long is Long_Integer; - -- Note: the above types are subtypes deliberately, and it - -- is part of this spec that the above correspondences are - -- guaranteed. This means that it is legitimate to, for - -- example, use Integer instead of int. We provide these - -- synonyms for clarity, but in some cases it may be - -- convenient to use the underlying types (for example to - -- avoid an unnecessary dependency of a spec on the spec - -- of this unit). - type size_t is mod 2 ** Standard'Address_Size; - NULL_Stream : constant FILEs; - -- Value returned (NULL in C) to indicate an - -- fdopen/fopen/tmpfile error - ---------------------------------- - -- Constants Defined in stdio.h -- - ---------------------------------- - EOF : constant int; - -- Used by a number of routines to indicate error or - -- end of file - IOFBF : constant int; - IOLBF : constant int; - IONBF : constant int; - -- Used to indicate buffering mode for setvbuf call - SEEK_CUR : constant int; - SEEK_END : constant int; - SEEK_SET : constant int; - -- Used to indicate origin for fseek call - function stdin return FILEs; - function stdout return FILEs; - function stderr return FILEs; - -- Streams associated with standard files - -------------------------- - -- Standard C functions -- - -------------------------- - -- The functions selected below are ones that are - -- available in UNIX (but not necessarily in ANSI C). - -- These are very thin interfaces - -- which copy exactly the C headers. For more - -- documentation on these functions, see the Microsoft C - -- "Run-Time Library Reference" (Microsoft Press, 1990, - -- ISBN 1-55615-225-6), which includes useful information - -- on system compatibility. - procedure clearerr (stream : FILEs); - function fclose (stream : FILEs) return int; - function fdopen (handle : int; mode : chars) return FILEs; - function feof (stream : FILEs) return int; - function ferror (stream : FILEs) return int; - function fflush (stream : FILEs) return int; - function fgetc (stream : FILEs) return int; - function fgets (strng : chars; n : int; stream : FILEs) - return chars; - function fileno (stream : FILEs) return int; - function fopen (filename : chars; Mode : chars) - return FILEs; - -- Note: to maintain target independence, use - -- text_translation_required, a boolean variable defined in - -- a-sysdep.c to deal with the target dependent text - -- translation requirement. If this variable is set, - -- then b/t should be appended to the standard mode - -- argument to set the text translation mode off or on - -- as required. - function fputc (C : int; stream : FILEs) return int; - function fputs (Strng : chars; Stream : FILEs) return int; - function fread - (buffer : voids; - size : size_t; - count : size_t; - stream : FILEs) - return size_t; - function freopen - (filename : chars; - mode : chars; - stream : FILEs) - return FILEs; - function fseek - (stream : FILEs; - offset : long; - origin : int) - return int; - function ftell (stream : FILEs) return long; - function fwrite - (buffer : voids; - size : size_t; - count : size_t; - stream : FILEs) - return size_t; - function isatty (handle : int) return int; - procedure mktemp (template : chars); - -- The return value (which is just a pointer to template) - -- is discarded - procedure rewind (stream : FILEs); - function rmtmp return int; - function setvbuf - (stream : FILEs; - buffer : chars; - mode : int; - size : size_t) - return int; +@tab - function tmpfile return FILEs; - function ungetc (c : int; stream : FILEs) return int; - function unlink (filename : chars) return int; - --------------------- - -- Extra functions -- - --------------------- - -- These functions supply slightly thicker bindings than - -- those above. They are derived from functions in the - -- C Run-Time Library, but may do a bit more work than - -- just directly calling one of the Library functions. - function is_regular_file (handle : int) return int; - -- Tests if given handle is for a regular file (result 1) - -- or for a non-regular file (pipe or device, result 0). - --------------------------------- - -- Control of Text/Binary Mode -- - --------------------------------- - -- If text_translation_required is true, then the following - -- functions may be used to dynamically switch a file from - -- binary to text mode or vice versa. These functions have - -- no effect if text_translation_required is false (i.e.@: in - -- normal UNIX mode). Use fileno to get a stream handle. - procedure set_binary_mode (handle : int); - procedure set_text_mode (handle : int); - ---------------------------- - -- Full Path Name support -- - ---------------------------- - procedure full_name (nam : chars; buffer : chars); - -- Given a NUL terminated string representing a file - -- name, returns in buffer a NUL terminated string - -- representing the full path name for the file name. - -- On systems where it is relevant the drive is also - -- part of the full path name. It is the responsibility - -- of the caller to pass an actual parameter for buffer - -- that is big enough for any full path name. Use - -- max_path_len given below as the size of buffer. - max_path_len : integer; - -- Maximum length of an allowable full path name on the - -- system, including a terminating NUL character. -end Interfaces.C_Streams; -@end smallexample +-- GNAT -@node Interfacing to C Streams -@section Interfacing to C Streams +@item -@noindent -The packages in this section permit interfacing Ada files to C Stream -operations. +@cite{Discard_Names} -@smallexample @c ada - with Interfaces.C_Streams; - package Ada.Sequential_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Sequential_IO.C_Streams; - - with Interfaces.C_Streams; - package Ada.Direct_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Direct_IO.C_Streams; - - with Interfaces.C_Streams; - package Ada.Text_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Text_IO.C_Streams; - - with Interfaces.C_Streams; - package Ada.Wide_Text_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Wide_Text_IO.C_Streams; - - with Interfaces.C_Streams; - package Ada.Wide_Wide_Text_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Wide_Wide_Text_IO.C_Streams; +@tab + +@item + +@cite{External_Tag} + +@tab + +@item + +@cite{Favor_Top_Level} - with Interfaces.C_Streams; - package Ada.Stream_IO.C_Streams is - function C_Stream (F : File_Type) - return Interfaces.C_Streams.FILEs; - procedure Open - (File : in out File_Type; - Mode : in File_Mode; - C_Stream : in Interfaces.C_Streams.FILEs; - Form : in String := ""); - end Ada.Stream_IO.C_Streams; -@end smallexample +@tab -@noindent -In each of these six packages, the @code{C_Stream} function obtains the -@code{FILE} pointer from a currently opened Ada file. It is then -possible to use the @code{Interfaces.C_Streams} package to operate on -this stream, or the stream can be passed to a C program which can -operate on it directly. Of course the program is responsible for -ensuring that only appropriate sequences of operations are executed. +-- GNAT -One particular use of relevance to an Ada program is that the -@code{setvbuf} function can be used to control the buffering of the -stream used by an Ada file. In the absence of such a call the standard -default buffering is used. +@item -The @code{Open} procedures in these packages open a file giving an -existing C Stream instead of a file name. Typically this stream is -imported from a C program, allowing an Ada file to operate on an -existing C file. +@cite{Inline} -@node The GNAT Library -@chapter The GNAT Library +@tab -@noindent -The GNAT library contains a number of general and special purpose packages. -It represents functionality that the GNAT developers have found useful, and -which is made available to GNAT users. The packages described here are fully -supported, and upwards compatibility will be maintained in future releases, -so you can use these facilities with the confidence that the same functionality -will be available in future releases. +@item -The chapter here simply gives a brief summary of the facilities available. -The full documentation is found in the spec file for the package. The full -sources of these library packages, including both spec and body, are provided -with all GNAT releases. For example, to find out the full specifications of -the SPITBOL pattern matching capability, including a full tutorial and -extensive examples, look in the @file{g-spipat.ads} file in the library. +@cite{Inline_Always} -For each entry here, the package name (as it would appear in a @code{with} -clause) is given, followed by the name of the corresponding spec file in -parentheses. The packages are children in four hierarchies, @code{Ada}, -@code{Interfaces}, @code{System}, and @code{GNAT}, the latter being a -GNAT-specific hierarchy. +@tab -Note that an application program should only use packages in one of these -four hierarchies if the package is defined in the Ada Reference Manual, -or is listed in this section of the GNAT Programmers Reference Manual. -All other units should be considered internal implementation units and -should not be directly @code{with}'ed by application code. The use of -a @code{with} statement that references one of these internal implementation -units makes an application potentially dependent on changes in versions -of GNAT, and will generate a warning message. +-- GNAT -@menu -* Ada.Characters.Latin_9 (a-chlat9.ads):: -* Ada.Characters.Wide_Latin_1 (a-cwila1.ads):: -* Ada.Characters.Wide_Latin_9 (a-cwila9.ads):: -* Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads):: -* Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads):: -* Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads):: -* Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads):: -* Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads):: -* Ada.Containers.Formal_Ordered_Maps (a-cforma.ads):: -* Ada.Containers.Formal_Ordered_Sets (a-cforse.ads):: -* Ada.Containers.Formal_Vectors (a-cofove.ads):: -* Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads):: -* Ada.Containers.Bounded_Holders (a-coboho.ads):: -* Ada.Command_Line.Environment (a-colien.ads):: -* Ada.Command_Line.Remove (a-colire.ads):: -* Ada.Command_Line.Response_File (a-clrefi.ads):: -* Ada.Direct_IO.C_Streams (a-diocst.ads):: -* Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads):: -* Ada.Exceptions.Last_Chance_Handler (a-elchha.ads):: -* Ada.Exceptions.Traceback (a-exctra.ads):: -* Ada.Sequential_IO.C_Streams (a-siocst.ads):: -* Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads):: -* Ada.Strings.Unbounded.Text_IO (a-suteio.ads):: -* Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads):: -* Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads):: -* Ada.Text_IO.C_Streams (a-tiocst.ads):: -* Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads):: -* Ada.Wide_Characters.Unicode (a-wichun.ads):: -* Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads):: -* Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads):: -* Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads):: -* Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads):: -* Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads):: -* GNAT.Altivec (g-altive.ads):: -* GNAT.Altivec.Conversions (g-altcon.ads):: -* GNAT.Altivec.Vector_Operations (g-alveop.ads):: -* GNAT.Altivec.Vector_Types (g-alvety.ads):: -* GNAT.Altivec.Vector_Views (g-alvevi.ads):: -* GNAT.Array_Split (g-arrspl.ads):: -* GNAT.AWK (g-awk.ads):: -* GNAT.Bounded_Buffers (g-boubuf.ads):: -* GNAT.Bounded_Mailboxes (g-boumai.ads):: -* GNAT.Bubble_Sort (g-bubsor.ads):: -* GNAT.Bubble_Sort_A (g-busora.ads):: -* GNAT.Bubble_Sort_G (g-busorg.ads):: -* GNAT.Byte_Order_Mark (g-byorma.ads):: -* GNAT.Byte_Swapping (g-bytswa.ads):: -* GNAT.Calendar (g-calend.ads):: -* GNAT.Calendar.Time_IO (g-catiio.ads):: -* GNAT.Case_Util (g-casuti.ads):: -* GNAT.CGI (g-cgi.ads):: -* GNAT.CGI.Cookie (g-cgicoo.ads):: -* GNAT.CGI.Debug (g-cgideb.ads):: -* GNAT.Command_Line (g-comlin.ads):: -* GNAT.Compiler_Version (g-comver.ads):: -* GNAT.Ctrl_C (g-ctrl_c.ads):: -* GNAT.CRC32 (g-crc32.ads):: -* GNAT.Current_Exception (g-curexc.ads):: -* GNAT.Debug_Pools (g-debpoo.ads):: -* GNAT.Debug_Utilities (g-debuti.ads):: -* GNAT.Decode_String (g-decstr.ads):: -* GNAT.Decode_UTF8_String (g-deutst.ads):: -* GNAT.Directory_Operations (g-dirope.ads):: -* GNAT.Directory_Operations.Iteration (g-diopit.ads):: -* GNAT.Dynamic_HTables (g-dynhta.ads):: -* GNAT.Dynamic_Tables (g-dyntab.ads):: -* GNAT.Encode_String (g-encstr.ads):: -* GNAT.Encode_UTF8_String (g-enutst.ads):: -* GNAT.Exception_Actions (g-excact.ads):: -* GNAT.Exception_Traces (g-exctra.ads):: -* GNAT.Exceptions (g-except.ads):: -* GNAT.Expect (g-expect.ads):: -* GNAT.Expect.TTY (g-exptty.ads):: -* GNAT.Float_Control (g-flocon.ads):: -* GNAT.Formatted_String (g-forstr.ads):: -* GNAT.Heap_Sort (g-heasor.ads):: -* GNAT.Heap_Sort_A (g-hesora.ads):: -* GNAT.Heap_Sort_G (g-hesorg.ads):: -* GNAT.HTable (g-htable.ads):: -* GNAT.IO (g-io.ads):: -* GNAT.IO_Aux (g-io_aux.ads):: -* GNAT.Lock_Files (g-locfil.ads):: -* GNAT.MBBS_Discrete_Random (g-mbdira.ads):: -* GNAT.MBBS_Float_Random (g-mbflra.ads):: -* GNAT.MD5 (g-md5.ads):: -* GNAT.Memory_Dump (g-memdum.ads):: -* GNAT.Most_Recent_Exception (g-moreex.ads):: -* GNAT.OS_Lib (g-os_lib.ads):: -* GNAT.Perfect_Hash_Generators (g-pehage.ads):: -* GNAT.Random_Numbers (g-rannum.ads):: -* GNAT.Regexp (g-regexp.ads):: -* GNAT.Registry (g-regist.ads):: -* GNAT.Regpat (g-regpat.ads):: -* GNAT.Rewrite_Data (g-rewdat.ads):: -* GNAT.Secondary_Stack_Info (g-sestin.ads):: -* GNAT.Semaphores (g-semaph.ads):: -* GNAT.Serial_Communications (g-sercom.ads):: -* GNAT.SHA1 (g-sha1.ads):: -* GNAT.SHA224 (g-sha224.ads):: -* GNAT.SHA256 (g-sha256.ads):: -* GNAT.SHA384 (g-sha384.ads):: -* GNAT.SHA512 (g-sha512.ads):: -* GNAT.Signals (g-signal.ads):: -* GNAT.Sockets (g-socket.ads):: -* GNAT.Source_Info (g-souinf.ads):: -* GNAT.Spelling_Checker (g-speche.ads):: -* GNAT.Spelling_Checker_Generic (g-spchge.ads):: -* GNAT.Spitbol.Patterns (g-spipat.ads):: -* GNAT.Spitbol (g-spitbo.ads):: -* GNAT.Spitbol.Table_Boolean (g-sptabo.ads):: -* GNAT.Spitbol.Table_Integer (g-sptain.ads):: -* GNAT.Spitbol.Table_VString (g-sptavs.ads):: -* GNAT.SSE (g-sse.ads):: -* GNAT.SSE.Vector_Types (g-ssvety.ads):: -* GNAT.Strings (g-string.ads):: -* GNAT.String_Split (g-strspl.ads):: -* GNAT.Table (g-table.ads):: -* GNAT.Task_Lock (g-tasloc.ads):: -* GNAT.Threads (g-thread.ads):: -* GNAT.Time_Stamp (g-timsta.ads):: -* GNAT.Traceback (g-traceb.ads):: -* GNAT.Traceback.Symbolic (g-trasym.ads):: -* GNAT.UTF_32 (g-utf_32.ads):: -* GNAT.UTF_32_Spelling_Checker (g-u3spch.ads):: -* GNAT.Wide_Spelling_Checker (g-wispch.ads):: -* GNAT.Wide_String_Split (g-wistsp.ads):: -* GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads):: -* GNAT.Wide_Wide_String_Split (g-zistsp.ads):: -* Interfaces.C.Extensions (i-cexten.ads):: -* Interfaces.C.Streams (i-cstrea.ads):: -* Interfaces.Packed_Decimal (i-pacdec.ads):: -* Interfaces.VxWorks (i-vxwork.ads):: -* Interfaces.VxWorks.IO (i-vxwoio.ads):: -* System.Address_Image (s-addima.ads):: -* System.Assertions (s-assert.ads):: -* System.Atomic_Counters (s-atocou.ads):: -* System.Memory (s-memory.ads):: -* System.Multiprocessors (s-multip.ads):: -* System.Multiprocessors.Dispatching_Domains (s-mudido.ads):: -* System.Partition_Interface (s-parint.ads):: -* System.Pool_Global (s-pooglo.ads):: -* System.Pool_Local (s-pooloc.ads):: -* System.Restrictions (s-restri.ads):: -* System.Rident (s-rident.ads):: -* System.Strings.Stream_Ops (s-ststop.ads):: -* System.Unsigned_Types (s-unstyp.ads):: -* System.Wch_Cnv (s-wchcnv.ads):: -* System.Wch_Con (s-wchcon.ads):: -@end menu +@item -@node Ada.Characters.Latin_9 (a-chlat9.ads) -@section @code{Ada.Characters.Latin_9} (@file{a-chlat9.ads}) -@cindex @code{Ada.Characters.Latin_9} (@file{a-chlat9.ads}) -@cindex Latin_9 constants for Character +@cite{Invariant} -@noindent -This child of @code{Ada.Characters} -provides a set of definitions corresponding to those in the -RM-defined package @code{Ada.Characters.Latin_1} but with the -few modifications required for @code{Latin-9} -The provision of such a package -is specifically authorized by the Ada Reference Manual -(RM A.3.3(27)). +@tab -@node Ada.Characters.Wide_Latin_1 (a-cwila1.ads) -@section @code{Ada.Characters.Wide_Latin_1} (@file{a-cwila1.ads}) -@cindex @code{Ada.Characters.Wide_Latin_1} (@file{a-cwila1.ads}) -@cindex Latin_1 constants for Wide_Character +-- GNAT -@noindent -This child of @code{Ada.Characters} -provides a set of definitions corresponding to those in the -RM-defined package @code{Ada.Characters.Latin_1} but with the -types of the constants being @code{Wide_Character} -instead of @code{Character}. The provision of such a package -is specifically authorized by the Ada Reference Manual -(RM A.3.3(27)). +@item -@node Ada.Characters.Wide_Latin_9 (a-cwila9.ads) -@section @code{Ada.Characters.Wide_Latin_9} (@file{a-cwila1.ads}) -@cindex @code{Ada.Characters.Wide_Latin_9} (@file{a-cwila1.ads}) -@cindex Latin_9 constants for Wide_Character +@cite{Machine_Radix} -@noindent -This child of @code{Ada.Characters} -provides a set of definitions corresponding to those in the -GNAT defined package @code{Ada.Characters.Latin_9} but with the -types of the constants being @code{Wide_Character} -instead of @code{Character}. The provision of such a package -is specifically authorized by the Ada Reference Manual -(RM A.3.3(27)). +@tab -@node Ada.Characters.Wide_Wide_Latin_1 (a-chzla1.ads) -@section @code{Ada.Characters.Wide_Wide_Latin_1} (@file{a-chzla1.ads}) -@cindex @code{Ada.Characters.Wide_Wide_Latin_1} (@file{a-chzla1.ads}) -@cindex Latin_1 constants for Wide_Wide_Character +@item -@noindent -This child of @code{Ada.Characters} -provides a set of definitions corresponding to those in the -RM-defined package @code{Ada.Characters.Latin_1} but with the -types of the constants being @code{Wide_Wide_Character} -instead of @code{Character}. The provision of such a package -is specifically authorized by the Ada Reference Manual -(RM A.3.3(27)). +@cite{No_Return} -@node Ada.Characters.Wide_Wide_Latin_9 (a-chzla9.ads) -@section @code{Ada.Characters.Wide_Wide_Latin_9} (@file{a-chzla9.ads}) -@cindex @code{Ada.Characters.Wide_Wide_Latin_9} (@file{a-chzla9.ads}) -@cindex Latin_9 constants for Wide_Wide_Character +@tab -@noindent -This child of @code{Ada.Characters} -provides a set of definitions corresponding to those in the -GNAT defined package @code{Ada.Characters.Latin_9} but with the -types of the constants being @code{Wide_Wide_Character} -instead of @code{Character}. The provision of such a package -is specifically authorized by the Ada Reference Manual -(RM A.3.3(27)). +@item -@node Ada.Containers.Formal_Doubly_Linked_Lists (a-cfdlli.ads) -@section @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@file{a-cfdlli.ads}) -@cindex @code{Ada.Containers.Formal_Doubly_Linked_Lists} (@file{a-cfdlli.ads}) -@cindex Formal container for doubly linked lists +@cite{Object_Size} -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for doubly linked lists, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@tab -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +-- GNAT -@node Ada.Containers.Formal_Hashed_Maps (a-cfhama.ads) -@section @code{Ada.Containers.Formal_Hashed_Maps} (@file{a-cfhama.ads}) -@cindex @code{Ada.Containers.Formal_Hashed_Maps} (@file{a-cfhama.ads}) -@cindex Formal container for hashed maps +@item -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for hashed maps, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@cite{Pack} -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@tab -@node Ada.Containers.Formal_Hashed_Sets (a-cfhase.ads) -@section @code{Ada.Containers.Formal_Hashed_Sets} (@file{a-cfhase.ads}) -@cindex @code{Ada.Containers.Formal_Hashed_Sets} (@file{a-cfhase.ads}) -@cindex Formal container for hashed sets +@item -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for hashed sets, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@cite{Persistent_BSS} -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@tab -@node Ada.Containers.Formal_Ordered_Maps (a-cforma.ads) -@section @code{Ada.Containers.Formal_Ordered_Maps} (@file{a-cforma.ads}) -@cindex @code{Ada.Containers.Formal_Ordered_Maps} (@file{a-cforma.ads}) -@cindex Formal container for ordered maps +-- GNAT -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for ordered maps, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@item -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@cite{Post} -@node Ada.Containers.Formal_Ordered_Sets (a-cforse.ads) -@section @code{Ada.Containers.Formal_Ordered_Sets} (@file{a-cforse.ads}) -@cindex @code{Ada.Containers.Formal_Ordered_Sets} (@file{a-cforse.ads}) -@cindex Formal container for ordered sets +@tab -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for ordered sets, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@item -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@cite{Pre} -@node Ada.Containers.Formal_Vectors (a-cofove.ads) -@section @code{Ada.Containers.Formal_Vectors} (@file{a-cofove.ads}) -@cindex @code{Ada.Containers.Formal_Vectors} (@file{a-cofove.ads}) -@cindex Formal container for vectors +@tab -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for vectors, meant to facilitate formal -verification of code using such containers. The specification of this -unit is compatible with SPARK 2014. +@item -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@cite{Predicate} -@node Ada.Containers.Formal_Indefinite_Vectors (a-cfinve.ads) -@section @code{Ada.Containers.Formal_Indefinite_Vectors} (@file{a-cfinve.ads}) -@cindex @code{Ada.Containers.Formal_Indefinite_Vectors} (@file{a-cfinve.ads}) -@cindex Formal container for vectors +@tab -@noindent -This child of @code{Ada.Containers} defines a modified version of the -Ada 2005 container for vectors of indefinite elements, meant to -facilitate formal verification of code using such containers. The -specification of this unit is compatible with SPARK 2014. +@item -Note that although this container was designed with formal verification -in mind, it may well be generally useful in that it is a simplified more -efficient version than the one defined in the standard. In particular it -does not have the complex overhead required to detect cursor tampering. +@cite{Preelaborable_Initialization} -@node Ada.Containers.Bounded_Holders (a-coboho.ads) -@section @code{Ada.Containers.Bounded_Holders} (@file{a-coboho.ads}) -@cindex @code{Ada.Containers.Bounded_Holders} (@file{a-coboho.ads}) -@cindex Formal container for vectors +@tab -@noindent -This child of @code{Ada.Containers} defines a modified version of -Indefinite_Holders that avoids heap allocation. +@item -@node Ada.Command_Line.Environment (a-colien.ads) -@section @code{Ada.Command_Line.Environment} (@file{a-colien.ads}) -@cindex @code{Ada.Command_Line.Environment} (@file{a-colien.ads}) -@cindex Environment entries +@cite{Pure_Function} -@noindent -This child of @code{Ada.Command_Line} -provides a mechanism for obtaining environment values on systems -where this concept makes sense. +@tab -@node Ada.Command_Line.Remove (a-colire.ads) -@section @code{Ada.Command_Line.Remove} (@file{a-colire.ads}) -@cindex @code{Ada.Command_Line.Remove} (@file{a-colire.ads}) -@cindex Removing command line arguments -@cindex Command line, argument removal +-- GNAT -@noindent -This child of @code{Ada.Command_Line} -provides a mechanism for logically removing -arguments from the argument list. Once removed, an argument is not visible -to further calls on the subprograms in @code{Ada.Command_Line} will not -see the removed argument. +@item -@node Ada.Command_Line.Response_File (a-clrefi.ads) -@section @code{Ada.Command_Line.Response_File} (@file{a-clrefi.ads}) -@cindex @code{Ada.Command_Line.Response_File} (@file{a-clrefi.ads}) -@cindex Response file for command line -@cindex Command line, response file -@cindex Command line, handling long command lines +@cite{Remote_Access_Type} -@noindent -This child of @code{Ada.Command_Line} provides a mechanism facilities for -getting command line arguments from a text file, called a "response file". -Using a response file allow passing a set of arguments to an executable longer -than the maximum allowed by the system on the command line. +@tab -@node Ada.Direct_IO.C_Streams (a-diocst.ads) -@section @code{Ada.Direct_IO.C_Streams} (@file{a-diocst.ads}) -@cindex @code{Ada.Direct_IO.C_Streams} (@file{a-diocst.ads}) -@cindex C Streams, Interfacing with Direct_IO +-- GNAT -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Direct_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +@item -@node Ada.Exceptions.Is_Null_Occurrence (a-einuoc.ads) -@section @code{Ada.Exceptions.Is_Null_Occurrence} (@file{a-einuoc.ads}) -@cindex @code{Ada.Exceptions.Is_Null_Occurrence} (@file{a-einuoc.ads}) -@cindex Null_Occurrence, testing for +@cite{Shared} -@noindent -This child subprogram provides a way of testing for the null -exception occurrence (@code{Null_Occurrence}) without raising -an exception. +@tab -@node Ada.Exceptions.Last_Chance_Handler (a-elchha.ads) -@section @code{Ada.Exceptions.Last_Chance_Handler} (@file{a-elchha.ads}) -@cindex @code{Ada.Exceptions.Last_Chance_Handler} (@file{a-elchha.ads}) -@cindex Null_Occurrence, testing for +-- GNAT -@noindent -This child subprogram is used for handling otherwise unhandled -exceptions (hence the name last chance), and perform clean ups before -terminating the program. Note that this subprogram never returns. +@item -@node Ada.Exceptions.Traceback (a-exctra.ads) -@section @code{Ada.Exceptions.Traceback} (@file{a-exctra.ads}) -@cindex @code{Ada.Exceptions.Traceback} (@file{a-exctra.ads}) -@cindex Traceback for Exception Occurrence +@cite{Size} -@noindent -This child package provides the subprogram (@code{Tracebacks}) to -give a traceback array of addresses based on an exception -occurrence. +@tab -@node Ada.Sequential_IO.C_Streams (a-siocst.ads) -@section @code{Ada.Sequential_IO.C_Streams} (@file{a-siocst.ads}) -@cindex @code{Ada.Sequential_IO.C_Streams} (@file{a-siocst.ads}) -@cindex C Streams, Interfacing with Sequential_IO +@item -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Sequential_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +@cite{Storage_Pool} -@node Ada.Streams.Stream_IO.C_Streams (a-ssicst.ads) -@section @code{Ada.Streams.Stream_IO.C_Streams} (@file{a-ssicst.ads}) -@cindex @code{Ada.Streams.Stream_IO.C_Streams} (@file{a-ssicst.ads}) -@cindex C Streams, Interfacing with Stream_IO +@tab -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Stream_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +@item -@node Ada.Strings.Unbounded.Text_IO (a-suteio.ads) -@section @code{Ada.Strings.Unbounded.Text_IO} (@file{a-suteio.ads}) -@cindex @code{Ada.Strings.Unbounded.Text_IO} (@file{a-suteio.ads}) -@cindex @code{Unbounded_String}, IO support -@cindex @code{Text_IO}, extensions for unbounded strings +@cite{Storage_Size} -@noindent -This package provides subprograms for Text_IO for unbounded -strings, avoiding the necessity for an intermediate operation -with ordinary strings. +@tab -@node Ada.Strings.Wide_Unbounded.Wide_Text_IO (a-swuwti.ads) -@section @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@file{a-swuwti.ads}) -@cindex @code{Ada.Strings.Wide_Unbounded.Wide_Text_IO} (@file{a-swuwti.ads}) -@cindex @code{Unbounded_Wide_String}, IO support -@cindex @code{Text_IO}, extensions for unbounded wide strings +@item -@noindent -This package provides subprograms for Text_IO for unbounded -wide strings, avoiding the necessity for an intermediate operation -with ordinary wide strings. +@cite{Stream_Size} -@node Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO (a-szuzti.ads) -@section @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@file{a-szuzti.ads}) -@cindex @code{Ada.Strings.Wide_Wide_Unbounded.Wide_Wide_Text_IO} (@file{a-szuzti.ads}) -@cindex @code{Unbounded_Wide_Wide_String}, IO support -@cindex @code{Text_IO}, extensions for unbounded wide wide strings +@tab -@noindent -This package provides subprograms for Text_IO for unbounded -wide wide strings, avoiding the necessity for an intermediate operation -with ordinary wide wide strings. +@item -@node Ada.Text_IO.C_Streams (a-tiocst.ads) -@section @code{Ada.Text_IO.C_Streams} (@file{a-tiocst.ads}) -@cindex @code{Ada.Text_IO.C_Streams} (@file{a-tiocst.ads}) -@cindex C Streams, Interfacing with @code{Text_IO} +@cite{Suppress} -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Text_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +@tab -@node Ada.Text_IO.Reset_Standard_Files (a-tirsfi.ads) -@section @code{Ada.Text_IO.Reset_Standard_Files} (@file{a-tirsfi.ads}) -@cindex @code{Ada.Text_IO.Reset_Standard_Files} (@file{a-tirsfi.ads}) -@cindex @code{Text_IO} resetting standard files +@item -@noindent -This procedure is used to reset the status of the standard files used -by Ada.Text_IO. This is useful in a situation (such as a restart in an -embedded application) where the status of the files may change during -execution (for example a standard input file may be redefined to be -interactive). +@cite{Suppress_Debug_Info} -@node Ada.Wide_Characters.Unicode (a-wichun.ads) -@section @code{Ada.Wide_Characters.Unicode} (@file{a-wichun.ads}) -@cindex @code{Ada.Wide_Characters.Unicode} (@file{a-wichun.ads}) -@cindex Unicode categorization, Wide_Character +@tab -@noindent -This package provides subprograms that allow categorization of -Wide_Character values according to Unicode categories. +-- GNAT -@node Ada.Wide_Text_IO.C_Streams (a-wtcstr.ads) -@section @code{Ada.Wide_Text_IO.C_Streams} (@file{a-wtcstr.ads}) -@cindex @code{Ada.Wide_Text_IO.C_Streams} (@file{a-wtcstr.ads}) -@cindex C Streams, Interfacing with @code{Wide_Text_IO} +@item -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Wide_Text_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +@cite{Test_Case} -@node Ada.Wide_Text_IO.Reset_Standard_Files (a-wrstfi.ads) -@section @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@file{a-wrstfi.ads}) -@cindex @code{Ada.Wide_Text_IO.Reset_Standard_Files} (@file{a-wrstfi.ads}) -@cindex @code{Wide_Text_IO} resetting standard files +@tab -@noindent -This procedure is used to reset the status of the standard files used -by Ada.Wide_Text_IO. This is useful in a situation (such as a restart in an -embedded application) where the status of the files may change during -execution (for example a standard input file may be redefined to be -interactive). +-- GNAT -@node Ada.Wide_Wide_Characters.Unicode (a-zchuni.ads) -@section @code{Ada.Wide_Wide_Characters.Unicode} (@file{a-zchuni.ads}) -@cindex @code{Ada.Wide_Wide_Characters.Unicode} (@file{a-zchuni.ads}) -@cindex Unicode categorization, Wide_Wide_Character +@item -@noindent -This package provides subprograms that allow categorization of -Wide_Wide_Character values according to Unicode categories. +@cite{Thread_Local_Storage} -@node Ada.Wide_Wide_Text_IO.C_Streams (a-ztcstr.ads) -@section @code{Ada.Wide_Wide_Text_IO.C_Streams} (@file{a-ztcstr.ads}) -@cindex @code{Ada.Wide_Wide_Text_IO.C_Streams} (@file{a-ztcstr.ads}) -@cindex C Streams, Interfacing with @code{Wide_Wide_Text_IO} +@tab -@noindent -This package provides subprograms that allow interfacing between -C streams and @code{Wide_Wide_Text_IO}. The stream identifier can be -extracted from a file opened on the Ada side, and an Ada file -can be constructed from a stream opened on the C side. +-- GNAT -@node Ada.Wide_Wide_Text_IO.Reset_Standard_Files (a-zrstfi.ads) -@section @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@file{a-zrstfi.ads}) -@cindex @code{Ada.Wide_Wide_Text_IO.Reset_Standard_Files} (@file{a-zrstfi.ads}) -@cindex @code{Wide_Wide_Text_IO} resetting standard files +@item -@noindent -This procedure is used to reset the status of the standard files used -by Ada.Wide_Wide_Text_IO. This is useful in a situation (such as a -restart in an embedded application) where the status of the files may -change during execution (for example a standard input file may be -redefined to be interactive). +@cite{Type_Invariant} -@node GNAT.Altivec (g-altive.ads) -@section @code{GNAT.Altivec} (@file{g-altive.ads}) -@cindex @code{GNAT.Altivec} (@file{g-altive.ads}) -@cindex AltiVec +@tab -@noindent -This is the root package of the GNAT AltiVec binding. It provides -definitions of constants and types common to all the versions of the -binding. +@item -@node GNAT.Altivec.Conversions (g-altcon.ads) -@section @code{GNAT.Altivec.Conversions} (@file{g-altcon.ads}) -@cindex @code{GNAT.Altivec.Conversions} (@file{g-altcon.ads}) -@cindex AltiVec +@cite{Unchecked_Union} -@noindent -This package provides the Vector/View conversion routines. +@tab -@node GNAT.Altivec.Vector_Operations (g-alveop.ads) -@section @code{GNAT.Altivec.Vector_Operations} (@file{g-alveop.ads}) -@cindex @code{GNAT.Altivec.Vector_Operations} (@file{g-alveop.ads}) -@cindex AltiVec +@item -@noindent -This package exposes the Ada interface to the AltiVec operations on -vector objects. A soft emulation is included by default in the GNAT -library. The hard binding is provided as a separate package. This unit -is common to both bindings. +@cite{Universal_Aliasing} -@node GNAT.Altivec.Vector_Types (g-alvety.ads) -@section @code{GNAT.Altivec.Vector_Types} (@file{g-alvety.ads}) -@cindex @code{GNAT.Altivec.Vector_Types} (@file{g-alvety.ads}) -@cindex AltiVec +@tab -@noindent -This package exposes the various vector types part of the Ada binding -to AltiVec facilities. +-- GNAT -@node GNAT.Altivec.Vector_Views (g-alvevi.ads) -@section @code{GNAT.Altivec.Vector_Views} (@file{g-alvevi.ads}) -@cindex @code{GNAT.Altivec.Vector_Views} (@file{g-alvevi.ads}) -@cindex AltiVec +@item -@noindent -This package provides public 'View' data types from/to which private -vector representations can be converted via -GNAT.Altivec.Conversions. This allows convenient access to individual -vector elements and provides a simple way to initialize vector -objects. +@cite{Unmodified} -@node GNAT.Array_Split (g-arrspl.ads) -@section @code{GNAT.Array_Split} (@file{g-arrspl.ads}) -@cindex @code{GNAT.Array_Split} (@file{g-arrspl.ads}) -@cindex Array splitter +@tab -@noindent -Useful array-manipulation routines: given a set of separators, split -an array wherever the separators appear, and provide direct access -to the resulting slices. +-- GNAT -@node GNAT.AWK (g-awk.ads) -@section @code{GNAT.AWK} (@file{g-awk.ads}) -@cindex @code{GNAT.AWK} (@file{g-awk.ads}) -@cindex Parsing -@cindex AWK +@item -@noindent -Provides AWK-like parsing functions, with an easy interface for parsing one -or more files containing formatted data. The file is viewed as a database -where each record is a line and a field is a data element in this line. +@cite{Unreferenced} -@node GNAT.Bounded_Buffers (g-boubuf.ads) -@section @code{GNAT.Bounded_Buffers} (@file{g-boubuf.ads}) -@cindex @code{GNAT.Bounded_Buffers} (@file{g-boubuf.ads}) -@cindex Parsing -@cindex Bounded Buffers +@tab -@noindent -Provides a concurrent generic bounded buffer abstraction. Instances are -useful directly or as parts of the implementations of other abstractions, -such as mailboxes. +-- GNAT -@node GNAT.Bounded_Mailboxes (g-boumai.ads) -@section @code{GNAT.Bounded_Mailboxes} (@file{g-boumai.ads}) -@cindex @code{GNAT.Bounded_Mailboxes} (@file{g-boumai.ads}) -@cindex Parsing -@cindex Mailboxes +@item -@noindent -Provides a thread-safe asynchronous intertask mailbox communication facility. +@cite{Unreferenced_Objects} -@node GNAT.Bubble_Sort (g-bubsor.ads) -@section @code{GNAT.Bubble_Sort} (@file{g-bubsor.ads}) -@cindex @code{GNAT.Bubble_Sort} (@file{g-bubsor.ads}) -@cindex Sorting -@cindex Bubble sort +@tab -@noindent -Provides a general implementation of bubble sort usable for sorting arbitrary -data items. Exchange and comparison procedures are provided by passing -access-to-procedure values. +-- GNAT + +@item -@node GNAT.Bubble_Sort_A (g-busora.ads) -@section @code{GNAT.Bubble_Sort_A} (@file{g-busora.ads}) -@cindex @code{GNAT.Bubble_Sort_A} (@file{g-busora.ads}) -@cindex Sorting -@cindex Bubble sort +@cite{Unsuppress} -@noindent -Provides a general implementation of bubble sort usable for sorting arbitrary -data items. Move and comparison procedures are provided by passing -access-to-procedure values. This is an older version, retained for -compatibility. Usually @code{GNAT.Bubble_Sort} will be preferable. +@tab -@node GNAT.Bubble_Sort_G (g-busorg.ads) -@section @code{GNAT.Bubble_Sort_G} (@file{g-busorg.ads}) -@cindex @code{GNAT.Bubble_Sort_G} (@file{g-busorg.ads}) -@cindex Sorting -@cindex Bubble sort +@item -@noindent -Similar to @code{Bubble_Sort_A} except that the move and sorting procedures -are provided as generic parameters, this improves efficiency, especially -if the procedures can be inlined, at the expense of duplicating code for -multiple instantiations. +@cite{Value_Size} -@node GNAT.Byte_Order_Mark (g-byorma.ads) -@section @code{GNAT.Byte_Order_Mark} (@file{g-byorma.ads}) -@cindex @code{GNAT.Byte_Order_Mark} (@file{g-byorma.ads}) -@cindex UTF-8 representation -@cindex Wide characte representations +@tab -@noindent -Provides a routine which given a string, reads the start of the string to -see whether it is one of the standard byte order marks (BOM's) which signal -the encoding of the string. The routine includes detection of special XML -sequences for various UCS input formats. +-- GNAT -@node GNAT.Byte_Swapping (g-bytswa.ads) -@section @code{GNAT.Byte_Swapping} (@file{g-bytswa.ads}) -@cindex @code{GNAT.Byte_Swapping} (@file{g-bytswa.ads}) -@cindex Byte swapping -@cindex Endianness +@item -@noindent -General routines for swapping the bytes in 2-, 4-, and 8-byte quantities. -Machine-specific implementations are available in some cases. +@cite{Volatile} -@node GNAT.Calendar (g-calend.ads) -@section @code{GNAT.Calendar} (@file{g-calend.ads}) -@cindex @code{GNAT.Calendar} (@file{g-calend.ads}) -@cindex @code{Calendar} - -@noindent -Extends the facilities provided by @code{Ada.Calendar} to include handling -of days of the week, an extended @code{Split} and @code{Time_Of} capability. -Also provides conversion of @code{Ada.Calendar.Time} values to and from the -C @code{timeval} format. - -@node GNAT.Calendar.Time_IO (g-catiio.ads) -@section @code{GNAT.Calendar.Time_IO} (@file{g-catiio.ads}) -@cindex @code{Calendar} -@cindex Time -@cindex @code{GNAT.Calendar.Time_IO} (@file{g-catiio.ads}) - -@node GNAT.Case_Util (g-casuti.ads) -@section @code{GNAT.Case_Util} (@file{g-casuti.ads}) -@cindex @code{GNAT.Case_Util} (@file{g-casuti.ads}) -@cindex Casing utilities -@cindex Character handling (@code{GNAT.Case_Util}) - -@noindent -A set of simple routines for handling upper and lower casing of strings -without the overhead of the full casing tables -in @code{Ada.Characters.Handling}. +@tab -@node GNAT.CGI (g-cgi.ads) -@section @code{GNAT.CGI} (@file{g-cgi.ads}) -@cindex @code{GNAT.CGI} (@file{g-cgi.ads}) -@cindex CGI (Common Gateway Interface) +@item -@noindent -This is a package for interfacing a GNAT program with a Web server via the -Common Gateway Interface (CGI)@. Basically this package parses the CGI -parameters, which are a set of key/value pairs sent by the Web server. It -builds a table whose index is the key and provides some services to deal -with this table. +@cite{Volatile_Components} -@node GNAT.CGI.Cookie (g-cgicoo.ads) -@section @code{GNAT.CGI.Cookie} (@file{g-cgicoo.ads}) -@cindex @code{GNAT.CGI.Cookie} (@file{g-cgicoo.ads}) -@cindex CGI (Common Gateway Interface) cookie support -@cindex Cookie support in CGI +@tab -@noindent -This is a package to interface a GNAT program with a Web server via the -Common Gateway Interface (CGI). It exports services to deal with Web -cookies (piece of information kept in the Web client software). +@item -@node GNAT.CGI.Debug (g-cgideb.ads) -@section @code{GNAT.CGI.Debug} (@file{g-cgideb.ads}) -@cindex @code{GNAT.CGI.Debug} (@file{g-cgideb.ads}) -@cindex CGI (Common Gateway Interface) debugging +@cite{Warnings} -@noindent -This is a package to help debugging CGI (Common Gateway Interface) -programs written in Ada. +@tab -@node GNAT.Command_Line (g-comlin.ads) -@section @code{GNAT.Command_Line} (@file{g-comlin.ads}) -@cindex @code{GNAT.Command_Line} (@file{g-comlin.ads}) -@cindex Command line +-- GNAT + +@end multitable -@noindent -Provides a high level interface to @code{Ada.Command_Line} facilities, -including the ability to scan for named switches with optional parameters -and expand file names using wild card notations. -@node GNAT.Compiler_Version (g-comver.ads) -@section @code{GNAT.Compiler_Version} (@file{g-comver.ads}) -@cindex @code{GNAT.Compiler_Version} (@file{g-comver.ads}) -@cindex Compiler Version -@cindex Version, of compiler +@quotation -@noindent -Provides a routine for obtaining the version of the compiler used to -compile the program. More accurately this is the version of the binder -used to bind the program (this will normally be the same as the version -of the compiler if a consistent tool set is used to compile all units -of a partition). +Note that for aspects with an expression, e.g. @cite{Size}, the expression is +treated like a default expression (visibility is analyzed at the point of +occurrence of the aspect, but evaluation of the expression occurs at the +freeze point of the entity involved). + +RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6) +3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03 +(2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2) +9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2) +12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1) +13.03.01 (0) +@end quotation -@node GNAT.Ctrl_C (g-ctrl_c.ads) -@section @code{GNAT.Ctrl_C} (@file{g-ctrl_c.ads}) -@cindex @code{GNAT.Ctrl_C} (@file{g-ctrl_c.ads}) -@cindex Interrupt +@geindex AI-0128 (Ada 2012 feature) -@noindent -Provides a simple interface to handle Ctrl-C keyboard events. -@node GNAT.CRC32 (g-crc32.ads) -@section @code{GNAT.CRC32} (@file{g-crc32.ads}) -@cindex @code{GNAT.CRC32} (@file{g-crc32.ads}) -@cindex CRC32 -@cindex Cyclic Redundancy Check +@itemize * -@noindent -This package implements the CRC-32 algorithm. For a full description -of this algorithm see -``Computation of Cyclic Redundancy Checks via Table Look-Up'', -@cite{Communications of the ACM}, Vol.@: 31 No.@: 8, pp.@: 1008-1013, -Aug.@: 1988. Sarwate, D.V@. +@item +@emph{AI-0128 Inequality is a primitive operation (0000-00-00)} -@node GNAT.Current_Exception (g-curexc.ads) -@section @code{GNAT.Current_Exception} (@file{g-curexc.ads}) -@cindex @code{GNAT.Current_Exception} (@file{g-curexc.ads}) -@cindex Current exception -@cindex Exception retrieval +If an equality operator ("=") is declared for a type, then the implicitly +declared inequality operator ("/=") is a primitive operation of the type. +This is the only reasonable interpretation, and is the one always implemented +by GNAT, but the RM was not entirely clear in making this point. -@noindent -Provides access to information on the current exception that has been raised -without the need for using the Ada 95 / Ada 2005 exception choice parameter -specification syntax. -This is particularly useful in simulating typical facilities for -obtaining information about exceptions provided by Ada 83 compilers. +RM References: 3.02.03 (6) 6.06 (6) +@end itemize -@node GNAT.Debug_Pools (g-debpoo.ads) -@section @code{GNAT.Debug_Pools} (@file{g-debpoo.ads}) -@cindex @code{GNAT.Debug_Pools} (@file{g-debpoo.ads}) -@cindex Debugging -@cindex Debug pools -@cindex Memory corruption debugging +@geindex AI-0003 (Ada 2012 feature) -@noindent -Provide a debugging storage pools that helps tracking memory corruption -problems. @xref{The GNAT Debug Pool Facility,,, gnat_ugn, -@value{EDITION} User's Guide}. -@node GNAT.Debug_Utilities (g-debuti.ads) -@section @code{GNAT.Debug_Utilities} (@file{g-debuti.ads}) -@cindex @code{GNAT.Debug_Utilities} (@file{g-debuti.ads}) -@cindex Debugging +@itemize * -@noindent -Provides a few useful utilities for debugging purposes, including conversion -to and from string images of address values. Supports both C and Ada formats -for hexadecimal literals. +@item +@emph{AI-0003 Qualified expressions as names (2010-07-11)} -@node GNAT.Decode_String (g-decstr.ads) -@section @code{GNAT.Decode_String} (@file{g-decstr.ads}) -@cindex @code{GNAT.Decode_String} (@file{g-decstr.ads}) -@cindex Decoding strings -@cindex String decoding -@cindex Wide character encoding -@cindex UTF-8 -@cindex Unicode +In Ada 2012, a qualified expression is considered to be syntactically a name, +meaning that constructs such as @cite{A'(F(X)).B} are now legal. This is +useful in disambiguating some cases of overloading. -@noindent -A generic package providing routines for decoding wide character and wide wide -character strings encoded as sequences of 8-bit characters using a specified -encoding method. Includes validation routines, and also routines for stepping -to next or previous encoded character in an encoded string. -Useful in conjunction with Unicode character coding. Note there is a -preinstantiation for UTF-8. See next entry. +RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3) +5.04 (7) +@end itemize -@node GNAT.Decode_UTF8_String (g-deutst.ads) -@section @code{GNAT.Decode_UTF8_String} (@file{g-deutst.ads}) -@cindex @code{GNAT.Decode_UTF8_String} (@file{g-deutst.ads}) -@cindex Decoding strings -@cindex Decoding UTF-8 strings -@cindex UTF-8 string decoding -@cindex Wide character decoding -@cindex UTF-8 -@cindex Unicode - -@noindent -A preinstantiation of GNAT.Decode_Strings for UTF-8 encoding. +@geindex AI-0120 (Ada 2012 feature) -@node GNAT.Directory_Operations (g-dirope.ads) -@section @code{GNAT.Directory_Operations} (@file{g-dirope.ads}) -@cindex @code{GNAT.Directory_Operations} (@file{g-dirope.ads}) -@cindex Directory operations -@noindent -Provides a set of routines for manipulating directories, including changing -the current directory, making new directories, and scanning the files in a -directory. +@itemize * -@node GNAT.Directory_Operations.Iteration (g-diopit.ads) -@section @code{GNAT.Directory_Operations.Iteration} (@file{g-diopit.ads}) -@cindex @code{GNAT.Directory_Operations.Iteration} (@file{g-diopit.ads}) -@cindex Directory operations iteration +@item +@emph{AI-0120 Constant instance of protected object (0000-00-00)} -@noindent -A child unit of GNAT.Directory_Operations providing additional operations -for iterating through directories. +This is an RM editorial change only. The section that lists objects that are +constant failed to include the current instance of a protected object +within a protected function. This has always been treated as a constant +in GNAT. -@node GNAT.Dynamic_HTables (g-dynhta.ads) -@section @code{GNAT.Dynamic_HTables} (@file{g-dynhta.ads}) -@cindex @code{GNAT.Dynamic_HTables} (@file{g-dynhta.ads}) -@cindex Hash tables +RM References: 3.03 (21) +@end itemize -@noindent -A generic implementation of hash tables that can be used to hash arbitrary -data. Provided in two forms, a simple form with built in hash functions, -and a more complex form in which the hash function is supplied. +@geindex AI-0008 (Ada 2012 feature) -@noindent -This package provides a facility similar to that of @code{GNAT.HTable}, -except that this package declares a type that can be used to define -dynamic instances of the hash table, while an instantiation of -@code{GNAT.HTable} creates a single instance of the hash table. -@node GNAT.Dynamic_Tables (g-dyntab.ads) -@section @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads}) -@cindex @code{GNAT.Dynamic_Tables} (@file{g-dyntab.ads}) -@cindex Table implementation -@cindex Arrays, extendable +@itemize * -@noindent -A generic package providing a single dimension array abstraction where the -length of the array can be dynamically modified. +@item +@emph{AI-0008 General access to constrained objects (0000-00-00)} -@noindent -This package provides a facility similar to that of @code{GNAT.Table}, -except that this package declares a type that can be used to define -dynamic instances of the table, while an instantiation of -@code{GNAT.Table} creates a single instance of the table type. - -@node GNAT.Encode_String (g-encstr.ads) -@section @code{GNAT.Encode_String} (@file{g-encstr.ads}) -@cindex @code{GNAT.Encode_String} (@file{g-encstr.ads}) -@cindex Encoding strings -@cindex String encoding -@cindex Wide character encoding -@cindex UTF-8 -@cindex Unicode - -@noindent -A generic package providing routines for encoding wide character and wide -wide character strings as sequences of 8-bit characters using a specified -encoding method. Useful in conjunction with Unicode character coding. -Note there is a preinstantiation for UTF-8. See next entry. +The wording in the RM implied that if you have a general access to a +constrained object, it could be used to modify the discriminants. This was +obviously not intended. @cite{Constraint_Error} should be raised, and GNAT +has always done so in this situation. -@node GNAT.Encode_UTF8_String (g-enutst.ads) -@section @code{GNAT.Encode_UTF8_String} (@file{g-enutst.ads}) -@cindex @code{GNAT.Encode_UTF8_String} (@file{g-enutst.ads}) -@cindex Encoding strings -@cindex Encoding UTF-8 strings -@cindex UTF-8 string encoding -@cindex Wide character encoding -@cindex UTF-8 -@cindex Unicode - -@noindent -A preinstantiation of GNAT.Encode_Strings for UTF-8 encoding. +RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2) +@end itemize -@node GNAT.Exception_Actions (g-excact.ads) -@section @code{GNAT.Exception_Actions} (@file{g-excact.ads}) -@cindex @code{GNAT.Exception_Actions} (@file{g-excact.ads}) -@cindex Exception actions +@geindex AI-0093 (Ada 2012 feature) -@noindent -Provides callbacks when an exception is raised. Callbacks can be registered -for specific exceptions, or when any exception is raised. This -can be used for instance to force a core dump to ease debugging. -@node GNAT.Exception_Traces (g-exctra.ads) -@section @code{GNAT.Exception_Traces} (@file{g-exctra.ads}) -@cindex @code{GNAT.Exception_Traces} (@file{g-exctra.ads}) -@cindex Exception traces -@cindex Debugging +@itemize * -@noindent -Provides an interface allowing to control automatic output upon exception -occurrences. +@item +@emph{AI-0093 Additional rules use immutably limited (0000-00-00)} -@node GNAT.Exceptions (g-except.ads) -@section @code{GNAT.Exceptions} (@file{g-expect.ads}) -@cindex @code{GNAT.Exceptions} (@file{g-expect.ads}) -@cindex Exceptions, Pure -@cindex Pure packages, exceptions +This is an editorial change only, to make more widespread use of the Ada 2012 +'immutably limited'. -@noindent -Normally it is not possible to raise an exception with -a message from a subprogram in a pure package, since the -necessary types and subprograms are in @code{Ada.Exceptions} -which is not a pure unit. @code{GNAT.Exceptions} provides a -facility for getting around this limitation for a few -predefined exceptions, and for example allow raising -@code{Constraint_Error} with a message from a pure subprogram. +RM References: 3.03 (23.4/3) +@end itemize -@node GNAT.Expect (g-expect.ads) -@section @code{GNAT.Expect} (@file{g-expect.ads}) -@cindex @code{GNAT.Expect} (@file{g-expect.ads}) +@geindex AI-0096 (Ada 2012 feature) -@noindent -Provides a set of subprograms similar to what is available -with the standard Tcl Expect tool. -It allows you to easily spawn and communicate with an external process. -You can send commands or inputs to the process, and compare the output -with some expected regular expression. Currently @code{GNAT.Expect} -is implemented on all native GNAT ports except for OpenVMS@. -It is not implemented for cross ports, and in particular is not -implemented for VxWorks or LynxOS@. -@node GNAT.Expect.TTY (g-exptty.ads) -@section @code{GNAT.Expect.TTY} (@file{g-exptty.ads}) -@cindex @code{GNAT.Expect.TTY} (@file{g-exptty.ads}) +@itemize * -@noindent -As GNAT.Expect but using pseudo-terminal. -Currently @code{GNAT.Expect.TTY} is implemented on all native GNAT -ports except for OpenVMS@. It is not implemented for cross ports, and -in particular is not implemented for VxWorks or LynxOS@. +@item +@emph{AI-0096 Deriving from formal private types (2010-07-20)} -@node GNAT.Float_Control (g-flocon.ads) -@section @code{GNAT.Float_Control} (@file{g-flocon.ads}) -@cindex @code{GNAT.Float_Control} (@file{g-flocon.ads}) -@cindex Floating-Point Processor +In general it is illegal for a type derived from a formal limited type to be +nonlimited. This AI makes an exception to this rule: derivation is legal +if it appears in the private part of the generic, and the formal type is not +tagged. If the type is tagged, the legality check must be applied to the +private part of the package. -@noindent -Provides an interface for resetting the floating-point processor into the -mode required for correct semantic operation in Ada. Some third party -library calls may cause this mode to be modified, and the Reset procedure -in this package can be used to reestablish the required mode. +RM References: 3.04 (5.1/2) 6.02 (7) +@end itemize -@node GNAT.Formatted_String (g-forstr.ads) -@section @code{GNAT.Formatted_String} (@file{g-forstr.ads}) -@cindex @code{GNAT.Formatted_String} (@file{g-forstr.ads}) -@cindex Formatted String +@geindex AI-0181 (Ada 2012 feature) -@noindent -Provides support for C/C++ printf() formatted strings. The format is -copied from the printf() routine and should therefore gives identical -output. Some generic routines are provided to be able to use types -derived from Integer, Float or enumerations as values for the -formatted string. -@node GNAT.Heap_Sort (g-heasor.ads) -@section @code{GNAT.Heap_Sort} (@file{g-heasor.ads}) -@cindex @code{GNAT.Heap_Sort} (@file{g-heasor.ads}) -@cindex Sorting +@itemize * -@noindent -Provides a general implementation of heap sort usable for sorting arbitrary -data items. Exchange and comparison procedures are provided by passing -access-to-procedure values. The algorithm used is a modified heap sort -that performs approximately N*log(N) comparisons in the worst case. +@item +@emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)} -@node GNAT.Heap_Sort_A (g-hesora.ads) -@section @code{GNAT.Heap_Sort_A} (@file{g-hesora.ads}) -@cindex @code{GNAT.Heap_Sort_A} (@file{g-hesora.ads}) -@cindex Sorting +From Ada 2005 on, soft hyphen is considered a non-graphic character, which +means that it has a special name (@cite{SOFT_HYPHEN}) in conjunction with the +@cite{Image} and @cite{Value} attributes for the character types. Strictly +speaking this is an inconsistency with Ada 95, but in practice the use of +these attributes is so obscure that it will not cause problems. -@noindent -Provides a general implementation of heap sort usable for sorting arbitrary -data items. Move and comparison procedures are provided by passing -access-to-procedure values. The algorithm used is a modified heap sort -that performs approximately N*log(N) comparisons in the worst case. -This differs from @code{GNAT.Heap_Sort} in having a less convenient -interface, but may be slightly more efficient. +RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21) +@end itemize -@node GNAT.Heap_Sort_G (g-hesorg.ads) -@section @code{GNAT.Heap_Sort_G} (@file{g-hesorg.ads}) -@cindex @code{GNAT.Heap_Sort_G} (@file{g-hesorg.ads}) -@cindex Sorting +@geindex AI-0182 (Ada 2012 feature) -@noindent -Similar to @code{Heap_Sort_A} except that the move and sorting procedures -are provided as generic parameters, this improves efficiency, especially -if the procedures can be inlined, at the expense of duplicating code for -multiple instantiations. -@node GNAT.HTable (g-htable.ads) -@section @code{GNAT.HTable} (@file{g-htable.ads}) -@cindex @code{GNAT.HTable} (@file{g-htable.ads}) -@cindex Hash tables +@itemize * -@noindent -A generic implementation of hash tables that can be used to hash arbitrary -data. Provides two approaches, one a simple static approach, and the other -allowing arbitrary dynamic hash tables. +@item +@emph{AI-0182 Additional forms for `Character'Value} (0000-00-00)` -@node GNAT.IO (g-io.ads) -@section @code{GNAT.IO} (@file{g-io.ads}) -@cindex @code{GNAT.IO} (@file{g-io.ads}) -@cindex Simple I/O -@cindex Input/Output facilities +This AI allows @cite{Character'Value} to accept the string @cite{'?'} where +@cite{?} is any character including non-graphic control characters. GNAT has +always accepted such strings. It also allows strings such as +@cite{HEX_00000041} to be accepted, but GNAT does not take advantage of this +permission and raises @cite{Constraint_Error}, as is certainly still +permitted. -@noindent -A simple preelaborable input-output package that provides a subset of -simple Text_IO functions for reading characters and strings from -Standard_Input, and writing characters, strings and integers to either -Standard_Output or Standard_Error. +RM References: 3.05 (56/2) +@end itemize -@node GNAT.IO_Aux (g-io_aux.ads) -@section @code{GNAT.IO_Aux} (@file{g-io_aux.ads}) -@cindex @code{GNAT.IO_Aux} (@file{g-io_aux.ads}) -@cindex Text_IO -@cindex Input/Output facilities +@geindex AI-0214 (Ada 2012 feature) -Provides some auxiliary functions for use with Text_IO, including a test -for whether a file exists, and functions for reading a line of text. -@node GNAT.Lock_Files (g-locfil.ads) -@section @code{GNAT.Lock_Files} (@file{g-locfil.ads}) -@cindex @code{GNAT.Lock_Files} (@file{g-locfil.ads}) -@cindex File locking -@cindex Locking using files +@itemize * -@noindent -Provides a general interface for using files as locks. Can be used for -providing program level synchronization. +@item +@emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)} -@node GNAT.MBBS_Discrete_Random (g-mbdira.ads) -@section @code{GNAT.MBBS_Discrete_Random} (@file{g-mbdira.ads}) -@cindex @code{GNAT.MBBS_Discrete_Random} (@file{g-mbdira.ads}) -@cindex Random number generation +Ada 2012 relaxes the restriction that forbids discriminants of tagged types +to have default expressions by allowing them when the type is limited. It +is often useful to define a default value for a discriminant even though +it can't be changed by assignment. -@noindent -The original implementation of @code{Ada.Numerics.Discrete_Random}. Uses -a modified version of the Blum-Blum-Shub generator. +RM References: 3.07 (9.1/2) 3.07.02 (3) +@end itemize -@node GNAT.MBBS_Float_Random (g-mbflra.ads) -@section @code{GNAT.MBBS_Float_Random} (@file{g-mbflra.ads}) -@cindex @code{GNAT.MBBS_Float_Random} (@file{g-mbflra.ads}) -@cindex Random number generation +@geindex AI-0102 (Ada 2012 feature) -@noindent -The original implementation of @code{Ada.Numerics.Float_Random}. Uses -a modified version of the Blum-Blum-Shub generator. -@node GNAT.MD5 (g-md5.ads) -@section @code{GNAT.MD5} (@file{g-md5.ads}) -@cindex @code{GNAT.MD5} (@file{g-md5.ads}) -@cindex Message Digest MD5 +@itemize * -@noindent -Implements the MD5 Message-Digest Algorithm as described in RFC 1321, and -the HMAC-MD5 message authentication function as described in RFC 2104 and -FIPS PUB 198. +@item +@emph{AI-0102 Some implicit conversions are illegal (0000-00-00)} -@node GNAT.Memory_Dump (g-memdum.ads) -@section @code{GNAT.Memory_Dump} (@file{g-memdum.ads}) -@cindex @code{GNAT.Memory_Dump} (@file{g-memdum.ads}) -@cindex Dump Memory +It is illegal to assign an anonymous access constant to an anonymous access +variable. The RM did not have a clear rule to prevent this, but GNAT has +always generated an error for this usage. -@noindent -Provides a convenient routine for dumping raw memory to either the -standard output or standard error files. Uses GNAT.IO for actual -output. +RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2) +@end itemize -@node GNAT.Most_Recent_Exception (g-moreex.ads) -@section @code{GNAT.Most_Recent_Exception} (@file{g-moreex.ads}) -@cindex @code{GNAT.Most_Recent_Exception} (@file{g-moreex.ads}) -@cindex Exception, obtaining most recent +@geindex AI-0158 (Ada 2012 feature) -@noindent -Provides access to the most recently raised exception. Can be used for -various logging purposes, including duplicating functionality of some -Ada 83 implementation dependent extensions. -@node GNAT.OS_Lib (g-os_lib.ads) -@section @code{GNAT.OS_Lib} (@file{g-os_lib.ads}) -@cindex @code{GNAT.OS_Lib} (@file{g-os_lib.ads}) -@cindex Operating System interface -@cindex Spawn capability +@itemize * -@noindent -Provides a range of target independent operating system interface functions, -including time/date management, file operations, subprocess management, -including a portable spawn procedure, and access to environment variables -and error return codes. +@item +@emph{AI-0158 Generalizing membership tests (2010-09-16)} -@node GNAT.Perfect_Hash_Generators (g-pehage.ads) -@section @code{GNAT.Perfect_Hash_Generators} (@file{g-pehage.ads}) -@cindex @code{GNAT.Perfect_Hash_Generators} (@file{g-pehage.ads}) -@cindex Hash functions +This AI extends the syntax of membership tests to simplify complex conditions +that can be expressed as membership in a subset of values of any type. It +introduces syntax for a list of expressions that may be used in loop contexts +as well. -@noindent -Provides a generator of static minimal perfect hash functions. No -collisions occur and each item can be retrieved from the table in one -probe (perfect property). The hash table size corresponds to the exact -size of the key set and no larger (minimal property). The key set has to -be know in advance (static property). The hash functions are also order -preserving. If w2 is inserted after w1 in the generator, their -hashcode are in the same order. These hashing functions are very -convenient for use with realtime applications. +RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27) +@end itemize -@node GNAT.Random_Numbers (g-rannum.ads) -@section @code{GNAT.Random_Numbers} (@file{g-rannum.ads}) -@cindex @code{GNAT.Random_Numbers} (@file{g-rannum.ads}) -@cindex Random number generation +@geindex AI-0173 (Ada 2012 feature) -@noindent -Provides random number capabilities which extend those available in the -standard Ada library and are more convenient to use. -@node GNAT.Regexp (g-regexp.ads) -@section @code{GNAT.Regexp} (@file{g-regexp.ads}) -@cindex @code{GNAT.Regexp} (@file{g-regexp.ads}) -@cindex Regular expressions -@cindex Pattern matching +@itemize * -@noindent -A simple implementation of regular expressions, using a subset of regular -expression syntax copied from familiar Unix style utilities. This is the -simplest of the three pattern matching packages provided, and is particularly -suitable for ``file globbing'' applications. +@item +@emph{AI-0173 Testing if tags represent abstract types (2010-07-03)} -@node GNAT.Registry (g-regist.ads) -@section @code{GNAT.Registry} (@file{g-regist.ads}) -@cindex @code{GNAT.Registry} (@file{g-regist.ads}) -@cindex Windows Registry +The function @cite{Ada.Tags.Type_Is_Abstract} returns @cite{True} if invoked +with the tag of an abstract type, and @cite{False} otherwise. -@noindent -This is a high level binding to the Windows registry. It is possible to -do simple things like reading a key value, creating a new key. For full -registry API, but at a lower level of abstraction, refer to the Win32.Winreg -package provided with the Win32Ada binding +RM References: 3.09 (7.4/2) 3.09 (12.4/2) +@end itemize -@node GNAT.Regpat (g-regpat.ads) -@section @code{GNAT.Regpat} (@file{g-regpat.ads}) -@cindex @code{GNAT.Regpat} (@file{g-regpat.ads}) -@cindex Regular expressions -@cindex Pattern matching +@geindex AI-0076 (Ada 2012 feature) -@noindent -A complete implementation of Unix-style regular expression matching, copied -from the original V7 style regular expression library written in C by -Henry Spencer (and binary compatible with this C library). -@node GNAT.Rewrite_Data (g-rewdat.ads) -@section @code{GNAT.Rewrite_Data} (@file{g-rewdat.ads}) -@cindex @code{GNAT.Rewrite_Data} (@file{g-rewdat.ads}) -@cindex Rewrite data +@itemize * -@noindent -A unit to rewrite on-the-fly string occurrences in a stream of -data. The implementation has a very minimal memory footprint as the -full content to be processed is not loaded into memory all at once. This makes -this interface usable for large files or socket streams. +@item +@emph{AI-0076 function with controlling result (0000-00-00)} -@node GNAT.Secondary_Stack_Info (g-sestin.ads) -@section @code{GNAT.Secondary_Stack_Info} (@file{g-sestin.ads}) -@cindex @code{GNAT.Secondary_Stack_Info} (@file{g-sestin.ads}) -@cindex Secondary Stack Info +This is an editorial change only. The RM defines calls with controlling +results, but uses the term 'function with controlling result' without an +explicit definition. -@noindent -Provide the capability to query the high water mark of the current task's -secondary stack. +RM References: 3.09.02 (2/2) +@end itemize -@node GNAT.Semaphores (g-semaph.ads) -@section @code{GNAT.Semaphores} (@file{g-semaph.ads}) -@cindex @code{GNAT.Semaphores} (@file{g-semaph.ads}) -@cindex Semaphores +@geindex AI-0126 (Ada 2012 feature) -@noindent -Provides classic counting and binary semaphores using protected types. -@node GNAT.Serial_Communications (g-sercom.ads) -@section @code{GNAT.Serial_Communications} (@file{g-sercom.ads}) -@cindex @code{GNAT.Serial_Communications} (@file{g-sercom.ads}) -@cindex Serial_Communications +@itemize * -@noindent -Provides a simple interface to send and receive data over a serial -port. This is only supported on GNU/Linux and Windows. +@item +@emph{AI-0126 Dispatching with no declared operation (0000-00-00)} -@node GNAT.SHA1 (g-sha1.ads) -@section @code{GNAT.SHA1} (@file{g-sha1.ads}) -@cindex @code{GNAT.SHA1} (@file{g-sha1.ads}) -@cindex Secure Hash Algorithm SHA-1 +This AI clarifies dispatching rules, and simply confirms that dispatching +executes the operation of the parent type when there is no explicitly or +implicitly declared operation for the descendant type. This has always been +the case in all versions of GNAT. -@noindent -Implements the SHA-1 Secure Hash Algorithm as described in FIPS PUB 180-3 -and RFC 3174, and the HMAC-SHA1 message authentication function as described -in RFC 2104 and FIPS PUB 198. +RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2) +@end itemize -@node GNAT.SHA224 (g-sha224.ads) -@section @code{GNAT.SHA224} (@file{g-sha224.ads}) -@cindex @code{GNAT.SHA224} (@file{g-sha224.ads}) -@cindex Secure Hash Algorithm SHA-224 +@geindex AI-0097 (Ada 2012 feature) -@noindent -Implements the SHA-224 Secure Hash Algorithm as described in FIPS PUB 180-3, -and the HMAC-SHA224 message authentication function as described -in RFC 2104 and FIPS PUB 198. -@node GNAT.SHA256 (g-sha256.ads) -@section @code{GNAT.SHA256} (@file{g-sha256.ads}) -@cindex @code{GNAT.SHA256} (@file{g-sha256.ads}) -@cindex Secure Hash Algorithm SHA-256 +@itemize * -@noindent -Implements the SHA-256 Secure Hash Algorithm as described in FIPS PUB 180-3, -and the HMAC-SHA256 message authentication function as described -in RFC 2104 and FIPS PUB 198. +@item +@emph{AI-0097 Treatment of abstract null extension (2010-07-19)} -@node GNAT.SHA384 (g-sha384.ads) -@section @code{GNAT.SHA384} (@file{g-sha384.ads}) -@cindex @code{GNAT.SHA384} (@file{g-sha384.ads}) -@cindex Secure Hash Algorithm SHA-384 +The RM as written implied that in some cases it was possible to create an +object of an abstract type, by having an abstract extension inherit a non- +abstract constructor from its parent type. This mistake has been corrected +in GNAT and in the RM, and this construct is now illegal. -@noindent -Implements the SHA-384 Secure Hash Algorithm as described in FIPS PUB 180-3, -and the HMAC-SHA384 message authentication function as described -in RFC 2104 and FIPS PUB 198. +RM References: 3.09.03 (4/2) +@end itemize -@node GNAT.SHA512 (g-sha512.ads) -@section @code{GNAT.SHA512} (@file{g-sha512.ads}) -@cindex @code{GNAT.SHA512} (@file{g-sha512.ads}) -@cindex Secure Hash Algorithm SHA-512 +@geindex AI-0203 (Ada 2012 feature) -@noindent -Implements the SHA-512 Secure Hash Algorithm as described in FIPS PUB 180-3, -and the HMAC-SHA512 message authentication function as described -in RFC 2104 and FIPS PUB 198. -@node GNAT.Signals (g-signal.ads) -@section @code{GNAT.Signals} (@file{g-signal.ads}) -@cindex @code{GNAT.Signals} (@file{g-signal.ads}) -@cindex Signals +@itemize * -@noindent -Provides the ability to manipulate the blocked status of signals on supported -targets. +@item +@emph{AI-0203 Extended return cannot be abstract (0000-00-00)} -@node GNAT.Sockets (g-socket.ads) -@section @code{GNAT.Sockets} (@file{g-socket.ads}) -@cindex @code{GNAT.Sockets} (@file{g-socket.ads}) -@cindex Sockets +A return_subtype_indication cannot denote an abstract subtype. GNAT has never +permitted such usage. -@noindent -A high level and portable interface to develop sockets based applications. -This package is based on the sockets thin binding found in -@code{GNAT.Sockets.Thin}. Currently @code{GNAT.Sockets} is implemented -on all native GNAT ports except for OpenVMS@. It is not implemented -for the LynxOS@ cross port. +RM References: 3.09.03 (8/3) +@end itemize -@node GNAT.Source_Info (g-souinf.ads) -@section @code{GNAT.Source_Info} (@file{g-souinf.ads}) -@cindex @code{GNAT.Source_Info} (@file{g-souinf.ads}) -@cindex Source Information +@geindex AI-0198 (Ada 2012 feature) -@noindent -Provides subprograms that give access to source code information known at -compile time, such as the current file name and line number. Also provides -subprograms yielding the date and time of the current compilation (like the -C macros @code{__DATE__} and @code{__TIME__}) -@node GNAT.Spelling_Checker (g-speche.ads) -@section @code{GNAT.Spelling_Checker} (@file{g-speche.ads}) -@cindex @code{GNAT.Spelling_Checker} (@file{g-speche.ads}) -@cindex Spell checking +@itemize * -@noindent -Provides a function for determining whether one string is a plausible -near misspelling of another string. +@item +@emph{AI-0198 Inheriting abstract operators (0000-00-00)} -@node GNAT.Spelling_Checker_Generic (g-spchge.ads) -@section @code{GNAT.Spelling_Checker_Generic} (@file{g-spchge.ads}) -@cindex @code{GNAT.Spelling_Checker_Generic} (@file{g-spchge.ads}) -@cindex Spell checking +This AI resolves a conflict between two rules involving inherited abstract +operations and predefined operators. If a derived numeric type inherits +an abstract operator, it overrides the predefined one. This interpretation +was always the one implemented in GNAT. -@noindent -Provides a generic function that can be instantiated with a string type for -determining whether one string is a plausible near misspelling of another -string. +RM References: 3.09.03 (4/3) +@end itemize -@node GNAT.Spitbol.Patterns (g-spipat.ads) -@section @code{GNAT.Spitbol.Patterns} (@file{g-spipat.ads}) -@cindex @code{GNAT.Spitbol.Patterns} (@file{g-spipat.ads}) -@cindex SPITBOL pattern matching -@cindex Pattern matching +@geindex AI-0073 (Ada 2012 feature) -@noindent -A complete implementation of SNOBOL4 style pattern matching. This is the -most elaborate of the pattern matching packages provided. It fully duplicates -the SNOBOL4 dynamic pattern construction and matching capabilities, using the -efficient algorithm developed by Robert Dewar for the SPITBOL system. -@node GNAT.Spitbol (g-spitbo.ads) -@section @code{GNAT.Spitbol} (@file{g-spitbo.ads}) -@cindex @code{GNAT.Spitbol} (@file{g-spitbo.ads}) -@cindex SPITBOL interface +@itemize * -@noindent -The top level package of the collection of SPITBOL-style functionality, this -package provides basic SNOBOL4 string manipulation functions, such as -Pad, Reverse, Trim, Substr capability, as well as a generic table function -useful for constructing arbitrary mappings from strings in the style of -the SNOBOL4 TABLE function. +@item +@emph{AI-0073 Functions returning abstract types (2010-07-10)} -@node GNAT.Spitbol.Table_Boolean (g-sptabo.ads) -@section @code{GNAT.Spitbol.Table_Boolean} (@file{g-sptabo.ads}) -@cindex @code{GNAT.Spitbol.Table_Boolean} (@file{g-sptabo.ads}) -@cindex Sets of strings -@cindex SPITBOL Tables +This AI covers a number of issues regarding returning abstract types. In +particular generic functions cannot have abstract result types or access +result types designated an abstract type. There are some other cases which +are detailed in the AI. Note that this binding interpretation has not been +retrofitted to operate before Ada 2012 mode, since it caused a significant +number of regressions. -@noindent -A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} -for type @code{Standard.Boolean}, giving an implementation of sets of -string values. +RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2) +@end itemize -@node GNAT.Spitbol.Table_Integer (g-sptain.ads) -@section @code{GNAT.Spitbol.Table_Integer} (@file{g-sptain.ads}) -@cindex @code{GNAT.Spitbol.Table_Integer} (@file{g-sptain.ads}) -@cindex Integer maps -@cindex Maps -@cindex SPITBOL Tables +@geindex AI-0070 (Ada 2012 feature) -@noindent -A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} -for type @code{Standard.Integer}, giving an implementation of maps -from string to integer values. -@node GNAT.Spitbol.Table_VString (g-sptavs.ads) -@section @code{GNAT.Spitbol.Table_VString} (@file{g-sptavs.ads}) -@cindex @code{GNAT.Spitbol.Table_VString} (@file{g-sptavs.ads}) -@cindex String maps -@cindex Maps -@cindex SPITBOL Tables +@itemize * -@noindent -A library level of instantiation of @code{GNAT.Spitbol.Patterns.Table} for -a variable length string type, giving an implementation of general -maps from strings to strings. +@item +@emph{AI-0070 Elaboration of interface types (0000-00-00)} -@node GNAT.SSE (g-sse.ads) -@section @code{GNAT.SSE} (@file{g-sse.ads}) -@cindex @code{GNAT.SSE} (@file{g-sse.ads}) +This is an editorial change only, there are no testable consequences short of +checking for the absence of generated code for an interface declaration. -@noindent -Root of a set of units aimed at offering Ada bindings to a subset of -the Intel(r) Streaming SIMD Extensions with GNAT on the x86 family of -targets. It exposes vector component types together with a general -introduction to the binding contents and use. +RM References: 3.09.04 (18/2) +@end itemize -@node GNAT.SSE.Vector_Types (g-ssvety.ads) -@section @code{GNAT.SSE.Vector_Types} (@file{g-ssvety.ads}) -@cindex @code{GNAT.SSE.Vector_Types} (@file{g-ssvety.ads}) +@geindex AI-0208 (Ada 2012 feature) -@noindent -SSE vector types for use with SSE related intrinsics. -@node GNAT.Strings (g-string.ads) -@section @code{GNAT.Strings} (@file{g-string.ads}) -@cindex @code{GNAT.Strings} (@file{g-string.ads}) +@itemize * -@noindent -Common String access types and related subprograms. Basically it -defines a string access and an array of string access types. +@item +@emph{AI-0208 Characteristics of incomplete views (0000-00-00)} -@node GNAT.String_Split (g-strspl.ads) -@section @code{GNAT.String_Split} (@file{g-strspl.ads}) -@cindex @code{GNAT.String_Split} (@file{g-strspl.ads}) -@cindex String splitter +The wording in the Ada 2005 RM concerning characteristics of incomplete views +was incorrect and implied that some programs intended to be legal were now +illegal. GNAT had never considered such programs illegal, so it has always +implemented the intent of this AI. -@noindent -Useful string manipulation routines: given a set of separators, split -a string wherever the separators appear, and provide direct access -to the resulting slices. This package is instantiated from -@code{GNAT.Array_Split}. +RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2) +@end itemize -@node GNAT.Table (g-table.ads) -@section @code{GNAT.Table} (@file{g-table.ads}) -@cindex @code{GNAT.Table} (@file{g-table.ads}) -@cindex Table implementation -@cindex Arrays, extendable +@geindex AI-0162 (Ada 2012 feature) -@noindent -A generic package providing a single dimension array abstraction where the -length of the array can be dynamically modified. -@noindent -This package provides a facility similar to that of @code{GNAT.Dynamic_Tables}, -except that this package declares a single instance of the table type, -while an instantiation of @code{GNAT.Dynamic_Tables} creates a type that can be -used to define dynamic instances of the table. +@itemize * -@node GNAT.Task_Lock (g-tasloc.ads) -@section @code{GNAT.Task_Lock} (@file{g-tasloc.ads}) -@cindex @code{GNAT.Task_Lock} (@file{g-tasloc.ads}) -@cindex Task synchronization -@cindex Task locking -@cindex Locking +@item +@emph{AI-0162 Incomplete type completed by partial view (2010-09-15)} -@noindent -A very simple facility for locking and unlocking sections of code using a -single global task lock. Appropriate for use in situations where contention -between tasks is very rarely expected. +Incomplete types are made more useful by allowing them to be completed by +private types and private extensions. -@node GNAT.Threads (g-thread.ads) -@section @code{GNAT.Threads} (@file{g-thread.ads}) -@cindex @code{GNAT.Threads} (@file{g-thread.ads}) -@cindex Foreign threads -@cindex Threads, foreign +RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2) +@end itemize -@noindent -Provides facilities for dealing with foreign threads which need to be known -by the GNAT run-time system. Consult the documentation of this package for -further details if your program has threads that are created by a non-Ada -environment which then accesses Ada code. +@geindex AI-0098 (Ada 2012 feature) -@node GNAT.Time_Stamp (g-timsta.ads) -@section @code{GNAT.Time_Stamp} (@file{g-timsta.ads}) -@cindex @code{GNAT.Time_Stamp} (@file{g-timsta.ads}) -@cindex Time stamp -@cindex Current time -@noindent -Provides a simple function that returns a string YYYY-MM-DD HH:MM:SS.SS that -represents the current date and time in ISO 8601 format. This is a very simple -routine with minimal code and there are no dependencies on any other unit. +@itemize * -@node GNAT.Traceback (g-traceb.ads) -@section @code{GNAT.Traceback} (@file{g-traceb.ads}) -@cindex @code{GNAT.Traceback} (@file{g-traceb.ads}) -@cindex Trace back facilities +@item +@emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)} -@noindent -Provides a facility for obtaining non-symbolic traceback information, useful -in various debugging situations. +An unintentional omission in the RM implied some inconsistent restrictions on +the use of anonymous access to subprogram values. These restrictions were not +intentional, and have never been enforced by GNAT. -@node GNAT.Traceback.Symbolic (g-trasym.ads) -@section @code{GNAT.Traceback.Symbolic} (@file{g-trasym.ads}) -@cindex @code{GNAT.Traceback.Symbolic} (@file{g-trasym.ads}) -@cindex Trace back facilities +RM References: 3.10.01 (6) 3.10.01 (9.2/2) +@end itemize -@node GNAT.UTF_32 (g-utf_32.ads) -@section @code{GNAT.UTF_32} (@file{g-table.ads}) -@cindex @code{GNAT.UTF_32} (@file{g-table.ads}) -@cindex Wide character codes +@geindex AI-0199 (Ada 2012 feature) -@noindent -This is a package intended to be used in conjunction with the -@code{Wide_Character} type in Ada 95 and the -@code{Wide_Wide_Character} type in Ada 2005 (available -in @code{GNAT} in Ada 2005 mode). This package contains -Unicode categorization routines, as well as lexical -categorization routines corresponding to the Ada 2005 -lexical rules for identifiers and strings, and also a -lower case to upper case fold routine corresponding to -the Ada 2005 rules for identifier equivalence. -@node GNAT.UTF_32_Spelling_Checker (g-u3spch.ads) -@section @code{GNAT.Wide_Spelling_Checker} (@file{g-u3spch.ads}) -@cindex @code{GNAT.Wide_Spelling_Checker} (@file{g-u3spch.ads}) -@cindex Spell checking +@itemize * -@noindent -Provides a function for determining whether one wide wide string is a plausible -near misspelling of another wide wide string, where the strings are represented -using the UTF_32_String type defined in System.Wch_Cnv. +@item +@emph{AI-0199 Aggregate with anonymous access components (2010-07-14)} + +A choice list in a record aggregate can include several components of +(distinct) anonymous access types as long as they have matching designated +subtypes. -@node GNAT.Wide_Spelling_Checker (g-wispch.ads) -@section @code{GNAT.Wide_Spelling_Checker} (@file{g-wispch.ads}) -@cindex @code{GNAT.Wide_Spelling_Checker} (@file{g-wispch.ads}) -@cindex Spell checking +RM References: 4.03.01 (16) +@end itemize -@noindent -Provides a function for determining whether one wide string is a plausible -near misspelling of another wide string. +@geindex AI-0220 (Ada 2012 feature) -@node GNAT.Wide_String_Split (g-wistsp.ads) -@section @code{GNAT.Wide_String_Split} (@file{g-wistsp.ads}) -@cindex @code{GNAT.Wide_String_Split} (@file{g-wistsp.ads}) -@cindex Wide_String splitter -@noindent -Useful wide string manipulation routines: given a set of separators, split -a wide string wherever the separators appear, and provide direct access -to the resulting slices. This package is instantiated from -@code{GNAT.Array_Split}. +@itemize * -@node GNAT.Wide_Wide_Spelling_Checker (g-zspche.ads) -@section @code{GNAT.Wide_Wide_Spelling_Checker} (@file{g-zspche.ads}) -@cindex @code{GNAT.Wide_Wide_Spelling_Checker} (@file{g-zspche.ads}) -@cindex Spell checking +@item +@emph{AI-0220 Needed components for aggregates (0000-00-00)} -@noindent -Provides a function for determining whether one wide wide string is a plausible -near misspelling of another wide wide string. +This AI addresses a wording problem in the RM that appears to permit some +complex cases of aggregates with non-static discriminants. GNAT has always +implemented the intended semantics. -@node GNAT.Wide_Wide_String_Split (g-zistsp.ads) -@section @code{GNAT.Wide_Wide_String_Split} (@file{g-zistsp.ads}) -@cindex @code{GNAT.Wide_Wide_String_Split} (@file{g-zistsp.ads}) -@cindex Wide_Wide_String splitter +RM References: 4.03.01 (17) +@end itemize -@noindent -Useful wide wide string manipulation routines: given a set of separators, split -a wide wide string wherever the separators appear, and provide direct access -to the resulting slices. This package is instantiated from -@code{GNAT.Array_Split}. +@geindex AI-0147 (Ada 2012 feature) -@node Interfaces.C.Extensions (i-cexten.ads) -@section @code{Interfaces.C.Extensions} (@file{i-cexten.ads}) -@cindex @code{Interfaces.C.Extensions} (@file{i-cexten.ads}) -@noindent -This package contains additional C-related definitions, intended -for use with either manually or automatically generated bindings -to C libraries. +@itemize * -@node Interfaces.C.Streams (i-cstrea.ads) -@section @code{Interfaces.C.Streams} (@file{i-cstrea.ads}) -@cindex @code{Interfaces.C.Streams} (@file{i-cstrea.ads}) -@cindex C streams, interfacing +@item +@emph{AI-0147 Conditional expressions (2009-03-29)} -@noindent -This package is a binding for the most commonly used operations -on C streams. +Conditional expressions are permitted. The form of such an expression is: -@node Interfaces.Packed_Decimal (i-pacdec.ads) -@section @code{Interfaces.Packed_Decimal} (@file{i-pacdec.ads}) -@cindex @code{Interfaces.Packed_Decimal} (@file{i-pacdec.ads}) -@cindex IBM Packed Format -@cindex Packed Decimal +@example +(if expr then expr @{elsif expr then expr@} [else expr]) +@end example -@noindent -This package provides a set of routines for conversions to and -from a packed decimal format compatible with that used on IBM -mainframes. +The parentheses can be omitted in contexts where parentheses are present +anyway, such as subprogram arguments and pragma arguments. If the @strong{else} +clause is omitted, @strong{else} @emph{True} is assumed; +thus @code{(if A then B)} is a way to conveniently represent +@emph{(A implies B)} in standard logic. -@node Interfaces.VxWorks (i-vxwork.ads) -@section @code{Interfaces.VxWorks} (@file{i-vxwork.ads}) -@cindex @code{Interfaces.VxWorks} (@file{i-vxwork.ads}) -@cindex Interfacing to VxWorks -@cindex VxWorks, interfacing +RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2) +4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2) +@end itemize -@noindent -This package provides a limited binding to the VxWorks API. -In particular, it interfaces with the -VxWorks hardware interrupt facilities. +@geindex AI-0037 (Ada 2012 feature) -@node Interfaces.VxWorks.IO (i-vxwoio.ads) -@section @code{Interfaces.VxWorks.IO} (@file{i-vxwoio.ads}) -@cindex @code{Interfaces.VxWorks.IO} (@file{i-vxwoio.ads}) -@cindex Interfacing to VxWorks' I/O -@cindex VxWorks, I/O interfacing -@cindex VxWorks, Get_Immediate -@cindex Get_Immediate, VxWorks -@noindent -This package provides a binding to the ioctl (IO/Control) -function of VxWorks, defining a set of option values and -function codes. A particular use of this package is -to enable the use of Get_Immediate under VxWorks. +@itemize * -@node System.Address_Image (s-addima.ads) -@section @code{System.Address_Image} (@file{s-addima.ads}) -@cindex @code{System.Address_Image} (@file{s-addima.ads}) -@cindex Address image -@cindex Image, of an address +@item +@emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)} -@noindent -This function provides a useful debugging -function that gives an (implementation dependent) -string which identifies an address. +This AI confirms that an association of the form @cite{Indx => <>} in an +array aggregate must raise @cite{Constraint_Error} if @cite{Indx} +is out of range. The RM specified a range check on other associations, but +not when the value of the association was defaulted. GNAT has always inserted +a constraint check on the index value. -@node System.Assertions (s-assert.ads) -@section @code{System.Assertions} (@file{s-assert.ads}) -@cindex @code{System.Assertions} (@file{s-assert.ads}) -@cindex Assertions -@cindex Assert_Failure, exception +RM References: 4.03.03 (29) +@end itemize -@noindent -This package provides the declaration of the exception raised -by an run-time assertion failure, as well as the routine that -is used internally to raise this assertion. +@geindex AI-0123 (Ada 2012 feature) -@node System.Atomic_Counters (s-atocou.ads) -@section @code{System.Atomic_Counters} (@file{s-atocou.ads}) -@cindex @code{System.Atomic_Counters} (@file{s-atocou.ads}) -@noindent -This package provides the declaration of an atomic counter type, -together with efficient routines (using hardware -synchronization primitives) for incrementing, decrementing, -and testing of these counters. This package is implemented -on most targets, including all Alpha, ia64, PowerPC, SPARC V9, -x86, and x86_64 platforms. +@itemize * -@node System.Memory (s-memory.ads) -@section @code{System.Memory} (@file{s-memory.ads}) -@cindex @code{System.Memory} (@file{s-memory.ads}) -@cindex Memory allocation +@item +@emph{AI-0123 Composability of equality (2010-04-13)} -@noindent -This package provides the interface to the low level routines used -by the generated code for allocation and freeing storage for the -default storage pool (analogous to the C routines malloc and free. -It also provides a reallocation interface analogous to the C routine -realloc. The body of this unit may be modified to provide alternative -allocation mechanisms for the default pool, and in addition, direct -calls to this unit may be made for low level allocation uses (for -example see the body of @code{GNAT.Tables}). +Equality of untagged record composes, so that the predefined equality for a +composite type that includes a component of some untagged record type +@cite{R} uses the equality operation of @cite{R} (which may be user-defined +or predefined). This makes the behavior of untagged records identical to that +of tagged types in this respect. + +This change is an incompatibility with previous versions of Ada, but it +corrects a non-uniformity that was often a source of confusion. Analysis of +a large number of industrial programs indicates that in those rare cases +where a composite type had an untagged record component with a user-defined +equality, either there was no use of the composite equality, or else the code +expected the same composability as for tagged types, and thus had a bug that +would be fixed by this change. + +RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24) +8.05.04 (8) +@end itemize -@node System.Multiprocessors (s-multip.ads) -@section @code{System.Multiprocessors} (@file{s-multip.ads}) -@cindex @code{System.Multiprocessors} (@file{s-multip.ads}) -@cindex Multiprocessor interface -This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but -in GNAT we also make it available in Ada 95 and Ada 2005 (where it is -technically an implementation-defined addition). +@geindex AI-0088 (Ada 2012 feature) -@node System.Multiprocessors.Dispatching_Domains (s-mudido.ads) -@section @code{System.Multiprocessors.Dispatching_Domains} (@file{s-mudido.ads}) -@cindex @code{System.Multiprocessors.Dispatching_Domains} (@file{s-mudido.ads}) -@cindex Multiprocessor interface -This is an Ada 2012 unit defined in the Ada 2012 Reference Manual, but -in GNAT we also make it available in Ada 95 and Ada 2005 (where it is -technically an implementation-defined addition). -@node System.Partition_Interface (s-parint.ads) -@section @code{System.Partition_Interface} (@file{s-parint.ads}) -@cindex @code{System.Partition_Interface} (@file{s-parint.ads}) -@cindex Partition interfacing functions +@itemize * -@noindent -This package provides facilities for partition interfacing. It -is used primarily in a distribution context when using Annex E -with @code{GLADE}. +@item +@emph{AI-0088 The value of exponentiation (0000-00-00)} -@node System.Pool_Global (s-pooglo.ads) -@section @code{System.Pool_Global} (@file{s-pooglo.ads}) -@cindex @code{System.Pool_Global} (@file{s-pooglo.ads}) -@cindex Storage pool, global -@cindex Global storage pool +This AI clarifies the equivalence rule given for the dynamic semantics of +exponentiation: the value of the operation can be obtained by repeated +multiplication, but the operation can be implemented otherwise (for example +using the familiar divide-by-two-and-square algorithm, even if this is less +accurate), and does not imply repeated reads of a volatile base. -@noindent -This package provides a storage pool that is equivalent to the default -storage pool used for access types for which no pool is specifically -declared. It uses malloc/free to allocate/free and does not attempt to -do any automatic reclamation. +RM References: 4.05.06 (11) +@end itemize -@node System.Pool_Local (s-pooloc.ads) -@section @code{System.Pool_Local} (@file{s-pooloc.ads}) -@cindex @code{System.Pool_Local} (@file{s-pooloc.ads}) -@cindex Storage pool, local -@cindex Local storage pool +@geindex AI-0188 (Ada 2012 feature) -@noindent -This package provides a storage pool that is intended for use with locally -defined access types. It uses malloc/free for allocate/free, and maintains -a list of allocated blocks, so that all storage allocated for the pool can -be freed automatically when the pool is finalized. -@node System.Restrictions (s-restri.ads) -@section @code{System.Restrictions} (@file{s-restri.ads}) -@cindex @code{System.Restrictions} (@file{s-restri.ads}) -@cindex Run-time restrictions access +@itemize * -@noindent -This package provides facilities for accessing at run time -the status of restrictions specified at compile time for -the partition. Information is available both with regard -to actual restrictions specified, and with regard to -compiler determined information on which restrictions -are violated by one or more packages in the partition. +@item +@emph{AI-0188 Case expressions (2010-01-09)} -@node System.Rident (s-rident.ads) -@section @code{System.Rident} (@file{s-rident.ads}) -@cindex @code{System.Rident} (@file{s-rident.ads}) -@cindex Restrictions definitions +Case expressions are permitted. This allows use of constructs such as: -@noindent -This package provides definitions of the restrictions -identifiers supported by GNAT, and also the format of -the restrictions provided in package System.Restrictions. -It is not normally necessary to @code{with} this generic package -since the necessary instantiation is included in -package System.Restrictions. +@example +X := (case Y is when 1 => 2, when 2 => 3, when others => 31) +@end example -@node System.Strings.Stream_Ops (s-ststop.ads) -@section @code{System.Strings.Stream_Ops} (@file{s-ststop.ads}) -@cindex @code{System.Strings.Stream_Ops} (@file{s-ststop.ads}) -@cindex Stream operations -@cindex String stream operations +RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33) +@end itemize -@noindent -This package provides a set of stream subprograms for standard string types. -It is intended primarily to support implicit use of such subprograms when -stream attributes are applied to string types, but the subprograms in this -package can be used directly by application programs. +@geindex AI-0104 (Ada 2012 feature) -@node System.Unsigned_Types (s-unstyp.ads) -@section @code{System.Unsigned_Types} (@file{s-unstyp.ads}) -@cindex @code{System.Unsigned_Types} (@file{s-unstyp.ads}) -@noindent -This package contains definitions of standard unsigned types that -correspond in size to the standard signed types declared in Standard, -and (unlike the types in Interfaces) have corresponding names. It -also contains some related definitions for other specialized types -used by the compiler in connection with packed array types. +@itemize * -@node System.Wch_Cnv (s-wchcnv.ads) -@section @code{System.Wch_Cnv} (@file{s-wchcnv.ads}) -@cindex @code{System.Wch_Cnv} (@file{s-wchcnv.ads}) -@cindex Wide Character, Representation -@cindex Wide String, Conversion -@cindex Representation of wide characters +@item +@emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)} -@noindent -This package provides routines for converting between -wide and wide wide characters and a representation as a value of type -@code{Standard.String}, using a specified wide character -encoding method. It uses definitions in -package @code{System.Wch_Con}. +The assignment @code{Ptr := new not null Some_Ptr;} will raise +@code{Constraint_Error} because the default value of the allocated object is +@strong{null}. This useless construct is illegal in Ada 2012. -@node System.Wch_Con (s-wchcon.ads) -@section @code{System.Wch_Con} (@file{s-wchcon.ads}) -@cindex @code{System.Wch_Con} (@file{s-wchcon.ads}) +RM References: 4.08 (2) +@end itemize -@noindent -This package provides definitions and descriptions of -the various methods used for encoding wide characters -in ordinary strings. These definitions are used by -the package @code{System.Wch_Cnv}. +@geindex AI-0157 (Ada 2012 feature) -@node Interfacing to Other Languages -@chapter Interfacing to Other Languages -@noindent -The facilities in annex B of the Ada Reference Manual are fully -implemented in GNAT, and in addition, a full interface to C++ is -provided. -@menu -* Interfacing to C:: -* Interfacing to C++:: -* Interfacing to COBOL:: -* Interfacing to Fortran:: -* Interfacing to non-GNAT Ada code:: -@end menu +@itemize * -@node Interfacing to C -@section Interfacing to C +@item +@emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)} -@noindent -Interfacing to C with GNAT can use one of two approaches: +Allocation and Deallocation from an empty storage pool (i.e. allocation or +deallocation of a pointer for which a static storage size clause of zero +has been given) is now illegal and is detected as such. GNAT +previously gave a warning but not an error. -@itemize @bullet -@item -The types in the package @code{Interfaces.C} may be used. -@item -Standard Ada types may be used directly. This may be less portable to -other compilers, but will work on all GNAT compilers, which guarantee -correspondence between the C and Ada types. +RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17) @end itemize -@noindent -Pragma @code{Convention C} may be applied to Ada types, but mostly has no -effect, since this is the default. The following table shows the -correspondence between Ada scalar types and the corresponding C types. - -@table @code -@item Integer -@code{int} -@item Short_Integer -@code{short} -@item Short_Short_Integer -@code{signed char} -@item Long_Integer -@code{long} -@item Long_Long_Integer -@code{long long} -@item Short_Float -@code{float} -@item Float -@code{float} -@item Long_Float -@code{double} -@item Long_Long_Float -This is the longest floating-point type supported by the hardware. -@end table +@geindex AI-0179 (Ada 2012 feature) -@noindent -Additionally, there are the following general correspondences between Ada -and C types: -@itemize @bullet -@item -Ada enumeration types map to C enumeration types directly if pragma -@code{Convention C} is specified, which causes them to have int -length. Without pragma @code{Convention C}, Ada enumeration types map to -8, 16, or 32 bits (i.e.@: C types @code{signed char}, @code{short}, -@code{int}, respectively) depending on the number of values passed. -This is the only case in which pragma @code{Convention C} affects the -representation of an Ada type. -@item -Ada access types map to C pointers, except for the case of pointers to -unconstrained types in Ada, which have no direct C equivalent. +@itemize * -@item -Ada arrays map directly to C arrays. +@item +@emph{AI-0179 Statement not required after label (2010-04-10)} -@item -Ada records map directly to C structures. +It is not necessary to have a statement following a label, so a label +can appear at the end of a statement sequence without the need for putting a +null statement afterwards, but it is not allowable to have only labels and +no real statements in a statement sequence. -@item -Packed Ada records map to C structures where all members are bit fields -of the length corresponding to the @code{@var{type}'Size} value in Ada. +RM References: 5.01 (2) @end itemize -@node Interfacing to C++ -@section Interfacing to C++ +@geindex AI-0139-2 (Ada 2012 feature) -@noindent -The interface to C++ makes use of the following pragmas, which are -primarily intended to be constructed automatically using a binding generator -tool, although it is possible to construct them by hand. -Using these pragmas it is possible to achieve complete -inter-operability between Ada tagged types and C++ class definitions. -See @ref{Implementation Defined Pragmas}, for more details. +@itemize * -@table @code -@item pragma CPP_Class ([Entity =>] @var{LOCAL_NAME}) -The argument denotes an entity in the current declarative region that is -declared as a tagged or untagged record type. It indicates that the type -corresponds to an externally declared C++ class type, and is to be laid -out the same way that C++ would lay out the type. +@item +@emph{AI-0139-2 Syntactic sugar for iterators (2010-09-29)} -Note: Pragma @code{CPP_Class} is currently obsolete. It is supported -for backward compatibility but its functionality is available -using pragma @code{Import} with @code{Convention} = @code{CPP}. +The new syntax for iterating over arrays and containers is now implemented. +Iteration over containers is for now limited to read-only iterators. Only +default iterators are supported, with the syntax: @cite{for Elem of C}. -@item pragma CPP_Constructor ([Entity =>] @var{LOCAL_NAME}) -This pragma identifies an imported function (imported in the usual way -with pragma @code{Import}) as corresponding to a C++ constructor. -@end table +RM References: 5.05 +@end itemize -A few restrictions are placed on the use of the @code{Access} attribute -in conjunction with subprograms subject to convention @code{CPP}: the -attribute may be used neither on primitive operations of a tagged -record type with convention @code{CPP}, imported or not, nor on -subprograms imported with pragma @code{CPP_Constructor}. +@geindex AI-0134 (Ada 2012 feature) -In addition, C++ exceptions are propagated and can be handled in an -@code{others} choice of an exception handler. The corresponding Ada -occurrence has no message, and the simple name of the exception identity -contains @samp{Foreign_Exception}. Finalization and awaiting dependent -tasks works properly when such foreign exceptions are propagated. -It is also possible to import a C++ exception using the following syntax: +@itemize * -@smallexample @c ada -LOCAL_NAME : exception; -pragma Import (Cpp, - [Entity =>] LOCAL_NAME, - [External_Name =>] static_string_EXPRESSION); -@end smallexample +@item +@emph{AI-0134 Profiles must match for full conformance (0000-00-00)} -@noindent -The @code{External_Name} is the name of the C++ RTTI symbol. You can then -cover a specific C++ exception in an exception handler. +For full conformance, the profiles of anonymous-access-to-subprogram +parameters must match. GNAT has always enforced this rule. -@node Interfacing to COBOL -@section Interfacing to COBOL +RM References: 6.03.01 (18) +@end itemize -@noindent -Interfacing to COBOL is achieved as described in section B.4 of -the Ada Reference Manual. +@geindex AI-0207 (Ada 2012 feature) -@node Interfacing to Fortran -@section Interfacing to Fortran -@noindent -Interfacing to Fortran is achieved as described in section B.5 of the -Ada Reference Manual. The pragma @code{Convention Fortran}, applied to a -multi-dimensional array causes the array to be stored in column-major -order as required for convenient interface to Fortran. +@itemize * -@node Interfacing to non-GNAT Ada code -@section Interfacing to non-GNAT Ada code +@item +@emph{AI-0207 Mode conformance and access constant (0000-00-00)} -It is possible to specify the convention @code{Ada} in a pragma -@code{Import} or pragma @code{Export}. However this refers to -the calling conventions used by GNAT, which may or may not be -similar enough to those used by some other Ada 83 / Ada 95 / Ada 2005 -compiler to allow interoperation. +This AI confirms that access_to_constant indication must match for mode +conformance. This was implemented in GNAT when the qualifier was originally +introduced in Ada 2005. -If arguments types are kept simple, and if the foreign compiler generally -follows system calling conventions, then it may be possible to integrate -files compiled by other Ada compilers, provided that the elaboration -issues are adequately addressed (for example by eliminating the -need for any load time elaboration). +RM References: 6.03.01 (16/2) +@end itemize -In particular, GNAT running on VMS is designed to -be highly compatible with the DEC Ada 83 compiler, so this is one -case in which it is possible to import foreign units of this type, -provided that the data items passed are restricted to simple scalar -values or simple record types without variants, or simple array -types with fixed bounds. +@geindex AI-0046 (Ada 2012 feature) -@node Specialized Needs Annexes -@chapter Specialized Needs Annexes -@noindent -Ada 95 and Ada 2005 define a number of Specialized Needs Annexes, which are not -required in all implementations. However, as described in this chapter, -GNAT implements all of these annexes: +@itemize * -@table @asis -@item Systems Programming (Annex C) -The Systems Programming Annex is fully implemented. +@item +@emph{AI-0046 Null exclusion match for full conformance (2010-07-17)} -@item Real-Time Systems (Annex D) -The Real-Time Systems Annex is fully implemented. +For full conformance, in the case of access parameters, the null exclusion +must match (either both or neither must have @code{not null}). -@item Distributed Systems (Annex E) -Stub generation is fully implemented in the GNAT compiler. In addition, -a complete compatible PCS is available as part of the GLADE system, -a separate product. When the two -products are used in conjunction, this annex is fully implemented. +RM References: 6.03.02 (18) +@end itemize -@item Information Systems (Annex F) -The Information Systems annex is fully implemented. +@geindex AI-0118 (Ada 2012 feature) -@item Numerics (Annex G) -The Numerics Annex is fully implemented. -@item Safety and Security / High-Integrity Systems (Annex H) -The Safety and Security Annex (termed the High-Integrity Systems Annex -in Ada 2005) is fully implemented. -@end table +@itemize * -@node Implementation of Specific Ada Features -@chapter Implementation of Specific Ada Features +@item +@emph{AI-0118 The association of parameter associations (0000-00-00)} -@noindent -This chapter describes the GNAT implementation of several Ada language -facilities. +This AI clarifies the rules for named associations in subprogram calls and +generic instantiations. The rules have been in place since Ada 83. -@menu -* Machine Code Insertions:: -* GNAT Implementation of Tasking:: -* GNAT Implementation of Shared Passive Packages:: -* Code Generation for Array Aggregates:: -* The Size of Discriminated Records with Default Discriminants:: -* Strict Conformance to the Ada Reference Manual:: -@end menu +RM References: 6.04.01 (2) 12.03 (9) +@end itemize -@node Machine Code Insertions -@section Machine Code Insertions -@cindex Machine Code insertions +@geindex AI-0196 (Ada 2012 feature) -@noindent -Package @code{Machine_Code} provides machine code support as described -in the Ada Reference Manual in two separate forms: -@itemize @bullet -@item -Machine code statements, consisting of qualified expressions that -fit the requirements of RM section 13.8. -@item -An intrinsic callable procedure, providing an alternative mechanism of -including machine instructions in a subprogram. + +@itemize * + +@item +@emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)} + +Null exclusion checks are not made for @cite{**out**} parameters when +evaluating the actual parameters. GNAT has never generated these checks. + +RM References: 6.04.01 (13) @end itemize -@noindent -The two features are similar, and both are closely related to the mechanism -provided by the asm instruction in the GNU C compiler. Full understanding -and use of the facilities in this package requires understanding the asm -instruction, see @ref{Extended Asm,,, gcc, Using the GNU Compiler -Collection (GCC)}. +@geindex AI-0015 (Ada 2012 feature) -Calls to the function @code{Asm} and the procedure @code{Asm} have identical -semantic restrictions and effects as described below. Both are provided so -that the procedure call can be used as a statement, and the function call -can be used to form a code_statement. -Consider this C @code{asm} instruction: -@smallexample - asm ("fsinx %1 %0" : "=f" (result) : "f" (angle)); -@end smallexample +@itemize * -@noindent -The equivalent can be written for GNAT as: +@item +@emph{AI-0015 Constant return objects (0000-00-00)} -@smallexample @c ada -Asm ("fsinx %1 %0", - My_Float'Asm_Output ("=f", result), - My_Float'Asm_Input ("f", angle)); -@end smallexample +The return object declared in an @emph{extended_return_statement} may be +declared constant. This was always intended, and GNAT has always allowed it. -@noindent -The first argument to @code{Asm} is the assembler template, and is -identical to what is used in GNU C@. This string must be a static -expression. The second argument is the output operand list. It is -either a single @code{Asm_Output} attribute reference, or a list of such -references enclosed in parentheses (technically an array aggregate of -such references). +RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2) +6.05 (5.7/2) +@end itemize -The @code{Asm_Output} attribute denotes a function that takes two -parameters. The first is a string, the second is the name of a variable -of the type designated by the attribute prefix. The first (string) -argument is required to be a static expression and designates the -constraint (@pxref{Constraints,,, gcc, Using the GNU Compiler -Collection (GCC)}) -for the parameter (e.g.@: what kind of register is required). The second -argument is the variable to be written or updated with the -result. The possible values for constraint are the same as those used in -the RTL, and are dependent on the configuration file used to build the -GCC back end. If there are no output operands, then this argument may -either be omitted, or explicitly given as @code{No_Output_Operands}. -No support is provided for GNU C's symbolic names for output parameters. +@geindex AI-0032 (Ada 2012 feature) -The second argument of @code{@var{my_float}'Asm_Output} functions as -though it were an @code{out} parameter, which is a little curious, but -all names have the form of expressions, so there is no syntactic -irregularity, even though normally functions would not be permitted -@code{out} parameters. The third argument is the list of input -operands. It is either a single @code{Asm_Input} attribute reference, or -a list of such references enclosed in parentheses (technically an array -aggregate of such references). -The @code{Asm_Input} attribute denotes a function that takes two -parameters. The first is a string, the second is an expression of the -type designated by the prefix. The first (string) argument is required -to be a static expression, and is the constraint for the parameter, -(e.g.@: what kind of register is required). The second argument is the -value to be used as the input argument. The possible values for the -constraint are the same as those used in the RTL, and are dependent on -the configuration file used to built the GCC back end. -No support is provided for GNU C's symbolic names for input parameters. +@itemize * -If there are no input operands, this argument may either be omitted, or -explicitly given as @code{No_Input_Operands}. The fourth argument, not -present in the above example, is a list of register names, called the -@dfn{clobber} argument. This argument, if given, must be a static string -expression, and is a space or comma separated list of names of registers -that must be considered destroyed as a result of the @code{Asm} call. If -this argument is the null string (the default value), then the code -generator assumes that no additional registers are destroyed. -In addition to registers, the special clobbers @code{memory} and -@code{cc} as described in the GNU C docs are both supported. +@item +@emph{AI-0032 Extended return for class-wide functions (0000-00-00)} -The fifth argument, not present in the above example, called the -@dfn{volatile} argument, is by default @code{False}. It can be set to -the literal value @code{True} to indicate to the code generator that all -optimizations with respect to the instruction specified should be -suppressed, and in particular an instruction that has outputs -will still be generated, even if none of the outputs are -used. @xref{Volatile,,, -gcc, Using the GNU Compiler Collection (GCC)}, for the full description. -Generally it is strongly advisable to use Volatile for any ASM statement -that is missing either input or output operands or to avoid unwanted -optimizations. A warning is generated if this advice is not followed. +If a function returns a class-wide type, the object of an extended return +statement can be declared with a specific type that is covered by the class- +wide type. This has been implemented in GNAT since the introduction of +extended returns. Note AI-0103 complements this AI by imposing matching +rules for constrained return types. -No support is provided for GNU C's @code{asm goto} feature. +RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2) +6.05 (8/2) +@end itemize -The @code{Asm} subprograms may be used in two ways. First the procedure -forms can be used anywhere a procedure call would be valid, and -correspond to what the RM calls ``intrinsic'' routines. Such calls can -be used to intersperse machine instructions with other Ada statements. -Second, the function forms, which return a dummy value of the limited -private type @code{Asm_Insn}, can be used in code statements, and indeed -this is the only context where such calls are allowed. Code statements -appear as aggregates of the form: +@geindex AI-0103 (Ada 2012 feature) -@smallexample @c ada -Asm_Insn'(Asm (@dots{})); -Asm_Insn'(Asm_Volatile (@dots{})); -@end smallexample -@noindent -In accordance with RM rules, such code statements are allowed only -within subprograms whose entire body consists of such statements. It is -not permissible to intermix such statements with other Ada statements. +@itemize * -Typically the form using intrinsic procedure calls is more convenient -and more flexible. The code statement form is provided to meet the RM -suggestion that such a facility should be made available. The following -is the exact syntax of the call to @code{Asm}. As usual, if named notation -is used, the arguments may be given in arbitrary order, following the -normal rules for use of positional and named arguments: +@item +@emph{AI-0103 Static matching for extended return (2010-07-23)} -@smallexample -ASM_CALL ::= Asm ( - [Template =>] static_string_EXPRESSION - [,[Outputs =>] OUTPUT_OPERAND_LIST ] - [,[Inputs =>] INPUT_OPERAND_LIST ] - [,[Clobber =>] static_string_EXPRESSION ] - [,[Volatile =>] static_boolean_EXPRESSION] ) +If the return subtype of a function is an elementary type or a constrained +type, the subtype indication in an extended return statement must match +statically this return subtype. -OUTPUT_OPERAND_LIST ::= - [PREFIX.]No_Output_Operands -| OUTPUT_OPERAND_ATTRIBUTE -| (OUTPUT_OPERAND_ATTRIBUTE @{,OUTPUT_OPERAND_ATTRIBUTE@}) +RM References: 6.05 (5.2/2) +@end itemize -OUTPUT_OPERAND_ATTRIBUTE ::= - SUBTYPE_MARK'Asm_Output (static_string_EXPRESSION, NAME) +@geindex AI-0058 (Ada 2012 feature) -INPUT_OPERAND_LIST ::= - [PREFIX.]No_Input_Operands -| INPUT_OPERAND_ATTRIBUTE -| (INPUT_OPERAND_ATTRIBUTE @{,INPUT_OPERAND_ATTRIBUTE@}) -INPUT_OPERAND_ATTRIBUTE ::= - SUBTYPE_MARK'Asm_Input (static_string_EXPRESSION, EXPRESSION) -@end smallexample +@itemize * -@noindent -The identifiers @code{No_Input_Operands} and @code{No_Output_Operands} -are declared in the package @code{Machine_Code} and must be referenced -according to normal visibility rules. In particular if there is no -@code{use} clause for this package, then appropriate package name -qualification is required. +@item +@emph{AI-0058 Abnormal completion of an extended return (0000-00-00)} -@node GNAT Implementation of Tasking -@section GNAT Implementation of Tasking +The RM had some incorrect wording implying wrong treatment of abnormal +completion in an extended return. GNAT has always implemented the intended +correct semantics as described by this AI. -@noindent -This chapter outlines the basic GNAT approach to tasking (in particular, -a multi-layered library for portability) and discusses issues related -to compliance with the Real-Time Systems Annex. +RM References: 6.05 (22/2) +@end itemize -@menu -* Mapping Ada Tasks onto the Underlying Kernel Threads:: -* Ensuring Compliance with the Real-Time Annex:: -@end menu +@geindex AI-0050 (Ada 2012 feature) -@node Mapping Ada Tasks onto the Underlying Kernel Threads -@subsection Mapping Ada Tasks onto the Underlying Kernel Threads -@noindent -GNAT's run-time support comprises two layers: +@itemize * + +@item +@emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)} -@itemize @bullet -@item GNARL (GNAT Run-time Layer) -@item GNULL (GNAT Low-level Library) +The implementation permissions for raising @cite{Constraint_Error} early on a function call +when it was clear an exception would be raised were over-permissive and allowed +mishandling of discriminants in some cases. GNAT did +not take advantage of these incorrect permissions in any case. + +RM References: 6.05 (24/2) @end itemize -@noindent -In GNAT, Ada's tasking services rely on a platform and OS independent -layer known as GNARL@. This code is responsible for implementing the -correct semantics of Ada's task creation, rendezvous, protected -operations etc. +@geindex AI-0125 (Ada 2012 feature) -GNARL decomposes Ada's tasking semantics into simpler lower level -operations such as create a thread, set the priority of a thread, -yield, create a lock, lock/unlock, etc. The spec for these low-level -operations constitutes GNULLI, the GNULL Interface. This interface is -directly inspired from the POSIX real-time API@. -If the underlying executive or OS implements the POSIX standard -faithfully, the GNULL Interface maps as is to the services offered by -the underlying kernel. Otherwise, some target dependent glue code maps -the services offered by the underlying kernel to the semantics expected -by GNARL@. +@itemize * -Whatever the underlying OS (VxWorks, UNIX, Windows, etc.) the -key point is that each Ada task is mapped on a thread in the underlying -kernel. For example, in the case of VxWorks, one Ada task = one VxWorks task. +@item +@emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)} -In addition Ada task priorities map onto the underlying thread priorities. -Mapping Ada tasks onto the underlying kernel threads has several advantages: +In Ada 2012, the declaration of a primitive operation of a type extension +or private extension can also override an inherited primitive that is not +visible at the point of this declaration. -@itemize @bullet -@item -The underlying scheduler is used to schedule the Ada tasks. This -makes Ada tasks as efficient as kernel threads from a scheduling -standpoint. +RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2) +@end itemize -@item -Interaction with code written in C containing threads is eased -since at the lowest level Ada tasks and C threads map onto the same -underlying kernel concept. +@geindex AI-0062 (Ada 2012 feature) -@item -When an Ada task is blocked during I/O the remaining Ada tasks are -able to proceed. -@item -On multiprocessor systems Ada tasks can execute in parallel. +@itemize * + +@item +@emph{AI-0062 Null exclusions and deferred constants (0000-00-00)} + +A full constant may have a null exclusion even if its associated deferred +constant does not. GNAT has always allowed this. + +RM References: 7.04 (6/2) 7.04 (7.1/2) @end itemize -@noindent -Some threads libraries offer a mechanism to fork a new process, with the -child process duplicating the threads from the parent. -GNAT does not -support this functionality when the parent contains more than one task. -@cindex Forking a new process +@geindex AI-0178 (Ada 2012 feature) -@node Ensuring Compliance with the Real-Time Annex -@subsection Ensuring Compliance with the Real-Time Annex -@cindex Real-Time Systems Annex compliance -@noindent -Although mapping Ada tasks onto -the underlying threads has significant advantages, it does create some -complications when it comes to respecting the scheduling semantics -specified in the real-time annex (Annex D). +@itemize * -For instance the Annex D requirement for the @code{FIFO_Within_Priorities} -scheduling policy states: +@item +@emph{AI-0178 Incomplete views are limited (0000-00-00)} -@quotation -@emph{When the active priority of a ready task that is not running -changes, or the setting of its base priority takes effect, the -task is removed from the ready queue for its old active priority -and is added at the tail of the ready queue for its new active -priority, except in the case where the active priority is lowered -due to the loss of inherited priority, in which case the task is -added at the head of the ready queue for its new active priority.} -@end quotation +This AI clarifies the role of incomplete views and plugs an omission in the +RM. GNAT always correctly restricted the use of incomplete views and types. -@noindent -While most kernels do put tasks at the end of the priority queue when -a task changes its priority, (which respects the main -FIFO_Within_Priorities requirement), almost none keep a thread at the -beginning of its priority queue when its priority drops from the loss -of inherited priority. +RM References: 7.05 (3/2) 7.05 (6/2) +@end itemize -As a result most vendors have provided incomplete Annex D implementations. +@geindex AI-0087 (Ada 2012 feature) -The GNAT run-time, has a nice cooperative solution to this problem -which ensures that accurate FIFO_Within_Priorities semantics are -respected. -The principle is as follows. When an Ada task T is about to start -running, it checks whether some other Ada task R with the same -priority as T has been suspended due to the loss of priority -inheritance. If this is the case, T yields and is placed at the end of -its priority queue. When R arrives at the front of the queue it -executes. +@itemize * -Note that this simple scheme preserves the relative order of the tasks -that were ready to execute in the priority queue where R has been -placed at the end. +@item +@emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)} -@node GNAT Implementation of Shared Passive Packages -@section GNAT Implementation of Shared Passive Packages -@cindex Shared passive packages +The actual for a formal nonlimited derived type cannot be limited. In +particular, a formal derived type that extends a limited interface but which +is not explicitly limited cannot be instantiated with a limited type. -@noindent -GNAT fully implements the pragma @code{Shared_Passive} for -@cindex pragma @code{Shared_Passive} -the purpose of designating shared passive packages. -This allows the use of passive partitions in the -context described in the Ada Reference Manual; i.e., for communication -between separate partitions of a distributed application using the -features in Annex E. -@cindex Annex E -@cindex Distribution Systems Annex +RM References: 7.05 (5/2) 12.05.01 (5.1/2) +@end itemize -However, the implementation approach used by GNAT provides for more -extensive usage as follows: +@geindex AI-0099 (Ada 2012 feature) -@table @emph -@item Communication between separate programs -This allows separate programs to access the data in passive -partitions, using protected objects for synchronization where -needed. The only requirement is that the two programs have a -common shared file system. It is even possible for programs -running on different machines with different architectures -(e.g.@: different endianness) to communicate via the data in -a passive partition. +@itemize * -@item Persistence between program runs +@item +@emph{AI-0099 Tag determines whether finalization needed (0000-00-00)} -The data in a passive package can persist from one run of a -program to another, so that a later program sees the final -values stored by a previous run of the same program. +This AI clarifies that 'needs finalization' is part of dynamic semantics, +and therefore depends on the run-time characteristics of an object (i.e. its +tag) and not on its nominal type. As the AI indicates: "we do not expect +this to affect any implementation'@w{'}. -@end table +RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2) +@end itemize -@noindent -The implementation approach used is to store the data in files. A -separate stream file is created for each object in the package, and -an access to an object causes the corresponding file to be read or -written. +@geindex AI-0064 (Ada 2012 feature) -The environment variable @code{SHARED_MEMORY_DIRECTORY} should be -@cindex @code{SHARED_MEMORY_DIRECTORY} environment variable -set to the directory to be used for these files. -The files in this directory -have names that correspond to their fully qualified names. For -example, if we have the package -@smallexample @c ada -package X is - pragma Shared_Passive (X); - Y : Integer; - Z : Float; -end X; -@end smallexample +@itemize * -@noindent -and the environment variable is set to @code{/stemp/}, then the files created -will have the names: +@item +@emph{AI-0064 Redundant finalization rule (0000-00-00)} -@smallexample -/stemp/x.y -/stemp/x.z -@end smallexample +This is an editorial change only. The intended behavior is already checked +by an existing ACATS test, which GNAT has always executed correctly. -@noindent -These files are created when a value is initially written to the object, and -the files are retained until manually deleted. This provides the persistence -semantics. If no file exists, it means that no partition has assigned a value -to the variable; in this case the initial value declared in the package -will be used. This model ensures that there are no issues in synchronizing -the elaboration process, since elaboration of passive packages elaborates the -initial values, but does not create the files. +RM References: 7.06.01 (17.1/1) +@end itemize -The files are written using normal @code{Stream_IO} access. -If you want to be able -to communicate between programs or partitions running on different -architectures, then you should use the XDR versions of the stream attribute -routines, since these are architecture independent. +@geindex AI-0026 (Ada 2012 feature) -If active synchronization is required for access to the variables in the -shared passive package, then as described in the Ada Reference Manual, the -package may contain protected objects used for this purpose. In this case -a lock file (whose name is @file{___lock} (three underscores) -is created in the shared memory directory. -@cindex @file{___lock} file (for shared passive packages) -This is used to provide the required locking -semantics for proper protected object synchronization. -As of January 2003, GNAT supports shared passive packages on all platforms -except for OpenVMS. +@itemize * -@node Code Generation for Array Aggregates -@section Code Generation for Array Aggregates +@item +@emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)} -@menu -* Static constant aggregates with static bounds:: -* Constant aggregates with unconstrained nominal types:: -* Aggregates with static bounds:: -* Aggregates with non-static bounds:: -* Aggregates in assignment statements:: -@end menu +Record representation clauses concerning Unchecked_Union types cannot mention +the discriminant of the type. The type of a component declared in the variant +part of an Unchecked_Union cannot be controlled, have controlled components, +nor have protected or task parts. If an Unchecked_Union type is declared +within the body of a generic unit or its descendants, then the type of a +component declared in the variant part cannot be a formal private type or a +formal private extension declared within the same generic unit. -@noindent -Aggregates have a rich syntax and allow the user to specify the values of -complex data structures by means of a single construct. As a result, the -code generated for aggregates can be quite complex and involve loops, case -statements and multiple assignments. In the simplest cases, however, the -compiler will recognize aggregates whose components and constraints are -fully static, and in those cases the compiler will generate little or no -executable code. The following is an outline of the code that GNAT generates -for various aggregate constructs. For further details, you will find it -useful to examine the output produced by the -gnatG flag to see the expanded -source that is input to the code generator. You may also want to examine -the assembly code generated at various levels of optimization. +RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2) +@end itemize -The code generated for aggregates depends on the context, the component values, -and the type. In the context of an object declaration the code generated is -generally simpler than in the case of an assignment. As a general rule, static -component values and static subtypes also lead to simpler code. +@geindex AI-0205 (Ada 2012 feature) -@node Static constant aggregates with static bounds -@subsection Static constant aggregates with static bounds -@noindent -For the declarations: -@smallexample @c ada - type One_Dim is array (1..10) of integer; - ar0 : constant One_Dim := (1, 2, 3, 4, 5, 6, 7, 8, 9, 0); -@end smallexample +@itemize * -@noindent -GNAT generates no executable code: the constant ar0 is placed in static memory. -The same is true for constant aggregates with named associations: +@item +@emph{AI-0205 Extended return declares visible name (0000-00-00)} -@smallexample @c ada - Cr1 : constant One_Dim := (4 => 16, 2 => 4, 3 => 9, 1 => 1, 5 .. 10 => 0); - Cr3 : constant One_Dim := (others => 7777); -@end smallexample +This AI corrects a simple omission in the RM. Return objects have always +been visible within an extended return statement. -@noindent -The same is true for multidimensional constant arrays such as: +RM References: 8.03 (17) +@end itemize -@smallexample @c ada - type two_dim is array (1..3, 1..3) of integer; - Unit : constant two_dim := ( (1,0,0), (0,1,0), (0,0,1)); -@end smallexample +@geindex AI-0042 (Ada 2012 feature) -@noindent -The same is true for arrays of one-dimensional arrays: the following are -static: -@smallexample @c ada -type ar1b is array (1..3) of boolean; -type ar_ar is array (1..3) of ar1b; -None : constant ar1b := (others => false); -- fully static -None2 : constant ar_ar := (1..3 => None); -- fully static -@end smallexample +@itemize * -@noindent -However, for multidimensional aggregates with named associations, GNAT will -generate assignments and loops, even if all associations are static. The -following two declarations generate a loop for the first dimension, and -individual component assignments for the second dimension: +@item +@emph{AI-0042 Overriding versus implemented-by (0000-00-00)} -@smallexample @c ada -Zero1: constant two_dim := (1..3 => (1..3 => 0)); -Zero2: constant two_dim := (others => (others => 0)); -@end smallexample +This AI fixes a wording gap in the RM. An operation of a synchronized +interface can be implemented by a protected or task entry, but the abstract +operation is not being overridden in the usual sense, and it must be stated +separately that this implementation is legal. This has always been the case +in GNAT. -@node Constant aggregates with unconstrained nominal types -@subsection Constant aggregates with unconstrained nominal types +RM References: 9.01 (9.2/2) 9.04 (11.1/2) +@end itemize -@noindent -In such cases the aggregate itself establishes the subtype, so that -associations with @code{others} cannot be used. GNAT determines the -bounds for the actual subtype of the aggregate, and allocates the -aggregate statically as well. No code is generated for the following: +@geindex AI-0030 (Ada 2012 feature) -@smallexample @c ada - type One_Unc is array (natural range <>) of integer; - Cr_Unc : constant One_Unc := (12,24,36); -@end smallexample -@node Aggregates with static bounds -@subsection Aggregates with static bounds +@itemize * -@noindent -In all previous examples the aggregate was the initial (and immutable) value -of a constant. If the aggregate initializes a variable, then code is generated -for it as a combination of individual assignments and loops over the target -object. The declarations +@item +@emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)} -@smallexample @c ada - Cr_Var1 : One_Dim := (2, 5, 7, 11, 0, 0, 0, 0, 0, 0); - Cr_Var2 : One_Dim := (others > -1); -@end smallexample +Requeue is permitted to a protected, synchronized or task interface primitive +providing it is known that the overriding operation is an entry. Otherwise +the requeue statement has the same effect as a procedure call. Use of pragma +@cite{Implemented} provides a way to impose a static requirement on the +overriding operation by adhering to one of the implementation kinds: entry, +protected procedure or any of the above. -@noindent -generate the equivalent of +RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5) +9.05.04 (6) 9.05.04 (7) 9.05.04 (12) +@end itemize -@smallexample @c ada - Cr_Var1 (1) := 2; - Cr_Var1 (2) := 3; - Cr_Var1 (3) := 5; - Cr_Var1 (4) := 11; +@geindex AI-0201 (Ada 2012 feature) - for I in Cr_Var2'range loop - Cr_Var2 (I) := -1; - end loop; -@end smallexample -@node Aggregates with non-static bounds -@subsection Aggregates with non-static bounds +@itemize * + +@item +@emph{AI-0201 Independence of atomic object components (2010-07-22)} -@noindent -If the bounds of the aggregate are not statically compatible with the bounds -of the nominal subtype of the target, then constraint checks have to be -generated on the bounds. For a multidimensional array, constraint checks may -have to be applied to sub-arrays individually, if they do not have statically -compatible subtypes. +If an Atomic object has a pragma @cite{Pack} or a @cite{Component_Size} +attribute, then individual components may not be addressable by independent +tasks. However, if the representation clause has no effect (is confirming), +then independence is not compromised. Furthermore, in GNAT, specification of +other appropriately addressable component sizes (e.g. 16 for 8-bit +characters) also preserves independence. GNAT now gives very clear warnings +both for the declaration of such a type, and for any assignment to its components. -@node Aggregates in assignment statements -@subsection Aggregates in assignment statements +RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2) +@end itemize -@noindent -In general, aggregate assignment requires the construction of a temporary, -and a copy from the temporary to the target of the assignment. This is because -it is not always possible to convert the assignment into a series of individual -component assignments. For example, consider the simple case: +@geindex AI-0009 (Ada 2012 feature) -@smallexample @c ada - A := (A(2), A(1)); -@end smallexample -@noindent -This cannot be converted into: +@itemize * -@smallexample @c ada - A(1) := A(2); - A(2) := A(1); -@end smallexample +@item +@emph{AI-0009 Pragma Independent[_Components] (2010-07-23)} -@noindent -So the aggregate has to be built first in a separate location, and then -copied into the target. GNAT recognizes simple cases where this intermediate -step is not required, and the assignments can be performed in place, directly -into the target. The following sufficient criteria are applied: +This AI introduces the new pragmas @cite{Independent} and +@cite{Independent_Components}, +which control guaranteeing independence of access to objects and components. +The AI also requires independence not unaffected by confirming rep clauses. -@itemize @bullet -@item -The bounds of the aggregate are static, and the associations are static. -@item -The components of the aggregate are static constants, names of -simple variables that are not renamings, or expressions not involving -indexed components whose operands obey these rules. +RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2) +C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14) @end itemize -@noindent -If any of these conditions are violated, the aggregate will be built in -a temporary (created either by the front-end or the code generator) and then -that temporary will be copied onto the target. +@geindex AI-0072 (Ada 2012 feature) -@node The Size of Discriminated Records with Default Discriminants -@section The Size of Discriminated Records with Default Discriminants -@noindent -If a discriminated type @code{T} has discriminants with default values, it is -possible to declare an object of this type without providing an explicit -constraint: +@itemize * -@smallexample @c ada -@group -type Size is range 1..100; +@item +@emph{AI-0072 Task signalling using 'Terminated (0000-00-00)} -type Rec (D : Size := 15) is record - Name : String (1..D); -end T; +This AI clarifies that task signalling for reading @cite{'Terminated} only +occurs if the result is True. GNAT semantics has always been consistent with +this notion of task signalling. -Word : Rec; -@end group -@end smallexample +RM References: 9.10 (6.1/1) +@end itemize -@noindent -Such an object is said to be @emph{unconstrained}. -The discriminant of the object -can be modified by a full assignment to the object, as long as it preserves the -relation between the value of the discriminant, and the value of the components -that depend on it: +@geindex AI-0108 (Ada 2012 feature) -@smallexample @c ada -@group -Word := (3, "yes"); -Word := (5, "maybe"); +@itemize * -Word := (5, "no"); -- raises Constraint_Error -@end group -@end smallexample +@item +@emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)} -@noindent -In order to support this behavior efficiently, an unconstrained object is -given the maximum size that any value of the type requires. In the case -above, @code{Word} has storage for the discriminant and for -a @code{String} of length 100. -It is important to note that unconstrained objects do not require dynamic -allocation. It would be an improper implementation to place on the heap those -components whose size depends on discriminants. (This improper implementation -was used by some Ada83 compilers, where the @code{Name} component above -would have -been stored as a pointer to a dynamic string). Following the principle that -dynamic storage management should never be introduced implicitly, -an Ada compiler should reserve the full size for an unconstrained declared -object, and place it on the stack. +This AI confirms that an incomplete type from a limited view does not have +discriminants. This has always been the case in GNAT. -This maximum size approach -has been a source of surprise to some users, who expect the default -values of the discriminants to determine the size reserved for an -unconstrained object: ``If the default is 15, why should the object occupy -a larger size?'' -The answer, of course, is that the discriminant may be later modified, -and its full range of values must be taken into account. This is why the -declaration: +RM References: 10.01.01 (12.3/2) +@end itemize -@smallexample -@group -type Rec (D : Positive := 15) is record - Name : String (1..D); -end record; +@geindex AI-0129 (Ada 2012 feature) -Too_Large : Rec; -@end group -@end smallexample -@noindent -is flagged by the compiler with a warning: -an attempt to create @code{Too_Large} will raise @code{Storage_Error}, -because the required size includes @code{Positive'Last} -bytes. As the first example indicates, the proper approach is to declare an -index type of ``reasonable'' range so that unconstrained objects are not too -large. +@itemize * -One final wrinkle: if the object is declared to be @code{aliased}, or if it is -created in the heap by means of an allocator, then it is @emph{not} -unconstrained: -it is constrained by the default values of the discriminants, and those values -cannot be modified by full assignment. This is because in the presence of -aliasing all views of the object (which may be manipulated by different tasks, -say) must be consistent, so it is imperative that the object, once created, -remain invariant. +@item +@emph{AI-0129 Limited views and incomplete types (0000-00-00)} -@node Strict Conformance to the Ada Reference Manual -@section Strict Conformance to the Ada Reference Manual +This AI clarifies the description of limited views: a limited view of a +package includes only one view of a type that has an incomplete declaration +and a full declaration (there is no possible ambiguity in a client package). +This AI also fixes an omission: a nested package in the private part has no +limited view. GNAT always implemented this correctly. -@noindent -The dynamic semantics defined by the Ada Reference Manual impose a set of -run-time checks to be generated. By default, the GNAT compiler will insert many -run-time checks into the compiled code, including most of those required by the -Ada Reference Manual. However, there are three checks that are not enabled -in the default mode for efficiency reasons: arithmetic overflow checking for -integer operations (including division by zero), checks for access before -elaboration on subprogram calls, and stack overflow checking (most operating -systems do not perform this check by default). +RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2) +@end itemize -Strict conformance to the Ada Reference Manual can be achieved by adding -three compiler options for overflow checking for integer operations -(@option{-gnato}), dynamic checks for access-before-elaboration on subprogram -calls and generic instantiations (@option{-gnatE}), and stack overflow -checking (@option{-fstack-check}). +@geindex AI-0077 (Ada 2012 feature) -Note that the result of a floating point arithmetic operation in overflow and -invalid situations, when the @code{Machine_Overflows} attribute of the result -type is @code{False}, is to generate IEEE NaN and infinite values. This is the -case for machines compliant with the IEEE floating-point standard, but on -machines that are not fully compliant with this standard, such as Alpha, the -@option{-mieee} compiler flag must be used for achieving IEEE confirming -behavior (although at the cost of a significant performance penalty), so -infinite and NaN values are properly generated. +@itemize * -@node Implementation of Ada 2012 Features -@chapter Implementation of Ada 2012 Features -@cindex Ada 2012 implementation status +@item +@emph{AI-0077 Limited withs and scope of declarations (0000-00-00)} -This chapter contains a complete list of Ada 2012 features that have been -implemented as of GNAT version 6.4. Generally, these features are only -available if the @option{-gnat12} (Ada 2012 features enabled) flag is set -@cindex @option{-gnat12} option -or if the configuration pragma @code{Ada_2012} is used. -@cindex pragma @code{Ada_2012} -@cindex configuration pragma @code{Ada_2012} -@cindex @code{Ada_2012} configuration pragma -However, new pragmas, attributes, and restrictions are -unconditionally available, since the Ada 95 standard allows the addition of -new pragmas, attributes, and restrictions (there are exceptions, which are -documented in the individual descriptions), and also certain packages -were made available in earlier versions of Ada. +This AI clarifies that a declaration does not include a context clause, +and confirms that it is illegal to have a context in which both a limited +and a nonlimited view of a package are accessible. Such double visibility +was always rejected by GNAT. -An ISO date (YYYY-MM-DD) appears in parentheses on the description line. -This date shows the implementation date of the feature. Any wavefront -subsequent to this date will contain the indicated feature, as will any -subsequent releases. A date of 0000-00-00 means that GNAT has always -implemented the feature, or implemented it as soon as it appeared as a -binding interpretation. +RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2) +@end itemize -Each feature corresponds to an Ada Issue (``AI'') approved by the Ada -standardization group (ISO/IEC JTC1/SC22/WG9) for inclusion in Ada 2012. -The features are ordered based on the relevant sections of the Ada -Reference Manual (``RM''). When a given AI relates to multiple points -in the RM, the earliest is used. +@geindex AI-0122 (Ada 2012 feature) -A complete description of the AIs may be found in -@url{www.ada-auth.org/ai05-summary.html}. -@itemize @bullet +@itemize * -@item -@emph{AI-0176 Quantified expressions (2010-09-29)} -@cindex AI-0176 (Ada 2012 feature) +@item +@emph{AI-0122 Private with and children of generics (0000-00-00)} -@noindent - Both universally and existentially quantified expressions are implemented. - They use the new syntax for iterators proposed in AI05-139-2, as well as - the standard Ada loop syntax. +This AI clarifies the visibility of private children of generic units within +instantiations of a parent. GNAT has always handled this correctly. -@noindent - RM References: 1.01.04 (12) 2.09 (2/2) 4.04 (7) 4.05.09 (0) +RM References: 10.01.02 (12/2) +@end itemize -@item -@emph{AI-0079 Allow @i{other_format} characters in source (2010-07-10)} -@cindex AI-0079 (Ada 2012 feature) +@geindex AI-0040 (Ada 2012 feature) -@noindent - Wide characters in the unicode category @i{other_format} are now allowed in - source programs between tokens, but not within a token such as an identifier. -@noindent - RM References: 2.01 (4/2) 2.02 (7) +@itemize * -@item -@emph{AI-0091 Do not allow @i{other_format} in identifiers (0000-00-00)} -@cindex AI-0091 (Ada 2012 feature) +@item +@emph{AI-0040 Limited with clauses on descendant (0000-00-00)} -@noindent - Wide characters in the unicode category @i{other_format} are not permitted - within an identifier, since this can be a security problem. The error - message for this case has been improved to be more specific, but GNAT has - never allowed such characters to appear in identifiers. +This AI confirms that a limited with clause in a child unit cannot name +an ancestor of the unit. This has always been checked in GNAT. -@noindent - RM References: 2.03 (3.1/2) 2.03 (4/2) 2.03 (5/2) 2.03 (5.1/2) 2.03 (5.2/2) 2.03 (5.3/2) 2.09 (2/2) +RM References: 10.01.02 (20/2) +@end itemize -@item -@emph{AI-0100 Placement of pragmas (2010-07-01)} -@cindex AI-0100 (Ada 2012 feature) +@geindex AI-0132 (Ada 2012 feature) -@noindent - This AI is an earlier version of AI-163. It simplifies the rules - for legal placement of pragmas. In the case of lists that allow pragmas, if - the list may have no elements, then the list may consist solely of pragmas. -@noindent - RM References: 2.08 (7) +@itemize * -@item -@emph{AI-0163 Pragmas in place of null (2010-07-01)} -@cindex AI-0163 (Ada 2012 feature) +@item +@emph{AI-0132 Placement of library unit pragmas (0000-00-00)} -@noindent - A statement sequence may be composed entirely of pragmas. It is no longer - necessary to add a dummy @code{null} statement to make the sequence legal. +This AI fills a gap in the description of library unit pragmas. The pragma +clearly must apply to a library unit, even if it does not carry the name +of the enclosing unit. GNAT has always enforced the required check. -@noindent - RM References: 2.08 (7) 2.08 (16) +RM References: 10.01.05 (7) +@end itemize +@geindex AI-0034 (Ada 2012 feature) -@item -@emph{AI-0080 ``View of'' not needed if clear from context (0000-00-00)} -@cindex AI-0080 (Ada 2012 feature) -@noindent - This is an editorial change only, described as non-testable in the AI. +@itemize * -@noindent - RM References: 3.01 (7) +@item +@emph{AI-0034 Categorization of limited views (0000-00-00)} +The RM makes certain limited with clauses illegal because of categorization +considerations, when the corresponding normal with would be legal. This is +not intended, and GNAT has always implemented the recommended behavior. -@item -@emph{AI-0183 Aspect specifications (2010-08-16)} -@cindex AI-0183 (Ada 2012 feature) - -@noindent - Aspect specifications have been fully implemented except for pre and post- - conditions, and type invariants, which have their own separate AI's. All - forms of declarations listed in the AI are supported. The following is a - list of the aspects supported (with GNAT implementation aspects marked) - -@multitable {@code{Preelaborable_Initialization}} {--GNAT} -@item @code{Ada_2005} @tab -- GNAT -@item @code{Ada_2012} @tab -- GNAT -@item @code{Address} @tab -@item @code{Alignment} @tab -@item @code{Atomic} @tab -@item @code{Atomic_Components} @tab -@item @code{Bit_Order} @tab -@item @code{Component_Size} @tab -@item @code{Contract_Cases} @tab -- GNAT -@item @code{Discard_Names} @tab -@item @code{External_Tag} @tab -@item @code{Favor_Top_Level} @tab -- GNAT -@item @code{Inline} @tab -@item @code{Inline_Always} @tab -- GNAT -@item @code{Invariant} @tab -- GNAT -@item @code{Machine_Radix} @tab -@item @code{No_Return} @tab -@item @code{Object_Size} @tab -- GNAT -@item @code{Pack} @tab -@item @code{Persistent_BSS} @tab -- GNAT -@item @code{Post} @tab -@item @code{Pre} @tab -@item @code{Predicate} @tab -@item @code{Preelaborable_Initialization} @tab -@item @code{Pure_Function} @tab -- GNAT -@item @code{Remote_Access_Type} @tab -- GNAT -@item @code{Shared} @tab -- GNAT -@item @code{Size} @tab -@item @code{Storage_Pool} @tab -@item @code{Storage_Size} @tab -@item @code{Stream_Size} @tab -@item @code{Suppress} @tab -@item @code{Suppress_Debug_Info} @tab -- GNAT -@item @code{Test_Case} @tab -- GNAT -@item @code{Thread_Local_Storage} @tab -- GNAT -@item @code{Type_Invariant} @tab -@item @code{Unchecked_Union} @tab -@item @code{Universal_Aliasing} @tab -- GNAT -@item @code{Unmodified} @tab -- GNAT -@item @code{Unreferenced} @tab -- GNAT -@item @code{Unreferenced_Objects} @tab -- GNAT -@item @code{Unsuppress} @tab -@item @code{Value_Size} @tab -- GNAT -@item @code{Volatile} @tab -@item @code{Volatile_Components} -@item @code{Warnings} @tab -- GNAT -@end multitable +RM References: 10.02.01 (11/1) 10.02.01 (17/2) +@end itemize -@noindent - Note that for aspects with an expression, e.g. @code{Size}, the expression is - treated like a default expression (visibility is analyzed at the point of - occurrence of the aspect, but evaluation of the expression occurs at the - freeze point of the entity involved). +@geindex AI-0035 (Ada 2012 feature) -@noindent - RM References: 3.02.01 (3) 3.02.02 (2) 3.03.01 (2/2) 3.08 (6) - 3.09.03 (1.1/2) 6.01 (2/2) 6.07 (2/2) 9.05.02 (2/2) 7.01 (3) 7.03 - (2) 7.03 (3) 9.01 (2/2) 9.01 (3/2) 9.04 (2/2) 9.04 (3/2) - 9.05.02 (2/2) 11.01 (2) 12.01 (3) 12.03 (2/2) 12.04 (2/2) 12.05 (2) - 12.06 (2.1/2) 12.06 (2.2/2) 12.07 (2) 13.01 (0.1/2) 13.03 (5/1) - 13.03.01 (0) +@itemize * -@item -@emph{AI-0128 Inequality is a primitive operation (0000-00-00)} -@cindex AI-0128 (Ada 2012 feature) +@item +@emph{AI-0035 Inconsistencies with Pure units (0000-00-00)} -@noindent - If an equality operator ("=") is declared for a type, then the implicitly - declared inequality operator ("/=") is a primitive operation of the type. - This is the only reasonable interpretation, and is the one always implemented - by GNAT, but the RM was not entirely clear in making this point. +This AI remedies some inconsistencies in the legality rules for Pure units. +Derived access types are legal in a pure unit (on the assumption that the +rule for a zero storage pool size has been enforced on the ancestor type). +The rules are enforced in generic instances and in subunits. GNAT has always +implemented the recommended behavior. -@noindent - RM References: 3.02.03 (6) 6.06 (6) +RM References: 10.02.01 (15.1/2) 10.02.01 (15.4/2) 10.02.01 (15.5/2) 10.02.01 (17/2) +@end itemize -@item -@emph{AI-0003 Qualified expressions as names (2010-07-11)} -@cindex AI-0003 (Ada 2012 feature) +@geindex AI-0219 (Ada 2012 feature) -@noindent - In Ada 2012, a qualified expression is considered to be syntactically a name, - meaning that constructs such as @code{A'(F(X)).B} are now legal. This is - useful in disambiguating some cases of overloading. -@noindent - RM References: 3.03 (11) 3.03 (21) 4.01 (2) 4.04 (7) 4.07 (3) - 5.04 (7) +@itemize * -@item -@emph{AI-0120 Constant instance of protected object (0000-00-00)} -@cindex AI-0120 (Ada 2012 feature) +@item +@emph{AI-0219 Pure permissions and limited parameters (2010-05-25)} -@noindent - This is an RM editorial change only. The section that lists objects that are - constant failed to include the current instance of a protected object - within a protected function. This has always been treated as a constant - in GNAT. +This AI refines the rules for the cases with limited parameters which do not +allow the implementations to omit 'redundant'. GNAT now properly conforms +to the requirements of this binding interpretation. -@noindent - RM References: 3.03 (21) +RM References: 10.02.01 (18/2) +@end itemize -@item -@emph{AI-0008 General access to constrained objects (0000-00-00)} -@cindex AI-0008 (Ada 2012 feature) +@geindex AI-0043 (Ada 2012 feature) -@noindent - The wording in the RM implied that if you have a general access to a - constrained object, it could be used to modify the discriminants. This was - obviously not intended. @code{Constraint_Error} should be raised, and GNAT - has always done so in this situation. -@noindent - RM References: 3.03 (23) 3.10.02 (26/2) 4.01 (9) 6.04.01 (17) 8.05.01 (5/2) +@itemize * +@item +@emph{AI-0043 Rules about raising exceptions (0000-00-00)} -@item -@emph{AI-0093 Additional rules use immutably limited (0000-00-00)} -@cindex AI-0093 (Ada 2012 feature) +This AI covers various omissions in the RM regarding the raising of +exceptions. GNAT has always implemented the intended semantics. -@noindent - This is an editorial change only, to make more widespread use of the Ada 2012 - ``immutably limited''. +RM References: 11.04.01 (10.1/2) 11 (2) +@end itemize -@noindent - RM References: 3.03 (23.4/3) +@geindex AI-0200 (Ada 2012 feature) +@itemize * -@item -@emph{AI-0096 Deriving from formal private types (2010-07-20)} -@cindex AI-0096 (Ada 2012 feature) +@item +@emph{AI-0200 Mismatches in formal package declarations (0000-00-00)} -@noindent - In general it is illegal for a type derived from a formal limited type to be - nonlimited. This AI makes an exception to this rule: derivation is legal - if it appears in the private part of the generic, and the formal type is not - tagged. If the type is tagged, the legality check must be applied to the - private part of the package. +This AI plugs a gap in the RM which appeared to allow some obviously intended +illegal instantiations. GNAT has never allowed these instantiations. -@noindent - RM References: 3.04 (5.1/2) 6.02 (7) +RM References: 12.07 (16) +@end itemize +@geindex AI-0112 (Ada 2012 feature) -@item -@emph{AI-0181 Soft hyphen is a non-graphic character (2010-07-23)} -@cindex AI-0181 (Ada 2012 feature) -@noindent - From Ada 2005 on, soft hyphen is considered a non-graphic character, which - means that it has a special name (@code{SOFT_HYPHEN}) in conjunction with the - @code{Image} and @code{Value} attributes for the character types. Strictly - speaking this is an inconsistency with Ada 95, but in practice the use of - these attributes is so obscure that it will not cause problems. +@itemize * -@noindent - RM References: 3.05.02 (2/2) A.01 (35/2) A.03.03 (21) +@item +@emph{AI-0112 Detection of duplicate pragmas (2010-07-24)} +This AI concerns giving names to various representation aspects, but the +practical effect is simply to make the use of duplicate +@cite{Atomic[_Components]}, +@cite{Volatile[_Components]}, and +@cite{Independent[_Components]} pragmas illegal, and GNAT +now performs this required check. -@item -@emph{AI-0182 Additional forms for @code{Character'Value} (0000-00-00)} -@cindex AI-0182 (Ada 2012 feature) +RM References: 13.01 (8) +@end itemize -@noindent - This AI allows @code{Character'Value} to accept the string @code{'?'} where - @code{?} is any character including non-graphic control characters. GNAT has - always accepted such strings. It also allows strings such as - @code{HEX_00000041} to be accepted, but GNAT does not take advantage of this - permission and raises @code{Constraint_Error}, as is certainly still - permitted. +@geindex AI-0106 (Ada 2012 feature) -@noindent - RM References: 3.05 (56/2) +@itemize * -@item -@emph{AI-0214 Defaulted discriminants for limited tagged (2010-10-01)} -@cindex AI-0214 (Ada 2012 feature) +@item +@emph{AI-0106 No representation pragmas on generic formals (0000-00-00)} -@noindent - Ada 2012 relaxes the restriction that forbids discriminants of tagged types - to have default expressions by allowing them when the type is limited. It - is often useful to define a default value for a discriminant even though - it can't be changed by assignment. +The RM appeared to allow representation pragmas on generic formal parameters, +but this was not intended, and GNAT has never permitted this usage. -@noindent - RM References: 3.07 (9.1/2) 3.07.02 (3) +RM References: 13.01 (9.1/1) +@end itemize +@geindex AI-0012 (Ada 2012 feature) -@item -@emph{AI-0102 Some implicit conversions are illegal (0000-00-00)} -@cindex AI-0102 (Ada 2012 feature) -@noindent - It is illegal to assign an anonymous access constant to an anonymous access - variable. The RM did not have a clear rule to prevent this, but GNAT has - always generated an error for this usage. +@itemize * -@noindent - RM References: 3.07 (16) 3.07.01 (9) 6.04.01 (6) 8.06 (27/2) +@item +@emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)} +It is now illegal to give an inappropriate component size or a pragma +@cite{Pack} that attempts to change the component size in the case of atomic +or aliased components. Previously GNAT ignored such an attempt with a +warning. -@item -@emph{AI-0158 Generalizing membership tests (2010-09-16)} -@cindex AI-0158 (Ada 2012 feature) +RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21) +@end itemize -@noindent - This AI extends the syntax of membership tests to simplify complex conditions - that can be expressed as membership in a subset of values of any type. It - introduces syntax for a list of expressions that may be used in loop contexts - as well. +@geindex AI-0039 (Ada 2012 feature) -@noindent - RM References: 3.08.01 (5) 4.04 (3) 4.05.02 (3) 4.05.02 (5) 4.05.02 (27) +@itemize * -@item -@emph{AI-0173 Testing if tags represent abstract types (2010-07-03)} -@cindex AI-0173 (Ada 2012 feature) +@item +@emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)} -@noindent - The function @code{Ada.Tags.Type_Is_Abstract} returns @code{True} if invoked - with the tag of an abstract type, and @code{False} otherwise. +The RM permitted the use of dynamic expressions (such as @code{ptr.all})` +for stream attributes, but these were never useful and are now illegal. GNAT +has always regarded such expressions as illegal. -@noindent - RM References: 3.09 (7.4/2) 3.09 (12.4/2) +RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2) +@end itemize +@geindex AI-0095 (Ada 2012 feature) -@item -@emph{AI-0076 function with controlling result (0000-00-00)} -@cindex AI-0076 (Ada 2012 feature) +@itemize * -@noindent - This is an editorial change only. The RM defines calls with controlling - results, but uses the term ``function with controlling result'' without an - explicit definition. +@item +@emph{AI-0095 Address of intrinsic subprograms (0000-00-00)} -@noindent - RM References: 3.09.02 (2/2) +The prefix of @cite{'Address} cannot statically denote a subprogram with +convention @cite{Intrinsic}. The use of the @cite{Address} attribute raises +@cite{Program_Error} if the prefix denotes a subprogram with convention +@cite{Intrinsic}. +RM References: 13.03 (11/1) +@end itemize -@item -@emph{AI-0126 Dispatching with no declared operation (0000-00-00)} -@cindex AI-0126 (Ada 2012 feature) +@geindex AI-0116 (Ada 2012 feature) -@noindent - This AI clarifies dispatching rules, and simply confirms that dispatching - executes the operation of the parent type when there is no explicitly or - implicitly declared operation for the descendant type. This has always been - the case in all versions of GNAT. -@noindent - RM References: 3.09.02 (20/2) 3.09.02 (20.1/2) 3.09.02 (20.2/2) +@itemize * +@item +@emph{AI-0116 Alignment of class-wide objects (0000-00-00)} -@item -@emph{AI-0097 Treatment of abstract null extension (2010-07-19)} -@cindex AI-0097 (Ada 2012 feature) +This AI requires that the alignment of a class-wide object be no greater +than the alignment of any type in the class. GNAT has always followed this +recommendation. -@noindent - The RM as written implied that in some cases it was possible to create an - object of an abstract type, by having an abstract extension inherit a non- - abstract constructor from its parent type. This mistake has been corrected - in GNAT and in the RM, and this construct is now illegal. +RM References: 13.03 (29) 13.11 (16) +@end itemize -@noindent - RM References: 3.09.03 (4/2) +@geindex AI-0146 (Ada 2012 feature) -@item -@emph{AI-0203 Extended return cannot be abstract (0000-00-00)} -@cindex AI-0203 (Ada 2012 feature) +@itemize * -@noindent - A return_subtype_indication cannot denote an abstract subtype. GNAT has never - permitted such usage. +@item +@emph{AI-0146 Type invariants (2009-09-21)} -@noindent - RM References: 3.09.03 (8/3) +Type invariants may be specified for private types using the aspect notation. +Aspect @cite{Type_Invariant} may be specified for any private type, +@cite{Type_Invariant'Class} can +only be specified for tagged types, and is inherited by any descendent of the +tagged types. The invariant is a boolean expression that is tested for being +true in the following situations: conversions to the private type, object +declarations for the private type that are default initialized, and +[@strong{in}] @strong{out} +parameters and returned result on return from any primitive operation for +the type that is visible to a client. +GNAT defines the synonyms @cite{Invariant} for @cite{Type_Invariant} and +@cite{Invariant'Class} for @cite{Type_Invariant'Class}. + +RM References: 13.03.03 (00) +@end itemize +@geindex AI-0078 (Ada 2012 feature) -@item -@emph{AI-0198 Inheriting abstract operators (0000-00-00)} -@cindex AI-0198 (Ada 2012 feature) -@noindent - This AI resolves a conflict between two rules involving inherited abstract - operations and predefined operators. If a derived numeric type inherits - an abstract operator, it overrides the predefined one. This interpretation - was always the one implemented in GNAT. +@itemize * -@noindent - RM References: 3.09.03 (4/3) +@item +@emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)} -@item -@emph{AI-0073 Functions returning abstract types (2010-07-10)} -@cindex AI-0073 (Ada 2012 feature) +In Ada 2012, compilers are required to support unchecked conversion where the +target alignment is a multiple of the source alignment. GNAT always supported +this case (and indeed all cases of differing alignments, doing copies where +required if the alignment was reduced). -@noindent - This AI covers a number of issues regarding returning abstract types. In - particular generic functions cannot have abstract result types or access - result types designated an abstract type. There are some other cases which - are detailed in the AI. Note that this binding interpretation has not been - retrofitted to operate before Ada 2012 mode, since it caused a significant - number of regressions. +RM References: 13.09 (7) +@end itemize -@noindent - RM References: 3.09.03 (8) 3.09.03 (10) 6.05 (8/2) +@geindex AI-0195 (Ada 2012 feature) -@item -@emph{AI-0070 Elaboration of interface types (0000-00-00)} -@cindex AI-0070 (Ada 2012 feature) +@itemize * -@noindent - This is an editorial change only, there are no testable consequences short of - checking for the absence of generated code for an interface declaration. +@item +@emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)} -@noindent - RM References: 3.09.04 (18/2) +The handling of invalid values is now designated to be implementation +defined. This is a documentation change only, requiring Annex M in the GNAT +Reference Manual to document this handling. +In GNAT, checks for invalid values are made +only when necessary to avoid erroneous behavior. Operations like assignments +which cannot cause erroneous behavior ignore the possibility of invalid +values and do not do a check. The date given above applies only to the +documentation change, this behavior has always been implemented by GNAT. +RM References: 13.09.01 (10) +@end itemize -@item -@emph{AI-0208 Characteristics of incomplete views (0000-00-00)} -@cindex AI-0208 (Ada 2012 feature) +@geindex AI-0193 (Ada 2012 feature) -@noindent - The wording in the Ada 2005 RM concerning characteristics of incomplete views - was incorrect and implied that some programs intended to be legal were now - illegal. GNAT had never considered such programs illegal, so it has always - implemented the intent of this AI. -@noindent - RM References: 3.10.01 (2.4/2) 3.10.01 (2.6/2) +@itemize * +@item +@emph{AI-0193 Alignment of allocators (2010-09-16)} -@item -@emph{AI-0162 Incomplete type completed by partial view (2010-09-15)} -@cindex AI-0162 (Ada 2012 feature) +This AI introduces a new attribute @cite{Max_Alignment_For_Allocation}, +analogous to @cite{Max_Size_In_Storage_Elements}, but for alignment instead +of size. -@noindent - Incomplete types are made more useful by allowing them to be completed by - private types and private extensions. +RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1) +13.11.01 (2) 13.11.01 (3) +@end itemize -@noindent - RM References: 3.10.01 (2.5/2) 3.10.01 (2.6/2) 3.10.01 (3) 3.10.01 (4/2) +@geindex AI-0177 (Ada 2012 feature) +@itemize * -@item -@emph{AI-0098 Anonymous subprogram access restrictions (0000-00-00)} -@cindex AI-0098 (Ada 2012 feature) +@item +@emph{AI-0177 Parameterized expressions (2010-07-10)} -@noindent - An unintentional omission in the RM implied some inconsistent restrictions on - the use of anonymous access to subprogram values. These restrictions were not - intentional, and have never been enforced by GNAT. +The new Ada 2012 notion of parameterized expressions is implemented. The form +is: -@noindent - RM References: 3.10.01 (6) 3.10.01 (9.2/2) +@example +function-specification is (expression) +@end example +This is exactly equivalent to the +corresponding function body that returns the expression, but it can appear +in a package spec. Note that the expression must be parenthesized. -@item -@emph{AI-0199 Aggregate with anonymous access components (2010-07-14)} -@cindex AI-0199 (Ada 2012 feature) +RM References: 13.11.01 (3/2) +@end itemize -@noindent - A choice list in a record aggregate can include several components of - (distinct) anonymous access types as long as they have matching designated - subtypes. +@geindex AI-0033 (Ada 2012 feature) -@noindent - RM References: 4.03.01 (16) +@itemize * -@item -@emph{AI-0220 Needed components for aggregates (0000-00-00)} -@cindex AI-0220 (Ada 2012 feature) +@item +@emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)} -@noindent - This AI addresses a wording problem in the RM that appears to permit some - complex cases of aggregates with non-static discriminants. GNAT has always - implemented the intended semantics. +Neither of these two pragmas may appear within a generic template, because +the generic might be instantiated at other than the library level. -@noindent - RM References: 4.03.01 (17) +RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2) +@end itemize -@item -@emph{AI-0147 Conditional expressions (2009-03-29)} -@cindex AI-0147 (Ada 2012 feature) +@geindex AI-0161 (Ada 2012 feature) -@noindent - Conditional expressions are permitted. The form of such an expression is: -@smallexample - (@b{if} @i{expr} @b{then} @i{expr} @{@b{elsif} @i{expr} @b{then} @i{expr}@} [@b{else} @i{expr}]) -@end smallexample +@itemize * - The parentheses can be omitted in contexts where parentheses are present - anyway, such as subprogram arguments and pragma arguments. If the @b{else} - clause is omitted, @b{else True} is assumed; - thus @code{(@b{if} A @b{then} B)} is a way to conveniently represent - @emph{(A implies B)} in standard logic. +@item +@emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)} -@noindent - RM References: 4.03.03 (15) 4.04 (1) 4.04 (7) 4.05.07 (0) 4.07 (2) - 4.07 (3) 4.09 (12) 4.09 (33) 5.03 (3) 5.03 (4) 7.05 (2.1/2) +A new restriction @cite{No_Default_Stream_Attributes} prevents the use of any +of the default stream attributes for elementary types. If this restriction is +in force, then it is necessary to provide explicit subprograms for any +stream attributes used. +RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2) +@end itemize -@item -@emph{AI-0037 Out-of-range box associations in aggregate (0000-00-00)} -@cindex AI-0037 (Ada 2012 feature) +@geindex AI-0194 (Ada 2012 feature) -@noindent - This AI confirms that an association of the form @code{Indx => <>} in an - array aggregate must raise @code{Constraint_Error} if @code{Indx} - is out of range. The RM specified a range check on other associations, but - not when the value of the association was defaulted. GNAT has always inserted - a constraint check on the index value. -@noindent - RM References: 4.03.03 (29) +@itemize * +@item +@emph{AI-0194 Value of Stream_Size attribute (0000-00-00)} -@item -@emph{AI-0123 Composability of equality (2010-04-13)} -@cindex AI-0123 (Ada 2012 feature) +The @cite{Stream_Size} attribute returns the default number of bits in the +stream representation of the given type. +This value is not affected by the presence +of stream subprogram attributes for the type. GNAT has always implemented +this interpretation. -@noindent - Equality of untagged record composes, so that the predefined equality for a - composite type that includes a component of some untagged record type - @code{R} uses the equality operation of @code{R} (which may be user-defined - or predefined). This makes the behavior of untagged records identical to that - of tagged types in this respect. +RM References: 13.13.02 (1.2/2) +@end itemize - This change is an incompatibility with previous versions of Ada, but it - corrects a non-uniformity that was often a source of confusion. Analysis of - a large number of industrial programs indicates that in those rare cases - where a composite type had an untagged record component with a user-defined - equality, either there was no use of the composite equality, or else the code - expected the same composability as for tagged types, and thus had a bug that - would be fixed by this change. +@geindex AI-0109 (Ada 2012 feature) -@noindent - RM References: 4.05.02 (9.7/2) 4.05.02 (14) 4.05.02 (15) 4.05.02 (24) - 8.05.04 (8) +@itemize * -@item -@emph{AI-0088 The value of exponentiation (0000-00-00)} -@cindex AI-0088 (Ada 2012 feature) +@item +@emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)} -@noindent - This AI clarifies the equivalence rule given for the dynamic semantics of - exponentiation: the value of the operation can be obtained by repeated - multiplication, but the operation can be implemented otherwise (for example - using the familiar divide-by-two-and-square algorithm, even if this is less - accurate), and does not imply repeated reads of a volatile base. +This AI is an editorial change only. It removes the need for a tag check +that can never fail. -@noindent - RM References: 4.05.06 (11) +RM References: 13.13.02 (34/2) +@end itemize -@item -@emph{AI-0188 Case expressions (2010-01-09)} -@cindex AI-0188 (Ada 2012 feature) +@geindex AI-0007 (Ada 2012 feature) -@noindent - Case expressions are permitted. This allows use of constructs such as: -@smallexample - X := (@b{case} Y @b{is when} 1 => 2, @b{when} 2 => 3, @b{when others} => 31) -@end smallexample -@noindent - RM References: 4.05.07 (0) 4.05.08 (0) 4.09 (12) 4.09 (33) +@itemize * -@item -@emph{AI-0104 Null exclusion and uninitialized allocator (2010-07-15)} -@cindex AI-0104 (Ada 2012 feature) +@item +@emph{AI-0007 Stream read and private scalar types (0000-00-00)} -@noindent - The assignment @code{Ptr := @b{new not null} Some_Ptr;} will raise - @code{Constraint_Error} because the default value of the allocated object is - @b{null}. This useless construct is illegal in Ada 2012. +The RM as written appeared to limit the possibilities of declaring read +attribute procedures for private scalar types. This limitation was not +intended, and has never been enforced by GNAT. -@noindent - RM References: 4.08 (2) +RM References: 13.13.02 (50/2) 13.13.02 (51/2) +@end itemize -@item -@emph{AI-0157 Allocation/Deallocation from empty pool (2010-07-11)} -@cindex AI-0157 (Ada 2012 feature) +@geindex AI-0065 (Ada 2012 feature) -@noindent - Allocation and Deallocation from an empty storage pool (i.e. allocation or - deallocation of a pointer for which a static storage size clause of zero - has been given) is now illegal and is detected as such. GNAT - previously gave a warning but not an error. -@noindent - RM References: 4.08 (5.3/2) 13.11.02 (4) 13.11.02 (17) +@itemize * -@item -@emph{AI-0179 Statement not required after label (2010-04-10)} -@cindex AI-0179 (Ada 2012 feature) +@item +@emph{AI-0065 Remote access types and external streaming (0000-00-00)} -@noindent - It is not necessary to have a statement following a label, so a label - can appear at the end of a statement sequence without the need for putting a - null statement afterwards, but it is not allowable to have only labels and - no real statements in a statement sequence. +This AI clarifies the fact that all remote access types support external +streaming. This fixes an obvious oversight in the definition of the +language, and GNAT always implemented the intended correct rules. -@noindent - RM References: 5.01 (2) +RM References: 13.13.02 (52/2) +@end itemize +@geindex AI-0019 (Ada 2012 feature) -@item -@emph{AI-139-2 Syntactic sugar for iterators (2010-09-29)} -@cindex AI-139-2 (Ada 2012 feature) -@noindent - The new syntax for iterating over arrays and containers is now implemented. - Iteration over containers is for now limited to read-only iterators. Only - default iterators are supported, with the syntax: @code{@b{for} Elem @b{of} C}. +@itemize * -@noindent - RM References: 5.05 +@item +@emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)} -@item -@emph{AI-0134 Profiles must match for full conformance (0000-00-00)} -@cindex AI-0134 (Ada 2012 feature) +The RM suggests that primitive subprograms of a specific tagged type are +frozen when the tagged type is frozen. This would be an incompatible change +and is not intended. GNAT has never attempted this kind of freezing and its +behavior is consistent with the recommendation of this AI. -@noindent - For full conformance, the profiles of anonymous-access-to-subprogram - parameters must match. GNAT has always enforced this rule. +RM References: 13.14 (2) 13.14 (3/1) 13.14 (8.1/1) 13.14 (10) 13.14 (14) 13.14 (15.1/2) +@end itemize -@noindent - RM References: 6.03.01 (18) +@geindex AI-0017 (Ada 2012 feature) -@item -@emph{AI-0207 Mode conformance and access constant (0000-00-00)} -@cindex AI-0207 (Ada 2012 feature) -@noindent - This AI confirms that access_to_constant indication must match for mode - conformance. This was implemented in GNAT when the qualifier was originally - introduced in Ada 2005. +@itemize * -@noindent - RM References: 6.03.01 (16/2) +@item +@emph{AI-0017 Freezing and incomplete types (0000-00-00)} +So-called 'Taft-amendment types' (i.e., types that are completed in package +bodies) are not frozen by the occurrence of bodies in the +enclosing declarative part. GNAT always implemented this properly. -@item -@emph{AI-0046 Null exclusion match for full conformance (2010-07-17)} -@cindex AI-0046 (Ada 2012 feature) +RM References: 13.14 (3/1) +@end itemize -@noindent - For full conformance, in the case of access parameters, the null exclusion - must match (either both or neither must have @code{@b{not null}}). +@geindex AI-0060 (Ada 2012 feature) -@noindent - RM References: 6.03.02 (18) +@itemize * -@item -@emph{AI-0118 The association of parameter associations (0000-00-00)} -@cindex AI-0118 (Ada 2012 feature) +@item +@emph{AI-0060 Extended definition of remote access types (0000-00-00)} + +This AI extends the definition of remote access types to include access +to limited, synchronized, protected or task class-wide interface types. +GNAT already implemented this extension. -@noindent - This AI clarifies the rules for named associations in subprogram calls and - generic instantiations. The rules have been in place since Ada 83. +RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18) +@end itemize -@noindent - RM References: 6.04.01 (2) 12.03 (9) +@geindex AI-0114 (Ada 2012 feature) -@item -@emph{AI-0196 Null exclusion tests for out parameters (0000-00-00)} -@cindex AI-0196 (Ada 2012 feature) +@itemize * -@noindent - Null exclusion checks are not made for @code{@b{out}} parameters when - evaluating the actual parameters. GNAT has never generated these checks. +@item +@emph{AI-0114 Classification of letters (0000-00-00)} -@noindent - RM References: 6.04.01 (13) +The code points 170 (@cite{FEMININE ORDINAL INDICATOR}), +181 (@cite{MICRO SIGN}), and +186 (@cite{MASCULINE ORDINAL INDICATOR}) are technically considered +lower case letters by Unicode. +However, they are not allowed in identifiers, and they +return @cite{False} to @cite{Ada.Characters.Handling.Is_Letter/Is_Lower}. +This behavior is consistent with that defined in Ada 95. -@item -@emph{AI-0015 Constant return objects (0000-00-00)} -@cindex AI-0015 (Ada 2012 feature) +RM References: A.03.02 (59) A.04.06 (7) +@end itemize -@noindent - The return object declared in an @i{extended_return_statement} may be - declared constant. This was always intended, and GNAT has always allowed it. +@geindex AI-0185 (Ada 2012 feature) -@noindent - RM References: 6.05 (2.1/2) 3.03 (10/2) 3.03 (21) 6.05 (5/2) - 6.05 (5.7/2) +@itemize * -@item -@emph{AI-0032 Extended return for class-wide functions (0000-00-00)} -@cindex AI-0032 (Ada 2012 feature) +@item +@emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)} -@noindent - If a function returns a class-wide type, the object of an extended return - statement can be declared with a specific type that is covered by the class- - wide type. This has been implemented in GNAT since the introduction of - extended returns. Note AI-0103 complements this AI by imposing matching - rules for constrained return types. +Two new packages @cite{Ada.Wide_[Wide_]Characters.Handling} provide +classification functions for @cite{Wide_Character} and +@cite{Wide_Wide_Character}, as well as providing +case folding routines for @cite{Wide_[Wide_]Character} and +@cite{Wide_[Wide_]String}. -@noindent - RM References: 6.05 (5.2/2) 6.05 (5.3/2) 6.05 (5.6/2) 6.05 (5.8/2) - 6.05 (8/2) +RM References: A.03.05 (0) A.03.06 (0) +@end itemize -@item -@emph{AI-0103 Static matching for extended return (2010-07-23)} -@cindex AI-0103 (Ada 2012 feature) +@geindex AI-0031 (Ada 2012 feature) -@noindent - If the return subtype of a function is an elementary type or a constrained - type, the subtype indication in an extended return statement must match - statically this return subtype. -@noindent - RM References: 6.05 (5.2/2) +@itemize * +@item +@emph{AI-0031 Add From parameter to Find_Token (2010-07-25)} -@item -@emph{AI-0058 Abnormal completion of an extended return (0000-00-00)} -@cindex AI-0058 (Ada 2012 feature) +A new version of @cite{Find_Token} is added to all relevant string packages, +with an extra parameter @cite{From}. Instead of starting at the first +character of the string, the search for a matching Token starts at the +character indexed by the value of @cite{From}. +These procedures are available in all versions of Ada +but if used in versions earlier than Ada 2012 they will generate a warning +that an Ada 2012 subprogram is being used. -@noindent - The RM had some incorrect wording implying wrong treatment of abnormal - completion in an extended return. GNAT has always implemented the intended - correct semantics as described by this AI. +RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51) +A.04.05 (46) +@end itemize -@noindent - RM References: 6.05 (22/2) +@geindex AI-0056 (Ada 2012 feature) -@item -@emph{AI-0050 Raising Constraint_Error early for function call (0000-00-00)} -@cindex AI-0050 (Ada 2012 feature) +@itemize * -@noindent - The implementation permissions for raising @code{Constraint_Error} early on a function call when it was clear an exception would be raised were over-permissive and allowed mishandling of discriminants in some cases. GNAT did - not take advantage of these incorrect permissions in any case. +@item +@emph{AI-0056 Index on null string returns zero (0000-00-00)} -@noindent - RM References: 6.05 (24/2) +The wording in the Ada 2005 RM implied an incompatible handling of the +@cite{Index} functions, resulting in raising an exception instead of +returning zero in some situations. +This was not intended and has been corrected. +GNAT always returned zero, and is thus consistent with this AI. +RM References: A.04.03 (56.2/2) A.04.03 (58.5/2) +@end itemize -@item -@emph{AI-0125 Nonoverridable operations of an ancestor (2010-09-28)} -@cindex AI-0125 (Ada 2012 feature) +@geindex AI-0137 (Ada 2012 feature) -@noindent - In Ada 2012, the declaration of a primitive operation of a type extension - or private extension can also override an inherited primitive that is not - visible at the point of this declaration. -@noindent - RM References: 7.03.01 (6) 8.03 (23) 8.03.01 (5/2) 8.03.01 (6/2) +@itemize * -@item -@emph{AI-0062 Null exclusions and deferred constants (0000-00-00)} -@cindex AI-0062 (Ada 2012 feature) +@item +@emph{AI-0137 String encoding package (2010-03-25)} -@noindent - A full constant may have a null exclusion even if its associated deferred - constant does not. GNAT has always allowed this. +The packages @cite{Ada.Strings.UTF_Encoding}, together with its child +packages, @cite{Conversions}, @cite{Strings}, @cite{Wide_Strings}, +and @cite{Wide_Wide_Strings} have been +implemented. These packages (whose documentation can be found in the spec +files @code{a-stuten.ads}, @code{a-suenco.ads}, @code{a-suenst.ads}, +@code{a-suewst.ads}, @code{a-suezst.ads}) allow encoding and decoding of +@cite{String}, @cite{Wide_String}, and @cite{Wide_Wide_String} +values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and +UTF-16), as well as conversions between the different UTF encodings. With +the exception of @cite{Wide_Wide_Strings}, these packages are available in +Ada 95 and Ada 2005 mode as well as Ada 2012 mode. +The @cite{Wide_Wide_Strings package} +is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95 +mode since it uses @cite{Wide_Wide_Character}). + +RM References: A.04.11 +@end itemize -@noindent - RM References: 7.04 (6/2) 7.04 (7.1/2) +@geindex AI-0038 (Ada 2012 feature) -@item -@emph{AI-0178 Incomplete views are limited (0000-00-00)} -@cindex AI-0178 (Ada 2012 feature) +@itemize * -@noindent - This AI clarifies the role of incomplete views and plugs an omission in the - RM. GNAT always correctly restricted the use of incomplete views and types. +@item +@emph{AI-0038 Minor errors in Text_IO (0000-00-00)} -@noindent - RM References: 7.05 (3/2) 7.05 (6/2) +These are minor errors in the description on three points. The intent on +all these points has always been clear, and GNAT has always implemented the +correct intended semantics. -@item -@emph{AI-0087 Actual for formal nonlimited derived type (2010-07-15)} -@cindex AI-0087 (Ada 2012 feature) +RM References: A.10.05 (37) A.10.07 (8/1) A.10.07 (10) A.10.07 (12) A.10.08 (10) A.10.08 (24) +@end itemize -@noindent - The actual for a formal nonlimited derived type cannot be limited. In - particular, a formal derived type that extends a limited interface but which - is not explicitly limited cannot be instantiated with a limited type. +@geindex AI-0044 (Ada 2012 feature) -@noindent - RM References: 7.05 (5/2) 12.05.01 (5.1/2) -@item -@emph{AI-0099 Tag determines whether finalization needed (0000-00-00)} -@cindex AI-0099 (Ada 2012 feature) +@itemize * -@noindent - This AI clarifies that ``needs finalization'' is part of dynamic semantics, - and therefore depends on the run-time characteristics of an object (i.e. its - tag) and not on its nominal type. As the AI indicates: ``we do not expect - this to affect any implementation''. +@item +@emph{AI-0044 Restrictions on container instantiations (0000-00-00)} -@noindent - RM References: 7.06.01 (6) 7.06.01 (7) 7.06.01 (8) 7.06.01 (9/2) +This AI places restrictions on allowed instantiations of generic containers. +These restrictions are not checked by the compiler, so there is nothing to +change in the implementation. This affects only the RM documentation. +RM References: A.18 (4/2) A.18.02 (231/2) A.18.03 (145/2) A.18.06 (56/2) A.18.08 (66/2) A.18.09 (79/2) A.18.26 (5/2) A.18.26 (9/2) +@end itemize +@geindex AI-0127 (Ada 2012 feature) -@item -@emph{AI-0064 Redundant finalization rule (0000-00-00)} -@cindex AI-0064 (Ada 2012 feature) -@noindent - This is an editorial change only. The intended behavior is already checked - by an existing ACATS test, which GNAT has always executed correctly. +@itemize * -@noindent - RM References: 7.06.01 (17.1/1) +@item +@emph{AI-0127 Adding Locale Capabilities (2010-09-29)} -@item -@emph{AI-0026 Missing rules for Unchecked_Union (2010-07-07)} -@cindex AI-0026 (Ada 2012 feature) +This package provides an interface for identifying the current locale. -@noindent - Record representation clauses concerning Unchecked_Union types cannot mention - the discriminant of the type. The type of a component declared in the variant - part of an Unchecked_Union cannot be controlled, have controlled components, - nor have protected or task parts. If an Unchecked_Union type is declared - within the body of a generic unit or its descendants, then the type of a - component declared in the variant part cannot be a formal private type or a - formal private extension declared within the same generic unit. +RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06 +A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13 +@end itemize -@noindent - RM References: 7.06 (9.4/2) B.03.03 (9/2) B.03.03 (10/2) +@geindex AI-0002 (Ada 2012 feature) -@item -@emph{AI-0205 Extended return declares visible name (0000-00-00)} -@cindex AI-0205 (Ada 2012 feature) +@itemize * -@noindent - This AI corrects a simple omission in the RM. Return objects have always - been visible within an extended return statement. +@item +@emph{AI-0002 Export C with unconstrained arrays (0000-00-00)} -@noindent - RM References: 8.03 (17) +The compiler is not required to support exporting an Ada subprogram with +convention C if there are parameters or a return type of an unconstrained +array type (such as @cite{String}). GNAT allows such declarations but +generates warnings. It is possible, but complicated, to write the +corresponding C code and certainly such code would be specific to GNAT and +non-portable. +RM References: B.01 (17) B.03 (62) B.03 (71.1/2) +@end itemize -@item -@emph{AI-0042 Overriding versus implemented-by (0000-00-00)} -@cindex AI-0042 (Ada 2012 feature) +@geindex AI05-0216 (Ada 2012 feature) -@noindent - This AI fixes a wording gap in the RM. An operation of a synchronized - interface can be implemented by a protected or task entry, but the abstract - operation is not being overridden in the usual sense, and it must be stated - separately that this implementation is legal. This has always been the case - in GNAT. -@noindent - RM References: 9.01 (9.2/2) 9.04 (11.1/2) +@itemize * -@item -@emph{AI-0030 Requeue on synchronized interfaces (2010-07-19)} -@cindex AI-0030 (Ada 2012 feature) +@item +@emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)} -@noindent - Requeue is permitted to a protected, synchronized or task interface primitive - providing it is known that the overriding operation is an entry. Otherwise - the requeue statement has the same effect as a procedure call. Use of pragma - @code{Implemented} provides a way to impose a static requirement on the - overriding operation by adhering to one of the implementation kinds: entry, - protected procedure or any of the above. +It is clearly the intention that @cite{No_Task_Hierarchy} is intended to +forbid tasks declared locally within subprograms, or functions returning task +objects, and that is the implementation that GNAT has always provided. +However the language in the RM was not sufficiently clear on this point. +Thus this is a documentation change in the RM only. -@noindent - RM References: 9.05 (9) 9.05.04 (2) 9.05.04 (3) 9.05.04 (5) - 9.05.04 (6) 9.05.04 (7) 9.05.04 (12) +RM References: D.07 (3/3) +@end itemize +@geindex AI-0211 (Ada 2012 feature) -@item -@emph{AI-0201 Independence of atomic object components (2010-07-22)} -@cindex AI-0201 (Ada 2012 feature) -@noindent - If an Atomic object has a pragma @code{Pack} or a @code{Component_Size} - attribute, then individual components may not be addressable by independent - tasks. However, if the representation clause has no effect (is confirming), - then independence is not compromised. Furthermore, in GNAT, specification of - other appropriately addressable component sizes (e.g. 16 for 8-bit - characters) also preserves independence. GNAT now gives very clear warnings - both for the declaration of such a type, and for any assignment to its components. +@itemize * -@noindent - RM References: 9.10 (1/3) C.06 (22/2) C.06 (23/2) +@item +@emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)} -@item -@emph{AI-0009 Pragma Independent[_Components] (2010-07-23)} -@cindex AI-0009 (Ada 2012 feature) +The restriction @cite{No_Relative_Delays} forbids any calls to the subprogram +@cite{Ada.Real_Time.Timing_Events.Set_Handler}. -@noindent - This AI introduces the new pragmas @code{Independent} and - @code{Independent_Components}, - which control guaranteeing independence of access to objects and components. - The AI also requires independence not unaffected by confirming rep clauses. +RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2) +@end itemize -@noindent - RM References: 9.10 (1) 13.01 (15/1) 13.02 (9) 13.03 (13) C.06 (2) - C.06 (4) C.06 (6) C.06 (9) C.06 (13) C.06 (14) +@geindex AI-0190 (Ada 2012 feature) -@item -@emph{AI-0072 Task signalling using 'Terminated (0000-00-00)} -@cindex AI-0072 (Ada 2012 feature) +@itemize * -@noindent - This AI clarifies that task signalling for reading @code{'Terminated} only - occurs if the result is True. GNAT semantics has always been consistent with - this notion of task signalling. +@item +@emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)} -@noindent - RM References: 9.10 (6.1/1) +This AI introduces a new pragma @cite{Default_Storage_Pool}, which can be +used to control storage pools globally. +In particular, you can force every access +type that is used for allocation (@strong{new}) to have an explicit storage pool, +or you can declare a pool globally to be used for all access types that lack +an explicit one. -@item -@emph{AI-0108 Limited incomplete view and discriminants (0000-00-00)} -@cindex AI-0108 (Ada 2012 feature) +RM References: D.07 (8) +@end itemize -@noindent - This AI confirms that an incomplete type from a limited view does not have - discriminants. This has always been the case in GNAT. +@geindex AI-0189 (Ada 2012 feature) -@noindent - RM References: 10.01.01 (12.3/2) -@item -@emph{AI-0129 Limited views and incomplete types (0000-00-00)} -@cindex AI-0129 (Ada 2012 feature) +@itemize * -@noindent - This AI clarifies the description of limited views: a limited view of a - package includes only one view of a type that has an incomplete declaration - and a full declaration (there is no possible ambiguity in a client package). - This AI also fixes an omission: a nested package in the private part has no - limited view. GNAT always implemented this correctly. +@item +@emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)} -@noindent - RM References: 10.01.01 (12.2/2) 10.01.01 (12.3/2) +This AI introduces a new restriction @cite{No_Allocators_After_Elaboration}, +which says that no dynamic allocation will occur once elaboration is +completed. +In general this requires a run-time check, which is not required, and which +GNAT does not attempt. But the static cases of allocators in a task body or +in the body of the main program are detected and flagged at compile or bind +time. +RM References: D.07 (19.1/2) H.04 (23.3/2) +@end itemize +@geindex AI-0171 (Ada 2012 feature) -@item -@emph{AI-0077 Limited withs and scope of declarations (0000-00-00)} -@cindex AI-0077 (Ada 2012 feature) -@noindent - This AI clarifies that a declaration does not include a context clause, - and confirms that it is illegal to have a context in which both a limited - and a nonlimited view of a package are accessible. Such double visibility - was always rejected by GNAT. +@itemize * -@noindent - RM References: 10.01.02 (12/2) 10.01.02 (21/2) 10.01.02 (22/2) +@item +@emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)} -@item -@emph{AI-0122 Private with and children of generics (0000-00-00)} -@cindex AI-0122 (Ada 2012 feature) +A new package @cite{System.Multiprocessors} is added, together with the +definition of pragma @cite{CPU} for controlling task affinity. A new no +dependence restriction, on @cite{System.Multiprocessors.Dispatching_Domains}, +is added to the Ravenscar profile. -@noindent - This AI clarifies the visibility of private children of generic units within - instantiations of a parent. GNAT has always handled this correctly. +RM References: D.13.01 (4/2) D.16 +@end itemize -@noindent - RM References: 10.01.02 (12/2) +@geindex AI-0210 (Ada 2012 feature) +@itemize * -@item -@emph{AI-0040 Limited with clauses on descendant (0000-00-00)} -@cindex AI-0040 (Ada 2012 feature) +@item +@emph{AI-0210 Correct Timing_Events metric (0000-00-00)} -@noindent - This AI confirms that a limited with clause in a child unit cannot name - an ancestor of the unit. This has always been checked in GNAT. +This is a documentation only issue regarding wording of metric requirements, +that does not affect the implementation of the compiler. -@noindent - RM References: 10.01.02 (20/2) +RM References: D.15 (24/2) +@end itemize -@item -@emph{AI-0132 Placement of library unit pragmas (0000-00-00)} -@cindex AI-0132 (Ada 2012 feature) +@geindex AI-0206 (Ada 2012 feature) -@noindent - This AI fills a gap in the description of library unit pragmas. The pragma - clearly must apply to a library unit, even if it does not carry the name - of the enclosing unit. GNAT has always enforced the required check. -@noindent - RM References: 10.01.05 (7) +@itemize * +@item +@emph{AI-0206 Remote types packages and preelaborate (2010-07-24)} -@item -@emph{AI-0034 Categorization of limited views (0000-00-00)} -@cindex AI-0034 (Ada 2012 feature) +Remote types packages are now allowed to depend on preelaborated packages. +This was formerly considered illegal. -@noindent - The RM makes certain limited with clauses illegal because of categorization - considerations, when the corresponding normal with would be legal. This is - not intended, and GNAT has always implemented the recommended behavior. +RM References: E.02.02 (6) +@end itemize -@noindent - RM References: 10.02.01 (11/1) 10.02.01 (17/2) +@geindex AI-0152 (Ada 2012 feature) -@item -@emph{AI-0035 Inconsistencies with Pure units (0000-00-00)} -@cindex AI-0035 (Ada 2012 feature) +@itemize * -@noindent - This AI remedies some inconsistencies in the legality rules for Pure units. - Derived access types are legal in a pure unit (on the assumption that the - rule for a zero storage pool size has been enforced on the ancestor type). - The rules are enforced in generic instances and in subunits. GNAT has always - implemented the recommended behavior. +@item +@emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)} -@noindent - RM References: 10.02.01 (15.1/2) 10.02.01 (15.4/2) 10.02.01 (15.5/2) 10.02.01 (17/2) +Restriction @cite{No_Anonymous_Allocators} prevents the use of allocators +where the type of the returned value is an anonymous access type. +RM References: H.04 (8/1) +@end itemize -@item -@emph{AI-0219 Pure permissions and limited parameters (2010-05-25)} -@cindex AI-0219 (Ada 2012 feature) +@node Obsolescent Features,Compatibility and Porting Guide,Implementation of Ada 2012 Features,Top +@anchor{gnat_rm/obsolescent_features id1}@anchor{3c7}@anchor{gnat_rm/obsolescent_features doc}@anchor{3c8}@anchor{gnat_rm/obsolescent_features obsolescent-features}@anchor{15} +@chapter Obsolescent Features -@noindent - This AI refines the rules for the cases with limited parameters which do not - allow the implementations to omit ``redundant''. GNAT now properly conforms - to the requirements of this binding interpretation. -@noindent - RM References: 10.02.01 (18/2) +This chapter describes features that are provided by GNAT, but are +considered obsolescent since there are preferred ways of achieving +the same effect. These features are provided solely for historical +compatibility purposes. -@item -@emph{AI-0043 Rules about raising exceptions (0000-00-00)} -@cindex AI-0043 (Ada 2012 feature) +@menu +* pragma No_Run_Time:: +* pragma Ravenscar:: +* pragma Restricted_Run_Time:: +* pragma Task_Info:: +* package System.Task_Info (s-tasinf.ads): package System Task_Info s-tasinf ads. -@noindent - This AI covers various omissions in the RM regarding the raising of - exceptions. GNAT has always implemented the intended semantics. +@end menu -@noindent - RM References: 11.04.01 (10.1/2) 11 (2) +@node pragma No_Run_Time,pragma Ravenscar,,Obsolescent Features +@anchor{gnat_rm/obsolescent_features id2}@anchor{3c9}@anchor{gnat_rm/obsolescent_features pragma-no-run-time}@anchor{3ca} +@section pragma No_Run_Time -@item -@emph{AI-0200 Mismatches in formal package declarations (0000-00-00)} -@cindex AI-0200 (Ada 2012 feature) +The pragma @cite{No_Run_Time} is used to achieve an affect similar +to the use of the "Zero Foot Print" configurable run time, but without +requiring a specially configured run time. The result of using this +pragma, which must be used for all units in a partition, is to restrict +the use of any language features requiring run-time support code. The +preferred usage is to use an appropriately configured run-time that +includes just those features that are to be made accessible. -@noindent - This AI plugs a gap in the RM which appeared to allow some obviously intended - illegal instantiations. GNAT has never allowed these instantiations. +@node pragma Ravenscar,pragma Restricted_Run_Time,pragma No_Run_Time,Obsolescent Features +@anchor{gnat_rm/obsolescent_features id3}@anchor{3cb}@anchor{gnat_rm/obsolescent_features pragma-ravenscar}@anchor{3cc} +@section pragma Ravenscar -@noindent - RM References: 12.07 (16) +The pragma @cite{Ravenscar} has exactly the same effect as pragma +@cite{Profile (Ravenscar)}. The latter usage is preferred since it +is part of the new Ada 2005 standard. -@item -@emph{AI-0112 Detection of duplicate pragmas (2010-07-24)} -@cindex AI-0112 (Ada 2012 feature) +@node pragma Restricted_Run_Time,pragma Task_Info,pragma Ravenscar,Obsolescent Features +@anchor{gnat_rm/obsolescent_features pragma-restricted-run-time}@anchor{3cd}@anchor{gnat_rm/obsolescent_features id4}@anchor{3ce} +@section pragma Restricted_Run_Time -@noindent - This AI concerns giving names to various representation aspects, but the - practical effect is simply to make the use of duplicate - @code{Atomic}[@code{_Components}], - @code{Volatile}[@code{_Components}] and - @code{Independent}[@code{_Components}] pragmas illegal, and GNAT - now performs this required check. -@noindent - RM References: 13.01 (8) +The pragma @cite{Restricted_Run_Time} has exactly the same effect as +pragma @cite{Profile (Restricted)}. The latter usage is +preferred since the Ada 2005 pragma @cite{Profile} is intended for +this kind of implementation dependent addition. -@item -@emph{AI-0106 No representation pragmas on generic formals (0000-00-00)} -@cindex AI-0106 (Ada 2012 feature) +@node pragma Task_Info,package System Task_Info s-tasinf ads,pragma Restricted_Run_Time,Obsolescent Features +@anchor{gnat_rm/obsolescent_features pragma-task-info}@anchor{3cf}@anchor{gnat_rm/obsolescent_features id5}@anchor{3d0} +@section pragma Task_Info -@noindent - The RM appeared to allow representation pragmas on generic formal parameters, - but this was not intended, and GNAT has never permitted this usage. -@noindent - RM References: 13.01 (9.1/1) +The functionality provided by pragma @cite{Task_Info} is now part of the +Ada language. The @cite{CPU} aspect and the package +@cite{System.Multiprocessors} offer a less system-dependent way to specify +task affinity or to query the number of processsors. +Syntax -@item -@emph{AI-0012 Pack/Component_Size for aliased/atomic (2010-07-15)} -@cindex AI-0012 (Ada 2012 feature) +@example +pragma Task_Info (EXPRESSION); +@end example -@noindent - It is now illegal to give an inappropriate component size or a pragma - @code{Pack} that attempts to change the component size in the case of atomic - or aliased components. Previously GNAT ignored such an attempt with a - warning. +This pragma appears within a task definition (like pragma +@cite{Priority}) and applies to the task in which it appears. The +argument must be of type @cite{System.Task_Info.Task_Info_Type}. +The @cite{Task_Info} pragma provides system dependent control over +aspects of tasking implementation, for example, the ability to map +tasks to specific processors. For details on the facilities available +for the version of GNAT that you are using, see the documentation +in the spec of package System.Task_Info in the runtime +library. -@noindent - RM References: 13.02 (6.1/2) 13.02 (7) C.06 (10) C.06 (11) C.06 (21) +@node package System Task_Info s-tasinf ads,,pragma Task_Info,Obsolescent Features +@anchor{gnat_rm/obsolescent_features package-system-task-info}@anchor{3d1}@anchor{gnat_rm/obsolescent_features package-system-task-info-s-tasinf-ads}@anchor{3d2} +@section package System.Task_Info (@code{s-tasinf.ads}) -@item -@emph{AI-0039 Stream attributes cannot be dynamic (0000-00-00)} -@cindex AI-0039 (Ada 2012 feature) +This package provides target dependent functionality that is used +to support the @cite{Task_Info} pragma. The predefined Ada package +@cite{System.Multiprocessors} and the @cite{CPU} aspect now provide a +standard replacement for GNAT's @cite{Task_Info} functionality. -@noindent - The RM permitted the use of dynamic expressions (such as @code{ptr.@b{all})} - for stream attributes, but these were never useful and are now illegal. GNAT - has always regarded such expressions as illegal. +@node Compatibility and Porting Guide,GNU Free Documentation License,Obsolescent Features,Top +@anchor{gnat_rm/compatibility_and_porting_guide compatibility-and-porting-guide}@anchor{16}@anchor{gnat_rm/compatibility_and_porting_guide doc}@anchor{3d3}@anchor{gnat_rm/compatibility_and_porting_guide id1}@anchor{3d4} +@chapter Compatibility and Porting Guide -@noindent - RM References: 13.03 (4) 13.03 (6) 13.13.02 (38/2) +This chapter presents some guidelines for developing portable Ada code, +describes the compatibility issues that may arise between +GNAT and other Ada compilation systems (including those for Ada 83), +and shows how GNAT can expedite porting +applications developed in other Ada environments. -@item -@emph{AI-0095 Address of intrinsic subprograms (0000-00-00)} -@cindex AI-0095 (Ada 2012 feature) +@menu +* Writing Portable Fixed-Point Declarations:: +* Compatibility with Ada 83:: +* Compatibility between Ada 95 and Ada 2005:: +* Implementation-dependent characteristics:: +* Compatibility with Other Ada Systems:: +* Representation Clauses:: +* Compatibility with HP Ada 83:: -@noindent - The prefix of @code{'Address} cannot statically denote a subprogram with - convention @code{Intrinsic}. The use of the @code{Address} attribute raises - @code{Program_Error} if the prefix denotes a subprogram with convention - @code{Intrinsic}. +@end menu -@noindent - RM References: 13.03 (11/1) +@node Writing Portable Fixed-Point Declarations,Compatibility with Ada 83,,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide id2}@anchor{3d5}@anchor{gnat_rm/compatibility_and_porting_guide writing-portable-fixed-point-declarations}@anchor{3d6} +@section Writing Portable Fixed-Point Declarations -@item -@emph{AI-0116 Alignment of class-wide objects (0000-00-00)} -@cindex AI-0116 (Ada 2012 feature) +The Ada Reference Manual gives an implementation freedom to choose bounds +that are narrower by @cite{Small} from the given bounds. +For example, if we write -@noindent - This AI requires that the alignment of a class-wide object be no greater - than the alignment of any type in the class. GNAT has always followed this - recommendation. +@example +type F1 is delta 1.0 range -128.0 .. +128.0; +@end example -@noindent - RM References: 13.03 (29) 13.11 (16) +then the implementation is allowed to choose -128.0 .. +127.0 if it +likes, but is not required to do so. +This leads to possible portability problems, so let's have a closer +look at this, and figure out how to avoid these problems. -@item -@emph{AI-0146 Type invariants (2009-09-21)} -@cindex AI-0146 (Ada 2012 feature) - -@noindent - Type invariants may be specified for private types using the aspect notation. - Aspect @code{Type_Invariant} may be specified for any private type, - @code{Type_Invariant'Class} can - only be specified for tagged types, and is inherited by any descendent of the - tagged types. The invariant is a boolean expression that is tested for being - true in the following situations: conversions to the private type, object - declarations for the private type that are default initialized, and - [@b{in}] @b{out} - parameters and returned result on return from any primitive operation for - the type that is visible to a client. - GNAT defines the synonyms @code{Invariant} for @code{Type_Invariant} and - @code{Invariant'Class} for @code{Type_Invariant'Class}. - -@noindent - RM References: 13.03.03 (00) +First, why does this freedom exist, and why would an implementation +take advantage of it? To answer this, take a closer look at the type +declaration for @cite{F1} above. If the compiler uses the given bounds, +it would need 9 bits to hold the largest positive value (and typically +that means 16 bits on all machines). But if the implementation chooses +the +127.0 bound then it can fit values of the type in 8 bits. -@item -@emph{AI-0078 Relax Unchecked_Conversion alignment rules (0000-00-00)} -@cindex AI-0078 (Ada 2012 feature) +Why not make the user write +127.0 if that's what is wanted? +The rationale is that if you are thinking of fixed point +as a kind of 'poor man's floating-point', then you don't want +to be thinking about the scaled integers that are used in its +representation. Let's take another example: -@noindent - In Ada 2012, compilers are required to support unchecked conversion where the - target alignment is a multiple of the source alignment. GNAT always supported - this case (and indeed all cases of differing alignments, doing copies where - required if the alignment was reduced). +@example +type F2 is delta 2.0**(-15) range -1.0 .. +1.0; +@end example -@noindent - RM References: 13.09 (7) +Looking at this declaration, it seems casually as though +it should fit in 16 bits, but again that extra positive value ++1.0 has the scaled integer equivalent of 2**15 which is one too +big for signed 16 bits. The implementation can treat this as: +@example +type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15)); +@end example -@item -@emph{AI-0195 Invalid value handling is implementation defined (2010-07-03)} -@cindex AI-0195 (Ada 2012 feature) +and the Ada language design team felt that this was too annoying +to require. We don't need to debate this decision at this point, +since it is well established (the rule about narrowing the ranges +dates to Ada 83). -@noindent - The handling of invalid values is now designated to be implementation - defined. This is a documentation change only, requiring Annex M in the GNAT - Reference Manual to document this handling. - In GNAT, checks for invalid values are made - only when necessary to avoid erroneous behavior. Operations like assignments - which cannot cause erroneous behavior ignore the possibility of invalid - values and do not do a check. The date given above applies only to the - documentation change, this behavior has always been implemented by GNAT. +But the important point is that an implementation is not required +to do this narrowing, so we have a potential portability problem. +We could imagine three types of implementation: -@noindent - RM References: 13.09.01 (10) -@item -@emph{AI-0193 Alignment of allocators (2010-09-16)} -@cindex AI-0193 (Ada 2012 feature) +@enumerate a -@noindent - This AI introduces a new attribute @code{Max_Alignment_For_Allocation}, - analogous to @code{Max_Size_In_Storage_Elements}, but for alignment instead - of size. +@item +those that narrow the range automatically if they can figure +out that the narrower range will allow storage in a smaller machine unit, -@noindent - RM References: 13.11 (16) 13.11 (21) 13.11.01 (0) 13.11.01 (1) - 13.11.01 (2) 13.11.01 (3) +@item +those that will narrow only if forced to by a @cite{'Size} clause, and +@item +those that will never narrow. +@end enumerate -@item -@emph{AI-0177 Parameterized expressions (2010-07-10)} -@cindex AI-0177 (Ada 2012 feature) +Now if we are language theoreticians, we can imagine a fourth +approach: to narrow all the time, e.g. to treat -@noindent - The new Ada 2012 notion of parameterized expressions is implemented. The form - is: -@smallexample - @i{function specification} @b{is} (@i{expression}) -@end smallexample +@example +type F3 is delta 1.0 range -10.0 .. +23.0; +@end example -@noindent - This is exactly equivalent to the - corresponding function body that returns the expression, but it can appear - in a package spec. Note that the expression must be parenthesized. +as though it had been written: -@noindent - RM References: 13.11.01 (3/2) +@example +type F3 is delta 1.0 range -9.0 .. +22.0; +@end example -@item -@emph{AI-0033 Attach/Interrupt_Handler in generic (2010-07-24)} -@cindex AI-0033 (Ada 2012 feature) +But although technically allowed, such a behavior would be hostile and silly, +and no real compiler would do this. All real compilers will fall into one of +the categories (a), (b) or (c) above. -@noindent - Neither of these two pragmas may appear within a generic template, because - the generic might be instantiated at other than the library level. +So, how do you get the compiler to do what you want? The answer is give the +actual bounds you want, and then use a @cite{'Small} clause and a +@cite{'Size} clause to absolutely pin down what the compiler does. +E.g., for @cite{F2} above, we will write: -@noindent - RM References: 13.11.02 (16) C.03.01 (7/2) C.03.01 (8/2) +@example +My_Small : constant := 2.0**(-15); +My_First : constant := -1.0; +My_Last : constant := +1.0 - My_Small; +type F2 is delta My_Small range My_First .. My_Last; +@end example -@item -@emph{AI-0161 Restriction No_Default_Stream_Attributes (2010-09-11)} -@cindex AI-0161 (Ada 2012 feature) +and then add -@noindent - A new restriction @code{No_Default_Stream_Attributes} prevents the use of any - of the default stream attributes for elementary types. If this restriction is - in force, then it is necessary to provide explicit subprograms for any - stream attributes used. +@example +for F2'Small use my_Small; +for F2'Size use 16; +@end example -@noindent - RM References: 13.12.01 (4/2) 13.13.02 (40/2) 13.13.02 (52/2) +In practice all compilers will do the same thing here and will give you +what you want, so the above declarations are fully portable. If you really +want to play language lawyer and guard against ludicrous behavior by the +compiler you could add -@item -@emph{AI-0194 Value of Stream_Size attribute (0000-00-00)} -@cindex AI-0194 (Ada 2012 feature) +@example +Test1 : constant := 1 / Boolean'Pos (F2'First = My_First); +Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last); +@end example -@noindent - The @code{Stream_Size} attribute returns the default number of bits in the - stream representation of the given type. - This value is not affected by the presence - of stream subprogram attributes for the type. GNAT has always implemented - this interpretation. +One or other or both are allowed to be illegal if the compiler is +behaving in a silly manner, but at least the silly compiler will not +get away with silently messing with your (very clear) intentions. -@noindent - RM References: 13.13.02 (1.2/2) +If you follow this scheme you will be guaranteed that your fixed-point +types will be portable. -@item -@emph{AI-0109 Redundant check in S'Class'Input (0000-00-00)} -@cindex AI-0109 (Ada 2012 feature) +@node Compatibility with Ada 83,Compatibility between Ada 95 and Ada 2005,Writing Portable Fixed-Point Declarations,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-ada-83}@anchor{3d7}@anchor{gnat_rm/compatibility_and_porting_guide id3}@anchor{3d8} +@section Compatibility with Ada 83 -@noindent - This AI is an editorial change only. It removes the need for a tag check - that can never fail. -@noindent - RM References: 13.13.02 (34/2) +@geindex Compatibility (between Ada 83 and Ada 95 / Ada 2005 / Ada 2012) -@item -@emph{AI-0007 Stream read and private scalar types (0000-00-00)} -@cindex AI-0007 (Ada 2012 feature) +Ada 95 and the subsequent revisions Ada 2005 and Ada 2012 +are highly upwards compatible with Ada 83. In +particular, the design intention was that the difficulties associated +with moving from Ada 83 to later versions of the standard should be no greater +than those that occur when moving from one Ada 83 system to another. -@noindent - The RM as written appeared to limit the possibilities of declaring read - attribute procedures for private scalar types. This limitation was not - intended, and has never been enforced by GNAT. +However, there are a number of points at which there are minor +incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains +full details of these issues as they relate to Ada 95, +and should be consulted for a complete treatment. +In practice the +following subsections treat the most likely issues to be encountered. -@noindent - RM References: 13.13.02 (50/2) 13.13.02 (51/2) +@menu +* Legal Ada 83 programs that are illegal in Ada 95:: +* More deterministic semantics:: +* Changed semantics:: +* Other language compatibility issues:: +@end menu -@item -@emph{AI-0065 Remote access types and external streaming (0000-00-00)} -@cindex AI-0065 (Ada 2012 feature) +@node Legal Ada 83 programs that are illegal in Ada 95,More deterministic semantics,,Compatibility with Ada 83 +@anchor{gnat_rm/compatibility_and_porting_guide id4}@anchor{3d9}@anchor{gnat_rm/compatibility_and_porting_guide legal-ada-83-programs-that-are-illegal-in-ada-95}@anchor{3da} +@subsection Legal Ada 83 programs that are illegal in Ada 95 -@noindent - This AI clarifies the fact that all remote access types support external - streaming. This fixes an obvious oversight in the definition of the - language, and GNAT always implemented the intended correct rules. -@noindent - RM References: 13.13.02 (52/2) +Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in +Ada 95 and later versions of the standard: -@item -@emph{AI-0019 Freezing of primitives for tagged types (0000-00-00)} -@cindex AI-0019 (Ada 2012 feature) -@noindent - The RM suggests that primitive subprograms of a specific tagged type are - frozen when the tagged type is frozen. This would be an incompatible change - and is not intended. GNAT has never attempted this kind of freezing and its - behavior is consistent with the recommendation of this AI. +@itemize * -@noindent - RM References: 13.14 (2) 13.14 (3/1) 13.14 (8.1/1) 13.14 (10) 13.14 (14) 13.14 (15.1/2) +@item +@emph{Character literals} -@item -@emph{AI-0017 Freezing and incomplete types (0000-00-00)} -@cindex AI-0017 (Ada 2012 feature) +Some uses of character literals are ambiguous. Since Ada 95 has introduced +@cite{Wide_Character} as a new predefined character type, some uses of +character literals that were legal in Ada 83 are illegal in Ada 95. +For example: -@noindent - So-called ``Taft-amendment types'' (i.e., types that are completed in package - bodies) are not frozen by the occurrence of bodies in the - enclosing declarative part. GNAT always implemented this properly. +@example +for Char in 'A' .. 'Z' loop ... end loop; +@end example + +The problem is that 'A' and 'Z' could be from either +@cite{Character} or @cite{Wide_Character}. The simplest correction +is to make the type explicit; e.g.: + +@example +for Char in Character range 'A' .. 'Z' loop ... end loop; +@end example + +@item +@emph{New reserved words} + +The identifiers @cite{abstract}, @cite{aliased}, @cite{protected}, +@cite{requeue}, @cite{tagged}, and @cite{until} are reserved in Ada 95. +Existing Ada 83 code using any of these identifiers must be edited to +use some alternative name. + +@item +@emph{Freezing rules} + +The rules in Ada 95 are slightly different with regard to the point at +which entities are frozen, and representation pragmas and clauses are +not permitted past the freeze point. This shows up most typically in +the form of an error message complaining that a representation item +appears too late, and the appropriate corrective action is to move +the item nearer to the declaration of the entity to which it refers. + +A particular case is that representation pragmas +cannot be applied to a subprogram body. If necessary, a separate subprogram +declaration must be introduced to which the pragma can be applied. + +@item +@emph{Optional bodies for library packages} + +In Ada 83, a package that did not require a package body was nevertheless +allowed to have one. This lead to certain surprises in compiling large +systems (situations in which the body could be unexpectedly ignored by the +binder). In Ada 95, if a package does not require a body then it is not +permitted to have a body. To fix this problem, simply remove a redundant +body if it is empty, or, if it is non-empty, introduce a dummy declaration +into the spec that makes the body required. One approach is to add a private +part to the package declaration (if necessary), and define a parameterless +procedure called @cite{Requires_Body}, which must then be given a dummy +procedure body in the package body, which then becomes required. +Another approach (assuming that this does not introduce elaboration +circularities) is to add an @cite{Elaborate_Body} pragma to the package spec, +since one effect of this pragma is to require the presence of a package body. + +@item +@emph{Numeric_Error is the same exception as Constraint_Error} + +In Ada 95, the exception @cite{Numeric_Error} is a renaming of @cite{Constraint_Error}. +This means that it is illegal to have separate exception handlers for +the two exceptions. The fix is simply to remove the handler for the +@cite{Numeric_Error} case (since even in Ada 83, a compiler was free to raise +@cite{Constraint_Error} in place of @cite{Numeric_Error} in all cases). + +@item +@emph{Indefinite subtypes in generics} + +In Ada 83, it was permissible to pass an indefinite type (e.g, @cite{String}) +as the actual for a generic formal private type, but then the instantiation +would be illegal if there were any instances of declarations of variables +of this type in the generic body. In Ada 95, to avoid this clear violation +of the methodological principle known as the 'contract model', +the generic declaration explicitly indicates whether +or not such instantiations are permitted. If a generic formal parameter +has explicit unknown discriminants, indicated by using @cite{(<>)} after the +subtype name, then it can be instantiated with indefinite types, but no +stand-alone variables can be declared of this type. Any attempt to declare +such a variable will result in an illegality at the time the generic is +declared. If the @cite{(<>)} notation is not used, then it is illegal +to instantiate the generic with an indefinite type. +This is the potential incompatibility issue when porting Ada 83 code to Ada 95. +It will show up as a compile time error, and +the fix is usually simply to add the @cite{(<>)} to the generic declaration. +@end itemize -@noindent - RM References: 13.14 (3/1) +@node More deterministic semantics,Changed semantics,Legal Ada 83 programs that are illegal in Ada 95,Compatibility with Ada 83 +@anchor{gnat_rm/compatibility_and_porting_guide more-deterministic-semantics}@anchor{3db}@anchor{gnat_rm/compatibility_and_porting_guide id5}@anchor{3dc} +@subsection More deterministic semantics -@item -@emph{AI-0060 Extended definition of remote access types (0000-00-00)} -@cindex AI-0060 (Ada 2012 feature) -@noindent - This AI extends the definition of remote access types to include access - to limited, synchronized, protected or task class-wide interface types. - GNAT already implemented this extension. +@itemize * -@noindent - RM References: A (4) E.02.02 (9/1) E.02.02 (9.2/1) E.02.02 (14/2) E.02.02 (18) +@item +@emph{Conversions} -@item -@emph{AI-0114 Classification of letters (0000-00-00)} -@cindex AI-0114 (Ada 2012 feature) +Conversions from real types to integer types round away from 0. In Ada 83 +the conversion Integer(2.5) could deliver either 2 or 3 as its value. This +implementation freedom was intended to support unbiased rounding in +statistical applications, but in practice it interfered with portability. +In Ada 95 the conversion semantics are unambiguous, and rounding away from 0 +is required. Numeric code may be affected by this change in semantics. +Note, though, that this issue is no worse than already existed in Ada 83 +when porting code from one vendor to another. -@noindent - The code points 170 (@code{FEMININE ORDINAL INDICATOR}), - 181 (@code{MICRO SIGN}), and - 186 (@code{MASCULINE ORDINAL INDICATOR}) are technically considered - lower case letters by Unicode. - However, they are not allowed in identifiers, and they - return @code{False} to @code{Ada.Characters.Handling.Is_Letter/Is_Lower}. - This behavior is consistent with that defined in Ada 95. +@item +@emph{Tasking} -@noindent - RM References: A.03.02 (59) A.04.06 (7) +The Real-Time Annex introduces a set of policies that define the behavior of +features that were implementation dependent in Ada 83, such as the order in +which open select branches are executed. +@end itemize +@node Changed semantics,Other language compatibility issues,More deterministic semantics,Compatibility with Ada 83 +@anchor{gnat_rm/compatibility_and_porting_guide id6}@anchor{3dd}@anchor{gnat_rm/compatibility_and_porting_guide changed-semantics}@anchor{3de} +@subsection Changed semantics -@item -@emph{AI-0185 Ada.Wide_[Wide_]Characters.Handling (2010-07-06)} -@cindex AI-0185 (Ada 2012 feature) -@noindent - Two new packages @code{Ada.Wide_[Wide_]Characters.Handling} provide - classification functions for @code{Wide_Character} and - @code{Wide_Wide_Character}, as well as providing - case folding routines for @code{Wide_[Wide_]Character} and - @code{Wide_[Wide_]String}. +The worst kind of incompatibility is one where a program that is legal in +Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not +possible in Ada 83. Fortunately this is extremely rare, but the one +situation that you should be alert to is the change in the predefined type +@cite{Character} from 7-bit ASCII to 8-bit Latin-1. -@noindent - RM References: A.03.05 (0) A.03.06 (0) +@quotation +@geindex Latin-1 +@end quotation -@item -@emph{AI-0031 Add From parameter to Find_Token (2010-07-25)} -@cindex AI-0031 (Ada 2012 feature) -@noindent - A new version of @code{Find_Token} is added to all relevant string packages, - with an extra parameter @code{From}. Instead of starting at the first - character of the string, the search for a matching Token starts at the - character indexed by the value of @code{From}. - These procedures are available in all versions of Ada - but if used in versions earlier than Ada 2012 they will generate a warning - that an Ada 2012 subprogram is being used. +@itemize * + +@item +@emph{Range of type `Character`} + +The range of @cite{Standard.Character} is now the full 256 characters +of Latin-1, whereas in most Ada 83 implementations it was restricted +to 128 characters. Although some of the effects of +this change will be manifest in compile-time rejection of legal +Ada 83 programs it is possible for a working Ada 83 program to have +a different effect in Ada 95, one that was not permitted in Ada 83. +As an example, the expression +@cite{Character'Pos(Character'Last)} returned @cite{127} in Ada 83 and now +delivers @cite{255} as its value. +In general, you should look at the logic of any +character-processing Ada 83 program and see whether it needs to be adapted +to work correctly with Latin-1. Note that the predefined Ada 95 API has a +character handling package that may be relevant if code needs to be adapted +to account for the additional Latin-1 elements. +The desirable fix is to +modify the program to accommodate the full character set, but in some cases +it may be convenient to define a subtype or derived type of Character that +covers only the restricted range. +@end itemize -@noindent - RM References: A.04.03 (16) A.04.03 (67) A.04.03 (68/1) A.04.04 (51) - A.04.05 (46) +@node Other language compatibility issues,,Changed semantics,Compatibility with Ada 83 +@anchor{gnat_rm/compatibility_and_porting_guide other-language-compatibility-issues}@anchor{3df}@anchor{gnat_rm/compatibility_and_porting_guide id7}@anchor{3e0} +@subsection Other language compatibility issues -@item -@emph{AI-0056 Index on null string returns zero (0000-00-00)} -@cindex AI-0056 (Ada 2012 feature) -@noindent - The wording in the Ada 2005 RM implied an incompatible handling of the - @code{Index} functions, resulting in raising an exception instead of - returning zero in some situations. - This was not intended and has been corrected. - GNAT always returned zero, and is thus consistent with this AI. +@itemize * -@noindent - RM References: A.04.03 (56.2/2) A.04.03 (58.5/2) +@item +@emph{-gnat83} switch +All implementations of GNAT provide a switch that causes GNAT to operate +in Ada 83 mode. In this mode, some but not all compatibility problems +of the type described above are handled automatically. For example, the +new reserved words introduced in Ada 95 and Ada 2005 are treated simply +as identifiers as in Ada 83. However, +in practice, it is usually advisable to make the necessary modifications +to the program to remove the need for using this switch. +See the @cite{Compiling Different Versions of Ada} section in +the @cite{GNAT User's Guide}. -@item -@emph{AI-0137 String encoding package (2010-03-25)} -@cindex AI-0137 (Ada 2012 feature) - -@noindent - The packages @code{Ada.Strings.UTF_Encoding}, together with its child - packages, @code{Conversions}, @code{Strings}, @code{Wide_Strings}, - and @code{Wide_Wide_Strings} have been - implemented. These packages (whose documentation can be found in the spec - files @file{a-stuten.ads}, @file{a-suenco.ads}, @file{a-suenst.ads}, - @file{a-suewst.ads}, @file{a-suezst.ads}) allow encoding and decoding of - @code{String}, @code{Wide_String}, and @code{Wide_Wide_String} - values using UTF coding schemes (including UTF-8, UTF-16LE, UTF-16BE, and - UTF-16), as well as conversions between the different UTF encodings. With - the exception of @code{Wide_Wide_Strings}, these packages are available in - Ada 95 and Ada 2005 mode as well as Ada 2012 mode. - The @code{Wide_Wide_Strings package} - is available in Ada 2005 mode as well as Ada 2012 mode (but not in Ada 95 - mode since it uses @code{Wide_Wide_Character}). - -@noindent - RM References: A.04.11 +@item +Support for removed Ada 83 pragmas and attributes -@item -@emph{AI-0038 Minor errors in Text_IO (0000-00-00)} -@cindex AI-0038 (Ada 2012 feature) +A number of pragmas and attributes from Ada 83 were removed from Ada 95, +generally because they were replaced by other mechanisms. Ada 95 and Ada 2005 +compilers are allowed, but not required, to implement these missing +elements. In contrast with some other compilers, GNAT implements all +such pragmas and attributes, eliminating this compatibility concern. These +include @cite{pragma Interface} and the floating point type attributes +(@cite{Emax}, @cite{Mantissa}, etc.), among other items. +@end itemize -@noindent - These are minor errors in the description on three points. The intent on - all these points has always been clear, and GNAT has always implemented the - correct intended semantics. +@node Compatibility between Ada 95 and Ada 2005,Implementation-dependent characteristics,Compatibility with Ada 83,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide compatibility-between-ada-95-and-ada-2005}@anchor{3e1}@anchor{gnat_rm/compatibility_and_porting_guide id8}@anchor{3e2} +@section Compatibility between Ada 95 and Ada 2005 -@noindent - RM References: A.10.05 (37) A.10.07 (8/1) A.10.07 (10) A.10.07 (12) A.10.08 (10) A.10.08 (24) -@item -@emph{AI-0044 Restrictions on container instantiations (0000-00-00)} -@cindex AI-0044 (Ada 2012 feature) +@geindex Compatibility between Ada 95 and Ada 2005 -@noindent - This AI places restrictions on allowed instantiations of generic containers. - These restrictions are not checked by the compiler, so there is nothing to - change in the implementation. This affects only the RM documentation. +Although Ada 2005 was designed to be upwards compatible with Ada 95, there are +a number of incompatibilities. Several are enumerated below; +for a complete description please see the +@cite{Annotated Ada 2005 Reference Manual}, or section 9.1.1 in +@cite{Rationale for Ada 2005}. -@noindent - RM References: A.18 (4/2) A.18.02 (231/2) A.18.03 (145/2) A.18.06 (56/2) A.18.08 (66/2) A.18.09 (79/2) A.18.26 (5/2) A.18.26 (9/2) -@item -@emph{AI-0127 Adding Locale Capabilities (2010-09-29)} -@cindex AI-0127 (Ada 2012 feature) +@itemize * -@noindent - This package provides an interface for identifying the current locale. +@item +@emph{New reserved words.} -@noindent - RM References: A.19 A.19.01 A.19.02 A.19.03 A.19.05 A.19.06 - A.19.07 A.19.08 A.19.09 A.19.10 A.19.11 A.19.12 A.19.13 +The words @cite{interface}, @cite{overriding} and @cite{synchronized} are +reserved in Ada 2005. +A pre-Ada 2005 program that uses any of these as an identifier will be +illegal. +@item +@emph{New declarations in predefined packages.} +A number of packages in the predefined environment contain new declarations: +@cite{Ada.Exceptions}, @cite{Ada.Real_Time}, @cite{Ada.Strings}, +@cite{Ada.Strings.Fixed}, @cite{Ada.Strings.Bounded}, +@cite{Ada.Strings.Unbounded}, @cite{Ada.Strings.Wide_Fixed}, +@cite{Ada.Strings.Wide_Bounded}, @cite{Ada.Strings.Wide_Unbounded}, +@cite{Ada.Tags}, @cite{Ada.Text_IO}, and @cite{Interfaces.C}. +If an Ada 95 program does a @cite{with} and @cite{use} of any of these +packages, the new declarations may cause name clashes. -@item -@emph{AI-0002 Export C with unconstrained arrays (0000-00-00)} -@cindex AI-0002 (Ada 2012 feature) +@item +@emph{Access parameters.} -@noindent - The compiler is not required to support exporting an Ada subprogram with - convention C if there are parameters or a return type of an unconstrained - array type (such as @code{String}). GNAT allows such declarations but - generates warnings. It is possible, but complicated, to write the - corresponding C code and certainly such code would be specific to GNAT and - non-portable. +A nondispatching subprogram with an access parameter cannot be renamed +as a dispatching operation. This was permitted in Ada 95. -@noindent - RM References: B.01 (17) B.03 (62) B.03 (71.1/2) +@item +@emph{Access types, discriminants, and constraints.} +Rule changes in this area have led to some incompatibilities; for example, +constrained subtypes of some access types are not permitted in Ada 2005. -@item -@emph{AI-0216 No_Task_Hierarchy forbids local tasks (0000-00-00)} -@cindex AI05-0216 (Ada 2012 feature) +@item +@emph{Aggregates for limited types.} -@noindent - It is clearly the intention that @code{No_Task_Hierarchy} is intended to - forbid tasks declared locally within subprograms, or functions returning task - objects, and that is the implementation that GNAT has always provided. - However the language in the RM was not sufficiently clear on this point. - Thus this is a documentation change in the RM only. +The allowance of aggregates for limited types in Ada 2005 raises the +possibility of ambiguities in legal Ada 95 programs, since additional types +now need to be considered in expression resolution. -@noindent - RM References: D.07 (3/3) +@item +@emph{Fixed-point multiplication and division.} -@item -@emph{AI-0211 No_Relative_Delays forbids Set_Handler use (2010-07-09)} -@cindex AI-0211 (Ada 2012 feature) +Certain expressions involving '*' or '/' for a fixed-point type, which +were legal in Ada 95 and invoked the predefined versions of these operations, +are now ambiguous. +The ambiguity may be resolved either by applying a type conversion to the +expression, or by explicitly invoking the operation from package +@cite{Standard}. -@noindent - The restriction @code{No_Relative_Delays} forbids any calls to the subprogram - @code{Ada.Real_Time.Timing_Events.Set_Handler}. +@item +@emph{Return-by-reference types.} -@noindent - RM References: D.07 (5) D.07 (10/2) D.07 (10.4/2) D.07 (10.7/2) +The Ada 95 return-by-reference mechanism has been removed. Instead, the user +can declare a function returning a value from an anonymous access type. +@end itemize -@item -@emph{AI-0190 pragma Default_Storage_Pool (2010-09-15)} -@cindex AI-0190 (Ada 2012 feature) +@node Implementation-dependent characteristics,Compatibility with Other Ada Systems,Compatibility between Ada 95 and Ada 2005,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide implementation-dependent-characteristics}@anchor{3e3}@anchor{gnat_rm/compatibility_and_porting_guide id9}@anchor{3e4} +@section Implementation-dependent characteristics -@noindent - This AI introduces a new pragma @code{Default_Storage_Pool}, which can be - used to control storage pools globally. - In particular, you can force every access - type that is used for allocation (@b{new}) to have an explicit storage pool, - or you can declare a pool globally to be used for all access types that lack - an explicit one. -@noindent - RM References: D.07 (8) +Although the Ada language defines the semantics of each construct as +precisely as practical, in some situations (for example for reasons of +efficiency, or where the effect is heavily dependent on the host or target +platform) the implementation is allowed some freedom. In porting Ada 83 +code to GNAT, you need to be aware of whether / how the existing code +exercised such implementation dependencies. Such characteristics fall into +several categories, and GNAT offers specific support in assisting the +transition from certain Ada 83 compilers. -@item -@emph{AI-0189 No_Allocators_After_Elaboration (2010-01-23)} -@cindex AI-0189 (Ada 2012 feature) +@menu +* Implementation-defined pragmas:: +* Implementation-defined attributes:: +* Libraries:: +* Elaboration order:: +* Target-specific aspects:: -@noindent - This AI introduces a new restriction @code{No_Allocators_After_Elaboration}, - which says that no dynamic allocation will occur once elaboration is - completed. - In general this requires a run-time check, which is not required, and which - GNAT does not attempt. But the static cases of allocators in a task body or - in the body of the main program are detected and flagged at compile or bind - time. +@end menu -@noindent - RM References: D.07 (19.1/2) H.04 (23.3/2) +@node Implementation-defined pragmas,Implementation-defined attributes,,Implementation-dependent characteristics +@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-pragmas}@anchor{3e5}@anchor{gnat_rm/compatibility_and_porting_guide id10}@anchor{3e6} +@subsection Implementation-defined pragmas + + +Ada compilers are allowed to supplement the language-defined pragmas, and +these are a potential source of non-portability. All GNAT-defined pragmas +are described in the @cite{Implementation Defined Pragmas} chapter of the +@cite{GNAT Reference Manual}, and these include several that are specifically +intended to correspond to other vendors' Ada 83 pragmas. +For migrating from VADS, the pragma @cite{Use_VADS_Size} may be useful. +For compatibility with HP Ada 83, GNAT supplies the pragmas +@cite{Extend_System}, @cite{Ident}, @cite{Inline_Generic}, +@cite{Interface_Name}, @cite{Passive}, @cite{Suppress_All}, +and @cite{Volatile}. +Other relevant pragmas include @cite{External} and @cite{Link_With}. +Some vendor-specific +Ada 83 pragmas (@cite{Share_Generic}, @cite{Subtitle}, and @cite{Title}) are +recognized, thus +avoiding compiler rejection of units that contain such pragmas; they are not +relevant in a GNAT context and hence are not otherwise implemented. + +@node Implementation-defined attributes,Libraries,Implementation-defined pragmas,Implementation-dependent characteristics +@anchor{gnat_rm/compatibility_and_porting_guide id11}@anchor{3e7}@anchor{gnat_rm/compatibility_and_porting_guide implementation-defined-attributes}@anchor{3e8} +@subsection Implementation-defined attributes + + +Analogous to pragmas, the set of attributes may be extended by an +implementation. All GNAT-defined attributes are described in +@cite{Implementation Defined Attributes} section of the +@cite{GNAT Reference Manual}, and these include several that are specifically intended +to correspond to other vendors' Ada 83 attributes. For migrating from VADS, +the attribute @cite{VADS_Size} may be useful. For compatibility with HP +Ada 83, GNAT supplies the attributes @cite{Bit}, @cite{Machine_Size} and +@cite{Type_Class}. + +@node Libraries,Elaboration order,Implementation-defined attributes,Implementation-dependent characteristics +@anchor{gnat_rm/compatibility_and_porting_guide libraries}@anchor{3e9}@anchor{gnat_rm/compatibility_and_porting_guide id12}@anchor{3ea} +@subsection Libraries + + +Vendors may supply libraries to supplement the standard Ada API. If Ada 83 +code uses vendor-specific libraries then there are several ways to manage +this in Ada 95 and later versions of the standard: + + +@itemize * + +@item +If the source code for the libraries (specs and bodies) are +available, then the libraries can be migrated in the same way as the +application. + +@item +If the source code for the specs but not the bodies are +available, then you can reimplement the bodies. + +@item +Some features introduced by Ada 95 obviate the need for library support. For +example most Ada 83 vendors supplied a package for unsigned integers. The +Ada 95 modular type feature is the preferred way to handle this need, so +instead of migrating or reimplementing the unsigned integer package it may +be preferable to retrofit the application using modular types. +@end itemize -@item -@emph{AI-0171 Pragma CPU and Ravenscar Profile (2010-09-24)} -@cindex AI-0171 (Ada 2012 feature) +@node Elaboration order,Target-specific aspects,Libraries,Implementation-dependent characteristics +@anchor{gnat_rm/compatibility_and_porting_guide elaboration-order}@anchor{3eb}@anchor{gnat_rm/compatibility_and_porting_guide id13}@anchor{3ec} +@subsection Elaboration order + + +The implementation can choose any elaboration order consistent with the unit +dependency relationship. This freedom means that some orders can result in +Program_Error being raised due to an 'Access Before Elaboration': an attempt +to invoke a subprogram its body has been elaborated, or to instantiate a +generic before the generic body has been elaborated. By default GNAT +attempts to choose a safe order (one that will not encounter access before +elaboration problems) by implicitly inserting @cite{Elaborate} or +@cite{Elaborate_All} pragmas where +needed. However, this can lead to the creation of elaboration circularities +and a resulting rejection of the program by gnatbind. This issue is +thoroughly described in the @cite{Elaboration Order Handling in GNAT} appendix +in the @cite{GNAT User's Guide}. +In brief, there are several +ways to deal with this situation: + + +@itemize * + +@item +Modify the program to eliminate the circularities, e.g., by moving +elaboration-time code into explicitly-invoked procedures + +@item +Constrain the elaboration order by including explicit @cite{Elaborate_Body} or +@cite{Elaborate} pragmas, and then inhibit the generation of implicit +@cite{Elaborate_All} +pragmas either globally (as an effect of the @emph{-gnatE} switch) or locally +(by selectively suppressing elaboration checks via pragma +@cite{Suppress(Elaboration_Check)} when it is safe to do so). +@end itemize -@noindent - A new package @code{System.Multiprocessors} is added, together with the - definition of pragma @code{CPU} for controlling task affinity. A new no - dependence restriction, on @code{System.Multiprocessors.Dispatching_Domains}, - is added to the Ravenscar profile. +@node Target-specific aspects,,Elaboration order,Implementation-dependent characteristics +@anchor{gnat_rm/compatibility_and_porting_guide target-specific-aspects}@anchor{3ed}@anchor{gnat_rm/compatibility_and_porting_guide id14}@anchor{3ee} +@subsection Target-specific aspects -@noindent - RM References: D.13.01 (4/2) D.16 +Low-level applications need to deal with machine addresses, data +representations, interfacing with assembler code, and similar issues. If +such an Ada 83 application is being ported to different target hardware (for +example where the byte endianness has changed) then you will need to +carefully examine the program logic; the porting effort will heavily depend +on the robustness of the original design. Moreover, Ada 95 (and thus +Ada 2005 and Ada 2012) are sometimes +incompatible with typical Ada 83 compiler practices regarding implicit +packing, the meaning of the Size attribute, and the size of access values. +GNAT's approach to these issues is described in @ref{3ef,,Representation Clauses}. -@item -@emph{AI-0210 Correct Timing_Events metric (0000-00-00)} -@cindex AI-0210 (Ada 2012 feature) +@node Compatibility with Other Ada Systems,Representation Clauses,Implementation-dependent characteristics,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide id15}@anchor{3f0}@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-other-ada-systems}@anchor{3f1} +@section Compatibility with Other Ada Systems -@noindent - This is a documentation only issue regarding wording of metric requirements, - that does not affect the implementation of the compiler. -@noindent - RM References: D.15 (24/2) +If programs avoid the use of implementation dependent and +implementation defined features, as documented in the +@cite{Ada Reference Manual}, there should be a high degree of portability between +GNAT and other Ada systems. The following are specific items which +have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95 +compilers, but do not affect porting code to GNAT. +(As of January 2007, GNAT is the only compiler available for Ada 2005; +the following issues may or may not arise for Ada 2005 programs +when other compilers appear.) -@item -@emph{AI-0206 Remote types packages and preelaborate (2010-07-24)} -@cindex AI-0206 (Ada 2012 feature) +@itemize * -@noindent - Remote types packages are now allowed to depend on preelaborated packages. - This was formerly considered illegal. +@item +@emph{Ada 83 Pragmas and Attributes} -@noindent - RM References: E.02.02 (6) +Ada 95 compilers are allowed, but not required, to implement the missing +Ada 83 pragmas and attributes that are no longer defined in Ada 95. +GNAT implements all such pragmas and attributes, eliminating this as +a compatibility concern, but some other Ada 95 compilers reject these +pragmas and attributes. +@item +@emph{Specialized Needs Annexes} +GNAT implements the full set of special needs annexes. At the +current time, it is the only Ada 95 compiler to do so. This means that +programs making use of these features may not be portable to other Ada +95 compilation systems. -@item -@emph{AI-0152 Restriction No_Anonymous_Allocators (2010-09-08)} -@cindex AI-0152 (Ada 2012 feature) +@item +@emph{Representation Clauses} -@noindent - Restriction @code{No_Anonymous_Allocators} prevents the use of allocators - where the type of the returned value is an anonymous access type. +Some other Ada 95 compilers implement only the minimal set of +representation clauses required by the Ada 95 reference manual. GNAT goes +far beyond this minimal set, as described in the next section. +@end itemize -@noindent - RM References: H.04 (8/1) +@node Representation Clauses,Compatibility with HP Ada 83,Compatibility with Other Ada Systems,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide representation-clauses}@anchor{3ef}@anchor{gnat_rm/compatibility_and_porting_guide id16}@anchor{3f2} +@section Representation Clauses + + +The Ada 83 reference manual was quite vague in describing both the minimal +required implementation of representation clauses, and also their precise +effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the +minimal set of capabilities required is still quite limited. + +GNAT implements the full required set of capabilities in +Ada 95 and Ada 2005, but also goes much further, and in particular +an effort has been made to be compatible with existing Ada 83 usage to the +greatest extent possible. + +A few cases exist in which Ada 83 compiler behavior is incompatible with +the requirements in Ada 95 (and thus also Ada 2005). These are instances of +intentional or accidental dependence on specific implementation dependent +characteristics of these Ada 83 compilers. The following is a list of +the cases most likely to arise in existing Ada 83 code. + + +@itemize * + +@item +@emph{Implicit Packing} + +Some Ada 83 compilers allowed a Size specification to cause implicit +packing of an array or record. This could cause expensive implicit +conversions for change of representation in the presence of derived +types, and the Ada design intends to avoid this possibility. +Subsequent AI's were issued to make it clear that such implicit +change of representation in response to a Size clause is inadvisable, +and this recommendation is represented explicitly in the Ada 95 (and Ada 2005) +Reference Manuals as implementation advice that is followed by GNAT. +The problem will show up as an error +message rejecting the size clause. The fix is simply to provide +the explicit pragma @cite{Pack}, or for more fine tuned control, provide +a Component_Size clause. + +@item +@emph{Meaning of Size Attribute} + +The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as +the minimal number of bits required to hold values of the type. For example, +on a 32-bit machine, the size of @cite{Natural} will typically be 31 and not +32 (since no sign bit is required). Some Ada 83 compilers gave 31, and +some 32 in this situation. This problem will usually show up as a compile +time error, but not always. It is a good idea to check all uses of the +'Size attribute when porting Ada 83 code. The GNAT specific attribute +Object_Size can provide a useful way of duplicating the behavior of +some Ada 83 compiler systems. + +@item +@emph{Size of Access Types} + +A common assumption in Ada 83 code is that an access type is in fact a pointer, +and that therefore it will be the same size as a System.Address value. This +assumption is true for GNAT in most cases with one exception. For the case of +a pointer to an unconstrained array type (where the bounds may vary from one +value of the access type to another), the default is to use a 'fat pointer', +which is represented as two separate pointers, one to the bounds, and one to +the array. This representation has a number of advantages, including improved +efficiency. However, it may cause some difficulties in porting existing Ada 83 +code which makes the assumption that, for example, pointers fit in 32 bits on +a machine with 32-bit addressing. + +To get around this problem, GNAT also permits the use of 'thin pointers' for +access types in this case (where the designated type is an unconstrained array +type). These thin pointers are indeed the same size as a System.Address value. +To specify a thin pointer, use a size clause for the type, for example: + +@example +type X is access all String; +for X'Size use Standard'Address_Size; +@end example + +which will cause the type X to be represented using a single pointer. +When using this representation, the bounds are right behind the array. +This representation is slightly less efficient, and does not allow quite +such flexibility in the use of foreign pointers or in using the +Unrestricted_Access attribute to create pointers to non-aliased objects. +But for any standard portable use of the access type it will work in +a functionally correct manner and allow porting of existing code. +Note that another way of forcing a thin pointer representation +is to use a component size clause for the element size in an array, +or a record representation clause for an access field in a record. + +See the documentation of Unrestricted_Access in the GNAT RM for a +full discussion of possible problems using this attribute in conjunction +with thin pointers. @end itemize +@node Compatibility with HP Ada 83,,Representation Clauses,Compatibility and Porting Guide +@anchor{gnat_rm/compatibility_and_porting_guide compatibility-with-hp-ada-83}@anchor{3f3}@anchor{gnat_rm/compatibility_and_porting_guide id17}@anchor{3f4} +@section Compatibility with HP Ada 83 -@node Obsolescent Features -@chapter Obsolescent Features -@noindent -This chapter describes features that are provided by GNAT, but are -considered obsolescent since there are preferred ways of achieving -the same effect. These features are provided solely for historical -compatibility purposes. +All the HP Ada 83 pragmas and attributes are recognized, although only a subset +of them can sensibly be implemented. The description of pragmas in +@ref{7,,Implementation Defined Pragmas} indicates whether or not they are +applicable to GNAT. -@menu -* pragma No_Run_Time:: -* pragma Ravenscar:: -* pragma Restricted_Run_Time:: -* pragma Task_Info:: -* System.Task_Info (s-tasinf.ads):: -@end menu -@node pragma No_Run_Time -@section pragma No_Run_Time +@itemize * -The pragma @code{No_Run_Time} is used to achieve an affect similar -to the use of the "Zero Foot Print" configurable run time, but without -requiring a specially configured run time. The result of using this -pragma, which must be used for all units in a partition, is to restrict -the use of any language features requiring run-time support code. The -preferred usage is to use an appropriately configured run-time that -includes just those features that are to be made accessible. +@item +@emph{Default floating-point representation} -@node pragma Ravenscar -@section pragma Ravenscar +In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83, +it is VMS format. -The pragma @code{Ravenscar} has exactly the same effect as pragma -@code{Profile (Ravenscar)}. The latter usage is preferred since it -is part of the new Ada 2005 standard. +@item +@emph{System} -@node pragma Restricted_Run_Time -@section pragma Restricted_Run_Time +the package System in GNAT exactly corresponds to the definition in the +Ada 95 reference manual, which means that it excludes many of the +HP Ada 83 extensions. However, a separate package Aux_DEC is provided +that contains the additional definitions, and a special pragma, +Extend_System allows this package to be treated transparently as an +extension of package System. +@end itemize -The pragma @code{Restricted_Run_Time} has exactly the same effect as -pragma @code{Profile (Restricted)}. The latter usage is -preferred since the Ada 2005 pragma @code{Profile} is intended for -this kind of implementation dependent addition. +@node GNU Free Documentation License,Index,Compatibility and Porting Guide,Top +@anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{3f5}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{3f6} +@chapter GNU Free Documentation License + + +Version 1.3, 3 November 2008 + +Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc +@indicateurl{http://fsf.org/} + +Everyone is permitted to copy and distribute verbatim copies of this +license document, but changing it is not allowed. + +@strong{Preamble} + +The purpose of this License is to make a manual, textbook, or other +functional and useful document "free" in the sense of freedom: to +assure everyone the effective freedom to copy and redistribute it, +with or without modifying it, either commercially or noncommercially. +Secondarily, this License preserves for the author and publisher a way +to get credit for their work, while not being considered responsible +for modifications made by others. + +This License is a kind of "copyleft", which means that derivative +works of the document must themselves be free in the same sense. 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The predefined Ada package - @code{System.Multiprocessors} and the @code{CPU} aspect now provide a -standard replacement for GNAT's @code{Task_Info} functionality. +with the Invariant Sections being LIST THEIR TITLES, with the +Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. +@end quotation + +If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. -@include fdl.texi -@c GNU Free Documentation License +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. -@node Concept Index +@node Index,,GNU Free Documentation License,Top @unnumbered Index -@printindex cp -@contents +@printindex ge + +@c %**end of body @bye diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi index 17f2414ea49..87becc74819 100644 --- a/gcc/ada/gnat_ugn.texi +++ b/gcc/ada/gnat_ugn.texi @@ -1,29558 +1,36266 @@ - \input texinfo @c -*-texinfo-*- @c %**start of header - -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo -@c o -@c GNAT DOCUMENTATION o -@c o -@c G N A T _ U G N o -@c o -@c Copyright (C) 1992-2015, Free Software Foundation, Inc. o -@c o -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo - @setfilename gnat_ugn.info - -@copying -Copyright @copyright{} 1995-2015 Free Software Foundation, -Inc. - -Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, with no Front-Cover Texts and with no Back-Cover -Texts. A copy of the license is included in the section entitled -``GNU Free Documentation License''. -@end copying - -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo -@c -@c GNAT_UGN Style Guide -@c -@c 1. Always put a @noindent on the line before the first paragraph -@c after any of these commands: -@c -@c @chapter -@c @section -@c @subsection -@c @subsubsection -@c @subsubsubsection -@c -@c @end smallexample -@c @end itemize -@c @end enumerate -@c -@c 2. DO NOT use @example. Use @smallexample instead. -@c a) DO NOT use highlighting commands (@b{}, @i{}) inside an @smallexample -@c context. These can interfere with the readability of the texi -@c source file. Instead, use one of the following annotated -@c @smallexample commands, and preprocess the texi file with the -@c ada2texi tool (which generates appropriate highlighting): -@c @smallexample @c ada -@c @smallexample @c adanocomment -@c @smallexample @c projectfile -@c b) The "@c ada" markup will result in boldface for reserved words -@c and italics for comments -@c c) The "@c adanocomment" markup will result only in boldface for -@c reserved words (comments are left alone) -@c d) The "@c projectfile" markup is like "@c ada" except that the set -@c of reserved words include the new reserved words for project files -@c -@c 3. Each @chapter, @section, @subsection, @subsubsection, etc. -@c command must be preceded by two empty lines -@c -@c 4. The @item command should be on a line of its own if it is in an -@c @itemize or @enumerate command. -@c -@c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali" -@c or "ali". -@c -@c 6. DO NOT put trailing spaces at the end of a line. Such spaces will -@c cause the document build to fail. -@c -@c 7. DO NOT use @cartouche for examples that are longer than around 10 lines. -@c This command inhibits page breaks, so long examples in a @cartouche can -@c lead to large, ugly patches of empty space on a page. -@c -@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo - -@set NOW January 2007 -@c This flag is used where the text refers to conditions that exist when the -@c text was entered into the document but which may change over time. -@c Update the setting for the flag, and (if necessary) the text surrounding, -@c the references to the flag, on future doc revisions: -@c search for @value{NOW}. - -@set FSFEDITION -@set EDITION GNAT - -@set PLATFORM - -@c @ovar(ARG) -@c ---------- -@c The ARG is an optional argument. To be used for macro arguments in -@c their documentation (@defmac). -@macro ovar{varname} -@r{[}@var{\varname\}@r{]}@c -@end macro -@c Status as of November 2009: -@c Unfortunately texi2pdf and texi2html treat the trailing "@c" -@c differently, and faulty output is produced by one or the other -@c depending on whether the "@c" is present or absent. -@c As a result, the @ovar macro is not used, and all invocations -@c of the @ovar macro have been expanded inline. - - -@settitle @value{EDITION} User's Guide -@dircategory GNU Ada tools +@documentencoding UTF-8 +@ifinfo +@*Generated by Sphinx 1.2.2.@* +@end ifinfo +@settitle GNAT User's Guide for Native Platforms +@defindex ge +@paragraphindent 0 +@exampleindent 4 +@finalout +@dircategory @direntry -* @value{EDITION} User's Guide: (gnat_ugn). @value{PLATFORM} +* gnat_ugn: (gnat_ugn.info). gnat_ugn @end direntry -@include gcc-common.texi - -@setchapternewpage odd -@syncodeindex fn cp +@definfoenclose strong,`,' +@definfoenclose emph,`,' @c %**end of header -@titlepage -@title @value{EDITION} User's Guide +@copying +@quotation +GNAT User's Guide for Native Platforms , February 20, 2015 -@sp 2 +AdaCore -@subtitle GNAT, The GNU Ada Development Environment -@versionsubtitle -@author AdaCore +Copyright @copyright{} 2008-2015, Free Software Foundation +@end quotation -@page -@vskip 0pt plus 1filll +@end copying +@titlepage +@title GNAT User's Guide for Native Platforms @insertcopying - @end titlepage +@contents + +@c %** start of user preamble + +@c %** end of user preamble @ifnottex -@node Top, About This Guide, (dir), (dir) -@top @value{EDITION} User's Guide +@node Top +@top GNAT User's Guide for Native Platforms +@insertcopying +@end ifnottex + +@c %**start of body +@anchor{gnat_ugn doc}@anchor{0} +@emph{GNAT, The GNU Ada Development Environment} -@noindent -@value{EDITION} User's Guide @value{PLATFORM} -@noindent -GNAT, The GNU Ada Development Environment@* +@include gcc-common.texi GCC version @value{version-GCC}@* +AdaCore -@noindent -AdaCore@* +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with the Front-Cover Texts being +"GNAT User's Guide for Native Platforms", +and with no Back-Cover Texts. A copy of the license is +included in the section entitled @ref{1,,GNU Free Documentation License}. @menu -* About This Guide:: -* Getting Started with GNAT:: -* The GNAT Compilation Model:: -* Compiling with gcc:: -* Binding with gnatbind:: -* Linking with gnatlink:: -* The GNAT Make Program gnatmake:: -* Improving Performance:: -* Renaming Files with gnatchop:: -* Configuration Pragmas:: -* Handling Arbitrary File Naming Conventions with gnatname:: -* GNAT Project Manager:: -* Tools Supporting Project Files:: -* The Cross-Referencing Tools gnatxref and gnatfind:: -@ifclear FSFEDITION -* The GNAT Pretty-Printer gnatpp:: -* The Ada-to-XML converter gnat2xml:: -* The GNAT Metrics Tool gnatmetric:: -@end ifclear -* File Name Krunching with gnatkr:: -* Preprocessing with gnatprep:: -* The GNAT Library Browser gnatls:: -* Cleaning Up with gnatclean:: -* GNAT and Libraries:: -* Using the GNU make Utility:: -* Memory Management Issues:: -* Stack Related Facilities:: -@ifclear FSFEDITION -* Verifying Properties with gnatcheck:: -* Creating Sample Bodies with gnatstub:: -* Creating Unit Tests with gnattest:: -@end ifclear -* Performing Dimensionality Analysis in GNAT:: -* Generating Ada Bindings for C and C++ headers:: -* Other Utility Programs:: -* Code Coverage and Profiling:: -* Running and Debugging Ada Programs:: -* Platform-Specific Information for the Run-Time Libraries:: -* Example of Binder Output File:: -* Elaboration Order Handling in GNAT:: -* Overflow Check Handling in GNAT:: -* Conditional Compilation:: -* Inline Assembler:: -* Writing Portable Fixed-Point Declarations:: -* Compatibility and Porting Guide:: -* Microsoft Windows Topics:: -* Mac OS Topics:: -* GNU Free Documentation License:: -* Index:: -@end menu -@end ifnottex +* About This Guide:: +* Getting Started with GNAT:: +* The GNAT Compilation Model:: +* Building Executable Programs with GNAT:: +* GNAT Project Manager:: +* Tools Supporting Project Files:: +* GNAT Utility Programs:: +* GNAT and Program Execution:: +* Platform-Specific Information:: +* Example of Binder Output File:: +* Elaboration Order Handling in GNAT:: +* Inline Assembler:: +* GNU Free Documentation License:: +* Index:: + +@detailmenu + --- The Detailed Node Listing --- + +About This Guide + +* What This Guide Contains:: +* What You Should Know before Reading This Guide:: +* Related Information:: +* A Note to Readers of Previous Versions of the Manual:: +* Conventions:: + +Getting Started with GNAT + +* Running GNAT:: +* Running a Simple Ada Program:: +* Running a Program with Multiple Units:: +* Using the gnatmake Utility:: + +The GNAT Compilation Model + +* Source Representation:: +* Foreign Language Representation:: +* File Naming Topics and Utilities:: +* Configuration Pragmas:: +* Generating Object Files:: +* Source Dependencies:: +* The Ada Library Information Files:: +* Binding an Ada Program:: +* GNAT and Libraries:: +* Conditional Compilation:: +* Mixed Language Programming:: +* GNAT and Other Compilation Models:: +* Using GNAT Files with External Tools:: + +Foreign Language Representation -@node About This Guide -@unnumbered About This Guide +* Latin-1:: +* Other 8-Bit Codes:: +* Wide_Character Encodings:: +* Wide_Wide_Character Encodings:: + +File Naming Topics and Utilities -@noindent -This guide describes the use of @value{EDITION}, -a compiler and software development -toolset for the full Ada programming language. -It documents the features of the compiler and tools, and explains -how to use them to build Ada applications. +* File Naming Rules:: +* Using Other File Names:: +* Alternative File Naming Schemes:: +* Handling Arbitrary File Naming Conventions with gnatname:: +* File Name Krunching with gnatkr:: +* Renaming Files with gnatchop:: -@value{EDITION} implements Ada 95, Ada 2005 and Ada 2012, and it may also be -invoked in Ada 83 compatibility mode. -By default, @value{EDITION} assumes Ada 2012, but you can override with a -compiler switch (@pxref{Compiling Different Versions of Ada}) -to explicitly specify the language version. -Throughout this manual, references to ``Ada'' without a year suffix -apply to all Ada 95/2005/2012 versions of the language. +Handling Arbitrary File Naming Conventions with gnatname -@ifclear FSFEDITION -For ease of exposition, ``@value{EDITION}'' will be referred to simply as -``GNAT'' in the remainder of this document. -@end ifclear +* Arbitrary File Naming Conventions:: +* Running gnatname:: +* Switches for gnatname:: +* Examples of gnatname Usage:: +File Name Krunching with gnatkr -@menu -* What This Guide Contains:: -* What You Should Know before Reading This Guide:: -* Related Information:: -* Conventions:: -@end menu +* About gnatkr:: +* Using gnatkr:: +* Krunching Method:: +* Examples of gnatkr Usage:: -@node What This Guide Contains -@unnumberedsec What This Guide Contains +Renaming Files with gnatchop -@noindent -This guide contains the following chapters: -@itemize @bullet +* Handling Files with Multiple Units:: +* Operating gnatchop in Compilation Mode:: +* Command Line for gnatchop:: +* Switches for gnatchop:: +* Examples of gnatchop Usage:: -@item -@ref{Getting Started with GNAT}, describes how to get started compiling -and running Ada programs with the GNAT Ada programming environment. -@item -@ref{The GNAT Compilation Model}, describes the compilation model used -by GNAT. +Configuration Pragmas -@item -@ref{Compiling with gcc}, describes how to compile -Ada programs with @command{gcc}, the Ada compiler. +* Handling of Configuration Pragmas:: +* The Configuration Pragmas Files:: -@item -@ref{Binding with gnatbind}, describes how to -perform binding of Ada programs with @code{gnatbind}, the GNAT binding -utility. +GNAT and Libraries -@item -@ref{Linking with gnatlink}, -describes @command{gnatlink}, a -program that provides for linking using the GNAT run-time library to -construct a program. @command{gnatlink} can also incorporate foreign language -object units into the executable. +* Introduction to Libraries in GNAT:: +* General Ada Libraries:: +* Stand-alone Ada Libraries:: +* Rebuilding the GNAT Run-Time Library:: -@item -@ref{The GNAT Make Program gnatmake}, describes @command{gnatmake}, a -utility that automatically determines the set of sources -needed by an Ada compilation unit, and executes the necessary compilations -binding and link. +General Ada Libraries + +* Building a library:: +* Installing a library:: +* Using a library:: + +Stand-alone Ada Libraries + +* Introduction to Stand-alone Libraries:: +* Building a Stand-alone Library:: +* Creating a Stand-alone Library to be used in a non-Ada context:: +* Restrictions in Stand-alone Libraries:: -@item -@ref{Improving Performance}, shows various techniques for making your -Ada program run faster or take less space and describes the effect of -the compiler's optimization switch. -It also describes -@ifclear FSFEDITION -the @command{gnatelim} tool and -@end ifclear -unused subprogram/data elimination. +Conditional Compilation -@item -@ref{Renaming Files with gnatchop}, describes -@code{gnatchop}, a utility that allows you to preprocess a file that -contains Ada source code, and split it into one or more new files, one -for each compilation unit. +* Modeling Conditional Compilation in Ada:: +* Preprocessing with gnatprep:: +* Integrated Preprocessing:: -@item -@ref{Configuration Pragmas}, describes the configuration pragmas -handled by GNAT. +Modeling Conditional Compilation in Ada -@item -@ref{Handling Arbitrary File Naming Conventions with gnatname}, -shows how to override the default GNAT file naming conventions, -either for an individual unit or globally. +* Use of Boolean Constants:: +* Debugging - A Special Case:: +* Conditionalizing Declarations:: +* Use of Alternative Implementations:: +* Preprocessing:: -@item -@ref{GNAT Project Manager}, describes how to use project files -to organize large projects. +Preprocessing with gnatprep + +* Preprocessing Symbols:: +* Using gnatprep:: +* Switches for gnatprep:: +* Form of Definitions File:: +* Form of Input Text for gnatprep:: -@item -@ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses -@code{gnatxref} and @code{gnatfind}, two tools that provide an easy -way to navigate through sources. +Mixed Language Programming -@ifclear FSFEDITION -@item -@ref{The GNAT Pretty-Printer gnatpp}, shows how to produce a reformatted -version of an Ada source file with control over casing, indentation, -comment placement, and other elements of program presentation style. -@end ifclear +* Interfacing to C:: +* Calling Conventions:: +* Building Mixed Ada and C++ Programs:: +* Generating Ada Bindings for C and C++ headers:: -@ifclear FSFEDITION -@item -@ref{The Ada-to-XML converter gnat2xml}, shows how to convert Ada -source code into XML. -@end ifclear +Building Mixed Ada and C++ Programs -@ifclear FSFEDITION -@item -@ref{The GNAT Metrics Tool gnatmetric}, shows how to compute various -metrics for an Ada source file, such as the number of types and subprograms, -and assorted complexity measures. -@end ifclear +* Interfacing to C++:: +* Linking a Mixed C++ & Ada Program:: +* A Simple Example:: +* Interfacing with C++ constructors:: +* Interfacing with C++ at the Class Level:: -@item -@ref{File Name Krunching with gnatkr}, describes the @code{gnatkr} -file name krunching utility, used to handle shortened -file names on operating systems with a limit on the length of names. +Generating Ada Bindings for C and C++ headers -@item -@ref{Preprocessing with gnatprep}, describes @code{gnatprep}, a -preprocessor utility that allows a single source file to be used to -generate multiple or parameterized source files by means of macro -substitution. +* Running the binding generator:: +* Generating bindings for C++ headers:: +* Switches:: -@item -@ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a -utility that displays information about compiled units, including dependences -on the corresponding sources files, and consistency of compilations. +GNAT and Other Compilation Models -@item -@ref{Cleaning Up with gnatclean}, describes @code{gnatclean}, a utility -to delete files that are produced by the compiler, binder and linker. +* Comparison between GNAT and C/C++ Compilation Models:: +* Comparison between GNAT and Conventional Ada Library Models:: -@item -@ref{GNAT and Libraries}, describes the process of creating and using -Libraries with GNAT. It also describes how to recompile the GNAT run-time -library. +Using GNAT Files with External Tools -@item -@ref{Using the GNU make Utility}, describes some techniques for using -the GNAT toolset in Makefiles. +* Using Other Utility Programs with GNAT:: +* The External Symbol Naming Scheme of GNAT:: -@item -@ref{Memory Management Issues}, describes some useful predefined storage pools -and in particular the GNAT Debug Pool facility, which helps detect incorrect -memory references. -@ifclear FSFEDITION -It also describes @command{gnatmem}, a utility that monitors dynamic -allocation and deallocation and helps detect ``memory leaks''. -@end ifclear +Building Executable Programs with GNAT -@item -@ref{Stack Related Facilities}, describes some useful tools associated with -stack checking and analysis. +* Building with gnatmake:: +* Compiling with gcc:: +* Compiler Switches:: +* Binding with gnatbind:: +* Linking with gnatlink:: +* Using the GNU make Utility:: -@ifclear FSFEDITION -@item -@ref{Verifying Properties with gnatcheck}, discusses @code{gnatcheck}, -a utility that checks Ada code against a set of rules. +Building with gnatmake -@item -@ref{Creating Sample Bodies with gnatstub}, discusses @code{gnatstub}, -a utility that generates empty but compilable bodies for library units. -@end ifclear +* Running gnatmake:: +* Switches for gnatmake:: +* Mode Switches for gnatmake:: +* Notes on the Command Line:: +* How gnatmake Works:: +* Examples of gnatmake Usage:: -@ifclear FSFEDITION -@item -@ref{Creating Unit Tests with gnattest}, discusses @code{gnattest}, -a utility that generates unit testing templates for library units. -@end ifclear +Compiling with gcc -@item -@ref{Performing Dimensionality Analysis in GNAT}, describes the Ada 2012 -facilities used in GNAT to declare dimensioned objects, and to verify that -uses of these objects are consistent with their given physical dimensions -(so that meters cannot be assigned to kilograms, and so on). +* Compiling Programs:: +* Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL. +* Order of Compilation Issues:: +* Examples:: -@item -@ref{Generating Ada Bindings for C and C++ headers}, describes how to -generate automatically Ada bindings from C and C++ headers. +Compiler Switches -@item -@ref{Other Utility Programs}, discusses several other GNAT utilities, -including @code{gnathtml}. +* Alphabetical List of All Switches:: +* Output and Error Message Control:: +* Warning Message Control:: +* Debugging and Assertion Control:: +* Validity Checking:: +* Style Checking:: +* Run-Time Checks:: +* Using gcc for Syntax Checking:: +* Using gcc for Semantic Checking:: +* Compiling Different Versions of Ada:: +* Character Set Control:: +* File Naming Control:: +* Subprogram Inlining Control:: +* Auxiliary Output Control:: +* Debugging Control:: +* Exception Handling Control:: +* Units to Sources Mapping Files:: +* Code Generation Control:: + +Binding with gnatbind + +* Running gnatbind:: +* Switches for gnatbind:: +* Command-Line Access:: +* Search Paths for gnatbind:: +* Examples of gnatbind Usage:: + +Switches for gnatbind + +* Consistency-Checking Modes:: +* Binder Error Message Control:: +* Elaboration Control:: +* Output Control:: +* Dynamic Allocation Control:: +* Binding with Non-Ada Main Programs:: +* Binding Programs with No Main Subprogram:: + +Linking with gnatlink + +* Running gnatlink:: +* Switches for gnatlink:: + +Using the GNU make Utility + +* Using gnatmake in a Makefile:: +* Automatically Creating a List of Directories:: +* Generating the Command Line Switches:: +* Overcoming Command Line Length Limits:: + +GNAT Project Manager + +* Introduction:: +* Building With Projects:: +* Organizing Projects into Subsystems:: +* Scenarios in Projects:: +* Library Projects:: +* Project Extension:: +* Aggregate Projects:: +* Aggregate Library Projects:: +* Project File Reference:: + +Building With Projects + +* Source Files and Directories:: +* Duplicate Sources in Projects:: +* Object and Exec Directory:: +* Main Subprograms:: +* Tools Options in Project Files:: +* Compiling with Project Files:: +* Executable File Names:: +* Avoid Duplication With Variables:: +* Naming Schemes:: +* Installation:: +* Distributed support:: + +Organizing Projects into Subsystems + +* Project Dependencies:: +* Cyclic Project Dependencies:: +* Sharing Between Projects:: +* Global Attributes:: + +Library Projects + +* Building Libraries:: +* Using Library Projects:: +* Stand-alone Library Projects:: +* Installing a library with project files:: + +Project Extension + +* Project Hierarchy Extension:: + +Aggregate Projects + +* Building all main programs from a single project tree:: +* Building a set of projects with a single command:: +* Define a build environment:: +* Performance improvements in builder:: +* Syntax of aggregate projects:: +* package Builder in aggregate projects:: + +Aggregate Library Projects + +* Building aggregate library projects:: +* Syntax of aggregate library projects:: + +Project File Reference + +* Project Declaration:: +* Qualified Projects:: +* Declarations:: +* Packages:: +* Expressions:: +* External Values:: +* Typed String Declaration:: +* Variables:: +* Case Constructions:: +* Attributes:: + +Attributes + +* Project Level Attributes:: +* Package Binder Attributes:: +* Package Builder Attributes:: +* Package Clean Attributes:: +* Package Compiler Attributes:: +* Package Cross_Reference Attributes:: +* Package Finder Attributes:: +* Package gnatls Attributes:: +* Package IDE Attributes:: +* Package Install Attributes:: +* Package Linker Attributes:: +* Package Naming Attributes:: +* Package Remote Attributes:: +* Package Stack Attributes:: +* Package Synchronize Attributes:: -@item -@ref{Code Coverage and Profiling}, describes how to perform a structural -coverage and profile the execution of Ada programs. +Tools Supporting Project Files -@item -@ref{Running and Debugging Ada Programs}, describes how to run and debug -Ada programs. +* gnatmake and Project Files:: +* The GNAT Driver and Project Files:: +gnatmake and Project Files -@item -@ref{Platform-Specific Information for the Run-Time Libraries}, -describes the various run-time -libraries supported by GNAT on various platforms and explains how to -choose a particular library. +* Switches Related to Project Files:: +* Switches and Project Files:: +* Specifying Configuration Pragmas:: +* Project Files and Main Subprograms:: +* Library Project Files:: + +GNAT Utility Programs + +* The File Cleanup Utility gnatclean:: +* The GNAT Library Browser gnatls:: +* The Cross-Referencing Tools gnatxref and gnatfind:: +* The Ada to HTML Converter gnathtml:: + +The File Cleanup Utility gnatclean -@item -@ref{Example of Binder Output File}, shows the source code for the binder -output file for a sample program. +* Running gnatclean:: +* Switches for gnatclean:: + +The GNAT Library Browser gnatls + +* Running gnatls:: +* Switches for gnatls:: +* Example of gnatls Usage:: -@item -@ref{Elaboration Order Handling in GNAT}, describes how GNAT helps -you deal with elaboration order issues. +The Cross-Referencing Tools gnatxref and gnatfind -@item -@ref{Overflow Check Handling in GNAT}, describes how GNAT helps -you deal with arithmetic overflow issues. +* gnatxref Switches:: +* gnatfind Switches:: +* Project Files for gnatxref and gnatfind:: +* Regular Expressions in gnatfind and gnatxref:: +* Examples of gnatxref Usage:: +* Examples of gnatfind Usage:: -@item -@ref{Conditional Compilation}, describes how to model conditional compilation, -both with Ada in general and with GNAT facilities in particular. +Examples of gnatxref Usage -@item -@ref{Inline Assembler}, shows how to use the inline assembly facility -in an Ada program. +* General Usage:: +* Using gnatxref with vi:: -@item -@ref{Writing Portable Fixed-Point Declarations}, gives some guidance on -defining portable fixed-point types. +The Ada to HTML Converter gnathtml -@item -@ref{Compatibility and Porting Guide}, contains sections on compatibility -of GNAT with other Ada development environments (including Ada 83 systems), -to assist in porting code from those environments. +* Invoking gnathtml:: +* Installing gnathtml:: -@item -@ref{Microsoft Windows Topics}, presents information relevant to the -Microsoft Windows platform. +GNAT and Program Execution -@item -@ref{Mac OS Topics}, presents information relevant to Apple's OS X -platform. -@end itemize +* Running and Debugging Ada Programs:: +* Code Coverage and Profiling:: +* Improving Performance:: +* Overflow Check Handling in GNAT:: +* Performing Dimensionality Analysis in GNAT:: +* Stack Related Facilities:: +* Memory Management Issues:: -@c ************************************************* -@node What You Should Know before Reading This Guide -@c ************************************************* -@unnumberedsec What You Should Know before Reading This Guide +Running and Debugging Ada Programs -@cindex Ada 95 Language Reference Manual -@cindex Ada 2005 Language Reference Manual -@noindent -This guide assumes a basic familiarity with the Ada 95 language, as -described in the International Standard ANSI/ISO/IEC-8652:1995, January -1995. -It does not require knowledge of the new features introduced by Ada 2005, -(officially known as ISO/IEC 8652:1995 with Technical Corrigendum 1 -and Amendment 1). -Both reference manuals are included in the GNAT documentation -package. +* The GNAT Debugger GDB:: +* Running GDB:: +* Introduction to GDB Commands:: +* Using Ada Expressions:: +* Calling User-Defined Subprograms:: +* Using the next Command in a Function:: +* Stopping When Ada Exceptions Are Raised:: +* Ada Tasks:: +* Debugging Generic Units:: +* Remote Debugging with gdbserver:: +* GNAT Abnormal Termination or Failure to Terminate:: +* Naming Conventions for GNAT Source Files:: +* Getting Internal Debugging Information:: +* Stack Traceback:: -@node Related Information -@unnumberedsec Related Information +Stack Traceback -@noindent -For further information about related tools, refer to the following -documents: +* Non-Symbolic Traceback:: +* Symbolic Traceback:: -@itemize @bullet -@item -@xref{Top, GNAT Reference Manual, About This Guide, gnat_rm, GNAT -Reference Manual}, which contains all reference material for the GNAT -implementation of Ada. +Code Coverage and Profiling -@item -@cite{Using the GNAT Programming Studio}, which describes the GPS -Integrated Development Environment. +* Code Coverage of Ada Programs with gcov:: +* Profiling an Ada Program with gprof:: -@item -@cite{GNAT Programming Studio Tutorial}, which introduces the -main GPS features through examples. +Code Coverage of Ada Programs with gcov -@item -@cite{Ada 95 Reference Manual}, which contains reference -material for the Ada 95 programming language. +* Quick startup guide:: +* GNAT specifics:: -@item -@cite{Ada 2005 Reference Manual}, which contains reference -material for the Ada 2005 programming language. +Profiling an Ada Program with gprof -@item -@xref{Top,, Debugging with GDB, gdb, Debugging with GDB}, -for all details on the use of the GNU source-level debugger. +* Compilation for profiling:: +* Program execution:: +* Running gprof:: +* Interpretation of profiling results:: -@item -@xref{Top,, The extensible self-documenting text editor, emacs, -GNU Emacs Manual}, -for full information on the extensible editor and programming -environment Emacs. +Improving Performance -@end itemize +* Performance Considerations:: +* Text_IO Suggestions:: +* Reducing Size of Executables with Unused Subprogram/Data Elimination:: -@c ************** -@node Conventions -@unnumberedsec Conventions -@cindex Conventions -@cindex Typographical conventions +Performance Considerations -@noindent -Following are examples of the typographical and graphic conventions used -in this guide: +* Controlling Run-Time Checks:: +* Use of Restrictions:: +* Optimization Levels:: +* Debugging Optimized Code:: +* Inlining of Subprograms:: +* Floating_Point_Operations:: +* Vectorization of loops:: +* Other Optimization Switches:: +* Optimization and Strict Aliasing:: +* Aliased Variables and Optimization:: +* Atomic Variables and Optimization:: +* Passive Task Optimization:: -@itemize @bullet -@item -@code{Functions}, @command{utility program names}, @code{standard names}, -and @code{classes}. +Reducing Size of Executables with Unused Subprogram/Data Elimination -@item -@option{Option flags} +* About unused subprogram/data elimination:: +* Compilation options:: +* Example of unused subprogram/data elimination:: -@item -@file{File names}, @samp{button names}, and @samp{field names}. +Overflow Check Handling in GNAT -@item -@code{Variables}, @env{environment variables}, and @var{metasyntactic -variables}. +* Background:: +* Overflow Checking Modes in GNAT:: +* Specifying the Desired Mode:: +* Default Settings:: +* Implementation Notes:: -@item -@emph{Emphasis}. +Stack Related Facilities -@item -@r{[}optional information or parameters@r{]} +* Stack Overflow Checking:: +* Static Stack Usage Analysis:: +* Dynamic Stack Usage Analysis:: -@item -Examples are described by text -@smallexample -and then shown this way. -@end smallexample -@end itemize +Memory Management Issues -@noindent -Commands that are entered by the user are preceded in this manual by the -characters @w{``@code{$ }''} (dollar sign followed by space). If your system -uses this sequence as a prompt, then the commands will appear exactly as -you see them in the manual. If your system uses some other prompt, then -the command will appear with the @code{$} replaced by whatever prompt -character you are using. +* Some Useful Memory Pools:: +* The GNAT Debug Pool Facility:: -Full file names are shown with the ``@code{/}'' character -as the directory separator; e.g., @file{parent-dir/subdir/myfile.adb}. -If you are using GNAT on a Windows platform, please note that -the ``@code{\}'' character should be used instead. +Platform-Specific Information -@c **************************** -@node Getting Started with GNAT -@chapter Getting Started with GNAT +* Run-Time Libraries:: +* Specifying a Run-Time Library:: +* Microsoft Windows Topics:: +* Mac OS Topics:: -@noindent -This chapter describes some simple ways of using GNAT to build -executable Ada programs. -@ref{Running GNAT}, through @ref{Using the gnatmake Utility}, -show how to use the command line environment. -@ref{Introduction to GPS}, provides a brief -introduction to the GNAT Programming Studio, a visually-oriented -Integrated Development Environment for GNAT. -GPS offers a graphical ``look and feel'', support for development in -other programming languages, comprehensive browsing features, and -many other capabilities. -For information on GPS please refer to -@cite{Using the GNAT Programming Studio}. +Run-Time Libraries -@menu -* Running GNAT:: -* Running a Simple Ada Program:: -* Running a Program with Multiple Units:: -* Using the gnatmake Utility:: -* Introduction to GPS:: -@end menu +* Summary of Run-Time Configurations:: -@node Running GNAT -@section Running GNAT +Specifying a Run-Time Library -@noindent -Three steps are needed to create an executable file from an Ada source -file: +* Choosing the Scheduling Policy:: +* Solaris-Specific Considerations:: +* Solaris Threads Issues:: +* AIX-Specific Considerations:: -@enumerate -@item -The source file(s) must be compiled. -@item -The file(s) must be bound using the GNAT binder. -@item -All appropriate object files must be linked to produce an executable. -@end enumerate +Microsoft Windows Topics -@noindent -All three steps are most commonly handled by using the @command{gnatmake} -utility program that, given the name of the main program, automatically -performs the necessary compilation, binding and linking steps. +* Using GNAT on Windows:: +* Using a network installation of GNAT:: +* CONSOLE and WINDOWS subsystems:: +* Temporary Files:: +* Mixed-Language Programming on Windows:: -@node Running a Simple Ada Program -@section Running a Simple Ada Program +Mixed-Language Programming on Windows -@noindent -Any text editor may be used to prepare an Ada program. -(If @code{Emacs} is -used, the optional Ada mode may be helpful in laying out the program.) -The -program text is a normal text file. We will assume in our initial -example that you have used your editor to prepare the following -standard format text file: +* Windows Calling Conventions:: +* Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs. +* Using DLLs with GNAT:: +* Building DLLs with GNAT Project files:: +* Building DLLs with GNAT:: +* Building DLLs with gnatdll:: +* Ada DLLs and Finalization:: +* Creating a Spec for Ada DLLs:: +* GNAT and Windows Resources:: +* Debugging a DLL:: +* Setting Stack Size from gnatlink:: +* Setting Heap Size from gnatlink:: -@smallexample @c ada -@cartouche -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{procedure} Hello @b{is} -@b{begin} - Put_Line ("Hello WORLD!"); -@b{end} Hello; -@end cartouche -@end smallexample +Windows Calling Conventions -@noindent -This file should be named @file{hello.adb}. -With the normal default file naming conventions, GNAT requires -that each file -contain a single compilation unit whose file name is the -unit name, -with periods replaced by hyphens; the -extension is @file{ads} for a -spec and @file{adb} for a body. -You can override this default file naming convention by use of the -special pragma @code{Source_File_Name} (@pxref{Using Other File Names}). -Alternatively, if you want to rename your files according to this default -convention, which is probably more convenient if you will be using GNAT -for all your compilations, then the @code{gnatchop} utility -can be used to generate correctly-named source files -(@pxref{Renaming Files with gnatchop}). +* C Calling Convention:: +* Stdcall Calling Convention:: +* Win32 Calling Convention:: +* DLL Calling Convention:: -You can compile the program using the following command (@code{$} is used -as the command prompt in the examples in this document): +Using DLLs with GNAT -@smallexample -$ gcc -c hello.adb -@end smallexample +* Creating an Ada Spec for the DLL Services:: +* Creating an Import Library:: -@noindent -@command{gcc} is the command used to run the compiler. This compiler is -capable of compiling programs in several languages, including Ada and -C. It assumes that you have given it an Ada program if the file extension is -either @file{.ads} or @file{.adb}, and it will then call -the GNAT compiler to compile the specified file. +Building DLLs with gnatdll -The @option{-c} switch is required. It tells @command{gcc} to only do a -compilation. (For C programs, @command{gcc} can also do linking, but this -capability is not used directly for Ada programs, so the @option{-c} -switch must always be present.) +* Limitations When Using Ada DLLs from Ada:: +* Exporting Ada Entities:: +* Ada DLLs and Elaboration:: -This compile command generates a file -@file{hello.o}, which is the object -file corresponding to your Ada program. It also generates -an ``Ada Library Information'' file @file{hello.ali}, -which contains additional information used to check -that an Ada program is consistent. -To build an executable file, -use @code{gnatbind} to bind the program -and @command{gnatlink} to link it. The -argument to both @code{gnatbind} and @command{gnatlink} is the name of the -@file{ALI} file, but the default extension of @file{.ali} can -be omitted. This means that in the most common case, the argument -is simply the name of the main program: +Creating a Spec for Ada DLLs -@smallexample -$ gnatbind hello -$ gnatlink hello -@end smallexample +* Creating the Definition File:: +* Using gnatdll:: -@noindent -A simpler method of carrying out these steps is to use -@command{gnatmake}, -a master program that invokes all the required -compilation, binding and linking tools in the correct order. In particular, -@command{gnatmake} automatically recompiles any sources that have been -modified since they were last compiled, or sources that depend -on such modified sources, so that ``version skew'' is avoided. -@cindex Version skew (avoided by @command{gnatmake}) +GNAT and Windows Resources -@smallexample -$ gnatmake hello.adb -@end smallexample +* Building Resources:: +* Compiling Resources:: +* Using Resources:: -@noindent -The result is an executable program called @file{hello}, which can be -run by entering: +Debugging a DLL -@smallexample -$ hello -@end smallexample +* Program and DLL Both Built with GCC/GNAT:: +* Program Built with Foreign Tools and DLL Built with GCC/GNAT:: -@noindent -assuming that the current directory is on the search path -for executable programs. +Mac OS Topics -@noindent -and, if all has gone well, you will see +* Codesigning the Debugger:: -@smallexample -Hello WORLD! -@end smallexample +Elaboration Order Handling in GNAT -@noindent -appear in response to this command. +* Elaboration Code:: +* Checking the Elaboration Order:: +* Controlling the Elaboration Order:: +* Controlling Elaboration in GNAT - Internal Calls:: +* Controlling Elaboration in GNAT - External Calls:: +* Default Behavior in GNAT - Ensuring Safety:: +* Treatment of Pragma Elaborate:: +* Elaboration Issues for Library Tasks:: +* Mixing Elaboration Models:: +* What to Do If the Default Elaboration Behavior Fails:: +* Elaboration for Indirect Calls:: +* Summary of Procedures for Elaboration Control:: +* Other Elaboration Order Considerations:: +* Determining the Chosen Elaboration Order:: -@c **************************************** -@node Running a Program with Multiple Units -@section Running a Program with Multiple Units +Inline Assembler -@noindent -Consider a slightly more complicated example that has three files: a -main program, and the spec and body of a package: +* Basic Assembler Syntax:: +* A Simple Example of Inline Assembler:: +* Output Variables in Inline Assembler:: +* Input Variables in Inline Assembler:: +* Inlining Inline Assembler Code:: +* Other Asm Functionality:: -@smallexample @c ada -@cartouche -@group -@b{package} Greetings @b{is} - @b{procedure} Hello; - @b{procedure} Goodbye; -@b{end} Greetings; - -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{package} @b{body} Greetings @b{is} - @b{procedure} Hello @b{is} - @b{begin} - Put_Line ("Hello WORLD!"); - @b{end} Hello; +Other Asm Functionality - @b{procedure} Goodbye @b{is} - @b{begin} - Put_Line ("Goodbye WORLD!"); - @b{end} Goodbye; -@b{end} Greetings; -@end group - -@group -@b{with} Greetings; -@b{procedure} Gmain @b{is} -@b{begin} - Greetings.Hello; - Greetings.Goodbye; -@b{end} Gmain; -@end group -@end cartouche -@end smallexample +* The Clobber Parameter:: +* The Volatile Parameter:: -@noindent -Following the one-unit-per-file rule, place this program in the -following three separate files: +@end detailmenu +@end menu -@table @file -@item greetings.ads -spec of package @code{Greetings} +@node About This Guide,Getting Started with GNAT,Top,Top +@anchor{gnat_ugn/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_ugn/about_this_guide doc}@anchor{3}@anchor{gnat_ugn/about_this_guide gnat-user-s-guide-for-native-platforms}@anchor{4}@anchor{gnat_ugn/about_this_guide id1}@anchor{5} +@chapter About This Guide -@item greetings.adb -body of package @code{Greetings} -@item gmain.adb -body of main program -@end table -@noindent -To build an executable version of -this program, we could use four separate steps to compile, bind, and link -the program, as follows: +This guide describes the use of GNAT, +a compiler and software development +toolset for the full Ada programming language. +It documents the features of the compiler and tools, and explains +how to use them to build Ada applications. -@smallexample -$ gcc -c gmain.adb -$ gcc -c greetings.adb -$ gnatbind gmain -$ gnatlink gmain -@end smallexample +GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be +invoked in Ada 83 compatibility mode. +By default, GNAT assumes Ada 2012, but you can override with a +compiler switch (@ref{6,,Compiling Different Versions of Ada}) +to explicitly specify the language version. +Throughout this manual, references to 'Ada' without a year suffix +apply to all Ada 95/2005/2012 versions of the language. -@noindent -Note that there is no required order of compilation when using GNAT. -In particular it is perfectly fine to compile the main program first. -Also, it is not necessary to compile package specs in the case where -there is an accompanying body; you only need to compile the body. If you want -to submit these files to the compiler for semantic checking and not code -generation, then use the -@option{-gnatc} switch: +@menu +* What This Guide Contains:: +* What You Should Know before Reading This Guide:: +* Related Information:: +* A Note to Readers of Previous Versions of the Manual:: +* Conventions:: -@smallexample -$ gcc -c greetings.ads -gnatc -@end smallexample +@end menu -@noindent -Although the compilation can be done in separate steps as in the -above example, in practice it is almost always more convenient -to use the @command{gnatmake} tool. All you need to know in this case -is the name of the main program's source file. The effect of the above four -commands can be achieved with a single one: +@node What This Guide Contains,What You Should Know before Reading This Guide,,About This Guide +@anchor{gnat_ugn/about_this_guide what-this-guide-contains}@anchor{7} +@section What This Guide Contains -@smallexample -$ gnatmake gmain.adb -@end smallexample -@noindent -In the next section we discuss the advantages of using @command{gnatmake} in -more detail. +This guide contains the following chapters: -@c ***************************** -@node Using the gnatmake Utility -@section Using the @command{gnatmake} Utility -@noindent -If you work on a program by compiling single components at a time using -@command{gcc}, you typically keep track of the units you modify. In order to -build a consistent system, you compile not only these units, but also any -units that depend on the units you have modified. -For example, in the preceding case, -if you edit @file{gmain.adb}, you only need to recompile that file. But if -you edit @file{greetings.ads}, you must recompile both -@file{greetings.adb} and @file{gmain.adb}, because both files contain -units that depend on @file{greetings.ads}. +@itemize * -@code{gnatbind} will warn you if you forget one of these compilation -steps, so that it is impossible to generate an inconsistent program as a -result of forgetting to do a compilation. Nevertheless it is tedious and -error-prone to keep track of dependencies among units. -One approach to handle the dependency-bookkeeping is to use a -makefile. However, makefiles present maintenance problems of their own: -if the dependencies change as you change the program, you must make -sure that the makefile is kept up-to-date manually, which is also an -error-prone process. +@item +@ref{8,,Getting Started with GNAT} describes how to get started compiling +and running Ada programs with the GNAT Ada programming environment. -The @command{gnatmake} utility takes care of these details automatically. -Invoke it using either one of the following forms: +@item +@ref{9,,The GNAT Compilation Model} describes the compilation model used +by GNAT. -@smallexample -$ gnatmake gmain.adb -$ gnatmake gmain -@end smallexample +@item +@ref{a,,Building Executable Programs with GNAT} describes how to use the +main GNAT tools to build executable programs, and it also gives examples of +using the GNU make utility with GNAT. -@noindent -The argument is the name of the file containing the main program; -you may omit the extension. @command{gnatmake} -examines the environment, automatically recompiles any files that need -recompiling, and binds and links the resulting set of object files, -generating the executable file, @file{gmain}. -In a large program, it -can be extremely helpful to use @command{gnatmake}, because working out by hand -what needs to be recompiled can be difficult. +@item +@ref{b,,GNAT Project Manager} describes how to use project files +to organize large projects. -Note that @command{gnatmake} -takes into account all the Ada rules that -establish dependencies among units. These include dependencies that result -from inlining subprogram bodies, and from -generic instantiation. Unlike some other -Ada make tools, @command{gnatmake} does not rely on the dependencies that were -found by the compiler on a previous compilation, which may possibly -be wrong when sources change. @command{gnatmake} determines the exact set of -dependencies from scratch each time it is run. +@item +@ref{c,,Tools Supporting Project Files} described how to use the project +facility in conjunction with various GNAT tools. +@item +@ref{d,,GNAT Utility Programs} explains the various utility programs that +are included in the GNAT environment -@node Introduction to GPS -@section Introduction to GPS -@cindex GPS (GNAT Programming Studio) -@cindex GNAT Programming Studio (GPS) -@noindent -Although the command line interface (@command{gnatmake}, etc.) alone -is sufficient, a graphical Interactive Development -Environment can make it easier for you to compose, navigate, and debug -programs. This section describes the main features of GPS -(``GNAT Programming Studio''), the GNAT graphical IDE. -You will see how to use GPS to build and debug an executable, and -you will also learn some of the basics of the GNAT ``project'' facility. - -GPS enables you to do much more than is presented here; -e.g., you can produce a call graph, interface to a third-party -Version Control System, and inspect the generated assembly language -for a program. -Indeed, GPS also supports languages other than Ada. -Such additional information, and an explanation of all of the GPS menu -items. may be found in the on-line help, which includes -a user's guide and a tutorial (these are also accessible from the GNAT -startup menu). +@item +@ref{e,,GNAT and Program Execution} covers a number of topics related to +running, debugging, and tuning the performace of programs developed +with GNAT +@end itemize -@menu -* Building a New Program with GPS:: -* Simple Debugging with GPS:: -@end menu +Appendices cover several additional topics: -@node Building a New Program with GPS -@subsection Building a New Program with GPS -@noindent -GPS invokes the GNAT compilation tools using information -contained in a @emph{project} (also known as a @emph{project file}): -a collection of properties such -as source directories, identities of main subprograms, tool switches, etc., -and their associated values. -See @ref{GNAT Project Manager} for details. -In order to run GPS, you will need to either create a new project -or else open an existing one. - -This section will explain how you can use GPS to create a project, -to associate Ada source files with a project, and to build and run -programs. - -@enumerate -@item @emph{Creating a project} - -Invoke GPS, either from the command line or the platform's IDE. -After it starts, GPS will display a ``Welcome'' screen with three -radio buttons: - -@itemize @bullet -@item -@code{Start with default project in directory} -@item -@code{Create new project with wizard} +@itemize * -@item -@code{Open existing project} -@end itemize +@item +@ref{f,,Platform-Specific Information} describes the different run-time +library implementations and also presents information on how to use +GNAT on several specific platforms -@noindent -Select @code{Create new project with wizard} and press @code{OK}. -A new window will appear. In the text box labeled with -@code{Enter the name of the project to create}, type @file{sample} -as the project name. -In the next box, browse to choose the directory in which you -would like to create the project file. -After selecting an appropriate directory, press @code{Forward}. - -A window will appear with the title -@code{Version Control System Configuration}. -Simply press @code{Forward}. - -A window will appear with the title -@code{Please select the source directories for this project}. -The directory that you specified for the project file will be selected -by default as the one to use for sources; simply press @code{Forward}. - -A window will appear with the title -@code{Please select the build directory for this project}. -The directory that you specified for the project file will be selected -by default for object files and executables; -simply press @code{Forward}. - -A window will appear with the title -@code{Please select the main units for this project}. -You will supply this information later, after creating the source file. -Simply press @code{Forward} for now. - -A window will appear with the title -@code{Please select the switches to build the project}. -Press @code{Apply}. This will create a project file named -@file{sample.prj} in the directory that you had specified. - -@item @emph{Creating and saving the source file} - -After you create the new project, a GPS window will appear, which is -partitioned into two main sections: - -@itemize @bullet -@item -A @emph{Workspace area}, initially greyed out, which you will use for -creating and editing source files +@item +@ref{10,,Example of Binder Output File} shows the source code for the binder +output file for a sample program. -@item -Directly below, a @emph{Messages area}, which initially displays a -``Welcome'' message. -(If the Messages area is not visible, drag its border upward to expand it.) +@item +@ref{11,,Elaboration Order Handling in GNAT} describes how GNAT helps +you deal with elaboration order issues. + +@item +@ref{12,,Inline Assembler} shows how to use the inline assembly facility +in an Ada program. @end itemize -@noindent -Select @code{File} on the menu bar, and then the @code{New} command. -The Workspace area will become white, and you can now -enter the source program explicitly. -Type the following text - -@smallexample @c ada -@group -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{procedure} Hello @b{is} -@b{begin} - Put_Line("Hello from GPS!"); -@b{end} Hello; -@end group -@end smallexample - -@noindent -Select @code{File}, then @code{Save As}, and enter the source file name -@file{hello.adb}. -The file will be saved in the same directory you specified as the -location of the default project file. - -@item @emph{Updating the project file} - -You need to add the new source file to the project. -To do this, select -the @code{Project} menu and then @code{Edit project properties}. -Click the @code{Main files} tab on the left, and then the -@code{Add} button. -Choose @file{hello.adb} from the list, and press @code{Open}. -The project settings window will reflect this action. -Click @code{OK}. - -@item @emph{Building and running the program} - -In the main GPS window, now choose the @code{Build} menu, then @code{Make}, -and select @file{hello.adb}. -The Messages window will display the resulting invocations of @command{gcc}, -@command{gnatbind}, and @command{gnatlink} -(reflecting the default switch settings from the -project file that you created) and then a ``successful compilation/build'' -message. - -To run the program, choose the @code{Build} menu, then @code{Run}, and -select @command{hello}. -An @emph{Arguments Selection} window will appear. -There are no command line arguments, so just click @code{OK}. - -The Messages window will now display the program's output (the string -@code{Hello from GPS}), and at the bottom of the GPS window a status -update is displayed (@code{Run: hello}). -Close the GPS window (or select @code{File}, then @code{Exit}) to -terminate this GPS session. -@end enumerate +@node What You Should Know before Reading This Guide,Related Information,What This Guide Contains,About This Guide +@anchor{gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide}@anchor{13} +@section What You Should Know before Reading This Guide -@node Simple Debugging with GPS -@subsection Simple Debugging with GPS -@noindent -This section illustrates basic debugging techniques (setting breakpoints, -examining/modifying variables, single stepping). - -@enumerate -@item @emph{Opening a project} - -Start GPS and select @code{Open existing project}; browse to -specify the project file @file{sample.prj} that you had created in the -earlier example. - -@item @emph{Creating a source file} - -Select @code{File}, then @code{New}, and type in the following program: - -@smallexample @c ada -@group -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{procedure} Example @b{is} - Line : String (1..80); - N : Natural; -@b{begin} - Put_Line("Type a line of text at each prompt; an empty line to exit"); - @b{loop} - Put(": "); - Get_Line (Line, N); - Put_Line (Line (1..N) ); - @b{exit} @b{when} N=0; - @b{end} @b{loop}; -@b{end} Example; -@end group -@end smallexample - -@noindent -Select @code{File}, then @code{Save as}, and enter the file name -@file{example.adb}. - -@item @emph{Updating the project file} - -Add @code{Example} as a new main unit for the project: -@enumerate a -@item -Select @code{Project}, then @code{Edit Project Properties}. -@item -Select the @code{Main files} tab, click @code{Add}, then -select the file @file{example.adb} from the list, and -click @code{Open}. -You will see the file name appear in the list of main units +@geindex Ada 95 Language Reference Manual -@item -Click @code{OK} -@end enumerate +@geindex Ada 2005 Language Reference Manual -@item @emph{Building/running the executable} +This guide assumes a basic familiarity with the Ada 95 language, as +described in the International Standard ANSI/ISO/IEC-8652:1995, January +1995. +It does not require knowledge of the features introduced by Ada 2005 +or Ada 2012. +Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in +the GNAT documentation package. -To build the executable -select @code{Build}, then @code{Make}, and then choose @file{example.adb}. +@node Related Information,A Note to Readers of Previous Versions of the Manual,What You Should Know before Reading This Guide,About This Guide +@anchor{gnat_ugn/about_this_guide related-information}@anchor{14} +@section Related Information -Run the program to see its effect (in the Messages area). -Each line that you enter is displayed; an empty line will -cause the loop to exit and the program to terminate. -@item @emph{Debugging the program} +For further information about Ada and related tools, please refer to the +following documents: -Note that the @option{-g} switches to @command{gcc} and @command{gnatlink}, -which are required for debugging, are on by default when you create -a new project. -Thus unless you intentionally remove these settings, you will be able -to debug any program that you develop using GPS. -@enumerate a -@item @emph{Initializing} +@itemize * -Select @code{Debug}, then @code{Initialize}, then @file{example} +@item +@cite{Ada 95 Reference Manual}, @cite{Ada 2005 Reference Manual}, and +@cite{Ada 2012 Reference Manual}, which contain reference +material for the several revisions of the Ada language standard. -@item @emph{Setting a breakpoint} +@item +@cite{GNAT Reference_Manual}, which contains all reference material for the GNAT +implementation of Ada. -After performing the initialization step, you will observe a small -icon to the right of each line number. -This serves as a toggle for breakpoints; clicking the icon will -set a breakpoint at the corresponding line (the icon will change to -a red circle with an ``x''), and clicking it again -will remove the breakpoint / reset the icon. +@item +@cite{Using the GNAT Programming Studio}, which describes the GPS +Integrated Development Environment. -For purposes of this example, set a breakpoint at line 10 (the -statement @code{Put_Line@ (Line@ (1..N));} +@item +@cite{GNAT Programming Studio Tutorial}, which introduces the +main GPS features through examples. -@item @emph{Starting program execution} +@item +@cite{Debugging with GDB}, +for all details on the use of the GNU source-level debugger. -Select @code{Debug}, then @code{Run}. When the -@code{Program Arguments} window appears, click @code{OK}. -A console window will appear; enter some line of text, -e.g.