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8 @settitle GNAT User's Guide for Native Platforms
13 @dircategory GNU Ada Tools
15 * gnat_ugn: (gnat_ugn.info). gnat_ugn
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24 GNAT User's Guide for Native Platforms , Jun 21, 2019
28 Copyright @copyright{} 2008-2019, Free Software Foundation
34 @title GNAT User's Guide for Native Platforms
39 @c %** start of user preamble
41 @c %** end of user preamble
45 @top GNAT User's Guide for Native Platforms
50 @anchor{gnat_ugn doc}@anchor{0}
51 @emph{GNAT, The GNU Ada Development Environment}
54 @include gcc-common.texi
55 GCC version @value{version-GCC}@*
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.3 or
60 any later version published by the Free Software Foundation; with no
61 Invariant Sections, with the Front-Cover Texts being
62 "GNAT User's Guide for Native Platforms",
63 and with no Back-Cover Texts. A copy of the license is
64 included in the section entitled @ref{1,,GNU Free Documentation License}.
68 * Getting Started with GNAT::
69 * The GNAT Compilation Model::
70 * Building Executable Programs with GNAT::
71 * GNAT Utility Programs::
72 * GNAT and Program Execution::
73 * Platform-Specific Information::
74 * Example of Binder Output File::
75 * Elaboration Order Handling in GNAT::
77 * GNU Free Documentation License::
81 --- The Detailed Node Listing ---
85 * What This Guide Contains::
86 * What You Should Know before Reading This Guide::
87 * Related Information::
88 * A Note to Readers of Previous Versions of the Manual::
91 Getting Started with GNAT
94 * Running a Simple Ada Program::
95 * Running a Program with Multiple Units::
96 * Using the gnatmake Utility::
98 The GNAT Compilation Model
100 * Source Representation::
101 * Foreign Language Representation::
102 * File Naming Topics and Utilities::
103 * Configuration Pragmas::
104 * Generating Object Files::
105 * Source Dependencies::
106 * The Ada Library Information Files::
107 * Binding an Ada Program::
108 * GNAT and Libraries::
109 * Conditional Compilation::
110 * Mixed Language Programming::
111 * GNAT and Other Compilation Models::
112 * Using GNAT Files with External Tools::
114 Foreign Language Representation
117 * Other 8-Bit Codes::
118 * Wide_Character Encodings::
119 * Wide_Wide_Character Encodings::
121 File Naming Topics and Utilities
123 * File Naming Rules::
124 * Using Other File Names::
125 * Alternative File Naming Schemes::
126 * Handling Arbitrary File Naming Conventions with gnatname::
127 * File Name Krunching with gnatkr::
128 * Renaming Files with gnatchop::
130 Handling Arbitrary File Naming Conventions with gnatname
132 * Arbitrary File Naming Conventions::
134 * Switches for gnatname::
135 * Examples of gnatname Usage::
137 File Name Krunching with gnatkr
142 * Examples of gnatkr Usage::
144 Renaming Files with gnatchop
146 * Handling Files with Multiple Units::
147 * Operating gnatchop in Compilation Mode::
148 * Command Line for gnatchop::
149 * Switches for gnatchop::
150 * Examples of gnatchop Usage::
152 Configuration Pragmas
154 * Handling of Configuration Pragmas::
155 * The Configuration Pragmas Files::
159 * Introduction to Libraries in GNAT::
160 * General Ada Libraries::
161 * Stand-alone Ada Libraries::
162 * Rebuilding the GNAT Run-Time Library::
164 General Ada Libraries
166 * Building a library::
167 * Installing a library::
170 Stand-alone Ada Libraries
172 * Introduction to Stand-alone Libraries::
173 * Building a Stand-alone Library::
174 * Creating a Stand-alone Library to be used in a non-Ada context::
175 * Restrictions in Stand-alone Libraries::
177 Conditional Compilation
179 * Modeling Conditional Compilation in Ada::
180 * Preprocessing with gnatprep::
181 * Integrated Preprocessing::
183 Modeling Conditional Compilation in Ada
185 * Use of Boolean Constants::
186 * Debugging - A Special Case::
187 * Conditionalizing Declarations::
188 * Use of Alternative Implementations::
191 Preprocessing with gnatprep
193 * Preprocessing Symbols::
195 * Switches for gnatprep::
196 * Form of Definitions File::
197 * Form of Input Text for gnatprep::
199 Mixed Language Programming
202 * Calling Conventions::
203 * Building Mixed Ada and C++ Programs::
204 * Generating Ada Bindings for C and C++ headers::
205 * Generating C Headers for Ada Specifications::
207 Building Mixed Ada and C++ Programs
209 * Interfacing to C++::
210 * Linking a Mixed C++ & Ada Program::
212 * Interfacing with C++ constructors::
213 * Interfacing with C++ at the Class Level::
215 Generating Ada Bindings for C and C++ headers
217 * Running the Binding Generator::
218 * Generating Bindings for C++ Headers::
221 Generating C Headers for Ada Specifications
223 * Running the C Header Generator::
225 GNAT and Other Compilation Models
227 * Comparison between GNAT and C/C++ Compilation Models::
228 * Comparison between GNAT and Conventional Ada Library Models::
230 Using GNAT Files with External Tools
232 * Using Other Utility Programs with GNAT::
233 * The External Symbol Naming Scheme of GNAT::
235 Building Executable Programs with GNAT
237 * Building with gnatmake::
238 * Compiling with gcc::
239 * Compiler Switches::
241 * Binding with gnatbind::
242 * Linking with gnatlink::
243 * Using the GNU make Utility::
245 Building with gnatmake
248 * Switches for gnatmake::
249 * Mode Switches for gnatmake::
250 * Notes on the Command Line::
251 * How gnatmake Works::
252 * Examples of gnatmake Usage::
256 * Compiling Programs::
257 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
258 * Order of Compilation Issues::
263 * Alphabetical List of All Switches::
264 * Output and Error Message Control::
265 * Warning Message Control::
266 * Debugging and Assertion Control::
267 * Validity Checking::
270 * Using gcc for Syntax Checking::
271 * Using gcc for Semantic Checking::
272 * Compiling Different Versions of Ada::
273 * Character Set Control::
274 * File Naming Control::
275 * Subprogram Inlining Control::
276 * Auxiliary Output Control::
277 * Debugging Control::
278 * Exception Handling Control::
279 * Units to Sources Mapping Files::
280 * Code Generation Control::
282 Binding with gnatbind
285 * Switches for gnatbind::
286 * Command-Line Access::
287 * Search Paths for gnatbind::
288 * Examples of gnatbind Usage::
290 Switches for gnatbind
292 * Consistency-Checking Modes::
293 * Binder Error Message Control::
294 * Elaboration Control::
296 * Dynamic Allocation Control::
297 * Binding with Non-Ada Main Programs::
298 * Binding Programs with No Main Subprogram::
300 Linking with gnatlink
303 * Switches for gnatlink::
305 Using the GNU make Utility
307 * Using gnatmake in a Makefile::
308 * Automatically Creating a List of Directories::
309 * Generating the Command Line Switches::
310 * Overcoming Command Line Length Limits::
312 GNAT Utility Programs
314 * The File Cleanup Utility gnatclean::
315 * The GNAT Library Browser gnatls::
316 * The Cross-Referencing Tools gnatxref and gnatfind::
317 * The Ada to HTML Converter gnathtml::
319 The File Cleanup Utility gnatclean
321 * Running gnatclean::
322 * Switches for gnatclean::
324 The GNAT Library Browser gnatls
327 * Switches for gnatls::
328 * Example of gnatls Usage::
330 The Cross-Referencing Tools gnatxref and gnatfind
332 * gnatxref Switches::
333 * gnatfind Switches::
334 * Configuration Files for gnatxref and gnatfind::
335 * Regular Expressions in gnatfind and gnatxref::
336 * Examples of gnatxref Usage::
337 * Examples of gnatfind Usage::
339 Examples of gnatxref Usage
342 * Using gnatxref with vi::
344 The Ada to HTML Converter gnathtml
346 * Invoking gnathtml::
347 * Installing gnathtml::
349 GNAT and Program Execution
351 * Running and Debugging Ada Programs::
353 * Improving Performance::
354 * Overflow Check Handling in GNAT::
355 * Performing Dimensionality Analysis in GNAT::
356 * Stack Related Facilities::
357 * Memory Management Issues::
359 Running and Debugging Ada Programs
361 * The GNAT Debugger GDB::
363 * Introduction to GDB Commands::
364 * Using Ada Expressions::
365 * Calling User-Defined Subprograms::
366 * Using the next Command in a Function::
367 * Stopping When Ada Exceptions Are Raised::
369 * Debugging Generic Units::
370 * Remote Debugging with gdbserver::
371 * GNAT Abnormal Termination or Failure to Terminate::
372 * Naming Conventions for GNAT Source Files::
373 * Getting Internal Debugging Information::
375 * Pretty-Printers for the GNAT runtime::
379 * Non-Symbolic Traceback::
380 * Symbolic Traceback::
384 * Profiling an Ada Program with gprof::
386 Profiling an Ada Program with gprof
388 * Compilation for profiling::
389 * Program execution::
391 * Interpretation of profiling results::
393 Improving Performance
395 * Performance Considerations::
396 * Text_IO Suggestions::
397 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
399 Performance Considerations
401 * Controlling Run-Time Checks::
402 * Use of Restrictions::
403 * Optimization Levels::
404 * Debugging Optimized Code::
405 * Inlining of Subprograms::
406 * Floating_Point_Operations::
407 * Vectorization of loops::
408 * Other Optimization Switches::
409 * Optimization and Strict Aliasing::
410 * Aliased Variables and Optimization::
411 * Atomic Variables and Optimization::
412 * Passive Task Optimization::
414 Reducing Size of Executables with Unused Subprogram/Data Elimination
416 * About unused subprogram/data elimination::
417 * Compilation options::
418 * Example of unused subprogram/data elimination::
420 Overflow Check Handling in GNAT
423 * Management of Overflows in GNAT::
424 * Specifying the Desired Mode::
426 * Implementation Notes::
428 Stack Related Facilities
430 * Stack Overflow Checking::
431 * Static Stack Usage Analysis::
432 * Dynamic Stack Usage Analysis::
434 Memory Management Issues
436 * Some Useful Memory Pools::
437 * The GNAT Debug Pool Facility::
439 Platform-Specific Information
441 * Run-Time Libraries::
442 * Specifying a Run-Time Library::
444 * Microsoft Windows Topics::
449 * Summary of Run-Time Configurations::
451 Specifying a Run-Time Library
453 * Choosing the Scheduling Policy::
457 * Required Packages on GNU/Linux::
459 Microsoft Windows Topics
461 * Using GNAT on Windows::
462 * Using a network installation of GNAT::
463 * CONSOLE and WINDOWS subsystems::
465 * Disabling Command Line Argument Expansion::
466 * Windows Socket Timeouts::
467 * Mixed-Language Programming on Windows::
468 * Windows Specific Add-Ons::
470 Mixed-Language Programming on Windows
472 * Windows Calling Conventions::
473 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
474 * Using DLLs with GNAT::
475 * Building DLLs with GNAT Project files::
476 * Building DLLs with GNAT::
477 * Building DLLs with gnatdll::
478 * Ada DLLs and Finalization::
479 * Creating a Spec for Ada DLLs::
480 * GNAT and Windows Resources::
481 * Using GNAT DLLs from Microsoft Visual Studio Applications::
483 * Setting Stack Size from gnatlink::
484 * Setting Heap Size from gnatlink::
486 Windows Calling Conventions
488 * C Calling Convention::
489 * Stdcall Calling Convention::
490 * Win32 Calling Convention::
491 * DLL Calling Convention::
495 * Creating an Ada Spec for the DLL Services::
496 * Creating an Import Library::
498 Building DLLs with gnatdll
500 * Limitations When Using Ada DLLs from Ada::
501 * Exporting Ada Entities::
502 * Ada DLLs and Elaboration::
504 Creating a Spec for Ada DLLs
506 * Creating the Definition File::
509 GNAT and Windows Resources
511 * Building Resources::
512 * Compiling Resources::
517 * Program and DLL Both Built with GCC/GNAT::
518 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
520 Windows Specific Add-Ons
527 * Codesigning the Debugger::
529 Elaboration Order Handling in GNAT
532 * Elaboration Order::
533 * Checking the Elaboration Order::
534 * Controlling the Elaboration Order in Ada::
535 * Controlling the Elaboration Order in GNAT::
536 * Mixing Elaboration Models::
538 * SPARK Diagnostics::
539 * Elaboration Circularities::
540 * Resolving Elaboration Circularities::
541 * Elaboration-related Compiler Switches::
542 * Summary of Procedures for Elaboration Control::
543 * Inspecting the Chosen Elaboration Order::
547 * Basic Assembler Syntax::
548 * A Simple Example of Inline Assembler::
549 * Output Variables in Inline Assembler::
550 * Input Variables in Inline Assembler::
551 * Inlining Inline Assembler Code::
552 * Other Asm Functionality::
554 Other Asm Functionality
556 * The Clobber Parameter::
557 * The Volatile Parameter::
562 @node About This Guide,Getting Started with GNAT,Top,Top
563 @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}
564 @chapter About This Guide
568 This guide describes the use of GNAT,
569 a compiler and software development
570 toolset for the full Ada programming language.
571 It documents the features of the compiler and tools, and explains
572 how to use them to build Ada applications.
574 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
575 invoked in Ada 83 compatibility mode.
576 By default, GNAT assumes Ada 2012, but you can override with a
577 compiler switch (@ref{6,,Compiling Different Versions of Ada})
578 to explicitly specify the language version.
579 Throughout this manual, references to 'Ada' without a year suffix
580 apply to all Ada 95/2005/2012 versions of the language.
583 * What This Guide Contains::
584 * What You Should Know before Reading This Guide::
585 * Related Information::
586 * A Note to Readers of Previous Versions of the Manual::
591 @node What This Guide Contains,What You Should Know before Reading This Guide,,About This Guide
592 @anchor{gnat_ugn/about_this_guide what-this-guide-contains}@anchor{7}
593 @section What This Guide Contains
596 This guide contains the following chapters:
602 @ref{8,,Getting Started with GNAT} describes how to get started compiling
603 and running Ada programs with the GNAT Ada programming environment.
606 @ref{9,,The GNAT Compilation Model} describes the compilation model used
610 @ref{a,,Building Executable Programs with GNAT} describes how to use the
611 main GNAT tools to build executable programs, and it also gives examples of
612 using the GNU make utility with GNAT.
615 @ref{b,,GNAT Utility Programs} explains the various utility programs that
616 are included in the GNAT environment
619 @ref{c,,GNAT and Program Execution} covers a number of topics related to
620 running, debugging, and tuning the performace of programs developed
624 Appendices cover several additional topics:
630 @ref{d,,Platform-Specific Information} describes the different run-time
631 library implementations and also presents information on how to use
632 GNAT on several specific platforms
635 @ref{e,,Example of Binder Output File} shows the source code for the binder
636 output file for a sample program.
639 @ref{f,,Elaboration Order Handling in GNAT} describes how GNAT helps
640 you deal with elaboration order issues.
643 @ref{10,,Inline Assembler} shows how to use the inline assembly facility
647 @node What You Should Know before Reading This Guide,Related Information,What This Guide Contains,About This Guide
648 @anchor{gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide}@anchor{11}
649 @section What You Should Know before Reading This Guide
652 @geindex Ada 95 Language Reference Manual
654 @geindex Ada 2005 Language Reference Manual
656 This guide assumes a basic familiarity with the Ada 95 language, as
657 described in the International Standard ANSI/ISO/IEC-8652:1995, January
659 It does not require knowledge of the features introduced by Ada 2005
661 Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in
662 the GNAT documentation package.
664 @node Related Information,A Note to Readers of Previous Versions of the Manual,What You Should Know before Reading This Guide,About This Guide
665 @anchor{gnat_ugn/about_this_guide related-information}@anchor{12}
666 @section Related Information
669 For further information about Ada and related tools, please refer to the
676 @cite{Ada 95 Reference Manual}, @cite{Ada 2005 Reference Manual}, and
677 @cite{Ada 2012 Reference Manual}, which contain reference
678 material for the several revisions of the Ada language standard.
681 @cite{GNAT Reference_Manual}, which contains all reference material for the GNAT
682 implementation of Ada.
685 @cite{Using the GNAT Programming Studio}, which describes the GPS
686 Integrated Development Environment.
689 @cite{GNAT Programming Studio Tutorial}, which introduces the
690 main GPS features through examples.
693 @cite{Debugging with GDB},
694 for all details on the use of the GNU source-level debugger.
697 @cite{GNU Emacs Manual},
698 for full information on the extensible editor and programming
702 @node A Note to Readers of Previous Versions of the Manual,Conventions,Related Information,About This Guide
703 @anchor{gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual}@anchor{13}
704 @section A Note to Readers of Previous Versions of the Manual
707 In early 2015 the GNAT manuals were transitioned to the
708 reStructuredText (rst) / Sphinx documentation generator technology.
709 During that process the @cite{GNAT User's Guide} was reorganized
710 so that related topics would be described together in the same chapter
711 or appendix. Here's a summary of the major changes realized in
712 the new document structure.
718 @ref{9,,The GNAT Compilation Model} has been extended so that it now covers
719 the following material:
725 The @code{gnatname}, @code{gnatkr}, and @code{gnatchop} tools
728 @ref{14,,Configuration Pragmas}
731 @ref{15,,GNAT and Libraries}
734 @ref{16,,Conditional Compilation} including @ref{17,,Preprocessing with gnatprep}
735 and @ref{18,,Integrated Preprocessing}
738 @ref{19,,Generating Ada Bindings for C and C++ headers}
741 @ref{1a,,Using GNAT Files with External Tools}
745 @ref{a,,Building Executable Programs with GNAT} is a new chapter consolidating
746 the following content:
752 @ref{1b,,Building with gnatmake}
755 @ref{1c,,Compiling with gcc}
758 @ref{1d,,Binding with gnatbind}
761 @ref{1e,,Linking with gnatlink}
764 @ref{1f,,Using the GNU make Utility}
768 @ref{b,,GNAT Utility Programs} is a new chapter consolidating the information about several
776 @ref{20,,The File Cleanup Utility gnatclean}
779 @ref{21,,The GNAT Library Browser gnatls}
782 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
785 @ref{23,,The Ada to HTML Converter gnathtml}
789 @ref{c,,GNAT and Program Execution} is a new chapter consolidating the following:
795 @ref{24,,Running and Debugging Ada Programs}
801 @ref{26,,Improving Performance}
804 @ref{27,,Overflow Check Handling in GNAT}
807 @ref{28,,Performing Dimensionality Analysis in GNAT}
810 @ref{29,,Stack Related Facilities}
813 @ref{2a,,Memory Management Issues}
817 @ref{d,,Platform-Specific Information} is a new appendix consolidating the following:
823 @ref{2b,,Run-Time Libraries}
826 @ref{2c,,Microsoft Windows Topics}
829 @ref{2d,,Mac OS Topics}
833 The @emph{Compatibility and Porting Guide} appendix has been moved to the
834 @cite{GNAT Reference Manual}. It now includes a section
835 @emph{Writing Portable Fixed-Point Declarations} which was previously
836 a separate chapter in the @cite{GNAT User's Guide}.
839 @node Conventions,,A Note to Readers of Previous Versions of the Manual,About This Guide
840 @anchor{gnat_ugn/about_this_guide conventions}@anchor{2e}
845 @geindex typographical
847 @geindex Typographical conventions
849 Following are examples of the typographical and graphic conventions used
856 @code{Functions}, @code{utility program names}, @code{standard names},
872 [optional information or parameters]
875 Examples are described by text
878 and then shown this way.
882 Commands that are entered by the user are shown as preceded by a prompt string
883 comprising the @code{$} character followed by a space.
886 Full file names are shown with the '/' character
887 as the directory separator; e.g., @code{parent-dir/subdir/myfile.adb}.
888 If you are using GNAT on a Windows platform, please note that
889 the '\' character should be used instead.
892 @node Getting Started with GNAT,The GNAT Compilation Model,About This Guide,Top
893 @anchor{gnat_ugn/getting_started_with_gnat getting-started-with-gnat}@anchor{8}@anchor{gnat_ugn/getting_started_with_gnat doc}@anchor{2f}@anchor{gnat_ugn/getting_started_with_gnat id1}@anchor{30}
894 @chapter Getting Started with GNAT
897 This chapter describes how to use GNAT's command line interface to build
898 executable Ada programs.
899 On most platforms a visually oriented Integrated Development Environment
900 is also available, the GNAT Programming Studio (GPS).
901 GPS offers a graphical "look and feel", support for development in
902 other programming languages, comprehensive browsing features, and
903 many other capabilities.
904 For information on GPS please refer to
905 @cite{Using the GNAT Programming Studio}.
909 * Running a Simple Ada Program::
910 * Running a Program with Multiple Units::
911 * Using the gnatmake Utility::
915 @node Running GNAT,Running a Simple Ada Program,,Getting Started with GNAT
916 @anchor{gnat_ugn/getting_started_with_gnat running-gnat}@anchor{31}@anchor{gnat_ugn/getting_started_with_gnat id2}@anchor{32}
917 @section Running GNAT
920 Three steps are needed to create an executable file from an Ada source
927 The source file(s) must be compiled.
930 The file(s) must be bound using the GNAT binder.
933 All appropriate object files must be linked to produce an executable.
936 All three steps are most commonly handled by using the @code{gnatmake}
937 utility program that, given the name of the main program, automatically
938 performs the necessary compilation, binding and linking steps.
940 @node Running a Simple Ada Program,Running a Program with Multiple Units,Running GNAT,Getting Started with GNAT
941 @anchor{gnat_ugn/getting_started_with_gnat running-a-simple-ada-program}@anchor{33}@anchor{gnat_ugn/getting_started_with_gnat id3}@anchor{34}
942 @section Running a Simple Ada Program
945 Any text editor may be used to prepare an Ada program.
946 (If Emacs is used, the optional Ada mode may be helpful in laying out the
948 The program text is a normal text file. We will assume in our initial
949 example that you have used your editor to prepare the following
950 standard format text file:
953 with Ada.Text_IO; use Ada.Text_IO;
956 Put_Line ("Hello WORLD!");
960 This file should be named @code{hello.adb}.
961 With the normal default file naming conventions, GNAT requires
963 contain a single compilation unit whose file name is the
965 with periods replaced by hyphens; the
966 extension is @code{ads} for a
967 spec and @code{adb} for a body.
968 You can override this default file naming convention by use of the
969 special pragma @code{Source_File_Name} (for further information please
970 see @ref{35,,Using Other File Names}).
971 Alternatively, if you want to rename your files according to this default
972 convention, which is probably more convenient if you will be using GNAT
973 for all your compilations, then the @code{gnatchop} utility
974 can be used to generate correctly-named source files
975 (see @ref{36,,Renaming Files with gnatchop}).
977 You can compile the program using the following command (@code{$} is used
978 as the command prompt in the examples in this document):
984 @code{gcc} is the command used to run the compiler. This compiler is
985 capable of compiling programs in several languages, including Ada and
986 C. It assumes that you have given it an Ada program if the file extension is
987 either @code{.ads} or @code{.adb}, and it will then call
988 the GNAT compiler to compile the specified file.
990 The @code{-c} switch is required. It tells @code{gcc} to only do a
991 compilation. (For C programs, @code{gcc} can also do linking, but this
992 capability is not used directly for Ada programs, so the @code{-c}
993 switch must always be present.)
995 This compile command generates a file
996 @code{hello.o}, which is the object
997 file corresponding to your Ada program. It also generates
998 an 'Ada Library Information' file @code{hello.ali},
999 which contains additional information used to check
1000 that an Ada program is consistent.
1001 To build an executable file,
1002 use @code{gnatbind} to bind the program
1003 and @code{gnatlink} to link it. The
1004 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1005 @code{ALI} file, but the default extension of @code{.ali} can
1006 be omitted. This means that in the most common case, the argument
1007 is simply the name of the main program:
1014 A simpler method of carrying out these steps is to use @code{gnatmake},
1015 a master program that invokes all the required
1016 compilation, binding and linking tools in the correct order. In particular,
1017 @code{gnatmake} automatically recompiles any sources that have been
1018 modified since they were last compiled, or sources that depend
1019 on such modified sources, so that 'version skew' is avoided.
1021 @geindex Version skew (avoided by `@w{`}gnatmake`@w{`})
1024 $ gnatmake hello.adb
1027 The result is an executable program called @code{hello}, which can be
1034 assuming that the current directory is on the search path
1035 for executable programs.
1037 and, if all has gone well, you will see:
1043 appear in response to this command.
1045 @node Running a Program with Multiple Units,Using the gnatmake Utility,Running a Simple Ada Program,Getting Started with GNAT
1046 @anchor{gnat_ugn/getting_started_with_gnat id4}@anchor{37}@anchor{gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units}@anchor{38}
1047 @section Running a Program with Multiple Units
1050 Consider a slightly more complicated example that has three files: a
1051 main program, and the spec and body of a package:
1054 package Greetings is
1059 with Ada.Text_IO; use Ada.Text_IO;
1060 package body Greetings is
1063 Put_Line ("Hello WORLD!");
1066 procedure Goodbye is
1068 Put_Line ("Goodbye WORLD!");
1080 Following the one-unit-per-file rule, place this program in the
1081 following three separate files:
1086 @item @emph{greetings.ads}
1088 spec of package @code{Greetings}
1090 @item @emph{greetings.adb}
1092 body of package @code{Greetings}
1094 @item @emph{gmain.adb}
1096 body of main program
1099 To build an executable version of
1100 this program, we could use four separate steps to compile, bind, and link
1101 the program, as follows:
1105 $ gcc -c greetings.adb
1110 Note that there is no required order of compilation when using GNAT.
1111 In particular it is perfectly fine to compile the main program first.
1112 Also, it is not necessary to compile package specs in the case where
1113 there is an accompanying body; you only need to compile the body. If you want
1114 to submit these files to the compiler for semantic checking and not code
1115 generation, then use the @code{-gnatc} switch:
1118 $ gcc -c greetings.ads -gnatc
1121 Although the compilation can be done in separate steps as in the
1122 above example, in practice it is almost always more convenient
1123 to use the @code{gnatmake} tool. All you need to know in this case
1124 is the name of the main program's source file. The effect of the above four
1125 commands can be achieved with a single one:
1128 $ gnatmake gmain.adb
1131 In the next section we discuss the advantages of using @code{gnatmake} in
1134 @node Using the gnatmake Utility,,Running a Program with Multiple Units,Getting Started with GNAT
1135 @anchor{gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility}@anchor{39}@anchor{gnat_ugn/getting_started_with_gnat id5}@anchor{3a}
1136 @section Using the @code{gnatmake} Utility
1139 If you work on a program by compiling single components at a time using
1140 @code{gcc}, you typically keep track of the units you modify. In order to
1141 build a consistent system, you compile not only these units, but also any
1142 units that depend on the units you have modified.
1143 For example, in the preceding case,
1144 if you edit @code{gmain.adb}, you only need to recompile that file. But if
1145 you edit @code{greetings.ads}, you must recompile both
1146 @code{greetings.adb} and @code{gmain.adb}, because both files contain
1147 units that depend on @code{greetings.ads}.
1149 @code{gnatbind} will warn you if you forget one of these compilation
1150 steps, so that it is impossible to generate an inconsistent program as a
1151 result of forgetting to do a compilation. Nevertheless it is tedious and
1152 error-prone to keep track of dependencies among units.
1153 One approach to handle the dependency-bookkeeping is to use a
1154 makefile. However, makefiles present maintenance problems of their own:
1155 if the dependencies change as you change the program, you must make
1156 sure that the makefile is kept up-to-date manually, which is also an
1157 error-prone process.
1159 The @code{gnatmake} utility takes care of these details automatically.
1160 Invoke it using either one of the following forms:
1163 $ gnatmake gmain.adb
1167 The argument is the name of the file containing the main program;
1168 you may omit the extension. @code{gnatmake}
1169 examines the environment, automatically recompiles any files that need
1170 recompiling, and binds and links the resulting set of object files,
1171 generating the executable file, @code{gmain}.
1172 In a large program, it
1173 can be extremely helpful to use @code{gnatmake}, because working out by hand
1174 what needs to be recompiled can be difficult.
1176 Note that @code{gnatmake} takes into account all the Ada rules that
1177 establish dependencies among units. These include dependencies that result
1178 from inlining subprogram bodies, and from
1179 generic instantiation. Unlike some other
1180 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1181 found by the compiler on a previous compilation, which may possibly
1182 be wrong when sources change. @code{gnatmake} determines the exact set of
1183 dependencies from scratch each time it is run.
1185 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
1187 @node The GNAT Compilation Model,Building Executable Programs with GNAT,Getting Started with GNAT,Top
1188 @anchor{gnat_ugn/the_gnat_compilation_model doc}@anchor{3b}@anchor{gnat_ugn/the_gnat_compilation_model the-gnat-compilation-model}@anchor{9}@anchor{gnat_ugn/the_gnat_compilation_model id1}@anchor{3c}
1189 @chapter The GNAT Compilation Model
1192 @geindex GNAT compilation model
1194 @geindex Compilation model
1196 This chapter describes the compilation model used by GNAT. Although
1197 similar to that used by other languages such as C and C++, this model
1198 is substantially different from the traditional Ada compilation models,
1199 which are based on a centralized program library. The chapter covers
1200 the following material:
1206 Topics related to source file makeup and naming
1212 @ref{3d,,Source Representation}
1215 @ref{3e,,Foreign Language Representation}
1218 @ref{3f,,File Naming Topics and Utilities}
1222 @ref{14,,Configuration Pragmas}
1225 @ref{40,,Generating Object Files}
1228 @ref{41,,Source Dependencies}
1231 @ref{42,,The Ada Library Information Files}
1234 @ref{43,,Binding an Ada Program}
1237 @ref{15,,GNAT and Libraries}
1240 @ref{16,,Conditional Compilation}
1243 @ref{44,,Mixed Language Programming}
1246 @ref{45,,GNAT and Other Compilation Models}
1249 @ref{1a,,Using GNAT Files with External Tools}
1253 * Source Representation::
1254 * Foreign Language Representation::
1255 * File Naming Topics and Utilities::
1256 * Configuration Pragmas::
1257 * Generating Object Files::
1258 * Source Dependencies::
1259 * The Ada Library Information Files::
1260 * Binding an Ada Program::
1261 * GNAT and Libraries::
1262 * Conditional Compilation::
1263 * Mixed Language Programming::
1264 * GNAT and Other Compilation Models::
1265 * Using GNAT Files with External Tools::
1269 @node Source Representation,Foreign Language Representation,,The GNAT Compilation Model
1270 @anchor{gnat_ugn/the_gnat_compilation_model source-representation}@anchor{3d}@anchor{gnat_ugn/the_gnat_compilation_model id2}@anchor{46}
1271 @section Source Representation
1282 Ada source programs are represented in standard text files, using
1283 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1284 7-bit ASCII set, plus additional characters used for
1285 representing foreign languages (see @ref{3e,,Foreign Language Representation}
1286 for support of non-USA character sets). The format effector characters
1287 are represented using their standard ASCII encodings, as follows:
1292 @multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
1369 Source files are in standard text file format. In addition, GNAT will
1370 recognize a wide variety of stream formats, in which the end of
1371 physical lines is marked by any of the following sequences:
1372 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1373 in accommodating files that are imported from other operating systems.
1375 @geindex End of source file; Source file@comma{} end
1377 @geindex SUB (control character)
1379 The end of a source file is normally represented by the physical end of
1380 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1381 recognized as signalling the end of the source file. Again, this is
1382 provided for compatibility with other operating systems where this
1383 code is used to represent the end of file.
1385 @geindex spec (definition)
1386 @geindex compilation (definition)
1388 Each file contains a single Ada compilation unit, including any pragmas
1389 associated with the unit. For example, this means you must place a
1390 package declaration (a package @emph{spec}) and the corresponding body in
1391 separate files. An Ada @emph{compilation} (which is a sequence of
1392 compilation units) is represented using a sequence of files. Similarly,
1393 you will place each subunit or child unit in a separate file.
1395 @node Foreign Language Representation,File Naming Topics and Utilities,Source Representation,The GNAT Compilation Model
1396 @anchor{gnat_ugn/the_gnat_compilation_model foreign-language-representation}@anchor{3e}@anchor{gnat_ugn/the_gnat_compilation_model id3}@anchor{47}
1397 @section Foreign Language Representation
1400 GNAT supports the standard character sets defined in Ada as well as
1401 several other non-standard character sets for use in localized versions
1402 of the compiler (@ref{48,,Character Set Control}).
1406 * Other 8-Bit Codes::
1407 * Wide_Character Encodings::
1408 * Wide_Wide_Character Encodings::
1412 @node Latin-1,Other 8-Bit Codes,,Foreign Language Representation
1413 @anchor{gnat_ugn/the_gnat_compilation_model id4}@anchor{49}@anchor{gnat_ugn/the_gnat_compilation_model latin-1}@anchor{4a}
1419 The basic character set is Latin-1. This character set is defined by ISO
1420 standard 8859, part 1. The lower half (character codes @code{16#00#}
1421 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper
1422 half is used to represent additional characters. These include extended letters
1423 used by European languages, such as French accents, the vowels with umlauts
1424 used in German, and the extra letter A-ring used in Swedish.
1426 @geindex Ada.Characters.Latin_1
1428 For a complete list of Latin-1 codes and their encodings, see the source
1429 file of library unit @code{Ada.Characters.Latin_1} in file
1430 @code{a-chlat1.ads}.
1431 You may use any of these extended characters freely in character or
1432 string literals. In addition, the extended characters that represent
1433 letters can be used in identifiers.
1435 @node Other 8-Bit Codes,Wide_Character Encodings,Latin-1,Foreign Language Representation
1436 @anchor{gnat_ugn/the_gnat_compilation_model other-8-bit-codes}@anchor{4b}@anchor{gnat_ugn/the_gnat_compilation_model id5}@anchor{4c}
1437 @subsection Other 8-Bit Codes
1440 GNAT also supports several other 8-bit coding schemes:
1449 @item @emph{ISO 8859-2 (Latin-2)}
1451 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1462 @item @emph{ISO 8859-3 (Latin-3)}
1464 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1475 @item @emph{ISO 8859-4 (Latin-4)}
1477 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1488 @item @emph{ISO 8859-5 (Cyrillic)}
1490 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1491 lowercase equivalence.
1494 @geindex ISO 8859-15
1501 @item @emph{ISO 8859-15 (Latin-9)}
1503 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1504 lowercase equivalence
1507 @geindex code page 437 (IBM PC)
1512 @item @emph{IBM PC (code page 437)}
1514 This code page is the normal default for PCs in the U.S. It corresponds
1515 to the original IBM PC character set. This set has some, but not all, of
1516 the extended Latin-1 letters, but these letters do not have the same
1517 encoding as Latin-1. In this mode, these letters are allowed in
1518 identifiers with uppercase and lowercase equivalence.
1521 @geindex code page 850 (IBM PC)
1526 @item @emph{IBM PC (code page 850)}
1528 This code page is a modification of 437 extended to include all the
1529 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1530 mode, all these letters are allowed in identifiers with uppercase and
1531 lowercase equivalence.
1533 @item @emph{Full Upper 8-bit}
1535 Any character in the range 80-FF allowed in identifiers, and all are
1536 considered distinct. In other words, there are no uppercase and lowercase
1537 equivalences in this range. This is useful in conjunction with
1538 certain encoding schemes used for some foreign character sets (e.g.,
1539 the typical method of representing Chinese characters on the PC).
1541 @item @emph{No Upper-Half}
1543 No upper-half characters in the range 80-FF are allowed in identifiers.
1544 This gives Ada 83 compatibility for identifier names.
1547 For precise data on the encodings permitted, and the uppercase and lowercase
1548 equivalences that are recognized, see the file @code{csets.adb} in
1549 the GNAT compiler sources. You will need to obtain a full source release
1550 of GNAT to obtain this file.
1552 @node Wide_Character Encodings,Wide_Wide_Character Encodings,Other 8-Bit Codes,Foreign Language Representation
1553 @anchor{gnat_ugn/the_gnat_compilation_model id6}@anchor{4d}@anchor{gnat_ugn/the_gnat_compilation_model wide-character-encodings}@anchor{4e}
1554 @subsection Wide_Character Encodings
1557 GNAT allows wide character codes to appear in character and string
1558 literals, and also optionally in identifiers, by means of the following
1559 possible encoding schemes:
1564 @item @emph{Hex Coding}
1566 In this encoding, a wide character is represented by the following five
1573 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1574 characters (using uppercase letters) of the wide character code. For
1575 example, ESC A345 is used to represent the wide character with code
1577 This scheme is compatible with use of the full Wide_Character set.
1579 @item @emph{Upper-Half Coding}
1581 @geindex Upper-Half Coding
1583 The wide character with encoding @code{16#abcd#} where the upper bit is on
1584 (in other words, 'a' is in the range 8-F) is represented as two bytes,
1585 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1586 character, but is not required to be in the upper half. This method can
1587 be also used for shift-JIS or EUC, where the internal coding matches the
1590 @item @emph{Shift JIS Coding}
1592 @geindex Shift JIS Coding
1594 A wide character is represented by a two-character sequence,
1596 @code{16#cd#}, with the restrictions described for upper-half encoding as
1597 described above. The internal character code is the corresponding JIS
1598 character according to the standard algorithm for Shift-JIS
1599 conversion. Only characters defined in the JIS code set table can be
1600 used with this encoding method.
1602 @item @emph{EUC Coding}
1606 A wide character is represented by a two-character sequence
1608 @code{16#cd#}, with both characters being in the upper half. The internal
1609 character code is the corresponding JIS character according to the EUC
1610 encoding algorithm. Only characters defined in the JIS code set table
1611 can be used with this encoding method.
1613 @item @emph{UTF-8 Coding}
1615 A wide character is represented using
1616 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1617 10646-1/Am.2. Depending on the character value, the representation
1618 is a one, two, or three byte sequence:
1621 16#0000#-16#007f#: 2#0xxxxxxx#
1622 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
1623 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
1626 where the @code{xxx} bits correspond to the left-padded bits of the
1627 16-bit character value. Note that all lower half ASCII characters
1628 are represented as ASCII bytes and all upper half characters and
1629 other wide characters are represented as sequences of upper-half
1630 (The full UTF-8 scheme allows for encoding 31-bit characters as
1631 6-byte sequences, and in the following section on wide wide
1632 characters, the use of these sequences is documented).
1634 @item @emph{Brackets Coding}
1636 In this encoding, a wide character is represented by the following eight
1643 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1644 characters (using uppercase letters) of the wide character code. For
1645 example, ['A345'] is used to represent the wide character with code
1646 @code{16#A345#}. It is also possible (though not required) to use the
1647 Brackets coding for upper half characters. For example, the code
1648 @code{16#A3#} can be represented as @code{['A3']}.
1650 This scheme is compatible with use of the full Wide_Character set,
1651 and is also the method used for wide character encoding in some standard
1652 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1657 Some of these coding schemes do not permit the full use of the
1658 Ada character set. For example, neither Shift JIS nor EUC allow the
1659 use of the upper half of the Latin-1 set.
1663 @node Wide_Wide_Character Encodings,,Wide_Character Encodings,Foreign Language Representation
1664 @anchor{gnat_ugn/the_gnat_compilation_model id7}@anchor{4f}@anchor{gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings}@anchor{50}
1665 @subsection Wide_Wide_Character Encodings
1668 GNAT allows wide wide character codes to appear in character and string
1669 literals, and also optionally in identifiers, by means of the following
1670 possible encoding schemes:
1675 @item @emph{UTF-8 Coding}
1677 A wide character is represented using
1678 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1679 10646-1/Am.2. Depending on the character value, the representation
1680 of character codes with values greater than 16#FFFF# is a
1681 is a four, five, or six byte sequence:
1684 16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx
1686 16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx
1688 16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx
1689 10xxxxxx 10xxxxxx 10xxxxxx
1692 where the @code{xxx} bits correspond to the left-padded bits of the
1693 32-bit character value.
1695 @item @emph{Brackets Coding}
1697 In this encoding, a wide wide character is represented by the following ten or
1698 twelve byte character sequence:
1702 [ " a b c d e f g h " ]
1705 where @code{a-h} are the six or eight hexadecimal
1706 characters (using uppercase letters) of the wide wide character code. For
1707 example, ["1F4567"] is used to represent the wide wide character with code
1708 @code{16#001F_4567#}.
1710 This scheme is compatible with use of the full Wide_Wide_Character set,
1711 and is also the method used for wide wide character encoding in some standard
1712 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1715 @node File Naming Topics and Utilities,Configuration Pragmas,Foreign Language Representation,The GNAT Compilation Model
1716 @anchor{gnat_ugn/the_gnat_compilation_model id8}@anchor{51}@anchor{gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities}@anchor{3f}
1717 @section File Naming Topics and Utilities
1720 GNAT has a default file naming scheme and also provides the user with
1721 a high degree of control over how the names and extensions of the
1722 source files correspond to the Ada compilation units that they contain.
1725 * File Naming Rules::
1726 * Using Other File Names::
1727 * Alternative File Naming Schemes::
1728 * Handling Arbitrary File Naming Conventions with gnatname::
1729 * File Name Krunching with gnatkr::
1730 * Renaming Files with gnatchop::
1734 @node File Naming Rules,Using Other File Names,,File Naming Topics and Utilities
1735 @anchor{gnat_ugn/the_gnat_compilation_model file-naming-rules}@anchor{52}@anchor{gnat_ugn/the_gnat_compilation_model id9}@anchor{53}
1736 @subsection File Naming Rules
1739 The default file name is determined by the name of the unit that the
1740 file contains. The name is formed by taking the full expanded name of
1741 the unit and replacing the separating dots with hyphens and using
1742 lowercase for all letters.
1744 An exception arises if the file name generated by the above rules starts
1745 with one of the characters
1746 @code{a}, @code{g}, @code{i}, or @code{s}, and the second character is a
1747 minus. In this case, the character tilde is used in place
1748 of the minus. The reason for this special rule is to avoid clashes with
1749 the standard names for child units of the packages System, Ada,
1750 Interfaces, and GNAT, which use the prefixes
1751 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
1754 The file extension is @code{.ads} for a spec and
1755 @code{.adb} for a body. The following table shows some
1756 examples of these rules.
1761 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
1768 Ada Compilation Unit
1788 @code{arith_functions.ads}
1792 Arith_Functions (package spec)
1796 @code{arith_functions.adb}
1800 Arith_Functions (package body)
1804 @code{func-spec.ads}
1808 Func.Spec (child package spec)
1812 @code{func-spec.adb}
1816 Func.Spec (child package body)
1824 Sub (subunit of Main)
1832 A.Bad (child package body)
1838 Following these rules can result in excessively long
1839 file names if corresponding
1840 unit names are long (for example, if child units or subunits are
1841 heavily nested). An option is available to shorten such long file names
1842 (called file name 'krunching'). This may be particularly useful when
1843 programs being developed with GNAT are to be used on operating systems
1844 with limited file name lengths. @ref{54,,Using gnatkr}.
1846 Of course, no file shortening algorithm can guarantee uniqueness over
1847 all possible unit names; if file name krunching is used, it is your
1848 responsibility to ensure no name clashes occur. Alternatively you
1849 can specify the exact file names that you want used, as described
1850 in the next section. Finally, if your Ada programs are migrating from a
1851 compiler with a different naming convention, you can use the gnatchop
1852 utility to produce source files that follow the GNAT naming conventions.
1853 (For details see @ref{36,,Renaming Files with gnatchop}.)
1855 Note: in the case of Windows or Mac OS operating systems, case is not
1856 significant. So for example on Windows if the canonical name is
1857 @code{main-sub.adb}, you can use the file name @code{Main-Sub.adb} instead.
1858 However, case is significant for other operating systems, so for example,
1859 if you want to use other than canonically cased file names on a Unix system,
1860 you need to follow the procedures described in the next section.
1862 @node Using Other File Names,Alternative File Naming Schemes,File Naming Rules,File Naming Topics and Utilities
1863 @anchor{gnat_ugn/the_gnat_compilation_model id10}@anchor{55}@anchor{gnat_ugn/the_gnat_compilation_model using-other-file-names}@anchor{35}
1864 @subsection Using Other File Names
1869 In the previous section, we have described the default rules used by
1870 GNAT to determine the file name in which a given unit resides. It is
1871 often convenient to follow these default rules, and if you follow them,
1872 the compiler knows without being explicitly told where to find all
1875 @geindex Source_File_Name pragma
1877 However, in some cases, particularly when a program is imported from
1878 another Ada compiler environment, it may be more convenient for the
1879 programmer to specify which file names contain which units. GNAT allows
1880 arbitrary file names to be used by means of the Source_File_Name pragma.
1881 The form of this pragma is as shown in the following examples:
1884 pragma Source_File_Name (My_Utilities.Stacks,
1885 Spec_File_Name => "myutilst_a.ada");
1886 pragma Source_File_name (My_Utilities.Stacks,
1887 Body_File_Name => "myutilst.ada");
1890 As shown in this example, the first argument for the pragma is the unit
1891 name (in this example a child unit). The second argument has the form
1892 of a named association. The identifier
1893 indicates whether the file name is for a spec or a body;
1894 the file name itself is given by a string literal.
1896 The source file name pragma is a configuration pragma, which means that
1897 normally it will be placed in the @code{gnat.adc}
1898 file used to hold configuration
1899 pragmas that apply to a complete compilation environment.
1900 For more details on how the @code{gnat.adc} file is created and used
1901 see @ref{56,,Handling of Configuration Pragmas}.
1905 GNAT allows completely arbitrary file names to be specified using the
1906 source file name pragma. However, if the file name specified has an
1907 extension other than @code{.ads} or @code{.adb} it is necessary to use
1908 a special syntax when compiling the file. The name in this case must be
1909 preceded by the special sequence @code{-x} followed by a space and the name
1910 of the language, here @code{ada}, as in:
1913 $ gcc -c -x ada peculiar_file_name.sim
1916 @code{gnatmake} handles non-standard file names in the usual manner (the
1917 non-standard file name for the main program is simply used as the
1918 argument to gnatmake). Note that if the extension is also non-standard,
1919 then it must be included in the @code{gnatmake} command, it may not
1922 @node Alternative File Naming Schemes,Handling Arbitrary File Naming Conventions with gnatname,Using Other File Names,File Naming Topics and Utilities
1923 @anchor{gnat_ugn/the_gnat_compilation_model id11}@anchor{57}@anchor{gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes}@anchor{58}
1924 @subsection Alternative File Naming Schemes
1927 @geindex File naming schemes
1928 @geindex alternative
1932 The previous section described the use of the @code{Source_File_Name}
1933 pragma to allow arbitrary names to be assigned to individual source files.
1934 However, this approach requires one pragma for each file, and especially in
1935 large systems can result in very long @code{gnat.adc} files, and also create
1936 a maintenance problem.
1938 @geindex Source_File_Name pragma
1940 GNAT also provides a facility for specifying systematic file naming schemes
1941 other than the standard default naming scheme previously described. An
1942 alternative scheme for naming is specified by the use of
1943 @code{Source_File_Name} pragmas having the following format:
1946 pragma Source_File_Name (
1947 Spec_File_Name => FILE_NAME_PATTERN
1948 [ , Casing => CASING_SPEC]
1949 [ , Dot_Replacement => STRING_LITERAL ] );
1951 pragma Source_File_Name (
1952 Body_File_Name => FILE_NAME_PATTERN
1953 [ , Casing => CASING_SPEC ]
1954 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1956 pragma Source_File_Name (
1957 Subunit_File_Name => FILE_NAME_PATTERN
1958 [ , Casing => CASING_SPEC ]
1959 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1961 FILE_NAME_PATTERN ::= STRING_LITERAL
1962 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
1965 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
1966 It contains a single asterisk character, and the unit name is substituted
1967 systematically for this asterisk. The optional parameter
1968 @code{Casing} indicates
1969 whether the unit name is to be all upper-case letters, all lower-case letters,
1970 or mixed-case. If no
1971 @code{Casing} parameter is used, then the default is all
1974 The optional @code{Dot_Replacement} string is used to replace any periods
1975 that occur in subunit or child unit names. If no @code{Dot_Replacement}
1976 argument is used then separating dots appear unchanged in the resulting
1978 Although the above syntax indicates that the
1979 @code{Casing} argument must appear
1980 before the @code{Dot_Replacement} argument, but it
1981 is also permissible to write these arguments in the opposite order.
1983 As indicated, it is possible to specify different naming schemes for
1984 bodies, specs, and subunits. Quite often the rule for subunits is the
1985 same as the rule for bodies, in which case, there is no need to give
1986 a separate @code{Subunit_File_Name} rule, and in this case the
1987 @code{Body_File_name} rule is used for subunits as well.
1989 The separate rule for subunits can also be used to implement the rather
1990 unusual case of a compilation environment (e.g., a single directory) which
1991 contains a subunit and a child unit with the same unit name. Although
1992 both units cannot appear in the same partition, the Ada Reference Manual
1993 allows (but does not require) the possibility of the two units coexisting
1994 in the same environment.
1996 The file name translation works in the following steps:
2002 If there is a specific @code{Source_File_Name} pragma for the given unit,
2003 then this is always used, and any general pattern rules are ignored.
2006 If there is a pattern type @code{Source_File_Name} pragma that applies to
2007 the unit, then the resulting file name will be used if the file exists. If
2008 more than one pattern matches, the latest one will be tried first, and the
2009 first attempt resulting in a reference to a file that exists will be used.
2012 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2013 for which the corresponding file exists, then the standard GNAT default
2014 naming rules are used.
2017 As an example of the use of this mechanism, consider a commonly used scheme
2018 in which file names are all lower case, with separating periods copied
2019 unchanged to the resulting file name, and specs end with @code{.1.ada}, and
2020 bodies end with @code{.2.ada}. GNAT will follow this scheme if the following
2024 pragma Source_File_Name
2025 (Spec_File_Name => ".1.ada");
2026 pragma Source_File_Name
2027 (Body_File_Name => ".2.ada");
2030 The default GNAT scheme is actually implemented by providing the following
2031 default pragmas internally:
2034 pragma Source_File_Name
2035 (Spec_File_Name => ".ads", Dot_Replacement => "-");
2036 pragma Source_File_Name
2037 (Body_File_Name => ".adb", Dot_Replacement => "-");
2040 Our final example implements a scheme typically used with one of the
2041 Ada 83 compilers, where the separator character for subunits was '__'
2042 (two underscores), specs were identified by adding @code{_.ADA}, bodies
2043 by adding @code{.ADA}, and subunits by
2044 adding @code{.SEP}. All file names were
2045 upper case. Child units were not present of course since this was an
2046 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2047 the same double underscore separator for child units.
2050 pragma Source_File_Name
2051 (Spec_File_Name => "_.ADA",
2052 Dot_Replacement => "__",
2053 Casing = Uppercase);
2054 pragma Source_File_Name
2055 (Body_File_Name => ".ADA",
2056 Dot_Replacement => "__",
2057 Casing = Uppercase);
2058 pragma Source_File_Name
2059 (Subunit_File_Name => ".SEP",
2060 Dot_Replacement => "__",
2061 Casing = Uppercase);
2066 @node Handling Arbitrary File Naming Conventions with gnatname,File Name Krunching with gnatkr,Alternative File Naming Schemes,File Naming Topics and Utilities
2067 @anchor{gnat_ugn/the_gnat_compilation_model handling-arbitrary-file-naming-conventions-with-gnatname}@anchor{59}@anchor{gnat_ugn/the_gnat_compilation_model id12}@anchor{5a}
2068 @subsection Handling Arbitrary File Naming Conventions with @code{gnatname}
2071 @geindex File Naming Conventions
2074 * Arbitrary File Naming Conventions::
2075 * Running gnatname::
2076 * Switches for gnatname::
2077 * Examples of gnatname Usage::
2081 @node Arbitrary File Naming Conventions,Running gnatname,,Handling Arbitrary File Naming Conventions with gnatname
2082 @anchor{gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions}@anchor{5b}@anchor{gnat_ugn/the_gnat_compilation_model id13}@anchor{5c}
2083 @subsubsection Arbitrary File Naming Conventions
2086 The GNAT compiler must be able to know the source file name of a compilation
2087 unit. When using the standard GNAT default file naming conventions
2088 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
2089 does not need additional information.
2091 When the source file names do not follow the standard GNAT default file naming
2092 conventions, the GNAT compiler must be given additional information through
2093 a configuration pragmas file (@ref{14,,Configuration Pragmas})
2095 When the non-standard file naming conventions are well-defined,
2096 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
2097 (@ref{58,,Alternative File Naming Schemes}) may be sufficient. However,
2098 if the file naming conventions are irregular or arbitrary, a number
2099 of pragma @code{Source_File_Name} for individual compilation units
2101 To help maintain the correspondence between compilation unit names and
2102 source file names within the compiler,
2103 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
2106 @node Running gnatname,Switches for gnatname,Arbitrary File Naming Conventions,Handling Arbitrary File Naming Conventions with gnatname
2107 @anchor{gnat_ugn/the_gnat_compilation_model running-gnatname}@anchor{5d}@anchor{gnat_ugn/the_gnat_compilation_model id14}@anchor{5e}
2108 @subsubsection Running @code{gnatname}
2111 The usual form of the @code{gnatname} command is:
2114 $ gnatname [ switches ] naming_pattern [ naming_patterns ]
2115 [--and [ switches ] naming_pattern [ naming_patterns ]]
2118 All of the arguments are optional. If invoked without any argument,
2119 @code{gnatname} will display its usage.
2121 When used with at least one naming pattern, @code{gnatname} will attempt to
2122 find all the compilation units in files that follow at least one of the
2123 naming patterns. To find these compilation units,
2124 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
2127 One or several Naming Patterns may be given as arguments to @code{gnatname}.
2128 Each Naming Pattern is enclosed between double quotes (or single
2130 A Naming Pattern is a regular expression similar to the wildcard patterns
2131 used in file names by the Unix shells or the DOS prompt.
2133 @code{gnatname} may be called with several sections of directories/patterns.
2134 Sections are separated by the switch @code{--and}. In each section, there must be
2135 at least one pattern. If no directory is specified in a section, the current
2136 directory (or the project directory if @code{-P} is used) is implied.
2137 The options other that the directory switches and the patterns apply globally
2138 even if they are in different sections.
2140 Examples of Naming Patterns are:
2148 For a more complete description of the syntax of Naming Patterns,
2149 see the second kind of regular expressions described in @code{g-regexp.ads}
2150 (the 'Glob' regular expressions).
2152 When invoked without the switch @code{-P}, @code{gnatname} will create a
2153 configuration pragmas file @code{gnat.adc} in the current working directory,
2154 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
2157 @node Switches for gnatname,Examples of gnatname Usage,Running gnatname,Handling Arbitrary File Naming Conventions with gnatname
2158 @anchor{gnat_ugn/the_gnat_compilation_model id15}@anchor{5f}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatname}@anchor{60}
2159 @subsubsection Switches for @code{gnatname}
2162 Switches for @code{gnatname} must precede any specified Naming Pattern.
2164 You may specify any of the following switches to @code{gnatname}:
2166 @geindex --version (gnatname)
2171 @item @code{--version}
2173 Display Copyright and version, then exit disregarding all other options.
2176 @geindex --help (gnatname)
2183 If @code{--version} was not used, display usage, then exit disregarding
2186 @item @code{--subdirs=@emph{dir}}
2188 Real object, library or exec directories are subdirectories <dir> of the
2191 @item @code{--no-backup}
2193 Do not create a backup copy of an existing project file.
2197 Start another section of directories/patterns.
2200 @geindex -c (gnatname)
2205 @item @code{-c@emph{filename}}
2207 Create a configuration pragmas file @code{filename} (instead of the default
2209 There may be zero, one or more space between @code{-c} and
2211 @code{filename} may include directory information. @code{filename} must be
2212 writable. There may be only one switch @code{-c}.
2213 When a switch @code{-c} is
2214 specified, no switch @code{-P} may be specified (see below).
2217 @geindex -d (gnatname)
2222 @item @code{-d@emph{dir}}
2224 Look for source files in directory @code{dir}. There may be zero, one or more
2225 spaces between @code{-d} and @code{dir}.
2226 @code{dir} may end with @code{/**}, that is it may be of the form
2227 @code{root_dir/**}. In this case, the directory @code{root_dir} and all of its
2228 subdirectories, recursively, have to be searched for sources.
2229 When a switch @code{-d}
2230 is specified, the current working directory will not be searched for source
2231 files, unless it is explicitly specified with a @code{-d}
2232 or @code{-D} switch.
2233 Several switches @code{-d} may be specified.
2234 If @code{dir} is a relative path, it is relative to the directory of
2235 the configuration pragmas file specified with switch
2237 or to the directory of the project file specified with switch
2239 if neither switch @code{-c}
2240 nor switch @code{-P} are specified, it is relative to the
2241 current working directory. The directory
2242 specified with switch @code{-d} must exist and be readable.
2245 @geindex -D (gnatname)
2250 @item @code{-D@emph{filename}}
2252 Look for source files in all directories listed in text file @code{filename}.
2253 There may be zero, one or more spaces between @code{-D}
2254 and @code{filename}.
2255 @code{filename} must be an existing, readable text file.
2256 Each nonempty line in @code{filename} must be a directory.
2257 Specifying switch @code{-D} is equivalent to specifying as many
2258 switches @code{-d} as there are nonempty lines in
2263 Follow symbolic links when processing project files.
2265 @geindex -f (gnatname)
2267 @item @code{-f@emph{pattern}}
2269 Foreign patterns. Using this switch, it is possible to add sources of languages
2270 other than Ada to the list of sources of a project file.
2271 It is only useful if a -P switch is used.
2275 gnatname -Pprj -f"*.c" "*.ada"
2278 will look for Ada units in all files with the @code{.ada} extension,
2279 and will add to the list of file for project @code{prj.gpr} the C files
2280 with extension @code{.c}.
2282 @geindex -h (gnatname)
2286 Output usage (help) information. The output is written to @code{stdout}.
2288 @geindex -P (gnatname)
2290 @item @code{-P@emph{proj}}
2292 Create or update project file @code{proj}. There may be zero, one or more space
2293 between @code{-P} and @code{proj}. @code{proj} may include directory
2294 information. @code{proj} must be writable.
2295 There may be only one switch @code{-P}.
2296 When a switch @code{-P} is specified,
2297 no switch @code{-c} may be specified.
2298 On all platforms, except on VMS, when @code{gnatname} is invoked for an
2299 existing project file <proj>.gpr, a backup copy of the project file is created
2300 in the project directory with file name <proj>.gpr.saved_x. 'x' is the first
2301 non negative number that makes this backup copy a new file.
2303 @geindex -v (gnatname)
2307 Verbose mode. Output detailed explanation of behavior to @code{stdout}.
2308 This includes name of the file written, the name of the directories to search
2309 and, for each file in those directories whose name matches at least one of
2310 the Naming Patterns, an indication of whether the file contains a unit,
2311 and if so the name of the unit.
2314 @geindex -v -v (gnatname)
2321 Very Verbose mode. In addition to the output produced in verbose mode,
2322 for each file in the searched directories whose name matches none of
2323 the Naming Patterns, an indication is given that there is no match.
2325 @geindex -x (gnatname)
2327 @item @code{-x@emph{pattern}}
2329 Excluded patterns. Using this switch, it is possible to exclude some files
2330 that would match the name patterns. For example,
2333 gnatname -x "*_nt.ada" "*.ada"
2336 will look for Ada units in all files with the @code{.ada} extension,
2337 except those whose names end with @code{_nt.ada}.
2340 @node Examples of gnatname Usage,,Switches for gnatname,Handling Arbitrary File Naming Conventions with gnatname
2341 @anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage}@anchor{61}@anchor{gnat_ugn/the_gnat_compilation_model id16}@anchor{62}
2342 @subsubsection Examples of @code{gnatname} Usage
2346 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
2349 In this example, the directory @code{/home/me} must already exist
2350 and be writable. In addition, the directory
2351 @code{/home/me/sources} (specified by
2352 @code{-d sources}) must exist and be readable.
2354 Note the optional spaces after @code{-c} and @code{-d}.
2357 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
2358 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
2361 Note that several switches @code{-d} may be used,
2362 even in conjunction with one or several switches
2363 @code{-D}. Several Naming Patterns and one excluded pattern
2364 are used in this example.
2366 @node File Name Krunching with gnatkr,Renaming Files with gnatchop,Handling Arbitrary File Naming Conventions with gnatname,File Naming Topics and Utilities
2367 @anchor{gnat_ugn/the_gnat_compilation_model file-name-krunching-with-gnatkr}@anchor{63}@anchor{gnat_ugn/the_gnat_compilation_model id17}@anchor{64}
2368 @subsection File Name Krunching with @code{gnatkr}
2373 This section discusses the method used by the compiler to shorten
2374 the default file names chosen for Ada units so that they do not
2375 exceed the maximum length permitted. It also describes the
2376 @code{gnatkr} utility that can be used to determine the result of
2377 applying this shortening.
2382 * Krunching Method::
2383 * Examples of gnatkr Usage::
2387 @node About gnatkr,Using gnatkr,,File Name Krunching with gnatkr
2388 @anchor{gnat_ugn/the_gnat_compilation_model id18}@anchor{65}@anchor{gnat_ugn/the_gnat_compilation_model about-gnatkr}@anchor{66}
2389 @subsubsection About @code{gnatkr}
2392 The default file naming rule in GNAT
2393 is that the file name must be derived from
2394 the unit name. The exact default rule is as follows:
2400 Take the unit name and replace all dots by hyphens.
2403 If such a replacement occurs in the
2404 second character position of a name, and the first character is
2405 @code{a}, @code{g}, @code{s}, or @code{i},
2406 then replace the dot by the character
2410 The reason for this exception is to avoid clashes
2411 with the standard names for children of System, Ada, Interfaces,
2412 and GNAT, which use the prefixes
2413 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
2417 The @code{-gnatk@emph{nn}}
2418 switch of the compiler activates a 'krunching'
2419 circuit that limits file names to nn characters (where nn is a decimal
2422 The @code{gnatkr} utility can be used to determine the krunched name for
2423 a given file, when krunched to a specified maximum length.
2425 @node Using gnatkr,Krunching Method,About gnatkr,File Name Krunching with gnatkr
2426 @anchor{gnat_ugn/the_gnat_compilation_model id19}@anchor{67}@anchor{gnat_ugn/the_gnat_compilation_model using-gnatkr}@anchor{54}
2427 @subsubsection Using @code{gnatkr}
2430 The @code{gnatkr} command has the form:
2433 $ gnatkr name [ length ]
2436 @code{name} is the uncrunched file name, derived from the name of the unit
2437 in the standard manner described in the previous section (i.e., in particular
2438 all dots are replaced by hyphens). The file name may or may not have an
2439 extension (defined as a suffix of the form period followed by arbitrary
2440 characters other than period). If an extension is present then it will
2441 be preserved in the output. For example, when krunching @code{hellofile.ads}
2442 to eight characters, the result will be hellofil.ads.
2444 Note: for compatibility with previous versions of @code{gnatkr} dots may
2445 appear in the name instead of hyphens, but the last dot will always be
2446 taken as the start of an extension. So if @code{gnatkr} is given an argument
2447 such as @code{Hello.World.adb} it will be treated exactly as if the first
2448 period had been a hyphen, and for example krunching to eight characters
2449 gives the result @code{hellworl.adb}.
2451 Note that the result is always all lower case.
2452 Characters of the other case are folded as required.
2454 @code{length} represents the length of the krunched name. The default
2455 when no argument is given is 8 characters. A length of zero stands for
2456 unlimited, in other words do not chop except for system files where the
2457 implied crunching length is always eight characters.
2459 The output is the krunched name. The output has an extension only if the
2460 original argument was a file name with an extension.
2462 @node Krunching Method,Examples of gnatkr Usage,Using gnatkr,File Name Krunching with gnatkr
2463 @anchor{gnat_ugn/the_gnat_compilation_model id20}@anchor{68}@anchor{gnat_ugn/the_gnat_compilation_model krunching-method}@anchor{69}
2464 @subsubsection Krunching Method
2467 The initial file name is determined by the name of the unit that the file
2468 contains. The name is formed by taking the full expanded name of the
2469 unit and replacing the separating dots with hyphens and
2471 for all letters, except that a hyphen in the second character position is
2472 replaced by a tilde if the first character is
2473 @code{a}, @code{i}, @code{g}, or @code{s}.
2474 The extension is @code{.ads} for a
2475 spec and @code{.adb} for a body.
2476 Krunching does not affect the extension, but the file name is shortened to
2477 the specified length by following these rules:
2483 The name is divided into segments separated by hyphens, tildes or
2484 underscores and all hyphens, tildes, and underscores are
2485 eliminated. If this leaves the name short enough, we are done.
2488 If the name is too long, the longest segment is located (left-most
2489 if there are two of equal length), and shortened by dropping
2490 its last character. This is repeated until the name is short enough.
2492 As an example, consider the krunching of @code{our-strings-wide_fixed.adb}
2493 to fit the name into 8 characters as required by some operating systems:
2496 our-strings-wide_fixed 22
2497 our strings wide fixed 19
2498 our string wide fixed 18
2499 our strin wide fixed 17
2500 our stri wide fixed 16
2501 our stri wide fixe 15
2502 our str wide fixe 14
2509 Final file name: oustwifi.adb
2513 The file names for all predefined units are always krunched to eight
2514 characters. The krunching of these predefined units uses the following
2515 special prefix replacements:
2518 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx}
2562 These system files have a hyphen in the second character position. That
2563 is why normal user files replace such a character with a
2564 tilde, to avoid confusion with system file names.
2566 As an example of this special rule, consider
2567 @code{ada-strings-wide_fixed.adb}, which gets krunched as follows:
2570 ada-strings-wide_fixed 22
2571 a- strings wide fixed 18
2572 a- string wide fixed 17
2573 a- strin wide fixed 16
2574 a- stri wide fixed 15
2575 a- stri wide fixe 14
2582 Final file name: a-stwifi.adb
2586 Of course no file shortening algorithm can guarantee uniqueness over all
2587 possible unit names, and if file name krunching is used then it is your
2588 responsibility to ensure that no name clashes occur. The utility
2589 program @code{gnatkr} is supplied for conveniently determining the
2590 krunched name of a file.
2592 @node Examples of gnatkr Usage,,Krunching Method,File Name Krunching with gnatkr
2593 @anchor{gnat_ugn/the_gnat_compilation_model id21}@anchor{6a}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage}@anchor{6b}
2594 @subsubsection Examples of @code{gnatkr} Usage
2598 $ gnatkr very_long_unit_name.ads --> velounna.ads
2599 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
2600 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
2601 $ gnatkr grandparent-parent-child --> grparchi
2602 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
2603 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
2606 @node Renaming Files with gnatchop,,File Name Krunching with gnatkr,File Naming Topics and Utilities
2607 @anchor{gnat_ugn/the_gnat_compilation_model id22}@anchor{6c}@anchor{gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop}@anchor{36}
2608 @subsection Renaming Files with @code{gnatchop}
2613 This section discusses how to handle files with multiple units by using
2614 the @code{gnatchop} utility. This utility is also useful in renaming
2615 files to meet the standard GNAT default file naming conventions.
2618 * Handling Files with Multiple Units::
2619 * Operating gnatchop in Compilation Mode::
2620 * Command Line for gnatchop::
2621 * Switches for gnatchop::
2622 * Examples of gnatchop Usage::
2626 @node Handling Files with Multiple Units,Operating gnatchop in Compilation Mode,,Renaming Files with gnatchop
2627 @anchor{gnat_ugn/the_gnat_compilation_model id23}@anchor{6d}@anchor{gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units}@anchor{6e}
2628 @subsubsection Handling Files with Multiple Units
2631 The basic compilation model of GNAT requires that a file submitted to the
2632 compiler have only one unit and there be a strict correspondence
2633 between the file name and the unit name.
2635 The @code{gnatchop} utility allows both of these rules to be relaxed,
2636 allowing GNAT to process files which contain multiple compilation units
2637 and files with arbitrary file names. @code{gnatchop}
2638 reads the specified file and generates one or more output files,
2639 containing one unit per file. The unit and the file name correspond,
2640 as required by GNAT.
2642 If you want to permanently restructure a set of 'foreign' files so that
2643 they match the GNAT rules, and do the remaining development using the
2644 GNAT structure, you can simply use @code{gnatchop} once, generate the
2645 new set of files and work with them from that point on.
2647 Alternatively, if you want to keep your files in the 'foreign' format,
2648 perhaps to maintain compatibility with some other Ada compilation
2649 system, you can set up a procedure where you use @code{gnatchop} each
2650 time you compile, regarding the source files that it writes as temporary
2651 files that you throw away.
2653 Note that if your file containing multiple units starts with a byte order
2654 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
2655 will each start with a copy of this BOM, meaning that they can be compiled
2656 automatically in UTF-8 mode without needing to specify an explicit encoding.
2658 @node Operating gnatchop in Compilation Mode,Command Line for gnatchop,Handling Files with Multiple Units,Renaming Files with gnatchop
2659 @anchor{gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode}@anchor{6f}@anchor{gnat_ugn/the_gnat_compilation_model id24}@anchor{70}
2660 @subsubsection Operating gnatchop in Compilation Mode
2663 The basic function of @code{gnatchop} is to take a file with multiple units
2664 and split it into separate files. The boundary between files is reasonably
2665 clear, except for the issue of comments and pragmas. In default mode, the
2666 rule is that any pragmas between units belong to the previous unit, except
2667 that configuration pragmas always belong to the following unit. Any comments
2668 belong to the following unit. These rules
2669 almost always result in the right choice of
2670 the split point without needing to mark it explicitly and most users will
2671 find this default to be what they want. In this default mode it is incorrect to
2672 submit a file containing only configuration pragmas, or one that ends in
2673 configuration pragmas, to @code{gnatchop}.
2675 However, using a special option to activate 'compilation mode',
2677 can perform another function, which is to provide exactly the semantics
2678 required by the RM for handling of configuration pragmas in a compilation.
2679 In the absence of configuration pragmas (at the main file level), this
2680 option has no effect, but it causes such configuration pragmas to be handled
2681 in a quite different manner.
2683 First, in compilation mode, if @code{gnatchop} is given a file that consists of
2684 only configuration pragmas, then this file is appended to the
2685 @code{gnat.adc} file in the current directory. This behavior provides
2686 the required behavior described in the RM for the actions to be taken
2687 on submitting such a file to the compiler, namely that these pragmas
2688 should apply to all subsequent compilations in the same compilation
2689 environment. Using GNAT, the current directory, possibly containing a
2690 @code{gnat.adc} file is the representation
2691 of a compilation environment. For more information on the
2692 @code{gnat.adc} file, see @ref{56,,Handling of Configuration Pragmas}.
2694 Second, in compilation mode, if @code{gnatchop}
2695 is given a file that starts with
2696 configuration pragmas, and contains one or more units, then these
2697 configuration pragmas are prepended to each of the chopped files. This
2698 behavior provides the required behavior described in the RM for the
2699 actions to be taken on compiling such a file, namely that the pragmas
2700 apply to all units in the compilation, but not to subsequently compiled
2703 Finally, if configuration pragmas appear between units, they are appended
2704 to the previous unit. This results in the previous unit being illegal,
2705 since the compiler does not accept configuration pragmas that follow
2706 a unit. This provides the required RM behavior that forbids configuration
2707 pragmas other than those preceding the first compilation unit of a
2710 For most purposes, @code{gnatchop} will be used in default mode. The
2711 compilation mode described above is used only if you need exactly
2712 accurate behavior with respect to compilations, and you have files
2713 that contain multiple units and configuration pragmas. In this
2714 circumstance the use of @code{gnatchop} with the compilation mode
2715 switch provides the required behavior, and is for example the mode
2716 in which GNAT processes the ACVC tests.
2718 @node Command Line for gnatchop,Switches for gnatchop,Operating gnatchop in Compilation Mode,Renaming Files with gnatchop
2719 @anchor{gnat_ugn/the_gnat_compilation_model id25}@anchor{71}@anchor{gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop}@anchor{72}
2720 @subsubsection Command Line for @code{gnatchop}
2723 The @code{gnatchop} command has the form:
2726 $ gnatchop switches file_name [file_name ...]
2730 The only required argument is the file name of the file to be chopped.
2731 There are no restrictions on the form of this file name. The file itself
2732 contains one or more Ada units, in normal GNAT format, concatenated
2733 together. As shown, more than one file may be presented to be chopped.
2735 When run in default mode, @code{gnatchop} generates one output file in
2736 the current directory for each unit in each of the files.
2738 @code{directory}, if specified, gives the name of the directory to which
2739 the output files will be written. If it is not specified, all files are
2740 written to the current directory.
2742 For example, given a
2743 file called @code{hellofiles} containing
2748 with Ada.Text_IO; use Ada.Text_IO;
2758 $ gnatchop hellofiles
2761 generates two files in the current directory, one called
2762 @code{hello.ads} containing the single line that is the procedure spec,
2763 and the other called @code{hello.adb} containing the remaining text. The
2764 original file is not affected. The generated files can be compiled in
2767 When gnatchop is invoked on a file that is empty or that contains only empty
2768 lines and/or comments, gnatchop will not fail, but will not produce any
2771 For example, given a
2772 file called @code{toto.txt} containing
2784 will not produce any new file and will result in the following warnings:
2787 toto.txt:1:01: warning: empty file, contains no compilation units
2788 no compilation units found
2789 no source files written
2792 @node Switches for gnatchop,Examples of gnatchop Usage,Command Line for gnatchop,Renaming Files with gnatchop
2793 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatchop}@anchor{73}@anchor{gnat_ugn/the_gnat_compilation_model id26}@anchor{74}
2794 @subsubsection Switches for @code{gnatchop}
2797 @code{gnatchop} recognizes the following switches:
2799 @geindex --version (gnatchop)
2804 @item @code{--version}
2806 Display Copyright and version, then exit disregarding all other options.
2809 @geindex --help (gnatchop)
2816 If @code{--version} was not used, display usage, then exit disregarding
2820 @geindex -c (gnatchop)
2827 Causes @code{gnatchop} to operate in compilation mode, in which
2828 configuration pragmas are handled according to strict RM rules. See
2829 previous section for a full description of this mode.
2831 @item @code{-gnat@emph{xxx}}
2833 This passes the given @code{-gnat@emph{xxx}} switch to @code{gnat} which is
2834 used to parse the given file. Not all @emph{xxx} options make sense,
2835 but for example, the use of @code{-gnati2} allows @code{gnatchop} to
2836 process a source file that uses Latin-2 coding for identifiers.
2840 Causes @code{gnatchop} to generate a brief help summary to the standard
2841 output file showing usage information.
2844 @geindex -k (gnatchop)
2849 @item @code{-k@emph{mm}}
2851 Limit generated file names to the specified number @code{mm}
2853 This is useful if the
2854 resulting set of files is required to be interoperable with systems
2855 which limit the length of file names.
2856 No space is allowed between the @code{-k} and the numeric value. The numeric
2857 value may be omitted in which case a default of @code{-k8},
2859 with DOS-like file systems, is used. If no @code{-k} switch
2861 there is no limit on the length of file names.
2864 @geindex -p (gnatchop)
2871 Causes the file modification time stamp of the input file to be
2872 preserved and used for the time stamp of the output file(s). This may be
2873 useful for preserving coherency of time stamps in an environment where
2874 @code{gnatchop} is used as part of a standard build process.
2877 @geindex -q (gnatchop)
2884 Causes output of informational messages indicating the set of generated
2885 files to be suppressed. Warnings and error messages are unaffected.
2888 @geindex -r (gnatchop)
2890 @geindex Source_Reference pragmas
2897 Generate @code{Source_Reference} pragmas. Use this switch if the output
2898 files are regarded as temporary and development is to be done in terms
2899 of the original unchopped file. This switch causes
2900 @code{Source_Reference} pragmas to be inserted into each of the
2901 generated files to refers back to the original file name and line number.
2902 The result is that all error messages refer back to the original
2904 In addition, the debugging information placed into the object file (when
2905 the @code{-g} switch of @code{gcc} or @code{gnatmake} is
2907 also refers back to this original file so that tools like profilers and
2908 debuggers will give information in terms of the original unchopped file.
2910 If the original file to be chopped itself contains
2911 a @code{Source_Reference}
2912 pragma referencing a third file, then gnatchop respects
2913 this pragma, and the generated @code{Source_Reference} pragmas
2914 in the chopped file refer to the original file, with appropriate
2915 line numbers. This is particularly useful when @code{gnatchop}
2916 is used in conjunction with @code{gnatprep} to compile files that
2917 contain preprocessing statements and multiple units.
2920 @geindex -v (gnatchop)
2927 Causes @code{gnatchop} to operate in verbose mode. The version
2928 number and copyright notice are output, as well as exact copies of
2929 the gnat1 commands spawned to obtain the chop control information.
2932 @geindex -w (gnatchop)
2939 Overwrite existing file names. Normally @code{gnatchop} regards it as a
2940 fatal error if there is already a file with the same name as a
2941 file it would otherwise output, in other words if the files to be
2942 chopped contain duplicated units. This switch bypasses this
2943 check, and causes all but the last instance of such duplicated
2944 units to be skipped.
2947 @geindex --GCC= (gnatchop)
2952 @item @code{--GCC=@emph{xxxx}}
2954 Specify the path of the GNAT parser to be used. When this switch is used,
2955 no attempt is made to add the prefix to the GNAT parser executable.
2958 @node Examples of gnatchop Usage,,Switches for gnatchop,Renaming Files with gnatchop
2959 @anchor{gnat_ugn/the_gnat_compilation_model id27}@anchor{75}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage}@anchor{76}
2960 @subsubsection Examples of @code{gnatchop} Usage
2964 $ gnatchop -w hello_s.ada prerelease/files
2967 Chops the source file @code{hello_s.ada}. The output files will be
2968 placed in the directory @code{prerelease/files},
2970 files with matching names in that directory (no files in the current
2971 directory are modified).
2977 Chops the source file @code{archive}
2978 into the current directory. One
2979 useful application of @code{gnatchop} is in sending sets of sources
2980 around, for example in email messages. The required sources are simply
2981 concatenated (for example, using a Unix @code{cat}
2983 @code{gnatchop} is used at the other end to reconstitute the original
2987 $ gnatchop file1 file2 file3 direc
2990 Chops all units in files @code{file1}, @code{file2}, @code{file3}, placing
2991 the resulting files in the directory @code{direc}. Note that if any units
2992 occur more than once anywhere within this set of files, an error message
2993 is generated, and no files are written. To override this check, use the
2995 in which case the last occurrence in the last file will
2996 be the one that is output, and earlier duplicate occurrences for a given
2997 unit will be skipped.
2999 @node Configuration Pragmas,Generating Object Files,File Naming Topics and Utilities,The GNAT Compilation Model
3000 @anchor{gnat_ugn/the_gnat_compilation_model id28}@anchor{77}@anchor{gnat_ugn/the_gnat_compilation_model configuration-pragmas}@anchor{14}
3001 @section Configuration Pragmas
3004 @geindex Configuration pragmas
3007 @geindex configuration
3009 Configuration pragmas include those pragmas described as
3010 such in the Ada Reference Manual, as well as
3011 implementation-dependent pragmas that are configuration pragmas.
3012 See the @code{Implementation_Defined_Pragmas} chapter in the
3013 @cite{GNAT_Reference_Manual} for details on these
3014 additional GNAT-specific configuration pragmas.
3015 Most notably, the pragma @code{Source_File_Name}, which allows
3016 specifying non-default names for source files, is a configuration
3017 pragma. The following is a complete list of configuration pragmas
3027 Allow_Integer_Address
3030 Assume_No_Invalid_Values
3032 Check_Float_Overflow
3036 Compile_Time_Warning
3038 Compiler_Unit_Warning
3040 Convention_Identifier
3043 Default_Scalar_Storage_Order
3044 Default_Storage_Pool
3045 Disable_Atomic_Synchronization
3049 Enable_Atomic_Synchronization
3052 External_Name_Casing
3061 No_Component_Reordering
3062 No_Heap_Finalization
3068 Overriding_Renamings
3069 Partition_Elaboration_Policy
3072 Prefix_Exception_Messages
3073 Priority_Specific_Dispatching
3076 Propagate_Exceptions
3083 Restrictions_Warnings
3085 Short_Circuit_And_Or
3088 Source_File_Name_Project
3092 Suppress_Exception_Locations
3093 Task_Dispatching_Policy
3094 Unevaluated_Use_Of_Old
3101 Wide_Character_Encoding
3105 * Handling of Configuration Pragmas::
3106 * The Configuration Pragmas Files::
3110 @node Handling of Configuration Pragmas,The Configuration Pragmas Files,,Configuration Pragmas
3111 @anchor{gnat_ugn/the_gnat_compilation_model id29}@anchor{78}@anchor{gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas}@anchor{56}
3112 @subsection Handling of Configuration Pragmas
3115 Configuration pragmas may either appear at the start of a compilation
3116 unit, or they can appear in a configuration pragma file to apply to
3117 all compilations performed in a given compilation environment.
3119 GNAT also provides the @code{gnatchop} utility to provide an automatic
3120 way to handle configuration pragmas following the semantics for
3121 compilations (that is, files with multiple units), described in the RM.
3122 See @ref{6f,,Operating gnatchop in Compilation Mode} for details.
3123 However, for most purposes, it will be more convenient to edit the
3124 @code{gnat.adc} file that contains configuration pragmas directly,
3125 as described in the following section.
3127 In the case of @code{Restrictions} pragmas appearing as configuration
3128 pragmas in individual compilation units, the exact handling depends on
3129 the type of restriction.
3131 Restrictions that require partition-wide consistency (like
3132 @code{No_Tasking}) are
3133 recognized wherever they appear
3134 and can be freely inherited, e.g. from a @emph{with}ed unit to the @emph{with}ing
3135 unit. This makes sense since the binder will in any case insist on seeing
3136 consistent use, so any unit not conforming to any restrictions that are
3137 anywhere in the partition will be rejected, and you might as well find
3138 that out at compile time rather than at bind time.
3140 For restrictions that do not require partition-wide consistency, e.g.
3141 SPARK or No_Implementation_Attributes, in general the restriction applies
3142 only to the unit in which the pragma appears, and not to any other units.
3144 The exception is No_Elaboration_Code which always applies to the entire
3145 object file from a compilation, i.e. to the body, spec, and all subunits.
3146 This restriction can be specified in a configuration pragma file, or it
3147 can be on the body and/or the spec (in eithe case it applies to all the
3148 relevant units). It can appear on a subunit only if it has previously
3149 appeared in the body of spec.
3151 @node The Configuration Pragmas Files,,Handling of Configuration Pragmas,Configuration Pragmas
3152 @anchor{gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files}@anchor{79}@anchor{gnat_ugn/the_gnat_compilation_model id30}@anchor{7a}
3153 @subsection The Configuration Pragmas Files
3158 In GNAT a compilation environment is defined by the current
3159 directory at the time that a compile command is given. This current
3160 directory is searched for a file whose name is @code{gnat.adc}. If
3161 this file is present, it is expected to contain one or more
3162 configuration pragmas that will be applied to the current compilation.
3163 However, if the switch @code{-gnatA} is used, @code{gnat.adc} is not
3164 considered. When taken into account, @code{gnat.adc} is added to the
3165 dependencies, so that if @code{gnat.adc} is modified later, an invocation of
3166 @code{gnatmake} will recompile the source.
3168 Configuration pragmas may be entered into the @code{gnat.adc} file
3169 either by running @code{gnatchop} on a source file that consists only of
3170 configuration pragmas, or more conveniently by direct editing of the
3171 @code{gnat.adc} file, which is a standard format source file.
3173 Besides @code{gnat.adc}, additional files containing configuration
3174 pragmas may be applied to the current compilation using the switch
3175 @code{-gnatec=@emph{path}} where @code{path} must designate an existing file that
3176 contains only configuration pragmas. These configuration pragmas are
3177 in addition to those found in @code{gnat.adc} (provided @code{gnat.adc}
3178 is present and switch @code{-gnatA} is not used).
3180 It is allowable to specify several switches @code{-gnatec=}, all of which
3181 will be taken into account.
3183 Files containing configuration pragmas specified with switches
3184 @code{-gnatec=} are added to the dependencies, unless they are
3185 temporary files. A file is considered temporary if its name ends in
3186 @code{.tmp} or @code{.TMP}. Certain tools follow this naming
3187 convention because they pass information to @code{gcc} via
3188 temporary files that are immediately deleted; it doesn't make sense to
3189 depend on a file that no longer exists. Such tools include
3190 @code{gprbuild}, @code{gnatmake}, and @code{gnatcheck}.
3192 If you are using project file, a separate mechanism is provided using
3196 @c See :ref:`Specifying_Configuration_Pragmas` for more details.
3198 @node Generating Object Files,Source Dependencies,Configuration Pragmas,The GNAT Compilation Model
3199 @anchor{gnat_ugn/the_gnat_compilation_model generating-object-files}@anchor{40}@anchor{gnat_ugn/the_gnat_compilation_model id31}@anchor{7b}
3200 @section Generating Object Files
3203 An Ada program consists of a set of source files, and the first step in
3204 compiling the program is to generate the corresponding object files.
3205 These are generated by compiling a subset of these source files.
3206 The files you need to compile are the following:
3212 If a package spec has no body, compile the package spec to produce the
3213 object file for the package.
3216 If a package has both a spec and a body, compile the body to produce the
3217 object file for the package. The source file for the package spec need
3218 not be compiled in this case because there is only one object file, which
3219 contains the code for both the spec and body of the package.
3222 For a subprogram, compile the subprogram body to produce the object file
3223 for the subprogram. The spec, if one is present, is as usual in a
3224 separate file, and need not be compiled.
3233 In the case of subunits, only compile the parent unit. A single object
3234 file is generated for the entire subunit tree, which includes all the
3238 Compile child units independently of their parent units
3239 (though, of course, the spec of all the ancestor unit must be present in order
3240 to compile a child unit).
3245 Compile generic units in the same manner as any other units. The object
3246 files in this case are small dummy files that contain at most the
3247 flag used for elaboration checking. This is because GNAT always handles generic
3248 instantiation by means of macro expansion. However, it is still necessary to
3249 compile generic units, for dependency checking and elaboration purposes.
3252 The preceding rules describe the set of files that must be compiled to
3253 generate the object files for a program. Each object file has the same
3254 name as the corresponding source file, except that the extension is
3257 You may wish to compile other files for the purpose of checking their
3258 syntactic and semantic correctness. For example, in the case where a
3259 package has a separate spec and body, you would not normally compile the
3260 spec. However, it is convenient in practice to compile the spec to make
3261 sure it is error-free before compiling clients of this spec, because such
3262 compilations will fail if there is an error in the spec.
3264 GNAT provides an option for compiling such files purely for the
3265 purposes of checking correctness; such compilations are not required as
3266 part of the process of building a program. To compile a file in this
3267 checking mode, use the @code{-gnatc} switch.
3269 @node Source Dependencies,The Ada Library Information Files,Generating Object Files,The GNAT Compilation Model
3270 @anchor{gnat_ugn/the_gnat_compilation_model id32}@anchor{7c}@anchor{gnat_ugn/the_gnat_compilation_model source-dependencies}@anchor{41}
3271 @section Source Dependencies
3274 A given object file clearly depends on the source file which is compiled
3275 to produce it. Here we are using "depends" in the sense of a typical
3276 @code{make} utility; in other words, an object file depends on a source
3277 file if changes to the source file require the object file to be
3279 In addition to this basic dependency, a given object may depend on
3280 additional source files as follows:
3286 If a file being compiled @emph{with}s a unit @code{X}, the object file
3287 depends on the file containing the spec of unit @code{X}. This includes
3288 files that are @emph{with}ed implicitly either because they are parents
3289 of @emph{with}ed child units or they are run-time units required by the
3290 language constructs used in a particular unit.
3293 If a file being compiled instantiates a library level generic unit, the
3294 object file depends on both the spec and body files for this generic
3298 If a file being compiled instantiates a generic unit defined within a
3299 package, the object file depends on the body file for the package as
3300 well as the spec file.
3305 @geindex -gnatn switch
3311 If a file being compiled contains a call to a subprogram for which
3312 pragma @code{Inline} applies and inlining is activated with the
3313 @code{-gnatn} switch, the object file depends on the file containing the
3314 body of this subprogram as well as on the file containing the spec. Note
3315 that for inlining to actually occur as a result of the use of this switch,
3316 it is necessary to compile in optimizing mode.
3318 @geindex -gnatN switch
3320 The use of @code{-gnatN} activates inlining optimization
3321 that is performed by the front end of the compiler. This inlining does
3322 not require that the code generation be optimized. Like @code{-gnatn},
3323 the use of this switch generates additional dependencies.
3325 When using a gcc-based back end (in practice this means using any version
3326 of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of
3327 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
3328 Historically front end inlining was more extensive than the gcc back end
3329 inlining, but that is no longer the case.
3332 If an object file @code{O} depends on the proper body of a subunit through
3333 inlining or instantiation, it depends on the parent unit of the subunit.
3334 This means that any modification of the parent unit or one of its subunits
3335 affects the compilation of @code{O}.
3338 The object file for a parent unit depends on all its subunit body files.
3341 The previous two rules meant that for purposes of computing dependencies and
3342 recompilation, a body and all its subunits are treated as an indivisible whole.
3344 These rules are applied transitively: if unit @code{A} @emph{with}s
3345 unit @code{B}, whose elaboration calls an inlined procedure in package
3346 @code{C}, the object file for unit @code{A} will depend on the body of
3347 @code{C}, in file @code{c.adb}.
3349 The set of dependent files described by these rules includes all the
3350 files on which the unit is semantically dependent, as dictated by the
3351 Ada language standard. However, it is a superset of what the
3352 standard describes, because it includes generic, inline, and subunit
3355 An object file must be recreated by recompiling the corresponding source
3356 file if any of the source files on which it depends are modified. For
3357 example, if the @code{make} utility is used to control compilation,
3358 the rule for an Ada object file must mention all the source files on
3359 which the object file depends, according to the above definition.
3360 The determination of the necessary
3361 recompilations is done automatically when one uses @code{gnatmake}.
3364 @node The Ada Library Information Files,Binding an Ada Program,Source Dependencies,The GNAT Compilation Model
3365 @anchor{gnat_ugn/the_gnat_compilation_model id33}@anchor{7d}@anchor{gnat_ugn/the_gnat_compilation_model the-ada-library-information-files}@anchor{42}
3366 @section The Ada Library Information Files
3369 @geindex Ada Library Information files
3373 Each compilation actually generates two output files. The first of these
3374 is the normal object file that has a @code{.o} extension. The second is a
3375 text file containing full dependency information. It has the same
3376 name as the source file, but an @code{.ali} extension.
3377 This file is known as the Ada Library Information (@code{ALI}) file.
3378 The following information is contained in the @code{ALI} file.
3384 Version information (indicates which version of GNAT was used to compile
3385 the unit(s) in question)
3388 Main program information (including priority and time slice settings,
3389 as well as the wide character encoding used during compilation).
3392 List of arguments used in the @code{gcc} command for the compilation
3395 Attributes of the unit, including configuration pragmas used, an indication
3396 of whether the compilation was successful, exception model used etc.
3399 A list of relevant restrictions applying to the unit (used for consistency)
3403 Categorization information (e.g., use of pragma @code{Pure}).
3406 Information on all @emph{with}ed units, including presence of
3407 @code{Elaborate} or @code{Elaborate_All} pragmas.
3410 Information from any @code{Linker_Options} pragmas used in the unit
3413 Information on the use of @code{Body_Version} or @code{Version}
3414 attributes in the unit.
3417 Dependency information. This is a list of files, together with
3418 time stamp and checksum information. These are files on which
3419 the unit depends in the sense that recompilation is required
3420 if any of these units are modified.
3423 Cross-reference data. Contains information on all entities referenced
3424 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
3425 provide cross-reference information.
3428 For a full detailed description of the format of the @code{ALI} file,
3429 see the source of the body of unit @code{Lib.Writ}, contained in file
3430 @code{lib-writ.adb} in the GNAT compiler sources.
3432 @node Binding an Ada Program,GNAT and Libraries,The Ada Library Information Files,The GNAT Compilation Model
3433 @anchor{gnat_ugn/the_gnat_compilation_model id34}@anchor{7e}@anchor{gnat_ugn/the_gnat_compilation_model binding-an-ada-program}@anchor{43}
3434 @section Binding an Ada Program
3437 When using languages such as C and C++, once the source files have been
3438 compiled the only remaining step in building an executable program
3439 is linking the object modules together. This means that it is possible to
3440 link an inconsistent version of a program, in which two units have
3441 included different versions of the same header.
3443 The rules of Ada do not permit such an inconsistent program to be built.
3444 For example, if two clients have different versions of the same package,
3445 it is illegal to build a program containing these two clients.
3446 These rules are enforced by the GNAT binder, which also determines an
3447 elaboration order consistent with the Ada rules.
3449 The GNAT binder is run after all the object files for a program have
3450 been created. It is given the name of the main program unit, and from
3451 this it determines the set of units required by the program, by reading the
3452 corresponding ALI files. It generates error messages if the program is
3453 inconsistent or if no valid order of elaboration exists.
3455 If no errors are detected, the binder produces a main program, in Ada by
3456 default, that contains calls to the elaboration procedures of those
3457 compilation unit that require them, followed by
3458 a call to the main program. This Ada program is compiled to generate the
3459 object file for the main program. The name of
3460 the Ada file is @code{b~xxx}.adb` (with the corresponding spec
3461 @code{b~xxx}.ads`) where @code{xxx} is the name of the
3464 Finally, the linker is used to build the resulting executable program,
3465 using the object from the main program from the bind step as well as the
3466 object files for the Ada units of the program.