@: @code{abcde}, at the prompt. -The program will pause execution when it gets to the -breakpoint, and the corresponding line is highlighted. +@item +@cite{GNU Emacs Manual}, +for full information on the extensible editor and programming +environment Emacs. +@end itemize -@item @emph{Examining a variable} +@node A Note to Readers of Previous Versions of the Manual,Conventions,Related Information,About This Guide +@anchor{gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual}@anchor{15} +@section A Note to Readers of Previous Versions of the Manual -Move the mouse over one of the occurrences of the variable @code{N}. -You will see the value (5) displayed, in ``tool tip'' fashion. -Right click on @code{N}, select @code{Debug}, then select @code{Display N}. -You will see information about @code{N} appear in the @code{Debugger Data} -pane, showing the value as 5. -@item @emph{Assigning a new value to a variable} +In early 2015 the GNAT manuals were transitioned to the +reStructuredText (rst) / Sphinx documentation generator technology. +During that process the @cite{GNAT User's Guide} was reorganized +so that related topics would be described together in the same chapter +or appendix. Here's a summary of the major changes realized in +the new document structure. -Right click on the @code{N} in the @code{Debugger Data} pane, and -select @code{Set value of N}. -When the input window appears, enter the value @code{4} and click -@code{OK}. -This value does not automatically appear in the @code{Debugger Data} -pane; to see it, right click again on the @code{N} in the -@code{Debugger Data} pane and select @code{Update value}. -The new value, 4, will appear in red. -@item @emph{Single stepping} +@itemize * -Select @code{Debug}, then @code{Next}. -This will cause the next statement to be executed, in this case the -call of @code{Put_Line} with the string slice. -Notice in the console window that the displayed string is simply -@code{abcd} and not @code{abcde} which you had entered. -This is because the upper bound of the slice is now 4 rather than 5. +@item +@ref{9,,The GNAT Compilation Model} has been extended so that it now covers +the following material: -@item @emph{Removing a breakpoint} -Toggle the breakpoint icon at line 10. +@itemize - -@item @emph{Resuming execution from a breakpoint} +@item +The @cite{gnatname}, @cite{gnatkr}, and @cite{gnatchop} tools -Select @code{Debug}, then @code{Continue}. -The program will reach the next iteration of the loop, and -wait for input after displaying the prompt. -This time, just hit the @kbd{Enter} key. -The value of @code{N} will be 0, and the program will terminate. -The console window will disappear. -@end enumerate -@end enumerate +@item +@ref{16,,Configuration Pragmas} -@node The GNAT Compilation Model -@chapter The GNAT Compilation Model -@cindex GNAT compilation model -@cindex Compilation model +@item +@ref{17,,GNAT and Libraries} -@menu -* Source Representation:: -* Foreign Language Representation:: -* File Naming Rules:: -* Using Other File Names:: -* Alternative File Naming Schemes:: -* Generating Object Files:: -* Source Dependencies:: -* The Ada Library Information Files:: -* Binding an Ada Program:: -* Mixed Language Programming:: -* Building Mixed Ada & C++ Programs:: -* Comparison between GNAT and C/C++ Compilation Models:: -* Comparison between GNAT and Conventional Ada Library Models:: -@end menu +@item +@ref{18,,Conditional Compilation} including @ref{19,,Preprocessing with gnatprep} +and @ref{1a,,Integrated Preprocessing} -@noindent -This chapter describes the compilation model used by GNAT. Although -similar to that used by other languages, such as C and C++, this model -is substantially different from the traditional Ada compilation models, -which are based on a library. The model is initially described without -reference to the library-based model. If you have not previously used an -Ada compiler, you need only read the first part of this chapter. The -last section describes and discusses the differences between the GNAT -model and the traditional Ada compiler models. If you have used other -Ada compilers, this section will help you to understand those -differences, and the advantages of the GNAT model. - -@node Source Representation -@section Source Representation -@cindex Latin-1 +@item +@ref{1b,,Generating Ada Bindings for C and C++ headers} -@noindent -Ada source programs are represented in standard text files, using -Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar -7-bit ASCII set, plus additional characters used for -representing foreign languages (@pxref{Foreign Language Representation} -for support of non-USA character sets). The format effector characters -are represented using their standard ASCII encodings, as follows: +@item +@ref{1c,,Using GNAT Files with External Tools} +@end itemize -@table @code -@item VT -@findex VT -Vertical tab, @code{16#0B#} +@item +@ref{a,,Building Executable Programs with GNAT} is a new chapter consolidating +the following content: -@item HT -@findex HT -Horizontal tab, @code{16#09#} -@item CR -@findex CR -Carriage return, @code{16#0D#} +@itemize - -@item LF -@findex LF -Line feed, @code{16#0A#} +@item +@ref{1d,,Building with gnatmake} -@item FF -@findex FF -Form feed, @code{16#0C#} -@end table +@item +@ref{1e,,Compiling with gcc} -@noindent -Source files are in standard text file format. In addition, GNAT will -recognize a wide variety of stream formats, in which the end of -physical lines is marked by any of the following sequences: -@code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful -in accommodating files that are imported from other operating systems. +@item +@ref{1f,,Binding with gnatbind} -@cindex End of source file -@cindex Source file, end -@findex SUB -The end of a source file is normally represented by the physical end of -file. However, the control character @code{16#1A#} (@code{SUB}) is also -recognized as signalling the end of the source file. Again, this is -provided for compatibility with other operating systems where this -code is used to represent the end of file. +@item +@ref{20,,Linking with gnatlink} -Each file contains a single Ada compilation unit, including any pragmas -associated with the unit. For example, this means you must place a -package declaration (a package @dfn{spec}) and the corresponding body in -separate files. An Ada @dfn{compilation} (which is a sequence of -compilation units) is represented using a sequence of files. Similarly, -you will place each subunit or child unit in a separate file. +@item +@ref{21,,Using the GNU make Utility} +@end itemize -@node Foreign Language Representation -@section Foreign Language Representation +@item +@ref{d,,GNAT Utility Programs} is a new chapter consolidating the information about several +GNAT tools: -@noindent -GNAT supports the standard character sets defined in Ada as well as -several other non-standard character sets for use in localized versions -of the compiler (@pxref{Character Set Control}). -@menu -* Latin-1:: -* Other 8-Bit Codes:: -* Wide_Character Encodings:: -* Wide_Wide_Character Encodings:: -@end menu -@node Latin-1 -@subsection Latin-1 -@cindex Latin-1 -@noindent -The basic character set is Latin-1. This character set is defined by ISO -standard 8859, part 1. The lower half (character codes @code{16#00#} -@dots{} @code{16#7F#)} is identical to standard ASCII coding, but the upper -half is used to represent additional characters. These include extended letters -used by European languages, such as French accents, the vowels with umlauts -used in German, and the extra letter A-ring used in Swedish. +@itemize - -@findex Ada.Characters.Latin_1 -For a complete list of Latin-1 codes and their encodings, see the source -file of library unit @code{Ada.Characters.Latin_1} in file -@file{a-chlat1.ads}. -You may use any of these extended characters freely in character or -string literals. In addition, the extended characters that represent -letters can be used in identifiers. +@item +@ref{22,,The File Cleanup Utility gnatclean} -@node Other 8-Bit Codes -@subsection Other 8-Bit Codes +@item +@ref{23,,The GNAT Library Browser gnatls} -@noindent -GNAT also supports several other 8-bit coding schemes: +@item +@ref{24,,The Cross-Referencing Tools gnatxref and gnatfind} -@table @asis -@item ISO 8859-2 (Latin-2) -@cindex Latin-2 -@cindex ISO 8859-2 -Latin-2 letters allowed in identifiers, with uppercase and lowercase -equivalence. +@item +@ref{25,,The Ada to HTML Converter gnathtml} +@end itemize -@item ISO 8859-3 (Latin-3) -@cindex Latin-3 -@cindex ISO 8859-3 -Latin-3 letters allowed in identifiers, with uppercase and lowercase -equivalence. +@item +@ref{e,,GNAT and Program Execution} is a new chapter consolidating the following: -@item ISO 8859-4 (Latin-4) -@cindex Latin-4 -@cindex ISO 8859-4 -Latin-4 letters allowed in identifiers, with uppercase and lowercase -equivalence. -@item ISO 8859-5 (Cyrillic) -@cindex ISO 8859-5 -@cindex Cyrillic -ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and -lowercase equivalence. +@itemize - -@item ISO 8859-15 (Latin-9) -@cindex ISO 8859-15 -@cindex Latin-9 -ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and -lowercase equivalence +@item +@ref{26,,Running and Debugging Ada Programs} -@item IBM PC (code page 437) -@cindex code page 437 -This code page is the normal default for PCs in the U.S. It corresponds -to the original IBM PC character set. This set has some, but not all, of -the extended Latin-1 letters, but these letters do not have the same -encoding as Latin-1. In this mode, these letters are allowed in -identifiers with uppercase and lowercase equivalence. +@item +@ref{27,,Code Coverage and Profiling} -@item IBM PC (code page 850) -@cindex code page 850 -This code page is a modification of 437 extended to include all the -Latin-1 letters, but still not with the usual Latin-1 encoding. In this -mode, all these letters are allowed in identifiers with uppercase and -lowercase equivalence. +@item +@ref{28,,Improving Performance} -@item Full Upper 8-bit -Any character in the range 80-FF allowed in identifiers, and all are -considered distinct. In other words, there are no uppercase and lowercase -equivalences in this range. This is useful in conjunction with -certain encoding schemes used for some foreign character sets (e.g., -the typical method of representing Chinese characters on the PC). +@item +@ref{29,,Overflow Check Handling in GNAT} -@item No Upper-Half -No upper-half characters in the range 80-FF are allowed in identifiers. -This gives Ada 83 compatibility for identifier names. -@end table +@item +@ref{2a,,Performing Dimensionality Analysis in GNAT} -@noindent -For precise data on the encodings permitted, and the uppercase and lowercase -equivalences that are recognized, see the file @file{csets.adb} in -the GNAT compiler sources. You will need to obtain a full source release -of GNAT to obtain this file. +@item +@ref{2b,,Stack Related Facilities} -@node Wide_Character Encodings -@subsection Wide_Character Encodings +@item +@ref{2c,,Memory Management Issues} +@end itemize -@noindent -GNAT allows wide character codes to appear in character and string -literals, and also optionally in identifiers, by means of the following -possible encoding schemes: +@item +@ref{f,,Platform-Specific Information} is a new appendix consolidating the following: -@table @asis -@item Hex Coding -In this encoding, a wide character is represented by the following five -character sequence: +@itemize - -@smallexample -ESC a b c d -@end smallexample +@item +@ref{2d,,Run-Time Libraries} -@noindent -Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal -characters (using uppercase letters) of the wide character code. For -example, ESC A345 is used to represent the wide character with code -@code{16#A345#}. -This scheme is compatible with use of the full Wide_Character set. +@item +@ref{2e,,Microsoft Windows Topics} -@item Upper-Half Coding -@cindex Upper-Half Coding -The wide character with encoding @code{16#abcd#} where the upper bit is on -(in other words, ``a'' is in the range 8-F) is represented as two bytes, -@code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control -character, but is not required to be in the upper half. This method can -be also used for shift-JIS or EUC, where the internal coding matches the -external coding. +@item +@ref{2f,,Mac OS Topics} +@end itemize -@item Shift JIS Coding -@cindex Shift JIS Coding -A wide character is represented by a two-character sequence, -@code{16#ab#} and -@code{16#cd#}, with the restrictions described for upper-half encoding as -described above. The internal character code is the corresponding JIS -character according to the standard algorithm for Shift-JIS -conversion. Only characters defined in the JIS code set table can be -used with this encoding method. +@item +The @cite{Compatibility and Porting Guide} appendix has been moved to the +@cite{GNAT Reference Manual}. It now includes a section +@cite{Writing Portable Fixed-Point Declarations} which was previously +a separate chapter in the @cite{GNAT User's Guide}. +@end itemize -@item EUC Coding -@cindex EUC Coding -A wide character is represented by a two-character sequence -@code{16#ab#} and -@code{16#cd#}, with both characters being in the upper half. The internal -character code is the corresponding JIS character according to the EUC -encoding algorithm. Only characters defined in the JIS code set table -can be used with this encoding method. +@node Conventions,,A Note to Readers of Previous Versions of the Manual,About This Guide +@anchor{gnat_ugn/about_this_guide conventions}@anchor{30} +@section Conventions -@item UTF-8 Coding -A wide character is represented using -UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO -10646-1/Am.2. Depending on the character value, the representation -is a one, two, or three byte sequence: -@smallexample -@iftex -@leftskip=.7cm -@end iftex -16#0000#-16#007f#: 2#0@var{xxxxxxx}# -16#0080#-16#07ff#: 2#110@var{xxxxx}# 2#10@var{xxxxxx}# -16#0800#-16#ffff#: 2#1110@var{xxxx}# 2#10@var{xxxxxx}# 2#10@var{xxxxxx}# - -@end smallexample - -@noindent -where the @var{xxx} bits correspond to the left-padded bits of the -16-bit character value. Note that all lower half ASCII characters -are represented as ASCII bytes and all upper half characters and -other wide characters are represented as sequences of upper-half -(The full UTF-8 scheme allows for encoding 31-bit characters as -6-byte sequences, and in the following section on wide wide -characters, the use of these sequences is documented). -@item Brackets Coding -In this encoding, a wide character is represented by the following eight -character sequence: +@geindex Conventions +@geindex typographical -@smallexample -[ " a b c d " ] -@end smallexample +@geindex Typographical conventions -@noindent -Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal -characters (using uppercase letters) of the wide character code. For -example, [``A345''] is used to represent the wide character with code -@code{16#A345#}. It is also possible (though not required) to use the -Brackets coding for upper half characters. For example, the code -@code{16#A3#} can be represented as @code{[``A3'']}. +Following are examples of the typographical and graphic conventions used +in this guide: -This scheme is compatible with use of the full Wide_Character set, -and is also the method used for wide character encoding in some standard -ACATS (Ada Conformity Assessment Test Suite) test suite distributions. -@end table +@itemize * -@noindent -Note: Some of these coding schemes do not permit the full use of the -Ada character set. For example, neither Shift JIS, nor EUC allow the -use of the upper half of the Latin-1 set. +@item +@cite{Functions}, @cite{utility program names}, @cite{standard names}, +and @cite{classes}. -@node Wide_Wide_Character Encodings -@subsection Wide_Wide_Character Encodings +@item +@cite{Option flags} -@noindent -GNAT allows wide wide character codes to appear in character and string -literals, and also optionally in identifiers, by means of the following -possible encoding schemes: +@item +@code{File names} -@table @asis +@item +@cite{Variables} -@item UTF-8 Coding -A wide character is represented using -UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO -10646-1/Am.2. Depending on the character value, the representation -of character codes with values greater than 16#FFFF# is a -is a four, five, or six byte sequence: +@item +@emph{Emphasis} -@smallexample -@iftex -@leftskip=.7cm -@end iftex -16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx - 10xxxxxx -16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx - 10xxxxxx 10xxxxxx -16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx - 10xxxxxx 10xxxxxx 10xxxxxx -@end smallexample +@item +[optional information or parameters] -@noindent -where the @var{xxx} bits correspond to the left-padded bits of the -32-bit character value. +@item +Examples are described by text -@item Brackets Coding -In this encoding, a wide wide character is represented by the following ten or -twelve byte character sequence: +@example +and then shown this way. +@end example -@smallexample -[ " a b c d e f " ] -[ " a b c d e f g h " ] -@end smallexample +@item +Commands that are entered by the user are shown as preceded by a prompt string +comprising the @code{$} character followed by a space. -@noindent -Where @code{a-h} are the six or eight hexadecimal -characters (using uppercase letters) of the wide wide character code. For -example, ["1F4567"] is used to represent the wide wide character with code -@code{16#001F_4567#}. +@item +Full file names are shown with the '/' character +as the directory separator; e.g., @code{parent-dir/subdir/myfile.adb}. +If you are using GNAT on a Windows platform, please note that +the '\' character should be used instead. +@end itemize -This scheme is compatible with use of the full Wide_Wide_Character set, -and is also the method used for wide wide character encoding in some standard -ACATS (Ada Conformity Assessment Test Suite) test suite distributions. +@node Getting Started with GNAT,The GNAT Compilation Model,About This Guide,Top +@anchor{gnat_ugn/getting_started_with_gnat getting-started-with-gnat}@anchor{8}@anchor{gnat_ugn/getting_started_with_gnat doc}@anchor{31}@anchor{gnat_ugn/getting_started_with_gnat id1}@anchor{32} +@chapter Getting Started with GNAT -@end table -@node File Naming Rules -@section File Naming Rules +This chapter describes how to use GNAT's command line interface to build +executable Ada programs. +On most platforms a visually oriented Integrated Development Environment +is also available, the GNAT Programming Studio (GPS). +GPS offers a graphical "look and feel", support for development in +other programming languages, comprehensive browsing features, and +many other capabilities. +For information on GPS please refer to +@cite{Using the GNAT Programming Studio}. -@noindent -The default file name is determined by the name of the unit that the -file contains. The name is formed by taking the full expanded name of -the unit and replacing the separating dots with hyphens and using -lowercase for all letters. +@menu +* Running GNAT:: +* Running a Simple Ada Program:: +* Running a Program with Multiple Units:: +* Using the gnatmake Utility:: -An exception arises if the file name generated by the above rules starts -with one of the characters -@samp{a}, @samp{g}, @samp{i}, or @samp{s}, -and the second character is a -minus. In this case, the character tilde is used in place -of the minus. The reason for this special rule is to avoid clashes with -the standard names for child units of the packages System, Ada, -Interfaces, and GNAT, which use the prefixes -@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-}, -respectively. +@end menu -The file extension is @file{.ads} for a spec and -@file{.adb} for a body. The following list shows some -examples of these rules. +@node Running GNAT,Running a Simple Ada Program,,Getting Started with GNAT +@anchor{gnat_ugn/getting_started_with_gnat running-gnat}@anchor{33}@anchor{gnat_ugn/getting_started_with_gnat id2}@anchor{34} +@section Running GNAT -@table @file -@item main.ads -Main (spec) -@item main.adb -Main (body) -@item arith_functions.ads -Arith_Functions (package spec) -@item arith_functions.adb -Arith_Functions (package body) -@item func-spec.ads -Func.Spec (child package spec) -@item func-spec.adb -Func.Spec (child package body) -@item main-sub.adb -Sub (subunit of Main) -@item a~bad.adb -A.Bad (child package body) -@end table -@noindent -Following these rules can result in excessively long -file names if corresponding -unit names are long (for example, if child units or subunits are -heavily nested). An option is available to shorten such long file names -(called file name ``krunching''). This may be particularly useful when -programs being developed with GNAT are to be used on operating systems -with limited file name lengths. @xref{Using gnatkr}. +Three steps are needed to create an executable file from an Ada source +file: -Of course, no file shortening algorithm can guarantee uniqueness over -all possible unit names; if file name krunching is used, it is your -responsibility to ensure no name clashes occur. Alternatively you -can specify the exact file names that you want used, as described -in the next section. Finally, if your Ada programs are migrating from a -compiler with a different naming convention, you can use the gnatchop -utility to produce source files that follow the GNAT naming conventions. -(For details @pxref{Renaming Files with gnatchop}.) -Note: in the case of @code{Windows NT/XP} or @code{OpenVMS} operating -systems, case is not significant. So for example on @code{Windows XP} -if the canonical name is @code{main-sub.adb}, you can use the file name -@code{Main-Sub.adb} instead. However, case is significant for other -operating systems, so for example, if you want to use other than -canonically cased file names on a Unix system, you need to follow -the procedures described in the next section. +@itemize * -@node Using Other File Names -@section Using Other File Names -@cindex File names +@item +The source file(s) must be compiled. -@noindent -In the previous section, we have described the default rules used by -GNAT to determine the file name in which a given unit resides. It is -often convenient to follow these default rules, and if you follow them, -the compiler knows without being explicitly told where to find all -the files it needs. +@item +The file(s) must be bound using the GNAT binder. -However, in some cases, particularly when a program is imported from -another Ada compiler environment, it may be more convenient for the -programmer to specify which file names contain which units. GNAT allows -arbitrary file names to be used by means of the Source_File_Name pragma. -The form of this pragma is as shown in the following examples: -@cindex Source_File_Name pragma +@item +All appropriate object files must be linked to produce an executable. +@end itemize -@smallexample @c ada -@cartouche -@b{pragma} Source_File_Name (My_Utilities.Stacks, - Spec_File_Name => "myutilst_a.ada"); -@b{pragma} Source_File_name (My_Utilities.Stacks, - Body_File_Name => "myutilst.ada"); -@end cartouche -@end smallexample +All three steps are most commonly handled by using the @emph{gnatmake} +utility program that, given the name of the main program, automatically +performs the necessary compilation, binding and linking steps. -@noindent -As shown in this example, the first argument for the pragma is the unit -name (in this example a child unit). The second argument has the form -of a named association. The identifier -indicates whether the file name is for a spec or a body; -the file name itself is given by a string literal. +@node Running a Simple Ada Program,Running a Program with Multiple Units,Running GNAT,Getting Started with GNAT +@anchor{gnat_ugn/getting_started_with_gnat running-a-simple-ada-program}@anchor{35}@anchor{gnat_ugn/getting_started_with_gnat id3}@anchor{36} +@section Running a Simple Ada Program -The source file name pragma is a configuration pragma, which means that -normally it will be placed in the @file{gnat.adc} -file used to hold configuration -pragmas that apply to a complete compilation environment. -For more details on how the @file{gnat.adc} file is created and used -see @ref{Handling of Configuration Pragmas}. -@cindex @file{gnat.adc} -GNAT allows completely arbitrary file names to be specified using the -source file name pragma. However, if the file name specified has an -extension other than @file{.ads} or @file{.adb} it is necessary to use -a special syntax when compiling the file. The name in this case must be -preceded by the special sequence @option{-x} followed by a space and the name -of the language, here @code{ada}, as in: +Any text editor may be used to prepare an Ada program. +(If Emacs is used, the optional Ada mode may be helpful in laying out the +program.) +The program text is a normal text file. We will assume in our initial +example that you have used your editor to prepare the following +standard format text file: -@smallexample -$ gcc -c -x ada peculiar_file_name.sim -@end smallexample +@example +with Ada.Text_IO; use Ada.Text_IO; +procedure Hello is +begin + Put_Line ("Hello WORLD!"); +end Hello; +@end example -@noindent -@command{gnatmake} handles non-standard file names in the usual manner (the -non-standard file name for the main program is simply used as the -argument to gnatmake). Note that if the extension is also non-standard, -then it must be included in the @command{gnatmake} command, it may not -be omitted. +This file should be named @code{hello.adb}. +With the normal default file naming conventions, GNAT requires +that each file +contain a single compilation unit whose file name is the +unit name, +with periods replaced by hyphens; the +extension is @code{ads} for a +spec and @code{adb} for a body. +You can override this default file naming convention by use of the +special pragma @cite{Source_File_Name} (for further information please +see @ref{37,,Using Other File Names}). +Alternatively, if you want to rename your files according to this default +convention, which is probably more convenient if you will be using GNAT +for all your compilations, then the @cite{gnatchop} utility +can be used to generate correctly-named source files +(see @ref{38,,Renaming Files with gnatchop}). -@node Alternative File Naming Schemes -@section Alternative File Naming Schemes -@cindex File naming schemes, alternative -@cindex File names +You can compile the program using the following command (@cite{$} is used +as the command prompt in the examples in this document): -In the previous section, we described the use of the @code{Source_File_Name} -pragma to allow arbitrary names to be assigned to individual source files. -However, this approach requires one pragma for each file, and especially in -large systems can result in very long @file{gnat.adc} files, and also create -a maintenance problem. +@example +$ gcc -c hello.adb +@end example -GNAT also provides a facility for specifying systematic file naming schemes -other than the standard default naming scheme previously described. An -alternative scheme for naming is specified by the use of -@code{Source_File_Name} pragmas having the following format: -@cindex Source_File_Name pragma +@emph{gcc} is the command used to run the compiler. This compiler is +capable of compiling programs in several languages, including Ada and +C. It assumes that you have given it an Ada program if the file extension is +either @code{.ads} or @code{.adb}, and it will then call +the GNAT compiler to compile the specified file. -@smallexample @c ada -@b{pragma} Source_File_Name ( - Spec_File_Name => FILE_NAME_PATTERN - @r{[},Casing => CASING_SPEC@r{]} - @r{[},Dot_Replacement => STRING_LITERAL@r{]}); +The @code{-c} switch is required. It tells @emph{gcc} to only do a +compilation. (For C programs, @emph{gcc} can also do linking, but this +capability is not used directly for Ada programs, so the @code{-c} +switch must always be present.) -@b{pragma} Source_File_Name ( - Body_File_Name => FILE_NAME_PATTERN - @r{[},Casing => CASING_SPEC@r{]} - @r{[},Dot_Replacement => STRING_LITERAL@r{]}); +This compile command generates a file +@code{hello.o}, which is the object +file corresponding to your Ada program. It also generates +an 'Ada Library Information' file @code{hello.ali}, +which contains additional information used to check +that an Ada program is consistent. +To build an executable file, +use @cite{gnatbind} to bind the program +and @emph{gnatlink} to link it. The +argument to both @cite{gnatbind} and @emph{gnatlink} is the name of the +@code{ALI} file, but the default extension of @code{.ali} can +be omitted. This means that in the most common case, the argument +is simply the name of the main program: -@b{pragma} Source_File_Name ( - Subunit_File_Name => FILE_NAME_PATTERN - @r{[},Casing => CASING_SPEC@r{]} - @r{[},Dot_Replacement => STRING_LITERAL@r{]}); +@example +$ gnatbind hello +$ gnatlink hello +@end example -FILE_NAME_PATTERN ::= STRING_LITERAL -CASING_SPEC ::= Lowercase | Uppercase | Mixedcase -@end smallexample +A simpler method of carrying out these steps is to use @emph{gnatmake}, +a master program that invokes all the required +compilation, binding and linking tools in the correct order. In particular, +@emph{gnatmake} automatically recompiles any sources that have been +modified since they were last compiled, or sources that depend +on such modified sources, so that 'version skew' is avoided. -@noindent -The @code{FILE_NAME_PATTERN} string shows how the file name is constructed. -It contains a single asterisk character, and the unit name is substituted -systematically for this asterisk. The optional parameter -@code{Casing} indicates -whether the unit name is to be all upper-case letters, all lower-case letters, -or mixed-case. If no -@code{Casing} parameter is used, then the default is all -lower-case. +@geindex Version skew (avoided by *gnatmake*) -The optional @code{Dot_Replacement} string is used to replace any periods -that occur in subunit or child unit names. If no @code{Dot_Replacement} -argument is used then separating dots appear unchanged in the resulting -file name. -Although the above syntax indicates that the -@code{Casing} argument must appear -before the @code{Dot_Replacement} argument, but it -is also permissible to write these arguments in the opposite order. +@example +$ gnatmake hello.adb +@end example -As indicated, it is possible to specify different naming schemes for -bodies, specs, and subunits. Quite often the rule for subunits is the -same as the rule for bodies, in which case, there is no need to give -a separate @code{Subunit_File_Name} rule, and in this case the -@code{Body_File_name} rule is used for subunits as well. +The result is an executable program called @code{hello}, which can be +run by entering: -The separate rule for subunits can also be used to implement the rather -unusual case of a compilation environment (e.g.@: a single directory) which -contains a subunit and a child unit with the same unit name. Although -both units cannot appear in the same partition, the Ada Reference Manual -allows (but does not require) the possibility of the two units coexisting -in the same environment. +@example +$ hello +@end example -The file name translation works in the following steps: +assuming that the current directory is on the search path +for executable programs. -@itemize @bullet +and, if all has gone well, you will see: -@item -If there is a specific @code{Source_File_Name} pragma for the given unit, -then this is always used, and any general pattern rules are ignored. +@example +Hello WORLD! +@end example -@item -If there is a pattern type @code{Source_File_Name} pragma that applies to -the unit, then the resulting file name will be used if the file exists. If -more than one pattern matches, the latest one will be tried first, and the -first attempt resulting in a reference to a file that exists will be used. +appear in response to this command. -@item -If no pattern type @code{Source_File_Name} pragma that applies to the unit -for which the corresponding file exists, then the standard GNAT default -naming rules are used. +@node Running a Program with Multiple Units,Using the gnatmake Utility,Running a Simple Ada Program,Getting Started with GNAT +@anchor{gnat_ugn/getting_started_with_gnat id4}@anchor{39}@anchor{gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units}@anchor{3a} +@section Running a Program with Multiple Units -@end itemize -@noindent -As an example of the use of this mechanism, consider a commonly used scheme -in which file names are all lower case, with separating periods copied -unchanged to the resulting file name, and specs end with @file{.1.ada}, and -bodies end with @file{.2.ada}. GNAT will follow this scheme if the following -two pragmas appear: +Consider a slightly more complicated example that has three files: a +main program, and the spec and body of a package: -@smallexample @c ada -@b{pragma} Source_File_Name - (Spec_File_Name => "*.1.ada"); -@b{pragma} Source_File_Name - (Body_File_Name => "*.2.ada"); -@end smallexample +@example +package Greetings is + procedure Hello; + procedure Goodbye; +end Greetings; -@noindent -The default GNAT scheme is actually implemented by providing the following -default pragmas internally: +with Ada.Text_IO; use Ada.Text_IO; +package body Greetings is + procedure Hello is + begin + Put_Line ("Hello WORLD!"); + end Hello; -@smallexample @c ada -@b{pragma} Source_File_Name - (Spec_File_Name => "*.ads", Dot_Replacement => "-"); -@b{pragma} Source_File_Name - (Body_File_Name => "*.adb", Dot_Replacement => "-"); -@end smallexample + procedure Goodbye is + begin + Put_Line ("Goodbye WORLD!"); + end Goodbye; +end Greetings; -@noindent -Our final example implements a scheme typically used with one of the -Ada 83 compilers, where the separator character for subunits was ``__'' -(two underscores), specs were identified by adding @file{_.ADA}, bodies -by adding @file{.ADA}, and subunits by -adding @file{.SEP}. All file names were -upper case. Child units were not present of course since this was an -Ada 83 compiler, but it seems reasonable to extend this scheme to use -the same double underscore separator for child units. +with Greetings; +procedure Gmain is +begin + Greetings.Hello; + Greetings.Goodbye; +end Gmain; +@end example -@smallexample @c ada -@b{pragma} Source_File_Name - (Spec_File_Name => "*_.ADA", - Dot_Replacement => "__", - Casing = Uppercase); -@b{pragma} Source_File_Name - (Body_File_Name => "*.ADA", - Dot_Replacement => "__", - Casing = Uppercase); -@b{pragma} Source_File_Name - (Subunit_File_Name => "*.SEP", - Dot_Replacement => "__", - Casing = Uppercase); -@end smallexample +Following the one-unit-per-file rule, place this program in the +following three separate files: -@node Generating Object Files -@section Generating Object Files -@noindent -An Ada program consists of a set of source files, and the first step in -compiling the program is to generate the corresponding object files. -These are generated by compiling a subset of these source files. -The files you need to compile are the following: +@table @asis -@itemize @bullet -@item -If a package spec has no body, compile the package spec to produce the -object file for the package. +@item @emph{greetings.ads} -@item -If a package has both a spec and a body, compile the body to produce the -object file for the package. The source file for the package spec need -not be compiled in this case because there is only one object file, which -contains the code for both the spec and body of the package. +spec of package @cite{Greetings} -@item -For a subprogram, compile the subprogram body to produce the object file -for the subprogram. The spec, if one is present, is as usual in a -separate file, and need not be compiled. +@item @emph{greetings.adb} -@item -@cindex Subunits -In the case of subunits, only compile the parent unit. A single object -file is generated for the entire subunit tree, which includes all the -subunits. +body of package @cite{Greetings} -@item -Compile child units independently of their parent units -(though, of course, the spec of all the ancestor unit must be present in order -to compile a child unit). +@item @emph{gmain.adb} -@item -@cindex Generics -Compile generic units in the same manner as any other units. The object -files in this case are small dummy files that contain at most the -flag used for elaboration checking. This is because GNAT always handles generic -instantiation by means of macro expansion. However, it is still necessary to -compile generic units, for dependency checking and elaboration purposes. -@end itemize +body of main program +@end table -@noindent -The preceding rules describe the set of files that must be compiled to -generate the object files for a program. Each object file has the same -name as the corresponding source file, except that the extension is -@file{.o} as usual. +To build an executable version of +this program, we could use four separate steps to compile, bind, and link +the program, as follows: -You may wish to compile other files for the purpose of checking their -syntactic and semantic correctness. For example, in the case where a -package has a separate spec and body, you would not normally compile the -spec. However, it is convenient in practice to compile the spec to make -sure it is error-free before compiling clients of this spec, because such -compilations will fail if there is an error in the spec. +@example +$ gcc -c gmain.adb +$ gcc -c greetings.adb +$ gnatbind gmain +$ gnatlink gmain +@end example -GNAT provides an option for compiling such files purely for the -purposes of checking correctness; such compilations are not required as -part of the process of building a program. To compile a file in this -checking mode, use the @option{-gnatc} switch. +Note that there is no required order of compilation when using GNAT. +In particular it is perfectly fine to compile the main program first. +Also, it is not necessary to compile package specs in the case where +there is an accompanying body; you only need to compile the body. If you want +to submit these files to the compiler for semantic checking and not code +generation, then use the @code{-gnatc} switch: -@node Source Dependencies -@section Source Dependencies +@example +$ gcc -c greetings.ads -gnatc +@end example -@noindent -A given object file clearly depends on the source file which is compiled -to produce it. Here we are using @dfn{depends} in the sense of a typical -@code{make} utility; in other words, an object file depends on a source -file if changes to the source file require the object file to be -recompiled. -In addition to this basic dependency, a given object may depend on -additional source files as follows: +Although the compilation can be done in separate steps as in the +above example, in practice it is almost always more convenient +to use the @emph{gnatmake} tool. All you need to know in this case +is the name of the main program's source file. The effect of the above four +commands can be achieved with a single one: -@itemize @bullet -@item -If a file being compiled @code{with}'s a unit @var{X}, the object file -depends on the file containing the spec of unit @var{X}. This includes -files that are @code{with}'ed implicitly either because they are parents -of @code{with}'ed child units or they are run-time units required by the -language constructs used in a particular unit. +@example +$ gnatmake gmain.adb +@end example -@item -If a file being compiled instantiates a library level generic unit, the -object file depends on both the spec and body files for this generic -unit. +In the next section we discuss the advantages of using @emph{gnatmake} in +more detail. -@item -If a file being compiled instantiates a generic unit defined within a -package, the object file depends on the body file for the package as -well as the spec file. +@node Using the gnatmake Utility,,Running a Program with Multiple Units,Getting Started with GNAT +@anchor{gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility}@anchor{3b}@anchor{gnat_ugn/getting_started_with_gnat id5}@anchor{3c} +@section Using the @emph{gnatmake} Utility -@item -@findex Inline -@cindex @option{-gnatn} switch -If a file being compiled contains a call to a subprogram for which -pragma @code{Inline} applies and inlining is activated with the -@option{-gnatn} switch, the object file depends on the file containing the -body of this subprogram as well as on the file containing the spec. Note -that for inlining to actually occur as a result of the use of this switch, -it is necessary to compile in optimizing mode. -@cindex @option{-gnatN} switch -The use of @option{-gnatN} activates inlining optimization -that is performed by the front end of the compiler. This inlining does -not require that the code generation be optimized. Like @option{-gnatn}, -the use of this switch generates additional dependencies. +If you work on a program by compiling single components at a time using +@emph{gcc}, you typically keep track of the units you modify. In order to +build a consistent system, you compile not only these units, but also any +units that depend on the units you have modified. +For example, in the preceding case, +if you edit @code{gmain.adb}, you only need to recompile that file. But if +you edit @code{greetings.ads}, you must recompile both +@code{greetings.adb} and @code{gmain.adb}, because both files contain +units that depend on @code{greetings.ads}. -When using a gcc-based back end (in practice this means using any version -of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of -@option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred. -Historically front end inlining was more extensive than the gcc back end -inlining, but that is no longer the case. +@emph{gnatbind} will warn you if you forget one of these compilation +steps, so that it is impossible to generate an inconsistent program as a +result of forgetting to do a compilation. Nevertheless it is tedious and +error-prone to keep track of dependencies among units. +One approach to handle the dependency-bookkeeping is to use a +makefile. However, makefiles present maintenance problems of their own: +if the dependencies change as you change the program, you must make +sure that the makefile is kept up-to-date manually, which is also an +error-prone process. -@item -If an object file @file{O} depends on the proper body of a subunit through -inlining or instantiation, it depends on the parent unit of the subunit. -This means that any modification of the parent unit or one of its subunits -affects the compilation of @file{O}. +The @emph{gnatmake} utility takes care of these details automatically. +Invoke it using either one of the following forms: -@item -The object file for a parent unit depends on all its subunit body files. +@example +$ gnatmake gmain.adb +$ gnatmake gmain +@end example -@item -The previous two rules meant that for purposes of computing dependencies and -recompilation, a body and all its subunits are treated as an indivisible whole. +The argument is the name of the file containing the main program; +you may omit the extension. @emph{gnatmake} +examines the environment, automatically recompiles any files that need +recompiling, and binds and links the resulting set of object files, +generating the executable file, @code{gmain}. +In a large program, it +can be extremely helpful to use @emph{gnatmake}, because working out by hand +what needs to be recompiled can be difficult. -@noindent -These rules are applied transitively: if unit @code{A} @code{with}'s -unit @code{B}, whose elaboration calls an inlined procedure in package -@code{C}, the object file for unit @code{A} will depend on the body of -@code{C}, in file @file{c.adb}. +Note that @emph{gnatmake} takes into account all the Ada rules that +establish dependencies among units. These include dependencies that result +from inlining subprogram bodies, and from +generic instantiation. Unlike some other +Ada make tools, @emph{gnatmake} does not rely on the dependencies that were +found by the compiler on a previous compilation, which may possibly +be wrong when sources change. @emph{gnatmake} determines the exact set of +dependencies from scratch each time it is run. -The set of dependent files described by these rules includes all the -files on which the unit is semantically dependent, as dictated by the -Ada language standard. However, it is a superset of what the -standard describes, because it includes generic, inline, and subunit -dependencies. +@c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit -An object file must be recreated by recompiling the corresponding source -file if any of the source files on which it depends are modified. For -example, if the @code{make} utility is used to control compilation, -the rule for an Ada object file must mention all the source files on -which the object file depends, according to the above definition. -The determination of the necessary -recompilations is done automatically when one uses @command{gnatmake}. -@end itemize +@node The GNAT Compilation Model,Building Executable Programs with GNAT,Getting Started with GNAT,Top +@anchor{gnat_ugn/the_gnat_compilation_model doc}@anchor{3d}@anchor{gnat_ugn/the_gnat_compilation_model the-gnat-compilation-model}@anchor{9}@anchor{gnat_ugn/the_gnat_compilation_model id1}@anchor{3e} +@chapter The GNAT Compilation Model -@node The Ada Library Information Files -@section The Ada Library Information Files -@cindex Ada Library Information files -@cindex @file{ALI} files -@noindent -Each compilation actually generates two output files. The first of these -is the normal object file that has a @file{.o} extension. The second is a -text file containing full dependency information. It has the same -name as the source file, but an @file{.ali} extension. -This file is known as the Ada Library Information (@file{ALI}) file. -The following information is contained in the @file{ALI} file. +@geindex GNAT compilation model -@itemize @bullet -@item -Version information (indicates which version of GNAT was used to compile -the unit(s) in question) - -@item -Main program information (including priority and time slice settings, -as well as the wide character encoding used during compilation). - -@item -List of arguments used in the @command{gcc} command for the compilation +@geindex Compilation model -@item -Attributes of the unit, including configuration pragmas used, an indication -of whether the compilation was successful, exception model used etc. +This chapter describes the compilation model used by GNAT. Although +similar to that used by other languages such as C and C++, this model +is substantially different from the traditional Ada compilation models, +which are based on a centralized program library. The chapter covers +the following material: -@item -A list of relevant restrictions applying to the unit (used for consistency) -checking. -@item -Categorization information (e.g.@: use of pragma @code{Pure}). +@itemize * -@item -Information on all @code{with}'ed units, including presence of -@code{Elaborate} or @code{Elaborate_All} pragmas. +@item +Topics related to source file makeup and naming -@item -Information from any @code{Linker_Options} pragmas used in the unit -@item -Information on the use of @code{Body_Version} or @code{Version} -attributes in the unit. +@itemize * -@item -Dependency information. This is a list of files, together with -time stamp and checksum information. These are files on which -the unit depends in the sense that recompilation is required -if any of these units are modified. +@item +@ref{3f,,Source Representation} -@item -Cross-reference data. Contains information on all entities referenced -in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to -provide cross-reference information. +@item +@ref{40,,Foreign Language Representation} +@item +@ref{41,,File Naming Topics and Utilities} @end itemize -@noindent -For a full detailed description of the format of the @file{ALI} file, -see the source of the body of unit @code{Lib.Writ}, contained in file -@file{lib-writ.adb} in the GNAT compiler sources. +@item +@ref{16,,Configuration Pragmas} -@node Binding an Ada Program -@section Binding an Ada Program +@item +@ref{42,,Generating Object Files} -@noindent -When using languages such as C and C++, once the source files have been -compiled the only remaining step in building an executable program -is linking the object modules together. This means that it is possible to -link an inconsistent version of a program, in which two units have -included different versions of the same header. +@item +@ref{43,,Source Dependencies} -The rules of Ada do not permit such an inconsistent program to be built. -For example, if two clients have different versions of the same package, -it is illegal to build a program containing these two clients. -These rules are enforced by the GNAT binder, which also determines an -elaboration order consistent with the Ada rules. +@item +@ref{44,,The Ada Library Information Files} -The GNAT binder is run after all the object files for a program have -been created. It is given the name of the main program unit, and from -this it determines the set of units required by the program, by reading the -corresponding ALI files. It generates error messages if the program is -inconsistent or if no valid order of elaboration exists. +@item +@ref{45,,Binding an Ada Program} -If no errors are detected, the binder produces a main program, in Ada by -default, that contains calls to the elaboration procedures of those -compilation unit that require them, followed by -a call to the main program. This Ada program is compiled to generate the -object file for the main program. The name of -the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec -@file{b~@var{xxx}.ads}) where @var{xxx} is the name of the -main program unit. +@item +@ref{17,,GNAT and Libraries} -Finally, the linker is used to build the resulting executable program, -using the object from the main program from the bind step as well as the -object files for the Ada units of the program. +@item +@ref{18,,Conditional Compilation} -@node Mixed Language Programming -@section Mixed Language Programming -@cindex Mixed Language Programming +@item +@ref{46,,Mixed Language Programming} -@noindent -This section describes how to develop a mixed-language program, -specifically one that comprises units in both Ada and C. +@item +@ref{47,,GNAT and Other Compilation Models} + +@item +@ref{1c,,Using GNAT Files with External Tools} +@end itemize @menu -* Interfacing to C:: -* Calling Conventions:: +* Source Representation:: +* Foreign Language Representation:: +* File Naming Topics and Utilities:: +* Configuration Pragmas:: +* Generating Object Files:: +* Source Dependencies:: +* The Ada Library Information Files:: +* Binding an Ada Program:: +* GNAT and Libraries:: +* Conditional Compilation:: +* Mixed Language Programming:: +* GNAT and Other Compilation Models:: +* Using GNAT Files with External Tools:: + @end menu -@node Interfacing to C -@subsection Interfacing to C -@noindent -Interfacing Ada with a foreign language such as C involves using -compiler directives to import and/or export entity definitions in each -language---using @code{extern} statements in C, for instance, and the -@code{Import}, @code{Export}, and @code{Convention} pragmas in Ada. -A full treatment of these topics is provided in Appendix B, section 1 -of the Ada Reference Manual. +@node Source Representation,Foreign Language Representation,,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model source-representation}@anchor{3f}@anchor{gnat_ugn/the_gnat_compilation_model id2}@anchor{48} +@section Source Representation -There are two ways to build a program using GNAT that contains some Ada -sources and some foreign language sources, depending on whether or not -the main subprogram is written in Ada. Here is a source example with -the main subprogram in Ada: -@smallexample -/* file1.c */ -#include +@geindex Latin-1 -void print_num (int num) -@{ - printf ("num is %d.\n", num); - return; -@} +@geindex VT +@geindex HT +@geindex CR +@geindex LF +@geindex FF -/* file2.c */ +Ada source programs are represented in standard text files, using +Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar +7-bit ASCII set, plus additional characters used for +representing foreign languages (see @ref{40,,Foreign Language Representation} +for support of non-USA character sets). The format effector characters +are represented using their standard ASCII encodings, as follows: -/* num_from_Ada is declared in my_main.adb */ -extern int num_from_Ada; +@quotation -int get_num (void) -@{ - return num_from_Ada; -@} -@end smallexample -@smallexample @c ada --- my_main.adb -procedure My_Main is +@multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxx} +@item - -- Declare then export an Integer entity called num_from_Ada - My_Num : Integer := 10; - pragma Export (C, My_Num, "num_from_Ada"); +Character - -- Declare an Ada function spec for Get_Num, then use - -- C function get_num for the implementation. - function Get_Num return Integer; - pragma Import (C, Get_Num, "get_num"); +@tab - -- Declare an Ada procedure spec for Print_Num, then use - -- C function print_num for the implementation. - procedure Print_Num (Num : Integer); - pragma Import (C, Print_Num, "print_num"; +Effect -begin - Print_Num (Get_Num); -end My_Main; -@end smallexample +@tab -@enumerate -@item -To build this example, first compile the foreign language files to -generate object files: -@smallexample -gcc -c file1.c -gcc -c file2.c -@end smallexample +Code @item -Then, compile the Ada units to produce a set of object files and ALI -files: -@smallexample -gnatmake -c my_main.adb -@end smallexample -@item -Run the Ada binder on the Ada main program: -@smallexample -gnatbind my_main.ali -@end smallexample +@code{VT} + +@tab + +Vertical tab + +@tab + +@cite{16#0B#} @item -Link the Ada main program, the Ada objects and the other language -objects: -@smallexample -gnatlink my_main.ali file1.o file2.o -@end smallexample -@end enumerate -The last three steps can be grouped in a single command: -@smallexample -gnatmake my_main.adb -largs file1.o file2.o -@end smallexample +@code{HT} -@cindex Binder output file -@noindent -If the main program is in a language other than Ada, then you may have -more than one entry point into the Ada subsystem. You must use a special -binder option to generate callable routines that initialize and -finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}). -Calls to the initialization and finalization routines must be inserted -in the main program, or some other appropriate point in the code. The -call to initialize the Ada units must occur before the first Ada -subprogram is called, and the call to finalize the Ada units must occur -after the last Ada subprogram returns. The binder will place the -initialization and finalization subprograms into the -@file{b~@var{xxx}.adb} file where they can be accessed by your C -sources. To illustrate, we have the following example: +@tab -@smallexample -/* main.c */ -extern void adainit (void); -extern void adafinal (void); -extern int add (int, int); -extern int sub (int, int); +Horizontal tab -int main (int argc, char *argv[]) -@{ - int a = 21, b = 7; +@tab - adainit(); +@cite{16#09#} - /* Should print "21 + 7 = 28" */ - printf ("%d + %d = %d\n", a, b, add (a, b)); - /* Should print "21 - 7 = 14" */ - printf ("%d - %d = %d\n", a, b, sub (a, b)); +@item - adafinal(); -@} -@end smallexample +@code{CR} -@smallexample @c ada --- unit1.ads -package Unit1 is - function Add (A, B : Integer) return Integer; - pragma Export (C, Add, "add"); -end Unit1; +@tab --- unit1.adb -package body Unit1 is - function Add (A, B : Integer) return Integer is - begin - return A + B; - end Add; -end Unit1; +Carriage return --- unit2.ads -package Unit2 is - function Sub (A, B : Integer) return Integer; - pragma Export (C, Sub, "sub"); -end Unit2; +@tab --- unit2.adb -package body Unit2 is - function Sub (A, B : Integer) return Integer is - begin - return A - B; - end Sub; -end Unit2; -@end smallexample +@cite{16#0D#} -@enumerate @item -The build procedure for this application is similar to the last -example's. First, compile the foreign language files to generate object -files: -@smallexample -gcc -c main.c -@end smallexample -@item -Next, compile the Ada units to produce a set of object files and ALI -files: -@smallexample -gnatmake -c unit1.adb -gnatmake -c unit2.adb -@end smallexample +@code{LF} -@item -Run the Ada binder on every generated ALI file. Make sure to use the -@option{-n} option to specify a foreign main program: -@smallexample -gnatbind -n unit1.ali unit2.ali -@end smallexample +@tab -@item -Link the Ada main program, the Ada objects and the foreign language -objects. You need only list the last ALI file here: -@smallexample -gnatlink unit2.ali main.o -o exec_file -@end smallexample +Line feed -This procedure yields a binary executable called @file{exec_file}. -@end enumerate +@tab -@noindent -Depending on the circumstances (for example when your non-Ada main object -does not provide symbol @code{main}), you may also need to instruct the -GNAT linker not to include the standard startup objects by passing the -@option{-nostartfiles} switch to @command{gnatlink}. +@cite{16#0A#} -@node Calling Conventions -@subsection Calling Conventions -@cindex Foreign Languages -@cindex Calling Conventions -GNAT follows standard calling sequence conventions and will thus interface -to any other language that also follows these conventions. The following -Convention identifiers are recognized by GNAT: +@item -@table @code -@cindex Interfacing to Ada -@cindex Other Ada compilers -@cindex Convention Ada -@item Ada -This indicates that the standard Ada calling sequence will be -used and all Ada data items may be passed without any limitations in the -case where GNAT is used to generate both the caller and callee. It is also -possible to mix GNAT generated code and code generated by another Ada -compiler. In this case, the data types should be restricted to simple -cases, including primitive types. Whether complex data types can be passed -depends on the situation. Probably it is safe to pass simple arrays, such -as arrays of integers or floats. Records may or may not work, depending -on whether both compilers lay them out identically. Complex structures -involving variant records, access parameters, tasks, or protected types, -are unlikely to be able to be passed. +@code{FF} -Note that in the case of GNAT running -on a platform that supports HP Ada 83, a higher degree of compatibility -can be guaranteed, and in particular records are laid out in an identical -manner in the two compilers. Note also that if output from two different -compilers is mixed, the program is responsible for dealing with elaboration -issues. Probably the safest approach is to write the main program in the -version of Ada other than GNAT, so that it takes care of its own elaboration -requirements, and then call the GNAT-generated adainit procedure to ensure -elaboration of the GNAT components. Consult the documentation of the other -Ada compiler for further details on elaboration. +@tab -However, it is not possible to mix the tasking run time of GNAT and -HP Ada 83, All the tasking operations must either be entirely within -GNAT compiled sections of the program, or entirely within HP Ada 83 -compiled sections of the program. +Form feed -@cindex Interfacing to Assembly -@cindex Convention Assembler -@item Assembler -Specifies assembler as the convention. In practice this has the -same effect as convention Ada (but is not equivalent in the sense of being -considered the same convention). +@tab -@cindex Convention Asm -@findex Asm -@item Asm -Equivalent to Assembler. +@cite{16#0C#} -@cindex Interfacing to COBOL -@cindex Convention COBOL -@findex COBOL -@item COBOL -Data will be passed according to the conventions described -in section B.4 of the Ada Reference Manual. +@end multitable -@findex C -@cindex Interfacing to C -@cindex Convention C -@item C -Data will be passed according to the conventions described -in section B.3 of the Ada Reference Manual. +@end quotation -A note on interfacing to a C ``varargs'' function: -@findex C varargs function -@cindex Interfacing to C varargs function -@cindex varargs function interfaces +Source files are in standard text file format. In addition, GNAT will +recognize a wide variety of stream formats, in which the end of +physical lines is marked by any of the following sequences: +@cite{LF}, @cite{CR}, @cite{CR-LF}, or @cite{LF-CR}. This is useful +in accommodating files that are imported from other operating systems. -@itemize @bullet -@item -In C, @code{varargs} allows a function to take a variable number of -arguments. There is no direct equivalent in this to Ada. One -approach that can be used is to create a C wrapper for each -different profile and then interface to this C wrapper. For -example, to print an @code{int} value using @code{printf}, -create a C function @code{printfi} that takes two arguments, a -pointer to a string and an int, and calls @code{printf}. -Then in the Ada program, use pragma @code{Import} to -interface to @code{printfi}. +@geindex End of source file; Source file@comma{} end -@item -It may work on some platforms to directly interface to -a @code{varargs} function by providing a specific Ada profile -for a particular call. However, this does not work on -all platforms, since there is no guarantee that the -calling sequence for a two argument normal C function -is the same as for calling a @code{varargs} C function with -the same two arguments. -@end itemize +@geindex SUB (control character) -@cindex Convention Default -@findex Default -@item Default -Equivalent to C. +The end of a source file is normally represented by the physical end of +file. However, the control character @cite{16#1A#} (@code{SUB}) is also +recognized as signalling the end of the source file. Again, this is +provided for compatibility with other operating systems where this +code is used to represent the end of file. -@cindex Convention External -@findex External -@item External -Equivalent to C. +@geindex spec (definition) +@geindex compilation (definition) -@findex C++ -@cindex Interfacing to C++ -@cindex Convention C++ -@item C_Plus_Plus (or CPP) -This stands for C++. For most purposes this is identical to C. -See the separate description of the specialized GNAT pragmas relating to -C++ interfacing for further details. +Each file contains a single Ada compilation unit, including any pragmas +associated with the unit. For example, this means you must place a +package declaration (a package @cite{spec}) and the corresponding body in +separate files. An Ada @cite{compilation} (which is a sequence of +compilation units) is represented using a sequence of files. Similarly, +you will place each subunit or child unit in a separate file. -@findex Fortran -@cindex Interfacing to Fortran -@cindex Convention Fortran -@item Fortran -Data will be passed according to the conventions described -in section B.5 of the Ada Reference Manual. +@node Foreign Language Representation,File Naming Topics and Utilities,Source Representation,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model foreign-language-representation}@anchor{40}@anchor{gnat_ugn/the_gnat_compilation_model id3}@anchor{49} +@section Foreign Language Representation -@item Intrinsic -This applies to an intrinsic operation, as defined in the Ada -Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram, -this means that the body of the subprogram is provided by the compiler itself, -usually by means of an efficient code sequence, and that the user does not -supply an explicit body for it. In an application program, the pragma may -be applied to the following sets of names: -@itemize @bullet -@item -Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, -Shift_Right_Arithmetic. The corresponding subprogram declaration must have -two formal parameters. The -first one must be a signed integer type or a modular type with a binary -modulus, and the second parameter must be of type Natural. -The return type must be the same as the type of the first argument. The size -of this type can only be 8, 16, 32, or 64. - -@item -Binary arithmetic operators: ``+'', ``-'', ``*'', ``/'' -The corresponding operator declaration must have parameters and result type -that have the same root numeric type (for example, all three are long_float -types). This simplifies the definition of operations that use type checking -to perform dimensional checks: - -@smallexample @c ada -@b{type} Distance @b{is} @b{new} Long_Float; -@b{type} Time @b{is} @b{new} Long_Float; -@b{type} Velocity @b{is} @b{new} Long_Float; -@b{function} "/" (D : Distance; T : Time) - @b{return} Velocity; -@b{pragma} Import (Intrinsic, "/"); -@end smallexample - -@noindent -This common idiom is often programmed with a generic definition and an -explicit body. The pragma makes it simpler to introduce such declarations. -It incurs no overhead in compilation time or code size, because it is -implemented as a single machine instruction. - -@item -General subprogram entities, to bind an Ada subprogram declaration to -a compiler builtin by name with back-ends where such interfaces are -available. A typical example is the set of ``__builtin'' functions -exposed by the GCC back-end, as in the following example: +GNAT supports the standard character sets defined in Ada as well as +several other non-standard character sets for use in localized versions +of the compiler (@ref{4a,,Character Set Control}). -@smallexample @c ada - @b{function} builtin_sqrt (F : Float) @b{return} Float; - @b{pragma} Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf"); -@end smallexample +@menu +* Latin-1:: +* Other 8-Bit Codes:: +* Wide_Character Encodings:: +* Wide_Wide_Character Encodings:: -Most of the GCC builtins are accessible this way, and as for other -import conventions (e.g. C), it is the user's responsibility to ensure -that the Ada subprogram profile matches the underlying builtin -expectations. -@end itemize +@end menu -@noindent +@node Latin-1,Other 8-Bit Codes,,Foreign Language Representation +@anchor{gnat_ugn/the_gnat_compilation_model id4}@anchor{4b}@anchor{gnat_ugn/the_gnat_compilation_model latin-1}@anchor{4c} +@subsection Latin-1 -@findex Stdcall -@cindex Convention Stdcall -@item Stdcall -This is relevant only to Windows XP/2000/NT implementations of GNAT, -and specifies that the @code{Stdcall} calling sequence will be used, -as defined by the NT API. Nevertheless, to ease building -cross-platform bindings this convention will be handled as a @code{C} calling -convention on non-Windows platforms. -@findex DLL -@cindex Convention DLL -@item DLL -This is equivalent to @code{Stdcall}. +@geindex Latin-1 -@findex Win32 -@cindex Convention Win32 -@item Win32 -This is equivalent to @code{Stdcall}. +The basic character set is Latin-1. This character set is defined by ISO +standard 8859, part 1. The lower half (character codes @cite{16#00#} +... @cite{16#7F#)} is identical to standard ASCII coding, but the upper +half is used to represent additional characters. These include extended letters +used by European languages, such as French accents, the vowels with umlauts +used in German, and the extra letter A-ring used in Swedish. -@findex Stubbed -@cindex Convention Stubbed -@item Stubbed -This is a special convention that indicates that the compiler -should provide a stub body that raises @code{Program_Error}. -@end table +@geindex Ada.Characters.Latin_1 -@noindent -GNAT additionally provides a useful pragma @code{Convention_Identifier} -that can be used to parameterize conventions and allow additional synonyms -to be specified. For example if you have legacy code in which the convention -identifier Fortran77 was used for Fortran, you can use the configuration -pragma: +For a complete list of Latin-1 codes and their encodings, see the source +file of library unit @cite{Ada.Characters.Latin_1} in file +@code{a-chlat1.ads}. +You may use any of these extended characters freely in character or +string literals. In addition, the extended characters that represent +letters can be used in identifiers. -@smallexample @c ada -@b{pragma} Convention_Identifier (Fortran77, Fortran); -@end smallexample +@node Other 8-Bit Codes,Wide_Character Encodings,Latin-1,Foreign Language Representation +@anchor{gnat_ugn/the_gnat_compilation_model other-8-bit-codes}@anchor{4d}@anchor{gnat_ugn/the_gnat_compilation_model id5}@anchor{4e} +@subsection Other 8-Bit Codes -@noindent -And from now on the identifier Fortran77 may be used as a convention -identifier (for example in an @code{Import} pragma) with the same -meaning as Fortran. -@node Building Mixed Ada & C++ Programs -@section Building Mixed Ada and C++ Programs +GNAT also supports several other 8-bit coding schemes: -@noindent -A programmer inexperienced with mixed-language development may find that -building an application containing both Ada and C++ code can be a -challenge. This section gives a few -hints that should make this task easier. The first section addresses -the differences between interfacing with C and interfacing with C++. -The second section -looks into the delicate problem of linking the complete application from -its Ada and C++ parts. The last section gives some hints on how the GNAT -run-time library can be adapted in order to allow inter-language dispatching -with a new C++ compiler. +@geindex Latin-2 -@menu -* Interfacing to C++:: -* Linking a Mixed C++ & Ada Program:: -* A Simple Example:: -* Interfacing with C++ constructors:: -* Interfacing with C++ at the Class Level:: -@end menu +@geindex ISO 8859-2 -@node Interfacing to C++ -@subsection Interfacing to C++ -@noindent -GNAT supports interfacing with the G++ compiler (or any C++ compiler -generating code that is compatible with the G++ Application Binary -Interface ---see http://www.codesourcery.com/archives/cxx-abi). +@table @asis -@noindent -Interfacing can be done at 3 levels: simple data, subprograms, and -classes. In the first two cases, GNAT offers a specific @code{Convention -C_Plus_Plus} (or @code{CPP}) that behaves exactly like @code{Convention C}. -Usually, C++ mangles the names of subprograms. To generate proper mangled -names automatically, see @ref{Generating Ada Bindings for C and C++ headers}). -This problem can also be addressed manually in two ways: +@item @emph{ISO 8859-2 (Latin-2)} -@itemize @bullet -@item -by modifying the C++ code in order to force a C convention using -the @code{extern "C"} syntax. +Latin-2 letters allowed in identifiers, with uppercase and lowercase +equivalence. +@end table -@item -by figuring out the mangled name (using e.g. @command{nm}) and using it as the -Link_Name argument of the pragma import. -@end itemize +@geindex Latin-3 -@noindent -Interfacing at the class level can be achieved by using the GNAT specific -pragmas such as @code{CPP_Constructor}. @xref{Interfacing to C++,,, -gnat_rm, GNAT Reference Manual}, for additional information. +@geindex ISO 8859-3 -@node Linking a Mixed C++ & Ada Program -@subsection Linking a Mixed C++ & Ada Program -@noindent -Usually the linker of the C++ development system must be used to link -mixed applications because most C++ systems will resolve elaboration -issues (such as calling constructors on global class instances) -transparently during the link phase. GNAT has been adapted to ease the -use of a foreign linker for the last phase. Three cases can be -considered: -@enumerate +@table @asis -@item -Using GNAT and G++ (GNU C++ compiler) from the same GCC installation: -The C++ linker can simply be called by using the C++ specific driver -called @code{g++}. +@item @emph{ISO 8859-3 (Latin-3)} -Note that if the C++ code uses inline functions, you will need to -compile your C++ code with the @code{-fkeep-inline-functions} switch in -order to provide an existing function implementation that the Ada code can -link with. +Latin-3 letters allowed in identifiers, with uppercase and lowercase +equivalence. +@end table -@smallexample -$ g++ -c -fkeep-inline-functions file1.C -$ g++ -c -fkeep-inline-functions file2.C -$ gnatmake ada_unit -largs file1.o file2.o --LINK=g++ -@end smallexample +@geindex Latin-4 -@item -Using GNAT and G++ from two different GCC installations: If both -compilers are on the @env{PATH}, the previous method may be used. It is -important to note that environment variables such as -@env{C_INCLUDE_PATH}, @env{GCC_EXEC_PREFIX}, @env{BINUTILS_ROOT}, and -@env{GCC_ROOT} will affect both compilers -at the same time and may make one of the two compilers operate -improperly if set during invocation of the wrong compiler. It is also -very important that the linker uses the proper @file{libgcc.a} GCC -library -- that is, the one from the C++ compiler installation. The -implicit link command as suggested in the @command{gnatmake} command -from the former example can be replaced by an explicit link command with -the full-verbosity option in order to verify which library is used: -@smallexample -$ gnatbind ada_unit -$ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++ -@end smallexample -If there is a problem due to interfering environment variables, it can -be worked around by using an intermediate script. The following example -shows the proper script to use when GNAT has not been installed at its -default location and g++ has been installed at its default location: +@geindex ISO 8859-4 -@smallexample -$ cat ./my_script -#!/bin/sh -unset BINUTILS_ROOT -unset GCC_ROOT -c++ $* -$ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script -@end smallexample -@item -Using a non-GNU C++ compiler: The commands previously described can be -used to insure that the C++ linker is used. Nonetheless, you need to add -a few more parameters to the link command line, depending on the exception -mechanism used. +@table @asis -If the @code{setjmp/longjmp} exception mechanism is used, only the paths -to the libgcc libraries are required: +@item @emph{ISO 8859-4 (Latin-4)} -@smallexample -$ cat ./my_script -#!/bin/sh -CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` -$ gnatlink ada_unit file1.o file2.o --LINK=./my_script -@end smallexample +Latin-4 letters allowed in identifiers, with uppercase and lowercase +equivalence. +@end table -Where CC is the name of the non-GNU C++ compiler. +@geindex ISO 8859-5 -If the @code{zero cost} exception mechanism is used, and the platform -supports automatic registration of exception tables (e.g.@: Solaris), -paths to more objects are required: +@geindex Cyrillic -@smallexample -$ cat ./my_script -#!/bin/sh -CC `gcc -print-file-name=crtbegin.o` $* \ -`gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \ -`gcc -print-file-name=crtend.o` -$ gnatlink ada_unit file1.o file2.o --LINK=./my_script -@end smallexample -If the @code{zero cost} exception mechanism is used, and the platform -doesn't support automatic registration of exception tables (e.g.@: HP-UX -or AIX), the simple approach described above will not work and -a pre-linking phase using GNAT will be necessary. +@table @asis -@end enumerate +@item @emph{ISO 8859-5 (Cyrillic)} -Another alternative is to use the @command{gprbuild} multi-language builder -which has a large knowledge base and knows how to link Ada and C++ code -together automatically in most cases. +ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and +lowercase equivalence. +@end table -@node A Simple Example -@subsection A Simple Example -@noindent -The following example, provided as part of the GNAT examples, shows how -to achieve procedural interfacing between Ada and C++ in both -directions. The C++ class A has two methods. The first method is exported -to Ada by the means of an extern C wrapper function. The second method -calls an Ada subprogram. On the Ada side, The C++ calls are modelled by -a limited record with a layout comparable to the C++ class. The Ada -subprogram, in turn, calls the C++ method. So, starting from the C++ -main program, the process passes back and forth between the two -languages. +@geindex ISO 8859-15 -@noindent -Here are the compilation commands: -@smallexample -$ gnatmake -c simple_cpp_interface -$ g++ -c cpp_main.C -$ g++ -c ex7.C -$ gnatbind -n simple_cpp_interface -$ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ - -lstdc++ ex7.o cpp_main.o -@end smallexample +@geindex Latin-9 -@noindent -Here are the corresponding sources: -@smallexample -//cpp_main.C +@table @asis -#include "ex7.h" +@item @emph{ISO 8859-15 (Latin-9)} -extern "C" @{ - void adainit (void); - void adafinal (void); - void method1 (A *t); -@} +ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and +lowercase equivalence +@end table -void method1 (A *t) -@{ - t->method1 (); -@} +@geindex code page 437 (IBM PC) -int main () -@{ - A obj; - adainit (); - obj.method2 (3030); - adafinal (); -@} -//ex7.h +@table @asis -class Origin @{ - public: - int o_value; -@}; -class A : public Origin @{ - public: - void method1 (void); - void method2 (int v); - A(); - int a_value; -@}; +@item @emph{IBM PC (code page 437)} -//ex7.C +This code page is the normal default for PCs in the U.S. It corresponds +to the original IBM PC character set. This set has some, but not all, of +the extended Latin-1 letters, but these letters do not have the same +encoding as Latin-1. In this mode, these letters are allowed in +identifiers with uppercase and lowercase equivalence. +@end table -#include "ex7.h" -#include +@geindex code page 850 (IBM PC) -extern "C" @{ void ada_method2 (A *t, int v);@} -void A::method1 (void) -@{ - a_value = 2020; - printf ("in A::method1, a_value = %d \n",a_value); +@table @asis -@} +@item @emph{IBM PC (code page 850)} -void A::method2 (int v) -@{ - ada_method2 (this, v); - printf ("in A::method2, a_value = %d \n",a_value); +This code page is a modification of 437 extended to include all the +Latin-1 letters, but still not with the usual Latin-1 encoding. In this +mode, all these letters are allowed in identifiers with uppercase and +lowercase equivalence. -@} +@item @emph{Full Upper 8-bit} -A::A(void) -@{ - a_value = 1010; - printf ("in A::A, a_value = %d \n",a_value); -@} -@end smallexample +Any character in the range 80-FF allowed in identifiers, and all are +considered distinct. In other words, there are no uppercase and lowercase +equivalences in this range. This is useful in conjunction with +certain encoding schemes used for some foreign character sets (e.g., +the typical method of representing Chinese characters on the PC). -@smallexample @c ada ---@i{ Ada sources} -@b{package} @b{body} Simple_Cpp_Interface @b{is} +@item @emph{No Upper-Half} - @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer) @b{is} - @b{begin} - Method1 (This); - This.A_Value := V; - @b{end} Ada_Method2; +No upper-half characters in the range 80-FF are allowed in identifiers. +This gives Ada 83 compatibility for identifier names. +@end table -@b{end} Simple_Cpp_Interface; +For precise data on the encodings permitted, and the uppercase and lowercase +equivalences that are recognized, see the file @code{csets.adb} in +the GNAT compiler sources. You will need to obtain a full source release +of GNAT to obtain this file. -@b{with} System; -@b{package} Simple_Cpp_Interface @b{is} - @b{type} A @b{is} @b{limited} - @b{record} - Vptr : System.Address; - O_Value : Integer; - A_Value : Integer; - @b{end} @b{record}; - @b{pragma} Convention (C, A); +@node Wide_Character Encodings,Wide_Wide_Character Encodings,Other 8-Bit Codes,Foreign Language Representation +@anchor{gnat_ugn/the_gnat_compilation_model id6}@anchor{4f}@anchor{gnat_ugn/the_gnat_compilation_model wide-character-encodings}@anchor{50} +@subsection Wide_Character Encodings - @b{procedure} Method1 (This : @b{in} @b{out} A); - @b{pragma} Import (C, Method1); - @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer); - @b{pragma} Export (C, Ada_Method2); +GNAT allows wide character codes to appear in character and string +literals, and also optionally in identifiers, by means of the following +possible encoding schemes: -@b{end} Simple_Cpp_Interface; -@end smallexample -@node Interfacing with C++ constructors -@subsection Interfacing with C++ constructors -@noindent +@table @asis -In order to interface with C++ constructors GNAT provides the -@code{pragma CPP_Constructor} (@xref{Interfacing to C++,,, -gnat_rm, GNAT Reference Manual}, for additional information). -In this section we present some common uses of C++ constructors -in mixed-languages programs in GNAT. +@item @emph{Hex Coding} -Let us assume that we need to interface with the following -C++ class: +In this encoding, a wide character is represented by the following five +character sequence: -@smallexample -@b{class} Root @{ -@b{public}: - int a_value; - int b_value; - @b{virtual} int Get_Value (); - Root(); // Default constructor - Root(int v); // 1st non-default constructor - Root(int v, int w); // 2nd non-default constructor -@}; -@end smallexample +@example +ESC a b c d +@end example -For this purpose we can write the following package spec (further -information on how to build this spec is available in -@ref{Interfacing with C++ at the Class Level} and -@ref{Generating Ada Bindings for C and C++ headers}). +where @cite{a}, @cite{b}, @cite{c}, @cite{d} are the four hexadecimal +characters (using uppercase letters) of the wide character code. For +example, ESC A345 is used to represent the wide character with code +@cite{16#A345#}. +This scheme is compatible with use of the full Wide_Character set. -@smallexample @c ada -@b{with} Interfaces.C; @b{use} Interfaces.C; -@b{package} Pkg_Root @b{is} - @b{type} Root @b{is} @b{tagged} @b{limited} @b{record} - A_Value : int; - B_Value : int; - @b{end} @b{record}; - @b{pragma} Import (CPP, Root); +@item @emph{Upper-Half Coding} - @b{function} Get_Value (Obj : Root) @b{return} int; - @b{pragma} Import (CPP, Get_Value); +@geindex Upper-Half Coding - @b{function} Constructor @b{return} Root; - @b{pragma} Cpp_Constructor (Constructor, "_ZN4RootC1Ev"); +The wide character with encoding @cite{16#abcd#} where the upper bit is on +(in other words, 'a' is in the range 8-F) is represented as two bytes, +@cite{16#ab#} and @cite{16#cd#}. The second byte cannot be a format control +character, but is not required to be in the upper half. This method can +be also used for shift-JIS or EUC, where the internal coding matches the +external coding. - @b{function} Constructor (v : Integer) @b{return} Root; - @b{pragma} Cpp_Constructor (Constructor, "_ZN4RootC1Ei"); +@item @emph{Shift JIS Coding} - @b{function} Constructor (v, w : Integer) @b{return} Root; - @b{pragma} Cpp_Constructor (Constructor, "_ZN4RootC1Eii"); -@b{end} Pkg_Root; -@end smallexample +@geindex Shift JIS Coding -On the Ada side the constructor is represented by a function (whose -name is arbitrary) that returns the classwide type corresponding to -the imported C++ class. Although the constructor is described as a -function, it is typically a procedure with an extra implicit argument -(the object being initialized) at the implementation level. GNAT -issues the appropriate call, whatever it is, to get the object -properly initialized. +A wide character is represented by a two-character sequence, +@cite{16#ab#} and +@cite{16#cd#}, with the restrictions described for upper-half encoding as +described above. The internal character code is the corresponding JIS +character according to the standard algorithm for Shift-JIS +conversion. Only characters defined in the JIS code set table can be +used with this encoding method. -Constructors can only appear in the following contexts: +@item @emph{EUC Coding} -@itemize @bullet -@item -On the right side of an initialization of an object of type @var{T}. -@item -On the right side of an initialization of a record component of type @var{T}. -@item -In an Ada 2005 limited aggregate. -@item -In an Ada 2005 nested limited aggregate. -@item -In an Ada 2005 limited aggregate that initializes an object built in -place by an extended return statement. -@end itemize +@geindex EUC Coding -@noindent -In a declaration of an object whose type is a class imported from C++, -either the default C++ constructor is implicitly called by GNAT, or -else the required C++ constructor must be explicitly called in the -expression that initializes the object. For example: +A wide character is represented by a two-character sequence +@cite{16#ab#} and +@cite{16#cd#}, with both characters being in the upper half. The internal +character code is the corresponding JIS character according to the EUC +encoding algorithm. Only characters defined in the JIS code set table +can be used with this encoding method. -@smallexample @c ada - Obj1 : Root; - Obj2 : Root := Constructor; - Obj3 : Root := Constructor (v => 10); - Obj4 : Root := Constructor (30, 40); -@end smallexample +@item @emph{UTF-8 Coding} -The first two declarations are equivalent: in both cases the default C++ -constructor is invoked (in the former case the call to the constructor is -implicit, and in the latter case the call is explicit in the object -declaration). @code{Obj3} is initialized by the C++ non-default constructor -that takes an integer argument, and @code{Obj4} is initialized by the -non-default C++ constructor that takes two integers. +A wide character is represented using +UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO +10646-1/Am.2. Depending on the character value, the representation +is a one, two, or three byte sequence: -Let us derive the imported C++ class in the Ada side. For example: +@example +16#0000#-16#007f#: 2#0`xxxxxxx`# +16#0080#-16#07ff#: 2#110`xxxxx`# 2#10`xxxxxx`# +16#0800#-16#ffff#: 2#1110`xxxx`# 2#10`xxxxxx`# 2#10`xxxxxx`# +@end example -@smallexample @c ada - @b{type} DT @b{is} @b{new} Root @b{with} @b{record} - C_Value : Natural := 2009; - @b{end} @b{record}; -@end smallexample +where the @cite{xxx} bits correspond to the left-padded bits of the +16-bit character value. Note that all lower half ASCII characters +are represented as ASCII bytes and all upper half characters and +other wide characters are represented as sequences of upper-half +(The full UTF-8 scheme allows for encoding 31-bit characters as +6-byte sequences, and in the following section on wide wide +characters, the use of these sequences is documented). -In this case the components DT inherited from the C++ side must be -initialized by a C++ constructor, and the additional Ada components -of type DT are initialized by GNAT. The initialization of such an -object is done either by default, or by means of a function returning -an aggregate of type DT, or by means of an extension aggregate. +@item @emph{Brackets Coding} -@smallexample @c ada - Obj5 : DT; - Obj6 : DT := Function_Returning_DT (50); - Obj7 : DT := (Constructor (30,40) @b{with} C_Value => 50); -@end smallexample +In this encoding, a wide character is represented by the following eight +character sequence: -The declaration of @code{Obj5} invokes the default constructors: the -C++ default constructor of the parent type takes care of the initialization -of the components inherited from Root, and GNAT takes care of the default -initialization of the additional Ada components of type DT (that is, -@code{C_Value} is initialized to value 2009). The order of invocation of -the constructors is consistent with the order of elaboration required by -Ada and C++. That is, the constructor of the parent type is always called -before the constructor of the derived type. +@example +[ " a b c d " ] +@end example -Let us now consider a record that has components whose type is imported -from C++. For example: +where @cite{a}, @cite{b}, @cite{c}, @cite{d} are the four hexadecimal +characters (using uppercase letters) of the wide character code. For +example, ['A345'] is used to represent the wide character with code +@cite{16#A345#}. It is also possible (though not required) to use the +Brackets coding for upper half characters. For example, the code +@cite{16#A3#} can be represented as @cite{['A3']}. -@smallexample @c ada - @b{type} Rec1 @b{is} @b{limited} @b{record} - Data1 : Root := Constructor (10); - Value : Natural := 1000; - @b{end} @b{record}; +This scheme is compatible with use of the full Wide_Character set, +and is also the method used for wide character encoding in some standard +ACATS (Ada Conformity Assessment Test Suite) test suite distributions. +@end table - @b{type} Rec2 (D : Integer := 20) @b{is} @b{limited} @b{record} - Rec : Rec1; - Data2 : Root := Constructor (D, 30); - @b{end} @b{record}; -@end smallexample +@cartouche +@quotation Note +Some of these coding schemes do not permit the full use of the +Ada character set. For example, neither Shift JIS nor EUC allow the +use of the upper half of the Latin-1 set. +@end quotation +@end cartouche -The initialization of an object of type @code{Rec2} will call the -non-default C++ constructors specified for the imported components. -For example: +@node Wide_Wide_Character Encodings,,Wide_Character Encodings,Foreign Language Representation +@anchor{gnat_ugn/the_gnat_compilation_model id7}@anchor{51}@anchor{gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings}@anchor{52} +@subsection Wide_Wide_Character Encodings -@smallexample @c ada - Obj8 : Rec2 (40); -@end smallexample -Using Ada 2005 we can use limited aggregates to initialize an object -invoking C++ constructors that differ from those specified in the type -declarations. For example: +GNAT allows wide wide character codes to appear in character and string +literals, and also optionally in identifiers, by means of the following +possible encoding schemes: -@smallexample @c ada - Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16), - @b{others} => <>), - @b{others} => <>); -@end smallexample -The above declaration uses an Ada 2005 limited aggregate to -initialize @code{Obj9}, and the C++ constructor that has two integer -arguments is invoked to initialize the @code{Data1} component instead -of the constructor specified in the declaration of type @code{Rec1}. In -Ada 2005 the box in the aggregate indicates that unspecified components -are initialized using the expression (if any) available in the component -declaration. That is, in this case discriminant @code{D} is initialized -to value @code{20}, @code{Value} is initialized to value 1000, and the -non-default C++ constructor that handles two integers takes care of -initializing component @code{Data2} with values @code{20,30}. +@table @asis -In Ada 2005 we can use the extended return statement to build the Ada -equivalent to C++ non-default constructors. For example: +@item @emph{UTF-8 Coding} -@smallexample @c ada - @b{function} Constructor (V : Integer) @b{return} Rec2 @b{is} - @b{begin} - @b{return} Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20), - @b{others} => <>), - @b{others} => <>) @b{do} - --@i{ Further actions required for construction of} - --@i{ objects of type Rec2} - ... - @b{end} @b{record}; - @b{end} Constructor; -@end smallexample +A wide character is represented using +UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO +10646-1/Am.2. Depending on the character value, the representation +of character codes with values greater than 16#FFFF# is a +is a four, five, or six byte sequence: -In this example the extended return statement construct is used to -build in place the returned object whose components are initialized -by means of a limited aggregate. Any further action associated with -the constructor can be placed inside the construct. +@example +16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx + 10xxxxxx +16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx + 10xxxxxx 10xxxxxx +16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx + 10xxxxxx 10xxxxxx 10xxxxxx +@end example -@node Interfacing with C++ at the Class Level -@subsection Interfacing with C++ at the Class Level -@noindent -In this section we demonstrate the GNAT features for interfacing with -C++ by means of an example making use of Ada 2005 abstract interface -types. This example consists of a classification of animals; classes -have been used to model our main classification of animals, and -interfaces provide support for the management of secondary -classifications. We first demonstrate a case in which the types and -constructors are defined on the C++ side and imported from the Ada -side, and latter the reverse case. +where the @cite{xxx} bits correspond to the left-padded bits of the +32-bit character value. -The root of our derivation will be the @code{Animal} class, with a -single private attribute (the @code{Age} of the animal), a constructor, -and two public primitives to set and get the value of this attribute. +@item @emph{Brackets Coding} -@smallexample -@b{class} Animal @{ - @b{public}: - @b{virtual} void Set_Age (int New_Age); - @b{virtual} int Age (); - Animal() @{Age_Count = 0;@}; - @b{private}: - int Age_Count; -@}; -@end smallexample +In this encoding, a wide wide character is represented by the following ten or +twelve byte character sequence: -Abstract interface types are defined in C++ by means of classes with pure -virtual functions and no data members. In our example we will use two -interfaces that provide support for the common management of @code{Carnivore} -and @code{Domestic} animals: +@example +[ " a b c d e f " ] +[ " a b c d e f g h " ] +@end example -@smallexample -@b{class} Carnivore @{ -@b{public}: - @b{virtual} int Number_Of_Teeth () = 0; -@}; +where @cite{a-h} are the six or eight hexadecimal +characters (using uppercase letters) of the wide wide character code. For +example, ["1F4567"] is used to represent the wide wide character with code +@cite{16#001F_4567#}. -@b{class} Domestic @{ -@b{public}: - @b{virtual void} Set_Owner (char* Name) = 0; -@}; -@end smallexample +This scheme is compatible with use of the full Wide_Wide_Character set, +and is also the method used for wide wide character encoding in some standard +ACATS (Ada Conformity Assessment Test Suite) test suite distributions. +@end table -Using these declarations, we can now say that a @code{Dog} is an animal that is -both Carnivore and Domestic, that is: +@node File Naming Topics and Utilities,Configuration Pragmas,Foreign Language Representation,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id8}@anchor{53}@anchor{gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities}@anchor{41} +@section File Naming Topics and Utilities -@smallexample -@b{class} Dog : Animal, Carnivore, Domestic @{ - @b{public}: - @b{virtual} int Number_Of_Teeth (); - @b{virtual} void Set_Owner (char* Name); - Dog(); // Constructor - @b{private}: - int Tooth_Count; - char *Owner; -@}; -@end smallexample +GNAT has a default file naming scheme and also provides the user with +a high degree of control over how the names and extensions of the +source files correspond to the Ada compilation units that they contain. -In the following examples we will assume that the previous declarations are -located in a file named @code{animals.h}. The following package demonstrates -how to import these C++ declarations from the Ada side: +@menu +* File Naming Rules:: +* Using Other File Names:: +* Alternative File Naming Schemes:: +* Handling Arbitrary File Naming Conventions with gnatname:: +* File Name Krunching with gnatkr:: +* Renaming Files with gnatchop:: -@smallexample @c ada -@b{with} Interfaces.C.Strings; @b{use} Interfaces.C.Strings; -@b{package} Animals @b{is} - @b{type} Carnivore @b{is} @b{limited} interface; - @b{pragma} Convention (C_Plus_Plus, Carnivore); - @b{function} Number_Of_Teeth (X : Carnivore) - @b{return} Natural @b{is} @b{abstract}; - - @b{type} Domestic @b{is} @b{limited} interface; - @b{pragma} Convention (C_Plus_Plus, Domestic); - @b{procedure} Set_Owner - (X : @b{in} @b{out} Domestic; - Name : Chars_Ptr) @b{is} @b{abstract}; - - @b{type} Animal @b{is} @b{tagged} @b{limited} @b{record} - Age : Natural; - @b{end} @b{record}; - @b{pragma} Import (C_Plus_Plus, Animal); +@end menu - @b{procedure} Set_Age (X : @b{in} @b{out} Animal; Age : Integer); - @b{pragma} Import (C_Plus_Plus, Set_Age); +@node File Naming Rules,Using Other File Names,,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model file-naming-rules}@anchor{54}@anchor{gnat_ugn/the_gnat_compilation_model id9}@anchor{55} +@subsection File Naming Rules - @b{function} Age (X : Animal) @b{return} Integer; - @b{pragma} Import (C_Plus_Plus, Age); - @b{function} New_Animal @b{return} Animal; - @b{pragma} CPP_Constructor (New_Animal); - @b{pragma} Import (CPP, New_Animal, "_ZN6AnimalC1Ev"); +The default file name is determined by the name of the unit that the +file contains. The name is formed by taking the full expanded name of +the unit and replacing the separating dots with hyphens and using +lowercase for all letters. - @b{type} Dog @b{is} @b{new} Animal @b{and} Carnivore @b{and} Domestic @b{with} @b{record} - Tooth_Count : Natural; - Owner : String (1 .. 30); - @b{end} @b{record}; - @b{pragma} Import (C_Plus_Plus, Dog); +An exception arises if the file name generated by the above rules starts +with one of the characters +@cite{a}, @cite{g}, @cite{i}, or @cite{s}, and the second character is a +minus. In this case, the character tilde is used in place +of the minus. The reason for this special rule is to avoid clashes with +the standard names for child units of the packages System, Ada, +Interfaces, and GNAT, which use the prefixes +@cite{s-}, @cite{a-}, @cite{i-}, and @cite{g-}, +respectively. - @b{function} Number_Of_Teeth (A : Dog) @b{return} Natural; - @b{pragma} Import (C_Plus_Plus, Number_Of_Teeth); +The file extension is @code{.ads} for a spec and +@code{.adb} for a body. The following table shows some +examples of these rules. - @b{procedure} Set_Owner (A : @b{in} @b{out} Dog; Name : Chars_Ptr); - @b{pragma} Import (C_Plus_Plus, Set_Owner); +@quotation - @b{function} New_Dog @b{return} Dog; - @b{pragma} CPP_Constructor (New_Dog); - @b{pragma} Import (CPP, New_Dog, "_ZN3DogC2Ev"); -@b{end} Animals; -@end smallexample -Thanks to the compatibility between GNAT run-time structures and the C++ ABI, -interfacing with these C++ classes is easy. The only requirement is that all -the primitives and components must be declared exactly in the same order in -the two languages. +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item -Regarding the abstract interfaces, we must indicate to the GNAT compiler by -means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass -the arguments to the called primitives will be the same as for C++. For the -imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus} -to indicate that they have been defined on the C++ side; this is required -because the dispatch table associated with these tagged types will be built -in the C++ side and therefore will not contain the predefined Ada primitives -which Ada would otherwise expect. +Source File -As the reader can see there is no need to indicate the C++ mangled names -associated with each subprogram because it is assumed that all the calls to -these primitives will be dispatching calls. The only exception is the -constructor, which must be registered with the compiler by means of -@code{pragma CPP_Constructor} and needs to provide its associated C++ -mangled name because the Ada compiler generates direct calls to it. +@tab -With the above packages we can now declare objects of type Dog on the Ada side -and dispatch calls to the corresponding subprograms on the C++ side. We can -also extend the tagged type Dog with further fields and primitives, and -override some of its C++ primitives on the Ada side. For example, here we have -a type derivation defined on the Ada side that inherits all the dispatching -primitives of the ancestor from the C++ side. +Ada Compilation Unit -@smallexample -@b{with} Animals; @b{use} Animals; -@b{package} Vaccinated_Animals @b{is} - @b{type} Vaccinated_Dog @b{is new} Dog @b{with null record}; - @b{function} Vaccination_Expired (A : Vaccinated_Dog) @b{return} Boolean; -@b{end} Vaccinated_Animals; -@end smallexample +@item -It is important to note that, because of the ABI compatibility, the programmer -does not need to add any further information to indicate either the object -layout or the dispatch table entry associated with each dispatching operation. +@code{main.ads} -Now let us define all the types and constructors on the Ada side and export -them to C++, using the same hierarchy of our previous example: +@tab -@smallexample @c ada -@b{with} Interfaces.C.Strings; -@b{use} Interfaces.C.Strings; -@b{package} Animals @b{is} - @b{type} Carnivore @b{is} @b{limited} interface; - @b{pragma} Convention (C_Plus_Plus, Carnivore); - @b{function} Number_Of_Teeth (X : Carnivore) - @b{return} Natural @b{is} @b{abstract}; - - @b{type} Domestic @b{is} @b{limited} interface; - @b{pragma} Convention (C_Plus_Plus, Domestic); - @b{procedure} Set_Owner - (X : @b{in} @b{out} Domestic; - Name : Chars_Ptr) @b{is} @b{abstract}; - - @b{type} Animal @b{is} @b{tagged} @b{record} - Age : Natural; - @b{end} @b{record}; - @b{pragma} Convention (C_Plus_Plus, Animal); +Main (spec) - @b{procedure} Set_Age (X : @b{in} @b{out} Animal; Age : Integer); - @b{pragma} Export (C_Plus_Plus, Set_Age); +@item - @b{function} Age (X : Animal) @b{return} Integer; - @b{pragma} Export (C_Plus_Plus, Age); +@code{main.adb} - @b{function} New_Animal @b{return} Animal'Class; - @b{pragma} Export (C_Plus_Plus, New_Animal); +@tab - @b{type} Dog @b{is} @b{new} Animal @b{and} Carnivore @b{and} Domestic @b{with} @b{record} - Tooth_Count : Natural; - Owner : String (1 .. 30); - @b{end} @b{record}; - @b{pragma} Convention (C_Plus_Plus, Dog); +Main (body) - @b{function} Number_Of_Teeth (A : Dog) @b{return} Natural; - @b{pragma} Export (C_Plus_Plus, Number_Of_Teeth); +@item - @b{procedure} Set_Owner (A : @b{in} @b{out} Dog; Name : Chars_Ptr); - @b{pragma} Export (C_Plus_Plus, Set_Owner); +@code{arith_functions.ads} - @b{function} New_Dog @b{return} Dog'Class; - @b{pragma} Export (C_Plus_Plus, New_Dog); -@b{end} Animals; -@end smallexample +@tab -Compared with our previous example the only differences are the use of -@code{pragma Convention} (instead of @code{pragma Import}), and the use of -@code{pragma Export} to indicate to the GNAT compiler that the primitives will -be available to C++. Thanks to the ABI compatibility, on the C++ side there is -nothing else to be done; as explained above, the only requirement is that all -the primitives and components are declared in exactly the same order. +Arith_Functions (package spec) -For completeness, let us see a brief C++ main program that uses the -declarations available in @code{animals.h} (presented in our first example) to -import and use the declarations from the Ada side, properly initializing and -finalizing the Ada run-time system along the way: +@item -@smallexample -@b{#include} "animals.h" -@b{#include} -@b{using namespace} std; +@code{arith_functions.adb} -void Check_Carnivore (Carnivore *obj) @{@dots{}@} -void Check_Domestic (Domestic *obj) @{@dots{}@} -void Check_Animal (Animal *obj) @{@dots{}@} -void Check_Dog (Dog *obj) @{@dots{}@} +@tab -@b{extern} "C" @{ - void adainit (void); - void adafinal (void); - Dog* new_dog (); -@} +Arith_Functions (package body) -void test () -@{ - Dog *obj = new_dog(); // Ada constructor - Check_Carnivore (obj); // Check secondary DT - Check_Domestic (obj); // Check secondary DT - Check_Animal (obj); // Check primary DT - Check_Dog (obj); // Check primary DT -@} +@item -int main () -@{ - adainit (); test(); adafinal (); - return 0; -@} -@end smallexample +@code{func-spec.ads} -@node Comparison between GNAT and C/C++ Compilation Models -@section Comparison between GNAT and C/C++ Compilation Models +@tab -@noindent -The GNAT model of compilation is close to the C and C++ models. You can -think of Ada specs as corresponding to header files in C. As in C, you -don't need to compile specs; they are compiled when they are used. The -Ada @code{with} is similar in effect to the @code{#include} of a C -header. +Func.Spec (child package spec) -One notable difference is that, in Ada, you may compile specs separately -to check them for semantic and syntactic accuracy. This is not always -possible with C headers because they are fragments of programs that have -less specific syntactic or semantic rules. +@item -The other major difference is the requirement for running the binder, -which performs two important functions. First, it checks for -consistency. In C or C++, the only defense against assembling -inconsistent programs lies outside the compiler, in a makefile, for -example. The binder satisfies the Ada requirement that it be impossible -to construct an inconsistent program when the compiler is used in normal -mode. +@code{func-spec.adb} -@cindex Elaboration order control -The other important function of the binder is to deal with elaboration -issues. There are also elaboration issues in C++ that are handled -automatically. This automatic handling has the advantage of being -simpler to use, but the C++ programmer has no control over elaboration. -Where @code{gnatbind} might complain there was no valid order of -elaboration, a C++ compiler would simply construct a program that -malfunctioned at run time. +@tab -@node Comparison between GNAT and Conventional Ada Library Models -@section Comparison between GNAT and Conventional Ada Library Models +Func.Spec (child package body) -@noindent -This section is intended for Ada programmers who have -used an Ada compiler implementing the traditional Ada library -model, as described in the Ada Reference Manual. +@item -@cindex GNAT library -In GNAT, there is no ``library'' in the normal sense. Instead, the set of -source files themselves acts as the library. Compiling Ada programs does -not generate any centralized information, but rather an object file and -a ALI file, which are of interest only to the binder and linker. -In a traditional system, the compiler reads information not only from -the source file being compiled, but also from the centralized library. -This means that the effect of a compilation depends on what has been -previously compiled. In particular: +@code{main-sub.adb} -@itemize @bullet -@item -When a unit is @code{with}'ed, the unit seen by the compiler corresponds -to the version of the unit most recently compiled into the library. +@tab + +Sub (subunit of Main) @item -Inlining is effective only if the necessary body has already been -compiled into the library. -@item -Compiling a unit may obsolete other units in the library. -@end itemize +@code{a~bad.adb} -@noindent -In GNAT, compiling one unit never affects the compilation of any other -units because the compiler reads only source files. Only changes to source -files can affect the results of a compilation. In particular: +@tab -@itemize @bullet -@item -When a unit is @code{with}'ed, the unit seen by the compiler corresponds -to the source version of the unit that is currently accessible to the -compiler. +A.Bad (child package body) -@item -@cindex Inlining -Inlining requires the appropriate source files for the package or -subprogram bodies to be available to the compiler. Inlining is always -effective, independent of the order in which units are complied. +@end multitable -@item -Compiling a unit never affects any other compilations. The editing of -sources may cause previous compilations to be out of date if they -depended on the source file being modified. -@end itemize +@end quotation -@noindent -The most important result of these differences is that order of compilation -is never significant in GNAT. There is no situation in which one is -required to do one compilation before another. What shows up as order of -compilation requirements in the traditional Ada library becomes, in -GNAT, simple source dependencies; in other words, there is only a set -of rules saying what source files must be present when a file is -compiled. +Following these rules can result in excessively long +file names if corresponding +unit names are long (for example, if child units or subunits are +heavily nested). An option is available to shorten such long file names +(called file name 'krunching'). This may be particularly useful when +programs being developed with GNAT are to be used on operating systems +with limited file name lengths. @ref{56,,Using gnatkr}. +Of course, no file shortening algorithm can guarantee uniqueness over +all possible unit names; if file name krunching is used, it is your +responsibility to ensure no name clashes occur. Alternatively you +can specify the exact file names that you want used, as described +in the next section. Finally, if your Ada programs are migrating from a +compiler with a different naming convention, you can use the gnatchop +utility to produce source files that follow the GNAT naming conventions. +(For details see @ref{38,,Renaming Files with gnatchop}.) -@c ************************* -@node Compiling with gcc -@chapter Compiling with @command{gcc} +Note: in the case of Windows or Mac OS operating systems, case is not +significant. So for example on @cite{Windows} if the canonical name is +@cite{main-sub.adb}, you can use the file name @code{Main-Sub.adb} instead. +However, case is significant for other operating systems, so for example, +if you want to use other than canonically cased file names on a Unix system, +you need to follow the procedures described in the next section. -@noindent -This chapter discusses how to compile Ada programs using the @command{gcc} -command. It also describes the set of switches -that can be used to control the behavior of the compiler. -@menu -* Compiling Programs:: -* Switches for gcc:: -* Search Paths and the Run-Time Library (RTL):: -* Order of Compilation Issues:: -* Examples:: -@end menu +@node Using Other File Names,Alternative File Naming Schemes,File Naming Rules,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model id10}@anchor{57}@anchor{gnat_ugn/the_gnat_compilation_model using-other-file-names}@anchor{37} +@subsection Using Other File Names -@node Compiling Programs -@section Compiling Programs -@noindent -The first step in creating an executable program is to compile the units -of the program using the @command{gcc} command. You must compile the -following files: +@geindex File names -@itemize @bullet -@item -the body file (@file{.adb}) for a library level subprogram or generic -subprogram +In the previous section, we have described the default rules used by +GNAT to determine the file name in which a given unit resides. It is +often convenient to follow these default rules, and if you follow them, +the compiler knows without being explicitly told where to find all +the files it needs. -@item -the spec file (@file{.ads}) for a library level package or generic -package that has no body +@geindex Source_File_Name pragma -@item -the body file (@file{.adb}) for a library level package -or generic package that has a body +However, in some cases, particularly when a program is imported from +another Ada compiler environment, it may be more convenient for the +programmer to specify which file names contain which units. GNAT allows +arbitrary file names to be used by means of the Source_File_Name pragma. +The form of this pragma is as shown in the following examples: -@end itemize +@example +pragma Source_File_Name (My_Utilities.Stacks, + Spec_File_Name => "myutilst_a.ada"); +pragma Source_File_name (My_Utilities.Stacks, + Body_File_Name => "myutilst.ada"); +@end example -@noindent -You need @emph{not} compile the following files +As shown in this example, the first argument for the pragma is the unit +name (in this example a child unit). The second argument has the form +of a named association. The identifier +indicates whether the file name is for a spec or a body; +the file name itself is given by a string literal. -@itemize @bullet +The source file name pragma is a configuration pragma, which means that +normally it will be placed in the @code{gnat.adc} +file used to hold configuration +pragmas that apply to a complete compilation environment. +For more details on how the @code{gnat.adc} file is created and used +see @ref{58,,Handling of Configuration Pragmas}. -@item -the spec of a library unit which has a body +@geindex gnat.adc -@item -subunits -@end itemize +GNAT allows completely arbitrary file names to be specified using the +source file name pragma. However, if the file name specified has an +extension other than @code{.ads} or @code{.adb} it is necessary to use +a special syntax when compiling the file. The name in this case must be +preceded by the special sequence @emph{-x} followed by a space and the name +of the language, here @cite{ada}, as in: -@noindent -because they are compiled as part of compiling related units. GNAT -package specs -when the corresponding body is compiled, and subunits when the parent is -compiled. +@example +$ gcc -c -x ada peculiar_file_name.sim +@end example -@cindex cannot generate code -If you attempt to compile any of these files, you will get one of the -following error messages (where @var{fff} is the name of the file you -compiled): +@cite{gnatmake} handles non-standard file names in the usual manner (the +non-standard file name for the main program is simply used as the +argument to gnatmake). Note that if the extension is also non-standard, +then it must be included in the @cite{gnatmake} command, it may not +be omitted. -@smallexample -cannot generate code for file @var{fff} (package spec) -to check package spec, use -gnatc +@node Alternative File Naming Schemes,Handling Arbitrary File Naming Conventions with gnatname,Using Other File Names,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model id11}@anchor{59}@anchor{gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes}@anchor{5a} +@subsection Alternative File Naming Schemes -cannot generate code for file @var{fff} (missing subunits) -to check parent unit, use -gnatc -cannot generate code for file @var{fff} (subprogram spec) -to check subprogram spec, use -gnatc +@geindex File naming schemes +@geindex alternative -cannot generate code for file @var{fff} (subunit) -to check subunit, use -gnatc -@end smallexample +@geindex File names -@noindent -As indicated by the above error messages, if you want to submit -one of these files to the compiler to check for correct semantics -without generating code, then use the @option{-gnatc} switch. +The previous section described the use of the @cite{Source_File_Name} +pragma to allow arbitrary names to be assigned to individual source files. +However, this approach requires one pragma for each file, and especially in +large systems can result in very long @code{gnat.adc} files, and also create +a maintenance problem. -The basic command for compiling a file containing an Ada unit is +@geindex Source_File_Name pragma -@smallexample -@c $ gcc -c @ovar{switches} @file{file name} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gcc -c @r{[}@var{switches}@r{]} @file{file name} -@end smallexample +GNAT also provides a facility for specifying systematic file naming schemes +other than the standard default naming scheme previously described. An +alternative scheme for naming is specified by the use of +@cite{Source_File_Name} pragmas having the following format: -@noindent -where @var{file name} is the name of the Ada file (usually -having an extension -@file{.ads} for a spec or @file{.adb} for a body). -You specify the -@option{-c} switch to tell @command{gcc} to compile, but not link, the file. -The result of a successful compilation is an object file, which has the -same name as the source file but an extension of @file{.o} and an Ada -Library Information (ALI) file, which also has the same name as the -source file, but with @file{.ali} as the extension. GNAT creates these -two output files in the current directory, but you may specify a source -file in any directory using an absolute or relative path specification -containing the directory information. +@example +pragma Source_File_Name ( + Spec_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC] + [ , Dot_Replacement => STRING_LITERAL ] ); -@findex gnat1 -@command{gcc} is actually a driver program that looks at the extensions of -the file arguments and loads the appropriate compiler. For example, the -GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}. -These programs are in directories known to the driver program (in some -configurations via environment variables you set), but need not be in -your path. The @command{gcc} driver also calls the assembler and any other -utilities needed to complete the generation of the required object -files. +pragma Source_File_Name ( + Body_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC ] + [ , Dot_Replacement => STRING_LITERAL ] ) ; -It is possible to supply several file names on the same @command{gcc} -command. This causes @command{gcc} to call the appropriate compiler for -each file. For example, the following command lists two separate -files to be compiled: +pragma Source_File_Name ( + Subunit_File_Name => FILE_NAME_PATTERN + [ , Casing => CASING_SPEC ] + [ , Dot_Replacement => STRING_LITERAL ] ) ; -@smallexample -$ gcc -c x.adb y.adb -@end smallexample +FILE_NAME_PATTERN ::= STRING_LITERAL +CASING_SPEC ::= Lowercase | Uppercase | Mixedcase +@end example -@noindent -calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and -@file{y.adb}. -The compiler generates two object files @file{x.o} and @file{y.o} -and the two ALI files @file{x.ali} and @file{y.ali}. -Any switches apply to all the files listed, +The @cite{FILE_NAME_PATTERN} string shows how the file name is constructed. +It contains a single asterisk character, and the unit name is substituted +systematically for this asterisk. The optional parameter +@cite{Casing} indicates +whether the unit name is to be all upper-case letters, all lower-case letters, +or mixed-case. If no +@cite{Casing} parameter is used, then the default is all +lower-case. -@node Switches for gcc -@section Switches for @command{gcc} +The optional @cite{Dot_Replacement} string is used to replace any periods +that occur in subunit or child unit names. If no @cite{Dot_Replacement} +argument is used then separating dots appear unchanged in the resulting +file name. +Although the above syntax indicates that the +@cite{Casing} argument must appear +before the @cite{Dot_Replacement} argument, but it +is also permissible to write these arguments in the opposite order. -@noindent -The @command{gcc} command accepts switches that control the -compilation process. These switches are fully described in this section. -First we briefly list all the switches, in alphabetical order, then we -describe the switches in more detail in functionally grouped sections. +As indicated, it is possible to specify different naming schemes for +bodies, specs, and subunits. Quite often the rule for subunits is the +same as the rule for bodies, in which case, there is no need to give +a separate @cite{Subunit_File_Name} rule, and in this case the +@cite{Body_File_name} rule is used for subunits as well. -More switches exist for GCC than those documented here, especially -for specific targets. However, their use is not recommended as -they may change code generation in ways that are incompatible with -the Ada run-time library, or can cause inconsistencies between -compilation units. +The separate rule for subunits can also be used to implement the rather +unusual case of a compilation environment (e.g., a single directory) which +contains a subunit and a child unit with the same unit name. Although +both units cannot appear in the same partition, the Ada Reference Manual +allows (but does not require) the possibility of the two units coexisting +in the same environment. -@menu -* Output and Error Message Control:: -* Warning Message Control:: -* Debugging and Assertion Control:: -* Validity Checking:: -* Style Checking:: -* Run-Time Checks:: -* Using gcc for Syntax Checking:: -* Using gcc for Semantic Checking:: -* Compiling Different Versions of Ada:: -* Character Set Control:: -* File Naming Control:: -* Subprogram Inlining Control:: -* Auxiliary Output Control:: -* Debugging Control:: -* Exception Handling Control:: -* Units to Sources Mapping Files:: -* Integrated Preprocessing:: -* Code Generation Control:: -@end menu +The file name translation works in the following steps: -@table @option -@c !sort! -@cindex @option{-b} (@command{gcc}) -@item -b @var{target} -Compile your program to run on @var{target}, which is the name of a -system configuration. You must have a GNAT cross-compiler built if -@var{target} is not the same as your host system. -@item -B@var{dir} -@cindex @option{-B} (@command{gcc}) -Load compiler executables (for example, @code{gnat1}, the Ada compiler) -from @var{dir} instead of the default location. Only use this switch -when multiple versions of the GNAT compiler are available. -@xref{Directory Options,, Options for Directory Search, gcc, Using the -GNU Compiler Collection (GCC)}, for further details. You would normally -use the @option{-b} or @option{-V} switch instead. +@itemize * -@item -c -@cindex @option{-c} (@command{gcc}) -Compile. Always use this switch when compiling Ada programs. +@item +If there is a specific @cite{Source_File_Name} pragma for the given unit, +then this is always used, and any general pattern rules are ignored. -Note: for some other languages when using @command{gcc}, notably in -the case of C and C++, it is possible to use -use @command{gcc} without a @option{-c} switch to -compile and link in one step. In the case of GNAT, you -cannot use this approach, because the binder must be run -and @command{gcc} cannot be used to run the GNAT binder. +@item +If there is a pattern type @cite{Source_File_Name} pragma that applies to +the unit, then the resulting file name will be used if the file exists. If +more than one pattern matches, the latest one will be tried first, and the +first attempt resulting in a reference to a file that exists will be used. -@item -fcallgraph-info@r{[}=su,da@r{]} -@cindex @option{-fcallgraph-info} (@command{gcc}) -Makes the compiler output callgraph information for the program, on a -per-file basis. The information is generated in the VCG format. It can -be decorated with additional, per-node and/or per-edge information, if a -list of comma-separated markers is additionally specified. When the -@var{su} marker is specified, the callgraph is decorated with stack usage information; it is equivalent to @option{-fstack-usage}. When the @var{da} -marker is specified, the callgraph is decorated with information about -dynamically allocated objects. +@item +If no pattern type @cite{Source_File_Name} pragma that applies to the unit +for which the corresponding file exists, then the standard GNAT default +naming rules are used. +@end itemize -@item -fdump-scos -@cindex @option{-fdump-scos} (@command{gcc}) -Generates SCO (Source Coverage Obligation) information in the ALI file. -This information is used by advanced coverage tools. See unit @file{SCOs} -in the compiler sources for details in files @file{scos.ads} and -@file{scos.adb}. +As an example of the use of this mechanism, consider a commonly used scheme +in which file names are all lower case, with separating periods copied +unchanged to the resulting file name, and specs end with @code{.1.ada}, and +bodies end with @code{.2.ada}. GNAT will follow this scheme if the following +two pragmas appear: -@item -fdump-xref -@cindex @option{-fdump-xref} (@command{gcc}) -Generates cross reference information in GLI files for C and C++ sources. -The GLI files have the same syntax as the ALI files for Ada, and can be used -for source navigation in IDEs and on the command line using e.g. gnatxref -and the @option{--ext=gli} switch. +@example +pragma Source_File_Name + (Spec_File_Name => ".1.ada"); +pragma Source_File_Name + (Body_File_Name => ".2.ada"); +@end example -@item -flto@r{[}=n@r{]} -@cindex @option{-flto} (@command{gcc}) -Enables Link Time Optimization. This switch must be used in conjunction -with the traditional @option{-Ox} switches and instructs the compiler to -defer most optimizations until the link stage. The advantage of this -approach is that the compiler can do a whole-program analysis and choose -the best interprocedural optimization strategy based on a complete view -of the program, instead of a fragmentary view with the usual approach. -This can also speed up the compilation of big programs and reduce the -size of the executable, compared with a traditional per-unit compilation -with inlining across modules enabled by the @option{-gnatn} switch. -The drawback of this approach is that it may require more memory and that -the debugging information generated by -g with it might be hardly usable. -The switch, as well as the accompanying @option{-Ox} switches, must be -specified both for the compilation and the link phases. -If the @var{n} parameter is specified, the optimization and final code -generation at link time are executed using @var{n} parallel jobs by -means of an installed @command{make} program. - -@item -fno-inline -@cindex @option{-fno-inline} (@command{gcc}) -Suppresses all inlining, even if other optimization or inlining -switches are set. This includes suppression of inlining that -results from the use of the pragma @code{Inline_Always}. -Any occurrences of pragma @code{Inline} or @code{Inline_Always} -are ignored, and @option{-gnatn} and @option{-gnatN} have no -effects if this switch is present. Note that inlining can also -be suppressed on a finer-grained basis with pragma @code{No_Inline}. - -@item -fno-inline-functions -@cindex @option{-fno-inline-functions} (@command{gcc}) -Suppresses automatic inlining of subprograms, which is enabled -if @option{-O3} is used. +The default GNAT scheme is actually implemented by providing the following +default pragmas internally: -@item -fno-inline-small-functions -@cindex @option{-fno-inline-small-functions} (@command{gcc}) -Suppresses automatic inlining of small subprograms, which is enabled -if @option{-O2} is used. +@example +pragma Source_File_Name + (Spec_File_Name => ".ads", Dot_Replacement => "-"); +pragma Source_File_Name + (Body_File_Name => ".adb", Dot_Replacement => "-"); +@end example -@item -fno-inline-functions-called-once -@cindex @option{-fno-inline-functions-called-once} (@command{gcc}) -Suppresses inlining of subprograms local to the unit and called once -from within it, which is enabled if @option{-O1} is used. +Our final example implements a scheme typically used with one of the +Ada 83 compilers, where the separator character for subunits was '__' +(two underscores), specs were identified by adding @code{_.ADA}, bodies +by adding @code{.ADA}, and subunits by +adding @code{.SEP}. All file names were +upper case. Child units were not present of course since this was an +Ada 83 compiler, but it seems reasonable to extend this scheme to use +the same double underscore separator for child units. -@item -fno-ivopts -@cindex @option{-fno-ivopts} (@command{gcc}) -Suppresses high-level loop induction variable optimizations, which are -enabled if @option{-O1} is used. These optimizations are generally -profitable but, for some specific cases of loops with numerous uses -of the iteration variable that follow a common pattern, they may end -up destroying the regularity that could be exploited at a lower level -and thus producing inferior code. +@example +pragma Source_File_Name + (Spec_File_Name => "_.ADA", + Dot_Replacement => "__", + Casing = Uppercase); +pragma Source_File_Name + (Body_File_Name => ".ADA", + Dot_Replacement => "__", + Casing = Uppercase); +pragma Source_File_Name + (Subunit_File_Name => ".SEP", + Dot_Replacement => "__", + Casing = Uppercase); +@end example -@item -fno-strict-aliasing -@cindex @option{-fno-strict-aliasing} (@command{gcc}) -Causes the compiler to avoid assumptions regarding non-aliasing -of objects of different types. See -@ref{Optimization and Strict Aliasing} for details. +@geindex gnatname -@item -fstack-check -@cindex @option{-fstack-check} (@command{gcc}) -Activates stack checking. -See @ref{Stack Overflow Checking} for details. +@node Handling Arbitrary File Naming Conventions with gnatname,File Name Krunching with gnatkr,Alternative File Naming Schemes,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model handling-arbitrary-file-naming-conventions-with-gnatname}@anchor{5b}@anchor{gnat_ugn/the_gnat_compilation_model id12}@anchor{5c} +@subsection Handling Arbitrary File Naming Conventions with @cite{gnatname} -@item -fstack-usage -@cindex @option{-fstack-usage} (@command{gcc}) -Makes the compiler output stack usage information for the program, on a -per-subprogram basis. See @ref{Static Stack Usage Analysis} for details. -@item -g -@cindex @option{-g} (@command{gcc}) -Generate debugging information. This information is stored in the object -file and copied from there to the final executable file by the linker, -where it can be read by the debugger. You must use the -@option{-g} switch if you plan on using the debugger. +@geindex File Naming Conventions -@item -gnat83 -@cindex @option{-gnat83} (@command{gcc}) -Enforce Ada 83 restrictions. +@menu +* Arbitrary File Naming Conventions:: +* Running gnatname:: +* Switches for gnatname:: +* Examples of gnatname Usage:: -@item -gnat95 -@cindex @option{-gnat95} (@command{gcc}) -Enforce Ada 95 restrictions. +@end menu -Note: for compatibility with some Ada 95 compilers which support only -the @code{overriding} keyword of Ada 2005, the @option{-gnatd.D} switch can -be used along with @option{-gnat95} to achieve a similar effect with GNAT. +@node Arbitrary File Naming Conventions,Running gnatname,,Handling Arbitrary File Naming Conventions with gnatname +@anchor{gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions}@anchor{5d}@anchor{gnat_ugn/the_gnat_compilation_model id13}@anchor{5e} +@subsubsection Arbitrary File Naming Conventions -@option{-gnatd.D} instructs GNAT to consider @code{overriding} as a keyword -and handle its associated semantic checks, even in Ada 95 mode. -@item -gnat05 -@cindex @option{-gnat05} (@command{gcc}) -Allow full Ada 2005 features. +The GNAT compiler must be able to know the source file name of a compilation +unit. When using the standard GNAT default file naming conventions +(@cite{.ads} for specs, @cite{.adb} for bodies), the GNAT compiler +does not need additional information. -@item -gnat2005 -@cindex @option{-gnat2005} (@command{gcc}) -Allow full Ada 2005 features (same as @option{-gnat05}) +When the source file names do not follow the standard GNAT default file naming +conventions, the GNAT compiler must be given additional information through +a configuration pragmas file (@ref{16,,Configuration Pragmas}) +or a project file. +When the non-standard file naming conventions are well-defined, +a small number of pragmas @cite{Source_File_Name} specifying a naming pattern +(@ref{5a,,Alternative File Naming Schemes}) may be sufficient. However, +if the file naming conventions are irregular or arbitrary, a number +of pragma @cite{Source_File_Name} for individual compilation units +must be defined. +To help maintain the correspondence between compilation unit names and +source file names within the compiler, +GNAT provides a tool @cite{gnatname} to generate the required pragmas for a +set of files. -@item -gnat12 -@cindex @option{-gnat12} (@command{gcc}) +@node Running gnatname,Switches for gnatname,Arbitrary File Naming Conventions,Handling Arbitrary File Naming Conventions with gnatname +@anchor{gnat_ugn/the_gnat_compilation_model running-gnatname}@anchor{5f}@anchor{gnat_ugn/the_gnat_compilation_model id14}@anchor{60} +@subsubsection Running @cite{gnatname} -@item -gnat2012 -@cindex @option{-gnat2012} (@command{gcc}) -Allow full Ada 2012 features (same as @option{-gnat12}) -@item -gnata -@cindex @option{-gnata} (@command{gcc}) -Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be -activated. Note that these pragmas can also be controlled using the -configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}. -It also activates pragmas @code{Check}, @code{Precondition}, and -@code{Postcondition}. Note that these pragmas can also be controlled -using the configuration pragma @code{Check_Policy}. In Ada 2012, it -also activates all assertions defined in the RM as aspects: preconditions, -postconditions, type invariants and (sub)type predicates. In all Ada modes, -corresponding pragmas for type invariants and (sub)type predicates are -also activated. The default is that all these assertions are disabled, -and have no effect, other than being checked for syntactic validity, and -in the case of subtype predicates, constructions such as membership tests -still test predicates even if assertions are turned off. +The usual form of the @cite{gnatname} command is: -@item -gnatA -@cindex @option{-gnatA} (@command{gcc}) -Avoid processing @file{gnat.adc}. If a @file{gnat.adc} file is present, -it will be ignored. +@example +$ gnatname [`switches`] `naming_pattern` [`naming_patterns`] + [--and [`switches`] `naming_pattern` [`naming_patterns`]] +@end example -@item -gnatb -@cindex @option{-gnatb} (@command{gcc}) -Generate brief messages to @file{stderr} even if verbose mode set. +All of the arguments are optional. If invoked without any argument, +@cite{gnatname} will display its usage. -@item -gnatB -@cindex @option{-gnatB} (@command{gcc}) -Assume no invalid (bad) values except for 'Valid attribute use -(@pxref{Validity Checking}). +When used with at least one naming pattern, @cite{gnatname} will attempt to +find all the compilation units in files that follow at least one of the +naming patterns. To find these compilation units, +@cite{gnatname} will use the GNAT compiler in syntax-check-only mode on all +regular files. -@item -gnatc -@cindex @option{-gnatc} (@command{gcc}) -Check syntax and semantics only (no code generation attempted). When the -compiler is invoked by @command{gnatmake}, if the switch @option{-gnatc} is -only given to the compiler (after @option{-cargs} or in package Compiler of -the project file, @command{gnatmake} will fail because it will not find the -object file after compilation. If @command{gnatmake} is called with -@option{-gnatc} as a builder switch (before @option{-cargs} or in package -Builder of the project file) then @command{gnatmake} will not fail because -it will not look for the object files after compilation, and it will not try -to build and link. This switch may not be given if a previous @code{-gnatR} -switch has been given, since @code{-gnatR} requires that the code generator -be called to complete determination of representation information. +One or several Naming Patterns may be given as arguments to @cite{gnatname}. +Each Naming Pattern is enclosed between double quotes (or single +quotes on Windows). +A Naming Pattern is a regular expression similar to the wildcard patterns +used in file names by the Unix shells or the DOS prompt. -@item -gnatC -@cindex @option{-gnatC} (@command{gcc}) -Generate CodePeer intermediate format (no code generation attempted). -This switch will generate an intermediate representation suitable for -use by CodePeer (@file{.scil} files). This switch is not compatible with -code generation (it will, among other things, disable some switches such -as -gnatn, and enable others such as -gnata). +@cite{gnatname} may be called with several sections of directories/patterns. +Sections are separated by switch @cite{--and}. In each section, there must be +at least one pattern. If no directory is specified in a section, the current +directory (or the project directory is @cite{-P} is used) is implied. +The options other that the directory switches and the patterns apply globally +even if they are in different sections. -@item -gnatd -@cindex @option{-gnatd} (@command{gcc}) -Specify debug options for the compiler. The string of characters after -the @option{-gnatd} specify the specific debug options. The possible -characters are 0-9, a-z, A-Z, optionally preceded by a dot. See -compiler source file @file{debug.adb} for details of the implemented -debug options. Certain debug options are relevant to applications -programmers, and these are documented at appropriate points in this -users guide. +Examples of Naming Patterns are: -@item -gnatD -@cindex @option{-gnatD[nn]} (@command{gcc}) -Create expanded source files for source level debugging. This switch -also suppress generation of cross-reference information -(see @option{-gnatx}). Note that this switch is not allowed if a previous --gnatR switch has been given, since these two switches are not compatible. +@example +"*.[12].ada" +"*.ad[sb]*" +"body_*" "spec_*" +@end example -@item -gnateA -@cindex @option{-gnateA} (@command{gcc}) -Check that the actual parameters of a subprogram call are not aliases of one -another. To qualify as aliasing, the actuals must denote objects of a composite -type, their memory locations must be identical or overlapping, and at least one -of the corresponding formal parameters must be of mode OUT or IN OUT. +For a more complete description of the syntax of Naming Patterns, +see the second kind of regular expressions described in @code{g-regexp.ads} +(the 'Glob' regular expressions). -@smallexample -type Rec_Typ is record - Data : Integer := 0; -end record; +When invoked with no switch @cite{-P}, @cite{gnatname} will create a +configuration pragmas file @code{gnat.adc} in the current working directory, +with pragmas @cite{Source_File_Name} for each file that contains a valid Ada +unit. -function Self (Val : Rec_Typ) return Rec_Typ is -begin - return Val; -end Self; +@node Switches for gnatname,Examples of gnatname Usage,Running gnatname,Handling Arbitrary File Naming Conventions with gnatname +@anchor{gnat_ugn/the_gnat_compilation_model id15}@anchor{61}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatname}@anchor{62} +@subsubsection Switches for @cite{gnatname} -procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is -begin - null; -end Detect_Aliasing; -Obj : Rec_Typ; +Switches for @cite{gnatname} must precede any specified Naming Pattern. -Detect_Aliasing (Obj, Obj); -Detect_Aliasing (Obj, Self (Obj)); -@end smallexample +You may specify any of the following switches to @cite{gnatname}: -In the example above, the first call to @code{Detect_Aliasing} fails with a -@code{Program_Error} at runtime because the actuals for @code{Val_1} and -@code{Val_2} denote the same object. The second call executes without raising -an exception because @code{Self(Obj)} produces an anonymous object which does -not share the memory location of @code{Obj}. +@geindex --version (gnatname) -@item -gnatec=@var{path} -@cindex @option{-gnatec} (@command{gcc}) -Specify a configuration pragma file -(the equal sign is optional) -(@pxref{The Configuration Pragmas Files}). -@item -gnateC -@cindex @option{-gnateC} (@command{gcc}) -Generate CodePeer messages in a compiler-like format. This switch is only -effective if @option{-gnatcC} is also specified and requires an installation -of CodePeer. +@table @asis -@item -gnated -@cindex @option{-gnated} (@command{gcc}) -Disable atomic synchronization +@item @code{--version} -@item -gnateDsymbol@r{[}=@var{value}@r{]} -@cindex @option{-gnateD} (@command{gcc}) -Defines a symbol, associated with @var{value}, for preprocessing. -(@pxref{Integrated Preprocessing}). +Display Copyright and version, then exit disregarding all other options. +@end table -@item -gnateE -@cindex @option{-gnateE} (@command{gcc}) -Generate extra information in exception messages. In particular, display -extra column information and the value and range associated with index and -range check failures, and extra column information for access checks. -In cases where the compiler is able to determine at compile time that -a check will fail, it gives a warning, and the extra information is not -produced at run time. +@geindex --help (gnatname) -@item -gnatef -@cindex @option{-gnatef} (@command{gcc}) -Display full source path name in brief error messages. -@item -gnateF -@cindex @option{-gnateF} (@command{gcc}) -Check for overflow on all floating-point operations, including those -for unconstrained predefined types. See description of pragma -@code{Check_Float_Overflow} in GNAT RM. +@table @asis -@item -gnateG -@cindex @option{-gnateG} (@command{gcc}) -Save result of preprocessing in a text file. +@item @code{--help} -@item -gnatei@var{nnn} -@cindex @option{-gnatei} (@command{gcc}) -Set maximum number of instantiations during compilation of a single unit to -@var{nnn}. This may be useful in increasing the default maximum of 8000 for -the rare case when a single unit legitimately exceeds this limit. +If @emph{--version} was not used, display usage, then exit disregarding +all other options. -@item -gnateI@var{nnn} -@cindex @option{-gnateI} (@command{gcc}) -Indicates that the source is a multi-unit source and that the index of the -unit to compile is @var{nnn}. @var{nnn} needs to be a positive number and need -to be a valid index in the multi-unit source. +@item @code{--subdirs=@emph{dir}} -@item -gnatel -@cindex @option{-gnatel} (@command{gcc}) -This switch can be used with the static elaboration model to issue info -messages showing -where implicit @code{pragma Elaborate} and @code{pragma Elaborate_All} -are generated. This is useful in diagnosing elaboration circularities -caused by these implicit pragmas when using the static elaboration -model. See See the section in this guide on elaboration checking for -further details. These messages are not generated by default, and are -intended only for temporary use when debugging circularity problems. +Real object, library or exec directories are subdirectories of the +specified ones. -@item -gnateL -@cindex @option{-gnatel} (@command{gcc}) -This switch turns off the info messages about implicit elaboration pragmas. +@item @code{--no-backup} -@item -gnatem=@var{path} -@cindex @option{-gnatem} (@command{gcc}) -Specify a mapping file -(the equal sign is optional) -(@pxref{Units to Sources Mapping Files}). +Do not create a backup copy of an existing project file. -@item -gnatep=@var{file} -@cindex @option{-gnatep} (@command{gcc}) -Specify a preprocessing data file -(the equal sign is optional) -(@pxref{Integrated Preprocessing}). +@item @code{--and} -@item -gnateP -@cindex @option{-gnateP} (@command{gcc}) -Turn categorization dependency errors into warnings. -Ada requires that units that WITH one another have compatible categories, for -example a Pure unit cannot WITH a Preelaborate unit. If this switch is used, -these errors become warnings (which can be ignored, or suppressed in the usual -manner). This can be useful in some specialized circumstances such as the -temporary use of special test software. +Start another section of directories/patterns. +@end table -@item -gnateS -@cindex @option{-gnateS} (@command{gcc}) -Synonym of @option{-fdump-scos}, kept for backwards compatibility. +@geindex -c (gnatname) -@item -gnatet=@var{path} -@cindex @option{-gnatet=file} (@command{gcc}) -Generate target dependent information. The format of the output file is -described in the section about switch @option{-gnateT}. -@item -gnateT=@var{path} -@cindex @option{-gnateT} (@command{gcc}) -Read target dependent information, such as endianness or sizes and alignments -of base type. If this switch is passed, the default target dependent -information of the compiler is replaced by the one read from the input file. -This is used by tools other than the compiler, e.g. to do -semantic analysis of programs that will run on some other target than -the machine on which the tool is run. +@table @asis -The following target dependent values should be defined, -where @code{Nat} denotes a natural integer value, @code{Pos} denotes a -positive integer value, and fields marked with a question mark are -boolean fields, where a value of 0 is False, and a value of 1 is True: +@item @code{-c@emph{filename}} -@smallexample -Bits_BE : Nat; -- Bits stored big-endian? -Bits_Per_Unit : Pos; -- Bits in a storage unit -Bits_Per_Word : Pos; -- Bits in a word -Bytes_BE : Nat; -- Bytes stored big-endian? -Char_Size : Pos; -- Standard.Character'Size -Double_Float_Alignment : Nat; -- Alignment of double float -Double_Scalar_Alignment : Nat; -- Alignment of double length scalar -Double_Size : Pos; -- Standard.Long_Float'Size -Float_Size : Pos; -- Standard.Float'Size -Float_Words_BE : Nat; -- Float words stored big-endian? -Int_Size : Pos; -- Standard.Integer'Size -Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size -Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size -Long_Size : Pos; -- Standard.Long_Integer'Size -Maximum_Alignment : Pos; -- Maximum permitted alignment -Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field -Pointer_Size : Pos; -- System.Address'Size -Short_Enums : Nat; -- Short foreign convention enums? -Short_Size : Pos; -- Standard.Short_Integer'Size -Strict_Alignment : Nat; -- Strict alignment? -System_Allocator_Alignment : Nat; -- Alignment for malloc calls -Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size -Words_BE : Nat; -- Words stored big-endian? -@end smallexample +Create a configuration pragmas file @code{filename} (instead of the default +@code{gnat.adc}). +There may be zero, one or more space between @emph{-c} and +@code{filename}. +@code{filename} may include directory information. @code{filename} must be +writable. There may be only one switch @emph{-c}. +When a switch @emph{-c} is +specified, no switch @emph{-P} may be specified (see below). +@end table -The format of the input file is as follows. First come the values of -the variables defined above, with one line per value: +@geindex -d (gnatname) -@smallexample -name value -@end smallexample -where @code{name} is the name of the parameter, spelled out in full, -and cased as in the above list, and @code{value} is an unsigned decimal -integer. Two or more blanks separates the name from the value. +@table @asis -All the variables must be present, in alphabetical order (i.e. the -same order as the list above). +@item @code{-d@emph{dir}} -Then there is a blank line to separate the two parts of the file. Then -come the lines showing the floating-point types to be registered, with -one line per registered mode: +Look for source files in directory @code{dir}. There may be zero, one or more +spaces between @emph{-d} and @code{dir}. +@code{dir} may end with @cite{/**}, that is it may be of the form +@cite{root_dir/**}. In this case, the directory @cite{root_dir} and all of its +subdirectories, recursively, have to be searched for sources. +When a switch @emph{-d} +is specified, the current working directory will not be searched for source +files, unless it is explicitly specified with a @emph{-d} +or @emph{-D} switch. +Several switches @emph{-d} may be specified. +If @code{dir} is a relative path, it is relative to the directory of +the configuration pragmas file specified with switch +@emph{-c}, +or to the directory of the project file specified with switch +@emph{-P} or, +if neither switch @emph{-c} +nor switch @emph{-P} are specified, it is relative to the +current working directory. The directory +specified with switch @emph{-d} must exist and be readable. +@end table -@smallexample -name digs float_rep size alignment -@end smallexample +@geindex -D (gnatname) -where @code{name} is the string name of the type (which can have -single spaces embedded in the name (e.g. long double), @code{digs} is -the number of digits for the floating-point type, @code{float_rep} is -the float representation (I/V/A for IEEE-754-Binary, Vax_Native, -AAMP), @code{size} is the size in bits, @code{alignment} is the -alignment in bits. The name is followed by at least two blanks, fields -are separated by at least one blank, and a LF character immediately -follows the alignment field. -Here is an example of a target parameterization file: +@table @asis -@smallexample -Bits_BE 0 -Bits_Per_Unit 8 -Bits_Per_Word 64 -Bytes_BE 0 -Char_Size 8 -Double_Float_Alignment 0 -Double_Scalar_Alignment 0 -Double_Size 64 -Float_Size 32 -Float_Words_BE 0 -Int_Size 64 -Long_Double_Size 128 -Long_Long_Size 64 -Long_Size 64 -Maximum_Alignment 16 -Max_Unaligned_Field 64 -Pointer_Size 64 -Short_Size 16 -Strict_Alignment 0 -System_Allocator_Alignment 16 -Wchar_T_Size 32 -Words_BE 0 +@item @code{-D@emph{filename}} -float 15 I 64 64 -double 15 I 64 64 -long double 18 I 80 128 -TF 33 I 128 128 -@end smallexample +Look for source files in all directories listed in text file @code{filename}. +There may be zero, one or more spaces between @emph{-D} +and @code{filename}. +@code{filename} must be an existing, readable text file. +Each nonempty line in @code{filename} must be a directory. +Specifying switch @emph{-D} is equivalent to specifying as many +switches @emph{-d} as there are nonempty lines in +@code{file}. -@item -gnateu -@cindex @option{-gnateu} (@command{gcc}) -Ignore unrecognized validity, warning, and style switches that -appear after this switch is given. This may be useful when -compiling sources developed on a later version of the compiler -with an earlier version. Of course the earlier version must -support this switch. +@item @code{-eL} -@item -gnateV -@cindex @option{-gnateV} (@command{gcc}) -Check that all actual parameters of a subprogram call are valid according to -the rules of validity checking (@pxref{Validity Checking}). +Follow symbolic links when processing project files. -@item -gnateY -@cindex @option{-gnateY} (@command{gcc}) -Ignore all STYLE_CHECKS pragmas. Full legality checks -are still carried out, but the pragmas have no effect -on what style checks are active. This allows all style -checking options to be controlled from the command line. +@geindex -f (gnatname) -@item -gnatE -@cindex @option{-gnatE} (@command{gcc}) -Full dynamic elaboration checks. +@item @code{-f@emph{pattern}} -@item -gnatf -@cindex @option{-gnatf} (@command{gcc}) -Full errors. Multiple errors per line, all undefined references, do not -attempt to suppress cascaded errors. +Foreign patterns. Using this switch, it is possible to add sources of languages +other than Ada to the list of sources of a project file. +It is only useful if a -P switch is used. +For example, -@item -gnatF -@cindex @option{-gnatF} (@command{gcc}) -Externals names are folded to all uppercase. +@example +gnatname -Pprj -f"*.c" "*.ada" +@end example -@item -gnatg -@cindex @option{-gnatg} (@command{gcc}) -Internal GNAT implementation mode. This should not be used for -applications programs, it is intended only for use by the compiler -and its run-time library. For documentation, see the GNAT sources. -Note that @option{-gnatg} implies -@option{-gnatw.ge} and -@option{-gnatyg} -so that all standard warnings and all standard style options are turned on. -All warnings and style messages are treated as errors. +will look for Ada units in all files with the @code{.ada} extension, +and will add to the list of file for project @code{prj.gpr} the C files +with extension @code{.c}. -@item -gnatG=nn -@cindex @option{-gnatG[nn]} (@command{gcc}) -List generated expanded code in source form. +@geindex -h (gnatname) -@item -gnath -@cindex @option{-gnath} (@command{gcc}) -Output usage information. The output is written to @file{stdout}. +@item @code{-h} -@item -gnati@var{c} -@cindex @option{-gnati} (@command{gcc}) -Identifier character set -(@var{c}=1/2/3/4/8/9/p/f/n/w). -For details of the possible selections for @var{c}, -see @ref{Character Set Control}. +Output usage (help) information. The output is written to @code{stdout}. -@item -gnatI -@cindex @option{-gnatI} (@command{gcc}) -Ignore representation clauses. When this switch is used, -representation clauses are treated as comments. This is useful -when initially porting code where you want to ignore rep clause -problems, and also for compiling foreign code (particularly -for use with ASIS). The representation clauses that are ignored -are: enumeration_representation_clause, record_representation_clause, -and attribute_definition_clause for the following attributes: -Address, Alignment, Bit_Order, Component_Size, Machine_Radix, -Object_Size, Size, Small, Stream_Size, and Value_Size. -Note that this option should be used only for compiling -- the -code is likely to malfunction at run time. +@geindex -P (gnatname) -Note that when @code{-gnatct} is used to generate trees for input -into @code{ASIS} tools, these representation clauses are removed -from the tree and ignored. This means that the tool will not see them. +@item @code{-P@emph{proj}} -@item -gnatjnn -@cindex @option{-gnatjnn} (@command{gcc}) -Reformat error messages to fit on nn character lines +Create or update project file @code{proj}. There may be zero, one or more space +between @emph{-P} and @code{proj}. @code{proj} may include directory +information. @code{proj} must be writable. +There may be only one switch @emph{-P}. +When a switch @emph{-P} is specified, +no switch @emph{-c} may be specified. +On all platforms, except on VMS, when @cite{gnatname} is invoked for an +existing project file .gpr, a backup copy of the project file is created +in the project directory with file name .gpr.saved_x. 'x' is the first +non negative number that makes this backup copy a new file. -@item -gnatk=@var{n} -@cindex @option{-gnatk} (@command{gcc}) -Limit file names to @var{n} (1-999) characters (@code{k} = krunch). +@geindex -v (gnatname) -@item -gnatl -@cindex @option{-gnatl} (@command{gcc}) -Output full source listing with embedded error messages. +@item @code{-v} -@item -gnatL -@cindex @option{-gnatL} (@command{gcc}) -Used in conjunction with -gnatG or -gnatD to intersperse original -source lines (as comment lines with line numbers) in the expanded -source output. +Verbose mode. Output detailed explanation of behavior to @code{stdout}. +This includes name of the file written, the name of the directories to search +and, for each file in those directories whose name matches at least one of +the Naming Patterns, an indication of whether the file contains a unit, +and if so the name of the unit. +@end table -@item -gnatm=@var{n} -@cindex @option{-gnatm} (@command{gcc}) -Limit number of detected error or warning messages to @var{n} -where @var{n} is in the range 1..999999. The default setting if -no switch is given is 9999. If the number of warnings reaches this -limit, then a message is output and further warnings are suppressed, -but the compilation is continued. If the number of error messages -reaches this limit, then a message is output and the compilation -is abandoned. The equal sign here is optional. A value of zero -means that no limit applies. +@geindex -v -v (gnatname) -@item -gnatn[12] -@cindex @option{-gnatn} (@command{gcc}) -Activate inlining for subprograms for which pragma @code{Inline} is -specified. This inlining is performed by the GCC back-end. An optional -digit sets the inlining level: 1 for moderate inlining across modules -or 2 for full inlining across modules. If no inlining level is specified, -the compiler will pick it based on the optimization level. -@item -gnatN -@cindex @option{-gnatN} (@command{gcc}) -Activate front end inlining for subprograms for which -pragma @code{Inline} is specified. This inlining is performed -by the front end and will be visible in the -@option{-gnatG} output. +@table @asis -When using a gcc-based back end (in practice this means using any version -of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of -@option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred. -Historically front end inlining was more extensive than the gcc back end -inlining, but that is no longer the case. +@item @code{-v -v} -@item -gnato0 -@cindex @option{-gnato0} (@command{gcc}) -Suppresses overflow checking. This causes the behavior of the compiler to -match the default for older versions where overflow checking was suppressed -by default. This is equivalent to having -@code{pragma Suppress (Overflow_Mode)} in a configuration pragma file. +Very Verbose mode. In addition to the output produced in verbose mode, +for each file in the searched directories whose name matches none of +the Naming Patterns, an indication is given that there is no match. -@item -gnato?? -@cindex @option{-gnato??} (@command{gcc}) -Set default mode for handling generation of code to avoid intermediate -arithmetic overflow. Here `@code{??}' is two digits, a -single digit, or nothing. Each digit is one of the digits `@code{1}' -through `@code{3}': - -@itemize @bullet -@item @code{1}: -all intermediate overflows checked against base type (@code{STRICT}) -@item @code{2}: -minimize intermediate overflows (@code{MINIMIZED}) -@item @code{3}: -eliminate intermediate overflows (@code{ELIMINATED}) -@end itemize +@geindex -x (gnatname) -If only one digit appears then it applies to all -cases; if two digits are given, then the first applies outside -assertions, and the second within assertions. +@item @code{-x@emph{pattern}} -If no digits follow the @option{-gnato}, then it is equivalent to -@option{-gnato11}, -causing all intermediate overflows to be handled in strict mode. +Excluded patterns. Using this switch, it is possible to exclude some files +that would match the name patterns. For example, -This switch also causes arithmetic overflow checking to be performed -(as though @code{pragma Unsuppress (Overflow_Mode)} had been specified. +@example +gnatname -x "*_nt.ada" "*.ada" +@end example -The default if no option @option{-gnato} is given is that overflow handling -is in @code{STRICT} mode (computations done using the base type), and that -overflow checking is enabled. +will look for Ada units in all files with the @code{.ada} extension, +except those whose names end with @code{_nt.ada}. +@end table -Note that division by zero is a separate check that is not -controlled by this switch (division by zero checking is on by default). +@node Examples of gnatname Usage,,Switches for gnatname,Handling Arbitrary File Naming Conventions with gnatname +@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage}@anchor{63}@anchor{gnat_ugn/the_gnat_compilation_model id16}@anchor{64} +@subsubsection Examples of @cite{gnatname} Usage -See also @ref{Specifying the Desired Mode}. -@item -gnatp -@cindex @option{-gnatp} (@command{gcc}) -Suppress all checks. See @ref{Run-Time Checks} for details. This switch -has no effect if cancelled by a subsequent @option{-gnat-p} switch. +@example +$ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*" +@end example -@item -gnat-p -@cindex @option{-gnat-p} (@command{gcc}) -Cancel effect of previous @option{-gnatp} switch. +In this example, the directory @code{/home/me} must already exist +and be writable. In addition, the directory +@code{/home/me/sources} (specified by +@emph{-d sources}) must exist and be readable. -@item -gnatP -@cindex @option{-gnatP} (@command{gcc}) -Enable polling. This is required on some systems (notably Windows NT) to -obtain asynchronous abort and asynchronous transfer of control capability. -@xref{Pragma Polling,,, gnat_rm, GNAT Reference Manual}, for full -details. +Note the optional spaces after @emph{-c} and @emph{-d}. -@item -gnatq -@cindex @option{-gnatq} (@command{gcc}) -Don't quit. Try semantics, even if parse errors. +@example +$ gnatname -P/home/me/proj -x "*_nt_body.ada" +-dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*" +@end example -@item -gnatQ -@cindex @option{-gnatQ} (@command{gcc}) -Don't quit. Generate @file{ALI} and tree files even if illegalities. -Note that code generation is still suppressed in the presence of any -errors, so even with @option{-gnatQ} no object file is generated. +Note that several switches @emph{-d} may be used, +even in conjunction with one or several switches +@emph{-D}. Several Naming Patterns and one excluded pattern +are used in this example. -@item -gnatr -@cindex @option{-gnatr} (@command{gcc}) -Treat pragma Restrictions as Restriction_Warnings. +@node File Name Krunching with gnatkr,Renaming Files with gnatchop,Handling Arbitrary File Naming Conventions with gnatname,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model file-name-krunching-with-gnatkr}@anchor{65}@anchor{gnat_ugn/the_gnat_compilation_model id17}@anchor{66} +@subsection File Name Krunching with @cite{gnatkr} -@item -gnatR@r{[}0@r{/}1@r{/}2@r{/}3@r{[}s@r{]]} -@cindex @option{-gnatR} (@command{gcc}) -Output representation information for declared types and objects. -Note that this switch is not allowed if a previous @code{-gnatD} switch has -been given, since these two switches are not compatible. -@item -gnatRm[s] -Output convention and parameter passing mechanisms for all subprograms. +@geindex gnatkr -@item -gnats -@cindex @option{-gnats} (@command{gcc}) -Syntax check only. +This chapter discusses the method used by the compiler to shorten +the default file names chosen for Ada units so that they do not +exceed the maximum length permitted. It also describes the +@cite{gnatkr} utility that can be used to determine the result of +applying this shortening. -@item -gnatS -@cindex @option{-gnatS} (@command{gcc}) -Print package Standard. +@menu +* About gnatkr:: +* Using gnatkr:: +* Krunching Method:: +* Examples of gnatkr Usage:: -@item -gnatt -@cindex @option{-gnatt} (@command{gcc}) -Generate tree output file. +@end menu -@item -gnatT@var{nnn} -@cindex @option{-gnatT} (@command{gcc}) -All compiler tables start at @var{nnn} times usual starting size. +@node About gnatkr,Using gnatkr,,File Name Krunching with gnatkr +@anchor{gnat_ugn/the_gnat_compilation_model id18}@anchor{67}@anchor{gnat_ugn/the_gnat_compilation_model about-gnatkr}@anchor{68} +@subsubsection About @cite{gnatkr} -@item -gnatu -@cindex @option{-gnatu} (@command{gcc}) -List units for this compilation. -@item -gnatU -@cindex @option{-gnatU} (@command{gcc}) -Tag all error messages with the unique string ``error:'' +The default file naming rule in GNAT +is that the file name must be derived from +the unit name. The exact default rule is as follows: -@item -gnatv -@cindex @option{-gnatv} (@command{gcc}) -Verbose mode. Full error output with source lines to @file{stdout}. -@item -gnatV -@cindex @option{-gnatV} (@command{gcc}) -Control level of validity checking (@pxref{Validity Checking}). +@itemize * -@item -gnatw@var{xxx} -@cindex @option{-gnatw} (@command{gcc}) -Warning mode where -@var{xxx} is a string of option letters that denotes -the exact warnings that -are enabled or disabled (@pxref{Warning Message Control}). +@item +Take the unit name and replace all dots by hyphens. -@item -gnatW@var{e} -@cindex @option{-gnatW} (@command{gcc}) -Wide character encoding method -(@var{e}=n/h/u/s/e/8). +@item +If such a replacement occurs in the +second character position of a name, and the first character is +@code{a}, @code{g}, @code{s}, or @code{i}, +then replace the dot by the character +@code{~} (tilde) +instead of a minus. -@item -gnatx -@cindex @option{-gnatx} (@command{gcc}) -Suppress generation of cross-reference information. +The reason for this exception is to avoid clashes +with the standard names for children of System, Ada, Interfaces, +and GNAT, which use the prefixes +@code{s-}, @code{a-}, @code{i-}, and @code{g-}, +respectively. +@end itemize -@item -gnatX -@cindex @option{-gnatX} (@command{gcc}) -Enable GNAT implementation extensions and latest Ada version. +The @code{-gnatk@emph{nn}} +switch of the compiler activates a 'krunching' +circuit that limits file names to nn characters (where nn is a decimal +integer). -@item -gnaty -@cindex @option{-gnaty} (@command{gcc}) -Enable built-in style checks (@pxref{Style Checking}). +The @cite{gnatkr} utility can be used to determine the krunched name for +a given file, when krunched to a specified maximum length. -@item -gnatz@var{m} -@cindex @option{-gnatz} (@command{gcc}) -Distribution stub generation and compilation -(@var{m}=r/c for receiver/caller stubs). +@node Using gnatkr,Krunching Method,About gnatkr,File Name Krunching with gnatkr +@anchor{gnat_ugn/the_gnat_compilation_model id19}@anchor{69}@anchor{gnat_ugn/the_gnat_compilation_model using-gnatkr}@anchor{56} +@subsubsection Using @cite{gnatkr} -@item -I@var{dir} -@cindex @option{-I} (@command{gcc}) -@cindex RTL -Direct GNAT to search the @var{dir} directory for source files needed by -the current compilation -(@pxref{Search Paths and the Run-Time Library (RTL)}). -@item -I- -@cindex @option{-I-} (@command{gcc}) -@cindex RTL -Except for the source file named in the command line, do not look for source -files in the directory containing the source file named in the command line -(@pxref{Search Paths and the Run-Time Library (RTL)}). - -@item -mbig-switch -@cindex @option{-mbig-switch} (@command{gcc}) -@cindex @code{case} statement (effect of @option{-mbig-switch} option) -This standard gcc switch causes the compiler to use larger offsets in its -jump table representation for @code{case} statements. -This may result in less efficient code, but is sometimes necessary -(for example on HP-UX targets) -@cindex HP-UX and @option{-mbig-switch} option -in order to compile large and/or nested @code{case} statements. - -@item -o @var{file} -@cindex @option{-o} (@command{gcc}) -This switch is used in @command{gcc} to redirect the generated object file -and its associated ALI file. Beware of this switch with GNAT, because it may -cause the object file and ALI file to have different names which in turn -may confuse the binder and the linker. +The @cite{gnatkr} command has the form: -@item -nostdinc -@cindex @option{-nostdinc} (@command{gcc}) -Inhibit the search of the default location for the GNAT Run Time -Library (RTL) source files. +@example +$ gnatkr `name` [`length`] +@end example -@item -nostdlib -@cindex @option{-nostdlib} (@command{gcc}) -Inhibit the search of the default location for the GNAT Run Time -Library (RTL) ALI files. +@cite{name} is the uncrunched file name, derived from the name of the unit +in the standard manner described in the previous section (i.e., in particular +all dots are replaced by hyphens). The file name may or may not have an +extension (defined as a suffix of the form period followed by arbitrary +characters other than period). If an extension is present then it will +be preserved in the output. For example, when krunching @code{hellofile.ads} +to eight characters, the result will be hellofil.ads. -@c @item -O@ovar{n} -@c Expanding @ovar macro inline (explanation in macro def comments) -@item -O@r{[}@var{n}@r{]} -@cindex @option{-O} (@command{gcc}) -@var{n} controls the optimization level. +Note: for compatibility with previous versions of @cite{gnatkr} dots may +appear in the name instead of hyphens, but the last dot will always be +taken as the start of an extension. So if @cite{gnatkr} is given an argument +such as @code{Hello.World.adb} it will be treated exactly as if the first +period had been a hyphen, and for example krunching to eight characters +gives the result @code{hellworl.adb}. -@table @asis -@item n = 0 -No optimization, the default setting if no @option{-O} appears +Note that the result is always all lower case. +Characters of the other case are folded as required. -@item n = 1 -Normal optimization, the default if you specify @option{-O} without -an operand. A good compromise between code quality and compilation -time. +@cite{length} represents the length of the krunched name. The default +when no argument is given is 8 characters. A length of zero stands for +unlimited, in other words do not chop except for system files where the +implied crunching length is always eight characters. -@item n = 2 -Extensive optimization, may improve execution time, possibly at the cost of -substantially increased compilation time. +The output is the krunched name. The output has an extension only if the +original argument was a file name with an extension. -@item n = 3 -Same as @option{-O2}, and also includes inline expansion for small subprograms -in the same unit. +@node Krunching Method,Examples of gnatkr Usage,Using gnatkr,File Name Krunching with gnatkr +@anchor{gnat_ugn/the_gnat_compilation_model id20}@anchor{6a}@anchor{gnat_ugn/the_gnat_compilation_model krunching-method}@anchor{6b} +@subsubsection Krunching Method -@item n = s -Optimize space usage -@end table -@noindent -See also @ref{Optimization Levels}. +The initial file name is determined by the name of the unit that the file +contains. The name is formed by taking the full expanded name of the +unit and replacing the separating dots with hyphens and +using lowercase +for all letters, except that a hyphen in the second character position is +replaced by a tilde if the first character is +@code{a}, @code{i}, @code{g}, or @code{s}. +The extension is @cite{.ads} for a +spec and @cite{.adb} for a body. +Krunching does not affect the extension, but the file name is shortened to +the specified length by following these rules: -@item -pass-exit-codes -@cindex @option{-pass-exit-codes} (@command{gcc}) -Catch exit codes from the compiler and use the most meaningful as -exit status. +@itemize * -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gcc}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). +@item +The name is divided into segments separated by hyphens, tildes or +underscores and all hyphens, tildes, and underscores are +eliminated. If this leaves the name short enough, we are done. -@item -S -@cindex @option{-S} (@command{gcc}) -Used in place of @option{-c} to -cause the assembler source file to be -generated, using @file{.s} as the extension, -instead of the object file. -This may be useful if you need to examine the generated assembly code. +@item +If the name is too long, the longest segment is located (left-most +if there are two of equal length), and shortened by dropping +its last character. This is repeated until the name is short enough. -@item -fverbose-asm -@cindex @option{-fverbose-asm} (@command{gcc}) -Used in conjunction with @option{-S} -to cause the generated assembly code file to be annotated with variable -names, making it significantly easier to follow. +As an example, consider the krunching of @code{our-strings-wide_fixed.adb} +to fit the name into 8 characters as required by some operating systems: -@item -v -@cindex @option{-v} (@command{gcc}) -Show commands generated by the @command{gcc} driver. Normally used only for -debugging purposes or if you need to be sure what version of the -compiler you are executing. +@example +our-strings-wide_fixed 22 +our strings wide fixed 19 +our string wide fixed 18 +our strin wide fixed 17 +our stri wide fixed 16 +our stri wide fixe 15 +our str wide fixe 14 +our str wid fixe 13 +our str wid fix 12 +ou str wid fix 11 +ou st wid fix 10 +ou st wi fix 9 +ou st wi fi 8 +Final file name: oustwifi.adb +@end example -@item -V @var{ver} -@cindex @option{-V} (@command{gcc}) -Execute @var{ver} version of the compiler. This is the @command{gcc} -version, not the GNAT version. +@item +The file names for all predefined units are always krunched to eight +characters. The krunching of these predefined units uses the following +special prefix replacements: -@item -w -@cindex @option{-w} (@command{gcc}) -Turn off warnings generated by the back end of the compiler. Use of -this switch also causes the default for front end warnings to be set -to suppress (as though @option{-gnatws} had appeared at the start of -the options). -@end table +@multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} +@item -@c Combining qualifiers does not work on VMS -You may combine a sequence of GNAT switches into a single switch. For -example, the combined switch +Prefix -@cindex Combining GNAT switches -@smallexample --gnatofi3 -@end smallexample +@tab -@noindent -is equivalent to specifying the following sequence of switches: +Replacement -@smallexample --gnato -gnatf -gnati3 -@end smallexample +@item -@noindent -The following restrictions apply to the combination of switches -in this manner: +@code{ada-} -@itemize @bullet -@item -The switch @option{-gnatc} if combined with other switches must come -first in the string. +@tab -@item -The switch @option{-gnats} if combined with other switches must come -first in the string. +@code{a-} @item -The switches -@option{-gnatzc} and @option{-gnatzr} may not be combined with any other -switches, and only one of them may appear in the command line. +@code{gnat-} -@item -The switch @option{-gnat-p} may not be combined with any other switch. +@tab -@item -Once a ``y'' appears in the string (that is a use of the @option{-gnaty} -switch), then all further characters in the switch are interpreted -as style modifiers (see description of @option{-gnaty}). +@code{g-} @item -Once a ``d'' appears in the string (that is a use of the @option{-gnatd} -switch), then all further characters in the switch are interpreted -as debug flags (see description of @option{-gnatd}). -@item -Once a ``w'' appears in the string (that is a use of the @option{-gnatw} -switch), then all further characters in the switch are interpreted -as warning mode modifiers (see description of @option{-gnatw}). +@code{interfac es-} -@item -Once a ``V'' appears in the string (that is a use of the @option{-gnatV} -switch), then all further characters in the switch are interpreted -as validity checking options (@pxref{Validity Checking}). +@tab -@item -Option ``em'', ``ec'', ``ep'', ``l='' and ``R'' must be the last options in -a combined list of options. -@end itemize +@code{i-} -@node Output and Error Message Control -@subsection Output and Error Message Control -@findex stderr +@item -@noindent -The standard default format for error messages is called ``brief format''. -Brief format messages are written to @file{stderr} (the standard error -file) and have the following form: +@code{system-} -@smallexample -e.adb:3:04: Incorrect spelling of keyword "function" -e.adb:4:20: ";" should be "is" -@end smallexample +@tab -@noindent -The first integer after the file name is the line number in the file, -and the second integer is the column number within the line. -@code{GPS} can parse the error messages -and point to the referenced character. -The following switches provide control over the error message -format: +@code{s-} -@table @option -@c !sort! -@item -gnatv -@cindex @option{-gnatv} (@command{gcc}) -@findex stdout -The v stands for verbose. -The effect of this setting is to write long-format error -messages to @file{stdout} (the standard output file. -The same program compiled with the -@option{-gnatv} switch would generate: +@end multitable -@smallexample -@cartouche -3. funcion X (Q : Integer) - | ->>> Incorrect spelling of keyword "function" -4. return Integer; - | ->>> ";" should be "is" -@end cartouche -@end smallexample -@noindent -The vertical bar indicates the location of the error, and the @samp{>>>} -prefix can be used to search for error messages. When this switch is -used the only source lines output are those with errors. +These system files have a hyphen in the second character position. That +is why normal user files replace such a character with a +tilde, to avoid confusion with system file names. -@item -gnatl -@cindex @option{-gnatl} (@command{gcc}) -The @code{l} stands for list. -This switch causes a full listing of -the file to be generated. In the case where a body is -compiled, the corresponding spec is also listed, along -with any subunits. Typical output from compiling a package -body @file{p.adb} might look like: +As an example of this special rule, consider +@code{ada-strings-wide_fixed.adb}, which gets krunched as follows: -@smallexample @c ada -@cartouche - Compiling: p.adb +@example +ada-strings-wide_fixed 22 +a- strings wide fixed 18 +a- string wide fixed 17 +a- strin wide fixed 16 +a- stri wide fixed 15 +a- stri wide fixe 14 +a- str wide fixe 13 +a- str wid fixe 12 +a- str wid fix 11 +a- st wid fix 10 +a- st wi fix 9 +a- st wi fi 8 +Final file name: a-stwifi.adb +@end example +@end itemize - 1. @b{package} @b{body} p @b{is} - 2. @b{procedure} a; - 3. @b{procedure} a @b{is} @b{separate}; - 4. @b{begin} - 5. @b{null} - | - >>> missing ";" +Of course no file shortening algorithm can guarantee uniqueness over all +possible unit names, and if file name krunching is used then it is your +responsibility to ensure that no name clashes occur. The utility +program @cite{gnatkr} is supplied for conveniently determining the +krunched name of a file. - 6. @b{end}; +@node Examples of gnatkr Usage,,Krunching Method,File Name Krunching with gnatkr +@anchor{gnat_ugn/the_gnat_compilation_model id21}@anchor{6c}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage}@anchor{6d} +@subsubsection Examples of @cite{gnatkr} Usage -Compiling: p.ads - 1. @b{package} p @b{is} - 2. @b{pragma} Elaborate_Body - | - >>> missing ";" +@example +$ gnatkr very_long_unit_name.ads --> velounna.ads +$ gnatkr grandparent-parent-child.ads --> grparchi.ads +$ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads +$ gnatkr grandparent-parent-child --> grparchi +$ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads +$ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads +@end example - 3. @b{end} p; +@node Renaming Files with gnatchop,,File Name Krunching with gnatkr,File Naming Topics and Utilities +@anchor{gnat_ugn/the_gnat_compilation_model id22}@anchor{6e}@anchor{gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop}@anchor{38} +@subsection Renaming Files with @cite{gnatchop} -Compiling: p-a.adb - 1. @b{separate} p - | - >>> missing "(" +@geindex gnatchop - 2. @b{procedure} a @b{is} - 3. @b{begin} - 4. @b{null} - | - >>> missing ";" +This chapter discusses how to handle files with multiple units by using +the @cite{gnatchop} utility. This utility is also useful in renaming +files to meet the standard GNAT default file naming conventions. - 5. @b{end}; -@end cartouche -@end smallexample +@menu +* Handling Files with Multiple Units:: +* Operating gnatchop in Compilation Mode:: +* Command Line for gnatchop:: +* Switches for gnatchop:: +* Examples of gnatchop Usage:: -@noindent -@findex stderr -When you specify the @option{-gnatv} or @option{-gnatl} switches and -standard output is redirected, a brief summary is written to -@file{stderr} (standard error) giving the number of error messages and -warning messages generated. +@end menu -@item -gnatl=file -@cindex @option{-gnatl=fname} (@command{gcc}) -This has the same effect as @option{-gnatl} except that the output is -written to a file instead of to standard output. If the given name -@file{fname} does not start with a period, then it is the full name -of the file to be written. If @file{fname} is an extension, it is -appended to the name of the file being compiled. For example, if -file @file{xyz.adb} is compiled with @option{-gnatl=.lst}, -then the output is written to file xyz.adb.lst. +@node Handling Files with Multiple Units,Operating gnatchop in Compilation Mode,,Renaming Files with gnatchop +@anchor{gnat_ugn/the_gnat_compilation_model id23}@anchor{6f}@anchor{gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units}@anchor{70} +@subsubsection Handling Files with Multiple Units -@item -gnatU -@cindex @option{-gnatU} (@command{gcc}) -This switch forces all error messages to be preceded by the unique -string ``error:''. This means that error messages take a few more -characters in space, but allows easy searching for and identification -of error messages. -@item -gnatb -@cindex @option{-gnatb} (@command{gcc}) -The @code{b} stands for brief. -This switch causes GNAT to generate the -brief format error messages to @file{stderr} (the standard error -file) as well as the verbose -format message or full listing (which as usual is written to -@file{stdout} (the standard output file). +The basic compilation model of GNAT requires that a file submitted to the +compiler have only one unit and there be a strict correspondence +between the file name and the unit name. -@item -gnatm=@var{n} -@cindex @option{-gnatm} (@command{gcc}) -The @code{m} stands for maximum. -@var{n} is a decimal integer in the -range of 1 to 999999 and limits the number of error or warning -messages to be generated. For example, using -@option{-gnatm2} might yield +The @cite{gnatchop} utility allows both of these rules to be relaxed, +allowing GNAT to process files which contain multiple compilation units +and files with arbitrary file names. @cite{gnatchop} +reads the specified file and generates one or more output files, +containing one unit per file. The unit and the file name correspond, +as required by GNAT. -@smallexample -e.adb:3:04: Incorrect spelling of keyword "function" -e.adb:5:35: missing ".." -fatal error: maximum number of errors detected -compilation abandoned -@end smallexample +If you want to permanently restructure a set of 'foreign' files so that +they match the GNAT rules, and do the remaining development using the +GNAT structure, you can simply use @emph{gnatchop} once, generate the +new set of files and work with them from that point on. -@noindent -The default setting if -no switch is given is 9999. If the number of warnings reaches this -limit, then a message is output and further warnings are suppressed, -but the compilation is continued. If the number of error messages -reaches this limit, then a message is output and the compilation -is abandoned. A value of zero means that no limit applies. +Alternatively, if you want to keep your files in the 'foreign' format, +perhaps to maintain compatibility with some other Ada compilation +system, you can set up a procedure where you use @emph{gnatchop} each +time you compile, regarding the source files that it writes as temporary +files that you throw away. -@noindent -Note that the equal sign is optional, so the switches -@option{-gnatm2} and @option{-gnatm=2} are equivalent. +Note that if your file containing multiple units starts with a byte order +mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop +will each start with a copy of this BOM, meaning that they can be compiled +automatically in UTF-8 mode without needing to specify an explicit encoding. -@item -gnatf -@cindex @option{-gnatf} (@command{gcc}) -@cindex Error messages, suppressing -The @code{f} stands for full. -Normally, the compiler suppresses error messages that are likely to be -redundant. This switch causes all error -messages to be generated. In particular, in the case of -references to undefined variables. If a given variable is referenced -several times, the normal format of messages is -@smallexample -e.adb:7:07: "V" is undefined (more references follow) -@end smallexample +@node Operating gnatchop in Compilation Mode,Command Line for gnatchop,Handling Files with Multiple Units,Renaming Files with gnatchop +@anchor{gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode}@anchor{71}@anchor{gnat_ugn/the_gnat_compilation_model id24}@anchor{72} +@subsubsection Operating gnatchop in Compilation Mode -@noindent -where the parenthetical comment warns that there are additional -references to the variable @code{V}. Compiling the same program with the -@option{-gnatf} switch yields -@smallexample -e.adb:7:07: "V" is undefined -e.adb:8:07: "V" is undefined -e.adb:8:12: "V" is undefined -e.adb:8:16: "V" is undefined -e.adb:9:07: "V" is undefined -e.adb:9:12: "V" is undefined -@end smallexample +The basic function of @cite{gnatchop} is to take a file with multiple units +and split it into separate files. The boundary between files is reasonably +clear, except for the issue of comments and pragmas. In default mode, the +rule is that any pragmas between units belong to the previous unit, except +that configuration pragmas always belong to the following unit. Any comments +belong to the following unit. These rules +almost always result in the right choice of +the split point without needing to mark it explicitly and most users will +find this default to be what they want. In this default mode it is incorrect to +submit a file containing only configuration pragmas, or one that ends in +configuration pragmas, to @cite{gnatchop}. -@noindent -The @option{-gnatf} switch also generates additional information for -some error messages. Some examples are: +However, using a special option to activate 'compilation mode', +@cite{gnatchop} +can perform another function, which is to provide exactly the semantics +required by the RM for handling of configuration pragmas in a compilation. +In the absence of configuration pragmas (at the main file level), this +option has no effect, but it causes such configuration pragmas to be handled +in a quite different manner. -@itemize @bullet -@item -Details on possibly non-portable unchecked conversion -@item -List possible interpretations for ambiguous calls -@item -Additional details on incorrect parameters -@end itemize +First, in compilation mode, if @cite{gnatchop} is given a file that consists of +only configuration pragmas, then this file is appended to the +@code{gnat.adc} file in the current directory. This behavior provides +the required behavior described in the RM for the actions to be taken +on submitting such a file to the compiler, namely that these pragmas +should apply to all subsequent compilations in the same compilation +environment. Using GNAT, the current directory, possibly containing a +@code{gnat.adc} file is the representation +of a compilation environment. For more information on the +@code{gnat.adc} file, see @ref{58,,Handling of Configuration Pragmas}. -@item -gnatjnn -@cindex @option{-gnatjnn} (@command{gcc}) -In normal operation mode (or if @option{-gnatj0} is used), then error messages -with continuation lines are treated as though the continuation lines were -separate messages (and so a warning with two continuation lines counts as -three warnings, and is listed as three separate messages). +Second, in compilation mode, if @cite{gnatchop} +is given a file that starts with +configuration pragmas, and contains one or more units, then these +configuration pragmas are prepended to each of the chopped files. This +behavior provides the required behavior described in the RM for the +actions to be taken on compiling such a file, namely that the pragmas +apply to all units in the compilation, but not to subsequently compiled +units. -If the @option{-gnatjnn} switch is used with a positive value for nn, then -messages are output in a different manner. A message and all its continuation -lines are treated as a unit, and count as only one warning or message in the -statistics totals. Furthermore, the message is reformatted so that no line -is longer than nn characters. +Finally, if configuration pragmas appear between units, they are appended +to the previous unit. This results in the previous unit being illegal, +since the compiler does not accept configuration pragmas that follow +a unit. This provides the required RM behavior that forbids configuration +pragmas other than those preceding the first compilation unit of a +compilation. -@item -gnatq -@cindex @option{-gnatq} (@command{gcc}) -The @code{q} stands for quit (really ``don't quit''). -In normal operation mode, the compiler first parses the program and -determines if there are any syntax errors. If there are, appropriate -error messages are generated and compilation is immediately terminated. -This switch tells -GNAT to continue with semantic analysis even if syntax errors have been -found. This may enable the detection of more errors in a single run. On -the other hand, the semantic analyzer is more likely to encounter some -internal fatal error when given a syntactically invalid tree. +For most purposes, @cite{gnatchop} will be used in default mode. The +compilation mode described above is used only if you need exactly +accurate behavior with respect to compilations, and you have files +that contain multiple units and configuration pragmas. In this +circumstance the use of @cite{gnatchop} with the compilation mode +switch provides the required behavior, and is for example the mode +in which GNAT processes the ACVC tests. -@item -gnatQ -@cindex @option{-gnatQ} (@command{gcc}) -In normal operation mode, the @file{ALI} file is not generated if any -illegalities are detected in the program. The use of @option{-gnatQ} forces -generation of the @file{ALI} file. This file is marked as being in -error, so it cannot be used for binding purposes, but it does contain -reasonably complete cross-reference information, and thus may be useful -for use by tools (e.g., semantic browsing tools or integrated development -environments) that are driven from the @file{ALI} file. This switch -implies @option{-gnatq}, since the semantic phase must be run to get a -meaningful ALI file. +@node Command Line for gnatchop,Switches for gnatchop,Operating gnatchop in Compilation Mode,Renaming Files with gnatchop +@anchor{gnat_ugn/the_gnat_compilation_model id25}@anchor{73}@anchor{gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop}@anchor{74} +@subsubsection Command Line for @cite{gnatchop} -In addition, if @option{-gnatt} is also specified, then the tree file is -generated even if there are illegalities. It may be useful in this case -to also specify @option{-gnatq} to ensure that full semantic processing -occurs. The resulting tree file can be processed by ASIS, for the purpose -of providing partial information about illegal units, but if the error -causes the tree to be badly malformed, then ASIS may crash during the -analysis. -When @option{-gnatQ} is used and the generated @file{ALI} file is marked as -being in error, @command{gnatmake} will attempt to recompile the source when it -finds such an @file{ALI} file, including with switch @option{-gnatc}. +The @cite{gnatchop} command has the form: -Note that @option{-gnatQ} has no effect if @option{-gnats} is specified, -since ALI files are never generated if @option{-gnats} is set. +@example +$ gnatchop switches file_name [file_name ...] + [directory] +@end example -@end table +The only required argument is the file name of the file to be chopped. +There are no restrictions on the form of this file name. The file itself +contains one or more Ada units, in normal GNAT format, concatenated +together. As shown, more than one file may be presented to be chopped. -@node Warning Message Control -@subsection Warning Message Control -@cindex Warning messages -@noindent -In addition to error messages, which correspond to illegalities as defined -in the Ada Reference Manual, the compiler detects two kinds of warning -situations. +When run in default mode, @cite{gnatchop} generates one output file in +the current directory for each unit in each of the files. -First, the compiler considers some constructs suspicious and generates a -warning message to alert you to a possible error. Second, if the -compiler detects a situation that is sure to raise an exception at -run time, it generates a warning message. The following shows an example -of warning messages: -@smallexample -e.adb:4:24: warning: creation of object may raise Storage_Error -e.adb:10:17: warning: static value out of range -e.adb:10:17: warning: "Constraint_Error" will be raised at run time -@end smallexample +@cite{directory}, if specified, gives the name of the directory to which +the output files will be written. If it is not specified, all files are +written to the current directory. -@noindent -GNAT considers a large number of situations as appropriate -for the generation of warning messages. As always, warnings are not -definite indications of errors. For example, if you do an out-of-range -assignment with the deliberate intention of raising a -@code{Constraint_Error} exception, then the warning that may be -issued does not indicate an error. Some of the situations for which GNAT -issues warnings (at least some of the time) are given in the following -list. This list is not complete, and new warnings are often added to -subsequent versions of GNAT. The list is intended to give a general idea -of the kinds of warnings that are generated. +For example, given a +file called @code{hellofiles} containing -@itemize @bullet -@item -Possible infinitely recursive calls +@example +procedure Hello; -@item -Out-of-range values being assigned +with Ada.Text_IO; use Ada.Text_IO; +procedure Hello is +begin + Put_Line ("Hello"); +end Hello; +@end example -@item -Possible order of elaboration problems +the command -@item -Size not a multiple of alignment for a record type +@example +$ gnatchop hellofiles +@end example -@item -Assertions (pragma Assert) that are sure to fail +generates two files in the current directory, one called +@code{hello.ads} containing the single line that is the procedure spec, +and the other called @code{hello.adb} containing the remaining text. The +original file is not affected. The generated files can be compiled in +the normal manner. -@item -Unreachable code +When gnatchop is invoked on a file that is empty or that contains only empty +lines and/or comments, gnatchop will not fail, but will not produce any +new sources. -@item -Address clauses with possibly unaligned values, or where an attempt is -made to overlay a smaller variable with a larger one. +For example, given a +file called @code{toto.txt} containing -@item -Fixed-point type declarations with a null range +@example +-- Just a comment +@end example -@item -Direct_IO or Sequential_IO instantiated with a type that has access values +the command -@item -Variables that are never assigned a value +@example +$ gnatchop toto.txt +@end example -@item -Variables that are referenced before being initialized +will not produce any new file and will result in the following warnings: -@item -Task entries with no corresponding @code{accept} statement +@example +toto.txt:1:01: warning: empty file, contains no compilation units +no compilation units found +no source files written +@end example -@item -Duplicate accepts for the same task entry in a @code{select} +@node Switches for gnatchop,Examples of gnatchop Usage,Command Line for gnatchop,Renaming Files with gnatchop +@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatchop}@anchor{75}@anchor{gnat_ugn/the_gnat_compilation_model id26}@anchor{76} +@subsubsection Switches for @cite{gnatchop} -@item -Objects that take too much storage -@item -Unchecked conversion between types of differing sizes +@emph{gnatchop} recognizes the following switches: -@item -Missing @code{return} statement along some execution path in a function +@geindex --version (gnatchop) -@item -Incorrect (unrecognized) pragmas -@item -Incorrect external names +@table @asis -@item -Allocation from empty storage pool +@item @code{--version} -@item -Potentially blocking operation in protected type +Display Copyright and version, then exit disregarding all other options. +@end table -@item -Suspicious parenthesization of expressions +@geindex --help (gnatchop) -@item -Mismatching bounds in an aggregate -@item -Attempt to return local value by reference +@table @asis -@item -Premature instantiation of a generic body +@item @code{--help} -@item -Attempt to pack aliased components +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table -@item -Out of bounds array subscripts +@geindex -c (gnatchop) -@item -Wrong length on string assignment -@item -Violations of style rules if style checking is enabled +@table @asis -@item -Unused @code{with} clauses +@item @code{-c} -@item -@code{Bit_Order} usage that does not have any effect +Causes @cite{gnatchop} to operate in compilation mode, in which +configuration pragmas are handled according to strict RM rules. See +previous section for a full description of this mode. -@item -@code{Standard.Duration} used to resolve universal fixed expression +@item @code{-gnat@emph{xxx}} -@item -Dereference of possibly null value +This passes the given @emph{-gnat`xxx*` switch to `gnat` which is +used to parse the given file. Not all `xxx` options make sense, +but for example, the use of *-gnati2} allows @cite{gnatchop} to +process a source file that uses Latin-2 coding for identifiers. -@item -Declaration that is likely to cause storage error +@item @code{-h} -@item -Internal GNAT unit @code{with}'ed by application unit +Causes @cite{gnatchop} to generate a brief help summary to the standard +output file showing usage information. +@end table -@item -Values known to be out of range at compile time +@geindex -k (gnatchop) -@item -Unreferenced or unmodified variables. Note that a special -exemption applies to variables which contain any of the substrings -@code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables -are considered likely to be intentionally used in a situation where -otherwise a warning would be given, so warnings of this kind are -always suppressed for such variables. -@item -Address overlays that could clobber memory +@table @asis -@item -Unexpected initialization when address clause present +@item @code{-k@emph{mm}} -@item -Bad alignment for address clause +Limit generated file names to the specified number @cite{mm} +of characters. +This is useful if the +resulting set of files is required to be interoperable with systems +which limit the length of file names. +No space is allowed between the @emph{-k} and the numeric value. The numeric +value may be omitted in which case a default of @emph{-k8}, +suitable for use +with DOS-like file systems, is used. If no @emph{-k} switch +is present then +there is no limit on the length of file names. +@end table -@item -Useless type conversions +@geindex -p (gnatchop) -@item -Redundant assignment statements and other redundant constructs -@item -Useless exception handlers +@table @asis -@item -Accidental hiding of name by child unit +@item @code{-p} -@item -Access before elaboration detected at compile time +Causes the file modification time stamp of the input file to be +preserved and used for the time stamp of the output file(s). This may be +useful for preserving coherency of time stamps in an environment where +@cite{gnatchop} is used as part of a standard build process. +@end table -@item -A range in a @code{for} loop that is known to be null or might be null +@geindex -q (gnatchop) -@end itemize -@noindent -The following section lists compiler switches that are available -to control the handling of warning messages. It is also possible -to exercise much finer control over what warnings are issued and -suppressed using the GNAT pragma Warnings, @xref{Pragma Warnings,,, -gnat_rm, GNAT Reference manual}. +@table @asis -@table @option -@c !sort! -@item -gnatwa -@emph{Activate most optional warnings.} -@cindex @option{-gnatwa} (@command{gcc}) -This switch activates most optional warning messages. See the remaining list -in this section for details on optional warning messages that can be -individually controlled. The warnings that are not turned on by this -switch are: +@item @code{-q} -@itemize -@item @option{-gnatwd} (implicit dereferencing) -@item @option{-gnatw.d} (tag warnings with -gnatw switch) -@item @option{-gnatwh} (hiding) -@item @option{-gnatw.h} (holes in record layouts) -@item @option{-gnatw.k} (redefinition of names in standard) -@item @option{-gnatwl} (elaboration warnings) -@item @option{-gnatw.l} (inherited aspects) -@item @option{-gnatw.n} (atomic synchronization) -@item @option{-gnatwo} (address clause overlay) -@item @option{-gnatw.o} (values set by out parameters ignored) -@item @option{-gnatw.s} (overridden size clause) -@item @option{-gnatwt} (tracking of deleted conditional code) -@item @option{-gnatw.u} (unordered enumeration) -@item @option{-gnatw.w} (use of Warnings Off) -@item @option{-gnatw.y} (reasons for package needing body) -@end itemize +Causes output of informational messages indicating the set of generated +files to be suppressed. Warnings and error messages are unaffected. +@end table -All other optional warnings are turned on. +@geindex -r (gnatchop) -@item -gnatwA -@emph{Suppress all optional errors.} -@cindex @option{-gnatwA} (@command{gcc}) -This switch suppresses all optional warning messages, see remaining list -in this section for details on optional warning messages that can be -individually controlled. Note that unlike switch @option{-gnatws}, the -use of switch @option{-gnatwA} does not suppress warnings that are -normally given unconditionally and cannot be individually controlled -(for example, the warning about a missing exit path in a function). -Also, again unlike switch @option{-gnatws}, warnings suppressed by -the use of switch @option{-gnatwA} can be individually turned back -on. For example the use of switch @option{-gnatwA} followed by -switch @option{-gnatwd} will suppress all optional warnings except -the warnings for implicit dereferencing. +@geindex Source_Reference pragmas -@item -gnatw.a -@emph{Activate warnings on failing assertions.} -@cindex @option{-gnatw.a} (@command{gcc}) -@cindex Assert failures -This switch activates warnings for assertions where the compiler can tell at -compile time that the assertion will fail. Note that this warning is given -even if assertions are disabled. The default is that such warnings are -generated. -@item -gnatw.A -@emph{Suppress warnings on failing assertions.} -@cindex @option{-gnatw.A} (@command{gcc}) -@cindex Assert failures -This switch suppresses warnings for assertions where the compiler can tell at -compile time that the assertion will fail. +@table @asis -@item -gnatwb -@emph{Activate warnings on bad fixed values.} -@cindex @option{-gnatwb} (@command{gcc}) -@cindex Bad fixed values -@cindex Fixed-point Small value -@cindex Small value -This switch activates warnings for static fixed-point expressions whose -value is not an exact multiple of Small. Such values are implementation -dependent, since an implementation is free to choose either of the multiples -that surround the value. GNAT always chooses the closer one, but this is not -required behavior, and it is better to specify a value that is an exact -multiple, ensuring predictable execution. The default is that such warnings -are not generated. +@item @code{-r} -@item -gnatwB -@emph{Suppress warnings on bad fixed values.} -@cindex @option{-gnatwB} (@command{gcc}) -This switch suppresses warnings for static fixed-point expressions whose -value is not an exact multiple of Small. +Generate @cite{Source_Reference} pragmas. Use this switch if the output +files are regarded as temporary and development is to be done in terms +of the original unchopped file. This switch causes +@cite{Source_Reference} pragmas to be inserted into each of the +generated files to refers back to the original file name and line number. +The result is that all error messages refer back to the original +unchopped file. +In addition, the debugging information placed into the object file (when +the @emph{-g} switch of @emph{gcc} or @emph{gnatmake} is +specified) +also refers back to this original file so that tools like profilers and +debuggers will give information in terms of the original unchopped file. -@item -gnatw.b -@emph{Activate warnings on biased representation.} -@cindex @option{-gnatw.b} (@command{gcc}) -@cindex Biased representation -This switch activates warnings when a size clause, value size clause, component -clause, or component size clause forces the use of biased representation for an -integer type (e.g. representing a range of 10..11 in a single bit by using 0/1 -to represent 10/11). The default is that such warnings are generated. +If the original file to be chopped itself contains +a @cite{Source_Reference} +pragma referencing a third file, then gnatchop respects +this pragma, and the generated @cite{Source_Reference} pragmas +in the chopped file refer to the original file, with appropriate +line numbers. This is particularly useful when @cite{gnatchop} +is used in conjunction with @cite{gnatprep} to compile files that +contain preprocessing statements and multiple units. +@end table -@item -gnatw.B -@emph{Suppress warnings on biased representation.} -@cindex @option{-gnatwB} (@command{gcc}) -This switch suppresses warnings for representation clauses that force the use -of biased representation. +@geindex -v (gnatchop) -@item -gnatwc -@emph{Activate warnings on conditionals.} -@cindex @option{-gnatwc} (@command{gcc}) -@cindex Conditionals, constant -This switch activates warnings for conditional expressions used in -tests that are known to be True or False at compile time. The default -is that such warnings are not generated. -Note that this warning does -not get issued for the use of boolean variables or constants whose -values are known at compile time, since this is a standard technique -for conditional compilation in Ada, and this would generate too many -false positive warnings. -This warning option also activates a special test for comparisons using -the operators ``>='' and`` <=''. -If the compiler can tell that only the equality condition is possible, -then it will warn that the ``>'' or ``<'' part of the test -is useless and that the operator could be replaced by ``=''. -An example would be comparing a @code{Natural} variable <= 0. +@table @asis -This warning option also generates warnings if -one or both tests is optimized away in a membership test for integer -values if the result can be determined at compile time. Range tests on -enumeration types are not included, since it is common for such tests -to include an end point. +@item @code{-v} -This warning can also be turned on using @option{-gnatwa}. +Causes @cite{gnatchop} to operate in verbose mode. The version +number and copyright notice are output, as well as exact copies of +the gnat1 commands spawned to obtain the chop control information. +@end table -@item -gnatwC -@emph{Suppress warnings on conditionals.} -@cindex @option{-gnatwC} (@command{gcc}) -This switch suppresses warnings for conditional expressions used in -tests that are known to be True or False at compile time. +@geindex -w (gnatchop) -@item -gnatw.c -@emph{Activate warnings on missing component clauses.} -@cindex @option{-gnatw.c} (@command{gcc}) -@cindex Component clause, missing -This switch activates warnings for record components where a record -representation clause is present and has component clauses for the -majority, but not all, of the components. A warning is given for each -component for which no component clause is present. -@item -gnatw.C -@emph{Suppress warnings on missing component clauses.} -@cindex @option{-gnatwC} (@command{gcc}) -This switch suppresses warnings for record components that are -missing a component clause in the situation described above. +@table @asis -@item -gnatwd -@emph{Activate warnings on implicit dereferencing.} -@cindex @option{-gnatwd} (@command{gcc}) -If this switch is set, then the use of a prefix of an access type -in an indexed component, slice, or selected component without an -explicit @code{.all} will generate a warning. With this warning -enabled, access checks occur only at points where an explicit -@code{.all} appears in the source code (assuming no warnings are -generated as a result of this switch). The default is that such -warnings are not generated. +@item @code{-w} -@item -gnatwD -@emph{Suppress warnings on implicit dereferencing.} -@cindex @option{-gnatwD} (@command{gcc}) -@cindex Implicit dereferencing -@cindex Dereferencing, implicit -This switch suppresses warnings for implicit dereferences in -indexed components, slices, and selected components. +Overwrite existing file names. Normally @cite{gnatchop} regards it as a +fatal error if there is already a file with the same name as a +file it would otherwise output, in other words if the files to be +chopped contain duplicated units. This switch bypasses this +check, and causes all but the last instance of such duplicated +units to be skipped. +@end table -@item -gnatw.d -@emph{Activate tagging of warning and info messages.} -@cindex @option{-gnatw.d} (@command{gcc}) -If this switch is set, then warning messages are tagged, with one of the -following strings: +@geindex --GCC= (gnatchop) -@table @option -@item [-gnatw?] -Used to tag warnings controlled by the switch @option{-gnatwx} where x -is a letter a-z. +@table @asis -@item [-gnatw.?] -Used to tag warnings controlled by the switch @option{-gnatw.x} where x -is a letter a-z. +@item @code{--GCC=@emph{xxxx}} -@item [-gnatel] -Used to tag elaboration information (info) messages generated when the -static model of elaboration is used and the @option{-gnatel} switch is set. +Specify the path of the GNAT parser to be used. When this switch is used, +no attempt is made to add the prefix to the GNAT parser executable. +@end table -@item [restriction warning] -Used to tag warning messages for restriction violations, activated by use -of the pragma @option{Restriction_Warnings}. +@node Examples of gnatchop Usage,,Switches for gnatchop,Renaming Files with gnatchop +@anchor{gnat_ugn/the_gnat_compilation_model id27}@anchor{77}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage}@anchor{78} +@subsubsection Examples of @cite{gnatchop} Usage -@item [warning-as-error] -Used to tag warning messages that have been converted to error messages by -use of the pragma Warning_As_Error. Note that such warnings are prefixed by -the string "error: " rather than "warning: ". -@item [enabled by default] -Used to tag all other warnings that are always given by default, unless -warnings are completely suppressed using pragma @option{Warnings(Off)} or -the switch @option{-gnatws}. +@example +$ gnatchop -w hello_s.ada prerelease/files +@end example -@end table +Chops the source file @code{hello_s.ada}. The output files will be +placed in the directory @code{prerelease/files}, +overwriting any +files with matching names in that directory (no files in the current +directory are modified). -@item -gnatw.D -@emph{Deactivate tagging of warning and info messages messages.} -@cindex @option{-gnatw.d} (@command{gcc}) -If this switch is set, then warning messages return to the default -mode in which warnings and info messages are not tagged as described above for -@code{-gnatw.d}. +@example +$ gnatchop archive +@end example -@item -gnatwe -@emph{Treat warnings and style checks as errors.} -@cindex @option{-gnatwe} (@command{gcc}) -@cindex Warnings, treat as error -This switch causes warning messages and style check messages to be -treated as errors. -The warning string still appears, but the warning messages are counted -as errors, and prevent the generation of an object file. Note that this -is the only -gnatw switch that affects the handling of style check messages. -Note also that this switch has no effect on info (information) messages, which -are not treated as errors if this switch is present. +Chops the source file @code{archive} +into the current directory. One +useful application of @cite{gnatchop} is in sending sets of sources +around, for example in email messages. The required sources are simply +concatenated (for example, using a Unix @cite{cat} +command), and then +@emph{gnatchop} is used at the other end to reconstitute the original +file names. -@item -gnatw.e -@emph{Activate every optional warning} -@cindex @option{-gnatw.e} (@command{gcc}) -@cindex Warnings, activate every optional warning -This switch activates all optional warnings, including those which -are not activated by @code{-gnatwa}. The use of this switch is not -recommended for normal use. If you turn this switch on, it is almost -certain that you will get large numbers of useless warnings. The -warnings that are excluded from @code{-gnatwa} are typically highly -specialized warnings that are suitable for use only in code that has -been specifically designed according to specialized coding rules. +@example +$ gnatchop file1 file2 file3 direc +@end example -@item -gnatwf -@emph{Activate warnings on unreferenced formals.} -@cindex @option{-gnatwf} (@command{gcc}) -@cindex Formals, unreferenced -This switch causes a warning to be generated if a formal parameter -is not referenced in the body of the subprogram. This warning can -also be turned on using @option{-gnatwu}. The -default is that these warnings are not generated. +Chops all units in files @code{file1}, @code{file2}, @code{file3}, placing +the resulting files in the directory @code{direc}. Note that if any units +occur more than once anywhere within this set of files, an error message +is generated, and no files are written. To override this check, use the +@emph{-w} switch, +in which case the last occurrence in the last file will +be the one that is output, and earlier duplicate occurrences for a given +unit will be skipped. -@item -gnatwF -@emph{Suppress warnings on unreferenced formals.} -@cindex @option{-gnatwF} (@command{gcc}) -This switch suppresses warnings for unreferenced formal -parameters. Note that the -combination @option{-gnatwu} followed by @option{-gnatwF} has the -effect of warning on unreferenced entities other than subprogram -formals. +@node Configuration Pragmas,Generating Object Files,File Naming Topics and Utilities,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id28}@anchor{79}@anchor{gnat_ugn/the_gnat_compilation_model configuration-pragmas}@anchor{16} +@section Configuration Pragmas -@item -gnatw.f -@emph{Activate warnings on suspicious subprogram 'Access.} -@cindex @option{-gnatw.f} (@command{gcc}) -This switch causes a warning to be generated if @code{P'Access} occurs -in the same package where subprogram P is declared, and the -@code{P'Access} is evaluated at elaboration time, and occurs before -the body of P has been elaborated. For example, if we have -@code{X : T := P'Access;}, then if X.all is subsequently called before -the body of P is elaborated, it could cause -access-before-elaboration. The default is that these warnings are not -generated. -@item -gnatw.F -@emph{Suppress warnings on suspicious subprogram 'Access.} -@cindex @option{-gnatw.F} (@command{gcc}) -This switch suppresses warnings for suspicious subprogram 'Access. +@geindex Configuration pragmas -@item -gnatwg -@emph{Activate warnings on unrecognized pragmas.} -@cindex @option{-gnatwg} (@command{gcc}) -@cindex Pragmas, unrecognized -This switch causes a warning to be generated if an unrecognized -pragma is encountered. Apart from issuing this warning, the -pragma is ignored and has no effect. The default -is that such warnings are issued (satisfying the Ada Reference -Manual requirement that such warnings appear). +@geindex Pragmas +@geindex configuration -@item -gnatwG -@emph{Suppress warnings on unrecognized pragmas.} -@cindex @option{-gnatwG} (@command{gcc}) -This switch suppresses warnings for unrecognized pragmas. +Configuration pragmas include those pragmas described as +such in the Ada Reference Manual, as well as +implementation-dependent pragmas that are configuration pragmas. +See the @cite{Implementation_Defined_Pragmas} chapter in the +@cite{GNAT_Reference_Manual} for details on these +additional GNAT-specific configuration pragmas. +Most notably, the pragma @cite{Source_File_Name}, which allows +specifying non-default names for source files, is a configuration +pragma. The following is a complete list of configuration pragmas +recognized by GNAT: -@item -gnatw.g -@emph{Warnings used for GNAT sources} -@cindex @option{-gnatw.g} (@command{gcc}) -This switch sets the warning categories that are used by the standard -GNAT style. Currently this is equivalent to -@option{-gnatwAao.sI.C.V.X} -but more warnings may be added in the future without advanced notice. +@example +Ada_83 +Ada_95 +Ada_05 +Ada_2005 +Ada_12 +Ada_2012 +Allow_Integer_Address +Annotate +Assertion_Policy +Assume_No_Invalid_Values +C_Pass_By_Copy +Check_Name +Check_Policy +Compile_Time_Error +Compile_Time_Warning +Compiler_Unit +Component_Alignment +Convention_Identifier +Debug_Policy +Detect_Blocking +Default_Storage_Pool +Discard_Names +Elaboration_Checks +Eliminate +Extend_System +Extensions_Allowed +External_Name_Casing +Fast_Math +Favor_Top_Level +Float_Representation +Implicit_Packing +Initialize_Scalars +Interrupt_State +License +Locking_Policy +Long_Float +No_Run_Time +No_Strict_Aliasing +Normalize_Scalars +Optimize_Alignment +Persistent_BSS +Polling +Priority_Specific_Dispatching +Profile +Profile_Warnings +Propagate_Exceptions +Queuing_Policy +Ravenscar +Restricted_Run_Time +Restrictions +Restrictions_Warnings +Reviewable +Short_Circuit_And_Or +Source_File_Name +Source_File_Name_Project +SPARK_Mode +Style_Checks +Suppress +Suppress_Exception_Locations +Task_Dispatching_Policy +Universal_Data +Unsuppress +Use_VADS_Size +Validity_Checks +Warnings +Wide_Character_Encoding +@end example -@item -gnatwh -@emph{Activate warnings on hiding.} -@cindex @option{-gnatwh} (@command{gcc}) -@cindex Hiding of Declarations -This switch activates warnings on hiding declarations. -A declaration is considered hiding -if it is for a non-overloadable entity, and it declares an entity with the -same name as some other entity that is directly or use-visible. The default -is that such warnings are not generated. +@menu +* Handling of Configuration Pragmas:: +* The Configuration Pragmas Files:: -@item -gnatwH -@emph{Suppress warnings on hiding.} -@cindex @option{-gnatwH} (@command{gcc}) -This switch suppresses warnings on hiding declarations. +@end menu -@item -gnatw.h -@emph{Activate warnings on holes/gaps in records.} -@cindex @option{-gnatw.h} (@command{gcc}) -@cindex Record Representation (gaps) -This switch activates warnings on component clauses in record -representation clauses that leave holes (gaps) in the record layout. -If this warning option is active, then record representation clauses -should specify a contiguous layout, adding unused fill fields if needed. +@node Handling of Configuration Pragmas,The Configuration Pragmas Files,,Configuration Pragmas +@anchor{gnat_ugn/the_gnat_compilation_model id29}@anchor{7a}@anchor{gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas}@anchor{58} +@subsection Handling of Configuration Pragmas -@item -gnatw.H -@emph{Suppress warnings on holes/gaps in records.} -@cindex @option{-gnatw.H} (@command{gcc}) -This switch suppresses warnings on component clauses in record -representation clauses that leave holes (haps) in the record layout. -@item -gnatwi -@emph{Activate warnings on implementation units.} -@cindex @option{-gnatwi} (@command{gcc}) -This switch activates warnings for a @code{with} of an internal GNAT -implementation unit, defined as any unit from the @code{Ada}, -@code{Interfaces}, @code{GNAT}, - or @code{System} -hierarchies that is not -documented in either the Ada Reference Manual or the GNAT -Programmer's Reference Manual. Such units are intended only -for internal implementation purposes and should not be @code{with}'ed -by user programs. The default is that such warnings are generated +Configuration pragmas may either appear at the start of a compilation +unit, or they can appear in a configuration pragma file to apply to +all compilations performed in a given compilation environment. -@item -gnatwI -@emph{Disable warnings on implementation units.} -@cindex @option{-gnatwI} (@command{gcc}) -This switch disables warnings for a @code{with} of an internal GNAT -implementation unit. +GNAT also provides the @cite{gnatchop} utility to provide an automatic +way to handle configuration pragmas following the semantics for +compilations (that is, files with multiple units), described in the RM. +See @ref{71,,Operating gnatchop in Compilation Mode} for details. +However, for most purposes, it will be more convenient to edit the +@code{gnat.adc} file that contains configuration pragmas directly, +as described in the following section. -@item -gnatw.i -@emph{Activate warnings on overlapping actuals.} -@cindex @option{-gnatw.i} (@command{gcc}) -This switch enables a warning on statically detectable overlapping actuals in -a subprogram call, when one of the actuals is an in-out parameter, and the -types of the actuals are not by-copy types. This warning is off by default. +In the case of @cite{Restrictions} pragmas appearing as configuration +pragmas in individual compilation units, the exact handling depends on +the type of restriction. -@item -gnatw.I -@emph{Disable warnings on overlapping actuals.} -@cindex @option{-gnatw.I} (@command{gcc}) -This switch disables warnings on overlapping actuals in a call.. +Restrictions that require partition-wide consistency (like +@cite{No_Tasking}) are +recognized wherever they appear +and can be freely inherited, e.g. from a @emph{with}ed unit to the @emph{with}ing +unit. This makes sense since the binder will in any case insist on seeing +consistent use, so any unit not conforming to any restrictions that are +anywhere in the partition will be rejected, and you might as well find +that out at compile time rather than at bind time. -@item -gnatwj -@emph{Activate warnings on obsolescent features (Annex J).} -@cindex @option{-gnatwj} (@command{gcc}) -@cindex Features, obsolescent -@cindex Obsolescent features -If this warning option is activated, then warnings are generated for -calls to subprograms marked with @code{pragma Obsolescent} and -for use of features in Annex J of the Ada Reference Manual. In the -case of Annex J, not all features are flagged. In particular use -of the renamed packages (like @code{Text_IO}) and use of package -@code{ASCII} are not flagged, since these are very common and -would generate many annoying positive warnings. The default is that -such warnings are not generated. +For restrictions that do not require partition-wide consistency, e.g. +SPARK or No_Implementation_Attributes, in general the restriction applies +only to the unit in which the pragma appears, and not to any other units. -In addition to the above cases, warnings are also generated for -GNAT features that have been provided in past versions but which -have been superseded (typically by features in the new Ada standard). -For example, @code{pragma Ravenscar} will be flagged since its -function is replaced by @code{pragma Profile(Ravenscar)}, and -@code{pragma Interface_Name} will be flagged since its function -is replaced by @code{pragma Import}. +The exception is No_Elaboration_Code which always applies to the entire +object file from a compilation, i.e. to the body, spec, and all subunits. +This restriction can be specified in a configuration pragma file, or it +can be on the body and/or the spec (in eithe case it applies to all the +relevant units). It can appear on a subunit only if it has previously +appeared in the body of spec. -Note that this warning option functions differently from the -restriction @code{No_Obsolescent_Features} in two respects. -First, the restriction applies only to annex J features. -Second, the restriction does flag uses of package @code{ASCII}. +@node The Configuration Pragmas Files,,Handling of Configuration Pragmas,Configuration Pragmas +@anchor{gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files}@anchor{7b}@anchor{gnat_ugn/the_gnat_compilation_model id30}@anchor{7c} +@subsection The Configuration Pragmas Files -@item -gnatwJ -@emph{Suppress warnings on obsolescent features (Annex J).} -@cindex @option{-gnatwJ} (@command{gcc}) -This switch disables warnings on use of obsolescent features. -@item -gnatwk -@emph{Activate warnings on variables that could be constants.} -@cindex @option{-gnatwk} (@command{gcc}) -This switch activates warnings for variables that are initialized but -never modified, and then could be declared constants. The default is that -such warnings are not given. +@geindex gnat.adc -@item -gnatwK -@emph{Suppress warnings on variables that could be constants.} -@cindex @option{-gnatwK} (@command{gcc}) -This switch disables warnings on variables that could be declared constants. +In GNAT a compilation environment is defined by the current +directory at the time that a compile command is given. This current +directory is searched for a file whose name is @code{gnat.adc}. If +this file is present, it is expected to contain one or more +configuration pragmas that will be applied to the current compilation. +However, if the switch @emph{-gnatA} is used, @code{gnat.adc} is not +considered. When taken into account, @code{gnat.adc} is added to the +dependencies, so that if @code{gnat.adc} is modified later, an invocation of +@emph{gnatmake} will recompile the source. -@item -gnatw.k -@emph{Activate warnings on redefinition of names in standard.} -@cindex @option{-gnatw.k} (@command{gcc}) -This switch activates warnings for declarations that declare a name that -is defined in package Standard. Such declarations can be confusing, -especially since the names in package Standard continue to be directly -visible, meaning that use visibiliy on such redeclared names does not -work as expected. Names of discriminants and components in records are -not included in this check. +Configuration pragmas may be entered into the @code{gnat.adc} file +either by running @cite{gnatchop} on a source file that consists only of +configuration pragmas, or more conveniently by direct editing of the +@code{gnat.adc} file, which is a standard format source file. -@item -gnatw.K -@emph{Suppress warnings on redefinition of names in standard.} -@cindex @option{-gnatwK} (@command{gcc}) -This switch activates warnings for declarations that declare a name that -is defined in package Standard. +Besides @code{gnat.adc}, additional files containing configuration +pragmas may be applied to the current compilation using the switch +@code{-gnatec=@emph{path}} where @cite{path} must designate an existing file that +contains only configuration pragmas. These configuration pragmas are +in addition to those found in @code{gnat.adc} (provided @code{gnat.adc} +is present and switch @emph{-gnatA} is not used). -@item -gnatwl -@emph{Activate warnings for elaboration pragmas.} -@cindex @option{-gnatwl} (@command{gcc}) -@cindex Elaboration, warnings -This switch activates warnings for possible elaboration problems, -including suspicious use -of @code{Elaborate} pragmas, when using the static elaboration model, and -possible situations that may raise @code{Program_Error} when using the -dynamic elaboration model. -See the section in this guide on elaboration checking for further details. -The default is that such warnings -are not generated. +It is allowable to specify several switches @emph{-gnatec=}, all of which +will be taken into account. -@item -gnatwL -@emph{Suppress warnings for elaboration pragmas.} -@cindex @option{-gnatwL} (@command{gcc}) -This switch suppresses warnings for possible elaboration problems. +Files containing configuration pragmas specified with switches +@emph{-gnatec=} are added to the dependencies, unless they are +temporary files. A file is considered temporary if its name ends in +@code{.tmp} or @code{.TMP}. Certain tools follow this naming +convention because they pass information to @emph{gcc} via +temporary files that are immediately deleted; it doesn't make sense to +depend on a file that no longer exists. Such tools include +@emph{gprbuild}, @emph{gnatmake}, and @emph{gnatcheck}. -@item -gnatw.l -@emph{List inherited aspects.} -@cindex @option{-gnatw.l} (@command{gcc}) -This switch causes the compiler to list inherited invariants, -preconditions, and postconditions from Type_Invariant'Class, Invariant'Class, -Pre'Class, and Post'Class aspects. Also list inherited subtype predicates. +If you are using project file, a separate mechanism is provided using +project attributes, see @ref{7d,,Specifying Configuration Pragmas} for more +details. -@item -gnatw.L -@emph{Suppress listing of inherited aspects.} -@cindex @option{-gnatw.L} (@command{gcc}) -This switch suppresses listing of inherited aspects. +@node Generating Object Files,Source Dependencies,Configuration Pragmas,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model generating-object-files}@anchor{42}@anchor{gnat_ugn/the_gnat_compilation_model id31}@anchor{7e} +@section Generating Object Files -@item -gnatwm -@emph{Activate warnings on modified but unreferenced variables.} -@cindex @option{-gnatwm} (@command{gcc}) -This switch activates warnings for variables that are assigned (using -an initialization value or with one or more assignment statements) but -whose value is never read. The warning is suppressed for volatile -variables and also for variables that are renamings of other variables -or for which an address clause is given. -The default is that these warnings are not given. -@item -gnatwM -@emph{Disable warnings on modified but unreferenced variables.} -@cindex @option{-gnatwM} (@command{gcc}) -This switch disables warnings for variables that are assigned or -initialized, but never read. +An Ada program consists of a set of source files, and the first step in +compiling the program is to generate the corresponding object files. +These are generated by compiling a subset of these source files. +The files you need to compile are the following: -@item -gnatw.m -@emph{Activate warnings on suspicious modulus values.} -@cindex @option{-gnatw.m} (@command{gcc}) -This switch activates warnings for modulus values that seem suspicious. -The cases caught are where the size is the same as the modulus (e.g. -a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64 -with no size clause. The guess in both cases is that 2**x was intended -rather than x. In addition expressions of the form 2*x for small x -generate a warning (the almost certainly accurate guess being that -2**x was intended). The default is that these warnings are given. -@item -gnatw.M -@emph{Disable warnings on suspicious modulus values.} -@cindex @option{-gnatw.M} (@command{gcc}) -This switch disables warnings for suspicious modulus values. +@itemize * -@item -gnatwn -@emph{Set normal warnings mode.} -@cindex @option{-gnatwn} (@command{gcc}) -This switch sets normal warning mode, in which enabled warnings are -issued and treated as warnings rather than errors. This is the default -mode. the switch @option{-gnatwn} can be used to cancel the effect of -an explicit @option{-gnatws} or -@option{-gnatwe}. It also cancels the effect of the -implicit @option{-gnatwe} that is activated by the -use of @option{-gnatg}. +@item +If a package spec has no body, compile the package spec to produce the +object file for the package. -@item -gnatw.n -@emph{Activate warnings on atomic synchronization.} -@cindex @option{-gnatw.n} (@command{gcc}) -@cindex Atomic Synchronization, warnings -This switch actives warnings when an access to an atomic variable -requires the generation of atomic synchronization code. These -warnings are off by default. -@item -gnatw.N -@emph{Suppress warnings on atomic synchronization.} -@cindex @option{-gnatw.n} (@command{gcc}) -@cindex Atomic Synchronization, warnings -This switch suppresses warnings when an access to an atomic variable -requires the generation of atomic synchronization code. +@item +If a package has both a spec and a body, compile the body to produce the +object file for the package. The source file for the package spec need +not be compiled in this case because there is only one object file, which +contains the code for both the spec and body of the package. -@item -gnatwo -@emph{Activate warnings on address clause overlays.} -@cindex @option{-gnatwo} (@command{gcc}) -@cindex Address Clauses, warnings -This switch activates warnings for possibly unintended initialization -effects of defining address clauses that cause one variable to overlap -another. The default is that such warnings are generated. +@item +For a subprogram, compile the subprogram body to produce the object file +for the subprogram. The spec, if one is present, is as usual in a +separate file, and need not be compiled. +@end itemize -@item -gnatwO -@emph{Suppress warnings on address clause overlays.} -@cindex @option{-gnatwO} (@command{gcc}) -This switch suppresses warnings on possibly unintended initialization -effects of defining address clauses that cause one variable to overlap -another. +@geindex Subunits -@item -gnatw.o -@emph{Activate warnings on modified but unreferenced out parameters.} -@cindex @option{-gnatw.o} (@command{gcc}) -This switch activates warnings for variables that are modified by using -them as actuals for a call to a procedure with an out mode formal, where -the resulting assigned value is never read. It is applicable in the case -where there is more than one out mode formal. If there is only one out -mode formal, the warning is issued by default (controlled by -gnatwu). -The warning is suppressed for volatile -variables and also for variables that are renamings of other variables -or for which an address clause is given. -The default is that these warnings are not given. -@item -gnatw.O -@emph{Disable warnings on modified but unreferenced out parameters.} -@cindex @option{-gnatw.O} (@command{gcc}) -This switch suppresses warnings for variables that are modified by using -them as actuals for a call to a procedure with an out mode formal, where -the resulting assigned value is never read. +@itemize * -@item -gnatwp -@emph{Activate warnings on ineffective pragma Inlines.} -@cindex @option{-gnatwp} (@command{gcc}) -@cindex Inlining, warnings -This switch activates warnings for failure of front end inlining -(activated by @option{-gnatN}) to inline a particular call. There are -many reasons for not being able to inline a call, including most -commonly that the call is too complex to inline. The default is -that such warnings are not given. -Warnings on ineffective inlining by the gcc back-end can be activated -separately, using the gcc switch -Winline. +@item +In the case of subunits, only compile the parent unit. A single object +file is generated for the entire subunit tree, which includes all the +subunits. -@item -gnatwP -@emph{Suppress warnings on ineffective pragma Inlines.} -@cindex @option{-gnatwP} (@command{gcc}) -This switch suppresses warnings on ineffective pragma Inlines. If the -inlining mechanism cannot inline a call, it will simply ignore the -request silently. +@item +Compile child units independently of their parent units +(though, of course, the spec of all the ancestor unit must be present in order +to compile a child unit). -@item -gnatw.p -@emph{Activate warnings on parameter ordering.} -@cindex @option{-gnatw.p} (@command{gcc}) -@cindex Parameter order, warnings -This switch activates warnings for cases of suspicious parameter -ordering when the list of arguments are all simple identifiers that -match the names of the formals, but are in a different order. The -warning is suppressed if any use of named parameter notation is used, -so this is the appropriate way to suppress a false positive (and -serves to emphasize that the "misordering" is deliberate). The -default is that such warnings are not given. +@geindex Generics -@item -gnatw.P -@emph{Suppress warnings on parameter ordering.} -@cindex @option{-gnatw.P} (@command{gcc}) -This switch suppresses warnings on cases of suspicious parameter -ordering. +@item +Compile generic units in the same manner as any other units. The object +files in this case are small dummy files that contain at most the +flag used for elaboration checking. This is because GNAT always handles generic +instantiation by means of macro expansion. However, it is still necessary to +compile generic units, for dependency checking and elaboration purposes. +@end itemize -@item -gnatwq -@emph{Activate warnings on questionable missing parentheses.} -@cindex @option{-gnatwq} (@command{gcc}) -@cindex Parentheses, warnings -This switch activates warnings for cases where parentheses are not used and -the result is potential ambiguity from a readers point of view. For example -(not a > b) when a and b are modular means ((not a) > b) and very likely the -programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and -quite likely ((-x) mod 5) was intended. In such situations it seems best to -follow the rule of always parenthesizing to make the association clear, and -this warning switch warns if such parentheses are not present. The default -is that these warnings are given. +The preceding rules describe the set of files that must be compiled to +generate the object files for a program. Each object file has the same +name as the corresponding source file, except that the extension is +@code{.o} as usual. -@item -gnatwQ -@emph{Suppress warnings on questionable missing parentheses.} -@cindex @option{-gnatwQ} (@command{gcc}) -This switch suppresses warnings for cases where the association is not -clear and the use of parentheses is preferred. +You may wish to compile other files for the purpose of checking their +syntactic and semantic correctness. For example, in the case where a +package has a separate spec and body, you would not normally compile the +spec. However, it is convenient in practice to compile the spec to make +sure it is error-free before compiling clients of this spec, because such +compilations will fail if there is an error in the spec. -@item -gnatwr -@emph{Activate warnings on redundant constructs.} -@cindex @option{-gnatwr} (@command{gcc}) -This switch activates warnings for redundant constructs. The following -is the current list of constructs regarded as redundant: +GNAT provides an option for compiling such files purely for the +purposes of checking correctness; such compilations are not required as +part of the process of building a program. To compile a file in this +checking mode, use the @emph{-gnatc} switch. -@itemize @bullet -@item -Assignment of an item to itself. -@item -Type conversion that converts an expression to its own type. -@item -Use of the attribute @code{Base} where @code{typ'Base} is the same -as @code{typ}. -@item -Use of pragma @code{Pack} when all components are placed by a record -representation clause. -@item -Exception handler containing only a reraise statement (raise with no -operand) which has no effect. -@item -Use of the operator abs on an operand that is known at compile time -to be non-negative -@item -Comparison of boolean expressions to an explicit True value. -@end itemize +@node Source Dependencies,The Ada Library Information Files,Generating Object Files,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id32}@anchor{7f}@anchor{gnat_ugn/the_gnat_compilation_model source-dependencies}@anchor{43} +@section Source Dependencies -The default is that warnings for redundant constructs are not given. -@item -gnatwR -@emph{Suppress warnings on redundant constructs.} -@cindex @option{-gnatwR} (@command{gcc}) -This switch suppresses warnings for redundant constructs. +A given object file clearly depends on the source file which is compiled +to produce it. Here we are using "depends" in the sense of a typical +@cite{make} utility; in other words, an object file depends on a source +file if changes to the source file require the object file to be +recompiled. +In addition to this basic dependency, a given object may depend on +additional source files as follows: -@item -gnatw.r -@emph{Activate warnings for object renaming function.} -@cindex @option{-gnatw.r} (@command{gcc}) -This switch activates warnings for an object renaming that renames a -function call, which is equivalent to a constant declaration (as -opposed to renaming the function itself). The default is that these -warnings are given. -@item -gnatw.R -@emph{Suppress warnings for object renaming function.} -@cindex @option{-gnatwT} (@command{gcc}) -This switch suppresses warnings for object renaming function. +@itemize * -@item -gnatws -@emph{Suppress all warnings.} -@cindex @option{-gnatws} (@command{gcc}) -This switch completely suppresses the -output of all warning messages from the GNAT front end, including -both warnings that can be controlled by switches described in this -section, and those that are normally given unconditionally. The -effect of this suppress action can only be cancelled by a subsequent -use of the switch @option{-gnatwn}. +@item +If a file being compiled @emph{with}s a unit @cite{X}, the object file +depends on the file containing the spec of unit @cite{X}. This includes +files that are @emph{with}ed implicitly either because they are parents +of @emph{with}ed child units or they are run-time units required by the +language constructs used in a particular unit. -Note that switch @option{-gnatws} does not suppress -warnings from the @command{gcc} back end. -To suppress these back end warnings as well, use the switch @option{-w} -in addition to @option{-gnatws}. Also this switch has no effect on the -handling of style check messages. +@item +If a file being compiled instantiates a library level generic unit, the +object file depends on both the spec and body files for this generic +unit. -@item -gnatw.s -@emph{Activate warnings on overridden size clauses.} -@cindex @option{-gnatw.s} (@command{gcc}) -@cindex Record Representation (component sizes) -This switch activates warnings on component clauses in record -representation clauses where the length given overrides that -specified by an explicit size clause for the component type. A -warning is similarly given in the array case if a specified -component size overrides an explicit size clause for the array -component type. +@item +If a file being compiled instantiates a generic unit defined within a +package, the object file depends on the body file for the package as +well as the spec file. +@end itemize -@item -gnatw.S -@emph{Suppress warnings on overridden size clauses.} -@cindex @option{-gnatw.S} (@command{gcc}) -This switch suppresses warnings on component clauses in record -representation clauses that override size clauses, and similar -warnings when an array component size overrides a size clause. +@geindex Inline -@item -gnatwt -@emph{Activate warnings for tracking of deleted conditional code.} -@cindex @option{-gnatwt} (@command{gcc}) -@cindex Deactivated code, warnings -@cindex Deleted code, warnings -This switch activates warnings for tracking of code in conditionals (IF and -CASE statements) that is detected to be dead code which cannot be executed, and -which is removed by the front end. This warning is off by default. This may be -useful for detecting deactivated code in certified applications. +@geindex -gnatn switch -@item -gnatwT -@emph{Suppress warnings for tracking of deleted conditional code.} -@cindex @option{-gnatwT} (@command{gcc}) -This switch suppresses warnings for tracking of deleted conditional code. -@item -gnatw.t -@emph{Activate warnings on suspicious contracts.} -@cindex @option{-gnatw.t} (@command{gcc}) -This switch activates warnings on suspicious postconditions (whether a -pragma @code{Postcondition} or a @code{Post} aspect in Ada 2012) -and suspicious contract cases (pragma @code{Contract_Cases}). A -function postcondition or contract case is suspicious when no postcondition -or contract case for this function mentions the result of the function. -A procedure postcondition or contract case is suspicious when it only -refers to the pre-state of the procedure, because in that case it should -rather be expressed as a precondition. The default is that such warnings -are not generated. +@itemize * -@item -gnatw.T -@emph{Suppress warnings on suspicious contracts.} -@cindex @option{-gnatw.T} (@command{gcc}) -This switch suppresses warnings on suspicious postconditions. +@item +If a file being compiled contains a call to a subprogram for which +pragma @cite{Inline} applies and inlining is activated with the +@emph{-gnatn} switch, the object file depends on the file containing the +body of this subprogram as well as on the file containing the spec. Note +that for inlining to actually occur as a result of the use of this switch, +it is necessary to compile in optimizing mode. -@item -gnatwu -@emph{Activate warnings on unused entities.} -@cindex @option{-gnatwu} (@command{gcc}) -This switch activates warnings to be generated for entities that -are declared but not referenced, and for units that are @code{with}'ed -and not -referenced. In the case of packages, a warning is also generated if -no entities in the package are referenced. This means that if a with'ed -package is referenced but the only references are in @code{use} -clauses or @code{renames} -declarations, a warning is still generated. A warning is also generated -for a generic package that is @code{with}'ed but never instantiated. -In the case where a package or subprogram body is compiled, and there -is a @code{with} on the corresponding spec -that is only referenced in the body, -a warning is also generated, noting that the -@code{with} can be moved to the body. The default is that -such warnings are not generated. -This switch also activates warnings on unreferenced formals -(it includes the effect of @option{-gnatwf}). +@geindex -gnatN switch -@item -gnatwU -@emph{Suppress warnings on unused entities.} -@cindex @option{-gnatwU} (@command{gcc}) -This switch suppresses warnings for unused entities and packages. -It also turns off warnings on unreferenced formals (and thus includes -the effect of @option{-gnatwF}). +The use of @emph{-gnatN} activates inlining optimization +that is performed by the front end of the compiler. This inlining does +not require that the code generation be optimized. Like @emph{-gnatn}, +the use of this switch generates additional dependencies. -@item -gnatw.u -@emph{Activate warnings on unordered enumeration types.} -@cindex @option{-gnatw.u} (@command{gcc}) -This switch causes enumeration types to be considered as conceptually -unordered, unless an explicit pragma @code{Ordered} is given for the type. -The effect is to generate warnings in clients that use explicit comparisons -or subranges, since these constructs both treat objects of the type as -ordered. (A @emph{client} is defined as a unit that is other than the unit in -which the type is declared, or its body or subunits.) Please refer to -the description of pragma @code{Ordered} in the -@cite{@value{EDITION} Reference Manual} for further details. -The default is that such warnings are not generated. +When using a gcc-based back end (in practice this means using any version +of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of +@emph{-gnatN} is deprecated, and the use of @emph{-gnatn} is preferred. +Historically front end inlining was more extensive than the gcc back end +inlining, but that is no longer the case. -@item -gnatw.U -@emph{Deactivate warnings on unordered enumeration types.} -@cindex @option{-gnatw.U} (@command{gcc}) -This switch causes all enumeration types to be considered as ordered, so -that no warnings are given for comparisons or subranges for any type. +@item +If an object file @code{O} depends on the proper body of a subunit through +inlining or instantiation, it depends on the parent unit of the subunit. +This means that any modification of the parent unit or one of its subunits +affects the compilation of @code{O}. -@item -gnatwv -@emph{Activate warnings on unassigned variables.} -@cindex @option{-gnatwv} (@command{gcc}) -@cindex Unassigned variable warnings -This switch activates warnings for access to variables which -may not be properly initialized. The default is that -such warnings are generated. +@item +The object file for a parent unit depends on all its subunit body files. -@item -gnatwV -@emph{Suppress warnings on unassigned variables.} -@cindex @option{-gnatwV} (@command{gcc}) -This switch suppresses warnings for access to variables which -may not be properly initialized. -For variables of a composite type, the warning can also be suppressed in -Ada 2005 by using a default initialization with a box. For example, if -Table is an array of records whose components are only partially uninitialized, -then the following code: +@item +The previous two rules meant that for purposes of computing dependencies and +recompilation, a body and all its subunits are treated as an indivisible whole. -@smallexample @c ada - Tab : Table := (@b{others} => <>); -@end smallexample +These rules are applied transitively: if unit @cite{A} @emph{with}s +unit @cite{B}, whose elaboration calls an inlined procedure in package +@cite{C}, the object file for unit @cite{A} will depend on the body of +@cite{C}, in file @code{c.adb}. -will suppress warnings on subsequent statements that access components -of variable Tab. +The set of dependent files described by these rules includes all the +files on which the unit is semantically dependent, as dictated by the +Ada language standard. However, it is a superset of what the +standard describes, because it includes generic, inline, and subunit +dependencies. -@item -gnatw.v -@emph{Activate info messages for non-default bit order.} -@cindex @option{-gnatw.v} (@command{gcc}) -@cindex bit order warnings -This switch activates messages (labeled "info", they are not warnings, -just informational messages) about the effects of non-default bit-order -on records to which a component clause is applied. The effect of specifying -non-default bit ordering is a bit subtle (and changed with Ada 2005), so -these messages, which are given by default, are useful in understanding the -exact consequences of using this feature. +An object file must be recreated by recompiling the corresponding source +file if any of the source files on which it depends are modified. For +example, if the @cite{make} utility is used to control compilation, +the rule for an Ada object file must mention all the source files on +which the object file depends, according to the above definition. +The determination of the necessary +recompilations is done automatically when one uses @emph{gnatmake}. +@end itemize -@item -gnatw.V -@emph{Suppress info messages for non-default bit order.} -@cindex @option{-gnatw.V} (@command{gcc}) -This switch suppresses information messages for the effects of specifying -non-default bit order on record components with component clauses. +@node The Ada Library Information Files,Binding an Ada Program,Source Dependencies,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id33}@anchor{80}@anchor{gnat_ugn/the_gnat_compilation_model the-ada-library-information-files}@anchor{44} +@section The Ada Library Information Files -@item -gnatww -@emph{Activate warnings on wrong low bound assumption.} -@cindex @option{-gnatww} (@command{gcc}) -@cindex String indexing warnings -This switch activates warnings for indexing an unconstrained string parameter -with a literal or S'Length. This is a case where the code is assuming that the -low bound is one, which is in general not true (for example when a slice is -passed). The default is that such warnings are generated. -@item -gnatwW -@emph{Suppress warnings on wrong low bound assumption.} -@cindex @option{-gnatwW} (@command{gcc}) -This switch suppresses warnings for indexing an unconstrained string parameter -with a literal or S'Length. Note that this warning can also be suppressed -in a particular case by adding an -assertion that the lower bound is 1, -as shown in the following example. +@geindex Ada Library Information files -@smallexample @c ada - @b{procedure} K (S : String) @b{is} - @b{pragma} Assert (S'First = 1); - @dots{} -@end smallexample +@geindex ALI files -@item -gnatw.w -@emph{Activate warnings on Warnings Off pragmas} -@cindex @option{-gnatw.w} (@command{gcc}) -@cindex Warnings Off control -This switch activates warnings for use of @code{pragma Warnings (Off, entity)} -where either the pragma is entirely useless (because it suppresses no -warnings), or it could be replaced by @code{pragma Unreferenced} or -@code{pragma Unmodified}. -Also activates warnings for the case of -Warnings (Off, String), where either there is no matching -Warnings (On, String), or the Warnings (Off) did not suppress any warning. -The default is that these warnings are not given. +Each compilation actually generates two output files. The first of these +is the normal object file that has a @code{.o} extension. The second is a +text file containing full dependency information. It has the same +name as the source file, but an @code{.ali} extension. +This file is known as the Ada Library Information (@code{ALI}) file. +The following information is contained in the @code{ALI} file. -@item -gnatw.W -@emph{Suppress warnings on unnecessary Warnings Off pragmas} -@cindex @option{-gnatw.W} (@command{gcc}) -This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}. -@item -gnatwx -@emph{Activate warnings on Export/Import pragmas.} -@cindex @option{-gnatwx} (@command{gcc}) -@cindex Export/Import pragma warnings -This switch activates warnings on Export/Import pragmas when -the compiler detects a possible conflict between the Ada and -foreign language calling sequences. For example, the use of -default parameters in a convention C procedure is dubious -because the C compiler cannot supply the proper default, so -a warning is issued. The default is that such warnings are -generated. +@itemize * -@item -gnatwX -@emph{Suppress warnings on Export/Import pragmas.} -@cindex @option{-gnatwX} (@command{gcc}) -This switch suppresses warnings on Export/Import pragmas. -The sense of this is that you are telling the compiler that -you know what you are doing in writing the pragma, and it -should not complain at you. +@item +Version information (indicates which version of GNAT was used to compile +the unit(s) in question) -@item -gnatw.x -@emph{Activate warnings for No_Exception_Propagation mode.} -@cindex @option{-gnatwm} (@command{gcc}) -This switch activates warnings for exception usage when pragma Restrictions -(No_Exception_Propagation) is in effect. Warnings are given for implicit or -explicit exception raises which are not covered by a local handler, and for -exception handlers which do not cover a local raise. The default is that these -warnings are not given. +@item +Main program information (including priority and time slice settings, +as well as the wide character encoding used during compilation). -@item -gnatw.X -@emph{Disable warnings for No_Exception_Propagation mode.} -This switch disables warnings for exception usage when pragma Restrictions -(No_Exception_Propagation) is in effect. +@item +List of arguments used in the @emph{gcc} command for the compilation -@item -gnatwy -@emph{Activate warnings for Ada compatibility issues.} -@cindex @option{-gnatwy} (@command{gcc}) -@cindex Ada compatibility issues warnings -For the most part, newer versions of Ada are upwards compatible -with older versions. For example, Ada 2005 programs will almost -always work when compiled as Ada 2012. -However there are some exceptions (for example the fact that -@code{some} is now a reserved word in Ada 2012). This -switch activates several warnings to help in identifying -and correcting such incompatibilities. The default is that -these warnings are generated. Note that at one point Ada 2005 -was called Ada 0Y, hence the choice of character. +@item +Attributes of the unit, including configuration pragmas used, an indication +of whether the compilation was successful, exception model used etc. -@item -gnatwY -@emph{Disable warnings for Ada compatibility issues.} -@cindex @option{-gnatwY} (@command{gcc}) -@cindex Ada compatibility issues warnings -This switch suppresses the warnings intended to help in identifying -incompatibilities between Ada language versions. +@item +A list of relevant restrictions applying to the unit (used for consistency) +checking. -@item -gnatw.y -@emph{Activate information messages for why package spec needs body} -@cindex @option{-gnatw.y} (@command{gcc}) -@cindex Package spec needing body -There are a number of cases in which a package spec needs a body. -For example, the use of pragma Elaborate_Body, or the declaration -of a procedure specification requiring a completion. This switch -causes information messages to be output showing why a package -specification requires a body. This can be useful in the case of -a large package specification which is unexpectedly requiring a -body. The default is that such information messages are not output. +@item +Categorization information (e.g., use of pragma @cite{Pure}). -@item -gnatw.Y -@emph{Disable information messages for why package spec needs body} -@cindex @option{-gnatw.Y} (@command{gcc}) -@cindex No information messages for why package spec needs body -This switch suppresses the output of information messages showing why -a package specification needs a body. +@item +Information on all @emph{with}ed units, including presence of +Elaborate` or @cite{Elaborate_All} pragmas. -@item -gnatwz -@emph{Activate warnings on unchecked conversions.} -@cindex @option{-gnatwz} (@command{gcc}) -@cindex Unchecked_Conversion warnings -This switch activates warnings for unchecked conversions -where the types are known at compile time to have different -sizes. The default -is that such warnings are generated. Warnings are also -generated for subprogram pointers with different conventions, -and, on VMS only, for data pointers with different conventions. +@item +Information from any @cite{Linker_Options} pragmas used in the unit -@item -gnatwZ -@emph{Suppress warnings on unchecked conversions.} -@cindex @option{-gnatwZ} (@command{gcc}) -This switch suppresses warnings for unchecked conversions -where the types are known at compile time to have different -sizes or conventions. +@item +Information on the use of @cite{Body_Version} or @cite{Version} +attributes in the unit. -@item -gnatw.z -@emph{Activate warnings for size not a multiple of alignment.} -@cindex @option{-gnatw.z} (@command{gcc}) -@cindex Size/Alignment warnings -This switch activates warnings for cases of record types with -specified @code{Size} and @code{Alignment} attributes where the -size is not a multiple of the alignment, resulting in an object -size that is greater than the specified size. The default -is that such warnings are generated. +@item +Dependency information. This is a list of files, together with +time stamp and checksum information. These are files on which +the unit depends in the sense that recompilation is required +if any of these units are modified. -@item -gnatw.Z -@emph{Suppress warnings for size not a multiple of alignment.} -@cindex @option{-gnatw.Z} (@command{gcc}) -@cindex Size/Alignment warnings -This switch suppresses warnings for cases of record types with -specified @code{Size} and @code{Alignment} attributes where the -size is not a multiple of the alignment, resulting in an object -size that is greater than the specified size. -The warning can also be -suppressed by giving an explicit @code{Object_Size} value. - -@item -Wunused -@cindex @option{-Wunused} -The warnings controlled by the @option{-gnatw} switch are generated by -the front end of the compiler. The @option{GCC} back end can provide -additional warnings and they are controlled by the @option{-W} switch. -For example, @option{-Wunused} activates back end -warnings for entities that are declared but not referenced. +@item +Cross-reference data. Contains information on all entities referenced +in the unit. Used by tools like @cite{gnatxref} and @cite{gnatfind} to +provide cross-reference information. +@end itemize -@item -Wuninitialized -@cindex @option{-Wuninitialized} -Similarly, @option{-Wuninitialized} activates -the back end warning for uninitialized variables. This switch must be -used in conjunction with an optimization level greater than zero. +For a full detailed description of the format of the @code{ALI} file, +see the source of the body of unit @cite{Lib.Writ}, contained in file +@code{lib-writ.adb} in the GNAT compiler sources. -@item -Wstack-usage=@var{len} -@cindex @option{-Wstack-usage} -Warn if the stack usage of a subprogram might be larger than @var{len} bytes. -See @ref{Static Stack Usage Analysis} for details. +@node Binding an Ada Program,GNAT and Libraries,The Ada Library Information Files,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id34}@anchor{81}@anchor{gnat_ugn/the_gnat_compilation_model binding-an-ada-program}@anchor{45} +@section Binding an Ada Program -@item -Wall -@cindex @option{-Wall} -This switch enables most warnings from the @option{GCC} back end. -The code generator detects a number of warning situations that are missed -by the @option{GNAT} front end, and this switch can be used to activate them. -The use of this switch also sets the default front end warning mode to -@option{-gnatwa}, that is, most front end warnings activated as well. -@item -w -@cindex @option{-w} -Conversely, this switch suppresses warnings from the @option{GCC} back end. -The use of this switch also sets the default front end warning mode to -@option{-gnatws}, that is, front end warnings suppressed as well. +When using languages such as C and C++, once the source files have been +compiled the only remaining step in building an executable program +is linking the object modules together. This means that it is possible to +link an inconsistent version of a program, in which two units have +included different versions of the same header. -@item -Werror -@cindex @option{-Werror} -This switch causes warnings from the @option{GCC} back end to be treated as -errors. The warning string still appears, but the warning messages are -counted as errors, and prevent the generation of an object file. +The rules of Ada do not permit such an inconsistent program to be built. +For example, if two clients have different versions of the same package, +it is illegal to build a program containing these two clients. +These rules are enforced by the GNAT binder, which also determines an +elaboration order consistent with the Ada rules. -@end table +The GNAT binder is run after all the object files for a program have +been created. It is given the name of the main program unit, and from +this it determines the set of units required by the program, by reading the +corresponding ALI files. It generates error messages if the program is +inconsistent or if no valid order of elaboration exists. -@noindent -A string of warning parameters can be used in the same parameter. For example: +If no errors are detected, the binder produces a main program, in Ada by +default, that contains calls to the elaboration procedures of those +compilation unit that require them, followed by +a call to the main program. This Ada program is compiled to generate the +object file for the main program. The name of +the Ada file is @code{b~xxx}.adb` (with the corresponding spec +@code{b~xxx}.ads`) where @cite{xxx} is the name of the +main program unit. -@smallexample --gnatwaGe -@end smallexample +Finally, the linker is used to build the resulting executable program, +using the object from the main program from the bind step as well as the +object files for the Ada units of the program. -@noindent -will turn on all optional warnings except for unrecognized pragma warnings, -and also specify that warnings should be treated as errors. +@node GNAT and Libraries,Conditional Compilation,Binding an Ada Program,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-libraries}@anchor{17}@anchor{gnat_ugn/the_gnat_compilation_model id35}@anchor{82} +@section GNAT and Libraries -When no switch @option{-gnatw} is used, this is equivalent to: - -@table @option -@c !sort! -@item -gnatw.a -@item -gnatwB -@item -gnatw.b -@item -gnatwC -@item -gnatw.C -@item -gnatwD -@item -gnatwF -@item -gnatwg -@item -gnatwH -@item -gnatwi -@item -gnatw.I -@item -gnatwJ -@item -gnatwK -@item -gnatwL -@item -gnatw.L -@item -gnatwM -@item -gnatw.m -@item -gnatwn -@item -gnatwo -@item -gnatw.O -@item -gnatwP -@item -gnatw.P -@item -gnatwq -@item -gnatwR -@item -gnatw.R -@item -gnatw.S -@item -gnatwT -@item -gnatw.T -@item -gnatwU -@item -gnatwv -@item -gnatww -@item -gnatw.W -@item -gnatwx -@item -gnatw.X -@item -gnatwy -@item -gnatwz - -@end table - -@node Debugging and Assertion Control -@subsection Debugging and Assertion Control -@table @option -@item -gnata -@cindex @option{-gnata} (@command{gcc}) -@findex Assert -@findex Debug -@cindex Assertions +@geindex Library building and using -@noindent -The pragmas @code{Assert} and @code{Debug} normally have no effect and -are ignored. This switch, where @samp{a} stands for assert, causes -@code{Assert} and @code{Debug} pragmas to be activated. +This chapter describes how to build and use libraries with GNAT, and also shows +how to recompile the GNAT run-time library. You should be familiar with the +Project Manager facility (@ref{b,,GNAT Project Manager}) before reading this +chapter. -The pragmas have the form: +@menu +* Introduction to Libraries in GNAT:: +* General Ada Libraries:: +* Stand-alone Ada Libraries:: +* Rebuilding the GNAT Run-Time Library:: -@smallexample -@cartouche - @b{pragma} Assert (@var{Boolean-expression} @r{[}, - @var{static-string-expression}@r{]}) - @b{pragma} Debug (@var{procedure call}) -@end cartouche -@end smallexample +@end menu -@noindent -The @code{Assert} pragma causes @var{Boolean-expression} to be tested. -If the result is @code{True}, the pragma has no effect (other than -possible side effects from evaluating the expression). If the result is -@code{False}, the exception @code{Assert_Failure} declared in the package -@code{System.Assertions} is -raised (passing @var{static-string-expression}, if present, as the -message associated with the exception). If no string expression is -given the default is a string giving the file name and line number -of the pragma. +@node Introduction to Libraries in GNAT,General Ada Libraries,,GNAT and Libraries +@anchor{gnat_ugn/the_gnat_compilation_model introduction-to-libraries-in-gnat}@anchor{83}@anchor{gnat_ugn/the_gnat_compilation_model id36}@anchor{84} +@subsection Introduction to Libraries in GNAT -The @code{Debug} pragma causes @var{procedure} to be called. Note that -@code{pragma Debug} may appear within a declaration sequence, allowing -debugging procedures to be called between declarations. -@end table +A library is, conceptually, a collection of objects which does not have its +own main thread of execution, but rather provides certain services to the +applications that use it. A library can be either statically linked with the +application, in which case its code is directly included in the application, +or, on platforms that support it, be dynamically linked, in which case +its code is shared by all applications making use of this library. -@node Validity Checking -@subsection Validity Checking -@findex Validity Checking +GNAT supports both types of libraries. +In the static case, the compiled code can be provided in different ways. The +simplest approach is to provide directly the set of objects resulting from +compilation of the library source files. Alternatively, you can group the +objects into an archive using whatever commands are provided by the operating +system. For the latter case, the objects are grouped into a shared library. -@noindent -The Ada Reference Manual defines the concept of invalid values (see -RM 13.9.1). The primary source of invalid values is uninitialized -variables. A scalar variable that is left uninitialized may contain -an invalid value; the concept of invalid does not apply to access or -composite types. +In the GNAT environment, a library has three types of components: -It is an error to read an invalid value, but the RM does not require -run-time checks to detect such errors, except for some minimal -checking to prevent erroneous execution (i.e. unpredictable -behavior). This corresponds to the @option{-gnatVd} switch below, -which is the default. For example, by default, if the expression of a -case statement is invalid, it will raise Constraint_Error rather than -causing a wild jump, and if an array index on the left-hand side of an -assignment is invalid, it will raise Constraint_Error rather than -overwriting an arbitrary memory location. -The @option{-gnatVa} may be used to enable additional validity checks, -which are not required by the RM. These checks are often very -expensive (which is why the RM does not require them). These checks -are useful in tracking down uninitialized variables, but they are -not usually recommended for production builds, and in particular -we do not recommend using these extra validity checking options in -combination with optimization, since this can confuse the optimizer. -If performance is a consideration, leading to the need to optimize, -then the validity checking options should not be used. +@itemize * -The other @option{-gnatV@var{x}} switches below allow finer-grained -control; you can enable whichever validity checks you desire. However, -for most debugging purposes, @option{-gnatVa} is sufficient, and the -default @option{-gnatVd} (i.e. standard Ada behavior) is usually -sufficient for non-debugging use. +@item +Source files, -The @option{-gnatB} switch tells the compiler to assume that all -values are valid (that is, within their declared subtype range) -except in the context of a use of the Valid attribute. This means -the compiler can generate more efficient code, since the range -of values is better known at compile time. However, an uninitialized -variable can cause wild jumps and memory corruption in this mode. +@item +@code{ALI} files (see @ref{44,,The Ada Library Information Files}), and -The @option{-gnatV@var{x}} switch allows control over the validity -checking mode as described below. -The @code{x} argument is a string of letters that -indicate validity checks that are performed or not performed in addition -to the default checks required by Ada as described above. +@item +Object files, an archive or a shared library. +@end itemize -@table @option -@c !sort! -@item -gnatVa -@emph{All validity checks.} -@cindex @option{-gnatVa} (@command{gcc}) -All validity checks are turned on. -That is, @option{-gnatVa} is -equivalent to @option{gnatVcdfimorst}. +A GNAT library may expose all its source files, which is useful for +documentation purposes. Alternatively, it may expose only the units needed by +an external user to make use of the library. That is to say, the specs +reflecting the library services along with all the units needed to compile +those specs, which can include generic bodies or any body implementing an +inlined routine. In the case of @emph{stand-alone libraries} those exposed +units are called @emph{interface units} (@ref{85,,Stand-alone Ada Libraries}). -@item -gnatVc -@emph{Validity checks for copies.} -@cindex @option{-gnatVc} (@command{gcc}) -The right hand side of assignments, and the initializing values of -object declarations are validity checked. +All compilation units comprising an application, including those in a library, +need to be elaborated in an order partially defined by Ada's semantics. GNAT +computes the elaboration order from the @code{ALI} files and this is why they +constitute a mandatory part of GNAT libraries. +@emph{Stand-alone libraries} are the exception to this rule because a specific +library elaboration routine is produced independently of the application(s) +using the library. -@item -gnatVd -@emph{Default (RM) validity checks.} -@cindex @option{-gnatVd} (@command{gcc}) -Some validity checks are done by default following normal Ada semantics -(RM 13.9.1 (9-11)). -A check is done in case statements that the expression is within the range -of the subtype. If it is not, Constraint_Error is raised. -For assignments to array components, a check is done that the expression used -as index is within the range. If it is not, Constraint_Error is raised. -Both these validity checks may be turned off using switch @option{-gnatVD}. -They are turned on by default. If @option{-gnatVD} is specified, a subsequent -switch @option{-gnatVd} will leave the checks turned on. -Switch @option{-gnatVD} should be used only if you are sure that all such -expressions have valid values. If you use this switch and invalid values -are present, then the program is erroneous, and wild jumps or memory -overwriting may occur. +@node General Ada Libraries,Stand-alone Ada Libraries,Introduction to Libraries in GNAT,GNAT and Libraries +@anchor{gnat_ugn/the_gnat_compilation_model general-ada-libraries}@anchor{86}@anchor{gnat_ugn/the_gnat_compilation_model id37}@anchor{87} +@subsection General Ada Libraries -@item -gnatVe -@emph{Validity checks for elementary components.} -@cindex @option{-gnatVe} (@command{gcc}) -In the absence of this switch, assignments to record or array components are -not validity checked, even if validity checks for assignments generally -(@option{-gnatVc}) are turned on. In Ada, assignment of composite values do not -require valid data, but assignment of individual components does. So for -example, there is a difference between copying the elements of an array with a -slice assignment, compared to assigning element by element in a loop. This -switch allows you to turn off validity checking for components, even when they -are assigned component by component. -@item -gnatVf -@emph{Validity checks for floating-point values.} -@cindex @option{-gnatVf} (@command{gcc}) -In the absence of this switch, validity checking occurs only for discrete -values. If @option{-gnatVf} is specified, then validity checking also applies -for floating-point values, and NaNs and infinities are considered invalid, -as well as out of range values for constrained types. Note that this means -that standard IEEE infinity mode is not allowed. The exact contexts -in which floating-point values are checked depends on the setting of other -options. For example, -@option{-gnatVif} or -@option{-gnatVfi} -(the order does not matter) specifies that floating-point parameters of mode -@code{in} should be validity checked. +@menu +* Building a library:: +* Installing a library:: +* Using a library:: -@item -gnatVi -@emph{Validity checks for @code{in} mode parameters} -@cindex @option{-gnatVi} (@command{gcc}) -Arguments for parameters of mode @code{in} are validity checked in function -and procedure calls at the point of call. +@end menu -@item -gnatVm -@emph{Validity checks for @code{in out} mode parameters.} -@cindex @option{-gnatVm} (@command{gcc}) -Arguments for parameters of mode @code{in out} are validity checked in -procedure calls at the point of call. The @code{'m'} here stands for -modify, since this concerns parameters that can be modified by the call. -Note that there is no specific option to test @code{out} parameters, -but any reference within the subprogram will be tested in the usual -manner, and if an invalid value is copied back, any reference to it -will be subject to validity checking. +@node Building a library,Installing a library,,General Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model building-a-library}@anchor{88}@anchor{gnat_ugn/the_gnat_compilation_model id38}@anchor{89} +@subsubsection Building a library -@item -gnatVn -@emph{No validity checks.} -@cindex @option{-gnatVn} (@command{gcc}) -This switch turns off all validity checking, including the default checking -for case statements and left hand side subscripts. Note that the use of -the switch @option{-gnatp} suppresses all run-time checks, including -validity checks, and thus implies @option{-gnatVn}. When this switch -is used, it cancels any other @option{-gnatV} previously issued. -@item -gnatVo -@emph{Validity checks for operator and attribute operands.} -@cindex @option{-gnatVo} (@command{gcc}) -Arguments for predefined operators and attributes are validity checked. -This includes all operators in package @code{Standard}, -the shift operators defined as intrinsic in package @code{Interfaces} -and operands for attributes such as @code{Pos}. Checks are also made -on individual component values for composite comparisons, and on the -expressions in type conversions and qualified expressions. Checks are -also made on explicit ranges using @samp{..} (e.g.@: slices, loops etc). +The easiest way to build a library is to use the Project Manager, +which supports a special type of project called a @emph{Library Project} +(see @ref{8a,,Library Projects}). -@item -gnatVp -@emph{Validity checks for parameters.} -@cindex @option{-gnatVp} (@command{gcc}) -This controls the treatment of parameters within a subprogram (as opposed -to @option{-gnatVi} and @option{-gnatVm} which control validity testing -of parameters on a call. If either of these call options is used, then -normally an assumption is made within a subprogram that the input arguments -have been validity checking at the point of call, and do not need checking -again within a subprogram). If @option{-gnatVp} is set, then this assumption -is not made, and parameters are not assumed to be valid, so their validity -will be checked (or rechecked) within the subprogram. +A project is considered a library project, when two project-level attributes +are defined in it: @cite{Library_Name} and @cite{Library_Dir}. In order to +control different aspects of library configuration, additional optional +project-level attributes can be specified: -@item -gnatVr -@emph{Validity checks for function returns.} -@cindex @option{-gnatVr} (@command{gcc}) -The expression in @code{return} statements in functions is validity -checked. -@item -gnatVs -@emph{Validity checks for subscripts.} -@cindex @option{-gnatVs} (@command{gcc}) -All subscripts expressions are checked for validity, whether they appear -on the right side or left side (in default mode only left side subscripts -are validity checked). +@itemize * -@item -gnatVt -@emph{Validity checks for tests.} -@cindex @option{-gnatVt} (@command{gcc}) -Expressions used as conditions in @code{if}, @code{while} or @code{exit} -statements are checked, as well as guard expressions in entry calls. +@item -@end table +@table @asis -@noindent -The @option{-gnatV} switch may be followed by -a string of letters -to turn on a series of validity checking options. -For example, -@option{-gnatVcr} -specifies that in addition to the default validity checking, copies and -function return expressions are to be validity checked. -In order to make it easier -to specify the desired combination of effects, -the upper case letters @code{CDFIMORST} may -be used to turn off the corresponding lower case option. -Thus -@option{-gnatVaM} -turns on all validity checking options except for -checking of @code{@b{in out}} procedure arguments. +@item @emph{Library_Kind} -The specification of additional validity checking generates extra code (and -in the case of @option{-gnatVa} the code expansion can be substantial). -However, these additional checks can be very useful in detecting -uninitialized variables, incorrect use of unchecked conversion, and other -errors leading to invalid values. The use of pragma @code{Initialize_Scalars} -is useful in conjunction with the extra validity checking, since this -ensures that wherever possible uninitialized variables have invalid values. +This attribute controls whether the library is to be static or dynamic +@end table -See also the pragma @code{Validity_Checks} which allows modification of -the validity checking mode at the program source level, and also allows for -temporary disabling of validity checks. +@item -@node Style Checking -@subsection Style Checking -@findex Style checking +@table @asis -@noindent -The @option{-gnatyx} switch -@cindex @option{-gnaty} (@command{gcc}) -causes the compiler to -enforce specified style rules. A limited set of style rules has been used -in writing the GNAT sources themselves. This switch allows user programs -to activate all or some of these checks. If the source program fails a -specified style check, an appropriate message is given, preceded by -the character sequence ``(style)''. This message does not prevent -successful compilation (unless the @option{-gnatwe} switch is used). +@item @emph{Library_Version} -Note that this is by no means intended to be a general facility for -checking arbitrary coding standards. It is simply an embedding of the -style rules we have chosen for the GNAT sources. If you are starting -a project which does not have established style standards, you may -find it useful to adopt the entire set of GNAT coding standards, or -some subset of them. -@ifclear FSFEDITION -If you already have an established set of coding -standards, then the selected style checking options may -indeed correspond to choices you have made, but for general checking -of an existing set of coding rules, you should look to the gnatcheck -tool, which is designed for that purpose. -@end ifclear - -The string @var{x} is a sequence of letters or digits -indicating the particular style -checks to be performed. The following checks are defined: +This attribute specifies the library version; this value is used +during dynamic linking of shared libraries to determine if the currently +installed versions of the binaries are compatible. +@end table -@table @option -@c !sort! -@item 0-9 -@emph{Specify indentation level.} -If a digit from 1-9 appears -in the string after @option{-gnaty} -then proper indentation is checked, with the digit indicating the -indentation level required. A value of zero turns off this style check. -The general style of required indentation is as specified by -the examples in the Ada Reference Manual. Full line comments must be -aligned with the @code{--} starting on a column that is a multiple of -the alignment level, or they may be aligned the same way as the following -non-blank line (this is useful when full line comments appear in the middle -of a statement, or they may be aligned with the source line on the previous -non-blank line. +@item +@emph{Library_Options} -@item a -@emph{Check attribute casing.} -Attribute names, including the case of keywords such as @code{digits} -used as attributes names, must be written in mixed case, that is, the -initial letter and any letter following an underscore must be uppercase. -All other letters must be lowercase. +@item -@item A -@emph{Use of array index numbers in array attributes.} -When using the array attributes First, Last, Range, -or Length, the index number must be omitted for one-dimensional arrays -and is required for multi-dimensional arrays. +@table @asis -@item b -@emph{Blanks not allowed at statement end.} -Trailing blanks are not allowed at the end of statements. The purpose of this -rule, together with h (no horizontal tabs), is to enforce a canonical format -for the use of blanks to separate source tokens. +@item @emph{Library_GCC} -@item B -@emph{Check Boolean operators.} -The use of AND/OR operators is not permitted except in the cases of modular -operands, array operands, and simple stand-alone boolean variables or -boolean constants. In all other cases @code{and then}/@code{or else} are -required. +These attributes specify additional low-level options to be used during +library generation, and redefine the actual application used to generate +library. +@end table +@end itemize -@item c -@emph{Check comments, double space.} -Comments must meet the following set of rules: +The GNAT Project Manager takes full care of the library maintenance task, +including recompilation of the source files for which objects do not exist +or are not up to date, assembly of the library archive, and installation of +the library (i.e., copying associated source, object and @code{ALI} files +to the specified location). -@itemize @bullet +Here is a simple library project file: -@item -The ``@code{--}'' that starts the column must either start in column one, -or else at least one blank must precede this sequence. +@example +project My_Lib is + for Source_Dirs use ("src1", "src2"); + for Object_Dir use "obj"; + for Library_Name use "mylib"; + for Library_Dir use "lib"; + for Library_Kind use "dynamic"; +end My_lib; +@end example -@item -Comments that follow other tokens on a line must have at least one blank -following the ``@code{--}'' at the start of the comment. +and the compilation command to build and install the library: -@item -Full line comments must have at least two blanks following the -``@code{--}'' that starts the comment, with the following exceptions. +@example +$ gnatmake -Pmy_lib +@end example -@item -A line consisting only of the ``@code{--}'' characters, possibly preceded -by blanks is permitted. +It is not entirely trivial to perform manually all the steps required to +produce a library. We recommend that you use the GNAT Project Manager +for this task. In special cases where this is not desired, the necessary +steps are discussed below. -@item -A comment starting with ``@code{--x}'' where @code{x} is a special character -is permitted. -This allows proper processing of the output generated by specialized tools -including @command{gnatprep} (where ``@code{--!}'' is used) and the SPARK -annotation -language (where ``@code{--#}'' is used). For the purposes of this rule, a -special character is defined as being in one of the ASCII ranges -@code{16#21#@dots{}16#2F#} or @code{16#3A#@dots{}16#3F#}. -Note that this usage is not permitted -in GNAT implementation units (i.e., when @option{-gnatg} is used). +There are various possibilities for compiling the units that make up the +library: for example with a Makefile (@ref{21,,Using the GNU make Utility}) or +with a conventional script. For simple libraries, it is also possible to create +a dummy main program which depends upon all the packages that comprise the +interface of the library. This dummy main program can then be given to +@emph{gnatmake}, which will ensure that all necessary objects are built. -@item -A line consisting entirely of minus signs, possibly preceded by blanks, is -permitted. This allows the construction of box comments where lines of minus -signs are used to form the top and bottom of the box. +After this task is accomplished, you should follow the standard procedure +of the underlying operating system to produce the static or shared library. -@item -A comment that starts and ends with ``@code{--}'' is permitted as long as at -least one blank follows the initial ``@code{--}''. Together with the preceding -rule, this allows the construction of box comments, as shown in the following -example: -@smallexample ---------------------------- --- This is a box comment -- --- with two text lines. -- ---------------------------- -@end smallexample -@end itemize +Here is an example of such a dummy program: -@item C -@emph{Check comments, single space.} -This is identical to @code{c} except that only one space -is required following the @code{--} of a comment instead of two. +@example +with My_Lib.Service1; +with My_Lib.Service2; +with My_Lib.Service3; +procedure My_Lib_Dummy is +begin + null; +end; +@end example -@item d -@emph{Check no DOS line terminators present.} -All lines must be terminated by a single ASCII.LF -character (in particular the DOS line terminator sequence CR/LF is not -allowed). +Here are the generic commands that will build an archive or a shared library. -@item e -@emph{Check end/exit labels.} -Optional labels on @code{end} statements ending subprograms and on -@code{exit} statements exiting named loops, are required to be present. +@example +# compiling the library +$ gnatmake -c my_lib_dummy.adb -@item f -@emph{No form feeds or vertical tabs.} -Neither form feeds nor vertical tab characters are permitted -in the source text. +# we don't need the dummy object itself +$ rm my_lib_dummy.o my_lib_dummy.ali -@item g -@emph{GNAT style mode.} -The set of style check switches is set to match that used by the GNAT sources. -This may be useful when developing code that is eventually intended to be -incorporated into GNAT. Currently this is equivalent to @option{-gnatwydISux}) -but additional style switches may be added to this set in the future without -advance notice. +# create an archive with the remaining objects +$ ar rc libmy_lib.a *.o +# some systems may require "ranlib" to be run as well -@item h -@emph{No horizontal tabs.} -Horizontal tab characters are not permitted in the source text. -Together with the b (no blanks at end of line) check, this -enforces a canonical form for the use of blanks to separate -source tokens. +# or create a shared library +$ gcc -shared -o libmy_lib.so *.o +# some systems may require the code to have been compiled with -fPIC -@item i -@emph{Check if-then layout.} -The keyword @code{then} must appear either on the same -line as corresponding @code{if}, or on a line on its own, lined -up under the @code{if}. +# remove the object files that are now in the library +$ rm *.o -@item I -@emph{check mode IN keywords.} -Mode @code{in} (the default mode) is not -allowed to be given explicitly. @code{in out} is fine, -but not @code{in} on its own. +# Make the ALI files read-only so that gnatmake will not try to +# regenerate the objects that are in the library +$ chmod -w *.ali +@end example -@item k -@emph{Check keyword casing.} -All keywords must be in lower case (with the exception of keywords -such as @code{digits} used as attribute names to which this check -does not apply). +Please note that the library must have a name of the form @code{lib@emph{xxx}.a} +or @code{lib@emph{xxx}.so} (or @code{lib@emph{xxx}.dll} on Windows) in order to +be accessed by the directive @code{-l@emph{xxx}} at link time. -@item l -@emph{Check layout.} -Layout of statement and declaration constructs must follow the -recommendations in the Ada Reference Manual, as indicated by the -form of the syntax rules. For example an @code{else} keyword must -be lined up with the corresponding @code{if} keyword. +@node Installing a library,Using a library,Building a library,General Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model installing-a-library}@anchor{8b}@anchor{gnat_ugn/the_gnat_compilation_model id39}@anchor{8c} +@subsubsection Installing a library -There are two respects in which the style rule enforced by this check -option are more liberal than those in the Ada Reference Manual. First -in the case of record declarations, it is permissible to put the -@code{record} keyword on the same line as the @code{type} keyword, and -then the @code{end} in @code{end record} must line up under @code{type}. -This is also permitted when the type declaration is split on two lines. -For example, any of the following three layouts is acceptable: -@smallexample @c ada -@cartouche -@b{type} q @b{is} @b{record} - a : integer; - b : integer; -@b{end} @b{record}; +@geindex ADA_PROJECT_PATH -@b{type} q @b{is} - @b{record} - a : integer; - b : integer; - @b{end} @b{record}; +@geindex GPR_PROJECT_PATH -@b{type} q @b{is} - @b{record} - a : integer; - b : integer; -@b{end} @b{record}; +If you use project files, library installation is part of the library build +process (@ref{8d,,Installing a library with project files}). -@end cartouche -@end smallexample +When project files are not an option, it is also possible, but not recommended, +to install the library so that the sources needed to use the library are on the +Ada source path and the ALI files & libraries be on the Ada Object path (see +@ref{8e,,Search Paths and the Run-Time Library (RTL)}. Alternatively, the system +administrator can place general-purpose libraries in the default compiler +paths, by specifying the libraries' location in the configuration files +@code{ada_source_path} and @code{ada_object_path}. These configuration files +must be located in the GNAT installation tree at the same place as the gcc spec +file. The location of the gcc spec file can be determined as follows: -@noindent -Second, in the case of a block statement, a permitted alternative -is to put the block label on the same line as the @code{declare} or -@code{begin} keyword, and then line the @code{end} keyword up under -the block label. For example both the following are permitted: +@example +$ gcc -v +@end example -@smallexample @c ada -@cartouche -Block : @b{declare} - A : Integer := 3; -@b{begin} - Proc (A, A); -@b{end} Block; +The configuration files mentioned above have a simple format: each line +must contain one unique directory name. +Those names are added to the corresponding path +in their order of appearance in the file. The names can be either absolute +or relative; in the latter case, they are relative to where theses files +are located. -Block : - @b{declare} - A : Integer := 3; - @b{begin} - Proc (A, A); - @b{end} Block; -@end cartouche -@end smallexample +The files @code{ada_source_path} and @code{ada_object_path} might not be +present in a +GNAT installation, in which case, GNAT will look for its run-time library in +the directories @code{adainclude} (for the sources) and @code{adalib} (for the +objects and @code{ALI} files). When the files exist, the compiler does not +look in @code{adainclude} and @code{adalib}, and thus the +@code{ada_source_path} file +must contain the location for the GNAT run-time sources (which can simply +be @code{adainclude}). In the same way, the @code{ada_object_path} file must +contain the location for the GNAT run-time objects (which can simply +be @code{adalib}). -@noindent -The same alternative format is allowed for loops. For example, both of -the following are permitted: +You can also specify a new default path to the run-time library at compilation +time with the switch @emph{--RTS=rts-path}. You can thus choose / change +the run-time library you want your program to be compiled with. This switch is +recognized by @emph{gcc}, @emph{gnatmake}, @emph{gnatbind}, +@emph{gnatls}, @emph{gnatfind} and @emph{gnatxref}. -@smallexample @c ada -@cartouche -Clear : @b{while} J < 10 @b{loop} - A (J) := 0; -@b{end} @b{loop} Clear; +It is possible to install a library before or after the standard GNAT +library, by reordering the lines in the configuration files. In general, a +library must be installed before the GNAT library if it redefines +any part of it. -Clear : - @b{while} J < 10 @b{loop} - A (J) := 0; - @b{end} @b{loop} Clear; -@end cartouche -@end smallexample +@node Using a library,,Installing a library,General Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model using-a-library}@anchor{8f}@anchor{gnat_ugn/the_gnat_compilation_model id40}@anchor{90} +@subsubsection Using a library -@item Lnnn -@emph{Set maximum nesting level.} -The maximum level of nesting of constructs (including subprograms, loops, -blocks, packages, and conditionals) may not exceed the given value -@option{nnn}. A value of zero disconnects this style check. -@item m -@emph{Check maximum line length.} -The length of source lines must not exceed 79 characters, including -any trailing blanks. The value of 79 allows convenient display on an -80 character wide device or window, allowing for possible special -treatment of 80 character lines. Note that this count is of -characters in the source text. This means that a tab character counts -as one character in this count and a wide character sequence counts as -a single character (however many bytes are needed in the encoding). +Once again, the project facility greatly simplifies the use of +libraries. In this context, using a library is just a matter of adding a +@emph{with} clause in the user project. For instance, to make use of the +library @cite{My_Lib} shown in examples in earlier sections, you can +write: -@item Mnnn -@emph{Set maximum line length.} -The length of lines must not exceed the -given value @option{nnn}. The maximum value that can be specified is 32767. -If neither style option for setting the line length is used, then the -default is 255. This also controls the maximum length of lexical elements, -where the only restriction is that they must fit on a single line. +@example +with "my_lib"; +project My_Proj is + ... +end My_Proj; +@end example -@item n -@emph{Check casing of entities in Standard.} -Any identifier from Standard must be cased -to match the presentation in the Ada Reference Manual (for example, -@code{Integer} and @code{ASCII.NUL}). +Even if you have a third-party, non-Ada library, you can still use GNAT's +Project Manager facility to provide a wrapper for it. For example, the +following project, when @emph{with}ed by your main project, will link with the +third-party library @code{liba.a}: + +@example +project Liba is + for Externally_Built use "true"; + for Source_Files use (); + for Library_Dir use "lib"; + for Library_Name use "a"; + for Library_Kind use "static"; +end Liba; +@end example + +This is an alternative to the use of @cite{pragma Linker_Options}. It is +especially interesting in the context of systems with several interdependent +static libraries where finding a proper linker order is not easy and best be +left to the tools having visibility over project dependence information. -@item N -@emph{Turn off all style checks.} -All style check options are turned off. +In order to use an Ada library manually, you need to make sure that this +library is on both your source and object path +(see @ref{8e,,Search Paths and the Run-Time Library (RTL)} +and @ref{91,,Search Paths for gnatbind}). Furthermore, when the objects are grouped +in an archive or a shared library, you need to specify the desired +library at link time. -@item o -@emph{Check order of subprogram bodies.} -All subprogram bodies in a given scope -(e.g.@: a package body) must be in alphabetical order. The ordering -rule uses normal Ada rules for comparing strings, ignoring casing -of letters, except that if there is a trailing numeric suffix, then -the value of this suffix is used in the ordering (e.g.@: Junk2 comes -before Junk10). +For example, you can use the library @code{mylib} installed in +@code{/dir/my_lib_src} and @code{/dir/my_lib_obj} with the following commands: -@item O -@emph{Check that overriding subprograms are explicitly marked as such.} -The declaration of a primitive operation of a type extension that overrides -an inherited operation must carry an overriding indicator. +@example +$ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\ + -largs -lmy_lib +@end example -@item p -@emph{Check pragma casing.} -Pragma names must be written in mixed case, that is, the -initial letter and any letter following an underscore must be uppercase. -All other letters must be lowercase. An exception is that SPARK_Mode is -allowed as an alternative for Spark_Mode. +This can be expressed more simply: -@item r -@emph{Check references.} -All identifier references must be cased in the same way as the -corresponding declaration. No specific casing style is imposed on -identifiers. The only requirement is for consistency of references -with declarations. +@example +$ gnatmake my_appl +@end example -@item s -@emph{Check separate specs.} -Separate declarations (``specs'') are required for subprograms (a -body is not allowed to serve as its own declaration). The only -exception is that parameterless library level procedures are -not required to have a separate declaration. This exception covers -the most frequent form of main program procedures. +when the following conditions are met: -@item S -@emph{Check no statements after @code{then}/@code{else}.} -No statements are allowed -on the same line as a @code{then} or @code{else} keyword following the -keyword in an @code{if} statement. @code{or else} and @code{and then} are not -affected, and a special exception allows a pragma to appear after @code{else}. -@item t -@emph{Check token spacing.} -The following token spacing rules are enforced: +@itemize * -@itemize @bullet +@item +@code{/dir/my_lib_src} has been added by the user to the environment +variable +@geindex ADA_INCLUDE_PATH +@geindex environment variable; ADA_INCLUDE_PATH +@code{ADA_INCLUDE_PATH}, or by the administrator to the file +@code{ada_source_path} -@item -The keywords @code{abs} and @code{not} must be followed by a space. +@item +@code{/dir/my_lib_obj} has been added by the user to the environment +variable +@geindex ADA_OBJECTS_PATH +@geindex environment variable; ADA_OBJECTS_PATH +@code{ADA_OBJECTS_PATH}, or by the administrator to the file +@code{ada_object_path} -@item -The token @code{=>} must be surrounded by spaces. +@item +a pragma @cite{Linker_Options} has been added to one of the sources. +For example: -@item -The token @code{<>} must be preceded by a space or a left parenthesis. +@example +pragma Linker_Options ("-lmy_lib"); +@end example +@end itemize -@item -Binary operators other than @code{**} must be surrounded by spaces. -There is no restriction on the layout of the @code{**} binary operator. +Note that you may also load a library dynamically at +run time given its filename, as illustrated in the GNAT @code{plugins} example +in the directory @code{share/examples/gnat/plugins} within the GNAT +install area. -@item -Colon must be surrounded by spaces. +@node Stand-alone Ada Libraries,Rebuilding the GNAT Run-Time Library,General Ada Libraries,GNAT and Libraries +@anchor{gnat_ugn/the_gnat_compilation_model stand-alone-ada-libraries}@anchor{85}@anchor{gnat_ugn/the_gnat_compilation_model id41}@anchor{92} +@subsection Stand-alone Ada Libraries -@item -Colon-equal (assignment, initialization) must be surrounded by spaces. -@item -Comma must be the first non-blank character on the line, or be -immediately preceded by a non-blank character, and must be followed -by a space. +@geindex Stand-alone libraries -@item -If the token preceding a left parenthesis ends with a letter or digit, then -a space must separate the two tokens. +@menu +* Introduction to Stand-alone Libraries:: +* Building a Stand-alone Library:: +* Creating a Stand-alone Library to be used in a non-Ada context:: +* Restrictions in Stand-alone Libraries:: -@item -if the token following a right parenthesis starts with a letter or digit, then -a space must separate the two tokens. +@end menu -@item -A right parenthesis must either be the first non-blank character on -a line, or it must be preceded by a non-blank character. +@node Introduction to Stand-alone Libraries,Building a Stand-alone Library,,Stand-alone Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model introduction-to-stand-alone-libraries}@anchor{93}@anchor{gnat_ugn/the_gnat_compilation_model id42}@anchor{94} +@subsubsection Introduction to Stand-alone Libraries -@item -A semicolon must not be preceded by a space, and must not be followed by -a non-blank character. -@item -A unary plus or minus may not be followed by a space. +A Stand-alone Library (abbreviated 'SAL') is a library that contains the +necessary code to +elaborate the Ada units that are included in the library. In contrast with +an ordinary library, which consists of all sources, objects and @code{ALI} +files of the +library, a SAL may specify a restricted subset of compilation units +to serve as a library interface. In this case, the fully +self-sufficient set of files will normally consist of an objects +archive, the sources of interface units' specs, and the @code{ALI} +files of interface units. +If an interface spec contains a generic unit or an inlined subprogram, +the body's +source must also be provided; if the units that must be provided in the source +form depend on other units, the source and @code{ALI} files of those must +also be provided. -@item -A vertical bar must be surrounded by spaces. -@end itemize +The main purpose of a SAL is to minimize the recompilation overhead of client +applications when a new version of the library is installed. Specifically, +if the interface sources have not changed, client applications do not need to +be recompiled. If, furthermore, a SAL is provided in the shared form and its +version, controlled by @cite{Library_Version} attribute, is not changed, +then the clients do not need to be relinked. -Exactly one blank (and no other white space) must appear between -a @code{not} token and a following @code{in} token. +SALs also allow the library providers to minimize the amount of library source +text exposed to the clients. Such 'information hiding' might be useful or +necessary for various reasons. -@item u -@emph{Check unnecessary blank lines.