3468 @node GNAT and Libraries,Conditional Compilation,Binding an Ada Program,The GNAT Compilation Model
3469 @anchor{gnat_ugn/the_gnat_compilation_model gnat-and-libraries}@anchor{15}@anchor{gnat_ugn/the_gnat_compilation_model id35}@anchor{7f}
3470 @section GNAT and Libraries
3473 @geindex Library building and using
3475 This section describes how to build and use libraries with GNAT, and also shows
3476 how to recompile the GNAT run-time library. You should be familiar with the
3477 Project Manager facility (see the @emph{GNAT_Project_Manager} chapter of the
3478 @emph{GPRbuild User's Guide}) before reading this chapter.
3481 * Introduction to Libraries in GNAT::
3482 * General Ada Libraries::
3483 * Stand-alone Ada Libraries::
3484 * Rebuilding the GNAT Run-Time Library::
3488 @node Introduction to Libraries in GNAT,General Ada Libraries,,GNAT and Libraries
3489 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-libraries-in-gnat}@anchor{80}@anchor{gnat_ugn/the_gnat_compilation_model id36}@anchor{81}
3490 @subsection Introduction to Libraries in GNAT
3493 A library is, conceptually, a collection of objects which does not have its
3494 own main thread of execution, but rather provides certain services to the
3495 applications that use it. A library can be either statically linked with the
3496 application, in which case its code is directly included in the application,
3497 or, on platforms that support it, be dynamically linked, in which case
3498 its code is shared by all applications making use of this library.
3500 GNAT supports both types of libraries.
3501 In the static case, the compiled code can be provided in different ways. The
3502 simplest approach is to provide directly the set of objects resulting from
3503 compilation of the library source files. Alternatively, you can group the
3504 objects into an archive using whatever commands are provided by the operating
3505 system. For the latter case, the objects are grouped into a shared library.
3507 In the GNAT environment, a library has three types of components:
3516 @code{ALI} files (see @ref{42,,The Ada Library Information Files}), and
3519 Object files, an archive or a shared library.
3522 A GNAT library may expose all its source files, which is useful for
3523 documentation purposes. Alternatively, it may expose only the units needed by
3524 an external user to make use of the library. That is to say, the specs
3525 reflecting the library services along with all the units needed to compile
3526 those specs, which can include generic bodies or any body implementing an
3527 inlined routine. In the case of @emph{stand-alone libraries} those exposed
3528 units are called @emph{interface units} (@ref{82,,Stand-alone Ada Libraries}).
3530 All compilation units comprising an application, including those in a library,
3531 need to be elaborated in an order partially defined by Ada's semantics. GNAT
3532 computes the elaboration order from the @code{ALI} files and this is why they
3533 constitute a mandatory part of GNAT libraries.
3534 @emph{Stand-alone libraries} are the exception to this rule because a specific
3535 library elaboration routine is produced independently of the application(s)
3538 @node General Ada Libraries,Stand-alone Ada Libraries,Introduction to Libraries in GNAT,GNAT and Libraries
3539 @anchor{gnat_ugn/the_gnat_compilation_model general-ada-libraries}@anchor{83}@anchor{gnat_ugn/the_gnat_compilation_model id37}@anchor{84}
3540 @subsection General Ada Libraries
3544 * Building a library::
3545 * Installing a library::
3550 @node Building a library,Installing a library,,General Ada Libraries
3551 @anchor{gnat_ugn/the_gnat_compilation_model building-a-library}@anchor{85}@anchor{gnat_ugn/the_gnat_compilation_model id38}@anchor{86}
3552 @subsubsection Building a library
3555 The easiest way to build a library is to use the Project Manager,
3556 which supports a special type of project called a @emph{Library Project}
3557 (see the @emph{Library Projects} section in the @emph{GNAT Project Manager}
3558 chapter of the @emph{GPRbuild User's Guide}).
3560 A project is considered a library project, when two project-level attributes
3561 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
3562 control different aspects of library configuration, additional optional
3563 project-level attributes can be specified:
3572 @item @code{Library_Kind}
3574 This attribute controls whether the library is to be static or dynamic
3581 @item @code{Library_Version}
3583 This attribute specifies the library version; this value is used
3584 during dynamic linking of shared libraries to determine if the currently
3585 installed versions of the binaries are compatible.
3589 @code{Library_Options}
3595 @item @code{Library_GCC}
3597 These attributes specify additional low-level options to be used during
3598 library generation, and redefine the actual application used to generate
3603 The GNAT Project Manager takes full care of the library maintenance task,
3604 including recompilation of the source files for which objects do not exist
3605 or are not up to date, assembly of the library archive, and installation of
3606 the library (i.e., copying associated source, object and @code{ALI} files
3607 to the specified location).
3609 Here is a simple library project file:
3613 for Source_Dirs use ("src1", "src2");
3614 for Object_Dir use "obj";
3615 for Library_Name use "mylib";
3616 for Library_Dir use "lib";
3617 for Library_Kind use "dynamic";
3621 and the compilation command to build and install the library:
3627 It is not entirely trivial to perform manually all the steps required to
3628 produce a library. We recommend that you use the GNAT Project Manager
3629 for this task. In special cases where this is not desired, the necessary
3630 steps are discussed below.
3632 There are various possibilities for compiling the units that make up the
3633 library: for example with a Makefile (@ref{1f,,Using the GNU make Utility}) or
3634 with a conventional script. For simple libraries, it is also possible to create
3635 a dummy main program which depends upon all the packages that comprise the
3636 interface of the library. This dummy main program can then be given to
3637 @code{gnatmake}, which will ensure that all necessary objects are built.
3639 After this task is accomplished, you should follow the standard procedure
3640 of the underlying operating system to produce the static or shared library.
3642 Here is an example of such a dummy program:
3645 with My_Lib.Service1;
3646 with My_Lib.Service2;
3647 with My_Lib.Service3;
3648 procedure My_Lib_Dummy is
3654 Here are the generic commands that will build an archive or a shared library.
3657 # compiling the library
3658 $ gnatmake -c my_lib_dummy.adb
3660 # we don't need the dummy object itself
3661 $ rm my_lib_dummy.o my_lib_dummy.ali
3663 # create an archive with the remaining objects
3664 $ ar rc libmy_lib.a *.o
3665 # some systems may require "ranlib" to be run as well
3667 # or create a shared library
3668 $ gcc -shared -o libmy_lib.so *.o
3669 # some systems may require the code to have been compiled with -fPIC
3671 # remove the object files that are now in the library
3674 # Make the ALI files read-only so that gnatmake will not try to
3675 # regenerate the objects that are in the library
3679 Please note that the library must have a name of the form @code{lib@emph{xxx}.a}
3680 or @code{lib@emph{xxx}.so} (or @code{lib@emph{xxx}.dll} on Windows) in order to
3681 be accessed by the directive @code{-l@emph{xxx}} at link time.
3683 @node Installing a library,Using a library,Building a library,General Ada Libraries
3684 @anchor{gnat_ugn/the_gnat_compilation_model installing-a-library}@anchor{87}@anchor{gnat_ugn/the_gnat_compilation_model id39}@anchor{88}
3685 @subsubsection Installing a library
3688 @geindex ADA_PROJECT_PATH
3690 @geindex GPR_PROJECT_PATH
3692 If you use project files, library installation is part of the library build
3693 process (see the @emph{Installing a Library with Project Files} section of the
3694 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}).
3696 When project files are not an option, it is also possible, but not recommended,
3697 to install the library so that the sources needed to use the library are on the
3698 Ada source path and the ALI files & libraries be on the Ada Object path (see
3699 @ref{89,,Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
3700 administrator can place general-purpose libraries in the default compiler
3701 paths, by specifying the libraries' location in the configuration files
3702 @code{ada_source_path} and @code{ada_object_path}. These configuration files
3703 must be located in the GNAT installation tree at the same place as the gcc spec
3704 file. The location of the gcc spec file can be determined as follows:
3710 The configuration files mentioned above have a simple format: each line
3711 must contain one unique directory name.
3712 Those names are added to the corresponding path
3713 in their order of appearance in the file. The names can be either absolute
3714 or relative; in the latter case, they are relative to where theses files
3717 The files @code{ada_source_path} and @code{ada_object_path} might not be
3719 GNAT installation, in which case, GNAT will look for its run-time library in
3720 the directories @code{adainclude} (for the sources) and @code{adalib} (for the
3721 objects and @code{ALI} files). When the files exist, the compiler does not
3722 look in @code{adainclude} and @code{adalib}, and thus the
3723 @code{ada_source_path} file
3724 must contain the location for the GNAT run-time sources (which can simply
3725 be @code{adainclude}). In the same way, the @code{ada_object_path} file must
3726 contain the location for the GNAT run-time objects (which can simply
3729 You can also specify a new default path to the run-time library at compilation
3730 time with the switch @code{--RTS=rts-path}. You can thus choose / change
3731 the run-time library you want your program to be compiled with. This switch is
3732 recognized by @code{gcc}, @code{gnatmake}, @code{gnatbind},
3733 @code{gnatls}, @code{gnatfind} and @code{gnatxref}.
3735 It is possible to install a library before or after the standard GNAT
3736 library, by reordering the lines in the configuration files. In general, a
3737 library must be installed before the GNAT library if it redefines
3740 @node Using a library,,Installing a library,General Ada Libraries
3741 @anchor{gnat_ugn/the_gnat_compilation_model using-a-library}@anchor{8a}@anchor{gnat_ugn/the_gnat_compilation_model id40}@anchor{8b}
3742 @subsubsection Using a library
3745 Once again, the project facility greatly simplifies the use of
3746 libraries. In this context, using a library is just a matter of adding a
3747 @emph{with} clause in the user project. For instance, to make use of the
3748 library @code{My_Lib} shown in examples in earlier sections, you can
3758 Even if you have a third-party, non-Ada library, you can still use GNAT's
3759 Project Manager facility to provide a wrapper for it. For example, the
3760 following project, when @emph{with}ed by your main project, will link with the
3761 third-party library @code{liba.a}:
3765 for Externally_Built use "true";
3766 for Source_Files use ();
3767 for Library_Dir use "lib";
3768 for Library_Name use "a";
3769 for Library_Kind use "static";
3773 This is an alternative to the use of @code{pragma Linker_Options}. It is
3774 especially interesting in the context of systems with several interdependent
3775 static libraries where finding a proper linker order is not easy and best be
3776 left to the tools having visibility over project dependence information.
3778 In order to use an Ada library manually, you need to make sure that this
3779 library is on both your source and object path
3780 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}
3781 and @ref{8c,,Search Paths for gnatbind}). Furthermore, when the objects are grouped
3782 in an archive or a shared library, you need to specify the desired
3783 library at link time.
3785 For example, you can use the library @code{mylib} installed in
3786 @code{/dir/my_lib_src} and @code{/dir/my_lib_obj} with the following commands:
3789 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\
3793 This can be expressed more simply:
3799 when the following conditions are met:
3805 @code{/dir/my_lib_src} has been added by the user to the environment
3807 @geindex ADA_INCLUDE_PATH
3808 @geindex environment variable; ADA_INCLUDE_PATH
3809 @code{ADA_INCLUDE_PATH}, or by the administrator to the file
3810 @code{ada_source_path}
3813 @code{/dir/my_lib_obj} has been added by the user to the environment
3815 @geindex ADA_OBJECTS_PATH
3816 @geindex environment variable; ADA_OBJECTS_PATH
3817 @code{ADA_OBJECTS_PATH}, or by the administrator to the file
3818 @code{ada_object_path}
3821 a pragma @code{Linker_Options} has been added to one of the sources.
3825 pragma Linker_Options ("-lmy_lib");
3829 Note that you may also load a library dynamically at
3830 run time given its filename, as illustrated in the GNAT @code{plugins} example
3831 in the directory @code{share/examples/gnat/plugins} within the GNAT
3834 @node Stand-alone Ada Libraries,Rebuilding the GNAT Run-Time Library,General Ada Libraries,GNAT and Libraries
3835 @anchor{gnat_ugn/the_gnat_compilation_model stand-alone-ada-libraries}@anchor{82}@anchor{gnat_ugn/the_gnat_compilation_model id41}@anchor{8d}
3836 @subsection Stand-alone Ada Libraries
3839 @geindex Stand-alone libraries
3842 * Introduction to Stand-alone Libraries::
3843 * Building a Stand-alone Library::
3844 * Creating a Stand-alone Library to be used in a non-Ada context::
3845 * Restrictions in Stand-alone Libraries::
3849 @node Introduction to Stand-alone Libraries,Building a Stand-alone Library,,Stand-alone Ada Libraries
3850 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-stand-alone-libraries}@anchor{8e}@anchor{gnat_ugn/the_gnat_compilation_model id42}@anchor{8f}
3851 @subsubsection Introduction to Stand-alone Libraries
3854 A Stand-alone Library (abbreviated 'SAL') is a library that contains the
3856 elaborate the Ada units that are included in the library. In contrast with
3857 an ordinary library, which consists of all sources, objects and @code{ALI}
3859 library, a SAL may specify a restricted subset of compilation units
3860 to serve as a library interface. In this case, the fully
3861 self-sufficient set of files will normally consist of an objects
3862 archive, the sources of interface units' specs, and the @code{ALI}
3863 files of interface units.
3864 If an interface spec contains a generic unit or an inlined subprogram,
3866 source must also be provided; if the units that must be provided in the source
3867 form depend on other units, the source and @code{ALI} files of those must
3870 The main purpose of a SAL is to minimize the recompilation overhead of client
3871 applications when a new version of the library is installed. Specifically,
3872 if the interface sources have not changed, client applications do not need to
3873 be recompiled. If, furthermore, a SAL is provided in the shared form and its
3874 version, controlled by @code{Library_Version} attribute, is not changed,
3875 then the clients do not need to be relinked.
3877 SALs also allow the library providers to minimize the amount of library source
3878 text exposed to the clients. Such 'information hiding' might be useful or
3879 necessary for various reasons.
3881 Stand-alone libraries are also well suited to be used in an executable whose
3882 main routine is not written in Ada.
3884 @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
3885 @anchor{gnat_ugn/the_gnat_compilation_model id43}@anchor{90}@anchor{gnat_ugn/the_gnat_compilation_model building-a-stand-alone-library}@anchor{91}
3886 @subsubsection Building a Stand-alone Library
3889 GNAT's Project facility provides a simple way of building and installing
3890 stand-alone libraries; see the @emph{Stand-alone Library Projects} section
3891 in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}.
3892 To be a Stand-alone Library Project, in addition to the two attributes
3893 that make a project a Library Project (@code{Library_Name} and
3894 @code{Library_Dir}; see the @emph{Library Projects} section in the
3895 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}),
3896 the attribute @code{Library_Interface} must be defined. For example:
3899 for Library_Dir use "lib_dir";
3900 for Library_Name use "dummy";
3901 for Library_Interface use ("int1", "int1.child");
3904 Attribute @code{Library_Interface} has a non-empty string list value,
3905 each string in the list designating a unit contained in an immediate source
3906 of the project file.
3908 When a Stand-alone Library is built, first the binder is invoked to build
3909 a package whose name depends on the library name
3910 (@code{b~dummy.ads/b} in the example above).
3911 This binder-generated package includes initialization and
3912 finalization procedures whose
3913 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
3915 above). The object corresponding to this package is included in the library.
3917 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
3918 calling of these procedures if a static SAL is built, or if a shared SAL
3920 with the project-level attribute @code{Library_Auto_Init} set to
3923 For a Stand-Alone Library, only the @code{ALI} files of the Interface Units
3924 (those that are listed in attribute @code{Library_Interface}) are copied to
3925 the Library Directory. As a consequence, only the Interface Units may be
3926 imported from Ada units outside of the library. If other units are imported,
3927 the binding phase will fail.
3929 It is also possible to build an encapsulated library where not only
3930 the code to elaborate and finalize the library is embedded but also
3931 ensuring that the library is linked only against static
3932 libraries. So an encapsulated library only depends on system
3933 libraries, all other code, including the GNAT runtime, is embedded. To
3934 build an encapsulated library the attribute
3935 @code{Library_Standalone} must be set to @code{encapsulated}:
3938 for Library_Dir use "lib_dir";
3939 for Library_Name use "dummy";
3940 for Library_Kind use "dynamic";
3941 for Library_Interface use ("int1", "int1.child");
3942 for Library_Standalone use "encapsulated";
3945 The default value for this attribute is @code{standard} in which case
3946 a stand-alone library is built.
3948 The attribute @code{Library_Src_Dir} may be specified for a
3949 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
3950 single string value. Its value must be the path (absolute or relative to the
3951 project directory) of an existing directory. This directory cannot be the
3952 object directory or one of the source directories, but it can be the same as
3953 the library directory. The sources of the Interface
3954 Units of the library that are needed by an Ada client of the library will be
3955 copied to the designated directory, called the Interface Copy directory.
3956 These sources include the specs of the Interface Units, but they may also
3957 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
3958 are used, or when there is a generic unit in the spec. Before the sources
3959 are copied to the Interface Copy directory, an attempt is made to delete all
3960 files in the Interface Copy directory.
3962 Building stand-alone libraries by hand is somewhat tedious, but for those
3963 occasions when it is necessary here are the steps that you need to perform:
3969 Compile all library sources.
3972 Invoke the binder with the switch @code{-n} (No Ada main program),
3973 with all the @code{ALI} files of the interfaces, and
3974 with the switch @code{-L} to give specific names to the @code{init}
3975 and @code{final} procedures. For example:
3978 $ gnatbind -n int1.ali int2.ali -Lsal1
3982 Compile the binder generated file:
3989 Link the dynamic library with all the necessary object files,
3990 indicating to the linker the names of the @code{init} (and possibly
3991 @code{final}) procedures for automatic initialization (and finalization).
3992 The built library should be placed in a directory different from
3993 the object directory.
3996 Copy the @code{ALI} files of the interface to the library directory,
3997 add in this copy an indication that it is an interface to a SAL
3998 (i.e., add a word @code{SL} on the line in the @code{ALI} file that starts
3999 with letter 'P') and make the modified copy of the @code{ALI} file
4003 Using SALs is not different from using other libraries
4004 (see @ref{8a,,Using a library}).
4006 @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
4007 @anchor{gnat_ugn/the_gnat_compilation_model creating-a-stand-alone-library-to-be-used-in-a-non-ada-context}@anchor{92}@anchor{gnat_ugn/the_gnat_compilation_model id44}@anchor{93}
4008 @subsubsection Creating a Stand-alone Library to be used in a non-Ada context
4011 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
4014 The only extra step required is to ensure that library interface subprograms
4015 are compatible with the main program, by means of @code{pragma Export}
4016 or @code{pragma Convention}.
4018 Here is an example of simple library interface for use with C main program:
4021 package My_Package is
4023 procedure Do_Something;
4024 pragma Export (C, Do_Something, "do_something");
4026 procedure Do_Something_Else;
4027 pragma Export (C, Do_Something_Else, "do_something_else");
4032 On the foreign language side, you must provide a 'foreign' view of the
4033 library interface; remember that it should contain elaboration routines in
4034 addition to interface subprograms.
4036 The example below shows the content of @code{mylib_interface.h} (note
4037 that there is no rule for the naming of this file, any name can be used)
4040 /* the library elaboration procedure */
4041 extern void mylibinit (void);
4043 /* the library finalization procedure */
4044 extern void mylibfinal (void);
4046 /* the interface exported by the library */
4047 extern void do_something (void);
4048 extern void do_something_else (void);
4051 Libraries built as explained above can be used from any program, provided
4052 that the elaboration procedures (named @code{mylibinit} in the previous
4053 example) are called before the library services are used. Any number of
4054 libraries can be used simultaneously, as long as the elaboration
4055 procedure of each library is called.
4057 Below is an example of a C program that uses the @code{mylib} library.
4060 #include "mylib_interface.h"
4065 /* First, elaborate the library before using it */
4068 /* Main program, using the library exported entities */
4070 do_something_else ();
4072 /* Library finalization at the end of the program */
4078 Note that invoking any library finalization procedure generated by
4079 @code{gnatbind} shuts down the Ada run-time environment.
4081 finalization of all Ada libraries must be performed at the end of the program.
4082 No call to these libraries or to the Ada run-time library should be made
4083 after the finalization phase.
4085 Note also that special care must be taken with multi-tasks
4086 applications. The initialization and finalization routines are not
4087 protected against concurrent access. If such requirement is needed it
4088 must be ensured at the application level using a specific operating
4089 system services like a mutex or a critical-section.
4091 @node Restrictions in Stand-alone Libraries,,Creating a Stand-alone Library to be used in a non-Ada context,Stand-alone Ada Libraries
4092 @anchor{gnat_ugn/the_gnat_compilation_model id45}@anchor{94}@anchor{gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries}@anchor{95}
4093 @subsubsection Restrictions in Stand-alone Libraries
4096 The pragmas listed below should be used with caution inside libraries,
4097 as they can create incompatibilities with other Ada libraries:
4103 pragma @code{Locking_Policy}
4106 pragma @code{Partition_Elaboration_Policy}
4109 pragma @code{Queuing_Policy}
4112 pragma @code{Task_Dispatching_Policy}
4115 pragma @code{Unreserve_All_Interrupts}
4118 When using a library that contains such pragmas, the user must make sure
4119 that all libraries use the same pragmas with the same values. Otherwise,
4120 @code{Program_Error} will
4121 be raised during the elaboration of the conflicting
4122 libraries. The usage of these pragmas and its consequences for the user
4123 should therefore be well documented.
4125 Similarly, the traceback in the exception occurrence mechanism should be
4126 enabled or disabled in a consistent manner across all libraries.
4127 Otherwise, Program_Error will be raised during the elaboration of the
4128 conflicting libraries.
4130 If the @code{Version} or @code{Body_Version}
4131 attributes are used inside a library, then you need to
4132 perform a @code{gnatbind} step that specifies all @code{ALI} files in all
4133 libraries, so that version identifiers can be properly computed.
4134 In practice these attributes are rarely used, so this is unlikely
4135 to be a consideration.
4137 @node Rebuilding the GNAT Run-Time Library,,Stand-alone Ada Libraries,GNAT and Libraries
4138 @anchor{gnat_ugn/the_gnat_compilation_model id46}@anchor{96}@anchor{gnat_ugn/the_gnat_compilation_model rebuilding-the-gnat-run-time-library}@anchor{97}
4139 @subsection Rebuilding the GNAT Run-Time Library
4142 @geindex GNAT Run-Time Library
4145 @geindex Building the GNAT Run-Time Library
4147 @geindex Rebuilding the GNAT Run-Time Library
4149 @geindex Run-Time Library
4152 It may be useful to recompile the GNAT library in various contexts, the
4153 most important one being the use of partition-wide configuration pragmas
4154 such as @code{Normalize_Scalars}. A special Makefile called
4155 @code{Makefile.adalib} is provided to that effect and can be found in
4156 the directory containing the GNAT library. The location of this
4157 directory depends on the way the GNAT environment has been installed and can
4158 be determined by means of the command:
4164 The last entry in the object search path usually contains the
4165 gnat library. This Makefile contains its own documentation and in
4166 particular the set of instructions needed to rebuild a new library and
4169 @geindex Conditional compilation
4171 @node Conditional Compilation,Mixed Language Programming,GNAT and Libraries,The GNAT Compilation Model
4172 @anchor{gnat_ugn/the_gnat_compilation_model id47}@anchor{98}@anchor{gnat_ugn/the_gnat_compilation_model conditional-compilation}@anchor{16}
4173 @section Conditional Compilation
4176 This section presents some guidelines for modeling conditional compilation in Ada and describes the
4177 gnatprep preprocessor utility.
4179 @geindex Conditional compilation
4182 * Modeling Conditional Compilation in Ada::
4183 * Preprocessing with gnatprep::
4184 * Integrated Preprocessing::
4188 @node Modeling Conditional Compilation in Ada,Preprocessing with gnatprep,,Conditional Compilation
4189 @anchor{gnat_ugn/the_gnat_compilation_model modeling-conditional-compilation-in-ada}@anchor{99}@anchor{gnat_ugn/the_gnat_compilation_model id48}@anchor{9a}
4190 @subsection Modeling Conditional Compilation in Ada
4193 It is often necessary to arrange for a single source program
4194 to serve multiple purposes, where it is compiled in different
4195 ways to achieve these different goals. Some examples of the
4196 need for this feature are
4202 Adapting a program to a different hardware environment
4205 Adapting a program to a different target architecture
4208 Turning debugging features on and off
4211 Arranging for a program to compile with different compilers
4214 In C, or C++, the typical approach would be to use the preprocessor
4215 that is defined as part of the language. The Ada language does not
4216 contain such a feature. This is not an oversight, but rather a very
4217 deliberate design decision, based on the experience that overuse of
4218 the preprocessing features in C and C++ can result in programs that
4219 are extremely difficult to maintain. For example, if we have ten
4220 switches that can be on or off, this means that there are a thousand
4221 separate programs, any one of which might not even be syntactically
4222 correct, and even if syntactically correct, the resulting program
4223 might not work correctly. Testing all combinations can quickly become
4226 Nevertheless, the need to tailor programs certainly exists, and in
4227 this section we will discuss how this can
4228 be achieved using Ada in general, and GNAT in particular.
4231 * Use of Boolean Constants::
4232 * Debugging - A Special Case::
4233 * Conditionalizing Declarations::
4234 * Use of Alternative Implementations::
4239 @node Use of Boolean Constants,Debugging - A Special Case,,Modeling Conditional Compilation in Ada
4240 @anchor{gnat_ugn/the_gnat_compilation_model id49}@anchor{9b}@anchor{gnat_ugn/the_gnat_compilation_model use-of-boolean-constants}@anchor{9c}
4241 @subsubsection Use of Boolean Constants
4244 In the case where the difference is simply which code
4245 sequence is executed, the cleanest solution is to use Boolean
4246 constants to control which code is executed.
4249 FP_Initialize_Required : constant Boolean := True;
4251 if FP_Initialize_Required then
4256 Not only will the code inside the @code{if} statement not be executed if
4257 the constant Boolean is @code{False}, but it will also be completely
4258 deleted from the program.
4259 However, the code is only deleted after the @code{if} statement
4260 has been checked for syntactic and semantic correctness.
4261 (In contrast, with preprocessors the code is deleted before the
4262 compiler ever gets to see it, so it is not checked until the switch
4265 @geindex Preprocessors (contrasted with conditional compilation)
4267 Typically the Boolean constants will be in a separate package,
4272 FP_Initialize_Required : constant Boolean := True;
4273 Reset_Available : constant Boolean := False;
4278 The @code{Config} package exists in multiple forms for the various targets,
4279 with an appropriate script selecting the version of @code{Config} needed.
4280 Then any other unit requiring conditional compilation can do a @emph{with}
4281 of @code{Config} to make the constants visible.
4283 @node Debugging - A Special Case,Conditionalizing Declarations,Use of Boolean Constants,Modeling Conditional Compilation in Ada
4284 @anchor{gnat_ugn/the_gnat_compilation_model debugging-a-special-case}@anchor{9d}@anchor{gnat_ugn/the_gnat_compilation_model id50}@anchor{9e}
4285 @subsubsection Debugging - A Special Case
4288 A common use of conditional code is to execute statements (for example
4289 dynamic checks, or output of intermediate results) under control of a
4290 debug switch, so that the debugging behavior can be turned on and off.
4291 This can be done using a Boolean constant to control whether the code
4296 Put_Line ("got to the first stage!");
4303 if Debugging and then Temperature > 999.0 then
4304 raise Temperature_Crazy;
4308 @geindex pragma Assert
4310 Since this is a common case, there are special features to deal with
4311 this in a convenient manner. For the case of tests, Ada 2005 has added
4312 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
4313 on the @code{Assert} pragma that has always been available in GNAT, so this
4314 feature may be used with GNAT even if you are not using Ada 2005 features.
4315 The use of pragma @code{Assert} is described in the
4316 @cite{GNAT_Reference_Manual}, but as an
4317 example, the last test could be written:
4320 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
4326 pragma Assert (Temperature <= 999.0);
4329 In both cases, if assertions are active and the temperature is excessive,
4330 the exception @code{Assert_Failure} will be raised, with the given string in
4331 the first case or a string indicating the location of the pragma in the second
4332 case used as the exception message.
4334 @geindex pragma Assertion_Policy
4336 You can turn assertions on and off by using the @code{Assertion_Policy}
4339 @geindex -gnata switch
4341 This is an Ada 2005 pragma which is implemented in all modes by
4342 GNAT. Alternatively, you can use the @code{-gnata} switch
4343 to enable assertions from the command line, which applies to
4344 all versions of Ada.
4346 @geindex pragma Debug
4348 For the example above with the @code{Put_Line}, the GNAT-specific pragma
4349 @code{Debug} can be used:
4352 pragma Debug (Put_Line ("got to the first stage!"));
4355 If debug pragmas are enabled, the argument, which must be of the form of
4356 a procedure call, is executed (in this case, @code{Put_Line} will be called).
4357 Only one call can be present, but of course a special debugging procedure
4358 containing any code you like can be included in the program and then
4359 called in a pragma @code{Debug} argument as needed.
4361 One advantage of pragma @code{Debug} over the @code{if Debugging then}
4362 construct is that pragma @code{Debug} can appear in declarative contexts,
4363 such as at the very beginning of a procedure, before local declarations have
4366 @geindex pragma Debug_Policy
4368 Debug pragmas are enabled using either the @code{-gnata} switch that also
4369 controls assertions, or with a separate Debug_Policy pragma.
4371 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
4372 in Ada 95 and Ada 83 programs as well), and is analogous to
4373 pragma @code{Assertion_Policy} to control assertions.
4375 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
4376 and thus they can appear in @code{gnat.adc} if you are not using a
4377 project file, or in the file designated to contain configuration pragmas
4379 They then apply to all subsequent compilations. In practice the use of
4380 the @code{-gnata} switch is often the most convenient method of controlling
4381 the status of these pragmas.
4383 Note that a pragma is not a statement, so in contexts where a statement
4384 sequence is required, you can't just write a pragma on its own. You have
4385 to add a @code{null} statement.
4389 ... -- some statements
4391 pragma Assert (Num_Cases < 10);
4396 @node Conditionalizing Declarations,Use of Alternative Implementations,Debugging - A Special Case,Modeling Conditional Compilation in Ada
4397 @anchor{gnat_ugn/the_gnat_compilation_model conditionalizing-declarations}@anchor{9f}@anchor{gnat_ugn/the_gnat_compilation_model id51}@anchor{a0}
4398 @subsubsection Conditionalizing Declarations
4401 In some cases it may be necessary to conditionalize declarations to meet
4402 different requirements. For example we might want a bit string whose length
4403 is set to meet some hardware message requirement.
4405 This may be possible using declare blocks controlled
4406 by conditional constants:
4409 if Small_Machine then
4411 X : Bit_String (1 .. 10);
4417 X : Large_Bit_String (1 .. 1000);
4424 Note that in this approach, both declarations are analyzed by the
4425 compiler so this can only be used where both declarations are legal,
4426 even though one of them will not be used.
4428 Another approach is to define integer constants, e.g., @code{Bits_Per_Word},
4429 or Boolean constants, e.g., @code{Little_Endian}, and then write declarations
4430 that are parameterized by these constants. For example
4434 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
4438 If @code{Bits_Per_Word} is set to 32, this generates either
4442 Field1 at 0 range 0 .. 32;
4446 for the big endian case, or
4450 Field1 at 0 range 10 .. 32;
4454 for the little endian case. Since a powerful subset of Ada expression
4455 notation is usable for creating static constants, clever use of this
4456 feature can often solve quite difficult problems in conditionalizing
4457 compilation (note incidentally that in Ada 95, the little endian
4458 constant was introduced as @code{System.Default_Bit_Order}, so you do not
4459 need to define this one yourself).
4461 @node Use of Alternative Implementations,Preprocessing,Conditionalizing Declarations,Modeling Conditional Compilation in Ada
4462 @anchor{gnat_ugn/the_gnat_compilation_model use-of-alternative-implementations}@anchor{a1}@anchor{gnat_ugn/the_gnat_compilation_model id52}@anchor{a2}
4463 @subsubsection Use of Alternative Implementations
4466 In some cases, none of the approaches described above are adequate. This
4467 can occur for example if the set of declarations required is radically
4468 different for two different configurations.
4470 In this situation, the official Ada way of dealing with conditionalizing
4471 such code is to write separate units for the different cases. As long as
4472 this does not result in excessive duplication of code, this can be done
4473 without creating maintenance problems. The approach is to share common
4474 code as far as possible, and then isolate the code and declarations
4475 that are different. Subunits are often a convenient method for breaking
4476 out a piece of a unit that is to be conditionalized, with separate files
4477 for different versions of the subunit for different targets, where the
4478 build script selects the right one to give to the compiler.
4480 @geindex Subunits (and conditional compilation)
4482 As an example, consider a situation where a new feature in Ada 2005
4483 allows something to be done in a really nice way. But your code must be able
4484 to compile with an Ada 95 compiler. Conceptually you want to say:
4488 ... neat Ada 2005 code
4490 ... not quite as neat Ada 95 code
4494 where @code{Ada_2005} is a Boolean constant.
4496 But this won't work when @code{Ada_2005} is set to @code{False},
4497 since the @code{then} clause will be illegal for an Ada 95 compiler.
4498 (Recall that although such unreachable code would eventually be deleted
4499 by the compiler, it still needs to be legal. If it uses features
4500 introduced in Ada 2005, it will be illegal in Ada 95.)
4505 procedure Insert is separate;
4508 Then we have two files for the subunit @code{Insert}, with the two sets of
4510 If the package containing this is called @code{File_Queries}, then we might
4517 @code{file_queries-insert-2005.adb}
4520 @code{file_queries-insert-95.adb}
4523 and the build script renames the appropriate file to @code{file_queries-insert.adb} and then carries out the compilation.
4525 This can also be done with project files' naming schemes. For example:
4528 for body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
4531 Note also that with project files it is desirable to use a different extension
4532 than @code{ads} / @code{adb} for alternative versions. Otherwise a naming
4533 conflict may arise through another commonly used feature: to declare as part
4534 of the project a set of directories containing all the sources obeying the
4535 default naming scheme.
4537 The use of alternative units is certainly feasible in all situations,
4538 and for example the Ada part of the GNAT run-time is conditionalized
4539 based on the target architecture using this approach. As a specific example,
4540 consider the implementation of the AST feature in VMS. There is one
4541 spec: @code{s-asthan.ads} which is the same for all architectures, and three
4551 @item @code{s-asthan.adb}
4553 used for all non-VMS operating systems
4560 @item @code{s-asthan-vms-alpha.adb}
4562 used for VMS on the Alpha
4569 @item @code{s-asthan-vms-ia64.adb}
4571 used for VMS on the ia64
4575 The dummy version @code{s-asthan.adb} simply raises exceptions noting that
4576 this operating system feature is not available, and the two remaining
4577 versions interface with the corresponding versions of VMS to provide
4578 VMS-compatible AST handling. The GNAT build script knows the architecture
4579 and operating system, and automatically selects the right version,
4580 renaming it if necessary to @code{s-asthan.adb} before the run-time build.
4582 Another style for arranging alternative implementations is through Ada's
4583 access-to-subprogram facility.
4584 In case some functionality is to be conditionally included,
4585 you can declare an access-to-procedure variable @code{Ref} that is initialized
4586 to designate a 'do nothing' procedure, and then invoke @code{Ref.all}
4588 In some library package, set @code{Ref} to @code{Proc'Access} for some
4589 procedure @code{Proc} that performs the relevant processing.
4590 The initialization only occurs if the library package is included in the
4592 The same idea can also be implemented using tagged types and dispatching
4595 @node Preprocessing,,Use of Alternative Implementations,Modeling Conditional Compilation in Ada
4596 @anchor{gnat_ugn/the_gnat_compilation_model preprocessing}@anchor{a3}@anchor{gnat_ugn/the_gnat_compilation_model id53}@anchor{a4}
4597 @subsubsection Preprocessing
4600 @geindex Preprocessing
4602 Although it is quite possible to conditionalize code without the use of
4603 C-style preprocessing, as described earlier in this section, it is
4604 nevertheless convenient in some cases to use the C approach. Moreover,
4605 older Ada compilers have often provided some preprocessing capability,
4606 so legacy code may depend on this approach, even though it is not
4609 To accommodate such use, GNAT provides a preprocessor (modeled to a large
4610 extent on the various preprocessors that have been used
4611 with legacy code on other compilers, to enable easier transition).
4615 The preprocessor may be used in two separate modes. It can be used quite
4616 separately from the compiler, to generate a separate output source file
4617 that is then fed to the compiler as a separate step. This is the
4618 @code{gnatprep} utility, whose use is fully described in
4619 @ref{17,,Preprocessing with gnatprep}.
4621 The preprocessing language allows such constructs as
4624 #if DEBUG or else (PRIORITY > 4) then
4625 sequence of declarations
4627 completely different sequence of declarations
4631 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
4632 defined either on the command line or in a separate file.
4634 The other way of running the preprocessor is even closer to the C style and
4635 often more convenient. In this approach the preprocessing is integrated into
4636 the compilation process. The compiler is given the preprocessor input which
4637 includes @code{#if} lines etc, and then the compiler carries out the
4638 preprocessing internally and processes the resulting output.
4639 For more details on this approach, see @ref{18,,Integrated Preprocessing}.
4641 @node Preprocessing with gnatprep,Integrated Preprocessing,Modeling Conditional Compilation in Ada,Conditional Compilation
4642 @anchor{gnat_ugn/the_gnat_compilation_model id54}@anchor{a5}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-with-gnatprep}@anchor{17}
4643 @subsection Preprocessing with @code{gnatprep}
4648 @geindex Preprocessing (gnatprep)
4650 This section discusses how to use GNAT's @code{gnatprep} utility for simple
4652 Although designed for use with GNAT, @code{gnatprep} does not depend on any
4653 special GNAT features.
4654 For further discussion of conditional compilation in general, see
4655 @ref{16,,Conditional Compilation}.
4658 * Preprocessing Symbols::
4660 * Switches for gnatprep::
4661 * Form of Definitions File::
4662 * Form of Input Text for gnatprep::
4666 @node Preprocessing Symbols,Using gnatprep,,Preprocessing with gnatprep
4667 @anchor{gnat_ugn/the_gnat_compilation_model id55}@anchor{a6}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-symbols}@anchor{a7}
4668 @subsubsection Preprocessing Symbols
4671 Preprocessing symbols are defined in @emph{definition files} and referenced in the
4672 sources to be preprocessed. A preprocessing symbol is an identifier, following
4673 normal Ada (case-insensitive) rules for its syntax, with the restriction that
4674 all characters need to be in the ASCII set (no accented letters).
4676 @node Using gnatprep,Switches for gnatprep,Preprocessing Symbols,Preprocessing with gnatprep
4677 @anchor{gnat_ugn/the_gnat_compilation_model using-gnatprep}@anchor{a8}@anchor{gnat_ugn/the_gnat_compilation_model id56}@anchor{a9}
4678 @subsubsection Using @code{gnatprep}
4681 To call @code{gnatprep} use:
4684 $ gnatprep [ switches ] infile outfile [ deffile ]
4696 @item @emph{switches}
4698 is an optional sequence of switches as described in the next section.
4707 is the full name of the input file, which is an Ada source
4708 file containing preprocessor directives.
4715 @item @emph{outfile}
4717 is the full name of the output file, which is an Ada source
4718 in standard Ada form. When used with GNAT, this file name will
4719 normally have an @code{ads} or @code{adb} suffix.
4726 @item @code{deffile}
4728 is the full name of a text file containing definitions of
4729 preprocessing symbols to be referenced by the preprocessor. This argument is
4730 optional, and can be replaced by the use of the @code{-D} switch.
4734 @node Switches for gnatprep,Form of Definitions File,Using gnatprep,Preprocessing with gnatprep
4735 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatprep}@anchor{aa}@anchor{gnat_ugn/the_gnat_compilation_model id57}@anchor{ab}
4736 @subsubsection Switches for @code{gnatprep}
4739 @geindex --version (gnatprep)
4744 @item @code{--version}
4746 Display Copyright and version, then exit disregarding all other options.
4749 @geindex --help (gnatprep)
4756 If @code{--version} was not used, display usage and then exit disregarding
4760 @geindex -b (gnatprep)
4767 Causes both preprocessor lines and the lines deleted by
4768 preprocessing to be replaced by blank lines in the output source file,
4769 preserving line numbers in the output file.
4772 @geindex -c (gnatprep)
4779 Causes both preprocessor lines and the lines deleted
4780 by preprocessing to be retained in the output source as comments marked
4781 with the special string @code{"--! "}. This option will result in line numbers
4782 being preserved in the output file.
4785 @geindex -C (gnatprep)
4792 Causes comments to be scanned. Normally comments are ignored by gnatprep.
4793 If this option is specified, then comments are scanned and any $symbol
4794 substitutions performed as in program text. This is particularly useful
4795 when structured comments are used (e.g., for programs written in a
4796 pre-2014 version of the SPARK Ada subset). Note that this switch is not
4797 available when doing integrated preprocessing (it would be useless in
4798 this context since comments are ignored by the compiler in any case).
4801 @geindex -D (gnatprep)
4806 @item @code{-D@emph{symbol}[=@emph{value}]}
4808 Defines a new preprocessing symbol with the specified value. If no value is given
4809 on the command line, then symbol is considered to be @code{True}. This switch
4810 can be used in place of a definition file.
4813 @geindex -r (gnatprep)
4820 Causes a @code{Source_Reference} pragma to be generated that
4821 references the original input file, so that error messages will use
4822 the file name of this original file. The use of this switch implies
4823 that preprocessor lines are not to be removed from the file, so its
4824 use will force @code{-b} mode if @code{-c}
4825 has not been specified explicitly.
4827 Note that if the file to be preprocessed contains multiple units, then
4828 it will be necessary to @code{gnatchop} the output file from
4829 @code{gnatprep}. If a @code{Source_Reference} pragma is present
4830 in the preprocessed file, it will be respected by
4832 so that the final chopped files will correctly refer to the original
4833 input source file for @code{gnatprep}.
4836 @geindex -s (gnatprep)
4843 Causes a sorted list of symbol names and values to be
4844 listed on the standard output file.
4847 @geindex -T (gnatprep)
4854 Use LF as line terminators when writing files. By default the line terminator
4855 of the host (LF under unix, CR/LF under Windows) is used.
4858 @geindex -u (gnatprep)
4865 Causes undefined symbols to be treated as having the value FALSE in the context
4866 of a preprocessor test. In the absence of this option, an undefined symbol in
4867 a @code{#if} or @code{#elsif} test will be treated as an error.
4870 @geindex -v (gnatprep)
4877 Verbose mode: generates more output about work done.
4880 Note: if neither @code{-b} nor @code{-c} is present,
4881 then preprocessor lines and
4882 deleted lines are completely removed from the output, unless -r is
4883 specified, in which case -b is assumed.
4885 @node Form of Definitions File,Form of Input Text for gnatprep,Switches for gnatprep,Preprocessing with gnatprep
4886 @anchor{gnat_ugn/the_gnat_compilation_model form-of-definitions-file}@anchor{ac}@anchor{gnat_ugn/the_gnat_compilation_model id58}@anchor{ad}
4887 @subsubsection Form of Definitions File
4890 The definitions file contains lines of the form:
4896 where @code{symbol} is a preprocessing symbol, and @code{value} is one of the following:
4902 Empty, corresponding to a null substitution,
4905 A string literal using normal Ada syntax, or
4908 Any sequence of characters from the set @{letters, digits, period, underline@}.
4911 Comment lines may also appear in the definitions file, starting with
4912 the usual @code{--},
4913 and comments may be added to the definitions lines.
4915 @node Form of Input Text for gnatprep,,Form of Definitions File,Preprocessing with gnatprep
4916 @anchor{gnat_ugn/the_gnat_compilation_model id59}@anchor{ae}@anchor{gnat_ugn/the_gnat_compilation_model form-of-input-text-for-gnatprep}@anchor{af}
4917 @subsubsection Form of Input Text for @code{gnatprep}
4920 The input text may contain preprocessor conditional inclusion lines,
4921 as well as general symbol substitution sequences.
4923 The preprocessor conditional inclusion commands have the form:
4926 #if <expression> [then]
4928 #elsif <expression> [then]
4930 #elsif <expression> [then]
4938 In this example, <expression> is defined by the following grammar:
4941 <expression> ::= <symbol>
4942 <expression> ::= <symbol> = "<value>"
4943 <expression> ::= <symbol> = <symbol>
4944 <expression> ::= <symbol> = <integer>
4945 <expression> ::= <symbol> > <integer>
4946 <expression> ::= <symbol> >= <integer>
4947 <expression> ::= <symbol> < <integer>
4948 <expression> ::= <symbol> <= <integer>
4949 <expression> ::= <symbol> 'Defined
4950 <expression> ::= not <expression>
4951 <expression> ::= <expression> and <expression>
4952 <expression> ::= <expression> or <expression>
4953 <expression> ::= <expression> and then <expression>
4954 <expression> ::= <expression> or else <expression>
4955 <expression> ::= ( <expression> )
4958 Note the following restriction: it is not allowed to have "and" or "or"
4959 following "not" in the same expression without parentheses. For example, this
4966 This can be expressed instead as one of the following forms:
4973 For the first test (<expression> ::= <symbol>) the symbol must have
4974 either the value true or false, that is to say the right-hand of the
4975 symbol definition must be one of the (case-insensitive) literals
4976 @code{True} or @code{False}. If the value is true, then the
4977 corresponding lines are included, and if the value is false, they are
4980 When comparing a symbol to an integer, the integer is any non negative
4981 literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or
4982 2#11#. The symbol value must also be a non negative integer. Integer values
4983 in the range 0 .. 2**31-1 are supported.
4985 The test (<expression> ::= <symbol>'Defined) is true only if
4986 the symbol has been defined in the definition file or by a @code{-D}
4987 switch on the command line. Otherwise, the test is false.
4989 The equality tests are case insensitive, as are all the preprocessor lines.
4991 If the symbol referenced is not defined in the symbol definitions file,
4992 then the effect depends on whether or not switch @code{-u}
4993 is specified. If so, then the symbol is treated as if it had the value
4994 false and the test fails. If this switch is not specified, then
4995 it is an error to reference an undefined symbol. It is also an error to
4996 reference a symbol that is defined with a value other than @code{True}
4999 The use of the @code{not} operator inverts the sense of this logical test.
5000 The @code{not} operator cannot be combined with the @code{or} or @code{and}
5001 operators, without parentheses. For example, "if not X or Y then" is not
5002 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
5004 The @code{then} keyword is optional as shown
5006 The @code{#} must be the first non-blank character on a line, but
5007 otherwise the format is free form. Spaces or tabs may appear between
5008 the @code{#} and the keyword. The keywords and the symbols are case
5009 insensitive as in normal Ada code. Comments may be used on a
5010 preprocessor line, but other than that, no other tokens may appear on a
5011 preprocessor line. Any number of @code{elsif} clauses can be present,
5012 including none at all. The @code{else} is optional, as in Ada.
5014 The @code{#} marking the start of a preprocessor line must be the first
5015 non-blank character on the line, i.e., it must be preceded only by
5016 spaces or horizontal tabs.
5018 Symbol substitution outside of preprocessor lines is obtained by using
5025 anywhere within a source line, except in a comment or within a
5026 string literal. The identifier
5027 following the @code{$} must match one of the symbols defined in the symbol
5028 definition file, and the result is to substitute the value of the
5029 symbol in place of @code{$symbol} in the output file.
5031 Note that although the substitution of strings within a string literal
5032 is not possible, it is possible to have a symbol whose defined value is
5033 a string literal. So instead of setting XYZ to @code{hello} and writing:
5036 Header : String := "$XYZ";
5039 you should set XYZ to @code{"hello"} and write:
5042 Header : String := $XYZ;
5045 and then the substitution will occur as desired.
5047 @node Integrated Preprocessing,,Preprocessing with gnatprep,Conditional Compilation
5048 @anchor{gnat_ugn/the_gnat_compilation_model id60}@anchor{b0}@anchor{gnat_ugn/the_gnat_compilation_model integrated-preprocessing}@anchor{18}
5049 @subsection Integrated Preprocessing
5052 As noted above, a file to be preprocessed consists of Ada source code
5053 in which preprocessing lines have been inserted. However,
5054 instead of using @code{gnatprep} to explicitly preprocess a file as a separate
5055 step before compilation, you can carry out the preprocessing implicitly
5056 as part of compilation. Such @emph{integrated preprocessing}, which is the common
5057 style with C, is performed when either or both of the following switches
5058 are passed to the compiler:
5066 @code{-gnatep}, which specifies the @emph{preprocessor data file}.
5067 This file dictates how the source files will be preprocessed (e.g., which
5068 symbol definition files apply to which sources).
5071 @code{-gnateD}, which defines values for preprocessing symbols.
5075 Integrated preprocessing applies only to Ada source files, it is
5076 not available for configuration pragma files.
5078 With integrated preprocessing, the output from the preprocessor is not,
5079 by default, written to any external file. Instead it is passed
5080 internally to the compiler. To preserve the result of
5081 preprocessing in a file, either run @code{gnatprep}
5082 in standalone mode or else supply the @code{-gnateG} switch
5083 (described below) to the compiler.
5085 When using project files:
5093 the builder switch @code{-x} should be used if any Ada source is
5094 compiled with @code{gnatep=}, so that the compiler finds the
5095 @emph{preprocessor data file}.
5098 the preprocessing data file and the symbol definition files should be
5099 located in the source directories of the project.
5103 Note that the @code{gnatmake} switch @code{-m} will almost
5104 always trigger recompilation for sources that are preprocessed,
5105 because @code{gnatmake} cannot compute the checksum of the source after
5108 The actual preprocessing function is described in detail in
5109 @ref{17,,Preprocessing with gnatprep}. This section explains the switches
5110 that relate to integrated preprocessing.
5112 @geindex -gnatep (gcc)
5117 @item @code{-gnatep=@emph{preprocessor_data_file}}
5119 This switch specifies the file name (without directory
5120 information) of the preprocessor data file. Either place this file
5121 in one of the source directories, or, when using project
5122 files, reference the project file's directory via the
5123 @code{project_name'Project_Dir} project attribute; e.g:
5130 for Switches ("Ada") use
5131 ("-gnatep=" & Prj'Project_Dir & "prep.def");
5137 A preprocessor data file is a text file that contains @emph{preprocessor
5138 control lines}. A preprocessor control line directs the preprocessing of
5139 either a particular source file, or, analogous to @code{others} in Ada,
5140 all sources not specified elsewhere in the preprocessor data file.
5141 A preprocessor control line
5142 can optionally identify a @emph{definition file} that assigns values to
5143 preprocessor symbols, as well as a list of switches that relate to
5145 Empty lines and comments (using Ada syntax) are also permitted, with no
5148 Here's an example of a preprocessor data file:
5153 "toto.adb" "prep.def" -u
5154 -- Preprocess toto.adb, using definition file prep.def
5155 -- Undefined symbols are treated as False
5158 -- Preprocess all other sources without using a definition file
5159 -- Suppressed lined are commented
5160 -- Symbol VERSION has the value V101
5162 "tata.adb" "prep2.def" -s
5163 -- Preprocess tata.adb, using definition file prep2.def
5164 -- List all symbols with their values
5168 A preprocessor control line has the following syntax:
5173 <preprocessor_control_line> ::=
5174 <preprocessor_input> [ <definition_file_name> ] @{ <switch> @}
5176 <preprocessor_input> ::= <source_file_name> | '*'
5178 <definition_file_name> ::= <string_literal>
5180 <source_file_name> := <string_literal>
5182 <switch> := (See below for list)
5186 Thus each preprocessor control line starts with either a literal string or
5193 A literal string is the file name (without directory information) of the source
5194 file that will be input to the preprocessor.
5197 The character '*' is a wild-card indicator; the additional parameters on the line
5198 indicate the preprocessing for all the sources
5199 that are not specified explicitly on other lines (the order of the lines is not
5203 It is an error to have two lines with the same file name or two
5204 lines starting with the character '*'.
5206 After the file name or '*', an optional literal string specifies the name of
5207 the definition file to be used for preprocessing
5208 (@ref{ac,,Form of Definitions File}). The definition files are found by the
5209 compiler in one of the source directories. In some cases, when compiling
5210 a source in a directory other than the current directory, if the definition
5211 file is in the current directory, it may be necessary to add the current
5212 directory as a source directory through the @code{-I} switch; otherwise
5213 the compiler would not find the definition file.
5215 Finally, switches similar to those of @code{gnatprep} may optionally appear:
5222 Causes both preprocessor lines and the lines deleted by
5223 preprocessing to be replaced by blank lines, preserving the line number.
5224 This switch is always implied; however, if specified after @code{-c}
5225 it cancels the effect of @code{-c}.
5229 Causes both preprocessor lines and the lines deleted
5230 by preprocessing to be retained as comments marked
5231 with the special string '@cite{--!}'.
5233 @item @code{-D@emph{symbol}=@emph{new_value}}
5235 Define or redefine @code{symbol} to have @code{new_value} as its value.
5236 The permitted form for @code{symbol} is either an Ada identifier, or any Ada reserved word
5237 aside from @code{if},
5238 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5239 The permitted form for @code{new_value} is a literal string, an Ada identifier or any Ada reserved
5240 word. A symbol declared with this switch replaces a symbol with the
5241 same name defined in a definition file.
5245 Causes a sorted list of symbol names and values to be
5246 listed on the standard output file.
5250 Causes undefined symbols to be treated as having the value @code{FALSE}
5252 of a preprocessor test. In the absence of this option, an undefined symbol in
5253 a @code{#if} or @code{#elsif} test will be treated as an error.
5257 @geindex -gnateD (gcc)
5262 @item @code{-gnateD@emph{symbol}[=@emph{new_value}]}
5264 Define or redefine @code{symbol} to have @code{new_value} as its value. If no value
5265 is supplied, then the value of @code{symbol} is @code{True}.
5266 The form of @code{symbol} is an identifier, following normal Ada (case-insensitive)
5267 rules for its syntax, and @code{new_value} is either an arbitrary string between double
5268 quotes or any sequence (including an empty sequence) of characters from the
5269 set (letters, digits, period, underline).
5270 Ada reserved words may be used as symbols, with the exceptions of @code{if},
5271 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5280 -gnateDFoo=\"Foo-Bar\"
5284 A symbol declared with this switch on the command line replaces a
5285 symbol with the same name either in a definition file or specified with a
5286 switch @code{-D} in the preprocessor data file.
5288 This switch is similar to switch @code{-D} of @code{gnatprep}.
5290 @item @code{-gnateG}
5292 When integrated preprocessing is performed on source file @code{filename.extension},
5293 create or overwrite @code{filename.extension.prep} to contain
5294 the result of the preprocessing.
5295 For example if the source file is @code{foo.adb} then
5296 the output file will be @code{foo.adb.prep}.
5299 @node Mixed Language Programming,GNAT and Other Compilation Models,Conditional Compilation,The GNAT Compilation Model
5300 @anchor{gnat_ugn/the_gnat_compilation_model mixed-language-programming}@anchor{44}@anchor{gnat_ugn/the_gnat_compilation_model id61}@anchor{b1}
5301 @section Mixed Language Programming
5304 @geindex Mixed Language Programming
5306 This section describes how to develop a mixed-language program,
5307 with a focus on combining Ada with C or C++.
5310 * Interfacing to C::
5311 * Calling Conventions::
5312 * Building Mixed Ada and C++ Programs::
5313 * Generating Ada Bindings for C and C++ headers::
5314 * Generating C Headers for Ada Specifications::
5318 @node Interfacing to C,Calling Conventions,,Mixed Language Programming
5319 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-to-c}@anchor{b2}@anchor{gnat_ugn/the_gnat_compilation_model id62}@anchor{b3}
5320 @subsection Interfacing to C
5323 Interfacing Ada with a foreign language such as C involves using
5324 compiler directives to import and/or export entity definitions in each
5325 language -- using @code{extern} statements in C, for instance, and the
5326 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
5327 A full treatment of these topics is provided in Appendix B, section 1
5328 of the Ada Reference Manual.
5330 There are two ways to build a program using GNAT that contains some Ada
5331 sources and some foreign language sources, depending on whether or not
5332 the main subprogram is written in Ada. Here is a source example with
5333 the main subprogram in Ada:
5339 void print_num (int num)
5341 printf ("num is %d.\\n", num);
5349 /* num_from_Ada is declared in my_main.adb */
5350 extern int num_from_Ada;
5354 return num_from_Ada;
5360 procedure My_Main is
5362 -- Declare then export an Integer entity called num_from_Ada
5363 My_Num : Integer := 10;
5364 pragma Export (C, My_Num, "num_from_Ada");
5366 -- Declare an Ada function spec for Get_Num, then use
5367 -- C function get_num for the implementation.
5368 function Get_Num return Integer;
5369 pragma Import (C, Get_Num, "get_num");
5371 -- Declare an Ada procedure spec for Print_Num, then use
5372 -- C function print_num for the implementation.
5373 procedure Print_Num (Num : Integer);
5374 pragma Import (C, Print_Num, "print_num");
5377 Print_Num (Get_Num);
5381 To build this example:
5387 First compile the foreign language files to
5388 generate object files:
5396 Then, compile the Ada units to produce a set of object files and ALI
5400 $ gnatmake -c my_main.adb
5404 Run the Ada binder on the Ada main program:
5407 $ gnatbind my_main.ali
5411 Link the Ada main program, the Ada objects and the other language
5415 $ gnatlink my_main.ali file1.o file2.o
5419 The last three steps can be grouped in a single command:
5422 $ gnatmake my_main.adb -largs file1.o file2.o
5425 @geindex Binder output file
5427 If the main program is in a language other than Ada, then you may have
5428 more than one entry point into the Ada subsystem. You must use a special
5429 binder option to generate callable routines that initialize and
5430 finalize the Ada units (@ref{b4,,Binding with Non-Ada Main Programs}).
5431 Calls to the initialization and finalization routines must be inserted
5432 in the main program, or some other appropriate point in the code. The
5433 call to initialize the Ada units must occur before the first Ada
5434 subprogram is called, and the call to finalize the Ada units must occur
5435 after the last Ada subprogram returns. The binder will place the
5436 initialization and finalization subprograms into the
5437 @code{b~xxx.adb} file where they can be accessed by your C
5438 sources. To illustrate, we have the following example:
5442 extern void adainit (void);
5443 extern void adafinal (void);
5444 extern int add (int, int);
5445 extern int sub (int, int);
5447 int main (int argc, char *argv[])
5453 /* Should print "21 + 7 = 28" */
5454 printf ("%d + %d = %d\\n", a, b, add (a, b));
5456 /* Should print "21 - 7 = 14" */
5457 printf ("%d - %d = %d\\n", a, b, sub (a, b));
5466 function Add (A, B : Integer) return Integer;
5467 pragma Export (C, Add, "add");
5473 package body Unit1 is
5474 function Add (A, B : Integer) return Integer is
5484 function Sub (A, B : Integer) return Integer;
5485 pragma Export (C, Sub, "sub");
5491 package body Unit2 is
5492 function Sub (A, B : Integer) return Integer is
5499 The build procedure for this application is similar to the last
5506 First, compile the foreign language files to generate object files:
5513 Next, compile the Ada units to produce a set of object files and ALI
5517 $ gnatmake -c unit1.adb
5518 $ gnatmake -c unit2.adb
5522 Run the Ada binder on every generated ALI file. Make sure to use the
5523 @code{-n} option to specify a foreign main program:
5526 $ gnatbind -n unit1.ali unit2.ali
5530 Link the Ada main program, the Ada objects and the foreign language
5531 objects. You need only list the last ALI file here:
5534 $ gnatlink unit2.ali main.o -o exec_file
5537 This procedure yields a binary executable called @code{exec_file}.
5540 Depending on the circumstances (for example when your non-Ada main object
5541 does not provide symbol @code{main}), you may also need to instruct the
5542 GNAT linker not to include the standard startup objects by passing the
5543 @code{-nostartfiles} switch to @code{gnatlink}.
5545 @node Calling Conventions,Building Mixed Ada and C++ Programs,Interfacing to C,Mixed Language Programming
5546 @anchor{gnat_ugn/the_gnat_compilation_model calling-conventions}@anchor{b5}@anchor{gnat_ugn/the_gnat_compilation_model id63}@anchor{b6}
5547 @subsection Calling Conventions
5550 @geindex Foreign Languages
5552 @geindex Calling Conventions
5554 GNAT follows standard calling sequence conventions and will thus interface
5555 to any other language that also follows these conventions. The following
5556 Convention identifiers are recognized by GNAT:
5558 @geindex Interfacing to Ada
5560 @geindex Other Ada compilers
5562 @geindex Convention Ada
5569 This indicates that the standard Ada calling sequence will be
5570 used and all Ada data items may be passed without any limitations in the
5571 case where GNAT is used to generate both the caller and callee. It is also
5572 possible to mix GNAT generated code and code generated by another Ada
5573 compiler. In this case, the data types should be restricted to simple
5574 cases, including primitive types. Whether complex data types can be passed
5575 depends on the situation. Probably it is safe to pass simple arrays, such
5576 as arrays of integers or floats. Records may or may not work, depending
5577 on whether both compilers lay them out identically. Complex structures
5578 involving variant records, access parameters, tasks, or protected types,
5579 are unlikely to be able to be passed.
5581 Note that in the case of GNAT running
5582 on a platform that supports HP Ada 83, a higher degree of compatibility
5583 can be guaranteed, and in particular records are laid out in an identical
5584 manner in the two compilers. Note also that if output from two different
5585 compilers is mixed, the program is responsible for dealing with elaboration
5586 issues. Probably the safest approach is to write the main program in the
5587 version of Ada other than GNAT, so that it takes care of its own elaboration
5588 requirements, and then call the GNAT-generated adainit procedure to ensure
5589 elaboration of the GNAT components. Consult the documentation of the other
5590 Ada compiler for further details on elaboration.
5592 However, it is not possible to mix the tasking run time of GNAT and
5593 HP Ada 83, All the tasking operations must either be entirely within
5594 GNAT compiled sections of the program, or entirely within HP Ada 83
5595 compiled sections of the program.
5598 @geindex Interfacing to Assembly
5600 @geindex Convention Assembler
5605 @item @code{Assembler}
5607 Specifies assembler as the convention. In practice this has the
5608 same effect as convention Ada (but is not equivalent in the sense of being
5609 considered the same convention).
5612 @geindex Convention Asm
5621 Equivalent to Assembler.
5623 @geindex Interfacing to COBOL
5625 @geindex Convention COBOL
5635 Data will be passed according to the conventions described
5636 in section B.4 of the Ada Reference Manual.
5641 @geindex Interfacing to C
5643 @geindex Convention C
5650 Data will be passed according to the conventions described
5651 in section B.3 of the Ada Reference Manual.
5653 A note on interfacing to a C 'varargs' function:
5657 @geindex C varargs function
5659 @geindex Interfacing to C varargs function
5661 @geindex varargs function interfaces
5663 In C, @code{varargs} allows a function to take a variable number of
5664 arguments. There is no direct equivalent in this to Ada. One
5665 approach that can be used is to create a C wrapper for each
5666 different profile and then interface to this C wrapper. For
5667 example, to print an @code{int} value using @code{printf},
5668 create a C function @code{printfi} that takes two arguments, a
5669 pointer to a string and an int, and calls @code{printf}.
5670 Then in the Ada program, use pragma @code{Import} to
5671 interface to @code{printfi}.
5673 It may work on some platforms to directly interface to
5674 a @code{varargs} function by providing a specific Ada profile
5675 for a particular call. However, this does not work on
5676 all platforms, since there is no guarantee that the
5677 calling sequence for a two argument normal C function
5678 is the same as for calling a @code{varargs} C function with
5679 the same two arguments.
5683 @geindex Convention Default
5690 @item @code{Default}
5695 @geindex Convention External
5702 @item @code{External}
5709 @geindex Interfacing to C++
5711 @geindex Convention C++
5716 @item @code{C_Plus_Plus} (or @code{CPP})
5718 This stands for C++. For most purposes this is identical to C.
5719 See the separate description of the specialized GNAT pragmas relating to
5720 C++ interfacing for further details.
5725 @geindex Interfacing to Fortran
5727 @geindex Convention Fortran
5732 @item @code{Fortran}
5734 Data will be passed according to the conventions described
5735 in section B.5 of the Ada Reference Manual.
5737 @item @code{Intrinsic}
5739 This applies to an intrinsic operation, as defined in the Ada
5740 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
5741 this means that the body of the subprogram is provided by the compiler itself,
5742 usually by means of an efficient code sequence, and that the user does not
5743 supply an explicit body for it. In an application program, the pragma may
5744 be applied to the following sets of names:
5750 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic.
5751 The corresponding subprogram declaration must have
5752 two formal parameters. The
5753 first one must be a signed integer type or a modular type with a binary
5754 modulus, and the second parameter must be of type Natural.
5755 The return type must be the same as the type of the first argument. The size
5756 of this type can only be 8, 16, 32, or 64.
5759 Binary arithmetic operators: '+', '-', '*', '/'.
5760 The corresponding operator declaration must have parameters and result type
5761 that have the same root numeric type (for example, all three are long_float
5762 types). This simplifies the definition of operations that use type checking
5763 to perform dimensional checks:
5767 type Distance is new Long_Float;
5768 type Time is new Long_Float;
5769 type Velocity is new Long_Float;
5770 function "/" (D : Distance; T : Time)
5772 pragma Import (Intrinsic, "/");
5774 This common idiom is often programmed with a generic definition and an
5775 explicit body. The pragma makes it simpler to introduce such declarations.
5776 It incurs no overhead in compilation time or code size, because it is
5777 implemented as a single machine instruction.
5784 General subprogram entities. This is used to bind an Ada subprogram
5786 a compiler builtin by name with back-ends where such interfaces are
5787 available. A typical example is the set of @code{__builtin} functions
5788 exposed by the GCC back-end, as in the following example:
5791 function builtin_sqrt (F : Float) return Float;
5792 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
5795 Most of the GCC builtins are accessible this way, and as for other
5796 import conventions (e.g. C), it is the user's responsibility to ensure
5797 that the Ada subprogram profile matches the underlying builtin
5804 @geindex Convention Stdcall
5809 @item @code{Stdcall}
5811 This is relevant only to Windows implementations of GNAT,
5812 and specifies that the @code{Stdcall} calling sequence will be used,
5813 as defined by the NT API. Nevertheless, to ease building
5814 cross-platform bindings this convention will be handled as a @code{C} calling
5815 convention on non-Windows platforms.
5820 @geindex Convention DLL
5827 This is equivalent to @code{Stdcall}.
5832 @geindex Convention Win32
5839 This is equivalent to @code{Stdcall}.
5844 @geindex Convention Stubbed
5849 @item @code{Stubbed}
5851 This is a special convention that indicates that the compiler
5852 should provide a stub body that raises @code{Program_Error}.
5855 GNAT additionally provides a useful pragma @code{Convention_Identifier}
5856 that can be used to parameterize conventions and allow additional synonyms
5857 to be specified. For example if you have legacy code in which the convention
5858 identifier Fortran77 was used for Fortran, you can use the configuration
5862 pragma Convention_Identifier (Fortran77, Fortran);
5865 And from now on the identifier Fortran77 may be used as a convention
5866 identifier (for example in an @code{Import} pragma) with the same
5869 @node Building Mixed Ada and C++ Programs,Generating Ada Bindings for C and C++ headers,Calling Conventions,Mixed Language Programming
5870 @anchor{gnat_ugn/the_gnat_compilation_model id64}@anchor{b7}@anchor{gnat_ugn/the_gnat_compilation_model building-mixed-ada-and-c-programs}@anchor{b8}
5871 @subsection Building Mixed Ada and C++ Programs
5874 A programmer inexperienced with mixed-language development may find that
5875 building an application containing both Ada and C++ code can be a
5876 challenge. This section gives a few hints that should make this task easier.
5879 * Interfacing to C++::
5880 * Linking a Mixed C++ & Ada Program::
5881 * A Simple Example::
5882 * Interfacing with C++ constructors::
5883 * Interfacing with C++ at the Class Level::
5887 @node Interfacing to C++,Linking a Mixed C++ & Ada Program,,Building Mixed Ada and C++ Programs
5888 @anchor{gnat_ugn/the_gnat_compilation_model id65}@anchor{b9}@anchor{gnat_ugn/the_gnat_compilation_model id66}@anchor{ba}
5889 @subsubsection Interfacing to C++
5892 GNAT supports interfacing with the G++ compiler (or any C++ compiler
5893 generating code that is compatible with the G++ Application Binary
5894 Interface ---see @indicateurl{http://www.codesourcery.com/archives/cxx-abi}).
5896 Interfacing can be done at 3 levels: simple data, subprograms, and
5897 classes. In the first two cases, GNAT offers a specific @code{Convention C_Plus_Plus}
5898 (or @code{CPP}) that behaves exactly like @code{Convention C}.
5899 Usually, C++ mangles the names of subprograms. To generate proper mangled
5900 names automatically, see @ref{19,,Generating Ada Bindings for C and C++ headers}).
5901 This problem can also be addressed manually in two ways:
5907 by modifying the C++ code in order to force a C convention using
5908 the @code{extern "C"} syntax.
5911 by figuring out the mangled name (using e.g. @code{nm}) and using it as the
5912 Link_Name argument of the pragma import.
5915 Interfacing at the class level can be achieved by using the GNAT specific
5916 pragmas such as @code{CPP_Constructor}. See the @cite{GNAT_Reference_Manual} for additional information.
5918 @node Linking a Mixed C++ & Ada Program,A Simple Example,Interfacing to C++,Building Mixed Ada and C++ Programs
5919 @anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-ada-program}@anchor{bb}@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-and-ada-program}@anchor{bc}
5920 @subsubsection Linking a Mixed C++ & Ada Program
5923 Usually the linker of the C++ development system must be used to link
5924 mixed applications because most C++ systems will resolve elaboration
5925 issues (such as calling constructors on global class instances)
5926 transparently during the link phase. GNAT has been adapted to ease the
5927 use of a foreign linker for the last phase. Three cases can be
5934 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
5935 The C++ linker can simply be called by using the C++ specific driver
5938 Note that if the C++ code uses inline functions, you will need to
5939 compile your C++ code with the @code{-fkeep-inline-functions} switch in
5940 order to provide an existing function implementation that the Ada code can
5944 $ g++ -c -fkeep-inline-functions file1.C
5945 $ g++ -c -fkeep-inline-functions file2.C
5946 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
5950 Using GNAT and G++ from two different GCC installations: If both
5951 compilers are on the :envvar`PATH`, the previous method may be used. It is
5952 important to note that environment variables such as
5953 @geindex C_INCLUDE_PATH
5954 @geindex environment variable; C_INCLUDE_PATH
5955 @code{C_INCLUDE_PATH},
5956 @geindex GCC_EXEC_PREFIX
5957 @geindex environment variable; GCC_EXEC_PREFIX
5958 @code{GCC_EXEC_PREFIX},
5959 @geindex BINUTILS_ROOT
5960 @geindex environment variable; BINUTILS_ROOT
5961 @code{BINUTILS_ROOT}, and
5963 @geindex environment variable; GCC_ROOT
5964 @code{GCC_ROOT} will affect both compilers
5965 at the same time and may make one of the two compilers operate
5966 improperly if set during invocation of the wrong compiler. It is also
5967 very important that the linker uses the proper @code{libgcc.a} GCC
5968 library -- that is, the one from the C++ compiler installation. The
5969 implicit link command as suggested in the @code{gnatmake} command
5970 from the former example can be replaced by an explicit link command with
5971 the full-verbosity option in order to verify which library is used:
5975 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
5978 If there is a problem due to interfering environment variables, it can
5979 be worked around by using an intermediate script. The following example
5980 shows the proper script to use when GNAT has not been installed at its
5981 default location and g++ has been installed at its default location:
5989 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
5993 Using a non-GNU C++ compiler: The commands previously described can be
5994 used to insure that the C++ linker is used. Nonetheless, you need to add
5995 a few more parameters to the link command line, depending on the exception
5998 If the @code{setjmp} / @code{longjmp} exception mechanism is used, only the paths
5999 to the @code{libgcc} libraries are required:
6004 CC $* gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a
6005 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6008 where CC is the name of the non-GNU C++ compiler.
6010 If the "zero cost" exception mechanism is used, and the platform
6011 supports automatic registration of exception tables (e.g., Solaris),
6012 paths to more objects are required:
6017 CC gcc -print-file-name=crtbegin.o $* \\
6018 gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a \\
6019 gcc -print-file-name=crtend.o
6020 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6023 If the "zero cost exception" mechanism is used, and the platform
6024 doesn't support automatic registration of exception tables (e.g., HP-UX
6025 or AIX), the simple approach described above will not work and
6026 a pre-linking phase using GNAT will be necessary.
6029 Another alternative is to use the @code{gprbuild} multi-language builder
6030 which has a large knowledge base and knows how to link Ada and C++ code
6031 together automatically in most cases.
6033 @node A Simple Example,Interfacing with C++ constructors,Linking a Mixed C++ & Ada Program,Building Mixed Ada and C++ Programs
6034 @anchor{gnat_ugn/the_gnat_compilation_model id67}@anchor{bd}@anchor{gnat_ugn/the_gnat_compilation_model a-simple-example}@anchor{be}
6035 @subsubsection A Simple Example
6038 The following example, provided as part of the GNAT examples, shows how
6039 to achieve procedural interfacing between Ada and C++ in both
6040 directions. The C++ class A has two methods. The first method is exported
6041 to Ada by the means of an extern C wrapper function. The second method
6042 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
6043 a limited record with a layout comparable to the C++ class. The Ada
6044 subprogram, in turn, calls the C++ method. So, starting from the C++
6045 main program, the process passes back and forth between the two
6048 Here are the compilation commands:
6051 $ gnatmake -c simple_cpp_interface
6054 $ gnatbind -n simple_cpp_interface
6055 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o
6058 Here are the corresponding sources:
6066 void adainit (void);
6067 void adafinal (void);
6068 void method1 (A *t);
6092 class A : public Origin @{
6094 void method1 (void);
6095 void method2 (int v);
6107 extern "C" @{ void ada_method2 (A *t, int v);@}
6109 void A::method1 (void)
6112 printf ("in A::method1, a_value = %d \\n",a_value);
6115 void A::method2 (int v)
6117 ada_method2 (this, v);
6118 printf ("in A::method2, a_value = %d \\n",a_value);
6124 printf ("in A::A, a_value = %d \\n",a_value);
6129 -- simple_cpp_interface.ads
6131 package Simple_Cpp_Interface is
6134 Vptr : System.Address;
6138 pragma Convention (C, A);
6140 procedure Method1 (This : in out A);
6141 pragma Import (C, Method1);
6143 procedure Ada_Method2 (This : in out A; V : Integer);
6144 pragma Export (C, Ada_Method2);
6146 end Simple_Cpp_Interface;
6150 -- simple_cpp_interface.adb
6151 package body Simple_Cpp_Interface is
6153 procedure Ada_Method2 (This : in out A; V : Integer) is
6159 end Simple_Cpp_Interface;
6162 @node Interfacing with C++ constructors,Interfacing with C++ at the Class Level,A Simple Example,Building Mixed Ada and C++ Programs
6163 @anchor{gnat_ugn/the_gnat_compilation_model id68}@anchor{bf}@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-constructors}@anchor{c0}
6164 @subsubsection Interfacing with C++ constructors
6167 In order to interface with C++ constructors GNAT provides the
6168 @code{pragma CPP_Constructor} (see the @cite{GNAT_Reference_Manual}
6169 for additional information).
6170 In this section we present some common uses of C++ constructors
6171 in mixed-languages programs in GNAT.
6173 Let us assume that we need to interface with the following
6181 virtual int Get_Value ();
6182 Root(); // Default constructor
6183 Root(int v); // 1st non-default constructor
6184 Root(int v, int w); // 2nd non-default constructor
6188 For this purpose we can write the following package spec (further
6189 information on how to build this spec is available in
6190 @ref{c1,,Interfacing with C++ at the Class Level} and
6191 @ref{19,,Generating Ada Bindings for C and C++ headers}).
6194 with Interfaces.C; use Interfaces.C;
6196 type Root is tagged limited record
6200 pragma Import (CPP, Root);
6202 function Get_Value (Obj : Root) return int;
6203 pragma Import (CPP, Get_Value);
6205 function Constructor return Root;
6206 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
6208 function Constructor (v : Integer) return Root;
6209 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
6211 function Constructor (v, w : Integer) return Root;
6212 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
6216 On the Ada side the constructor is represented by a function (whose
6217 name is arbitrary) that returns the classwide type corresponding to
6218 the imported C++ class. Although the constructor is described as a
6219 function, it is typically a procedure with an extra implicit argument
6220 (the object being initialized) at the implementation level. GNAT
6221 issues the appropriate call, whatever it is, to get the object
6222 properly initialized.
6224 Constructors can only appear in the following contexts:
6230 On the right side of an initialization of an object of type @code{T}.
6233 On the right side of an initialization of a record component of type @code{T}.
6236 In an Ada 2005 limited aggregate.
6239 In an Ada 2005 nested limited aggregate.
6242 In an Ada 2005 limited aggregate that initializes an object built in
6243 place by an extended return statement.
6246 In a declaration of an object whose type is a class imported from C++,
6247 either the default C++ constructor is implicitly called by GNAT, or
6248 else the required C++ constructor must be explicitly called in the
6249 expression that initializes the object. For example:
6253 Obj2 : Root := Constructor;
6254 Obj3 : Root := Constructor (v => 10);
6255 Obj4 : Root := Constructor (30, 40);
6258 The first two declarations are equivalent: in both cases the default C++
6259 constructor is invoked (in the former case the call to the constructor is
6260 implicit, and in the latter case the call is explicit in the object
6261 declaration). @code{Obj3} is initialized by the C++ non-default constructor
6262 that takes an integer argument, and @code{Obj4} is initialized by the
6263 non-default C++ constructor that takes two integers.
6265 Let us derive the imported C++ class in the Ada side. For example:
6268 type DT is new Root with record
6269 C_Value : Natural := 2009;
6273 In this case the components DT inherited from the C++ side must be
6274 initialized by a C++ constructor, and the additional Ada components
6275 of type DT are initialized by GNAT. The initialization of such an
6276 object is done either by default, or by means of a function returning
6277 an aggregate of type DT, or by means of an extension aggregate.
6281 Obj6 : DT := Function_Returning_DT (50);
6282 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
6285 The declaration of @code{Obj5} invokes the default constructors: the
6286 C++ default constructor of the parent type takes care of the initialization
6287 of the components inherited from Root, and GNAT takes care of the default
6288 initialization of the additional Ada components of type DT (that is,
6289 @code{C_Value} is initialized to value 2009). The order of invocation of
6290 the constructors is consistent with the order of elaboration required by
6291 Ada and C++. That is, the constructor of the parent type is always called
6292 before the constructor of the derived type.
6294 Let us now consider a record that has components whose type is imported
6295 from C++. For example:
6298 type Rec1 is limited record
6299 Data1 : Root := Constructor (10);
6300 Value : Natural := 1000;
6303 type Rec2 (D : Integer := 20) is limited record
6305 Data2 : Root := Constructor (D, 30);
6309 The initialization of an object of type @code{Rec2} will call the
6310 non-default C++ constructors specified for the imported components.
6317 Using Ada 2005 we can use limited aggregates to initialize an object
6318 invoking C++ constructors that differ from those specified in the type
6319 declarations. For example:
6322 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
6327 The above declaration uses an Ada 2005 limited aggregate to
6328 initialize @code{Obj9}, and the C++ constructor that has two integer
6329 arguments is invoked to initialize the @code{Data1} component instead
6330 of the constructor specified in the declaration of type @code{Rec1}. In
6331 Ada 2005 the box in the aggregate indicates that unspecified components
6332 are initialized using the expression (if any) available in the component
6333 declaration. That is, in this case discriminant @code{D} is initialized
6334 to value @code{20}, @code{Value} is initialized to value 1000, and the
6335 non-default C++ constructor that handles two integers takes care of
6336 initializing component @code{Data2} with values @code{20,30}.
6338 In Ada 2005 we can use the extended return statement to build the Ada
6339 equivalent to C++ non-default constructors. For example:
6342 function Constructor (V : Integer) return Rec2 is
6344 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
6347 -- Further actions required for construction of
6348 -- objects of type Rec2
6354 In this example the extended return statement construct is used to
6355 build in place the returned object whose components are initialized
6356 by means of a limited aggregate. Any further action associated with
6357 the constructor can be placed inside the construct.
6359 @node Interfacing with C++ at the Class Level,,Interfacing with C++ constructors,Building Mixed Ada and C++ Programs
6360 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-at-the-class-level}@anchor{c1}@anchor{gnat_ugn/the_gnat_compilation_model id69}@anchor{c2}
6361 @subsubsection Interfacing with C++ at the Class Level
6364 In this section we demonstrate the GNAT features for interfacing with
6365 C++ by means of an example making use of Ada 2005 abstract interface
6366 types. This example consists of a classification of animals; classes
6367 have been used to model our main classification of animals, and
6368 interfaces provide support for the management of secondary
6369 classifications. We first demonstrate a case in which the types and
6370 constructors are defined on the C++ side and imported from the Ada
6371 side, and latter the reverse case.
6373 The root of our derivation will be the @code{Animal} class, with a
6374 single private attribute (the @code{Age} of the animal), a constructor,
6375 and two public primitives to set and get the value of this attribute.
6380 virtual void Set_Age (int New_Age);
6382 Animal() @{Age_Count = 0;@};
6388 Abstract interface types are defined in C++ by means of classes with pure
6389 virtual functions and no data members. In our example we will use two
6390 interfaces that provide support for the common management of @code{Carnivore}
6391 and @code{Domestic} animals:
6396 virtual int Number_Of_Teeth () = 0;
6401 virtual void Set_Owner (char* Name) = 0;
6405 Using these declarations, we can now say that a @code{Dog} is an animal that is
6406 both Carnivore and Domestic, that is:
6409 class Dog : Animal, Carnivore, Domestic @{
6411 virtual int Number_Of_Teeth ();
6412 virtual void Set_Owner (char* Name);
6414 Dog(); // Constructor
6421 In the following examples we will assume that the previous declarations are
6422 located in a file named @code{animals.h}. The following package demonstrates
6423 how to import these C++ declarations from the Ada side:
6426 with Interfaces.C.Strings; use Interfaces.C.Strings;
6428 type Carnivore is limited interface;
6429 pragma Convention (C_Plus_Plus, Carnivore);
6430 function Number_Of_Teeth (X : Carnivore)
6431 return Natural is abstract;
6433 type Domestic is limited interface;
6434 pragma Convention (C_Plus_Plus, Domestic);
6436 (X : in out Domestic;
6437 Name : Chars_Ptr) is abstract;
6439 type Animal is tagged limited record
6442 pragma Import (C_Plus_Plus, Animal);
6444 procedure Set_Age (X : in out Animal; Age : Integer);
6445 pragma Import (C_Plus_Plus, Set_Age);
6447 function Age (X : Animal) return Integer;
6448 pragma Import (C_Plus_Plus, Age);
6450 function New_Animal return Animal;
6451 pragma CPP_Constructor (New_Animal);
6452 pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev");
6454 type Dog is new Animal and Carnivore and Domestic with record
6455 Tooth_Count : Natural;
6458 pragma Import (C_Plus_Plus, Dog);
6460 function Number_Of_Teeth (A : Dog) return Natural;
6461 pragma Import (C_Plus_Plus, Number_Of_Teeth);
6463 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6464 pragma Import (C_Plus_Plus, Set_Owner);
6466 function New_Dog return Dog;
6467 pragma CPP_Constructor (New_Dog);
6468 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
6472 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
6473 interfacing with these C++ classes is easy. The only requirement is that all
6474 the primitives and components must be declared exactly in the same order in
6477 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
6478 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
6479 the arguments to the called primitives will be the same as for C++. For the
6480 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
6481 to indicate that they have been defined on the C++ side; this is required
6482 because the dispatch table associated with these tagged types will be built
6483 in the C++ side and therefore will not contain the predefined Ada primitives
6484 which Ada would otherwise expect.
6486 As the reader can see there is no need to indicate the C++ mangled names
6487 associated with each subprogram because it is assumed that all the calls to
6488 these primitives will be dispatching calls. The only exception is the
6489 constructor, which must be registered with the compiler by means of
6490 @code{pragma CPP_Constructor} and needs to provide its associated C++
6491 mangled name because the Ada compiler generates direct calls to it.
6493 With the above packages we can now declare objects of type Dog on the Ada side
6494 and dispatch calls to the corresponding subprograms on the C++ side. We can
6495 also extend the tagged type Dog with further fields and primitives, and
6496 override some of its C++ primitives on the Ada side. For example, here we have
6497 a type derivation defined on the Ada side that inherits all the dispatching
6498 primitives of the ancestor from the C++ side.
6501 with Animals; use Animals;
6502 package Vaccinated_Animals is
6503 type Vaccinated_Dog is new Dog with null record;
6504 function Vaccination_Expired (A : Vaccinated_Dog) return Boolean;
6505 end Vaccinated_Animals;
6508 It is important to note that, because of the ABI compatibility, the programmer
6509 does not need to add any further information to indicate either the object
6510 layout or the dispatch table entry associated with each dispatching operation.
6512 Now let us define all the types and constructors on the Ada side and export
6513 them to C++, using the same hierarchy of our previous example:
6516 with Interfaces.C.Strings;
6517 use Interfaces.C.Strings;
6519 type Carnivore is limited interface;
6520 pragma Convention (C_Plus_Plus, Carnivore);
6521 function Number_Of_Teeth (X : Carnivore)
6522 return Natural is abstract;
6524 type Domestic is limited interface;
6525 pragma Convention (C_Plus_Plus, Domestic);
6527 (X : in out Domestic;
6528 Name : Chars_Ptr) is abstract;
6530 type Animal is tagged record
6533 pragma Convention (C_Plus_Plus, Animal);
6535 procedure Set_Age (X : in out Animal; Age : Integer);
6536 pragma Export (C_Plus_Plus, Set_Age);
6538 function Age (X : Animal) return Integer;
6539 pragma Export (C_Plus_Plus, Age);
6541 function New_Animal return Animal'Class;
6542 pragma Export (C_Plus_Plus, New_Animal);
6544 type Dog is new Animal and Carnivore and Domestic with record
6545 Tooth_Count : Natural;
6546 Owner : String (1 .. 30);
6548 pragma Convention (C_Plus_Plus, Dog);
6550 function Number_Of_Teeth (A : Dog) return Natural;
6551 pragma Export (C_Plus_Plus, Number_Of_Teeth);
6553 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6554 pragma Export (C_Plus_Plus, Set_Owner);
6556 function New_Dog return Dog'Class;
6557 pragma Export (C_Plus_Plus, New_Dog);
6561 Compared with our previous example the only differences are the use of
6562 @code{pragma Convention} (instead of @code{pragma Import}), and the use of
6563 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
6564 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
6565 nothing else to be done; as explained above, the only requirement is that all
6566 the primitives and components are declared in exactly the same order.
6568 For completeness, let us see a brief C++ main program that uses the
6569 declarations available in @code{animals.h} (presented in our first example) to
6570 import and use the declarations from the Ada side, properly initializing and
6571 finalizing the Ada run-time system along the way:
6574 #include "animals.h"
6576 using namespace std;
6578 void Check_Carnivore (Carnivore *obj) @{...@}
6579 void Check_Domestic (Domestic *obj) @{...@}
6580 void Check_Animal (Animal *obj) @{...@}
6581 void Check_Dog (Dog *obj) @{...@}
6584 void adainit (void);
6585 void adafinal (void);
6591 Dog *obj = new_dog(); // Ada constructor
6592 Check_Carnivore (obj); // Check secondary DT
6593 Check_Domestic (obj); // Check secondary DT
6594 Check_Animal (obj); // Check primary DT
6595 Check_Dog (obj); // Check primary DT
6600 adainit (); test(); adafinal ();
6605 @node Generating Ada Bindings for C and C++ headers,Generating C Headers for Ada Specifications,Building Mixed Ada and C++ Programs,Mixed Language Programming
6606 @anchor{gnat_ugn/the_gnat_compilation_model id70}@anchor{c3}@anchor{gnat_ugn/the_gnat_compilation_model generating-ada-bindings-for-c-and-c-headers}@anchor{19}
6607 @subsection Generating Ada Bindings for C and C++ headers
6610 @geindex Binding generation (for C and C++ headers)
6612 @geindex C headers (binding generation)
6614 @geindex C++ headers (binding generation)
6616 GNAT includes a binding generator for C and C++ headers which is
6617 intended to do 95% of the tedious work of generating Ada specs from C
6618 or C++ header files.
6620 Note that this capability is not intended to generate 100% correct Ada specs,
6621 and will is some cases require manual adjustments, although it can often
6622 be used out of the box in practice.
6624 Some of the known limitations include:
6630 only very simple character constant macros are translated into Ada
6631 constants. Function macros (macros with arguments) are partially translated
6632 as comments, to be completed manually if needed.
6635 some extensions (e.g. vector types) are not supported
6638 pointers to pointers or complex structures are mapped to System.Address
6641 identifiers with identical name (except casing) will generate compilation
6642 errors (e.g. @code{shm_get} vs @code{SHM_GET}).
6645 The code is generated using Ada 2012 syntax, which makes it easier to interface
6646 with other languages. In most cases you can still use the generated binding
6647 even if your code is compiled using earlier versions of Ada (e.g. @code{-gnat95}).
6650 * Running the Binding Generator::
6651 * Generating Bindings for C++ Headers::
6656 @node Running the Binding Generator,Generating Bindings for C++ Headers,,Generating Ada Bindings for C and C++ headers
6657 @anchor{gnat_ugn/the_gnat_compilation_model id71}@anchor{c4}@anchor{gnat_ugn/the_gnat_compilation_model running-the-binding-generator}@anchor{c5}
6658 @subsubsection Running the Binding Generator
6661 The binding generator is part of the @code{gcc} compiler and can be
6662 invoked via the @code{-fdump-ada-spec} switch, which will generate Ada
6663 spec files for the header files specified on the command line, and all
6664 header files needed by these files transitively. For example:
6667 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
6671 will generate, under GNU/Linux, the following files: @code{time_h.ads},
6672 @code{bits_time_h.ads}, @code{stddef_h.ads}, @code{bits_types_h.ads} which
6673 correspond to the files @code{/usr/include/time.h},
6674 @code{/usr/include/bits/time.h}, etc..., and will then compile these Ada specs
6677 The @code{-C} switch tells @code{gcc} to extract comments from headers,
6678 and will attempt to generate corresponding Ada comments.
6680 If you want to generate a single Ada file and not the transitive closure, you
6681 can use instead the @code{-fdump-ada-spec-slim} switch.
6683 You can optionally specify a parent unit, of which all generated units will
6684 be children, using @code{-fada-spec-parent=@emph{unit}}.
6686 Note that we recommend when possible to use the @emph{g++} driver to
6687 generate bindings, even for most C headers, since this will in general
6688 generate better Ada specs. For generating bindings for C++ headers, it is
6689 mandatory to use the @emph{g++} command, or @emph{gcc -x c++} which
6690 is equivalent in this case. If @emph{g++} cannot work on your C headers
6691 because of incompatibilities between C and C++, then you can fallback to
6694 For an example of better bindings generated from the C++ front-end,
6695 the name of the parameters (when available) are actually ignored by the C
6696 front-end. Consider the following C header:
6699 extern void foo (int variable);
6702 with the C front-end, @code{variable} is ignored, and the above is handled as:
6705 extern void foo (int);
6708 generating a generic:
6711 procedure foo (param1 : int);
6714 with the C++ front-end, the name is available, and we generate:
6717 procedure foo (variable : int);
6720 In some cases, the generated bindings will be more complete or more meaningful
6721 when defining some macros, which you can do via the @code{-D} switch. This
6722 is for example the case with @code{Xlib.h} under GNU/Linux:
6725 $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
6728 The above will generate more complete bindings than a straight call without
6729 the @code{-DXLIB_ILLEGAL_ACCESS} switch.
6731 In other cases, it is not possible to parse a header file in a stand-alone
6732 manner, because other include files need to be included first. In this
6733 case, the solution is to create a small header file including the needed
6734 @code{#include} and possible @code{#define} directives. For example, to
6735 generate Ada bindings for @code{readline/readline.h}, you need to first
6736 include @code{stdio.h}, so you can create a file with the following two
6737 lines in e.g. @code{readline1.h}:
6741 #include <readline/readline.h>
6744 and then generate Ada bindings from this file:
6747 $ g++ -c -fdump-ada-spec readline1.h
6750 @node Generating Bindings for C++ Headers,Switches,Running the Binding Generator,Generating Ada Bindings for C and C++ headers
6751 @anchor{gnat_ugn/the_gnat_compilation_model id72}@anchor{c6}@anchor{gnat_ugn/the_gnat_compilation_model generating-bindings-for-c-headers}@anchor{c7}
6752 @subsubsection Generating Bindings for C++ Headers
6755 Generating bindings for C++ headers is done using the same options, always
6756 with the @emph{g++} compiler. Note that generating Ada spec from C++ headers is a
6757 much more complex job and support for C++ headers is much more limited that
6758 support for C headers. As a result, you will need to modify the resulting
6759 bindings by hand more extensively when using C++ headers.
6761 In this mode, C++ classes will be mapped to Ada tagged types, constructors
6762 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
6763 multiple inheritance of abstract classes will be mapped to Ada interfaces
6764 (see the @emph{Interfacing to C++} section in the @cite{GNAT Reference Manual}
6765 for additional information on interfacing to C++).