} -Unnecessary blank lines are not allowed. A blank line is considered -unnecessary if it appears at the end of the file, or if more than -one blank line occurs in sequence. +Stand-alone libraries are also well suited to be used in an executable whose +main routine is not written in Ada. -@item x -@emph{Check extra parentheses.} -Unnecessary extra level of parentheses (C-style) are not allowed -around conditions in @code{if} statements, @code{while} statements and -@code{exit} statements. +@node Building a Stand-alone Library,Creating a Stand-alone Library to be used in a non-Ada context,Introduction to Stand-alone Libraries,Stand-alone Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model id43}@anchor{95}@anchor{gnat_ugn/the_gnat_compilation_model building-a-stand-alone-library}@anchor{96} +@subsubsection Building a Stand-alone Library -@item y -@emph{Set all standard style check options} -This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking -options enabled with the exception of @option{-gnatyB}, @option{-gnatyd}, -@option{-gnatyI}, @option{-gnatyLnnn}, @option{-gnatyo}, @option{-gnatyO}, -@option{-gnatyS}, @option{-gnatyu}, and @option{-gnatyx}. -@item - -@emph{Remove style check options} -This causes any subsequent options in the string to act as canceling the -corresponding style check option. To cancel maximum nesting level control, -use @option{L} parameter witout any integer value after that, because any -digit following @option{-} in the parameter string of the @option{-gnaty} -option will be threated as canceling indentation check. The same is true -for @option{M} parameter. @option{y} and @option{N} parameters are not -allowed after @option{-}. +GNAT's Project facility provides a simple way of building and installing +stand-alone libraries; see @ref{97,,Stand-alone Library Projects}. +To be a Stand-alone Library Project, in addition to the two attributes +that make a project a Library Project (@cite{Library_Name} and +@cite{Library_Dir}; see @ref{8a,,Library Projects}), the attribute +@cite{Library_Interface} must be defined. For example: -@item + -This causes any subsequent options in the string to enable the corresponding -style check option. That is, it cancels the effect of a previous -, -if any. +@example +for Library_Dir use "lib_dir"; +for Library_Name use "dummy"; +for Library_Interface use ("int1", "int1.child"); +@end example -@end table +Attribute @cite{Library_Interface} has a non-empty string list value, +each string in the list designating a unit contained in an immediate source +of the project file. -@noindent -In the above rules, appearing in column one is always permitted, that is, -counts as meeting either a requirement for a required preceding space, -or as meeting a requirement for no preceding space. +When a Stand-alone Library is built, first the binder is invoked to build +a package whose name depends on the library name +(@code{b~dummy.ads/b} in the example above). +This binder-generated package includes initialization and +finalization procedures whose +names depend on the library name (@cite{dummyinit} and @cite{dummyfinal} +in the example +above). The object corresponding to this package is included in the library. -Appearing at the end of a line is also always permitted, that is, counts -as meeting either a requirement for a following space, or as meeting -a requirement for no following space. +You must ensure timely (e.g., prior to any use of interfaces in the SAL) +calling of these procedures if a static SAL is built, or if a shared SAL +is built +with the project-level attribute @cite{Library_Auto_Init} set to +@cite{"false"}. -@noindent -If any of these style rules is violated, a message is generated giving -details on the violation. The initial characters of such messages are -always ``@code{(style)}''. Note that these messages are treated as warning -messages, so they normally do not prevent the generation of an object -file. The @option{-gnatwe} switch can be used to treat warning messages, -including style messages, as fatal errors. +For a Stand-Alone Library, only the @code{ALI} files of the Interface Units +(those that are listed in attribute @cite{Library_Interface}) are copied to +the Library Directory. As a consequence, only the Interface Units may be +imported from Ada units outside of the library. If other units are imported, +the binding phase will fail. -The switch -@option{-gnaty} on its own (that is not -followed by any letters or digits) is equivalent -to the use of @option{-gnatyy} as described above, that is all -built-in standard style check options are enabled. +It is also possible to build an encapsulated library where not only +the code to elaborate and finalize the library is embedded but also +ensuring that the library is linked only against static +libraries. So an encapsulated library only depends on system +libraries, all other code, including the GNAT runtime, is embedded. To +build an encapsulated library the attribute +@cite{Library_Standalone} must be set to @cite{encapsulated}: +@example +for Library_Dir use "lib_dir"; +for Library_Name use "dummy"; +for Library_Kind use "dynamic"; +for Library_Interface use ("int1", "int1.child"); +for Library_Standalone use "encapsulated"; +@end example -The switch -@option{-gnatyN} -clears any previously set style checks. +The default value for this attribute is @cite{standard} in which case +a stand-alone library is built. -@node Run-Time Checks -@subsection Run-Time Checks -@cindex Division by zero -@cindex Access before elaboration -@cindex Checks, division by zero -@cindex Checks, access before elaboration -@cindex Checks, stack overflow checking +The attribute @cite{Library_Src_Dir} may be specified for a +Stand-Alone Library. @cite{Library_Src_Dir} is a simple attribute that has a +single string value. Its value must be the path (absolute or relative to the +project directory) of an existing directory. This directory cannot be the +object directory or one of the source directories, but it can be the same as +the library directory. The sources of the Interface +Units of the library that are needed by an Ada client of the library will be +copied to the designated directory, called the Interface Copy directory. +These sources include the specs of the Interface Units, but they may also +include bodies and subunits, when pragmas @cite{Inline} or @cite{Inline_Always} +are used, or when there is a generic unit in the spec. Before the sources +are copied to the Interface Copy directory, an attempt is made to delete all +files in the Interface Copy directory. -@noindent -By default, the following checks are suppressed: integer overflow -checks, stack overflow checks, and checks for access before -elaboration on subprogram calls. All other checks, including range -checks and array bounds checks, are turned on by default. The -following @command{gcc} switches refine this default behavior. - -@table @option -@c !sort! -@item -gnatp -@cindex @option{-gnatp} (@command{gcc}) -@cindex Suppressing checks -@cindex Checks, suppressing -@findex Suppress -This switch causes the unit to be compiled -as though @code{pragma Suppress (All_checks)} -had been present in the source. Validity checks are also eliminated (in -other words @option{-gnatp} also implies @option{-gnatVn}. -Use this switch to improve the performance -of the code at the expense of safety in the presence of invalid data or -program bugs. +Building stand-alone libraries by hand is somewhat tedious, but for those +occasions when it is necessary here are the steps that you need to perform: -Note that when checks are suppressed, the compiler is allowed, but not -required, to omit the checking code. If the run-time cost of the -checking code is zero or near-zero, the compiler will generate it even -if checks are suppressed. In particular, if the compiler can prove -that a certain check will necessarily fail, it will generate code to -do an unconditional ``raise'', even if checks are suppressed. The -compiler warns in this case. Another case in which checks may not be -eliminated is when they are embedded in certain run time routines such -as math library routines. -Of course, run-time checks are omitted whenever the compiler can prove -that they will not fail, whether or not checks are suppressed. +@itemize * -Note that if you suppress a check that would have failed, program -execution is erroneous, which means the behavior is totally -unpredictable. The program might crash, or print wrong answers, or -do anything else. It might even do exactly what you wanted it to do -(and then it might start failing mysteriously next week or next -year). The compiler will generate code based on the assumption that -the condition being checked is true, which can result in erroneous -execution if that assumption is wrong. +@item +Compile all library sources. -The checks subject to suppression include all the checks defined by -the Ada standard, the additional implementation defined checks -@code{Alignment_Check}, -@code{Duplicated_Tag_Check}, @code{Predicate_Check}, and -@code{Validity_Check}, as well as any checks introduced using -@code{pragma Check_Name}. Note that @code{Atomic_Synchronization} -is not automatically suppressed by use of this option. +@item +Invoke the binder with the switch @emph{-n} (No Ada main program), +with all the @code{ALI} files of the interfaces, and +with the switch @emph{-L} to give specific names to the @cite{init} +and @cite{final} procedures. For example: -If the code depends on certain checks being active, you can use -pragma @code{Unsuppress} either as a configuration pragma or as -a local pragma to make sure that a specified check is performed -even if @option{gnatp} is specified. - -The @option{-gnatp} switch has no effect if a subsequent -@option{-gnat-p} switch appears. - -@item -gnat-p -@cindex @option{-gnat-p} (@command{gcc}) -@cindex Suppressing checks -@cindex Checks, suppressing -@findex Suppress -This switch cancels the effect of a previous @option{gnatp} switch. - -@item -gnato?? -@cindex @option{-gnato??} (@command{gcc}) -@cindex Overflow checks -@cindex Overflow mode -@cindex Check, overflow -This switch controls the mode used for computing intermediate -arithmetic integer operations, and also enables overflow checking. -For a full description of overflow mode and checking control, see -the ``Overflow Check Handling in GNAT'' appendix in this -User's Guide. +@example +$ gnatbind -n int1.ali int2.ali -Lsal1 +@end example -Overflow checks are always enabled by this switch. The argument -controls the mode, using the codes +@item +Compile the binder generated file: -@itemize -@item 1 = STRICT -In STRICT mode, intermediate operations are always done using the -base type, and overflow checking ensures that the result is within -the base type range. +@example +$ gcc -c b~int2.adb +@end example -@item 2 = MINIMIZED -In MINIMIZED mode, overflows in intermediate operations are avoided -where possible by using a larger integer type for the computation -(typically @code{Long_Long_Integer}). Overflow checking ensures that -the result fits in this larger integer type. +@item +Link the dynamic library with all the necessary object files, +indicating to the linker the names of the @cite{init} (and possibly +@cite{final}) procedures for automatic initialization (and finalization). +The built library should be placed in a directory different from +the object directory. -@item 3 = ELIMINATED -In ELIMINATED mode, overflows in intermediate operations are avoided -by using multi-precision arithmetic. In this case, overflow checking -has no effect on intermediate operations (since overflow is impossible). +@item +Copy the @cite{ALI} files of the interface to the library directory, +add in this copy an indication that it is an interface to a SAL +(i.e., add a word @emph{SL} on the line in the @code{ALI} file that starts +with letter 'P') and make the modified copy of the @code{ALI} file +read-only. @end itemize -If two digits are present after @option{-gnato} then the first digit -sets the mode for expressions outside assertions, and the second digit -sets the mode for expressions within assertions. Here assertions is used -in the technical sense (which includes for example precondition and -postcondition expressions). +Using SALs is not different from using other libraries +(see @ref{8f,,Using a library}). -If one digit is present, the corresponding mode is applicable to both -expressions within and outside assertion expressions. +@node Creating a Stand-alone Library to be used in a non-Ada context,Restrictions in Stand-alone Libraries,Building a Stand-alone Library,Stand-alone Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model creating-a-stand-alone-library-to-be-used-in-a-non-ada-context}@anchor{98}@anchor{gnat_ugn/the_gnat_compilation_model id44}@anchor{99} +@subsubsection Creating a Stand-alone Library to be used in a non-Ada context -If no digits are present, the default is to enable overflow checks -and set STRICT mode for both kinds of expressions. This is compatible -with the use of @option{-gnato} in previous versions of GNAT. -@findex Machine_Overflows -Note that the @option{-gnato??} switch does not affect the code generated -for any floating-point operations; it applies only to integer semantics. -For floating-point, @value{EDITION} has the @code{Machine_Overflows} -attribute set to @code{False} and the normal mode of operation is to -generate IEEE NaN and infinite values on overflow or invalid operations -(such as dividing 0.0 by 0.0). +It is easy to adapt the SAL build procedure discussed above for use of a SAL in +a non-Ada context. -The reason that we distinguish overflow checking from other kinds of -range constraint checking is that a failure of an overflow check, unlike -for example the failure of a range check, can result in an incorrect -value, but cannot cause random memory destruction (like an out of range -subscript), or a wild jump (from an out of range case value). Overflow -checking is also quite expensive in time and space, since in general it -requires the use of double length arithmetic. +The only extra step required is to ensure that library interface subprograms +are compatible with the main program, by means of @cite{pragma Export} +or @cite{pragma Convention}. -Note again that the default is @option{-gnato00}, -so overflow checking is not performed in default mode. This means that out of -the box, with the default settings, @value{EDITION} does not do all the checks -expected from the language description in the Ada Reference Manual. -If you want all constraint checks to be performed, as described in this Manual, -then you must explicitly use the @option{-gnato??} -switch either on the @command{gnatmake} or @command{gcc} command. +Here is an example of simple library interface for use with C main program: -@item -gnatE -@cindex @option{-gnatE} (@command{gcc}) -@cindex Elaboration checks -@cindex Check, elaboration -Enables dynamic checks for access-before-elaboration -on subprogram calls and generic instantiations. -Note that @option{-gnatE} is not necessary for safety, because in the -default mode, GNAT ensures statically that the checks would not fail. -For full details of the effect and use of this switch, -@xref{Compiling with gcc}. +@example +package My_Package is -@item -fstack-check -@cindex @option{-fstack-check} (@command{gcc}) -@cindex Stack Overflow Checking -@cindex Checks, stack overflow checking -Activates stack overflow checking. For full details of the effect and use of -this switch see @ref{Stack Overflow Checking}. -@end table + procedure Do_Something; + pragma Export (C, Do_Something, "do_something"); -@findex Unsuppress -@noindent -The setting of these switches only controls the default setting of the -checks. You may modify them using either @code{Suppress} (to remove -checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in -the program source. + procedure Do_Something_Else; + pragma Export (C, Do_Something_Else, "do_something_else"); -@node Using gcc for Syntax Checking -@subsection Using @command{gcc} for Syntax Checking -@table @option -@item -gnats -@cindex @option{-gnats} (@command{gcc}) +end My_Package; +@end example -@noindent -The @code{s} stands for ``syntax''. +On the foreign language side, you must provide a 'foreign' view of the +library interface; remember that it should contain elaboration routines in +addition to interface subprograms. -Run GNAT in syntax checking only mode. For -example, the command +The example below shows the content of @cite{mylib_interface.h} (note +that there is no rule for the naming of this file, any name can be used) -@smallexample -$ gcc -c -gnats x.adb -@end smallexample +@example +/* the library elaboration procedure */ +extern void mylibinit (void); -@noindent -compiles file @file{x.adb} in syntax-check-only mode. You can check a -series of files in a single command -, and can use wild cards to specify such a group of files. -Note that you must specify the @option{-c} (compile -only) flag in addition to the @option{-gnats} flag. -. -You may use other switches in conjunction with @option{-gnats}. In -particular, @option{-gnatl} and @option{-gnatv} are useful to control the -format of any generated error messages. +/* the library finalization procedure */ +extern void mylibfinal (void); -When the source file is empty or contains only empty lines and/or comments, -the output is a warning: +/* the interface exported by the library */ +extern void do_something (void); +extern void do_something_else (void); +@end example -@smallexample -$ gcc -c -gnats -x ada toto.txt -toto.txt:1:01: warning: empty file, contains no compilation units -$ -@end smallexample +Libraries built as explained above can be used from any program, provided +that the elaboration procedures (named @cite{mylibinit} in the previous +example) are called before the library services are used. Any number of +libraries can be used simultaneously, as long as the elaboration +procedure of each library is called. -Otherwise, the output is simply the error messages, if any. No object file or -ALI file is generated by a syntax-only compilation. Also, no units other -than the one specified are accessed. For example, if a unit @code{X} -@code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax -check only mode does not access the source file containing unit -@code{Y}. +Below is an example of a C program that uses the @cite{mylib} library. -@cindex Multiple units, syntax checking -Normally, GNAT allows only a single unit in a source file. However, this -restriction does not apply in syntax-check-only mode, and it is possible -to check a file containing multiple compilation units concatenated -together. This is primarily used by the @code{gnatchop} utility -(@pxref{Renaming Files with gnatchop}). -@end table +@example +#include "mylib_interface.h" -@node Using gcc for Semantic Checking -@subsection Using @command{gcc} for Semantic Checking -@table @option -@item -gnatc -@cindex @option{-gnatc} (@command{gcc}) +int +main (void) +@{ + /* First, elaborate the library before using it */ + mylibinit (); -@noindent -The @code{c} stands for ``check''. -Causes the compiler to operate in semantic check mode, -with full checking for all illegalities specified in the -Ada Reference Manual, but without generation of any object code -(no object file is generated). + /* Main program, using the library exported entities */ + do_something (); + do_something_else (); -Because dependent files must be accessed, you must follow the GNAT -semantic restrictions on file structuring to operate in this mode: + /* Library finalization at the end of the program */ + mylibfinal (); + return 0; +@} +@end example -@itemize @bullet -@item -The needed source files must be accessible -(@pxref{Search Paths and the Run-Time Library (RTL)}). +Note that invoking any library finalization procedure generated by +@cite{gnatbind} shuts down the Ada run-time environment. +Consequently, the +finalization of all Ada libraries must be performed at the end of the program. +No call to these libraries or to the Ada run-time library should be made +after the finalization phase. -@item -Each file must contain only one compilation unit. +Note also that special care must be taken with multi-tasks +applications. The initialization and finalization routines are not +protected against concurrent access. If such requirement is needed it +must be ensured at the application level using a specific operating +system services like a mutex or a critical-section. -@item -The file name and unit name must match (@pxref{File Naming Rules}). -@end itemize +@node Restrictions in Stand-alone Libraries,,Creating a Stand-alone Library to be used in a non-Ada context,Stand-alone Ada Libraries +@anchor{gnat_ugn/the_gnat_compilation_model id45}@anchor{9a}@anchor{gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries}@anchor{9b} +@subsubsection Restrictions in Stand-alone Libraries -The output consists of error messages as appropriate. No object file is -generated. An @file{ALI} file is generated for use in the context of -cross-reference tools, but this file is marked as not being suitable -for binding (since no object file is generated). -The checking corresponds exactly to the notion of -legality in the Ada Reference Manual. -Any unit can be compiled in semantics-checking-only mode, including -units that would not normally be compiled (subunits, -and specifications where a separate body is present). -@end table +The pragmas listed below should be used with caution inside libraries, +as they can create incompatibilities with other Ada libraries: -@node Compiling Different Versions of Ada -@subsection Compiling Different Versions of Ada -@noindent -The switches described in this section allow you to explicitly specify -the version of the Ada language that your programs are written in. -The default mode is Ada 2012, -but you can also specify Ada 95, Ada 2005 mode, or -indicate Ada 83 compatibility mode. +@itemize * -@table @option -@cindex Compatibility with Ada 83 +@item +pragma @cite{Locking_Policy} -@item -gnat83 (Ada 83 Compatibility Mode) -@cindex @option{-gnat83} (@command{gcc}) -@cindex ACVC, Ada 83 tests -@cindex Ada 83 mode +@item +pragma @cite{Partition_Elaboration_Policy} -@noindent -Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch -specifies that the program is to be compiled in Ada 83 mode. With -@option{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83 -semantics where this can be done easily. -It is not possible to guarantee this switch does a perfect -job; some subtle tests, such as are -found in earlier ACVC tests (and that have been removed from the ACATS suite -for Ada 95), might not compile correctly. -Nevertheless, this switch may be useful in some circumstances, for example -where, due to contractual reasons, existing code needs to be maintained -using only Ada 83 features. +@item +pragma @cite{Queuing_Policy} -With few exceptions (most notably the need to use @code{<>} on -@cindex Generic formal parameters -unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005 -reserved words, and the use of packages -with optional bodies), it is not necessary to specify the -@option{-gnat83} switch when compiling Ada 83 programs, because, with rare -exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus -a correct Ada 83 program is usually also a correct program -in these later versions of the language standard. -For further information, please refer to @ref{Compatibility and Porting Guide}. +@item +pragma @cite{Task_Dispatching_Policy} -@item -gnat95 (Ada 95 mode) -@cindex @option{-gnat95} (@command{gcc}) -@cindex Ada 95 mode +@item +pragma @cite{Unreserve_All_Interrupts} +@end itemize -@noindent -This switch directs the compiler to implement the Ada 95 version of the -language. -Since Ada 95 is almost completely upwards -compatible with Ada 83, Ada 83 programs may generally be compiled using -this switch (see the description of the @option{-gnat83} switch for further -information about Ada 83 mode). -If an Ada 2005 program is compiled in Ada 95 mode, -uses of the new Ada 2005 features will cause error -messages or warnings. +When using a library that contains such pragmas, the user must make sure +that all libraries use the same pragmas with the same values. Otherwise, +@cite{Program_Error} will +be raised during the elaboration of the conflicting +libraries. The usage of these pragmas and its consequences for the user +should therefore be well documented. -This switch also can be used to cancel the effect of a previous -@option{-gnat83}, @option{-gnat05/2005}, or @option{-gnat12/2012} -switch earlier in the command line. +Similarly, the traceback in the exception occurrence mechanism should be +enabled or disabled in a consistent manner across all libraries. +Otherwise, Program_Error will be raised during the elaboration of the +conflicting libraries. -@item -gnat05 or -gnat2005 (Ada 2005 mode) -@cindex @option{-gnat05} (@command{gcc}) -@cindex @option{-gnat2005} (@command{gcc}) -@cindex Ada 2005 mode +If the @cite{Version} or @cite{Body_Version} +attributes are used inside a library, then you need to +perform a @cite{gnatbind} step that specifies all @code{ALI} files in all +libraries, so that version identifiers can be properly computed. +In practice these attributes are rarely used, so this is unlikely +to be a consideration. -@noindent -This switch directs the compiler to implement the Ada 2005 version of the -language, as documented in the official Ada standards document. -Since Ada 2005 is almost completely upwards -compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs -may generally be compiled using this switch (see the description of the -@option{-gnat83} and @option{-gnat95} switches for further -information). +@node Rebuilding the GNAT Run-Time Library,,Stand-alone Ada Libraries,GNAT and Libraries +@anchor{gnat_ugn/the_gnat_compilation_model id46}@anchor{9c}@anchor{gnat_ugn/the_gnat_compilation_model rebuilding-the-gnat-run-time-library}@anchor{9d} +@subsection Rebuilding the GNAT Run-Time Library -@item -gnat12 or -gnat2012 (Ada 2012 mode) -@cindex @option{-gnat12} (@command{gcc}) -@cindex @option{-gnat2012} (@command{gcc}) -@cindex Ada 2012 mode -@noindent -This switch directs the compiler to implement the Ada 2012 version of the -language (also the default). -Since Ada 2012 is almost completely upwards -compatible with Ada 2005 (and thus also with Ada 83, and Ada 95), -Ada 83 and Ada 95 programs -may generally be compiled using this switch (see the description of the -@option{-gnat83}, @option{-gnat95}, and @option{-gnat05/2005} switches -for further information). +@geindex GNAT Run-Time Library +@geindex rebuilding -@item -gnatX (Enable GNAT Extensions) -@cindex @option{-gnatX} (@command{gcc}) -@cindex Ada language extensions -@cindex GNAT extensions +@geindex Building the GNAT Run-Time Library -@noindent -This switch directs the compiler to implement the latest version of the -language (currently Ada 2012) and also to enable certain GNAT implementation -extensions that are not part of any Ada standard. For a full list of these -extensions, see the GNAT reference manual. +@geindex Rebuilding the GNAT Run-Time Library -@end table +@geindex Run-Time Library +@geindex rebuilding -@node Character Set Control -@subsection Character Set Control -@table @option -@item -gnati@var{c} -@cindex @option{-gnati} (@command{gcc}) +It may be useful to recompile the GNAT library in various contexts, the +most important one being the use of partition-wide configuration pragmas +such as @cite{Normalize_Scalars}. A special Makefile called +@cite{Makefile.adalib} is provided to that effect and can be found in +the directory containing the GNAT library. The location of this +directory depends on the way the GNAT environment has been installed and can +be determined by means of the command: -@noindent -Normally GNAT recognizes the Latin-1 character set in source program -identifiers, as described in the Ada Reference Manual. -This switch causes -GNAT to recognize alternate character sets in identifiers. @var{c} is a -single character indicating the character set, as follows: +@example +$ gnatls -v +@end example -@table @code -@item 1 -ISO 8859-1 (Latin-1) identifiers +The last entry in the object search path usually contains the +gnat library. This Makefile contains its own documentation and in +particular the set of instructions needed to rebuild a new library and +to use it. -@item 2 -ISO 8859-2 (Latin-2) letters allowed in identifiers +@geindex Conditional compilation -@item 3 -ISO 8859-3 (Latin-3) letters allowed in identifiers +@node Conditional Compilation,Mixed Language Programming,GNAT and Libraries,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id47}@anchor{9e}@anchor{gnat_ugn/the_gnat_compilation_model conditional-compilation}@anchor{18} +@section Conditional Compilation -@item 4 -ISO 8859-4 (Latin-4) letters allowed in identifiers -@item 5 -ISO 8859-5 (Cyrillic) letters allowed in identifiers +This section presents some guidelines for modeling conditional compilation in Ada and describes the +gnatprep preprocessor utility. -@item 9 -ISO 8859-15 (Latin-9) letters allowed in identifiers +@geindex Conditional compilation -@item p -IBM PC letters (code page 437) allowed in identifiers +@menu +* Modeling Conditional Compilation in Ada:: +* Preprocessing with gnatprep:: +* Integrated Preprocessing:: -@item 8 -IBM PC letters (code page 850) allowed in identifiers +@end menu -@item f -Full upper-half codes allowed in identifiers +@node Modeling Conditional Compilation in Ada,Preprocessing with gnatprep,,Conditional Compilation +@anchor{gnat_ugn/the_gnat_compilation_model modeling-conditional-compilation-in-ada}@anchor{9f}@anchor{gnat_ugn/the_gnat_compilation_model id48}@anchor{a0} +@subsection Modeling Conditional Compilation in Ada -@item n -No upper-half codes allowed in identifiers -@item w -Wide-character codes (that is, codes greater than 255) -allowed in identifiers -@end table +It is often necessary to arrange for a single source program +to serve multiple purposes, where it is compiled in different +ways to achieve these different goals. Some examples of the +need for this feature are -@xref{Foreign Language Representation}, for full details on the -implementation of these character sets. -@item -gnatW@var{e} -@cindex @option{-gnatW} (@command{gcc}) -Specify the method of encoding for wide characters. -@var{e} is one of the following: +@itemize * -@table @code +@item +Adapting a program to a different hardware environment -@item h -Hex encoding (brackets coding also recognized) +@item +Adapting a program to a different target architecture -@item u -Upper half encoding (brackets encoding also recognized) +@item +Turning debugging features on and off -@item s -Shift/JIS encoding (brackets encoding also recognized) +@item +Arranging for a program to compile with different compilers +@end itemize -@item e -EUC encoding (brackets encoding also recognized) +In C, or C++, the typical approach would be to use the preprocessor +that is defined as part of the language. The Ada language does not +contain such a feature. This is not an oversight, but rather a very +deliberate design decision, based on the experience that overuse of +the preprocessing features in C and C++ can result in programs that +are extremely difficult to maintain. For example, if we have ten +switches that can be on or off, this means that there are a thousand +separate programs, any one of which might not even be syntactically +correct, and even if syntactically correct, the resulting program +might not work correctly. Testing all combinations can quickly become +impossible. -@item 8 -UTF-8 encoding (brackets encoding also recognized) +Nevertheless, the need to tailor programs certainly exists, and in +this section we will discuss how this can +be achieved using Ada in general, and GNAT in particular. -@item b -Brackets encoding only (default value) -@end table -For full details on these encoding -methods see @ref{Wide_Character Encodings}. -Note that brackets coding is always accepted, even if one of the other -options is specified, so for example @option{-gnatW8} specifies that both -brackets and UTF-8 encodings will be recognized. The units that are -with'ed directly or indirectly will be scanned using the specified -representation scheme, and so if one of the non-brackets scheme is -used, it must be used consistently throughout the program. However, -since brackets encoding is always recognized, it may be conveniently -used in standard libraries, allowing these libraries to be used with -any of the available coding schemes. +@menu +* Use of Boolean Constants:: +* Debugging - A Special Case:: +* Conditionalizing Declarations:: +* Use of Alternative Implementations:: +* Preprocessing:: -Note that brackets encoding only applies to program text. Within comments, -brackets are considered to be normal graphic characters, and bracket sequences -are never recognized as wide characters. +@end menu -If no @option{-gnatW?} parameter is present, then the default -representation is normally Brackets encoding only. However, if the -first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard -byte order mark or BOM for UTF-8), then these three characters are -skipped and the default representation for the file is set to UTF-8. +@node Use of Boolean Constants,Debugging - A Special Case,,Modeling Conditional Compilation in Ada +@anchor{gnat_ugn/the_gnat_compilation_model id49}@anchor{a1}@anchor{gnat_ugn/the_gnat_compilation_model use-of-boolean-constants}@anchor{a2} +@subsubsection Use of Boolean Constants -Note that the wide character representation that is specified (explicitly -or by default) for the main program also acts as the default encoding used -for Wide_Text_IO files if not specifically overridden by a WCEM form -parameter. -@end table +In the case where the difference is simply which code +sequence is executed, the cleanest solution is to use Boolean +constants to control which code is executed. -When no @option{-gnatW?} is specified, then characters (other than wide -characters represented using brackets notation) are treated as 8-bit -Latin-1 codes. The codes recognized are the Latin-1 graphic characters, -and ASCII format effectors (CR, LF, HT, VT). Other lower half control -characters in the range 16#00#..16#1F# are not accepted in program text -or in comments. Upper half control characters (16#80#..16#9F#) are rejected -in program text, but allowed and ignored in comments. Note in particular -that the Next Line (NEL) character whose encoding is 16#85# is not recognized -as an end of line in this default mode. If your source program contains -instances of the NEL character used as a line terminator, -you must use UTF-8 encoding for the whole -source program. In default mode, all lines must be ended by a standard -end of line sequence (CR, CR/LF, or LF). +@example +FP_Initialize_Required : constant Boolean := True; +... +if FP_Initialize_Required then +... +end if; +@end example -Note that the convention of simply accepting all upper half characters in -comments means that programs that use standard ASCII for program text, but -UTF-8 encoding for comments are accepted in default mode, providing that the -comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator. -This is a common mode for many programs with foreign language comments. +Not only will the code inside the @cite{if} statement not be executed if +the constant Boolean is @cite{False}, but it will also be completely +deleted from the program. +However, the code is only deleted after the @cite{if} statement +has been checked for syntactic and semantic correctness. +(In contrast, with preprocessors the code is deleted before the +compiler ever gets to see it, so it is not checked until the switch +is turned on.) -@node File Naming Control -@subsection File Naming Control +@geindex Preprocessors (contrasted with conditional compilation) -@table @option -@item -gnatk@var{n} -@cindex @option{-gnatk} (@command{gcc}) -Activates file name ``krunching''. @var{n}, a decimal integer in the range -1-999, indicates the maximum allowable length of a file name (not -including the @file{.ads} or @file{.adb} extension). The default is not -to enable file name krunching. +Typically the Boolean constants will be in a separate package, +something like: -For the source file naming rules, @xref{File Naming Rules}. -@end table +@example +package Config is + FP_Initialize_Required : constant Boolean := True; + Reset_Available : constant Boolean := False; + ... +end Config; +@end example -@node Subprogram Inlining Control -@subsection Subprogram Inlining Control +The @cite{Config} package exists in multiple forms for the various targets, +with an appropriate script selecting the version of @cite{Config} needed. +Then any other unit requiring conditional compilation can do a @emph{with} +of @cite{Config} to make the constants visible. -@table @option -@c !sort! -@item -gnatn[12] -@cindex @option{-gnatn} (@command{gcc}) -The @code{n} here is intended to suggest the first syllable of the -word ``inline''. -GNAT recognizes and processes @code{Inline} pragmas. However, for the -inlining to actually occur, optimization must be enabled and, in order -to enable inlining of subprograms specified by pragma @code{Inline}, -you must also specify this switch. -In the absence of this switch, GNAT does not attempt -inlining and does not need to access the bodies of -subprograms for which @code{pragma Inline} is specified if they are not -in the current unit. +@node Debugging - A Special Case,Conditionalizing Declarations,Use of Boolean Constants,Modeling Conditional Compilation in Ada +@anchor{gnat_ugn/the_gnat_compilation_model debugging-a-special-case}@anchor{a3}@anchor{gnat_ugn/the_gnat_compilation_model id50}@anchor{a4} +@subsubsection Debugging - A Special Case -You can optionally specify the inlining level: 1 for moderate inlining across -modules, which is a good compromise between compilation times and performances -at run time, or 2 for full inlining across modules, which may bring about -longer compilation times. If no inlining level is specified, the compiler will -pick it based on the optimization level: 1 for @option{-O1}, @option{-O2} or -@option{-Os} and 2 for @option{-O3}. -If you specify this switch the compiler will access these bodies, -creating an extra source dependency for the resulting object file, and -where possible, the call will be inlined. -For further details on when inlining is possible -see @ref{Inlining of Subprograms}. +A common use of conditional code is to execute statements (for example +dynamic checks, or output of intermediate results) under control of a +debug switch, so that the debugging behavior can be turned on and off. +This can be done using a Boolean constant to control whether the code +is active: -@item -gnatN -@cindex @option{-gnatN} (@command{gcc}) -This switch activates front-end inlining which also -generates additional dependencies. +@example +if Debugging then + Put_Line ("got to the first stage!"); +end if; +@end example -When using a gcc-based back end (in practice this means using any version -of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of -@option{-gnatN} is deprecated, and the use of @option{-gnatn} is preferred. -Historically front end inlining was more extensive than the gcc back end -inlining, but that is no longer the case. -@end table +or -@node Auxiliary Output Control -@subsection Auxiliary Output Control +@example +if Debugging and then Temperature > 999.0 then + raise Temperature_Crazy; +end if; +@end example -@table @option -@item -gnatt -@cindex @option{-gnatt} (@command{gcc}) -@cindex Writing internal trees -@cindex Internal trees, writing to file -Causes GNAT to write the internal tree for a unit to a file (with the -extension @file{.adt}. -This not normally required, but is used by separate analysis tools. -Typically -these tools do the necessary compilations automatically, so you should -not have to specify this switch in normal operation. -Note that the combination of switches @option{-gnatct} -generates a tree in the form required by ASIS applications. +@geindex pragma Assert -@item -gnatu -@cindex @option{-gnatu} (@command{gcc}) -Print a list of units required by this compilation on @file{stdout}. -The listing includes all units on which the unit being compiled depends -either directly or indirectly. +Since this is a common case, there are special features to deal with +this in a convenient manner. For the case of tests, Ada 2005 has added +a pragma @cite{Assert} that can be used for such tests. This pragma is modeled +on the @cite{Assert} pragma that has always been available in GNAT, so this +feature may be used with GNAT even if you are not using Ada 2005 features. +The use of pragma @cite{Assert} is described in the +@cite{GNAT_Reference_Manual}, but as an +example, the last test could be written: -@item -pass-exit-codes -@cindex @option{-pass-exit-codes} (@command{gcc}) -If this switch is not used, the exit code returned by @command{gcc} when -compiling multiple files indicates whether all source files have -been successfully used to generate object files or not. +@example +pragma Assert (Temperature <= 999.0, "Temperature Crazy"); +@end example -When @option{-pass-exit-codes} is used, @command{gcc} exits with an extended -exit status and allows an integrated development environment to better -react to a compilation failure. Those exit status are: +or simply -@table @asis -@item 5 -There was an error in at least one source file. -@item 3 -At least one source file did not generate an object file. -@item 2 -The compiler died unexpectedly (internal error for example). -@item 0 -An object file has been generated for every source file. -@end table -@end table +@example +pragma Assert (Temperature <= 999.0); +@end example -@node Debugging Control -@subsection Debugging Control +In both cases, if assertions are active and the temperature is excessive, +the exception @cite{Assert_Failure} will be raised, with the given string in +the first case or a string indicating the location of the pragma in the second +case used as the exception message. -@table @option -@c !sort! -@cindex Debugging options -@item -gnatd@var{x} -@cindex @option{-gnatd} (@command{gcc}) -Activate internal debugging switches. @var{x} is a letter or digit, or -string of letters or digits, which specifies the type of debugging -outputs desired. Normally these are used only for internal development -or system debugging purposes. You can find full documentation for these -switches in the body of the @code{Debug} unit in the compiler source -file @file{debug.adb}. +@geindex pragma Assertion_Policy -@item -gnatG[=nn] -@cindex @option{-gnatG} (@command{gcc}) -This switch causes the compiler to generate auxiliary output containing -a pseudo-source listing of the generated expanded code. Like most Ada -compilers, GNAT works by first transforming the high level Ada code into -lower level constructs. For example, tasking operations are transformed -into calls to the tasking run-time routines. A unique capability of GNAT -is to list this expanded code in a form very close to normal Ada source. -This is very useful in understanding the implications of various Ada -usage on the efficiency of the generated code. There are many cases in -Ada (e.g.@: the use of controlled types), where simple Ada statements can -generate a lot of run-time code. By using @option{-gnatG} you can identify -these cases, and consider whether it may be desirable to modify the coding -approach to improve efficiency. +You can turn assertions on and off by using the @cite{Assertion_Policy} +pragma. -The optional parameter @code{nn} if present after -gnatG specifies an -alternative maximum line length that overrides the normal default of 72. -This value is in the range 40-999999, values less than 40 being silently -reset to 40. The equal sign is optional. +@geindex -gnata switch -The format of the output is very similar to standard Ada source, and is -easily understood by an Ada programmer. The following special syntactic -additions correspond to low level features used in the generated code that -do not have any exact analogies in pure Ada source form. The following -is a partial list of these special constructions. See the spec -of package @code{Sprint} in file @file{sprint.ads} for a full list. +This is an Ada 2005 pragma which is implemented in all modes by +GNAT. Alternatively, you can use the @emph{-gnata} switch +to enable assertions from the command line, which applies to +all versions of Ada. -If the switch @option{-gnatL} is used in conjunction with -@cindex @option{-gnatL} (@command{gcc}) -@option{-gnatG}, then the original source lines are interspersed -in the expanded source (as comment lines with the original line number). +@geindex pragma Debug -@table @code -@item new @var{xxx} @r{[}storage_pool = @var{yyy}@r{]} -Shows the storage pool being used for an allocator. +For the example above with the @cite{Put_Line}, the GNAT-specific pragma +@cite{Debug} can be used: -@item at end @var{procedure-name}; -Shows the finalization (cleanup) procedure for a scope. +@example +pragma Debug (Put_Line ("got to the first stage!")); +@end example -@item (if @var{expr} then @var{expr} else @var{expr}) -Conditional expression equivalent to the @code{x?y:z} construction in C. +If debug pragmas are enabled, the argument, which must be of the form of +a procedure call, is executed (in this case, @cite{Put_Line} will be called). +Only one call can be present, but of course a special debugging procedure +containing any code you like can be included in the program and then +called in a pragma @cite{Debug} argument as needed. -@item @var{target}^(@var{source}) -A conversion with floating-point truncation instead of rounding. +One advantage of pragma @cite{Debug} over the @cite{if Debugging then} +construct is that pragma @cite{Debug} can appear in declarative contexts, +such as at the very beginning of a procedure, before local declarations have +been elaborated. -@item @var{target}?(@var{source}) -A conversion that bypasses normal Ada semantic checking. In particular -enumeration types and fixed-point types are treated simply as integers. +@geindex pragma Debug_Policy -@item @var{target}?^(@var{source}) -Combines the above two cases. +Debug pragmas are enabled using either the @emph{-gnata} switch that also +controls assertions, or with a separate Debug_Policy pragma. -@item @var{x} #/ @var{y} -@itemx @var{x} #mod @var{y} -@itemx @var{x} #* @var{y} -@itemx @var{x} #rem @var{y} -A division or multiplication of fixed-point values which are treated as -integers without any kind of scaling. +The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used +in Ada 95 and Ada 83 programs as well), and is analogous to +pragma @cite{Assertion_Policy} to control assertions. -@item free @var{expr} @r{[}storage_pool = @var{xxx}@r{]} -Shows the storage pool associated with a @code{free} statement. +@cite{Assertion_Policy} and @cite{Debug_Policy} are configuration pragmas, +and thus they can appear in @code{gnat.adc} if you are not using a +project file, or in the file designated to contain configuration pragmas +in a project file. +They then apply to all subsequent compilations. In practice the use of +the @emph{-gnata} switch is often the most convenient method of controlling +the status of these pragmas. -@item [subtype or type declaration] -Used to list an equivalent declaration for an internally generated -type that is referenced elsewhere in the listing. +Note that a pragma is not a statement, so in contexts where a statement +sequence is required, you can't just write a pragma on its own. You have +to add a @cite{null} statement. -@c @item freeze @var{type-name} @ovar{actions} -@c Expanding @ovar macro inline (explanation in macro def comments) -@item freeze @var{type-name} @r{[}@var{actions}@r{]} -Shows the point at which @var{type-name} is frozen, with possible -associated actions to be performed at the freeze point. +@example +if ... then + ... -- some statements +else + pragma Assert (Num_Cases < 10); + null; +end if; +@end example -@item reference @var{itype} -Reference (and hence definition) to internal type @var{itype}. +@node Conditionalizing Declarations,Use of Alternative Implementations,Debugging - A Special Case,Modeling Conditional Compilation in Ada +@anchor{gnat_ugn/the_gnat_compilation_model conditionalizing-declarations}@anchor{a5}@anchor{gnat_ugn/the_gnat_compilation_model id51}@anchor{a6} +@subsubsection Conditionalizing Declarations -@item @var{function-name}! (@var{arg}, @var{arg}, @var{arg}) -Intrinsic function call. -@item @var{label-name} : label -Declaration of label @var{labelname}. +In some cases it may be necessary to conditionalize declarations to meet +different requirements. For example we might want a bit string whose length +is set to meet some hardware message requirement. -@item #$ @var{subprogram-name} -An implicit call to a run-time support routine -(to meet the requirement of H.3.1(9) in a -convenient manner). +This may be possible using declare blocks controlled +by conditional constants: -@item @var{expr} && @var{expr} && @var{expr} @dots{} && @var{expr} -A multiple concatenation (same effect as @var{expr} & @var{expr} & -@var{expr}, but handled more efficiently). +@example +if Small_Machine then + declare + X : Bit_String (1 .. 10); + begin + ... + end; +else + declare + X : Large_Bit_String (1 .. 1000); + begin + ... + end; +end if; +@end example -@item [constraint_error] -Raise the @code{Constraint_Error} exception. +Note that in this approach, both declarations are analyzed by the +compiler so this can only be used where both declarations are legal, +even though one of them will not be used. -@item @var{expression}'reference -A pointer to the result of evaluating @var{expression}. +Another approach is to define integer constants, e.g., @cite{Bits_Per_Word}, +or Boolean constants, e.g., @cite{Little_Endian}, and then write declarations +that are parameterized by these constants. For example -@item @var{target-type}!(@var{source-expression}) -An unchecked conversion of @var{source-expression} to @var{target-type}. +@example +for Rec use + Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word; +end record; +@end example -@item [@var{numerator}/@var{denominator}] -Used to represent internal real literals (that) have no exact -representation in base 2-16 (for example, the result of compile time -evaluation of the expression 1.0/27.0). -@end table +If @cite{Bits_Per_Word} is set to 32, this generates either -@item -gnatD[=nn] -@cindex @option{-gnatD} (@command{gcc}) -When used in conjunction with @option{-gnatG}, this switch causes -the expanded source, as described above for -@option{-gnatG} to be written to files with names -@file{xxx.dg}, where @file{xxx} is the normal file name, -instead of to the standard output file. For -example, if the source file name is @file{hello.adb}, then a file -@file{hello.adb.dg} will be written. The debugging -information generated by the @command{gcc} @option{-g} switch -will refer to the generated @file{xxx.dg} file. This allows -you to do source level debugging using the generated code which is -sometimes useful for complex code, for example to find out exactly -which part of a complex construction raised an exception. This switch -also suppress generation of cross-reference information (see -@option{-gnatx}) since otherwise the cross-reference information -would refer to the @file{.dg} file, which would cause -confusion since this is not the original source file. +@example +for Rec use + Field1 at 0 range 0 .. 32; +end record; +@end example -Note that @option{-gnatD} actually implies @option{-gnatG} -automatically, so it is not necessary to give both options. -In other words @option{-gnatD} is equivalent to @option{-gnatDG}). +for the big endian case, or -If the switch @option{-gnatL} is used in conjunction with -@cindex @option{-gnatL} (@command{gcc}) -@option{-gnatDG}, then the original source lines are interspersed -in the expanded source (as comment lines with the original line number). +@example +for Rec use record + Field1 at 0 range 10 .. 32; +end record; +@end example -The optional parameter @code{nn} if present after -gnatD specifies an -alternative maximum line length that overrides the normal default of 72. -This value is in the range 40-999999, values less than 40 being silently -reset to 40. The equal sign is optional. +for the little endian case. Since a powerful subset of Ada expression +notation is usable for creating static constants, clever use of this +feature can often solve quite difficult problems in conditionalizing +compilation (note incidentally that in Ada 95, the little endian +constant was introduced as @cite{System.Default_Bit_Order}, so you do not +need to define this one yourself). -@item -gnatr -@cindex @option{-gnatr} (@command{gcc}) -@cindex pragma Restrictions -This switch causes pragma Restrictions to be treated as Restriction_Warnings -so that violation of restrictions causes warnings rather than illegalities. -This is useful during the development process when new restrictions are added -or investigated. The switch also causes pragma Profile to be treated as -Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set -restriction warnings rather than restrictions. +@node Use of Alternative Implementations,Preprocessing,Conditionalizing Declarations,Modeling Conditional Compilation in Ada +@anchor{gnat_ugn/the_gnat_compilation_model use-of-alternative-implementations}@anchor{a7}@anchor{gnat_ugn/the_gnat_compilation_model id52}@anchor{a8} +@subsubsection Use of Alternative Implementations -@item -gnatR@r{[}0@r{|}1@r{|}2@r{|}3@r{[}s@r{]]} -@cindex @option{-gnatR} (@command{gcc}) -This switch controls output from the compiler of a listing showing -representation information for declared types and objects. For -@option{-gnatR0}, no information is output (equivalent to omitting -the @option{-gnatR} switch). For @option{-gnatR1} (which is the default, -so @option{-gnatR} with no parameter has the same effect), size and alignment -information is listed for declared array and record types. For -@option{-gnatR2}, size and alignment information is listed for all -declared types and objects. The @code{Linker_Section} is also listed for any -entity for which the @code{Linker_Section} is set explicitly or implicitly (the -latter case occurs for objects of a type for which a @code{Linker_Section} -is set). -Finally @option{-gnatR3} includes symbolic -expressions for values that are computed at run time for -variant records. These symbolic expressions have a mostly obvious -format with #n being used to represent the value of the n'th -discriminant. See source files @file{repinfo.ads/adb} in the -@code{GNAT} sources for full details on the format of @option{-gnatR3} -output. If the switch is followed by an s (e.g.@: @option{-gnatR2s}), then -the output is to a file with the name @file{file.rep} where -file is the name of the corresponding source file. +In some cases, none of the approaches described above are adequate. This +can occur for example if the set of declarations required is radically +different for two different configurations. -@item -gnatRm[s] -This form of the switch controls output of subprogram conventions -and parameter passing mechanisms for all subprograms. A following -@code{s} means output to a file as described above. +In this situation, the official Ada way of dealing with conditionalizing +such code is to write separate units for the different cases. As long as +this does not result in excessive duplication of code, this can be done +without creating maintenance problems. The approach is to share common +code as far as possible, and then isolate the code and declarations +that are different. Subunits are often a convenient method for breaking +out a piece of a unit that is to be conditionalized, with separate files +for different versions of the subunit for different targets, where the +build script selects the right one to give to the compiler. -Note that it is possible for record components to have zero size. In -this case, the component clause uses an obvious extension of permitted -Ada syntax, for example @code{at 0 range 0 .. -1}. +@geindex Subunits (and conditional compilation) -Representation information requires that code be generated (since it is the -code generator that lays out complex data structures). If an attempt is made -to output representation information when no code is generated, for example -when a subunit is compiled on its own, then no information can be generated -and the compiler outputs a message to this effect. +As an example, consider a situation where a new feature in Ada 2005 +allows something to be done in a really nice way. But your code must be able +to compile with an Ada 95 compiler. Conceptually you want to say: -@item -gnatS -@cindex @option{-gnatS} (@command{gcc}) -The use of the switch @option{-gnatS} for an -Ada compilation will cause the compiler to output a -representation of package Standard in a form very -close to standard Ada. It is not quite possible to -do this entirely in standard Ada (since new -numeric base types cannot be created in standard -Ada), but the output is easily -readable to any Ada programmer, and is useful to -determine the characteristics of target dependent -types in package Standard. +@example +if Ada_2005 then + ... neat Ada 2005 code +else + ... not quite as neat Ada 95 code +end if; +@end example -@item -gnatx -@cindex @option{-gnatx} (@command{gcc}) -Normally the compiler generates full cross-referencing information in -the @file{ALI} file. This information is used by a number of tools, -including @code{gnatfind} and @code{gnatxref}. The @option{-gnatx} switch -suppresses this information. This saves some space and may slightly -speed up compilation, but means that these tools cannot be used. -@end table +where @cite{Ada_2005} is a Boolean constant. -@node Exception Handling Control -@subsection Exception Handling Control +But this won't work when @cite{Ada_2005} is set to @cite{False}, +since the @cite{then} clause will be illegal for an Ada 95 compiler. +(Recall that although such unreachable code would eventually be deleted +by the compiler, it still needs to be legal. If it uses features +introduced in Ada 2005, it will be illegal in Ada 95.) -@noindent -GNAT uses two methods for handling exceptions at run-time. The -@code{setjmp/longjmp} method saves the context when entering -a frame with an exception handler. Then when an exception is -raised, the context can be restored immediately, without the -need for tracing stack frames. This method provides very fast -exception propagation, but introduces significant overhead for -the use of exception handlers, even if no exception is raised. +So instead we write -The other approach is called ``zero cost'' exception handling. -With this method, the compiler builds static tables to describe -the exception ranges. No dynamic code is required when entering -a frame containing an exception handler. When an exception is -raised, the tables are used to control a back trace of the -subprogram invocation stack to locate the required exception -handler. This method has considerably poorer performance for -the propagation of exceptions, but there is no overhead for -exception handlers if no exception is raised. Note that in this -mode and in the context of mixed Ada and C/C++ programming, -to propagate an exception through a C/C++ code, the C/C++ code -must be compiled with the @option{-funwind-tables} GCC's -option. +@example +procedure Insert is separate; +@end example -The following switches may be used to control which of the -two exception handling methods is used. +Then we have two files for the subunit @cite{Insert}, with the two sets of +code. +If the package containing this is called @cite{File_Queries}, then we might +have two files -@table @option -@c !sort! -@item --RTS=sjlj -@cindex @option{--RTS=sjlj} (@command{gnatmake}) -This switch causes the setjmp/longjmp run-time (when available) to be used -for exception handling. If the default -mechanism for the target is zero cost exceptions, then -this switch can be used to modify this default, and must be -used for all units in the partition. -This option is rarely used. One case in which it may be -advantageous is if you have an application where exception -raising is common and the overall performance of the -application is improved by favoring exception propagation. +@itemize * -@item --RTS=zcx -@cindex @option{--RTS=zcx} (@command{gnatmake}) -@cindex Zero Cost Exceptions -This switch causes the zero cost approach to be used -for exception handling. If this is the default mechanism for the -target (see below), then this switch is unneeded. If the default -mechanism for the target is setjmp/longjmp exceptions, then -this switch can be used to modify this default, and must be -used for all units in the partition. -This option can only be used if the zero cost approach -is available for the target in use, otherwise it will generate an error. -@end table +@item +@code{file_queries-insert-2005.adb} -@noindent -The same option @option{--RTS} must be used both for @command{gcc} -and @command{gnatbind}. Passing this option to @command{gnatmake} -(@pxref{Switches for gnatmake}) will ensure the required consistency -through the compilation and binding steps. +@item +@code{file_queries-insert-95.adb} +@end itemize -@node Units to Sources Mapping Files -@subsection Units to Sources Mapping Files - -@table @option - -@item -gnatem=@var{path} -@cindex @option{-gnatem} (@command{gcc}) -A mapping file is a way to communicate to the compiler two mappings: -from unit names to file names (without any directory information) and from -file names to path names (with full directory information). These mappings -are used by the compiler to short-circuit the path search. +and the build script renames the appropriate file to @code{file_queries-insert.adb} and then carries out the compilation. -The use of mapping files is not required for correct operation of the -compiler, but mapping files can improve efficiency, particularly when -sources are read over a slow network connection. In normal operation, -you need not be concerned with the format or use of mapping files, -and the @option{-gnatem} switch is not a switch that you would use -explicitly. It is intended primarily for use by automatic tools such as -@command{gnatmake} running under the project file facility. The -description here of the format of mapping files is provided -for completeness and for possible use by other tools. +This can also be done with project files' naming schemes. For example: -A mapping file is a sequence of sets of three lines. In each set, the -first line is the unit name, in lower case, with @code{%s} appended -for specs and @code{%b} appended for bodies; the second line is the -file name; and the third line is the path name. +@example +for body ("File_Queries.Insert") use "file_queries-insert-2005.ada"; +@end example -Example: -@smallexample - main%b - main.2.ada - /gnat/project1/sources/main.2.ada -@end smallexample +Note also that with project files it is desirable to use a different extension +than @code{ads} / @code{adb} for alternative versions. Otherwise a naming +conflict may arise through another commonly used feature: to declare as part +of the project a set of directories containing all the sources obeying the +default naming scheme. -When the switch @option{-gnatem} is specified, the compiler will -create in memory the two mappings from the specified file. If there is -any problem (nonexistent file, truncated file or duplicate entries), -no mapping will be created. +The use of alternative units is certainly feasible in all situations, +and for example the Ada part of the GNAT run-time is conditionalized +based on the target architecture using this approach. As a specific example, +consider the implementation of the AST feature in VMS. There is one +spec: @code{s-asthan.ads} which is the same for all architectures, and three +bodies: -Several @option{-gnatem} switches may be specified; however, only the -last one on the command line will be taken into account. -When using a project file, @command{gnatmake} creates a temporary -mapping file and communicates it to the compiler using this switch. +@itemize * -@end table +@item -@node Integrated Preprocessing -@subsection Integrated Preprocessing +@table @asis -@noindent -GNAT sources may be preprocessed immediately before compilation. -In this case, the actual -text of the source is not the text of the source file, but is derived from it -through a process called preprocessing. Integrated preprocessing is specified -through switches @option{-gnatep} and/or @option{-gnateD}. @option{-gnatep} -indicates, through a text file, the preprocessing data to be used. -@option{-gnateD} specifies or modifies the values of preprocessing symbol. -Note that integrated preprocessing applies only to Ada source files, it is -not available for configuration pragma files. +@item @code{s-asthan.adb} -@noindent -Note that when integrated preprocessing is used, the output from the -preprocessor is not written to any external file. Instead it is passed -internally to the compiler. If you need to preserve the result of -preprocessing in a file, then you should use @command{gnatprep} -to perform the desired preprocessing in stand-alone mode. +used for all non-VMS operating systems +@end table -@noindent -It is recommended that @command{gnatmake} switch -s should be -used when Integrated Preprocessing is used. The reason is that preprocessing -with another Preprocessing Data file without changing the sources will -not trigger recompilation without this switch. +@item -@noindent -Note that @command{gnatmake} switch -m will almost -always trigger recompilation for sources that are preprocessed, -because @command{gnatmake} cannot compute the checksum of the source after -preprocessing. +@table @asis -@noindent -The actual preprocessing function is described in details in section -@ref{Preprocessing with gnatprep}. This section only describes how integrated -preprocessing is triggered and parameterized. +@item @code{s-asthan-vms-alpha.adb} -@table @code +used for VMS on the Alpha +@end table -@item -gnatep=@var{file} -@cindex @option{-gnatep} (@command{gcc}) -This switch indicates to the compiler the file name (without directory -information) of the preprocessor data file to use. The preprocessor data file -should be found in the source directories. Note that when the compiler is -called by a builder such as (@command{gnatmake} with a project -file, if the object directory is not also a source directory, the builder needs -to be called with @option{-x}. +@item -@noindent -A preprocessing data file is a text file with significant lines indicating -how should be preprocessed either a specific source or all sources not -mentioned in other lines. A significant line is a nonempty, non-comment line. -Comments are similar to Ada comments. +@table @asis -@noindent -Each significant line starts with either a literal string or the character '*'. -A literal string is the file name (without directory information) of the source -to preprocess. A character '*' indicates the preprocessing for all the sources -that are not specified explicitly on other lines (order of the lines is not -significant). It is an error to have two lines with the same file name or two -lines starting with the character '*'. +@item @code{s-asthan-vms-ia64.adb} -@noindent -After the file name or the character '*', another optional literal string -indicating the file name of the definition file to be used for preprocessing -(@pxref{Form of Definitions File}). The definition files are found by the -compiler in one of the source directories. In some cases, when compiling -a source in a directory other than the current directory, if the definition -file is in the current directory, it may be necessary to add the current -directory as a source directory through switch -I., otherwise -the compiler would not find the definition file. +used for VMS on the ia64 +@end table +@end itemize -@noindent -Then, optionally, switches similar to those of @code{gnatprep} may -be found. Those switches are: +The dummy version @code{s-asthan.adb} simply raises exceptions noting that +this operating system feature is not available, and the two remaining +versions interface with the corresponding versions of VMS to provide +VMS-compatible AST handling. The GNAT build script knows the architecture +and operating system, and automatically selects the right version, +renaming it if necessary to @code{s-asthan.adb} before the run-time build. -@table @code +Another style for arranging alternative implementations is through Ada's +access-to-subprogram facility. +In case some functionality is to be conditionally included, +you can declare an access-to-procedure variable @cite{Ref} that is initialized +to designate a 'do nothing' procedure, and then invoke @cite{Ref.all} +when appropriate. +In some library package, set @cite{Ref} to @cite{Proc'Access} for some +procedure @cite{Proc} that performs the relevant processing. +The initialization only occurs if the library package is included in the +program. +The same idea can also be implemented using tagged types and dispatching +calls. -@item -b -Causes both preprocessor lines and the lines deleted by -preprocessing to be replaced by blank lines, preserving the line number. -This switch is always implied; however, if specified after @option{-c} -it cancels the effect of @option{-c}. +@node Preprocessing,,Use of Alternative Implementations,Modeling Conditional Compilation in Ada +@anchor{gnat_ugn/the_gnat_compilation_model preprocessing}@anchor{a9}@anchor{gnat_ugn/the_gnat_compilation_model id53}@anchor{aa} +@subsubsection Preprocessing -@item -c -Causes both preprocessor lines and the lines deleted -by preprocessing to be retained as comments marked -with the special string ``@code{--! }''. -@item -Dsymbol=value -Define or redefine a symbol, associated with value. A symbol is an Ada -identifier, or an Ada reserved word, with the exception of @code{if}, -@code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}. -@code{value} is either a literal string, an Ada identifier or any Ada reserved -word. A symbol declared with this switch replaces a symbol with the -same name defined in a definition file. +@geindex Preprocessing -@item -s -Causes a sorted list of symbol names and values to be -listed on the standard output file. +Although it is quite possible to conditionalize code without the use of +C-style preprocessing, as described earlier in this section, it is +nevertheless convenient in some cases to use the C approach. Moreover, +older Ada compilers have often provided some preprocessing capability, +so legacy code may depend on this approach, even though it is not +standard. -@item -u -Causes undefined symbols to be treated as having the value @code{FALSE} -in the context -of a preprocessor test. In the absence of this option, an undefined symbol in -a @code{#if} or @code{#elsif} test will be treated as an error. +To accommodate such use, GNAT provides a preprocessor (modeled to a large +extent on the various preprocessors that have been used +with legacy code on other compilers, to enable easier transition). -@end table +@geindex gnatprep -@noindent -Examples of valid lines in a preprocessor data file: +The preprocessor may be used in two separate modes. It can be used quite +separately from the compiler, to generate a separate output source file +that is then fed to the compiler as a separate step. This is the +@cite{gnatprep} utility, whose use is fully described in +@ref{19,,Preprocessing with gnatprep}. -@smallexample - "toto.adb" "prep.def" -u - -- preprocess "toto.adb", using definition file "prep.def", - -- undefined symbol are False. +The preprocessing language allows such constructs as - * -c -DVERSION=V101 - -- preprocess all other sources without a definition file; - -- suppressed lined are commented; symbol VERSION has the value V101. +@example +#if DEBUG or else (PRIORITY > 4) then + bunch of declarations +#else + completely different bunch of declarations +#end if; +@end example - "titi.adb" "prep2.def" -s - -- preprocess "titi.adb", using definition file "prep2.def"; - -- list all symbols with their values. -@end smallexample +The values of the symbols @cite{DEBUG} and @cite{PRIORITY} can be +defined either on the command line or in a separate file. -@item -gnateDsymbol@r{[}=value@r{]} -@cindex @option{-gnateD} (@command{gcc}) -Define or redefine a preprocessing symbol, associated with value. If no value -is given on the command line, then the value of the symbol is @code{True}. -A symbol is an identifier, following normal Ada (case-insensitive) -rules for its syntax, and value is either an arbitrary string between double -quotes or any sequence (including an empty sequence) of characters from the -set (letters, digits, period, underline). -Ada reserved words may be used as symbols, with the exceptions of @code{if}, -@code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}. +The other way of running the preprocessor is even closer to the C style and +often more convenient. In this approach the preprocessing is integrated into +the compilation process. The compiler is fed the preprocessor input which +includes @cite{#if} lines etc, and then the compiler carries out the +preprocessing internally and processes the resulting output. +For more details on this approach, see @ref{1a,,Integrated Preprocessing}. -@noindent -Examples: +@node Preprocessing with gnatprep,Integrated Preprocessing,Modeling Conditional Compilation in Ada,Conditional Compilation +@anchor{gnat_ugn/the_gnat_compilation_model id54}@anchor{ab}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-with-gnatprep}@anchor{19} +@subsection Preprocessing with @cite{gnatprep} -@smallexample - -gnateDToto=Titi - -gnateDFoo - -gnateDFoo=\"Foo-Bar\" -@end smallexample -@noindent -A symbol declared with this switch on the command line replaces a -symbol with the same name either in a definition file or specified with a -switch -D in the preprocessor data file. +@geindex gnatprep -@noindent -This switch is similar to switch @option{-D} of @code{gnatprep}. +@geindex Preprocessing (gnatprep) -@item -gnateG -When integrated preprocessing is performed and the preprocessor modifies -the source text, write the result of this preprocessing into a file -.prep. +This section discusses how to use GNAT's @cite{gnatprep} utility for simple +preprocessing. +Although designed for use with GNAT, @cite{gnatprep} does not depend on any +special GNAT features. +For further discussion of conditional compilation in general, see +@ref{18,,Conditional Compilation}. -@end table +@menu +* Preprocessing Symbols:: +* Using gnatprep:: +* Switches for gnatprep:: +* Form of Definitions File:: +* Form of Input Text for gnatprep:: -@node Code Generation Control -@subsection Code Generation Control +@end menu -@noindent +@node Preprocessing Symbols,Using gnatprep,,Preprocessing with gnatprep +@anchor{gnat_ugn/the_gnat_compilation_model id55}@anchor{ac}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-symbols}@anchor{ad} +@subsubsection Preprocessing Symbols -The GCC technology provides a wide range of target dependent -@option{-m} switches for controlling -details of code generation with respect to different versions of -architectures. This includes variations in instruction sets (e.g.@: -different members of the power pc family), and different requirements -for optimal arrangement of instructions (e.g.@: different members of -the x86 family). The list of available @option{-m} switches may be -found in the GCC documentation. -Use of these @option{-m} switches may in some cases result in improved -code performance. +Preprocessing symbols are defined in definition files and referred to in +sources to be preprocessed. A Preprocessing symbol is an identifier, following +normal Ada (case-insensitive) rules for its syntax, with the restriction that +all characters need to be in the ASCII set (no accented letters). -The @value{EDITION} technology is tested and qualified without any -@option{-m} switches, -so generally the most reliable approach is to avoid the use of these -switches. However, we generally expect most of these switches to work -successfully with @value{EDITION}, and many customers have reported successful -use of these options. +@node Using gnatprep,Switches for gnatprep,Preprocessing Symbols,Preprocessing with gnatprep +@anchor{gnat_ugn/the_gnat_compilation_model using-gnatprep}@anchor{ae}@anchor{gnat_ugn/the_gnat_compilation_model id56}@anchor{af} +@subsubsection Using @cite{gnatprep} -Our general advice is to avoid the use of @option{-m} switches unless -special needs lead to requirements in this area. In particular, -there is no point in using @option{-m} switches to improve performance -unless you actually see a performance improvement. +To call @cite{gnatprep} use: -@node Search Paths and the Run-Time Library (RTL) -@section Search Paths and the Run-Time Library (RTL) +@example +$ gnatprep [`switches`] `infile` `outfile` [`deffile`] +@end example -@noindent -With the GNAT source-based library system, the compiler must be able to -find source files for units that are needed by the unit being compiled. -Search paths are used to guide this process. +where -The compiler compiles one source file whose name must be given -explicitly on the command line. In other words, no searching is done -for this file. To find all other source files that are needed (the most -common being the specs of units), the compiler examines the following -directories, in the following order: -@enumerate -@item -The directory containing the source file of the main unit being compiled -(the file name on the command line). +@itemize * -@item -Each directory named by an @option{-I} switch given on the -@command{gcc} command line, in the order given. +@item -@item -@findex ADA_PRJ_INCLUDE_FILE -Each of the directories listed in the text file whose name is given -by the @env{ADA_PRJ_INCLUDE_FILE} environment variable. +@table @asis -@noindent -@env{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat -driver when project files are used. It should not normally be set -by other means. +@item @emph{switches} -@item -@findex ADA_INCLUDE_PATH -Each of the directories listed in the value of the -@env{ADA_INCLUDE_PATH} environment variable. -Construct this value -exactly as the @env{PATH} environment variable: a list of directory -names separated by colons (semicolons when working with the NT version). +is an optional sequence of switches as described in the next section. +@end table -@item -The content of the @file{ada_source_path} file which is part of the GNAT -installation tree and is used to store standard libraries such as the -GNAT Run Time Library (RTL) source files. -@ref{Installing a library} -@end enumerate +@item -@noindent -Specifying the switch @option{-I-} -inhibits the use of the directory -containing the source file named in the command line. You can still -have this directory on your search path, but in this case it must be -explicitly requested with a @option{-I} switch. +@table @asis -Specifying the switch @option{-nostdinc} -inhibits the search of the default location for the GNAT Run Time -Library (RTL) source files. +@item @emph{infile} -The compiler outputs its object files and ALI files in the current -working directory. -Caution: The object file can be redirected with the @option{-o} switch; -however, @command{gcc} and @code{gnat1} have not been coordinated on this -so the @file{ALI} file will not go to the right place. Therefore, you should -avoid using the @option{-o} switch. - -@findex System.IO -The packages @code{Ada}, @code{System}, and @code{Interfaces} and their -children make up the GNAT RTL, together with the simple @code{System.IO} -package used in the @code{"Hello World"} example. The sources for these units -are needed by the compiler and are kept together in one directory. Not -all of the bodies are needed, but all of the sources are kept together -anyway. In a normal installation, you need not specify these directory -names when compiling or binding. Either the environment variables or -the built-in defaults cause these files to be found. +is the full name of the input file, which is an Ada source +file containing preprocessor directives. +@end table -In addition to the language-defined hierarchies (@code{System}, @code{Ada} and -@code{Interfaces}), the GNAT distribution provides a fourth hierarchy, -consisting of child units of @code{GNAT}. This is a collection of generally -useful types, subprograms, etc. @xref{Top, GNAT Reference Manual, About -This Guid, gnat_rm, GNAT Reference Manual}, for further details. +@item -Besides simplifying access to the RTL, a major use of search paths is -in compiling sources from multiple directories. This can make -development environments much more flexible. +@table @asis -@node Order of Compilation Issues -@section Order of Compilation Issues +@item @emph{outfile} -@noindent -If, in our earlier example, there was a spec for the @code{hello} -procedure, it would be contained in the file @file{hello.ads}; yet this -file would not have to be explicitly compiled. This is the result of the -model we chose to implement library management. Some of the consequences -of this model are as follows: +is the full name of the output file, which is an Ada source +in standard Ada form. When used with GNAT, this file name will +normally have an ads or adb suffix. +@end table -@itemize @bullet -@item -There is no point in compiling specs (except for package -specs with no bodies) because these are compiled as needed by clients. If -you attempt a useless compilation, you will receive an error message. -It is also useless to compile subunits because they are compiled as needed -by the parent. +@item -@item -There are no order of compilation requirements: performing a -compilation never obsoletes anything. The only way you can obsolete -something and require recompilations is to modify one of the -source files on which it depends. +@table @asis -@item -There is no library as such, apart from the ALI files -(@pxref{The Ada Library Information Files}, for information on the format -of these files). For now we find it convenient to create separate ALI files, -but eventually the information therein may be incorporated into the object -file directly. +@item @emph{deffile} -@item -When you compile a unit, the source files for the specs of all units -that it @code{with}'s, all its subunits, and the bodies of any generics it -instantiates must be available (reachable by the search-paths mechanism -described above), or you will receive a fatal error message. +is the full name of a text file containing definitions of +preprocessing symbols to be referenced by the preprocessor. This argument is +optional, and can be replaced by the use of the @emph{-D} switch. +@end table @end itemize -@node Examples -@section Examples +@node Switches for gnatprep,Form of Definitions File,Using gnatprep,Preprocessing with gnatprep +@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatprep}@anchor{b0}@anchor{gnat_ugn/the_gnat_compilation_model id57}@anchor{b1} +@subsubsection Switches for @cite{gnatprep} -@noindent -The following are some typical Ada compilation command line examples: -@table @code -@item $ gcc -c xyz.adb -Compile body in file @file{xyz.adb} with all default options. +@geindex -b (gnatprep) -@item $ gcc -c -O2 -gnata xyz-def.adb -Compile the child unit package in file @file{xyz-def.adb} with extensive -optimizations, and pragma @code{Assert}/@code{Debug} statements -enabled. +@table @asis -@item $ gcc -c -gnatc abc-def.adb -Compile the subunit in file @file{abc-def.adb} in semantic-checking-only -mode. -@end table +@item @code{-b} -@node Binding with gnatbind -@chapter Binding with @code{gnatbind} -@findex gnatbind +Causes both preprocessor lines and the lines deleted by +preprocessing to be replaced by blank lines in the output source file, +preserving line numbers in the output file. +@end table -@menu -* Running gnatbind:: -* Switches for gnatbind:: -* Command-Line Access:: -* Search Paths for gnatbind:: -* Examples of gnatbind Usage:: -@end menu +@geindex -c (gnatprep) -@noindent -This chapter describes the GNAT binder, @code{gnatbind}, which is used -to bind compiled GNAT objects. -Note: to invoke @code{gnatbind} with a project file, use the @code{gnat} -driver (see @ref{The GNAT Driver and Project Files}). +@table @asis -The @code{gnatbind} program performs four separate functions: +@item @code{-c} -@enumerate -@item -Checks that a program is consistent, in accordance with the rules in -Chapter 10 of the Ada Reference Manual. In particular, error -messages are generated if a program uses inconsistent versions of a -given unit. +Causes both preprocessor lines and the lines deleted +by preprocessing to be retained in the output source as comments marked +with the special string @cite{"--! "}. This option will result in line numbers +being preserved in the output file. +@end table -@item -Checks that an acceptable order of elaboration exists for the program -and issues an error message if it cannot find an order of elaboration -that satisfies the rules in Chapter 10 of the Ada Language Manual. +@geindex -C (gnatprep) -@item -Generates a main program incorporating the given elaboration order. -This program is a small Ada package (body and spec) that -must be subsequently compiled -using the GNAT compiler. The necessary compilation step is usually -performed automatically by @command{gnatlink}. The two most important -functions of this program -are to call the elaboration routines of units in an appropriate order -and to call the main program. -@item -Determines the set of object files required by the given main program. -This information is output in the forms of comments in the generated program, -to be read by the @command{gnatlink} utility used to link the Ada application. -@end enumerate +@table @asis -@node Running gnatbind -@section Running @code{gnatbind} +@item @code{-C} -@noindent -The form of the @code{gnatbind} command is +Causes comments to be scanned. Normally comments are ignored by gnatprep. +If this option is specified, then comments are scanned and any $symbol +substitutions performed as in program text. This is particularly useful +when structured comments are used (e.g., when writing programs in the +SPARK dialect of Ada). Note that this switch is not available when +doing integrated preprocessing (it would be useless in this context +since comments are ignored by the compiler in any case). +@end table -@smallexample -@c $ gnatbind @ovar{switches} @var{mainprog}@r{[}.ali@r{]} @ovar{switches} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatbind @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]} @r{[}@var{switches}@r{]} -@end smallexample +@geindex -D (gnatprep) -@noindent -where @file{@var{mainprog}.adb} is the Ada file containing the main program -unit body. @code{gnatbind} constructs an Ada -package in two files whose names are -@file{b~@var{mainprog}.ads}, and @file{b~@var{mainprog}.adb}. -For example, if given the -parameter @file{hello.ali}, for a main program contained in file -@file{hello.adb}, the binder output files would be @file{b~hello.ads} -and @file{b~hello.adb}. -When doing consistency checking, the binder takes into consideration -any source files it can locate. For example, if the binder determines -that the given main program requires the package @code{Pack}, whose -@file{.ALI} -file is @file{pack.ali} and whose corresponding source spec file is -@file{pack.ads}, it attempts to locate the source file @file{pack.ads} -(using the same search path conventions as previously described for the -@command{gcc} command). If it can locate this source file, it checks that -the time stamps -or source checksums of the source and its references to in @file{ALI} files -match. In other words, any @file{ALI} files that mentions this spec must have -resulted from compiling this version of the source file (or in the case -where the source checksums match, a version close enough that the -difference does not matter). +@table @asis -@cindex Source files, use by binder -The effect of this consistency checking, which includes source files, is -that the binder ensures that the program is consistent with the latest -version of the source files that can be located at bind time. Editing a -source file without compiling files that depend on the source file cause -error messages to be generated by the binder. +@item @code{-D@emph{symbol}=@emph{value}} -For example, suppose you have a main program @file{hello.adb} and a -package @code{P}, from file @file{p.ads} and you perform the following -steps: +Defines a new preprocessing symbol, associated with value. If no value is given +on the command line, then symbol is considered to be @cite{True}. This switch +can be used in place of a definition file. +@end table -@enumerate -@item -Enter @code{gcc -c hello.adb} to compile the main program. +@geindex -r (gnatprep) -@item -Enter @code{gcc -c p.ads} to compile package @code{P}. -@item -Edit file @file{p.ads}. +@table @asis -@item -Enter @code{gnatbind hello}. -@end enumerate +@item @code{-r} -@noindent -At this point, the file @file{p.ali} contains an out-of-date time stamp -because the file @file{p.ads} has been edited. The attempt at binding -fails, and the binder generates the following error messages: +Causes a @cite{Source_Reference} pragma to be generated that +references the original input file, so that error messages will use +the file name of this original file. The use of this switch implies +that preprocessor lines are not to be removed from the file, so its +use will force @emph{-b} mode if @emph{-c} +has not been specified explicitly. -@smallexample -error: "hello.adb" must be recompiled ("p.ads" has been modified) -error: "p.ads" has been modified and must be recompiled -@end smallexample +Note that if the file to be preprocessed contains multiple units, then +it will be necessary to @cite{gnatchop} the output file from +@cite{gnatprep}. If a @cite{Source_Reference} pragma is present +in the preprocessed file, it will be respected by +@cite{gnatchop -r} +so that the final chopped files will correctly refer to the original +input source file for @cite{gnatprep}. +@end table -@noindent -Now both files must be recompiled as indicated, and then the bind can -succeed, generating a main program. You need not normally be concerned -with the contents of this file, but for reference purposes a sample -binder output file is given in @ref{Example of Binder Output File}. +@geindex -s (gnatprep) -In most normal usage, the default mode of @command{gnatbind} which is to -generate the main package in Ada, as described in the previous section. -In particular, this means that any Ada programmer can read and understand -the generated main program. It can also be debugged just like any other -Ada code provided the @option{-g} switch is used for -@command{gnatbind} and @command{gnatlink}. -@node Switches for gnatbind -@section Switches for @command{gnatbind} +@table @asis -@noindent -The following switches are available with @code{gnatbind}; details will -be presented in subsequent sections. +@item @code{-s} -@menu -* Consistency-Checking Modes:: -* Binder Error Message Control:: -* Elaboration Control:: -* Output Control:: -* Dynamic Allocation Control:: -* Binding with Non-Ada Main Programs:: -* Binding Programs with No Main Subprogram:: -@end menu +Causes a sorted list of symbol names and values to be +listed on the standard output file. +@end table -@table @option -@c !sort! +@geindex -u (gnatprep) -@item --version -@cindex @option{--version} @command{gnatbind} -Display Copyright and version, then exit disregarding all other options. -@item --help -@cindex @option{--help} @command{gnatbind} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +@table @asis -@item -a -@cindex @option{-a} @command{gnatbind} -Indicates that, if supported by the platform, the adainit procedure should -be treated as an initialisation routine by the linker (a constructor). This -is intended to be used by the Project Manager to automatically initialize -shared Stand-Alone Libraries. +@item @code{-u} -@item -aO -@cindex @option{-aO} (@command{gnatbind}) -Specify directory to be searched for ALI files. +Causes undefined symbols to be treated as having the value FALSE in the context +of a preprocessor test. In the absence of this option, an undefined symbol in +a @cite{#if} or @cite{#elsif} test will be treated as an error. +@end table -@item -aI -@cindex @option{-aI} (@command{gnatbind}) -Specify directory to be searched for source file. +Note: if neither @emph{-b} nor @emph{-c} is present, +then preprocessor lines and +deleted lines are completely removed from the output, unless -r is +specified, in which case -b is assumed. -@item -A@r{[=}@var{filename}@r{]} -@cindex @option{-A} (@command{gnatbind}) -Output ALI list (to standard output or to the named file). +@node Form of Definitions File,Form of Input Text for gnatprep,Switches for gnatprep,Preprocessing with gnatprep +@anchor{gnat_ugn/the_gnat_compilation_model form-of-definitions-file}@anchor{b2}@anchor{gnat_ugn/the_gnat_compilation_model id58}@anchor{b3} +@subsubsection Form of Definitions File -@item -b -@cindex @option{-b} (@command{gnatbind}) -Generate brief messages to @file{stderr} even if verbose mode set. -@item -c -@cindex @option{-c} (@command{gnatbind}) -Check only, no generation of binder output file. +The definitions file contains lines of the form: -@item -d@var{nn}@r{[}k@r{|}m@r{]} -@cindex @option{-d@var{nn}@r{[}k@r{|}m@r{]}} (@command{gnatbind}) -This switch can be used to change the default task stack size value -to a specified size @var{nn}, which is expressed in bytes by default, or -in kilobytes when suffixed with @var{k} or in megabytes when suffixed -with @var{m}. -In the absence of a @samp{@r{[}k@r{|}m@r{]}} suffix, this switch is equivalent, -in effect, to completing all task specs with -@smallexample @c ada - @b{pragma} Storage_Size (nn); -@end smallexample -When they do not already have such a pragma. +@example +symbol := value +@end example -@item -D@var{nn}@r{[}k@r{|}m@r{]} -@cindex @option{-D} (@command{gnatbind}) -This switch can be used to change the default secondary stack size value -to a specified size @var{nn}, which is expressed in bytes by default, or -in kilobytes when suffixed with @var{k} or in megabytes when suffixed -with @var{m}. +where @cite{symbol} is a preprocessing symbol, and @cite{value} is one of the following: -The secondary stack is used to deal with functions that return a variable -sized result, for example a function returning an unconstrained -String. There are two ways in which this secondary stack is allocated. -For most targets, the secondary stack is growing on demand and is allocated -as a chain of blocks in the heap. The -D option is not very -relevant. It only give some control over the size of the allocated -blocks (whose size is the minimum of the default secondary stack size value, -and the actual size needed for the current allocation request). +@itemize * -For certain targets, notably VxWorks 653, -the secondary stack is allocated by carving off a fixed ratio chunk of the -primary task stack. The -D option is used to define the -size of the environment task's secondary stack. +@item +Empty, corresponding to a null substitution, -@item -e -@cindex @option{-e} (@command{gnatbind}) -Output complete list of elaboration-order dependencies. +@item +A string literal using normal Ada syntax, or -@item -E -@cindex @option{-E} (@command{gnatbind}) -Store tracebacks in exception occurrences when the target supports it. -@ignore -@c The following may get moved to an appendix -This option is currently supported on the following targets: -all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks. -@end ignore -See also the packages @code{GNAT.Traceback} and -@code{GNAT.Traceback.Symbolic} for more information. -Note that on x86 ports, you must not use @option{-fomit-frame-pointer} -@command{gcc} option. - -@item -F -@cindex @option{-F} (@command{gnatbind}) -Force the checks of elaboration flags. @command{gnatbind} does not normally -generate checks of elaboration flags for the main executable, except when -a Stand-Alone Library is used. However, there are cases when this cannot be -detected by gnatbind. An example is importing an interface of a Stand-Alone -Library through a pragma Import and only specifying through a linker switch -this Stand-Alone Library. This switch is used to guarantee that elaboration -flag checks are generated. +@item +Any sequence of characters from the set @{letters, digits, period, underline@}. +@end itemize -@item -h -@cindex @option{-h} (@command{gnatbind}) -Output usage (help) information +Comment lines may also appear in the definitions file, starting with +the usual @code{--}, +and comments may be added to the definitions lines. -@item -H32 -@cindex @option{-H32} (@command{gnatbind}) -Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types). -For further details see @ref{Dynamic Allocation Control}. +@node Form of Input Text for gnatprep,,Form of Definitions File,Preprocessing with gnatprep +@anchor{gnat_ugn/the_gnat_compilation_model id59}@anchor{b4}@anchor{gnat_ugn/the_gnat_compilation_model form-of-input-text-for-gnatprep}@anchor{b5} +@subsubsection Form of Input Text for @cite{gnatprep} -@item -H64 -@cindex @option{-H64} (@command{gnatbind}) -Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types). -@cindex @code{__gnat_malloc} -For further details see @ref{Dynamic Allocation Control}. -@item -I -@cindex @option{-I} (@command{gnatbind}) -Specify directory to be searched for source and ALI files. +The input text may contain preprocessor conditional inclusion lines, +as well as general symbol substitution sequences. -@item -I- -@cindex @option{-I-} (@command{gnatbind}) -Do not look for sources in the current directory where @code{gnatbind} was -invoked, and do not look for ALI files in the directory containing the -ALI file named in the @code{gnatbind} command line. +The preprocessor conditional inclusion commands have the form: -@item -l -@cindex @option{-l} (@command{gnatbind}) -Output chosen elaboration order. +@example +#if [then] + lines +#elsif [then] + lines +#elsif [then] + lines +... +#else + lines +#end if; +@end example + +In this example, is defined by the following grammar: + +@example + ::= + ::= = "" + ::= = + ::= = + ::= > + ::= >= + ::= < + ::= <= + ::= 'Defined + ::= not + ::= and + ::= or + ::= and then + ::= or else + ::= ( ) +@end example + +Note the following restriction: it is not allowed to have "and" or "or" +following "not" in the same expression without parentheses. For example, this +is not allowed: -@item -L@var{xxx} -@cindex @option{-L} (@command{gnatbind}) -Bind the units for library building. In this case the adainit and -adafinal procedures (@pxref{Binding with Non-Ada Main Programs}) -are renamed to @var{xxx}init and -@var{xxx}final. -Implies -n. -(@xref{GNAT and Libraries}, for more details.) - -@item -Mxyz -@cindex @option{-M} (@command{gnatbind}) -Rename generated main program from main to xyz. This option is -supported on cross environments only. +@example +not X or Y +@end example -@item -m@var{n} -@cindex @option{-m} (@command{gnatbind}) -Limit number of detected errors or warnings to @var{n}, where @var{n} is -in the range 1..999999. The default value if no switch is -given is 9999. If the number of warnings reaches this limit, then a -message is output and further warnings are suppressed, the bind -continues in this case. If the number of errors reaches this -limit, then a message is output and the bind is abandoned. -A value of zero means that no limit is enforced. The equal -sign is optional. +This can be expressed instead as one of the following forms: -@item -n -@cindex @option{-n} (@command{gnatbind}) -No main program. +@example +(not X) or Y +not (X or Y) +@end example -@item -nostdinc -@cindex @option{-nostdinc} (@command{gnatbind}) -Do not look for sources in the system default directory. +For the first test ( ::= ) the symbol must have +either the value true or false, that is to say the right-hand of the +symbol definition must be one of the (case-insensitive) literals +@cite{True} or @cite{False}. If the value is true, then the +corresponding lines are included, and if the value is false, they are +excluded. -@item -nostdlib -@cindex @option{-nostdlib} (@command{gnatbind}) -Do not look for library files in the system default directory. +When comparing a symbol to an integer, the integer is any non negative +literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or +2#11#. The symbol value must also be a non negative integer. Integer values +in the range 0 .. 2**31-1 are supported. -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@code{gnatbind}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). +The test ( ::= 'Defined) is true only if +the symbol has been defined in the definition file or by a @emph{-D} +switch on the command line. Otherwise, the test is false. -@item -o @var{file} -@cindex @option{-o } (@command{gnatbind}) -Name the output file @var{file} (default is @file{b~@var{xxx}.adb}). -Note that if this option is used, then linking must be done manually, -gnatlink cannot be used. +The equality tests are case insensitive, as are all the preprocessor lines. -@item -O@r{[=}@var{filename}@r{]} -@cindex @option{-O} (@command{gnatbind}) -Output object list (to standard output or to the named file). +If the symbol referenced is not defined in the symbol definitions file, +then the effect depends on whether or not switch @emph{-u} +is specified. If so, then the symbol is treated as if it had the value +false and the test fails. If this switch is not specified, then +it is an error to reference an undefined symbol. It is also an error to +reference a symbol that is defined with a value other than @cite{True} +or @cite{False}. -@item -p -@cindex @option{-p} (@command{gnatbind}) -Pessimistic (worst-case) elaboration order +The use of the @cite{not} operator inverts the sense of this logical test. +The @cite{not} operator cannot be combined with the @cite{or} or @cite{and} +operators, without parentheses. For example, "if not X or Y then" is not +allowed, but "if (not X) or Y then" and "if not (X or Y) then" are. -@item -P -@cindex @option{-P} (@command{gnatbind}) -Generate binder file suitable for CodePeer. +The @cite{then} keyword is optional as shown -@item -R -@cindex @option{-R} (@command{gnatbind}) -Output closure source list, which includes all non-run-time units that are -included in the bind. +The @cite{#} must be the first non-blank character on a line, but +otherwise the format is free form. Spaces or tabs may appear between +the @cite{#} and the keyword. The keywords and the symbols are case +insensitive as in normal Ada code. Comments may be used on a +preprocessor line, but other than that, no other tokens may appear on a +preprocessor line. Any number of @cite{elsif} clauses can be present, +including none at all. The @cite{else} is optional, as in Ada. -@item -Ra -@cindex @option{-Ra} (@command{gnatbind}) -Like @option{-R} but the list includes run-time units. +The @cite{#} marking the start of a preprocessor line must be the first +non-blank character on the line, i.e., it must be preceded only by +spaces or horizontal tabs. -@item -s -@cindex @option{-s} (@command{gnatbind}) -Require all source files to be present. +Symbol substitution outside of preprocessor lines is obtained by using +the sequence: -@item -S@var{xxx} -@cindex @option{-S} (@command{gnatbind}) -Specifies the value to be used when detecting uninitialized scalar -objects with pragma Initialize_Scalars. -The @var{xxx} string specified with the switch is one of: -@itemize @bullet +@example +$symbol +@end example -@item ``@option{in}'' for an invalid value -If zero is invalid for the discrete type in question, -then the scalar value is set to all zero bits. -For signed discrete types, the largest possible negative value of -the underlying scalar is set (i.e. a one bit followed by all zero bits). -For unsigned discrete types, the underlying scalar value is set to all -one bits. For floating-point types, a NaN value is set -(see body of package System.Scalar_Values for exact values). +anywhere within a source line, except in a comment or within a +string literal. The identifier +following the @cite{$} must match one of the symbols defined in the symbol +definition file, and the result is to substitute the value of the +symbol in place of @cite{$symbol} in the output file. -@item ``@option{lo}'' for low value -If zero is invalid for the discrete type in question, -then the scalar value is set to all zero bits. -For signed discrete types, the largest possible negative value of -the underlying scalar is set (i.e. a one bit followed by all zero bits). -For unsigned discrete types, the underlying scalar value is set to all -zero bits. For floating-point, a small value is set -(see body of package System.Scalar_Values for exact values). +Note that although the substitution of strings within a string literal +is not possible, it is possible to have a symbol whose defined value is +a string literal. So instead of setting XYZ to @cite{hello} and writing: -@item ``@option{hi}'' for high value -If zero is invalid for the discrete type in question, -then the scalar value is set to all one bits. -For signed discrete types, the largest possible positive value of -the underlying scalar is set (i.e. a zero bit followed by all one bits). -For unsigned discrete types, the underlying scalar value is set to all -one bits. For floating-point, a large value is set -(see body of package System.Scalar_Values for exact values). +@example +Header : String := "$XYZ"; +@end example -@item ``@option{@var{xx}}'' for hex value (two hex digits) -The underlying scalar is set to a value consisting of repeated bytes, whose -value corresponds to the given value. For example if @option{BF} is given, -then a 32-bit scalar value will be set to the bit patterm 16#BFBFBFBF#. -@end itemize +you should set XYZ to @cite{"hello"} and write: -In addition, you can specify @option{-Sev} to indicate that the value is -to be set at run time. In this case, the program will look for an environment -@cindex GNAT_INIT_SCALARS -variable of the form @env{GNAT_INIT_SCALARS=@var{xx}}, where @var{xx} is one -of @option{in/lo/hi/@var{xx}} with the same meanings as above. -If no environment variable is found, or if it does not have a valid value, -then the default is @option{in} (invalid values). +@example +Header : String := $XYZ; +@end example -@item -static -@cindex @option{-static} (@code{gnatbind}) -Link against a static GNAT run time. +and then the substitution will occur as desired. -@item -shared -@cindex @option{-shared} (@code{gnatbind}) -Link against a shared GNAT run time when available. +@node Integrated Preprocessing,,Preprocessing with gnatprep,Conditional Compilation +@anchor{gnat_ugn/the_gnat_compilation_model id60}@anchor{b6}@anchor{gnat_ugn/the_gnat_compilation_model integrated-preprocessing}@anchor{1a} +@subsection Integrated Preprocessing -@item -t -@cindex @option{-t} (@code{gnatbind}) -Tolerate time stamp and other consistency errors -@item -T@var{n} -@cindex @option{-T} (@code{gnatbind}) -Set the time slice value to @var{n} milliseconds. If the system supports -the specification of a specific time slice value, then the indicated value -is used. If the system does not support specific time slice values, but -does support some general notion of round-robin scheduling, then any -nonzero value will activate round-robin scheduling. +GNAT sources may be preprocessed immediately before compilation. +In this case, the actual +text of the source is not the text of the source file, but is derived from it +through a process called preprocessing. Integrated preprocessing is specified +through switches @emph{-gnatep} and/or @emph{-gnateD}. @emph{-gnatep} +indicates, through a text file, the preprocessing data to be used. +@code{-gnateD} specifies or modifies the values of preprocessing symbol. +Note that integrated preprocessing applies only to Ada source files, it is +not available for configuration pragma files. -A value of zero is treated specially. It turns off time -slicing, and in addition, indicates to the tasking run time that the -semantics should match as closely as possible the Annex D -requirements of the Ada RM, and in particular sets the default -scheduling policy to @code{FIFO_Within_Priorities}. +Note that when integrated preprocessing is used, the output from the +preprocessor is not written to any external file. Instead it is passed +internally to the compiler. If you need to preserve the result of +preprocessing in a file, then you should use @emph{gnatprep} +to perform the desired preprocessing in stand-alone mode. -@item -u@var{n} -@cindex @option{-u} (@code{gnatbind}) -Enable dynamic stack usage, with @var{n} results stored and displayed -at program termination. A result is generated when a task -terminates. Results that can't be stored are displayed on the fly, at -task termination. This option is currently not supported on Itanium -platforms. (See @ref{Dynamic Stack Usage Analysis} for details.) +It is recommended that @emph{gnatmake} switch -s should be +used when Integrated Preprocessing is used. The reason is that preprocessing +with another Preprocessing Data file without changing the sources will +not trigger recompilation without this switch. -@item -v -@cindex @option{-v} (@code{gnatbind}) -Verbose mode. Write error messages, header, summary output to -@file{stdout}. +Note that @emph{gnatmake} switch -m will almost +always trigger recompilation for sources that are preprocessed, +because @emph{gnatmake} cannot compute the checksum of the source after +preprocessing. -@item -w@var{x} -@cindex @option{-w} (@code{gnatbind}) -Warning mode (@var{x}=s/e for suppress/treat as error) +The actual preprocessing function is described in detail in section +@ref{19,,Preprocessing with gnatprep}. This section only describes how integrated +preprocessing is triggered and parameterized. +@geindex -gnatep (gcc) -@item -Wx@var{e} -@cindex @option{-Wx} (@code{gnatbind}) -Override default wide character encoding for standard Text_IO files. - -@item -x -@cindex @option{-x} (@code{gnatbind}) -Exclude source files (check object consistency only). +@table @asis -@item -X@var{nnn} -@cindex @option{-X@var{nnn}} (@code{gnatbind}) -Set default exit status value, normally 0 for POSIX compliance. +@item @code{-gnatep=@emph{file}} +This switch indicates to the compiler the file name (without directory +information) of the preprocessor data file to use. The preprocessor data file +should be found in the source directories. Note that when the compiler is +called by a builder such as (@emph{gnatmake} with a project +file, if the object directory is not also a source directory, the builder needs +to be called with @emph{-x}. -@item -y -@cindex @option{-y} (@code{gnatbind}) -Enable leap seconds support in @code{Ada.Calendar} and its children. +A preprocessing data file is a text file with significant lines indicating +how should be preprocessed either a specific source or all sources not +mentioned in other lines. A significant line is a nonempty, non-comment line. +Comments are similar to Ada comments. -@item -z -@cindex @option{-z} (@code{gnatbind}) -No main subprogram. -@end table +Each significant line starts with either a literal string or the character '*'. +A literal string is the file name (without directory information) of the source +to preprocess. A character '*' indicates the preprocessing for all the sources +that are not specified explicitly on other lines (order of the lines is not +significant). It is an error to have two lines with the same file name or two +lines starting with the character '*'. -@noindent -You may obtain this listing of switches by running @code{gnatbind} with -no arguments. +After the file name or the character '*', another optional literal string +indicating the file name of the definition file to be used for preprocessing +(@ref{b2,,Form of Definitions File}). The definition files are found by the +compiler in one of the source directories. In some cases, when compiling +a source in a directory other than the current directory, if the definition +file is in the current directory, it may be necessary to add the current +directory as a source directory through switch -I., otherwise +the compiler would not find the definition file. -@node Consistency-Checking Modes -@subsection Consistency-Checking Modes +Then, optionally, switches similar to those of @cite{gnatprep} may +be found. Those switches are: -@noindent -As described earlier, by default @code{gnatbind} checks -that object files are consistent with one another and are consistent -with any source files it can locate. The following switches control binder -access to sources. -@table @option -@c !sort! -@item -s -@cindex @option{-s} (@code{gnatbind}) -Require source files to be present. In this mode, the binder must be -able to locate all source files that are referenced, in order to check -their consistency. In normal mode, if a source file cannot be located it -is simply ignored. If you specify this switch, a missing source -file is an error. +@table @asis -@item -Wx@var{e} -@cindex @option{-Wx} (@code{gnatbind}) -Override default wide character encoding for standard Text_IO files. -Normally the default wide character encoding method used for standard -[Wide_[Wide_]]Text_IO files is taken from the encoding specified for -the main source input (see description of switch -@option{-gnatWx} for the compiler). The -use of this switch for the binder (which has the same set of -possible arguments) overrides this default as specified. +@item @code{-b} -@item -x -@cindex @option{-x} (@code{gnatbind}) -Exclude source files. In this mode, the binder only checks that ALI -files are consistent with one another. Source files are not accessed. -The binder runs faster in this mode, and there is still a guarantee that -the resulting program is self-consistent. -If a source file has been edited since it was last compiled, and you -specify this switch, the binder will not detect that the object -file is out of date with respect to the source file. Note that this is the -mode that is automatically used by @command{gnatmake} because in this -case the checking against sources has already been performed by -@command{gnatmake} in the course of compilation (i.e.@: before binding). +Causes both preprocessor lines and the lines deleted by +preprocessing to be replaced by blank lines, preserving the line number. +This switch is always implied; however, if specified after @emph{-c} +it cancels the effect of @emph{-c}. -@end table +@item @code{-c} -@node Binder Error Message Control -@subsection Binder Error Message Control +Causes both preprocessor lines and the lines deleted +by preprocessing to be retained as comments marked +with the special string '@cite{--!}'. -@noindent -The following switches provide control over the generation of error -messages from the binder: +@item @code{-Dsymbol=@emph{value}} -@table @option -@c !sort! -@item -v -@cindex @option{-v} (@code{gnatbind}) -Verbose mode. In the normal mode, brief error messages are generated to -@file{stderr}. If this switch is present, a header is written -to @file{stdout} and any error messages are directed to @file{stdout}. -All that is written to @file{stderr} is a brief summary message. +Define or redefine a symbol, associated with value. A symbol is an Ada +identifier, or an Ada reserved word, with the exception of @cite{if}, +@cite{else}, @cite{elsif}, @cite{end}, @cite{and}, @cite{or} and @cite{then}. +@cite{value} is either a literal string, an Ada identifier or any Ada reserved +word. A symbol declared with this switch replaces a symbol with the +same name defined in a definition file. -@item -b -@cindex @option{-b} (@code{gnatbind}) -Generate brief error messages to @file{stderr} even if verbose mode is -specified. This is relevant only when used with the -@option{-v} switch. +@item @code{-s} -@item -m@var{n} -@cindex @option{-m} (@code{gnatbind}) -Limits the number of error messages to @var{n}, a decimal integer in the -range 1-999. The binder terminates immediately if this limit is reached. +Causes a sorted list of symbol names and values to be +listed on the standard output file. -@item -M@var{xxx} -@cindex @option{-M} (@code{gnatbind}) -Renames the generated main program from @code{main} to @code{xxx}. -This is useful in the case of some cross-building environments, where -the actual main program is separate from the one generated -by @code{gnatbind}. +@item @code{-u} -@item -ws -@cindex @option{-ws} (@code{gnatbind}) -@cindex Warnings -Suppress all warning messages. +Causes undefined symbols to be treated as having the value @cite{FALSE} +in the context +of a preprocessor test. In the absence of this option, an undefined symbol in +a @cite{#if} or @cite{#elsif} test will be treated as an error. +@end table -@item -we -@cindex @option{-we} (@code{gnatbind}) -Treat any warning messages as fatal errors. +Examples of valid lines in a preprocessor data file: +@example +"toto.adb" "prep.def" -u +-- preprocess "toto.adb", using definition file "prep.def", +-- undefined symbol are False. -@item -t -@cindex @option{-t} (@code{gnatbind}) -@cindex Time stamp checks, in binder -@cindex Binder consistency checks -@cindex Consistency checks, in binder -The binder performs a number of consistency checks including: +* -c -DVERSION=V101 +-- preprocess all other sources without a definition file; +-- suppressed lined are commented; symbol VERSION has the value V101. -@itemize @bullet -@item -Check that time stamps of a given source unit are consistent -@item -Check that checksums of a given source unit are consistent -@item -Check that consistent versions of @code{GNAT} were used for compilation -@item -Check consistency of configuration pragmas as required -@end itemize +"titi.adb" "prep2.def" -s +-- preprocess "titi.adb", using definition file "prep2.def"; +-- list all symbols with their values. +@end example +@end table -@noindent -Normally failure of such checks, in accordance with the consistency -requirements of the Ada Reference Manual, causes error messages to be -generated which abort the binder and prevent the output of a binder -file and subsequent link to obtain an executable. +@geindex -gnateD (gcc) -The @option{-t} switch converts these error messages -into warnings, so that -binding and linking can continue to completion even in the presence of such -errors. The result may be a failed link (due to missing symbols), or a -non-functional executable which has undefined semantics. -@emph{This means that -@option{-t} should be used only in unusual situations, -with extreme care.} -@end table -@node Elaboration Control -@subsection Elaboration Control +@table @asis -@noindent -The following switches provide additional control over the elaboration -order. For full details see @ref{Elaboration Order Handling in GNAT}. +@item @code{-gnateDsymbol[=value]} -@table @option -@item -p -@cindex @option{-p} (@code{gnatbind}) -Normally the binder attempts to choose an elaboration order that is -likely to minimize the likelihood of an elaboration order error resulting -in raising a @code{Program_Error} exception. This switch reverses the -action of the binder, and requests that it deliberately choose an order -that is likely to maximize the likelihood of an elaboration error. -This is useful in ensuring portability and avoiding dependence on -accidental fortuitous elaboration ordering. +Define or redefine a preprocessing symbol, associated with value. If no value +is given on the command line, then the value of the symbol is @cite{True}. +A symbol is an identifier, following normal Ada (case-insensitive) +rules for its syntax, and value is either an arbitrary string between double +quotes or any sequence (including an empty sequence) of characters from the +set (letters, digits, period, underline). +Ada reserved words may be used as symbols, with the exceptions of @cite{if}, +@cite{else}, @cite{elsif}, @cite{end}, @cite{and}, @cite{or} and @cite{then}. -Normally it only makes sense to use the @option{-p} -switch if dynamic -elaboration checking is used (@option{-gnatE} switch used for compilation). -This is because in the default static elaboration mode, all necessary -@code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted. -These implicit pragmas are still respected by the binder in -@option{-p} mode, so a -safe elaboration order is assured. +Examples: -Note that @option{-p} is not intended for -production use; it is more for debugging/experimental use. -@end table +@example +-gnateDToto=Titi +-gnateDFoo +-gnateDFoo=\"Foo-Bar\" +@end example -@node Output Control -@subsection Output Control +A symbol declared with this switch on the command line replaces a +symbol with the same name either in a definition file or specified with a +switch -D in the preprocessor data file. -@noindent -The following switches allow additional control over the output -generated by the binder. +This switch is similar to switch @emph{-D} of @cite{gnatprep}. -@table @option -@c !sort! +@item @code{-gnateG} -@item -c -@cindex @option{-c} (@code{gnatbind}) -Check only. Do not generate the binder output file. In this mode the -binder performs all error checks but does not generate an output file. +When integrated preprocessing is performed and the preprocessor modifies +the source text, write the result of this preprocessing into a file +.prep. +@end table -@item -e -@cindex @option{-e} (@code{gnatbind}) -Output complete list of elaboration-order dependencies, showing the -reason for each dependency. This output can be rather extensive but may -be useful in diagnosing problems with elaboration order. The output is -written to @file{stdout}. +@node Mixed Language Programming,GNAT and Other Compilation Models,Conditional Compilation,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model mixed-language-programming}@anchor{46}@anchor{gnat_ugn/the_gnat_compilation_model id61}@anchor{b7} +@section Mixed Language Programming -@item -h -@cindex @option{-h} (@code{gnatbind}) -Output usage information. The output is written to @file{stdout}. -@item -K -@cindex @option{-K} (@code{gnatbind}) -Output linker options to @file{stdout}. Includes library search paths, -contents of pragmas Ident and Linker_Options, and libraries added -by @code{gnatbind}. +@geindex Mixed Language Programming -@item -l -@cindex @option{-l} (@code{gnatbind}) -Output chosen elaboration order. The output is written to @file{stdout}. +This section describes how to develop a mixed-language program, +with a focus on combining Ada with C or C++. -@item -O -@cindex @option{-O} (@code{gnatbind}) -Output full names of all the object files that must be linked to provide -the Ada component of the program. The output is written to @file{stdout}. -This list includes the files explicitly supplied and referenced by the user -as well as implicitly referenced run-time unit files. The latter are -omitted if the corresponding units reside in shared libraries. The -directory names for the run-time units depend on the system configuration. +@menu +* Interfacing to C:: +* Calling Conventions:: +* Building Mixed Ada and C++ Programs:: +* Generating Ada Bindings for C and C++ headers:: -@item -o @var{file} -@cindex @option{-o} (@code{gnatbind}) -Set name of output file to @var{file} instead of the normal -@file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada -binder generated body filename. -Note that if this option is used, then linking must be done manually. -It is not possible to use gnatlink in this case, since it cannot locate -the binder file. +@end menu -@item -r -@cindex @option{-r} (@code{gnatbind}) -Generate list of @code{pragma Restrictions} that could be applied to -the current unit. This is useful for code audit purposes, and also may -be used to improve code generation in some cases. +@node Interfacing to C,Calling Conventions,,Mixed Language Programming +@anchor{gnat_ugn/the_gnat_compilation_model interfacing-to-c}@anchor{b8}@anchor{gnat_ugn/the_gnat_compilation_model id62}@anchor{b9} +@subsection Interfacing to C -@end table -@node Dynamic Allocation Control -@subsection Dynamic Allocation Control +Interfacing Ada with a foreign language such as C involves using +compiler directives to import and/or export entity definitions in each +language -- using @cite{extern} statements in C, for instance, and the +@cite{Import}, @cite{Export}, and @cite{Convention} pragmas in Ada. +A full treatment of these topics is provided in Appendix B, section 1 +of the Ada Reference Manual. -@noindent -The heap control switches -- @option{-H32} and @option{-H64} -- -determine whether dynamic allocation uses 32-bit or 64-bit memory. -They only affect compiler-generated allocations via @code{__gnat_malloc}; -explicit calls to @code{malloc} and related functions from the C -run-time library are unaffected. +There are two ways to build a program using GNAT that contains some Ada +sources and some foreign language sources, depending on whether or not +the main subprogram is written in Ada. Here is a source example with +the main subprogram in Ada: -@table @option -@item -H32 -Allocate memory on 32-bit heap +@example +/* file1.c */ +#include -@item -H64 -Allocate memory on 64-bit heap. This is the default -unless explicitly overridden by a @code{'Size} clause on the access type. -@end table +void print_num (int num) +@{ + printf ("num is %d.\\n", num); + return; +@} +@end example -@noindent -These switches are only effective on VMS platforms. +@example +/* file2.c */ +/* num_from_Ada is declared in my_main.adb */ +extern int num_from_Ada; -@node Binding with Non-Ada Main Programs -@subsection Binding with Non-Ada Main Programs +int get_num (void) +@{ + return num_from_Ada; +@} +@end example -@noindent -In our description so far we have assumed that the main -program is in Ada, and that the task of the binder is to generate a -corresponding function @code{main} that invokes this Ada main -program. GNAT also supports the building of executable programs where -the main program is not in Ada, but some of the called routines are -written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}). -The following switch is used in this situation: +@example +-- my_main.adb +procedure My_Main is -@table @option -@item -n -@cindex @option{-n} (@code{gnatbind}) -No main program. The main program is not in Ada. -@end table + -- Declare then export an Integer entity called num_from_Ada + My_Num : Integer := 10; + pragma Export (C, My_Num, "num_from_Ada"); -@noindent -In this case, most of the functions of the binder are still required, -but instead of generating a main program, the binder generates a file -containing the following callable routines: + -- Declare an Ada function spec for Get_Num, then use + -- C function get_num for the implementation. + function Get_Num return Integer; + pragma Import (C, Get_Num, "get_num"); -@table @code -@item adainit -@findex adainit -You must call this routine to initialize the Ada part of the program by -calling the necessary elaboration routines. A call to @code{adainit} is -required before the first call to an Ada subprogram. + -- Declare an Ada procedure spec for Print_Num, then use + -- C function print_num for the implementation. + procedure Print_Num (Num : Integer); + pragma Import (C, Print_Num, "print_num"; -Note that it is assumed that the basic execution environment must be setup -to be appropriate for Ada execution at the point where the first Ada -subprogram is called. In particular, if the Ada code will do any -floating-point operations, then the FPU must be setup in an appropriate -manner. For the case of the x86, for example, full precision mode is -required. The procedure GNAT.Float_Control.Reset may be used to ensure -that the FPU is in the right state. +begin + Print_Num (Get_Num); +end My_Main; +@end example -@item adafinal -@findex adafinal -You must call this routine to perform any library-level finalization -required by the Ada subprograms. A call to @code{adafinal} is required -after the last call to an Ada subprogram, and before the program -terminates. -@end table +To build this example: -@noindent -If the @option{-n} switch -@cindex @option{-n} (@command{gnatbind}) -@cindex Binder, multiple input files -is given, more than one ALI file may appear on -the command line for @code{gnatbind}. The normal @dfn{closure} -calculation is performed for each of the specified units. Calculating -the closure means finding out the set of units involved by tracing -@code{with} references. The reason it is necessary to be able to -specify more than one ALI file is that a given program may invoke two or -more quite separate groups of Ada units. -The binder takes the name of its output file from the last specified ALI -file, unless overridden by the use of the @option{-o file}. -@cindex @option{-o} (@command{gnatbind}) -The output is an Ada unit in source form that can be compiled with GNAT. -This compilation occurs automatically as part of the @command{gnatlink} -processing. +@itemize * -Currently the GNAT run time requires a FPU using 80 bits mode -precision. Under targets where this is not the default it is required to -call GNAT.Float_Control.Reset before using floating point numbers (this -include float computation, float input and output) in the Ada code. A -side effect is that this could be the wrong mode for the foreign code -where floating point computation could be broken after this call. +@item +First compile the foreign language files to +generate object files: -@node Binding Programs with No Main Subprogram -@subsection Binding Programs with No Main Subprogram +@example +$ gcc -c file1.c +$ gcc -c file2.c +@end example -@noindent -It is possible to have an Ada program which does not have a main -subprogram. This program will call the elaboration routines of all the -packages, then the finalization routines. +@item +Then, compile the Ada units to produce a set of object files and ALI +files: -The following switch is used to bind programs organized in this manner: +@example +$ gnatmake -c my_main.adb +@end example -@table @option -@item -z -@cindex @option{-z} (@code{gnatbind}) -Normally the binder checks that the unit name given on the command line -corresponds to a suitable main subprogram. When this switch is used, -a list of ALI files can be given, and the execution of the program -consists of elaboration of these units in an appropriate order. Note -that the default wide character encoding method for standard Text_IO -files is always set to Brackets if this switch is set (you can use -the binder switch -@option{-Wx} to override this default). -@end table +@item +Run the Ada binder on the Ada main program: -@node Command-Line Access -@section Command-Line Access +@example +$ gnatbind my_main.ali +@end example -@noindent -The package @code{Ada.Command_Line} provides access to the command-line -arguments and program name. In order for this interface to operate -correctly, the two variables +@item +Link the Ada main program, the Ada objects and the other language +objects: -@smallexample -@group -int gnat_argc; -char **gnat_argv; -@end group -@end smallexample +@example +$ gnatlink my_main.ali file1.o file2.o +@end example +@end itemize -@noindent -@findex gnat_argv -@findex gnat_argc -are declared in one of the GNAT library routines. These variables must -be set from the actual @code{argc} and @code{argv} values passed to the -main program. With no @option{n} present, @code{gnatbind} -generates the C main program to automatically set these variables. -If the @option{n} switch is used, there is no automatic way to -set these variables. If they are not set, the procedures in -@code{Ada.Command_Line} will not be available, and any attempt to use -them will raise @code{Constraint_Error}. If command line access is -required, your main program must set @code{gnat_argc} and -@code{gnat_argv} from the @code{argc} and @code{argv} values passed to -it. +The last three steps can be grouped in a single command: -@node Search Paths for gnatbind -@section Search Paths for @code{gnatbind} +@example +$ gnatmake my_main.adb -largs file1.o file2.o +@end example -@noindent -The binder takes the name of an ALI file as its argument and needs to -locate source files as well as other ALI files to verify object consistency. +@geindex Binder output file -For source files, it follows exactly the same search rules as @command{gcc} -(@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the -directories searched are: +If the main program is in a language other than Ada, then you may have +more than one entry point into the Ada subsystem. You must use a special +binder option to generate callable routines that initialize and +finalize the Ada units (@ref{ba,,Binding with Non-Ada Main Programs}). +Calls to the initialization and finalization routines must be inserted +in the main program, or some other appropriate point in the code. The +call to initialize the Ada units must occur before the first Ada +subprogram is called, and the call to finalize the Ada units must occur +after the last Ada subprogram returns. The binder will place the +initialization and finalization subprograms into the +@code{b~xxx.adb} file where they can be accessed by your C +sources. To illustrate, we have the following example: -@enumerate -@item -The directory containing the ALI file named in the command line, unless -the switch @option{-I-} is specified. +@example +/* main.c */ +extern void adainit (void); +extern void adafinal (void); +extern int add (int, int); +extern int sub (int, int); -@item -All directories specified by @option{-I} -switches on the @code{gnatbind} -command line, in the order given. +int main (int argc, char *argv[]) +@{ + int a = 21, b = 7; -@item -@findex ADA_PRJ_OBJECTS_FILE -Each of the directories listed in the text file whose name is given -by the @env{ADA_PRJ_OBJECTS_FILE} environment variable. + adainit(); -@noindent -@env{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat -driver when project files are used. It should not normally be set -by other means. + /* Should print "21 + 7 = 28" */ + printf ("%d + %d = %d\\n", a, b, add (a, b)); -@item -@findex ADA_OBJECTS_PATH -Each of the directories listed in the value of the -@env{ADA_OBJECTS_PATH} environment variable. -Construct this value -exactly as the @env{PATH} environment variable: a list of directory -names separated by colons (semicolons when working with the NT version -of GNAT). + /* Should print "21 - 7 = 14" */ + printf ("%d - %d = %d\\n", a, b, sub (a, b)); -@item -The content of the @file{ada_object_path} file which is part of the GNAT -installation tree and is used to store standard libraries such as the -GNAT Run Time Library (RTL) unless the switch @option{-nostdlib} is -specified. -@ref{Installing a library} -@end enumerate + adafinal(); +@} +@end example -@noindent -In the binder the switch @option{-I} -@cindex @option{-I} (@command{gnatbind}) -is used to specify both source and -library file paths. Use @option{-aI} -@cindex @option{-aI} (@command{gnatbind}) -instead if you want to specify -source paths only, and @option{-aO} -@cindex @option{-aO} (@command{gnatbind}) -if you want to specify library paths -only. This means that for the binder -@option{-I}@var{dir} is equivalent to -@option{-aI}@var{dir} -@option{-aO}@var{dir}. -The binder generates the bind file (a C language source file) in the -current working directory. +@example +-- unit1.ads +package Unit1 is + function Add (A, B : Integer) return Integer; + pragma Export (C, Add, "add"); +end Unit1; +@end example -@findex Ada -@findex System -@findex Interfaces -@findex GNAT -The packages @code{Ada}, @code{System}, and @code{Interfaces} and their -children make up the GNAT Run-Time Library, together with the package -GNAT and its children, which contain a set of useful additional -library functions provided by GNAT. The sources for these units are -needed by the compiler and are kept together in one directory. The ALI -files and object files generated by compiling the RTL are needed by the -binder and the linker and are kept together in one directory, typically -different from the directory containing the sources. In a normal -installation, you need not specify these directory names when compiling -or binding. Either the environment variables or the built-in defaults -cause these files to be found. +@example +-- unit1.adb +package body Unit1 is + function Add (A, B : Integer) return Integer is + begin + return A + B; + end Add; +end Unit1; +@end example -Besides simplifying access to the RTL, a major use of search paths is -in compiling sources from multiple directories. This can make -development environments much more flexible. +@example +-- unit2.ads +package Unit2 is + function Sub (A, B : Integer) return Integer; + pragma Export (C, Sub, "sub"); +end Unit2; +@end example -@node Examples of gnatbind Usage -@section Examples of @code{gnatbind} Usage +@example +-- unit2.adb +package body Unit2 is + function Sub (A, B : Integer) return Integer is + begin + return A - B; + end Sub; +end Unit2; +@end example -@noindent -This section contains a number of examples of using the GNAT binding -utility @code{gnatbind}. +The build procedure for this application is similar to the last +example's: -@table @code -@item gnatbind hello -The main program @code{Hello} (source program in @file{hello.adb}) is -bound using the standard switch settings. The generated main program is -@file{b~hello.adb}. This is the normal, default use of the binder. -@item gnatbind hello -o mainprog.adb -The main program @code{Hello} (source program in @file{hello.adb}) is -bound using the standard switch settings. The generated main program is -@file{mainprog.adb} with the associated spec in -@file{mainprog.ads}. Note that you must specify the body here not the -spec. Note that if this option is used, then linking must be done manually, -since gnatlink will not be able to find the generated file. -@end table +@itemize * -@c ------------------------------------ -@node Linking with gnatlink -@chapter Linking with @command{gnatlink} -@c ------------------------------------ -@findex gnatlink +@item +First, compile the foreign language files to generate object files: -@noindent -This chapter discusses @command{gnatlink}, a tool that links -an Ada program and builds an executable file. This utility -invokes the system linker (via the @command{gcc} command) -with a correct list of object files and library references. -@command{gnatlink} automatically determines the list of files and -references for the Ada part of a program. It uses the binder file -generated by the @command{gnatbind} to determine this list. +@example +$ gcc -c main.c +@end example -Note: to invoke @code{gnatlink} with a project file, use the @code{gnat} -driver (see @ref{The GNAT Driver and Project Files}). +@item +Next, compile the Ada units to produce a set of object files and ALI +files: -@menu -* Running gnatlink:: -* Switches for gnatlink:: -@end menu +@example +$ gnatmake -c unit1.adb +$ gnatmake -c unit2.adb +@end example -@node Running gnatlink -@section Running @command{gnatlink} +@item +Run the Ada binder on every generated ALI file. Make sure to use the +@code{-n} option to specify a foreign main program: -@noindent -The form of the @command{gnatlink} command is +@example +$ gnatbind -n unit1.ali unit2.ali +@end example -@smallexample -@c $ gnatlink @ovar{switches} @var{mainprog}@r{[}.ali@r{]} -@c @ovar{non-Ada objects} @ovar{linker options} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatlink @r{[}@var{switches}@r{]} @var{mainprog}@r{[}.ali@r{]} - @r{[}@var{non-Ada objects}@r{]} @r{[}@var{linker options}@r{]} +@item +Link the Ada main program, the Ada objects and the foreign language +objects. You need only list the last ALI file here: -@end smallexample +@example +$ gnatlink unit2.ali main.o -o exec_file +@end example -@noindent -The arguments of @command{gnatlink} (switches, main @file{ALI} file, -non-Ada objects -or linker options) may be in any order, provided that no non-Ada object may -be mistaken for a main @file{ALI} file. -Any file name @file{F} without the @file{.ali} -extension will be taken as the main @file{ALI} file if a file exists -whose name is the concatenation of @file{F} and @file{.ali}. - -@noindent -@file{@var{mainprog}.ali} references the ALI file of the main program. -The @file{.ali} extension of this file can be omitted. From this -reference, @command{gnatlink} locates the corresponding binder file -@file{b~@var{mainprog}.adb} and, using the information in this file along -with the list of non-Ada objects and linker options, constructs a -linker command file to create the executable. +This procedure yields a binary executable called @code{exec_file}. +@end itemize -The arguments other than the @command{gnatlink} switches and the main -@file{ALI} file are passed to the linker uninterpreted. -They typically include the names of -object files for units written in other languages than Ada and any library -references required to resolve references in any of these foreign language -units, or in @code{Import} pragmas in any Ada units. +Depending on the circumstances (for example when your non-Ada main object +does not provide symbol @cite{main}), you may also need to instruct the +GNAT linker not to include the standard startup objects by passing the +@code{-nostartfiles} switch to @cite{gnatlink}. -@var{linker options} is an optional list of linker specific -switches. -The default linker called by gnatlink is @command{gcc} which in -turn calls the appropriate system linker. +@node Calling Conventions,Building Mixed Ada and C++ Programs,Interfacing to C,Mixed Language Programming +@anchor{gnat_ugn/the_gnat_compilation_model calling-conventions}@anchor{bb}@anchor{gnat_ugn/the_gnat_compilation_model id63}@anchor{bc} +@subsection Calling Conventions -One useful option for the linker is @option{-s}: it reduces the size of the -executable by removing all symbol table and relocation information from the -executable. -Standard options for the linker such as @option{-lmy_lib} or -@option{-Ldir} can be added as is. -For options that are not recognized by -@command{gcc} as linker options, use the @command{gcc} switches -@option{-Xlinker} or @option{-Wl,}. +@geindex Foreign Languages -Refer to the GCC documentation for -details. +@geindex Calling Conventions -Here is an example showing how to generate a linker map: +GNAT follows standard calling sequence conventions and will thus interface +to any other language that also follows these conventions. The following +Convention identifiers are recognized by GNAT: -@smallexample -$ gnatlink my_prog -Wl,-Map,MAPFILE -@end smallexample +@geindex Interfacing to Ada -Using @var{linker options} it is possible to set the program stack and -heap size. -See @ref{Setting Stack Size from gnatlink} and -@ref{Setting Heap Size from gnatlink}. +@geindex Other Ada compilers -@command{gnatlink} determines the list of objects required by the Ada -program and prepends them to the list of objects passed to the linker. -@command{gnatlink} also gathers any arguments set by the use of -@code{pragma Linker_Options} and adds them to the list of arguments -presented to the linker. +@geindex Convention Ada -@node Switches for gnatlink -@section Switches for @command{gnatlink} +@table @asis -@noindent -The following switches are available with the @command{gnatlink} utility: +@item @emph{Ada} -@table @option -@c !sort! +This indicates that the standard Ada calling sequence will be +used and all Ada data items may be passed without any limitations in the +case where GNAT is used to generate both the caller and callee. It is also +possible to mix GNAT generated code and code generated by another Ada +compiler. In this case, the data types should be restricted to simple +cases, including primitive types. Whether complex data types can be passed +depends on the situation. Probably it is safe to pass simple arrays, such +as arrays of integers or floats. Records may or may not work, depending +on whether both compilers lay them out identically. Complex structures +involving variant records, access parameters, tasks, or protected types, +are unlikely to be able to be passed. -@item --version -@cindex @option{--version} @command{gnatlink} -Display Copyright and version, then exit disregarding all other options. +Note that in the case of GNAT running +on a platform that supports HP Ada 83, a higher degree of compatibility +can be guaranteed, and in particular records are laid out in an identical +manner in the two compilers. Note also that if output from two different +compilers is mixed, the program is responsible for dealing with elaboration +issues. Probably the safest approach is to write the main program in the +version of Ada other than GNAT, so that it takes care of its own elaboration +requirements, and then call the GNAT-generated adainit procedure to ensure +elaboration of the GNAT components. Consult the documentation of the other +Ada compiler for further details on elaboration. -@item --help -@cindex @option{--help} @command{gnatlink} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +However, it is not possible to mix the tasking run time of GNAT and +HP Ada 83, All the tasking operations must either be entirely within +GNAT compiled sections of the program, or entirely within HP Ada 83 +compiled sections of the program. +@end table -@item -f -@cindex Command line length -@cindex @option{-f} (@command{gnatlink}) -On some targets, the command line length is limited, and @command{gnatlink} -will generate a separate file for the linker if the list of object files -is too long. -The @option{-f} switch forces this file -to be generated even if -the limit is not exceeded. This is useful in some cases to deal with -special situations where the command line length is exceeded. +@geindex Interfacing to Assembly -@item -g -@cindex Debugging information, including -@cindex @option{-g} (@command{gnatlink}) -The option to include debugging information causes the Ada bind file (in -other words, @file{b~@var{mainprog}.adb}) to be compiled with -@option{-g}. -In addition, the binder does not delete the @file{b~@var{mainprog}.adb}, -@file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files. -Without @option{-g}, the binder removes these files by -default. The same procedure apply if a C bind file was generated using -@option{-C} @code{gnatbind} option, in this case the filenames -are @file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}. - -@item -n -@cindex @option{-n} (@command{gnatlink}) -Do not compile the file generated by the binder. This may be used when -a link is rerun with different options, but there is no need to recompile -the binder file. +@geindex Convention Assembler -@item -v -@cindex @option{-v} (@command{gnatlink}) -Causes additional information to be output, including a full list of the -included object files. This switch option is most useful when you want -to see what set of object files are being used in the link step. -@item -v -v -@cindex @option{-v -v} (@command{gnatlink}) -Very verbose mode. Requests that the compiler operate in verbose mode when -it compiles the binder file, and that the system linker run in verbose mode. +@table @asis -@item -o @var{exec-name} -@cindex @option{-o} (@command{gnatlink}) -@var{exec-name} specifies an alternate name for the generated -executable program. If this switch is omitted, the executable has the same -name as the main unit. For example, @code{gnatlink try.ali} creates -an executable called @file{try}. +@item @emph{Assembler} -@item -b @var{target} -@cindex @option{-b} (@command{gnatlink}) -Compile your program to run on @var{target}, which is the name of a -system configuration. You must have a GNAT cross-compiler built if -@var{target} is not the same as your host system. +Specifies assembler as the convention. In practice this has the +same effect as convention Ada (but is not equivalent in the sense of being +considered the same convention). +@end table -@item -B@var{dir} -@cindex @option{-B} (@command{gnatlink}) -Load compiler executables (for example, @code{gnat1}, the Ada compiler) -from @var{dir} instead of the default location. Only use this switch -when multiple versions of the GNAT compiler are available. -@xref{Directory Options,,, gcc, The GNU Compiler Collection}, -for further details. You would normally use the @option{-b} or -@option{-V} switch instead. +@geindex Convention Asm -@item -M -When linking an executable, create a map file. The name of the map file -has the same name as the executable with extension ".map". +@geindex Asm -@item -M=mapfile -When linking an executable, create a map file. The name of the map file is -"mapfile". -@item --GCC=@var{compiler_name} -@cindex @option{--GCC=compiler_name} (@command{gnatlink}) -Program used for compiling the binder file. The default is -@command{gcc}. You need to use quotes around @var{compiler_name} if -@code{compiler_name} contains spaces or other separator characters. -As an example @option{--GCC="foo -x -y"} will instruct @command{gnatlink} to -use @code{foo -x -y} as your compiler. Note that switch @option{-c} is always -inserted after your command name. Thus in the above example the compiler -command that will be used by @command{gnatlink} will be @code{foo -c -x -y}. -A limitation of this syntax is that the name and path name of the executable -itself must not include any embedded spaces. If the compiler executable is -different from the default one (gcc or -gcc), then the back-end -switches in the ALI file are not used to compile the binder generated source. -For example, this is the case with @option{--GCC="foo -x -y"}. But the back end -switches will be used for @option{--GCC="gcc -gnatv"}. If several -@option{--GCC=compiler_name} are used, only the last @var{compiler_name} -is taken into account. However, all the additional switches are also taken -into account. Thus, -@option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to -@option{--GCC="bar -x -y -z -t"}. +@table @asis -@item --LINK=@var{name} -@cindex @option{--LINK=} (@command{gnatlink}) -@var{name} is the name of the linker to be invoked. This is especially -useful in mixed language programs since languages such as C++ require -their own linker to be used. When this switch is omitted, the default -name for the linker is @command{gcc}. When this switch is used, the -specified linker is called instead of @command{gcc} with exactly the same -parameters that would have been passed to @command{gcc} so if the desired -linker requires different parameters it is necessary to use a wrapper -script that massages the parameters before invoking the real linker. It -may be useful to control the exact invocation by using the verbose -switch. +@item @emph{Asm} +Equivalent to Assembler. +@geindex Interfacing to COBOL +@geindex Convention COBOL @end table -@node The GNAT Make Program gnatmake -@chapter The GNAT Make Program @command{gnatmake} -@findex gnatmake +@geindex COBOL -@menu -* Running gnatmake:: -* Switches for gnatmake:: -* Mode Switches for gnatmake:: -* Notes on the Command Line:: -* How gnatmake Works:: -* Examples of gnatmake Usage:: -@end menu -@noindent -A typical development cycle when working on an Ada program consists of -the following steps: -@enumerate -@item -Edit some sources to fix bugs. +@table @asis -@item -Add enhancements. +@item @emph{COBOL} -@item -Compile all sources affected. +Data will be passed according to the conventions described +in section B.4 of the Ada Reference Manual. +@end table -@item -Rebind and relink. +@geindex C -@item -Test. -@end enumerate +@geindex Interfacing to C -@noindent -The third step can be tricky, because not only do the modified files -@cindex Dependency rules -have to be compiled, but any files depending on these files must also be -recompiled. The dependency rules in Ada can be quite complex, especially -in the presence of overloading, @code{use} clauses, generics and inlined -subprograms. +@geindex Convention C -@command{gnatmake} automatically takes care of the third and fourth steps -of this process. It determines which sources need to be compiled, -compiles them, and binds and links the resulting object files. -Unlike some other Ada make programs, the dependencies are always -accurately recomputed from the new sources. The source based approach of -the GNAT compilation model makes this possible. This means that if -changes to the source program cause corresponding changes in -dependencies, they will always be tracked exactly correctly by -@command{gnatmake}. +@table @asis -@node Running gnatmake -@section Running @command{gnatmake} +@item @emph{C} -@noindent -The usual form of the @command{gnatmake} command is +Data will be passed according to the conventions described +in section B.3 of the Ada Reference Manual. -@smallexample -@c $ gnatmake @ovar{switches} @var{file_name} -@c @ovar{file_names} @ovar{mode_switches} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatmake @r{[}@var{switches}@r{]} @var{file_name} - @r{[}@var{file_names}@r{]} @r{[}@var{mode_switches}@r{]} -@end smallexample +A note on interfacing to a C 'varargs' function: -@noindent -The only required argument is one @var{file_name}, which specifies -a compilation unit that is a main program. Several @var{file_names} can be -specified: this will result in several executables being built. -If @code{switches} are present, they can be placed before the first -@var{file_name}, between @var{file_names} or after the last @var{file_name}. -If @var{mode_switches} are present, they must always be placed after -the last @var{file_name} and all @code{switches}. +@quotation -If you are using standard file extensions (@file{.adb} and @file{.ads}), then the -extension may be omitted from the @var{file_name} arguments. However, if -you are using non-standard extensions, then it is required that the -extension be given. A relative or absolute directory path can be -specified in a @var{file_name}, in which case, the input source file will -be searched for in the specified directory only. Otherwise, the input -source file will first be searched in the directory where -@command{gnatmake} was invoked and if it is not found, it will be search on -the source path of the compiler as described in -@ref{Search Paths and the Run-Time Library (RTL)}. +@geindex C varargs function -All @command{gnatmake} output (except when you specify -@option{-M}) is to -@file{stderr}. The output produced by the -@option{-M} switch is send to -@file{stdout}. +@geindex Interfacing to C varargs function -@node Switches for gnatmake -@section Switches for @command{gnatmake} +@geindex varargs function interfaces -@noindent -You may specify any of the following switches to @command{gnatmake}: +In C, @cite{varargs} allows a function to take a variable number of +arguments. There is no direct equivalent in this to Ada. One +approach that can be used is to create a C wrapper for each +different profile and then interface to this C wrapper. For +example, to print an @cite{int} value using @cite{printf}, +create a C function @cite{printfi} that takes two arguments, a +pointer to a string and an int, and calls @cite{printf}. +Then in the Ada program, use pragma @cite{Import} to +interface to @cite{printfi}. -@table @option -@c !sort! +It may work on some platforms to directly interface to +a @cite{varargs} function by providing a specific Ada profile +for a particular call. However, this does not work on +all platforms, since there is no guarantee that the +calling sequence for a two argument normal C function +is the same as for calling a @cite{varargs} C function with +the same two arguments. +@end quotation +@end table -@item --version -@cindex @option{--version} @command{gnatmake} -Display Copyright and version, then exit disregarding all other options. +@geindex Convention Default -@item --help -@cindex @option{--help} @command{gnatmake} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +@geindex Default -@item --GCC=@var{compiler_name} -@cindex @option{--GCC=compiler_name} (@command{gnatmake}) -Program used for compiling. The default is `@command{gcc}'. You need to use -quotes around @var{compiler_name} if @code{compiler_name} contains -spaces or other separator characters. As an example @option{--GCC="foo -x --y"} will instruct @command{gnatmake} to use @code{foo -x -y} as your -compiler. A limitation of this syntax is that the name and path name of -the executable itself must not include any embedded spaces. Note that -switch @option{-c} is always inserted after your command name. Thus in the -above example the compiler command that will be used by @command{gnatmake} -will be @code{foo -c -x -y}. If several @option{--GCC=compiler_name} are -used, only the last @var{compiler_name} is taken into account. However, -all the additional switches are also taken into account. Thus, -@option{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to -@option{--GCC="bar -x -y -z -t"}. - -@item --GNATBIND=@var{binder_name} -@cindex @option{--GNATBIND=binder_name} (@command{gnatmake}) -Program used for binding. The default is `@code{gnatbind}'. You need to -use quotes around @var{binder_name} if @var{binder_name} contains spaces -or other separator characters. As an example @option{--GNATBIND="bar -x --y"} will instruct @command{gnatmake} to use @code{bar -x -y} as your -binder. Binder switches that are normally appended by @command{gnatmake} -to `@code{gnatbind}' are now appended to the end of @code{bar -x -y}. -A limitation of this syntax is that the name and path name of the executable -itself must not include any embedded spaces. -@item --GNATLINK=@var{linker_name} -@cindex @option{--GNATLINK=linker_name} (@command{gnatmake}) -Program used for linking. The default is `@command{gnatlink}'. You need to -use quotes around @var{linker_name} if @var{linker_name} contains spaces -or other separator characters. As an example @option{--GNATLINK="lan -x --y"} will instruct @command{gnatmake} to use @code{lan -x -y} as your -linker. Linker switches that are normally appended by @command{gnatmake} to -`@command{gnatlink}' are now appended to the end of @code{lan -x -y}. -A limitation of this syntax is that the name and path name of the executable -itself must not include any embedded spaces. +@table @asis +@item @emph{Default} -@item --subdirs=subdir -Actual object directory of each project file is the subdirectory subdir of the -object directory specified or defaulted in the project file. +Equivalent to C. +@end table -@item --single-compile-per-obj-dir -Disallow simultaneous compilations in the same object directory when -project files are used. +@geindex Convention External -@item --unchecked-shared-lib-imports -By default, shared library projects are not allowed to import static library -projects. When this switch is used on the command line, this restriction is -relaxed. +@geindex External -@item --source-info= -Specify a source info file. This switch is active only when project files -are used. If the source info file is specified as a relative path, then it is -relative to the object directory of the main project. If the source info file -does not exist, then after the Project Manager has successfully parsed and -processed the project files and found the sources, it creates the source info -file. If the source info file already exists and can be read successfully, -then the Project Manager will get all the needed information about the sources -from the source info file and will not look for them. This reduces the time -to process the project files, especially when looking for sources that take a -long time. If the source info file exists but cannot be parsed successfully, -the Project Manager will attempt to recreate it. If the Project Manager fails -to create the source info file, a message is issued, but gnatmake does not -fail. @command{gnatmake} "trusts" the source info file. This means that -if the source files have changed (addition, deletion, moving to a different -source directory), then the source info file need to be deleted and recreated. -@item --create-map-file -When linking an executable, create a map file. The name of the map file -has the same name as the executable with extension ".map". +@table @asis -@item --create-map-file=mapfile -When linking an executable, create a map file. The name of the map file is -"mapfile". +@item @emph{External} +Equivalent to C. +@end table -@item -a -@cindex @option{-a} (@command{gnatmake}) -Consider all files in the make process, even the GNAT internal system -files (for example, the predefined Ada library files), as well as any -locked files. Locked files are files whose ALI file is write-protected. -By default, -@command{gnatmake} does not check these files, -because the assumption is that the GNAT internal files are properly up -to date, and also that any write protected ALI files have been properly -installed. Note that if there is an installation problem, such that one -of these files is not up to date, it will be properly caught by the -binder. -You may have to specify this switch if you are working on GNAT -itself. The switch @option{-a} is also useful -in conjunction with @option{-f} -if you need to recompile an entire application, -including run-time files, using special configuration pragmas, -such as a @code{Normalize_Scalars} pragma. +@geindex C++ -By default -@code{gnatmake -a} compiles all GNAT -internal files with -@code{gcc -c -gnatpg} rather than @code{gcc -c}. +@geindex Interfacing to C++ -@item -b -@cindex @option{-b} (@command{gnatmake}) -Bind only. Can be combined with @option{-c} to do -compilation and binding, but no link. -Can be combined with @option{-l} -to do binding and linking. When not combined with -@option{-c} -all the units in the closure of the main program must have been previously -compiled and must be up to date. The root unit specified by @var{file_name} -may be given without extension, with the source extension or, if no GNAT -Project File is specified, with the ALI file extension. +@geindex Convention C++ -@item -c -@cindex @option{-c} (@command{gnatmake}) -Compile only. Do not perform binding, except when @option{-b} -is also specified. Do not perform linking, except if both -@option{-b} and -@option{-l} are also specified. -If the root unit specified by @var{file_name} is not a main unit, this is the -default. Otherwise @command{gnatmake} will attempt binding and linking -unless all objects are up to date and the executable is more recent than -the objects. -@item -C -@cindex @option{-C} (@command{gnatmake}) -Use a temporary mapping file. A mapping file is a way to communicate -to the compiler two mappings: from unit names to file names (without -any directory information) and from file names to path names (with -full directory information). A mapping file can make the compiler's -file searches faster, especially if there are many source directories, -or the sources are read over a slow network connection. If -@option{-P} is used, a mapping file is always used, so -@option{-C} is unnecessary; in this case the mapping file -is initially populated based on the project file. If -@option{-C} is used without -@option{-P}, -the mapping file is initially empty. Each invocation of the compiler -will add any newly accessed sources to the mapping file. +@table @asis -@item -C=@var{file} -@cindex @option{-C=} (@command{gnatmake}) -Use a specific mapping file. The file, specified as a path name (absolute or -relative) by this switch, should already exist, otherwise the switch is -ineffective. The specified mapping file will be communicated to the compiler. -This switch is not compatible with a project file -(-P@var{file}) or with multiple compiling processes -(-jnnn, when nnn is greater than 1). +@item @emph{C_Plus_Plus (or CPP)} -@item -d -@cindex @option{-d} (@command{gnatmake}) -Display progress for each source, up to date or not, as a single line +This stands for C++. For most purposes this is identical to C. +See the separate description of the specialized GNAT pragmas relating to +C++ interfacing for further details. +@end table -@smallexample -completed x out of y (zz%) -@end smallexample +@geindex Fortran -If the file needs to be compiled this is displayed after the invocation of -the compiler. These lines are displayed even in quiet output mode. +@geindex Interfacing to Fortran -@item -D @var{dir} -@cindex @option{-D} (@command{gnatmake}) -Put all object files and ALI file in directory @var{dir}. -If the @option{-D} switch is not used, all object files -and ALI files go in the current working directory. +@geindex Convention Fortran -This switch cannot be used when using a project file. -@item -eInnn -@cindex @option{-eI} (@command{gnatmake}) -Indicates that the main source is a multi-unit source and the rank of the unit -in the source file is nnn. nnn needs to be a positive number and a valid -index in the source. This switch cannot be used when @command{gnatmake} is -invoked for several mains. +@table @asis -@item -eL -@cindex @option{-eL} (@command{gnatmake}) -@cindex symbolic links -Follow all symbolic links when processing project files. -This should be used if your project uses symbolic links for files or -directories, but is not needed in other cases. +@item @emph{Fortran} -@cindex naming scheme -This also assumes that no directory matches the naming scheme for files (for -instance that you do not have a directory called "sources.ads" when using the -default GNAT naming scheme). +Data will be passed according to the conventions described +in section B.5 of the Ada Reference Manual. -When you do not have to use this switch (i.e.@: by default), gnatmake is able to -save a lot of system calls (several per source file and object file), which -can result in a significant speed up to load and manipulate a project file, -especially when using source files from a remote system. +@item @emph{Intrinsic} +This applies to an intrinsic operation, as defined in the Ada +Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram, +this means that the body of the subprogram is provided by the compiler itself, +usually by means of an efficient code sequence, and that the user does not +supply an explicit body for it. In an application program, the pragma may +be applied to the following sets of names: -@item -eS -@cindex @option{-eS} (@command{gnatmake}) -Output the commands for the compiler, the binder and the linker -on standard output, -instead of standard error. -@item -f -@cindex @option{-f} (@command{gnatmake}) -Force recompilations. Recompile all sources, even though some object -files may be up to date, but don't recompile predefined or GNAT internal -files or locked files (files with a write-protected ALI file), -unless the @option{-a} switch is also specified. +@itemize * -@item -F -@cindex @option{-F} (@command{gnatmake}) -When using project files, if some errors or warnings are detected during -parsing and verbose mode is not in effect (no use of switch --v), then error lines start with the full path name of the project -file, rather than its simple file name. +@item +Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic. +The corresponding subprogram declaration must have +two formal parameters. The +first one must be a signed integer type or a modular type with a binary +modulus, and the second parameter must be of type Natural. +The return type must be the same as the type of the first argument. The size +of this type can only be 8, 16, 32, or 64. -@item -g -@cindex @option{-g} (@command{gnatmake}) -Enable debugging. This switch is simply passed to the compiler and to the -linker. +@item +Binary arithmetic operators: '+', '-', '*', '/'. +The corresponding operator declaration must have parameters and result type +that have the same root numeric type (for example, all three are long_float +types). This simplifies the definition of operations that use type checking +to perform dimensional checks: +@end itemize -@item -i -@cindex @option{-i} (@command{gnatmake}) -In normal mode, @command{gnatmake} compiles all object files and ALI files -into the current directory. If the @option{-i} switch is used, -then instead object files and ALI files that already exist are overwritten -in place. This means that once a large project is organized into separate -directories in the desired manner, then @command{gnatmake} will automatically -maintain and update this organization. If no ALI files are found on the -Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}), -the new object and ALI files are created in the -directory containing the source being compiled. If another organization -is desired, where objects and sources are kept in different directories, -a useful technique is to create dummy ALI files in the desired directories. -When detecting such a dummy file, @command{gnatmake} will be forced to -recompile the corresponding source file, and it will be put the resulting -object and ALI files in the directory where it found the dummy file. +@c code-block: ada +@c +@c type Distance is new Long_Float; +@c type Time is new Long_Float; +@c type Velocity is new Long_Float; +@c function "/" (D : Distance; T : Time) +@c return Velocity; +@c pragma Import (Intrinsic, "/"); +@c +@c This common idiom is often programmed with a generic definition and an +@c explicit body. The pragma makes it simpler to introduce such declarations. +@c It incurs no overhead in compilation time or code size, because it is +@c implemented as a single machine instruction. + + +@itemize * + +@item +General subprogram entities. This is used to bind an Ada subprogram +declaration to +a compiler builtin by name with back-ends where such interfaces are +available. A typical example is the set of @cite{__builtin} functions +exposed by the GCC back-end, as in the following example: -@item -j@var{n} -@cindex @option{-j} (@command{gnatmake}) -@cindex Parallel make -Use @var{n} processes to carry out the (re)compilations. On a multiprocessor -machine compilations will occur in parallel. If @var{n} is 0, then the -maximum number of parallel compilations is the number of core processors -on the platform. In the event of compilation errors, messages from various -compilations might get interspersed (but @command{gnatmake} will give you the -full ordered list of failing compiles at the end). If this is problematic, -rerun the make process with n set to 1 to get a clean list of messages. +@example +function builtin_sqrt (F : Float) return Float; +pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf"); +@end example -@item -k -@cindex @option{-k} (@command{gnatmake}) -Keep going. Continue as much as possible after a compilation error. To -ease the programmer's task in case of compilation errors, the list of -sources for which the compile fails is given when @command{gnatmake} -terminates. +Most of the GCC builtins are accessible this way, and as for other +import conventions (e.g. C), it is the user's responsibility to ensure +that the Ada subprogram profile matches the underlying builtin +expectations. +@end itemize +@end table -If @command{gnatmake} is invoked with several @file{file_names} and with this -switch, if there are compilation errors when building an executable, -@command{gnatmake} will not attempt to build the following executables. +@geindex Stdcall -@item -l -@cindex @option{-l} (@command{gnatmake}) -Link only. Can be combined with @option{-b} to binding -and linking. Linking will not be performed if combined with -@option{-c} -but not with @option{-b}. -When not combined with @option{-b} -all the units in the closure of the main program must have been previously -compiled and must be up to date, and the main program needs to have been bound. -The root unit specified by @var{file_name} -may be given without extension, with the source extension or, if no GNAT -Project File is specified, with the ALI file extension. +@geindex Convention Stdcall -@item -m -@cindex @option{-m} (@command{gnatmake}) -Specify that the minimum necessary amount of recompilations -be performed. In this mode @command{gnatmake} ignores time -stamp differences when the only -modifications to a source file consist in adding/removing comments, -empty lines, spaces or tabs. This means that if you have changed the -comments in a source file or have simply reformatted it, using this -switch will tell @command{gnatmake} not to recompile files that depend on it -(provided other sources on which these files depend have undergone no -semantic modifications). Note that the debugging information may be -out of date with respect to the sources if the @option{-m} switch causes -a compilation to be switched, so the use of this switch represents a -trade-off between compilation time and accurate debugging information. -@item -M -@cindex Dependencies, producing list -@cindex @option{-M} (@command{gnatmake}) -Check if all objects are up to date. If they are, output the object -dependences to @file{stdout} in a form that can be directly exploited in -a @file{Makefile}. By default, each source file is prefixed with its -(relative or absolute) directory name. This name is whatever you -specified in the various @option{-aI} -and @option{-I} switches. If you use -@code{gnatmake -M} -@option{-q} -(see below), only the source file names, -without relative paths, are output. If you just specify the -@option{-M} -switch, dependencies of the GNAT internal system files are omitted. This -is typically what you want. If you also specify -the @option{-a} switch, -dependencies of the GNAT internal files are also listed. Note that -dependencies of the objects in external Ada libraries (see switch -@option{-aL}@var{dir} in the following list) -are never reported. +@table @asis -@item -n -@cindex @option{-n} (@command{gnatmake}) -Don't compile, bind, or link. Checks if all objects are up to date. -If they are not, the full name of the first file that needs to be -recompiled is printed. -Repeated use of this option, followed by compiling the indicated source -file, will eventually result in recompiling all required units. +@item @emph{Stdcall} -@item -o @var{exec_name} -@cindex @option{-o} (@command{gnatmake}) -Output executable name. The name of the final executable program will be -@var{exec_name}. If the @option{-o} switch is omitted the default -name for the executable will be the name of the input file in appropriate form -for an executable file on the host system. +This is relevant only to Windows XP/2000/NT implementations of GNAT, +and specifies that the @cite{Stdcall} calling sequence will be used, +as defined by the NT API. Nevertheless, to ease building +cross-platform bindings this convention will be handled as a @cite{C} calling +convention on non-Windows platforms. +@end table -This switch cannot be used when invoking @command{gnatmake} with several -@file{file_names}. +@geindex DLL -@item -p or --create-missing-dirs -@cindex @option{-p} (@command{gnatmake}) -When using project files (-P@var{project}), create -automatically missing object directories, library directories and exec -directories. +@geindex Convention DLL -@item -P@var{project} -@cindex @option{-P} (@command{gnatmake}) -Use project file @var{project}. Only one such switch can be used. -@xref{gnatmake and Project Files}. -@item -q -@cindex @option{-q} (@command{gnatmake}) -Quiet. When this flag is not set, the commands carried out by -@command{gnatmake} are displayed. +@table @asis -@item -s -@cindex @option{-s} (@command{gnatmake}) -Recompile if compiler switches have changed since last compilation. -All compiler switches but -I and -o are taken into account in the -following way: -orders between different ``first letter'' switches are ignored, but -orders between same switches are taken into account. For example, -@option{-O -O2} is different than @option{-O2 -O}, but @option{-g -O} -is equivalent to @option{-O -g}. +@item @emph{DLL} -This switch is recommended when Integrated Preprocessing is used. +This is equivalent to @cite{Stdcall}. +@end table -@item -u -@cindex @option{-u} (@command{gnatmake}) -Unique. Recompile at most the main files. It implies -c. Combined with --f, it is equivalent to calling the compiler directly. Note that using --u with a project file and no main has a special meaning -(@pxref{Project Files and Main Subprograms}). +@geindex Win32 -@item -U -@cindex @option{-U} (@command{gnatmake}) -When used without a project file or with one or several mains on the command -line, is equivalent to -u. When used with a project file and no main -on the command line, all sources of all project files are checked and compiled -if not up to date, and libraries are rebuilt, if necessary. +@geindex Convention Win32 -@item -v -@cindex @option{-v} (@command{gnatmake}) -Verbose. Display the reason for all recompilations @command{gnatmake} -decides are necessary, with the highest verbosity level. -@item -vl -@cindex @option{-vl} (@command{gnatmake}) -Verbosity level Low. Display fewer lines than in verbosity Medium. +@table @asis -@item -vm -@cindex @option{-vm} (@command{gnatmake}) -Verbosity level Medium. Potentially display fewer lines than in verbosity High. +@item @emph{Win32} -@item -vh -@cindex @option{-vm} (@command{gnatmake}) -Verbosity level High. Equivalent to -v. +This is equivalent to @cite{Stdcall}. +@end table -@item -vP@emph{x} -Indicate the verbosity of the parsing of GNAT project files. -@xref{Switches Related to Project Files}. +@geindex Stubbed -@item -x -@cindex @option{-x} (@command{gnatmake}) -Indicate that sources that are not part of any Project File may be compiled. -Normally, when using Project Files, only sources that are part of a Project -File may be compile. When this switch is used, a source outside of all Project -Files may be compiled. The ALI file and the object file will be put in the -object directory of the main Project. The compilation switches used will only -be those specified on the command line. Even when -@option{-x} is used, mains specified on the -command line need to be sources of a project file. +@geindex Convention Stubbed -@item -X@var{name=value} -Indicate that external variable @var{name} has the value @var{value}. -The Project Manager will use this value for occurrences of -@code{external(name)} when parsing the project file. -@xref{Switches Related to Project Files}. -@item -z -@cindex @option{-z} (@command{gnatmake}) -No main subprogram. Bind and link the program even if the unit name -given on the command line is a package name. The resulting executable -will execute the elaboration routines of the package and its closure, -then the finalization routines. +@table @asis -@end table +@item @emph{Stubbed} -@table @asis -@item @command{gcc} @asis{switches} -Any uppercase or multi-character switch that is not a @command{gnatmake} switch -is passed to @command{gcc} (e.g.@: @option{-O}, @option{-gnato,} etc.) +This is a special convention that indicates that the compiler +should provide a stub body that raises @cite{Program_Error}. @end table -@noindent -Source and library search path switches: +GNAT additionally provides a useful pragma @cite{Convention_Identifier} +that can be used to parameterize conventions and allow additional synonyms +to be specified. For example if you have legacy code in which the convention +identifier Fortran77 was used for Fortran, you can use the configuration +pragma: -@table @option -@c !sort! -@item -aI@var{dir} -@cindex @option{-aI} (@command{gnatmake}) -When looking for source files also look in directory @var{dir}. -The order in which source files search is undertaken is -described in @ref{Search Paths and the Run-Time Library (RTL)}. - -@item -aL@var{dir} -@cindex @option{-aL} (@command{gnatmake}) -Consider @var{dir} as being an externally provided Ada library. -Instructs @command{gnatmake} to skip compilation units whose @file{.ALI} -files have been located in directory @var{dir}. This allows you to have -missing bodies for the units in @var{dir} and to ignore out of date bodies -for the same units. You still need to specify -the location of the specs for these units by using the switches -@option{-aI@var{dir}} -or @option{-I@var{dir}}. -Note: this switch is provided for compatibility with previous versions -of @command{gnatmake}. The easier method of causing standard libraries -to be excluded from consideration is to write-protect the corresponding -ALI files. +@example +pragma Convention_Identifier (Fortran77, Fortran); +@end example -@item -aO@var{dir} -@cindex @option{-aO} (@command{gnatmake}) -When searching for library and object files, look in directory -@var{dir}. The order in which library files are searched is described in -@ref{Search Paths for gnatbind}. - -@item -A@var{dir} -@cindex Search paths, for @command{gnatmake} -@cindex @option{-A} (@command{gnatmake}) -Equivalent to @option{-aL@var{dir} --aI@var{dir}}. - -@item -I@var{dir} -@cindex @option{-I} (@command{gnatmake}) -Equivalent to @option{-aO@var{dir} --aI@var{dir}}. - -@item -I- -@cindex @option{-I-} (@command{gnatmake}) -@cindex Source files, suppressing search -Do not look for source files in the directory containing the source -file named in the command line. -Do not look for ALI or object files in the directory -where @command{gnatmake} was invoked. +And from now on the identifier Fortran77 may be used as a convention +identifier (for example in an @cite{Import} pragma) with the same +meaning as Fortran. -@item -L@var{dir} -@cindex @option{-L} (@command{gnatmake}) -@cindex Linker libraries -Add directory @var{dir} to the list of directories in which the linker -will search for libraries. This is equivalent to -@option{-largs -L}@var{dir}. -Furthermore, under Windows, the sources pointed to by the libraries path -set in the registry are not searched for. +@node Building Mixed Ada and C++ Programs,Generating Ada Bindings for C and C++ headers,Calling Conventions,Mixed Language Programming +@anchor{gnat_ugn/the_gnat_compilation_model id64}@anchor{bd}@anchor{gnat_ugn/the_gnat_compilation_model building-mixed-ada-and-c-programs}@anchor{be} +@subsection Building Mixed Ada and C++ Programs -@item -nostdinc -@cindex @option{-nostdinc} (@command{gnatmake}) -Do not look for source files in the system default directory. -@item -nostdlib -@cindex @option{-nostdlib} (@command{gnatmake}) -Do not look for library files in the system default directory. +A programmer inexperienced with mixed-language development may find that +building an application containing both Ada and C++ code can be a +challenge. This section gives a few hints that should make this task easier. -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatmake}) -Specifies the default location of the runtime library. GNAT looks for the -runtime -in the following directories, and stops as soon as a valid runtime is found -(@file{adainclude} or @file{ada_source_path}, and @file{adalib} or -@file{ada_object_path} present): +@menu +* Interfacing to C++:: +* Linking a Mixed C++ & Ada Program:: +* A Simple Example:: +* Interfacing with C++ constructors:: +* Interfacing with C++ at the Class Level:: -@itemize @bullet -@item /$rts_path +@end menu -@item /$rts_path +@node Interfacing to C++,Linking a Mixed C++ & Ada Program,,Building Mixed Ada and C++ Programs +@anchor{gnat_ugn/the_gnat_compilation_model id65}@anchor{bf}@anchor{gnat_ugn/the_gnat_compilation_model id66}@anchor{c0} +@subsubsection Interfacing to C++ -@item /rts-$rts_path -@end itemize -@noindent -The selected path is handled like a normal RTS path. +GNAT supports interfacing with the G++ compiler (or any C++ compiler +generating code that is compatible with the G++ Application Binary +Interface ---see @indicateurl{http://www.codesourcery.com/archives/cxx-abi}). -@end table +Interfacing can be done at 3 levels: simple data, subprograms, and +classes. In the first two cases, GNAT offers a specific @cite{Convention C_Plus_Plus} +(or @cite{CPP}) that behaves exactly like @cite{Convention C}. +Usually, C++ mangles the names of subprograms. To generate proper mangled +names automatically, see @ref{1b,,Generating Ada Bindings for C and C++ headers}). +This problem can also be addressed manually in two ways: -@node Mode Switches for gnatmake -@section Mode Switches for @command{gnatmake} -@noindent -The mode switches (referred to as @code{mode_switches}) allow the -inclusion of switches that are to be passed to the compiler itself, the -binder or the linker. The effect of a mode switch is to cause all -subsequent switches up to the end of the switch list, or up to the next -mode switch, to be interpreted as switches to be passed on to the -designated component of GNAT. +@itemize * -@table @option -@c !sort! -@item -cargs @var{switches} -@cindex @option{-cargs} (@command{gnatmake}) -Compiler switches. Here @var{switches} is a list of switches -that are valid switches for @command{gcc}. They will be passed on to -all compile steps performed by @command{gnatmake}. - -@item -bargs @var{switches} -@cindex @option{-bargs} (@command{gnatmake}) -Binder switches. Here @var{switches} is a list of switches -that are valid switches for @code{gnatbind}. They will be passed on to -all bind steps performed by @command{gnatmake}. - -@item -largs @var{switches} -@cindex @option{-largs} (@command{gnatmake}) -Linker switches. Here @var{switches} is a list of switches -that are valid switches for @command{gnatlink}. They will be passed on to -all link steps performed by @command{gnatmake}. - -@item -margs @var{switches} -@cindex @option{-margs} (@command{gnatmake}) -Make switches. The switches are directly interpreted by @command{gnatmake}, -regardless of any previous occurrence of @option{-cargs}, @option{-bargs} -or @option{-largs}. -@end table - -@node Notes on the Command Line -@section Notes on the Command Line - -@noindent -This section contains some additional useful notes on the operation -of the @command{gnatmake} command. +@item +by modifying the C++ code in order to force a C convention using +the @cite{extern "C"} syntax. -@itemize @bullet -@item -@cindex Recompilation, by @command{gnatmake} -If @command{gnatmake} finds no ALI files, it recompiles the main program -and all other units required by the main program. -This means that @command{gnatmake} -can be used for the initial compile, as well as during subsequent steps of -the development cycle. +@item +by figuring out the mangled name (using e.g. @emph{nm}) and using it as the +Link_Name argument of the pragma import. +@end itemize -@item -If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb} -is a subunit or body of a generic unit, @command{gnatmake} recompiles -@file{@var{file}.adb} (because it finds no ALI) and stops, issuing a -warning. +Interfacing at the class level can be achieved by using the GNAT specific +pragmas such as @cite{CPP_Constructor}. See the @cite{GNAT_Reference_Manual} for additional information. -@item -In @command{gnatmake} the switch @option{-I} -is used to specify both source and -library file paths. Use @option{-aI} -instead if you just want to specify -source paths only and @option{-aO} -if you want to specify library paths -only. +@node Linking a Mixed C++ & Ada Program,A Simple Example,Interfacing to C++,Building Mixed Ada and C++ Programs +@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-ada-program}@anchor{c1}@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-and-ada-program}@anchor{c2} +@subsubsection Linking a Mixed C++ & Ada Program -@item -@command{gnatmake} will ignore any files whose ALI file is write-protected. -This may conveniently be used to exclude standard libraries from -consideration and in particular it means that the use of the -@option{-f} switch will not recompile these files -unless @option{-a} is also specified. -@item -@command{gnatmake} has been designed to make the use of Ada libraries -particularly convenient. Assume you have an Ada library organized -as follows: @i{obj-dir} contains the objects and ALI files for -of your Ada compilation units, -whereas @i{include-dir} contains the -specs of these units, but no bodies. Then to compile a unit -stored in @code{main.adb}, which uses this Ada library you would just type +Usually the linker of the C++ development system must be used to link +mixed applications because most C++ systems will resolve elaboration +issues (such as calling constructors on global class instances) +transparently during the link phase. GNAT has been adapted to ease the +use of a foreign linker for the last phase. Three cases can be +considered: -@smallexample -$ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main -@end smallexample -@item -Using @command{gnatmake} along with the -@option{-m (minimal recompilation)} -switch provides a mechanism for avoiding unnecessary recompilations. Using -this switch, -you can update the comments/format of your -source files without having to recompile everything. Note, however, that -adding or deleting lines in a source files may render its debugging -info obsolete. If the file in question is a spec, the impact is rather -limited, as that debugging info will only be useful during the -elaboration phase of your program. For bodies the impact can be more -significant. In all events, your debugger will warn you if a source file -is more recent than the corresponding object, and alert you to the fact -that the debugging information may be out of date. -@end itemize +@itemize * -@node How gnatmake Works -@section How @command{gnatmake} Works +@item +Using GNAT and G++ (GNU C++ compiler) from the same GCC installation: +The C++ linker can simply be called by using the C++ specific driver +called @cite{g++}. -@noindent -Generally @command{gnatmake} automatically performs all necessary -recompilations and you don't need to worry about how it works. However, -it may be useful to have some basic understanding of the @command{gnatmake} -approach and in particular to understand how it uses the results of -previous compilations without incorrectly depending on them. +Note that if the C++ code uses inline functions, you will need to +compile your C++ code with the @cite{-fkeep-inline-functions} switch in +order to provide an existing function implementation that the Ada code can +link with. -First a definition: an object file is considered @dfn{up to date} if the -corresponding ALI file exists and if all the source files listed in the -dependency section of this ALI file have time stamps matching those in -the ALI file. This means that neither the source file itself nor any -files that it depends on have been modified, and hence there is no need -to recompile this file. +@example +$ g++ -c -fkeep-inline-functions file1.C +$ g++ -c -fkeep-inline-functions file2.C +$ gnatmake ada_unit -largs file1.o file2.o --LINK=g++ +@end example -@command{gnatmake} works by first checking if the specified main unit is up -to date. If so, no compilations are required for the main unit. If not, -@command{gnatmake} compiles the main program to build a new ALI file that -reflects the latest sources. Then the ALI file of the main unit is -examined to find all the source files on which the main program depends, -and @command{gnatmake} recursively applies the above procedure on all these -files. +@item +Using GNAT and G++ from two different GCC installations: If both +compilers are on the :envvar`PATH`, the previous method may be used. It is +important to note that environment variables such as +@geindex C_INCLUDE_PATH +@geindex environment variable; C_INCLUDE_PATH +@code{C_INCLUDE_PATH}, +@geindex GCC_EXEC_PREFIX +@geindex environment variable; GCC_EXEC_PREFIX +@code{GCC_EXEC_PREFIX}, +@geindex BINUTILS_ROOT +@geindex environment variable; BINUTILS_ROOT +@code{BINUTILS_ROOT}, and +@geindex GCC_ROOT +@geindex environment variable; GCC_ROOT +@code{GCC_ROOT} will affect both compilers +at the same time and may make one of the two compilers operate +improperly if set during invocation of the wrong compiler. It is also +very important that the linker uses the proper @code{libgcc.a} GCC +library -- that is, the one from the C++ compiler installation. The +implicit link command as suggested in the @cite{gnatmake} command +from the former example can be replaced by an explicit link command with +the full-verbosity option in order to verify which library is used: -This process ensures that @command{gnatmake} only trusts the dependencies -in an existing ALI file if they are known to be correct. Otherwise it -always recompiles to determine a new, guaranteed accurate set of -dependencies. As a result the program is compiled ``upside down'' from what may -be more familiar as the required order of compilation in some other Ada -systems. In particular, clients are compiled before the units on which -they depend. The ability of GNAT to compile in any order is critical in -allowing an order of compilation to be chosen that guarantees that -@command{gnatmake} will recompute a correct set of new dependencies if -necessary. +@example +$ gnatbind ada_unit +$ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++ +@end example -When invoking @command{gnatmake} with several @var{file_names}, if a unit is -imported by several of the executables, it will be recompiled at most once. +If there is a problem due to interfering environment variables, it can +be worked around by using an intermediate script. The following example +shows the proper script to use when GNAT has not been installed at its +default location and g++ has been installed at its default location: -Note: when using non-standard naming conventions -(@pxref{Using Other File Names}), changing through a configuration pragmas -file the version of a source and invoking @command{gnatmake} to recompile may -have no effect, if the previous version of the source is still accessible -by @command{gnatmake}. It may be necessary to use the switch --f. +@example +$ cat ./my_script +#!/bin/sh +unset BINUTILS_ROOT +unset GCC_ROOT +c++ $* +$ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script +@end example -@node Examples of gnatmake Usage -@section Examples of @command{gnatmake} Usage +@item +Using a non-GNU C++ compiler: The commands previously described can be +used to insure that the C++ linker is used. Nonetheless, you need to add +a few more parameters to the link command line, depending on the exception +mechanism used. -@table @code -@item gnatmake hello.adb -Compile all files necessary to bind and link the main program -@file{hello.adb} (containing unit @code{Hello}) and bind and link the -resulting object files to generate an executable file @file{hello}. +If the @cite{setjmp/longjmp} exception mechanism is used, only the paths +to the libgcc libraries are required: -@item gnatmake main1 main2 main3 -Compile all files necessary to bind and link the main programs -@file{main1.adb} (containing unit @code{Main1}), @file{main2.adb} -(containing unit @code{Main2}) and @file{main3.adb} -(containing unit @code{Main3}) and bind and link the resulting object files -to generate three executable files @file{main1}, -@file{main2} -and @file{main3}. +@example +$ cat ./my_script +#!/bin/sh +CC $* `gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` +$ gnatlink ada_unit file1.o file2.o --LINK=./my_script +@end example -@item gnatmake -q Main_Unit -cargs -O2 -bargs -l +where CC is the name of the non-GNU C++ compiler. -Compile all files necessary to bind and link the main program unit -@code{Main_Unit} (from file @file{main_unit.adb}). All compilations will -be done with optimization level 2 and the order of elaboration will be -listed by the binder. @command{gnatmake} will operate in quiet mode, not -displaying commands it is executing. -@end table +If the @cite{zero cost} exception mechanism is used, and the platform +supports automatic registration of exception tables (e.g., Solaris), +paths to more objects are required: -@c ************************* -@node Improving Performance -@chapter Improving Performance -@cindex Improving performance +@example +$ cat ./my_script +#!/bin/sh +CC `gcc -print-file-name=crtbegin.o` $* \\ +`gcc -print-file-name=libgcc.a` `gcc -print-file-name=libgcc_eh.a` \\ +`gcc -print-file-name=crtend.o` +$ gnatlink ada_unit file1.o file2.o --LINK=./my_script +@end example -@noindent -This chapter presents several topics related to program performance. -It first describes some of the tradeoffs that need to be considered -and some of the techniques for making your program run faster. -It then documents -@ifclear FSFEDITION -the @command{gnatelim} tool and -@end ifclear -unused subprogram/data -elimination feature, which can reduce the size of program executables. +If the "zero cost exception" mechanism is used, and the platform +doesn't support automatic registration of exception tables (e.g., HP-UX +or AIX), the simple approach described above will not work and +a pre-linking phase using GNAT will be necessary. +@end itemize -@ifnottex -@menu -* Performance Considerations:: -* Text_IO Suggestions:: -@ifclear FSFEDITION -* Reducing Size of Ada Executables with gnatelim:: -@end ifclear -* Reducing Size of Executables with unused subprogram/data elimination:: -@end menu -@end ifnottex +Another alternative is to use the @strong{gprbuild} multi-language builder +which has a large knowledge base and knows how to link Ada and C++ code +together automatically in most cases. -@c ***************************** -@node Performance Considerations -@section Performance Considerations +@node A Simple Example,Interfacing with C++ constructors,Linking a Mixed C++ & Ada Program,Building Mixed Ada and C++ Programs +@anchor{gnat_ugn/the_gnat_compilation_model id67}@anchor{c3}@anchor{gnat_ugn/the_gnat_compilation_model a-simple-example}@anchor{c4} +@subsubsection A Simple Example -@noindent -The GNAT system provides a number of options that allow a trade-off -between -@itemize @bullet -@item -performance of the generated code +The following example, provided as part of the GNAT examples, shows how +to achieve procedural interfacing between Ada and C++ in both +directions. The C++ class A has two methods. The first method is exported +to Ada by the means of an extern C wrapper function. The second method +calls an Ada subprogram. On the Ada side, The C++ calls are modelled by +a limited record with a layout comparable to the C++ class. The Ada +subprogram, in turn, calls the C++ method. So, starting from the C++ +main program, the process passes back and forth between the two +languages. -@item -speed of compilation +Here are the compilation commands: -@item -minimization of dependences and recompilation +@example +$ gnatmake -c simple_cpp_interface +$ g++ -c cpp_main.C +$ g++ -c ex7.C +$ gnatbind -n simple_cpp_interface +$ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o +@end example -@item -the degree of run-time checking. -@end itemize +Here are the corresponding sources: -@noindent -The defaults (if no options are selected) aim at improving the speed -of compilation and minimizing dependences, at the expense of performance -of the generated code: +@example +//cpp_main.C -@itemize @bullet -@item -no optimization +#include "ex7.h" -@item -no inlining of subprogram calls +extern "C" @{ + void adainit (void); + void adafinal (void); + void method1 (A *t); +@} -@item -all run-time checks enabled except overflow and elaboration checks -@end itemize +void method1 (A *t) +@{ + t->method1 (); +@} -@noindent -These options are suitable for most program development purposes. This -chapter describes how you can modify these choices, and also provides -some guidelines on debugging optimized code. +int main () +@{ + A obj; + adainit (); + obj.method2 (3030); + adafinal (); +@} +@end example -@menu -* Controlling Run-Time Checks:: -* Use of Restrictions:: -* Optimization Levels:: -* Debugging Optimized Code:: -* Inlining of Subprograms:: -* Vectorization of loops:: -* Other Optimization Switches:: -* Optimization and Strict Aliasing:: -* Aliased Variables and Optimization:: -* Atomic Variables and Optimization:: -* Passive Task Optimization:: +@example +//ex7.h -@end menu +class Origin @{ + public: + int o_value; +@}; +class A : public Origin @{ + public: + void method1 (void); + void method2 (int v); + A(); + int a_value; +@}; +@end example -@node Controlling Run-Time Checks -@subsection Controlling Run-Time Checks +@example +//ex7.C -@noindent -By default, GNAT generates all run-time checks, except integer overflow -checks, stack overflow checks, and checks for access before elaboration on -subprogram calls. The latter are not required in default mode, because all -necessary checking is done at compile time. -@cindex @option{-gnatp} (@command{gcc}) -@cindex @option{-gnato} (@command{gcc}) -Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to -be modified. @xref{Run-Time Checks}. +#include "ex7.h" +#include -Our experience is that the default is suitable for most development -purposes. +extern "C" @{ void ada_method2 (A *t, int v);@} -We treat integer overflow specially because these -are quite expensive and in our experience are not as important as other -run-time checks in the development process. Note that division by zero -is not considered an overflow check, and divide by zero checks are -generated where required by default. +void A::method1 (void) +@{ + a_value = 2020; + printf ("in A::method1, a_value = %d \\n",a_value); +@} -Elaboration checks are off by default, and also not needed by default, since -GNAT uses a static elaboration analysis approach that avoids the need for -run-time checking. This manual contains a full chapter discussing the issue -of elaboration checks, and if the default is not satisfactory for your use, -you should read this chapter. +void A::method2 (int v) +@{ + ada_method2 (this, v); + printf ("in A::method2, a_value = %d \\n",a_value); +@} -For validity checks, the minimal checks required by the Ada Reference -Manual (for case statements and assignments to array elements) are on -by default. These can be suppressed by use of the @option{-gnatVn} switch. -Note that in Ada 83, there were no validity checks, so if the Ada 83 mode -is acceptable (or when comparing GNAT performance with an Ada 83 compiler), -it may be reasonable to routinely use @option{-gnatVn}. Validity checks -are also suppressed entirely if @option{-gnatp} is used. - -@cindex Overflow checks -@cindex Checks, overflow -@findex Suppress -@findex Unsuppress -@cindex pragma Suppress -@cindex pragma Unsuppress -Note that the setting of the switches controls the default setting of -the checks. They may be modified using either @code{pragma Suppress} (to -remove checks) or @code{pragma Unsuppress} (to add back suppressed -checks) in the program source. +A::A(void) +@{ + a_value = 1010; + printf ("in A::A, a_value = %d \\n",a_value); +@} +@end example + +@example +-- simple_cpp_interface.ads +with System; +package Simple_Cpp_Interface is + type A is limited + record + Vptr : System.Address; + O_Value : Integer; + A_Value : Integer; + end record; + pragma Convention (C, A); -@node Use of Restrictions -@subsection Use of Restrictions + procedure Method1 (This : in out A); + pragma Import (C, Method1); -@noindent -The use of pragma Restrictions allows you to control which features are -permitted in your program. Apart from the obvious point that if you avoid -relatively expensive features like finalization (enforceable by the use -of pragma Restrictions (No_Finalization), the use of this pragma does not -affect the generated code in most cases. + procedure Ada_Method2 (This : in out A; V : Integer); + pragma Export (C, Ada_Method2); -One notable exception to this rule is that the possibility of task abort -results in some distributed overhead, particularly if finalization or -exception handlers are used. The reason is that certain sections of code -have to be marked as non-abortable. +end Simple_Cpp_Interface; +@end example -If you use neither the @code{abort} statement, nor asynchronous transfer -of control (@code{select @dots{} then abort}), then this distributed overhead -is removed, which may have a general positive effect in improving -overall performance. Especially code involving frequent use of tasking -constructs and controlled types will show much improved performance. -The relevant restrictions pragmas are +@example +-- simple_cpp_interface.adb +package body Simple_Cpp_Interface is -@smallexample @c ada - @b{pragma} Restrictions (No_Abort_Statements); - @b{pragma} Restrictions (Max_Asynchronous_Select_Nesting => 0); -@end smallexample + procedure Ada_Method2 (This : in out A; V : Integer) is + begin + Method1 (This); + This.A_Value := V; + end Ada_Method2; -@noindent -It is recommended that these restriction pragmas be used if possible. Note -that this also means that you can write code without worrying about the -possibility of an immediate abort at any point. +end Simple_Cpp_Interface; +@end example -@node Optimization Levels -@subsection Optimization Levels -@cindex @option{-O} (@command{gcc}) +@node Interfacing with C++ constructors,Interfacing with C++ at the Class Level,A Simple Example,Building Mixed Ada and C++ Programs +@anchor{gnat_ugn/the_gnat_compilation_model id68}@anchor{c5}@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-constructors}@anchor{c6} +@subsubsection Interfacing with C++ constructors -@noindent -Without any optimization option, -the compiler's goal is to reduce the cost of -compilation and to make debugging produce the expected results. -Statements are independent: if you stop the program with a breakpoint between -statements, you can then assign a new value to any variable or change -the program counter to any other statement in the subprogram and get exactly -the results you would expect from the source code. -Turning on optimization makes the compiler attempt to improve the -performance and/or code size at the expense of compilation time and -possibly the ability to debug the program. +In order to interface with C++ constructors GNAT provides the +@cite{pragma CPP_Constructor} (see the @cite{GNAT_Reference_Manual} +for additional information). +In this section we present some common uses of C++ constructors +in mixed-languages programs in GNAT. -If you use multiple --O options, with or without level numbers, -the last such option is the one that is effective. +Let us assume that we need to interface with the following +C++ class: -@noindent -The default is optimization off. This results in the fastest compile -times, but GNAT makes absolutely no attempt to optimize, and the -generated programs are considerably larger and slower than when -optimization is enabled. You can use the -@option{-O} switch (the permitted forms are @option{-O0}, @option{-O1} -@option{-O2}, @option{-O3}, and @option{-Os}) -to @command{gcc} to control the optimization level: +@example +class Root @{ +public: + int a_value; + int b_value; + virtual int Get_Value (); + Root(); // Default constructor + Root(int v); // 1st non-default constructor + Root(int v, int w); // 2nd non-default constructor +@}; +@end example -@table @option -@item -O0 -No optimization (the default); -generates unoptimized code but has -the fastest compilation time. +For this purpose we can write the following package spec (further +information on how to build this spec is available in +@ref{c7,,Interfacing with C++ at the Class Level} and +@ref{1b,,Generating Ada Bindings for C and C++ headers}). -Note that many other compilers do fairly extensive optimization -even if ``no optimization'' is specified. With gcc, it is -very unusual to use -O0 for production if -execution time is of any concern, since -O0 -really does mean no optimization at all. This difference between -gcc and other compilers should be kept in mind when doing -performance comparisons. +@example +with Interfaces.C; use Interfaces.C; +package Pkg_Root is + type Root is tagged limited record + A_Value : int; + B_Value : int; + end record; + pragma Import (CPP, Root); -@item -O1 -Moderate optimization; -optimizes reasonably well but does not -degrade compilation time significantly. + function Get_Value (Obj : Root) return int; + pragma Import (CPP, Get_Value); -@item -O2 -Full optimization; -generates highly optimized code and has -the slowest compilation time. + function Constructor return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev"); -@item -O3 -Full optimization as in @option{-O2}; -also uses more aggressive automatic inlining of subprograms within a unit -(@pxref{Inlining of Subprograms}) and attempts to vectorize loops. + function Constructor (v : Integer) return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei"); -@item -Os -Optimize space usage (code and data) of resulting program. -@end table + function Constructor (v, w : Integer) return Root; + pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii"); +end Pkg_Root; +@end example -@noindent -Higher optimization levels perform more global transformations on the -program and apply more expensive analysis algorithms in order to generate -faster and more compact code. The price in compilation time, and the -resulting improvement in execution time, -both depend on the particular application and the hardware environment. -You should experiment to find the best level for your application. +On the Ada side the constructor is represented by a function (whose +name is arbitrary) that returns the classwide type corresponding to +the imported C++ class. Although the constructor is described as a +function, it is typically a procedure with an extra implicit argument +(the object being initialized) at the implementation level. GNAT +issues the appropriate call, whatever it is, to get the object +properly initialized. -Since the precise set of optimizations done at each level will vary from -release to release (and sometime from target to target), it is best to think -of the optimization settings in general terms. -@xref{Optimize Options,, Options That Control Optimization, gcc, Using -the GNU Compiler Collection (GCC)}, for details about -the @option{-O} settings and a number of @option{-f} options that -individually enable or disable specific optimizations. +Constructors can only appear in the following contexts: -Unlike some other compilation systems, @command{gcc} has -been tested extensively at all optimization levels. There are some bugs -which appear only with optimization turned on, but there have also been -bugs which show up only in @emph{unoptimized} code. Selecting a lower -level of optimization does not improve the reliability of the code -generator, which in practice is highly reliable at all optimization -levels. -Note regarding the use of @option{-O3}: The use of this optimization level -is generally discouraged with GNAT, since it often results in larger -executables which may run more slowly. See further discussion of this point -in @ref{Inlining of Subprograms}. +@itemize * -@node Debugging Optimized Code -@subsection Debugging Optimized Code -@cindex Debugging optimized code -@cindex Optimization and debugging +@item +On the right side of an initialization of an object of type @cite{T}. -@noindent -Although it is possible to do a reasonable amount of debugging at -nonzero optimization levels, -the higher the level the more likely that -source-level constructs will have been eliminated by optimization. -For example, if a loop is strength-reduced, the loop -control variable may be completely eliminated and thus cannot be -displayed in the debugger. -This can only happen at @option{-O2} or @option{-O3}. -Explicit temporary variables that you code might be eliminated at -level @option{-O1} or higher. +@item +On the right side of an initialization of a record component of type @cite{T}. -The use of the @option{-g} switch, -@cindex @option{-g} (@command{gcc}) -which is needed for source-level debugging, -affects the size of the program executable on disk, -and indeed the debugging information can be quite large. -However, it has no effect on the generated code (and thus does not -degrade performance) +@item +In an Ada 2005 limited aggregate. -Since the compiler generates debugging tables for a compilation unit before -it performs optimizations, the optimizing transformations may invalidate some -of the debugging data. You therefore need to anticipate certain -anomalous situations that may arise while debugging optimized code. -These are the most common cases: +@item +In an Ada 2005 nested limited aggregate. -@enumerate -@item -@i{The ``hopping Program Counter'':} Repeated @code{step} or @code{next} -commands show -the PC bouncing back and forth in the code. This may result from any of -the following optimizations: +@item +In an Ada 2005 limited aggregate that initializes an object built in +place by an extended return statement. +@end itemize -@itemize @bullet -@item -@i{Common subexpression elimination:} using a single instance of code for a -quantity that the source computes several times. As a result you -may not be able to stop on what looks like a statement. +In a declaration of an object whose type is a class imported from C++, +either the default C++ constructor is implicitly called by GNAT, or +else the required C++ constructor must be explicitly called in the +expression that initializes the object. For example: -@item -@i{Invariant code motion:} moving an expression that does not change within a -loop, to the beginning of the loop. +@example +Obj1 : Root; +Obj2 : Root := Constructor; +Obj3 : Root := Constructor (v => 10); +Obj4 : Root := Constructor (30, 40); +@end example -@item -@i{Instruction scheduling:} moving instructions so as to -overlap loads and stores (typically) with other code, or in -general to move computations of values closer to their uses. Often -this causes you to pass an assignment statement without the assignment -happening and then later bounce back to the statement when the -value is actually needed. Placing a breakpoint on a line of code -and then stepping over it may, therefore, not always cause all the -expected side-effects. -@end itemize +The first two declarations are equivalent: in both cases the default C++ +constructor is invoked (in the former case the call to the constructor is +implicit, and in the latter case the call is explicit in the object +declaration). @cite{Obj3} is initialized by the C++ non-default constructor +that takes an integer argument, and @cite{Obj4} is initialized by the +non-default C++ constructor that takes two integers. -@item -@i{The ``big leap'':} More commonly known as @emph{cross-jumping}, in which -two identical pieces of code are merged and the program counter suddenly -jumps to a statement that is not supposed to be executed, simply because -it (and the code following) translates to the same thing as the code -that @emph{was} supposed to be executed. This effect is typically seen in -sequences that end in a jump, such as a @code{goto}, a @code{return}, or -a @code{break} in a C @code{switch} statement. +Let us derive the imported C++ class in the Ada side. For example: -@item -@i{The ``roving variable'':} The symptom is an unexpected value in a variable. -There are various reasons for this effect: +@example +type DT is new Root with record + C_Value : Natural := 2009; +end record; +@end example -@itemize @bullet -@item -In a subprogram prologue, a parameter may not yet have been moved to its -``home''. +In this case the components DT inherited from the C++ side must be +initialized by a C++ constructor, and the additional Ada components +of type DT are initialized by GNAT. The initialization of such an +object is done either by default, or by means of a function returning +an aggregate of type DT, or by means of an extension aggregate. -@item -A variable may be dead, and its register re-used. This is -probably the most common cause. +@example +Obj5 : DT; +Obj6 : DT := Function_Returning_DT (50); +Obj7 : DT := (Constructor (30,40) with C_Value => 50); +@end example -@item -As mentioned above, the assignment of a value to a variable may -have been moved. +The declaration of @cite{Obj5} invokes the default constructors: the +C++ default constructor of the parent type takes care of the initialization +of the components inherited from Root, and GNAT takes care of the default +initialization of the additional Ada components of type DT (that is, +@cite{C_Value} is initialized to value 2009). The order of invocation of +the constructors is consistent with the order of elaboration required by +Ada and C++. That is, the constructor of the parent type is always called +before the constructor of the derived type. -@item -A variable may be eliminated entirely by value propagation or -other means. In this case, GCC may incorrectly generate debugging -information for the variable -@end itemize +Let us now consider a record that has components whose type is imported +from C++. For example: -@noindent -In general, when an unexpected value appears for a local variable or parameter -you should first ascertain if that value was actually computed by -your program, as opposed to being incorrectly reported by the debugger. -Record fields or -array elements in an object designated by an access value -are generally less of a problem, once you have ascertained that the access -value is sensible. -Typically, this means checking variables in the preceding code and in the -calling subprogram to verify that the value observed is explainable from other -values (one must apply the procedure recursively to those -other values); or re-running the code and stopping a little earlier -(perhaps before the call) and stepping to better see how the variable obtained -the value in question; or continuing to step @emph{from} the point of the -strange value to see if code motion had simply moved the variable's -assignments later. -@end enumerate +@example +type Rec1 is limited record + Data1 : Root := Constructor (10); + Value : Natural := 1000; +end record; -@noindent -In light of such anomalies, a recommended technique is to use @option{-O0} -early in the software development cycle, when extensive debugging capabilities -are most needed, and then move to @option{-O1} and later @option{-O2} as -the debugger becomes less critical. -Whether to use the @option{-g} switch in the release version is -a release management issue. -Note that if you use @option{-g} you can then use the @command{strip} program -on the resulting executable, -which removes both debugging information and global symbols. +type Rec2 (D : Integer := 20) is limited record + Rec : Rec1; + Data2 : Root := Constructor (D, 30); +end record; +@end example -@node Inlining of Subprograms -@subsection Inlining of Subprograms +The initialization of an object of type @cite{Rec2} will call the +non-default C++ constructors specified for the imported components. +For example: -@noindent -A call to a subprogram in the current unit is inlined if all the -following conditions are met: +@example +Obj8 : Rec2 (40); +@end example -@itemize @bullet -@item -The optimization level is at least @option{-O1}. +Using Ada 2005 we can use limited aggregates to initialize an object +invoking C++ constructors that differ from those specified in the type +declarations. For example: -@item -The called subprogram is suitable for inlining: It must be small enough -and not contain something that @command{gcc} cannot support in inlined -subprograms. +@example +Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16), + others => <>), + others => <>); +@end example -@item -@cindex pragma Inline -@findex Inline -Any one of the following applies: @code{pragma Inline} is applied to the -subprogram and the @option{-gnatn} switch is specified; the -subprogram is local to the unit and called once from within it; the -subprogram is small and optimization level @option{-O2} is specified; -optimization level @option{-O3} is specified. -@end itemize +The above declaration uses an Ada 2005 limited aggregate to +initialize @cite{Obj9}, and the C++ constructor that has two integer +arguments is invoked to initialize the @cite{Data1} component instead +of the constructor specified in the declaration of type @cite{Rec1}. In +Ada 2005 the box in the aggregate indicates that unspecified components +are initialized using the expression (if any) available in the component +declaration. That is, in this case discriminant @cite{D} is initialized +to value @cite{20}, @cite{Value} is initialized to value 1000, and the +non-default C++ constructor that handles two integers takes care of +initializing component @cite{Data2} with values @cite{20@comma{}30}. -@noindent -Calls to subprograms in @code{with}'ed units are normally not inlined. -To achieve actual inlining (that is, replacement of the call by the code -in the body of the subprogram), the following conditions must all be true: +In Ada 2005 we can use the extended return statement to build the Ada +equivalent to C++ non-default constructors. For example: -@itemize @bullet -@item -The optimization level is at least @option{-O1}. +@example +function Constructor (V : Integer) return Rec2 is +begin + return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20), + others => <>), + others => <>) do + -- Further actions required for construction of + -- objects of type Rec2 + ... + end record; +end Constructor; +@end example -@item -The called subprogram is suitable for inlining: It must be small enough -and not contain something that @command{gcc} cannot support in inlined -subprograms. +In this example the extended return statement construct is used to +build in place the returned object whose components are initialized +by means of a limited aggregate. Any further action associated with +the constructor can be placed inside the construct. -@item -The call appears in a body (not in a package spec). +@node Interfacing with C++ at the Class Level,,Interfacing with C++ constructors,Building Mixed Ada and C++ Programs +@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-at-the-class-level}@anchor{c7}@anchor{gnat_ugn/the_gnat_compilation_model id69}@anchor{c8} +@subsubsection Interfacing with C++ at the Class Level -@item -There is a @code{pragma Inline} for the subprogram. -@item -The @option{-gnatn} switch is used on the command line. -@end itemize +In this section we demonstrate the GNAT features for interfacing with +C++ by means of an example making use of Ada 2005 abstract interface +types. This example consists of a classification of animals; classes +have been used to model our main classification of animals, and +interfaces provide support for the management of secondary +classifications. We first demonstrate a case in which the types and +constructors are defined on the C++ side and imported from the Ada +side, and latter the reverse case. -Even if all these conditions are met, it may not be possible for -the compiler to inline the call, due to the length of the body, -or features in the body that make it impossible for the compiler -to do the inlining. +The root of our derivation will be the @cite{Animal} class, with a +single private attribute (the @cite{Age} of the animal), a constructor, +and two public primitives to set and get the value of this attribute. -Note that specifying the @option{-gnatn} switch causes additional -compilation dependencies. Consider the following: +@example +class Animal @{ + public: + virtual void Set_Age (int New_Age); + virtual int Age (); + Animal() @{Age_Count = 0;@}; + private: + int Age_Count; +@}; +@end example -@smallexample @c ada -@cartouche -@b{package} R @b{is} - @b{procedure} Q; - @b{pragma} Inline (Q); -@b{end} R; -@b{package} @b{body} R @b{is} - @dots{} -@b{end} R; - -@b{with} R; -@b{procedure} Main @b{is} -@b{begin} - @dots{} - R.Q; -@b{end} Main; -@end cartouche -@end smallexample - -@noindent -With the default behavior (no @option{-gnatn} switch specified), the -compilation of the @code{Main} procedure depends only on its own source, -@file{main.adb}, and the spec of the package in file @file{r.ads}. This -means that editing the body of @code{R} does not require recompiling -@code{Main}. - -On the other hand, the call @code{R.Q} is not inlined under these -circumstances. If the @option{-gnatn} switch is present when @code{Main} -is compiled, the call will be inlined if the body of @code{Q} is small -enough, but now @code{Main} depends on the body of @code{R} in -@file{r.adb} as well as on the spec. This means that if this body is edited, -the main program must be recompiled. Note that this extra dependency -occurs whether or not the call is in fact inlined by @command{gcc}. +Abstract interface types are defined in C++ by means of classes with pure +virtual functions and no data members. In our example we will use two +interfaces that provide support for the common management of @cite{Carnivore} +and @cite{Domestic} animals: -The use of front end inlining with @option{-gnatN} generates similar -additional dependencies. +@example +class Carnivore @{ +public: + virtual int Number_Of_Teeth () = 0; +@}; -@cindex @option{-fno-inline} (@command{gcc}) -Note: The @option{-fno-inline} switch -can be used to prevent -all inlining. This switch overrides all other conditions and ensures -that no inlining occurs. The extra dependences resulting from -@option{-gnatn} will still be active, even if -this switch is used to suppress the resulting inlining actions. +class Domestic @{ +public: + virtual void Set_Owner (char* Name) = 0; +@}; +@end example -@cindex @option{-fno-inline-functions} (@command{gcc}) -Note: The @option{-fno-inline-functions} switch can be used to prevent -automatic inlining of subprograms if @option{-O3} is used. +Using these declarations, we can now say that a @cite{Dog} is an animal that is +both Carnivore and Domestic, that is: -@cindex @option{-fno-inline-small-functions} (@command{gcc}) -Note: The @option{-fno-inline-small-functions} switch can be used to prevent -automatic inlining of small subprograms if @option{-O2} is used. +@example +class Dog : Animal, Carnivore, Domestic @{ + public: + virtual int Number_Of_Teeth (); + virtual void Set_Owner (char* Name); -@cindex @option{-fno-inline-functions-called-once} (@command{gcc}) -Note: The @option{-fno-inline-functions-called-once} switch -can be used to prevent inlining of subprograms local to the unit -and called once from within it if @option{-O1} is used. - -Note regarding the use of @option{-O3}: @option{-gnatn} is made up of two -sub-switches @option{-gnatn1} and @option{-gnatn2} that can be directly -specified in lieu of it, @option{-gnatn} being translated into one of them -based on the optimization level. With @option{-O2} or below, @option{-gnatn} -is equivalent to @option{-gnatn1} which activates pragma @code{Inline} with -moderate inlining across modules. With @option{-O3}, @option{-gnatn} is -equivalent to @option{-gnatn2} which activates pragma @code{Inline} with -full inlining across modules. If you have used pragma @code{Inline} in appropriate cases, then it is usually much better to use @option{-O2} and @option{-gnatn} and avoid the use of @option{-O3} which has the additional -effect of inlining subprograms you did not think should be inlined. We have -found that the use of @option{-O3} may slow down the compilation and increase -the code size by performing excessive inlining, leading to increased -instruction cache pressure from the increased code size and thus minor -performance improvements. So the bottom line here is that you should not -automatically assume that @option{-O3} is better than @option{-O2}, and -indeed you should use @option{-O3} only if tests show that it actually -improves performance for your program. + Dog(); // Constructor + private: + int Tooth_Count; + char *Owner; +@}; +@end example -@node Vectorization of loops -@subsection Vectorization of loops -@cindex Optimization Switches +In the following examples we will assume that the previous declarations are +located in a file named @cite{animals.h}. The following package demonstrates +how to import these C++ declarations from the Ada side: -You can take advantage of the auto-vectorizer present in the @command{gcc} -back end to vectorize loops with GNAT. The corresponding command line switch -is @option{-ftree-vectorize} but, as it is enabled by default at @option{-O3} -and other aggressive optimizations helpful for vectorization also are enabled -by default at this level, using @option{-O3} directly is recommended. +@example +with Interfaces.C.Strings; use Interfaces.C.Strings; +package Animals is + type Carnivore is limited interface; + pragma Convention (C_Plus_Plus, Carnivore); + function Number_Of_Teeth (X : Carnivore) + return Natural is abstract; + + type Domestic is limited interface; + pragma Convention (C_Plus_Plus, Domestic); + procedure Set_Owner + (X : in out Domestic; + Name : Chars_Ptr) is abstract; + + type Animal is tagged limited record + Age : Natural; + end record; + pragma Import (C_Plus_Plus, Animal); -You also need to make sure that the target architecture features a supported -SIMD instruction set. For example, for the x86 architecture, you should at -least specify @option{-msse2} to get significant vectorization (but you don't -need to specify it for x86-64 as it is part of the base 64-bit architecture). -Similarly, for the PowerPC architecture, you should specify @option{-maltivec}. + procedure Set_Age (X : in out Animal; Age : Integer); + pragma Import (C_Plus_Plus, Set_Age); -The preferred loop form for vectorization is the @code{for} iteration scheme. -Loops with a @code{while} iteration scheme can also be vectorized if they are -very simple, but the vectorizer will quickly give up otherwise. With either -iteration scheme, the flow of control must be straight, in particular no -@code{exit} statement may appear in the loop body. The loop may however -contain a single nested loop, if it can be vectorized when considered alone: + function Age (X : Animal) return Integer; + pragma Import (C_Plus_Plus, Age); -@smallexample @c ada -@cartouche - A : @b{array} (1..4, 1..4) @b{of} Long_Float; - S : @b{array} (1..4) @b{of} Long_Float; - - @b{procedure} Sum @b{is} - @b{begin} - @b{for} I @b{in} A'Range(1) @b{loop} - @b{for} J @b{in} A'Range(2) @b{loop} - S (I) := S (I) + A (I, J); - @b{end} @b{loop}; - @b{end} @b{loop}; - @b{end} Sum; -@end cartouche -@end smallexample + function New_Animal return Animal; + pragma CPP_Constructor (New_Animal); + pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev"); -The vectorizable operations depend on the targeted SIMD instruction set, but -the adding and some of the multiplying operators are generally supported, as -well as the logical operators for modular types. Note that, in the former -case, enabling overflow checks, for example with @option{-gnato}, totally -disables vectorization. The other checks are not supposed to have the same -definitive effect, although compiling with @option{-gnatp} might well reveal -cases where some checks do thwart vectorization. + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : Natural; + Owner : String (1 .. 30); + end record; + pragma Import (C_Plus_Plus, Dog); -Type conversions may also prevent vectorization if they involve semantics that -are not directly supported by the code generator or the SIMD instruction set. -A typical example is direct conversion from floating-point to integer types. -The solution in this case is to use the following idiom: + function Number_Of_Teeth (A : Dog) return Natural; + pragma Import (C_Plus_Plus, Number_Of_Teeth); -@smallexample @c ada - Integer (S'Truncation (F)) -@end smallexample + procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); + pragma Import (C_Plus_Plus, Set_Owner); -@noindent -if @code{S} is the subtype of floating-point object @code{F}. + function New_Dog return Dog; + pragma CPP_Constructor (New_Dog); + pragma Import (CPP, New_Dog, "_ZN3DogC2Ev"); +end Animals; +@end example -In most cases, the vectorizable loops are loops that iterate over arrays. -All kinds of array types are supported, i.e. constrained array types with -static bounds: +Thanks to the compatibility between GNAT run-time structures and the C++ ABI, +interfacing with these C++ classes is easy. The only requirement is that all +the primitives and components must be declared exactly in the same order in +the two languages. -@smallexample @c ada - @b{type} Array_Type @b{is} @b{array} (1 .. 4) @b{of} Long_Float; -@end smallexample +Regarding the abstract interfaces, we must indicate to the GNAT compiler by +means of a @cite{pragma Convention (C_Plus_Plus)}, the convention used to pass +the arguments to the called primitives will be the same as for C++. For the +imported classes we use @cite{pragma Import} with convention @cite{C_Plus_Plus} +to indicate that they have been defined on the C++ side; this is required +because the dispatch table associated with these tagged types will be built +in the C++ side and therefore will not contain the predefined Ada primitives +which Ada would otherwise expect. -@noindent -constrained array types with dynamic bounds: +As the reader can see there is no need to indicate the C++ mangled names +associated with each subprogram because it is assumed that all the calls to +these primitives will be dispatching calls. The only exception is the +constructor, which must be registered with the compiler by means of +@cite{pragma CPP_Constructor} and needs to provide its associated C++ +mangled name because the Ada compiler generates direct calls to it. -@smallexample @c ada - @b{type} Array_Type @b{is} @b{array} (1 .. Q.N) @b{of} Long_Float; +With the above packages we can now declare objects of type Dog on the Ada side +and dispatch calls to the corresponding subprograms on the C++ side. We can +also extend the tagged type Dog with further fields and primitives, and +override some of its C++ primitives on the Ada side. For example, here we have +a type derivation defined on the Ada side that inherits all the dispatching +primitives of the ancestor from the C++ side. - @b{type} Array_Type @b{is} @b{array} (Q.K .. 4) @b{of} Long_Float; +@example +with Animals; use Animals; +package Vaccinated_Animals is + type Vaccinated_Dog is new Dog with null record; + function Vaccination_Expired (A : Vaccinated_Dog) return Boolean; +end Vaccinated_Animals; +@end example - @b{type} Array_Type @b{is} @b{array} (Q.K .. Q.N) @b{of} Long_Float; -@end smallexample +It is important to note that, because of the ABI compatibility, the programmer +does not need to add any further information to indicate either the object +layout or the dispatch table entry associated with each dispatching operation. -@noindent -or unconstrained array types: +Now let us define all the types and constructors on the Ada side and export +them to C++, using the same hierarchy of our previous example: -@smallexample @c ada - @b{type} Array_Type @b{is} @b{array} (Positive @b{range} <>) @b{of} Long_Float; -@end smallexample +@example +with Interfaces.C.Strings; +use Interfaces.C.Strings; +package Animals is + type Carnivore is limited interface; + pragma Convention (C_Plus_Plus, Carnivore); + function Number_Of_Teeth (X : Carnivore) + return Natural is abstract; + + type Domestic is limited interface; + pragma Convention (C_Plus_Plus, Domestic); + procedure Set_Owner + (X : in out Domestic; + Name : Chars_Ptr) is abstract; + + type Animal is tagged record + Age : Natural; + end record; + pragma Convention (C_Plus_Plus, Animal); -@noindent -The quality of the generated code decreases when the dynamic aspect of the -array type increases, the worst code being generated for unconstrained array -types. This is so because, the less information the compiler has about the -bounds of the array, the more fallback code it needs to generate in order to -fix things up at run time. + procedure Set_Age (X : in out Animal; Age : Integer); + pragma Export (C_Plus_Plus, Set_Age); -It is possible to specify that a given loop should be subject to vectorization -preferably to other optimizations by means of pragma @code{Loop_Optimize}: + function Age (X : Animal) return Integer; + pragma Export (C_Plus_Plus, Age); -@smallexample @c ada - @b{pragma} Loop_Optimize (Vector); -@end smallexample + function New_Animal return Animal'Class; + pragma Export (C_Plus_Plus, New_Animal); -@noindent -placed immediately within the loop will convey the appropriate hint to the -compiler for this loop. + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : Natural; + Owner : String (1 .. 30); + end record; + pragma Convention (C_Plus_Plus, Dog); -It is also possible to help the compiler generate better vectorized code -for a given loop by asserting that there are no loop-carried dependencies -in the loop. Consider for example the procedure: + function Number_Of_Teeth (A : Dog) return Natural; + pragma Export (C_Plus_Plus, Number_Of_Teeth); -@smallexample @c ada - @b{type} Arr @b{is} @b{array} (1 .. 4) @b{of} Long_Float; + procedure Set_Owner (A : in out Dog; Name : Chars_Ptr); + pragma Export (C_Plus_Plus, Set_Owner); - @b{procedure} Add (X, Y : @b{not} @b{null} @b{access} Arr; R : @b{not} @b{null} @b{access} Arr) @b{is} - @b{begin} - @b{for} I @b{in} Arr'Range @b{loop} - R(I) := X(I) + Y(I); - @b{end} @b{loop}; - @b{end}; -@end smallexample + function New_Dog return Dog'Class; + pragma Export (C_Plus_Plus, New_Dog); +end Animals; +@end example -@noindent -By default, the compiler cannot unconditionally vectorize the loop because -assigning to a component of the array designated by R in one iteration could -change the value read from the components of the array designated by X or Y -in a later iteration. As a result, the compiler will generate two versions -of the loop in the object code, one vectorized and the other not vectorized, -as well as a test to select the appropriate version at run time. This can -be overcome by another hint: +Compared with our previous example the only differences are the use of +@cite{pragma Convention} (instead of @cite{pragma Import}), and the use of +@cite{pragma Export} to indicate to the GNAT compiler that the primitives will +be available to C++. Thanks to the ABI compatibility, on the C++ side there is +nothing else to be done; as explained above, the only requirement is that all +the primitives and components are declared in exactly the same order. -@smallexample @c ada - @b{pragma} Loop_Optimize (Ivdep); -@end smallexample +For completeness, let us see a brief C++ main program that uses the +declarations available in @cite{animals.h} (presented in our first example) to +import and use the declarations from the Ada side, properly initializing and +finalizing the Ada run-time system along the way: -@noindent -placed immediately within the loop will tell the compiler that it can safely -omit the non-vectorized version of the loop as well as the run-time test. +@example +#include "animals.h" +#include +using namespace std; -@node Other Optimization Switches -@subsection Other Optimization Switches -@cindex Optimization Switches +void Check_Carnivore (Carnivore *obj) @{...@} +void Check_Domestic (Domestic *obj) @{...@} +void Check_Animal (Animal *obj) @{...@} +void Check_Dog (Dog *obj) @{...@} -Since @code{GNAT} uses the @command{gcc} back end, all the specialized -@command{gcc} optimization switches are potentially usable. These switches -have not been extensively tested with GNAT but can generally be expected -to work. Examples of switches in this category are @option{-funroll-loops} -and the various target-specific @option{-m} options (in particular, it has -been observed that @option{-march=xxx} can significantly improve performance -on appropriate machines). For full details of these switches, see -@ref{Submodel Options,, Hardware Models and Configurations, gcc, Using -the GNU Compiler Collection (GCC)}. +extern "C" @{ + void adainit (void); + void adafinal (void); + Dog* new_dog (); +@} -@node Optimization and Strict Aliasing -@subsection Optimization and Strict Aliasing -@cindex Aliasing -@cindex Strict Aliasing -@cindex No_Strict_Aliasing +void test () +@{ + Dog *obj = new_dog(); // Ada constructor + Check_Carnivore (obj); // Check secondary DT + Check_Domestic (obj); // Check secondary DT + Check_Animal (obj); // Check primary DT + Check_Dog (obj); // Check primary DT +@} -@noindent -The strong typing capabilities of Ada allow an optimizer to generate -efficient code in situations where other languages would be forced to -make worst case assumptions preventing such optimizations. Consider -the following example: +int main () +@{ + adainit (); test(); adafinal (); + return 0; +@} +@end example -@smallexample @c ada -@cartouche -@b{procedure} R @b{is} - @b{type} Int1 @b{is} @b{new} Integer; - @b{type} Int2 @b{is} @b{new} Integer; - @b{type} Int1A @b{is} @b{access} Int1; - @b{type} Int2A @b{is} @b{access} Int2; - Int1V : Int1A; - Int2V : Int2A; - @dots{} - -@b{begin} - @dots{} - @b{for} J @b{in} Data'Range @b{loop} - @b{if} Data (J) = Int1V.@b{all} @b{then} - Int2V.@b{all} := Int2V.@b{all} + 1; - @b{end} @b{if}; - @b{end} @b{loop}; - @dots{} -@b{end} R; -@end cartouche -@end smallexample - -@noindent -In this example, since the variable @code{Int1V} can only access objects -of type @code{Int1}, and @code{Int2V} can only access objects of type -@code{Int2}, there is no possibility that the assignment to -@code{Int2V.all} affects the value of @code{Int1V.all}. This means that -the compiler optimizer can "know" that the value @code{Int1V.all} is constant -for all iterations of the loop and avoid the extra memory reference -required to dereference it each time through the loop. +@node Generating Ada Bindings for C and C++ headers,,Building Mixed Ada and C++ Programs,Mixed Language Programming +@anchor{gnat_ugn/the_gnat_compilation_model id70}@anchor{c9}@anchor{gnat_ugn/the_gnat_compilation_model generating-ada-bindings-for-c-and-c-headers}@anchor{1b} +@subsection Generating Ada Bindings for C and C++ headers -This kind of optimization, called strict aliasing analysis, is -triggered by specifying an optimization level of @option{-O2} or -higher or @option{-Os} and allows @code{GNAT} to generate more efficient code -when access values are involved. -However, although this optimization is always correct in terms of -the formal semantics of the Ada Reference Manual, difficulties can -arise if features like @code{Unchecked_Conversion} are used to break -the typing system. Consider the following complete program example: +@geindex Binding generation (for C and C++ headers) -@smallexample @c ada -@cartouche -@b{package} p1 @b{is} - @b{type} int1 @b{is} @b{new} integer; - @b{type} int2 @b{is} @b{new} integer; - @b{type} a1 @b{is} @b{access} int1; - @b{type} a2 @b{is} @b{access} int2; -@b{end} p1; - -@b{with} p1; @b{use} p1; -@b{package} p2 @b{is} - @b{function} to_a2 (Input : a1) @b{return} a2; -@b{end} p2; - -@b{with} Unchecked_Conversion; -@b{package} @b{body} p2 @b{is} - @b{function} to_a2 (Input : a1) @b{return} a2 @b{is} - @b{function} to_a2u @b{is} - @b{new} Unchecked_Conversion (a1, a2); - @b{begin} - @b{return} to_a2u (Input); - @b{end} to_a2; -@b{end} p2; - -@b{with} p2; @b{use} p2; -@b{with} p1; @b{use} p1; -@b{with} Text_IO; @b{use} Text_IO; -@b{procedure} m @b{is} - v1 : a1 := @b{new} int1; - v2 : a2 := to_a2 (v1); -@b{begin} - v1.@b{all} := 1; - v2.@b{all} := 0; - put_line (int1'image (v1.@b{all})); -@b{end}; -@end cartouche -@end smallexample +@geindex C headers (binding generation) -@noindent -This program prints out 0 in @option{-O0} or @option{-O1} -mode, but it prints out 1 in @option{-O2} mode. That's -because in strict aliasing mode, the compiler can and -does assume that the assignment to @code{v2.all} could not -affect the value of @code{v1.all}, since different types -are involved. +@geindex C++ headers (binding generation) -This behavior is not a case of non-conformance with the standard, since -the Ada RM specifies that an unchecked conversion where the resulting -bit pattern is not a correct value of the target type can result in an -abnormal value and attempting to reference an abnormal value makes the -execution of a program erroneous. That's the case here since the result -does not point to an object of type @code{int2}. This means that the -effect is entirely unpredictable. +GNAT includes a binding generator for C and C++ headers which is +intended to do 95% of the tedious work of generating Ada specs from C +or C++ header files. -However, although that explanation may satisfy a language -lawyer, in practice an applications programmer expects an -unchecked conversion involving pointers to create true -aliases and the behavior of printing 1 seems plain wrong. -In this case, the strict aliasing optimization is unwelcome. +Note that this capability is not intended to generate 100% correct Ada specs, +and will is some cases require manual adjustments, although it can often +be used out of the box in practice. -Indeed the compiler recognizes this possibility, and the -unchecked conversion generates a warning: +Some of the known limitations include: -@smallexample -p2.adb:5:07: warning: possible aliasing problem with type "a2" -p2.adb:5:07: warning: use -fno-strict-aliasing switch for references -p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);" -@end smallexample -@noindent -Unfortunately the problem is recognized when compiling the body of -package @code{p2}, but the actual "bad" code is generated while -compiling the body of @code{m} and this latter compilation does not see -the suspicious @code{Unchecked_Conversion}. +@itemize * -As implied by the warning message, there are approaches you can use to -avoid the unwanted strict aliasing optimization in a case like this. +@item +only very simple character constant macros are translated into Ada +constants. Function macros (macros with arguments) are partially translated +as comments, to be completed manually if needed. -One possibility is to simply avoid the use of @option{-O2}, but -that is a bit drastic, since it throws away a number of useful -optimizations that do not involve strict aliasing assumptions. +@item +some extensions (e.g. vector types) are not supported -A less drastic approach is to compile the program using the -option @option{-fno-strict-aliasing}. Actually it is only the -unit containing the dereferencing of the suspicious pointer -that needs to be compiled. So in this case, if we compile -unit @code{m} with this switch, then we get the expected -value of zero printed. Analyzing which units might need -the switch can be painful, so a more reasonable approach -is to compile the entire program with options @option{-O2} -and @option{-fno-strict-aliasing}. If the performance is -satisfactory with this combination of options, then the -advantage is that the entire issue of possible "wrong" -optimization due to strict aliasing is avoided. +@item +pointers to pointers or complex structures are mapped to System.Address -To avoid the use of compiler switches, the configuration -pragma @code{No_Strict_Aliasing} with no parameters may be -used to specify that for all access types, the strict -aliasing optimization should be suppressed. +@item +identifiers with identical name (except casing) will generate compilation +errors (e.g. @cite{shm_get} vs @cite{SHM_GET}). +@end itemize -However, these approaches are still overkill, in that they causes -all manipulations of all access values to be deoptimized. A more -refined approach is to concentrate attention on the specific -access type identified as problematic. +The code generated is using the Ada 2005 syntax, which makes it +easier to interface with other languages than previous versions of Ada. -First, if a careful analysis of uses of the pointer shows -that there are no possible problematic references, then -the warning can be suppressed by bracketing the -instantiation of @code{Unchecked_Conversion} to turn -the warning off: +@menu +* Running the binding generator:: +* Generating bindings for C++ headers:: +* Switches:: -@smallexample @c ada - @b{pragma} Warnings (Off); - @b{function} to_a2u @b{is} - @b{new} Unchecked_Conversion (a1, a2); - @b{pragma} Warnings (On); -@end smallexample +@end menu -@noindent -Of course that approach is not appropriate for this particular -example, since indeed there is a problematic reference. In this -case we can take one of two other approaches. +@node Running the binding generator,Generating bindings for C++ headers,,Generating Ada Bindings for C and C++ headers +@anchor{gnat_ugn/the_gnat_compilation_model id71}@anchor{ca}@anchor{gnat_ugn/the_gnat_compilation_model running-the-binding-generator}@anchor{cb} +@subsubsection Running the binding generator -The first possibility is to move the instantiation of unchecked -conversion to the unit in which the type is declared. In -this example, we would move the instantiation of -@code{Unchecked_Conversion} from the body of package -@code{p2} to the spec of package @code{p1}. Now the -warning disappears. That's because any use of the -access type knows there is a suspicious unchecked -conversion, and the strict aliasing optimization -is automatically suppressed for the type. -If it is not practical to move the unchecked conversion to the same unit -in which the destination access type is declared (perhaps because the -source type is not visible in that unit), you may use pragma -@code{No_Strict_Aliasing} for the type. This pragma must occur in the -same declarative sequence as the declaration of the access type: +The binding generator is part of the @emph{gcc} compiler and can be +invoked via the @emph{-fdump-ada-spec} switch, which will generate Ada +spec files for the header files specified on the command line, and all +header files needed by these files transitively. For example: -@smallexample @c ada - @b{type} a2 @b{is} @b{access} int2; - @b{pragma} No_Strict_Aliasing (a2); -@end smallexample +@example +$ g++ -c -fdump-ada-spec -C /usr/include/time.h +$ gcc -c -gnat05 *.ads +@end example -@noindent -Here again, the compiler now knows that the strict aliasing optimization -should be suppressed for any reference to type @code{a2} and the -expected behavior is obtained. +will generate, under GNU/Linux, the following files: @code{time_h.ads}, +@code{bits_time_h.ads}, @code{stddef_h.ads}, @code{bits_types_h.ads} which +correspond to the files @code{/usr/include/time.h}, +@code{/usr/include/bits/time.h}, etc..., and will then compile in Ada 2005 +mode these Ada specs. -Finally, note that although the compiler can generate warnings for -simple cases of unchecked conversions, there are tricker and more -indirect ways of creating type incorrect aliases which the compiler -cannot detect. Examples are the use of address overlays and unchecked -conversions involving composite types containing access types as -components. In such cases, no warnings are generated, but there can -still be aliasing problems. One safe coding practice is to forbid the -use of address clauses for type overlaying, and to allow unchecked -conversion only for primitive types. This is not really a significant -restriction since any possible desired effect can be achieved by -unchecked conversion of access values. +The @cite{-C} switch tells @emph{gcc} to extract comments from headers, +and will attempt to generate corresponding Ada comments. -The aliasing analysis done in strict aliasing mode can certainly -have significant benefits. We have seen cases of large scale -application code where the time is increased by up to 5% by turning -this optimization off. If you have code that includes significant -usage of unchecked conversion, you might want to just stick with -@option{-O1} and avoid the entire issue. If you get adequate -performance at this level of optimization level, that's probably -the safest approach. If tests show that you really need higher -levels of optimization, then you can experiment with @option{-O2} -and @option{-O2 -fno-strict-aliasing} to see how much effect this -has on size and speed of the code. If you really need to use -@option{-O2} with strict aliasing in effect, then you should -review any uses of unchecked conversion of access types, -particularly if you are getting the warnings described above. +If you want to generate a single Ada file and not the transitive closure, you +can use instead the @emph{-fdump-ada-spec-slim} switch. -@node Aliased Variables and Optimization -@subsection Aliased Variables and Optimization -@cindex Aliasing -There are scenarios in which programs may -use low level techniques to modify variables -that otherwise might be considered to be unassigned. For example, -a variable can be passed to a procedure by reference, which takes -the address of the parameter and uses the address to modify the -variable's value, even though it is passed as an IN parameter. -Consider the following example: +You can optionally specify a parent unit, of which all generated units will +be children, using @cite{-fada-spec-parent=`@w{`}unit}. -@smallexample @c ada -@b{procedure} P @b{is} - Max_Length : @b{constant} Natural := 16; - @b{type} Char_Ptr @b{is} @b{access} @b{all} Character; +Note that we recommend when possible to use the @emph{g++} driver to +generate bindings, even for most C headers, since this will in general +generate better Ada specs. For generating bindings for C++ headers, it is +mandatory to use the @emph{g++} command, or @emph{gcc -x c++} which +is equivalent in this case. If @emph{g++} cannot work on your C headers +because of incompatibilities between C and C++, then you can fallback to +@emph{gcc} instead. - @b{procedure} Get_String(Buffer: Char_Ptr; Size : Integer); - @b{pragma} Import (C, Get_String, "get_string"); +For an example of better bindings generated from the C++ front-end, +the name of the parameters (when available) are actually ignored by the C +front-end. Consider the following C header: - Name : @b{aliased} String (1 .. Max_Length) := (@b{others} => ' '); - Temp : Char_Ptr; +@example +extern void foo (int variable); +@end example - @b{function} Addr (S : String) @b{return} Char_Ptr @b{is} - @b{function} To_Char_Ptr @b{is} - @b{new} Ada.Unchecked_Conversion (System.Address, Char_Ptr); - @b{begin} - @b{return} To_Char_Ptr (S (S'First)'Address); - @b{end}; +with the C front-end, @cite{variable} is ignored, and the above is handled as: -@b{begin} - Temp := Addr (Name); - Get_String (Temp, Max_Length); -@b{end}; -@end smallexample +@example +extern void foo (int); +@end example -@noindent -where Get_String is a C function that uses the address in Temp to -modify the variable @code{Name}. This code is dubious, and arguably -erroneous, and the compiler would be entitled to assume that -@code{Name} is never modified, and generate code accordingly. +generating a generic: -However, in practice, this would cause some existing code that -seems to work with no optimization to start failing at high -levels of optimzization. +@example +procedure foo (param1 : int); +@end example -What the compiler does for such cases is to assume that marking -a variable as aliased indicates that some "funny business" may -be going on. The optimizer recognizes the aliased keyword and -inhibits optimizations that assume the value cannot be assigned. -This means that the above example will in fact "work" reliably, -that is, it will produce the expected results. +with the C++ front-end, the name is available, and we generate: -@node Atomic Variables and Optimization -@subsection Atomic Variables and Optimization -@cindex Atomic -There are two considerations with regard to performance when -atomic variables are used. +@example +procedure foo (variable : int); +@end example -First, the RM only guarantees that access to atomic variables -be atomic, it has nothing to say about how this is achieved, -though there is a strong implication that this should not be -achieved by explicit locking code. Indeed GNAT will never -generate any locking code for atomic variable access (it will -simply reject any attempt to make a variable or type atomic -if the atomic access cannot be achieved without such locking code). +In some cases, the generated bindings will be more complete or more meaningful +when defining some macros, which you can do via the @emph{-D} switch. This +is for example the case with @code{Xlib.h} under GNU/Linux: -That being said, it is important to understand that you cannot -assume that the entire variable will always be accessed. Consider -this example: +@example +$ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h +@end example -@smallexample @c ada -@b{type} R @b{is} @b{record} - A,B,C,D : Character; -@b{end} @b{record}; -@b{for} R'Size @b{use} 32; -@b{for} R'Alignment @b{use} 4; +The above will generate more complete bindings than a straight call without +the @emph{-DXLIB_ILLEGAL_ACCESS} switch. -RV : R; -@b{pragma} Atomic (RV); -X : Character; -... -X := RV.B; -@end smallexample +In other cases, it is not possible to parse a header file in a stand-alone +manner, because other include files need to be included first. In this +case, the solution is to create a small header file including the needed +@cite{#include} and possible @cite{#define} directives. For example, to +generate Ada bindings for @code{readline/readline.h}, you need to first +include @code{stdio.h}, so you can create a file with the following two +lines in e.g. @code{readline1.h}: -@noindent -You cannot assume that the reference to @code{RV.B} -will read the entire 32-bit -variable with a single load instruction. It is perfectly legitimate if -the hardware allows it to do a byte read of just the B field. This read -is still atomic, which is all the RM requires. GNAT can and does take -advantage of this, depending on the architecture and optimization level. -Any assumption to the contrary is non-portable and risky. Even if you -examine the assembly language and see a full 32-bit load, this might -change in a future version of the compiler. +@example +#include +#include +@end example -If your application requires that all accesses to @code{RV} in this -example be full 32-bit loads, you need to make a copy for the access -as in: +and then generate Ada bindings from this file: -@smallexample @c ada -@b{declare} - RV_Copy : @b{constant} R := RV; -@b{begin} - X := RV_Copy.B; -@b{end}; -@end smallexample +@example +$ g++ -c -fdump-ada-spec readline1.h +@end example +@node Generating bindings for C++ headers,Switches,Running the binding generator,Generating Ada Bindings for C and C++ headers +@anchor{gnat_ugn/the_gnat_compilation_model id72}@anchor{cc}@anchor{gnat_ugn/the_gnat_compilation_model generating-bindings-for-c-headers}@anchor{cd} +@subsubsection Generating bindings for C++ headers -@noindent -Now the reference to RV must read the whole variable. -Actually one can imagine some compiler which figures -out that the whole copy is not required (because only -the B field is actually accessed), but GNAT -certainly won't do that, and we don't know of any -compiler that would not handle this right, and the -above code will in practice work portably across -all architectures (that permit the Atomic declaration). -The second issue with atomic variables has to do with -the possible requirement of generating synchronization -code. For more details on this, consult the sections on -the pragmas Enable/Disable_Atomic_Synchronization in the -GNAT Reference Manual. If performance is critical, and -such synchronization code is not required, it may be -useful to disable it. +Generating bindings for C++ headers is done using the same options, always +with the @emph{g++} compiler. Note that generating Ada spec from C++ headers is a +much more complex job and support for C++ headers is much more limited that +support for C headers. As a result, you will need to modify the resulting +bindings by hand more extensively when using C++ headers. -@node Passive Task Optimization -@subsection Passive Task Optimization -@cindex Passive Task +In this mode, C++ classes will be mapped to Ada tagged types, constructors +will be mapped using the @cite{CPP_Constructor} pragma, and when possible, +multiple inheritance of abstract classes will be mapped to Ada interfaces +(see the @emph{Interfacing to C++} section in the @cite{GNAT Reference Manual} +for additional information on interfacing to C++). -A passive task is one which is sufficiently simple that -in theory a compiler could recognize it an implement it -efficiently without creating a new thread. The original design -of Ada 83 had in mind this kind of passive task optimization, but -only a few Ada 83 compilers attempted it. The problem was that -it was difficult to determine the exact conditions under which -the optimization was possible. The result is a very fragile -optimization where a very minor change in the program can -suddenly silently make a task non-optimizable. +For example, given the following C++ header file: -With the revisiting of this issue in Ada 95, there was general -agreement that this approach was fundamentally flawed, and the -notion of protected types was introduced. When using protected -types, the restrictions are well defined, and you KNOW that the -operations will be optimized, and furthermore this optimized -performance is fully portable. +@example +class Carnivore @{ +public: + virtual int Number_Of_Teeth () = 0; +@}; -Although it would theoretically be possible for GNAT to attempt to -do this optimization, but it really doesn't make sense in the -context of Ada 95, and none of the Ada 95 compilers implement -this optimization as far as we know. In particular GNAT never -attempts to perform this optimization. +class Domestic @{ +public: + virtual void Set_Owner (char* Name) = 0; +@}; -In any new Ada 95 code that is written, you should always -use protected types in place of tasks that might be able to -be optimized in this manner. -Of course this does not help if you have legacy Ada 83 code -that depends on this optimization, but it is unusual to encounter -a case where the performance gains from this optimization -are significant. +class Animal @{ +public: + int Age_Count; + virtual void Set_Age (int New_Age); +@}; -Your program should work correctly without this optimization. If -you have performance problems, then the most practical -approach is to figure out exactly where these performance problems -arise, and update those particular tasks to be protected types. Note -that typically clients of the tasks who call entries, will not have -to be modified, only the task definition itself. +class Dog : Animal, Carnivore, Domestic @{ + public: + int Tooth_Count; + char *Owner; + virtual int Number_Of_Teeth (); + virtual void Set_Owner (char* Name); + Dog(); +@}; +@end example -@node Text_IO Suggestions -@section @code{Text_IO} Suggestions -@cindex @code{Text_IO} and performance +The corresponding Ada code is generated: -@noindent -The @code{Ada.Text_IO} package has fairly high overheads due in part to -the requirement of maintaining page and line counts. If performance -is critical, a recommendation is to use @code{Stream_IO} instead of -@code{Text_IO} for volume output, since this package has less overhead. +@example +package Class_Carnivore is + type Carnivore is limited interface; + pragma Import (CPP, Carnivore); -If @code{Text_IO} must be used, note that by default output to the standard -output and standard error files is unbuffered (this provides better -behavior when output statements are used for debugging, or if the -progress of a program is observed by tracking the output, e.g. by -using the Unix @command{tail -f} command to watch redirected output. + function Number_Of_Teeth (this : access Carnivore) return int is abstract; +end; +use Class_Carnivore; -If you are generating large volumes of output with @code{Text_IO} and -performance is an important factor, use a designated file instead -of the standard output file, or change the standard output file to -be buffered using @code{Interfaces.C_Streams.setvbuf}. +package Class_Domestic is + type Domestic is limited interface; + pragma Import (CPP, Domestic); + procedure Set_Owner + (this : access Domestic; + Name : Interfaces.C.Strings.chars_ptr) is abstract; +end; +use Class_Domestic; -@ifclear FSFEDITION -@node Reducing Size of Ada Executables with gnatelim -@section Reducing Size of Ada Executables with @code{gnatelim} -@findex gnatelim +package Class_Animal is + type Animal is tagged limited record + Age_Count : aliased int; + end record; + pragma Import (CPP, Animal); -@noindent -This section describes @command{gnatelim}, a tool which detects unused -subprograms and helps the compiler to create a smaller executable for your -program. + procedure Set_Age (this : access Animal; New_Age : int); + pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi"); +end; +use Class_Animal; -@menu -* About gnatelim:: -* Running gnatelim:: -* Processing Precompiled Libraries:: -* Correcting the List of Eliminate Pragmas:: -* Making Your Executables Smaller:: -* Summary of the gnatelim Usage Cycle:: -@end menu +package Class_Dog is + type Dog is new Animal and Carnivore and Domestic with record + Tooth_Count : aliased int; + Owner : Interfaces.C.Strings.chars_ptr; + end record; + pragma Import (CPP, Dog); -@node About gnatelim -@subsection About @code{gnatelim} - -@noindent -When a program shares a set of Ada -packages with other programs, it may happen that this program uses -only a fraction of the subprograms defined in these packages. The code -created for these unused subprograms increases the size of the executable. - -@code{gnatelim} tracks unused subprograms in an Ada program and -outputs a list of GNAT-specific pragmas @code{Eliminate} marking all the -subprograms that are declared but never called. By placing the list of -@code{Eliminate} pragmas in the GNAT configuration file @file{gnat.adc} and -recompiling your program, you may decrease the size of its executable, -because the compiler will not generate the code for 'eliminated' subprograms. -@xref{Pragma Eliminate,,, gnat_rm, GNAT Reference Manual}, for more -information about this pragma. - -@code{gnatelim} needs as its input data the name of the main subprogram. - -If a set of source files is specified as @code{gnatelim} arguments, it -treats these files as a complete set of sources making up a program to -analyse, and analyses only these sources. - -After a full successful build of the main subprogram @code{gnatelim} can be -called without specifying sources to analyse, in this case it computes -the source closure of the main unit from the @file{ALI} files. - -If the set of sources to be processed by @code{gnatelim} contains sources with -preprocessing directives -then the needed options should be provided to run preprocessor as a part of -the @command{gnatelim} call, and the generated set of pragmas @code{Eliminate} -will correspond to preprocessed sources. - -The following command will create the set of @file{ALI} files needed for -@code{gnatelim}: - -@smallexample -$ gnatmake -c Main_Prog -@end smallexample - -Note that @code{gnatelim} does not need object files. - -@node Running gnatelim -@subsection Running @code{gnatelim} - -@noindent -@code{gnatelim} has the following command-line interface: - -@smallexample -$ gnatelim [@var{switches}] -main=@var{main_unit_name} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]} -@end smallexample - -@noindent -@var{main_unit_name} should be a name of a source file that contains the main -subprogram of a program (partition). - -Each @var{filename} is the name (including the extension) of a source -file to process. ``Wildcards'' are allowed, and -the file name may contain path information. - -@samp{@var{gcc_switches}} is a list of switches for -@command{gcc}. They will be passed on to all compiler invocations made by -@command{gnatelim} to generate the ASIS trees. Here you can provide -@option{-I} switches to form the source search path, -use the @option{-gnatec} switch to set the configuration file, -use the @option{-gnat05} switch if sources should be compiled in -Ada 2005 mode etc. - -@code{gnatelim} has the following switches: - -@table @option -@c !sort! -@item --version -@cindex @option{--version} @command{gnatelim} -Display Copyright and version, then exit disregarding all other options. + function Number_Of_Teeth (this : access Dog) return int; + pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv"); -@item --help -@cindex @option{--help} @command{gnatelim} -Display usage, then exit disregarding all other options. + procedure Set_Owner + (this : access Dog; Name : Interfaces.C.Strings.chars_ptr); + pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc"); -@item -P @var{file} -@cindex @option{-P} @command{gnatelim} -Indicates the name of the project file that describes the set of sources -to be processed. + function New_Dog return Dog; + pragma CPP_Constructor (New_Dog); + pragma Import (CPP, New_Dog, "_ZN3DogC1Ev"); +end; +use Class_Dog; +@end example -@item -X@var{name}=@var{value} -@cindex @option{-X} @command{gnatelim} -Indicates that external variable @var{name} in the argument project -has the value @var{value}. Has no effect if no project is specified as -tool argument. +@node Switches,,Generating bindings for C++ headers,Generating Ada Bindings for C and C++ headers +@anchor{gnat_ugn/the_gnat_compilation_model switches}@anchor{ce}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation}@anchor{cf} +@subsubsection Switches -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatelim}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). - -@item -files=@var{filename} -@cindex @option{-files} (@code{gnatelim}) -Take the argument source files from the specified file. This file should be an -ordinary text file containing file names separated by spaces or -line breaks. You can use this switch more than once in the same call to -@command{gnatelim}. You also can combine this switch with -an explicit list of files. - -@item -log -@cindex @option{-log} (@command{gnatelim}) -Duplicate all the output sent to @file{stderr} into a log file. The log file -is named @file{gnatelim.log} and is located in the current directory. - -@ignore -@item -log=@var{filename} -@cindex @option{-log} (@command{gnatelim}) -Duplicate all the output sent to @file{stderr} into a specified log file. -@end ignore - -@cindex @option{--no-elim-dispatch} (@command{gnatelim}) -@item --no-elim-dispatch -Do not generate pragmas for dispatching operations. - -@item --ignore=@var{filename} -@cindex @option{--ignore} (@command{gnatelim}) -Do not generate pragmas for subprograms declared in the sources -listed in a specified file - -@cindex @option{-o} (@command{gnatelim}) -@item -o=@var{report_file} -Put @command{gnatelim} output into a specified file. If this file already exists, -it is overridden. If this switch is not used, @command{gnatelim} outputs its results -into @file{stderr} - -@item -j@var{n} -@cindex @option{-j} (@command{gnatelim}) -Use @var{n} processes to carry out the tree creations (internal representations -of the argument sources). On a multiprocessor machine this speeds up processing -of big sets of argument sources. If @var{n} is 0, then the maximum number of -parallel tree creations is the number of core processors on the platform. - -@item -q -@cindex @option{-q} (@command{gnatelim}) -Quiet mode: by default @code{gnatelim} outputs to the standard error -stream the number of program units left to be processed. This option turns -this trace off. - -@cindex @option{-t} (@command{gnatelim}) -@item -t -Print out execution time. - -@item -v -@cindex @option{-v} (@command{gnatelim}) -Verbose mode: @code{gnatelim} version information is printed as Ada -comments to the standard output stream. Also, in addition to the number of -program units left @code{gnatelim} will output the name of the current unit -being processed. - -@item -wq -@cindex @option{-wq} (@command{gnatelim}) -Quiet warning mode - some warnings are suppressed. In particular warnings that -indicate that the analysed set of sources is incomplete to make up a -partition and that some subprogram bodies are missing are not generated. -@end table - -@noindent -Note: to invoke @command{gnatelim} with a project file, use the @code{gnat} -driver (see @ref{The GNAT Driver and Project Files}). - -@node Processing Precompiled Libraries -@subsection Processing Precompiled Libraries - -@noindent -If some program uses a precompiled Ada library, it can be processed by -@code{gnatelim} in a usual way. @code{gnatelim} will newer generate an -Eliminate pragma for a subprogram if the body of this subprogram has not -been analysed, this is a typical case for subprograms from precompiled -libraries. Switch @option{-wq} may be used to suppress -warnings about missing source files and non-analyzed subprogram bodies -that can be generated when processing precompiled Ada libraries. - -@node Correcting the List of Eliminate Pragmas -@subsection Correcting the List of Eliminate Pragmas - -@noindent -In some rare cases @code{gnatelim} may try to eliminate -subprograms that are actually called in the program. In this case, the -compiler will generate an error message of the form: - -@smallexample -main.adb:4:08: cannot reference subprogram "P" eliminated at elim.out:5 -@end smallexample - -@noindent -You will need to manually remove the wrong @code{Eliminate} pragmas from -the configuration file indicated in the error message. You should recompile -your program from scratch after that, because you need a consistent -configuration file(s) during the entire compilation. - -@node Making Your Executables Smaller -@subsection Making Your Executables Smaller - -@noindent -In order to get a smaller executable for your program you now have to -recompile the program completely with the configuration file containing -pragmas Eliminate generated by gnatelim. If these pragmas are placed in -@file{gnat.adc} file located in your current directory, just do: - -@smallexample -$ gnatmake -f main_prog -@end smallexample - -@noindent -(Use the @option{-f} option for @command{gnatmake} to -recompile everything -with the set of pragmas @code{Eliminate} that you have obtained with -@command{gnatelim}). - -Be aware that the set of @code{Eliminate} pragmas is specific to each -program. It is not recommended to merge sets of @code{Eliminate} -pragmas created for different programs in one configuration file. - -@node Summary of the gnatelim Usage Cycle -@subsection Summary of the @code{gnatelim} Usage Cycle - -@noindent -Here is a quick summary of the steps to be taken in order to reduce -the size of your executables with @code{gnatelim}. You may use -other GNAT options to control the optimization level, -to produce the debugging information, to set search path, etc. - -@enumerate -@item -Create a complete set of @file{ALI} files (if the program has not been -built already) -@smallexample -$ gnatmake -c main_prog -@end smallexample +@geindex -fdump-ada-spec (gcc) -@item -Generate a list of @code{Eliminate} pragmas in default configuration file -@file{gnat.adc} in the current directory -@smallexample -$ gnatelim main_prog >@r{[}>@r{]} gnat.adc -@end smallexample -@item -Recompile the application +@table @asis -@smallexample -$ gnatmake -f main_prog -@end smallexample +@item @code{-fdump-ada-spec} -@end enumerate -@end ifclear +Generate Ada spec files for the given header files transitively (including +all header files that these headers depend upon). +@end table -@node Reducing Size of Executables with unused subprogram/data elimination -@section Reducing Size of Executables with Unused Subprogram/Data Elimination -@findex unused subprogram/data elimination +@geindex -fdump-ada-spec-slim (gcc) -@noindent -This section describes how you can eliminate unused subprograms and data from -your executable just by setting options at compilation time. -@menu -* About unused subprogram/data elimination:: -* Compilation options:: -* Example of unused subprogram/data elimination:: -@end menu +@table @asis -@node About unused subprogram/data elimination -@subsection About unused subprogram/data elimination +@item @code{-fdump-ada-spec-slim} -@noindent -By default, an executable contains all code and data of its composing objects -(directly linked or coming from statically linked libraries), even data or code -never used by this executable. +Generate Ada spec files for the header files specified on the command line +only. +@end table -This feature will allow you to eliminate such unused code from your -executable, making it smaller (in disk and in memory). +@geindex -fada-spec-parent (gcc) -This functionality is available on all Linux platforms except for the IA-64 -architecture and on all cross platforms using the ELF binary file format. -In both cases GNU binutils version 2.16 or later are required to enable it. -@node Compilation options -@subsection Compilation options +@table @asis -@noindent -The operation of eliminating the unused code and data from the final executable -is directly performed by the linker. +@item @code{-fada-spec-parent=@emph{unit}} -In order to do this, it has to work with objects compiled with the -following options: -@option{-ffunction-sections} @option{-fdata-sections}. -@cindex @option{-ffunction-sections} (@command{gcc}) -@cindex @option{-fdata-sections} (@command{gcc}) -These options are usable with C and Ada files. -They will place respectively each -function or data in a separate section in the resulting object file. +Specifies that all files generated by @emph{-fdump-ada-spec*} are +to be child units of the specified parent unit. +@end table -Once the objects and static libraries are created with these options, the -linker can perform the dead code elimination. You can do this by setting -the @option{-Wl,--gc-sections} option to gcc command or in the -@option{-largs} section of @command{gnatmake}. This will perform a -garbage collection of code and data never referenced. +@geindex -C (gcc) -If the linker performs a partial link (@option{-r} linker option), then you -will need to provide the entry point using the @option{-e} / @option{--entry} -linker option. -Note that objects compiled without the @option{-ffunction-sections} and -@option{-fdata-sections} options can still be linked with the executable. -However, no dead code elimination will be performed on those objects (they will -be linked as is). +@table @asis -The GNAT static library is now compiled with -ffunction-sections and --fdata-sections on some platforms. This allows you to eliminate the unused code -and data of the GNAT library from your executable. +@item @code{-C} -@node Example of unused subprogram/data elimination -@subsection Example of unused subprogram/data elimination +Extract comments from headers and generate Ada comments in the Ada spec files. +@end table -@noindent -Here is a simple example: +@node GNAT and Other Compilation Models,Using GNAT Files with External Tools,Mixed Language Programming,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model id73}@anchor{d0}@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models}@anchor{47} +@section GNAT and Other Compilation Models -@smallexample @c ada -@b{with} Aux; -@b{procedure} Test @b{is} -@b{begin} - Aux.Used (10); -@b{end} Test; +This section compares the GNAT model with the approaches taken in +other environents, first the C/C++ model and then the mechanism that +has been used in other Ada systems, in particular those traditionally +used for Ada 83. -@b{package} Aux @b{is} - Used_Data : Integer; - Unused_Data : Integer; +@menu +* Comparison between GNAT and C/C++ Compilation Models:: +* Comparison between GNAT and Conventional Ada Library Models:: - @b{procedure} Used (Data : Integer); - @b{procedure} Unused (Data : Integer); -@b{end} Aux; +@end menu -@b{package} @b{body} Aux @b{is} - @b{procedure} Used (Data : Integer) @b{is} - @b{begin} - Used_Data := Data; - @b{end} Used; +@node Comparison between GNAT and C/C++ Compilation Models,Comparison between GNAT and Conventional Ada Library Models,,GNAT and Other Compilation Models +@anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models}@anchor{d1}@anchor{gnat_ugn/the_gnat_compilation_model id74}@anchor{d2} +@subsection Comparison between GNAT and C/C++ Compilation Models - @b{procedure} Unused (Data : Integer) @b{is} - @b{begin} - Unused_Data := Data; - @b{end} Unused; -@b{end} Aux; -@end smallexample -@noindent -@code{Unused} and @code{Unused_Data} are never referenced in this code -excerpt, and hence they may be safely removed from the final executable. +The GNAT model of compilation is close to the C and C++ models. You can +think of Ada specs as corresponding to header files in C. As in C, you +don't need to compile specs; they are compiled when they are used. The +Ada @emph{with} is similar in effect to the @cite{#include} of a C +header. -@smallexample -$ gnatmake test +One notable difference is that, in Ada, you may compile specs separately +to check them for semantic and syntactic accuracy. This is not always +possible with C headers because they are fragments of programs that have +less specific syntactic or semantic rules. -$ nm test | grep used -020015f0 T aux__unused -02005d88 B aux__unused_data -020015cc T aux__used -02005d84 B aux__used_data +The other major difference is the requirement for running the binder, +which performs two important functions. First, it checks for +consistency. In C or C++, the only defense against assembling +inconsistent programs lies outside the compiler, in a makefile, for +example. The binder satisfies the Ada requirement that it be impossible +to construct an inconsistent program when the compiler is used in normal +mode. -$ gnatmake test -cargs -fdata-sections -ffunction-sections \ - -largs -Wl,--gc-sections +@geindex Elaboration order control -$ nm test | grep used -02005350 T aux__used -0201ffe0 B aux__used_data -@end smallexample +The other important function of the binder is to deal with elaboration +issues. There are also elaboration issues in C++ that are handled +automatically. This automatic handling has the advantage of being +simpler to use, but the C++ programmer has no control over elaboration. +Where @cite{gnatbind} might complain there was no valid order of +elaboration, a C++ compiler would simply construct a program that +malfunctioned at run time. -@noindent -It can be observed that the procedure @code{Unused} and the object -@code{Unused_Data} are removed by the linker when using the -appropriate options. +@node Comparison between GNAT and Conventional Ada Library Models,,Comparison between GNAT and C/C++ Compilation Models,GNAT and Other Compilation Models +@anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models}@anchor{d3}@anchor{gnat_ugn/the_gnat_compilation_model id75}@anchor{d4} +@subsection Comparison between GNAT and Conventional Ada Library Models -@c ******************************** -@node Renaming Files with gnatchop -@chapter Renaming Files with @code{gnatchop} -@findex gnatchop -@noindent -This chapter discusses how to handle files with multiple units by using -the @code{gnatchop} utility. This utility is also useful in renaming -files to meet the standard GNAT default file naming conventions. +This section is intended for Ada programmers who have +used an Ada compiler implementing the traditional Ada library +model, as described in the Ada Reference Manual. -@menu -* Handling Files with Multiple Units:: -* Operating gnatchop in Compilation Mode:: -* Command Line for gnatchop:: -* Switches for gnatchop:: -* Examples of gnatchop Usage:: -@end menu +@geindex GNAT library -@node Handling Files with Multiple Units -@section Handling Files with Multiple Units +In GNAT, there is no 'library' in the normal sense. Instead, the set of +source files themselves acts as the library. Compiling Ada programs does +not generate any centralized information, but rather an object file and +a ALI file, which are of interest only to the binder and linker. +In a traditional system, the compiler reads information not only from +the source file being compiled, but also from the centralized library. +This means that the effect of a compilation depends on what has been +previously compiled. In particular: -@noindent -The basic compilation model of GNAT requires that a file submitted to the -compiler have only one unit and there be a strict correspondence -between the file name and the unit name. -The @code{gnatchop} utility allows both of these rules to be relaxed, -allowing GNAT to process files which contain multiple compilation units -and files with arbitrary file names. @code{gnatchop} -reads the specified file and generates one or more output files, -containing one unit per file. The unit and the file name correspond, -as required by GNAT. +@itemize * -If you want to permanently restructure a set of ``foreign'' files so that -they match the GNAT rules, and do the remaining development using the -GNAT structure, you can simply use @command{gnatchop} once, generate the -new set of files and work with them from that point on. +@item +When a unit is @emph{with}ed, the unit seen by the compiler corresponds +to the version of the unit most recently compiled into the library. -Alternatively, if you want to keep your files in the ``foreign'' format, -perhaps to maintain compatibility with some other Ada compilation -system, you can set up a procedure where you use @command{gnatchop} each -time you compile, regarding the source files that it writes as temporary -files that you throw away. +@item +Inlining is effective only if the necessary body has already been +compiled into the library. -Note that if your file containing multiple units starts with a byte order -mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop -will each start with a copy of this BOM, meaning that they can be compiled -automatically in UTF-8 mode without needing to specify an explicit encoding. +@item +Compiling a unit may obsolete other units in the library. +@end itemize -@node Operating gnatchop in Compilation Mode -@section Operating gnatchop in Compilation Mode +In GNAT, compiling one unit never affects the compilation of any other +units because the compiler reads only source files. Only changes to source +files can affect the results of a compilation. In particular: -@noindent -The basic function of @code{gnatchop} is to take a file with multiple units -and split it into separate files. The boundary between files is reasonably -clear, except for the issue of comments and pragmas. In default mode, the -rule is that any pragmas between units belong to the previous unit, except -that configuration pragmas always belong to the following unit. Any comments -belong to the following unit. These rules -almost always result in the right choice of -the split point without needing to mark it explicitly and most users will -find this default to be what they want. In this default mode it is incorrect to -submit a file containing only configuration pragmas, or one that ends in -configuration pragmas, to @code{gnatchop}. -However, using a special option to activate ``compilation mode'', -@code{gnatchop} -can perform another function, which is to provide exactly the semantics -required by the RM for handling of configuration pragmas in a compilation. -In the absence of configuration pragmas (at the main file level), this -option has no effect, but it causes such configuration pragmas to be handled -in a quite different manner. - -First, in compilation mode, if @code{gnatchop} is given a file that consists of -only configuration pragmas, then this file is appended to the -@file{gnat.adc} file in the current directory. This behavior provides -the required behavior described in the RM for the actions to be taken -on submitting such a file to the compiler, namely that these pragmas -should apply to all subsequent compilations in the same compilation -environment. Using GNAT, the current directory, possibly containing a -@file{gnat.adc} file is the representation -of a compilation environment. For more information on the -@file{gnat.adc} file, see @ref{Handling of Configuration Pragmas}. +@itemize * -Second, in compilation mode, if @code{gnatchop} -is given a file that starts with -configuration pragmas, and contains one or more units, then these -configuration pragmas are prepended to each of the chopped files. This -behavior provides the required behavior described in the RM for the -actions to be taken on compiling such a file, namely that the pragmas -apply to all units in the compilation, but not to subsequently compiled -units. +@item +When a unit is @emph{with}ed, the unit seen by the compiler corresponds +to the source version of the unit that is currently accessible to the +compiler. -Finally, if configuration pragmas appear between units, they are appended -to the previous unit. This results in the previous unit being illegal, -since the compiler does not accept configuration pragmas that follow -a unit. This provides the required RM behavior that forbids configuration -pragmas other than those preceding the first compilation unit of a -compilation. +@geindex Inlining -For most purposes, @code{gnatchop} will be used in default mode. The -compilation mode described above is used only if you need exactly -accurate behavior with respect to compilations, and you have files -that contain multiple units and configuration pragmas. In this -circumstance the use of @code{gnatchop} with the compilation mode -switch provides the required behavior, and is for example the mode -in which GNAT processes the ACVC tests. +@item +Inlining requires the appropriate source files for the package or +subprogram bodies to be available to the compiler. Inlining is always +effective, independent of the order in which units are compiled. -@node Command Line for gnatchop -@section Command Line for @code{gnatchop} +@item +Compiling a unit never affects any other compilations. The editing of +sources may cause previous compilations to be out of date if they +depended on the source file being modified. +@end itemize -@noindent -The @code{gnatchop} command has the form: +The most important result of these differences is that order of compilation +is never significant in GNAT. There is no situation in which one is +required to do one compilation before another. What shows up as order of +compilation requirements in the traditional Ada library becomes, in +GNAT, simple source dependencies; in other words, there is only a set +of rules saying what source files must be present when a file is +compiled. -@smallexample -@c $ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]} -@c @ovar{directory} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatchop switches @var{file name} @r{[}@var{file name} @dots{}@r{]} - @r{[}@var{directory}@r{]} -@end smallexample +@node Using GNAT Files with External Tools,,GNAT and Other Compilation Models,The GNAT Compilation Model +@anchor{gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools}@anchor{1c}@anchor{gnat_ugn/the_gnat_compilation_model id76}@anchor{d5} +@section Using GNAT Files with External Tools -@noindent -The only required argument is the file name of the file to be chopped. -There are no restrictions on the form of this file name. The file itself -contains one or more Ada units, in normal GNAT format, concatenated -together. As shown, more than one file may be presented to be chopped. -When run in default mode, @code{gnatchop} generates one output file in -the current directory for each unit in each of the files. +This section explains how files that are produced by GNAT may be +used with tools designed for other languages. -@var{directory}, if specified, gives the name of the directory to which -the output files will be written. If it is not specified, all files are -written to the current directory. +@menu +* Using Other Utility Programs with GNAT:: +* The External Symbol Naming Scheme of GNAT:: -For example, given a -file called @file{hellofiles} containing +@end menu -@smallexample @c ada -@group -@cartouche -@b{procedure} hello; +@node Using Other Utility Programs with GNAT,The External Symbol Naming Scheme of GNAT,,Using GNAT Files with External Tools +@anchor{gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat}@anchor{d6}@anchor{gnat_ugn/the_gnat_compilation_model id77}@anchor{d7} +@subsection Using Other Utility Programs with GNAT -@b{with} Text_IO; @b{use} Text_IO; -@b{procedure} hello @b{is} -@b{begin} - Put_Line ("Hello"); -@b{end} hello; -@end cartouche -@end group -@end smallexample -@noindent -the command +The object files generated by GNAT are in standard system format and in +particular the debugging information uses this format. This means +programs generated by GNAT can be used with existing utilities that +depend on these formats. -@smallexample -$ gnatchop hellofiles -@end smallexample +In general, any utility program that works with C will also often work with +Ada programs generated by GNAT. This includes software utilities such as +gprof (a profiling program), gdb (the FSF debugger), and utilities such +as Purify. -@noindent -generates two files in the current directory, one called -@file{hello.ads} containing the single line that is the procedure spec, -and the other called @file{hello.adb} containing the remaining text. The -original file is not affected. The generated files can be compiled in -the normal manner. +@node The External Symbol Naming Scheme of GNAT,,Using Other Utility Programs with GNAT,Using GNAT Files with External Tools +@anchor{gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat}@anchor{d8}@anchor{gnat_ugn/the_gnat_compilation_model id78}@anchor{d9} +@subsection The External Symbol Naming Scheme of GNAT -@noindent -When gnatchop is invoked on a file that is empty or that contains only empty -lines and/or comments, gnatchop will not fail, but will not produce any -new sources. -For example, given a -file called @file{toto.txt} containing +In order to interpret the output from GNAT, when using tools that are +originally intended for use with other languages, it is useful to +understand the conventions used to generate link names from the Ada +entity names. -@smallexample @c ada -@group -@cartouche ---@i{ Just a comment} -@end cartouche -@end group -@end smallexample +All link names are in all lowercase letters. With the exception of library +procedure names, the mechanism used is simply to use the full expanded +Ada name with dots replaced by double underscores. For example, suppose +we have the following package spec: -@noindent -the command +@example +package QRS is + MN : Integer; +end QRS; +@end example -@smallexample -$ gnatchop toto.txt -@end smallexample +@geindex pragma Export -@noindent -will not produce any new file and will result in the following warnings: +The variable @cite{MN} has a full expanded Ada name of @cite{QRS.MN}, so +the corresponding link name is @cite{qrs__mn}. +Of course if a @cite{pragma Export} is used this may be overridden: -@smallexample -toto.txt:1:01: warning: empty file, contains no compilation units -no compilation units found -no source files written -@end smallexample +@example +package Exports is + Var1 : Integer; + pragma Export (Var1, C, External_Name => "var1_name"); + Var2 : Integer; + pragma Export (Var2, C, Link_Name => "var2_link_name"); +end Exports; +@end example -@node Switches for gnatchop -@section Switches for @code{gnatchop} +In this case, the link name for @cite{Var1} is whatever link name the +C compiler would assign for the C function @cite{var1_name}. This typically +would be either @cite{var1_name} or @cite{_var1_name}, depending on operating +system conventions, but other possibilities exist. The link name for +@cite{Var2} is @cite{var2_link_name}, and this is not operating system +dependent. -@noindent -@command{gnatchop} recognizes the following switches: +One exception occurs for library level procedures. A potential ambiguity +arises between the required name @cite{_main} for the C main program, +and the name we would otherwise assign to an Ada library level procedure +called @cite{Main} (which might well not be the main program). -@table @option -@c !sort! +To avoid this ambiguity, we attach the prefix @cite{_ada_} to such +names. So if we have a library level procedure such as: -@item --version -@cindex @option{--version} @command{gnatchop} -Display Copyright and version, then exit disregarding all other options. +@example +procedure Hello (S : String); +@end example -@item --help -@cindex @option{--help} @command{gnatchop} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +the external name of this procedure will be @cite{_ada_hello}. -@item -c -@cindex @option{-c} (@code{gnatchop}) -Causes @code{gnatchop} to operate in compilation mode, in which -configuration pragmas are handled according to strict RM rules. See -previous section for a full description of this mode. +@c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit -@item -gnat@var{xxx} -This passes the given @option{-gnat@var{xxx}} switch to @code{gnat} which is -used to parse the given file. Not all @var{xxx} options make sense, -but for example, the use of @option{-gnati2} allows @code{gnatchop} to -process a source file that uses Latin-2 coding for identifiers. +@node Building Executable Programs with GNAT,GNAT Project Manager,The GNAT Compilation Model,Top +@anchor{gnat_ugn/building_executable_programs_with_gnat building-executable-programs-with-gnat}@anchor{a}@anchor{gnat_ugn/building_executable_programs_with_gnat doc}@anchor{da}@anchor{gnat_ugn/building_executable_programs_with_gnat id1}@anchor{db} +@chapter Building Executable Programs with GNAT -@item -h -Causes @code{gnatchop} to generate a brief help summary to the standard -output file showing usage information. -@item -k@var{mm} -@cindex @option{-k} (@code{gnatchop}) -Limit generated file names to the specified number @code{mm} -of characters. -This is useful if the -resulting set of files is required to be interoperable with systems -which limit the length of file names. -No space is allowed between the @option{-k} and the numeric value. The numeric -value may be omitted in which case a default of @option{-k8}, -suitable for use -with DOS-like file systems, is used. If no @option{-k} switch -is present then -there is no limit on the length of file names. +This chapter describes first the gnatmake tool +(@ref{1d,,Building with gnatmake}), +which automatically determines the set of sources +needed by an Ada compilation unit and executes the necessary +(re)compilations, binding and linking. +It also explains how to use each tool individually: the +compiler (gcc, see @ref{1e,,Compiling with gcc}), +binder (gnatbind, see @ref{1f,,Binding with gnatbind}), +and linker (gnatlink, see @ref{20,,Linking with gnatlink}) +to build executable programs. +Finally, this chapter provides examples of +how to make use of the general GNU make mechanism +in a GNAT context (see @ref{21,,Using the GNU make Utility}). -@item -p -@cindex @option{-p} (@code{gnatchop}) -Causes the file modification time stamp of the input file to be -preserved and used for the time stamp of the output file(s). This may be -useful for preserving coherency of time stamps in an environment where -@code{gnatchop} is used as part of a standard build process. +@menu +* Building with gnatmake:: +* Compiling with gcc:: +* Compiler Switches:: +* Binding with gnatbind:: +* Linking with gnatlink:: +* Using the GNU make Utility:: -@item -q -@cindex @option{-q} (@code{gnatchop}) -Causes output of informational messages indicating the set of generated -files to be suppressed. Warnings and error messages are unaffected. +@end menu -@item -r -@cindex @option{-r} (@code{gnatchop}) -@findex Source_Reference -Generate @code{Source_Reference} pragmas. Use this switch if the output -files are regarded as temporary and development is to be done in terms -of the original unchopped file. This switch causes -@code{Source_Reference} pragmas to be inserted into each of the -generated files to refers back to the original file name and line number. -The result is that all error messages refer back to the original -unchopped file. -In addition, the debugging information placed into the object file (when -the @option{-g} switch of @command{gcc} or @command{gnatmake} is -specified) -also refers back to this original file so that tools like profilers and -debuggers will give information in terms of the original unchopped file. +@node Building with gnatmake,Compiling with gcc,,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake}@anchor{1d}@anchor{gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake}@anchor{dc} +@section Building with @emph{gnatmake} -If the original file to be chopped itself contains -a @code{Source_Reference} -pragma referencing a third file, then gnatchop respects -this pragma, and the generated @code{Source_Reference} pragmas -in the chopped file refer to the original file, with appropriate -line numbers. This is particularly useful when @code{gnatchop} -is used in conjunction with @code{gnatprep} to compile files that -contain preprocessing statements and multiple units. -@item -v -@cindex @option{-v} (@code{gnatchop}) -Causes @code{gnatchop} to operate in verbose mode. The version -number and copyright notice are output, as well as exact copies of -the gnat1 commands spawned to obtain the chop control information. +@geindex gnatmake -@item -w -@cindex @option{-w} (@code{gnatchop}) -Overwrite existing file names. Normally @code{gnatchop} regards it as a -fatal error if there is already a file with the same name as a -file it would otherwise output, in other words if the files to be -chopped contain duplicated units. This switch bypasses this -check, and causes all but the last instance of such duplicated -units to be skipped. +A typical development cycle when working on an Ada program consists of +the following steps: -@item --GCC=@var{xxxx} -@cindex @option{--GCC=} (@code{gnatchop}) -Specify the path of the GNAT parser to be used. When this switch is used, -no attempt is made to add the prefix to the GNAT parser executable. -@end table -@node Examples of gnatchop Usage -@section Examples of @code{gnatchop} Usage +@enumerate -@table @code -@item gnatchop -w hello_s.ada prerelease/files +@item +Edit some sources to fix bugs; -Chops the source file @file{hello_s.ada}. The output files will be -placed in the directory @file{prerelease/files}, -overwriting any -files with matching names in that directory (no files in the current -directory are modified). +@item +Add enhancements; -@item gnatchop archive -Chops the source file @file{archive} -into the current directory. One -useful application of @code{gnatchop} is in sending sets of sources -around, for example in email messages. The required sources are simply -concatenated (for example, using a Unix @code{cat} -command), and then -@command{gnatchop} is used at the other end to reconstitute the original -file names. +@item +Compile all sources affected; -@item gnatchop file1 file2 file3 direc -Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing -the resulting files in the directory @file{direc}. Note that if any units -occur more than once anywhere within this set of files, an error message -is generated, and no files are written. To override this check, use the -@option{-w} switch, -in which case the last occurrence in the last file will -be the one that is output, and earlier duplicate occurrences for a given -unit will be skipped. -@end table +@item +Rebind and relink; and -@node Configuration Pragmas -@chapter Configuration Pragmas -@cindex Configuration pragmas -@cindex Pragmas, configuration +@item +Test. +@end enumerate -@menu -* Handling of Configuration Pragmas:: -* The Configuration Pragmas Files:: -@end menu +@geindex Dependency rules (compilation) -@noindent -Configuration pragmas include those pragmas described as -such in the Ada Reference Manual, as well as -implementation-dependent pragmas that are configuration pragmas. -@xref{Implementation Defined Pragmas,,, gnat_rm, GNAT Reference Manual}, -for details on these additional GNAT-specific configuration pragmas. -Most notably, the pragma @code{Source_File_Name}, which allows -specifying non-default names for source files, is a configuration -pragma. The following is a complete list of configuration pragmas -recognized by GNAT: +The third step in particular can be tricky, because not only do the modified +files have to be compiled, but any files depending on these files must also be +recompiled. The dependency rules in Ada can be quite complex, especially +in the presence of overloading, @cite{use} clauses, generics and inlined +subprograms. -@smallexample - Ada_83 - Ada_95 - Ada_05 - Ada_2005 - Ada_12 - Ada_2012 - Allow_Integer_Address - Annotate - Assertion_Policy - Assume_No_Invalid_Values - C_Pass_By_Copy - Check_Name - Check_Policy - Compile_Time_Error - Compile_Time_Warning - Compiler_Unit - Component_Alignment - Convention_Identifier - Debug_Policy - Detect_Blocking - Default_Storage_Pool - Discard_Names - Elaboration_Checks - Eliminate - Extend_System - Extensions_Allowed - External_Name_Casing - Fast_Math - Favor_Top_Level - Float_Representation - Implicit_Packing - Initialize_Scalars - Interrupt_State - License - Locking_Policy - Long_Float - No_Run_Time - No_Strict_Aliasing - Normalize_Scalars - Optimize_Alignment - Persistent_BSS - Polling - Priority_Specific_Dispatching - Profile - Profile_Warnings - Propagate_Exceptions - Queuing_Policy - Ravenscar - Restricted_Run_Time - Restrictions - Restrictions_Warnings - Reviewable - Short_Circuit_And_Or - Source_File_Name - Source_File_Name_Project - SPARK_Mode - Style_Checks - Suppress - Suppress_Exception_Locations - Task_Dispatching_Policy - Universal_Data - Unsuppress - Use_VADS_Size - Validity_Checks - Warnings - Wide_Character_Encoding -@end smallexample - -@node Handling of Configuration Pragmas -@section Handling of Configuration Pragmas +@emph{gnatmake} automatically takes care of the third and fourth steps +of this process. It determines which sources need to be compiled, +compiles them, and binds and links the resulting object files. -Configuration pragmas may either appear at the start of a compilation -unit, or they can appear in a configuration pragma file to apply to -all compilations performed in a given compilation environment. +Unlike some other Ada make programs, the dependencies are always +accurately recomputed from the new sources. The source based approach of +the GNAT compilation model makes this possible. This means that if +changes to the source program cause corresponding changes in +dependencies, they will always be tracked exactly correctly by +@emph{gnatmake}. -GNAT also provides the @code{gnatchop} utility to provide an automatic -way to handle configuration pragmas following the semantics for -compilations (that is, files with multiple units), described in the RM. -See @ref{Operating gnatchop in Compilation Mode} for details. -However, for most purposes, it will be more convenient to edit the -@file{gnat.adc} file that contains configuration pragmas directly, -as described in the following section. +Note that for advanced description of project structure, we recommend creating +a project file as explained in @ref{b,,GNAT Project Manager} and use the +@emph{gprbuild} tool which supports building with project files and works similarly +to @emph{gnatmake}. -In the case of @code{Restrictions} pragmas appearing as configuration -pragmas in individual compilation units, the exact handling depends on -the type of restriction. +@menu +* Running gnatmake:: +* Switches for gnatmake:: +* Mode Switches for gnatmake:: +* Notes on the Command Line:: +* How gnatmake Works:: +* Examples of gnatmake Usage:: -Restrictions that require partition-wide consistency (like -@code{No_Tasking}) are -recognized wherever they appear -and can be freely inherited, e.g. from a with'ed unit to the with'ing -unit. This makes sense since the binder will in any case insist on seeing -consistent use, so any unit not conforming to any restrictions that are -anywhere in the partition will be rejected, and you might as well find -that out at compile time rather than at bind time. +@end menu -For restrictions that do not require partition-wide consistency, e.g. -SPARK or No_Implementation_Attributes, in general the restriction applies -only to the unit in which the pragma appears, and not to any other units. +@node Running gnatmake,Switches for gnatmake,,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatmake}@anchor{dd}@anchor{gnat_ugn/building_executable_programs_with_gnat id2}@anchor{de} +@subsection Running @emph{gnatmake} -The exception is No_Elaboration_Code which always applies to the entire -object file from a compilation, i.e. to the body, spec, and all subunits. -This restriction can be specified in a configuration pragma file, or it -can be on the body and/or the spec (in eithe case it applies to all the -relevant units). It can appear on a subunit only if it has previously -appeared in the body of spec. -@node The Configuration Pragmas Files -@section The Configuration Pragmas Files -@cindex @file{gnat.adc} +The usual form of the @emph{gnatmake} command is -@noindent -In GNAT a compilation environment is defined by the current -directory at the time that a compile command is given. This current -directory is searched for a file whose name is @file{gnat.adc}. If -this file is present, it is expected to contain one or more -configuration pragmas that will be applied to the current compilation. -However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not -considered. When taken into account, @file{gnat.adc} is added to the -dependencies, so that if @file{gnat.adc} is modified later, an invocation of -@command{gnatmake} will recompile the source. +@example +$ gnatmake [] [] [] +@end example -Configuration pragmas may be entered into the @file{gnat.adc} file -either by running @code{gnatchop} on a source file that consists only of -configuration pragmas, or more conveniently by direct editing of the -@file{gnat.adc} file, which is a standard format source file. +The only required argument is one @cite{file_name}, which specifies +a compilation unit that is a main program. Several @cite{file_names} can be +specified: this will result in several executables being built. +If @cite{switches} are present, they can be placed before the first +@cite{file_name}, between @cite{file_names} or after the last @cite{file_name}. +If @cite{mode_switches} are present, they must always be placed after +the last @cite{file_name} and all @cite{switches}. + +If you are using standard file extensions (@code{.adb} and +@code{.ads}), then the +extension may be omitted from the @cite{file_name} arguments. However, if +you are using non-standard extensions, then it is required that the +extension be given. A relative or absolute directory path can be +specified in a @cite{file_name}, in which case, the input source file will +be searched for in the specified directory only. Otherwise, the input +source file will first be searched in the directory where +@emph{gnatmake} was invoked and if it is not found, it will be search on +the source path of the compiler as described in +@ref{8e,,Search Paths and the Run-Time Library (RTL)}. -In addition to @file{gnat.adc}, additional files containing configuration -pragmas may be applied to the current compilation using the switch -@option{-gnatec=}@var{path}. @var{path} must designate an existing file that -contains only configuration pragmas. These configuration pragmas are -in addition to those found in @file{gnat.adc} (provided @file{gnat.adc} -is present and switch @option{-gnatA} is not used). +All @emph{gnatmake} output (except when you specify @emph{-M}) is sent to +@code{stderr}. The output produced by the +@emph{-M} switch is sent to @code{stdout}. -It is allowable to specify several switches @option{-gnatec=}, all of which -will be taken into account. +@node Switches for gnatmake,Mode Switches for gnatmake,Running gnatmake,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake}@anchor{df}@anchor{gnat_ugn/building_executable_programs_with_gnat id3}@anchor{e0} +@subsection Switches for @emph{gnatmake} -Files containing configuration pragmas specified with switches -@option{-gnatec=} are added to the dependencies, unless they are -temporary files. A file is considered temporary if its name ends in -@file{.tmp} or @file{.TMP}. Certain tools follow this naming -convention because they pass information to @command{gcc} via -temporary files that are immediately deleted; it doesn't make sense to -depend on a file that no longer exists. Such tools include -@command{gprbuild}, @command{gnatmake}, and @command{gnatcheck}. -If you are using project file, a separate mechanism is provided using -project attributes, see @ref{Specifying Configuration Pragmas} for more -details. +You may specify any of the following switches to @emph{gnatmake}: +@geindex --version (gnatmake) -@node Handling Arbitrary File Naming Conventions with gnatname -@chapter Handling Arbitrary File Naming Conventions with @code{gnatname} -@cindex Arbitrary File Naming Conventions -@menu -* Arbitrary File Naming Conventions:: -* Running gnatname:: -* Switches for gnatname:: -* Examples of gnatname Usage:: -@end menu +@table @asis -@node Arbitrary File Naming Conventions -@section Arbitrary File Naming Conventions +@item @code{--version} -@noindent -The GNAT compiler must be able to know the source file name of a compilation -unit. When using the standard GNAT default file naming conventions -(@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler -does not need additional information. +Display Copyright and version, then exit disregarding all other options. +@end table -@noindent -When the source file names do not follow the standard GNAT default file naming -conventions, the GNAT compiler must be given additional information through -a configuration pragmas file (@pxref{Configuration Pragmas}) -or a project file. -When the non-standard file naming conventions are well-defined, -a small number of pragmas @code{Source_File_Name} specifying a naming pattern -(@pxref{Alternative File Naming Schemes}) may be sufficient. However, -if the file naming conventions are irregular or arbitrary, a number -of pragma @code{Source_File_Name} for individual compilation units -must be defined. -To help maintain the correspondence between compilation unit names and -source file names within the compiler, -GNAT provides a tool @code{gnatname} to generate the required pragmas for a -set of files. +@geindex --help (gnatmake) -@node Running gnatname -@section Running @code{gnatname} -@noindent -The usual form of the @code{gnatname} command is +@table @asis -@smallexample -@c $ gnatname @ovar{switches} @var{naming_pattern} @ovar{naming_patterns} -@c @r{[}--and @ovar{switches} @var{naming_pattern} @ovar{naming_patterns}@r{]} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatname @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]} - @r{[}--and @r{[}@var{switches}@r{]} @var{naming_pattern} @r{[}@var{naming_patterns}@r{]}@r{]} -@end smallexample +@item @code{--help} -@noindent -All of the arguments are optional. If invoked without any argument, -@code{gnatname} will display its usage. +If @code{--version} was not used, display usage, then exit disregarding +all other options. +@end table -@noindent -When used with at least one naming pattern, @code{gnatname} will attempt to -find all the compilation units in files that follow at least one of the -naming patterns. To find these compilation units, -@code{gnatname} will use the GNAT compiler in syntax-check-only mode on all -regular files. +@geindex --GCC=compiler_name (gnatmake) -@noindent -One or several Naming Patterns may be given as arguments to @code{gnatname}. -Each Naming Pattern is enclosed between double quotes (or single -quotes on Windows). -A Naming Pattern is a regular expression similar to the wildcard patterns -used in file names by the Unix shells or the DOS prompt. -@noindent -@code{gnatname} may be called with several sections of directories/patterns. -Sections are separated by switch @code{--and}. In each section, there must be -at least one pattern. If no directory is specified in a section, the current -directory (or the project directory is @code{-P} is used) is implied. -The options other that the directory switches and the patterns apply globally -even if they are in different sections. +@table @asis -@noindent -Examples of Naming Patterns are +@item @code{--GCC=@emph{compiler_name}} -@smallexample - "*.[12].ada" - "*.ad[sb]*" - "body_*" "spec_*" -@end smallexample +Program used for compiling. The default is @code{gcc}. You need to use +quotes around @cite{compiler_name} if @cite{compiler_name} contains +spaces or other separator characters. +As an example @code{--GCC="foo -x -y"} +will instruct @emph{gnatmake} to use @code{foo -x -y} as your +compiler. A limitation of this syntax is that the name and path name of +the executable itself must not include any embedded spaces. Note that +switch @code{-c} is always inserted after your command name. Thus in the +above example the compiler command that will be used by @emph{gnatmake} +will be @code{foo -c -x -y}. If several @code{--GCC=compiler_name} are +used, only the last @cite{compiler_name} is taken into account. However, +all the additional switches are also taken into account. Thus, +@code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to +@code{--GCC="bar -x -y -z -t"}. +@end table -@noindent -For a more complete description of the syntax of Naming Patterns, -see the second kind of regular expressions described in @file{g-regexp.ads} -(the ``Glob'' regular expressions). +@geindex --GNATBIND=binder_name (gnatmake) -@noindent -When invoked with no switch @code{-P}, @code{gnatname} will create a -configuration pragmas file @file{gnat.adc} in the current working directory, -with pragmas @code{Source_File_Name} for each file that contains a valid Ada -unit. -@node Switches for gnatname -@section Switches for @code{gnatname} +@table @asis -@noindent -Switches for @code{gnatname} must precede any specified Naming Pattern. +@item @code{--GNATBIND=@emph{binder_name}} -@noindent -You may specify any of the following switches to @code{gnatname}: +Program used for binding. The default is @code{gnatbind}. You need to +use quotes around @cite{binder_name} if @cite{binder_name} contains spaces +or other separator characters. +As an example @code{--GNATBIND="bar -x -y"} +will instruct @emph{gnatmake} to use @cite{bar -x -y} as your +binder. Binder switches that are normally appended by @emph{gnatmake} +to @code{gnatbind} are now appended to the end of @cite{bar -x -y}. +A limitation of this syntax is that the name and path name of the executable +itself must not include any embedded spaces. +@end table -@table @option -@c !sort! +@geindex --GNATLINK=linker_name (gnatmake) -@item --version -@cindex @option{--version} @command{gnatname} -Display Copyright and version, then exit disregarding all other options. -@item --help -@cindex @option{--help} @command{gnatname} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +@table @asis -@item --subdirs= -Real object, library or exec directories are subdirectories of the -specified ones. +@item @code{--GNATLINK=@emph{linker_name}} -@item --no-backup -Do not create a backup copy of an existing project file. +Program used for linking. The default is @code{gnatlink}. You need to +use quotes around @cite{linker_name} if @cite{linker_name} contains spaces +or other separator characters. +As an example @code{--GNATLINK="lan -x -y"} +will instruct @emph{gnatmake} to use @code{lan -x -y} as your +linker. Linker switches that are normally appended by @code{gnatmake} to +@code{gnatlink} are now appended to the end of @code{lan -x -y}. +A limitation of this syntax is that the name and path name of the executable +itself must not include any embedded spaces. -@item --and -Start another section of directories/patterns. +@item @code{--create-map-file} -@item -c@file{file} -@cindex @option{-c} (@code{gnatname}) -Create a configuration pragmas file @file{file} (instead of the default -@file{gnat.adc}). -There may be zero, one or more space between @option{-c} and -@file{file}. -@file{file} may include directory information. @file{file} must be -writable. There may be only one switch @option{-c}. -When a switch @option{-c} is -specified, no switch @option{-P} may be specified (see below). - -@item -d@file{dir} -@cindex @option{-d} (@code{gnatname}) -Look for source files in directory @file{dir}. There may be zero, one or more -spaces between @option{-d} and @file{dir}. -@file{dir} may end with @code{/**}, that is it may be of the form -@code{root_dir/**}. In this case, the directory @code{root_dir} and all of its -subdirectories, recursively, have to be searched for sources. -When a switch @option{-d} -is specified, the current working directory will not be searched for source -files, unless it is explicitly specified with a @option{-d} -or @option{-D} switch. -Several switches @option{-d} may be specified. -If @file{dir} is a relative path, it is relative to the directory of -the configuration pragmas file specified with switch -@option{-c}, -or to the directory of the project file specified with switch -@option{-P} or, -if neither switch @option{-c} -nor switch @option{-P} are specified, it is relative to the -current working directory. The directory -specified with switch @option{-d} must exist and be readable. - -@item -D@file{file} -@cindex @option{-D} (@code{gnatname}) -Look for source files in all directories listed in text file @file{file}. -There may be zero, one or more spaces between @option{-D} -and @file{file}. -@file{file} must be an existing, readable text file. -Each nonempty line in @file{file} must be a directory. -Specifying switch @option{-D} is equivalent to specifying as many -switches @option{-d} as there are nonempty lines in -@file{file}. - -@item -eL -Follow symbolic links when processing project files. +When linking an executable, create a map file. The name of the map file +has the same name as the executable with extension ".map". -@item -f@file{pattern} -@cindex @option{-f} (@code{gnatname}) -Foreign patterns. Using this switch, it is possible to add sources of languages -other than Ada to the list of sources of a project file. -It is only useful if a -P switch is used. -For example, -@smallexample -gnatname -Pprj -f"*.c" "*.ada" -@end smallexample -@noindent -will look for Ada units in all files with the @file{.ada} extension, -and will add to the list of file for project @file{prj.gpr} the C files -with extension @file{.c}. - -@item -h -@cindex @option{-h} (@code{gnatname}) -Output usage (help) information. The output is written to @file{stdout}. - -@item -P@file{proj} -@cindex @option{-P} (@code{gnatname}) -Create or update project file @file{proj}. There may be zero, one or more space -between @option{-P} and @file{proj}. @file{proj} may include directory -information. @file{proj} must be writable. -There may be only one switch @option{-P}. -When a switch @option{-P} is specified, -no switch @option{-c} may be specified. -On all platforms, except on VMS, when @code{gnatname} is invoked for an -existing project file .gpr, a backup copy of the project file is created -in the project directory with file name .gpr.saved_x. 'x' is the first -non negative number that makes this backup copy a new file. +@item @code{--create-map-file=@emph{mapfile}} -@item -v -@cindex @option{-v} (@code{gnatname}) -Verbose mode. Output detailed explanation of behavior to @file{stdout}. -This includes name of the file written, the name of the directories to search -and, for each file in those directories whose name matches at least one of -the Naming Patterns, an indication of whether the file contains a unit, -and if so the name of the unit. +When linking an executable, create a map file with the specified name. +@end table -@item -v -v -@cindex @option{-v -v} (@code{gnatname}) -Very Verbose mode. In addition to the output produced in verbose mode, -for each file in the searched directories whose name matches none of -the Naming Patterns, an indication is given that there is no match. +@geindex --create-missing-dirs (gnatmake) -@item -x@file{pattern} -@cindex @option{-x} (@code{gnatname}) -Excluded patterns. Using this switch, it is possible to exclude some files -that would match the name patterns. For example, -@smallexample -gnatname -x "*_nt.ada" "*.ada" -@end smallexample -@noindent -will look for Ada units in all files with the @file{.ada} extension, -except those whose names end with @file{_nt.ada}. -@end table +@table @asis -@node Examples of gnatname Usage -@section Examples of @code{gnatname} Usage +@item @code{--create-missing-dirs} +When using project files (@code{-P@emph{project}}), automatically create +missing object directories, library directories and exec +directories. -@smallexample -$ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*" -@end smallexample +@item @code{--single-compile-per-obj-dir} -@noindent -In this example, the directory @file{/home/me} must already exist -and be writable. In addition, the directory -@file{/home/me/sources} (specified by -@option{-d sources}) must exist and be readable. +Disallow simultaneous compilations in the same object directory when +project files are used. -Note the optional spaces after @option{-c} and @option{-d}. +@item @code{--subdirs=@emph{subdir}} -@smallexample -$ gnatname -P/home/me/proj -x "*_nt_body.ada" - -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*" -@end smallexample +Actual object directory of each project file is the subdirectory subdir of the +object directory specified or defaulted in the project file. -Note that several switches @option{-d} may be used, -even in conjunction with one or several switches -@option{-D}. Several Naming Patterns and one excluded pattern -are used in this example. +@item @code{--unchecked-shared-lib-imports} -@c ***************************************** -@c * G N A T P r o j e c t M a n a g e r * -@c ***************************************** +By default, shared library projects are not allowed to import static library +projects. When this switch is used on the command line, this restriction is +relaxed. -@c ------ macros for projects.texi -@c These macros are needed when building the gprbuild documentation, but -@c should have no effect in the gnat user's guide +@item @code{--source-info=@emph{source info file}} -@macro CODESAMPLE{TXT} -@smallexample -@group -\TXT\ -@end group -@end smallexample -@end macro +Specify a source info file. This switch is active only when project files +are used. If the source info file is specified as a relative path, then it is +relative to the object directory of the main project. If the source info file +does not exist, then after the Project Manager has successfully parsed and +processed the project files and found the sources, it creates the source info +file. If the source info file already exists and can be read successfully, +then the Project Manager will get all the needed information about the sources +from the source info file and will not look for them. This reduces the time +to process the project files, especially when looking for sources that take a +long time. If the source info file exists but cannot be parsed successfully, +the Project Manager will attempt to recreate it. If the Project Manager fails +to create the source info file, a message is issued, but gnatmake does not +fail. @emph{gnatmake} "trusts" the source info file. This means that +if the source files have changed (addition, deletion, moving to a different +source directory), then the source info file need to be deleted and recreated. +@end table -@macro PROJECTFILE{TXT} -@CODESAMPLE{\TXT\} -@end macro +@geindex -a (gnatmake) -@c simulates a newline when in a @CODESAMPLE -@macro NL{} -@end macro -@macro TIP{TXT} -@quotation -@noindent -\TXT\ -@end quotation -@end macro +@table @asis -@macro TIPHTML{TXT} -\TXT\ -@end macro +@item @code{-a} -@macro IMPORTANT{TXT} -@quotation -@noindent -\TXT\ -@end quotation +Consider all files in the make process, even the GNAT internal system +files (for example, the predefined Ada library files), as well as any +locked files. Locked files are files whose ALI file is write-protected. +By default, +@emph{gnatmake} does not check these files, +because the assumption is that the GNAT internal files are properly up +to date, and also that any write protected ALI files have been properly +installed. Note that if there is an installation problem, such that one +of these files is not up to date, it will be properly caught by the +binder. +You may have to specify this switch if you are working on GNAT +itself. The switch @code{-a} is also useful +in conjunction with @code{-f} +if you need to recompile an entire application, +including run-time files, using special configuration pragmas, +such as a @cite{Normalize_Scalars} pragma. -@end macro +By default +@code{gnatmake -a} compiles all GNAT +internal files with +@code{gcc -c -gnatpg} rather than @code{gcc -c}. +@end table -@macro NOTE{TXT} -@quotation -@noindent -\TXT\ -@end quotation -@end macro +@geindex -b (gnatmake) -@include projects.texi -@c --------------------------------------------- -@c Tools Supporting Project Files -@c --------------------------------------------- +@table @asis -@node Tools Supporting Project Files -@chapter Tools Supporting Project Files +@item @code{-b} -@noindent +Bind only. Can be combined with @emph{-c} to do +compilation and binding, but no link. +Can be combined with @emph{-l} +to do binding and linking. When not combined with +@emph{-c} +all the units in the closure of the main program must have been previously +compiled and must be up to date. The root unit specified by @cite{file_name} +may be given without extension, with the source extension or, if no GNAT +Project File is specified, with the ALI file extension. +@end table -@menu -* gnatmake and Project Files:: -* The GNAT Driver and Project Files:: -@end menu +@geindex -c (gnatmake) -@c --------------------------------------------- -@node gnatmake and Project Files -@section gnatmake and Project Files -@c --------------------------------------------- -@noindent -This section covers several topics related to @command{gnatmake} and -project files: defining switches for @command{gnatmake} -and for the tools that it invokes; specifying configuration pragmas; -the use of the @code{Main} attribute; building and rebuilding library project -files. +@table @asis -@menu -* Switches Related to Project Files:: -* Switches and Project Files:: -* Specifying Configuration Pragmas:: -* Project Files and Main Subprograms:: -* Library Project Files:: -@end menu +@item @code{-c} -@c --------------------------------------------- -@node Switches Related to Project Files -@subsection Switches Related to Project Files -@c --------------------------------------------- +Compile only. Do not perform binding, except when @emph{-b} +is also specified. Do not perform linking, except if both +@emph{-b} and +@emph{-l} are also specified. +If the root unit specified by @cite{file_name} is not a main unit, this is the +default. Otherwise @emph{gnatmake} will attempt binding and linking +unless all objects are up to date and the executable is more recent than +the objects. +@end table -@noindent -The following switches are used by GNAT tools that support project files: +@geindex -C (gnatmake) -@table @option -@item -P@var{project} -@cindex @option{-P} (any project-aware tool) -Indicates the name of a project file. This project file will be parsed with -the verbosity indicated by @option{-vP@emph{x}}, -if any, and using the external references indicated -by @option{-X} switches, if any. -There may zero, one or more spaces between @option{-P} and @var{project}. +@table @asis -There must be only one @option{-P} switch on the command line. +@item @code{-C} -Since the Project Manager parses the project file only after all the switches -on the command line are checked, the order of the switches -@option{-P}, -@option{-vP@emph{x}} -or @option{-X} is not significant. +Use a temporary mapping file. A mapping file is a way to communicate +to the compiler two mappings: from unit names to file names (without +any directory information) and from file names to path names (with +full directory information). A mapping file can make the compiler's +file searches faster, especially if there are many source directories, +or the sources are read over a slow network connection. If +@emph{-P} is used, a mapping file is always used, so +@emph{-C} is unnecessary; in this case the mapping file +is initially populated based on the project file. If +@emph{-C} is used without +@emph{-P}, +the mapping file is initially empty. Each invocation of the compiler +will add any newly accessed sources to the mapping file. +@end table -@item -X@var{name=value} -@cindex @option{-X} (any project-aware tool) -Indicates that external variable @var{name} has the value @var{value}. -The Project Manager will use this value for occurrences of -@code{external(name)} when parsing the project file. +@geindex -C= (gnatmake) -If @var{name} or @var{value} includes a space, then @var{name=value} should be -put between quotes. -@smallexample - -XOS=NT - -X"user=John Doe" -@end smallexample -Several @option{-X} switches can be used simultaneously. -If several @option{-X} switches specify the same -@var{name}, only the last one is used. +@table @asis -An external variable specified with a @option{-X} switch -takes precedence over the value of the same name in the environment. +@item @code{-C=@emph{file}} -@item -vP@emph{x} -@cindex @option{-vP} (any project-aware tool) -Indicates the verbosity of the parsing of GNAT project files. +Use a specific mapping file. The file, specified as a path name (absolute or +relative) by this switch, should already exist, otherwise the switch is +ineffective. The specified mapping file will be communicated to the compiler. +This switch is not compatible with a project file +(-P`file`) or with multiple compiling processes +(-jnnn, when nnn is greater than 1). +@end table -@option{-vP0} means Default; -@option{-vP1} means Medium; -@option{-vP2} means High. +@geindex -d (gnatmake) -The default is Default: no output for syntactically correct -project files. -If several @option{-vP@emph{x}} switches are present, -only the last one is used. +@table @asis -@item -aP -@cindex @option{-aP} (any project-aware tool) -Add directory at the beginning of the project search path, in order, -after the current working directory. +@item @code{-d} -@item -eL -@cindex @option{-eL} (any project-aware tool) -Follow all symbolic links when processing project files. +Display progress for each source, up to date or not, as a single line: -@item --subdirs= -@cindex @option{--subdirs=} (gnatmake and gnatclean) -This switch is recognized by @command{gnatmake} and @command{gnatclean}. It -indicate that the real directories (except the source directories) are the -subdirectories of the directories specified in the project files. -This applies in particular to object directories, library directories and -exec directories. If the subdirectories do not exist, they are created -automatically. +@example +completed x out of y (zz%) +@end example +If the file needs to be compiled this is displayed after the invocation of +the compiler. These lines are displayed even in quiet output mode. @end table -@c --------------------------------------------- -@node Switches and Project Files -@subsection Switches and Project Files -@c --------------------------------------------- +@geindex -D (gnatmake) -@noindent -For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and -@code{Linker}, you can specify a @code{Default_Switches} -attribute, a @code{Switches} attribute, or both; -as their names imply, these switch-related -attributes affect the switches that are used for each of these GNAT -components when -@command{gnatmake} is invoked. As will be explained below, these -component-specific switches precede -the switches provided on the @command{gnatmake} command line. +@table @asis -The @code{Default_Switches} attribute is an attribute -indexed by language name (case insensitive) whose value is a string list. -For example: +@item @code{-D @emph{dir}} -@smallexample @c projectfile -@group -@b{package} Compiler @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-gnaty", - "-v"); -@b{end} Compiler; -@end group -@end smallexample +Put all object files and ALI file in directory @cite{dir}. +If the @emph{-D} switch is not used, all object files +and ALI files go in the current working directory. -@noindent -The @code{Switches} attribute is indexed on a file name (which may or may -not be case sensitive, depending -on the operating system) whose value is a string list. For example: +This switch cannot be used when using a project file. +@end table -@smallexample @c projectfile -@group -@b{package} Builder @b{is} - @b{for} Switches ("main1.adb") - @b{use} ("-O2"); - @b{for} Switches ("main2.adb") - @b{use} ("-g"); -@b{end} Builder; -@end group -@end smallexample - -@noindent -For the @code{Builder} package, the file names must designate source files -for main subprograms. For the @code{Binder} and @code{Linker} packages, the -file names must designate @file{ALI} or source files for main subprograms. -In each case just the file name without an explicit extension is acceptable. +@geindex -eI (gnatmake) -For each tool used in a program build (@command{gnatmake}, the compiler, the -binder, and the linker), the corresponding package @dfn{contributes} a set of -switches for each file on which the tool is invoked, based on the -switch-related attributes defined in the package. -In particular, the switches -that each of these packages contributes for a given file @var{f} comprise: -@itemize @bullet -@item the value of attribute @code{Switches (@var{f})}, - if it is specified in the package for the given file, -@item otherwise, the value of @code{Default_Switches ("Ada")}, - if it is specified in the package. +@table @asis -@end itemize +@item @code{-eI@emph{nnn}} -@noindent -If neither of these attributes is defined in the package, then the package does -not contribute any switches for the given file. +Indicates that the main source is a multi-unit source and the rank of the unit +in the source file is nnn. nnn needs to be a positive number and a valid +index in the source. This switch cannot be used when @emph{gnatmake} is +invoked for several mains. +@end table -When @command{gnatmake} is invoked on a file, the switches comprise -two sets, in the following order: those contributed for the file -by the @code{Builder} package; -and the switches passed on the command line. +@geindex -eL (gnatmake) -When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file, -the switches passed to the tool comprise three sets, -in the following order: +@geindex symbolic links -@enumerate -@item -the applicable switches contributed for the file -by the @code{Builder} package in the project file supplied on the command line; -@item -those contributed for the file by the package (in the relevant project file -- -see below) corresponding to the tool; and +@table @asis -@item -the applicable switches passed on the command line. -@end enumerate +@item @code{-eL} -The term @emph{applicable switches} reflects the fact that -@command{gnatmake} switches may or may not be passed to individual -tools, depending on the individual switch. +Follow all symbolic links when processing project files. +This should be used if your project uses symbolic links for files or +directories, but is not needed in other cases. -@command{gnatmake} may invoke the compiler on source files from different -projects. The Project Manager will use the appropriate project file to -determine the @code{Compiler} package for each source file being compiled. -Likewise for the @code{Binder} and @code{Linker} packages. +@geindex naming scheme -As an example, consider the following package in a project file: +This also assumes that no directory matches the naming scheme for files (for +instance that you do not have a directory called "sources.ads" when using the +default GNAT naming scheme). -@smallexample @c projectfile -@group -@b{project} Proj1 @b{is} - @b{package} Compiler @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-g"); - @b{for} Switches ("a.adb") - @b{use} ("-O1"); - @b{for} Switches ("b.adb") - @b{use} ("-O2", - "-gnaty"); - @b{end} Compiler; -@b{end} Proj1; -@end group -@end smallexample - -@noindent -If @command{gnatmake} is invoked with this project file, and it needs to -compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then -@file{a.adb} will be compiled with the switch -@option{-O1}, -@file{b.adb} with switches -@option{-O2} -and @option{-gnaty}, -and @file{c.adb} with @option{-g}. +When you do not have to use this switch (i.e., by default), gnatmake is able to +save a lot of system calls (several per source file and object file), which +can result in a significant speed up to load and manipulate a project file, +especially when using source files from a remote system. +@end table -The following example illustrates the ordering of the switches -contributed by different packages: +@geindex -eS (gnatmake) -@smallexample @c projectfile -@group -@b{project} Proj2 @b{is} - @b{package} Builder @b{is} - @b{for} Switches ("main.adb") - @b{use} ("-g", - "-O1", - "-f"); - @b{end} Builder; -@end group - -@group - @b{package} Compiler @b{is} - @b{for} Switches ("main.adb") - @b{use} ("-O2"); - @b{end} Compiler; -@b{end} Proj2; -@end group -@end smallexample - -@noindent -If you issue the command: -@smallexample - gnatmake -Pproj2 -O0 main -@end smallexample +@table @asis -@noindent -then the compiler will be invoked on @file{main.adb} with the following -sequence of switches +@item @code{-eS} -@smallexample - -g -O1 -O2 -O0 -@end smallexample +Output the commands for the compiler, the binder and the linker +on standard output, +instead of standard error. +@end table -@noindent -with the last @option{-O} -switch having precedence over the earlier ones; -several other switches -(such as @option{-c}) are added implicitly. +@geindex -f (gnatmake) -The switches -@option{-g} -and @option{-O1} are contributed by package -@code{Builder}, @option{-O2} is contributed -by the package @code{Compiler} -and @option{-O0} comes from the command line. -The @option{-g} -switch will also be passed in the invocation of -@command{Gnatlink.} +@table @asis -A final example illustrates switch contributions from packages in different -project files: +@item @code{-f} -@smallexample @c projectfile -@group -@b{project} Proj3 @b{is} - @b{for} Source_Files @b{use} ("pack.ads", "pack.adb"); - @b{package} Compiler @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-gnata"); - @b{end} Compiler; -@b{end} Proj3; -@end group - -@group -@b{with} "Proj3"; -@b{project} Proj4 @b{is} - @b{for} Source_Files @b{use} ("foo_main.adb", "bar_main.adb"); - @b{package} Builder @b{is} - @b{for} Switches ("foo_main.adb") - @b{use} ("-s", - "-g"); - @b{end} Builder; -@b{end} Proj4; -@end group - -@group ---@i{ Ada source file:} -@b{with} Pack; -@b{procedure} Foo_Main @b{is} - @dots{} -@b{end} Foo_Main; -@end group -@end smallexample - -@noindent -If the command is -@smallexample -gnatmake -PProj4 foo_main.adb -cargs -gnato -@end smallexample - -@noindent -then the switches passed to the compiler for @file{foo_main.adb} are -@option{-g} (contributed by the package @code{Proj4.Builder}) and -@option{-gnato} (passed on the command line). -When the imported package @code{Pack} is compiled, the switches used -are @option{-g} from @code{Proj4.Builder}, -@option{-gnata} (contributed from package @code{Proj3.Compiler}, -and @option{-gnato} from the command line. - -When using @command{gnatmake} with project files, some switches or -arguments may be expressed as relative paths. As the working directory where -compilation occurs may change, these relative paths are converted to absolute -paths. For the switches found in a project file, the relative paths -are relative to the project file directory, for the switches on the command -line, they are relative to the directory where @command{gnatmake} is invoked. -The switches for which this occurs are: --I, --A, --L, --aO, --aL, --aI, as well as all arguments that are not switches (arguments to -switch --o, object files specified in package @code{Linker} or after --largs on the command line). The exception to this rule is the switch ---RTS= for which a relative path argument is never converted. +Force recompilations. Recompile all sources, even though some object +files may be up to date, but don't recompile predefined or GNAT internal +files or locked files (files with a write-protected ALI file), +unless the @emph{-a} switch is also specified. +@end table -@c --------------------------------------------- -@node Specifying Configuration Pragmas -@subsection Specifying Configuration Pragmas -@c --------------------------------------------- +@geindex -F (gnatmake) -@noindent -When using @command{gnatmake} with project files, if there exists a file -@file{gnat.adc} that contains configuration pragmas, this file will be -ignored. -Configuration pragmas can be defined by means of the following attributes in -project files: @code{Global_Configuration_Pragmas} in package @code{Builder} -and @code{Local_Configuration_Pragmas} in package @code{Compiler}. +@table @asis -Both these attributes are single string attributes. Their values is the path -name of a file containing configuration pragmas. If a path name is relative, -then it is relative to the project directory of the project file where the -attribute is defined. +@item @code{-F} -When compiling a source, the configuration pragmas used are, in order, -those listed in the file designated by attribute -@code{Global_Configuration_Pragmas} in package @code{Builder} of the main -project file, if it is specified, and those listed in the file designated by -attribute @code{Local_Configuration_Pragmas} in package @code{Compiler} of -the project file of the source, if it exists. +When using project files, if some errors or warnings are detected during +parsing and verbose mode is not in effect (no use of switch +-v), then error lines start with the full path name of the project +file, rather than its simple file name. +@end table -@c --------------------------------------------- -@node Project Files and Main Subprograms -@subsection Project Files and Main Subprograms -@c --------------------------------------------- +@geindex -g (gnatmake) -@noindent -When using a project file, you can invoke @command{gnatmake} -with one or several main subprograms, by specifying their source files on the -command line. -@smallexample - gnatmake -Pprj main1.adb main2.adb main3.adb -@end smallexample +@table @asis -@noindent -Each of these needs to be a source file of the same project, except -when the switch -u is used. +@item @code{-g} -When -u is not used, all the mains need to be sources of the -same project, one of the project in the tree rooted at the project specified -on the command line. The package @code{Builder} of this common project, the -"main project" is the one that is considered by @command{gnatmake}. +Enable debugging. This switch is simply passed to the compiler and to the +linker. +@end table -When -u is used, the specified source files may be in projects -imported directly or indirectly by the project specified on the command line. -Note that if such a source file is not part of the project specified on the -command line, the switches found in package @code{Builder} of the -project specified on the command line, if any, that are transmitted -to the compiler will still be used, not those found in the project file of -the source file. +@geindex -i (gnatmake) -When using a project file, you can also invoke @command{gnatmake} without -explicitly specifying any main, and the effect depends on whether you have -defined the @code{Main} attribute. This attribute has a string list value, -where each element in the list is the name of a source file (the file -extension is optional) that contains a unit that can be a main subprogram. -If the @code{Main} attribute is defined in a project file as a non-empty -string list and the switch @option{-u} is not used on the command -line, then invoking @command{gnatmake} with this project file but without any -main on the command line is equivalent to invoking @command{gnatmake} with all -the file names in the @code{Main} attribute on the command line. +@table @asis -Example: -@smallexample @c projectfile -@group - @b{project} Prj @b{is} - @b{for} Main @b{use} ("main1.adb", "main2.adb", "main3.adb"); - @b{end} Prj; -@end group -@end smallexample - -@noindent -With this project file, @code{"gnatmake -Pprj"} -is equivalent to -@code{"gnatmake -Pprj main1.adb main2.adb main3.adb"}. +@item @code{-i} -When the project attribute @code{Main} is not specified, or is specified -as an empty string list, or when the switch @option{-u} is used on the command -line, then invoking @command{gnatmake} with no main on the command line will -result in all immediate sources of the project file being checked, and -potentially recompiled. Depending on the presence of the switch @option{-u}, -sources from other project files on which the immediate sources of the main -project file depend are also checked and potentially recompiled. In other -words, the @option{-u} switch is applied to all of the immediate sources of the -main project file. +In normal mode, @emph{gnatmake} compiles all object files and ALI files +into the current directory. If the @emph{-i} switch is used, +then instead object files and ALI files that already exist are overwritten +in place. This means that once a large project is organized into separate +directories in the desired manner, then @emph{gnatmake} will automatically +maintain and update this organization. If no ALI files are found on the +Ada object path (see @ref{8e,,Search Paths and the Run-Time Library (RTL)}), +the new object and ALI files are created in the +directory containing the source being compiled. If another organization +is desired, where objects and sources are kept in different directories, +a useful technique is to create dummy ALI files in the desired directories. +When detecting such a dummy file, @emph{gnatmake} will be forced to +recompile the corresponding source file, and it will be put the resulting +object and ALI files in the directory where it found the dummy file. +@end table -When no main is specified on the command line and attribute @code{Main} exists -and includes several mains, or when several mains are specified on the -command line, the default switches in package @code{Builder} will -be used for all mains, even if there are specific switches -specified for one or several mains. +@geindex -j (gnatmake) -But the switches from package @code{Binder} or @code{Linker} will be -the specific switches for each main, if they are specified. +@geindex Parallel make -@c --------------------------------------------- -@node Library Project Files -@subsection Library Project Files -@c --------------------------------------------- -@noindent -When @command{gnatmake} is invoked with a main project file that is a library -project file, it is not allowed to specify one or more mains on the command -line. +@table @asis -When a library project file is specified, switches -b and --l have special meanings. +@item @code{-j@emph{n}} -@itemize @bullet -@item -b is only allowed for stand-alone libraries. It indicates - to @command{gnatmake} that @command{gnatbind} should be invoked for the - library. +Use @cite{n} processes to carry out the (re)compilations. On a multiprocessor +machine compilations will occur in parallel. If @cite{n} is 0, then the +maximum number of parallel compilations is the number of core processors +on the platform. In the event of compilation errors, messages from various +compilations might get interspersed (but @emph{gnatmake} will give you the +full ordered list of failing compiles at the end). If this is problematic, +rerun the make process with n set to 1 to get a clean list of messages. +@end table -@item -l may be used for all library projects. It indicates - to @command{gnatmake} that the binder generated file should be compiled - (in the case of a stand-alone library) and that the library should be built. -@end itemize +@geindex -k (gnatmake) -@c --------------------------------------------- -@node The GNAT Driver and Project Files -@section The GNAT Driver and Project Files -@c --------------------------------------------- -@noindent -A number of GNAT tools, other than @command{gnatmake} -can benefit from project files: -(@command{gnatbind}, -@ifclear FSFEDITION -@command{gnatcheck}, -@end ifclear -@command{gnatclean}, -@ifclear FSFEDITION -@command{gnatelim}, -@end ifclear -@command{gnatfind}, -@command{gnatlink}, -@command{gnatls}, -@ifclear FSFEDITION -@command{gnatmetric}, -@command{gnatpp}, -@command{gnatstub}, -@end ifclear -and @command{gnatxref}). However, none of these tools can be invoked -directly with a project file switch (@option{-P}). -They must be invoked through the @command{gnat} driver. - -The @command{gnat} driver is a wrapper that accepts a number of commands and -calls the corresponding tool. It was designed initially for VMS platforms (to -convert VMS qualifiers to Unix-style switches), but it is now available on all -GNAT platforms. +@table @asis -On non-VMS platforms, the @command{gnat} driver accepts the following commands -(case insensitive): +@item @code{-k} -@itemize @bullet -@item BIND to invoke @command{gnatbind} -@item CHOP to invoke @command{gnatchop} -@item CLEAN to invoke @command{gnatclean} -@item COMP or COMPILE to invoke the compiler -@ifclear FSFEDITION -@item ELIM to invoke @command{gnatelim} -@end ifclear -@item FIND to invoke @command{gnatfind} -@item KR or KRUNCH to invoke @command{gnatkr} -@item LINK to invoke @command{gnatlink} -@item LS or LIST to invoke @command{gnatls} -@item MAKE to invoke @command{gnatmake} -@item NAME to invoke @command{gnatname} -@item PREP or PREPROCESS to invoke @command{gnatprep} -@ifclear FSFEDITION -@item PP or PRETTY to invoke @command{gnatpp} -@item METRIC to invoke @command{gnatmetric} -@item STUB to invoke @command{gnatstub} -@end ifclear -@item XREF to invoke @command{gnatxref} +Keep going. Continue as much as possible after a compilation error. To +ease the programmer's task in case of compilation errors, the list of +sources for which the compile fails is given when @emph{gnatmake} +terminates. -@end itemize +If @emph{gnatmake} is invoked with several @code{file_names} and with this +switch, if there are compilation errors when building an executable, +@emph{gnatmake} will not attempt to build the following executables. +@end table -@noindent -(note that the compiler is invoked using the command -@command{gnatmake -f -u -c}). +@geindex -l (gnatmake) -On non-VMS platforms, between @command{gnat} and the command, two -special switches may be used: -@itemize @bullet -@item @command{-v} to display the invocation of the tool. -@item @command{-dn} to prevent the @command{gnat} driver from removing - the temporary files it has created. These temporary files are - configuration files and temporary file list files. +@table @asis -@end itemize +@item @code{-l} -@noindent -The command may be followed by switches and arguments for the invoked -tool. +Link only. Can be combined with @emph{-b} to binding +and linking. Linking will not be performed if combined with +@emph{-c} +but not with @emph{-b}. +When not combined with @emph{-b} +all the units in the closure of the main program must have been previously +compiled and must be up to date, and the main program needs to have been bound. +The root unit specified by @cite{file_name} +may be given without extension, with the source extension or, if no GNAT +Project File is specified, with the ALI file extension. +@end table -@smallexample - gnat bind -C main.ali - gnat ls -a main - gnat chop foo.txt -@end smallexample +@geindex -m (gnatmake) -@noindent -Switches may also be put in text files, one switch per line, and the text -files may be specified with their path name preceded by '@@'. -@smallexample - gnat bind @@args.txt main.ali -@end smallexample - -@noindent -In addition, for commands BIND, COMP or COMPILE, FIND, -@ifclear FSFEDITION -ELIM, -@end ifclear -LS or LIST, LINK, -@ifclear FSFEDITION -METRIC, -PP or PRETTY, -STUB, -@end ifclear -and XREF, the project file related switches -(@option{-P}, -@option{-X} and -@option{-vPx}) may be used in addition to -the switches of the invoking tool. - -@ifclear FSFEDITION -When GNAT PP or GNAT PRETTY is used with a project file, but with no source -specified on the command line, it invokes @command{gnatpp} with all -the immediate sources of the specified project file. -@end ifclear - -@ifclear FSFEDITION -When GNAT METRIC is used with a project file, but with no source -specified on the command line, it invokes @command{gnatmetric} -with all the immediate sources of the specified project file and with -@option{-d} with the parameter pointing to the object directory -of the project. -@end ifclear - -@ifclear FSFEDITION -In addition, when GNAT PP, GNAT PRETTY or GNAT METRIC is used with -a project file, no source is specified on the command line and -switch -U is specified on the command line, then -the underlying tool (gnatpp or -gnatmetric) is invoked for all sources of all projects, -not only for the immediate sources of the main project. -(-U stands for Universal or Union of the project files of the project tree) -@end ifclear +@table @asis -For each of the following commands, there is optionally a corresponding -package in the main project. +@item @code{-m} -@itemize @bullet -@item package @code{Binder} for command BIND (invoking @code{gnatbind}) +Specify that the minimum necessary amount of recompilations +be performed. In this mode @emph{gnatmake} ignores time +stamp differences when the only +modifications to a source file consist in adding/removing comments, +empty lines, spaces or tabs. This means that if you have changed the +comments in a source file or have simply reformatted it, using this +switch will tell @emph{gnatmake} not to recompile files that depend on it +(provided other sources on which these files depend have undergone no +semantic modifications). Note that the debugging information may be +out of date with respect to the sources if the @emph{-m} switch causes +a compilation to be switched, so the use of this switch represents a +trade-off between compilation time and accurate debugging information. +@end table -@ifclear FSFEDITION -@item package @code{Check} for command CHECK (invoking - @code{gnatcheck}) -@end ifclear +@geindex Dependencies +@geindex producing list -@item package @code{Compiler} for command COMP or COMPILE (invoking the compiler) +@geindex -M (gnatmake) -@item package @code{Cross_Reference} for command XREF (invoking - @code{gnatxref}) -@ifclear FSFEDITION -@item package @code{Eliminate} for command ELIM (invoking - @code{gnatelim}) -@end ifclear +@table @asis -@item package @code{Finder} for command FIND (invoking @code{gnatfind}) +@item @code{-M} -@item package @code{Gnatls} for command LS or LIST (invoking @code{gnatls}) +Check if all objects are up to date. If they are, output the object +dependences to @code{stdout} in a form that can be directly exploited in +a @code{Makefile}. By default, each source file is prefixed with its +(relative or absolute) directory name. This name is whatever you +specified in the various @emph{-aI} +and @emph{-I} switches. If you use +@cite{gnatmake -M} @emph{-q} +(see below), only the source file names, +without relative paths, are output. If you just specify the @emph{-M} +switch, dependencies of the GNAT internal system files are omitted. This +is typically what you want. If you also specify +the @emph{-a} switch, +dependencies of the GNAT internal files are also listed. Note that +dependencies of the objects in external Ada libraries (see +switch @code{-aL@emph{dir}} in the following list) +are never reported. +@end table -@ifclear FSFEDITION -@item package @code{Gnatstub} for command STUB - (invoking @code{gnatstub}) -@end ifclear +@geindex -n (gnatmake) -@item package @code{Linker} for command LINK (invoking @code{gnatlink}) -@ifclear FSFEDITION -@item package @code{Check} for command CHECK - (invoking @code{gnatcheck}) -@end ifclear +@table @asis -@ifclear FSFEDITION -@item package @code{Metrics} for command METRIC - (invoking @code{gnatmetric}) -@end ifclear +@item @code{-n} -@ifclear FSFEDITION -@item package @code{Pretty_Printer} for command PP or PRETTY - (invoking @code{gnatpp}) -@end ifclear +Don't compile, bind, or link. Checks if all objects are up to date. +If they are not, the full name of the first file that needs to be +recompiled is printed. +Repeated use of this option, followed by compiling the indicated source +file, will eventually result in recompiling all required units. +@end table -@end itemize +@geindex -o (gnatmake) -@noindent -Package @code{Gnatls} has a unique attribute @code{Switches}, -a simple variable with a string list value. It contains switches -for the invocation of @code{gnatls}. - -@smallexample @c projectfile -@group -@b{project} Proj1 @b{is} - @b{package} gnatls @b{is} - @b{for} Switches - @b{use} ("-a", - "-v"); - @b{end} gnatls; -@b{end} Proj1; -@end group -@end smallexample -@noindent -All other packages have two attribute @code{Switches} and -@code{Default_Switches}. +@table @asis -@code{Switches} is an indexed attribute, indexed by the -source file name, that has a string list value: the switches to be -used when the tool corresponding to the package is invoked for the specific -source file. +@item @code{-o @emph{exec_name}} -@code{Default_Switches} is an attribute, -indexed by the programming language that has a string list value. -@code{Default_Switches ("Ada")} contains the -switches for the invocation of the tool corresponding -to the package, except if a specific @code{Switches} attribute -is specified for the source file. +Output executable name. The name of the final executable program will be +@cite{exec_name}. If the @emph{-o} switch is omitted the default +name for the executable will be the name of the input file in appropriate form +for an executable file on the host system. -@smallexample @c projectfile -@group -@b{project} Proj @b{is} +This switch cannot be used when invoking @emph{gnatmake} with several +@code{file_names}. +@end table - @b{for} Source_Dirs @b{use} ("**"); +@geindex -p (gnatmake) - @b{package} gnatls @b{is} - @b{for} Switches @b{use} - ("-a", - "-v"); - @b{end} gnatls; -@end group -@group - @b{package} Compiler @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-gnatv", - "-gnatwa"); - @b{end} Binder; -@end group -@group +@table @asis - @b{package} Binder @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-C", - "-e"); - @b{end} Binder; -@end group -@group - - @b{package} Linker @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-C"); - @b{for} Switches ("main.adb") - @b{use} ("-C", - "-v", - "-v"); - @b{end} Linker; -@end group -@group +@item @code{-p} - @b{package} Finder @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-a", - "-f"); - @b{end} Finder; -@end group -@group +Same as @code{--create-missing-dirs} +@end table - @b{package} Cross_Reference @b{is} - @b{for} Default_Switches ("Ada") - @b{use} ("-a", - "-f", - "-d", - "-u"); - @b{end} Cross_Reference; -@b{end} Proj; -@end group -@end smallexample +@geindex -P (gnatmake) -@noindent -With the above project file, commands such as -@smallexample - gnat comp -Pproj main - gnat ls -Pproj main - gnat xref -Pproj main - gnat bind -Pproj main.ali - gnat link -Pproj main.ali -@end smallexample +@table @asis -@noindent -will set up the environment properly and invoke the tool with the switches -found in the package corresponding to the tool: -@code{Default_Switches ("Ada")} for all tools, -except @code{Switches ("main.adb")} -for @code{gnatlink}. -@ifclear FSFEDITION -It is also possible to invoke some of the tools, -(@code{gnatcheck}, -@code{gnatmetric}, -and @code{gnatpp}) -on a set of project units thanks to the combination of the switches -@option{-P}, @option{-U} and possibly the main unit when one is interested -in its closure. For instance, -@smallexample -gnat metric -Pproj -@end smallexample - -@noindent -will compute the metrics for all the immediate units of project -@code{proj}. -@smallexample -gnat metric -Pproj -U -@end smallexample - -@noindent -will compute the metrics for all the units of the closure of projects -rooted at @code{proj}. -@smallexample -gnat metric -Pproj -U main_unit -@end smallexample - -@noindent -will compute the metrics for the closure of units rooted at -@code{main_unit}. This last possibility relies implicitly -on @command{gnatbind}'s option @option{-R}. But if the argument files for the -tool invoked by the @command{gnat} driver are explicitly specified -either directly or through the tool @option{-files} option, then the tool -is called only for these explicitly specified files. -@end ifclear - -@c ***************************************** -@c * Cross-referencing tools -@c ***************************************** - -@node The Cross-Referencing Tools gnatxref and gnatfind -@chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind} -@findex gnatxref -@findex gnatfind - -@noindent -The compiler generates cross-referencing information (unless -you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files. -This information indicates where in the source each entity is declared and -referenced. Note that entities in package Standard are not included, but -entities in all other predefined units are included in the output. +@item @code{-P@emph{project}} -Before using any of these two tools, you need to compile successfully your -application, so that GNAT gets a chance to generate the cross-referencing -information. +Use project file @cite{project}. Only one such switch can be used. +@ref{e1,,gnatmake and Project Files}. +@end table -The two tools @code{gnatxref} and @code{gnatfind} take advantage of this -information to provide the user with the capability to easily locate the -declaration and references to an entity. These tools are quite similar, -the difference being that @code{gnatfind} is intended for locating -definitions and/or references to a specified entity or entities, whereas -@code{gnatxref} is oriented to generating a full report of all -cross-references. +@geindex -q (gnatmake) -To use these tools, you must not compile your application using the -@option{-gnatx} switch on the @command{gnatmake} command line -(@pxref{The GNAT Make Program gnatmake}). Otherwise, cross-referencing -information will not be generated. -Note: to invoke @code{gnatxref} or @code{gnatfind} with a project file, -use the @code{gnat} driver (see @ref{The GNAT Driver and Project Files}). +@table @asis -@menu -* Switches for gnatxref:: -* Switches for gnatfind:: -* Project Files for gnatxref and gnatfind:: -* Regular Expressions in gnatfind and gnatxref:: -* Examples of gnatxref Usage:: -* Examples of gnatfind Usage:: -@end menu +@item @code{-q} -@node Switches for gnatxref -@section @code{gnatxref} Switches +Quiet. When this flag is not set, the commands carried out by +@emph{gnatmake} are displayed. +@end table -@noindent -The command invocation for @code{gnatxref} is: -@smallexample -@c $ gnatxref @ovar{switches} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatxref @r{[}@var{switches}@r{]} @var{sourcefile1} @r{[}@var{sourcefile2} @dots{}@r{]} -@end smallexample +@geindex -s (gnatmake) -@noindent -where -@table @var -@item sourcefile1 -@itemx sourcefile2 -identifies the source files for which a report is to be generated. The -``with''ed units will be processed too. You must provide at least one file. +@table @asis -These file names are considered to be regular expressions, so for instance -specifying @file{source*.adb} is the same as giving every file in the current -directory whose name starts with @file{source} and whose extension is -@file{adb}. +@item @code{-s} -You shouldn't specify any directory name, just base names. @command{gnatxref} -and @command{gnatfind} will be able to locate these files by themselves using -the source path. If you specify directories, no result is produced. +Recompile if compiler switches have changed since last compilation. +All compiler switches but -I and -o are taken into account in the +following way: +orders between different 'first letter' switches are ignored, but +orders between same switches are taken into account. For example, +@emph{-O -O2} is different than @emph{-O2 -O}, but @emph{-g -O} +is equivalent to @emph{-O -g}. +This switch is recommended when Integrated Preprocessing is used. @end table -@noindent -The switches can be: -@table @option -@c !sort! -@item --version -@cindex @option{--version} @command{gnatxref} -Display Copyright and version, then exit disregarding all other options. +@geindex -u (gnatmake) -@item --help -@cindex @option{--help} @command{gnatxref} -If @option{--version} was not used, display usage, then exit disregarding -all other options. -@item -a -@cindex @option{-a} (@command{gnatxref}) -If this switch is present, @code{gnatfind} and @code{gnatxref} will parse -the read-only files found in the library search path. Otherwise, these files -will be ignored. This option can be used to protect Gnat sources or your own -libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref} -much faster, and their output much smaller. Read-only here refers to access -or permissions status in the file system for the current user. +@table @asis -@item -aIDIR -@cindex @option{-aIDIR} (@command{gnatxref}) -When looking for source files also look in directory DIR. The order in which -source file search is undertaken is the same as for @command{gnatmake}. +@item @code{-u} -@item -aODIR -@cindex @option{-aODIR} (@command{gnatxref}) -When searching for library and object files, look in directory -DIR. The order in which library files are searched is the same as for -@command{gnatmake}. +Unique. Recompile at most the main files. It implies -c. Combined with +-f, it is equivalent to calling the compiler directly. Note that using +-u with a project file and no main has a special meaning +(@ref{e2,,Project Files and Main Subprograms}). +@end table -@item -nostdinc -@cindex @option{-nostdinc} (@command{gnatxref}) -Do not look for sources in the system default directory. +@geindex -U (gnatmake) -@item -nostdlib -@cindex @option{-nostdlib} (@command{gnatxref}) -Do not look for library files in the system default directory. -@item --ext=@var{extension} -@cindex @option{--ext} (@command{gnatxref}) -Specify an alternate ali file extension. The default is @code{ali} and other -extensions (e.g. @code{gli} for C/C++ sources when using @option{-fdump-xref}) -may be specified via this switch. Note that if this switch overrides the -default, which means that only the new extension will be considered. +@table @asis -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatxref}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). +@item @code{-U} -@item -d -@cindex @option{-d} (@command{gnatxref}) -If this switch is set @code{gnatxref} will output the parent type -reference for each matching derived types. +When used without a project file or with one or several mains on the command +line, is equivalent to -u. When used with a project file and no main +on the command line, all sources of all project files are checked and compiled +if not up to date, and libraries are rebuilt, if necessary. +@end table -@item -f -@cindex @option{-f} (@command{gnatxref}) -If this switch is set, the output file names will be preceded by their -directory (if the file was found in the search path). If this switch is -not set, the directory will not be printed. +@geindex -v (gnatmake) -@item -g -@cindex @option{-g} (@command{gnatxref}) -If this switch is set, information is output only for library-level -entities, ignoring local entities. The use of this switch may accelerate -@code{gnatfind} and @code{gnatxref}. -@item -IDIR -@cindex @option{-IDIR} (@command{gnatxref}) -Equivalent to @samp{-aODIR -aIDIR}. +@table @asis -@item -pFILE -@cindex @option{-pFILE} (@command{gnatxref}) -Specify a project file to use @xref{GNAT Project Manager}. -If you need to use the @file{.gpr} -project files, you should use gnatxref through the GNAT driver -(@command{gnat xref -Pproject}). +@item @code{-v} -By default, @code{gnatxref} and @code{gnatfind} will try to locate a -project file in the current directory. +Verbose. Display the reason for all recompilations @emph{gnatmake} +decides are necessary, with the highest verbosity level. +@end table -If a project file is either specified or found by the tools, then the content -of the source directory and object directory lines are added as if they -had been specified respectively by @samp{-aI} -and @samp{-aO}. -@item -u -Output only unused symbols. This may be really useful if you give your -main compilation unit on the command line, as @code{gnatxref} will then -display every unused entity and 'with'ed package. +@geindex -vl (gnatmake) -@item -v -Instead of producing the default output, @code{gnatxref} will generate a -@file{tags} file that can be used by vi. For examples how to use this -feature, see @ref{Examples of gnatxref Usage}. The tags file is output -to the standard output, thus you will have to redirect it to a file. +@table @asis + +@item @code{-vl} + +Verbosity level Low. Display fewer lines than in verbosity Medium. @end table -@noindent -All these switches may be in any order on the command line, and may even -appear after the file names. They need not be separated by spaces, thus -you can say @samp{gnatxref -ag} instead of -@samp{gnatxref -a -g}. +@geindex -vm (gnatmake) -@node Switches for gnatfind -@section @code{gnatfind} Switches -@noindent -The command line for @code{gnatfind} is: +@table @asis -@smallexample -@c $ gnatfind @ovar{switches} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]} -@c @r{[}@var{file1} @var{file2} @dots{}] -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatfind @r{[}@var{switches}@r{]} @var{pattern}@r{[}:@var{sourcefile}@r{[}:@var{line}@r{[}:@var{column}@r{]]]} - @r{[}@var{file1} @var{file2} @dots{}@r{]} -@end smallexample +@item @code{-vm} -@noindent -where +Verbosity level Medium. Potentially display fewer lines than in verbosity High. +@end table -@table @var -@item pattern -An entity will be output only if it matches the regular expression found -in @var{pattern}, see @ref{Regular Expressions in gnatfind and gnatxref}. +@geindex -vm (gnatmake) -Omitting the pattern is equivalent to specifying @samp{*}, which -will match any entity. Note that if you do not provide a pattern, you -have to provide both a sourcefile and a line. -Entity names are given in Latin-1, with uppercase/lowercase equivalence -for matching purposes. At the current time there is no support for -8-bit codes other than Latin-1, or for wide characters in identifiers. +@table @asis -@item sourcefile -@code{gnatfind} will look for references, bodies or declarations -of symbols referenced in @file{@var{sourcefile}}, at line @var{line} -and column @var{column}. See @ref{Examples of gnatfind Usage} -for syntax examples. +@item @code{-vh} -@item line -is a decimal integer identifying the line number containing -the reference to the entity (or entities) to be located. +Verbosity level High. Equivalent to -v. -@item column -is a decimal integer identifying the exact location on the -line of the first character of the identifier for the -entity reference. Columns are numbered from 1. +@item @code{-vP@emph{x}} -@item file1 file2 @dots{} -The search will be restricted to these source files. If none are given, then -the search will be done for every library file in the search path. -These file must appear only after the pattern or sourcefile. +Indicate the verbosity of the parsing of GNAT project files. +See @ref{e3,,Switches Related to Project Files}. +@end table -These file names are considered to be regular expressions, so for instance -specifying @file{source*.adb} is the same as giving every file in the current -directory whose name starts with @file{source} and whose extension is -@file{adb}. +@geindex -x (gnatmake) -The location of the spec of the entity will always be displayed, even if it -isn't in one of @file{@var{file1}}, @file{@var{file2}},@enddots{} The -occurrences of the entity in the separate units of the ones given on the -command line will also be displayed. -Note that if you specify at least one file in this part, @code{gnatfind} may -sometimes not be able to find the body of the subprograms. +@table @asis + +@item @code{-x} +Indicate that sources that are not part of any Project File may be compiled. +Normally, when using Project Files, only sources that are part of a Project +File may be compile. When this switch is used, a source outside of all Project +Files may be compiled. The ALI file and the object file will be put in the +object directory of the main Project. The compilation switches used will only +be those specified on the command line. Even when +@emph{-x} is used, mains specified on the +command line need to be sources of a project file. + +@item @code{-X@emph{name}=@emph{value}} + +Indicate that external variable @cite{name} has the value @cite{value}. +The Project Manager will use this value for occurrences of +@cite{external(name)} when parsing the project file. +@ref{e3,,Switches Related to Project Files}. @end table -@noindent -At least one of 'sourcefile' or 'pattern' has to be present on -the command line. +@geindex -z (gnatmake) -The following switches are available: -@table @option -@c !sort! -@cindex @option{--version} @command{gnatfind} -Display Copyright and version, then exit disregarding all other options. +@table @asis -@item --help -@cindex @option{--help} @command{gnatfind} -If @option{--version} was not used, display usage, then exit disregarding -all other options. +@item @code{-z} -@item -a -@cindex @option{-a} (@command{gnatfind}) -If this switch is present, @code{gnatfind} and @code{gnatxref} will parse -the read-only files found in the library search path. Otherwise, these files -will be ignored. This option can be used to protect Gnat sources or your own -libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref} -much faster, and their output much smaller. Read-only here refers to access -or permission status in the file system for the current user. - -@item -aIDIR -@cindex @option{-aIDIR} (@command{gnatfind}) -When looking for source files also look in directory DIR. The order in which -source file search is undertaken is the same as for @command{gnatmake}. - -@item -aODIR -@cindex @option{-aODIR} (@command{gnatfind}) -When searching for library and object files, look in directory -DIR. The order in which library files are searched is the same as for -@command{gnatmake}. +No main subprogram. Bind and link the program even if the unit name +given on the command line is a package name. The resulting executable +will execute the elaboration routines of the package and its closure, +then the finalization routines. +@end table -@item -nostdinc -@cindex @option{-nostdinc} (@command{gnatfind}) -Do not look for sources in the system default directory. +@subsubheading GCC switches -@item -nostdlib -@cindex @option{-nostdlib} (@command{gnatfind}) -Do not look for library files in the system default directory. -@item --ext=@var{extension} -@cindex @option{--ext} (@command{gnatfind}) -Specify an alternate ali file extension. The default is @code{ali} and other -extensions (e.g. @code{gli} for C/C++ sources when using @option{-fdump-xref}) -may be specified via this switch. Note that if this switch overrides the -default, which means that only the new extension will be considered. +Any uppercase or multi-character switch that is not a @emph{gnatmake} switch +is passed to @emph{gcc} (e.g., @emph{-O}, @emph{-gnato,} etc.) -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatfind}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). +@subsubheading Source and library search path switches -@item -d -@cindex @option{-d} (@code{gnatfind}) -If this switch is set, then @code{gnatfind} will output the parent type -reference for each matching derived types. -@item -e -@cindex @option{-e} (@command{gnatfind}) -By default, @code{gnatfind} accept the simple regular expression set for -@samp{pattern}. If this switch is set, then the pattern will be -considered as full Unix-style regular expression. +@geindex -aI (gnatmake) -@item -f -@cindex @option{-f} (@command{gnatfind}) -If this switch is set, the output file names will be preceded by their -directory (if the file was found in the search path). If this switch is -not set, the directory will not be printed. -@item -g -@cindex @option{-g} (@command{gnatfind}) -If this switch is set, information is output only for library-level -entities, ignoring local entities. The use of this switch may accelerate -@code{gnatfind} and @code{gnatxref}. +@table @asis -@item -IDIR -@cindex @option{-IDIR} (@command{gnatfind}) -Equivalent to @samp{-aODIR -aIDIR}. +@item @code{-aI@emph{dir}} -@item -pFILE -@cindex @option{-pFILE} (@command{gnatfind}) -Specify a project file (@pxref{GNAT Project Manager}) to use. -By default, @code{gnatxref} and @code{gnatfind} will try to locate a -project file in the current directory. +When looking for source files also look in directory @cite{dir}. +The order in which source files search is undertaken is +described in @ref{8e,,Search Paths and the Run-Time Library (RTL)}. +@end table -If a project file is either specified or found by the tools, then the content -of the source directory and object directory lines are added as if they -had been specified respectively by @samp{-aI} and -@samp{-aO}. +@geindex -aL (gnatmake) -@item -r -@cindex @option{-r} (@command{gnatfind}) -By default, @code{gnatfind} will output only the information about the -declaration, body or type completion of the entities. If this switch is -set, the @code{gnatfind} will locate every reference to the entities in -the files specified on the command line (or in every file in the search -path if no file is given on the command line). -@item -s -@cindex @option{-s} (@command{gnatfind}) -If this switch is set, then @code{gnatfind} will output the content -of the Ada source file lines were the entity was found. +@table @asis -@item -t -@cindex @option{-t} (@command{gnatfind}) -If this switch is set, then @code{gnatfind} will output the type hierarchy for -the specified type. It act like -d option but recursively from parent -type to parent type. When this switch is set it is not possible to -specify more than one file. +@item @code{-aL@emph{dir}} +Consider @cite{dir} as being an externally provided Ada library. +Instructs @emph{gnatmake} to skip compilation units whose @code{.ALI} +files have been located in directory @cite{dir}. This allows you to have +missing bodies for the units in @cite{dir} and to ignore out of date bodies +for the same units. You still need to specify +the location of the specs for these units by using the switches +@code{-aI@emph{dir}} or @code{-I@emph{dir}}. +Note: this switch is provided for compatibility with previous versions +of @emph{gnatmake}. The easier method of causing standard libraries +to be excluded from consideration is to write-protect the corresponding +ALI files. @end table -@noindent -All these switches may be in any order on the command line, and may even -appear after the file names. They need not be separated by spaces, thus -you can say @samp{gnatxref -ag} instead of -@samp{gnatxref -a -g}. - -As stated previously, gnatfind will search in every directory in the -search path. You can force it to look only in the current directory if -you specify @code{*} at the end of the command line. - -@node Project Files for gnatxref and gnatfind -@section Project Files for @command{gnatxref} and @command{gnatfind} - -@noindent -Project files allow a programmer to specify how to compile its -application, where to find sources, etc. These files are used -primarily by GPS, but they can also be used -by the two tools -@code{gnatxref} and @code{gnatfind}. +@geindex -aO (gnatmake) -A project file name must end with @file{.gpr}. If a single one is -present in the current directory, then @code{gnatxref} and @code{gnatfind} will -extract the information from it. If multiple project files are found, none of -them is read, and you have to use the @samp{-p} switch to specify the one -you want to use. -The following lines can be included, even though most of them have default -values which can be used in most cases. -The lines can be entered in any order in the file. -Except for @file{src_dir} and @file{obj_dir}, you can only have one instance of -each line. If you have multiple instances, only the last one is taken into -account. +@table @asis -@table @code -@item src_dir=DIR -[default: @code{"./"}] -specifies a directory where to look for source files. Multiple @code{src_dir} -lines can be specified and they will be searched in the order they -are specified. +@item @code{-aO@emph{dir}} -@item obj_dir=DIR -[default: @code{"./"}] -specifies a directory where to look for object and library files. Multiple -@code{obj_dir} lines can be specified, and they will be searched in the order -they are specified +When searching for library and object files, look in directory +@cite{dir}. The order in which library files are searched is described in +@ref{91,,Search Paths for gnatbind}. +@end table -@item comp_opt=SWITCHES -[default: @code{""}] -creates a variable which can be referred to subsequently by using -the @code{$@{comp_opt@}} notation. This is intended to store the default -switches given to @command{gnatmake} and @command{gcc}. +@geindex Search paths +@geindex for gnatmake -@item bind_opt=SWITCHES -[default: @code{""}] -creates a variable which can be referred to subsequently by using -the @samp{$@{bind_opt@}} notation. This is intended to store the default -switches given to @command{gnatbind}. +@geindex -A (gnatmake) -@item link_opt=SWITCHES -[default: @code{""}] -creates a variable which can be referred to subsequently by using -the @samp{$@{link_opt@}} notation. This is intended to store the default -switches given to @command{gnatlink}. -@item main=EXECUTABLE -[default: @code{""}] -specifies the name of the executable for the application. This variable can -be referred to in the following lines by using the @samp{$@{main@}} notation. +@table @asis -@item comp_cmd=COMMAND -[default: @code{"gcc -c -I$@{src_dir@} -g -gnatq"}] -specifies the command used to compile a single file in the application. +@item @code{-A@emph{dir}} -@item make_cmd=COMMAND -[default: @code{"gnatmake $@{main@} -aI$@{src_dir@} --aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@} --bargs $@{bind_opt@} -largs $@{link_opt@}"}] -specifies the command used to recompile the whole application. +Equivalent to @code{-aL@emph{dir}} @code{-aI@emph{dir}}. -@item run_cmd=COMMAND -[default: @code{"$@{main@}"}] -specifies the command used to run the application. +@geindex -I (gnatmake) -@item debug_cmd=COMMAND -[default: @code{"gdb $@{main@}"}] -specifies the command used to debug the application +@item @code{-I@emph{dir}} +Equivalent to @code{-aO@emph{dir} -aI@emph{dir}}. @end table -@noindent -@command{gnatxref} and @command{gnatfind} only take into account the -@code{src_dir} and @code{obj_dir} lines, and ignore the others. - -@node Regular Expressions in gnatfind and gnatxref -@section Regular Expressions in @code{gnatfind} and @code{gnatxref} - -@noindent -As specified in the section about @command{gnatfind}, the pattern can be a -regular expression. Actually, there are to set of regular expressions -which are recognized by the program: - -@table @code -@item globbing patterns -These are the most usual regular expression. They are the same that you -generally used in a Unix shell command line, or in a DOS session. - -Here is a more formal grammar: -@smallexample -@group -@iftex -@leftskip=.5cm -@end iftex -regexp ::= term -term ::= elmt -- matches elmt -term ::= elmt elmt -- concatenation (elmt then elmt) -term ::= * -- any string of 0 or more characters -term ::= ? -- matches any character -term ::= [char @{char@}] -- matches any character listed -term ::= [char - char] -- matches any character in range -@end group -@end smallexample +@geindex -I- (gnatmake) -@item full regular expression -The second set of regular expressions is much more powerful. This is the -type of regular expressions recognized by utilities such a @file{grep}. +@geindex Source files +@geindex suppressing search -The following is the form of a regular expression, expressed in Ada -reference manual style BNF is as follows -@smallexample -@iftex -@leftskip=.5cm -@end iftex -@group -regexp ::= term @{| term@} -- alternation (term or term @dots{}) +@table @asis -term ::= item @{item@} -- concatenation (item then item) +@item @code{-I-} -item ::= elmt -- match elmt -item ::= elmt * -- zero or more elmt's -item ::= elmt + -- one or more elmt's -item ::= elmt ? -- matches elmt or nothing -@end group -@group -elmt ::= nschar -- matches given character -elmt ::= [nschar @{nschar@}] -- matches any character listed -elmt ::= [^ nschar @{nschar@}] -- matches any character not listed -elmt ::= [char - char] -- matches chars in given range -elmt ::= \ char -- matches given character -elmt ::= . -- matches any single character -elmt ::= ( regexp ) -- parens used for grouping +Do not look for source files in the directory containing the source +file named in the command line. +Do not look for ALI or object files in the directory +where @emph{gnatmake} was invoked. +@end table -char ::= any character, including special characters -nschar ::= any character except ()[].*+?^ -@end group -@end smallexample +@geindex -L (gnatmake) -Following are a few examples: +@geindex Linker libraries -@table @samp -@item abcde|fghi -will match any of the two strings @samp{abcde} and @samp{fghi}, -@item abc*d -will match any string like @samp{abd}, @samp{abcd}, @samp{abccd}, -@samp{abcccd}, and so on, +@table @asis -@item [a-z]+ -will match any string which has only lowercase characters in it (and at -least one character. +@item @code{-L@emph{dir}} +Add directory @cite{dir} to the list of directories in which the linker +will search for libraries. This is equivalent to +@code{-largs} @code{-L@emph{dir}}. +Furthermore, under Windows, the sources pointed to by the libraries path +set in the registry are not searched for. @end table -@end table - -@node Examples of gnatxref Usage -@section Examples of @code{gnatxref} Usage - -@subsection General Usage - -@noindent -For the following examples, we will consider the following units: -@smallexample @c ada -@group -@cartouche -main.ads: -1: @b{with} Bar; -2: @b{package} Main @b{is} -3: @b{procedure} Foo (B : @b{in} Integer); -4: C : Integer; -5: @b{private} -6: D : Integer; -7: @b{end} Main; - -main.adb: -1: @b{package} @b{body} Main @b{is} -2: @b{procedure} Foo (B : @b{in} Integer) @b{is} -3: @b{begin} -4: C := B; -5: D := B; -6: Bar.Print (B); -7: Bar.Print (C); -8: @b{end} Foo; -9: @b{end} Main; +@geindex -nostdinc (gnatmake) -bar.ads: -1: @b{package} Bar @b{is} -2: @b{procedure} Print (B : Integer); -3: @b{end} bar; -@end cartouche -@end group -@end smallexample -@table @code +@table @asis -@noindent -The first thing to do is to recompile your application (for instance, in -that case just by doing a @samp{gnatmake main}, so that GNAT generates -the cross-referencing information. -You can then issue any of the following commands: +@item @code{-nostdinc} -@item gnatxref main.adb -@code{gnatxref} generates cross-reference information for main.adb -and every unit 'with'ed by main.adb. +Do not look for source files in the system default directory. +@end table -The output would be: -@smallexample -@iftex -@leftskip=0cm -@end iftex -B Type: Integer - Decl: bar.ads 2:22 -B Type: Integer - Decl: main.ads 3:20 - Body: main.adb 2:20 - Ref: main.adb 4:13 5:13 6:19 -Bar Type: Unit - Decl: bar.ads 1:9 - Ref: main.adb 6:8 7:8 - main.ads 1:6 -C Type: Integer - Decl: main.ads 4:5 - Modi: main.adb 4:8 - Ref: main.adb 7:19 -D Type: Integer - Decl: main.ads 6:5 - Modi: main.adb 5:8 -Foo Type: Unit - Decl: main.ads 3:15 - Body: main.adb 2:15 -Main Type: Unit - Decl: main.ads 2:9 - Body: main.adb 1:14 -Print Type: Unit - Decl: bar.ads 2:15 - Ref: main.adb 6:12 7:12 -@end smallexample +@geindex -nostdlib (gnatmake) -@noindent -that is the entity @code{Main} is declared in main.ads, line 2, column 9, -its body is in main.adb, line 1, column 14 and is not referenced any where. -The entity @code{Print} is declared in bar.ads, line 2, column 15 and it -is referenced in main.adb, line 6 column 12 and line 7 column 12. +@table @asis -@item gnatxref package1.adb package2.ads -@code{gnatxref} will generates cross-reference information for -package1.adb, package2.ads and any other package 'with'ed by any -of these. +@item @code{-nostdlib} +Do not look for library files in the system default directory. @end table -@subsection Using gnatxref with vi - -@code{gnatxref} can generate a tags file output, which can be used -directly from @command{vi}. Note that the standard version of @command{vi} -will not work properly with overloaded symbols. Consider using another -free implementation of @command{vi}, such as @command{vim}. - -@smallexample -$ gnatxref -v gnatfind.adb > tags -@end smallexample +@geindex --RTS (gnatmake) -@noindent -will generate the tags file for @code{gnatfind} itself (if the sources -are in the search path!). -From @command{vi}, you can then use the command @samp{:tag @var{entity}} -(replacing @var{entity} by whatever you are looking for), and vi will -display a new file with the corresponding declaration of entity. +@table @asis -@node Examples of gnatfind Usage -@section Examples of @code{gnatfind} Usage +@item @code{--RTS=@emph{rts-path}} -@table @code +Specifies the default location of the runtime library. GNAT looks for the +runtime +in the following directories, and stops as soon as a valid runtime is found +(@code{adainclude} or @code{ada_source_path}, and @code{adalib} or +@code{ada_object_path} present): -@item gnatfind -f xyz:main.adb -Find declarations for all entities xyz referenced at least once in -main.adb. The references are search in every library file in the search -path. -The directories will be printed as well (as the @samp{-f} -switch is set) +@itemize * -The output will look like: -@smallexample -directory/main.ads:106:14: xyz <= declaration -directory/main.adb:24:10: xyz <= body -directory/foo.ads:45:23: xyz <= declaration -@end smallexample +@item +@emph{/$rts_path} -@noindent -that is to say, one of the entities xyz found in main.adb is declared at -line 12 of main.ads (and its body is in main.adb), and another one is -declared at line 45 of foo.ads +@item +@emph{/$rts_path} -@item gnatfind -fs xyz:main.adb -This is the same command as the previous one, instead @code{gnatfind} will -display the content of the Ada source file lines. +@item +@emph{/rts-$rts_path} -The output will look like: +@item +The selected path is handled like a normal RTS path. +@end itemize +@end table -@smallexample -directory/main.ads:106:14: xyz <= declaration - procedure xyz; -directory/main.adb:24:10: xyz <= body - procedure xyz is -directory/foo.ads:45:23: xyz <= declaration - xyz : Integer; -@end smallexample +@node Mode Switches for gnatmake,Notes on the Command Line,Switches for gnatmake,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat id4}@anchor{e4}@anchor{gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake}@anchor{e5} +@subsection Mode Switches for @emph{gnatmake} -@noindent -This can make it easier to find exactly the location your are looking -for. -@item gnatfind -r "*x*":main.ads:123 foo.adb -Find references to all entities containing an x that are -referenced on line 123 of main.ads. -The references will be searched only in main.ads and foo.adb. +The mode switches (referred to as @cite{mode_switches}) allow the +inclusion of switches that are to be passed to the compiler itself, the +binder or the linker. The effect of a mode switch is to cause all +subsequent switches up to the end of the switch list, or up to the next +mode switch, to be interpreted as switches to be passed on to the +designated component of GNAT. -@item gnatfind main.ads:123 -Find declarations and bodies for all entities that are referenced on -line 123 of main.ads. +@geindex -cargs (gnatmake) -This is the same as @code{gnatfind "*":main.adb:123}. -@item gnatfind mydir/main.adb:123:45 -Find the declaration for the entity referenced at column 45 in -line 123 of file main.adb in directory mydir. Note that it -is usual to omit the identifier name when the column is given, -since the column position identifies a unique reference. +@table @asis -The column has to be the beginning of the identifier, and should not -point to any character in the middle of the identifier. +@item @code{-cargs @emph{switches}} +Compiler switches. Here @cite{switches} is a list of switches +that are valid switches for @emph{gcc}. They will be passed on to +all compile steps performed by @emph{gnatmake}. @end table -@ifclear FSFEDITION -@c ********************************* -@node The GNAT Pretty-Printer gnatpp -@chapter The GNAT Pretty-Printer @command{gnatpp} -@findex gnatpp -@cindex Pretty-Printer +@geindex -bargs (gnatmake) -@menu -* Switches for gnatpp:: -* Formatting Rules:: -@end menu -@noindent -The @command{gnatpp} tool is an ASIS-based utility -for source reformatting / pretty-printing. -It takes an Ada source file as input and generates a reformatted -version as output. -You can specify various style directives via switches; e.g., -identifier case conventions, rules of indentation, and comment layout. - -Note: A newly-redesigned set of formatting algorithms used by gnatpp -is now available. -To invoke the old formatting algorithms, use the @option{--pp-old} switch. -Support for @option{--pp-old} will be removed in some future version. - -To produce a reformatted file, @command{gnatpp} invokes the Ada -compiler and generates and uses the ASIS tree for the input source; -thus the input must be legal Ada code, and the tool should have all the -information needed to compile the input source. To provide this information, -you may specify as a tool parameter the project file the input source belongs to -(or you may call @command{gnatpp} -through the @command{gnat} driver (see @ref{The GNAT Driver and -Project Files}). Another possibility is to specify the source search -path and needed configuration files in @option{-cargs} section of @command{gnatpp} -call, see the description of the @command{gnatpp} switches below. - -@command{gnatpp} cannot process sources that contain -preprocessing directives. - -The @command{gnatpp} command has the form - -@smallexample -@c $ gnatpp @ovar{switches} @var{filename} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatpp @r{[}@var{switches}@r{]} @var{filename} @r{[}-cargs @var{gcc_switches}@r{]} -@end smallexample - -@noindent -where -@itemize @bullet -@item -@var{switches} is an optional sequence of switches defining such properties as -the formatting rules, the source search path, and the destination for the -output source file +@table @asis -@item -@var{filename} is the name (including the extension) of the source file to -reformat; wildcards or several file names on the same gnatpp command are -allowed. The file name may contain path information; it does not have to -follow the GNAT file naming rules +@item @code{-bargs @emph{switches}} -@item -@samp{@var{gcc_switches}} is a list of switches for -@command{gcc}. They will be passed on to all compiler invocations made by -@command{gnatpp} to generate the ASIS trees. Here you can provide -@option{-I} switches to form the source search path, -use the @option{-gnatec} switch to set the configuration file, etc. -@end itemize +Binder switches. Here @cite{switches} is a list of switches +that are valid switches for @cite{gnatbind}. They will be passed on to +all bind steps performed by @emph{gnatmake}. +@end table -@node Switches for gnatpp -@section Switches for @command{gnatpp} +@geindex -largs (gnatmake) -@noindent -The following subsections describe the various switches accepted by -@command{gnatpp}, organized by category. -You specify a switch by supplying a name and generally also a value. -In many cases the values for a switch with a given name are incompatible with -each other -(for example the switch that controls the casing of a reserved word may have -exactly one value: upper case, lower case, or -mixed case) and thus exactly one such switch can be in effect for an -invocation of @command{gnatpp}. -If more than one is supplied, the last one is used. -However, some values for the same switch are mutually compatible. -You may supply several such switches to @command{gnatpp}, but then -each must be specified in full, with both the name and the value. -Abbreviated forms (the name appearing once, followed by each value) are -not permitted. +@table @asis +@item @code{-largs @emph{switches}} -@menu -* Alignment Control:: -* Casing Control:: -* General Text Layout Control:: -* Other Formatting Options:: -* Setting the Source Search Path:: -* Output File Control:: -* Other gnatpp Switches:: -@end menu +Linker switches. Here @cite{switches} is a list of switches +that are valid switches for @emph{gnatlink}. They will be passed on to +all link steps performed by @emph{gnatmake}. +@end table -@node Alignment Control -@subsection Alignment Control -@cindex Alignment control in @command{gnatpp} +@geindex -margs (gnatmake) -@noindent -Programs can be easier to read if certain constructs are vertically aligned. -By default alignment of the following constructs is set ON: -@code{:} in declarations, @code{:=} in initializations in declarations -@code{:=} in assignment statements, @code{=>} in associations, and -@code{at} keywords in the component clauses in record -representation clauses. -@table @option -@cindex @option{-A@var{n}} (@command{gnatpp}) +@table @asis -@item -A0 -Set alignment to OFF +@item @code{-margs @emph{switches}} -@item -A1 -Set alignment to ON +Make switches. The switches are directly interpreted by @emph{gnatmake}, +regardless of any previous occurrence of @emph{-cargs}, @emph{-bargs} +or @emph{-largs}. @end table -@node Casing Control -@subsection Casing Control -@cindex Casing control in @command{gnatpp} +@node Notes on the Command Line,How gnatmake Works,Mode Switches for gnatmake,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat id5}@anchor{e6}@anchor{gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line}@anchor{e7} +@subsection Notes on the Command Line -@noindent -@command{gnatpp} allows you to specify the casing for reserved words, -pragma names, attribute designators and identifiers. -For identifiers you may define a -general rule for name casing but also override this rule -via a set of dictionary files. -Three types of casing are supported: lower case, upper case, and mixed case. -``Mixed case'' means that the first letter, and also each letter immediately -following an underscore, are converted to their uppercase forms; -all the other letters are converted to their lowercase forms. +This section contains some additional useful notes on the operation +of the @emph{gnatmake} command. -@table @option -@cindex @option{-a@var{x}} (@command{gnatpp}) -@item -aL -Attribute designators are lower case - -@item -aU -Attribute designators are upper case - -@item -aM -Attribute designators are mixed case (this is the default) - -@cindex @option{-k@var{x}} (@command{gnatpp}) -@item -kL -Keywords (technically, these are known in Ada as @emph{reserved words}) are -lower case (this is the default) - -@item -kU -Keywords are upper case - -@cindex @option{-n@var{x}} (@command{gnatpp}) -@item -nD -Name casing for defining occurrences are as they appear in the source file -(this is the default) - -@item -nU -Names are in upper case - -@item -nL -Names are in lower case - -@item -nM -Names are in mixed case - -@cindex @option{-ne@var{x}} (@command{gnatpp}) -@item -neD -Enumeration literal casing for defining occurrences are as they appear in the -source file. Overrides -n casing setting. - -@item -neU -Enumeration literals are in upper case. Overrides -n casing -setting. - -@item -neL -Enumeration literals are in lower case. Overrides -n casing -setting. - -@item -neM -Enumeration literals are in mixed case. Overrides -n casing -setting. - -@cindex @option{-nt@var{x}} (@command{gnatpp}) -@item -neD -Names introduced by type and subtype declarations are always -cased as they appear in the declaration in the source file. -Overrides -n casing setting. - -@item -ntU -Names introduced by type and subtype declarations are always in -upper case. Overrides -n casing setting. - -@item -ntL -Names introduced by type and subtype declarations are always in -lower case. Overrides -n casing setting. - -@item -ntM -Names introduced by type and subtype declarations are always in -mixed case. Overrides -n casing setting. - -@item -nnU -Names introduced by number declarations are always in -upper case. Overrides -n casing setting. - -@item -nnL -Names introduced by number declarations are always in -lower case. Overrides -n casing setting. - -@item -nnM -Names introduced by number declarations are always in -mixed case. Overrides -n casing setting. - -@cindex @option{-p@var{x}} (@command{gnatpp}) -@item -pL -Pragma names are lower case - -@item -pU -Pragma names are upper case - -@item -pM -Pragma names are mixed case (this is the default) - -@item -D@var{file} -@cindex @option{-D} (@command{gnatpp}) -Use @var{file} as a @emph{dictionary file} that defines -the casing for a set of specified names, -thereby overriding the effect on these names by -any explicit or implicit --n switch. -To supply more than one dictionary file, -use several @option{-D} switches. - -@noindent -@option{gnatpp} implicitly uses a @emph{default dictionary file} -to define the casing for the Ada predefined names and -the names declared in the GNAT libraries. - -@item -D- -@cindex @option{-D-} (@command{gnatpp}) -Do not use the default dictionary file; -instead, use the casing -defined by a @option{-n} switch and any explicit -dictionary file(s) -@end table - -@noindent -The structure of a dictionary file, and details on the conventions -used in the default dictionary file, are defined in @ref{Name Casing}. - -The @option{-D-} and -@option{-D@var{file}} switches are mutually -compatible. - -@noindent -This group of @command{gnatpp} switches controls the layout of comments and -complex syntactic constructs. See @ref{Formatting Comments} for details -on their effect. - -@table @option -@cindex @option{-c@var{n}} (@command{gnatpp}) -@item -c0 -All comments remain unchanged. - -@item -c1 -GNAT-style comment line indentation. -This is the default. - -@item -c3 -GNAT-style comment beginning. - -@item -c4 -Fill comment blocks. - -@item -c5 -Keep unchanged special form comments. -This is the default. - -@item --comments-only -@cindex @option{--comments-only} @command{gnatpp} -Format just the comments. - -@cindex @option{--no-separate-is} (@command{gnatpp}) -@item --no-separate-is -Do not place the keyword @code{is} on a separate line in a subprogram body in -case if the spec occupies more than one line. - -@cindex @option{--separate-loop-then} (@command{gnatpp}) -@item --separate-loop-then -Place the keyword @code{loop} in FOR and WHILE loop statements and the -keyword @code{then} in IF statements on a separate line. - -@cindex @option{--no-separate-loop-then} (@command{gnatpp}) -@item --no-separate-loop-then -Do not place the keyword @code{loop} in FOR and WHILE loop statements and the -keyword @code{then} in IF statements on a separate line. This option is -incompatible with @option{--separate-loop-then} option. - -@cindex @option{--use-on-new-line} (@command{gnatpp}) -@item --use-on-new-line -Start each USE clause in a context clause from a separate line. - -@cindex @option{--insert-blank-lines} (@command{gnatpp}) -@item --insert-blank-lines -Insert blank lines where appropriate (between bodies and other large -constructs). - -@cindex @option{--preserve-blank-lines} (@command{gnatpp}) -@item --preserve-blank-lines -Preserve blank lines in the input. By default, gnatpp will squeeze -multiple blank lines down to one. - -@end table - -@noindent -The @option{-c} switches are compatible with one another, except that -the @option{-c0} switch disables all other comment formatting -switches. +@geindex Recompilation (by gnatmake) -@node General Text Layout Control -@subsection General Text Layout Control +@itemize * -@noindent -These switches allow control over line length and indentation. +@item +If @emph{gnatmake} finds no ALI files, it recompiles the main program +and all other units required by the main program. +This means that @emph{gnatmake} +can be used for the initial compile, as well as during subsequent steps of +the development cycle. -@table @option -@item -M@var{nnn} -@cindex @option{-M} (@command{gnatpp}) -Maximum line length, @var{nnn} from 32@dots{}256, the default value is 79 - -@item -i@var{nnn} -@cindex @option{-i} (@command{gnatpp}) -Indentation level, @var{nnn} from 1@dots{}9, the default value is 3 - -@item -cl@var{nnn} -@cindex @option{-cl} (@command{gnatpp}) -Indentation level for continuation lines (relative to the line being -continued), @var{nnn} from 1@dots{}9. -The default -value is one less than the (normal) indentation level, unless the -indentation is set to 1 (in which case the default value for continuation -line indentation is also 1) -@end table - -@node Other Formatting Options -@subsection Other Formatting Options - -@noindent -These switches control other formatting not listed above. - -@table @option -@item --decimal-grouping=@var{n} -@cindex @option{--decimal-grouping} @command{gnatpp} -Put underscores in decimal literals (numeric literals without a base) -every @var{n} characters. If a literal already has one or more -underscores, it is not modified. For example, with -@code{--decimal-grouping=3}, @code{1000000} will be changed to -@code{1_000_000}. - -@item --based-grouping=@var{n} -@cindex @option{--based-grouping} @command{gnatpp} -Same as @code{--decimal-grouping}, but for based literals. For -example, with @code{--based-grouping=4}, @code{16#0001FFFE#} will be -changed to @code{16#0001_FFFE#}. - -@item --split-line-before-op -@cindex @option{--split-line-before-op} (@command{gnatpp}) -If it is necessary to split a line at a binary operator, by default -the line is split after the operator. With this option, it is split -before the operator. - -@item --RM-style-spacing -@cindex @option{--RM-style-spacing} (@command{gnatpp}) -Do not insert an extra blank before various occurrences of -`(' and `:'. This also turns off alignment. - -@item -ff -@cindex @option{-ff} (@command{gnatpp}) -Insert a Form Feed character after a pragma Page. - -@item --call_threshold=@var{nnn} -@cindex @option{--call_threshold} (@command{gnatpp}) -If the number of parameter associations is greater than @var{nnn} and if at -least one association uses named notation, start each association from -a new line. If @var{nnn} is 0, no check for the number of associations -is made; this is the default. - -@item --par_threshold=@var{nnn} -@cindex @option{--par_threshold} (@command{gnatpp}) -If the number of parameter specifications is greater than @var{nnn} -(or equal to @var{nnn} in case of a function), start each specification from -a new line. This feature is disabled by default. -@end table - -@node Setting the Source Search Path -@subsection Setting the Source Search Path - -@noindent -To define the search path for the input source file, @command{gnatpp} -uses the same switches as the GNAT compiler, with the same effects: - -@table @option -@item -I@var{dir} -@cindex @option{-I} (@command{gnatpp}) - -@item -I- -@cindex @option{-I-} (@command{gnatpp}) - -@item -gnatec=@var{path} -@cindex @option{-gnatec} (@command{gnatpp}) - -@end table - -@node Output File Control -@subsection Output File Control - -@noindent -By default the output is sent to a file whose name is obtained by appending -the @file{.pp} suffix to the name of the input file. -If the file with this name already exists, it is overwritten. -Thus if the input file is @file{my_ada_proc.adb} then -@command{gnatpp} will produce @file{my_ada_proc.adb.pp} -as output file. -The output may be redirected by the following switches: - -@table @option -@item --output-dir=@var{dir} -@cindex @option{--output-dir} (@command{gnatpp}) -Generate output file in directory @file{dir} with the same name as the input -file. If @file{dir} is the same as the directory containing the input file, -the input file is not processed; use @option{-rnb} -if you want to update the input file in place. - -@item -pipe -@cindex @option{-pipe} (@command{gnatpp}) -Send the output to @code{Standard_Output} - -@item -o @var{output_file} -@cindex @option{-o} (@code{gnatpp}) -Write the output into @var{output_file}. -If @var{output_file} already exists, @command{gnatpp} terminates without -reading or processing the input file. - -@item -of @var{output_file} -@cindex @option{-of} (@command{gnatpp}) -Write the output into @var{output_file}, overwriting the existing file -(if one is present). - -@item -r -@cindex @option{-r} (@command{gnatpp}) -Replace the input source file with the reformatted output, and copy the -original input source into the file whose name is obtained by appending the -@file{.npp} suffix to the name of the input file. -If a file with this name already exists, @command{gnatpp} terminates without -reading or processing the input file. - -@item -rf -@cindex @option{-rf} (@code{gnatpp}) -Like @option{-r} except that if the file with the specified name -already exists, it is overwritten. - -@item -rnb -@cindex @option{-rnb} (@command{gnatpp}) -Replace the input source file with the reformatted output without -creating any backup copy of the input source. - -@item --eol=@var{xxx} -@cindex @option{--eol} (@code{gnatpp}) -Specifies the line-ending style of the reformatted output file. The @var{xxx} -string specified with the switch may be: -@itemize @bullet -@item ``@option{dos}'' MS DOS style, lines end with CR LF characters -@item ``@option{crlf}'' -the same as @option{dos} -@item ``@option{unix}'' UNIX style, lines end with LF character -@item ``@option{lf}'' -the same as @option{unix} -@end itemize +@item +If you enter @code{gnatmake foo.adb}, where @code{foo} +is a subunit or body of a generic unit, @emph{gnatmake} recompiles +@code{foo.adb} (because it finds no ALI) and stops, issuing a +warning. -@item -W@var{e} -@cindex @option{-W} (@command{gnatpp}) -Specify the wide character encoding method for the input and output files. -@var{e} is one of the following: +@item +In @emph{gnatmake} the switch @emph{-I} +is used to specify both source and +library file paths. Use @emph{-aI} +instead if you just want to specify +source paths only and @emph{-aO} +if you want to specify library paths +only. -@itemize @bullet +@item +@emph{gnatmake} will ignore any files whose ALI file is write-protected. +This may conveniently be used to exclude standard libraries from +consideration and in particular it means that the use of the +@emph{-f} switch will not recompile these files +unless @emph{-a} is also specified. -@item h -Hex encoding +@item +@emph{gnatmake} has been designed to make the use of Ada libraries +particularly convenient. Assume you have an Ada library organized +as follows: @emph{obj-dir} contains the objects and ALI files for +of your Ada compilation units, +whereas @emph{include-dir} contains the +specs of these units, but no bodies. Then to compile a unit +stored in @cite{main.adb}, which uses this Ada library you would just type: -@item u -Upper half encoding +@example +$ gnatmake -aI`include-dir` -aL`obj-dir` main +@end example -@item s -Shift/JIS encoding +@item +Using @emph{gnatmake} along with the @emph{-m (minimal recompilation)} +switch provides a mechanism for avoiding unnecessary recompilations. Using +this switch, +you can update the comments/format of your +source files without having to recompile everything. Note, however, that +adding or deleting lines in a source files may render its debugging +info obsolete. If the file in question is a spec, the impact is rather +limited, as that debugging info will only be useful during the +elaboration phase of your program. For bodies the impact can be more +significant. In all events, your debugger will warn you if a source file +is more recent than the corresponding object, and alert you to the fact +that the debugging information may be out of date. +@end itemize -@item e -EUC encoding +@node How gnatmake Works,Examples of gnatmake Usage,Notes on the Command Line,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat id6}@anchor{e8}@anchor{gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works}@anchor{e9} +@subsection How @emph{gnatmake} Works -@item 8 -UTF-8 encoding -@item b -Brackets encoding (default value) -@end itemize +Generally @emph{gnatmake} automatically performs all necessary +recompilations and you don't need to worry about how it works. However, +it may be useful to have some basic understanding of the @emph{gnatmake} +approach and in particular to understand how it uses the results of +previous compilations without incorrectly depending on them. -@end table +First a definition: an object file is considered @emph{up to date} if the +corresponding ALI file exists and if all the source files listed in the +dependency section of this ALI file have time stamps matching those in +the ALI file. This means that neither the source file itself nor any +files that it depends on have been modified, and hence there is no need +to recompile this file. -@noindent -Options @option{-o} and -@option{-of} are allowed only if the call to gnatpp -contains only one file to reformat. -Option -@option{--eol} -and -@option{-W} -cannot be used together -with @option{-pipe} option. - -@node Other gnatpp Switches -@subsection Other @code{gnatpp} Switches - -@noindent -The additional @command{gnatpp} switches are defined in this subsection. - -@table @option -@item --version -@cindex @option{--version} @command{gnatpp} -Display copyright and version, then exit disregarding all other options. - -@item --help -@cindex @option{--help} @command{gnatpp} -Display usage, then exit disregarding all other options. - -@item -P @var{file} -@cindex @option{-P} @command{gnatpp} -Indicates the name of the project file that describes the set of sources -to be processed. The exact set of argument sources depends on other options -specified; see below. - -@item -U -@cindex @option{-U} @command{gnatpp} -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), process -all the units of the closure of the argument project. Otherwise this option -has no effect. - -@item -U @var{main_unit} -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), process -the closure of units rooted at @var{main_unit}. Otherwise this option -has no effect. - -@item -X@var{name}=@var{value} -@cindex @option{-X} @command{gnatpp} -Indicates that external variable @var{name} in the argument project -has the value @var{value}. Has no effect if no project is specified as -tool argument. - -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatpp}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). - -@item --incremental -@cindex @option{--incremental} @command{gnatpp} -Incremental processing on a per-file basis. Source files are only -processed if they have been modified, or if files they depend on have -been modified. This is similar to the way gnatmake/gprbuild only -compiles files that need to be recompiled. A project file is required -in this mode, and the gnat driver (as in @command{gnat pretty}) is not -supported. - -@item --pp-off=@var{xxx} -@cindex @option{--pp-off} @command{gnatpp} -Use @code{--xxx} as the command to turn off pretty printing, instead -of the default @code{--!pp off}. - -@item --pp-on=@var{xxx} -@cindex @option{--pp-on} @command{gnatpp} -Use @code{--xxx} as the command to turn pretty printing back on, instead -of the default @code{--!pp on}. - -@item --pp-old -@cindex @option{--pp-old} @command{gnatpp} -Use the old formatting algorithms. - -@item -files @var{filename} -@cindex @option{-files} (@code{gnatpp}) -Take the argument source files from the specified file. This file should be an -ordinary text file containing file names separated by spaces or -line breaks. You can use this switch more than once in the same call to -@command{gnatpp}. You also can combine this switch with an explicit list of +@emph{gnatmake} works by first checking if the specified main unit is up +to date. If so, no compilations are required for the main unit. If not, +@emph{gnatmake} compiles the main program to build a new ALI file that +reflects the latest sources. Then the ALI file of the main unit is +examined to find all the source files on which the main program depends, +and @emph{gnatmake} recursively applies the above procedure on all these files. -@item -j@var{n} -@cindex @option{-j} (@command{gnatpp}) -Without @option{--incremental}, use @var{n} processes to carry out the -tree creations (internal representations of the argument sources). On -a multiprocessor machine this speeds up processing of big sets of -argument sources. If @var{n} is 0, then the maximum number of parallel -tree creations is the number of core processors on the platform. This -option cannot be used together with @option{-r}, -@option{-rf} or -@option{-rnb} option. - -With @option{--incremental}, use @var{n} @command{gnatpp} processes to -perform pretty-printing in parallel. @var{n} = 0 means the same as -above. In this case, @option{-r}, -@option{-rf} or -@option{-rnb} options are allowed. - -@cindex @option{-t} (@command{gnatpp}) -@item -t -Print out execution time. +This process ensures that @emph{gnatmake} only trusts the dependencies +in an existing ALI file if they are known to be correct. Otherwise it +always recompiles to determine a new, guaranteed accurate set of +dependencies. As a result the program is compiled 'upside down' from what may +be more familiar as the required order of compilation in some other Ada +systems. In particular, clients are compiled before the units on which +they depend. The ability of GNAT to compile in any order is critical in +allowing an order of compilation to be chosen that guarantees that +@emph{gnatmake} will recompute a correct set of new dependencies if +necessary. -@item -v -@cindex @option{-v} (@command{gnatpp}) -Verbose mode +When invoking @emph{gnatmake} with several @cite{file_names}, if a unit is +imported by several of the executables, it will be recompiled at most once. -@item -q -@cindex @option{-q} (@command{gnatpp}) -Quiet mode -@end table +Note: when using non-standard naming conventions +(@ref{37,,Using Other File Names}), changing through a configuration pragmas +file the version of a source and invoking @emph{gnatmake} to recompile may +have no effect, if the previous version of the source is still accessible +by @emph{gnatmake}. It may be necessary to use the switch +-f. -@noindent -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), and no -@option{-U} is specified, then the set of processed sources is -all the immediate units of the argument project. +@node Examples of gnatmake Usage,,How gnatmake Works,Building with gnatmake +@anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage}@anchor{ea}@anchor{gnat_ugn/building_executable_programs_with_gnat id7}@anchor{eb} +@subsection Examples of @emph{gnatmake} Usage -@node Formatting Rules -@section Formatting Rules -@noindent -The following subsections show how @command{gnatpp} treats white space, -comments, program layout, and name casing. -They provide detailed descriptions of the switches shown above. +@table @asis -@menu -* Disabling Pretty Printing:: -* White Space and Empty Lines:: -* Formatting Comments:: -* Name Casing:: -@end menu +@item @emph{gnatmake hello.adb} -@node Disabling Pretty Printing -@subsection Disabling Pretty Printing +Compile all files necessary to bind and link the main program +@code{hello.adb} (containing unit @cite{Hello}) and bind and link the +resulting object files to generate an executable file @code{hello}. -@noindent -Pretty printing is highly heuristic in nature, and sometimes doesn't -do exactly what you want. If you wish to format a certain region of -code by hand, you can turn off pretty printing in that region by -surrounding it with special comments that start with @code{--!pp off} -and @code{--!pp on}. The text in that region will then be reproduced -verbatim in the output with no formatting. +@item @emph{gnatmake main1 main2 main3} -To disable pretty printing for the whole file, put @code{--!pp off} at -the top, with no following @code{--!pp on}. +Compile all files necessary to bind and link the main programs +@code{main1.adb} (containing unit @cite{Main1}), @code{main2.adb} +(containing unit @cite{Main2}) and @code{main3.adb} +(containing unit @cite{Main3}) and bind and link the resulting object files +to generate three executable files @code{main1}, +@code{main2} and @code{main3}. -The comments must appear on a line by themselves, with nothing -preceding except spaces. The initial text of the comment must be -exactly @code{--!pp off} or @code{--!pp on} (case sensitive), but may -be followed by arbitrary additional text. For example: +@item @emph{gnatmake -q Main_Unit -cargs -O2 -bargs -l} -@smallexample @c ada -@cartouche -@b{package} Interrupts @b{is} - --@i{!pp off -- turn off pretty printing so "Interrupt_Kind" lines up} - @b{type} Interrupt_Kind @b{is} - (Asynchronous_Interrupt_Kind, - Synchronous_Interrupt_Kind, - Green_Interrupt_Kind); - --@i{!pp on -- reenable pretty printing} +Compile all files necessary to bind and link the main program unit +@cite{Main_Unit} (from file @code{main_unit.adb}). All compilations will +be done with optimization level 2 and the order of elaboration will be +listed by the binder. @emph{gnatmake} will operate in quiet mode, not +displaying commands it is executing. +@end table - ... -@end cartouche -@end smallexample - -You can specify different comment strings using the @code{--pp-off} -and @code{--pp-on} switches. For example, if you say @code{gnatpp ---pp-off=' pp-' *.ad?} then gnatpp will recognize comments of the form -@code{-- pp-} instead of @code{--!pp off} for disabling pretty -printing. Note that the leading @code{--} of the comment is not -included in the argument to these switches. - -@node White Space and Empty Lines -@subsection White Space and Empty Lines - -@noindent -@command{gnatpp} does not have an option to control space characters. -It will add or remove spaces according to the style illustrated by the -examples in the @cite{Ada Reference Manual}. -The output file will contain no lines with trailing white space. - -By default, a sequence of one or more blank lines in the input is -converted to a single blank line in the output; multiple blank lines -are squeezed down to one. -The @option{--preserve-blank-lines} option -turns off the squeezing; each blank line in the input is copied -to the output. -The @option{--insert-blank-lines} option -causes additional blank lines to be inserted if not already -present in the input (e.g. between bodies). - -@node Formatting Comments -@subsection Formatting Comments - -@noindent -Comments in Ada code are of two kinds: -@itemize @bullet -@item -a @emph{whole-line comment}, which appears by itself (possibly preceded by -white space) on a line +@node Compiling with gcc,Compiler Switches,Building with gnatmake,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc}@anchor{1e}@anchor{gnat_ugn/building_executable_programs_with_gnat id8}@anchor{ec} +@section Compiling with @emph{gcc} -@item -an @emph{end-of-line comment}, which follows some other Ada code on -the same line. -@end itemize -@noindent -A whole-line comment is indented according to the surrounding code, -with some exceptions. -Comments that start in column 1 are kept there. -If possible, comments are not moved so far to the right that the maximum -line length is exceeded. -The @option{-c0} option -turns off comment formatting. -Special-form comments such as SPARK-style @code{--#...} are left alone. - -For an end-of-line comment, @command{gnatpp} tries to leave the same -number of spaces between the end of the preceding Ada code and the -beginning of the comment as appear in the original source. - -@noindent -The @option{-c3} switch -(GNAT style comment beginning) has the following -effect: - -@itemize @bullet -@item -For each whole-line comment that does not end with two hyphens, -@command{gnatpp} inserts spaces if necessary after the starting two hyphens -to ensure that there are at least two spaces between these hyphens and the -first non-blank character of the comment. -@end itemize +This section discusses how to compile Ada programs using the @emph{gcc} +command. It also describes the set of switches +that can be used to control the behavior of the compiler. -@noindent -The @option{-c4} switch specifies that -whole-line comments that form a paragraph will be filled in typical -word processor style (that is, moving words between lines to make the -lines other than the last similar in length ). - -@noindent -The @option{--comments-only} switch specifies that only the comments -are formatted; the rest of the program text is left alone. The -comments are formatted according to the -c3 and -c4 switches; other -formatting switches are ignored. For example, @option{--comments-only --c4} means to fill comment paragraphs, and do nothing else. Likewise, -@option{--comments-only -c3} ensures comments start with at least two -spaces after @code{--}, and @option{--comments-only -c3 -c4} does -both. If @option{--comments-only} is given without @option{-c3} or -@option{-c4}, then gnatpp doesn't format anything. - -@node Name Casing -@subsection Name Casing - -@noindent -@command{gnatpp} always converts the usage occurrence of a (simple) name to -the same casing as the corresponding defining identifier. - -You control the casing for defining occurrences via the -@option{-n} switch. -With @option{-nD} (``as declared'', which is the default), -defining occurrences appear exactly as in the source file -where they are declared. -The other values for this switch --- -@option{-nU}, -@option{-nL}, -@option{-nM} --- -result in -upper, lower, or mixed case, respectively. -If @command{gnatpp} changes the casing of a defining -occurrence, it analogously changes the casing of all the -usage occurrences of this name. - -If the defining occurrence of a name is not in the source compilation unit -currently being processed by @command{gnatpp}, the casing of each reference to -this name is changed according to the value of the @option{-n} -switch (subject to the dictionary file mechanism described below). -Thus @command{gnatpp} acts as though the @option{-n} switch -had affected the -casing for the defining occurrence of the name. - -The options -@option{-a@var{x}}, -@option{-k@var{x}}, -@option{-ne@var{x}}, -@option{-nt@var{x}}, -@option{-nn@var{x}}, and -@option{-p@var{x}} -allow finer-grained control over casing for -attributes, keywords, enumeration literals, -types, named numbers and pragmas, respectively. -@option{-nt@var{x}} covers subtypes and -task and protected bodies as well. - -Some names may need to be spelled with casing conventions that are not -covered by the upper-, lower-, and mixed-case transformations. -You can arrange correct casing by placing such names in a -@emph{dictionary file}, -and then supplying a @option{-D} switch. -The casing of names from dictionary files overrides -any @option{-n} switch. - -To handle the casing of Ada predefined names and the names from GNAT libraries, -@command{gnatpp} assumes a default dictionary file. -The name of each predefined entity is spelled with the same casing as is used -for the entity in the @cite{Ada Reference Manual} (usually mixed case). -The name of each entity in the GNAT libraries is spelled with the same casing -as is used in the declaration of that entity. - -The @w{@option{-D-}} switch suppresses the use of -the default dictionary file. Instead, the casing for predefined and -GNAT-defined names will be established by the -@option{-n} switch or explicit dictionary files. For -example, by default the names @code{Ada.Text_IO} and -@code{GNAT.OS_Lib} will appear as just shown, even in the presence of -a @option{-nU} switch. To ensure that even -such names are rendered in uppercase, additionally supply the -@w{@option{-D-}} switch (or else place these names -in upper case in a dictionary file). - -A dictionary file is a plain text file; each line in this file can be -either a blank line (containing only space characters), an Ada comment -line, or the specification of exactly one @emph{casing schema}. - -A casing schema is a string that has the following syntax: - -@smallexample -@cartouche - @var{casing_schema} ::= @var{identifier} | *@var{simple_identifier}* +@menu +* Compiling Programs:: +* Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL. +* Order of Compilation Issues:: +* Examples:: - @var{simple_identifier} ::= @var{letter}@{@var{letter_or_digit}@} -@end cartouche -@end smallexample +@end menu -@noindent -(See @cite{Ada Reference Manual}, Section 2.3) for the definition of the -@var{identifier} lexical element and the @var{letter_or_digit} category.) +@node Compiling Programs,Search Paths and the Run-Time Library RTL,,Compiling with gcc +@anchor{gnat_ugn/building_executable_programs_with_gnat compiling-programs}@anchor{ed}@anchor{gnat_ugn/building_executable_programs_with_gnat id9}@anchor{ee} +@subsection Compiling Programs -The casing schema string can be followed by white space and/or an Ada-style -comment; any amount of white space is allowed before the string. -If a dictionary file is passed as -the value of a @option{-D@var{file}} switch -then for every -simple name and every identifier, @command{gnatpp} checks if the dictionary -defines the casing for the name or for some of its parts (the term ``subword'' -is used below to denote the part of a name which is delimited by ``_'' or by -the beginning or end of the word and which does not contain any ``_'' inside): +The first step in creating an executable program is to compile the units +of the program using the @emph{gcc} command. You must compile the +following files: -@itemize @bullet -@item -if the whole name is in the dictionary, @command{gnatpp} uses for this name -the casing defined by the dictionary; no subwords are checked for this word -@item -for every subword @command{gnatpp} checks if the dictionary contains the -corresponding string of the form @code{*@var{simple_identifier}*}, -and if it does, the casing of this @var{simple_identifier} is used -for this subword +@itemize * -@item -if the whole name does not contain any ``_'' inside, and if for this name -the dictionary contains two entries - one of the form @var{identifier}, -and another - of the form *@var{simple_identifier}*, then the first one -is applied to define the casing of this name +@item +the body file (@code{.adb}) for a library level subprogram or generic +subprogram -@item -if more than one dictionary file is passed as @command{gnatpp} switches, each -dictionary adds new casing exceptions and overrides all the existing casing -exceptions set by the previous dictionaries +@item +the spec file (@code{.ads}) for a library level package or generic +package that has no body -@item -when @command{gnatpp} checks if the word or subword is in the dictionary, -this check is not case sensitive +@item +the body file (@code{.adb}) for a library level package +or generic package that has a body @end itemize -@noindent -For example, suppose we have the following source to reformat: - -@smallexample @c ada -@cartouche -@b{procedure} test @b{is} - name1 : integer := 1; - name4_name3_name2 : integer := 2; - name2_name3_name4 : Boolean; - name1_var : Float; -@b{begin} - name2_name3_name4 := name4_name3_name2 > name1; -@b{end}; -@end cartouche -@end smallexample - -@noindent -And suppose we have two dictionaries: - -@smallexample -@cartouche -@i{dict1:} - NAME1 - *NaMe3* - *Name1* -@end cartouche - -@cartouche -@i{dict2:} - *NAME3* -@end cartouche -@end smallexample +You need @emph{not} compile the following files -@noindent -If @command{gnatpp} is called with the following switches: -@smallexample -@command{gnatpp -nM -D dict1 -D dict2 test.adb} -@end smallexample +@itemize * -@noindent -then we will get the following name casing in the @command{gnatpp} output: +@item +the spec of a library unit which has a body -@smallexample @c ada -@cartouche -@b{procedure} Test @b{is} - NAME1 : Integer := 1; - Name4_NAME3_Name2 : Integer := 2; - Name2_NAME3_Name4 : Boolean; - Name1_Var : Float; -@b{begin} - Name2_NAME3_Name4 := Name4_NAME3_Name2 > NAME1; -@b{end} Test; -@end cartouche -@end smallexample -@end ifclear +@item +subunits +@end itemize -@ifclear FSFEDITION -@c ********************************* -@node The Ada-to-XML converter gnat2xml -@chapter The Ada-to-XML converter @command{gnat2xml} -@findex gnat2xml -@cindex XML generation +because they are compiled as part of compiling related units. GNAT +package specs +when the corresponding body is compiled, and subunits when the parent is +compiled. -@noindent -The @command{gnat2xml} tool is an ASIS-based utility that converts -Ada source code into XML. +@geindex cannot generate code -@menu -* Switches for gnat2xml:: -* Other Programs:: -* Structure of the XML:: -* Generating Representation Clauses:: -@end menu +If you attempt to compile any of these files, you will get one of the +following error messages (where @cite{fff} is the name of the file you +compiled): -@node Switches for gnat2xml -@section Switches for @command{gnat2xml} +@quotation -@noindent -@command{gnat2xml} takes Ada source code as input, and produces XML -that conforms to the schema. +@example +cannot generate code for file `fff` (package spec) +to check package spec, use -gnatc -Usage: +cannot generate code for file `fff` (missing subunits) +to check parent unit, use -gnatc -@smallexample -gnat2xml [options] filenames [-files filename] [-cargs gcc_switches] -@end smallexample +cannot generate code for file `fff` (subprogram spec) +to check subprogram spec, use -gnatc -@noindent -options: -@smallexample --h ---help -- generate usage information and quit, ignoring all other options ---version -- print version and quit, ignoring all other options +cannot generate code for file `fff` (subunit) +to check subunit, use -gnatc +@end example +@end quotation --P @file{file} -- indicates the name of the project file that describes - the set of sources to be processed. The exact set of argument - sources depends on other options specified, see below. +As indicated by the above error messages, if you want to submit +one of these files to the compiler to check for correct semantics +without generating code, then use the @emph{-gnatc} switch. --U -- if a project file is specified and no argument source is explicitly - specified, process all the units of the closure of the argument project. - Otherwise this option has no effect. +The basic command for compiling a file containing an Ada unit is: --U @var{main_unit} -- if a project file is specified and no argument source - is explicitly specified (either directly or by means of @option{-files} - option), process the closure of units rooted at @var{main_unit}. - Otherwise this option has no effect. +@example +$ gcc -c [switches] +@end example --X@var{name}=@var{value} -- indicates that external variable @var{name} in - the argument project has the value @var{value}. Has no effect if no - project is specified as tool argument. +where @cite{file name} is the name of the Ada file (usually +having an extension @code{.ads} for a spec or @code{.adb} for a body). +You specify the +@code{-c} switch to tell @emph{gcc} to compile, but not link, the file. +The result of a successful compilation is an object file, which has the +same name as the source file but an extension of @code{.o} and an Ada +Library Information (ALI) file, which also has the same name as the +source file, but with @code{.ali} as the extension. GNAT creates these +two output files in the current directory, but you may specify a source +file in any directory using an absolute or relative path specification +containing the directory information. ---RTS=@var{rts-path} -- Specifies the default location of the runtime - library. Same meaning as the equivalent @command{gnatmake} flag - (@pxref{Switches for gnatmake}). +@geindex gnat1 ---incremental -- incremental processing on a per-file basis. Source files are - only processed if they have been modified, or if files they depend - on have been modified. This is similar to the way gnatmake/gprbuild - only compiles files that need to be recompiled. A project file - is required in this mode. +@emph{gcc} is actually a driver program that looks at the extensions of +the file arguments and loads the appropriate compiler. For example, the +GNU C compiler is @code{cc1}, and the Ada compiler is @code{gnat1}. +These programs are in directories known to the driver program (in some +configurations via environment variables you set), but need not be in +your path. The @emph{gcc} driver also calls the assembler and any other +utilities needed to complete the generation of the required object +files. --j@var{n} -- In @option{--incremental} mode, use @var{n} @command{gnat2xml} - processes to perform XML generation in parallel. If @var{n} is 0, then - the maximum number of parallel tree creations is the number of core - processors on the platform. +It is possible to supply several file names on the same @emph{gcc} +command. This causes @emph{gcc} to call the appropriate compiler for +each file. For example, the following command lists two separate +files to be compiled: ---output-dir=@var{dir} -- generate one .xml file for each Ada source file, in - directory @file{dir}. (Default is to generate the XML to standard - output.) +@example +$ gcc -c x.adb y.adb +@end example --I - directories to search for dependencies - You can also set the ADA_INCLUDE_PATH environment variable for this. +calls @cite{gnat1} (the Ada compiler) twice to compile @code{x.adb} and +@code{y.adb}. +The compiler generates two object files @code{x.o} and @code{y.o} +and the two ALI files @code{x.ali} and @code{y.ali}. ---compact -- debugging version, with interspersed source, and a more - compact representation of "sloc". This version does not conform - to any schema. +Any switches apply to all the files listed, see @ref{ef,,Compiler Switches} for a +list of available @emph{gcc} switches. ---rep-clauses -- generate representation clauses (see ``Generating - Representation Clauses'' below). +@node Search Paths and the Run-Time Library RTL,Order of Compilation Issues,Compiling Programs,Compiling with gcc +@anchor{gnat_ugn/building_executable_programs_with_gnat id10}@anchor{f0}@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl}@anchor{8e} +@subsection Search Paths and the Run-Time Library (RTL) --files=filename - the name of a text file containing a list - of Ada source files to process --q -- quiet --v -- verbose +With the GNAT source-based library system, the compiler must be able to +find source files for units that are needed by the unit being compiled. +Search paths are used to guide this process. --cargs ... -- options to pass to gcc -@end smallexample +The compiler compiles one source file whose name must be given +explicitly on the command line. In other words, no searching is done +for this file. To find all other source files that are needed (the most +common being the specs of units), the compiler examines the following +directories, in the following order: -@noindent -If a project file is specified and no argument source is explicitly -specified, and no @option{-U} is specified, then the set of processed -sources is all the immediate units of the argument project. -Example: +@itemize * -@smallexample -gnat2xml -v -output-dir=xml-files *.ad[sb] -@end smallexample - -@noindent -The above will create *.xml files in the @file{xml-files} subdirectory. -For example, if there is an Ada package Mumble.Dumble, whose spec and -body source code lives in mumble-dumble.ads and mumble-dumble.adb, -the above will produce xml-files/mumble-dumble.ads.xml and -xml-files/mumble-dumble.adb.xml. - -@node Other Programs -@section Other Programs - -@noindent -The distribution includes two other programs that are related to -@command{gnat2xml}: - -@command{gnat2xsd} is the schema generator, which generates the schema -to standard output, based on the structure of Ada as encoded by -ASIS. You don't need to run @command{gnat2xsd} in order to use -@command{gnat2xml}. To generate the schema, type: - -@smallexample -gnat2xsd > ada-schema.xsd -@end smallexample - -@noindent -@command{gnat2xml} generates XML files that will validate against -@file{ada-schema.xsd}. - -@command{xml2gnat} is a back-translator that translates the XML back -into Ada source code. The Ada generated by @command{xml2gnat} has -identical semantics to the original Ada code passed to -@command{gnat2xml}. It is not textually identical, however --- for -example, no attempt is made to preserve the original indentation. - -@node Structure of the XML -@section Structure of the XML - -@noindent -The primary documentation for the structure of the XML generated by -@command{gnat2xml} is the schema (see @command{gnat2xsd} above). The -following documentation gives additional details needed to understand -the schema and therefore the XML. - -The elements listed under Defining Occurrences, Usage Occurrences, and -Other Elements represent the syntactic structure of the Ada program. -Element names are given in lower case, with the corresponding element -type Capitalized_Like_This. The element and element type names are -derived directly from the ASIS enumeration type Flat_Element_Kinds, -declared in Asis.Extensions.Flat_Kinds, with the leading ``An_'' or ``A_'' -removed. For example, the ASIS enumeration literal -An_Assignment_Statement corresponds to the XML element -assignment_statement of XML type Assignment_Statement. - -To understand the details of the schema and the corresponding XML, it is -necessary to understand the ASIS standard, as well as the GNAT-specific -extension to ASIS. - -A defining occurrence is an identifier (or character literal or operator -symbol) declared by a declaration. A usage occurrence is an identifier -(or ...) that references such a declared entity. For example, in: - -@smallexample -type T is range 1..10; -X, Y : constant T := 1; -@end smallexample - -@noindent -The first ``T'' is the defining occurrence of a type. The ``X'' is the -defining occurrence of a constant, as is the ``Y'', and the second ``T'' is -a usage occurrence referring to the defining occurrence of T. - -Each element has a 'sloc' (source location), and subelements for each -syntactic subtree, reflecting the Ada grammar as implemented by ASIS. -The types of subelements are as defined in the ASIS standard. For -example, for the right-hand side of an assignment_statement we have -the following comment in asis-statements.ads: - -@smallexample ------------------------------------------------------------------------------- --- 18.3 function Assignment_Expression ------------------------------------------------------------------------------- - - function Assignment_Expression - (Statement : Asis.Statement) - return Asis.Expression; - ------------------------------------------------------------------------------- -... --- Returns the expression from the right hand side of the assignment. -... --- Returns Element_Kinds: --- An_Expression -@end smallexample +@item +The directory containing the source file of the main unit being compiled +(the file name on the command line). -@noindent -The corresponding sub-element of type Assignment_Statement is: +@item +Each directory named by an @emph{-I} switch given on the @emph{gcc} +command line, in the order given. -@smallexample - -@end smallexample +@geindex ADA_PRJ_INCLUDE_FILE -@noindent -where Expression_Class is defined by an xsd:choice of all the -various kinds of expression. +@item +Each of the directories listed in the text file whose name is given +by the +@geindex ADA_PRJ_INCLUDE_FILE +@geindex environment variable; ADA_PRJ_INCLUDE_FILE +@code{ADA_PRJ_INCLUDE_FILE} environment variable. +@geindex ADA_PRJ_INCLUDE_FILE +@geindex environment variable; ADA_PRJ_INCLUDE_FILE +@code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat +driver when project files are used. It should not normally be set +by other means. -The 'sloc' of each element indicates the starting and ending line and -column numbers. Column numbers are character counts; that is, a tab -counts as 1, not as however many spaces it might expand to. +@geindex ADA_INCLUDE_PATH -Subelements of type Element have names ending in ``_q'' (for ASIS -``Query''), and those of type Element_List end in ``_ql'' (``Query returning -List''). +@item +Each of the directories listed in the value of the +@geindex ADA_INCLUDE_PATH +@geindex environment variable; ADA_INCLUDE_PATH +@code{ADA_INCLUDE_PATH} environment variable. +Construct this value +exactly as the +@geindex PATH +@geindex environment variable; PATH +@code{PATH} environment variable: a list of directory +names separated by colons (semicolons when working with the NT version). -Some subelements are ``Boolean''. For example, Private_Type_Definition -has has_abstract_q and has_limited_q, to indicate whether those -keywords are present, as in @code{type T is abstract limited -private;}. False is represented by a Nil_Element. True is represented -by an element type specific to that query (for example, Abstract and -Limited). +@item +The content of the @code{ada_source_path} file which is part of the GNAT +installation tree and is used to store standard libraries such as the +GNAT Run Time Library (RTL) source files. +@ref{8b,,Installing a library} +@end itemize -The root of the tree is a Compilation_Unit, with attributes: +Specifying the switch @emph{-I-} +inhibits the use of the directory +containing the source file named in the command line. You can still +have this directory on your search path, but in this case it must be +explicitly requested with a @emph{-I} switch. -@itemize @bullet -@item -unit_kind, unit_class, and unit_origin. These are strings that match the -enumeration literals of types Unit_Kinds, Unit_Classes, and Unit_Origins -in package Asis. +Specifying the switch @emph{-nostdinc} +inhibits the search of the default location for the GNAT Run Time +Library (RTL) source files. -@item -unit_full_name is the full expanded name of the unit, starting from a -root library unit. So for @code{package P.Q.R is ...}, -@code{unit_full_name="P.Q.R"}. Same for @code{separate (P.Q) package R is ...}. +The compiler outputs its object files and ALI files in the current +working directory. +Caution: The object file can be redirected with the @emph{-o} switch; +however, @emph{gcc} and @cite{gnat1} have not been coordinated on this +so the @code{ALI} file will not go to the right place. Therefore, you should +avoid using the @emph{-o} switch. -@item -def_name is the same as unit_full_name for library units; for subunits, -it is just the simple name. +@geindex System.IO -@item -source_file is the name of the Ada source file. For example, for -the spec of @code{P.Q.R}, @code{source_file="p-q-r.ads"}. This allows one to -interpret the source locations --- the ``sloc'' of all elements -within this Compilation_Unit refers to line and column numbers -within the named file. -@end itemize +The packages @cite{Ada}, @cite{System}, and @cite{Interfaces} and their +children make up the GNAT RTL, together with the simple @cite{System.IO} +package used in the @cite{"Hello World"} example. The sources for these units +are needed by the compiler and are kept together in one directory. Not +all of the bodies are needed, but all of the sources are kept together +anyway. In a normal installation, you need not specify these directory +names when compiling or binding. Either the environment variables or +the built-in defaults cause these files to be found. -@noindent -Defining occurrences have these attributes: +In addition to the language-defined hierarchies (@cite{System}, @cite{Ada} and +@cite{Interfaces}), the GNAT distribution provides a fourth hierarchy, +consisting of child units of @cite{GNAT}. This is a collection of generally +useful types, subprograms, etc. See the @cite{GNAT_Reference_Manual} +for further details. -@itemize @bullet -@item -def_name is the simple name of the declared entity, as written in the Ada -source code. +Besides simplifying access to the RTL, a major use of search paths is +in compiling sources from multiple directories. This can make +development environments much more flexible. -@item -def is a unique URI of the form: +@node Order of Compilation Issues,Examples,Search Paths and the Run-Time Library RTL,Compiling with gcc +@anchor{gnat_ugn/building_executable_programs_with_gnat id11}@anchor{f1}@anchor{gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues}@anchor{f2} +@subsection Order of Compilation Issues - ada://kind/fully/qualified/name -where: +If, in our earlier example, there was a spec for the @cite{hello} +procedure, it would be contained in the file @code{hello.ads}; yet this +file would not have to be explicitly compiled. This is the result of the +model we chose to implement library management. Some of the consequences +of this model are as follows: - kind indicates the kind of Ada entity being declared (see below), and - fully/qualified/name, is the fully qualified name of the Ada - entity, with each of ``fully'', ``qualified'', and ``name'' being - mangled for uniqueness. We do not document the mangling - algorithm, which is subject to change; we just guarantee that the - names are unique in the face of overloading. +@itemize * -@item -type is the type of the declared object, or @code{null} for -declarations of things other than objects. -@end itemize +@item +There is no point in compiling specs (except for package +specs with no bodies) because these are compiled as needed by clients. If +you attempt a useless compilation, you will receive an error message. +It is also useless to compile subunits because they are compiled as needed +by the parent. -@noindent -Usage occurrences have these attributes: +@item +There are no order of compilation requirements: performing a +compilation never obsoletes anything. The only way you can obsolete +something and require recompilations is to modify one of the +source files on which it depends. -@itemize @bullet -@item -ref_name is the same as the def_name of the corresponding defining -occurrence. This attribute is not of much use, because of -overloading; use ref for lookups, instead. +@item +There is no library as such, apart from the ALI files +(@ref{44,,The Ada Library Information Files}, for information on the format +of these files). For now we find it convenient to create separate ALI files, +but eventually the information therein may be incorporated into the object +file directly. -@item -ref is the same as the def of the corresponding defining -occurrence. +@item +When you compile a unit, the source files for the specs of all units +that it @emph{with}s, all its subunits, and the bodies of any generics it +instantiates must be available (reachable by the search-paths mechanism +described above), or you will receive a fatal error message. @end itemize -@noindent -In summary, @code{def_name} and @code{ref_name} are as in the source -code of the declaration, possibly overloaded, whereas @code{def} and -@code{ref} are unique-ified. +@node Examples,,Order of Compilation Issues,Compiling with gcc +@anchor{gnat_ugn/building_executable_programs_with_gnat id12}@anchor{f3}@anchor{gnat_ugn/building_executable_programs_with_gnat examples}@anchor{f4} +@subsection Examples -Literal elements have this attribute: -@itemize @bullet -@item -lit_val is the value of the literal as written in the source text, -appropriately escaped (e.g. @code{"} ---> @code{"}). This applies -only to numeric and string literals. Enumeration literals in Ada are -not really "literals" in the usual sense; they are usage occurrences, -and have ref_name and ref as described above. Note also that string -literals used as operator symbols are treated as defining or usage -occurrences, not as literals. -@end itemize - -@noindent -Elements that can syntactically represent names and expressions (which -includes usage occurrences, plus function calls and so forth) have this -attribute: - -@itemize @bullet -@item -type. If the element represents an expression or the name of an object, -'type' is the 'def' for the defining occurrence of the type of that -expression or name. Names of other kinds of entities, such as package -names and type names, do not have a type in Ada; these have type="null" -in the XML. -@end itemize +The following are some typical Ada compilation command line examples: -@noindent -Pragma elements have this attribute: +@example +$ gcc -c xyz.adb +@end example -@itemize @bullet -@item -pragma_name is the name of the pragma. For language-defined pragmas, the -pragma name is redundant with the element kind (for example, an -assert_pragma element necessarily has pragma_name="Assert"). However, all -implementation-defined pragmas are lumped together in ASIS as a single -element kind (for example, the GNAT-specific pragma Unreferenced is -represented by an implementation_defined_pragma element with -pragma_name="Unreferenced"). -@end itemize +Compile body in file @code{xyz.adb} with all default options. -@noindent -Defining occurrences of formal parameters and generic formal objects have this -attribute: +@example +$ gcc -c -O2 -gnata xyz-def.adb +@end example -@itemize @bullet -@item -mode indicates that the parameter is of mode 'in', 'in out', or 'out'. -@end itemize +Compile the child unit package in file @code{xyz-def.adb} with extensive +optimizations, and pragma @cite{Assert}/@cite{Debug} statements +enabled. -@noindent -All elements other than Not_An_Element have this attribute: +@example +$ gcc -c -gnatc abc-def.adb +@end example -@itemize @bullet -@item -checks is a comma-separated list of run-time checks that are needed -for that element. The possible checks are: do_accessibility_check, -do_discriminant_check,do_division_check,do_length_check, -do_overflow_check,do_range_check,do_storage_check,do_tag_check. -@end itemize +Compile the subunit in file @code{abc-def.adb} in semantic-checking-only +mode. -@noindent -The "kind" part of the "def" and "ref" attributes is taken from the ASIS -enumeration type Flat_Declaration_Kinds, declared in -Asis.Extensions.Flat_Kinds, with the leading "An_" or "A_" removed, and -any trailing "_Declaration" or "_Specification" removed. Thus, the -possible kinds are as follows: - -@smallexample -ordinary_type -task_type -protected_type -incomplete_type -tagged_incomplete_type -private_type -private_extension -subtype -variable -constant -deferred_constant -single_task -single_protected -integer_number -real_number -enumeration_literal -discriminant -component -loop_parameter -generalized_iterator -element_iterator -procedure -function -parameter -procedure_body -function_body -return_variable -return_constant -null_procedure -expression_function -package -package_body -object_renaming -exception_renaming -package_renaming -procedure_renaming -function_renaming -generic_package_renaming -generic_procedure_renaming -generic_function_renaming -task_body -protected_body -entry -entry_body -entry_index -procedure_body_stub -function_body_stub -package_body_stub -task_body_stub -protected_body_stub -exception -choice_parameter -generic_procedure -generic_function -generic_package -package_instantiation -procedure_instantiation -function_instantiation -formal_object -formal_type -formal_incomplete_type -formal_procedure -formal_function -formal_package -formal_package_declaration_with_box -@end smallexample - -@node Generating Representation Clauses -@section Generating Representation Clauses - -@noindent -If the @option{--rep-clauses} switch is given, @command{gnat2xml} will -generate representation clauses for certain types showing the -representation chosen by the compiler. The information is produced by -the ASIS ``Data Decomposition'' facility --- see the -@code{Asis.Data_Decomposition} package for details. - -Not all types are supported. For example, @code{Type_Model_Kind} must -be @code{A_Simple_Static_Model}. Types declared within generic units -have no representation. The clauses that are generated include -@code{attribute_definition_clauses} for @code{Size} and -@code{Component_Size}, as well as -@code{record_representation_clauses}. - -There is no guarantee that the generated representation clauses could -have actually come from legal Ada code; Ada has some restrictions that -are not necessarily obeyed by the generated clauses. - -The representation clauses are surrounded by comment elements to -indicate that they are automatically generated, something like this: - -@smallexample - -... - -... - -... -@end smallexample +@node Compiler Switches,Binding with gnatbind,Compiling with gcc,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat compiler-switches}@anchor{f5}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gcc}@anchor{ef} +@section Compiler Switches -@end ifclear -@ifclear FSFEDITION -@c ********************************* -@node The GNAT Metrics Tool gnatmetric -@chapter The GNAT Metrics Tool @command{gnatmetric} -@findex gnatmetric -@cindex Metric tool +The @emph{gcc} command accepts switches that control the +compilation process. These switches are fully described in this section: +first an alphabetical listing of all switches with a brief description, +and then functionally grouped sets of switches with more detailed +information. -@noindent -The @command{gnatmetric} tool is an ASIS-based utility -for computing various program metrics. -It takes an Ada source file as input and generates a file containing the -metrics data as output. Various switches control which -metrics are computed and output. +More switches exist for GCC than those documented here, especially +for specific targets. However, their use is not recommended as +they may change code generation in ways that are incompatible with +the Ada run-time library, or can cause inconsistencies between +compilation units. @menu -* Switches for gnatmetric:: -@end menu - -To compute program metrics, @command{gnatmetric} invokes the Ada -compiler and generates and uses the ASIS tree for the input source; -thus the input must be legal Ada code, and the tool should have all the -information needed to compile the input source. To provide this information, -you may specify as a tool parameter the project file the input source belongs to -(or you may call @command{gnatmetric} -through the @command{gnat} driver (see @ref{The GNAT Driver and -Project Files}). Another possibility is to specify the source search -path and needed configuration files in @option{-cargs} section of @command{gnatmetric} -call, see the description of the @command{gnatmetric} switches below. - -If the set of sources to be processed by @code{gnatmetric} contains sources with -preprocessing directives -then the needed options should be provided to run preprocessor as a part of -the @command{gnatmetric} call, and the computed metrics -will correspond to preprocessed sources. - - -The @command{gnatmetric} command has the form - -@smallexample -@c $ gnatmetric @ovar{switches} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatmetric @r{[}@var{switches}@r{]} @{@var{filename}@} @r{[}-cargs @var{gcc_switches}@r{]} -@end smallexample - -@noindent -where -@itemize @bullet -@item -@var{switches} specify the metrics to compute and define the destination for -the output - -@item -Each @var{filename} is the name (including the extension) of a source -file to process. ``Wildcards'' are allowed, and -the file name may contain path information. -If no @var{filename} is supplied, then the @var{switches} list must contain -at least one -@option{-files} switch (@pxref{Other gnatmetric Switches}). -Including both a @option{-files} switch and one or more -@var{filename} arguments is permitted. +* Alphabetical List of All Switches:: +* Output and Error Message Control:: +* Warning Message Control:: +* Debugging and Assertion Control:: +* Validity Checking:: +* Style Checking:: +* Run-Time Checks:: +* Using gcc for Syntax Checking:: +* Using gcc for Semantic Checking:: +* Compiling Different Versions of Ada:: +* Character Set Control:: +* File Naming Control:: +* Subprogram Inlining Control:: +* Auxiliary Output Control:: +* Debugging Control:: +* Exception Handling Control:: +* Units to Sources Mapping Files:: +* Code Generation Control:: -@item -@samp{@var{gcc_switches}} is a list of switches for -@command{gcc}. They will be passed on to all compiler invocations made by -@command{gnatmetric} to generate the ASIS trees. Here you can provide -@option{-I} switches to form the source search path, -and use the @option{-gnatec} switch to set the configuration file, -use the @option{-gnat05} switch if sources should be compiled in -Ada 2005 mode etc. -@end itemize +@end menu -@node Switches for gnatmetric -@section Switches for @command{gnatmetric} +@node Alphabetical List of All Switches,Output and Error Message Control,,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id13}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches}@anchor{f7} +@subsection Alphabetical List of All Switches -@noindent -The following subsections describe the various switches accepted by -@command{gnatmetric}, organized by category. -@menu -* Output Files Control:: -* Disable Metrics For Local Units:: -* Specifying a set of metrics to compute:: -* Other gnatmetric Switches:: -@ignore -* Generate project-wide metrics:: -@end ignore -@end menu +@geindex -b (gcc) -@node Output Files Control -@subsection Output File Control -@cindex Output file control in @command{gnatmetric} - -@noindent -@command{gnatmetric} has two output formats. It can generate a -textual (human-readable) form, and also XML. By default only textual -output is generated. - -When generating the output in textual form, @command{gnatmetric} creates -for each Ada source file a corresponding text file -containing the computed metrics, except for the case when the set of metrics -specified by gnatmetric parameters consists only of metrics that are computed -for the whole set of analyzed sources, but not for each Ada source. -By default, the name of the file containing metric information for a source -is obtained by appending the @file{.metrix} suffix to the -name of the input source file. If not otherwise specified and no project file -is specified as @command{gnatmetric} option this file is placed in the same -directory as where the source file is located. If @command{gnatmetric} has a -project file as its parameter, it places all the generated files in the -object directory of the project (or in the project source directory if the -project does not define an objects directory), if @option{--subdirs} option -is specified, the files are placed in the subrirectory of this directory -specified by this option. - -All the output information generated in XML format is placed in a single -file. By default the name of this file is @file{metrix.xml}. -If not otherwise specified and if no project file is specified -as @command{gnatmetric} option this file is placed in the -current directory. - -Some of the computed metrics are summed over the units passed to -@command{gnatmetric}; for example, the total number of lines of code. -By default this information is sent to @file{stdout}, but a file -can be specified with the @option{-og} switch. - -The following switches control the @command{gnatmetric} output: - -@table @option -@cindex @option{-x} (@command{gnatmetric}) -@item -x -Generate the XML output - -@cindex @option{-xs} (@command{gnatmetric}) -@item -xs -Generate the XML output and the XML schema file that describes the structure -of the XML metric report, this schema is assigned to the XML file. The schema -file has the same name as the XML output file with @file{.xml} suffix replaced -with @file{.xsd} - -@cindex @option{-nt} (@command{gnatmetric}) -@item -nt -Do not generate the output in text form (implies @option{-x}) - -@cindex @option{-d} (@command{gnatmetric}) -@item -d @var{output_dir} -Put text files with detailed metrics into @var{output_dir} - -@cindex @option{-o} (@command{gnatmetric}) -@item -o @var{file_suffix} -Use @var{file_suffix}, instead of @file{.metrix} -in the name of the output file. - -@cindex @option{-og} (@command{gnatmetric}) -@item -og @var{file_name} -Put global metrics into @var{file_name} - -@cindex @option{-ox} (@command{gnatmetric}) -@item -ox @var{file_name} -Put the XML output into @var{file_name} (also implies @option{-x}) - -@cindex @option{-sfn} (@command{gnatmetric}) -@item -sfn -Use ``short'' source file names in the output. (The @command{gnatmetric} -output includes the name(s) of the Ada source file(s) from which the metrics -are computed. By default each name includes the absolute path. The -@option{-sfn} switch causes @command{gnatmetric} -to exclude all directory information from the file names that are output.) - -@end table - -@node Disable Metrics For Local Units -@subsection Disable Metrics For Local Units -@cindex Disable Metrics For Local Units in @command{gnatmetric} - -@noindent -@command{gnatmetric} relies on the GNAT compilation model @minus{} -one compilation -unit per one source file. It computes line metrics for the whole source -file, and it also computes syntax -and complexity metrics for the file's outermost unit. - -By default, @command{gnatmetric} will also compute all metrics for certain -kinds of locally declared program units: - -@itemize @bullet -@item -subprogram (and generic subprogram) bodies; -@item -package (and generic package) specs and bodies; +@table @asis -@item -task object and type specifications and bodies; +@item @code{-b @emph{target}} -@item -protected object and type specifications and bodies. -@end itemize +Compile your program to run on @cite{target}, which is the name of a +system configuration. You must have a GNAT cross-compiler built if +@cite{target} is not the same as your host system. +@end table -@noindent -These kinds of entities will be referred to as -@emph{eligible local program units}, or simply @emph{eligible local units}, -@cindex Eligible local unit (for @command{gnatmetric}) -in the discussion below. +@geindex -B (gcc) -Note that a subprogram declaration, generic instantiation, -or renaming declaration only receives metrics -computation when it appear as the outermost entity -in a source file. -Suppression of metrics computation for eligible local units can be -obtained via the following switch: +@table @asis -@table @option -@cindex @option{-nolocal} (@command{gnatmetric}) -@item -nolocal -Do not compute detailed metrics for eligible local program units +@item @code{-B@emph{dir}} +Load compiler executables (for example, @cite{gnat1}, the Ada compiler) +from @cite{dir} instead of the default location. Only use this switch +when multiple versions of the GNAT compiler are available. +See the "Options for Directory Search" section in the +@cite{Using the GNU Compiler Collection (GCC)} manual for further details. +You would normally use the @emph{-b} or @emph{-V} switch instead. @end table -@node Specifying a set of metrics to compute -@subsection Specifying a set of metrics to compute +@geindex -c (gcc) -@noindent -By default all the metrics are computed and reported. The switches -described in this subsection allow you to control, on an individual -basis, whether metrics are computed and -reported. If at least one positive metric -switch is specified (that is, a switch that defines that a given -metric or set of metrics is to be computed), then only -explicitly specified metrics are reported. - -@menu -* Line Metrics Control:: -* Syntax Metrics Control:: -* Complexity Metrics Control:: -* Coupling Metrics Control:: -@end menu -@node Line Metrics Control -@subsubsection Line Metrics Control -@cindex Line metrics control in @command{gnatmetric} +@table @asis -@noindent -For any (legal) source file, and for each of its -eligible local program units, @command{gnatmetric} computes the following -metrics: +@item @code{-c} -@itemize @bullet -@item -the total number of lines; +Compile. Always use this switch when compiling Ada programs. -@item -the total number of code lines (i.e., non-blank lines that are not comments) +Note: for some other languages when using @emph{gcc}, notably in +the case of C and C++, it is possible to use +use @emph{gcc} without a @emph{-c} switch to +compile and link in one step. In the case of GNAT, you +cannot use this approach, because the binder must be run +and @emph{gcc} cannot be used to run the GNAT binder. +@end table -@item -the number of comment lines +@geindex -fcallgraph-info (gcc) -@item -the number of code lines containing end-of-line comments; -@item -the comment percentage: the ratio between the number of lines that contain -comments and the number of all non-blank lines, expressed as a percentage; +@table @asis -@item -the number of empty lines and lines containing only space characters and/or -format effectors (blank lines) +@item @code{-fcallgraph-info[=su,da]} -@item -the average number of code lines in subprogram bodies, task bodies, entry -bodies and statement sequences in package bodies (this metric is only computed -across the whole set of the analyzed units) +Makes the compiler output callgraph information for the program, on a +per-file basis. The information is generated in the VCG format. It can +be decorated with additional, per-node and/or per-edge information, if a +list of comma-separated markers is additionally specified. When the +@cite{su} marker is specified, the callgraph is decorated with stack usage +information; it is equivalent to @emph{-fstack-usage}. When the @cite{da} +marker is specified, the callgraph is decorated with information about +dynamically allocated objects. +@end table -@end itemize +@geindex -fdump-scos (gcc) -@noindent -@command{gnatmetric} sums the values of the line metrics for all the -files being processed and then generates the cumulative results. The tool -also computes for all the files being processed the average number of code -lines in bodies. -You can use the following switches to select the specific line metrics -to be computed and reported. +@table @asis -@table @option -@cindex @option{--lines@var{x}} (@command{gnatmetric}) +@item @code{-fdump-scos} -@cindex @option{--no-lines@var{x}} +Generates SCO (Source Coverage Obligation) information in the ALI file. +This information is used by advanced coverage tools. See unit @code{SCOs} +in the compiler sources for details in files @code{scos.ads} and +@code{scos.adb}. +@end table -@item --lines-all -Report all the line metrics +@geindex -fdump-xref (gcc) -@item --no-lines-all -Do not report any of line metrics -@item --lines -Report the number of all lines +@table @asis -@item --no-lines -Do not report the number of all lines +@item @code{-fdump-xref} -@item --lines-code -Report the number of code lines +Generates cross reference information in GLI files for C and C++ sources. +The GLI files have the same syntax as the ALI files for Ada, and can be used +for source navigation in IDEs and on the command line using e.g. gnatxref +and the @emph{--ext=gli} switch. +@end table -@item --no-lines-code -Do not report the number of code lines +@geindex -flto (gcc) -@item --lines-comment -Report the number of comment lines -@item --no-lines-comment -Do not report the number of comment lines +@table @asis -@item --lines-eol-comment -Report the number of code lines containing -end-of-line comments +@item @code{-flto[=@emph{n}]} -@item --no-lines-eol-comment -Do not report the number of code lines containing -end-of-line comments +Enables Link Time Optimization. This switch must be used in conjunction +with the traditional @emph{-Ox} switches and instructs the compiler to +defer most optimizations until the link stage. The advantage of this +approach is that the compiler can do a whole-program analysis and choose +the best interprocedural optimization strategy based on a complete view +of the program, instead of a fragmentary view with the usual approach. +This can also speed up the compilation of big programs and reduce the +size of the executable, compared with a traditional per-unit compilation +with inlining across modules enabled by the @emph{-gnatn} switch. +The drawback of this approach is that it may require more memory and that +the debugging information generated by -g with it might be hardly usable. +The switch, as well as the accompanying @emph{-Ox} switches, must be +specified both for the compilation and the link phases. +If the @cite{n} parameter is specified, the optimization and final code +generation at link time are executed using @cite{n} parallel jobs by +means of an installed @emph{make} program. +@end table -@item --lines-ratio -Report the comment percentage in the program text +@geindex -fno-inline (gcc) -@item --no-lines-ratio -Do not report the comment percentage in the program text -@item --lines-blank -Report the number of blank lines +@table @asis -@item --no-lines-blank -Do not report the number of blank lines +@item @code{-fno-inline} -@item --lines-average -Report the average number of code lines in subprogram bodies, task bodies, -entry bodies and statement sequences in package bodies. The metric is computed -and reported for the whole set of processed Ada sources only. +Suppresses all inlining, unless requested with pragma @cite{Inline_Always}. The +effect is enforced regardless of other optimization or inlining switches. +Note that inlining can also be suppressed on a finer-grained basis with +pragma @cite{No_Inline}. +@end table -@item --no-lines-average -Do not report the average number of code lines in subprogram bodies, -task bodies, entry bodies and statement sequences in package bodies. +@geindex -fno-inline-functions (gcc) -@end table -@node Syntax Metrics Control -@subsubsection Syntax Metrics Control -@cindex Syntax metrics control in @command{gnatmetric} +@table @asis -@noindent -@command{gnatmetric} computes various syntactic metrics for the -outermost unit and for each eligible local unit: +@item @code{-fno-inline-functions} -@table @emph -@item LSLOC (``Logical Source Lines Of Code'') -The total number of declarations and the total number of statements. Note -that the definition of declarations is the one given in the reference -manual: +Suppresses automatic inlining of subprograms, which is enabled +if @emph{-O3} is used. +@end table -@noindent -``Each of the following is defined to be a declaration: any basic_declaration; -an enumeration_literal_specification; a discriminant_specification; -a component_declaration; a loop_parameter_specification; a -parameter_specification; a subprogram_body; an entry_declaration; -an entry_index_specification; a choice_parameter_specification; -a generic_formal_parameter_declaration.'' +@geindex -fno-inline-small-functions (gcc) -This means for example that each enumeration literal adds one to the count, -as well as each subprogram parameter. -Thus the results from this metric will be significantly greater than might -be expected from a naive view of counting semicolons. +@table @asis -@item Maximal static nesting level of inner program units -According to -@cite{Ada Reference Manual}, 10.1(1), ``A program unit is either a -package, a task unit, a protected unit, a -protected entry, a generic unit, or an explicitly declared subprogram other -than an enumeration literal.'' +@item @code{-fno-inline-small-functions} -@item Maximal nesting level of composite syntactic constructs -This corresponds to the notion of the -maximum nesting level in the GNAT built-in style checks -(@pxref{Style Checking}) +Suppresses automatic inlining of small subprograms, which is enabled +if @emph{-O2} is used. @end table -@noindent -For the outermost unit in the file, @command{gnatmetric} additionally computes -the following metrics: +@geindex -fno-inline-functions-called-once (gcc) -@table @emph -@item Public subprograms -This metric is computed for package specs. It is the -number of subprograms and generic subprograms declared in the visible -part (including the visible part of nested packages, protected objects, and -protected types). -@item All subprograms -This metric is computed for bodies and subunits. The -metric is equal to a total number of subprogram bodies in the compilation -unit. -Neither generic instantiations nor renamings-as-a-body nor body stubs -are counted. Any subprogram body is counted, independently of its nesting -level and enclosing constructs. Generic bodies and bodies of protected -subprograms are counted in the same way as ``usual'' subprogram bodies. - -@item Public types -This metric is computed for package specs and -generic package declarations. It is the total number of types -that can be referenced from outside this compilation unit, plus the -number of types from all the visible parts of all the visible generic -packages. Generic formal types are not counted. Only types, not subtypes, -are included. - -@noindent -Along with the total number of public types, the following -types are counted and reported separately: - -@itemize @bullet -@item -Abstract types +@table @asis -@item -Root tagged types (abstract, non-abstract, private, non-private). Type -extensions are @emph{not} counted +@item @code{-fno-inline-functions-called-once} -@item -Private types (including private extensions) +Suppresses inlining of subprograms local to the unit and called once +from within it, which is enabled if @emph{-O1} is used. +@end table -@item -Task types +@geindex -fno-ivopts (gcc) -@item -Protected types -@end itemize +@table @asis -@item All types -This metric is computed for any compilation unit. It is equal to the total -number of the declarations of different types given in the compilation unit. -The private and the corresponding full type declaration are counted as one -type declaration. Incomplete type declarations and generic formal types -are not counted. -No distinction is made among different kinds of types (abstract, -private etc.); the total number of types is computed and reported. +@item @code{-fno-ivopts} +Suppresses high-level loop induction variable optimizations, which are +enabled if @emph{-O1} is used. These optimizations are generally +profitable but, for some specific cases of loops with numerous uses +of the iteration variable that follow a common pattern, they may end +up destroying the regularity that could be exploited at a lower level +and thus producing inferior code. @end table -@noindent -By default, all the syntax metrics are computed and reported. You can use the -following switches to select specific syntax metrics. +@geindex -fno-strict-aliasing (gcc) -@table @option -@cindex @option{--syntax@var{x}} (@command{gnatmetric}) +@table @asis -@cindex @option{--no-syntax@var{x}} (@command{gnatmetric}) +@item @code{-fno-strict-aliasing} -@item --syntax-all -Report all the syntax metrics +Causes the compiler to avoid assumptions regarding non-aliasing +of objects of different types. See +@ref{f8,,Optimization and Strict Aliasing} for details. +@end table -@item --no-syntax-all -Do not report any of syntax metrics +@geindex -fstack-check (gcc) -@item --declarations -Report the total number of declarations -@item --no-declarations -Do not report the total number of declarations +@table @asis -@item --statements -Report the total number of statements +@item @code{-fstack-check} -@item --no-statements -Do not report the total number of statements +Activates stack checking. +See @ref{f9,,Stack Overflow Checking} for details. +@end table -@item --public-subprograms -Report the number of public subprograms in a compilation unit +@geindex -fstack-usage (gcc) -@item --no-public-subprograms -Do not report the number of public subprograms in a compilation unit -@item --all-subprograms -Report the number of all the subprograms in a compilation unit +@table @asis -@item --no-all-subprograms -Do not report the number of all the subprograms in a compilation unit +@item @code{-fstack-usage} -@item --public-types -Report the number of public types in a compilation unit +Makes the compiler output stack usage information for the program, on a +per-subprogram basis. See @ref{fa,,Static Stack Usage Analysis} for details. +@end table -@item --no-public-types -Do not report the number of public types in a compilation unit +@geindex -g (gcc) -@item --all-types -Report the number of all the types in a compilation unit -@item --no-all-types -Do not report the number of all the types in a compilation unit +@table @asis -@item --unit-nesting -Report the maximal program unit nesting level +@item @code{-g} -@item --no-unit-nesting -Do not report the maximal program unit nesting level +Generate debugging information. This information is stored in the object +file and copied from there to the final executable file by the linker, +where it can be read by the debugger. You must use the +@emph{-g} switch if you plan on using the debugger. +@end table -@item --construct-nesting -Report the maximal construct nesting level +@geindex -gnat05 (gcc) -@item --no-construct-nesting -Do not report the maximal construct nesting level -@end table +@table @asis -@node Complexity Metrics Control -@subsubsection Complexity Metrics Control -@cindex Complexity metrics control in @command{gnatmetric} +@item @code{-gnat05} -@noindent -For a program unit that is an executable body (a subprogram body (including -generic bodies), task body, entry body or a package body containing -its own statement sequence) @command{gnatmetric} computes the following -complexity metrics: +Allow full Ada 2005 features. +@end table -@itemize @bullet -@item -McCabe cyclomatic complexity; +@geindex -gnat12 (gcc) -@item -McCabe essential complexity; -@item -maximal loop nesting level; +@table @asis -@item -extra exit points (for subprograms); -@end itemize +@item @code{-gnat12} -@noindent -The McCabe cyclomatic complexity metric is defined -in @url{http://www.mccabe.com/pdf/mccabe-nist235r.pdf} +Allow full Ada 2012 features. +@end table -According to McCabe, both control statements and short-circuit control forms -should be taken into account when computing cyclomatic complexity. -For Ada 2012 we have also take into account conditional expressions -and quantified expressions. For each body, we compute three metric values: +@geindex -gnat83 (gcc) -@itemize @bullet -@item -the complexity introduced by control -statements only, without taking into account short-circuit forms -(referred as @code{statement complexity} in @command{gnatmetric} output), +@geindex -gnat2005 (gcc) -@item -the complexity introduced by short-circuit control forms only -(referred as @code{expression complexity} in @command{gnatmetric} output), and -@item -the total -cyclomatic complexity, which is the sum of these two values -(referred as @code{cyclomatic complexity} in @command{gnatmetric} output). -@end itemize +@table @asis -@noindent - -The cyclomatic complexity is also computed for Ada 2012 expression functions. -An expression function cannot have statements as its components, so only one -metric value is computed as a cyclomatic complexity of an expression function. - -The origin of cyclomatic complexity metric is the need to estimate the number -of independent paths in the control flow graph that in turn gives the number -of tests needed to satisfy paths coverage testing completeness criterion. -Considered from the testing point of view, a static Ada @code{loop} (that is, -the @code{loop} statement having static subtype in loop parameter -specification) does not add to cyclomatic complexity. By providing -@option{--no-static-loop} option a user -may specify that such loops should not be counted when computing the -cyclomatic complexity metric - -The Ada essential complexity metric is a McCabe cyclomatic complexity metric -counted for the code that is reduced by excluding all the pure structural Ada -control statements. An compound statement is considered as a non-structural -if it contains a @code{raise} or @code{return} statement as it subcomponent, -or if it contains a @code{goto} statement that transfers the control outside -the operator. A selective accept statement with @code{terminate} alternative -is considered as non-structural statement. When computing this metric, -@code{exit} statements are treated in the same way as @code{goto} -statements unless @option{-ne} option is specified. - -The Ada essential complexity metric defined here is intended to quantify -the extent to which the software is unstructured. It is adapted from -the McCabe essential complexity metric defined in -@url{http://www.mccabe.com/pdf/mccabe-nist235r.pdf} but is modified to be more -suitable for typical Ada usage. For example, short circuit forms -are not penalized as unstructured in the Ada essential complexity metric. - -When computing cyclomatic and essential complexity, @command{gnatmetric} skips -the code in the exception handlers and in all the nested program units. The -code of assertions and predicates (that is, subprogram preconditions and -postconditions, subtype predicates and type invariants) is also skipped. - -By default, all the complexity metrics are computed and reported. -For more fine-grained control you can use -the following switches: - -@table @option -@cindex @option{-complexity@var{x}} (@command{gnatmetric}) - -@cindex @option{--no-complexity@var{x}} - -@item --complexity-all -Report all the complexity metrics - -@item --no-complexity-all -Do not report any of complexity metrics - -@item --complexity-cyclomatic -Report the McCabe Cyclomatic Complexity - -@item --no-complexity-cyclomatic -Do not report the McCabe Cyclomatic Complexity - -@item --complexity-essential -Report the Essential Complexity - -@item --no-complexity-essential -Do not report the Essential Complexity - -@item --loop-nesting -Report maximal loop nesting level - -@item --no-loop-nesting -Do not report maximal loop nesting level - -@item --complexity-average -Report the average McCabe Cyclomatic Complexity for all the subprogram bodies, -task bodies, entry bodies and statement sequences in package bodies. -The metric is computed and reported for whole set of processed Ada sources -only. +@item @code{-gnat2005} -@item --no-complexity-average -Do not report the average McCabe Cyclomatic Complexity for all the subprogram -bodies, task bodies, entry bodies and statement sequences in package bodies +Allow full Ada 2005 features (same as @emph{-gnat05}) +@end table -@cindex @option{-ne} (@command{gnatmetric}) -@item -ne -Do not consider @code{exit} statements as @code{goto}s when -computing Essential Complexity +@geindex -gnat2012 (gcc) -@cindex @option{--no-static-loop} (@command{gnatmetric}) -@item --no-static-loop -Do not consider static loops when computing cyclomatic complexity -@item --extra-exit-points -Report the extra exit points for subprogram bodies. As an exit point, this -metric counts @code{return} statements and raise statements in case when the -raised exception is not handled in the same body. In case of a function this -metric subtracts 1 from the number of exit points, because a function body -must contain at least one @code{return} statement. +@table @asis -@item --no-extra-exit-points -Do not report the extra exit points for subprogram bodies -@end table +@item @code{-gnat2012} +Allow full Ada 2012 features (same as @emph{-gnat12}) -@node Coupling Metrics Control -@subsubsection Coupling Metrics Control -@cindex Coupling metrics control in @command{gnatmetric} +@item @code{-gnat83} -@noindent -@cindex Coupling metrics (in @command{gnatmetric}) -Coupling metrics measure the dependencies between a given entity and other -entities in the program. This information is useful since high coupling -may signal potential issues with maintainability as the program evolves. +Enforce Ada 83 restrictions. +@end table -@command{gnatmetric} computes the following coupling metrics: +@geindex -gnat95 (gcc) -@itemize @bullet -@item -@emph{object-oriented coupling}, for classes in traditional object-oriented -sense; +@table @asis -@item -@emph{unit coupling}, for all the program units making up a program; +@item @code{-gnat95} -@item -@emph{control coupling}, reflecting dependencies between a unit and -other units that contain subprograms. -@end itemize +Enforce Ada 95 restrictions. -@noindent -Two kinds of coupling metrics are computed: - -@itemize @bullet -@item fan-out coupling (``efferent coupling''): -@cindex fan-out coupling -@cindex efferent coupling -the number of entities the given entity depends upon. This metric -reflects how the given entity depends on the changes in the -``external world''. - -@item fan-in coupling (``afferent'' coupling): -@cindex fan-in coupling -@cindex afferent coupling -the number of entities that depend on a given entity. -This metric reflects how the ``external world'' depends on the changes in a -given entity. -@end itemize +Note: for compatibility with some Ada 95 compilers which support only +the @cite{overriding} keyword of Ada 2005, the @emph{-gnatd.D} switch can +be used along with @emph{-gnat95} to achieve a similar effect with GNAT. -@noindent -Object-oriented coupling metrics measure the dependencies -between a given class (or a group of classes) and the other classes in the -program. In this subsection the term ``class'' is used in its traditional -object-oriented programming sense (an instantiable module that contains data -and/or method members). A @emph{category} (of classes) is a group of closely -related classes that are reused and/or modified together. - -A class @code{K}'s fan-out coupling is the number of classes -that @code{K} depends upon. -A category's fan-out coupling is the number of classes outside the -category that the classes inside the category depend upon. - -A class @code{K}'s fan-in coupling is the number of classes -that depend upon @code{K}. -A category's fan-in coupling is the number of classes outside the -category that depend on classes belonging to the category. - -Ada's object-oriented paradigm separates the instantiable entity -(type) from the module (package), so the definition of the coupling -metrics for Ada maps the class and class category notions -onto Ada constructs. - -For the coupling metrics, several kinds of modules that define a tagged type -or an interface type -- library packages, library generic packages, and -library generic package instantiations -- are considered to be classes. -A category consists of a library package (or -a library generic package) that defines a tagged or an interface type, -together with all its descendant (generic) packages that define tagged -or interface types. Thus a -category is an Ada hierarchy of library-level program units. Class -coupling in Ada is referred to as ``tagged coupling'', and category coupling -is referred to as ``hierarchy coupling''. - -For any package serving as a class, its body and subunits (if any) are -considered together with its spec when computing dependencies, and coupling -metrics are reported for spec units only. Dependencies between classes -mean Ada semantic dependencies. For object-oriented coupling -metrics, only dependencies on units treated as classes are -considered. - -Similarly, for unit and control coupling an entity is considered to be the -conceptual construct consisting of the entity's specification, body, and -any subunits (transitively). -@command{gnatmetric} computes -the dependencies of all these units as a whole, but -metrics are only reported for spec -units (or for a subprogram body unit in case if there is no -separate spec for the given subprogram). - -For unit coupling, dependencies are computed between all kinds of program -units. For control coupling, the dependencies of a given unit are limited to -those units that define subprograms. Thus control fan-out coupling is reported -for all units, but control fan-in coupling is only reported for units -that define subprograms. - -The following simple example illustrates the difference between unit coupling -and control coupling metrics: - -@smallexample @c ada -@group -@b{package} Lib_1 @b{is} - @b{function} F_1 (I : Integer) @b{return} Integer; -@b{end} Lib_1; -@end group - -@group -@b{package} Lib_2 @b{is} - @b{type} T_2 @b{is} @b{new} Integer; -@b{end} Lib_2; -@end group - -@group -@b{package} @b{body} Lib_1 @b{is} - @b{function} F_1 (I : Integer) @b{return} Integer @b{is} - @b{begin} - @b{return} I + 1; - @b{end} F_1; -@b{end} Lib_1; -@end group - -@group -@b{with} Lib_2; @b{use} Lib_2; -@b{package} Pack @b{is} - Var : T_2; - @b{function} Fun (I : Integer) @b{return} Integer; -@b{end} Pack; -@end group - -@group -@b{with} Lib_1; @b{use} Lib_1; -@b{package} @b{body} Pack @b{is} - @b{function} Fun (I : Integer) @b{return} Integer @b{is} - @b{begin} - @b{return} F_1 (I); - @b{end} Fun; -@b{end} Pack; -@end group -@end smallexample - -@noindent -If we apply @command{gnatmetric} with the @option{--coupling-all} option to -these units, the result will be: - -@smallexample -@group -Coupling metrics: -================= - Unit Lib_1 (C:\customers\662\L406-007\lib_1.ads) - control fan-out coupling : 0 - control fan-in coupling : 1 - unit fan-out coupling : 0 - unit fan-in coupling : 1 -@end group - -@group - Unit Pack (C:\customers\662\L406-007\pack.ads) - control fan-out coupling : 1 - control fan-in coupling : 0 - unit fan-out coupling : 2 - unit fan-in coupling : 0 -@end group - -@group - Unit Lib_2 (C:\customers\662\L406-007\lib_2.ads) - control fan-out coupling : 0 - unit fan-out coupling : 0 - unit fan-in coupling : 1 -@end group -@end smallexample - -@noindent -The result does not contain values for object-oriented -coupling because none of the argument units contains a tagged type and -therefore none of these units can be treated as a class. - -The @code{Pack} package (spec and body) depends on two -units -- @code{Lib_1} @code{and Lib_2} -- and so its unit fan-out coupling -is 2. Since nothing depends on it, its unit fan-in coupling is 0, as -is its control fan-in coupling. Only one of the units @code{Pack} depends -upon defines a subprogram, so its control fan-out coupling is 1. - -@code{Lib_2} depends on nothing, so its fan-out metrics are 0. It does -not define any subprograms, so it has no control fan-in metric. -One unit (@code{Pack}) depends on it , so its unit fan-in coupling is 1. - -@code{Lib_1} is similar to @code{Lib_2}, but it does define a subprogram. -Its control fan-in coupling is 1 (because there is one unit -depending on it). - -When computing coupling metrics, @command{gnatmetric} counts only -dependencies between units that are arguments of the @command{gnatmetric} -invocation. Coupling metrics are program-wide (or project-wide) metrics, so -you should invoke @command{gnatmetric} for -the complete set of sources comprising your program. This can be done -by invoking @command{gnatmetric} with the corresponding project file -and with the @option{-U} option. - -By default, all the coupling metrics are disabled. You can use the following -switches to specify the coupling metrics to be computed and reported: - -@table @option - -@cindex @option{--tagged-coupling@var{x}} (@command{gnatmetric}) -@cindex @option{--hierarchy-coupling@var{x}} (@command{gnatmetric}) -@cindex @option{--unit-coupling@var{x}} (@command{gnatmetric}) -@cindex @option{--control-coupling@var{x}} (@command{gnatmetric}) - - -@item --coupling-all -Report all the coupling metrics - -@item --tagged-coupling-out -Report tagged (class) fan-out coupling - -@item --tagged-coupling-in -Report tagged (class) fan-in coupling - -@item --hierarchy-coupling-out -Report hierarchy (category) fan-out coupling - -@item --hierarchy-coupling-in -Report hierarchy (category) fan-in coupling - -@item --unit-coupling-out -Report unit fan-out coupling - -@item --unit-coupling-in -Report unit fan-in coupling - -@item --control-coupling-out -Report control fan-out coupling - -@item --control-coupling-in -Report control fan-in coupling -@end table - -@node Other gnatmetric Switches -@subsection Other @code{gnatmetric} Switches +@emph{-gnatd.D} instructs GNAT to consider @cite{overriding} as a keyword +and handle its associated semantic checks, even in Ada 95 mode. +@end table -@noindent -Additional @command{gnatmetric} switches are as follows: - -@table @option -@item --version -@cindex @option{--version} @command{gnatmetric} -Display Copyright and version, then exit disregarding all other options. +@geindex -gnata (gcc) -@item --help -@cindex @option{--help} @command{gnatmetric} -Display usage, then exit disregarding all other options. - -@item -P @var{file} -@cindex @option{-P} @command{gnatmetric} -Indicates the name of the project file that describes the set of sources -to be processed. The exact set of argument sources depends on other options -specified, see below. - -@item -U -@cindex @option{-U} @command{gnatmetric} -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), process -all the units of the closure of the argument project. Otherwise this option -has no effect. - -@item -U @var{main_unit} -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), process -the closure of units rooted at @var{main_unit}. Otherwise this option -has no effect. - -@item -X@var{name}=@var{value} -@cindex @option{-X} @command{gnatmetric} -Indicates that external variable @var{name} in the argument project -has the value @var{value}. Has no effect if no project is specified as -tool argument. - -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatmetric}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). - -@item --subdirs=@var{dir} -@cindex @option{--subdirs=@var{dir}} @command{gnatmetric} -Use the specified subdirectory of the project objects file (or of the -project file directory if the project does not specify an object directory) -for tool output files. Has no effect if no project is specified as -tool argument r if @option{--no_objects_dir} is specified. - -@item --no_objects_dir -@cindex @option{--no_objects_dir} @command{gnatmetric} -Place all the result files into the current directory instead of -project objects directory. This corresponds to the @command{gnatcheck} -behavior when it is called with the project file from the -GNAT driver. Has no effect if no project is specified. - -@item -files @var{filename} -@cindex @option{-files} (@code{gnatmetric}) -Take the argument source files from the specified file. This file should be an -ordinary text file containing file names separated by spaces or -line breaks. You can use this switch more than once in the same call to -@command{gnatmetric}. You also can combine this switch with -an explicit list of files. - -@item -j@var{n} -@cindex @option{-j} (@command{gnatmetric}) -Use @var{n} processes to carry out the tree creations (internal representations -of the argument sources). On a multiprocessor machine this speeds up processing -of big sets of argument sources. If @var{n} is 0, then the maximum number of -parallel tree creations is the number of core processors on the platform. - -@cindex @option{-t} (@command{gnatmetric}) -@item -t -Print out execution time. - -@item -v -@cindex @option{-v} (@command{gnatmetric}) -Verbose mode; -@command{gnatmetric} generates version information and then -a trace of sources being processed. - -@item -q -@cindex @option{-q} (@command{gnatmetric}) -Quiet mode. -@end table - -@noindent -If a project file is specified and no argument source is explicitly -specified (either directly or by means of @option{-files} option), and no -@option{-U} is specified, then the set of processed sources is -all the immediate units of the argument project. - - -@ignore -@node Generate project-wide metrics -@subsection Generate project-wide metrics - -In order to compute metrics on all units of a given project, you can use -the @command{gnat} driver along with the @option{-P} option: -@smallexample - gnat metric -Pproj -@end smallexample - -@noindent -If the project @code{proj} depends upon other projects, you can compute -the metrics on the project closure using the @option{-U} option: -@smallexample - gnat metric -Pproj -U -@end smallexample - -@noindent -Finally, if not all the units are relevant to a particular main -program in the project closure, you can generate metrics for the set -of units needed to create a given main program (unit closure) using -the @option{-U} option followed by the name of the main unit: -@smallexample - gnat metric -Pproj -U main -@end smallexample -@end ignore -@end ifclear - - -@c *********************************** -@node File Name Krunching with gnatkr -@chapter File Name Krunching with @code{gnatkr} -@findex gnatkr - -@noindent -This chapter discusses the method used by the compiler to shorten -the default file names chosen for Ada units so that they do not -exceed the maximum length permitted. It also describes the -@code{gnatkr} utility that can be used to determine the result of -applying this shortening. -@menu -* About gnatkr:: -* Using gnatkr:: -* Krunching Method:: -* Examples of gnatkr Usage:: -@end menu -@node About gnatkr -@section About @code{gnatkr} +@table @asis -@noindent -The default file naming rule in GNAT -is that the file name must be derived from -the unit name. The exact default rule is as follows: -@itemize @bullet -@item -Take the unit name and replace all dots by hyphens. -@item -If such a replacement occurs in the -second character position of a name, and the first character is -@samp{a}, @samp{g}, @samp{s}, or @samp{i}, -then replace the dot by the character -@samp{~} (tilde) -instead of a minus. -@end itemize -The reason for this exception is to avoid clashes -with the standard names for children of System, Ada, Interfaces, -and GNAT, which use the prefixes -@samp{s-}, @samp{a-}, @samp{i-}, and @samp{g-}, -respectively. +@item @code{-gnata} -The @option{-gnatk@var{nn}} -switch of the compiler activates a ``krunching'' -circuit that limits file names to nn characters (where nn is a decimal -integer). For example, using OpenVMS, -where the maximum file name length is -39, the value of nn is usually set to 39, but if you want to generate -a set of files that would be usable if ported to a system with some -different maximum file length, then a different value can be specified. -The default value of 39 for OpenVMS need not be specified. - -The @code{gnatkr} utility can be used to determine the krunched name for -a given file, when krunched to a specified maximum length. +Assertions enabled. @cite{Pragma Assert} and @cite{pragma Debug} to be +activated. Note that these pragmas can also be controlled using the +configuration pragmas @cite{Assertion_Policy} and @cite{Debug_Policy}. +It also activates pragmas @cite{Check}, @cite{Precondition}, and +@cite{Postcondition}. Note that these pragmas can also be controlled +using the configuration pragma @cite{Check_Policy}. In Ada 2012, it +also activates all assertions defined in the RM as aspects: preconditions, +postconditions, type invariants and (sub)type predicates. In all Ada modes, +corresponding pragmas for type invariants and (sub)type predicates are +also activated. The default is that all these assertions are disabled, +and have no effect, other than being checked for syntactic validity, and +in the case of subtype predicates, constructions such as membership tests +still test predicates even if assertions are turned off. +@end table -@node Using gnatkr -@section Using @code{gnatkr} +@geindex -gnatA (gcc) -@noindent -The @code{gnatkr} command has the form -@smallexample -@c $ gnatkr @var{name} @ovar{length} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatkr @var{name} @r{[}@var{length}@r{]} -@end smallexample +@table @asis +@item @code{-gnatA} -@noindent -@var{name} is the uncrunched file name, derived from the name of the unit -in the standard manner described in the previous section (i.e., in particular -all dots are replaced by hyphens). The file name may or may not have an -extension (defined as a suffix of the form period followed by arbitrary -characters other than period). If an extension is present then it will -be preserved in the output. For example, when krunching @file{hellofile.ads} -to eight characters, the result will be hellofil.ads. +Avoid processing @code{gnat.adc}. If a @code{gnat.adc} file is present, +it will be ignored. +@end table -Note: for compatibility with previous versions of @code{gnatkr} dots may -appear in the name instead of hyphens, but the last dot will always be -taken as the start of an extension. So if @code{gnatkr} is given an argument -such as @file{Hello.World.adb} it will be treated exactly as if the first -period had been a hyphen, and for example krunching to eight characters -gives the result @file{hellworl.adb}. +@geindex -gnatb (gcc) -Note that the result is always all lower case (except on OpenVMS where it is -all upper case). Characters of the other case are folded as required. -@var{length} represents the length of the krunched name. The default -when no argument is given is 8 characters. A length of zero stands for -unlimited, in other words do not chop except for system files where the -implied crunching length is always eight characters. +@table @asis -@noindent -The output is the krunched name. The output has an extension only if the -original argument was a file name with an extension. +@item @code{-gnatb} -@node Krunching Method -@section Krunching Method +Generate brief messages to @code{stderr} even if verbose mode set. +@end table -@noindent -The initial file name is determined by the name of the unit that the file -contains. The name is formed by taking the full expanded name of the -unit and replacing the separating dots with hyphens and -using lowercase -for all letters, except that a hyphen in the second character position is -replaced by a tilde if the first character is -@samp{a}, @samp{i}, @samp{g}, or @samp{s}. -The extension is @code{.ads} for a -spec and @code{.adb} for a body. -Krunching does not affect the extension, but the file name is shortened to -the specified length by following these rules: +@geindex -gnatB (gcc) -@itemize @bullet -@item -The name is divided into segments separated by hyphens, tildes or -underscores and all hyphens, tildes, and underscores are -eliminated. If this leaves the name short enough, we are done. -@item -If the name is too long, the longest segment is located (left-most -if there are two of equal length), and shortened by dropping -its last character. This is repeated until the name is short enough. +@table @asis -As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb} -to fit the name into 8 characters as required by some operating systems. +@item @code{-gnatB} -@smallexample -our-strings-wide_fixed 22 -our strings wide fixed 19 -our string wide fixed 18 -our strin wide fixed 17 -our stri wide fixed 16 -our stri wide fixe 15 -our str wide fixe 14 -our str wid fixe 13 -our str wid fix 12 -ou str wid fix 11 -ou st wid fix 10 -ou st wi fix 9 -ou st wi fi 8 -Final file name: oustwifi.adb -@end smallexample +Assume no invalid (bad) values except for 'Valid attribute use +(@ref{fb,,Validity Checking}). +@end table -@item -The file names for all predefined units are always krunched to eight -characters. The krunching of these predefined units uses the following -special prefix replacements: +@geindex -gnatc (gcc) -@table @file -@item ada- -replaced by @file{a-} -@item gnat- -replaced by @file{g-} +@table @asis -@item interfaces- -replaced by @file{i-} +@item @code{-gnatc} -@item system- -replaced by @file{s-} +Check syntax and semantics only (no code generation attempted). When the +compiler is invoked by @emph{gnatmake}, if the switch @emph{-gnatc} is +only given to the compiler (after @emph{-cargs} or in package Compiler of +the project file, @emph{gnatmake} will fail because it will not find the +object file after compilation. If @emph{gnatmake} is called with +@emph{-gnatc} as a builder switch (before @emph{-cargs} or in package +Builder of the project file) then @emph{gnatmake} will not fail because +it will not look for the object files after compilation, and it will not try +to build and link. This switch may not be given if a previous @cite{-gnatR} +switch has been given, since @cite{-gnatR} requires that the code generator +be called to complete determination of representation information. @end table -These system files have a hyphen in the second character position. That -is why normal user files replace such a character with a -tilde, to -avoid confusion with system file names. +@geindex -gnatC (gcc) -As an example of this special rule, consider -@*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows: -@smallexample -ada-strings-wide_fixed 22 -a- strings wide fixed 18 -a- string wide fixed 17 -a- strin wide fixed 16 -a- stri wide fixed 15 -a- stri wide fixe 14 -a- str wide fixe 13 -a- str wid fixe 12 -a- str wid fix 11 -a- st wid fix 10 -a- st wi fix 9 -a- st wi fi 8 -Final file name: a-stwifi.adb -@end smallexample -@end itemize +@table @asis -Of course no file shortening algorithm can guarantee uniqueness over all -possible unit names, and if file name krunching is used then it is your -responsibility to ensure that no name clashes occur. The utility -program @code{gnatkr} is supplied for conveniently determining the -krunched name of a file. +@item @code{-gnatC} -@node Examples of gnatkr Usage -@section Examples of @code{gnatkr} Usage +Generate CodePeer intermediate format (no code generation attempted). +This switch will generate an intermediate representation suitable for +use by CodePeer (@code{.scil} files). This switch is not compatible with +code generation (it will, among other things, disable some switches such +as -gnatn, and enable others such as -gnata). +@end table -@smallexample -@iftex -@leftskip=0cm -@end iftex -$ gnatkr very_long_unit_name.ads --> velounna.ads -$ gnatkr grandparent-parent-child.ads --> grparchi.ads -$ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads -$ gnatkr grandparent-parent-child --> grparchi -$ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads -$ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads -@end smallexample +@geindex -gnatd (gcc) -@node Preprocessing with gnatprep -@chapter Preprocessing with @code{gnatprep} -@findex gnatprep -@noindent -This chapter discusses how to use GNAT's @code{gnatprep} utility for simple -preprocessing. -Although designed for use with GNAT, @code{gnatprep} does not depend on any -special GNAT features. -For further discussion of conditional compilation in general, see -@ref{Conditional Compilation}. +@table @asis -@menu -* Preprocessing Symbols:: -* Using gnatprep:: -* Switches for gnatprep:: -* Form of Definitions File:: -* Form of Input Text for gnatprep:: -@end menu +@item @code{-gnatd} -@node Preprocessing Symbols -@section Preprocessing Symbols +Specify debug options for the compiler. The string of characters after +the @emph{-gnatd} specify the specific debug options. The possible +characters are 0-9, a-z, A-Z, optionally preceded by a dot. See +compiler source file @code{debug.adb} for details of the implemented +debug options. Certain debug options are relevant to applications +programmers, and these are documented at appropriate points in this +users guide. +@end table -@noindent -Preprocessing symbols are defined in definition files and referred to in -sources to be preprocessed. A Preprocessing symbol is an identifier, following -normal Ada (case-insensitive) rules for its syntax, with the restriction that -all characters need to be in the ASCII set (no accented letters). +@geindex -gnatD[nn] (gcc) -@node Using gnatprep -@section Using @code{gnatprep} -@noindent -To call @code{gnatprep} use +@table @asis -@smallexample -@c $ gnatprep @ovar{switches} @var{infile} @var{outfile} @ovar{deffile} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatprep @r{[}@var{switches}@r{]} @var{infile} @var{outfile} @r{[}@var{deffile}@r{]} -@end smallexample +@item @code{-gnatD} -@noindent -where -@table @var -@item switches -is an optional sequence of switches as described in the next section. +Create expanded source files for source level debugging. This switch +also suppress generation of cross-reference information +(see @emph{-gnatx}). Note that this switch is not allowed if a previous +-gnatR switch has been given, since these two switches are not compatible. +@end table -@item infile -is the full name of the input file, which is an Ada source -file containing preprocessor directives. +@geindex -gnateA (gcc) -@item outfile -is the full name of the output file, which is an Ada source -in standard Ada form. When used with GNAT, this file name will -normally have an ads or adb suffix. -@item deffile -is the full name of a text file containing definitions of -preprocessing symbols to be referenced by the preprocessor. This argument is -optional, and can be replaced by the use of the @option{-D} switch. +@table @asis -@end table +@item @code{-gnateA} -@node Switches for gnatprep -@section Switches for @code{gnatprep} +Check that the actual parameters of a subprogram call are not aliases of one +another. To qualify as aliasing, the actuals must denote objects of a composite +type, their memory locations must be identical or overlapping, and at least one +of the corresponding formal parameters must be of mode OUT or IN OUT. -@table @option -@c !sort! +@example +type Rec_Typ is record + Data : Integer := 0; +end record; -@item -b -@cindex @option{-b} (@command{gnatprep}) -Causes both preprocessor lines and the lines deleted by -preprocessing to be replaced by blank lines in the output source file, -preserving line numbers in the output file. +function Self (Val : Rec_Typ) return Rec_Typ is +begin + return Val; +end Self; -@item -c -@cindex @option{-c} (@command{gnatprep}) -Causes both preprocessor lines and the lines deleted -by preprocessing to be retained in the output source as comments marked -with the special string @code{"--! "}. This option will result in line numbers -being preserved in the output file. +procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is +begin + null; +end Detect_Aliasing; -@item -C -@cindex @option{-C} (@command{gnatprep}) -Causes comments to be scanned. Normally comments are ignored by gnatprep. -If this option is specified, then comments are scanned and any $symbol -substitutions performed as in program text. This is particularly useful -when structured comments are used (e.g., when writing programs in the -SPARK dialect of Ada). Note that this switch is not available when -doing integrated preprocessing (it would be useless in this context -since comments are ignored by the compiler in any case). +Obj : Rec_Typ; -@item -Dsymbol=value -@cindex @option{-D} (@command{gnatprep}) -Defines a new preprocessing symbol, associated with value. If no value is given -on the command line, then symbol is considered to be @code{True}. This switch -can be used in place of a definition file. +Detect_Aliasing (Obj, Obj); +Detect_Aliasing (Obj, Self (Obj)); +@end example +In the example above, the first call to @cite{Detect_Aliasing} fails with a +@cite{Program_Error} at runtime because the actuals for @cite{Val_1} and +@cite{Val_2} denote the same object. The second call executes without raising +an exception because @cite{Self(Obj)} produces an anonymous object which does +not share the memory location of @cite{Obj}. +@end table -@item -r -@cindex @option{-r} (@command{gnatprep}) -Causes a @code{Source_Reference} pragma to be generated that -references the original input file, so that error messages will use -the file name of this original file. The use of this switch implies -that preprocessor lines are not to be removed from the file, so its -use will force @option{-b} mode if -@option{-c} -has not been specified explicitly. +@geindex -gnatec (gcc) -Note that if the file to be preprocessed contains multiple units, then -it will be necessary to @code{gnatchop} the output file from -@code{gnatprep}. If a @code{Source_Reference} pragma is present -in the preprocessed file, it will be respected by -@code{gnatchop -r} -so that the final chopped files will correctly refer to the original -input source file for @code{gnatprep}. -@item -s -@cindex @option{-s} (@command{gnatprep}) -Causes a sorted list of symbol names and values to be -listed on the standard output file. +@table @asis -@item -u -@cindex @option{-u} (@command{gnatprep}) -Causes undefined symbols to be treated as having the value FALSE in the context -of a preprocessor test. In the absence of this option, an undefined symbol in -a @code{#if} or @code{#elsif} test will be treated as an error. +@item @code{-gnatec=@emph{path}} +Specify a configuration pragma file +(the equal sign is optional) +(@ref{7b,,The Configuration Pragmas Files}). @end table -@noindent -Note: if neither @option{-b} nor @option{-c} is present, -then preprocessor lines and -deleted lines are completely removed from the output, unless -r is -specified, in which case -b is assumed. +@geindex -gnateC (gcc) -@node Form of Definitions File -@section Form of Definitions File -@noindent -The definitions file contains lines of the form +@table @asis -@smallexample -symbol := value -@end smallexample +@item @code{-gnateC} -@noindent -where symbol is a preprocessing symbol, and value is one of the following: +Generate CodePeer messages in a compiler-like format. This switch is only +effective if @emph{-gnatcC} is also specified and requires an installation +of CodePeer. +@end table -@itemize @bullet -@item -Empty, corresponding to a null substitution -@item -A string literal using normal Ada syntax -@item -Any sequence of characters from the set -(letters, digits, period, underline). -@end itemize +@geindex -gnated (gcc) -@noindent -Comment lines may also appear in the definitions file, starting with -the usual @code{--}, -and comments may be added to the definitions lines. -@node Form of Input Text for gnatprep -@section Form of Input Text for @code{gnatprep} +@table @asis -@noindent -The input text may contain preprocessor conditional inclusion lines, -as well as general symbol substitution sequences. +@item @code{-gnated} -The preprocessor conditional inclusion commands have the form +Disable atomic synchronization +@end table -@smallexample -@group -@cartouche -#if @i{expression} @r{[}then@r{]} - lines -#elsif @i{expression} @r{[}then@r{]} - lines -#elsif @i{expression} @r{[}then@r{]} - lines -@dots{} -#else - lines -#end if; -@end cartouche -@end group -@end smallexample - -@noindent -In this example, @i{expression} is defined by the following grammar: -@smallexample -@i{expression} ::= -@i{expression} ::= = "" -@i{expression} ::= = -@i{expression} ::= = -@i{expression} ::= > -@i{expression} ::= >= -@i{expression} ::= < -@i{expression} ::= <= -@i{expression} ::= 'Defined -@i{expression} ::= not @i{expression} -@i{expression} ::= @i{expression} and @i{expression} -@i{expression} ::= @i{expression} or @i{expression} -@i{expression} ::= @i{expression} and then @i{expression} -@i{expression} ::= @i{expression} or else @i{expression} -@i{expression} ::= ( @i{expression} ) -@end smallexample - -The following restriction exists: it is not allowed to have "and" or "or" -following "not" in the same expression without parentheses. For example, this -is not allowed: +@geindex -gnateD (gcc) -@smallexample - not X or Y -@end smallexample -This should be one of the following: +@table @asis -@smallexample - (not X) or Y - not (X or Y) -@end smallexample +@item @code{-gnateDsymbol[=@emph{value}]} -@noindent -For the first test (@i{expression} ::= ) the symbol must have -either the value true or false, that is to say the right-hand of the -symbol definition must be one of the (case-insensitive) literals -@code{True} or @code{False}. If the value is true, then the -corresponding lines are included, and if the value is false, they are -excluded. +Defines a symbol, associated with @cite{value}, for preprocessing. +(@ref{1a,,Integrated Preprocessing}). +@end table -When comparing a symbol to an integer, the integer is any non negative -literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or -2#11#. The symbol value must also be a non negative integer. Integer values -in the range 0 .. 2**31-1 are supported. +@geindex -gnateE (gcc) -The test (@i{expression} ::= @code{'Defined}) is true only if -the symbol has been defined in the definition file or by a @option{-D} -switch on the command line. Otherwise, the test is false. -The equality tests are case insensitive, as are all the preprocessor lines. +@table @asis -If the symbol referenced is not defined in the symbol definitions file, -then the effect depends on whether or not switch @option{-u} -is specified. If so, then the symbol is treated as if it had the value -false and the test fails. If this switch is not specified, then -it is an error to reference an undefined symbol. It is also an error to -reference a symbol that is defined with a value other than @code{True} -or @code{False}. +@item @code{-gnateE} -The use of the @code{not} operator inverts the sense of this logical test. -The @code{not} operator cannot be combined with the @code{or} or @code{and} -operators, without parentheses. For example, "if not X or Y then" is not -allowed, but "if (not X) or Y then" and "if not (X or Y) then" are. +Generate extra information in exception messages. In particular, display +extra column information and the value and range associated with index and +range check failures, and extra column information for access checks. +In cases where the compiler is able to determine at compile time that +a check will fail, it gives a warning, and the extra information is not +produced at run time. +@end table -The @code{then} keyword is optional as shown +@geindex -gnatef (gcc) -The @code{#} must be the first non-blank character on a line, but -otherwise the format is free form. Spaces or tabs may appear between -the @code{#} and the keyword. The keywords and the symbols are case -insensitive as in normal Ada code. Comments may be used on a -preprocessor line, but other than that, no other tokens may appear on a -preprocessor line. Any number of @code{elsif} clauses can be present, -including none at all. The @code{else} is optional, as in Ada. -The @code{#} marking the start of a preprocessor line must be the first -non-blank character on the line, i.e., it must be preceded only by -spaces or horizontal tabs. +@table @asis -Symbol substitution outside of preprocessor lines is obtained by using -the sequence +@item @code{-gnatef} -@smallexample -$symbol -@end smallexample +Display full source path name in brief error messages. +@end table -@noindent -anywhere within a source line, except in a comment or within a -string literal. The identifier -following the @code{$} must match one of the symbols defined in the symbol -definition file, and the result is to substitute the value of the -symbol in place of @code{$symbol} in the output file. +@geindex -gnateF (gcc) -Note that although the substitution of strings within a string literal -is not possible, it is possible to have a symbol whose defined value is -a string literal. So instead of setting XYZ to @code{hello} and writing: -@smallexample -Header : String := "$XYZ"; -@end smallexample +@table @asis -@noindent -you should set XYZ to @code{"hello"} and write: +@item @code{-gnateF} -@smallexample -Header : String := $XYZ; -@end smallexample +Check for overflow on all floating-point operations, including those +for unconstrained predefined types. See description of pragma +@cite{Check_Float_Overflow} in GNAT RM. +@end table -@noindent -and then the substitution will occur as desired. +@geindex -gnateG (gcc) -@node The GNAT Library Browser gnatls -@chapter The GNAT Library Browser @code{gnatls} -@findex gnatls -@cindex Library browser -@noindent -@code{gnatls} is a tool that outputs information about compiled -units. It gives the relationship between objects, unit names and source -files. It can also be used to check the source dependencies of a unit -as well as various characteristics. +@table @asis -Note: to invoke @code{gnatls} with a project file, use the @code{gnat} -driver (see @ref{The GNAT Driver and Project Files}). +@item @code{-gnateG} -@menu -* Running gnatls:: -* Switches for gnatls:: -* Examples of gnatls Usage:: -@end menu +Save result of preprocessing in a text file. +@end table -@node Running gnatls -@section Running @code{gnatls} +@geindex -gnatei (gcc) -@noindent -The @code{gnatls} command has the form -@smallexample -$ gnatls switches @var{object_or_ali_file} -@end smallexample +@table @asis -@noindent -The main argument is the list of object or @file{ali} files -(@pxref{The Ada Library Information Files}) -for which information is requested. +@item @code{-gnatei@emph{nnn}} -In normal mode, without additional option, @code{gnatls} produces a -four-column listing. Each line represents information for a specific -object. The first column gives the full path of the object, the second -column gives the name of the principal unit in this object, the third -column gives the status of the source and the fourth column gives the -full path of the source representing this unit. -Here is a simple example of use: +Set maximum number of instantiations during compilation of a single unit to +@cite{nnn}. This may be useful in increasing the default maximum of 8000 for +the rare case when a single unit legitimately exceeds this limit. +@end table -@smallexample -$ gnatls *.o -./demo1.o demo1 DIF demo1.adb -./demo2.o demo2 OK demo2.adb -./hello.o h1 OK hello.adb -./instr-child.o instr.child MOK instr-child.adb -./instr.o instr OK instr.adb -./tef.o tef DIF tef.adb -./text_io_example.o text_io_example OK text_io_example.adb -./tgef.o tgef DIF tgef.adb -@end smallexample +@geindex -gnateI (gcc) -@noindent -The first line can be interpreted as follows: the main unit which is -contained in -object file @file{demo1.o} is demo1, whose main source is in -@file{demo1.adb}. Furthermore, the version of the source used for the -compilation of demo1 has been modified (DIF). Each source file has a status -qualifier which can be: -@table @code -@item OK (unchanged) -The version of the source file used for the compilation of the -specified unit corresponds exactly to the actual source file. +@table @asis -@item MOK (slightly modified) -The version of the source file used for the compilation of the -specified unit differs from the actual source file but not enough to -require recompilation. If you use gnatmake with the qualifier -@option{-m (minimal recompilation)}, a file marked -MOK will not be recompiled. +@item @code{-gnateI@emph{nnn}} -@item DIF (modified) -No version of the source found on the path corresponds to the source -used to build this object. +Indicates that the source is a multi-unit source and that the index of the +unit to compile is @cite{nnn}. @cite{nnn} needs to be a positive number and need +to be a valid index in the multi-unit source. +@end table -@item ??? (file not found) -No source file was found for this unit. +@geindex -gnatel (gcc) -@item HID (hidden, unchanged version not first on PATH) -The version of the source that corresponds exactly to the source used -for compilation has been found on the path but it is hidden by another -version of the same source that has been modified. -@end table +@table @asis -@node Switches for gnatls -@section Switches for @code{gnatls} +@item @code{-gnatel} -@noindent -@code{gnatls} recognizes the following switches: +This switch can be used with the static elaboration model to issue info +messages showing +where implicit @cite{pragma Elaborate} and @cite{pragma Elaborate_All} +are generated. This is useful in diagnosing elaboration circularities +caused by these implicit pragmas when using the static elaboration +model. See See the section in this guide on elaboration checking for +further details. These messages are not generated by default, and are +intended only for temporary use when debugging circularity problems. +@end table -@table @option -@c !sort! -@cindex @option{--version} @command{gnatls} -Display Copyright and version, then exit disregarding all other options. +@geindex -gnatel (gcc) -@item --help -@cindex @option{--help} @command{gnatls} -If @option{--version} was not used, display usage, then exit disregarding -all other options. -@item -a -@cindex @option{-a} (@code{gnatls}) -Consider all units, including those of the predefined Ada library. -Especially useful with @option{-d}. +@table @asis -@item -d -@cindex @option{-d} (@code{gnatls}) -List sources from which specified units depend on. +@item @code{-gnateL} -@item -h -@cindex @option{-h} (@code{gnatls}) -Output the list of options. +This switch turns off the info messages about implicit elaboration pragmas. +@end table -@item -o -@cindex @option{-o} (@code{gnatls}) -Only output information about object files. +@geindex -gnatem (gcc) -@item -s -@cindex @option{-s} (@code{gnatls}) -Only output information about source files. -@item -u -@cindex @option{-u} (@code{gnatls}) -Only output information about compilation units. +@table @asis -@item -files=@var{file} -@cindex @option{-files} (@code{gnatls}) -Take as arguments the files listed in text file @var{file}. -Text file @var{file} may contain empty lines that are ignored. -Each nonempty line should contain the name of an existing file. -Several such switches may be specified simultaneously. +@item @code{-gnatem=@emph{path}} -@item -aO@var{dir} -@itemx -aI@var{dir} -@itemx -I@var{dir} -@itemx -I- -@itemx -nostdinc -@cindex @option{-aO} (@code{gnatls}) -@cindex @option{-aI} (@code{gnatls}) -@cindex @option{-I} (@code{gnatls}) -@cindex @option{-I-} (@code{gnatls}) -Source path manipulation. Same meaning as the equivalent @command{gnatmake} -flags (@pxref{Switches for gnatmake}). - -@item -aP@var{dir} -@cindex @option{-aP} (@code{gnatls}) -Add @var{dir} at the beginning of the project search dir. - -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@code{gnatls}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). +Specify a mapping file +(the equal sign is optional) +(@ref{fc,,Units to Sources Mapping Files}). +@end table -@item -v -@cindex @option{-v} (@code{gnatls}) -Verbose mode. Output the complete source, object and project paths. Do not use -the default column layout but instead use long format giving as much as -information possible on each requested units, including special -characteristics such as: +@geindex -gnatep (gcc) -@table @code -@item Preelaborable -The unit is preelaborable in the Ada sense. -@item No_Elab_Code -No elaboration code has been produced by the compiler for this unit. +@table @asis -@item Pure -The unit is pure in the Ada sense. +@item @code{-gnatep=@emph{file}} -@item Elaborate_Body -The unit contains a pragma Elaborate_Body. +Specify a preprocessing data file +(the equal sign is optional) +(@ref{1a,,Integrated Preprocessing}). +@end table -@item Remote_Types -The unit contains a pragma Remote_Types. +@geindex -gnateP (gcc) -@item Shared_Passive -The unit contains a pragma Shared_Passive. -@item Predefined -This unit is part of the predefined environment and cannot be modified -by the user. +@table @asis -@item Remote_Call_Interface -The unit contains a pragma Remote_Call_Interface. +@item @code{-gnateP} +Turn categorization dependency errors into warnings. +Ada requires that units that WITH one another have compatible categories, for +example a Pure unit cannot WITH a Preelaborate unit. If this switch is used, +these errors become warnings (which can be ignored, or suppressed in the usual +manner). This can be useful in some specialized circumstances such as the +temporary use of special test software. @end table +@geindex -gnateS (gcc) + + +@table @asis + +@item @code{-gnateS} + +Synonym of @emph{-fdump-scos}, kept for backwards compatibility. @end table -@node Examples of gnatls Usage -@section Example of @code{gnatls} Usage +@geindex -gnatet=file (gcc) -@noindent -Example of using the verbose switch. Note how the source and -object paths are affected by the -I switch. -@smallexample -$ gnatls -v -I.. demo1.o +@table @asis -GNATLS 5.03w (20041123-34) -Copyright 1997-2004 Free Software Foundation, Inc. +@item @code{-gnatet=@emph{path}} -Source Search Path: - - ../ - /home/comar/local/adainclude/ +Generate target dependent information. The format of the output file is +described in the section about switch @emph{-gnateT}. +@end table -Object Search Path: - - ../ - /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/ +@geindex -gnateT (gcc) -Project Search Path: - - /home/comar/local/lib/gnat/ -./demo1.o - Unit => - Name => demo1 - Kind => subprogram body - Flags => No_Elab_Code - Source => demo1.adb modified -@end smallexample +@table @asis -@noindent -The following is an example of use of the dependency list. -Note the use of the -s switch -which gives a straight list of source files. This can be useful for -building specialized scripts. +@item @code{-gnateT=@emph{path}} -@smallexample -$ gnatls -d demo2.o -./demo2.o demo2 OK demo2.adb - OK gen_list.ads - OK gen_list.adb - OK instr.ads - OK instr-child.ads +Read target dependent information, such as endianness or sizes and alignments +of base type. If this switch is passed, the default target dependent +information of the compiler is replaced by the one read from the input file. +This is used by tools other than the compiler, e.g. to do +semantic analysis of programs that will run on some other target than +the machine on which the tool is run. -$ gnatls -d -s -a demo1.o -demo1.adb -/home/comar/local/adainclude/ada.ads -/home/comar/local/adainclude/a-finali.ads -/home/comar/local/adainclude/a-filico.ads -/home/comar/local/adainclude/a-stream.ads -/home/comar/local/adainclude/a-tags.ads -gen_list.ads -gen_list.adb -/home/comar/local/adainclude/gnat.ads -/home/comar/local/adainclude/g-io.ads -instr.ads -/home/comar/local/adainclude/system.ads -/home/comar/local/adainclude/s-exctab.ads -/home/comar/local/adainclude/s-finimp.ads -/home/comar/local/adainclude/s-finroo.ads -/home/comar/local/adainclude/s-secsta.ads -/home/comar/local/adainclude/s-stalib.ads -/home/comar/local/adainclude/s-stoele.ads -/home/comar/local/adainclude/s-stratt.ads -/home/comar/local/adainclude/s-tasoli.ads -/home/comar/local/adainclude/s-unstyp.ads -/home/comar/local/adainclude/unchconv.ads -@end smallexample +The following target dependent values should be defined, +where @cite{Nat} denotes a natural integer value, @cite{Pos} denotes a +positive integer value, and fields marked with a question mark are +boolean fields, where a value of 0 is False, and a value of 1 is True: +@example +Bits_BE : Nat; -- Bits stored big-endian? +Bits_Per_Unit : Pos; -- Bits in a storage unit +Bits_Per_Word : Pos; -- Bits in a word +Bytes_BE : Nat; -- Bytes stored big-endian? +Char_Size : Pos; -- Standard.Character'Size +Double_Float_Alignment : Nat; -- Alignment of double float +Double_Scalar_Alignment : Nat; -- Alignment of double length scalar +Double_Size : Pos; -- Standard.Long_Float'Size +Float_Size : Pos; -- Standard.Float'Size +Float_Words_BE : Nat; -- Float words stored big-endian? +Int_Size : Pos; -- Standard.Integer'Size +Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size +Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size +Long_Size : Pos; -- Standard.Long_Integer'Size +Maximum_Alignment : Pos; -- Maximum permitted alignment +Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field +Pointer_Size : Pos; -- System.Address'Size +Short_Enums : Nat; -- Short foreign convention enums? +Short_Size : Pos; -- Standard.Short_Integer'Size +Strict_Alignment : Nat; -- Strict alignment? +System_Allocator_Alignment : Nat; -- Alignment for malloc calls +Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size +Words_BE : Nat; -- Words stored big-endian? +@end example -@node Cleaning Up with gnatclean -@chapter Cleaning Up with @code{gnatclean} -@findex gnatclean -@cindex Cleaning tool +The format of the input file is as follows. First come the values of +the variables defined above, with one line per value: -@noindent -@code{gnatclean} is a tool that allows the deletion of files produced by the -compiler, binder and linker, including ALI files, object files, tree files, -expanded source files, library files, interface copy source files, binder -generated files and executable files. +@example +name value +@end example -@menu -* Running gnatclean:: -* Switches for gnatclean:: -@c * Examples of gnatclean Usage:: -@end menu +where @cite{name} is the name of the parameter, spelled out in full, +and cased as in the above list, and @cite{value} is an unsigned decimal +integer. Two or more blanks separates the name from the value. -@node Running gnatclean -@section Running @code{gnatclean} +All the variables must be present, in alphabetical order (i.e. the +same order as the list above). -@noindent -The @code{gnatclean} command has the form: +Then there is a blank line to separate the two parts of the file. Then +come the lines showing the floating-point types to be registered, with +one line per registered mode: -@smallexample -$ gnatclean switches @var{names} -@end smallexample +@example +name digs float_rep size alignment +@end example -@noindent -@var{names} is a list of source file names. Suffixes @code{.ads} and -@code{adb} may be omitted. If a project file is specified using switch -@code{-P}, then @var{names} may be completely omitted. +where @cite{name} is the string name of the type (which can have +single spaces embedded in the name (e.g. long double), @cite{digs} is +the number of digits for the floating-point type, @cite{float_rep} is +the float representation (I/V/A for IEEE-754-Binary, Vax_Native, +AAMP), @cite{size} is the size in bits, @cite{alignment} is the +alignment in bits. The name is followed by at least two blanks, fields +are separated by at least one blank, and a LF character immediately +follows the alignment field. -@noindent -In normal mode, @code{gnatclean} delete the files produced by the compiler and, -if switch @code{-c} is not specified, by the binder and -the linker. In informative-only mode, specified by switch -@code{-n}, the list of files that would have been deleted in -normal mode is listed, but no file is actually deleted. +Here is an example of a target parameterization file: -@node Switches for gnatclean -@section Switches for @code{gnatclean} +@example +Bits_BE 0 +Bits_Per_Unit 8 +Bits_Per_Word 64 +Bytes_BE 0 +Char_Size 8 +Double_Float_Alignment 0 +Double_Scalar_Alignment 0 +Double_Size 64 +Float_Size 32 +Float_Words_BE 0 +Int_Size 64 +Long_Double_Size 128 +Long_Long_Size 64 +Long_Size 64 +Maximum_Alignment 16 +Max_Unaligned_Field 64 +Pointer_Size 64 +Short_Size 16 +Strict_Alignment 0 +System_Allocator_Alignment 16 +Wchar_T_Size 32 +Words_BE 0 -@noindent -@code{gnatclean} recognizes the following switches: +float 15 I 64 64 +double 15 I 64 64 +long double 18 I 80 128 +TF 33 I 128 128 +@end example +@end table -@table @option -@c !sort! -@cindex @option{--version} @command{gnatclean} -Display Copyright and version, then exit disregarding all other options. +@geindex -gnateu (gcc) -@item --help -@cindex @option{--help} @command{gnatclean} -If @option{--version} was not used, display usage, then exit disregarding -all other options. -@item --subdirs=subdir -Actual object directory of each project file is the subdirectory subdir of the -object directory specified or defaulted in the project file. +@table @asis -@item --unchecked-shared-lib-imports -By default, shared library projects are not allowed to import static library -projects. When this switch is used on the command line, this restriction is -relaxed. +@item @code{-gnateu} -@item -c -@cindex @option{-c} (@code{gnatclean}) -Only attempt to delete the files produced by the compiler, not those produced -by the binder or the linker. The files that are not to be deleted are library -files, interface copy files, binder generated files and executable files. +Ignore unrecognized validity, warning, and style switches that +appear after this switch is given. This may be useful when +compiling sources developed on a later version of the compiler +with an earlier version. Of course the earlier version must +support this switch. +@end table -@item -D @var{dir} -@cindex @option{-D} (@code{gnatclean}) -Indicate that ALI and object files should normally be found in directory -@var{dir}. +@geindex -gnateV (gcc) -@item -F -@cindex @option{-F} (@code{gnatclean}) -When using project files, if some errors or warnings are detected during -parsing and verbose mode is not in effect (no use of switch --v), then error lines start with the full path name of the project -file, rather than its simple file name. -@item -h -@cindex @option{-h} (@code{gnatclean}) -Output a message explaining the usage of @code{gnatclean}. +@table @asis -@item -n -@cindex @option{-n} (@code{gnatclean}) -Informative-only mode. Do not delete any files. Output the list of the files -that would have been deleted if this switch was not specified. +@item @code{-gnateV} -@item -P@var{project} -@cindex @option{-P} (@code{gnatclean}) -Use project file @var{project}. Only one such switch can be used. -When cleaning a project file, the files produced by the compilation of the -immediate sources or inherited sources of the project files are to be -deleted. This is not depending on the presence or not of executable names -on the command line. +Check that all actual parameters of a subprogram call are valid according to +the rules of validity checking (@ref{fb,,Validity Checking}). +@end table -@item -q -@cindex @option{-q} (@code{gnatclean}) -Quiet output. If there are no errors, do not output anything, except in -verbose mode (switch -v) or in informative-only mode -(switch -n). +@geindex -gnateY (gcc) -@item -r -@cindex @option{-r} (@code{gnatclean}) -When a project file is specified (using switch -P), -clean all imported and extended project files, recursively. If this switch -is not specified, only the files related to the main project file are to be -deleted. This switch has no effect if no project file is specified. -@item -v -@cindex @option{-v} (@code{gnatclean}) -Verbose mode. +@table @asis -@item -vP@emph{x} -@cindex @option{-vP} (@code{gnatclean}) -Indicates the verbosity of the parsing of GNAT project files. -@xref{Switches Related to Project Files}. +@item @code{-gnateY} -@item -X@var{name=value} -@cindex @option{-X} (@code{gnatclean}) -Indicates that external variable @var{name} has the value @var{value}. -The Project Manager will use this value for occurrences of -@code{external(name)} when parsing the project file. -@xref{Switches Related to Project Files}. +Ignore all STYLE_CHECKS pragmas. Full legality checks +are still carried out, but the pragmas have no effect +on what style checks are active. This allows all style +checking options to be controlled from the command line. +@end table -@item -aO@var{dir} -@cindex @option{-aO} (@code{gnatclean}) -When searching for ALI and object files, look in directory -@var{dir}. +@geindex -gnatE (gcc) -@item -I@var{dir} -@cindex @option{-I} (@code{gnatclean}) -Equivalent to @option{-aO@var{dir}}. -@item -I- -@cindex @option{-I-} (@code{gnatclean}) -@cindex Source files, suppressing search -Do not look for ALI or object files in the directory -where @code{gnatclean} was invoked. +@table @asis +@item @code{-gnatE} + +Full dynamic elaboration checks. @end table -@c @node Examples of gnatclean Usage -@c @section Examples of @code{gnatclean} Usage +@geindex -gnatf (gcc) -@node GNAT and Libraries -@chapter GNAT and Libraries -@cindex Library, building, installing, using -@noindent -This chapter describes how to build and use libraries with GNAT, and also shows -how to recompile the GNAT run-time library. You should be familiar with the -Project Manager facility (@pxref{GNAT Project Manager}) before reading this -chapter. +@table @asis -@menu -* Introduction to Libraries in GNAT:: -* General Ada Libraries:: -* Stand-alone Ada Libraries:: -* Rebuilding the GNAT Run-Time Library:: -@end menu +@item @code{-gnatf} -@node Introduction to Libraries in GNAT -@section Introduction to Libraries in GNAT +Full errors. Multiple errors per line, all undefined references, do not +attempt to suppress cascaded errors. +@end table -@noindent -A library is, conceptually, a collection of objects which does not have its -own main thread of execution, but rather provides certain services to the -applications that use it. A library can be either statically linked with the -application, in which case its code is directly included in the application, -or, on platforms that support it, be dynamically linked, in which case -its code is shared by all applications making use of this library. +@geindex -gnatF (gcc) -GNAT supports both types of libraries. -In the static case, the compiled code can be provided in different ways. The -simplest approach is to provide directly the set of objects resulting from -compilation of the library source files. Alternatively, you can group the -objects into an archive using whatever commands are provided by the operating -system. For the latter case, the objects are grouped into a shared library. -In the GNAT environment, a library has three types of components: -@itemize @bullet -@item -Source files. -@item -@file{ALI} files. -@xref{The Ada Library Information Files}. -@item -Object files, an archive or a shared library. -@end itemize +@table @asis -@noindent -A GNAT library may expose all its source files, which is useful for -documentation purposes. Alternatively, it may expose only the units needed by -an external user to make use of the library. That is to say, the specs -reflecting the library services along with all the units needed to compile -those specs, which can include generic bodies or any body implementing an -inlined routine. In the case of @emph{stand-alone libraries} those exposed -units are called @emph{interface units} (@pxref{Stand-alone Ada Libraries}). +@item @code{-gnatF} -All compilation units comprising an application, including those in a library, -need to be elaborated in an order partially defined by Ada's semantics. GNAT -computes the elaboration order from the @file{ALI} files and this is why they -constitute a mandatory part of GNAT libraries. -@emph{Stand-alone libraries} are the exception to this rule because a specific -library elaboration routine is produced independently of the application(s) -using the library. +Externals names are folded to all uppercase. +@end table -@node General Ada Libraries -@section General Ada Libraries +@geindex -gnatg (gcc) -@menu -* Building a library:: -* Installing a library:: -* Using a library:: -@end menu -@node Building a library -@subsection Building a library +@table @asis -@noindent -The easiest way to build a library is to use the Project Manager, -which supports a special type of project called a @emph{Library Project} -(@pxref{Library Projects}). +@item @code{-gnatg} -A project is considered a library project, when two project-level attributes -are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to -control different aspects of library configuration, additional optional -project-level attributes can be specified: -@table @code -@item Library_Kind -This attribute controls whether the library is to be static or dynamic +Internal GNAT implementation mode. This should not be used for +applications programs, it is intended only for use by the compiler +and its run-time library. For documentation, see the GNAT sources. +Note that @emph{-gnatg} implies +@emph{-gnatw.ge} and +@emph{-gnatyg} +so that all standard warnings and all standard style options are turned on. +All warnings and style messages are treated as errors. +@end table -@item Library_Version -This attribute specifies the library version; this value is used -during dynamic linking of shared libraries to determine if the currently -installed versions of the binaries are compatible. +@geindex -gnatG[nn] (gcc) -@item Library_Options -@item Library_GCC -These attributes specify additional low-level options to be used during -library generation, and redefine the actual application used to generate -library. -@end table -@noindent -The GNAT Project Manager takes full care of the library maintenance task, -including recompilation of the source files for which objects do not exist -or are not up to date, assembly of the library archive, and installation of -the library (i.e., copying associated source, object and @file{ALI} files -to the specified location). +@table @asis -Here is a simple library project file: -@smallexample @c ada -project My_Lib @b{is} - @b{for} Source_Dirs @b{use} ("src1", "src2"); - @b{for} Object_Dir @b{use} "obj"; - @b{for} Library_Name @b{use} "mylib"; - @b{for} Library_Dir @b{use} "lib"; - @b{for} Library_Kind @b{use} "dynamic"; -@b{end} My_lib; -@end smallexample - -@noindent -and the compilation command to build and install the library: +@item @code{-gnatG=nn} -@smallexample @c ada - $ gnatmake -Pmy_lib -@end smallexample +List generated expanded code in source form. +@end table -@noindent -It is not entirely trivial to perform manually all the steps required to -produce a library. We recommend that you use the GNAT Project Manager -for this task. In special cases where this is not desired, the necessary -steps are discussed below. +@geindex -gnath (gcc) -There are various possibilities for compiling the units that make up the -library: for example with a Makefile (@pxref{Using the GNU make Utility}) or -with a conventional script. For simple libraries, it is also possible to create -a dummy main program which depends upon all the packages that comprise the -interface of the library. This dummy main program can then be given to -@command{gnatmake}, which will ensure that all necessary objects are built. -After this task is accomplished, you should follow the standard procedure -of the underlying operating system to produce the static or shared library. +@table @asis -Here is an example of such a dummy program: -@smallexample @c ada -@group -@b{with} My_Lib.Service1; -@b{with} My_Lib.Service2; -@b{with} My_Lib.Service3; -@b{procedure} My_Lib_Dummy @b{is} -@b{begin} - @b{null}; -@b{end}; -@end group -@end smallexample - -@noindent -Here are the generic commands that will build an archive or a shared library. +@item @code{-gnath} -@smallexample -# compiling the library -$ gnatmake -c my_lib_dummy.adb +Output usage information. The output is written to @code{stdout}. +@end table -# we don't need the dummy object itself -$ rm my_lib_dummy.o my_lib_dummy.ali +@geindex -gnati (gcc) -# create an archive with the remaining objects -$ ar rc libmy_lib.a *.o -# some systems may require "ranlib" to be run as well -# or create a shared library -$ gcc -shared -o libmy_lib.so *.o -# some systems may require the code to have been compiled with -fPIC +@table @asis -# remove the object files that are now in the library -$ rm *.o +@item @code{-gnati@emph{c}} -# Make the ALI files read-only so that gnatmake will not try to -# regenerate the objects that are in the library -$ chmod -w *.ali -@end smallexample +Identifier character set (@cite{c} = 1/2/3/4/8/9/p/f/n/w). +For details of the possible selections for @cite{c}, +see @ref{4a,,Character Set Control}. +@end table -@noindent -Please note that the library must have a name of the form @file{lib@var{xxx}.a} -or @file{lib@var{xxx}.so} (or @file{lib@var{xxx}.dll} on Windows) in order to -be accessed by the directive @option{-l@var{xxx}} at link time. +@geindex -gnatI (gcc) -@node Installing a library -@subsection Installing a library -@cindex @code{ADA_PROJECT_PATH} -@cindex @code{GPR_PROJECT_PATH} -@noindent -If you use project files, library installation is part of the library build -process (@pxref{Installing a library with project files}). +@table @asis -When project files are not an option, it is also possible, but not recommended, -to install the library so that the sources needed to use the library are on the -Ada source path and the ALI files & libraries be on the Ada Object path (see -@ref{Search Paths and the Run-Time Library (RTL)}. Alternatively, the system -administrator can place general-purpose libraries in the default compiler -paths, by specifying the libraries' location in the configuration files -@file{ada_source_path} and @file{ada_object_path}. These configuration files -must be located in the GNAT installation tree at the same place as the gcc spec -file. The location of the gcc spec file can be determined as follows: -@smallexample -$ gcc -v -@end smallexample +@item @code{-gnatI} -@noindent -The configuration files mentioned above have a simple format: each line -must contain one unique directory name. -Those names are added to the corresponding path -in their order of appearance in the file. The names can be either absolute -or relative; in the latter case, they are relative to where theses files -are located. +Ignore representation clauses. When this switch is used, +representation clauses are treated as comments. This is useful +when initially porting code where you want to ignore rep clause +problems, and also for compiling foreign code (particularly +for use with ASIS). The representation clauses that are ignored +are: enumeration_representation_clause, record_representation_clause, +and attribute_definition_clause for the following attributes: +Address, Alignment, Bit_Order, Component_Size, Machine_Radix, +Object_Size, Size, Small, Stream_Size, and Value_Size. +Note that this option should be used only for compiling -- the +code is likely to malfunction at run time. -The files @file{ada_source_path} and @file{ada_object_path} might not be -present in a -GNAT installation, in which case, GNAT will look for its run-time library in -the directories @file{adainclude} (for the sources) and @file{adalib} (for the -objects and @file{ALI} files). When the files exist, the compiler does not -look in @file{adainclude} and @file{adalib}, and thus the -@file{ada_source_path} file -must contain the location for the GNAT run-time sources (which can simply -be @file{adainclude}). In the same way, the @file{ada_object_path} file must -contain the location for the GNAT run-time objects (which can simply -be @file{adalib}). +Note that when @cite{-gnatct} is used to generate trees for input +into @cite{ASIS} tools, these representation clauses are removed +from the tree and ignored. This means that the tool will not see them. +@end table -You can also specify a new default path to the run-time library at compilation -time with the switch @option{--RTS=rts-path}. You can thus choose / change -the run-time library you want your program to be compiled with. This switch is -recognized by @command{gcc}, @command{gnatmake}, @command{gnatbind}, -@command{gnatls}, @command{gnatfind} and @command{gnatxref}. +@geindex -gnatjnn (gcc) -It is possible to install a library before or after the standard GNAT -library, by reordering the lines in the configuration files. In general, a -library must be installed before the GNAT library if it redefines -any part of it. -@node Using a library -@subsection Using a library +@table @asis -@noindent Once again, the project facility greatly simplifies the use of -libraries. In this context, using a library is just a matter of adding a -@code{with} clause in the user project. For instance, to make use of the -library @code{My_Lib} shown in examples in earlier sections, you can -write: +@item @code{-gnatj@emph{nn}} -@smallexample @c projectfile -@b{with} "my_lib"; -@b{project} My_Proj @b{is} - @dots{} -@b{end} My_Proj; -@end smallexample +Reformat error messages to fit on @cite{nn} character lines +@end table -Even if you have a third-party, non-Ada library, you can still use GNAT's -Project Manager facility to provide a wrapper for it. For example, the -following project, when @code{with}ed by your main project, will link with the -third-party library @file{liba.a}: - -@smallexample @c projectfile -@group -@b{project} Liba @b{is} - @b{for} Externally_Built @b{use} "true"; - @b{for} Source_Files @b{use} (); - @b{for} Library_Dir @b{use} "lib"; - @b{for} Library_Name @b{use} "a"; - @b{for} Library_Kind @b{use} "static"; -@b{end} Liba; -@end group -@end smallexample -This is an alternative to the use of @code{pragma Linker_Options}. It is -especially interesting in the context of systems with several interdependent -static libraries where finding a proper linker order is not easy and best be -left to the tools having visibility over project dependence information. +@geindex -gnatk (gcc) -@noindent -In order to use an Ada library manually, you need to make sure that this -library is on both your source and object path -(see @ref{Search Paths and the Run-Time Library (RTL)} -and @ref{Search Paths for gnatbind}). Furthermore, when the objects are grouped -in an archive or a shared library, you need to specify the desired -library at link time. -For example, you can use the library @file{mylib} installed in -@file{/dir/my_lib_src} and @file{/dir/my_lib_obj} with the following commands: +@table @asis -@smallexample -$ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \ - -largs -lmy_lib -@end smallexample +@item @code{-gnatk=@emph{n}} -@noindent -This can be expressed more simply: -@smallexample -$ gnatmake my_appl -@end smallexample -@noindent -when the following conditions are met: -@itemize @bullet -@item -@file{/dir/my_lib_src} has been added by the user to the environment -variable @env{ADA_INCLUDE_PATH}, or by the administrator to the file -@file{ada_source_path} -@item -@file{/dir/my_lib_obj} has been added by the user to the environment -variable @env{ADA_OBJECTS_PATH}, or by the administrator to the file -@file{ada_object_path} -@item -a pragma @code{Linker_Options} has been added to one of the sources. -For example: +Limit file names to @cite{n} (1-999) characters (@cite{k} = krunch). +@end table -@smallexample @c ada -@b{pragma} Linker_Options ("-lmy_lib"); -@end smallexample -@end itemize +@geindex -gnatl (gcc) -Note that you may also load a library dynamically at -run time given its filename, as illustrated in the GNAT @file{plugins} example -in the directory @file{share/examples/gnat/plugins} within the GNAT -install area. -@node Stand-alone Ada Libraries -@section Stand-alone Ada Libraries -@cindex Stand-alone library, building, using +@table @asis -@menu -* Introduction to Stand-alone Libraries:: -* Building a Stand-alone Library:: -* Creating a Stand-alone Library to be used in a non-Ada context:: -* Restrictions in Stand-alone Libraries:: -@end menu +@item @code{-gnatl} -@node Introduction to Stand-alone Libraries -@subsection Introduction to Stand-alone Libraries +Output full source listing with embedded error messages. +@end table -@noindent -A Stand-alone Library (abbreviated ``SAL'') is a library that contains the -necessary code to -elaborate the Ada units that are included in the library. In contrast with -an ordinary library, which consists of all sources, objects and @file{ALI} -files of the -library, a SAL may specify a restricted subset of compilation units -to serve as a library interface. In this case, the fully -self-sufficient set of files will normally consist of an objects -archive, the sources of interface units' specs, and the @file{ALI} -files of interface units. -If an interface spec contains a generic unit or an inlined subprogram, -the body's -source must also be provided; if the units that must be provided in the source -form depend on other units, the source and @file{ALI} files of those must -also be provided. +@geindex -gnatL (gcc) -The main purpose of a SAL is to minimize the recompilation overhead of client -applications when a new version of the library is installed. Specifically, -if the interface sources have not changed, client applications do not need to -be recompiled. If, furthermore, a SAL is provided in the shared form and its -version, controlled by @code{Library_Version} attribute, is not changed, -then the clients do not need to be relinked. -SALs also allow the library providers to minimize the amount of library source -text exposed to the clients. Such ``information hiding'' might be useful or -necessary for various reasons. +@table @asis -Stand-alone libraries are also well suited to be used in an executable whose -main routine is not written in Ada. +@item @code{-gnatL} -@node Building a Stand-alone Library -@subsection Building a Stand-alone Library +Used in conjunction with -gnatG or -gnatD to intersperse original +source lines (as comment lines with line numbers) in the expanded +source output. +@end table -@noindent -GNAT's Project facility provides a simple way of building and installing -stand-alone libraries; see @ref{Stand-alone Library Projects}. -To be a Stand-alone Library Project, in addition to the two attributes -that make a project a Library Project (@code{Library_Name} and -@code{Library_Dir}; see @ref{Library Projects}), the attribute -@code{Library_Interface} must be defined. For example: - -@smallexample @c projectfile -@group - @b{for} Library_Dir @b{use} "lib_dir"; - @b{for} Library_Name @b{use} "dummy"; - @b{for} Library_Interface @b{use} ("int1", "int1.child"); -@end group -@end smallexample - -@noindent -Attribute @code{Library_Interface} has a non-empty string list value, -each string in the list designating a unit contained in an immediate source -of the project file. +@geindex -gnatm (gcc) -When a Stand-alone Library is built, first the binder is invoked to build -a package whose name depends on the library name -(@file{b~dummy.ads/b} in the example above). -This binder-generated package includes initialization and -finalization procedures whose -names depend on the library name (@code{dummyinit} and @code{dummyfinal} -in the example -above). The object corresponding to this package is included in the library. -You must ensure timely (e.g., prior to any use of interfaces in the SAL) -calling of these procedures if a static SAL is built, or if a shared SAL -is built -with the project-level attribute @code{Library_Auto_Init} set to -@code{"false"}. +@table @asis -For a Stand-Alone Library, only the @file{ALI} files of the Interface Units -(those that are listed in attribute @code{Library_Interface}) are copied to -the Library Directory. As a consequence, only the Interface Units may be -imported from Ada units outside of the library. If other units are imported, -the binding phase will fail. +@item @code{-gnatm=@emph{n}} -@noindent -It is also possible to build an encapsulated library where not only -the code to elaborate and finalize the library is embedded but also -ensuring that the library is linked only against static -libraries. So an encapsulated library only depends on system -libraries, all other code, including the GNAT runtime, is embedded. To -build an encapsulated library the attribute -@code{Library_Standalone} must be set to @code{encapsulated}: - -@smallexample @c projectfile -@group - @b{for} Library_Dir @b{use} "lib_dir"; - @b{for} Library_Name @b{use} "dummy"; - @b{for} Library_Kind @b{use} "dynamic"; - @b{for} Library_Interface @b{use} ("int1", "int1.child"); - @b{for} Library_Standalone @b{use} "encapsulated"; -@end group -@end smallexample - -@noindent -The default value for this attribute is @code{standard} in which case -a stand-alone library is built. +Limit number of detected error or warning messages to @cite{n} +where @cite{n} is in the range 1..999999. The default setting if +no switch is given is 9999. If the number of warnings reaches this +limit, then a message is output and further warnings are suppressed, +but the compilation is continued. If the number of error messages +reaches this limit, then a message is output and the compilation +is abandoned. The equal sign here is optional. A value of zero +means that no limit applies. +@end table -The attribute @code{Library_Src_Dir} may be specified for a -Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a -single string value. Its value must be the path (absolute or relative to the -project directory) of an existing directory. This directory cannot be the -object directory or one of the source directories, but it can be the same as -the library directory. The sources of the Interface -Units of the library that are needed by an Ada client of the library will be -copied to the designated directory, called the Interface Copy directory. -These sources include the specs of the Interface Units, but they may also -include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always} -are used, or when there is a generic unit in the spec. Before the sources -are copied to the Interface Copy directory, an attempt is made to delete all -files in the Interface Copy directory. +@geindex -gnatn (gcc) -Building stand-alone libraries by hand is somewhat tedious, but for those -occasions when it is necessary here are the steps that you need to perform: -@itemize @bullet -@item -Compile all library sources. -@item -Invoke the binder with the switch @option{-n} (No Ada main program), -with all the @file{ALI} files of the interfaces, and -with the switch @option{-L} to give specific names to the @code{init} -and @code{final} procedures. For example: -@smallexample - gnatbind -n int1.ali int2.ali -Lsal1 -@end smallexample +@table @asis -@item -Compile the binder generated file: -@smallexample - gcc -c b~int2.adb -@end smallexample +@item @code{-gnatn[12]} -@item -Link the dynamic library with all the necessary object files, -indicating to the linker the names of the @code{init} (and possibly -@code{final}) procedures for automatic initialization (and finalization). -The built library should be placed in a directory different from -the object directory. +Activate inlining for subprograms for which pragma @cite{Inline} is +specified. This inlining is performed by the GCC back-end. An optional +digit sets the inlining level: 1 for moderate inlining across modules +or 2 for full inlining across modules. If no inlining level is specified, +the compiler will pick it based on the optimization level. +@end table -@item -Copy the @code{ALI} files of the interface to the library directory, -add in this copy an indication that it is an interface to a SAL -(i.e., add a word @option{SL} on the line in the @file{ALI} file that starts -with letter ``P'') and make the modified copy of the @file{ALI} file -read-only. -@end itemize +@geindex -gnatN (gcc) -@noindent -Using SALs is not different from using other libraries -(see @ref{Using a library}). -@node Creating a Stand-alone Library to be used in a non-Ada context -@subsection Creating a Stand-alone Library to be used in a non-Ada context +@table @asis -@noindent -It is easy to adapt the SAL build procedure discussed above for use of a SAL in -a non-Ada context. +@item @code{-gnatN} -The only extra step required is to ensure that library interface subprograms -are compatible with the main program, by means of @code{pragma Export} -or @code{pragma Convention}. +Activate front end inlining for subprograms for which +pragma @cite{Inline} is specified. This inlining is performed +by the front end and will be visible in the +@emph{-gnatG} output. -Here is an example of simple library interface for use with C main program: +When using a gcc-based back end (in practice this means using any version +of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of +@emph{-gnatN} is deprecated, and the use of @emph{-gnatn} is preferred. +Historically front end inlining was more extensive than the gcc back end +inlining, but that is no longer the case. +@end table -@smallexample @c ada -@b{package} My_Package @b{is} +@geindex -gnato0 (gcc) - @b{procedure} Do_Something; - @b{pragma} Export (C, Do_Something, "do_something"); - @b{procedure} Do_Something_Else; - @b{pragma} Export (C, Do_Something_Else, "do_something_else"); +@table @asis -@b{end} My_Package; -@end smallexample +@item @code{-gnato0} -@noindent -On the foreign language side, you must provide a ``foreign'' view of the -library interface; remember that it should contain elaboration routines in -addition to interface subprograms. +Suppresses overflow checking. This causes the behavior of the compiler to +match the default for older versions where overflow checking was suppressed +by default. This is equivalent to having +@cite{pragma Suppress (Overflow_Mode)} in a configuration pragma file. +@end table -The example below shows the content of @code{mylib_interface.h} (note -that there is no rule for the naming of this file, any name can be used) -@smallexample -/* the library elaboration procedure */ -extern void mylibinit (void); +@geindex -gnato?? (gcc) -/* the library finalization procedure */ -extern void mylibfinal (void); -/* the interface exported by the library */ -extern void do_something (void); -extern void do_something_else (void); -@end smallexample +@table @asis -@noindent -Libraries built as explained above can be used from any program, provided -that the elaboration procedures (named @code{mylibinit} in the previous -example) are called before the library services are used. Any number of -libraries can be used simultaneously, as long as the elaboration -procedure of each library is called. +@item @code{-gnato??} -Below is an example of a C program that uses the @code{mylib} library. +Set default mode for handling generation of code to avoid intermediate +arithmetic overflow. Here @cite{??} is two digits, a +single digit, or nothing. Each digit is one of the digits @cite{1} +through @cite{3}: -@smallexample -#include "mylib_interface.h" -int -main (void) -@{ - /* First, elaborate the library before using it */ - mylibinit (); +@multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item - /* Main program, using the library exported entities */ - do_something (); - do_something_else (); +Digit - /* Library finalization at the end of the program */ - mylibfinal (); - return 0; -@} -@end smallexample +@tab -@noindent -Note that invoking any library finalization procedure generated by -@code{gnatbind} shuts down the Ada run-time environment. -Consequently, the -finalization of all Ada libraries must be performed at the end of the program. -No call to these libraries or to the Ada run-time library should be made -after the finalization phase. +Interpretation -@noindent -Note also that special care must be taken with multi-tasks -applications. The initialization and finalization routines are not -protected against concurrent access. If such requirement is needed it -must be ensured at the application level using a specific operating -system services like a mutex or a critical-section. +@item -@node Restrictions in Stand-alone Libraries -@subsection Restrictions in Stand-alone Libraries +@emph{1} -@noindent -The pragmas listed below should be used with caution inside libraries, -as they can create incompatibilities with other Ada libraries: -@itemize @bullet -@item pragma @code{Locking_Policy} -@item pragma @code{Partition_Elaboration_Policy} -@item pragma @code{Queuing_Policy} -@item pragma @code{Task_Dispatching_Policy} -@item pragma @code{Unreserve_All_Interrupts} -@end itemize +@tab -@noindent -When using a library that contains such pragmas, the user must make sure -that all libraries use the same pragmas with the same values. Otherwise, -@code{Program_Error} will -be raised during the elaboration of the conflicting -libraries. The usage of these pragmas and its consequences for the user -should therefore be well documented. +All intermediate overflows checked against base type (@cite{STRICT}) -Similarly, the traceback in the exception occurrence mechanism should be -enabled or disabled in a consistent manner across all libraries. -Otherwise, Program_Error will be raised during the elaboration of the -conflicting libraries. +@item -If the @code{Version} or @code{Body_Version} -attributes are used inside a library, then you need to -perform a @code{gnatbind} step that specifies all @file{ALI} files in all -libraries, so that version identifiers can be properly computed. -In practice these attributes are rarely used, so this is unlikely -to be a consideration. +@emph{2} -@node Rebuilding the GNAT Run-Time Library -@section Rebuilding the GNAT Run-Time Library -@cindex GNAT Run-Time Library, rebuilding -@cindex Building the GNAT Run-Time Library -@cindex Rebuilding the GNAT Run-Time Library -@cindex Run-Time Library, rebuilding +@tab -@noindent -It may be useful to recompile the GNAT library in various contexts, the -most important one being the use of partition-wide configuration pragmas -such as @code{Normalize_Scalars}. A special Makefile called -@code{Makefile.adalib} is provided to that effect and can be found in -the directory containing the GNAT library. The location of this -directory depends on the way the GNAT environment has been installed and can -be determined by means of the command: +Minimize intermediate overflows (@cite{MINIMIZED}) -@smallexample -$ gnatls -v -@end smallexample +@item -@noindent -The last entry in the object search path usually contains the -gnat library. This Makefile contains its own documentation and in -particular the set of instructions needed to rebuild a new library and -to use it. +@emph{3} -@node Using the GNU make Utility -@chapter Using the GNU @code{make} Utility -@findex make +@tab -@noindent -This chapter offers some examples of makefiles that solve specific -problems. It does not explain how to write a makefile (@pxref{Top,, GNU -make, make, GNU @code{make}}), nor does it try to replace the -@command{gnatmake} utility (@pxref{The GNAT Make Program gnatmake}). +Eliminate intermediate overflows (@cite{ELIMINATED}) -All the examples in this section are specific to the GNU version of -make. Although @command{make} is a standard utility, and the basic language -is the same, these examples use some advanced features found only in -@code{GNU make}. +@end multitable -@menu -* Using gnatmake in a Makefile:: -* Automatically Creating a List of Directories:: -* Generating the Command Line Switches:: -* Overcoming Command Line Length Limits:: -@end menu -@node Using gnatmake in a Makefile -@section Using gnatmake in a Makefile -@findex makefile -@cindex GNU make +If only one digit appears then it applies to all +cases; if two digits are given, then the first applies outside +assertions, and the second within assertions. -@noindent -Complex project organizations can be handled in a very powerful way by -using GNU make combined with gnatmake. For instance, here is a Makefile -which allows you to build each subsystem of a big project into a separate -shared library. Such a makefile allows you to significantly reduce the link -time of very big applications while maintaining full coherence at -each step of the build process. +If no digits follow the @emph{-gnato}, then it is equivalent to +@emph{-gnato11}, +causing all intermediate overflows to be handled in strict mode. -The list of dependencies are handled automatically by -@command{gnatmake}. The Makefile is simply used to call gnatmake in each of -the appropriate directories. +This switch also causes arithmetic overflow checking to be performed +(as though @cite{pragma Unsuppress (Overflow_Mode)} had been specified. -Note that you should also read the example on how to automatically -create the list of directories -(@pxref{Automatically Creating a List of Directories}) -which might help you in case your project has a lot of subdirectories. +The default if no option @emph{-gnato} is given is that overflow handling +is in @cite{STRICT} mode (computations done using the base type), and that +overflow checking is enabled. -@smallexample -@iftex -@leftskip=0cm -@font@heightrm=cmr8 -@heightrm -@end iftex -## This Makefile is intended to be used with the following directory -## configuration: -## - The sources are split into a series of csc (computer software components) -## Each of these csc is put in its own directory. -## Their name are referenced by the directory names. -## They will be compiled into shared library (although this would also work -## with static libraries -## - The main program (and possibly other packages that do not belong to any -## csc is put in the top level directory (where the Makefile is). -## toplevel_dir __ first_csc (sources) __ lib (will contain the library) -## \_ second_csc (sources) __ lib (will contain the library) -## \_ @dots{} -## Although this Makefile is build for shared library, it is easy to modify -## to build partial link objects instead (modify the lines with -shared and -## gnatlink below) -## -## With this makefile, you can change any file in the system or add any new -## file, and everything will be recompiled correctly (only the relevant shared -## objects will be recompiled, and the main program will be re-linked). +Note that division by zero is a separate check that is not +controlled by this switch (division by zero checking is on by default). -# The list of computer software component for your project. This might be -# generated automatically. -CSC_LIST=aa bb cc +See also @ref{fd,,Specifying the Desired Mode}. +@end table -# Name of the main program (no extension) -MAIN=main +@geindex -gnatp (gcc) -# If we need to build objects with -fPIC, uncomment the following line -#NEED_FPIC=-fPIC -# The following variable should give the directory containing libgnat.so -# You can get this directory through 'gnatls -v'. This is usually the last -# directory in the Object_Path. -GLIB=@dots{} +@table @asis -# The directories for the libraries -# (This macro expands the list of CSC to the list of shared libraries, you -# could simply use the expanded form: -# LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so -LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@} +@item @code{-gnatp} -$@{MAIN@}: objects $@{LIB_DIR@} - gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared - gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@} +Suppress all checks. See @ref{fe,,Run-Time Checks} for details. This switch +has no effect if cancelled by a subsequent @emph{-gnat-p} switch. +@end table -objects:: - # recompile the sources - gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@} +@geindex -gnat-p (gcc) -# Note: In a future version of GNAT, the following commands will be simplified -# by a new tool, gnatmlib -$@{LIB_DIR@}: - mkdir -p $@{dir $@@ @} - cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat - cd $@{dir $@@ @} && cp -f ../*.ali . -# The dependencies for the modules -# Note that we have to force the expansion of *.o, since in some cases -# make won't be able to do it itself. -aa/lib/libaa.so: $@{wildcard aa/*.o@} -bb/lib/libbb.so: $@{wildcard bb/*.o@} -cc/lib/libcc.so: $@{wildcard cc/*.o@} +@table @asis -# Make sure all of the shared libraries are in the path before starting the -# program -run:: - LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@} +@item @code{-gnat-p} -clean:: - $@{RM@} -rf $@{CSC_LIST:%=%/lib@} - $@{RM@} $@{CSC_LIST:%=%/*.ali@} - $@{RM@} $@{CSC_LIST:%=%/*.o@} - $@{RM@} *.o *.ali $@{MAIN@} -@end smallexample +Cancel effect of previous @emph{-gnatp} switch. +@end table -@node Automatically Creating a List of Directories -@section Automatically Creating a List of Directories +@geindex -gnatP (gcc) -@noindent -In most makefiles, you will have to specify a list of directories, and -store it in a variable. For small projects, it is often easier to -specify each of them by hand, since you then have full control over what -is the proper order for these directories, which ones should be -included. -However, in larger projects, which might involve hundreds of -subdirectories, it might be more convenient to generate this list -automatically. +@table @asis -The example below presents two methods. The first one, although less -general, gives you more control over the list. It involves wildcard -characters, that are automatically expanded by @command{make}. Its -shortcoming is that you need to explicitly specify some of the -organization of your project, such as for instance the directory tree -depth, whether some directories are found in a separate tree, @enddots{} +@item @code{-gnatP} -The second method is the most general one. It requires an external -program, called @command{find}, which is standard on all Unix systems. All -the directories found under a given root directory will be added to the -list. +Enable polling. This is required on some systems (notably Windows NT) to +obtain asynchronous abort and asynchronous transfer of control capability. +See @cite{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full +details. +@end table -@smallexample -@iftex -@leftskip=0cm -@font@heightrm=cmr8 -@heightrm -@end iftex -# The examples below are based on the following directory hierarchy: -# All the directories can contain any number of files -# ROOT_DIRECTORY -> a -> aa -> aaa -# -> ab -# -> ac -# -> b -> ba -> baa -# -> bb -# -> bc -# This Makefile creates a variable called DIRS, that can be reused any time -# you need this list (see the other examples in this section) +@geindex -gnatq (gcc) -# The root of your project's directory hierarchy -ROOT_DIRECTORY=. -#### -# First method: specify explicitly the list of directories -# This allows you to specify any subset of all the directories you need. -#### +@table @asis -DIRS := a/aa/ a/ab/ b/ba/ +@item @code{-gnatq} -#### -# Second method: use wildcards -# Note that the argument(s) to wildcard below should end with a '/'. -# Since wildcards also return file names, we have to filter them out -# to avoid duplicate directory names. -# We thus use make's @code{dir} and @code{sort} functions. -# It sets DIRs to the following value (note that the directories aaa and baa -# are not given, unless you change the arguments to wildcard). -# DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/ -#### +Don't quit. Try semantics, even if parse errors. +@end table -DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/ - $@{ROOT_DIRECTORY@}/*/*/@}@}@} +@geindex -gnatQ (gcc) -#### -# Third method: use an external program -# This command is much faster if run on local disks, avoiding NFS slowdowns. -# This is the most complete command: it sets DIRs to the following value: -# DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc -#### -DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@} +@table @asis -@end smallexample +@item @code{-gnatQ} -@node Generating the Command Line Switches -@section Generating the Command Line Switches +Don't quit. Generate @code{ALI} and tree files even if illegalities. +Note that code generation is still suppressed in the presence of any +errors, so even with @emph{-gnatQ} no object file is generated. +@end table -@noindent -Once you have created the list of directories as explained in the -previous section (@pxref{Automatically Creating a List of Directories}), -you can easily generate the command line arguments to pass to gnatmake. +@geindex -gnatr (gcc) -For the sake of completeness, this example assumes that the source path -is not the same as the object path, and that you have two separate lists -of directories. -@smallexample -# see "Automatically creating a list of directories" to create -# these variables -SOURCE_DIRS= -OBJECT_DIRS= +@table @asis -GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@} -GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@} +@item @code{-gnatr} -all: - gnatmake $@{GNATMAKE_SWITCHES@} main_unit -@end smallexample +Treat pragma Restrictions as Restriction_Warnings. +@end table -@node Overcoming Command Line Length Limits -@section Overcoming Command Line Length Limits +@geindex -gnatR (gcc) -@noindent -One problem that might be encountered on big projects is that many -operating systems limit the length of the command line. It is thus hard to give -gnatmake the list of source and object directories. -This example shows how you can set up environment variables, which will -make @command{gnatmake} behave exactly as if the directories had been -specified on the command line, but have a much higher length limit (or -even none on most systems). +@table @asis -It assumes that you have created a list of directories in your Makefile, -using one of the methods presented in -@ref{Automatically Creating a List of Directories}. -For the sake of completeness, we assume that the object -path (where the ALI files are found) is different from the sources patch. +@item @code{-gnatR[0/1/2/3[s]]} -Note a small trick in the Makefile below: for efficiency reasons, we -create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are -expanded immediately by @code{make}. This way we overcome the standard -make behavior which is to expand the variables only when they are -actually used. +Output representation information for declared types and objects. +Note that this switch is not allowed if a previous @cite{-gnatD} switch has +been given, since these two switches are not compatible. -On Windows, if you are using the standard Windows command shell, you must -replace colons with semicolons in the assignments to these variables. +@item @code{-gnatRm[s]} -@smallexample -@iftex -@leftskip=0cm -@font@heightrm=cmr8 -@heightrm -@end iftex -# In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH. -# This is the same thing as putting the -I arguments on the command line. -# (the equivalent of using -aI on the command line would be to define -# only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH). -# You can of course have different values for these variables. -# -# Note also that we need to keep the previous values of these variables, since -# they might have been set before running 'make' to specify where the GNAT -# library is installed. +Output convention and parameter passing mechanisms for all subprograms. +@end table -# see "Automatically creating a list of directories" to create these -# variables -SOURCE_DIRS= -OBJECT_DIRS= +@geindex -gnats (gcc) -empty:= -space:=$@{empty@} $@{empty@} -SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@} -OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@} -ADA_INCLUDE_PATH += $@{SOURCE_LIST@} -ADA_OBJECTS_PATH += $@{OBJECT_LIST@} -export ADA_INCLUDE_PATH -export ADA_OBJECTS_PATH -all: - gnatmake main_unit -@end smallexample +@table @asis -@node Memory Management Issues -@chapter Memory Management Issues +@item @code{-gnats} -@noindent -This chapter describes some useful memory pools provided in the GNAT library -and in particular the GNAT Debug Pool facility, which can be used to detect -incorrect uses of access values (including ``dangling references''). -@ifclear FSFEDITION -It also describes the @command{gnatmem} tool, which can be used to track down -``memory leaks''. -@end ifclear +Syntax check only. +@end table -@menu -* Some Useful Memory Pools:: -* The GNAT Debug Pool Facility:: -@ifclear FSFEDITION -* The gnatmem Tool:: -@end ifclear -@end menu +@geindex -gnatS (gcc) -@node Some Useful Memory Pools -@section Some Useful Memory Pools -@findex Memory Pool -@cindex storage, pool -@noindent -The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool -storage pool. Allocations use the standard system call @code{malloc} while -deallocations use the standard system call @code{free}. No reclamation is -performed when the pool goes out of scope. For performance reasons, the -standard default Ada allocators/deallocators do not use any explicit storage -pools but if they did, they could use this storage pool without any change in -behavior. That is why this storage pool is used when the user -manages to make the default implicit allocator explicit as in this example: -@smallexample @c ada - @b{type} T1 @b{is} @b{access} Something; - --@i{ no Storage pool is defined for T2} - @b{type} T2 @b{is} @b{access} Something_Else; - @b{for} T2'Storage_Pool @b{use} T1'Storage_Pool; - --@i{ the above is equivalent to} - @b{for} T2'Storage_Pool @b{use} System.Pool_Global.Global_Pool_Object; -@end smallexample - -@noindent -The @code{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage -pool. The allocation strategy is similar to @code{Pool_Local}'s -except that the all -storage allocated with this pool is reclaimed when the pool object goes out of -scope. This pool provides a explicit mechanism similar to the implicit one -provided by several Ada 83 compilers for allocations performed through a local -access type and whose purpose was to reclaim memory when exiting the -scope of a given local access. As an example, the following program does not -leak memory even though it does not perform explicit deallocation: +@table @asis -@smallexample @c ada -@b{with} System.Pool_Local; -@b{procedure} Pooloc1 @b{is} - @b{procedure} Internal @b{is} - @b{type} A @b{is} @b{access} Integer; - X : System.Pool_Local.Unbounded_Reclaim_Pool; - @b{for} A'Storage_Pool @b{use} X; - v : A; - @b{begin} - @b{for} I @b{in} 1 .. 50 @b{loop} - v := @b{new} Integer; - @b{end} @b{loop}; - @b{end} Internal; -@b{begin} - @b{for} I @b{in} 1 .. 100 @b{loop} - Internal; - @b{end} @b{loop}; -@b{end} Pooloc1; -@end smallexample +@item @code{-gnatS} -@noindent -The @code{System.Pool_Size} package implements the Stack_Bounded_Pool used when -@code{Storage_Size} is specified for an access type. -The whole storage for the pool is -allocated at once, usually on the stack at the point where the access type is -elaborated. It is automatically reclaimed when exiting the scope where the -access type is defined. This package is not intended to be used directly by the -user and it is implicitly used for each such declaration: +Print package Standard. +@end table -@smallexample @c ada - @b{type} T1 @b{is} @b{access} Something; - @b{for} T1'Storage_Size @b{use} 10_000; -@end smallexample +@geindex -gnatt (gcc) -@node The GNAT Debug Pool Facility -@section The GNAT Debug Pool Facility -@findex Debug Pool -@cindex storage, pool, memory corruption -@noindent -The use of unchecked deallocation and unchecked conversion can easily -lead to incorrect memory references. The problems generated by such -references are usually difficult to tackle because the symptoms can be -very remote from the origin of the problem. In such cases, it is -very helpful to detect the problem as early as possible. This is the -purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}. +@table @asis -In order to use the GNAT specific debugging pool, the user must -associate a debug pool object with each of the access types that may be -related to suspected memory problems. See Ada Reference Manual 13.11. -@smallexample @c ada -@b{type} Ptr @b{is} @b{access} Some_Type; -Pool : GNAT.Debug_Pools.Debug_Pool; -@b{for} Ptr'Storage_Pool @b{use} Pool; -@end smallexample +@item @code{-gnatt} -@noindent -@code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of -pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools, -allow the user to redefine allocation and deallocation strategies. They -also provide a checkpoint for each dereference, through the use of -the primitive operation @code{Dereference} which is implicitly called at -each dereference of an access value. +Generate tree output file. +@end table -Once an access type has been associated with a debug pool, operations on -values of the type may raise four distinct exceptions, -which correspond to four potential kinds of memory corruption: -@itemize @bullet -@item -@code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage} -@item -@code{GNAT.Debug_Pools.Accessing_Deallocated_Storage} -@item -@code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage} -@item -@code{GNAT.Debug_Pools.Freeing_Deallocated_Storage } -@end itemize +@geindex -gnatT (gcc) -@noindent -For types associated with a Debug_Pool, dynamic allocation is performed using -the standard GNAT allocation routine. References to all allocated chunks of -memory are kept in an internal dictionary. Several deallocation strategies are -provided, whereupon the user can choose to release the memory to the system, -keep it allocated for further invalid access checks, or fill it with an easily -recognizable pattern for debug sessions. The memory pattern is the old IBM -hexadecimal convention: @code{16#DEADBEEF#}. -See the documentation in the file g-debpoo.ads for more information on the -various strategies. +@table @asis -Upon each dereference, a check is made that the access value denotes a -properly allocated memory location. Here is a complete example of use of -@code{Debug_Pools}, that includes typical instances of memory corruption: -@smallexample @c ada -@iftex -@leftskip=0cm -@end iftex -@b{with} Gnat.Io; @b{use} Gnat.Io; -@b{with} Unchecked_Deallocation; -@b{with} Unchecked_Conversion; -@b{with} GNAT.Debug_Pools; -@b{with} System.Storage_Elements; -@b{with} Ada.Exceptions; @b{use} Ada.Exceptions; -@b{procedure} Debug_Pool_Test @b{is} - - @b{type} T @b{is} @b{access} Integer; - @b{type} U @b{is} @b{access} @b{all} T; +@item @code{-gnatT@emph{nnn}} - P : GNAT.Debug_Pools.Debug_Pool; - @b{for} T'Storage_Pool @b{use} P; +All compiler tables start at @cite{nnn} times usual starting size. +@end table - @b{procedure} Free @b{is} @b{new} Unchecked_Deallocation (Integer, T); - @b{function} UC @b{is} @b{new} Unchecked_Conversion (U, T); - A, B : @b{aliased} T; +@geindex -gnatu (gcc) - @b{procedure} Info @b{is} @b{new} GNAT.Debug_Pools.Print_Info(Put_Line); -@b{begin} - Info (P); - A := @b{new} Integer; - B := @b{new} Integer; - B := A; - Info (P); - Free (A); - @b{begin} - Put_Line (Integer'Image(B.@b{all})); - @b{exception} - @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E)); - @b{end}; - @b{begin} - Free (B); - @b{exception} - @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E)); - @b{end}; - B := UC(A'Access); - @b{begin} - Put_Line (Integer'Image(B.@b{all})); - @b{exception} - @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E)); - @b{end}; - @b{begin} - Free (B); - @b{exception} - @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E)); - @b{end}; - Info (P); -@b{end} Debug_Pool_Test; -@end smallexample +@table @asis -@noindent -The debug pool mechanism provides the following precise diagnostics on the -execution of this erroneous program: -@smallexample -Debug Pool info: - Total allocated bytes : 0 - Total deallocated bytes : 0 - Current Water Mark: 0 - High Water Mark: 0 +@item @code{-gnatu} -Debug Pool info: - Total allocated bytes : 8 - Total deallocated bytes : 0 - Current Water Mark: 8 - High Water Mark: 8 +List units for this compilation. +@end table -raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE -raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE -raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE -raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE -Debug Pool info: - Total allocated bytes : 8 - Total deallocated bytes : 4 - Current Water Mark: 4 - High Water Mark: 8 -@end smallexample - -@ifclear FSFEDITION -@node The gnatmem Tool -@section The @command{gnatmem} Tool -@findex gnatmem - -@noindent -The @code{gnatmem} utility monitors dynamic allocation and -deallocation activity in a program, and displays information about -incorrect deallocations and possible sources of memory leaks. -It is designed to work in association with a static runtime library -only and in this context provides three types of information: -@itemize @bullet -@item -General information concerning memory management, such as the total -number of allocations and deallocations, the amount of allocated -memory and the high water mark, i.e.@: the largest amount of allocated -memory in the course of program execution. +@geindex -gnatU (gcc) -@item -Backtraces for all incorrect deallocations, that is to say deallocations -which do not correspond to a valid allocation. -@item -Information on each allocation that is potentially the origin of a memory -leak. -@end itemize +@table @asis -@menu -* Running gnatmem:: -* Switches for gnatmem:: -* Example of gnatmem Usage:: -@end menu +@item @code{-gnatU} -@node Running gnatmem -@subsection Running @code{gnatmem} - -@noindent -@code{gnatmem} makes use of the output created by the special version of -allocation and deallocation routines that record call information. This allows -it to obtain accurate dynamic memory usage history at a minimal cost to the -execution speed. Note however, that @code{gnatmem} is not supported on all -platforms (currently, it is supported on AIX, HP-UX, GNU/Linux, Solaris and -Windows NT/2000/XP (x86). - -@noindent -The @code{gnatmem} command has the form - -@smallexample -@c $ gnatmem @ovar{switches} user_program -@c Expanding @ovar macro inline (explanation in macro def comments) - $ gnatmem @r{[}@var{switches}@r{]} @var{user_program} -@end smallexample - -@noindent -The program must have been linked with the instrumented version of the -allocation and deallocation routines. This is done by linking with the -@file{libgmem.a} library. For correct symbolic backtrace information, -the user program should be compiled with debugging options -(see @ref{Switches for gcc}). For example to build @file{my_program}: - -@smallexample -$ gnatmake -g my_program -largs -lgmem -@end smallexample - -@noindent -As library @file{libgmem.a} contains an alternate body for package -@code{System.Memory}, @file{s-memory.adb} should not be compiled and linked -when an executable is linked with library @file{libgmem.a}. It is then not -recommended to use @command{gnatmake} with switch @option{-a}. - -@noindent -When @file{my_program} is executed, the file @file{gmem.out} is produced. -This file contains information about all allocations and deallocations -performed by the program. It is produced by the instrumented allocations and -deallocations routines and will be used by @code{gnatmem}. - -In order to produce symbolic backtrace information for allocations and -deallocations performed by the GNAT run-time library, you need to use a -version of that library that has been compiled with the @option{-g} switch -(see @ref{Rebuilding the GNAT Run-Time Library}). - -Gnatmem must be supplied with the @file{gmem.out} file and the executable to -examine. If the location of @file{gmem.out} file was not explicitly supplied by -@option{-i} switch, gnatmem will assume that this file can be found in the -current directory. For example, after you have executed @file{my_program}, -@file{gmem.out} can be analyzed by @code{gnatmem} using the command: - -@smallexample -$ gnatmem my_program -@end smallexample - -@noindent -This will produce the output with the following format: - -*************** debut cc -@smallexample -$ gnatmem my_program - -Global information ------------------- - Total number of allocations : 45 - Total number of deallocations : 6 - Final Water Mark (non freed mem) : 11.29 Kilobytes - High Water Mark : 11.40 Kilobytes - -. -. -. -Allocation Root # 2 -------------------- - Number of non freed allocations : 11 - Final Water Mark (non freed mem) : 1.16 Kilobytes - High Water Mark : 1.27 Kilobytes - Backtrace : - my_program.adb:23 my_program.alloc -. -. -. -@end smallexample - -The first block of output gives general information. In this case, the -Ada construct ``@code{@b{new}}'' was executed 45 times, and only 6 calls to an -Unchecked_Deallocation routine occurred. - -@noindent -Subsequent paragraphs display information on all allocation roots. -An allocation root is a specific point in the execution of the program -that generates some dynamic allocation, such as a ``@code{@b{new}}'' -construct. This root is represented by an execution backtrace (or subprogram -call stack). By default the backtrace depth for allocations roots is 1, so -that a root corresponds exactly to a source location. The backtrace can -be made deeper, to make the root more specific. - -@node Switches for gnatmem -@subsection Switches for @code{gnatmem} - -@noindent -@code{gnatmem} recognizes the following switches: - -@table @option - -@item -q -@cindex @option{-q} (@code{gnatmem}) -Quiet. Gives the minimum output needed to identify the origin of the -memory leaks. Omits statistical information. - -@item @var{N} -@cindex @var{N} (@code{gnatmem}) -N is an integer literal (usually between 1 and 10) which controls the -depth of the backtraces defining allocation root. The default value for -N is 1. The deeper the backtrace, the more precise the localization of -the root. Note that the total number of roots can depend on this -parameter. This parameter must be specified @emph{before} the name of the -executable to be analyzed, to avoid ambiguity. - -@item -b n -@cindex @option{-b} (@code{gnatmem}) -This switch has the same effect as just depth parameter. - -@item -i @var{file} -@cindex @option{-i} (@code{gnatmem}) -Do the @code{gnatmem} processing starting from @file{file}, rather than -@file{gmem.out} in the current directory. - -@item -m n -@cindex @option{-m} (@code{gnatmem}) -This switch causes @code{gnatmem} to mask the allocation roots that have less -than n leaks. The default value is 1. Specifying the value of 0 will allow -examination of even the roots that did not result in leaks. - -@item -s order -@cindex @option{-s} (@code{gnatmem}) -This switch causes @code{gnatmem} to sort the allocation roots according to the -specified order of sort criteria, each identified by a single letter. The -currently supported criteria are @code{n, h, w} standing respectively for -number of unfreed allocations, high watermark, and final watermark -corresponding to a specific root. The default order is @code{nwh}. - -@item -t -@cindex @option{-t} (@code{gnatmem}) -This switch causes memory allocated size to be always output in bytes. -Default @code{gnatmem} behavior is to show memory sizes less then 1 kilobyte -in bytes, from 1 kilobyte till 1 megabyte in kilobytes and the rest in -megabytes. - -@end table - -@node Example of gnatmem Usage -@subsection Example of @code{gnatmem} Usage - -@noindent -The following example shows the use of @code{gnatmem} -on a simple memory-leaking program. -Suppose that we have the following Ada program: - -@smallexample @c ada -@group -@cartouche -@b{with} Unchecked_Deallocation; -@b{procedure} Test_Gm @b{is} - - @b{type} T @b{is} @b{array} (1..1000) @b{of} Integer; - @b{type} Ptr @b{is} @b{access} T; - @b{procedure} Free @b{is} @b{new} Unchecked_Deallocation (T, Ptr); - A : Ptr; - - @b{procedure} My_Alloc @b{is} - @b{begin} - A := @b{new} T; - @b{end} My_Alloc; - - @b{procedure} My_DeAlloc @b{is} - B : Ptr := A; - @b{begin} - Free (B); - @b{end} My_DeAlloc; - -@b{begin} - My_Alloc; - @b{for} I @b{in} 1 .. 5 @b{loop} - @b{for} J @b{in} I .. 