6767 For example, given the following C++ header file:
6772 virtual int Number_Of_Teeth () = 0;
6777 virtual void Set_Owner (char* Name) = 0;
6783 virtual void Set_Age (int New_Age);
6786 class Dog : Animal, Carnivore, Domestic @{
6791 virtual int Number_Of_Teeth ();
6792 virtual void Set_Owner (char* Name);
6798 The corresponding Ada code is generated:
6801 package Class_Carnivore is
6802 type Carnivore is limited interface;
6803 pragma Import (CPP, Carnivore);
6805 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
6807 use Class_Carnivore;
6809 package Class_Domestic is
6810 type Domestic is limited interface;
6811 pragma Import (CPP, Domestic);
6814 (this : access Domestic;
6815 Name : Interfaces.C.Strings.chars_ptr) is abstract;
6819 package Class_Animal is
6820 type Animal is tagged limited record
6821 Age_Count : aliased int;
6823 pragma Import (CPP, Animal);
6825 procedure Set_Age (this : access Animal; New_Age : int);
6826 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
6830 package Class_Dog is
6831 type Dog is new Animal and Carnivore and Domestic with record
6832 Tooth_Count : aliased int;
6833 Owner : Interfaces.C.Strings.chars_ptr;
6835 pragma Import (CPP, Dog);
6837 function Number_Of_Teeth (this : access Dog) return int;
6838 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
6841 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
6842 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
6844 function New_Dog return Dog;
6845 pragma CPP_Constructor (New_Dog);
6846 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
6851 @node Switches,,Generating Bindings for C++ Headers,Generating Ada Bindings for C and C++ headers
6852 @anchor{gnat_ugn/the_gnat_compilation_model switches}@anchor{c8}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation}@anchor{c9}
6853 @subsubsection Switches
6856 @geindex -fdump-ada-spec (gcc)
6861 @item @code{-fdump-ada-spec}
6863 Generate Ada spec files for the given header files transitively (including
6864 all header files that these headers depend upon).
6867 @geindex -fdump-ada-spec-slim (gcc)
6872 @item @code{-fdump-ada-spec-slim}
6874 Generate Ada spec files for the header files specified on the command line
6878 @geindex -fada-spec-parent (gcc)
6883 @item @code{-fada-spec-parent=@emph{unit}}
6885 Specifies that all files generated by @code{-fdump-ada-spec} are
6886 to be child units of the specified parent unit.
6896 Extract comments from headers and generate Ada comments in the Ada spec files.
6899 @node Generating C Headers for Ada Specifications,,Generating Ada Bindings for C and C++ headers,Mixed Language Programming
6900 @anchor{gnat_ugn/the_gnat_compilation_model generating-c-headers-for-ada-specifications}@anchor{ca}@anchor{gnat_ugn/the_gnat_compilation_model id73}@anchor{cb}
6901 @subsection Generating C Headers for Ada Specifications
6904 @geindex Binding generation (for Ada specs)
6906 @geindex C headers (binding generation)
6908 GNAT includes a C header generator for Ada specifications which supports
6909 Ada types that have a direct mapping to C types. This includes in particular
6925 Composition of the above types
6928 Constant declarations
6934 Subprogram declarations
6938 * Running the C Header Generator::
6942 @node Running the C Header Generator,,,Generating C Headers for Ada Specifications
6943 @anchor{gnat_ugn/the_gnat_compilation_model running-the-c-header-generator}@anchor{cc}
6944 @subsubsection Running the C Header Generator
6947 The C header generator is part of the GNAT compiler and can be invoked via
6948 the @code{-gnatceg} combination of switches, which will generate a @code{.h}
6949 file corresponding to the given input file (Ada spec or body). Note that
6950 only spec files are processed in any case, so giving a spec or a body file
6951 as input is equivalent. For example:
6954 $ gcc -c -gnatceg pack1.ads
6957 will generate a self-contained file called @code{pack1.h} including
6958 common definitions from the Ada Standard package, followed by the
6959 definitions included in @code{pack1.ads}, as well as all the other units
6960 withed by this file.
6962 For instance, given the following Ada files:
6966 type Int is range 1 .. 10;
6975 Field1, Field2 : Pack2.Int;
6978 Global : Rec := (1, 2);
6980 procedure Proc1 (R : Rec);
6981 procedure Proc2 (R : in out Rec);
6985 The above @code{gcc} command will generate the following @code{pack1.h} file:
6988 /* Standard definitions skipped */
6991 typedef short_short_integer pack2__TintB;
6992 typedef pack2__TintB pack2__int;
6993 #endif /* PACK2_ADS */
6997 typedef struct _pack1__rec @{
7001 extern pack1__rec pack1__global;
7002 extern void pack1__proc1(const pack1__rec r);
7003 extern void pack1__proc2(pack1__rec *r);
7004 #endif /* PACK1_ADS */
7007 You can then @code{include} @code{pack1.h} from a C source file and use the types,
7008 call subprograms, reference objects, and constants.
7010 @node GNAT and Other Compilation Models,Using GNAT Files with External Tools,Mixed Language Programming,The GNAT Compilation Model
7011 @anchor{gnat_ugn/the_gnat_compilation_model id74}@anchor{cd}@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models}@anchor{45}
7012 @section GNAT and Other Compilation Models
7015 This section compares the GNAT model with the approaches taken in
7016 other environents, first the C/C++ model and then the mechanism that
7017 has been used in other Ada systems, in particular those traditionally
7021 * Comparison between GNAT and C/C++ Compilation Models::
7022 * Comparison between GNAT and Conventional Ada Library Models::
7026 @node Comparison between GNAT and C/C++ Compilation Models,Comparison between GNAT and Conventional Ada Library Models,,GNAT and Other Compilation Models
7027 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models}@anchor{ce}@anchor{gnat_ugn/the_gnat_compilation_model id75}@anchor{cf}
7028 @subsection Comparison between GNAT and C/C++ Compilation Models
7031 The GNAT model of compilation is close to the C and C++ models. You can
7032 think of Ada specs as corresponding to header files in C. As in C, you
7033 don't need to compile specs; they are compiled when they are used. The
7034 Ada @emph{with} is similar in effect to the @code{#include} of a C
7037 One notable difference is that, in Ada, you may compile specs separately
7038 to check them for semantic and syntactic accuracy. This is not always
7039 possible with C headers because they are fragments of programs that have
7040 less specific syntactic or semantic rules.
7042 The other major difference is the requirement for running the binder,
7043 which performs two important functions. First, it checks for
7044 consistency. In C or C++, the only defense against assembling
7045 inconsistent programs lies outside the compiler, in a makefile, for
7046 example. The binder satisfies the Ada requirement that it be impossible
7047 to construct an inconsistent program when the compiler is used in normal
7050 @geindex Elaboration order control
7052 The other important function of the binder is to deal with elaboration
7053 issues. There are also elaboration issues in C++ that are handled
7054 automatically. This automatic handling has the advantage of being
7055 simpler to use, but the C++ programmer has no control over elaboration.
7056 Where @code{gnatbind} might complain there was no valid order of
7057 elaboration, a C++ compiler would simply construct a program that
7058 malfunctioned at run time.
7060 @node Comparison between GNAT and Conventional Ada Library Models,,Comparison between GNAT and C/C++ Compilation Models,GNAT and Other Compilation Models
7061 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models}@anchor{d0}@anchor{gnat_ugn/the_gnat_compilation_model id76}@anchor{d1}
7062 @subsection Comparison between GNAT and Conventional Ada Library Models
7065 This section is intended for Ada programmers who have
7066 used an Ada compiler implementing the traditional Ada library
7067 model, as described in the Ada Reference Manual.
7069 @geindex GNAT library
7071 In GNAT, there is no 'library' in the normal sense. Instead, the set of
7072 source files themselves acts as the library. Compiling Ada programs does
7073 not generate any centralized information, but rather an object file and
7074 a ALI file, which are of interest only to the binder and linker.
7075 In a traditional system, the compiler reads information not only from
7076 the source file being compiled, but also from the centralized library.
7077 This means that the effect of a compilation depends on what has been
7078 previously compiled. In particular:
7084 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7085 to the version of the unit most recently compiled into the library.
7088 Inlining is effective only if the necessary body has already been
7089 compiled into the library.
7092 Compiling a unit may obsolete other units in the library.
7095 In GNAT, compiling one unit never affects the compilation of any other
7096 units because the compiler reads only source files. Only changes to source
7097 files can affect the results of a compilation. In particular:
7103 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7104 to the source version of the unit that is currently accessible to the
7110 Inlining requires the appropriate source files for the package or
7111 subprogram bodies to be available to the compiler. Inlining is always
7112 effective, independent of the order in which units are compiled.
7115 Compiling a unit never affects any other compilations. The editing of
7116 sources may cause previous compilations to be out of date if they
7117 depended on the source file being modified.
7120 The most important result of these differences is that order of compilation
7121 is never significant in GNAT. There is no situation in which one is
7122 required to do one compilation before another. What shows up as order of
7123 compilation requirements in the traditional Ada library becomes, in
7124 GNAT, simple source dependencies; in other words, there is only a set
7125 of rules saying what source files must be present when a file is
7128 @node Using GNAT Files with External Tools,,GNAT and Other Compilation Models,The GNAT Compilation Model
7129 @anchor{gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools}@anchor{1a}@anchor{gnat_ugn/the_gnat_compilation_model id77}@anchor{d2}
7130 @section Using GNAT Files with External Tools
7133 This section explains how files that are produced by GNAT may be
7134 used with tools designed for other languages.
7137 * Using Other Utility Programs with GNAT::
7138 * The External Symbol Naming Scheme of GNAT::
7142 @node Using Other Utility Programs with GNAT,The External Symbol Naming Scheme of GNAT,,Using GNAT Files with External Tools
7143 @anchor{gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat}@anchor{d3}@anchor{gnat_ugn/the_gnat_compilation_model id78}@anchor{d4}
7144 @subsection Using Other Utility Programs with GNAT
7147 The object files generated by GNAT are in standard system format and in
7148 particular the debugging information uses this format. This means
7149 programs generated by GNAT can be used with existing utilities that
7150 depend on these formats.
7152 In general, any utility program that works with C will also often work with
7153 Ada programs generated by GNAT. This includes software utilities such as
7154 gprof (a profiling program), gdb (the FSF debugger), and utilities such
7157 @node The External Symbol Naming Scheme of GNAT,,Using Other Utility Programs with GNAT,Using GNAT Files with External Tools
7158 @anchor{gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat}@anchor{d5}@anchor{gnat_ugn/the_gnat_compilation_model id79}@anchor{d6}
7159 @subsection The External Symbol Naming Scheme of GNAT
7162 In order to interpret the output from GNAT, when using tools that are
7163 originally intended for use with other languages, it is useful to
7164 understand the conventions used to generate link names from the Ada
7167 All link names are in all lowercase letters. With the exception of library
7168 procedure names, the mechanism used is simply to use the full expanded
7169 Ada name with dots replaced by double underscores. For example, suppose
7170 we have the following package spec:
7178 @geindex pragma Export
7180 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
7181 the corresponding link name is @code{qrs__mn}.
7182 Of course if a @code{pragma Export} is used this may be overridden:
7187 pragma Export (Var1, C, External_Name => "var1_name");
7189 pragma Export (Var2, C, Link_Name => "var2_link_name");
7193 In this case, the link name for @code{Var1} is whatever link name the
7194 C compiler would assign for the C function @code{var1_name}. This typically
7195 would be either @code{var1_name} or @code{_var1_name}, depending on operating
7196 system conventions, but other possibilities exist. The link name for
7197 @code{Var2} is @code{var2_link_name}, and this is not operating system
7200 One exception occurs for library level procedures. A potential ambiguity
7201 arises between the required name @code{_main} for the C main program,
7202 and the name we would otherwise assign to an Ada library level procedure
7203 called @code{Main} (which might well not be the main program).
7205 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
7206 names. So if we have a library level procedure such as:
7209 procedure Hello (S : String);
7212 the external name of this procedure will be @code{_ada_hello}.
7214 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
7216 @node Building Executable Programs with GNAT,GNAT Utility Programs,The GNAT Compilation Model,Top
7217 @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{d7}@anchor{gnat_ugn/building_executable_programs_with_gnat id1}@anchor{d8}
7218 @chapter Building Executable Programs with GNAT
7221 This chapter describes first the gnatmake tool
7222 (@ref{1b,,Building with gnatmake}),
7223 which automatically determines the set of sources
7224 needed by an Ada compilation unit and executes the necessary
7225 (re)compilations, binding and linking.
7226 It also explains how to use each tool individually: the
7227 compiler (gcc, see @ref{1c,,Compiling with gcc}),
7228 binder (gnatbind, see @ref{1d,,Binding with gnatbind}),
7229 and linker (gnatlink, see @ref{1e,,Linking with gnatlink})
7230 to build executable programs.
7231 Finally, this chapter provides examples of
7232 how to make use of the general GNU make mechanism
7233 in a GNAT context (see @ref{1f,,Using the GNU make Utility}).
7237 * Building with gnatmake::
7238 * Compiling with gcc::
7239 * Compiler Switches::
7241 * Binding with gnatbind::
7242 * Linking with gnatlink::
7243 * Using the GNU make Utility::
7247 @node Building with gnatmake,Compiling with gcc,,Building Executable Programs with GNAT
7248 @anchor{gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake}@anchor{1b}@anchor{gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake}@anchor{d9}
7249 @section Building with @code{gnatmake}
7254 A typical development cycle when working on an Ada program consists of
7255 the following steps:
7261 Edit some sources to fix bugs;
7267 Compile all sources affected;
7270 Rebind and relink; and
7276 @geindex Dependency rules (compilation)
7278 The third step in particular can be tricky, because not only do the modified
7279 files have to be compiled, but any files depending on these files must also be
7280 recompiled. The dependency rules in Ada can be quite complex, especially
7281 in the presence of overloading, @code{use} clauses, generics and inlined
7284 @code{gnatmake} automatically takes care of the third and fourth steps
7285 of this process. It determines which sources need to be compiled,
7286 compiles them, and binds and links the resulting object files.
7288 Unlike some other Ada make programs, the dependencies are always
7289 accurately recomputed from the new sources. The source based approach of
7290 the GNAT compilation model makes this possible. This means that if
7291 changes to the source program cause corresponding changes in
7292 dependencies, they will always be tracked exactly correctly by
7295 Note that for advanced forms of project structure, we recommend creating
7296 a project file as explained in the @emph{GNAT_Project_Manager} chapter in the
7297 @emph{GPRbuild User's Guide}, and using the
7298 @code{gprbuild} tool which supports building with project files and works similarly
7302 * Running gnatmake::
7303 * Switches for gnatmake::
7304 * Mode Switches for gnatmake::
7305 * Notes on the Command Line::
7306 * How gnatmake Works::
7307 * Examples of gnatmake Usage::
7311 @node Running gnatmake,Switches for gnatmake,,Building with gnatmake
7312 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatmake}@anchor{da}@anchor{gnat_ugn/building_executable_programs_with_gnat id2}@anchor{db}
7313 @subsection Running @code{gnatmake}
7316 The usual form of the @code{gnatmake} command is
7319 $ gnatmake [<switches>] <file_name> [<file_names>] [<mode_switches>]
7322 The only required argument is one @code{file_name}, which specifies
7323 a compilation unit that is a main program. Several @code{file_names} can be
7324 specified: this will result in several executables being built.
7325 If @code{switches} are present, they can be placed before the first
7326 @code{file_name}, between @code{file_names} or after the last @code{file_name}.
7327 If @code{mode_switches} are present, they must always be placed after
7328 the last @code{file_name} and all @code{switches}.
7330 If you are using standard file extensions (@code{.adb} and
7331 @code{.ads}), then the
7332 extension may be omitted from the @code{file_name} arguments. However, if
7333 you are using non-standard extensions, then it is required that the
7334 extension be given. A relative or absolute directory path can be
7335 specified in a @code{file_name}, in which case, the input source file will
7336 be searched for in the specified directory only. Otherwise, the input
7337 source file will first be searched in the directory where
7338 @code{gnatmake} was invoked and if it is not found, it will be search on
7339 the source path of the compiler as described in
7340 @ref{89,,Search Paths and the Run-Time Library (RTL)}.
7342 All @code{gnatmake} output (except when you specify @code{-M}) is sent to
7343 @code{stderr}. The output produced by the
7344 @code{-M} switch is sent to @code{stdout}.
7346 @node Switches for gnatmake,Mode Switches for gnatmake,Running gnatmake,Building with gnatmake
7347 @anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake}@anchor{dc}@anchor{gnat_ugn/building_executable_programs_with_gnat id3}@anchor{dd}
7348 @subsection Switches for @code{gnatmake}
7351 You may specify any of the following switches to @code{gnatmake}:
7353 @geindex --version (gnatmake)
7358 @item @code{--version}
7360 Display Copyright and version, then exit disregarding all other options.
7363 @geindex --help (gnatmake)
7370 If @code{--version} was not used, display usage, then exit disregarding
7374 @geindex --GCC=compiler_name (gnatmake)
7379 @item @code{--GCC=@emph{compiler_name}}
7381 Program used for compiling. The default is @code{gcc}. You need to use
7382 quotes around @code{compiler_name} if @code{compiler_name} contains
7383 spaces or other separator characters.
7384 As an example @code{--GCC="foo -x -y"}
7385 will instruct @code{gnatmake} to use @code{foo -x -y} as your
7386 compiler. A limitation of this syntax is that the name and path name of
7387 the executable itself must not include any embedded spaces. Note that
7388 switch @code{-c} is always inserted after your command name. Thus in the
7389 above example the compiler command that will be used by @code{gnatmake}
7390 will be @code{foo -c -x -y}. If several @code{--GCC=compiler_name} are
7391 used, only the last @code{compiler_name} is taken into account. However,
7392 all the additional switches are also taken into account. Thus,
7393 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7394 @code{--GCC="bar -x -y -z -t"}.
7397 @geindex --GNATBIND=binder_name (gnatmake)
7402 @item @code{--GNATBIND=@emph{binder_name}}
7404 Program used for binding. The default is @code{gnatbind}. You need to
7405 use quotes around @code{binder_name} if @code{binder_name} contains spaces
7406 or other separator characters.
7407 As an example @code{--GNATBIND="bar -x -y"}
7408 will instruct @code{gnatmake} to use @code{bar -x -y} as your
7409 binder. Binder switches that are normally appended by @code{gnatmake}
7410 to @code{gnatbind} are now appended to the end of @code{bar -x -y}.
7411 A limitation of this syntax is that the name and path name of the executable
7412 itself must not include any embedded spaces.
7415 @geindex --GNATLINK=linker_name (gnatmake)
7420 @item @code{--GNATLINK=@emph{linker_name}}
7422 Program used for linking. The default is @code{gnatlink}. You need to
7423 use quotes around @code{linker_name} if @code{linker_name} contains spaces
7424 or other separator characters.
7425 As an example @code{--GNATLINK="lan -x -y"}
7426 will instruct @code{gnatmake} to use @code{lan -x -y} as your
7427 linker. Linker switches that are normally appended by @code{gnatmake} to
7428 @code{gnatlink} are now appended to the end of @code{lan -x -y}.
7429 A limitation of this syntax is that the name and path name of the executable
7430 itself must not include any embedded spaces.
7432 @item @code{--create-map-file}
7434 When linking an executable, create a map file. The name of the map file
7435 has the same name as the executable with extension ".map".
7437 @item @code{--create-map-file=@emph{mapfile}}
7439 When linking an executable, create a map file with the specified name.
7442 @geindex --create-missing-dirs (gnatmake)
7447 @item @code{--create-missing-dirs}
7449 When using project files (@code{-P@emph{project}}), automatically create
7450 missing object directories, library directories and exec
7453 @item @code{--single-compile-per-obj-dir}
7455 Disallow simultaneous compilations in the same object directory when
7456 project files are used.
7458 @item @code{--subdirs=@emph{subdir}}
7460 Actual object directory of each project file is the subdirectory subdir of the
7461 object directory specified or defaulted in the project file.
7463 @item @code{--unchecked-shared-lib-imports}
7465 By default, shared library projects are not allowed to import static library
7466 projects. When this switch is used on the command line, this restriction is
7469 @item @code{--source-info=@emph{source info file}}
7471 Specify a source info file. This switch is active only when project files
7472 are used. If the source info file is specified as a relative path, then it is
7473 relative to the object directory of the main project. If the source info file
7474 does not exist, then after the Project Manager has successfully parsed and
7475 processed the project files and found the sources, it creates the source info
7476 file. If the source info file already exists and can be read successfully,
7477 then the Project Manager will get all the needed information about the sources
7478 from the source info file and will not look for them. This reduces the time
7479 to process the project files, especially when looking for sources that take a
7480 long time. If the source info file exists but cannot be parsed successfully,
7481 the Project Manager will attempt to recreate it. If the Project Manager fails
7482 to create the source info file, a message is issued, but gnatmake does not
7483 fail. @code{gnatmake} "trusts" the source info file. This means that
7484 if the source files have changed (addition, deletion, moving to a different
7485 source directory), then the source info file need to be deleted and recreated.
7488 @geindex -a (gnatmake)
7495 Consider all files in the make process, even the GNAT internal system
7496 files (for example, the predefined Ada library files), as well as any
7497 locked files. Locked files are files whose ALI file is write-protected.
7499 @code{gnatmake} does not check these files,
7500 because the assumption is that the GNAT internal files are properly up
7501 to date, and also that any write protected ALI files have been properly
7502 installed. Note that if there is an installation problem, such that one
7503 of these files is not up to date, it will be properly caught by the
7505 You may have to specify this switch if you are working on GNAT
7506 itself. The switch @code{-a} is also useful
7507 in conjunction with @code{-f}
7508 if you need to recompile an entire application,
7509 including run-time files, using special configuration pragmas,
7510 such as a @code{Normalize_Scalars} pragma.
7513 @code{gnatmake -a} compiles all GNAT
7515 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
7518 @geindex -b (gnatmake)
7525 Bind only. Can be combined with @code{-c} to do
7526 compilation and binding, but no link.
7527 Can be combined with @code{-l}
7528 to do binding and linking. When not combined with
7530 all the units in the closure of the main program must have been previously
7531 compiled and must be up to date. The root unit specified by @code{file_name}
7532 may be given without extension, with the source extension or, if no GNAT
7533 Project File is specified, with the ALI file extension.
7536 @geindex -c (gnatmake)
7543 Compile only. Do not perform binding, except when @code{-b}
7544 is also specified. Do not perform linking, except if both
7546 @code{-l} are also specified.
7547 If the root unit specified by @code{file_name} is not a main unit, this is the
7548 default. Otherwise @code{gnatmake} will attempt binding and linking
7549 unless all objects are up to date and the executable is more recent than
7553 @geindex -C (gnatmake)
7560 Use a temporary mapping file. A mapping file is a way to communicate
7561 to the compiler two mappings: from unit names to file names (without
7562 any directory information) and from file names to path names (with
7563 full directory information). A mapping file can make the compiler's
7564 file searches faster, especially if there are many source directories,
7565 or the sources are read over a slow network connection. If
7566 @code{-P} is used, a mapping file is always used, so
7567 @code{-C} is unnecessary; in this case the mapping file
7568 is initially populated based on the project file. If
7569 @code{-C} is used without
7571 the mapping file is initially empty. Each invocation of the compiler
7572 will add any newly accessed sources to the mapping file.
7575 @geindex -C= (gnatmake)
7580 @item @code{-C=@emph{file}}
7582 Use a specific mapping file. The file, specified as a path name (absolute or
7583 relative) by this switch, should already exist, otherwise the switch is
7584 ineffective. The specified mapping file will be communicated to the compiler.
7585 This switch is not compatible with a project file
7586 (-P`file`) or with multiple compiling processes
7587 (-jnnn, when nnn is greater than 1).
7590 @geindex -d (gnatmake)
7597 Display progress for each source, up to date or not, as a single line:
7600 completed x out of y (zz%)
7603 If the file needs to be compiled this is displayed after the invocation of
7604 the compiler. These lines are displayed even in quiet output mode.
7607 @geindex -D (gnatmake)
7612 @item @code{-D @emph{dir}}
7614 Put all object files and ALI file in directory @code{dir}.
7615 If the @code{-D} switch is not used, all object files
7616 and ALI files go in the current working directory.
7618 This switch cannot be used when using a project file.
7621 @geindex -eI (gnatmake)
7626 @item @code{-eI@emph{nnn}}
7628 Indicates that the main source is a multi-unit source and the rank of the unit
7629 in the source file is nnn. nnn needs to be a positive number and a valid
7630 index in the source. This switch cannot be used when @code{gnatmake} is
7631 invoked for several mains.
7634 @geindex -eL (gnatmake)
7636 @geindex symbolic links
7643 Follow all symbolic links when processing project files.
7644 This should be used if your project uses symbolic links for files or
7645 directories, but is not needed in other cases.
7647 @geindex naming scheme
7649 This also assumes that no directory matches the naming scheme for files (for
7650 instance that you do not have a directory called "sources.ads" when using the
7651 default GNAT naming scheme).
7653 When you do not have to use this switch (i.e., by default), gnatmake is able to
7654 save a lot of system calls (several per source file and object file), which
7655 can result in a significant speed up to load and manipulate a project file,
7656 especially when using source files from a remote system.
7659 @geindex -eS (gnatmake)
7666 Output the commands for the compiler, the binder and the linker
7668 instead of standard error.
7671 @geindex -f (gnatmake)
7678 Force recompilations. Recompile all sources, even though some object
7679 files may be up to date, but don't recompile predefined or GNAT internal
7680 files or locked files (files with a write-protected ALI file),
7681 unless the @code{-a} switch is also specified.
7684 @geindex -F (gnatmake)
7691 When using project files, if some errors or warnings are detected during
7692 parsing and verbose mode is not in effect (no use of switch
7693 -v), then error lines start with the full path name of the project
7694 file, rather than its simple file name.
7697 @geindex -g (gnatmake)
7704 Enable debugging. This switch is simply passed to the compiler and to the
7708 @geindex -i (gnatmake)
7715 In normal mode, @code{gnatmake} compiles all object files and ALI files
7716 into the current directory. If the @code{-i} switch is used,
7717 then instead object files and ALI files that already exist are overwritten
7718 in place. This means that once a large project is organized into separate
7719 directories in the desired manner, then @code{gnatmake} will automatically
7720 maintain and update this organization. If no ALI files are found on the
7721 Ada object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)}),
7722 the new object and ALI files are created in the
7723 directory containing the source being compiled. If another organization
7724 is desired, where objects and sources are kept in different directories,
7725 a useful technique is to create dummy ALI files in the desired directories.
7726 When detecting such a dummy file, @code{gnatmake} will be forced to
7727 recompile the corresponding source file, and it will be put the resulting
7728 object and ALI files in the directory where it found the dummy file.
7731 @geindex -j (gnatmake)
7733 @geindex Parallel make
7738 @item @code{-j@emph{n}}
7740 Use @code{n} processes to carry out the (re)compilations. On a multiprocessor
7741 machine compilations will occur in parallel. If @code{n} is 0, then the
7742 maximum number of parallel compilations is the number of core processors
7743 on the platform. In the event of compilation errors, messages from various
7744 compilations might get interspersed (but @code{gnatmake} will give you the
7745 full ordered list of failing compiles at the end). If this is problematic,
7746 rerun the make process with n set to 1 to get a clean list of messages.
7749 @geindex -k (gnatmake)
7756 Keep going. Continue as much as possible after a compilation error. To
7757 ease the programmer's task in case of compilation errors, the list of
7758 sources for which the compile fails is given when @code{gnatmake}
7761 If @code{gnatmake} is invoked with several @code{file_names} and with this
7762 switch, if there are compilation errors when building an executable,
7763 @code{gnatmake} will not attempt to build the following executables.
7766 @geindex -l (gnatmake)
7773 Link only. Can be combined with @code{-b} to binding
7774 and linking. Linking will not be performed if combined with
7776 but not with @code{-b}.
7777 When not combined with @code{-b}
7778 all the units in the closure of the main program must have been previously
7779 compiled and must be up to date, and the main program needs to have been bound.
7780 The root unit specified by @code{file_name}
7781 may be given without extension, with the source extension or, if no GNAT
7782 Project File is specified, with the ALI file extension.
7785 @geindex -m (gnatmake)
7792 Specify that the minimum necessary amount of recompilations
7793 be performed. In this mode @code{gnatmake} ignores time
7794 stamp differences when the only
7795 modifications to a source file consist in adding/removing comments,
7796 empty lines, spaces or tabs. This means that if you have changed the
7797 comments in a source file or have simply reformatted it, using this
7798 switch will tell @code{gnatmake} not to recompile files that depend on it
7799 (provided other sources on which these files depend have undergone no
7800 semantic modifications). Note that the debugging information may be
7801 out of date with respect to the sources if the @code{-m} switch causes
7802 a compilation to be switched, so the use of this switch represents a
7803 trade-off between compilation time and accurate debugging information.
7806 @geindex Dependencies
7807 @geindex producing list
7809 @geindex -M (gnatmake)
7816 Check if all objects are up to date. If they are, output the object
7817 dependences to @code{stdout} in a form that can be directly exploited in
7818 a @code{Makefile}. By default, each source file is prefixed with its
7819 (relative or absolute) directory name. This name is whatever you
7820 specified in the various @code{-aI}
7821 and @code{-I} switches. If you use
7822 @code{gnatmake -M} @code{-q}
7823 (see below), only the source file names,
7824 without relative paths, are output. If you just specify the @code{-M}
7825 switch, dependencies of the GNAT internal system files are omitted. This
7826 is typically what you want. If you also specify
7827 the @code{-a} switch,
7828 dependencies of the GNAT internal files are also listed. Note that
7829 dependencies of the objects in external Ada libraries (see
7830 switch @code{-aL@emph{dir}} in the following list)
7834 @geindex -n (gnatmake)
7841 Don't compile, bind, or link. Checks if all objects are up to date.
7842 If they are not, the full name of the first file that needs to be
7843 recompiled is printed.
7844 Repeated use of this option, followed by compiling the indicated source
7845 file, will eventually result in recompiling all required units.
7848 @geindex -o (gnatmake)
7853 @item @code{-o @emph{exec_name}}
7855 Output executable name. The name of the final executable program will be
7856 @code{exec_name}. If the @code{-o} switch is omitted the default
7857 name for the executable will be the name of the input file in appropriate form
7858 for an executable file on the host system.
7860 This switch cannot be used when invoking @code{gnatmake} with several
7864 @geindex -p (gnatmake)
7871 Same as @code{--create-missing-dirs}
7874 @geindex -P (gnatmake)
7879 @item @code{-P@emph{project}}
7881 Use project file @code{project}. Only one such switch can be used.
7885 @c :ref:`gnatmake_and_Project_Files`.
7887 @geindex -q (gnatmake)
7894 Quiet. When this flag is not set, the commands carried out by
7895 @code{gnatmake} are displayed.
7898 @geindex -s (gnatmake)
7905 Recompile if compiler switches have changed since last compilation.
7906 All compiler switches but -I and -o are taken into account in the
7908 orders between different 'first letter' switches are ignored, but
7909 orders between same switches are taken into account. For example,
7910 @code{-O -O2} is different than @code{-O2 -O}, but @code{-g -O}
7911 is equivalent to @code{-O -g}.
7913 This switch is recommended when Integrated Preprocessing is used.
7916 @geindex -u (gnatmake)
7923 Unique. Recompile at most the main files. It implies -c. Combined with
7924 -f, it is equivalent to calling the compiler directly. Note that using
7925 -u with a project file and no main has a special meaning.
7929 @c (See :ref:`Project_Files_and_Main_Subprograms`.)
7931 @geindex -U (gnatmake)
7938 When used without a project file or with one or several mains on the command
7939 line, is equivalent to -u. When used with a project file and no main
7940 on the command line, all sources of all project files are checked and compiled
7941 if not up to date, and libraries are rebuilt, if necessary.
7944 @geindex -v (gnatmake)
7951 Verbose. Display the reason for all recompilations @code{gnatmake}
7952 decides are necessary, with the highest verbosity level.
7955 @geindex -vl (gnatmake)
7962 Verbosity level Low. Display fewer lines than in verbosity Medium.
7965 @geindex -vm (gnatmake)
7972 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
7975 @geindex -vm (gnatmake)
7982 Verbosity level High. Equivalent to -v.
7984 @item @code{-vP@emph{x}}
7986 Indicate the verbosity of the parsing of GNAT project files.
7987 See @ref{de,,Switches Related to Project Files}.
7990 @geindex -x (gnatmake)
7997 Indicate that sources that are not part of any Project File may be compiled.
7998 Normally, when using Project Files, only sources that are part of a Project
7999 File may be compile. When this switch is used, a source outside of all Project
8000 Files may be compiled. The ALI file and the object file will be put in the
8001 object directory of the main Project. The compilation switches used will only
8002 be those specified on the command line. Even when
8003 @code{-x} is used, mains specified on the
8004 command line need to be sources of a project file.
8006 @item @code{-X@emph{name}=@emph{value}}
8008 Indicate that external variable @code{name} has the value @code{value}.
8009 The Project Manager will use this value for occurrences of
8010 @code{external(name)} when parsing the project file.
8011 @ref{de,,Switches Related to Project Files}.
8014 @geindex -z (gnatmake)
8021 No main subprogram. Bind and link the program even if the unit name
8022 given on the command line is a package name. The resulting executable
8023 will execute the elaboration routines of the package and its closure,
8024 then the finalization routines.
8027 @subsubheading GCC switches
8030 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8031 is passed to @code{gcc} (e.g., @code{-O}, @code{-gnato,} etc.)
8033 @subsubheading Source and library search path switches
8036 @geindex -aI (gnatmake)
8041 @item @code{-aI@emph{dir}}
8043 When looking for source files also look in directory @code{dir}.
8044 The order in which source files search is undertaken is
8045 described in @ref{89,,Search Paths and the Run-Time Library (RTL)}.
8048 @geindex -aL (gnatmake)
8053 @item @code{-aL@emph{dir}}
8055 Consider @code{dir} as being an externally provided Ada library.
8056 Instructs @code{gnatmake} to skip compilation units whose @code{.ALI}
8057 files have been located in directory @code{dir}. This allows you to have
8058 missing bodies for the units in @code{dir} and to ignore out of date bodies
8059 for the same units. You still need to specify
8060 the location of the specs for these units by using the switches
8061 @code{-aI@emph{dir}} or @code{-I@emph{dir}}.
8062 Note: this switch is provided for compatibility with previous versions
8063 of @code{gnatmake}. The easier method of causing standard libraries
8064 to be excluded from consideration is to write-protect the corresponding
8068 @geindex -aO (gnatmake)
8073 @item @code{-aO@emph{dir}}
8075 When searching for library and object files, look in directory
8076 @code{dir}. The order in which library files are searched is described in
8077 @ref{8c,,Search Paths for gnatbind}.
8080 @geindex Search paths
8081 @geindex for gnatmake
8083 @geindex -A (gnatmake)
8088 @item @code{-A@emph{dir}}
8090 Equivalent to @code{-aL@emph{dir}} @code{-aI@emph{dir}}.
8092 @geindex -I (gnatmake)
8094 @item @code{-I@emph{dir}}
8096 Equivalent to @code{-aO@emph{dir} -aI@emph{dir}}.
8099 @geindex -I- (gnatmake)
8101 @geindex Source files
8102 @geindex suppressing search
8109 Do not look for source files in the directory containing the source
8110 file named in the command line.
8111 Do not look for ALI or object files in the directory
8112 where @code{gnatmake} was invoked.
8115 @geindex -L (gnatmake)
8117 @geindex Linker libraries
8122 @item @code{-L@emph{dir}}
8124 Add directory @code{dir} to the list of directories in which the linker
8125 will search for libraries. This is equivalent to
8126 @code{-largs} @code{-L@emph{dir}}.
8127 Furthermore, under Windows, the sources pointed to by the libraries path
8128 set in the registry are not searched for.
8131 @geindex -nostdinc (gnatmake)
8136 @item @code{-nostdinc}
8138 Do not look for source files in the system default directory.
8141 @geindex -nostdlib (gnatmake)
8146 @item @code{-nostdlib}
8148 Do not look for library files in the system default directory.
8151 @geindex --RTS (gnatmake)
8156 @item @code{--RTS=@emph{rts-path}}
8158 Specifies the default location of the run-time library. GNAT looks for the
8160 in the following directories, and stops as soon as a valid run-time is found
8161 (@code{adainclude} or @code{ada_source_path}, and @code{adalib} or
8162 @code{ada_object_path} present):
8168 @emph{<current directory>/$rts_path}
8171 @emph{<default-search-dir>/$rts_path}
8174 @emph{<default-search-dir>/rts-$rts_path}
8177 The selected path is handled like a normal RTS path.
8181 @node Mode Switches for gnatmake,Notes on the Command Line,Switches for gnatmake,Building with gnatmake
8182 @anchor{gnat_ugn/building_executable_programs_with_gnat id4}@anchor{df}@anchor{gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake}@anchor{e0}
8183 @subsection Mode Switches for @code{gnatmake}
8186 The mode switches (referred to as @code{mode_switches}) allow the
8187 inclusion of switches that are to be passed to the compiler itself, the
8188 binder or the linker. The effect of a mode switch is to cause all
8189 subsequent switches up to the end of the switch list, or up to the next
8190 mode switch, to be interpreted as switches to be passed on to the
8191 designated component of GNAT.
8193 @geindex -cargs (gnatmake)
8198 @item @code{-cargs @emph{switches}}
8200 Compiler switches. Here @code{switches} is a list of switches
8201 that are valid switches for @code{gcc}. They will be passed on to
8202 all compile steps performed by @code{gnatmake}.
8205 @geindex -bargs (gnatmake)
8210 @item @code{-bargs @emph{switches}}
8212 Binder switches. Here @code{switches} is a list of switches
8213 that are valid switches for @code{gnatbind}. They will be passed on to
8214 all bind steps performed by @code{gnatmake}.
8217 @geindex -largs (gnatmake)
8222 @item @code{-largs @emph{switches}}
8224 Linker switches. Here @code{switches} is a list of switches
8225 that are valid switches for @code{gnatlink}. They will be passed on to
8226 all link steps performed by @code{gnatmake}.
8229 @geindex -margs (gnatmake)
8234 @item @code{-margs @emph{switches}}
8236 Make switches. The switches are directly interpreted by @code{gnatmake},
8237 regardless of any previous occurrence of @code{-cargs}, @code{-bargs}
8241 @node Notes on the Command Line,How gnatmake Works,Mode Switches for gnatmake,Building with gnatmake
8242 @anchor{gnat_ugn/building_executable_programs_with_gnat id5}@anchor{e1}@anchor{gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line}@anchor{e2}
8243 @subsection Notes on the Command Line
8246 This section contains some additional useful notes on the operation
8247 of the @code{gnatmake} command.
8249 @geindex Recompilation (by gnatmake)
8255 If @code{gnatmake} finds no ALI files, it recompiles the main program
8256 and all other units required by the main program.
8257 This means that @code{gnatmake}
8258 can be used for the initial compile, as well as during subsequent steps of
8259 the development cycle.
8262 If you enter @code{gnatmake foo.adb}, where @code{foo}
8263 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8264 @code{foo.adb} (because it finds no ALI) and stops, issuing a
8268 In @code{gnatmake} the switch @code{-I}
8269 is used to specify both source and
8270 library file paths. Use @code{-aI}
8271 instead if you just want to specify
8272 source paths only and @code{-aO}
8273 if you want to specify library paths
8277 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8278 This may conveniently be used to exclude standard libraries from
8279 consideration and in particular it means that the use of the
8280 @code{-f} switch will not recompile these files
8281 unless @code{-a} is also specified.
8284 @code{gnatmake} has been designed to make the use of Ada libraries
8285 particularly convenient. Assume you have an Ada library organized
8286 as follows: @emph{obj-dir} contains the objects and ALI files for
8287 of your Ada compilation units,
8288 whereas @emph{include-dir} contains the
8289 specs of these units, but no bodies. Then to compile a unit
8290 stored in @code{main.adb}, which uses this Ada library you would just type:
8293 $ gnatmake -aI`include-dir` -aL`obj-dir` main
8297 Using @code{gnatmake} along with the @code{-m (minimal recompilation)}
8298 switch provides a mechanism for avoiding unnecessary recompilations. Using
8300 you can update the comments/format of your
8301 source files without having to recompile everything. Note, however, that
8302 adding or deleting lines in a source files may render its debugging
8303 info obsolete. If the file in question is a spec, the impact is rather
8304 limited, as that debugging info will only be useful during the
8305 elaboration phase of your program. For bodies the impact can be more
8306 significant. In all events, your debugger will warn you if a source file
8307 is more recent than the corresponding object, and alert you to the fact
8308 that the debugging information may be out of date.
8311 @node How gnatmake Works,Examples of gnatmake Usage,Notes on the Command Line,Building with gnatmake
8312 @anchor{gnat_ugn/building_executable_programs_with_gnat id6}@anchor{e3}@anchor{gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works}@anchor{e4}
8313 @subsection How @code{gnatmake} Works
8316 Generally @code{gnatmake} automatically performs all necessary
8317 recompilations and you don't need to worry about how it works. However,
8318 it may be useful to have some basic understanding of the @code{gnatmake}
8319 approach and in particular to understand how it uses the results of
8320 previous compilations without incorrectly depending on them.
8322 First a definition: an object file is considered @emph{up to date} if the
8323 corresponding ALI file exists and if all the source files listed in the
8324 dependency section of this ALI file have time stamps matching those in
8325 the ALI file. This means that neither the source file itself nor any
8326 files that it depends on have been modified, and hence there is no need
8327 to recompile this file.
8329 @code{gnatmake} works by first checking if the specified main unit is up
8330 to date. If so, no compilations are required for the main unit. If not,
8331 @code{gnatmake} compiles the main program to build a new ALI file that
8332 reflects the latest sources. Then the ALI file of the main unit is
8333 examined to find all the source files on which the main program depends,
8334 and @code{gnatmake} recursively applies the above procedure on all these
8337 This process ensures that @code{gnatmake} only trusts the dependencies
8338 in an existing ALI file if they are known to be correct. Otherwise it
8339 always recompiles to determine a new, guaranteed accurate set of
8340 dependencies. As a result the program is compiled 'upside down' from what may
8341 be more familiar as the required order of compilation in some other Ada
8342 systems. In particular, clients are compiled before the units on which
8343 they depend. The ability of GNAT to compile in any order is critical in
8344 allowing an order of compilation to be chosen that guarantees that
8345 @code{gnatmake} will recompute a correct set of new dependencies if
8348 When invoking @code{gnatmake} with several @code{file_names}, if a unit is
8349 imported by several of the executables, it will be recompiled at most once.
8351 Note: when using non-standard naming conventions
8352 (@ref{35,,Using Other File Names}), changing through a configuration pragmas
8353 file the version of a source and invoking @code{gnatmake} to recompile may
8354 have no effect, if the previous version of the source is still accessible
8355 by @code{gnatmake}. It may be necessary to use the switch
8358 @node Examples of gnatmake Usage,,How gnatmake Works,Building with gnatmake
8359 @anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage}@anchor{e5}@anchor{gnat_ugn/building_executable_programs_with_gnat id7}@anchor{e6}
8360 @subsection Examples of @code{gnatmake} Usage
8366 @item @emph{gnatmake hello.adb}
8368 Compile all files necessary to bind and link the main program
8369 @code{hello.adb} (containing unit @code{Hello}) and bind and link the
8370 resulting object files to generate an executable file @code{hello}.
8372 @item @emph{gnatmake main1 main2 main3}
8374 Compile all files necessary to bind and link the main programs
8375 @code{main1.adb} (containing unit @code{Main1}), @code{main2.adb}
8376 (containing unit @code{Main2}) and @code{main3.adb}
8377 (containing unit @code{Main3}) and bind and link the resulting object files
8378 to generate three executable files @code{main1},
8379 @code{main2} and @code{main3}.
8381 @item @emph{gnatmake -q Main_Unit -cargs -O2 -bargs -l}
8383 Compile all files necessary to bind and link the main program unit
8384 @code{Main_Unit} (from file @code{main_unit.adb}). All compilations will
8385 be done with optimization level 2 and the order of elaboration will be
8386 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8387 displaying commands it is executing.
8390 @node Compiling with gcc,Compiler Switches,Building with gnatmake,Building Executable Programs with GNAT
8391 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc}@anchor{1c}@anchor{gnat_ugn/building_executable_programs_with_gnat id8}@anchor{e7}
8392 @section Compiling with @code{gcc}
8395 This section discusses how to compile Ada programs using the @code{gcc}
8396 command. It also describes the set of switches
8397 that can be used to control the behavior of the compiler.
8400 * Compiling Programs::
8401 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
8402 * Order of Compilation Issues::
8407 @node Compiling Programs,Search Paths and the Run-Time Library RTL,,Compiling with gcc
8408 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-programs}@anchor{e8}@anchor{gnat_ugn/building_executable_programs_with_gnat id9}@anchor{e9}
8409 @subsection Compiling Programs
8412 The first step in creating an executable program is to compile the units
8413 of the program using the @code{gcc} command. You must compile the
8420 the body file (@code{.adb}) for a library level subprogram or generic
8424 the spec file (@code{.ads}) for a library level package or generic
8425 package that has no body
8428 the body file (@code{.adb}) for a library level package
8429 or generic package that has a body
8432 You need @emph{not} compile the following files
8438 the spec of a library unit which has a body
8444 because they are compiled as part of compiling related units. GNAT
8446 when the corresponding body is compiled, and subunits when the parent is
8449 @geindex cannot generate code
8451 If you attempt to compile any of these files, you will get one of the
8452 following error messages (where @code{fff} is the name of the file you
8458 cannot generate code for file `@w{`}fff`@w{`} (package spec)
8459 to check package spec, use -gnatc
8461 cannot generate code for file `@w{`}fff`@w{`} (missing subunits)
8462 to check parent unit, use -gnatc
8464 cannot generate code for file `@w{`}fff`@w{`} (subprogram spec)
8465 to check subprogram spec, use -gnatc
8467 cannot generate code for file `@w{`}fff`@w{`} (subunit)
8468 to check subunit, use -gnatc
8472 As indicated by the above error messages, if you want to submit
8473 one of these files to the compiler to check for correct semantics
8474 without generating code, then use the @code{-gnatc} switch.
8476 The basic command for compiling a file containing an Ada unit is:
8479 $ gcc -c [switches] <file name>
8482 where @code{file name} is the name of the Ada file (usually
8483 having an extension @code{.ads} for a spec or @code{.adb} for a body).
8485 @code{-c} switch to tell @code{gcc} to compile, but not link, the file.
8486 The result of a successful compilation is an object file, which has the
8487 same name as the source file but an extension of @code{.o} and an Ada
8488 Library Information (ALI) file, which also has the same name as the
8489 source file, but with @code{.ali} as the extension. GNAT creates these
8490 two output files in the current directory, but you may specify a source
8491 file in any directory using an absolute or relative path specification
8492 containing the directory information.
8494 TESTING: the @code{--foobar@emph{NN}} switch
8498 @code{gcc} is actually a driver program that looks at the extensions of
8499 the file arguments and loads the appropriate compiler. For example, the
8500 GNU C compiler is @code{cc1}, and the Ada compiler is @code{gnat1}.
8501 These programs are in directories known to the driver program (in some
8502 configurations via environment variables you set), but need not be in
8503 your path. The @code{gcc} driver also calls the assembler and any other
8504 utilities needed to complete the generation of the required object
8507 It is possible to supply several file names on the same @code{gcc}
8508 command. This causes @code{gcc} to call the appropriate compiler for
8509 each file. For example, the following command lists two separate
8510 files to be compiled:
8513 $ gcc -c x.adb y.adb
8516 calls @code{gnat1} (the Ada compiler) twice to compile @code{x.adb} and
8518 The compiler generates two object files @code{x.o} and @code{y.o}
8519 and the two ALI files @code{x.ali} and @code{y.ali}.
8521 Any switches apply to all the files listed, see @ref{ea,,Compiler Switches} for a
8522 list of available @code{gcc} switches.
8524 @node Search Paths and the Run-Time Library RTL,Order of Compilation Issues,Compiling Programs,Compiling with gcc
8525 @anchor{gnat_ugn/building_executable_programs_with_gnat id10}@anchor{eb}@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl}@anchor{89}
8526 @subsection Search Paths and the Run-Time Library (RTL)
8529 With the GNAT source-based library system, the compiler must be able to
8530 find source files for units that are needed by the unit being compiled.
8531 Search paths are used to guide this process.
8533 The compiler compiles one source file whose name must be given
8534 explicitly on the command line. In other words, no searching is done
8535 for this file. To find all other source files that are needed (the most
8536 common being the specs of units), the compiler examines the following
8537 directories, in the following order:
8543 The directory containing the source file of the main unit being compiled
8544 (the file name on the command line).
8547 Each directory named by an @code{-I} switch given on the @code{gcc}
8548 command line, in the order given.
8550 @geindex ADA_PRJ_INCLUDE_FILE
8553 Each of the directories listed in the text file whose name is given
8555 @geindex ADA_PRJ_INCLUDE_FILE
8556 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8557 @code{ADA_PRJ_INCLUDE_FILE} environment variable.
8558 @geindex ADA_PRJ_INCLUDE_FILE
8559 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8560 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat
8561 driver when project files are used. It should not normally be set
8564 @geindex ADA_INCLUDE_PATH
8567 Each of the directories listed in the value of the
8568 @geindex ADA_INCLUDE_PATH
8569 @geindex environment variable; ADA_INCLUDE_PATH
8570 @code{ADA_INCLUDE_PATH} environment variable.
8571 Construct this value
8574 @geindex environment variable; PATH
8575 @code{PATH} environment variable: a list of directory
8576 names separated by colons (semicolons when working with the NT version).
8579 The content of the @code{ada_source_path} file which is part of the GNAT
8580 installation tree and is used to store standard libraries such as the
8581 GNAT Run Time Library (RTL) source files.
8582 @ref{87,,Installing a library}
8585 Specifying the switch @code{-I-}
8586 inhibits the use of the directory
8587 containing the source file named in the command line. You can still
8588 have this directory on your search path, but in this case it must be
8589 explicitly requested with a @code{-I} switch.
8591 Specifying the switch @code{-nostdinc}
8592 inhibits the search of the default location for the GNAT Run Time
8593 Library (RTL) source files.
8595 The compiler outputs its object files and ALI files in the current
8597 Caution: The object file can be redirected with the @code{-o} switch;
8598 however, @code{gcc} and @code{gnat1} have not been coordinated on this
8599 so the @code{ALI} file will not go to the right place. Therefore, you should
8600 avoid using the @code{-o} switch.
8604 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8605 children make up the GNAT RTL, together with the simple @code{System.IO}
8606 package used in the @code{"Hello World"} example. The sources for these units
8607 are needed by the compiler and are kept together in one directory. Not
8608 all of the bodies are needed, but all of the sources are kept together
8609 anyway. In a normal installation, you need not specify these directory
8610 names when compiling or binding. Either the environment variables or
8611 the built-in defaults cause these files to be found.
8613 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
8614 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
8615 consisting of child units of @code{GNAT}. This is a collection of generally
8616 useful types, subprograms, etc. See the @cite{GNAT_Reference_Manual}
8617 for further details.
8619 Besides simplifying access to the RTL, a major use of search paths is
8620 in compiling sources from multiple directories. This can make
8621 development environments much more flexible.
8623 @node Order of Compilation Issues,Examples,Search Paths and the Run-Time Library RTL,Compiling with gcc
8624 @anchor{gnat_ugn/building_executable_programs_with_gnat id11}@anchor{ec}@anchor{gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues}@anchor{ed}
8625 @subsection Order of Compilation Issues
8628 If, in our earlier example, there was a spec for the @code{hello}
8629 procedure, it would be contained in the file @code{hello.ads}; yet this
8630 file would not have to be explicitly compiled. This is the result of the
8631 model we chose to implement library management. Some of the consequences
8632 of this model are as follows:
8638 There is no point in compiling specs (except for package
8639 specs with no bodies) because these are compiled as needed by clients. If
8640 you attempt a useless compilation, you will receive an error message.
8641 It is also useless to compile subunits because they are compiled as needed
8645 There are no order of compilation requirements: performing a
8646 compilation never obsoletes anything. The only way you can obsolete
8647 something and require recompilations is to modify one of the
8648 source files on which it depends.
8651 There is no library as such, apart from the ALI files
8652 (@ref{42,,The Ada Library Information Files}, for information on the format
8653 of these files). For now we find it convenient to create separate ALI files,
8654 but eventually the information therein may be incorporated into the object
8658 When you compile a unit, the source files for the specs of all units
8659 that it @emph{with}s, all its subunits, and the bodies of any generics it
8660 instantiates must be available (reachable by the search-paths mechanism
8661 described above), or you will receive a fatal error message.
8664 @node Examples,,Order of Compilation Issues,Compiling with gcc
8665 @anchor{gnat_ugn/building_executable_programs_with_gnat id12}@anchor{ee}@anchor{gnat_ugn/building_executable_programs_with_gnat examples}@anchor{ef}
8666 @subsection Examples
8669 The following are some typical Ada compilation command line examples:
8675 Compile body in file @code{xyz.adb} with all default options.
8678 $ gcc -c -O2 -gnata xyz-def.adb
8681 Compile the child unit package in file @code{xyz-def.adb} with extensive
8682 optimizations, and pragma @code{Assert}/@cite{Debug} statements
8686 $ gcc -c -gnatc abc-def.adb
8689 Compile the subunit in file @code{abc-def.adb} in semantic-checking-only
8692 @node Compiler Switches,Linker Switches,Compiling with gcc,Building Executable Programs with GNAT
8693 @anchor{gnat_ugn/building_executable_programs_with_gnat compiler-switches}@anchor{f0}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gcc}@anchor{ea}
8694 @section Compiler Switches
8697 The @code{gcc} command accepts switches that control the
8698 compilation process. These switches are fully described in this section:
8699 first an alphabetical listing of all switches with a brief description,
8700 and then functionally grouped sets of switches with more detailed
8703 More switches exist for GCC than those documented here, especially
8704 for specific targets. However, their use is not recommended as
8705 they may change code generation in ways that are incompatible with
8706 the Ada run-time library, or can cause inconsistencies between
8710 * Alphabetical List of All Switches::
8711 * Output and Error Message Control::
8712 * Warning Message Control::
8713 * Debugging and Assertion Control::
8714 * Validity Checking::
8717 * Using gcc for Syntax Checking::
8718 * Using gcc for Semantic Checking::
8719 * Compiling Different Versions of Ada::
8720 * Character Set Control::
8721 * File Naming Control::
8722 * Subprogram Inlining Control::
8723 * Auxiliary Output Control::
8724 * Debugging Control::
8725 * Exception Handling Control::
8726 * Units to Sources Mapping Files::
8727 * Code Generation Control::
8731 @node Alphabetical List of All Switches,Output and Error Message Control,,Compiler Switches
8732 @anchor{gnat_ugn/building_executable_programs_with_gnat id13}@anchor{f1}@anchor{gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches}@anchor{f2}
8733 @subsection Alphabetical List of All Switches
8741 @item @code{-b @emph{target}}
8743 Compile your program to run on @code{target}, which is the name of a
8744 system configuration. You must have a GNAT cross-compiler built if
8745 @code{target} is not the same as your host system.
8753 @item @code{-B@emph{dir}}
8755 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8756 from @code{dir} instead of the default location. Only use this switch
8757 when multiple versions of the GNAT compiler are available.
8758 See the "Options for Directory Search" section in the
8759 @cite{Using the GNU Compiler Collection (GCC)} manual for further details.
8760 You would normally use the @code{-b} or @code{-V} switch instead.
8770 Compile. Always use this switch when compiling Ada programs.
8772 Note: for some other languages when using @code{gcc}, notably in
8773 the case of C and C++, it is possible to use
8774 use @code{gcc} without a @code{-c} switch to
8775 compile and link in one step. In the case of GNAT, you
8776 cannot use this approach, because the binder must be run
8777 and @code{gcc} cannot be used to run the GNAT binder.
8780 @geindex -fcallgraph-info (gcc)
8785 @item @code{-fcallgraph-info[=su,da]}
8787 Makes the compiler output callgraph information for the program, on a
8788 per-file basis. The information is generated in the VCG format. It can
8789 be decorated with additional, per-node and/or per-edge information, if a
8790 list of comma-separated markers is additionally specified. When the
8791 @code{su} marker is specified, the callgraph is decorated with stack usage
8792 information; it is equivalent to @code{-fstack-usage}. When the @code{da}
8793 marker is specified, the callgraph is decorated with information about
8794 dynamically allocated objects.
8797 @geindex -fdump-scos (gcc)
8802 @item @code{-fdump-scos}
8804 Generates SCO (Source Coverage Obligation) information in the ALI file.
8805 This information is used by advanced coverage tools. See unit @code{SCOs}
8806 in the compiler sources for details in files @code{scos.ads} and
8810 @geindex -fgnat-encodings (gcc)
8815 @item @code{-fgnat-encodings=[all|gdb|minimal]}
8817 This switch controls the balance between GNAT encodings and standard DWARF
8818 emitted in the debug information.
8821 @geindex -flto (gcc)
8826 @item @code{-flto[=@emph{n}]}
8828 Enables Link Time Optimization. This switch must be used in conjunction
8829 with the @code{-Ox} switches (but not with the @code{-gnatn} switch
8830 since it is a full replacement for the latter) and instructs the compiler
8831 to defer most optimizations until the link stage. The advantage of this
8832 approach is that the compiler can do a whole-program analysis and choose
8833 the best interprocedural optimization strategy based on a complete view
8834 of the program, instead of a fragmentary view with the usual approach.
8835 This can also speed up the compilation of big programs and reduce the
8836 size of the executable, compared with a traditional per-unit compilation
8837 with inlining across units enabled by the @code{-gnatn} switch.
8838 The drawback of this approach is that it may require more memory and that
8839 the debugging information generated by -g with it might be hardly usable.
8840 The switch, as well as the accompanying @code{-Ox} switches, must be
8841 specified both for the compilation and the link phases.
8842 If the @code{n} parameter is specified, the optimization and final code
8843 generation at link time are executed using @code{n} parallel jobs by
8844 means of an installed @code{make} program.
8847 @geindex -fno-inline (gcc)
8852 @item @code{-fno-inline}
8854 Suppresses all inlining, unless requested with pragma @code{Inline_Always}. The
8855 effect is enforced regardless of other optimization or inlining switches.
8856 Note that inlining can also be suppressed on a finer-grained basis with
8857 pragma @code{No_Inline}.
8860 @geindex -fno-inline-functions (gcc)
8865 @item @code{-fno-inline-functions}
8867 Suppresses automatic inlining of subprograms, which is enabled
8868 if @code{-O3} is used.
8871 @geindex -fno-inline-small-functions (gcc)
8876 @item @code{-fno-inline-small-functions}
8878 Suppresses automatic inlining of small subprograms, which is enabled
8879 if @code{-O2} is used.
8882 @geindex -fno-inline-functions-called-once (gcc)
8887 @item @code{-fno-inline-functions-called-once}
8889 Suppresses inlining of subprograms local to the unit and called once
8890 from within it, which is enabled if @code{-O1} is used.
8893 @geindex -fno-ivopts (gcc)
8898 @item @code{-fno-ivopts}
8900 Suppresses high-level loop induction variable optimizations, which are
8901 enabled if @code{-O1} is used. These optimizations are generally
8902 profitable but, for some specific cases of loops with numerous uses
8903 of the iteration variable that follow a common pattern, they may end
8904 up destroying the regularity that could be exploited at a lower level
8905 and thus producing inferior code.
8908 @geindex -fno-strict-aliasing (gcc)
8913 @item @code{-fno-strict-aliasing}
8915 Causes the compiler to avoid assumptions regarding non-aliasing
8916 of objects of different types. See
8917 @ref{f3,,Optimization and Strict Aliasing} for details.
8920 @geindex -fno-strict-overflow (gcc)
8925 @item @code{-fno-strict-overflow}
8927 Causes the compiler to avoid assumptions regarding the rules of signed
8928 integer overflow. These rules specify that signed integer overflow will
8929 result in a Constraint_Error exception at run time and are enforced in
8930 default mode by the compiler, so this switch should not be necessary in
8931 normal operating mode. It might be useful in conjunction with @code{-gnato0}
8932 for very peculiar cases of low-level programming.
8935 @geindex -fstack-check (gcc)
8940 @item @code{-fstack-check}
8942 Activates stack checking.
8943 See @ref{f4,,Stack Overflow Checking} for details.
8946 @geindex -fstack-usage (gcc)
8951 @item @code{-fstack-usage}
8953 Makes the compiler output stack usage information for the program, on a
8954 per-subprogram basis. See @ref{f5,,Static Stack Usage Analysis} for details.
8964 Generate debugging information. This information is stored in the object
8965 file and copied from there to the final executable file by the linker,
8966 where it can be read by the debugger. You must use the
8967 @code{-g} switch if you plan on using the debugger.
8970 @geindex -gnat05 (gcc)
8975 @item @code{-gnat05}
8977 Allow full Ada 2005 features.
8980 @geindex -gnat12 (gcc)
8985 @item @code{-gnat12}
8987 Allow full Ada 2012 features.
8990 @geindex -gnat83 (gcc)
8992 @geindex -gnat2005 (gcc)
8997 @item @code{-gnat2005}
8999 Allow full Ada 2005 features (same as @code{-gnat05})
9002 @geindex -gnat2012 (gcc)
9007 @item @code{-gnat2012}
9009 Allow full Ada 2012 features (same as @code{-gnat12})
9011 @item @code{-gnat83}
9013 Enforce Ada 83 restrictions.
9016 @geindex -gnat95 (gcc)
9021 @item @code{-gnat95}
9023 Enforce Ada 95 restrictions.
9025 Note: for compatibility with some Ada 95 compilers which support only
9026 the @code{overriding} keyword of Ada 2005, the @code{-gnatd.D} switch can
9027 be used along with @code{-gnat95} to achieve a similar effect with GNAT.
9029 @code{-gnatd.D} instructs GNAT to consider @code{overriding} as a keyword
9030 and handle its associated semantic checks, even in Ada 95 mode.
9033 @geindex -gnata (gcc)
9040 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
9041 activated. Note that these pragmas can also be controlled using the
9042 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
9043 It also activates pragmas @code{Check}, @code{Precondition}, and
9044 @code{Postcondition}. Note that these pragmas can also be controlled
9045 using the configuration pragma @code{Check_Policy}. In Ada 2012, it
9046 also activates all assertions defined in the RM as aspects: preconditions,
9047 postconditions, type invariants and (sub)type predicates. In all Ada modes,
9048 corresponding pragmas for type invariants and (sub)type predicates are
9049 also activated. The default is that all these assertions are disabled,
9050 and have no effect, other than being checked for syntactic validity, and
9051 in the case of subtype predicates, constructions such as membership tests
9052 still test predicates even if assertions are turned off.
9055 @geindex -gnatA (gcc)
9062 Avoid processing @code{gnat.adc}. If a @code{gnat.adc} file is present,
9066 @geindex -gnatb (gcc)
9073 Generate brief messages to @code{stderr} even if verbose mode set.
9076 @geindex -gnatB (gcc)
9083 Assume no invalid (bad) values except for 'Valid attribute use
9084 (@ref{f6,,Validity Checking}).
9087 @geindex -gnatc (gcc)
9094 Check syntax and semantics only (no code generation attempted). When the
9095 compiler is invoked by @code{gnatmake}, if the switch @code{-gnatc} is
9096 only given to the compiler (after @code{-cargs} or in package Compiler of
9097 the project file, @code{gnatmake} will fail because it will not find the
9098 object file after compilation. If @code{gnatmake} is called with
9099 @code{-gnatc} as a builder switch (before @code{-cargs} or in package
9100 Builder of the project file) then @code{gnatmake} will not fail because
9101 it will not look for the object files after compilation, and it will not try
9105 @geindex -gnatC (gcc)
9112 Generate CodePeer intermediate format (no code generation attempted).
9113 This switch will generate an intermediate representation suitable for
9114 use by CodePeer (@code{.scil} files). This switch is not compatible with
9115 code generation (it will, among other things, disable some switches such
9116 as -gnatn, and enable others such as -gnata).
9119 @geindex -gnatd (gcc)
9126 Specify debug options for the compiler. The string of characters after
9127 the @code{-gnatd} specify the specific debug options. The possible
9128 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
9129 compiler source file @code{debug.adb} for details of the implemented
9130 debug options. Certain debug options are relevant to applications
9131 programmers, and these are documented at appropriate points in this
9135 @geindex -gnatD[nn] (gcc)
9142 Create expanded source files for source level debugging. This switch
9143 also suppresses generation of cross-reference information
9144 (see @code{-gnatx}). Note that this switch is not allowed if a previous
9145 -gnatR switch has been given, since these two switches are not compatible.
9148 @geindex -gnateA (gcc)
9153 @item @code{-gnateA}
9155 Check that the actual parameters of a subprogram call are not aliases of one
9156 another. To qualify as aliasing, the actuals must denote objects of a composite
9157 type, their memory locations must be identical or overlapping, and at least one
9158 of the corresponding formal parameters must be of mode OUT or IN OUT.
9161 type Rec_Typ is record
9162 Data : Integer := 0;
9165 function Self (Val : Rec_Typ) return Rec_Typ is
9170 procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is
9173 end Detect_Aliasing;
9177 Detect_Aliasing (Obj, Obj);
9178 Detect_Aliasing (Obj, Self (Obj));
9181 In the example above, the first call to @code{Detect_Aliasing} fails with a
9182 @code{Program_Error} at run time because the actuals for @code{Val_1} and
9183 @code{Val_2} denote the same object. The second call executes without raising
9184 an exception because @code{Self(Obj)} produces an anonymous object which does
9185 not share the memory location of @code{Obj}.
9188 @geindex -gnatec (gcc)
9193 @item @code{-gnatec=@emph{path}}
9195 Specify a configuration pragma file
9196 (the equal sign is optional)
9197 (@ref{79,,The Configuration Pragmas Files}).
9200 @geindex -gnateC (gcc)
9205 @item @code{-gnateC}
9207 Generate CodePeer messages in a compiler-like format. This switch is only
9208 effective if @code{-gnatcC} is also specified and requires an installation
9212 @geindex -gnated (gcc)
9217 @item @code{-gnated}
9219 Disable atomic synchronization
9222 @geindex -gnateD (gcc)
9227 @item @code{-gnateDsymbol[=@emph{value}]}
9229 Defines a symbol, associated with @code{value}, for preprocessing.
9230 (@ref{18,,Integrated Preprocessing}).
9233 @geindex -gnateE (gcc)
9238 @item @code{-gnateE}
9240 Generate extra information in exception messages. In particular, display
9241 extra column information and the value and range associated with index and
9242 range check failures, and extra column information for access checks.
9243 In cases where the compiler is able to determine at compile time that
9244 a check will fail, it gives a warning, and the extra information is not
9245 produced at run time.
9248 @geindex -gnatef (gcc)
9253 @item @code{-gnatef}
9255 Display full source path name in brief error messages.
9258 @geindex -gnateF (gcc)
9263 @item @code{-gnateF}
9265 Check for overflow on all floating-point operations, including those
9266 for unconstrained predefined types. See description of pragma
9267 @code{Check_Float_Overflow} in GNAT RM.
9270 @geindex -gnateg (gcc)
9277 The @code{-gnatc} switch must always be specified before this switch, e.g.
9278 @code{-gnatceg}. Generate a C header from the Ada input file. See
9279 @ref{ca,,Generating C Headers for Ada Specifications} for more
9283 @geindex -gnateG (gcc)
9288 @item @code{-gnateG}
9290 Save result of preprocessing in a text file.
9293 @geindex -gnatei (gcc)
9298 @item @code{-gnatei@emph{nnn}}
9300 Set maximum number of instantiations during compilation of a single unit to
9301 @code{nnn}. This may be useful in increasing the default maximum of 8000 for
9302 the rare case when a single unit legitimately exceeds this limit.
9305 @geindex -gnateI (gcc)
9310 @item @code{-gnateI@emph{nnn}}
9312 Indicates that the source is a multi-unit source and that the index of the
9313 unit to compile is @code{nnn}. @code{nnn} needs to be a positive number and need
9314 to be a valid index in the multi-unit source.
9317 @geindex -gnatel (gcc)
9322 @item @code{-gnatel}
9324 This switch can be used with the static elaboration model to issue info
9326 where implicit @code{pragma Elaborate} and @code{pragma Elaborate_All}
9327 are generated. This is useful in diagnosing elaboration circularities
9328 caused by these implicit pragmas when using the static elaboration
9329 model. See See the section in this guide on elaboration checking for
9330 further details. These messages are not generated by default, and are
9331 intended only for temporary use when debugging circularity problems.
9334 @geindex -gnatel (gcc)
9339 @item @code{-gnateL}
9341 This switch turns off the info messages about implicit elaboration pragmas.
9344 @geindex -gnatem (gcc)
9349 @item @code{-gnatem=@emph{path}}
9351 Specify a mapping file
9352 (the equal sign is optional)
9353 (@ref{f7,,Units to Sources Mapping Files}).
9356 @geindex -gnatep (gcc)
9361 @item @code{-gnatep=@emph{file}}
9363 Specify a preprocessing data file
9364 (the equal sign is optional)
9365 (@ref{18,,Integrated Preprocessing}).
9368 @geindex -gnateP (gcc)
9373 @item @code{-gnateP}
9375 Turn categorization dependency errors into warnings.
9376 Ada requires that units that WITH one another have compatible categories, for
9377 example a Pure unit cannot WITH a Preelaborate unit. If this switch is used,
9378 these errors become warnings (which can be ignored, or suppressed in the usual
9379 manner). This can be useful in some specialized circumstances such as the
9380 temporary use of special test software.
9383 @geindex -gnateS (gcc)
9388 @item @code{-gnateS}
9390 Synonym of @code{-fdump-scos}, kept for backwards compatibility.
9393 @geindex -gnatet=file (gcc)
9398 @item @code{-gnatet=@emph{path}}
9400 Generate target dependent information. The format of the output file is
9401 described in the section about switch @code{-gnateT}.
9404 @geindex -gnateT (gcc)
9409 @item @code{-gnateT=@emph{path}}
9411 Read target dependent information, such as endianness or sizes and alignments
9412 of base type. If this switch is passed, the default target dependent
9413 information of the compiler is replaced by the one read from the input file.
9414 This is used by tools other than the compiler, e.g. to do
9415 semantic analysis of programs that will run on some other target than
9416 the machine on which the tool is run.
9418 The following target dependent values should be defined,
9419 where @code{Nat} denotes a natural integer value, @code{Pos} denotes a
9420 positive integer value, and fields marked with a question mark are
9421 boolean fields, where a value of 0 is False, and a value of 1 is True:
9424 Bits_BE : Nat; -- Bits stored big-endian?
9425 Bits_Per_Unit : Pos; -- Bits in a storage unit
9426 Bits_Per_Word : Pos; -- Bits in a word
9427 Bytes_BE : Nat; -- Bytes stored big-endian?
9428 Char_Size : Pos; -- Standard.Character'Size
9429 Double_Float_Alignment : Nat; -- Alignment of double float
9430 Double_Scalar_Alignment : Nat; -- Alignment of double length scalar
9431 Double_Size : Pos; -- Standard.Long_Float'Size
9432 Float_Size : Pos; -- Standard.Float'Size
9433 Float_Words_BE : Nat; -- Float words stored big-endian?
9434 Int_Size : Pos; -- Standard.Integer'Size
9435 Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size
9436 Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size
9437 Long_Size : Pos; -- Standard.Long_Integer'Size
9438 Maximum_Alignment : Pos; -- Maximum permitted alignment
9439 Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field
9440 Pointer_Size : Pos; -- System.Address'Size
9441 Short_Enums : Nat; -- Foreign enums use short size?
9442 Short_Size : Pos; -- Standard.Short_Integer'Size
9443 Strict_Alignment : Nat; -- Strict alignment?
9444 System_Allocator_Alignment : Nat; -- Alignment for malloc calls
9445 Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size
9446 Words_BE : Nat; -- Words stored big-endian?
9449 @code{Bits_Per_Unit} is the number of bits in a storage unit, the equivalent of
9450 GCC macro @code{BITS_PER_UNIT} documented as follows: @cite{Define this macro to be the number of bits in an addressable storage unit (byte); normally 8.}
9452 @code{Bits_Per_Word} is the number of bits in a machine word, the equivalent of
9453 GCC macro @code{BITS_PER_WORD} documented as follows: @cite{Number of bits in a word; normally 32.}
9455 @code{Double_Scalar_Alignment} is the alignment for a scalar whose size is two
9456 machine words. It should be the same as the alignment for C @code{long_long} on
9459 @code{Maximum_Alignment} is the maximum alignment that the compiler might choose
9460 by default for a type or object, which is also the maximum alignment that can
9461 be specified in GNAT. It is computed for GCC backends as @code{BIGGEST_ALIGNMENT
9462 / BITS_PER_UNIT} where GCC macro @code{BIGGEST_ALIGNMENT} is documented as
9463 follows: @cite{Biggest alignment that any data type can require on this machine@comma{} in bits.}
9465 @code{Max_Unaligned_Field} is the maximum size for unaligned bit field, which is
9466 64 for the majority of GCC targets (but can be different on some targets like
9469 @code{Strict_Alignment} is the equivalent of GCC macro @code{STRICT_ALIGNMENT}
9470 documented as follows: @cite{Define this macro to be the value 1 if instructions will fail to work if given data not on the nominal alignment. If instructions will merely go slower in that case@comma{} define this macro as 0.}
9472 @code{System_Allocator_Alignment} is the guaranteed alignment of data returned
9473 by calls to @code{malloc}.
9475 The format of the input file is as follows. First come the values of
9476 the variables defined above, with one line per value:
9482 where @code{name} is the name of the parameter, spelled out in full,
9483 and cased as in the above list, and @code{value} is an unsigned decimal
9484 integer. Two or more blanks separates the name from the value.
9486 All the variables must be present, in alphabetical order (i.e. the
9487 same order as the list above).
9489 Then there is a blank line to separate the two parts of the file. Then
9490 come the lines showing the floating-point types to be registered, with
9491 one line per registered mode:
9494 name digs float_rep size alignment
9497 where @code{name} is the string name of the type (which can have
9498 single spaces embedded in the name (e.g. long double), @code{digs} is
9499 the number of digits for the floating-point type, @code{float_rep} is
9500 the float representation (I/V/A for IEEE-754-Binary, Vax_Native,
9501 AAMP), @code{size} is the size in bits, @code{alignment} is the
9502 alignment in bits. The name is followed by at least two blanks, fields
9503 are separated by at least one blank, and a LF character immediately
9504 follows the alignment field.
9506 Here is an example of a target parameterization file:
9514 Double_Float_Alignment 0
9515 Double_Scalar_Alignment 0
9520 Long_Double_Size 128
9523 Maximum_Alignment 16
9524 Max_Unaligned_Field 64
9528 System_Allocator_Alignment 16
9534 long double 18 I 80 128
9539 @geindex -gnateu (gcc)
9544 @item @code{-gnateu}
9546 Ignore unrecognized validity, warning, and style switches that
9547 appear after this switch is given. This may be useful when
9548 compiling sources developed on a later version of the compiler
9549 with an earlier version. Of course the earlier version must
9550 support this switch.
9553 @geindex -gnateV (gcc)
9558 @item @code{-gnateV}
9560 Check that all actual parameters of a subprogram call are valid according to
9561 the rules of validity checking (@ref{f6,,Validity Checking}).
9564 @geindex -gnateY (gcc)
9569 @item @code{-gnateY}
9571 Ignore all STYLE_CHECKS pragmas. Full legality checks
9572 are still carried out, but the pragmas have no effect
9573 on what style checks are active. This allows all style
9574 checking options to be controlled from the command line.
9577 @geindex -gnatE (gcc)
9584 Dynamic elaboration checking mode enabled. For further details see
9585 @ref{f,,Elaboration Order Handling in GNAT}.
9588 @geindex -gnatf (gcc)
9595 Full errors. Multiple errors per line, all undefined references, do not
9596 attempt to suppress cascaded errors.
9599 @geindex -gnatF (gcc)
9606 Externals names are folded to all uppercase.
9609 @geindex -gnatg (gcc)
9616 Internal GNAT implementation mode. This should not be used for applications
9617 programs, it is intended only for use by the compiler and its run-time
9618 library. For documentation, see the GNAT sources. Note that @code{-gnatg}
9619 implies @code{-gnatw.ge} and @code{-gnatyg} so that all standard
9620 warnings and all standard style options are turned on. All warnings and style
9621 messages are treated as errors.
9624 @geindex -gnatG[nn] (gcc)
9629 @item @code{-gnatG=nn}
9631 List generated expanded code in source form.
9634 @geindex -gnath (gcc)
9641 Output usage information. The output is written to @code{stdout}.
9644 @geindex -gnatH (gcc)
9651 Legacy elaboration-checking mode enabled. When this switch is in effect,
9652 the pre-18.x access-before-elaboration model becomes the de facto model.
9653 For further details see @ref{f,,Elaboration Order Handling in GNAT}.
9656 @geindex -gnati (gcc)
9661 @item @code{-gnati@emph{c}}
9663 Identifier character set (@code{c} = 1/2/3/4/8/9/p/f/n/w).
9664 For details of the possible selections for @code{c},
9665 see @ref{48,,Character Set Control}.
9668 @geindex -gnatI (gcc)
9675 Ignore representation clauses. When this switch is used,
9676 representation clauses are treated as comments. This is useful
9677 when initially porting code where you want to ignore rep clause
9678 problems, and also for compiling foreign code (particularly
9679 for use with ASIS). The representation clauses that are ignored
9680 are: enumeration_representation_clause, record_representation_clause,
9681 and attribute_definition_clause for the following attributes:
9682 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
9683 Object_Size, Scalar_Storage_Order, Size, Small, Stream_Size,
9684 and Value_Size. Pragma Default_Scalar_Storage_Order is also ignored.
9685 Note that this option should be used only for compiling -- the
9686 code is likely to malfunction at run time.
9688 Note that when @code{-gnatct} is used to generate trees for input
9689 into ASIS tools, these representation clauses are removed
9690 from the tree and ignored. This means that the tool will not see them.
9693 @geindex -gnatjnn (gcc)
9698 @item @code{-gnatj@emph{nn}}
9700 Reformat error messages to fit on @code{nn} character lines
9703 @geindex -gnatJ (gcc)
9710 Permissive elaboration-checking mode enabled. When this switch is in effect,
9711 the post-18.x access-before-elaboration model ignores potential issues with:
9720 Activations of tasks defined in instances
9726 Calls from within an instance to its enclosing context
9729 Calls through generic formal parameters
9732 Calls to subprograms defined in instances
9738 Indirect calls using 'Access
9747 Synchronous task suspension
9750 and does not emit compile-time diagnostics or run-time checks. For further
9751 details see @ref{f,,Elaboration Order Handling in GNAT}.
9754 @geindex -gnatk (gcc)
9759 @item @code{-gnatk=@emph{n}}
9761 Limit file names to @code{n} (1-999) characters (@code{k} = krunch).
9764 @geindex -gnatl (gcc)
9771 Output full source listing with embedded error messages.
9774 @geindex -gnatL (gcc)
9781 Used in conjunction with -gnatG or -gnatD to intersperse original
9782 source lines (as comment lines with line numbers) in the expanded
9786 @geindex -gnatm (gcc)
9791 @item @code{-gnatm=@emph{n}}
9793 Limit number of detected error or warning messages to @code{n}
9794 where @code{n} is in the range 1..999999. The default setting if
9795 no switch is given is 9999. If the number of warnings reaches this
9796 limit, then a message is output and further warnings are suppressed,
9797 but the compilation is continued. If the number of error messages
9798 reaches this limit, then a message is output and the compilation
9799 is abandoned. The equal sign here is optional. A value of zero
9800 means that no limit applies.
9803 @geindex -gnatn (gcc)
9808 @item @code{-gnatn[12]}
9810 Activate inlining across units for subprograms for which pragma @code{Inline}
9811 is specified. This inlining is performed by the GCC back-end. An optional
9812 digit sets the inlining level: 1 for moderate inlining across units
9813 or 2 for full inlining across units. If no inlining level is specified,
9814 the compiler will pick it based on the optimization level.
9817 @geindex -gnatN (gcc)
9824 Activate front end inlining for subprograms for which
9825 pragma @code{Inline} is specified. This inlining is performed
9826 by the front end and will be visible in the
9827 @code{-gnatG} output.
9829 When using a gcc-based back end (in practice this means using any version
9830 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
9831 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
9832 Historically front end inlining was more extensive than the gcc back end
9833 inlining, but that is no longer the case.
9836 @geindex -gnato0 (gcc)
9841 @item @code{-gnato0}
9843 Suppresses overflow checking. This causes the behavior of the compiler to
9844 match the default for older versions where overflow checking was suppressed
9845 by default. This is equivalent to having
9846 @code{pragma Suppress (Overflow_Check)} in a configuration pragma file.
9849 @geindex -gnato?? (gcc)
9854 @item @code{-gnato??}
9856 Set default mode for handling generation of code to avoid intermediate
9857 arithmetic overflow. Here @code{??} is two digits, a
9858 single digit, or nothing. Each digit is one of the digits @code{1}
9862 @multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
9877 All intermediate overflows checked against base type (@code{STRICT})
9885 Minimize intermediate overflows (@code{MINIMIZED})
9893 Eliminate intermediate overflows (@code{ELIMINATED})
9898 If only one digit appears, then it applies to all
9899 cases; if two digits are given, then the first applies outside
9900 assertions, pre/postconditions, and type invariants, and the second
9901 applies within assertions, pre/postconditions, and type invariants.
9903 If no digits follow the @code{-gnato}, then it is equivalent to
9905 causing all intermediate overflows to be handled in strict
9908 This switch also causes arithmetic overflow checking to be performed
9909 (as though @code{pragma Unsuppress (Overflow_Check)} had been specified).
9911 The default if no option @code{-gnato} is given is that overflow handling
9912 is in @code{STRICT} mode (computations done using the base type), and that
9913 overflow checking is enabled.
9915 Note that division by zero is a separate check that is not
9916 controlled by this switch (divide-by-zero checking is on by default).
9918 See also @ref{f8,,Specifying the Desired Mode}.
9921 @geindex -gnatp (gcc)
9928 Suppress all checks. See @ref{f9,,Run-Time Checks} for details. This switch
9929 has no effect if cancelled by a subsequent @code{-gnat-p} switch.
9932 @geindex -gnat-p (gcc)
9937 @item @code{-gnat-p}
9939 Cancel effect of previous @code{-gnatp} switch.
9942 @geindex -gnatP (gcc)
9949 Enable polling. This is required on some systems (notably Windows NT) to
9950 obtain asynchronous abort and asynchronous transfer of control capability.
9951 See @code{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full
9955 @geindex -gnatq (gcc)
9962 Don't quit. Try semantics, even if parse errors.
9965 @geindex -gnatQ (gcc)
9972 Don't quit. Generate @code{ALI} and tree files even if illegalities.
9973 Note that code generation is still suppressed in the presence of any
9974 errors, so even with @code{-gnatQ} no object file is generated.
9977 @geindex -gnatr (gcc)
9984 Treat pragma Restrictions as Restriction_Warnings.
9987 @geindex -gnatR (gcc)
9992 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
9994 Output representation information for declared types, objects and
9995 subprograms. Note that this switch is not allowed if a previous
9996 @code{-gnatD} switch has been given, since these two switches
10000 @geindex -gnats (gcc)
10005 @item @code{-gnats}
10010 @geindex -gnatS (gcc)
10015 @item @code{-gnatS}
10017 Print package Standard.
10020 @geindex -gnatt (gcc)
10025 @item @code{-gnatt}
10027 Generate tree output file.
10030 @geindex -gnatT (gcc)
10035 @item @code{-gnatT@emph{nnn}}
10037 All compiler tables start at @code{nnn} times usual starting size.
10040 @geindex -gnatu (gcc)
10045 @item @code{-gnatu}
10047 List units for this compilation.
10050 @geindex -gnatU (gcc)
10055 @item @code{-gnatU}
10057 Tag all error messages with the unique string 'error:'
10060 @geindex -gnatv (gcc)
10065 @item @code{-gnatv}
10067 Verbose mode. Full error output with source lines to @code{stdout}.
10070 @geindex -gnatV (gcc)
10075 @item @code{-gnatV}
10077 Control level of validity checking (@ref{f6,,Validity Checking}).
10080 @geindex -gnatw (gcc)
10085 @item @code{-gnatw@emph{xxx}}
10088 @code{xxx} is a string of option letters that denotes
10089 the exact warnings that
10090 are enabled or disabled (@ref{fa,,Warning Message Control}).
10093 @geindex -gnatW (gcc)
10098 @item @code{-gnatW@emph{e}}
10100 Wide character encoding method
10101 (@code{e}=n/h/u/s/e/8).
10104 @geindex -gnatx (gcc)
10109 @item @code{-gnatx}
10111 Suppress generation of cross-reference information.
10114 @geindex -gnatX (gcc)
10119 @item @code{-gnatX}
10121 Enable GNAT implementation extensions and latest Ada version.
10124 @geindex -gnaty (gcc)
10129 @item @code{-gnaty}
10131 Enable built-in style checks (@ref{fb,,Style Checking}).
10134 @geindex -gnatz (gcc)
10139 @item @code{-gnatz@emph{m}}
10141 Distribution stub generation and compilation
10142 (@code{m}=r/c for receiver/caller stubs).
10150 @item @code{-I@emph{dir}}
10154 Direct GNAT to search the @code{dir} directory for source files needed by
10155 the current compilation
10156 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10168 Except for the source file named in the command line, do not look for source
10169 files in the directory containing the source file named in the command line
10170 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10178 @item @code{-o @emph{file}}
10180 This switch is used in @code{gcc} to redirect the generated object file
10181 and its associated ALI file. Beware of this switch with GNAT, because it may
10182 cause the object file and ALI file to have different names which in turn
10183 may confuse the binder and the linker.
10186 @geindex -nostdinc (gcc)
10191 @item @code{-nostdinc}
10193 Inhibit the search of the default location for the GNAT Run Time
10194 Library (RTL) source files.
10197 @geindex -nostdlib (gcc)
10202 @item @code{-nostdlib}
10204 Inhibit the search of the default location for the GNAT Run Time
10205 Library (RTL) ALI files.
10213 @item @code{-O[@emph{n}]}
10215 @code{n} controls the optimization level:
10218 @multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
10233 No optimization, the default setting if no @code{-O} appears
10241 Normal optimization, the default if you specify @code{-O} without an
10242 operand. A good compromise between code quality and compilation
10251 Extensive optimization, may improve execution time, possibly at
10252 the cost of substantially increased compilation time.
10260 Same as @code{-O2}, and also includes inline expansion for small
10261 subprograms in the same unit.
10269 Optimize space usage
10274 See also @ref{fc,,Optimization Levels}.
10277 @geindex -pass-exit-codes (gcc)
10282 @item @code{-pass-exit-codes}
10284 Catch exit codes from the compiler and use the most meaningful as
10288 @geindex --RTS (gcc)
10293 @item @code{--RTS=@emph{rts-path}}
10295 Specifies the default location of the run-time library. Same meaning as the
10296 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
10306 Used in place of @code{-c} to
10307 cause the assembler source file to be
10308 generated, using @code{.s} as the extension,
10309 instead of the object file.
10310 This may be useful if you need to examine the generated assembly code.
10313 @geindex -fverbose-asm (gcc)
10318 @item @code{-fverbose-asm}
10320 Used in conjunction with @code{-S}
10321 to cause the generated assembly code file to be annotated with variable
10322 names, making it significantly easier to follow.
10332 Show commands generated by the @code{gcc} driver. Normally used only for
10333 debugging purposes or if you need to be sure what version of the
10334 compiler you are executing.
10342 @item @code{-V @emph{ver}}
10344 Execute @code{ver} version of the compiler. This is the @code{gcc}
10345 version, not the GNAT version.
10355 Turn off warnings generated by the back end of the compiler. Use of
10356 this switch also causes the default for front end warnings to be set
10357 to suppress (as though @code{-gnatws} had appeared at the start of
10361 @geindex Combining GNAT switches
10363 You may combine a sequence of GNAT switches into a single switch. For
10364 example, the combined switch
10373 is equivalent to specifying the following sequence of switches:
10378 -gnato -gnatf -gnati3
10382 The following restrictions apply to the combination of switches
10389 The switch @code{-gnatc} if combined with other switches must come
10390 first in the string.
10393 The switch @code{-gnats} if combined with other switches must come
10394 first in the string.
10398 @code{-gnatzc} and @code{-gnatzr} may not be combined with any other
10399 switches, and only one of them may appear in the command line.
10402 The switch @code{-gnat-p} may not be combined with any other switch.
10405 Once a 'y' appears in the string (that is a use of the @code{-gnaty}
10406 switch), then all further characters in the switch are interpreted
10407 as style modifiers (see description of @code{-gnaty}).
10410 Once a 'd' appears in the string (that is a use of the @code{-gnatd}
10411 switch), then all further characters in the switch are interpreted
10412 as debug flags (see description of @code{-gnatd}).
10415 Once a 'w' appears in the string (that is a use of the @code{-gnatw}
10416 switch), then all further characters in the switch are interpreted
10417 as warning mode modifiers (see description of @code{-gnatw}).
10420 Once a 'V' appears in the string (that is a use of the @code{-gnatV}
10421 switch), then all further characters in the switch are interpreted
10422 as validity checking options (@ref{f6,,Validity Checking}).
10425 Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in
10426 a combined list of options.
10429 @node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches
10430 @anchor{gnat_ugn/building_executable_programs_with_gnat id14}@anchor{fd}@anchor{gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control}@anchor{fe}
10431 @subsection Output and Error Message Control
10436 The standard default format for error messages is called 'brief format'.
10437 Brief format messages are written to @code{stderr} (the standard error
10438 file) and have the following form:
10441 e.adb:3:04: Incorrect spelling of keyword "function"
10442 e.adb:4:20: ";" should be "is"
10445 The first integer after the file name is the line number in the file,
10446 and the second integer is the column number within the line.
10447 @code{GPS} can parse the error messages
10448 and point to the referenced character.
10449 The following switches provide control over the error message
10452 @geindex -gnatv (gcc)
10457 @item @code{-gnatv}
10459 The @code{v} stands for verbose.
10460 The effect of this setting is to write long-format error
10461 messages to @code{stdout} (the standard output file.
10462 The same program compiled with the
10463 @code{-gnatv} switch would generate:
10466 3. funcion X (Q : Integer)
10468 >>> Incorrect spelling of keyword "function"
10471 >>> ";" should be "is"
10474 The vertical bar indicates the location of the error, and the @code{>>>}
10475 prefix can be used to search for error messages. When this switch is
10476 used the only source lines output are those with errors.
10479 @geindex -gnatl (gcc)
10484 @item @code{-gnatl}
10486 The @code{l} stands for list.
10487 This switch causes a full listing of
10488 the file to be generated. In the case where a body is
10489 compiled, the corresponding spec is also listed, along
10490 with any subunits. Typical output from compiling a package
10491 body @code{p.adb} might look like:
10496 1. package body p is
10498 3. procedure a is separate;
10509 2. pragma Elaborate_Body
10530 When you specify the @code{-gnatv} or @code{-gnatl} switches and
10531 standard output is redirected, a brief summary is written to
10532 @code{stderr} (standard error) giving the number of error messages and
10533 warning messages generated.
10536 @geindex -gnatl=fname (gcc)
10541 @item @code{-gnatl=@emph{fname}}
10543 This has the same effect as @code{-gnatl} except that the output is
10544 written to a file instead of to standard output. If the given name
10545 @code{fname} does not start with a period, then it is the full name
10546 of the file to be written. If @code{fname} is an extension, it is
10547 appended to the name of the file being compiled. For example, if
10548 file @code{xyz.adb} is compiled with @code{-gnatl=.lst},
10549 then the output is written to file xyz.adb.lst.
10552 @geindex -gnatU (gcc)
10557 @item @code{-gnatU}
10559 This switch forces all error messages to be preceded by the unique
10560 string 'error:'. This means that error messages take a few more
10561 characters in space, but allows easy searching for and identification
10565 @geindex -gnatb (gcc)
10570 @item @code{-gnatb}
10572 The @code{b} stands for brief.
10573 This switch causes GNAT to generate the
10574 brief format error messages to @code{stderr} (the standard error
10575 file) as well as the verbose
10576 format message or full listing (which as usual is written to
10577 @code{stdout} (the standard output file).
10580 @geindex -gnatm (gcc)
10585 @item @code{-gnatm=@emph{n}}
10587 The @code{m} stands for maximum.
10588 @code{n} is a decimal integer in the
10589 range of 1 to 999999 and limits the number of error or warning
10590 messages to be generated. For example, using
10591 @code{-gnatm2} might yield
10594 e.adb:3:04: Incorrect spelling of keyword "function"
10595 e.adb:5:35: missing ".."
10596 fatal error: maximum number of errors detected
10597 compilation abandoned
10600 The default setting if
10601 no switch is given is 9999. If the number of warnings reaches this
10602 limit, then a message is output and further warnings are suppressed,
10603 but the compilation is continued. If the number of error messages
10604 reaches this limit, then a message is output and the compilation
10605 is abandoned. A value of zero means that no limit applies.
10607 Note that the equal sign is optional, so the switches
10608 @code{-gnatm2} and @code{-gnatm=2} are equivalent.