5 @b{loop} - My_Alloc; - @b{end} @b{loop}; - My_Dealloc; - @b{end} @b{loop}; -@b{end}; -@end cartouche -@end group -@end smallexample - -@noindent -The program needs to be compiled with debugging option and linked with -@code{gmem} library: - -@smallexample -$ gnatmake -g test_gm -largs -lgmem -@end smallexample - -@noindent -Then we execute the program as usual: - -@smallexample -$ test_gm -@end smallexample - -@noindent -Then @code{gnatmem} is invoked simply with -@smallexample -$ gnatmem test_gm -@end smallexample - -@noindent -which produces the following output (result may vary on different platforms): - -@smallexample -Global information ------------------- - Total number of allocations : 18 - Total number of deallocations : 5 - Final Water Mark (non freed mem) : 53.00 Kilobytes - High Water Mark : 56.90 Kilobytes - -Allocation Root # 1 -------------------- - Number of non freed allocations : 11 - Final Water Mark (non freed mem) : 42.97 Kilobytes - High Water Mark : 46.88 Kilobytes - Backtrace : - test_gm.adb:11 test_gm.my_alloc - -Allocation Root # 2 -------------------- - Number of non freed allocations : 1 - Final Water Mark (non freed mem) : 10.02 Kilobytes - High Water Mark : 10.02 Kilobytes - Backtrace : - s-secsta.adb:81 system.secondary_stack.ss_init - -Allocation Root # 3 -------------------- - Number of non freed allocations : 1 - Final Water Mark (non freed mem) : 12 Bytes - High Water Mark : 12 Bytes - Backtrace : - s-secsta.adb:181 system.secondary_stack.ss_init -@end smallexample - -@noindent -Note that the GNAT run time contains itself a certain number of -allocations that have no corresponding deallocation, -as shown here for root #2 and root -#3. This is a normal behavior when the number of non-freed allocations -is one, it allocates dynamic data structures that the run time needs for -the complete lifetime of the program. Note also that there is only one -allocation root in the user program with a single line back trace: -test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the -program shows that 'My_Alloc' is called at 2 different points in the -source (line 21 and line 24). If those two allocation roots need to be -distinguished, the backtrace depth parameter can be used: - -@smallexample -$ gnatmem 3 test_gm -@end smallexample - -@noindent -which will give the following output: - -@smallexample -Global information ------------------- - Total number of allocations : 18 - Total number of deallocations : 5 - Final Water Mark (non freed mem) : 53.00 Kilobytes - High Water Mark : 56.90 Kilobytes - -Allocation Root # 1 -------------------- - Number of non freed allocations : 10 - Final Water Mark (non freed mem) : 39.06 Kilobytes - High Water Mark : 42.97 Kilobytes - Backtrace : - test_gm.adb:11 test_gm.my_alloc - test_gm.adb:24 test_gm - b_test_gm.c:52 main - -Allocation Root # 2 -------------------- - Number of non freed allocations : 1 - Final Water Mark (non freed mem) : 10.02 Kilobytes - High Water Mark : 10.02 Kilobytes - Backtrace : - s-secsta.adb:81 system.secondary_stack.ss_init - s-secsta.adb:283 - b_test_gm.c:33 adainit - -Allocation Root # 3 -------------------- - Number of non freed allocations : 1 - Final Water Mark (non freed mem) : 3.91 Kilobytes - High Water Mark : 3.91 Kilobytes - Backtrace : - test_gm.adb:11 test_gm.my_alloc - test_gm.adb:21 test_gm - b_test_gm.c:52 main - -Allocation Root # 4 -------------------- - Number of non freed allocations : 1 - Final Water Mark (non freed mem) : 12 Bytes - High Water Mark : 12 Bytes - Backtrace : - s-secsta.adb:181 system.secondary_stack.ss_init - s-secsta.adb:283 - b_test_gm.c:33 adainit -@end smallexample - -@noindent -The allocation root #1 of the first example has been split in 2 roots #1 -and #3 thanks to the more precise associated backtrace. -@end ifclear - -@node Stack Related Facilities -@chapter Stack Related Facilities - -@noindent -This chapter describes some useful tools associated with stack -checking and analysis. In -particular, it deals with dynamic and static stack usage measurements. +Tag all error messages with the unique string 'error:' +@end table -@menu -* Stack Overflow Checking:: -* Static Stack Usage Analysis:: -* Dynamic Stack Usage Analysis:: -@end menu +@geindex -gnatv (gcc) -@node Stack Overflow Checking -@section Stack Overflow Checking -@cindex Stack Overflow Checking -@cindex -fstack-check -@noindent -For most operating systems, @command{gcc} does not perform stack overflow -checking by default. This means that if the main environment task or -some other task exceeds the available stack space, then unpredictable -behavior will occur. Most native systems offer some level of protection by -adding a guard page at the end of each task stack. This mechanism is usually -not enough for dealing properly with stack overflow situations because -a large local variable could ``jump'' above the guard page. -Furthermore, when the -guard page is hit, there may not be any space left on the stack for executing -the exception propagation code. Enabling stack checking avoids -such situations. +@table @asis -To activate stack checking, compile all units with the gcc option -@option{-fstack-check}. For example: +@item @code{-gnatv} -@smallexample -gcc -c -fstack-check package1.adb -@end smallexample +Verbose mode. Full error output with source lines to @code{stdout}. +@end table -@noindent -Units compiled with this option will generate extra instructions to check -that any use of the stack (for procedure calls or for declaring local -variables in declare blocks) does not exceed the available stack space. -If the space is exceeded, then a @code{Storage_Error} exception is raised. +@geindex -gnatV (gcc) -For declared tasks, the stack size is controlled by the size -given in an applicable @code{Storage_Size} pragma or by the value specified -at bind time with @option{-d} (@pxref{Switches for gnatbind}) or is set to -the default size as defined in the GNAT runtime otherwise. -For the environment task, the stack size depends on -system defaults and is unknown to the compiler. Stack checking -may still work correctly if a fixed -size stack is allocated, but this cannot be guaranteed. -To ensure that a clean exception is signalled for stack -overflow, set the environment variable -@env{GNAT_STACK_LIMIT} to indicate the maximum -stack area that can be used, as in: -@cindex GNAT_STACK_LIMIT +@table @asis -@smallexample -SET GNAT_STACK_LIMIT 1600 -@end smallexample +@item @code{-gnatV} -@noindent -The limit is given in kilobytes, so the above declaration would -set the stack limit of the environment task to 1.6 megabytes. -Note that the only purpose of this usage is to limit the amount -of stack used by the environment task. If it is necessary to -increase the amount of stack for the environment task, then this -is an operating systems issue, and must be addressed with the -appropriate operating systems commands. +Control level of validity checking (@ref{fb,,Validity Checking}). +@end table -@node Static Stack Usage Analysis -@section Static Stack Usage Analysis -@cindex Static Stack Usage Analysis -@cindex -fstack-usage +@geindex -gnatw (gcc) -@noindent -A unit compiled with @option{-fstack-usage} will generate an extra file -that specifies -the maximum amount of stack used, on a per-function basis. -The file has the same -basename as the target object file with a @file{.su} extension. -Each line of this file is made up of three fields: -@itemize -@item -The name of the function. -@item -A number of bytes. -@item -One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}. -@end itemize +@table @asis -The second field corresponds to the size of the known part of the function -frame. +@item @code{-gnatw@emph{xxx}} -The qualifier @code{static} means that the function frame size -is purely static. -It usually means that all local variables have a static size. -In this case, the second field is a reliable measure of the function stack -utilization. +Warning mode where +@cite{xxx} is a string of option letters that denotes +the exact warnings that +are enabled or disabled (@ref{ff,,Warning Message Control}). +@end table -The qualifier @code{dynamic} means that the function frame size is not static. -It happens mainly when some local variables have a dynamic size. When this -qualifier appears alone, the second field is not a reliable measure -of the function stack analysis. When it is qualified with @code{bounded}, it -means that the second field is a reliable maximum of the function stack -utilization. +@geindex -gnatW (gcc) -A unit compiled with @option{-Wstack-usage} will issue a warning for each -subprogram whose stack usage might be larger than the specified amount of -bytes. The wording is in keeping with the qualifier documented above. -@node Dynamic Stack Usage Analysis -@section Dynamic Stack Usage Analysis +@table @asis -@noindent -It is possible to measure the maximum amount of stack used by a task, by -adding a switch to @command{gnatbind}, as: +@item @code{-gnatW@emph{e}} -@smallexample -$ gnatbind -u0 file -@end smallexample +Wide character encoding method +(@cite{e}=n/h/u/s/e/8). +@end table -@noindent -With this option, at each task termination, its stack usage is output on -@file{stderr}. -It is not always convenient to output the stack usage when the program -is still running. Hence, it is possible to delay this output until program -termination. for a given number of tasks specified as the argument of the -@option{-u} option. For instance: +@geindex -gnatx (gcc) -@smallexample -$ gnatbind -u100 file -@end smallexample -@noindent -will buffer the stack usage information of the first 100 tasks to terminate and -output this info at program termination. Results are displayed in four -columns: +@table @asis -@noindent -Index | Task Name | Stack Size | Stack Usage +@item @code{-gnatx} -@noindent -where: +Suppress generation of cross-reference information. +@end table -@table @emph -@item Index -is a number associated with each task. +@geindex -gnatX (gcc) -@item Task Name -is the name of the task analyzed. -@item Stack Size -is the maximum size for the stack. +@table @asis -@item Stack Usage -is the measure done by the stack analyzer. In order to prevent overflow, the stack -is not entirely analyzed, and it's not possible to know exactly how -much has actually been used. +@item @code{-gnatX} +Enable GNAT implementation extensions and latest Ada version. @end table -@noindent -The environment task stack, e.g., the stack that contains the main unit, is -only processed when the environment variable GNAT_STACK_LIMIT is set. - -@noindent -The package @code{GNAT.Task_Stack_Usage} provides facilities to get -stack usage reports at run-time. See its body for the details. +@geindex -gnaty (gcc) -@ifclear FSFEDITION -@c ********************************* -@c * GNATCHECK * -@c ********************************* -@node Verifying Properties with gnatcheck -@chapter Verifying Properties with @command{gnatcheck} -@findex gnatcheck -@cindex @command{gnatcheck} - -@noindent -The @command{gnatcheck} tool is an ASIS-based utility that checks properties -of Ada source files according to a given set of semantic rules. -@cindex ASIS - -In order to check compliance with a given rule, @command{gnatcheck} has to -semantically analyze the Ada sources. -Therefore, checks can only be performed on -legal Ada units. Moreover, when a unit depends semantically upon units located -outside the current directory, the source search path has to be provided when -calling @command{gnatcheck}, either through a specified project file or -through @command{gnatcheck} switches. - -For full details, refer to @cite{GNATcheck Reference Manual} document. -@end ifclear - -@ifclear FSFEDITION -@c ********************************* -@node Creating Sample Bodies with gnatstub -@chapter Creating Sample Bodies with @command{gnatstub} -@findex gnatstub - -@noindent -@command{gnatstub} creates empty but compilable bodies -for library unit declarations and empty but compilable -subunit for body stubs. - -To create a body or a subunit, @command{gnatstub} invokes the Ada -compiler and generates and uses the ASIS tree for the input source; -thus the input must be legal Ada code, and the tool should have all the -information needed to compile the input source. To provide this information, -you may specify as a tool parameter the project file the input source belongs to -(or you may call @command{gnatstub} -through the @command{gnat} driver (see @ref{The GNAT Driver and -Project Files}). Another possibility is to specify the source search -path and needed configuration files in @option{-cargs} section of @command{gnatstub} -call, see the description of the @command{gnatstub} switches below. - -If the @command{gnatstub} argument source contains preprocessing directives -then the needed options should be provided to run preprocessor as a part of -the @command{gnatstub} call, and the generated body stub will correspond to -the preprocessed source. - -By default, all the program unit bodies generated by @code{gnatstub} -raise the predefined @code{Program_Error} exception, which will catch -accidental calls of generated stubs. This behavior can be changed with -option @option{--no-exception} (see below). -@menu -* Running gnatstub:: -* Switches for gnatstub:: -@end menu +@table @asis -@node Running gnatstub -@section Running @command{gnatstub} +@item @code{-gnaty} -@noindent -@command{gnatstub} has a command-line interface of the form: +Enable built-in style checks (@ref{100,,Style Checking}). +@end table -@smallexample -@c $ gnatstub @ovar{switches} @var{filename} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatstub @r{[}@var{switches}@r{]} @var{filename} @r{[}-cargs @var{gcc_switches}@r{]} -@end smallexample +@geindex -gnatz (gcc) -@noindent -where -@table @var -@item filename -is the name of the source file that contains a library unit declaration -for which a body must be created or a library unit body for which subunits -must be created for the body stubs declared in this body. -The file name may contain the path information. -If the name does not follow GNAT file naming conventions and a set -of seitches does not contain a project file that defines naming -conventions, the name of the body file must -be provided -explicitly as the value of the @option{-o@var{body-name}} option. -If the file name follows the GNAT file naming -conventions and the name of the body file is not provided, -@command{gnatstub} -takes the naming conventions for the generated source from the -project file provided as a parameter of @option{-P} switch if any, -or creates the name file to generate using the standard GNAT -naming conventions. - -@item @samp{@var{gcc_switches}} is a list of switches for -@command{gcc}. They will be passed on to all compiler invocations made by -@command{gnatstub} to generate the ASIS trees. Here you can provide -@option{-I} switches to form the source search path, -use the @option{-gnatec} switch to set the configuration file, -use the @option{-gnat05} switch if sources should be compiled in -Ada 2005 mode etc. - -@item switches -is an optional sequence of switches as described in the next section -@end table - -@node Switches for gnatstub -@section Switches for @command{gnatstub} - -@table @option -@c !sort! - -@item --version -@cindex @option{--version} @command{gnatstub} -Display Copyright and version, then exit disregarding all other options. -@item --help -@cindex @option{--help} @command{gnatstub} -Display usage, then exit disregarding all other options. +@table @asis -@item -P @var{file} -@cindex @option{-P} @command{gnatstub} -Indicates the name of the project file that describes the set of sources -to be processed. +@item @code{-gnatz@emph{m}} -@item -X@var{name}=@var{value} -@cindex @option{-X} @command{gnatstub} -Indicates that external variable @var{name} in the argument project -has the value @var{value}. Has no effect if no project is specified as -tool argument. +Distribution stub generation and compilation +(@cite{m}=r/c for receiver/caller stubs). +@end table -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnatstub}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). - -@item --subunits -@cindex @option{--subunits} (@command{gnatstub}) -Generate subunits for body stubs. If this switch is specified, -@command{gnatstub} expects a library unit body as an agrument file, -otherwise a library unit declaration is expected. If a body stub -already has a corresponding subunit, @command{gnatstub} does not -generate anything for it. - -@item -f -@cindex @option{-f} (@command{gnatstub}) -If the destination directory already contains a file with the name of the -body file -for the argument spec file, replace it with the generated body stub. -This switch cannot be used together with @option{--subunits}. - -@item -hs -@cindex @option{-hs} (@command{gnatstub}) -Put the comment header (i.e., all the comments preceding the -compilation unit) from the source of the library unit declaration -into the body stub. - -@item -hg -@cindex @option{-hg} (@command{gnatstub}) -Put a sample comment header into the body stub. - -@item --header-file=@var{filename} -@cindex @option{--header-file} (@command{gnatstub}) -Use the content of the file as the comment header for a generated body stub. - -@item -IDIR -@cindex @option{-IDIR} (@command{gnatstub}) -@itemx -I- -@cindex @option{-I-} (@command{gnatstub}) -These switches have the same meaning as in calls to -@command{gcc}. -They define the source search path in the call to -@command{gcc} issued -by @command{gnatstub} to compile an argument source file. - -@item -gnatec@var{PATH} -@cindex @option{-gnatec} (@command{gnatstub}) -This switch has the same meaning as in calls to @command{gcc}. -It defines the additional configuration file to be passed to the call to -@command{gcc} issued -by @command{gnatstub} to compile an argument source file. - -@item -gnatyM@var{n} -@cindex @option{-gnatyM} (@command{gnatstub}) -(@var{n} is a non-negative integer). Set the maximum line length that is -allowed in a source file. The default is 79. The maximum value that can be -specified is 32767. Note that in the special case of configuration -pragma files, the maximum is always 32767 regardless of whether or -not this switch appears. - -@item -gnaty@var{n} -@cindex @option{-gnaty} (@command{gnatstub}) -(@var{n} is a non-negative integer from 1 to 9). Set the indentation level in -the generated body sample to @var{n}. -The default indentation is 3. - -@item -gnatyo -@cindex @option{-gnatyo} (@command{gnatstub}) -Order local bodies alphabetically. (By default local bodies are ordered -in the same way as the corresponding local specs in the argument spec file.) - -@item -i@var{n} -@cindex @option{-i} (@command{gnatstub}) -Same as @option{-gnaty@var{n}} - -@item -k -@cindex @option{-k} (@command{gnatstub}) -Do not remove the tree file (i.e., the snapshot of the compiler internal -structures used by @command{gnatstub}) after creating the body stub. - -@item -l@var{n} -@cindex @option{-l} (@command{gnatstub}) -Same as @option{-gnatyM@var{n}} - -@item --no-exception -@cindex @option{--no-exception} (@command{gnatstub}) -Avoid raising PROGRAM_ERROR in the generated bodies of program unit stubs. -This is not always possible for function stubs. - -@item --no-local-header -@cindex @option{--no-local-header} (@command{gnatstub}) -Do not place local comment header with unit name before body stub for a -unit. +@geindex -I (gcc) -@item -o @var{body-name} -@cindex @option{-o} (@command{gnatstub}) -Body file name. This should be set if the argument file name does not -follow -the GNAT file naming -conventions. If this switch is omitted the default name for the body will be -obtained -from the argument file name according to the GNAT file naming conventions. -@item --dir=@var{dir-name} -@cindex @option{--dir} (@command{gnatstub}) -The path to the directory to place the generated files into. -If this switch is not set, the generated library unit body is -placed in the current directory, and generated sununits - -in the directory where the argument body is located. +@table @asis -@item -W@var{e} -@cindex @option{-W} (@command{gnatstub}) -Specify the wide character encoding method for the output body file. -@var{e} is one of the following: +@item @code{-I@emph{dir}} -@itemize @bullet +@geindex RTL -@item h -Hex encoding +Direct GNAT to search the @cite{dir} directory for source files needed by +the current compilation +(see @ref{8e,,Search Paths and the Run-Time Library (RTL)}). +@end table -@item u -Upper half encoding +@geindex -I- (gcc) -@item s -Shift/JIS encoding -@item e -EUC encoding +@table @asis -@item 8 -UTF-8 encoding +@item @code{-I-} -@item b -Brackets encoding (default value) -@end itemize +@geindex RTL -@item -q -@cindex @option{-q} (@command{gnatstub}) -Quiet mode: do not generate a confirmation when a body is -successfully created, and do not generate a message when a body is not -required for an -argument unit. - -@item -r -@cindex @option{-r} (@command{gnatstub}) -Reuse the tree file (if it exists) instead of creating it. Instead of -creating the tree file for the library unit declaration, @command{gnatstub} -tries to find it in the current directory and use it for creating -a body. If the tree file is not found, no body is created. This option -also implies @option{-k}, whether or not -the latter is set explicitly. - -@item -t -@cindex @option{-t} (@command{gnatstub}) -Overwrite the existing tree file. If the current directory already -contains the file which, according to the GNAT file naming rules should -be considered as a tree file for the argument source file, -@command{gnatstub} -will refuse to create the tree file needed to create a sample body -unless this option is set. - -@item -v -@cindex @option{-v} (@command{gnatstub}) -Verbose mode: generate version information. - -@end table -@end ifclear - -@ifclear FSFEDITION -@c ********************************* -@node Creating Unit Tests with gnattest -@chapter Creating Unit Tests with @command{gnattest} -@findex gnattest - -@noindent -@command{gnattest} is an ASIS-based utility that creates unit-test skeletons -as well as a test driver infrastructure (harness). @command{gnattest} creates -a skeleton for each visible subprogram in the packages under consideration when -they do not exist already. - -The user can choose to generate a single test driver -that will run all individual tests, or separate test drivers for each test. The -second option allows much greater flexibility in test execution environment, -allows to benefit from parallel tests execution to increase performance, and -provides stubbing support. - -@command{gnattest} also has a mode of operation where it acts as the test -aggregator when multiple test executables must be run, in particular when -the separate test drivers were generated. In this mode it handles individual -tests execution and upon completion reports the summary results of the test -run. - -In order to process source files from a project, @command{gnattest} has to -semantically analyze the sources. Therefore, test skeletons can only be -generated for legal Ada units. If a unit is dependent on other units, -those units should be among the source files of the project or of other projects -imported by this one. - -Generated skeletons and harnesses are based on the AUnit testing framework. -AUnit is an Ada adaptation of the xxxUnit testing frameworks, similar to JUnit -for Java or CppUnit for C++. While it is advised that gnattest users read -the AUnit manual, deep knowledge of AUnit is not necessary for using gnattest. -For correct operation of @command{gnattest}, AUnit should be installed and -aunit.gpr must be on the project path. This happens automatically when Aunit -is installed at its default location. +Except for the source file named in the command line, do not look for source +files in the directory containing the source file named in the command line +(see @ref{8e,,Search Paths and the Run-Time Library (RTL)}). +@end table -@menu -* Running gnattest:: -* Switches for gnattest in framework generation mode:: -* Switches for gnattest in tests execution mode:: -* Project Attributes for gnattest:: -* Simple Example:: -* Setting Up and Tearing Down the Testing Environment:: -* Regenerating Tests:: -* Default Test Behavior:: -* Testing Primitive Operations of Tagged Types:: -* Testing Inheritance:: -* Tagged Types Substitutability Testing:: -* Testing with Contracts:: -* Additional Tests:: -* Individual Test Drivers:: -* Stubbing:: -* Putting Tests under Version Control:: -* Support for other platforms/run-times:: -* Current Limitations:: -@end menu +@geindex -o (gcc) -@node Running gnattest -@section Running @command{gnattest} -@noindent -@b{In the framework generation mode}, @command{gnattest} has a command-line -interface of the form +@table @asis -@smallexample -@c $ gnattest @var{-Pprojname} @ovar{switches} @ovar{filename} @ovar{directory} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnattest @var{-Pprojname} @r{[}@var{--harness-dir=dirname}@r{]} @r{[}@var{switches}@r{]} @r{[}@var{filename}@r{]} @r{[}-cargs @var{gcc_switches}@r{]} -@end smallexample +@item @code{-o @emph{file}} -@noindent -where -@table @var +This switch is used in @emph{gcc} to redirect the generated object file +and its associated ALI file. Beware of this switch with GNAT, because it may +cause the object file and ALI file to have different names which in turn +may confuse the binder and the linker. +@end table -@item -Pprojname -specifies the project defining the location of source files. When no -file names are provided on the command line, all sources in the project -are used as input. This switch is required. +@geindex -nostdinc (gcc) -@item filename -is the name of the source file containing the library unit package declaration -for which a test package will be created. The file name may be given with a -path. -@item @samp{@var{gcc_switches}} -is a list of switches for -@command{gcc}. These switches will be passed on to all compiler invocations -made by @command{gnattest} to generate a set of ASIS trees. Here you can provide -@option{-I} switches to form the source search path, -use the @option{-gnatec} switch to set the configuration file, -use the @option{-gnat05} switch if sources should be compiled in -Ada 2005 mode, etc. +@table @asis -@item switches -is an optional sequence of switches as described in the next section. +@item @code{-nostdinc} +Inhibit the search of the default location for the GNAT Run Time +Library (RTL) source files. @end table -@command{gnattest} results can be found in two different places. +@geindex -nostdlib (gcc) -@itemize @bullet -@item automatic harness: -the harness code, which is located by default in "gnattest/harness" directory -that is created in the object directory of corresponding project file. All of -this code is generated completely automatically and can be destroyed and -regenerated at will. It is not recommended to modify this code manually, since -it could easily be overridden by mistake. The entry point in the harness code is -the project file named @command{test_driver.gpr}. Tests can be compiled and run -using a command such as: -@smallexample -gnatmake -P/test_driver -test_runner -@end smallexample +@table @asis -Note that you might need to specify the necessary values of scenario variables -when you are not using the AUnit defaults. +@item @code{-nostdlib} -@item actual unit test skeletons: -a test skeleton for each visible subprogram is created in a separate file, if it -doesn't exist already. By default, those separate test files are located in a -"gnattest/tests" directory that is created in the object directory of -corresponding project file. For example, if a source file my_unit.ads in -directory src contains a visible subprogram Proc, then the corresponding unit -test will be found in file src/tests/my_unit-test_data-tests.adb and will be -called Test_Proc_. is a signature encoding used to differentiate -test names in case of overloading. +Inhibit the search of the default location for the GNAT Run Time +Library (RTL) ALI files. +@end table -Note that if the project already has both my_unit.ads and my_unit-test_data.ads, -this will cause a name conflict with the generated test package. -@end itemize +@geindex -O (gcc) -@noindent -@b{In the tests execution mode mode}, @command{gnattest} has a command-line -interface of the form +@table @asis -@smallexample -@c $ gnattest @var{-Pprojname} @ovar{switches} @ovar{filename} @ovar{directory} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnattest @var{test_drivers.list} @r{[}@var{switches}@r{]} -@end smallexample +@item @code{-O[@emph{n}]} -@noindent -where -@table @var +@cite{n} controls the optimization level: -@item test_drivers.list -is the name of the text file containing the list of executables to treat as -test drivers. This file is automatically generated by gnattest, but can be -hand-edited to add or remove tests. This switch is required. -@item switches -is an optional sequence of switches as described below. +@multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item -@end table +@emph{n} +@tab -@node Switches for gnattest in framework generation mode -@section Switches for @command{gnattest} in framework generation mode +Effect -@table @option -@c !sort! +@item -@item -q -@cindex @option{-q} (@command{gnattest}) -Quiet mode: suppresses noncritical output messages. +@emph{0} -@item -v -@cindex @option{-v} (@command{gnattest}) -Verbose mode: generates version information if specified by itself on the -command line. If specified via GNATtest_Switches, produces output -about the execution of the tool. +@tab -@item -r -@cindex @option{-r} (@command{gnattest}) -Recursively considers all sources from all projects. +No optimization, the default setting if no @emph{-O} appears +@item -@item -X@var{name=value} -@cindex @option{-X} (@command{gnattest}) -Indicate that external variable @var{name} has the value @var{value}. +@emph{1} -@item --RTS=@var{rts-path} -@cindex @option{--RTS} (@command{gnattest}) -Specifies the default location of the runtime library. Same meaning as the -equivalent @command{gnatmake} flag (@pxref{Switches for gnatmake}). - - -@item --additional-tests=@var{projname} -@cindex @option{--additional-tests} (@command{gnattest}) -Sources described in @var{projname} are considered potential additional -manual tests to be added to the test suite. - -@item --harness-only -@cindex @option{--harness-only} (@command{gnattest}) -When this option is given, @command{gnattest} creates a harness for all -sources, treating them as test packages. - -@item --separate-drivers -@cindex @option{--separate-drivers} (@command{gnattest}) -Generates a separate test driver for each test, rather than a single -executable incorporating all tests. - -@item --stub -@cindex @option{--stub} (@command{gnattest}) -Generates the testing framework that uses subsystem stubbing to isolate the -code under test. - - -@item --harness-dir=@var{dirname} -@cindex @option{--harness-dir} (@command{gnattest}) -Specifies the directory that will hold the harness packages and project file -for the test driver. If the @var{dirname} is a relative path, it is considered -relative to the object directory of the project file. - -@item --tests-dir=@var{dirname} -@cindex @option{--tests-dir} (@command{gnattest}) -All test packages are placed in the @var{dirname} directory. -If the @var{dirname} is a relative path, it is considered relative to the object -directory of the project file. When all sources from all projects are taken -recursively from all projects, @var{dirname} directories are created for each -project in their object directories and test packages are placed accordingly. - -@item --subdir=@var{dirname} -@cindex @option{--subdir} (@command{gnattest}) -Test packages are placed in a subdirectory of the corresponding source -directory, with the name @var{dirname}. Thus, each set of unit tests is located -in a subdirectory of the code under test. If the sources are in separate -directories, each source directory has a test subdirectory named @var{dirname}. - -@item --tests-root=@var{dirname} -@cindex @option{--tests-root} (@command{gnattest}) -The hierarchy of source directories, if any, is recreated in the @var{dirname} -directory, with test packages placed in directories corresponding to those -of the sources. -If the @var{dirname} is a relative path, it is considered relative to the object -directory of the project file. When projects are considered recursively, -directory hierarchies of tested sources are -recreated for each project in their object directories and test packages are -placed accordingly. - -@item --stubs-dir=@var{dirname} -@cindex @option{--stubs-dir} (@command{gnattest}) -The hierarchy of directories containing stubbed units is recreated in -the @var{dirname} directory, with stubs placed in directories corresponding to -projects they are derived from. -If the @var{dirname} is a relative path, it is considered relative to the object -directory of the project file. When projects are considered recursively, -directory hierarchies of stubs are -recreated for each project in their object directories and test packages are -placed accordingly. - - -@item --validate-type-extensions -@cindex @option{--validate-type-extensions} (@command{gnattest}) -Enables substitution check: run all tests from all parents in order -to check substitutability in accordance with LSP. - -@item --skeleton-default=@var{val} -@cindex @option{--skeleton-default} (@command{gnattest}) -Specifies the default behavior of generated skeletons. @var{val} can be either -"fail" or "pass", "fail" being the default. - -@item --passed-tests=@var{val} -@cindex @option{--passed-tests} (@command{gnattest}) -Specifies whether or not passed tests should be shown. @var{val} can be either -"show" or "hide", "show" being the default. - -@item --exit-status=@var{val} -@cindex @option{--exit-status} (@command{gnattest}) -Specifies whether or not generated test driver should return failure exit -status if at least one test fails or crashes. @var{val} can be either -"on" or "off", "off" being the default. - -@item --omit-sloc -@cindex @option{--omit-sloc} (@command{gnattest}) -Suppresses comment line containing file name and line number of corresponding -subprograms in test skeletons. - -@item --no-command-line -@cindex @option{--no-command-line} (@command{gnattest}) -Don't add command line support to test driver. Note that regardless of this -switch, @command{gnattest} will automatically refrain from adding command -line support if it detects that the selected run-time doesn't provide -this capability. - - -@item --separates -@cindex @option{--separates} (@command{gnattest}) -Bodies of all test routines are generated as separates. Note that this mode is -kept for compatibility reasons only and it is not advised to use it due to -possible problems with hash in names of test skeletons when using an -inconsistent casing. Separate test skeletons can be incorporated to monolith -test package with improved hash being used by using @option{--transition} -switch. +@tab +Normal optimization, the default if you specify @emph{-O} without an +operand. A good compromise between code quality and compilation +time. -@item --transition -@cindex @option{--transition} (@command{gnattest}) -This allows transition from separate test routines to monolith test packages. -All matching test routines are overwritten with contents of corresponding -separates. Note that if separate test routines had any manually added with -clauses they will be moved to the test package body as is and have to be moved -by hand. +@item -@item --test-duration -@cindex @option{--test-duration} (@command{gnattest}) -Adds time measurements for each test in generated test driver. +@emph{2} -@end table +@tab -@option{--tests_root}, @option{--subdir} and @option{--tests-dir} switches are -mutually exclusive. +Extensive optimization, may improve execution time, possibly at +the cost of substantially increased compilation time. +@item -@node Switches for gnattest in tests execution mode -@section Switches for @command{gnattest} in tests execution mode +@emph{3} -@table @option -@c !sort! +@tab -@item --passed-tests=@var{val} -@cindex @option{--passed-tests} (@command{gnattest}) -Specifies whether or not passed tests should be shown. @var{val} can be either -"show" or "hide", "show" being the default. +Same as @emph{-O2}, and also includes inline expansion for small +subprograms in the same unit. -@item --queues=@var{n}, -j@var{n} -@cindex @option{--queues} (@command{gnattest}) -@cindex @option{-j} (@command{gnattest}) -Runs @var{n} tests in parallel (default is 1). +@item -@end table +@emph{s} +@tab -@node Project Attributes for gnattest -@section Project Attributes for @command{gnattest} +Optimize space usage -@noindent +@end multitable -Most of the command-line options can also be passed to the tool by adding -special attributes to the project file. Those attributes should be put in -package gnattest. Here is the list of attributes: -@itemize @bullet +See also @ref{101,,Optimization Levels}. +@end table -@item Tests_Root -is used to select the same output mode as with the --tests-root option. -This attribute cannot be used together with Subdir or Tests_Dir. +@geindex -pass-exit-codes (gcc) -@item Subdir -is used to select the same output mode as with the --subdir option. -This attribute cannot be used together with Tests_Root or Tests_Dir. -@item Tests_Dir -is used to select the same output mode as with the --tests-dir option. -This attribute cannot be used together with Subdir or Tests_Root. +@table @asis -@item Harness_Dir -is used to specify the directory in which to place harness packages and project -file for the test driver, otherwise specified by --harness-dir. +@item @code{-pass-exit-codes} -@item Additional_Tests -is used to specify the project file, otherwise given by ---additional-tests switch. +Catch exit codes from the compiler and use the most meaningful as +exit status. +@end table -@item Skeletons_Default -is used to specify the default behaviour of test skeletons, otherwise -specified by --skeleton-default option. The value of this attribute -should be either "pass" or "fail". +@geindex --RTS (gcc) -@end itemize -Each of those attributes can be overridden from the command line if needed. -Other @command{gnattest} switches can also be passed via the project -file as an attribute list called GNATtest_Switches. +@table @asis -@node Simple Example -@section Simple Example +@item @code{--RTS=@emph{rts-path}} -@noindent +Specifies the default location of the runtime library. Same meaning as the +equivalent @emph{gnatmake} flag (@ref{df,,Switches for gnatmake}). +@end table -Let's take a very simple example using the first @command{gnattest} example -located in: +@geindex -S (gcc) -@smallexample -/share/examples/gnattest/simple -@end smallexample -This project contains a simple package containing one subprogram. By running gnattest: +@table @asis -@smallexample -$ gnattest --harness-dir=driver -Psimple.gpr -@end smallexample +@item @code{-S} -a test driver is created in directory "driver". It can be compiled and run: +Used in place of @emph{-c} to +cause the assembler source file to be +generated, using @code{.s} as the extension, +instead of the object file. +This may be useful if you need to examine the generated assembly code. +@end table -@smallexample -$ cd obj/driver -$ gnatmake -Ptest_driver -$ test_runner -@end smallexample +@geindex -fverbose-asm (gcc) -One failed test with diagnosis "test not implemented" is reported. -Since no special output option was specified, the test package Simple.Tests -is located in: -@smallexample -/share/examples/gnattest/simple/obj/gnattest/tests -@end smallexample +@table @asis -For each package containing visible subprograms, a child test package is -generated. It contains one test routine per tested subprogram. Each -declaration of a test subprogram has a comment specifying which tested -subprogram it corresponds to. Bodies of test routines are placed in test package -bodies and are surrounded by special comment sections. Those comment sections -should not be removed or modified in order for gnattest to be able to regenerate -test packages and keep already written tests in place. -The test routine Test_Inc_5eaee3 located at simple-test_data-tests.adb contains -a single statement: a call to procedure Assert. It has two arguments: -the Boolean expression we want to check and the diagnosis message to display if -the condition is false. +@item @code{-fverbose-asm} -That is where actual testing code should be written after a proper setup. -An actual check can be performed by replacing the Assert call with: +Used in conjunction with @emph{-S} +to cause the generated assembly code file to be annotated with variable +names, making it significantly easier to follow. +@end table -@smallexample @c ada -Assert (Inc (1) = 2, "wrong incrementation"); -@end smallexample +@geindex -v (gcc) -After recompiling and running the test driver, one successfully passed test -is reported. -@node Setting Up and Tearing Down the Testing Environment -@section Setting Up and Tearing Down the Testing Environment +@table @asis -@noindent +@item @code{-v} -Besides test routines themselves, each test package has a parent package -Test_Data that has two procedures: Set_Up and Tear_Down. This package is never -overwritten by the tool. Set_Up is called before each test routine of the -package and Tear_Down is called after each test routine. Those two procedures -can be used to perform necessary initialization and finalization, -memory allocation, etc. Test type declared in Test_Data package is parent type -for the test type of test package and can have user-defined components whose -values can be set by Set_Up routine and used in test routines afterwards. +Show commands generated by the @emph{gcc} driver. Normally used only for +debugging purposes or if you need to be sure what version of the +compiler you are executing. +@end table -@node Regenerating Tests -@section Regenerating Tests +@geindex -V (gcc) -@noindent -Bodies of test routines and test_data packages are never overridden after they -have been created once. As long as the name of the subprogram, full expanded Ada -names, and the order of its parameters is the same, and comment sections are -intact the old test routine will fit in its place and no test skeleton will be -generated for the subprogram. +@table @asis -This can be demonstrated with the previous example. By uncommenting declaration -and body of function Dec in simple.ads and simple.adb, running -@command{gnattest} on the project, and then running the test driver: +@item @code{-V @emph{ver}} -@smallexample -gnattest --harness-dir=driver -Psimple.gpr -cd obj/driver -gnatmake -Ptest_driver -test_runner -@end smallexample +Execute @cite{ver} version of the compiler. This is the @emph{gcc} +version, not the GNAT version. +@end table -the old test is not replaced with a stub, nor is it lost, but a new test -skeleton is created for function Dec. +@geindex -w (gcc) -The only way of regenerating tests skeletons is to remove the previously created -tests together with corresponding comment sections. -@node Default Test Behavior -@section Default Test Behavior +@table @asis -@noindent +@item @code{-w} -The generated test driver can treat unimplemented tests in two ways: -either count them all as failed (this is useful to see which tests are still -left to implement) or as passed (to sort out unimplemented ones from those -actually failing). - -The test driver accepts a switch to specify this behavior: ---skeleton-default=val, where val is either "pass" or "fail" (exactly as for -@command{gnattest}). - -The default behavior of the test driver is set with the same switch -as passed to gnattest when generating the test driver. - -Passing it to the driver generated on the first example: - -@smallexample -test_runner --skeleton-default=pass -@end smallexample - -makes both tests pass, even the unimplemented one. - -@node Testing Primitive Operations of Tagged Types -@section Testing Primitive Operations of Tagged Types - -@noindent - -Creation of test skeletons for primitive operations of tagged types entails -a number of features. Test routines for all primitives of a given tagged type -are placed in a separate child package named according to the tagged type. For -example, if you have tagged type T in package P, all tests for primitives -of T will be in P.T_Test_Data.T_Tests. - -Consider running gnattest on the second example (note: actual tests for this -example already exist, so there's no need to worry if the tool reports that -no new stubs were generated): - -@smallexample -cd /share/examples/gnattest/tagged_rec -gnattest --harness-dir=driver -Ptagged_rec.gpr -@end smallexample - -Taking a closer look at the test type declared in the test package -Speed1.Controller_Test_Data is necessary. It is declared in: - -@smallexample -/share/examples/gnattest/tagged_rec/obj/gnattest/tests -@end smallexample - -Test types are direct or indirect descendants of -AUnit.Test_Fixtures.Test_Fixture type. In the case of nonprimitive tested -subprograms, the user doesn't need to be concerned with them. However, -when generating test packages for primitive operations, there are some things -the user needs to know. - -Type Test_Controller has components that allow assignment of various -derivations of type Controller. And if you look at the specification of -package Speed2.Auto_Controller, you will see that Test_Auto_Controller -actually derives from Test_Controller rather than AUnit type Test_Fixture. -Thus, test types mirror the hierarchy of tested types. - -The Set_Up procedure of Test_Data package corresponding to a test package -of primitive operations of type T assigns to Fixture a reference to an -object of that exact type T. Notice, however, that if the tagged type has -discriminants, the Set_Up only has a commented template for setting -up the fixture, since filling the discriminant with actual value is up -to the user. - -The knowledge of the structure of test types allows additional testing -without additional effort. Those possibilities are described below. - -@node Testing Inheritance -@section Testing Inheritance - -@noindent - -Since the test type hierarchy mimics the hierarchy of tested types, the -inheritance of tests takes place. An example of such inheritance can be -seen by running the test driver generated for the second example. As previously -mentioned, actual tests are already written for this example. - -@smallexample -cd obj/driver -gnatmake -Ptest_driver -test_runner -@end smallexample - -There are 6 passed tests while there are only 5 testable subprograms. The test -routine for function Speed has been inherited and run against objects of the -derived type. - -@node Tagged Types Substitutability Testing -@section Tagged Types Substitutability Testing - -@noindent - -Tagged Types Substitutability Testing is a way of verifying the global type -consistency by testing. Global type consistency is a principle stating that if -S is a subtype of T (in Ada, S is a derived type of tagged type T), -then objects of type T may be replaced with objects of type S (that is, -objects of type S may be substituted for objects of type T), without -altering any of the desirable properties of the program. When the properties -of the program are expressed in the form of subprogram preconditions and -postconditions (let's call them pre and post), the principle is formulated as -relations between the pre and post of primitive operations and the pre and post -of their derived operations. The pre of a derived operation should not be -stronger than the original pre, and the post of the derived operation should -not be weaker than the original post. Those relations ensure that verifying if -a dispatching call is safe can be done just by using the pre and post of the -root operation. - -Verifying global type consistency by testing consists of running all the unit -tests associated with the primitives of a given tagged type with objects of its -derived types. - -In the example used in the previous section, there was clearly a violation of -type consistency. The overriding primitive Adjust_Speed in package Speed2 -removes the functionality of the overridden primitive and thus doesn't respect -the consistency principle. -Gnattest has a special option to run overridden parent tests against objects -of the type which have overriding primitives: - -@smallexample -gnattest --harness-dir=driver --validate-type-extensions -Ptagged_rec.gpr -cd obj/driver -gnatmake -Ptest_driver -test_runner -@end smallexample - -While all the tests pass by themselves, the parent test for Adjust_Speed fails -against objects of the derived type. - -Non-overridden tests are already inherited for derived test types, so the ---validate-type-extensions enables the application of overriden tests to objects -of derived types. - -@node Testing with Contracts -@section Testing with Contracts - -@noindent - -@command{gnattest} supports pragmas Precondition, Postcondition, and Test_Case, -as well as corresponding aspects. -Test routines are generated, one per each Test_Case associated with a tested -subprogram. Those test routines have special wrappers for tested functions -that have composition of pre- and postcondition of the subprogram with -"requires" and "ensures" of the Test_Case (depending on the mode, pre and post -either count for Nominal mode or do not count for Robustness mode). - -The third example demonstrates how this works: - -@smallexample -cd /share/examples/gnattest/contracts -gnattest --harness-dir=driver -Pcontracts.gpr -@end smallexample - -Putting actual checks within the range of the contract does not cause any -error reports. For example, for the test routine which corresponds to -test case 1: - -@smallexample @c ada -Assert (Sqrt (9.0) = 3.0, "wrong sqrt"); -@end smallexample - -and for the test routine corresponding to test case 2: - -@smallexample @c ada -Assert (Sqrt (-5.0) = -1.0, "wrong error indication"); -@end smallexample - -are acceptable: - -@smallexample -cd obj/driver -gnatmake -Ptest_driver -test_runner -@end smallexample - -However, by changing 9.0 to 25.0 and 3.0 to 5.0, for example, you can get -a precondition violation for test case one. Also, by using any otherwise -correct but positive pair of numbers in the second test routine, you can also -get a precondition violation. Postconditions are checked and reported -the same way. - -@node Additional Tests -@section Additional Tests - -@noindent -@command{gnattest} can add user-written tests to the main suite of the test -driver. @command{gnattest} traverses the given packages and searches for test -routines. All procedures with a single in out parameter of a type which is -derived from AUnit.Test_Fixtures.Test_Fixture and that are declared in package -specifications are added to the suites and are then executed by the test driver. -(Set_Up and Tear_Down are filtered out.) - -An example illustrates two ways of creating test harnesses for user-written -tests. Directory additional_tests contains an AUnit-based test driver written -by hand. - -@smallexample -/share/examples/gnattest/additional_tests/ -@end smallexample - -To create a test driver for already-written tests, use the --harness-only -option: +Turn off warnings generated by the back end of the compiler. Use of +this switch also causes the default for front end warnings to be set +to suppress (as though @emph{-gnatws} had appeared at the start of +the options). +@end table -@smallexample -gnattest -Padditional/harness/harness.gpr --harness-dir=harness_only \ - --harness-only -gnatmake -Pharness_only/test_driver.gpr -harness_only/test_runner -@end smallexample - -Additional tests can also be executed together with generated tests: - -@smallexample -gnattest -Psimple.gpr --additional-tests=additional/harness/harness.gpr \ - --harness-dir=mixing -gnatmake -Pmixing/test_driver.gpr -mixing/test_runner -@end smallexample - - -@node Individual Test Drivers -@section Individual Test Drivers - -@noindent -By default, @command{gnattest} generates a monolithic test driver that -aggregates the individual tests into a single executable. It is also possible -to generate separate executables for each test, by passing the switch -@option{--separate-drivers}. This approach scales better for large testing -campaigns, especially involving target architectures with limited resources -typical for embedded development. It can also provide a major performance -benefit on multi-core systems by allowing simultaneous execution of multiple -tests. - -@command{gnattest} can take charge of executing the individual tests; for this, -instead of passing a project file, a text file containing the list of -executables can be passed. Such a file is automatically generated by gnattest -under the name @option{test_drivers.list}, but it can be -hand-edited to add or remove tests, or replaced. The individual tests can -also be executed standalone, or from any user-defined scripted framework. - - -@node Stubbing -@section Stubbing - -@noindent -Depending on the testing campaign, it is sometimes necessary to isolate the -part of the algorithm under test from its dependencies. This is accomplished -via @emph{stubbing}, i.e. replacing the subprograms that are called from the -subprogram under test by stand-in subprograms that match the profiles of the -original ones, but simply return predetermined values required by the test -scenario. - -This mode of test harness generation is activated by the switch @option{--stub}. - -The implementation approach chosen by @command{gnattest} is as follows. -For each package under consideration all the packages it is directly depending -on are stubbed, excluding the generic packages and package instantiations. -The stubs are shared for each package under test. The specs of packages to stub -remain intact, while their bodies are replaced, and hide the original bodies by -means of extending projects. Also, for each stubbed -package, a child package with setter routines for each subprogram declaration -is created. These setters are meant to be used to set the behaviour of -stubbed subprograms from within test cases. - -Note that subprograms belonging to the same package as the subprogram under -test are not stubbed. This guarantees that the sources being tested are -exactly the sources used for production, which is an important property for -establishing the traceability between the testing campaign and production code. - -Due to the nature of stubbing process, this mode implies the switch -@option{--separate-drivers}, i.e. an individual test driver (with the -corresponding hierarchy of extending projects) is generated for each test. - -@quotation Note -Developing a stubs-based testing campaign requires -good understanding of the infrastructure created by @command{gnattest} for -this purpose. We recommend following the stubbing tutorials provided -under @file{/share/examples/gnattest/stubbing*} before -attempting to use this powerful feature. -@end quotation +@geindex Combining GNAT switches -@node Putting Tests under Version Control -@section Putting Tests under Version Control +You may combine a sequence of GNAT switches into a single switch. For +example, the combined switch -@noindent -As has been stated earlier, @command{gnattest} generates two different types -of code, test skeletons and harness. The harness is generated completely -automatically each time, does not require manual changes and therefore should -not be put under version control. -It makes sense to put under version control files containing test data packages, -both specs and bodies, and files containing bodies of test packages. Note that -test package specs are also generated automatically each time and should not be -put under version control. -Option @option{--omit-sloc} may be usefull when putting test packages under VCS. +@quotation -@node Support for other platforms/run-times -@section Support for other platforms/run-times +@example +-gnatofi3 +@end example +@end quotation -@noindent -@command{gnattest} can be used to generate the test harness for platforms -and run-time libraries others than the default native target with the -default full run-time. For example, when using a limited run-time library -such as Zero FootPrint (ZFP), a simplified harness is generated. +is equivalent to specifying the following sequence of switches: -Two variables are used to tell the underlying AUnit framework how to generate -the test harness: @code{PLATFORM}, which identifies the target, and -@code{RUNTIME}, used to determine the run-time library for which the harness -is generated. Corresponding prefix should also be used when calling -@command{gnattest} for non-native targets. For example, the following options -are used to generate the AUnit test harness for a PowerPC ELF target using -the ZFP run-time library: +@quotation -@smallexample -powerpc-elf-gnattest -Psimple.gpr -XPLATFORM=powerpc-elf -XRUNTIME=zfp -@end smallexample +@example +-gnato -gnatf -gnati3 +@end example +@end quotation -@node Current Limitations -@section Current Limitations +The following restrictions apply to the combination of switches +in this manner: -@noindent -The tool currently does not support following features: +@itemize * -@itemize @bullet -@item generic tests for nested generic packages and their instantiations -@item tests for protected subprograms and entries +@item +The switch @emph{-gnatc} if combined with other switches must come +first in the string. -@end itemize -@end ifclear +@item +The switch @emph{-gnats} if combined with other switches must come +first in the string. +@item +The switches +@emph{-gnatzc} and @emph{-gnatzr} may not be combined with any other +switches, and only one of them may appear in the command line. -@c ********************************* -@node Performing Dimensionality Analysis in GNAT -@chapter Performing Dimensionality Analysis in GNAT -@cindex Dimensionality analysis +@item +The switch @emph{-gnat-p} may not be combined with any other switch. -@noindent -The GNAT compiler now supports dimensionality checking. The user can -specify physical units for objects, and the compiler will verify that uses -of these objects are compatible with their dimensions, in a fashion that is -familiar to engineering practice. The dimensions of algebraic expressions -(including powers with static exponents) are computed from their constituents. +@item +Once a 'y' appears in the string (that is a use of the @emph{-gnaty} +switch), then all further characters in the switch are interpreted +as style modifiers (see description of @emph{-gnaty}). -This feature depends on Ada 2012 aspect specifications, and is available from -version 7.0.1 of GNAT onwards. -The GNAT-specific aspect @code{Dimension_System} -@cindex @code{Dimension_System} aspect -allows you to define a system of units; the aspect @code{Dimension} -@cindex @code{Dimension} aspect -then allows the user to declare dimensioned quantities within a given system. -(These aspects are described in the @i{Implementation Defined Aspects} -chapter of the @i{GNAT Reference Manual}). +@item +Once a 'd' appears in the string (that is a use of the @emph{-gnatd} +switch), then all further characters in the switch are interpreted +as debug flags (see description of @emph{-gnatd}). -The major advantage of this model is that it does not require the declaration of -multiple operators for all possible combinations of types: it is only necessary -to use the proper subtypes in object declarations. +@item +Once a 'w' appears in the string (that is a use of the @emph{-gnatw} +switch), then all further characters in the switch are interpreted +as warning mode modifiers (see description of @emph{-gnatw}). -The simplest way to impose dimensionality checking on a computation is to make -use of the package @code{System.Dim.Mks}, -@cindex @code{System.Dim.Mks} package (GNAT library) -which is part of the GNAT library. This -package defines a floating-point type @code{MKS_Type}, -@cindex @code{MKS_Type} type -for which a sequence of -dimension names are specified, together with their conventional abbreviations. -The following should be read together with the full specification of the -package, in file @file{s-dimmks.ads}. -@cindex @file{s-dimmks.ads} file - -@smallexample @c ada -@group - @b{type} Mks_Type @b{is} @b{new} Long_Long_Float - @b{with} - Dimension_System => ( - (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), - (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), - (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), - (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), - (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"), - (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), - (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); -@end group -@end smallexample - -@noindent -The package then defines a series of subtypes that correspond to these -conventional units. For example: +@item +Once a 'V' appears in the string (that is a use of the @emph{-gnatV} +switch), then all further characters in the switch are interpreted +as validity checking options (@ref{fb,,Validity Checking}). -@smallexample @c ada -@group - @b{subtype} Length @b{is} Mks_Type - @b{with} - Dimension => (Symbol => 'm', Meter => 1, @b{others} => 0); -@end group -@end smallexample +@item +Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in +a combined list of options. +@end itemize -@noindent -and similarly for @code{Mass}, @code{Time}, @code{Electric_Current}, -@code{Thermodynamic_Temperature}, @code{Amount_Of_Substance}, and -@code{Luminous_Intensity} (the standard set of units of the SI system). +@node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id14}@anchor{102}@anchor{gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control}@anchor{103} +@subsection Output and Error Message Control -The package also defines conventional names for values of each unit, for -example: -@smallexample @c ada -@group - m : @b{constant} Length := 1.0; - kg : @b{constant} Mass := 1.0; - s : @b{constant} Time := 1.0; - A : @b{constant} Electric_Current := 1.0; -@end group -@end smallexample +@geindex stderr -@noindent -as well as useful multiples of these units: +The standard default format for error messages is called 'brief format'. +Brief format messages are written to @code{stderr} (the standard error +file) and have the following form: -@smallexample @c ada -@group - cm : @b{constant} Length := 1.0E-02; - g : @b{constant} Mass := 1.0E-03; - min : @b{constant} Time := 60.0; - day : @b{constant} Time := 60.0 * 24.0 * min; - ... -@end group -@end smallexample +@example +e.adb:3:04: Incorrect spelling of keyword "function" +e.adb:4:20: ";" should be "is" +@end example -@noindent -Using this package, you can then define a derived unit by -providing the aspect that -specifies its dimensions within the MKS system, as well as the string to -be used for output of a value of that unit: +The first integer after the file name is the line number in the file, +and the second integer is the column number within the line. +@cite{GPS} can parse the error messages +and point to the referenced character. +The following switches provide control over the error message +format: -@smallexample @c ada -@group - @b{subtype} Acceleration @b{is} Mks_Type - @b{with} Dimension => ("m/sec^2", - Meter => 1, - Second => -2, - @b{others} => 0); -@end group -@end smallexample - -@noindent -Here is a complete example of use: +@geindex -gnatv (gcc) -@smallexample @c ada -@group -@b{with} System.Dim.MKS; @b{use} System.Dim.Mks; -@b{with} System.Dim.Mks_IO; @b{use} System.Dim.Mks_IO; -@b{with} Text_IO; @b{use} Text_IO; -@b{procedure} Free_Fall @b{is} - @b{subtype} Acceleration @b{is} Mks_Type - @b{with} Dimension => ("m/sec^2", 1, 0, -2, @b{others} => 0); - G : @b{constant} acceleration := 9.81 * m / (s ** 2); - T : Time := 10.0*s; - Distance : Length; -@end group -@group -@b{begin} - Put ("Gravitational constant: "); - Put (G, Aft => 2, Exp => 0); Put_Line (""); - Distance := 0.5 * G * T ** 2; - Put ("distance travelled in 10 seconds of free fall "); - Put (Distance, Aft => 2, Exp => 0); - Put_Line (""); -@b{end} Free_Fall; -@end group -@end smallexample -@noindent -Execution of this program yields: -@smallexample -@group -Gravitational constant: 9.81 m/sec^2 -distance travelled in 10 seconds of free fall 490.50 m -@end group -@end smallexample +@table @asis -@noindent -However, incorrect assignments such as: +@item @code{-gnatv} -@smallexample @c ada -@group - Distance := 5.0; - Distance := 5.0 * kg: -@end group -@end smallexample +The @cite{v} stands for verbose. +The effect of this setting is to write long-format error +messages to @code{stdout} (the standard output file. +The same program compiled with the +@emph{-gnatv} switch would generate: -@noindent -are rejected with the following diagnoses: +@example +3. funcion X (Q : Integer) + | +>>> Incorrect spelling of keyword "function" +4. return Integer; + | +>>> ";" should be "is" +@end example -@smallexample -@group - Distance := 5.0; - >>> dimensions mismatch in assignment - >>> left-hand side has dimension [L] - >>> right-hand side is dimensionless -@end group - -@group - Distance := 5.0 * kg: - >>> dimensions mismatch in assignment - >>> left-hand side has dimension [L] - >>> right-hand side has dimension [M] -@end group -@end smallexample - -@noindent -The dimensions of an expression are properly displayed, even if there is -no explicit subtype for it. If we add to the program: +The vertical bar indicates the location of the error, and the @code{>>>} +prefix can be used to search for error messages. When this switch is +used the only source lines output are those with errors. +@end table -@smallexample @c ada -@group - Put ("Final velocity: "); - Put (G * T, Aft =>2, Exp =>0); - Put_Line (""); -@end group -@end smallexample +@geindex -gnatl (gcc) -@noindent -then the output includes: -@smallexample - Final velocity: 98.10 m.s**(-1) -@end smallexample +@table @asis -@c ********************************* -@node Generating Ada Bindings for C and C++ headers -@chapter Generating Ada Bindings for C and C++ headers -@findex binding +@item @code{-gnatl} -@noindent -GNAT now comes with a binding generator for C and C++ headers which is -intended to do 95% of the tedious work of generating Ada specs from C -or C++ header files. +The @cite{l} stands for list. +This switch causes a full listing of +the file to be generated. In the case where a body is +compiled, the corresponding spec is also listed, along +with any subunits. Typical output from compiling a package +body @code{p.adb} might look like: -Note that this capability is not intended to generate 100% correct Ada specs, -and will is some cases require manual adjustments, although it can often -be used out of the box in practice. +@example +Compiling: p.adb -Some of the known limitations include: + 1. package body p is + 2. procedure a; + 3. procedure a is separate; + 4. begin + 5. null + | + >>> missing ";" -@itemize @bullet -@item only very simple character constant macros are translated into Ada -constants. Function macros (macros with arguments) are partially translated -as comments, to be completed manually if needed. -@item some extensions (e.g. vector types) are not supported -@item pointers to pointers or complex structures are mapped to System.Address -@item identifiers with identical name (except casing) will generate compilation - errors (e.g. @code{shm_get} vs @code{SHM_GET}). -@end itemize + 6. end; -The code generated is using the Ada 2005 syntax, which makes it -easier to interface with other languages than previous versions of Ada. +Compiling: p.ads -@menu -* Running the binding generator:: -* Generating bindings for C++ headers:: -* Switches:: -@end menu + 1. package p is + 2. pragma Elaborate_Body + | + >>> missing ";" -@node Running the binding generator -@section Running the binding generator + 3. end p; -@noindent -The binding generator is part of the @command{gcc} compiler and can be -invoked via the @option{-fdump-ada-spec} switch, which will generate Ada -spec files for the header files specified on the command line, and all -header files needed by these files transitively. For example: +Compiling: p-a.adb -@smallexample -$ g++ -c -fdump-ada-spec -C /usr/include/time.h -$ gcc -c -gnat05 *.ads -@end smallexample + 1. separate p + | + >>> missing "(" -will generate, under GNU/Linux, the following files: @file{time_h.ads}, -@file{bits_time_h.ads}, @file{stddef_h.ads}, @file{bits_types_h.ads} which -correspond to the files @file{/usr/include/time.h}, -@file{/usr/include/bits/time.h}, etc@dots{}, and will then compile in Ada 2005 -mode these Ada specs. + 2. procedure a is + 3. begin + 4. null + | + >>> missing ";" -The @code{-C} switch tells @command{gcc} to extract comments from headers, -and will attempt to generate corresponding Ada comments. + 5. end; +@end example -If you want to generate a single Ada file and not the transitive closure, you -can use instead the @option{-fdump-ada-spec-slim} switch. +When you specify the @emph{-gnatv} or @emph{-gnatl} switches and +standard output is redirected, a brief summary is written to +@code{stderr} (standard error) giving the number of error messages and +warning messages generated. +@end table -You can optionally specify a parent unit, of which all generated units will -be children, using @code{-fada-spec-parent=}@var{unit}. +@geindex -gnatl=fname (gcc) -Note that we recommend when possible to use the @command{g++} driver to -generate bindings, even for most C headers, since this will in general -generate better Ada specs. For generating bindings for C++ headers, it is -mandatory to use the @command{g++} command, or @command{gcc -x c++} which -is equivalent in this case. If @command{g++} cannot work on your C headers -because of incompatibilities between C and C++, then you can fallback to -@command{gcc} instead. -For an example of better bindings generated from the C++ front-end, -the name of the parameters (when available) are actually ignored by the C -front-end. Consider the following C header: +@table @asis -@smallexample -extern void foo (int variable); -@end smallexample +@item @code{-gnatl=@emph{fname}} -with the C front-end, @code{variable} is ignored, and the above is handled as: +This has the same effect as @emph{-gnatl} except that the output is +written to a file instead of to standard output. If the given name +@code{fname} does not start with a period, then it is the full name +of the file to be written. If @code{fname} is an extension, it is +appended to the name of the file being compiled. For example, if +file @code{xyz.adb} is compiled with @emph{-gnatl=.lst}, +then the output is written to file xyz.adb.lst. +@end table -@smallexample -extern void foo (int); -@end smallexample +@geindex -gnatU (gcc) -generating a generic: -@smallexample -procedure foo (param1 : int); -@end smallexample +@table @asis -with the C++ front-end, the name is available, and we generate: +@item @code{-gnatU} -@smallexample -procedure foo (variable : int); -@end smallexample +This switch forces all error messages to be preceded by the unique +string 'error:'. This means that error messages take a few more +characters in space, but allows easy searching for and identification +of error messages. +@end table -In some cases, the generated bindings will be more complete or more meaningful -when defining some macros, which you can do via the @option{-D} switch. This -is for example the case with @file{Xlib.h} under GNU/Linux: +@geindex -gnatb (gcc) -@smallexample -g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h -@end smallexample -The above will generate more complete bindings than a straight call without -the @option{-DXLIB_ILLEGAL_ACCESS} switch. +@table @asis -In other cases, it is not possible to parse a header file in a stand-alone -manner, because other include files need to be included first. In this -case, the solution is to create a small header file including the needed -@code{#include} and possible @code{#define} directives. For example, to -generate Ada bindings for @file{readline/readline.h}, you need to first -include @file{stdio.h}, so you can create a file with the following two -lines in e.g. @file{readline1.h}: +@item @code{-gnatb} -@smallexample -#include -#include -@end smallexample +The @cite{b} stands for brief. +This switch causes GNAT to generate the +brief format error messages to @code{stderr} (the standard error +file) as well as the verbose +format message or full listing (which as usual is written to +@code{stdout} (the standard output file). +@end table -and then generate Ada bindings from this file: +@geindex -gnatm (gcc) -@smallexample -$ g++ -c -fdump-ada-spec readline1.h -@end smallexample -@node Generating bindings for C++ headers -@section Generating bindings for C++ headers +@table @asis -@noindent -Generating bindings for C++ headers is done using the same options, always -with the @command{g++} compiler. +@item @code{-gnatm=@emph{n}} -In this mode, C++ classes will be mapped to Ada tagged types, constructors -will be mapped using the @code{CPP_Constructor} pragma, and when possible, -multiple inheritance of abstract classes will be mapped to Ada interfaces -(@xref{Interfacing to C++,,,gnat_rm, GNAT Reference Manual}, for additional -information on interfacing to C++). +The @cite{m} stands for maximum. +@cite{n} is a decimal integer in the +range of 1 to 999999 and limits the number of error or warning +messages to be generated. For example, using +@emph{-gnatm2} might yield -For example, given the following C++ header file: +@example +e.adb:3:04: Incorrect spelling of keyword "function" +e.adb:5:35: missing ".." +fatal error: maximum number of errors detected +compilation abandoned +@end example -@smallexample -@group -@cartouche -class Carnivore @{ -public: - virtual int Number_Of_Teeth () = 0; -@}; +The default setting if +no switch is given is 9999. If the number of warnings reaches this +limit, then a message is output and further warnings are suppressed, +but the compilation is continued. If the number of error messages +reaches this limit, then a message is output and the compilation +is abandoned. A value of zero means that no limit applies. -class Domestic @{ -public: - virtual void Set_Owner (char* Name) = 0; -@}; +Note that the equal sign is optional, so the switches +@emph{-gnatm2} and @emph{-gnatm=2} are equivalent. +@end table -class Animal @{ -public: - int Age_Count; - virtual void Set_Age (int New_Age); -@}; +@geindex -gnatf (gcc) -class Dog : Animal, Carnivore, Domestic @{ - public: - int Tooth_Count; - char *Owner; - virtual int Number_Of_Teeth (); - virtual void Set_Owner (char* Name); +@table @asis - Dog(); -@}; -@end cartouche -@end group -@end smallexample +@item @code{-gnatf} -The corresponding Ada code is generated: +@geindex Error messages +@geindex suppressing -@smallexample @c ada -@group -@cartouche - @b{package} Class_Carnivore @b{is} - @b{type} Carnivore @b{is} @b{limited} interface; - @b{pragma} Import (CPP, Carnivore); - - @b{function} Number_Of_Teeth (this : @b{access} Carnivore) @b{return} int @b{is} @b{abstract}; - @b{end}; - @b{use} Class_Carnivore; - - @b{package} Class_Domestic @b{is} - @b{type} Domestic @b{is} @b{limited} interface; - @b{pragma} Import (CPP, Domestic); - - @b{procedure} Set_Owner - (this : @b{access} Domestic; - Name : Interfaces.C.Strings.chars_ptr) @b{is} @b{abstract}; - @b{end}; - @b{use} Class_Domestic; - - @b{package} Class_Animal @b{is} - @b{type} Animal @b{is} @b{tagged} @b{limited} @b{record} - Age_Count : @b{aliased} int; - @b{end} @b{record}; - @b{pragma} Import (CPP, Animal); - - @b{procedure} Set_Age (this : @b{access} Animal; New_Age : int); - @b{pragma} Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi"); - @b{end}; - @b{use} Class_Animal; - - @b{package} Class_Dog @b{is} - @b{type} Dog @b{is} @b{new} Animal @b{and} Carnivore @b{and} Domestic @b{with} @b{record} - Tooth_Count : @b{aliased} int; - Owner : Interfaces.C.Strings.chars_ptr; - @b{end} @b{record}; - @b{pragma} Import (CPP, Dog); - - @b{function} Number_Of_Teeth (this : @b{access} Dog) @b{return} int; - @b{pragma} Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv"); - - @b{procedure} Set_Owner - (this : @b{access} Dog; Name : Interfaces.C.Strings.chars_ptr); - @b{pragma} Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc"); - - @b{function} New_Dog @b{return} Dog; - @b{pragma} CPP_Constructor (New_Dog); - @b{pragma} Import (CPP, New_Dog, "_ZN3DogC1Ev"); - @b{end}; - @b{use} Class_Dog; -@end cartouche -@end group -@end smallexample +The @cite{f} stands for full. +Normally, the compiler suppresses error messages that are likely to be +redundant. This switch causes all error +messages to be generated. In particular, in the case of +references to undefined variables. If a given variable is referenced +several times, the normal format of messages is -@node Switches -@section Switches +@example +e.adb:7:07: "V" is undefined (more references follow) +@end example -@table @option -@item -fdump-ada-spec -@cindex @option{-fdump-ada-spec} (@command{gcc}) -Generate Ada spec files for the given header files transitively (including -all header files that these headers depend upon). +where the parenthetical comment warns that there are additional +references to the variable @cite{V}. Compiling the same program with the +@emph{-gnatf} switch yields -@item -fdump-ada-spec-slim -@cindex @option{-fdump-ada-spec-slim} (@command{gcc}) -Generate Ada spec files for the header files specified on the command line -only. +@example +e.adb:7:07: "V" is undefined +e.adb:8:07: "V" is undefined +e.adb:8:12: "V" is undefined +e.adb:8:16: "V" is undefined +e.adb:9:07: "V" is undefined +e.adb:9:12: "V" is undefined +@end example -@item -fada-spec-parent=@var{unit} -@cindex -fada-spec-parent (@command{gcc}) -Specifies that all files generated by @option{-fdump-ada-spec*} are -to be child units of the specified parent unit. +The @emph{-gnatf} switch also generates additional information for +some error messages. Some examples are: -@item -C -@cindex @option{-C} (@command{gcc}) -Extract comments from headers and generate Ada comments in the Ada spec files. -@end table -@node Other Utility Programs -@chapter Other Utility Programs +@itemize * -@noindent -This chapter discusses some other utility programs available in the Ada -environment. +@item +Details on possibly non-portable unchecked conversion -@menu -* Using Other Utility Programs with GNAT:: -* The External Symbol Naming Scheme of GNAT:: -* Converting Ada Files to html with gnathtml:: -* Installing gnathtml:: -@end menu +@item +List possible interpretations for ambiguous calls -@node Using Other Utility Programs with GNAT -@section Using Other Utility Programs with GNAT +@item +Additional details on incorrect parameters +@end itemize +@end table -@noindent -The object files generated by GNAT are in standard system format and in -particular the debugging information uses this format. This means -programs generated by GNAT can be used with existing utilities that -depend on these formats. +@geindex -gnatjnn (gcc) -In general, any utility program that works with C will also often work with -Ada programs generated by GNAT. This includes software utilities such as -gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such -as Purify. -@node The External Symbol Naming Scheme of GNAT -@section The External Symbol Naming Scheme of GNAT +@table @asis -@noindent -In order to interpret the output from GNAT, when using tools that are -originally intended for use with other languages, it is useful to -understand the conventions used to generate link names from the Ada -entity names. +@item @code{-gnatjnn} -All link names are in all lowercase letters. With the exception of library -procedure names, the mechanism used is simply to use the full expanded -Ada name with dots replaced by double underscores. For example, suppose -we have the following package spec: +In normal operation mode (or if @emph{-gnatj0} is used), then error messages +with continuation lines are treated as though the continuation lines were +separate messages (and so a warning with two continuation lines counts as +three warnings, and is listed as three separate messages). -@smallexample @c ada -@group -@cartouche -@b{package} QRS @b{is} - MN : Integer; -@b{end} QRS; -@end cartouche -@end group -@end smallexample +If the @emph{-gnatjnn} switch is used with a positive value for nn, then +messages are output in a different manner. A message and all its continuation +lines are treated as a unit, and count as only one warning or message in the +statistics totals. Furthermore, the message is reformatted so that no line +is longer than nn characters. +@end table -@noindent -The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so -the corresponding link name is @code{qrs__mn}. -@findex Export -Of course if a @code{pragma Export} is used this may be overridden: +@geindex -gnatq (gcc) -@smallexample @c ada -@group -@cartouche -@b{package} Exports @b{is} - Var1 : Integer; - @b{pragma} Export (Var1, C, External_Name => "var1_name"); - Var2 : Integer; - @b{pragma} Export (Var2, C, Link_Name => "var2_link_name"); -@b{end} Exports; -@end cartouche -@end group -@end smallexample -@noindent -In this case, the link name for @var{Var1} is whatever link name the -C compiler would assign for the C function @var{var1_name}. This typically -would be either @var{var1_name} or @var{_var1_name}, depending on operating -system conventions, but other possibilities exist. The link name for -@var{Var2} is @var{var2_link_name}, and this is not operating system -dependent. +@table @asis -@findex _main -One exception occurs for library level procedures. A potential ambiguity -arises between the required name @code{_main} for the C main program, -and the name we would otherwise assign to an Ada library level procedure -called @code{Main} (which might well not be the main program). +@item @code{-gnatq} -To avoid this ambiguity, we attach the prefix @code{_ada_} to such -names. So if we have a library level procedure such as +The @cite{q} stands for quit (really 'don't quit'). +In normal operation mode, the compiler first parses the program and +determines if there are any syntax errors. If there are, appropriate +error messages are generated and compilation is immediately terminated. +This switch tells +GNAT to continue with semantic analysis even if syntax errors have been +found. This may enable the detection of more errors in a single run. On +the other hand, the semantic analyzer is more likely to encounter some +internal fatal error when given a syntactically invalid tree. +@end table -@smallexample @c ada -@group -@cartouche -@b{procedure} Hello (S : String); -@end cartouche -@end group -@end smallexample +@geindex -gnatQ (gcc) -@noindent -the external name of this procedure will be @var{_ada_hello}. +@table @asis -@node Converting Ada Files to html with gnathtml -@section Converting Ada Files to HTML with @code{gnathtml} +@item @code{-gnatQ} -@noindent -This @code{Perl} script allows Ada source files to be browsed using -standard Web browsers. For installation procedure, see the section -@xref{Installing gnathtml}. +In normal operation mode, the @code{ALI} file is not generated if any +illegalities are detected in the program. The use of @emph{-gnatQ} forces +generation of the @code{ALI} file. This file is marked as being in +error, so it cannot be used for binding purposes, but it does contain +reasonably complete cross-reference information, and thus may be useful +for use by tools (e.g., semantic browsing tools or integrated development +environments) that are driven from the @code{ALI} file. This switch +implies @emph{-gnatq}, since the semantic phase must be run to get a +meaningful ALI file. -Ada reserved keywords are highlighted in a bold font and Ada comments in -a blue font. Unless your program was compiled with the gcc @option{-gnatx} -switch to suppress the generation of cross-referencing information, user -defined variables and types will appear in a different color; you will -be able to click on any identifier and go to its declaration. +In addition, if @emph{-gnatt} is also specified, then the tree file is +generated even if there are illegalities. It may be useful in this case +to also specify @emph{-gnatq} to ensure that full semantic processing +occurs. The resulting tree file can be processed by ASIS, for the purpose +of providing partial information about illegal units, but if the error +causes the tree to be badly malformed, then ASIS may crash during the +analysis. -The command line is as follow: -@smallexample -@c $ perl gnathtml.pl @ovar{switches} @var{ada-files} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ perl gnathtml.pl @r{[}@var{switches}@r{]} @var{ada-files} -@end smallexample +When @emph{-gnatQ} is used and the generated @code{ALI} file is marked as +being in error, @emph{gnatmake} will attempt to recompile the source when it +finds such an @code{ALI} file, including with switch @emph{-gnatc}. -@noindent -You can pass it as many Ada files as you want. @code{gnathtml} will generate -an html file for every ada file, and a global file called @file{index.htm}. -This file is an index of every identifier defined in the files. +Note that @emph{-gnatQ} has no effect if @emph{-gnats} is specified, +since ALI files are never generated if @emph{-gnats} is set. +@end table -The available switches are the following ones: +@node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{ff}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{104} +@subsection Warning Message Control -@table @option -@item -83 -@cindex @option{-83} (@code{gnathtml}) -Only the Ada 83 subset of keywords will be highlighted. -@item -cc @var{color} -@cindex @option{-cc} (@code{gnathtml}) -This option allows you to change the color used for comments. The default -value is green. The color argument can be any name accepted by html. +@geindex Warning messages -@item -d -@cindex @option{-d} (@code{gnathtml}) -If the Ada files depend on some other files (for instance through -@code{with} clauses, the latter files will also be converted to html. -Only the files in the user project will be converted to html, not the files -in the run-time library itself. +In addition to error messages, which correspond to illegalities as defined +in the Ada Reference Manual, the compiler detects two kinds of warning +situations. -@item -D -@cindex @option{-D} (@code{gnathtml}) -This command is the same as @option{-d} above, but @command{gnathtml} will -also look for files in the run-time library, and generate html files for them. +First, the compiler considers some constructs suspicious and generates a +warning message to alert you to a possible error. Second, if the +compiler detects a situation that is sure to raise an exception at +run time, it generates a warning message. The following shows an example +of warning messages: -@item -ext @var{extension} -@cindex @option{-ext} (@code{gnathtml}) -This option allows you to change the extension of the generated HTML files. -If you do not specify an extension, it will default to @file{htm}. +@example +e.adb:4:24: warning: creation of object may raise Storage_Error +e.adb:10:17: warning: static value out of range +e.adb:10:17: warning: "Constraint_Error" will be raised at run time +@end example -@item -f -@cindex @option{-f} (@code{gnathtml}) -By default, gnathtml will generate html links only for global entities -('with'ed units, global variables and types,@dots{}). If you specify -@option{-f} on the command line, then links will be generated for local -entities too. +GNAT considers a large number of situations as appropriate +for the generation of warning messages. As always, warnings are not +definite indications of errors. For example, if you do an out-of-range +assignment with the deliberate intention of raising a +@cite{Constraint_Error} exception, then the warning that may be +issued does not indicate an error. Some of the situations for which GNAT +issues warnings (at least some of the time) are given in the following +list. This list is not complete, and new warnings are often added to +subsequent versions of GNAT. The list is intended to give a general idea +of the kinds of warnings that are generated. -@item -l @var{number} -@cindex @option{-l} (@code{gnathtml}) -If this switch is provided and @var{number} is not 0, then -@code{gnathtml} will number the html files every @var{number} line. -@item -I @var{dir} -@cindex @option{-I} (@code{gnathtml}) -Specify a directory to search for library files (@file{.ALI} files) and -source files. You can provide several -I switches on the command line, -and the directories will be parsed in the order of the command line. +@itemize * -@item -o @var{dir} -@cindex @option{-o} (@code{gnathtml}) -Specify the output directory for html files. By default, gnathtml will -saved the generated html files in a subdirectory named @file{html/}. +@item +Possible infinitely recursive calls -@item -p @var{file} -@cindex @option{-p} (@code{gnathtml}) -If you are using Emacs and the most recent Emacs Ada mode, which provides -a full Integrated Development Environment for compiling, checking, -running and debugging applications, you may use @file{.gpr} files -to give the directories where Emacs can find sources and object files. +@item +Out-of-range values being assigned -Using this switch, you can tell gnathtml to use these files. -This allows you to get an html version of your application, even if it -is spread over multiple directories. +@item +Possible order of elaboration problems -@item -sc @var{color} -@cindex @option{-sc} (@code{gnathtml}) -This switch allows you to change the color used for symbol -definitions. -The default value is red. The color argument can be any name accepted by html. +@item +Size not a multiple of alignment for a record type -@item -t @var{file} -@cindex @option{-t} (@code{gnathtml}) -This switch provides the name of a file. This file contains a list of -file names to be converted, and the effect is exactly as though they had -appeared explicitly on the command line. This -is the recommended way to work around the command line length limit on some -systems. +@item +Assertions (pragma Assert) that are sure to fail -@end table +@item +Unreachable code -@node Installing gnathtml -@section Installing @code{gnathtml} +@item +Address clauses with possibly unaligned values, or where an attempt is +made to overlay a smaller variable with a larger one. -@noindent -@code{Perl} needs to be installed on your machine to run this script. -@code{Perl} is freely available for almost every architecture and -Operating System via the Internet. +@item +Fixed-point type declarations with a null range -On Unix systems, you may want to modify the first line of the script -@code{gnathtml}, to explicitly tell the Operating system where Perl -is. The syntax of this line is: -@smallexample -#!full_path_name_to_perl -@end smallexample +@item +Direct_IO or Sequential_IO instantiated with a type that has access values -@noindent -Alternatively, you may run the script using the following command line: +@item +Variables that are never assigned a value -@smallexample -@c $ perl gnathtml.pl @ovar{switches} @var{files} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ perl gnathtml.pl @r{[}@var{switches}@r{]} @var{files} -@end smallexample +@item +Variables that are referenced before being initialized +@item +Task entries with no corresponding @cite{accept} statement -@c ****************************** -@node Code Coverage and Profiling -@chapter Code Coverage and Profiling -@cindex Code Coverage -@cindex Profiling +@item +Duplicate accepts for the same task entry in a @cite{select} -@noindent -This chapter describes how to use @code{gcov} - coverage testing tool - and -@code{gprof} - profiler tool - on your Ada programs. +@item +Objects that take too much storage -@menu -* Code Coverage of Ada Programs with gcov:: -* Profiling an Ada Program with gprof:: -@end menu +@item +Unchecked conversion between types of differing sizes -@node Code Coverage of Ada Programs with gcov -@section Code Coverage of Ada Programs with gcov -@cindex gcov -@cindex -fprofile-arcs -@cindex -ftest-coverage -@cindex -coverage -@cindex Code Coverage +@item +Missing @cite{return} statement along some execution path in a function -@noindent -@code{gcov} is a test coverage program: it analyzes the execution of a given -program on selected tests, to help you determine the portions of the program -that are still untested. +@item +Incorrect (unrecognized) pragmas -@code{gcov} is part of the GCC suite, and is described in detail in the GCC -User's Guide. You can refer to this documentation for a more complete -description. +@item +Incorrect external names -This chapter provides a quick startup guide, and -details some Gnat-specific features. +@item +Allocation from empty storage pool -@menu -* Quick startup guide:: -* Gnat specifics:: -@end menu +@item +Potentially blocking operation in protected type -@node Quick startup guide -@subsection Quick startup guide +@item +Suspicious parenthesization of expressions -In order to perform coverage analysis of a program using @code{gcov}, 3 -steps are needed: +@item +Mismatching bounds in an aggregate -@itemize @bullet -@item -Code instrumentation during the compilation process -@item -Execution of the instrumented program -@item -Execution of the @code{gcov} tool to generate the result. -@end itemize +@item +Attempt to return local value by reference -The code instrumentation needed by gcov is created at the object level: -The source code is not modified in any way, because the instrumentation code is -inserted by gcc during the compilation process. To compile your code with code -coverage activated, you need to recompile your whole project using the -switches -@code{-fprofile-arcs} and @code{-ftest-coverage}, and link it using -@code{-fprofile-arcs}. +@item +Premature instantiation of a generic body -@smallexample -$ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \ - -largs -fprofile-arcs -@end smallexample +@item +Attempt to pack aliased components -This compilation process will create @file{.gcno} files together with -the usual object files. +@item +Out of bounds array subscripts -Once the program is compiled with coverage instrumentation, you can -run it as many times as needed - on portions of a test suite for -example. The first execution will produce @file{.gcda} files at the -same location as the @file{.gcno} files. The following executions -will update those files, so that a cumulative result of the covered -portions of the program is generated. +@item +Wrong length on string assignment -Finally, you need to call the @code{gcov} tool. The different options of -@code{gcov} are available in the GCC User's Guide, section 'Invoking gcov'. +@item +Violations of style rules if style checking is enabled -This will create annotated source files with a @file{.gcov} extension: -@file{my_main.adb} file will be analysed in @file{my_main.adb.gcov}. +@item +Unused @emph{with} clauses -@node Gnat specifics -@subsection Gnat specifics +@item +@cite{Bit_Order} usage that does not have any effect -Because Ada semantics, portions of the source code may be shared among -several object files. This is the case for example when generics are -involved, when inlining is active or when declarations generate initialisation -calls. In order to take -into account this shared code, you need to call @code{gcov} on all -source files of the tested program at once. +@item +@cite{Standard.Duration} used to resolve universal fixed expression -The list of source files might exceed the system's maximum command line -length. In order to bypass this limitation, a new mechanism has been -implemented in @code{gcov}: you can now list all your project's files into a -text file, and provide this file to gcov as a parameter, preceded by a @@ -(e.g. @samp{gcov @@mysrclist.txt}). +@item +Dereference of possibly null value -Note that on AIX compiling a static library with @code{-fprofile-arcs} is -not supported as there can be unresolved symbols during the final link. +@item +Declaration that is likely to cause storage error -@node Profiling an Ada Program with gprof -@section Profiling an Ada Program with gprof -@cindex gprof -@cindex -pg -@cindex Profiling +@item +Internal GNAT unit @emph{with}ed by application unit -@noindent -This section is not meant to be an exhaustive documentation of @code{gprof}. -Full documentation for it can be found in the GNU Profiler User's Guide -documentation that is part of this GNAT distribution. +@item +Values known to be out of range at compile time -Profiling a program helps determine the parts of a program that are executed -most often, and are therefore the most time-consuming. +@item +Unreferenced or unmodified variables. Note that a special +exemption applies to variables which contain any of the substrings +@cite{DISCARD@comma{} DUMMY@comma{} IGNORE@comma{} JUNK@comma{} UNUSED}, in any casing. Such variables +are considered likely to be intentionally used in a situation where +otherwise a warning would be given, so warnings of this kind are +always suppressed for such variables. -@code{gprof} is the standard GNU profiling tool; it has been enhanced to -better handle Ada programs and multitasking. -It is currently supported on the following platforms -@itemize @bullet -@item -linux x86/x86_64 -@item -solaris sparc/sparc64/x86 -@item -windows x86 -@end itemize +@item +Address overlays that could clobber memory -@noindent -In order to profile a program using @code{gprof}, 3 steps are needed: +@item +Unexpected initialization when address clause present -@itemize @bullet -@item -Code instrumentation, requiring a full recompilation of the project with the -proper switches. -@item -Execution of the program under the analysis conditions, i.e. with the desired -input. -@item -Analysis of the results using the @code{gprof} tool. +@item +Bad alignment for address clause + +@item +Useless type conversions + +@item +Redundant assignment statements and other redundant constructs + +@item +Useless exception handlers + +@item +Accidental hiding of name by child unit + +@item +Access before elaboration detected at compile time + +@item +A range in a @cite{for} loop that is known to be null or might be null @end itemize -@noindent -The following sections detail the different steps, and indicate how -to interpret the results: -@menu -* Compilation for profiling:: -* Program execution:: -* Running gprof:: -* Interpretation of profiling results:: -@end menu +The following section lists compiler switches that are available +to control the handling of warning messages. It is also possible +to exercise much finer control over what warnings are issued and +suppressed using the GNAT pragma Warnings (see the description +of the pragma in the @cite{GNAT_Reference_manual}). -@node Compilation for profiling -@subsection Compilation for profiling -@cindex -pg -@cindex Profiling +@geindex -gnatwa (gcc) -In order to profile a program the first step is to tell the compiler -to generate the necessary profiling information. The compiler switch to be used -is @code{-pg}, which must be added to other compilation switches. This -switch needs to be specified both during compilation and link stages, and can -be specified once when using gnatmake: -@smallexample -gnatmake -f -pg -P my_project -@end smallexample +@table @asis + +@item @code{-gnatwa} -@noindent -Note that only the objects that were compiled with the @samp{-pg} switch will -be profiled; if you need to profile your whole project, use the @samp{-f} -gnatmake switch to force full recompilation. +@emph{Activate most optional warnings.} -@node Program execution -@subsection Program execution +This switch activates most optional warning messages. See the remaining list +in this section for details on optional warning messages that can be +individually controlled. The warnings that are not turned on by this +switch are: -@noindent -Once the program has been compiled for profiling, you can run it as usual. -The only constraint imposed by profiling is that the program must terminate -normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be -properly analyzed. +@itemize * -Once the program completes execution, a data file called @file{gmon.out} is -generated in the directory where the program was launched from. If this file -already exists, it will be overwritten. +@item +@code{-gnatwd} (implicit dereferencing) -@node Running gprof -@subsection Running gprof +@item +@code{-gnatw.d} (tag warnings with -gnatw switch) -@noindent -The @code{gprof} tool is called as follow: +@item +@code{-gnatwh} (hiding) -@smallexample -gprof my_prog gmon.out -@end smallexample +@item +@code{-gnatw.h} (holes in record layouts) -@noindent -or simpler: +@item +@code{-gnatw.k} (redefinition of names in standard) -@smallexample -gprof my_prog -@end smallexample +@item +@code{-gnatwl} (elaboration warnings) -@noindent -The complete form of the gprof command line is the following: +@item +@code{-gnatw.l} (inherited aspects) -@smallexample -gprof [switches] [executable [data-file]] -@end smallexample +@item +@code{-gnatw.n} (atomic synchronization) -@noindent -@code{gprof} supports numerous switch. The order of these -switch does not matter. The full list of options can be found in -the GNU Profiler User's Guide documentation that comes with this documentation. +@item +@code{-gnatwo} (address clause overlay) -The following is the subset of those switches that is most relevant: +@item +@code{-gnatw.o} (values set by out parameters ignored) -@table @option +@item +@code{-gnatw.s} (overridden size clause) -@item --demangle[=@var{style}] -@itemx --no-demangle -@cindex @option{--demangle} (@code{gprof}) -These options control whether symbol names should be demangled when -printing output. The default is to demangle C++ symbols. The -@code{--no-demangle} option may be used to turn off demangling. Different -compilers have different mangling styles. The optional demangling style -argument can be used to choose an appropriate demangling style for your -compiler, in particular Ada symbols generated by GNAT can be demangled using -@code{--demangle=gnat}. +@item +@code{-gnatwt} (tracking of deleted conditional code) -@item -e @var{function_name} -@cindex @option{-e} (@code{gprof}) -The @samp{-e @var{function}} option tells @code{gprof} not to print -information about the function @var{function_name} (and its -children@dots{}) in the call graph. The function will still be listed -as a child of any functions that call it, but its index number will be -shown as @samp{[not printed]}. More than one @samp{-e} option may be -given; only one @var{function_name} may be indicated with each @samp{-e} -option. +@item +@code{-gnatw.u} (unordered enumeration) -@item -E @var{function_name} -@cindex @option{-E} (@code{gprof}) -The @code{-E @var{function}} option works like the @code{-e} option, but -execution time spent in the function (and children who were not called from -anywhere else), will not be used to compute the percentages-of-time for -the call graph. More than one @samp{-E} option may be given; only one -@var{function_name} may be indicated with each @samp{-E} option. - -@item -f @var{function_name} -@cindex @option{-f} (@code{gprof}) -The @samp{-f @var{function}} option causes @code{gprof} to limit the -call graph to the function @var{function_name} and its children (and -their children@dots{}). More than one @samp{-f} option may be given; -only one @var{function_name} may be indicated with each @samp{-f} -option. +@item +@code{-gnatw.w} (use of Warnings Off) -@item -F @var{function_name} -@cindex @option{-F} (@code{gprof}) -The @samp{-F @var{function}} option works like the @code{-f} option, but -only time spent in the function and its children (and their -children@dots{}) will be used to determine total-time and -percentages-of-time for the call graph. More than one @samp{-F} option -may be given; only one @var{function_name} may be indicated with each -@samp{-F} option. The @samp{-F} option overrides the @samp{-E} option. +@item +@code{-gnatw.y} (reasons for package needing body) +@end itemize +All other optional warnings are turned on. @end table -@node Interpretation of profiling results -@subsection Interpretation of profiling results +@geindex -gnatwA (gcc) -@noindent -The results of the profiling analysis are represented by two arrays: the -'flat profile' and the 'call graph'. Full documentation of those outputs -can be found in the GNU Profiler User's Guide. +@table @asis -The flat profile shows the time spent in each function of the program, and how -many time it has been called. This allows you to locate easily the most -time-consuming functions. +@item @code{-gnatwA} -The call graph shows, for each subprogram, the subprograms that call it, -and the subprograms that it calls. It also provides an estimate of the time -spent in each of those callers/called subprograms. +@emph{Suppress all optional errors.} -@c ****************************** -@node Running and Debugging Ada Programs -@chapter Running and Debugging Ada Programs -@cindex Debugging +This switch suppresses all optional warning messages, see remaining list +in this section for details on optional warning messages that can be +individually controlled. Note that unlike switch @emph{-gnatws}, the +use of switch @emph{-gnatwA} does not suppress warnings that are +normally given unconditionally and cannot be individually controlled +(for example, the warning about a missing exit path in a function). +Also, again unlike switch @emph{-gnatws}, warnings suppressed by +the use of switch @emph{-gnatwA} can be individually turned back +on. For example the use of switch @emph{-gnatwA} followed by +switch @emph{-gnatwd} will suppress all optional warnings except +the warnings for implicit dereferencing. +@end table -@noindent -This chapter discusses how to debug Ada programs. +@geindex -gnatw.a (gcc) -An incorrect Ada program may be handled in three ways by the GNAT compiler: -@enumerate -@item -The illegality may be a violation of the static semantics of Ada. In -that case GNAT diagnoses the constructs in the program that are illegal. -It is then a straightforward matter for the user to modify those parts of -the program. +@table @asis -@item -The illegality may be a violation of the dynamic semantics of Ada. In -that case the program compiles and executes, but may generate incorrect -results, or may terminate abnormally with some exception. +@item @code{-gnatw.a} -@item -When presented with a program that contains convoluted errors, GNAT -itself may terminate abnormally without providing full diagnostics on -the incorrect user program. -@end enumerate +@emph{Activate warnings on failing assertions.} -@menu -* The GNAT Debugger GDB:: -* Running GDB:: -* Introduction to GDB Commands:: -* Using Ada Expressions:: -* Calling User-Defined Subprograms:: -* Using the Next Command in a Function:: -* Ada Exceptions:: -* Ada Tasks:: -* Debugging Generic Units:: -* Remote Debugging with gdbserver:: -* GNAT Abnormal Termination or Failure to Terminate:: -* Naming Conventions for GNAT Source Files:: -* Getting Internal Debugging Information:: -* Stack Traceback:: -@end menu +@geindex Assert failures -@cindex Debugger -@findex gdb +This switch activates warnings for assertions where the compiler can tell at +compile time that the assertion will fail. Note that this warning is given +even if assertions are disabled. The default is that such warnings are +generated. +@end table -@node The GNAT Debugger GDB -@section The GNAT Debugger GDB +@geindex -gnatw.A (gcc) -@noindent -@code{GDB} is a general purpose, platform-independent debugger that -can be used to debug mixed-language programs compiled with @command{gcc}, -and in particular is capable of debugging Ada programs compiled with -GNAT. The latest versions of @code{GDB} are Ada-aware and can handle -complex Ada data structures. -@xref{Top,, Debugging with GDB, gdb, Debugging with GDB}, -for full details on the usage of @code{GDB}, including a section on -its usage on programs. This manual should be consulted for full -details. The section that follows is a brief introduction to the -philosophy and use of @code{GDB}. +@table @asis -When GNAT programs are compiled, the compiler optionally writes debugging -information into the generated object file, including information on -line numbers, and on declared types and variables. This information is -separate from the generated code. It makes the object files considerably -larger, but it does not add to the size of the actual executable that -will be loaded into memory, and has no impact on run-time performance. The -generation of debug information is triggered by the use of the --g switch in the @command{gcc} or @command{gnatmake} command -used to carry out the compilations. It is important to emphasize that -the use of these options does not change the generated code. +@item @code{-gnatw.A} -The debugging information is written in standard system formats that -are used by many tools, including debuggers and profilers. The format -of the information is typically designed to describe C types and -semantics, but GNAT implements a translation scheme which allows full -details about Ada types and variables to be encoded into these -standard C formats. Details of this encoding scheme may be found in -the file exp_dbug.ads in the GNAT source distribution. However, the -details of this encoding are, in general, of no interest to a user, -since @code{GDB} automatically performs the necessary decoding. +@emph{Suppress warnings on failing assertions.} -When a program is bound and linked, the debugging information is -collected from the object files, and stored in the executable image of -the program. Again, this process significantly increases the size of -the generated executable file, but it does not increase the size of -the executable program itself. Furthermore, if this program is run in -the normal manner, it runs exactly as if the debug information were -not present, and takes no more actual memory. +@geindex Assert failures -However, if the program is run under control of @code{GDB}, the -debugger is activated. The image of the program is loaded, at which -point it is ready to run. If a run command is given, then the program -will run exactly as it would have if @code{GDB} were not present. This -is a crucial part of the @code{GDB} design philosophy. @code{GDB} is -entirely non-intrusive until a breakpoint is encountered. If no -breakpoint is ever hit, the program will run exactly as it would if no -debugger were present. When a breakpoint is hit, @code{GDB} accesses -the debugging information and can respond to user commands to inspect -variables, and more generally to report on the state of execution. +This switch suppresses warnings for assertions where the compiler can tell at +compile time that the assertion will fail. +@end table -@c ************** -@node Running GDB -@section Running GDB +@geindex -gnatwb (gcc) -@noindent -This section describes how to initiate the debugger. -@c The above sentence is really just filler, but it was otherwise -@c clumsy to get the first paragraph nonindented given the conditional -@c nature of the description -The debugger can be launched from a @code{GPS} menu or -directly from the command line. The description below covers the latter use. -All the commands shown can be used in the @code{GPS} debug console window, -but there are usually more GUI-based ways to achieve the same effect. +@table @asis -The command to run @code{GDB} is +@item @code{-gnatwb} -@smallexample -$ gdb program -@end smallexample +@emph{Activate warnings on bad fixed values.} -@noindent -where @code{program} is the name of the executable file. This -activates the debugger and results in a prompt for debugger commands. -The simplest command is simply @code{run}, which causes the program to run -exactly as if the debugger were not present. The following section -describes some of the additional commands that can be given to @code{GDB}. +@geindex Bad fixed values -@c ******************************* -@node Introduction to GDB Commands -@section Introduction to GDB Commands +@geindex Fixed-point Small value -@noindent -@code{GDB} contains a large repertoire of commands. @xref{Top,, -Debugging with GDB, gdb, Debugging with GDB}, -for extensive documentation on the use -of these commands, together with examples of their use. Furthermore, -the command @command{help} invoked from within GDB activates a simple help -facility which summarizes the available commands and their options. -In this section we summarize a few of the most commonly -used commands to give an idea of what @code{GDB} is about. You should create -a simple program with debugging information and experiment with the use of -these @code{GDB} commands on the program as you read through the -following section. +@geindex Small value -@table @code -@item set args @var{arguments} -The @var{arguments} list above is a list of arguments to be passed to -the program on a subsequent run command, just as though the arguments -had been entered on a normal invocation of the program. The @code{set args} -command is not needed if the program does not require arguments. +This switch activates warnings for static fixed-point expressions whose +value is not an exact multiple of Small. Such values are implementation +dependent, since an implementation is free to choose either of the multiples +that surround the value. GNAT always chooses the closer one, but this is not +required behavior, and it is better to specify a value that is an exact +multiple, ensuring predictable execution. The default is that such warnings +are not generated. +@end table -@item run -The @code{run} command causes execution of the program to start from -the beginning. If the program is already running, that is to say if -you are currently positioned at a breakpoint, then a prompt will ask -for confirmation that you want to abandon the current execution and -restart. +@geindex -gnatwB (gcc) -@item breakpoint @var{location} -The breakpoint command sets a breakpoint, that is to say a point at which -execution will halt and @code{GDB} will await further -commands. @var{location} is -either a line number within a file, given in the format @code{file:linenumber}, -or it is the name of a subprogram. If you request that a breakpoint be set on -a subprogram that is overloaded, a prompt will ask you to specify on which of -those subprograms you want to breakpoint. You can also -specify that all of them should be breakpointed. If the program is run -and execution encounters the breakpoint, then the program -stops and @code{GDB} signals that the breakpoint was encountered by -printing the line of code before which the program is halted. -@item catch exception @var{name} -This command causes the program execution to stop whenever exception -@var{name} is raised. If @var{name} is omitted, then the execution is -suspended when any exception is raised. +@table @asis -@item print @var{expression} -This will print the value of the given expression. Most simple -Ada expression formats are properly handled by @code{GDB}, so the expression -can contain function calls, variables, operators, and attribute references. +@item @code{-gnatwB} -@item continue -Continues execution following a breakpoint, until the next breakpoint or the -termination of the program. +@emph{Suppress warnings on bad fixed values.} -@item step -Executes a single line after a breakpoint. If the next statement -is a subprogram call, execution continues into (the first statement of) -the called subprogram. +This switch suppresses warnings for static fixed-point expressions whose +value is not an exact multiple of Small. +@end table -@item next -Executes a single line. If this line is a subprogram call, executes and -returns from the call. +@geindex -gnatw.b (gcc) -@item list -Lists a few lines around the current source location. In practice, it -is usually more convenient to have a separate edit window open with the -relevant source file displayed. Successive applications of this command -print subsequent lines. The command can be given an argument which is a -line number, in which case it displays a few lines around the specified one. -@item backtrace -Displays a backtrace of the call chain. This command is typically -used after a breakpoint has occurred, to examine the sequence of calls that -leads to the current breakpoint. The display includes one line for each -activation record (frame) corresponding to an active subprogram. +@table @asis -@item up -At a breakpoint, @code{GDB} can display the values of variables local -to the current frame. The command @code{up} can be used to -examine the contents of other active frames, by moving the focus up -the stack, that is to say from callee to caller, one frame at a time. +@item @code{-gnatw.b} -@item down -Moves the focus of @code{GDB} down from the frame currently being -examined to the frame of its callee (the reverse of the previous command), +@emph{Activate warnings on biased representation.} -@item frame @var{n} -Inspect the frame with the given number. The value 0 denotes the frame -of the current breakpoint, that is to say the top of the call stack. +@geindex Biased representation -@item kill -Kills the child process in which the program is running under GDB. -This may be useful for several purposes: -@itemize @bullet -@item -It allows you to recompile and relink your program, since on many systems -you cannot regenerate an executable file while it is running in a process. -@item -You can run your program outside the debugger, on systems that do not -permit executing a program outside GDB while breakpoints are set -within GDB. -@item -It allows you to debug a core dump rather than a running process. -@end itemize +This switch activates warnings when a size clause, value size clause, component +clause, or component size clause forces the use of biased representation for an +integer type (e.g. representing a range of 10..11 in a single bit by using 0/1 +to represent 10/11). The default is that such warnings are generated. @end table -@noindent -The above list is a very short introduction to the commands that -@code{GDB} provides. Important additional capabilities, including conditional -breakpoints, the ability to execute command sequences on a breakpoint, -the ability to debug at the machine instruction level and many other -features are described in detail in @ref{Top,, Debugging with GDB, gdb, -Debugging with GDB}. Note that most commands can be abbreviated -(for example, c for continue, bt for backtrace). +@geindex -gnatwB (gcc) -@node Using Ada Expressions -@section Using Ada Expressions -@cindex Ada expressions -@noindent -@code{GDB} supports a fairly large subset of Ada expression syntax, with some -extensions. The philosophy behind the design of this subset is +@table @asis -@itemize @bullet -@item -That @code{GDB} should provide basic literals and access to operations for -arithmetic, dereferencing, field selection, indexing, and subprogram calls, -leaving more sophisticated computations to subprograms written into the -program (which therefore may be called from @code{GDB}). +@item @code{-gnatw.B} -@item -That type safety and strict adherence to Ada language restrictions -are not particularly important to the @code{GDB} user. +@emph{Suppress warnings on biased representation.} -@item -That brevity is important to the @code{GDB} user. -@end itemize +This switch suppresses warnings for representation clauses that force the use +of biased representation. +@end table -@noindent -Thus, for brevity, the debugger acts as if there were -implicit @code{with} and @code{use} clauses in effect for all user-written -packages, thus making it unnecessary to fully qualify most names with -their packages, regardless of context. Where this causes ambiguity, -@code{GDB} asks the user's intent. +@geindex -gnatwc (gcc) -For details on the supported Ada syntax, see @ref{Top,, Debugging with -GDB, gdb, Debugging with GDB}. -@node Calling User-Defined Subprograms -@section Calling User-Defined Subprograms +@table @asis -@noindent -An important capability of @code{GDB} is the ability to call user-defined -subprograms while debugging. This is achieved simply by entering -a subprogram call statement in the form: +@item @code{-gnatwc} -@smallexample -call subprogram-name (parameters) -@end smallexample +@emph{Activate warnings on conditionals.} -@noindent -The keyword @code{call} can be omitted in the normal case where the -@code{subprogram-name} does not coincide with any of the predefined -@code{GDB} commands. +@geindex Conditionals +@geindex constant -The effect is to invoke the given subprogram, passing it the -list of parameters that is supplied. The parameters can be expressions and -can include variables from the program being debugged. The -subprogram must be defined -at the library level within your program, and @code{GDB} will call the -subprogram within the environment of your program execution (which -means that the subprogram is free to access or even modify variables -within your program). +This switch activates warnings for conditional expressions used in +tests that are known to be True or False at compile time. The default +is that such warnings are not generated. +Note that this warning does +not get issued for the use of boolean variables or constants whose +values are known at compile time, since this is a standard technique +for conditional compilation in Ada, and this would generate too many +false positive warnings. -The most important use of this facility is in allowing the inclusion of -debugging routines that are tailored to particular data structures -in your program. Such debugging routines can be written to provide a suitably -high-level description of an abstract type, rather than a low-level dump -of its physical layout. After all, the standard -@code{GDB print} command only knows the physical layout of your -types, not their abstract meaning. Debugging routines can provide information -at the desired semantic level and are thus enormously useful. +This warning option also activates a special test for comparisons using +the operators '>=' and' <='. +If the compiler can tell that only the equality condition is possible, +then it will warn that the '>' or '<' part of the test +is useless and that the operator could be replaced by '='. +An example would be comparing a @cite{Natural} variable <= 0. -For example, when debugging GNAT itself, it is crucial to have access to -the contents of the tree nodes used to represent the program internally. -But tree nodes are represented simply by an integer value (which in turn -is an index into a table of nodes). -Using the @code{print} command on a tree node would simply print this integer -value, which is not very useful. But the PN routine (defined in file -treepr.adb in the GNAT sources) takes a tree node as input, and displays -a useful high level representation of the tree node, which includes the -syntactic category of the node, its position in the source, the integers -that denote descendant nodes and parent node, as well as varied -semantic information. To study this example in more detail, you might want to -look at the body of the PN procedure in the stated file. +This warning option also generates warnings if +one or both tests is optimized away in a membership test for integer +values if the result can be determined at compile time. Range tests on +enumeration types are not included, since it is common for such tests +to include an end point. -Another useful application of this capability is to deal with situations of -complex data which are not handled suitably by GDB. For example, if you specify -Convention Fortran for a multi-dimensional array, GDB does not know that -the ordering of array elements has been switched and will not properly -address the array elements. In such a case, instead of trying to print the -elements directly from GDB, you can write a callable procedure that prints -the elements in the desired format. +This warning can also be turned on using @emph{-gnatwa}. +@end table -@node Using the Next Command in a Function -@section Using the Next Command in a Function +@geindex -gnatwC (gcc) -@noindent -When you use the @code{next} command in a function, the current source -location will advance to the next statement as usual. A special case -arises in the case of a @code{return} statement. -Part of the code for a return statement is the ``epilogue'' of the function. -This is the code that returns to the caller. There is only one copy of -this epilogue code, and it is typically associated with the last return -statement in the function if there is more than one return. In some -implementations, this epilogue is associated with the first statement -of the function. +@table @asis -The result is that if you use the @code{next} command from a return -statement that is not the last return statement of the function you -may see a strange apparent jump to the last return statement or to -the start of the function. You should simply ignore this odd jump. -The value returned is always that from the first return statement -that was stepped through. +@item @code{-gnatwC} -@node Ada Exceptions -@section Stopping when Ada Exceptions are Raised -@cindex Exceptions +@emph{Suppress warnings on conditionals.} -@noindent -You can set catchpoints that stop the program execution when your program -raises selected exceptions. +This switch suppresses warnings for conditional expressions used in +tests that are known to be True or False at compile time. +@end table -@table @code -@item catch exception -Set a catchpoint that stops execution whenever (any task in the) program -raises any exception. +@geindex -gnatw.c (gcc) -@item catch exception @var{name} -Set a catchpoint that stops execution whenever (any task in the) program -raises the exception @var{name}. -@item catch exception unhandled -Set a catchpoint that stops executing whenever (any task in the) program -raises an exception for which there is no handler. +@table @asis -@item info exceptions -@itemx info exceptions @var{regexp} -The @code{info exceptions} command permits the user to examine all defined -exceptions within Ada programs. With a regular expression, @var{regexp}, as -argument, prints out only those exceptions whose name matches @var{regexp}. -@end table +@item @code{-gnatw.c} -@node Ada Tasks -@section Ada Tasks -@cindex Tasks +@emph{Activate warnings on missing component clauses.} -@noindent -@code{GDB} allows the following task-related commands: +@geindex Component clause +@geindex missing -@table @code -@item info tasks -This command shows a list of current Ada tasks, as in the following example: +This switch activates warnings for record components where a record +representation clause is present and has component clauses for the +majority, but not all, of the components. A warning is given for each +component for which no component clause is present. +@end table -@smallexample -@iftex -@leftskip=0cm -@end iftex -(gdb) info tasks - ID TID P-ID Thread Pri State Name - 1 8088000 0 807e000 15 Child Activation Wait main_task - 2 80a4000 1 80ae000 15 Accept/Select Wait b - 3 809a800 1 80a4800 15 Child Activation Wait a -* 4 80ae800 3 80b8000 15 Running c -@end smallexample +@geindex -gnatwC (gcc) -@noindent -In this listing, the asterisk before the first task indicates it to be the -currently running task. The first column lists the task ID that is used -to refer to tasks in the following commands. -@item break @var{linespec} task @var{taskid} -@itemx break @var{linespec} task @var{taskid} if @dots{} -@cindex Breakpoints and tasks -These commands are like the @code{break @dots{} thread @dots{}}. -@var{linespec} specifies source lines. +@table @asis -Use the qualifier @samp{task @var{taskid}} with a breakpoint command -to specify that you only want @code{GDB} to stop the program when a -particular Ada task reaches this breakpoint. @var{taskid} is one of the -numeric task identifiers assigned by @code{GDB}, shown in the first -column of the @samp{info tasks} display. +@item @code{-gnatw.C} -If you do not specify @samp{task @var{taskid}} when you set a -breakpoint, the breakpoint applies to @emph{all} tasks of your -program. +@emph{Suppress warnings on missing component clauses.} -You can use the @code{task} qualifier on conditional breakpoints as -well; in this case, place @samp{task @var{taskid}} before the -breakpoint condition (before the @code{if}). +This switch suppresses warnings for record components that are +missing a component clause in the situation described above. +@end table -@item task @var{taskno} -@cindex Task switching +@geindex -gnatwd (gcc) -This command allows switching to the task referred by @var{taskno}. In -particular, this allows browsing of the backtrace of the specified -task. It is advisable to switch back to the original task before -continuing execution otherwise the scheduling of the program may be -perturbed. -@end table -@noindent -For more detailed information on the tasking support, -see @ref{Top,, Debugging with GDB, gdb, Debugging with GDB}. +@table @asis -@node Debugging Generic Units -@section Debugging Generic Units -@cindex Debugging Generic Units -@cindex Generics +@item @code{-gnatwd} -@noindent -GNAT always uses code expansion for generic instantiation. This means that -each time an instantiation occurs, a complete copy of the original code is -made, with appropriate substitutions of formals by actuals. +@emph{Activate warnings on implicit dereferencing.} -It is not possible to refer to the original generic entities in -@code{GDB}, but it is always possible to debug a particular instance of -a generic, by using the appropriate expanded names. For example, if we have +If this switch is set, then the use of a prefix of an access type +in an indexed component, slice, or selected component without an +explicit @cite{.all} will generate a warning. With this warning +enabled, access checks occur only at points where an explicit +@cite{.all} appears in the source code (assuming no warnings are +generated as a result of this switch). The default is that such +warnings are not generated. +@end table -@smallexample @c ada -@group -@cartouche -@b{procedure} g @b{is} +@geindex -gnatwD (gcc) - @b{generic} @b{package} k @b{is} - @b{procedure} kp (v1 : @b{in} @b{out} integer); - @b{end} k; - @b{package} @b{body} k @b{is} - @b{procedure} kp (v1 : @b{in} @b{out} integer) @b{is} - @b{begin} - v1 := v1 + 1; - @b{end} kp; - @b{end} k; +@table @asis - @b{package} k1 @b{is} @b{new} k; - @b{package} k2 @b{is} @b{new} k; +@item @code{-gnatwD} - var : integer := 1; +@emph{Suppress warnings on implicit dereferencing.} -@b{begin} - k1.kp (var); - k2.kp (var); - k1.kp (var); - k2.kp (var); -@b{end}; -@end cartouche -@end group -@end smallexample +@geindex Implicit dereferencing -@noindent -Then to break on a call to procedure kp in the k2 instance, simply -use the command: +@geindex Dereferencing +@geindex implicit -@smallexample -(gdb) break g.k2.kp -@end smallexample +This switch suppresses warnings for implicit dereferences in +indexed components, slices, and selected components. +@end table -@noindent -When the breakpoint occurs, you can step through the code of the -instance in the normal manner and examine the values of local variables, as for -other units. +@geindex -gnatw.d (gcc) -@node Remote Debugging with gdbserver -@section Remote Debugging with gdbserver -@cindex Remote Debugging with gdbserver -@noindent -On platforms where gdbserver is supported, it is possible to use this tool -to debug your application remotely. This can be useful in situations -where the program needs to be run on a target host that is different -from the host used for development, particularly when the target has -a limited amount of resources (either CPU and/or memory). +@table @asis -To do so, start your program using gdbserver on the target machine. -gdbserver then automatically suspends the execution of your program -at its entry point, waiting for a debugger to connect to it. The -following commands starts an application and tells gdbserver to -wait for a connection with the debugger on localhost port 4444. +@item @code{-gnatw.d} -@smallexample -$ gdbserver localhost:4444 program -Process program created; pid = 5685 -Listening on port 4444 -@end smallexample +@emph{Activate tagging of warning and info messages.} -Once gdbserver has started listening, we can tell the debugger to establish -a connection with this gdbserver, and then start the same debugging session -as if the program was being debugged on the same host, directly under -the control of GDB. +If this switch is set, then warning messages are tagged, with one of the +following strings: -@smallexample -$ gdb program -(gdb) target remote targethost:4444 -Remote debugging using targethost:4444 -0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so. -(gdb) b foo.adb:3 -Breakpoint 1 at 0x401f0c: file foo.adb, line 3. -(gdb) continue -Continuing. +@quotation -Breakpoint 1, foo () at foo.adb:4 -4 end foo; -@end smallexample -It is also possible to use gdbserver to attach to an already running -program, in which case the execution of that program is simply suspended -until the connection between the debugger and gdbserver is established. +@itemize - -For more information on how to use gdbserver, @ref{Top, Server, Using -the gdbserver Program, gdb, Debugging with GDB}. @value{EDITION} provides support -for gdbserver on x86-linux, x86-windows and x86_64-linux. +@item +@emph{[-gnatw?]} +Used to tag warnings controlled by the switch @emph{-gnatwx} where x +is a letter a-z. -@node GNAT Abnormal Termination or Failure to Terminate -@section GNAT Abnormal Termination or Failure to Terminate -@cindex GNAT Abnormal Termination or Failure to Terminate +@item +@emph{[-gnatw.?]} +Used to tag warnings controlled by the switch @emph{-gnatw.x} where x +is a letter a-z. -@noindent -When presented with programs that contain serious errors in syntax -or semantics, -GNAT may on rare occasions experience problems in operation, such -as aborting with a -segmentation fault or illegal memory access, raising an internal -exception, terminating abnormally, or failing to terminate at all. -In such cases, you can activate -various features of GNAT that can help you pinpoint the construct in your -program that is the likely source of the problem. +@item +@emph{[-gnatel]} +Used to tag elaboration information (info) messages generated when the +static model of elaboration is used and the @emph{-gnatel} switch is set. -The following strategies are presented in increasing order of -difficulty, corresponding to your experience in using GNAT and your -familiarity with compiler internals. +@item +@emph{[restriction warning]} +Used to tag warning messages for restriction violations, activated by use +of the pragma @emph{Restriction_Warnings}. -@enumerate -@item -Run @command{gcc} with the @option{-gnatf}. This first -switch causes all errors on a given line to be reported. In its absence, -only the first error on a line is displayed. +@item +@emph{[warning-as-error]} +Used to tag warning messages that have been converted to error messages by +use of the pragma Warning_As_Error. Note that such warnings are prefixed by +the string "error: " rather than "warning: ". -The @option{-gnatdO} switch causes errors to be displayed as soon as they -are encountered, rather than after compilation is terminated. If GNAT -terminates prematurely or goes into an infinite loop, the last error -message displayed may help to pinpoint the culprit. +@item +@emph{[enabled by default]} +Used to tag all other warnings that are always given by default, unless +warnings are completely suppressed using pragma @emph{Warnings(Off)} or +the switch @emph{-gnatws}. +@end itemize +@end quotation +@end table -@item -Run @command{gcc} with the @option{-v (verbose)} switch. In this -mode, @command{gcc} produces ongoing information about the progress of the -compilation and provides the name of each procedure as code is -generated. This switch allows you to find which Ada procedure was being -compiled when it encountered a code generation problem. +@geindex -gnatw.d (gcc) -@item -@cindex @option{-gnatdc} switch -Run @command{gcc} with the @option{-gnatdc} switch. This is a GNAT specific -switch that does for the front-end what @option{-v} does -for the back end. The system prints the name of each unit, -either a compilation unit or nested unit, as it is being analyzed. -@item -Finally, you can start -@code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the -front-end of GNAT, and can be run independently (normally it is just -called from @command{gcc}). You can use @code{gdb} on @code{gnat1} as you -would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The -@code{where} command is the first line of attack; the variable -@code{lineno} (seen by @code{print lineno}), used by the second phase of -@code{gnat1} and by the @command{gcc} backend, indicates the source line at -which the execution stopped, and @code{input_file name} indicates the name of -the source file. -@end enumerate -@node Naming Conventions for GNAT Source Files -@section Naming Conventions for GNAT Source Files +@table @asis -@noindent -In order to examine the workings of the GNAT system, the following -brief description of its organization may be helpful: +@item @code{-gnatw.D} -@itemize @bullet -@item -Files with prefix @file{sc} contain the lexical scanner. +@emph{Deactivate tagging of warning and info messages messages.} -@item -All files prefixed with @file{par} are components of the parser. The -numbers correspond to chapters of the Ada Reference Manual. For example, -parsing of select statements can be found in @file{par-ch9.adb}. +If this switch is set, then warning messages return to the default +mode in which warnings and info messages are not tagged as described above for +@cite{-gnatw.d}. +@end table -@item -All files prefixed with @file{sem} perform semantic analysis. The -numbers correspond to chapters of the Ada standard. For example, all -issues involving context clauses can be found in @file{sem_ch10.adb}. In -addition, some features of the language require sufficient special processing -to justify their own semantic files: sem_aggr for aggregates, sem_disp for -dynamic dispatching, etc. +@geindex -gnatwe (gcc) -@item -All files prefixed with @file{exp} perform normalization and -expansion of the intermediate representation (abstract syntax tree, or AST). -these files use the same numbering scheme as the parser and semantics files. -For example, the construction of record initialization procedures is done in -@file{exp_ch3.adb}. +@geindex Warnings +@geindex treat as error -@item -The files prefixed with @file{bind} implement the binder, which -verifies the consistency of the compilation, determines an order of -elaboration, and generates the bind file. -@item -The files @file{atree.ads} and @file{atree.adb} detail the low-level -data structures used by the front-end. +@table @asis -@item -The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of -the abstract syntax tree as produced by the parser. +@item @code{-gnatwe} -@item -The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of -all entities, computed during semantic analysis. +@emph{Treat warnings and style checks as errors.} -@item -Library management issues are dealt with in files with prefix -@file{lib}. +This switch causes warning messages and style check messages to be +treated as errors. +The warning string still appears, but the warning messages are counted +as errors, and prevent the generation of an object file. Note that this +is the only -gnatw switch that affects the handling of style check messages. +Note also that this switch has no effect on info (information) messages, which +are not treated as errors if this switch is present. +@end table -@item -@findex Ada -@cindex Annex A -Ada files with the prefix @file{a-} are children of @code{Ada}, as -defined in Annex A. +@geindex -gnatw.e (gcc) -@item -@findex Interfaces -@cindex Annex B -Files with prefix @file{i-} are children of @code{Interfaces}, as -defined in Annex B. -@item -@findex System -Files with prefix @file{s-} are children of @code{System}. This includes -both language-defined children and GNAT run-time routines. +@table @asis -@item -@findex GNAT -Files with prefix @file{g-} are children of @code{GNAT}. These are useful -general-purpose packages, fully documented in their specs. All -the other @file{.c} files are modifications of common @command{gcc} files. -@end itemize +@item @code{-gnatw.e} -@node Getting Internal Debugging Information -@section Getting Internal Debugging Information +@emph{Activate every optional warning} -@noindent -Most compilers have internal debugging switches and modes. GNAT -does also, except GNAT internal debugging switches and modes are not -secret. A summary and full description of all the compiler and binder -debug flags are in the file @file{debug.adb}. You must obtain the -sources of the compiler to see the full detailed effects of these flags. +@geindex Warnings +@geindex activate every optional warning -The switches that print the source of the program (reconstructed from -the internal tree) are of general interest for user programs, as are the -options to print -the full internal tree, and the entity table (the symbol table -information). The reconstructed source provides a readable version of the -program after the front-end has completed analysis and expansion, -and is useful when studying the performance of specific constructs. -For example, constraint checks are indicated, complex aggregates -are replaced with loops and assignments, and tasking primitives -are replaced with run-time calls. +This switch activates all optional warnings, including those which +are not activated by @cite{-gnatwa}. The use of this switch is not +recommended for normal use. If you turn this switch on, it is almost +certain that you will get large numbers of useless warnings. The +warnings that are excluded from @cite{-gnatwa} are typically highly +specialized warnings that are suitable for use only in code that has +been specifically designed according to specialized coding rules. +@end table -@node Stack Traceback -@section Stack Traceback -@cindex traceback -@cindex stack traceback -@cindex stack unwinding +@geindex -gnatwf (gcc) -@noindent -Traceback is a mechanism to display the sequence of subprogram calls that -leads to a specified execution point in a program. Often (but not always) -the execution point is an instruction at which an exception has been raised. -This mechanism is also known as @i{stack unwinding} because it obtains -its information by scanning the run-time stack and recovering the activation -records of all active subprograms. Stack unwinding is one of the most -important tools for program debugging. -The first entry stored in traceback corresponds to the deepest calling level, -that is to say the subprogram currently executing the instruction -from which we want to obtain the traceback. +@table @asis -Note that there is no runtime performance penalty when stack traceback -is enabled, and no exception is raised during program execution. +@item @code{-gnatwf} -@menu -* Non-Symbolic Traceback:: -* Symbolic Traceback:: -@end menu +@emph{Activate warnings on unreferenced formals.} -@node Non-Symbolic Traceback -@subsection Non-Symbolic Traceback -@cindex traceback, non-symbolic +@geindex Formals +@geindex unreferenced -@noindent -Note: this feature is not supported on all platforms. See -@file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported -platforms. +This switch causes a warning to be generated if a formal parameter +is not referenced in the body of the subprogram. This warning can +also be turned on using @emph{-gnatwu}. The +default is that these warnings are not generated. +@end table -@menu -* Tracebacks From an Unhandled Exception:: -* Tracebacks From Exception Occurrences (non-symbolic):: -* Tracebacks From Anywhere in a Program (non-symbolic):: -@end menu +@geindex -gnatwF (gcc) -@node Tracebacks From an Unhandled Exception -@subsubsection Tracebacks From an Unhandled Exception -@noindent -A runtime non-symbolic traceback is a list of addresses of call instructions. -To enable this feature you must use the @option{-E} -@code{gnatbind}'s option. With this option a stack traceback is stored as part -of exception information. You can retrieve this information using the -@code{addr2line} tool. +@table @asis -Here is a simple example: +@item @code{-gnatwF} -@smallexample @c ada -@cartouche -@b{procedure} STB @b{is} +@emph{Suppress warnings on unreferenced formals.} - @b{procedure} P1 @b{is} - @b{begin} - @b{raise} Constraint_Error; - @b{end} P1; +This switch suppresses warnings for unreferenced formal +parameters. Note that the +combination @emph{-gnatwu} followed by @emph{-gnatwF} has the +effect of warning on unreferenced entities other than subprogram +formals. +@end table - @b{procedure} P2 @b{is} - @b{begin} - P1; - @b{end} P2; +@geindex -gnatwg (gcc) -@b{begin} - P2; -@b{end} STB; -@end cartouche -@end smallexample -@smallexample -$ gnatmake stb -bargs -E -$ stb +@table @asis -Execution terminated by unhandled exception -Exception name: CONSTRAINT_ERROR -Message: stb.adb:5 -Call stack traceback locations: -0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 -@end smallexample +@item @code{-gnatwg} -@noindent -As we see the traceback lists a sequence of addresses for the unhandled -exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to -guess that this exception come from procedure P1. To translate these -addresses into the source lines where the calls appear, the -@code{addr2line} tool, described below, is invaluable. The use of this tool -requires the program to be compiled with debug information. +@emph{Activate warnings on unrecognized pragmas.} -@smallexample -$ gnatmake -g stb -bargs -E -$ stb +@geindex Pragmas +@geindex unrecognized -Execution terminated by unhandled exception -Exception name: CONSTRAINT_ERROR -Message: stb.adb:5 -Call stack traceback locations: -0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 +This switch causes a warning to be generated if an unrecognized +pragma is encountered. Apart from issuing this warning, the +pragma is ignored and has no effect. The default +is that such warnings are issued (satisfying the Ada Reference +Manual requirement that such warnings appear). +@end table -$ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 - 0x4011f1 0x77e892a4 +@geindex -gnatwG (gcc) -00401373 at d:/stb/stb.adb:5 -0040138B at d:/stb/stb.adb:10 -0040139C at d:/stb/stb.adb:14 -00401335 at d:/stb/b~stb.adb:104 -004011C4 at /build/@dots{}/crt1.c:200 -004011F1 at /build/@dots{}/crt1.c:222 -77E892A4 in ?? at ??:0 -@end smallexample -@noindent -The @code{addr2line} tool has several other useful options: +@table @asis -@table @code -@item --functions -to get the function name corresponding to any location +@item @code{-gnatwG} + +@emph{Suppress warnings on unrecognized pragmas.} -@item --demangle=gnat -to use the gnat decoding mode for the function names. Note that -for binutils version 2.9.x the option is simply @option{--demangle}. +This switch suppresses warnings for unrecognized pragmas. @end table -@smallexample -$ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b - 0x40139c 0x401335 0x4011c4 0x4011f1 +@geindex -gnatw.g (gcc) -00401373 in stb.p1 at d:/stb/stb.adb:5 -0040138B in stb.p2 at d:/stb/stb.adb:10 -0040139C in stb at d:/stb/stb.adb:14 -00401335 in main at d:/stb/b~stb.adb:104 -004011C4 in <__mingw_CRTStartup> at /build/@dots{}/crt1.c:200 -004011F1 in at /build/@dots{}/crt1.c:222 -@end smallexample -@noindent -From this traceback we can see that the exception was raised in -@file{stb.adb} at line 5, which was reached from a procedure call in -@file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file, -which contains the call to the main program. -@xref{Running gnatbind}. The remaining entries are assorted runtime routines, -and the output will vary from platform to platform. +@table @asis -It is also possible to use @code{GDB} with these traceback addresses to debug -the program. For example, we can break at a given code location, as reported -in the stack traceback: +@item @code{-gnatw.g} -@smallexample -$ gdb -nw stb -@noindent -Furthermore, this feature is not implemented inside Windows DLL. Only -the non-symbolic traceback is reported in this case. +@emph{Warnings used for GNAT sources} -(gdb) break *0x401373 -Breakpoint 1 at 0x401373: file stb.adb, line 5. -@end smallexample +This switch sets the warning categories that are used by the standard +GNAT style. Currently this is equivalent to +@emph{-gnatwAao.sI.C.V.X} +but more warnings may be added in the future without advanced notice. +@end table -@noindent -It is important to note that the stack traceback addresses -do not change when debug information is included. This is particularly useful -because it makes it possible to release software without debug information (to -minimize object size), get a field report that includes a stack traceback -whenever an internal bug occurs, and then be able to retrieve the sequence -of calls with the same program compiled with debug information. +@geindex -gnatwh (gcc) -@node Tracebacks From Exception Occurrences (non-symbolic) -@subsubsection Tracebacks From Exception Occurrences -@noindent -Non-symbolic tracebacks are obtained by using the @option{-E} binder argument. -The stack traceback is attached to the exception information string, and can -be retrieved in an exception handler within the Ada program, by means of the -Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example: +@table @asis -@smallexample @c ada -@b{with} Ada.Text_IO; -@b{with} Ada.Exceptions; +@item @code{-gnatwh} -@b{procedure} STB @b{is} +@emph{Activate warnings on hiding.} - @b{use} Ada; - @b{use} Ada.Exceptions; +@geindex Hiding of Declarations - @b{procedure} P1 @b{is} - K : Positive := 1; - @b{begin} - K := K - 1; - @b{exception} - @b{when} E : @b{others} => - Text_IO.Put_Line (Exception_Information (E)); - @b{end} P1; +This switch activates warnings on hiding declarations. +A declaration is considered hiding +if it is for a non-overloadable entity, and it declares an entity with the +same name as some other entity that is directly or use-visible. The default +is that such warnings are not generated. +@end table - @b{procedure} P2 @b{is} - @b{begin} - P1; - @b{end} P2; +@geindex -gnatwH (gcc) -@b{begin} - P2; -@b{end} STB; -@end smallexample -@noindent -This program will output: +@table @asis -@smallexample -$ stb +@item @code{-gnatwH} -Exception name: CONSTRAINT_ERROR -Message: stb.adb:12 -Call stack traceback locations: -0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4 -@end smallexample +@emph{Suppress warnings on hiding.} -@node Tracebacks From Anywhere in a Program (non-symbolic) -@subsubsection Tracebacks From Anywhere in a Program +This switch suppresses warnings on hiding declarations. +@end table -@noindent -It is also possible to retrieve a stack traceback from anywhere in a -program. For this you need to -use the @code{GNAT.Traceback} API. This package includes a procedure called -@code{Call_Chain} that computes a complete stack traceback, as well as useful -display procedures described below. It is not necessary to use the -@option{-E gnatbind} option in this case, because the stack traceback mechanism -is invoked explicitly. +@geindex -gnatw.h (gcc) -@noindent -In the following example we compute a traceback at a specific location in -the program, and we display it using @code{GNAT.Debug_Utilities.Image} to -convert addresses to strings: -@smallexample @c ada -@b{with} Ada.Text_IO; -@b{with} GNAT.Traceback; -@b{with} GNAT.Debug_Utilities; +@table @asis -@b{procedure} STB @b{is} +@item @code{-gnatw.h} - @b{use} Ada; - @b{use} GNAT; - @b{use} GNAT.Traceback; +@emph{Activate warnings on holes/gaps in records.} - @b{procedure} P1 @b{is} - TB : Tracebacks_Array (1 .. 10); - --@i{ We are asking for a maximum of 10 stack frames.} - Len : Natural; - --@i{ Len will receive the actual number of stack frames returned.} - @b{begin} - Call_Chain (TB, Len); +@geindex Record Representation (gaps) - Text_IO.Put ("In STB.P1 : "); +This switch activates warnings on component clauses in record +representation clauses that leave holes (gaps) in the record layout. +If this warning option is active, then record representation clauses +should specify a contiguous layout, adding unused fill fields if needed. +@end table - @b{for} K @b{in} 1 .. Len @b{loop} - Text_IO.Put (Debug_Utilities.Image (TB (K))); - Text_IO.Put (' '); - @b{end} @b{loop}; +@geindex -gnatw.H (gcc) - Text_IO.New_Line; - @b{end} P1; - @b{procedure} P2 @b{is} - @b{begin} - P1; - @b{end} P2; +@table @asis -@b{begin} - P2; -@b{end} STB; -@end smallexample +@item @code{-gnatw.H} -@smallexample -$ gnatmake -g stb -$ stb +@emph{Suppress warnings on holes/gaps in records.} -In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C# -16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4# -@end smallexample +This switch suppresses warnings on component clauses in record +representation clauses that leave holes (haps) in the record layout. +@end table -@noindent -You can then get further information by invoking the @code{addr2line} -tool as described earlier (note that the hexadecimal addresses -need to be specified in C format, with a leading ``0x''). +@geindex -gnatwi (gcc) -@node Symbolic Traceback -@subsection Symbolic Traceback -@cindex traceback, symbolic -@noindent -A symbolic traceback is a stack traceback in which procedure names are -associated with each code location. +@table @asis -@noindent -Note that this feature is not supported on all platforms. See -@file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete -list of currently supported platforms. +@item @code{-gnatwi} -@noindent -Note that the symbolic traceback requires that the program be compiled -with debug information. If it is not compiled with debug information -only the non-symbolic information will be valid. +@emph{Activate warnings on implementation units.} -@menu -* Tracebacks From Exception Occurrences (symbolic):: -* Tracebacks From Anywhere in a Program (symbolic):: -@end menu +This switch activates warnings for a @emph{with} of an internal GNAT +implementation unit, defined as any unit from the @cite{Ada}, +@cite{Interfaces}, @cite{GNAT}, +or @cite{System} +hierarchies that is not +documented in either the Ada Reference Manual or the GNAT +Programmer's Reference Manual. Such units are intended only +for internal implementation purposes and should not be @emph{with}ed +by user programs. The default is that such warnings are generated +@end table -@node Tracebacks From Exception Occurrences (symbolic) -@subsubsection Tracebacks From Exception Occurrences +@geindex -gnatwI (gcc) -@smallexample @c ada -@b{with} Ada.Text_IO; -@b{with} GNAT.Traceback.Symbolic; -@b{procedure} STB @b{is} +@table @asis - @b{procedure} P1 @b{is} - @b{begin} - @b{raise} Constraint_Error; - @b{end} P1; +@item @code{-gnatwI} - @b{procedure} P2 @b{is} - @b{begin} - P1; - @b{end} P2; +@emph{Disable warnings on implementation units.} - @b{procedure} P3 @b{is} - @b{begin} - P2; - @b{end} P3; +This switch disables warnings for a @emph{with} of an internal GNAT +implementation unit. +@end table -@b{begin} - P3; -@b{exception} - @b{when} E : @b{others} => - Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E)); -@b{end} STB; -@end smallexample +@geindex -gnatw.i (gcc) -@smallexample -$ gnatmake -g .\stb -bargs -E -$ stb -0040149F in stb.p1 at stb.adb:8 -004014B7 in stb.p2 at stb.adb:13 -004014CF in stb.p3 at stb.adb:18 -004015DD in ada.stb at stb.adb:22 -00401461 in main at b~stb.adb:168 -004011C4 in __mingw_CRTStartup at crt1.c:200 -004011F1 in mainCRTStartup at crt1.c:222 -77E892A4 in ?? at ??:0 -@end smallexample +@table @asis -@noindent -In the above example the ``.\'' syntax in the @command{gnatmake} command -is currently required by @command{addr2line} for files that are in -the current working directory. -Moreover, the exact sequence of linker options may vary from platform -to platform. -The above @option{-largs} section is for Windows platforms. By contrast, -under Unix there is no need for the @option{-largs} section. -Differences across platforms are due to details of linker implementation. +@item @code{-gnatw.i} -@node Tracebacks From Anywhere in a Program (symbolic) -@subsubsection Tracebacks From Anywhere in a Program +@emph{Activate warnings on overlapping actuals.} -@noindent -It is possible to get a symbolic stack traceback -from anywhere in a program, just as for non-symbolic tracebacks. -The first step is to obtain a non-symbolic -traceback, and then call @code{Symbolic_Traceback} to compute the symbolic -information. Here is an example: +This switch enables a warning on statically detectable overlapping actuals in +a subprogram call, when one of the actuals is an in-out parameter, and the +types of the actuals are not by-copy types. This warning is off by default. +@end table -@smallexample @c ada -@b{with} Ada.Text_IO; -@b{with} GNAT.Traceback; -@b{with} GNAT.Traceback.Symbolic; +@geindex -gnatw.I (gcc) -@b{procedure} STB @b{is} - @b{use} Ada; - @b{use} GNAT.Traceback; - @b{use} GNAT.Traceback.Symbolic; +@table @asis - @b{procedure} P1 @b{is} - TB : Tracebacks_Array (1 .. 10); - --@i{ We are asking for a maximum of 10 stack frames.} - Len : Natural; - --@i{ Len will receive the actual number of stack frames returned.} - @b{begin} - Call_Chain (TB, Len); - Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len))); - @b{end} P1; +@item @code{-gnatw.I} - @b{procedure} P2 @b{is} - @b{begin} - P1; - @b{end} P2; +@emph{Disable warnings on overlapping actuals.} -@b{begin} - P2; -@b{end} STB; -@end smallexample +This switch disables warnings on overlapping actuals in a call.. +@end table -@c ****************************** +@geindex -gnatwj (gcc) -@c ************************************** -@node Platform-Specific Information for the Run-Time Libraries -@appendix Platform-Specific Information for the Run-Time Libraries -@cindex Tasking and threads libraries -@cindex Threads libraries and tasking -@cindex Run-time libraries (platform-specific information) -@noindent -The GNAT run-time implementation may vary with respect to both the -underlying threads library and the exception handling scheme. -For threads support, one or more of the following are supplied: -@itemize @bullet -@item @b{native threads library}, a binding to the thread package from -the underlying operating system +@table @asis -@item @b{pthreads library} (Sparc Solaris only), a binding to the Solaris -POSIX thread package -@end itemize +@item @code{-gnatwj} -@noindent -For exception handling, either or both of two models are supplied: -@itemize @bullet -@item @b{Zero-Cost Exceptions} (``ZCX''),@footnote{ -Most programs should experience a substantial speed improvement by -being compiled with a ZCX run-time. -This is especially true for -tasking applications or applications with many exception handlers.} -@cindex Zero-Cost Exceptions -@cindex ZCX (Zero-Cost Exceptions) -which uses binder-generated tables that -are interrogated at run time to locate a handler +@emph{Activate warnings on obsolescent features (Annex J).} -@item @b{setjmp / longjmp} (``SJLJ''), -@cindex setjmp/longjmp Exception Model -@cindex SJLJ (setjmp/longjmp Exception Model) -which uses dynamically-set data to establish -the set of handlers -@end itemize +@geindex Features +@geindex obsolescent -@noindent -This appendix summarizes which combinations of threads and exception support -are supplied on various GNAT platforms. -It then shows how to select a particular library either -permanently or temporarily, -explains the properties of (and tradeoffs among) the various threads -libraries, and provides some additional -information about several specific platforms. +@geindex Obsolescent features -@menu -* Summary of Run-Time Configurations:: -* Specifying a Run-Time Library:: -* Choosing the Scheduling Policy:: -* Solaris-Specific Considerations:: -* Linux-Specific Considerations:: -* AIX-Specific Considerations:: -* RTX-Specific Considerations:: -* HP-UX-Specific Considerations:: -@end menu +If this warning option is activated, then warnings are generated for +calls to subprograms marked with @cite{pragma Obsolescent} and +for use of features in Annex J of the Ada Reference Manual. In the +case of Annex J, not all features are flagged. In particular use +of the renamed packages (like @cite{Text_IO}) and use of package +@cite{ASCII} are not flagged, since these are very common and +would generate many annoying positive warnings. The default is that +such warnings are not generated. -@node Summary of Run-Time Configurations -@section Summary of Run-Time Configurations - -@multitable @columnfractions .30 .70 -@item @b{alpha-openvms} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native VMS threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native TRU64 threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{ia64-hp_linux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{ia64-hpux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native HP-UX threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{ia64-openvms} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native VMS threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{ia64-sgi_linux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{pa-hpux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native HP-UX threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native HP-UX threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{ppc-aix} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native AIX threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native AIX threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{ppc-darwin} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native MacOS threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{sparc-solaris} @tab -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native Solaris threads library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-pthread} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native Solaris threads library -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{sparc64-solaris} @tab -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native Solaris threads library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{x86-linux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{x86-lynx} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native LynxOS threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{x86-solaris} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native Solaris threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native Solaris threads library -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{x86-windows} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab native Win32 threads -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab native Win32 threads -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @b{x86-windows-rtx} -@item @code{@ @ }@i{rts-rtx-rtss (default)} -@item @code{@ @ @ @ }Tasking @tab RTX real-time subsystem RTSS threads (kernel mode) -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@item @code{@ @ }@i{rts-rtx-w32} -@item @code{@ @ @ @ }Tasking @tab RTX Win32 threads (user mode) -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @b{x86_64-linux} -@item @code{@ @ }@i{rts-native (default)} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab ZCX -@* -@item @code{@ @ }@i{rts-sjlj} -@item @code{@ @ @ @ }Tasking @tab pthread library -@item @code{@ @ @ @ }Exceptions @tab SJLJ -@* -@end multitable +In addition to the above cases, warnings are also generated for +GNAT features that have been provided in past versions but which +have been superseded (typically by features in the new Ada standard). +For example, @cite{pragma Ravenscar} will be flagged since its +function is replaced by @cite{pragma Profile(Ravenscar)}, and +@cite{pragma Interface_Name} will be flagged since its function +is replaced by @cite{pragma Import}. -@node Specifying a Run-Time Library -@section Specifying a Run-Time Library +Note that this warning option functions differently from the +restriction @cite{No_Obsolescent_Features} in two respects. +First, the restriction applies only to annex J features. +Second, the restriction does flag uses of package @cite{ASCII}. -@noindent -The @file{adainclude} subdirectory containing the sources of the GNAT -run-time library, and the @file{adalib} subdirectory containing the -@file{ALI} files and the static and/or shared GNAT library, are located -in the gcc target-dependent area: +@item @code{-gnatwJ} -@smallexample -target=$prefix/lib/gcc/gcc-@i{dumpmachine}/gcc-@i{dumpversion}/ -@end smallexample +@emph{Suppress warnings on obsolescent features (Annex J).} +.. index:: -gnatwJ (gcc) -@noindent -As indicated above, on some platforms several run-time libraries are supplied. -These libraries are installed in the target dependent area and -contain a complete source and binary subdirectory. The detailed description -below explains the differences between the different libraries in terms of -their thread support. +This switch disables warnings on use of obsolescent features. -The default run-time library (when GNAT is installed) is @emph{rts-native}. -This default run time is selected by the means of soft links. -For example on x86-linux: +@item @code{-gnatwk} -@smallexample -@group - $(target-dir) - | - +--- adainclude----------+ - | | - +--- adalib-----------+ | - | | | - +--- rts-native | | - | | | | - | +--- adainclude <---+ - | | | - | +--- adalib <----+ - | - +--- rts-sjlj - | - +--- adainclude - | - +--- adalib -@end group -@end smallexample - -@noindent -If the @i{rts-sjlj} library is to be selected on a permanent basis, -these soft links can be modified with the following commands: +@emph{Activate warnings on variables that could be constants.} +.. index:: -gnatwk (gcc) -@smallexample -$ cd $target -$ rm -f adainclude adalib -$ ln -s rts-sjlj/adainclude adainclude -$ ln -s rts-sjlj/adalib adalib -@end smallexample +This switch activates warnings for variables that are initialized but +never modified, and then could be declared constants. The default is that +such warnings are not given. +@end table -@noindent -Alternatively, you can specify @file{rts-sjlj/adainclude} in the file -@file{$target/ada_source_path} and @file{rts-sjlj/adalib} in -@file{$target/ada_object_path}. +@geindex -gnatwK (gcc) -Selecting another run-time library temporarily can be -achieved by using the @option{--RTS} switch, e.g., @option{--RTS=sjlj} -@cindex @option{--RTS} option -@node Choosing the Scheduling Policy -@section Choosing the Scheduling Policy +@table @asis -@noindent -When using a POSIX threads implementation, you have a choice of several -scheduling policies: @code{SCHED_FIFO}, -@cindex @code{SCHED_FIFO} scheduling policy -@code{SCHED_RR} -@cindex @code{SCHED_RR} scheduling policy -and @code{SCHED_OTHER}. -@cindex @code{SCHED_OTHER} scheduling policy -Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO} -or @code{SCHED_RR} requires special (e.g., root) privileges. - -By default, GNAT uses the @code{SCHED_OTHER} policy. To specify -@code{SCHED_FIFO}, -@cindex @code{SCHED_FIFO} scheduling policy -you can use one of the following: +@item @code{-gnatwK} -@itemize @bullet -@item -@code{pragma Time_Slice (0.0)} -@cindex pragma Time_Slice -@item -the corresponding binder option @option{-T0} -@cindex @option{-T0} option -@item -@code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)} -@cindex pragma Task_Dispatching_Policy -@end itemize +@emph{Suppress warnings on variables that could be constants.} -@noindent -To specify @code{SCHED_RR}, -@cindex @code{SCHED_RR} scheduling policy -you should use @code{pragma Time_Slice} with a -value greater than @code{0.0}, or else use the corresponding @option{-T} -binder option. +This switch disables warnings on variables that could be declared constants. +@end table -@node Solaris-Specific Considerations -@section Solaris-Specific Considerations -@cindex Solaris Sparc threads libraries +@geindex -gnatw.k (gcc) -@noindent -This section addresses some topics related to the various threads libraries -on Sparc Solaris. -@menu -* Solaris Threads Issues:: -@end menu +@table @asis -@node Solaris Threads Issues -@subsection Solaris Threads Issues +@item @code{-gnatw.k} -@noindent -GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time -library based on POSIX threads --- @emph{rts-pthread}. -@cindex rts-pthread threads library -This run-time library has the advantage of being mostly shared across all -POSIX-compliant thread implementations, and it also provides under -@w{Solaris 8} the @code{PTHREAD_PRIO_INHERIT} -@cindex @code{PTHREAD_PRIO_INHERIT} policy (under rts-pthread) -and @code{PTHREAD_PRIO_PROTECT} -@cindex @code{PTHREAD_PRIO_PROTECT} policy (under rts-pthread) -semantics that can be selected using the predefined pragma -@code{Locking_Policy} -@cindex pragma Locking_Policy (under rts-pthread) -with respectively -@code{Inheritance_Locking} and @code{Ceiling_Locking} as the policy. -@cindex @code{Inheritance_Locking} (under rts-pthread) -@cindex @code{Ceiling_Locking} (under rts-pthread) +@emph{Activate warnings on redefinition of names in standard.} -As explained above, the native run-time library is based on the Solaris thread -library (@code{libthread}) and is the default library. +This switch activates warnings for declarations that declare a name that +is defined in package Standard. Such declarations can be confusing, +especially since the names in package Standard continue to be directly +visible, meaning that use visibiliy on such redeclared names does not +work as expected. Names of discriminants and components in records are +not included in this check. +@end table -When the Solaris threads library is used (this is the default), programs -compiled with GNAT can automatically take advantage of -and can thus execute on multiple processors. -The user can alternatively specify a processor on which the program should run -to emulate a single-processor system. The multiprocessor / uniprocessor choice -is made by -setting the environment variable @env{GNAT_PROCESSOR} -@cindex @env{GNAT_PROCESSOR} environment variable (on Sparc Solaris) -to one of the following: +@geindex -gnatwK (gcc) -@table @code -@item -2 -Use the default configuration (run the program on all -available processors) - this is the same as having @code{GNAT_PROCESSOR} -unset -@item -1 -Let the run-time implementation choose one processor and run the program on -that processor +@table @asis + +@item @code{-gnatw.K} -@item 0 .. Last_Proc -Run the program on the specified processor. -@code{Last_Proc} is equal to @code{_SC_NPROCESSORS_CONF - 1} -(where @code{_SC_NPROCESSORS_CONF} is a system variable). +@emph{Suppress warnings on redefinition of names in standard.} + +This switch activates warnings for declarations that declare a name that +is defined in package Standard. @end table -@node Linux-Specific Considerations -@section Linux-Specific Considerations -@cindex Linux threads libraries +@geindex -gnatwl (gcc) -@noindent -On GNU/Linux without NPTL support (usually system with GNU C Library -older than 2.3), the signal model is not POSIX compliant, which means -that to send a signal to the process, you need to send the signal to all -threads, e.g.@: by using @code{killpg()}. -@node AIX-Specific Considerations -@section AIX-Specific Considerations -@cindex AIX resolver library +@table @asis -@noindent -On AIX, the resolver library initializes some internal structure on -the first call to @code{get*by*} functions, which are used to implement -@code{GNAT.Sockets.Get_Host_By_Name} and -@code{GNAT.Sockets.Get_Host_By_Address}. -If such initialization occurs within an Ada task, and the stack size for -the task is the default size, a stack overflow may occur. +@item @code{-gnatwl} -To avoid this overflow, the user should either ensure that the first call -to @code{GNAT.Sockets.Get_Host_By_Name} or -@code{GNAT.Sockets.Get_Host_By_Addrss} -occurs in the environment task, or use @code{pragma Storage_Size} to -specify a sufficiently large size for the stack of the task that contains -this call. +@emph{Activate warnings for elaboration pragmas.} -@node RTX-Specific Considerations -@section RTX-Specific Considerations -@cindex RTX libraries +@geindex Elaboration +@geindex warnings -@noindent -The Real-time Extension (RTX) to Windows is based on the Windows Win32 -API. Applications can be built to work in two different modes: +This switch activates warnings for possible elaboration problems, +including suspicious use +of @cite{Elaborate} pragmas, when using the static elaboration model, and +possible situations that may raise @cite{Program_Error} when using the +dynamic elaboration model. +See the section in this guide on elaboration checking for further details. +The default is that such warnings +are not generated. +@end table -@itemize @bullet -@item -Windows executables that run in Ring 3 to utilize memory protection -(@emph{rts-rtx-w32}). +@geindex -gnatwL (gcc) -@item -Real-time subsystem (RTSS) executables that run in Ring 0, where -performance can be optimized with RTSS applications taking precedent -over all Windows applications (@emph{rts-rtx-rtss}). This mode requires -the Microsoft linker to handle RTSS libraries. -@end itemize +@table @asis -@node HP-UX-Specific Considerations -@section HP-UX-Specific Considerations -@cindex HP-UX Scheduling +@item @code{-gnatwL} -@noindent -On HP-UX, appropriate privileges are required to change the scheduling -parameters of a task. The calling process must have appropriate -privileges or be a member of a group having @code{PRIV_RTSCHED} access to -successfully change the scheduling parameters. +@emph{Suppress warnings for elaboration pragmas.} -By default, GNAT uses the @code{SCHED_HPUX} policy. To have access to the -priority range 0-31 either the @code{FIFO_Within_Priorities} or the -@code{Round_Robin_Within_Priorities} scheduling policies need to be set. +This switch suppresses warnings for possible elaboration problems. +@end table -To specify the @code{FIFO_Within_Priorities} scheduling policy you can use -one of the following: +@geindex -gnatw.l (gcc) -@itemize @bullet -@item -@code{pragma Time_Slice (0.0)} -@cindex pragma Time_Slice -@item -the corresponding binder option @option{-T0} -@cindex @option{-T0} option -@item -@code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)} -@cindex pragma Task_Dispatching_Policy -@end itemize -@noindent -To specify the @code{Round_Robin_Within_Priorities}, scheduling policy -you should use @code{pragma Time_Slice} with a -value greater than @code{0.0}, or use the corresponding @option{-T} -binder option, or set the @code{pragma Task_Dispatching_Policy -(Round_Robin_Within_Priorities)}. +@table @asis -@c ******************************* -@node Example of Binder Output File -@appendix Example of Binder Output File +@item @code{-gnatw.l} -@noindent -This Appendix displays the source code for @command{gnatbind}'s output -file generated for a simple ``Hello World'' program. -Comments have been added for clarification purposes. +@emph{List inherited aspects.} -@smallexample @c adanocomment -@iftex -@leftskip=0cm -@end iftex --- The package is called Ada_Main unless this name is actually used --- as a unit name in the partition, in which case some other unique --- name is used. +This switch causes the compiler to list inherited invariants, +preconditions, and postconditions from Type_Invariant'Class, Invariant'Class, +Pre'Class, and Post'Class aspects. Also list inherited subtype predicates. +@end table -@b{pragma} Ada_95; -@b{with} System; -@b{package} ada_main @b{is} - @b{pragma} Warnings (Off); +@geindex -gnatw.L (gcc) - -- The main program saves the parameters (argument count, - -- argument values, environment pointer) in global variables - -- for later access by other units including - -- Ada.Command_Line. - gnat_argc : Integer; - gnat_argv : System.Address; - gnat_envp : System.Address; +@table @asis - -- The actual variables are stored in a library routine. This - -- is useful for some shared library situations, where there - -- are problems if variables are not in the library. +@item @code{-gnatw.L} - @b{pragma} Import (C, gnat_argc); - @b{pragma} Import (C, gnat_argv); - @b{pragma} Import (C, gnat_envp); +@emph{Suppress listing of inherited aspects.} - -- The exit status is similarly an external location +This switch suppresses listing of inherited aspects. +@end table - gnat_exit_status : Integer; - @b{pragma} Import (C, gnat_exit_status); +@geindex -gnatwm (gcc) - GNAT_Version : @b{constant} String := - "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL; - @b{pragma} Export (C, GNAT_Version, "__gnat_version"); - Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL; - @b{pragma} Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name"); +@table @asis - -- This is the generated adainit routine that performs - -- initialization at the start of execution. In the case - -- where Ada is the main program, this main program makes - -- a call to adainit at program startup. +@item @code{-gnatwm} - @b{procedure} adainit; - @b{pragma} Export (C, adainit, "adainit"); +@emph{Activate warnings on modified but unreferenced variables.} - -- This is the generated adafinal routine that performs - -- finalization at the end of execution. In the case where - -- Ada is the main program, this main program makes a call - -- to adafinal at program termination. +This switch activates warnings for variables that are assigned (using +an initialization value or with one or more assignment statements) but +whose value is never read. The warning is suppressed for volatile +variables and also for variables that are renamings of other variables +or for which an address clause is given. +The default is that these warnings are not given. +@end table - @b{procedure} adafinal; - @b{pragma} Export (C, adafinal, "adafinal"); +@geindex -gnatwM (gcc) - -- This routine is called at the start of execution. It is - -- a dummy routine that is used by the debugger to breakpoint - -- at the start of execution. - -- This is the actual generated main program (it would be - -- suppressed if the no main program switch were used). As - -- required by standard system conventions, this program has - -- the external name main. +@table @asis - @b{function} main - (argc : Integer; - argv : System.Address; - envp : System.Address) - @b{return} Integer; - @b{pragma} Export (C, main, "main"); +@item @code{-gnatwM} - -- The following set of constants give the version - -- identification values for every unit in the bound - -- partition. This identification is computed from all - -- dependent semantic units, and corresponds to the - -- string that would be returned by use of the - -- Body_Version or Version attributes. +@emph{Disable warnings on modified but unreferenced variables.} - -- The following Export pragmas export the version numbers - -- with symbolic names ending in B (for body) or S - -- (for spec) so that they can be located in a link. The - -- information provided here is sufficient to track down - -- the exact versions of units used in a given build. +This switch disables warnings for variables that are assigned or +initialized, but never read. +@end table +@geindex -gnatw.m (gcc) - @b{type} Version_32 @b{is} @b{mod} 2 ** 32; - u00001 : @b{constant} Version_32 := 16#8ad6e54a#; - @b{pragma} Export (C, u00001, "helloB"); - u00002 : @b{constant} Version_32 := 16#fbff4c67#; - @b{pragma} Export (C, u00002, "system__standard_libraryB"); - u00003 : @b{constant} Version_32 := 16#1ec6fd90#; - @b{pragma} Export (C, u00003, "system__standard_libraryS"); - u00004 : @b{constant} Version_32 := 16#3ffc8e18#; - @b{pragma} Export (C, u00004, "adaS"); - u00005 : @b{constant} Version_32 := 16#28f088c2#; - @b{pragma} Export (C, u00005, "ada__text_ioB"); - u00006 : @b{constant} Version_32 := 16#f372c8ac#; - @b{pragma} Export (C, u00006, "ada__text_ioS"); - u00007 : @b{constant} Version_32 := 16#2c143749#; - @b{pragma} Export (C, u00007, "ada__exceptionsB"); - u00008 : @b{constant} Version_32 := 16#f4f0cce8#; - @b{pragma} Export (C, u00008, "ada__exceptionsS"); - u00009 : @b{constant} Version_32 := 16#a46739c0#; - @b{pragma} Export (C, u00009, "ada__exceptions__last_chance_handlerB"); - u00010 : @b{constant} Version_32 := 16#3aac8c92#; - @b{pragma} Export (C, u00010, "ada__exceptions__last_chance_handlerS"); - u00011 : @b{constant} Version_32 := 16#1d274481#; - @b{pragma} Export (C, u00011, "systemS"); - u00012 : @b{constant} Version_32 := 16#a207fefe#; - @b{pragma} Export (C, u00012, "system__soft_linksB"); - u00013 : @b{constant} Version_32 := 16#467d9556#; - @b{pragma} Export (C, u00013, "system__soft_linksS"); - u00014 : @b{constant} Version_32 := 16#b01dad17#; - @b{pragma} Export (C, u00014, "system__parametersB"); - u00015 : @b{constant} Version_32 := 16#630d49fe#; - @b{pragma} Export (C, u00015, "system__parametersS"); - u00016 : @b{constant} Version_32 := 16#b19b6653#; - @b{pragma} Export (C, u00016, "system__secondary_stackB"); - u00017 : @b{constant} Version_32 := 16#b6468be8#; - @b{pragma} Export (C, u00017, "system__secondary_stackS"); - u00018 : @b{constant} Version_32 := 16#39a03df9#; - @b{pragma} Export (C, u00018, "system__storage_elementsB"); - u00019 : @b{constant} Version_32 := 16#30e40e85#; - @b{pragma} Export (C, u00019, "system__storage_elementsS"); - u00020 : @b{constant} Version_32 := 16#41837d1e#; - @b{pragma} Export (C, u00020, "system__stack_checkingB"); - u00021 : @b{constant} Version_32 := 16#93982f69#; - @b{pragma} Export (C, u00021, "system__stack_checkingS"); - u00022 : @b{constant} Version_32 := 16#393398c1#; - @b{pragma} Export (C, u00022, "system__exception_tableB"); - u00023 : @b{constant} Version_32 := 16#b33e2294#; - @b{pragma} Export (C, u00023, "system__exception_tableS"); - u00024 : @b{constant} Version_32 := 16#ce4af020#; - @b{pragma} Export (C, u00024, "system__exceptionsB"); - u00025 : @b{constant} Version_32 := 16#75442977#; - @b{pragma} Export (C, u00025, "system__exceptionsS"); - u00026 : @b{constant} Version_32 := 16#37d758f1#; - @b{pragma} Export (C, u00026, "system__exceptions__machineS"); - u00027 : @b{constant} Version_32 := 16#b895431d#; - @b{pragma} Export (C, u00027, "system__exceptions_debugB"); - u00028 : @b{constant} Version_32 := 16#aec55d3f#; - @b{pragma} Export (C, u00028, "system__exceptions_debugS"); - u00029 : @b{constant} Version_32 := 16#570325c8#; - @b{pragma} Export (C, u00029, "system__img_intB"); - u00030 : @b{constant} Version_32 := 16#1ffca443#; - @b{pragma} Export (C, u00030, "system__img_intS"); - u00031 : @b{constant} Version_32 := 16#b98c3e16#; - @b{pragma} Export (C, u00031, "system__tracebackB"); - u00032 : @b{constant} Version_32 := 16#831a9d5a#; - @b{pragma} Export (C, u00032, "system__tracebackS"); - u00033 : @b{constant} Version_32 := 16#9ed49525#; - @b{pragma} Export (C, u00033, "system__traceback_entriesB"); - u00034 : @b{constant} Version_32 := 16#1d7cb2f1#; - @b{pragma} Export (C, u00034, "system__traceback_entriesS"); - u00035 : @b{constant} Version_32 := 16#8c33a517#; - @b{pragma} Export (C, u00035, "system__wch_conB"); - u00036 : @b{constant} Version_32 := 16#065a6653#; - @b{pragma} Export (C, u00036, "system__wch_conS"); - u00037 : @b{constant} Version_32 := 16#9721e840#; - @b{pragma} Export (C, u00037, "system__wch_stwB"); - u00038 : @b{constant} Version_32 := 16#2b4b4a52#; - @b{pragma} Export (C, u00038, "system__wch_stwS"); - u00039 : @b{constant} Version_32 := 16#92b797cb#; - @b{pragma} Export (C, u00039, "system__wch_cnvB"); - u00040 : @b{constant} Version_32 := 16#09eddca0#; - @b{pragma} Export (C, u00040, "system__wch_cnvS"); - u00041 : @b{constant} Version_32 := 16#6033a23f#; - @b{pragma} Export (C, u00041, "interfacesS"); - u00042 : @b{constant} Version_32 := 16#ece6fdb6#; - @b{pragma} Export (C, u00042, "system__wch_jisB"); - u00043 : @b{constant} Version_32 := 16#899dc581#; - @b{pragma} Export (C, u00043, "system__wch_jisS"); - u00044 : @b{constant} Version_32 := 16#10558b11#; - @b{pragma} Export (C, u00044, "ada__streamsB"); - u00045 : @b{constant} Version_32 := 16#2e6701ab#; - @b{pragma} Export (C, u00045, "ada__streamsS"); - u00046 : @b{constant} Version_32 := 16#db5c917c#; - @b{pragma} Export (C, u00046, "ada__io_exceptionsS"); - u00047 : @b{constant} Version_32 := 16#12c8cd7d#; - @b{pragma} Export (C, u00047, "ada__tagsB"); - u00048 : @b{constant} Version_32 := 16#ce72c228#; - @b{pragma} Export (C, u00048, "ada__tagsS"); - u00049 : @b{constant} Version_32 := 16#c3335bfd#; - @b{pragma} Export (C, u00049, "system__htableB"); - u00050 : @b{constant} Version_32 := 16#99e5f76b#; - @b{pragma} Export (C, u00050, "system__htableS"); - u00051 : @b{constant} Version_32 := 16#089f5cd0#; - @b{pragma} Export (C, u00051, "system__string_hashB"); - u00052 : @b{constant} Version_32 := 16#3bbb9c15#; - @b{pragma} Export (C, u00052, "system__string_hashS"); - u00053 : @b{constant} Version_32 := 16#807fe041#; - @b{pragma} Export (C, u00053, "system__unsigned_typesS"); - u00054 : @b{constant} Version_32 := 16#d27be59e#; - @b{pragma} Export (C, u00054, "system__val_lluB"); - u00055 : @b{constant} Version_32 := 16#fa8db733#; - @b{pragma} Export (C, u00055, "system__val_lluS"); - u00056 : @b{constant} Version_32 := 16#27b600b2#; - @b{pragma} Export (C, u00056, "system__val_utilB"); - u00057 : @b{constant} Version_32 := 16#b187f27f#; - @b{pragma} Export (C, u00057, "system__val_utilS"); - u00058 : @b{constant} Version_32 := 16#d1060688#; - @b{pragma} Export (C, u00058, "system__case_utilB"); - u00059 : @b{constant} Version_32 := 16#392e2d56#; - @b{pragma} Export (C, u00059, "system__case_utilS"); - u00060 : @b{constant} Version_32 := 16#84a27f0d#; - @b{pragma} Export (C, u00060, "interfaces__c_streamsB"); - u00061 : @b{constant} Version_32 := 16#8bb5f2c0#; - @b{pragma} Export (C, u00061, "interfaces__c_streamsS"); - u00062 : @b{constant} Version_32 := 16#6db6928f#; - @b{pragma} Export (C, u00062, "system__crtlS"); - u00063 : @b{constant} Version_32 := 16#4e6a342b#; - @b{pragma} Export (C, u00063, "system__file_ioB"); - u00064 : @b{constant} Version_32 := 16#ba56a5e4#; - @b{pragma} Export (C, u00064, "system__file_ioS"); - u00065 : @b{constant} Version_32 := 16#b7ab275c#; - @b{pragma} Export (C, u00065, "ada__finalizationB"); - u00066 : @b{constant} Version_32 := 16#19f764ca#; - @b{pragma} Export (C, u00066, "ada__finalizationS"); - u00067 : @b{constant} Version_32 := 16#95817ed8#; - @b{pragma} Export (C, u00067, "system__finalization_rootB"); - u00068 : @b{constant} Version_32 := 16#52d53711#; - @b{pragma} Export (C, u00068, "system__finalization_rootS"); - u00069 : @b{constant} Version_32 := 16#769e25e6#; - @b{pragma} Export (C, u00069, "interfaces__cB"); - u00070 : @b{constant} Version_32 := 16#4a38bedb#; - @b{pragma} Export (C, u00070, "interfaces__cS"); - u00071 : @b{constant} Version_32 := 16#07e6ee66#; - @b{pragma} Export (C, u00071, "system__os_libB"); - u00072 : @b{constant} Version_32 := 16#d7b69782#; - @b{pragma} Export (C, u00072, "system__os_libS"); - u00073 : @b{constant} Version_32 := 16#1a817b8e#; - @b{pragma} Export (C, u00073, "system__stringsB"); - u00074 : @b{constant} Version_32 := 16#639855e7#; - @b{pragma} Export (C, u00074, "system__stringsS"); - u00075 : @b{constant} Version_32 := 16#e0b8de29#; - @b{pragma} Export (C, u00075, "system__file_control_blockS"); - u00076 : @b{constant} Version_32 := 16#b5b2aca1#; - @b{pragma} Export (C, u00076, "system__finalization_mastersB"); - u00077 : @b{constant} Version_32 := 16#69316dc1#; - @b{pragma} Export (C, u00077, "system__finalization_mastersS"); - u00078 : @b{constant} Version_32 := 16#57a37a42#; - @b{pragma} Export (C, u00078, "system__address_imageB"); - u00079 : @b{constant} Version_32 := 16#bccbd9bb#; - @b{pragma} Export (C, u00079, "system__address_imageS"); - u00080 : @b{constant} Version_32 := 16#7268f812#; - @b{pragma} Export (C, u00080, "system__img_boolB"); - u00081 : @b{constant} Version_32 := 16#e8fe356a#; - @b{pragma} Export (C, u00081, "system__img_boolS"); - u00082 : @b{constant} Version_32 := 16#d7aac20c#; - @b{pragma} Export (C, u00082, "system__ioB"); - u00083 : @b{constant} Version_32 := 16#8365b3ce#; - @b{pragma} Export (C, u00083, "system__ioS"); - u00084 : @b{constant} Version_32 := 16#6d4d969a#; - @b{pragma} Export (C, u00084, "system__storage_poolsB"); - u00085 : @b{constant} Version_32 := 16#e87cc305#; - @b{pragma} Export (C, u00085, "system__storage_poolsS"); - u00086 : @b{constant} Version_32 := 16#e34550ca#; - @b{pragma} Export (C, u00086, "system__pool_globalB"); - u00087 : @b{constant} Version_32 := 16#c88d2d16#; - @b{pragma} Export (C, u00087, "system__pool_globalS"); - u00088 : @b{constant} Version_32 := 16#9d39c675#; - @b{pragma} Export (C, u00088, "system__memoryB"); - u00089 : @b{constant} Version_32 := 16#445a22b5#; - @b{pragma} Export (C, u00089, "system__memoryS"); - u00090 : @b{constant} Version_32 := 16#6a859064#; - @b{pragma} Export (C, u00090, "system__storage_pools__subpoolsB"); - u00091 : @b{constant} Version_32 := 16#e3b008dc#; - @b{pragma} Export (C, u00091, "system__storage_pools__subpoolsS"); - u00092 : @b{constant} Version_32 := 16#63f11652#; - @b{pragma} Export (C, u00092, "system__storage_pools__subpools__finalizationB"); - u00093 : @b{constant} Version_32 := 16#fe2f4b3a#; - @b{pragma} Export (C, u00093, "system__storage_pools__subpools__finalizationS"); - -- BEGIN ELABORATION ORDER - -- ada%s - -- interfaces%s - -- system%s - -- system.case_util%s - -- system.case_util%b - -- system.htable%s - -- system.img_bool%s - -- system.img_bool%b - -- system.img_int%s - -- system.img_int%b - -- system.io%s - -- system.io%b - -- system.parameters%s - -- system.parameters%b - -- system.crtl%s - -- interfaces.c_streams%s - -- interfaces.c_streams%b - -- system.standard_library%s - -- system.exceptions_debug%s - -- system.exceptions_debug%b - -- system.storage_elements%s - -- system.storage_elements%b - -- system.stack_checking%s - -- system.stack_checking%b - -- system.string_hash%s - -- system.string_hash%b - -- system.htable%b - -- system.strings%s - -- system.strings%b - -- system.os_lib%s - -- system.traceback_entries%s - -- system.traceback_entries%b - -- ada.exceptions%s - -- system.soft_links%s - -- system.unsigned_types%s - -- system.val_llu%s - -- system.val_util%s - -- system.val_util%b - -- system.val_llu%b - -- system.wch_con%s - -- system.wch_con%b - -- system.wch_cnv%s - -- system.wch_jis%s - -- system.wch_jis%b - -- system.wch_cnv%b - -- system.wch_stw%s - -- system.wch_stw%b - -- ada.exceptions.last_chance_handler%s - -- ada.exceptions.last_chance_handler%b - -- system.address_image%s - -- system.exception_table%s - -- system.exception_table%b - -- ada.io_exceptions%s - -- ada.tags%s - -- ada.streams%s - -- ada.streams%b - -- interfaces.c%s - -- system.exceptions%s - -- system.exceptions%b - -- system.exceptions.machine%s - -- system.finalization_root%s - -- system.finalization_root%b - -- ada.finalization%s - -- ada.finalization%b - -- system.storage_pools%s - -- system.storage_pools%b - -- system.finalization_masters%s - -- system.storage_pools.subpools%s - -- system.storage_pools.subpools.finalization%s - -- system.storage_pools.subpools.finalization%b - -- system.memory%s - -- system.memory%b - -- system.standard_library%b - -- system.pool_global%s - -- system.pool_global%b - -- system.file_control_block%s - -- system.file_io%s - -- system.secondary_stack%s - -- system.file_io%b - -- system.storage_pools.subpools%b - -- system.finalization_masters%b - -- interfaces.c%b - -- ada.tags%b - -- system.soft_links%b - -- system.os_lib%b - -- system.secondary_stack%b - -- system.address_image%b - -- system.traceback%s - -- ada.exceptions%b - -- system.traceback%b - -- ada.text_io%s - -- ada.text_io%b - -- hello%b - -- END ELABORATION ORDER +@table @asis -@b{end} ada_main; +@item @code{-gnatw.m} -@b{pragma} Ada_95; --- The following source file name pragmas allow the generated file --- names to be unique for different main programs. They are needed --- since the package name will always be Ada_Main. +@emph{Activate warnings on suspicious modulus values.} -@b{pragma} Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads"); -@b{pragma} Source_File_Name (ada_main, Body_File_Name => "b~hello.adb"); +This switch activates warnings for modulus values that seem suspicious. +The cases caught are where the size is the same as the modulus (e.g. +a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64 +with no size clause. The guess in both cases is that 2**x was intended +rather than x. In addition expressions of the form 2*x for small x +generate a warning (the almost certainly accurate guess being that +2**x was intended). The default is that these warnings are given. +@end table -@b{pragma} Suppress (Overflow_Check); -@b{with} Ada.Exceptions; +@geindex -gnatw.M (gcc) --- Generated package body for Ada_Main starts here -@b{package} @b{body} ada_main @b{is} - @b{pragma} Warnings (Off); +@table @asis - -- These values are reference counter associated to units which have - -- been elaborated. It is also used to avoid elaborating the - -- same unit twice. +@item @code{-gnatw.M} - E72 : Short_Integer; @b{pragma} Import (Ada, E72, "system__os_lib_E"); - E13 : Short_Integer; @b{pragma} Import (Ada, E13, "system__soft_links_E"); - E23 : Short_Integer; @b{pragma} Import (Ada, E23, "system__exception_table_E"); - E46 : Short_Integer; @b{pragma} Import (Ada, E46, "ada__io_exceptions_E"); - E48 : Short_Integer; @b{pragma} Import (Ada, E48, "ada__tags_E"); - E45 : Short_Integer; @b{pragma} Import (Ada, E45, "ada__streams_E"); - E70 : Short_Integer; @b{pragma} Import (Ada, E70, "interfaces__c_E"); - E25 : Short_Integer; @b{pragma} Import (Ada, E25, "system__exceptions_E"); - E68 : Short_Integer; @b{pragma} Import (Ada, E68, "system__finalization_root_E"); - E66 : Short_Integer; @b{pragma} Import (Ada, E66, "ada__finalization_E"); - E85 : Short_Integer; @b{pragma} Import (Ada, E85, "system__storage_pools_E"); - E77 : Short_Integer; @b{pragma} Import (Ada, E77, "system__finalization_masters_E"); - E91 : Short_Integer; @b{pragma} Import (Ada, E91, "system__storage_pools__subpools_E"); - E87 : Short_Integer; @b{pragma} Import (Ada, E87, "system__pool_global_E"); - E75 : Short_Integer; @b{pragma} Import (Ada, E75, "system__file_control_block_E"); - E64 : Short_Integer; @b{pragma} Import (Ada, E64, "system__file_io_E"); - E17 : Short_Integer; @b{pragma} Import (Ada, E17, "system__secondary_stack_E"); - E06 : Short_Integer; @b{pragma} Import (Ada, E06, "ada__text_io_E"); - - Local_Priority_Specific_Dispatching : @b{constant} String := ""; - Local_Interrupt_States : @b{constant} String := ""; +@emph{Disable warnings on suspicious modulus values.} - Is_Elaborated : Boolean := False; +This switch disables warnings for suspicious modulus values. +@end table -@findex finalize_library - @b{procedure} finalize_library @b{is} - @b{begin} - E06 := E06 - 1; - @b{declare} - @b{procedure} F1; - @b{pragma} Import (Ada, F1, "ada__text_io__finalize_spec"); - @b{begin} - F1; - @b{end}; - E77 := E77 - 1; - E91 := E91 - 1; - @b{declare} - @b{procedure} F2; - @b{pragma} Import (Ada, F2, "system__file_io__finalize_body"); - @b{begin} - E64 := E64 - 1; - F2; - @b{end}; - @b{declare} - @b{procedure} F3; - @b{pragma} Import (Ada, F3, "system__file_control_block__finalize_spec"); - @b{begin} - E75 := E75 - 1; - F3; - @b{end}; - E87 := E87 - 1; - @b{declare} - @b{procedure} F4; - @b{pragma} Import (Ada, F4, "system__pool_global__finalize_spec"); - @b{begin} - F4; - @b{end}; - @b{declare} - @b{procedure} F5; - @b{pragma} Import (Ada, F5, "system__storage_pools__subpools__finalize_spec"); - @b{begin} - F5; - @b{end}; - @b{declare} - @b{procedure} F6; - @b{pragma} Import (Ada, F6, "system__finalization_masters__finalize_spec"); - @b{begin} - F6; - @b{end}; - @b{declare} - @b{procedure} Reraise_Library_Exception_If_Any; - @b{pragma} Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any"); - @b{begin} - Reraise_Library_Exception_If_Any; - @b{end}; - @b{end} finalize_library; +@geindex -gnatwn (gcc) - ------------- - -- adainit -- - ------------- -@findex adainit - @b{procedure} adainit @b{is} +@table @asis - Main_Priority : Integer; - @b{pragma} Import (C, Main_Priority, "__gl_main_priority"); - Time_Slice_Value : Integer; - @b{pragma} Import (C, Time_Slice_Value, "__gl_time_slice_val"); - WC_Encoding : Character; - @b{pragma} Import (C, WC_Encoding, "__gl_wc_encoding"); - Locking_Policy : Character; - pragma Import (C, Locking_Policy, "__gl_locking_policy"); - Queuing_Policy : Character; - @b{pragma} Import (C, Queuing_Policy, "__gl_queuing_policy"); - Task_Dispatching_Policy : Character; - @b{pragma} Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy"); - Priority_Specific_Dispatching : System.Address; - @b{pragma} Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching"); - Num_Specific_Dispatching : Integer; - @b{pragma} Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching"); - Main_CPU : Integer; - @b{pragma} Import (C, Main_CPU, "__gl_main_cpu"); - Interrupt_States : System.Address; - @b{pragma} Import (C, Interrupt_States, "__gl_interrupt_states"); - Num_Interrupt_States : Integer; - @b{pragma} Import (C, Num_Interrupt_States, "__gl_num_interrupt_states"); - Unreserve_All_Interrupts : Integer; - @b{pragma} Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts"); - Detect_Blocking : Integer; - @b{pragma} Import (C, Detect_Blocking, "__gl_detect_blocking"); - Default_Stack_Size : Integer; - @b{pragma} Import (C, Default_Stack_Size, "__gl_default_stack_size"); - Leap_Seconds_Support : Integer; - @b{pragma} Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support"); +@item @code{-gnatwn} - procedure Runtime_Initialize; - @b{pragma} Import (C, Runtime_Initialize, "__gnat_runtime_initialize"); +@emph{Set normal warnings mode.} - Finalize_Library_Objects : No_Param_Proc; - @b{pragma} Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects"); +This switch sets normal warning mode, in which enabled warnings are +issued and treated as warnings rather than errors. This is the default +mode. the switch @emph{-gnatwn} can be used to cancel the effect of +an explicit @emph{-gnatws} or +@emph{-gnatwe}. It also cancels the effect of the +implicit @emph{-gnatwe} that is activated by the +use of @emph{-gnatg}. +@end table - -- Start of processing for adainit +@geindex -gnatw.n (gcc) - @b{begin} +@geindex Atomic Synchronization +@geindex warnings - -- Record various information for this partition. The values - -- are derived by the binder from information stored in the ali - -- files by the compiler. - @b{if} Is_Elaborated @b{then} - @b{return}; - @b{end if}; - Is_Elaborated := True; - Main_Priority := -1; - Time_Slice_Value := -1; - WC_Encoding := 'b'; - Locking_Policy := ' '; - Queuing_Policy := ' '; - Task_Dispatching_Policy := ' '; - Priority_Specific_Dispatching := - Local_Priority_Specific_Dispatching'Address; - Num_Specific_Dispatching := 0; - Main_CPU := -1; - Interrupt_States := Local_Interrupt_States'Address; - Num_Interrupt_States := 0; - Unreserve_All_Interrupts := 0; - Detect_Blocking := 0; - Default_Stack_Size := -1; - Leap_Seconds_Support := 0; +@table @asis - Runtime_Initialize; +@item @code{-gnatw.n} - Finalize_Library_Objects := finalize_library'access; +@emph{Activate warnings on atomic synchronization.} - -- Now we have the elaboration calls for all units in the partition. - -- The Elab_Spec and Elab_Body attributes generate references to the - -- implicit elaboration procedures generated by the compiler for - -- each unit that requires elaboration. Increment a counter of - -- reference for each unit. +This switch actives warnings when an access to an atomic variable +requires the generation of atomic synchronization code. These +warnings are off by default. +@end table - System.Soft_Links'Elab_Spec; - System.Exception_Table'Elab_Body; - E23 := E23 + 1; - Ada.Io_Exceptions'Elab_Spec; - E46 := E46 + 1; - Ada.Tags'Elab_Spec; - Ada.Streams'Elab_Spec; - E45 := E45 + 1; - Interfaces.C'Elab_Spec; - System.Exceptions'Elab_Spec; - E25 := E25 + 1; - System.Finalization_Root'Elab_Spec; - E68 := E68 + 1; - Ada.Finalization'Elab_Spec; - E66 := E66 + 1; - System.Storage_Pools'Elab_Spec; - E85 := E85 + 1; - System.Finalization_Masters'Elab_Spec; - System.Storage_Pools.Subpools'Elab_Spec; - System.Pool_Global'Elab_Spec; - E87 := E87 + 1; - System.File_Control_Block'Elab_Spec; - E75 := E75 + 1; - System.File_Io'Elab_Body; - E64 := E64 + 1; - E91 := E91 + 1; - System.Finalization_Masters'Elab_Body; - E77 := E77 + 1; - E70 := E70 + 1; - Ada.Tags'Elab_Body; - E48 := E48 + 1; - System.Soft_Links'Elab_Body; - E13 := E13 + 1; - System.Os_Lib'Elab_Body; - E72 := E72 + 1; - System.Secondary_Stack'Elab_Body; - E17 := E17 + 1; - Ada.Text_Io'Elab_Spec; - Ada.Text_Io'Elab_Body; - E06 := E06 + 1; - @b{end} adainit; - - -------------- - -- adafinal -- - -------------- - -@findex adafinal - @b{procedure} adafinal @b{is} - @b{procedure} s_stalib_adafinal; - @b{pragma} Import (C, s_stalib_adafinal, "system__standard_library__adafinal"); +@geindex -gnatw.N (gcc) - @b{procedure} Runtime_Finalize; - @b{pragma} Import (C, Runtime_Finalize, "__gnat_runtime_finalize"); - @b{begin} - @b{if not} Is_Elaborated @b{then} - @b{return}; - @b{end if}; - Is_Elaborated := False; - Runtime_Finalize; - s_stalib_adafinal; - @b{end} adafinal; +@table @asis - -- We get to the main program of the partition by using - -- pragma Import because if we try to with the unit and - -- call it Ada style, then not only do we waste time - -- recompiling it, but also, we don't really know the right - -- switches (e.g.@: identifier character set) to be used - -- to compile it. +@item @code{-gnatw.N} - @b{procedure} Ada_Main_Program; - @b{pragma} Import (Ada, Ada_Main_Program, "_ada_hello"); +@emph{Suppress warnings on atomic synchronization.} - ---------- - -- main -- - ---------- +@geindex Atomic Synchronization +@geindex warnings - -- main is actually a function, as in the ANSI C standard, - -- defined to return the exit status. The three parameters - -- are the argument count, argument values and environment - -- pointer. +This switch suppresses warnings when an access to an atomic variable +requires the generation of atomic synchronization code. +@end table -@findex Main Program - @b{function} main - (argc : Integer; - argv : System.Address; - envp : System.Address) - @b{return} Integer - @b{is} - -- The initialize routine performs low level system - -- initialization using a standard library routine which - -- sets up signal handling and performs any other - -- required setup. The routine can be found in file - -- a-init.c. +@geindex -gnatwo (gcc) -@findex __gnat_initialize - @b{procedure} initialize; - @b{pragma} Import (C, initialize, "__gnat_initialize"); +@geindex Address Clauses +@geindex warnings - -- The finalize routine performs low level system - -- finalization using a standard library routine. The - -- routine is found in file a-final.c and in the standard - -- distribution is a dummy routine that does nothing, so - -- really this is a hook for special user finalization. -@findex __gnat_finalize - @b{procedure} finalize; - @b{pragma} Import (C, finalize, "__gnat_finalize"); +@table @asis - -- The following is to initialize the SEH exceptions +@item @code{-gnatwo} - SEH : @b{aliased array} (1 .. 2) of Integer; +@emph{Activate warnings on address clause overlays.} - Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address; - @b{pragma} Volatile (Ensure_Reference); +This switch activates warnings for possibly unintended initialization +effects of defining address clauses that cause one variable to overlap +another. The default is that such warnings are generated. +@end table - -- Start of processing for main +@geindex -gnatwO (gcc) - @b{begin} - -- Save global variables - gnat_argc := argc; - gnat_argv := argv; - gnat_envp := envp; +@table @asis - -- Call low level system initialization +@item @code{-gnatwO} - Initialize (SEH'Address); +@emph{Suppress warnings on address clause overlays.} - -- Call our generated Ada initialization routine +This switch suppresses warnings on possibly unintended initialization +effects of defining address clauses that cause one variable to overlap +another. +@end table - adainit; +@geindex -gnatw.o (gcc) - -- Now we call the main program of the partition - Ada_Main_Program; +@table @asis - -- Perform Ada finalization +@item @code{-gnatw.o} - adafinal; +@emph{Activate warnings on modified but unreferenced out parameters.} - -- Perform low level system finalization +This switch activates warnings for variables that are modified by using +them as actuals for a call to a procedure with an out mode formal, where +the resulting assigned value is never read. It is applicable in the case +where there is more than one out mode formal. If there is only one out +mode formal, the warning is issued by default (controlled by -gnatwu). +The warning is suppressed for volatile +variables and also for variables that are renamings of other variables +or for which an address clause is given. +The default is that these warnings are not given. +@end table - Finalize; +@geindex -gnatw.O (gcc) - -- Return the proper exit status - @b{return} (gnat_exit_status); - @b{end}; --- This section is entirely comments, so it has no effect on the --- compilation of the Ada_Main package. It provides the list of --- object files and linker options, as well as some standard --- libraries needed for the link. The gnatlink utility parses --- this b~hello.adb file to read these comment lines to generate --- the appropriate command line arguments for the call to the --- system linker. The BEGIN/END lines are used for sentinels for --- this parsing operation. +@table @asis --- The exact file names will of course depend on the environment, --- host/target and location of files on the host system. +@item @code{-gnatw.O} -@findex Object file list --- BEGIN Object file/option list - -- ./hello.o - -- -L./ - -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/ - -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a --- END Object file/option list +@emph{Disable warnings on modified but unreferenced out parameters.} -@b{end} ada_main; -@end smallexample +This switch suppresses warnings for variables that are modified by using +them as actuals for a call to a procedure with an out mode formal, where +the resulting assigned value is never read. +@end table -@noindent -The Ada code in the above example is exactly what is generated by the -binder. We have added comments to more clearly indicate the function -of each part of the generated @code{Ada_Main} package. +@geindex -gnatwp (gcc) -The code is standard Ada in all respects, and can be processed by any -tools that handle Ada. In particular, it is possible to use the debugger -in Ada mode to debug the generated @code{Ada_Main} package. For example, -suppose that for reasons that you do not understand, your program is crashing -during elaboration of the body of @code{Ada.Text_IO}. To locate this bug, -you can place a breakpoint on the call: +@geindex Inlining +@geindex warnings -@smallexample @c ada -Ada.Text_Io'Elab_Body; -@end smallexample -@noindent -and trace the elaboration routine for this package to find out where -the problem might be (more usually of course you would be debugging -elaboration code in your own application). +@table @asis -@node Elaboration Order Handling in GNAT -@appendix Elaboration Order Handling in GNAT -@cindex Order of elaboration -@cindex Elaboration control +@item @code{-gnatwp} -@menu -* Elaboration Code:: -* Checking the Elaboration Order:: -* Controlling the Elaboration Order:: -* Controlling Elaboration in GNAT - Internal Calls:: -* Controlling Elaboration in GNAT - External Calls:: -* Default Behavior in GNAT - Ensuring Safety:: -* Treatment of Pragma Elaborate:: -* Elaboration Issues for Library Tasks:: -* Mixing Elaboration Models:: -* What to Do If the Default Elaboration Behavior Fails:: -* Elaboration for Indirect Calls:: -* Summary of Procedures for Elaboration Control:: -* Other Elaboration Order Considerations:: -* Determining the Chosen Elaboration Order:: -@end menu +@emph{Activate warnings on ineffective pragma Inlines.} -@noindent -This chapter describes the handling of elaboration code in Ada and -in GNAT, and discusses how the order of elaboration of program units can -be controlled in GNAT, either automatically or with explicit programming -features. +This switch activates warnings for failure of front end inlining +(activated by @emph{-gnatN}) to inline a particular call. There are +many reasons for not being able to inline a call, including most +commonly that the call is too complex to inline. The default is +that such warnings are not given. +Warnings on ineffective inlining by the gcc back-end can be activated +separately, using the gcc switch -Winline. +@end table -@node Elaboration Code -@section Elaboration Code +@geindex -gnatwP (gcc) -@noindent -Ada provides rather general mechanisms for executing code at elaboration -time, that is to say before the main program starts executing. Such code arises -in three contexts: @table @asis -@item Initializers for variables. -Variables declared at the library level, in package specs or bodies, can -require initialization that is performed at elaboration time, as in: -@smallexample @c ada -@cartouche -Sqrt_Half : Float := Sqrt (0.5); -@end cartouche -@end smallexample -@item Package initialization code -Code in a @code{BEGIN-END} section at the outer level of a package body is -executed as part of the package body elaboration code. +@item @code{-gnatwP} -@item Library level task allocators -Tasks that are declared using task allocators at the library level -start executing immediately and hence can execute at elaboration time. +@emph{Suppress warnings on ineffective pragma Inlines.} + +This switch suppresses warnings on ineffective pragma Inlines. If the +inlining mechanism cannot inline a call, it will simply ignore the +request silently. @end table -@noindent -Subprogram calls are possible in any of these contexts, which means that -any arbitrary part of the program may be executed as part of the elaboration -code. It is even possible to write a program which does all its work at -elaboration time, with a null main program, although stylistically this -would usually be considered an inappropriate way to structure -a program. +@geindex -gnatw.p (gcc) -An important concern arises in the context of elaboration code: -we have to be sure that it is executed in an appropriate order. What we -have is a series of elaboration code sections, potentially one section -for each unit in the program. It is important that these execute -in the correct order. Correctness here means that, taking the above -example of the declaration of @code{Sqrt_Half}, -if some other piece of -elaboration code references @code{Sqrt_Half}, -then it must run after the -section of elaboration code that contains the declaration of -@code{Sqrt_Half}. +@geindex Parameter order +@geindex warnings -There would never be any order of elaboration problem if we made a rule -that whenever you @code{with} a unit, you must elaborate both the spec and body -of that unit before elaborating the unit doing the @code{with}'ing: -@smallexample @c ada -@group -@cartouche -@b{with} Unit_1; -@b{package} Unit_2 @b{is} @dots{} -@end cartouche -@end group -@end smallexample +@table @asis -@noindent -would require that both the body and spec of @code{Unit_1} be elaborated -before the spec of @code{Unit_2}. However, a rule like that would be far too -restrictive. In particular, it would make it impossible to have routines -in separate packages that were mutually recursive. +@item @code{-gnatw.p} -You might think that a clever enough compiler could look at the actual -elaboration code and determine an appropriate correct order of elaboration, -but in the general case, this is not possible. Consider the following -example. +@emph{Activate warnings on parameter ordering.} -In the body of @code{Unit_1}, we have a procedure @code{Func_1} -that references -the variable @code{Sqrt_1}, which is declared in the elaboration code -of the body of @code{Unit_1}: +This switch activates warnings for cases of suspicious parameter +ordering when the list of arguments are all simple identifiers that +match the names of the formals, but are in a different order. The +warning is suppressed if any use of named parameter notation is used, +so this is the appropriate way to suppress a false positive (and +serves to emphasize that the "misordering" is deliberate). The +default is that such warnings are not given. +@end table -@smallexample @c ada -@cartouche -Sqrt_1 : Float := Sqrt (0.1); -@end cartouche -@end smallexample +@geindex -gnatw.P (gcc) -@noindent -The elaboration code of the body of @code{Unit_1} also contains: -@smallexample @c ada -@group -@cartouche -@b{if} expression_1 = 1 @b{then} - Q := Unit_2.Func_2; -@b{end} @b{if}; -@end cartouche -@end group -@end smallexample +@table @asis -@noindent -@code{Unit_2} is exactly parallel, -it has a procedure @code{Func_2} that references -the variable @code{Sqrt_2}, which is declared in the elaboration code of -the body @code{Unit_2}: +@item @code{-gnatw.P} -@smallexample @c ada -@cartouche -Sqrt_2 : Float := Sqrt (0.1); -@end cartouche -@end smallexample +@emph{Suppress warnings on parameter ordering.} -@noindent -The elaboration code of the body of @code{Unit_2} also contains: +This switch suppresses warnings on cases of suspicious parameter +ordering. +@end table -@smallexample @c ada -@group -@cartouche -@b{if} expression_2 = 2 @b{then} - Q := Unit_1.Func_1; -@b{end} @b{if}; -@end cartouche -@end group -@end smallexample +@geindex -gnatwq (gcc) -@noindent -Now the question is, which of the following orders of elaboration is -acceptable: +@geindex Parentheses +@geindex warnings -@smallexample -@group -Spec of Unit_1 -Spec of Unit_2 -Body of Unit_1 -Body of Unit_2 -@end group -@end smallexample -@noindent -or +@table @asis -@smallexample -@group -Spec of Unit_2 -Spec of Unit_1 -Body of Unit_2 -Body of Unit_1 -@end group -@end smallexample +@item @code{-gnatwq} -@noindent -If you carefully analyze the flow here, you will see that you cannot tell -at compile time the answer to this question. -If @code{expression_1} is not equal to 1, -and @code{expression_2} is not equal to 2, -then either order is acceptable, because neither of the function calls is -executed. If both tests evaluate to true, then neither order is acceptable -and in fact there is no correct order. +@emph{Activate warnings on questionable missing parentheses.} -If one of the two expressions is true, and the other is false, then one -of the above orders is correct, and the other is incorrect. For example, -if @code{expression_1} /= 1 and @code{expression_2} = 2, -then the call to @code{Func_1} -will occur, but not the call to @code{Func_2.} -This means that it is essential -to elaborate the body of @code{Unit_1} before -the body of @code{Unit_2}, so the first -order of elaboration is correct and the second is wrong. +This switch activates warnings for cases where parentheses are not used and +the result is potential ambiguity from a readers point of view. For example +(not a > b) when a and b are modular means ((not a) > b) and very likely the +programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and +quite likely ((-x) mod 5) was intended. In such situations it seems best to +follow the rule of always parenthesizing to make the association clear, and +this warning switch warns if such parentheses are not present. The default +is that these warnings are given. +@end table -By making @code{expression_1} and @code{expression_2} -depend on input data, or perhaps -the time of day, we can make it impossible for the compiler or binder -to figure out which of these expressions will be true, and hence it -is impossible to guarantee a safe order of elaboration at run time. - -@node Checking the Elaboration Order -@section Checking the Elaboration Order +@geindex -gnatwQ (gcc) -@noindent -In some languages that involve the same kind of elaboration problems, -e.g.@: Java and C++, the programmer is expected to worry about these -ordering problems himself, and it is common to -write a program in which an incorrect elaboration order gives -surprising results, because it references variables before they -are initialized. -Ada is designed to be a safe language, and a programmer-beware approach is -clearly not sufficient. Consequently, the language provides three lines -of defense: @table @asis -@item Standard rules -Some standard rules restrict the possible choice of elaboration -order. In particular, if you @code{with} a unit, then its spec is always -elaborated before the unit doing the @code{with}. Similarly, a parent -spec is always elaborated before the child spec, and finally -a spec is always elaborated before its corresponding body. -@item Dynamic elaboration checks -@cindex Elaboration checks -@cindex Checks, elaboration -Dynamic checks are made at run time, so that if some entity is accessed -before it is elaborated (typically by means of a subprogram call) -then the exception (@code{Program_Error}) is raised. +@item @code{-gnatwQ} -@item Elaboration control -Facilities are provided for the programmer to specify the desired order -of elaboration. +@emph{Suppress warnings on questionable missing parentheses.} + +This switch suppresses warnings for cases where the association is not +clear and the use of parentheses is preferred. @end table -Let's look at these facilities in more detail. First, the rules for -dynamic checking. One possible rule would be simply to say that the -exception is raised if you access a variable which has not yet been -elaborated. The trouble with this approach is that it could require -expensive checks on every variable reference. Instead Ada has two -rules which are a little more restrictive, but easier to check, and -easier to state: +@geindex -gnatwr (gcc) + @table @asis -@item Restrictions on calls -A subprogram can only be called at elaboration time if its body -has been elaborated. The rules for elaboration given above guarantee -that the spec of the subprogram has been elaborated before the -call, but not the body. If this rule is violated, then the -exception @code{Program_Error} is raised. -@item Restrictions on instantiations -A generic unit can only be instantiated if the body of the generic -unit has been elaborated. Again, the rules for elaboration given above -guarantee that the spec of the generic unit has been elaborated -before the instantiation, but not the body. If this rule is -violated, then the exception @code{Program_Error} is raised. -@end table +@item @code{-gnatwr} -@noindent -The idea is that if the body has been elaborated, then any variables -it references must have been elaborated; by checking for the body being -elaborated we guarantee that none of its references causes any -trouble. As we noted above, this is a little too restrictive, because a -subprogram that has no non-local references in its body may in fact be safe -to call. However, it really would be unsafe to rely on this, because -it would mean that the caller was aware of details of the implementation -in the body. This goes against the basic tenets of Ada. +@emph{Activate warnings on redundant constructs.} -A plausible implementation can be described as follows. -A Boolean variable is associated with each subprogram -and each generic unit. This variable is initialized to False, and is set to -True at the point body is elaborated. Every call or instantiation checks the -variable, and raises @code{Program_Error} if the variable is False. +This switch activates warnings for redundant constructs. The following +is the current list of constructs regarded as redundant: -Note that one might think that it would be good enough to have one Boolean -variable for each package, but that would not deal with cases of trying -to call a body in the same package as the call -that has not been elaborated yet. -Of course a compiler may be able to do enough analysis to optimize away -some of the Boolean variables as unnecessary, and @code{GNAT} indeed -does such optimizations, but still the easiest conceptual model is to -think of there being one variable per subprogram. -@node Controlling the Elaboration Order -@section Controlling the Elaboration Order +@itemize * -@noindent -In the previous section we discussed the rules in Ada which ensure -that @code{Program_Error} is raised if an incorrect elaboration order is -chosen. This prevents erroneous executions, but we need mechanisms to -specify a correct execution and avoid the exception altogether. -To achieve this, Ada provides a number of features for controlling -the order of elaboration. We discuss these features in this section. +@item +Assignment of an item to itself. -First, there are several ways of indicating to the compiler that a given -unit has no elaboration problems: +@item +Type conversion that converts an expression to its own type. -@table @asis -@item packages that do not require a body -A library package that does not require a body does not permit -a body (this rule was introduced in Ada 95). -Thus if we have a such a package, as in: +@item +Use of the attribute @cite{Base} where @cite{typ'Base} is the same +as @cite{typ}. -@smallexample @c ada -@group -@cartouche -@b{package} Definitions @b{is} - @b{generic} - @b{type} m @b{is} @b{new} integer; - @b{package} Subp @b{is} - @b{type} a @b{is} @b{array} (1 .. 10) @b{of} m; - @b{type} b @b{is} @b{array} (1 .. 20) @b{of} m; - @b{end} Subp; -@b{end} Definitions; -@end cartouche -@end group -@end smallexample +@item +Use of pragma @cite{Pack} when all components are placed by a record +representation clause. -@noindent -A package that @code{with}'s @code{Definitions} may safely instantiate -@code{Definitions.Subp} because the compiler can determine that there -definitely is no package body to worry about in this case +@item +Exception handler containing only a reraise statement (raise with no +operand) which has no effect. -@item pragma Pure -@cindex pragma Pure -@findex Pure -Places sufficient restrictions on a unit to guarantee that -no call to any subprogram in the unit can result in an -elaboration problem. This means that the compiler does not need -to worry about the point of elaboration of such units, and in -particular, does not need to check any calls to any subprograms -in this unit. +@item +Use of the operator abs on an operand that is known at compile time +to be non-negative -@item pragma Preelaborate -@findex Preelaborate -@cindex pragma Preelaborate -This pragma places slightly less stringent restrictions on a unit than -does pragma Pure, -but these restrictions are still sufficient to ensure that there -are no elaboration problems with any calls to the unit. +@item +Comparison of boolean expressions to an explicit True value. +@end itemize -@item pragma Elaborate_Body -@findex Elaborate_Body -@cindex pragma Elaborate_Body -This pragma requires that the body of a unit be elaborated immediately -after its spec. Suppose a unit @code{A} has such a pragma, -and unit @code{B} does -a @code{with} of unit @code{A}. Recall that the standard rules require -the spec of unit @code{A} -to be elaborated before the @code{with}'ing unit; given the pragma in -@code{A}, we also know that the body of @code{A} -will be elaborated before @code{B}, so -that calls to @code{A} are safe and do not need a check. -@end table - -@noindent -Note that, -unlike pragma @code{Pure} and pragma @code{Preelaborate}, -the use of -@code{Elaborate_Body} does not guarantee that the program is -free of elaboration problems, because it may not be possible -to satisfy the requested elaboration order. -Let's go back to the example with @code{Unit_1} and @code{Unit_2}. -If a programmer -marks @code{Unit_1} as @code{Elaborate_Body}, -and not @code{Unit_2,} then the order of -elaboration will be: +The default is that warnings for redundant constructs are not given. +@end table -@smallexample -@group -Spec of Unit_2 -Spec of Unit_1 -Body of Unit_1 -Body of Unit_2 -@end group -@end smallexample +@geindex -gnatwR (gcc) -@noindent -Now that means that the call to @code{Func_1} in @code{Unit_2} -need not be checked, -it must be safe. But the call to @code{Func_2} in -@code{Unit_1} may still fail if -@code{Expression_1} is equal to 1, -and the programmer must still take -responsibility for this not being the case. -If all units carry a pragma @code{Elaborate_Body}, then all problems are -eliminated, except for calls entirely within a body, which are -in any case fully under programmer control. However, using the pragma -everywhere is not always possible. -In particular, for our @code{Unit_1}/@code{Unit_2} example, if -we marked both of them as having pragma @code{Elaborate_Body}, then -clearly there would be no possible elaboration order. +@table @asis + +@item @code{-gnatwR} + +@emph{Suppress warnings on redundant constructs.} + +This switch suppresses warnings for redundant constructs. +@end table + +@geindex -gnatw.r (gcc) -The above pragmas allow a server to guarantee safe use by clients, and -clearly this is the preferable approach. Consequently a good rule -is to mark units as @code{Pure} or @code{Preelaborate} if possible, -and if this is not possible, -mark them as @code{Elaborate_Body} if possible. -As we have seen, there are situations where neither of these -three pragmas can be used. -So we also provide methods for clients to control the -order of elaboration of the servers on which they depend: @table @asis -@item pragma Elaborate (unit) -@findex Elaborate -@cindex pragma Elaborate -This pragma is placed in the context clause, after a @code{with} clause, -and it requires that the body of the named unit be elaborated before -the unit in which the pragma occurs. The idea is to use this pragma -if the current unit calls at elaboration time, directly or indirectly, -some subprogram in the named unit. -@item pragma Elaborate_All (unit) -@findex Elaborate_All -@cindex pragma Elaborate_All -This is a stronger version of the Elaborate pragma. Consider the -following example: +@item @code{-gnatw.r} -@smallexample -Unit A @code{with}'s unit B and calls B.Func in elab code -Unit B @code{with}'s unit C, and B.Func calls C.Func -@end smallexample - -@noindent -Now if we put a pragma @code{Elaborate (B)} -in unit @code{A}, this ensures that the -body of @code{B} is elaborated before the call, but not the -body of @code{C}, so -the call to @code{C.Func} could still cause @code{Program_Error} to -be raised. +@emph{Activate warnings for object renaming function.} -The effect of a pragma @code{Elaborate_All} is stronger, it requires -not only that the body of the named unit be elaborated before the -unit doing the @code{with}, but also the bodies of all units that the -named unit uses, following @code{with} links transitively. For example, -if we put a pragma @code{Elaborate_All (B)} in unit @code{A}, -then it requires -not only that the body of @code{B} be elaborated before @code{A}, -but also the -body of @code{C}, because @code{B} @code{with}'s @code{C}. +This switch activates warnings for an object renaming that renames a +function call, which is equivalent to a constant declaration (as +opposed to renaming the function itself). The default is that these +warnings are given. @end table -@noindent -We are now in a position to give a usage rule in Ada for avoiding -elaboration problems, at least if dynamic dispatching and access to -subprogram values are not used. We will handle these cases separately -later. +@geindex -gnatwT (gcc) -The rule is simple. If a unit has elaboration code that can directly or -indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate -a generic package in a @code{with}'ed unit, -then if the @code{with}'ed unit does not have -pragma @code{Pure} or @code{Preelaborate}, then the client should have -a pragma @code{Elaborate_All} -for the @code{with}'ed unit. By following this rule a client is -assured that calls can be made without risk of an exception. -For generic subprogram instantiations, the rule can be relaxed to -require only a pragma @code{Elaborate} since elaborating the body -of a subprogram cannot cause any transitive elaboration (we are -not calling the subprogram in this case, just elaborating its -declaration). +@table @asis + +@item @code{-gnatw.R} + +@emph{Suppress warnings for object renaming function.} + +This switch suppresses warnings for object renaming function. +@end table + +@geindex -gnatws (gcc) -If this rule is not followed, then a program may be in one of four -states: @table @asis -@item No order exists -No order of elaboration exists which follows the rules, taking into -account any @code{Elaborate}, @code{Elaborate_All}, -or @code{Elaborate_Body} pragmas. In -this case, an Ada compiler must diagnose the situation at bind -time, and refuse to build an executable program. -@item One or more orders exist, all incorrect -One or more acceptable elaboration orders exist, and all of them -generate an elaboration order problem. In this case, the binder -can build an executable program, but @code{Program_Error} will be raised -when the program is run. +@item @code{-gnatws} -@item Several orders exist, some right, some incorrect -One or more acceptable elaboration orders exists, and some of them -work, and some do not. The programmer has not controlled -the order of elaboration, so the binder may or may not pick one of -the correct orders, and the program may or may not raise an -exception when it is run. This is the worst case, because it means -that the program may fail when moved to another compiler, or even -another version of the same compiler. +@emph{Suppress all warnings.} -@item One or more orders exists, all correct -One ore more acceptable elaboration orders exist, and all of them -work. In this case the program runs successfully. This state of -affairs can be guaranteed by following the rule we gave above, but -may be true even if the rule is not followed. +This switch completely suppresses the +output of all warning messages from the GNAT front end, including +both warnings that can be controlled by switches described in this +section, and those that are normally given unconditionally. The +effect of this suppress action can only be cancelled by a subsequent +use of the switch @emph{-gnatwn}. + +Note that switch @emph{-gnatws} does not suppress +warnings from the @emph{gcc} back end. +To suppress these back end warnings as well, use the switch @emph{-w} +in addition to @emph{-gnatws}. Also this switch has no effect on the +handling of style check messages. @end table -@noindent -Note that one additional advantage of following our rules on the use -of @code{Elaborate} and @code{Elaborate_All} -is that the program continues to stay in the ideal (all orders OK) state -even if maintenance -changes some bodies of some units. Conversely, if a program that does -not follow this rule happens to be safe at some point, this state of affairs -may deteriorate silently as a result of maintenance changes. +@geindex -gnatw.s (gcc) -You may have noticed that the above discussion did not mention -the use of @code{Elaborate_Body}. This was a deliberate omission. If you -@code{with} an @code{Elaborate_Body} unit, it still may be the case that -code in the body makes calls to some other unit, so it is still necessary -to use @code{Elaborate_All} on such units. +@geindex Record Representation (component sizes) -@node Controlling Elaboration in GNAT - Internal Calls -@section Controlling Elaboration in GNAT - Internal Calls -@noindent -In the case of internal calls, i.e., calls within a single package, the -programmer has full control over the order of elaboration, and it is up -to the programmer to elaborate declarations in an appropriate order. For -example writing: +@table @asis -@smallexample @c ada -@group -@cartouche -@b{function} One @b{return} Float; +@item @code{-gnatw.s} -Q : Float := One; +@emph{Activate warnings on overridden size clauses.} -@b{function} One @b{return} Float @b{is} -@b{begin} - @b{return} 1.0; -@b{end} One; -@end cartouche -@end group -@end smallexample +This switch activates warnings on component clauses in record +representation clauses where the length given overrides that +specified by an explicit size clause for the component type. A +warning is similarly given in the array case if a specified +component size overrides an explicit size clause for the array +component type. +@end table -@noindent -will obviously raise @code{Program_Error} at run time, because function -One will be called before its body is elaborated. In this case GNAT will -generate a warning that the call will raise @code{Program_Error}: +@geindex -gnatw.S (gcc) -@smallexample -@group -@cartouche - 1. procedure y is - 2. function One return Float; - 3. - 4. Q : Float := One; - | - >>> warning: cannot call "One" before body is elaborated - >>> warning: Program_Error will be raised at run time - 5. - 6. function One return Float is - 7. begin - 8. return 1.0; - 9. end One; -10. -11. begin -12. null; -13. end; -@end cartouche -@end group -@end smallexample +@table @asis -@noindent -Note that in this particular case, it is likely that the call is safe, because -the function @code{One} does not access any global variables. -Nevertheless in Ada, we do not want the validity of the check to depend on -the contents of the body (think about the separate compilation case), so this -is still wrong, as we discussed in the previous sections. +@item @code{-gnatw.S} -The error is easily corrected by rearranging the declarations so that the -body of @code{One} appears before the declaration containing the call -(note that in Ada 95 and Ada 2005, -declarations can appear in any order, so there is no restriction that -would prevent this reordering, and if we write: +@emph{Suppress warnings on overridden size clauses.} -@smallexample @c ada -@group -@cartouche -@b{function} One @b{return} Float; +This switch suppresses warnings on component clauses in record +representation clauses that override size clauses, and similar +warnings when an array component size overrides a size clause. +@end table -@b{function} One @b{return} Float @b{is} -@b{begin} - @b{return} 1.0; -@b{end} One; +@geindex -gnatwt (gcc) -Q : Float := One; -@end cartouche -@end group -@end smallexample +@geindex Deactivated code +@geindex warnings -@noindent -then all is well, no warning is generated, and no -@code{Program_Error} exception -will be raised. -Things are more complicated when a chain of subprograms is executed: +@geindex Deleted code +@geindex warnings -@smallexample @c ada -@group -@cartouche -@b{function} A @b{return} Integer; -@b{function} B @b{return} Integer; -@b{function} C @b{return} Integer; -@b{function} B @b{return} Integer @b{is} @b{begin} @b{return} A; @b{end}; -@b{function} C @b{return} Integer @b{is} @b{begin} @b{return} B; @b{end}; +@table @asis -X : Integer := C; +@item @code{-gnatwt} -@b{function} A @b{return} Integer @b{is} @b{begin} @b{return} 1; @b{end}; -@end cartouche -@end group -@end smallexample - -@noindent -Now the call to @code{C} -at elaboration time in the declaration of @code{X} is correct, because -the body of @code{C} is already elaborated, -and the call to @code{B} within the body of -@code{C} is correct, but the call -to @code{A} within the body of @code{B} is incorrect, because the body -of @code{A} has not been elaborated, so @code{Program_Error} -will be raised on the call to @code{A}. -In this case GNAT will generate a -warning that @code{Program_Error} may be -raised at the point of the call. Let's look at the warning: +@emph{Activate warnings for tracking of deleted conditional code.} -@smallexample -@group -@cartouche - 1. procedure x is - 2. function A return Integer; - 3. function B return Integer; - 4. function C return Integer; - 5. - 6. function B return Integer is begin return A; end; - | - >>> warning: call to "A" before body is elaborated may - raise Program_Error - >>> warning: "B" called at line 7 - >>> warning: "C" called at line 9 - - 7. function C return Integer is begin return B; end; - 8. - 9. X : Integer := C; -10. -11. function A return Integer is begin return 1; end; -12. -13. begin -14. null; -15. end; -@end cartouche -@end group -@end smallexample +This switch activates warnings for tracking of code in conditionals (IF and +CASE statements) that is detected to be dead code which cannot be executed, and +which is removed by the front end. This warning is off by default. This may be +useful for detecting deactivated code in certified applications. +@end table -@noindent -Note that the message here says ``may raise'', instead of the direct case, -where the message says ``will be raised''. That's because whether -@code{A} is -actually called depends in general on run-time flow of control. -For example, if the body of @code{B} said +@geindex -gnatwT (gcc) -@smallexample @c ada -@group -@cartouche -@b{function} B @b{return} Integer @b{is} -@b{begin} - @b{if} some-condition-depending-on-input-data @b{then} - @b{return} A; - @b{else} - @b{return} 1; - @b{end} @b{if}; -@b{end} B; -@end cartouche -@end group -@end smallexample -@noindent -then we could not know until run time whether the incorrect call to A would -actually occur, so @code{Program_Error} might -or might not be raised. It is possible for a compiler to -do a better job of analyzing bodies, to -determine whether or not @code{Program_Error} -might be raised, but it certainly -couldn't do a perfect job (that would require solving the halting problem -and is provably impossible), and because this is a warning anyway, it does -not seem worth the effort to do the analysis. Cases in which it -would be relevant are rare. +@table @asis -In practice, warnings of either of the forms given -above will usually correspond to -real errors, and should be examined carefully and eliminated. -In the rare case where a warning is bogus, it can be suppressed by any of -the following methods: +@item @code{-gnatwT} -@itemize @bullet -@item -Compile with the @option{-gnatws} switch set +@emph{Suppress warnings for tracking of deleted conditional code.} -@item -Suppress @code{Elaboration_Check} for the called subprogram +This switch suppresses warnings for tracking of deleted conditional code. +@end table -@item -Use pragma @code{Warnings_Off} to turn warnings off for the call -@end itemize +@geindex -gnatw.t (gcc) -@noindent -For the internal elaboration check case, -GNAT by default generates the -necessary run-time checks to ensure -that @code{Program_Error} is raised if any -call fails an elaboration check. Of course this can only happen if a -warning has been issued as described above. The use of pragma -@code{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress -some of these checks, meaning that it may be possible (but is not -guaranteed) for a program to be able to call a subprogram whose body -is not yet elaborated, without raising a @code{Program_Error} exception. -@node Controlling Elaboration in GNAT - External Calls -@section Controlling Elaboration in GNAT - External Calls +@table @asis -@noindent -The previous section discussed the case in which the execution of a -particular thread of elaboration code occurred entirely within a -single unit. This is the easy case to handle, because a programmer -has direct and total control over the order of elaboration, and -furthermore, checks need only be generated in cases which are rare -and which the compiler can easily detect. -The situation is more complex when separate compilation is taken into account. -Consider the following: +@item @code{-gnatw.t} -@smallexample @c ada -@cartouche -@group -@b{package} Math @b{is} - @b{function} Sqrt (Arg : Float) @b{return} Float; -@b{end} Math; - -@b{package} @b{body} Math @b{is} - @b{function} Sqrt (Arg : Float) @b{return} Float @b{is} - @b{begin} - @dots{} - @b{end} Sqrt; -@b{end} Math; -@end group -@group -@b{with} Math; -@b{package} Stuff @b{is} - X : Float := Math.Sqrt (0.5); -@b{end} Stuff; - -@b{with} Stuff; -@b{procedure} Main @b{is} -@b{begin} - @dots{} -@b{end} Main; -@end group -@end cartouche -@end smallexample +@emph{Activate warnings on suspicious contracts.} -@noindent -where @code{Main} is the main program. When this program is executed, the -elaboration code must first be executed, and one of the jobs of the -binder is to determine the order in which the units of a program are -to be elaborated. In this case we have four units: the spec and body -of @code{Math}, -the spec of @code{Stuff} and the body of @code{Main}). -In what order should the four separate sections of elaboration code -be executed? +This switch activates warnings on suspicious contracts. This includes +warnings on suspicious postconditions (whether a pragma @cite{Postcondition} or a +@cite{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect +@cite{Contract_Cases}). A function postcondition or contract case is suspicious +when no postcondition or contract case for this function mentions the result +of the function. A procedure postcondition or contract case is suspicious +when it only refers to the pre-state of the procedure, because in that case +it should rather be expressed as a precondition. This switch also controls +warnings on suspicious cases of expressions typically found in contracts like +quantified expressions and uses of Update attribute. The default is that such +warnings are generated. +@end table -There are some restrictions in the order of elaboration that the binder -can choose. In particular, if unit U has a @code{with} -for a package @code{X}, then you -are assured that the spec of @code{X} -is elaborated before U , but you are -not assured that the body of @code{X} -is elaborated before U. -This means that in the above case, the binder is allowed to choose the -order: +@geindex -gnatw.T (gcc) -@smallexample -spec of Math -spec of Stuff -body of Math -body of Main -@end smallexample -@noindent -but that's not good, because now the call to @code{Math.Sqrt} -that happens during -the elaboration of the @code{Stuff} -spec happens before the body of @code{Math.Sqrt} is -elaborated, and hence causes @code{Program_Error} exception to be raised. -At first glance, one might say that the binder is misbehaving, because -obviously you want to elaborate the body of something you @code{with} -first, but -that is not a general rule that can be followed in all cases. Consider +@table @asis -@smallexample @c ada -@group -@cartouche -@b{package} X @b{is} @dots{} +@item @code{-gnatw.T} -@b{package} Y @b{is} @dots{} +@emph{Suppress warnings on suspicious contracts.} -@b{with} X; -@b{package} @b{body} Y @b{is} @dots{} +This switch suppresses warnings on suspicious contracts. +@end table -@b{with} Y; -@b{package} @b{body} X @b{is} @dots{} -@end cartouche -@end group -@end smallexample +@geindex -gnatwu (gcc) -@noindent -This is a common arrangement, and, apart from the order of elaboration -problems that might arise in connection with elaboration code, this works fine. -A rule that says that you must first elaborate the body of anything you -@code{with} cannot work in this case: -the body of @code{X} @code{with}'s @code{Y}, -which means you would have to -elaborate the body of @code{Y} first, but that @code{with}'s @code{X}, -which means -you have to elaborate the body of @code{X} first, but @dots{} and we have a -loop that cannot be broken. -It is true that the binder can in many cases guess an order of elaboration -that is unlikely to cause a @code{Program_Error} -exception to be raised, and it tries to do so (in the -above example of @code{Math/Stuff/Spec}, the GNAT binder will -by default -elaborate the body of @code{Math} right after its spec, so all will be well). +@table @asis -However, a program that blindly relies on the binder to be helpful can -get into trouble, as we discussed in the previous sections, so -GNAT -provides a number of facilities for assisting the programmer in -developing programs that are robust with respect to elaboration order. +@item @code{-gnatwu} -@node Default Behavior in GNAT - Ensuring Safety -@section Default Behavior in GNAT - Ensuring Safety +@emph{Activate warnings on unused entities.} -@noindent -The default behavior in GNAT ensures elaboration safety. In its -default mode GNAT implements the -rule we previously described as the right approach. Let's restate it: +This switch activates warnings to be generated for entities that +are declared but not referenced, and for units that are @emph{with}ed +and not +referenced. In the case of packages, a warning is also generated if +no entities in the package are referenced. This means that if a with'ed +package is referenced but the only references are in @cite{use} +clauses or @cite{renames} +declarations, a warning is still generated. A warning is also generated +for a generic package that is @emph{with}ed but never instantiated. +In the case where a package or subprogram body is compiled, and there +is a @emph{with} on the corresponding spec +that is only referenced in the body, +a warning is also generated, noting that the +@emph{with} can be moved to the body. The default is that +such warnings are not generated. +This switch also activates warnings on unreferenced formals +(it includes the effect of @emph{-gnatwf}). +@end table -@itemize -@item -@emph{If a unit has elaboration code that can directly or indirectly make a -call to a subprogram in a @code{with}'ed unit, or instantiate a generic -package in a @code{with}'ed unit, then if the @code{with}'ed unit -does not have pragma @code{Pure} or -@code{Preelaborate}, then the client should have an -@code{Elaborate_All} pragma for the @code{with}'ed unit.} +@geindex -gnatwU (gcc) -@emph{In the case of instantiating a generic subprogram, it is always -sufficient to have only an @code{Elaborate} pragma for the -@code{with}'ed unit.} -@end itemize -@noindent -By following this rule a client is assured that calls and instantiations -can be made without risk of an exception. +@table @asis -In this mode GNAT traces all calls that are potentially made from -elaboration code, and puts in any missing implicit @code{Elaborate} -and @code{Elaborate_All} pragmas. -The advantage of this approach is that no elaboration problems -are possible if the binder can find an elaboration order that is -consistent with these implicit @code{Elaborate} and -@code{Elaborate_All} pragmas. The -disadvantage of this approach is that no such order may exist. +@item @code{-gnatwU} -If the binder does not generate any diagnostics, then it means that it has -found an elaboration order that is guaranteed to be safe. However, the binder -may still be relying on implicitly generated @code{Elaborate} and -@code{Elaborate_All} pragmas so portability to other compilers than GNAT is not -guaranteed. +@emph{Suppress warnings on unused entities.} -If it is important to guarantee portability, then the compilations should -use the -@option{-gnatel} -(info messages for elaboration prag mas) switch. This will cause info messages -to be generated indicating the missing @code{Elaborate} and -@code{Elaborate_All} pragmas. -Consider the following source program: +This switch suppresses warnings for unused entities and packages. +It also turns off warnings on unreferenced formals (and thus includes +the effect of @emph{-gnatwF}). +@end table -@smallexample @c ada -@group -@cartouche -@b{with} k; -@b{package} j @b{is} - m : integer := k.r; -@b{end}; -@end cartouche -@end group -@end smallexample +@geindex -gnatw.u (gcc) -@noindent -where it is clear that there -should be a pragma @code{Elaborate_All} -for unit @code{k}. An implicit pragma will be generated, and it is -likely that the binder will be able to honor it. However, if you want -to port this program to some other Ada compiler than GNAT. -it is safer to include the pragma explicitly in the source. If this -unit is compiled with the -@option{-gnatel} -switch, then the compiler outputs an information message: -@smallexample -@group -@cartouche -1. with k; -2. package j is -3. m : integer := k.r; - | - >>> info: call to "r" may raise Program_Error - >>> info: missing pragma Elaborate_All for "k" +@table @asis -4. end; -@end cartouche -@end group -@end smallexample +@item @code{-gnatw.u} -@noindent -and these messages can be used as a guide for supplying manually -the missing pragmas. It is usually a bad idea to use this -option during development. That's because it will tell you when -you need to put in a pragma, but cannot tell you when it is time -to take it out. So the use of pragma @code{Elaborate_All} may lead to -unnecessary dependencies and even false circularities. +@emph{Activate warnings on unordered enumeration types.} -This default mode is more restrictive than the Ada Reference -Manual, and it is possible to construct programs which will compile -using the dynamic model described there, but will run into a -circularity using the safer static model we have described. +This switch causes enumeration types to be considered as conceptually +unordered, unless an explicit pragma @cite{Ordered} is given for the type. +The effect is to generate warnings in clients that use explicit comparisons +or subranges, since these constructs both treat objects of the type as +ordered. (A @emph{client} is defined as a unit that is other than the unit in +which the type is declared, or its body or subunits.) Please refer to +the description of pragma @cite{Ordered} in the +@cite{GNAT Reference Manual} for further details. +The default is that such warnings are not generated. +@end table -Of course any Ada compiler must be able to operate in a mode -consistent with the requirements of the Ada Reference Manual, -and in particular must have the capability of implementing the -standard dynamic model of elaboration with run-time checks. +@geindex -gnatw.U (gcc) -In GNAT, this standard mode can be achieved either by the use of -the @option{-gnatE} switch on the compiler (@command{gcc} or -@command{gnatmake}) command, or by the use of the configuration pragma: -@smallexample @c ada -@b{pragma} Elaboration_Checks (DYNAMIC); -@end smallexample +@table @asis -@noindent -Either approach will cause the unit affected to be compiled using the -standard dynamic run-time elaboration checks described in the Ada -Reference Manual. The static model is generally preferable, since it -is clearly safer to rely on compile and link time checks rather than -run-time checks. However, in the case of legacy code, it may be -difficult to meet the requirements of the static model. This -issue is further discussed in -@ref{What to Do If the Default Elaboration Behavior Fails}. +@item @code{-gnatw.U} -Note that the static model provides a strict subset of the allowed -behavior and programs of the Ada Reference Manual, so if you do -adhere to the static model and no circularities exist, -then you are assured that your program will -work using the dynamic model, providing that you remove any -pragma Elaborate statements from the source. +@emph{Deactivate warnings on unordered enumeration types.} -@node Treatment of Pragma Elaborate -@section Treatment of Pragma Elaborate -@cindex Pragma Elaborate +This switch causes all enumeration types to be considered as ordered, so +that no warnings are given for comparisons or subranges for any type. +@end table -@noindent -The use of @code{pragma Elaborate} -should generally be avoided in Ada 95 and Ada 2005 programs, -since there is no guarantee that transitive calls -will be properly handled. Indeed at one point, this pragma was placed -in Annex J (Obsolescent Features), on the grounds that it is never useful. +@geindex -gnatwv (gcc) -Now that's a bit restrictive. In practice, the case in which -@code{pragma Elaborate} is useful is when the caller knows that there -are no transitive calls, or that the called unit contains all necessary -transitive @code{pragma Elaborate} statements, and legacy code often -contains such uses. +@geindex Unassigned variable warnings -Strictly speaking the static mode in GNAT should ignore such pragmas, -since there is no assurance at compile time that the necessary safety -conditions are met. In practice, this would cause GNAT to be incompatible -with correctly written Ada 83 code that had all necessary -@code{pragma Elaborate} statements in place. Consequently, we made the -decision that GNAT in its default mode will believe that if it encounters -a @code{pragma Elaborate} then the programmer knows what they are doing, -and it will trust that no elaboration errors can occur. -The result of this decision is two-fold. First to be safe using the -static mode, you should remove all @code{pragma Elaborate} statements. -Second, when fixing circularities in existing code, you can selectively -use @code{pragma Elaborate} statements to convince the static mode of -GNAT that it need not generate an implicit @code{pragma Elaborate_All} -statement. +@table @asis -When using the static mode with @option{-gnatwl}, any use of -@code{pragma Elaborate} will generate a warning about possible -problems. +@item @code{-gnatwv} -@node Elaboration Issues for Library Tasks -@section Elaboration Issues for Library Tasks -@cindex Library tasks, elaboration issues -@cindex Elaboration of library tasks +@emph{Activate warnings on unassigned variables.} -@noindent -In this section we examine special elaboration issues that arise for -programs that declare library level tasks. +This switch activates warnings for access to variables which +may not be properly initialized. The default is that +such warnings are generated. +@end table -Generally the model of execution of an Ada program is that all units are -elaborated, and then execution of the program starts. However, the -declaration of library tasks definitely does not fit this model. The -reason for this is that library tasks start as soon as they are declared -(more precisely, as soon as the statement part of the enclosing package -body is reached), that is to say before elaboration -of the program is complete. This means that if such a task calls a -subprogram, or an entry in another task, the callee may or may not be -elaborated yet, and in the standard -Reference Manual model of dynamic elaboration checks, you can even -get timing dependent Program_Error exceptions, since there can be -a race between the elaboration code and the task code. +@geindex -gnatwV (gcc) -The static model of elaboration in GNAT seeks to avoid all such -dynamic behavior, by being conservative, and the conservative -approach in this particular case is to assume that all the code -in a task body is potentially executed at elaboration time if -a task is declared at the library level. -This can definitely result in unexpected circularities. Consider -the following example +@table @asis -@smallexample @c ada -@b{package} Decls @b{is} - @b{task} Lib_Task @b{is} - @b{entry} Start; - @b{end} Lib_Task; +@item @code{-gnatwV} - @b{type} My_Int @b{is} @b{new} Integer; +@emph{Suppress warnings on unassigned variables.} - @b{function} Ident (M : My_Int) @b{return} My_Int; -@b{end} Decls; +This switch suppresses warnings for access to variables which +may not be properly initialized. +For variables of a composite type, the warning can also be suppressed in +Ada 2005 by using a default initialization with a box. For example, if +Table is an array of records whose components are only partially uninitialized, +then the following code: -@b{with} Utils; -@b{package} @b{body} Decls @b{is} - @b{task} @b{body} Lib_Task @b{is} - @b{begin} - @b{accept} Start; - Utils.Put_Val (2); - @b{end} Lib_Task; - - @b{function} Ident (M : My_Int) @b{return} My_Int @b{is} - @b{begin} - @b{return} M; - @b{end} Ident; -@b{end} Decls; - -@b{with} Decls; -@b{package} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls.My_Int); -@b{end} Utils; - -@b{with} Text_IO; -@b{package} @b{body} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls.My_Int) @b{is} - @b{begin} - Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); - @b{end} Put_Val; -@b{end} Utils; +@example +Tab : Table := (others => <>); +@end example -@b{with} Decls; -@b{procedure} Main @b{is} -@b{begin} - Decls.Lib_Task.Start; -@b{end}; -@end smallexample +will suppress warnings on subsequent statements that access components +of variable Tab. +@end table -@noindent -If the above example is compiled in the default static elaboration -mode, then a circularity occurs. The circularity comes from the call -@code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since -this call occurs in elaboration code, we need an implicit pragma -@code{Elaborate_All} for @code{Utils}. This means that not only must -the spec and body of @code{Utils} be elaborated before the body -of @code{Decls}, but also the spec and body of any unit that is -@code{with'ed} by the body of @code{Utils} must also be elaborated before -the body of @code{Decls}. This is the transitive implication of -pragma @code{Elaborate_All} and it makes sense, because in general -the body of @code{Put_Val} might have a call to something in a -@code{with'ed} unit. - -In this case, the body of Utils (actually its spec) @code{with's} -@code{Decls}. Unfortunately this means that the body of @code{Decls} -must be elaborated before itself, in case there is a call from the -body of @code{Utils}. +@geindex -gnatw.v (gcc) -Here is the exact chain of events we are worrying about: +@geindex bit order warnings -@enumerate -@item -In the body of @code{Decls} a call is made from within the body of a library -task to a subprogram in the package @code{Utils}. Since this call may -occur at elaboration time (given that the task is activated at elaboration -time), we have to assume the worst, i.e., that the -call does happen at elaboration time. -@item -This means that the body and spec of @code{Util} must be elaborated before -the body of @code{Decls} so that this call does not cause an access before -elaboration. +@table @asis -@item -Within the body of @code{Util}, specifically within the body of -@code{Util.Put_Val} there may be calls to any unit @code{with}'ed -by this package. +@item @code{-gnatw.v} -@item -One such @code{with}'ed package is package @code{Decls}, so there -might be a call to a subprogram in @code{Decls} in @code{Put_Val}. -In fact there is such a call in this example, but we would have to -assume that there was such a call even if it were not there, since -we are not supposed to write the body of @code{Decls} knowing what -is in the body of @code{Utils}; certainly in the case of the -static elaboration model, the compiler does not know what is in -other bodies and must assume the worst. +@emph{Activate info messages for non-default bit order.} -@item -This means that the spec and body of @code{Decls} must also be -elaborated before we elaborate the unit containing the call, but -that unit is @code{Decls}! This means that the body of @code{Decls} -must be elaborated before itself, and that's a circularity. -@end enumerate +This switch activates messages (labeled "info", they are not warnings, +just informational messages) about the effects of non-default bit-order +on records to which a component clause is applied. The effect of specifying +non-default bit ordering is a bit subtle (and changed with Ada 2005), so +these messages, which are given by default, are useful in understanding the +exact consequences of using this feature. +@end table -@noindent -Indeed, if you add an explicit pragma @code{Elaborate_All} for @code{Utils} in -the body of @code{Decls} you will get a true Ada Reference Manual -circularity that makes the program illegal. +@geindex -gnatw.V (gcc) -In practice, we have found that problems with the static model of -elaboration in existing code often arise from library tasks, so -we must address this particular situation. -Note that if we compile and run the program above, using the dynamic model of -elaboration (that is to say use the @option{-gnatE} switch), -then it compiles, binds, -links, and runs, printing the expected result of 2. Therefore in some sense -the circularity here is only apparent, and we need to capture -the properties of this program that distinguish it from other library-level -tasks that have real elaboration problems. +@table @asis -We have four possible answers to this question: +@item @code{-gnatw.V} -@itemize @bullet +@emph{Suppress info messages for non-default bit order.} -@item -Use the dynamic model of elaboration. +This switch suppresses information messages for the effects of specifying +non-default bit order on record components with component clauses. +@end table -If we use the @option{-gnatE} switch, then as noted above, the program works. -Why is this? If we examine the task body, it is apparent that the task cannot -proceed past the -@code{accept} statement until after elaboration has been completed, because -the corresponding entry call comes from the main program, not earlier. -This is why the dynamic model works here. But that's really giving -up on a precise analysis, and we prefer to take this approach only if we cannot -solve the -problem in any other manner. So let us examine two ways to reorganize -the program to avoid the potential elaboration problem. +@geindex -gnatww (gcc) -@item -Split library tasks into separate packages. +@geindex String indexing warnings -Write separate packages, so that library tasks are isolated from -other declarations as much as possible. Let us look at a variation on -the above program. -@smallexample @c ada -@b{package} Decls1 @b{is} - @b{task} Lib_Task @b{is} - @b{entry} Start; - @b{end} Lib_Task; -@b{end} Decls1; - -@b{with} Utils; -@b{package} @b{body} Decls1 @b{is} - @b{task} @b{body} Lib_Task @b{is} - @b{begin} - @b{accept} Start; - Utils.Put_Val (2); - @b{end} Lib_Task; -@b{end} Decls1; - -@b{package} Decls2 @b{is} - @b{type} My_Int @b{is} @b{new} Integer; - @b{function} Ident (M : My_Int) @b{return} My_Int; -@b{end} Decls2; - -@b{with} Utils; -@b{package} @b{body} Decls2 @b{is} - @b{function} Ident (M : My_Int) @b{return} My_Int @b{is} - @b{begin} - @b{return} M; - @b{end} Ident; -@b{end} Decls2; - -@b{with} Decls2; -@b{package} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls2.My_Int); -@b{end} Utils; - -@b{with} Text_IO; -@b{package} @b{body} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls2.My_Int) @b{is} - @b{begin} - Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg))); - @b{end} Put_Val; -@b{end} Utils; +@table @asis -@b{with} Decls1; -@b{procedure} Main @b{is} -@b{begin} - Decls1.Lib_Task.Start; -@b{end}; -@end smallexample +@item @code{-gnatww} -@noindent -All we have done is to split @code{Decls} into two packages, one -containing the library task, and one containing everything else. Now -there is no cycle, and the program compiles, binds, links and executes -using the default static model of elaboration. +@emph{Activate warnings on wrong low bound assumption.} -@item -Declare separate task types. +This switch activates warnings for indexing an unconstrained string parameter +with a literal or S'Length. This is a case where the code is assuming that the +low bound is one, which is in general not true (for example when a slice is +passed). The default is that such warnings are generated. +@end table -A significant part of the problem arises because of the use of the -single task declaration form. This means that the elaboration of -the task type, and the elaboration of the task itself (i.e.@: the -creation of the task) happen at the same time. A good rule -of style in Ada is to always create explicit task types. By -following the additional step of placing task objects in separate -packages from the task type declaration, many elaboration problems -are avoided. Here is another modified example of the example program: +@geindex -gnatwW (gcc) -@smallexample @c ada -@b{package} Decls @b{is} - @b{task} @b{type} Lib_Task_Type @b{is} - @b{entry} Start; - @b{end} Lib_Task_Type; - @b{type} My_Int @b{is} @b{new} Integer; +@table @asis - @b{function} Ident (M : My_Int) @b{return} My_Int; -@b{end} Decls; +@item @code{-gnatwW} -@b{with} Utils; -@b{package} @b{body} Decls @b{is} - @b{task} @b{body} Lib_Task_Type @b{is} - @b{begin} - @b{accept} Start; - Utils.Put_Val (2); - @b{end} Lib_Task_Type; - - @b{function} Ident (M : My_Int) @b{return} My_Int @b{is} - @b{begin} - @b{return} M; - @b{end} Ident; -@b{end} Decls; - -@b{with} Decls; -@b{package} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls.My_Int); -@b{end} Utils; - -@b{with} Text_IO; -@b{package} @b{body} Utils @b{is} - @b{procedure} Put_Val (Arg : Decls.My_Int) @b{is} - @b{begin} - Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); - @b{end} Put_Val; -@b{end} Utils; +@emph{Suppress warnings on wrong low bound assumption.} -@b{with} Decls; -@b{package} Declst @b{is} - Lib_Task : Decls.Lib_Task_Type; -@b{end} Declst; +This switch suppresses warnings for indexing an unconstrained string parameter +with a literal or S'Length. Note that this warning can also be suppressed +in a particular case by adding an assertion that the lower bound is 1, +as shown in the following example: -@b{with} Declst; -@b{procedure} Main @b{is} -@b{begin} - Declst.Lib_Task.Start; -@b{end}; -@end smallexample +@example +procedure K (S : String) is + pragma Assert (S'First = 1); + ... +@end example +@end table -@noindent -What we have done here is to replace the @code{task} declaration in -package @code{Decls} with a @code{task type} declaration. Then we -introduce a separate package @code{Declst} to contain the actual -task object. This separates the elaboration issues for -the @code{task type} -declaration, which causes no trouble, from the elaboration issues -of the task object, which is also unproblematic, since it is now independent -of the elaboration of @code{Utils}. -This separation of concerns also corresponds to -a generally sound engineering principle of separating declarations -from instances. This version of the program also compiles, binds, links, -and executes, generating the expected output. +@geindex -gnatw.w (gcc) -@item -Use No_Entry_Calls_In_Elaboration_Code restriction. -@cindex No_Entry_Calls_In_Elaboration_Code +@geindex Warnings Off control -The previous two approaches described how a program can be restructured -to avoid the special problems caused by library task bodies. in practice, -however, such restructuring may be difficult to apply to existing legacy code, -so we must consider solutions that do not require massive rewriting. -Let us consider more carefully why our original sample program works -under the dynamic model of elaboration. The reason is that the code -in the task body blocks immediately on the @code{accept} -statement. Now of course there is nothing to prohibit elaboration -code from making entry calls (for example from another library level task), -so we cannot tell in isolation that -the task will not execute the accept statement during elaboration. +@table @asis -However, in practice it is very unusual to see elaboration code -make any entry calls, and the pattern of tasks starting -at elaboration time and then immediately blocking on @code{accept} or -@code{select} statements is very common. What this means is that -the compiler is being too pessimistic when it analyzes the -whole package body as though it might be executed at elaboration -time. +@item @code{-gnatw.w} -If we know that the elaboration code contains no entry calls, (a very safe -assumption most of the time, that could almost be made the default -behavior), then we can compile all units of the program under control -of the following configuration pragma: +@emph{Activate warnings on Warnings Off pragmas} -@smallexample -pragma Restrictions (No_Entry_Calls_In_Elaboration_Code); -@end smallexample +This switch activates warnings for use of @cite{pragma Warnings (Off@comma{} entity)} +where either the pragma is entirely useless (because it suppresses no +warnings), or it could be replaced by @cite{pragma Unreferenced} or +@cite{pragma Unmodified}. +Also activates warnings for the case of +Warnings (Off, String), where either there is no matching +Warnings (On, String), or the Warnings (Off) did not suppress any warning. +The default is that these warnings are not given. +@end table -@noindent -This pragma can be placed in the @file{gnat.adc} file in the usual -manner. If we take our original unmodified program and compile it -in the presence of a @file{gnat.adc} containing the above pragma, -then once again, we can compile, bind, link, and execute, obtaining -the expected result. In the presence of this pragma, the compiler does -not trace calls in a task body, that appear after the first @code{accept} -or @code{select} statement, and therefore does not report a potential -circularity in the original program. +@geindex -gnatw.W (gcc) -The compiler will check to the extent it can that the above -restriction is not violated, but it is not always possible to do a -complete check at compile time, so it is important to use this -pragma only if the stated restriction is in fact met, that is to say -no task receives an entry call before elaboration of all units is completed. -@end itemize +@table @asis -@node Mixing Elaboration Models -@section Mixing Elaboration Models -@noindent -So far, we have assumed that the entire program is either compiled -using the dynamic model or static model, ensuring consistency. It -is possible to mix the two models, but rules have to be followed -if this mixing is done to ensure that elaboration checks are not -omitted. +@item @code{-gnatw.W} -The basic rule is that @emph{a unit compiled with the static model cannot -be @code{with'ed} by a unit compiled with the dynamic model}. The -reason for this is that in the static model, a unit assumes that -its clients guarantee to use (the equivalent of) pragma -@code{Elaborate_All} so that no elaboration checks are required -in inner subprograms, and this assumption is violated if the -client is compiled with dynamic checks. +@emph{Suppress warnings on unnecessary Warnings Off pragmas} -The precise rule is as follows. A unit that is compiled with dynamic -checks can only @code{with} a unit that meets at least one of the -following criteria: +This switch suppresses warnings for use of @cite{pragma Warnings (Off@comma{} ...)}. +@end table -@itemize @bullet +@geindex -gnatwx (gcc) -@item -The @code{with'ed} unit is itself compiled with dynamic elaboration -checks (that is with the @option{-gnatE} switch. +@geindex Export/Import pragma warnings -@item -The @code{with'ed} unit is an internal GNAT implementation unit from -the System, Interfaces, Ada, or GNAT hierarchies. -@item -The @code{with'ed} unit has pragma Preelaborate or pragma Pure. +@table @asis -@item -The @code{with'ing} unit (that is the client) has an explicit pragma -@code{Elaborate_All} for the @code{with'ed} unit. +@item @code{-gnatwx} -@end itemize +@emph{Activate warnings on Export/Import pragmas.} -@noindent -If this rule is violated, that is if a unit with dynamic elaboration -checks @code{with's} a unit that does not meet one of the above four -criteria, then the binder (@code{gnatbind}) will issue a warning -similar to that in the following example: +This switch activates warnings on Export/Import pragmas when +the compiler detects a possible conflict between the Ada and +foreign language calling sequences. For example, the use of +default parameters in a convention C procedure is dubious +because the C compiler cannot supply the proper default, so +a warning is issued. The default is that such warnings are +generated. +@end table -@smallexample -warning: "x.ads" has dynamic elaboration checks and with's -warning: "y.ads" which has static elaboration checks -@end smallexample +@geindex -gnatwX (gcc) -@noindent -These warnings indicate that the rule has been violated, and that as a result -elaboration checks may be missed in the resulting executable file. -This warning may be suppressed using the @option{-ws} binder switch -in the usual manner. -One useful application of this mixing rule is in the case of a subsystem -which does not itself @code{with} units from the remainder of the -application. In this case, the entire subsystem can be compiled with -dynamic checks to resolve a circularity in the subsystem, while -allowing the main application that uses this subsystem to be compiled -using the more reliable default static model. +@table @asis -@node What to Do If the Default Elaboration Behavior Fails -@section What to Do If the Default Elaboration Behavior Fails +@item @code{-gnatwX} -@noindent -If the binder cannot find an acceptable order, it outputs detailed -diagnostics. For example: -@smallexample -@group -@iftex -@leftskip=0cm -@end iftex -error: elaboration circularity detected -info: "proc (body)" must be elaborated before "pack (body)" -info: reason: Elaborate_All probably needed in unit "pack (body)" -info: recompile "pack (body)" with -gnatel -info: for full details -info: "proc (body)" -info: is needed by its spec: -info: "proc (spec)" -info: which is withed by: -info: "pack (body)" -info: "pack (body)" must be elaborated before "proc (body)" -info: reason: pragma Elaborate in unit "proc (body)" -@end group +@emph{Suppress warnings on Export/Import pragmas.} + +This switch suppresses warnings on Export/Import pragmas. +The sense of this is that you are telling the compiler that +you know what you are doing in writing the pragma, and it +should not complain at you. +@end table -@end smallexample +@geindex -gnatwm (gcc) -@noindent -In this case we have a cycle that the binder cannot break. On the one -hand, there is an explicit pragma Elaborate in @code{proc} for -@code{pack}. This means that the body of @code{pack} must be elaborated -before the body of @code{proc}. On the other hand, there is elaboration -code in @code{pack} that calls a subprogram in @code{proc}. This means -that for maximum safety, there should really be a pragma -Elaborate_All in @code{pack} for @code{proc} which would require that -the body of @code{proc} be elaborated before the body of -@code{pack}. Clearly both requirements cannot be satisfied. -Faced with a circularity of this kind, you have three different options. @table @asis -@item Fix the program -The most desirable option from the point of view of long-term maintenance -is to rearrange the program so that the elaboration problems are avoided. -One useful technique is to place the elaboration code into separate -child packages. Another is to move some of the initialization code to -explicitly called subprograms, where the program controls the order -of initialization explicitly. Although this is the most desirable option, -it may be impractical and involve too much modification, especially in -the case of complex legacy code. -@item Perform dynamic checks -If the compilations are done using the -@option{-gnatE} -(dynamic elaboration check) switch, then GNAT behaves in a quite different -manner. Dynamic checks are generated for all calls that could possibly result -in raising an exception. With this switch, the compiler does not generate -implicit @code{Elaborate} or @code{Elaborate_All} pragmas. The behavior then is -exactly as specified in the @cite{Ada Reference Manual}. -The binder will generate -an executable program that may or may not raise @code{Program_Error}, and then -it is the programmer's job to ensure that it does not raise an exception. Note -that it is important to compile all units with the switch, it cannot be used -selectively. +@item @code{-gnatw.x} -@item Suppress checks -The drawback of dynamic checks is that they generate a -significant overhead at run time, both in space and time. If you -are absolutely sure that your program cannot raise any elaboration -exceptions, and you still want to use the dynamic elaboration model, -then you can use the configuration pragma -@code{Suppress (Elaboration_Check)} to suppress all such checks. For -example this pragma could be placed in the @file{gnat.adc} file. +@emph{Activate warnings for No_Exception_Propagation mode.} -@item Suppress checks selectively -When you know that certain calls or instantiations in elaboration code cannot -possibly lead to an elaboration error, and the binder nevertheless complains -about implicit @code{Elaborate} and @code{Elaborate_All} pragmas that lead to -elaboration circularities, it is possible to remove those warnings locally and -obtain a program that will bind. Clearly this can be unsafe, and it is the -responsibility of the programmer to make sure that the resulting program has no -elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can be -used with different granularity to suppress warnings and break elaboration -circularities: +This switch activates warnings for exception usage when pragma Restrictions +(No_Exception_Propagation) is in effect. Warnings are given for implicit or +explicit exception raises which are not covered by a local handler, and for +exception handlers which do not cover a local raise. The default is that these +warnings are not given. -@itemize @bullet -@item -Place the pragma that names the called subprogram in the declarative part -that contains the call. +@item @code{-gnatw.X} -@item -Place the pragma in the declarative part, without naming an entity. This -disables warnings on all calls in the corresponding declarative region. +@emph{Disable warnings for No_Exception_Propagation mode.} -@item -Place the pragma in the package spec that declares the called subprogram, -and name the subprogram. This disables warnings on all elaboration calls to -that subprogram. +This switch disables warnings for exception usage when pragma Restrictions +(No_Exception_Propagation) is in effect. +@end table -@item -Place the pragma in the package spec that declares the called subprogram, -without naming any entity. This disables warnings on all elaboration calls to -all subprograms declared in this spec. +@geindex -gnatwy (gcc) -@item Use Pragma Elaborate -As previously described in section @xref{Treatment of Pragma Elaborate}, -GNAT in static mode assumes that a @code{pragma} Elaborate indicates correctly -that no elaboration checks are required on calls to the designated unit. -There may be cases in which the caller knows that no transitive calls -can occur, so that a @code{pragma Elaborate} will be sufficient in a -case where @code{pragma Elaborate_All} would cause a circularity. -@end itemize +@geindex Ada compatibility issues warnings -@noindent -These five cases are listed in order of decreasing safety, and therefore -require increasing programmer care in their application. Consider the -following program: -@smallexample @c adanocomment -@b{package} Pack1 @b{is} - @b{function} F1 @b{return} Integer; - X1 : Integer; -@b{end} Pack1; +@table @asis -@b{package} Pack2 @b{is} - @b{function} F2 @b{return} Integer; - @b{function} Pure (x : integer) @b{return} integer; - -- pragma Suppress (Elaboration_Check, On => Pure); -- (3) - -- pragma Suppress (Elaboration_Check); -- (4) -@b{end} Pack2; - -@b{with} Pack2; -@b{package} @b{body} Pack1 @b{is} - @b{function} F1 @b{return} Integer @b{is} - @b{begin} - @b{return} 100; - @b{end} F1; - Val : integer := Pack2.Pure (11); -- Elab. call (1) -@b{begin} - @b{declare} - -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1) - -- pragma Suppress(Elaboration_Check); -- (2) - @b{begin} - X1 := Pack2.F2 + 1; -- Elab. call (2) - @b{end}; -@b{end} Pack1; - -@b{with} Pack1; -@b{package} @b{body} Pack2 @b{is} - @b{function} F2 @b{return} Integer @b{is} - @b{begin} - @b{return} Pack1.F1; - @b{end} F2; - @b{function} Pure (x : integer) @b{return} integer @b{is} - @b{begin} - @b{return} x ** 3 - 3 * x; - @b{end}; -@b{end} Pack2; - -@b{with} Pack1, Ada.Text_IO; -@b{procedure} Proc3 @b{is} -@b{begin} - Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101 -@b{end} Proc3; -@end smallexample -In the absence of any pragmas, an attempt to bind this program produces -the following diagnostics: -@smallexample -@group -@iftex -@leftskip=.5cm -@end iftex -error: elaboration circularity detected -info: "pack1 (body)" must be elaborated before "pack1 (body)" -info: reason: Elaborate_All probably needed in unit "pack1 (body)" -info: recompile "pack1 (body)" with -gnatel for full details -info: "pack1 (body)" -info: must be elaborated along with its spec: -info: "pack1 (spec)" -info: which is withed by: -info: "pack2 (body)" -info: which must be elaborated along with its spec: -info: "pack2 (spec)" -info: which is withed by: -info: "pack1 (body)" -@end group -@end smallexample -The sources of the circularity are the two calls to @code{Pack2.Pure} and -@code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to -F2 is safe, even though F2 calls F1, because the call appears after the -elaboration of the body of F1. Therefore the pragma (1) is safe, and will -remove the warning on the call. It is also possible to use pragma (2) -because there are no other potentially unsafe calls in the block. +@item @code{-gnatwy} -@noindent -The call to @code{Pure} is safe because this function does not depend on the -state of @code{Pack2}. Therefore any call to this function is safe, and it -is correct to place pragma (3) in the corresponding package spec. +@emph{Activate warnings for Ada compatibility issues.} -@noindent -Finally, we could place pragma (4) in the spec of @code{Pack2} to disable -warnings on all calls to functions declared therein. Note that this is not -necessarily safe, and requires more detailed examination of the subprogram -bodies involved. In particular, a call to @code{F2} requires that @code{F1} -be already elaborated. +For the most part, newer versions of Ada are upwards compatible +with older versions. For example, Ada 2005 programs will almost +always work when compiled as Ada 2012. +However there are some exceptions (for example the fact that +@cite{some} is now a reserved word in Ada 2012). This +switch activates several warnings to help in identifying +and correcting such incompatibilities. The default is that +these warnings are generated. Note that at one point Ada 2005 +was called Ada 0Y, hence the choice of character. @end table -@noindent -It is hard to generalize on which of these four approaches should be -taken. Obviously if it is possible to fix the program so that the default -treatment works, this is preferable, but this may not always be practical. -It is certainly simple enough to use -@option{-gnatE} -but the danger in this case is that, even if the GNAT binder -finds a correct elaboration order, it may not always do so, -and certainly a binder from another Ada compiler might not. A -combination of testing and analysis (for which the -information messages generated with the -@option{-gnatel} -switch can be useful) must be used to ensure that the program is free -of errors. One switch that is useful in this testing is the -@option{-p (pessimistic elaboration order)} -switch for -@code{gnatbind}. -Normally the binder tries to find an order that has the best chance -of avoiding elaboration problems. However, if this switch is used, the binder -plays a devil's advocate role, and tries to choose the order that -has the best chance of failing. If your program works even with this -switch, then it has a better chance of being error free, but this is still -not a guarantee. +@geindex -gnatwY (gcc) -For an example of this approach in action, consider the C-tests (executable -tests) from the ACVC suite. If these are compiled and run with the default -treatment, then all but one of them succeed without generating any error -diagnostics from the binder. However, there is one test that fails, and -this is not surprising, because the whole point of this test is to ensure -that the compiler can handle cases where it is impossible to determine -a correct order statically, and it checks that an exception is indeed -raised at run time. +@geindex Ada compatibility issues warnings -This one test must be compiled and run using the -@option{-gnatE} -switch, and then it passes. Alternatively, the entire suite can -be run using this switch. It is never wrong to run with the dynamic -elaboration switch if your code is correct, and we assume that the -C-tests are indeed correct (it is less efficient, but efficiency is -not a factor in running the ACVC tests.) -@node Elaboration for Indirect Calls -@section Elaboration for Indirect Calls -@cindex Dispatching calls -@cindex Indirect calls +@table @asis -@noindent -In rare cases, the static elaboration model fails to prevent -dispatching calls to not-yet-elaborated subprograms. In such cases, we -fall back to run-time checks; premature calls to any primitive -operation of a tagged type before the body of the operation has been -elaborated will raise @code{Program_Error}. +@item @code{-gnatwY} -Access-to-subprogram types, however, are handled conservatively, and -do not require run-time checks. This was not true in earlier versions -of the compiler; you can use the @option{-gnatd.U} debug switch to -revert to the old behavior if the new conservative behavior causes -elaboration cycles. Here, ``conservative'' means that if you do -@code{P'Access} during elaboration, the compiler will assume that you -might call @code{P} indirectly during elaboration, so it adds an -implicit @code{pragma Elaborate_All} on the library unit containing -@code{P}. The @option{-gnatd.U} switch is safe if you know there are -no such calls. If the program worked before, it will continue to work -with @option{-gnatd.U}. But beware that code modifications such as -adding an indirect call can cause erroneous behavior in the presence -of @option{-gnatd.U}. +@emph{Disable warnings for Ada compatibility issues.} -@node Summary of Procedures for Elaboration Control -@section Summary of Procedures for Elaboration Control -@cindex Elaboration control +This switch suppresses the warnings intended to help in identifying +incompatibilities between Ada language versions. +@end table -@noindent -First, compile your program with the default options, using none of -the special elaboration control switches. If the binder successfully -binds your program, then you can be confident that, apart from issues -raised by the use of access-to-subprogram types and dynamic dispatching, -the program is free of elaboration errors. If it is important that the -program be portable to other compilers than GNAT, then use the -@option{-gnatel} -switch to generate messages about missing @code{Elaborate} or -@code{Elaborate_All} pragmas, and supply the missing pragmas. +@geindex -gnatw.y (gcc) -If the program fails to bind using the default static elaboration -handling, then you can fix the program to eliminate the binder -message, or recompile the entire program with the -@option{-gnatE} switch to generate dynamic elaboration checks, -and, if you are sure there really are no elaboration problems, -use a global pragma @code{Suppress (Elaboration_Check)}. +@geindex Package spec needing body -@node Other Elaboration Order Considerations -@section Other Elaboration Order Considerations -@noindent -This section has been entirely concerned with the issue of finding a valid -elaboration order, as defined by the Ada Reference Manual. In a case -where several elaboration orders are valid, the task is to find one -of the possible valid elaboration orders (and the static model in GNAT -will ensure that this is achieved). -The purpose of the elaboration rules in the Ada Reference Manual is to -make sure that no entity is accessed before it has been elaborated. For -a subprogram, this means that the spec and body must have been elaborated -before the subprogram is called. For an object, this means that the object -must have been elaborated before its value is read or written. A violation -of either of these two requirements is an access before elaboration order, -and this section has been all about avoiding such errors. +@table @asis -In the case where more than one order of elaboration is possible, in the -sense that access before elaboration errors are avoided, then any one of -the orders is ``correct'' in the sense that it meets the requirements of -the Ada Reference Manual, and no such error occurs. +@item @code{-gnatw.y} -However, it may be the case for a given program, that there are -constraints on the order of elaboration that come not from consideration -of avoiding elaboration errors, but rather from extra-lingual logic -requirements. Consider this example: +@emph{Activate information messages for why package spec needs body} -@smallexample @c ada -@b{with} Init_Constants; -@b{package} Constants @b{is} - X : Integer := 0; - Y : Integer := 0; -@b{end} Constants; +There are a number of cases in which a package spec needs a body. +For example, the use of pragma Elaborate_Body, or the declaration +of a procedure specification requiring a completion. This switch +causes information messages to be output showing why a package +specification requires a body. This can be useful in the case of +a large package specification which is unexpectedly requiring a +body. The default is that such information messages are not output. +@end table -@b{package} Init_Constants @b{is} - @b{procedure} P; --@i{ require a body} -@b{end} Init_Constants; +@geindex -gnatw.Y (gcc) -@b{with} Constants; -@b{package} @b{body} Init_Constants @b{is} - @b{procedure} P @b{is} @b{begin} @b{null}; @b{end}; -@b{begin} - Constants.X := 3; - Constants.Y := 4; -@b{end} Init_Constants; +@geindex No information messages for why package spec needs body -@b{with} Constants; -@b{package} Calc @b{is} - Z : Integer := Constants.X + Constants.Y; -@b{end} Calc; -@b{with} Calc; -@b{with} Text_IO; @b{use} Text_IO; -@b{procedure} Main @b{is} -@b{begin} - Put_Line (Calc.Z'Img); -@b{end} Main; -@end smallexample +@table @asis -@noindent -In this example, there is more than one valid order of elaboration. For -example both the following are correct orders: +@item @code{-gnatw.Y} -@smallexample -Init_Constants spec -Constants spec -Calc spec -Init_Constants body -Main body +@emph{Disable information messages for why package spec needs body} - and +This switch suppresses the output of information messages showing why +a package specification needs a body. +@end table -Init_Constants spec -Init_Constants body -Constants spec -Calc spec -Main body -@end smallexample +@geindex -gnatwz (gcc) -@noindent -There is no language rule to prefer one or the other, both are correct -from an order of elaboration point of view. But the programmatic effects -of the two orders are very different. In the first, the elaboration routine -of @code{Calc} initializes @code{Z} to zero, and then the main program -runs with this value of zero. But in the second order, the elaboration -routine of @code{Calc} runs after the body of Init_Constants has set -@code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main} -runs. +@geindex Unchecked_Conversion warnings -One could perhaps by applying pretty clever non-artificial intelligence -to the situation guess that it is more likely that the second order of -elaboration is the one desired, but there is no formal linguistic reason -to prefer one over the other. In fact in this particular case, GNAT will -prefer the second order, because of the rule that bodies are elaborated -as soon as possible, but it's just luck that this is what was wanted -(if indeed the second order was preferred). -If the program cares about the order of elaboration routines in a case like -this, it is important to specify the order required. In this particular -case, that could have been achieved by adding to the spec of Calc: +@table @asis -@smallexample @c ada -@b{pragma} Elaborate_All (Constants); -@end smallexample +@item @code{-gnatwz} -@noindent -which requires that the body (if any) and spec of @code{Constants}, -as well as the body and spec of any unit @code{with}'ed by -@code{Constants} be elaborated before @code{Calc} is elaborated. +@emph{Activate warnings on unchecked conversions.} -Clearly no automatic method can always guess which alternative you require, -and if you are working with legacy code that had constraints of this kind -which were not properly specified by adding @code{Elaborate} or -@code{Elaborate_All} pragmas, then indeed it is possible that two different -compilers can choose different orders. +This switch activates warnings for unchecked conversions +where the types are known at compile time to have different +sizes. The default is that such warnings are generated. Warnings are also +generated for subprogram pointers with different conventions. +@end table -However, GNAT does attempt to diagnose the common situation where there -are uninitialized variables in the visible part of a package spec, and the -corresponding package body has an elaboration block that directly or -indirectly initialized one or more of these variables. This is the situation -in which a pragma Elaborate_Body is usually desirable, and GNAT will generate -a warning that suggests this addition if it detects this situation. +@geindex -gnatwZ (gcc) -The @code{gnatbind} -@option{-p} switch may be useful in smoking -out problems. This switch causes bodies to be elaborated as late as possible -instead of as early as possible. In the example above, it would have forced -the choice of the first elaboration order. If you get different results -when using this switch, and particularly if one set of results is right, -and one is wrong as far as you are concerned, it shows that you have some -missing @code{Elaborate} pragmas. For the example above, we have the -following output: -@smallexample -gnatmake -f -q main -main - 7 -gnatmake -f -q main -bargs -p -main - 0 -@end smallexample +@table @asis -@noindent -It is of course quite unlikely that both these results are correct, so -it is up to you in a case like this to investigate the source of the -difference, by looking at the two elaboration orders that are chosen, -and figuring out which is correct, and then adding the necessary -@code{Elaborate} or @code{Elaborate_All} pragmas to ensure the desired order. +@item @code{-gnatwZ} -@node Determining the Chosen Elaboration Order -@section Determining the Chosen Elaboration Order -@noindent +@emph{Suppress warnings on unchecked conversions.} -To see the elaboration order that the binder chooses, you can look at -the last part of the b~xxx.adb binder output file. Here is an example: +This switch suppresses warnings for unchecked conversions +where the types are known at compile time to have different +sizes or conventions. +@end table -@smallexample @c ada -System.Soft_Links'Elab_Body; -E14 := True; -System.Secondary_Stack'Elab_Body; -E18 := True; -System.Exception_Table'Elab_Body; -E24 := True; -Ada.Io_Exceptions'Elab_Spec; -E67 := True; -Ada.Tags'Elab_Spec; -Ada.Streams'Elab_Spec; -E43 := True; -Interfaces.C'Elab_Spec; -E69 := True; -System.Finalization_Root'Elab_Spec; -E60 := True; -System.Os_Lib'Elab_Body; -E71 := True; -System.Finalization_Implementation'Elab_Spec; -System.Finalization_Implementation'Elab_Body; -E62 := True; -Ada.Finalization'Elab_Spec; -E58 := True; -Ada.Finalization.List_Controller'Elab_Spec; -E76 := True; -System.File_Control_Block'Elab_Spec; -E74 := True; -System.File_Io'Elab_Body; -E56 := True; -Ada.Tags'Elab_Body; -E45 := True; -Ada.Text_Io'Elab_Spec; -Ada.Text_Io'Elab_Body; -E07 := True; -@end smallexample +@geindex -gnatw.z (gcc) -@noindent -Here Elab_Spec elaborates the spec -and Elab_Body elaborates the body. The assignments to the Exx flags -flag that the corresponding body is now elaborated. +@geindex Size/Alignment warnings -You can also ask the binder to generate a more -readable list of the elaboration order using the -@code{-l} switch when invoking the binder. Here is -an example of the output generated by this switch: -@smallexample -ada (spec) -interfaces (spec) -system (spec) -system.case_util (spec) -system.case_util (body) -system.concat_2 (spec) -system.concat_2 (body) -system.concat_3 (spec) -system.concat_3 (body) -system.htable (spec) -system.parameters (spec) -system.parameters (body) -system.crtl (spec) -interfaces.c_streams (spec) -interfaces.c_streams (body) -system.restrictions (spec) -system.restrictions (body) -system.standard_library (spec) -system.exceptions (spec) -system.exceptions (body) -system.storage_elements (spec) -system.storage_elements (body) -system.secondary_stack (spec) -system.stack_checking (spec) -system.stack_checking (body) -system.string_hash (spec) -system.string_hash (body) -system.htable (body) -system.strings (spec) -system.strings (body) -system.traceback (spec) -system.traceback (body) -system.traceback_entries (spec) -system.traceback_entries (body) -ada.exceptions (spec) -ada.exceptions.last_chance_handler (spec) -system.soft_links (spec) -system.soft_links (body) -ada.exceptions.last_chance_handler (body) -system.secondary_stack (body) -system.exception_table (spec) -system.exception_table (body) -ada.io_exceptions (spec) -ada.tags (spec) -ada.streams (spec) -interfaces.c (spec) -interfaces.c (body) -system.finalization_root (spec) -system.finalization_root (body) -system.memory (spec) -system.memory (body) -system.standard_library (body) -system.os_lib (spec) -system.os_lib (body) -system.unsigned_types (spec) -system.stream_attributes (spec) -system.stream_attributes (body) -system.finalization_implementation (spec) -system.finalization_implementation (body) -ada.finalization (spec) -ada.finalization (body) -ada.finalization.list_controller (spec) -ada.finalization.list_controller (body) -system.file_control_block (spec) -system.file_io (spec) -system.file_io (body) -system.val_uns (spec) -system.val_util (spec) -system.val_util (body) -system.val_uns (body) -system.wch_con (spec) -system.wch_con (body) -system.wch_cnv (spec) -system.wch_jis (spec) -system.wch_jis (body) -system.wch_cnv (body) -system.wch_stw (spec) -system.wch_stw (body) -ada.tags (body) -ada.exceptions (body) -ada.text_io (spec) -ada.text_io (body) -text_io (spec) -gdbstr (body) -@end smallexample +@table @asis -@c ********************************** -@node Overflow Check Handling in GNAT -@appendix Overflow Check Handling in GNAT -@cindex Overflow checks -@cindex Checks (overflow) -@c ********************************** +@item @code{-gnatw.z} -@menu -* Background:: -* Overflow Checking Modes in GNAT:: -* Specifying the Desired Mode:: -* Default Settings:: -* Implementation Notes:: -@end menu +@emph{Activate warnings for size not a multiple of alignment.} +This switch activates warnings for cases of record types with +specified @cite{Size} and @cite{Alignment} attributes where the +size is not a multiple of the alignment, resulting in an object +size that is greater than the specified size. The default +is that such warnings are generated. +@end table -@node Background -@section Background +@geindex -gnatw.Z (gcc) -@noindent -Overflow checks are checks that the compiler may make to ensure -that intermediate results are not out of range. For example: +@geindex Size/Alignment warnings -@smallexample @c ada - A : Integer; - ... - A := A + 1; -@end smallexample -@noindent -if @code{A} has the value @code{Integer'Last}, then the addition may cause -overflow since the result is out of range of the type @code{Integer}. -In this case @code{Constraint_Error} will be raised if checks are -enabled. +@table @asis -A trickier situation arises in examples like the following: +@item @code{-gnatw.Z} -@smallexample @c ada - A, C : Integer; - ... - A := (A + 1) + C; -@end smallexample +@emph{Suppress warnings for size not a multiple of alignment.} -@noindent -where @code{A} is @code{Integer'Last} and @code{C} is @code{-1}. -Now the final result of the expression on the right hand side is -@code{Integer'Last} which is in range, but the question arises whether the -intermediate addition of @code{(A + 1)} raises an overflow error. +This switch suppresses warnings for cases of record types with +specified @cite{Size} and @cite{Alignment} attributes where the +size is not a multiple of the alignment, resulting in an object +size that is greater than the specified size. +The warning can also be +suppressed by giving an explicit @cite{Object_Size} value. +@end table -The (perhaps surprising) answer is that the Ada language -definition does not answer this question. Instead it leaves -it up to the implementation to do one of two things if overflow -checks are enabled. +@geindex -Wunused (gcc) -@itemize @bullet -@item -raise an exception (@code{Constraint_Error}), or -@item -yield the correct mathematical result which is then used in -subsequent operations. -@end itemize +@table @asis -@noindent -If the compiler chooses the first approach, then the assignment of this -example will indeed raise @code{Constraint_Error} if overflow checking is -enabled, or result in erroneous execution if overflow checks are suppressed. +@item @code{-Wunused} -But if the compiler -chooses the second approach, then it can perform both additions yielding -the correct mathematical result, which is in range, so no exception -will be raised, and the right result is obtained, regardless of whether -overflow checks are suppressed. +The warnings controlled by the @emph{-gnatw} switch are generated by +the front end of the compiler. The @emph{GCC} back end can provide +additional warnings and they are controlled by the @emph{-W} switch. +For example, @emph{-Wunused} activates back end +warnings for entities that are declared but not referenced. +@end table -Note that in the first example an -exception will be raised in either case, since if the compiler -gives the correct mathematical result for the addition, it will -be out of range of the target type of the assignment, and thus -fails the range check. +@geindex -Wuninitialized (gcc) -This lack of specified behavior in the handling of overflow for -intermediate results is a source of non-portability, and can thus -be problematic when programs are ported. Most typically this arises -in a situation where the original compiler did not raise an exception, -and then the application is moved to a compiler where the check is -performed on the intermediate result and an unexpected exception is -raised. -Furthermore, when using Ada 2012's preconditions and other -assertion forms, another issue arises. Consider: +@table @asis -@smallexample @c ada - @b{procedure} P (A, B : Integer) @b{with} - Pre => A + B <= Integer'Last; -@end smallexample +@item @code{-Wuninitialized} -@noindent -One often wants to regard arithmetic in a context like this from -a mathematical point of view. So for example, if the two actual parameters -for a call to @code{P} are both @code{Integer'Last}, then -the precondition should be regarded as False. If we are executing -in a mode with run-time checks enabled for preconditions, then we would -like this precondition to fail, rather than raising an exception -because of the intermediate overflow. +Similarly, @emph{-Wuninitialized} activates +the back end warning for uninitialized variables. This switch must be +used in conjunction with an optimization level greater than zero. +@end table -However, the language definition leaves the specification of -whether the above condition fails (raising @code{Assert_Error}) or -causes an intermediate overflow (raising @code{Constraint_Error}) -up to the implementation. +@geindex -Wstack-usage (gcc) -The situation is worse in a case such as the following: -@smallexample @c ada - @b{procedure} Q (A, B, C : Integer) @b{with} - Pre => A + B + C <= Integer'Last; -@end smallexample +@table @asis -@noindent -Consider the call +@item @code{-Wstack-usage=@emph{len}} -@smallexample @c ada - Q (A => Integer'Last, B => 1, C => -1); -@end smallexample +Warn if the stack usage of a subprogram might be larger than @cite{len} bytes. +See @ref{fa,,Static Stack Usage Analysis} for details. +@end table -@noindent -From a mathematical point of view the precondition -is True, but at run time we may (but are not guaranteed to) get an -exception raised because of the intermediate overflow (and we really -would prefer this precondition to be considered True at run time). +@geindex -Wall (gcc) -@node Overflow Checking Modes in GNAT -@section Overflow Checking Modes in GNAT -@noindent -To deal with the portability issue, and with the problem of -mathematical versus run-time interpretation of the expressions in -assertions, GNAT provides comprehensive control over the handling -of intermediate overflow. GNAT can operate in three modes, and -furthemore, permits separate selection of operating modes for -the expressions within assertions (here the term ``assertions'' -is used in the technical sense, which includes preconditions and so forth) -and for expressions appearing outside assertions. +@table @asis -The three modes are: +@item @code{-Wall} -@itemize @bullet -@item @i{Use base type for intermediate operations} (@code{STRICT}) - - In this mode, all intermediate results for predefined arithmetic - operators are computed using the base type, and the result must - be in range of the base type. If this is not the - case then either an exception is raised (if overflow checks are - enabled) or the execution is erroneous (if overflow checks are suppressed). - This is the normal default mode. - -@item @i{Most intermediate overflows avoided} (@code{MINIMIZED}) - - In this mode, the compiler attempts to avoid intermediate overflows by - using a larger integer type, typically @code{Long_Long_Integer}, - as the type in which arithmetic is - performed for predefined arithmetic operators. This may be slightly more - expensive at - run time (compared to suppressing intermediate overflow checks), though - the cost is negligible on modern 64-bit machines. For the examples given - earlier, no intermediate overflows would have resulted in exceptions, - since the intermediate results are all in the range of - @code{Long_Long_Integer} (typically 64-bits on nearly all implementations - of GNAT). In addition, if checks are enabled, this reduces the number of - checks that must be made, so this choice may actually result in an - improvement in space and time behavior. - - However, there are cases where @code{Long_Long_Integer} is not large - enough, consider the following example: - -@smallexample @c ada - @b{procedure} R (A, B, C, D : Integer) @b{with} - Pre => (A**2 * B**2) / (C**2 * D**2) <= 10; -@end smallexample - - where @code{A} = @code{B} = @code{C} = @code{D} = @code{Integer'Last}. - Now the intermediate results are - out of the range of @code{Long_Long_Integer} even though the final result - is in range and the precondition is True (from a mathematical point - of view). In such a case, operating in this mode, an overflow occurs - for the intermediate computation (which is why this mode - says @i{most} intermediate overflows are avoided). In this case, - an exception is raised if overflow checks are enabled, and the - execution is erroneous if overflow checks are suppressed. - -@item @i{All intermediate overflows avoided} (@code{ELIMINATED}) - - In this mode, the compiler avoids all intermediate overflows - by using arbitrary precision arithmetic as required. In this - mode, the above example with @code{A**2 * B**2} would - not cause intermediate overflow, because the intermediate result - would be evaluated using sufficient precision, and the result - of evaluating the precondition would be True. - - This mode has the advantage of avoiding any intermediate - overflows, but at the expense of significant run-time overhead, - including the use of a library (included automatically in this - mode) for multiple-precision arithmetic. - - This mode provides cleaner semantics for assertions, since now - the run-time behavior emulates true arithmetic behavior for the - predefined arithmetic operators, meaning that there is never a - conflict between the mathematical view of the assertion, and its - run-time behavior. - - Note that in this mode, the behavior is unaffected by whether or - not overflow checks are suppressed, since overflow does not occur. - It is possible for gigantic intermediate expressions to raise - @code{Storage_Error} as a result of attempting to compute the - results of such expressions (e.g. @code{Integer'Last ** Integer'Last}) - but overflow is impossible. +This switch enables most warnings from the @emph{GCC} back end. +The code generator detects a number of warning situations that are missed +by the @emph{GNAT} front end, and this switch can be used to activate them. +The use of this switch also sets the default front end warning mode to +@emph{-gnatwa}, that is, most front end warnings activated as well. +@end table +@geindex -w (gcc) -@end itemize -@noindent - Note that these modes apply only to the evaluation of predefined - arithmetic, membership, and comparison operators for signed integer - aritmetic. +@table @asis - For fixed-point arithmetic, checks can be suppressed. But if checks - are enabled - then fixed-point values are always checked for overflow against the - base type for intermediate expressions (that is such checks always - operate in the equivalent of @code{STRICT} mode). +@item @code{-w} - For floating-point, on nearly all architectures, @code{Machine_Overflows} - is False, and IEEE infinities are generated, so overflow exceptions - are never raised. If you want to avoid infinities, and check that - final results of expressions are in range, then you can declare a - constrained floating-point type, and range checks will be carried - out in the normal manner (with infinite values always failing all - range checks). +Conversely, this switch suppresses warnings from the @emph{GCC} back end. +The use of this switch also sets the default front end warning mode to +@emph{-gnatws}, that is, front end warnings suppressed as well. +@end table +@geindex -Werror (gcc) -@c ------------------------- -@node Specifying the Desired Mode -@section Specifying the Desired Mode -@noindent -The desired mode of for handling intermediate overflow can be specified using -either the @code{Overflow_Mode} pragma or an equivalent compiler switch. -The pragma has the form -@cindex pragma @code{Overflow_Mode} +@table @asis -@smallexample @c ada - @b{pragma} Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]); -@end smallexample +@item @code{-Werror} -@noindent -where @code{MODE} is one of +This switch causes warnings from the @emph{GCC} back end to be treated as +errors. The warning string still appears, but the warning messages are +counted as errors, and prevent the generation of an object file. +@end table -@itemize @bullet -@item @code{STRICT}: intermediate overflows checked (using base type) -@item @code{MINIMIZED}: minimize intermediate overflows -@item @code{ELIMINATED}: eliminate intermediate overflows -@end itemize +A string of warning parameters can be used in the same parameter. For example: -@noindent -The case is ignored, so @code{MINIMIZED}, @code{Minimized} and -@code{minimized} all have the same effect. +@example +-gnatwaGe +@end example -If only the @code{General} parameter is present, then the given @code{MODE} -applies -to expressions both within and outside assertions. If both arguments -are present, then @code{General} applies to expressions outside assertions, -and @code{Assertions} applies to expressions within assertions. For example: +will turn on all optional warnings except for unrecognized pragma warnings, +and also specify that warnings should be treated as errors. -@smallexample @c ada - @b{pragma} Overflow_Mode - (General => Minimized, Assertions => Eliminated); -@end smallexample +When no switch @emph{-gnatw} is used, this is equivalent to: -@noindent -specifies that general expressions outside assertions be evaluated -in ``minimize intermediate overflows'' mode, and expressions within -assertions be evaluated in ``eliminate intermediate overflows'' mode. -This is often a reasonable choice, avoiding excessive overhead -outside assertions, but assuring a high degree of portability -when importing code from another compiler, while incurring -the extra overhead for assertion expressions to ensure that -the behavior at run time matches the expected mathematical -behavior. +@quotation -The @code{Overflow_Mode} pragma has the same scoping and placement -rules as pragma @code{Suppress}, so it can occur either as a -configuration pragma, specifying a default for the whole -program, or in a declarative scope, where it applies to the -remaining declarations and statements in that scope. -Note that pragma @code{Overflow_Mode} does not affect whether -overflow checks are enabled or suppressed. It only controls the -method used to compute intermediate values. To control whether -overflow checking is enabled or suppressed, use pragma @code{Suppress} -or @code{Unsuppress} in the usual manner +@itemize * -Additionally, a compiler switch @option{-gnato?} or @option{-gnato??} -can be used to control the checking mode default (which can be subsequently -overridden using pragmas). -@cindex @option{-gnato?} (gcc) -@cindex @option{-gnato??} (gcc) - -Here `@code{?}' is one of the digits `@code{1}' through `@code{3}': - -@itemize @bullet -@item @code{1}: -use base type for intermediate operations (@code{STRICT}) -@item @code{2}: -minimize intermediate overflows (@code{MINIMIZED}) -@item @code{3}: -eliminate intermediate overflows (@code{ELIMINATED}) -@end itemize +@item +@code{-gnatw.a} -@noindent -As with the pragma, if only one digit appears then it applies to all -cases; if two digits are given, then the first applies outside -assertions, and the second within assertions. Thus the equivalent -of the example pragma above would be -@option{-gnato23}. +@item +@code{-gnatwB} -If no digits follow the @option{-gnato}, then it is equivalent to -@option{-gnato11}, -causing all intermediate operations to be computed using the base -type (@code{STRICT} mode). +@item +@code{-gnatw.b} -In addition to setting the mode used for computation of intermediate -results, the @code{-gnato} switch also enables overflow checking (which -is suppressed by default). It thus combines the effect of using -a pragma @code{Overflow_Mode} and pragma @code{Unsuppress}. +@item +@code{-gnatwC} +@item +@code{-gnatw.C} -@c ------------------------- -@node Default Settings -@section Default Settings +@item +@code{-gnatwD} -The default mode for overflow checks is +@item +@code{-gnatwF} -@smallexample - General => Strict -@end smallexample +@item +@code{-gnatwg} -@noindent -which causes all computations both inside and outside assertions to use -the base type. In addition overflow checks are suppressed. +@item +@code{-gnatwH} -This retains compatibility with previous versions of -GNAT which suppressed overflow checks by default and always -used the base type for computation of intermediate results. +@item +@code{-gnatwi} -The switch @option{-gnato} (with no digits following) is equivalent to -@cindex @option{-gnato} (gcc) +@item +@code{-gnatw.I} -@smallexample - General => Strict -@end smallexample +@item +@code{-gnatwJ} -@noindent -which causes overflow checking of all intermediate overflows -both inside and outside assertions against the base type. -This provides compatibility -with this switch as implemented in previous versions of GNAT. +@item +@code{-gnatwK} -The pragma @code{Suppress (Overflow_Check)} disables overflow -checking, but it has no effect on the method used for computing -intermediate results. +@item +@code{-gnatwL} -The pragma @code{Unsuppress (Overflow_Check)} enables overflow -checking, but it has no effect on the method used for computing -intermediate results. +@item +@code{-gnatw.L} -@c ------------------------- -@node Implementation Notes -@section Implementation Notes +@item +@code{-gnatwM} -In practice on typical 64-bit machines, the @code{MINIMIZED} mode is -reasonably efficient, and can be generally used. It also helps -to ensure compatibility with code imported from some other -compiler to GNAT. +@item +@code{-gnatw.m} -Setting all intermediate overflows checking (@code{CHECKED} mode) -makes sense if you want to -make sure that your code is compatible with any other possible -Ada implementation. This may be useful in ensuring portability -for code that is to be exported to some other compiler than GNAT. +@item +@code{-gnatwn} +@item +@code{-gnatwo} -The Ada standard allows the reassociation of expressions at -the same precedence level if no parentheses are present. For -example, @w{@code{A+B+C}} parses as though it were @w{@code{(A+B)+C}}, but -the compiler can reintepret this as @w{@code{A+(B+C)}}, possibly -introducing or eliminating an overflow exception. The GNAT -compiler never takes advantage of this freedom, and the -expression @w{@code{A+B+C}} will be evaluated as @w{@code{(A+B)+C}}. -If you need the other order, you can write the parentheses -explicitly @w{@code{A+(B+C)}} and GNAT will respect this order. +@item +@code{-gnatw.O} -The use of @code{ELIMINATED} mode will cause the compiler to -automatically include an appropriate arbitrary precision -integer arithmetic package. The compiler will make calls -to this package, though only in cases where it cannot be -sure that @code{Long_Long_Integer} is sufficient to guard against -intermediate overflows. This package does not use dynamic -alllocation, but it does use the secondary stack, so an -appropriate secondary stack package must be present (this -is always true for standard full Ada, but may require -specific steps for restricted run times such as ZFP). +@item +@code{-gnatwP} -Although @code{ELIMINATED} mode causes expressions to use arbitrary -precision arithmetic, avoiding overflow, the final result -must be in an appropriate range. This is true even if the -final result is of type @code{[Long_[Long_]]Integer'Base}, which -still has the same bounds as its associated constrained -type at run-time. +@item +@code{-gnatw.P} -Currently, the @code{ELIMINATED} mode is only available on target -platforms for which @code{Long_Long_Integer} is 64-bits (nearly all GNAT -platforms). +@item +@code{-gnatwq} -@c ******************************* -@node Conditional Compilation -@appendix Conditional Compilation -@c ******************************* -@cindex Conditional compilation +@item +@code{-gnatwR} -@noindent -It is often necessary to arrange for a single source program -to serve multiple purposes, where it is compiled in different -ways to achieve these different goals. Some examples of the -need for this feature are +@item +@code{-gnatw.R} -@itemize @bullet -@item Adapting a program to a different hardware environment -@item Adapting a program to a different target architecture -@item Turning debugging features on and off -@item Arranging for a program to compile with different compilers -@end itemize +@item +@code{-gnatw.S} -@noindent -In C, or C++, the typical approach would be to use the preprocessor -that is defined as part of the language. The Ada language does not -contain such a feature. This is not an oversight, but rather a very -deliberate design decision, based on the experience that overuse of -the preprocessing features in C and C++ can result in programs that -are extremely difficult to maintain. For example, if we have ten -switches that can be on or off, this means that there are a thousand -separate programs, any one of which might not even be syntactically -correct, and even if syntactically correct, the resulting program -might not work correctly. Testing all combinations can quickly become -impossible. - -Nevertheless, the need to tailor programs certainly exists, and in -this Appendix we will discuss how this can -be achieved using Ada in general, and GNAT in particular. +@item +@code{-gnatwT} -@menu -* Use of Boolean Constants:: -* Debugging - A Special Case:: -* Conditionalizing Declarations:: -* Use of Alternative Implementations:: -* Preprocessing:: -@end menu +@item +@code{-gnatw.T} -@node Use of Boolean Constants -@section Use of Boolean Constants +@item +@code{-gnatwU} -@noindent -In the case where the difference is simply which code -sequence is executed, the cleanest solution is to use Boolean -constants to control which code is executed. +@item +@code{-gnatwv} -@smallexample @c ada -@group -FP_Initialize_Required : @b{constant} Boolean := True; -@dots{} -@b{if} FP_Initialize_Required @b{then} -@dots{} -@b{end} @b{if}; -@end group -@end smallexample - -@noindent -Not only will the code inside the @code{if} statement not be executed if -the constant Boolean is @code{False}, but it will also be completely -deleted from the program. -However, the code is only deleted after the @code{if} statement -has been checked for syntactic and semantic correctness. -(In contrast, with preprocessors the code is deleted before the -compiler ever gets to see it, so it is not checked until the switch -is turned on.) -@cindex Preprocessors (contrasted with conditional compilation) +@item +@code{-gnatww} -Typically the Boolean constants will be in a separate package, -something like: +@item +@code{-gnatw.W} -@smallexample @c ada -@group -@b{package} Config @b{is} - FP_Initialize_Required : @b{constant} Boolean := True; - Reset_Available : @b{constant} Boolean := False; - @dots{} -@b{end} Config; -@end group -@end smallexample +@item +@code{-gnatwx} -@noindent -The @code{Config} package exists in multiple forms for the various targets, -with an appropriate script selecting the version of @code{Config} needed. -Then any other unit requiring conditional compilation can do a @code{with} -of @code{Config} to make the constants visible. +@item +@code{-gnatw.X} +@item +@code{-gnatwy} -@node Debugging - A Special Case -@section Debugging - A Special Case +@item +@code{-gnatwz} +@end itemize +@end quotation -@noindent -A common use of conditional code is to execute statements (for example -dynamic checks, or output of intermediate results) under control of a -debug switch, so that the debugging behavior can be turned on and off. -This can be done using a Boolean constant to control whether the code -is active: +@node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control}@anchor{105}@anchor{gnat_ugn/building_executable_programs_with_gnat id16}@anchor{106} +@subsection Debugging and Assertion Control -@smallexample @c ada -@group -@b{if} Debugging @b{then} - Put_Line ("got to the first stage!"); -@b{end} @b{if}; -@end group -@end smallexample -@noindent -or +@geindex -gnata (gcc) -@smallexample @c ada -@group -@b{if} Debugging @b{and} @b{then} Temperature > 999.0 @b{then} - @b{raise} Temperature_Crazy; -@b{end} @b{if}; -@end group -@end smallexample -@noindent -Since this is a common case, there are special features to deal with -this in a convenient manner. For the case of tests, Ada 2005 has added -a pragma @code{Assert} that can be used for such tests. This pragma is modeled -@cindex pragma @code{Assert} -on the @code{Assert} pragma that has always been available in GNAT, so this -feature may be used with GNAT even if you are not using Ada 2005 features. -The use of pragma @code{Assert} is described in -@ref{Pragma Assert,,, gnat_rm, GNAT Reference Manual}, but as an -example, the last test could be written: +@table @asis -@smallexample @c ada -@b{pragma} Assert (Temperature <= 999.0, "Temperature Crazy"); -@end smallexample +@item @code{-gnata} -@noindent -or simply +@geindex Assert -@smallexample @c ada -@b{pragma} Assert (Temperature <= 999.0); -@end smallexample +@geindex Debug -@noindent -In both cases, if assertions are active and the temperature is excessive, -the exception @code{Assert_Failure} will be raised, with the given string in -the first case or a string indicating the location of the pragma in the second -case used as the exception message. +@geindex Assertions -You can turn assertions on and off by using the @code{Assertion_Policy} -pragma. -@cindex pragma @code{Assertion_Policy} -This is an Ada 2005 pragma which is implemented in all modes by -GNAT, but only in the latest versions of GNAT which include Ada 2005 -capability. Alternatively, you can use the @option{-gnata} switch -@cindex @option{-gnata} switch -to enable assertions from the command line (this is recognized by all versions -of GNAT). +The pragmas @cite{Assert} and @cite{Debug} normally have no effect and +are ignored. This switch, where @code{a} stands for assert, causes +@cite{Assert} and @cite{Debug} pragmas to be activated. -For the example above with the @code{Put_Line}, the GNAT-specific pragma -@code{Debug} can be used: -@cindex pragma @code{Debug} +The pragmas have the form: -@smallexample @c ada -@b{pragma} Debug (Put_Line ("got to the first stage!")); -@end smallexample +@example +pragma Assert ( [, ]) +pragma Debug () +@end example -@noindent -If debug pragmas are enabled, the argument, which must be of the form of -a procedure call, is executed (in this case, @code{Put_Line} will be called). -Only one call can be present, but of course a special debugging procedure -containing any code you like can be included in the program and then -called in a pragma @code{Debug} argument as needed. +The @cite{Assert} pragma causes @cite{Boolean-expression} to be tested. +If the result is @cite{True}, the pragma has no effect (other than +possible side effects from evaluating the expression). If the result is +@cite{False}, the exception @cite{Assert_Failure} declared in the package +@cite{System.Assertions} is +raised (passing @cite{static-string-expression}, if present, as the +message associated with the exception). If no string expression is +given the default is a string giving the file name and line number +of the pragma. -One advantage of pragma @code{Debug} over the @code{if Debugging then} -construct is that pragma @code{Debug} can appear in declarative contexts, -such as at the very beginning of a procedure, before local declarations have -been elaborated. +The @cite{Debug} pragma causes @cite{procedure} to be called. Note that +@cite{pragma Debug} may appear within a declaration sequence, allowing +debugging procedures to be called between declarations. +@end table -Debug pragmas are enabled using either the @option{-gnata} switch that also -controls assertions, or with a separate Debug_Policy pragma. -@cindex pragma @code{Debug_Policy} -The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used -in Ada 95 and Ada 83 programs as well), and is analogous to -pragma @code{Assertion_Policy} to control assertions. +@node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{fb}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{107} +@subsection Validity Checking -@code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas, -and thus they can appear in @file{gnat.adc} if you are not using a -project file, or in the file designated to contain configuration pragmas -in a project file. -They then apply to all subsequent compilations. In practice the use of -the @option{-gnata} switch is often the most convenient method of controlling -the status of these pragmas. -Note that a pragma is not a statement, so in contexts where a statement -sequence is required, you can't just write a pragma on its own. You have -to add a @code{null} statement. +@geindex Validity Checking -@smallexample @c ada -@group -@b{if} @dots{} @b{then} - @dots{} -- some statements -@b{else} - @b{pragma} Assert (Num_Cases < 10); - @b{null}; -@b{end} @b{if}; -@end group -@end smallexample +The Ada Reference Manual defines the concept of invalid values (see +RM 13.9.1). The primary source of invalid values is uninitialized +variables. A scalar variable that is left uninitialized may contain +an invalid value; the concept of invalid does not apply to access or +composite types. +It is an error to read an invalid value, but the RM does not require +run-time checks to detect such errors, except for some minimal +checking to prevent erroneous execution (i.e. unpredictable +behavior). This corresponds to the @emph{-gnatVd} switch below, +which is the default. For example, by default, if the expression of a +case statement is invalid, it will raise Constraint_Error rather than +causing a wild jump, and if an array index on the left-hand side of an +assignment is invalid, it will raise Constraint_Error rather than +overwriting an arbitrary memory location. -@node Conditionalizing Declarations -@section Conditionalizing Declarations +The @emph{-gnatVa} may be used to enable additional validity checks, +which are not required by the RM. These checks are often very +expensive (which is why the RM does not require them). These checks +are useful in tracking down uninitialized variables, but they are +not usually recommended for production builds, and in particular +we do not recommend using these extra validity checking options in +combination with optimization, since this can confuse the optimizer. +If performance is a consideration, leading to the need to optimize, +then the validity checking options should not be used. -@noindent -In some cases, it may be necessary to conditionalize declarations to meet -different requirements. For example we might want a bit string whose length -is set to meet some hardware message requirement. +The other @emph{-gnatV}@code{x} switches below allow finer-grained +control; you can enable whichever validity checks you desire. However, +for most debugging purposes, @emph{-gnatVa} is sufficient, and the +default @emph{-gnatVd} (i.e. standard Ada behavior) is usually +sufficient for non-debugging use. -In some cases, it may be possible to do this using declare blocks controlled -by conditional constants: +The @emph{-gnatB} switch tells the compiler to assume that all +values are valid (that is, within their declared subtype range) +except in the context of a use of the Valid attribute. This means +the compiler can generate more efficient code, since the range +of values is better known at compile time. However, an uninitialized +variable can cause wild jumps and memory corruption in this mode. -@smallexample @c ada -@group -@b{if} Small_Machine @b{then} - @b{declare} - X : Bit_String (1 .. 10); - @b{begin} - @dots{} - @b{end}; -@b{else} - @b{declare} - X : Large_Bit_String (1 .. 1000); - @b{begin} - @dots{} - @b{end}; -@b{end} @b{if}; -@end group -@end smallexample - -@noindent -Note that in this approach, both declarations are analyzed by the -compiler so this can only be used where both declarations are legal, -even though one of them will not be used. +The @emph{-gnatV}@code{x} switch allows control over the validity +checking mode as described below. +The @code{x} argument is a string of letters that +indicate validity checks that are performed or not performed in addition +to the default checks required by Ada as described above. -Another approach is to define integer constants, e.g.@: @code{Bits_Per_Word}, -or Boolean constants, e.g.@: @code{Little_Endian}, and then write declarations -that are parameterized by these constants. For example +@geindex -gnatVa (gcc) -@smallexample @c ada -@group -@b{for} Rec @b{use} - Field1 @b{at} 0 @b{range} Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word; -@b{end} @b{record}; -@end group -@end smallexample - -@noindent -If @code{Bits_Per_Word} is set to 32, this generates either - -@smallexample @c ada -@group -@b{for} Rec @b{use} - Field1 @b{at} 0 @b{range} 0 .. 32; -@b{end} @b{record}; -@end group -@end smallexample - -@noindent -for the big endian case, or -@smallexample @c ada -@group -@b{for} Rec @b{use} @b{record} - Field1 @b{at} 0 @b{range} 10 .. 32; -@b{end} @b{record}; -@end group -@end smallexample +@table @asis -@noindent -for the little endian case. Since a powerful subset of Ada expression -notation is usable for creating static constants, clever use of this -feature can often solve quite difficult problems in conditionalizing -compilation (note incidentally that in Ada 95, the little endian -constant was introduced as @code{System.Default_Bit_Order}, so you do not -need to define this one yourself). +@item @code{-gnatVa} +@emph{All validity checks.} -@node Use of Alternative Implementations -@section Use of Alternative Implementations +All validity checks are turned on. +That is, @emph{-gnatVa} is +equivalent to @emph{gnatVcdfimorst}. +@end table -@noindent -In some cases, none of the approaches described above are adequate. This -can occur for example if the set of declarations required is radically -different for two different configurations. +@geindex -gnatVc (gcc) -In this situation, the official Ada way of dealing with conditionalizing -such code is to write separate units for the different cases. As long as -this does not result in excessive duplication of code, this can be done -without creating maintenance problems. The approach is to share common -code as far as possible, and then isolate the code and declarations -that are different. Subunits are often a convenient method for breaking -out a piece of a unit that is to be conditionalized, with separate files -for different versions of the subunit for different targets, where the -build script selects the right one to give to the compiler. -@cindex Subunits (and conditional compilation) -As an example, consider a situation where a new feature in Ada 2005 -allows something to be done in a really nice way. But your code must be able -to compile with an Ada 95 compiler. Conceptually you want to say: +@table @asis -@smallexample @c ada -@group -@b{if} Ada_2005 @b{then} - @dots{} neat Ada 2005 code -@b{else} - @dots{} not quite as neat Ada 95 code -@b{end} @b{if}; -@end group -@end smallexample - -@noindent -where @code{Ada_2005} is a Boolean constant. - -But this won't work when @code{Ada_2005} is set to @code{False}, -since the @code{then} clause will be illegal for an Ada 95 compiler. -(Recall that although such unreachable code would eventually be deleted -by the compiler, it still needs to be legal. If it uses features -introduced in Ada 2005, it will be illegal in Ada 95.) +@item @code{-gnatVc} -So instead we write +@emph{Validity checks for copies.} -@smallexample @c ada -@b{procedure} Insert @b{is} @b{separate}; -@end smallexample +The right hand side of assignments, and the initializing values of +object declarations are validity checked. +@end table -@noindent -Then we have two files for the subunit @code{Insert}, with the two sets of -code. -If the package containing this is called @code{File_Queries}, then we might -have two files +@geindex -gnatVd (gcc) -@itemize @bullet -@item @file{file_queries-insert-2005.adb} -@item @file{file_queries-insert-95.adb} -@end itemize -@noindent -and the build script renames the appropriate file to +@table @asis -@smallexample -file_queries-insert.adb -@end smallexample +@item @code{-gnatVd} -@noindent -and then carries out the compilation. +@emph{Default (RM) validity checks.} -This can also be done with project files' naming schemes. For example: +Some validity checks are done by default following normal Ada semantics +(RM 13.9.1 (9-11)). +A check is done in case statements that the expression is within the range +of the subtype. If it is not, Constraint_Error is raised. +For assignments to array components, a check is done that the expression used +as index is within the range. If it is not, Constraint_Error is raised. +Both these validity checks may be turned off using switch @emph{-gnatVD}. +They are turned on by default. If @emph{-gnatVD} is specified, a subsequent +switch @emph{-gnatVd} will leave the checks turned on. +Switch @emph{-gnatVD} should be used only if you are sure that all such +expressions have valid values. If you use this switch and invalid values +are present, then the program is erroneous, and wild jumps or memory +overwriting may occur. +@end table -@smallexample @c project -For Body ("File_Queries.Insert") use "file_queries-insert-2005.ada"; -@end smallexample +@geindex -gnatVe (gcc) -@noindent -Note also that with project files it is desirable to use a different extension -than @file{ads} / @file{adb} for alternative versions. Otherwise a naming -conflict may arise through another commonly used feature: to declare as part -of the project a set of directories containing all the sources obeying the -default naming scheme. -The use of alternative units is certainly feasible in all situations, -and for example the Ada part of the GNAT run-time is conditionalized -based on the target architecture using this approach. As a specific example, -consider the implementation of the AST feature in VMS. There is one -spec: +@table @asis -@smallexample -s-asthan.ads -@end smallexample +@item @code{-gnatVe} -@noindent -which is the same for all architectures, and three bodies: +@emph{Validity checks for elementary components.} -@table @file -@item s-asthan.adb -used for all non-VMS operating systems -@item s-asthan-vms-alpha.adb -used for VMS on the Alpha -@item s-asthan-vms-ia64.adb -used for VMS on the ia64 +In the absence of this switch, assignments to record or array components are +not validity checked, even if validity checks for assignments generally +(@emph{-gnatVc}) are turned on. In Ada, assignment of composite values do not +require valid data, but assignment of individual components does. So for +example, there is a difference between copying the elements of an array with a +slice assignment, compared to assigning element by element in a loop. This +switch allows you to turn off validity checking for components, even when they +are assigned component by component. @end table -@noindent -The dummy version @file{s-asthan.adb} simply raises exceptions noting that -this operating system feature is not available, and the two remaining -versions interface with the corresponding versions of VMS to provide -VMS-compatible AST handling. The GNAT build script knows the architecture -and operating system, and automatically selects the right version, -renaming it if necessary to @file{s-asthan.adb} before the run-time build. +@geindex -gnatVf (gcc) -Another style for arranging alternative implementations is through Ada's -access-to-subprogram facility. -In case some functionality is to be conditionally included, -you can declare an access-to-procedure variable @code{Ref} that is initialized -to designate a ``do nothing'' procedure, and then invoke @code{Ref.all} -when appropriate. -In some library package, set @code{Ref} to @code{Proc'Access} for some -procedure @code{Proc} that performs the relevant processing. -The initialization only occurs if the library package is included in the -program. -The same idea can also be implemented using tagged types and dispatching -calls. +@table @asis -@node Preprocessing -@section Preprocessing -@cindex Preprocessing +@item @code{-gnatVf} -@noindent -Although it is quite possible to conditionalize code without the use of -C-style preprocessing, as described earlier in this section, it is -nevertheless convenient in some cases to use the C approach. Moreover, -older Ada compilers have often provided some preprocessing capability, -so legacy code may depend on this approach, even though it is not -standard. +@emph{Validity checks for floating-point values.} -To accommodate such use, GNAT provides a preprocessor (modeled to a large -extent on the various preprocessors that have been used -with legacy code on other compilers, to enable easier transition). +In the absence of this switch, validity checking occurs only for discrete +values. If @emph{-gnatVf} is specified, then validity checking also applies +for floating-point values, and NaNs and infinities are considered invalid, +as well as out of range values for constrained types. Note that this means +that standard IEEE infinity mode is not allowed. The exact contexts +in which floating-point values are checked depends on the setting of other +options. For example, @emph{-gnatVif} or @emph{-gnatVfi} +(the order does not matter) specifies that floating-point parameters of mode +@cite{in} should be validity checked. +@end table -The preprocessor may be used in two separate modes. It can be used quite -separately from the compiler, to generate a separate output source file -that is then fed to the compiler as a separate step. This is the -@code{gnatprep} utility, whose use is fully described in -@ref{Preprocessing with gnatprep}. -@cindex @code{gnatprep} +@geindex -gnatVi (gcc) -The preprocessing language allows such constructs as -@smallexample -@group -#if DEBUG or else (PRIORITY > 4) then - bunch of declarations -#else - completely different bunch of declarations -#end if; -@end group -@end smallexample +@table @asis -@noindent -The values of the symbols @code{DEBUG} and @code{PRIORITY} can be -defined either on the command line or in a separate file. +@item @code{-gnatVi} -The other way of running the preprocessor is even closer to the C style and -often more convenient. In this approach the preprocessing is integrated into -the compilation process. The compiler is fed the preprocessor input which -includes @code{#if} lines etc, and then the compiler carries out the -preprocessing internally and processes the resulting output. -For more details on this approach, see @ref{Integrated Preprocessing}. +@emph{Validity checks for `in} mode parameters` +Arguments for parameters of mode @cite{in} are validity checked in function +and procedure calls at the point of call. +@end table -@c ******************************* -@node Inline Assembler -@appendix Inline Assembler -@c ******************************* +@geindex -gnatVm (gcc) -@noindent -If you need to write low-level software that interacts directly -with the hardware, Ada provides two ways to incorporate assembly -language code into your program. First, you can import and invoke -external routines written in assembly language, an Ada feature fully -supported by GNAT@. However, for small sections of code it may be simpler -or more efficient to include assembly language statements directly -in your Ada source program, using the facilities of the implementation-defined -package @code{System.Machine_Code}, which incorporates the gcc -Inline Assembler. The Inline Assembler approach offers a number of advantages, -including the following: -@itemize @bullet -@item No need to use non-Ada tools -@item Consistent interface over different targets -@item Automatic usage of the proper calling conventions -@item Access to Ada constants and variables -@item Definition of intrinsic routines -@item Possibility of inlining a subprogram comprising assembler code -@item Code optimizer can take Inline Assembler code into account -@end itemize +@table @asis -This chapter presents a series of examples to show you how to use -the Inline Assembler. Although it focuses on the Intel x86, -the general approach applies also to other processors. -It is assumed that you are familiar with Ada -and with assembly language programming. +@item @code{-gnatVm} -@menu -* Basic Assembler Syntax:: -* A Simple Example of Inline Assembler:: -* Output Variables in Inline Assembler:: -* Input Variables in Inline Assembler:: -* Inlining Inline Assembler Code:: -* Other Asm Functionality:: -@end menu +@emph{Validity checks for `in out} mode parameters.` -@c --------------------------------------------------------------------------- -@node Basic Assembler Syntax -@section Basic Assembler Syntax +Arguments for parameters of mode @cite{in out} are validity checked in +procedure calls at the point of call. The @cite{'m'} here stands for +modify, since this concerns parameters that can be modified by the call. +Note that there is no specific option to test @cite{out} parameters, +but any reference within the subprogram will be tested in the usual +manner, and if an invalid value is copied back, any reference to it +will be subject to validity checking. +@end table + +@geindex -gnatVn (gcc) -@noindent -The assembler used by GNAT and gcc is based not on the Intel assembly -language, but rather on a language that descends from the AT&T Unix -assembler @emph{as} (and which is often referred to as ``AT&T syntax''). -The following table summarizes the main features of @emph{as} syntax -and points out the differences from the Intel conventions. -See the gcc @emph{as} and @emph{gas} (an @emph{as} macro -pre-processor) documentation for further information. @table @asis -@item Register names -gcc / @emph{as}: Prefix with ``%''; for example @code{%eax} -@* -Intel: No extra punctuation; for example @code{eax} - -@item Immediate operand -gcc / @emph{as}: Prefix with ``$''; for example @code{$4} -@* -Intel: No extra punctuation; for example @code{4} - -@item Address -gcc / @emph{as}: Prefix with ``$''; for example @code{$loc} -@* -Intel: No extra punctuation; for example @code{loc} - -@item Memory contents -gcc / @emph{as}: No extra punctuation; for example @code{loc} -@* -Intel: Square brackets; for example @code{[loc]} - -@item Register contents -gcc / @emph{as}: Parentheses; for example @code{(%eax)} -@* -Intel: Square brackets; for example @code{[eax]} - -@item Hexadecimal numbers -gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0} -@* -Intel: Trailing ``h''; for example @code{A0h} - -@item Operand size -gcc / @emph{as}: Explicit in op code; for example @code{movw} to move -a 16-bit word -@* -Intel: Implicit, deduced by assembler; for example @code{mov} - -@item Instruction repetition -gcc / @emph{as}: Split into two lines; for example -@* -@code{rep} -@* -@code{stosl} -@* -Intel: Keep on one line; for example @code{rep stosl} - -@item Order of operands -gcc / @emph{as}: Source first; for example @code{movw $4, %eax} -@* -Intel: Destination first; for example @code{mov eax, 4} -@end table - -@c --------------------------------------------------------------------------- -@node A Simple Example of Inline Assembler -@section A Simple Example of Inline Assembler -@noindent -The following example will generate a single assembly language statement, -@code{nop}, which does nothing. Despite its lack of run-time effect, -the example will be useful in illustrating the basics of -the Inline Assembler facility. +@item @code{-gnatVn} -@smallexample @c ada -@group -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Nothing @b{is} -@b{begin} - Asm ("nop"); -@b{end} Nothing; -@end group -@end smallexample +@emph{No validity checks.} -@code{Asm} is a procedure declared in package @code{System.Machine_Code}; -here it takes one parameter, a @emph{template string} that must be a static -expression and that will form the generated instruction. -@code{Asm} may be regarded as a compile-time procedure that parses -the template string and additional parameters (none here), -from which it generates a sequence of assembly language instructions. +This switch turns off all validity checking, including the default checking +for case statements and left hand side subscripts. Note that the use of +the switch @emph{-gnatp} suppresses all run-time checks, including +validity checks, and thus implies @emph{-gnatVn}. When this switch +is used, it cancels any other @emph{-gnatV} previously issued. -The examples in this chapter will illustrate several of the forms -for invoking @code{Asm}; a complete specification of the syntax -is found in @ref{Machine Code Insertions,,, gnat_rm, GNAT Reference -Manual}. +@item @code{-gnatVo} -Under the standard GNAT conventions, the @code{Nothing} procedure -should be in a file named @file{nothing.adb}. -You can build the executable in the usual way: -@smallexample -gnatmake nothing -@end smallexample -However, the interesting aspect of this example is not its run-time behavior -but rather the generated assembly code. -To see this output, invoke the compiler as follows: -@smallexample - gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb} -@end smallexample -where the options are: +@emph{Validity checks for operator and attribute operands.} +.. index:: -gnatVo (gcc) -@table @code -@item -c -compile only (no bind or link) -@item -S -generate assembler listing -@item -fomit-frame-pointer -do not set up separate stack frames -@item -gnatp -do not add runtime checks +Arguments for predefined operators and attributes are validity checked. +This includes all operators in package @cite{Standard}, +the shift operators defined as intrinsic in package @cite{Interfaces} +and operands for attributes such as @cite{Pos}. Checks are also made +on individual component values for composite comparisons, and on the +expressions in type conversions and qualified expressions. Checks are +also made on explicit ranges using @code{..} (e.g., slices, loops etc). @end table -This gives a human-readable assembler version of the code. The resulting -file will have the same name as the Ada source file, but with a @code{.s} -extension. In our example, the file @file{nothing.s} has the following -contents: - -@smallexample -@group -.file "nothing.adb" -gcc2_compiled.: -___gnu_compiled_ada: -.text - .align 4 -.globl __ada_nothing -__ada_nothing: -#APP - nop -#NO_APP - jmp L1 - .align 2,0x90 -L1: - ret -@end group -@end smallexample - -The assembly code you included is clearly indicated by -the compiler, between the @code{#APP} and @code{#NO_APP} -delimiters. The character before the 'APP' and 'NOAPP' -can differ on different targets. For example, GNU/Linux uses '#APP' while -on NT you will see '/APP'. +@geindex -gnatVp (gcc) -If you make a mistake in your assembler code (such as using the -wrong size modifier, or using a wrong operand for the instruction) GNAT -will report this error in a temporary file, which will be deleted when -the compilation is finished. Generating an assembler file will help -in such cases, since you can assemble this file separately using the -@emph{as} assembler that comes with gcc. -Assembling the file using the command +@table @asis -@smallexample -as @file{nothing.s} -@end smallexample -@noindent -will give you error messages whose lines correspond to the assembler -input file, so you can easily find and correct any mistakes you made. -If there are no errors, @emph{as} will generate an object file -@file{nothing.out}. +@item @code{-gnatVp} -@c --------------------------------------------------------------------------- -@node Output Variables in Inline Assembler -@section Output Variables in Inline Assembler +@emph{Validity checks for parameters.} -@noindent -The examples in this section, showing how to access the processor flags, -illustrate how to specify the destination operands for assembly language -statements. +This controls the treatment of parameters within a subprogram (as opposed +to @emph{-gnatVi} and @emph{-gnatVm} which control validity testing +of parameters on a call. If either of these call options is used, then +normally an assumption is made within a subprogram that the input arguments +have been validity checking at the point of call, and do not need checking +again within a subprogram). If @emph{-gnatVp} is set, then this assumption +is not made, and parameters are not assumed to be valid, so their validity +will be checked (or rechecked) within the subprogram. +@end table -@smallexample @c ada -@group -@b{with} Interfaces; @b{use} Interfaces; -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Get_Flags @b{is} - Flags : Unsigned_32; - @b{use} ASCII; -@b{begin} - Asm ("pushfl" & LF & HT & --@i{ push flags on stack} - "popl %%eax" & LF & HT & --@i{ load eax with flags} - "movl %%eax, %0", --@i{ store flags in variable} - Outputs => Unsigned_32'Asm_Output ("=g", Flags)); - Put_Line ("Flags register:" & Flags'Img); -@b{end} Get_Flags; -@end group -@end smallexample +@geindex -gnatVr (gcc) -In order to have a nicely aligned assembly listing, we have separated -multiple assembler statements in the Asm template string with linefeed -(ASCII.LF) and horizontal tab (ASCII.HT) characters. -The resulting section of the assembly output file is: -@smallexample -@group -#APP - pushfl - popl %eax - movl %eax, -40(%ebp) -#NO_APP -@end group -@end smallexample +@table @asis -It would have been legal to write the Asm invocation as: +@item @code{-gnatVr} -@smallexample -Asm ("pushfl popl %%eax movl %%eax, %0") -@end smallexample +@emph{Validity checks for function returns.} -but in the generated assembler file, this would come out as: +The expression in @cite{return} statements in functions is validity +checked. +@end table -@smallexample -#APP - pushfl popl %eax movl %eax, -40(%ebp) -#NO_APP -@end smallexample +@geindex -gnatVs (gcc) -which is not so convenient for the human reader. -We use Ada comments -at the end of each line to explain what the assembler instructions -actually do. This is a useful convention. +@table @asis -When writing Inline Assembler instructions, you need to precede each register -and variable name with a percent sign. Since the assembler already requires -a percent sign at the beginning of a register name, you need two consecutive -percent signs for such names in the Asm template string, thus @code{%%eax}. -In the generated assembly code, one of the percent signs will be stripped off. +@item @code{-gnatVs} -Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output -variables: operands you later define using @code{Input} or @code{Output} -parameters to @code{Asm}. -An output variable is illustrated in -the third statement in the Asm template string: -@smallexample -movl %%eax, %0 -@end smallexample -The intent is to store the contents of the eax register in a variable that can -be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not -necessarily work, since the compiler might optimize by using a register -to hold Flags, and the expansion of the @code{movl} instruction would not be -aware of this optimization. The solution is not to store the result directly -but rather to advise the compiler to choose the correct operand form; -that is the purpose of the @code{%0} output variable. +@emph{Validity checks for subscripts.} -Information about the output variable is supplied in the @code{Outputs} -parameter to @code{Asm}: -@smallexample -Outputs => Unsigned_32'Asm_Output ("=g", Flags)); -@end smallexample +All subscripts expressions are checked for validity, whether they appear +on the right side or left side (in default mode only left side subscripts +are validity checked). +@end table -The output is defined by the @code{Asm_Output} attribute of the target type; -the general format is -@smallexample -Type'Asm_Output (constraint_string, variable_name) -@end smallexample +@geindex -gnatVt (gcc) -The constraint string directs the compiler how -to store/access the associated variable. In the example -@smallexample -Unsigned_32'Asm_Output ("=m", Flags); -@end smallexample -the @code{"m"} (memory) constraint tells the compiler that the variable -@code{Flags} should be stored in a memory variable, thus preventing -the optimizer from keeping it in a register. In contrast, -@smallexample -Unsigned_32'Asm_Output ("=r", Flags); -@end smallexample -uses the @code{"r"} (register) constraint, telling the compiler to -store the variable in a register. -If the constraint is preceded by the equal character (@strong{=}), it tells -the compiler that the variable will be used to store data into it. +@table @asis -In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint, -allowing the optimizer to choose whatever it deems best. +@item @code{-gnatVt} -There are a fairly large number of constraints, but the ones that are -most useful (for the Intel x86 processor) are the following: +@emph{Validity checks for tests.} -@table @code -@item = -output constraint -@item g -global (i.e.@: can be stored anywhere) -@item m -in memory -@item I -a constant -@item a -use eax -@item b -use ebx -@item c -use ecx -@item d -use edx -@item S -use esi -@item D -use edi -@item r -use one of eax, ebx, ecx or edx -@item q -use one of eax, ebx, ecx, edx, esi or edi +Expressions used as conditions in @cite{if}, @cite{while} or @cite{exit} +statements are checked, as well as guard expressions in entry calls. @end table -The full set of constraints is described in the gcc and @emph{as} -documentation; note that it is possible to combine certain constraints -in one constraint string. +The @emph{-gnatV} switch may be followed by a string of letters +to turn on a series of validity checking options. +For example, @code{-gnatVcr} +specifies that in addition to the default validity checking, copies and +function return expressions are to be validity checked. +In order to make it easier to specify the desired combination of effects, +the upper case letters @cite{CDFIMORST} may +be used to turn off the corresponding lower case option. +Thus @code{-gnatVaM} turns on all validity checking options except for +checking of @cite{**in out**} procedure arguments. -You specify the association of an output variable with an assembler operand -through the @code{%}@emph{n} notation, where @emph{n} is a non-negative -integer. Thus in -@smallexample @c ada -@group -Asm ("pushfl" & LF & HT & --@i{ push flags on stack} - "popl %%eax" & LF & HT & --@i{ load eax with flags} - "movl %%eax, %0", --@i{ store flags in variable} - Outputs => Unsigned_32'Asm_Output ("=g", Flags)); -@end group -@end smallexample -@noindent -@code{%0} will be replaced in the expanded code by the appropriate operand, -whatever -the compiler decided for the @code{Flags} variable. +The specification of additional validity checking generates extra code (and +in the case of @emph{-gnatVa} the code expansion can be substantial). +However, these additional checks can be very useful in detecting +uninitialized variables, incorrect use of unchecked conversion, and other +errors leading to invalid values. The use of pragma @cite{Initialize_Scalars} +is useful in conjunction with the extra validity checking, since this +ensures that wherever possible uninitialized variables have invalid values. -In general, you may have any number of output variables: -@itemize @bullet -@item -Count the operands starting at 0; thus @code{%0}, @code{%1}, etc. -@item -Specify the @code{Outputs} parameter as a parenthesized comma-separated list -of @code{Asm_Output} attributes -@end itemize +See also the pragma @cite{Validity_Checks} which allows modification of +the validity checking mode at the program source level, and also allows for +temporary disabling of validity checks. -For example: -@smallexample @c ada -@group -Asm ("movl %%eax, %0" & LF & HT & - "movl %%ebx, %1" & LF & HT & - "movl %%ecx, %2", - Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), --@i{ %0 = Var_A} - Unsigned_32'Asm_Output ("=g", Var_B), --@i{ %1 = Var_B} - Unsigned_32'Asm_Output ("=g", Var_C))); --@i{ %2 = Var_C} -@end group -@end smallexample -@noindent -where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables -in the Ada program. +@node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{108}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{100} +@subsection Style Checking -As a variation on the @code{Get_Flags} example, we can use the constraints -string to direct the compiler to store the eax register into the @code{Flags} -variable, instead of including the store instruction explicitly in the -@code{Asm} template string: - -@smallexample @c ada -@group -@b{with} Interfaces; @b{use} Interfaces; -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Get_Flags_2 @b{is} - Flags : Unsigned_32; - @b{use} ASCII; -@b{begin} - Asm ("pushfl" & LF & HT & --@i{ push flags on stack} - "popl %%eax", --@i{ save flags in eax} - Outputs => Unsigned_32'Asm_Output ("=a", Flags)); - Put_Line ("Flags register:" & Flags'Img); -@b{end} Get_Flags_2; -@end group -@end smallexample -@noindent -The @code{"a"} constraint tells the compiler that the @code{Flags} -variable will come from the eax register. Here is the resulting code: +@geindex Style checking -@smallexample -@group -#APP - pushfl - popl %eax -#NO_APP - movl %eax,-40(%ebp) -@end group -@end smallexample +@geindex -gnaty (gcc) -@noindent -The compiler generated the store of eax into Flags after -expanding the assembler code. +The @emph{-gnatyx} switch causes the compiler to +enforce specified style rules. A limited set of style rules has been used +in writing the GNAT sources themselves. This switch allows user programs +to activate all or some of these checks. If the source program fails a +specified style check, an appropriate message is given, preceded by +the character sequence '(style)'. This message does not prevent +successful compilation (unless the @emph{-gnatwe} switch is used). -Actually, there was no need to pop the flags into the eax register; -more simply, we could just pop the flags directly into the program variable: +Note that this is by no means intended to be a general facility for +checking arbitrary coding standards. It is simply an embedding of the +style rules we have chosen for the GNAT sources. If you are starting +a project which does not have established style standards, you may +find it useful to adopt the entire set of GNAT coding standards, or +some subset of them. -@smallexample @c ada -@group -@b{with} Interfaces; @b{use} Interfaces; -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Get_Flags_3 @b{is} - Flags : Unsigned_32; - @b{use} ASCII; -@b{begin} - Asm ("pushfl" & LF & HT & --@i{ push flags on stack} - "pop %0", --@i{ save flags in Flags} - Outputs => Unsigned_32'Asm_Output ("=g", Flags)); - Put_Line ("Flags register:" & Flags'Img); -@b{end} Get_Flags_3; -@end group -@end smallexample -@c --------------------------------------------------------------------------- -@node Input Variables in Inline Assembler -@section Input Variables in Inline Assembler +The string @cite{x} is a sequence of letters or digits +indicating the particular style +checks to be performed. The following checks are defined: -@noindent -The example in this section illustrates how to specify the source operands -for assembly language statements. -The program simply increments its input value by 1: +@geindex -gnaty[0-9] (gcc) -@smallexample @c ada -@group -@b{with} Interfaces; @b{use} Interfaces; -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Increment @b{is} - @b{function} Incr (Value : Unsigned_32) @b{return} Unsigned_32 @b{is} - Result : Unsigned_32; - @b{begin} - Asm ("incl %0", - Outputs => Unsigned_32'Asm_Output ("=a", Result), - Inputs => Unsigned_32'Asm_Input ("a", Value)); - @b{return} Result; - @b{end} Incr; +@table @asis - Value : Unsigned_32; +@item @code{-gnaty0} -@b{begin} - Value := 5; - Put_Line ("Value before is" & Value'Img); - Value := Incr (Value); - Put_Line ("Value after is" & Value'Img); -@b{end} Increment; -@end group -@end smallexample +@emph{Specify indentation level.} -The @code{Outputs} parameter to @code{Asm} specifies -that the result will be in the eax register and that it is to be stored -in the @code{Result} variable. +If a digit from 1-9 appears +in the string after @emph{-gnaty} +then proper indentation is checked, with the digit indicating the +indentation level required. A value of zero turns off this style check. +The general style of required indentation is as specified by +the examples in the Ada Reference Manual. Full line comments must be +aligned with the @cite{--} starting on a column that is a multiple of +the alignment level, or they may be aligned the same way as the following +non-blank line (this is useful when full line comments appear in the middle +of a statement, or they may be aligned with the source line on the previous +non-blank line. +@end table -The @code{Inputs} parameter looks much like the @code{Outputs} parameter, -but with an @code{Asm_Input} attribute. -The @code{"="} constraint, indicating an output value, is not present. +@geindex -gnatya (gcc) -You can have multiple input variables, in the same way that you can have more -than one output variable. -The parameter count (%0, %1) etc, still starts at the first output statement, -and continues with the input statements. +@table @asis -Just as the @code{Outputs} parameter causes the register to be stored into the -target variable after execution of the assembler statements, so does the -@code{Inputs} parameter cause its variable to be loaded into the register -before execution of the assembler statements. +@item @code{-gnatya} -Thus the effect of the @code{Asm} invocation is: -@enumerate -@item load the 32-bit value of @code{Value} into eax -@item execute the @code{incl %eax} instruction -@item store the contents of eax into the @code{Result} variable -@end enumerate +@emph{Check attribute casing.} -The resulting assembler file (with @option{-O2} optimization) contains: -@smallexample -@group -_increment__incr.1: - subl $4,%esp - movl 8(%esp),%eax -#APP - incl %eax -#NO_APP - movl %eax,%edx - movl %ecx,(%esp) - addl $4,%esp - ret -@end group -@end smallexample +Attribute names, including the case of keywords such as @cite{digits} +used as attributes names, must be written in mixed case, that is, the +initial letter and any letter following an underscore must be uppercase. +All other letters must be lowercase. +@end table -@c --------------------------------------------------------------------------- -@node Inlining Inline Assembler Code -@section Inlining Inline Assembler Code +@geindex -gnatyA (gcc) -@noindent -For a short subprogram such as the @code{Incr} function in the previous -section, the overhead of the call and return (creating / deleting the stack -frame) can be significant, compared to the amount of code in the subprogram -body. A solution is to apply Ada's @code{Inline} pragma to the subprogram, -which directs the compiler to expand invocations of the subprogram at the -point(s) of call, instead of setting up a stack frame for out-of-line calls. -Here is the resulting program: -@smallexample @c ada -@group -@b{with} Interfaces; @b{use} Interfaces; -@b{with} Ada.Text_IO; @b{use} Ada.Text_IO; -@b{with} System.Machine_Code; @b{use} System.Machine_Code; -@b{procedure} Increment_2 @b{is} +@table @asis - @b{function} Incr (Value : Unsigned_32) @b{return} Unsigned_32 @b{is} - Result : Unsigned_32; - @b{begin} - Asm ("incl %0", - Outputs => Unsigned_32'Asm_Output ("=a", Result), - Inputs => Unsigned_32'Asm_Input ("a", Value)); - @b{return} Result; - @b{end} Incr; - @b{pragma} Inline (Increment); +@item @code{-gnatyA} - Value : Unsigned_32; +@emph{Use of array index numbers in array attributes.} -@b{begin} - Value := 5; - Put_Line ("Value before is" & Value'Img); - Value := Increment (Value); - Put_Line ("Value after is" & Value'Img); -@b{end} Increment_2; -@end group -@end smallexample - -Compile the program with both optimization (@option{-O2}) and inlining -(@option{-gnatn}) enabled. - -The @code{Incr} function is still compiled as usual, but at the -point in @code{Increment} where our function used to be called: +When using the array attributes First, Last, Range, +or Length, the index number must be omitted for one-dimensional arrays +and is required for multi-dimensional arrays. +@end table -@smallexample -@group -pushl %edi -call _increment__incr.1 -@end group -@end smallexample +@geindex -gnatyb (gcc) -@noindent -the code for the function body directly appears: -@smallexample -@group -movl %esi,%eax -#APP - incl %eax -#NO_APP - movl %eax,%edx -@end group -@end smallexample +@table @asis -@noindent -thus saving the overhead of stack frame setup and an out-of-line call. +@item @code{-gnatyb} -@c --------------------------------------------------------------------------- -@node Other Asm Functionality -@section Other @code{Asm} Functionality +@emph{Blanks not allowed at statement end.} -@noindent -This section describes two important parameters to the @code{Asm} -procedure: @code{Clobber}, which identifies register usage; -and @code{Volatile}, which inhibits unwanted optimizations. +Trailing blanks are not allowed at the end of statements. The purpose of this +rule, together with h (no horizontal tabs), is to enforce a canonical format +for the use of blanks to separate source tokens. +@end table -@menu -* The Clobber Parameter:: -* The Volatile Parameter:: -@end menu +@geindex -gnatyB (gcc) -@c --------------------------------------------------------------------------- -@node The Clobber Parameter -@subsection The @code{Clobber} Parameter -@noindent -One of the dangers of intermixing assembly language and a compiled language -such as Ada is that the compiler needs to be aware of which registers are -being used by the assembly code. In some cases, such as the earlier examples, -the constraint string is sufficient to indicate register usage (e.g., -@code{"a"} for -the eax register). But more generally, the compiler needs an explicit -identification of the registers that are used by the Inline Assembly -statements. +@table @asis -Using a register that the compiler doesn't know about -could be a side effect of an instruction (like @code{mull} -storing its result in both eax and edx). -It can also arise from explicit register usage in your -assembly code; for example: -@smallexample -@group -Asm ("movl %0, %%ebx" & LF & HT & - "movl %%ebx, %1", - Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), - Inputs => Unsigned_32'Asm_Input ("g", Var_In)); -@end group -@end smallexample -@noindent -where the compiler (since it does not analyze the @code{Asm} template string) -does not know you are using the ebx register. +@item @code{-gnatyB} -In such cases you need to supply the @code{Clobber} parameter to @code{Asm}, -to identify the registers that will be used by your assembly code: +@emph{Check Boolean operators.} -@smallexample -@group -Asm ("movl %0, %%ebx" & LF & HT & - "movl %%ebx, %1", - Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), - Inputs => Unsigned_32'Asm_Input ("g", Var_In), - Clobber => "ebx"); -@end group -@end smallexample +The use of AND/OR operators is not permitted except in the cases of modular +operands, array operands, and simple stand-alone boolean variables or +boolean constants. In all other cases @cite{and then}/@cite{or else} are +required. +@end table -The Clobber parameter is a static string expression specifying the -register(s) you are using. Note that register names are @emph{not} prefixed -by a percent sign. Also, if more than one register is used then their names -are separated by commas; e.g., @code{"eax, ebx"} +@geindex -gnatyc (gcc) -The @code{Clobber} parameter has several additional uses: -@enumerate -@item Use ``register'' name @code{cc} to indicate that flags might have changed -@item Use ``register'' name @code{memory} if you changed a memory location -@end enumerate -@c --------------------------------------------------------------------------- -@node The Volatile Parameter -@subsection The @code{Volatile} Parameter -@cindex Volatile parameter +@table @asis -@noindent -Compiler optimizations in the presence of Inline Assembler may sometimes have -unwanted effects. For example, when an @code{Asm} invocation with an input -variable is inside a loop, the compiler might move the loading of the input -variable outside the loop, regarding it as a one-time initialization. +@item @code{-gnatyc} -If this effect is not desired, you can disable such optimizations by setting -the @code{Volatile} parameter to @code{True}; for example: +@emph{Check comments, double space.} -@smallexample @c ada -@group -Asm ("movl %0, %%ebx" & LF & HT & - "movl %%ebx, %1", - Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), - Inputs => Unsigned_32'Asm_Input ("g", Var_In), - Clobber => "ebx", - Volatile => True); -@end group -@end smallexample +Comments must meet the following set of rules: -By default, @code{Volatile} is set to @code{False} unless there is no -@code{Outputs} parameter. -Although setting @code{Volatile} to @code{True} prevents unwanted -optimizations, it will also disable other optimizations that might be -important for efficiency. In general, you should set @code{Volatile} -to @code{True} only if the compiler's optimizations have created -problems. -@c END OF INLINE ASSEMBLER CHAPTER -@c =============================== - - -@c ***************************************** -@c Writing Portable Fixed-Point Declarations -@c ***************************************** -@node Writing Portable Fixed-Point Declarations -@appendix Writing Portable Fixed-Point Declarations -@cindex Fixed-point types (writing portable declarations) - -@noindent -The Ada Reference Manual gives an implementation freedom to choose bounds -that are narrower by @code{Small} from the given bounds. -For example, if we write - -@smallexample @c ada - type F1 is delta 1.0 range -128.0 .. +128.0; -@end smallexample - -@noindent -then the implementation is allowed to choose -128.0 .. +127.0 if it -likes, but is not required to do so. - -This leads to possible portability problems, so let's have a closer -look at this, and figure out how to avoid these problems. - -First, why does this freedom exist, and why would an implementation -take advantage of it? To answer this, take a closer look at the type -declaration for @code{F1} above. If the compiler uses the given bounds, -it would need 9 bits to hold the largest positive value (and typically -that means 16 bits on all machines). But if the implementation chooses -the +127.0 bound then it can fit values of the type in 8 bits. - -Why not make the user write +127.0 if that's what is wanted? -The rationale is that if you are thinking of fixed point -as a kind of ``poor man's floating-point'', then you don't want -to be thinking about the scaled integers that are used in its -representation. Let's take another example: - -@smallexample @c ada - type F2 is delta 2.0**(-15) range -1.0 .. +1.0; -@end smallexample - -@noindent -Looking at this declaration, it seems casually as though -it should fit in 16 bits, but again that extra positive value -+1.0 has the scaled integer equivalent of 2**15 which is one too -big for signed 16 bits. The implementation can treat this as: - -@smallexample @c ada - type F2 is delta 2.0**(-15) range -1.0 .. +1.0-(2.0**(-15)); -@end smallexample - -@noindent -and the Ada language design team felt that this was too annoying -to require. We don't need to debate this decision at this point, -since it is well established (the rule about narrowing the ranges -dates to Ada 83). - -But the important point is that an implementation is not required -to do this narrowing, so we have a potential portability problem. -We could imagine three types of implementation: - -@enumerate a -@item -those that narrow the range automatically if they can figure -out that the narrower range will allow storage in a smaller machine unit, +@itemize * -@item -those that will narrow only if forced to by a @code{'Size} clause, and +@item +The '@cite{--}' that starts the column must either start in column one, +or else at least one blank must precede this sequence. -@item -those that will never narrow. -@end enumerate +@item +Comments that follow other tokens on a line must have at least one blank +following the '@cite{--}' at the start of the comment. -@noindent -Now if we are language theoreticians, we can imagine a fourth -approach: is to narrow all the time, e.g. to treat - -@smallexample @c ada - type F3 is delta 1.0 range -10.0 .. +23.0; -@end smallexample - -@noindent -as though it had been written: - -@smallexample @c ada - type F3 is delta 1.0 range -9.0 .. +22.0; -@end smallexample - -@noindent -But although technically allowed, such a behavior would be hostile and silly, -and no real compiler would do this. All real compilers will fall into one of -the categories (a), (b) or (c) above. - -So, how do you get the compiler to do what you want? The answer is give the -actual bounds you want, and then use a @code{'Small} clause and a -@code{'Size} clause to absolutely pin down what the compiler does. -E.g., for @code{F2} above, we will write: - -@smallexample @c ada -@group - My_Small : constant := 2.0**(-15); - My_First : constant := -1.0; - My_Last : constant := +1.0 - My_Small; - - type F2 is delta My_Small range My_First .. My_Last; -@end group -@end smallexample - -@noindent -and then add - -@smallexample @c ada -@group - for F2'Small use my_Small; - for F2'Size use 16; -@end group -@end smallexample - -@noindent -In practice all compilers will do the same thing here and will give you -what you want, so the above declarations are fully portable. If you really -want to play language lawyer and guard against ludicrous behavior by the -compiler you could add - -@smallexample @c ada -@group - Test1 : constant := 1 / Boolean'Pos (F2'First = My_First); - Test2 : constant := 1 / Boolean'Pos (F2'Last = My_Last); -@end group -@end smallexample - -@noindent -One or other or both are allowed to be illegal if the compiler is -behaving in a silly manner, but at least the silly compiler will not -get away with silently messing with your (very clear) intentions. - -If you follow this scheme you will be guaranteed that your fixed-point -types will be portable. - - -@c *********************************** -@c * Compatibility and Porting Guide * -@c *********************************** -@node Compatibility and Porting Guide -@appendix Compatibility and Porting Guide - -@noindent -This chapter describes the compatibility issues that may arise between -GNAT and other Ada compilation systems (including those for Ada 83), -and shows how GNAT can expedite porting -applications developed in other Ada environments. +@item +Full line comments must have at least two blanks following the +'@cite{--}' that starts the comment, with the following exceptions. -@menu -* Compatibility with Ada 83:: -* Compatibility between Ada 95 and Ada 2005:: -* Implementation-dependent characteristics:: -* Compatibility with Other Ada Systems:: -* Representation Clauses:: -@c Brief section is only in non-VMS version -@c Full chapter is in VMS version -* Compatibility with HP Ada 83:: -@end menu +@item +A line consisting only of the '@cite{--}' characters, possibly preceded +by blanks is permitted. -@node Compatibility with Ada 83 -@section Compatibility with Ada 83 -@cindex Compatibility (between Ada 83 and Ada 95 / Ada 2005) +@item +A comment starting with '@cite{--x}' where @cite{x} is a special character +is permitted. +This allows proper processing of the output generated by specialized tools +including @emph{gnatprep} (where '@cite{--!}' is used) and the SPARK +annotation +language (where '@cite{--#}' is used). For the purposes of this rule, a +special character is defined as being in one of the ASCII ranges +@cite{16#21#...16#2F#} or @cite{16#3A#...16#3F#}. +Note that this usage is not permitted +in GNAT implementation units (i.e., when @emph{-gnatg} is used). -@noindent -Ada 95 and Ada 2005 are highly upwards compatible with Ada 83. In -particular, the design intention was that the difficulties associated -with moving from Ada 83 to Ada 95 or Ada 2005 should be no greater than those -that occur when moving from one Ada 83 system to another. +@item +A line consisting entirely of minus signs, possibly preceded by blanks, is +permitted. This allows the construction of box comments where lines of minus +signs are used to form the top and bottom of the box. -However, there are a number of points at which there are minor -incompatibilities. The @cite{Ada 95 Annotated Reference Manual} contains -full details of these issues, -and should be consulted for a complete treatment. -In practice the -following subsections treat the most likely issues to be encountered. +@item +A comment that starts and ends with '@cite{--}' is permitted as long as at +least one blank follows the initial '@cite{--}'. Together with the preceding +rule, this allows the construction of box comments, as shown in the following +example: -@menu -* Legal Ada 83 programs that are illegal in Ada 95:: -* More deterministic semantics:: -* Changed semantics:: -* Other language compatibility issues:: -@end menu +@example +--------------------------- +-- This is a box comment -- +-- with two text lines. -- +--------------------------- +@end example +@end itemize +@end table -@node Legal Ada 83 programs that are illegal in Ada 95 -@subsection Legal Ada 83 programs that are illegal in Ada 95 +@geindex -gnatyC (gcc) -Some legal Ada 83 programs are illegal (i.e., they will fail to compile) in -Ada 95 and thus also in Ada 2005: -@table @emph -@item Character literals -Some uses of character literals are ambiguous. Since Ada 95 has introduced -@code{Wide_Character} as a new predefined character type, some uses of -character literals that were legal in Ada 83 are illegal in Ada 95. -For example: -@smallexample @c ada - @b{for} Char @b{in} 'A' .. 'Z' @b{loop} @dots{} @b{end} @b{loop}; -@end smallexample - -@noindent -The problem is that @code{'A'} and @code{'Z'} could be from either -@code{Character} or @code{Wide_Character}. The simplest correction -is to make the type explicit; e.g.: -@smallexample @c ada - @b{for} Char @b{in} Character @b{range} 'A' .. 'Z' @b{loop} @dots{} @b{end} @b{loop}; -@end smallexample - -@item New reserved words -The identifiers @code{abstract}, @code{aliased}, @code{protected}, -@code{requeue}, @code{tagged}, and @code{until} are reserved in Ada 95. -Existing Ada 83 code using any of these identifiers must be edited to -use some alternative name. - -@item Freezing rules -The rules in Ada 95 are slightly different with regard to the point at -which entities are frozen, and representation pragmas and clauses are -not permitted past the freeze point. This shows up most typically in -the form of an error message complaining that a representation item -appears too late, and the appropriate corrective action is to move -the item nearer to the declaration of the entity to which it refers. - -A particular case is that representation pragmas -cannot be applied to a subprogram body. If necessary, a separate subprogram -declaration must be introduced to which the pragma can be applied. - -@item Optional bodies for library packages -In Ada 83, a package that did not require a package body was nevertheless -allowed to have one. This lead to certain surprises in compiling large -systems (situations in which the body could be unexpectedly ignored by the -binder). In Ada 95, if a package does not require a body then it is not -permitted to have a body. To fix this problem, simply remove a redundant -body if it is empty, or, if it is non-empty, introduce a dummy declaration -into the spec that makes the body required. One approach is to add a private -part to the package declaration (if necessary), and define a parameterless -procedure called @code{Requires_Body}, which must then be given a dummy -procedure body in the package body, which then becomes required. -Another approach (assuming that this does not introduce elaboration -circularities) is to add an @code{Elaborate_Body} pragma to the package spec, -since one effect of this pragma is to require the presence of a package body. - -@item @code{Numeric_Error} is now the same as @code{Constraint_Error} -In Ada 95, the exception @code{Numeric_Error} is a renaming of -@code{Constraint_Error}. -This means that it is illegal to have separate exception handlers for -the two exceptions. The fix is simply to remove the handler for the -@code{Numeric_Error} case (since even in Ada 83, a compiler was free to raise -@code{Constraint_Error} in place of @code{Numeric_Error} in all cases). - -@item Indefinite subtypes in generics -In Ada 83, it was permissible to pass an indefinite type (e.g.@: @code{String}) -as the actual for a generic formal private type, but then the instantiation -would be illegal if there were any instances of declarations of variables -of this type in the generic body. In Ada 95, to avoid this clear violation -of the methodological principle known as the ``contract model'', -the generic declaration explicitly indicates whether -or not such instantiations are permitted. If a generic formal parameter -has explicit unknown discriminants, indicated by using @code{(<>)} after the -subtype name, then it can be instantiated with indefinite types, but no -stand-alone variables can be declared of this type. Any attempt to declare -such a variable will result in an illegality at the time the generic is -declared. If the @code{(<>)} notation is not used, then it is illegal -to instantiate the generic with an indefinite type. -This is the potential incompatibility issue when porting Ada 83 code to Ada 95. -It will show up as a compile time error, and -the fix is usually simply to add the @code{(<>)} to the generic declaration. -@end table - -@node More deterministic semantics -@subsection More deterministic semantics - -@table @emph -@item Conversions -Conversions from real types to integer types round away from 0. In Ada 83 -the conversion Integer(2.5) could deliver either 2 or 3 as its value. This -implementation freedom was intended to support unbiased rounding in -statistical applications, but in practice it interfered with portability. -In Ada 95 the conversion semantics are unambiguous, and rounding away from 0 -is required. Numeric code may be affected by this change in semantics. -Note, though, that this issue is no worse than already existed in Ada 83 -when porting code from one vendor to another. - -@item Tasking -The Real-Time Annex introduces a set of policies that define the behavior of -features that were implementation dependent in Ada 83, such as the order in -which open select branches are executed. -@end table - -@node Changed semantics -@subsection Changed semantics - -@noindent -The worst kind of incompatibility is one where a program that is legal in -Ada 83 is also legal in Ada 95 but can have an effect in Ada 95 that was not -possible in Ada 83. Fortunately this is extremely rare, but the one -situation that you should be alert to is the change in the predefined type -@code{Character} from 7-bit ASCII to 8-bit Latin-1. - -@table @emph -@item Range of type @code{Character} -The range of @code{Standard.Character} is now the full 256 characters -of Latin-1, whereas in most Ada 83 implementations it was restricted -to 128 characters. Although some of the effects of -this change will be manifest in compile-time rejection of legal -Ada 83 programs it is possible for a working Ada 83 program to have -a different effect in Ada 95, one that was not permitted in Ada 83. -As an example, the expression -@code{Character'Pos(Character'Last)} returned @code{127} in Ada 83 and now -delivers @code{255} as its value. -In general, you should look at the logic of any -character-processing Ada 83 program and see whether it needs to be adapted -to work correctly with Latin-1. Note that the predefined Ada 95 API has a -character handling package that may be relevant if code needs to be adapted -to account for the additional Latin-1 elements. -The desirable fix is to -modify the program to accommodate the full character set, but in some cases -it may be convenient to define a subtype or derived type of Character that -covers only the restricted range. -@cindex Latin-1 -@end table - -@node Other language compatibility issues -@subsection Other language compatibility issues - -@table @emph -@item @option{-gnat83} switch -All implementations of GNAT provide a switch that causes GNAT to operate -in Ada 83 mode. In this mode, some but not all compatibility problems -of the type described above are handled automatically. For example, the -new reserved words introduced in Ada 95 and Ada 2005 are treated simply -as identifiers as in Ada 83. -However, -in practice, it is usually advisable to make the necessary modifications -to the program to remove the need for using this switch. -See @ref{Compiling Different Versions of Ada}. - -@item Support for removed Ada 83 pragmas and attributes -A number of pragmas and attributes from Ada 83 were removed from Ada 95, -generally because they were replaced by other mechanisms. Ada 95 and Ada 2005 -compilers are allowed, but not required, to implement these missing -elements. In contrast with some other compilers, GNAT implements all -such pragmas and attributes, eliminating this compatibility concern. These -include @code{pragma Interface} and the floating point type attributes -(@code{Emax}, @code{Mantissa}, etc.), among other items. -@end table - - -@node Compatibility between Ada 95 and Ada 2005 -@section Compatibility between Ada 95 and Ada 2005 -@cindex Compatibility between Ada 95 and Ada 2005 - -@noindent -Although Ada 2005 was designed to be upwards compatible with Ada 95, there are -a number of incompatibilities. Several are enumerated below; -for a complete description please see the -Annotated Ada 2005 Reference Manual, or section 9.1.1 in -@cite{Rationale for Ada 2005}. - -@table @emph -@item New reserved words. -The words @code{interface}, @code{overriding} and @code{synchronized} are -reserved in Ada 2005. -A pre-Ada 2005 program that uses any of these as an identifier will be -illegal. - -@item New declarations in predefined packages. -A number of packages in the predefined environment contain new declarations: -@code{Ada.Exceptions}, @code{Ada.Real_Time}, @code{Ada.Strings}, -@code{Ada.Strings.Fixed}, @code{Ada.Strings.Bounded}, -@code{Ada.Strings.Unbounded}, @code{Ada.Strings.Wide_Fixed}, -@code{Ada.Strings.Wide_Bounded}, @code{Ada.Strings.Wide_Unbounded}, -@code{Ada.Tags}, @code{Ada.Text_IO}, and @code{Interfaces.C}. -If an Ada 95 program does a @code{with} and @code{use} of any of these -packages, the new declarations may cause name clashes. - -@item Access parameters. -A nondispatching subprogram with an access parameter cannot be renamed -as a dispatching operation. This was permitted in Ada 95. - -@item Access types, discriminants, and constraints. -Rule changes in this area have led to some incompatibilities; for example, -constrained subtypes of some access types are not permitted in Ada 2005. - -@item Aggregates for limited types. -The allowance of aggregates for limited types in Ada 2005 raises the -possibility of ambiguities in legal Ada 95 programs, since additional types -now need to be considered in expression resolution. - -@item Fixed-point multiplication and division. -Certain expressions involving ``*'' or ``/'' for a fixed-point type, which -were legal in Ada 95 and invoked the predefined versions of these operations, -are now ambiguous. -The ambiguity may be resolved either by applying a type conversion to the -expression, or by explicitly invoking the operation from package -@code{Standard}. - -@item Return-by-reference types. -The Ada 95 return-by-reference mechanism has been removed. Instead, the user -can declare a function returning a value from an anonymous access type. -@end table - - -@node Implementation-dependent characteristics -@section Implementation-dependent characteristics -@noindent -Although the Ada language defines the semantics of each construct as -precisely as practical, in some situations (for example for reasons of -efficiency, or where the effect is heavily dependent on the host or target -platform) the implementation is allowed some freedom. In porting Ada 83 -code to GNAT, you need to be aware of whether / how the existing code -exercised such implementation dependencies. Such characteristics fall into -several categories, and GNAT offers specific support in assisting the -transition from certain Ada 83 compilers. +@table @asis -@menu -* Implementation-defined pragmas:: -* Implementation-defined attributes:: -* Libraries:: -* Elaboration order:: -* Target-specific aspects:: -@end menu +@item @code{-gnatyC} -@node Implementation-defined pragmas -@subsection Implementation-defined pragmas - -@noindent -Ada compilers are allowed to supplement the language-defined pragmas, and -these are a potential source of non-portability. All GNAT-defined pragmas -are described in @ref{Implementation Defined Pragmas,,, gnat_rm, GNAT -Reference Manual}, and these include several that are specifically -intended to correspond to other vendors' Ada 83 pragmas. -For migrating from VADS, the pragma @code{Use_VADS_Size} may be useful. -For compatibility with HP Ada 83, GNAT supplies the pragmas -@code{Extend_System}, @code{Ident}, @code{Inline_Generic}, -@code{Interface_Name}, @code{Passive}, @code{Suppress_All}, -and @code{Volatile}. -Other relevant pragmas include @code{External} and @code{Link_With}. -Some vendor-specific -Ada 83 pragmas (@code{Share_Generic}, @code{Subtitle}, and @code{Title}) are -recognized, thus -avoiding compiler rejection of units that contain such pragmas; they are not -relevant in a GNAT context and hence are not otherwise implemented. - -@node Implementation-defined attributes -@subsection Implementation-defined attributes - -Analogous to pragmas, the set of attributes may be extended by an -implementation. All GNAT-defined attributes are described in -@ref{Implementation Defined Attributes,,, gnat_rm, GNAT Reference -Manual}, and these include several that are specifically intended -to correspond to other vendors' Ada 83 attributes. For migrating from VADS, -the attribute @code{VADS_Size} may be useful. For compatibility with HP -Ada 83, GNAT supplies the attributes @code{Bit}, @code{Machine_Size} and -@code{Type_Class}. - -@node Libraries -@subsection Libraries -@noindent -Vendors may supply libraries to supplement the standard Ada API. If Ada 83 -code uses vendor-specific libraries then there are several ways to manage -this in Ada 95 or Ada 2005: -@enumerate -@item -If the source code for the libraries (specs and bodies) are -available, then the libraries can be migrated in the same way as the -application. -@item -If the source code for the specs but not the bodies are -available, then you can reimplement the bodies. -@item -Some features introduced by Ada 95 obviate the need for library support. For -example most Ada 83 vendors supplied a package for unsigned integers. The -Ada 95 modular type feature is the preferred way to handle this need, so -instead of migrating or reimplementing the unsigned integer package it may -be preferable to retrofit the application using modular types. -@end enumerate +@emph{Check comments, single space.} -@node Elaboration order -@subsection Elaboration order -@noindent -The implementation can choose any elaboration order consistent with the unit -dependency relationship. This freedom means that some orders can result in -Program_Error being raised due to an ``Access Before Elaboration'': an attempt -to invoke a subprogram its body has been elaborated, or to instantiate a -generic before the generic body has been elaborated. By default GNAT -attempts to choose a safe order (one that will not encounter access before -elaboration problems) by implicitly inserting @code{Elaborate} or -@code{Elaborate_All} pragmas where -needed. However, this can lead to the creation of elaboration circularities -and a resulting rejection of the program by gnatbind. This issue is -thoroughly described in @ref{Elaboration Order Handling in GNAT}. -In brief, there are several -ways to deal with this situation: - -@itemize @bullet -@item -Modify the program to eliminate the circularities, e.g.@: by moving -elaboration-time code into explicitly-invoked procedures -@item -Constrain the elaboration order by including explicit @code{Elaborate_Body} or -@code{Elaborate} pragmas, and then inhibit the generation of implicit -@code{Elaborate_All} -pragmas either globally (as an effect of the @option{-gnatE} switch) or locally -(by selectively suppressing elaboration checks via pragma -@code{Suppress(Elaboration_Check)} when it is safe to do so). -@end itemize +This is identical to @cite{c} except that only one space +is required following the @cite{--} of a comment instead of two. +@end table -@node Target-specific aspects -@subsection Target-specific aspects -@noindent -Low-level applications need to deal with machine addresses, data -representations, interfacing with assembler code, and similar issues. If -such an Ada 83 application is being ported to different target hardware (for -example where the byte endianness has changed) then you will need to -carefully examine the program logic; the porting effort will heavily depend -on the robustness of the original design. Moreover, Ada 95 (and thus -Ada 2005) are sometimes -incompatible with typical Ada 83 compiler practices regarding implicit -packing, the meaning of the Size attribute, and the size of access values. -GNAT's approach to these issues is described in @ref{Representation Clauses}. - -@node Compatibility with Other Ada Systems -@section Compatibility with Other Ada Systems - -@noindent -If programs avoid the use of implementation dependent and -implementation defined features, as documented in the @cite{Ada -Reference Manual}, there should be a high degree of portability between -GNAT and other Ada systems. The following are specific items which -have proved troublesome in moving Ada 95 programs from GNAT to other Ada 95 -compilers, but do not affect porting code to GNAT@. -(As of @value{NOW}, GNAT is the only compiler available for Ada 2005; -the following issues may or may not arise for Ada 2005 programs -when other compilers appear.) - -@table @emph -@item Ada 83 Pragmas and Attributes -Ada 95 compilers are allowed, but not required, to implement the missing -Ada 83 pragmas and attributes that are no longer defined in Ada 95. -GNAT implements all such pragmas and attributes, eliminating this as -a compatibility concern, but some other Ada 95 compilers reject these -pragmas and attributes. - -@item Specialized Needs Annexes -GNAT implements the full set of special needs annexes. At the -current time, it is the only Ada 95 compiler to do so. This means that -programs making use of these features may not be portable to other Ada -95 compilation systems. - -@item Representation Clauses -Some other Ada 95 compilers implement only the minimal set of -representation clauses required by the Ada 95 reference manual. GNAT goes -far beyond this minimal set, as described in the next section. -@end table - -@node Representation Clauses -@section Representation Clauses - -@noindent -The Ada 83 reference manual was quite vague in describing both the minimal -required implementation of representation clauses, and also their precise -effects. Ada 95 (and thus also Ada 2005) are much more explicit, but the -minimal set of capabilities required is still quite limited. - -GNAT implements the full required set of capabilities in -Ada 95 and Ada 2005, but also goes much further, and in particular -an effort has been made to be compatible with existing Ada 83 usage to the -greatest extent possible. - -A few cases exist in which Ada 83 compiler behavior is incompatible with -the requirements in Ada 95 (and thus also Ada 2005). These are instances of -intentional or accidental dependence on specific implementation dependent -characteristics of these Ada 83 compilers. The following is a list of -the cases most likely to arise in existing Ada 83 code. - -@table @emph -@item Implicit Packing -Some Ada 83 compilers allowed a Size specification to cause implicit -packing of an array or record. This could cause expensive implicit -conversions for change of representation in the presence of derived -types, and the Ada design intends to avoid this possibility. -Subsequent AI's were issued to make it clear that such implicit -change of representation in response to a Size clause is inadvisable, -and this recommendation is represented explicitly in the Ada 95 (and Ada 2005) -Reference Manuals as implementation advice that is followed by GNAT@. -The problem will show up as an error -message rejecting the size clause. The fix is simply to provide -the explicit pragma @code{Pack}, or for more fine tuned control, provide -a Component_Size clause. - -@item Meaning of Size Attribute -The Size attribute in Ada 95 (and Ada 2005) for discrete types is defined as -the minimal number of bits required to hold values of the type. For example, -on a 32-bit machine, the size of @code{Natural} will typically be 31 and not -32 (since no sign bit is required). Some Ada 83 compilers gave 31, and -some 32 in this situation. This problem will usually show up as a compile -time error, but not always. It is a good idea to check all uses of the -'Size attribute when porting Ada 83 code. The GNAT specific attribute -Object_Size can provide a useful way of duplicating the behavior of -some Ada 83 compiler systems. - -@item Size of Access Types -A common assumption in Ada 83 code is that an access type is in fact a pointer, -and that therefore it will be the same size as a System.Address value. This -assumption is true for GNAT in most cases with one exception. For the case of -a pointer to an unconstrained array type (where the bounds may vary from one -value of the access type to another), the default is to use a ``fat pointer'', -which is represented as two separate pointers, one to the bounds, and one to -the array. This representation has a number of advantages, including improved -efficiency. However, it may cause some difficulties in porting existing Ada 83 -code which makes the assumption that, for example, pointers fit in 32 bits on -a machine with 32-bit addressing. - -To get around this problem, GNAT also permits the use of ``thin pointers'' for -access types in this case (where the designated type is an unconstrained array -type). These thin pointers are indeed the same size as a System.Address value. -To specify a thin pointer, use a size clause for the type, for example: - -@smallexample @c ada -@b{type} X @b{is} @b{access} @b{all} String; -@b{for} X'Size @b{use} Standard'Address_Size; -@end smallexample - -@noindent -which will cause the type X to be represented using a single pointer. -When using this representation, the bounds are right behind the array. -This representation is slightly less efficient, and does not allow quite -such flexibility in the use of foreign pointers or in using the -Unrestricted_Access attribute to create pointers to non-aliased objects. -But for any standard portable use of the access type it will work in -a functionally correct manner and allow porting of existing code. -Note that another way of forcing a thin pointer representation -is to use a component size clause for the element size in an array, -or a record representation clause for an access field in a record. - -See the documentation of Unrestricted_Access in the GNAT RM for a -full discussion of possible problems using this attribute in conjunction -with thin pointers. -@end table - -@c This brief section is only in the non-VMS version -@c The complete chapter on HP Ada is in the VMS version -@node Compatibility with HP Ada 83 -@section Compatibility with HP Ada 83 - -@noindent -The VMS version of GNAT fully implements all the pragmas and attributes -provided by HP Ada 83, as well as providing the standard HP Ada 83 -libraries, including Starlet. In addition, data layouts and parameter -passing conventions are highly compatible. This means that porting -existing HP Ada 83 code to GNAT in VMS systems should be easier than -most other porting efforts. The following are some of the most -significant differences between GNAT and HP Ada 83. - -@table @emph -@item Default floating-point representation -In GNAT, the default floating-point format is IEEE, whereas in HP Ada 83, -it is VMS format. GNAT does implement the necessary pragmas -(Long_Float, Float_Representation) for changing this default. - -@item System -The package System in GNAT exactly corresponds to the definition in the -Ada 95 reference manual, which means that it excludes many of the -HP Ada 83 extensions. However, a separate package Aux_DEC is provided -that contains the additional definitions, and a special pragma, -Extend_System allows this package to be treated transparently as an -extension of package System. - -@item To_Address -The definitions provided by Aux_DEC are exactly compatible with those -in the HP Ada 83 version of System, with one exception. -HP Ada provides the following declarations: - -@smallexample @c ada -TO_ADDRESS (INTEGER) -TO_ADDRESS (UNSIGNED_LONGWORD) -TO_ADDRESS (@i{universal_integer}) -@end smallexample - -@noindent -The version of TO_ADDRESS taking a @i{universal integer} argument is in fact -an extension to Ada 83 not strictly compatible with the reference manual. -In GNAT, we are constrained to be exactly compatible with the standard, -and this means we cannot provide this capability. In HP Ada 83, the -point of this definition is to deal with a call like: - -@smallexample @c ada -TO_ADDRESS (16#12777#); -@end smallexample - -@noindent -Normally, according to the Ada 83 standard, one would expect this to be -ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms -of TO_ADDRESS@. However, in HP Ada 83, there is no ambiguity, since the -definition using @i{universal_integer} takes precedence. - -In GNAT, since the version with @i{universal_integer} cannot be supplied, it -is not possible to be 100% compatible. Since there are many programs using -numeric constants for the argument to TO_ADDRESS, the decision in GNAT was -to change the name of the function in the UNSIGNED_LONGWORD case, so the -declarations provided in the GNAT version of AUX_Dec are: - -@smallexample @c ada -@b{function} To_Address (X : Integer) @b{return} Address; -@b{pragma} Pure_Function (To_Address); - -@b{function} To_Address_Long (X : Unsigned_Longword) - @b{return} Address; -@b{pragma} Pure_Function (To_Address_Long); -@end smallexample - -@noindent -This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must -change the name to TO_ADDRESS_LONG@. - -@item Task_Id values -The Task_Id values assigned will be different in the two systems, and GNAT -does not provide a specified value for the Task_Id of the environment task, -which in GNAT is treated like any other declared task. -@end table - -@noindent -For full details on these and other less significant compatibility issues, -see appendix E of the HP publication entitled @cite{HP Ada, Technical -Overview and Comparison on HP Platforms}. - -For GNAT running on other than VMS systems, all the HP Ada 83 pragmas and -attributes are recognized, although only a subset of them can sensibly -be implemented. The description of pragmas in @ref{Implementation -Defined Pragmas,,, gnat_rm, GNAT Reference Manual} -indicates whether or not they are applicable to non-VMS systems. - - -@c ************************************************ -@node Microsoft Windows Topics -@appendix Microsoft Windows Topics -@cindex Windows NT -@cindex Windows 95 -@cindex Windows 98 - -@noindent -This chapter describes topics that are specific to the Microsoft Windows -platforms (NT, 2000, and XP Professional). +@geindex -gnatyd (gcc) -@menu -@ifclear FSFEDITION -* Installing from the Command Line:: -@end ifclear -* Using GNAT on Windows:: -* Using a network installation of GNAT:: -* CONSOLE and WINDOWS subsystems:: -* Temporary Files:: -* Mixed-Language Programming on Windows:: -* Windows Calling Conventions:: -* Introduction to Dynamic Link Libraries (DLLs):: -* Using DLLs with GNAT:: -* Building DLLs with GNAT Project files:: -* Building DLLs with GNAT:: -* Building DLLs with gnatdll:: -* GNAT and Windows Resources:: -* Debugging a DLL:: -* Setting Stack Size from gnatlink:: -* Setting Heap Size from gnatlink:: -@end menu -@ifclear FSFEDITION -@node Installing from the Command Line -@section Installing from the Command Line -@cindex Batch installation -@cindex Silent installation -@cindex Unassisted installation +@table @asis -@noindent -By default the @value{EDITION} installers display a GUI that prompts the user -to enter installation path and similar information, and guide him through the -installation process. It is also possible to perform silent installations -using the command-line interface. +@item @code{-gnatyd} -In order to install one of the @value{EDITION} installers from the command -line you should pass parameter @code{/S} (and, optionally, -@code{/D=}) as command-line arguments. +@emph{Check no DOS line terminators present.} -@ifset PROEDITION -For example, for an unattended installation of -@value{EDITION} 7.0.2 into the default directory -@code{C:\GNATPRO\7.0.2} you would run: +All lines must be terminated by a single ASCII.LF +character (in particular the DOS line terminator sequence CR/LF is not +allowed). +@end table -@smallexample -gnatpro-7.0.2-i686-pc-mingw32-bin.exe /S -@end smallexample +@geindex -gnatye (gcc) -To install into a custom directory, say, @code{C:\TOOLS\GNATPRO\7.0.2}: -@smallexample -gnatpro-7.0.2-i686-pc-mingw32-bin /S /D=C:\TOOLS\GNATPRO\7.0.2 -@end smallexample -@end ifset +@table @asis -@ifset GPLEDITION -For example, for an unattended installation of -@value{EDITION} 2012 into @code{C:\GNAT\2012}: +@item @code{-gnatye} -@smallexample -gnat-gpl-2012-i686-pc-mingw32-bin /S /D=C:\GNAT\2012 -@end smallexample -@end ifset +@emph{Check end/exit labels.} -You can use the same syntax for all installers. +Optional labels on @cite{end} statements ending subprograms and on +@cite{exit} statements exiting named loops, are required to be present. +@end table -Note that unattended installations don't modify system path, nor create file -associations, so such activities need to be done by hand. -@end ifclear +@geindex -gnatyf (gcc) -@node Using GNAT on Windows -@section Using GNAT on Windows -@noindent -One of the strengths of the GNAT technology is that its tool set -(@command{gcc}, @command{gnatbind}, @command{gnatlink}, @command{gnatmake}, the -@code{gdb} debugger, etc.) is used in the same way regardless of the -platform. +@table @asis -On Windows this tool set is complemented by a number of Microsoft-specific -tools that have been provided to facilitate interoperability with Windows -when this is required. With these tools: +@item @code{-gnatyf} -@itemize @bullet +@emph{No form feeds or vertical tabs.} -@item -You can build applications using the @code{CONSOLE} or @code{WINDOWS} -subsystems. +Neither form feeds nor vertical tab characters are permitted +in the source text. +@end table -@item -You can use any Dynamically Linked Library (DLL) in your Ada code (both -relocatable and non-relocatable DLLs are supported). +@geindex -gnatyg (gcc) -@item -You can build Ada DLLs for use in other applications. These applications -can be written in a language other than Ada (e.g., C, C++, etc). Again both -relocatable and non-relocatable Ada DLLs are supported. -@item -You can include Windows resources in your Ada application. +@table @asis -@item -You can use or create COM/DCOM objects. -@end itemize +@item @code{-gnatyg} -@noindent -Immediately below are listed all known general GNAT-for-Windows restrictions. -Other restrictions about specific features like Windows Resources and DLLs -are listed in separate sections below. +@emph{GNAT style mode.} -@itemize @bullet +The set of style check switches is set to match that used by the GNAT sources. +This may be useful when developing code that is eventually intended to be +incorporated into GNAT. Currently this is equivalent to @emph{-gnatwydISux}) +but additional style switches may be added to this set in the future without +advance notice. +@end table -@item -It is not possible to use @code{GetLastError} and @code{SetLastError} -when tasking, protected records, or exceptions are used. In these -cases, in order to implement Ada semantics, the GNAT run-time system -calls certain Win32 routines that set the last error variable to 0 upon -success. It should be possible to use @code{GetLastError} and -@code{SetLastError} when tasking, protected record, and exception -features are not used, but it is not guaranteed to work. +@geindex -gnatyh (gcc) -@item -It is not possible to link against Microsoft C++ libraries except for -import libraries. Interfacing must be done by the mean of DLLs. -@item -It is possible to link against Microsoft C libraries. Yet the preferred -solution is to use C/C++ compiler that comes with @value{EDITION}, since it -doesn't require having two different development environments and makes the -inter-language debugging experience smoother. +@table @asis -@item -When the compilation environment is located on FAT32 drives, users may -experience recompilations of the source files that have not changed if -Daylight Saving Time (DST) state has changed since the last time files -were compiled. NTFS drives do not have this problem. +@item @code{-gnatyh} -@item -No components of the GNAT toolset use any entries in the Windows -registry. The only entries that can be created are file associations and -PATH settings, provided the user has chosen to create them at installation -time, as well as some minimal book-keeping information needed to correctly -uninstall or integrate different GNAT products. -@end itemize +@emph{No horizontal tabs.} -@node Using a network installation of GNAT -@section Using a network installation of GNAT +Horizontal tab characters are not permitted in the source text. +Together with the b (no blanks at end of line) check, this +enforces a canonical form for the use of blanks to separate +source tokens. +@end table -@noindent -Make sure the system on which GNAT is installed is accessible from the -current machine, i.e., the install location is shared over the network. -Shared resources are accessed on Windows by means of UNC paths, which -have the format @code{\\server\sharename\path} +@geindex -gnatyi (gcc) -In order to use such a network installation, simply add the UNC path of the -@file{bin} directory of your GNAT installation in front of your PATH. For -example, if GNAT is installed in @file{\GNAT} directory of a share location -called @file{c-drive} on a machine @file{LOKI}, the following command will -make it available: -@code{@ @ @ path \\loki\c-drive\gnat\bin;%path%} +@table @asis -Be aware that every compilation using the network installation results in the -transfer of large amounts of data across the network and will likely cause -serious performance penalty. +@item @code{-gnatyi} -@node CONSOLE and WINDOWS subsystems -@section CONSOLE and WINDOWS subsystems -@cindex CONSOLE Subsystem -@cindex WINDOWS Subsystem -@cindex -mwindows +@emph{Check if-then layout.} -@noindent -There are two main subsystems under Windows. The @code{CONSOLE} subsystem -(which is the default subsystem) will always create a console when -launching the application. This is not something desirable when the -application has a Windows GUI. To get rid of this console the -application must be using the @code{WINDOWS} subsystem. To do so -the @option{-mwindows} linker option must be specified. +The keyword @cite{then} must appear either on the same +line as corresponding @cite{if}, or on a line on its own, lined +up under the @cite{if}. +@end table -@smallexample -$ gnatmake winprog -largs -mwindows -@end smallexample +@geindex -gnatyI (gcc) -@node Temporary Files -@section Temporary Files -@cindex Temporary files -@noindent -It is possible to control where temporary files gets created by setting -the @env{TMP} environment variable. The file will be created: +@table @asis -@itemize -@item Under the directory pointed to by the @env{TMP} environment variable if -this directory exists. +@item @code{-gnatyI} -@item Under @file{c:\temp}, if the @env{TMP} environment variable is not -set (or not pointing to a directory) and if this directory exists. +@emph{check mode IN keywords.} -@item Under the current working directory otherwise. -@end itemize +Mode @cite{in} (the default mode) is not +allowed to be given explicitly. @cite{in out} is fine, +but not @cite{in} on its own. +@end table -@noindent -This allows you to determine exactly where the temporary -file will be created. This is particularly useful in networked -environments where you may not have write access to some -directories. +@geindex -gnatyk (gcc) -@node Mixed-Language Programming on Windows -@section Mixed-Language Programming on Windows -@noindent -Developing pure Ada applications on Windows is no different than on -other GNAT-supported platforms. However, when developing or porting an -application that contains a mix of Ada and C/C++, the choice of your -Windows C/C++ development environment conditions your overall -interoperability strategy. +@table @asis -If you use @command{gcc} or Microsoft C to compile the non-Ada part of -your application, there are no Windows-specific restrictions that -affect the overall interoperability with your Ada code. If you do want -to use the Microsoft tools for your C++ code, you have two choices: +@item @code{-gnatyk} -@enumerate -@item -Encapsulate your C++ code in a DLL to be linked with your Ada -application. In this case, use the Microsoft or whatever environment to -build the DLL and use GNAT to build your executable -(@pxref{Using DLLs with GNAT}). +@emph{Check keyword casing.} -@item -Or you can encapsulate your Ada code in a DLL to be linked with the -other part of your application. In this case, use GNAT to build the DLL -(@pxref{Building DLLs with GNAT Project files}) and use the Microsoft -or whatever environment to build your executable. -@end enumerate +All keywords must be in lower case (with the exception of keywords +such as @cite{digits} used as attribute names to which this check +does not apply). +@end table -In addition to the description about C main in -@pxref{Mixed Language Programming} section, if the C main uses a -stand-alone library it is required on x86-windows to -setup the SEH context. For this the C main must looks like this: +@geindex -gnatyl (gcc) -@smallexample -/* main.c */ -extern void adainit (void); -extern void adafinal (void); -extern void __gnat_initialize(void*); -extern void call_to_ada (void); -int main (int argc, char *argv[]) -@{ - int SEH [2]; +@table @asis - /* Initialize the SEH context */ - __gnat_initialize (&SEH); +@item @code{-gnatyl} - adainit(); +@emph{Check layout.} - /* Then call Ada services in the stand-alone library */ +Layout of statement and declaration constructs must follow the +recommendations in the Ada Reference Manual, as indicated by the +form of the syntax rules. For example an @cite{else} keyword must +be lined up with the corresponding @cite{if} keyword. - call_to_ada(); +There are two respects in which the style rule enforced by this check +option are more liberal than those in the Ada Reference Manual. First +in the case of record declarations, it is permissible to put the +@cite{record} keyword on the same line as the @cite{type} keyword, and +then the @cite{end} in @cite{end record} must line up under @cite{type}. +This is also permitted when the type declaration is split on two lines. +For example, any of the following three layouts is acceptable: - adafinal(); -@} -@end smallexample +@example +type q is record + a : integer; + b : integer; +end record; -Note that this is not needed on x86_64-windows where the Windows -native SEH support is used. +type q is + record + a : integer; + b : integer; + end record; -@node Windows Calling Conventions -@section Windows Calling Conventions -@findex Stdcall -@findex APIENTRY +type q is + record + a : integer; + b : integer; +end record; +@end example -This section pertain only to Win32. On Win64 there is a single native -calling convention. All convention specifiers are ignored on this -platform. +Second, in the case of a block statement, a permitted alternative +is to put the block label on the same line as the @cite{declare} or +@cite{begin} keyword, and then line the @cite{end} keyword up under +the block label. For example both the following are permitted: -@menu -* C Calling Convention:: -* Stdcall Calling Convention:: -* Win32 Calling Convention:: -* DLL Calling Convention:: -@end menu +@example +Block : declare + A : Integer := 3; +begin + Proc (A, A); +end Block; -@noindent -When a subprogram @code{F} (caller) calls a subprogram @code{G} -(callee), there are several ways to push @code{G}'s parameters on the -stack and there are several possible scenarios to clean up the stack -upon @code{G}'s return. A calling convention is an agreed upon software -protocol whereby the responsibilities between the caller (@code{F}) and -the callee (@code{G}) are clearly defined. Several calling conventions -are available for Windows: +Block : + declare + A : Integer := 3; + begin + Proc (A, A); + end Block; +@end example -@itemize @bullet -@item -@code{C} (Microsoft defined) +The same alternative format is allowed for loops. For example, both of +the following are permitted: -@item -@code{Stdcall} (Microsoft defined) +@example +Clear : while J < 10 loop + A (J) := 0; +end loop Clear; -@item -@code{Win32} (GNAT specific) +Clear : + while J < 10 loop + A (J) := 0; + end loop Clear; +@end example +@end table -@item -@code{DLL} (GNAT specific) -@end itemize +@geindex -gnatyLnnn (gcc) -@node C Calling Convention -@subsection @code{C} Calling Convention -@noindent -This is the default calling convention used when interfacing to C/C++ -routines compiled with either @command{gcc} or Microsoft Visual C++. +@table @asis -In the @code{C} calling convention subprogram parameters are pushed on the -stack by the caller from right to left. The caller itself is in charge of -cleaning up the stack after the call. In addition, the name of a routine -with @code{C} calling convention is mangled by adding a leading underscore. +@item @code{-gnatyL} -The name to use on the Ada side when importing (or exporting) a routine -with @code{C} calling convention is the name of the routine. For -instance the C function: +@emph{Set maximum nesting level.} -@smallexample -int get_val (long); -@end smallexample +The maximum level of nesting of constructs (including subprograms, loops, +blocks, packages, and conditionals) may not exceed the given value +@emph{nnn}. A value of zero disconnects this style check. +@end table -@noindent -should be imported from Ada as follows: +@geindex -gnatym (gcc) -@smallexample @c ada -@group -@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int; -@b{pragma} Import (C, Get_Val, External_Name => "get_val"); -@end group -@end smallexample -@noindent -Note that in this particular case the @code{External_Name} parameter could -have been omitted since, when missing, this parameter is taken to be the -name of the Ada entity in lower case. When the @code{Link_Name} parameter -is missing, as in the above example, this parameter is set to be the -@code{External_Name} with a leading underscore. +@table @asis -When importing a variable defined in C, you should always use the @code{C} -calling convention unless the object containing the variable is part of a -DLL (in which case you should use the @code{Stdcall} calling -convention, @pxref{Stdcall Calling Convention}). +@item @code{-gnatym} -@node Stdcall Calling Convention -@subsection @code{Stdcall} Calling Convention +@emph{Check maximum line length.} -@noindent -This convention, which was the calling convention used for Pascal -programs, is used by Microsoft for all the routines in the Win32 API for -efficiency reasons. It must be used to import any routine for which this -convention was specified. +The length of source lines must not exceed 79 characters, including +any trailing blanks. The value of 79 allows convenient display on an +80 character wide device or window, allowing for possible special +treatment of 80 character lines. Note that this count is of +characters in the source text. This means that a tab character counts +as one character in this count and a wide character sequence counts as +a single character (however many bytes are needed in the encoding). +@end table -In the @code{Stdcall} calling convention subprogram parameters are pushed -on the stack by the caller from right to left. The callee (and not the -caller) is in charge of cleaning the stack on routine exit. In addition, -the name of a routine with @code{Stdcall} calling convention is mangled by -adding a leading underscore (as for the @code{C} calling convention) and a -trailing @code{@@}@code{@var{nn}}, where @var{nn} is the overall size (in -bytes) of the parameters passed to the routine. +@geindex -gnatyMnnn (gcc) -The name to use on the Ada side when importing a C routine with a -@code{Stdcall} calling convention is the name of the C routine. The leading -underscore and trailing @code{@@}@code{@var{nn}} are added automatically by -the compiler. For instance the Win32 function: -@smallexample -@b{APIENTRY} int get_val (long); -@end smallexample +@table @asis -@noindent -should be imported from Ada as follows: +@item @code{-gnatyM} -@smallexample @c ada -@group -@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int; -@b{pragma} Import (Stdcall, Get_Val); ---@i{ On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"} -@end group -@end smallexample +@emph{Set maximum line length.} -@noindent -As for the @code{C} calling convention, when the @code{External_Name} -parameter is missing, it is taken to be the name of the Ada entity in lower -case. If instead of writing the above import pragma you write: +The length of lines must not exceed the +given value @emph{nnn}. The maximum value that can be specified is 32767. +If neither style option for setting the line length is used, then the +default is 255. This also controls the maximum length of lexical elements, +where the only restriction is that they must fit on a single line. +@end table -@smallexample @c ada -@group -@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int; -@b{pragma} Import (Stdcall, Get_Val, External_Name => "retrieve_val"); -@end group -@end smallexample - -@noindent -then the imported routine is @code{_retrieve_val@@4}. However, if instead -of specifying the @code{External_Name} parameter you specify the -@code{Link_Name} as in the following example: - -@smallexample @c ada -@group -@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int; -@b{pragma} Import (Stdcall, Get_Val, Link_Name => "retrieve_val"); -@end group -@end smallexample - -@noindent -then the imported routine is @code{retrieve_val}, that is, there is no -decoration at all. No leading underscore and no Stdcall suffix -@code{@@}@code{@var{nn}}. +@geindex -gnatyn (gcc) -@noindent -This is especially important as in some special cases a DLL's entry -point name lacks a trailing @code{@@}@code{@var{nn}} while the exported -name generated for a call has it. -@noindent -It is also possible to import variables defined in a DLL by using an -import pragma for a variable. As an example, if a DLL contains a -variable defined as: +@table @asis -@smallexample -int my_var; -@end smallexample +@item @code{-gnatyn} -@noindent -then, to access this variable from Ada you should write: +@emph{Check casing of entities in Standard.} -@smallexample @c ada -@group -My_Var : Interfaces.C.int; -@b{pragma} Import (Stdcall, My_Var); -@end group -@end smallexample +Any identifier from Standard must be cased +to match the presentation in the Ada Reference Manual (for example, +@cite{Integer} and @cite{ASCII.NUL}). +@end table -@noindent -Note that to ease building cross-platform bindings this convention -will be handled as a @code{C} calling convention on non-Windows platforms. +@geindex -gnatyN (gcc) -@node Win32 Calling Convention -@subsection @code{Win32} Calling Convention -@noindent -This convention, which is GNAT-specific is fully equivalent to the -@code{Stdcall} calling convention described above. +@table @asis -@node DLL Calling Convention -@subsection @code{DLL} Calling Convention +@item @code{-gnatyN} -@noindent -This convention, which is GNAT-specific is fully equivalent to the -@code{Stdcall} calling convention described above. +@emph{Turn off all style checks.} -@node Introduction to Dynamic Link Libraries (DLLs) -@section Introduction to Dynamic Link Libraries (DLLs) -@findex DLL +All style check options are turned off. +@end table -@noindent -A Dynamically Linked Library (DLL) is a library that can be shared by -several applications running under Windows. A DLL can contain any number of -routines and variables. +@geindex -gnatyo (gcc) -One advantage of DLLs is that you can change and enhance them without -forcing all the applications that depend on them to be relinked or -recompiled. However, you should be aware than all calls to DLL routines are -slower since, as you will understand below, such calls are indirect. -To illustrate the remainder of this section, suppose that an application -wants to use the services of a DLL @file{API.dll}. To use the services -provided by @file{API.dll} you must statically link against the DLL or -an import library which contains a jump table with an entry for each -routine and variable exported by the DLL. In the Microsoft world this -import library is called @file{API.lib}. When using GNAT this import -library is called either @file{libAPI.dll.a}, @file{libapi.dll.a}, -@file{libAPI.a} or @file{libapi.a} (names are case insensitive). +@table @asis -After you have linked your application with the DLL or the import library -and you run your application, here is what happens: +@item @code{-gnatyo} -@enumerate -@item -Your application is loaded into memory. +@emph{Check order of subprogram bodies.} -@item -The DLL @file{API.dll} is mapped into the address space of your -application. This means that: +All subprogram bodies in a given scope +(e.g., a package body) must be in alphabetical order. The ordering +rule uses normal Ada rules for comparing strings, ignoring casing +of letters, except that if there is a trailing numeric suffix, then +the value of this suffix is used in the ordering (e.g., Junk2 comes +before Junk10). +@end table -@itemize @bullet -@item -The DLL will use the stack of the calling thread. +@geindex -gnatyO (gcc) -@item -The DLL will use the virtual address space of the calling process. -@item -The DLL will allocate memory from the virtual address space of the calling -process. +@table @asis -@item -Handles (pointers) can be safely exchanged between routines in the DLL -routines and routines in the application using the DLL. -@end itemize +@item @code{-gnatyO} -@item -The entries in the jump table (from the import library @file{libAPI.dll.a} -or @file{API.lib} or automatically created when linking against a DLL) -which is part of your application are initialized with the addresses -of the routines and variables in @file{API.dll}. +@emph{Check that overriding subprograms are explicitly marked as such.} -@item -If present in @file{API.dll}, routines @code{DllMain} or -@code{DllMainCRTStartup} are invoked. These routines typically contain -the initialization code needed for the well-being of the routines and -variables exported by the DLL. -@end enumerate +The declaration of a primitive operation of a type extension that overrides +an inherited operation must carry an overriding indicator. +@end table -@noindent -There is an additional point which is worth mentioning. In the Windows -world there are two kind of DLLs: relocatable and non-relocatable -DLLs. Non-relocatable DLLs can only be loaded at a very specific address -in the target application address space. If the addresses of two -non-relocatable DLLs overlap and these happen to be used by the same -application, a conflict will occur and the application will run -incorrectly. Hence, when possible, it is always preferable to use and -build relocatable DLLs. Both relocatable and non-relocatable DLLs are -supported by GNAT. Note that the @option{-s} linker option (see GNU Linker -User's Guide) removes the debugging symbols from the DLL but the DLL can -still be relocated. +@geindex -gnatyp (gcc) -As a side note, an interesting difference between Microsoft DLLs and -Unix shared libraries, is the fact that on most Unix systems all public -routines are exported by default in a Unix shared library, while under -Windows it is possible (but not required) to list exported routines in -a definition file (@pxref{The Definition File}). -@node Using DLLs with GNAT -@section Using DLLs with GNAT +@table @asis -@menu -* Creating an Ada Spec for the DLL Services:: -* Creating an Import Library:: -@end menu +@item @code{-gnatyp} -@noindent -To use the services of a DLL, say @file{API.dll}, in your Ada application -you must have: +@emph{Check pragma casing.} -@enumerate -@item -The Ada spec for the routines and/or variables you want to access in -@file{API.dll}. If not available this Ada spec must be built from the C/C++ -header files provided with the DLL. +Pragma names must be written in mixed case, that is, the +initial letter and any letter following an underscore must be uppercase. +All other letters must be lowercase. An exception is that SPARK_Mode is +allowed as an alternative for Spark_Mode. +@end table -@item -The import library (@file{libAPI.dll.a} or @file{API.lib}). As previously -mentioned an import library is a statically linked library containing the -import table which will be filled at load time to point to the actual -@file{API.dll} routines. Sometimes you don't have an import library for the -DLL you want to use. The following sections will explain how to build -one. Note that this is optional. +@geindex -gnatyr (gcc) -@item -The actual DLL, @file{API.dll}. -@end enumerate -@noindent -Once you have all the above, to compile an Ada application that uses the -services of @file{API.dll} and whose main subprogram is @code{My_Ada_App}, -you simply issue the command +@table @asis -@smallexample -$ gnatmake my_ada_app -largs -lAPI -@end smallexample +@item @code{-gnatyr} -@noindent -The argument @option{-largs -lAPI} at the end of the @command{gnatmake} command -tells the GNAT linker to look for an import library. The linker will -look for a library name in this specific order: +@emph{Check references.} -@enumerate -@item @file{libAPI.dll.a} -@item @file{API.dll.a} -@item @file{libAPI.a} -@item @file{API.lib} -@item @file{libAPI.dll} -@item @file{API.dll} -@end enumerate +All identifier references must be cased in the same way as the +corresponding declaration. No specific casing style is imposed on +identifiers. The only requirement is for consistency of references +with declarations. +@end table -The first three are the GNU style import libraries. The third is the -Microsoft style import libraries. The last two are the actual DLL names. +@geindex -gnatys (gcc) -Note that if the Ada package spec for @file{API.dll} contains the -following pragma -@smallexample @c ada -@b{pragma} Linker_Options ("-lAPI"); -@end smallexample +@table @asis -@noindent -you do not have to add @option{-largs -lAPI} at the end of the -@command{gnatmake} command. +@item @code{-gnatys} -If any one of the items above is missing you will have to create it -yourself. The following sections explain how to do so using as an -example a fictitious DLL called @file{API.dll}. +@emph{Check separate specs.} -@node Creating an Ada Spec for the DLL Services -@subsection Creating an Ada Spec for the DLL Services +Separate declarations ('specs') are required for subprograms (a +body is not allowed to serve as its own declaration). The only +exception is that parameterless library level procedures are +not required to have a separate declaration. This exception covers +the most frequent form of main program procedures. +@end table -@noindent -A DLL typically comes with a C/C++ header file which provides the -definitions of the routines and variables exported by the DLL. The Ada -equivalent of this header file is a package spec that contains definitions -for the imported entities. If the DLL you intend to use does not come with -an Ada spec you have to generate one such spec yourself. For example if -the header file of @file{API.dll} is a file @file{api.h} containing the -following two definitions: +@geindex -gnatyS (gcc) -@smallexample -@group -@cartouche -int some_var; -int get (char *); -@end cartouche -@end group -@end smallexample -@noindent -then the equivalent Ada spec could be: +@table @asis -@smallexample @c ada -@group -@cartouche -@b{with} Interfaces.C.Strings; -@b{package} API @b{is} - @b{use} Interfaces; +@item @code{-gnatyS} - Some_Var : C.int; - @b{function} Get (Str : C.Strings.Chars_Ptr) @b{return} C.int; +@emph{Check no statements after then/else.} -@b{private} - @b{pragma} Import (C, Get); - @b{pragma} Import (DLL, Some_Var); -@b{end} API; -@end cartouche -@end group -@end smallexample +No statements are allowed +on the same line as a @cite{then} or @cite{else} keyword following the +keyword in an @cite{if} statement. @cite{or else} and @cite{and then} are not +affected, and a special exception allows a pragma to appear after @cite{else}. +@end table -@node Creating an Import Library -@subsection Creating an Import Library -@cindex Import library +@geindex -gnatyt (gcc) -@menu -* The Definition File:: -* GNAT-Style Import Library:: -* Microsoft-Style Import Library:: -@end menu -@noindent -If a Microsoft-style import library @file{API.lib} or a GNAT-style -import library @file{libAPI.dll.a} or @file{libAPI.a} is available -with @file{API.dll} you can skip this section. You can also skip this -section if @file{API.dll} or @file{libAPI.dll} is built with GNU tools -as in this case it is possible to link directly against the -DLL. Otherwise read on. +@table @asis -@node The Definition File -@subsubsection The Definition File -@cindex Definition file -@findex .def +@item @code{-gnatyt} -@noindent -As previously mentioned, and unlike Unix systems, the list of symbols -that are exported from a DLL must be provided explicitly in Windows. -The main goal of a definition file is precisely that: list the symbols -exported by a DLL. A definition file (usually a file with a @code{.def} -suffix) has the following structure: +@emph{Check token spacing.} -@smallexample -@group -@cartouche -@r{[}LIBRARY @var{name}@r{]} -@r{[}DESCRIPTION @var{string}@r{]} -EXPORTS - @var{symbol1} - @var{symbol2} - @dots{} -@end cartouche -@end group -@end smallexample +The following token spacing rules are enforced: -@table @code -@item LIBRARY @var{name} -This section, which is optional, gives the name of the DLL. -@item DESCRIPTION @var{string} -This section, which is optional, gives a description string that will be -embedded in the import library. +@itemize * -@item EXPORTS -This section gives the list of exported symbols (procedures, functions or -variables). For instance in the case of @file{API.dll} the @code{EXPORTS} -section of @file{API.def} looks like: +@item +The keywords @cite{abs} and @cite{not} must be followed by a space. -@smallexample -@group -@cartouche -EXPORTS - some_var - get -@end cartouche -@end group -@end smallexample -@end table +@item +The token @cite{=>} must be surrounded by spaces. -@noindent -Note that you must specify the correct suffix (@code{@@}@code{@var{nn}}) -(@pxref{Windows Calling Conventions}) for a Stdcall -calling convention function in the exported symbols list. +@item +The token @cite{<>} must be preceded by a space or a left parenthesis. + +@item +Binary operators other than @cite{**} must be surrounded by spaces. +There is no restriction on the layout of the @cite{**} binary operator. + +@item +Colon must be surrounded by spaces. + +@item +Colon-equal (assignment, initialization) must be surrounded by spaces. + +@item +Comma must be the first non-blank character on the line, or be +immediately preceded by a non-blank character, and must be followed +by a space. + +@item +If the token preceding a left parenthesis ends with a letter or digit, then +a space must separate the two tokens. + +@item +If the token following a right parenthesis starts with a letter or digit, then +a space must separate the two tokens. + +@item +A right parenthesis must either be the first non-blank character on +a line, or it must be preceded by a non-blank character. + +@item +A semicolon must not be preceded by a space, and must not be followed by +a non-blank character. + +@item +A unary plus or minus may not be followed by a space. + +@item +A vertical bar must be surrounded by spaces. +@end itemize + +Exactly one blank (and no other white space) must appear between +a @cite{not} token and a following @cite{in} token. +@end table + +@geindex -gnatyu (gcc) + + +@table @asis + +@item @code{-gnatyu} + +@emph{Check unnecessary blank lines.} + +Unnecessary blank lines are not allowed. A blank line is considered +unnecessary if it appears at the end of the file, or if more than +one blank line occurs in sequence. +@end table + +@geindex -gnatyx (gcc) + + +@table @asis + +@item @code{-gnatyx} + +@emph{Check extra parentheses.} + +Unnecessary extra level of parentheses (C-style) are not allowed +around conditions in @cite{if} statements, @cite{while} statements and +@cite{exit} statements. +@end table + +@geindex -gnatyy (gcc) + + +@table @asis + +@item @code{-gnatyy} + +@emph{Set all standard style check options} + +This is equivalent to @cite{gnaty3aAbcefhiklmnprst}, that is all checking +options enabled with the exception of @emph{-gnatyB}, @emph{-gnatyd}, +@emph{-gnatyI}, @emph{-gnatyLnnn}, @emph{-gnatyo}, @emph{-gnatyO}, +@emph{-gnatyS}, @emph{-gnatyu}, and @emph{-gnatyx}. +@end table + +@geindex -gnaty- (gcc) + + +@table @asis + +@item @code{-gnaty-} + +@emph{Remove style check options} + +This causes any subsequent options in the string to act as canceling the +corresponding style check option. To cancel maximum nesting level control, +use @emph{L} parameter witout any integer value after that, because any +digit following @emph{-} in the parameter string of the @emph{-gnaty} +option will be threated as canceling indentation check. The same is true +for @emph{M} parameter. @emph{y} and @emph{N} parameters are not +allowed after @emph{-}. +@end table + +@geindex -gnaty+ (gcc) + + +@table @asis + +@item @code{-gnaty+} + +@emph{Enable style check options} + +This causes any subsequent options in the string to enable the corresponding +style check option. That is, it cancels the effect of a previous -, +if any. +@end table + +@c end of switch description (leave this comment to ease automatic parsing for + +@c GPS + +In the above rules, appearing in column one is always permitted, that is, +counts as meeting either a requirement for a required preceding space, +or as meeting a requirement for no preceding space. + +Appearing at the end of a line is also always permitted, that is, counts +as meeting either a requirement for a following space, or as meeting +a requirement for no following space. + +If any of these style rules is violated, a message is generated giving +details on the violation. The initial characters of such messages are +always '@cite{(style)}'. Note that these messages are treated as warning +messages, so they normally do not prevent the generation of an object +file. The @emph{-gnatwe} switch can be used to treat warning messages, +including style messages, as fatal errors. + +The switch @code{-gnaty} on its own (that is not +followed by any letters or digits) is equivalent +to the use of @emph{-gnatyy} as described above, that is all +built-in standard style check options are enabled. + +The switch @code{-gnatyN} clears any previously set style checks. + +@node Run-Time Checks,Using gcc for Syntax Checking,Style Checking,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat run-time-checks}@anchor{fe}@anchor{gnat_ugn/building_executable_programs_with_gnat id19}@anchor{109} +@subsection Run-Time Checks + + +@geindex Division by zero + +@geindex Access before elaboration + +@geindex Checks +@geindex division by zero + +@geindex Checks +@geindex access before elaboration + +@geindex Checks +@geindex stack overflow checking + +By default, the following checks are suppressed: integer overflow +checks, stack overflow checks, and checks for access before +elaboration on subprogram calls. All other checks, including range +checks and array bounds checks, are turned on by default. The +following @emph{gcc} switches refine this default behavior. + +@geindex -gnatp (gcc) + + +@table @asis + +@item @code{-gnatp} + +@geindex Suppressing checks + +@geindex Checks +@geindex suppressing + +This switch causes the unit to be compiled +as though @cite{pragma Suppress (All_checks)} +had been present in the source. Validity checks are also eliminated (in +other words @emph{-gnatp} also implies @emph{-gnatVn}. +Use this switch to improve the performance +of the code at the expense of safety in the presence of invalid data or +program bugs. + +Note that when checks are suppressed, the compiler is allowed, but not +required, to omit the checking code. If the run-time cost of the +checking code is zero or near-zero, the compiler will generate it even +if checks are suppressed. In particular, if the compiler can prove +that a certain check will necessarily fail, it will generate code to +do an unconditional 'raise', even if checks are suppressed. The +compiler warns in this case. Another case in which checks may not be +eliminated is when they are embedded in certain run time routines such +as math library routines. + +Of course, run-time checks are omitted whenever the compiler can prove +that they will not fail, whether or not checks are suppressed. + +Note that if you suppress a check that would have failed, program +execution is erroneous, which means the behavior is totally +unpredictable. The program might crash, or print wrong answers, or +do anything else. It might even do exactly what you wanted it to do +(and then it might start failing mysteriously next week or next +year). The compiler will generate code based on the assumption that +the condition being checked is true, which can result in erroneous +execution if that assumption is wrong. + +The checks subject to suppression include all the checks defined by +the Ada standard, the additional implementation defined checks +@cite{Alignment_Check}, +@cite{Duplicated_Tag_Check}, @cite{Predicate_Check}, and +@cite{Validity_Check}, as well as any checks introduced using +@cite{pragma Check_Name}. Note that @cite{Atomic_Synchronization} +is not automatically suppressed by use of this option. + +If the code depends on certain checks being active, you can use +pragma @cite{Unsuppress} either as a configuration pragma or as +a local pragma to make sure that a specified check is performed +even if @emph{gnatp} is specified. + +The @emph{-gnatp} switch has no effect if a subsequent +@emph{-gnat-p} switch appears. +@end table + +@geindex -gnat-p (gcc) + +@geindex Suppressing checks + +@geindex Checks +@geindex suppressing + +@geindex Suppress + + +@table @asis + +@item @code{-gnat-p} + +This switch cancels the effect of a previous @emph{gnatp} switch. +@end table + +@geindex -gnato?? (gcc) + +@geindex Overflow checks + +@geindex Overflow mode + +@geindex Check +@geindex overflow + + +@table @asis + +@item @code{-gnato??} + +This switch controls the mode used for computing intermediate +arithmetic integer operations, and also enables overflow checking. +For a full description of overflow mode and checking control, see +the 'Overflow Check Handling in GNAT' appendix in this +User's Guide. + +Overflow checks are always enabled by this switch. The argument +controls the mode, using the codes + + +@table @asis + +@item @emph{1 = STRICT} + +In STRICT mode, intermediate operations are always done using the +base type, and overflow checking ensures that the result is within +the base type range. + +@item @emph{2 = MINIMIZED} + +In MINIMIZED mode, overflows in intermediate operations are avoided +where possible by using a larger integer type for the computation +(typically @cite{Long_Long_Integer}). Overflow checking ensures that +the result fits in this larger integer type. + +@item @emph{3 = ELIMINATED} + +In ELIMINATED mode, overflows in intermediate operations are avoided +by using multi-precision arithmetic. In this case, overflow checking +has no effect on intermediate operations (since overflow is impossible). +@end table + +If two digits are present after @emph{-gnato} then the first digit +sets the mode for expressions outside assertions, and the second digit +sets the mode for expressions within assertions. Here assertions is used +in the technical sense (which includes for example precondition and +postcondition expressions). + +If one digit is present, the corresponding mode is applicable to both +expressions within and outside assertion expressions. + +If no digits are present, the default is to enable overflow checks +and set STRICT mode for both kinds of expressions. This is compatible +with the use of @emph{-gnato} in previous versions of GNAT. + +@geindex Machine_Overflows + +Note that the @emph{-gnato??} switch does not affect the code generated +for any floating-point operations; it applies only to integer semantics. +For floating-point, GNAT has the @cite{Machine_Overflows} +attribute set to @cite{False} and the normal mode of operation is to +generate IEEE NaN and infinite values on overflow or invalid operations +(such as dividing 0.0 by 0.0). + +The reason that we distinguish overflow checking from other kinds of +range constraint checking is that a failure of an overflow check, unlike +for example the failure of a range check, can result in an incorrect +value, but cannot cause random memory destruction (like an out of range +subscript), or a wild jump (from an out of range case value). Overflow +checking is also quite expensive in time and space, since in general it +requires the use of double length arithmetic. + +Note again that the default is @emph{-gnato00}, +so overflow checking is not performed in default mode. This means that out of +the box, with the default settings, GNAT does not do all the checks +expected from the language description in the Ada Reference Manual. +If you want all constraint checks to be performed, as described in this Manual, +then you must explicitly use the @emph{-gnato??} +switch either on the @emph{gnatmake} or @emph{gcc} command. +@end table + +@geindex -gnatE (gcc) + +@geindex Elaboration checks + +@geindex Check +@geindex elaboration + + +@table @asis + +@item @code{-gnatE} + +Enables dynamic checks for access-before-elaboration +on subprogram calls and generic instantiations. +Note that @emph{-gnatE} is not necessary for safety, because in the +default mode, GNAT ensures statically that the checks would not fail. +For full details of the effect and use of this switch, +@ref{1e,,Compiling with gcc}. +@end table + +@geindex -fstack-check (gcc) + +@geindex Stack Overflow Checking + +@geindex Checks +@geindex stack overflow checking + + +@table @asis + +@item @code{-fstack-check} + +Activates stack overflow checking. For full details of the effect and use of +this switch see @ref{f9,,Stack Overflow Checking}. +@end table + +@geindex Unsuppress + +The setting of these switches only controls the default setting of the +checks. You may modify them using either @cite{Suppress} (to remove +checks) or @cite{Unsuppress} (to add back suppressed checks) pragmas in +the program source. + +@node Using gcc for Syntax Checking,Using gcc for Semantic Checking,Run-Time Checks,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id20}@anchor{10a}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-syntax-checking}@anchor{10b} +@subsection Using @emph{gcc} for Syntax Checking + + +@geindex -gnats (gcc) + + +@table @asis + +@item @code{-gnats} + +The @cite{s} stands for 'syntax'. + +Run GNAT in syntax checking only mode. For +example, the command + +@example +$ gcc -c -gnats x.adb +@end example + +compiles file @code{x.adb} in syntax-check-only mode. You can check a +series of files in a single command +, and can use wild cards to specify such a group of files. +Note that you must specify the @emph{-c} (compile +only) flag in addition to the @emph{-gnats} flag. + +You may use other switches in conjunction with @emph{-gnats}. In +particular, @emph{-gnatl} and @emph{-gnatv} are useful to control the +format of any generated error messages. + +When the source file is empty or contains only empty lines and/or comments, +the output is a warning: + +@example +$ gcc -c -gnats -x ada toto.txt +toto.txt:1:01: warning: empty file, contains no compilation units +$ +@end example + +Otherwise, the output is simply the error messages, if any. No object file or +ALI file is generated by a syntax-only compilation. Also, no units other +than the one specified are accessed. For example, if a unit @cite{X} +@emph{with}s a unit @cite{Y}, compiling unit @cite{X} in syntax +check only mode does not access the source file containing unit +@cite{Y}. + +@geindex Multiple units +@geindex syntax checking + +Normally, GNAT allows only a single unit in a source file. However, this +restriction does not apply in syntax-check-only mode, and it is possible +to check a file containing multiple compilation units concatenated +together. This is primarily used by the @cite{gnatchop} utility +(@ref{38,,Renaming Files with gnatchop}). +@end table + +@node Using gcc for Semantic Checking,Compiling Different Versions of Ada,Using gcc for Syntax Checking,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id21}@anchor{10c}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-semantic-checking}@anchor{10d} +@subsection Using @emph{gcc} for Semantic Checking + + +@geindex -gnatc (gcc) + + +@table @asis + +@item @code{-gnatc} + +The @cite{c} stands for 'check'. +Causes the compiler to operate in semantic check mode, +with full checking for all illegalities specified in the +Ada Reference Manual, but without generation of any object code +(no object file is generated). + +Because dependent files must be accessed, you must follow the GNAT +semantic restrictions on file structuring to operate in this mode: + + +@itemize * + +@item +The needed source files must be accessible +(see @ref{8e,,Search Paths and the Run-Time Library (RTL)}). + +@item +Each file must contain only one compilation unit. + +@item +The file name and unit name must match (@ref{54,,File Naming Rules}). +@end itemize + +The output consists of error messages as appropriate. No object file is +generated. An @code{ALI} file is generated for use in the context of +cross-reference tools, but this file is marked as not being suitable +for binding (since no object file is generated). +The checking corresponds exactly to the notion of +legality in the Ada Reference Manual. + +Any unit can be compiled in semantics-checking-only mode, including +units that would not normally be compiled (subunits, +and specifications where a separate body is present). +@end table + +@node Compiling Different Versions of Ada,Character Set Control,Using gcc for Semantic Checking,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat compiling-different-versions-of-ada}@anchor{6}@anchor{gnat_ugn/building_executable_programs_with_gnat id22}@anchor{10e} +@subsection Compiling Different Versions of Ada + + +The switches described in this section allow you to explicitly specify +the version of the Ada language that your programs are written in. +The default mode is Ada 2012, +but you can also specify Ada 95, Ada 2005 mode, or +indicate Ada 83 compatibility mode. + +@geindex Compatibility with Ada 83 + +@geindex -gnat83 (gcc) + +@geindex ACVC +@geindex Ada 83 tests + +@geindex Ada 83 mode + + +@table @asis + +@item @code{-gnat83 (Ada 83 Compatibility Mode)} + +Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch +specifies that the program is to be compiled in Ada 83 mode. With +@emph{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83 +semantics where this can be done easily. +It is not possible to guarantee this switch does a perfect +job; some subtle tests, such as are +found in earlier ACVC tests (and that have been removed from the ACATS suite +for Ada 95), might not compile correctly. +Nevertheless, this switch may be useful in some circumstances, for example +where, due to contractual reasons, existing code needs to be maintained +using only Ada 83 features. + +With few exceptions (most notably the need to use @cite{<>} on +.. index:: Generic formal parameters + +unconstrained generic formal parameters, the use of the new Ada 95 / Ada 2005 +reserved words, and the use of packages +with optional bodies), it is not necessary to specify the +@emph{-gnat83} switch when compiling Ada 83 programs, because, with rare +exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus +a correct Ada 83 program is usually also a correct program +in these later versions of the language standard. For further information +please refer to the @cite{Compatibility_and_Porting_Guide} chapter in the +@cite{GNAT Reference Manual}. +@end table + +@geindex -gnat95 (gcc) + +@geindex Ada 95 mode + + +@table @asis + +@item @code{-gnat95} (Ada 95 mode) + +This switch directs the compiler to implement the Ada 95 version of the +language. +Since Ada 95 is almost completely upwards +compatible with Ada 83, Ada 83 programs may generally be compiled using +this switch (see the description of the @emph{-gnat83} switch for further +information about Ada 83 mode). +If an Ada 2005 program is compiled in Ada 95 mode, +uses of the new Ada 2005 features will cause error +messages or warnings. + +This switch also can be used to cancel the effect of a previous +@emph{-gnat83}, @emph{-gnat05/2005}, or @emph{-gnat12/2012} +switch earlier in the command line. +@end table + +@geindex -gnat05 (gcc) + +@geindex -gnat2005 (gcc) + +@geindex Ada 2005 mode + + +@table @asis + +@item @code{-gnat05} or @code{-gnat2005} (Ada 2005 mode) + +This switch directs the compiler to implement the Ada 2005 version of the +language, as documented in the official Ada standards document. +Since Ada 2005 is almost completely upwards +compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs +may generally be compiled using this switch (see the description of the +@emph{-gnat83} and @emph{-gnat95} switches for further +information). +@end table + +@geindex -gnat12 (gcc) + +@geindex -gnat2012 (gcc) + +@geindex Ada 2012 mode + + +@table @asis + +@item @code{-gnat12} or @code{-gnat2012} (Ada 2012 mode) + +This switch directs the compiler to implement the Ada 2012 version of the +language (also the default). +Since Ada 2012 is almost completely upwards +compatible with Ada 2005 (and thus also with Ada 83, and Ada 95), +Ada 83 and Ada 95 programs +may generally be compiled using this switch (see the description of the +@emph{-gnat83}, @emph{-gnat95}, and @emph{-gnat05/2005} switches +for further information). +@end table + +@geindex -gnatX (gcc) + +@geindex Ada language extensions + +@geindex GNAT extensions + + +@table @asis + +@item @code{-gnatX} (Enable GNAT Extensions) + +This switch directs the compiler to implement the latest version of the +language (currently Ada 2012) and also to enable certain GNAT implementation +extensions that are not part of any Ada standard. For a full list of these +extensions, see the GNAT reference manual. +@end table + +@node Character Set Control,File Naming Control,Compiling Different Versions of Ada,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id23}@anchor{10f}@anchor{gnat_ugn/building_executable_programs_with_gnat character-set-control}@anchor{4a} +@subsection Character Set Control + + +@geindex -gnati (gcc) + + +@table @asis + +@item @code{-gnati@emph{c}} + +Normally GNAT recognizes the Latin-1 character set in source program +identifiers, as described in the Ada Reference Manual. +This switch causes +GNAT to recognize alternate character sets in identifiers. @cite{c} is a +single character indicating the character set, as follows: + + +@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item + +@emph{1} + +@tab + +ISO 8859-1 (Latin-1) identifiers + +@item + +@emph{2} + +@tab + +ISO 8859-2 (Latin-2) letters allowed in identifiers + +@item + +@emph{3} + +@tab + +ISO 8859-3 (Latin-3) letters allowed in identifiers + +@item + +@emph{4} + +@tab + +ISO 8859-4 (Latin-4) letters allowed in identifiers + +@item + +@emph{5} + +@tab + +ISO 8859-5 (Cyrillic) letters allowed in identifiers + +@item + +@emph{9} + +@tab + +ISO 8859-15 (Latin-9) letters allowed in identifiers + +@item + +@emph{p} + +@tab + +IBM PC letters (code page 437) allowed in identifiers + +@item + +@emph{8} + +@tab + +IBM PC letters (code page 850) allowed in identifiers + +@item + +@emph{f} + +@tab + +Full upper-half codes allowed in identifiers + +@item + +@emph{n} + +@tab + +No upper-half codes allowed in identifiers + +@item + +@emph{w} + +@tab + +Wide-character codes (that is, codes greater than 255) +allowed in identifiers + +@end multitable + + +See @ref{40,,Foreign Language Representation} for full details on the +implementation of these character sets. +@end table + +@geindex -gnatW (gcc) + + +@table @asis + +@item @code{-gnatW@emph{e}} + +Specify the method of encoding for wide characters. +@cite{e} is one of the following: + + +@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item + +@emph{h} + +@tab + +Hex encoding (brackets coding also recognized) + +@item + +@emph{u} + +@tab + +Upper half encoding (brackets encoding also recognized) + +@item + +@emph{s} + +@tab + +Shift/JIS encoding (brackets encoding also recognized) + +@item + +@emph{e} + +@tab + +EUC encoding (brackets encoding also recognized) + +@item + +@emph{8} + +@tab + +UTF-8 encoding (brackets encoding also recognized) + +@item + +@emph{b} + +@tab + +Brackets encoding only (default value) + +@end multitable + + +For full details on these encoding +methods see @ref{50,,Wide_Character Encodings}. +Note that brackets coding is always accepted, even if one of the other +options is specified, so for example @emph{-gnatW8} specifies that both +brackets and UTF-8 encodings will be recognized. The units that are +with'ed directly or indirectly will be scanned using the specified +representation scheme, and so if one of the non-brackets scheme is +used, it must be used consistently throughout the program. However, +since brackets encoding is always recognized, it may be conveniently +used in standard libraries, allowing these libraries to be used with +any of the available coding schemes. + +Note that brackets encoding only applies to program text. Within comments, +brackets are considered to be normal graphic characters, and bracket sequences +are never recognized as wide characters. + +If no @emph{-gnatW?} parameter is present, then the default +representation is normally Brackets encoding only. However, if the +first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard +byte order mark or BOM for UTF-8), then these three characters are +skipped and the default representation for the file is set to UTF-8. + +Note that the wide character representation that is specified (explicitly +or by default) for the main program also acts as the default encoding used +for Wide_Text_IO files if not specifically overridden by a WCEM form +parameter. +@end table + +When no @emph{-gnatW?} is specified, then characters (other than wide +characters represented using brackets notation) are treated as 8-bit +Latin-1 codes. The codes recognized are the Latin-1 graphic characters, +and ASCII format effectors (CR, LF, HT, VT). Other lower half control +characters in the range 16#00#..16#1F# are not accepted in program text +or in comments. Upper half control characters (16#80#..16#9F#) are rejected +in program text, but allowed and ignored in comments. Note in particular +that the Next Line (NEL) character whose encoding is 16#85# is not recognized +as an end of line in this default mode. If your source program contains +instances of the NEL character used as a line terminator, +you must use UTF-8 encoding for the whole +source program. In default mode, all lines must be ended by a standard +end of line sequence (CR, CR/LF, or LF). + +Note that the convention of simply accepting all upper half characters in +comments means that programs that use standard ASCII for program text, but +UTF-8 encoding for comments are accepted in default mode, providing that the +comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator. +This is a common mode for many programs with foreign language comments. + +@node File Naming Control,Subprogram Inlining Control,Character Set Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat file-naming-control}@anchor{110}@anchor{gnat_ugn/building_executable_programs_with_gnat id24}@anchor{111} +@subsection File Naming Control + + +@geindex -gnatk (gcc) + + +@table @asis + +@item @code{-gnatk@emph{n}} + +Activates file name 'krunching'. @cite{n}, a decimal integer in the range +1-999, indicates the maximum allowable length of a file name (not +including the @code{.ads} or @code{.adb} extension). The default is not +to enable file name krunching. + +For the source file naming rules, @ref{54,,File Naming Rules}. +@end table + +@node Subprogram Inlining Control,Auxiliary Output Control,File Naming Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control}@anchor{112}@anchor{gnat_ugn/building_executable_programs_with_gnat id25}@anchor{113} +@subsection Subprogram Inlining Control + + +@geindex -gnatn (gcc) + + +@table @asis + +@item @code{-gnatn[12]} + +The @cite{n} here is intended to suggest the first syllable of the +word 'inline'. +GNAT recognizes and processes @cite{Inline} pragmas. However, for the +inlining to actually occur, optimization must be enabled and, in order +to enable inlining of subprograms specified by pragma @cite{Inline}, +you must also specify this switch. +In the absence of this switch, GNAT does not attempt +inlining and does not need to access the bodies of +subprograms for which @cite{pragma Inline} is specified if they are not +in the current unit. + +You can optionally specify the inlining level: 1 for moderate inlining across +modules, which is a good compromise between compilation times and performances +at run time, or 2 for full inlining across modules, which may bring about +longer compilation times. If no inlining level is specified, the compiler will +pick it based on the optimization level: 1 for @emph{-O1}, @emph{-O2} or +@emph{-Os} and 2 for @emph{-O3}. + +If you specify this switch the compiler will access these bodies, +creating an extra source dependency for the resulting object file, and +where possible, the call will be inlined. +For further details on when inlining is possible +see @ref{114,,Inlining of Subprograms}. +@end table + +@geindex -gnatN (gcc) + + +@table @asis + +@item @code{-gnatN} + +This switch activates front-end inlining which also +generates additional dependencies. + +When using a gcc-based back end (in practice this means using any version +of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of +@emph{-gnatN} is deprecated, and the use of @emph{-gnatn} is preferred. +Historically front end inlining was more extensive than the gcc back end +inlining, but that is no longer the case. +@end table + +@node Auxiliary Output Control,Debugging Control,Subprogram Inlining Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control}@anchor{115}@anchor{gnat_ugn/building_executable_programs_with_gnat id26}@anchor{116} +@subsection Auxiliary Output Control + + +@geindex -gnatt (gcc) + +@geindex Writing internal trees + +@geindex Internal trees +@geindex writing to file + + +@table @asis + +@item @code{-gnatt} + +Causes GNAT to write the internal tree for a unit to a file (with the +extension @code{.adt}. +This not normally required, but is used by separate analysis tools. +Typically +these tools do the necessary compilations automatically, so you should +not have to specify this switch in normal operation. +Note that the combination of switches @emph{-gnatct} +generates a tree in the form required by ASIS applications. +@end table + +@geindex -gnatu (gcc) + + +@table @asis + +@item @code{-gnatu} + +Print a list of units required by this compilation on @code{stdout}. +The listing includes all units on which the unit being compiled depends +either directly or indirectly. +@end table + +@geindex -pass-exit-codes (gcc) + + +@table @asis + +@item @code{-pass-exit-codes} + +If this switch is not used, the exit code returned by @emph{gcc} when +compiling multiple files indicates whether all source files have +been successfully used to generate object files or not. + +When @emph{-pass-exit-codes} is used, @emph{gcc} exits with an extended +exit status and allows an integrated development environment to better +react to a compilation failure. Those exit status are: + + +@multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item + +@emph{5} + +@tab + +There was an error in at least one source file. + +@item + +@emph{3} + +@tab + +At least one source file did not generate an object file. + +@item + +@emph{2} + +@tab + +The compiler died unexpectedly (internal error for example). + +@item + +@emph{0} + +@tab + +An object file has been generated for every source file. + +@end multitable + +@end table + +@node Debugging Control,Exception Handling Control,Auxiliary Output Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat debugging-control}@anchor{117}@anchor{gnat_ugn/building_executable_programs_with_gnat id27}@anchor{118} +@subsection Debugging Control + + +@quotation + +@geindex Debugging options +@end quotation + +@geindex -gnatd (gcc) + + +@table @asis + +@item @code{-gnatd@emph{x}} + +Activate internal debugging switches. @cite{x} is a letter or digit, or +string of letters or digits, which specifies the type of debugging +outputs desired. Normally these are used only for internal development +or system debugging purposes. You can find full documentation for these +switches in the body of the @cite{Debug} unit in the compiler source +file @code{debug.adb}. +@end table + +@geindex -gnatG (gcc) + + +@table @asis + +@item @code{-gnatG[=@emph{nn}]} + +This switch causes the compiler to generate auxiliary output containing +a pseudo-source listing of the generated expanded code. Like most Ada +compilers, GNAT works by first transforming the high level Ada code into +lower level constructs. For example, tasking operations are transformed +into calls to the tasking run-time routines. A unique capability of GNAT +is to list this expanded code in a form very close to normal Ada source. +This is very useful in understanding the implications of various Ada +usage on the efficiency of the generated code. There are many cases in +Ada (e.g., the use of controlled types), where simple Ada statements can +generate a lot of run-time code. By using @emph{-gnatG} you can identify +these cases, and consider whether it may be desirable to modify the coding +approach to improve efficiency. + +The optional parameter @cite{nn} if present after -gnatG specifies an +alternative maximum line length that overrides the normal default of 72. +This value is in the range 40-999999, values less than 40 being silently +reset to 40. The equal sign is optional. + +The format of the output is very similar to standard Ada source, and is +easily understood by an Ada programmer. The following special syntactic +additions correspond to low level features used in the generated code that +do not have any exact analogies in pure Ada source form. The following +is a partial list of these special constructions. See the spec +of package @cite{Sprint} in file @code{sprint.ads} for a full list. + +@geindex -gnatL (gcc) + +If the switch @emph{-gnatL} is used in conjunction with +@emph{-gnatG}, then the original source lines are interspersed +in the expanded source (as comment lines with the original line number). + + +@table @asis + +@item @code{new @emph{xxx} [storage_pool = @emph{yyy}]} + +Shows the storage pool being used for an allocator. + +@item @code{at end @emph{procedure-name};} + +Shows the finalization (cleanup) procedure for a scope. + +@item @code{(if @emph{expr} then @emph{expr} else @emph{expr})} + +Conditional expression equivalent to the @cite{x?y:z} construction in C. + +@item @code{@emph{target}^(@emph{source})} + +A conversion with floating-point truncation instead of rounding. + +@item @code{@emph{target}?(@emph{source})} + +A conversion that bypasses normal Ada semantic checking. In particular +enumeration types and fixed-point types are treated simply as integers. + +@item @code{@emph{target}?^(@emph{source})} + +Combines the above two cases. +@end table + +@code{@emph{x} #/ @emph{y}} + +@code{@emph{x} #mod @emph{y}} + +@code{@emph{x} # @emph{y}} + + +@table @asis + +@item @code{@emph{x} #rem @emph{y}} + +A division or multiplication of fixed-point values which are treated as +integers without any kind of scaling. + +@item @code{free @emph{expr} [storage_pool = @emph{xxx}]} + +Shows the storage pool associated with a @cite{free} statement. + +@item @code{[subtype or type declaration]} + +Used to list an equivalent declaration for an internally generated +type that is referenced elsewhere in the listing. + +@item @code{freeze @emph{type-name} [@emph{actions}]} + +Shows the point at which @cite{type-name} is frozen, with possible +associated actions to be performed at the freeze point. + +@item @code{reference @emph{itype}} + +Reference (and hence definition) to internal type @cite{itype}. + +@item @code{@emph{function-name}! (@emph{arg}, @emph{arg}, @emph{arg})} + +Intrinsic function call. + +@item @code{@emph{label-name} : label} + +Declaration of label @cite{labelname}. + +@item @code{#$ @emph{subprogram-name}} + +An implicit call to a run-time support routine +(to meet the requirement of H.3.1(9) in a +convenient manner). + +@item @code{@emph{expr} && @emph{expr} && @emph{expr} ... && @emph{expr}} + +A multiple concatenation (same effect as @cite{expr} & @cite{expr} & +@cite{expr}, but handled more efficiently). + +@item @code{[constraint_error]} + +Raise the @cite{Constraint_Error} exception. + +@item @code{@emph{expression}'reference} + +A pointer to the result of evaluating @{expression@}. + +@item @code{@emph{target-type}!(@emph{source-expression})} + +An unchecked conversion of @cite{source-expression} to @cite{target-type}. + +@item @code{[@emph{numerator}/@emph{denominator}]} + +Used to represent internal real literals (that) have no exact +representation in base 2-16 (for example, the result of compile time +evaluation of the expression 1.0/27.0). +@end table +@end table + +@geindex -gnatD (gcc) + + +@table @asis + +@item @code{-gnatD[=nn]} + +When used in conjunction with @emph{-gnatG}, this switch causes +the expanded source, as described above for +@emph{-gnatG} to be written to files with names +@code{xxx.dg}, where @code{xxx} is the normal file name, +instead of to the standard output file. For +example, if the source file name is @code{hello.adb}, then a file +@code{hello.adb.dg} will be written. The debugging +information generated by the @emph{gcc} @emph{-g} switch +will refer to the generated @code{xxx.dg} file. This allows +you to do source level debugging using the generated code which is +sometimes useful for complex code, for example to find out exactly +which part of a complex construction raised an exception. This switch +also suppress generation of cross-reference information (see +@emph{-gnatx}) since otherwise the cross-reference information +would refer to the @code{.dg} file, which would cause +confusion since this is not the original source file. + +Note that @emph{-gnatD} actually implies @emph{-gnatG} +automatically, so it is not necessary to give both options. +In other words @emph{-gnatD} is equivalent to @emph{-gnatDG}). + +@geindex -gnatL (gcc) + +If the switch @emph{-gnatL} is used in conjunction with +@emph{-gnatDG}, then the original source lines are interspersed +in the expanded source (as comment lines with the original line number). + +The optional parameter @cite{nn} if present after -gnatD specifies an +alternative maximum line length that overrides the normal default of 72. +This value is in the range 40-999999, values less than 40 being silently +reset to 40. The equal sign is optional. +@end table + +@geindex -gnatr (gcc) + +@geindex pragma Restrictions + + +@table @asis + +@item @code{-gnatr} + +This switch causes pragma Restrictions to be treated as Restriction_Warnings +so that violation of restrictions causes warnings rather than illegalities. +This is useful during the development process when new restrictions are added +or investigated. The switch also causes pragma Profile to be treated as +Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set +restriction warnings rather than restrictions. +@end table + +@geindex -gnatR (gcc) + + +@table @asis + +@item @code{-gnatR[0|1|2|3[s]]} + +This switch controls output from the compiler of a listing showing +representation information for declared types and objects. For +@emph{-gnatR0}, no information is output (equivalent to omitting +the @emph{-gnatR} switch). For @emph{-gnatR1} (which is the default, +so @emph{-gnatR} with no parameter has the same effect), size and alignment +information is listed for declared array and record types. For +@emph{-gnatR2}, size and alignment information is listed for all +declared types and objects. The @cite{Linker_Section} is also listed for any +entity for which the @cite{Linker_Section} is set explicitly or implicitly (the +latter case occurs for objects of a type for which a @cite{Linker_Section} +is set). + +Finally @emph{-gnatR3} includes symbolic +expressions for values that are computed at run time for +variant records. These symbolic expressions have a mostly obvious +format with #n being used to represent the value of the n'th +discriminant. See source files @code{repinfo.ads/adb} in the +@cite{GNAT} sources for full details on the format of @emph{-gnatR3} +output. If the switch is followed by an s (e.g., @emph{-gnatR2s}), then +the output is to a file with the name @code{file.rep} where +file is the name of the corresponding source file. + +@item @code{-gnatRm[s]} + +This form of the switch controls output of subprogram conventions +and parameter passing mechanisms for all subprograms. A following +@cite{s} means output to a file as described above. + +Note that it is possible for record components to have zero size. In +this case, the component clause uses an obvious extension of permitted +Ada syntax, for example @cite{at 0 range 0 .. -1}. + +Representation information requires that code be generated (since it is the +code generator that lays out complex data structures). If an attempt is made +to output representation information when no code is generated, for example +when a subunit is compiled on its own, then no information can be generated +and the compiler outputs a message to this effect. +@end table + +@geindex -gnatS (gcc) + + +@table @asis + +@item @code{-gnatS} + +The use of the switch @emph{-gnatS} for an +Ada compilation will cause the compiler to output a +representation of package Standard in a form very +close to standard Ada. It is not quite possible to +do this entirely in standard Ada (since new +numeric base types cannot be created in standard +Ada), but the output is easily +readable to any Ada programmer, and is useful to +determine the characteristics of target dependent +types in package Standard. +@end table + +@geindex -gnatx (gcc) + + +@table @asis + +@item @code{-gnatx} + +Normally the compiler generates full cross-referencing information in +the @code{ALI} file. This information is used by a number of tools, +including @cite{gnatfind} and @cite{gnatxref}. The @emph{-gnatx} switch +suppresses this information. This saves some space and may slightly +speed up compilation, but means that these tools cannot be used. +@end table + +@node Exception Handling Control,Units to Sources Mapping Files,Debugging Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id28}@anchor{119}@anchor{gnat_ugn/building_executable_programs_with_gnat exception-handling-control}@anchor{11a} +@subsection Exception Handling Control + + +GNAT uses two methods for handling exceptions at run-time. The +@cite{setjmp/longjmp} method saves the context when entering +a frame with an exception handler. Then when an exception is +raised, the context can be restored immediately, without the +need for tracing stack frames. This method provides very fast +exception propagation, but introduces significant overhead for +the use of exception handlers, even if no exception is raised. + +The other approach is called 'zero cost' exception handling. +With this method, the compiler builds static tables to describe +the exception ranges. No dynamic code is required when entering +a frame containing an exception handler. When an exception is +raised, the tables are used to control a back trace of the +subprogram invocation stack to locate the required exception +handler. This method has considerably poorer performance for +the propagation of exceptions, but there is no overhead for +exception handlers if no exception is raised. Note that in this +mode and in the context of mixed Ada and C/C++ programming, +to propagate an exception through a C/C++ code, the C/C++ code +must be compiled with the @emph{-funwind-tables} GCC's +option. + +The following switches may be used to control which of the +two exception handling methods is used. + +@geindex --RTS=sjlj (gnatmake) + + +@table @asis + +@item @code{--RTS=sjlj} + +This switch causes the setjmp/longjmp run-time (when available) to be used +for exception handling. If the default +mechanism for the target is zero cost exceptions, then +this switch can be used to modify this default, and must be +used for all units in the partition. +This option is rarely used. One case in which it may be +advantageous is if you have an application where exception +raising is common and the overall performance of the +application is improved by favoring exception propagation. +@end table + +@geindex --RTS=zcx (gnatmake) + +@geindex Zero Cost Exceptions + + +@table @asis + +@item @code{--RTS=zcx} + +This switch causes the zero cost approach to be used +for exception handling. If this is the default mechanism for the +target (see below), then this switch is unneeded. If the default +mechanism for the target is setjmp/longjmp exceptions, then +this switch can be used to modify this default, and must be +used for all units in the partition. +This option can only be used if the zero cost approach +is available for the target in use, otherwise it will generate an error. +@end table + +The same option @emph{--RTS} must be used both for @emph{gcc} +and @emph{gnatbind}. Passing this option to @emph{gnatmake} +(@ref{df,,Switches for gnatmake}) will ensure the required consistency +through the compilation and binding steps. + +@node Units to Sources Mapping Files,Code Generation Control,Exception Handling Control,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat id29}@anchor{11b}@anchor{gnat_ugn/building_executable_programs_with_gnat units-to-sources-mapping-files}@anchor{fc} +@subsection Units to Sources Mapping Files + + +@geindex -gnatem (gcc) + + +@table @asis + +@item @code{-gnatem=@emph{path}} + +A mapping file is a way to communicate to the compiler two mappings: +from unit names to file names (without any directory information) and from +file names to path names (with full directory information). These mappings +are used by the compiler to short-circuit the path search. + +The use of mapping files is not required for correct operation of the +compiler, but mapping files can improve efficiency, particularly when +sources are read over a slow network connection. In normal operation, +you need not be concerned with the format or use of mapping files, +and the @emph{-gnatem} switch is not a switch that you would use +explicitly. It is intended primarily for use by automatic tools such as +@emph{gnatmake} running under the project file facility. The +description here of the format of mapping files is provided +for completeness and for possible use by other tools. + +A mapping file is a sequence of sets of three lines. In each set, the +first line is the unit name, in lower case, with @cite{%s} appended +for specs and @cite{%b} appended for bodies; the second line is the +file name; and the third line is the path name. + +Example: + +@example +main%b +main.2.ada +/gnat/project1/sources/main.2.ada +@end example + +When the switch @emph{-gnatem} is specified, the compiler will +create in memory the two mappings from the specified file. If there is +any problem (nonexistent file, truncated file or duplicate entries), +no mapping will be created. + +Several @emph{-gnatem} switches may be specified; however, only the +last one on the command line will be taken into account. + +When using a project file, @emph{gnatmake} creates a temporary +mapping file and communicates it to the compiler using this switch. +@end table + +@node Code Generation Control,,Units to Sources Mapping Files,Compiler Switches +@anchor{gnat_ugn/building_executable_programs_with_gnat code-generation-control}@anchor{11c}@anchor{gnat_ugn/building_executable_programs_with_gnat id30}@anchor{11d} +@subsection Code Generation Control + + +The GCC technology provides a wide range of target dependent +@code{-m} switches for controlling +details of code generation with respect to different versions of +architectures. This includes variations in instruction sets (e.g., +different members of the power pc family), and different requirements +for optimal arrangement of instructions (e.g., different members of +the x86 family). The list of available @emph{-m} switches may be +found in the GCC documentation. + +Use of these @emph{-m} switches may in some cases result in improved +code performance. + +The GNAT technology is tested and qualified without any +@code{-m} switches, +so generally the most reliable approach is to avoid the use of these +switches. However, we generally expect most of these switches to work +successfully with GNAT, and many customers have reported successful +use of these options. + +Our general advice is to avoid the use of @emph{-m} switches unless +special needs lead to requirements in this area. In particular, +there is no point in using @emph{-m} switches to improve performance +unless you actually see a performance improvement. + +@node Binding with gnatbind,Linking with gnatlink,Compiler Switches,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind}@anchor{1f}@anchor{gnat_ugn/building_executable_programs_with_gnat id31}@anchor{11e} +@section Binding with @cite{gnatbind} + + +@geindex gnatbind + +This chapter describes the GNAT binder, @cite{gnatbind}, which is used +to bind compiled GNAT objects. + +Note: to invoke @cite{gnatbind} with a project file, use the @cite{gnat} +driver (see @ref{11f,,The GNAT Driver and Project Files}). + +The @cite{gnatbind} program performs four separate functions: + + +@itemize * + +@item +Checks that a program is consistent, in accordance with the rules in +Chapter 10 of the Ada Reference Manual. In particular, error +messages are generated if a program uses inconsistent versions of a +given unit. + +@item +Checks that an acceptable order of elaboration exists for the program +and issues an error message if it cannot find an order of elaboration +that satisfies the rules in Chapter 10 of the Ada Language Manual. + +@item +Generates a main program incorporating the given elaboration order. +This program is a small Ada package (body and spec) that +must be subsequently compiled +using the GNAT compiler. The necessary compilation step is usually +performed automatically by @emph{gnatlink}. The two most important +functions of this program +are to call the elaboration routines of units in an appropriate order +and to call the main program. + +@item +Determines the set of object files required by the given main program. +This information is output in the forms of comments in the generated program, +to be read by the @emph{gnatlink} utility used to link the Ada application. +@end itemize + +@menu +* Running gnatbind:: +* Switches for gnatbind:: +* Command-Line Access:: +* Search Paths for gnatbind:: +* Examples of gnatbind Usage:: + +@end menu + +@node Running gnatbind,Switches for gnatbind,,Binding with gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatbind}@anchor{120}@anchor{gnat_ugn/building_executable_programs_with_gnat id32}@anchor{121} +@subsection Running @cite{gnatbind} + + +The form of the @cite{gnatbind} command is + +@example +$ gnatbind [`switches`] `mainprog`[.ali] [`switches`] +@end example + +where @code{mainprog.adb} is the Ada file containing the main program +unit body. @cite{gnatbind} constructs an Ada +package in two files whose names are +@code{b~mainprog.ads}, and @code{b~mainprog.adb}. +For example, if given the +parameter @code{hello.ali}, for a main program contained in file +@code{hello.adb}, the binder output files would be @code{b~hello.ads} +and @code{b~hello.adb}. + +When doing consistency checking, the binder takes into consideration +any source files it can locate. For example, if the binder determines +that the given main program requires the package @cite{Pack}, whose +@code{.ALI} +file is @code{pack.ali} and whose corresponding source spec file is +@code{pack.ads}, it attempts to locate the source file @code{pack.ads} +(using the same search path conventions as previously described for the +@emph{gcc} command). If it can locate this source file, it checks that +the time stamps +or source checksums of the source and its references to in @code{ALI} files +match. In other words, any @code{ALI} files that mentions this spec must have +resulted from compiling this version of the source file (or in the case +where the source checksums match, a version close enough that the +difference does not matter). + +@geindex Source files +@geindex use by binder + +The effect of this consistency checking, which includes source files, is +that the binder ensures that the program is consistent with the latest +version of the source files that can be located at bind time. Editing a +source file without compiling files that depend on the source file cause +error messages to be generated by the binder. + +For example, suppose you have a main program @code{hello.adb} and a +package @cite{P}, from file @code{p.ads} and you perform the following +steps: + + +@itemize * + +@item +Enter @cite{gcc -c hello.adb} to compile the main program. + +@item +Enter @cite{gcc -c p.ads} to compile package @cite{P}. + +@item +Edit file @code{p.ads}. + +@item +Enter @cite{gnatbind hello}. +@end itemize + +At this point, the file @code{p.ali} contains an out-of-date time stamp +because the file @code{p.ads} has been edited. The attempt at binding +fails, and the binder generates the following error messages: + +@example +error: "hello.adb" must be recompiled ("p.ads" has been modified) +error: "p.ads" has been modified and must be recompiled +@end example + +Now both files must be recompiled as indicated, and then the bind can +succeed, generating a main program. You need not normally be concerned +with the contents of this file, but for reference purposes a sample +binder output file is given in @ref{10,,Example of Binder Output File}. + +In most normal usage, the default mode of @emph{gnatbind} which is to +generate the main package in Ada, as described in the previous section. +In particular, this means that any Ada programmer can read and understand +the generated main program. It can also be debugged just like any other +Ada code provided the @emph{-g} switch is used for +@emph{gnatbind} and @emph{gnatlink}. + +@node Switches for gnatbind,Command-Line Access,Running gnatbind,Binding with gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat id33}@anchor{122}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind}@anchor{123} +@subsection Switches for @emph{gnatbind} + + +The following switches are available with @cite{gnatbind}; details will +be presented in subsequent sections. + +@geindex --version (gnatbind) + + +@table @asis + +@item @code{--version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatbind) + + +@table @asis + +@item @code{--help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table + +@geindex -a (gnatbind) + + +@table @asis + +@item @code{-a} + +Indicates that, if supported by the platform, the adainit procedure should +be treated as an initialisation routine by the linker (a constructor). This +is intended to be used by the Project Manager to automatically initialize +shared Stand-Alone Libraries. +@end table + +@geindex -aO (gnatbind) + + +@table @asis + +@item @code{-aO} + +Specify directory to be searched for ALI files. +@end table + +@geindex -aI (gnatbind) + + +@table @asis + +@item @code{-aI} + +Specify directory to be searched for source file. +@end table + +@geindex -A (gnatbind) + + +@table @asis + +@item @code{-A[=@emph{filename}]} + +Output ALI list (to standard output or to the named file). +@end table + +@geindex -b (gnatbind) + + +@table @asis + +@item @code{-b} + +Generate brief messages to @code{stderr} even if verbose mode set. +@end table + +@geindex -c (gnatbind) + + +@table @asis + +@item @code{-c} + +Check only, no generation of binder output file. +@end table + +@geindex -dnn[k|m] (gnatbind) + + +@table @asis + +@item @code{-d@emph{nn}[k|m]} + +This switch can be used to change the default task stack size value +to a specified size @cite{nn}, which is expressed in bytes by default, or +in kilobytes when suffixed with @cite{k} or in megabytes when suffixed +with @cite{m}. +In the absence of a @code{[k|m]} suffix, this switch is equivalent, +in effect, to completing all task specs with + +@example +pragma Storage_Size (nn); +@end example + +When they do not already have such a pragma. +@end table + +@geindex -D (gnatbind) + + +@table @asis + +@item @code{-D@emph{nn}[k|m]} + +This switch can be used to change the default secondary stack size value +to a specified size @cite{nn}, which is expressed in bytes by default, or +in kilobytes when suffixed with @cite{k} or in megabytes when suffixed +with @cite{m}. + +The secondary stack is used to deal with functions that return a variable +sized result, for example a function returning an unconstrained +String. There are two ways in which this secondary stack is allocated. + +For most targets, the secondary stack is growing on demand and is allocated +as a chain of blocks in the heap. The -D option is not very +relevant. It only give some control over the size of the allocated +blocks (whose size is the minimum of the default secondary stack size value, +and the actual size needed for the current allocation request). + +For certain targets, notably VxWorks 653, +the secondary stack is allocated by carving off a fixed ratio chunk of the +primary task stack. The -D option is used to define the +size of the environment task's secondary stack. +@end table + +@geindex -e (gnatbind) + + +@table @asis + +@item @code{-e} + +Output complete list of elaboration-order dependencies. +@end table + +@geindex -E (gnatbind) + + +@table @asis + +@item @code{-E} + +Store tracebacks in exception occurrences when the target supports it. + +See also the packages @cite{GNAT.Traceback} and +@cite{GNAT.Traceback.Symbolic} for more information. +Note that on x86 ports, you must not use @emph{-fomit-frame-pointer} +@emph{gcc} option. +@end table + +@geindex -F (gnatbind) + + +@table @asis + +@item @code{-F} + +Force the checks of elaboration flags. @emph{gnatbind} does not normally +generate checks of elaboration flags for the main executable, except when +a Stand-Alone Library is used. However, there are cases when this cannot be +detected by gnatbind. An example is importing an interface of a Stand-Alone +Library through a pragma Import and only specifying through a linker switch +this Stand-Alone Library. This switch is used to guarantee that elaboration +flag checks are generated. +@end table + +@geindex -h (gnatbind) + + +@table @asis + +@item @code{-h} + +Output usage (help) information + +@geindex -H32 (gnatbind) + +@item @code{-H32} + +Use 32-bit allocations for @cite{__gnat_malloc} (and thus for access types). +For further details see @ref{124,,Dynamic Allocation Control}. + +@geindex -H64 (gnatbind) + +@geindex __gnat_malloc + +@item @code{-H64} + +Use 64-bit allocations for @cite{__gnat_malloc} (and thus for access types). +For further details see @ref{124,,Dynamic Allocation Control}. + +@geindex -I (gnatbind) + +@item @code{-I} + +Specify directory to be searched for source and ALI files. + +@geindex -I- (gnatbind) + +@item @code{-I-} + +Do not look for sources in the current directory where @cite{gnatbind} was +invoked, and do not look for ALI files in the directory containing the +ALI file named in the @cite{gnatbind} command line. + +@geindex -l (gnatbind) + +@item @code{-l} + +Output chosen elaboration order. + +@geindex -L (gnatbind) + +@item @code{-L@emph{xxx}} + +Bind the units for library building. In this case the adainit and +adafinal procedures (@ref{ba,,Binding with Non-Ada Main Programs}) +are renamed to @cite{xxx`init and `xxx`final. Implies -n. (:ref:`GNAT_and_Libraries}, for more details.) + +@geindex -M (gnatbind) + +@item @code{-M@emph{xyz}} + +Rename generated main program from main to xyz. This option is +supported on cross environments only. + +@geindex -m (gnatbind) + +@item @code{-m@emph{n}} + +Limit number of detected errors or warnings to @cite{n}, where @cite{n} is +in the range 1..999999. The default value if no switch is +given is 9999. If the number of warnings reaches this limit, then a +message is output and further warnings are suppressed, the bind +continues in this case. If the number of errors reaches this +limit, then a message is output and the bind is abandoned. +A value of zero means that no limit is enforced. The equal +sign is optional. + +@geindex -n (gnatbind) + +@item @code{-n} + +No main program. + +@geindex -nostdinc (gnatbind) + +@item @code{-nostdinc} + +Do not look for sources in the system default directory. + +@geindex -nostdlib (gnatbind) + +@item @code{-nostdlib} + +Do not look for library files in the system default directory. + +@geindex --RTS (gnatbind) + +@item @code{--RTS=@emph{rts-path}} + +Specifies the default location of the runtime library. Same meaning as the +equivalent @emph{gnatmake} flag (@ref{df,,Switches for gnatmake}). + +@geindex -o (gnatbind) + +@item @code{-o @emph{file}} + +Name the output file @cite{file} (default is @code{b~`xxx}.adb`). +Note that if this option is used, then linking must be done manually, +gnatlink cannot be used. + +@geindex -O (gnatbind) + +@item @code{-O[=@emph{filename}]} + +Output object list (to standard output or to the named file). + +@geindex -p (gnatbind) + +@item @code{-p} + +Pessimistic (worst-case) elaboration order + +@geindex -P (gnatbind) + +@item @code{-P} + +Generate binder file suitable for CodePeer. + +@geindex -R (gnatbind) + +@item @code{-R} + +Output closure source list, which includes all non-run-time units that are +included in the bind. + +@geindex -Ra (gnatbind) + +@item @code{-Ra} + +Like @emph{-R} but the list includes run-time units. + +@geindex -s (gnatbind) + +@item @code{-s} + +Require all source files to be present. + +@geindex -S (gnatbind) + +@item @code{-S@emph{xxx}} + +Specifies the value to be used when detecting uninitialized scalar +objects with pragma Initialize_Scalars. +The @cite{xxx} string specified with the switch is one of: + + +@itemize * + +@item +@code{in} for an invalid value*. + +If zero is invalid for the discrete type in question, +then the scalar value is set to all zero bits. +For signed discrete types, the largest possible negative value of +the underlying scalar is set (i.e. a one bit followed by all zero bits). +For unsigned discrete types, the underlying scalar value is set to all +one bits. For floating-point types, a NaN value is set +(see body of package System.Scalar_Values for exact values). + +@item +@code{lo} for low value. + +If zero is invalid for the discrete type in question, +then the scalar value is set to all zero bits. +For signed discrete types, the largest possible negative value of +the underlying scalar is set (i.e. a one bit followed by all zero bits). +For unsigned discrete types, the underlying scalar value is set to all +zero bits. For floating-point, a small value is set +(see body of package System.Scalar_Values for exact values). + +@item +@code{hi} for high value. + +If zero is invalid for the discrete type in question, +then the scalar value is set to all one bits. +For signed discrete types, the largest possible positive value of +the underlying scalar is set (i.e. a zero bit followed by all one bits). +For unsigned discrete types, the underlying scalar value is set to all +one bits. For floating-point, a large value is set +(see body of package System.Scalar_Values for exact values). + +@item +@cite{xx} for hex value (two hex digits). + +The underlying scalar is set to a value consisting of repeated bytes, whose +value corresponds to the given value. For example if @code{BF} is given, +then a 32-bit scalar value will be set to the bit patterm @code{16#BFBFBFBF#}. +@end itemize + +@geindex GNAT_INIT_SCALARS + +In addition, you can specify @emph{-Sev} to indicate that the value is +to be set at run time. In this case, the program will look for an environment +variable of the form @code{GNAT_INIT_SCALARS=@emph{yy}}, where @cite{yy} is one +of @emph{in/lo/hi/`xx*` with the same meanings as above. +If no environment variable is found, or if it does not have a valid value, +then the default is *in} (invalid values). +@end table + +@geindex -static (gnatbind) + + +@table @asis + +@item @code{-static} + +Link against a static GNAT run time. + +@geindex -shared (gnatbind) + +@item @code{-shared} + +Link against a shared GNAT run time when available. + +@geindex -t (gnatbind) + +@item @code{-t} + +Tolerate time stamp and other consistency errors + +@geindex -T (gnatbind) + +@item @code{-T@emph{n}} + +Set the time slice value to @cite{n} milliseconds. If the system supports +the specification of a specific time slice value, then the indicated value +is used. If the system does not support specific time slice values, but +does support some general notion of round-robin scheduling, then any +nonzero value will activate round-robin scheduling. + +A value of zero is treated specially. It turns off time +slicing, and in addition, indicates to the tasking run time that the +semantics should match as closely as possible the Annex D +requirements of the Ada RM, and in particular sets the default +scheduling policy to @cite{FIFO_Within_Priorities}. + +@geindex -u (gnatbind) + +@item @code{-u@emph{n}} + +Enable dynamic stack usage, with @cite{n} results stored and displayed +at program termination. A result is generated when a task +terminates. Results that can't be stored are displayed on the fly, at +task termination. This option is currently not supported on Itanium +platforms. (See @ref{125,,Dynamic Stack Usage Analysis} for details.) + +@geindex -v (gnatbind) + +@item @code{-v} + +Verbose mode. Write error messages, header, summary output to +@code{stdout}. + +@geindex -w (gnatbind) + +@item @code{-w@emph{x}} + +Warning mode; @cite{x} = s/e for suppress/treat as error + +@geindex -Wx (gnatbind) + +@item @code{-Wx@emph{e}} + +Override default wide character encoding for standard Text_IO files. + +@geindex -x (gnatbind) + +@item @code{-x} + +Exclude source files (check object consistency only). + +@geindex -Xnnn (gnatbind) + +@item @code{-X@emph{nnn}} + +Set default exit status value, normally 0 for POSIX compliance. + +@geindex -y (gnatbind) + +@item @code{-y} + +Enable leap seconds support in @cite{Ada.Calendar} and its children. + +@geindex -z (gnatbind) + +@item @code{-z} + +No main subprogram. +@end table + +You may obtain this listing of switches by running @cite{gnatbind} with +no arguments. + +@menu +* Consistency-Checking Modes:: +* Binder Error Message Control:: +* Elaboration Control:: +* Output Control:: +* Dynamic Allocation Control:: +* Binding with Non-Ada Main Programs:: +* Binding Programs with No Main Subprogram:: + +@end menu + +@node Consistency-Checking Modes,Binder Error Message Control,,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes}@anchor{126}@anchor{gnat_ugn/building_executable_programs_with_gnat id34}@anchor{127} +@subsubsection Consistency-Checking Modes + + +As described earlier, by default @cite{gnatbind} checks +that object files are consistent with one another and are consistent +with any source files it can locate. The following switches control binder +access to sources. + +@quotation + +@geindex -s (gnatbind) +@end quotation + + +@table @asis + +@item @code{-s} + +Require source files to be present. In this mode, the binder must be +able to locate all source files that are referenced, in order to check +their consistency. In normal mode, if a source file cannot be located it +is simply ignored. If you specify this switch, a missing source +file is an error. + +@geindex -Wx (gnatbind) + +@item @code{-Wx@emph{e}} + +Override default wide character encoding for standard Text_IO files. +Normally the default wide character encoding method used for standard +[Wide_[Wide_]]Text_IO files is taken from the encoding specified for +the main source input (see description of switch +@emph{-gnatWx} for the compiler). The +use of this switch for the binder (which has the same set of +possible arguments) overrides this default as specified. + +@geindex -x (gnatbind) + +@item @code{-x} + +Exclude source files. In this mode, the binder only checks that ALI +files are consistent with one another. Source files are not accessed. +The binder runs faster in this mode, and there is still a guarantee that +the resulting program is self-consistent. +If a source file has been edited since it was last compiled, and you +specify this switch, the binder will not detect that the object +file is out of date with respect to the source file. Note that this is the +mode that is automatically used by @emph{gnatmake} because in this +case the checking against sources has already been performed by +@emph{gnatmake} in the course of compilation (i.e., before binding). +@end table + +@node Binder Error Message Control,Elaboration Control,Consistency-Checking Modes,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat id35}@anchor{128}@anchor{gnat_ugn/building_executable_programs_with_gnat binder-error-message-control}@anchor{129} +@subsubsection Binder Error Message Control + + +The following switches provide control over the generation of error +messages from the binder: + +@quotation + +@geindex -v (gnatbind) +@end quotation + + +@table @asis + +@item @code{-v} + +Verbose mode. In the normal mode, brief error messages are generated to +@code{stderr}. If this switch is present, a header is written +to @code{stdout} and any error messages are directed to @code{stdout}. +All that is written to @code{stderr} is a brief summary message. + +@geindex -b (gnatbind) + +@item @code{-b} + +Generate brief error messages to @code{stderr} even if verbose mode is +specified. This is relevant only when used with the +@emph{-v} switch. + +@geindex -m (gnatbind) + +@item @code{-m@emph{n}} + +Limits the number of error messages to @cite{n}, a decimal integer in the +range 1-999. The binder terminates immediately if this limit is reached. + +@geindex -M (gnatbind) + +@item @code{-M@emph{xxx}} + +Renames the generated main program from @cite{main} to @cite{xxx}. +This is useful in the case of some cross-building environments, where +the actual main program is separate from the one generated +by @cite{gnatbind}. + +@geindex -ws (gnatbind) + +@geindex Warnings + +@item @code{-ws} + +Suppress all warning messages. + +@geindex -we (gnatbind) + +@item @code{-we} + +Treat any warning messages as fatal errors. + +@geindex -t (gnatbind) + +@geindex Time stamp checks +@geindex in binder + +@geindex Binder consistency checks + +@geindex Consistency checks +@geindex in binder + +@item @code{-t} + +The binder performs a number of consistency checks including: + + +@itemize * + +@item +Check that time stamps of a given source unit are consistent + +@item +Check that checksums of a given source unit are consistent + +@item +Check that consistent versions of @cite{GNAT} were used for compilation + +@item +Check consistency of configuration pragmas as required +@end itemize + +Normally failure of such checks, in accordance with the consistency +requirements of the Ada Reference Manual, causes error messages to be +generated which abort the binder and prevent the output of a binder +file and subsequent link to obtain an executable. + +The @emph{-t} switch converts these error messages +into warnings, so that +binding and linking can continue to completion even in the presence of such +errors. The result may be a failed link (due to missing symbols), or a +non-functional executable which has undefined semantics. + +@cartouche +@quotation Note +This means that @emph{-t} should be used only in unusual situations, +with extreme care. +@end quotation +@end cartouche +@end table + +@node Elaboration Control,Output Control,Binder Error Message Control,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat id36}@anchor{12a}@anchor{gnat_ugn/building_executable_programs_with_gnat elaboration-control}@anchor{12b} +@subsubsection Elaboration Control + + +The following switches provide additional control over the elaboration +order. For full details see @ref{11,,Elaboration Order Handling in GNAT}. + +@quotation + +@geindex -p (gnatbind) +@end quotation + + +@table @asis + +@item @code{-p} + +Normally the binder attempts to choose an elaboration order that is +likely to minimize the likelihood of an elaboration order error resulting +in raising a @cite{Program_Error} exception. This switch reverses the +action of the binder, and requests that it deliberately choose an order +that is likely to maximize the likelihood of an elaboration error. +This is useful in ensuring portability and avoiding dependence on +accidental fortuitous elaboration ordering. + +Normally it only makes sense to use the @emph{-p} +switch if dynamic +elaboration checking is used (@emph{-gnatE} switch used for compilation). +This is because in the default static elaboration mode, all necessary +@cite{Elaborate} and @cite{Elaborate_All} pragmas are implicitly inserted. +These implicit pragmas are still respected by the binder in +@emph{-p} mode, so a +safe elaboration order is assured. + +Note that @emph{-p} is not intended for +production use; it is more for debugging/experimental use. +@end table + +@node Output Control,Dynamic Allocation Control,Elaboration Control,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat output-control}@anchor{12c}@anchor{gnat_ugn/building_executable_programs_with_gnat id37}@anchor{12d} +@subsubsection Output Control + + +The following switches allow additional control over the output +generated by the binder. + +@quotation + +@geindex -c (gnatbind) +@end quotation + + +@table @asis + +@item @code{-c} + +Check only. Do not generate the binder output file. In this mode the +binder performs all error checks but does not generate an output file. + +@geindex -e (gnatbind) + +@item @code{-e} + +Output complete list of elaboration-order dependencies, showing the +reason for each dependency. This output can be rather extensive but may +be useful in diagnosing problems with elaboration order. The output is +written to @code{stdout}. + +@geindex -h (gnatbind) + +@item @code{-h} + +Output usage information. The output is written to @code{stdout}. + +@geindex -K (gnatbind) + +@item @code{-K} + +Output linker options to @code{stdout}. Includes library search paths, +contents of pragmas Ident and Linker_Options, and libraries added +by @cite{gnatbind}. + +@geindex -l (gnatbind) + +@item @code{-l} + +Output chosen elaboration order. The output is written to @code{stdout}. + +@geindex -O (gnatbind) + +@item @code{-O} + +Output full names of all the object files that must be linked to provide +the Ada component of the program. The output is written to @code{stdout}. +This list includes the files explicitly supplied and referenced by the user +as well as implicitly referenced run-time unit files. The latter are +omitted if the corresponding units reside in shared libraries. The +directory names for the run-time units depend on the system configuration. + +@geindex -o (gnatbind) + +@item @code{-o @emph{file}} + +Set name of output file to @cite{file} instead of the normal +@code{b~`mainprog}.adb` default. Note that @cite{file} denote the Ada +binder generated body filename. +Note that if this option is used, then linking must be done manually. +It is not possible to use gnatlink in this case, since it cannot locate +the binder file. + +@geindex -r (gnatbind) + +@item @code{-r} + +Generate list of @cite{pragma Restrictions} that could be applied to +the current unit. This is useful for code audit purposes, and also may +be used to improve code generation in some cases. +@end table + +@node Dynamic Allocation Control,Binding with Non-Ada Main Programs,Output Control,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control}@anchor{124}@anchor{gnat_ugn/building_executable_programs_with_gnat id38}@anchor{12e} +@subsubsection Dynamic Allocation Control + + +The heap control switches -- @emph{-H32} and @emph{-H64} -- +determine whether dynamic allocation uses 32-bit or 64-bit memory. +They only affect compiler-generated allocations via @cite{__gnat_malloc}; +explicit calls to @cite{malloc} and related functions from the C +run-time library are unaffected. + + +@table @asis + +@item @code{-H32} + +Allocate memory on 32-bit heap + +@item @code{-H64} + +Allocate memory on 64-bit heap. This is the default +unless explicitly overridden by a @cite{'Size} clause on the access type. +@end table + +These switches are only effective on VMS platforms. + +@node Binding with Non-Ada Main Programs,Binding Programs with No Main Subprogram,Dynamic Allocation Control,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-non-ada-main-programs}@anchor{ba}@anchor{gnat_ugn/building_executable_programs_with_gnat id39}@anchor{12f} +@subsubsection Binding with Non-Ada Main Programs + + +The description so far has assumed that the main +program is in Ada, and that the task of the binder is to generate a +corresponding function @cite{main} that invokes this Ada main +program. GNAT also supports the building of executable programs where +the main program is not in Ada, but some of the called routines are +written in Ada and compiled using GNAT (@ref{46,,Mixed Language Programming}). +The following switch is used in this situation: + +@quotation + +@geindex -n (gnatbind) +@end quotation + + +@table @asis + +@item @code{-n} + +No main program. The main program is not in Ada. +@end table + +In this case, most of the functions of the binder are still required, +but instead of generating a main program, the binder generates a file +containing the following callable routines: + +@quotation + +@geindex adainit + + +@table @asis + +@item @emph{adainit} + +You must call this routine to initialize the Ada part of the program by +calling the necessary elaboration routines. A call to @cite{adainit} is +required before the first call to an Ada subprogram. + +Note that it is assumed that the basic execution environment must be setup +to be appropriate for Ada execution at the point where the first Ada +subprogram is called. In particular, if the Ada code will do any +floating-point operations, then the FPU must be setup in an appropriate +manner. For the case of the x86, for example, full precision mode is +required. The procedure GNAT.Float_Control.Reset may be used to ensure +that the FPU is in the right state. +@end table + +@geindex adafinal + + +@table @asis + +@item @emph{adafinal} + +You must call this routine to perform any library-level finalization +required by the Ada subprograms. A call to @cite{adafinal} is required +after the last call to an Ada subprogram, and before the program +terminates. +@end table +@end quotation + +@geindex -n (gnatbind) + +@geindex Binder +@geindex multiple input files + +If the @emph{-n} switch +is given, more than one ALI file may appear on +the command line for @cite{gnatbind}. The normal @emph{closure} +calculation is performed for each of the specified units. Calculating +the closure means finding out the set of units involved by tracing +@emph{with} references. The reason it is necessary to be able to +specify more than one ALI file is that a given program may invoke two or +more quite separate groups of Ada units. + +The binder takes the name of its output file from the last specified ALI +file, unless overridden by the use of the @emph{-o file}. + +@geindex -o (gnatbind) + +The output is an Ada unit in source form that can be compiled with GNAT. +This compilation occurs automatically as part of the @emph{gnatlink} +processing. + +Currently the GNAT run time requires a FPU using 80 bits mode +precision. Under targets where this is not the default it is required to +call GNAT.Float_Control.Reset before using floating point numbers (this +include float computation, float input and output) in the Ada code. A +side effect is that this could be the wrong mode for the foreign code +where floating point computation could be broken after this call. + +@node Binding Programs with No Main Subprogram,,Binding with Non-Ada Main Programs,Switches for gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat binding-programs-with-no-main-subprogram}@anchor{130}@anchor{gnat_ugn/building_executable_programs_with_gnat id40}@anchor{131} +@subsubsection Binding Programs with No Main Subprogram + + +It is possible to have an Ada program which does not have a main +subprogram. This program will call the elaboration routines of all the +packages, then the finalization routines. + +The following switch is used to bind programs organized in this manner: + +@quotation + +@geindex -z (gnatbind) +@end quotation + + +@table @asis + +@item @code{-z} + +Normally the binder checks that the unit name given on the command line +corresponds to a suitable main subprogram. When this switch is used, +a list of ALI files can be given, and the execution of the program +consists of elaboration of these units in an appropriate order. Note +that the default wide character encoding method for standard Text_IO +files is always set to Brackets if this switch is set (you can use +the binder switch +@emph{-Wx} to override this default). +@end table + +@node Command-Line Access,Search Paths for gnatbind,Switches for gnatbind,Binding with gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat id41}@anchor{132}@anchor{gnat_ugn/building_executable_programs_with_gnat command-line-access}@anchor{133} +@subsection Command-Line Access + + +The package @cite{Ada.Command_Line} provides access to the command-line +arguments and program name. In order for this interface to operate +correctly, the two variables + +@example +int gnat_argc; +char **gnat_argv; +@end example + +@geindex gnat_argv + +@geindex gnat_argc + +are declared in one of the GNAT library routines. These variables must +be set from the actual @cite{argc} and @cite{argv} values passed to the +main program. With no @emph{n} present, @cite{gnatbind} +generates the C main program to automatically set these variables. +If the @emph{n} switch is used, there is no automatic way to +set these variables. If they are not set, the procedures in +@cite{Ada.Command_Line} will not be available, and any attempt to use +them will raise @cite{Constraint_Error}. If command line access is +required, your main program must set @cite{gnat_argc} and +@cite{gnat_argv} from the @cite{argc} and @cite{argv} values passed to +it. + +@node Search Paths for gnatbind,Examples of gnatbind Usage,Command-Line Access,Binding with gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-for-gnatbind}@anchor{91}@anchor{gnat_ugn/building_executable_programs_with_gnat id42}@anchor{134} +@subsection Search Paths for @cite{gnatbind} + + +The binder takes the name of an ALI file as its argument and needs to +locate source files as well as other ALI files to verify object consistency. + +For source files, it follows exactly the same search rules as @emph{gcc} +(see @ref{8e,,Search Paths and the Run-Time Library (RTL)}). For ALI files the +directories searched are: + + +@itemize * + +@item +The directory containing the ALI file named in the command line, unless +the switch @emph{-I-} is specified. + +@item +All directories specified by @emph{-I} +switches on the @cite{gnatbind} +command line, in the order given. + +@geindex ADA_PRJ_OBJECTS_FILE + +@item +Each of the directories listed in the text file whose name is given +by the +@geindex ADA_PRJ_OBJECTS_FILE +@geindex environment variable; ADA_PRJ_OBJECTS_FILE +@code{ADA_PRJ_OBJECTS_FILE} environment variable. + +@geindex ADA_PRJ_OBJECTS_FILE +@geindex environment variable; ADA_PRJ_OBJECTS_FILE +@code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat +driver when project files are used. It should not normally be set +by other means. + +@geindex ADA_OBJECTS_PATH + +@item +Each of the directories listed in the value of the +@geindex ADA_OBJECTS_PATH +@geindex environment variable; ADA_OBJECTS_PATH +@code{ADA_OBJECTS_PATH} environment variable. +Construct this value +exactly as the +@geindex PATH +@geindex environment variable; PATH +@code{PATH} environment variable: a list of directory +names separated by colons (semicolons when working with the NT version +of GNAT). + +@item +The content of the @code{ada_object_path} file which is part of the GNAT +installation tree and is used to store standard libraries such as the +GNAT Run Time Library (RTL) unless the switch @emph{-nostdlib} is +specified. See @ref{8b,,Installing a library} +@end itemize + +@geindex -I (gnatbind) + +@geindex -aI (gnatbind) + +@geindex -aO (gnatbind) + +In the binder the switch @emph{-I} +is used to specify both source and +library file paths. Use @emph{-aI} +instead if you want to specify +source paths only, and @emph{-aO} +if you want to specify library paths +only. This means that for the binder +@code{-I@emph{dir}} is equivalent to +@code{-aI@emph{dir}} +@code{-aO`@emph{dir}}. +The binder generates the bind file (a C language source file) in the +current working directory. + +@geindex Ada + +@geindex System + +@geindex Interfaces + +@geindex GNAT + +The packages @cite{Ada}, @cite{System}, and @cite{Interfaces} and their +children make up the GNAT Run-Time Library, together with the package +GNAT and its children, which contain a set of useful additional +library functions provided by GNAT. The sources for these units are +needed by the compiler and are kept together in one directory. The ALI +files and object files generated by compiling the RTL are needed by the +binder and the linker and are kept together in one directory, typically +different from the directory containing the sources. In a normal +installation, you need not specify these directory names when compiling +or binding. Either the environment variables or the built-in defaults +cause these files to be found. + +Besides simplifying access to the RTL, a major use of search paths is +in compiling sources from multiple directories. This can make +development environments much more flexible. + +@node Examples of gnatbind Usage,,Search Paths for gnatbind,Binding with gnatbind +@anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatbind-usage}@anchor{135}@anchor{gnat_ugn/building_executable_programs_with_gnat id43}@anchor{136} +@subsection Examples of @cite{gnatbind} Usage + + +Here are some examples of @cite{gnatbind} invovations: + +@quotation + +@example +gnatbind hello +@end example + +The main program @cite{Hello} (source program in @code{hello.adb}) is +bound using the standard switch settings. The generated main program is +@code{b~hello.adb}. This is the normal, default use of the binder. + +@example +gnatbind hello -o mainprog.adb +@end example + +The main program @cite{Hello} (source program in @code{hello.adb}) is +bound using the standard switch settings. The generated main program is +@code{mainprog.adb} with the associated spec in +@code{mainprog.ads}. Note that you must specify the body here not the +spec. Note that if this option is used, then linking must be done manually, +since gnatlink will not be able to find the generated file. +@end quotation + +@node Linking with gnatlink,Using the GNU make Utility,Binding with gnatbind,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat id44}@anchor{137}@anchor{gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink}@anchor{20} +@section Linking with @emph{gnatlink} + + +@c index: ! gnatlink + +This chapter discusses @emph{gnatlink}, a tool that links +an Ada program and builds an executable file. This utility +invokes the system linker (via the @emph{gcc} command) +with a correct list of object files and library references. +@emph{gnatlink} automatically determines the list of files and +references for the Ada part of a program. It uses the binder file +generated by the @emph{gnatbind} to determine this list. + +Note: to invoke @cite{gnatlink} with a project file, use the @cite{gnat} +driver (see @ref{11f,,The GNAT Driver and Project Files}). + +@menu +* Running gnatlink:: +* Switches for gnatlink:: + +@end menu + +@node Running gnatlink,Switches for gnatlink,,Linking with gnatlink +@anchor{gnat_ugn/building_executable_programs_with_gnat id45}@anchor{138}@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatlink}@anchor{139} +@subsection Running @emph{gnatlink} + + +The form of the @emph{gnatlink} command is + +@example +$ gnatlink [`switches`] `mainprog`[.ali] + [`non-Ada objects`] [`linker options`] +@end example + +The arguments of @emph{gnatlink} (switches, main @code{ALI} file, +non-Ada objects +or linker options) may be in any order, provided that no non-Ada object may +be mistaken for a main @code{ALI} file. +Any file name @code{F} without the @code{.ali} +extension will be taken as the main @code{ALI} file if a file exists +whose name is the concatenation of @code{F} and @code{.ali}. + +@code{mainprog.ali} references the ALI file of the main program. +The @code{.ali} extension of this file can be omitted. From this +reference, @emph{gnatlink} locates the corresponding binder file +@code{b~mainprog.adb} and, using the information in this file along +with the list of non-Ada objects and linker options, constructs a +linker command file to create the executable. + +The arguments other than the @emph{gnatlink} switches and the main +@code{ALI} file are passed to the linker uninterpreted. +They typically include the names of +object files for units written in other languages than Ada and any library +references required to resolve references in any of these foreign language +units, or in @cite{Import} pragmas in any Ada units. + +@cite{linker options} is an optional list of linker specific +switches. +The default linker called by gnatlink is @emph{gcc} which in +turn calls the appropriate system linker. + +One useful option for the linker is @emph{-s}: it reduces the size of the +executable by removing all symbol table and relocation information from the +executable. + +Standard options for the linker such as @emph{-lmy_lib} or +@emph{-Ldir} can be added as is. +For options that are not recognized by +@emph{gcc} as linker options, use the @emph{gcc} switches +@emph{-Xlinker} or @emph{-Wl,}. + +Refer to the GCC documentation for +details. + +Here is an example showing how to generate a linker map: + +@example +$ gnatlink my_prog -Wl,-Map,MAPFILE +@end example + +Using @cite{linker options} it is possible to set the program stack and +heap size. +See @ref{13a,,Setting Stack Size from gnatlink} and +@ref{13b,,Setting Heap Size from gnatlink}. + +@emph{gnatlink} determines the list of objects required by the Ada +program and prepends them to the list of objects passed to the linker. +@emph{gnatlink} also gathers any arguments set by the use of +@cite{pragma Linker_Options} and adds them to the list of arguments +presented to the linker. + +@node Switches for gnatlink,,Running gnatlink,Linking with gnatlink +@anchor{gnat_ugn/building_executable_programs_with_gnat id46}@anchor{13c}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink}@anchor{13d} +@subsection Switches for @emph{gnatlink} + + +The following switches are available with the @emph{gnatlink} utility: + +@geindex --version (gnatlink) + + +@table @asis + +@item @code{--version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatlink) + + +@table @asis + +@item @code{--help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table + +@geindex Command line length + +@geindex -f (gnatlink) + + +@table @asis + +@item @code{-f} + +On some targets, the command line length is limited, and @emph{gnatlink} +will generate a separate file for the linker if the list of object files +is too long. +The @emph{-f} switch forces this file +to be generated even if +the limit is not exceeded. This is useful in some cases to deal with +special situations where the command line length is exceeded. +@end table + +@geindex Debugging information +@geindex including + +@geindex -g (gnatlink) + + +@table @asis + +@item @code{-g} + +The option to include debugging information causes the Ada bind file (in +other words, @code{b~mainprog.adb}) to be compiled with @emph{-g}. +In addition, the binder does not delete the @code{b~mainprog.adb}, +@code{b~mainprog.o} and @code{b~mainprog.ali} files. +Without @emph{-g}, the binder removes these files by default. +@end table + +@geindex -n (gnatlink) + + +@table @asis + +@item @code{-n} + +Do not compile the file generated by the binder. This may be used when +a link is rerun with different options, but there is no need to recompile +the binder file. +@end table + +@geindex -v (gnatlink) + + +@table @asis + +@item @code{-v} + +Verbose mode. Causes additional information to be output, including a full +list of the included object files. +This switch option is most useful when you want +to see what set of object files are being used in the link step. +@end table + +@geindex -v -v (gnatlink) + + +@table @asis + +@item @code{-v -v} + +Very verbose mode. Requests that the compiler operate in verbose mode when +it compiles the binder file, and that the system linker run in verbose mode. +@end table + +@geindex -o (gnatlink) + + +@table @asis + +@item @code{-o @emph{exec-name}} + +@cite{exec-name} specifies an alternate name for the generated +executable program. If this switch is omitted, the executable has the same +name as the main unit. For example, @cite{gnatlink try.ali} creates +an executable called @code{try}. +@end table + +@geindex -b (gnatlink) + + +@table @asis + +@item @code{-b @emph{target}} + +Compile your program to run on @cite{target}, which is the name of a +system configuration. You must have a GNAT cross-compiler built if +@cite{target} is not the same as your host system. +@end table + +@geindex -B (gnatlink) + + +@table @asis + +@item @code{-B@emph{dir}} + +Load compiler executables (for example, @cite{gnat1}, the Ada compiler) +from @cite{dir} instead of the default location. Only use this switch +when multiple versions of the GNAT compiler are available. +See the @cite{Directory Options} section in @cite{The_GNU_Compiler_Collection} +for further details. You would normally use the @emph{-b} or +@emph{-V} switch instead. +@end table + +@geindex -M (gnatlink) + + +@table @asis + +@item @code{-M} + +When linking an executable, create a map file. The name of the map file +has the same name as the executable with extension ".map". +@end table + +@geindex -M= (gnatlink) + + +@table @asis + +@item @code{-M=@emph{mapfile}} + +When linking an executable, create a map file. The name of the map file is +@cite{mapfile}. +@end table + +@geindex --GCC=compiler_name (gnatlink) + + +@table @asis + +@item @code{--GCC=@emph{compiler_name}} + +Program used for compiling the binder file. The default is +@code{gcc}. You need to use quotes around @cite{compiler_name} if +@cite{compiler_name} contains spaces or other separator characters. +As an example @code{--GCC="foo -x -y"} will instruct @emph{gnatlink} to +use @code{foo -x -y} as your compiler. Note that switch @code{-c} is always +inserted after your command name. Thus in the above example the compiler +command that will be used by @emph{gnatlink} will be @code{foo -c -x -y}. +A limitation of this syntax is that the name and path name of the executable +itself must not include any embedded spaces. If the compiler executable is +different from the default one (gcc or -gcc), then the back-end +switches in the ALI file are not used to compile the binder generated source. +For example, this is the case with @code{--GCC="foo -x -y"}. But the back end +switches will be used for @code{--GCC="gcc -gnatv"}. If several +@code{--GCC=compiler_name} are used, only the last @cite{compiler_name} +is taken into account. However, all the additional switches are also taken +into account. Thus, +@code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to +@code{--GCC="bar -x -y -z -t"}. +@end table + +@geindex --LINK= (gnatlink) + + +@table @asis + +@item @code{--LINK=@emph{name}} + +@cite{name} is the name of the linker to be invoked. This is especially +useful in mixed language programs since languages such as C++ require +their own linker to be used. When this switch is omitted, the default +name for the linker is @emph{gcc}. When this switch is used, the +specified linker is called instead of @emph{gcc} with exactly the same +parameters that would have been passed to @emph{gcc} so if the desired +linker requires different parameters it is necessary to use a wrapper +script that massages the parameters before invoking the real linker. It +may be useful to control the exact invocation by using the verbose +switch. +@end table + +@node Using the GNU make Utility,,Linking with gnatlink,Building Executable Programs with GNAT +@anchor{gnat_ugn/building_executable_programs_with_gnat id47}@anchor{13e}@anchor{gnat_ugn/building_executable_programs_with_gnat using-the-gnu-make-utility}@anchor{21} +@section Using the GNU @cite{make} Utility + + +@geindex make (GNU) +@geindex GNU make + +This chapter offers some examples of makefiles that solve specific +problems. It does not explain how to write a makefile, nor does it try to replace the +@emph{gnatmake} utility (@ref{1d,,Building with gnatmake}). + +All the examples in this section are specific to the GNU version of +make. Although @emph{make} is a standard utility, and the basic language +is the same, these examples use some advanced features found only in +@cite{GNU make}. + +@menu +* Using gnatmake in a Makefile:: +* Automatically Creating a List of Directories:: +* Generating the Command Line Switches:: +* Overcoming Command Line Length Limits:: + +@end menu + +@node Using gnatmake in a Makefile,Automatically Creating a List of Directories,,Using the GNU make Utility +@anchor{gnat_ugn/building_executable_programs_with_gnat using-gnatmake-in-a-makefile}@anchor{13f}@anchor{gnat_ugn/building_executable_programs_with_gnat id48}@anchor{140} +@subsection Using gnatmake in a Makefile + + +@c index makefile (GNU make) + +Complex project organizations can be handled in a very powerful way by +using GNU make combined with gnatmake. For instance, here is a Makefile +which allows you to build each subsystem of a big project into a separate +shared library. Such a makefile allows you to significantly reduce the link +time of very big applications while maintaining full coherence at +each step of the build process. + +The list of dependencies are handled automatically by +@emph{gnatmake}. The Makefile is simply used to call gnatmake in each of +the appropriate directories. + +Note that you should also read the example on how to automatically +create the list of directories +(@ref{141,,Automatically Creating a List of Directories}) +which might help you in case your project has a lot of subdirectories. + +@example +## This Makefile is intended to be used with the following directory +## configuration: +## - The sources are split into a series of csc (computer software components) +## Each of these csc is put in its own directory. +## Their name are referenced by the directory names. +## They will be compiled into shared library (although this would also work +## with static libraries +## - The main program (and possibly other packages that do not belong to any +## csc is put in the top level directory (where the Makefile is). +## toplevel_dir __ first_csc (sources) __ lib (will contain the library) +## \\_ second_csc (sources) __ lib (will contain the library) +## \\_ ... +## Although this Makefile is build for shared library, it is easy to modify +## to build partial link objects instead (modify the lines with -shared and +## gnatlink below) +## +## With this makefile, you can change any file in the system or add any new +## file, and everything will be recompiled correctly (only the relevant shared +## objects will be recompiled, and the main program will be re-linked). + +# The list of computer software component for your project. This might be +# generated automatically. +CSC_LIST=aa bb cc + +# Name of the main program (no extension) +MAIN=main + +# If we need to build objects with -fPIC, uncomment the following line +#NEED_FPIC=-fPIC + +# The following variable should give the directory containing libgnat.so +# You can get this directory through 'gnatls -v'. This is usually the last +# directory in the Object_Path. +GLIB=... + +# The directories for the libraries +# (This macro expands the list of CSC to the list of shared libraries, you +# could simply use the expanded form: +# LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so +LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@} + +$@{MAIN@}: objects $@{LIB_DIR@} + gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared + gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@} + +objects:: + # recompile the sources + gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@} + +# Note: In a future version of GNAT, the following commands will be simplified +# by a new tool, gnatmlib +$@{LIB_DIR@}: + mkdir -p $@{dir $@@ @} + cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat + cd $@{dir $@@ @} && cp -f ../*.ali . + +# The dependencies for the modules +# Note that we have to force the expansion of *.o, since in some cases +# make won't be able to do it itself. +aa/lib/libaa.so: $@{wildcard aa/*.o@} +bb/lib/libbb.so: $@{wildcard bb/*.o@} +cc/lib/libcc.so: $@{wildcard cc/*.o@} + +# Make sure all of the shared libraries are in the path before starting the +# program +run:: + LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@} + +clean:: + $@{RM@} -rf $@{CSC_LIST:%=%/lib@} + $@{RM@} $@{CSC_LIST:%=%/*.ali@} + $@{RM@} $@{CSC_LIST:%=%/*.o@} + $@{RM@} *.o *.ali $@{MAIN@} +@end example + +@node Automatically Creating a List of Directories,Generating the Command Line Switches,Using gnatmake in a Makefile,Using the GNU make Utility +@anchor{gnat_ugn/building_executable_programs_with_gnat automatically-creating-a-list-of-directories}@anchor{141}@anchor{gnat_ugn/building_executable_programs_with_gnat id49}@anchor{142} +@subsection Automatically Creating a List of Directories + + +In most makefiles, you will have to specify a list of directories, and +store it in a variable. For small projects, it is often easier to +specify each of them by hand, since you then have full control over what +is the proper order for these directories, which ones should be +included. + +However, in larger projects, which might involve hundreds of +subdirectories, it might be more convenient to generate this list +automatically. + +The example below presents two methods. The first one, although less +general, gives you more control over the list. It involves wildcard +characters, that are automatically expanded by @emph{make}. Its +shortcoming is that you need to explicitly specify some of the +organization of your project, such as for instance the directory tree +depth, whether some directories are found in a separate tree, etc. + +The second method is the most general one. It requires an external +program, called @emph{find}, which is standard on all Unix systems. All +the directories found under a given root directory will be added to the +list. + +@example +# The examples below are based on the following directory hierarchy: +# All the directories can contain any number of files +# ROOT_DIRECTORY -> a -> aa -> aaa +# -> ab +# -> ac +# -> b -> ba -> baa +# -> bb +# -> bc +# This Makefile creates a variable called DIRS, that can be reused any time +# you need this list (see the other examples in this section) + +# The root of your project's directory hierarchy +ROOT_DIRECTORY=. + +#### +# First method: specify explicitly the list of directories +# This allows you to specify any subset of all the directories you need. +#### + +DIRS := a/aa/ a/ab/ b/ba/ + +#### +# Second method: use wildcards +# Note that the argument(s) to wildcard below should end with a '/'. +# Since wildcards also return file names, we have to filter them out +# to avoid duplicate directory names. +# We thus use make's `dir` and `sort` functions. +# It sets DIRs to the following value (note that the directories aaa and baa +# are not given, unless you change the arguments to wildcard). +# DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/ +#### + +DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/ + $@{ROOT_DIRECTORY@}/*/*/@}@}@} + +#### +# Third method: use an external program +# This command is much faster if run on local disks, avoiding NFS slowdowns. +# This is the most complete command: it sets DIRs to the following value: +# DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc +#### + +DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@} +@end example + +@node Generating the Command Line Switches,Overcoming Command Line Length Limits,Automatically Creating a List of Directories,Using the GNU make Utility +@anchor{gnat_ugn/building_executable_programs_with_gnat id50}@anchor{143}@anchor{gnat_ugn/building_executable_programs_with_gnat generating-the-command-line-switches}@anchor{144} +@subsection Generating the Command Line Switches + + +Once you have created the list of directories as explained in the +previous section (@ref{141,,Automatically Creating a List of Directories}), +you can easily generate the command line arguments to pass to gnatmake. + +For the sake of completeness, this example assumes that the source path +is not the same as the object path, and that you have two separate lists +of directories. + +@example +# see "Automatically creating a list of directories" to create +# these variables +SOURCE_DIRS= +OBJECT_DIRS= + +GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@} +GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@} + +all: + gnatmake $@{GNATMAKE_SWITCHES@} main_unit +@end example + +@node Overcoming Command Line Length Limits,,Generating the Command Line Switches,Using the GNU make Utility +@anchor{gnat_ugn/building_executable_programs_with_gnat overcoming-command-line-length-limits}@anchor{145}@anchor{gnat_ugn/building_executable_programs_with_gnat id51}@anchor{146} +@subsection Overcoming Command Line Length Limits + + +One problem that might be encountered on big projects is that many +operating systems limit the length of the command line. It is thus hard to give +gnatmake the list of source and object directories. + +This example shows how you can set up environment variables, which will +make @emph{gnatmake} behave exactly as if the directories had been +specified on the command line, but have a much higher length limit (or +even none on most systems). + +It assumes that you have created a list of directories in your Makefile, +using one of the methods presented in +@ref{141,,Automatically Creating a List of Directories}. +For the sake of completeness, we assume that the object +path (where the ALI files are found) is different from the sources patch. + +Note a small trick in the Makefile below: for efficiency reasons, we +create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are +expanded immediately by @cite{make}. This way we overcome the standard +make behavior which is to expand the variables only when they are +actually used. + +On Windows, if you are using the standard Windows command shell, you must +replace colons with semicolons in the assignments to these variables. + +@example +# In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH. +# This is the same thing as putting the -I arguments on the command line. +# (the equivalent of using -aI on the command line would be to define +# only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH). +# You can of course have different values for these variables. +# +# Note also that we need to keep the previous values of these variables, since +# they might have been set before running 'make' to specify where the GNAT +# library is installed. + +# see "Automatically creating a list of directories" to create these +# variables +SOURCE_DIRS= +OBJECT_DIRS= + +empty:= +space:=$@{empty@} $@{empty@} +SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@} +OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@} +ADA_INCLUDE_PATH += $@{SOURCE_LIST@} +ADA_OBJECTS_PATH += $@{OBJECT_LIST@} +export ADA_INCLUDE_PATH +export ADA_OBJECTS_PATH + +all: + gnatmake main_unit +@end example + +@c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + +@node GNAT Project Manager,Tools Supporting Project Files,Building Executable Programs with GNAT,Top +@anchor{gnat_ugn/gnat_project_manager doc}@anchor{147}@anchor{gnat_ugn/gnat_project_manager gnat-project-manager}@anchor{b}@anchor{gnat_ugn/gnat_project_manager id1}@anchor{148} +@chapter GNAT Project Manager + + +@menu +* Introduction:: +* Building With Projects:: +* Organizing Projects into Subsystems:: +* Scenarios in Projects:: +* Library Projects:: +* Project Extension:: +* Aggregate Projects:: +* Aggregate Library Projects:: +* Project File Reference:: + +@end menu + +@node Introduction,Building With Projects,,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager introduction}@anchor{149}@anchor{gnat_ugn/gnat_project_manager gnat-project-manager-introduction}@anchor{14a} +@section Introduction + + +This chapter describes GNAT's @emph{Project Manager}, a facility that allows +you to manage complex builds involving a number of source files, directories, +and options for different system configurations. In particular, +project files allow you to specify: + + +@itemize * + +@item +The directory or set of directories containing the source files, and/or the +names of the specific source files themselves + +@item +The directory in which the compiler's output +(@code{ALI} files, object files, tree files, etc.) is to be placed + +@item +The directory in which the executable programs are to be placed + +@item +Switch settings for any of the project-enabled tools; +you can apply these settings either globally or to individual compilation units. + +@item +The source files containing the main subprogram(s) to be built + +@item +The source programming language(s) + +@item +Source file naming conventions; you can specify these either globally or for +individual compilation units (see @ref{14b,,Naming Schemes}). + +@item +Change any of the above settings depending on external values, thus enabling +the reuse of the projects in various @strong{scenarios} (see @ref{14c,,Scenarios in Projects}). + +@item +Automatically build libraries as part of the build process +(see @ref{8a,,Library Projects}). +@end itemize + +Project files are written in a syntax close to that of Ada, using familiar +notions such as packages, context clauses, declarations, default values, +assignments, and inheritance (see @ref{14d,,Project File Reference}). + +Project files can be built hierarchically from other project files, simplifying +complex system integration and project reuse (see @ref{14e,,Organizing Projects into Subsystems}). + + +@itemize * + +@item +One project can import other projects containing needed source files. +More generally, the Project Manager lets you structure large development +efforts into hierarchical subsystems, where build decisions are delegated +to the subsystem level, and thus different compilation environments +(switch settings) used for different subsystems. + +@item +You can organize GNAT projects in a hierarchy: a child project +can extend a parent project, inheriting the parent's source files and +optionally overriding any of them with alternative versions +(see @ref{14f,,Project Extension}). +@end itemize + +Several tools support project files, generally in addition to specifying +the information on the command line itself). They share common switches +to control the loading of the project (in particular +@code{-P@emph{projectfile}} and +@code{-X@emph{vbl}=@emph{value}}). + +The Project Manager supports a wide range of development strategies, +for systems of all sizes. Here are some typical practices that are +easily handled: + + +@itemize * + +@item +Using a common set of source files and generating object files in different +directories via different switch settings. It can be used for instance, for +generating separate sets of object files for debugging and for production. + +@item +Using a mostly-shared set of source files with different versions of +some units or subunits. It can be used for instance, for grouping and hiding +all OS dependencies in a small number of implementation units. +@end itemize + +Project files can be used to achieve some of the effects of a source +versioning system (for example, defining separate projects for +the different sets of sources that comprise different releases) but the +Project Manager is independent of any source configuration management tool +that might be used by the developers. + +The various sections below introduce the different concepts related to +projects. Each section starts with examples and use cases, and then goes into +the details of related project file capabilities. + +@node Building With Projects,Organizing Projects into Subsystems,Introduction,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager building-with-projects}@anchor{150}@anchor{gnat_ugn/gnat_project_manager id2}@anchor{151} +@section Building With Projects + + +In its simplest form, a unique project is used to build a single executable. +This section concentrates on such a simple setup. Later sections will extend +this basic model to more complex setups. + +The following concepts are the foundation of project files, and will be further +detailed later in this documentation. They are summarized here as a reference. + + +@table @asis + +@item @strong{Project file}: + +A text file using an Ada-like syntax, generally using the @code{.gpr} +extension. It defines build-related characteristics of an application. +The characteristics include the list of sources, the location of those +sources, the location for the generated object files, the name of +the main program, and the options for the various tools involved in the +build process. + +@item @strong{Project attribute}: + +A specific project characteristic is defined by an attribute clause. Its +value is a string or a sequence of strings. All settings in a project +are defined through a list of predefined attributes with precise +semantics. See @ref{152,,Attributes}. + +@item @strong{Package in a project}: + +Global attributes are defined at the top level of a project. +Attributes affecting specific tools are grouped in a +package whose name is related to tool's function. The most common +packages are @cite{Builder}, @cite{Compiler}, @cite{Binder}, +and @cite{Linker}. See @ref{153,,Packages}. + +@item @strong{Project variables}: + +In addition to attributes, a project can use variables to store intermediate +values and avoid duplication in complex expressions. It can be initialized +with a value coming from the environment. +A frequent use of variables is to define scenarios. +See @ref{154,,External Values}, @ref{14c,,Scenarios in Projects}, and @ref{155,,Variables}. + +@item @strong{Source files} and @strong{source directories}: + +A source file is associated with a language through a naming convention. For +instance, @cite{foo.c} is typically the name of a C source file; +@cite{bar.ads} or @cite{bar.1.ada} are two common naming conventions for a +file containing an Ada spec. A compilation unit is often composed of a main +source file and potentially several auxiliary ones, such as header files in C. +The naming conventions can be user defined @ref{14b,,Naming Schemes}, and will +drive the builder to call the appropriate compiler for the given source file. +Source files are searched for in the source directories associated with the +project through the @strong{Source_Dirs} attribute. By default, all the files (in +these source directories) following the naming conventions associated with the +declared languages are considered to be part of the project. It is also +possible to limit the list of source files using the @strong{Source_Files} or +@strong{Source_List_File} attributes. Note that those last two attributes only +accept basenames with no directory information. + +@item @strong{Object files} and @strong{object directory}: + +An object file is an intermediate file produced by the compiler from a +compilation unit. It is used by post-compilation tools to produce +final executables or libraries. Object files produced in the context of +a given project are stored in a single directory that can be specified by the +@strong{Object_Dir} attribute. In order to store objects in +two or more object directories, the system must be split into +distinct subsystems with their own project file. +@end table + +The following subsections introduce gradually all the attributes of interest +for simple build needs. Here is the simple setup that will be used in the +following examples. + +The Ada source files @code{pack.ads}, @code{pack.adb}, and @code{proc.adb} are in +the @code{common/} directory. The file @code{proc.adb} contains an Ada main +subprogram @cite{Proc} that @emph{with}s package @cite{Pack}. We want to compile +these source files with the switch +@emph{-O2}, and put the resulting files in +the directory @code{obj/}. + +@example +common/ + pack.ads + pack.adb + proc.adb +common/obj/ + proc.ali, proc.o pack.ali, pack.o +@end example + +Our project is to be called @emph{Build}. The name of the +file is the name of the project (case-insensitive) with the +@code{.gpr} extension, therefore the project file name is @code{build.gpr}. This +is not mandatory, but a warning is issued when this convention is not followed. + +This is a very simple example, and as stated above, a single project +file is enough for it. We will thus create a new file, that for now +should contain the following code: + +@example +project Build is +end Build; +@end example + +@menu +* Source Files and Directories:: +* Duplicate Sources in Projects:: +* Object and Exec Directory:: +* Main Subprograms:: +* Tools Options in Project Files:: +* Compiling with Project Files:: +* Executable File Names:: +* Avoid Duplication With Variables:: +* Naming Schemes:: +* Installation:: +* Distributed support:: + +@end menu + +@node Source Files and Directories,Duplicate Sources in Projects,,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id3}@anchor{156}@anchor{gnat_ugn/gnat_project_manager source-files-and-directories}@anchor{157} +@subsection Source Files and Directories + + +When you create a new project, the first thing to describe is how to find the +corresponding source files. These are the only settings that are needed by all +the tools that will use this project (builder, compiler, binder and linker for +the compilation, IDEs to edit the source files,...). + +@geindex Source directories (GNAT Project Manager) + +The first step is to declare the source directories, which are the directories +to be searched to find source files. In the case of the example, +the @code{common} directory is the only source directory. + +@geindex Source_Dirs (GNAT Project Manager) + +There are several ways of defining source directories: + + +@itemize * + +@item +When the attribute @strong{Source_Dirs} is not used, a project contains a +single source directory which is the one where the project file itself +resides. In our example, if @code{build.gpr} is placed in the @code{common} +directory, the project has the needed implicit source directory. + +@item +The attribute @strong{Source_Dirs} can be set to a list of path names, one +for each of the source directories. Such paths can either be absolute +names (for instance @code{"/usr/local/common/"} on UNIX), or relative to the +directory in which the project file resides (for instance "." if +@code{build.gpr} is inside @code{common/}, or "common" if it is one level up). +Each of the source directories must exist and be readable. + +@geindex portability of path names (GNAT Project Manager) + +The syntax for directories is platform specific. For portability, however, +the project manager will always properly translate UNIX-like path names to +the native format of the specific platform. For instance, when the same +project file is to be used both on Unix and Windows, "/" should be used as +the directory separator rather than "\". + +@item +The attribute @strong{Source_Dirs} can automatically include subdirectories +using a special syntax inspired by some UNIX shells. If any of the paths in +the list ends with "@code{**}", then that path and all its subdirectories +(recursively) are included in the list of source directories. For instance, +@code{**} and @code{./**} represent the complete directory tree rooted at +the directory in which the project file resides. + +@geindex Source directories (GNAT Project Manager) + +@geindex Excluded_Source_Dirs (GNAT Project Manager) + +When using that construct, it can sometimes be convenient to also use the +attribute @strong{Excluded_Source_Dirs}, which is also a list of paths. Each entry +specifies a directory whose immediate content, not including subdirs, is to +be excluded. It is also possible to exclude a complete directory subtree +using the "**" notation. + +@geindex Ignore_Source_Sub_Dirs (GNAT Project Manager) + +It is often desirable to remove, from the source directories, directory +subtrees rooted at some subdirectories. An example is the subdirectories +created by a Version Control System such as Subversion that creates directory +subtrees rooted at subdirectories ".svn". To do that, attribute +@strong{Ignore_Source_Sub_Dirs} can be used. It specifies the list of simple +file names for the roots of these undesirable directory subtrees. + +@c code-block: ada-project +@c +@c for Source_Dirs use ("./**"); +@c for Ignore_Source_Sub_Dirs use (".svn"); +@end itemize + +When applied to the simple example, and because we generally prefer to have +the project file at the toplevel directory rather than mixed with the sources, +we will create the following file + +@c code-block: ada-project +@c +@c build.gpr +@c project Build is +@c for Source_Dirs use ("common"); -- <<<< +@c end Build; + +Once source directories have been specified, one may need to indicate +source files of interest. By default, all source files present in the source +directories are considered by the project manager. When this is not desired, +it is possible to specify the list of sources to consider explicitly. +In such a case, only source file base names are indicated and not +their absolute or relative path names. The project manager is in charge of +locating the specified source files in the specified source directories. + + +@itemize * + +@item +By default, the project manager searches for all source files of all +specified languages in all the source directories. + +Since the project manager was initially developed for Ada environments, the +default language is usually Ada and the above project file is complete: it +defines without ambiguity the sources composing the project: that is to say, +all the sources in subdirectory "common" for the default language (Ada) using +the default naming convention. + +@geindex Languages (GNAT Project Manager) + +However, when compiling a multi-language application, or a pure C +application, the project manager must be told which languages are of +interest, which is done by setting the @strong{Languages} attribute to a list of +strings, each of which is the name of a language. Tools like +@emph{gnatmake} only know about Ada, while other tools like +@emph{gprbuild} know about many more languages such as C, C++, Fortran, +assembly and others can be added dynamically. + +@geindex Naming scheme (GNAT Project Manager) + +Even when using only Ada, the default naming might not be suitable. Indeed, +how does the project manager recognizes an "Ada file" from any other +file? Project files can describe the naming scheme used for source files, +and override the default (see @ref{14b,,Naming Schemes}). The default is the +standard GNAT extension (@code{.adb} for bodies and @code{.ads} for +specs), which is what is used in our example, explaining why no naming scheme +is explicitly specified. +See @ref{14b,,Naming Schemes}. + +@geindex Source_Files (GNAT Project Manager) + +@item +@cite{Source_Files}. +In some cases, source directories might contain files that should not be +included in a project. One can specify the explicit list of file names to +be considered through the @strong{Source_Files} attribute. +When this attribute is defined, instead of looking at every file in the +source directories, the project manager takes only those names into +consideration reports errors if they cannot be found in the source +directories or does not correspond to the naming scheme. + +@item +For various reasons, it is sometimes useful to have a project with no +sources (most of the time because the attributes defined in the project +file will be reused in other projects, as explained in +@ref{14e,,Organizing Projects into Subsystems}. To do this, the attribute +@emph{Source_Files} is set to the empty list, i.e. @cite{()}. Alternatively, +@emph{Source_Dirs} can be set to the empty list, with the same +result. + +@geindex Source_List_File (GNAT Project Manager) + +@item +@cite{Source_List_File}. +If there is a great number of files, it might be more convenient to use +the attribute @strong{Source_List_File}, which specifies the full path of a file. +This file must contain a list of source file names (one per line, no +directory information) that are searched as if they had been defined +through @emph{Source_Files}. Such a file can easily be created through +external tools. + +A warning is issued if both attributes @cite{Source_Files} and +@cite{Source_List_File} are given explicit values. In this case, the +attribute @cite{Source_Files} prevails. + +@geindex Excluded_Source_Files (GNAT Project Manager) + +@geindex Locally_Removed_Files (GNAT Project Manager) + +@geindex Excluded_Source_List_File (GNAT Project Manager) + +@item +@cite{Excluded_Source_Files}. +Specifying an explicit list of files is not always convenient.It might be +more convenient to use the default search rules with specific exceptions. +This can be done thanks to the attribute @strong{Excluded_Source_Files} +(or its synonym @strong{Locally_Removed_Files}). +Its value is the list of file names that should not be taken into account. +This attribute is often used when extending a project, +see @ref{14f,,Project Extension}. A similar attribute +@strong{Excluded_Source_List_File} plays the same +role but takes the name of file containing file names similarly to +@cite{Source_List_File}. +@end itemize + +In most simple cases, such as the above example, the default source file search +behavior provides the expected result, and we do not need to add anything after +setting @cite{Source_Dirs}. The project manager automatically finds +@code{pack.ads}, @code{pack.adb}, and @code{proc.adb} as source files of the +project. + +Note that by default a warning is issued when a project has no sources attached +to it and this is not explicitly indicated in the project file. + +@node Duplicate Sources in Projects,Object and Exec Directory,Source Files and Directories,Building With Projects +@anchor{gnat_ugn/gnat_project_manager duplicate-sources-in-projects}@anchor{158}@anchor{gnat_ugn/gnat_project_manager id4}@anchor{159} +@subsection Duplicate Sources in Projects + + +If the order of the source directories is known statically, that is if +@cite{"/**"} is not used in the string list @cite{Source_Dirs}, then there may +be several files with the same name sitting in different directories of the +project. In this case, only the file in the first directory is considered as a +source of the project and the others are hidden. If @cite{"/**"} is used in the +string list @cite{Source_Dirs}, it is an error to have several files with the +same name in the same directory @cite{"/**"} subtree, since there would be an +ambiguity as to which one should be used. However, two files with the same name +may exist in two single directories or directory subtrees. In this case, the +one in the first directory or directory subtree is a source of the project. + +If there are two sources in different directories of the same @cite{"/**"} +subtree, one way to resolve the problem is to exclude the directory of the +file that should not be used as a source of the project. + +@node Object and Exec Directory,Main Subprograms,Duplicate Sources in Projects,Building With Projects +@anchor{gnat_ugn/gnat_project_manager object-and-exec-directory}@anchor{15a}@anchor{gnat_ugn/gnat_project_manager id5}@anchor{15b} +@subsection Object and Exec Directory + + +The next step when writing a project is to indicate where the compiler should +put the object files. In fact, the compiler and other tools might create +several different kind of files (for GNAT, there is the object file and the ALI +file for instance). One of the important concepts in projects is that most +tools may consider source directories as read-only and do not attempt to create +new or temporary files there. Instead, all files are created in the object +directory. It is of course not true for project-aware IDEs, whose purpose it is +to create the source files. + +@geindex Object_Dir (GNAT Project Manager) + +The object directory is specified through the @strong{Object_Dir} attribute. +Its value is the path to the object directory, either absolute or +relative to the directory containing the project file. This +directory must already exist and be readable and writable, although +some tools have a switch to create the directory if needed (See +the switch @cite{-p} for @emph{gnatmake} +and @emph{gprbuild}). + +If the attribute @cite{Object_Dir} is not specified, it defaults to +the project directory, that is the directory containing the project file. + +For our example, we can specify the object dir in this way: + +@c code-block: ada-project +@c +@c project Build is +@c for Source_Dirs use ("common"); +@c for Object_Dir use "obj"; -- <<<< +@c end Build; + +As mentioned earlier, there is a single object directory per project. As a +result, if you have an existing system where the object files are spread across +several directories, you can either move all of them into the same directory if +you want to build it with a single project file, or study the section on +subsystems (see @ref{14e,,Organizing Projects into Subsystems}) to see how each +separate object directory can be associated with one of the subsystems +constituting the application. + +When the @emph{linker} is called, it usually creates an executable. By +default, this executable is placed in the object directory of the project. It +might be convenient to store it in its own directory. + +@geindex Exec_Dir (GNAT Project Manager) + +This can be done through the @cite{Exec_Dir} attribute, which, like +@emph{Object_Dir} contains a single absolute or relative path and must point to +an existing and writable directory, unless you ask the tool to create it on +your behalf. When not specified, It defaults to the object directory and +therefore to the project file's directory if neither @emph{Object_Dir} nor +@emph{Exec_Dir} was specified. + +In the case of the example, let's place the executable in the root +of the hierarchy, ie the same directory as @code{build.gpr}. Hence +the project file is now + +@c code-block: ada-project +@c +@c project Build is +@c for Source_Dirs use ("common"); +@c for Object_Dir use "obj"; +@c for Exec_Dir use "."; -- <<<< +@c end Build; + +@node Main Subprograms,Tools Options in Project Files,Object and Exec Directory,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id6}@anchor{15c}@anchor{gnat_ugn/gnat_project_manager main-subprograms}@anchor{15d} +@subsection Main Subprograms + + +In the previous section, executables were mentioned. The project manager needs +to be taught what they are. In a project file, an executable is indicated by +pointing to the source file of a main subprogram. In C this is the file that +contains the @cite{main} function, and in Ada the file that contains the main +unit. + +There can be any number of such main files within a given project, and thus +several executables can be built in the context of a single project file. Of +course, one given executable might not (and in fact will not) need all the +source files referenced by the project. As opposed to other build environments +such as @emph{makefile}, one does not need to specify the list of +dependencies of each executable, the project-aware builder knows enough of the +semantics of the languages to build and link only the necessary elements. + +@geindex Main (GNAT Project Manager) + +The list of main files is specified via the @strong{Main} attribute. It contains +a list of file names (no directories). If a project defines this +attribute, it is not necessary to identify main files on the +command line when invoking a builder, and editors like +@emph{GPS} will be able to create extra menus to spawn or debug the +corresponding executables. + +@c code-block: ada-project +@c +@c project Build is +@c for Source_Dirs use ("common"); +@c for Object_Dir use "obj"; +@c for Exec_Dir use "."; +@c for Main use ("proc.adb"); -- <<<< +@c end Build; + +If this attribute is defined in the project, then spawning the builder +with a command such as + +@example +gprbuild -Pbuild +@end example + +automatically builds all the executables corresponding to the files +listed in the @emph{Main} attribute. It is possible to specify one +or more executables on the command line to build a subset of them. + +@node Tools Options in Project Files,Compiling with Project Files,Main Subprograms,Building With Projects +@anchor{gnat_ugn/gnat_project_manager tools-options-in-project-files}@anchor{15e}@anchor{gnat_ugn/gnat_project_manager id7}@anchor{15f} +@subsection Tools Options in Project Files + + +We now have a project file that fully describes our environment, and can be +used to build the application with a simple @emph{gprbuild} command as seen +in the previous section. In fact, the empty project we showed immediately at +the beginning (with no attribute at all) could already fulfill that need if it +was put in the @code{common} directory. + +Of course, we might want more control. This section shows you how to specify +the compilation switches that the various tools involved in the building of the +executable should use. + +@geindex command line length (GNAT Project Manager) + +Since source names and locations are described in the project file, it is not +necessary to use switches on the command line for this purpose (switches such +as -I for gcc). This removes a major source of command line length overflow. +Clearly, the builders will have to communicate this information one way or +another to the underlying compilers and tools they call but they usually use +response files for this and thus are not subject to command line overflows. + +Several tools participate to the creation of an executable: the compiler +produces object files from the source files; the binder (in the Ada case) +creates a "source" file that takes care, among other things, of elaboration +issues and global variable initialization; and the linker gathers everything +into a single executable that users can execute. All these tools are known to +the project manager and will be called with user defined switches from the +project files. However, we need to introduce a new project file concept to +express the switches to be used for any of the tools involved in the build. + +@geindex project file packages (GNAT Project Manager) + +A project file is subdivided into zero or more @strong{packages}, each of which +contains the attributes specific to one tool (or one set of tools). Project +files use an Ada-like syntax for packages. Package names permitted in project +files are restricted to a predefined set (see @ref{153,,Packages}), and the contents +of packages are limited to a small set of constructs and attributes +(see @ref{152,,Attributes}). + +Our example project file can be extended with the following empty packages. At +this stage, they could all be omitted since they are empty, but they show which +packages would be involved in the build process. + +@c code-block: ada-project +@c +@c project Build is +@c for Source_Dirs use ("common"); +@c for Object_Dir use "obj"; +@c for Exec_Dir use "."; +@c for Main use ("proc.adb"); +@c +@c package Builder is --<<< for gnatmake and gprbuild +@c end Builder; +@c +@c package Compiler is --<<< for the compiler +@c end Compiler; +@c +@c package Binder is --<<< for the binder +@c end Binder; +@c +@c package Linker is --<<< for the linker +@c end Linker; +@c end Build; + +Let's first examine the compiler switches. As stated in the initial description +of the example, we want to compile all files with @emph{-O2}. This is a +compiler switch, although it is usual, on the command line, to pass it to the +builder which then passes it to the compiler. It is recommended to use directly +the right package, which will make the setup easier to understand for other +people. + +Several attributes can be used to specify the switches: + +@geindex Default_Switches (GNAT Project Manager) + +@strong{Default_Switches}: + +@quotation + +This is the first mention in this manual of an @strong{indexed attribute}. When +this attribute is defined, one must supply an @emph{index} in the form of a +literal string. +In the case of @emph{Default_Switches}, the index is the name of the +language to which the switches apply (since a different compiler will +likely be used for each language, and each compiler has its own set of +switches). The value of the attribute is a list of switches. + +In this example, we want to compile all Ada source files with the switch +@emph{-O2}, and the resulting project file is as follows +(only the @cite{Compiler} package is shown): + +@c code-block: ada-project +@c +@c package Compiler is +@c for Default_Switches ("Ada") use ("-O2"); +@c end Compiler; +@end quotation + +@geindex Switches (GNAT Project Manager) + +@strong{Switches}: + +@quotation + +In some cases, we might want to use specific switches +for one or more files. For instance, compiling @code{proc.adb} might not be +possible at high level of optimization because of a compiler issue. +In such a case, the @emph{Switches} +attribute (indexed on the file name) can be used and will override the +switches defined by @emph{Default_Switches}. Our project file would +become: + +@c code-block: ada-project +@c +@c +@c package Compiler is +@c for Default_Switches ("Ada") +@c use ("-O2"); +@c for Switches ("proc.adb") +@c use ("-O0"); +@c end Compiler; + +@cite{Switches} may take a pattern as an index, such as in: + +@c code-block: ada-project +@c +@c package Compiler is +@c for Default_Switches ("Ada") +@c use ("-O2"); +@c for Switches ("pkg*") +@c use ("-O0"); +@c end Compiler; + +Sources @code{pkg.adb} and @code{pkg-child.adb} would be compiled with -O0, +not -O2. + +@cite{Switches} can also be given a language name as index instead of a file +name in which case it has the same semantics as @emph{Default_Switches}. +However, indexes with wild cards are never valid for language name. +@end quotation + +@geindex Local_Configuration_Pragmas (GNAT Project Manager) + +@strong{Local_Configuration_Pragmas}: + +@quotation + +This attribute may specify the path +of a file containing configuration pragmas for use by the Ada compiler, +such as @cite{pragma Restrictions (No_Tasking)}. These pragmas will be +used for all the sources of the project. +@end quotation + +The switches for the other tools are defined in a similar manner through the +@strong{Default_Switches} and @strong{Switches} attributes, respectively in the +@emph{Builder} package (for @emph{gnatmake} and @emph{gprbuild}), +the @emph{Binder} package (binding Ada executables) and the @emph{Linker} +package (for linking executables). + +@node Compiling with Project Files,Executable File Names,Tools Options in Project Files,Building With Projects +@anchor{gnat_ugn/gnat_project_manager compiling-with-project-files}@anchor{160}@anchor{gnat_ugn/gnat_project_manager id8}@anchor{161} +@subsection Compiling with Project Files + + +Now that our project files are written, let's build our executable. +Here is the command we would use from the command line: + +@example +gnatmake -Pbuild +@end example + +This will automatically build the executables specified through the +@emph{Main} attribute: for each, it will compile or recompile the +sources for which the object file does not exist or is not up-to-date; it +will then run the binder; and finally run the linker to create the +executable itself. + +@emph{gnatmake} only knows how to handle Ada files. By using +@emph{gprbuild} as a builder, you could automatically manage C files the +same way: create the file @code{utils.c} in the @code{common} directory, +set the attribute @emph{Languages} to @cite{"(Ada@comma{} C)"}, and run + +@example +gprbuild -Pbuild +@end example + +Gprbuild knows how to recompile the C files and will +recompile them only if one of their dependencies has changed. No direct +indication on how to build the various elements is given in the +project file, which describes the project properties rather than a +set of actions to be executed. Here is the invocation of +@emph{gprbuild} when building a multi-language program: + +@example +$ gprbuild -Pbuild +gcc -c proc.adb +gcc -c pack.adb +gcc -c utils.c +gprbind proc +... +gcc proc.o -o proc +@end example + +Notice the three steps described earlier: + + +@itemize * + +@item +The first three gcc commands correspond to the compilation phase. + +@item +The gprbind command corresponds to the post-compilation phase. + +@item +The last gcc command corresponds to the final link. +@end itemize + +@geindex -v option (for GPRbuild) + +The default output of GPRbuild's execution is kept reasonably simple and easy +to understand. In particular, some of the less frequently used commands are not +shown, and some parameters are abbreviated. So it is not possible to rerun the +effect of the @emph{gprbuild} command by cut-and-pasting its output. +GPRbuild's option @cite{-v} provides a much more verbose output which includes, +among other information, more complete compilation, post-compilation and link +commands. + +@node Executable File Names,Avoid Duplication With Variables,Compiling with Project Files,Building With Projects +@anchor{gnat_ugn/gnat_project_manager executable-file-names}@anchor{162}@anchor{gnat_ugn/gnat_project_manager id9}@anchor{163} +@subsection Executable File Names + + +@geindex Executable (GNAT Project Manager) + +By default, the executable name corresponding to a main file is +computed from the main source file name. Through the attribute +@strong{Builder.Executable}, it is possible to change this default. + +For instance, instead of building @emph{proc} (or @emph{proc.exe} +on Windows), we could configure our project file to build "proc1" +(resp proc1.exe) with the following addition: + +@example +project Build is + ... -- same as before + package Builder is + for Executable ("proc.adb") use "proc1"; + end Builder +end Build; +@end example + +@geindex Executable_Suffix (GNAT Project Manager) + +Attribute @strong{Executable_Suffix}, when specified, may change the suffix +of the executable files, when no attribute @cite{Executable} applies: +its value replaces the platform-specific executable suffix. +The default executable suffix is empty on UNIX and ".exe" on Windows. + +It is also possible to change the name of the produced executable by using the +command line switch @emph{-o}. When several mains are defined in the project, +it is not possible to use the @emph{-o} switch and the only way to change the +names of the executable is provided by Attributes @cite{Executable} and +@cite{Executable_Suffix}. + +@node Avoid Duplication With Variables,Naming Schemes,Executable File Names,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id10}@anchor{164}@anchor{gnat_ugn/gnat_project_manager avoid-duplication-with-variables}@anchor{165} +@subsection Avoid Duplication With Variables + + +To illustrate some other project capabilities, here is a slightly more complex +project using similar sources and a main program in C: + +@example +project C_Main is + for Languages use ("Ada", "C"); + for Source_Dirs use ("common"); + for Object_Dir use "obj"; + for Main use ("main.c"); + package Compiler is + C_Switches := ("-pedantic"); + for Default_Switches ("C") use C_Switches; + for Default_Switches ("Ada") use ("-gnaty"); + for Switches ("main.c") use C_Switches & ("-g"); + end Compiler; +end C_Main; +@end example + +This project has many similarities with the previous one. +As expected, its @cite{Main} attribute now refers to a C source. +The attribute @emph{Exec_Dir} is now omitted, thus the resulting +executable will be put in the directory @code{obj}. + +The most noticeable difference is the use of a variable in the +@emph{Compiler} package to store settings used in several attributes. +This avoids text duplication, and eases maintenance (a single place to +modify if we want to add new switches for C files). We will revisit +the use of variables in the context of scenarios (see @ref{14c,,Scenarios in Projects}). + +In this example, we see how the file @code{main.c} can be compiled with +the switches used for all the other C files, plus @emph{-g}. +In this specific situation the use of a variable could have been +replaced by a reference to the @cite{Default_Switches} attribute: + +@example +for Switches ("c_main.c") use Compiler'Default_Switches ("C") & ("-g"); +@end example + +Note the tick (@emph{'}) used to refer to attributes defined in a package. + +Here is the output of the GPRbuild command using this project: + +@example +$ gprbuild -Pc_main +gcc -c -pedantic -g main.c +gcc -c -gnaty proc.adb +gcc -c -gnaty pack.adb +gcc -c -pedantic utils.c +gprbind main.bexch +... +gcc main.o -o main +@end example + +The default switches for Ada sources, +the default switches for C sources (in the compilation of @code{lib.c}), +and the specific switches for @code{main.c} have all been taken into +account. + +@node Naming Schemes,Installation,Avoid Duplication With Variables,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id11}@anchor{166}@anchor{gnat_ugn/gnat_project_manager naming-schemes}@anchor{14b} +@subsection Naming Schemes + + +Sometimes an Ada software system is ported from one compilation environment to +another (say GNAT), and the file are not named using the default GNAT +conventions. Instead of changing all the file names, which for a variety of +reasons might not be possible, you can define the relevant file naming scheme +in the @strong{Naming} package of your project file. + +The naming scheme has two distinct goals for the project manager: it +allows finding of source files when searching in the source +directories, and given a source file name it makes it possible to guess +the associated language, and thus the compiler to use. + +Note that the use by the Ada compiler of pragmas Source_File_Name is not +supported when using project files. You must use the features described in this +paragraph. You can however specify other configuration pragmas. + +The following attributes can be defined in package @cite{Naming}: + +@geindex Casing (GNAT Project Manager) + +@strong{Casing}: + +@quotation + +Its value must be one of @cite{"lowercase"} (the default if +unspecified), @cite{"uppercase"} or @cite{"mixedcase"}. It describes the +casing of file names with regards to the Ada unit name. Given an Ada unit +My_Unit, the file name will respectively be @code{my_unit.adb} (lowercase), +@code{MY_UNIT.ADB} (uppercase) or @code{My_Unit.adb} (mixedcase). +On Windows, file names are case insensitive, so this attribute is +irrelevant. +@end quotation + +@geindex Dot_Replacement (GNAT Project Manager) + +@strong{Dot_Replacement}: + +@quotation + +This attribute specifies the string that should replace the "." in unit +names. Its default value is @cite{"-"} so that a unit +@cite{Parent.Child} is expected to be found in the file +@code{parent-child.adb}. The replacement string must satisfy the following +requirements to avoid ambiguities in the naming scheme: + + +@itemize * + +@item +It must not be empty + +@item +It cannot start or end with an alphanumeric character + +@item +It cannot be a single underscore + +@item +It cannot start with an underscore followed by an alphanumeric + +@item +It cannot contain a dot @cite{'.'} except if the entire string is @cite{"."