10611 @geindex -gnatf (gcc)
10616 @item @code{-gnatf}
10618 @geindex Error messages
10619 @geindex suppressing
10621 The @code{f} stands for full.
10622 Normally, the compiler suppresses error messages that are likely to be
10623 redundant. This switch causes all error
10624 messages to be generated. In particular, in the case of
10625 references to undefined variables. If a given variable is referenced
10626 several times, the normal format of messages is
10629 e.adb:7:07: "V" is undefined (more references follow)
10632 where the parenthetical comment warns that there are additional
10633 references to the variable @code{V}. Compiling the same program with the
10634 @code{-gnatf} switch yields
10637 e.adb:7:07: "V" is undefined
10638 e.adb:8:07: "V" is undefined
10639 e.adb:8:12: "V" is undefined
10640 e.adb:8:16: "V" is undefined
10641 e.adb:9:07: "V" is undefined
10642 e.adb:9:12: "V" is undefined
10645 The @code{-gnatf} switch also generates additional information for
10646 some error messages. Some examples are:
10652 Details on possibly non-portable unchecked conversion
10655 List possible interpretations for ambiguous calls
10658 Additional details on incorrect parameters
10662 @geindex -gnatjnn (gcc)
10667 @item @code{-gnatjnn}
10669 In normal operation mode (or if @code{-gnatj0} is used), then error messages
10670 with continuation lines are treated as though the continuation lines were
10671 separate messages (and so a warning with two continuation lines counts as
10672 three warnings, and is listed as three separate messages).
10674 If the @code{-gnatjnn} switch is used with a positive value for nn, then
10675 messages are output in a different manner. A message and all its continuation
10676 lines are treated as a unit, and count as only one warning or message in the
10677 statistics totals. Furthermore, the message is reformatted so that no line
10678 is longer than nn characters.
10681 @geindex -gnatq (gcc)
10686 @item @code{-gnatq}
10688 The @code{q} stands for quit (really 'don't quit').
10689 In normal operation mode, the compiler first parses the program and
10690 determines if there are any syntax errors. If there are, appropriate
10691 error messages are generated and compilation is immediately terminated.
10693 GNAT to continue with semantic analysis even if syntax errors have been
10694 found. This may enable the detection of more errors in a single run. On
10695 the other hand, the semantic analyzer is more likely to encounter some
10696 internal fatal error when given a syntactically invalid tree.
10699 @geindex -gnatQ (gcc)
10704 @item @code{-gnatQ}
10706 In normal operation mode, the @code{ALI} file is not generated if any
10707 illegalities are detected in the program. The use of @code{-gnatQ} forces
10708 generation of the @code{ALI} file. This file is marked as being in
10709 error, so it cannot be used for binding purposes, but it does contain
10710 reasonably complete cross-reference information, and thus may be useful
10711 for use by tools (e.g., semantic browsing tools or integrated development
10712 environments) that are driven from the @code{ALI} file. This switch
10713 implies @code{-gnatq}, since the semantic phase must be run to get a
10714 meaningful ALI file.
10716 In addition, if @code{-gnatt} is also specified, then the tree file is
10717 generated even if there are illegalities. It may be useful in this case
10718 to also specify @code{-gnatq} to ensure that full semantic processing
10719 occurs. The resulting tree file can be processed by ASIS, for the purpose
10720 of providing partial information about illegal units, but if the error
10721 causes the tree to be badly malformed, then ASIS may crash during the
10724 When @code{-gnatQ} is used and the generated @code{ALI} file is marked as
10725 being in error, @code{gnatmake} will attempt to recompile the source when it
10726 finds such an @code{ALI} file, including with switch @code{-gnatc}.
10728 Note that @code{-gnatQ} has no effect if @code{-gnats} is specified,
10729 since ALI files are never generated if @code{-gnats} is set.
10732 @node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches
10733 @anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{fa}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{ff}
10734 @subsection Warning Message Control
10737 @geindex Warning messages
10739 In addition to error messages, which correspond to illegalities as defined
10740 in the Ada Reference Manual, the compiler detects two kinds of warning
10743 First, the compiler considers some constructs suspicious and generates a
10744 warning message to alert you to a possible error. Second, if the
10745 compiler detects a situation that is sure to raise an exception at
10746 run time, it generates a warning message. The following shows an example
10747 of warning messages:
10750 e.adb:4:24: warning: creation of object may raise Storage_Error
10751 e.adb:10:17: warning: static value out of range
10752 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
10755 GNAT considers a large number of situations as appropriate
10756 for the generation of warning messages. As always, warnings are not
10757 definite indications of errors. For example, if you do an out-of-range
10758 assignment with the deliberate intention of raising a
10759 @code{Constraint_Error} exception, then the warning that may be
10760 issued does not indicate an error. Some of the situations for which GNAT
10761 issues warnings (at least some of the time) are given in the following
10762 list. This list is not complete, and new warnings are often added to
10763 subsequent versions of GNAT. The list is intended to give a general idea
10764 of the kinds of warnings that are generated.
10770 Possible infinitely recursive calls
10773 Out-of-range values being assigned
10776 Possible order of elaboration problems
10779 Size not a multiple of alignment for a record type
10782 Assertions (pragma Assert) that are sure to fail
10788 Address clauses with possibly unaligned values, or where an attempt is
10789 made to overlay a smaller variable with a larger one.
10792 Fixed-point type declarations with a null range
10795 Direct_IO or Sequential_IO instantiated with a type that has access values
10798 Variables that are never assigned a value
10801 Variables that are referenced before being initialized
10804 Task entries with no corresponding @code{accept} statement
10807 Duplicate accepts for the same task entry in a @code{select}
10810 Objects that take too much storage
10813 Unchecked conversion between types of differing sizes
10816 Missing @code{return} statement along some execution path in a function
10819 Incorrect (unrecognized) pragmas
10822 Incorrect external names
10825 Allocation from empty storage pool
10828 Potentially blocking operation in protected type
10831 Suspicious parenthesization of expressions
10834 Mismatching bounds in an aggregate
10837 Attempt to return local value by reference
10840 Premature instantiation of a generic body
10843 Attempt to pack aliased components
10846 Out of bounds array subscripts
10849 Wrong length on string assignment
10852 Violations of style rules if style checking is enabled
10855 Unused @emph{with} clauses
10858 @code{Bit_Order} usage that does not have any effect
10861 @code{Standard.Duration} used to resolve universal fixed expression
10864 Dereference of possibly null value
10867 Declaration that is likely to cause storage error
10870 Internal GNAT unit @emph{with}ed by application unit
10873 Values known to be out of range at compile time
10876 Unreferenced or unmodified variables. Note that a special
10877 exemption applies to variables which contain any of the substrings
10878 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables
10879 are considered likely to be intentionally used in a situation where
10880 otherwise a warning would be given, so warnings of this kind are
10881 always suppressed for such variables.
10884 Address overlays that could clobber memory
10887 Unexpected initialization when address clause present
10890 Bad alignment for address clause
10893 Useless type conversions
10896 Redundant assignment statements and other redundant constructs
10899 Useless exception handlers
10902 Accidental hiding of name by child unit
10905 Access before elaboration detected at compile time
10908 A range in a @code{for} loop that is known to be null or might be null
10911 The following section lists compiler switches that are available
10912 to control the handling of warning messages. It is also possible
10913 to exercise much finer control over what warnings are issued and
10914 suppressed using the GNAT pragma Warnings (see the description
10915 of the pragma in the @cite{GNAT_Reference_manual}).
10917 @geindex -gnatwa (gcc)
10922 @item @code{-gnatwa}
10924 @emph{Activate most optional warnings.}
10926 This switch activates most optional warning messages. See the remaining list
10927 in this section for details on optional warning messages that can be
10928 individually controlled. The warnings that are not turned on by this
10935 @code{-gnatwd} (implicit dereferencing)
10938 @code{-gnatw.d} (tag warnings with -gnatw switch)
10941 @code{-gnatwh} (hiding)
10944 @code{-gnatw.h} (holes in record layouts)
10947 @code{-gnatw.j} (late primitives of tagged types)
10950 @code{-gnatw.k} (redefinition of names in standard)
10953 @code{-gnatwl} (elaboration warnings)
10956 @code{-gnatw.l} (inherited aspects)
10959 @code{-gnatw.n} (atomic synchronization)
10962 @code{-gnatwo} (address clause overlay)
10965 @code{-gnatw.o} (values set by out parameters ignored)
10968 @code{-gnatw.q} (questionable layout of record types)
10971 @code{-gnatw.s} (overridden size clause)
10974 @code{-gnatwt} (tracking of deleted conditional code)
10977 @code{-gnatw.u} (unordered enumeration)
10980 @code{-gnatw.w} (use of Warnings Off)
10983 @code{-gnatw.y} (reasons for package needing body)
10986 All other optional warnings are turned on.
10989 @geindex -gnatwA (gcc)
10994 @item @code{-gnatwA}
10996 @emph{Suppress all optional errors.}
10998 This switch suppresses all optional warning messages, see remaining list
10999 in this section for details on optional warning messages that can be
11000 individually controlled. Note that unlike switch @code{-gnatws}, the
11001 use of switch @code{-gnatwA} does not suppress warnings that are
11002 normally given unconditionally and cannot be individually controlled
11003 (for example, the warning about a missing exit path in a function).
11004 Also, again unlike switch @code{-gnatws}, warnings suppressed by
11005 the use of switch @code{-gnatwA} can be individually turned back
11006 on. For example the use of switch @code{-gnatwA} followed by
11007 switch @code{-gnatwd} will suppress all optional warnings except
11008 the warnings for implicit dereferencing.
11011 @geindex -gnatw.a (gcc)
11016 @item @code{-gnatw.a}
11018 @emph{Activate warnings on failing assertions.}
11020 @geindex Assert failures
11022 This switch activates warnings for assertions where the compiler can tell at
11023 compile time that the assertion will fail. Note that this warning is given
11024 even if assertions are disabled. The default is that such warnings are
11028 @geindex -gnatw.A (gcc)
11033 @item @code{-gnatw.A}
11035 @emph{Suppress warnings on failing assertions.}
11037 @geindex Assert failures
11039 This switch suppresses warnings for assertions where the compiler can tell at
11040 compile time that the assertion will fail.
11043 @geindex -gnatwb (gcc)
11048 @item @code{-gnatwb}
11050 @emph{Activate warnings on bad fixed values.}
11052 @geindex Bad fixed values
11054 @geindex Fixed-point Small value
11056 @geindex Small value
11058 This switch activates warnings for static fixed-point expressions whose
11059 value is not an exact multiple of Small. Such values are implementation
11060 dependent, since an implementation is free to choose either of the multiples
11061 that surround the value. GNAT always chooses the closer one, but this is not
11062 required behavior, and it is better to specify a value that is an exact
11063 multiple, ensuring predictable execution. The default is that such warnings
11067 @geindex -gnatwB (gcc)
11072 @item @code{-gnatwB}
11074 @emph{Suppress warnings on bad fixed values.}
11076 This switch suppresses warnings for static fixed-point expressions whose
11077 value is not an exact multiple of Small.
11080 @geindex -gnatw.b (gcc)
11085 @item @code{-gnatw.b}
11087 @emph{Activate warnings on biased representation.}
11089 @geindex Biased representation
11091 This switch activates warnings when a size clause, value size clause, component
11092 clause, or component size clause forces the use of biased representation for an
11093 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
11094 to represent 10/11). The default is that such warnings are generated.
11097 @geindex -gnatwB (gcc)
11102 @item @code{-gnatw.B}
11104 @emph{Suppress warnings on biased representation.}
11106 This switch suppresses warnings for representation clauses that force the use
11107 of biased representation.
11110 @geindex -gnatwc (gcc)
11115 @item @code{-gnatwc}
11117 @emph{Activate warnings on conditionals.}
11119 @geindex Conditionals
11122 This switch activates warnings for conditional expressions used in
11123 tests that are known to be True or False at compile time. The default
11124 is that such warnings are not generated.
11125 Note that this warning does
11126 not get issued for the use of boolean variables or constants whose
11127 values are known at compile time, since this is a standard technique
11128 for conditional compilation in Ada, and this would generate too many
11129 false positive warnings.
11131 This warning option also activates a special test for comparisons using
11132 the operators '>=' and' <='.
11133 If the compiler can tell that only the equality condition is possible,
11134 then it will warn that the '>' or '<' part of the test
11135 is useless and that the operator could be replaced by '='.
11136 An example would be comparing a @code{Natural} variable <= 0.
11138 This warning option also generates warnings if
11139 one or both tests is optimized away in a membership test for integer
11140 values if the result can be determined at compile time. Range tests on
11141 enumeration types are not included, since it is common for such tests
11142 to include an end point.
11144 This warning can also be turned on using @code{-gnatwa}.
11147 @geindex -gnatwC (gcc)
11152 @item @code{-gnatwC}
11154 @emph{Suppress warnings on conditionals.}
11156 This switch suppresses warnings for conditional expressions used in
11157 tests that are known to be True or False at compile time.
11160 @geindex -gnatw.c (gcc)
11165 @item @code{-gnatw.c}
11167 @emph{Activate warnings on missing component clauses.}
11169 @geindex Component clause
11172 This switch activates warnings for record components where a record
11173 representation clause is present and has component clauses for the
11174 majority, but not all, of the components. A warning is given for each
11175 component for which no component clause is present.
11178 @geindex -gnatwC (gcc)
11183 @item @code{-gnatw.C}
11185 @emph{Suppress warnings on missing component clauses.}
11187 This switch suppresses warnings for record components that are
11188 missing a component clause in the situation described above.
11191 @geindex -gnatwd (gcc)
11196 @item @code{-gnatwd}
11198 @emph{Activate warnings on implicit dereferencing.}
11200 If this switch is set, then the use of a prefix of an access type
11201 in an indexed component, slice, or selected component without an
11202 explicit @code{.all} will generate a warning. With this warning
11203 enabled, access checks occur only at points where an explicit
11204 @code{.all} appears in the source code (assuming no warnings are
11205 generated as a result of this switch). The default is that such
11206 warnings are not generated.
11209 @geindex -gnatwD (gcc)
11214 @item @code{-gnatwD}
11216 @emph{Suppress warnings on implicit dereferencing.}
11218 @geindex Implicit dereferencing
11220 @geindex Dereferencing
11223 This switch suppresses warnings for implicit dereferences in
11224 indexed components, slices, and selected components.
11227 @geindex -gnatw.d (gcc)
11232 @item @code{-gnatw.d}
11234 @emph{Activate tagging of warning and info messages.}
11236 If this switch is set, then warning messages are tagged, with one of the
11246 Used to tag warnings controlled by the switch @code{-gnatwx} where x
11251 Used to tag warnings controlled by the switch @code{-gnatw.x} where x
11256 Used to tag elaboration information (info) messages generated when the
11257 static model of elaboration is used and the @code{-gnatel} switch is set.
11260 @emph{[restriction warning]}
11261 Used to tag warning messages for restriction violations, activated by use
11262 of the pragma @code{Restriction_Warnings}.
11265 @emph{[warning-as-error]}
11266 Used to tag warning messages that have been converted to error messages by
11267 use of the pragma Warning_As_Error. Note that such warnings are prefixed by
11268 the string "error: " rather than "warning: ".
11271 @emph{[enabled by default]}
11272 Used to tag all other warnings that are always given by default, unless
11273 warnings are completely suppressed using pragma @emph{Warnings(Off)} or
11274 the switch @code{-gnatws}.
11279 @geindex -gnatw.d (gcc)
11284 @item @code{-gnatw.D}
11286 @emph{Deactivate tagging of warning and info messages messages.}
11288 If this switch is set, then warning messages return to the default
11289 mode in which warnings and info messages are not tagged as described above for
11293 @geindex -gnatwe (gcc)
11296 @geindex treat as error
11301 @item @code{-gnatwe}
11303 @emph{Treat warnings and style checks as errors.}
11305 This switch causes warning messages and style check messages to be
11307 The warning string still appears, but the warning messages are counted
11308 as errors, and prevent the generation of an object file. Note that this
11309 is the only -gnatw switch that affects the handling of style check messages.
11310 Note also that this switch has no effect on info (information) messages, which
11311 are not treated as errors if this switch is present.
11314 @geindex -gnatw.e (gcc)
11319 @item @code{-gnatw.e}
11321 @emph{Activate every optional warning.}
11324 @geindex activate every optional warning
11326 This switch activates all optional warnings, including those which
11327 are not activated by @code{-gnatwa}. The use of this switch is not
11328 recommended for normal use. If you turn this switch on, it is almost
11329 certain that you will get large numbers of useless warnings. The
11330 warnings that are excluded from @code{-gnatwa} are typically highly
11331 specialized warnings that are suitable for use only in code that has
11332 been specifically designed according to specialized coding rules.
11335 @geindex -gnatwE (gcc)
11338 @geindex treat as error
11343 @item @code{-gnatwE}
11345 @emph{Treat all run-time exception warnings as errors.}
11347 This switch causes warning messages regarding errors that will be raised
11348 during run-time execution to be treated as errors.
11351 @geindex -gnatwf (gcc)
11356 @item @code{-gnatwf}
11358 @emph{Activate warnings on unreferenced formals.}
11361 @geindex unreferenced
11363 This switch causes a warning to be generated if a formal parameter
11364 is not referenced in the body of the subprogram. This warning can
11365 also be turned on using @code{-gnatwu}. The
11366 default is that these warnings are not generated.
11369 @geindex -gnatwF (gcc)
11374 @item @code{-gnatwF}
11376 @emph{Suppress warnings on unreferenced formals.}
11378 This switch suppresses warnings for unreferenced formal
11379 parameters. Note that the
11380 combination @code{-gnatwu} followed by @code{-gnatwF} has the
11381 effect of warning on unreferenced entities other than subprogram
11385 @geindex -gnatwg (gcc)
11390 @item @code{-gnatwg}
11392 @emph{Activate warnings on unrecognized pragmas.}
11395 @geindex unrecognized
11397 This switch causes a warning to be generated if an unrecognized
11398 pragma is encountered. Apart from issuing this warning, the
11399 pragma is ignored and has no effect. The default
11400 is that such warnings are issued (satisfying the Ada Reference
11401 Manual requirement that such warnings appear).
11404 @geindex -gnatwG (gcc)
11409 @item @code{-gnatwG}
11411 @emph{Suppress warnings on unrecognized pragmas.}
11413 This switch suppresses warnings for unrecognized pragmas.
11416 @geindex -gnatw.g (gcc)
11421 @item @code{-gnatw.g}
11423 @emph{Warnings used for GNAT sources.}
11425 This switch sets the warning categories that are used by the standard
11426 GNAT style. Currently this is equivalent to
11427 @code{-gnatwAao.q.s.CI.V.X.Z}
11428 but more warnings may be added in the future without advanced notice.
11431 @geindex -gnatwh (gcc)
11436 @item @code{-gnatwh}
11438 @emph{Activate warnings on hiding.}
11440 @geindex Hiding of Declarations
11442 This switch activates warnings on hiding declarations that are considered
11443 potentially confusing. Not all cases of hiding cause warnings; for example an
11444 overriding declaration hides an implicit declaration, which is just normal
11445 code. The default is that warnings on hiding are not generated.
11448 @geindex -gnatwH (gcc)
11453 @item @code{-gnatwH}
11455 @emph{Suppress warnings on hiding.}
11457 This switch suppresses warnings on hiding declarations.
11460 @geindex -gnatw.h (gcc)
11465 @item @code{-gnatw.h}
11467 @emph{Activate warnings on holes/gaps in records.}
11469 @geindex Record Representation (gaps)
11471 This switch activates warnings on component clauses in record
11472 representation clauses that leave holes (gaps) in the record layout.
11473 If this warning option is active, then record representation clauses
11474 should specify a contiguous layout, adding unused fill fields if needed.
11477 @geindex -gnatw.H (gcc)
11482 @item @code{-gnatw.H}
11484 @emph{Suppress warnings on holes/gaps in records.}
11486 This switch suppresses warnings on component clauses in record
11487 representation clauses that leave holes (haps) in the record layout.
11490 @geindex -gnatwi (gcc)
11495 @item @code{-gnatwi}
11497 @emph{Activate warnings on implementation units.}
11499 This switch activates warnings for a @emph{with} of an internal GNAT
11500 implementation unit, defined as any unit from the @code{Ada},
11501 @code{Interfaces}, @code{GNAT},
11503 hierarchies that is not
11504 documented in either the Ada Reference Manual or the GNAT
11505 Programmer's Reference Manual. Such units are intended only
11506 for internal implementation purposes and should not be @emph{with}ed
11507 by user programs. The default is that such warnings are generated
11510 @geindex -gnatwI (gcc)
11515 @item @code{-gnatwI}
11517 @emph{Disable warnings on implementation units.}
11519 This switch disables warnings for a @emph{with} of an internal GNAT
11520 implementation unit.
11523 @geindex -gnatw.i (gcc)
11528 @item @code{-gnatw.i}
11530 @emph{Activate warnings on overlapping actuals.}
11532 This switch enables a warning on statically detectable overlapping actuals in
11533 a subprogram call, when one of the actuals is an in-out parameter, and the
11534 types of the actuals are not by-copy types. This warning is off by default.
11537 @geindex -gnatw.I (gcc)
11542 @item @code{-gnatw.I}
11544 @emph{Disable warnings on overlapping actuals.}
11546 This switch disables warnings on overlapping actuals in a call..
11549 @geindex -gnatwj (gcc)
11554 @item @code{-gnatwj}
11556 @emph{Activate warnings on obsolescent features (Annex J).}
11559 @geindex obsolescent
11561 @geindex Obsolescent features
11563 If this warning option is activated, then warnings are generated for
11564 calls to subprograms marked with @code{pragma Obsolescent} and
11565 for use of features in Annex J of the Ada Reference Manual. In the
11566 case of Annex J, not all features are flagged. In particular use
11567 of the renamed packages (like @code{Text_IO}) and use of package
11568 @code{ASCII} are not flagged, since these are very common and
11569 would generate many annoying positive warnings. The default is that
11570 such warnings are not generated.
11572 In addition to the above cases, warnings are also generated for
11573 GNAT features that have been provided in past versions but which
11574 have been superseded (typically by features in the new Ada standard).
11575 For example, @code{pragma Ravenscar} will be flagged since its
11576 function is replaced by @code{pragma Profile(Ravenscar)}, and
11577 @code{pragma Interface_Name} will be flagged since its function
11578 is replaced by @code{pragma Import}.
11580 Note that this warning option functions differently from the
11581 restriction @code{No_Obsolescent_Features} in two respects.
11582 First, the restriction applies only to annex J features.
11583 Second, the restriction does flag uses of package @code{ASCII}.
11586 @geindex -gnatwJ (gcc)
11591 @item @code{-gnatwJ}
11593 @emph{Suppress warnings on obsolescent features (Annex J).}
11595 This switch disables warnings on use of obsolescent features.
11598 @geindex -gnatw.j (gcc)
11603 @item @code{-gnatw.j}
11605 @emph{Activate warnings on late declarations of tagged type primitives.}
11607 This switch activates warnings on visible primitives added to a
11608 tagged type after deriving a private extension from it.
11611 @geindex -gnatw.J (gcc)
11616 @item @code{-gnatw.J}
11618 @emph{Suppress warnings on late declarations of tagged type primitives.}
11620 This switch suppresses warnings on visible primitives added to a
11621 tagged type after deriving a private extension from it.
11624 @geindex -gnatwk (gcc)
11629 @item @code{-gnatwk}
11631 @emph{Activate warnings on variables that could be constants.}
11633 This switch activates warnings for variables that are initialized but
11634 never modified, and then could be declared constants. The default is that
11635 such warnings are not given.
11638 @geindex -gnatwK (gcc)
11643 @item @code{-gnatwK}
11645 @emph{Suppress warnings on variables that could be constants.}
11647 This switch disables warnings on variables that could be declared constants.
11650 @geindex -gnatw.k (gcc)
11655 @item @code{-gnatw.k}
11657 @emph{Activate warnings on redefinition of names in standard.}
11659 This switch activates warnings for declarations that declare a name that
11660 is defined in package Standard. Such declarations can be confusing,
11661 especially since the names in package Standard continue to be directly
11662 visible, meaning that use visibiliy on such redeclared names does not
11663 work as expected. Names of discriminants and components in records are
11664 not included in this check.
11667 @geindex -gnatwK (gcc)
11672 @item @code{-gnatw.K}
11674 @emph{Suppress warnings on redefinition of names in standard.}
11676 This switch activates warnings for declarations that declare a name that
11677 is defined in package Standard.
11680 @geindex -gnatwl (gcc)
11685 @item @code{-gnatwl}
11687 @emph{Activate warnings for elaboration pragmas.}
11689 @geindex Elaboration
11692 This switch activates warnings for possible elaboration problems,
11693 including suspicious use
11694 of @code{Elaborate} pragmas, when using the static elaboration model, and
11695 possible situations that may raise @code{Program_Error} when using the
11696 dynamic elaboration model.
11697 See the section in this guide on elaboration checking for further details.
11698 The default is that such warnings
11702 @geindex -gnatwL (gcc)
11707 @item @code{-gnatwL}
11709 @emph{Suppress warnings for elaboration pragmas.}
11711 This switch suppresses warnings for possible elaboration problems.
11714 @geindex -gnatw.l (gcc)
11719 @item @code{-gnatw.l}
11721 @emph{List inherited aspects.}
11723 This switch causes the compiler to list inherited invariants,
11724 preconditions, and postconditions from Type_Invariant'Class, Invariant'Class,
11725 Pre'Class, and Post'Class aspects. Also list inherited subtype predicates.
11728 @geindex -gnatw.L (gcc)
11733 @item @code{-gnatw.L}
11735 @emph{Suppress listing of inherited aspects.}
11737 This switch suppresses listing of inherited aspects.
11740 @geindex -gnatwm (gcc)
11745 @item @code{-gnatwm}
11747 @emph{Activate warnings on modified but unreferenced variables.}
11749 This switch activates warnings for variables that are assigned (using
11750 an initialization value or with one or more assignment statements) but
11751 whose value is never read. The warning is suppressed for volatile
11752 variables and also for variables that are renamings of other variables
11753 or for which an address clause is given.
11754 The default is that these warnings are not given.
11757 @geindex -gnatwM (gcc)
11762 @item @code{-gnatwM}
11764 @emph{Disable warnings on modified but unreferenced variables.}
11766 This switch disables warnings for variables that are assigned or
11767 initialized, but never read.
11770 @geindex -gnatw.m (gcc)
11775 @item @code{-gnatw.m}
11777 @emph{Activate warnings on suspicious modulus values.}
11779 This switch activates warnings for modulus values that seem suspicious.
11780 The cases caught are where the size is the same as the modulus (e.g.
11781 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
11782 with no size clause. The guess in both cases is that 2**x was intended
11783 rather than x. In addition expressions of the form 2*x for small x
11784 generate a warning (the almost certainly accurate guess being that
11785 2**x was intended). The default is that these warnings are given.
11788 @geindex -gnatw.M (gcc)
11793 @item @code{-gnatw.M}
11795 @emph{Disable warnings on suspicious modulus values.}
11797 This switch disables warnings for suspicious modulus values.
11800 @geindex -gnatwn (gcc)
11805 @item @code{-gnatwn}
11807 @emph{Set normal warnings mode.}
11809 This switch sets normal warning mode, in which enabled warnings are
11810 issued and treated as warnings rather than errors. This is the default
11811 mode. the switch @code{-gnatwn} can be used to cancel the effect of
11812 an explicit @code{-gnatws} or
11813 @code{-gnatwe}. It also cancels the effect of the
11814 implicit @code{-gnatwe} that is activated by the
11815 use of @code{-gnatg}.
11818 @geindex -gnatw.n (gcc)
11820 @geindex Atomic Synchronization
11826 @item @code{-gnatw.n}
11828 @emph{Activate warnings on atomic synchronization.}
11830 This switch actives warnings when an access to an atomic variable
11831 requires the generation of atomic synchronization code. These
11832 warnings are off by default.
11835 @geindex -gnatw.N (gcc)
11840 @item @code{-gnatw.N}
11842 @emph{Suppress warnings on atomic synchronization.}
11844 @geindex Atomic Synchronization
11847 This switch suppresses warnings when an access to an atomic variable
11848 requires the generation of atomic synchronization code.
11851 @geindex -gnatwo (gcc)
11853 @geindex Address Clauses
11859 @item @code{-gnatwo}
11861 @emph{Activate warnings on address clause overlays.}
11863 This switch activates warnings for possibly unintended initialization
11864 effects of defining address clauses that cause one variable to overlap
11865 another. The default is that such warnings are generated.
11868 @geindex -gnatwO (gcc)
11873 @item @code{-gnatwO}
11875 @emph{Suppress warnings on address clause overlays.}
11877 This switch suppresses warnings on possibly unintended initialization
11878 effects of defining address clauses that cause one variable to overlap
11882 @geindex -gnatw.o (gcc)
11887 @item @code{-gnatw.o}
11889 @emph{Activate warnings on modified but unreferenced out parameters.}
11891 This switch activates warnings for variables that are modified by using
11892 them as actuals for a call to a procedure with an out mode formal, where
11893 the resulting assigned value is never read. It is applicable in the case
11894 where there is more than one out mode formal. If there is only one out
11895 mode formal, the warning is issued by default (controlled by -gnatwu).
11896 The warning is suppressed for volatile
11897 variables and also for variables that are renamings of other variables
11898 or for which an address clause is given.
11899 The default is that these warnings are not given.
11902 @geindex -gnatw.O (gcc)
11907 @item @code{-gnatw.O}
11909 @emph{Disable warnings on modified but unreferenced out parameters.}
11911 This switch suppresses warnings for variables that are modified by using
11912 them as actuals for a call to a procedure with an out mode formal, where
11913 the resulting assigned value is never read.
11916 @geindex -gnatwp (gcc)
11924 @item @code{-gnatwp}
11926 @emph{Activate warnings on ineffective pragma Inlines.}
11928 This switch activates warnings for failure of front end inlining
11929 (activated by @code{-gnatN}) to inline a particular call. There are
11930 many reasons for not being able to inline a call, including most
11931 commonly that the call is too complex to inline. The default is
11932 that such warnings are not given.
11933 Warnings on ineffective inlining by the gcc back-end can be activated
11934 separately, using the gcc switch -Winline.
11937 @geindex -gnatwP (gcc)
11942 @item @code{-gnatwP}
11944 @emph{Suppress warnings on ineffective pragma Inlines.}
11946 This switch suppresses warnings on ineffective pragma Inlines. If the
11947 inlining mechanism cannot inline a call, it will simply ignore the
11951 @geindex -gnatw.p (gcc)
11953 @geindex Parameter order
11959 @item @code{-gnatw.p}
11961 @emph{Activate warnings on parameter ordering.}
11963 This switch activates warnings for cases of suspicious parameter
11964 ordering when the list of arguments are all simple identifiers that
11965 match the names of the formals, but are in a different order. The
11966 warning is suppressed if any use of named parameter notation is used,
11967 so this is the appropriate way to suppress a false positive (and
11968 serves to emphasize that the "misordering" is deliberate). The
11969 default is that such warnings are not given.
11972 @geindex -gnatw.P (gcc)
11977 @item @code{-gnatw.P}
11979 @emph{Suppress warnings on parameter ordering.}
11981 This switch suppresses warnings on cases of suspicious parameter
11985 @geindex -gnatwq (gcc)
11987 @geindex Parentheses
11993 @item @code{-gnatwq}
11995 @emph{Activate warnings on questionable missing parentheses.}
11997 This switch activates warnings for cases where parentheses are not used and
11998 the result is potential ambiguity from a readers point of view. For example
11999 (not a > b) when a and b are modular means ((not a) > b) and very likely the
12000 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
12001 quite likely ((-x) mod 5) was intended. In such situations it seems best to
12002 follow the rule of always parenthesizing to make the association clear, and
12003 this warning switch warns if such parentheses are not present. The default
12004 is that these warnings are given.
12007 @geindex -gnatwQ (gcc)
12012 @item @code{-gnatwQ}
12014 @emph{Suppress warnings on questionable missing parentheses.}
12016 This switch suppresses warnings for cases where the association is not
12017 clear and the use of parentheses is preferred.
12020 @geindex -gnatw.q (gcc)
12028 @item @code{-gnatw.q}
12030 @emph{Activate warnings on questionable layout of record types.}
12032 This switch activates warnings for cases where the default layout of
12033 a record type, that is to say the layout of its components in textual
12034 order of the source code, would very likely cause inefficiencies in
12035 the code generated by the compiler, both in terms of space and speed
12036 during execution. One warning is issued for each problematic component
12037 without representation clause in the nonvariant part and then in each
12038 variant recursively, if any.
12040 The purpose of these warnings is neither to prescribe an optimal layout
12041 nor to force the use of representation clauses, but rather to get rid of
12042 the most blatant inefficiencies in the layout. Therefore, the default
12043 layout is matched against the following synthetic ordered layout and
12044 the deviations are flagged on a component-by-component basis:
12050 first all components or groups of components whose length is fixed
12051 and a multiple of the storage unit,
12054 then the remaining components whose length is fixed and not a multiple
12055 of the storage unit,
12058 then the remaining components whose length doesn't depend on discriminants
12059 (that is to say, with variable but uniform length for all objects),
12062 then all components whose length depends on discriminants,
12065 finally the variant part (if any),
12068 for the nonvariant part and for each variant recursively, if any.
12070 The exact wording of the warning depends on whether the compiler is allowed
12071 to reorder the components in the record type or precluded from doing it by
12072 means of pragma @code{No_Component_Reordering}.
12074 The default is that these warnings are not given.
12077 @geindex -gnatw.Q (gcc)
12082 @item @code{-gnatw.Q}
12084 @emph{Suppress warnings on questionable layout of record types.}
12086 This switch suppresses warnings for cases where the default layout of
12087 a record type would very likely cause inefficiencies.
12090 @geindex -gnatwr (gcc)
12095 @item @code{-gnatwr}
12097 @emph{Activate warnings on redundant constructs.}
12099 This switch activates warnings for redundant constructs. The following
12100 is the current list of constructs regarded as redundant:
12106 Assignment of an item to itself.
12109 Type conversion that converts an expression to its own type.
12112 Use of the attribute @code{Base} where @code{typ'Base} is the same
12116 Use of pragma @code{Pack} when all components are placed by a record
12117 representation clause.
12120 Exception handler containing only a reraise statement (raise with no
12121 operand) which has no effect.
12124 Use of the operator abs on an operand that is known at compile time
12128 Comparison of an object or (unary or binary) operation of boolean type to
12129 an explicit True value.
12132 The default is that warnings for redundant constructs are not given.
12135 @geindex -gnatwR (gcc)
12140 @item @code{-gnatwR}
12142 @emph{Suppress warnings on redundant constructs.}
12144 This switch suppresses warnings for redundant constructs.
12147 @geindex -gnatw.r (gcc)
12152 @item @code{-gnatw.r}
12154 @emph{Activate warnings for object renaming function.}
12156 This switch activates warnings for an object renaming that renames a
12157 function call, which is equivalent to a constant declaration (as
12158 opposed to renaming the function itself). The default is that these
12159 warnings are given.
12162 @geindex -gnatwT (gcc)
12167 @item @code{-gnatw.R}
12169 @emph{Suppress warnings for object renaming function.}
12171 This switch suppresses warnings for object renaming function.
12174 @geindex -gnatws (gcc)
12179 @item @code{-gnatws}
12181 @emph{Suppress all warnings.}
12183 This switch completely suppresses the
12184 output of all warning messages from the GNAT front end, including
12185 both warnings that can be controlled by switches described in this
12186 section, and those that are normally given unconditionally. The
12187 effect of this suppress action can only be cancelled by a subsequent
12188 use of the switch @code{-gnatwn}.
12190 Note that switch @code{-gnatws} does not suppress
12191 warnings from the @code{gcc} back end.
12192 To suppress these back end warnings as well, use the switch @code{-w}
12193 in addition to @code{-gnatws}. Also this switch has no effect on the
12194 handling of style check messages.
12197 @geindex -gnatw.s (gcc)
12199 @geindex Record Representation (component sizes)
12204 @item @code{-gnatw.s}
12206 @emph{Activate warnings on overridden size clauses.}
12208 This switch activates warnings on component clauses in record
12209 representation clauses where the length given overrides that
12210 specified by an explicit size clause for the component type. A
12211 warning is similarly given in the array case if a specified
12212 component size overrides an explicit size clause for the array
12216 @geindex -gnatw.S (gcc)
12221 @item @code{-gnatw.S}
12223 @emph{Suppress warnings on overridden size clauses.}
12225 This switch suppresses warnings on component clauses in record
12226 representation clauses that override size clauses, and similar
12227 warnings when an array component size overrides a size clause.
12230 @geindex -gnatwt (gcc)
12232 @geindex Deactivated code
12235 @geindex Deleted code
12241 @item @code{-gnatwt}
12243 @emph{Activate warnings for tracking of deleted conditional code.}
12245 This switch activates warnings for tracking of code in conditionals (IF and
12246 CASE statements) that is detected to be dead code which cannot be executed, and
12247 which is removed by the front end. This warning is off by default. This may be
12248 useful for detecting deactivated code in certified applications.
12251 @geindex -gnatwT (gcc)
12256 @item @code{-gnatwT}
12258 @emph{Suppress warnings for tracking of deleted conditional code.}
12260 This switch suppresses warnings for tracking of deleted conditional code.
12263 @geindex -gnatw.t (gcc)
12268 @item @code{-gnatw.t}
12270 @emph{Activate warnings on suspicious contracts.}
12272 This switch activates warnings on suspicious contracts. This includes
12273 warnings on suspicious postconditions (whether a pragma @code{Postcondition} or a
12274 @code{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect
12275 @code{Contract_Cases}). A function postcondition or contract case is suspicious
12276 when no postcondition or contract case for this function mentions the result
12277 of the function. A procedure postcondition or contract case is suspicious
12278 when it only refers to the pre-state of the procedure, because in that case
12279 it should rather be expressed as a precondition. This switch also controls
12280 warnings on suspicious cases of expressions typically found in contracts like
12281 quantified expressions and uses of Update attribute. The default is that such
12282 warnings are generated.
12285 @geindex -gnatw.T (gcc)
12290 @item @code{-gnatw.T}
12292 @emph{Suppress warnings on suspicious contracts.}
12294 This switch suppresses warnings on suspicious contracts.
12297 @geindex -gnatwu (gcc)
12302 @item @code{-gnatwu}
12304 @emph{Activate warnings on unused entities.}
12306 This switch activates warnings to be generated for entities that
12307 are declared but not referenced, and for units that are @emph{with}ed
12309 referenced. In the case of packages, a warning is also generated if
12310 no entities in the package are referenced. This means that if a with'ed
12311 package is referenced but the only references are in @code{use}
12312 clauses or @code{renames}
12313 declarations, a warning is still generated. A warning is also generated
12314 for a generic package that is @emph{with}ed but never instantiated.
12315 In the case where a package or subprogram body is compiled, and there
12316 is a @emph{with} on the corresponding spec
12317 that is only referenced in the body,
12318 a warning is also generated, noting that the
12319 @emph{with} can be moved to the body. The default is that
12320 such warnings are not generated.
12321 This switch also activates warnings on unreferenced formals
12322 (it includes the effect of @code{-gnatwf}).
12325 @geindex -gnatwU (gcc)
12330 @item @code{-gnatwU}
12332 @emph{Suppress warnings on unused entities.}
12334 This switch suppresses warnings for unused entities and packages.
12335 It also turns off warnings on unreferenced formals (and thus includes
12336 the effect of @code{-gnatwF}).
12339 @geindex -gnatw.u (gcc)
12344 @item @code{-gnatw.u}
12346 @emph{Activate warnings on unordered enumeration types.}
12348 This switch causes enumeration types to be considered as conceptually
12349 unordered, unless an explicit pragma @code{Ordered} is given for the type.
12350 The effect is to generate warnings in clients that use explicit comparisons
12351 or subranges, since these constructs both treat objects of the type as
12352 ordered. (A @emph{client} is defined as a unit that is other than the unit in
12353 which the type is declared, or its body or subunits.) Please refer to
12354 the description of pragma @code{Ordered} in the
12355 @cite{GNAT Reference Manual} for further details.
12356 The default is that such warnings are not generated.
12359 @geindex -gnatw.U (gcc)
12364 @item @code{-gnatw.U}
12366 @emph{Deactivate warnings on unordered enumeration types.}
12368 This switch causes all enumeration types to be considered as ordered, so
12369 that no warnings are given for comparisons or subranges for any type.
12372 @geindex -gnatwv (gcc)
12374 @geindex Unassigned variable warnings
12379 @item @code{-gnatwv}
12381 @emph{Activate warnings on unassigned variables.}
12383 This switch activates warnings for access to variables which
12384 may not be properly initialized. The default is that
12385 such warnings are generated.
12388 @geindex -gnatwV (gcc)
12393 @item @code{-gnatwV}
12395 @emph{Suppress warnings on unassigned variables.}
12397 This switch suppresses warnings for access to variables which
12398 may not be properly initialized.
12399 For variables of a composite type, the warning can also be suppressed in
12400 Ada 2005 by using a default initialization with a box. For example, if
12401 Table is an array of records whose components are only partially uninitialized,
12402 then the following code:
12405 Tab : Table := (others => <>);
12408 will suppress warnings on subsequent statements that access components
12412 @geindex -gnatw.v (gcc)
12414 @geindex bit order warnings
12419 @item @code{-gnatw.v}
12421 @emph{Activate info messages for non-default bit order.}
12423 This switch activates messages (labeled "info", they are not warnings,
12424 just informational messages) about the effects of non-default bit-order
12425 on records to which a component clause is applied. The effect of specifying
12426 non-default bit ordering is a bit subtle (and changed with Ada 2005), so
12427 these messages, which are given by default, are useful in understanding the
12428 exact consequences of using this feature.
12431 @geindex -gnatw.V (gcc)
12436 @item @code{-gnatw.V}
12438 @emph{Suppress info messages for non-default bit order.}
12440 This switch suppresses information messages for the effects of specifying
12441 non-default bit order on record components with component clauses.
12444 @geindex -gnatww (gcc)
12446 @geindex String indexing warnings
12451 @item @code{-gnatww}
12453 @emph{Activate warnings on wrong low bound assumption.}
12455 This switch activates warnings for indexing an unconstrained string parameter
12456 with a literal or S'Length. This is a case where the code is assuming that the
12457 low bound is one, which is in general not true (for example when a slice is
12458 passed). The default is that such warnings are generated.
12461 @geindex -gnatwW (gcc)
12466 @item @code{-gnatwW}
12468 @emph{Suppress warnings on wrong low bound assumption.}
12470 This switch suppresses warnings for indexing an unconstrained string parameter
12471 with a literal or S'Length. Note that this warning can also be suppressed
12472 in a particular case by adding an assertion that the lower bound is 1,
12473 as shown in the following example:
12476 procedure K (S : String) is
12477 pragma Assert (S'First = 1);
12482 @geindex -gnatw.w (gcc)
12484 @geindex Warnings Off control
12489 @item @code{-gnatw.w}
12491 @emph{Activate warnings on Warnings Off pragmas.}
12493 This switch activates warnings for use of @code{pragma Warnings (Off, entity)}
12494 where either the pragma is entirely useless (because it suppresses no
12495 warnings), or it could be replaced by @code{pragma Unreferenced} or
12496 @code{pragma Unmodified}.
12497 Also activates warnings for the case of
12498 Warnings (Off, String), where either there is no matching
12499 Warnings (On, String), or the Warnings (Off) did not suppress any warning.
12500 The default is that these warnings are not given.
12503 @geindex -gnatw.W (gcc)
12508 @item @code{-gnatw.W}
12510 @emph{Suppress warnings on unnecessary Warnings Off pragmas.}
12512 This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}.
12515 @geindex -gnatwx (gcc)
12517 @geindex Export/Import pragma warnings
12522 @item @code{-gnatwx}
12524 @emph{Activate warnings on Export/Import pragmas.}
12526 This switch activates warnings on Export/Import pragmas when
12527 the compiler detects a possible conflict between the Ada and
12528 foreign language calling sequences. For example, the use of
12529 default parameters in a convention C procedure is dubious
12530 because the C compiler cannot supply the proper default, so
12531 a warning is issued. The default is that such warnings are
12535 @geindex -gnatwX (gcc)
12540 @item @code{-gnatwX}
12542 @emph{Suppress warnings on Export/Import pragmas.}
12544 This switch suppresses warnings on Export/Import pragmas.
12545 The sense of this is that you are telling the compiler that
12546 you know what you are doing in writing the pragma, and it
12547 should not complain at you.
12550 @geindex -gnatwm (gcc)
12555 @item @code{-gnatw.x}
12557 @emph{Activate warnings for No_Exception_Propagation mode.}
12559 This switch activates warnings for exception usage when pragma Restrictions
12560 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
12561 explicit exception raises which are not covered by a local handler, and for
12562 exception handlers which do not cover a local raise. The default is that
12563 these warnings are given for units that contain exception handlers.
12565 @item @code{-gnatw.X}
12567 @emph{Disable warnings for No_Exception_Propagation mode.}
12569 This switch disables warnings for exception usage when pragma Restrictions
12570 (No_Exception_Propagation) is in effect.
12573 @geindex -gnatwy (gcc)
12575 @geindex Ada compatibility issues warnings
12580 @item @code{-gnatwy}
12582 @emph{Activate warnings for Ada compatibility issues.}
12584 For the most part, newer versions of Ada are upwards compatible
12585 with older versions. For example, Ada 2005 programs will almost
12586 always work when compiled as Ada 2012.
12587 However there are some exceptions (for example the fact that
12588 @code{some} is now a reserved word in Ada 2012). This
12589 switch activates several warnings to help in identifying
12590 and correcting such incompatibilities. The default is that
12591 these warnings are generated. Note that at one point Ada 2005
12592 was called Ada 0Y, hence the choice of character.
12595 @geindex -gnatwY (gcc)
12597 @geindex Ada compatibility issues warnings
12602 @item @code{-gnatwY}
12604 @emph{Disable warnings for Ada compatibility issues.}
12606 This switch suppresses the warnings intended to help in identifying
12607 incompatibilities between Ada language versions.
12610 @geindex -gnatw.y (gcc)
12612 @geindex Package spec needing body
12617 @item @code{-gnatw.y}
12619 @emph{Activate information messages for why package spec needs body.}
12621 There are a number of cases in which a package spec needs a body.
12622 For example, the use of pragma Elaborate_Body, or the declaration
12623 of a procedure specification requiring a completion. This switch
12624 causes information messages to be output showing why a package
12625 specification requires a body. This can be useful in the case of
12626 a large package specification which is unexpectedly requiring a
12627 body. The default is that such information messages are not output.
12630 @geindex -gnatw.Y (gcc)
12632 @geindex No information messages for why package spec needs body
12637 @item @code{-gnatw.Y}
12639 @emph{Disable information messages for why package spec needs body.}
12641 This switch suppresses the output of information messages showing why
12642 a package specification needs a body.
12645 @geindex -gnatwz (gcc)
12647 @geindex Unchecked_Conversion warnings
12652 @item @code{-gnatwz}
12654 @emph{Activate warnings on unchecked conversions.}
12656 This switch activates warnings for unchecked conversions
12657 where the types are known at compile time to have different
12658 sizes. The default is that such warnings are generated. Warnings are also
12659 generated for subprogram pointers with different conventions.
12662 @geindex -gnatwZ (gcc)
12667 @item @code{-gnatwZ}
12669 @emph{Suppress warnings on unchecked conversions.}
12671 This switch suppresses warnings for unchecked conversions
12672 where the types are known at compile time to have different
12673 sizes or conventions.
12676 @geindex -gnatw.z (gcc)
12678 @geindex Size/Alignment warnings
12683 @item @code{-gnatw.z}
12685 @emph{Activate warnings for size not a multiple of alignment.}
12687 This switch activates warnings for cases of array and record types
12688 with specified @code{Size} and @code{Alignment} attributes where the
12689 size is not a multiple of the alignment, resulting in an object
12690 size that is greater than the specified size. The default
12691 is that such warnings are generated.
12694 @geindex -gnatw.Z (gcc)
12696 @geindex Size/Alignment warnings
12701 @item @code{-gnatw.Z}
12703 @emph{Suppress warnings for size not a multiple of alignment.}
12705 This switch suppresses warnings for cases of array and record types
12706 with specified @code{Size} and @code{Alignment} attributes where the
12707 size is not a multiple of the alignment, resulting in an object
12708 size that is greater than the specified size. The warning can also
12709 be suppressed by giving an explicit @code{Object_Size} value.
12712 @geindex -Wunused (gcc)
12717 @item @code{-Wunused}
12719 The warnings controlled by the @code{-gnatw} switch are generated by
12720 the front end of the compiler. The GCC back end can provide
12721 additional warnings and they are controlled by the @code{-W} switch.
12722 For example, @code{-Wunused} activates back end
12723 warnings for entities that are declared but not referenced.
12726 @geindex -Wuninitialized (gcc)
12731 @item @code{-Wuninitialized}
12733 Similarly, @code{-Wuninitialized} activates
12734 the back end warning for uninitialized variables. This switch must be
12735 used in conjunction with an optimization level greater than zero.
12738 @geindex -Wstack-usage (gcc)
12743 @item @code{-Wstack-usage=@emph{len}}
12745 Warn if the stack usage of a subprogram might be larger than @code{len} bytes.
12746 See @ref{f5,,Static Stack Usage Analysis} for details.
12749 @geindex -Wall (gcc)
12756 This switch enables most warnings from the GCC back end.
12757 The code generator detects a number of warning situations that are missed
12758 by the GNAT front end, and this switch can be used to activate them.
12759 The use of this switch also sets the default front end warning mode to
12760 @code{-gnatwa}, that is, most front end warnings activated as well.
12770 Conversely, this switch suppresses warnings from the GCC back end.
12771 The use of this switch also sets the default front end warning mode to
12772 @code{-gnatws}, that is, front end warnings suppressed as well.
12775 @geindex -Werror (gcc)
12780 @item @code{-Werror}
12782 This switch causes warnings from the GCC back end to be treated as
12783 errors. The warning string still appears, but the warning messages are
12784 counted as errors, and prevent the generation of an object file.
12787 A string of warning parameters can be used in the same parameter. For example:
12793 will turn on all optional warnings except for unrecognized pragma warnings,
12794 and also specify that warnings should be treated as errors.
12796 When no switch @code{-gnatw} is used, this is equivalent to:
12943 @node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches
12944 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control}@anchor{100}@anchor{gnat_ugn/building_executable_programs_with_gnat id16}@anchor{101}
12945 @subsection Debugging and Assertion Control
12948 @geindex -gnata (gcc)
12953 @item @code{-gnata}
12959 @geindex Assertions
12961 @geindex Precondition
12963 @geindex Postcondition
12965 @geindex Type invariants
12967 @geindex Subtype predicates
12969 The @code{-gnata} option is equivalent to the following @code{Assertion_Policy} pragma:
12972 pragma Assertion_Policy (Check);
12975 Which is a shorthand for:
12978 pragma Assertion_Policy
12980 Static_Predicate => Check,
12981 Dynamic_Predicate => Check,
12983 Pre'Class => Check,
12985 Post'Class => Check,
12986 Type_Invariant => Check,
12987 Type_Invariant'Class => Check);
12990 The pragmas @code{Assert} and @code{Debug} normally have no effect and
12991 are ignored. This switch, where @code{a} stands for 'assert', causes
12992 pragmas @code{Assert} and @code{Debug} to be activated. This switch also
12993 causes preconditions, postconditions, subtype predicates, and
12994 type invariants to be activated.
12996 The pragmas have the form:
12999 pragma Assert (<Boolean-expression> [, <static-string-expression>])
13000 pragma Debug (<procedure call>)
13001 pragma Type_Invariant (<type-local-name>, <Boolean-expression>)
13002 pragma Predicate (<type-local-name>, <Boolean-expression>)
13003 pragma Precondition (<Boolean-expression>, <string-expression>)
13004 pragma Postcondition (<Boolean-expression>, <string-expression>)
13007 The aspects have the form:
13010 with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate]
13011 => <Boolean-expression>;
13014 The @code{Assert} pragma causes @code{Boolean-expression} to be tested.
13015 If the result is @code{True}, the pragma has no effect (other than
13016 possible side effects from evaluating the expression). If the result is
13017 @code{False}, the exception @code{Assert_Failure} declared in the package
13018 @code{System.Assertions} is raised (passing @code{static-string-expression}, if
13019 present, as the message associated with the exception). If no string
13020 expression is given, the default is a string containing the file name and
13021 line number of the pragma.
13023 The @code{Debug} pragma causes @code{procedure} to be called. Note that
13024 @code{pragma Debug} may appear within a declaration sequence, allowing
13025 debugging procedures to be called between declarations.
13027 For the aspect specification, the @code{Boolean-expression} is evaluated.
13028 If the result is @code{True}, the aspect has no effect. If the result
13029 is @code{False}, the exception @code{Assert_Failure} is raised.
13032 @node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches
13033 @anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{102}
13034 @subsection Validity Checking
13037 @geindex Validity Checking
13039 The Ada Reference Manual defines the concept of invalid values (see
13040 RM 13.9.1). The primary source of invalid values is uninitialized
13041 variables. A scalar variable that is left uninitialized may contain
13042 an invalid value; the concept of invalid does not apply to access or
13045 It is an error to read an invalid value, but the RM does not require
13046 run-time checks to detect such errors, except for some minimal
13047 checking to prevent erroneous execution (i.e. unpredictable
13048 behavior). This corresponds to the @code{-gnatVd} switch below,
13049 which is the default. For example, by default, if the expression of a
13050 case statement is invalid, it will raise Constraint_Error rather than
13051 causing a wild jump, and if an array index on the left-hand side of an
13052 assignment is invalid, it will raise Constraint_Error rather than
13053 overwriting an arbitrary memory location.
13055 The @code{-gnatVa} may be used to enable additional validity checks,
13056 which are not required by the RM. These checks are often very
13057 expensive (which is why the RM does not require them). These checks
13058 are useful in tracking down uninitialized variables, but they are
13059 not usually recommended for production builds, and in particular
13060 we do not recommend using these extra validity checking options in
13061 combination with optimization, since this can confuse the optimizer.
13062 If performance is a consideration, leading to the need to optimize,
13063 then the validity checking options should not be used.
13065 The other @code{-gnatV@emph{x}} switches below allow finer-grained
13066 control; you can enable whichever validity checks you desire. However,
13067 for most debugging purposes, @code{-gnatVa} is sufficient, and the
13068 default @code{-gnatVd} (i.e. standard Ada behavior) is usually
13069 sufficient for non-debugging use.
13071 The @code{-gnatB} switch tells the compiler to assume that all
13072 values are valid (that is, within their declared subtype range)
13073 except in the context of a use of the Valid attribute. This means
13074 the compiler can generate more efficient code, since the range
13075 of values is better known at compile time. However, an uninitialized
13076 variable can cause wild jumps and memory corruption in this mode.
13078 The @code{-gnatV@emph{x}} switch allows control over the validity
13079 checking mode as described below.
13080 The @code{x} argument is a string of letters that
13081 indicate validity checks that are performed or not performed in addition
13082 to the default checks required by Ada as described above.
13084 @geindex -gnatVa (gcc)
13089 @item @code{-gnatVa}
13091 @emph{All validity checks.}
13093 All validity checks are turned on.
13094 That is, @code{-gnatVa} is
13095 equivalent to @code{gnatVcdfimorst}.
13098 @geindex -gnatVc (gcc)
13103 @item @code{-gnatVc}
13105 @emph{Validity checks for copies.}
13107 The right hand side of assignments, and the initializing values of
13108 object declarations are validity checked.
13111 @geindex -gnatVd (gcc)
13116 @item @code{-gnatVd}
13118 @emph{Default (RM) validity checks.}
13120 Some validity checks are done by default following normal Ada semantics
13121 (RM 13.9.1 (9-11)).
13122 A check is done in case statements that the expression is within the range
13123 of the subtype. If it is not, Constraint_Error is raised.
13124 For assignments to array components, a check is done that the expression used
13125 as index is within the range. If it is not, Constraint_Error is raised.
13126 Both these validity checks may be turned off using switch @code{-gnatVD}.
13127 They are turned on by default. If @code{-gnatVD} is specified, a subsequent
13128 switch @code{-gnatVd} will leave the checks turned on.
13129 Switch @code{-gnatVD} should be used only if you are sure that all such
13130 expressions have valid values. If you use this switch and invalid values
13131 are present, then the program is erroneous, and wild jumps or memory
13132 overwriting may occur.
13135 @geindex -gnatVe (gcc)
13140 @item @code{-gnatVe}
13142 @emph{Validity checks for elementary components.}
13144 In the absence of this switch, assignments to record or array components are
13145 not validity checked, even if validity checks for assignments generally
13146 (@code{-gnatVc}) are turned on. In Ada, assignment of composite values do not
13147 require valid data, but assignment of individual components does. So for
13148 example, there is a difference between copying the elements of an array with a
13149 slice assignment, compared to assigning element by element in a loop. This
13150 switch allows you to turn off validity checking for components, even when they
13151 are assigned component by component.
13154 @geindex -gnatVf (gcc)
13159 @item @code{-gnatVf}
13161 @emph{Validity checks for floating-point values.}
13163 In the absence of this switch, validity checking occurs only for discrete
13164 values. If @code{-gnatVf} is specified, then validity checking also applies
13165 for floating-point values, and NaNs and infinities are considered invalid,
13166 as well as out of range values for constrained types. Note that this means
13167 that standard IEEE infinity mode is not allowed. The exact contexts
13168 in which floating-point values are checked depends on the setting of other
13169 options. For example, @code{-gnatVif} or @code{-gnatVfi}
13170 (the order does not matter) specifies that floating-point parameters of mode
13171 @code{in} should be validity checked.
13174 @geindex -gnatVi (gcc)
13179 @item @code{-gnatVi}
13181 @emph{Validity checks for `@w{`}in`@w{`} mode parameters.}
13183 Arguments for parameters of mode @code{in} are validity checked in function
13184 and procedure calls at the point of call.
13187 @geindex -gnatVm (gcc)
13192 @item @code{-gnatVm}
13194 @emph{Validity checks for `@w{`}in out`@w{`} mode parameters.}
13196 Arguments for parameters of mode @code{in out} are validity checked in
13197 procedure calls at the point of call. The @code{'m'} here stands for
13198 modify, since this concerns parameters that can be modified by the call.
13199 Note that there is no specific option to test @code{out} parameters,
13200 but any reference within the subprogram will be tested in the usual
13201 manner, and if an invalid value is copied back, any reference to it
13202 will be subject to validity checking.
13205 @geindex -gnatVn (gcc)
13210 @item @code{-gnatVn}
13212 @emph{No validity checks.}
13214 This switch turns off all validity checking, including the default checking
13215 for case statements and left hand side subscripts. Note that the use of
13216 the switch @code{-gnatp} suppresses all run-time checks, including
13217 validity checks, and thus implies @code{-gnatVn}. When this switch
13218 is used, it cancels any other @code{-gnatV} previously issued.
13221 @geindex -gnatVo (gcc)
13226 @item @code{-gnatVo}
13228 @emph{Validity checks for operator and attribute operands.}
13230 Arguments for predefined operators and attributes are validity checked.
13231 This includes all operators in package @code{Standard},
13232 the shift operators defined as intrinsic in package @code{Interfaces}
13233 and operands for attributes such as @code{Pos}. Checks are also made
13234 on individual component values for composite comparisons, and on the
13235 expressions in type conversions and qualified expressions. Checks are
13236 also made on explicit ranges using @code{..} (e.g., slices, loops etc).
13239 @geindex -gnatVp (gcc)
13244 @item @code{-gnatVp}
13246 @emph{Validity checks for parameters.}
13248 This controls the treatment of parameters within a subprogram (as opposed
13249 to @code{-gnatVi} and @code{-gnatVm} which control validity testing
13250 of parameters on a call. If either of these call options is used, then
13251 normally an assumption is made within a subprogram that the input arguments
13252 have been validity checking at the point of call, and do not need checking
13253 again within a subprogram). If @code{-gnatVp} is set, then this assumption
13254 is not made, and parameters are not assumed to be valid, so their validity
13255 will be checked (or rechecked) within the subprogram.
13258 @geindex -gnatVr (gcc)
13263 @item @code{-gnatVr}
13265 @emph{Validity checks for function returns.}
13267 The expression in @code{return} statements in functions is validity
13271 @geindex -gnatVs (gcc)
13276 @item @code{-gnatVs}
13278 @emph{Validity checks for subscripts.}
13280 All subscripts expressions are checked for validity, whether they appear
13281 on the right side or left side (in default mode only left side subscripts
13282 are validity checked).
13285 @geindex -gnatVt (gcc)
13290 @item @code{-gnatVt}
13292 @emph{Validity checks for tests.}
13294 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
13295 statements are checked, as well as guard expressions in entry calls.
13298 The @code{-gnatV} switch may be followed by a string of letters
13299 to turn on a series of validity checking options.
13300 For example, @code{-gnatVcr}
13301 specifies that in addition to the default validity checking, copies and
13302 function return expressions are to be validity checked.
13303 In order to make it easier to specify the desired combination of effects,
13304 the upper case letters @code{CDFIMORST} may
13305 be used to turn off the corresponding lower case option.
13306 Thus @code{-gnatVaM} turns on all validity checking options except for
13307 checking of @code{in out} parameters.
13309 The specification of additional validity checking generates extra code (and
13310 in the case of @code{-gnatVa} the code expansion can be substantial).
13311 However, these additional checks can be very useful in detecting
13312 uninitialized variables, incorrect use of unchecked conversion, and other
13313 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
13314 is useful in conjunction with the extra validity checking, since this
13315 ensures that wherever possible uninitialized variables have invalid values.
13317 See also the pragma @code{Validity_Checks} which allows modification of
13318 the validity checking mode at the program source level, and also allows for
13319 temporary disabling of validity checks.
13321 @node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches
13322 @anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{103}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{fb}
13323 @subsection Style Checking
13326 @geindex Style checking
13328 @geindex -gnaty (gcc)
13330 The @code{-gnatyx} switch causes the compiler to
13331 enforce specified style rules. A limited set of style rules has been used
13332 in writing the GNAT sources themselves. This switch allows user programs
13333 to activate all or some of these checks. If the source program fails a
13334 specified style check, an appropriate message is given, preceded by
13335 the character sequence '(style)'. This message does not prevent
13336 successful compilation (unless the @code{-gnatwe} switch is used).
13338 Note that this is by no means intended to be a general facility for
13339 checking arbitrary coding standards. It is simply an embedding of the
13340 style rules we have chosen for the GNAT sources. If you are starting
13341 a project which does not have established style standards, you may
13342 find it useful to adopt the entire set of GNAT coding standards, or
13343 some subset of them.
13346 The string @code{x} is a sequence of letters or digits
13347 indicating the particular style
13348 checks to be performed. The following checks are defined:
13350 @geindex -gnaty[0-9] (gcc)
13355 @item @code{-gnaty0}
13357 @emph{Specify indentation level.}
13359 If a digit from 1-9 appears
13360 in the string after @code{-gnaty}
13361 then proper indentation is checked, with the digit indicating the
13362 indentation level required. A value of zero turns off this style check.
13363 The general style of required indentation is as specified by
13364 the examples in the Ada Reference Manual. Full line comments must be
13365 aligned with the @code{--} starting on a column that is a multiple of
13366 the alignment level, or they may be aligned the same way as the following
13367 non-blank line (this is useful when full line comments appear in the middle
13368 of a statement, or they may be aligned with the source line on the previous
13372 @geindex -gnatya (gcc)
13377 @item @code{-gnatya}
13379 @emph{Check attribute casing.}
13381 Attribute names, including the case of keywords such as @code{digits}
13382 used as attributes names, must be written in mixed case, that is, the
13383 initial letter and any letter following an underscore must be uppercase.
13384 All other letters must be lowercase.
13387 @geindex -gnatyA (gcc)
13392 @item @code{-gnatyA}
13394 @emph{Use of array index numbers in array attributes.}
13396 When using the array attributes First, Last, Range,
13397 or Length, the index number must be omitted for one-dimensional arrays
13398 and is required for multi-dimensional arrays.
13401 @geindex -gnatyb (gcc)
13406 @item @code{-gnatyb}
13408 @emph{Blanks not allowed at statement end.}
13410 Trailing blanks are not allowed at the end of statements. The purpose of this
13411 rule, together with h (no horizontal tabs), is to enforce a canonical format
13412 for the use of blanks to separate source tokens.
13415 @geindex -gnatyB (gcc)
13420 @item @code{-gnatyB}
13422 @emph{Check Boolean operators.}
13424 The use of AND/OR operators is not permitted except in the cases of modular
13425 operands, array operands, and simple stand-alone boolean variables or
13426 boolean constants. In all other cases @code{and then}/@cite{or else} are
13430 @geindex -gnatyc (gcc)
13435 @item @code{-gnatyc}
13437 @emph{Check comments, double space.}
13439 Comments must meet the following set of rules:
13445 The @code{--} that starts the column must either start in column one,
13446 or else at least one blank must precede this sequence.
13449 Comments that follow other tokens on a line must have at least one blank
13450 following the @code{--} at the start of the comment.
13453 Full line comments must have at least two blanks following the
13454 @code{--} that starts the comment, with the following exceptions.
13457 A line consisting only of the @code{--} characters, possibly preceded
13458 by blanks is permitted.
13461 A comment starting with @code{--x} where @code{x} is a special character
13463 This allows proper processing of the output from specialized tools
13464 such as @code{gnatprep} (where @code{--!} is used) and in earlier versions of the SPARK
13466 language (where @code{--#} is used). For the purposes of this rule, a
13467 special character is defined as being in one of the ASCII ranges
13468 @code{16#21#...16#2F#} or @code{16#3A#...16#3F#}.
13469 Note that this usage is not permitted
13470 in GNAT implementation units (i.e., when @code{-gnatg} is used).
13473 A line consisting entirely of minus signs, possibly preceded by blanks, is
13474 permitted. This allows the construction of box comments where lines of minus
13475 signs are used to form the top and bottom of the box.
13478 A comment that starts and ends with @code{--} is permitted as long as at
13479 least one blank follows the initial @code{--}. Together with the preceding
13480 rule, this allows the construction of box comments, as shown in the following
13484 ---------------------------
13485 -- This is a box comment --
13486 -- with two text lines. --
13487 ---------------------------
13492 @geindex -gnatyC (gcc)
13497 @item @code{-gnatyC}
13499 @emph{Check comments, single space.}
13501 This is identical to @code{c} except that only one space
13502 is required following the @code{--} of a comment instead of two.
13505 @geindex -gnatyd (gcc)
13510 @item @code{-gnatyd}
13512 @emph{Check no DOS line terminators present.}
13514 All lines must be terminated by a single ASCII.LF
13515 character (in particular the DOS line terminator sequence CR/LF is not
13519 @geindex -gnatyD (gcc)
13524 @item @code{-gnatyD}
13526 @emph{Check declared identifiers in mixed case.}
13528 Declared identifiers must be in mixed case, as in
13529 This_Is_An_Identifier. Use -gnatyr in addition to ensure
13530 that references match declarations.
13533 @geindex -gnatye (gcc)
13538 @item @code{-gnatye}
13540 @emph{Check end/exit labels.}
13542 Optional labels on @code{end} statements ending subprograms and on
13543 @code{exit} statements exiting named loops, are required to be present.
13546 @geindex -gnatyf (gcc)
13551 @item @code{-gnatyf}
13553 @emph{No form feeds or vertical tabs.}
13555 Neither form feeds nor vertical tab characters are permitted
13556 in the source text.
13559 @geindex -gnatyg (gcc)
13564 @item @code{-gnatyg}
13566 @emph{GNAT style mode.}
13568 The set of style check switches is set to match that used by the GNAT sources.
13569 This may be useful when developing code that is eventually intended to be
13570 incorporated into GNAT. Currently this is equivalent to @code{-gnatwydISux})
13571 but additional style switches may be added to this set in the future without
13575 @geindex -gnatyh (gcc)
13580 @item @code{-gnatyh}
13582 @emph{No horizontal tabs.}
13584 Horizontal tab characters are not permitted in the source text.
13585 Together with the b (no blanks at end of line) check, this
13586 enforces a canonical form for the use of blanks to separate
13590 @geindex -gnatyi (gcc)
13595 @item @code{-gnatyi}
13597 @emph{Check if-then layout.}
13599 The keyword @code{then} must appear either on the same
13600 line as corresponding @code{if}, or on a line on its own, lined
13601 up under the @code{if}.
13604 @geindex -gnatyI (gcc)
13609 @item @code{-gnatyI}
13611 @emph{check mode IN keywords.}
13613 Mode @code{in} (the default mode) is not
13614 allowed to be given explicitly. @code{in out} is fine,
13615 but not @code{in} on its own.
13618 @geindex -gnatyk (gcc)
13623 @item @code{-gnatyk}
13625 @emph{Check keyword casing.}
13627 All keywords must be in lower case (with the exception of keywords
13628 such as @code{digits} used as attribute names to which this check
13632 @geindex -gnatyl (gcc)
13637 @item @code{-gnatyl}
13639 @emph{Check layout.}
13641 Layout of statement and declaration constructs must follow the
13642 recommendations in the Ada Reference Manual, as indicated by the
13643 form of the syntax rules. For example an @code{else} keyword must
13644 be lined up with the corresponding @code{if} keyword.
13646 There are two respects in which the style rule enforced by this check
13647 option are more liberal than those in the Ada Reference Manual. First
13648 in the case of record declarations, it is permissible to put the
13649 @code{record} keyword on the same line as the @code{type} keyword, and
13650 then the @code{end} in @code{end record} must line up under @code{type}.
13651 This is also permitted when the type declaration is split on two lines.
13652 For example, any of the following three layouts is acceptable:
13673 Second, in the case of a block statement, a permitted alternative
13674 is to put the block label on the same line as the @code{declare} or
13675 @code{begin} keyword, and then line the @code{end} keyword up under
13676 the block label. For example both the following are permitted:
13693 The same alternative format is allowed for loops. For example, both of
13694 the following are permitted:
13697 Clear : while J < 10 loop
13708 @geindex -gnatyLnnn (gcc)
13713 @item @code{-gnatyL}
13715 @emph{Set maximum nesting level.}
13717 The maximum level of nesting of constructs (including subprograms, loops,
13718 blocks, packages, and conditionals) may not exceed the given value
13719 @emph{nnn}. A value of zero disconnects this style check.
13722 @geindex -gnatym (gcc)
13727 @item @code{-gnatym}
13729 @emph{Check maximum line length.}
13731 The length of source lines must not exceed 79 characters, including
13732 any trailing blanks. The value of 79 allows convenient display on an
13733 80 character wide device or window, allowing for possible special
13734 treatment of 80 character lines. Note that this count is of
13735 characters in the source text. This means that a tab character counts
13736 as one character in this count and a wide character sequence counts as
13737 a single character (however many bytes are needed in the encoding).
13740 @geindex -gnatyMnnn (gcc)
13745 @item @code{-gnatyM}
13747 @emph{Set maximum line length.}
13749 The length of lines must not exceed the
13750 given value @emph{nnn}. The maximum value that can be specified is 32767.
13751 If neither style option for setting the line length is used, then the
13752 default is 255. This also controls the maximum length of lexical elements,
13753 where the only restriction is that they must fit on a single line.
13756 @geindex -gnatyn (gcc)
13761 @item @code{-gnatyn}
13763 @emph{Check casing of entities in Standard.}
13765 Any identifier from Standard must be cased
13766 to match the presentation in the Ada Reference Manual (for example,
13767 @code{Integer} and @code{ASCII.NUL}).
13770 @geindex -gnatyN (gcc)
13775 @item @code{-gnatyN}
13777 @emph{Turn off all style checks.}
13779 All style check options are turned off.
13782 @geindex -gnatyo (gcc)
13787 @item @code{-gnatyo}
13789 @emph{Check order of subprogram bodies.}
13791 All subprogram bodies in a given scope
13792 (e.g., a package body) must be in alphabetical order. The ordering
13793 rule uses normal Ada rules for comparing strings, ignoring casing
13794 of letters, except that if there is a trailing numeric suffix, then
13795 the value of this suffix is used in the ordering (e.g., Junk2 comes
13799 @geindex -gnatyO (gcc)
13804 @item @code{-gnatyO}
13806 @emph{Check that overriding subprograms are explicitly marked as such.}
13808 This applies to all subprograms of a derived type that override a primitive
13809 operation of the type, for both tagged and untagged types. In particular,
13810 the declaration of a primitive operation of a type extension that overrides
13811 an inherited operation must carry an overriding indicator. Another case is
13812 the declaration of a function that overrides a predefined operator (such
13813 as an equality operator).
13816 @geindex -gnatyp (gcc)
13821 @item @code{-gnatyp}
13823 @emph{Check pragma casing.}
13825 Pragma names must be written in mixed case, that is, the
13826 initial letter and any letter following an underscore must be uppercase.
13827 All other letters must be lowercase. An exception is that SPARK_Mode is
13828 allowed as an alternative for Spark_Mode.
13831 @geindex -gnatyr (gcc)
13836 @item @code{-gnatyr}
13838 @emph{Check references.}
13840 All identifier references must be cased in the same way as the
13841 corresponding declaration. No specific casing style is imposed on
13842 identifiers. The only requirement is for consistency of references
13846 @geindex -gnatys (gcc)
13851 @item @code{-gnatys}
13853 @emph{Check separate specs.}
13855 Separate declarations ('specs') are required for subprograms (a
13856 body is not allowed to serve as its own declaration). The only
13857 exception is that parameterless library level procedures are
13858 not required to have a separate declaration. This exception covers
13859 the most frequent form of main program procedures.
13862 @geindex -gnatyS (gcc)
13867 @item @code{-gnatyS}
13869 @emph{Check no statements after then/else.}
13871 No statements are allowed
13872 on the same line as a @code{then} or @code{else} keyword following the
13873 keyword in an @code{if} statement. @code{or else} and @code{and then} are not
13874 affected, and a special exception allows a pragma to appear after @code{else}.
13877 @geindex -gnatyt (gcc)
13882 @item @code{-gnatyt}
13884 @emph{Check token spacing.}
13886 The following token spacing rules are enforced:
13892 The keywords @code{abs} and @code{not} must be followed by a space.
13895 The token @code{=>} must be surrounded by spaces.
13898 The token @code{<>} must be preceded by a space or a left parenthesis.
13901 Binary operators other than @code{**} must be surrounded by spaces.
13902 There is no restriction on the layout of the @code{**} binary operator.
13905 Colon must be surrounded by spaces.
13908 Colon-equal (assignment, initialization) must be surrounded by spaces.
13911 Comma must be the first non-blank character on the line, or be
13912 immediately preceded by a non-blank character, and must be followed
13916 If the token preceding a left parenthesis ends with a letter or digit, then
13917 a space must separate the two tokens.
13920 If the token following a right parenthesis starts with a letter or digit, then
13921 a space must separate the two tokens.
13924 A right parenthesis must either be the first non-blank character on
13925 a line, or it must be preceded by a non-blank character.
13928 A semicolon must not be preceded by a space, and must not be followed by
13929 a non-blank character.
13932 A unary plus or minus may not be followed by a space.
13935 A vertical bar must be surrounded by spaces.
13938 Exactly one blank (and no other white space) must appear between
13939 a @code{not} token and a following @code{in} token.
13942 @geindex -gnatyu (gcc)
13947 @item @code{-gnatyu}
13949 @emph{Check unnecessary blank lines.}
13951 Unnecessary blank lines are not allowed. A blank line is considered
13952 unnecessary if it appears at the end of the file, or if more than
13953 one blank line occurs in sequence.
13956 @geindex -gnatyx (gcc)
13961 @item @code{-gnatyx}
13963 @emph{Check extra parentheses.}
13965 Unnecessary extra level of parentheses (C-style) are not allowed
13966 around conditions in @code{if} statements, @code{while} statements and
13967 @code{exit} statements.
13970 @geindex -gnatyy (gcc)
13975 @item @code{-gnatyy}
13977 @emph{Set all standard style check options.}
13979 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
13980 options enabled with the exception of @code{-gnatyB}, @code{-gnatyd},
13981 @code{-gnatyI}, @code{-gnatyLnnn}, @code{-gnatyo}, @code{-gnatyO},
13982 @code{-gnatyS}, @code{-gnatyu}, and @code{-gnatyx}.
13985 @geindex -gnaty- (gcc)
13990 @item @code{-gnaty-}
13992 @emph{Remove style check options.}
13994 This causes any subsequent options in the string to act as canceling the
13995 corresponding style check option. To cancel maximum nesting level control,
13996 use the @code{L} parameter without any integer value after that, because any
13997 digit following @emph{-} in the parameter string of the @code{-gnaty}
13998 option will be treated as canceling the indentation check. The same is true
13999 for the @code{M} parameter. @code{y} and @code{N} parameters are not
14000 allowed after @emph{-}.
14003 @geindex -gnaty+ (gcc)
14008 @item @code{-gnaty+}
14010 @emph{Enable style check options.}
14012 This causes any subsequent options in the string to enable the corresponding
14013 style check option. That is, it cancels the effect of a previous -,
14017 @c end of switch description (leave this comment to ease automatic parsing for
14021 In the above rules, appearing in column one is always permitted, that is,
14022 counts as meeting either a requirement for a required preceding space,
14023 or as meeting a requirement for no preceding space.
14025 Appearing at the end of a line is also always permitted, that is, counts
14026 as meeting either a requirement for a following space, or as meeting
14027 a requirement for no following space.
14029 If any of these style rules is violated, a message is generated giving
14030 details on the violation. The initial characters of such messages are
14031 always '@cite{(style)}'. Note that these messages are treated as warning
14032 messages, so they normally do not prevent the generation of an object
14033 file. The @code{-gnatwe} switch can be used to treat warning messages,
14034 including style messages, as fatal errors.
14036 The switch @code{-gnaty} on its own (that is not
14037 followed by any letters or digits) is equivalent
14038 to the use of @code{-gnatyy} as described above, that is all
14039 built-in standard style check options are enabled.
14041 The switch @code{-gnatyN} clears any previously set style checks.
14043 @node Run-Time Checks,Using gcc for Syntax Checking,Style Checking,Compiler Switches
14044 @anchor{gnat_ugn/building_executable_programs_with_gnat run-time-checks}@anchor{f9}@anchor{gnat_ugn/building_executable_programs_with_gnat id19}@anchor{104}
14045 @subsection Run-Time Checks
14048 @geindex Division by zero
14050 @geindex Access before elaboration
14053 @geindex division by zero
14056 @geindex access before elaboration
14059 @geindex stack overflow checking
14061 By default, the following checks are suppressed: stack overflow
14062 checks, and checks for access before elaboration on subprogram
14063 calls. All other checks, including overflow checks, range checks and
14064 array bounds checks, are turned on by default. The following @code{gcc}
14065 switches refine this default behavior.
14067 @geindex -gnatp (gcc)
14072 @item @code{-gnatp}
14074 @geindex Suppressing checks
14077 @geindex suppressing
14079 This switch causes the unit to be compiled
14080 as though @code{pragma Suppress (All_checks)}
14081 had been present in the source. Validity checks are also eliminated (in
14082 other words @code{-gnatp} also implies @code{-gnatVn}.
14083 Use this switch to improve the performance
14084 of the code at the expense of safety in the presence of invalid data or
14087 Note that when checks are suppressed, the compiler is allowed, but not
14088 required, to omit the checking code. If the run-time cost of the
14089 checking code is zero or near-zero, the compiler will generate it even
14090 if checks are suppressed. In particular, if the compiler can prove
14091 that a certain check will necessarily fail, it will generate code to
14092 do an unconditional 'raise', even if checks are suppressed. The
14093 compiler warns in this case. Another case in which checks may not be
14094 eliminated is when they are embedded in certain run-time routines such
14095 as math library routines.
14097 Of course, run-time checks are omitted whenever the compiler can prove
14098 that they will not fail, whether or not checks are suppressed.
14100 Note that if you suppress a check that would have failed, program
14101 execution is erroneous, which means the behavior is totally
14102 unpredictable. The program might crash, or print wrong answers, or
14103 do anything else. It might even do exactly what you wanted it to do
14104 (and then it might start failing mysteriously next week or next
14105 year). The compiler will generate code based on the assumption that
14106 the condition being checked is true, which can result in erroneous
14107 execution if that assumption is wrong.
14109 The checks subject to suppression include all the checks defined by the Ada
14110 standard, the additional implementation defined checks @code{Alignment_Check},
14111 @code{Duplicated_Tag_Check}, @code{Predicate_Check}, @code{Container_Checks}, @code{Tampering_Check},
14112 and @code{Validity_Check}, as well as any checks introduced using @code{pragma Check_Name}.
14113 Note that @code{Atomic_Synchronization} is not automatically suppressed by use of this option.
14115 If the code depends on certain checks being active, you can use
14116 pragma @code{Unsuppress} either as a configuration pragma or as
14117 a local pragma to make sure that a specified check is performed
14118 even if @code{gnatp} is specified.
14120 The @code{-gnatp} switch has no effect if a subsequent
14121 @code{-gnat-p} switch appears.
14124 @geindex -gnat-p (gcc)
14126 @geindex Suppressing checks
14129 @geindex suppressing
14136 @item @code{-gnat-p}
14138 This switch cancels the effect of a previous @code{gnatp} switch.
14141 @geindex -gnato?? (gcc)
14143 @geindex Overflow checks
14145 @geindex Overflow mode
14153 @item @code{-gnato??}
14155 This switch controls the mode used for computing intermediate
14156 arithmetic integer operations, and also enables overflow checking.
14157 For a full description of overflow mode and checking control, see
14158 the 'Overflow Check Handling in GNAT' appendix in this
14161 Overflow checks are always enabled by this switch. The argument
14162 controls the mode, using the codes
14167 @item @emph{1 = STRICT}
14169 In STRICT mode, intermediate operations are always done using the
14170 base type, and overflow checking ensures that the result is within
14171 the base type range.
14173 @item @emph{2 = MINIMIZED}
14175 In MINIMIZED mode, overflows in intermediate operations are avoided
14176 where possible by using a larger integer type for the computation
14177 (typically @code{Long_Long_Integer}). Overflow checking ensures that
14178 the result fits in this larger integer type.
14180 @item @emph{3 = ELIMINATED}
14182 In ELIMINATED mode, overflows in intermediate operations are avoided
14183 by using multi-precision arithmetic. In this case, overflow checking
14184 has no effect on intermediate operations (since overflow is impossible).
14187 If two digits are present after @code{-gnato} then the first digit
14188 sets the mode for expressions outside assertions, and the second digit
14189 sets the mode for expressions within assertions. Here assertions is used
14190 in the technical sense (which includes for example precondition and
14191 postcondition expressions).
14193 If one digit is present, the corresponding mode is applicable to both
14194 expressions within and outside assertion expressions.
14196 If no digits are present, the default is to enable overflow checks
14197 and set STRICT mode for both kinds of expressions. This is compatible
14198 with the use of @code{-gnato} in previous versions of GNAT.
14200 @geindex Machine_Overflows
14202 Note that the @code{-gnato??} switch does not affect the code generated
14203 for any floating-point operations; it applies only to integer semantics.
14204 For floating-point, GNAT has the @code{Machine_Overflows}
14205 attribute set to @code{False} and the normal mode of operation is to
14206 generate IEEE NaN and infinite values on overflow or invalid operations
14207 (such as dividing 0.0 by 0.0).
14209 The reason that we distinguish overflow checking from other kinds of
14210 range constraint checking is that a failure of an overflow check, unlike
14211 for example the failure of a range check, can result in an incorrect
14212 value, but cannot cause random memory destruction (like an out of range
14213 subscript), or a wild jump (from an out of range case value). Overflow
14214 checking is also quite expensive in time and space, since in general it
14215 requires the use of double length arithmetic.
14217 Note again that the default is @code{-gnato11} (equivalent to @code{-gnato1}),
14218 so overflow checking is performed in STRICT mode by default.
14221 @geindex -gnatE (gcc)
14223 @geindex Elaboration checks
14226 @geindex elaboration
14231 @item @code{-gnatE}
14233 Enables dynamic checks for access-before-elaboration
14234 on subprogram calls and generic instantiations.
14235 Note that @code{-gnatE} is not necessary for safety, because in the
14236 default mode, GNAT ensures statically that the checks would not fail.
14237 For full details of the effect and use of this switch,
14238 @ref{1c,,Compiling with gcc}.
14241 @geindex -fstack-check (gcc)
14243 @geindex Stack Overflow Checking
14246 @geindex stack overflow checking
14251 @item @code{-fstack-check}
14253 Activates stack overflow checking. For full details of the effect and use of
14254 this switch see @ref{f4,,Stack Overflow Checking}.
14257 @geindex Unsuppress
14259 The setting of these switches only controls the default setting of the
14260 checks. You may modify them using either @code{Suppress} (to remove
14261 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
14262 the program source.
14264 @node Using gcc for Syntax Checking,Using gcc for Semantic Checking,Run-Time Checks,Compiler Switches
14265 @anchor{gnat_ugn/building_executable_programs_with_gnat id20}@anchor{105}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-syntax-checking}@anchor{106}
14266 @subsection Using @code{gcc} for Syntax Checking
14269 @geindex -gnats (gcc)
14274 @item @code{-gnats}
14276 The @code{s} stands for 'syntax'.
14278 Run GNAT in syntax checking only mode. For
14279 example, the command
14282 $ gcc -c -gnats x.adb
14285 compiles file @code{x.adb} in syntax-check-only mode. You can check a
14286 series of files in a single command
14287 , and can use wildcards to specify such a group of files.
14288 Note that you must specify the @code{-c} (compile
14289 only) flag in addition to the @code{-gnats} flag.
14291 You may use other switches in conjunction with @code{-gnats}. In
14292 particular, @code{-gnatl} and @code{-gnatv} are useful to control the
14293 format of any generated error messages.
14295 When the source file is empty or contains only empty lines and/or comments,
14296 the output is a warning:
14299 $ gcc -c -gnats -x ada toto.txt
14300 toto.txt:1:01: warning: empty file, contains no compilation units
14304 Otherwise, the output is simply the error messages, if any. No object file or
14305 ALI file is generated by a syntax-only compilation. Also, no units other
14306 than the one specified are accessed. For example, if a unit @code{X}
14307 @emph{with}s a unit @code{Y}, compiling unit @code{X} in syntax
14308 check only mode does not access the source file containing unit
14311 @geindex Multiple units
14312 @geindex syntax checking
14314 Normally, GNAT allows only a single unit in a source file. However, this
14315 restriction does not apply in syntax-check-only mode, and it is possible
14316 to check a file containing multiple compilation units concatenated
14317 together. This is primarily used by the @code{gnatchop} utility
14318 (@ref{36,,Renaming Files with gnatchop}).
14321 @node Using gcc for Semantic Checking,Compiling Different Versions of Ada,Using gcc for Syntax Checking,Compiler Switches
14322 @anchor{gnat_ugn/building_executable_programs_with_gnat id21}@anchor{107}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-semantic-checking}@anchor{108}
14323 @subsection Using @code{gcc} for Semantic Checking
14326 @geindex -gnatc (gcc)
14331 @item @code{-gnatc}
14333 The @code{c} stands for 'check'.
14334 Causes the compiler to operate in semantic check mode,
14335 with full checking for all illegalities specified in the
14336 Ada Reference Manual, but without generation of any object code
14337 (no object file is generated).
14339 Because dependent files must be accessed, you must follow the GNAT
14340 semantic restrictions on file structuring to operate in this mode:
14346 The needed source files must be accessible
14347 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
14350 Each file must contain only one compilation unit.
14353 The file name and unit name must match (@ref{52,,File Naming Rules}).
14356 The output consists of error messages as appropriate. No object file is
14357 generated. An @code{ALI} file is generated for use in the context of
14358 cross-reference tools, but this file is marked as not being suitable
14359 for binding (since no object file is generated).
14360 The checking corresponds exactly to the notion of
14361 legality in the Ada Reference Manual.
14363 Any unit can be compiled in semantics-checking-only mode, including
14364 units that would not normally be compiled (subunits,
14365 and specifications where a separate body is present).
14368 @node Compiling Different Versions of Ada,Character Set Control,Using gcc for Semantic Checking,Compiler Switches
14369 @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{109}
14370 @subsection Compiling Different Versions of Ada
14373 The switches described in this section allow you to explicitly specify
14374 the version of the Ada language that your programs are written in.
14375 The default mode is Ada 2012,
14376 but you can also specify Ada 95, Ada 2005 mode, or
14377 indicate Ada 83 compatibility mode.
14379 @geindex Compatibility with Ada 83
14381 @geindex -gnat83 (gcc)
14384 @geindex Ada 83 tests
14386 @geindex Ada 83 mode
14391 @item @code{-gnat83} (Ada 83 Compatibility Mode)
14393 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
14394 specifies that the program is to be compiled in Ada 83 mode. With
14395 @code{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
14396 semantics where this can be done easily.
14397 It is not possible to guarantee this switch does a perfect
14398 job; some subtle tests, such as are
14399 found in earlier ACVC tests (and that have been removed from the ACATS suite
14400 for Ada 95), might not compile correctly.
14401 Nevertheless, this switch may be useful in some circumstances, for example
14402 where, due to contractual reasons, existing code needs to be maintained
14403 using only Ada 83 features.
14405 With few exceptions (most notably the need to use @code{<>} on
14407 @geindex Generic formal parameters
14408 generic formal parameters,
14409 the use of the new Ada 95 / Ada 2005
14410 reserved words, and the use of packages
14411 with optional bodies), it is not necessary to specify the
14412 @code{-gnat83} switch when compiling Ada 83 programs, because, with rare
14413 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
14414 a correct Ada 83 program is usually also a correct program
14415 in these later versions of the language standard. For further information
14416 please refer to the @emph{Compatibility and Porting Guide} chapter in the
14417 @cite{GNAT Reference Manual}.
14420 @geindex -gnat95 (gcc)
14422 @geindex Ada 95 mode
14427 @item @code{-gnat95} (Ada 95 mode)
14429 This switch directs the compiler to implement the Ada 95 version of the
14431 Since Ada 95 is almost completely upwards
14432 compatible with Ada 83, Ada 83 programs may generally be compiled using
14433 this switch (see the description of the @code{-gnat83} switch for further
14434 information about Ada 83 mode).
14435 If an Ada 2005 program is compiled in Ada 95 mode,
14436 uses of the new Ada 2005 features will cause error
14437 messages or warnings.
14439 This switch also can be used to cancel the effect of a previous
14440 @code{-gnat83}, @code{-gnat05/2005}, or @code{-gnat12/2012}
14441 switch earlier in the command line.
14444 @geindex -gnat05 (gcc)
14446 @geindex -gnat2005 (gcc)
14448 @geindex Ada 2005 mode
14453 @item @code{-gnat05} or @code{-gnat2005} (Ada 2005 mode)
14455 This switch directs the compiler to implement the Ada 2005 version of the
14456 language, as documented in the official Ada standards document.
14457 Since Ada 2005 is almost completely upwards
14458 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
14459 may generally be compiled using this switch (see the description of the
14460 @code{-gnat83} and @code{-gnat95} switches for further
14464 @geindex -gnat12 (gcc)
14466 @geindex -gnat2012 (gcc)
14468 @geindex Ada 2012 mode
14473 @item @code{-gnat12} or @code{-gnat2012} (Ada 2012 mode)
14475 This switch directs the compiler to implement the Ada 2012 version of the
14476 language (also the default).
14477 Since Ada 2012 is almost completely upwards
14478 compatible with Ada 2005 (and thus also with Ada 83, and Ada 95),
14479 Ada 83 and Ada 95 programs
14480 may generally be compiled using this switch (see the description of the
14481 @code{-gnat83}, @code{-gnat95}, and @code{-gnat05/2005} switches
14482 for further information).
14485 @geindex -gnatX (gcc)
14487 @geindex Ada language extensions
14489 @geindex GNAT extensions
14494 @item @code{-gnatX} (Enable GNAT Extensions)
14496 This switch directs the compiler to implement the latest version of the
14497 language (currently Ada 2012) and also to enable certain GNAT implementation
14498 extensions that are not part of any Ada standard. For a full list of these
14499 extensions, see the GNAT reference manual.
14502 @node Character Set Control,File Naming Control,Compiling Different Versions of Ada,Compiler Switches
14503 @anchor{gnat_ugn/building_executable_programs_with_gnat id23}@anchor{10a}@anchor{gnat_ugn/building_executable_programs_with_gnat character-set-control}@anchor{48}
14504 @subsection Character Set Control
14507 @geindex -gnati (gcc)
14512 @item @code{-gnati@emph{c}}
14514 Normally GNAT recognizes the Latin-1 character set in source program
14515 identifiers, as described in the Ada Reference Manual.
14517 GNAT to recognize alternate character sets in identifiers. @code{c} is a
14518 single character indicating the character set, as follows:
14521 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14528 ISO 8859-1 (Latin-1) identifiers
14536 ISO 8859-2 (Latin-2) letters allowed in identifiers
14544 ISO 8859-3 (Latin-3) letters allowed in identifiers
14552 ISO 8859-4 (Latin-4) letters allowed in identifiers
14560 ISO 8859-5 (Cyrillic) letters allowed in identifiers
14568 ISO 8859-15 (Latin-9) letters allowed in identifiers
14576 IBM PC letters (code page 437) allowed in identifiers
14584 IBM PC letters (code page 850) allowed in identifiers
14592 Full upper-half codes allowed in identifiers
14600 No upper-half codes allowed in identifiers
14608 Wide-character codes (that is, codes greater than 255)
14609 allowed in identifiers
14614 See @ref{3e,,Foreign Language Representation} for full details on the
14615 implementation of these character sets.
14618 @geindex -gnatW (gcc)
14623 @item @code{-gnatW@emph{e}}
14625 Specify the method of encoding for wide characters.
14626 @code{e} is one of the following:
14629 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14636 Hex encoding (brackets coding also recognized)
14644 Upper half encoding (brackets encoding also recognized)
14652 Shift/JIS encoding (brackets encoding also recognized)
14660 EUC encoding (brackets encoding also recognized)
14668 UTF-8 encoding (brackets encoding also recognized)
14676 Brackets encoding only (default value)
14681 For full details on these encoding
14682 methods see @ref{4e,,Wide_Character Encodings}.