} +@end itemize +@end quotation + +@geindex Spec_Suffix (GNAT Project Manager) + +@geindex Specification_Suffix (GNAT Project Manager) + +@strong{Spec_Suffix} and @strong{Specification_Suffix}: + +@quotation + +For Ada, these attributes give the suffix used in file names that contain +specifications. For other languages, they give the extension for files +that contain declaration (header files in C for instance). The attribute +is indexed on the language. +The two attributes are equivalent, but the latter is obsolescent. + +If the value of the attribute is the empty string, it indicates to the +Project Manager that the only specifications/header files for the language +are those specified with attributes @cite{Spec} or +@cite{Specification_Exceptions}. + +If @cite{Spec_Suffix ("Ada")} is not specified, then the default is +@cite{".ads"}. + +A non empty value must satisfy the following requirements: + + +@itemize * + +@item +It must include at least one dot + +@item +If @cite{Dot_Replacement} is a single dot, then it cannot include +more than one dot. +@end itemize +@end quotation + +@geindex Body_Suffix (GNAT Project Manager) + +@geindex Implementation_Suffix (GNAT Project Manager) + +@strong{Body_Suffix} and @strong{Implementation_Suffix}: + +@quotation + +These attributes give the extension used for file names that contain +code (bodies in Ada). They are indexed on the language. The second +version is obsolescent and fully replaced by the first attribute. + +For each language of a project, one of these two attributes need to be +specified, either in the project itself or in the configuration project file. + +If the value of the attribute is the empty string, it indicates to the +Project Manager that the only source files for the language +are those specified with attributes @cite{Body} or +@cite{Implementation_Exceptions}. + +These attributes must satisfy the same requirements as @cite{Spec_Suffix}. +In addition, they must be different from any of the values in +@cite{Spec_Suffix}. +If @cite{Body_Suffix ("Ada")} is not specified, then the default is +@cite{".adb"}. + +If @cite{Body_Suffix ("Ada")} and @cite{Spec_Suffix ("Ada")} end with the +same string, then a file name that ends with the longest of these two +suffixes will be a body if the longest suffix is @cite{Body_Suffix ("Ada")} +or a spec if the longest suffix is @cite{Spec_Suffix ("Ada")}. + +If the suffix does not start with a '.', a file with a name exactly equal to +the suffix will also be part of the project (for instance if you define the +suffix as @cite{Makefile.in}, a file called @code{Makefile.in} will be part +of the project. This capability is usually not interesting when building. +However, it might become useful when a project is also used to +find the list of source files in an editor, like the GNAT Programming System +(GPS). +@end quotation + +@geindex Separate_Suffix (GNAT Project Manager) + +@strong{Separate_Suffix}: + +@quotation + +This attribute is specific to Ada. It denotes the suffix used in file names +that contain separate bodies. If it is not specified, then it defaults to +same value as @cite{Body_Suffix ("Ada")}. + +The value of this attribute cannot be the empty string. + +Otherwise, the same rules apply as for the +@cite{Body_Suffix} attribute. The only accepted index is "Ada". +@end quotation + +@strong{Spec} or @strong{Specification}: + +@quotation + +@geindex Spec (GNAT Project Manager) + +@geindex Specification (GNAT Project Manager) + +This attribute @cite{Spec} can be used to define the source file name for a +given Ada compilation unit's spec. The index is the literal name of the Ada +unit (case insensitive). The value is the literal base name of the file that +contains this unit's spec (case sensitive or insensitive depending on the +operating system). This attribute allows the definition of exceptions to the +general naming scheme, in case some files do not follow the usual +convention. + +When a source file contains several units, the relative position of the unit +can be indicated. The first unit in the file is at position 1 + +@example +for Spec ("MyPack.MyChild") use "mypack.mychild.spec"; +for Spec ("top") use "foo.a" at 1; +for Spec ("foo") use "foo.a" at 2; +@end example +@end quotation + +@geindex Body (GNAT Project Manager) + +@geindex Implementation (GNAT Project Manager) + +@strong{Body} or @strong{Implementation}: + +@quotation + +These attribute play the same role as @emph{Spec} for Ada bodies. +@end quotation + +@geindex Specification_Exceptions (GNAT Project Manager) + +@geindex Implementation_Exceptions (GNAT Project Manager) + +@strong{Specification_Exceptions} and @strong{Implementation_Exceptions}: + +@quotation + +These attributes define exceptions to the naming scheme for languages +other than Ada. They are indexed on the language name, and contain +a list of file names respectively for headers and source code. +@end quotation + +For example, the following package models the Apex file naming rules: + +@example +package Naming is + for Casing use "lowercase"; + for Dot_Replacement use "."; + for Spec_Suffix ("Ada") use ".1.ada"; + for Body_Suffix ("Ada") use ".2.ada"; +end Naming; +@end example + +@node Installation,Distributed support,Naming Schemes,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id12}@anchor{167}@anchor{gnat_ugn/gnat_project_manager installation}@anchor{168} +@subsection Installation + + +After building an application or a library it is often required to +install it into the development environment. For instance this step is +required if the library is to be used by another application. +The @emph{gprinstall} tool provides an easy way to install +libraries, executable or object code generated during the build. The +@strong{Install} package can be used to change the default locations. + +The following attributes can be defined in package @cite{Install}: + +@geindex Active (GNAT Project Manager) + + +@table @asis + +@item @strong{Active} + +Whether the project is to be installed, values are @cite{true} +(default) or @cite{false}. +@end table + +@geindex Artifacts (GNAT Project Manager) + +@strong{Artifacts} + +@quotation + +An array attribute to declare a set of files not part of the sources +to be installed. The array discriminant is the directory where the +file is to be installed. If a relative directory then Prefix (see +below) is prepended. +@end quotation + +@geindex Prefix (GNAT Project Manager) + +@strong{Prefix}: + +@quotation + +Root directory for the installation. +@end quotation + +@strong{Exec_Subdir} + +@quotation + +Subdirectory of @strong{Prefix} where executables are to be +installed. Default is @strong{bin}. +@end quotation + +@strong{Lib_Subdir} + +@quotation + +Subdirectory of @strong{Prefix} where directory with the library or object +files is to be installed. Default is @strong{lib}. +@end quotation + +@strong{Sources_Subdir} + +@quotation + +Subdirectory of @strong{Prefix} where directory with sources is to be +installed. Default is @strong{include}. +@end quotation + +@strong{Project_Subdir} + +@quotation + +Subdirectory of @strong{Prefix} where the generated project file is to be +installed. Default is @strong{share/gpr}. +@end quotation + +@strong{Mode} + +@quotation + +The installation mode, it is either @strong{dev} (default) or @strong{usage}. +See @strong{gprbuild} user's guide for details. +@end quotation + +@strong{Install_Name} + +@quotation + +Specify the name to use for recording the installation. The default is +the project name without the extension. +@end quotation + +@node Distributed support,,Installation,Building With Projects +@anchor{gnat_ugn/gnat_project_manager id13}@anchor{169}@anchor{gnat_ugn/gnat_project_manager distributed-support}@anchor{16a} +@subsection Distributed support + + +For large projects the compilation time can become a limitation in +the development cycle. To cope with that, GPRbuild supports +distributed compilation. + +The following attributes can be defined in package @cite{Remote}: + +@geindex Root_Dir (GNAT Project Manager) + +@strong{Root_Dir}: + +@quotation + +Root directory of the project's sources. The default value is the +project's directory. +@end quotation + +@node Organizing Projects into Subsystems,Scenarios in Projects,Building With Projects,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager organizing-projects-into-subsystems}@anchor{14e}@anchor{gnat_ugn/gnat_project_manager id14}@anchor{16b} +@section Organizing Projects into Subsystems + + +A @strong{subsystem} is a coherent part of the complete system to be built. It is +represented by a set of sources and one single object directory. A system can +be composed of a single subsystem when it is simple as we have seen in the +first section. Complex systems are usually composed of several interdependent +subsystems. A subsystem is dependent on another subsystem if knowledge of the +other one is required to build it, and in particular if visibility on some of +the sources of this other subsystem is required. Each subsystem is usually +represented by its own project file. + +In this section, the previous example is being extended. Let's assume some +sources of our @cite{Build} project depend on other sources. +For instance, when building a graphical interface, it is usual to depend upon +a graphical library toolkit such as GtkAda. Furthermore, we also need +sources from a logging module we had previously written. + +@menu +* Project Dependencies:: +* Cyclic Project Dependencies:: +* Sharing Between Projects:: +* Global Attributes:: + +@end menu + +@node Project Dependencies,Cyclic Project Dependencies,,Organizing Projects into Subsystems +@anchor{gnat_ugn/gnat_project_manager project-dependencies}@anchor{16c}@anchor{gnat_ugn/gnat_project_manager id15}@anchor{16d} +@subsection Project Dependencies + + +GtkAda comes with its own project file (appropriately called +@code{gtkada.gpr}), and we will assume we have already built a project +called @code{logging.gpr} for the logging module. With the information provided +so far in @code{build.gpr}, building the application would fail with an error +indicating that the gtkada and logging units that are relied upon by the sources +of this project cannot be found. + +This is solved by adding the following @strong{with} clauses at the beginning of our +project: + +@example +with "gtkada.gpr"; +with "a/b/logging.gpr"; +project Build is + ... -- as before +end Build; +@end example + +@geindex Externally_Built (GNAT Project Manager) + +When such a project is compiled, @emph{gprbuild} will automatically check +the other projects and recompile their sources when needed. It will also +recompile the sources from @cite{Build} when needed, and finally create the +executable. In some cases, the implementation units needed to recompile a +project are not available, or come from some third party and you do not want to +recompile it yourself. In this case, set the attribute @strong{Externally_Built} to +"true", indicating to the builder that this project can be assumed to be +up-to-date, and should not be considered for recompilation. In Ada, if the +sources of this externally built project were compiled with another version of +the compiler or with incompatible options, the binder will issue an error. + +The project's @emph{with} clause has several effects. It provides source +visibility between projects during the compilation process. It also guarantees +that the necessary object files from @cite{Logging} and @cite{GtkAda} are +available when linking @cite{Build}. + +As can be seen in this example, the syntax for importing projects is similar +to the syntax for importing compilation units in Ada. However, project files +use literal strings instead of names, and the @emph{with} clause identifies +project files rather than packages. + +Each literal string after @emph{with} is the path +(absolute or relative) to a project file. The @cite{.gpr} extension is +optional, although we recommend adding it. If no extension is specified, +and no project file with the @code{.gpr} extension is found, then +the file is searched for exactly as written in the @emph{with} clause, +that is with no extension. + +As mentioned above, the path after a @emph{with} has to be a literal +string, and you cannot use concatenation, or lookup the value of external +variables to change the directories from which a project is loaded. +A solution if you need something like this is to use aggregate projects +(see @ref{16e,,Aggregate Projects}). + +@geindex project path (GNAT Project Manager) + +When a relative path or a base name is used, the +project files are searched relative to each of the directories in the +@strong{project path}. This path includes all the directories found with the +following algorithm, in this order; the first matching file is used: + + +@itemize * + +@item +First, the file is searched relative to the directory that contains the +current project file. + +@geindex GPR_PROJECT_PATH_FILE (GNAT Project Manager) + +@geindex GPR_PROJECT_PATH (GNAT Project Manager) + +@geindex ADA_PROJECT_PATH (GNAT Project Manager) + +@item +Then it is searched relative to all the directories specified in the +environment variables @strong{GPR_PROJECT_PATH_FILE}, +@strong{GPR_PROJECT_PATH} and @strong{ADA_PROJECT_PATH} (in that order) if they exist. +The value of @strong{GPR_PROJECT_PATH_FILE}, when defined, is the path name of +a text file that contains project directory path names, one per line. +@strong{GPR_PROJECT_PATH} and @strong{ADA_PROJECT_PATH}, when defined, contain +project directory path names separated by directory separators. +@strong{ADA_PROJECT_PATH} is used for compatibility, it is recommended to +use @strong{GPR_PROJECT_PATH_FILE} or @strong{GPR_PROJECT_PATH}. + +@item +Finally, it is searched relative to the default project directories. +Such directories depend on the tool used. The locations searched in the +specified order are: + + +@itemize * + +@item +@code{//lib/gnat} +(for @emph{gnatmake} in all cases, and for @emph{gprbuild} if option +@emph{--target} is specified) + +@item +@code{//share/gpr} +(for @emph{gnatmake} in all cases, and for @emph{gprbuild} if option +@emph{--target} is specified) + +@item +@code{/share/gpr/} +(for @emph{gnatmake} and @emph{gprbuild}) + +@item +@code{/lib/gnat/} +(for @emph{gnatmake} and @emph{gprbuild}) +@end itemize + +In our example, @code{gtkada.gpr} is found in the predefined directory if +it was installed at the same root as GNAT. +@end itemize + +Some tools also support extending the project path from the command line, +generally through the @emph{-aP}. You can see the value of the project +path by using the @emph{gnatls -v} command. + +Any symbolic link will be fully resolved in the directory of the +importing project file before the imported project file is examined. + +Any source file in the imported project can be used by the sources of the +importing project, transitively. +Thus if @cite{A} imports @cite{B}, which imports @cite{C}, the sources of +@cite{A} may depend on the sources of @cite{C}, even if @cite{A} does not +import @cite{C} explicitly. However, this is not recommended, because if +and when @cite{B} ceases to import @cite{C}, some sources in @cite{A} will +no longer compile. @emph{gprbuild} has a switch @emph{--no-indirect-imports} +that will report such indirect dependencies. + +@cartouche +@quotation Note +One very important aspect of a project hierarchy is that +@strong{a given source can only belong to one project} (otherwise the project manager +would not know which settings apply to it and when to recompile it). It means +that different project files do not usually share source directories or +when they do, they need to specify precisely which project owns which sources +using attribute @cite{Source_Files} or equivalent. By contrast, 2 projects +can each own a source with the same base file name as long as they live in +different directories. The latter is not true for Ada Sources because of the +correlation between source files and Ada units. +@end quotation +@end cartouche + +@node Cyclic Project Dependencies,Sharing Between Projects,Project Dependencies,Organizing Projects into Subsystems +@anchor{gnat_ugn/gnat_project_manager id16}@anchor{16f}@anchor{gnat_ugn/gnat_project_manager cyclic-project-dependencies}@anchor{170} +@subsection Cyclic Project Dependencies + + +Cyclic dependencies are mostly forbidden: +if @cite{A} imports @cite{B} (directly or indirectly) then @cite{B} +is not allowed to import @cite{A}. However, there are cases when cyclic +dependencies would be beneficial. For these cases, another form of import +between projects exists: the @strong{limited with}. A project @cite{A} that +imports a project @cite{B} with a straight @emph{with} may also be imported, +directly or indirectly, by @cite{B} through a @cite{limited with}. + +The difference between straight @emph{with} and @cite{limited with} is that +the name of a project imported with a @cite{limited with} cannot be used in the +project importing it. In particular, its packages cannot be renamed and +its variables cannot be referred to. + +@example +with "b.gpr"; +with "c.gpr"; +project A is + for Exec_Dir use B'Exec_Dir; -- ok +end A; + +limited with "a.gpr"; -- Cyclic dependency: A -> B -> A +project B is + for Exec_Dir use A'Exec_Dir; -- not ok +end B; + +with "d.gpr"; +project C is +end C; + +limited with "a.gpr"; -- Cyclic dependency: A -> C -> D -> A +project D is + for Exec_Dir use A'Exec_Dir; -- not ok +end D; +@end example + +@node Sharing Between Projects,Global Attributes,Cyclic Project Dependencies,Organizing Projects into Subsystems +@anchor{gnat_ugn/gnat_project_manager sharing-between-projects}@anchor{171}@anchor{gnat_ugn/gnat_project_manager id17}@anchor{172} +@subsection Sharing Between Projects + + +When building an application, it is common to have similar needs in several of +the projects corresponding to the subsystems under construction. For instance, +they will all have the same compilation switches. + +As seen before (see @ref{15e,,Tools Options in Project Files}), setting compilation +switches for all sources of a subsystem is simple: it is just a matter of +adding a @cite{Compiler.Default_Switches} attribute to each project files with +the same value. Of course, that means duplication of data, and both places need +to be changed in order to recompile the whole application with different +switches. It can become a real problem if there are many subsystems and thus +many project files to edit. + +There are two main approaches to avoiding this duplication: + + +@itemize * + +@item +Since @code{build.gpr} imports @code{logging.gpr}, we could change it +to reference the attribute in Logging, either through a package renaming, +or by referencing the attribute. The following example shows both cases: + +@example +project Logging is + package Compiler is + for Switches ("Ada") + use ("-O2"); + end Compiler; + package Binder is + for Switches ("Ada") + use ("-E"); + end Binder; +end Logging; + +with "logging.gpr"; +project Build is + package Compiler renames Logging.Compiler; + package Binder is + for Switches ("Ada") use Logging.Binder'Switches ("Ada"); + end Binder; +end Build; +@end example + +The solution used for @cite{Compiler} gets the same value for all +attributes of the package, but you cannot modify anything from the +package (adding extra switches or some exceptions). The second +version is more flexible, but more verbose. + +If you need to refer to the value of a variable in an imported +project, rather than an attribute, the syntax is similar but uses +a "." rather than an apostrophe. For instance: + +@example +with "imported"; +project Main is + Var1 := Imported.Var; +end Main; +@end example + +@item +The second approach is to define the switches in a third project. +That project is set up without any sources (so that, as opposed to +the first example, none of the project plays a special role), and +will only be used to define the attributes. Such a project is +typically called @code{shared.gpr}. + +@example +abstract project Shared is + for Source_Files use (); -- no sources + package Compiler is + for Switches ("Ada") + use ("-O2"); + end Compiler; +end Shared; + +with "shared.gpr"; +project Logging is + package Compiler renames Shared.Compiler; +end Logging; + +with "shared.gpr"; +project Build is + package Compiler renames Shared.Compiler; +end Build; +@end example + +As for the first example, we could have chosen to set the attributes +one by one rather than to rename a package. The reason we explicitly +indicate that @cite{Shared} has no sources is so that it can be created +in any directory and we are sure it shares no sources with @cite{Build} +or @cite{Logging}, which of course would be invalid. + +@geindex project qualifier (GNAT Project Manager) + +Note the additional use of the @strong{abstract} qualifier in @code{shared.gpr}. +This qualifier is optional, but helps convey the message that we do not +intend this project to have sources (see @ref{173,,Qualified Projects} for +more qualifiers). +@end itemize + +@node Global Attributes,,Sharing Between Projects,Organizing Projects into Subsystems +@anchor{gnat_ugn/gnat_project_manager global-attributes}@anchor{174}@anchor{gnat_ugn/gnat_project_manager id18}@anchor{175} +@subsection Global Attributes + + +We have already seen many examples of attributes used to specify a special +option of one of the tools involved in the build process. Most of those +attributes are project specific. That it to say, they only affect the invocation +of tools on the sources of the project where they are defined. + +There are a few additional attributes that apply to all projects in a +hierarchy as long as they are defined on the "main" project. +The main project is the project explicitly mentioned on the command-line. +The project hierarchy is the "with"-closure of the main project. + +Here is a list of commonly used global attributes: + +@geindex Global_Configuration_Pragmas (GNAT Project Manager) + +@strong{Builder.Global_Configuration_Pragmas}: + +@quotation + +This attribute points to a file that contains configuration pragmas +to use when building executables. These pragmas apply for all +executables built from this project hierarchy. As we have seen before, +additional pragmas can be specified on a per-project basis by setting the +@cite{Compiler.Local_Configuration_Pragmas} attribute. +@end quotation + +@geindex Global_Compilation_Switches (GNAT Project Manager) + +@strong{Builder.Global_Compilation_Switches}: + +@quotation + +This attribute is a list of compiler switches to use when compiling any +source file in the project hierarchy. These switches are used in addition +to the ones defined in the @cite{Compiler} package, which only apply to +the sources of the corresponding project. This attribute is indexed on +the name of the language. +@end quotation + +Using such global capabilities is convenient. It can also lead to unexpected +behavior. Especially when several subsystems are shared among different main +projects and the different global attributes are not +compatible. Note that using aggregate projects can be a safer and more powerful +replacement to global attributes. + +@node Scenarios in Projects,Library Projects,Organizing Projects into Subsystems,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager id19}@anchor{176}@anchor{gnat_ugn/gnat_project_manager scenarios-in-projects}@anchor{14c} +@section Scenarios in Projects + + +Various aspects of the projects can be modified based on @strong{scenarios}. These +are user-defined modes that change the behavior of a project. Typical +examples are the setup of platform-specific compiler options, or the use of +a debug and a release mode (the former would activate the generation of debug +information, while the second will focus on improving code optimization). + +Let's enhance our example to support debug and release modes. The issue is to +let the user choose what kind of system he is building: use @emph{-g} as +compiler switches in debug mode and @emph{-O2} in release mode. We will also +set up the projects so that we do not share the same object directory in both +modes; otherwise switching from one to the other might trigger more +recompilations than needed or mix objects from the two modes. + +One naive approach is to create two different project files, say +@code{build_debug.gpr} and @code{build_release.gpr}, that set the appropriate +attributes as explained in previous sections. This solution does not scale +well, because in the presence of multiple projects depending on each other, you +will also have to duplicate the complete hierarchy and adapt the project files +to point to the right copies. + +@geindex scenarios (GNAT Project Manager) + +Instead, project files support the notion of scenarios controlled +by external values. Such values can come from several sources (in decreasing +order of priority): + +@geindex -X (usage with GNAT Project Manager) + + +@table @asis + +@item @strong{Command line}: + +When launching @emph{gnatmake} or @emph{gprbuild}, the user can pass +extra @emph{-X} switches to define the external value. In +our case, the command line might look like + +@example +gnatmake -Pbuild.gpr -Xmode=debug +@end example + +or + +@example +gnatmake -Pbuild.gpr -Xmode=release +@end example + +@item @strong{Environment variables}: + +When the external value does not come from the command line, it can come from +the value of environment variables of the appropriate name. +In our case, if an environment variable called "mode" +exists, its value will be taken into account. +@end table + +@geindex external (GNAT Project Manager) + +@strong{External function second parameter}. + +We now need to get that value in the project. The general form is to use +the predefined function @strong{external} which returns the current value of +the external. For instance, we could set up the object directory to point to +either @code{obj/debug} or @code{obj/release} by changing our project to + +@example +project Build is + for Object_Dir use "obj/" & external ("mode", "debug"); + ... -- as before +end Build; +@end example + +The second parameter to @cite{external} is optional, and is the default +value to use if "mode" is not set from the command line or the environment. + +In order to set the switches according to the different scenarios, other +constructs have to be introduced such as typed variables and case constructions. + +@geindex typed variable (GNAT Project Manager) + +@geindex case construction (GNAT Project Manager) + +A @strong{typed variable} is a variable that +can take only a limited number of values, similar to an enumeration in Ada. +Such a variable can then be used in a @strong{case construction} and create conditional +sections in the project. The following example shows how this can be done: + +@example +project Build is + type Mode_Type is ("debug", "release"); -- all possible values + Mode : Mode_Type := external ("mode", "debug"); -- a typed variable + + package Compiler is + case Mode is + when "debug" => + for Switches ("Ada") + use ("-g"); + when "release" => + for Switches ("Ada") + use ("-O2"); + end case; + end Compiler; +end Build; +@end example + +The project has suddenly grown in size, but has become much more flexible. +@cite{Mode_Type} defines the only valid values for the @cite{mode} variable. If +any other value is read from the environment, an error is reported and the +project is considered as invalid. + +The @cite{Mode} variable is initialized with an external value +defaulting to @cite{"debug"}. This default could be omitted and that would +force the user to define the value. Finally, we can use a case construction to set the +switches depending on the scenario the user has chosen. + +Most aspects of the projects can depend on scenarios. The notable exception +are project dependencies (@emph{with} clauses), which cannot depend on a scenario. + +Scenarios work the same way with @strong{project hierarchies}: you can either +duplicate a variable similar to @cite{Mode} in each of the project (as long +as the first argument to @cite{external} is always the same and the type is +the same), or simply set the variable in the @code{shared.gpr} project +(see @ref{171,,Sharing Between Projects}). + +@node Library Projects,Project Extension,Scenarios in Projects,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager library-projects}@anchor{8a}@anchor{gnat_ugn/gnat_project_manager id20}@anchor{177} +@section Library Projects + + +So far, we have seen examples of projects that create executables. However, +it is also possible to create libraries instead. A @strong{library} is a specific +type of subsystem where, for convenience, objects are grouped together +using system-specific means such as archives or windows DLLs. + +Library projects provide a system- and language-independent way of building +both @strong{static} and @strong{dynamic} libraries. They also support the concept of +@strong{standalone libraries} (SAL) which offer two significant properties: the +elaboration (e.g. initialization) of the library is either automatic or +very simple; a change in the +implementation part of the library implies minimal post-compilation actions on +the complete system and potentially no action at all for the rest of the +system in the case of dynamic SALs. + +There is a restriction on shared library projects: by default, they are only +allowed to import other shared library projects. They are not allowed to +import non library projects or static library projects. + +The GNAT Project Manager takes complete care of the library build, rebuild and +installation tasks, including recompilation of the source files for which +objects do not exist or are not up to date, assembly of the library archive, and +installation of the library (i.e., copying associated source, object and +@code{ALI} files to the specified location). + +@menu +* Building Libraries:: +* Using Library Projects:: +* Stand-alone Library Projects:: +* Installing a library with project files:: + +@end menu + +@node Building Libraries,Using Library Projects,,Library Projects +@anchor{gnat_ugn/gnat_project_manager id21}@anchor{178}@anchor{gnat_ugn/gnat_project_manager building-libraries}@anchor{179} +@subsection Building Libraries + + +Let's enhance our example and transform the @cite{logging} subsystem into a +library. In order to do so, a few changes need to be made to +@code{logging.gpr}. Some attributes need to be defined: at least +@cite{Library_Name} and @cite{Library_Dir}; in addition, some other attributes +can be used to specify specific aspects of the library. For readability, it is +also recommended (although not mandatory), to use the qualifier @cite{library} +in front of the @cite{project} keyword. + +@geindex Library_Name (GNAT Project Manager) + +@strong{Library_Name}: + +@quotation + +This attribute is the name of the library to be built. There is no +restriction on the name of a library imposed by the project manager, except +for stand-alone libraries whose names must follow the syntax of Ada +identifiers; however, there may be system-specific restrictions on the name. +In general, it is recommended to stick to alphanumeric characters (and +possibly single underscores) to help portability. +@end quotation + +@geindex Library_Dir (GNAT Project Manager) + +@strong{Library_Dir}: + +@quotation + +This attribute is the path (absolute or relative) of the directory where +the library is to be installed. In the process of building a library, +the sources are compiled, the object files end up in the explicit or +implicit @cite{Object_Dir} directory. When all sources of a library +are compiled, some of the compilation artifacts, including the library itself, +are copied to the library_dir directory. This directory must exist and be +writable. It must also be different from the object directory so that cleanup +activities in the Library_Dir do not affect recompilation needs. +@end quotation + +Here is the new version of @code{logging.gpr} that makes it a library: + +@example +library project Logging is -- "library" is optional + for Library_Name use "logging"; -- will create "liblogging.a" on Unix + for Object_Dir use "obj"; + for Library_Dir use "lib"; -- different from object_dir +end Logging; +@end example + +Once the above two attributes are defined, the library project is valid and +is enough for building a library with default characteristics. +Other library-related attributes can be used to change the defaults: + +@geindex Library_Kind (GNAT Project Manager) + +@strong{Library_Kind}: + +@quotation + +The value of this attribute must be either @cite{"static"}, @cite{"dynamic"} or +@cite{"relocatable"} (the latter is a synonym for dynamic). It indicates +which kind of library should be built (the default is to build a +static library, that is an archive of object files that can potentially +be linked into a static executable). When the library is set to be dynamic, +a separate image is created that will be loaded independently, usually +at the start of the main program execution. Support for dynamic libraries is +very platform specific, for instance on Windows it takes the form of a DLL +while on GNU/Linux, it is a dynamic elf image whose suffix is usually +@code{.so}. Library project files, on the other hand, can be written in +a platform independent way so that the same project file can be used to build +a library on different operating systems. + +If you need to build both a static and a dynamic library, it is recommended +to use two different object directories, since in some cases some extra code +needs to be generated for the latter. For such cases, one can either define +two different project files, or a single one that uses scenarios to indicate +the various kinds of library to be built and their corresponding object_dir. +@end quotation + +@geindex Library_ALI_Dir (GNAT Project Manager) + +@strong{Library_ALI_Dir}: + +@quotation + +This attribute may be specified to indicate the directory where the ALI +files of the library are installed. By default, they are copied into the +@cite{Library_Dir} directory, but as for the executables where we have a +separate @cite{Exec_Dir} attribute, you might want to put them in a separate +directory since there can be hundreds of them. The same restrictions as for +the @cite{Library_Dir} attribute apply. +@end quotation + +@geindex Library_Version (GNAT Project Manager) + +@strong{Library_Version}: + +@quotation + +This attribute is platform dependent, and has no effect on Windows. +On Unix, it is used only for dynamic libraries as the internal +name of the library (the @cite{"soname"}). If the library file name (built +from the @cite{Library_Name}) is different from the @cite{Library_Version}, +then the library file will be a symbolic link to the actual file whose name +will be @cite{Library_Version}. This follows the usual installation schemes +for dynamic libraries on many Unix systems. + +@example +project Logging is + Version := "1"; + for Library_Dir use "lib"; + for Library_Name use "logging"; + for Library_Kind use "dynamic"; + for Library_Version use "liblogging.so." & Version; +end Logging; +@end example + +After the compilation, the directory @code{lib} will contain both a +@code{libdummy.so.1} library and a symbolic link to it called +@code{libdummy.so}. +@end quotation + +@geindex Library_GCC (GNAT Project Manager) + +@strong{Library_GCC}: + +@quotation + +This attribute is the name of the tool to use instead of "gcc" to link shared +libraries. A common use of this attribute is to define a wrapper script that +accomplishes specific actions before calling gcc (which itself calls the +linker to build the library image). +@end quotation + +@geindex Library_Options (GNAT Project Manager) + +@strong{Library_Options}: + +@quotation + +This attribute may be used to specify additional switches (last switches) +when linking a shared library. + +It may also be used to add foreign object files to a static library. +Each string in Library_Options is an absolute or relative path of an object +file. When a relative path, it is relative to the object directory. +@end quotation + +@geindex Leading_Library_Options (GNAT Project Manager) + +@strong{Leading_Library_Options}: + +@quotation + +This attribute, that is taken into account only by @emph{gprbuild}, may be +used to specified leading options (first switches) when linking a shared +library. +@end quotation + +@geindex Linker_Options (GNAT Project Manager) + +@strong{Linker.Linker_Options}: + +@quotation + +This attribute specifies additional switches to be given to the linker when +linking an executable. It is ignored when defined in the main project and +taken into account in all other projects that are imported directly or +indirectly. These switches complement the @cite{Linker.Switches} +defined in the main project. This is useful when a particular subsystem +depends on an external library: adding this dependency as a +@cite{Linker_Options} in the project of the subsystem is more convenient than +adding it to all the @cite{Linker.Switches} of the main projects that depend +upon this subsystem. +@end quotation + +@node Using Library Projects,Stand-alone Library Projects,Building Libraries,Library Projects +@anchor{gnat_ugn/gnat_project_manager id22}@anchor{17a}@anchor{gnat_ugn/gnat_project_manager using-library-projects}@anchor{17b} +@subsection Using Library Projects + + +When the builder detects that a project file is a library project file, it +recompiles all sources of the project that need recompilation and rebuild the +library if any of the sources have been recompiled. It then groups all object +files into a single file, which is a shared or a static library. This library +can later on be linked with multiple executables. Note that the use +of shard libraries reduces the size of the final executable and can also reduce +the memory footprint at execution time when the library is shared among several +executables. + +It is also possible to build @strong{multi-language libraries}. When using +@emph{gprbuild} as a builder, multi-language library projects allow naturally +the creation of multi-language libraries . @emph{gnatmake}, does not try to +compile non Ada sources. However, when the project is multi-language, it will +automatically link all object files found in the object directory, whether or +not they were compiled from an Ada source file. This specific behavior does not +apply to Ada-only projects which only take into account the objects +corresponding to the sources of the project. + +A non-library project can import a library project. When the builder is invoked +on the former, the library of the latter is only rebuilt when absolutely +necessary. For instance, if a unit of the library is not up-to-date but none of +the executables need this unit, then the unit is not recompiled and the library +is not reassembled. For instance, let's assume in our example that logging has +the following sources: @code{log1.ads}, @code{log1.adb}, @code{log2.ads} and +@code{log2.adb}. If @code{log1.adb} has been modified, then the library +@code{liblogging} will be rebuilt when compiling all the sources of +@cite{Build} only if @code{proc.ads}, @code{pack.ads} or @code{pack.adb} +include a @cite{"with Log1"}. + +To ensure that all the sources in the @cite{Logging} library are +up to date, and that all the sources of @cite{Build} are also up to date, +the following two commands need to be used: + +@example +gnatmake -Plogging.gpr +gnatmake -Pbuild.gpr +@end example + +All @code{ALI} files will also be copied from the object directory to the +library directory. To build executables, @emph{gnatmake} will use the +library rather than the individual object files. + +Library projects can also be useful to describe a library that needs to be used +but, for some reason, cannot be rebuilt. For instance, it is the case when some +of the library sources are not available. Such library projects need to use the +@cite{Externally_Built} attribute as in the example below: + +@c code-block: ada-project +@c +@c library project Extern_Lib is +@c for Languages use ("Ada", "C"); +@c for Source_Dirs use ("lib_src"); +@c for Library_Dir use "lib2"; +@c for Library_Kind use "dynamic"; +@c for Library_Name use "l2"; +@c for Externally_Built use "true"; -- <<<< +@c end Extern_Lib; + +In the case of externally built libraries, the @cite{Object_Dir} +attribute does not need to be specified because it will never be +used. + +The main effect of using such an externally built library project is mostly to +affect the linker command in order to reference the desired library. It can +also be achieved by using @cite{Linker.Linker_Options} or @cite{Linker.Switches} +in the project corresponding to the subsystem needing this external library. +This latter method is more straightforward in simple cases but when several +subsystems depend upon the same external library, finding the proper place +for the @cite{Linker.Linker_Options} might not be easy and if it is +not placed properly, the final link command is likely to present ordering issues. +In such a situation, it is better to use the externally built library project +so that all other subsystems depending on it can declare this dependency thanks +to a project @emph{with} clause, which in turn will trigger the builder to find +the proper order of libraries in the final link command. + +@node Stand-alone Library Projects,Installing a library with project files,Using Library Projects,Library Projects +@anchor{gnat_ugn/gnat_project_manager id23}@anchor{17c}@anchor{gnat_ugn/gnat_project_manager stand-alone-library-projects}@anchor{97} +@subsection Stand-alone Library Projects + + +@geindex standalone libraries (usage with GNAT Project Manager) + +A @strong{stand-alone library} is a library that contains the necessary code to +elaborate the Ada units that are included in the library. A stand-alone +library is a convenient way to add an Ada subsystem to a more global system +whose main is not in Ada since it makes the elaboration of the Ada part mostly +transparent. However, stand-alone libraries are also useful when the main is in +Ada: they provide a means for minimizing relinking & redeployment of complex +systems when localized changes are made. + +The name of a stand-alone library, specified with attribute +@cite{Library_Name}, must have the syntax of an Ada identifier. + +The most prominent characteristic of a stand-alone library is that it offers a +distinction between interface units and implementation units. Only the former +are visible to units outside the library. A stand-alone library project is thus +characterised by a third attribute, usually @strong{Library_Interface}, in addition +to the two attributes that make a project a Library Project +(@cite{Library_Name} and @cite{Library_Dir}). This third attribute may also be +@strong{Interfaces}. @strong{Library_Interface} only works when the interface is in Ada +and takes a list of units as parameter. @strong{Interfaces} works for any supported +language and takes a list of sources as parameter. + +@geindex Library_Interface (GNAT Project Manager) + +@strong{Library_Interface}: + +@quotation + +This attribute defines an explicit subset of the units of the project. Units +from projects importing this library project may only "with" units whose +sources are listed in the @cite{Library_Interface}. Other sources are +considered implementation units. + +@example +for Library_Dir use "lib"; +for Library_Name use "logging"; +for Library_Interface use ("lib1", "lib2"); -- unit names +@end example +@end quotation + +@strong{Interfaces} + +@quotation + +This attribute defines an explicit subset of the source files of a project. +Sources from projects importing this project, can only depend on sources from +this subset. This attribute can be used on non library projects. It can also +be used as a replacement for attribute @cite{Library_Interface}, in which +case, units have to be replaced by source files. For multi-language library +projects, it is the only way to make the project a Stand-Alone Library project +whose interface is not purely Ada. +@end quotation + +@geindex Library_Standalone (GNAT Project Manager) + +@strong{Library_Standalone}: + +@quotation + +This attribute defines the kind of standalone library to +build. Values are either @cite{standard} (the default), @cite{no} or +@cite{encapsulated}. When @cite{standard} is used the code to elaborate and +finalize the library is embedded, when @cite{encapsulated} is used the +library can furthermore depend only on static libraries (including +the GNAT runtime). This attribute can be set to @cite{no} to make it clear +that the library should not be standalone in which case the +@cite{Library_Interface} should not defined. Note that this attribute +only applies to shared libraries, so @cite{Library_Kind} must be set +to @cite{dynamic}. + +@example +for Library_Dir use "lib"; +for Library_Name use "logging"; +for Library_Kind use "dynamic"; +for Library_Interface use ("lib1", "lib2"); -- unit names +for Library_Standalone use "encapsulated"; +@end example +@end quotation + +In order to include the elaboration code in the stand-alone library, the binder +is invoked on the closure of the library units creating a package whose name +depends on the library name (b~logging.ads/b in the example). +This binder-generated package includes @strong{initialization} and @strong{finalization} +procedures whose names depend on the library name (@cite{logginginit} and +@cite{loggingfinal} in the example). The object corresponding to this package is +included in the library. + +@geindex Library_Auto_Init (GNAT Project Manager) + +@strong{Library_Auto_Init}: + +@quotation + +A dynamic stand-alone Library is automatically initialized +if automatic initialization of Stand-alone Libraries is supported on the +platform and if attribute @strong{Library_Auto_Init} is not specified or +is specified with the value "true". A static Stand-alone Library is never +automatically initialized. Specifying "false" for this attribute +prevents automatic initialization. + +When a non-automatically initialized stand-alone library is used in an +executable, its initialization procedure must be called before any service of +the library is used. When the main subprogram is in Ada, it may mean that the +initialization procedure has to be called during elaboration of another +package. +@end quotation + +@geindex Library_Dir (GNAT Project Manager) + +@strong{Library_Dir}: + +@quotation + +For a stand-alone library, only the @code{ALI} files of the interface units +(those that are listed in attribute @cite{Library_Interface}) are copied to +the library directory. As a consequence, only the interface units may be +imported from Ada units outside of the library. If other units are imported, +the binding phase will fail. +@end quotation + +@strong{Binder.Default_Switches}: + +@quotation + +When a stand-alone library is bound, the switches that are specified in +the attribute @strong{Binder.Default_Switches ("Ada")} are +used in the call to @emph{gnatbind}. +@end quotation + +@geindex Library_Src_Dir (GNAT Project Manager) + +@strong{Library_Src_Dir}: + +@quotation + +This attribute defines the location (absolute or relative to the project +directory) where the sources of the interface units are copied at +installation time. +These sources includes the specs of the interface units along with the +closure of sources necessary to compile them successfully. That may include +bodies and subunits, when pragmas @cite{Inline} are used, or when there are +generic units in specs. This directory cannot point to the object directory +or one of the source directories, but it can point to the library directory, +which is the default value for this attribute. +@end quotation + +@geindex Library_Symbol_Policy (GNAT Project Manager) + +@strong{Library_Symbol_Policy}: + +@quotation + +This attribute controls the export of symbols and, on some platforms (like +VMS) that have the notions of major and minor IDs built in the library +files, it controls the setting of these IDs. It is not supported on all +platforms (where it will just have no effect). It may have one of the +following values: + + +@itemize * + +@item +@cite{"autonomous"} or @cite{"default"}: exported symbols are not controlled + +@item +@cite{"compliant"}: if attribute @strong{Library_Reference_Symbol_File} +is not defined, then it is equivalent to policy "autonomous". If there +are exported symbols in the reference symbol file that are not in the +object files of the interfaces, the major ID of the library is increased. +If there are symbols in the object files of the interfaces that are not +in the reference symbol file, these symbols are put at the end of the list +in the newly created symbol file and the minor ID is increased. + +@item +@cite{"controlled"}: the attribute @strong{Library_Reference_Symbol_File} must be +defined. The library will fail to build if the exported symbols in the +object files of the interfaces do not match exactly the symbol in the +symbol file. + +@item +@cite{"restricted"}: The attribute @strong{Library_Symbol_File} must be defined. +The library will fail to build if there are symbols in the symbol file that +are not in the exported symbols of the object files of the interfaces. +Additional symbols in the object files are not added to the symbol file. + +@item +@cite{"direct"}: The attribute @strong{Library_Symbol_File} must be defined and +must designate an existing file in the object directory. This symbol file +is passed directly to the underlying linker without any symbol processing. +@end itemize +@end quotation + +@geindex Library_Reference_Symbol_File (GNAT Project Manager) + +@strong{Library_Reference_Symbol_File} + +@quotation + +This attribute may define the path name of a reference symbol file that is +read when the symbol policy is either "compliant" or "controlled", on +platforms that support symbol control, such as VMS, when building a +stand-alone library. The path may be an absolute path or a path relative +to the project directory. +@end quotation + +@geindex Library_Symbol_File (GNAT Project Manager) + +@strong{Library_Symbol_File} + +@quotation + +This attribute may define the name of the symbol file to be created when +building a stand-alone library when the symbol policy is either "compliant", +"controlled" or "restricted", on platforms that support symbol control, +such as VMS. When symbol policy is "direct", then a file with this name +must exist in the object directory. +@end quotation + +@node Installing a library with project files,,Stand-alone Library Projects,Library Projects +@anchor{gnat_ugn/gnat_project_manager installing-a-library-with-project-files}@anchor{8d}@anchor{gnat_ugn/gnat_project_manager id24}@anchor{17d} +@subsection Installing a library with project files + + +When using project files, a usable version of the library is created in the +directory specified by the @cite{Library_Dir} attribute of the library +project file. Thus no further action is needed in order to make use of +the libraries that are built as part of the general application build. + +You may want to install a library in a context different from where the library +is built. This situation arises with third party suppliers, who may want +to distribute a library in binary form where the user is not expected to be +able to recompile the library. The simplest option in this case is to provide +a project file slightly different from the one used to build the library, by +using the @cite{externally_built} attribute. See @ref{17b,,Using Library Projects} + +Another option is to use @emph{gprinstall} to install the library in a +different context than the build location. @emph{gprinstall} automatically +generates a project to use this library, and also copies the minimum set of +sources needed to use the library to the install location. +@ref{168,,Installation} + +@node Project Extension,Aggregate Projects,Library Projects,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager id25}@anchor{17e}@anchor{gnat_ugn/gnat_project_manager project-extension}@anchor{14f} +@section Project Extension + + +During development of a large system, it is sometimes necessary to use +modified versions of some of the source files, without changing the original +sources. This can be achieved through the @strong{project extension} facility. + +Suppose for instance that our example @cite{Build} project is built every night +for the whole team, in some shared directory. A developer usually needs to work +on a small part of the system, and might not want to have a copy of all the +sources and all the object files (mostly because that would require too much +disk space, time to recompile everything). He prefers to be able to override +some of the source files in his directory, while taking advantage of all the +object files generated at night. + +Another example can be taken from large software systems, where it is common to have +multiple implementations of a common interface; in Ada terms, multiple +versions of a package body for the same spec. For example, one implementation +might be safe for use in tasking programs, while another might be used only +in sequential applications. This can be modeled in GNAT using the concept +of @emph{project extension}. If one project (the 'child') @emph{extends} +another project (the 'parent') then by default all source files of the +parent project are inherited by the child, but the child project can +override any of the parent's source files with new versions, and can also +add new files or remove unnecessary ones. +This facility is the project analog of a type extension in +object-oriented programming. Project hierarchies are permitted (an extending +project may itself be extended), and a project that +extends a project can also import other projects. + +A third example is that of using project extensions to provide different +versions of the same system. For instance, assume that a @cite{Common} +project is used by two development branches. One of the branches has now +been frozen, and no further change can be done to it or to @cite{Common}. +However, the other development branch still needs evolution of @cite{Common}. +Project extensions provide a flexible solution to create a new version +of a subsystem while sharing and reusing as much as possible from the original +one. + +A project extension implicitly inherits all the sources and objects from the +project it extends. It is possible to create a new version of some of the +sources in one of the additional source directories of the extending +project. Those new versions hide the original versions. Adding new sources or +removing existing ones is also possible. Here is an example on how to extend +the project @cite{Build} from previous examples: + +@example +project Work extends "../bld/build.gpr" is +end Work; +@end example + +The project after @strong{extends} is the one being extended. As usual, it can be +specified using an absolute path, or a path relative to any of the directories +in the project path (see @ref{16c,,Project Dependencies}). This project does not +specify source or object directories, so the default values for these +attributes will be used that is to say the current directory (where project +@cite{Work} is placed). We can compile that project with + +@example +gprbuild -Pwork +@end example + +If no sources have been placed in the current directory, this command +won't do anything, since this project does not change the +sources it inherited from @cite{Build}, therefore all the object files +in @cite{Build} and its dependencies are still valid and are reused +automatically. + +Suppose we now want to supply an alternate version of @code{pack.adb} but use +the existing versions of @code{pack.ads} and @code{proc.adb}. We can create +the new file in Work's current directory (likely by copying the one from the +@cite{Build} project and making changes to it. If new packages are needed at +the same time, we simply create new files in the source directory of the +extending project. + +When we recompile, @emph{gprbuild} will now automatically recompile +this file (thus creating @code{pack.o} in the current directory) and +any file that depends on it (thus creating @code{proc.o}). Finally, the +executable is also linked locally. + +Note that we could have obtained the desired behavior using project import +rather than project inheritance. A @cite{base} project would contain the +sources for @code{pack.ads} and @code{proc.adb}, and @cite{Work} would +import @cite{base} and add @code{pack.adb}. In this scenario, @cite{base} +cannot contain the original version of @code{pack.adb} otherwise there would be +2 versions of the same unit in the closure of the project and this is not +allowed. Generally speaking, it is not recommended to put the spec and the +body of a unit in different projects since this affects their autonomy and +reusability. + +In a project file that extends another project, it is possible to +indicate that an inherited source is @strong{not part} of the sources of the +extending project. This is necessary sometimes when a package spec has +been overridden and no longer requires a body: in this case, it is +necessary to indicate that the inherited body is not part of the sources +of the project, otherwise there will be a compilation error +when compiling the spec. + +@geindex Excluded_Source_Files (GNAT Project Manager) + +@geindex Excluded_Source_List_File (GNAT Project Manager) + +For that purpose, the attribute @strong{Excluded_Source_Files} is used. +Its value is a list of file names. +It is also possible to use attribute @cite{Excluded_Source_List_File}. +Its value is the path of a text file containing one file name per +line. + +@example +project Work extends "../bld/build.gpr" is + for Source_Files use ("pack.ads"); + -- New spec of Pkg does not need a completion + for Excluded_Source_Files use ("pack.adb"); +end Work; +@end example + +All packages that are not declared in the extending project are inherited from +the project being extended, with their attributes, with the exception of +@cite{Linker'Linker_Options} which is never inherited. In particular, an +extending project retains all the switches specified in the project being +extended. + +At the project level, if they are not declared in the extending project, some +attributes are inherited from the project being extended. They are: +@cite{Languages}, @cite{Main} (for a root non library project) and +@cite{Library_Name} (for a project extending a library project). + +@menu +* Project Hierarchy Extension:: + +@end menu + +@node Project Hierarchy Extension,,,Project Extension +@anchor{gnat_ugn/gnat_project_manager project-hierarchy-extension}@anchor{17f}@anchor{gnat_ugn/gnat_project_manager id26}@anchor{180} +@subsection Project Hierarchy Extension + + +One of the fundamental restrictions in project extension is the following: +@strong{A project is not allowed to import directly or indirectly at the same time an extending project and one of its ancestors}. + +For example, consider the following hierarchy of projects. + +@example +a.gpr contains package A1 +b.gpr, imports a.gpr and contains B1, which depends on A1 +c.gpr, imports b.gpr and contains C1, which depends on B1 +@end example + +If we want to locally extend the packages @cite{A1} and @cite{C1}, we need to +create several extending projects: + +@example +a_ext.gpr which extends a.gpr, and overrides A1 +b_ext.gpr which extends b.gpr and imports a_ext.gpr +c_ext.gpr which extends c.gpr, imports b_ext.gpr and overrides C1 +@end example + +@example +project A_Ext extends "a.gpr" is + for Source_Files use ("a1.adb", "a1.ads"); +end A_Ext; + +with "a_ext.gpr"; +project B_Ext extends "b.gpr" is +end B_Ext; + +with "b_ext.gpr"; +project C_Ext extends "c.gpr" is + for Source_Files use ("c1.adb"); +end C_Ext; +@end example + +The extension @code{b_ext.gpr} is required, even though we are not overriding +any of the sources of @code{b.gpr} because otherwise @code{c_expr.gpr} would +import @code{b.gpr} which itself knows nothing about @code{a_ext.gpr}. + +@geindex extends all (GNAT Project Manager) + +When extending a large system spanning multiple projects, it is often +inconvenient to extend every project in the hierarchy that is impacted by a +small change introduced in a low layer. In such cases, it is possible to create +an @strong{implicit extension} of an entire hierarchy using @strong{extends all} +relationship. + +When the project is extended using @cite{extends all} inheritance, all projects +that are imported by it, both directly and indirectly, are considered virtually +extended. That is, the project manager creates implicit projects +that extend every project in the hierarchy; all these implicit projects do not +control sources on their own and use the object directory of +the "extending all" project. + +It is possible to explicitly extend one or more projects in the hierarchy +in order to modify the sources. These extending projects must be imported by +the "extending all" project, which will replace the corresponding virtual +projects with the explicit ones. + +When building such a project hierarchy extension, the project manager will +ensure that both modified sources and sources in implicit extending projects +that depend on them are recompiled. + +Thus, in our example we could create the following projects instead: + +@example +a_ext.gpr, extends a.gpr and overrides A1 +c_ext.gpr, "extends all" c.gpr, imports a_ext.gpr and overrides C1 +@end example + +@example +project A_Ext extends "a.gpr" is + for Source_Files use ("a1.adb", "a1.ads"); +end A_Ext; + +with "a_ext.gpr"; +project C_Ext extends all "c.gpr" is + for Source_Files use ("c1.adb"); +end C_Ext; +@end example + +When building project @code{c_ext.gpr}, the entire modified project space is +considered for recompilation, including the sources of @code{b.gpr} that are +impacted by the changes in @cite{A1} and @cite{C1}. + +@node Aggregate Projects,Aggregate Library Projects,Project Extension,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager aggregate-projects}@anchor{16e}@anchor{gnat_ugn/gnat_project_manager id27}@anchor{181} +@section Aggregate Projects + + +Aggregate projects are an extension of the project paradigm, and are +meant to solve a few specific use cases that cannot be solved directly +using standard projects. This section will go over a few of these use +cases to try to explain what you can use aggregate projects for. + +@menu +* Building all main programs from a single project tree:: +* Building a set of projects with a single command:: +* Define a build environment:: +* Performance improvements in builder:: +* Syntax of aggregate projects:: +* package Builder in aggregate projects:: + +@end menu + +@node Building all main programs from a single project tree,Building a set of projects with a single command,,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager id28}@anchor{182}@anchor{gnat_ugn/gnat_project_manager building-all-main-programs-from-a-single-project-tree}@anchor{183} +@subsection Building all main programs from a single project tree + + +Most often, an application is organized into modules and submodules, +which are very conveniently represented as a project tree or graph +(the root project A @emph{with}s the projects for each modules (say B and C), +which in turn @emph{with} projects for submodules. + +Very often, modules will build their own executables (for testing +purposes for instance), or libraries (for easier reuse in various +contexts). + +However, if you build your project through @emph{gnatmake} or +@emph{gprbuild}, using a syntax similar to + +@example +gprbuild -PA.gpr +@end example + +this will only rebuild the main programs of project A, not those of the +imported projects B and C. Therefore you have to spawn several +@emph{gnatmake} commands, one per project, to build all executables. +This is a little inconvenient, but more importantly is inefficient +because @emph{gnatmake} needs to do duplicate work to ensure that sources are +up-to-date, and cannot easily compile things in parallel when using +the -j switch. + +Also libraries are always rebuilt when building a project. + +You could therefore define an aggregate project Agg that groups A, B +and C. Then, when you build with + +@example +gprbuild -PAgg.gpr +@end example + +this will build all mains from A, B and C. + +@example +aggregate project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); +end Agg; +@end example + +If B or C do not define any main program (through their Main +attribute), all their sources are built. When you do not group them +in the aggregate project, only those sources that are needed by A +will be built. + +If you add a main to a project P not already explicitly referenced in the +aggregate project, you will need to add "p.gpr" in the list of project +files for the aggregate project, or the main will not be built when +building the aggregate project. + +Aggregate projects are supported only with @emph{gprbuild}, not with +@emph{gnatmake}. + +@node Building a set of projects with a single command,Define a build environment,Building all main programs from a single project tree,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager building-a-set-of-projects-with-a-single-command}@anchor{184}@anchor{gnat_ugn/gnat_project_manager id29}@anchor{185} +@subsection Building a set of projects with a single command + + +One other case is when you have multiple applications and libraries +that are built independently from each other (but can be built in +parallel). For instance, you have a project tree rooted at A, and +another one (which might share some subprojects) rooted at B. + +Using only @emph{gprbuild}, you could do + +@example +gprbuild -PA.gpr +gprbuild -PB.gpr +@end example + +to build both. But again, @emph{gprbuild} has to do some duplicate work for +those files that are shared between the two, and cannot truly build +things in parallel efficiently. + +If the two projects are really independent, share no sources other +than through a common subproject, and have no source files with a +common basename, you could create a project C that imports A and +B. But these restrictions are often too strong, and one has to build +them independently. An aggregate project does not have these +limitations and can aggregate two project trees that have common +sources. + +This scenario is particularly useful in environments like VxWorks 653 +where the applications running in the multiple partitions can be built +in parallel through a single @emph{gprbuild} command. This also works nicely +with Annex E. + +@node Define a build environment,Performance improvements in builder,Building a set of projects with a single command,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager id30}@anchor{186}@anchor{gnat_ugn/gnat_project_manager define-a-build-environment}@anchor{187} +@subsection Define a build environment + + +The environment variables at the time you launch @emph{gprbuild} +will influence the view these tools have of the project +(PATH to find the compiler, ADA_PROJECT_PATH or GPR_PROJECT_PATH to find the +projects, environment variables that are referenced in project files +through the "external" built-in function, ...). Several command line switches +can be used to override those (-X or -aP), but on some systems and +with some projects, this might make the command line too long, and on +all systems often make it hard to read. + +An aggregate project can be used to set the environment for all +projects built through that aggregate. One of the nice aspects is that +you can put the aggregate project under configuration management, and +make sure all your user have a consistent environment when +building. The syntax looks like + +@example +aggregate project Agg is + for Project_Files use ("A.gpr", "B.gpr"); + for Project_Path use ("../dir1", "../dir1/dir2"); + for External ("BUILD") use "PRODUCTION"; + + package Builder is + for Switches ("Ada") use ("-q"); + end Builder; +end Agg; +@end example + +One of the often requested features in projects is to be able to +reference external variables in @emph{with} declarations, as in + +@example +with external("SETUP") & "path/prj.gpr"; -- ILLEGAL +project MyProject is + ... +end MyProject; +@end example + +For various reasons, this is not allowed. But using aggregate projects provide +an elegant solution. For instance, you could use a project file like: + +@example +aggregate project Agg is + for Project_Path use (external("SETUP") & "path"); + for Project_Files use ("myproject.gpr"); +end Agg; + +with "prj.gpr"; -- searched on Agg'Project_Path +project MyProject is + ... +end MyProject; +@end example + +@node Performance improvements in builder,Syntax of aggregate projects,Define a build environment,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager performance-improvements-in-builder}@anchor{188}@anchor{gnat_ugn/gnat_project_manager id31}@anchor{189} +@subsection Performance improvements in builder + + +The loading of aggregate projects is optimized in @emph{gprbuild}, +so that all files are searched for only once on the disk +(thus reducing the number of system calls and contributing to faster +compilation times, especially on systems with sources on remote +servers). As part of the loading, @emph{gprbuild} +computes how and where a source file should be compiled, and even if it is +found several times in the aggregated projects it will be compiled only +once. + +Since there is no ambiguity as to which switches should be used, files +can be compiled in parallel (through the usual -j switch) and this can +be done while maximizing the use of CPUs (compared to launching +multiple @emph{gprbuild} and @emph{gnatmake} commands in parallel). + +@node Syntax of aggregate projects,package Builder in aggregate projects,Performance improvements in builder,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager id32}@anchor{18a}@anchor{gnat_ugn/gnat_project_manager syntax-of-aggregate-projects}@anchor{18b} +@subsection Syntax of aggregate projects + + +An aggregate project follows the general syntax of project files. The +recommended extension is still @code{.gpr}. However, a special +@cite{aggregate} qualifier must be put before the keyword +@cite{project}. + +An aggregate project cannot @emph{with} any other project (standard or +aggregate), except an abstract project which can be used to share attribute +values. Also, aggregate projects cannot be extended or imported though a +@emph{with} clause by any other project. Building other aggregate projects from +an aggregate project is done through the Project_Files attribute (see below). + +An aggregate project does not have any source files directly (only +through other standard projects). Therefore a number of the standard +attributes and packages are forbidden in an aggregate project. Here is the +(non exhaustive) list: + + +@itemize * + +@item +Languages + +@item +Source_Files, Source_List_File and other attributes dealing with +list of sources. + +@item +Source_Dirs, Exec_Dir and Object_Dir + +@item +Library_Dir, Library_Name and other library-related attributes + +@item +Main + +@item +Roots + +@item +Externally_Built + +@item +Inherit_Source_Path + +@item +Excluded_Source_Dirs + +@item +Locally_Removed_Files + +@item +Excluded_Source_Files + +@item +Excluded_Source_List_File + +@item +Interfaces +@end itemize + +The only package that is authorized (albeit optional) is +Builder. Other packages (in particular Compiler, Binder and Linker) +are forbidden. + +The following three attributes can be used only in an aggregate project: + +@geindex Project_Files (GNAT Project Manager) + +@strong{Project_Files}: + +@quotation + +This attribute is compulsory (or else we are not aggregating any project, +and thus not doing anything). It specifies a list of @code{.gpr} files +that are grouped in the aggregate. The list may be empty. The project +files can be either other aggregate projects, or standard projects. When +grouping standard projects, you can have both the root of a project tree +(and you do not need to specify all its imported projects), and any project +within the tree. + +Basically, the idea is to specify all those projects that have +main programs you want to build and link, or libraries you want to +build. You can even specify projects that do not use the Main +attribute nor the @cite{Library_*} attributes, and the result will be to +build all their source files (not just the ones needed by other +projects). + +The file can include paths (absolute or relative). Paths are relative to +the location of the aggregate project file itself (if you use a base name, +we expect to find the .gpr file in the same directory as the aggregate +project file). The environment variables @cite{ADA_PROJECT_PATH}, +@cite{GPR_PROJECT_PATH} and @cite{GPR_PROJECT_PATH_FILE} are not used to find +the project files. The extension @code{.gpr} is mandatory, since this attribute +contains file names, not project names. + +Paths can also include the @cite{"*"} and @cite{"**"} globbing patterns. The +latter indicates that any subdirectory (recursively) will be +searched for matching files. The latter (@cite{"**"}) can only occur at the +last position in the directory part (ie @cite{"a/**/*.gpr"} is supported, but +not @cite{"**/a/*.gpr"}). Starting the pattern with @cite{"**"} is equivalent +to starting with @cite{"./**"}. + +For now, the pattern @cite{"*"} is only allowed in the filename part, not +in the directory part. This is mostly for efficiency reasons to limit the +number of system calls that are needed. + +Here are a few valid examples: + +@example +for Project_Files use ("a.gpr", "subdir/b.gpr"); +-- two specific projects relative to the directory of agg.gpr + +for Project_Files use ("/.gpr"); +-- all projects recursively +@end example +@end quotation + +@geindex Project_Path (GNAT Project Manager) + +@strong{Project_Path}: + +@quotation + +This attribute can be used to specify a list of directories in +which to look for project files in @emph{with} declarations. + +When you specify a project in Project_Files (say @cite{x/y/a.gpr}), and +@cite{a.gpr} imports a project @cite{b.gpr}, only @cite{b.gpr} is searched in +the project path. @cite{a.gpr} must be exactly at +@cite{/x/y/a.gpr}. + +This attribute, however, does not affect the search for the aggregated +project files specified with @cite{Project_Files}. + +Each aggregate project has its own @cite{Project_Path} (that is if +@cite{agg1.gpr} includes @cite{agg2.gpr}, they can potentially both have a +different @cite{Project_Path}). + +This project path is defined as the concatenation, in that order, of: + + +@itemize * + +@item +the current directory; + +@item +followed by the command line -aP switches; + +@item +then the directories from the GPR_PROJECT_PATH and ADA_PROJECT_PATH environment +variables; + +@item +then the directories from the Project_Path attribute; + +@item +and finally the predefined directories. +@end itemize + +In the example above, agg2.gpr's project path is not influenced by +the attribute agg1'Project_Path, nor is agg1 influenced by +agg2'Project_Path. + +This can potentially lead to errors. Consider the following example: + +@c -- +@c -- +---------------+ +----------------+ +@c -- | Agg1.gpr |-=--includes--=-->| Agg2.gpr | +@c -- | 'project_path| | 'project_path | +@c -- | | | | +@c -- +---------------+ +----------------+ +@c -- : : +@c -- includes includes +@c -- : : +@c -- v v +@c -- +-------+ +---------+ +@c -- | P.gpr |<---------- withs --------| Q.gpr | +@c -- +-------+---------\ +---------+ +@c -- | | +@c -- withs | +@c -- | | +@c -- v v +@c -- +-------+ +---------+ +@c -- | R.gpr | | R'.gpr | +@c -- +-------+ +---------+ + +@image{project-manager-figure,,,,png} + +When looking for p.gpr, both aggregates find the same physical file on +the disk. However, it might happen that with their different project +paths, both aggregate projects would in fact find a different r.gpr. +Since we have a common project (p.gpr) "with"ing two different r.gpr, +this will be reported as an error by the builder. + +Directories are relative to the location of the aggregate project file. + +Example: + +@example +for Project_Path use ("/usr/local/gpr", "gpr/"); +@end example +@end quotation + +@geindex External (GNAT Project Manager) + +@strong{External}: + +@quotation + +This attribute can be used to set the value of environment +variables as retrieved through the @cite{external} function +in projects. It does not affect the environment variables +themselves (so for instance you cannot use it to change the value +of your PATH as seen from the spawned compiler). + +This attribute affects the external values as seen in the rest of +the aggregate project, and in the aggregated projects. + +The exact value of external a variable comes from one of three +sources (each level overrides the previous levels): + + +@itemize * + +@item +An External attribute in aggregate project, for instance +@cite{for External ("BUILD_MODE") use "DEBUG"}; + +@item +Environment variables. +These override the value given by the attribute, so that +users can override the value set in the (presumably shared +with others team members) aggregate project. + +@item +The -X command line switch to @emph{gprbuild}. +This always takes precedence. +@end itemize + +This attribute is only taken into account in the main aggregate +project (i.e. the one specified on the command line to @emph{gprbuild}), +and ignored in other aggregate projects. It is invalid +in standard projects. +The goal is to have a consistent value in all +projects that are built through the aggregate, which would not +be the case in the diamond case: A groups the aggregate +projects B and C, which both (either directly or indirectly) +build the project P. If B and C could set different values for +the environment variables, we would have two different views of +P, which in particular might impact the list of source files in P. +@end quotation + +@node package Builder in aggregate projects,,Syntax of aggregate projects,Aggregate Projects +@anchor{gnat_ugn/gnat_project_manager package-builder-in-aggregate-projects}@anchor{18c}@anchor{gnat_ugn/gnat_project_manager id33}@anchor{18d} +@subsection package Builder in aggregate projects + + +As mentioned above, only the package Builder can be specified in +an aggregate project. In this package, only the following attributes +are valid: + +@geindex Switches (GNAT Project Manager) + +@strong{Switches}: + +@quotation + +This attribute gives the list of switches to use for @emph{gprbuild}. +Because no mains can be specified for aggregate projects, the only possible +index for attribute @cite{Switches} is @cite{others}. All other indexes will +be ignored. + +Example: + +@example +for Switches (others) use ("-v", "-k", "-j8"); +@end example + +These switches are only read from the main aggregate project (the +one passed on the command line), and ignored in all other aggregate +projects or projects. + +It can only contain builder switches, not compiler switches. +@end quotation + +@geindex Global_Compilation_Switches (GNAT Project Manager) + +@strong{Global_Compilation_Switches} + +@quotation + +This attribute gives the list of compiler switches for the various +languages. For instance, + +@example +for Global_Compilation_Switches ("Ada") use ("O1", "-g"); +for Global_Compilation_Switches ("C") use ("-O2"); +@end example + +This attribute is only taken into account in the aggregate project +specified on the command line, not in other aggregate projects. + +In the projects grouped by that aggregate, the attribute +Builder.Global_Compilation_Switches is also ignored. However, the +attribute Compiler.Default_Switches will be taken into account (but +that of the aggregate have higher priority). The attribute +Compiler.Switches is also taken into account and can be used to +override the switches for a specific file. As a result, it always +has priority. + +The rules are meant to avoid ambiguities when compiling. For +instance, aggregate project Agg groups the projects A and B, that +both depend on C. Here is an extra for all of these projects: + +@example +aggregate project Agg is + for Project_Files use ("a.gpr", "b.gpr"); + package Builder is + for Global_Compilation_Switches ("Ada") use ("-O2"); + end Builder; +end Agg; + +with "c.gpr"; +project A is + package Builder is + for Global_Compilation_Switches ("Ada") use ("-O1"); + -- ignored + end Builder; + + package Compiler is + for Default_Switches ("Ada") + use ("-O1", "-g"); + for Switches ("a_file1.adb") + use ("-O0"); + end Compiler; +end A; + +with "c.gpr"; +project B is + package Compiler is + for Default_Switches ("Ada") use ("-O0"); + end Compiler; +end B; + +project C is + package Compiler is + for Default_Switches ("Ada") + use ("-O3", + "-gnatn"); + for Switches ("c_file1.adb") + use ("-O0", "-g"); + end Compiler; +end C; +@end example + +then the following switches are used: + + +@itemize * + +@item +all files from project A except a_file1.adb are compiled +with "-O2 -g", since the aggregate project has priority. + +@item +the file a_file1.adb is compiled with +"-O0", since the Compiler.Switches has priority + +@item +all files from project B are compiled with +"-O2", since the aggregate project has priority + +@item +all files from C are compiled with "-O2 -gnatn", except for +c_file1.adb which is compiled with "-O0 -g" +@end itemize + +Even though C is seen through two paths (through A and through +B), the switches used by the compiler are unambiguous. +@end quotation + +@geindex Global_Configuration_Pragmas (GNAT Project Manager) + +@strong{Global_Configuration_Pragmas} + +@quotation + +This attribute can be used to specify a file containing +configuration pragmas, to be passed to the Ada compiler. Since we +ignore the package Builder in other aggregate projects and projects, +only those pragmas defined in the main aggregate project will be +taken into account. + +Projects can locally add to those by using the +@cite{Compiler.Local_Configuration_Pragmas} attribute if they need. +@end quotation + +@geindex Global_Config_File (GNAT Project Manager) + +@strong{Global_Config_File} + +@quotation + +This attribute, indexed with a language name, can be used to specify a config +when compiling sources of the language. For Ada, these files are configuration +pragmas files. +@end quotation + +For projects that are built through the aggregate, the package Builder +is ignored, except for the Executable attribute which specifies the +name of the executables resulting from the link of the main programs, and +for the Executable_Suffix. + +@node Aggregate Library Projects,Project File Reference,Aggregate Projects,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager id34}@anchor{18e}@anchor{gnat_ugn/gnat_project_manager aggregate-library-projects}@anchor{18f} +@section Aggregate Library Projects + + +Aggregate library projects make it possible to build a single library +using object files built using other standard or library +projects. This gives the flexibility to describe an application as +having multiple modules (a GUI, database access, ...) using different +project files (so possibly built with different compiler options) and +yet create a single library (static or relocatable) out of the +corresponding object files. + +@menu +* Building aggregate library projects:: +* Syntax of aggregate library projects:: + +@end menu + +@node Building aggregate library projects,Syntax of aggregate library projects,,Aggregate Library Projects +@anchor{gnat_ugn/gnat_project_manager building-aggregate-library-projects}@anchor{190}@anchor{gnat_ugn/gnat_project_manager id35}@anchor{191} +@subsection Building aggregate library projects + + +For example, we can define an aggregate project Agg that groups A, B +and C: + +@example +aggregate library project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); + for Library_Name use ("agg"); + for Library_Dir use ("lagg"); +end Agg; +@end example + +Then, when you build with: + +@example +gprbuild agg.gpr +@end example + +This will build all units from projects A, B and C and will create a +static library named @code{libagg.a} in the @code{lagg} +directory. An aggregate library project has the same set of +restriction as a standard library project. + +Note that a shared aggregate library project cannot aggregate a +static library project. In platforms where a compiler option is +required to create relocatable object files, a Builder package in the +aggregate library project may be used: + +@example +aggregate library project Agg is + for Project_Files use ("a.gpr", "b.gpr", "c.gpr"); + for Library_Name use ("agg"); + for Library_Dir use ("lagg"); + for Library_Kind use "relocatable"; + + package Builder is + for Global_Compilation_Switches ("Ada") use ("-fPIC"); + end Builder; +end Agg; +@end example + +With the above aggregate library Builder package, the @cite{-fPIC} +option will be passed to the compiler when building any source code +from projects @code{a.gpr}, @code{b.gpr} and @code{c.gpr}. + +@node Syntax of aggregate library projects,,Building aggregate library projects,Aggregate Library Projects +@anchor{gnat_ugn/gnat_project_manager syntax-of-aggregate-library-projects}@anchor{192}@anchor{gnat_ugn/gnat_project_manager id36}@anchor{193} +@subsection Syntax of aggregate library projects + + +An aggregate library project follows the general syntax of project +files. The recommended extension is still @code{.gpr}. However, a special +@cite{aggregate library} qualifier must be put before the keyword +@cite{project}. + +An aggregate library project cannot @emph{with} any other project +(standard or aggregate), except an abstract project which can be used +to share attribute values. + +An aggregate library project does not have any source files directly (only +through other standard projects). Therefore a number of the standard +attributes and packages are forbidden in an aggregate library +project. Here is the (non exhaustive) list: + + +@itemize * + +@item +Languages + +@item +Source_Files, Source_List_File and other attributes dealing with +list of sources. + +@item +Source_Dirs, Exec_Dir and Object_Dir + +@item +Main + +@item +Roots + +@item +Externally_Built + +@item +Inherit_Source_Path + +@item +Excluded_Source_Dirs + +@item +Locally_Removed_Files + +@item +Excluded_Source_Files + +@item +Excluded_Source_List_File + +@item +Interfaces +@end itemize + +The only package that is authorized (albeit optional) is Builder. + +The Project_Files attribute (See @ref{16e,,Aggregate Projects}) is used to +described the aggregated projects whose object files have to be +included into the aggregate library. The environment variables +@cite{ADA_PROJECT_PATH}, @cite{GPR_PROJECT_PATH} and +@cite{GPR_PROJECT_PATH_FILE} are not used to find the project files. + +@node Project File Reference,,Aggregate Library Projects,GNAT Project Manager +@anchor{gnat_ugn/gnat_project_manager id37}@anchor{194}@anchor{gnat_ugn/gnat_project_manager project-file-reference}@anchor{14d} +@section Project File Reference + + +This section describes the syntactic structure of project files, the various +constructs that can be used. Finally, it ends with a summary of all available +attributes. + +@menu +* Project Declaration:: +* Qualified Projects:: +* Declarations:: +* Packages:: +* Expressions:: +* External Values:: +* Typed String Declaration:: +* Variables:: +* Case Constructions:: +* Attributes:: + +@end menu + +@node Project Declaration,Qualified Projects,,Project File Reference +@anchor{gnat_ugn/gnat_project_manager id38}@anchor{195}@anchor{gnat_ugn/gnat_project_manager project-declaration}@anchor{196} +@subsection Project Declaration + + +Project files have an Ada-like syntax. The minimal project file is: + +@example +project Empty is +end Empty; +@end example + +The identifier @cite{Empty} is the name of the project. +This project name must be present after the reserved +word @cite{end} at the end of the project file, followed by a semi-colon. + +@strong{Identifiers} (i.e., the user-defined names such as project or variable names) +have the same syntax as Ada identifiers: they must start with a letter, +and be followed by zero or more letters, digits or underscore characters; +it is also illegal to have two underscores next to each other. Identifiers +are always case-insensitive ("Name" is the same as "name"). + +@example +simple_name ::= identifier +name ::= simple_name @{ . simple_name @} +@end example + +@strong{Strings} are used for values of attributes or as indexes for these +attributes. They are in general case sensitive, except when noted +otherwise (in particular, strings representing file names will be case +insensitive on some systems, so that "file.adb" and "File.adb" both +represent the same file). + +@strong{Reserved words} are the same as for standard Ada 95, and cannot +be used for identifiers. In particular, the following words are currently +used in project files, but others could be added later on. In bold are the +extra reserved words in project files: +@code{all}, @code{at}, @code{case}, @code{end}, @code{for}, @code{is}, @code{limited}, +@code{null}, @code{others}, @code{package}, @code{renames}, @code{type}, @code{use}, @code{when}, +@code{with}, @strong{extends}, @strong{external}, @strong{project}. + +@strong{Comments} in project files have the same syntax as in Ada, two consecutive +hyphens through the end of the line. + +A project may be an @strong{independent project}, entirely defined by a single +project file. Any source file in an independent project depends only +on the predefined library and other source files in the same project. +But a project may also depend on other projects, either by importing them +through @strong{with clauses}, or by @strong{extending} at most one other project. Both +types of dependency can be used in the same project. + +A path name denotes a project file. It can be absolute or relative. +An absolute path name includes a sequence of directories, in the syntax of +the host operating system, that identifies uniquely the project file in the +file system. A relative path name identifies the project file, relative +to the directory that contains the current project, or relative to a +directory listed in the environment variables ADA_PROJECT_PATH and +GPR_PROJECT_PATH. Path names are case sensitive if file names in the host +operating system are case sensitive. As a special case, the directory +separator can always be "/" even on Windows systems, so that project files +can be made portable across architectures. +The syntax of the environment variables ADA_PROJECT_PATH and +GPR_PROJECT_PATH is a list of directory names separated by colons on UNIX and +semicolons on Windows. + +A given project name can appear only once in a context clause. + +It is illegal for a project imported by a context clause to refer, directly +or indirectly, to the project in which this context clause appears (the +dependency graph cannot contain cycles), except when one of the with clauses +in the cycle is a @strong{limited with}. + +@example +with "other_project.gpr"; +project My_Project extends "extended.gpr" is +end My_Project; +@end example + +These dependencies form a @strong{directed graph}, potentially cyclic when using +@strong{limited with}. The subgraph reflecting the @strong{extends} relations is a tree. + +A project's @strong{immediate sources} are the source files directly defined by +that project, either implicitly by residing in the project source directories, +or explicitly through any of the source-related attributes. +More generally, a project's @strong{sources} are the immediate sources of the +project together with the immediate sources (unless overridden) of any project +on which it depends directly or indirectly. + +A @strong{project hierarchy} can be created, where projects are children of +other projects. The name of such a child project must be @cite{Parent.Child}, +where @cite{Parent} is the name of the parent project. In particular, this +makes all @emph{with} clauses of the parent project automatically visible +in the child project. + +@example +project ::= context_clause project_declaration + +context_clause ::= @{with_clause@} +with_clause ::= *with* path_name @{ , path_name @} ; +path_name ::= string_literal + +project_declaration ::= simple_project_declaration | project_extension +simple_project_declaration ::= + project name is + @{declarative_item@} + end simple_name; +@end example + +@node Qualified Projects,Declarations,Project Declaration,Project File Reference +@anchor{gnat_ugn/gnat_project_manager qualified-projects}@anchor{173}@anchor{gnat_ugn/gnat_project_manager id39}@anchor{197} +@subsection Qualified Projects + + +Before the reserved @cite{project}, there may be one or two @strong{qualifiers}, that +is identifiers or reserved words, to qualify the project. +The current list of qualifiers is: + + +@table @asis + +@item @strong{abstract}: + +Qualifies a project with no sources. +Such a project must either have no declaration of attributes @cite{Source_Dirs}, +@cite{Source_Files}, @cite{Languages} or @cite{Source_List_File}, or one of +@cite{Source_Dirs}, @cite{Source_Files}, or @cite{Languages} must be declared +as empty. If it extends another project, the project it extends must also be a +qualified abstract project. + +@item @strong{standard}: + +A standard project is a non library project with sources. +This is the default (implicit) qualifier. + +@item @strong{aggregate}: + +A project whose sources are aggregated from other project files. + +@item @strong{aggregate library}: + +A library whose sources are aggregated from other project +or library project files. + +@item @strong{library}: + +A library project must declare both attributes +Library_Name` and @cite{Library_Dir}. + +@item @strong{configuration}: + +A configuration project cannot be in a project tree. +It describes compilers and other tools to @emph{gprbuild}. +@end table + +@node Declarations,Packages,Qualified Projects,Project File Reference +@anchor{gnat_ugn/gnat_project_manager declarations}@anchor{198}@anchor{gnat_ugn/gnat_project_manager id40}@anchor{199} +@subsection Declarations + + +Declarations introduce new entities that denote types, variables, attributes, +and packages. Some declarations can only appear immediately within a project +declaration. Others can appear within a project or within a package. + +@example +declarative_item ::= simple_declarative_item + | typed_string_declaration + | package_declaration + +simple_declarative_item ::= variable_declaration + | typed_variable_declaration + | attribute_declaration + | case_construction + | empty_declaration + +empty_declaration ::= *null* ; +@end example + +An empty declaration is allowed anywhere a declaration is allowed. It has +no effect. + +@node Packages,Expressions,Declarations,Project File Reference +@anchor{gnat_ugn/gnat_project_manager packages}@anchor{153}@anchor{gnat_ugn/gnat_project_manager id41}@anchor{19a} +@subsection Packages + + +A project file may contain @strong{packages}, that group attributes (typically +all the attributes that are used by one of the GNAT tools). + +A package with a given name may only appear once in a project file. +The following packages are currently supported in project files +(See @ref{152,,Attributes} for the list of attributes that each can contain). + + +@table @asis + +@item @emph{Binder} + +This package specifies characteristics useful when invoking the binder either +directly via the @emph{gnat} driver or when using a builder such as +@emph{gnatmake} or @emph{gprbuild}. See @ref{15d,,Main Subprograms}. + +@item @emph{Builder} + +This package specifies the compilation options used when building an +executable or a library for a project. Most of the options should be +set in one of @cite{Compiler}, @cite{Binder} or @cite{Linker} packages, +but there are some general options that should be defined in this +package. See @ref{15d,,Main Subprograms}, and @ref{162,,Executable File Names} in +particular. +@end table + + + +@table @asis + +@item @emph{Clean} + +This package specifies the options used when cleaning a project or a project +tree using the tools @emph{gnatclean} or @emph{gprclean}. + +@item @emph{Compiler} + +This package specifies the compilation options used by the compiler for +each languages. See @ref{15e,,Tools Options in Project Files}. + +@item @emph{Cross_Reference} + +This package specifies the options used when calling the library tool +@emph{gnatxref} via the @emph{gnat} driver. Its attributes +@strong{Default_Switches} and @strong{Switches} have the same semantics as for the +package @cite{Builder}. +@end table + + + +@table @asis + +@item @emph{Finder} + +This package specifies the options used when calling the search tool +@emph{gnatfind} via the @emph{gnat} driver. Its attributes +@strong{Default_Switches} and @strong{Switches} have the same semantics as for the +package @cite{Builder}. + +@item @emph{Gnatls} + +This package specifies the options to use when invoking @emph{gnatls} +via the @emph{gnat} driver. +@end table + + + +@table @asis + +@item @emph{IDE} + +This package specifies the options used when starting an integrated +development environment, for instance @emph{GPS} or @emph{Gnatbench}. + +@item @emph{Install} + +This package specifies the options used when installing a project +with @emph{gprinstall}. See @ref{168,,Installation}. + +@item @emph{Linker} + +This package specifies the options used by the linker. +See @ref{15d,,Main Subprograms}. +@end table + + + +@table @asis + +@item @emph{Naming} + +@quotation + +This package specifies the naming conventions that apply +to the source files in a project. In particular, these conventions are +used to automatically find all source files in the source directories, +or given a file name to find out its language for proper processing. +See @ref{14b,,Naming Schemes}. +@end quotation + +@c only: PRO or GPL +@c +@c *Pretty_Printer* +@c This package specifies the options used when calling the formatting tool +@c *gnatpp* via the *gnat* driver. Its attributes +@c **Default_Switches** and **Switches** have the same semantics as for the +@c package `Builder`. + +@item @emph{Remote} + +This package is used by @emph{gprbuild} to describe how distributed +compilation should be done. + +@item @emph{Stack} + +This package specifies the options used when calling the tool +@emph{gnatstack} via the @emph{gnat} driver. Its attributes +@strong{Default_Switches} and @strong{Switches} have the same semantics as for the +package @cite{Builder}. + +@item @emph{Synchronize} + +This package specifies the options used when calling the tool +@emph{gnatsync} via the @emph{gnat} driver. +@end table + +In its simplest form, a package may be empty: + +@example +project Simple is + package Builder is + end Builder; +end Simple; +@end example + +A package may contain @strong{attribute declarations}, +@strong{variable declarations} and @strong{case constructions}, as will be +described below. + +When there is ambiguity between a project name and a package name, +the name always designates the project. To avoid possible confusion, it is +always a good idea to avoid naming a project with one of the +names allowed for packages or any name that starts with @cite{gnat}. + +A package can also be defined by a @strong{renaming declaration}. The new package +renames a package declared in a different project file, and has the same +attributes as the package it renames. The name of the renamed package +must be the same as the name of the renaming package. The project must +contain a package declaration with this name, and the project +must appear in the context clause of the current project, or be its parent +project. It is not possible to add or override attributes to the renaming +project. If you need to do so, you should use an @strong{extending declaration} +(see below). + +Packages that are renamed in other project files often come from project files +that have no sources: they are just used as templates. Any modification in the +template will be reflected automatically in all the project files that rename +a package from the template. This is a very common way to share settings +between projects. + +Finally, a package can also be defined by an @strong{extending declaration}. This is +similar to a @strong{renaming declaration}, except that it is possible to add or +override attributes. + +@example +package_declaration ::= package_spec | package_renaming | package_extension +package_spec ::= + package simple_name is + @{simple_declarative_item@} + end package_identifier ; +package_renaming ::== + package simple_name renames simple_name.package_identifier ; +package_extension ::== + package simple_name extends simple_name.package_identifier is + @{simple_declarative_item@} + end package_identifier ; +@end example + +@node Expressions,External Values,Packages,Project File Reference +@anchor{gnat_ugn/gnat_project_manager expressions}@anchor{19b}@anchor{gnat_ugn/gnat_project_manager id42}@anchor{19c} +@subsection Expressions + + +An expression is any value that can be assigned to an attribute or a +variable. It is either a literal value, or a construct requiring runtime +computation by the project manager. In a project file, the computed value of +an expression is either a string or a list of strings. + +A string value is one of: + + +@itemize * + +@item +A literal string, for instance @cite{"comm/my_proj.gpr"} + +@item +The name of a variable that evaluates to a string (see @ref{155,,Variables}) + +@item +The name of an attribute that evaluates to a string (see @ref{152,,Attributes}) + +@item +An external reference (see @ref{154,,External Values}) + +@item +A concatenation of the above, as in @cite{"prefix_" & Var}. +@end itemize + +A list of strings is one of the following: + + +@itemize * + +@item +A parenthesized comma-separated list of zero or more string expressions, for +instance @cite{(File_Name@comma{} "gnat.adc"@comma{} File_Name & ".orig")} or @cite{()}. + +@item +The name of a variable that evaluates to a list of strings + +@item +The name of an attribute that evaluates to a list of strings + +@item +A concatenation of a list of strings and a string (as defined above), for +instance @cite{("A"@comma{} "B") & "C"} + +@item +A concatenation of two lists of strings +@end itemize + +The following is the grammar for expressions + +@example +string_literal ::= "@{string_element@}" -- Same as Ada +string_expression ::= string_literal + | *variable_*name + | external_value + | attribute_reference + | ( string_expression @{ & string_expression @} ) +string_list ::= ( string_expression @{ , string_expression @} ) + | *string_variable*_name + | *string_*attribute_reference +term ::= string_expression | string_list +expression ::= term @{ & term @} -- Concatenation +@end example + +Concatenation involves strings and list of strings. As soon as a list of +strings is involved, the result of the concatenation is a list of strings. The +following Ada declarations show the existing operators: + +@example +function "&" (X : String; Y : String) return String; +function "&" (X : String_List; Y : String) return String_List; +function "&" (X : String_List; Y : String_List) return String_List; +@end example + +Here are some specific examples: + +@example +List := () & File_Name; -- One string in this list +List2 := List & (File_Name & ".orig"); -- Two strings +Big_List := List & Lists2; -- Three strings +Illegal := "gnat.adc" & List2; -- Illegal, must start with list +@end example + +@node External Values,Typed String Declaration,Expressions,Project File Reference +@anchor{gnat_ugn/gnat_project_manager external-values}@anchor{154}@anchor{gnat_ugn/gnat_project_manager id43}@anchor{19d} +@subsection External Values + + +An external value is an expression whose value is obtained from the command +that invoked the processing of the current project file (typically a +@emph{gnatmake} or @emph{gprbuild} command). + +There are two kinds of external values, one that returns a single string, and +one that returns a string list. + +The syntax of a single string external value is: + +@example +external_value ::= *external* ( string_literal [, string_literal] ) +@end example + +The first string_literal is the string to be used on the command line or +in the environment to specify the external value. The second string_literal, +if present, is the default to use if there is no specification for this +external value either on the command line or in the environment. + +Typically, the external value will either exist in the +environment variables +or be specified on the command line through the +@code{-X@emph{vbl}=@emph{value}} switch. If both +are specified, then the command line value is used, so that a user can more +easily override the value. + +The function @cite{external} always returns a string. It is an error if the +value was not found in the environment and no default was specified in the +call to @cite{external}. + +An external reference may be part of a string expression or of a string +list expression, and can therefore appear in a variable declaration or +an attribute declaration. + +Most of the time, this construct is used to initialize typed variables, which +are then used in @strong{case} constructions to control the value assigned to +attributes in various scenarios. Thus such variables are often called +@strong{scenario variables}. + +The syntax for a string list external value is: + +@example +external_value ::= *external_as_list* ( string_literal , string_literal ) +@end example + +The first string_literal is the string to be used on the command line or +in the environment to specify the external value. The second string_literal is +the separator between each component of the string list. + +If the external value does not exist in the environment or on the command line, +the result is an empty list. This is also the case, if the separator is an +empty string or if the external value is only one separator. + +Any separator at the beginning or at the end of the external value is +discarded. Then, if there is no separator in the external value, the result is +a string list with only one string. Otherwise, any string between the beginning +and the first separator, between two consecutive separators and between the +last separator and the end are components of the string list. + +@example +*external_as_list* ("SWITCHES", ",") +@end example + +If the external value is "-O2,-g", +the result is ("-O2", "-g"). + +If the external value is ",-O2,-g,", +the result is also ("-O2", "-g"). + +if the external value is "-gnatv", +the result is ("-gnatv"). + +If the external value is ",,", the result is (""). + +If the external value is ",", the result is (), the empty string list. + +@node Typed String Declaration,Variables,External Values,Project File Reference +@anchor{gnat_ugn/gnat_project_manager id44}@anchor{19e}@anchor{gnat_ugn/gnat_project_manager typed-string-declaration}@anchor{19f} +@subsection Typed String Declaration + + +A @strong{type declaration} introduces a discrete set of string literals. +If a string variable is declared to have this type, its value +is restricted to the given set of literals. These are the only named +types in project files. A string type may only be declared at the project +level, not inside a package. + +@example +typed_string_declaration ::= + *type* **_simple_name *is* ( string_literal @{, string_literal@} ); +@end example + +The string literals in the list are case sensitive and must all be different. +They may include any graphic characters allowed in Ada, including spaces. +Here is an example of a string type declaration: + +@example +type OS is ("NT", "nt", "Unix", "GNU/Linux", "other OS"); +@end example + +Variables of a string type are called @strong{typed variables}; all other +variables are called @strong{untyped variables}. Typed variables are +particularly useful in @cite{case} constructions, to support conditional +attribute declarations. (See @ref{1a0,,Case Constructions}). + +A string type may be referenced by its name if it has been declared in the same +project file, or by an expanded name whose prefix is the name of the project +in which it is declared. + +@node Variables,Case Constructions,Typed String Declaration,Project File Reference +@anchor{gnat_ugn/gnat_project_manager variables}@anchor{155}@anchor{gnat_ugn/gnat_project_manager id45}@anchor{1a1} +@subsection Variables + + +@strong{Variables} store values (strings or list of strings) and can appear +as part of an expression. The declaration of a variable creates the +variable and assigns the value of the expression to it. The name of the +variable is available immediately after the assignment symbol, if you +need to reuse its old value to compute the new value. Before the completion +of its first declaration, the value of a variable defaults to the empty +string (""). + +A @strong{typed} variable can be used as part of a @strong{case} expression to +compute the value, but it can only be declared once in the project file, +so that all case constructions see the same value for the variable. This +provides more consistency and makes the project easier to understand. +The syntax for its declaration is identical to the Ada syntax for an +object declaration. In effect, a typed variable acts as a constant. + +An @strong{untyped} variable can be declared and overridden multiple times +within the same project. It is declared implicitly through an Ada +assignment. The first declaration establishes the kind of the variable +(string or list of strings) and successive declarations must respect +the initial kind. Assignments are executed in the order in which they +appear, so the new value replaces the old one and any subsequent reference +to the variable uses the new value. + +A variable may be declared at the project file level, or within a package. + +@example +typed_variable_declaration ::= + **simple_name : **name := string_expression; + +variable_declaration ::= **simple_name := expression; +@end example + +Here are some examples of variable declarations: + +@example +This_OS : OS := external ("OS"); -- a typed variable declaration +That_OS := "GNU/Linux"; -- an untyped variable declaration + +Name := "readme.txt"; +Save_Name := Name & ".saved"; + +Empty_List := (); +List_With_One_Element := ("-gnaty"); +List_With_Two_Elements := List_With_One_Element & "-gnatg"; +Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"); +@end example + +A @strong{variable reference} may take several forms: + + +@itemize * + +@item +The simple variable name, for a variable in the current package (if any) +or in the current project + +@item +An expanded name, whose prefix is a context name. +@end itemize + +A @strong{context} may be one of the following: + + +@itemize * + +@item +The name of an existing package in the current project + +@item +The name of an imported project of the current project + +@item +The name of an ancestor project (i.e., a project extended by the current +project, either directly or indirectly) + +@item +An expanded name whose prefix is an imported/parent project name, and +whose selector is a package name in that project. +@end itemize + +@node Case Constructions,Attributes,Variables,Project File Reference +@anchor{gnat_ugn/gnat_project_manager id46}@anchor{1a2}@anchor{gnat_ugn/gnat_project_manager case-constructions}@anchor{1a0} +@subsection Case Constructions + + +A @strong{case} construction is used in a project file to effect conditional +behavior. Through this construction, you can set the value of attributes +and variables depending on the value previously assigned to a typed +variable. + +All choices in a choice list must be distinct. Unlike Ada, the choice +lists of all alternatives do not need to include all values of the type. +An @cite{others} choice must appear last in the list of alternatives. + +The syntax of a @cite{case} construction is based on the Ada case construction +(although the @cite{null} declaration for empty alternatives is optional). + +The case expression must be a string variable, either typed or not, whose value +is often given by an external reference (see @ref{154,,External Values}). + +Each alternative starts with the reserved word @cite{when}, either a list of +literal strings separated by the @cite{"|"} character or the reserved word +@cite{others}, and the @cite{"=>"} token. +When the case expression is a typed string variable, each literal string must +belong to the string type that is the type of the case variable. +After each @cite{=>}, there are zero or more declarations. The only +declarations allowed in a case construction are other case constructions, +attribute declarations and variable declarations. String type declarations and +package declarations are not allowed. Variable declarations are restricted to +variables that have already been declared before the case construction. + +@example +case_construction ::= + *case* **name *is* @{case_item@} *end case* ; + +case_item ::= + *when* discrete_choice_list => + @{case_declaration + | attribute_declaration + | variable_declaration + | empty_declaration@} + +discrete_choice_list ::= string_literal @{| string_literal@} | *others* +@end example + +Here is a typical example, with a typed string variable: + +@example +project MyProj is + type OS_Type is ("GNU/Linux", "Unix", "NT", "VMS"); + OS : OS_Type := external ("OS", "GNU/Linux"); + + package Compiler is + case OS is + when "GNU/Linux" | "Unix" => + for Switches ("Ada") + use ("-gnath"); + when "NT" => + for Switches ("Ada") + use ("-gnatP"); + when others => + null; + end case; + end Compiler; +end MyProj; +@end example + +@node Attributes,,Case Constructions,Project File Reference +@anchor{gnat_ugn/gnat_project_manager id47}@anchor{1a3}@anchor{gnat_ugn/gnat_project_manager attributes}@anchor{152} +@subsection Attributes + + +A project (and its packages) may have @strong{attributes} that define +the project's properties. Some attributes have values that are strings; +others have values that are string lists. + +@example +attribute_declaration ::= + simple_attribute_declaration | indexed_attribute_declaration + +simple_attribute_declaration ::= *for* attribute_designator *use* expression ; + +indexed_attribute_declaration ::= + *for* **simple_name ( string_literal) *use* expression ; + +attribute_designator ::= + **simple_name + | **simple_name ( string_literal ) +@end example + +There are two categories of attributes: @strong{simple attributes} +and @strong{indexed attributes}. +Each simple attribute has a default value: the empty string (for string +attributes) and the empty list (for string list attributes). +An attribute declaration defines a new value for an attribute, and overrides +the previous value. The syntax of a simple attribute declaration is similar to +that of an attribute definition clause in Ada. + +Some attributes are indexed. These attributes are mappings whose +domain is a set of strings. They are declared one association +at a time, by specifying a point in the domain and the corresponding image +of the attribute. +Like untyped variables and simple attributes, indexed attributes +may be declared several times. Each declaration supplies a new value for the +attribute, and replaces the previous setting. + +Here are some examples of attribute declarations: + +@example +-- simple attributes +for Object_Dir use "objects"; +for Source_Dirs use ("units", "test/drivers"); + +-- indexed attributes +for Body ("main") use "Main.ada"; +for Switches ("main.ada") + use ("-v", "-gnatv"); +for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g"; + +-- indexed attributes copy (from package Builder in project Default) +-- The package name must always be specified, even if it is the current +-- package. +for Default_Switches use Default.Builder'Default_Switches; +@end example + +Attributes references may appear anywhere in expressions, and are used +to retrieve the value previously assigned to the attribute. If an attribute +has not been set in a given package or project, its value defaults to the +empty string or the empty list, with some exceptions. + +@example +attribute_reference ::= + attribute_prefix ' *_*simple_name [ (string_literal) ] +attribute_prefix ::= *project* + | **simple_name + | package_identifier + | **simple_name . package_identifier +@end example + +Examples are: + +@example +'Object_Dir +Naming'Dot_Replacement +Imported_Project'Source_Dirs +Imported_Project.Naming'Casing +Builder'Default_Switches ("Ada") +@end example + +The exceptions to the empty defaults are: + + +@itemize * + +@item +Object_Dir: default is "." + +@item +Exec_Dir: default is 'Object_Dir, that is the value of attribute +Object_Dir in the same project, declared or defaulted. + +@item +Source_Dirs: default is (".") +@end itemize + +The prefix of an attribute may be: + + +@itemize * + +@item +@cite{project} for an attribute of the current project + +@item +The name of an existing package of the current project + +@item +The name of an imported project + +@item +The name of a parent project that is extended by the current project + +@item +An expanded name whose prefix is imported/parent project name, +and whose selector is a package name +@end itemize + +In the following sections, all predefined attributes are succinctly described, +first the project level attributes, that is those attributes that are not in a +package, then the attributes in the different packages. + +It is possible for different tools to dynamically create new packages with +attributes, or new attributes in predefined packages. These attributes are +not documented here. + +The attributes under Configuration headings are usually found only in +configuration project files. + +The characteristics of each attribute are indicated as follows: + + +@itemize * + +@item +@strong{Type of value} + +The value of an attribute may be a single string, indicated by the word +"single", or a string list, indicated by the word "list". + +@item +@strong{Read-only} + +When the attribute is read-only, that is when it is not allowed to declare +the attribute, this is indicated by the words "read-only". + +@item +@strong{Optional index} + +If it is allowed in the value of the attribute (both single and list) to have +an optional index, this is indicated by the words "optional index". + +@item +@strong{Indexed attribute} + +When it is an indexed attribute, this is indicated by the word "indexed". + +@item +@strong{Case-sensitivity of the index} + +For an indexed attribute, if the index is case-insensitive, this is indicated +by the words "case-insensitive index". + +@item +@strong{File name index} + +For an indexed attribute, when the index is a file name, this is indicated by +the words "file name index". The index may or may not be case-sensitive, +depending on the platform. + +@item +@strong{others allowed in index} + +For an indexed attribute, if it is allowed to use @strong{others} as the index, +this is indicated by the words "others allowed". + +When @strong{others} is used as the index of an indexed attribute, the value of +the attribute indexed by @strong{others} is used when no other index would apply. +@end itemize + +@menu +* Project Level Attributes:: +* Package Binder Attributes:: +* Package Builder Attributes:: +* Package Clean Attributes:: +* Package Compiler Attributes:: +* Package Cross_Reference Attributes:: +* Package Finder Attributes:: +* Package gnatls Attributes:: +* Package IDE Attributes:: +* Package Install Attributes:: +* Package Linker Attributes:: +* Package Naming Attributes:: +* Package Remote Attributes:: +* Package Stack Attributes:: +* Package Synchronize Attributes:: + +@end menu + +@node Project Level Attributes,Package Binder Attributes,,Attributes +@anchor{gnat_ugn/gnat_project_manager project-level-attributes}@anchor{1a4}@anchor{gnat_ugn/gnat_project_manager id48}@anchor{1a5} +@subsubsection Project Level Attributes + + + +@itemize * + +@item +@strong{General} + + +@itemize * + +@item +@strong{Name}: single, read-only + +The name of the project. + +@item +@strong{Project_Dir}: single, read-only + +The path name of the project directory. + +@item +@strong{Main}: list, optional index + +The list of main sources for the executables. + +@item +@strong{Languages}: list + +The list of languages of the sources of the project. + +@item +@strong{Roots}: list, indexed, file name index + +The index is the file name of an executable source. Indicates the list of units +from the main project that need to be bound and linked with their closures +with the executable. The index is either a file name, a language name or "*". +The roots for an executable source are those in @strong{Roots} with an index that +is the executable source file name, if declared. Otherwise, they are those in +@strong{Roots} with an index that is the language name of the executable source, +if present. Otherwise, they are those in @strong{Roots ("*")}, if declared. If none +of these three possibilities are declared, then there are no roots for the +executable source. + +@item +@strong{Externally_Built}: single + +Indicates if the project is externally built. +Only case-insensitive values allowed are "true" and "false", the default. +@end itemize + +@item +@strong{Directories} + + +@itemize * + +@item +@strong{Object_Dir}: single + +Indicates the object directory for the project. + +@item +@strong{Exec_Dir}: single + +Indicates the exec directory for the project, that is the directory where the +executables are. + +@item +@strong{Source_Dirs}: list + +The list of source directories of the project. + +@item +@strong{Inherit_Source_Path}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of language names. Indicates that +in the source search path of the index language the source directories of +the languages in the list should be included. + +Example: + +@example +for Inherit_Source_Path ("C++") use ("C"); +@end example + +@item +@strong{Exclude_Source_Dirs}: list + +The list of directories that are included in Source_Dirs but are not source +directories of the project. + +@item +@strong{Ignore_Source_Sub_Dirs}: list + +Value is a list of simple names for subdirectories that are removed from the +list of source directories, including theur subdirectories. +@end itemize + +@item +@strong{Source Files} + + +@itemize * + +@item +@strong{Source_Files}: list + +Value is a list of source file simple names. + +@item +@strong{Locally_Removed_Files}: list + +Obsolescent. Equivalent to Excluded_Source_Files. + +@item +@strong{Excluded_Source_Files}: list + +Value is a list of simple file names that are not sources of the project. +Allows to remove sources that are inherited or found in the source directories +and that match the naming scheme. + +@item +@strong{Source_List_File}: single + +Value is a text file name that contains a list of source file simple names, +one on each line. + +@item +@strong{Excluded_Source_List_File}: single + +Value is a text file name that contains a list of file simple names that +are not sources of the project. + +@item +@strong{Interfaces}: list + +Value is a list of file names that constitutes the interfaces of the project. +@end itemize + +@item +@strong{Aggregate Projects} + + +@itemize * + +@item +@strong{Project_Files}: list + +Value is the list of aggregated projects. + +@item +@strong{Project_Path}: list + +Value is a list of directories that are added to the project search path when +looking for the aggregated projects. + +@item +@strong{External}: single, indexed + +Index is the name of an external reference. Value is the value of the +external reference to be used when parsing the aggregated projects. +@end itemize + +@item +@strong{Libraries} + + +@itemize * + +@item +@strong{Library_Dir}: single + +Value is the name of the library directory. This attribute needs to be +declared for each library project. + +@item +@strong{Library_Name}: single + +Value is the name of the library. This attribute needs to be declared or +inherited for each library project. + +@item +@strong{Library_Kind}: single + +Specifies the kind of library: static library (archive) or shared library. +Case-insensitive values must be one of "static" for archives (the default) or +"dynamic" or "relocatable" for shared libraries. + +@item +@strong{Library_Version}: single + +Value is the name of the library file. + +@item +@strong{Library_Interface}: list + +Value is the list of unit names that constitutes the interfaces +of a Stand-Alone Library project. + +@item +@strong{Library_Standalone}: single + +Specifies if a Stand-Alone Library (SAL) is encapsulated or not. +Only authorized case-insensitive values are "standard" for non encapsulated +SALs, "encapsulated" for encapsulated SALs or "no" for non SAL library project. + +@item +@strong{Library_Encapsulated_Options}: list + +Value is a list of options that need to be used when linking an encapsulated +Stand-Alone Library. + +@item +@strong{Library_Encapsulated_Supported}: single + +Indicates if encapsulated Stand-Alone Libraries are supported. Only +authorized case-insensitive values are "true" and "false" (the default). + +@item +@strong{Library_Auto_Init}: single + +Indicates if a Stand-Alone Library is auto-initialized. Only authorized +case-insentive values are "true" and "false". + +@item +@strong{Leading_Library_Options}: list + +Value is a list of options that are to be used at the beginning of +the command line when linking a shared library. + +@item +@strong{Library_Options}: list + +Value is a list of options that are to be used when linking a shared library. + +@item +@strong{Library_Rpath_Options}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of options for an invocation of the +compiler of the language. This invocation is done for a shared library project +with sources of the language. The output of the invocation is the path name +of a shared library file. The directory name is to be put in the run path +option switch when linking the shared library for the project. + +@item +@strong{Library_Src_Dir}: single + +Value is the name of the directory where copies of the sources of the +interfaces of a Stand-Alone Library are to be copied. + +@item +@strong{Library_ALI_Dir}: single + +Value is the name of the directory where the ALI files of the interfaces +of a Stand-Alone Library are to be copied. When this attribute is not declared, +the directory is the library directory. + +@item +@strong{Library_gcc}: single + +Obsolescent attribute. Specify the linker driver used to link a shared library. +Use instead attribute Linker'Driver. + +@item +@strong{Library_Symbol_File}: single + +Value is the name of the library symbol file. + +@item +@strong{Library_Symbol_Policy}: single + +Indicates the symbol policy kind. Only authorized case-insensitive values are +"autonomous", "default", "compliant", "controlled" or "direct". + +@item +@strong{Library_Reference_Symbol_File}: single + +Value is the name of the reference symbol file. +@end itemize + +@item +@strong{Configuration - General} + + +@itemize * + +@item +@strong{Default_Language}: single + +Value is the case-insensitive name of the language of a project when attribute +Languages is not specified. + +@item +@strong{Run_Path_Option}: list + +Value is the list of switches to be used when specifying the run path option +in an executable. + +@item +@strong{Run_Path_Origin}: single + +Value is the the string that may replace the path name of the executable +directory in the run path options. + +@item +@strong{Separate_Run_Path_Options}: single + +Indicates if there may be several run path options specified when linking an +executable. Only authorized case-insensitive values are "true" or "false" (the +default). + +@item +@strong{Toolchain_Version}: single, indexed, case-insensitive index + +Index is a language name. Specify the version of a toolchain for a language. + +@item +@strong{Toolchain_Description}: single, indexed, case-insensitive index + +Obsolescent. No longer used. + +@item +@strong{Object_Generated}: single, indexed, case-insensitive index + +Index is a language name. Indicates if invoking the compiler for a language +produces an object file. Only authorized case-insensitive values are "false" +and "true" (the default). + +@item +@strong{Objects_Linked}: single, indexed, case-insensitive index + +Index is a language name. Indicates if the object files created by the compiler +for a language need to be linked in the executable. Only authorized +case-insensitive values are "false" and "true" (the default). + +@item +@strong{Target}: single + +Value is the name of the target platform. Taken into account only in the main +project. + +@item +@strong{Runtime}: single, indexed, case-insensitive index + +Index is a language name. Indicates the runtime directory that is to be used +when using the compiler of the language. Taken into account only in the main +project. +@end itemize + +@item +@strong{Configuration - Libraries} + + +@itemize * + +@item +@strong{Library_Builder}: single + +Value is the path name of the application that is to be used to build +libraries. Usually the path name of "gprlib". + +@item +@strong{Library_Support}: single + +Indicates the level of support of libraries. Only authorized case-insensitive +values are "static_only", "full" or "none" (the default). +@end itemize + +@item +@strong{Configuration - Archives} + + +@itemize * + +@item +@strong{Archive_Builder}: list + +Value is the name of the application to be used to create a static library +(archive), followed by the options to be used. + +@item +@strong{Archive_Builder_Append_Option}: list + +Value is the list of options to be used when invoking the archive builder +to add project files into an archive. + +@item +@strong{Archive_Indexer}: list + +Value is the name of the archive indexer, followed by the required options. + +@item +@strong{Archive_Suffix}: single + +Value is the extension of archives. When not declared, the extension is ".a". + +@item +@strong{Library_Partial_Linker}: list + +Value is the name of the partial linker executable, followed by the required +options. +@end itemize + +@item +@strong{Configuration - Shared Libraries} + + +@itemize * + +@item +@strong{Shared_Library_Prefix}: single + +Value is the prefix in the name of shared library files. When not declared, +the prefix is "lib". + +@item +@strong{Shared_Library_Suffix}: single + +Value is the the extension of the name of shared library files. When not +declared, the extension is ".so". + +@item +@strong{Symbolic_Link_Supported}: single + +Indicates if symbolic links are supported on the platform. Only authorized +case-insensitive values are "true" and "false" (the default). + +@item +@strong{Library_Major_Minor_Id_Supported}: single + +Indicates if major and minor ids for shared library names are supported on +the platform. Only authorized case-insensitive values are "true" and "false" +(the default). + +@item +@strong{Library_Auto_Init_Supported}: single + +Indicates if auto-initialization of Stand-Alone Libraries is supported. Only +authorized case-insensitive values are "true" and "false" (the default). + +@item +@strong{Shared_Library_Minimum_Switches}: list + +Value is the list of required switches when linking a shared library. + +@item +@strong{Library_Version_Switches}: list + +Value is the list of switches to specify a internal name for a shared library. + +@item +@strong{Library_Install_Name_Option}: single + +Value is the name of the option that needs to be used, concatenated with the +path name of the library file, when linking a shared library. + +@item +@strong{Runtime_Library_Dir}: single, indexed, case-insensitive index + +Index is a language name. Value is the path name of the directory where the +runtime libraries are located. + +@item +@strong{Runtime_Source_Dir}: single, indexed, case-insensitive index + +Index is a language name. Value is the path name of the directory where the +sources of runtime libraries are located. +@end itemize +@end itemize + +@node Package Binder Attributes,Package Builder Attributes,Project Level Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-binder-attributes}@anchor{1a6}@anchor{gnat_ugn/gnat_project_manager id49}@anchor{1a7} +@subsubsection Package Binder Attributes + + + +@itemize * + +@item +@strong{General} + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used when binding +code of the language, if there is no applicable attribute Switches. + +@item +@strong{Switches}: list, optional index, indexed, +case-insensitive index, others allowed + +Index is either a language name or a source file name. Value is the list of +switches to be used when binding code. Index is either the source file name +of the executable to be bound or the language name of the code to be bound. +@end itemize + +@item +@strong{Configuration - Binding} + + +@itemize * + +@item +@strong{Driver}: single, indexed, case-insensitive index + +Index is a language name. Value is the name of the application to be used when +binding code of the language. + +@item +@strong{Required_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of the required switches to be +used when binding code of the language. + +@item +@strong{Prefix}: single, indexed, case-insensitive index + +Index is a language name. Value is a prefix to be used for the binder exchange +file name for the language. Used to have different binder exchange file names +when binding different languages. + +@item +@strong{Objects_Path}: single,indexed, case-insensitive index + +Index is a language name. Value is the name of the environment variable that +contains the path for the object directories. + +@item +@strong{Object_Path_File}: single,indexed, case-insensitive index + +Index is a language name. Value is the name of the environment variable. The +value of the environment variable is the path name of a text file that +contains the list of object directories. +@end itemize +@end itemize + +@node Package Builder Attributes,Package Clean Attributes,Package Binder Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-builder-attributes}@anchor{1a8}@anchor{gnat_ugn/gnat_project_manager id50}@anchor{1a9} +@subsubsection Package Builder Attributes + + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of builder switches to be used when +building an executable of the language, if there is no applicable attribute +Switches. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is either a language name or a source file name. Value is the list of +builder switches to be used when building an executable. Index is either the +source file name of the executable to be built or its language name. + +@item +@strong{Global_Compilation_Switches}: list, optional index, indexed, +case-insensitive index + +Index is either a language name or a source file name. Value is the list of +compilation switches to be used when building an executable. Index is either +the source file name of the executable to be built or its language name. + +@item +@strong{Executable}: single, indexed, case-insensitive index + +Index is an executable source file name. Value is the simple file name of the +executable to be built. + +@item +@strong{Executable_Suffix}: single + +Value is the extension of the file names of executable. When not specified, +the extension is the default extension of executables on the platform. + +@item +@strong{Global_Configuration_Pragmas}: single + +Value is the file name of a configuration pragmas file that is specified to +the Ada compiler when compiling any Ada source in the project tree. + +@item +@strong{Global_Config_File}: single, indexed, case-insensitive index + +Index is a language name. Value is the file name of a configuration file that +is specified to the compiler when compiling any source of the language in the +project tree. +@end itemize + + +@node Package Clean Attributes,Package Compiler Attributes,Package Builder Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-clean-attributes}@anchor{1aa}@anchor{gnat_ugn/gnat_project_manager id52}@anchor{1ab} +@subsubsection Package Clean Attributes + + + +@itemize * + +@item +@strong{Switches}: list + +Value is a list of switches to be used by the cleaning application. + +@item +@strong{Source_Artifact_Extensions}: list, indexed, case-insensitive index + +Index is a language names. Value is the list of extensions for file names +derived from object file names that need to be cleaned in the object +directory of the project. + +@item +@strong{Object_Artifact_Extensions}: list, indexed, case-insensitive index + +Index is a language names. Value is the list of extensions for file names +derived from source file names that need to be cleaned in the object +directory of the project. + +@item +@strong{Artifacts_In_Object_Dir}: single + +Value is a list of file names expressed as regular expressions that are to be +deleted by gprclean in the object directory of the project. + +@item +@strong{Artifacts_In_Exec_Dir}: single + +Value is list of file names expressed as regular expressions that are to be +deleted by gprclean in the exec directory of the main project. +@end itemize + +@node Package Compiler Attributes,Package Cross_Reference Attributes,Package Clean Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id53}@anchor{1ac}@anchor{gnat_ugn/gnat_project_manager package-compiler-attributes}@anchor{1ad} +@subsubsection Package Compiler Attributes + + + +@itemize * + +@item +@strong{General} + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of switches to be used when invoking +the compiler for the language for a source of the project, if there is no +applicable attribute Switches. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is a source file name or a language name. Value is the list of switches +to be used when invoking the compiler for the source or for its language. + +@item +@strong{Local_Configuration_Pragmas}: single + +Value is the file name of a configuration pragmas file that is specified to +the Ada compiler when compiling any Ada source in the project. + +@item +@strong{Local_Config_File}: single, indexed, case-insensitive index + +Index is a language name. Value is the file name of a configuration file that +is specified to the compiler when compiling any source of the language in the +project. +@end itemize + +@item +@strong{Configuration - Compiling} + + +@itemize * + +@item +@strong{Driver}: single, indexed, case-insensitive index + +Index is a language name. Value is the name of the executable for the compiler +of the language. + +@item +@strong{Language_Kind}: single, indexed, case-insensitive index + +Index is a language name. Indicates the kind of the language, either file based +or unit based. Only authorized case-insensitive values are "unit_based" and +"file_based" (the default). + +@item +@strong{Dependency_Kind}: single, indexed, case-insensitive index + +Index is a language name. Indicates how the dependencies are handled for the +language. Only authorized case-insensitive values are "makefile", "ali_file", +"ali_closure" or "none" (the default). + +@item +@strong{Required_Switches}: list, indexed, case-insensitive index + +Equivalent to attribute Leading_Required_Switches. + +@item +@strong{Leading_Required_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of the minimum switches to be used +at the beginning of the command line when invoking the compiler for the +language. + +@item +@strong{Trailing_Required_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of the minimum switches to be used +at the end of the command line when invoking the compiler for the language. + +@item +@strong{PIC_Option}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used when +compiling a source of the language when the project is a shared library +project. + +@item +@strong{Path_Syntax}: single, indexed, case-insensitive index + +Index is a language name. Value is the kind of path syntax to be used when +invoking the compiler for the language. Only authorized case-insensitive +values are "canonical" and "host" (the default). + +@item +@strong{Source_File_Switches}: single, indexed, case-insensitive index + +Index is a language name. Value is a list of switches to be used just before +the path name of the source to compile when invoking the compiler for a source +of the language. + +@item +@strong{Object_File_Suffix}: single, indexed, case-insensitive index + +Index is a language name. Value is the extension of the object files created +by the compiler of the language. When not specified, the extension is the +default one for the platform. + +@item +@strong{Object_File_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used by the +compiler of the language to specify the path name of the object file. When not +specified, the switch used is "-o". + +@item +@strong{Multi_Unit_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used to compile +a unit in a multi unit source of the language. The index of the unit in the +source is concatenated with the last switches in the list. + +@item +@strong{Multi_Unit_Object_Separator}: single, indexed, case-insensitive index + +Index is a language name. Value is the string to be used in the object file +name before the index of the unit, when compiling a unit in a multi unit source +of the language. +@end itemize + +@item +@strong{Configuration - Mapping Files} + + +@itemize * + +@item +@strong{Mapping_File_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used to specify +a mapping file when invoking the compiler for a source of the language. + +@item +@strong{Mapping_Spec_Suffix}: single, indexed, case-insensitive index + +Index is a language name. Value is the suffix to be used in a mapping file +to indicate that the source is a spec. + +@item +@strong{Mapping_Body_Suffix}: single, indexed, case-insensitive index + +Index is a language name. Value is the suffix to be used in a mapping file +to indicate that the source is a body. +@end itemize + +@item +@strong{Configuration - Config Files} + + +@itemize * + +@item +@strong{Config_File_Switches}: list: single, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to specify to the +compiler of the language a configuration file. + +@item +@strong{Config_Body_File_Name}: single, indexed, case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration specific to a body of the language in a configuration +file. + +@item +@strong{Config_Body_File_Name_Index}: single, indexed, case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration specific to the body a unit in a multi unit source of the +language in a configuration file. + +@item +@strong{Config_Body_File_Name_Pattern}: single, indexed, +case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration for all bodies of the languages in a configuration file. + +@item +@strong{Config_Spec_File_Name}: single, indexed, case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration specific to a spec of the language in a configuration +file. + +@item +@strong{Config_Spec_File_Name_Index}: single, indexed, case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration specific to the spec a unit in a multi unit source of the +language in a configuration file. + +@item +@strong{Config_Spec_File_Name_Pattern}: single, indexed, +case-insensitive index + +Index is a language name. Value is the template to be used to indicate a +configuration for all specs of the languages in a configuration file. + +@item +@strong{Config_File_Unique}: single, indexed, case-insensitive index + +Index is a language name. Indicates if there should be only one configuration +file specified to the compiler of the language. Only authorized +case-insensitive values are "true" and "false" (the default). +@end itemize + +@item +@strong{Configuration - Dependencies} + + +@itemize * + +@item +@strong{Dependency_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to be used to specify +to the compiler the dependency file when the dependency kind of the language is +file based, and when Dependency_Driver is not specified for the language. + +@item +@strong{Dependency_Driver}: list, indexed, case-insensitive index + +Index is a language name. Value is the name of the executable to be used to +create the dependency file for a source of the language, followed by the +required switches. +@end itemize + +@item +@strong{Configuration - Search Paths} + + +@itemize * + +@item +@strong{Include_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to specify to the +compiler of the language to indicate a directory to look for sources. + +@item +@strong{Include_Path}: single, indexed, case-insensitive index + +Index is a language name. Value is the name of an environment variable that +contains the path of all the directories that the compiler of the language +may search for sources. + +@item +@strong{Include_Path_File}: single, indexed, case-insensitive index + +Index is a language name. Value is the name of an environment variable the +value of which is the path name of a text file that contains the directories +that the compiler of the language may search for sources. + +@item +@strong{Object_Path_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is the list of switches to specify to the +compiler of the language the name of a text file that contains the list of +object directories. When this attribute is not declared, the text file is +not created. +@end itemize +@end itemize + +@node Package Cross_Reference Attributes,Package Finder Attributes,Package Compiler Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id54}@anchor{1ae}@anchor{gnat_ugn/gnat_project_manager package-cross-reference-attributes}@anchor{1af} +@subsubsection Package Cross_Reference Attributes + + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of switches to be used when invoking +@cite{gnatxref} for a source of the language, if there is no applicable +attribute Switches. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is a source file name. Value is the list of switches to be used when +invoking @cite{gnatxref} for the source. +@end itemize + + +@node Package Finder Attributes,Package gnatls Attributes,Package Cross_Reference Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id56}@anchor{1b0}@anchor{gnat_ugn/gnat_project_manager package-finder-attributes}@anchor{1b1} +@subsubsection Package Finder Attributes + + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of switches to be used when invoking +@cite{gnatfind} for a source of the language, if there is no applicable +attribute Switches. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is a source file name. Value is the list of switches to be used when +invoking @cite{gnatfind} for the source. +@end itemize + +@node Package gnatls Attributes,Package IDE Attributes,Package Finder Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-gnatls-attributes}@anchor{1b2}@anchor{gnat_ugn/gnat_project_manager id57}@anchor{1b3} +@subsubsection Package gnatls Attributes + + + +@itemize * + +@item +@strong{Switches}: list + +Value is a list of switches to be used when invoking @cite{gnatls}. +@end itemize + + +@node Package IDE Attributes,Package Install Attributes,Package gnatls Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id58}@anchor{1b4}@anchor{gnat_ugn/gnat_project_manager package-ide-attributes}@anchor{1b5} +@subsubsection Package IDE Attributes + + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed + +Index is the name of an external tool that the GNAT Programming System (GPS) +is supporting. Value is a list of switches to use when invoking that tool. + +@item +@strong{Remote_Host}: single + +Value is a string that designates the remote host in a cross-compilation +environment, to be used for remote compilation and debugging. This attribute +should not be specified when running on the local machine. + +@item +@strong{Program_Host}: single + +Value is a string that specifies the name of IP address of the embedded target +in a cross-compilation environment, on which the program should execute. + +@item +@strong{Communication_Protocol}: single + +Value is the name of the protocol to use to communicate with the target +in a cross-compilation environment, for example @cite{"wtx"} or +@cite{"vxworks"}. + +@item +@strong{Compiler_Command}: single, indexed, case-insensitive index + +Index is a language Name. Value is a string that denotes the command to be +used to invoke the compiler. The value of @cite{Compiler_Command ("Ada")} is +expected to be compatible with @emph{gnatmake}, in particular in +the handling of switches. + +@item +@strong{Debugger_Command}: single + +Value is a string that specifies the name of the debugger to be used, such as +gdb, powerpc-wrs-vxworks-gdb or gdb-4. + +@item +@strong{gnatlist}: single + +Value is a string that specifies the name of the @emph{gnatls} utility +to be used to retrieve information about the predefined path; for example, +@cite{"gnatls"}, @cite{"powerpc-wrs-vxworks-gnatls"}. + +@item +@strong{VCS_Kind}: single + +Value is a string used to specify the Version Control System (VCS) to be used +for this project, for example "Subversion", "ClearCase". If the +value is set to "Auto", the IDE will try to detect the actual VCS used +on the list of supported ones. + +@item +@strong{VCS_File_Check}: single + +Value is a string that specifies the command used by the VCS to check +the validity of a file, either when the user explicitly asks for a check, +or as a sanity check before doing the check-in. + +@item +@strong{VCS_Log_Check}: single + +Value is a string that specifies the command used by the VCS to check +the validity of a log file. + +@item +@strong{Documentation_Dir}: single + +Value is the directory used to generate the documentation of source code. +@end itemize + +@node Package Install Attributes,Package Linker Attributes,Package IDE Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-install-attributes}@anchor{1b6}@anchor{gnat_ugn/gnat_project_manager id59}@anchor{1b7} +@subsubsection Package Install Attributes + + + +@itemize * + +@item +@strong{Artifacts}: list, indexed + +An array attribute to declare a set of files not part of the sources +to be installed. The array discriminant is the directory where the +file is to be installed. If a relative directory then Prefix (see +below) is prepended. + +@item +@strong{Prefix}: single + +Value is the install destination directory. + +@item +@strong{Sources_Subdir}: single + +Value is the sources directory or subdirectory of Prefix. + +@item +@strong{Exec_Subdir}: single + +Value is the executables directory or subdirectory of Prefix. + +@item +@strong{Lib_Subdir}: single + +Value is library directory or subdirectory of Prefix. + +@item +@strong{Project_Subdir}: single + +Value is the project directory or subdirectory of Prefix. + +@item +@strong{Active}: single + +Indicates that the project is to be installed or not. Case-insensitive value +"false" means that the project is not to be installed, all other values mean +that the project is to be installed. + +@item +@strong{Mode}: single + +Value is the installation mode, it is either @strong{dev} (default) or @strong{usage}. + +@item +@strong{Install_Name}: single + +Specify the name to use for recording the installation. The default is +the project name without the extension. +@end itemize + +@node Package Linker Attributes,Package Naming Attributes,Package Install Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id60}@anchor{1b8}@anchor{gnat_ugn/gnat_project_manager package-linker-attributes}@anchor{1b9} +@subsubsection Package Linker Attributes + + + +@itemize * + +@item +@strong{General} + + +@itemize * + +@item +@strong{Required_Switches}: list + +Value is a list of switches that are required when invoking the linker to link +an executable. + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of switches for the linker when +linking an executable for a main source of the language, when there is no +applicable Switches. + +@item +@strong{Leading_Switches}: list, optional index, indexed, +case-insensitive index, others allowed + +Index is a source file name or a language name. Value is the list of switches +to be used at the beginning of the command line when invoking the linker to +build an executable for the source or for its language. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is a source file name or a language name. Value is the list of switches +to be used when invoking the linker to build an executable for the source or +for its language. + +@item +@strong{Trailing_Switches}: list, optional index, indexed, +case-insensitive index, others allowed + +Index is a source file name or a language name. Value is the list of switches +to be used at the end of the command line when invoking the linker to +build an executable for the source or for its language. These switches may +override the Required_Switches. + +@item +@strong{Linker_Options}: list + +Value is a list of switches/options that are to be added when linking an +executable from a project importing the current project directly or indirectly. +Linker_Options are not used when linking an executable from the current +project. + +@item +@strong{Map_File_Option}: single + +Value is the switch to specify the map file name that the linker needs to +create. +@end itemize + +@item +@strong{Configuration - Linking} + + +@itemize * + +@item +@strong{Driver}: single + +Value is the name of the linker executable. +@end itemize + +@item +@strong{Configuration - Response Files} + + +@itemize * + +@item +@strong{Max_Command_Line_Length}: single + +Value is the maximum number of character in the command line when invoking +the linker to link an executable. + +@item +@strong{Response_File_Format}: single + +Indicates the kind of response file to create when the length of the linking +command line is too large. Only authorized case-insensitive values are "none", +"gnu", "object_list", "gcc_gnu", "gcc_option_list" and "gcc_object_list". + +@item +@strong{Response_File_Switches}: list + +Value is the list of switches to specify a response file to the linker. +@end itemize +@end itemize + +@c only PRO or GPL +@c +@c .. _Package_Metrics_Attribute: +@c +@c Package Metrics Attribute +@c ^^^^^^^^^^^^^^^^^^^^^^^^^ +@c +@c * **Default_Switches**: list, indexed, case-insensitive index +@c +@c Index is a language name. Value is a list of switches to be used when invoking +@c `gnatmetric` for a source of the language, if there is no applicable +@c attribute Switches. +@c +@c * **Switches**: list, optional index, indexed, case-insensitive index, +@c others allowed +@c +@c Index is a source file name. Value is the list of switches to be used when +@c invoking `gnatmetric` for the source. + +@node Package Naming Attributes,Package Remote Attributes,Package Linker Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-naming-attributes}@anchor{1ba}@anchor{gnat_ugn/gnat_project_manager id61}@anchor{1bb} +@subsubsection Package Naming Attributes + + + +@itemize * + +@item +@strong{Specification_Suffix}: single, indexed, case-insensitive index + +Equivalent to attribute Spec_Suffix. + +@item +@strong{Spec_Suffix}: single, indexed, case-insensitive index + +Index is a language name. Value is the extension of file names for specs of +the language. + +@item +@strong{Implementation_Suffix}: single, indexed, case-insensitive index + +Equivalent to attribute Body_Suffix. + +@item +@strong{Body_Suffix}: single, indexed, case-insensitive index + +Index is a language name. Value is the extension of file names for bodies of +the language. + +@item +@strong{Separate_Suffix}: single + +Value is the extension of file names for subunits of Ada. + +@item +@strong{Casing}: single + +Indicates the casing of sources of the Ada language. Only authorized +case-insensitive values are "lowercase", "uppercase" and "mixedcase". + +@item +@strong{Dot_Replacement}: single + +Value is the string that replace the dot of unit names in the source file names +of the Ada language. + +@item +@strong{Specification}: single, optional index, indexed, +case-insensitive index + +Equivalent to attribute Spec. + +@item +@strong{Spec}: single, optional index, indexed, case-insensitive index + +Index is a unit name. Value is the file name of the spec of the unit. + +@item +@strong{Implementation}: single, optional index, indexed, +case-insensitive index + +Equivalent to attribute Body. + +@item +@strong{Body}: single, optional index, indexed, case-insensitive index + +Index is a unit name. Value is the file name of the body of the unit. + +@item +@strong{Specification_Exceptions}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of specs for the language that do not +necessarily follow the naming scheme for the language and that may or may not +be found in the source directories of the project. + +@item +@strong{Implementation_Exceptions}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of bodies for the language that do not +necessarily follow the naming scheme for the language and that may or may not +be found in the source directories of the project. +@end itemize + + +@node Package Remote Attributes,Package Stack Attributes,Package Naming Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-remote-attributes}@anchor{1bc}@anchor{gnat_ugn/gnat_project_manager id63}@anchor{1bd} +@subsubsection Package Remote Attributes + + + +@itemize * + +@item +@strong{Included_Patterns}: list + +If this attribute is defined it sets the patterns to +synchronized from the master to the slaves. It is exclusive +with Excluded_Patterns, that is it is an error to define +both. + +@item +@strong{Included_Artifact_Patterns}: list + +If this attribute is defined it sets the patterns of compilation +artifacts to synchronized from the slaves to the build master. +This attribute replace the default hard-coded patterns. + +@item +@strong{Excluded_Patterns}: list + +Set of patterns to ignore when synchronizing sources from the build +master to the slaves. A set of predefined patterns are supported +(e.g. *.o, *.ali, *.exe, etc.), this attributes make it possible to +add some more patterns. + +@item +@strong{Root_Dir}: single + +Value is the root directory used by the slave machines. +@end itemize + +@node Package Stack Attributes,Package Synchronize Attributes,Package Remote Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager id64}@anchor{1be}@anchor{gnat_ugn/gnat_project_manager package-stack-attributes}@anchor{1bf} +@subsubsection Package Stack Attributes + + + +@itemize * + +@item +@strong{Switches}: list + +Value is the list of switches to be used when invoking @cite{gnatstack}. +@end itemize + +@node Package Synchronize Attributes,,Package Stack Attributes,Attributes +@anchor{gnat_ugn/gnat_project_manager package-synchronize-attributes}@anchor{1c0} +@subsubsection Package Synchronize Attributes + + + +@itemize * + +@item +@strong{Default_Switches}: list, indexed, case-insensitive index + +Index is a language name. Value is a list of switches to be used when invoking +@cite{gnatsync} for a source of the language, if there is no applicable +attribute Switches. + +@item +@strong{Switches}: list, optional index, indexed, case-insensitive index, +others allowed + +Index is a source file name. Value is the list of switches to be used when +invoking @cite{gnatsync} for the source. +@end itemize + +@node Tools Supporting Project Files,GNAT Utility Programs,GNAT Project Manager,Top +@anchor{gnat_ugn/tools_supporting_project_files doc}@anchor{1c1}@anchor{gnat_ugn/tools_supporting_project_files tools-supporting-project-files}@anchor{c}@anchor{gnat_ugn/tools_supporting_project_files id1}@anchor{1c2} +@chapter Tools Supporting Project Files + + +This section describes how project files can be used in conjunction with a number of +GNAT tools. + +@menu +* gnatmake and Project Files:: +* The GNAT Driver and Project Files:: + +@end menu + +@node gnatmake and Project Files,The GNAT Driver and Project Files,,Tools Supporting Project Files +@anchor{gnat_ugn/tools_supporting_project_files id2}@anchor{1c3}@anchor{gnat_ugn/tools_supporting_project_files gnatmake-and-project-files}@anchor{e1} +@section gnatmake and Project Files + + +This section covers several topics related to @emph{gnatmake} and +project files: defining switches for @emph{gnatmake} +and for the tools that it invokes; specifying configuration pragmas; +the use of the @cite{Main} attribute; building and rebuilding library project +files. + +@menu +* Switches Related to Project Files:: +* Switches and Project Files:: +* Specifying Configuration Pragmas:: +* Project Files and Main Subprograms:: +* Library Project Files:: + +@end menu + +@node Switches Related to Project Files,Switches and Project Files,,gnatmake and Project Files +@anchor{gnat_ugn/tools_supporting_project_files switches-related-to-project-files}@anchor{e3}@anchor{gnat_ugn/tools_supporting_project_files id3}@anchor{1c4} +@subsection Switches Related to Project Files + + +The following switches are used by GNAT tools that support project files: + +@quotation + +@geindex -P (any project-aware tool) +@end quotation + + +@table @asis + +@item @code{-P@emph{project}} + +Indicates the name of a project file. This project file will be parsed with +the verbosity indicated by @emph{-vP*x*}, +if any, and using the external references indicated +by @emph{-X} switches, if any. +There may zero, one or more spaces between @emph{-P} and @cite{project}. + +There must be only one @emph{-P} switch on the command line. + +Since the Project Manager parses the project file only after all the switches +on the command line are checked, the order of the switches +@emph{-P}, +@emph{-vP*x*} +or @emph{-X} is not significant. + +@geindex -X (any project-aware tool) + +@item @code{-X@emph{name}=@emph{value}} + +Indicates that external variable @cite{name} has the value @cite{value}. +The Project Manager will use this value for occurrences of +@cite{external(name)} when parsing the project file. + +If @cite{name} or @cite{value} includes a space, then @cite{name=value} should be +put between quotes. + +@example +-XOS=NT +-X"user=John Doe" +@end example + +Several @emph{-X} switches can be used simultaneously. +If several @emph{-X} switches specify the same +@cite{name}, only the last one is used. + +An external variable specified with a @emph{-X} switch +takes precedence over the value of the same name in the environment. + +@geindex -vP (any project-aware tool) + +@item @code{-vP@emph{x}} + +Indicates the verbosity of the parsing of GNAT project files. + +@emph{-vP0} means Default; +@emph{-vP1} means Medium; +@emph{-vP2} means High. + +The default is Default: no output for syntactically correct +project files. +If several @emph{-vP*x*} switches are present, +only the last one is used. + +@geindex -aP (any project-aware tool) + +@item @code{-aP@emph{dir}} + +Add directory @cite{dir} at the beginning of the project search path, in order, +after the current working directory. + +@geindex -eL (any project-aware tool) + +@item @code{-eL} + +Follow all symbolic links when processing project files. + +@geindex --subdirs= (gnatmake and gnatclean) + +@item @code{--subdirs=@emph{subdir}} + +This switch is recognized by @emph{gnatmake} and @emph{gnatclean}. It +indicate that the real directories (except the source directories) are the +subdirectories @cite{subdir} of the directories specified in the project files. +This applies in particular to object directories, library directories and +exec directories. If the subdirectories do not exist, they are created +automatically. +@end table + +@node Switches and Project Files,Specifying Configuration Pragmas,Switches Related to Project Files,gnatmake and Project Files +@anchor{gnat_ugn/tools_supporting_project_files id4}@anchor{1c5}@anchor{gnat_ugn/tools_supporting_project_files switches-and-project-files}@anchor{1c6} +@subsection Switches and Project Files + + +For each of the packages @cite{Builder}, @cite{Compiler}, @cite{Binder}, and +@cite{Linker}, you can specify a @cite{Default_Switches} +attribute, a @cite{Switches} attribute, or both; +as their names imply, these switch-related +attributes affect the switches that are used for each of these GNAT +components when +@emph{gnatmake} is invoked. As will be explained below, these +component-specific switches precede +the switches provided on the @emph{gnatmake} command line. + +The @cite{Default_Switches} attribute is an attribute +indexed by language name (case insensitive) whose value is a string list. +For example: + +@quotation + +@example +package Compiler is + for Default_Switches ("Ada") + use ("-gnaty", + "-v"); +end Compiler; +@end example +@end quotation + +The @cite{Switches} attribute is indexed on a file name (which may or may +not be case sensitive, depending +on the operating system) whose value is a string list. For example: + +@quotation + +@example +package Builder is + for Switches ("main1.adb") + use ("-O2"); + for Switches ("main2.adb") + use ("-g"); +end Builder; +@end example +@end quotation + +For the @cite{Builder} package, the file names must designate source files +for main subprograms. For the @cite{Binder} and @cite{Linker} packages, the +file names must designate @code{ALI} or source files for main subprograms. +In each case just the file name without an explicit extension is acceptable. + +For each tool used in a program build (@emph{gnatmake}, the compiler, the +binder, and the linker), the corresponding package @@dfn@{contributes@} a set of +switches for each file on which the tool is invoked, based on the +switch-related attributes defined in the package. +In particular, the switches +that each of these packages contributes for a given file @cite{f} comprise: + + +@itemize * + +@item +the value of attribute @cite{Switches (`f})`, +if it is specified in the package for the given file, + +@item +otherwise, the value of @cite{Default_Switches ("Ada")}, +if it is specified in the package. +@end itemize + +If neither of these attributes is defined in the package, then the package does +not contribute any switches for the given file. + +When @emph{gnatmake} is invoked on a file, the switches comprise +two sets, in the following order: those contributed for the file +by the @cite{Builder} package; +and the switches passed on the command line. + +When @emph{gnatmake} invokes a tool (compiler, binder, linker) on a file, +the switches passed to the tool comprise three sets, +in the following order: + + +@itemize * + +@item +the applicable switches contributed for the file +by the @cite{Builder} package in the project file supplied on the command line; + +@item +those contributed for the file by the package (in the relevant project file -- +see below) corresponding to the tool; and + +@item +the applicable switches passed on the command line. +@end itemize + +The term @emph{applicable switches} reflects the fact that +@emph{gnatmake} switches may or may not be passed to individual +tools, depending on the individual switch. + +@emph{gnatmake} may invoke the compiler on source files from different +projects. The Project Manager will use the appropriate project file to +determine the @cite{Compiler} package for each source file being compiled. +Likewise for the @cite{Binder} and @cite{Linker} packages. + +As an example, consider the following package in a project file: + +@quotation + +@example +project Proj1 is + package Compiler is + for Default_Switches ("Ada") + use ("-g"); + for Switches ("a.adb") + use ("-O1"); + for Switches ("b.adb") + use ("-O2", + "-gnaty"); + end Compiler; +end Proj1; +@end example +@end quotation + +If @emph{gnatmake} is invoked with this project file, and it needs to +compile, say, the files @code{a.adb}, @code{b.adb}, and @code{c.adb}, then +@code{a.adb} will be compiled with the switch @emph{-O1}, +@code{b.adb} with switches @emph{-O2} and @emph{-gnaty}, +and @code{c.adb} with @emph{-g}. + +The following example illustrates the ordering of the switches +contributed by different packages: + +@quotation + +@example +project Proj2 is + package Builder is + for Switches ("main.adb") + use ("-g", + "-O1", + "-f"); + end Builder; + + package Compiler is + for Switches ("main.adb") + use ("-O2"); + end Compiler; +end Proj2; +@end example +@end quotation + +If you issue the command: + +@quotation + +@example +$ gnatmake -Pproj2 -O0 main +@end example +@end quotation + +then the compiler will be invoked on @code{main.adb} with the following +sequence of switches + +@quotation + +@example +-g -O1 -O2 -O0 +@end example +@end quotation + +with the last @emph{-O} +switch having precedence over the earlier ones; +several other switches +(such as @emph{-c}) are added implicitly. + +The switches @emph{-g} +and @emph{-O1} are contributed by package +@cite{Builder}, @emph{-O2} is contributed +by the package @cite{Compiler} +and @emph{-O0} comes from the command line. + +The @emph{-g} switch will also be passed in the invocation of +@emph{Gnatlink.} + +A final example illustrates switch contributions from packages in different +project files: + +@quotation + +@example +project Proj3 is + for Source_Files use ("pack.ads", "pack.adb"); + package Compiler is + for Default_Switches ("Ada") + use ("-gnata"); + end Compiler; +end Proj3; + +with "Proj3"; +project Proj4 is + for Source_Files use ("foo_main.adb", "bar_main.adb"); + package Builder is + for Switches ("foo_main.adb") + use ("-s", + "-g"); + end Builder; +end Proj4; +@end example + +@example +-- Ada source file: +with Pack; +procedure Foo_Main is + ... +end Foo_Main; +@end example +@end quotation + +If the command is + +@quotation + +@example +$ gnatmake -PProj4 foo_main.adb -cargs -gnato +@end example +@end quotation + +then the switches passed to the compiler for @code{foo_main.adb} are +@emph{-g} (contributed by the package @cite{Proj4.Builder}) and +@emph{-gnato} (passed on the command line). +When the imported package @cite{Pack} is compiled, the switches used +are @emph{-g} from @cite{Proj4.Builder}, +@emph{-gnata} (contributed from package @cite{Proj3.Compiler}, +and @emph{-gnato} from the command line. + +When using @emph{gnatmake} with project files, some switches or +arguments may be expressed as relative paths. As the working directory where +compilation occurs may change, these relative paths are converted to absolute +paths. For the switches found in a project file, the relative paths +are relative to the project file directory, for the switches on the command +line, they are relative to the directory where @emph{gnatmake} is invoked. +The switches for which this occurs are: +-I, +-A, +-L, +-aO, +-aL, +-aI, as well as all arguments that are not switches (arguments to +switch +-o, object files specified in package @cite{Linker} or after +-largs on the command line). The exception to this rule is the switch +--RTS= for which a relative path argument is never converted. + +@node Specifying Configuration Pragmas,Project Files and Main Subprograms,Switches and Project Files,gnatmake and Project Files +@anchor{gnat_ugn/tools_supporting_project_files id5}@anchor{1c7}@anchor{gnat_ugn/tools_supporting_project_files specifying-configuration-pragmas}@anchor{7d} +@subsection Specifying Configuration Pragmas + + +When using @emph{gnatmake} with project files, if there exists a file +@code{gnat.adc} that contains configuration pragmas, this file will be +ignored. + +Configuration pragmas can be defined by means of the following attributes in +project files: @cite{Global_Configuration_Pragmas} in package @cite{Builder} +and @cite{Local_Configuration_Pragmas} in package @cite{Compiler}. + +Both these attributes are single string attributes. Their values is the path +name of a file containing configuration pragmas. If a path name is relative, +then it is relative to the project directory of the project file where the +attribute is defined. + +When compiling a source, the configuration pragmas used are, in order, +those listed in the file designated by attribute +@cite{Global_Configuration_Pragmas} in package @cite{Builder} of the main +project file, if it is specified, and those listed in the file designated by +attribute @cite{Local_Configuration_Pragmas} in package @cite{Compiler} of +the project file of the source, if it exists. + +@node Project Files and Main Subprograms,Library Project Files,Specifying Configuration Pragmas,gnatmake and Project Files +@anchor{gnat_ugn/tools_supporting_project_files id6}@anchor{1c8}@anchor{gnat_ugn/tools_supporting_project_files project-files-and-main-subprograms}@anchor{e2} +@subsection Project Files and Main Subprograms + + +When using a project file, you can invoke @emph{gnatmake} +with one or several main subprograms, by specifying their source files on the +command line. + +@quotation + +@example +$ gnatmake -Pprj main1.adb main2.adb main3.adb +@end example +@end quotation + +Each of these needs to be a source file of the same project, except +when the switch @cite{-u} is used. + +When @cite{-u} is not used, all the mains need to be sources of the +same project, one of the project in the tree rooted at the project specified +on the command line. The package @cite{Builder} of this common project, the +"main project" is the one that is considered by @emph{gnatmake}. + +When @cite{-u} is used, the specified source files may be in projects +imported directly or indirectly by the project specified on the command line. +Note that if such a source file is not part of the project specified on the +command line, the switches found in package @cite{Builder} of the +project specified on the command line, if any, that are transmitted +to the compiler will still be used, not those found in the project file of +the source file. + +When using a project file, you can also invoke @emph{gnatmake} without +explicitly specifying any main, and the effect depends on whether you have +defined the @cite{Main} attribute. This attribute has a string list value, +where each element in the list is the name of a source file (the file +extension is optional) that contains a unit that can be a main subprogram. + +If the @cite{Main} attribute is defined in a project file as a non-empty +string list and the switch @emph{-u} is not used on the command +line, then invoking @emph{gnatmake} with this project file but without any +main on the command line is equivalent to invoking @emph{gnatmake} with all +the file names in the @cite{Main} attribute on the command line. + +Example: + +@quotation + +@example +project Prj is + for Main use ("main1.adb", "main2.adb", "main3.adb"); +end Prj; +@end example +@end quotation + +With this project file, @cite{"gnatmake -Pprj"} +is equivalent to +@cite{"gnatmake -Pprj main1.adb main2.adb main3.adb"}. + +When the project attribute @cite{Main} is not specified, or is specified +as an empty string list, or when the switch @emph{-u} is used on the command +line, then invoking @emph{gnatmake} with no main on the command line will +result in all immediate sources of the project file being checked, and +potentially recompiled. Depending on the presence of the switch @emph{-u}, +sources from other project files on which the immediate sources of the main +project file depend are also checked and potentially recompiled. In other +words, the @emph{-u} switch is applied to all of the immediate sources of the +main project file. + +When no main is specified on the command line and attribute @cite{Main} exists +and includes several mains, or when several mains are specified on the +command line, the default switches in package @cite{Builder} will +be used for all mains, even if there are specific switches +specified for one or several mains. + +But the switches from package @cite{Binder} or @cite{Linker} will be +the specific switches for each main, if they are specified. + +@node Library Project Files,,Project Files and Main Subprograms,gnatmake and Project Files +@anchor{gnat_ugn/tools_supporting_project_files id7}@anchor{1c9}@anchor{gnat_ugn/tools_supporting_project_files library-project-files}@anchor{1ca} +@subsection Library Project Files + + +When @emph{gnatmake} is invoked with a main project file that is a library +project file, it is not allowed to specify one or more mains on the command +line. + +When a library project file is specified, switches @cite{-b} and +@cite{-l} have special meanings. + + +@itemize * + +@item +@cite{-b} is only allowed for stand-alone libraries. It indicates +to @emph{gnatmake} that @emph{gnatbind} should be invoked for the +library. + +@item +@cite{-l} may be used for all library projects. It indicates +to @emph{gnatmake} that the binder generated file should be compiled +(in the case of a stand-alone library) and that the library should be built. +@end itemize + +@node The GNAT Driver and Project Files,,gnatmake and Project Files,Tools Supporting Project Files +@anchor{gnat_ugn/tools_supporting_project_files id8}@anchor{1cb}@anchor{gnat_ugn/tools_supporting_project_files the-gnat-driver-and-project-files}@anchor{11f} +@section The GNAT Driver and Project Files + + +A number of GNAT tools beyond @emph{gnatmake} +can benefit from project files: + + + +@itemize * + +@item +@emph{gnatbind} + +@item +@emph{gnatclean} + +@item +@emph{gnatfind} + +@item +@emph{gnatlink} + +@item +@emph{gnatls} + +@item +@emph{gnatxref} +@end itemize + +However, none of these tools can be invoked +directly with a project file switch (@emph{-P}). +They must be invoked through the @emph{gnat} driver. + +The @emph{gnat} driver is a wrapper that accepts a number of commands and +calls the corresponding tool. It was designed initially for VMS platforms (to +convert VMS qualifiers to Unix-style switches), but it is now available on all +GNAT platforms. + +On non-VMS platforms, the @emph{gnat} driver accepts the following commands +(case insensitive): + + + +@itemize * + +@item +BIND to invoke @emph{gnatbind} + +@item +CHOP to invoke @emph{gnatchop} + +@item +CLEAN to invoke @emph{gnatclean} + +@item +COMP or COMPILE to invoke the compiler + +@item +FIND to invoke @emph{gnatfind} + +@item +KR or KRUNCH to invoke @emph{gnatkr} + +@item +LINK to invoke @emph{gnatlink} + +@item +LS or LIST to invoke @emph{gnatls} + +@item +MAKE to invoke @emph{gnatmake} + +@item +NAME to invoke @emph{gnatname} + +@item +PREP or PREPROCESS to invoke @emph{gnatprep} + +@item +XREF to invoke @emph{gnatxref} +@end itemize + +Note that the command +@emph{gnatmake -c -f -u} is used to invoke the compiler. + +On non-VMS platforms, between @emph{gnat} and the command, two +special switches may be used: + + +@itemize * + +@item +@emph{-v} to display the invocation of the tool. + +@item +@emph{-dn} to prevent the @emph{gnat} driver from removing +the temporary files it has created. These temporary files are +configuration files and temporary file list files. +@end itemize + +The command may be followed by switches and arguments for the invoked +tool. + +@quotation + +@example +$ gnat bind -C main.ali +$ gnat ls -a main +$ gnat chop foo.txt +@end example +@end quotation + +Switches may also be put in text files, one switch per line, and the text +files may be specified with their path name preceded by '@@'. + +@quotation + +@example +$ gnat bind @@args.txt main.ali +@end example +@end quotation + +In addition, for the following commands the project file related switches +(@emph{-P}, @emph{-X} and @emph{-vPx}) may be used in addition to +the switches of the invoking tool: + + + +@itemize * + +@item +BIND + +@item +COMP or COMPILE + +@item +FIND + +@item +LS or LIST + +@item +LINK + +@item +XREF +@end itemize + + +For each of the following commands, there is optionally a corresponding +package in the main project. + + + +@itemize * + +@item +package @cite{Binder} for command BIND (invoking @cite{gnatbind}) + +@item +package @cite{Compiler} for command COMP or COMPILE (invoking the compiler) + +@item +package @cite{Cross_Reference} for command XREF (invoking @cite{gnatxref}) + +@item +package @cite{Finder} for command FIND (invoking @cite{gnatfind}) + +@item +package @cite{Gnatls} for command LS or LIST (invoking @cite{gnatls}) + +@item +package @cite{Linker} for command LINK (invoking @cite{gnatlink}) +@end itemize + +Package @cite{Gnatls} has a unique attribute @cite{Switches}, +a simple variable with a string list value. It contains switches +for the invocation of @cite{gnatls}. + +@quotation + +@example +project Proj1 is + package gnatls is + for Switches + use ("-a", + "-v"); + end gnatls; +end Proj1; +@end example +@end quotation + +All other packages have two attribute @cite{Switches} and +@cite{Default_Switches}. + +@cite{Switches} is an indexed attribute, indexed by the +source file name, that has a string list value: the switches to be +used when the tool corresponding to the package is invoked for the specific +source file. + +@cite{Default_Switches} is an attribute, +indexed by the programming language that has a string list value. +@cite{Default_Switches ("Ada")} contains the +switches for the invocation of the tool corresponding +to the package, except if a specific @cite{Switches} attribute +is specified for the source file. + +@quotation + +@example +project Proj is + + for Source_Dirs use (""); + + package gnatls is + for Switches use + ("-a", + "-v"); + end gnatls; + + package Compiler is + for Default_Switches ("Ada") + use ("-gnatv", + "-gnatwa"); + end Binder; + + package Binder is + for Default_Switches ("Ada") + use ("-C", + "-e"); + end Binder; + + package Linker is + for Default_Switches ("Ada") + use ("-C"); + for Switches ("main.adb") + use ("-C", + "-v", + "-v"); + end Linker; + + package Finder is + for Default_Switches ("Ada") + use ("-a", + "-f"); + end Finder; + + package Cross_Reference is + for Default_Switches ("Ada") + use ("-a", + "-f", + "-d", + "-u"); + end Cross_Reference; +end Proj; +@end example +@end quotation + +With the above project file, commands such as + +@quotation + +@example +$ gnat comp -Pproj main +$ gnat ls -Pproj main +$ gnat xref -Pproj main +$ gnat bind -Pproj main.ali +$ gnat link -Pproj main.ali +@end example +@end quotation + +will set up the environment properly and invoke the tool with the switches +found in the package corresponding to the tool: +@cite{Default_Switches ("Ada")} for all tools, +except @cite{Switches ("main.adb")} +for @cite{gnatlink}. + + +@node GNAT Utility Programs,GNAT and Program Execution,Tools Supporting Project Files,Top +@anchor{gnat_ugn/gnat_utility_programs doc}@anchor{1cc}@anchor{gnat_ugn/gnat_utility_programs gnat-utility-programs}@anchor{d}@anchor{gnat_ugn/gnat_utility_programs id1}@anchor{1cd} +@chapter GNAT Utility Programs + + +This chapter describes a number of utility programs: + + + +@itemize * + +@item +@ref{22,,The File Cleanup Utility gnatclean} + +@item +@ref{23,,The GNAT Library Browser gnatls} + +@item +@ref{24,,The Cross-Referencing Tools gnatxref and gnatfind} + +@item +@ref{25,,The Ada to HTML Converter gnathtml} +@end itemize + +Other GNAT utilities are described elsewhere in this manual: + + +@itemize * + +@item +@ref{5b,,Handling Arbitrary File Naming Conventions with gnatname} + +@item +@ref{65,,File Name Krunching with gnatkr} + +@item +@ref{38,,Renaming Files with gnatchop} + +@item +@ref{19,,Preprocessing with gnatprep} +@end itemize + +@menu +* The File Cleanup Utility gnatclean:: +* The GNAT Library Browser gnatls:: +* The Cross-Referencing Tools gnatxref and gnatfind:: +* The Ada to HTML Converter gnathtml:: + +@end menu + +@node The File Cleanup Utility gnatclean,The GNAT Library Browser gnatls,,GNAT Utility Programs +@anchor{gnat_ugn/gnat_utility_programs id2}@anchor{1ce}@anchor{gnat_ugn/gnat_utility_programs the-file-cleanup-utility-gnatclean}@anchor{22} +@section The File Cleanup Utility @emph{gnatclean} + + +@geindex File cleanup tool + +@geindex gnatclean + +@cite{gnatclean} is a tool that allows the deletion of files produced by the +compiler, binder and linker, including ALI files, object files, tree files, +expanded source files, library files, interface copy source files, binder +generated files and executable files. + +@menu +* Running gnatclean:: +* Switches for gnatclean:: + +@end menu + +@node Running gnatclean,Switches for gnatclean,,The File Cleanup Utility gnatclean +@anchor{gnat_ugn/gnat_utility_programs running-gnatclean}@anchor{1cf}@anchor{gnat_ugn/gnat_utility_programs id3}@anchor{1d0} +@subsection Running @cite{gnatclean} + + +The @cite{gnatclean} command has the form: + +@quotation + +@example +$ gnatclean switches `names` +@end example +@end quotation + +where @cite{names} is a list of source file names. Suffixes @code{.ads} and +@code{adb} may be omitted. If a project file is specified using switch +@code{-P}, then @cite{names} may be completely omitted. + +In normal mode, @cite{gnatclean} delete the files produced by the compiler and, +if switch @cite{-c} is not specified, by the binder and +the linker. In informative-only mode, specified by switch +@cite{-n}, the list of files that would have been deleted in +normal mode is listed, but no file is actually deleted. + +@node Switches for gnatclean,,Running gnatclean,The File Cleanup Utility gnatclean +@anchor{gnat_ugn/gnat_utility_programs id4}@anchor{1d1}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatclean}@anchor{1d2} +@subsection Switches for @cite{gnatclean} + + +@cite{gnatclean} recognizes the following switches: + +@geindex --version (gnatclean) + + +@table @asis + +@item @code{--version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatclean) + + +@table @asis + +@item @code{--help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. + +@item @code{--subdirs=@emph{subdir}} + +Actual object directory of each project file is the subdirectory subdir of the +object directory specified or defaulted in the project file. + +@item @code{--unchecked-shared-lib-imports} + +By default, shared library projects are not allowed to import static library +projects. When this switch is used on the command line, this restriction is +relaxed. +@end table + +@geindex -c (gnatclean) + + +@table @asis + +@item @code{-c} + +Only attempt to delete the files produced by the compiler, not those produced +by the binder or the linker. The files that are not to be deleted are library +files, interface copy files, binder generated files and executable files. +@end table + +@geindex -D (gnatclean) + + +@table @asis + +@item @code{-D @emph{dir}} + +Indicate that ALI and object files should normally be found in directory @cite{dir}. +@end table + +@geindex -F (gnatclean) + + +@table @asis + +@item @code{-F} + +When using project files, if some errors or warnings are detected during +parsing and verbose mode is not in effect (no use of switch +-v), then error lines start with the full path name of the project +file, rather than its simple file name. +@end table + +@geindex -h (gnatclean) + + +@table @asis + +@item @code{-h} + +Output a message explaining the usage of @cite{gnatclean}. +@end table + +@geindex -n (gnatclean) + + +@table @asis + +@item @code{-n} + +Informative-only mode. Do not delete any files. Output the list of the files +that would have been deleted if this switch was not specified. +@end table + +@geindex -P (gnatclean) + + +@table @asis + +@item @code{-P@emph{project}} + +Use project file @cite{project}. Only one such switch can be used. +When cleaning a project file, the files produced by the compilation of the +immediate sources or inherited sources of the project files are to be +deleted. This is not depending on the presence or not of executable names +on the command line. +@end table + +@geindex -q (gnatclean) + + +@table @asis + +@item @code{-q} + +Quiet output. If there are no errors, do not output anything, except in +verbose mode (switch -v) or in informative-only mode +(switch -n). +@end table + +@geindex -r (gnatclean) + + +@table @asis + +@item @code{-r} + +When a project file is specified (using switch -P), +clean all imported and extended project files, recursively. If this switch +is not specified, only the files related to the main project file are to be +deleted. This switch has no effect if no project file is specified. +@end table + +@geindex -v (gnatclean) + + +@table @asis + +@item @code{-v} + +Verbose mode. +@end table + +@geindex -vP (gnatclean) + + +@table @asis + +@item @code{-vP@emph{x}} + +Indicates the verbosity of the parsing of GNAT project files. +@ref{e3,,Switches Related to Project Files}. +@end table + +@geindex -X (gnatclean) + + +@table @asis + +@item @code{-X@emph{name}=@emph{value}} + +Indicates that external variable @cite{name} has the value @cite{value}. +The Project Manager will use this value for occurrences of +@cite{external(name)} when parsing the project file. +@ref{e3,,Switches Related to Project Files}. +@end table + +@geindex -aO (gnatclean) + + +@table @asis + +@item @code{-aO@emph{dir}} + +When searching for ALI and object files, look in directory @cite{dir}. +@end table + +@geindex -I (gnatclean) + + +@table @asis + +@item @code{-I@emph{dir}} + +Equivalent to @code{-aO@emph{dir}}. +@end table + +@geindex -I- (gnatclean) + +@geindex Source files +@geindex suppressing search + + +@table @asis + +@item @code{-I-} + +Do not look for ALI or object files in the directory +where @cite{gnatclean} was invoked. +@end table + +@node The GNAT Library Browser gnatls,The Cross-Referencing Tools gnatxref and gnatfind,The File Cleanup Utility gnatclean,GNAT Utility Programs +@anchor{gnat_ugn/gnat_utility_programs the-gnat-library-browser-gnatls}@anchor{23}@anchor{gnat_ugn/gnat_utility_programs id5}@anchor{1d3} +@section The GNAT Library Browser @cite{gnatls} + + +@geindex Library browser + +@c index: ! gnatls + +@cite{gnatls} is a tool that outputs information about compiled +units. It gives the relationship between objects, unit names and source +files. It can also be used to check the source dependencies of a unit +as well as various characteristics. + +Note: to invoke @cite{gnatls} with a project file, use the @cite{gnat} +driver (see @ref{11f,,The GNAT Driver and Project Files}). + +@menu +* Running gnatls:: +* Switches for gnatls:: +* Example of gnatls Usage:: + +@end menu + +@node Running gnatls,Switches for gnatls,,The GNAT Library Browser gnatls +@anchor{gnat_ugn/gnat_utility_programs id6}@anchor{1d4}@anchor{gnat_ugn/gnat_utility_programs running-gnatls}@anchor{1d5} +@subsection Running @cite{gnatls} + + +The @cite{gnatls} command has the form + +@quotation + +@example +$ gnatls switches `object_or_ali_file` +@end example +@end quotation + +The main argument is the list of object or @code{ali} files +(see @ref{44,,The Ada Library Information Files}) +for which information is requested. + +In normal mode, without additional option, @cite{gnatls} produces a +four-column listing. Each line represents information for a specific +object. The first column gives the full path of the object, the second +column gives the name of the principal unit in this object, the third +column gives the status of the source and the fourth column gives the +full path of the source representing this unit. +Here is a simple example of use: + +@quotation + +@example +$ gnatls *.o +./demo1.o demo1 DIF demo1.adb +./demo2.o demo2 OK demo2.adb +./hello.o h1 OK hello.adb +./instr-child.o instr.child MOK instr-child.adb +./instr.o instr OK instr.adb +./tef.o tef DIF tef.adb +./text_io_example.o text_io_example OK text_io_example.adb +./tgef.o tgef DIF tgef.adb +@end example +@end quotation + +The first line can be interpreted as follows: the main unit which is +contained in +object file @code{demo1.o} is demo1, whose main source is in +@code{demo1.adb}. Furthermore, the version of the source used for the +compilation of demo1 has been modified (DIF). Each source file has a status +qualifier which can be: + + +@table @asis + +@item @emph{OK (unchanged)} + +The version of the source file used for the compilation of the +specified unit corresponds exactly to the actual source file. + +@item @emph{MOK (slightly modified)} + +The version of the source file used for the compilation of the +specified unit differs from the actual source file but not enough to +require recompilation. If you use gnatmake with the qualifier +@emph{-m (minimal recompilation)}, a file marked +MOK will not be recompiled. + +@item @emph{DIF (modified)} + +No version of the source found on the path corresponds to the source +used to build this object. + +@item @emph{??? (file not found)} + +No source file was found for this unit. + +@item @emph{HID (hidden, unchanged version not first on PATH)} + +The version of the source that corresponds exactly to the source used +for compilation has been found on the path but it is hidden by another +version of the same source that has been modified. +@end table + +@node Switches for gnatls,Example of gnatls Usage,Running gnatls,The GNAT Library Browser gnatls +@anchor{gnat_ugn/gnat_utility_programs id7}@anchor{1d6}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatls}@anchor{1d7} +@subsection Switches for @cite{gnatls} + + +@cite{gnatls} recognizes the following switches: + +@geindex --version (gnatls) + + +@table @asis + +@item @code{--version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatls) + + +@table @asis + +@item @code{*--help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table + +@geindex -a (gnatls) + + +@table @asis + +@item @code{-a} + +Consider all units, including those of the predefined Ada library. +Especially useful with @emph{-d}. +@end table + +@geindex -d (gnatls) + + +@table @asis + +@item @code{-d} + +List sources from which specified units depend on. +@end table + +@geindex -h (gnatls) + + +@table @asis + +@item @code{-h} + +Output the list of options. +@end table + +@geindex -o (gnatls) + + +@table @asis + +@item @code{-o} + +Only output information about object files. +@end table + +@geindex -s (gnatls) + + +@table @asis + +@item @code{-s} + +Only output information about source files. +@end table + +@geindex -u (gnatls) + + +@table @asis + +@item @code{-u} + +Only output information about compilation units. +@end table + +@geindex -files (gnatls) + + +@table @asis + +@item @code{-files=@emph{file}} + +Take as arguments the files listed in text file @cite{file}. +Text file @cite{file} may contain empty lines that are ignored. +Each nonempty line should contain the name of an existing file. +Several such switches may be specified simultaneously. +@end table + +@geindex -aO (gnatls) + +@geindex -aI (gnatls) + +@geindex -I (gnatls) + +@geindex -I- (gnatls) + + +@table @asis + +@item @code{-aO@emph{dir}}, @code{-aI@emph{dir}}, @code{-I@emph{dir}}, @code{-I-}, @code{-nostdinc} + +Source path manipulation. Same meaning as the equivalent @emph{gnatmake} +flags (@ref{df,,Switches for gnatmake}). +@end table + +@geindex -aP (gnatls) + + +@table @asis + +@item @code{-aP@emph{dir}} + +Add @cite{dir} at the beginning of the project search dir. +@end table + +@geindex --RTS (gnatls) + + +@table @asis + +@item @code{--RTS=@emph{rts-path}`} + +Specifies the default location of the runtime library. Same meaning as the +equivalent @emph{gnatmake} flag (@ref{df,,Switches for gnatmake}). +@end table + +@geindex -v (gnatls) + + +@table @asis + +@item @code{-v} + +Verbose mode. Output the complete source, object and project paths. Do not use +the default column layout but instead use long format giving as much as +information possible on each requested units, including special +characteristics such as: + + +@itemize * + +@item +@emph{Preelaborable}: The unit is preelaborable in the Ada sense. + +@item +@emph{No_Elab_Code}: No elaboration code has been produced by the compiler for this unit. + +@item +@emph{Pure}: The unit is pure in the Ada sense. + +@item +@emph{Elaborate_Body}: The unit contains a pragma Elaborate_Body. + +@item +@emph{Remote_Types}: The unit contains a pragma Remote_Types. + +@item +@emph{Shared_Passive}: The unit contains a pragma Shared_Passive. + +@item +@emph{Predefined}: This unit is part of the predefined environment and cannot be modified +by the user. + +@item +@emph{Remote_Call_Interface}: The unit contains a pragma Remote_Call_Interface. +@end itemize +@end table + +@node Example of gnatls Usage,,Switches for gnatls,The GNAT Library Browser gnatls +@anchor{gnat_ugn/gnat_utility_programs id8}@anchor{1d8}@anchor{gnat_ugn/gnat_utility_programs example-of-gnatls-usage}@anchor{1d9} +@subsection Example of @cite{gnatls} Usage + + +Example of using the verbose switch. Note how the source and +object paths are affected by the -I switch. + +@quotation + +@example +$ gnatls -v -I.. demo1.o + +GNATLS 5.03w (20041123-34) +Copyright 1997-2004 Free Software Foundation, Inc. + +Source Search Path: + + ../ + /home/comar/local/adainclude/ + +Object Search Path: + + ../ + /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/ + +Project Search Path: + + /home/comar/local/lib/gnat/ + +./demo1.o + Unit => + Name => demo1 + Kind => subprogram body + Flags => No_Elab_Code + Source => demo1.adb modified +@end example +@end quotation + +The following is an example of use of the dependency list. +Note the use of the -s switch +which gives a straight list of source files. This can be useful for +building specialized scripts. + +@quotation + +@example +$ gnatls -d demo2.o +./demo2.o demo2 OK demo2.adb + OK gen_list.ads + OK gen_list.adb + OK instr.ads + OK instr-child.ads + +$ gnatls -d -s -a demo1.o +demo1.adb +/home/comar/local/adainclude/ada.ads +/home/comar/local/adainclude/a-finali.ads +/home/comar/local/adainclude/a-filico.ads +/home/comar/local/adainclude/a-stream.ads +/home/comar/local/adainclude/a-tags.ads +gen_list.ads +gen_list.adb +/home/comar/local/adainclude/gnat.ads +/home/comar/local/adainclude/g-io.ads +instr.ads +/home/comar/local/adainclude/system.ads +/home/comar/local/adainclude/s-exctab.ads +/home/comar/local/adainclude/s-finimp.ads +/home/comar/local/adainclude/s-finroo.ads +/home/comar/local/adainclude/s-secsta.ads +/home/comar/local/adainclude/s-stalib.ads +/home/comar/local/adainclude/s-stoele.ads +/home/comar/local/adainclude/s-stratt.ads +/home/comar/local/adainclude/s-tasoli.ads +/home/comar/local/adainclude/s-unstyp.ads +/home/comar/local/adainclude/unchconv.ads +@end example +@end quotation + +@node The Cross-Referencing Tools gnatxref and gnatfind,The Ada to HTML Converter gnathtml,The GNAT Library Browser gnatls,GNAT Utility Programs +@anchor{gnat_ugn/gnat_utility_programs the-cross-referencing-tools-gnatxref-and-gnatfind}@anchor{24}@anchor{gnat_ugn/gnat_utility_programs id9}@anchor{1da} +@section The Cross-Referencing Tools @cite{gnatxref} and @cite{gnatfind} + + +@geindex gnatxref + +@geindex gnatfind + +The compiler generates cross-referencing information (unless +you set the @code{-gnatx} switch), which are saved in the @code{.ali} files. +This information indicates where in the source each entity is declared and +referenced. Note that entities in package Standard are not included, but +entities in all other predefined units are included in the output. + +Before using any of these two tools, you need to compile successfully your +application, so that GNAT gets a chance to generate the cross-referencing +information. + +The two tools @cite{gnatxref} and @cite{gnatfind} take advantage of this +information to provide the user with the capability to easily locate the +declaration and references to an entity. These tools are quite similar, +the difference being that @cite{gnatfind} is intended for locating +definitions and/or references to a specified entity or entities, whereas +@cite{gnatxref} is oriented to generating a full report of all +cross-references. + +To use these tools, you must not compile your application using the +@emph{-gnatx} switch on the @emph{gnatmake} command line +(see @ref{1d,,Building with gnatmake}). Otherwise, cross-referencing +information will not be generated. + +Note: to invoke @cite{gnatxref} or @cite{gnatfind} with a project file, +use the @cite{gnat} driver (see @ref{11f,,The GNAT Driver and Project Files}). + +@menu +* gnatxref Switches:: +* gnatfind Switches:: +* Project Files for gnatxref and gnatfind:: +* Regular Expressions in gnatfind and gnatxref:: +* Examples of gnatxref Usage:: +* Examples of gnatfind Usage:: + +@end menu + +@node gnatxref Switches,gnatfind Switches,,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs id10}@anchor{1db}@anchor{gnat_ugn/gnat_utility_programs gnatxref-switches}@anchor{1dc} +@subsection @cite{gnatxref} Switches + + +The command invocation for @cite{gnatxref} is: + +@quotation + +@example +$ gnatxref [`switches`] `sourcefile1` [`sourcefile2` ...] +@end example +@end quotation + +where + + +@table @asis + +@item @emph{sourcefile1} [, @emph{sourcefile2} ...] + +identify the source files for which a report is to be generated. The +'with'ed units will be processed too. You must provide at least one file. + +These file names are considered to be regular expressions, so for instance +specifying @code{source*.adb} is the same as giving every file in the current +directory whose name starts with @code{source} and whose extension is +@code{adb}. + +You shouldn't specify any directory name, just base names. @emph{gnatxref} +and @emph{gnatfind} will be able to locate these files by themselves using +the source path. If you specify directories, no result is produced. +@end table + +The following switches are available for @emph{gnatxref}: + +@geindex --version (gnatxref) + + +@table @asis + +@item @code{-version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatxref) + + +@table @asis + +@item @code{-help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table + +@geindex -a (gnatxref) + + +@table @asis + +@item @code{a} + +If this switch is present, @cite{gnatfind} and @cite{gnatxref} will parse +the read-only files found in the library search path. Otherwise, these files +will be ignored. This option can be used to protect Gnat sources or your own +libraries from being parsed, thus making @cite{gnatfind} and @cite{gnatxref} +much faster, and their output much smaller. Read-only here refers to access +or permissions status in the file system for the current user. +@end table + +@geindex -aIDIR (gnatxref) + + +@table @asis + +@item @code{aI@emph{DIR}} + +When looking for source files also look in directory DIR. The order in which +source file search is undertaken is the same as for @emph{gnatmake}. +@end table + +@geindex -aODIR (gnatxref) + + +@table @asis + +@item @code{aO@emph{DIR}} + +When searching for library and object files, look in directory +DIR. The order in which library files are searched is the same as for +@emph{gnatmake}. +@end table + +@geindex -nostdinc (gnatxref) + + +@table @asis + +@item @code{nostdinc} + +Do not look for sources in the system default directory. +@end table + +@geindex -nostdlib (gnatxref) + + +@table @asis + +@item @code{nostdlib} + +Do not look for library files in the system default directory. +@end table + +@geindex --ext (gnatxref) + + +@table @asis + +@item @code{-ext=@emph{extension}} + +Specify an alternate ali file extension. The default is @cite{ali} and other +extensions (e.g. @cite{gli} for C/C++ sources when using @emph{-fdump-xref}) +may be specified via this switch. Note that if this switch overrides the +default, which means that only the new extension will be considered. +@end table + +@geindex --RTS (gnatxref) + + +@table @asis + +@item @code{-RTS=@emph{rts-path}} + +Specifies the default location of the runtime library. Same meaning as the +equivalent @emph{gnatmake} flag (@ref{df,,Switches for gnatmake}). +@end table + +@geindex -d (gnatxref) + + +@table @asis + +@item @code{d} + +If this switch is set @cite{gnatxref} will output the parent type +reference for each matching derived types. +@end table + +@geindex -f (gnatxref) + + +@table @asis + +@item @code{f} + +If this switch is set, the output file names will be preceded by their +directory (if the file was found in the search path). If this switch is +not set, the directory will not be printed. +@end table + +@geindex -g (gnatxref) + + +@table @asis + +@item @code{g} + +If this switch is set, information is output only for library-level +entities, ignoring local entities. The use of this switch may accelerate +@cite{gnatfind} and @cite{gnatxref}. +@end table + +@geindex -IDIR (gnatxref) + + +@table @asis + +@item @code{I@emph{DIR}} + +Equivalent to @code{-aODIR -aIDIR}. +@end table + +@geindex -pFILE (gnatxref) + + +@table @asis + +@item @code{p@emph{FILE}} + +Specify a project file to use @ref{b,,GNAT Project Manager}. +If you need to use the @code{.gpr} +project files, you should use gnatxref through the GNAT driver +(@emph{gnat xref -Pproject}). + +By default, @cite{gnatxref} and @cite{gnatfind} will try to locate a +project file in the current directory. + +If a project file is either specified or found by the tools, then the content +of the source directory and object directory lines are added as if they +had been specified respectively by @code{-aI} +and @code{-aO}. + +@item @code{u} + +Output only unused symbols. This may be really useful if you give your +main compilation unit on the command line, as @cite{gnatxref} will then +display every unused entity and 'with'ed package. + +@item @code{v} + +Instead of producing the default output, @cite{gnatxref} will generate a +@code{tags} file that can be used by vi. For examples how to use this +feature, see @ref{1dd,,Examples of gnatxref Usage}. The tags file is output +to the standard output, thus you will have to redirect it to a file. +@end table + +All these switches may be in any order on the command line, and may even +appear after the file names. They need not be separated by spaces, thus +you can say @code{gnatxref -ag} instead of @code{gnatxref -a -g}. + +@node gnatfind Switches,Project Files for gnatxref and gnatfind,gnatxref Switches,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs id11}@anchor{1de}@anchor{gnat_ugn/gnat_utility_programs gnatfind-switches}@anchor{1df} +@subsection @cite{gnatfind} Switches + + +The command invocation for @cite{gnatfind} is: + +@quotation + +@example +$ gnatfind [`switches`] `pattern`[:`sourcefile`[:`line`[:`column`]]] + [`file1` `file2` ...] +@end example +@end quotation + +with the following iterpretation of the command arguments: + + +@table @asis + +@item @emph{pattern} + +An entity will be output only if it matches the regular expression found +in @cite{pattern}, see @ref{1e0,,Regular Expressions in gnatfind and gnatxref}. + +Omitting the pattern is equivalent to specifying @code{*}, which +will match any entity. Note that if you do not provide a pattern, you +have to provide both a sourcefile and a line. + +Entity names are given in Latin-1, with uppercase/lowercase equivalence +for matching purposes. At the current time there is no support for +8-bit codes other than Latin-1, or for wide characters in identifiers. + +@item @emph{sourcefile} + +@cite{gnatfind} will look for references, bodies or declarations +of symbols referenced in @code{sourcefile}, at line @cite{line} +and column @cite{column}. See @ref{1e1,,Examples of gnatfind Usage} +for syntax examples. + +@item @emph{line} + +A decimal integer identifying the line number containing +the reference to the entity (or entities) to be located. + +@item @emph{column} + +A decimal integer identifying the exact location on the +line of the first character of the identifier for the +entity reference. Columns are numbered from 1. + +@item @emph{file1 file2 ...} + +The search will be restricted to these source files. If none are given, then +the search will be conducted for every library file in the search path. +These files must appear only after the pattern or sourcefile. + +These file names are considered to be regular expressions, so for instance +specifying @code{source*.adb} is the same as giving every file in the current +directory whose name starts with @code{source} and whose extension is +@code{adb}. + +The location of the spec of the entity will always be displayed, even if it +isn't in one of @code{file1}, @code{file2}, ... The +occurrences of the entity in the separate units of the ones given on the +command line will also be displayed. + +Note that if you specify at least one file in this part, @cite{gnatfind} may +sometimes not be able to find the body of the subprograms. +@end table + +At least one of 'sourcefile' or 'pattern' has to be present on +the command line. + +The following switches are available: + +@geindex --version (gnatfind) + + +@table @asis + +@item @code{--version} + +Display Copyright and version, then exit disregarding all other options. +@end table + +@geindex --help (gnatfind) + + +@table @asis + +@item @code{-help} + +If @emph{--version} was not used, display usage, then exit disregarding +all other options. +@end table + +@geindex -a (gnatfind) + + +@table @asis + +@item @code{a} + +If this switch is present, @cite{gnatfind} and @cite{gnatxref} will parse +the read-only files found in the library search path. Otherwise, these files +will be ignored. This option can be used to protect Gnat sources or your own +libraries from being parsed, thus making @cite{gnatfind} and @cite{gnatxref} +much faster, and their output much smaller. Read-only here refers to access +or permission status in the file system for the current user. +@end table + +@geindex -aIDIR (gnatfind) + + +@table @asis + +@item @code{aI@emph{DIR}} + +When looking for source files also look in directory DIR. The order in which +source file search is undertaken is the same as for @emph{gnatmake}. +@end table + +@geindex -aODIR (gnatfind) + + +@table @asis + +@item @code{aO@emph{DIR}} + +When searching for library and object files, look in directory +DIR. The order in which library files are searched is the same as for +@emph{gnatmake}. +@end table + +@geindex -nostdinc (gnatfind) + + +@table @asis + +@item @code{nostdinc} + +Do not look for sources in the system default directory. +@end table + +@geindex -nostdlib (gnatfind) + + +@table @asis + +@item @code{nostdlib} + +Do not look for library files in the system default directory. +@end table + +@geindex --ext (gnatfind) + + +@table @asis + +@item @code{-ext=@emph{extension}} + +Specify an alternate ali file extension. The default is @cite{ali} and other +extensions (e.g. @cite{gli} for C/C++ sources when using @emph{-fdump-xref}) +may be specified via this switch. Note that if this switch overrides the +default, which means that only the new extension will be considered. +@end table + +@geindex --RTS (gnatfind) + + +@table @asis + +@item @code{-RTS=@emph{rts-path}} + +Specifies the default location of the runtime library. Same meaning as the +equivalent @emph{gnatmake} flag (@ref{df,,Switches for gnatmake}). +@end table + +@geindex -d (gnatfind) + + +@table @asis + +@item @code{d} + +If this switch is set, then @cite{gnatfind} will output the parent type +reference for each matching derived types. +@end table + +@geindex -e (gnatfind) + + +@table @asis + +@item @code{e} + +By default, @cite{gnatfind} accept the simple regular expression set for +@cite{pattern}. If this switch is set, then the pattern will be +considered as full Unix-style regular expression. +@end table + +@geindex -f (gnatfind) + + +@table @asis + +@item @code{f} + +If this switch is set, the output file names will be preceded by their +directory (if the file was found in the search path). If this switch is +not set, the directory will not be printed. +@end table + +@geindex -g (gnatfind) + + +@table @asis + +@item @code{g} + +If this switch is set, information is output only for library-level +entities, ignoring local entities. The use of this switch may accelerate +@cite{gnatfind} and @cite{gnatxref}. +@end table + +@geindex -IDIR (gnatfind) + + +@table @asis + +@item @code{I@emph{DIR}} + +Equivalent to @code{-aODIR -aIDIR}. +@end table + +@geindex -pFILE (gnatfind) + + +@table @asis + +@item @code{p@emph{FILE}} + +Specify a project file (@ref{b,,GNAT Project Manager}) to use. +By default, @cite{gnatxref} and @cite{gnatfind} will try to locate a +project file in the current directory. + +If a project file is either specified or found by the tools, then the content +of the source directory and object directory lines are added as if they +had been specified respectively by @code{-aI} and +@code{-aO}. +@end table + +@geindex -r (gnatfind) + + +@table @asis + +@item @code{r} + +By default, @cite{gnatfind} will output only the information about the +declaration, body or type completion of the entities. If this switch is +set, the @cite{gnatfind} will locate every reference to the entities in +the files specified on the command line (or in every file in the search +path if no file is given on the command line). +@end table + +@geindex -s (gnatfind) + + +@table @asis + +@item @code{s} + +If this switch is set, then @cite{gnatfind} will output the content +of the Ada source file lines were the entity was found. +@end table + +@geindex -t (gnatfind) + + +@table @asis + +@item @code{t} + +If this switch is set, then @cite{gnatfind} will output the type hierarchy for +the specified type. It act like -d option but recursively from parent +type to parent type. When this switch is set it is not possible to +specify more than one file. +@end table + +All these switches may be in any order on the command line, and may even +appear after the file names. They need not be separated by spaces, thus +you can say @code{gnatxref -ag} instead of +@code{gnatxref -a -g}. + +As stated previously, gnatfind will search in every directory in the +search path. You can force it to look only in the current directory if +you specify @cite{*} at the end of the command line. + +@node Project Files for gnatxref and gnatfind,Regular Expressions in gnatfind and gnatxref,gnatfind Switches,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs project-files-for-gnatxref-and-gnatfind}@anchor{1e2}@anchor{gnat_ugn/gnat_utility_programs id12}@anchor{1e3} +@subsection Project Files for @emph{gnatxref} and @emph{gnatfind} + + +Project files allow a programmer to specify how to compile its +application, where to find sources, etc. These files are used +primarily by GPS, but they can also be used +by the two tools @cite{gnatxref} and @cite{gnatfind}. + +A project file name must end with @code{.gpr}. If a single one is +present in the current directory, then @cite{gnatxref} and @cite{gnatfind} will +extract the information from it. If multiple project files are found, none of +them is read, and you have to use the @code{-p} switch to specify the one +you want to use. + +The following lines can be included, even though most of them have default +values which can be used in most cases. +The lines can be entered in any order in the file. +Except for @code{src_dir} and @code{obj_dir}, you can only have one instance of +each line. If you have multiple instances, only the last one is taken into +account. + + +@itemize * + +@item + +@table @asis + +@item @emph{src_dir=DIR} + +[default: @cite{"./"}]. +Specifies a directory where to look for source files. Multiple @cite{src_dir} +lines can be specified and they will be searched in the order they +are specified. +@end table + +@item + +@table @asis + +@item @emph{obj_dir=DIR} + +[default: @cite{"./"}]. +Specifies a directory where to look for object and library files. Multiple +@cite{obj_dir} lines can be specified, and they will be searched in the order +they are specified +@end table + +@item + +@table @asis + +@item @emph{comp_opt=SWITCHES} + +[default: @cite{""}]. +Creates a variable which can be referred to subsequently by using +the @cite{$@{comp_opt@}} notation. This is intended to store the default +switches given to @emph{gnatmake} and @emph{gcc}. +@end table + +@item + +@table @asis + +@item @emph{bind_opt=SWITCHES} + +[default: @cite{""}]. +Creates a variable which can be referred to subsequently by using +the @code{$@emph{bind_opt}} notation. This is intended to store the default +switches given to @emph{gnatbind}. +@end table + +@item + +@table @asis + +@item @emph{link_opt=SWITCHES} + +[default: @cite{""}]. +Creates a variable which can be referred to subsequently by using +the @code{$@emph{link_opt}} notation. This is intended to store the default +switches given to @emph{gnatlink}. +@end table + +@item + +@table @asis + +@item @emph{main=EXECUTABLE} + +[default: @cite{""}]. +Specifies the name of the executable for the application. This variable can +be referred to in the following lines by using the @code{@emph{$@{main}} notation. +@end table + +@item + +@table @asis + +@item @emph{comp_cmd=COMMAND} + +[default: @cite{"gcc -c -I$@{src_dir@} -g -gnatq"}]. +Specifies the command used to compile a single file in the application. +@end table + +@item + +@table @asis + +@item @emph{make_cmd=COMMAND} + +[default: @cite{"gnatmake $@{main@} -aI$@{src_dir@} -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@} -bargs $@{bind_opt@} -largs $@{link_opt@}"}]. +Specifies the command used to recompile the whole application. +@end table + +@item + +@table @asis + +@item @emph{run_cmd=COMMAND} + +[default: @cite{"$@{main@}"}]. +Specifies the command used to run the application. +@end table + +@item + +@table @asis + +@item @emph{debug_cmd=COMMAND} + +[default: @cite{"gdb $@{main@}"}]. +Specifies the command used to debug the application +@end table +@end itemize + +@emph{gnatxref} and @emph{gnatfind} only take into account the +@cite{src_dir} and @cite{obj_dir} lines, and ignore the others. + +@node Regular Expressions in gnatfind and gnatxref,Examples of gnatxref Usage,Project Files for gnatxref and gnatfind,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs id13}@anchor{1e4}@anchor{gnat_ugn/gnat_utility_programs regular-expressions-in-gnatfind-and-gnatxref}@anchor{1e0} +@subsection Regular Expressions in @cite{gnatfind} and @cite{gnatxref} + + +As specified in the section about @emph{gnatfind}, the pattern can be a +regular expression. Two kinds of regular expressions +are recognized: + + +@itemize * + +@item + +@table @asis + +@item @emph{Globbing pattern} + +These are the most common regular expression. They are the same as are +generally used in a Unix shell command line, or in a DOS session. + +Here is a more formal grammar: + +@example +regexp ::= term +term ::= elmt -- matches elmt +term ::= elmt elmt -- concatenation (elmt then elmt) +term ::= * -- any string of 0 or more characters +term ::= ? -- matches any character +term ::= [char @{char@}] -- matches any character listed +term ::= [char - char] -- matches any character in range +@end example +@end table + +@item + +@table @asis + +@item @emph{Full regular expression} + +The second set of regular expressions is much more powerful. This is the +type of regular expressions recognized by utilities such as @code{grep}. + +The following is the form of a regular expression, expressed in same BNF +style as is found in the Ada Reference Manual: + +@example +regexp ::= term @{| term@} -- alternation (term or term ...) + +term ::= item @{item@} -- concatenation (item then item) + +item ::= elmt -- match elmt +item ::= elmt * -- zero or more elmt's +item ::= elmt + -- one or more elmt's +item ::= elmt ? -- matches elmt or nothing + +elmt ::= nschar -- matches given character +elmt ::= [nschar @{nschar@}] -- matches any character listed +elmt ::= [^ nschar @{nschar@}] -- matches any character not listed +elmt ::= [char - char] -- matches chars in given range +elmt ::= \\ char -- matches given character +elmt ::= . -- matches any single character +elmt ::= ( regexp ) -- parens used for grouping + +char ::= any character, including special characters +nschar ::= any character except ()[].*+?^ +@end example + +Here are a few examples: + +@quotation + + +@table @asis + +@item @code{abcde|fghi} + +will match any of the two strings @code{abcde} and @code{fghi}, + +@item @code{abc*d} + +will match any string like @code{abd}, @code{abcd}, @code{abccd}, +@code{abcccd}, and so on, + +@item @code{[a-z]+} + +will match any string which has only lowercase characters in it (and at +least one character. +@end table +@end quotation +@end table +@end itemize + +@node Examples of gnatxref Usage,Examples of gnatfind Usage,Regular Expressions in gnatfind and gnatxref,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatxref-usage}@anchor{1dd}@anchor{gnat_ugn/gnat_utility_programs id14}@anchor{1e5} +@subsection Examples of @cite{gnatxref} Usage + + +@menu +* General Usage:: +* Using gnatxref with vi:: + +@end menu + +@node General Usage,Using gnatxref with vi,,Examples of gnatxref Usage +@anchor{gnat_ugn/gnat_utility_programs general-usage}@anchor{1e6} +@subsubsection General Usage + + +For the following examples, we will consider the following units: + +@quotation + +@example +main.ads: +1: with Bar; +2: package Main is +3: procedure Foo (B : in Integer); +4: C : Integer; +5: private +6: D : Integer; +7: end Main; + +main.adb: +1: package body Main is +2: procedure Foo (B : in Integer) is +3: begin +4: C := B; +5: D := B; +6: Bar.Print (B); +7: Bar.Print (C); +8: end Foo; +9: end Main; + +bar.ads: +1: package Bar is +2: procedure Print (B : Integer); +3: end bar; +@end example +@end quotation + +The first thing to do is to recompile your application (for instance, in +that case just by doing a @code{gnatmake main}, so that GNAT generates +the cross-referencing information. +You can then issue any of the following commands: + +@quotation + + +@itemize * + +@item +@code{gnatxref main.adb} +@cite{gnatxref} generates cross-reference information for main.adb +and every unit 'with'ed by main.adb. + +The output would be: + +@quotation + +@example +B Type: Integer + Decl: bar.ads 2:22 +B Type: Integer + Decl: main.ads 3:20 + Body: main.adb 2:20 + Ref: main.adb 4:13 5:13 6:19 +Bar Type: Unit + Decl: bar.ads 1:9 + Ref: main.adb 6:8 7:8 + main.ads 1:6 +C Type: Integer + Decl: main.ads 4:5 + Modi: main.adb 4:8 + Ref: main.adb 7:19 +D Type: Integer + Decl: main.ads 6:5 + Modi: main.adb 5:8 +Foo Type: Unit + Decl: main.ads 3:15 + Body: main.adb 2:15 +Main Type: Unit + Decl: main.ads 2:9 + Body: main.adb 1:14 +Print Type: Unit + Decl: bar.ads 2:15 + Ref: main.adb 6:12 7:12 +@end example +@end quotation + +This shows that the entity @cite{Main} is declared in main.ads, line 2, column 9, +its body is in main.adb, line 1, column 14 and is not referenced any where. + +The entity @cite{Print} is declared in bar.ads, line 2, column 15 and it +is referenced in main.adb, line 6 column 12 and line 7 column 12. + +@item +@code{gnatxref package1.adb package2.ads} +@cite{gnatxref} will generates cross-reference information for +package1.adb, package2.ads and any other package 'with'ed by any +of these. +@end itemize +@end quotation + +@node Using gnatxref with vi,,General Usage,Examples of gnatxref Usage +@anchor{gnat_ugn/gnat_utility_programs using-gnatxref-with-vi}@anchor{1e7} +@subsubsection Using gnatxref with vi + + +@cite{gnatxref} can generate a tags file output, which can be used +directly from @emph{vi}. Note that the standard version of @emph{vi} +will not work properly with overloaded symbols. Consider using another +free implementation of @emph{vi}, such as @emph{vim}. + +@quotation + +@example +$ gnatxref -v gnatfind.adb > tags +@end example +@end quotation + +The following command will generate the tags file for @cite{gnatfind} itself +(if the sources are in the search path!): + +@quotation + +@example +$ gnatxref -v gnatfind.adb > tags +@end example +@end quotation + +From @emph{vi}, you can then use the command @code{:tag @emph{entity}} +(replacing @cite{entity} by whatever you are looking for), and vi will +display a new file with the corresponding declaration of entity. + +@node Examples of gnatfind Usage,,Examples of gnatxref Usage,The Cross-Referencing Tools gnatxref and gnatfind +@anchor{gnat_ugn/gnat_utility_programs id15}@anchor{1e8}@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatfind-usage}@anchor{1e1} +@subsection Examples of @cite{gnatfind} Usage + + + +@itemize * + +@item +@code{gnatfind -f xyz:main.adb} +Find declarations for all entities xyz referenced at least once in +main.adb. The references are search in every library file in the search +path. + +The directories will be printed as well (as the @code{-f} +switch is set) + +The output will look like: + +@quotation + +@example +directory/main.ads:106:14: xyz <= declaration +directory/main.adb:24:10: xyz <= body +directory/foo.ads:45:23: xyz <= declaration +@end example +@end quotation + +I.e., one of the entities xyz found in main.adb is declared at +line 12 of main.ads (and its body is in main.adb), and another one is +declared at line 45 of foo.ads + +@item +@code{gnatfind -fs xyz:main.adb} +This is the same command as the previous one, but @cite{gnatfind} will +display the content of the Ada source file lines. + +The output will look like: + +@example +directory/main.ads:106:14: xyz <= declaration + procedure xyz; +directory/main.adb:24:10: xyz <= body + procedure xyz is +directory/foo.ads:45:23: xyz <= declaration + xyz : Integer; +@end example + +This can make it easier to find exactly the location your are looking +for. + +@item +@code{gnatfind -r "*x*":main.ads:123 foo.adb} +Find references to all entities containing an x that are +referenced on line 123 of main.ads. +The references will be searched only in main.ads and foo.adb. + +@item +@code{gnatfind main.ads:123} +Find declarations and bodies for all entities that are referenced on +line 123 of main.ads. + +This is the same as @code{gnatfind "*":main.adb:123`} + +@item +@code{gnatfind mydir/main.adb:123:45} +Find the declaration for the entity referenced at column 45 in +line 123 of file main.adb in directory mydir. Note that it +is usual to omit the identifier name when the column is given, +since the column position identifies a unique reference. + +The column has to be the beginning of the identifier, and should not +point to any character in the middle of the identifier. +@end itemize + +@node The Ada to HTML Converter gnathtml,,The Cross-Referencing Tools gnatxref and gnatfind,GNAT Utility Programs +@anchor{gnat_ugn/gnat_utility_programs the-ada-to-html-converter-gnathtml}@anchor{25}@anchor{gnat_ugn/gnat_utility_programs id16}@anchor{1e9} +@section The Ada to HTML Converter @cite{gnathtml} + + +@geindex gnathtml + +@emph{gnathtml} is a Perl script that allows Ada source files to be browsed using +standard Web browsers. For installation information, see @ref{1ea,,Installing gnathtml}. + +Ada reserved keywords are highlighted in a bold font and Ada comments in +a blue font. Unless your program was compiled with the gcc @emph{-gnatx} +switch to suppress the generation of cross-referencing information, user +defined variables and types will appear in a different color; you will +be able to click on any identifier and go to its declaration. + +@menu +* Invoking gnathtml:: +* Installing gnathtml:: + +@end menu + +@node Invoking gnathtml,Installing gnathtml,,The Ada to HTML Converter gnathtml +@anchor{gnat_ugn/gnat_utility_programs invoking-gnathtml}@anchor{1eb}@anchor{gnat_ugn/gnat_utility_programs id17}@anchor{1ec} +@subsection Invoking @emph{gnathtml} + + +The command line is as follows: + +@quotation + +@example +$ perl gnathtml.pl [`switches`] `ada-files` +@end example +@end quotation + +You can specify as many Ada files as you want. @cite{gnathtml} will generate +an html file for every ada file, and a global file called @code{index.htm}. +This file is an index of every identifier defined in the files. + +The following switches are available: + +@geindex -83 (gnathtml) + + +@table @asis + +@item @code{83} + +Only the Ada 83 subset of keywords will be highlighted. +@end table + +@geindex -cc (gnathtml) + + +@table @asis + +@item @code{cc @emph{color}} + +This option allows you to change the color used for comments. The default +value is green. The color argument can be any name accepted by html. +@end table + +@geindex -d (gnathtml) + + +@table @asis + +@item @code{d} + +If the Ada files depend on some other files (for instance through +@cite{with} clauses, the latter files will also be converted to html. +Only the files in the user project will be converted to html, not the files +in the run-time library itself. +@end table + +@geindex -D (gnathtml) + + +@table @asis + +@item @code{D} + +This command is the same as @emph{-d} above, but @emph{gnathtml} will +also look for files in the run-time library, and generate html files for them. +@end table + +@geindex -ext (gnathtml) + + +@table @asis + +@item @code{ext @emph{extension}} + +This option allows you to change the extension of the generated HTML files. +If you do not specify an extension, it will default to @code{htm}. +@end table + +@geindex -f (gnathtml) + + +@table @asis + +@item @code{f} + +By default, gnathtml will generate html links only for global entities +('with'ed units, global variables and types,...). If you specify +@emph{-f} on the command line, then links will be generated for local +entities too. +@end table + +@geindex -l (gnathtml) + + +@table @asis + +@item @code{l @emph{number}} + +If this switch is provided and @cite{number} is not 0, then +@cite{gnathtml} will number the html files every @cite{number} line. +@end table + +@geindex -I (gnathtml) + + +@table @asis + +@item @code{I @emph{dir}} + +Specify a directory to search for library files (@code{.ALI} files) and +source files. You can provide several -I switches on the command line, +and the directories will be parsed in the order of the command line. +@end table + +@geindex -o (gnathtml) + + +@table @asis + +@item @code{o @emph{dir}} + +Specify the output directory for html files. By default, gnathtml will +saved the generated html files in a subdirectory named @code{html/}. +@end table + +@geindex -p (gnathtml) + + +@table @asis + +@item @code{p @emph{file}} + +If you are using Emacs and the most recent Emacs Ada mode, which provides +a full Integrated Development Environment for compiling, checking, +running and debugging applications, you may use @code{.gpr} files +to give the directories where Emacs can find sources and object files. + +Using this switch, you can tell gnathtml to use these files. +This allows you to get an html version of your application, even if it +is spread over multiple directories. +@end table + +@geindex -sc (gnathtml) + + +@table @asis + +@item @code{sc @emph{color}} + +This switch allows you to change the color used for symbol +definitions. +The default value is red. The color argument can be any name accepted by html. +@end table + +@geindex -t (gnathtml) + + +@table @asis + +@item @code{t @emph{file}} + +This switch provides the name of a file. This file contains a list of +file names to be converted, and the effect is exactly as though they had +appeared explicitly on the command line. This +is the recommended way to work around the command line length limit on some +systems. +@end table + +@node Installing gnathtml,,Invoking gnathtml,The Ada to HTML Converter gnathtml +@anchor{gnat_ugn/gnat_utility_programs installing-gnathtml}@anchor{1ea}@anchor{gnat_ugn/gnat_utility_programs id18}@anchor{1ed} +@subsection Installing @cite{gnathtml} + + +@cite{Perl} needs to be installed on your machine to run this script. +@cite{Perl} is freely available for almost every architecture and +operating system via the Internet. + +On Unix systems, you may want to modify the first line of the script +@cite{gnathtml}, to explicitly specify where Perl +is located. The syntax of this line is: + +@quotation + +@example +#!full_path_name_to_perl +@end example +@end quotation + +Alternatively, you may run the script using the following command line: + +@quotation + +@example +$ perl gnathtml.pl [`switches`] `files` +@end example +@end quotation + +@c -- +---------------------------------------------------------------------+ + +@c -- | The following sections are present only in the PRO and GPL editions | + +@c -- +---------------------------------------------------------------------+ + + + + + + + +@c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + +@node GNAT and Program Execution,Platform-Specific Information,GNAT Utility Programs,Top +@anchor{gnat_ugn/gnat_and_program_execution gnat-and-program-execution}@anchor{e}@anchor{gnat_ugn/gnat_and_program_execution doc}@anchor{1ee}@anchor{gnat_ugn/gnat_and_program_execution id1}@anchor{1ef} +@chapter GNAT and Program Execution + + +This chapter covers several topics: + + +@itemize * + +@item +@ref{1f0,,Running and Debugging Ada Programs} + +@item +@ref{1f1,,Code Coverage and Profiling} + +@item +@ref{1f2,,Improving Performance} + +@item +@ref{1f3,,Overflow Check Handling in GNAT} + +@item +@ref{1f4,,Performing Dimensionality Analysis in GNAT} + +@item +@ref{1f5,,Stack Related Facilities} + +@item +@ref{1f6,,Memory Management Issues} +@end itemize + +@menu +* Running and Debugging Ada Programs:: +* Code Coverage and Profiling:: +* Improving Performance:: +* Overflow Check Handling in GNAT:: +* Performing Dimensionality Analysis in GNAT:: +* Stack Related Facilities:: +* Memory Management Issues:: + +@end menu + +@node Running and Debugging Ada Programs,Code Coverage and Profiling,,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution id2}@anchor{1f0}@anchor{gnat_ugn/gnat_and_program_execution running-and-debugging-ada-programs}@anchor{26} +@section Running and Debugging Ada Programs + + +@geindex Debugging + +This section discusses how to debug Ada programs. + +An incorrect Ada program may be handled in three ways by the GNAT compiler: + + +@itemize * + +@item +The illegality may be a violation of the static semantics of Ada. In +that case GNAT diagnoses the constructs in the program that are illegal. +It is then a straightforward matter for the user to modify those parts of +the program. + +@item +The illegality may be a violation of the dynamic semantics of Ada. In +that case the program compiles and executes, but may generate incorrect +results, or may terminate abnormally with some exception. + +@item +When presented with a program that contains convoluted errors, GNAT +itself may terminate abnormally without providing full diagnostics on +the incorrect user program. +@end itemize + +@geindex Debugger + +@geindex gdb + +@menu +* The GNAT Debugger GDB:: +* Running GDB:: +* Introduction to GDB Commands:: +* Using Ada Expressions:: +* Calling User-Defined Subprograms:: +* Using the next Command in a Function:: +* Stopping When Ada Exceptions Are Raised:: +* Ada Tasks:: +* Debugging Generic Units:: +* Remote Debugging with gdbserver:: +* GNAT Abnormal Termination or Failure to Terminate:: +* Naming Conventions for GNAT Source Files:: +* Getting Internal Debugging Information:: +* Stack Traceback:: + +@end menu + +@node The GNAT Debugger GDB,Running GDB,,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debugger-gdb}@anchor{1f7}@anchor{gnat_ugn/gnat_and_program_execution id3}@anchor{1f8} +@subsection The GNAT Debugger GDB + + +@cite{GDB} is a general purpose, platform-independent debugger that +can be used to debug mixed-language programs compiled with @emph{gcc}, +and in particular is capable of debugging Ada programs compiled with +GNAT. The latest versions of @cite{GDB} are Ada-aware and can handle +complex Ada data structures. + +See @cite{Debugging with GDB}, +for full details on the usage of @cite{GDB}, including a section on +its usage on programs. This manual should be consulted for full +details. The section that follows is a brief introduction to the +philosophy and use of @cite{GDB}. + +When GNAT programs are compiled, the compiler optionally writes debugging +information into the generated object file, including information on +line numbers, and on declared types and variables. This information is +separate from the generated code. It makes the object files considerably +larger, but it does not add to the size of the actual executable that +will be loaded into memory, and has no impact on run-time performance. The +generation of debug information is triggered by the use of the +-g switch in the @emph{gcc} or @emph{gnatmake} command +used to carry out the compilations. It is important to emphasize that +the use of these options does not change the generated code. + +The debugging information is written in standard system formats that +are used by many tools, including debuggers and profilers. The format +of the information is typically designed to describe C types and +semantics, but GNAT implements a translation scheme which allows full +details about Ada types and variables to be encoded into these +standard C formats. Details of this encoding scheme may be found in +the file exp_dbug.ads in the GNAT source distribution. However, the +details of this encoding are, in general, of no interest to a user, +since @cite{GDB} automatically performs the necessary decoding. + +When a program is bound and linked, the debugging information is +collected from the object files, and stored in the executable image of +the program. Again, this process significantly increases the size of +the generated executable file, but it does not increase the size of +the executable program itself. Furthermore, if this program is run in +the normal manner, it runs exactly as if the debug information were +not present, and takes no more actual memory. + +However, if the program is run under control of @cite{GDB}, the +debugger is activated. The image of the program is loaded, at which +point it is ready to run. If a run command is given, then the program +will run exactly as it would have if @cite{GDB} were not present. This +is a crucial part of the @cite{GDB} design philosophy. @cite{GDB} is +entirely non-intrusive until a breakpoint is encountered. If no +breakpoint is ever hit, the program will run exactly as it would if no +debugger were present. When a breakpoint is hit, @cite{GDB} accesses +the debugging information and can respond to user commands to inspect +variables, and more generally to report on the state of execution. + +@node Running GDB,Introduction to GDB Commands,The GNAT Debugger GDB,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution id4}@anchor{1f9}@anchor{gnat_ugn/gnat_and_program_execution running-gdb}@anchor{1fa} +@subsection Running GDB + + +This section describes how to initiate the debugger. + +The debugger can be launched from a @cite{GPS} menu or +directly from the command line. The description below covers the latter use. +All the commands shown can be used in the @cite{GPS} debug console window, +but there are usually more GUI-based ways to achieve the same effect. + +The command to run @cite{GDB} is + +@quotation + +@example +$ gdb program +@end example +@end quotation + +where @cite{program} is the name of the executable file. This +activates the debugger and results in a prompt for debugger commands. +The simplest command is simply @cite{run}, which causes the program to run +exactly as if the debugger were not present. The following section +describes some of the additional commands that can be given to @cite{GDB}. + +@node Introduction to GDB Commands,Using Ada Expressions,Running GDB,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution introduction-to-gdb-commands}@anchor{1fb}@anchor{gnat_ugn/gnat_and_program_execution id5}@anchor{1fc} +@subsection Introduction to GDB Commands + + +@cite{GDB} contains a large repertoire of commands. +See @cite{Debugging with GDB} for extensive documentation on the use +of these commands, together with examples of their use. Furthermore, +the command @emph{help} invoked from within GDB activates a simple help +facility which summarizes the available commands and their options. +In this section we summarize a few of the most commonly +used commands to give an idea of what @cite{GDB} is about. You should create +a simple program with debugging information and experiment with the use of +these @cite{GDB} commands on the program as you read through the +following section. + + +@itemize * + +@item + +@table @asis + +@item @emph{set args `arguments`} + +The @cite{arguments} list above is a list of arguments to be passed to +the program on a subsequent run command, just as though the arguments +had been entered on a normal invocation of the program. The @cite{set args} +command is not needed if the program does not require arguments. +@end table + +@item + +@table @asis + +@item @emph{run} + +The @cite{run} command causes execution of the program to start from +the beginning. If the program is already running, that is to say if +you are currently positioned at a breakpoint, then a prompt will ask +for confirmation that you want to abandon the current execution and +restart. +@end table + +@item + +@table @asis + +@item @emph{breakpoint `location`} + +The breakpoint command sets a breakpoint, that is to say a point at which +execution will halt and @cite{GDB} will await further +commands. @cite{location} is +either a line number within a file, given in the format @cite{file:linenumber}, +or it is the name of a subprogram. If you request that a breakpoint be set on +a subprogram that is overloaded, a prompt will ask you to specify on which of +those subprograms you want to breakpoint. You can also +specify that all of them should be breakpointed. If the program is run +and execution encounters the breakpoint, then the program +stops and @cite{GDB} signals that the breakpoint was encountered by +printing the line of code before which the program is halted. +@end table + +@item + +@table @asis + +@item @emph{catch exception `name`} + +This command causes the program execution to stop whenever exception +@cite{name} is raised. If @cite{name} is omitted, then the execution is +suspended when any exception is raised. +@end table + +@item + +@table @asis + +@item @emph{print `expression`} + +This will print the value of the given expression. Most simple +Ada expression formats are properly handled by @cite{GDB}, so the expression +can contain function calls, variables, operators, and attribute references. +@end table + +@item + +@table @asis + +@item @emph{continue} + +Continues execution following a breakpoint, until the next breakpoint or the +termination of the program. +@end table + +@item + +@table @asis + +@item @emph{step} + +Executes a single line after a breakpoint. If the next statement +is a subprogram call, execution continues into (the first statement of) +the called subprogram. +@end table + +@item + +@table @asis + +@item @emph{next} + +Executes a single line. If this line is a subprogram call, executes and +returns from the call. +@end table + +@item + +@table @asis + +@item @emph{list} + +Lists a few lines around the current source location. In practice, it +is usually more convenient to have a separate edit window open with the +relevant source file displayed. Successive applications of this command +print subsequent lines. The command can be given an argument which is a +line number, in which case it displays a few lines around the specified one. +@end table + +@item + +@table @asis + +@item @emph{backtrace} + +Displays a backtrace of the call chain. This command is typically +used after a breakpoint has occurred, to examine the sequence of calls that +leads to the current breakpoint. The display includes one line for each +activation record (frame) corresponding to an active subprogram. +@end table + +@item + +@table @asis + +@item @emph{up} + +At a breakpoint, @cite{GDB} can display the values of variables local +to the current frame. The command @cite{up} can be used to +examine the contents of other active frames, by moving the focus up +the stack, that is to say from callee to caller, one frame at a time. +@end table + +@item + +@table @asis + +@item @emph{down} + +Moves the focus of @cite{GDB} down from the frame currently being +examined to the frame of its callee (the reverse of the previous command), +@end table + +@item + +@table @asis + +@item @emph{frame `n`} + +Inspect the frame with the given number. The value 0 denotes the frame +of the current breakpoint, that is to say the top of the call stack. +@end table + +@item + +@table @asis + +@item @emph{kill} + +Kills the child process in which the program is running under GDB. +This may be useful for several purposes: + + +@itemize * + +@item +It allows you to recompile and relink your program, since on many systems +you cannot regenerate an executable file while it is running in a process. + +@item +You can run your program outside the debugger, on systems that do not +permit executing a program outside GDB while breakpoints are set +within GDB. + +@item +It allows you to debug a core dump rather than a running process. +@end itemize +@end table +@end itemize + +The above list is a very short introduction to the commands that +@cite{GDB} provides. Important additional capabilities, including conditional +breakpoints, the ability to execute command sequences on a breakpoint, +the ability to debug at the machine instruction level and many other +features are described in detail in @cite{Debugging with GDB}. +Note that most commands can be abbreviated +(for example, c for continue, bt for backtrace). + +@node Using Ada Expressions,Calling User-Defined Subprograms,Introduction to GDB Commands,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution id6}@anchor{1fd}@anchor{gnat_ugn/gnat_and_program_execution using-ada-expressions}@anchor{1fe} +@subsection Using Ada Expressions + + +@geindex Ada expressions (in gdb) + +@cite{GDB} supports a fairly large subset of Ada expression syntax, with some +extensions. The philosophy behind the design of this subset is + +@quotation + + +@itemize * + +@item +That @cite{GDB} should provide basic literals and access to operations for +arithmetic, dereferencing, field selection, indexing, and subprogram calls, +leaving more sophisticated computations to subprograms written into the +program (which therefore may be called from @cite{GDB}). + +@item +That type safety and strict adherence to Ada language restrictions +are not particularly relevant in a debugging context. + +@item +That brevity is important to the @cite{GDB} user. +@end itemize +@end quotation + +Thus, for brevity, the debugger acts as if there were +implicit @cite{with} and @cite{use} clauses in effect for all user-written +packages, thus making it unnecessary to fully qualify most names with +their packages, regardless of context. Where this causes ambiguity, +@cite{GDB} asks the user's intent. + +For details on the supported Ada syntax, see @cite{Debugging with GDB}. + +@node Calling User-Defined Subprograms,Using the next Command in a Function,Using Ada Expressions,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution id7}@anchor{1ff}@anchor{gnat_ugn/gnat_and_program_execution calling-user-defined-subprograms}@anchor{200} +@subsection Calling User-Defined Subprograms + + +An important capability of @cite{GDB} is the ability to call user-defined +subprograms while debugging. This is achieved simply by entering +a subprogram call statement in the form: + +@quotation + +@example +call subprogram-name (parameters) +@end example +@end quotation + +The keyword @cite{call} can be omitted in the normal case where the +@cite{subprogram-name} does not coincide with any of the predefined +@cite{GDB} commands. + +The effect is to invoke the given subprogram, passing it the +list of parameters that is supplied. The parameters can be expressions and +can include variables from the program being debugged. The +subprogram must be defined +at the library level within your program, and @cite{GDB} will call the +subprogram within the environment of your program execution (which +means that the subprogram is free to access or even modify variables +within your program). + +The most important use of this facility is in allowing the inclusion of +debugging routines that are tailored to particular data structures +in your program. Such debugging routines can be written to provide a suitably +high-level description of an abstract type, rather than a low-level dump +of its physical layout. After all, the standard +@cite{GDB print} command only knows the physical layout of your +types, not their abstract meaning. Debugging routines can provide information +at the desired semantic level and are thus enormously useful. + +For example, when debugging GNAT itself, it is crucial to have access to +the contents of the tree nodes used to represent the program internally. +But tree nodes are represented simply by an integer value (which in turn +is an index into a table of nodes). +Using the @cite{print} command on a tree node would simply print this integer +value, which is not very useful. But the PN routine (defined in file +treepr.adb in the GNAT sources) takes a tree node as input, and displays +a useful high level representation of the tree node, which includes the +syntactic category of the node, its position in the source, the integers +that denote descendant nodes and parent node, as well as varied +semantic information. To study this example in more detail, you might want to +look at the body of the PN procedure in the stated file. + +Another useful application of this capability is to deal with situations of +complex data which are not handled suitably by GDB. For example, if you specify +Convention Fortran for a multi-dimensional array, GDB does not know that +the ordering of array elements has been switched and will not properly +address the array elements. In such a case, instead of trying to print the +elements directly from GDB, you can write a callable procedure that prints +the elements in the desired format. + +@node Using the next Command in a Function,Stopping When Ada Exceptions Are Raised,Calling User-Defined Subprograms,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution using-the-next-command-in-a-function}@anchor{201}@anchor{gnat_ugn/gnat_and_program_execution id8}@anchor{202} +@subsection Using the @emph{next} Command in a Function + + +When you use the @cite{next} command in a function, the current source +location will advance to the next statement as usual. A special case +arises in the case of a @cite{return} statement. + +Part of the code for a return statement is the 'epilogue' of the function. +This is the code that returns to the caller. There is only one copy of +this epilogue code, and it is typically associated with the last return +statement in the function if there is more than one return. In some +implementations, this epilogue is associated with the first statement +of the function. + +The result is that if you use the @cite{next} command from a return +statement that is not the last return statement of the function you +may see a strange apparent jump to the last return statement or to +the start of the function. You should simply ignore this odd jump. +The value returned is always that from the first return statement +that was stepped through. + +@node Stopping When Ada Exceptions Are Raised,Ada Tasks,Using the next Command in a Function,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution stopping-when-ada-exceptions-are-raised}@anchor{203}@anchor{gnat_ugn/gnat_and_program_execution id9}@anchor{204} +@subsection Stopping When Ada Exceptions Are Raised + + +@geindex Exceptions (in gdb) + +You can set catchpoints that stop the program execution when your program +raises selected exceptions. + + +@itemize * + +@item + +@table @asis + +@item @emph{catch exception} + +Set a catchpoint that stops execution whenever (any task in the) program +raises any exception. +@end table + +@item + +@table @asis + +@item @emph{catch exception `name`} + +Set a catchpoint that stops execution whenever (any task in the) program +raises the exception @cite{name}. +@end table + +@item + +@table @asis + +@item @emph{catch exception unhandled} + +Set a catchpoint that stops executing whenever (any task in the) program +raises an exception for which there is no handler. +@end table + +@item + +@table @asis + +@item @emph{info exceptions}, @emph{info exceptions `regexp`} + +The @cite{info exceptions} command permits the user to examine all defined +exceptions within Ada programs. With a regular expression, @cite{regexp}, as +argument, prints out only those exceptions whose name matches @cite{regexp}. +@end table +@end itemize + +@geindex Tasks (in gdb) + +@node Ada Tasks,Debugging Generic Units,Stopping When Ada Exceptions Are Raised,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution ada-tasks}@anchor{205}@anchor{gnat_ugn/gnat_and_program_execution id10}@anchor{206} +@subsection Ada Tasks + + +@cite{GDB} allows the following task-related commands: + + +@itemize * + +@item + +@table @asis + +@item @emph{info tasks} + +This command shows a list of current Ada tasks, as in the following example: + +@example +(gdb) info tasks + ID TID P-ID Thread Pri State Name + 1 8088000 0 807e000 15 Child Activation Wait main_task + 2 80a4000 1 80ae000 15 Accept/Select Wait b + 3 809a800 1 80a4800 15 Child Activation Wait a +* 4 80ae800 3 80b8000 15 Running c +@end example + +In this listing, the asterisk before the first task indicates it to be the +currently running task. The first column lists the task ID that is used +to refer to tasks in the following commands. +@end table +@end itemize + +@geindex Breakpoints and tasks + + +@itemize * + +@item +@emph{break `linespec` task `taskid`}, @emph{break `linespec` task `taskid` if ...} + +@quotation + +These commands are like the @cite{break ... thread ...}. +@cite{linespec} specifies source lines. + +Use the qualifier @code{task @emph{taskid}} with a breakpoint command +to specify that you only want @cite{GDB} to stop the program when a +particular Ada task reaches this breakpoint. @cite{taskid} is one of the +numeric task identifiers assigned by @cite{GDB}, shown in the first +column of the @code{info tasks} display. + +If you do not specify @code{task @emph{taskid}} when you set a +breakpoint, the breakpoint applies to @emph{all} tasks of your +program. + +You can use the @cite{task} qualifier on conditional breakpoints as +well; in this case, place @code{task @emph{taskid}} before the +breakpoint condition (before the @cite{if}). +@end quotation +@end itemize + +@geindex Task switching (in gdb) + + +@itemize * + +@item +@emph{task `taskno`} + +@quotation + +This command allows switching to the task referred by @cite{taskno}. In +particular, this allows browsing of the backtrace of the specified +task. It is advisable to switch back to the original task before +continuing execution otherwise the scheduling of the program may be +perturbed. +@end quotation +@end itemize + +For more detailed information on the tasking support, +see @cite{Debugging with GDB}. + +@geindex Debugging Generic Units + +@geindex Generics + +@node Debugging Generic Units,Remote Debugging with gdbserver,Ada Tasks,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution debugging-generic-units}@anchor{207}@anchor{gnat_ugn/gnat_and_program_execution id11}@anchor{208} +@subsection Debugging Generic Units + + +GNAT always uses code expansion for generic instantiation. This means that +each time an instantiation occurs, a complete copy of the original code is +made, with appropriate substitutions of formals by actuals. + +It is not possible to refer to the original generic entities in +@cite{GDB}, but it is always possible to debug a particular instance of +a generic, by using the appropriate expanded names. For example, if we have + +@quotation + +@example +procedure g is + + generic package k is + procedure kp (v1 : in out integer); + end k; + + package body k is + procedure kp (v1 : in out integer) is + begin + v1 := v1 + 1; + end kp; + end k; + + package k1 is new k; + package k2 is new k; + + var : integer := 1; + +begin + k1.kp (var); + k2.kp (var); + k1.kp (var); + k2.kp (var); +end; +@end example +@end quotation + +Then to break on a call to procedure kp in the k2 instance, simply +use the command: + +@quotation + +@example +(gdb) break g.k2.kp +@end example +@end quotation + +When the breakpoint occurs, you can step through the code of the +instance in the normal manner and examine the values of local variables, as for +other units. + +@geindex Remote Debugging with gdbserver + +@node Remote Debugging with gdbserver,GNAT Abnormal Termination or Failure to Terminate,Debugging Generic Units,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution remote-debugging-with-gdbserver}@anchor{209}@anchor{gnat_ugn/gnat_and_program_execution id12}@anchor{20a} +@subsection Remote Debugging with gdbserver + + +On platforms where gdbserver is supported, it is possible to use this tool +to debug your application remotely. This can be useful in situations +where the program needs to be run on a target host that is different +from the host used for development, particularly when the target has +a limited amount of resources (either CPU and/or memory). + +To do so, start your program using gdbserver on the target machine. +gdbserver then automatically suspends the execution of your program +at its entry point, waiting for a debugger to connect to it. The +following commands starts an application and tells gdbserver to +wait for a connection with the debugger on localhost port 4444. + +@quotation + +@example +$ gdbserver localhost:4444 program +Process program created; pid = 5685 +Listening on port 4444 +@end example +@end quotation + +Once gdbserver has started listening, we can tell the debugger to establish +a connection with this gdbserver, and then start the same debugging session +as if the program was being debugged on the same host, directly under +the control of GDB. + +@quotation + +@example +$ gdb program +(gdb) target remote targethost:4444 +Remote debugging using targethost:4444 +0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so. +(gdb) b foo.adb:3 +Breakpoint 1 at 0x401f0c: file foo.adb, line 3. +(gdb) continue +Continuing. + +Breakpoint 1, foo () at foo.adb:4 +4 end foo; +@end example +@end quotation + +It is also possible to use gdbserver to attach to an already running +program, in which case the execution of that program is simply suspended +until the connection between the debugger and gdbserver is established. + +For more information on how to use gdbserver, see the @emph{Using the gdbserver Program} +section in @cite{Debugging with GDB}. +GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux. + +@geindex Abnormal Termination or Failure to Terminate + +@node GNAT Abnormal Termination or Failure to Terminate,Naming Conventions for GNAT Source Files,Remote Debugging with gdbserver,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution gnat-abnormal-termination-or-failure-to-terminate}@anchor{20b}@anchor{gnat_ugn/gnat_and_program_execution id13}@anchor{20c} +@subsection GNAT Abnormal Termination or Failure to Terminate + + +When presented with programs that contain serious errors in syntax +or semantics, +GNAT may on rare occasions experience problems in operation, such +as aborting with a +segmentation fault or illegal memory access, raising an internal +exception, terminating abnormally, or failing to terminate at all. +In such cases, you can activate +various features of GNAT that can help you pinpoint the construct in your +program that is the likely source of the problem. + +The following strategies are presented in increasing order of +difficulty, corresponding to your experience in using GNAT and your +familiarity with compiler internals. + + +@itemize * + +@item +Run @emph{gcc} with the @emph{-gnatf}. This first +switch causes all errors on a given line to be reported. In its absence, +only the first error on a line is displayed. + +The @emph{-gnatdO} switch causes errors to be displayed as soon as they +are encountered, rather than after compilation is terminated. If GNAT +terminates prematurely or goes into an infinite loop, the last error +message displayed may help to pinpoint the culprit. + +@item +Run @emph{gcc} with the @emph{-v (verbose)} switch. In this +mode, @emph{gcc} produces ongoing information about the progress of the +compilation and provides the name of each procedure as code is +generated. This switch allows you to find which Ada procedure was being +compiled when it encountered a code generation problem. +@end itemize + +@geindex -gnatdc switch + + +@itemize * + +@item +Run @emph{gcc} with the @emph{-gnatdc} switch. This is a GNAT specific +switch that does for the front-end what @emph{-v} does +for the back end. The system prints the name of each unit, +either a compilation unit or nested unit, as it is being analyzed. + +@item +Finally, you can start +@cite{gdb} directly on the @cite{gnat1} executable. @cite{gnat1} is the +front-end of GNAT, and can be run independently (normally it is just +called from @emph{gcc}). You can use @cite{gdb} on @cite{gnat1} as you +would on a C program (but @ref{1f7,,The GNAT Debugger GDB} for caveats). The +@cite{where} command is the first line of attack; the variable +@cite{lineno} (seen by @cite{print lineno}), used by the second phase of +@cite{gnat1} and by the @emph{gcc} backend, indicates the source line at +which the execution stopped, and @cite{input_file name} indicates the name of +the source file. +@end itemize + +@node Naming Conventions for GNAT Source Files,Getting Internal Debugging Information,GNAT Abnormal Termination or Failure to Terminate,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution naming-conventions-for-gnat-source-files}@anchor{20d}@anchor{gnat_ugn/gnat_and_program_execution id14}@anchor{20e} +@subsection Naming Conventions for GNAT Source Files + + +In order to examine the workings of the GNAT system, the following +brief description of its organization may be helpful: + + +@itemize * + +@item +Files with prefix @code{sc} contain the lexical scanner. + +@item +All files prefixed with @code{par} are components of the parser. The +numbers correspond to chapters of the Ada Reference Manual. For example, +parsing of select statements can be found in @code{par-ch9.adb}. + +@item +All files prefixed with @code{sem} perform semantic analysis. The +numbers correspond to chapters of the Ada standard. For example, all +issues involving context clauses can be found in @code{sem_ch10.adb}. In +addition, some features of the language require sufficient special processing +to justify their own semantic files: sem_aggr for aggregates, sem_disp for +dynamic dispatching, etc. + +@item +All files prefixed with @code{exp} perform normalization and +expansion of the intermediate representation (abstract syntax tree, or AST). +these files use the same numbering scheme as the parser and semantics files. +For example, the construction of record initialization procedures is done in +@code{exp_ch3.adb}. + +@item +The files prefixed with @code{bind} implement the binder, which +verifies the consistency of the compilation, determines an order of +elaboration, and generates the bind file. + +@item +The files @code{atree.ads} and @code{atree.adb} detail the low-level +data structures used by the front-end. + +@item +The files @code{sinfo.ads} and @code{sinfo.adb} detail the structure of +the abstract syntax tree as produced by the parser. + +@item +The files @code{einfo.ads} and @code{einfo.adb} detail the attributes of +all entities, computed during semantic analysis. + +@item +Library management issues are dealt with in files with prefix +@code{lib}. + +@geindex Annex A (in Ada Reference Manual) + +@item +Ada files with the prefix @code{a-} are children of @cite{Ada}, as +defined in Annex A. + +@geindex Annex B (in Ada reference Manual) + +@item +Files with prefix @code{i-} are children of @cite{Interfaces}, as +defined in Annex B. + +@geindex System (package in Ada Reference Manual) + +@item +Files with prefix @code{s-} are children of @cite{System}. This includes +both language-defined children and GNAT run-time routines. + +@geindex GNAT (package) + +@item +Files with prefix @code{g-} are children of @cite{GNAT}. These are useful +general-purpose packages, fully documented in their specs. All +the other @code{.c} files are modifications of common @emph{gcc} files. +@end itemize + +@node Getting Internal Debugging Information,Stack Traceback,Naming Conventions for GNAT Source Files,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution id15}@anchor{20f}@anchor{gnat_ugn/gnat_and_program_execution getting-internal-debugging-information}@anchor{210} +@subsection Getting Internal Debugging Information + + +Most compilers have internal debugging switches and modes. GNAT +does also, except GNAT internal debugging switches and modes are not +secret. A summary and full description of all the compiler and binder +debug flags are in the file @code{debug.adb}. You must obtain the +sources of the compiler to see the full detailed effects of these flags. + +The switches that print the source of the program (reconstructed from +the internal tree) are of general interest for user programs, as are the +options to print +the full internal tree, and the entity table (the symbol table +information). The reconstructed source provides a readable version of the +program after the front-end has completed analysis and expansion, +and is useful when studying the performance of specific constructs. +For example, constraint checks are indicated, complex aggregates +are replaced with loops and assignments, and tasking primitives +are replaced with run-time calls. + +@geindex traceback + +@geindex stack traceback + +@geindex stack unwinding + +@node Stack Traceback,,Getting Internal Debugging Information,Running and Debugging Ada Programs +@anchor{gnat_ugn/gnat_and_program_execution stack-traceback}@anchor{211}@anchor{gnat_ugn/gnat_and_program_execution id16}@anchor{212} +@subsection Stack Traceback + + +Traceback is a mechanism to display the sequence of subprogram calls that +leads to a specified execution point in a program. Often (but not always) +the execution point is an instruction at which an exception has been raised. +This mechanism is also known as @emph{stack unwinding} because it obtains +its information by scanning the run-time stack and recovering the activation +records of all active subprograms. Stack unwinding is one of the most +important tools for program debugging. + +The first entry stored in traceback corresponds to the deepest calling level, +that is to say the subprogram currently executing the instruction +from which we want to obtain the traceback. + +Note that there is no runtime performance penalty when stack traceback +is enabled, and no exception is raised during program execution. + +@geindex traceback +@geindex non-symbolic + +@menu +* Non-Symbolic Traceback:: +* Symbolic Traceback:: + +@end menu + +@node Non-Symbolic Traceback,Symbolic Traceback,,Stack Traceback +@anchor{gnat_ugn/gnat_and_program_execution non-symbolic-traceback}@anchor{213}@anchor{gnat_ugn/gnat_and_program_execution id17}@anchor{214} +@subsubsection Non-Symbolic Traceback + + +Note: this feature is not supported on all platforms. See +@code{GNAT.Traceback} spec in @code{g-traceb.ads} +for a complete list of supported platforms. + +@subsubheading Tracebacks From an Unhandled Exception + + +A runtime non-symbolic traceback is a list of addresses of call instructions. +To enable this feature you must use the @emph{-E} +@cite{gnatbind}'s option. With this option a stack traceback is stored as part +of exception information. You can retrieve this information using the +@cite{addr2line} tool. + +Here is a simple example: + +@quotation + +@example +procedure STB is + + procedure P1 is + begin + raise Constraint_Error; + end P1; + + procedure P2 is + begin + P1; + end P2; + +begin + P2; +end STB; +@end example + +@example +$ gnatmake stb -bargs -E +$ stb + +Execution terminated by unhandled exception +Exception name: CONSTRAINT_ERROR +Message: stb.adb:5 +Call stack traceback locations: +0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 +@end example +@end quotation + +As we see the traceback lists a sequence of addresses for the unhandled +exception @cite{CONSTRAINT_ERROR} raised in procedure P1. It is easy to +guess that this exception come from procedure P1. To translate these +addresses into the source lines where the calls appear, the +@cite{addr2line} tool, described below, is invaluable. The use of this tool +requires the program to be compiled with debug information. + +@quotation + +@example +$ gnatmake -g stb -bargs -E +$ stb + +Execution terminated by unhandled exception +Exception name: CONSTRAINT_ERROR +Message: stb.adb:5 +Call stack traceback locations: +0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4 + +$ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 + 0x4011f1 0x77e892a4 + +00401373 at d:/stb/stb.adb:5 +0040138B at d:/stb/stb.adb:10 +0040139C at d:/stb/stb.adb:14 +00401335 at d:/stb/b~stb.adb:104 +004011C4 at /build/.../crt1.c:200 +004011F1 at /build/.../crt1.c:222 +77E892A4 in ?? at ??:0 +@end example +@end quotation + +The @cite{addr2line} tool has several other useful options: + +@quotation + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item + +@code{--functions} + +@tab + +to get the function name corresponding to any location + +@item + +@code{--demangle=gnat} + +@tab + +to use the gnat decoding mode for the function names. +Note that for binutils version 2.9.x the option is +simply @code{--demangle}. + +@end multitable + + +@example +$ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b + 0x40139c 0x401335 0x4011c4 0x4011f1 + +00401373 in stb.p1 at d:/stb/stb.adb:5 +0040138B in stb.p2 at d:/stb/stb.adb:10 +0040139C in stb at d:/stb/stb.adb:14 +00401335 in main at d:/stb/b~stb.adb:104 +004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200 +004011F1 in at /build/.../crt1.c:222 +@end example +@end quotation + +From this traceback we can see that the exception was raised in +@code{stb.adb} at line 5, which was reached from a procedure call in +@code{stb.adb} at line 10, and so on. The @code{b~std.adb} is the binder file, +which contains the call to the main program. +@ref{120,,Running gnatbind}. The remaining entries are assorted runtime routines, +and the output will vary from platform to platform. + +It is also possible to use @cite{GDB} with these traceback addresses to debug +the program. For example, we can break at a given code location, as reported +in the stack traceback: + +@quotation + +@example +$ gdb -nw stb +@end example +@end quotation + +Furthermore, this feature is not implemented inside Windows DLL. Only +the non-symbolic traceback is reported in this case. + +@quotation + +@example +(gdb) break *0x401373 +Breakpoint 1 at 0x401373: file stb.adb, line 5. +@end example +@end quotation + +It is important to note that the stack traceback addresses +do not change when debug information is included. This is particularly useful +because it makes it possible to release software without debug information (to +minimize object size), get a field report that includes a stack traceback +whenever an internal bug occurs, and then be able to retrieve the sequence +of calls with the same program compiled with debug information. + +@subsubheading Tracebacks From Exception Occurrences + + +Non-symbolic tracebacks are obtained by using the @emph{-E} binder argument. +The stack traceback is attached to the exception information string, and can +be retrieved in an exception handler within the Ada program, by means of the +Ada facilities defined in @cite{Ada.Exceptions}. Here is a simple example: + +@quotation + +@example +with Ada.Text_IO; +with Ada.Exceptions; + +procedure STB is + + use Ada; + use Ada.Exceptions; + + procedure P1 is + K : Positive := 1; + begin + K := K - 1; + exception + when E : others => + Text_IO.Put_Line (Exception_Information (E)); + end P1; + + procedure P2 is + begin + P1; + end P2; + +begin + P2; +end STB; +@end example +@end quotation + +This program will output: + +@quotation + +@example +$ stb + +Exception name: CONSTRAINT_ERROR +Message: stb.adb:12 +Call stack traceback locations: +0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4 +@end example +@end quotation + +@subsubheading Tracebacks From Anywhere in a Program + + +It is also possible to retrieve a stack traceback from anywhere in a +program. For this you need to +use the @cite{GNAT.Traceback} API. This package includes a procedure called +@cite{Call_Chain} that computes a complete stack traceback, as well as useful +display procedures described below. It is not necessary to use the +@emph{-E gnatbind} option in this case, because the stack traceback mechanism +is invoked explicitly. + +In the following example we compute a traceback at a specific location in +the program, and we display it using @cite{GNAT.Debug_Utilities.Image} to +convert addresses to strings: + +@quotation + +@example +with Ada.Text_IO; +with GNAT.Traceback; +with GNAT.Debug_Utilities; + +procedure STB is + + use Ada; + use GNAT; + use GNAT.Traceback; + + procedure P1 is + TB : Tracebacks_Array (1 .. 10); + -- We are asking for a maximum of 10 stack frames. + Len : Natural; + -- Len will receive the actual number of stack frames returned. + begin + Call_Chain (TB, Len); + + Text_IO.Put ("In STB.P1 : "); + + for K in 1 .. Len loop + Text_IO.Put (Debug_Utilities.Image (TB (K))); + Text_IO.Put (' '); + end loop; + + Text_IO.New_Line; + end P1; + + procedure P2 is + begin + P1; + end P2; + +begin + P2; +end STB; +@end example + +@example +$ gnatmake -g stb +$ stb + +In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C# +16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4# +@end example +@end quotation + +You can then get further information by invoking the @cite{addr2line} +tool as described earlier (note that the hexadecimal addresses +need to be specified in C format, with a leading '0x'). + +@geindex traceback +@geindex symbolic + +@node Symbolic Traceback,,Non-Symbolic Traceback,Stack Traceback +@anchor{gnat_ugn/gnat_and_program_execution id18}@anchor{215}@anchor{gnat_ugn/gnat_and_program_execution symbolic-traceback}@anchor{216} +@subsubsection Symbolic Traceback + + +A symbolic traceback is a stack traceback in which procedure names are +associated with each code location. + +Note that this feature is not supported on all platforms. See +@code{GNAT.Traceback.Symbolic} spec in @code{g-trasym.ads} for a complete +list of currently supported platforms. + +Note that the symbolic traceback requires that the program be compiled +with debug information. If it is not compiled with debug information +only the non-symbolic information will be valid. + +@subsubheading Tracebacks From Exception Occurrences + + +Here is an example: + +@quotation + +@example +with Ada.Text_IO; +with GNAT.Traceback.Symbolic; + +procedure STB is + + procedure P1 is + begin + raise Constraint_Error; + end P1; + + procedure P2 is + begin + P1; + end P2; + + procedure P3 is + begin + P2; + end P3; + +begin + P3; +exception + when E : others => + Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E)); +end STB; +@end example + +@example +$ gnatmake -g .\stb -bargs -E +$ stb + +0040149F in stb.p1 at stb.adb:8 +004014B7 in stb.p2 at stb.adb:13 +004014CF in stb.p3 at stb.adb:18 +004015DD in ada.stb at stb.adb:22 +00401461 in main at b~stb.adb:168 +004011C4 in __mingw_CRTStartup at crt1.c:200 +004011F1 in mainCRTStartup at crt1.c:222 +77E892A4 in ?? at ??:0 +@end example +@end quotation + +In the above example the @code{.\} syntax in the @emph{gnatmake} command +is currently required by @emph{addr2line} for files that are in +the current working directory. +Moreover, the exact sequence of linker options may vary from platform +to platform. +The above @emph{-largs} section is for Windows platforms. By contrast, +under Unix there is no need for the @emph{-largs} section. +Differences across platforms are due to details of linker implementation. + +@subsubheading Tracebacks From Anywhere in a Program + + +It is possible to get a symbolic stack traceback +from anywhere in a program, just as for non-symbolic tracebacks. +The first step is to obtain a non-symbolic +traceback, and then call @cite{Symbolic_Traceback} to compute the symbolic +information. Here is an example: + +@quotation + +@example +with Ada.Text_IO; +with GNAT.Traceback; +with GNAT.Traceback.Symbolic; + +procedure STB is + + use Ada; + use GNAT.Traceback; + use GNAT.Traceback.Symbolic; + + procedure P1 is + TB : Tracebacks_Array (1 .. 10); + -- We are asking for a maximum of 10 stack frames. + Len : Natural; + -- Len will receive the actual number of stack frames returned. + begin + Call_Chain (TB, Len); + Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len))); + end P1; + + procedure P2 is + begin + P1; + end P2; + +begin + P2; +end STB; +@end example +@end quotation + +@geindex Code Coverage + +@geindex Profiling + +@node Code Coverage and Profiling,Improving Performance,Running and Debugging Ada Programs,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution id19}@anchor{1f1}@anchor{gnat_ugn/gnat_and_program_execution code-coverage-and-profiling}@anchor{27} +@section Code Coverage and Profiling + + +This section describes how to use the @cite{gcov} coverage testing tool and +the @cite{gprof} profiler tool on Ada programs. + +@geindex gcov + +@menu +* Code Coverage of Ada Programs with gcov:: +* Profiling an Ada Program with gprof:: + +@end menu + +@node Code Coverage of Ada Programs with gcov,Profiling an Ada Program with gprof,,Code Coverage and Profiling +@anchor{gnat_ugn/gnat_and_program_execution id20}@anchor{217}@anchor{gnat_ugn/gnat_and_program_execution code-coverage-of-ada-programs-with-gcov}@anchor{218} +@subsection Code Coverage of Ada Programs with gcov + + +@cite{gcov} is a test coverage program: it analyzes the execution of a given +program on selected tests, to help you determine the portions of the program +that are still untested. + +@cite{gcov} is part of the GCC suite, and is described in detail in the GCC +User's Guide. You can refer to this documentation for a more complete +description. + +This chapter provides a quick startup guide, and +details some GNAT-specific features. + +@menu +* Quick startup guide:: +* GNAT specifics:: + +@end menu + +@node Quick startup guide,GNAT specifics,,Code Coverage of Ada Programs with gcov +@anchor{gnat_ugn/gnat_and_program_execution id21}@anchor{219}@anchor{gnat_ugn/gnat_and_program_execution quick-startup-guide}@anchor{21a} +@subsubsection Quick startup guide + + +In order to perform coverage analysis of a program using @cite{gcov}, several +steps are needed: + + +@enumerate + +@item +Instrument the code during the compilation process, + +@item +Execute the instrumented program, and + +@item +Invoke the @cite{gcov} tool to generate the coverage results. +@end enumerate + +@geindex -fprofile-arcs (gcc) + +@geindex -ftest-coverage (gcc + +@geindex -fprofile-arcs (gnatbind) + +The code instrumentation needed by gcov is created at the object level. +The source code is not modified in any way, because the instrumentation code is +inserted by gcc during the compilation process. To compile your code with code +coverage activated, you need to recompile your whole project using the +switches +@cite{-fprofile-arcs} and @cite{-ftest-coverage}, and link it using +@cite{-fprofile-arcs}. + +@quotation + +@example +$ gnatmake -P my_project.gpr -f -cargs -fprofile-arcs -ftest-coverage \\ + -largs -fprofile-arcs +@end example +@end quotation + +This compilation process will create @code{.gcno} files together with +the usual object files. + +Once the program is compiled with coverage instrumentation, you can +run it as many times as needed -- on portions of a test suite for +example. The first execution will produce @code{.gcda} files at the +same location as the @code{.gcno} files. Subsequent executions +will update those files, so that a cumulative result of the covered +portions of the program is generated. + +Finally, you need to call the @cite{gcov} tool. The different options of +@cite{gcov} are described in the GCC User's Guide, section 'Invoking gcov'. + +This will create annotated source files with a @code{.gcov} extension: +@code{my_main.adb} file will be analyzed in @code{my_main.adb.gcov}. + +@node GNAT specifics,,Quick startup guide,Code Coverage of Ada Programs with gcov +@anchor{gnat_ugn/gnat_and_program_execution gnat-specifics}@anchor{21b}@anchor{gnat_ugn/gnat_and_program_execution id22}@anchor{21c} +@subsubsection GNAT specifics + + +Because of Ada semantics, portions of the source code may be shared among +several object files. This is the case for example when generics are +involved, when inlining is active or when declarations generate initialisation +calls. In order to take +into account this shared code, you need to call @cite{gcov} on all +source files of the tested program at once. + +The list of source files might exceed the system's maximum command line +length. In order to bypass this limitation, a new mechanism has been +implemented in @cite{gcov}: you can now list all your project's files into a +text file, and provide this file to gcov as a parameter, preceded by a @code{@@} +(e.g. @code{gcov @@mysrclist.txt}). + +Note that on AIX compiling a static library with @cite{-fprofile-arcs} is +not supported as there can be unresolved symbols during the final link. + +@geindex gprof + +@geindex Profiling + +@node Profiling an Ada Program with gprof,,Code Coverage of Ada Programs with gcov,Code Coverage and Profiling +@anchor{gnat_ugn/gnat_and_program_execution profiling-an-ada-program-with-gprof}@anchor{21d}@anchor{gnat_ugn/gnat_and_program_execution id23}@anchor{21e} +@subsection Profiling an Ada Program with gprof + + +This section is not meant to be an exhaustive documentation of @cite{gprof}. +Full documentation for it can be found in the @cite{GNU Profiler User's Guide} +documentation that is part of this GNAT distribution. + +Profiling a program helps determine the parts of a program that are executed +most often, and are therefore the most time-consuming. + +@cite{gprof} is the standard GNU profiling tool; it has been enhanced to +better handle Ada programs and multitasking. +It is currently supported on the following platforms + + +@itemize * + +@item +linux x86/x86_64 + +@item +solaris sparc/sparc64/x86 + +@item +windows x86 +@end itemize + +In order to profile a program using @cite{gprof}, several steps are needed: + + +@enumerate + +@item +Instrument the code, which requires a full recompilation of the project with the +proper switches. + +@item +Execute the program under the analysis conditions, i.e. with the desired +input. + +@item +Analyze the results using the @cite{gprof} tool. +@end enumerate + +The following sections detail the different steps, and indicate how +to interpret the results. + +@menu +* Compilation for profiling:: +* Program execution:: +* Running gprof:: +* Interpretation of profiling results:: + +@end menu + +@node Compilation for profiling,Program execution,,Profiling an Ada Program with gprof +@anchor{gnat_ugn/gnat_and_program_execution id24}@anchor{21f}@anchor{gnat_ugn/gnat_and_program_execution compilation-for-profiling}@anchor{220} +@subsubsection Compilation for profiling + + +@geindex -pg (gcc) +@geindex for profiling + +@geindex -pg (gnatlink) +@geindex for profiling + +In order to profile a program the first step is to tell the compiler +to generate the necessary profiling information. The compiler switch to be used +is @code{-pg}, which must be added to other compilation switches. This +switch needs to be specified both during compilation and link stages, and can +be specified once when using gnatmake: + +@quotation + +@example +$ gnatmake -f -pg -P my_project +@end example +@end quotation + +Note that only the objects that were compiled with the @code{-pg} switch will +be profiled; if you need to profile your whole project, use the @code{-f} +gnatmake switch to force full recompilation. + +@node Program execution,Running gprof,Compilation for profiling,Profiling an Ada Program with gprof +@anchor{gnat_ugn/gnat_and_program_execution program-execution}@anchor{221}@anchor{gnat_ugn/gnat_and_program_execution id25}@anchor{222} +@subsubsection Program execution + + +Once the program has been compiled for profiling, you can run it as usual. + +The only constraint imposed by profiling is that the program must terminate +normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be +properly analyzed. + +Once the program completes execution, a data file called @code{gmon.out} is +generated in the directory where the program was launched from. If this file +already exists, it will be overwritten. + +@node Running gprof,Interpretation of profiling results,Program execution,Profiling an Ada Program with gprof +@anchor{gnat_ugn/gnat_and_program_execution running-gprof}@anchor{223}@anchor{gnat_ugn/gnat_and_program_execution id26}@anchor{224} +@subsubsection Running gprof + + +The @cite{gprof} tool is called as follow: + +@quotation + +@example +$ gprof my_prog gmon.out +@end example +@end quotation + +or simply: + +@quotation + +@example +$ gprof my_prog +@end example +@end quotation + +The complete form of the gprof command line is the following: + +@quotation + +@example +$ gprof [switches] [executable [data-file]] +@end example +@end quotation + +@cite{gprof} supports numerous switches. The order of these +switch does not matter. The full list of options can be found in +the GNU Profiler User's Guide documentation that comes with this documentation. + +The following is the subset of those switches that is most relevant: + +@geindex --demangle (gprof) + + +@table @asis + +@item @code{--demangle[=@emph{style}]}, @code{--no-demangle} + +These options control whether symbol names should be demangled when +printing output. The default is to demangle C++ symbols. The +@code{--no-demangle} option may be used to turn off demangling. Different +compilers have different mangling styles. The optional demangling style +argument can be used to choose an appropriate demangling style for your +compiler, in particular Ada symbols generated by GNAT can be demangled using +@code{--demangle=gnat}. +@end table + +@geindex -e (gprof) + + +@table @asis + +@item @code{-e @emph{function_name}} + +The @code{-e @emph{function}} option tells @cite{gprof} not to print +information about the function @cite{function_name} (and its +children...) in the call graph. The function will still be listed +as a child of any functions that call it, but its index number will be +shown as @code{[not printed]}. More than one @code{-e} option may be +given; only one @cite{function_name} may be indicated with each @code{-e} +option. +@end table + +@geindex -E (gprof) + + +@table @asis + +@item @code{-E @emph{function_name}} + +The @code{-E @emph{function}} option works like the @code{-e} option, but +execution time spent in the function (and children who were not called from +anywhere else), will not be used to compute the percentages-of-time for +the call graph. More than one @code{-E} option may be given; only one +@cite{function_name} may be indicated with each @code{-E} option. +@end table + +@geindex -f (gprof) + + +@table @asis + +@item @code{-f @emph{function_name}} + +The @code{-f @emph{function}} option causes @cite{gprof} to limit the +call graph to the function @cite{function_name} and its children (and +their children...). More than one @code{-f} option may be given; +only one @cite{function_name} may be indicated with each @code{-f} +option. +@end table + +@geindex -F (gprof) + + +@table @asis + +@item @code{-F @emph{function_name}} + +The @code{-F @emph{function}} option works like the @code{-f} option, but +only time spent in the function and its children (and their +children...) will be used to determine total-time and +percentages-of-time for the call graph. More than one @code{-F} option +may be given; only one @cite{function_name} may be indicated with each +@code{-F} option. The @code{-F} option overrides the @code{-E} option. +@end table + +@node Interpretation of profiling results,,Running gprof,Profiling an Ada Program with gprof +@anchor{gnat_ugn/gnat_and_program_execution id27}@anchor{225}@anchor{gnat_ugn/gnat_and_program_execution interpretation-of-profiling-results}@anchor{226} +@subsubsection Interpretation of profiling results + + +The results of the profiling analysis are represented by two arrays: the +'flat profile' and the 'call graph'. Full documentation of those outputs +can be found in the GNU Profiler User's Guide. + +The flat profile shows the time spent in each function of the program, and how +many time it has been called. This allows you to locate easily the most +time-consuming functions. + +The call graph shows, for each subprogram, the subprograms that call it, +and the subprograms that it calls. It also provides an estimate of the time +spent in each of those callers/called subprograms. + +@node Improving Performance,Overflow Check Handling in GNAT,Code Coverage and Profiling,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution improving-performance}@anchor{28}@anchor{gnat_ugn/gnat_and_program_execution id28}@anchor{1f2} +@section Improving Performance + + +@geindex Improving performance + +This section presents several topics related to program performance. +It first describes some of the tradeoffs that need to be considered +and some of the techniques for making your program run faster. + + +It then documents the unused subprogram/data elimination feature, +which can reduce the size of program executables. + +@menu +* Performance Considerations:: +* Text_IO Suggestions:: +* Reducing Size of Executables with Unused Subprogram/Data Elimination:: + +@end menu + +@node Performance Considerations,Text_IO Suggestions,,Improving Performance +@anchor{gnat_ugn/gnat_and_program_execution id29}@anchor{227}@anchor{gnat_ugn/gnat_and_program_execution performance-considerations}@anchor{228} +@subsection Performance Considerations + + +The GNAT system provides a number of options that allow a trade-off +between + + +@itemize * + +@item +performance of the generated code + +@item +speed of compilation + +@item +minimization of dependences and recompilation + +@item +the degree of run-time checking. +@end itemize + +The defaults (if no options are selected) aim at improving the speed +of compilation and minimizing dependences, at the expense of performance +of the generated code: + + +@itemize * + +@item +no optimization + +@item +no inlining of subprogram calls + +@item +all run-time checks enabled except overflow and elaboration checks +@end itemize + +These options are suitable for most program development purposes. This +section describes how you can modify these choices, and also provides +some guidelines on debugging optimized code. + +@menu +* Controlling Run-Time Checks:: +* Use of Restrictions:: +* Optimization Levels:: +* Debugging Optimized Code:: +* Inlining of Subprograms:: +* Floating_Point_Operations:: +* Vectorization of loops:: +* Other Optimization Switches:: +* Optimization and Strict Aliasing:: +* Aliased Variables and Optimization:: +* Atomic Variables and Optimization:: +* Passive Task Optimization:: + +@end menu + +@node Controlling Run-Time Checks,Use of Restrictions,,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution controlling-run-time-checks}@anchor{229}@anchor{gnat_ugn/gnat_and_program_execution id30}@anchor{22a} +@subsubsection Controlling Run-Time Checks + + +By default, GNAT generates all run-time checks, except integer overflow +checks, stack overflow checks, and checks for access before elaboration on +subprogram calls. The latter are not required in default mode, because all +necessary checking is done at compile time. + +@geindex -gnatp (gcc) + +@geindex -gnato (gcc) + +Two gnat switches, @emph{-gnatp} and @emph{-gnato} allow this default to +be modified. See @ref{fe,,Run-Time Checks}. + +Our experience is that the default is suitable for most development +purposes. + +We treat integer overflow specially because these +are quite expensive and in our experience are not as important as other +run-time checks in the development process. Note that division by zero +is not considered an overflow check, and divide by zero checks are +generated where required by default. + +Elaboration checks are off by default, and also not needed by default, since +GNAT uses a static elaboration analysis approach that avoids the need for +run-time checking. This manual contains a full chapter discussing the issue +of elaboration checks, and if the default is not satisfactory for your use, +you should read this chapter. + +For validity checks, the minimal checks required by the Ada Reference +Manual (for case statements and assignments to array elements) are on +by default. These can be suppressed by use of the @emph{-gnatVn} switch. +Note that in Ada 83, there were no validity checks, so if the Ada 83 mode +is acceptable (or when comparing GNAT performance with an Ada 83 compiler), +it may be reasonable to routinely use @emph{-gnatVn}. Validity checks +are also suppressed entirely if @emph{-gnatp} is used. + +@geindex Overflow checks + +@geindex Checks +@geindex overflow + +@geindex Suppress + +@geindex Unsuppress + +@geindex pragma Suppress + +@geindex pragma Unsuppress + +Note that the setting of the switches controls the default setting of +the checks. They may be modified using either @cite{pragma Suppress} (to +remove checks) or @cite{pragma Unsuppress} (to add back suppressed +checks) in the program source. + +@node Use of Restrictions,Optimization Levels,Controlling Run-Time Checks,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution use-of-restrictions}@anchor{22b}@anchor{gnat_ugn/gnat_and_program_execution id31}@anchor{22c} +@subsubsection Use of Restrictions + + +The use of pragma Restrictions allows you to control which features are +permitted in your program. Apart from the obvious point that if you avoid +relatively expensive features like finalization (enforceable by the use +of pragma Restrictions (No_Finalization), the use of this pragma does not +affect the generated code in most cases. + +One notable exception to this rule is that the possibility of task abort +results in some distributed overhead, particularly if finalization or +exception handlers are used. The reason is that certain sections of code +have to be marked as non-abortable. + +If you use neither the @cite{abort} statement, nor asynchronous transfer +of control (@cite{select ... then abort}), then this distributed overhead +is removed, which may have a general positive effect in improving +overall performance. Especially code involving frequent use of tasking +constructs and controlled types will show much improved performance. +The relevant restrictions pragmas are + +@quotation + +@example +pragma Restrictions (No_Abort_Statements); +pragma Restrictions (Max_Asynchronous_Select_Nesting => 0); +@end example +@end quotation + +It is recommended that these restriction pragmas be used if possible. Note +that this also means that you can write code without worrying about the +possibility of an immediate abort at any point. + +@node Optimization Levels,Debugging Optimized Code,Use of Restrictions,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id32}@anchor{22d}@anchor{gnat_ugn/gnat_and_program_execution optimization-levels}@anchor{101} +@subsubsection Optimization Levels + + +@geindex -O (gcc) + +Without any optimization option, +the compiler's goal is to reduce the cost of +compilation and to make debugging produce the expected results. +Statements are independent: if you stop the program with a breakpoint between +statements, you can then assign a new value to any variable or change +the program counter to any other statement in the subprogram and get exactly +the results you would expect from the source code. + +Turning on optimization makes the compiler attempt to improve the +performance and/or code size at the expense of compilation time and +possibly the ability to debug the program. + +If you use multiple +-O options, with or without level numbers, +the last such option is the one that is effective. + +The default is optimization off. This results in the fastest compile +times, but GNAT makes absolutely no attempt to optimize, and the +generated programs are considerably larger and slower than when +optimization is enabled. You can use the +@emph{-O} switch (the permitted forms are @emph{-O0}, @emph{-O1} +@emph{-O2}, @emph{-O3}, and @emph{-Os}) +to @emph{gcc} to control the optimization level: + + +@itemize * + +@item + +@table @asis + +@item @emph{-O0} + +No optimization (the default); +generates unoptimized code but has +the fastest compilation time. + +Note that many other compilers do fairly extensive optimization +even if 'no optimization' is specified. With gcc, it is +very unusual to use -O0 for production if +execution time is of any concern, since -O0 +really does mean no optimization at all. This difference between +gcc and other compilers should be kept in mind when doing +performance comparisons. +@end table + +@item + +@table @asis + +@item @emph{-O1} + +Moderate optimization; +optimizes reasonably well but does not +degrade compilation time significantly. +@end table + +@item + +@table @asis + +@item @emph{-O2} + +Full optimization; +generates highly optimized code and has +the slowest compilation time. +@end table + +@item + +@table @asis + +@item @emph{-O3} + +Full optimization as in @emph{-O2}; +also uses more aggressive automatic inlining of subprograms within a unit +(@ref{114,,Inlining of Subprograms}) and attempts to vectorize loops. +@end table + +@item + +@table @asis + +@item @emph{-Os} + +Optimize space usage (code and data) of resulting program. +@end table +@end itemize + +Higher optimization levels perform more global transformations on the +program and apply more expensive analysis algorithms in order to generate +faster and more compact code. The price in compilation time, and the +resulting improvement in execution time, +both depend on the particular application and the hardware environment. +You should experiment to find the best level for your application. + +Since the precise set of optimizations done at each level will vary from +release to release (and sometime from target to target), it is best to think +of the optimization settings in general terms. +See the @emph{Options That Control Optimization} section in +@cite{Using the GNU Compiler Collection (GCC)} +for details about +the @emph{-O} settings and a number of @emph{-f} options that +individually enable or disable specific optimizations. + +Unlike some other compilation systems, @emph{gcc} has +been tested extensively at all optimization levels. There are some bugs +which appear only with optimization turned on, but there have also been +bugs which show up only in @emph{unoptimized} code. Selecting a lower +level of optimization does not improve the reliability of the code +generator, which in practice is highly reliable at all optimization +levels. + +Note regarding the use of @emph{-O3}: The use of this optimization level +is generally discouraged with GNAT, since it often results in larger +executables which may run more slowly. See further discussion of this point +in @ref{114,,Inlining of Subprograms}. + +@node Debugging Optimized Code,Inlining of Subprograms,Optimization Levels,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id33}@anchor{22e}@anchor{gnat_ugn/gnat_and_program_execution debugging-optimized-code}@anchor{22f} +@subsubsection Debugging Optimized Code + + +@geindex Debugging optimized code + +@geindex Optimization and debugging + +Although it is possible to do a reasonable amount of debugging at +nonzero optimization levels, +the higher the level the more likely that +source-level constructs will have been eliminated by optimization. +For example, if a loop is strength-reduced, the loop +control variable may be completely eliminated and thus cannot be +displayed in the debugger. +This can only happen at @emph{-O2} or @emph{-O3}. +Explicit temporary variables that you code might be eliminated at +level @emph{-O1} or higher. + +@geindex -g (gcc) + +The use of the @emph{-g} switch, +which is needed for source-level debugging, +affects the size of the program executable on disk, +and indeed the debugging information can be quite large. +However, it has no effect on the generated code (and thus does not +degrade performance) + +Since the compiler generates debugging tables for a compilation unit before +it performs optimizations, the optimizing transformations may invalidate some +of the debugging data. You therefore need to anticipate certain +anomalous situations that may arise while debugging optimized code. +These are the most common cases: + + +@itemize * + +@item +@emph{The 'hopping Program Counter':} Repeated @cite{step} or @cite{next} +commands show +the PC bouncing back and forth in the code. This may result from any of +the following optimizations: + + +@itemize - + +@item +@emph{Common subexpression elimination:} using a single instance of code for a +quantity that the source computes several times. As a result you +may not be able to stop on what looks like a statement. + +@item +@emph{Invariant code motion:} moving an expression that does not change within a +loop, to the beginning of the loop. + +@item +@emph{Instruction scheduling:} moving instructions so as to +overlap loads and stores (typically) with other code, or in +general to move computations of values closer to their uses. Often +this causes you to pass an assignment statement without the assignment +happening and then later bounce back to the statement when the +value is actually needed. Placing a breakpoint on a line of code +and then stepping over it may, therefore, not always cause all the +expected side-effects. +@end itemize + +@item +@emph{The 'big leap':} More commonly known as @emph{cross-jumping}, in which +two identical pieces of code are merged and the program counter suddenly +jumps to a statement that is not supposed to be executed, simply because +it (and the code following) translates to the same thing as the code +that @emph{was} supposed to be executed. This effect is typically seen in +sequences that end in a jump, such as a @cite{goto}, a @cite{return}, or +a @cite{break} in a C @cite{switch} statement. + +@item +@emph{The 'roving variable':} The symptom is an unexpected value in a variable. +There are various reasons for this effect: + + +@itemize - + +@item +In a subprogram prologue, a parameter may not yet have been moved to its +'home'. + +@item +A variable may be dead, and its register re-used. This is +probably the most common cause. + +@item +As mentioned above, the assignment of a value to a variable may +have been moved. + +@item +A variable may be eliminated entirely by value propagation or +other means. In this case, GCC may incorrectly generate debugging +information for the variable +@end itemize + +In general, when an unexpected value appears for a local variable or parameter +you should first ascertain if that value was actually computed by +your program, as opposed to being incorrectly reported by the debugger. +Record fields or +array elements in an object designated by an access value +are generally less of a problem, once you have ascertained that the access +value is sensible. +Typically, this means checking variables in the preceding code and in the +calling subprogram to verify that the value observed is explainable from other +values (one must apply the procedure recursively to those +other values); or re-running the code and stopping a little earlier +(perhaps before the call) and stepping to better see how the variable obtained +the value in question; or continuing to step @emph{from} the point of the +strange value to see if code motion had simply moved the variable's +assignments later. +@end itemize + +In light of such anomalies, a recommended technique is to use @emph{-O0} +early in the software development cycle, when extensive debugging capabilities +are most needed, and then move to @emph{-O1} and later @emph{-O2} as +the debugger becomes less critical. +Whether to use the @emph{-g} switch in the release version is +a release management issue. +Note that if you use @emph{-g} you can then use the @emph{strip} program +on the resulting executable, +which removes both debugging information and global symbols. + +@node Inlining of Subprograms,Floating_Point_Operations,Debugging Optimized Code,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id34}@anchor{230}@anchor{gnat_ugn/gnat_and_program_execution inlining-of-subprograms}@anchor{114} +@subsubsection Inlining of Subprograms + + +A call to a subprogram in the current unit is inlined if all the +following conditions are met: + + +@itemize * + +@item +The optimization level is at least @emph{-O1}. + +@item +The called subprogram is suitable for inlining: It must be small enough +and not contain something that @emph{gcc} cannot support in inlined +subprograms. + +@geindex pragma Inline + +@geindex Inline + +@item +Any one of the following applies: @cite{pragma Inline} is applied to the +subprogram and the @emph{-gnatn} switch is specified; the +subprogram is local to the unit and called once from within it; the +subprogram is small and optimization level @emph{-O2} is specified; +optimization level @emph{-O3} is specified. +@end itemize + +Calls to subprograms in @emph{with}ed units are normally not inlined. +To achieve actual inlining (that is, replacement of the call by the code +in the body of the subprogram), the following conditions must all be true: + + +@itemize * + +@item +The optimization level is at least @emph{-O1}. + +@item +The called subprogram is suitable for inlining: It must be small enough +and not contain something that @emph{gcc} cannot support in inlined +subprograms. + +@item +The call appears in a body (not in a package spec). + +@item +There is a @cite{pragma Inline} for the subprogram. + +@item +The @emph{-gnatn} switch is used on the command line. +@end itemize + +Even if all these conditions are met, it may not be possible for +the compiler to inline the call, due to the length of the body, +or features in the body that make it impossible for the compiler +to do the inlining. + +Note that specifying the @emph{-gnatn} switch causes additional +compilation dependencies. Consider the following: + +@quotation + +@example +package R is + procedure Q; + pragma Inline (Q); +end R; +package body R is + ... +end R; + +with R; +procedure Main is +begin + ... + R.Q; +end Main; +@end example +@end quotation + +With the default behavior (no @emph{-gnatn} switch specified), the +compilation of the @cite{Main} procedure depends only on its own source, +@code{main.adb}, and the spec of the package in file @code{r.ads}. This +means that editing the body of @cite{R} does not require recompiling +@cite{Main}. + +On the other hand, the call @cite{R.Q} is not inlined under these +circumstances. If the @emph{-gnatn} switch is present when @cite{Main} +is compiled, the call will be inlined if the body of @cite{Q} is small +enough, but now @cite{Main} depends on the body of @cite{R} in +@code{r.adb} as well as on the spec. This means that if this body is edited, +the main program must be recompiled. Note that this extra dependency +occurs whether or not the call is in fact inlined by @emph{gcc}. + +The use of front end inlining with @emph{-gnatN} generates similar +additional dependencies. + +@geindex -fno-inline (gcc) + +Note: The @emph{-fno-inline} switch overrides all other conditions and ensures that +no inlining occurs, unless requested with pragma Inline_Always for gcc +back-ends. The extra dependences resulting from @emph{-gnatn} will still be active, +even if this switch is used to suppress the resulting inlining actions. + +@geindex -fno-inline-functions (gcc) + +Note: The @emph{-fno-inline-functions} switch can be used to prevent +automatic inlining of subprograms if @emph{-O3} is used. + +@geindex -fno-inline-small-functions (gcc) + +Note: The @emph{-fno-inline-small-functions} switch can be used to prevent +automatic inlining of small subprograms if @emph{-O2} is used. + +@geindex -fno-inline-functions-called-once (gcc) + +Note: The @emph{-fno-inline-functions-called-once} switch +can be used to prevent inlining of subprograms local to the unit +and called once from within it if @emph{-O1} is used. + +Note regarding the use of @emph{-O3}: @emph{-gnatn} is made up of two +sub-switches @emph{-gnatn1} and @emph{-gnatn2} that can be directly +specified in lieu of it, @emph{-gnatn} being translated into one of them +based on the optimization level. With @emph{-O2} or below, @emph{-gnatn} +is equivalent to @emph{-gnatn1} which activates pragma @cite{Inline} with +moderate inlining across modules. With @emph{-O3}, @emph{-gnatn} is +equivalent to @emph{-gnatn2} which activates pragma @cite{Inline} with +full inlining across modules. If you have used pragma @cite{Inline} in +appropriate cases, then it is usually much better to use @emph{-O2} +and @emph{-gnatn} and avoid the use of @emph{-O3} which has the additional +effect of inlining subprograms you did not think should be inlined. We have +found that the use of @emph{-O3} may slow down the compilation and increase +the code size by performing excessive inlining, leading to increased +instruction cache pressure from the increased code size and thus minor +performance improvements. So the bottom line here is that you should not +automatically assume that @emph{-O3} is better than @emph{-O2}, and +indeed you should use @emph{-O3} only if tests show that it actually +improves performance for your program. + +@node Floating_Point_Operations,Vectorization of loops,Inlining of Subprograms,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution floating-point-operations}@anchor{231}@anchor{gnat_ugn/gnat_and_program_execution id35}@anchor{232} +@subsubsection Floating_Point_Operations + + +@geindex Floating-Point Operations + +On almost all targets, GNAT maps Float and Long_Float to the 32-bit and +64-bit standard IEEE floating-point representations, and operations will +use standard IEEE arithmetic as provided by the processor. On most, but +not all, architectures, the attribute Machine_Overflows is False for these +types, meaning that the semantics of overflow is implementation-defined. +In the case of GNAT, these semantics correspond to the normal IEEE +treatment of infinities and NaN (not a number) values. For example, +1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By +avoiding explicit overflow checks, the performance is greatly improved +on many targets. However, if required, floating-point overflow can be +enabled by the use of the pragma Check_Float_Overflow. + +Another consideration that applies specifically to x86 32-bit +architectures is which form of floating-point arithmetic is used. +By default the operations use the old style x86 floating-point, +which implements an 80-bit extended precision form (on these +architectures the type Long_Long_Float corresponds to that form). +In addition, generation of efficient code in this mode means that +the extended precision form will be used for intermediate results. +This may be helpful in improving the final precision of a complex +expression. However it means that the results obtained on the x86 +will be different from those on other architectures, and for some +algorithms, the extra intermediate precision can be detrimental. + +In addition to this old-style floating-point, all modern x86 chips +implement an alternative floating-point operation model referred +to as SSE2. In this model there is no extended form, and furthermore +execution performance is significantly enhanced. To force GNAT to use +this more modern form, use both of the switches: + +@quotation + +-msse2 -mfpmath=sse +@end quotation + +A unit compiled with these switches will automatically use the more +efficient SSE2 instruction set for Float and Long_Float operations. +Note that the ABI has the same form for both floating-point models, +so it is permissible to mix units compiled with and without these +switches. + +@node Vectorization of loops,Other Optimization Switches,Floating_Point_Operations,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id36}@anchor{233}@anchor{gnat_ugn/gnat_and_program_execution vectorization-of-loops}@anchor{234} +@subsubsection Vectorization of loops + + +@geindex Optimization Switches + +You can take advantage of the auto-vectorizer present in the @emph{gcc} +back end to vectorize loops with GNAT. The corresponding command line switch +is @emph{-ftree-vectorize} but, as it is enabled by default at @emph{-O3} +and other aggressive optimizations helpful for vectorization also are enabled +by default at this level, using @emph{-O3} directly is recommended. + +You also need to make sure that the target architecture features a supported +SIMD instruction set. For example, for the x86 architecture, you should at +least specify @emph{-msse2} to get significant vectorization (but you don't +need to specify it for x86-64 as it is part of the base 64-bit architecture). +Similarly, for the PowerPC architecture, you should specify @emph{-maltivec}. + +The preferred loop form for vectorization is the @cite{for} iteration scheme. +Loops with a @cite{while} iteration scheme can also be vectorized if they are +very simple, but the vectorizer will quickly give up otherwise. With either +iteration scheme, the flow of control must be straight, in particular no +@cite{exit} statement may appear in the loop body. The loop may however +contain a single nested loop, if it can be vectorized when considered alone: + +@quotation + +@example +A : array (1..4, 1..4) of Long_Float; +S : array (1..4) of Long_Float; + +procedure Sum is +begin + for I in A'Range(1) loop + for J in A'Range(2) loop + S (I) := S (I) + A (I, J); + end loop; + end loop; +end Sum; +@end example +@end quotation + +The vectorizable operations depend on the targeted SIMD instruction set, but +the adding and some of the multiplying operators are generally supported, as +well as the logical operators for modular types. Note that, in the former +case, enabling overflow checks, for example with @emph{-gnato}, totally +disables vectorization. The other checks are not supposed to have the same +definitive effect, although compiling with @emph{-gnatp} might well reveal +cases where some checks do thwart vectorization. + +Type conversions may also prevent vectorization if they involve semantics that +are not directly supported by the code generator or the SIMD instruction set. +A typical example is direct conversion from floating-point to integer types. +The solution in this case is to use the following idiom: + +@quotation + +@example +Integer (S'Truncation (F)) +@end example +@end quotation + +if @cite{S} is the subtype of floating-point object @cite{F}. + +In most cases, the vectorizable loops are loops that iterate over arrays. +All kinds of array types are supported, i.e. constrained array types with +static bounds: + +@quotation + +@example +type Array_Type is array (1 .. 4) of Long_Float; +@end example +@end quotation + +constrained array types with dynamic bounds: + +@quotation + +@example +type Array_Type is array (1 .. Q.N) of Long_Float; + +type Array_Type is array (Q.K .. 4) of Long_Float; + +type Array_Type is array (Q.K .. Q.N) of Long_Float; +@end example +@end quotation + +or unconstrained array types: + +@quotation + +@example +type Array_Type is array (Positive range <>) of Long_Float; +@end example +@end quotation + +The quality of the generated code decreases when the dynamic aspect of the +array type increases, the worst code being generated for unconstrained array +types. This is so because, the less information the compiler has about the +bounds of the array, the more fallback code it needs to generate in order to +fix things up at run time. + +It is possible to specify that a given loop should be subject to vectorization +preferably to other optimizations by means of pragma @cite{Loop_Optimize}: + +@quotation + +@example +pragma Loop_Optimize (Vector); +@end example +@end quotation + +placed immediately within the loop will convey the appropriate hint to the +compiler for this loop. + +It is also possible to help the compiler generate better vectorized code +for a given loop by asserting that there are no loop-carried dependencies +in the loop. Consider for example the procedure: + +@quotation + +@example +type Arr is array (1 .. 