14683 Note that brackets coding is always accepted, even if one of the other
14684 options is specified, so for example @code{-gnatW8} specifies that both
14685 brackets and UTF-8 encodings will be recognized. The units that are
14686 with'ed directly or indirectly will be scanned using the specified
14687 representation scheme, and so if one of the non-brackets scheme is
14688 used, it must be used consistently throughout the program. However,
14689 since brackets encoding is always recognized, it may be conveniently
14690 used in standard libraries, allowing these libraries to be used with
14691 any of the available coding schemes.
14693 Note that brackets encoding only applies to program text. Within comments,
14694 brackets are considered to be normal graphic characters, and bracket sequences
14695 are never recognized as wide characters.
14697 If no @code{-gnatW?} parameter is present, then the default
14698 representation is normally Brackets encoding only. However, if the
14699 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
14700 byte order mark or BOM for UTF-8), then these three characters are
14701 skipped and the default representation for the file is set to UTF-8.
14703 Note that the wide character representation that is specified (explicitly
14704 or by default) for the main program also acts as the default encoding used
14705 for Wide_Text_IO files if not specifically overridden by a WCEM form
14709 When no @code{-gnatW?} is specified, then characters (other than wide
14710 characters represented using brackets notation) are treated as 8-bit
14711 Latin-1 codes. The codes recognized are the Latin-1 graphic characters,
14712 and ASCII format effectors (CR, LF, HT, VT). Other lower half control
14713 characters in the range 16#00#..16#1F# are not accepted in program text
14714 or in comments. Upper half control characters (16#80#..16#9F#) are rejected
14715 in program text, but allowed and ignored in comments. Note in particular
14716 that the Next Line (NEL) character whose encoding is 16#85# is not recognized
14717 as an end of line in this default mode. If your source program contains
14718 instances of the NEL character used as a line terminator,
14719 you must use UTF-8 encoding for the whole
14720 source program. In default mode, all lines must be ended by a standard
14721 end of line sequence (CR, CR/LF, or LF).
14723 Note that the convention of simply accepting all upper half characters in
14724 comments means that programs that use standard ASCII for program text, but
14725 UTF-8 encoding for comments are accepted in default mode, providing that the
14726 comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator.
14727 This is a common mode for many programs with foreign language comments.
14729 @node File Naming Control,Subprogram Inlining Control,Character Set Control,Compiler Switches
14730 @anchor{gnat_ugn/building_executable_programs_with_gnat file-naming-control}@anchor{10b}@anchor{gnat_ugn/building_executable_programs_with_gnat id24}@anchor{10c}
14731 @subsection File Naming Control
14734 @geindex -gnatk (gcc)
14739 @item @code{-gnatk@emph{n}}
14741 Activates file name 'krunching'. @code{n}, a decimal integer in the range
14742 1-999, indicates the maximum allowable length of a file name (not
14743 including the @code{.ads} or @code{.adb} extension). The default is not
14744 to enable file name krunching.
14746 For the source file naming rules, @ref{52,,File Naming Rules}.
14749 @node Subprogram Inlining Control,Auxiliary Output Control,File Naming Control,Compiler Switches
14750 @anchor{gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control}@anchor{10d}@anchor{gnat_ugn/building_executable_programs_with_gnat id25}@anchor{10e}
14751 @subsection Subprogram Inlining Control
14754 @geindex -gnatn (gcc)
14759 @item @code{-gnatn[12]}
14761 The @code{n} here is intended to suggest the first syllable of the word 'inline'.
14762 GNAT recognizes and processes @code{Inline} pragmas. However, for inlining to
14763 actually occur, optimization must be enabled and, by default, inlining of
14764 subprograms across units is not performed. If you want to additionally
14765 enable inlining of subprograms specified by pragma @code{Inline} across units,
14766 you must also specify this switch.
14768 In the absence of this switch, GNAT does not attempt inlining across units
14769 and does not access the bodies of subprograms for which @code{pragma Inline} is
14770 specified if they are not in the current unit.
14772 You can optionally specify the inlining level: 1 for moderate inlining across
14773 units, which is a good compromise between compilation times and performances
14774 at run time, or 2 for full inlining across units, which may bring about
14775 longer compilation times. If no inlining level is specified, the compiler will
14776 pick it based on the optimization level: 1 for @code{-O1}, @code{-O2} or
14777 @code{-Os} and 2 for @code{-O3}.
14779 If you specify this switch the compiler will access these bodies,
14780 creating an extra source dependency for the resulting object file, and
14781 where possible, the call will be inlined.
14782 For further details on when inlining is possible
14783 see @ref{10f,,Inlining of Subprograms}.
14786 @geindex -gnatN (gcc)
14791 @item @code{-gnatN}
14793 This switch activates front-end inlining which also
14794 generates additional dependencies.
14796 When using a gcc-based back end (in practice this means using any version
14797 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
14798 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
14799 Historically front end inlining was more extensive than the gcc back end
14800 inlining, but that is no longer the case.
14803 @node Auxiliary Output Control,Debugging Control,Subprogram Inlining Control,Compiler Switches
14804 @anchor{gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control}@anchor{110}@anchor{gnat_ugn/building_executable_programs_with_gnat id26}@anchor{111}
14805 @subsection Auxiliary Output Control
14808 @geindex -gnatt (gcc)
14810 @geindex Writing internal trees
14812 @geindex Internal trees
14813 @geindex writing to file
14818 @item @code{-gnatt}
14820 Causes GNAT to write the internal tree for a unit to a file (with the
14821 extension @code{.adt}.
14822 This not normally required, but is used by separate analysis tools.
14824 these tools do the necessary compilations automatically, so you should
14825 not have to specify this switch in normal operation.
14826 Note that the combination of switches @code{-gnatct}
14827 generates a tree in the form required by ASIS applications.
14830 @geindex -gnatu (gcc)
14835 @item @code{-gnatu}
14837 Print a list of units required by this compilation on @code{stdout}.
14838 The listing includes all units on which the unit being compiled depends
14839 either directly or indirectly.
14842 @geindex -pass-exit-codes (gcc)
14847 @item @code{-pass-exit-codes}
14849 If this switch is not used, the exit code returned by @code{gcc} when
14850 compiling multiple files indicates whether all source files have
14851 been successfully used to generate object files or not.
14853 When @code{-pass-exit-codes} is used, @code{gcc} exits with an extended
14854 exit status and allows an integrated development environment to better
14855 react to a compilation failure. Those exit status are:
14858 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14865 There was an error in at least one source file.
14873 At least one source file did not generate an object file.
14881 The compiler died unexpectedly (internal error for example).
14889 An object file has been generated for every source file.
14895 @node Debugging Control,Exception Handling Control,Auxiliary Output Control,Compiler Switches
14896 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-control}@anchor{112}@anchor{gnat_ugn/building_executable_programs_with_gnat id27}@anchor{113}
14897 @subsection Debugging Control
14902 @geindex Debugging options
14905 @geindex -gnatd (gcc)
14910 @item @code{-gnatd@emph{x}}
14912 Activate internal debugging switches. @code{x} is a letter or digit, or
14913 string of letters or digits, which specifies the type of debugging
14914 outputs desired. Normally these are used only for internal development
14915 or system debugging purposes. You can find full documentation for these
14916 switches in the body of the @code{Debug} unit in the compiler source
14917 file @code{debug.adb}.
14920 @geindex -gnatG (gcc)
14925 @item @code{-gnatG[=@emph{nn}]}
14927 This switch causes the compiler to generate auxiliary output containing
14928 a pseudo-source listing of the generated expanded code. Like most Ada
14929 compilers, GNAT works by first transforming the high level Ada code into
14930 lower level constructs. For example, tasking operations are transformed
14931 into calls to the tasking run-time routines. A unique capability of GNAT
14932 is to list this expanded code in a form very close to normal Ada source.
14933 This is very useful in understanding the implications of various Ada
14934 usage on the efficiency of the generated code. There are many cases in
14935 Ada (e.g., the use of controlled types), where simple Ada statements can
14936 generate a lot of run-time code. By using @code{-gnatG} you can identify
14937 these cases, and consider whether it may be desirable to modify the coding
14938 approach to improve efficiency.
14940 The optional parameter @code{nn} if present after -gnatG specifies an
14941 alternative maximum line length that overrides the normal default of 72.
14942 This value is in the range 40-999999, values less than 40 being silently
14943 reset to 40. The equal sign is optional.
14945 The format of the output is very similar to standard Ada source, and is
14946 easily understood by an Ada programmer. The following special syntactic
14947 additions correspond to low level features used in the generated code that
14948 do not have any exact analogies in pure Ada source form. The following
14949 is a partial list of these special constructions. See the spec
14950 of package @code{Sprint} in file @code{sprint.ads} for a full list.
14952 @geindex -gnatL (gcc)
14954 If the switch @code{-gnatL} is used in conjunction with
14955 @code{-gnatG}, then the original source lines are interspersed
14956 in the expanded source (as comment lines with the original line number).
14961 @item @code{new @emph{xxx} [storage_pool = @emph{yyy}]}
14963 Shows the storage pool being used for an allocator.
14965 @item @code{at end @emph{procedure-name};}
14967 Shows the finalization (cleanup) procedure for a scope.
14969 @item @code{(if @emph{expr} then @emph{expr} else @emph{expr})}
14971 Conditional expression equivalent to the @code{x?y:z} construction in C.
14973 @item @code{@emph{target}^(@emph{source})}
14975 A conversion with floating-point truncation instead of rounding.
14977 @item @code{@emph{target}?(@emph{source})}
14979 A conversion that bypasses normal Ada semantic checking. In particular
14980 enumeration types and fixed-point types are treated simply as integers.
14982 @item @code{@emph{target}?^(@emph{source})}
14984 Combines the above two cases.
14987 @code{@emph{x} #/ @emph{y}}
14989 @code{@emph{x} #mod @emph{y}}
14991 @code{@emph{x} # @emph{y}}
14996 @item @code{@emph{x} #rem @emph{y}}
14998 A division or multiplication of fixed-point values which are treated as
14999 integers without any kind of scaling.
15001 @item @code{free @emph{expr} [storage_pool = @emph{xxx}]}
15003 Shows the storage pool associated with a @code{free} statement.
15005 @item @code{[subtype or type declaration]}
15007 Used to list an equivalent declaration for an internally generated
15008 type that is referenced elsewhere in the listing.
15010 @item @code{freeze @emph{type-name} [@emph{actions}]}
15012 Shows the point at which @code{type-name} is frozen, with possible
15013 associated actions to be performed at the freeze point.
15015 @item @code{reference @emph{itype}}
15017 Reference (and hence definition) to internal type @code{itype}.
15019 @item @code{@emph{function-name}! (@emph{arg}, @emph{arg}, @emph{arg})}
15021 Intrinsic function call.
15023 @item @code{@emph{label-name} : label}
15025 Declaration of label @code{labelname}.
15027 @item @code{#$ @emph{subprogram-name}}
15029 An implicit call to a run-time support routine
15030 (to meet the requirement of H.3.1(9) in a
15031 convenient manner).
15033 @item @code{@emph{expr} && @emph{expr} && @emph{expr} ... && @emph{expr}}
15035 A multiple concatenation (same effect as @code{expr} & @code{expr} &
15036 @code{expr}, but handled more efficiently).
15038 @item @code{[constraint_error]}
15040 Raise the @code{Constraint_Error} exception.
15042 @item @code{@emph{expression}'reference}
15044 A pointer to the result of evaluating @{expression@}.
15046 @item @code{@emph{target-type}!(@emph{source-expression})}
15048 An unchecked conversion of @code{source-expression} to @code{target-type}.
15050 @item @code{[@emph{numerator}/@emph{denominator}]}
15052 Used to represent internal real literals (that) have no exact
15053 representation in base 2-16 (for example, the result of compile time
15054 evaluation of the expression 1.0/27.0).
15058 @geindex -gnatD (gcc)
15063 @item @code{-gnatD[=nn]}
15065 When used in conjunction with @code{-gnatG}, this switch causes
15066 the expanded source, as described above for
15067 @code{-gnatG} to be written to files with names
15068 @code{xxx.dg}, where @code{xxx} is the normal file name,
15069 instead of to the standard output file. For
15070 example, if the source file name is @code{hello.adb}, then a file
15071 @code{hello.adb.dg} will be written. The debugging
15072 information generated by the @code{gcc} @code{-g} switch
15073 will refer to the generated @code{xxx.dg} file. This allows
15074 you to do source level debugging using the generated code which is
15075 sometimes useful for complex code, for example to find out exactly
15076 which part of a complex construction raised an exception. This switch
15077 also suppresses generation of cross-reference information (see
15078 @code{-gnatx}) since otherwise the cross-reference information
15079 would refer to the @code{.dg} file, which would cause
15080 confusion since this is not the original source file.
15082 Note that @code{-gnatD} actually implies @code{-gnatG}
15083 automatically, so it is not necessary to give both options.
15084 In other words @code{-gnatD} is equivalent to @code{-gnatDG}).
15086 @geindex -gnatL (gcc)
15088 If the switch @code{-gnatL} is used in conjunction with
15089 @code{-gnatDG}, then the original source lines are interspersed
15090 in the expanded source (as comment lines with the original line number).
15092 The optional parameter @code{nn} if present after -gnatD specifies an
15093 alternative maximum line length that overrides the normal default of 72.
15094 This value is in the range 40-999999, values less than 40 being silently
15095 reset to 40. The equal sign is optional.
15098 @geindex -gnatr (gcc)
15100 @geindex pragma Restrictions
15105 @item @code{-gnatr}
15107 This switch causes pragma Restrictions to be treated as Restriction_Warnings
15108 so that violation of restrictions causes warnings rather than illegalities.
15109 This is useful during the development process when new restrictions are added
15110 or investigated. The switch also causes pragma Profile to be treated as
15111 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
15112 restriction warnings rather than restrictions.
15115 @geindex -gnatR (gcc)
15120 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
15122 This switch controls output from the compiler of a listing showing
15123 representation information for declared types, objects and subprograms.
15124 For @code{-gnatR0}, no information is output (equivalent to omitting
15125 the @code{-gnatR} switch). For @code{-gnatR1} (which is the default,
15126 so @code{-gnatR} with no parameter has the same effect), size and
15127 alignment information is listed for declared array and record types.
15129 For @code{-gnatR2}, size and alignment information is listed for all
15130 declared types and objects. The @code{Linker_Section} is also listed for any
15131 entity for which the @code{Linker_Section} is set explicitly or implicitly (the
15132 latter case occurs for objects of a type for which a @code{Linker_Section}
15135 For @code{-gnatR3}, symbolic expressions for values that are computed
15136 at run time for records are included. These symbolic expressions have
15137 a mostly obvious format with #n being used to represent the value of the
15138 n'th discriminant. See source files @code{repinfo.ads/adb} in the
15139 GNAT sources for full details on the format of @code{-gnatR3} output.
15141 For @code{-gnatR4}, information for relevant compiler-generated types
15142 is also listed, i.e. when they are structurally part of other declared
15145 If the switch is followed by an @code{e} (e.g. @code{-gnatR2e}), then
15146 extended representation information for record sub-components of records
15149 If the switch is followed by an @code{m} (e.g. @code{-gnatRm}), then
15150 subprogram conventions and parameter passing mechanisms for all the
15151 subprograms are included.
15153 If the switch is followed by a @code{j} (e.g., @code{-gnatRj}), then
15154 the output is in the JSON data interchange format specified by the
15155 ECMA-404 standard. The semantic description of this JSON output is
15156 available in the specification of the Repinfo unit present in the
15159 If the switch is followed by an @code{s} (e.g., @code{-gnatR3s}), then
15160 the output is to a file with the name @code{file.rep} where @code{file} is
15161 the name of the corresponding source file, except if @code{j} is also
15162 specified, in which case the file name is @code{file.json}.
15164 Note that it is possible for record components to have zero size. In
15165 this case, the component clause uses an obvious extension of permitted
15166 Ada syntax, for example @code{at 0 range 0 .. -1}.
15169 @geindex -gnatS (gcc)
15174 @item @code{-gnatS}
15176 The use of the switch @code{-gnatS} for an
15177 Ada compilation will cause the compiler to output a
15178 representation of package Standard in a form very
15179 close to standard Ada. It is not quite possible to
15180 do this entirely in standard Ada (since new
15181 numeric base types cannot be created in standard
15182 Ada), but the output is easily
15183 readable to any Ada programmer, and is useful to
15184 determine the characteristics of target dependent
15185 types in package Standard.
15188 @geindex -gnatx (gcc)
15193 @item @code{-gnatx}
15195 Normally the compiler generates full cross-referencing information in
15196 the @code{ALI} file. This information is used by a number of tools,
15197 including @code{gnatfind} and @code{gnatxref}. The @code{-gnatx} switch
15198 suppresses this information. This saves some space and may slightly
15199 speed up compilation, but means that these tools cannot be used.
15202 @geindex -fgnat-encodings (gcc)
15207 @item @code{-fgnat-encodings=[all|gdb|minimal]}
15209 This switch controls the balance between GNAT encodings and standard DWARF
15210 emitted in the debug information.
15212 Historically, old debug formats like stabs were not powerful enough to
15213 express some Ada types (for instance, variant records or fixed-point types).
15214 To work around this, GNAT introduced proprietary encodings that embed the
15215 missing information ("GNAT encodings").
15217 Recent versions of the DWARF debug information format are now able to
15218 correctly describe most of these Ada constructs ("standard DWARF"). As
15219 third-party tools started to use this format, GNAT has been enhanced to
15220 generate it. However, most tools (including GDB) are still relying on GNAT
15223 To support all tools, GNAT needs to be versatile about the balance between
15224 generation of GNAT encodings and standard DWARF. This is what
15225 @code{-fgnat-encodings} is about.
15231 @code{=all}: Emit all GNAT encodings, and then emit as much standard DWARF as
15232 possible so it does not conflict with GNAT encodings.
15235 @code{=gdb}: Emit as much standard DWARF as possible as long as the current
15236 GDB handles it. Emit GNAT encodings for the rest.
15239 @code{=minimal}: Emit as much standard DWARF as possible and emit GNAT
15240 encodings for the rest.
15244 @node Exception Handling Control,Units to Sources Mapping Files,Debugging Control,Compiler Switches
15245 @anchor{gnat_ugn/building_executable_programs_with_gnat id28}@anchor{114}@anchor{gnat_ugn/building_executable_programs_with_gnat exception-handling-control}@anchor{115}
15246 @subsection Exception Handling Control
15249 GNAT uses two methods for handling exceptions at run time. The
15250 @code{setjmp/longjmp} method saves the context when entering
15251 a frame with an exception handler. Then when an exception is
15252 raised, the context can be restored immediately, without the
15253 need for tracing stack frames. This method provides very fast
15254 exception propagation, but introduces significant overhead for
15255 the use of exception handlers, even if no exception is raised.
15257 The other approach is called 'zero cost' exception handling.
15258 With this method, the compiler builds static tables to describe
15259 the exception ranges. No dynamic code is required when entering
15260 a frame containing an exception handler. When an exception is
15261 raised, the tables are used to control a back trace of the
15262 subprogram invocation stack to locate the required exception
15263 handler. This method has considerably poorer performance for
15264 the propagation of exceptions, but there is no overhead for
15265 exception handlers if no exception is raised. Note that in this
15266 mode and in the context of mixed Ada and C/C++ programming,
15267 to propagate an exception through a C/C++ code, the C/C++ code
15268 must be compiled with the @code{-funwind-tables} GCC's
15271 The following switches may be used to control which of the
15272 two exception handling methods is used.
15274 @geindex --RTS=sjlj (gnatmake)
15279 @item @code{--RTS=sjlj}
15281 This switch causes the setjmp/longjmp run-time (when available) to be used
15282 for exception handling. If the default
15283 mechanism for the target is zero cost exceptions, then
15284 this switch can be used to modify this default, and must be
15285 used for all units in the partition.
15286 This option is rarely used. One case in which it may be
15287 advantageous is if you have an application where exception
15288 raising is common and the overall performance of the
15289 application is improved by favoring exception propagation.
15292 @geindex --RTS=zcx (gnatmake)
15294 @geindex Zero Cost Exceptions
15299 @item @code{--RTS=zcx}
15301 This switch causes the zero cost approach to be used
15302 for exception handling. If this is the default mechanism for the
15303 target (see below), then this switch is unneeded. If the default
15304 mechanism for the target is setjmp/longjmp exceptions, then
15305 this switch can be used to modify this default, and must be
15306 used for all units in the partition.
15307 This option can only be used if the zero cost approach
15308 is available for the target in use, otherwise it will generate an error.
15311 The same option @code{--RTS} must be used both for @code{gcc}
15312 and @code{gnatbind}. Passing this option to @code{gnatmake}
15313 (@ref{dc,,Switches for gnatmake}) will ensure the required consistency
15314 through the compilation and binding steps.
15316 @node Units to Sources Mapping Files,Code Generation Control,Exception Handling Control,Compiler Switches
15317 @anchor{gnat_ugn/building_executable_programs_with_gnat id29}@anchor{116}@anchor{gnat_ugn/building_executable_programs_with_gnat units-to-sources-mapping-files}@anchor{f7}
15318 @subsection Units to Sources Mapping Files
15321 @geindex -gnatem (gcc)
15326 @item @code{-gnatem=@emph{path}}
15328 A mapping file is a way to communicate to the compiler two mappings:
15329 from unit names to file names (without any directory information) and from
15330 file names to path names (with full directory information). These mappings
15331 are used by the compiler to short-circuit the path search.
15333 The use of mapping files is not required for correct operation of the
15334 compiler, but mapping files can improve efficiency, particularly when
15335 sources are read over a slow network connection. In normal operation,
15336 you need not be concerned with the format or use of mapping files,
15337 and the @code{-gnatem} switch is not a switch that you would use
15338 explicitly. It is intended primarily for use by automatic tools such as
15339 @code{gnatmake} running under the project file facility. The
15340 description here of the format of mapping files is provided
15341 for completeness and for possible use by other tools.
15343 A mapping file is a sequence of sets of three lines. In each set, the
15344 first line is the unit name, in lower case, with @code{%s} appended
15345 for specs and @code{%b} appended for bodies; the second line is the
15346 file name; and the third line is the path name.
15353 /gnat/project1/sources/main.2.ada
15356 When the switch @code{-gnatem} is specified, the compiler will
15357 create in memory the two mappings from the specified file. If there is
15358 any problem (nonexistent file, truncated file or duplicate entries),
15359 no mapping will be created.
15361 Several @code{-gnatem} switches may be specified; however, only the
15362 last one on the command line will be taken into account.
15364 When using a project file, @code{gnatmake} creates a temporary
15365 mapping file and communicates it to the compiler using this switch.
15368 @node Code Generation Control,,Units to Sources Mapping Files,Compiler Switches
15369 @anchor{gnat_ugn/building_executable_programs_with_gnat code-generation-control}@anchor{117}@anchor{gnat_ugn/building_executable_programs_with_gnat id30}@anchor{118}
15370 @subsection Code Generation Control
15373 The GCC technology provides a wide range of target dependent
15374 @code{-m} switches for controlling
15375 details of code generation with respect to different versions of
15376 architectures. This includes variations in instruction sets (e.g.,
15377 different members of the power pc family), and different requirements
15378 for optimal arrangement of instructions (e.g., different members of
15379 the x86 family). The list of available @code{-m} switches may be
15380 found in the GCC documentation.
15382 Use of these @code{-m} switches may in some cases result in improved
15385 The GNAT technology is tested and qualified without any
15386 @code{-m} switches,
15387 so generally the most reliable approach is to avoid the use of these
15388 switches. However, we generally expect most of these switches to work
15389 successfully with GNAT, and many customers have reported successful
15390 use of these options.
15392 Our general advice is to avoid the use of @code{-m} switches unless
15393 special needs lead to requirements in this area. In particular,
15394 there is no point in using @code{-m} switches to improve performance
15395 unless you actually see a performance improvement.
15397 @node Linker Switches,Binding with gnatbind,Compiler Switches,Building Executable Programs with GNAT
15398 @anchor{gnat_ugn/building_executable_programs_with_gnat linker-switches}@anchor{119}@anchor{gnat_ugn/building_executable_programs_with_gnat id31}@anchor{11a}
15399 @section Linker Switches
15402 Linker switches can be specified after @code{-largs} builder switch.
15404 @geindex -fuse-ld=name
15409 @item @code{-fuse-ld=@emph{name}}
15411 Linker to be used. The default is @code{bfd} for @code{ld.bfd},
15412 the alternative being @code{gold} for @code{ld.gold}. The later is
15413 a more recent and faster linker, but only available on GNU/Linux
15417 @node Binding with gnatbind,Linking with gnatlink,Linker Switches,Building Executable Programs with GNAT
15418 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind}@anchor{1d}@anchor{gnat_ugn/building_executable_programs_with_gnat id32}@anchor{11b}
15419 @section Binding with @code{gnatbind}
15424 This chapter describes the GNAT binder, @code{gnatbind}, which is used
15425 to bind compiled GNAT objects.
15427 The @code{gnatbind} program performs four separate functions:
15433 Checks that a program is consistent, in accordance with the rules in
15434 Chapter 10 of the Ada Reference Manual. In particular, error
15435 messages are generated if a program uses inconsistent versions of a
15439 Checks that an acceptable order of elaboration exists for the program
15440 and issues an error message if it cannot find an order of elaboration
15441 that satisfies the rules in Chapter 10 of the Ada Language Manual.
15444 Generates a main program incorporating the given elaboration order.
15445 This program is a small Ada package (body and spec) that
15446 must be subsequently compiled
15447 using the GNAT compiler. The necessary compilation step is usually
15448 performed automatically by @code{gnatlink}. The two most important
15449 functions of this program
15450 are to call the elaboration routines of units in an appropriate order
15451 and to call the main program.
15454 Determines the set of object files required by the given main program.
15455 This information is output in the forms of comments in the generated program,
15456 to be read by the @code{gnatlink} utility used to link the Ada application.
15460 * Running gnatbind::
15461 * Switches for gnatbind::
15462 * Command-Line Access::
15463 * Search Paths for gnatbind::
15464 * Examples of gnatbind Usage::
15468 @node Running gnatbind,Switches for gnatbind,,Binding with gnatbind
15469 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatbind}@anchor{11c}@anchor{gnat_ugn/building_executable_programs_with_gnat id33}@anchor{11d}
15470 @subsection Running @code{gnatbind}
15473 The form of the @code{gnatbind} command is
15476 $ gnatbind [ switches ] mainprog[.ali] [ switches ]
15479 where @code{mainprog.adb} is the Ada file containing the main program
15480 unit body. @code{gnatbind} constructs an Ada
15481 package in two files whose names are
15482 @code{b~mainprog.ads}, and @code{b~mainprog.adb}.
15483 For example, if given the
15484 parameter @code{hello.ali}, for a main program contained in file
15485 @code{hello.adb}, the binder output files would be @code{b~hello.ads}
15486 and @code{b~hello.adb}.
15488 When doing consistency checking, the binder takes into consideration
15489 any source files it can locate. For example, if the binder determines
15490 that the given main program requires the package @code{Pack}, whose
15492 file is @code{pack.ali} and whose corresponding source spec file is
15493 @code{pack.ads}, it attempts to locate the source file @code{pack.ads}
15494 (using the same search path conventions as previously described for the
15495 @code{gcc} command). If it can locate this source file, it checks that
15497 or source checksums of the source and its references to in @code{ALI} files
15498 match. In other words, any @code{ALI} files that mentions this spec must have
15499 resulted from compiling this version of the source file (or in the case
15500 where the source checksums match, a version close enough that the
15501 difference does not matter).
15503 @geindex Source files
15504 @geindex use by binder
15506 The effect of this consistency checking, which includes source files, is
15507 that the binder ensures that the program is consistent with the latest
15508 version of the source files that can be located at bind time. Editing a
15509 source file without compiling files that depend on the source file cause
15510 error messages to be generated by the binder.
15512 For example, suppose you have a main program @code{hello.adb} and a
15513 package @code{P}, from file @code{p.ads} and you perform the following
15520 Enter @code{gcc -c hello.adb} to compile the main program.
15523 Enter @code{gcc -c p.ads} to compile package @code{P}.
15526 Edit file @code{p.ads}.
15529 Enter @code{gnatbind hello}.
15532 At this point, the file @code{p.ali} contains an out-of-date time stamp
15533 because the file @code{p.ads} has been edited. The attempt at binding
15534 fails, and the binder generates the following error messages:
15537 error: "hello.adb" must be recompiled ("p.ads" has been modified)
15538 error: "p.ads" has been modified and must be recompiled
15541 Now both files must be recompiled as indicated, and then the bind can
15542 succeed, generating a main program. You need not normally be concerned
15543 with the contents of this file, but for reference purposes a sample
15544 binder output file is given in @ref{e,,Example of Binder Output File}.
15546 In most normal usage, the default mode of @code{gnatbind} which is to
15547 generate the main package in Ada, as described in the previous section.
15548 In particular, this means that any Ada programmer can read and understand
15549 the generated main program. It can also be debugged just like any other
15550 Ada code provided the @code{-g} switch is used for
15551 @code{gnatbind} and @code{gnatlink}.
15553 @node Switches for gnatbind,Command-Line Access,Running gnatbind,Binding with gnatbind
15554 @anchor{gnat_ugn/building_executable_programs_with_gnat id34}@anchor{11e}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind}@anchor{11f}
15555 @subsection Switches for @code{gnatbind}
15558 The following switches are available with @code{gnatbind}; details will
15559 be presented in subsequent sections.
15561 @geindex --version (gnatbind)
15566 @item @code{--version}
15568 Display Copyright and version, then exit disregarding all other options.
15571 @geindex --help (gnatbind)
15576 @item @code{--help}
15578 If @code{--version} was not used, display usage, then exit disregarding
15582 @geindex -a (gnatbind)
15589 Indicates that, if supported by the platform, the adainit procedure should
15590 be treated as an initialisation routine by the linker (a constructor). This
15591 is intended to be used by the Project Manager to automatically initialize
15592 shared Stand-Alone Libraries.
15595 @geindex -aO (gnatbind)
15602 Specify directory to be searched for ALI files.
15605 @geindex -aI (gnatbind)
15612 Specify directory to be searched for source file.
15615 @geindex -A (gnatbind)
15620 @item @code{-A[=@emph{filename}]}
15622 Output ALI list (to standard output or to the named file).
15625 @geindex -b (gnatbind)
15632 Generate brief messages to @code{stderr} even if verbose mode set.
15635 @geindex -c (gnatbind)
15642 Check only, no generation of binder output file.
15645 @geindex -dnn[k|m] (gnatbind)
15650 @item @code{-d@emph{nn}[k|m]}
15652 This switch can be used to change the default task stack size value
15653 to a specified size @code{nn}, which is expressed in bytes by default, or
15654 in kilobytes when suffixed with @code{k} or in megabytes when suffixed
15656 In the absence of a @code{[k|m]} suffix, this switch is equivalent,
15657 in effect, to completing all task specs with
15660 pragma Storage_Size (nn);
15663 When they do not already have such a pragma.
15666 @geindex -D (gnatbind)
15671 @item @code{-D@emph{nn}[k|m]}
15673 Set the default secondary stack size to @code{nn}. The suffix indicates whether
15674 the size is in bytes (no suffix), kilobytes (@code{k} suffix) or megabytes
15677 The secondary stack holds objects of unconstrained types that are returned by
15678 functions, for example unconstrained Strings. The size of the secondary stack
15679 can be dynamic or fixed depending on the target.
15681 For most targets, the secondary stack grows on demand and is implemented as
15682 a chain of blocks in the heap. In this case, the default secondary stack size
15683 determines the initial size of the secondary stack for each task and the
15684 smallest amount the secondary stack can grow by.
15686 For Ravenscar, ZFP, and Cert run-times the size of the secondary stack is
15687 fixed. This switch can be used to change the default size of these stacks.
15688 The default secondary stack size can be overridden on a per-task basis if
15689 individual tasks have different secondary stack requirements. This is
15690 achieved through the Secondary_Stack_Size aspect that takes the size of the
15691 secondary stack in bytes.
15694 @geindex -e (gnatbind)
15701 Output complete list of elaboration-order dependencies.
15704 @geindex -Ea (gnatbind)
15711 Store tracebacks in exception occurrences when the target supports it.
15712 The "a" is for "address"; tracebacks will contain hexadecimal addresses,
15713 unless symbolic tracebacks are enabled.
15715 See also the packages @code{GNAT.Traceback} and
15716 @code{GNAT.Traceback.Symbolic} for more information.
15717 Note that on x86 ports, you must not use @code{-fomit-frame-pointer}
15721 @geindex -Es (gnatbind)
15728 Store tracebacks in exception occurrences when the target supports it.
15729 The "s" is for "symbolic"; symbolic tracebacks are enabled.
15732 @geindex -E (gnatbind)
15739 Currently the same as @code{-Ea}.
15742 @geindex -f (gnatbind)
15747 @item @code{-f@emph{elab-order}}
15749 Force elaboration order. For further details see @ref{120,,Elaboration Control}
15750 and @ref{f,,Elaboration Order Handling in GNAT}.
15753 @geindex -F (gnatbind)
15760 Force the checks of elaboration flags. @code{gnatbind} does not normally
15761 generate checks of elaboration flags for the main executable, except when
15762 a Stand-Alone Library is used. However, there are cases when this cannot be
15763 detected by gnatbind. An example is importing an interface of a Stand-Alone
15764 Library through a pragma Import and only specifying through a linker switch
15765 this Stand-Alone Library. This switch is used to guarantee that elaboration
15766 flag checks are generated.
15769 @geindex -h (gnatbind)
15776 Output usage (help) information.
15779 @geindex -H (gnatbind)
15786 Legacy elaboration order model enabled. For further details see
15787 @ref{f,,Elaboration Order Handling in GNAT}.
15790 @geindex -H32 (gnatbind)
15797 Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types).
15798 For further details see @ref{121,,Dynamic Allocation Control}.
15801 @geindex -H64 (gnatbind)
15803 @geindex __gnat_malloc
15810 Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types).
15811 For further details see @ref{121,,Dynamic Allocation Control}.
15813 @geindex -I (gnatbind)
15817 Specify directory to be searched for source and ALI files.
15819 @geindex -I- (gnatbind)
15823 Do not look for sources in the current directory where @code{gnatbind} was
15824 invoked, and do not look for ALI files in the directory containing the
15825 ALI file named in the @code{gnatbind} command line.
15827 @geindex -l (gnatbind)
15831 Output chosen elaboration order.
15833 @geindex -L (gnatbind)
15835 @item @code{-L@emph{xxx}}
15837 Bind the units for library building. In this case the @code{adainit} and
15838 @code{adafinal} procedures (@ref{b4,,Binding with Non-Ada Main Programs})
15839 are renamed to @code{@emph{xxx}init} and
15840 @code{@emph{xxx}final}.
15842 (@ref{15,,GNAT and Libraries}, for more details.)
15844 @geindex -M (gnatbind)
15846 @item @code{-M@emph{xyz}}
15848 Rename generated main program from main to xyz. This option is
15849 supported on cross environments only.
15851 @geindex -m (gnatbind)
15853 @item @code{-m@emph{n}}
15855 Limit number of detected errors or warnings to @code{n}, where @code{n} is
15856 in the range 1..999999. The default value if no switch is
15857 given is 9999. If the number of warnings reaches this limit, then a
15858 message is output and further warnings are suppressed, the bind
15859 continues in this case. If the number of errors reaches this
15860 limit, then a message is output and the bind is abandoned.
15861 A value of zero means that no limit is enforced. The equal
15864 @geindex -n (gnatbind)
15870 @geindex -nostdinc (gnatbind)
15872 @item @code{-nostdinc}
15874 Do not look for sources in the system default directory.
15876 @geindex -nostdlib (gnatbind)
15878 @item @code{-nostdlib}
15880 Do not look for library files in the system default directory.
15882 @geindex --RTS (gnatbind)
15884 @item @code{--RTS=@emph{rts-path}}
15886 Specifies the default location of the run-time library. Same meaning as the
15887 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
15889 @geindex -o (gnatbind)
15891 @item @code{-o @emph{file}}
15893 Name the output file @code{file} (default is @code{b~`xxx}.adb`).
15894 Note that if this option is used, then linking must be done manually,
15895 gnatlink cannot be used.
15897 @geindex -O (gnatbind)
15899 @item @code{-O[=@emph{filename}]}
15901 Output object list (to standard output or to the named file).
15903 @geindex -p (gnatbind)
15907 Pessimistic (worst-case) elaboration order.
15909 @geindex -P (gnatbind)
15913 Generate binder file suitable for CodePeer.
15915 @geindex -R (gnatbind)
15919 Output closure source list, which includes all non-run-time units that are
15920 included in the bind.
15922 @geindex -Ra (gnatbind)
15926 Like @code{-R} but the list includes run-time units.
15928 @geindex -s (gnatbind)
15932 Require all source files to be present.
15934 @geindex -S (gnatbind)
15936 @item @code{-S@emph{xxx}}
15938 Specifies the value to be used when detecting uninitialized scalar
15939 objects with pragma Initialize_Scalars.
15940 The @code{xxx} string specified with the switch is one of:
15946 @code{in} for an invalid value.
15948 If zero is invalid for the discrete type in question,
15949 then the scalar value is set to all zero bits.
15950 For signed discrete types, the largest possible negative value of
15951 the underlying scalar is set (i.e. a one bit followed by all zero bits).
15952 For unsigned discrete types, the underlying scalar value is set to all
15953 one bits. For floating-point types, a NaN value is set
15954 (see body of package System.Scalar_Values for exact values).
15957 @code{lo} for low value.
15959 If zero is invalid for the discrete type in question,
15960 then the scalar value is set to all zero bits.
15961 For signed discrete types, the largest possible negative value of
15962 the underlying scalar is set (i.e. a one bit followed by all zero bits).
15963 For unsigned discrete types, the underlying scalar value is set to all
15964 zero bits. For floating-point, a small value is set
15965 (see body of package System.Scalar_Values for exact values).
15968 @code{hi} for high value.
15970 If zero is invalid for the discrete type in question,
15971 then the scalar value is set to all one bits.
15972 For signed discrete types, the largest possible positive value of
15973 the underlying scalar is set (i.e. a zero bit followed by all one bits).
15974 For unsigned discrete types, the underlying scalar value is set to all
15975 one bits. For floating-point, a large value is set
15976 (see body of package System.Scalar_Values for exact values).
15979 @code{xx} for hex value (two hex digits).
15981 The underlying scalar is set to a value consisting of repeated bytes, whose
15982 value corresponds to the given value. For example if @code{BF} is given,
15983 then a 32-bit scalar value will be set to the bit patterm @code{16#BFBFBFBF#}.
15986 @geindex GNAT_INIT_SCALARS
15988 In addition, you can specify @code{-Sev} to indicate that the value is
15989 to be set at run time. In this case, the program will look for an environment
15990 variable of the form @code{GNAT_INIT_SCALARS=@emph{yy}}, where @code{yy} is one
15991 of @code{in/lo/hi/@emph{xx}} with the same meanings as above.
15992 If no environment variable is found, or if it does not have a valid value,
15993 then the default is @code{in} (invalid values).
15996 @geindex -static (gnatbind)
16001 @item @code{-static}
16003 Link against a static GNAT run-time.
16005 @geindex -shared (gnatbind)
16007 @item @code{-shared}
16009 Link against a shared GNAT run-time when available.
16011 @geindex -t (gnatbind)
16015 Tolerate time stamp and other consistency errors.
16017 @geindex -T (gnatbind)
16019 @item @code{-T@emph{n}}
16021 Set the time slice value to @code{n} milliseconds. If the system supports
16022 the specification of a specific time slice value, then the indicated value
16023 is used. If the system does not support specific time slice values, but
16024 does support some general notion of round-robin scheduling, then any
16025 nonzero value will activate round-robin scheduling.
16027 A value of zero is treated specially. It turns off time
16028 slicing, and in addition, indicates to the tasking run-time that the
16029 semantics should match as closely as possible the Annex D
16030 requirements of the Ada RM, and in particular sets the default
16031 scheduling policy to @code{FIFO_Within_Priorities}.
16033 @geindex -u (gnatbind)
16035 @item @code{-u@emph{n}}
16037 Enable dynamic stack usage, with @code{n} results stored and displayed
16038 at program termination. A result is generated when a task
16039 terminates. Results that can't be stored are displayed on the fly, at
16040 task termination. This option is currently not supported on Itanium
16041 platforms. (See @ref{122,,Dynamic Stack Usage Analysis} for details.)
16043 @geindex -v (gnatbind)
16047 Verbose mode. Write error messages, header, summary output to
16050 @geindex -V (gnatbind)
16052 @item @code{-V@emph{key}=@emph{value}}
16054 Store the given association of @code{key} to @code{value} in the bind environment.
16055 Values stored this way can be retrieved at run time using
16056 @code{GNAT.Bind_Environment}.
16058 @geindex -w (gnatbind)
16060 @item @code{-w@emph{x}}
16062 Warning mode; @code{x} = s/e for suppress/treat as error.
16064 @geindex -Wx (gnatbind)
16066 @item @code{-Wx@emph{e}}
16068 Override default wide character encoding for standard Text_IO files.
16070 @geindex -x (gnatbind)
16074 Exclude source files (check object consistency only).
16076 @geindex -Xnnn (gnatbind)
16078 @item @code{-X@emph{nnn}}
16080 Set default exit status value, normally 0 for POSIX compliance.
16082 @geindex -y (gnatbind)
16086 Enable leap seconds support in @code{Ada.Calendar} and its children.
16088 @geindex -z (gnatbind)
16092 No main subprogram.
16095 You may obtain this listing of switches by running @code{gnatbind} with
16099 * Consistency-Checking Modes::
16100 * Binder Error Message Control::
16101 * Elaboration Control::
16103 * Dynamic Allocation Control::
16104 * Binding with Non-Ada Main Programs::
16105 * Binding Programs with No Main Subprogram::
16109 @node Consistency-Checking Modes,Binder Error Message Control,,Switches for gnatbind
16110 @anchor{gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes}@anchor{123}@anchor{gnat_ugn/building_executable_programs_with_gnat id35}@anchor{124}
16111 @subsubsection Consistency-Checking Modes
16114 As described earlier, by default @code{gnatbind} checks
16115 that object files are consistent with one another and are consistent
16116 with any source files it can locate. The following switches control binder
16121 @geindex -s (gnatbind)
16129 Require source files to be present. In this mode, the binder must be
16130 able to locate all source files that are referenced, in order to check
16131 their consistency. In normal mode, if a source file cannot be located it
16132 is simply ignored. If you specify this switch, a missing source
16135 @geindex -Wx (gnatbind)
16137 @item @code{-Wx@emph{e}}
16139 Override default wide character encoding for standard Text_IO files.
16140 Normally the default wide character encoding method used for standard
16141 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
16142 the main source input (see description of switch
16143 @code{-gnatWx} for the compiler). The
16144 use of this switch for the binder (which has the same set of
16145 possible arguments) overrides this default as specified.
16147 @geindex -x (gnatbind)
16151 Exclude source files. In this mode, the binder only checks that ALI
16152 files are consistent with one another. Source files are not accessed.
16153 The binder runs faster in this mode, and there is still a guarantee that
16154 the resulting program is self-consistent.
16155 If a source file has been edited since it was last compiled, and you
16156 specify this switch, the binder will not detect that the object
16157 file is out of date with respect to the source file. Note that this is the
16158 mode that is automatically used by @code{gnatmake} because in this
16159 case the checking against sources has already been performed by
16160 @code{gnatmake} in the course of compilation (i.e., before binding).
16163 @node Binder Error Message Control,Elaboration Control,Consistency-Checking Modes,Switches for gnatbind
16164 @anchor{gnat_ugn/building_executable_programs_with_gnat id36}@anchor{125}@anchor{gnat_ugn/building_executable_programs_with_gnat binder-error-message-control}@anchor{126}
16165 @subsubsection Binder Error Message Control
16168 The following switches provide control over the generation of error
16169 messages from the binder:
16173 @geindex -v (gnatbind)
16181 Verbose mode. In the normal mode, brief error messages are generated to
16182 @code{stderr}. If this switch is present, a header is written
16183 to @code{stdout} and any error messages are directed to @code{stdout}.
16184 All that is written to @code{stderr} is a brief summary message.
16186 @geindex -b (gnatbind)
16190 Generate brief error messages to @code{stderr} even if verbose mode is
16191 specified. This is relevant only when used with the
16194 @geindex -m (gnatbind)
16196 @item @code{-m@emph{n}}
16198 Limits the number of error messages to @code{n}, a decimal integer in the
16199 range 1-999. The binder terminates immediately if this limit is reached.
16201 @geindex -M (gnatbind)
16203 @item @code{-M@emph{xxx}}
16205 Renames the generated main program from @code{main} to @code{xxx}.
16206 This is useful in the case of some cross-building environments, where
16207 the actual main program is separate from the one generated
16208 by @code{gnatbind}.
16210 @geindex -ws (gnatbind)
16216 Suppress all warning messages.
16218 @geindex -we (gnatbind)
16222 Treat any warning messages as fatal errors.
16224 @geindex -t (gnatbind)
16226 @geindex Time stamp checks
16229 @geindex Binder consistency checks
16231 @geindex Consistency checks
16236 The binder performs a number of consistency checks including:
16242 Check that time stamps of a given source unit are consistent
16245 Check that checksums of a given source unit are consistent
16248 Check that consistent versions of @code{GNAT} were used for compilation
16251 Check consistency of configuration pragmas as required
16254 Normally failure of such checks, in accordance with the consistency
16255 requirements of the Ada Reference Manual, causes error messages to be
16256 generated which abort the binder and prevent the output of a binder
16257 file and subsequent link to obtain an executable.
16259 The @code{-t} switch converts these error messages
16260 into warnings, so that
16261 binding and linking can continue to completion even in the presence of such
16262 errors. The result may be a failed link (due to missing symbols), or a
16263 non-functional executable which has undefined semantics.
16267 This means that @code{-t} should be used only in unusual situations,
16273 @node Elaboration Control,Output Control,Binder Error Message Control,Switches for gnatbind
16274 @anchor{gnat_ugn/building_executable_programs_with_gnat id37}@anchor{127}@anchor{gnat_ugn/building_executable_programs_with_gnat elaboration-control}@anchor{120}
16275 @subsubsection Elaboration Control
16278 The following switches provide additional control over the elaboration
16279 order. For further details see @ref{f,,Elaboration Order Handling in GNAT}.
16281 @geindex -f (gnatbind)
16286 @item @code{-f@emph{elab-order}}
16288 Force elaboration order.
16290 @code{elab-order} should be the name of a "forced elaboration order file", that
16291 is, a text file containing library item names, one per line. A name of the
16292 form "some.unit%s" or "some.unit (spec)" denotes the spec of Some.Unit. A
16293 name of the form "some.unit%b" or "some.unit (body)" denotes the body of
16294 Some.Unit. Each pair of lines is taken to mean that there is an elaboration
16295 dependence of the second line on the first. For example, if the file
16305 then the spec of This will be elaborated before the body of This, and the
16306 body of This will be elaborated before the spec of That, and the spec of That
16307 will be elaborated before the body of That. The first and last of these three
16308 dependences are already required by Ada rules, so this file is really just
16309 forcing the body of This to be elaborated before the spec of That.
16311 The given order must be consistent with Ada rules, or else @code{gnatbind} will
16312 give elaboration cycle errors. For example, if you say x (body) should be
16313 elaborated before x (spec), there will be a cycle, because Ada rules require
16314 x (spec) to be elaborated before x (body); you can't have the spec and body
16315 both elaborated before each other.
16317 If you later add "with That;" to the body of This, there will be a cycle, in
16318 which case you should erase either "this (body)" or "that (spec)" from the
16319 above forced elaboration order file.
16321 Blank lines and Ada-style comments are ignored. Unit names that do not exist
16322 in the program are ignored. Units in the GNAT predefined library are also
16326 @geindex -p (gnatbind)
16333 Pessimistic elaboration order
16335 This switch is only applicable to the pre-20.x legacy elaboration models.
16336 The post-20.x elaboration model uses a more informed approach of ordering
16339 Normally the binder attempts to choose an elaboration order that is likely to
16340 minimize the likelihood of an elaboration order error resulting in raising a
16341 @code{Program_Error} exception. This switch reverses the action of the binder,
16342 and requests that it deliberately choose an order that is likely to maximize
16343 the likelihood of an elaboration error. This is useful in ensuring
16344 portability and avoiding dependence on accidental fortuitous elaboration
16347 Normally it only makes sense to use the @code{-p} switch if dynamic
16348 elaboration checking is used (@code{-gnatE} switch used for compilation).
16349 This is because in the default static elaboration mode, all necessary
16350 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
16351 These implicit pragmas are still respected by the binder in @code{-p}
16352 mode, so a safe elaboration order is assured.
16354 Note that @code{-p} is not intended for production use; it is more for
16355 debugging/experimental use.
16358 @node Output Control,Dynamic Allocation Control,Elaboration Control,Switches for gnatbind
16359 @anchor{gnat_ugn/building_executable_programs_with_gnat output-control}@anchor{128}@anchor{gnat_ugn/building_executable_programs_with_gnat id38}@anchor{129}
16360 @subsubsection Output Control
16363 The following switches allow additional control over the output
16364 generated by the binder.
16368 @geindex -c (gnatbind)
16376 Check only. Do not generate the binder output file. In this mode the
16377 binder performs all error checks but does not generate an output file.
16379 @geindex -e (gnatbind)
16383 Output complete list of elaboration-order dependencies, showing the
16384 reason for each dependency. This output can be rather extensive but may
16385 be useful in diagnosing problems with elaboration order. The output is
16386 written to @code{stdout}.
16388 @geindex -h (gnatbind)
16392 Output usage information. The output is written to @code{stdout}.
16394 @geindex -K (gnatbind)
16398 Output linker options to @code{stdout}. Includes library search paths,
16399 contents of pragmas Ident and Linker_Options, and libraries added
16400 by @code{gnatbind}.
16402 @geindex -l (gnatbind)
16406 Output chosen elaboration order. The output is written to @code{stdout}.
16408 @geindex -O (gnatbind)
16412 Output full names of all the object files that must be linked to provide
16413 the Ada component of the program. The output is written to @code{stdout}.
16414 This list includes the files explicitly supplied and referenced by the user
16415 as well as implicitly referenced run-time unit files. The latter are
16416 omitted if the corresponding units reside in shared libraries. The
16417 directory names for the run-time units depend on the system configuration.
16419 @geindex -o (gnatbind)
16421 @item @code{-o @emph{file}}
16423 Set name of output file to @code{file} instead of the normal
16424 @code{b~`mainprog}.adb` default. Note that @code{file} denote the Ada
16425 binder generated body filename.
16426 Note that if this option is used, then linking must be done manually.
16427 It is not possible to use gnatlink in this case, since it cannot locate
16430 @geindex -r (gnatbind)
16434 Generate list of @code{pragma Restrictions} that could be applied to
16435 the current unit. This is useful for code audit purposes, and also may
16436 be used to improve code generation in some cases.
16439 @node Dynamic Allocation Control,Binding with Non-Ada Main Programs,Output Control,Switches for gnatbind
16440 @anchor{gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control}@anchor{121}@anchor{gnat_ugn/building_executable_programs_with_gnat id39}@anchor{12a}
16441 @subsubsection Dynamic Allocation Control
16444 The heap control switches -- @code{-H32} and @code{-H64} --
16445 determine whether dynamic allocation uses 32-bit or 64-bit memory.
16446 They only affect compiler-generated allocations via @code{__gnat_malloc};
16447 explicit calls to @code{malloc} and related functions from the C
16448 run-time library are unaffected.
16455 Allocate memory on 32-bit heap
16459 Allocate memory on 64-bit heap. This is the default
16460 unless explicitly overridden by a @code{'Size} clause on the access type.
16463 These switches are only effective on VMS platforms.
16465 @node Binding with Non-Ada Main Programs,Binding Programs with No Main Subprogram,Dynamic Allocation Control,Switches for gnatbind
16466 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-non-ada-main-programs}@anchor{b4}@anchor{gnat_ugn/building_executable_programs_with_gnat id40}@anchor{12b}
16467 @subsubsection Binding with Non-Ada Main Programs
16470 The description so far has assumed that the main
16471 program is in Ada, and that the task of the binder is to generate a
16472 corresponding function @code{main} that invokes this Ada main
16473 program. GNAT also supports the building of executable programs where
16474 the main program is not in Ada, but some of the called routines are
16475 written in Ada and compiled using GNAT (@ref{44,,Mixed Language Programming}).
16476 The following switch is used in this situation:
16480 @geindex -n (gnatbind)
16488 No main program. The main program is not in Ada.
16491 In this case, most of the functions of the binder are still required,
16492 but instead of generating a main program, the binder generates a file
16493 containing the following callable routines:
16502 @item @code{adainit}
16504 You must call this routine to initialize the Ada part of the program by
16505 calling the necessary elaboration routines. A call to @code{adainit} is
16506 required before the first call to an Ada subprogram.
16508 Note that it is assumed that the basic execution environment must be setup
16509 to be appropriate for Ada execution at the point where the first Ada
16510 subprogram is called. In particular, if the Ada code will do any
16511 floating-point operations, then the FPU must be setup in an appropriate
16512 manner. For the case of the x86, for example, full precision mode is
16513 required. The procedure GNAT.Float_Control.Reset may be used to ensure
16514 that the FPU is in the right state.
16522 @item @code{adafinal}
16524 You must call this routine to perform any library-level finalization
16525 required by the Ada subprograms. A call to @code{adafinal} is required
16526 after the last call to an Ada subprogram, and before the program
16531 @geindex -n (gnatbind)
16534 @geindex multiple input files
16536 If the @code{-n} switch
16537 is given, more than one ALI file may appear on
16538 the command line for @code{gnatbind}. The normal @code{closure}
16539 calculation is performed for each of the specified units. Calculating
16540 the closure means finding out the set of units involved by tracing
16541 @emph{with} references. The reason it is necessary to be able to
16542 specify more than one ALI file is that a given program may invoke two or
16543 more quite separate groups of Ada units.
16545 The binder takes the name of its output file from the last specified ALI
16546 file, unless overridden by the use of the @code{-o file}.
16548 @geindex -o (gnatbind)
16550 The output is an Ada unit in source form that can be compiled with GNAT.
16551 This compilation occurs automatically as part of the @code{gnatlink}
16554 Currently the GNAT run-time requires a FPU using 80 bits mode
16555 precision. Under targets where this is not the default it is required to
16556 call GNAT.Float_Control.Reset before using floating point numbers (this
16557 include float computation, float input and output) in the Ada code. A
16558 side effect is that this could be the wrong mode for the foreign code
16559 where floating point computation could be broken after this call.
16561 @node Binding Programs with No Main Subprogram,,Binding with Non-Ada Main Programs,Switches for gnatbind
16562 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-programs-with-no-main-subprogram}@anchor{12c}@anchor{gnat_ugn/building_executable_programs_with_gnat id41}@anchor{12d}
16563 @subsubsection Binding Programs with No Main Subprogram
16566 It is possible to have an Ada program which does not have a main
16567 subprogram. This program will call the elaboration routines of all the
16568 packages, then the finalization routines.
16570 The following switch is used to bind programs organized in this manner:
16574 @geindex -z (gnatbind)
16582 Normally the binder checks that the unit name given on the command line
16583 corresponds to a suitable main subprogram. When this switch is used,
16584 a list of ALI files can be given, and the execution of the program
16585 consists of elaboration of these units in an appropriate order. Note
16586 that the default wide character encoding method for standard Text_IO
16587 files is always set to Brackets if this switch is set (you can use
16589 @code{-Wx} to override this default).
16592 @node Command-Line Access,Search Paths for gnatbind,Switches for gnatbind,Binding with gnatbind
16593 @anchor{gnat_ugn/building_executable_programs_with_gnat id42}@anchor{12e}@anchor{gnat_ugn/building_executable_programs_with_gnat command-line-access}@anchor{12f}
16594 @subsection Command-Line Access
16597 The package @code{Ada.Command_Line} provides access to the command-line
16598 arguments and program name. In order for this interface to operate
16599 correctly, the two variables
16610 are declared in one of the GNAT library routines. These variables must
16611 be set from the actual @code{argc} and @code{argv} values passed to the
16612 main program. With no @emph{n} present, @code{gnatbind}
16613 generates the C main program to automatically set these variables.
16614 If the @emph{n} switch is used, there is no automatic way to
16615 set these variables. If they are not set, the procedures in
16616 @code{Ada.Command_Line} will not be available, and any attempt to use
16617 them will raise @code{Constraint_Error}. If command line access is
16618 required, your main program must set @code{gnat_argc} and
16619 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
16622 @node Search Paths for gnatbind,Examples of gnatbind Usage,Command-Line Access,Binding with gnatbind
16623 @anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-for-gnatbind}@anchor{8c}@anchor{gnat_ugn/building_executable_programs_with_gnat id43}@anchor{130}
16624 @subsection Search Paths for @code{gnatbind}
16627 The binder takes the name of an ALI file as its argument and needs to
16628 locate source files as well as other ALI files to verify object consistency.
16630 For source files, it follows exactly the same search rules as @code{gcc}
16631 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). For ALI files the
16632 directories searched are:
16638 The directory containing the ALI file named in the command line, unless
16639 the switch @code{-I-} is specified.
16642 All directories specified by @code{-I}
16643 switches on the @code{gnatbind}
16644 command line, in the order given.
16646 @geindex ADA_PRJ_OBJECTS_FILE
16649 Each of the directories listed in the text file whose name is given
16651 @geindex ADA_PRJ_OBJECTS_FILE
16652 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16653 @code{ADA_PRJ_OBJECTS_FILE} environment variable.
16655 @geindex ADA_PRJ_OBJECTS_FILE
16656 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16657 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat
16658 driver when project files are used. It should not normally be set
16661 @geindex ADA_OBJECTS_PATH
16664 Each of the directories listed in the value of the
16665 @geindex ADA_OBJECTS_PATH
16666 @geindex environment variable; ADA_OBJECTS_PATH
16667 @code{ADA_OBJECTS_PATH} environment variable.
16668 Construct this value
16671 @geindex environment variable; PATH
16672 @code{PATH} environment variable: a list of directory
16673 names separated by colons (semicolons when working with the NT version
16677 The content of the @code{ada_object_path} file which is part of the GNAT
16678 installation tree and is used to store standard libraries such as the
16679 GNAT Run-Time Library (RTL) unless the switch @code{-nostdlib} is
16680 specified. See @ref{87,,Installing a library}
16683 @geindex -I (gnatbind)
16685 @geindex -aI (gnatbind)
16687 @geindex -aO (gnatbind)
16689 In the binder the switch @code{-I}
16690 is used to specify both source and
16691 library file paths. Use @code{-aI}
16692 instead if you want to specify
16693 source paths only, and @code{-aO}
16694 if you want to specify library paths
16695 only. This means that for the binder
16696 @code{-I@emph{dir}} is equivalent to
16697 @code{-aI@emph{dir}}
16698 @code{-aO`@emph{dir}}.
16699 The binder generates the bind file (a C language source file) in the
16700 current working directory.
16706 @geindex Interfaces
16710 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
16711 children make up the GNAT Run-Time Library, together with the package
16712 GNAT and its children, which contain a set of useful additional
16713 library functions provided by GNAT. The sources for these units are
16714 needed by the compiler and are kept together in one directory. The ALI
16715 files and object files generated by compiling the RTL are needed by the
16716 binder and the linker and are kept together in one directory, typically
16717 different from the directory containing the sources. In a normal
16718 installation, you need not specify these directory names when compiling
16719 or binding. Either the environment variables or the built-in defaults
16720 cause these files to be found.
16722 Besides simplifying access to the RTL, a major use of search paths is
16723 in compiling sources from multiple directories. This can make
16724 development environments much more flexible.
16726 @node Examples of gnatbind Usage,,Search Paths for gnatbind,Binding with gnatbind
16727 @anchor{gnat_ugn/building_executable_programs_with_gnat id44}@anchor{131}@anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatbind-usage}@anchor{132}
16728 @subsection Examples of @code{gnatbind} Usage
16731 Here are some examples of @code{gnatbind} invovations:
16739 The main program @code{Hello} (source program in @code{hello.adb}) is
16740 bound using the standard switch settings. The generated main program is
16741 @code{b~hello.adb}. This is the normal, default use of the binder.
16744 gnatbind hello -o mainprog.adb
16747 The main program @code{Hello} (source program in @code{hello.adb}) is
16748 bound using the standard switch settings. The generated main program is
16749 @code{mainprog.adb} with the associated spec in
16750 @code{mainprog.ads}. Note that you must specify the body here not the
16751 spec. Note that if this option is used, then linking must be done manually,
16752 since gnatlink will not be able to find the generated file.
16755 @node Linking with gnatlink,Using the GNU make Utility,Binding with gnatbind,Building Executable Programs with GNAT
16756 @anchor{gnat_ugn/building_executable_programs_with_gnat id45}@anchor{133}@anchor{gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink}@anchor{1e}
16757 @section Linking with @code{gnatlink}
16762 This chapter discusses @code{gnatlink}, a tool that links
16763 an Ada program and builds an executable file. This utility
16764 invokes the system linker (via the @code{gcc} command)
16765 with a correct list of object files and library references.
16766 @code{gnatlink} automatically determines the list of files and
16767 references for the Ada part of a program. It uses the binder file
16768 generated by the @code{gnatbind} to determine this list.
16771 * Running gnatlink::
16772 * Switches for gnatlink::
16776 @node Running gnatlink,Switches for gnatlink,,Linking with gnatlink
16777 @anchor{gnat_ugn/building_executable_programs_with_gnat id46}@anchor{134}@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatlink}@anchor{135}
16778 @subsection Running @code{gnatlink}
16781 The form of the @code{gnatlink} command is
16784 $ gnatlink [ switches ] mainprog [.ali]
16785 [ non-Ada objects ] [ linker options ]
16788 The arguments of @code{gnatlink} (switches, main @code{ALI} file,
16790 or linker options) may be in any order, provided that no non-Ada object may
16791 be mistaken for a main @code{ALI} file.
16792 Any file name @code{F} without the @code{.ali}
16793 extension will be taken as the main @code{ALI} file if a file exists
16794 whose name is the concatenation of @code{F} and @code{.ali}.
16796 @code{mainprog.ali} references the ALI file of the main program.
16797 The @code{.ali} extension of this file can be omitted. From this
16798 reference, @code{gnatlink} locates the corresponding binder file
16799 @code{b~mainprog.adb} and, using the information in this file along
16800 with the list of non-Ada objects and linker options, constructs a
16801 linker command file to create the executable.
16803 The arguments other than the @code{gnatlink} switches and the main
16804 @code{ALI} file are passed to the linker uninterpreted.
16805 They typically include the names of
16806 object files for units written in other languages than Ada and any library
16807 references required to resolve references in any of these foreign language
16808 units, or in @code{Import} pragmas in any Ada units.
16810 @code{linker options} is an optional list of linker specific
16812 The default linker called by gnatlink is @code{gcc} which in
16813 turn calls the appropriate system linker.
16815 One useful option for the linker is @code{-s}: it reduces the size of the
16816 executable by removing all symbol table and relocation information from the
16819 Standard options for the linker such as @code{-lmy_lib} or
16820 @code{-Ldir} can be added as is.
16821 For options that are not recognized by
16822 @code{gcc} as linker options, use the @code{gcc} switches
16823 @code{-Xlinker} or @code{-Wl,}.
16825 Refer to the GCC documentation for
16828 Here is an example showing how to generate a linker map:
16831 $ gnatlink my_prog -Wl,-Map,MAPFILE
16834 Using @code{linker options} it is possible to set the program stack and
16836 See @ref{136,,Setting Stack Size from gnatlink} and
16837 @ref{137,,Setting Heap Size from gnatlink}.
16839 @code{gnatlink} determines the list of objects required by the Ada
16840 program and prepends them to the list of objects passed to the linker.
16841 @code{gnatlink} also gathers any arguments set by the use of
16842 @code{pragma Linker_Options} and adds them to the list of arguments
16843 presented to the linker.
16845 @node Switches for gnatlink,,Running gnatlink,Linking with gnatlink
16846 @anchor{gnat_ugn/building_executable_programs_with_gnat id47}@anchor{138}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink}@anchor{139}
16847 @subsection Switches for @code{gnatlink}
16850 The following switches are available with the @code{gnatlink} utility:
16852 @geindex --version (gnatlink)
16857 @item @code{--version}
16859 Display Copyright and version, then exit disregarding all other options.
16862 @geindex --help (gnatlink)
16867 @item @code{--help}
16869 If @code{--version} was not used, display usage, then exit disregarding
16873 @geindex Command line length
16875 @geindex -f (gnatlink)
16882 On some targets, the command line length is limited, and @code{gnatlink}
16883 will generate a separate file for the linker if the list of object files
16885 The @code{-f} switch forces this file
16886 to be generated even if
16887 the limit is not exceeded. This is useful in some cases to deal with
16888 special situations where the command line length is exceeded.
16891 @geindex Debugging information
16894 @geindex -g (gnatlink)
16901 The option to include debugging information causes the Ada bind file (in
16902 other words, @code{b~mainprog.adb}) to be compiled with @code{-g}.
16903 In addition, the binder does not delete the @code{b~mainprog.adb},
16904 @code{b~mainprog.o} and @code{b~mainprog.ali} files.
16905 Without @code{-g}, the binder removes these files by default.
16908 @geindex -n (gnatlink)
16915 Do not compile the file generated by the binder. This may be used when
16916 a link is rerun with different options, but there is no need to recompile
16920 @geindex -v (gnatlink)
16927 Verbose mode. Causes additional information to be output, including a full
16928 list of the included object files.
16929 This switch option is most useful when you want
16930 to see what set of object files are being used in the link step.
16933 @geindex -v -v (gnatlink)
16940 Very verbose mode. Requests that the compiler operate in verbose mode when
16941 it compiles the binder file, and that the system linker run in verbose mode.
16944 @geindex -o (gnatlink)
16949 @item @code{-o @emph{exec-name}}
16951 @code{exec-name} specifies an alternate name for the generated
16952 executable program. If this switch is omitted, the executable has the same
16953 name as the main unit. For example, @code{gnatlink try.ali} creates
16954 an executable called @code{try}.
16957 @geindex -B (gnatlink)
16962 @item @code{-B@emph{dir}}
16964 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
16965 from @code{dir} instead of the default location. Only use this switch
16966 when multiple versions of the GNAT compiler are available.
16967 See the @code{Directory Options} section in @cite{The_GNU_Compiler_Collection}
16968 for further details. You would normally use the @code{-b} or
16969 @code{-V} switch instead.
16972 @geindex -M (gnatlink)
16979 When linking an executable, create a map file. The name of the map file
16980 has the same name as the executable with extension ".map".
16983 @geindex -M= (gnatlink)
16988 @item @code{-M=@emph{mapfile}}
16990 When linking an executable, create a map file. The name of the map file is
16994 @geindex --GCC=compiler_name (gnatlink)
16999 @item @code{--GCC=@emph{compiler_name}}
17001 Program used for compiling the binder file. The default is
17002 @code{gcc}. You need to use quotes around @code{compiler_name} if
17003 @code{compiler_name} contains spaces or other separator characters.
17004 As an example @code{--GCC="foo -x -y"} will instruct @code{gnatlink} to
17005 use @code{foo -x -y} as your compiler. Note that switch @code{-c} is always
17006 inserted after your command name. Thus in the above example the compiler
17007 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
17008 A limitation of this syntax is that the name and path name of the executable
17009 itself must not include any embedded spaces. If the compiler executable is
17010 different from the default one (gcc or <prefix>-gcc), then the back-end
17011 switches in the ALI file are not used to compile the binder generated source.
17012 For example, this is the case with @code{--GCC="foo -x -y"}. But the back end
17013 switches will be used for @code{--GCC="gcc -gnatv"}. If several
17014 @code{--GCC=compiler_name} are used, only the last @code{compiler_name}
17015 is taken into account. However, all the additional switches are also taken
17016 into account. Thus,
17017 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
17018 @code{--GCC="bar -x -y -z -t"}.
17021 @geindex --LINK= (gnatlink)
17026 @item @code{--LINK=@emph{name}}
17028 @code{name} is the name of the linker to be invoked. This is especially
17029 useful in mixed language programs since languages such as C++ require
17030 their own linker to be used. When this switch is omitted, the default
17031 name for the linker is @code{gcc}. When this switch is used, the
17032 specified linker is called instead of @code{gcc} with exactly the same
17033 parameters that would have been passed to @code{gcc} so if the desired
17034 linker requires different parameters it is necessary to use a wrapper
17035 script that massages the parameters before invoking the real linker. It
17036 may be useful to control the exact invocation by using the verbose
17040 @node Using the GNU make Utility,,Linking with gnatlink,Building Executable Programs with GNAT
17041 @anchor{gnat_ugn/building_executable_programs_with_gnat using-the-gnu-make-utility}@anchor{1f}@anchor{gnat_ugn/building_executable_programs_with_gnat id48}@anchor{13a}
17042 @section Using the GNU @code{make} Utility
17045 @geindex make (GNU)
17048 This chapter offers some examples of makefiles that solve specific
17049 problems. It does not explain how to write a makefile, nor does it try to replace the
17050 @code{gnatmake} utility (@ref{1b,,Building with gnatmake}).
17052 All the examples in this section are specific to the GNU version of
17053 make. Although @code{make} is a standard utility, and the basic language
17054 is the same, these examples use some advanced features found only in
17058 * Using gnatmake in a Makefile::
17059 * Automatically Creating a List of Directories::
17060 * Generating the Command Line Switches::
17061 * Overcoming Command Line Length Limits::
17065 @node Using gnatmake in a Makefile,Automatically Creating a List of Directories,,Using the GNU make Utility
17066 @anchor{gnat_ugn/building_executable_programs_with_gnat using-gnatmake-in-a-makefile}@anchor{13b}@anchor{gnat_ugn/building_executable_programs_with_gnat id49}@anchor{13c}
17067 @subsection Using gnatmake in a Makefile
17070 @c index makefile (GNU make)
17072 Complex project organizations can be handled in a very powerful way by
17073 using GNU make combined with gnatmake. For instance, here is a Makefile
17074 which allows you to build each subsystem of a big project into a separate
17075 shared library. Such a makefile allows you to significantly reduce the link
17076 time of very big applications while maintaining full coherence at
17077 each step of the build process.
17079 The list of dependencies are handled automatically by
17080 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
17081 the appropriate directories.
17083 Note that you should also read the example on how to automatically
17084 create the list of directories
17085 (@ref{13d,,Automatically Creating a List of Directories})
17086 which might help you in case your project has a lot of subdirectories.
17089 ## This Makefile is intended to be used with the following directory
17091 ## - The sources are split into a series of csc (computer software components)
17092 ## Each of these csc is put in its own directory.
17093 ## Their name are referenced by the directory names.
17094 ## They will be compiled into shared library (although this would also work
17095 ## with static libraries
17096 ## - The main program (and possibly other packages that do not belong to any
17097 ## csc is put in the top level directory (where the Makefile is).
17098 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
17099 ## \\_ second_csc (sources) __ lib (will contain the library)
17101 ## Although this Makefile is build for shared library, it is easy to modify
17102 ## to build partial link objects instead (modify the lines with -shared and
17105 ## With this makefile, you can change any file in the system or add any new
17106 ## file, and everything will be recompiled correctly (only the relevant shared
17107 ## objects will be recompiled, and the main program will be re-linked).
17109 # The list of computer software component for your project. This might be
17110 # generated automatically.
17113 # Name of the main program (no extension)
17116 # If we need to build objects with -fPIC, uncomment the following line
17119 # The following variable should give the directory containing libgnat.so
17120 # You can get this directory through 'gnatls -v'. This is usually the last
17121 # directory in the Object_Path.
17124 # The directories for the libraries
17125 # (This macro expands the list of CSC to the list of shared libraries, you
17126 # could simply use the expanded form:
17127 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
17128 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
17130 $@{MAIN@}: objects $@{LIB_DIR@}
17131 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17132 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17135 # recompile the sources
17136 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17138 # Note: In a future version of GNAT, the following commands will be simplified
17139 # by a new tool, gnatmlib
17141 mkdir -p $@{dir $@@ @}
17142 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17143 cd $@{dir $@@ @} && cp -f ../*.ali .
17145 # The dependencies for the modules
17146 # Note that we have to force the expansion of *.o, since in some cases
17147 # make won't be able to do it itself.
17148 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17149 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17150 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17152 # Make sure all of the shared libraries are in the path before starting the
17155 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17158 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17159 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17160 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17161 $@{RM@} *.o *.ali $@{MAIN@}
17164 @node Automatically Creating a List of Directories,Generating the Command Line Switches,Using gnatmake in a Makefile,Using the GNU make Utility
17165 @anchor{gnat_ugn/building_executable_programs_with_gnat id50}@anchor{13e}@anchor{gnat_ugn/building_executable_programs_with_gnat automatically-creating-a-list-of-directories}@anchor{13d}
17166 @subsection Automatically Creating a List of Directories
17169 In most makefiles, you will have to specify a list of directories, and
17170 store it in a variable. For small projects, it is often easier to
17171 specify each of them by hand, since you then have full control over what
17172 is the proper order for these directories, which ones should be
17175 However, in larger projects, which might involve hundreds of
17176 subdirectories, it might be more convenient to generate this list
17179 The example below presents two methods. The first one, although less
17180 general, gives you more control over the list. It involves wildcard
17181 characters, that are automatically expanded by @code{make}. Its
17182 shortcoming is that you need to explicitly specify some of the
17183 organization of your project, such as for instance the directory tree
17184 depth, whether some directories are found in a separate tree, etc.
17186 The second method is the most general one. It requires an external
17187 program, called @code{find}, which is standard on all Unix systems. All
17188 the directories found under a given root directory will be added to the
17192 # The examples below are based on the following directory hierarchy:
17193 # All the directories can contain any number of files
17194 # ROOT_DIRECTORY -> a -> aa -> aaa
17197 # -> b -> ba -> baa
17200 # This Makefile creates a variable called DIRS, that can be reused any time
17201 # you need this list (see the other examples in this section)
17203 # The root of your project's directory hierarchy
17207 # First method: specify explicitly the list of directories
17208 # This allows you to specify any subset of all the directories you need.
17211 DIRS := a/aa/ a/ab/ b/ba/
17214 # Second method: use wildcards
17215 # Note that the argument(s) to wildcard below should end with a '/'.
17216 # Since wildcards also return file names, we have to filter them out
17217 # to avoid duplicate directory names.
17218 # We thus use make's `@w{`}dir`@w{`} and `@w{`}sort`@w{`} functions.
17219 # It sets DIRs to the following value (note that the directories aaa and baa
17220 # are not given, unless you change the arguments to wildcard).
17221 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17224 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17225 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17228 # Third method: use an external program
17229 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17230 # This is the most complete command: it sets DIRs to the following value:
17231 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17234 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17237 @node Generating the Command Line Switches,Overcoming Command Line Length Limits,Automatically Creating a List of Directories,Using the GNU make Utility
17238 @anchor{gnat_ugn/building_executable_programs_with_gnat id51}@anchor{13f}@anchor{gnat_ugn/building_executable_programs_with_gnat generating-the-command-line-switches}@anchor{140}
17239 @subsection Generating the Command Line Switches
17242 Once you have created the list of directories as explained in the
17243 previous section (@ref{13d,,Automatically Creating a List of Directories}),
17244 you can easily generate the command line arguments to pass to gnatmake.
17246 For the sake of completeness, this example assumes that the source path
17247 is not the same as the object path, and that you have two separate lists
17251 # see "Automatically creating a list of directories" to create
17256 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17257 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17260 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17263 @node Overcoming Command Line Length Limits,,Generating the Command Line Switches,Using the GNU make Utility
17264 @anchor{gnat_ugn/building_executable_programs_with_gnat overcoming-command-line-length-limits}@anchor{141}@anchor{gnat_ugn/building_executable_programs_with_gnat id52}@anchor{142}
17265 @subsection Overcoming Command Line Length Limits
17268 One problem that might be encountered on big projects is that many
17269 operating systems limit the length of the command line. It is thus hard to give
17270 gnatmake the list of source and object directories.
17272 This example shows how you can set up environment variables, which will
17273 make @code{gnatmake} behave exactly as if the directories had been
17274 specified on the command line, but have a much higher length limit (or
17275 even none on most systems).
17277 It assumes that you have created a list of directories in your Makefile,
17278 using one of the methods presented in
17279 @ref{13d,,Automatically Creating a List of Directories}.
17280 For the sake of completeness, we assume that the object
17281 path (where the ALI files are found) is different from the sources patch.
17283 Note a small trick in the Makefile below: for efficiency reasons, we
17284 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17285 expanded immediately by @code{make}. This way we overcome the standard
17286 make behavior which is to expand the variables only when they are
17289 On Windows, if you are using the standard Windows command shell, you must
17290 replace colons with semicolons in the assignments to these variables.
17293 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
17294 # This is the same thing as putting the -I arguments on the command line.
17295 # (the equivalent of using -aI on the command line would be to define
17296 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
17297 # You can of course have different values for these variables.
17299 # Note also that we need to keep the previous values of these variables, since
17300 # they might have been set before running 'make' to specify where the GNAT
17301 # library is installed.
17303 # see "Automatically creating a list of directories" to create these
17309 space:=$@{empty@} $@{empty@}
17310 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17311 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17312 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17313 ADA_OBJECTS_PATH += $@{OBJECT_LIST@}
17314 export ADA_INCLUDE_PATH
17315 export ADA_OBJECTS_PATH
17321 @node GNAT Utility Programs,GNAT and Program Execution,Building Executable Programs with GNAT,Top
17322 @anchor{gnat_ugn/gnat_utility_programs doc}@anchor{143}@anchor{gnat_ugn/gnat_utility_programs gnat-utility-programs}@anchor{b}@anchor{gnat_ugn/gnat_utility_programs id1}@anchor{144}
17323 @chapter GNAT Utility Programs
17326 This chapter describes a number of utility programs:
17333 @ref{20,,The File Cleanup Utility gnatclean}
17336 @ref{21,,The GNAT Library Browser gnatls}
17339 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
17342 @ref{23,,The Ada to HTML Converter gnathtml}
17345 Other GNAT utilities are described elsewhere in this manual:
17351 @ref{59,,Handling Arbitrary File Naming Conventions with gnatname}
17354 @ref{63,,File Name Krunching with gnatkr}
17357 @ref{36,,Renaming Files with gnatchop}
17360 @ref{17,,Preprocessing with gnatprep}
17364 * The File Cleanup Utility gnatclean::
17365 * The GNAT Library Browser gnatls::
17366 * The Cross-Referencing Tools gnatxref and gnatfind::
17367 * The Ada to HTML Converter gnathtml::
17371 @node The File Cleanup Utility gnatclean,The GNAT Library Browser gnatls,,GNAT Utility Programs
17372 @anchor{gnat_ugn/gnat_utility_programs id2}@anchor{145}@anchor{gnat_ugn/gnat_utility_programs the-file-cleanup-utility-gnatclean}@anchor{20}
17373 @section The File Cleanup Utility @code{gnatclean}
17376 @geindex File cleanup tool
17380 @code{gnatclean} is a tool that allows the deletion of files produced by the
17381 compiler, binder and linker, including ALI files, object files, tree files,
17382 expanded source files, library files, interface copy source files, binder
17383 generated files and executable files.
17386 * Running gnatclean::
17387 * Switches for gnatclean::
17391 @node Running gnatclean,Switches for gnatclean,,The File Cleanup Utility gnatclean
17392 @anchor{gnat_ugn/gnat_utility_programs running-gnatclean}@anchor{146}@anchor{gnat_ugn/gnat_utility_programs id3}@anchor{147}
17393 @subsection Running @code{gnatclean}
17396 The @code{gnatclean} command has the form:
17401 $ gnatclean switches names
17405 where @code{names} is a list of source file names. Suffixes @code{.ads} and
17406 @code{adb} may be omitted. If a project file is specified using switch
17407 @code{-P}, then @code{names} may be completely omitted.
17409 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
17410 if switch @code{-c} is not specified, by the binder and
17411 the linker. In informative-only mode, specified by switch
17412 @code{-n}, the list of files that would have been deleted in
17413 normal mode is listed, but no file is actually deleted.
17415 @node Switches for gnatclean,,Running gnatclean,The File Cleanup Utility gnatclean
17416 @anchor{gnat_ugn/gnat_utility_programs id4}@anchor{148}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatclean}@anchor{149}
17417 @subsection Switches for @code{gnatclean}
17420 @code{gnatclean} recognizes the following switches:
17422 @geindex --version (gnatclean)
17427 @item @code{--version}
17429 Display copyright and version, then exit disregarding all other options.
17432 @geindex --help (gnatclean)
17437 @item @code{--help}
17439 If @code{--version} was not used, display usage, then exit disregarding
17442 @item @code{--subdirs=@emph{subdir}}
17444 Actual object directory of each project file is the subdirectory subdir of the
17445 object directory specified or defaulted in the project file.
17447 @item @code{--unchecked-shared-lib-imports}
17449 By default, shared library projects are not allowed to import static library
17450 projects. When this switch is used on the command line, this restriction is
17454 @geindex -c (gnatclean)
17461 Only attempt to delete the files produced by the compiler, not those produced
17462 by the binder or the linker. The files that are not to be deleted are library
17463 files, interface copy files, binder generated files and executable files.
17466 @geindex -D (gnatclean)
17471 @item @code{-D @emph{dir}}
17473 Indicate that ALI and object files should normally be found in directory @code{dir}.
17476 @geindex -F (gnatclean)
17483 When using project files, if some errors or warnings are detected during
17484 parsing and verbose mode is not in effect (no use of switch
17485 -v), then error lines start with the full path name of the project
17486 file, rather than its simple file name.
17489 @geindex -h (gnatclean)
17496 Output a message explaining the usage of @code{gnatclean}.
17499 @geindex -n (gnatclean)
17506 Informative-only mode. Do not delete any files. Output the list of the files
17507 that would have been deleted if this switch was not specified.
17510 @geindex -P (gnatclean)
17515 @item @code{-P@emph{project}}
17517 Use project file @code{project}. Only one such switch can be used.
17518 When cleaning a project file, the files produced by the compilation of the
17519 immediate sources or inherited sources of the project files are to be
17520 deleted. This is not depending on the presence or not of executable names
17521 on the command line.
17524 @geindex -q (gnatclean)
17531 Quiet output. If there are no errors, do not output anything, except in
17532 verbose mode (switch -v) or in informative-only mode
17536 @geindex -r (gnatclean)
17543 When a project file is specified (using switch -P),
17544 clean all imported and extended project files, recursively. If this switch
17545 is not specified, only the files related to the main project file are to be
17546 deleted. This switch has no effect if no project file is specified.
17549 @geindex -v (gnatclean)
17559 @geindex -vP (gnatclean)
17564 @item @code{-vP@emph{x}}
17566 Indicates the verbosity of the parsing of GNAT project files.
17567 @ref{de,,Switches Related to Project Files}.
17570 @geindex -X (gnatclean)
17575 @item @code{-X@emph{name}=@emph{value}}
17577 Indicates that external variable @code{name} has the value @code{value}.
17578 The Project Manager will use this value for occurrences of
17579 @code{external(name)} when parsing the project file.
17580 See @ref{de,,Switches Related to Project Files}.
17583 @geindex -aO (gnatclean)
17588 @item @code{-aO@emph{dir}}
17590 When searching for ALI and object files, look in directory @code{dir}.
17593 @geindex -I (gnatclean)
17598 @item @code{-I@emph{dir}}
17600 Equivalent to @code{-aO@emph{dir}}.
17603 @geindex -I- (gnatclean)
17605 @geindex Source files
17606 @geindex suppressing search
17613 Do not look for ALI or object files in the directory
17614 where @code{gnatclean} was invoked.
17617 @node The GNAT Library Browser gnatls,The Cross-Referencing Tools gnatxref and gnatfind,The File Cleanup Utility gnatclean,GNAT Utility Programs
17618 @anchor{gnat_ugn/gnat_utility_programs the-gnat-library-browser-gnatls}@anchor{21}@anchor{gnat_ugn/gnat_utility_programs id5}@anchor{14a}
17619 @section The GNAT Library Browser @code{gnatls}
17622 @geindex Library browser
17626 @code{gnatls} is a tool that outputs information about compiled
17627 units. It gives the relationship between objects, unit names and source
17628 files. It can also be used to check the source dependencies of a unit
17629 as well as various characteristics.
17633 * Switches for gnatls::
17634 * Example of gnatls Usage::
17638 @node Running gnatls,Switches for gnatls,,The GNAT Library Browser gnatls
17639 @anchor{gnat_ugn/gnat_utility_programs id6}@anchor{14b}@anchor{gnat_ugn/gnat_utility_programs running-gnatls}@anchor{14c}
17640 @subsection Running @code{gnatls}
17643 The @code{gnatls} command has the form
17648 $ gnatls switches object_or_ali_file
17652 The main argument is the list of object or @code{ali} files
17653 (see @ref{42,,The Ada Library Information Files})
17654 for which information is requested.
17656 In normal mode, without additional option, @code{gnatls} produces a
17657 four-column listing. Each line represents information for a specific
17658 object. The first column gives the full path of the object, the second
17659 column gives the name of the principal unit in this object, the third
17660 column gives the status of the source and the fourth column gives the
17661 full path of the source representing this unit.
17662 Here is a simple example of use:
17668 ./demo1.o demo1 DIF demo1.adb
17669 ./demo2.o demo2 OK demo2.adb
17670 ./hello.o h1 OK hello.adb
17671 ./instr-child.o instr.child MOK instr-child.adb
17672 ./instr.o instr OK instr.adb
17673 ./tef.o tef DIF tef.adb
17674 ./text_io_example.o text_io_example OK text_io_example.adb
17675 ./tgef.o tgef DIF tgef.adb
17679 The first line can be interpreted as follows: the main unit which is
17681 object file @code{demo1.o} is demo1, whose main source is in
17682 @code{demo1.adb}. Furthermore, the version of the source used for the
17683 compilation of demo1 has been modified (DIF). Each source file has a status
17684 qualifier which can be:
17689 @item @emph{OK (unchanged)}
17691 The version of the source file used for the compilation of the
17692 specified unit corresponds exactly to the actual source file.
17694 @item @emph{MOK (slightly modified)}
17696 The version of the source file used for the compilation of the
17697 specified unit differs from the actual source file but not enough to
17698 require recompilation. If you use gnatmake with the option
17699 @code{-m} (minimal recompilation), a file marked
17700 MOK will not be recompiled.
17702 @item @emph{DIF (modified)}
17704 No version of the source found on the path corresponds to the source
17705 used to build this object.
17707 @item @emph{??? (file not found)}
17709 No source file was found for this unit.
17711 @item @emph{HID (hidden, unchanged version not first on PATH)}
17713 The version of the source that corresponds exactly to the source used
17714 for compilation has been found on the path but it is hidden by another
17715 version of the same source that has been modified.
17718 @node Switches for gnatls,Example of gnatls Usage,Running gnatls,The GNAT Library Browser gnatls
17719 @anchor{gnat_ugn/gnat_utility_programs id7}@anchor{14d}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatls}@anchor{14e}
17720 @subsection Switches for @code{gnatls}
17723 @code{gnatls} recognizes the following switches:
17725 @geindex --version (gnatls)
17730 @item @code{--version}
17732 Display copyright and version, then exit disregarding all other options.
17735 @geindex --help (gnatls)
17740 @item @code{--help}
17742 If @code{--version} was not used, display usage, then exit disregarding
17746 @geindex -a (gnatls)
17753 Consider all units, including those of the predefined Ada library.
17754 Especially useful with @code{-d}.
17757 @geindex -d (gnatls)
17764 List sources from which specified units depend on.
17767 @geindex -h (gnatls)
17774 Output the list of options.
17777 @geindex -o (gnatls)
17784 Only output information about object files.
17787 @geindex -s (gnatls)
17794 Only output information about source files.
17797 @geindex -u (gnatls)
17804 Only output information about compilation units.
17807 @geindex -files (gnatls)
17812 @item @code{-files=@emph{file}}
17814 Take as arguments the files listed in text file @code{file}.
17815 Text file @code{file} may contain empty lines that are ignored.
17816 Each nonempty line should contain the name of an existing file.
17817 Several such switches may be specified simultaneously.
17820 @geindex -aO (gnatls)
17822 @geindex -aI (gnatls)
17824 @geindex -I (gnatls)
17826 @geindex -I- (gnatls)
17831 @item @code{-aO@emph{dir}}, @code{-aI@emph{dir}}, @code{-I@emph{dir}}, @code{-I-}, @code{-nostdinc}
17833 Source path manipulation. Same meaning as the equivalent @code{gnatmake}
17834 flags (@ref{dc,,Switches for gnatmake}).
17837 @geindex -aP (gnatls)
17842 @item @code{-aP@emph{dir}}
17844 Add @code{dir} at the beginning of the project search dir.
17847 @geindex --RTS (gnatls)
17852 @item @code{--RTS=@emph{rts-path}}
17854 Specifies the default location of the runtime library. Same meaning as the
17855 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
17858 @geindex -v (gnatls)
17865 Verbose mode. Output the complete source, object and project paths. Do not use
17866 the default column layout but instead use long format giving as much as
17867 information possible on each requested units, including special
17868 characteristics such as:
17874 @emph{Preelaborable}: The unit is preelaborable in the Ada sense.
17877 @emph{No_Elab_Code}: No elaboration code has been produced by the compiler for this unit.
17880 @emph{Pure}: The unit is pure in the Ada sense.
17883 @emph{Elaborate_Body}: The unit contains a pragma Elaborate_Body.
17886 @emph{Remote_Types}: The unit contains a pragma Remote_Types.
17889 @emph{Shared_Passive}: The unit contains a pragma Shared_Passive.
17892 @emph{Predefined}: This unit is part of the predefined environment and cannot be modified
17896 @emph{Remote_Call_Interface}: The unit contains a pragma Remote_Call_Interface.
17900 @node Example of gnatls Usage,,Switches for gnatls,The GNAT Library Browser gnatls
17901 @anchor{gnat_ugn/gnat_utility_programs id8}@anchor{14f}@anchor{gnat_ugn/gnat_utility_programs example-of-gnatls-usage}@anchor{150}
17902 @subsection Example of @code{gnatls} Usage
17905 Example of using the verbose switch. Note how the source and
17906 object paths are affected by the -I switch.
17911 $ gnatls -v -I.. demo1.o
17913 GNATLS 5.03w (20041123-34)
17914 Copyright 1997-2004 Free Software Foundation, Inc.
17916 Source Search Path:
17917 <Current_Directory>
17919 /home/comar/local/adainclude/
17921 Object Search Path:
17922 <Current_Directory>
17924 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
17926 Project Search Path:
17927 <Current_Directory>
17928 /home/comar/local/lib/gnat/
17933 Kind => subprogram body
17934 Flags => No_Elab_Code
17935 Source => demo1.adb modified
17939 The following is an example of use of the dependency list.
17940 Note the use of the -s switch
17941 which gives a straight list of source files. This can be useful for
17942 building specialized scripts.
17947 $ gnatls -d demo2.o
17948 ./demo2.o demo2 OK demo2.adb
17954 $ gnatls -d -s -a demo1.o
17956 /home/comar/local/adainclude/ada.ads
17957 /home/comar/local/adainclude/a-finali.ads
17958 /home/comar/local/adainclude/a-filico.ads
17959 /home/comar/local/adainclude/a-stream.ads
17960 /home/comar/local/adainclude/a-tags.ads
17963 /home/comar/local/adainclude/gnat.ads
17964 /home/comar/local/adainclude/g-io.ads
17966 /home/comar/local/adainclude/system.ads
17967 /home/comar/local/adainclude/s-exctab.ads
17968 /home/comar/local/adainclude/s-finimp.ads
17969 /home/comar/local/adainclude/s-finroo.ads
17970 /home/comar/local/adainclude/s-secsta.ads
17971 /home/comar/local/adainclude/s-stalib.ads
17972 /home/comar/local/adainclude/s-stoele.ads
17973 /home/comar/local/adainclude/s-stratt.ads
17974 /home/comar/local/adainclude/s-tasoli.ads
17975 /home/comar/local/adainclude/s-unstyp.ads
17976 /home/comar/local/adainclude/unchconv.ads
17980 @node The Cross-Referencing Tools gnatxref and gnatfind,The Ada to HTML Converter gnathtml,The GNAT Library Browser gnatls,GNAT Utility Programs
17981 @anchor{gnat_ugn/gnat_utility_programs the-cross-referencing-tools-gnatxref-and-gnatfind}@anchor{22}@anchor{gnat_ugn/gnat_utility_programs id9}@anchor{151}
17982 @section The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
17989 The compiler generates cross-referencing information (unless
17990 you set the @code{-gnatx} switch), which are saved in the @code{.ali} files.
17991 This information indicates where in the source each entity is declared and
17992 referenced. Note that entities in package Standard are not included, but
17993 entities in all other predefined units are included in the output.
17995 Before using any of these two tools, you need to compile successfully your
17996 application, so that GNAT gets a chance to generate the cross-referencing
17999 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
18000 information to provide the user with the capability to easily locate the
18001 declaration and references to an entity. These tools are quite similar,
18002 the difference being that @code{gnatfind} is intended for locating
18003 definitions and/or references to a specified entity or entities, whereas
18004 @code{gnatxref} is oriented to generating a full report of all
18007 To use these tools, you must not compile your application using the
18008 @code{-gnatx} switch on the @code{gnatmake} command line
18009 (see @ref{1b,,Building with gnatmake}). Otherwise, cross-referencing
18010 information will not be generated.
18013 * gnatxref Switches::
18014 * gnatfind Switches::
18015 * Configuration Files for gnatxref and gnatfind::
18016 * Regular Expressions in gnatfind and gnatxref::
18017 * Examples of gnatxref Usage::
18018 * Examples of gnatfind Usage::
18022 @node gnatxref Switches,gnatfind Switches,,The Cross-Referencing Tools gnatxref and gnatfind
18023 @anchor{gnat_ugn/gnat_utility_programs id10}@anchor{152}@anchor{gnat_ugn/gnat_utility_programs gnatxref-switches}@anchor{153}
18024 @subsection @code{gnatxref} Switches
18027 The command invocation for @code{gnatxref} is:
18032 $ gnatxref [ switches ] sourcefile1 [ sourcefile2 ... ]
18041 @item @code{sourcefile1} [, @code{sourcefile2} ...]
18043 identify the source files for which a report is to be generated. The
18044 @code{with}ed units will be processed too. You must provide at least one file.
18046 These file names are considered to be regular expressions, so for instance
18047 specifying @code{source*.adb} is the same as giving every file in the current
18048 directory whose name starts with @code{source} and whose extension is
18051 You shouldn't specify any directory name, just base names. @code{gnatxref}
18052 and @code{gnatfind} will be able to locate these files by themselves using
18053 the source path. If you specify directories, no result is produced.
18056 The following switches are available for @code{gnatxref}:
18058 @geindex --version (gnatxref)
18063 @item @code{--version}
18065 Display copyright and version, then exit disregarding all other options.
18068 @geindex --help (gnatxref)
18073 @item @code{--help}
18075 If @code{--version} was not used, display usage, then exit disregarding
18079 @geindex -a (gnatxref)
18086 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18087 the read-only files found in the library search path. Otherwise, these files
18088 will be ignored. This option can be used to protect Gnat sources or your own
18089 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18090 much faster, and their output much smaller. Read-only here refers to access
18091 or permissions status in the file system for the current user.
18094 @geindex -aIDIR (gnatxref)
18099 @item @code{-aI@emph{DIR}}
18101 When looking for source files also look in directory DIR. The order in which
18102 source file search is undertaken is the same as for @code{gnatmake}.
18105 @geindex -aODIR (gnatxref)
18110 @item @code{aO@emph{DIR}}
18112 When -searching for library and object files, look in directory
18113 DIR. The order in which library files are searched is the same as for
18117 @geindex -nostdinc (gnatxref)
18122 @item @code{-nostdinc}
18124 Do not look for sources in the system default directory.
18127 @geindex -nostdlib (gnatxref)
18132 @item @code{-nostdlib}
18134 Do not look for library files in the system default directory.
18137 @geindex --ext (gnatxref)
18142 @item @code{--ext=@emph{extension}}
18144 Specify an alternate ali file extension. The default is @code{ali} and other
18145 extensions (e.g. @code{gli} for C/C++ sources) may be specified via this switch.
18146 Note that if this switch overrides the default, only the new extension will
18150 @geindex --RTS (gnatxref)
18155 @item @code{--RTS=@emph{rts-path}}
18157 Specifies the default location of the runtime library. Same meaning as the
18158 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18161 @geindex -d (gnatxref)
18168 If this switch is set @code{gnatxref} will output the parent type
18169 reference for each matching derived types.
18172 @geindex -f (gnatxref)
18179 If this switch is set, the output file names will be preceded by their
18180 directory (if the file was found in the search path). If this switch is
18181 not set, the directory will not be printed.
18184 @geindex -g (gnatxref)
18191 If this switch is set, information is output only for library-level
18192 entities, ignoring local entities. The use of this switch may accelerate
18193 @code{gnatfind} and @code{gnatxref}.
18196 @geindex -IDIR (gnatxref)
18201 @item @code{-I@emph{DIR}}
18203 Equivalent to @code{-aODIR -aIDIR}.
18206 @geindex -pFILE (gnatxref)
18211 @item @code{-p@emph{FILE}}
18213 Specify a configuration file to use to list the source and object directories.
18215 If a file is specified, then the content of the source directory and object
18216 directory lines are added as if they had been specified respectively
18217 by @code{-aI} and @code{-aO}.
18219 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18220 of this configuration file.
18224 Output only unused symbols. This may be really useful if you give your
18225 main compilation unit on the command line, as @code{gnatxref} will then
18226 display every unused entity and 'with'ed package.
18230 Instead of producing the default output, @code{gnatxref} will generate a
18231 @code{tags} file that can be used by vi. For examples how to use this
18232 feature, see @ref{155,,Examples of gnatxref Usage}. The tags file is output
18233 to the standard output, thus you will have to redirect it to a file.
18236 All these switches may be in any order on the command line, and may even
18237 appear after the file names. They need not be separated by spaces, thus
18238 you can say @code{gnatxref -ag} instead of @code{gnatxref -a -g}.
18240 @node gnatfind Switches,Configuration Files for gnatxref and gnatfind,gnatxref Switches,The Cross-Referencing Tools gnatxref and gnatfind
18241 @anchor{gnat_ugn/gnat_utility_programs id11}@anchor{156}@anchor{gnat_ugn/gnat_utility_programs gnatfind-switches}@anchor{157}
18242 @subsection @code{gnatfind} Switches
18245 The command invocation for @code{gnatfind} is:
18250 $ gnatfind [ switches ] pattern[:sourcefile[:line[:column]]]
18255 with the following iterpretation of the command arguments:
18260 @item @emph{pattern}
18262 An entity will be output only if it matches the regular expression found
18263 in @emph{pattern}, see @ref{158,,Regular Expressions in gnatfind and gnatxref}.
18265 Omitting the pattern is equivalent to specifying @code{*}, which
18266 will match any entity. Note that if you do not provide a pattern, you
18267 have to provide both a sourcefile and a line.
18269 Entity names are given in Latin-1, with uppercase/lowercase equivalence
18270 for matching purposes. At the current time there is no support for
18271 8-bit codes other than Latin-1, or for wide characters in identifiers.
18273 @item @emph{sourcefile}
18275 @code{gnatfind} will look for references, bodies or declarations
18276 of symbols referenced in @code{sourcefile}, at line @code{line}
18277 and column @code{column}. See @ref{159,,Examples of gnatfind Usage}
18278 for syntax examples.
18282 A decimal integer identifying the line number containing
18283 the reference to the entity (or entities) to be located.
18285 @item @emph{column}
18287 A decimal integer identifying the exact location on the
18288 line of the first character of the identifier for the
18289 entity reference. Columns are numbered from 1.
18291 @item @emph{file1 file2 ...}
18293 The search will be restricted to these source files. If none are given, then
18294 the search will be conducted for every library file in the search path.
18295 These files must appear only after the pattern or sourcefile.
18297 These file names are considered to be regular expressions, so for instance
18298 specifying @code{source*.adb} is the same as giving every file in the current
18299 directory whose name starts with @code{source} and whose extension is
18302 The location of the spec of the entity will always be displayed, even if it
18303 isn't in one of @code{file1}, @code{file2}, ... The
18304 occurrences of the entity in the separate units of the ones given on the
18305 command line will also be displayed.
18307 Note that if you specify at least one file in this part, @code{gnatfind} may
18308 sometimes not be able to find the body of the subprograms.
18311 At least one of 'sourcefile' or 'pattern' has to be present on
18314 The following switches are available:
18316 @geindex --version (gnatfind)
18321 @item @code{--version}
18323 Display copyright and version, then exit disregarding all other options.
18326 @geindex --help (gnatfind)
18331 @item @code{--help}
18333 If @code{--version} was not used, display usage, then exit disregarding
18337 @geindex -a (gnatfind)
18344 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18345 the read-only files found in the library search path. Otherwise, these files
18346 will be ignored. This option can be used to protect Gnat sources or your own
18347 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18348 much faster, and their output much smaller. Read-only here refers to access
18349 or permission status in the file system for the current user.
18352 @geindex -aIDIR (gnatfind)
18357 @item @code{-aI@emph{DIR}}
18359 When looking for source files also look in directory DIR. The order in which
18360 source file search is undertaken is the same as for @code{gnatmake}.
18363 @geindex -aODIR (gnatfind)
18368 @item @code{-aO@emph{DIR}}
18370 When searching for library and object files, look in directory
18371 DIR. The order in which library files are searched is the same as for
18375 @geindex -nostdinc (gnatfind)
18380 @item @code{-nostdinc}
18382 Do not look for sources in the system default directory.
18385 @geindex -nostdlib (gnatfind)
18390 @item @code{-nostdlib}
18392 Do not look for library files in the system default directory.
18395 @geindex --ext (gnatfind)
18400 @item @code{--ext=@emph{extension}}
18402 Specify an alternate ali file extension. The default is @code{ali} and other
18403 extensions may be specified via this switch. Note that if this switch
18404 overrides the default, only the new extension will be considered.
18407 @geindex --RTS (gnatfind)
18412 @item @code{--RTS=@emph{rts-path}}
18414 Specifies the default location of the runtime library. Same meaning as the
18415 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18418 @geindex -d (gnatfind)
18425 If this switch is set, then @code{gnatfind} will output the parent type
18426 reference for each matching derived types.
18429 @geindex -e (gnatfind)
18436 By default, @code{gnatfind} accept the simple regular expression set for
18437 @code{pattern}. If this switch is set, then the pattern will be
18438 considered as full Unix-style regular expression.
18441 @geindex -f (gnatfind)
18448 If this switch is set, the output file names will be preceded by their
18449 directory (if the file was found in the search path). If this switch is
18450 not set, the directory will not be printed.
18453 @geindex -g (gnatfind)
18460 If this switch is set, information is output only for library-level
18461 entities, ignoring local entities. The use of this switch may accelerate
18462 @code{gnatfind} and @code{gnatxref}.
18465 @geindex -IDIR (gnatfind)
18470 @item @code{-I@emph{DIR}}
18472 Equivalent to @code{-aODIR -aIDIR}.
18475 @geindex -pFILE (gnatfind)
18480 @item @code{-p@emph{FILE}}
18482 Specify a configuration file to use to list the source and object directories.
18484 If a file is specified, then the content of the source directory and object
18485 directory lines are added as if they had been specified respectively
18486 by @code{-aI} and @code{-aO}.
18488 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18489 of this configuration file.
18492 @geindex -r (gnatfind)
18499 By default, @code{gnatfind} will output only the information about the
18500 declaration, body or type completion of the entities. If this switch is
18501 set, the @code{gnatfind} will locate every reference to the entities in
18502 the files specified on the command line (or in every file in the search
18503 path if no file is given on the command line).
18506 @geindex -s (gnatfind)
18513 If this switch is set, then @code{gnatfind} will output the content
18514 of the Ada source file lines were the entity was found.
18517 @geindex -t (gnatfind)
18524 If this switch is set, then @code{gnatfind} will output the type hierarchy for
18525 the specified type. It act like -d option but recursively from parent
18526 type to parent type. When this switch is set it is not possible to
18527 specify more than one file.
18530 All these switches may be in any order on the command line, and may even
18531 appear after the file names. They need not be separated by spaces, thus
18532 you can say @code{gnatxref -ag} instead of
18533 @code{gnatxref -a -g}.
18535 As stated previously, @code{gnatfind} will search in every directory in the
18536 search path. You can force it to look only in the current directory if
18537 you specify @code{*} at the end of the command line.
18539 @node Configuration Files for gnatxref and gnatfind,Regular Expressions in gnatfind and gnatxref,gnatfind Switches,The Cross-Referencing Tools gnatxref and gnatfind
18540 @anchor{gnat_ugn/gnat_utility_programs configuration-files-for-gnatxref-and-gnatfind}@anchor{154}@anchor{gnat_ugn/gnat_utility_programs id12}@anchor{15a}
18541 @subsection Configuration Files for @code{gnatxref} and @code{gnatfind}
18544 Configuration files are used by @code{gnatxref} and @code{gnatfind} to specify
18545 the list of source and object directories to consider. They can be
18546 specified via the @code{-p} switch.
18548 The following lines can be included, in any order in the file:
18557 @item @emph{src_dir=DIR}
18559 [default: @code{"./"}].
18560 Specifies a directory where to look for source files. Multiple @code{src_dir}
18561 lines can be specified and they will be searched in the order they
18569 @item @emph{obj_dir=DIR}
18571 [default: @code{"./"}].
18572 Specifies a directory where to look for object and library files. Multiple
18573 @code{obj_dir} lines can be specified, and they will be searched in the order
18578 Any other line will be silently ignored.
18580 @node Regular Expressions in gnatfind and gnatxref,Examples of gnatxref Usage,Configuration Files for gnatxref and gnatfind,The Cross-Referencing Tools gnatxref and gnatfind
18581 @anchor{gnat_ugn/gnat_utility_programs id13}@anchor{15b}@anchor{gnat_ugn/gnat_utility_programs regular-expressions-in-gnatfind-and-gnatxref}@anchor{158}
18582 @subsection Regular Expressions in @code{gnatfind} and @code{gnatxref}
18585 As specified in the section about @code{gnatfind}, the pattern can be a
18586 regular expression. Two kinds of regular expressions
18596 @item @emph{Globbing pattern}
18598 These are the most common regular expression. They are the same as are
18599 generally used in a Unix shell command line, or in a DOS session.
18601 Here is a more formal grammar:
18605 term ::= elmt -- matches elmt
18606 term ::= elmt elmt -- concatenation (elmt then elmt)
18607 term ::= * -- any string of 0 or more characters
18608 term ::= ? -- matches any character
18609 term ::= [char @{char@}] -- matches any character listed
18610 term ::= [char - char] -- matches any character in range
18618 @item @emph{Full regular expression}
18620 The second set of regular expressions is much more powerful. This is the
18621 type of regular expressions recognized by utilities such as @code{grep}.
18623 The following is the form of a regular expression, expressed in same BNF
18624 style as is found in the Ada Reference Manual:
18627 regexp ::= term @{| term@} -- alternation (term or term ...)
18629 term ::= item @{item@} -- concatenation (item then item)
18631 item ::= elmt -- match elmt
18632 item ::= elmt * -- zero or more elmt's
18633 item ::= elmt + -- one or more elmt's
18634 item ::= elmt ? -- matches elmt or nothing
18636 elmt ::= nschar -- matches given character
18637 elmt ::= [nschar @{nschar@}] -- matches any character listed
18638 elmt ::= [^ nschar @{nschar@}] -- matches any character not listed
18639 elmt ::= [char - char] -- matches chars in given range
18640 elmt ::= \\ char -- matches given character
18641 elmt ::= . -- matches any single character
18642 elmt ::= ( regexp ) -- parens used for grouping
18644 char ::= any character, including special characters
18645 nschar ::= any character except ()[].*+?^
18648 Here are a few examples:
18655 @item @code{abcde|fghi}
18657 will match any of the two strings @code{abcde} and @code{fghi},
18661 will match any string like @code{abd}, @code{abcd}, @code{abccd},
18662 @code{abcccd}, and so on,
18664 @item @code{[a-z]+}
18666 will match any string which has only lowercase characters in it (and at
18667 least one character.
18673 @node Examples of gnatxref Usage,Examples of gnatfind Usage,Regular Expressions in gnatfind and gnatxref,The Cross-Referencing Tools gnatxref and gnatfind
18674 @anchor{gnat_ugn/gnat_utility_programs examples-of-gnatxref-usage}@anchor{155}@anchor{gnat_ugn/gnat_utility_programs id14}@anchor{15c}
18675 @subsection Examples of @code{gnatxref} Usage
18680 * Using gnatxref with vi::
18684 @node General Usage,Using gnatxref with vi,,Examples of gnatxref Usage
18685 @anchor{gnat_ugn/gnat_utility_programs general-usage}@anchor{15d}
18686 @subsubsection General Usage
18689 For the following examples, we will consider the following units:
18697 3: procedure Foo (B : in Integer);
18704 1: package body Main is
18705 2: procedure Foo (B : in Integer) is
18716 2: procedure Print (B : Integer);
18721 The first thing to do is to recompile your application (for instance, in
18722 that case just by doing a @code{gnatmake main}, so that GNAT generates
18723 the cross-referencing information.
18724 You can then issue any of the following commands:
18732 @code{gnatxref main.adb}
18733 @code{gnatxref} generates cross-reference information for main.adb
18734 and every unit 'with'ed by main.adb.
18736 The output would be:
18744 Decl: main.ads 3:20
18745 Body: main.adb 2:20
18746 Ref: main.adb 4:13 5:13 6:19
18749 Ref: main.adb 6:8 7:8
18759 Decl: main.ads 3:15
18760 Body: main.adb 2:15
18763 Body: main.adb 1:14
18766 Ref: main.adb 6:12 7:12
18770 This shows that the entity @code{Main} is declared in main.ads, line 2, column 9,
18771 its body is in main.adb, line 1, column 14 and is not referenced any where.
18773 The entity @code{Print} is declared in @code{bar.ads}, line 2, column 15 and it
18774 is referenced in @code{main.adb}, line 6 column 12 and line 7 column 12.
18777 @code{gnatxref package1.adb package2.ads}
18778 @code{gnatxref} will generates cross-reference information for
18779 @code{package1.adb}, @code{package2.ads} and any other package @code{with}ed by any
18784 @node Using gnatxref with vi,,General Usage,Examples of gnatxref Usage
18785 @anchor{gnat_ugn/gnat_utility_programs using-gnatxref-with-vi}@anchor{15e}
18786 @subsubsection Using @code{gnatxref} with @code{vi}
18789 @code{gnatxref} can generate a tags file output, which can be used
18790 directly from @code{vi}. Note that the standard version of @code{vi}
18791 will not work properly with overloaded symbols. Consider using another
18792 free implementation of @code{vi}, such as @code{vim}.
18797 $ gnatxref -v gnatfind.adb > tags
18801 The following command will generate the tags file for @code{gnatfind} itself
18802 (if the sources are in the search path!):
18807 $ gnatxref -v gnatfind.adb > tags
18811 From @code{vi}, you can then use the command @code{:tag @emph{entity}}
18812 (replacing @code{entity} by whatever you are looking for), and vi will
18813 display a new file with the corresponding declaration of entity.
18815 @node Examples of gnatfind Usage,,Examples of gnatxref Usage,The Cross-Referencing Tools gnatxref and gnatfind
18816 @anchor{gnat_ugn/gnat_utility_programs id15}@anchor{15f}@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatfind-usage}@anchor{159}
18817 @subsection Examples of @code{gnatfind} Usage
18824 @code{gnatfind -f xyz:main.adb}
18825 Find declarations for all entities xyz referenced at least once in
18826 main.adb. The references are search in every library file in the search
18829 The directories will be printed as well (as the @code{-f}
18832 The output will look like:
18837 directory/main.ads:106:14: xyz <= declaration
18838 directory/main.adb:24:10: xyz <= body
18839 directory/foo.ads:45:23: xyz <= declaration
18843 I.e., one of the entities xyz found in main.adb is declared at
18844 line 12 of main.ads (and its body is in main.adb), and another one is
18845 declared at line 45 of foo.ads
18848 @code{gnatfind -fs xyz:main.adb}
18849 This is the same command as the previous one, but @code{gnatfind} will
18850 display the content of the Ada source file lines.
18852 The output will look like:
18855 directory/main.ads:106:14: xyz <= declaration
18857 directory/main.adb:24:10: xyz <= body
18859 directory/foo.ads:45:23: xyz <= declaration
18863 This can make it easier to find exactly the location your are looking
18867 @code{gnatfind -r "*x*":main.ads:123 foo.adb}
18868 Find references to all entities containing an x that are
18869 referenced on line 123 of main.ads.
18870 The references will be searched only in main.ads and foo.adb.
18873 @code{gnatfind main.ads:123}
18874 Find declarations and bodies for all entities that are referenced on
18875 line 123 of main.ads.
18877 This is the same as @code{gnatfind "*":main.adb:123`}
18880 @code{gnatfind mydir/main.adb:123:45}
18881 Find the declaration for the entity referenced at column 45 in
18882 line 123 of file main.adb in directory mydir. Note that it
18883 is usual to omit the identifier name when the column is given,
18884 since the column position identifies a unique reference.
18886 The column has to be the beginning of the identifier, and should not
18887 point to any character in the middle of the identifier.
18890 @node The Ada to HTML Converter gnathtml,,The Cross-Referencing Tools gnatxref and gnatfind,GNAT Utility Programs
18891 @anchor{gnat_ugn/gnat_utility_programs the-ada-to-html-converter-gnathtml}@anchor{23}@anchor{gnat_ugn/gnat_utility_programs id16}@anchor{160}
18892 @section The Ada to HTML Converter @code{gnathtml}
18897 @code{gnathtml} is a Perl script that allows Ada source files to be browsed using
18898 standard Web browsers. For installation information, see @ref{161,,Installing gnathtml}.
18900 Ada reserved keywords are highlighted in a bold font and Ada comments in
18901 a blue font. Unless your program was compiled with the gcc @code{-gnatx}
18902 switch to suppress the generation of cross-referencing information, user
18903 defined variables and types will appear in a different color; you will
18904 be able to click on any identifier and go to its declaration.
18907 * Invoking gnathtml::
18908 * Installing gnathtml::
18912 @node Invoking gnathtml,Installing gnathtml,,The Ada to HTML Converter gnathtml
18913 @anchor{gnat_ugn/gnat_utility_programs invoking-gnathtml}@anchor{162}@anchor{gnat_ugn/gnat_utility_programs id17}@anchor{163}
18914 @subsection Invoking @code{gnathtml}
18917 The command line is as follows:
18922 $ perl gnathtml.pl [ switches ] ada-files
18926 You can specify as many Ada files as you want. @code{gnathtml} will generate
18927 an html file for every ada file, and a global file called @code{index.htm}.
18928 This file is an index of every identifier defined in the files.
18930 The following switches are available:
18932 @geindex -83 (gnathtml)
18939 Only the Ada 83 subset of keywords will be highlighted.
18942 @geindex -cc (gnathtml)
18947 @item @code{cc @emph{color}}
18949 This option allows you to change the color used for comments. The default
18950 value is green. The color argument can be any name accepted by html.
18953 @geindex -d (gnathtml)
18960 If the Ada files depend on some other files (for instance through
18961 @code{with} clauses, the latter files will also be converted to html.
18962 Only the files in the user project will be converted to html, not the files
18963 in the run-time library itself.
18966 @geindex -D (gnathtml)
18973 This command is the same as @code{-d} above, but @code{gnathtml} will
18974 also look for files in the run-time library, and generate html files for them.
18977 @geindex -ext (gnathtml)
18982 @item @code{ext @emph{extension}}
18984 This option allows you to change the extension of the generated HTML files.
18985 If you do not specify an extension, it will default to @code{htm}.
18988 @geindex -f (gnathtml)
18995 By default, gnathtml will generate html links only for global entities
18996 ('with'ed units, global variables and types,...). If you specify
18997 @code{-f} on the command line, then links will be generated for local
19001 @geindex -l (gnathtml)
19006 @item @code{l @emph{number}}
19008 If this switch is provided and @code{number} is not 0, then
19009 @code{gnathtml} will number the html files every @code{number} line.
19012 @geindex -I (gnathtml)
19017 @item @code{I @emph{dir}}
19019 Specify a directory to search for library files (@code{.ALI} files) and
19020 source files. You can provide several -I switches on the command line,
19021 and the directories will be parsed in the order of the command line.
19024 @geindex -o (gnathtml)
19029 @item @code{o @emph{dir}}
19031 Specify the output directory for html files. By default, gnathtml will
19032 saved the generated html files in a subdirectory named @code{html/}.
19035 @geindex -p (gnathtml)
19040 @item @code{p @emph{file}}
19042 If you are using Emacs and the most recent Emacs Ada mode, which provides
19043 a full Integrated Development Environment for compiling, checking,
19044 running and debugging applications, you may use @code{.gpr} files
19045 to give the directories where Emacs can find sources and object files.
19047 Using this switch, you can tell gnathtml to use these files.
19048 This allows you to get an html version of your application, even if it
19049 is spread over multiple directories.
19052 @geindex -sc (gnathtml)
19057 @item @code{sc @emph{color}}
19059 This switch allows you to change the color used for symbol
19061 The default value is red. The color argument can be any name accepted by html.
19064 @geindex -t (gnathtml)
19069 @item @code{t @emph{file}}
19071 This switch provides the name of a file. This file contains a list of
19072 file names to be converted, and the effect is exactly as though they had
19073 appeared explicitly on the command line. This
19074 is the recommended way to work around the command line length limit on some
19078 @node Installing gnathtml,,Invoking gnathtml,The Ada to HTML Converter gnathtml
19079 @anchor{gnat_ugn/gnat_utility_programs installing-gnathtml}@anchor{161}@anchor{gnat_ugn/gnat_utility_programs id18}@anchor{164}
19080 @subsection Installing @code{gnathtml}
19083 @code{Perl} needs to be installed on your machine to run this script.
19084 @code{Perl} is freely available for almost every architecture and
19085 operating system via the Internet.
19087 On Unix systems, you may want to modify the first line of the script
19088 @code{gnathtml}, to explicitly specify where Perl
19089 is located. The syntax of this line is:
19094 #!full_path_name_to_perl
19098 Alternatively, you may run the script using the following command line:
19103 $ perl gnathtml.pl [ switches ] files
19107 @c -- +---------------------------------------------------------------------+
19109 @c -- | The following sections are present only in the PRO and GPL editions |
19111 @c -- +---------------------------------------------------------------------+
19121 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
19123 @node GNAT and Program Execution,Platform-Specific Information,GNAT Utility Programs,Top
19124 @anchor{gnat_ugn/gnat_and_program_execution gnat-and-program-execution}@anchor{c}@anchor{gnat_ugn/gnat_and_program_execution doc}@anchor{165}@anchor{gnat_ugn/gnat_and_program_execution id1}@anchor{166}
19125 @chapter GNAT and Program Execution
19128 This chapter covers several topics:
19134 @ref{167,,Running and Debugging Ada Programs}
19137 @ref{25,,Profiling}
19140 @ref{168,,Improving Performance}
19143 @ref{169,,Overflow Check Handling in GNAT}
19146 @ref{16a,,Performing Dimensionality Analysis in GNAT}
19149 @ref{16b,,Stack Related Facilities}
19152 @ref{16c,,Memory Management Issues}
19156 * Running and Debugging Ada Programs::
19158 * Improving Performance::
19159 * Overflow Check Handling in GNAT::
19160 * Performing Dimensionality Analysis in GNAT::
19161 * Stack Related Facilities::
19162 * Memory Management Issues::
19166 @node Running and Debugging Ada Programs,Profiling,,GNAT and Program Execution
19167 @anchor{gnat_ugn/gnat_and_program_execution id2}@anchor{167}@anchor{gnat_ugn/gnat_and_program_execution running-and-debugging-ada-programs}@anchor{24}
19168 @section Running and Debugging Ada Programs
19173 This section discusses how to debug Ada programs.
19175 An incorrect Ada program may be handled in three ways by the GNAT compiler:
19181 The illegality may be a violation of the static semantics of Ada. In
19182 that case GNAT diagnoses the constructs in the program that are illegal.
19183 It is then a straightforward matter for the user to modify those parts of
19187 The illegality may be a violation of the dynamic semantics of Ada. In
19188 that case the program compiles and executes, but may generate incorrect
19189 results, or may terminate abnormally with some exception.
19192 When presented with a program that contains convoluted errors, GNAT
19193 itself may terminate abnormally without providing full diagnostics on
19194 the incorrect user program.
19202 * The GNAT Debugger GDB::
19204 * Introduction to GDB Commands::
19205 * Using Ada Expressions::
19206 * Calling User-Defined Subprograms::
19207 * Using the next Command in a Function::
19208 * Stopping When Ada Exceptions Are Raised::
19210 * Debugging Generic Units::
19211 * Remote Debugging with gdbserver::
19212 * GNAT Abnormal Termination or Failure to Terminate::
19213 * Naming Conventions for GNAT Source Files::
19214 * Getting Internal Debugging Information::
19215 * Stack Traceback::
19216 * Pretty-Printers for the GNAT runtime::
19220 @node The GNAT Debugger GDB,Running GDB,,Running and Debugging Ada Programs
19221 @anchor{gnat_ugn/gnat_and_program_execution the-gnat-debugger-gdb}@anchor{16d}@anchor{gnat_ugn/gnat_and_program_execution id3}@anchor{16e}
19222 @subsection The GNAT Debugger GDB
19225 @code{GDB} is a general purpose, platform-independent debugger that
19226 can be used to debug mixed-language programs compiled with @code{gcc},
19227 and in particular is capable of debugging Ada programs compiled with
19228 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
19229 complex Ada data structures.
19231 See @cite{Debugging with GDB},
19232 for full details on the usage of @code{GDB}, including a section on
19233 its usage on programs. This manual should be consulted for full
19234 details. The section that follows is a brief introduction to the
19235 philosophy and use of @code{GDB}.
19237 When GNAT programs are compiled, the compiler optionally writes debugging
19238 information into the generated object file, including information on
19239 line numbers, and on declared types and variables. This information is
19240 separate from the generated code. It makes the object files considerably
19241 larger, but it does not add to the size of the actual executable that
19242 will be loaded into memory, and has no impact on run-time performance. The
19243 generation of debug information is triggered by the use of the
19244 @code{-g} switch in the @code{gcc} or @code{gnatmake} command
19245 used to carry out the compilations. It is important to emphasize that
19246 the use of these options does not change the generated code.
19248 The debugging information is written in standard system formats that
19249 are used by many tools, including debuggers and profilers. The format
19250 of the information is typically designed to describe C types and
19251 semantics, but GNAT implements a translation scheme which allows full
19252 details about Ada types and variables to be encoded into these
19253 standard C formats. Details of this encoding scheme may be found in
19254 the file exp_dbug.ads in the GNAT source distribution. However, the
19255 details of this encoding are, in general, of no interest to a user,
19256 since @code{GDB} automatically performs the necessary decoding.
19258 When a program is bound and linked, the debugging information is
19259 collected from the object files, and stored in the executable image of
19260 the program. Again, this process significantly increases the size of
19261 the generated executable file, but it does not increase the size of
19262 the executable program itself. Furthermore, if this program is run in
19263 the normal manner, it runs exactly as if the debug information were
19264 not present, and takes no more actual memory.
19266 However, if the program is run under control of @code{GDB}, the
19267 debugger is activated. The image of the program is loaded, at which
19268 point it is ready to run. If a run command is given, then the program
19269 will run exactly as it would have if @code{GDB} were not present. This
19270 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
19271 entirely non-intrusive until a breakpoint is encountered. If no
19272 breakpoint is ever hit, the program will run exactly as it would if no
19273 debugger were present. When a breakpoint is hit, @code{GDB} accesses
19274 the debugging information and can respond to user commands to inspect
19275 variables, and more generally to report on the state of execution.
19277 @node Running GDB,Introduction to GDB Commands,The GNAT Debugger GDB,Running and Debugging Ada Programs
19278 @anchor{gnat_ugn/gnat_and_program_execution id4}@anchor{16f}@anchor{gnat_ugn/gnat_and_program_execution running-gdb}@anchor{170}
19279 @subsection Running GDB
19282 This section describes how to initiate the debugger.
19284 The debugger can be launched from a @code{GPS} menu or
19285 directly from the command line. The description below covers the latter use.
19286 All the commands shown can be used in the @code{GPS} debug console window,
19287 but there are usually more GUI-based ways to achieve the same effect.
19289 The command to run @code{GDB} is
19298 where @code{program} is the name of the executable file. This
19299 activates the debugger and results in a prompt for debugger commands.
19300 The simplest command is simply @code{run}, which causes the program to run
19301 exactly as if the debugger were not present. The following section
19302 describes some of the additional commands that can be given to @code{GDB}.
19304 @node Introduction to GDB Commands,Using Ada Expressions,Running GDB,Running and Debugging Ada Programs
19305 @anchor{gnat_ugn/gnat_and_program_execution introduction-to-gdb-commands}@anchor{171}@anchor{gnat_ugn/gnat_and_program_execution id5}@anchor{172}
19306 @subsection Introduction to GDB Commands
19309 @code{GDB} contains a large repertoire of commands.
19310 See @cite{Debugging with GDB} for extensive documentation on the use
19311 of these commands, together with examples of their use. Furthermore,
19312 the command @emph{help} invoked from within GDB activates a simple help
19313 facility which summarizes the available commands and their options.
19314 In this section we summarize a few of the most commonly
19315 used commands to give an idea of what @code{GDB} is about. You should create
19316 a simple program with debugging information and experiment with the use of
19317 these @code{GDB} commands on the program as you read through the
19327 @item @code{set args @emph{arguments}}
19329 The @emph{arguments} list above is a list of arguments to be passed to
19330 the program on a subsequent run command, just as though the arguments
19331 had been entered on a normal invocation of the program. The @code{set args}
19332 command is not needed if the program does not require arguments.
19341 The @code{run} command causes execution of the program to start from
19342 the beginning. If the program is already running, that is to say if
19343 you are currently positioned at a breakpoint, then a prompt will ask
19344 for confirmation that you want to abandon the current execution and
19352 @item @code{breakpoint @emph{location}}
19354 The breakpoint command sets a breakpoint, that is to say a point at which
19355 execution will halt and @code{GDB} will await further
19356 commands. @emph{location} is
19357 either a line number within a file, given in the format @code{file:linenumber},
19358 or it is the name of a subprogram. If you request that a breakpoint be set on
19359 a subprogram that is overloaded, a prompt will ask you to specify on which of
19360 those subprograms you want to breakpoint. You can also
19361 specify that all of them should be breakpointed. If the program is run
19362 and execution encounters the breakpoint, then the program
19363 stops and @code{GDB} signals that the breakpoint was encountered by
19364 printing the line of code before which the program is halted.
19371 @item @code{catch exception @emph{name}}
19373 This command causes the program execution to stop whenever exception
19374 @code{name} is raised. If @code{name} is omitted, then the execution is
19375 suspended when any exception is raised.
19382 @item @code{print @emph{expression}}
19384 This will print the value of the given expression. Most simple
19385 Ada expression formats are properly handled by @code{GDB}, so the expression
19386 can contain function calls, variables, operators, and attribute references.
19393 @item @code{continue}
19395 Continues execution following a breakpoint, until the next breakpoint or the
19396 termination of the program.
19405 Executes a single line after a breakpoint. If the next statement
19406 is a subprogram call, execution continues into (the first statement of)
19407 the called subprogram.
19416 Executes a single line. If this line is a subprogram call, executes and
19417 returns from the call.
19426 Lists a few lines around the current source location. In practice, it
19427 is usually more convenient to have a separate edit window open with the
19428 relevant source file displayed. Successive applications of this command
19429 print subsequent lines. The command can be given an argument which is a
19430 line number, in which case it displays a few lines around the specified one.
19437 @item @code{backtrace}
19439 Displays a backtrace of the call chain. This command is typically
19440 used after a breakpoint has occurred, to examine the sequence of calls that
19441 leads to the current breakpoint. The display includes one line for each
19442 activation record (frame) corresponding to an active subprogram.
19451 At a breakpoint, @code{GDB} can display the values of variables local
19452 to the current frame. The command @code{up} can be used to
19453 examine the contents of other active frames, by moving the focus up
19454 the stack, that is to say from callee to caller, one frame at a time.
19463 Moves the focus of @code{GDB} down from the frame currently being
19464 examined to the frame of its callee (the reverse of the previous command),
19471 @item @code{frame @emph{n}}
19473 Inspect the frame with the given number. The value 0 denotes the frame
19474 of the current breakpoint, that is to say the top of the call stack.
19483 Kills the child process in which the program is running under GDB.
19484 This may be useful for several purposes:
19490 It allows you to recompile and relink your program, since on many systems
19491 you cannot regenerate an executable file while it is running in a process.
19494 You can run your program outside the debugger, on systems that do not
19495 permit executing a program outside GDB while breakpoints are set
19499 It allows you to debug a core dump rather than a running process.
19504 The above list is a very short introduction to the commands that
19505 @code{GDB} provides. Important additional capabilities, including conditional
19506 breakpoints, the ability to execute command sequences on a breakpoint,
19507 the ability to debug at the machine instruction level and many other
19508 features are described in detail in @cite{Debugging with GDB}.
19509 Note that most commands can be abbreviated
19510 (for example, c for continue, bt for backtrace).
19512 @node Using Ada Expressions,Calling User-Defined Subprograms,Introduction to GDB Commands,Running and Debugging Ada Programs
19513 @anchor{gnat_ugn/gnat_and_program_execution id6}@anchor{173}@anchor{gnat_ugn/gnat_and_program_execution using-ada-expressions}@anchor{174}
19514 @subsection Using Ada Expressions
19517 @geindex Ada expressions (in gdb)
19519 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
19520 extensions. The philosophy behind the design of this subset is
19528 That @code{GDB} should provide basic literals and access to operations for
19529 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
19530 leaving more sophisticated computations to subprograms written into the
19531 program (which therefore may be called from @code{GDB}).
19534 That type safety and strict adherence to Ada language restrictions
19535 are not particularly relevant in a debugging context.
19538 That brevity is important to the @code{GDB} user.
19542 Thus, for brevity, the debugger acts as if there were
19543 implicit @code{with} and @code{use} clauses in effect for all user-written
19544 packages, thus making it unnecessary to fully qualify most names with
19545 their packages, regardless of context. Where this causes ambiguity,
19546 @code{GDB} asks the user's intent.
19548 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
19550 @node Calling User-Defined Subprograms,Using the next Command in a Function,Using Ada Expressions,Running and Debugging Ada Programs
19551 @anchor{gnat_ugn/gnat_and_program_execution id7}@anchor{175}@anchor{gnat_ugn/gnat_and_program_execution calling-user-defined-subprograms}@anchor{176}
19552 @subsection Calling User-Defined Subprograms
19555 An important capability of @code{GDB} is the ability to call user-defined
19556 subprograms while debugging. This is achieved simply by entering
19557 a subprogram call statement in the form:
19562 call subprogram-name (parameters)
19566 The keyword @code{call} can be omitted in the normal case where the
19567 @code{subprogram-name} does not coincide with any of the predefined
19568 @code{GDB} commands.
19570 The effect is to invoke the given subprogram, passing it the
19571 list of parameters that is supplied. The parameters can be expressions and
19572 can include variables from the program being debugged. The
19573 subprogram must be defined
19574 at the library level within your program, and @code{GDB} will call the
19575 subprogram within the environment of your program execution (which
19576 means that the subprogram is free to access or even modify variables
19577 within your program).
19579 The most important use of this facility is in allowing the inclusion of
19580 debugging routines that are tailored to particular data structures
19581 in your program. Such debugging routines can be written to provide a suitably
19582 high-level description of an abstract type, rather than a low-level dump
19583 of its physical layout. After all, the standard
19584 @code{GDB print} command only knows the physical layout of your
19585 types, not their abstract meaning. Debugging routines can provide information
19586 at the desired semantic level and are thus enormously useful.
19588 For example, when debugging GNAT itself, it is crucial to have access to
19589 the contents of the tree nodes used to represent the program internally.
19590 But tree nodes are represented simply by an integer value (which in turn
19591 is an index into a table of nodes).
19592 Using the @code{print} command on a tree node would simply print this integer
19593 value, which is not very useful. But the PN routine (defined in file
19594 treepr.adb in the GNAT sources) takes a tree node as input, and displays
19595 a useful high level representation of the tree node, which includes the
19596 syntactic category of the node, its position in the source, the integers
19597 that denote descendant nodes and parent node, as well as varied
19598 semantic information. To study this example in more detail, you might want to
19599 look at the body of the PN procedure in the stated file.
19601 Another useful application of this capability is to deal with situations of
19602 complex data which are not handled suitably by GDB. For example, if you specify
19603 Convention Fortran for a multi-dimensional array, GDB does not know that
19604 the ordering of array elements has been switched and will not properly
19605 address the array elements. In such a case, instead of trying to print the
19606 elements directly from GDB, you can write a callable procedure that prints
19607 the elements in the desired format.
19609 @node Using the next Command in a Function,Stopping When Ada Exceptions Are Raised,Calling User-Defined Subprograms,Running and Debugging Ada Programs
19610 @anchor{gnat_ugn/gnat_and_program_execution using-the-next-command-in-a-function}@anchor{177}@anchor{gnat_ugn/gnat_and_program_execution id8}@anchor{178}
19611 @subsection Using the @emph{next} Command in a Function
19614 When you use the @code{next} command in a function, the current source
19615 location will advance to the next statement as usual. A special case
19616 arises in the case of a @code{return} statement.
19618 Part of the code for a return statement is the 'epilogue' of the function.
19619 This is the code that returns to the caller. There is only one copy of
19620 this epilogue code, and it is typically associated with the last return
19621 statement in the function if there is more than one return. In some
19622 implementations, this epilogue is associated with the first statement
19625 The result is that if you use the @code{next} command from a return
19626 statement that is not the last return statement of the function you
19627 may see a strange apparent jump to the last return statement or to
19628 the start of the function. You should simply ignore this odd jump.
19629 The value returned is always that from the first return statement
19630 that was stepped through.
19632 @node Stopping When Ada Exceptions Are Raised,Ada Tasks,Using the next Command in a Function,Running and Debugging Ada Programs
19633 @anchor{gnat_ugn/gnat_and_program_execution stopping-when-ada-exceptions-are-raised}@anchor{179}@anchor{gnat_ugn/gnat_and_program_execution id9}@anchor{17a}
19634 @subsection Stopping When Ada Exceptions Are Raised
19637 @geindex Exceptions (in gdb)
19639 You can set catchpoints that stop the program execution when your program
19640 raises selected exceptions.
19649 @item @code{catch exception}
19651 Set a catchpoint that stops execution whenever (any task in the) program
19652 raises any exception.
19659 @item @code{catch exception @emph{name}}
19661 Set a catchpoint that stops execution whenever (any task in the) program
19662 raises the exception @emph{name}.
19669 @item @code{catch exception unhandled}
19671 Set a catchpoint that stops executing whenever (any task in the) program
19672 raises an exception for which there is no handler.
19679 @item @code{info exceptions}, @code{info exceptions @emph{regexp}}
19681 The @code{info exceptions} command permits the user to examine all defined
19682 exceptions within Ada programs. With a regular expression, @emph{regexp}, as
19683 argument, prints out only those exceptions whose name matches @emph{regexp}.
19687 @geindex Tasks (in gdb)
19689 @node Ada Tasks,Debugging Generic Units,Stopping When Ada Exceptions Are Raised,Running and Debugging Ada Programs
19690 @anchor{gnat_ugn/gnat_and_program_execution ada-tasks}@anchor{17b}@anchor{gnat_ugn/gnat_and_program_execution id10}@anchor{17c}
19691 @subsection Ada Tasks
19694 @code{GDB} allows the following task-related commands:
19703 @item @code{info tasks}
19705 This command shows a list of current Ada tasks, as in the following example:
19709 ID TID P-ID Thread Pri State Name
19710 1 8088000 0 807e000 15 Child Activation Wait main_task
19711 2 80a4000 1 80ae000 15 Accept/Select Wait b
19712 3 809a800 1 80a4800 15 Child Activation Wait a
19713 * 4 80ae800 3 80b8000 15 Running c
19716 In this listing, the asterisk before the first task indicates it to be the
19717 currently running task. The first column lists the task ID that is used
19718 to refer to tasks in the following commands.
19722 @geindex Breakpoints and tasks
19728 @code{break`@w{`}*linespec* `@w{`}task} @emph{taskid}, @code{break} @emph{linespec} @code{task} @emph{taskid} @code{if} ...
19732 These commands are like the @code{break ... thread ...}.
19733 @emph{linespec} specifies source lines.
19735 Use the qualifier @code{task @emph{taskid}} with a breakpoint command
19736 to specify that you only want @code{GDB} to stop the program when a
19737 particular Ada task reaches this breakpoint. @emph{taskid} is one of the
19738 numeric task identifiers assigned by @code{GDB}, shown in the first
19739 column of the @code{info tasks} display.
19741 If you do not specify @code{task @emph{taskid}} when you set a
19742 breakpoint, the breakpoint applies to @emph{all} tasks of your
19745 You can use the @code{task} qualifier on conditional breakpoints as
19746 well; in this case, place @code{task @emph{taskid}} before the
19747 breakpoint condition (before the @code{if}).
19751 @geindex Task switching (in gdb)
19757 @code{task @emph{taskno}}
19761 This command allows switching to the task referred by @emph{taskno}. In
19762 particular, this allows browsing of the backtrace of the specified
19763 task. It is advisable to switch back to the original task before
19764 continuing execution otherwise the scheduling of the program may be
19769 For more detailed information on the tasking support,
19770 see @cite{Debugging with GDB}.
19772 @geindex Debugging Generic Units
19776 @node Debugging Generic Units,Remote Debugging with gdbserver,Ada Tasks,Running and Debugging Ada Programs
19777 @anchor{gnat_ugn/gnat_and_program_execution debugging-generic-units}@anchor{17d}@anchor{gnat_ugn/gnat_and_program_execution id11}@anchor{17e}
19778 @subsection Debugging Generic Units
19781 GNAT always uses code expansion for generic instantiation. This means that
19782 each time an instantiation occurs, a complete copy of the original code is
19783 made, with appropriate substitutions of formals by actuals.
19785 It is not possible to refer to the original generic entities in
19786 @code{GDB}, but it is always possible to debug a particular instance of
19787 a generic, by using the appropriate expanded names. For example, if we have
19794 generic package k is
19795 procedure kp (v1 : in out integer);
19799 procedure kp (v1 : in out integer) is
19805 package k1 is new k;
19806 package k2 is new k;
19808 var : integer := 1;
19819 Then to break on a call to procedure kp in the k2 instance, simply
19825 (gdb) break g.k2.kp
19829 When the breakpoint occurs, you can step through the code of the
19830 instance in the normal manner and examine the values of local variables, as for
19833 @geindex Remote Debugging with gdbserver
19835 @node Remote Debugging with gdbserver,GNAT Abnormal Termination or Failure to Terminate,Debugging Generic Units,Running and Debugging Ada Programs
19836 @anchor{gnat_ugn/gnat_and_program_execution remote-debugging-with-gdbserver}@anchor{17f}@anchor{gnat_ugn/gnat_and_program_execution id12}@anchor{180}
19837 @subsection Remote Debugging with gdbserver
19840 On platforms where gdbserver is supported, it is possible to use this tool
19841 to debug your application remotely. This can be useful in situations
19842 where the program needs to be run on a target host that is different
19843 from the host used for development, particularly when the target has
19844 a limited amount of resources (either CPU and/or memory).
19846 To do so, start your program using gdbserver on the target machine.
19847 gdbserver then automatically suspends the execution of your program
19848 at its entry point, waiting for a debugger to connect to it. The
19849 following commands starts an application and tells gdbserver to
19850 wait for a connection with the debugger on localhost port 4444.
19855 $ gdbserver localhost:4444 program
19856 Process program created; pid = 5685
19857 Listening on port 4444
19861 Once gdbserver has started listening, we can tell the debugger to establish
19862 a connection with this gdbserver, and then start the same debugging session
19863 as if the program was being debugged on the same host, directly under
19864 the control of GDB.
19870 (gdb) target remote targethost:4444
19871 Remote debugging using targethost:4444
19872 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
19874 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
19878 Breakpoint 1, foo () at foo.adb:4
19883 It is also possible to use gdbserver to attach to an already running
19884 program, in which case the execution of that program is simply suspended
19885 until the connection between the debugger and gdbserver is established.
19887 For more information on how to use gdbserver, see the @emph{Using the gdbserver Program}
19888 section in @cite{Debugging with GDB}.
19889 GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux.
19891 @geindex Abnormal Termination or Failure to Terminate
19893 @node GNAT Abnormal Termination or Failure to Terminate,Naming Conventions for GNAT Source Files,Remote Debugging with gdbserver,Running and Debugging Ada Programs
19894 @anchor{gnat_ugn/gnat_and_program_execution gnat-abnormal-termination-or-failure-to-terminate}@anchor{181}@anchor{gnat_ugn/gnat_and_program_execution id13}@anchor{182}
19895 @subsection GNAT Abnormal Termination or Failure to Terminate
19898 When presented with programs that contain serious errors in syntax
19900 GNAT may on rare occasions experience problems in operation, such
19902 segmentation fault or illegal memory access, raising an internal
19903 exception, terminating abnormally, or failing to terminate at all.
19904 In such cases, you can activate
19905 various features of GNAT that can help you pinpoint the construct in your
19906 program that is the likely source of the problem.
19908 The following strategies are presented in increasing order of
19909 difficulty, corresponding to your experience in using GNAT and your
19910 familiarity with compiler internals.
19916 Run @code{gcc} with the @code{-gnatf}. This first
19917 switch causes all errors on a given line to be reported. In its absence,
19918 only the first error on a line is displayed.
19920 The @code{-gnatdO} switch causes errors to be displayed as soon as they
19921 are encountered, rather than after compilation is terminated. If GNAT
19922 terminates prematurely or goes into an infinite loop, the last error
19923 message displayed may help to pinpoint the culprit.
19926 Run @code{gcc} with the @code{-v} (verbose) switch. In this
19927 mode, @code{gcc} produces ongoing information about the progress of the
19928 compilation and provides the name of each procedure as code is
19929 generated. This switch allows you to find which Ada procedure was being
19930 compiled when it encountered a code generation problem.
19933 @geindex -gnatdc switch
19939 Run @code{gcc} with the @code{-gnatdc} switch. This is a GNAT specific
19940 switch that does for the front-end what @code{-v} does
19941 for the back end. The system prints the name of each unit,
19942 either a compilation unit or nested unit, as it is being analyzed.
19945 Finally, you can start
19946 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
19947 front-end of GNAT, and can be run independently (normally it is just
19948 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
19949 would on a C program (but @ref{16d,,The GNAT Debugger GDB} for caveats). The
19950 @code{where} command is the first line of attack; the variable
19951 @code{lineno} (seen by @code{print lineno}), used by the second phase of
19952 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
19953 which the execution stopped, and @code{input_file name} indicates the name of
19957 @node Naming Conventions for GNAT Source Files,Getting Internal Debugging Information,GNAT Abnormal Termination or Failure to Terminate,Running and Debugging Ada Programs
19958 @anchor{gnat_ugn/gnat_and_program_execution naming-conventions-for-gnat-source-files}@anchor{183}@anchor{gnat_ugn/gnat_and_program_execution id14}@anchor{184}
19959 @subsection Naming Conventions for GNAT Source Files
19962 In order to examine the workings of the GNAT system, the following
19963 brief description of its organization may be helpful:
19969 Files with prefix @code{sc} contain the lexical scanner.
19972 All files prefixed with @code{par} are components of the parser. The
19973 numbers correspond to chapters of the Ada Reference Manual. For example,
19974 parsing of select statements can be found in @code{par-ch9.adb}.
19977 All files prefixed with @code{sem} perform semantic analysis. The
19978 numbers correspond to chapters of the Ada standard. For example, all
19979 issues involving context clauses can be found in @code{sem_ch10.adb}. In
19980 addition, some features of the language require sufficient special processing
19981 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
19982 dynamic dispatching, etc.
19985 All files prefixed with @code{exp} perform normalization and
19986 expansion of the intermediate representation (abstract syntax tree, or AST).
19987 these files use the same numbering scheme as the parser and semantics files.
19988 For example, the construction of record initialization procedures is done in
19989 @code{exp_ch3.adb}.
19992 The files prefixed with @code{bind} implement the binder, which
19993 verifies the consistency of the compilation, determines an order of
19994 elaboration, and generates the bind file.
19997 The files @code{atree.ads} and @code{atree.adb} detail the low-level
19998 data structures used by the front-end.
20001 The files @code{sinfo.ads} and @code{sinfo.adb} detail the structure of
20002 the abstract syntax tree as produced by the parser.
20005 The files @code{einfo.ads} and @code{einfo.adb} detail the attributes of
20006 all entities, computed during semantic analysis.
20009 Library management issues are dealt with in files with prefix
20012 @geindex Annex A (in Ada Reference Manual)
20015 Ada files with the prefix @code{a-} are children of @code{Ada}, as
20016 defined in Annex A.
20018 @geindex Annex B (in Ada reference Manual)
20021 Files with prefix @code{i-} are children of @code{Interfaces}, as
20022 defined in Annex B.
20024 @geindex System (package in Ada Reference Manual)
20027 Files with prefix @code{s-} are children of @code{System}. This includes
20028 both language-defined children and GNAT run-time routines.
20030 @geindex GNAT (package)
20033 Files with prefix @code{g-} are children of @code{GNAT}. These are useful
20034 general-purpose packages, fully documented in their specs. All
20035 the other @code{.c} files are modifications of common @code{gcc} files.
20038 @node Getting Internal Debugging Information,Stack Traceback,Naming Conventions for GNAT Source Files,Running and Debugging Ada Programs
20039 @anchor{gnat_ugn/gnat_and_program_execution id15}@anchor{185}@anchor{gnat_ugn/gnat_and_program_execution getting-internal-debugging-information}@anchor{186}
20040 @subsection Getting Internal Debugging Information
20043 Most compilers have internal debugging switches and modes. GNAT
20044 does also, except GNAT internal debugging switches and modes are not
20045 secret. A summary and full description of all the compiler and binder
20046 debug flags are in the file @code{debug.adb}. You must obtain the
20047 sources of the compiler to see the full detailed effects of these flags.
20049 The switches that print the source of the program (reconstructed from
20050 the internal tree) are of general interest for user programs, as are the
20052 the full internal tree, and the entity table (the symbol table
20053 information). The reconstructed source provides a readable version of the
20054 program after the front-end has completed analysis and expansion,
20055 and is useful when studying the performance of specific constructs.
20056 For example, constraint checks are indicated, complex aggregates
20057 are replaced with loops and assignments, and tasking primitives
20058 are replaced with run-time calls.
20062 @geindex stack traceback
20064 @geindex stack unwinding
20066 @node Stack Traceback,Pretty-Printers for the GNAT runtime,Getting Internal Debugging Information,Running and Debugging Ada Programs
20067 @anchor{gnat_ugn/gnat_and_program_execution stack-traceback}@anchor{187}@anchor{gnat_ugn/gnat_and_program_execution id16}@anchor{188}
20068 @subsection Stack Traceback
20071 Traceback is a mechanism to display the sequence of subprogram calls that
20072 leads to a specified execution point in a program. Often (but not always)
20073 the execution point is an instruction at which an exception has been raised.
20074 This mechanism is also known as @emph{stack unwinding} because it obtains
20075 its information by scanning the run-time stack and recovering the activation
20076 records of all active subprograms. Stack unwinding is one of the most
20077 important tools for program debugging.
20079 The first entry stored in traceback corresponds to the deepest calling level,
20080 that is to say the subprogram currently executing the instruction
20081 from which we want to obtain the traceback.
20083 Note that there is no runtime performance penalty when stack traceback
20084 is enabled, and no exception is raised during program execution.
20087 @geindex non-symbolic
20090 * Non-Symbolic Traceback::
20091 * Symbolic Traceback::
20095 @node Non-Symbolic Traceback,Symbolic Traceback,,Stack Traceback
20096 @anchor{gnat_ugn/gnat_and_program_execution non-symbolic-traceback}@anchor{189}@anchor{gnat_ugn/gnat_and_program_execution id17}@anchor{18a}
20097 @subsubsection Non-Symbolic Traceback
20100 Note: this feature is not supported on all platforms. See
20101 @code{GNAT.Traceback} spec in @code{g-traceb.ads}
20102 for a complete list of supported platforms.
20104 @subsubheading Tracebacks From an Unhandled Exception
20107 A runtime non-symbolic traceback is a list of addresses of call instructions.
20108 To enable this feature you must use the @code{-E}
20109 @code{gnatbind} option. With this option a stack traceback is stored as part
20110 of exception information. You can retrieve this information using the
20111 @code{addr2line} tool.
20113 Here is a simple example:
20122 raise Constraint_Error;
20136 $ gnatmake stb -bargs -E
20139 Execution terminated by unhandled exception
20140 Exception name: CONSTRAINT_ERROR
20142 Call stack traceback locations:
20143 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20147 As we see the traceback lists a sequence of addresses for the unhandled
20148 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
20149 guess that this exception come from procedure P1. To translate these
20150 addresses into the source lines where the calls appear, the
20151 @code{addr2line} tool, described below, is invaluable. The use of this tool
20152 requires the program to be compiled with debug information.
20157 $ gnatmake -g stb -bargs -E
20160 Execution terminated by unhandled exception
20161 Exception name: CONSTRAINT_ERROR
20163 Call stack traceback locations:
20164 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20166 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
20167 0x4011f1 0x77e892a4
20169 00401373 at d:/stb/stb.adb:5
20170 0040138B at d:/stb/stb.adb:10
20171 0040139C at d:/stb/stb.adb:14
20172 00401335 at d:/stb/b~stb.adb:104
20173 004011C4 at /build/.../crt1.c:200
20174 004011F1 at /build/.../crt1.c:222
20175 77E892A4 in ?? at ??:0
20179 The @code{addr2line} tool has several other useful options:
20184 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
20191 to get the function name corresponding to any location
20195 @code{--demangle=gnat}
20199 to use the gnat decoding mode for the function names.
20200 Note that for binutils version 2.9.x the option is
20201 simply @code{--demangle}.
20207 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
20208 0x40139c 0x401335 0x4011c4 0x4011f1
20210 00401373 in stb.p1 at d:/stb/stb.adb:5
20211 0040138B in stb.p2 at d:/stb/stb.adb:10
20212 0040139C in stb at d:/stb/stb.adb:14
20213 00401335 in main at d:/stb/b~stb.adb:104
20214 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
20215 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
20219 From this traceback we can see that the exception was raised in
20220 @code{stb.adb} at line 5, which was reached from a procedure call in
20221 @code{stb.adb} at line 10, and so on. The @code{b~std.adb} is the binder file,
20222 which contains the call to the main program.
20223 @ref{11c,,Running gnatbind}. The remaining entries are assorted runtime routines,
20224 and the output will vary from platform to platform.
20226 It is also possible to use @code{GDB} with these traceback addresses to debug
20227 the program. For example, we can break at a given code location, as reported
20228 in the stack traceback:
20237 Furthermore, this feature is not implemented inside Windows DLL. Only
20238 the non-symbolic traceback is reported in this case.
20243 (gdb) break *0x401373
20244 Breakpoint 1 at 0x401373: file stb.adb, line 5.
20248 It is important to note that the stack traceback addresses
20249 do not change when debug information is included. This is particularly useful
20250 because it makes it possible to release software without debug information (to
20251 minimize object size), get a field report that includes a stack traceback
20252 whenever an internal bug occurs, and then be able to retrieve the sequence
20253 of calls with the same program compiled with debug information.
20255 @subsubheading Tracebacks From Exception Occurrences
20258 Non-symbolic tracebacks are obtained by using the @code{-E} binder argument.
20259 The stack traceback is attached to the exception information string, and can
20260 be retrieved in an exception handler within the Ada program, by means of the
20261 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
20267 with Ada.Exceptions;
20272 use Ada.Exceptions;
20280 Text_IO.Put_Line (Exception_Information (E));
20294 This program will output:
20301 Exception name: CONSTRAINT_ERROR
20302 Message: stb.adb:12
20303 Call stack traceback locations:
20304 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
20308 @subsubheading Tracebacks From Anywhere in a Program
20311 It is also possible to retrieve a stack traceback from anywhere in a
20312 program. For this you need to
20313 use the @code{GNAT.Traceback} API. This package includes a procedure called
20314 @code{Call_Chain} that computes a complete stack traceback, as well as useful
20315 display procedures described below. It is not necessary to use the
20316 @code{-E} @code{gnatbind} option in this case, because the stack traceback mechanism
20317 is invoked explicitly.
20319 In the following example we compute a traceback at a specific location in
20320 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
20321 convert addresses to strings:
20327 with GNAT.Traceback;
20328 with GNAT.Debug_Utilities;
20334 use GNAT.Traceback;
20337 TB : Tracebacks_Array (1 .. 10);
20338 -- We are asking for a maximum of 10 stack frames.
20340 -- Len will receive the actual number of stack frames returned.
20342 Call_Chain (TB, Len);
20344 Text_IO.Put ("In STB.P1 : ");
20346 for K in 1 .. Len loop
20347 Text_IO.Put (Debug_Utilities.Image (TB (K)));
20368 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
20369 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
20373 You can then get further information by invoking the @code{addr2line}
20374 tool as described earlier (note that the hexadecimal addresses
20375 need to be specified in C format, with a leading '0x').
20380 @node Symbolic Traceback,,Non-Symbolic Traceback,Stack Traceback
20381 @anchor{gnat_ugn/gnat_and_program_execution id18}@anchor{18b}@anchor{gnat_ugn/gnat_and_program_execution symbolic-traceback}@anchor{18c}
20382 @subsubsection Symbolic Traceback
20385 A symbolic traceback is a stack traceback in which procedure names are
20386 associated with each code location.
20388 Note that this feature is not supported on all platforms. See
20389 @code{GNAT.Traceback.Symbolic} spec in @code{g-trasym.ads} for a complete
20390 list of currently supported platforms.
20392 Note that the symbolic traceback requires that the program be compiled
20393 with debug information. If it is not compiled with debug information
20394 only the non-symbolic information will be valid.
20396 @subsubheading Tracebacks From Exception Occurrences
20399 Here is an example:
20405 with GNAT.Traceback.Symbolic;
20411 raise Constraint_Error;
20428 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
20433 $ gnatmake -g .\stb -bargs -E
20436 0040149F in stb.p1 at stb.adb:8
20437 004014B7 in stb.p2 at stb.adb:13
20438 004014CF in stb.p3 at stb.adb:18
20439 004015DD in ada.stb at stb.adb:22
20440 00401461 in main at b~stb.adb:168
20441 004011C4 in __mingw_CRTStartup at crt1.c:200
20442 004011F1 in mainCRTStartup at crt1.c:222
20443 77E892A4 in ?? at ??:0
20447 In the above example the @code{.\} syntax in the @code{gnatmake} command
20448 is currently required by @code{addr2line} for files that are in
20449 the current working directory.
20450 Moreover, the exact sequence of linker options may vary from platform
20452 The above @code{-largs} section is for Windows platforms. By contrast,
20453 under Unix there is no need for the @code{-largs} section.
20454 Differences across platforms are due to details of linker implementation.
20456 @subsubheading Tracebacks From Anywhere in a Program
20459 It is possible to get a symbolic stack traceback
20460 from anywhere in a program, just as for non-symbolic tracebacks.
20461 The first step is to obtain a non-symbolic
20462 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
20463 information. Here is an example:
20469 with GNAT.Traceback;
20470 with GNAT.Traceback.Symbolic;
20475 use GNAT.Traceback;
20476 use GNAT.Traceback.Symbolic;
20479 TB : Tracebacks_Array (1 .. 10);
20480 -- We are asking for a maximum of 10 stack frames.
20482 -- Len will receive the actual number of stack frames returned.
20484 Call_Chain (TB, Len);
20485 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
20499 @subsubheading Automatic Symbolic Tracebacks
20502 Symbolic tracebacks may also be enabled by using the -Es switch to gnatbind (as
20503 in @code{gprbuild -g ... -bargs -Es}).
20504 This will cause the Exception_Information to contain a symbolic traceback,
20505 which will also be printed if an unhandled exception terminates the
20508 @node Pretty-Printers for the GNAT runtime,,Stack Traceback,Running and Debugging Ada Programs
20509 @anchor{gnat_ugn/gnat_and_program_execution id19}@anchor{18d}@anchor{gnat_ugn/gnat_and_program_execution pretty-printers-for-the-gnat-runtime}@anchor{18e}
20510 @subsection Pretty-Printers for the GNAT runtime
20513 As discussed in @cite{Calling User-Defined Subprograms}, GDB's
20514 @code{print} command only knows about the physical layout of program data
20515 structures and therefore normally displays only low-level dumps, which
20516 are often hard to understand.
20518 An example of this is when trying to display the contents of an Ada
20519 standard container, such as @code{Ada.Containers.Ordered_Maps.Map}:
20524 with Ada.Containers.Ordered_Maps;
20527 package Int_To_Nat is
20528 new Ada.Containers.Ordered_Maps (Integer, Natural);
20530 Map : Int_To_Nat.Map;
20532 Map.Insert (1, 10);
20533 Map.Insert (2, 20);
20534 Map.Insert (3, 30);
20536 Map.Clear; -- BREAK HERE
20541 When this program is built with debugging information and run under
20542 GDB up to the @code{Map.Clear} statement, trying to print @code{Map} will
20543 yield information that is only relevant to the developers of our standard
20565 Fortunately, GDB has a feature called pretty-printers@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Introduction},
20566 which allows customizing how GDB displays data structures. The GDB
20567 shipped with GNAT embeds such pretty-printers for the most common
20568 containers in the standard library. To enable them, either run the
20569 following command manually under GDB or add it to your @code{.gdbinit} file:
20574 python import gnatdbg; gnatdbg.setup()
20578 Once this is done, GDB's @code{print} command will automatically use
20579 these pretty-printers when appropriate. Using the previous example:
20585 $1 = pp.int_to_nat.map of length 3 = @{
20593 Pretty-printers are invoked each time GDB tries to display a value,
20594 including when displaying the arguments of a called subprogram (in
20595 GDB's @code{backtrace} command) or when printing the value returned by a
20596 function (in GDB's @code{finish} command).
20598 To display a value without involving pretty-printers, @code{print} can be
20599 invoked with its @code{/r} option:
20610 Finer control of pretty-printers is also possible: see GDB's online documentation@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Commands}
20611 for more information.
20615 @node Profiling,Improving Performance,Running and Debugging Ada Programs,GNAT and Program Execution
20616 @anchor{gnat_ugn/gnat_and_program_execution profiling}@anchor{25}@anchor{gnat_ugn/gnat_and_program_execution id20}@anchor{18f}
20620 This section describes how to use the the @code{gprof} profiler tool on Ada
20628 * Profiling an Ada Program with gprof::
20632 @node Profiling an Ada Program with gprof,,,Profiling
20633 @anchor{gnat_ugn/gnat_and_program_execution id21}@anchor{190}@anchor{gnat_ugn/gnat_and_program_execution profiling-an-ada-program-with-gprof}@anchor{191}
20634 @subsection Profiling an Ada Program with gprof
20637 This section is not meant to be an exhaustive documentation of @code{gprof}.
20638 Full documentation for it can be found in the @cite{GNU Profiler User's Guide}
20639 documentation that is part of this GNAT distribution.
20641 Profiling a program helps determine the parts of a program that are executed
20642 most often, and are therefore the most time-consuming.
20644 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
20645 better handle Ada programs and multitasking.
20646 It is currently supported on the following platforms
20658 In order to profile a program using @code{gprof}, several steps are needed:
20664 Instrument the code, which requires a full recompilation of the project with the
20668 Execute the program under the analysis conditions, i.e. with the desired
20672 Analyze the results using the @code{gprof} tool.
20675 The following sections detail the different steps, and indicate how
20676 to interpret the results.
20679 * Compilation for profiling::
20680 * Program execution::
20682 * Interpretation of profiling results::
20686 @node Compilation for profiling,Program execution,,Profiling an Ada Program with gprof
20687 @anchor{gnat_ugn/gnat_and_program_execution id22}@anchor{192}@anchor{gnat_ugn/gnat_and_program_execution compilation-for-profiling}@anchor{193}
20688 @subsubsection Compilation for profiling
20692 @geindex for profiling
20694 @geindex -pg (gnatlink)
20695 @geindex for profiling
20697 In order to profile a program the first step is to tell the compiler
20698 to generate the necessary profiling information. The compiler switch to be used
20699 is @code{-pg}, which must be added to other compilation switches. This
20700 switch needs to be specified both during compilation and link stages, and can
20701 be specified once when using gnatmake:
20706 $ gnatmake -f -pg -P my_project
20710 Note that only the objects that were compiled with the @code{-pg} switch will
20711 be profiled; if you need to profile your whole project, use the @code{-f}
20712 gnatmake switch to force full recompilation.
20714 @node Program execution,Running gprof,Compilation for profiling,Profiling an Ada Program with gprof
20715 @anchor{gnat_ugn/gnat_and_program_execution program-execution}@anchor{194}@anchor{gnat_ugn/gnat_and_program_execution id23}@anchor{195}
20716 @subsubsection Program execution
20719 Once the program has been compiled for profiling, you can run it as usual.
20721 The only constraint imposed by profiling is that the program must terminate
20722 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
20725 Once the program completes execution, a data file called @code{gmon.out} is
20726 generated in the directory where the program was launched from. If this file
20727 already exists, it will be overwritten.
20729 @node Running gprof,Interpretation of profiling results,Program execution,Profiling an Ada Program with gprof
20730 @anchor{gnat_ugn/gnat_and_program_execution running-gprof}@anchor{196}@anchor{gnat_ugn/gnat_and_program_execution id24}@anchor{197}
20731 @subsubsection Running gprof
20734 The @code{gprof} tool is called as follow:
20739 $ gprof my_prog gmon.out
20752 The complete form of the gprof command line is the following:
20757 $ gprof [switches] [executable [data-file]]
20761 @code{gprof} supports numerous switches. The order of these
20762 switch does not matter. The full list of options can be found in
20763 the GNU Profiler User's Guide documentation that comes with this documentation.
20765 The following is the subset of those switches that is most relevant:
20767 @geindex --demangle (gprof)
20772 @item @code{--demangle[=@emph{style}]}, @code{--no-demangle}
20774 These options control whether symbol names should be demangled when
20775 printing output. The default is to demangle C++ symbols. The
20776 @code{--no-demangle} option may be used to turn off demangling. Different
20777 compilers have different mangling styles. The optional demangling style
20778 argument can be used to choose an appropriate demangling style for your
20779 compiler, in particular Ada symbols generated by GNAT can be demangled using
20780 @code{--demangle=gnat}.
20783 @geindex -e (gprof)
20788 @item @code{-e @emph{function_name}}
20790 The @code{-e @emph{function}} option tells @code{gprof} not to print
20791 information about the function @code{function_name} (and its
20792 children...) in the call graph. The function will still be listed
20793 as a child of any functions that call it, but its index number will be
20794 shown as @code{[not printed]}. More than one @code{-e} option may be
20795 given; only one @code{function_name} may be indicated with each @code{-e}
20799 @geindex -E (gprof)
20804 @item @code{-E @emph{function_name}}
20806 The @code{-E @emph{function}} option works like the @code{-e} option, but
20807 execution time spent in the function (and children who were not called from
20808 anywhere else), will not be used to compute the percentages-of-time for
20809 the call graph. More than one @code{-E} option may be given; only one
20810 @code{function_name} may be indicated with each @code{-E`} option.
20813 @geindex -f (gprof)
20818 @item @code{-f @emph{function_name}}
20820 The @code{-f @emph{function}} option causes @code{gprof} to limit the
20821 call graph to the function @code{function_name} and its children (and
20822 their children...). More than one @code{-f} option may be given;
20823 only one @code{function_name} may be indicated with each @code{-f}
20827 @geindex -F (gprof)
20832 @item @code{-F @emph{function_name}}
20834 The @code{-F @emph{function}} option works like the @code{-f} option, but
20835 only time spent in the function and its children (and their
20836 children...) will be used to determine total-time and
20837 percentages-of-time for the call graph. More than one @code{-F} option
20838 may be given; only one @code{function_name} may be indicated with each
20839 @code{-F} option. The @code{-F} option overrides the @code{-E} option.
20842 @node Interpretation of profiling results,,Running gprof,Profiling an Ada Program with gprof
20843 @anchor{gnat_ugn/gnat_and_program_execution id25}@anchor{198}@anchor{gnat_ugn/gnat_and_program_execution interpretation-of-profiling-results}@anchor{199}
20844 @subsubsection Interpretation of profiling results
20847 The results of the profiling analysis are represented by two arrays: the
20848 'flat profile' and the 'call graph'. Full documentation of those outputs
20849 can be found in the GNU Profiler User's Guide.
20851 The flat profile shows the time spent in each function of the program, and how
20852 many time it has been called. This allows you to locate easily the most
20853 time-consuming functions.
20855 The call graph shows, for each subprogram, the subprograms that call it,
20856 and the subprograms that it calls. It also provides an estimate of the time
20857 spent in each of those callers/called subprograms.
20859 @node Improving Performance,Overflow Check Handling in GNAT,Profiling,GNAT and Program Execution
20860 @anchor{gnat_ugn/gnat_and_program_execution improving-performance}@anchor{26}@anchor{gnat_ugn/gnat_and_program_execution id26}@anchor{168}
20861 @section Improving Performance
20864 @geindex Improving performance
20866 This section presents several topics related to program performance.
20867 It first describes some of the tradeoffs that need to be considered
20868 and some of the techniques for making your program run faster.
20871 It then documents the unused subprogram/data elimination feature,
20872 which can reduce the size of program executables.
20875 * Performance Considerations::
20876 * Text_IO Suggestions::
20877 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
20881 @node Performance Considerations,Text_IO Suggestions,,Improving Performance
20882 @anchor{gnat_ugn/gnat_and_program_execution performance-considerations}@anchor{19a}@anchor{gnat_ugn/gnat_and_program_execution id27}@anchor{19b}
20883 @subsection Performance Considerations
20886 The GNAT system provides a number of options that allow a trade-off
20893 performance of the generated code
20896 speed of compilation
20899 minimization of dependences and recompilation
20902 the degree of run-time checking.
20905 The defaults (if no options are selected) aim at improving the speed
20906 of compilation and minimizing dependences, at the expense of performance
20907 of the generated code:
20916 no inlining of subprogram calls
20919 all run-time checks enabled except overflow and elaboration checks
20922 These options are suitable for most program development purposes. This
20923 section describes how you can modify these choices, and also provides
20924 some guidelines on debugging optimized code.
20927 * Controlling Run-Time Checks::
20928 * Use of Restrictions::
20929 * Optimization Levels::
20930 * Debugging Optimized Code::
20931 * Inlining of Subprograms::
20932 * Floating_Point_Operations::
20933 * Vectorization of loops::
20934 * Other Optimization Switches::
20935 * Optimization and Strict Aliasing::
20936 * Aliased Variables and Optimization::
20937 * Atomic Variables and Optimization::
20938 * Passive Task Optimization::
20942 @node Controlling Run-Time Checks,Use of Restrictions,,Performance Considerations
20943 @anchor{gnat_ugn/gnat_and_program_execution id28}@anchor{19c}@anchor{gnat_ugn/gnat_and_program_execution controlling-run-time-checks}@anchor{19d}
20944 @subsubsection Controlling Run-Time Checks
20947 By default, GNAT generates all run-time checks, except stack overflow
20948 checks, and checks for access before elaboration on subprogram
20949 calls. The latter are not required in default mode, because all
20950 necessary checking is done at compile time.
20952 @geindex -gnatp (gcc)
20954 @geindex -gnato (gcc)
20956 The gnat switch, @code{-gnatp} allows this default to be modified. See
20957 @ref{f9,,Run-Time Checks}.
20959 Our experience is that the default is suitable for most development
20962 Elaboration checks are off by default, and also not needed by default, since
20963 GNAT uses a static elaboration analysis approach that avoids the need for
20964 run-time checking. This manual contains a full chapter discussing the issue
20965 of elaboration checks, and if the default is not satisfactory for your use,
20966 you should read this chapter.
20968 For validity checks, the minimal checks required by the Ada Reference
20969 Manual (for case statements and assignments to array elements) are on
20970 by default. These can be suppressed by use of the @code{-gnatVn} switch.
20971 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
20972 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
20973 it may be reasonable to routinely use @code{-gnatVn}. Validity checks
20974 are also suppressed entirely if @code{-gnatp} is used.
20976 @geindex Overflow checks
20983 @geindex Unsuppress
20985 @geindex pragma Suppress
20987 @geindex pragma Unsuppress
20989 Note that the setting of the switches controls the default setting of
20990 the checks. They may be modified using either @code{pragma Suppress} (to
20991 remove checks) or @code{pragma Unsuppress} (to add back suppressed
20992 checks) in the program source.
20994 @node Use of Restrictions,Optimization Levels,Controlling Run-Time Checks,Performance Considerations
20995 @anchor{gnat_ugn/gnat_and_program_execution id29}@anchor{19e}@anchor{gnat_ugn/gnat_and_program_execution use-of-restrictions}@anchor{19f}
20996 @subsubsection Use of Restrictions
20999 The use of pragma Restrictions allows you to control which features are
21000 permitted in your program. Apart from the obvious point that if you avoid
21001 relatively expensive features like finalization (enforceable by the use
21002 of pragma Restrictions (No_Finalization), the use of this pragma does not
21003 affect the generated code in most cases.
21005 One notable exception to this rule is that the possibility of task abort
21006 results in some distributed overhead, particularly if finalization or
21007 exception handlers are used. The reason is that certain sections of code
21008 have to be marked as non-abortable.
21010 If you use neither the @code{abort} statement, nor asynchronous transfer
21011 of control (@code{select ... then abort}), then this distributed overhead
21012 is removed, which may have a general positive effect in improving
21013 overall performance. Especially code involving frequent use of tasking
21014 constructs and controlled types will show much improved performance.
21015 The relevant restrictions pragmas are
21020 pragma Restrictions (No_Abort_Statements);
21021 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
21025 It is recommended that these restriction pragmas be used if possible. Note
21026 that this also means that you can write code without worrying about the
21027 possibility of an immediate abort at any point.
21029 @node Optimization Levels,Debugging Optimized Code,Use of Restrictions,Performance Considerations
21030 @anchor{gnat_ugn/gnat_and_program_execution id30}@anchor{1a0}@anchor{gnat_ugn/gnat_and_program_execution optimization-levels}@anchor{fc}
21031 @subsubsection Optimization Levels
21036 Without any optimization option,
21037 the compiler's goal is to reduce the cost of
21038 compilation and to make debugging produce the expected results.
21039 Statements are independent: if you stop the program with a breakpoint between
21040 statements, you can then assign a new value to any variable or change
21041 the program counter to any other statement in the subprogram and get exactly
21042 the results you would expect from the source code.
21044 Turning on optimization makes the compiler attempt to improve the
21045 performance and/or code size at the expense of compilation time and
21046 possibly the ability to debug the program.
21048 If you use multiple
21049 -O options, with or without level numbers,
21050 the last such option is the one that is effective.
21052 The default is optimization off. This results in the fastest compile
21053 times, but GNAT makes absolutely no attempt to optimize, and the
21054 generated programs are considerably larger and slower than when
21055 optimization is enabled. You can use the
21056 @code{-O} switch (the permitted forms are @code{-O0}, @code{-O1}
21057 @code{-O2}, @code{-O3}, and @code{-Os})
21058 to @code{gcc} to control the optimization level:
21069 No optimization (the default);
21070 generates unoptimized code but has
21071 the fastest compilation time.
21073 Note that many other compilers do substantial optimization even
21074 if 'no optimization' is specified. With gcc, it is very unusual
21075 to use @code{-O0} for production if execution time is of any concern,
21076 since @code{-O0} means (almost) no optimization. This difference
21077 between gcc and other compilers should be kept in mind when
21078 doing performance comparisons.
21087 Moderate optimization;
21088 optimizes reasonably well but does not
21089 degrade compilation time significantly.
21099 generates highly optimized code and has
21100 the slowest compilation time.
21109 Full optimization as in @code{-O2};
21110 also uses more aggressive automatic inlining of subprograms within a unit
21111 (@ref{10f,,Inlining of Subprograms}) and attempts to vectorize loops.
21120 Optimize space usage (code and data) of resulting program.
21124 Higher optimization levels perform more global transformations on the
21125 program and apply more expensive analysis algorithms in order to generate
21126 faster and more compact code. The price in compilation time, and the
21127 resulting improvement in execution time,
21128 both depend on the particular application and the hardware environment.
21129 You should experiment to find the best level for your application.
21131 Since the precise set of optimizations done at each level will vary from
21132 release to release (and sometime from target to target), it is best to think
21133 of the optimization settings in general terms.
21134 See the @emph{Options That Control Optimization} section in
21135 @cite{Using the GNU Compiler Collection (GCC)}
21137 the @code{-O} settings and a number of @code{-f} options that
21138 individually enable or disable specific optimizations.
21140 Unlike some other compilation systems, @code{gcc} has
21141 been tested extensively at all optimization levels. There are some bugs
21142 which appear only with optimization turned on, but there have also been
21143 bugs which show up only in @emph{unoptimized} code. Selecting a lower
21144 level of optimization does not improve the reliability of the code
21145 generator, which in practice is highly reliable at all optimization
21148 Note regarding the use of @code{-O3}: The use of this optimization level
21149 ought not to be automatically preferred over that of level @code{-O2},
21150 since it often results in larger executables which may run more slowly.
21151 See further discussion of this point in @ref{10f,,Inlining of Subprograms}.
21153 @node Debugging Optimized Code,Inlining of Subprograms,Optimization Levels,Performance Considerations
21154 @anchor{gnat_ugn/gnat_and_program_execution debugging-optimized-code}@anchor{1a1}@anchor{gnat_ugn/gnat_and_program_execution id31}@anchor{1a2}
21155 @subsubsection Debugging Optimized Code
21158 @geindex Debugging optimized code
21160 @geindex Optimization and debugging
21162 Although it is possible to do a reasonable amount of debugging at
21163 nonzero optimization levels,
21164 the higher the level the more likely that
21165 source-level constructs will have been eliminated by optimization.
21166 For example, if a loop is strength-reduced, the loop
21167 control variable may be completely eliminated and thus cannot be
21168 displayed in the debugger.
21169 This can only happen at @code{-O2} or @code{-O3}.
21170 Explicit temporary variables that you code might be eliminated at
21171 level @code{-O1} or higher.
21175 The use of the @code{-g} switch,
21176 which is needed for source-level debugging,
21177 affects the size of the program executable on disk,
21178 and indeed the debugging information can be quite large.
21179 However, it has no effect on the generated code (and thus does not
21180 degrade performance)
21182 Since the compiler generates debugging tables for a compilation unit before
21183 it performs optimizations, the optimizing transformations may invalidate some
21184 of the debugging data. You therefore need to anticipate certain
21185 anomalous situations that may arise while debugging optimized code.
21186 These are the most common cases:
21192 @emph{The 'hopping Program Counter':} Repeated @code{step} or @code{next}
21194 the PC bouncing back and forth in the code. This may result from any of
21195 the following optimizations:
21201 @emph{Common subexpression elimination:} using a single instance of code for a
21202 quantity that the source computes several times. As a result you
21203 may not be able to stop on what looks like a statement.
21206 @emph{Invariant code motion:} moving an expression that does not change within a
21207 loop, to the beginning of the loop.
21210 @emph{Instruction scheduling:} moving instructions so as to
21211 overlap loads and stores (typically) with other code, or in
21212 general to move computations of values closer to their uses. Often
21213 this causes you to pass an assignment statement without the assignment
21214 happening and then later bounce back to the statement when the
21215 value is actually needed. Placing a breakpoint on a line of code
21216 and then stepping over it may, therefore, not always cause all the
21217 expected side-effects.
21221 @emph{The 'big leap':} More commonly known as @emph{cross-jumping}, in which
21222 two identical pieces of code are merged and the program counter suddenly
21223 jumps to a statement that is not supposed to be executed, simply because
21224 it (and the code following) translates to the same thing as the code
21225 that @emph{was} supposed to be executed. This effect is typically seen in
21226 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
21227 a @code{break} in a C @code{switch} statement.
21230 @emph{The 'roving variable':} The symptom is an unexpected value in a variable.
21231 There are various reasons for this effect:
21237 In a subprogram prologue, a parameter may not yet have been moved to its
21241 A variable may be dead, and its register re-used. This is
21242 probably the most common cause.
21245 As mentioned above, the assignment of a value to a variable may
21249 A variable may be eliminated entirely by value propagation or
21250 other means. In this case, GCC may incorrectly generate debugging
21251 information for the variable
21254 In general, when an unexpected value appears for a local variable or parameter
21255 you should first ascertain if that value was actually computed by
21256 your program, as opposed to being incorrectly reported by the debugger.
21258 array elements in an object designated by an access value
21259 are generally less of a problem, once you have ascertained that the access
21261 Typically, this means checking variables in the preceding code and in the
21262 calling subprogram to verify that the value observed is explainable from other
21263 values (one must apply the procedure recursively to those
21264 other values); or re-running the code and stopping a little earlier
21265 (perhaps before the call) and stepping to better see how the variable obtained
21266 the value in question; or continuing to step @emph{from} the point of the
21267 strange value to see if code motion had simply moved the variable's
21271 In light of such anomalies, a recommended technique is to use @code{-O0}
21272 early in the software development cycle, when extensive debugging capabilities
21273 are most needed, and then move to @code{-O1} and later @code{-O2} as
21274 the debugger becomes less critical.
21275 Whether to use the @code{-g} switch in the release version is
21276 a release management issue.
21277 Note that if you use @code{-g} you can then use the @code{strip} program
21278 on the resulting executable,
21279 which removes both debugging information and global symbols.
21281 @node Inlining of Subprograms,Floating_Point_Operations,Debugging Optimized Code,Performance Considerations
21282 @anchor{gnat_ugn/gnat_and_program_execution id32}@anchor{1a3}@anchor{gnat_ugn/gnat_and_program_execution inlining-of-subprograms}@anchor{10f}
21283 @subsubsection Inlining of Subprograms
21286 A call to a subprogram in the current unit is inlined if all the
21287 following conditions are met:
21293 The optimization level is at least @code{-O1}.
21296 The called subprogram is suitable for inlining: It must be small enough
21297 and not contain something that @code{gcc} cannot support in inlined
21300 @geindex pragma Inline
21305 Any one of the following applies: @code{pragma Inline} is applied to the
21306 subprogram; the subprogram is local to the unit and called once from
21307 within it; the subprogram is small and optimization level @code{-O2} is
21308 specified; optimization level @code{-O3} is specified.
21311 Calls to subprograms in @emph{with}ed units are normally not inlined.
21312 To achieve actual inlining (that is, replacement of the call by the code
21313 in the body of the subprogram), the following conditions must all be true:
21319 The optimization level is at least @code{-O1}.
21322 The called subprogram is suitable for inlining: It must be small enough
21323 and not contain something that @code{gcc} cannot support in inlined
21327 There is a @code{pragma Inline} for the subprogram.
21330 The @code{-gnatn} switch is used on the command line.
21333 Even if all these conditions are met, it may not be possible for
21334 the compiler to inline the call, due to the length of the body,
21335 or features in the body that make it impossible for the compiler
21336 to do the inlining.
21338 Note that specifying the @code{-gnatn} switch causes additional
21339 compilation dependencies. Consider the following:
21361 With the default behavior (no @code{-gnatn} switch specified), the
21362 compilation of the @code{Main} procedure depends only on its own source,
21363 @code{main.adb}, and the spec of the package in file @code{r.ads}. This
21364 means that editing the body of @code{R} does not require recompiling
21367 On the other hand, the call @code{R.Q} is not inlined under these
21368 circumstances. If the @code{-gnatn} switch is present when @code{Main}
21369 is compiled, the call will be inlined if the body of @code{Q} is small
21370 enough, but now @code{Main} depends on the body of @code{R} in
21371 @code{r.adb} as well as on the spec. This means that if this body is edited,
21372 the main program must be recompiled. Note that this extra dependency
21373 occurs whether or not the call is in fact inlined by @code{gcc}.
21375 The use of front end inlining with @code{-gnatN} generates similar
21376 additional dependencies.
21378 @geindex -fno-inline (gcc)
21380 Note: The @code{-fno-inline} switch overrides all other conditions and ensures that
21381 no inlining occurs, unless requested with pragma Inline_Always for @code{gcc}
21382 back-ends. The extra dependences resulting from @code{-gnatn} will still be active,
21383 even if this switch is used to suppress the resulting inlining actions.
21385 @geindex -fno-inline-functions (gcc)
21387 Note: The @code{-fno-inline-functions} switch can be used to prevent
21388 automatic inlining of subprograms if @code{-O3} is used.
21390 @geindex -fno-inline-small-functions (gcc)
21392 Note: The @code{-fno-inline-small-functions} switch can be used to prevent
21393 automatic inlining of small subprograms if @code{-O2} is used.
21395 @geindex -fno-inline-functions-called-once (gcc)
21397 Note: The @code{-fno-inline-functions-called-once} switch
21398 can be used to prevent inlining of subprograms local to the unit
21399 and called once from within it if @code{-O1} is used.
21401 Note regarding the use of @code{-O3}: @code{-gnatn} is made up of two
21402 sub-switches @code{-gnatn1} and @code{-gnatn2} that can be directly
21403 specified in lieu of it, @code{-gnatn} being translated into one of them
21404 based on the optimization level. With @code{-O2} or below, @code{-gnatn}
21405 is equivalent to @code{-gnatn1} which activates pragma @code{Inline} with
21406 moderate inlining across modules. With @code{-O3}, @code{-gnatn} is
21407 equivalent to @code{-gnatn2} which activates pragma @code{Inline} with
21408 full inlining across modules. If you have used pragma @code{Inline} in
21409 appropriate cases, then it is usually much better to use @code{-O2}
21410 and @code{-gnatn} and avoid the use of @code{-O3} which has the additional
21411 effect of inlining subprograms you did not think should be inlined. We have
21412 found that the use of @code{-O3} may slow down the compilation and increase
21413 the code size by performing excessive inlining, leading to increased
21414 instruction cache pressure from the increased code size and thus minor
21415 performance improvements. So the bottom line here is that you should not
21416 automatically assume that @code{-O3} is better than @code{-O2}, and
21417 indeed you should use @code{-O3} only if tests show that it actually
21418 improves performance for your program.
21420 @node Floating_Point_Operations,Vectorization of loops,Inlining of Subprograms,Performance Considerations
21421 @anchor{gnat_ugn/gnat_and_program_execution floating-point-operations}@anchor{1a4}@anchor{gnat_ugn/gnat_and_program_execution id33}@anchor{1a5}
21422 @subsubsection Floating_Point_Operations
21425 @geindex Floating-Point Operations
21427 On almost all targets, GNAT maps Float and Long_Float to the 32-bit and
21428 64-bit standard IEEE floating-point representations, and operations will
21429 use standard IEEE arithmetic as provided by the processor. On most, but
21430 not all, architectures, the attribute Machine_Overflows is False for these
21431 types, meaning that the semantics of overflow is implementation-defined.
21432 In the case of GNAT, these semantics correspond to the normal IEEE
21433 treatment of infinities and NaN (not a number) values. For example,
21434 1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By
21435 avoiding explicit overflow checks, the performance is greatly improved
21436 on many targets. However, if required, floating-point overflow can be
21437 enabled by the use of the pragma Check_Float_Overflow.
21439 Another consideration that applies specifically to x86 32-bit
21440 architectures is which form of floating-point arithmetic is used.
21441 By default the operations use the old style x86 floating-point,
21442 which implements an 80-bit extended precision form (on these
21443 architectures the type Long_Long_Float corresponds to that form).
21444 In addition, generation of efficient code in this mode means that
21445 the extended precision form will be used for intermediate results.
21446 This may be helpful in improving the final precision of a complex
21447 expression. However it means that the results obtained on the x86
21448 will be different from those on other architectures, and for some
21449 algorithms, the extra intermediate precision can be detrimental.
21451 In addition to this old-style floating-point, all modern x86 chips
21452 implement an alternative floating-point operation model referred
21453 to as SSE2. In this model there is no extended form, and furthermore
21454 execution performance is significantly enhanced. To force GNAT to use
21455 this more modern form, use both of the switches:
21459 -msse2 -mfpmath=sse
21462 A unit compiled with these switches will automatically use the more
21463 efficient SSE2 instruction set for Float and Long_Float operations.
21464 Note that the ABI has the same form for both floating-point models,
21465 so it is permissible to mix units compiled with and without these
21468 @node Vectorization of loops,Other Optimization Switches,Floating_Point_Operations,Performance Considerations
21469 @anchor{gnat_ugn/gnat_and_program_execution id34}@anchor{1a6}@anchor{gnat_ugn/gnat_and_program_execution vectorization-of-loops}@anchor{1a7}
21470 @subsubsection Vectorization of loops
21473 @geindex Optimization Switches
21475 You can take advantage of the auto-vectorizer present in the @code{gcc}
21476 back end to vectorize loops with GNAT. The corresponding command line switch
21477 is @code{-ftree-vectorize} but, as it is enabled by default at @code{-O3}
21478 and other aggressive optimizations helpful for vectorization also are enabled
21479 by default at this level, using @code{-O3} directly is recommended.
21481 You also need to make sure that the target architecture features a supported
21482 SIMD instruction set. For example, for the x86 architecture, you should at
21483 least specify @code{-msse2} to get significant vectorization (but you don't
21484 need to specify it for x86-64 as it is part of the base 64-bit architecture).
21485 Similarly, for the PowerPC architecture, you should specify @code{-maltivec}.
21487 The preferred loop form for vectorization is the @code{for} iteration scheme.
21488 Loops with a @code{while} iteration scheme can also be vectorized if they are
21489 very simple, but the vectorizer will quickly give up otherwise. With either
21490 iteration scheme, the flow of control must be straight, in particular no
21491 @code{exit} statement may appear in the loop body. The loop may however
21492 contain a single nested loop, if it can be vectorized when considered alone:
21497 A : array (1..4, 1..4) of Long_Float;
21498 S : array (1..4) of Long_Float;
21502 for I in A'Range(1) loop
21503 for J in A'Range(2) loop
21504 S (I) := S (I) + A (I, J);
21511 The vectorizable operations depend on the targeted SIMD instruction set, but
21512 the adding and some of the multiplying operators are generally supported, as
21513 well as the logical operators for modular types. Note that compiling
21514 with @code{-gnatp} might well reveal cases where some checks do thwart
21517 Type conversions may also prevent vectorization if they involve semantics that
21518 are not directly supported by the code generator or the SIMD instruction set.
21519 A typical example is direct conversion from floating-point to integer types.
21520 The solution in this case is to use the following idiom:
21525 Integer (S'Truncation (F))
21529 if @code{S} is the subtype of floating-point object @code{F}.