4) of Long_Float; + +procedure Add (X, Y : not null access Arr; R : not null access Arr) is +begin + for I in Arr'Range loop + R(I) := X(I) + Y(I); + end loop; +end; +@end example +@end quotation + +By default, the compiler cannot unconditionally vectorize the loop because +assigning to a component of the array designated by R in one iteration could +change the value read from the components of the array designated by X or Y +in a later iteration. As a result, the compiler will generate two versions +of the loop in the object code, one vectorized and the other not vectorized, +as well as a test to select the appropriate version at run time. This can +be overcome by another hint: + +@quotation + +@example +pragma Loop_Optimize (Ivdep); +@end example +@end quotation + +placed immediately within the loop will tell the compiler that it can safely +omit the non-vectorized version of the loop as well as the run-time test. + +@node Other Optimization Switches,Optimization and Strict Aliasing,Vectorization of loops,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id37}@anchor{235}@anchor{gnat_ugn/gnat_and_program_execution other-optimization-switches}@anchor{236} +@subsubsection Other Optimization Switches + + +@geindex Optimization Switches + +Since @cite{GNAT} uses the @emph{gcc} back end, all the specialized +@emph{gcc} optimization switches are potentially usable. These switches +have not been extensively tested with GNAT but can generally be expected +to work. Examples of switches in this category are @emph{-funroll-loops} +and the various target-specific @emph{-m} options (in particular, it has +been observed that @emph{-march=xxx} can significantly improve performance +on appropriate machines). For full details of these switches, see +the @cite{Submodel Options} section in the @cite{Hardware Models and Configurations} +chapter of @cite{Using the GNU Compiler Collection (GCC)}. + +@node Optimization and Strict Aliasing,Aliased Variables and Optimization,Other Optimization Switches,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution optimization-and-strict-aliasing}@anchor{f8}@anchor{gnat_ugn/gnat_and_program_execution id38}@anchor{237} +@subsubsection Optimization and Strict Aliasing + + +@geindex Aliasing + +@geindex Strict Aliasing + +@geindex No_Strict_Aliasing + +The strong typing capabilities of Ada allow an optimizer to generate +efficient code in situations where other languages would be forced to +make worst case assumptions preventing such optimizations. Consider +the following example: + +@quotation + +@example +procedure R is + type Int1 is new Integer; + type Int2 is new Integer; + type Int1A is access Int1; + type Int2A is access Int2; + Int1V : Int1A; + Int2V : Int2A; + ... + +begin + ... + for J in Data'Range loop + if Data (J) = Int1V.all then + Int2V.all := Int2V.all + 1; + end if; + end loop; + ... +end R; +@end example +@end quotation + +In this example, since the variable @cite{Int1V} can only access objects +of type @cite{Int1}, and @cite{Int2V} can only access objects of type +@cite{Int2}, there is no possibility that the assignment to +@cite{Int2V.all} affects the value of @cite{Int1V.all}. This means that +the compiler optimizer can "know" that the value @cite{Int1V.all} is constant +for all iterations of the loop and avoid the extra memory reference +required to dereference it each time through the loop. + +This kind of optimization, called strict aliasing analysis, is +triggered by specifying an optimization level of @emph{-O2} or +higher or @emph{-Os} and allows @cite{GNAT} to generate more efficient code +when access values are involved. + +However, although this optimization is always correct in terms of +the formal semantics of the Ada Reference Manual, difficulties can +arise if features like @cite{Unchecked_Conversion} are used to break +the typing system. Consider the following complete program example: + +@quotation + +@example +package p1 is + type int1 is new integer; + type int2 is new integer; + type a1 is access int1; + type a2 is access int2; +end p1; + +with p1; use p1; +package p2 is + function to_a2 (Input : a1) return a2; +end p2; + +with Unchecked_Conversion; +package body p2 is + function to_a2 (Input : a1) return a2 is + function to_a2u is + new Unchecked_Conversion (a1, a2); + begin + return to_a2u (Input); + end to_a2; +end p2; + +with p2; use p2; +with p1; use p1; +with Text_IO; use Text_IO; +procedure m is + v1 : a1 := new int1; + v2 : a2 := to_a2 (v1); +begin + v1.all := 1; + v2.all := 0; + put_line (int1'image (v1.all)); +end; +@end example +@end quotation + +This program prints out 0 in @emph{-O0} or @emph{-O1} +mode, but it prints out 1 in @emph{-O2} mode. That's +because in strict aliasing mode, the compiler can and +does assume that the assignment to @cite{v2.all} could not +affect the value of @cite{v1.all}, since different types +are involved. + +This behavior is not a case of non-conformance with the standard, since +the Ada RM specifies that an unchecked conversion where the resulting +bit pattern is not a correct value of the target type can result in an +abnormal value and attempting to reference an abnormal value makes the +execution of a program erroneous. That's the case here since the result +does not point to an object of type @cite{int2}. This means that the +effect is entirely unpredictable. + +However, although that explanation may satisfy a language +lawyer, in practice an applications programmer expects an +unchecked conversion involving pointers to create true +aliases and the behavior of printing 1 seems plain wrong. +In this case, the strict aliasing optimization is unwelcome. + +Indeed the compiler recognizes this possibility, and the +unchecked conversion generates a warning: + +@quotation + +@example +p2.adb:5:07: warning: possible aliasing problem with type "a2" +p2.adb:5:07: warning: use -fno-strict-aliasing switch for references +p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);" +@end example +@end quotation + +Unfortunately the problem is recognized when compiling the body of +package @cite{p2}, but the actual "bad" code is generated while +compiling the body of @cite{m} and this latter compilation does not see +the suspicious @cite{Unchecked_Conversion}. + +As implied by the warning message, there are approaches you can use to +avoid the unwanted strict aliasing optimization in a case like this. + +One possibility is to simply avoid the use of @emph{-O2}, but +that is a bit drastic, since it throws away a number of useful +optimizations that do not involve strict aliasing assumptions. + +A less drastic approach is to compile the program using the +option @emph{-fno-strict-aliasing}. Actually it is only the +unit containing the dereferencing of the suspicious pointer +that needs to be compiled. So in this case, if we compile +unit @cite{m} with this switch, then we get the expected +value of zero printed. Analyzing which units might need +the switch can be painful, so a more reasonable approach +is to compile the entire program with options @emph{-O2} +and @emph{-fno-strict-aliasing}. If the performance is +satisfactory with this combination of options, then the +advantage is that the entire issue of possible "wrong" +optimization due to strict aliasing is avoided. + +To avoid the use of compiler switches, the configuration +pragma @cite{No_Strict_Aliasing} with no parameters may be +used to specify that for all access types, the strict +aliasing optimization should be suppressed. + +However, these approaches are still overkill, in that they causes +all manipulations of all access values to be deoptimized. A more +refined approach is to concentrate attention on the specific +access type identified as problematic. + +First, if a careful analysis of uses of the pointer shows +that there are no possible problematic references, then +the warning can be suppressed by bracketing the +instantiation of @cite{Unchecked_Conversion} to turn +the warning off: + +@quotation + +@example +pragma Warnings (Off); +function to_a2u is + new Unchecked_Conversion (a1, a2); +pragma Warnings (On); +@end example +@end quotation + +Of course that approach is not appropriate for this particular +example, since indeed there is a problematic reference. In this +case we can take one of two other approaches. + +The first possibility is to move the instantiation of unchecked +conversion to the unit in which the type is declared. In +this example, we would move the instantiation of +@cite{Unchecked_Conversion} from the body of package +@cite{p2} to the spec of package @cite{p1}. Now the +warning disappears. That's because any use of the +access type knows there is a suspicious unchecked +conversion, and the strict aliasing optimization +is automatically suppressed for the type. + +If it is not practical to move the unchecked conversion to the same unit +in which the destination access type is declared (perhaps because the +source type is not visible in that unit), you may use pragma +@cite{No_Strict_Aliasing} for the type. This pragma must occur in the +same declarative sequence as the declaration of the access type: + +@quotation + +@example +type a2 is access int2; +pragma No_Strict_Aliasing (a2); +@end example +@end quotation + +Here again, the compiler now knows that the strict aliasing optimization +should be suppressed for any reference to type @cite{a2} and the +expected behavior is obtained. + +Finally, note that although the compiler can generate warnings for +simple cases of unchecked conversions, there are tricker and more +indirect ways of creating type incorrect aliases which the compiler +cannot detect. Examples are the use of address overlays and unchecked +conversions involving composite types containing access types as +components. In such cases, no warnings are generated, but there can +still be aliasing problems. One safe coding practice is to forbid the +use of address clauses for type overlaying, and to allow unchecked +conversion only for primitive types. This is not really a significant +restriction since any possible desired effect can be achieved by +unchecked conversion of access values. + +The aliasing analysis done in strict aliasing mode can certainly +have significant benefits. We have seen cases of large scale +application code where the time is increased by up to 5% by turning +this optimization off. If you have code that includes significant +usage of unchecked conversion, you might want to just stick with +@emph{-O1} and avoid the entire issue. If you get adequate +performance at this level of optimization level, that's probably +the safest approach. If tests show that you really need higher +levels of optimization, then you can experiment with @emph{-O2} +and @emph{-O2 -fno-strict-aliasing} to see how much effect this +has on size and speed of the code. If you really need to use +@emph{-O2} with strict aliasing in effect, then you should +review any uses of unchecked conversion of access types, +particularly if you are getting the warnings described above. + +@node Aliased Variables and Optimization,Atomic Variables and Optimization,Optimization and Strict Aliasing,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution aliased-variables-and-optimization}@anchor{238}@anchor{gnat_ugn/gnat_and_program_execution id39}@anchor{239} +@subsubsection Aliased Variables and Optimization + + +@geindex Aliasing + +There are scenarios in which programs may +use low level techniques to modify variables +that otherwise might be considered to be unassigned. For example, +a variable can be passed to a procedure by reference, which takes +the address of the parameter and uses the address to modify the +variable's value, even though it is passed as an IN parameter. +Consider the following example: + +@quotation + +@example +procedure P is + Max_Length : constant Natural := 16; + type Char_Ptr is access all Character; + + procedure Get_String(Buffer: Char_Ptr; Size : Integer); + pragma Import (C, Get_String, "get_string"); + + Name : aliased String (1 .. Max_Length) := (others => ' '); + Temp : Char_Ptr; + + function Addr (S : String) return Char_Ptr is + function To_Char_Ptr is + new Ada.Unchecked_Conversion (System.Address, Char_Ptr); + begin + return To_Char_Ptr (S (S'First)'Address); + end; + +begin + Temp := Addr (Name); + Get_String (Temp, Max_Length); +end; +@end example +@end quotation + +where Get_String is a C function that uses the address in Temp to +modify the variable @cite{Name}. This code is dubious, and arguably +erroneous, and the compiler would be entitled to assume that +@cite{Name} is never modified, and generate code accordingly. + +However, in practice, this would cause some existing code that +seems to work with no optimization to start failing at high +levels of optimzization. + +What the compiler does for such cases is to assume that marking +a variable as aliased indicates that some "funny business" may +be going on. The optimizer recognizes the aliased keyword and +inhibits optimizations that assume the value cannot be assigned. +This means that the above example will in fact "work" reliably, +that is, it will produce the expected results. + +@node Atomic Variables and Optimization,Passive Task Optimization,Aliased Variables and Optimization,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution atomic-variables-and-optimization}@anchor{23a}@anchor{gnat_ugn/gnat_and_program_execution id40}@anchor{23b} +@subsubsection Atomic Variables and Optimization + + +@geindex Atomic + +There are two considerations with regard to performance when +atomic variables are used. + +First, the RM only guarantees that access to atomic variables +be atomic, it has nothing to say about how this is achieved, +though there is a strong implication that this should not be +achieved by explicit locking code. Indeed GNAT will never +generate any locking code for atomic variable access (it will +simply reject any attempt to make a variable or type atomic +if the atomic access cannot be achieved without such locking code). + +That being said, it is important to understand that you cannot +assume that the entire variable will always be accessed. Consider +this example: + +@quotation + +@example +type R is record + A,B,C,D : Character; +end record; +for R'Size use 32; +for R'Alignment use 4; + +RV : R; +pragma Atomic (RV); +X : Character; +... +X := RV.B; +@end example +@end quotation + +You cannot assume that the reference to @cite{RV.B} +will read the entire 32-bit +variable with a single load instruction. It is perfectly legitimate if +the hardware allows it to do a byte read of just the B field. This read +is still atomic, which is all the RM requires. GNAT can and does take +advantage of this, depending on the architecture and optimization level. +Any assumption to the contrary is non-portable and risky. Even if you +examine the assembly language and see a full 32-bit load, this might +change in a future version of the compiler. + +If your application requires that all accesses to @cite{RV} in this +example be full 32-bit loads, you need to make a copy for the access +as in: + +@quotation + +@example +declare + RV_Copy : constant R := RV; +begin + X := RV_Copy.B; +end; +@end example +@end quotation + +Now the reference to RV must read the whole variable. +Actually one can imagine some compiler which figures +out that the whole copy is not required (because only +the B field is actually accessed), but GNAT +certainly won't do that, and we don't know of any +compiler that would not handle this right, and the +above code will in practice work portably across +all architectures (that permit the Atomic declaration). + +The second issue with atomic variables has to do with +the possible requirement of generating synchronization +code. For more details on this, consult the sections on +the pragmas Enable/Disable_Atomic_Synchronization in the +GNAT Reference Manual. If performance is critical, and +such synchronization code is not required, it may be +useful to disable it. + +@node Passive Task Optimization,,Atomic Variables and Optimization,Performance Considerations +@anchor{gnat_ugn/gnat_and_program_execution id41}@anchor{23c}@anchor{gnat_ugn/gnat_and_program_execution passive-task-optimization}@anchor{23d} +@subsubsection Passive Task Optimization + + +@geindex Passive Task + +A passive task is one which is sufficiently simple that +in theory a compiler could recognize it an implement it +efficiently without creating a new thread. The original design +of Ada 83 had in mind this kind of passive task optimization, but +only a few Ada 83 compilers attempted it. The problem was that +it was difficult to determine the exact conditions under which +the optimization was possible. The result is a very fragile +optimization where a very minor change in the program can +suddenly silently make a task non-optimizable. + +With the revisiting of this issue in Ada 95, there was general +agreement that this approach was fundamentally flawed, and the +notion of protected types was introduced. When using protected +types, the restrictions are well defined, and you KNOW that the +operations will be optimized, and furthermore this optimized +performance is fully portable. + +Although it would theoretically be possible for GNAT to attempt to +do this optimization, but it really doesn't make sense in the +context of Ada 95, and none of the Ada 95 compilers implement +this optimization as far as we know. In particular GNAT never +attempts to perform this optimization. + +In any new Ada 95 code that is written, you should always +use protected types in place of tasks that might be able to +be optimized in this manner. +Of course this does not help if you have legacy Ada 83 code +that depends on this optimization, but it is unusual to encounter +a case where the performance gains from this optimization +are significant. + +Your program should work correctly without this optimization. If +you have performance problems, then the most practical +approach is to figure out exactly where these performance problems +arise, and update those particular tasks to be protected types. Note +that typically clients of the tasks who call entries, will not have +to be modified, only the task definition itself. + +@node Text_IO Suggestions,Reducing Size of Executables with Unused Subprogram/Data Elimination,Performance Considerations,Improving Performance +@anchor{gnat_ugn/gnat_and_program_execution text-io-suggestions}@anchor{23e}@anchor{gnat_ugn/gnat_and_program_execution id42}@anchor{23f} +@subsection @cite{Text_IO} Suggestions + + +@geindex Text_IO and performance + +The @cite{Ada.Text_IO} package has fairly high overheads due in part to +the requirement of maintaining page and line counts. If performance +is critical, a recommendation is to use @cite{Stream_IO} instead of +@cite{Text_IO} for volume output, since this package has less overhead. + +If @cite{Text_IO} must be used, note that by default output to the standard +output and standard error files is unbuffered (this provides better +behavior when output statements are used for debugging, or if the +progress of a program is observed by tracking the output, e.g. by +using the Unix @emph{tail -f} command to watch redirected output. + +If you are generating large volumes of output with @cite{Text_IO} and +performance is an important factor, use a designated file instead +of the standard output file, or change the standard output file to +be buffered using @cite{Interfaces.C_Streams.setvbuf}. + +@node Reducing Size of Executables with Unused Subprogram/Data Elimination,,Text_IO Suggestions,Improving Performance +@anchor{gnat_ugn/gnat_and_program_execution id43}@anchor{240}@anchor{gnat_ugn/gnat_and_program_execution reducing-size-of-executables-with-unused-subprogram-data-elimination}@anchor{241} +@subsection Reducing Size of Executables with Unused Subprogram/Data Elimination + + +@geindex Uunused subprogram/data elimination + +This section describes how you can eliminate unused subprograms and data from +your executable just by setting options at compilation time. + +@menu +* About unused subprogram/data elimination:: +* Compilation options:: +* Example of unused subprogram/data elimination:: + +@end menu + +@node About unused subprogram/data elimination,Compilation options,,Reducing Size of Executables with Unused Subprogram/Data Elimination +@anchor{gnat_ugn/gnat_and_program_execution id44}@anchor{242}@anchor{gnat_ugn/gnat_and_program_execution about-unused-subprogram-data-elimination}@anchor{243} +@subsubsection About unused subprogram/data elimination + + +By default, an executable contains all code and data of its composing objects +(directly linked or coming from statically linked libraries), even data or code +never used by this executable. + +This feature will allow you to eliminate such unused code from your +executable, making it smaller (in disk and in memory). + +This functionality is available on all Linux platforms except for the IA-64 +architecture and on all cross platforms using the ELF binary file format. +In both cases GNU binutils version 2.16 or later are required to enable it. + +@node Compilation options,Example of unused subprogram/data elimination,About unused subprogram/data elimination,Reducing Size of Executables with Unused Subprogram/Data Elimination +@anchor{gnat_ugn/gnat_and_program_execution id45}@anchor{244}@anchor{gnat_ugn/gnat_and_program_execution compilation-options}@anchor{245} +@subsubsection Compilation options + + +The operation of eliminating the unused code and data from the final executable +is directly performed by the linker. + +@geindex -ffunction-sections (gcc) + +@geindex -fdata-sections (gcc) + +In order to do this, it has to work with objects compiled with the +following options: +@emph{-ffunction-sections} @emph{-fdata-sections}. + +These options are usable with C and Ada files. +They will place respectively each +function or data in a separate section in the resulting object file. + +Once the objects and static libraries are created with these options, the +linker can perform the dead code elimination. You can do this by setting +the @emph{-Wl,--gc-sections} option to gcc command or in the +@emph{-largs} section of @emph{gnatmake}. This will perform a +garbage collection of code and data never referenced. + +If the linker performs a partial link (@emph{-r} linker option), then you +will need to provide the entry point using the @emph{-e} / @emph{--entry} +linker option. + +Note that objects compiled without the @emph{-ffunction-sections} and +@emph{-fdata-sections} options can still be linked with the executable. +However, no dead code elimination will be performed on those objects (they will +be linked as is). + +The GNAT static library is now compiled with -ffunction-sections and +-fdata-sections on some platforms. This allows you to eliminate the unused code +and data of the GNAT library from your executable. + +@node Example of unused subprogram/data elimination,,Compilation options,Reducing Size of Executables with Unused Subprogram/Data Elimination +@anchor{gnat_ugn/gnat_and_program_execution id46}@anchor{246}@anchor{gnat_ugn/gnat_and_program_execution example-of-unused-subprogram-data-elimination}@anchor{247} +@subsubsection Example of unused subprogram/data elimination + + +Here is a simple example: + +@quotation + +@example +with Aux; + +procedure Test is +begin + Aux.Used (10); +end Test; + +package Aux is + Used_Data : Integer; + Unused_Data : Integer; + + procedure Used (Data : Integer); + procedure Unused (Data : Integer); +end Aux; + +package body Aux is + procedure Used (Data : Integer) is + begin + Used_Data := Data; + end Used; + + procedure Unused (Data : Integer) is + begin + Unused_Data := Data; + end Unused; +end Aux; +@end example +@end quotation + +@cite{Unused} and @cite{Unused_Data} are never referenced in this code +excerpt, and hence they may be safely removed from the final executable. + +@quotation + +@example +$ gnatmake test + +$ nm test | grep used +020015f0 T aux__unused +02005d88 B aux__unused_data +020015cc T aux__used +02005d84 B aux__used_data + +$ gnatmake test -cargs -fdata-sections -ffunction-sections \\ + -largs -Wl,--gc-sections + +$ nm test | grep used +02005350 T aux__used +0201ffe0 B aux__used_data +@end example +@end quotation + +It can be observed that the procedure @cite{Unused} and the object +@cite{Unused_Data} are removed by the linker when using the +appropriate options. + +@geindex Overflow checks + +@geindex Checks (overflow) + + +@node Overflow Check Handling in GNAT,Performing Dimensionality Analysis in GNAT,Improving Performance,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution id54}@anchor{1f3}@anchor{gnat_ugn/gnat_and_program_execution overflow-check-handling-in-gnat}@anchor{29} +@section Overflow Check Handling in GNAT + + +This section explains how to control the handling of overflow checks. + +@menu +* Background:: +* Overflow Checking Modes in GNAT:: +* Specifying the Desired Mode:: +* Default Settings:: +* Implementation Notes:: + +@end menu + +@node Background,Overflow Checking Modes in GNAT,,Overflow Check Handling in GNAT +@anchor{gnat_ugn/gnat_and_program_execution id55}@anchor{248}@anchor{gnat_ugn/gnat_and_program_execution background}@anchor{249} +@subsection Background + + +Overflow checks are checks that the compiler may make to ensure +that intermediate results are not out of range. For example: + +@quotation + +@example +A : Integer; +... +A := A + 1; +@end example +@end quotation + +If @cite{A} has the value @cite{Integer'Last}, then the addition may cause +overflow since the result is out of range of the type @cite{Integer}. +In this case @cite{Constraint_Error} will be raised if checks are +enabled. + +A trickier situation arises in examples like the following: + +@quotation + +@example +A, C : Integer; +... +A := (A + 1) + C; +@end example +@end quotation + +where @cite{A} is @cite{Integer'Last} and @cite{C} is @cite{-1}. +Now the final result of the expression on the right hand side is +@cite{Integer'Last} which is in range, but the question arises whether the +intermediate addition of @cite{(A + 1)} raises an overflow error. + +The (perhaps surprising) answer is that the Ada language +definition does not answer this question. Instead it leaves +it up to the implementation to do one of two things if overflow +checks are enabled. + + +@itemize * + +@item +raise an exception (@cite{Constraint_Error}), or + +@item +yield the correct mathematical result which is then used in +subsequent operations. +@end itemize + +If the compiler chooses the first approach, then the assignment of this +example will indeed raise @cite{Constraint_Error} if overflow checking is +enabled, or result in erroneous execution if overflow checks are suppressed. + +But if the compiler +chooses the second approach, then it can perform both additions yielding +the correct mathematical result, which is in range, so no exception +will be raised, and the right result is obtained, regardless of whether +overflow checks are suppressed. + +Note that in the first example an +exception will be raised in either case, since if the compiler +gives the correct mathematical result for the addition, it will +be out of range of the target type of the assignment, and thus +fails the range check. + +This lack of specified behavior in the handling of overflow for +intermediate results is a source of non-portability, and can thus +be problematic when programs are ported. Most typically this arises +in a situation where the original compiler did not raise an exception, +and then the application is moved to a compiler where the check is +performed on the intermediate result and an unexpected exception is +raised. + +Furthermore, when using Ada 2012's preconditions and other +assertion forms, another issue arises. Consider: + +@quotation + +@example +procedure P (A, B : Integer) with + Pre => A + B <= Integer'Last; +@end example +@end quotation + +One often wants to regard arithmetic in a context like this from +a mathematical point of view. So for example, if the two actual parameters +for a call to @cite{P} are both @cite{Integer'Last}, then +the precondition should be regarded as False. If we are executing +in a mode with run-time checks enabled for preconditions, then we would +like this precondition to fail, rather than raising an exception +because of the intermediate overflow. + +However, the language definition leaves the specification of +whether the above condition fails (raising @cite{Assert_Error}) or +causes an intermediate overflow (raising @cite{Constraint_Error}) +up to the implementation. + +The situation is worse in a case such as the following: + +@quotation + +@example +procedure Q (A, B, C : Integer) with + Pre => A + B + C <= Integer'Last; +@end example +@end quotation + +Consider the call + +@quotation + +@example +Q (A => Integer'Last, B => 1, C => -1); +@end example +@end quotation + +From a mathematical point of view the precondition +is True, but at run time we may (but are not guaranteed to) get an +exception raised because of the intermediate overflow (and we really +would prefer this precondition to be considered True at run time). + +@node Overflow Checking Modes in GNAT,Specifying the Desired Mode,Background,Overflow Check Handling in GNAT +@anchor{gnat_ugn/gnat_and_program_execution id56}@anchor{24a}@anchor{gnat_ugn/gnat_and_program_execution overflow-checking-modes-in-gnat}@anchor{24b} +@subsection Overflow Checking Modes in GNAT + + +To deal with the portability issue, and with the problem of +mathematical versus run-time interpretation of the expressions in +assertions, GNAT provides comprehensive control over the handling +of intermediate overflow. GNAT can operate in three modes, and +furthemore, permits separate selection of operating modes for +the expressions within assertions (here the term 'assertions' +is used in the technical sense, which includes preconditions and so forth) +and for expressions appearing outside assertions. + +The three modes are: + + +@itemize * + +@item +@emph{Use base type for intermediate operations} (@cite{STRICT}) + +In this mode, all intermediate results for predefined arithmetic +operators are computed using the base type, and the result must +be in range of the base type. If this is not the +case then either an exception is raised (if overflow checks are +enabled) or the execution is erroneous (if overflow checks are suppressed). +This is the normal default mode. + +@item +@emph{Most intermediate overflows avoided} (@cite{MINIMIZED}) + +In this mode, the compiler attempts to avoid intermediate overflows by +using a larger integer type, typically @cite{Long_Long_Integer}, +as the type in which arithmetic is +performed for predefined arithmetic operators. This may be slightly more +expensive at +run time (compared to suppressing intermediate overflow checks), though +the cost is negligible on modern 64-bit machines. For the examples given +earlier, no intermediate overflows would have resulted in exceptions, +since the intermediate results are all in the range of +@cite{Long_Long_Integer} (typically 64-bits on nearly all implementations +of GNAT). In addition, if checks are enabled, this reduces the number of +checks that must be made, so this choice may actually result in an +improvement in space and time behavior. + +However, there are cases where @cite{Long_Long_Integer} is not large +enough, consider the following example: + +@quotation + +@example +procedure R (A, B, C, D : Integer) with + Pre => (A**2 * B**2) / (C**2 * D**2) <= 10; +@end example +@end quotation + +where @cite{A} = @cite{B} = @cite{C} = @cite{D} = @cite{Integer'Last}. +Now the intermediate results are +out of the range of @cite{Long_Long_Integer} even though the final result +is in range and the precondition is True (from a mathematical point +of view). In such a case, operating in this mode, an overflow occurs +for the intermediate computation (which is why this mode +says @emph{most} intermediate overflows are avoided). In this case, +an exception is raised if overflow checks are enabled, and the +execution is erroneous if overflow checks are suppressed. + +@item +@emph{All intermediate overflows avoided} (@cite{ELIMINATED}) + +In this mode, the compiler avoids all intermediate overflows +by using arbitrary precision arithmetic as required. In this +mode, the above example with @cite{A**2 * B**2} would +not cause intermediate overflow, because the intermediate result +would be evaluated using sufficient precision, and the result +of evaluating the precondition would be True. + +This mode has the advantage of avoiding any intermediate +overflows, but at the expense of significant run-time overhead, +including the use of a library (included automatically in this +mode) for multiple-precision arithmetic. + +This mode provides cleaner semantics for assertions, since now +the run-time behavior emulates true arithmetic behavior for the +predefined arithmetic operators, meaning that there is never a +conflict between the mathematical view of the assertion, and its +run-time behavior. + +Note that in this mode, the behavior is unaffected by whether or +not overflow checks are suppressed, since overflow does not occur. +It is possible for gigantic intermediate expressions to raise +@cite{Storage_Error} as a result of attempting to compute the +results of such expressions (e.g. @cite{Integer'Last ** Integer'Last}) +but overflow is impossible. +@end itemize + +Note that these modes apply only to the evaluation of predefined +arithmetic, membership, and comparison operators for signed integer +aritmetic. + +For fixed-point arithmetic, checks can be suppressed. But if checks +are enabled +then fixed-point values are always checked for overflow against the +base type for intermediate expressions (that is such checks always +operate in the equivalent of @cite{STRICT} mode). + +For floating-point, on nearly all architectures, @cite{Machine_Overflows} +is False, and IEEE infinities are generated, so overflow exceptions +are never raised. If you want to avoid infinities, and check that +final results of expressions are in range, then you can declare a +constrained floating-point type, and range checks will be carried +out in the normal manner (with infinite values always failing all +range checks). + +@node Specifying the Desired Mode,Default Settings,Overflow Checking Modes in GNAT,Overflow Check Handling in GNAT +@anchor{gnat_ugn/gnat_and_program_execution specifying-the-desired-mode}@anchor{fd}@anchor{gnat_ugn/gnat_and_program_execution id57}@anchor{24c} +@subsection Specifying the Desired Mode + + +@geindex pragma Overflow_Mode + +The desired mode of for handling intermediate overflow can be specified using +either the @cite{Overflow_Mode} pragma or an equivalent compiler switch. +The pragma has the form + +@quotation + +@example +pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]); +@end example +@end quotation + +where @cite{MODE} is one of + + +@itemize * + +@item +@cite{STRICT}: intermediate overflows checked (using base type) + +@item +@cite{MINIMIZED}: minimize intermediate overflows + +@item +@cite{ELIMINATED}: eliminate intermediate overflows +@end itemize + +The case is ignored, so @cite{MINIMIZED}, @cite{Minimized} and +@cite{minimized} all have the same effect. + +If only the @cite{General} parameter is present, then the given @cite{MODE} +applies +to expressions both within and outside assertions. If both arguments +are present, then @cite{General} applies to expressions outside assertions, +and @cite{Assertions} applies to expressions within assertions. For example: + +@quotation + +@example +pragma Overflow_Mode + (General => Minimized, Assertions => Eliminated); +@end example +@end quotation + +specifies that general expressions outside assertions be evaluated +in 'minimize intermediate overflows' mode, and expressions within +assertions be evaluated in 'eliminate intermediate overflows' mode. +This is often a reasonable choice, avoiding excessive overhead +outside assertions, but assuring a high degree of portability +when importing code from another compiler, while incurring +the extra overhead for assertion expressions to ensure that +the behavior at run time matches the expected mathematical +behavior. + +The @cite{Overflow_Mode} pragma has the same scoping and placement +rules as pragma @cite{Suppress}, so it can occur either as a +configuration pragma, specifying a default for the whole +program, or in a declarative scope, where it applies to the +remaining declarations and statements in that scope. + +Note that pragma @cite{Overflow_Mode} does not affect whether +overflow checks are enabled or suppressed. It only controls the +method used to compute intermediate values. To control whether +overflow checking is enabled or suppressed, use pragma @cite{Suppress} +or @cite{Unsuppress} in the usual manner + +@geindex -gnato? (gcc) + +@geindex -gnato?? (gcc) + +Additionally, a compiler switch @emph{-gnato?} or @emph{-gnato??} +can be used to control the checking mode default (which can be subsequently +overridden using pragmas). + +Here @code{?} is one of the digits @code{1} through @code{3}: + +@quotation + + +@multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item + +@code{1} + +@tab + +use base type for intermediate operations (@cite{STRICT}) + +@item + +@code{2} + +@tab + +minimize intermediate overflows (@cite{MINIMIZED}) + +@item + +@code{3} + +@tab + +eliminate intermediate overflows (@cite{ELIMINATED}) + +@end multitable + +@end quotation + +As with the pragma, if only one digit appears then it applies to all +cases; if two digits are given, then the first applies outside +assertions, and the second within assertions. Thus the equivalent +of the example pragma above would be +@emph{-gnato23}. + +If no digits follow the @emph{-gnato}, then it is equivalent to +@emph{-gnato11}, +causing all intermediate operations to be computed using the base +type (@cite{STRICT} mode). + +In addition to setting the mode used for computation of intermediate +results, the @cite{-gnato} switch also enables overflow checking (which +is suppressed by default). It thus combines the effect of using +a pragma @cite{Overflow_Mode} and pragma @cite{Unsuppress}. + +@node Default Settings,Implementation Notes,Specifying the Desired Mode,Overflow Check Handling in GNAT +@anchor{gnat_ugn/gnat_and_program_execution id58}@anchor{24d}@anchor{gnat_ugn/gnat_and_program_execution default-settings}@anchor{24e} +@subsection Default Settings + + +The default mode for overflow checks is + +@quotation + +@example +General => Strict +@end example +@end quotation + +which causes all computations both inside and outside assertions to use +the base type. In addition overflow checks are suppressed. + +This retains compatibility with previous versions of +GNAT which suppressed overflow checks by default and always +used the base type for computation of intermediate results. + +The switch @emph{-gnato} (with no digits following) is equivalent to +.. index:: -gnato (gcc) + +@quotation + +@example +General => Strict +@end example +@end quotation + +which causes overflow checking of all intermediate overflows +both inside and outside assertions against the base type. +This provides compatibility +with this switch as implemented in previous versions of GNAT. + +The pragma @cite{Suppress (Overflow_Check)} disables overflow +checking, but it has no effect on the method used for computing +intermediate results. + +The pragma @cite{Unsuppress (Overflow_Check)} enables overflow +checking, but it has no effect on the method used for computing +intermediate results. + +@node Implementation Notes,,Default Settings,Overflow Check Handling in GNAT +@anchor{gnat_ugn/gnat_and_program_execution implementation-notes}@anchor{24f}@anchor{gnat_ugn/gnat_and_program_execution id59}@anchor{250} +@subsection Implementation Notes + + +In practice on typical 64-bit machines, the @cite{MINIMIZED} mode is +reasonably efficient, and can be generally used. It also helps +to ensure compatibility with code imported from some other +compiler to GNAT. + +Setting all intermediate overflows checking (@cite{CHECKED} mode) +makes sense if you want to +make sure that your code is compatible with any other possible +Ada implementation. This may be useful in ensuring portability +for code that is to be exported to some other compiler than GNAT. + +The Ada standard allows the reassociation of expressions at +the same precedence level if no parentheses are present. For +example, @cite{A+B+C} parses as though it were @cite{(A+B)+C}, but +the compiler can reintepret this as @cite{A+(B+C)}, possibly +introducing or eliminating an overflow exception. The GNAT +compiler never takes advantage of this freedom, and the +expression @cite{A+B+C} will be evaluated as @cite{(A+B)+C}. +If you need the other order, you can write the parentheses +explicitly @cite{A+(B+C)} and GNAT will respect this order. + +The use of @cite{ELIMINATED} mode will cause the compiler to +automatically include an appropriate arbitrary precision +integer arithmetic package. The compiler will make calls +to this package, though only in cases where it cannot be +sure that @cite{Long_Long_Integer} is sufficient to guard against +intermediate overflows. This package does not use dynamic +alllocation, but it does use the secondary stack, so an +appropriate secondary stack package must be present (this +is always true for standard full Ada, but may require +specific steps for restricted run times such as ZFP). + +Although @cite{ELIMINATED} mode causes expressions to use arbitrary +precision arithmetic, avoiding overflow, the final result +must be in an appropriate range. This is true even if the +final result is of type @cite{[Long_[Long_]]Integer'Base}, which +still has the same bounds as its associated constrained +type at run-time. + +Currently, the @cite{ELIMINATED} mode is only available on target +platforms for which @cite{Long_Long_Integer} is 64-bits (nearly all GNAT +platforms). + +@node Performing Dimensionality Analysis in GNAT,Stack Related Facilities,Overflow Check Handling in GNAT,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat}@anchor{2a}@anchor{gnat_ugn/gnat_and_program_execution id60}@anchor{1f4} +@section Performing Dimensionality Analysis in GNAT + + +@geindex Dimensionality analysis + +The GNAT compiler supports dimensionality checking. The user can +specify physical units for objects, and the compiler will verify that uses +of these objects are compatible with their dimensions, in a fashion that is +familiar to engineering practice. The dimensions of algebraic expressions +(including powers with static exponents) are computed from their constituents. + +@geindex Dimension_System aspect + +@geindex Dimension aspect + +This feature depends on Ada 2012 aspect specifications, and is available from +version 7.0.1 of GNAT onwards. +The GNAT-specific aspect @cite{Dimension_System} +allows you to define a system of units; the aspect @cite{Dimension} +then allows the user to declare dimensioned quantities within a given system. +(These aspects are described in the @emph{Implementation Defined Aspects} +chapter of the @emph{GNAT Reference Manual}). + +The major advantage of this model is that it does not require the declaration of +multiple operators for all possible combinations of types: it is only necessary +to use the proper subtypes in object declarations. + +@geindex System.Dim.Mks package (GNAT library) + +@geindex MKS_Type type + +The simplest way to impose dimensionality checking on a computation is to make +use of the package @cite{System.Dim.Mks}, +which is part of the GNAT library. This +package defines a floating-point type @cite{MKS_Type}, +for which a sequence of +dimension names are specified, together with their conventional abbreviations. +The following should be read together with the full specification of the +package, in file @code{s-dimmks.ads}. + +@quotation + +@geindex s-dimmks.ads file + +@example +type Mks_Type is new Long_Long_Float + with + Dimension_System => ( + (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'), + (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'), + (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'), + (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'), + (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"), + (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'), + (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J')); +@end example +@end quotation + +The package then defines a series of subtypes that correspond to these +conventional units. For example: + +@quotation + +@example +subtype Length is Mks_Type + with + Dimension => (Symbol => 'm', Meter => 1, others => 0); +@end example +@end quotation + +and similarly for @cite{Mass}, @cite{Time}, @cite{Electric_Current}, +@cite{Thermodynamic_Temperature}, @cite{Amount_Of_Substance}, and +@cite{Luminous_Intensity} (the standard set of units of the SI system). + +The package also defines conventional names for values of each unit, for +example: + +@quotation + +@c code-block":: ada +@c +@c m : constant Length := 1.0; +@c kg : constant Mass := 1.0; +@c s : constant Time := 1.0; +@c A : constant Electric_Current := 1.0; +@end quotation + +as well as useful multiples of these units: + +@quotation + +@example + cm : constant Length := 1.0E-02; + g : constant Mass := 1.0E-03; + min : constant Time := 60.0; + day : constant Time := 60.0 * 24.0 * min; +... +@end example +@end quotation + +Using this package, you can then define a derived unit by +providing the aspect that +specifies its dimensions within the MKS system, as well as the string to +be used for output of a value of that unit: + +@quotation + +@example +subtype Acceleration is Mks_Type + with Dimension => ("m/sec^2", + Meter => 1, + Second => -2, + others => 0); +@end example +@end quotation + +Here is a complete example of use: + +@quotation + +@example +with System.Dim.MKS; use System.Dim.Mks; +with System.Dim.Mks_IO; use System.Dim.Mks_IO; +with Text_IO; use Text_IO; +procedure Free_Fall is + subtype Acceleration is Mks_Type + with Dimension => ("m/sec^2", 1, 0, -2, others => 0); + G : constant acceleration := 9.81 * m / (s ** 2); + T : Time := 10.0*s; + Distance : Length; + +begin + Put ("Gravitational constant: "); + Put (G, Aft => 2, Exp => 0); Put_Line (""); + Distance := 0.5 * G * T ** 2; + Put ("distance travelled in 10 seconds of free fall "); + Put (Distance, Aft => 2, Exp => 0); + Put_Line (""); +end Free_Fall; +@end example +@end quotation + +Execution of this program yields: + +@quotation + +@example +Gravitational constant: 9.81 m/sec^2 +distance travelled in 10 seconds of free fall 490.50 m +@end example +@end quotation + +However, incorrect assignments such as: + +@quotation + +@example +Distance := 5.0; +Distance := 5.0 * kg: +@end example +@end quotation + +are rejected with the following diagnoses: + +@quotation + +@example +Distance := 5.0; + >>> dimensions mismatch in assignment + >>> left-hand side has dimension [L] + >>> right-hand side is dimensionless + +Distance := 5.0 * kg: + >>> dimensions mismatch in assignment + >>> left-hand side has dimension [L] + >>> right-hand side has dimension [M] +@end example +@end quotation + +The dimensions of an expression are properly displayed, even if there is +no explicit subtype for it. If we add to the program: + +@quotation + +@example +Put ("Final velocity: "); +Put (G * T, Aft =>2, Exp =>0); +Put_Line (""); +@end example +@end quotation + +then the output includes: + +@quotation + +@example +Final velocity: 98.10 m.s**(-1) +@end example +@end quotation + +@node Stack Related Facilities,Memory Management Issues,Performing Dimensionality Analysis in GNAT,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution id61}@anchor{1f5}@anchor{gnat_ugn/gnat_and_program_execution stack-related-facilities}@anchor{2b} +@section Stack Related Facilities + + +This section describes some useful tools associated with stack +checking and analysis. In +particular, it deals with dynamic and static stack usage measurements. + +@menu +* Stack Overflow Checking:: +* Static Stack Usage Analysis:: +* Dynamic Stack Usage Analysis:: + +@end menu + +@node Stack Overflow Checking,Static Stack Usage Analysis,,Stack Related Facilities +@anchor{gnat_ugn/gnat_and_program_execution id62}@anchor{251}@anchor{gnat_ugn/gnat_and_program_execution stack-overflow-checking}@anchor{f9} +@subsection Stack Overflow Checking + + +@geindex Stack Overflow Checking + +@geindex -fstack-check (gcc) + +For most operating systems, @emph{gcc} does not perform stack overflow +checking by default. This means that if the main environment task or +some other task exceeds the available stack space, then unpredictable +behavior will occur. Most native systems offer some level of protection by +adding a guard page at the end of each task stack. This mechanism is usually +not enough for dealing properly with stack overflow situations because +a large local variable could "jump" above the guard page. +Furthermore, when the +guard page is hit, there may not be any space left on the stack for executing +the exception propagation code. Enabling stack checking avoids +such situations. + +To activate stack checking, compile all units with the gcc option +@cite{-fstack-check}. For example: + +@quotation + +@example +$ gcc -c -fstack-check package1.adb +@end example +@end quotation + +Units compiled with this option will generate extra instructions to check +that any use of the stack (for procedure calls or for declaring local +variables in declare blocks) does not exceed the available stack space. +If the space is exceeded, then a @cite{Storage_Error} exception is raised. + +For declared tasks, the stack size is controlled by the size +given in an applicable @cite{Storage_Size} pragma or by the value specified +at bind time with @code{-d} (@ref{123,,Switches for gnatbind}) or is set to +the default size as defined in the GNAT runtime otherwise. + +@geindex GNAT_STACK_LIMIT + +For the environment task, the stack size depends on +system defaults and is unknown to the compiler. Stack checking +may still work correctly if a fixed +size stack is allocated, but this cannot be guaranteed. +To ensure that a clean exception is signalled for stack +overflow, set the environment variable +@geindex GNAT_STACK_LIMIT +@geindex environment variable; GNAT_STACK_LIMIT +@code{GNAT_STACK_LIMIT} to indicate the maximum +stack area that can be used, as in: + +@quotation + +@example +$ SET GNAT_STACK_LIMIT 1600 +@end example +@end quotation + +The limit is given in kilobytes, so the above declaration would +set the stack limit of the environment task to 1.6 megabytes. +Note that the only purpose of this usage is to limit the amount +of stack used by the environment task. If it is necessary to +increase the amount of stack for the environment task, then this +is an operating systems issue, and must be addressed with the +appropriate operating systems commands. + +@node Static Stack Usage Analysis,Dynamic Stack Usage Analysis,Stack Overflow Checking,Stack Related Facilities +@anchor{gnat_ugn/gnat_and_program_execution static-stack-usage-analysis}@anchor{fa}@anchor{gnat_ugn/gnat_and_program_execution id63}@anchor{252} +@subsection Static Stack Usage Analysis + + +@geindex Static Stack Usage Analysis + +@geindex -fstack-usage + +A unit compiled with @code{-fstack-usage} will generate an extra file +that specifies +the maximum amount of stack used, on a per-function basis. +The file has the same +basename as the target object file with a @code{.su} extension. +Each line of this file is made up of three fields: + + +@itemize * + +@item +The name of the function. + +@item +A number of bytes. + +@item +One or more qualifiers: @cite{static}, @cite{dynamic}, @cite{bounded}. +@end itemize + +The second field corresponds to the size of the known part of the function +frame. + +The qualifier @cite{static} means that the function frame size +is purely static. +It usually means that all local variables have a static size. +In this case, the second field is a reliable measure of the function stack +utilization. + +The qualifier @cite{dynamic} means that the function frame size is not static. +It happens mainly when some local variables have a dynamic size. When this +qualifier appears alone, the second field is not a reliable measure +of the function stack analysis. When it is qualified with @cite{bounded}, it +means that the second field is a reliable maximum of the function stack +utilization. + +A unit compiled with @code{-Wstack-usage} will issue a warning for each +subprogram whose stack usage might be larger than the specified amount of +bytes. The wording is in keeping with the qualifier documented above. + +@node Dynamic Stack Usage Analysis,,Static Stack Usage Analysis,Stack Related Facilities +@anchor{gnat_ugn/gnat_and_program_execution id64}@anchor{253}@anchor{gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis}@anchor{125} +@subsection Dynamic Stack Usage Analysis + + +It is possible to measure the maximum amount of stack used by a task, by +adding a switch to @emph{gnatbind}, as: + +@quotation + +@example +$ gnatbind -u0 file +@end example +@end quotation + +With this option, at each task termination, its stack usage is output on +@code{stderr}. +It is not always convenient to output the stack usage when the program +is still running. Hence, it is possible to delay this output until program +termination. for a given number of tasks specified as the argument of the +@code{-u} option. For instance: + +@quotation + +@example +$ gnatbind -u100 file +@end example +@end quotation + +will buffer the stack usage information of the first 100 tasks to terminate and +output this info at program termination. Results are displayed in four +columns: + +@quotation + +@example +Index | Task Name | Stack Size | Stack Usage +@end example +@end quotation + +where: + + +@itemize * + +@item +@emph{Index} is a number associated with each task. + +@item +@emph{Task Name} is the name of the task analyzed. + +@item +@emph{Stack Size} is the maximum size for the stack. + +@item +@emph{Stack Usage} is the measure done by the stack analyzer. +In order to prevent overflow, the stack +is not entirely analyzed, and it's not possible to know exactly how +much has actually been used. +@end itemize + +The environment task stack, e.g., the stack that contains the main unit, is +only processed when the environment variable GNAT_STACK_LIMIT is set. + +The package @cite{GNAT.Task_Stack_Usage} provides facilities to get +stack usage reports at run-time. See its body for the details. + +@node Memory Management Issues,,Stack Related Facilities,GNAT and Program Execution +@anchor{gnat_ugn/gnat_and_program_execution id65}@anchor{1f6}@anchor{gnat_ugn/gnat_and_program_execution memory-management-issues}@anchor{2c} +@section Memory Management Issues + + +This section describes some useful memory pools provided in the GNAT library +and in particular the GNAT Debug Pool facility, which can be used to detect +incorrect uses of access values (including 'dangling references'). + + +@menu +* Some Useful Memory Pools:: +* The GNAT Debug Pool Facility:: + +@end menu + +@node Some Useful Memory Pools,The GNAT Debug Pool Facility,,Memory Management Issues +@anchor{gnat_ugn/gnat_and_program_execution id66}@anchor{254}@anchor{gnat_ugn/gnat_and_program_execution some-useful-memory-pools}@anchor{255} +@subsection Some Useful Memory Pools + + +@geindex Memory Pool + +@geindex storage +@geindex pool + +The @cite{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool +storage pool. Allocations use the standard system call @cite{malloc} while +deallocations use the standard system call @cite{free}. No reclamation is +performed when the pool goes out of scope. For performance reasons, the +standard default Ada allocators/deallocators do not use any explicit storage +pools but if they did, they could use this storage pool without any change in +behavior. That is why this storage pool is used when the user +manages to make the default implicit allocator explicit as in this example: + +@quotation + +@example +type T1 is access Something; + -- no Storage pool is defined for T2 + +type T2 is access Something_Else; +for T2'Storage_Pool use T1'Storage_Pool; +-- the above is equivalent to +for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object; +@end example +@end quotation + +The @cite{System.Pool_Local} package offers the Unbounded_Reclaim_Pool storage +pool. The allocation strategy is similar to @cite{Pool_Local}'s +except that the all +storage allocated with this pool is reclaimed when the pool object goes out of +scope. This pool provides a explicit mechanism similar to the implicit one +provided by several Ada 83 compilers for allocations performed through a local +access type and whose purpose was to reclaim memory when exiting the +scope of a given local access. As an example, the following program does not +leak memory even though it does not perform explicit deallocation: + +@quotation + +@example +with System.Pool_Local; +procedure Pooloc1 is + procedure Internal is + type A is access Integer; + X : System.Pool_Local.Unbounded_Reclaim_Pool; + for A'Storage_Pool use X; + v : A; + begin + for I in 1 .. 50 loop + v := new Integer; + end loop; + end Internal; +begin + for I in 1 .. 100 loop + Internal; + end loop; +end Pooloc1; +@end example +@end quotation + +The @cite{System.Pool_Size} package implements the Stack_Bounded_Pool used when +@cite{Storage_Size} is specified for an access type. +The whole storage for the pool is +allocated at once, usually on the stack at the point where the access type is +elaborated. It is automatically reclaimed when exiting the scope where the +access type is defined. This package is not intended to be used directly by the +user and it is implicitly used for each such declaration: + +@quotation + +@example +type T1 is access Something; +for T1'Storage_Size use 10_000; +@end example +@end quotation + +@node The GNAT Debug Pool Facility,,Some Useful Memory Pools,Memory Management Issues +@anchor{gnat_ugn/gnat_and_program_execution id67}@anchor{256}@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility}@anchor{257} +@subsection The GNAT Debug Pool Facility + + +@geindex Debug Pool + +@geindex storage +@geindex pool +@geindex memory corruption + +The use of unchecked deallocation and unchecked conversion can easily +lead to incorrect memory references. The problems generated by such +references are usually difficult to tackle because the symptoms can be +very remote from the origin of the problem. In such cases, it is +very helpful to detect the problem as early as possible. This is the +purpose of the Storage Pool provided by @cite{GNAT.Debug_Pools}. + +In order to use the GNAT specific debugging pool, the user must +associate a debug pool object with each of the access types that may be +related to suspected memory problems. See Ada Reference Manual 13.11. + +@quotation + +@example +type Ptr is access Some_Type; +Pool : GNAT.Debug_Pools.Debug_Pool; +for Ptr'Storage_Pool use Pool; +@end example +@end quotation + +@cite{GNAT.Debug_Pools} is derived from a GNAT-specific kind of +pool: the @cite{Checked_Pool}. Such pools, like standard Ada storage pools, +allow the user to redefine allocation and deallocation strategies. They +also provide a checkpoint for each dereference, through the use of +the primitive operation @cite{Dereference} which is implicitly called at +each dereference of an access value. + +Once an access type has been associated with a debug pool, operations on +values of the type may raise four distinct exceptions, +which correspond to four potential kinds of memory corruption: + + +@itemize * + +@item +@cite{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage} + +@item +@cite{GNAT.Debug_Pools.Accessing_Deallocated_Storage} + +@item +@cite{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage} + +@item +@cite{GNAT.Debug_Pools.Freeing_Deallocated_Storage} +@end itemize + +For types associated with a Debug_Pool, dynamic allocation is performed using +the standard GNAT allocation routine. References to all allocated chunks of +memory are kept in an internal dictionary. Several deallocation strategies are +provided, whereupon the user can choose to release the memory to the system, +keep it allocated for further invalid access checks, or fill it with an easily +recognizable pattern for debug sessions. The memory pattern is the old IBM +hexadecimal convention: @cite{16#DEADBEEF#}. + +See the documentation in the file g-debpoo.ads for more information on the +various strategies. + +Upon each dereference, a check is made that the access value denotes a +properly allocated memory location. Here is a complete example of use of +@cite{Debug_Pools}, that includes typical instances of memory corruption: + +@quotation + +@example +with Gnat.Io; use Gnat.Io; +with Unchecked_Deallocation; +with Unchecked_Conversion; +with GNAT.Debug_Pools; +with System.Storage_Elements; +with Ada.Exceptions; use Ada.Exceptions; +procedure Debug_Pool_Test is + + type T is access Integer; + type U is access all T; + + P : GNAT.Debug_Pools.Debug_Pool; + for T'Storage_Pool use P; + + procedure Free is new Unchecked_Deallocation (Integer, T); + function UC is new Unchecked_Conversion (U, T); + A, B : aliased T; + + procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line); + +begin + Info (P); + A := new Integer; + B := new Integer; + B := A; + Info (P); + Free (A); + begin + Put_Line (Integer'Image(B.all)); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + begin + Free (B); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + B := UC(A'Access); + begin + Put_Line (Integer'Image(B.all)); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + begin + Free (B); + exception + when E : others => Put_Line ("raised: " & Exception_Name (E)); + end; + Info (P); +end Debug_Pool_Test; +@end example +@end quotation + +The debug pool mechanism provides the following precise diagnostics on the +execution of this erroneous program: + +@quotation + +@example +Debug Pool info: + Total allocated bytes : 0 + Total deallocated bytes : 0 + Current Water Mark: 0 + High Water Mark: 0 + +Debug Pool info: + Total allocated bytes : 8 + Total deallocated bytes : 0 + Current Water Mark: 8 + High Water Mark: 8 + +raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE +raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE +raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE +raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE +Debug Pool info: + Total allocated bytes : 8 + Total deallocated bytes : 4 + Current Water Mark: 4 + High Water Mark: 8 +@end example +@end quotation + + +@c -- Non-breaking space in running text +@c -- E.g. Ada |nbsp| 95 + +@node Platform-Specific Information,Example of Binder Output File,GNAT and Program Execution,Top +@anchor{gnat_ugn/platform_specific_information platform-specific-information}@anchor{f}@anchor{gnat_ugn/platform_specific_information doc}@anchor{258}@anchor{gnat_ugn/platform_specific_information id1}@anchor{259} +@chapter Platform-Specific Information + + +This appendix contains information relating to the implementation +of run-time libraries on various platforms and also covers +topics related to the GNAT implementation on Windows and Mac OS. + +@menu +* Run-Time Libraries:: +* Specifying a Run-Time Library:: +* Microsoft Windows Topics:: +* Mac OS Topics:: + +@end menu + +@node Run-Time Libraries,Specifying a Run-Time Library,,Platform-Specific Information +@anchor{gnat_ugn/platform_specific_information id2}@anchor{25a}@anchor{gnat_ugn/platform_specific_information run-time-libraries}@anchor{2d} +@section Run-Time Libraries + + +@geindex Tasking and threads libraries + +@geindex Threads libraries and tasking + +@geindex Run-time libraries (platform-specific information) + +The GNAT run-time implementation may vary with respect to both the +underlying threads library and the exception handling scheme. +For threads support, one or more of the following are supplied: + + +@itemize * + +@item +@strong{native threads library}, a binding to the thread package from +the underlying operating system + +@item +@strong{pthreads library} (Sparc Solaris only), a binding to the Solaris +POSIX thread package +@end itemize + +For exception handling, either or both of two models are supplied: + +@quotation + +@geindex Zero-Cost Exceptions + +@geindex ZCX (Zero-Cost Exceptions) +@end quotation + + +@itemize * + +@item +@strong{Zero-Cost Exceptions} ("ZCX"), +which uses binder-generated tables that +are interrogated at run time to locate a handler. + +@geindex setjmp/longjmp Exception Model + +@geindex SJLJ (setjmp/longjmp Exception Model) + +@item +@strong{setjmp / longjmp} ('SJLJ'), +which uses dynamically-set data to establish +the set of handlers +@end itemize + +Most programs should experience a substantial speed improvement by +being compiled with a ZCX run-time. +This is especially true for +tasking applications or applications with many exception handlers.@} + +This section summarizes which combinations of threads and exception support +are supplied on various GNAT platforms. +It then shows how to select a particular library either +permanently or temporarily, +explains the properties of (and tradeoffs among) the various threads +libraries, and provides some additional +information about several specific platforms. + +@menu +* Summary of Run-Time Configurations:: + +@end menu + +@node Summary of Run-Time Configurations,,,Run-Time Libraries +@anchor{gnat_ugn/platform_specific_information summary-of-run-time-configurations}@anchor{25b}@anchor{gnat_ugn/platform_specific_information id3}@anchor{25c} +@subsection Summary of Run-Time Configurations + + + +@multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx} +@headitem + +Platform + +@tab + +Run-Time + +@tab + +Tasking + +@tab + +Exceptions + +@item + +ppc-aix + +@tab + +rts-native +(default) + +@tab + +native AIX threads + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +native AIX threads + +@tab + +SJLJ + +@item + +sparc-solaris + +@tab + +rts-native +(default) + +@tab + +native Solaris +threads library + +@tab + +ZCX + +@item + +rts-pthread + +@tab + +pthread library + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +native Solaris +threads library + +@tab + +SJLJ + +@item + +sparc64-solaris + +@tab + +rts-native +(default) + +@tab + +native Solaris +threads library + +@tab + +ZCX + +@item + +x86-linux + +@tab + +rts-native +(default) + +@tab + +pthread library + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +pthread library + +@tab + +SJLJ + +@item + +x86-lynx + +@tab + +rts-native +(default) + +@tab + +native LynxOS threads + +@tab + +SJLJ + +@item + +x86-solaris + +@tab + +rts-native +(default) + +@tab + +native Solaris +threads library + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +native Solaris +threads library + +@tab + +SJLJ + +@item + +x86-windows + +@tab + +rts-native +(default) + +@tab + +native Win32 threads + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +native Win32 threads + +@tab + +SJLJ + +@item + +x86_64-linux + +@tab + +rts-native +(default) + +@tab + +pthread library + +@tab + +ZCX + +@item + +rts-sjlj + +@tab + +pthread library + +@tab + +SJLJ + +@end multitable + + +@node Specifying a Run-Time Library,Microsoft Windows Topics,Run-Time Libraries,Platform-Specific Information +@anchor{gnat_ugn/platform_specific_information specifying-a-run-time-library}@anchor{25d}@anchor{gnat_ugn/platform_specific_information id4}@anchor{25e} +@section Specifying a Run-Time Library + + +The @code{adainclude} subdirectory containing the sources of the GNAT +run-time library, and the @code{adalib} subdirectory containing the +@code{ALI} files and the static and/or shared GNAT library, are located +in the gcc target-dependent area: + +@quotation + +@example +target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/ +@end example +@end quotation + +As indicated above, on some platforms several run-time libraries are supplied. +These libraries are installed in the target dependent area and +contain a complete source and binary subdirectory. The detailed description +below explains the differences between the different libraries in terms of +their thread support. + +The default run-time library (when GNAT is installed) is @emph{rts-native}. +This default run time is selected by the means of soft links. +For example on x86-linux: + +@quotation + +@image{rtlibrary-structure,,,,png} +@end quotation + +@c -- +@c -- $(target-dir) +@c -- | +@c -- +--- adainclude----------+ +@c -- | | +@c -- +--- adalib-----------+ | +@c -- | | | +@c -- +--- rts-native | | +@c -- | | | | +@c -- | +--- adainclude <---+ +@c -- | | | +@c -- | +--- adalib <----+ +@c -- | +@c -- +--- rts-sjlj +@c -- | +@c -- +--- adainclude +@c -- | +@c -- +--- adalib + +If the @emph{rts-sjlj} library is to be selected on a permanent basis, +these soft links can be modified with the following commands: + +@quotation + +@example +$ cd $target +$ rm -f adainclude adalib +$ ln -s rts-sjlj/adainclude adainclude +$ ln -s rts-sjlj/adalib adalib +@end example +@end quotation + +Alternatively, you can specify @code{rts-sjlj/adainclude} in the file +@code{$target/ada_source_path} and @code{rts-sjlj/adalib} in +@code{$target/ada_object_path}. + +@geindex --RTS option + +Selecting another run-time library temporarily can be +achieved by using the @emph{--RTS} switch, e.g., @emph{--RTS=sjlj} +@anchor{gnat_ugn/platform_specific_information choosing-the-scheduling-policy}@anchor{25f} +@geindex SCHED_FIFO scheduling policy + +@geindex SCHED_RR scheduling policy + +@geindex SCHED_OTHER scheduling policy + +@menu +* Choosing the Scheduling Policy:: +* Solaris-Specific Considerations:: +* Solaris Threads Issues:: +* AIX-Specific Considerations:: + +@end menu + +@node Choosing the Scheduling Policy,Solaris-Specific Considerations,,Specifying a Run-Time Library +@anchor{gnat_ugn/platform_specific_information id5}@anchor{260} +@subsection Choosing the Scheduling Policy + + +When using a POSIX threads implementation, you have a choice of several +scheduling policies: @cite{SCHED_FIFO}, @cite{SCHED_RR} and @cite{SCHED_OTHER}. + +Typically, the default is @cite{SCHED_OTHER}, while using @cite{SCHED_FIFO} +or @cite{SCHED_RR} requires special (e.g., root) privileges. + +@geindex pragma Time_Slice + +@geindex -T0 option + +@geindex pragma Task_Dispatching_Policy + +By default, GNAT uses the @cite{SCHED_OTHER} policy. To specify +@cite{SCHED_FIFO}, +you can use one of the following: + + +@itemize * + +@item +@cite{pragma Time_Slice (0.0)} + +@item +the corresponding binder option @emph{-T0} + +@item +@cite{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)} +@end itemize + +To specify @cite{SCHED_RR}, +you should use @cite{pragma Time_Slice} with a +value greater than 0.0, or else use the corresponding @emph{-T} +binder option. + +@geindex Solaris Sparc threads libraries + +@node Solaris-Specific Considerations,Solaris Threads Issues,Choosing the Scheduling Policy,Specifying a Run-Time Library +@anchor{gnat_ugn/platform_specific_information id6}@anchor{261}@anchor{gnat_ugn/platform_specific_information solaris-specific-considerations}@anchor{262} +@subsection Solaris-Specific Considerations + + +This section addresses some topics related to the various threads libraries +on Sparc Solaris. + +@geindex rts-pthread threads library + +@node Solaris Threads Issues,AIX-Specific Considerations,Solaris-Specific Considerations,Specifying a Run-Time Library +@anchor{gnat_ugn/platform_specific_information id7}@anchor{263}@anchor{gnat_ugn/platform_specific_information solaris-threads-issues}@anchor{264} +@subsection Solaris Threads Issues + + +GNAT under Solaris/Sparc 32 bits comes with an alternate tasking run-time +library based on POSIX threads --- @emph{rts-pthread}. + +@geindex PTHREAD_PRIO_INHERIT policy (under rts-pthread) + +@geindex PTHREAD_PRIO_PROTECT policy (under rts-pthread) + +@geindex pragma Locking_Policy (under rts-pthread) + +@geindex Inheritance_Locking (under rts-pthread) + +@geindex Ceiling_Locking (under rts-pthread) + +This run-time library has the advantage of being mostly shared across all +POSIX-compliant thread implementations, and it also provides under +Solaris 8 the @cite{PTHREAD_PRIO_INHERIT} +and @cite{PTHREAD_PRIO_PROTECT} +semantics that can be selected using the predefined pragma +@cite{Locking_Policy} +with respectively +@cite{Inheritance_Locking} and @cite{Ceiling_Locking} as the policy. + +As explained above, the native run-time library is based on the Solaris thread +library (@cite{libthread}) and is the default library. + +@geindex GNAT_PROCESSOR environment variable (on Sparc Solaris) + +When the Solaris threads library is used (this is the default), programs +compiled with GNAT can automatically take advantage of +and can thus execute on multiple processors. +The user can alternatively specify a processor on which the program should run +to emulate a single-processor system. The multiprocessor / uniprocessor choice +is made by +setting the environment variable +@geindex GNAT_PROCESSOR +@geindex environment variable; GNAT_PROCESSOR +@code{GNAT_PROCESSOR} +to one of the following: + +@quotation + + +@multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@headitem + +@code{GNAT_PROCESSOR} Value + +@tab + +Effect + +@item + +@emph{-2} + +@tab + +Use the default configuration (run the program on all +available processors) - this is the same as having @cite{GNAT_PROCESSOR} +unset + +@item + +@emph{-1} + +@tab + +Let the run-time implementation choose one processor and run the +program on that processor + +@item + +@emph{0 .. Last_Proc} + +@tab + +Run the program on the specified processor. +@cite{Last_Proc} is equal to @cite{_SC_NPROCESSORS_CONF - 1} +(where @cite{_SC_NPROCESSORS_CONF} is a system variable). + +@end multitable + +@end quotation + +@node AIX-Specific Considerations,,Solaris Threads Issues,Specifying a Run-Time Library +@anchor{gnat_ugn/platform_specific_information aix-specific-considerations}@anchor{265}@anchor{gnat_ugn/platform_specific_information id8}@anchor{266} +@subsection AIX-Specific Considerations + + +@geindex AIX resolver library + +On AIX, the resolver library initializes some internal structure on +the first call to @cite{get*by*} functions, which are used to implement +@cite{GNAT.Sockets.Get_Host_By_Name} and +@cite{GNAT.Sockets.Get_Host_By_Address}. +If such initialization occurs within an Ada task, and the stack size for +the task is the default size, a stack overflow may occur. + +To avoid this overflow, the user should either ensure that the first call +to @cite{GNAT.Sockets.Get_Host_By_Name} or +@cite{GNAT.Sockets.Get_Host_By_Addrss} +occurs in the environment task, or use @cite{pragma Storage_Size} to +specify a sufficiently large size for the stack of the task that contains +this call. + +@geindex Windows NT + +@geindex Windows 95 + +@geindex Windows 98 + +@node Microsoft Windows Topics,Mac OS Topics,Specifying a Run-Time Library,Platform-Specific Information +@anchor{gnat_ugn/platform_specific_information microsoft-windows-topics}@anchor{2e}@anchor{gnat_ugn/platform_specific_information id9}@anchor{267} +@section Microsoft Windows Topics + + +This section describes topics that are specific to the Microsoft Windows +platforms. + + + + + +@menu +* Using GNAT on Windows:: +* Using a network installation of GNAT:: +* CONSOLE and WINDOWS subsystems:: +* Temporary Files:: +* Mixed-Language Programming on Windows:: + +@end menu + +@node Using GNAT on Windows,Using a network installation of GNAT,,Microsoft Windows Topics +@anchor{gnat_ugn/platform_specific_information using-gnat-on-windows}@anchor{268}@anchor{gnat_ugn/platform_specific_information id10}@anchor{269} +@subsection Using GNAT on Windows + + +One of the strengths of the GNAT technology is that its tool set +(@emph{gcc}, @emph{gnatbind}, @emph{gnatlink}, @emph{gnatmake}, the +@cite{gdb} debugger, etc.) is used in the same way regardless of the +platform. + +On Windows this tool set is complemented by a number of Microsoft-specific +tools that have been provided to facilitate interoperability with Windows +when this is required. With these tools: + + +@itemize * + +@item +You can build applications using the @cite{CONSOLE} or @cite{WINDOWS} +subsystems. + +@item +You can use any Dynamically Linked Library (DLL) in your Ada code (both +relocatable and non-relocatable DLLs are supported). + +@item +You can build Ada DLLs for use in other applications. These applications +can be written in a language other than Ada (e.g., C, C++, etc). Again both +relocatable and non-relocatable Ada DLLs are supported. + +@item +You can include Windows resources in your Ada application. + +@item +You can use or create COM/DCOM objects. +@end itemize + +Immediately below are listed all known general GNAT-for-Windows restrictions. +Other restrictions about specific features like Windows Resources and DLLs +are listed in separate sections below. + + +@itemize * + +@item +It is not possible to use @cite{GetLastError} and @cite{SetLastError} +when tasking, protected records, or exceptions are used. In these +cases, in order to implement Ada semantics, the GNAT run-time system +calls certain Win32 routines that set the last error variable to 0 upon +success. It should be possible to use @cite{GetLastError} and +@cite{SetLastError} when tasking, protected record, and exception +features are not used, but it is not guaranteed to work. + +@item +It is not possible to link against Microsoft C++ libraries except for +import libraries. Interfacing must be done by the mean of DLLs. + +@item +It is possible to link against Microsoft C libraries. Yet the preferred +solution is to use C/C++ compiler that comes with GNAT, since it +doesn't require having two different development environments and makes the +inter-language debugging experience smoother. + +@item +When the compilation environment is located on FAT32 drives, users may +experience recompilations of the source files that have not changed if +Daylight Saving Time (DST) state has changed since the last time files +were compiled. NTFS drives do not have this problem. + +@item +No components of the GNAT toolset use any entries in the Windows +registry. The only entries that can be created are file associations and +PATH settings, provided the user has chosen to create them at installation +time, as well as some minimal book-keeping information needed to correctly +uninstall or integrate different GNAT products. +@end itemize + +@node Using a network installation of GNAT,CONSOLE and WINDOWS subsystems,Using GNAT on Windows,Microsoft Windows Topics +@anchor{gnat_ugn/platform_specific_information id11}@anchor{26a}@anchor{gnat_ugn/platform_specific_information using-a-network-installation-of-gnat}@anchor{26b} +@subsection Using a network installation of GNAT + + +Make sure the system on which GNAT is installed is accessible from the +current machine, i.e., the install location is shared over the network. +Shared resources are accessed on Windows by means of UNC paths, which +have the format @cite{\\server\sharename\path} + +In order to use such a network installation, simply add the UNC path of the +@code{bin} directory of your GNAT installation in front of your PATH. For +example, if GNAT is installed in @code{\GNAT} directory of a share location +called @code{c-drive} on a machine @code{LOKI}, the following command will +make it available: + +@quotation + +@example +$ path \\loki\c-drive\gnat\bin;%path%` +@end example +@end quotation + +Be aware that every compilation using the network installation results in the +transfer of large amounts of data across the network and will likely cause +serious performance penalty. + +@node CONSOLE and WINDOWS subsystems,Temporary Files,Using a network installation of GNAT,Microsoft Windows Topics +@anchor{gnat_ugn/platform_specific_information id12}@anchor{26c}@anchor{gnat_ugn/platform_specific_information console-and-windows-subsystems}@anchor{26d} +@subsection CONSOLE and WINDOWS subsystems + + +@geindex CONSOLE Subsystem + +@geindex WINDOWS Subsystem + +@geindex -mwindows + +There are two main subsystems under Windows. The @cite{CONSOLE} subsystem +(which is the default subsystem) will always create a console when +launching the application. This is not something desirable when the +application has a Windows GUI. To get rid of this console the +application must be using the @cite{WINDOWS} subsystem. To do so +the @emph{-mwindows} linker option must be specified. + +@quotation + +@example +$ gnatmake winprog -largs -mwindows +@end example +@end quotation + +@node Temporary Files,Mixed-Language Programming on Windows,CONSOLE and WINDOWS subsystems,Microsoft Windows Topics +@anchor{gnat_ugn/platform_specific_information id13}@anchor{26e}@anchor{gnat_ugn/platform_specific_information temporary-files}@anchor{26f} +@subsection Temporary Files + + +@geindex Temporary files + +It is possible to control where temporary files gets created by setting +the +@geindex TMP +@geindex environment variable; TMP +@code{TMP} environment variable. The file will be created: + + +@itemize * + +@item +Under the directory pointed to by the +@geindex TMP +@geindex environment variable; TMP +@code{TMP} environment variable if +this directory exists. + +@item +Under @code{c:\temp}, if the +@geindex TMP +@geindex environment variable; TMP +@code{TMP} environment variable is not +set (or not pointing to a directory) and if this directory exists. + +@item +Under the current working directory otherwise. +@end itemize + +This allows you to determine exactly where the temporary +file will be created. This is particularly useful in networked +environments where you may not have write access to some +directories. + +@node Mixed-Language Programming on Windows,,Temporary Files,Microsoft Windows Topics +@anchor{gnat_ugn/platform_specific_information mixed-language-programming-on-windows}@anchor{270}@anchor{gnat_ugn/platform_specific_information id14}@anchor{271} +@subsection Mixed-Language Programming on Windows + + +Developing pure Ada applications on Windows is no different than on +other GNAT-supported platforms. However, when developing or porting an +application that contains a mix of Ada and C/C++, the choice of your +Windows C/C++ development environment conditions your overall +interoperability strategy. + +If you use @emph{gcc} or Microsoft C to compile the non-Ada part of +your application, there are no Windows-specific restrictions that +affect the overall interoperability with your Ada code. If you do want +to use the Microsoft tools for your C++ code, you have two choices: + + +@itemize * + +@item +Encapsulate your C++ code in a DLL to be linked with your Ada +application. In this case, use the Microsoft or whatever environment to +build the DLL and use GNAT to build your executable +(@ref{272,,Using DLLs with GNAT}). + +@item +Or you can encapsulate your Ada code in a DLL to be linked with the +other part of your application. In this case, use GNAT to build the DLL +(@ref{273,,Building DLLs with GNAT Project files}) and use the Microsoft +or whatever environment to build your executable. +@end itemize + +In addition to the description about C main in +@ref{46,,Mixed Language Programming} section, if the C main uses a +stand-alone library it is required on x86-windows to +setup the SEH context. For this the C main must looks like this: + +@quotation + +@example +/* main.c */ +extern void adainit (void); +extern void adafinal (void); +extern void __gnat_initialize(void*); +extern void call_to_ada (void); + +int main (int argc, char *argv[]) +@{ + int SEH [2]; + + /* Initialize the SEH context */ + __gnat_initialize (&SEH); + + adainit(); + + /* Then call Ada services in the stand-alone library */ + + call_to_ada(); + + adafinal(); +@} +@end example +@end quotation + +Note that this is not needed on x86_64-windows where the Windows +native SEH support is used. + +@menu +* Windows Calling Conventions:: +* Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs. +* Using DLLs with GNAT:: +* Building DLLs with GNAT Project files:: +* Building DLLs with GNAT:: +* Building DLLs with gnatdll:: +* Ada DLLs and Finalization:: +* Creating a Spec for Ada DLLs:: +* GNAT and Windows Resources:: +* Debugging a DLL:: +* Setting Stack Size from gnatlink:: +* Setting Heap Size from gnatlink:: + +@end menu + +@node Windows Calling Conventions,Introduction to Dynamic Link Libraries DLLs,,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information windows-calling-conventions}@anchor{274}@anchor{gnat_ugn/platform_specific_information id15}@anchor{275} +@subsubsection Windows Calling Conventions + + +@geindex Stdcall + +@geindex APIENTRY + +This section pertain only to Win32. On Win64 there is a single native +calling convention. All convention specifiers are ignored on this +platform. + +When a subprogram @cite{F} (caller) calls a subprogram @cite{G} +(callee), there are several ways to push @cite{G}'s parameters on the +stack and there are several possible scenarios to clean up the stack +upon @cite{G}'s return. A calling convention is an agreed upon software +protocol whereby the responsibilities between the caller (@cite{F}) and +the callee (@cite{G}) are clearly defined. Several calling conventions +are available for Windows: + + +@itemize * + +@item +@cite{C} (Microsoft defined) + +@item +@cite{Stdcall} (Microsoft defined) + +@item +@cite{Win32} (GNAT specific) + +@item +@cite{DLL} (GNAT specific) +@end itemize + +@menu +* C Calling Convention:: +* Stdcall Calling Convention:: +* Win32 Calling Convention:: +* DLL Calling Convention:: + +@end menu + +@node C Calling Convention,Stdcall Calling Convention,,Windows Calling Conventions +@anchor{gnat_ugn/platform_specific_information c-calling-convention}@anchor{276}@anchor{gnat_ugn/platform_specific_information id16}@anchor{277} +@subsubsection @cite{C} Calling Convention + + +This is the default calling convention used when interfacing to C/C++ +routines compiled with either @emph{gcc} or Microsoft Visual C++. + +In the @cite{C} calling convention subprogram parameters are pushed on the +stack by the caller from right to left. The caller itself is in charge of +cleaning up the stack after the call. In addition, the name of a routine +with @cite{C} calling convention is mangled by adding a leading underscore. + +The name to use on the Ada side when importing (or exporting) a routine +with @cite{C} calling convention is the name of the routine. For +instance the C function: + +@quotation + +@example +int get_val (long); +@end example +@end quotation + +should be imported from Ada as follows: + +@quotation + +@example +function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; +pragma Import (C, Get_Val, External_Name => "get_val"); +@end example +@end quotation + +Note that in this particular case the @cite{External_Name} parameter could +have been omitted since, when missing, this parameter is taken to be the +name of the Ada entity in lower case. When the @cite{Link_Name} parameter +is missing, as in the above example, this parameter is set to be the +@cite{External_Name} with a leading underscore. + +When importing a variable defined in C, you should always use the @cite{C} +calling convention unless the object containing the variable is part of a +DLL (in which case you should use the @cite{Stdcall} calling +convention, @ref{278,,Stdcall Calling Convention}). + +@node Stdcall Calling Convention,Win32 Calling Convention,C Calling Convention,Windows Calling Conventions +@anchor{gnat_ugn/platform_specific_information stdcall-calling-convention}@anchor{278}@anchor{gnat_ugn/platform_specific_information id17}@anchor{279} +@subsubsection @cite{Stdcall} Calling Convention + + +This convention, which was the calling convention used for Pascal +programs, is used by Microsoft for all the routines in the Win32 API for +efficiency reasons. It must be used to import any routine for which this +convention was specified. + +In the @cite{Stdcall} calling convention subprogram parameters are pushed +on the stack by the caller from right to left. The callee (and not the +caller) is in charge of cleaning the stack on routine exit. In addition, +the name of a routine with @cite{Stdcall} calling convention is mangled by +adding a leading underscore (as for the @cite{C} calling convention) and a +trailing @code{@@@emph{nn}}, where @cite{nn} is the overall size (in +bytes) of the parameters passed to the routine. + +The name to use on the Ada side when importing a C routine with a +@cite{Stdcall} calling convention is the name of the C routine. The leading +underscore and trailing @code{@@@emph{nn}} are added automatically by +the compiler. For instance the Win32 function: + +@quotation + +@example +APIENTRY int get_val (long); +@end example +@end quotation + +should be imported from Ada as follows: + +@quotation + +@example +function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; +pragma Import (Stdcall, Get_Val); +-- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4" +@end example +@end quotation + +As for the @cite{C} calling convention, when the @cite{External_Name} +parameter is missing, it is taken to be the name of the Ada entity in lower +case. If instead of writing the above import pragma you write: + +@quotation + +@example +function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; +pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val"); +@end example +@end quotation + +then the imported routine is @cite{_retrieve_val@@4}. However, if instead +of specifying the @cite{External_Name} parameter you specify the +@cite{Link_Name} as in the following example: + +@quotation + +@example +function Get_Val (V : Interfaces.C.long) return Interfaces.C.int; +pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val"); +@end example +@end quotation + +then the imported routine is @cite{retrieve_val}, that is, there is no +decoration at all. No leading underscore and no Stdcall suffix +@code{@@@emph{nn}}. + +This is especially important as in some special cases a DLL's entry +point name lacks a trailing @code{@@@emph{nn}} while the exported +name generated for a call has it. + +It is also possible to import variables defined in a DLL by using an +import pragma for a variable. As an example, if a DLL contains a +variable defined as: + +@quotation + +@example +int my_var; +@end example +@end quotation + +then, to access this variable from Ada you should write: + +@quotation + +@example +My_Var : Interfaces.C.int; +pragma Import (Stdcall, My_Var); +@end example +@end quotation + +Note that to ease building cross-platform bindings this convention +will be handled as a @cite{C} calling convention on non-Windows platforms. + +@node Win32 Calling Convention,DLL Calling Convention,Stdcall Calling Convention,Windows Calling Conventions +@anchor{gnat_ugn/platform_specific_information id18}@anchor{27a}@anchor{gnat_ugn/platform_specific_information win32-calling-convention}@anchor{27b} +@subsubsection @cite{Win32} Calling Convention + + +This convention, which is GNAT-specific is fully equivalent to the +@cite{Stdcall} calling convention described above. + +@node DLL Calling Convention,,Win32 Calling Convention,Windows Calling Conventions +@anchor{gnat_ugn/platform_specific_information id19}@anchor{27c}@anchor{gnat_ugn/platform_specific_information dll-calling-convention}@anchor{27d} +@subsubsection @cite{DLL} Calling Convention + + +This convention, which is GNAT-specific is fully equivalent to the +@cite{Stdcall} calling convention described above. + +@node Introduction to Dynamic Link Libraries DLLs,Using DLLs with GNAT,Windows Calling Conventions,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id20}@anchor{27e}@anchor{gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls}@anchor{27f} +@subsubsection Introduction to Dynamic Link Libraries (DLLs) + + +@geindex DLL + +A Dynamically Linked Library (DLL) is a library that can be shared by +several applications running under Windows. A DLL can contain any number of +routines and variables. + +One advantage of DLLs is that you can change and enhance them without +forcing all the applications that depend on them to be relinked or +recompiled. However, you should be aware than all calls to DLL routines are +slower since, as you will understand below, such calls are indirect. + +To illustrate the remainder of this section, suppose that an application +wants to use the services of a DLL @code{API.dll}. To use the services +provided by @code{API.dll} you must statically link against the DLL or +an import library which contains a jump table with an entry for each +routine and variable exported by the DLL. In the Microsoft world this +import library is called @code{API.lib}. When using GNAT this import +library is called either @code{libAPI.dll.a}, @code{libapi.dll.a}, +@code{libAPI.a} or @code{libapi.a} (names are case insensitive). + +After you have linked your application with the DLL or the import library +and you run your application, here is what happens: + + +@itemize * + +@item +Your application is loaded into memory. + +@item +The DLL @code{API.dll} is mapped into the address space of your +application. This means that: + + +@itemize - + +@item +The DLL will use the stack of the calling thread. + +@item +The DLL will use the virtual address space of the calling process. + +@item +The DLL will allocate memory from the virtual address space of the calling +process. + +@item +Handles (pointers) can be safely exchanged between routines in the DLL +routines and routines in the application using the DLL. +@end itemize + +@item +The entries in the jump table (from the import library @code{libAPI.dll.a} +or @code{API.lib} or automatically created when linking against a DLL) +which is part of your application are initialized with the addresses +of the routines and variables in @code{API.dll}. + +@item +If present in @code{API.dll}, routines @cite{DllMain} or +@cite{DllMainCRTStartup} are invoked. These routines typically contain +the initialization code needed for the well-being of the routines and +variables exported by the DLL. +@end itemize + +There is an additional point which is worth mentioning. In the Windows +world there are two kind of DLLs: relocatable and non-relocatable +DLLs. Non-relocatable DLLs can only be loaded at a very specific address +in the target application address space. If the addresses of two +non-relocatable DLLs overlap and these happen to be used by the same +application, a conflict will occur and the application will run +incorrectly. Hence, when possible, it is always preferable to use and +build relocatable DLLs. Both relocatable and non-relocatable DLLs are +supported by GNAT. Note that the @emph{-s} linker option (see GNU Linker +User's Guide) removes the debugging symbols from the DLL but the DLL can +still be relocated. + +As a side note, an interesting difference between Microsoft DLLs and +Unix shared libraries, is the fact that on most Unix systems all public +routines are exported by default in a Unix shared library, while under +Windows it is possible (but not required) to list exported routines in +a definition file (see @ref{280,,The Definition File}). + +@node Using DLLs with GNAT,Building DLLs with GNAT Project files,Introduction to Dynamic Link Libraries DLLs,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id21}@anchor{281}@anchor{gnat_ugn/platform_specific_information using-dlls-with-gnat}@anchor{272} +@subsubsection Using DLLs with GNAT + + +To use the services of a DLL, say @code{API.dll}, in your Ada application +you must have: + + +@itemize * + +@item +The Ada spec for the routines and/or variables you want to access in +@code{API.dll}. If not available this Ada spec must be built from the C/C++ +header files provided with the DLL. + +@item +The import library (@code{libAPI.dll.a} or @code{API.lib}). As previously +mentioned an import library is a statically linked library containing the +import table which will be filled at load time to point to the actual +@code{API.dll} routines. Sometimes you don't have an import library for the +DLL you want to use. The following sections will explain how to build +one. Note that this is optional. + +@item +The actual DLL, @code{API.dll}. +@end itemize + +Once you have all the above, to compile an Ada application that uses the +services of @code{API.dll} and whose main subprogram is @cite{My_Ada_App}, +you simply issue the command + +@quotation + +@example +$ gnatmake my_ada_app -largs -lAPI +@end example +@end quotation + +The argument @emph{-largs -lAPI} at the end of the @emph{gnatmake} command +tells the GNAT linker to look for an import library. The linker will +look for a library name in this specific order: + + +@itemize * + +@item +@code{libAPI.dll.a} + +@item +@code{API.dll.a} + +@item +@code{libAPI.a} + +@item +@code{API.lib} + +@item +@code{libAPI.dll} + +@item +@code{API.dll} +@end itemize + +The first three are the GNU style import libraries. The third is the +Microsoft style import libraries. The last two are the actual DLL names. + +Note that if the Ada package spec for @code{API.dll} contains the +following pragma + +@quotation + +@example +pragma Linker_Options ("-lAPI"); +@end example +@end quotation + +you do not have to add @emph{-largs -lAPI} at the end of the +@emph{gnatmake} command. + +If any one of the items above is missing you will have to create it +yourself. The following sections explain how to do so using as an +example a fictitious DLL called @code{API.dll}. + +@menu +* Creating an Ada Spec for the DLL Services:: +* Creating an Import Library:: + +@end menu + +@node Creating an Ada Spec for the DLL Services,Creating an Import Library,,Using DLLs with GNAT +@anchor{gnat_ugn/platform_specific_information creating-an-ada-spec-for-the-dll-services}@anchor{282}@anchor{gnat_ugn/platform_specific_information id22}@anchor{283} +@subsubsection Creating an Ada Spec for the DLL Services + + +A DLL typically comes with a C/C++ header file which provides the +definitions of the routines and variables exported by the DLL. The Ada +equivalent of this header file is a package spec that contains definitions +for the imported entities. If the DLL you intend to use does not come with +an Ada spec you have to generate one such spec yourself. For example if +the header file of @code{API.dll} is a file @code{api.h} containing the +following two definitions: + +@quotation + +@example +int some_var; +int get (char *); +@end example +@end quotation + +then the equivalent Ada spec could be: + +@quotation + +@example +with Interfaces.C.Strings; +package API is + use Interfaces; + + Some_Var : C.int; + function Get (Str : C.Strings.Chars_Ptr) return C.int; + +private + pragma Import (C, Get); + pragma Import (DLL, Some_Var); +end API; +@end example +@end quotation + +@node Creating an Import Library,,Creating an Ada Spec for the DLL Services,Using DLLs with GNAT +@anchor{gnat_ugn/platform_specific_information id23}@anchor{284}@anchor{gnat_ugn/platform_specific_information creating-an-import-library}@anchor{285} +@subsubsection Creating an Import Library + + +@geindex Import library + +If a Microsoft-style import library @code{API.lib} or a GNAT-style +import library @code{libAPI.dll.a} or @code{libAPI.a} is available +with @code{API.dll} you can skip this section. You can also skip this +section if @code{API.dll} or @code{libAPI.dll} is built with GNU tools +as in this case it is possible to link directly against the +DLL. Otherwise read on. + +@geindex Definition file +@anchor{gnat_ugn/platform_specific_information the-definition-file}@anchor{280} +@subsubheading The Definition File + + +As previously mentioned, and unlike Unix systems, the list of symbols +that are exported from a DLL must be provided explicitly in Windows. +The main goal of a definition file is precisely that: list the symbols +exported by a DLL. A definition file (usually a file with a @cite{.def} +suffix) has the following structure: + +@quotation + +@example +[LIBRARY `name`] +[DESCRIPTION `string`] +EXPORTS + `symbol1` + `symbol2` + ... +@end example +@end quotation + + +@table @asis + +@item @emph{LIBRARY `name`} + +This section, which is optional, gives the name of the DLL. + +@item @emph{DESCRIPTION `string`} + +This section, which is optional, gives a description string that will be +embedded in the import library. + +@item @emph{EXPORTS} + +This section gives the list of exported symbols (procedures, functions or +variables). For instance in the case of @code{API.dll} the @cite{EXPORTS} +section of @code{API.def} looks like: + +@example +EXPORTS + some_var + get +@end example +@end table + +Note that you must specify the correct suffix (@code{@@@emph{nn}}) +(see @ref{274,,Windows Calling Conventions}) for a Stdcall +calling convention function in the exported symbols list. + +There can actually be other sections in a definition file, but these +sections are not relevant to the discussion at hand. + +@subsubheading GNAT-Style Import Library + +@anchor{gnat_ugn/platform_specific_information gnat-style-import-library}@anchor{286} +To create a static import library from @code{API.dll} with the GNAT tools +you should proceed as follows: + + +@itemize * + +@item +Create the definition file @code{API.def} +(see @ref{280,,The Definition File}). +For that use the @cite{dll2def} tool as follows: + +@example +$ dll2def API.dll > API.def +@end example + +@cite{dll2def} is a very simple tool: it takes as input a DLL and prints +to standard output the list of entry points in the DLL. Note that if +some routines in the DLL have the @cite{Stdcall} convention +(@ref{274,,Windows Calling Conventions}) with stripped @code{@@@emph{nn}} +suffix then you'll have to edit @code{api.def} to add it, and specify +@emph{-k} to @emph{gnatdll} when creating the import library. + +Here are some hints to find the right @code{@@@emph{nn}} suffix. + + +@itemize - + +@item +If you have the Microsoft import library (.lib), it is possible to get +the right symbols by using Microsoft @cite{dumpbin} tool (see the +corresponding Microsoft documentation for further details). + +@example +$ dumpbin /exports api.lib +@end example + +@item +If you have a message about a missing symbol at link time the compiler +tells you what symbol is expected. You just have to go back to the +definition file and add the right suffix. +@end itemize + +@item +Build the import library @cite{libAPI.dll.a}, using @cite{gnatdll} +(see @ref{287,,Using gnatdll}) as follows: + +@example +$ gnatdll -e API.def -d API.dll +@end example + +@cite{gnatdll} takes as input a definition file @code{API.def} and the +name of the DLL containing the services listed in the definition file +@code{API.dll}. The name of the static import library generated is +computed from the name of the definition file as follows: if the +definition file name is @cite{xyz`}.def`, the import library name will +be @cite{lib`@w{`}xyz`}.a`. Note that in the previous example option +@emph{-e} could have been removed because the name of the definition +file (before the '@cite{.def}' suffix) is the same as the name of the +DLL (@ref{287,,Using gnatdll} for more information about @cite{gnatdll}). +@end itemize + +@subsubheading Microsoft-Style Import Library + + +With GNAT you can either use a GNAT-style or Microsoft-style import +library. A Microsoft import library is needed only if you plan to make an +Ada DLL available to applications developed with Microsoft +tools (@ref{270,,Mixed-Language Programming on Windows}). + +To create a Microsoft-style import library for @code{API.dll} you +should proceed as follows: + + +@itemize * + +@item +Create the definition file @code{API.def} from the DLL. For this use either +the @cite{dll2def} tool as described above or the Microsoft @cite{dumpbin} +tool (see the corresponding Microsoft documentation for further details). + +@item +Build the actual import library using Microsoft's @cite{lib} utility: + +@example +$ lib -machine:IX86 -def:API.def -out:API.lib +@end example + +If you use the above command the definition file @code{API.def} must +contain a line giving the name of the DLL: + +@example +LIBRARY "API" +@end example + +See the Microsoft documentation for further details about the usage of +@cite{lib}. +@end itemize + +@node Building DLLs with GNAT Project files,Building DLLs with GNAT,Using DLLs with GNAT,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id24}@anchor{288}@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files}@anchor{273} +@subsubsection Building DLLs with GNAT Project files + + +@geindex DLLs +@geindex building + +There is nothing specific to Windows in the build process. +@ref{8a,,Library Projects}. + +Due to a system limitation, it is not possible under Windows to create threads +when inside the @cite{DllMain} routine which is used for auto-initialization +of shared libraries, so it is not possible to have library level tasks in SALs. + +@node Building DLLs with GNAT,Building DLLs with gnatdll,Building DLLs with GNAT Project files,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat}@anchor{289}@anchor{gnat_ugn/platform_specific_information id25}@anchor{28a} +@subsubsection Building DLLs with GNAT + + +@geindex DLLs +@geindex building + +This section explain how to build DLLs using the GNAT built-in DLL +support. With the following procedure it is straight forward to build +and use DLLs with GNAT. + + +@itemize * + +@item +Building object files. +The first step is to build all objects files that are to be included +into the DLL. This is done by using the standard @emph{gnatmake} tool. + +@item +Building the DLL. +To build the DLL you must use @emph{gcc}'s @emph{-shared} and +@emph{-shared-libgcc} options. It is quite simple to use this method: + +@example +$ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ... +@end example + +It is important to note that in this case all symbols found in the +object files are automatically exported. It is possible to restrict +the set of symbols to export by passing to @emph{gcc} a definition +file (see @ref{280,,The Definition File}). +For example: + +@example +$ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ... +@end example + +If you use a definition file you must export the elaboration procedures +for every package that required one. Elaboration procedures are named +using the package name followed by "_E". + +@item +Preparing DLL to be used. +For the DLL to be used by client programs the bodies must be hidden +from it and the .ali set with read-only attribute. This is very important +otherwise GNAT will recompile all packages and will not actually use +the code in the DLL. For example: + +@example +$ mkdir apilib +$ copy *.ads *.ali api.dll apilib +$ attrib +R apilib\\*.ali +@end example +@end itemize + +At this point it is possible to use the DLL by directly linking +against it. Note that you must use the GNAT shared runtime when using +GNAT shared libraries. This is achieved by using @emph{-shared} binder's +option. + +@quotation + +@example +$ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI +@end example +@end quotation + +@node Building DLLs with gnatdll,Ada DLLs and Finalization,Building DLLs with GNAT,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnatdll}@anchor{28b}@anchor{gnat_ugn/platform_specific_information id26}@anchor{28c} +@subsubsection Building DLLs with gnatdll + + +@geindex DLLs +@geindex building + +Note that it is preferred to use GNAT Project files +(@ref{273,,Building DLLs with GNAT Project files}) or the built-in GNAT +DLL support (@ref{289,,Building DLLs with GNAT}) or to build DLLs. + +This section explains how to build DLLs containing Ada code using +@cite{gnatdll}. These DLLs will be referred to as Ada DLLs in the +remainder of this section. + +The steps required to build an Ada DLL that is to be used by Ada as well as +non-Ada applications are as follows: + + +@itemize * + +@item +You need to mark each Ada @emph{entity} exported by the DLL with a @cite{C} or +@cite{Stdcall} calling convention to avoid any Ada name mangling for the +entities exported by the DLL +(see @ref{28d,,Exporting Ada Entities}). You can +skip this step if you plan to use the Ada DLL only from Ada applications. + +@item +Your Ada code must export an initialization routine which calls the routine +@cite{adainit} generated by @emph{gnatbind} to perform the elaboration of +the Ada code in the DLL (@ref{28e,,Ada DLLs and Elaboration}). The initialization +routine exported by the Ada DLL must be invoked by the clients of the DLL +to initialize the DLL. + +@item +When useful, the DLL should also export a finalization routine which calls +routine @cite{adafinal} generated by @emph{gnatbind} to perform the +finalization of the Ada code in the DLL (@ref{28f,,Ada DLLs and Finalization}). +The finalization routine exported by the Ada DLL must be invoked by the +clients of the DLL when the DLL services are no further needed. + +@item +You must provide a spec for the services exported by the Ada DLL in each +of the programming languages to which you plan to make the DLL available. + +@item +You must provide a definition file listing the exported entities +(@ref{280,,The Definition File}). + +@item +Finally you must use @cite{gnatdll} to produce the DLL and the import +library (@ref{287,,Using gnatdll}). +@end itemize + +Note that a relocatable DLL stripped using the @cite{strip} +binutils tool will not be relocatable anymore. To build a DLL without +debug information pass @cite{-largs -s} to @cite{gnatdll}. This +restriction does not apply to a DLL built using a Library Project. +See @ref{8a,,Library Projects}. + +@c Limitations_When_Using_Ada_DLLs_from Ada: + +@menu +* Limitations When Using Ada DLLs from Ada:: +* Exporting Ada Entities:: +* Ada DLLs and Elaboration:: + +@end menu + +@node Limitations When Using Ada DLLs from Ada,Exporting Ada Entities,,Building DLLs with gnatdll +@anchor{gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada}@anchor{290} +@subsubsection Limitations When Using Ada DLLs from Ada + + +When using Ada DLLs from Ada applications there is a limitation users +should be aware of. Because on Windows the GNAT run time is not in a DLL of +its own, each Ada DLL includes a part of the GNAT run time. Specifically, +each Ada DLL includes the services of the GNAT run time that are necessary +to the Ada code inside the DLL. As a result, when an Ada program uses an +Ada DLL there are two independent GNAT run times: one in the Ada DLL and +one in the main program. + +It is therefore not possible to exchange GNAT run-time objects between the +Ada DLL and the main Ada program. Example of GNAT run-time objects are file +handles (e.g., @cite{Text_IO.File_Type}), tasks types, protected objects +types, etc. + +It is completely safe to exchange plain elementary, array or record types, +Windows object handles, etc. + +@node Exporting Ada Entities,Ada DLLs and Elaboration,Limitations When Using Ada DLLs from Ada,Building DLLs with gnatdll +@anchor{gnat_ugn/platform_specific_information exporting-ada-entities}@anchor{28d}@anchor{gnat_ugn/platform_specific_information id27}@anchor{291} +@subsubsection Exporting Ada Entities + + +@geindex Export table + +Building a DLL is a way to encapsulate a set of services usable from any +application. As a result, the Ada entities exported by a DLL should be +exported with the @cite{C} or @cite{Stdcall} calling conventions to avoid +any Ada name mangling. As an example here is an Ada package +@cite{API}, spec and body, exporting two procedures, a function, and a +variable: + +@quotation + +@example +with Interfaces.C; use Interfaces; +package API is + Count : C.int := 0; + function Factorial (Val : C.int) return C.int; + + procedure Initialize_API; + procedure Finalize_API; + -- Initialization & Finalization routines. More in the next section. +private + pragma Export (C, Initialize_API); + pragma Export (C, Finalize_API); + pragma Export (C, Count); + pragma Export (C, Factorial); +end API; +@end example + +@example +package body API is + function Factorial (Val : C.int) return C.int is + Fact : C.int := 1; + begin + Count := Count + 1; + for K in 1 .. Val loop + Fact := Fact * K; + end loop; + return Fact; + end Factorial; + + procedure Initialize_API is + procedure Adainit; + pragma Import (C, Adainit); + begin + Adainit; + end Initialize_API; + + procedure Finalize_API is + procedure Adafinal; + pragma Import (C, Adafinal); + begin + Adafinal; + end Finalize_API; +end API; +@end example +@end quotation + +If the Ada DLL you are building will only be used by Ada applications +you do not have to export Ada entities with a @cite{C} or @cite{Stdcall} +convention. As an example, the previous package could be written as +follows: + +@quotation + +@example +package API is + Count : Integer := 0; + function Factorial (Val : Integer) return Integer; + + procedure Initialize_API; + procedure Finalize_API; + -- Initialization and Finalization routines. +end API; +@end example + +@example +package body API is + function Factorial (Val : Integer) return Integer is + Fact : Integer := 1; + begin + Count := Count + 1; + for K in 1 .. Val loop + Fact := Fact * K; + end loop; + return Fact; + end Factorial; + + ... + -- The remainder of this package body is unchanged. +end API; +@end example +@end quotation + +Note that if you do not export the Ada entities with a @cite{C} or +@cite{Stdcall} convention you will have to provide the mangled Ada names +in the definition file of the Ada DLL +(@ref{292,,Creating the Definition File}). + +@node Ada DLLs and Elaboration,,Exporting Ada Entities,Building DLLs with gnatdll +@anchor{gnat_ugn/platform_specific_information ada-dlls-and-elaboration}@anchor{28e}@anchor{gnat_ugn/platform_specific_information id28}@anchor{293} +@subsubsection Ada DLLs and Elaboration + + +@geindex DLLs and elaboration + +The DLL that you are building contains your Ada code as well as all the +routines in the Ada library that are needed by it. The first thing a +user of your DLL must do is elaborate the Ada code +(@ref{11,,Elaboration Order Handling in GNAT}). + +To achieve this you must export an initialization routine +(@cite{Initialize_API} in the previous example), which must be invoked +before using any of the DLL services. This elaboration routine must call +the Ada elaboration routine @cite{adainit} generated by the GNAT binder +(@ref{ba,,Binding with Non-Ada Main Programs}). See the body of +@cite{Initialize_Api} for an example. Note that the GNAT binder is +automatically invoked during the DLL build process by the @cite{gnatdll} +tool (@ref{287,,Using gnatdll}). + +When a DLL is loaded, Windows systematically invokes a routine called +@cite{DllMain}. It would therefore be possible to call @cite{adainit} +directly from @cite{DllMain} without having to provide an explicit +initialization routine. Unfortunately, it is not possible to call +@cite{adainit} from the @cite{DllMain} if your program has library level +tasks because access to the @cite{DllMain} entry point is serialized by +the system (that is, only a single thread can execute 'through' it at a +time), which means that the GNAT run time will deadlock waiting for the +newly created task to complete its initialization. + +@node Ada DLLs and Finalization,Creating a Spec for Ada DLLs,Building DLLs with gnatdll,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id29}@anchor{294}@anchor{gnat_ugn/platform_specific_information ada-dlls-and-finalization}@anchor{28f} +@subsubsection Ada DLLs and Finalization + + +@geindex DLLs and finalization + +When the services of an Ada DLL are no longer needed, the client code should +invoke the DLL finalization routine, if available. The DLL finalization +routine is in charge of releasing all resources acquired by the DLL. In the +case of the Ada code contained in the DLL, this is achieved by calling +routine @cite{adafinal} generated by the GNAT binder +(@ref{ba,,Binding with Non-Ada Main Programs}). +See the body of @cite{Finalize_Api} for an +example. As already pointed out the GNAT binder is automatically invoked +during the DLL build process by the @cite{gnatdll} tool +(@ref{287,,Using gnatdll}). + +@node Creating a Spec for Ada DLLs,GNAT and Windows Resources,Ada DLLs and Finalization,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id30}@anchor{295}@anchor{gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls}@anchor{296} +@subsubsection Creating a Spec for Ada DLLs + + +To use the services exported by the Ada DLL from another programming +language (e.g., C), you have to translate the specs of the exported Ada +entities in that language. For instance in the case of @cite{API.dll}, +the corresponding C header file could look like: + +@quotation + +@example +extern int *_imp__count; +#define count (*_imp__count) +int factorial (int); +@end example +@end quotation + +It is important to understand that when building an Ada DLL to be used by +other Ada applications, you need two different specs for the packages +contained in the DLL: one for building the DLL and the other for using +the DLL. This is because the @cite{DLL} calling convention is needed to +use a variable defined in a DLL, but when building the DLL, the variable +must have either the @cite{Ada} or @cite{C} calling convention. As an +example consider a DLL comprising the following package @cite{API}: + +@quotation + +@example +package API is + Count : Integer := 0; + ... + -- Remainder of the package omitted. +end API; +@end example +@end quotation + +After producing a DLL containing package @cite{API}, the spec that +must be used to import @cite{API.Count} from Ada code outside of the +DLL is: + +@quotation + +@example +package API is + Count : Integer; + pragma Import (DLL, Count); +end API; +@end example +@end quotation + +@menu +* Creating the Definition File:: +* Using gnatdll:: + +@end menu + +@node Creating the Definition File,Using gnatdll,,Creating a Spec for Ada DLLs +@anchor{gnat_ugn/platform_specific_information creating-the-definition-file}@anchor{292}@anchor{gnat_ugn/platform_specific_information id31}@anchor{297} +@subsubsection Creating the Definition File + + +The definition file is the last file needed to build the DLL. It lists +the exported symbols. As an example, the definition file for a DLL +containing only package @cite{API} (where all the entities are exported +with a @cite{C} calling convention) is: + +@quotation + +@example +EXPORTS + count + factorial + finalize_api + initialize_api +@end example +@end quotation + +If the @cite{C} calling convention is missing from package @cite{API}, +then the definition file contains the mangled Ada names of the above +entities, which in this case are: + +@quotation + +@example +EXPORTS + api__count + api__factorial + api__finalize_api + api__initialize_api +@end example +@end quotation + +@node Using gnatdll,,Creating the Definition File,Creating a Spec for Ada DLLs +@anchor{gnat_ugn/platform_specific_information using-gnatdll}@anchor{287}@anchor{gnat_ugn/platform_specific_information id32}@anchor{298} +@subsubsection Using @cite{gnatdll} + + +@geindex gnatdll + +@cite{gnatdll} is a tool to automate the DLL build process once all the Ada +and non-Ada sources that make up your DLL have been compiled. +@cite{gnatdll} is actually in charge of two distinct tasks: build the +static import library for the DLL and the actual DLL. The form of the +@cite{gnatdll} command is + +@quotation + +@example +$ gnatdll [`switches`] `list-of-files` [-largs `opts`] +@end example +@end quotation + +where @cite{list-of-files} is a list of ALI and object files. The object +file list must be the exact list of objects corresponding to the non-Ada +sources whose services are to be included in the DLL. The ALI file list +must be the exact list of ALI files for the corresponding Ada sources +whose services are to be included in the DLL. If @cite{list-of-files} is +missing, only the static import library is generated. + +You may specify any of the following switches to @cite{gnatdll}: + +@quotation + +@geindex -a (gnatdll) +@end quotation + + +@table @asis + +@item @code{-a[@emph{address}]} + +Build a non-relocatable DLL at @cite{address}. If @cite{address} is not +specified the default address @cite{0x11000000} will be used. By default, +when this switch is missing, @cite{gnatdll} builds relocatable DLL. We +advise the reader to build relocatable DLL. + +@geindex -b (gnatdll) + +@item @code{-b @emph{address}} + +Set the relocatable DLL base address. By default the address is +@cite{0x11000000}. + +@geindex -bargs (gnatdll) + +@item @code{-bargs @emph{opts}} + +Binder options. Pass @cite{opts} to the binder. + +@geindex -d (gnatdll) + +@item @code{-d @emph{dllfile}} + +@cite{dllfile} is the name of the DLL. This switch must be present for +@cite{gnatdll} to do anything. The name of the generated import library is +obtained algorithmically from @cite{dllfile} as shown in the following +example: if @cite{dllfile} is @cite{xyz.dll}, the import library name is +@cite{libxyz.dll.a}. The name of the definition file to use (if not specified +by option @emph{-e}) is obtained algorithmically from @cite{dllfile} +as shown in the following example: +if @cite{dllfile} is @cite{xyz.dll}, the definition +file used is @cite{xyz.def}. + +@geindex -e (gnatdll) + +@item @code{-e @emph{deffile}} + +@cite{deffile} is the name of the definition file. + +@geindex -g (gnatdll) + +@item @code{-g} + +Generate debugging information. This information is stored in the object +file and copied from there to the final DLL file by the linker, +where it can be read by the debugger. You must use the +@emph{-g} switch if you plan on using the debugger or the symbolic +stack traceback. + +@geindex -h (gnatdll) + +@item @code{-h} + +Help mode. Displays @cite{gnatdll} switch usage information. + +@geindex -I (gnatdll) + +@item @code{-I@emph{dir}} + +Direct @cite{gnatdll} to search the @cite{dir} directory for source and +object files needed to build the DLL. +(@ref{8e,,Search Paths and the Run-Time Library (RTL)}). + +@geindex -k (gnatdll) + +@item @code{-k} + +Removes the @code{@@@emph{nn}} suffix from the import library's exported +names, but keeps them for the link names. You must specify this +option if you want to use a @cite{Stdcall} function in a DLL for which +the @code{@@@emph{nn}} suffix has been removed. This is the case for most +of the Windows NT DLL for example. This option has no effect when +@emph{-n} option is specified. + +@geindex -l (gnatdll) + +@item @code{-l @emph{file}} + +The list of ALI and object files used to build the DLL are listed in +@cite{file}, instead of being given in the command line. Each line in +@cite{file} contains the name of an ALI or object file. + +@geindex -n (gnatdll) + +@item @code{-n} + +No Import. Do not create the import library. + +@geindex -q (gnatdll) + +@item @code{-q} + +Quiet mode. Do not display unnecessary messages. + +@geindex -v (gnatdll) + +@item @code{-v} + +Verbose mode. Display extra information. + +@geindex -largs (gnatdll) + +@item @code{-largs @emph{opts}} + +Linker options. Pass @cite{opts} to the linker. +@end table + +@subsubheading @cite{gnatdll} Example + + +As an example the command to build a relocatable DLL from @code{api.adb} +once @code{api.adb} has been compiled and @code{api.def} created is + +@quotation + +@example +$ gnatdll -d api.dll api.ali +@end example +@end quotation + +The above command creates two files: @code{libapi.dll.a} (the import +library) and @code{api.dll} (the actual DLL). If you want to create +only the DLL, just type: + +@quotation + +@example +$ gnatdll -d api.dll -n api.ali +@end example +@end quotation + +Alternatively if you want to create just the import library, type: + +@quotation + +@example +$ gnatdll -d api.dll +@end example +@end quotation + +@subsubheading @cite{gnatdll} behind the Scenes + + +This section details the steps involved in creating a DLL. @cite{gnatdll} +does these steps for you. Unless you are interested in understanding what +goes on behind the scenes, you should skip this section. + +We use the previous example of a DLL containing the Ada package @cite{API}, +to illustrate the steps necessary to build a DLL. The starting point is a +set of objects that will make up the DLL and the corresponding ALI +files. In the case of this example this means that @code{api.o} and +@code{api.ali} are available. To build a relocatable DLL, @cite{gnatdll} does +the following: + + +@itemize * + +@item +@cite{gnatdll} builds the base file (@code{api.base}). A base file gives +the information necessary to generate relocation information for the +DLL. + +@example +$ gnatbind -n api +$ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base +@end example + +In addition to the base file, the @emph{gnatlink} command generates an +output file @code{api.jnk} which can be discarded. The @emph{-mdll} switch +asks @emph{gnatlink} to generate the routines @cite{DllMain} and +@cite{DllMainCRTStartup} that are called by the Windows loader when the DLL +is loaded into memory. + +@item +@cite{gnatdll} uses @cite{dlltool} (see @ref{299,,Using dlltool}) to build the +export table (@code{api.exp}). The export table contains the relocation +information in a form which can be used during the final link to ensure +that the Windows loader is able to place the DLL anywhere in memory. + +@example +$ dlltool --dllname api.dll --def api.def --base-file api.base \\ + --output-exp api.exp +@end example + +@item +@cite{gnatdll} builds the base file using the new export table. Note that +@emph{gnatbind} must be called once again since the binder generated file +has been deleted during the previous call to @emph{gnatlink}. + +@example +$ gnatbind -n api +$ gnatlink api -o api.jnk api.exp -mdll + -Wl,--base-file,api.base +@end example + +@item +@cite{gnatdll} builds the new export table using the new base file and +generates the DLL import library @code{libAPI.dll.a}. + +@example +$ dlltool --dllname api.dll --def api.def --base-file api.base \\ + --output-exp api.exp --output-lib libAPI.a +@end example + +@item +Finally @cite{gnatdll} builds the relocatable DLL using the final export +table. + +@example +$ gnatbind -n api +$ gnatlink api api.exp -o api.dll -mdll +@end example +@end itemize +@anchor{gnat_ugn/platform_specific_information using-dlltool}@anchor{299} +@subsubheading Using @cite{dlltool} + + +@cite{dlltool} is the low-level tool used by @cite{gnatdll} to build +DLLs and static import libraries. This section summarizes the most +common @cite{dlltool} switches. The form of the @cite{dlltool} command +is + +@quotation + +@example +$ dlltool [`switches`] +@end example +@end quotation + +@cite{dlltool} switches include: + +@geindex --base-file (dlltool) + + +@table @asis + +@item @code{--base-file @emph{basefile}} + +Read the base file @cite{basefile} generated by the linker. This switch +is used to create a relocatable DLL. +@end table + +@geindex --def (dlltool) + + +@table @asis + +@item @code{--def @emph{deffile}} + +Read the definition file. +@end table + +@geindex --dllname (dlltool) + + +@table @asis + +@item @code{--dllname @emph{name}} + +Gives the name of the DLL. This switch is used to embed the name of the +DLL in the static import library generated by @cite{dlltool} with switch +@emph{--output-lib}. +@end table + +@geindex -k (dlltool) + + +@table @asis + +@item @code{-k} + +Kill @code{@@@emph{nn}} from exported names +(@ref{274,,Windows Calling Conventions} +for a discussion about @cite{Stdcall}-style symbols. +@end table + +@geindex --help (dlltool) + + +@table @asis + +@item @code{--help} + +Prints the @cite{dlltool} switches with a concise description. +@end table + +@geindex --output-exp (dlltool) + + +@table @asis + +@item @code{--output-exp @emph{exportfile}} + +Generate an export file @cite{exportfile}. The export file contains the +export table (list of symbols in the DLL) and is used to create the DLL. +@end table + +@geindex --output-lib (dlltool) + + +@table @asis + +@item @code{--output-lib @emph{libfile}} + +Generate a static import library @cite{libfile}. +@end table + +@geindex -v (dlltool) + + +@table @asis + +@item @code{-v} + +Verbose mode. +@end table + +@geindex --as (dlltool) + + +@table @asis + +@item @code{--as @emph{assembler-name}} + +Use @cite{assembler-name} as the assembler. The default is @cite{as}. +@end table + +@node GNAT and Windows Resources,Debugging a DLL,Creating a Spec for Ada DLLs,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information gnat-and-windows-resources}@anchor{29a}@anchor{gnat_ugn/platform_specific_information id33}@anchor{29b} +@subsubsection GNAT and Windows Resources + + +@geindex Resources +@geindex windows + +Resources are an easy way to add Windows specific objects to your +application. The objects that can be added as resources include: + + +@itemize * + +@item +menus + +@item +accelerators + +@item +dialog boxes + +@item +string tables + +@item +bitmaps + +@item +cursors + +@item +icons + +@item +fonts + +@item +version information +@end itemize + +For example, a version information resource can be defined as follow and +embedded into an executable or DLL: + +A version information resource can be used to embed information into an +executable or a DLL. These information can be viewed using the file properties +from the Windows Explorer. Here is an example of a version information +resource: + +@quotation + +@example +1 VERSIONINFO +FILEVERSION 1,0,0,0 +PRODUCTVERSION 1,0,0,0 +BEGIN + BLOCK "StringFileInfo" + BEGIN + BLOCK "080904E4" + BEGIN + VALUE "CompanyName", "My Company Name" + VALUE "FileDescription", "My application" + VALUE "FileVersion", "1.0" + VALUE "InternalName", "my_app" + VALUE "LegalCopyright", "My Name" + VALUE "OriginalFilename", "my_app.exe" + VALUE "ProductName", "My App" + VALUE "ProductVersion", "1.0" + END + END + + BLOCK "VarFileInfo" + BEGIN + VALUE "Translation", 0x809, 1252 + END +END +@end example +@end quotation + +The value @cite{0809} (langID) is for the U.K English language and +@cite{04E4} (charsetID), which is equal to @cite{1252} decimal, for +multilingual. + +This section explains how to build, compile and use resources. Note that this +section does not cover all resource objects, for a complete description see +the corresponding Microsoft documentation. + +@menu +* Building Resources:: +* Compiling Resources:: +* Using Resources:: + +@end menu + +@node Building Resources,Compiling Resources,,GNAT and Windows Resources +@anchor{gnat_ugn/platform_specific_information building-resources}@anchor{29c}@anchor{gnat_ugn/platform_specific_information id34}@anchor{29d} +@subsubsection Building Resources + + +@geindex Resources +@geindex building + +A resource file is an ASCII file. By convention resource files have an +@code{.rc} extension. +The easiest way to build a resource file is to use Microsoft tools +such as @cite{imagedit.exe} to build bitmaps, icons and cursors and +@cite{dlgedit.exe} to build dialogs. +It is always possible to build an @code{.rc} file yourself by writing a +resource script. + +It is not our objective to explain how to write a resource file. A +complete description of the resource script language can be found in the +Microsoft documentation. + +@node Compiling Resources,Using Resources,Building Resources,GNAT and Windows Resources +@anchor{gnat_ugn/platform_specific_information compiling-resources}@anchor{29e}@anchor{gnat_ugn/platform_specific_information id35}@anchor{29f} +@subsubsection Compiling Resources + + +@geindex rc + +@geindex windres + +@geindex Resources +@geindex compiling + +This section describes how to build a GNAT-compatible (COFF) object file +containing the resources. This is done using the Resource Compiler +@cite{windres} as follows: + +@quotation + +@example +$ windres -i myres.rc -o myres.o +@end example +@end quotation + +By default @cite{windres} will run @emph{gcc} to preprocess the @code{.rc} +file. You can specify an alternate preprocessor (usually named +@code{cpp.exe}) using the @cite{windres} @emph{--preprocessor} +parameter. A list of all possible options may be obtained by entering +the command @cite{windres} @emph{--help}. + +It is also possible to use the Microsoft resource compiler @cite{rc.exe} +to produce a @code{.res} file (binary resource file). See the +corresponding Microsoft documentation for further details. In this case +you need to use @cite{windres} to translate the @code{.res} file to a +GNAT-compatible object file as follows: + +@quotation + +@example +$ windres -i myres.res -o myres.o +@end example +@end quotation + +@node Using Resources,,Compiling Resources,GNAT and Windows Resources +@anchor{gnat_ugn/platform_specific_information id36}@anchor{2a0}@anchor{gnat_ugn/platform_specific_information using-resources}@anchor{2a1} +@subsubsection Using Resources + + +@geindex Resources +@geindex using + +To include the resource file in your program just add the +GNAT-compatible object file for the resource(s) to the linker +arguments. With @emph{gnatmake} this is done by using the @emph{-largs} +option: + +@quotation + +@example +$ gnatmake myprog -largs myres.o +@end example +@end quotation + +@node Debugging a DLL,Setting Stack Size from gnatlink,GNAT and Windows Resources,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information id37}@anchor{2a2}@anchor{gnat_ugn/platform_specific_information debugging-a-dll}@anchor{2a3} +@subsubsection Debugging a DLL + + +@geindex DLL debugging + +Debugging a DLL is similar to debugging a standard program. But +we have to deal with two different executable parts: the DLL and the +program that uses it. We have the following four possibilities: + + +@itemize * + +@item +The program and the DLL are built with @cite{GCC/GNAT}. + +@item +The program is built with foreign tools and the DLL is built with +@cite{GCC/GNAT}. + +@item +The program is built with @cite{GCC/GNAT} and the DLL is built with +foreign tools. +@end itemize + +In this section we address only cases one and two above. +There is no point in trying to debug +a DLL with @cite{GNU/GDB}, if there is no GDB-compatible debugging +information in it. To do so you must use a debugger compatible with the +tools suite used to build the DLL. + +@menu +* Program and DLL Both Built with GCC/GNAT:: +* Program Built with Foreign Tools and DLL Built with GCC/GNAT:: + +@end menu + +@node Program and DLL Both Built with GCC/GNAT,Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Debugging a DLL +@anchor{gnat_ugn/platform_specific_information program-and-dll-both-built-with-gcc-gnat}@anchor{2a4}@anchor{gnat_ugn/platform_specific_information id38}@anchor{2a5} +@subsubsection Program and DLL Both Built with GCC/GNAT + + +This is the simplest case. Both the DLL and the program have @cite{GDB} +compatible debugging information. It is then possible to break anywhere in +the process. Let's suppose here that the main procedure is named +@cite{ada_main} and that in the DLL there is an entry point named +@cite{ada_dll}. + +The DLL (@ref{27f,,Introduction to Dynamic Link Libraries (DLLs)}) and +program must have been built with the debugging information (see GNAT -g +switch). Here are the step-by-step instructions for debugging it: + + +@itemize * + +@item +Launch @cite{GDB} on the main program. + +@example +$ gdb -nw ada_main +@end example + +@item +Start the program and stop at the beginning of the main procedure + +@example +(gdb) start +@end example + +This step is required to be able to set a breakpoint inside the DLL. As long +as the program is not run, the DLL is not loaded. This has the +consequence that the DLL debugging information is also not loaded, so it is not +possible to set a breakpoint in the DLL. + +@item +Set a breakpoint inside the DLL + +@example +(gdb) break ada_dll +(gdb) cont +@end example +@end itemize + +At this stage a breakpoint is set inside the DLL. From there on +you can use the standard approach to debug the whole program +(@ref{26,,Running and Debugging Ada Programs}). + +@node Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Program and DLL Both Built with GCC/GNAT,Debugging a DLL +@anchor{gnat_ugn/platform_specific_information program-built-with-foreign-tools-and-dll-built-with-gcc-gnat}@anchor{2a6}@anchor{gnat_ugn/platform_specific_information id39}@anchor{2a7} +@subsubsection Program Built with Foreign Tools and DLL Built with GCC/GNAT + + +In this case things are slightly more complex because it is not possible to +start the main program and then break at the beginning to load the DLL and the +associated DLL debugging information. It is not possible to break at the +beginning of the program because there is no @cite{GDB} debugging information, +and therefore there is no direct way of getting initial control. This +section addresses this issue by describing some methods that can be used +to break somewhere in the DLL to debug it. + +First suppose that the main procedure is named @cite{main} (this is for +example some C code built with Microsoft Visual C) and that there is a +DLL named @cite{test.dll} containing an Ada entry point named +@cite{ada_dll}. + +The DLL (see @ref{27f,,Introduction to Dynamic Link Libraries (DLLs)}) must have +been built with debugging information (see GNAT @cite{-g} option). + +@subsubheading Debugging the DLL Directly + + + +@itemize * + +@item +Find out the executable starting address + +@example +$ objdump --file-header main.exe +@end example + +The starting address is reported on the last line. For example: + +@example +main.exe: file format pei-i386 +architecture: i386, flags 0x0000010a: +EXEC_P, HAS_DEBUG, D_PAGED +start address 0x00401010 +@end example + +@item +Launch the debugger on the executable. + +@example +$ gdb main.exe +@end example + +@item +Set a breakpoint at the starting address, and launch the program. + +@example +$ (gdb) break *0x00401010 +$ (gdb) run +@end example + +The program will stop at the given address. + +@item +Set a breakpoint on a DLL subroutine. + +@example +(gdb) break ada_dll.adb:45 +@end example + +Or if you want to break using a symbol on the DLL, you need first to +select the Ada language (language used by the DLL). + +@example +(gdb) set language ada +(gdb) break ada_dll +@end example + +@item +Continue the program. + +@example +(gdb) cont +@end example + +This will run the program until it reaches the breakpoint that has been +set. From that point you can use the standard way to debug a program +as described in (@ref{26,,Running and Debugging Ada Programs}). +@end itemize + +It is also possible to debug the DLL by attaching to a running process. + +@subsubheading Attaching to a Running Process + + +@geindex DLL debugging +@geindex attach to process + +With @cite{GDB} it is always possible to debug a running process by +attaching to it. It is possible to debug a DLL this way. The limitation +of this approach is that the DLL must run long enough to perform the +attach operation. It may be useful for instance to insert a time wasting +loop in the code of the DLL to meet this criterion. + + +@itemize * + +@item +Launch the main program @code{main.exe}. + +@example +$ main +@end example + +@item +Use the Windows @emph{Task Manager} to find the process ID. Let's say +that the process PID for @code{main.exe} is 208. + +@item +Launch gdb. + +@example +$ gdb +@end example + +@item +Attach to the running process to be debugged. + +@example +(gdb) attach 208 +@end example + +@item +Load the process debugging information. + +@example +(gdb) symbol-file main.exe +@end example + +@item +Break somewhere in the DLL. + +@example +(gdb) break ada_dll +@end example + +@item +Continue process execution. + +@example +(gdb) cont +@end example +@end itemize + +This last step will resume the process execution, and stop at +the breakpoint we have set. From there you can use the standard +approach to debug a program as described in +@ref{26,,Running and Debugging Ada Programs}. + +@node Setting Stack Size from gnatlink,Setting Heap Size from gnatlink,Debugging a DLL,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink}@anchor{13a}@anchor{gnat_ugn/platform_specific_information id40}@anchor{2a8} +@subsubsection Setting Stack Size from @emph{gnatlink} + + +It is possible to specify the program stack size at link time. On modern +versions of Windows, starting with XP, this is mostly useful to set the size of +the main stack (environment task). The other task stacks are set with pragma +Storage_Size or with the @emph{gnatbind -d} command. + +Since older versions of Windows (2000, NT4, etc.) do not allow setting the +reserve size of individual tasks, the link-time stack size applies to all +tasks, and pragma Storage_Size has no effect. +In particular, Stack Overflow checks are made against this +link-time specified size. + +This setting can be done with @emph{gnatlink} using either of the following: + + +@itemize * + +@item +@emph{-Xlinker} linker option + +@example +$ gnatlink hello -Xlinker --stack=0x10000,0x1000 +@end example + +This sets the stack reserve size to 0x10000 bytes and the stack commit +size to 0x1000 bytes. + +@item +@emph{-Wl} linker option + +@example +$ gnatlink hello -Wl,--stack=0x1000000 +@end example + +This sets the stack reserve size to 0x1000000 bytes. Note that with +@emph{-Wl} option it is not possible to set the stack commit size +because the coma is a separator for this option. +@end itemize + +@node Setting Heap Size from gnatlink,,Setting Stack Size from gnatlink,Mixed-Language Programming on Windows +@anchor{gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink}@anchor{13b}@anchor{gnat_ugn/platform_specific_information id41}@anchor{2a9} +@subsubsection Setting Heap Size from @emph{gnatlink} + + +Under Windows systems, it is possible to specify the program heap size from +@emph{gnatlink} using either of the following: + + +@itemize * + +@item +@emph{-Xlinker} linker option + +@example +$ gnatlink hello -Xlinker --heap=0x10000,0x1000 +@end example + +This sets the heap reserve size to 0x10000 bytes and the heap commit +size to 0x1000 bytes. + +@item +@emph{-Wl} linker option + +@example +$ gnatlink hello -Wl,--heap=0x1000000 +@end example + +This sets the heap reserve size to 0x1000000 bytes. Note that with +@emph{-Wl} option it is not possible to set the heap commit size +because the coma is a separator for this option. +@end itemize + +@node Mac OS Topics,,Microsoft Windows Topics,Platform-Specific Information +@anchor{gnat_ugn/platform_specific_information mac-os-topics}@anchor{2f}@anchor{gnat_ugn/platform_specific_information id42}@anchor{2aa} +@section Mac OS Topics + + +@geindex OS X + +This section describes topics that are specific to Apple's OS X +platform. + +@menu +* Codesigning the Debugger:: + +@end menu + +@node Codesigning the Debugger,,,Mac OS Topics +@anchor{gnat_ugn/platform_specific_information codesigning-the-debugger}@anchor{2ab} +@subsection Codesigning the Debugger + + +The Darwin Kernel requires the debugger to have special permissions +before it is allowed to control other processes. These permissions +are granted by codesigning the GDB executable. Without these +permissions, the debugger will report error messages such as: + +@example +Starting program: /x/y/foo +Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5). +(please check gdb is codesigned - see taskgated(8)) +@end example + +Codesigning requires a certificate. The following procedure explains +how to create one: + + +@itemize * + +@item +Start the Keychain Access application (in +/Applications/Utilities/Keychain Access.app) + +@item +Select the Keychain Access -> Certificate Assistant -> +Create a Certificate... menu + +@item +Then: + + +@itemize * + +@item +Choose a name for the new certificate (this procedure will use +"gdb-cert" as an example) + +@item +Set "Identity Type" to "Self Signed Root" + +@item +Set "Certificate Type" to "Code Signing" + +@item +Activate the "Let me override defaults" option +@end itemize + +@item +Click several times on "Continue" until the "Specify a Location +For The Certificate" screen appears, then set "Keychain" to "System" + +@item +Click on "Continue" until the certificate is created + +@item +Finally, in the view, double-click on the new certificate, +and set "When using this certificate" to "Always Trust" + +@item +Exit the Keychain Access application and restart the computer +(this is unfortunately required) +@end itemize + +Once a certificate has been created, the debugger can be codesigned +as follow. In a Terminal, run the following command: + +@quotation + +@example +$ codesign -f -s "gdb-cert" /bin/gdb +@end example +@end quotation + +where "gdb-cert" should be replaced by the actual certificate +name chosen above, and should be replaced by +the location where you installed GNAT. Also, be sure that users are +in the Unix group @code{_developer}. + +@node Example of Binder Output File,Elaboration Order Handling in GNAT,Platform-Specific Information,Top +@anchor{gnat_ugn/example_of_binder_output example-of-binder-output-file}@anchor{10}@anchor{gnat_ugn/example_of_binder_output doc}@anchor{2ac}@anchor{gnat_ugn/example_of_binder_output id1}@anchor{2ad} +@chapter Example of Binder Output File + + +@geindex Binder output (example) + +This Appendix displays the source code for the output file +generated by @emph{gnatbind} for a simple 'Hello World' program. +Comments have been added for clarification purposes. + +@example +-- The package is called Ada_Main unless this name is actually used +-- as a unit name in the partition, in which case some other unique +-- name is used. + +pragma Ada_95; +with System; +package ada_main is + pragma Warnings (Off); + + -- The main program saves the parameters (argument count, + -- argument values, environment pointer) in global variables + -- for later access by other units including + -- Ada.Command_Line. + + gnat_argc : Integer; + gnat_argv : System.Address; + gnat_envp : System.Address; + + -- The actual variables are stored in a library routine. This + -- is useful for some shared library situations, where there + -- are problems if variables are not in the library. + + pragma Import (C, gnat_argc); + pragma Import (C, gnat_argv); + pragma Import (C, gnat_envp); + + -- The exit status is similarly an external location + + gnat_exit_status : Integer; + pragma Import (C, gnat_exit_status); + + GNAT_Version : constant String := + "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL; + pragma Export (C, GNAT_Version, "__gnat_version"); + + Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL; + pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name"); + + -- This is the generated adainit routine that performs + -- initialization at the start of execution. In the case + -- where Ada is the main program, this main program makes + -- a call to adainit at program startup. + + procedure adainit; + pragma Export (C, adainit, "adainit"); + + -- This is the generated adafinal routine that performs + -- finalization at the end of execution. In the case where + -- Ada is the main program, this main program makes a call + -- to adafinal at program termination. + + procedure adafinal; + pragma Export (C, adafinal, "adafinal"); + + -- This routine is called at the start of execution. It is + -- a dummy routine that is used by the debugger to breakpoint + -- at the start of execution. + + -- This is the actual generated main program (it would be + -- suppressed if the no main program switch were used). As + -- required by standard system conventions, this program has + -- the external name main. + + function main + (argc : Integer; + argv : System.Address; + envp : System.Address) + return Integer; + pragma Export (C, main, "main"); + + -- The following set of constants give the version + -- identification values for every unit in the bound + -- partition. This identification is computed from all + -- dependent semantic units, and corresponds to the + -- string that would be returned by use of the + -- Body_Version or Version attributes. + + -- The following Export pragmas export the version numbers + -- with symbolic names ending in B (for body) or S + -- (for spec) so that they can be located in a link. The + -- information provided here is sufficient to track down + -- the exact versions of units used in a given build. + + type Version_32 is mod 2 ** 32; + u00001 : constant Version_32 := 16#8ad6e54a#; + pragma Export (C, u00001, "helloB"); + u00002 : constant Version_32 := 16#fbff4c67#; + pragma Export (C, u00002, "system__standard_libraryB"); + u00003 : constant Version_32 := 16#1ec6fd90#; + pragma Export (C, u00003, "system__standard_libraryS"); + u00004 : constant Version_32 := 16#3ffc8e18#; + pragma Export (C, u00004, "adaS"); + u00005 : constant Version_32 := 16#28f088c2#; + pragma Export (C, u00005, "ada__text_ioB"); + u00006 : constant Version_32 := 16#f372c8ac#; + pragma Export (C, u00006, "ada__text_ioS"); + u00007 : constant Version_32 := 16#2c143749#; + pragma Export (C, u00007, "ada__exceptionsB"); + u00008 : constant Version_32 := 16#f4f0cce8#; + pragma Export (C, u00008, "ada__exceptionsS"); + u00009 : constant Version_32 := 16#a46739c0#; + pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB"); + u00010 : constant Version_32 := 16#3aac8c92#; + pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS"); + u00011 : constant Version_32 := 16#1d274481#; + pragma Export (C, u00011, "systemS"); + u00012 : constant Version_32 := 16#a207fefe#; + pragma Export (C, u00012, "system__soft_linksB"); + u00013 : constant Version_32 := 16#467d9556#; + pragma Export (C, u00013, "system__soft_linksS"); + u00014 : constant Version_32 := 16#b01dad17#; + pragma Export (C, u00014, "system__parametersB"); + u00015 : constant Version_32 := 16#630d49fe#; + pragma Export (C, u00015, "system__parametersS"); + u00016 : constant Version_32 := 16#b19b6653#; + pragma Export (C, u00016, "system__secondary_stackB"); + u00017 : constant Version_32 := 16#b6468be8#; + pragma Export (C, u00017, "system__secondary_stackS"); + u00018 : constant Version_32 := 16#39a03df9#; + pragma Export (C, u00018, "system__storage_elementsB"); + u00019 : constant Version_32 := 16#30e40e85#; + pragma Export (C, u00019, "system__storage_elementsS"); + u00020 : constant Version_32 := 16#41837d1e#; + pragma Export (C, u00020, "system__stack_checkingB"); + u00021 : constant Version_32 := 16#93982f69#; + pragma Export (C, u00021, "system__stack_checkingS"); + u00022 : constant Version_32 := 16#393398c1#; + pragma Export (C, u00022, "system__exception_tableB"); + u00023 : constant Version_32 := 16#b33e2294#; + pragma Export (C, u00023, "system__exception_tableS"); + u00024 : constant Version_32 := 16#ce4af020#; + pragma Export (C, u00024, "system__exceptionsB"); + u00025 : constant Version_32 := 16#75442977#; + pragma Export (C, u00025, "system__exceptionsS"); + u00026 : constant Version_32 := 16#37d758f1#; + pragma Export (C, u00026, "system__exceptions__machineS"); + u00027 : constant Version_32 := 16#b895431d#; + pragma Export (C, u00027, "system__exceptions_debugB"); + u00028 : constant Version_32 := 16#aec55d3f#; + pragma Export (C, u00028, "system__exceptions_debugS"); + u00029 : constant Version_32 := 16#570325c8#; + pragma Export (C, u00029, "system__img_intB"); + u00030 : constant Version_32 := 16#1ffca443#; + pragma Export (C, u00030, "system__img_intS"); + u00031 : constant Version_32 := 16#b98c3e16#; + pragma Export (C, u00031, "system__tracebackB"); + u00032 : constant Version_32 := 16#831a9d5a#; + pragma Export (C, u00032, "system__tracebackS"); + u00033 : constant Version_32 := 16#9ed49525#; + pragma Export (C, u00033, "system__traceback_entriesB"); + u00034 : constant Version_32 := 16#1d7cb2f1#; + pragma Export (C, u00034, "system__traceback_entriesS"); + u00035 : constant Version_32 := 16#8c33a517#; + pragma Export (C, u00035, "system__wch_conB"); + u00036 : constant Version_32 := 16#065a6653#; + pragma Export (C, u00036, "system__wch_conS"); + u00037 : constant Version_32 := 16#9721e840#; + pragma Export (C, u00037, "system__wch_stwB"); + u00038 : constant Version_32 := 16#2b4b4a52#; + pragma Export (C, u00038, "system__wch_stwS"); + u00039 : constant Version_32 := 16#92b797cb#; + pragma Export (C, u00039, "system__wch_cnvB"); + u00040 : constant Version_32 := 16#09eddca0#; + pragma Export (C, u00040, "system__wch_cnvS"); + u00041 : constant Version_32 := 16#6033a23f#; + pragma Export (C, u00041, "interfacesS"); + u00042 : constant Version_32 := 16#ece6fdb6#; + pragma Export (C, u00042, "system__wch_jisB"); + u00043 : constant Version_32 := 16#899dc581#; + pragma Export (C, u00043, "system__wch_jisS"); + u00044 : constant Version_32 := 16#10558b11#; + pragma Export (C, u00044, "ada__streamsB"); + u00045 : constant Version_32 := 16#2e6701ab#; + pragma Export (C, u00045, "ada__streamsS"); + u00046 : constant Version_32 := 16#db5c917c#; + pragma Export (C, u00046, "ada__io_exceptionsS"); + u00047 : constant Version_32 := 16#12c8cd7d#; + pragma Export (C, u00047, "ada__tagsB"); + u00048 : constant Version_32 := 16#ce72c228#; + pragma Export (C, u00048, "ada__tagsS"); + u00049 : constant Version_32 := 16#c3335bfd#; + pragma Export (C, u00049, "system__htableB"); + u00050 : constant Version_32 := 16#99e5f76b#; + pragma Export (C, u00050, "system__htableS"); + u00051 : constant Version_32 := 16#089f5cd0#; + pragma Export (C, u00051, "system__string_hashB"); + u00052 : constant Version_32 := 16#3bbb9c15#; + pragma Export (C, u00052, "system__string_hashS"); + u00053 : constant Version_32 := 16#807fe041#; + pragma Export (C, u00053, "system__unsigned_typesS"); + u00054 : constant Version_32 := 16#d27be59e#; + pragma Export (C, u00054, "system__val_lluB"); + u00055 : constant Version_32 := 16#fa8db733#; + pragma Export (C, u00055, "system__val_lluS"); + u00056 : constant Version_32 := 16#27b600b2#; + pragma Export (C, u00056, "system__val_utilB"); + u00057 : constant Version_32 := 16#b187f27f#; + pragma Export (C, u00057, "system__val_utilS"); + u00058 : constant Version_32 := 16#d1060688#; + pragma Export (C, u00058, "system__case_utilB"); + u00059 : constant Version_32 := 16#392e2d56#; + pragma Export (C, u00059, "system__case_utilS"); + u00060 : constant Version_32 := 16#84a27f0d#; + pragma Export (C, u00060, "interfaces__c_streamsB"); + u00061 : constant Version_32 := 16#8bb5f2c0#; + pragma Export (C, u00061, "interfaces__c_streamsS"); + u00062 : constant Version_32 := 16#6db6928f#; + pragma Export (C, u00062, "system__crtlS"); + u00063 : constant Version_32 := 16#4e6a342b#; + pragma Export (C, u00063, "system__file_ioB"); + u00064 : constant Version_32 := 16#ba56a5e4#; + pragma Export (C, u00064, "system__file_ioS"); + u00065 : constant Version_32 := 16#b7ab275c#; + pragma Export (C, u00065, "ada__finalizationB"); + u00066 : constant Version_32 := 16#19f764ca#; + pragma Export (C, u00066, "ada__finalizationS"); + u00067 : constant Version_32 := 16#95817ed8#; + pragma Export (C, u00067, "system__finalization_rootB"); + u00068 : constant Version_32 := 16#52d53711#; + pragma Export (C, u00068, "system__finalization_rootS"); + u00069 : constant Version_32 := 16#769e25e6#; + pragma Export (C, u00069, "interfaces__cB"); + u00070 : constant Version_32 := 16#4a38bedb#; + pragma Export (C, u00070, "interfaces__cS"); + u00071 : constant Version_32 := 16#07e6ee66#; + pragma Export (C, u00071, "system__os_libB"); + u00072 : constant Version_32 := 16#d7b69782#; + pragma Export (C, u00072, "system__os_libS"); + u00073 : constant Version_32 := 16#1a817b8e#; + pragma Export (C, u00073, "system__stringsB"); + u00074 : constant Version_32 := 16#639855e7#; + pragma Export (C, u00074, "system__stringsS"); + u00075 : constant Version_32 := 16#e0b8de29#; + pragma Export (C, u00075, "system__file_control_blockS"); + u00076 : constant Version_32 := 16#b5b2aca1#; + pragma Export (C, u00076, "system__finalization_mastersB"); + u00077 : constant Version_32 := 16#69316dc1#; + pragma Export (C, u00077, "system__finalization_mastersS"); + u00078 : constant Version_32 := 16#57a37a42#; + pragma Export (C, u00078, "system__address_imageB"); + u00079 : constant Version_32 := 16#bccbd9bb#; + pragma Export (C, u00079, "system__address_imageS"); + u00080 : constant Version_32 := 16#7268f812#; + pragma Export (C, u00080, "system__img_boolB"); + u00081 : constant Version_32 := 16#e8fe356a#; + pragma Export (C, u00081, "system__img_boolS"); + u00082 : constant Version_32 := 16#d7aac20c#; + pragma Export (C, u00082, "system__ioB"); + u00083 : constant Version_32 := 16#8365b3ce#; + pragma Export (C, u00083, "system__ioS"); + u00084 : constant Version_32 := 16#6d4d969a#; + pragma Export (C, u00084, "system__storage_poolsB"); + u00085 : constant Version_32 := 16#e87cc305#; + pragma Export (C, u00085, "system__storage_poolsS"); + u00086 : constant Version_32 := 16#e34550ca#; + pragma Export (C, u00086, "system__pool_globalB"); + u00087 : constant Version_32 := 16#c88d2d16#; + pragma Export (C, u00087, "system__pool_globalS"); + u00088 : constant Version_32 := 16#9d39c675#; + pragma Export (C, u00088, "system__memoryB"); + u00089 : constant Version_32 := 16#445a22b5#; + pragma Export (C, u00089, "system__memoryS"); + u00090 : constant Version_32 := 16#6a859064#; + pragma Export (C, u00090, "system__storage_pools__subpoolsB"); + u00091 : constant Version_32 := 16#e3b008dc#; + pragma Export (C, u00091, "system__storage_pools__subpoolsS"); + u00092 : constant Version_32 := 16#63f11652#; + pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB"); + u00093 : constant Version_32 := 16#fe2f4b3a#; + pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS"); + + -- BEGIN ELABORATION ORDER + -- ada%s + -- interfaces%s + -- system%s + -- system.case_util%s + -- system.case_util%b + -- system.htable%s + -- system.img_bool%s + -- system.img_bool%b + -- system.img_int%s + -- system.img_int%b + -- system.io%s + -- system.io%b + -- system.parameters%s + -- system.parameters%b + -- system.crtl%s + -- interfaces.c_streams%s + -- interfaces.c_streams%b + -- system.standard_library%s + -- system.exceptions_debug%s + -- system.exceptions_debug%b + -- system.storage_elements%s + -- system.storage_elements%b + -- system.stack_checking%s + -- system.stack_checking%b + -- system.string_hash%s + -- system.string_hash%b + -- system.htable%b + -- system.strings%s + -- system.strings%b + -- system.os_lib%s + -- system.traceback_entries%s + -- system.traceback_entries%b + -- ada.exceptions%s + -- system.soft_links%s + -- system.unsigned_types%s + -- system.val_llu%s + -- system.val_util%s + -- system.val_util%b + -- system.val_llu%b + -- system.wch_con%s + -- system.wch_con%b + -- system.wch_cnv%s + -- system.wch_jis%s + -- system.wch_jis%b + -- system.wch_cnv%b + -- system.wch_stw%s + -- system.wch_stw%b + -- ada.exceptions.last_chance_handler%s + -- ada.exceptions.last_chance_handler%b + -- system.address_image%s + -- system.exception_table%s + -- system.exception_table%b + -- ada.io_exceptions%s + -- ada.tags%s + -- ada.streams%s + -- ada.streams%b + -- interfaces.c%s + -- system.exceptions%s + -- system.exceptions%b + -- system.exceptions.machine%s + -- system.finalization_root%s + -- system.finalization_root%b + -- ada.finalization%s + -- ada.finalization%b + -- system.storage_pools%s + -- system.storage_pools%b + -- system.finalization_masters%s + -- system.storage_pools.subpools%s + -- system.storage_pools.subpools.finalization%s + -- system.storage_pools.subpools.finalization%b + -- system.memory%s + -- system.memory%b + -- system.standard_library%b + -- system.pool_global%s + -- system.pool_global%b + -- system.file_control_block%s + -- system.file_io%s + -- system.secondary_stack%s + -- system.file_io%b + -- system.storage_pools.subpools%b + -- system.finalization_masters%b + -- interfaces.c%b + -- ada.tags%b + -- system.soft_links%b + -- system.os_lib%b + -- system.secondary_stack%b + -- system.address_image%b + -- system.traceback%s + -- ada.exceptions%b + -- system.traceback%b + -- ada.text_io%s + -- ada.text_io%b + -- hello%b + -- END ELABORATION ORDER + +end ada_main; +@end example + +@example +pragma Ada_95; +-- The following source file name pragmas allow the generated file +-- names to be unique for different main programs. They are needed +-- since the package name will always be Ada_Main. + +pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads"); +pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb"); + +pragma Suppress (Overflow_Check); +with Ada.Exceptions; + +-- Generated package body for Ada_Main starts here + +package body ada_main is + pragma Warnings (Off); + + -- These values are reference counter associated to units which have + -- been elaborated. It is also used to avoid elaborating the + -- same unit twice. + + E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E"); + E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E"); + E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E"); + E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E"); + E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E"); + E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E"); + E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E"); + E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E"); + E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E"); + E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E"); + E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E"); + E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E"); + E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E"); + E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E"); + E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E"); + E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E"); + E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E"); + E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E"); + + Local_Priority_Specific_Dispatching : constant String := ""; + Local_Interrupt_States : constant String := ""; + + Is_Elaborated : Boolean := False; + + procedure finalize_library is + begin + E06 := E06 - 1; + declare + procedure F1; + pragma Import (Ada, F1, "ada__text_io__finalize_spec"); + begin + F1; + end; + E77 := E77 - 1; + E91 := E91 - 1; + declare + procedure F2; + pragma Import (Ada, F2, "system__file_io__finalize_body"); + begin + E64 := E64 - 1; + F2; + end; + declare + procedure F3; + pragma Import (Ada, F3, "system__file_control_block__finalize_spec"); + begin + E75 := E75 - 1; + F3; + end; + E87 := E87 - 1; + declare + procedure F4; + pragma Import (Ada, F4, "system__pool_global__finalize_spec"); + begin + F4; + end; + declare + procedure F5; + pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec"); + begin + F5; + end; + declare + procedure F6; + pragma Import (Ada, F6, "system__finalization_masters__finalize_spec"); + begin + F6; + end; + declare + procedure Reraise_Library_Exception_If_Any; + pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any"); + begin + Reraise_Library_Exception_If_Any; + end; + end finalize_library; + + ------------- + -- adainit -- + ------------- + + procedure adainit is + + Main_Priority : Integer; + pragma Import (C, Main_Priority, "__gl_main_priority"); + Time_Slice_Value : Integer; + pragma Import (C, Time_Slice_Value, "__gl_time_slice_val"); + WC_Encoding : Character; + pragma Import (C, WC_Encoding, "__gl_wc_encoding"); + Locking_Policy : Character; + pragma Import (C, Locking_Policy, "__gl_locking_policy"); + Queuing_Policy : Character; + pragma Import (C, Queuing_Policy, "__gl_queuing_policy"); + Task_Dispatching_Policy : Character; + pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy"); + Priority_Specific_Dispatching : System.Address; + pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching"); + Num_Specific_Dispatching : Integer; + pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching"); + Main_CPU : Integer; + pragma Import (C, Main_CPU, "__gl_main_cpu"); + Interrupt_States : System.Address; + pragma Import (C, Interrupt_States, "__gl_interrupt_states"); + Num_Interrupt_States : Integer; + pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states"); + Unreserve_All_Interrupts : Integer; + pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts"); + Detect_Blocking : Integer; + pragma Import (C, Detect_Blocking, "__gl_detect_blocking"); + Default_Stack_Size : Integer; + pragma Import (C, Default_Stack_Size, "__gl_default_stack_size"); + Leap_Seconds_Support : Integer; + pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support"); + + procedure Runtime_Initialize; + pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize"); + + Finalize_Library_Objects : No_Param_Proc; + pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects"); + + -- Start of processing for adainit + + begin + + -- Record various information for this partition. The values + -- are derived by the binder from information stored in the ali + -- files by the compiler. + + if Is_Elaborated then + return; + end if; + Is_Elaborated := True; + Main_Priority := -1; + Time_Slice_Value := -1; + WC_Encoding := 'b'; + Locking_Policy := ' '; + Queuing_Policy := ' '; + Task_Dispatching_Policy := ' '; + Priority_Specific_Dispatching := + Local_Priority_Specific_Dispatching'Address; + Num_Specific_Dispatching := 0; + Main_CPU := -1; + Interrupt_States := Local_Interrupt_States'Address; + Num_Interrupt_States := 0; + Unreserve_All_Interrupts := 0; + Detect_Blocking := 0; + Default_Stack_Size := -1; + Leap_Seconds_Support := 0; + + Runtime_Initialize; + + Finalize_Library_Objects := finalize_library'access; + + -- Now we have the elaboration calls for all units in the partition. + -- The Elab_Spec and Elab_Body attributes generate references to the + -- implicit elaboration procedures generated by the compiler for + -- each unit that requires elaboration. Increment a counter of + -- reference for each unit. + + System.Soft_Links'Elab_Spec; + System.Exception_Table'Elab_Body; + E23 := E23 + 1; + Ada.Io_Exceptions'Elab_Spec; + E46 := E46 + 1; + Ada.Tags'Elab_Spec; + Ada.Streams'Elab_Spec; + E45 := E45 + 1; + Interfaces.C'Elab_Spec; + System.Exceptions'Elab_Spec; + E25 := E25 + 1; + System.Finalization_Root'Elab_Spec; + E68 := E68 + 1; + Ada.Finalization'Elab_Spec; + E66 := E66 + 1; + System.Storage_Pools'Elab_Spec; + E85 := E85 + 1; + System.Finalization_Masters'Elab_Spec; + System.Storage_Pools.Subpools'Elab_Spec; + System.Pool_Global'Elab_Spec; + E87 := E87 + 1; + System.File_Control_Block'Elab_Spec; + E75 := E75 + 1; + System.File_Io'Elab_Body; + E64 := E64 + 1; + E91 := E91 + 1; + System.Finalization_Masters'Elab_Body; + E77 := E77 + 1; + E70 := E70 + 1; + Ada.Tags'Elab_Body; + E48 := E48 + 1; + System.Soft_Links'Elab_Body; + E13 := E13 + 1; + System.Os_Lib'Elab_Body; + E72 := E72 + 1; + System.Secondary_Stack'Elab_Body; + E17 := E17 + 1; + Ada.Text_Io'Elab_Spec; + Ada.Text_Io'Elab_Body; + E06 := E06 + 1; + end adainit; + + -------------- + -- adafinal -- + -------------- + + procedure adafinal is + procedure s_stalib_adafinal; + pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal"); + + procedure Runtime_Finalize; + pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize"); + + begin + if not Is_Elaborated then + return; + end if; + Is_Elaborated := False; + Runtime_Finalize; + s_stalib_adafinal; + end adafinal; + + -- We get to the main program of the partition by using + -- pragma Import because if we try to with the unit and + -- call it Ada style, then not only do we waste time + -- recompiling it, but also, we don't really know the right + -- switches (e.g.@@: identifier character set) to be used + -- to compile it. + + procedure Ada_Main_Program; + pragma Import (Ada, Ada_Main_Program, "_ada_hello"); + + ---------- + -- main -- + ---------- + + -- main is actually a function, as in the ANSI C standard, + -- defined to return the exit status. The three parameters + -- are the argument count, argument values and environment + -- pointer. + + function main + (argc : Integer; + argv : System.Address; + envp : System.Address) + return Integer + is + -- The initialize routine performs low level system + -- initialization using a standard library routine which + -- sets up signal handling and performs any other + -- required setup. The routine can be found in file + -- a-init.c. + + procedure initialize; + pragma Import (C, initialize, "__gnat_initialize"); + + -- The finalize routine performs low level system + -- finalization using a standard library routine. The + -- routine is found in file a-final.c and in the standard + -- distribution is a dummy routine that does nothing, so + -- really this is a hook for special user finalization. + + procedure finalize; + pragma Import (C, finalize, "__gnat_finalize"); + + -- The following is to initialize the SEH exceptions + + SEH : aliased array (1 .. 2) of Integer; + + Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address; + pragma Volatile (Ensure_Reference); + + -- Start of processing for main + + begin + -- Save global variables + + gnat_argc := argc; + gnat_argv := argv; + gnat_envp := envp; + + -- Call low level system initialization + + Initialize (SEH'Address); + + -- Call our generated Ada initialization routine + + adainit; + + -- Now we call the main program of the partition + + Ada_Main_Program; + + -- Perform Ada finalization + + adafinal; + + -- Perform low level system finalization + + Finalize; + + -- Return the proper exit status + return (gnat_exit_status); + end; + +-- This section is entirely comments, so it has no effect on the +-- compilation of the Ada_Main package. It provides the list of +-- object files and linker options, as well as some standard +-- libraries needed for the link. The gnatlink utility parses +-- this b~hello.adb file to read these comment lines to generate +-- the appropriate command line arguments for the call to the +-- system linker. The BEGIN/END lines are used for sentinels for +-- this parsing operation. + +-- The exact file names will of course depend on the environment, +-- host/target and location of files on the host system. + +-- BEGIN Object file/option list + -- ./hello.o + -- -L./ + -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/ + -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a +-- END Object file/option list + +end ada_main; +@end example + +The Ada code in the above example is exactly what is generated by the +binder. We have added comments to more clearly indicate the function +of each part of the generated @cite{Ada_Main} package. + +The code is standard Ada in all respects, and can be processed by any +tools that handle Ada. In particular, it is possible to use the debugger +in Ada mode to debug the generated @cite{Ada_Main} package. For example, +suppose that for reasons that you do not understand, your program is crashing +during elaboration of the body of @cite{Ada.Text_IO}. To locate this bug, +you can place a breakpoint on the call: + +@quotation + +@example +Ada.Text_Io'Elab_Body; +@end example +@end quotation + +and trace the elaboration routine for this package to find out where +the problem might be (more usually of course you would be debugging +elaboration code in your own application). + +@c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit + +@node Elaboration Order Handling in GNAT,Inline Assembler,Example of Binder Output File,Top +@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order-handling-in-gnat}@anchor{11}@anchor{gnat_ugn/elaboration_order_handling_in_gnat doc}@anchor{2ae}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id1}@anchor{2af} +@chapter Elaboration Order Handling in GNAT + + +@geindex Order of elaboration + +@geindex Elaboration control + +This appendix describes the handling of elaboration code in Ada and +in GNAT, and discusses how the order of elaboration of program units can +be controlled in GNAT, either automatically or with explicit programming +features. + +@menu +* Elaboration Code:: +* Checking the Elaboration Order:: +* Controlling the Elaboration Order:: +* Controlling Elaboration in GNAT - Internal Calls:: +* Controlling Elaboration in GNAT - External Calls:: +* Default Behavior in GNAT - Ensuring Safety:: +* Treatment of Pragma Elaborate:: +* Elaboration Issues for Library Tasks:: +* Mixing Elaboration Models:: +* What to Do If the Default Elaboration Behavior Fails:: +* Elaboration for Indirect Calls:: +* Summary of Procedures for Elaboration Control:: +* Other Elaboration Order Considerations:: +* Determining the Chosen Elaboration Order:: + +@end menu + +@node Elaboration Code,Checking the Elaboration Order,,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-code}@anchor{2b0}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id2}@anchor{2b1} +@section Elaboration Code + + +Ada provides rather general mechanisms for executing code at elaboration +time, that is to say before the main program starts executing. Such code arises +in three contexts: + + +@itemize * + +@item +@emph{Initializers for variables} + +Variables declared at the library level, in package specs or bodies, can +require initialization that is performed at elaboration time, as in: + +@example +Sqrt_Half : Float := Sqrt (0.5); +@end example + +@item +@emph{Package initialization code} + +Code in a @cite{BEGIN-END} section at the outer level of a package body is +executed as part of the package body elaboration code. + +@item +@emph{Library level task allocators} + +Tasks that are declared using task allocators at the library level +start executing immediately and hence can execute at elaboration time. +@end itemize + +Subprogram calls are possible in any of these contexts, which means that +any arbitrary part of the program may be executed as part of the elaboration +code. It is even possible to write a program which does all its work at +elaboration time, with a null main program, although stylistically this +would usually be considered an inappropriate way to structure +a program. + +An important concern arises in the context of elaboration code: +we have to be sure that it is executed in an appropriate order. What we +have is a series of elaboration code sections, potentially one section +for each unit in the program. It is important that these execute +in the correct order. Correctness here means that, taking the above +example of the declaration of @cite{Sqrt_Half}, +if some other piece of +elaboration code references @cite{Sqrt_Half}, +then it must run after the +section of elaboration code that contains the declaration of +@cite{Sqrt_Half}. + +There would never be any order of elaboration problem if we made a rule +that whenever you @emph{with} a unit, you must elaborate both the spec and body +of that unit before elaborating the unit doing the @emph{with}ing: + +@example +with Unit_1; +package Unit_2 is ... +@end example + +would require that both the body and spec of @cite{Unit_1} be elaborated +before the spec of @cite{Unit_2}. However, a rule like that would be far too +restrictive. In particular, it would make it impossible to have routines +in separate packages that were mutually recursive. + +You might think that a clever enough compiler could look at the actual +elaboration code and determine an appropriate correct order of elaboration, +but in the general case, this is not possible. Consider the following +example. + +In the body of @cite{Unit_1}, we have a procedure @cite{Func_1} +that references +the variable @cite{Sqrt_1}, which is declared in the elaboration code +of the body of @cite{Unit_1}: + +@example +Sqrt_1 : Float := Sqrt (0.1); +@end example + +The elaboration code of the body of @cite{Unit_1} also contains: + +@example +if expression_1 = 1 then + Q := Unit_2.Func_2; +end if; +@end example + +@cite{Unit_2} is exactly parallel, +it has a procedure @cite{Func_2} that references +the variable @cite{Sqrt_2}, which is declared in the elaboration code of +the body @cite{Unit_2}: + +@example +Sqrt_2 : Float := Sqrt (0.1); +@end example + +The elaboration code of the body of @cite{Unit_2} also contains: + +@example +if expression_2 = 2 then + Q := Unit_1.Func_1; +end if; +@end example + +Now the question is, which of the following orders of elaboration is +acceptable: + +@example +Spec of Unit_1 +Spec of Unit_2 +Body of Unit_1 +Body of Unit_2 +@end example + +or + +@example +Spec of Unit_2 +Spec of Unit_1 +Body of Unit_2 +Body of Unit_1 +@end example + +If you carefully analyze the flow here, you will see that you cannot tell +at compile time the answer to this question. +If @cite{expression_1} is not equal to 1, +and @cite{expression_2} is not equal to 2, +then either order is acceptable, because neither of the function calls is +executed. If both tests evaluate to true, then neither order is acceptable +and in fact there is no correct order. + +If one of the two expressions is true, and the other is false, then one +of the above orders is correct, and the other is incorrect. For example, +if @cite{expression_1} /= 1 and @cite{expression_2} = 2, +then the call to @cite{Func_1} +will occur, but not the call to @cite{Func_2.} +This means that it is essential +to elaborate the body of @cite{Unit_1} before +the body of @cite{Unit_2}, so the first +order of elaboration is correct and the second is wrong. + +By making @cite{expression_1} and @cite{expression_2} +depend on input data, or perhaps +the time of day, we can make it impossible for the compiler or binder +to figure out which of these expressions will be true, and hence it +is impossible to guarantee a safe order of elaboration at run time. + +@node Checking the Elaboration Order,Controlling the Elaboration Order,Elaboration Code,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat checking-the-elaboration-order}@anchor{2b2}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id3}@anchor{2b3} +@section Checking the Elaboration Order + + +In some languages that involve the same kind of elaboration problems, +e.g., Java and C++, the programmer needs to take these +ordering problems into account, and it is common to +write a program in which an incorrect elaboration order gives +surprising results, because it references variables before they +are initialized. +Ada is designed to be a safe language, and a programmer-beware approach is +clearly not sufficient. Consequently, the language provides three lines +of defense: + + +@itemize * + +@item +@emph{Standard rules} + +Some standard rules restrict the possible choice of elaboration +order. In particular, if you @emph{with} a unit, then its spec is always +elaborated before the unit doing the @emph{with}. Similarly, a parent +spec is always elaborated before the child spec, and finally +a spec is always elaborated before its corresponding body. +@end itemize + +@geindex Elaboration checks + +@geindex Checks +@geindex elaboration + + +@itemize * + +@item +@emph{Dynamic elaboration checks} + +Dynamic checks are made at run time, so that if some entity is accessed +before it is elaborated (typically by means of a subprogram call) +then the exception (@cite{Program_Error}) is raised. + +@item +@emph{Elaboration control} + +Facilities are provided for the programmer to specify the desired order +of elaboration. +@end itemize + +Let's look at these facilities in more detail. First, the rules for +dynamic checking. One possible rule would be simply to say that the +exception is raised if you access a variable which has not yet been +elaborated. The trouble with this approach is that it could require +expensive checks on every variable reference. Instead Ada has two +rules which are a little more restrictive, but easier to check, and +easier to state: + + +@itemize * + +@item +@emph{Restrictions on calls} + +A subprogram can only be called at elaboration time if its body +has been elaborated. The rules for elaboration given above guarantee +that the spec of the subprogram has been elaborated before the +call, but not the body. If this rule is violated, then the +exception @cite{Program_Error} is raised. + +@item +@emph{Restrictions on instantiations} + +A generic unit can only be instantiated if the body of the generic +unit has been elaborated. Again, the rules for elaboration given above +guarantee that the spec of the generic unit has been elaborated +before the instantiation, but not the body. If this rule is +violated, then the exception @cite{Program_Error} is raised. +@end itemize + +The idea is that if the body has been elaborated, then any variables +it references must have been elaborated; by checking for the body being +elaborated we guarantee that none of its references causes any +trouble. As we noted above, this is a little too restrictive, because a +subprogram that has no non-local references in its body may in fact be safe +to call. However, it really would be unsafe to rely on this, because +it would mean that the caller was aware of details of the implementation +in the body. This goes against the basic tenets of Ada. + +A plausible implementation can be described as follows. +A Boolean variable is associated with each subprogram +and each generic unit. This variable is initialized to False, and is set to +True at the point body is elaborated. Every call or instantiation checks the +variable, and raises @cite{Program_Error} if the variable is False. + +Note that one might think that it would be good enough to have one Boolean +variable for each package, but that would not deal with cases of trying +to call a body in the same package as the call +that has not been elaborated yet. +Of course a compiler may be able to do enough analysis to optimize away +some of the Boolean variables as unnecessary, and @cite{GNAT} indeed +does such optimizations, but still the easiest conceptual model is to +think of there being one variable per subprogram. + +@node Controlling the Elaboration Order,Controlling Elaboration in GNAT - Internal Calls,Checking the Elaboration Order,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id4}@anchor{2b4}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order}@anchor{2b5} +@section Controlling the Elaboration Order + + +In the previous section we discussed the rules in Ada which ensure +that @cite{Program_Error} is raised if an incorrect elaboration order is +chosen. This prevents erroneous executions, but we need mechanisms to +specify a correct execution and avoid the exception altogether. +To achieve this, Ada provides a number of features for controlling +the order of elaboration. We discuss these features in this section. + +First, there are several ways of indicating to the compiler that a given +unit has no elaboration problems: + + +@itemize * + +@item +@emph{packages that do not require a body} + +A library package that does not require a body does not permit +a body (this rule was introduced in Ada 95). +Thus if we have a such a package, as in: + +@example +package Definitions is + generic + type m is new integer; + package Subp is + type a is array (1 .. 10) of m; + type b is array (1 .. 20) of m; + end Subp; +end Definitions; +@end example + +A package that @emph{with}s @cite{Definitions} may safely instantiate +@cite{Definitions.Subp} because the compiler can determine that there +definitely is no package body to worry about in this case +@end itemize + +@geindex pragma Pure + + +@itemize * + +@item +@emph{pragma Pure} + +This pragma places sufficient restrictions on a unit to guarantee that +no call to any subprogram in the unit can result in an +elaboration problem. This means that the compiler does not need +to worry about the point of elaboration of such units, and in +particular, does not need to check any calls to any subprograms +in this unit. +@end itemize + +@geindex pragma Preelaborate + + +@itemize * + +@item +@emph{pragma Preelaborate} + +This pragma places slightly less stringent restrictions on a unit than +does pragma Pure, +but these restrictions are still sufficient to ensure that there +are no elaboration problems with any calls to the unit. +@end itemize + +@geindex pragma Elaborate_Body + + +@itemize * + +@item +@emph{pragma Elaborate_Body} + +This pragma requires that the body of a unit be elaborated immediately +after its spec. Suppose a unit @cite{A} has such a pragma, +and unit @cite{B} does +a @emph{with} of unit @cite{A}. Recall that the standard rules require +the spec of unit @cite{A} +to be elaborated before the @emph{with}ing unit; given the pragma in +@cite{A}, we also know that the body of @cite{A} +will be elaborated before @cite{B}, so +that calls to @cite{A} are safe and do not need a check. + +Note that, unlike pragma @cite{Pure} and pragma @cite{Preelaborate}, +the use of @cite{Elaborate_Body} does not guarantee that the program is +free of elaboration problems, because it may not be possible +to satisfy the requested elaboration order. +Let's go back to the example with @cite{Unit_1} and @cite{Unit_2}. +If a programmer marks @cite{Unit_1} as @cite{Elaborate_Body}, +and not @cite{Unit_2@comma{}} then the order of +elaboration will be: + +@example +Spec of Unit_2 +Spec of Unit_1 +Body of Unit_1 +Body of Unit_2 +@end example + +Now that means that the call to @cite{Func_1} in @cite{Unit_2} +need not be checked, +it must be safe. But the call to @cite{Func_2} in +@cite{Unit_1} may still fail if +@cite{Expression_1} is equal to 1, +and the programmer must still take +responsibility for this not being the case. + +If all units carry a pragma @cite{Elaborate_Body}, then all problems are +eliminated, except for calls entirely within a body, which are +in any case fully under programmer control. However, using the pragma +everywhere is not always possible. +In particular, for our @cite{Unit_1}/@cite{Unit_2} example, if +we marked both of them as having pragma @cite{Elaborate_Body}, then +clearly there would be no possible elaboration order. +@end itemize + +The above pragmas allow a server to guarantee safe use by clients, and +clearly this is the preferable approach. Consequently a good rule +is to mark units as @cite{Pure} or @cite{Preelaborate} if possible, +and if this is not possible, +mark them as @cite{Elaborate_Body} if possible. +As we have seen, there are situations where neither of these +three pragmas can be used. +So we also provide methods for clients to control the +order of elaboration of the servers on which they depend: + +@geindex pragma Elaborate + + +@itemize * + +@item +@emph{pragma Elaborate (unit)} + +This pragma is placed in the context clause, after a @emph{with} clause, +and it requires that the body of the named unit be elaborated before +the unit in which the pragma occurs. The idea is to use this pragma +if the current unit calls at elaboration time, directly or indirectly, +some subprogram in the named unit. +@end itemize + +@geindex pragma Elaborate_All + + +@itemize * + +@item +@emph{pragma Elaborate_All (unit)} + +This is a stronger version of the Elaborate pragma. Consider the +following example: + +@example +Unit A |withs| unit B and calls B.Func in elab code +Unit B |withs| unit C, and B.Func calls C.Func +@end example + +Now if we put a pragma @cite{Elaborate (B)} +in unit @cite{A}, this ensures that the +body of @cite{B} is elaborated before the call, but not the +body of @cite{C}, so +the call to @cite{C.Func} could still cause @cite{Program_Error} to +be raised. + +The effect of a pragma @cite{Elaborate_All} is stronger, it requires +not only that the body of the named unit be elaborated before the +unit doing the @emph{with}, but also the bodies of all units that the +named unit uses, following @emph{with} links transitively. For example, +if we put a pragma @cite{Elaborate_All (B)} in unit @cite{A}, +then it requires not only that the body of @cite{B} be elaborated before @cite{A}, +but also the body of @cite{C}, because @cite{B} @emph{with}s @cite{C}. +@end itemize + +We are now in a position to give a usage rule in Ada for avoiding +elaboration problems, at least if dynamic dispatching and access to +subprogram values are not used. We will handle these cases separately +later. + +The rule is simple: + +@emph{If a unit has elaboration code that can directly or +indirectly make a call to a subprogram in a |withed| unit, or instantiate +a generic package in a |withed| unit, +then if the |withed| unit does not have +pragma `Pure` or `Preelaborate`, then the client should have +a pragma `Elaborate_All`for the |withed| unit.*} + +By following this rule a client is +assured that calls can be made without risk of an exception. + +For generic subprogram instantiations, the rule can be relaxed to +require only a pragma @cite{Elaborate} since elaborating the body +of a subprogram cannot cause any transitive elaboration (we are +not calling the subprogram in this case, just elaborating its +declaration). + +If this rule is not followed, then a program may be in one of four +states: + + +@itemize * + +@item +@emph{No order exists} + +No order of elaboration exists which follows the rules, taking into +account any @cite{Elaborate}, @cite{Elaborate_All}, +or @cite{Elaborate_Body} pragmas. In +this case, an Ada compiler must diagnose the situation at bind +time, and refuse to build an executable program. + +@item +@emph{One or more orders exist, all incorrect} + +One or more acceptable elaboration orders exist, and all of them +generate an elaboration order problem. In this case, the binder +can build an executable program, but @cite{Program_Error} will be raised +when the program is run. + +@item +@emph{Several orders exist, some right, some incorrect} + +One or more acceptable elaboration orders exists, and some of them +work, and some do not. The programmer has not controlled +the order of elaboration, so the binder may or may not pick one of +the correct orders, and the program may or may not raise an +exception when it is run. This is the worst case, because it means +that the program may fail when moved to another compiler, or even +another version of the same compiler. + +@item +@emph{One or more orders exists, all correct} + +One ore more acceptable elaboration orders exist, and all of them +work. In this case the program runs successfully. This state of +affairs can be guaranteed by following the rule we gave above, but +may be true even if the rule is not followed. +@end itemize + +Note that one additional advantage of following our rules on the use +of @cite{Elaborate} and @cite{Elaborate_All} +is that the program continues to stay in the ideal (all orders OK) state +even if maintenance +changes some bodies of some units. Conversely, if a program that does +not follow this rule happens to be safe at some point, this state of affairs +may deteriorate silently as a result of maintenance changes. + +You may have noticed that the above discussion did not mention +the use of @cite{Elaborate_Body}. This was a deliberate omission. If you +@emph{with} an @cite{Elaborate_Body} unit, it still may be the case that +code in the body makes calls to some other unit, so it is still necessary +to use @cite{Elaborate_All} on such units. + +@node Controlling Elaboration in GNAT - Internal Calls,Controlling Elaboration in GNAT - External Calls,Controlling the Elaboration Order,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id5}@anchor{2b6}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-elaboration-in-gnat-internal-calls}@anchor{2b7} +@section Controlling Elaboration in GNAT - Internal Calls + + +In the case of internal calls, i.e., calls within a single package, the +programmer has full control over the order of elaboration, and it is up +to the programmer to elaborate declarations in an appropriate order. For +example writing: + +@example +function One return Float; + +Q : Float := One; + +function One return Float is +begin + return 1.0; +end One; +@end example + +will obviously raise @cite{Program_Error} at run time, because function +One will be called before its body is elaborated. In this case GNAT will +generate a warning that the call will raise @cite{Program_Error}: + +@example + 1. procedure y is + 2. function One return Float; + 3. + 4. Q : Float := One; + | + >>> warning: cannot call "One" before body is elaborated + >>> warning: Program_Error will be raised at run time + + 5. + 6. function One return Float is + 7. begin + 8. return 1.0; + 9. end One; +10. +11. begin +12. null; +13. end; +@end example + +Note that in this particular case, it is likely that the call is safe, because +the function @cite{One} does not access any global variables. +Nevertheless in Ada, we do not want the validity of the check to depend on +the contents of the body (think about the separate compilation case), so this +is still wrong, as we discussed in the previous sections. + +The error is easily corrected by rearranging the declarations so that the +body of @cite{One} appears before the declaration containing the call +(note that in Ada 95 as well as later versions of the Ada standard, +declarations can appear in any order, so there is no restriction that +would prevent this reordering, and if we write: + +@example +function One return Float; + +function One return Float is +begin + return 1.0; +end One; + +Q : Float := One; +@end example + +then all is well, no warning is generated, and no +@cite{Program_Error} exception +will be raised. +Things are more complicated when a chain of subprograms is executed: + +@example +function A return Integer; +function B return Integer; +function C return Integer; + +function B return Integer is begin return A; end; +function C return Integer is begin return B; end; + +X : Integer := C; + +function A return Integer is begin return 1; end; +@end example + +Now the call to @cite{C} +at elaboration time in the declaration of @cite{X} is correct, because +the body of @cite{C} is already elaborated, +and the call to @cite{B} within the body of +@cite{C} is correct, but the call +to @cite{A} within the body of @cite{B} is incorrect, because the body +of @cite{A} has not been elaborated, so @cite{Program_Error} +will be raised on the call to @cite{A}. +In this case GNAT will generate a +warning that @cite{Program_Error} may be +raised at the point of the call. Let's look at the warning: + +@example + 1. procedure x is + 2. function A return Integer; + 3. function B return Integer; + 4. function C return Integer; + 5. + 6. function B return Integer is begin return A; end; + | + >>> warning: call to "A" before body is elaborated may + raise Program_Error + >>> warning: "B" called at line 7 + >>> warning: "C" called at line 9 + + 7. function C return Integer is begin return B; end; + 8. + 9. X : Integer := C; +10. +11. function A return Integer is begin return 1; end; +12. +13. begin +14. null; +15. end; +@end example + +Note that the message here says 'may raise', instead of the direct case, +where the message says 'will be raised'. That's because whether +@cite{A} is +actually called depends in general on run-time flow of control. +For example, if the body of @cite{B} said + +@example +function B return Integer is +begin + if some-condition-depending-on-input-data then + return A; + else + return 1; + end if; +end B; +@end example + +then we could not know until run time whether the incorrect call to A would +actually occur, so @cite{Program_Error} might +or might not be raised. It is possible for a compiler to +do a better job of analyzing bodies, to +determine whether or not @cite{Program_Error} +might be raised, but it certainly +couldn't do a perfect job (that would require solving the halting problem +and is provably impossible), and because this is a warning anyway, it does +not seem worth the effort to do the analysis. Cases in which it +would be relevant are rare. + +In practice, warnings of either of the forms given +above will usually correspond to +real errors, and should be examined carefully and eliminated. +In the rare case where a warning is bogus, it can be suppressed by any of +the following methods: + + +@itemize * + +@item +Compile with the @emph{-gnatws} switch set + +@item +Suppress @cite{Elaboration_Check} for the called subprogram + +@item +Use pragma @cite{Warnings_Off} to turn warnings off for the call +@end itemize + +For the internal elaboration check case, +GNAT by default generates the +necessary run-time checks to ensure +that @cite{Program_Error} is raised if any +call fails an elaboration check. Of course this can only happen if a +warning has been issued as described above. The use of pragma +@cite{Suppress (Elaboration_Check)} may (but is not guaranteed to) suppress +some of these checks, meaning that it may be possible (but is not +guaranteed) for a program to be able to call a subprogram whose body +is not yet elaborated, without raising a @cite{Program_Error} exception. + +@node Controlling Elaboration in GNAT - External Calls,Default Behavior in GNAT - Ensuring Safety,Controlling Elaboration in GNAT - Internal Calls,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id6}@anchor{2b8}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-elaboration-in-gnat-external-calls}@anchor{2b9} +@section Controlling Elaboration in GNAT - External Calls + + +The previous section discussed the case in which the execution of a +particular thread of elaboration code occurred entirely within a +single unit. This is the easy case to handle, because a programmer +has direct and total control over the order of elaboration, and +furthermore, checks need only be generated in cases which are rare +and which the compiler can easily detect. +The situation is more complex when separate compilation is taken into account. +Consider the following: + +@example +package Math is + function Sqrt (Arg : Float) return Float; +end Math; + +package body Math is + function Sqrt (Arg : Float) return Float is + begin + ... + end Sqrt; +end Math; + +with Math; +package Stuff is + X : Float := Math.Sqrt (0.5); +end Stuff; + +with Stuff; +procedure Main is +begin + ... +end Main; +@end example + +where @cite{Main} is the main program. When this program is executed, the +elaboration code must first be executed, and one of the jobs of the +binder is to determine the order in which the units of a program are +to be elaborated. In this case we have four units: the spec and body +of @cite{Math}, +the spec of @cite{Stuff} and the body of @cite{Main}). +In what order should the four separate sections of elaboration code +be executed? + +There are some restrictions in the order of elaboration that the binder +can choose. In particular, if unit U has a @emph{with} +for a package @cite{X}, then you +are assured that the spec of @cite{X} +is elaborated before U , but you are +not assured that the body of @cite{X} +is elaborated before U. +This means that in the above case, the binder is allowed to choose the +order: + +@example +spec of Math +spec of Stuff +body of Math +body of Main +@end example + +but that's not good, because now the call to @cite{Math.Sqrt} +that happens during +the elaboration of the @cite{Stuff} +spec happens before the body of @cite{Math.Sqrt} is +elaborated, and hence causes @cite{Program_Error} exception to be raised. +At first glance, one might say that the binder is misbehaving, because +obviously you want to elaborate the body of something you @emph{with} first, but +that is not a general rule that can be followed in all cases. Consider + +@example +package X is ... + +package Y is ... + +with X; +package body Y is ... + +with Y; +package body X is ... +@end example + +This is a common arrangement, and, apart from the order of elaboration +problems that might arise in connection with elaboration code, this works fine. +A rule that says that you must first elaborate the body of anything you +@emph{with} cannot work in this case: +the body of @cite{X} @emph{with}s @cite{Y}, +which means you would have to +elaborate the body of @cite{Y} first, but that @emph{with}s @cite{X}, +which means +you have to elaborate the body of @cite{X} first, but ... and we have a +loop that cannot be broken. + +It is true that the binder can in many cases guess an order of elaboration +that is unlikely to cause a @cite{Program_Error} +exception to be raised, and it tries to do so (in the +above example of @cite{Math/Stuff/Spec}, the GNAT binder will +by default +elaborate the body of @cite{Math} right after its spec, so all will be well). + +However, a program that blindly relies on the binder to be helpful can +get into trouble, as we discussed in the previous sections, so GNAT +provides a number of facilities for assisting the programmer in +developing programs that are robust with respect to elaboration order. + +@node Default Behavior in GNAT - Ensuring Safety,Treatment of Pragma Elaborate,Controlling Elaboration in GNAT - External Calls,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id7}@anchor{2ba}@anchor{gnat_ugn/elaboration_order_handling_in_gnat default-behavior-in-gnat-ensuring-safety}@anchor{2bb} +@section Default Behavior in GNAT - Ensuring Safety + + +The default behavior in GNAT ensures elaboration safety. In its +default mode GNAT implements the +rule we previously described as the right approach. Let's restate it: + +@emph{If a unit has elaboration code that can directly or indirectly make a +call to a subprogram in a |withed| unit, or instantiate a generic +package in a |withed| unit, then if the |withed| unit +does not have pragma `Pure` or `Preelaborate`, then the client should have an +`Elaborate_All` pragma for the |withed| unit.} + +@emph{In the case of instantiating a generic subprogram, it is always +sufficient to have only an `Elaborate` pragma for the +|withed| unit.} + +By following this rule a client is assured that calls and instantiations +can be made without risk of an exception. + +In this mode GNAT traces all calls that are potentially made from +elaboration code, and puts in any missing implicit @cite{Elaborate} +and @cite{Elaborate_All} pragmas. +The advantage of this approach is that no elaboration problems +are possible if the binder can find an elaboration order that is +consistent with these implicit @cite{Elaborate} and +@cite{Elaborate_All} pragmas. The +disadvantage of this approach is that no such order may exist. + +If the binder does not generate any diagnostics, then it means that it has +found an elaboration order that is guaranteed to be safe. However, the binder +may still be relying on implicitly generated @cite{Elaborate} and +@cite{Elaborate_All} pragmas so portability to other compilers than GNAT is not +guaranteed. + +If it is important to guarantee portability, then the compilations should +use the @emph{-gnatel} +(info messages for elaboration pragmas) switch. This will cause info messages +to be generated indicating the missing @cite{Elaborate} and +@cite{Elaborate_All} pragmas. +Consider the following source program: + +@example +with k; +package j is + m : integer := k.r; +end; +@end example + +where it is clear that there +should be a pragma @cite{Elaborate_All} +for unit @cite{k}. An implicit pragma will be generated, and it is +likely that the binder will be able to honor it. However, if you want +to port this program to some other Ada compiler than GNAT. +it is safer to include the pragma explicitly in the source. If this +unit is compiled with the @emph{-gnatel} +switch, then the compiler outputs an information message: + +@example +1. with k; +2. package j is +3. m : integer := k.r; + | + >>> info: call to "r" may raise Program_Error + >>> info: missing pragma Elaborate_All for "k" + +4. end; +@end example + +and these messages can be used as a guide for supplying manually +the missing pragmas. It is usually a bad idea to use this +option during development. That's because it will tell you when +you need to put in a pragma, but cannot tell you when it is time +to take it out. So the use of pragma @cite{Elaborate_All} may lead to +unnecessary dependencies and even false circularities. + +This default mode is more restrictive than the Ada Reference +Manual, and it is possible to construct programs which will compile +using the dynamic model described there, but will run into a +circularity using the safer static model we have described. + +Of course any Ada compiler must be able to operate in a mode +consistent with the requirements of the Ada Reference Manual, +and in particular must have the capability of implementing the +standard dynamic model of elaboration with run-time checks. + +In GNAT, this standard mode can be achieved either by the use of +the @emph{-gnatE} switch on the compiler (@emph{gcc} or +@emph{gnatmake}) command, or by the use of the configuration pragma: + +@example +pragma Elaboration_Checks (DYNAMIC); +@end example + +Either approach will cause the unit affected to be compiled using the +standard dynamic run-time elaboration checks described in the Ada +Reference Manual. The static model is generally preferable, since it +is clearly safer to rely on compile and link time checks rather than +run-time checks. However, in the case of legacy code, it may be +difficult to meet the requirements of the static model. This +issue is further discussed in +@ref{2bc,,What to Do If the Default Elaboration Behavior Fails}. + +Note that the static model provides a strict subset of the allowed +behavior and programs of the Ada Reference Manual, so if you do +adhere to the static model and no circularities exist, +then you are assured that your program will +work using the dynamic model, providing that you remove any +pragma Elaborate statements from the source. + +@node Treatment of Pragma Elaborate,Elaboration Issues for Library Tasks,Default Behavior in GNAT - Ensuring Safety,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat treatment-of-pragma-elaborate}@anchor{2bd}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{2be} +@section Treatment of Pragma Elaborate + + +@geindex Pragma Elaborate + +The use of @cite{pragma Elaborate} +should generally be avoided in Ada 95 and Ada 2005 programs, +since there is no guarantee that transitive calls +will be properly handled. Indeed at one point, this pragma was placed +in Annex J (Obsolescent Features), on the grounds that it is never useful. + +Now that's a bit restrictive. In practice, the case in which +@cite{pragma Elaborate} is useful is when the caller knows that there +are no transitive calls, or that the called unit contains all necessary +transitive @cite{pragma Elaborate} statements, and legacy code often +contains such uses. + +Strictly speaking the static mode in GNAT should ignore such pragmas, +since there is no assurance at compile time that the necessary safety +conditions are met. In practice, this would cause GNAT to be incompatible +with correctly written Ada 83 code that had all necessary +@cite{pragma Elaborate} statements in place. Consequently, we made the +decision that GNAT in its default mode will believe that if it encounters +a @cite{pragma Elaborate} then the programmer knows what they are doing, +and it will trust that no elaboration errors can occur. + +The result of this decision is two-fold. First to be safe using the +static mode, you should remove all @cite{pragma Elaborate} statements. +Second, when fixing circularities in existing code, you can selectively +use @cite{pragma Elaborate} statements to convince the static mode of +GNAT that it need not generate an implicit @cite{pragma Elaborate_All} +statement. + +When using the static mode with @emph{-gnatwl}, any use of +@cite{pragma Elaborate} will generate a warning about possible +problems. + +@node Elaboration Issues for Library Tasks,Mixing Elaboration Models,Treatment of Pragma Elaborate,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-issues-for-library-tasks}@anchor{2bf}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id9}@anchor{2c0} +@section Elaboration Issues for Library Tasks + + +@geindex Library tasks +@geindex elaboration issues + +@geindex Elaboration of library tasks + +In this section we examine special elaboration issues that arise for +programs that declare library level tasks. + +Generally the model of execution of an Ada program is that all units are +elaborated, and then execution of the program starts. However, the +declaration of library tasks definitely does not fit this model. The +reason for this is that library tasks start as soon as they are declared +(more precisely, as soon as the statement part of the enclosing package +body is reached), that is to say before elaboration +of the program is complete. This means that if such a task calls a +subprogram, or an entry in another task, the callee may or may not be +elaborated yet, and in the standard +Reference Manual model of dynamic elaboration checks, you can even +get timing dependent Program_Error exceptions, since there can be +a race between the elaboration code and the task code. + +The static model of elaboration in GNAT seeks to avoid all such +dynamic behavior, by being conservative, and the conservative +approach in this particular case is to assume that all the code +in a task body is potentially executed at elaboration time if +a task is declared at the library level. + +This can definitely result in unexpected circularities. Consider +the following example + +@example +package Decls is + task Lib_Task is + entry Start; + end Lib_Task; + + type My_Int is new Integer; + + function Ident (M : My_Int) return My_Int; +end Decls; + +with Utils; +package body Decls is + task body Lib_Task is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task; + + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; +end Decls; + +with Decls; +package Utils is + procedure Put_Val (Arg : Decls.My_Int); +end Utils; + +with Text_IO; +package body Utils is + procedure Put_Val (Arg : Decls.My_Int) is + begin + Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); + end Put_Val; +end Utils; + +with Decls; +procedure Main is +begin + Decls.Lib_Task.Start; +end; +@end example + +If the above example is compiled in the default static elaboration +mode, then a circularity occurs. The circularity comes from the call +@cite{Utils.Put_Val} in the task body of @cite{Decls.Lib_Task}. Since +this call occurs in elaboration code, we need an implicit pragma +@cite{Elaborate_All} for @cite{Utils}. This means that not only must +the spec and body of @cite{Utils} be elaborated before the body +of @cite{Decls}, but also the spec and body of any unit that is +@emph{with}ed by the body of @cite{Utils} must also be elaborated before +the body of @cite{Decls}. This is the transitive implication of +pragma @cite{Elaborate_All} and it makes sense, because in general +the body of @cite{Put_Val} might have a call to something in a +@emph{with}ed unit. + +In this case, the body of Utils (actually its spec) @emph{with}s +@cite{Decls}. Unfortunately this means that the body of @cite{Decls} +must be elaborated before itself, in case there is a call from the +body of @cite{Utils}. + +Here is the exact chain of events we are worrying about: + + +@itemize * + +@item +In the body of @cite{Decls} a call is made from within the body of a library +task to a subprogram in the package @cite{Utils}. Since this call may +occur at elaboration time (given that the task is activated at elaboration +time), we have to assume the worst, i.e., that the +call does happen at elaboration time. + +@item +This means that the body and spec of @cite{Util} must be elaborated before +the body of @cite{Decls} so that this call does not cause an access before +elaboration. + +@item +Within the body of @cite{Util}, specifically within the body of +@cite{Util.Put_Val} there may be calls to any unit @emph{with}ed +by this package. + +@item +One such @emph{with}ed package is package @cite{Decls}, so there +might be a call to a subprogram in @cite{Decls} in @cite{Put_Val}. +In fact there is such a call in this example, but we would have to +assume that there was such a call even if it were not there, since +we are not supposed to write the body of @cite{Decls} knowing what +is in the body of @cite{Utils}; certainly in the case of the +static elaboration model, the compiler does not know what is in +other bodies and must assume the worst. + +@item +This means that the spec and body of @cite{Decls} must also be +elaborated before we elaborate the unit containing the call, but +that unit is @cite{Decls}! This means that the body of @cite{Decls} +must be elaborated before itself, and that's a circularity. +@end itemize + +Indeed, if you add an explicit pragma @cite{Elaborate_All} for @cite{Utils} in +the body of @cite{Decls} you will get a true Ada Reference Manual +circularity that makes the program illegal. + +In practice, we have found that problems with the static model of +elaboration in existing code often arise from library tasks, so +we must address this particular situation. + +Note that if we compile and run the program above, using the dynamic model of +elaboration (that is to say use the @emph{-gnatE} switch), +then it compiles, binds, +links, and runs, printing the expected result of 2. Therefore in some sense +the circularity here is only apparent, and we need to capture +the properties of this program that distinguish it from other library-level +tasks that have real elaboration problems. + +We have four possible answers to this question: + + +@itemize * + +@item +Use the dynamic model of elaboration. + +If we use the @emph{-gnatE} switch, then as noted above, the program works. +Why is this? If we examine the task body, it is apparent that the task cannot +proceed past the +@cite{accept} statement until after elaboration has been completed, because +the corresponding entry call comes from the main program, not earlier. +This is why the dynamic model works here. But that's really giving +up on a precise analysis, and we prefer to take this approach only if we cannot +solve the +problem in any other manner. So let us examine two ways to reorganize +the program to avoid the potential elaboration problem. + +@item +Split library tasks into separate packages. + +Write separate packages, so that library tasks are isolated from +other declarations as much as possible. Let us look at a variation on +the above program. + +@example +package Decls1 is + task Lib_Task is + entry Start; + end Lib_Task; +end Decls1; + +with Utils; +package body Decls1 is + task body Lib_Task is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task; +end Decls1; + +package Decls2 is + type My_Int is new Integer; + function Ident (M : My_Int) return My_Int; +end Decls2; + +with Utils; +package body Decls2 is + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; +end Decls2; + +with Decls2; +package Utils is + procedure Put_Val (Arg : Decls2.My_Int); +end Utils; + +with Text_IO; +package body Utils is + procedure Put_Val (Arg : Decls2.My_Int) is + begin + Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg))); + end Put_Val; +end Utils; + +with Decls1; +procedure Main is +begin + Decls1.Lib_Task.Start; +end; +@end example + +All we have done is to split @cite{Decls} into two packages, one +containing the library task, and one containing everything else. Now +there is no cycle, and the program compiles, binds, links and executes +using the default static model of elaboration. + +@item +Declare separate task types. + +A significant part of the problem arises because of the use of the +single task declaration form. This means that the elaboration of +the task type, and the elaboration of the task itself (i.e., the +creation of the task) happen at the same time. A good rule +of style in Ada is to always create explicit task types. By +following the additional step of placing task objects in separate +packages from the task type declaration, many elaboration problems +are avoided. Here is another modified example of the example program: + +@example +package Decls is + task type Lib_Task_Type is + entry Start; + end Lib_Task_Type; + + type My_Int is new Integer; + + function Ident (M : My_Int) return My_Int; +end Decls; + +with Utils; +package body Decls is + task body Lib_Task_Type is + begin + accept Start; + Utils.Put_Val (2); + end Lib_Task_Type; + + function Ident (M : My_Int) return My_Int is + begin + return M; + end Ident; +end Decls; + +with Decls; +package Utils is + procedure Put_Val (Arg : Decls.My_Int); +end Utils; + +with Text_IO; +package body Utils is + procedure Put_Val (Arg : Decls.My_Int) is + begin + Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg))); + end Put_Val; +end Utils; + +with Decls; +package Declst is + Lib_Task : Decls.Lib_Task_Type; +end Declst; + +with Declst; +procedure Main is +begin + Declst.Lib_Task.Start; +end; +@end example + +What we have done here is to replace the @cite{task} declaration in +package @cite{Decls} with a @cite{task type} declaration. Then we +introduce a separate package @cite{Declst} to contain the actual +task object. This separates the elaboration issues for +the @cite{task type} +declaration, which causes no trouble, from the elaboration issues +of the task object, which is also unproblematic, since it is now independent +of the elaboration of @cite{Utils}. +This separation of concerns also corresponds to +a generally sound engineering principle of separating declarations +from instances. This version of the program also compiles, binds, links, +and executes, generating the expected output. +@end itemize + +@geindex No_Entry_Calls_In_Elaboration_Code restriction + + +@itemize * + +@item +Use No_Entry_Calls_In_Elaboration_Code restriction. + +The previous two approaches described how a program can be restructured +to avoid the special problems caused by library task bodies. in practice, +however, such restructuring may be difficult to apply to existing legacy code, +so we must consider solutions that do not require massive rewriting. + +Let us consider more carefully why our original sample program works +under the dynamic model of elaboration. The reason is that the code +in the task body blocks immediately on the @cite{accept} +statement. Now of course there is nothing to prohibit elaboration +code from making entry calls (for example from another library level task), +so we cannot tell in isolation that +the task will not execute the accept statement during elaboration. + +However, in practice it is very unusual to see elaboration code +make any entry calls, and the pattern of tasks starting +at elaboration time and then immediately blocking on @cite{accept} or +@cite{select} statements is very common. What this means is that +the compiler is being too pessimistic when it analyzes the +whole package body as though it might be executed at elaboration +time. + +If we know that the elaboration code contains no entry calls, (a very safe +assumption most of the time, that could almost be made the default +behavior), then we can compile all units of the program under control +of the following configuration pragma: + +@example +pragma Restrictions (No_Entry_Calls_In_Elaboration_Code); +@end example + +This pragma can be placed in the @code{gnat.adc} file in the usual +manner. If we take our original unmodified program and compile it +in the presence of a @code{gnat.adc} containing the above pragma, +then once again, we can compile, bind, link, and execute, obtaining +the expected result. In the presence of this pragma, the compiler does +not trace calls in a task body, that appear after the first @cite{accept} +or @cite{select} statement, and therefore does not report a potential +circularity in the original program. + +The compiler will check to the extent it can that the above +restriction is not violated, but it is not always possible to do a +complete check at compile time, so it is important to use this +pragma only if the stated restriction is in fact met, that is to say +no task receives an entry call before elaboration of all units is completed. +@end itemize + +@node Mixing Elaboration Models,What to Do If the Default Elaboration Behavior Fails,Elaboration Issues for Library Tasks,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id10}@anchor{2c1}@anchor{gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models}@anchor{2c2} +@section Mixing Elaboration Models + + +So far, we have assumed that the entire program is either compiled +using the dynamic model or static model, ensuring consistency. It +is possible to mix the two models, but rules have to be followed +if this mixing is done to ensure that elaboration checks are not +omitted. + +The basic rule is that +@strong{a unit compiled with the static model cannot +be |withed| by a unit compiled with the dynamic model}. +The reason for this is that in the static model, a unit assumes that +its clients guarantee to use (the equivalent of) pragma +@cite{Elaborate_All} so that no elaboration checks are required +in inner subprograms, and this assumption is violated if the +client is compiled with dynamic checks. + +The precise rule is as follows. A unit that is compiled with dynamic +checks can only @emph{with} a unit that meets at least one of the +following criteria: + + +@itemize * + +@item +The @emph{with}ed unit is itself compiled with dynamic elaboration +checks (that is with the @emph{-gnatE} switch. + +@item +The @emph{with}ed unit is an internal GNAT implementation unit from +the System, Interfaces, Ada, or GNAT hierarchies. + +@item +The @emph{with}ed unit has pragma Preelaborate or pragma Pure. + +@item +The @emph{with}ing unit (that is the client) has an explicit pragma +@cite{Elaborate_All} for the @emph{with}ed unit. +@end itemize + +If this rule is violated, that is if a unit with dynamic elaboration +checks @emph{with}s a unit that does not meet one of the above four +criteria, then the binder (@cite{gnatbind}) will issue a warning +similar to that in the following example: + +@example +warning: "x.ads" has dynamic elaboration checks and with's +warning: "y.ads" which has static elaboration checks +@end example + +These warnings indicate that the rule has been violated, and that as a result +elaboration checks may be missed in the resulting executable file. +This warning may be suppressed using the @emph{-ws} binder switch +in the usual manner. + +One useful application of this mixing rule is in the case of a subsystem +which does not itself @emph{with} units from the remainder of the +application. In this case, the entire subsystem can be compiled with +dynamic checks to resolve a circularity in the subsystem, while +allowing the main application that uses this subsystem to be compiled +using the more reliable default static model. + +@node What to Do If the Default Elaboration Behavior Fails,Elaboration for Indirect Calls,Mixing Elaboration Models,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id11}@anchor{2c3}@anchor{gnat_ugn/elaboration_order_handling_in_gnat what-to-do-if-the-default-elaboration-behavior-fails}@anchor{2bc} +@section What to Do If the Default Elaboration Behavior Fails + + +If the binder cannot find an acceptable order, it outputs detailed +diagnostics. For example: + +@example +error: elaboration circularity detected +info: "proc (body)" must be elaborated before "pack (body)" +info: reason: Elaborate_All probably needed in unit "pack (body)" +info: recompile "pack (body)" with -gnatel +info: for full details +info: "proc (body)" +info: is needed by its spec: +info: "proc (spec)" +info: which is withed by: +info: "pack (body)" +info: "pack (body)" must be elaborated before "proc (body)" +info: reason: pragma Elaborate in unit "proc (body)" +@end example + +In this case we have a cycle that the binder cannot break. On the one +hand, there is an explicit pragma Elaborate in @cite{proc} for +@cite{pack}. This means that the body of @cite{pack} must be elaborated +before the body of @cite{proc}. On the other hand, there is elaboration +code in @cite{pack} that calls a subprogram in @cite{proc}. This means +that for maximum safety, there should really be a pragma +Elaborate_All in @cite{pack} for @cite{proc} which would require that +the body of @cite{proc} be elaborated before the body of +@cite{pack}. Clearly both requirements cannot be satisfied. +Faced with a circularity of this kind, you have three different options. + + +@itemize * + +@item +@emph{Fix the program} + +The most desirable option from the point of view of long-term maintenance +is to rearrange the program so that the elaboration problems are avoided. +One useful technique is to place the elaboration code into separate +child packages. Another is to move some of the initialization code to +explicitly called subprograms, where the program controls the order +of initialization explicitly. Although this is the most desirable option, +it may be impractical and involve too much modification, especially in +the case of complex legacy code. + +@item +@emph{Perform dynamic checks} + +If the compilations are done using the @emph{-gnatE} +(dynamic elaboration check) switch, then GNAT behaves in a quite different +manner. Dynamic checks are generated for all calls that could possibly result +in raising an exception. With this switch, the compiler does not generate +implicit @cite{Elaborate} or @cite{Elaborate_All} pragmas. The behavior then is +exactly as specified in the @cite{Ada Reference Manual}. +The binder will generate +an executable program that may or may not raise @cite{Program_Error}, and then +it is the programmer's job to ensure that it does not raise an exception. Note +that it is important to compile all units with the switch, it cannot be used +selectively. + +@item +@emph{Suppress checks} + +The drawback of dynamic checks is that they generate a +significant overhead at run time, both in space and time. If you +are absolutely sure that your program cannot raise any elaboration +exceptions, and you still want to use the dynamic elaboration model, +then you can use the configuration pragma +@cite{Suppress (Elaboration_Check)} to suppress all such checks. For +example this pragma could be placed in the @code{gnat.adc} file. + +@item +@emph{Suppress checks selectively} + +When you know that certain calls or instantiations in elaboration code cannot +possibly lead to an elaboration error, and the binder nevertheless complains +about implicit @cite{Elaborate} and @cite{Elaborate_All} pragmas that lead to +elaboration circularities, it is possible to remove those warnings locally and +obtain a program that will bind. Clearly this can be unsafe, and it is the +responsibility of the programmer to make sure that the resulting program has no +elaboration anomalies. The pragma @cite{Suppress (Elaboration_Check)} can be +used with different granularity to suppress warnings and break elaboration +circularities: + + +@itemize * + +@item +Place the pragma that names the called subprogram in the declarative part +that contains the call. + +@item +Place the pragma in the declarative part, without naming an entity. This +disables warnings on all calls in the corresponding declarative region. + +@item +Place the pragma in the package spec that declares the called subprogram, +and name the subprogram. This disables warnings on all elaboration calls to +that subprogram. + +@item +Place the pragma in the package spec that declares the called subprogram, +without naming any entity. This disables warnings on all elaboration calls to +all subprograms declared in this spec. + +@item +Use Pragma Elaborate. + +As previously described in section @ref{2bd,,Treatment of Pragma Elaborate}, +GNAT in static mode assumes that a @cite{pragma} Elaborate indicates correctly +that no elaboration checks are required on calls to the designated unit. +There may be cases in which the caller knows that no transitive calls +can occur, so that a @cite{pragma Elaborate} will be sufficient in a +case where @cite{pragma Elaborate_All} would cause a circularity. +@end itemize + +These five cases are listed in order of decreasing safety, and therefore +require increasing programmer care in their application. Consider the +following program: + +@example +package Pack1 is + function F1 return Integer; + X1 : Integer; +end Pack1; + +package Pack2 is + function F2 return Integer; + function Pure (x : integer) return integer; + -- pragma Suppress (Elaboration_Check, On => Pure); -- (3) + -- pragma Suppress (Elaboration_Check); -- (4) +end Pack2; + +with Pack2; +package body Pack1 is + function F1 return Integer is + begin + return 100; + end F1; + Val : integer := Pack2.Pure (11); -- Elab. call (1) +begin + declare + -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1) + -- pragma Suppress(Elaboration_Check); -- (2) + begin + X1 := Pack2.F2 + 1; -- Elab. call (2) + end; +end Pack1; + +with Pack1; +package body Pack2 is + function F2 return Integer is + begin + return Pack1.F1; + end F2; + function Pure (x : integer) return integer is + begin + return x ** 3 - 3 * x; + end; +end Pack2; + +with Pack1, Ada.Text_IO; +procedure Proc3 is +begin + Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101 +end Proc3; +@end example + +In the absence of any pragmas, an attempt to bind this program produces +the following diagnostics: + +@example +error: elaboration circularity detected +info: "pack1 (body)" must be elaborated before "pack1 (body)" +info: reason: Elaborate_All probably needed in unit "pack1 (body)" +info: recompile "pack1 (body)" with -gnatel for full details +info: "pack1 (body)" +info: must be elaborated along with its spec: +info: "pack1 (spec)" +info: which is withed by: +info: "pack2 (body)" +info: which must be elaborated along with its spec: +info: "pack2 (spec)" +info: which is withed by: +info: "pack1 (body)" +@end example + +The sources of the circularity are the two calls to @cite{Pack2.Pure} and +@cite{Pack2.F2} in the body of @cite{Pack1}. We can see that the call to +F2 is safe, even though F2 calls F1, because the call appears after the +elaboration of the body of F1. Therefore the pragma (1) is safe, and will +remove the warning on the call. It is also possible to use pragma (2) +because there are no other potentially unsafe calls in the block. + +The call to @cite{Pure} is safe because this function does not depend on the +state of @cite{Pack2}. Therefore any call to this function is safe, and it +is correct to place pragma (3) in the corresponding package spec. + +Finally, we could place pragma (4) in the spec of @cite{Pack2} to disable +warnings on all calls to functions declared therein. Note that this is not +necessarily safe, and requires more detailed examination of the subprogram +bodies involved. In particular, a call to @cite{F2} requires that @cite{F1} +be already elaborated. +@end itemize + +It is hard to generalize on which of these four approaches should be +taken. Obviously if it is possible to fix the program so that the default +treatment works, this is preferable, but this may not always be practical. +It is certainly simple enough to use @emph{-gnatE} +but the danger in this case is that, even if the GNAT binder +finds a correct elaboration order, it may not always do so, +and certainly a binder from another Ada compiler might not. A +combination of testing and analysis (for which the +information messages generated with the @emph{-gnatel} +switch can be useful) must be used to ensure that the program is free +of errors. One switch that is useful in this testing is the +@emph{-p (pessimistic elaboration order)} switch for @cite{gnatbind}. +Normally the binder tries to find an order that has the best chance +of avoiding elaboration problems. However, if this switch is used, the binder +plays a devil's advocate role, and tries to choose the order that +has the best chance of failing. If your program works even with this +switch, then it has a better chance of being error free, but this is still +not a guarantee. + +For an example of this approach in action, consider the C-tests (executable +tests) from the ACATS suite. If these are compiled and run with the default +treatment, then all but one of them succeed without generating any error +diagnostics from the binder. However, there is one test that fails, and +this is not surprising, because the whole point of this test is to ensure +that the compiler can handle cases where it is impossible to determine +a correct order statically, and it checks that an exception is indeed +raised at run time. + +This one test must be compiled and run using the @emph{-gnatE} +switch, and then it passes. Alternatively, the entire suite can +be run using this switch. It is never wrong to run with the dynamic +elaboration switch if your code is correct, and we assume that the +C-tests are indeed correct (it is less efficient, but efficiency is +not a factor in running the ACATS tests.) + +@node Elaboration for Indirect Calls,Summary of Procedures for Elaboration Control,What to Do If the Default Elaboration Behavior Fails,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id12}@anchor{2c4}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-for-indirect-calls}@anchor{2c5} +@section Elaboration for Indirect Calls + + +@geindex Dispatching calls + +@geindex Indirect calls + +In rare cases, the static elaboration model fails to prevent +dispatching calls to not-yet-elaborated subprograms. In such cases, we +fall back to run-time checks; premature calls to any primitive +operation of a tagged type before the body of the operation has been +elaborated will raise @cite{Program_Error}. + +Access-to-subprogram types, however, are handled conservatively, and +do not require run-time checks. This was not true in earlier versions +of the compiler; you can use the @emph{-gnatd.U} debug switch to +revert to the old behavior if the new conservative behavior causes +elaboration cycles. Here, 'conservative' means that if you do +@cite{P'Access} during elaboration, the compiler will assume that you +might call @cite{P} indirectly during elaboration, so it adds an +implicit @cite{pragma Elaborate_All} on the library unit containing +@cite{P}. The @emph{-gnatd.U} switch is safe if you know there are +no such calls. If the program worked before, it will continue to work +with @emph{-gnatd.U}. But beware that code modifications such as +adding an indirect call can cause erroneous behavior in the presence +of @emph{-gnatd.U}. + +@node Summary of Procedures for Elaboration Control,Other Elaboration Order Considerations,Elaboration for Indirect Calls,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id13}@anchor{2c6}@anchor{gnat_ugn/elaboration_order_handling_in_gnat summary-of-procedures-for-elaboration-control}@anchor{2c7} +@section Summary of Procedures for Elaboration Control + + +@geindex Elaboration control + +First, compile your program with the default options, using none of +the special elaboration control switches. If the binder successfully +binds your program, then you can be confident that, apart from issues +raised by the use of access-to-subprogram types and dynamic dispatching, +the program is free of elaboration errors. If it is important that the +program be portable to other compilers than GNAT, then use the +@emph{-gnatel} +switch to generate messages about missing @cite{Elaborate} or +@cite{Elaborate_All} pragmas, and supply the missing pragmas. + +If the program fails to bind using the default static elaboration +handling, then you can fix the program to eliminate the binder +message, or recompile the entire program with the +@emph{-gnatE} switch to generate dynamic elaboration checks, +and, if you are sure there really are no elaboration problems, +use a global pragma @cite{Suppress (Elaboration_Check)}. + +@node Other Elaboration Order Considerations,Determining the Chosen Elaboration Order,Summary of Procedures for Elaboration Control,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat id14}@anchor{2c8}@anchor{gnat_ugn/elaboration_order_handling_in_gnat other-elaboration-order-considerations}@anchor{2c9} +@section Other Elaboration Order Considerations + + +This section has been entirely concerned with the issue of finding a valid +elaboration order, as defined by the Ada Reference Manual. In a case +where several elaboration orders are valid, the task is to find one +of the possible valid elaboration orders (and the static model in GNAT +will ensure that this is achieved). + +The purpose of the elaboration rules in the Ada Reference Manual is to +make sure that no entity is accessed before it has been elaborated. For +a subprogram, this means that the spec and body must have been elaborated +before the subprogram is called. For an object, this means that the object +must have been elaborated before its value is read or written. A violation +of either of these two requirements is an access before elaboration order, +and this section has been all about avoiding such errors. + +In the case where more than one order of elaboration is possible, in the +sense that access before elaboration errors are avoided, then any one of +the orders is 'correct' in the sense that it meets the requirements of +the Ada Reference Manual, and no such error occurs. + +However, it may be the case for a given program, that there are +constraints on the order of elaboration that come not from consideration +of avoiding elaboration errors, but rather from extra-lingual logic +requirements. Consider this example: + +@example +with Init_Constants; +package Constants is + X : Integer := 0; + Y : Integer := 0; +end Constants; + +package Init_Constants is + procedure P; --* require a body* +end Init_Constants; + +with Constants; +package body Init_Constants is + procedure P is begin null; end; +begin + Constants.X := 3; + Constants.Y := 4; +end Init_Constants; + +with Constants; +package Calc is + Z : Integer := Constants.X + Constants.Y; +end Calc; + +with Calc; +with Text_IO; use Text_IO; +procedure Main is +begin + Put_Line (Calc.Z'Img); +end Main; +@end example + +In this example, there is more than one valid order of elaboration. For +example both the following are correct orders: + +@example +Init_Constants spec +Constants spec +Calc spec +Init_Constants body +Main body +@end example + +and + +@example +Init_Constants spec +Init_Constants body +Constants spec +Calc spec +Main body +@end example + +There is no language rule to prefer one or the other, both are correct +from an order of elaboration point of view. But the programmatic effects +of the two orders are very different. In the first, the elaboration routine +of @cite{Calc} initializes @cite{Z} to zero, and then the main program +runs with this value of zero. But in the second order, the elaboration +routine of @cite{Calc} runs after the body of Init_Constants has set +@cite{X} and @cite{Y} and thus @cite{Z} is set to 7 before @cite{Main} runs. + +One could perhaps by applying pretty clever non-artificial intelligence +to the situation guess that it is more likely that the second order of +elaboration is the one desired, but there is no formal linguistic reason +to prefer one over the other. In fact in this particular case, GNAT will +prefer the second order, because of the rule that bodies are elaborated +as soon as possible, but it's just luck that this is what was wanted +(if indeed the second order was preferred). + +If the program cares about the order of elaboration routines in a case like +this, it is important to specify the order required. In this particular +case, that could have been achieved by adding to the spec of Calc: + +@example +pragma Elaborate_All (Constants); +@end example + +which requires that the body (if any) and spec of @cite{Constants}, +as well as the body and spec of any unit @emph{with}ed by +@cite{Constants} be elaborated before @cite{Calc} is elaborated. + +Clearly no automatic method can always guess which alternative you require, +and if you are working with legacy code that had constraints of this kind +which were not properly specified by adding @cite{Elaborate} or +@cite{Elaborate_All} pragmas, then indeed it is possible that two different +compilers can choose different orders. + +However, GNAT does attempt to diagnose the common situation where there +are uninitialized variables in the visible part of a package spec, and the +corresponding package body has an elaboration block that directly or +indirectly initialized one or more of these variables. This is the situation +in which a pragma Elaborate_Body is usually desirable, and GNAT will generate +a warning that suggests this addition if it detects this situation. + +The @cite{gnatbind} @emph{-p} switch may be useful in smoking +out problems. This switch causes bodies to be elaborated as late as possible +instead of as early as possible. In the example above, it would have forced +the choice of the first elaboration order. If you get different results +when using this switch, and particularly if one set of results is right, +and one is wrong as far as you are concerned, it shows that you have some +missing @cite{Elaborate} pragmas. For the example above, we have the +following output: + +@example +$ gnatmake -f -q main +$ main + 7 +$ gnatmake -f -q main -bargs -p +$ main + 0 +@end example + +It is of course quite unlikely that both these results are correct, so +it is up to you in a case like this to investigate the source of the +difference, by looking at the two elaboration orders that are chosen, +and figuring out which is correct, and then adding the necessary +@cite{Elaborate} or @cite{Elaborate_All} pragmas to ensure the desired order. + +@node Determining the Chosen Elaboration Order,,Other Elaboration Order Considerations,Elaboration Order Handling in GNAT +@anchor{gnat_ugn/elaboration_order_handling_in_gnat determining-the-chosen-elaboration-order}@anchor{2ca}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id15}@anchor{2cb} +@section Determining the Chosen Elaboration Order + + +To see the elaboration order that the binder chooses, you can look at +the last part of the file:@cite{b~xxx.adb} binder output file. Here is an example: + +@example +System.Soft_Links'Elab_Body; +E14 := True; +System.Secondary_Stack'Elab_Body; +E18 := True; +System.Exception_Table'Elab_Body; +E24 := True; +Ada.Io_Exceptions'Elab_Spec; +E67 := True; +Ada.Tags'Elab_Spec; +Ada.Streams'Elab_Spec; +E43 := True; +Interfaces.C'Elab_Spec; +E69 := True; +System.Finalization_Root'Elab_Spec; +E60 := True; +System.Os_Lib'Elab_Body; +E71 := True; +System.Finalization_Implementation'Elab_Spec; +System.Finalization_Implementation'Elab_Body; +E62 := True; +Ada.Finalization'Elab_Spec; +E58 := True; +Ada.Finalization.List_Controller'Elab_Spec; +E76 := True; +System.File_Control_Block'Elab_Spec; +E74 := True; +System.File_Io'Elab_Body; +E56 := True; +Ada.Tags'Elab_Body; +E45 := True; +Ada.Text_Io'Elab_Spec; +Ada.Text_Io'Elab_Body; +E07 := True; +@end example + +Here Elab_Spec elaborates the spec +and Elab_Body elaborates the body. The assignments to the @code{E@emph{xx}} flags +flag that the corresponding body is now elaborated. + +You can also ask the binder to generate a more +readable list of the elaboration order using the +@cite{-l} switch when invoking the binder. Here is +an example of the output generated by this switch: + +@example +ada (spec) +interfaces (spec) +system (spec) +system.case_util (spec) +system.case_util (body) +system.concat_2 (spec) +system.concat_2 (body) +system.concat_3 (spec) +system.concat_3 (body) +system.htable (spec) +system.parameters (spec) +system.parameters (body) +system.crtl (spec) +interfaces.c_streams (spec) +interfaces.c_streams (body) +system.restrictions (spec) +system.restrictions (body) +system.standard_library (spec) +system.exceptions (spec) +system.exceptions (body) +system.storage_elements (spec) +system.storage_elements (body) +system.secondary_stack (spec) +system.stack_checking (spec) +system.stack_checking (body) +system.string_hash (spec) +system.string_hash (body) +system.htable (body) +system.strings (spec) +system.strings (body) +system.traceback (spec) +system.traceback (body) +system.traceback_entries (spec) +system.traceback_entries (body) +ada.exceptions (spec) +ada.exceptions.last_chance_handler (spec) +system.soft_links (spec) +system.soft_links (body) +ada.exceptions.last_chance_handler (body) +system.secondary_stack (body) +system.exception_table (spec) +system.exception_table (body) +ada.io_exceptions (spec) +ada.tags (spec) +ada.streams (spec) +interfaces.c (spec) +interfaces.c (body) +system.finalization_root (spec) +system.finalization_root (body) +system.memory (spec) +system.memory (body) +system.standard_library (body) +system.os_lib (spec) +system.os_lib (body) +system.unsigned_types (spec) +system.stream_attributes (spec) +system.stream_attributes (body) +system.finalization_implementation (spec) +system.finalization_implementation (body) +ada.finalization (spec) +ada.finalization (body) +ada.finalization.list_controller (spec) +ada.finalization.list_controller (body) +system.file_control_block (spec) +system.file_io (spec) +system.file_io (body) +system.val_uns (spec) +system.val_util (spec) +system.val_util (body) +system.val_uns (body) +system.wch_con (spec) +system.wch_con (body) +system.wch_cnv (spec) +system.wch_jis (spec) +system.wch_jis (body) +system.wch_cnv (body) +system.wch_stw (spec) +system.wch_stw (body) +ada.tags (body) +ada.exceptions (body) +ada.text_io (spec) +ada.text_io (body) +text_io (spec) +gdbstr (body) +@end example + +@node Inline Assembler,GNU Free Documentation License,Elaboration Order Handling in GNAT,Top +@anchor{gnat_ugn/inline_assembler inline-assembler}@anchor{12}@anchor{gnat_ugn/inline_assembler doc}@anchor{2cc}@anchor{gnat_ugn/inline_assembler id1}@anchor{2cd} +@chapter Inline Assembler + + +@geindex Inline Assembler + +If you need to write low-level software that interacts directly +with the hardware, Ada provides two ways to incorporate assembly +language code into your program. First, you can import and invoke +external routines written in assembly language, an Ada feature fully +supported by GNAT. However, for small sections of code it may be simpler +or more efficient to include assembly language statements directly +in your Ada source program, using the facilities of the implementation-defined +package @cite{System.Machine_Code}, which incorporates the gcc +Inline Assembler. The Inline Assembler approach offers a number of advantages, +including the following: -@noindent -There can actually be other sections in a definition file, but these -sections are not relevant to the discussion at hand. -@node GNAT-Style Import Library -@subsubsection GNAT-Style Import Library +@itemize * -@noindent -To create a static import library from @file{API.dll} with the GNAT tools -you should proceed as follows: +@item +No need to use non-Ada tools -@enumerate -@item -Create the definition file @file{API.def} (@pxref{The Definition File}). -For that use the @code{dll2def} tool as follows: +@item +Consistent interface over different targets -@smallexample -$ dll2def API.dll > API.def -@end smallexample +@item +Automatic usage of the proper calling conventions -@noindent -@code{dll2def} is a very simple tool: it takes as input a DLL and prints -to standard output the list of entry points in the DLL. Note that if -some routines in the DLL have the @code{Stdcall} convention -(@pxref{Windows Calling Conventions}) with stripped @code{@@}@var{nn} -suffix then you'll have to edit @file{api.def} to add it, and specify -@option{-k} to @command{gnatdll} when creating the import library. +@item +Access to Ada constants and variables -@noindent -Here are some hints to find the right @code{@@}@var{nn} suffix. +@item +Definition of intrinsic routines -@enumerate -@item -If you have the Microsoft import library (.lib), it is possible to get -the right symbols by using Microsoft @code{dumpbin} tool (see the -corresponding Microsoft documentation for further details). +@item +Possibility of inlining a subprogram comprising assembler code -@smallexample -$ dumpbin /exports api.lib -@end smallexample +@item +Code optimizer can take Inline Assembler code into account +@end itemize -@item -If you have a message about a missing symbol at link time the compiler -tells you what symbol is expected. You just have to go back to the -definition file and add the right suffix. -@end enumerate +This appendix presents a series of examples to show you how to use +the Inline Assembler. Although it focuses on the Intel x86, +the general approach applies also to other processors. +It is assumed that you are familiar with Ada +and with assembly language programming. -@item -Build the import library @code{libAPI.dll.a}, using @code{gnatdll} -(@pxref{Using gnatdll}) as follows: +@menu +* Basic Assembler Syntax:: +* A Simple Example of Inline Assembler:: +* Output Variables in Inline Assembler:: +* Input Variables in Inline Assembler:: +* Inlining Inline Assembler Code:: +* Other Asm Functionality:: -@smallexample -$ gnatdll -e API.def -d API.dll -@end smallexample +@end menu -@noindent -@code{gnatdll} takes as input a definition file @file{API.def} and the -name of the DLL containing the services listed in the definition file -@file{API.dll}. The name of the static import library generated is -computed from the name of the definition file as follows: if the -definition file name is @var{xyz}@code{.def}, the import library name will -be @code{lib}@var{xyz}@code{.a}. Note that in the previous example option -@option{-e} could have been removed because the name of the definition -file (before the ``@code{.def}'' suffix) is the same as the name of the -DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}). -@end enumerate +@node Basic Assembler Syntax,A Simple Example of Inline Assembler,,Inline Assembler +@anchor{gnat_ugn/inline_assembler id2}@anchor{2ce}@anchor{gnat_ugn/inline_assembler basic-assembler-syntax}@anchor{2cf} +@section Basic Assembler Syntax -@node Microsoft-Style Import Library -@subsubsection Microsoft-Style Import Library -@noindent -With GNAT you can either use a GNAT-style or Microsoft-style import -library. A Microsoft import library is needed only if you plan to make an -Ada DLL available to applications developed with Microsoft -tools (@pxref{Mixed-Language Programming on Windows}). +The assembler used by GNAT and gcc is based not on the Intel assembly +language, but rather on a language that descends from the AT&T Unix +assembler @emph{as} (and which is often referred to as 'AT&T syntax'). +The following table summarizes the main features of @emph{as} syntax +and points out the differences from the Intel conventions. +See the gcc @emph{as} and @emph{gas} (an @emph{as} macro +pre-processor) documentation for further information. -To create a Microsoft-style import library for @file{API.dll} you -should proceed as follows: -@enumerate -@item -Create the definition file @file{API.def} from the DLL. For this use either -the @code{dll2def} tool as described above or the Microsoft @code{dumpbin} -tool (see the corresponding Microsoft documentation for further details). +@display +@emph{Register names}@w{ } +@display +gcc / @emph{as}: Prefix with '%'; for example @cite{%eax}@w{ } +Intel: No extra punctuation; for example @cite{eax}@w{ } +@end display +@end display -@item -Build the actual import library using Microsoft's @code{lib} utility: -@smallexample -$ lib -machine:IX86 -def:API.def -out:API.lib -@end smallexample -@noindent -If you use the above command the definition file @file{API.def} must -contain a line giving the name of the DLL: -@smallexample -LIBRARY "API" -@end smallexample +@display +@emph{Immediate operand}@w{ } +@display +gcc / @emph{as}: Prefix with '$'; for example @cite{$4}@w{ } +Intel: No extra punctuation; for example @cite{4}@w{ } +@end display +@end display -@noindent -See the Microsoft documentation for further details about the usage of -@code{lib}. -@end enumerate -@node Building DLLs with GNAT Project files -@section Building DLLs with GNAT Project files -@cindex DLLs, building -@noindent -There is nothing specific to Windows in the build process. -@pxref{Library Projects}. -@noindent -Due to a system limitation, it is not possible under Windows to create threads -when inside the @code{DllMain} routine which is used for auto-initialization -of shared libraries, so it is not possible to have library level tasks in SALs. +@display +@emph{Address}@w{ } +@display +gcc / @emph{as}: Prefix with '$'; for example @cite{$loc}@w{ } +Intel: No extra punctuation; for example @cite{loc}@w{ } +@end display +@end display -@node Building DLLs with GNAT -@section Building DLLs with GNAT -@cindex DLLs, building -@noindent -This section explain how to build DLLs using the GNAT built-in DLL -support. With the following procedure it is straight forward to build -and use DLLs with GNAT. -@enumerate -@item building object files +@display +@emph{Memory contents}@w{ } +@display +gcc / @emph{as}: No extra punctuation; for example @cite{loc}@w{ } +Intel: Square brackets; for example @cite{[loc]}@w{ } +@end display +@end display -The first step is to build all objects files that are to be included -into the DLL. This is done by using the standard @command{gnatmake} tool. -@item building the DLL -To build the DLL you must use @command{gcc}'s @option{-shared} and -@option{-shared-libgcc} options. It is quite simple to use this method: -@smallexample -$ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o @dots{} -@end smallexample +@display +@emph{Register contents}@w{ } +@display +gcc / @emph{as}: Parentheses; for example @cite{(%eax)}@w{ } +Intel: Square brackets; for example @cite{[eax]}@w{ } +@end display +@end display -It is important to note that in this case all symbols found in the -object files are automatically exported. It is possible to restrict -the set of symbols to export by passing to @command{gcc} a definition -file, @pxref{The Definition File}. For example: -@smallexample -$ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o @dots{} -@end smallexample -If you use a definition file you must export the elaboration procedures -for every package that required one. Elaboration procedures are named -using the package name followed by "_E". -@item preparing DLL to be used +@display +@emph{Hexadecimal numbers}@w{ } +@display +gcc / @emph{as}: Leading '0x' (C language syntax); for example @cite{0xA0}@w{ } +Intel: Trailing 'h'; for example @cite{A0h}@w{ } +@end display +@end display -For the DLL to be used by client programs the bodies must be hidden -from it and the .ali set with read-only attribute. This is very important -otherwise GNAT will recompile all packages and will not actually use -the code in the DLL. For example: -@smallexample -$ mkdir apilib -$ copy *.ads *.ali api.dll apilib -$ attrib +R apilib\*.ali -@end smallexample -@end enumerate -At this point it is possible to use the DLL by directly linking -against it. Note that you must use the GNAT shared runtime when using -GNAT shared libraries. This is achieved by using @option{-shared} binder's -option. +@display +@emph{Operand size}@w{ } +@display +gcc / @emph{as}: Explicit in op code; for example @cite{movw} to move a 16-bit word@w{ } +Intel: Implicit, deduced by assembler; for example @cite{mov}@w{ } +@end display +@end display -@smallexample -$ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI -@end smallexample -@node Building DLLs with gnatdll -@section Building DLLs with gnatdll -@cindex DLLs, building -@menu -* Limitations When Using Ada DLLs from Ada:: -* Exporting Ada Entities:: -* Ada DLLs and Elaboration:: -* Ada DLLs and Finalization:: -* Creating a Spec for Ada DLLs:: -* Creating the Definition File:: -* Using gnatdll:: -@end menu -@noindent -Note that it is preferred to use GNAT Project files -(@pxref{Building DLLs with GNAT Project files}) or the built-in GNAT -DLL support (@pxref{Building DLLs with GNAT}) or to build DLLs. +@display +@emph{Instruction repetition}@w{ } +@display +gcc / @emph{as}: Split into two lines; for example@w{ } +@display +@cite{rep}@w{ } +@cite{stosl}@w{ } +@end display +Intel: Keep on one line; for example @cite{rep stosl}@w{ } +@end display +@end display -This section explains how to build DLLs containing Ada code using -@code{gnatdll}. These DLLs will be referred to as Ada DLLs in the -remainder of this section. -The steps required to build an Ada DLL that is to be used by Ada as well as -non-Ada applications are as follows: -@enumerate -@item -You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or -@code{Stdcall} calling convention to avoid any Ada name mangling for the -entities exported by the DLL (@pxref{Exporting Ada Entities}). You can -skip this step if you plan to use the Ada DLL only from Ada applications. -@item -Your Ada code must export an initialization routine which calls the routine -@code{adainit} generated by @command{gnatbind} to perform the elaboration of -the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization -routine exported by the Ada DLL must be invoked by the clients of the DLL -to initialize the DLL. +@display +@emph{Order of operands}@w{ } +@display +gcc / @emph{as}: Source first; for example @cite{movw $4@comma{} %eax}@w{ } +Intel: Destination first; for example @cite{mov eax@comma{} 4}@w{ } +@end display +@end display -@item -When useful, the DLL should also export a finalization routine which calls -routine @code{adafinal} generated by @command{gnatbind} to perform the -finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}). -The finalization routine exported by the Ada DLL must be invoked by the -clients of the DLL when the DLL services are no further needed. -@item -You must provide a spec for the services exported by the Ada DLL in each -of the programming languages to which you plan to make the DLL available. -@item -You must provide a definition file listing the exported entities -(@pxref{The Definition File}). +@node A Simple Example of Inline Assembler,Output Variables in Inline Assembler,Basic Assembler Syntax,Inline Assembler +@anchor{gnat_ugn/inline_assembler a-simple-example-of-inline-assembler}@anchor{2d0}@anchor{gnat_ugn/inline_assembler id3}@anchor{2d1} +@section A Simple Example of Inline Assembler -@item -Finally you must use @code{gnatdll} to produce the DLL and the import -library (@pxref{Using gnatdll}). -@end enumerate -@noindent -Note that a relocatable DLL stripped using the @code{strip} -binutils tool will not be relocatable anymore. To build a DLL without -debug information pass @code{-largs -s} to @code{gnatdll}. This -restriction does not apply to a DLL built using a Library Project. -@pxref{Library Projects}. +The following example will generate a single assembly language statement, +@cite{nop}, which does nothing. Despite its lack of run-time effect, +the example will be useful in illustrating the basics of +the Inline Assembler facility. -@node Limitations When Using Ada DLLs from Ada -@subsection Limitations When Using Ada DLLs from Ada +@quotation -@noindent -When using Ada DLLs from Ada applications there is a limitation users -should be aware of. Because on Windows the GNAT run time is not in a DLL of -its own, each Ada DLL includes a part of the GNAT run time. Specifically, -each Ada DLL includes the services of the GNAT run time that are necessary -to the Ada code inside the DLL. As a result, when an Ada program uses an -Ada DLL there are two independent GNAT run times: one in the Ada DLL and -one in the main program. +@example +with System.Machine_Code; use System.Machine_Code; +procedure Nothing is +begin + Asm ("nop"); +end Nothing; +@end example +@end quotation -It is therefore not possible to exchange GNAT run-time objects between the -Ada DLL and the main Ada program. Example of GNAT run-time objects are file -handles (e.g.@: @code{Text_IO.File_Type}), tasks types, protected objects -types, etc. +@cite{Asm} is a procedure declared in package @cite{System.Machine_Code}; +here it takes one parameter, a @emph{template string} that must be a static +expression and that will form the generated instruction. +@cite{Asm} may be regarded as a compile-time procedure that parses +the template string and additional parameters (none here), +from which it generates a sequence of assembly language instructions. -It is completely safe to exchange plain elementary, array or record types, -Windows object handles, etc. +The examples in this chapter will illustrate several of the forms +for invoking @cite{Asm}; a complete specification of the syntax +is found in the @cite{Machine_Code_Insertions} section of the +@cite{GNAT Reference Manual}. -@node Exporting Ada Entities -@subsection Exporting Ada Entities -@cindex Export table +Under the standard GNAT conventions, the @cite{Nothing} procedure +should be in a file named @code{nothing.adb}. +You can build the executable in the usual way: -@noindent -Building a DLL is a way to encapsulate a set of services usable from any -application. As a result, the Ada entities exported by a DLL should be -exported with the @code{C} or @code{Stdcall} calling conventions to avoid -any Ada name mangling. As an example here is an Ada package -@code{API}, spec and body, exporting two procedures, a function, and a -variable: +@quotation -@smallexample @c ada -@group -@cartouche -@b{with} Interfaces.C; @b{use} Interfaces; -@b{package} API @b{is} - Count : C.int := 0; - @b{function} Factorial (Val : C.int) @b{return} C.int; - - @b{procedure} Initialize_API; - @b{procedure} Finalize_API; - --@i{ Initialization & Finalization routines. More in the next section.} -@b{private} - @b{pragma} Export (C, Initialize_API); - @b{pragma} Export (C, Finalize_API); - @b{pragma} Export (C, Count); - @b{pragma} Export (C, Factorial); -@b{end} API; -@end cartouche -@end group -@end smallexample +@example +$ gnatmake nothing +@end example +@end quotation -@smallexample @c ada -@group -@cartouche -@b{package} @b{body} API @b{is} - @b{function} Factorial (Val : C.int) @b{return} C.int @b{is} - Fact : C.int := 1; - @b{begin} - Count := Count + 1; - @b{for} K @b{in} 1 .. Val @b{loop} - Fact := Fact * K; - @b{end} @b{loop}; - @b{return} Fact; - @b{end} Factorial; - - @b{procedure} Initialize_API @b{is} - @b{procedure} Adainit; - @b{pragma} Import (C, Adainit); - @b{begin} - Adainit; - @b{end} Initialize_API; +However, the interesting aspect of this example is not its run-time behavior +but rather the generated assembly code. +To see this output, invoke the compiler as follows: - @b{procedure} Finalize_API @b{is} - @b{procedure} Adafinal; - @b{pragma} Import (C, Adafinal); - @b{begin} - Adafinal; - @b{end} Finalize_API; -@b{end} API; -@end cartouche -@end group -@end smallexample +@quotation -@noindent -If the Ada DLL you are building will only be used by Ada applications -you do not have to export Ada entities with a @code{C} or @code{Stdcall} -convention. As an example, the previous package could be written as -follows: +@example +$ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb +@end example +@end quotation -@smallexample @c ada -@group -@cartouche -@b{package} API @b{is} - Count : Integer := 0; - @b{function} Factorial (Val : Integer) @b{return} Integer; +where the options are: - @b{procedure} Initialize_API; - @b{procedure} Finalize_API; - --@i{ Initialization and Finalization routines.} -@b{end} API; -@end cartouche -@end group -@end smallexample -@smallexample @c ada -@group -@cartouche -@b{package} @b{body} API @b{is} - @b{function} Factorial (Val : Integer) @b{return} Integer @b{is} - Fact : Integer := 1; - @b{begin} - Count := Count + 1; - @b{for} K @b{in} 1 .. Val @b{loop} - Fact := Fact * K; - @b{end} @b{loop}; - @b{return} Fact; - @b{end} Factorial; +@itemize * - @dots{} - --@i{ The remainder of this package body is unchanged.} -@b{end} API; -@end cartouche -@end group -@end smallexample +@item -@noindent -Note that if you do not export the Ada entities with a @code{C} or -@code{Stdcall} convention you will have to provide the mangled Ada names -in the definition file of the Ada DLL -(@pxref{Creating the Definition File}). +@table @asis -@node Ada DLLs and Elaboration -@subsection Ada DLLs and Elaboration -@cindex DLLs and elaboration +@item @code{-c} -@noindent -The DLL that you are building contains your Ada code as well as all the -routines in the Ada library that are needed by it. The first thing a -user of your DLL must do is elaborate the Ada code -(@pxref{Elaboration Order Handling in GNAT}). +compile only (no bind or link) +@end table -To achieve this you must export an initialization routine -(@code{Initialize_API} in the previous example), which must be invoked -before using any of the DLL services. This elaboration routine must call -the Ada elaboration routine @code{adainit} generated by the GNAT binder -(@pxref{Binding with Non-Ada Main Programs}). See the body of -@code{Initialize_Api} for an example. Note that the GNAT binder is -automatically invoked during the DLL build process by the @code{gnatdll} -tool (@pxref{Using gnatdll}). +@item -When a DLL is loaded, Windows systematically invokes a routine called -@code{DllMain}. It would therefore be possible to call @code{adainit} -directly from @code{DllMain} without having to provide an explicit -initialization routine. Unfortunately, it is not possible to call -@code{adainit} from the @code{DllMain} if your program has library level -tasks because access to the @code{DllMain} entry point is serialized by -the system (that is, only a single thread can execute ``through'' it at a -time), which means that the GNAT run time will deadlock waiting for the -newly created task to complete its initialization. +@table @asis -@node Ada DLLs and Finalization -@subsection Ada DLLs and Finalization -@cindex DLLs and finalization +@item @code{-S} -@noindent -When the services of an Ada DLL are no longer needed, the client code should -invoke the DLL finalization routine, if available. The DLL finalization -routine is in charge of releasing all resources acquired by the DLL. In the -case of the Ada code contained in the DLL, this is achieved by calling -routine @code{adafinal} generated by the GNAT binder -(@pxref{Binding with Non-Ada Main Programs}). -See the body of @code{Finalize_Api} for an -example. As already pointed out the GNAT binder is automatically invoked -during the DLL build process by the @code{gnatdll} tool -(@pxref{Using gnatdll}). +generate assembler listing +@end table -@node Creating a Spec for Ada DLLs -@subsection Creating a Spec for Ada DLLs +@item -@noindent -To use the services exported by the Ada DLL from another programming -language (e.g.@: C), you have to translate the specs of the exported Ada -entities in that language. For instance in the case of @code{API.dll}, -the corresponding C header file could look like: +@table @asis -@smallexample -@group -@cartouche -extern int *_imp__count; -#define count (*_imp__count) -int factorial (int); -@end cartouche -@end group -@end smallexample +@item @code{-fomit-frame-pointer} -@noindent -It is important to understand that when building an Ada DLL to be used by -other Ada applications, you need two different specs for the packages -contained in the DLL: one for building the DLL and the other for using -the DLL. This is because the @code{DLL} calling convention is needed to -use a variable defined in a DLL, but when building the DLL, the variable -must have either the @code{Ada} or @code{C} calling convention. As an -example consider a DLL comprising the following package @code{API}: +do not set up separate stack frames +@end table -@smallexample @c ada -@group -@cartouche -@b{package} API @b{is} - Count : Integer := 0; - @dots{} - --@i{ Remainder of the package omitted.} -@b{end} API; -@end cartouche -@end group -@end smallexample +@item -@noindent -After producing a DLL containing package @code{API}, the spec that -must be used to import @code{API.Count} from Ada code outside of the -DLL is: +@table @asis -@smallexample @c ada -@group -@cartouche -@b{package} API @b{is} - Count : Integer; - @b{pragma} Import (DLL, Count); -@b{end} API; -@end cartouche -@end group -@end smallexample +@item @code{-gnatp} -@node Creating the Definition File -@subsection Creating the Definition File +do not add runtime checks +@end table +@end itemize -@noindent -The definition file is the last file needed to build the DLL. It lists -the exported symbols. As an example, the definition file for a DLL -containing only package @code{API} (where all the entities are exported -with a @code{C} calling convention) is: +This gives a human-readable assembler version of the code. The resulting +file will have the same name as the Ada source file, but with a @cite{.s} +extension. In our example, the file @code{nothing.s} has the following +contents: -@smallexample -@group -@cartouche -EXPORTS - count - factorial - finalize_api - initialize_api -@end cartouche -@end group -@end smallexample +@quotation -@noindent -If the @code{C} calling convention is missing from package @code{API}, -then the definition file contains the mangled Ada names of the above -entities, which in this case are: +@example +.file "nothing.adb" +gcc2_compiled.: +___gnu_compiled_ada: +.text + .align 4 +.globl __ada_nothing +__ada_nothing: +#APP + nop +#NO_APP + jmp L1 + .align 2,0x90 +L1: + ret +@end example +@end quotation -@smallexample -@group -@cartouche -EXPORTS - api__count - api__factorial - api__finalize_api - api__initialize_api -@end cartouche -@end group -@end smallexample +The assembly code you included is clearly indicated by +the compiler, between the @cite{#APP} and @cite{#NO_APP} +delimiters. The character before the 'APP' and 'NOAPP' +can differ on different targets. For example, GNU/Linux uses '#APP' while +on NT you will see '/APP'. -@node Using gnatdll -@subsection Using @code{gnatdll} -@findex gnatdll +If you make a mistake in your assembler code (such as using the +wrong size modifier, or using a wrong operand for the instruction) GNAT +will report this error in a temporary file, which will be deleted when +the compilation is finished. Generating an assembler file will help +in such cases, since you can assemble this file separately using the +@emph{as} assembler that comes with gcc. -@menu -* gnatdll Example:: -* gnatdll behind the Scenes:: -* Using dlltool:: -@end menu +Assembling the file using the command -@noindent -@code{gnatdll} is a tool to automate the DLL build process once all the Ada -and non-Ada sources that make up your DLL have been compiled. -@code{gnatdll} is actually in charge of two distinct tasks: build the -static import library for the DLL and the actual DLL. The form of the -@code{gnatdll} command is +@quotation -@smallexample -@cartouche -@c $ gnatdll @ovar{switches} @var{list-of-files} @r{[}-largs @var{opts}@r{]} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ gnatdll @r{[}@var{switches}@r{]} @var{list-of-files} @r{[}-largs @var{opts}@r{]} -@end cartouche -@end smallexample +@example +$ as nothing.s +@end example +@end quotation -@noindent -where @var{list-of-files} is a list of ALI and object files. The object -file list must be the exact list of objects corresponding to the non-Ada -sources whose services are to be included in the DLL. The ALI file list -must be the exact list of ALI files for the corresponding Ada sources -whose services are to be included in the DLL. If @var{list-of-files} is -missing, only the static import library is generated. +will give you error messages whose lines correspond to the assembler +input file, so you can easily find and correct any mistakes you made. +If there are no errors, @emph{as} will generate an object file +@code{nothing.out}. -@noindent -You may specify any of the following switches to @code{gnatdll}: - -@table @code -@c @item -a@ovar{address} -@c Expanding @ovar macro inline (explanation in macro def comments) -@item -a@r{[}@var{address}@r{]} -@cindex @option{-a} (@code{gnatdll}) -Build a non-relocatable DLL at @var{address}. If @var{address} is not -specified the default address @var{0x11000000} will be used. By default, -when this switch is missing, @code{gnatdll} builds relocatable DLL. We -advise the reader to build relocatable DLL. +@node Output Variables in Inline Assembler,Input Variables in Inline Assembler,A Simple Example of Inline Assembler,Inline Assembler +@anchor{gnat_ugn/inline_assembler id4}@anchor{2d2}@anchor{gnat_ugn/inline_assembler output-variables-in-inline-assembler}@anchor{2d3} +@section Output Variables in Inline Assembler -@item -b @var{address} -@cindex @option{-b} (@code{gnatdll}) -Set the relocatable DLL base address. By default the address is -@code{0x11000000}. - -@item -bargs @var{opts} -@cindex @option{-bargs} (@code{gnatdll}) -Binder options. Pass @var{opts} to the binder. - -@item -d @var{dllfile} -@cindex @option{-d} (@code{gnatdll}) -@var{dllfile} is the name of the DLL. This switch must be present for -@code{gnatdll} to do anything. The name of the generated import library is -obtained algorithmically from @var{dllfile} as shown in the following -example: if @var{dllfile} is @code{xyz.dll}, the import library name is -@code{libxyz.dll.a}. The name of the definition file to use (if not specified -by option @option{-e}) is obtained algorithmically from @var{dllfile} -as shown in the following example: -if @var{dllfile} is @code{xyz.dll}, the definition -file used is @code{xyz.def}. -@item -e @var{deffile} -@cindex @option{-e} (@code{gnatdll}) -@var{deffile} is the name of the definition file. +The examples in this section, showing how to access the processor flags, +illustrate how to specify the destination operands for assembly language +statements. -@item -g -@cindex @option{-g} (@code{gnatdll}) -Generate debugging information. This information is stored in the object -file and copied from there to the final DLL file by the linker, -where it can be read by the debugger. You must use the -@option{-g} switch if you plan on using the debugger or the symbolic -stack traceback. +@quotation -@item -h -@cindex @option{-h} (@code{gnatdll}) -Help mode. Displays @code{gnatdll} switch usage information. +@example +with Interfaces; use Interfaces; +with Ada.Text_IO; use Ada.Text_IO; +with System.Machine_Code; use System.Machine_Code; +procedure Get_Flags is + Flags : Unsigned_32; + use ASCII; +begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax" & LF & HT & -- load eax with flags + "movl %%eax, %0", -- store flags in variable + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + Put_Line ("Flags register:" & Flags'Img); +end Get_Flags; +@end example +@end quotation -@item -Idir -@cindex @option{-I} (@code{gnatdll}) -Direct @code{gnatdll} to search the @var{dir} directory for source and -object files needed to build the DLL. -(@pxref{Search Paths and the Run-Time Library (RTL)}). +In order to have a nicely aligned assembly listing, we have separated +multiple assembler statements in the Asm template string with linefeed +(ASCII.LF) and horizontal tab (ASCII.HT) characters. +The resulting section of the assembly output file is: -@item -k -@cindex @option{-k} (@code{gnatdll}) -Removes the @code{@@}@var{nn} suffix from the import library's exported -names, but keeps them for the link names. You must specify this -option if you want to use a @code{Stdcall} function in a DLL for which -the @code{@@}@var{nn} suffix has been removed. This is the case for most -of the Windows NT DLL for example. This option has no effect when -@option{-n} option is specified. +@quotation -@item -l @var{file} -@cindex @option{-l} (@code{gnatdll}) -The list of ALI and object files used to build the DLL are listed in -@var{file}, instead of being given in the command line. Each line in -@var{file} contains the name of an ALI or object file. +@example +#APP + pushfl + popl %eax + movl %eax, -40(%ebp) +#NO_APP +@end example +@end quotation -@item -n -@cindex @option{-n} (@code{gnatdll}) -No Import. Do not create the import library. +It would have been legal to write the Asm invocation as: -@item -q -@cindex @option{-q} (@code{gnatdll}) -Quiet mode. Do not display unnecessary messages. +@quotation -@item -v -@cindex @option{-v} (@code{gnatdll}) -Verbose mode. Display extra information. +@example +Asm ("pushfl popl %%eax movl %%eax, %0") +@end example +@end quotation -@item -largs @var{opts} -@cindex @option{-largs} (@code{gnatdll}) -Linker options. Pass @var{opts} to the linker. -@end table +but in the generated assembler file, this would come out as: -@node gnatdll Example -@subsubsection @code{gnatdll} Example +@quotation -@noindent -As an example the command to build a relocatable DLL from @file{api.adb} -once @file{api.adb} has been compiled and @file{api.def} created is +@example +#APP + pushfl popl %eax movl %eax, -40(%ebp) +#NO_APP +@end example +@end quotation -@smallexample -$ gnatdll -d api.dll api.ali -@end smallexample +which is not so convenient for the human reader. -@noindent -The above command creates two files: @file{libapi.dll.a} (the import -library) and @file{api.dll} (the actual DLL). If you want to create -only the DLL, just type: +We use Ada comments +at the end of each line to explain what the assembler instructions +actually do. This is a useful convention. -@smallexample -$ gnatdll -d api.dll -n api.ali -@end smallexample +When writing Inline Assembler instructions, you need to precede each register +and variable name with a percent sign. Since the assembler already requires +a percent sign at the beginning of a register name, you need two consecutive +percent signs for such names in the Asm template string, thus @cite{%%eax}. +In the generated assembly code, one of the percent signs will be stripped off. -@noindent -Alternatively if you want to create just the import library, type: +Names such as @cite{%0}, @cite{%1}, @cite{%2}, etc., denote input or output +variables: operands you later define using @cite{Input} or @cite{Output} +parameters to @cite{Asm}. +An output variable is illustrated in +the third statement in the Asm template string: -@smallexample -$ gnatdll -d api.dll -@end smallexample +@quotation -@node gnatdll behind the Scenes -@subsubsection @code{gnatdll} behind the Scenes +@example +movl %%eax, %0 +@end example +@end quotation -@noindent -This section details the steps involved in creating a DLL. @code{gnatdll} -does these steps for you. Unless you are interested in understanding what -goes on behind the scenes, you should skip this section. +The intent is to store the contents of the eax register in a variable that can +be accessed in Ada. Simply writing @cite{movl %%eax@comma{} Flags} would not +necessarily work, since the compiler might optimize by using a register +to hold Flags, and the expansion of the @cite{movl} instruction would not be +aware of this optimization. The solution is not to store the result directly +but rather to advise the compiler to choose the correct operand form; +that is the purpose of the @cite{%0} output variable. -We use the previous example of a DLL containing the Ada package @code{API}, -to illustrate the steps necessary to build a DLL. The starting point is a -set of objects that will make up the DLL and the corresponding ALI -files. In the case of this example this means that @file{api.o} and -@file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does -the following: +Information about the output variable is supplied in the @cite{Outputs} +parameter to @cite{Asm}: -@enumerate -@item -@code{gnatdll} builds the base file (@file{api.base}). A base file gives -the information necessary to generate relocation information for the -DLL. +@quotation -@smallexample -@group -$ gnatbind -n api -$ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base -@end group -@end smallexample - -@noindent -In addition to the base file, the @command{gnatlink} command generates an -output file @file{api.jnk} which can be discarded. The @option{-mdll} switch -asks @command{gnatlink} to generate the routines @code{DllMain} and -@code{DllMainCRTStartup} that are called by the Windows loader when the DLL -is loaded into memory. +@example +Outputs => Unsigned_32'Asm_Output ("=g", Flags)); +@end example +@end quotation -@item -@code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the -export table (@file{api.exp}). The export table contains the relocation -information in a form which can be used during the final link to ensure -that the Windows loader is able to place the DLL anywhere in memory. +The output is defined by the @cite{Asm_Output} attribute of the target type; +the general format is -@smallexample -@group -$ dlltool --dllname api.dll --def api.def --base-file api.base \ - --output-exp api.exp -@end group -@end smallexample +@quotation -@item -@code{gnatdll} builds the base file using the new export table. Note that -@command{gnatbind} must be called once again since the binder generated file -has been deleted during the previous call to @command{gnatlink}. +@example +Type'Asm_Output (constraint_string, variable_name) +@end example +@end quotation -@smallexample -@group -$ gnatbind -n api -$ gnatlink api -o api.jnk api.exp -mdll - -Wl,--base-file,api.base -@end group -@end smallexample +The constraint string directs the compiler how +to store/access the associated variable. In the example -@item -@code{gnatdll} builds the new export table using the new base file and -generates the DLL import library @file{libAPI.dll.a}. +@quotation -@smallexample -@group -$ dlltool --dllname api.dll --def api.def --base-file api.base \ - --output-exp api.exp --output-lib libAPI.a -@end group -@end smallexample +@example +Unsigned_32'Asm_Output ("=m", Flags); +@end example +@end quotation -@item -Finally @code{gnatdll} builds the relocatable DLL using the final export -table. +the @cite{"m"} (memory) constraint tells the compiler that the variable +@cite{Flags} should be stored in a memory variable, thus preventing +the optimizer from keeping it in a register. In contrast, -@smallexample -@group -$ gnatbind -n api -$ gnatlink api api.exp -o api.dll -mdll -@end group -@end smallexample -@end enumerate +@quotation -@node Using dlltool -@subsubsection Using @code{dlltool} +@example +Unsigned_32'Asm_Output ("=r", Flags); +@end example +@end quotation -@noindent -@code{dlltool} is the low-level tool used by @code{gnatdll} to build -DLLs and static import libraries. This section summarizes the most -common @code{dlltool} switches. The form of the @code{dlltool} command -is +uses the @cite{"r"} (register) constraint, telling the compiler to +store the variable in a register. -@smallexample -@c $ dlltool @ovar{switches} -@c Expanding @ovar macro inline (explanation in macro def comments) -$ dlltool @r{[}@var{switches}@r{]} -@end smallexample +If the constraint is preceded by the equal character '=', it tells +the compiler that the variable will be used to store data into it. -@noindent -@code{dlltool} switches include: +In the @cite{Get_Flags} example, we used the @cite{"g"} (global) constraint, +allowing the optimizer to choose whatever it deems best. -@table @option -@item --base-file @var{basefile} -@cindex @option{--base-file} (@command{dlltool}) -Read the base file @var{basefile} generated by the linker. This switch -is used to create a relocatable DLL. +There are a fairly large number of constraints, but the ones that are +most useful (for the Intel x86 processor) are the following: -@item --def @var{deffile} -@cindex @option{--def} (@command{dlltool}) -Read the definition file. +@quotation -@item --dllname @var{name} -@cindex @option{--dllname} (@command{dlltool}) -Gives the name of the DLL. This switch is used to embed the name of the -DLL in the static import library generated by @code{dlltool} with switch -@option{--output-lib}. - -@item -k -@cindex @option{-k} (@command{dlltool}) -Kill @code{@@}@var{nn} from exported names -(@pxref{Windows Calling Conventions} -for a discussion about @code{Stdcall}-style symbols. - -@item --help -@cindex @option{--help} (@command{dlltool}) -Prints the @code{dlltool} switches with a concise description. - -@item --output-exp @var{exportfile} -@cindex @option{--output-exp} (@command{dlltool}) -Generate an export file @var{exportfile}. The export file contains the -export table (list of symbols in the DLL) and is used to create the DLL. -@item --output-lib @var{libfile} -@cindex @option{--output-lib} (@command{dlltool}) -Generate a static import library @var{libfile}. +@multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} +@item -@item -v -@cindex @option{-v} (@command{dlltool}) -Verbose mode. +@emph{=} -@item --as @var{assembler-name} -@cindex @option{--as} (@command{dlltool}) -Use @var{assembler-name} as the assembler. The default is @code{as}. -@end table +@tab -@node GNAT and Windows Resources -@section GNAT and Windows Resources -@cindex Resources, windows +output constraint -@menu -* Building Resources:: -* Compiling Resources:: -* Using Resources:: -@end menu +@item -@noindent -Resources are an easy way to add Windows specific objects to your -application. The objects that can be added as resources include: +@emph{g} -@itemize @bullet -@item menus +@tab -@item accelerators +global (i.e., can be stored anywhere) -@item dialog boxes +@item -@item string tables +@emph{m} -@item bitmaps +@tab -@item cursors +in memory -@item icons +@item -@item fonts +@emph{I} -@item version information -@end itemize +@tab -For example, a version information resource can be defined as follow and -embedded into an executable or DLL: +a constant -A version information resource can be used to embed information into an -executable or a DLL. These information can be viewed using the file properties -from the Windows Explorer. Here is an example of a version information -resource: +@item -@smallexample -@group -1 VERSIONINFO -FILEVERSION 1,0,0,0 -PRODUCTVERSION 1,0,0,0 -BEGIN - BLOCK "StringFileInfo" - BEGIN - BLOCK "080904E4" - BEGIN - VALUE "CompanyName", "My Company Name" - VALUE "FileDescription", "My application" - VALUE "FileVersion", "1.0" - VALUE "InternalName", "my_app" - VALUE "LegalCopyright", "My Name" - VALUE "OriginalFilename", "my_app.exe" - VALUE "ProductName", "My App" - VALUE "ProductVersion", "1.0" - END - END +@emph{a} - BLOCK "VarFileInfo" - BEGIN - VALUE "Translation", 0x809, 1252 - END -END -@end group -@end smallexample +@tab -The value @code{0809} (langID) is for the U.K English language and -@code{04E4} (charsetID), which is equal to @code{1252} decimal, for -multilingual. +use eax -@noindent -This section explains how to build, compile and use resources. Note that this -section does not cover all resource objects, for a complete description see -the corresponding Microsoft documentation. +@item -@node Building Resources -@subsection Building Resources -@cindex Resources, building +@emph{b} -@noindent -A resource file is an ASCII file. By convention resource files have an -@file{.rc} extension. -The easiest way to build a resource file is to use Microsoft tools -such as @code{imagedit.exe} to build bitmaps, icons and cursors and -@code{dlgedit.exe} to build dialogs. -It is always possible to build an @file{.rc} file yourself by writing a -resource script. +@tab -It is not our objective to explain how to write a resource file. A -complete description of the resource script language can be found in the -Microsoft documentation. +use ebx -@node Compiling Resources -@subsection Compiling Resources -@findex rc -@findex windres -@cindex Resources, compiling +@item -@noindent -This section describes how to build a GNAT-compatible (COFF) object file -containing the resources. This is done using the Resource Compiler -@code{windres} as follows: +@emph{c} -@smallexample -$ windres -i myres.rc -o myres.o -@end smallexample +@tab -@noindent -By default @code{windres} will run @command{gcc} to preprocess the @file{.rc} -file. You can specify an alternate preprocessor (usually named -@file{cpp.exe}) using the @code{windres} @option{--preprocessor} -parameter. A list of all possible options may be obtained by entering -the command @code{windres} @option{--help}. +use ecx -It is also possible to use the Microsoft resource compiler @code{rc.exe} -to produce a @file{.res} file (binary resource file). See the -corresponding Microsoft documentation for further details. In this case -you need to use @code{windres} to translate the @file{.res} file to a -GNAT-compatible object file as follows: +@item -@smallexample -$ windres -i myres.res -o myres.o -@end smallexample +@emph{d} -@node Using Resources -@subsection Using Resources -@cindex Resources, using +@tab -@noindent -To include the resource file in your program just add the -GNAT-compatible object file for the resource(s) to the linker -arguments. With @command{gnatmake} this is done by using the @option{-largs} -option: +use edx -@smallexample -$ gnatmake myprog -largs myres.o -@end smallexample +@item -@node Debugging a DLL -@section Debugging a DLL -@cindex DLL debugging +@emph{S} -@menu -* Program and DLL Both Built with GCC/GNAT:: -* Program Built with Foreign Tools and DLL Built with GCC/GNAT:: -@end menu +@tab -@noindent -Debugging a DLL is similar to debugging a standard program. But -we have to deal with two different executable parts: the DLL and the -program that uses it. We have the following four possibilities: +use esi -@enumerate 1 -@item -The program and the DLL are built with @code{GCC/GNAT}. -@item -The program is built with foreign tools and the DLL is built with -@code{GCC/GNAT}. @item -The program is built with @code{GCC/GNAT} and the DLL is built with -foreign tools. -@end enumerate -@noindent -In this section we address only cases one and two above. -There is no point in trying to debug -a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging -information in it. To do so you must use a debugger compatible with the -tools suite used to build the DLL. +@emph{D} -@node Program and DLL Both Built with GCC/GNAT -@subsection Program and DLL Both Built with GCC/GNAT +@tab -@noindent -This is the simplest case. Both the DLL and the program have @code{GDB} -compatible debugging information. It is then possible to break anywhere in -the process. Let's suppose here that the main procedure is named -@code{ada_main} and that in the DLL there is an entry point named -@code{ada_dll}. +use edi -@noindent -The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and -program must have been built with the debugging information (see GNAT -g -switch). Here are the step-by-step instructions for debugging it: +@item -@enumerate 1 -@item Launch @code{GDB} on the main program. +@emph{r} -@smallexample -$ gdb -nw ada_main -@end smallexample +@tab -@item Start the program and stop at the beginning of the main procedure +use one of eax, ebx, ecx or edx -@smallexample -(gdb) start -@end smallexample +@item -@noindent -This step is required to be able to set a breakpoint inside the DLL. As long -as the program is not run, the DLL is not loaded. This has the -consequence that the DLL debugging information is also not loaded, so it is not -possible to set a breakpoint in the DLL. +@emph{q} -@item Set a breakpoint inside the DLL +@tab -@smallexample -(gdb) break ada_dll -(gdb) cont -@end smallexample +use one of eax, ebx, ecx, edx, esi or edi -@end enumerate +@end multitable -@noindent -At this stage a breakpoint is set inside the DLL. From there on -you can use the standard approach to debug the whole program -(@pxref{Running and Debugging Ada Programs}). +@end quotation + +The full set of constraints is described in the gcc and @emph{as} +documentation; note that it is possible to combine certain constraints +in one constraint string. -@ignore -@c This used to work, probably because the DLLs were non-relocatable -@c keep this section around until the problem is sorted out. +You specify the association of an output variable with an assembler operand +through the @code{%@emph{n}} notation, where @emph{n} is a non-negative +integer. Thus in + +@quotation -To break on the @code{DllMain} routine it is not possible to follow -the procedure above. At the time the program stop on @code{ada_main} -the @code{DllMain} routine as already been called. Either you can use -the procedure below @pxref{Debugging the DLL Directly} or this procedure: +@example +Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax" & LF & HT & -- load eax with flags + "movl %%eax, %0", -- store flags in variable + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); +@end example +@end quotation -@enumerate 1 -@item Launch @code{GDB} on the main program. +@cite{%0} will be replaced in the expanded code by the appropriate operand, +whatever +the compiler decided for the @cite{Flags} variable. -@smallexample -$ gdb ada_main -@end smallexample +In general, you may have any number of output variables: -@item Load DLL symbols -@smallexample -(gdb) add-sym api.dll -@end smallexample +@itemize * -@item Set a breakpoint inside the DLL +@item +Count the operands starting at 0; thus @cite{%0}, @cite{%1}, etc. -@smallexample -(gdb) break ada_dll.adb:45 -@end smallexample +@item +Specify the @cite{Outputs} parameter as a parenthesized comma-separated list +of @cite{Asm_Output} attributes +@end itemize -Note that at this point it is not possible to break using the routine symbol -directly as the program is not yet running. The solution is to break -on the proper line (break in @file{ada_dll.adb} line 45). +For example: -@item Start the program +@quotation -@smallexample -(gdb) run -@end smallexample +@example +Asm ("movl %%eax, %0" & LF & HT & + "movl %%ebx, %1" & LF & HT & + "movl %%ecx, %2", + Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A + Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B + Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C +@end example +@end quotation -@end enumerate -@end ignore +where @cite{Var_A}, @cite{Var_B}, and @cite{Var_C} are variables +in the Ada program. -@node Program Built with Foreign Tools and DLL Built with GCC/GNAT -@subsection Program Built with Foreign Tools and DLL Built with GCC/GNAT +As a variation on the @cite{Get_Flags} example, we can use the constraints +string to direct the compiler to store the eax register into the @cite{Flags} +variable, instead of including the store instruction explicitly in the +@cite{Asm} template string: -@menu -* Debugging the DLL Directly:: -* Attaching to a Running Process:: -@end menu +@quotation -@noindent -In this case things are slightly more complex because it is not possible to -start the main program and then break at the beginning to load the DLL and the -associated DLL debugging information. It is not possible to break at the -beginning of the program because there is no @code{GDB} debugging information, -and therefore there is no direct way of getting initial control. This -section addresses this issue by describing some methods that can be used -to break somewhere in the DLL to debug it. +@example +with Interfaces; use Interfaces; +with Ada.Text_IO; use Ada.Text_IO; +with System.Machine_Code; use System.Machine_Code; +procedure Get_Flags_2 is + Flags : Unsigned_32; + use ASCII; +begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "popl %%eax", -- save flags in eax + Outputs => Unsigned_32'Asm_Output ("=a", Flags)); + Put_Line ("Flags register:" & Flags'Img); +end Get_Flags_2; +@end example +@end quotation -@noindent -First suppose that the main procedure is named @code{main} (this is for -example some C code built with Microsoft Visual C) and that there is a -DLL named @code{test.dll} containing an Ada entry point named -@code{ada_dll}. +The @cite{"a"} constraint tells the compiler that the @cite{Flags} +variable will come from the eax register. Here is the resulting code: -@noindent -The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have -been built with debugging information (see GNAT -g option). +@quotation -@node Debugging the DLL Directly -@subsubsection Debugging the DLL Directly +@example +#APP + pushfl + popl %eax +#NO_APP + movl %eax,-40(%ebp) +@end example +@end quotation -@enumerate 1 -@item -Find out the executable starting address +The compiler generated the store of eax into Flags after +expanding the assembler code. -@smallexample -$ objdump --file-header main.exe -@end smallexample +Actually, there was no need to pop the flags into the eax register; +more simply, we could just pop the flags directly into the program variable: -The starting address is reported on the last line. For example: +@quotation -@smallexample -main.exe: file format pei-i386 -architecture: i386, flags 0x0000010a: -EXEC_P, HAS_DEBUG, D_PAGED -start address 0x00401010 -@end smallexample +@example +with Interfaces; use Interfaces; +with Ada.Text_IO; use Ada.Text_IO; +with System.Machine_Code; use System.Machine_Code; +procedure Get_Flags_3 is + Flags : Unsigned_32; + use ASCII; +begin + Asm ("pushfl" & LF & HT & -- push flags on stack + "pop %0", -- save flags in Flags + Outputs => Unsigned_32'Asm_Output ("=g", Flags)); + Put_Line ("Flags register:" & Flags'Img); +end Get_Flags_3; +@end example +@end quotation -@item -Launch the debugger on the executable. +@node Input Variables in Inline Assembler,Inlining Inline Assembler Code,Output Variables in Inline Assembler,Inline Assembler +@anchor{gnat_ugn/inline_assembler id5}@anchor{2d4}@anchor{gnat_ugn/inline_assembler input-variables-in-inline-assembler}@anchor{2d5} +@section Input Variables in Inline Assembler -@smallexample -$ gdb main.exe -@end smallexample -@item -Set a breakpoint at the starting address, and launch the program. +The example in this section illustrates how to specify the source operands +for assembly language statements. +The program simply increments its input value by 1: -@smallexample -$ (gdb) break *0x00401010 -$ (gdb) run -@end smallexample +@quotation -The program will stop at the given address. +@example +with Interfaces; use Interfaces; +with Ada.Text_IO; use Ada.Text_IO; +with System.Machine_Code; use System.Machine_Code; +procedure Increment is -@item -Set a breakpoint on a DLL subroutine. + function Incr (Value : Unsigned_32) return Unsigned_32 is + Result : Unsigned_32; + begin + Asm ("incl %0", + Outputs => Unsigned_32'Asm_Output ("=a", Result), + Inputs => Unsigned_32'Asm_Input ("a", Value)); + return Result; + end Incr; -@smallexample -(gdb) break ada_dll.adb:45 -@end smallexample + Value : Unsigned_32; -Or if you want to break using a symbol on the DLL, you need first to -select the Ada language (language used by the DLL). +begin + Value := 5; + Put_Line ("Value before is" & Value'Img); + Value := Incr (Value); + Put_Line ("Value after is" & Value'Img); +end Increment; +@end example +@end quotation -@smallexample -(gdb) set language ada -(gdb) break ada_dll -@end smallexample +The @cite{Outputs} parameter to @cite{Asm} specifies +that the result will be in the eax register and that it is to be stored +in the @cite{Result} variable. -@item -Continue the program. +The @cite{Inputs} parameter looks much like the @cite{Outputs} parameter, +but with an @cite{Asm_Input} attribute. +The @cite{"="} constraint, indicating an output value, is not present. -@smallexample -(gdb) cont -@end smallexample +You can have multiple input variables, in the same way that you can have more +than one output variable. -@noindent -This will run the program until it reaches the breakpoint that has been -set. From that point you can use the standard way to debug a program -as described in (@pxref{Running and Debugging Ada Programs}). +The parameter count (%0, %1) etc, still starts at the first output statement, +and continues with the input statements. -@end enumerate +Just as the @cite{Outputs} parameter causes the register to be stored into the +target variable after execution of the assembler statements, so does the +@cite{Inputs} parameter cause its variable to be loaded into the register +before execution of the assembler statements. -@noindent -It is also possible to debug the DLL by attaching to a running process. +Thus the effect of the @cite{Asm} invocation is: -@node Attaching to a Running Process -@subsubsection Attaching to a Running Process -@cindex DLL debugging, attach to process -@noindent -With @code{GDB} it is always possible to debug a running process by -attaching to it. It is possible to debug a DLL this way. The limitation -of this approach is that the DLL must run long enough to perform the -attach operation. It may be useful for instance to insert a time wasting -loop in the code of the DLL to meet this criterion. +@itemize * -@enumerate 1 +@item +load the 32-bit value of @cite{Value} into eax -@item Launch the main program @file{main.exe}. +@item +execute the @cite{incl %eax} instruction -@smallexample -$ main -@end smallexample +@item +store the contents of eax into the @cite{Result} variable +@end itemize -@item Use the Windows @i{Task Manager} to find the process ID. Let's say -that the process PID for @file{main.exe} is 208. +The resulting assembler file (with @emph{-O2} optimization) contains: -@item Launch gdb. +@quotation -@smallexample -$ gdb -@end smallexample +@example +_increment__incr.1: + subl $4,%esp + movl 8(%esp),%eax +#APP + incl %eax +#NO_APP + movl %eax,%edx + movl %ecx,(%esp) + addl $4,%esp + ret +@end example +@end quotation -@item Attach to the running process to be debugged. +@node Inlining Inline Assembler Code,Other Asm Functionality,Input Variables in Inline Assembler,Inline Assembler +@anchor{gnat_ugn/inline_assembler id6}@anchor{2d6}@anchor{gnat_ugn/inline_assembler inlining-inline-assembler-code}@anchor{2d7} +@section Inlining Inline Assembler Code -@smallexample -(gdb) attach 208 -@end smallexample -@item Load the process debugging information. +For a short subprogram such as the @cite{Incr} function in the previous +section, the overhead of the call and return (creating / deleting the stack +frame) can be significant, compared to the amount of code in the subprogram +body. A solution is to apply Ada's @cite{Inline} pragma to the subprogram, +which directs the compiler to expand invocations of the subprogram at the +point(s) of call, instead of setting up a stack frame for out-of-line calls. +Here is the resulting program: -@smallexample -(gdb) symbol-file main.exe -@end smallexample +@quotation -@item Break somewhere in the DLL. +@example +with Interfaces; use Interfaces; +with Ada.Text_IO; use Ada.Text_IO; +with System.Machine_Code; use System.Machine_Code; +procedure Increment_2 is -@smallexample -(gdb) break ada_dll -@end smallexample + function Incr (Value : Unsigned_32) return Unsigned_32 is + Result : Unsigned_32; + begin + Asm ("incl %0", + Outputs => Unsigned_32'Asm_Output ("=a", Result), + Inputs => Unsigned_32'Asm_Input ("a", Value)); + return Result; + end Incr; + pragma Inline (Increment); -@item Continue process execution. + Value : Unsigned_32; -@smallexample -(gdb) cont -@end smallexample +begin + Value := 5; + Put_Line ("Value before is" & Value'Img); + Value := Increment (Value); + Put_Line ("Value after is" & Value'Img); +end Increment_2; +@end example +@end quotation -@end enumerate +Compile the program with both optimization (@emph{-O2}) and inlining +(@emph{-gnatn}) enabled. -@noindent -This last step will resume the process execution, and stop at -the breakpoint we have set. From there you can use the standard -approach to debug a program as described in -(@pxref{Running and Debugging Ada Programs}). +The @cite{Incr} function is still compiled as usual, but at the +point in @cite{Increment} where our function used to be called: -@node Setting Stack Size from gnatlink -@section Setting Stack Size from @command{gnatlink} +@quotation -@noindent -It is possible to specify the program stack size at link time. On modern -versions of Windows, starting with XP, this is mostly useful to set the size of -the main stack (environment task). The other task stacks are set with pragma -Storage_Size or with the @command{gnatbind -d} command. +@example +pushl %edi +call _increment__incr.1 +@end example +@end quotation -Since older versions of Windows (2000, NT4, etc.) do not allow setting the -reserve size of individual tasks, the link-time stack size applies to all -tasks, and pragma Storage_Size has no effect. -In particular, Stack Overflow checks are made against this -link-time specified size. +the code for the function body directly appears: -This setting can be done with -@command{gnatlink} using either: +@quotation -@itemize @bullet +@example +movl %esi,%eax +#APP + incl %eax +#NO_APP + movl %eax,%edx +@end example +@end quotation -@item using @option{-Xlinker} linker option +thus saving the overhead of stack frame setup and an out-of-line call. -@smallexample -$ gnatlink hello -Xlinker --stack=0x10000,0x1000 -@end smallexample +@node Other Asm Functionality,,Inlining Inline Assembler Code,Inline Assembler +@anchor{gnat_ugn/inline_assembler other-asm-functionality}@anchor{2d8}@anchor{gnat_ugn/inline_assembler id7}@anchor{2d9} +@section Other @cite{Asm} Functionality -This sets the stack reserve size to 0x10000 bytes and the stack commit -size to 0x1000 bytes. -@item using @option{-Wl} linker option +This section describes two important parameters to the @cite{Asm} +procedure: @cite{Clobber}, which identifies register usage; +and @cite{Volatile}, which inhibits unwanted optimizations. -@smallexample -$ gnatlink hello -Wl,--stack=0x1000000 -@end smallexample +@menu +* The Clobber Parameter:: +* The Volatile Parameter:: -This sets the stack reserve size to 0x1000000 bytes. Note that with -@option{-Wl} option it is not possible to set the stack commit size -because the coma is a separator for this option. +@end menu -@end itemize +@node The Clobber Parameter,The Volatile Parameter,,Other Asm Functionality +@anchor{gnat_ugn/inline_assembler the-clobber-parameter}@anchor{2da}@anchor{gnat_ugn/inline_assembler id8}@anchor{2db} +@subsection The @cite{Clobber} Parameter -@node Setting Heap Size from gnatlink -@section Setting Heap Size from @command{gnatlink} -@noindent -Under Windows systems, it is possible to specify the program heap size from -@command{gnatlink} using either: +One of the dangers of intermixing assembly language and a compiled language +such as Ada is that the compiler needs to be aware of which registers are +being used by the assembly code. In some cases, such as the earlier examples, +the constraint string is sufficient to indicate register usage (e.g., +@cite{"a"} for +the eax register). But more generally, the compiler needs an explicit +identification of the registers that are used by the Inline Assembly +statements. -@itemize @bullet +Using a register that the compiler doesn't know about +could be a side effect of an instruction (like @cite{mull} +storing its result in both eax and edx). +It can also arise from explicit register usage in your +assembly code; for example: -@item using @option{-Xlinker} linker option +@quotation -@smallexample -$ gnatlink hello -Xlinker --heap=0x10000,0x1000 -@end smallexample +@example +Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In)); +@end example +@end quotation -This sets the heap reserve size to 0x10000 bytes and the heap commit -size to 0x1000 bytes. +where the compiler (since it does not analyze the @cite{Asm} template string) +does not know you are using the ebx register. -@item using @option{-Wl} linker option +In such cases you need to supply the @cite{Clobber} parameter to @cite{Asm}, +to identify the registers that will be used by your assembly code: -@smallexample -$ gnatlink hello -Wl,--heap=0x1000000 -@end smallexample +@quotation -This sets the heap reserve size to 0x1000000 bytes. Note that with -@option{-Wl} option it is not possible to set the heap commit size -because the coma is a separator for this option. +@example +Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In), + Clobber => "ebx"); +@end example +@end quotation -@end itemize +The Clobber parameter is a static string expression specifying the +register(s) you are using. Note that register names are @emph{not} prefixed +by a percent sign. Also, if more than one register is used then their names +are separated by commas; e.g., @cite{"eax@comma{} ebx"} -@node Mac OS Topics -@appendix Mac OS Topics -@cindex OS X +The @cite{Clobber} parameter has several additional uses: -@noindent -This chapter describes topics that are specific to Apple's OS X -platform. -@menu -* Codesigning the Debugger:: -@end menu +@itemize * -@node Codesigning the Debugger -@section Codesigning the Debugger +@item +Use 'register' name @cite{cc} to indicate that flags might have changed -@noindent -The Darwin Kernel requires the debugger to have special permissions -before it is allowed to control other processes. These permissions -are granted by codesigning the GDB executable. Without these -permissions, the debugger will report error messages such as: +@item +Use 'register' name @cite{memory} if you changed a memory location +@end itemize -@smallexample -Starting program: /x/y/foo -Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5). - (please check gdb is codesigned - see taskgated(8)) -@end smallexample +@node The Volatile Parameter,,The Clobber Parameter,Other Asm Functionality +@anchor{gnat_ugn/inline_assembler the-volatile-parameter}@anchor{2dc}@anchor{gnat_ugn/inline_assembler id9}@anchor{2dd} +@subsection The @cite{Volatile} Parameter -Codesigning requires a certificate. The following procedure explains -how to create one: -@itemize @bullet -@item Start the Keychain Access application (in -/Applications/Utilities/Keychain Access.app) +@geindex Volatile parameter -@item Select the Keychain Access -> Certificate Assistant -> -Create a Certificate... menu +Compiler optimizations in the presence of Inline Assembler may sometimes have +unwanted effects. For example, when an @cite{Asm} invocation with an input +variable is inside a loop, the compiler might move the loading of the input +variable outside the loop, regarding it as a one-time initialization. -@item Then: +If this effect is not desired, you can disable such optimizations by setting +the @cite{Volatile} parameter to @cite{True}; for example: -@itemize @bullet -@item Choose a name for the new certificate (this procedure will use -"gdb-cert" as an example) +@quotation -@item Set "Identity Type" to "Self Signed Root" +@example +Asm ("movl %0, %%ebx" & LF & HT & + "movl %%ebx, %1", + Outputs => Unsigned_32'Asm_Output ("=g", Var_Out), + Inputs => Unsigned_32'Asm_Input ("g", Var_In), + Clobber => "ebx", + Volatile => True); +@end example +@end quotation -@item Set "Certificate Type" to "Code Signing" +By default, @cite{Volatile} is set to @cite{False} unless there is no +@cite{Outputs} parameter. -@item Activate the "Let me override defaults" option +Although setting @cite{Volatile} to @cite{True} prevents unwanted +optimizations, it will also disable other optimizations that might be +important for efficiency. In general, you should set @cite{Volatile} +to @cite{True} only if the compiler's optimizations have created +problems. -@end itemize +@node GNU Free Documentation License,Index,Inline Assembler,Top +@anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{2de}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{2df} +@chapter GNU Free Documentation License + + +Version 1.3, 3 November 2008 + +Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc +@indicateurl{http://fsf.org/} + +Everyone is permitted to copy and distribute verbatim copies of this +license document, but changing it is not allowed. + +@strong{Preamble} + +The purpose of this License is to make a manual, textbook, or other +functional and useful document "free" in the sense of freedom: to +assure everyone the effective freedom to copy and redistribute it, +with or without modifying it, either commercially or noncommercially. +Secondarily, this License preserves for the author and publisher a way +to get credit for their work, while not being considered responsible +for modifications made by others. + +This License is a kind of "copyleft", which means that derivative +works of the document must themselves be free in the same sense. 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If the Document already +includes a cover text for the same cover, previously added by you or +by arrangement made by the same entity you are acting on behalf of, +you may not add another; but you may replace the old one, on explicit +permission from the previous publisher that added the old one. + +The author(s) and publisher(s) of the Document do not by this License +give permission to use their names for publicity for or to assert or +imply endorsement of any Modified Version. + +@strong{5. COMBINING DOCUMENTS} + +You may combine the Document with other documents released under this +License, under the terms defined in section 4 above for modified +versions, provided that you include in the combination all of the +Invariant Sections of all of the original documents, unmodified, and +list them all as Invariant Sections of your combined work in its +license notice, and that you preserve all their Warranty Disclaimers. + +The combined work need only contain one copy of this License, and +multiple identical Invariant Sections may be replaced with a single +copy. If there are multiple Invariant Sections with the same name but +different contents, make the title of each such section unique by +adding at the end of it, in parentheses, the name of the original +author or publisher of that section if known, or else a unique number. +Make the same adjustment to the section titles in the list of +Invariant Sections in the license notice of the combined work. + +In the combination, you must combine any sections Entitled "History" +in the various original documents, forming one section Entitled +"History"; likewise combine any sections Entitled "Acknowledgements", +and any sections Entitled "Dedications". You must delete all sections +Entitled "Endorsements". + +@strong{6. COLLECTIONS OF DOCUMENTS} + +You may make a collection consisting of the Document and other documents +released under this License, and replace the individual copies of this +License in the various documents with a single copy that is included in +the collection, provided that you follow the rules of this License for +verbatim copying of each of the documents in all other respects. + +You may extract a single document from such a collection, and distribute +it individually under this License, provided you insert a copy of this +License into the extracted document, and follow this License in all +other respects regarding verbatim copying of that document. + +@strong{7. AGGREGATION WITH INDEPENDENT WORKS} + +A compilation of the Document or its derivatives with other separate +and independent documents or works, in or on a volume of a storage or +distribution medium, is called an "aggregate" if the copyright +resulting from the compilation is not used to limit the legal rights +of the compilation's users beyond what the individual works permit. +When the Document is included in an aggregate, this License does not +apply to the other works in the aggregate which are not themselves +derivative works of the Document. + +If the Cover Text requirement of section 3 is applicable to these +copies of the Document, then if the Document is less than one half of +the entire aggregate, the Document's Cover Texts may be placed on +covers that bracket the Document within the aggregate, or the +electronic equivalent of covers if the Document is in electronic form. +Otherwise they must appear on printed covers that bracket the whole +aggregate. + +@strong{8. TRANSLATION} + +Translation is considered a kind of modification, so you may +distribute translations of the Document under the terms of section 4. +Replacing Invariant Sections with translations requires special +permission from their copyright holders, but you may include +translations of some or all Invariant Sections in addition to the +original versions of these Invariant Sections. You may include a +translation of this License, and all the license notices in the +Document, and any Warranty Disclaimers, provided that you also include +the original English version of this License and the original versions +of those notices and disclaimers. In case of a disagreement between +the translation and the original version of this License or a notice +or disclaimer, the original version will prevail. + +If a section in the Document is Entitled "Acknowledgements", +"Dedications", or "History", the requirement (section 4) to Preserve +its Title (section 1) will typically require changing the actual +title. + +@strong{9. TERMINATION} + +You may not copy, modify, sublicense, or distribute the Document +except as expressly provided under this License. Any attempt +otherwise to copy, modify, sublicense, or distribute it is void, and +will automatically terminate your rights under this License. + +However, if you cease all violation of this License, then your license +from a particular copyright holder is reinstated (a) provisionally, +unless and until the copyright holder explicitly and finally +terminates your license, and (b) permanently, if the copyright holder +fails to notify you of the violation by some reasonable means prior to +60 days after the cessation. + +Moreover, your license from a particular copyright holder is +reinstated permanently if the copyright holder notifies you of the +violation by some reasonable means, this is the first time you have +received notice of violation of this License (for any work) from that +copyright holder, and you cure the violation prior to 30 days after +your receipt of the notice. + +Termination of your rights under this section does not terminate the +licenses of parties who have received copies or rights from you under +this License. If your rights have been terminated and not permanently +reinstated, receipt of a copy of some or all of the same material does +not give you any rights to use it. + +@strong{10. FUTURE REVISIONS OF THIS LICENSE} + +The Free Software Foundation may publish new, revised versions +of the GNU Free Documentation License from time to time. Such new +versions will be similar in spirit to the present version, but may +differ in detail to address new problems or concerns. See +@indicateurl{http://www.gnu.org/copyleft/}. + +Each version of the License is given a distinguishing version number. +If the Document specifies that a particular numbered version of this +License "or any later version" applies to it, you have the option of +following the terms and conditions either of that specified version or +of any later version that has been published (not as a draft) by the +Free Software Foundation. If the Document does not specify a version +number of this License, you may choose any version ever published (not +as a draft) by the Free Software Foundation. If the Document +specifies that a proxy can decide which future versions of this +License can be used, that proxy's public statement of acceptance of a +version permanently authorizes you to choose that version for the +Document. + +@strong{11. RELICENSING} + +"Massive Multiauthor Collaboration Site" (or "MMC Site") means any +World Wide Web server that publishes copyrightable works and also +provides prominent facilities for anybody to edit those works. A +public wiki that anybody can edit is an example of such a server. A +"Massive Multiauthor Collaboration" (or "MMC") contained in the +site means any set of copyrightable works thus published on the MMC +site. + +"CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 +license published by Creative Commons Corporation, a not-for-profit +corporation with a principal place of business in San Francisco, +California, as well as future copyleft versions of that license +published by that same organization. + +"Incorporate" means to publish or republish a Document, in whole or +in part, as part of another Document. + +An MMC is "eligible for relicensing" if it is licensed under this +License, and if all works that were first published under this License +somewhere other than this MMC, and subsequently incorporated in whole +or in part into the MMC, (1) had no cover texts or invariant sections, +and (2) were thus incorporated prior to November 1, 2008. + +The operator of an MMC Site may republish an MMC contained in the site +under CC-BY-SA on the same site at any time before August 1, 2009, +provided the MMC is eligible for relicensing. + +@strong{ADDENDUM: How to use this License for your documents} + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and +license notices just after the title page: -@item Finally, in the view, double-click on the new certificate, -and set "When using this certificate" to "Always Trust" +@quotation -@item Exit the Keychain Access application and restart the computer -(this is unfortunately required) +Copyright © YEAR YOUR NAME. +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 +or any later version published by the Free Software Foundation; +with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. +A copy of the license is included in the section entitled "GNU +Free Documentation License". +@end quotation -@end itemize +If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, +replace the "with ... Texts." line with this: -Once a certificate has been created, the debugger can be codesigned -as follow. In a Terminal, run the following command... +@quotation -@smallexample -codesign -f -s "gdb-cert" /bin/gdb -@end smallexample +with the Invariant Sections being LIST THEIR TITLES, with the +Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. +@end quotation -... where "gdb-cert" should be replaced by the actual certificate -name chosen above, and should be replaced by -the location where you installed GNAT. Also, be sure that users are -in the Unix group @samp{_developer}. +If you have Invariant Sections without Cover Texts, or some other +combination of the three, merge those two alternatives to suit the +situation. -@c ********************************** -@c * GNU Free Documentation License * -@c ********************************** -@include fdl.texi -@c GNU Free Documentation License +If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, +to permit their use in free software. -@node Index +@node Index,,GNU Free Documentation License,Top @unnumbered Index -@printindex cp -@contents -@c Put table of contents at end, otherwise it precedes the "title page" in -@c the .txt version -@c Edit the pdf file to move the contents to the beginning, after the title -@c page +@printindex ge + +@c %**end of body @bye -- 2.30.2