21531 In most cases, the vectorizable loops are loops that iterate over arrays.
21532 All kinds of array types are supported, i.e. constrained array types with
21538 type Array_Type is array (1 .. 4) of Long_Float;
21542 constrained array types with dynamic bounds:
21547 type Array_Type is array (1 .. Q.N) of Long_Float;
21549 type Array_Type is array (Q.K .. 4) of Long_Float;
21551 type Array_Type is array (Q.K .. Q.N) of Long_Float;
21555 or unconstrained array types:
21560 type Array_Type is array (Positive range <>) of Long_Float;
21564 The quality of the generated code decreases when the dynamic aspect of the
21565 array type increases, the worst code being generated for unconstrained array
21566 types. This is so because, the less information the compiler has about the
21567 bounds of the array, the more fallback code it needs to generate in order to
21568 fix things up at run time.
21570 It is possible to specify that a given loop should be subject to vectorization
21571 preferably to other optimizations by means of pragma @code{Loop_Optimize}:
21576 pragma Loop_Optimize (Vector);
21580 placed immediately within the loop will convey the appropriate hint to the
21581 compiler for this loop.
21583 It is also possible to help the compiler generate better vectorized code
21584 for a given loop by asserting that there are no loop-carried dependencies
21585 in the loop. Consider for example the procedure:
21590 type Arr is array (1 .. 4) of Long_Float;
21592 procedure Add (X, Y : not null access Arr; R : not null access Arr) is
21594 for I in Arr'Range loop
21595 R(I) := X(I) + Y(I);
21601 By default, the compiler cannot unconditionally vectorize the loop because
21602 assigning to a component of the array designated by R in one iteration could
21603 change the value read from the components of the array designated by X or Y
21604 in a later iteration. As a result, the compiler will generate two versions
21605 of the loop in the object code, one vectorized and the other not vectorized,
21606 as well as a test to select the appropriate version at run time. This can
21607 be overcome by another hint:
21612 pragma Loop_Optimize (Ivdep);
21616 placed immediately within the loop will tell the compiler that it can safely
21617 omit the non-vectorized version of the loop as well as the run-time test.
21619 @node Other Optimization Switches,Optimization and Strict Aliasing,Vectorization of loops,Performance Considerations
21620 @anchor{gnat_ugn/gnat_and_program_execution other-optimization-switches}@anchor{1a8}@anchor{gnat_ugn/gnat_and_program_execution id35}@anchor{1a9}
21621 @subsubsection Other Optimization Switches
21624 @geindex Optimization Switches
21626 Since GNAT uses the @code{gcc} back end, all the specialized
21627 @code{gcc} optimization switches are potentially usable. These switches
21628 have not been extensively tested with GNAT but can generally be expected
21629 to work. Examples of switches in this category are @code{-funroll-loops}
21630 and the various target-specific @code{-m} options (in particular, it has
21631 been observed that @code{-march=xxx} can significantly improve performance
21632 on appropriate machines). For full details of these switches, see
21633 the @emph{Submodel Options} section in the @emph{Hardware Models and Configurations}
21634 chapter of @cite{Using the GNU Compiler Collection (GCC)}.
21636 @node Optimization and Strict Aliasing,Aliased Variables and Optimization,Other Optimization Switches,Performance Considerations
21637 @anchor{gnat_ugn/gnat_and_program_execution optimization-and-strict-aliasing}@anchor{f3}@anchor{gnat_ugn/gnat_and_program_execution id36}@anchor{1aa}
21638 @subsubsection Optimization and Strict Aliasing
21643 @geindex Strict Aliasing
21645 @geindex No_Strict_Aliasing
21647 The strong typing capabilities of Ada allow an optimizer to generate
21648 efficient code in situations where other languages would be forced to
21649 make worst case assumptions preventing such optimizations. Consider
21650 the following example:
21656 type Int1 is new Integer;
21657 type Int2 is new Integer;
21658 type Int1A is access Int1;
21659 type Int2A is access Int2;
21666 for J in Data'Range loop
21667 if Data (J) = Int1V.all then
21668 Int2V.all := Int2V.all + 1;
21676 In this example, since the variable @code{Int1V} can only access objects
21677 of type @code{Int1}, and @code{Int2V} can only access objects of type
21678 @code{Int2}, there is no possibility that the assignment to
21679 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
21680 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
21681 for all iterations of the loop and avoid the extra memory reference
21682 required to dereference it each time through the loop.
21684 This kind of optimization, called strict aliasing analysis, is
21685 triggered by specifying an optimization level of @code{-O2} or
21686 higher or @code{-Os} and allows GNAT to generate more efficient code
21687 when access values are involved.
21689 However, although this optimization is always correct in terms of
21690 the formal semantics of the Ada Reference Manual, difficulties can
21691 arise if features like @code{Unchecked_Conversion} are used to break
21692 the typing system. Consider the following complete program example:
21698 type int1 is new integer;
21699 type int2 is new integer;
21700 type a1 is access int1;
21701 type a2 is access int2;
21706 function to_a2 (Input : a1) return a2;
21709 with Unchecked_Conversion;
21711 function to_a2 (Input : a1) return a2 is
21713 new Unchecked_Conversion (a1, a2);
21715 return to_a2u (Input);
21721 with Text_IO; use Text_IO;
21723 v1 : a1 := new int1;
21724 v2 : a2 := to_a2 (v1);
21728 put_line (int1'image (v1.all));
21733 This program prints out 0 in @code{-O0} or @code{-O1}
21734 mode, but it prints out 1 in @code{-O2} mode. That's
21735 because in strict aliasing mode, the compiler can and
21736 does assume that the assignment to @code{v2.all} could not
21737 affect the value of @code{v1.all}, since different types
21740 This behavior is not a case of non-conformance with the standard, since
21741 the Ada RM specifies that an unchecked conversion where the resulting
21742 bit pattern is not a correct value of the target type can result in an
21743 abnormal value and attempting to reference an abnormal value makes the
21744 execution of a program erroneous. That's the case here since the result
21745 does not point to an object of type @code{int2}. This means that the
21746 effect is entirely unpredictable.
21748 However, although that explanation may satisfy a language
21749 lawyer, in practice an applications programmer expects an
21750 unchecked conversion involving pointers to create true
21751 aliases and the behavior of printing 1 seems plain wrong.
21752 In this case, the strict aliasing optimization is unwelcome.
21754 Indeed the compiler recognizes this possibility, and the
21755 unchecked conversion generates a warning:
21760 p2.adb:5:07: warning: possible aliasing problem with type "a2"
21761 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
21762 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
21766 Unfortunately the problem is recognized when compiling the body of
21767 package @code{p2}, but the actual "bad" code is generated while
21768 compiling the body of @code{m} and this latter compilation does not see
21769 the suspicious @code{Unchecked_Conversion}.
21771 As implied by the warning message, there are approaches you can use to
21772 avoid the unwanted strict aliasing optimization in a case like this.
21774 One possibility is to simply avoid the use of @code{-O2}, but
21775 that is a bit drastic, since it throws away a number of useful
21776 optimizations that do not involve strict aliasing assumptions.
21778 A less drastic approach is to compile the program using the
21779 option @code{-fno-strict-aliasing}. Actually it is only the
21780 unit containing the dereferencing of the suspicious pointer
21781 that needs to be compiled. So in this case, if we compile
21782 unit @code{m} with this switch, then we get the expected
21783 value of zero printed. Analyzing which units might need
21784 the switch can be painful, so a more reasonable approach
21785 is to compile the entire program with options @code{-O2}
21786 and @code{-fno-strict-aliasing}. If the performance is
21787 satisfactory with this combination of options, then the
21788 advantage is that the entire issue of possible "wrong"
21789 optimization due to strict aliasing is avoided.
21791 To avoid the use of compiler switches, the configuration
21792 pragma @code{No_Strict_Aliasing} with no parameters may be
21793 used to specify that for all access types, the strict
21794 aliasing optimization should be suppressed.
21796 However, these approaches are still overkill, in that they causes
21797 all manipulations of all access values to be deoptimized. A more
21798 refined approach is to concentrate attention on the specific
21799 access type identified as problematic.
21801 First, if a careful analysis of uses of the pointer shows
21802 that there are no possible problematic references, then
21803 the warning can be suppressed by bracketing the
21804 instantiation of @code{Unchecked_Conversion} to turn
21810 pragma Warnings (Off);
21812 new Unchecked_Conversion (a1, a2);
21813 pragma Warnings (On);
21817 Of course that approach is not appropriate for this particular
21818 example, since indeed there is a problematic reference. In this
21819 case we can take one of two other approaches.
21821 The first possibility is to move the instantiation of unchecked
21822 conversion to the unit in which the type is declared. In
21823 this example, we would move the instantiation of
21824 @code{Unchecked_Conversion} from the body of package
21825 @code{p2} to the spec of package @code{p1}. Now the
21826 warning disappears. That's because any use of the
21827 access type knows there is a suspicious unchecked
21828 conversion, and the strict aliasing optimization
21829 is automatically suppressed for the type.
21831 If it is not practical to move the unchecked conversion to the same unit
21832 in which the destination access type is declared (perhaps because the
21833 source type is not visible in that unit), you may use pragma
21834 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
21835 same declarative sequence as the declaration of the access type:
21840 type a2 is access int2;
21841 pragma No_Strict_Aliasing (a2);
21845 Here again, the compiler now knows that the strict aliasing optimization
21846 should be suppressed for any reference to type @code{a2} and the
21847 expected behavior is obtained.
21849 Finally, note that although the compiler can generate warnings for
21850 simple cases of unchecked conversions, there are tricker and more
21851 indirect ways of creating type incorrect aliases which the compiler
21852 cannot detect. Examples are the use of address overlays and unchecked
21853 conversions involving composite types containing access types as
21854 components. In such cases, no warnings are generated, but there can
21855 still be aliasing problems. One safe coding practice is to forbid the
21856 use of address clauses for type overlaying, and to allow unchecked
21857 conversion only for primitive types. This is not really a significant
21858 restriction since any possible desired effect can be achieved by
21859 unchecked conversion of access values.
21861 The aliasing analysis done in strict aliasing mode can certainly
21862 have significant benefits. We have seen cases of large scale
21863 application code where the time is increased by up to 5% by turning
21864 this optimization off. If you have code that includes significant
21865 usage of unchecked conversion, you might want to just stick with
21866 @code{-O1} and avoid the entire issue. If you get adequate
21867 performance at this level of optimization level, that's probably
21868 the safest approach. If tests show that you really need higher
21869 levels of optimization, then you can experiment with @code{-O2}
21870 and @code{-O2 -fno-strict-aliasing} to see how much effect this
21871 has on size and speed of the code. If you really need to use
21872 @code{-O2} with strict aliasing in effect, then you should
21873 review any uses of unchecked conversion of access types,
21874 particularly if you are getting the warnings described above.
21876 @node Aliased Variables and Optimization,Atomic Variables and Optimization,Optimization and Strict Aliasing,Performance Considerations
21877 @anchor{gnat_ugn/gnat_and_program_execution id37}@anchor{1ab}@anchor{gnat_ugn/gnat_and_program_execution aliased-variables-and-optimization}@anchor{1ac}
21878 @subsubsection Aliased Variables and Optimization
21883 There are scenarios in which programs may
21884 use low level techniques to modify variables
21885 that otherwise might be considered to be unassigned. For example,
21886 a variable can be passed to a procedure by reference, which takes
21887 the address of the parameter and uses the address to modify the
21888 variable's value, even though it is passed as an IN parameter.
21889 Consider the following example:
21895 Max_Length : constant Natural := 16;
21896 type Char_Ptr is access all Character;
21898 procedure Get_String(Buffer: Char_Ptr; Size : Integer);
21899 pragma Import (C, Get_String, "get_string");
21901 Name : aliased String (1 .. Max_Length) := (others => ' ');
21904 function Addr (S : String) return Char_Ptr is
21905 function To_Char_Ptr is
21906 new Ada.Unchecked_Conversion (System.Address, Char_Ptr);
21908 return To_Char_Ptr (S (S'First)'Address);
21912 Temp := Addr (Name);
21913 Get_String (Temp, Max_Length);
21918 where Get_String is a C function that uses the address in Temp to
21919 modify the variable @code{Name}. This code is dubious, and arguably
21920 erroneous, and the compiler would be entitled to assume that
21921 @code{Name} is never modified, and generate code accordingly.
21923 However, in practice, this would cause some existing code that
21924 seems to work with no optimization to start failing at high
21925 levels of optimzization.
21927 What the compiler does for such cases is to assume that marking
21928 a variable as aliased indicates that some "funny business" may
21929 be going on. The optimizer recognizes the aliased keyword and
21930 inhibits optimizations that assume the value cannot be assigned.
21931 This means that the above example will in fact "work" reliably,
21932 that is, it will produce the expected results.
21934 @node Atomic Variables and Optimization,Passive Task Optimization,Aliased Variables and Optimization,Performance Considerations
21935 @anchor{gnat_ugn/gnat_and_program_execution atomic-variables-and-optimization}@anchor{1ad}@anchor{gnat_ugn/gnat_and_program_execution id38}@anchor{1ae}
21936 @subsubsection Atomic Variables and Optimization
21941 There are two considerations with regard to performance when
21942 atomic variables are used.
21944 First, the RM only guarantees that access to atomic variables
21945 be atomic, it has nothing to say about how this is achieved,
21946 though there is a strong implication that this should not be
21947 achieved by explicit locking code. Indeed GNAT will never
21948 generate any locking code for atomic variable access (it will
21949 simply reject any attempt to make a variable or type atomic
21950 if the atomic access cannot be achieved without such locking code).
21952 That being said, it is important to understand that you cannot
21953 assume that the entire variable will always be accessed. Consider
21960 A,B,C,D : Character;
21963 for R'Alignment use 4;
21966 pragma Atomic (RV);
21973 You cannot assume that the reference to @code{RV.B}
21974 will read the entire 32-bit
21975 variable with a single load instruction. It is perfectly legitimate if
21976 the hardware allows it to do a byte read of just the B field. This read
21977 is still atomic, which is all the RM requires. GNAT can and does take
21978 advantage of this, depending on the architecture and optimization level.
21979 Any assumption to the contrary is non-portable and risky. Even if you
21980 examine the assembly language and see a full 32-bit load, this might
21981 change in a future version of the compiler.
21983 If your application requires that all accesses to @code{RV} in this
21984 example be full 32-bit loads, you need to make a copy for the access
21991 RV_Copy : constant R := RV;
21998 Now the reference to RV must read the whole variable.
21999 Actually one can imagine some compiler which figures
22000 out that the whole copy is not required (because only
22001 the B field is actually accessed), but GNAT
22002 certainly won't do that, and we don't know of any
22003 compiler that would not handle this right, and the
22004 above code will in practice work portably across
22005 all architectures (that permit the Atomic declaration).
22007 The second issue with atomic variables has to do with
22008 the possible requirement of generating synchronization
22009 code. For more details on this, consult the sections on
22010 the pragmas Enable/Disable_Atomic_Synchronization in the
22011 GNAT Reference Manual. If performance is critical, and
22012 such synchronization code is not required, it may be
22013 useful to disable it.
22015 @node Passive Task Optimization,,Atomic Variables and Optimization,Performance Considerations
22016 @anchor{gnat_ugn/gnat_and_program_execution passive-task-optimization}@anchor{1af}@anchor{gnat_ugn/gnat_and_program_execution id39}@anchor{1b0}
22017 @subsubsection Passive Task Optimization
22020 @geindex Passive Task
22022 A passive task is one which is sufficiently simple that
22023 in theory a compiler could recognize it an implement it
22024 efficiently without creating a new thread. The original design
22025 of Ada 83 had in mind this kind of passive task optimization, but
22026 only a few Ada 83 compilers attempted it. The problem was that
22027 it was difficult to determine the exact conditions under which
22028 the optimization was possible. The result is a very fragile
22029 optimization where a very minor change in the program can
22030 suddenly silently make a task non-optimizable.
22032 With the revisiting of this issue in Ada 95, there was general
22033 agreement that this approach was fundamentally flawed, and the
22034 notion of protected types was introduced. When using protected
22035 types, the restrictions are well defined, and you KNOW that the
22036 operations will be optimized, and furthermore this optimized
22037 performance is fully portable.
22039 Although it would theoretically be possible for GNAT to attempt to
22040 do this optimization, but it really doesn't make sense in the
22041 context of Ada 95, and none of the Ada 95 compilers implement
22042 this optimization as far as we know. In particular GNAT never
22043 attempts to perform this optimization.
22045 In any new Ada 95 code that is written, you should always
22046 use protected types in place of tasks that might be able to
22047 be optimized in this manner.
22048 Of course this does not help if you have legacy Ada 83 code
22049 that depends on this optimization, but it is unusual to encounter
22050 a case where the performance gains from this optimization
22053 Your program should work correctly without this optimization. If
22054 you have performance problems, then the most practical
22055 approach is to figure out exactly where these performance problems
22056 arise, and update those particular tasks to be protected types. Note
22057 that typically clients of the tasks who call entries, will not have
22058 to be modified, only the task definition itself.
22060 @node Text_IO Suggestions,Reducing Size of Executables with Unused Subprogram/Data Elimination,Performance Considerations,Improving Performance
22061 @anchor{gnat_ugn/gnat_and_program_execution text-io-suggestions}@anchor{1b1}@anchor{gnat_ugn/gnat_and_program_execution id40}@anchor{1b2}
22062 @subsection @code{Text_IO} Suggestions
22065 @geindex Text_IO and performance
22067 The @code{Ada.Text_IO} package has fairly high overheads due in part to
22068 the requirement of maintaining page and line counts. If performance
22069 is critical, a recommendation is to use @code{Stream_IO} instead of
22070 @code{Text_IO} for volume output, since this package has less overhead.
22072 If @code{Text_IO} must be used, note that by default output to the standard
22073 output and standard error files is unbuffered (this provides better
22074 behavior when output statements are used for debugging, or if the
22075 progress of a program is observed by tracking the output, e.g. by
22076 using the Unix @emph{tail -f} command to watch redirected output.
22078 If you are generating large volumes of output with @code{Text_IO} and
22079 performance is an important factor, use a designated file instead
22080 of the standard output file, or change the standard output file to
22081 be buffered using @code{Interfaces.C_Streams.setvbuf}.
22083 @node Reducing Size of Executables with Unused Subprogram/Data Elimination,,Text_IO Suggestions,Improving Performance
22084 @anchor{gnat_ugn/gnat_and_program_execution id41}@anchor{1b3}@anchor{gnat_ugn/gnat_and_program_execution reducing-size-of-executables-with-unused-subprogram-data-elimination}@anchor{1b4}
22085 @subsection Reducing Size of Executables with Unused Subprogram/Data Elimination
22088 @geindex Uunused subprogram/data elimination
22090 This section describes how you can eliminate unused subprograms and data from
22091 your executable just by setting options at compilation time.
22094 * About unused subprogram/data elimination::
22095 * Compilation options::
22096 * Example of unused subprogram/data elimination::
22100 @node About unused subprogram/data elimination,Compilation options,,Reducing Size of Executables with Unused Subprogram/Data Elimination
22101 @anchor{gnat_ugn/gnat_and_program_execution id42}@anchor{1b5}@anchor{gnat_ugn/gnat_and_program_execution about-unused-subprogram-data-elimination}@anchor{1b6}
22102 @subsubsection About unused subprogram/data elimination
22105 By default, an executable contains all code and data of its composing objects
22106 (directly linked or coming from statically linked libraries), even data or code
22107 never used by this executable.
22109 This feature will allow you to eliminate such unused code from your
22110 executable, making it smaller (in disk and in memory).
22112 This functionality is available on all Linux platforms except for the IA-64
22113 architecture and on all cross platforms using the ELF binary file format.
22114 In both cases GNU binutils version 2.16 or later are required to enable it.
22116 @node Compilation options,Example of unused subprogram/data elimination,About unused subprogram/data elimination,Reducing Size of Executables with Unused Subprogram/Data Elimination
22117 @anchor{gnat_ugn/gnat_and_program_execution id43}@anchor{1b7}@anchor{gnat_ugn/gnat_and_program_execution compilation-options}@anchor{1b8}
22118 @subsubsection Compilation options
22121 The operation of eliminating the unused code and data from the final executable
22122 is directly performed by the linker.
22124 @geindex -ffunction-sections (gcc)
22126 @geindex -fdata-sections (gcc)
22128 In order to do this, it has to work with objects compiled with the
22130 @code{-ffunction-sections} @code{-fdata-sections}.
22132 These options are usable with C and Ada files.
22133 They will place respectively each
22134 function or data in a separate section in the resulting object file.
22136 Once the objects and static libraries are created with these options, the
22137 linker can perform the dead code elimination. You can do this by setting
22138 the @code{-Wl,--gc-sections} option to gcc command or in the
22139 @code{-largs} section of @code{gnatmake}. This will perform a
22140 garbage collection of code and data never referenced.
22142 If the linker performs a partial link (@code{-r} linker option), then you
22143 will need to provide the entry point using the @code{-e} / @code{--entry}
22146 Note that objects compiled without the @code{-ffunction-sections} and
22147 @code{-fdata-sections} options can still be linked with the executable.
22148 However, no dead code elimination will be performed on those objects (they will
22151 The GNAT static library is now compiled with -ffunction-sections and
22152 -fdata-sections on some platforms. This allows you to eliminate the unused code
22153 and data of the GNAT library from your executable.
22155 @node Example of unused subprogram/data elimination,,Compilation options,Reducing Size of Executables with Unused Subprogram/Data Elimination
22156 @anchor{gnat_ugn/gnat_and_program_execution example-of-unused-subprogram-data-elimination}@anchor{1b9}@anchor{gnat_ugn/gnat_and_program_execution id44}@anchor{1ba}
22157 @subsubsection Example of unused subprogram/data elimination
22160 Here is a simple example:
22173 Used_Data : Integer;
22174 Unused_Data : Integer;
22176 procedure Used (Data : Integer);
22177 procedure Unused (Data : Integer);
22180 package body Aux is
22181 procedure Used (Data : Integer) is
22186 procedure Unused (Data : Integer) is
22188 Unused_Data := Data;
22194 @code{Unused} and @code{Unused_Data} are never referenced in this code
22195 excerpt, and hence they may be safely removed from the final executable.
22202 $ nm test | grep used
22203 020015f0 T aux__unused
22204 02005d88 B aux__unused_data
22205 020015cc T aux__used
22206 02005d84 B aux__used_data
22208 $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
22209 -largs -Wl,--gc-sections
22211 $ nm test | grep used
22212 02005350 T aux__used
22213 0201ffe0 B aux__used_data
22217 It can be observed that the procedure @code{Unused} and the object
22218 @code{Unused_Data} are removed by the linker when using the
22219 appropriate options.
22221 @geindex Overflow checks
22223 @geindex Checks (overflow)
22226 @node Overflow Check Handling in GNAT,Performing Dimensionality Analysis in GNAT,Improving Performance,GNAT and Program Execution
22227 @anchor{gnat_ugn/gnat_and_program_execution id50}@anchor{169}@anchor{gnat_ugn/gnat_and_program_execution overflow-check-handling-in-gnat}@anchor{27}
22228 @section Overflow Check Handling in GNAT
22231 This section explains how to control the handling of overflow checks.
22235 * Management of Overflows in GNAT::
22236 * Specifying the Desired Mode::
22237 * Default Settings::
22238 * Implementation Notes::
22242 @node Background,Management of Overflows in GNAT,,Overflow Check Handling in GNAT
22243 @anchor{gnat_ugn/gnat_and_program_execution id51}@anchor{1bb}@anchor{gnat_ugn/gnat_and_program_execution background}@anchor{1bc}
22244 @subsection Background
22247 Overflow checks are checks that the compiler may make to ensure
22248 that intermediate results are not out of range. For example:
22259 If @code{A} has the value @code{Integer'Last}, then the addition may cause
22260 overflow since the result is out of range of the type @code{Integer}.
22261 In this case @code{Constraint_Error} will be raised if checks are
22264 A trickier situation arises in examples like the following:
22275 where @code{A} is @code{Integer'Last} and @code{C} is @code{-1}.
22276 Now the final result of the expression on the right hand side is
22277 @code{Integer'Last} which is in range, but the question arises whether the
22278 intermediate addition of @code{(A + 1)} raises an overflow error.
22280 The (perhaps surprising) answer is that the Ada language
22281 definition does not answer this question. Instead it leaves
22282 it up to the implementation to do one of two things if overflow
22283 checks are enabled.
22289 raise an exception (@code{Constraint_Error}), or
22292 yield the correct mathematical result which is then used in
22293 subsequent operations.
22296 If the compiler chooses the first approach, then the assignment of this
22297 example will indeed raise @code{Constraint_Error} if overflow checking is
22298 enabled, or result in erroneous execution if overflow checks are suppressed.
22300 But if the compiler
22301 chooses the second approach, then it can perform both additions yielding
22302 the correct mathematical result, which is in range, so no exception
22303 will be raised, and the right result is obtained, regardless of whether
22304 overflow checks are suppressed.
22306 Note that in the first example an
22307 exception will be raised in either case, since if the compiler
22308 gives the correct mathematical result for the addition, it will
22309 be out of range of the target type of the assignment, and thus
22310 fails the range check.
22312 This lack of specified behavior in the handling of overflow for
22313 intermediate results is a source of non-portability, and can thus
22314 be problematic when programs are ported. Most typically this arises
22315 in a situation where the original compiler did not raise an exception,
22316 and then the application is moved to a compiler where the check is
22317 performed on the intermediate result and an unexpected exception is
22320 Furthermore, when using Ada 2012's preconditions and other
22321 assertion forms, another issue arises. Consider:
22326 procedure P (A, B : Integer) with
22327 Pre => A + B <= Integer'Last;
22331 One often wants to regard arithmetic in a context like this from
22332 a mathematical point of view. So for example, if the two actual parameters
22333 for a call to @code{P} are both @code{Integer'Last}, then
22334 the precondition should be regarded as False. If we are executing
22335 in a mode with run-time checks enabled for preconditions, then we would
22336 like this precondition to fail, rather than raising an exception
22337 because of the intermediate overflow.
22339 However, the language definition leaves the specification of
22340 whether the above condition fails (raising @code{Assert_Error}) or
22341 causes an intermediate overflow (raising @code{Constraint_Error})
22342 up to the implementation.
22344 The situation is worse in a case such as the following:
22349 procedure Q (A, B, C : Integer) with
22350 Pre => A + B + C <= Integer'Last;
22359 Q (A => Integer'Last, B => 1, C => -1);
22363 From a mathematical point of view the precondition
22364 is True, but at run time we may (but are not guaranteed to) get an
22365 exception raised because of the intermediate overflow (and we really
22366 would prefer this precondition to be considered True at run time).
22368 @node Management of Overflows in GNAT,Specifying the Desired Mode,Background,Overflow Check Handling in GNAT
22369 @anchor{gnat_ugn/gnat_and_program_execution management-of-overflows-in-gnat}@anchor{1bd}@anchor{gnat_ugn/gnat_and_program_execution id52}@anchor{1be}
22370 @subsection Management of Overflows in GNAT
22373 To deal with the portability issue, and with the problem of
22374 mathematical versus run-time interpretation of the expressions in
22375 assertions, GNAT provides comprehensive control over the handling
22376 of intermediate overflow. GNAT can operate in three modes, and
22377 furthemore, permits separate selection of operating modes for
22378 the expressions within assertions (here the term 'assertions'
22379 is used in the technical sense, which includes preconditions and so forth)
22380 and for expressions appearing outside assertions.
22382 The three modes are:
22388 @emph{Use base type for intermediate operations} (@code{STRICT})
22390 In this mode, all intermediate results for predefined arithmetic
22391 operators are computed using the base type, and the result must
22392 be in range of the base type. If this is not the
22393 case then either an exception is raised (if overflow checks are
22394 enabled) or the execution is erroneous (if overflow checks are suppressed).
22395 This is the normal default mode.
22398 @emph{Most intermediate overflows avoided} (@code{MINIMIZED})
22400 In this mode, the compiler attempts to avoid intermediate overflows by
22401 using a larger integer type, typically @code{Long_Long_Integer},
22402 as the type in which arithmetic is
22403 performed for predefined arithmetic operators. This may be slightly more
22405 run time (compared to suppressing intermediate overflow checks), though
22406 the cost is negligible on modern 64-bit machines. For the examples given
22407 earlier, no intermediate overflows would have resulted in exceptions,
22408 since the intermediate results are all in the range of
22409 @code{Long_Long_Integer} (typically 64-bits on nearly all implementations
22410 of GNAT). In addition, if checks are enabled, this reduces the number of
22411 checks that must be made, so this choice may actually result in an
22412 improvement in space and time behavior.
22414 However, there are cases where @code{Long_Long_Integer} is not large
22415 enough, consider the following example:
22420 procedure R (A, B, C, D : Integer) with
22421 Pre => (A**2 * B**2) / (C**2 * D**2) <= 10;
22425 where @code{A} = @code{B} = @code{C} = @code{D} = @code{Integer'Last}.
22426 Now the intermediate results are
22427 out of the range of @code{Long_Long_Integer} even though the final result
22428 is in range and the precondition is True (from a mathematical point
22429 of view). In such a case, operating in this mode, an overflow occurs
22430 for the intermediate computation (which is why this mode
22431 says @emph{most} intermediate overflows are avoided). In this case,
22432 an exception is raised if overflow checks are enabled, and the
22433 execution is erroneous if overflow checks are suppressed.
22436 @emph{All intermediate overflows avoided} (@code{ELIMINATED})
22438 In this mode, the compiler avoids all intermediate overflows
22439 by using arbitrary precision arithmetic as required. In this
22440 mode, the above example with @code{A**2 * B**2} would
22441 not cause intermediate overflow, because the intermediate result
22442 would be evaluated using sufficient precision, and the result
22443 of evaluating the precondition would be True.
22445 This mode has the advantage of avoiding any intermediate
22446 overflows, but at the expense of significant run-time overhead,
22447 including the use of a library (included automatically in this
22448 mode) for multiple-precision arithmetic.
22450 This mode provides cleaner semantics for assertions, since now
22451 the run-time behavior emulates true arithmetic behavior for the
22452 predefined arithmetic operators, meaning that there is never a
22453 conflict between the mathematical view of the assertion, and its
22456 Note that in this mode, the behavior is unaffected by whether or
22457 not overflow checks are suppressed, since overflow does not occur.
22458 It is possible for gigantic intermediate expressions to raise
22459 @code{Storage_Error} as a result of attempting to compute the
22460 results of such expressions (e.g. @code{Integer'Last ** Integer'Last})
22461 but overflow is impossible.
22464 Note that these modes apply only to the evaluation of predefined
22465 arithmetic, membership, and comparison operators for signed integer
22468 For fixed-point arithmetic, checks can be suppressed. But if checks
22470 then fixed-point values are always checked for overflow against the
22471 base type for intermediate expressions (that is such checks always
22472 operate in the equivalent of @code{STRICT} mode).
22474 For floating-point, on nearly all architectures, @code{Machine_Overflows}
22475 is False, and IEEE infinities are generated, so overflow exceptions
22476 are never raised. If you want to avoid infinities, and check that
22477 final results of expressions are in range, then you can declare a
22478 constrained floating-point type, and range checks will be carried
22479 out in the normal manner (with infinite values always failing all
22482 @node Specifying the Desired Mode,Default Settings,Management of Overflows in GNAT,Overflow Check Handling in GNAT
22483 @anchor{gnat_ugn/gnat_and_program_execution specifying-the-desired-mode}@anchor{f8}@anchor{gnat_ugn/gnat_and_program_execution id53}@anchor{1bf}
22484 @subsection Specifying the Desired Mode
22487 @geindex pragma Overflow_Mode
22489 The desired mode of for handling intermediate overflow can be specified using
22490 either the @code{Overflow_Mode} pragma or an equivalent compiler switch.
22491 The pragma has the form
22496 pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]);
22500 where @code{MODE} is one of
22506 @code{STRICT}: intermediate overflows checked (using base type)
22509 @code{MINIMIZED}: minimize intermediate overflows
22512 @code{ELIMINATED}: eliminate intermediate overflows
22515 The case is ignored, so @code{MINIMIZED}, @code{Minimized} and
22516 @code{minimized} all have the same effect.
22518 If only the @code{General} parameter is present, then the given @code{MODE} applies
22519 to expressions both within and outside assertions. If both arguments
22520 are present, then @code{General} applies to expressions outside assertions,
22521 and @code{Assertions} applies to expressions within assertions. For example:
22526 pragma Overflow_Mode
22527 (General => Minimized, Assertions => Eliminated);
22531 specifies that general expressions outside assertions be evaluated
22532 in 'minimize intermediate overflows' mode, and expressions within
22533 assertions be evaluated in 'eliminate intermediate overflows' mode.
22534 This is often a reasonable choice, avoiding excessive overhead
22535 outside assertions, but assuring a high degree of portability
22536 when importing code from another compiler, while incurring
22537 the extra overhead for assertion expressions to ensure that
22538 the behavior at run time matches the expected mathematical
22541 The @code{Overflow_Mode} pragma has the same scoping and placement
22542 rules as pragma @code{Suppress}, so it can occur either as a
22543 configuration pragma, specifying a default for the whole
22544 program, or in a declarative scope, where it applies to the
22545 remaining declarations and statements in that scope.
22547 Note that pragma @code{Overflow_Mode} does not affect whether
22548 overflow checks are enabled or suppressed. It only controls the
22549 method used to compute intermediate values. To control whether
22550 overflow checking is enabled or suppressed, use pragma @code{Suppress}
22551 or @code{Unsuppress} in the usual manner.
22553 @geindex -gnato? (gcc)
22555 @geindex -gnato?? (gcc)
22557 Additionally, a compiler switch @code{-gnato?} or @code{-gnato??}
22558 can be used to control the checking mode default (which can be subsequently
22559 overridden using pragmas).
22561 Here @code{?} is one of the digits @code{1} through @code{3}:
22566 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
22573 use base type for intermediate operations (@code{STRICT})
22581 minimize intermediate overflows (@code{MINIMIZED})
22589 eliminate intermediate overflows (@code{ELIMINATED})
22595 As with the pragma, if only one digit appears then it applies to all
22596 cases; if two digits are given, then the first applies outside
22597 assertions, and the second within assertions. Thus the equivalent
22598 of the example pragma above would be
22601 If no digits follow the @code{-gnato}, then it is equivalent to
22603 causing all intermediate operations to be computed using the base
22604 type (@code{STRICT} mode).
22606 @node Default Settings,Implementation Notes,Specifying the Desired Mode,Overflow Check Handling in GNAT
22607 @anchor{gnat_ugn/gnat_and_program_execution id54}@anchor{1c0}@anchor{gnat_ugn/gnat_and_program_execution default-settings}@anchor{1c1}
22608 @subsection Default Settings
22611 The default mode for overflow checks is
22620 which causes all computations both inside and outside assertions to use
22623 This retains compatibility with previous versions of
22624 GNAT which suppressed overflow checks by default and always
22625 used the base type for computation of intermediate results.
22627 @c Sphinx allows no emphasis within :index: role. As a workaround we
22628 @c point the index to "switch" and use emphasis for "-gnato".
22631 @geindex -gnato (gcc)
22632 switch @code{-gnato} (with no digits following)
22642 which causes overflow checking of all intermediate overflows
22643 both inside and outside assertions against the base type.
22645 The pragma @code{Suppress (Overflow_Check)} disables overflow
22646 checking, but it has no effect on the method used for computing
22647 intermediate results.
22649 The pragma @code{Unsuppress (Overflow_Check)} enables overflow
22650 checking, but it has no effect on the method used for computing
22651 intermediate results.
22653 @node Implementation Notes,,Default Settings,Overflow Check Handling in GNAT
22654 @anchor{gnat_ugn/gnat_and_program_execution id55}@anchor{1c2}@anchor{gnat_ugn/gnat_and_program_execution implementation-notes}@anchor{1c3}
22655 @subsection Implementation Notes
22658 In practice on typical 64-bit machines, the @code{MINIMIZED} mode is
22659 reasonably efficient, and can be generally used. It also helps
22660 to ensure compatibility with code imported from some other
22663 Setting all intermediate overflows checking (@code{CHECKED} mode)
22664 makes sense if you want to
22665 make sure that your code is compatible with any other possible
22666 Ada implementation. This may be useful in ensuring portability
22667 for code that is to be exported to some other compiler than GNAT.
22669 The Ada standard allows the reassociation of expressions at
22670 the same precedence level if no parentheses are present. For
22671 example, @code{A+B+C} parses as though it were @code{(A+B)+C}, but
22672 the compiler can reintepret this as @code{A+(B+C)}, possibly
22673 introducing or eliminating an overflow exception. The GNAT
22674 compiler never takes advantage of this freedom, and the
22675 expression @code{A+B+C} will be evaluated as @code{(A+B)+C}.
22676 If you need the other order, you can write the parentheses
22677 explicitly @code{A+(B+C)} and GNAT will respect this order.
22679 The use of @code{ELIMINATED} mode will cause the compiler to
22680 automatically include an appropriate arbitrary precision
22681 integer arithmetic package. The compiler will make calls
22682 to this package, though only in cases where it cannot be
22683 sure that @code{Long_Long_Integer} is sufficient to guard against
22684 intermediate overflows. This package does not use dynamic
22685 alllocation, but it does use the secondary stack, so an
22686 appropriate secondary stack package must be present (this
22687 is always true for standard full Ada, but may require
22688 specific steps for restricted run times such as ZFP).
22690 Although @code{ELIMINATED} mode causes expressions to use arbitrary
22691 precision arithmetic, avoiding overflow, the final result
22692 must be in an appropriate range. This is true even if the
22693 final result is of type @code{[Long_[Long_]]Integer'Base}, which
22694 still has the same bounds as its associated constrained
22697 Currently, the @code{ELIMINATED} mode is only available on target
22698 platforms for which @code{Long_Long_Integer} is 64-bits (nearly all GNAT
22701 @node Performing Dimensionality Analysis in GNAT,Stack Related Facilities,Overflow Check Handling in GNAT,GNAT and Program Execution
22702 @anchor{gnat_ugn/gnat_and_program_execution id56}@anchor{16a}@anchor{gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat}@anchor{28}
22703 @section Performing Dimensionality Analysis in GNAT
22706 @geindex Dimensionality analysis
22708 The GNAT compiler supports dimensionality checking. The user can
22709 specify physical units for objects, and the compiler will verify that uses
22710 of these objects are compatible with their dimensions, in a fashion that is
22711 familiar to engineering practice. The dimensions of algebraic expressions
22712 (including powers with static exponents) are computed from their constituents.
22714 @geindex Dimension_System aspect
22716 @geindex Dimension aspect
22718 This feature depends on Ada 2012 aspect specifications, and is available from
22719 version 7.0.1 of GNAT onwards.
22720 The GNAT-specific aspect @code{Dimension_System}
22721 allows you to define a system of units; the aspect @code{Dimension}
22722 then allows the user to declare dimensioned quantities within a given system.
22723 (These aspects are described in the @emph{Implementation Defined Aspects}
22724 chapter of the @emph{GNAT Reference Manual}).
22726 The major advantage of this model is that it does not require the declaration of
22727 multiple operators for all possible combinations of types: it is only necessary
22728 to use the proper subtypes in object declarations.
22730 @geindex System.Dim.Mks package (GNAT library)
22732 @geindex MKS_Type type
22734 The simplest way to impose dimensionality checking on a computation is to make
22735 use of one of the instantiations of the package @code{System.Dim.Generic_Mks}, which
22736 are part of the GNAT library. This generic package defines a floating-point
22737 type @code{MKS_Type}, for which a sequence of dimension names are specified,
22738 together with their conventional abbreviations. The following should be read
22739 together with the full specification of the package, in file
22740 @code{s-digemk.ads}.
22744 @geindex s-digemk.ads file
22747 type Mks_Type is new Float_Type
22749 Dimension_System => (
22750 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
22751 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
22752 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
22753 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
22754 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"),
22755 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
22756 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
22760 The package then defines a series of subtypes that correspond to these
22761 conventional units. For example:
22766 subtype Length is Mks_Type
22768 Dimension => (Symbol => 'm', Meter => 1, others => 0);
22772 and similarly for @code{Mass}, @code{Time}, @code{Electric_Current},
22773 @code{Thermodynamic_Temperature}, @code{Amount_Of_Substance}, and
22774 @code{Luminous_Intensity} (the standard set of units of the SI system).
22776 The package also defines conventional names for values of each unit, for
22782 m : constant Length := 1.0;
22783 kg : constant Mass := 1.0;
22784 s : constant Time := 1.0;
22785 A : constant Electric_Current := 1.0;
22789 as well as useful multiples of these units:
22794 cm : constant Length := 1.0E-02;
22795 g : constant Mass := 1.0E-03;
22796 min : constant Time := 60.0;
22797 day : constant Time := 60.0 * 24.0 * min;
22802 There are three instantiations of @code{System.Dim.Generic_Mks} defined in the
22809 @code{System.Dim.Float_Mks} based on @code{Float} defined in @code{s-diflmk.ads}.
22812 @code{System.Dim.Long_Mks} based on @code{Long_Float} defined in @code{s-dilomk.ads}.
22815 @code{System.Dim.Mks} based on @code{Long_Long_Float} defined in @code{s-dimmks.ads}.
22818 Using one of these packages, you can then define a derived unit by providing
22819 the aspect that specifies its dimensions within the MKS system, as well as the
22820 string to be used for output of a value of that unit:
22825 subtype Acceleration is Mks_Type
22826 with Dimension => ("m/sec^2",
22833 Here is a complete example of use:
22838 with System.Dim.MKS; use System.Dim.Mks;
22839 with System.Dim.Mks_IO; use System.Dim.Mks_IO;
22840 with Text_IO; use Text_IO;
22841 procedure Free_Fall is
22842 subtype Acceleration is Mks_Type
22843 with Dimension => ("m/sec^2", 1, 0, -2, others => 0);
22844 G : constant acceleration := 9.81 * m / (s ** 2);
22845 T : Time := 10.0*s;
22849 Put ("Gravitational constant: ");
22850 Put (G, Aft => 2, Exp => 0); Put_Line ("");
22851 Distance := 0.5 * G * T ** 2;
22852 Put ("distance travelled in 10 seconds of free fall ");
22853 Put (Distance, Aft => 2, Exp => 0);
22859 Execution of this program yields:
22864 Gravitational constant: 9.81 m/sec^2
22865 distance travelled in 10 seconds of free fall 490.50 m
22869 However, incorrect assignments such as:
22875 Distance := 5.0 * kg;
22879 are rejected with the following diagnoses:
22885 >>> dimensions mismatch in assignment
22886 >>> left-hand side has dimension [L]
22887 >>> right-hand side is dimensionless
22889 Distance := 5.0 * kg:
22890 >>> dimensions mismatch in assignment
22891 >>> left-hand side has dimension [L]
22892 >>> right-hand side has dimension [M]
22896 The dimensions of an expression are properly displayed, even if there is
22897 no explicit subtype for it. If we add to the program:
22902 Put ("Final velocity: ");
22903 Put (G * T, Aft =>2, Exp =>0);
22908 then the output includes:
22913 Final velocity: 98.10 m.s**(-1)
22916 @geindex Dimensionable type
22918 @geindex Dimensioned subtype
22921 The type @code{Mks_Type} is said to be a @emph{dimensionable type} since it has a
22922 @code{Dimension_System} aspect, and the subtypes @code{Length}, @code{Mass}, etc.,
22923 are said to be @emph{dimensioned subtypes} since each one has a @code{Dimension}
22928 @geindex Dimension Vector (for a dimensioned subtype)
22930 @geindex Dimension aspect
22932 @geindex Dimension_System aspect
22935 The @code{Dimension} aspect of a dimensioned subtype @code{S} defines a mapping
22936 from the base type's Unit_Names to integer (or, more generally, rational)
22937 values. This mapping is the @emph{dimension vector} (also referred to as the
22938 @emph{dimensionality}) for that subtype, denoted by @code{DV(S)}, and thus for each
22939 object of that subtype. Intuitively, the value specified for each
22940 @code{Unit_Name} is the exponent associated with that unit; a zero value
22941 means that the unit is not used. For example:
22947 Acc : Acceleration;
22955 Here @code{DV(Acc)} = @code{DV(Acceleration)} =
22956 @code{(Meter=>1, Kilogram=>0, Second=>-2, Ampere=>0, Kelvin=>0, Mole=>0, Candela=>0)}.
22957 Symbolically, we can express this as @code{Meter / Second**2}.
22959 The dimension vector of an arithmetic expression is synthesized from the
22960 dimension vectors of its components, with compile-time dimensionality checks
22961 that help prevent mismatches such as using an @code{Acceleration} where a
22962 @code{Length} is required.
22964 The dimension vector of the result of an arithmetic expression @emph{expr}, or
22965 @code{DV(@emph{expr})}, is defined as follows, assuming conventional
22966 mathematical definitions for the vector operations that are used:
22972 If @emph{expr} is of the type @emph{universal_real}, or is not of a dimensioned subtype,
22973 then @emph{expr} is dimensionless; @code{DV(@emph{expr})} is the empty vector.
22976 @code{DV(@emph{op expr})}, where @emph{op} is a unary operator, is @code{DV(@emph{expr})}
22979 @code{DV(@emph{expr1 op expr2})} where @emph{op} is "+" or "-" is @code{DV(@emph{expr1})}
22980 provided that @code{DV(@emph{expr1})} = @code{DV(@emph{expr2})}.
22981 If this condition is not met then the construct is illegal.
22984 @code{DV(@emph{expr1} * @emph{expr2})} is @code{DV(@emph{expr1})} + @code{DV(@emph{expr2})},
22985 and @code{DV(@emph{expr1} / @emph{expr2})} = @code{DV(@emph{expr1})} - @code{DV(@emph{expr2})}.
22986 In this context if one of the @emph{expr}s is dimensionless then its empty
22987 dimension vector is treated as @code{(others => 0)}.
22990 @code{DV(@emph{expr} ** @emph{power})} is @emph{power} * @code{DV(@emph{expr})},
22991 provided that @emph{power} is a static rational value. If this condition is not
22992 met then the construct is illegal.
22995 Note that, by the above rules, it is illegal to use binary "+" or "-" to
22996 combine a dimensioned and dimensionless value. Thus an expression such as
22997 @code{acc-10.0} is illegal, where @code{acc} is an object of subtype
22998 @code{Acceleration}.
23000 The dimensionality checks for relationals use the same rules as
23001 for "+" and "-", except when comparing to a literal; thus
23019 and is thus illegal, but
23028 is accepted with a warning. Analogously a conditional expression requires the
23029 same dimension vector for each branch (with no exception for literals).
23031 The dimension vector of a type conversion @code{T(@emph{expr})} is defined
23032 as follows, based on the nature of @code{T}:
23038 If @code{T} is a dimensioned subtype then @code{DV(T(@emph{expr}))} is @code{DV(T)}
23039 provided that either @emph{expr} is dimensionless or
23040 @code{DV(T)} = @code{DV(@emph{expr})}. The conversion is illegal
23041 if @emph{expr} is dimensioned and @code{DV(@emph{expr})} /= @code{DV(T)}.
23042 Note that vector equality does not require that the corresponding
23043 Unit_Names be the same.
23045 As a consequence of the above rule, it is possible to convert between
23046 different dimension systems that follow the same international system
23047 of units, with the seven physical components given in the standard order
23048 (length, mass, time, etc.). Thus a length in meters can be converted to
23049 a length in inches (with a suitable conversion factor) but cannot be
23050 converted, for example, to a mass in pounds.
23053 If @code{T} is the base type for @emph{expr} (and the dimensionless root type of
23054 the dimension system), then @code{DV(T(@emph{expr}))} is @code{DV(expr)}.
23055 Thus, if @emph{expr} is of a dimensioned subtype of @code{T}, the conversion may
23056 be regarded as a "view conversion" that preserves dimensionality.
23058 This rule makes it possible to write generic code that can be instantiated
23059 with compatible dimensioned subtypes. The generic unit will contain
23060 conversions that will consequently be present in instantiations, but
23061 conversions to the base type will preserve dimensionality and make it
23062 possible to write generic code that is correct with respect to
23066 Otherwise (i.e., @code{T} is neither a dimensioned subtype nor a dimensionable
23067 base type), @code{DV(T(@emph{expr}))} is the empty vector. Thus a dimensioned
23068 value can be explicitly converted to a non-dimensioned subtype, which
23069 of course then escapes dimensionality analysis.
23072 The dimension vector for a type qualification @code{T'(@emph{expr})} is the same
23073 as for the type conversion @code{T(@emph{expr})}.
23075 An assignment statement
23084 requires @code{DV(Source)} = @code{DV(Target)}, and analogously for parameter
23085 passing (the dimension vector for the actual parameter must be equal to the
23086 dimension vector for the formal parameter).
23088 @node Stack Related Facilities,Memory Management Issues,Performing Dimensionality Analysis in GNAT,GNAT and Program Execution
23089 @anchor{gnat_ugn/gnat_and_program_execution id57}@anchor{16b}@anchor{gnat_ugn/gnat_and_program_execution stack-related-facilities}@anchor{29}
23090 @section Stack Related Facilities
23093 This section describes some useful tools associated with stack
23094 checking and analysis. In
23095 particular, it deals with dynamic and static stack usage measurements.
23098 * Stack Overflow Checking::
23099 * Static Stack Usage Analysis::
23100 * Dynamic Stack Usage Analysis::
23104 @node Stack Overflow Checking,Static Stack Usage Analysis,,Stack Related Facilities
23105 @anchor{gnat_ugn/gnat_and_program_execution id58}@anchor{1c4}@anchor{gnat_ugn/gnat_and_program_execution stack-overflow-checking}@anchor{f4}
23106 @subsection Stack Overflow Checking
23109 @geindex Stack Overflow Checking
23111 @geindex -fstack-check (gcc)
23113 For most operating systems, @code{gcc} does not perform stack overflow
23114 checking by default. This means that if the main environment task or
23115 some other task exceeds the available stack space, then unpredictable
23116 behavior will occur. Most native systems offer some level of protection by
23117 adding a guard page at the end of each task stack. This mechanism is usually
23118 not enough for dealing properly with stack overflow situations because
23119 a large local variable could "jump" above the guard page.
23120 Furthermore, when the
23121 guard page is hit, there may not be any space left on the stack for executing
23122 the exception propagation code. Enabling stack checking avoids
23125 To activate stack checking, compile all units with the @code{gcc} option
23126 @code{-fstack-check}. For example:
23131 $ gcc -c -fstack-check package1.adb
23135 Units compiled with this option will generate extra instructions to check
23136 that any use of the stack (for procedure calls or for declaring local
23137 variables in declare blocks) does not exceed the available stack space.
23138 If the space is exceeded, then a @code{Storage_Error} exception is raised.
23140 For declared tasks, the default stack size is defined by the GNAT runtime,
23141 whose size may be modified at bind time through the @code{-d} bind switch
23142 (@ref{11f,,Switches for gnatbind}). Task specific stack sizes may be set using the
23143 @code{Storage_Size} pragma.
23145 For the environment task, the stack size is determined by the operating system.
23146 Consequently, to modify the size of the environment task please refer to your
23147 operating system documentation.
23149 @node Static Stack Usage Analysis,Dynamic Stack Usage Analysis,Stack Overflow Checking,Stack Related Facilities
23150 @anchor{gnat_ugn/gnat_and_program_execution static-stack-usage-analysis}@anchor{f5}@anchor{gnat_ugn/gnat_and_program_execution id59}@anchor{1c5}
23151 @subsection Static Stack Usage Analysis
23154 @geindex Static Stack Usage Analysis
23156 @geindex -fstack-usage
23158 A unit compiled with @code{-fstack-usage} will generate an extra file
23160 the maximum amount of stack used, on a per-function basis.
23161 The file has the same
23162 basename as the target object file with a @code{.su} extension.
23163 Each line of this file is made up of three fields:
23169 The name of the function.
23175 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
23178 The second field corresponds to the size of the known part of the function
23181 The qualifier @code{static} means that the function frame size
23183 It usually means that all local variables have a static size.
23184 In this case, the second field is a reliable measure of the function stack
23187 The qualifier @code{dynamic} means that the function frame size is not static.
23188 It happens mainly when some local variables have a dynamic size. When this
23189 qualifier appears alone, the second field is not a reliable measure
23190 of the function stack analysis. When it is qualified with @code{bounded}, it
23191 means that the second field is a reliable maximum of the function stack
23194 A unit compiled with @code{-Wstack-usage} will issue a warning for each
23195 subprogram whose stack usage might be larger than the specified amount of
23196 bytes. The wording is in keeping with the qualifier documented above.
23198 @node Dynamic Stack Usage Analysis,,Static Stack Usage Analysis,Stack Related Facilities
23199 @anchor{gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis}@anchor{122}@anchor{gnat_ugn/gnat_and_program_execution id60}@anchor{1c6}
23200 @subsection Dynamic Stack Usage Analysis
23203 It is possible to measure the maximum amount of stack used by a task, by
23204 adding a switch to @code{gnatbind}, as:
23209 $ gnatbind -u0 file
23213 With this option, at each task termination, its stack usage is output on
23215 It is not always convenient to output the stack usage when the program
23216 is still running. Hence, it is possible to delay this output until program
23217 termination. for a given number of tasks specified as the argument of the
23218 @code{-u} option. For instance:
23223 $ gnatbind -u100 file
23227 will buffer the stack usage information of the first 100 tasks to terminate and
23228 output this info at program termination. Results are displayed in four
23234 Index | Task Name | Stack Size | Stack Usage
23244 @emph{Index} is a number associated with each task.
23247 @emph{Task Name} is the name of the task analyzed.
23250 @emph{Stack Size} is the maximum size for the stack.
23253 @emph{Stack Usage} is the measure done by the stack analyzer.
23254 In order to prevent overflow, the stack
23255 is not entirely analyzed, and it's not possible to know exactly how
23256 much has actually been used.
23259 By default the environment task stack, the stack that contains the main unit,
23260 is not processed. To enable processing of the environment task stack, the
23261 environment variable GNAT_STACK_LIMIT needs to be set to the maximum size of
23262 the environment task stack. This amount is given in kilobytes. For example:
23267 $ set GNAT_STACK_LIMIT 1600
23271 would specify to the analyzer that the environment task stack has a limit
23272 of 1.6 megabytes. Any stack usage beyond this will be ignored by the analysis.
23274 The package @code{GNAT.Task_Stack_Usage} provides facilities to get
23275 stack-usage reports at run time. See its body for the details.
23277 @node Memory Management Issues,,Stack Related Facilities,GNAT and Program Execution
23278 @anchor{gnat_ugn/gnat_and_program_execution id61}@anchor{16c}@anchor{gnat_ugn/gnat_and_program_execution memory-management-issues}@anchor{2a}
23279 @section Memory Management Issues
23282 This section describes some useful memory pools provided in the GNAT library
23283 and in particular the GNAT Debug Pool facility, which can be used to detect
23284 incorrect uses of access values (including 'dangling references').
23288 * Some Useful Memory Pools::
23289 * The GNAT Debug Pool Facility::
23293 @node Some Useful Memory Pools,The GNAT Debug Pool Facility,,Memory Management Issues
23294 @anchor{gnat_ugn/gnat_and_program_execution id62}@anchor{1c7}@anchor{gnat_ugn/gnat_and_program_execution some-useful-memory-pools}@anchor{1c8}
23295 @subsection Some Useful Memory Pools
23298 @geindex Memory Pool
23303 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
23304 storage pool. Allocations use the standard system call @code{malloc} while
23305 deallocations use the standard system call @code{free}. No reclamation is
23306 performed when the pool goes out of scope. For performance reasons, the
23307 standard default Ada allocators/deallocators do not use any explicit storage
23308 pools but if they did, they could use this storage pool without any change in
23309 behavior. That is why this storage pool is used when the user
23310 manages to make the default implicit allocator explicit as in this example:
23315 type T1 is access Something;
23316 -- no Storage pool is defined for T2
23318 type T2 is access Something_Else;
23319 for T2'Storage_Pool use T1'Storage_Pool;
23320 -- the above is equivalent to
23321 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
23325 The @code{System.Pool_Local} package offers the @code{Unbounded_Reclaim_Pool} storage
23326 pool. The allocation strategy is similar to @code{Pool_Local}
23327 except that the all
23328 storage allocated with this pool is reclaimed when the pool object goes out of
23329 scope. This pool provides a explicit mechanism similar to the implicit one
23330 provided by several Ada 83 compilers for allocations performed through a local
23331 access type and whose purpose was to reclaim memory when exiting the
23332 scope of a given local access. As an example, the following program does not
23333 leak memory even though it does not perform explicit deallocation:
23338 with System.Pool_Local;
23339 procedure Pooloc1 is
23340 procedure Internal is
23341 type A is access Integer;
23342 X : System.Pool_Local.Unbounded_Reclaim_Pool;
23343 for A'Storage_Pool use X;
23346 for I in 1 .. 50 loop
23351 for I in 1 .. 100 loop
23358 The @code{System.Pool_Size} package implements the @code{Stack_Bounded_Pool} used when
23359 @code{Storage_Size} is specified for an access type.
23360 The whole storage for the pool is
23361 allocated at once, usually on the stack at the point where the access type is
23362 elaborated. It is automatically reclaimed when exiting the scope where the
23363 access type is defined. This package is not intended to be used directly by the
23364 user and it is implicitly used for each such declaration:
23369 type T1 is access Something;
23370 for T1'Storage_Size use 10_000;
23374 @node The GNAT Debug Pool Facility,,Some Useful Memory Pools,Memory Management Issues
23375 @anchor{gnat_ugn/gnat_and_program_execution id63}@anchor{1c9}@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility}@anchor{1ca}
23376 @subsection The GNAT Debug Pool Facility
23379 @geindex Debug Pool
23383 @geindex memory corruption
23385 The use of unchecked deallocation and unchecked conversion can easily
23386 lead to incorrect memory references. The problems generated by such
23387 references are usually difficult to tackle because the symptoms can be
23388 very remote from the origin of the problem. In such cases, it is
23389 very helpful to detect the problem as early as possible. This is the
23390 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
23392 In order to use the GNAT specific debugging pool, the user must
23393 associate a debug pool object with each of the access types that may be
23394 related to suspected memory problems. See Ada Reference Manual 13.11.
23399 type Ptr is access Some_Type;
23400 Pool : GNAT.Debug_Pools.Debug_Pool;
23401 for Ptr'Storage_Pool use Pool;
23405 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
23406 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
23407 allow the user to redefine allocation and deallocation strategies. They
23408 also provide a checkpoint for each dereference, through the use of
23409 the primitive operation @code{Dereference} which is implicitly called at
23410 each dereference of an access value.
23412 Once an access type has been associated with a debug pool, operations on
23413 values of the type may raise four distinct exceptions,
23414 which correspond to four potential kinds of memory corruption:
23420 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
23423 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
23426 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
23429 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage}
23432 For types associated with a Debug_Pool, dynamic allocation is performed using
23433 the standard GNAT allocation routine. References to all allocated chunks of
23434 memory are kept in an internal dictionary. Several deallocation strategies are
23435 provided, whereupon the user can choose to release the memory to the system,
23436 keep it allocated for further invalid access checks, or fill it with an easily
23437 recognizable pattern for debug sessions. The memory pattern is the old IBM
23438 hexadecimal convention: @code{16#DEADBEEF#}.
23440 See the documentation in the file g-debpoo.ads for more information on the
23441 various strategies.
23443 Upon each dereference, a check is made that the access value denotes a
23444 properly allocated memory location. Here is a complete example of use of
23445 @code{Debug_Pools}, that includes typical instances of memory corruption:
23450 with Gnat.Io; use Gnat.Io;
23451 with Unchecked_Deallocation;
23452 with Unchecked_Conversion;
23453 with GNAT.Debug_Pools;
23454 with System.Storage_Elements;
23455 with Ada.Exceptions; use Ada.Exceptions;
23456 procedure Debug_Pool_Test is
23458 type T is access Integer;
23459 type U is access all T;
23461 P : GNAT.Debug_Pools.Debug_Pool;
23462 for T'Storage_Pool use P;
23464 procedure Free is new Unchecked_Deallocation (Integer, T);
23465 function UC is new Unchecked_Conversion (U, T);
23468 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
23478 Put_Line (Integer'Image(B.all));
23480 when E : others => Put_Line ("raised: " & Exception_Name (E));
23485 when E : others => Put_Line ("raised: " & Exception_Name (E));
23489 Put_Line (Integer'Image(B.all));
23491 when E : others => Put_Line ("raised: " & Exception_Name (E));
23496 when E : others => Put_Line ("raised: " & Exception_Name (E));
23499 end Debug_Pool_Test;
23503 The debug pool mechanism provides the following precise diagnostics on the
23504 execution of this erroneous program:
23510 Total allocated bytes : 0
23511 Total deallocated bytes : 0
23512 Current Water Mark: 0
23516 Total allocated bytes : 8
23517 Total deallocated bytes : 0
23518 Current Water Mark: 8
23521 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
23522 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
23523 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
23524 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
23526 Total allocated bytes : 8
23527 Total deallocated bytes : 4
23528 Current Water Mark: 4
23534 @c -- Non-breaking space in running text
23535 @c -- E.g. Ada |nbsp| 95
23537 @node Platform-Specific Information,Example of Binder Output File,GNAT and Program Execution,Top
23538 @anchor{gnat_ugn/platform_specific_information platform-specific-information}@anchor{d}@anchor{gnat_ugn/platform_specific_information doc}@anchor{1cb}@anchor{gnat_ugn/platform_specific_information id1}@anchor{1cc}
23539 @chapter Platform-Specific Information
23542 This appendix contains information relating to the implementation
23543 of run-time libraries on various platforms and also covers
23544 topics related to the GNAT implementation on Windows and Mac OS.
23547 * Run-Time Libraries::
23548 * Specifying a Run-Time Library::
23549 * GNU/Linux Topics::
23550 * Microsoft Windows Topics::
23555 @node Run-Time Libraries,Specifying a Run-Time Library,,Platform-Specific Information
23556 @anchor{gnat_ugn/platform_specific_information id2}@anchor{1cd}@anchor{gnat_ugn/platform_specific_information run-time-libraries}@anchor{2b}
23557 @section Run-Time Libraries
23560 @geindex Tasking and threads libraries
23562 @geindex Threads libraries and tasking
23564 @geindex Run-time libraries (platform-specific information)
23566 The GNAT run-time implementation may vary with respect to both the
23567 underlying threads library and the exception-handling scheme.
23568 For threads support, the default run-time will bind to the thread
23569 package of the underlying operating system.
23571 For exception handling, either or both of two models are supplied:
23575 @geindex Zero-Cost Exceptions
23577 @geindex ZCX (Zero-Cost Exceptions)
23584 @strong{Zero-Cost Exceptions} ("ZCX"),
23585 which uses binder-generated tables that
23586 are interrogated at run time to locate a handler.
23588 @geindex setjmp/longjmp Exception Model
23590 @geindex SJLJ (setjmp/longjmp Exception Model)
23593 @strong{setjmp / longjmp} ('SJLJ'),
23594 which uses dynamically-set data to establish
23595 the set of handlers
23598 Most programs should experience a substantial speed improvement by
23599 being compiled with a ZCX run-time.
23600 This is especially true for
23601 tasking applications or applications with many exception handlers.
23602 Note however that the ZCX run-time does not support asynchronous abort
23603 of tasks (@code{abort} and @code{select-then-abort} constructs) and will instead
23604 implement abort by polling points in the runtime. You can also add additional
23605 polling points explicitly if needed in your application via @code{pragma
23608 This section summarizes which combinations of threads and exception support
23609 are supplied on various GNAT platforms.
23612 * Summary of Run-Time Configurations::
23616 @node Summary of Run-Time Configurations,,,Run-Time Libraries
23617 @anchor{gnat_ugn/platform_specific_information summary-of-run-time-configurations}@anchor{1ce}@anchor{gnat_ugn/platform_specific_information id3}@anchor{1cf}
23618 @subsection Summary of Run-Time Configurations
23622 @multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx}
23679 native Win32 threads
23691 native Win32 threads
23716 @node Specifying a Run-Time Library,GNU/Linux Topics,Run-Time Libraries,Platform-Specific Information
23717 @anchor{gnat_ugn/platform_specific_information specifying-a-run-time-library}@anchor{1d0}@anchor{gnat_ugn/platform_specific_information id4}@anchor{1d1}
23718 @section Specifying a Run-Time Library
23721 The @code{adainclude} subdirectory containing the sources of the GNAT
23722 run-time library, and the @code{adalib} subdirectory containing the
23723 @code{ALI} files and the static and/or shared GNAT library, are located
23724 in the gcc target-dependent area:
23729 target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/
23733 As indicated above, on some platforms several run-time libraries are supplied.
23734 These libraries are installed in the target dependent area and
23735 contain a complete source and binary subdirectory. The detailed description
23736 below explains the differences between the different libraries in terms of
23737 their thread support.
23739 The default run-time library (when GNAT is installed) is @emph{rts-native}.
23740 This default run-time is selected by the means of soft links.
23741 For example on x86-linux:
23744 @c -- $(target-dir)
23746 @c -- +--- adainclude----------+
23748 @c -- +--- adalib-----------+ |
23750 @c -- +--- rts-native | |
23752 @c -- | +--- adainclude <---+
23754 @c -- | +--- adalib <----+
23756 @c -- +--- rts-sjlj
23758 @c -- +--- adainclude
23766 _______/ / \ \_________________
23769 ADAINCLUDE ADALIB rts-native rts-sjlj
23774 +-------------> adainclude adalib adainclude adalib
23777 +---------------------+
23779 Run-Time Library Directory Structure
23780 (Upper-case names and dotted/dashed arrows represent soft links)
23783 If the @emph{rts-sjlj} library is to be selected on a permanent basis,
23784 these soft links can be modified with the following commands:
23790 $ rm -f adainclude adalib
23791 $ ln -s rts-sjlj/adainclude adainclude
23792 $ ln -s rts-sjlj/adalib adalib
23796 Alternatively, you can specify @code{rts-sjlj/adainclude} in the file
23797 @code{$target/ada_source_path} and @code{rts-sjlj/adalib} in
23798 @code{$target/ada_object_path}.
23800 @geindex --RTS option
23802 Selecting another run-time library temporarily can be
23803 achieved by using the @code{--RTS} switch, e.g., @code{--RTS=sjlj}
23804 @anchor{gnat_ugn/platform_specific_information choosing-the-scheduling-policy}@anchor{1d2}
23805 @geindex SCHED_FIFO scheduling policy
23807 @geindex SCHED_RR scheduling policy
23809 @geindex SCHED_OTHER scheduling policy
23812 * Choosing the Scheduling Policy::
23816 @node Choosing the Scheduling Policy,,,Specifying a Run-Time Library
23817 @anchor{gnat_ugn/platform_specific_information id5}@anchor{1d3}
23818 @subsection Choosing the Scheduling Policy
23821 When using a POSIX threads implementation, you have a choice of several
23822 scheduling policies: @code{SCHED_FIFO}, @code{SCHED_RR} and @code{SCHED_OTHER}.
23824 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
23825 or @code{SCHED_RR} requires special (e.g., root) privileges.
23827 @geindex pragma Time_Slice
23829 @geindex -T0 option
23831 @geindex pragma Task_Dispatching_Policy
23833 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
23835 you can use one of the following:
23841 @code{pragma Time_Slice (0.0)}
23844 the corresponding binder option @code{-T0}
23847 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
23850 To specify @code{SCHED_RR},
23851 you should use @code{pragma Time_Slice} with a
23852 value greater than 0.0, or else use the corresponding @code{-T}
23855 To make sure a program is running as root, you can put something like
23856 this in a library package body in your application:
23861 function geteuid return Integer;
23862 pragma Import (C, geteuid, "geteuid");
23863 Ignore : constant Boolean :=
23864 (if geteuid = 0 then True else raise Program_Error with "must be root");
23868 It gets the effective user id, and if it's not 0 (i.e. root), it raises
23875 @node GNU/Linux Topics,Microsoft Windows Topics,Specifying a Run-Time Library,Platform-Specific Information
23876 @anchor{gnat_ugn/platform_specific_information id6}@anchor{1d4}@anchor{gnat_ugn/platform_specific_information gnu-linux-topics}@anchor{1d5}
23877 @section GNU/Linux Topics
23880 This section describes topics that are specific to GNU/Linux platforms.
23883 * Required Packages on GNU/Linux::
23887 @node Required Packages on GNU/Linux,,,GNU/Linux Topics
23888 @anchor{gnat_ugn/platform_specific_information id7}@anchor{1d6}@anchor{gnat_ugn/platform_specific_information required-packages-on-gnu-linux}@anchor{1d7}
23889 @subsection Required Packages on GNU/Linux
23892 GNAT requires the C library developer's package to be installed.
23893 The name of of that package depends on your GNU/Linux distribution:
23899 RedHat, SUSE: @code{glibc-devel};
23902 Debian, Ubuntu: @code{libc6-dev} (normally installed by default).
23905 If using the 32-bit version of GNAT on a 64-bit version of GNU/Linux,
23906 you'll need the 32-bit version of the following packages:
23912 RedHat, SUSE: @code{glibc.i686}, @code{glibc-devel.i686}, @code{ncurses-libs.i686}
23915 Debian, Ubuntu: @code{libc6:i386}, @code{libc6-dev:i386}, @code{lib32ncursesw5}
23918 Other GNU/Linux distributions might be choosing a different name
23919 for those packages.
23923 @node Microsoft Windows Topics,Mac OS Topics,GNU/Linux Topics,Platform-Specific Information
23924 @anchor{gnat_ugn/platform_specific_information microsoft-windows-topics}@anchor{2c}@anchor{gnat_ugn/platform_specific_information id8}@anchor{1d8}
23925 @section Microsoft Windows Topics
23928 This section describes topics that are specific to the Microsoft Windows
23933 * Using GNAT on Windows::
23934 * Using a network installation of GNAT::
23935 * CONSOLE and WINDOWS subsystems::
23936 * Temporary Files::
23937 * Disabling Command Line Argument Expansion::
23938 * Windows Socket Timeouts::
23939 * Mixed-Language Programming on Windows::
23940 * Windows Specific Add-Ons::
23944 @node Using GNAT on Windows,Using a network installation of GNAT,,Microsoft Windows Topics
23945 @anchor{gnat_ugn/platform_specific_information using-gnat-on-windows}@anchor{1d9}@anchor{gnat_ugn/platform_specific_information id9}@anchor{1da}
23946 @subsection Using GNAT on Windows
23949 One of the strengths of the GNAT technology is that its tool set
23950 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
23951 @code{gdb} debugger, etc.) is used in the same way regardless of the
23954 On Windows this tool set is complemented by a number of Microsoft-specific
23955 tools that have been provided to facilitate interoperability with Windows
23956 when this is required. With these tools:
23962 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
23966 You can use any Dynamically Linked Library (DLL) in your Ada code (both
23967 relocatable and non-relocatable DLLs are supported).
23970 You can build Ada DLLs for use in other applications. These applications
23971 can be written in a language other than Ada (e.g., C, C++, etc). Again both
23972 relocatable and non-relocatable Ada DLLs are supported.
23975 You can include Windows resources in your Ada application.
23978 You can use or create COM/DCOM objects.
23981 Immediately below are listed all known general GNAT-for-Windows restrictions.
23982 Other restrictions about specific features like Windows Resources and DLLs
23983 are listed in separate sections below.
23989 It is not possible to use @code{GetLastError} and @code{SetLastError}
23990 when tasking, protected records, or exceptions are used. In these
23991 cases, in order to implement Ada semantics, the GNAT run-time system
23992 calls certain Win32 routines that set the last error variable to 0 upon
23993 success. It should be possible to use @code{GetLastError} and
23994 @code{SetLastError} when tasking, protected record, and exception
23995 features are not used, but it is not guaranteed to work.
23998 It is not possible to link against Microsoft C++ libraries except for
23999 import libraries. Interfacing must be done by the mean of DLLs.
24002 It is possible to link against Microsoft C libraries. Yet the preferred
24003 solution is to use C/C++ compiler that comes with GNAT, since it
24004 doesn't require having two different development environments and makes the
24005 inter-language debugging experience smoother.
24008 When the compilation environment is located on FAT32 drives, users may
24009 experience recompilations of the source files that have not changed if
24010 Daylight Saving Time (DST) state has changed since the last time files
24011 were compiled. NTFS drives do not have this problem.
24014 No components of the GNAT toolset use any entries in the Windows
24015 registry. The only entries that can be created are file associations and
24016 PATH settings, provided the user has chosen to create them at installation
24017 time, as well as some minimal book-keeping information needed to correctly
24018 uninstall or integrate different GNAT products.
24021 @node Using a network installation of GNAT,CONSOLE and WINDOWS subsystems,Using GNAT on Windows,Microsoft Windows Topics
24022 @anchor{gnat_ugn/platform_specific_information id10}@anchor{1db}@anchor{gnat_ugn/platform_specific_information using-a-network-installation-of-gnat}@anchor{1dc}
24023 @subsection Using a network installation of GNAT
24026 Make sure the system on which GNAT is installed is accessible from the
24027 current machine, i.e., the install location is shared over the network.
24028 Shared resources are accessed on Windows by means of UNC paths, which
24029 have the format @code{\\\\server\\sharename\\path}
24031 In order to use such a network installation, simply add the UNC path of the
24032 @code{bin} directory of your GNAT installation in front of your PATH. For
24033 example, if GNAT is installed in @code{\GNAT} directory of a share location
24034 called @code{c-drive} on a machine @code{LOKI}, the following command will
24040 $ path \\loki\c-drive\gnat\bin;%path%`
24044 Be aware that every compilation using the network installation results in the
24045 transfer of large amounts of data across the network and will likely cause
24046 serious performance penalty.
24048 @node CONSOLE and WINDOWS subsystems,Temporary Files,Using a network installation of GNAT,Microsoft Windows Topics
24049 @anchor{gnat_ugn/platform_specific_information id11}@anchor{1dd}@anchor{gnat_ugn/platform_specific_information console-and-windows-subsystems}@anchor{1de}
24050 @subsection CONSOLE and WINDOWS subsystems
24053 @geindex CONSOLE Subsystem
24055 @geindex WINDOWS Subsystem
24059 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
24060 (which is the default subsystem) will always create a console when
24061 launching the application. This is not something desirable when the
24062 application has a Windows GUI. To get rid of this console the
24063 application must be using the @code{WINDOWS} subsystem. To do so
24064 the @code{-mwindows} linker option must be specified.
24069 $ gnatmake winprog -largs -mwindows
24073 @node Temporary Files,Disabling Command Line Argument Expansion,CONSOLE and WINDOWS subsystems,Microsoft Windows Topics
24074 @anchor{gnat_ugn/platform_specific_information id12}@anchor{1df}@anchor{gnat_ugn/platform_specific_information temporary-files}@anchor{1e0}
24075 @subsection Temporary Files
24078 @geindex Temporary files
24080 It is possible to control where temporary files gets created by setting
24083 @geindex environment variable; TMP
24084 @code{TMP} environment variable. The file will be created:
24090 Under the directory pointed to by the
24092 @geindex environment variable; TMP
24093 @code{TMP} environment variable if
24094 this directory exists.
24097 Under @code{c:\temp}, if the
24099 @geindex environment variable; TMP
24100 @code{TMP} environment variable is not
24101 set (or not pointing to a directory) and if this directory exists.
24104 Under the current working directory otherwise.
24107 This allows you to determine exactly where the temporary
24108 file will be created. This is particularly useful in networked
24109 environments where you may not have write access to some
24112 @node Disabling Command Line Argument Expansion,Windows Socket Timeouts,Temporary Files,Microsoft Windows Topics
24113 @anchor{gnat_ugn/platform_specific_information disabling-command-line-argument-expansion}@anchor{1e1}
24114 @subsection Disabling Command Line Argument Expansion
24117 @geindex Command Line Argument Expansion
24119 By default, an executable compiled for the Windows platform will do
24120 the following postprocessing on the arguments passed on the command
24127 If the argument contains the characters @code{*} and/or @code{?}, then
24128 file expansion will be attempted. For example, if the current directory
24129 contains @code{a.txt} and @code{b.txt}, then when calling:
24132 $ my_ada_program *.txt
24135 The following arguments will effectively be passed to the main program
24136 (for example when using @code{Ada.Command_Line.Argument}):
24139 Ada.Command_Line.Argument (1) -> "a.txt"
24140 Ada.Command_Line.Argument (2) -> "b.txt"
24144 Filename expansion can be disabled for a given argument by using single
24145 quotes. Thus, calling:
24148 $ my_ada_program '*.txt'
24154 Ada.Command_Line.Argument (1) -> "*.txt"
24158 Note that if the program is launched from a shell such as Cygwin Bash
24159 then quote removal might be performed by the shell.
24161 In some contexts it might be useful to disable this feature (for example if
24162 the program performs its own argument expansion). In order to do this, a C
24163 symbol needs to be defined and set to @code{0}. You can do this by
24164 adding the following code fragment in one of your Ada units:
24167 Do_Argv_Expansion : Integer := 0;
24168 pragma Export (C, Do_Argv_Expansion, "__gnat_do_argv_expansion");
24171 The results of previous examples will be respectively:
24174 Ada.Command_Line.Argument (1) -> "*.txt"
24180 Ada.Command_Line.Argument (1) -> "'*.txt'"
24183 @node Windows Socket Timeouts,Mixed-Language Programming on Windows,Disabling Command Line Argument Expansion,Microsoft Windows Topics
24184 @anchor{gnat_ugn/platform_specific_information windows-socket-timeouts}@anchor{1e2}
24185 @subsection Windows Socket Timeouts
24188 Microsoft Windows desktops older than @code{8.0} and Microsoft Windows Servers
24189 older than @code{2019} set a socket timeout 500 milliseconds longer than the value
24190 set by setsockopt with @code{SO_RCVTIMEO} and @code{SO_SNDTIMEO} options. The GNAT
24191 runtime makes a correction for the difference in the corresponding Windows
24192 versions. For Windows Server starting with version @code{2019}, the user must
24193 provide a manifest file for the GNAT runtime to be able to recognize that
24194 the Windows version does not need the timeout correction. The manifest file
24195 should be located in the same directory as the executable file, and its file
24196 name must match the executable name suffixed by @code{.manifest}. For example,
24197 if the executable name is @code{sock_wto.exe}, then the manifest file name
24198 has to be @code{sock_wto.exe.manifest}. The manifest file must contain at
24199 least the following data:
24202 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
24203 <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
24204 <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
24206 <!-- Windows Vista -->
24207 <supportedOS Id="@{e2011457-1546-43c5-a5fe-008deee3d3f0@}"/>
24209 <supportedOS Id="@{35138b9a-5d96-4fbd-8e2d-a2440225f93a@}"/>
24211 <supportedOS Id="@{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38@}"/>
24212 <!-- Windows 8.1 -->
24213 <supportedOS Id="@{1f676c76-80e1-4239-95bb-83d0f6d0da78@}"/>
24214 <!-- Windows 10 -->
24215 <supportedOS Id="@{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a@}"/>
24221 Without the manifest file, the socket timeout is going to be overcorrected on
24222 these Windows Server versions and the actual time is going to be 500
24223 milliseconds shorter than what was set with GNAT.Sockets.Set_Socket_Option.
24224 Note that on Microsoft Windows versions where correction is necessary, there
24225 is no way to set a socket timeout shorter than 500 ms. If a socket timeout
24226 shorter than 500 ms is needed on these Windows versions, a call to
24227 Check_Selector should be added before any socket read or write operations.
24229 @node Mixed-Language Programming on Windows,Windows Specific Add-Ons,Windows Socket Timeouts,Microsoft Windows Topics
24230 @anchor{gnat_ugn/platform_specific_information id13}@anchor{1e3}@anchor{gnat_ugn/platform_specific_information mixed-language-programming-on-windows}@anchor{1e4}
24231 @subsection Mixed-Language Programming on Windows
24234 Developing pure Ada applications on Windows is no different than on
24235 other GNAT-supported platforms. However, when developing or porting an
24236 application that contains a mix of Ada and C/C++, the choice of your
24237 Windows C/C++ development environment conditions your overall
24238 interoperability strategy.
24240 If you use @code{gcc} or Microsoft C to compile the non-Ada part of
24241 your application, there are no Windows-specific restrictions that
24242 affect the overall interoperability with your Ada code. If you do want
24243 to use the Microsoft tools for your C++ code, you have two choices:
24249 Encapsulate your C++ code in a DLL to be linked with your Ada
24250 application. In this case, use the Microsoft or whatever environment to
24251 build the DLL and use GNAT to build your executable
24252 (@ref{1e5,,Using DLLs with GNAT}).
24255 Or you can encapsulate your Ada code in a DLL to be linked with the
24256 other part of your application. In this case, use GNAT to build the DLL
24257 (@ref{1e6,,Building DLLs with GNAT Project files}) and use the Microsoft
24258 or whatever environment to build your executable.
24261 In addition to the description about C main in
24262 @ref{44,,Mixed Language Programming} section, if the C main uses a
24263 stand-alone library it is required on x86-windows to
24264 setup the SEH context. For this the C main must looks like this:
24270 extern void adainit (void);
24271 extern void adafinal (void);
24272 extern void __gnat_initialize(void*);
24273 extern void call_to_ada (void);
24275 int main (int argc, char *argv[])
24279 /* Initialize the SEH context */
24280 __gnat_initialize (&SEH);
24284 /* Then call Ada services in the stand-alone library */
24293 Note that this is not needed on x86_64-windows where the Windows
24294 native SEH support is used.
24297 * Windows Calling Conventions::
24298 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
24299 * Using DLLs with GNAT::
24300 * Building DLLs with GNAT Project files::
24301 * Building DLLs with GNAT::
24302 * Building DLLs with gnatdll::
24303 * Ada DLLs and Finalization::
24304 * Creating a Spec for Ada DLLs::
24305 * GNAT and Windows Resources::
24306 * Using GNAT DLLs from Microsoft Visual Studio Applications::
24307 * Debugging a DLL::
24308 * Setting Stack Size from gnatlink::
24309 * Setting Heap Size from gnatlink::
24313 @node Windows Calling Conventions,Introduction to Dynamic Link Libraries DLLs,,Mixed-Language Programming on Windows
24314 @anchor{gnat_ugn/platform_specific_information windows-calling-conventions}@anchor{1e7}@anchor{gnat_ugn/platform_specific_information id14}@anchor{1e8}
24315 @subsubsection Windows Calling Conventions
24322 This section pertain only to Win32. On Win64 there is a single native
24323 calling convention. All convention specifiers are ignored on this
24326 When a subprogram @code{F} (caller) calls a subprogram @code{G}
24327 (callee), there are several ways to push @code{G}'s parameters on the
24328 stack and there are several possible scenarios to clean up the stack
24329 upon @code{G}'s return. A calling convention is an agreed upon software
24330 protocol whereby the responsibilities between the caller (@code{F}) and
24331 the callee (@code{G}) are clearly defined. Several calling conventions
24332 are available for Windows:
24338 @code{C} (Microsoft defined)
24341 @code{Stdcall} (Microsoft defined)
24344 @code{Win32} (GNAT specific)
24347 @code{DLL} (GNAT specific)
24351 * C Calling Convention::
24352 * Stdcall Calling Convention::
24353 * Win32 Calling Convention::
24354 * DLL Calling Convention::
24358 @node C Calling Convention,Stdcall Calling Convention,,Windows Calling Conventions
24359 @anchor{gnat_ugn/platform_specific_information c-calling-convention}@anchor{1e9}@anchor{gnat_ugn/platform_specific_information id15}@anchor{1ea}
24360 @subsubsection @code{C} Calling Convention
24363 This is the default calling convention used when interfacing to C/C++
24364 routines compiled with either @code{gcc} or Microsoft Visual C++.
24366 In the @code{C} calling convention subprogram parameters are pushed on the
24367 stack by the caller from right to left. The caller itself is in charge of
24368 cleaning up the stack after the call. In addition, the name of a routine
24369 with @code{C} calling convention is mangled by adding a leading underscore.
24371 The name to use on the Ada side when importing (or exporting) a routine
24372 with @code{C} calling convention is the name of the routine. For
24373 instance the C function:
24378 int get_val (long);
24382 should be imported from Ada as follows:
24387 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24388 pragma Import (C, Get_Val, External_Name => "get_val");
24392 Note that in this particular case the @code{External_Name} parameter could
24393 have been omitted since, when missing, this parameter is taken to be the
24394 name of the Ada entity in lower case. When the @code{Link_Name} parameter
24395 is missing, as in the above example, this parameter is set to be the
24396 @code{External_Name} with a leading underscore.
24398 When importing a variable defined in C, you should always use the @code{C}
24399 calling convention unless the object containing the variable is part of a
24400 DLL (in which case you should use the @code{Stdcall} calling
24401 convention, @ref{1eb,,Stdcall Calling Convention}).
24403 @node Stdcall Calling Convention,Win32 Calling Convention,C Calling Convention,Windows Calling Conventions
24404 @anchor{gnat_ugn/platform_specific_information stdcall-calling-convention}@anchor{1eb}@anchor{gnat_ugn/platform_specific_information id16}@anchor{1ec}
24405 @subsubsection @code{Stdcall} Calling Convention
24408 This convention, which was the calling convention used for Pascal
24409 programs, is used by Microsoft for all the routines in the Win32 API for
24410 efficiency reasons. It must be used to import any routine for which this
24411 convention was specified.
24413 In the @code{Stdcall} calling convention subprogram parameters are pushed
24414 on the stack by the caller from right to left. The callee (and not the
24415 caller) is in charge of cleaning the stack on routine exit. In addition,
24416 the name of a routine with @code{Stdcall} calling convention is mangled by
24417 adding a leading underscore (as for the @code{C} calling convention) and a
24418 trailing @code{@@@emph{nn}}, where @code{nn} is the overall size (in
24419 bytes) of the parameters passed to the routine.
24421 The name to use on the Ada side when importing a C routine with a
24422 @code{Stdcall} calling convention is the name of the C routine. The leading
24423 underscore and trailing @code{@@@emph{nn}} are added automatically by
24424 the compiler. For instance the Win32 function:
24429 APIENTRY int get_val (long);
24433 should be imported from Ada as follows:
24438 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24439 pragma Import (Stdcall, Get_Val);
24440 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
24444 As for the @code{C} calling convention, when the @code{External_Name}
24445 parameter is missing, it is taken to be the name of the Ada entity in lower
24446 case. If instead of writing the above import pragma you write:
24451 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24452 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
24456 then the imported routine is @code{_retrieve_val@@4}. However, if instead
24457 of specifying the @code{External_Name} parameter you specify the
24458 @code{Link_Name} as in the following example:
24463 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24464 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
24468 then the imported routine is @code{retrieve_val}, that is, there is no
24469 decoration at all. No leading underscore and no Stdcall suffix
24470 @code{@@@emph{nn}}.
24472 This is especially important as in some special cases a DLL's entry
24473 point name lacks a trailing @code{@@@emph{nn}} while the exported
24474 name generated for a call has it.
24476 It is also possible to import variables defined in a DLL by using an
24477 import pragma for a variable. As an example, if a DLL contains a
24478 variable defined as:
24487 then, to access this variable from Ada you should write:
24492 My_Var : Interfaces.C.int;
24493 pragma Import (Stdcall, My_Var);
24497 Note that to ease building cross-platform bindings this convention
24498 will be handled as a @code{C} calling convention on non-Windows platforms.
24500 @node Win32 Calling Convention,DLL Calling Convention,Stdcall Calling Convention,Windows Calling Conventions
24501 @anchor{gnat_ugn/platform_specific_information win32-calling-convention}@anchor{1ed}@anchor{gnat_ugn/platform_specific_information id17}@anchor{1ee}
24502 @subsubsection @code{Win32} Calling Convention
24505 This convention, which is GNAT-specific is fully equivalent to the
24506 @code{Stdcall} calling convention described above.
24508 @node DLL Calling Convention,,Win32 Calling Convention,Windows Calling Conventions
24509 @anchor{gnat_ugn/platform_specific_information id18}@anchor{1ef}@anchor{gnat_ugn/platform_specific_information dll-calling-convention}@anchor{1f0}
24510 @subsubsection @code{DLL} Calling Convention
24513 This convention, which is GNAT-specific is fully equivalent to the
24514 @code{Stdcall} calling convention described above.
24516 @node Introduction to Dynamic Link Libraries DLLs,Using DLLs with GNAT,Windows Calling Conventions,Mixed-Language Programming on Windows
24517 @anchor{gnat_ugn/platform_specific_information id19}@anchor{1f1}@anchor{gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls}@anchor{1f2}
24518 @subsubsection Introduction to Dynamic Link Libraries (DLLs)
24523 A Dynamically Linked Library (DLL) is a library that can be shared by
24524 several applications running under Windows. A DLL can contain any number of
24525 routines and variables.
24527 One advantage of DLLs is that you can change and enhance them without
24528 forcing all the applications that depend on them to be relinked or
24529 recompiled. However, you should be aware than all calls to DLL routines are
24530 slower since, as you will understand below, such calls are indirect.
24532 To illustrate the remainder of this section, suppose that an application
24533 wants to use the services of a DLL @code{API.dll}. To use the services
24534 provided by @code{API.dll} you must statically link against the DLL or
24535 an import library which contains a jump table with an entry for each
24536 routine and variable exported by the DLL. In the Microsoft world this
24537 import library is called @code{API.lib}. When using GNAT this import
24538 library is called either @code{libAPI.dll.a}, @code{libapi.dll.a},
24539 @code{libAPI.a} or @code{libapi.a} (names are case insensitive).
24541 After you have linked your application with the DLL or the import library
24542 and you run your application, here is what happens:
24548 Your application is loaded into memory.
24551 The DLL @code{API.dll} is mapped into the address space of your
24552 application. This means that:
24558 The DLL will use the stack of the calling thread.
24561 The DLL will use the virtual address space of the calling process.
24564 The DLL will allocate memory from the virtual address space of the calling
24568 Handles (pointers) can be safely exchanged between routines in the DLL
24569 routines and routines in the application using the DLL.
24573 The entries in the jump table (from the import library @code{libAPI.dll.a}
24574 or @code{API.lib} or automatically created when linking against a DLL)
24575 which is part of your application are initialized with the addresses
24576 of the routines and variables in @code{API.dll}.
24579 If present in @code{API.dll}, routines @code{DllMain} or
24580 @code{DllMainCRTStartup} are invoked. These routines typically contain
24581 the initialization code needed for the well-being of the routines and
24582 variables exported by the DLL.
24585 There is an additional point which is worth mentioning. In the Windows
24586 world there are two kind of DLLs: relocatable and non-relocatable
24587 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
24588 in the target application address space. If the addresses of two
24589 non-relocatable DLLs overlap and these happen to be used by the same
24590 application, a conflict will occur and the application will run
24591 incorrectly. Hence, when possible, it is always preferable to use and
24592 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
24593 supported by GNAT. Note that the @code{-s} linker option (see GNU Linker
24594 User's Guide) removes the debugging symbols from the DLL but the DLL can
24595 still be relocated.
24597 As a side note, an interesting difference between Microsoft DLLs and
24598 Unix shared libraries, is the fact that on most Unix systems all public
24599 routines are exported by default in a Unix shared library, while under
24600 Windows it is possible (but not required) to list exported routines in
24601 a definition file (see @ref{1f3,,The Definition File}).
24603 @node Using DLLs with GNAT,Building DLLs with GNAT Project files,Introduction to Dynamic Link Libraries DLLs,Mixed-Language Programming on Windows
24604 @anchor{gnat_ugn/platform_specific_information id20}@anchor{1f4}@anchor{gnat_ugn/platform_specific_information using-dlls-with-gnat}@anchor{1e5}
24605 @subsubsection Using DLLs with GNAT
24608 To use the services of a DLL, say @code{API.dll}, in your Ada application
24615 The Ada spec for the routines and/or variables you want to access in
24616 @code{API.dll}. If not available this Ada spec must be built from the C/C++
24617 header files provided with the DLL.
24620 The import library (@code{libAPI.dll.a} or @code{API.lib}). As previously
24621 mentioned an import library is a statically linked library containing the
24622 import table which will be filled at load time to point to the actual
24623 @code{API.dll} routines. Sometimes you don't have an import library for the
24624 DLL you want to use. The following sections will explain how to build
24625 one. Note that this is optional.
24628 The actual DLL, @code{API.dll}.
24631 Once you have all the above, to compile an Ada application that uses the
24632 services of @code{API.dll} and whose main subprogram is @code{My_Ada_App},
24633 you simply issue the command
24638 $ gnatmake my_ada_app -largs -lAPI
24642 The argument @code{-largs -lAPI} at the end of the @code{gnatmake} command
24643 tells the GNAT linker to look for an import library. The linker will
24644 look for a library name in this specific order:
24650 @code{libAPI.dll.a}
24668 The first three are the GNU style import libraries. The third is the
24669 Microsoft style import libraries. The last two are the actual DLL names.
24671 Note that if the Ada package spec for @code{API.dll} contains the
24677 pragma Linker_Options ("-lAPI");
24681 you do not have to add @code{-largs -lAPI} at the end of the
24682 @code{gnatmake} command.
24684 If any one of the items above is missing you will have to create it
24685 yourself. The following sections explain how to do so using as an
24686 example a fictitious DLL called @code{API.dll}.
24689 * Creating an Ada Spec for the DLL Services::
24690 * Creating an Import Library::
24694 @node Creating an Ada Spec for the DLL Services,Creating an Import Library,,Using DLLs with GNAT
24695 @anchor{gnat_ugn/platform_specific_information id21}@anchor{1f5}@anchor{gnat_ugn/platform_specific_information creating-an-ada-spec-for-the-dll-services}@anchor{1f6}
24696 @subsubsection Creating an Ada Spec for the DLL Services
24699 A DLL typically comes with a C/C++ header file which provides the
24700 definitions of the routines and variables exported by the DLL. The Ada
24701 equivalent of this header file is a package spec that contains definitions
24702 for the imported entities. If the DLL you intend to use does not come with
24703 an Ada spec you have to generate one such spec yourself. For example if
24704 the header file of @code{API.dll} is a file @code{api.h} containing the
24705 following two definitions:
24715 then the equivalent Ada spec could be:
24720 with Interfaces.C.Strings;
24725 function Get (Str : C.Strings.Chars_Ptr) return C.int;
24728 pragma Import (C, Get);
24729 pragma Import (DLL, Some_Var);
24734 @node Creating an Import Library,,Creating an Ada Spec for the DLL Services,Using DLLs with GNAT
24735 @anchor{gnat_ugn/platform_specific_information id22}@anchor{1f7}@anchor{gnat_ugn/platform_specific_information creating-an-import-library}@anchor{1f8}
24736 @subsubsection Creating an Import Library
24739 @geindex Import library
24741 If a Microsoft-style import library @code{API.lib} or a GNAT-style
24742 import library @code{libAPI.dll.a} or @code{libAPI.a} is available
24743 with @code{API.dll} you can skip this section. You can also skip this
24744 section if @code{API.dll} or @code{libAPI.dll} is built with GNU tools
24745 as in this case it is possible to link directly against the
24746 DLL. Otherwise read on.
24748 @geindex Definition file
24749 @anchor{gnat_ugn/platform_specific_information the-definition-file}@anchor{1f3}
24750 @subsubheading The Definition File
24753 As previously mentioned, and unlike Unix systems, the list of symbols
24754 that are exported from a DLL must be provided explicitly in Windows.
24755 The main goal of a definition file is precisely that: list the symbols
24756 exported by a DLL. A definition file (usually a file with a @code{.def}
24757 suffix) has the following structure:
24762 [LIBRARY `@w{`}name`@w{`}]
24763 [DESCRIPTION `@w{`}string`@w{`}]
24765 `@w{`}symbol1`@w{`}
24766 `@w{`}symbol2`@w{`}
24774 @item @emph{LIBRARY name}
24776 This section, which is optional, gives the name of the DLL.
24778 @item @emph{DESCRIPTION string}
24780 This section, which is optional, gives a description string that will be
24781 embedded in the import library.
24783 @item @emph{EXPORTS}
24785 This section gives the list of exported symbols (procedures, functions or
24786 variables). For instance in the case of @code{API.dll} the @code{EXPORTS}
24787 section of @code{API.def} looks like:
24796 Note that you must specify the correct suffix (@code{@@@emph{nn}})
24797 (see @ref{1e7,,Windows Calling Conventions}) for a Stdcall
24798 calling convention function in the exported symbols list.
24800 There can actually be other sections in a definition file, but these
24801 sections are not relevant to the discussion at hand.
24802 @anchor{gnat_ugn/platform_specific_information create-def-file-automatically}@anchor{1f9}
24803 @subsubheading Creating a Definition File Automatically
24806 You can automatically create the definition file @code{API.def}
24807 (see @ref{1f3,,The Definition File}) from a DLL.
24808 For that use the @code{dlltool} program as follows:
24813 $ dlltool API.dll -z API.def --export-all-symbols
24816 Note that if some routines in the DLL have the @code{Stdcall} convention
24817 (@ref{1e7,,Windows Calling Conventions}) with stripped @code{@@@emph{nn}}
24818 suffix then you'll have to edit @code{api.def} to add it, and specify
24819 @code{-k} to @code{gnatdll} when creating the import library.
24821 Here are some hints to find the right @code{@@@emph{nn}} suffix.
24827 If you have the Microsoft import library (.lib), it is possible to get
24828 the right symbols by using Microsoft @code{dumpbin} tool (see the
24829 corresponding Microsoft documentation for further details).
24832 $ dumpbin /exports api.lib
24836 If you have a message about a missing symbol at link time the compiler
24837 tells you what symbol is expected. You just have to go back to the
24838 definition file and add the right suffix.
24841 @anchor{gnat_ugn/platform_specific_information gnat-style-import-library}@anchor{1fa}
24842 @subsubheading GNAT-Style Import Library
24845 To create a static import library from @code{API.dll} with the GNAT tools
24846 you should create the .def file, then use @code{gnatdll} tool
24847 (see @ref{1fb,,Using gnatdll}) as follows:
24852 $ gnatdll -e API.def -d API.dll
24855 @code{gnatdll} takes as input a definition file @code{API.def} and the
24856 name of the DLL containing the services listed in the definition file
24857 @code{API.dll}. The name of the static import library generated is
24858 computed from the name of the definition file as follows: if the
24859 definition file name is @code{xyz.def}, the import library name will
24860 be @code{libxyz.a}. Note that in the previous example option
24861 @code{-e} could have been removed because the name of the definition
24862 file (before the @code{.def} suffix) is the same as the name of the
24863 DLL (@ref{1fb,,Using gnatdll} for more information about @code{gnatdll}).
24865 @anchor{gnat_ugn/platform_specific_information msvs-style-import-library}@anchor{1fc}
24866 @subsubheading Microsoft-Style Import Library
24869 A Microsoft import library is needed only if you plan to make an
24870 Ada DLL available to applications developed with Microsoft
24871 tools (@ref{1e4,,Mixed-Language Programming on Windows}).
24873 To create a Microsoft-style import library for @code{API.dll} you
24874 should create the .def file, then build the actual import library using
24875 Microsoft's @code{lib} utility:
24880 $ lib -machine:IX86 -def:API.def -out:API.lib
24883 If you use the above command the definition file @code{API.def} must
24884 contain a line giving the name of the DLL:
24890 See the Microsoft documentation for further details about the usage of
24894 @node Building DLLs with GNAT Project files,Building DLLs with GNAT,Using DLLs with GNAT,Mixed-Language Programming on Windows
24895 @anchor{gnat_ugn/platform_specific_information id23}@anchor{1fd}@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files}@anchor{1e6}
24896 @subsubsection Building DLLs with GNAT Project files
24902 There is nothing specific to Windows in the build process.
24903 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
24904 chapter of the @emph{GPRbuild User's Guide}.
24906 Due to a system limitation, it is not possible under Windows to create threads
24907 when inside the @code{DllMain} routine which is used for auto-initialization
24908 of shared libraries, so it is not possible to have library level tasks in SALs.
24910 @node Building DLLs with GNAT,Building DLLs with gnatdll,Building DLLs with GNAT Project files,Mixed-Language Programming on Windows
24911 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat}@anchor{1fe}@anchor{gnat_ugn/platform_specific_information id24}@anchor{1ff}
24912 @subsubsection Building DLLs with GNAT
24918 This section explain how to build DLLs using the GNAT built-in DLL
24919 support. With the following procedure it is straight forward to build
24920 and use DLLs with GNAT.
24926 Building object files.
24927 The first step is to build all objects files that are to be included
24928 into the DLL. This is done by using the standard @code{gnatmake} tool.
24932 To build the DLL you must use the @code{gcc} @code{-shared} and
24933 @code{-shared-libgcc} options. It is quite simple to use this method:
24936 $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ...
24939 It is important to note that in this case all symbols found in the
24940 object files are automatically exported. It is possible to restrict
24941 the set of symbols to export by passing to @code{gcc} a definition
24942 file (see @ref{1f3,,The Definition File}).
24946 $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ...
24949 If you use a definition file you must export the elaboration procedures
24950 for every package that required one. Elaboration procedures are named
24951 using the package name followed by "_E".
24954 Preparing DLL to be used.
24955 For the DLL to be used by client programs the bodies must be hidden
24956 from it and the .ali set with read-only attribute. This is very important
24957 otherwise GNAT will recompile all packages and will not actually use
24958 the code in the DLL. For example:
24962 $ copy *.ads *.ali api.dll apilib
24963 $ attrib +R apilib\\*.ali
24967 At this point it is possible to use the DLL by directly linking
24968 against it. Note that you must use the GNAT shared runtime when using
24969 GNAT shared libraries. This is achieved by using the @code{-shared} binder
24975 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
24979 @node Building DLLs with gnatdll,Ada DLLs and Finalization,Building DLLs with GNAT,Mixed-Language Programming on Windows
24980 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnatdll}@anchor{200}@anchor{gnat_ugn/platform_specific_information id25}@anchor{201}
24981 @subsubsection Building DLLs with gnatdll
24987 Note that it is preferred to use GNAT Project files
24988 (@ref{1e6,,Building DLLs with GNAT Project files}) or the built-in GNAT
24989 DLL support (@ref{1fe,,Building DLLs with GNAT}) or to build DLLs.
24991 This section explains how to build DLLs containing Ada code using
24992 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
24993 remainder of this section.
24995 The steps required to build an Ada DLL that is to be used by Ada as well as
24996 non-Ada applications are as follows:
25002 You need to mark each Ada entity exported by the DLL with a @code{C} or
25003 @code{Stdcall} calling convention to avoid any Ada name mangling for the
25004 entities exported by the DLL
25005 (see @ref{202,,Exporting Ada Entities}). You can
25006 skip this step if you plan to use the Ada DLL only from Ada applications.
25009 Your Ada code must export an initialization routine which calls the routine
25010 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
25011 the Ada code in the DLL (@ref{203,,Ada DLLs and Elaboration}). The initialization
25012 routine exported by the Ada DLL must be invoked by the clients of the DLL
25013 to initialize the DLL.
25016 When useful, the DLL should also export a finalization routine which calls
25017 routine @code{adafinal} generated by @code{gnatbind} to perform the
25018 finalization of the Ada code in the DLL (@ref{204,,Ada DLLs and Finalization}).
25019 The finalization routine exported by the Ada DLL must be invoked by the
25020 clients of the DLL when the DLL services are no further needed.
25023 You must provide a spec for the services exported by the Ada DLL in each
25024 of the programming languages to which you plan to make the DLL available.
25027 You must provide a definition file listing the exported entities
25028 (@ref{1f3,,The Definition File}).
25031 Finally you must use @code{gnatdll} to produce the DLL and the import
25032 library (@ref{1fb,,Using gnatdll}).
25035 Note that a relocatable DLL stripped using the @code{strip}
25036 binutils tool will not be relocatable anymore. To build a DLL without
25037 debug information pass @code{-largs -s} to @code{gnatdll}. This
25038 restriction does not apply to a DLL built using a Library Project.
25039 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
25040 chapter of the @emph{GPRbuild User's Guide}.
25042 @c Limitations_When_Using_Ada_DLLs_from Ada:
25045 * Limitations When Using Ada DLLs from Ada::
25046 * Exporting Ada Entities::
25047 * Ada DLLs and Elaboration::
25051 @node Limitations When Using Ada DLLs from Ada,Exporting Ada Entities,,Building DLLs with gnatdll
25052 @anchor{gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada}@anchor{205}
25053 @subsubsection Limitations When Using Ada DLLs from Ada
25056 When using Ada DLLs from Ada applications there is a limitation users
25057 should be aware of. Because on Windows the GNAT run-time is not in a DLL of
25058 its own, each Ada DLL includes a part of the GNAT run-time. Specifically,
25059 each Ada DLL includes the services of the GNAT run-time that are necessary
25060 to the Ada code inside the DLL. As a result, when an Ada program uses an
25061 Ada DLL there are two independent GNAT run-times: one in the Ada DLL and
25062 one in the main program.
25064 It is therefore not possible to exchange GNAT run-time objects between the
25065 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
25066 handles (e.g., @code{Text_IO.File_Type}), tasks types, protected objects
25069 It is completely safe to exchange plain elementary, array or record types,
25070 Windows object handles, etc.
25072 @node Exporting Ada Entities,Ada DLLs and Elaboration,Limitations When Using Ada DLLs from Ada,Building DLLs with gnatdll
25073 @anchor{gnat_ugn/platform_specific_information exporting-ada-entities}@anchor{202}@anchor{gnat_ugn/platform_specific_information id26}@anchor{206}
25074 @subsubsection Exporting Ada Entities
25077 @geindex Export table
25079 Building a DLL is a way to encapsulate a set of services usable from any
25080 application. As a result, the Ada entities exported by a DLL should be
25081 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
25082 any Ada name mangling. As an example here is an Ada package
25083 @code{API}, spec and body, exporting two procedures, a function, and a
25089 with Interfaces.C; use Interfaces;
25091 Count : C.int := 0;
25092 function Factorial (Val : C.int) return C.int;
25094 procedure Initialize_API;
25095 procedure Finalize_API;
25096 -- Initialization & Finalization routines. More in the next section.
25098 pragma Export (C, Initialize_API);
25099 pragma Export (C, Finalize_API);
25100 pragma Export (C, Count);
25101 pragma Export (C, Factorial);
25106 package body API is
25107 function Factorial (Val : C.int) return C.int is
25110 Count := Count + 1;
25111 for K in 1 .. Val loop
25117 procedure Initialize_API is
25119 pragma Import (C, Adainit);
25122 end Initialize_API;
25124 procedure Finalize_API is
25125 procedure Adafinal;
25126 pragma Import (C, Adafinal);
25134 If the Ada DLL you are building will only be used by Ada applications
25135 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
25136 convention. As an example, the previous package could be written as
25143 Count : Integer := 0;
25144 function Factorial (Val : Integer) return Integer;
25146 procedure Initialize_API;
25147 procedure Finalize_API;
25148 -- Initialization and Finalization routines.
25153 package body API is
25154 function Factorial (Val : Integer) return Integer is
25155 Fact : Integer := 1;
25157 Count := Count + 1;
25158 for K in 1 .. Val loop
25165 -- The remainder of this package body is unchanged.
25170 Note that if you do not export the Ada entities with a @code{C} or
25171 @code{Stdcall} convention you will have to provide the mangled Ada names
25172 in the definition file of the Ada DLL
25173 (@ref{207,,Creating the Definition File}).
25175 @node Ada DLLs and Elaboration,,Exporting Ada Entities,Building DLLs with gnatdll
25176 @anchor{gnat_ugn/platform_specific_information ada-dlls-and-elaboration}@anchor{203}@anchor{gnat_ugn/platform_specific_information id27}@anchor{208}
25177 @subsubsection Ada DLLs and Elaboration
25180 @geindex DLLs and elaboration
25182 The DLL that you are building contains your Ada code as well as all the
25183 routines in the Ada library that are needed by it. The first thing a
25184 user of your DLL must do is elaborate the Ada code
25185 (@ref{f,,Elaboration Order Handling in GNAT}).
25187 To achieve this you must export an initialization routine
25188 (@code{Initialize_API} in the previous example), which must be invoked
25189 before using any of the DLL services. This elaboration routine must call
25190 the Ada elaboration routine @code{adainit} generated by the GNAT binder
25191 (@ref{b4,,Binding with Non-Ada Main Programs}). See the body of
25192 @code{Initialize_Api} for an example. Note that the GNAT binder is
25193 automatically invoked during the DLL build process by the @code{gnatdll}
25194 tool (@ref{1fb,,Using gnatdll}).
25196 When a DLL is loaded, Windows systematically invokes a routine called
25197 @code{DllMain}. It would therefore be possible to call @code{adainit}
25198 directly from @code{DllMain} without having to provide an explicit
25199 initialization routine. Unfortunately, it is not possible to call
25200 @code{adainit} from the @code{DllMain} if your program has library level
25201 tasks because access to the @code{DllMain} entry point is serialized by
25202 the system (that is, only a single thread can execute 'through' it at a
25203 time), which means that the GNAT run-time will deadlock waiting for the
25204 newly created task to complete its initialization.
25206 @node Ada DLLs and Finalization,Creating a Spec for Ada DLLs,Building DLLs with gnatdll,Mixed-Language Programming on Windows
25207 @anchor{gnat_ugn/platform_specific_information id28}@anchor{209}@anchor{gnat_ugn/platform_specific_information ada-dlls-and-finalization}@anchor{204}
25208 @subsubsection Ada DLLs and Finalization
25211 @geindex DLLs and finalization
25213 When the services of an Ada DLL are no longer needed, the client code should
25214 invoke the DLL finalization routine, if available. The DLL finalization
25215 routine is in charge of releasing all resources acquired by the DLL. In the
25216 case of the Ada code contained in the DLL, this is achieved by calling
25217 routine @code{adafinal} generated by the GNAT binder
25218 (@ref{b4,,Binding with Non-Ada Main Programs}).
25219 See the body of @code{Finalize_Api} for an
25220 example. As already pointed out the GNAT binder is automatically invoked
25221 during the DLL build process by the @code{gnatdll} tool
25222 (@ref{1fb,,Using gnatdll}).
25224 @node Creating a Spec for Ada DLLs,GNAT and Windows Resources,Ada DLLs and Finalization,Mixed-Language Programming on Windows
25225 @anchor{gnat_ugn/platform_specific_information id29}@anchor{20a}@anchor{gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls}@anchor{20b}
25226 @subsubsection Creating a Spec for Ada DLLs
25229 To use the services exported by the Ada DLL from another programming
25230 language (e.g., C), you have to translate the specs of the exported Ada
25231 entities in that language. For instance in the case of @code{API.dll},
25232 the corresponding C header file could look like:
25237 extern int *_imp__count;
25238 #define count (*_imp__count)
25239 int factorial (int);
25243 It is important to understand that when building an Ada DLL to be used by
25244 other Ada applications, you need two different specs for the packages
25245 contained in the DLL: one for building the DLL and the other for using
25246 the DLL. This is because the @code{DLL} calling convention is needed to
25247 use a variable defined in a DLL, but when building the DLL, the variable
25248 must have either the @code{Ada} or @code{C} calling convention. As an
25249 example consider a DLL comprising the following package @code{API}:
25255 Count : Integer := 0;
25257 -- Remainder of the package omitted.
25262 After producing a DLL containing package @code{API}, the spec that
25263 must be used to import @code{API.Count} from Ada code outside of the
25271 pragma Import (DLL, Count);
25277 * Creating the Definition File::
25282 @node Creating the Definition File,Using gnatdll,,Creating a Spec for Ada DLLs
25283 @anchor{gnat_ugn/platform_specific_information creating-the-definition-file}@anchor{207}@anchor{gnat_ugn/platform_specific_information id30}@anchor{20c}
25284 @subsubsection Creating the Definition File
25287 The definition file is the last file needed to build the DLL. It lists
25288 the exported symbols. As an example, the definition file for a DLL
25289 containing only package @code{API} (where all the entities are exported
25290 with a @code{C} calling convention) is:
25303 If the @code{C} calling convention is missing from package @code{API},
25304 then the definition file contains the mangled Ada names of the above
25305 entities, which in this case are:
25314 api__initialize_api
25318 @node Using gnatdll,,Creating the Definition File,Creating a Spec for Ada DLLs
25319 @anchor{gnat_ugn/platform_specific_information using-gnatdll}@anchor{1fb}@anchor{gnat_ugn/platform_specific_information id31}@anchor{20d}
25320 @subsubsection Using @code{gnatdll}
25325 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
25326 and non-Ada sources that make up your DLL have been compiled.
25327 @code{gnatdll} is actually in charge of two distinct tasks: build the
25328 static import library for the DLL and the actual DLL. The form of the
25329 @code{gnatdll} command is
25334 $ gnatdll [ switches ] list-of-files [ -largs opts ]
25338 where @code{list-of-files} is a list of ALI and object files. The object
25339 file list must be the exact list of objects corresponding to the non-Ada
25340 sources whose services are to be included in the DLL. The ALI file list
25341 must be the exact list of ALI files for the corresponding Ada sources
25342 whose services are to be included in the DLL. If @code{list-of-files} is
25343 missing, only the static import library is generated.
25345 You may specify any of the following switches to @code{gnatdll}:
25349 @geindex -a (gnatdll)
25355 @item @code{-a[@emph{address}]}
25357 Build a non-relocatable DLL at @code{address}. If @code{address} is not
25358 specified the default address @code{0x11000000} will be used. By default,
25359 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
25360 advise the reader to build relocatable DLL.
25362 @geindex -b (gnatdll)
25364 @item @code{-b @emph{address}}
25366 Set the relocatable DLL base address. By default the address is
25369 @geindex -bargs (gnatdll)
25371 @item @code{-bargs @emph{opts}}
25373 Binder options. Pass @code{opts} to the binder.
25375 @geindex -d (gnatdll)
25377 @item @code{-d @emph{dllfile}}
25379 @code{dllfile} is the name of the DLL. This switch must be present for
25380 @code{gnatdll} to do anything. The name of the generated import library is
25381 obtained algorithmically from @code{dllfile} as shown in the following
25382 example: if @code{dllfile} is @code{xyz.dll}, the import library name is
25383 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
25384 by option @code{-e}) is obtained algorithmically from @code{dllfile}
25385 as shown in the following example:
25386 if @code{dllfile} is @code{xyz.dll}, the definition
25387 file used is @code{xyz.def}.
25389 @geindex -e (gnatdll)
25391 @item @code{-e @emph{deffile}}
25393 @code{deffile} is the name of the definition file.
25395 @geindex -g (gnatdll)
25399 Generate debugging information. This information is stored in the object
25400 file and copied from there to the final DLL file by the linker,
25401 where it can be read by the debugger. You must use the
25402 @code{-g} switch if you plan on using the debugger or the symbolic
25405 @geindex -h (gnatdll)
25409 Help mode. Displays @code{gnatdll} switch usage information.
25411 @geindex -I (gnatdll)
25413 @item @code{-I@emph{dir}}
25415 Direct @code{gnatdll} to search the @code{dir} directory for source and
25416 object files needed to build the DLL.
25417 (@ref{89,,Search Paths and the Run-Time Library (RTL)}).
25419 @geindex -k (gnatdll)
25423 Removes the @code{@@@emph{nn}} suffix from the import library's exported
25424 names, but keeps them for the link names. You must specify this
25425 option if you want to use a @code{Stdcall} function in a DLL for which
25426 the @code{@@@emph{nn}} suffix has been removed. This is the case for most
25427 of the Windows NT DLL for example. This option has no effect when
25428 @code{-n} option is specified.
25430 @geindex -l (gnatdll)
25432 @item @code{-l @emph{file}}
25434 The list of ALI and object files used to build the DLL are listed in
25435 @code{file}, instead of being given in the command line. Each line in
25436 @code{file} contains the name of an ALI or object file.
25438 @geindex -n (gnatdll)
25442 No Import. Do not create the import library.
25444 @geindex -q (gnatdll)
25448 Quiet mode. Do not display unnecessary messages.
25450 @geindex -v (gnatdll)
25454 Verbose mode. Display extra information.
25456 @geindex -largs (gnatdll)
25458 @item @code{-largs @emph{opts}}
25460 Linker options. Pass @code{opts} to the linker.
25463 @subsubheading @code{gnatdll} Example
25466 As an example the command to build a relocatable DLL from @code{api.adb}
25467 once @code{api.adb} has been compiled and @code{api.def} created is
25472 $ gnatdll -d api.dll api.ali
25476 The above command creates two files: @code{libapi.dll.a} (the import
25477 library) and @code{api.dll} (the actual DLL). If you want to create
25478 only the DLL, just type:
25483 $ gnatdll -d api.dll -n api.ali
25487 Alternatively if you want to create just the import library, type:
25492 $ gnatdll -d api.dll
25496 @subsubheading @code{gnatdll} behind the Scenes
25499 This section details the steps involved in creating a DLL. @code{gnatdll}
25500 does these steps for you. Unless you are interested in understanding what
25501 goes on behind the scenes, you should skip this section.
25503 We use the previous example of a DLL containing the Ada package @code{API},
25504 to illustrate the steps necessary to build a DLL. The starting point is a
25505 set of objects that will make up the DLL and the corresponding ALI
25506 files. In the case of this example this means that @code{api.o} and
25507 @code{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
25514 @code{gnatdll} builds the base file (@code{api.base}). A base file gives
25515 the information necessary to generate relocation information for the
25520 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
25523 In addition to the base file, the @code{gnatlink} command generates an
25524 output file @code{api.jnk} which can be discarded. The @code{-mdll} switch
25525 asks @code{gnatlink} to generate the routines @code{DllMain} and
25526 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
25527 is loaded into memory.
25530 @code{gnatdll} uses @code{dlltool} (see @ref{20e,,Using dlltool}) to build the
25531 export table (@code{api.exp}). The export table contains the relocation
25532 information in a form which can be used during the final link to ensure
25533 that the Windows loader is able to place the DLL anywhere in memory.
25536 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25537 --output-exp api.exp
25541 @code{gnatdll} builds the base file using the new export table. Note that
25542 @code{gnatbind} must be called once again since the binder generated file
25543 has been deleted during the previous call to @code{gnatlink}.
25547 $ gnatlink api -o api.jnk api.exp -mdll
25548 -Wl,--base-file,api.base
25552 @code{gnatdll} builds the new export table using the new base file and
25553 generates the DLL import library @code{libAPI.dll.a}.
25556 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25557 --output-exp api.exp --output-lib libAPI.a
25561 Finally @code{gnatdll} builds the relocatable DLL using the final export
25566 $ gnatlink api api.exp -o api.dll -mdll
25569 @anchor{gnat_ugn/platform_specific_information using-dlltool}@anchor{20e}
25570 @subsubheading Using @code{dlltool}
25573 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
25574 DLLs and static import libraries. This section summarizes the most
25575 common @code{dlltool} switches. The form of the @code{dlltool} command
25581 $ dlltool [`switches`]
25585 @code{dlltool} switches include:
25587 @geindex --base-file (dlltool)
25592 @item @code{--base-file @emph{basefile}}
25594 Read the base file @code{basefile} generated by the linker. This switch
25595 is used to create a relocatable DLL.
25598 @geindex --def (dlltool)
25603 @item @code{--def @emph{deffile}}
25605 Read the definition file.
25608 @geindex --dllname (dlltool)
25613 @item @code{--dllname @emph{name}}
25615 Gives the name of the DLL. This switch is used to embed the name of the
25616 DLL in the static import library generated by @code{dlltool} with switch
25617 @code{--output-lib}.
25620 @geindex -k (dlltool)
25627 Kill @code{@@@emph{nn}} from exported names
25628 (@ref{1e7,,Windows Calling Conventions}
25629 for a discussion about @code{Stdcall}-style symbols.
25632 @geindex --help (dlltool)
25637 @item @code{--help}
25639 Prints the @code{dlltool} switches with a concise description.
25642 @geindex --output-exp (dlltool)
25647 @item @code{--output-exp @emph{exportfile}}
25649 Generate an export file @code{exportfile}. The export file contains the
25650 export table (list of symbols in the DLL) and is used to create the DLL.
25653 @geindex --output-lib (dlltool)
25658 @item @code{--output-lib @emph{libfile}}
25660 Generate a static import library @code{libfile}.
25663 @geindex -v (dlltool)
25673 @geindex --as (dlltool)
25678 @item @code{--as @emph{assembler-name}}
25680 Use @code{assembler-name} as the assembler. The default is @code{as}.
25683 @node GNAT and Windows Resources,Using GNAT DLLs from Microsoft Visual Studio Applications,Creating a Spec for Ada DLLs,Mixed-Language Programming on Windows
25684 @anchor{gnat_ugn/platform_specific_information gnat-and-windows-resources}@anchor{20f}@anchor{gnat_ugn/platform_specific_information id32}@anchor{210}
25685 @subsubsection GNAT and Windows Resources
25691 Resources are an easy way to add Windows specific objects to your
25692 application. The objects that can be added as resources include:
25722 version information
25725 For example, a version information resource can be defined as follow and
25726 embedded into an executable or DLL:
25728 A version information resource can be used to embed information into an
25729 executable or a DLL. These information can be viewed using the file properties
25730 from the Windows Explorer. Here is an example of a version information
25737 FILEVERSION 1,0,0,0
25738 PRODUCTVERSION 1,0,0,0
25740 BLOCK "StringFileInfo"
25744 VALUE "CompanyName", "My Company Name"
25745 VALUE "FileDescription", "My application"
25746 VALUE "FileVersion", "1.0"
25747 VALUE "InternalName", "my_app"
25748 VALUE "LegalCopyright", "My Name"
25749 VALUE "OriginalFilename", "my_app.exe"
25750 VALUE "ProductName", "My App"
25751 VALUE "ProductVersion", "1.0"
25755 BLOCK "VarFileInfo"
25757 VALUE "Translation", 0x809, 1252
25763 The value @code{0809} (langID) is for the U.K English language and
25764 @code{04E4} (charsetID), which is equal to @code{1252} decimal, for
25767 This section explains how to build, compile and use resources. Note that this
25768 section does not cover all resource objects, for a complete description see
25769 the corresponding Microsoft documentation.
25772 * Building Resources::
25773 * Compiling Resources::
25774 * Using Resources::
25778 @node Building Resources,Compiling Resources,,GNAT and Windows Resources
25779 @anchor{gnat_ugn/platform_specific_information building-resources}@anchor{211}@anchor{gnat_ugn/platform_specific_information id33}@anchor{212}
25780 @subsubsection Building Resources
25786 A resource file is an ASCII file. By convention resource files have an
25787 @code{.rc} extension.
25788 The easiest way to build a resource file is to use Microsoft tools
25789 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
25790 @code{dlgedit.exe} to build dialogs.
25791 It is always possible to build an @code{.rc} file yourself by writing a
25794 It is not our objective to explain how to write a resource file. A
25795 complete description of the resource script language can be found in the
25796 Microsoft documentation.
25798 @node Compiling Resources,Using Resources,Building Resources,GNAT and Windows Resources
25799 @anchor{gnat_ugn/platform_specific_information compiling-resources}@anchor{213}@anchor{gnat_ugn/platform_specific_information id34}@anchor{214}
25800 @subsubsection Compiling Resources
25810 This section describes how to build a GNAT-compatible (COFF) object file
25811 containing the resources. This is done using the Resource Compiler
25812 @code{windres} as follows:
25817 $ windres -i myres.rc -o myres.o
25821 By default @code{windres} will run @code{gcc} to preprocess the @code{.rc}
25822 file. You can specify an alternate preprocessor (usually named
25823 @code{cpp.exe}) using the @code{windres} @code{--preprocessor}
25824 parameter. A list of all possible options may be obtained by entering
25825 the command @code{windres} @code{--help}.
25827 It is also possible to use the Microsoft resource compiler @code{rc.exe}
25828 to produce a @code{.res} file (binary resource file). See the
25829 corresponding Microsoft documentation for further details. In this case
25830 you need to use @code{windres} to translate the @code{.res} file to a
25831 GNAT-compatible object file as follows:
25836 $ windres -i myres.res -o myres.o
25840 @node Using Resources,,Compiling Resources,GNAT and Windows Resources
25841 @anchor{gnat_ugn/platform_specific_information using-resources}@anchor{215}@anchor{gnat_ugn/platform_specific_information id35}@anchor{216}
25842 @subsubsection Using Resources
25848 To include the resource file in your program just add the
25849 GNAT-compatible object file for the resource(s) to the linker
25850 arguments. With @code{gnatmake} this is done by using the @code{-largs}
25856 $ gnatmake myprog -largs myres.o
25860 @node Using GNAT DLLs from Microsoft Visual Studio Applications,Debugging a DLL,GNAT and Windows Resources,Mixed-Language Programming on Windows
25861 @anchor{gnat_ugn/platform_specific_information using-gnat-dll-from-msvs}@anchor{217}@anchor{gnat_ugn/platform_specific_information using-gnat-dlls-from-microsoft-visual-studio-applications}@anchor{218}
25862 @subsubsection Using GNAT DLLs from Microsoft Visual Studio Applications
25865 @geindex Microsoft Visual Studio
25866 @geindex use with GNAT DLLs
25868 This section describes a common case of mixed GNAT/Microsoft Visual Studio
25869 application development, where the main program is developed using MSVS, and
25870 is linked with a DLL developed using GNAT. Such a mixed application should
25871 be developed following the general guidelines outlined above; below is the
25872 cookbook-style sequence of steps to follow:
25878 First develop and build the GNAT shared library using a library project
25879 (let's assume the project is @code{mylib.gpr}, producing the library @code{libmylib.dll}):
25885 $ gprbuild -p mylib.gpr
25893 Produce a .def file for the symbols you need to interface with, either by
25894 hand or automatically with possibly some manual adjustments
25895 (see @ref{1f9,,Creating Definition File Automatically}):
25901 $ dlltool libmylib.dll -z libmylib.def --export-all-symbols
25909 Make sure that MSVS command-line tools are accessible on the path.
25912 Create the Microsoft-style import library (see @ref{1fc,,MSVS-Style Import Library}):
25918 $ lib -machine:IX86 -def:libmylib.def -out:libmylib.lib
25922 If you are using a 64-bit toolchain, the above becomes...
25927 $ lib -machine:X64 -def:libmylib.def -out:libmylib.lib
25941 $ cl /O2 /MD main.c libmylib.lib
25949 Before running the executable, make sure you have set the PATH to the DLL,
25950 or copy the DLL into into the directory containing the .exe.
25953 @node Debugging a DLL,Setting Stack Size from gnatlink,Using GNAT DLLs from Microsoft Visual Studio Applications,Mixed-Language Programming on Windows
25954 @anchor{gnat_ugn/platform_specific_information id36}@anchor{219}@anchor{gnat_ugn/platform_specific_information debugging-a-dll}@anchor{21a}
25955 @subsubsection Debugging a DLL
25958 @geindex DLL debugging
25960 Debugging a DLL is similar to debugging a standard program. But
25961 we have to deal with two different executable parts: the DLL and the
25962 program that uses it. We have the following four possibilities:
25968 The program and the DLL are built with GCC/GNAT.
25971 The program is built with foreign tools and the DLL is built with
25975 The program is built with GCC/GNAT and the DLL is built with
25979 In this section we address only cases one and two above.
25980 There is no point in trying to debug
25981 a DLL with GNU/GDB, if there is no GDB-compatible debugging
25982 information in it. To do so you must use a debugger compatible with the
25983 tools suite used to build the DLL.
25986 * Program and DLL Both Built with GCC/GNAT::
25987 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
25991 @node Program and DLL Both Built with GCC/GNAT,Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Debugging a DLL
25992 @anchor{gnat_ugn/platform_specific_information id37}@anchor{21b}@anchor{gnat_ugn/platform_specific_information program-and-dll-both-built-with-gcc-gnat}@anchor{21c}
25993 @subsubsection Program and DLL Both Built with GCC/GNAT
25996 This is the simplest case. Both the DLL and the program have @code{GDB}
25997 compatible debugging information. It is then possible to break anywhere in
25998 the process. Let's suppose here that the main procedure is named
25999 @code{ada_main} and that in the DLL there is an entry point named
26002 The DLL (@ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) and
26003 program must have been built with the debugging information (see GNAT -g
26004 switch). Here are the step-by-step instructions for debugging it:
26010 Launch @code{GDB} on the main program.
26017 Start the program and stop at the beginning of the main procedure
26023 This step is required to be able to set a breakpoint inside the DLL. As long
26024 as the program is not run, the DLL is not loaded. This has the
26025 consequence that the DLL debugging information is also not loaded, so it is not
26026 possible to set a breakpoint in the DLL.
26029 Set a breakpoint inside the DLL
26032 (gdb) break ada_dll
26037 At this stage a breakpoint is set inside the DLL. From there on
26038 you can use the standard approach to debug the whole program
26039 (@ref{24,,Running and Debugging Ada Programs}).
26041 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Program and DLL Both Built with GCC/GNAT,Debugging a DLL
26042 @anchor{gnat_ugn/platform_specific_information program-built-with-foreign-tools-and-dll-built-with-gcc-gnat}@anchor{21d}@anchor{gnat_ugn/platform_specific_information id38}@anchor{21e}
26043 @subsubsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
26046 In this case things are slightly more complex because it is not possible to
26047 start the main program and then break at the beginning to load the DLL and the
26048 associated DLL debugging information. It is not possible to break at the
26049 beginning of the program because there is no @code{GDB} debugging information,
26050 and therefore there is no direct way of getting initial control. This
26051 section addresses this issue by describing some methods that can be used
26052 to break somewhere in the DLL to debug it.
26054 First suppose that the main procedure is named @code{main} (this is for
26055 example some C code built with Microsoft Visual C) and that there is a
26056 DLL named @code{test.dll} containing an Ada entry point named
26059 The DLL (see @ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) must have
26060 been built with debugging information (see the GNAT @code{-g} option).
26062 @subsubheading Debugging the DLL Directly
26069 Find out the executable starting address
26072 $ objdump --file-header main.exe
26075 The starting address is reported on the last line. For example:
26078 main.exe: file format pei-i386
26079 architecture: i386, flags 0x0000010a:
26080 EXEC_P, HAS_DEBUG, D_PAGED
26081 start address 0x00401010
26085 Launch the debugger on the executable.
26092 Set a breakpoint at the starting address, and launch the program.
26095 $ (gdb) break *0x00401010
26099 The program will stop at the given address.
26102 Set a breakpoint on a DLL subroutine.
26105 (gdb) break ada_dll.adb:45
26108 Or if you want to break using a symbol on the DLL, you need first to
26109 select the Ada language (language used by the DLL).
26112 (gdb) set language ada
26113 (gdb) break ada_dll
26117 Continue the program.
26123 This will run the program until it reaches the breakpoint that has been
26124 set. From that point you can use the standard way to debug a program
26125 as described in (@ref{24,,Running and Debugging Ada Programs}).
26128 It is also possible to debug the DLL by attaching to a running process.
26130 @subsubheading Attaching to a Running Process
26133 @geindex DLL debugging
26134 @geindex attach to process
26136 With @code{GDB} it is always possible to debug a running process by
26137 attaching to it. It is possible to debug a DLL this way. The limitation
26138 of this approach is that the DLL must run long enough to perform the
26139 attach operation. It may be useful for instance to insert a time wasting
26140 loop in the code of the DLL to meet this criterion.
26146 Launch the main program @code{main.exe}.
26153 Use the Windows @emph{Task Manager} to find the process ID. Let's say
26154 that the process PID for @code{main.exe} is 208.
26164 Attach to the running process to be debugged.
26171 Load the process debugging information.
26174 (gdb) symbol-file main.exe
26178 Break somewhere in the DLL.
26181 (gdb) break ada_dll
26185 Continue process execution.
26192 This last step will resume the process execution, and stop at
26193 the breakpoint we have set. From there you can use the standard
26194 approach to debug a program as described in
26195 @ref{24,,Running and Debugging Ada Programs}.
26197 @node Setting Stack Size from gnatlink,Setting Heap Size from gnatlink,Debugging a DLL,Mixed-Language Programming on Windows
26198 @anchor{gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink}@anchor{136}@anchor{gnat_ugn/platform_specific_information id39}@anchor{21f}
26199 @subsubsection Setting Stack Size from @code{gnatlink}
26202 It is possible to specify the program stack size at link time. On modern
26203 versions of Windows, starting with XP, this is mostly useful to set the size of
26204 the main stack (environment task). The other task stacks are set with pragma
26205 Storage_Size or with the @emph{gnatbind -d} command.
26207 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
26208 reserve size of individual tasks, the link-time stack size applies to all
26209 tasks, and pragma Storage_Size has no effect.
26210 In particular, Stack Overflow checks are made against this
26211 link-time specified size.
26213 This setting can be done with @code{gnatlink} using either of the following:
26219 @code{-Xlinker} linker option
26222 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
26225 This sets the stack reserve size to 0x10000 bytes and the stack commit
26226 size to 0x1000 bytes.
26229 @code{-Wl} linker option
26232 $ gnatlink hello -Wl,--stack=0x1000000
26235 This sets the stack reserve size to 0x1000000 bytes. Note that with
26236 @code{-Wl} option it is not possible to set the stack commit size
26237 because the comma is a separator for this option.
26240 @node Setting Heap Size from gnatlink,,Setting Stack Size from gnatlink,Mixed-Language Programming on Windows
26241 @anchor{gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink}@anchor{137}@anchor{gnat_ugn/platform_specific_information id40}@anchor{220}
26242 @subsubsection Setting Heap Size from @code{gnatlink}
26245 Under Windows systems, it is possible to specify the program heap size from
26246 @code{gnatlink} using either of the following:
26252 @code{-Xlinker} linker option
26255 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
26258 This sets the heap reserve size to 0x10000 bytes and the heap commit
26259 size to 0x1000 bytes.
26262 @code{-Wl} linker option
26265 $ gnatlink hello -Wl,--heap=0x1000000
26268 This sets the heap reserve size to 0x1000000 bytes. Note that with
26269 @code{-Wl} option it is not possible to set the heap commit size
26270 because the comma is a separator for this option.
26273 @node Windows Specific Add-Ons,,Mixed-Language Programming on Windows,Microsoft Windows Topics
26274 @anchor{gnat_ugn/platform_specific_information windows-specific-add-ons}@anchor{221}@anchor{gnat_ugn/platform_specific_information win32-specific-addons}@anchor{222}
26275 @subsection Windows Specific Add-Ons
26278 This section describes the Windows specific add-ons.
26286 @node Win32Ada,wPOSIX,,Windows Specific Add-Ons
26287 @anchor{gnat_ugn/platform_specific_information win32ada}@anchor{223}@anchor{gnat_ugn/platform_specific_information id41}@anchor{224}
26288 @subsubsection Win32Ada
26291 Win32Ada is a binding for the Microsoft Win32 API. This binding can be
26292 easily installed from the provided installer. To use the Win32Ada
26293 binding you need to use a project file, and adding a single with_clause
26294 will give you full access to the Win32Ada binding sources and ensure
26295 that the proper libraries are passed to the linker.
26302 for Sources use ...;
26307 To build the application you just need to call gprbuild for the
26308 application's project, here p.gpr:
26317 @node wPOSIX,,Win32Ada,Windows Specific Add-Ons
26318 @anchor{gnat_ugn/platform_specific_information id42}@anchor{225}@anchor{gnat_ugn/platform_specific_information wposix}@anchor{226}
26319 @subsubsection wPOSIX
26322 wPOSIX is a minimal POSIX binding whose goal is to help with building
26323 cross-platforms applications. This binding is not complete though, as
26324 the Win32 API does not provide the necessary support for all POSIX APIs.
26326 To use the wPOSIX binding you need to use a project file, and adding
26327 a single with_clause will give you full access to the wPOSIX binding
26328 sources and ensure that the proper libraries are passed to the linker.
26335 for Sources use ...;
26340 To build the application you just need to call gprbuild for the
26341 application's project, here p.gpr:
26350 @node Mac OS Topics,,Microsoft Windows Topics,Platform-Specific Information
26351 @anchor{gnat_ugn/platform_specific_information mac-os-topics}@anchor{2d}@anchor{gnat_ugn/platform_specific_information id43}@anchor{227}
26352 @section Mac OS Topics
26357 This section describes topics that are specific to Apple's OS X
26361 * Codesigning the Debugger::
26365 @node Codesigning the Debugger,,,Mac OS Topics
26366 @anchor{gnat_ugn/platform_specific_information codesigning-the-debugger}@anchor{228}
26367 @subsection Codesigning the Debugger
26370 The Darwin Kernel requires the debugger to have special permissions
26371 before it is allowed to control other processes. These permissions
26372 are granted by codesigning the GDB executable. Without these
26373 permissions, the debugger will report error messages such as:
26376 Starting program: /x/y/foo
26377 Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
26378 (please check gdb is codesigned - see taskgated(8))
26381 Codesigning requires a certificate. The following procedure explains
26388 Start the Keychain Access application (in
26389 /Applications/Utilities/Keychain Access.app)
26392 Select the Keychain Access -> Certificate Assistant ->
26393 Create a Certificate... menu
26402 Choose a name for the new certificate (this procedure will use
26403 "gdb-cert" as an example)
26406 Set "Identity Type" to "Self Signed Root"
26409 Set "Certificate Type" to "Code Signing"
26412 Activate the "Let me override defaults" option
26416 Click several times on "Continue" until the "Specify a Location
26417 For The Certificate" screen appears, then set "Keychain" to "System"
26420 Click on "Continue" until the certificate is created
26423 Finally, in the view, double-click on the new certificate,
26424 and set "When using this certificate" to "Always Trust"
26427 Exit the Keychain Access application and restart the computer
26428 (this is unfortunately required)
26431 Once a certificate has been created, the debugger can be codesigned
26432 as follow. In a Terminal, run the following command:
26437 $ codesign -f -s "gdb-cert" <gnat_install_prefix>/bin/gdb
26441 where "gdb-cert" should be replaced by the actual certificate
26442 name chosen above, and <gnat_install_prefix> should be replaced by
26443 the location where you installed GNAT. Also, be sure that users are
26444 in the Unix group @code{_developer}.
26446 @node Example of Binder Output File,Elaboration Order Handling in GNAT,Platform-Specific Information,Top
26447 @anchor{gnat_ugn/example_of_binder_output example-of-binder-output-file}@anchor{e}@anchor{gnat_ugn/example_of_binder_output doc}@anchor{229}@anchor{gnat_ugn/example_of_binder_output id1}@anchor{22a}
26448 @chapter Example of Binder Output File
26451 @geindex Binder output (example)
26453 This Appendix displays the source code for the output file
26454 generated by @emph{gnatbind} for a simple 'Hello World' program.
26455 Comments have been added for clarification purposes.
26458 -- The package is called Ada_Main unless this name is actually used
26459 -- as a unit name in the partition, in which case some other unique
26464 package ada_main is
26465 pragma Warnings (Off);
26467 -- The main program saves the parameters (argument count,
26468 -- argument values, environment pointer) in global variables
26469 -- for later access by other units including
26470 -- Ada.Command_Line.
26472 gnat_argc : Integer;
26473 gnat_argv : System.Address;
26474 gnat_envp : System.Address;
26476 -- The actual variables are stored in a library routine. This
26477 -- is useful for some shared library situations, where there
26478 -- are problems if variables are not in the library.
26480 pragma Import (C, gnat_argc);
26481 pragma Import (C, gnat_argv);
26482 pragma Import (C, gnat_envp);
26484 -- The exit status is similarly an external location
26486 gnat_exit_status : Integer;
26487 pragma Import (C, gnat_exit_status);
26489 GNAT_Version : constant String :=
26490 "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL;
26491 pragma Export (C, GNAT_Version, "__gnat_version");
26493 Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL;
26494 pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name");
26496 -- This is the generated adainit routine that performs
26497 -- initialization at the start of execution. In the case
26498 -- where Ada is the main program, this main program makes
26499 -- a call to adainit at program startup.
26502 pragma Export (C, adainit, "adainit");
26504 -- This is the generated adafinal routine that performs
26505 -- finalization at the end of execution. In the case where
26506 -- Ada is the main program, this main program makes a call
26507 -- to adafinal at program termination.
26509 procedure adafinal;
26510 pragma Export (C, adafinal, "adafinal");
26512 -- This routine is called at the start of execution. It is
26513 -- a dummy routine that is used by the debugger to breakpoint
26514 -- at the start of execution.
26516 -- This is the actual generated main program (it would be
26517 -- suppressed if the no main program switch were used). As
26518 -- required by standard system conventions, this program has
26519 -- the external name main.
26523 argv : System.Address;
26524 envp : System.Address)
26526 pragma Export (C, main, "main");
26528 -- The following set of constants give the version
26529 -- identification values for every unit in the bound
26530 -- partition. This identification is computed from all
26531 -- dependent semantic units, and corresponds to the
26532 -- string that would be returned by use of the
26533 -- Body_Version or Version attributes.
26535 -- The following Export pragmas export the version numbers
26536 -- with symbolic names ending in B (for body) or S
26537 -- (for spec) so that they can be located in a link. The
26538 -- information provided here is sufficient to track down
26539 -- the exact versions of units used in a given build.
26541 type Version_32 is mod 2 ** 32;
26542 u00001 : constant Version_32 := 16#8ad6e54a#;
26543 pragma Export (C, u00001, "helloB");
26544 u00002 : constant Version_32 := 16#fbff4c67#;
26545 pragma Export (C, u00002, "system__standard_libraryB");
26546 u00003 : constant Version_32 := 16#1ec6fd90#;
26547 pragma Export (C, u00003, "system__standard_libraryS");
26548 u00004 : constant Version_32 := 16#3ffc8e18#;
26549 pragma Export (C, u00004, "adaS");
26550 u00005 : constant Version_32 := 16#28f088c2#;
26551 pragma Export (C, u00005, "ada__text_ioB");
26552 u00006 : constant Version_32 := 16#f372c8ac#;
26553 pragma Export (C, u00006, "ada__text_ioS");
26554 u00007 : constant Version_32 := 16#2c143749#;
26555 pragma Export (C, u00007, "ada__exceptionsB");
26556 u00008 : constant Version_32 := 16#f4f0cce8#;
26557 pragma Export (C, u00008, "ada__exceptionsS");
26558 u00009 : constant Version_32 := 16#a46739c0#;
26559 pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB");
26560 u00010 : constant Version_32 := 16#3aac8c92#;
26561 pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS");
26562 u00011 : constant Version_32 := 16#1d274481#;
26563 pragma Export (C, u00011, "systemS");
26564 u00012 : constant Version_32 := 16#a207fefe#;
26565 pragma Export (C, u00012, "system__soft_linksB");
26566 u00013 : constant Version_32 := 16#467d9556#;
26567 pragma Export (C, u00013, "system__soft_linksS");
26568 u00014 : constant Version_32 := 16#b01dad17#;
26569 pragma Export (C, u00014, "system__parametersB");
26570 u00015 : constant Version_32 := 16#630d49fe#;
26571 pragma Export (C, u00015, "system__parametersS");
26572 u00016 : constant Version_32 := 16#b19b6653#;
26573 pragma Export (C, u00016, "system__secondary_stackB");
26574 u00017 : constant Version_32 := 16#b6468be8#;
26575 pragma Export (C, u00017, "system__secondary_stackS");
26576 u00018 : constant Version_32 := 16#39a03df9#;
26577 pragma Export (C, u00018, "system__storage_elementsB");
26578 u00019 : constant Version_32 := 16#30e40e85#;
26579 pragma Export (C, u00019, "system__storage_elementsS");
26580 u00020 : constant Version_32 := 16#41837d1e#;
26581 pragma Export (C, u00020, "system__stack_checkingB");
26582 u00021 : constant Version_32 := 16#93982f69#;
26583 pragma Export (C, u00021, "system__stack_checkingS");
26584 u00022 : constant Version_32 := 16#393398c1#;
26585 pragma Export (C, u00022, "system__exception_tableB");
26586 u00023 : constant Version_32 := 16#b33e2294#;
26587 pragma Export (C, u00023, "system__exception_tableS");
26588 u00024 : constant Version_32 := 16#ce4af020#;
26589 pragma Export (C, u00024, "system__exceptionsB");
26590 u00025 : constant Version_32 := 16#75442977#;
26591 pragma Export (C, u00025, "system__exceptionsS");
26592 u00026 : constant Version_32 := 16#37d758f1#;
26593 pragma Export (C, u00026, "system__exceptions__machineS");
26594 u00027 : constant Version_32 := 16#b895431d#;
26595 pragma Export (C, u00027, "system__exceptions_debugB");
26596 u00028 : constant Version_32 := 16#aec55d3f#;
26597 pragma Export (C, u00028, "system__exceptions_debugS");
26598 u00029 : constant Version_32 := 16#570325c8#;
26599 pragma Export (C, u00029, "system__img_intB");
26600 u00030 : constant Version_32 := 16#1ffca443#;
26601 pragma Export (C, u00030, "system__img_intS");
26602 u00031 : constant Version_32 := 16#b98c3e16#;
26603 pragma Export (C, u00031, "system__tracebackB");
26604 u00032 : constant Version_32 := 16#831a9d5a#;
26605 pragma Export (C, u00032, "system__tracebackS");
26606 u00033 : constant Version_32 := 16#9ed49525#;
26607 pragma Export (C, u00033, "system__traceback_entriesB");
26608 u00034 : constant Version_32 := 16#1d7cb2f1#;
26609 pragma Export (C, u00034, "system__traceback_entriesS");
26610 u00035 : constant Version_32 := 16#8c33a517#;
26611 pragma Export (C, u00035, "system__wch_conB");
26612 u00036 : constant Version_32 := 16#065a6653#;
26613 pragma Export (C, u00036, "system__wch_conS");
26614 u00037 : constant Version_32 := 16#9721e840#;
26615 pragma Export (C, u00037, "system__wch_stwB");
26616 u00038 : constant Version_32 := 16#2b4b4a52#;
26617 pragma Export (C, u00038, "system__wch_stwS");
26618 u00039 : constant Version_32 := 16#92b797cb#;
26619 pragma Export (C, u00039, "system__wch_cnvB");
26620 u00040 : constant Version_32 := 16#09eddca0#;
26621 pragma Export (C, u00040, "system__wch_cnvS");
26622 u00041 : constant Version_32 := 16#6033a23f#;
26623 pragma Export (C, u00041, "interfacesS");
26624 u00042 : constant Version_32 := 16#ece6fdb6#;
26625 pragma Export (C, u00042, "system__wch_jisB");
26626 u00043 : constant Version_32 := 16#899dc581#;
26627 pragma Export (C, u00043, "system__wch_jisS");
26628 u00044 : constant Version_32 := 16#10558b11#;
26629 pragma Export (C, u00044, "ada__streamsB");
26630 u00045 : constant Version_32 := 16#2e6701ab#;
26631 pragma Export (C, u00045, "ada__streamsS");
26632 u00046 : constant Version_32 := 16#db5c917c#;
26633 pragma Export (C, u00046, "ada__io_exceptionsS");
26634 u00047 : constant Version_32 := 16#12c8cd7d#;
26635 pragma Export (C, u00047, "ada__tagsB");
26636 u00048 : constant Version_32 := 16#ce72c228#;
26637 pragma Export (C, u00048, "ada__tagsS");
26638 u00049 : constant Version_32 := 16#c3335bfd#;
26639 pragma Export (C, u00049, "system__htableB");
26640 u00050 : constant Version_32 := 16#99e5f76b#;
26641 pragma Export (C, u00050, "system__htableS");
26642 u00051 : constant Version_32 := 16#089f5cd0#;
26643 pragma Export (C, u00051, "system__string_hashB");
26644 u00052 : constant Version_32 := 16#3bbb9c15#;
26645 pragma Export (C, u00052, "system__string_hashS");
26646 u00053 : constant Version_32 := 16#807fe041#;
26647 pragma Export (C, u00053, "system__unsigned_typesS");
26648 u00054 : constant Version_32 := 16#d27be59e#;
26649 pragma Export (C, u00054, "system__val_lluB");
26650 u00055 : constant Version_32 := 16#fa8db733#;
26651 pragma Export (C, u00055, "system__val_lluS");
26652 u00056 : constant Version_32 := 16#27b600b2#;
26653 pragma Export (C, u00056, "system__val_utilB");
26654 u00057 : constant Version_32 := 16#b187f27f#;
26655 pragma Export (C, u00057, "system__val_utilS");
26656 u00058 : constant Version_32 := 16#d1060688#;
26657 pragma Export (C, u00058, "system__case_utilB");
26658 u00059 : constant Version_32 := 16#392e2d56#;
26659 pragma Export (C, u00059, "system__case_utilS");
26660 u00060 : constant Version_32 := 16#84a27f0d#;
26661 pragma Export (C, u00060, "interfaces__c_streamsB");
26662 u00061 : constant Version_32 := 16#8bb5f2c0#;
26663 pragma Export (C, u00061, "interfaces__c_streamsS");
26664 u00062 : constant Version_32 := 16#6db6928f#;
26665 pragma Export (C, u00062, "system__crtlS");
26666 u00063 : constant Version_32 := 16#4e6a342b#;
26667 pragma Export (C, u00063, "system__file_ioB");
26668 u00064 : constant Version_32 := 16#ba56a5e4#;
26669 pragma Export (C, u00064, "system__file_ioS");
26670 u00065 : constant Version_32 := 16#b7ab275c#;
26671 pragma Export (C, u00065, "ada__finalizationB");
26672 u00066 : constant Version_32 := 16#19f764ca#;
26673 pragma Export (C, u00066, "ada__finalizationS");
26674 u00067 : constant Version_32 := 16#95817ed8#;
26675 pragma Export (C, u00067, "system__finalization_rootB");
26676 u00068 : constant Version_32 := 16#52d53711#;
26677 pragma Export (C, u00068, "system__finalization_rootS");
26678 u00069 : constant Version_32 := 16#769e25e6#;
26679 pragma Export (C, u00069, "interfaces__cB");
26680 u00070 : constant Version_32 := 16#4a38bedb#;
26681 pragma Export (C, u00070, "interfaces__cS");
26682 u00071 : constant Version_32 := 16#07e6ee66#;
26683 pragma Export (C, u00071, "system__os_libB");
26684 u00072 : constant Version_32 := 16#d7b69782#;
26685 pragma Export (C, u00072, "system__os_libS");
26686 u00073 : constant Version_32 := 16#1a817b8e#;
26687 pragma Export (C, u00073, "system__stringsB");
26688 u00074 : constant Version_32 := 16#639855e7#;
26689 pragma Export (C, u00074, "system__stringsS");
26690 u00075 : constant Version_32 := 16#e0b8de29#;
26691 pragma Export (C, u00075, "system__file_control_blockS");
26692 u00076 : constant Version_32 := 16#b5b2aca1#;
26693 pragma Export (C, u00076, "system__finalization_mastersB");
26694 u00077 : constant Version_32 := 16#69316dc1#;
26695 pragma Export (C, u00077, "system__finalization_mastersS");
26696 u00078 : constant Version_32 := 16#57a37a42#;
26697 pragma Export (C, u00078, "system__address_imageB");
26698 u00079 : constant Version_32 := 16#bccbd9bb#;
26699 pragma Export (C, u00079, "system__address_imageS");
26700 u00080 : constant Version_32 := 16#7268f812#;
26701 pragma Export (C, u00080, "system__img_boolB");
26702 u00081 : constant Version_32 := 16#e8fe356a#;
26703 pragma Export (C, u00081, "system__img_boolS");
26704 u00082 : constant Version_32 := 16#d7aac20c#;
26705 pragma Export (C, u00082, "system__ioB");
26706 u00083 : constant Version_32 := 16#8365b3ce#;
26707 pragma Export (C, u00083, "system__ioS");
26708 u00084 : constant Version_32 := 16#6d4d969a#;
26709 pragma Export (C, u00084, "system__storage_poolsB");
26710 u00085 : constant Version_32 := 16#e87cc305#;
26711 pragma Export (C, u00085, "system__storage_poolsS");
26712 u00086 : constant Version_32 := 16#e34550ca#;
26713 pragma Export (C, u00086, "system__pool_globalB");
26714 u00087 : constant Version_32 := 16#c88d2d16#;
26715 pragma Export (C, u00087, "system__pool_globalS");
26716 u00088 : constant Version_32 := 16#9d39c675#;
26717 pragma Export (C, u00088, "system__memoryB");
26718 u00089 : constant Version_32 := 16#445a22b5#;
26719 pragma Export (C, u00089, "system__memoryS");
26720 u00090 : constant Version_32 := 16#6a859064#;
26721 pragma Export (C, u00090, "system__storage_pools__subpoolsB");
26722 u00091 : constant Version_32 := 16#e3b008dc#;
26723 pragma Export (C, u00091, "system__storage_pools__subpoolsS");
26724 u00092 : constant Version_32 := 16#63f11652#;
26725 pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB");
26726 u00093 : constant Version_32 := 16#fe2f4b3a#;
26727 pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS");
26729 -- BEGIN ELABORATION ORDER
26733 -- system.case_util%s
26734 -- system.case_util%b
26736 -- system.img_bool%s
26737 -- system.img_bool%b
26738 -- system.img_int%s
26739 -- system.img_int%b
26742 -- system.parameters%s
26743 -- system.parameters%b
26745 -- interfaces.c_streams%s
26746 -- interfaces.c_streams%b
26747 -- system.standard_library%s
26748 -- system.exceptions_debug%s
26749 -- system.exceptions_debug%b
26750 -- system.storage_elements%s
26751 -- system.storage_elements%b
26752 -- system.stack_checking%s
26753 -- system.stack_checking%b
26754 -- system.string_hash%s
26755 -- system.string_hash%b
26757 -- system.strings%s
26758 -- system.strings%b
26760 -- system.traceback_entries%s
26761 -- system.traceback_entries%b
26762 -- ada.exceptions%s
26763 -- system.soft_links%s
26764 -- system.unsigned_types%s
26765 -- system.val_llu%s
26766 -- system.val_util%s
26767 -- system.val_util%b
26768 -- system.val_llu%b
26769 -- system.wch_con%s
26770 -- system.wch_con%b
26771 -- system.wch_cnv%s
26772 -- system.wch_jis%s
26773 -- system.wch_jis%b
26774 -- system.wch_cnv%b
26775 -- system.wch_stw%s
26776 -- system.wch_stw%b
26777 -- ada.exceptions.last_chance_handler%s
26778 -- ada.exceptions.last_chance_handler%b
26779 -- system.address_image%s
26780 -- system.exception_table%s
26781 -- system.exception_table%b
26782 -- ada.io_exceptions%s
26787 -- system.exceptions%s
26788 -- system.exceptions%b
26789 -- system.exceptions.machine%s
26790 -- system.finalization_root%s
26791 -- system.finalization_root%b
26792 -- ada.finalization%s
26793 -- ada.finalization%b
26794 -- system.storage_pools%s
26795 -- system.storage_pools%b
26796 -- system.finalization_masters%s
26797 -- system.storage_pools.subpools%s
26798 -- system.storage_pools.subpools.finalization%s
26799 -- system.storage_pools.subpools.finalization%b
26802 -- system.standard_library%b
26803 -- system.pool_global%s
26804 -- system.pool_global%b
26805 -- system.file_control_block%s
26806 -- system.file_io%s
26807 -- system.secondary_stack%s
26808 -- system.file_io%b
26809 -- system.storage_pools.subpools%b
26810 -- system.finalization_masters%b
26813 -- system.soft_links%b
26815 -- system.secondary_stack%b
26816 -- system.address_image%b
26817 -- system.traceback%s
26818 -- ada.exceptions%b
26819 -- system.traceback%b
26823 -- END ELABORATION ORDER
26830 -- The following source file name pragmas allow the generated file
26831 -- names to be unique for different main programs. They are needed
26832 -- since the package name will always be Ada_Main.
26834 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26835 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26837 pragma Suppress (Overflow_Check);
26838 with Ada.Exceptions;
26840 -- Generated package body for Ada_Main starts here
26842 package body ada_main is
26843 pragma Warnings (Off);
26845 -- These values are reference counter associated to units which have
26846 -- been elaborated. It is also used to avoid elaborating the
26847 -- same unit twice.
26849 E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E");
26850 E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E");
26851 E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E");
26852 E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E");
26853 E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E");
26854 E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E");
26855 E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E");
26856 E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E");
26857 E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E");
26858 E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E");
26859 E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E");
26860 E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E");
26861 E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E");
26862 E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E");
26863 E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E");
26864 E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E");
26865 E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E");
26866 E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E");
26868 Local_Priority_Specific_Dispatching : constant String := "";
26869 Local_Interrupt_States : constant String := "";
26871 Is_Elaborated : Boolean := False;
26873 procedure finalize_library is
26878 pragma Import (Ada, F1, "ada__text_io__finalize_spec");
26886 pragma Import (Ada, F2, "system__file_io__finalize_body");
26893 pragma Import (Ada, F3, "system__file_control_block__finalize_spec");
26901 pragma Import (Ada, F4, "system__pool_global__finalize_spec");
26907 pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec");
26913 pragma Import (Ada, F6, "system__finalization_masters__finalize_spec");
26918 procedure Reraise_Library_Exception_If_Any;
26919 pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any");
26921 Reraise_Library_Exception_If_Any;
26923 end finalize_library;
26929 procedure adainit is
26931 Main_Priority : Integer;
26932 pragma Import (C, Main_Priority, "__gl_main_priority");
26933 Time_Slice_Value : Integer;
26934 pragma Import (C, Time_Slice_Value, "__gl_time_slice_val");
26935 WC_Encoding : Character;
26936 pragma Import (C, WC_Encoding, "__gl_wc_encoding");
26937 Locking_Policy : Character;
26938 pragma Import (C, Locking_Policy, "__gl_locking_policy");
26939 Queuing_Policy : Character;
26940 pragma Import (C, Queuing_Policy, "__gl_queuing_policy");
26941 Task_Dispatching_Policy : Character;
26942 pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy");
26943 Priority_Specific_Dispatching : System.Address;
26944 pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching");
26945 Num_Specific_Dispatching : Integer;
26946 pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching");
26947 Main_CPU : Integer;
26948 pragma Import (C, Main_CPU, "__gl_main_cpu");
26949 Interrupt_States : System.Address;
26950 pragma Import (C, Interrupt_States, "__gl_interrupt_states");
26951 Num_Interrupt_States : Integer;
26952 pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states");
26953 Unreserve_All_Interrupts : Integer;
26954 pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");
26955 Detect_Blocking : Integer;
26956 pragma Import (C, Detect_Blocking, "__gl_detect_blocking");
26957 Default_Stack_Size : Integer;
26958 pragma Import (C, Default_Stack_Size, "__gl_default_stack_size");
26959 Leap_Seconds_Support : Integer;
26960 pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support");
26962 procedure Runtime_Initialize;
26963 pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize");
26965 Finalize_Library_Objects : No_Param_Proc;
26966 pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects");
26968 -- Start of processing for adainit
26972 -- Record various information for this partition. The values
26973 -- are derived by the binder from information stored in the ali
26974 -- files by the compiler.
26976 if Is_Elaborated then
26979 Is_Elaborated := True;
26980 Main_Priority := -1;
26981 Time_Slice_Value := -1;
26982 WC_Encoding := 'b';
26983 Locking_Policy := ' ';
26984 Queuing_Policy := ' ';
26985 Task_Dispatching_Policy := ' ';
26986 Priority_Specific_Dispatching :=
26987 Local_Priority_Specific_Dispatching'Address;
26988 Num_Specific_Dispatching := 0;
26990 Interrupt_States := Local_Interrupt_States'Address;
26991 Num_Interrupt_States := 0;
26992 Unreserve_All_Interrupts := 0;
26993 Detect_Blocking := 0;
26994 Default_Stack_Size := -1;
26995 Leap_Seconds_Support := 0;
26997 Runtime_Initialize;
26999 Finalize_Library_Objects := finalize_library'access;
27001 -- Now we have the elaboration calls for all units in the partition.
27002 -- The Elab_Spec and Elab_Body attributes generate references to the
27003 -- implicit elaboration procedures generated by the compiler for
27004 -- each unit that requires elaboration. Increment a counter of
27005 -- reference for each unit.
27007 System.Soft_Links'Elab_Spec;
27008 System.Exception_Table'Elab_Body;
27010 Ada.Io_Exceptions'Elab_Spec;
27012 Ada.Tags'Elab_Spec;
27013 Ada.Streams'Elab_Spec;
27015 Interfaces.C'Elab_Spec;
27016 System.Exceptions'Elab_Spec;
27018 System.Finalization_Root'Elab_Spec;
27020 Ada.Finalization'Elab_Spec;
27022 System.Storage_Pools'Elab_Spec;
27024 System.Finalization_Masters'Elab_Spec;
27025 System.Storage_Pools.Subpools'Elab_Spec;
27026 System.Pool_Global'Elab_Spec;
27028 System.File_Control_Block'Elab_Spec;
27030 System.File_Io'Elab_Body;
27033 System.Finalization_Masters'Elab_Body;
27036 Ada.Tags'Elab_Body;
27038 System.Soft_Links'Elab_Body;
27040 System.Os_Lib'Elab_Body;
27042 System.Secondary_Stack'Elab_Body;
27044 Ada.Text_Io'Elab_Spec;
27045 Ada.Text_Io'Elab_Body;
27053 procedure adafinal is
27054 procedure s_stalib_adafinal;
27055 pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal");
27057 procedure Runtime_Finalize;
27058 pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize");
27061 if not Is_Elaborated then
27064 Is_Elaborated := False;
27069 -- We get to the main program of the partition by using
27070 -- pragma Import because if we try to with the unit and
27071 -- call it Ada style, then not only do we waste time
27072 -- recompiling it, but also, we don't really know the right
27073 -- switches (e.g.@@: identifier character set) to be used
27076 procedure Ada_Main_Program;
27077 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27083 -- main is actually a function, as in the ANSI C standard,
27084 -- defined to return the exit status. The three parameters
27085 -- are the argument count, argument values and environment
27090 argv : System.Address;
27091 envp : System.Address)
27094 -- The initialize routine performs low level system
27095 -- initialization using a standard library routine which
27096 -- sets up signal handling and performs any other
27097 -- required setup. The routine can be found in file
27100 procedure initialize;
27101 pragma Import (C, initialize, "__gnat_initialize");
27103 -- The finalize routine performs low level system
27104 -- finalization using a standard library routine. The
27105 -- routine is found in file a-final.c and in the standard
27106 -- distribution is a dummy routine that does nothing, so
27107 -- really this is a hook for special user finalization.
27109 procedure finalize;
27110 pragma Import (C, finalize, "__gnat_finalize");
27112 -- The following is to initialize the SEH exceptions
27114 SEH : aliased array (1 .. 2) of Integer;
27116 Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address;
27117 pragma Volatile (Ensure_Reference);
27119 -- Start of processing for main
27122 -- Save global variables
27128 -- Call low level system initialization
27130 Initialize (SEH'Address);
27132 -- Call our generated Ada initialization routine
27136 -- Now we call the main program of the partition
27140 -- Perform Ada finalization
27144 -- Perform low level system finalization
27148 -- Return the proper exit status
27149 return (gnat_exit_status);
27152 -- This section is entirely comments, so it has no effect on the
27153 -- compilation of the Ada_Main package. It provides the list of
27154 -- object files and linker options, as well as some standard
27155 -- libraries needed for the link. The gnatlink utility parses
27156 -- this b~hello.adb file to read these comment lines to generate
27157 -- the appropriate command line arguments for the call to the
27158 -- system linker. The BEGIN/END lines are used for sentinels for
27159 -- this parsing operation.
27161 -- The exact file names will of course depend on the environment,
27162 -- host/target and location of files on the host system.
27164 -- BEGIN Object file/option list
27167 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27168 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27169 -- END Object file/option list
27174 The Ada code in the above example is exactly what is generated by the
27175 binder. We have added comments to more clearly indicate the function
27176 of each part of the generated @code{Ada_Main} package.
27178 The code is standard Ada in all respects, and can be processed by any
27179 tools that handle Ada. In particular, it is possible to use the debugger
27180 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27181 suppose that for reasons that you do not understand, your program is crashing
27182 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27183 you can place a breakpoint on the call:
27188 Ada.Text_Io'Elab_Body;
27192 and trace the elaboration routine for this package to find out where
27193 the problem might be (more usually of course you would be debugging
27194 elaboration code in your own application).
27196 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
27198 @node Elaboration Order Handling in GNAT,Inline Assembler,Example of Binder Output File,Top
27199 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order-handling-in-gnat}@anchor{f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat doc}@anchor{22b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id1}@anchor{22c}
27200 @chapter Elaboration Order Handling in GNAT
27203 @geindex Order of elaboration
27205 @geindex Elaboration control
27207 This appendix describes the handling of elaboration code in Ada and GNAT, and
27208 discusses how the order of elaboration of program units can be controlled in
27209 GNAT, either automatically or with explicit programming features.
27212 * Elaboration Code::
27213 * Elaboration Order::
27214 * Checking the Elaboration Order::
27215 * Controlling the Elaboration Order in Ada::
27216 * Controlling the Elaboration Order in GNAT::
27217 * Mixing Elaboration Models::
27218 * ABE Diagnostics::
27219 * SPARK Diagnostics::
27220 * Elaboration Circularities::
27221 * Resolving Elaboration Circularities::
27222 * Elaboration-related Compiler Switches::
27223 * Summary of Procedures for Elaboration Control::
27224 * Inspecting the Chosen Elaboration Order::
27228 @node Elaboration Code,Elaboration Order,,Elaboration Order Handling in GNAT
27229 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-code}@anchor{22d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id2}@anchor{22e}
27230 @section Elaboration Code
27233 Ada defines the term @emph{execution} as the process by which a construct achieves
27234 its run-time effect. This process is also referred to as @strong{elaboration} for
27235 declarations and @emph{evaluation} for expressions.
27237 The execution model in Ada allows for certain sections of an Ada program to be
27238 executed prior to execution of the program itself, primarily with the intent of
27239 initializing data. These sections are referred to as @strong{elaboration code}.
27240 Elaboration code is executed as follows:
27246 All partitions of an Ada program are executed in parallel with one another,
27247 possibly in a separate address space, and possibly on a separate computer.
27250 The execution of a partition involves running the environment task for that
27254 The environment task executes all elaboration code (if available) for all
27255 units within that partition. This code is said to be executed at
27256 @strong{elaboration time}.
27259 The environment task executes the Ada program (if available) for that
27263 In addition to the Ada terminology, this appendix defines the following terms:
27271 The act of calling a subprogram, instantiating a generic, or activating a
27277 A construct that is elaborated or invoked by elaboration code is referred to
27278 as an @emph{elaboration scenario} or simply a @strong{scenario}. GNAT recognizes the
27279 following scenarios:
27285 @code{'Access} of entries, operators, and subprograms
27288 Activation of tasks
27291 Calls to entries, operators, and subprograms
27294 Instantiations of generic templates
27300 A construct elaborated by a scenario is referred to as @emph{elaboration target}
27301 or simply @strong{target}. GNAT recognizes the following targets:
27307 For @code{'Access} of entries, operators, and subprograms, the target is the
27308 entry, operator, or subprogram being aliased.
27311 For activation of tasks, the target is the task body
27314 For calls to entries, operators, and subprograms, the target is the entry,
27315 operator, or subprogram being invoked.
27318 For instantiations of generic templates, the target is the generic template
27319 being instantiated.
27323 Elaboration code may appear in two distinct contexts:
27329 @emph{Library level}
27331 A scenario appears at the library level when it is encapsulated by a package
27332 [body] compilation unit, ignoring any other package [body] declarations in
27341 Val : ... := Server.Func;
27346 In the example above, the call to @code{Server.Func} is an elaboration scenario
27347 because it appears at the library level of package @code{Client}. Note that the
27348 declaration of package @code{Nested} is ignored according to the definition
27349 given above. As a result, the call to @code{Server.Func} will be invoked when
27350 the spec of unit @code{Client} is elaborated.
27353 @emph{Package body statements}
27355 A scenario appears within the statement sequence of a package body when it is
27356 bounded by the region starting from the @code{begin} keyword of the package body
27357 and ending at the @code{end} keyword of the package body.
27360 package body Client is
27370 In the example above, the call to @code{Proc} is an elaboration scenario because
27371 it appears within the statement sequence of package body @code{Client}. As a
27372 result, the call to @code{Proc} will be invoked when the body of @code{Client} is
27376 @node Elaboration Order,Checking the Elaboration Order,Elaboration Code,Elaboration Order Handling in GNAT
27377 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order}@anchor{22f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id3}@anchor{230}
27378 @section Elaboration Order
27381 The sequence by which the elaboration code of all units within a partition is
27382 executed is referred to as @strong{elaboration order}.
27384 Within a single unit, elaboration code is executed in sequential order.
27389 package body Client is
27390 Result : ... := Server.Func;
27393 package Inst is new Server.Gen;
27395 Inst.Eval (Result);
27403 In the example above, the elaboration order within package body @code{Client} is
27410 The object declaration of @code{Result} is elaborated.
27416 Function @code{Server.Func} is invoked.
27420 The subprogram body of @code{Proc} is elaborated.
27423 Procedure @code{Proc} is invoked.
27429 Generic unit @code{Server.Gen} is instantiated as @code{Inst}.
27432 Instance @code{Inst} is elaborated.
27435 Procedure @code{Inst.Eval} is invoked.
27439 The elaboration order of all units within a partition depends on the following
27446 @emph{with}ed units
27455 preelaborability of units
27458 presence of elaboration control pragmas
27461 invocations performed in elaboration code
27464 A program may have several elaboration orders depending on its structure.
27470 function Func (Index : Integer) return Integer;
27475 package body Server is
27476 Results : array (1 .. 5) of Integer := (1, 2, 3, 4, 5);
27478 function Func (Index : Integer) return Integer is
27480 return Results (Index);
27488 Val : constant Integer := Server.Func (3);
27494 procedure Main is begin null; end Main;
27498 The following elaboration order exhibits a fundamental problem referred to as
27499 @emph{access-before-elaboration} or simply @strong{ABE}.
27511 The elaboration of @code{Server}'s spec materializes function @code{Func}, making it
27512 callable. The elaboration of @code{Client}'s spec elaborates the declaration of
27513 @code{Val}. This invokes function @code{Server.Func}, however the body of
27514 @code{Server.Func} has not been elaborated yet because @code{Server}'s body comes
27515 after @code{Client}'s spec in the elaboration order. As a result, the value of
27516 constant @code{Val} is now undefined.
27518 Without any guarantees from the language, an undetected ABE problem may hinder
27519 proper initialization of data, which in turn may lead to undefined behavior at
27520 run time. To prevent such ABE problems, Ada employs dynamic checks in the same
27521 vein as index or null exclusion checks. A failed ABE check raises exception
27522 @code{Program_Error}.
27524 The following elaboration order avoids the ABE problem and the program can be
27525 successfully elaborated.
27537 Ada states that a total elaboration order must exist, but it does not define
27538 what this order is. A compiler is thus tasked with choosing a suitable
27539 elaboration order which satisfies the dependencies imposed by @emph{with} clauses,
27540 unit categorization, elaboration control pragmas, and invocations performed in
27541 elaboration code. Ideally an order that avoids ABE problems should be chosen,
27542 however a compiler may not always find such an order due to complications with
27543 respect to control and data flow.
27545 @node Checking the Elaboration Order,Controlling the Elaboration Order in Ada,Elaboration Order,Elaboration Order Handling in GNAT
27546 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id4}@anchor{231}@anchor{gnat_ugn/elaboration_order_handling_in_gnat checking-the-elaboration-order}@anchor{232}
27547 @section Checking the Elaboration Order
27550 To avoid placing the entire elaboration order burden on the programmer, Ada
27551 provides three lines of defense:
27557 @emph{Static semantics}
27559 Static semantic rules restrict the possible choice of elaboration order. For
27560 instance, if unit Client @emph{with}s unit Server, then the spec of Server is
27561 always elaborated prior to Client. The same principle applies to child units
27562 - the spec of a parent unit is always elaborated prior to the child unit.
27565 @emph{Dynamic semantics}
27567 Dynamic checks are performed at run time, to ensure that a target is
27568 elaborated prior to a scenario that invokes it, thus avoiding ABE problems.
27569 A failed run-time check raises exception @code{Program_Error}. The following
27570 restrictions apply:
27576 @emph{Restrictions on calls}
27578 An entry, operator, or subprogram can be called from elaboration code only
27579 when the corresponding body has been elaborated.
27582 @emph{Restrictions on instantiations}
27584 A generic unit can be instantiated by elaboration code only when the
27585 corresponding body has been elaborated.
27588 @emph{Restrictions on task activation}
27590 A task can be activated by elaboration code only when the body of the
27591 associated task type has been elaborated.
27594 The restrictions above can be summarized by the following rule:
27596 @emph{If a target has a body, then this body must be elaborated prior to the
27597 scenario that invokes the target.}
27600 @emph{Elaboration control}
27602 Pragmas are provided for the programmer to specify the desired elaboration
27606 @node Controlling the Elaboration Order in Ada,Controlling the Elaboration Order in GNAT,Checking the Elaboration Order,Elaboration Order Handling in GNAT
27607 @anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-ada}@anchor{233}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id5}@anchor{234}
27608 @section Controlling the Elaboration Order in Ada
27611 Ada provides several idioms and pragmas to aid the programmer with specifying
27612 the desired elaboration order and avoiding ABE problems altogether.
27618 @emph{Packages without a body}
27620 A library package which does not require a completing body does not suffer
27626 type Element is private;
27627 package Containers is
27628 type Element_Array is array (1 .. 10) of Element;
27633 In the example above, package @code{Pack} does not require a body because it
27634 does not contain any constructs which require completion in a body. As a
27635 result, generic @code{Pack.Containers} can be instantiated without encountering
27639 @geindex pragma Pure
27647 Pragma @code{Pure} places sufficient restrictions on a unit to guarantee that no
27648 scenario within the unit can result in an ABE problem.
27651 @geindex pragma Preelaborate
27657 @emph{pragma Preelaborate}
27659 Pragma @code{Preelaborate} is slightly less restrictive than pragma @code{Pure},
27660 but still strong enough to prevent ABE problems within a unit.
27663 @geindex pragma Elaborate_Body
27669 @emph{pragma Elaborate_Body}
27671 Pragma @code{Elaborate_Body} requires that the body of a unit is elaborated
27672 immediately after its spec. This restriction guarantees that no client
27673 scenario can invoke a server target before the target body has been
27674 elaborated because the spec and body are effectively "glued" together.
27678 pragma Elaborate_Body;
27680 function Func return Integer;
27685 package body Server is
27686 function Func return Integer is
27696 Val : constant Integer := Server.Func;
27700 In the example above, pragma @code{Elaborate_Body} guarantees the following
27709 because the spec of @code{Server} must be elaborated prior to @code{Client} by
27710 virtue of the @emph{with} clause, and in addition the body of @code{Server} must be
27711 elaborated immediately after the spec of @code{Server}.
27713 Removing pragma @code{Elaborate_Body} could result in the following incorrect
27722 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func} has
27723 not been elaborated yet.
27726 The pragmas outlined above allow a server unit to guarantee safe elaboration
27727 use by client units. Thus it is a good rule to mark units as @code{Pure} or
27728 @code{Preelaborate}, and if this is not possible, mark them as @code{Elaborate_Body}.
27730 There are however situations where @code{Pure}, @code{Preelaborate}, and
27731 @code{Elaborate_Body} are not applicable. Ada provides another set of pragmas for
27732 use by client units to help ensure the elaboration safety of server units they
27735 @geindex pragma Elaborate (Unit)
27741 @emph{pragma Elaborate (Unit)}
27743 Pragma @code{Elaborate} can be placed in the context clauses of a unit, after a
27744 @emph{with} clause. It guarantees that both the spec and body of its argument will
27745 be elaborated prior to the unit with the pragma. Note that other unrelated
27746 units may be elaborated in between the spec and the body.
27750 function Func return Integer;
27755 package body Server is
27756 function Func return Integer is
27765 pragma Elaborate (Server);
27767 Val : constant Integer := Server.Func;
27771 In the example above, pragma @code{Elaborate} guarantees the following
27780 Removing pragma @code{Elaborate} could result in the following incorrect
27789 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func}
27790 has not been elaborated yet.
27793 @geindex pragma Elaborate_All (Unit)
27799 @emph{pragma Elaborate_All (Unit)}
27801 Pragma @code{Elaborate_All} is placed in the context clauses of a unit, after
27802 a @emph{with} clause. It guarantees that both the spec and body of its argument
27803 will be elaborated prior to the unit with the pragma, as well as all units
27804 @emph{with}ed by the spec and body of the argument, recursively. Note that other
27805 unrelated units may be elaborated in between the spec and the body.
27809 function Factorial (Val : Natural) return Natural;
27814 package body Math is
27815 function Factorial (Val : Natural) return Natural is
27823 package Computer is
27824 type Operation_Kind is (None, Op_Factorial);
27828 Op : Operation_Kind) return Natural;
27834 package body Computer is
27837 Op : Operation_Kind) return Natural
27839 if Op = Op_Factorial then
27840 return Math.Factorial (Val);
27850 pragma Elaborate_All (Computer);
27852 Val : constant Natural :=
27853 Computer.Compute (123, Computer.Op_Factorial);
27857 In the example above, pragma @code{Elaborate_All} can result in the following
27868 Note that there are several allowable suborders for the specs and bodies of
27869 @code{Math} and @code{Computer}, but the point is that these specs and bodies will
27870 be elaborated prior to @code{Client}.
27872 Removing pragma @code{Elaborate_All} could result in the following incorrect
27883 where @code{Client} invokes @code{Computer.Compute}, which in turn invokes
27884 @code{Math.Factorial}, but the body of @code{Math.Factorial} has not been
27888 All pragmas shown above can be summarized by the following rule:
27890 @emph{If a client unit elaborates a server target directly or indirectly, then if
27891 the server unit requires a body and does not have pragma Pure, Preelaborate,
27892 or Elaborate_Body, then the client unit should have pragma Elaborate or
27893 Elaborate_All for the server unit.}
27895 If the rule outlined above is not followed, then a program may fall in one of
27896 the following states:
27902 @emph{No elaboration order exists}
27904 In this case a compiler must diagnose the situation, and refuse to build an
27905 executable program.
27908 @emph{One or more incorrect elaboration orders exist}
27910 In this case a compiler can build an executable program, but
27911 @code{Program_Error} will be raised when the program is run.
27914 @emph{Several elaboration orders exist, some correct, some incorrect}
27916 In this case the programmer has not controlled the elaboration order. As a
27917 result, a compiler may or may not pick one of the correct orders, and the
27918 program may or may not raise @code{Program_Error} when it is run. This is the
27919 worst possible state because the program may fail on another compiler, or
27920 even another version of the same compiler.
27923 @emph{One or more correct orders exist}
27925 In this case a compiler can build an executable program, and the program is
27926 run successfully. This state may be guaranteed by following the outlined
27927 rules, or may be the result of good program architecture.
27930 Note that one additional advantage of using @code{Elaborate} and @code{Elaborate_All}
27931 is that the program continues to stay in the last state (one or more correct
27932 orders exist) even if maintenance changes the bodies of targets.
27934 @node Controlling the Elaboration Order in GNAT,Mixing Elaboration Models,Controlling the Elaboration Order in Ada,Elaboration Order Handling in GNAT
27935 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id6}@anchor{235}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-gnat}@anchor{236}
27936 @section Controlling the Elaboration Order in GNAT
27939 In addition to Ada semantics and rules synthesized from them, GNAT offers
27940 three elaboration models to aid the programmer with specifying the correct
27941 elaboration order and to diagnose elaboration problems.
27943 @geindex Dynamic elaboration model
27949 @emph{Dynamic elaboration model}
27951 This is the most permissive of the three elaboration models and emulates the
27952 behavior specified by the Ada Reference Manual. When the dynamic model is in
27953 effect, GNAT makes the following assumptions:
27959 All code within all units in a partition is considered to be elaboration
27963 Some of the invocations in elaboration code may not take place at runtime
27964 due to conditional execution.
27967 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
27968 that invoke internal targets. In addition, GNAT generates run-time checks for
27969 all external targets and for all scenarios that may exhibit ABE problems.
27971 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
27972 preelaborability of units, and elaboration control pragmas. The dynamic model
27973 attempts to take all invocations in elaboration code into account. If an
27974 invocation leads to a circularity, GNAT ignores the invocation based on the
27975 assumptions stated above. An order obtained using the dynamic model may fail
27976 an ABE check at runtime when GNAT ignored an invocation.
27978 The dynamic model is enabled with compiler switch @code{-gnatE}.
27981 @geindex Static elaboration model
27987 @emph{Static elaboration model}
27989 This is the middle ground of the three models. When the static model is in
27990 effect, GNAT makes the following assumptions:
27996 Only code at the library level and in package body statements within all
27997 units in a partition is considered to be elaboration code.
28000 All invocations in elaboration will take place at runtime, regardless of
28001 conditional execution.
28004 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28005 that invoke internal targets. In addition, GNAT generates run-time checks for
28006 all external targets and for all scenarios that may exhibit ABE problems.
28008 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
28009 preelaborability of units, presence of elaboration control pragmas, and all
28010 invocations in elaboration code. An order obtained using the static model is
28011 guaranteed to be ABE problem-free, excluding dispatching calls and
28012 access-to-subprogram types.
28014 The static model is the default model in GNAT.
28017 @geindex SPARK elaboration model
28023 @emph{SPARK elaboration model}
28025 This is the most conservative of the three models and enforces the SPARK
28026 rules of elaboration as defined in the SPARK Reference Manual, section 7.7.
28027 The SPARK model is in effect only when a scenario and a target reside in a
28028 region subject to @code{SPARK_Mode On}, otherwise the dynamic or static model
28031 The SPARK model is enabled with compiler switch @code{-gnatd.v}.
28034 @geindex Legacy elaboration models
28040 @emph{Legacy elaboration models}
28042 In addition to the three elaboration models outlined above, GNAT provides the
28043 following legacy models:
28049 @cite{Legacy elaboration-checking model} available in pre-18.x versions of GNAT.
28050 This model is enabled with compiler switch @code{-gnatH}.
28053 @cite{Legacy elaboration-order model} available in pre-20.x versions of GNAT.
28054 This model is enabled with binder switch @code{-H}.
28058 @geindex Relaxed elaboration mode
28060 The dynamic, legacy, and static models can be relaxed using compiler switch
28061 @code{-gnatJ}, making them more permissive. Note that in this mode, GNAT
28062 may not diagnose certain elaboration issues or install run-time checks.
28064 @node Mixing Elaboration Models,ABE Diagnostics,Controlling the Elaboration Order in GNAT,Elaboration Order Handling in GNAT
28065 @anchor{gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models}@anchor{237}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id7}@anchor{238}
28066 @section Mixing Elaboration Models
28069 It is possible to mix units compiled with a different elaboration model,
28070 however the following rules must be observed:
28076 A client unit compiled with the dynamic model can only @emph{with} a server unit
28077 that meets at least one of the following criteria:
28083 The server unit is compiled with the dynamic model.
28086 The server unit is a GNAT implementation unit from the @code{Ada}, @code{GNAT},
28087 @code{Interfaces}, or @code{System} hierarchies.
28090 The server unit has pragma @code{Pure} or @code{Preelaborate}.
28093 The client unit has an explicit @code{Elaborate_All} pragma for the server
28098 These rules ensure that elaboration checks are not omitted. If the rules are
28099 violated, the binder emits a warning:
28104 warning: "x.ads" has dynamic elaboration checks and with's
28105 warning: "y.ads" which has static elaboration checks
28109 The warnings can be suppressed by binder switch @code{-ws}.
28111 @node ABE Diagnostics,SPARK Diagnostics,Mixing Elaboration Models,Elaboration Order Handling in GNAT
28112 @anchor{gnat_ugn/elaboration_order_handling_in_gnat abe-diagnostics}@anchor{239}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{23a}
28113 @section ABE Diagnostics
28116 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28117 that invoke internal targets, regardless of whether the dynamic, SPARK, or
28118 static model is in effect.
28120 Note that GNAT emits warnings rather than hard errors whenever it encounters an
28121 elaboration problem. This is because the elaboration model in effect may be too
28122 conservative, or a particular scenario may not be invoked due conditional
28123 execution. The warnings can be suppressed selectively with @code{pragma Warnings
28124 (Off)} or globally with compiler switch @code{-gnatwL}.
28126 A @emph{guaranteed ABE} arises when the body of a target is not elaborated early
28127 enough, and causes @emph{all} scenarios that directly invoke the target to fail.
28132 package body Guaranteed_ABE is
28133 function ABE return Integer;
28135 Val : constant Integer := ABE;
28137 function ABE return Integer is
28141 end Guaranteed_ABE;
28145 In the example above, the elaboration of @code{Guaranteed_ABE}'s body elaborates
28146 the declaration of @code{Val}. This invokes function @code{ABE}, however the body of
28147 @code{ABE} has not been elaborated yet. GNAT emits the following diagnostic:
28152 4. Val : constant Integer := ABE;
28154 >>> warning: cannot call "ABE" before body seen
28155 >>> warning: Program_Error will be raised at run time
28159 A @emph{conditional ABE} arises when the body of a target is not elaborated early
28160 enough, and causes @emph{some} scenarios that directly invoke the target to fail.
28165 1. package body Conditional_ABE is
28166 2. procedure Force_Body is null;
28169 5. with function Func return Integer;
28171 7. Val : constant Integer := Func;
28174 10. function ABE return Integer;
28176 12. function Cause_ABE return Boolean is
28177 13. package Inst is new Gen (ABE);
28182 18. Val : constant Boolean := Cause_ABE;
28184 20. function ABE return Integer is
28189 25. Safe : constant Boolean := Cause_ABE;
28190 26. end Conditional_ABE;
28194 In the example above, the elaboration of package body @code{Conditional_ABE}
28195 elaborates the declaration of @code{Val}. This invokes function @code{Cause_ABE},
28196 which instantiates generic unit @code{Gen} as @code{Inst}. The elaboration of
28197 @code{Inst} invokes function @code{ABE}, however the body of @code{ABE} has not been
28198 elaborated yet. GNAT emits the following diagnostic:
28203 13. package Inst is new Gen (ABE);
28205 >>> warning: in instantiation at line 7
28206 >>> warning: cannot call "ABE" before body seen
28207 >>> warning: Program_Error may be raised at run time
28208 >>> warning: body of unit "Conditional_ABE" elaborated
28209 >>> warning: function "Cause_ABE" called at line 18
28210 >>> warning: function "ABE" called at line 7, instance at line 13
28214 Note that the same ABE problem does not occur with the elaboration of
28215 declaration @code{Safe} because the body of function @code{ABE} has already been
28216 elaborated at that point.
28218 @node SPARK Diagnostics,Elaboration Circularities,ABE Diagnostics,Elaboration Order Handling in GNAT
28219 @anchor{gnat_ugn/elaboration_order_handling_in_gnat spark-diagnostics}@anchor{23b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id9}@anchor{23c}
28220 @section SPARK Diagnostics
28223 GNAT enforces the SPARK rules of elaboration as defined in the SPARK Reference
28224 Manual section 7.7 when compiler switch @code{-gnatd.v} is in effect. Note
28225 that GNAT emits hard errors whenever it encounters a violation of the SPARK
28232 2. package body SPARK_Diagnostics with SPARK_Mode is
28233 3. Val : constant Integer := Server.Func;
28235 >>> call to "Func" during elaboration in SPARK
28236 >>> unit "SPARK_Diagnostics" requires pragma "Elaborate_All" for "Server"
28237 >>> body of unit "SPARK_Model" elaborated
28238 >>> function "Func" called at line 3
28240 4. end SPARK_Diagnostics;
28244 @node Elaboration Circularities,Resolving Elaboration Circularities,SPARK Diagnostics,Elaboration Order Handling in GNAT
28245 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id10}@anchor{23d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-circularities}@anchor{23e}
28246 @section Elaboration Circularities
28249 An @strong{elaboration circularity} occurs whenever the elaboration of a set of
28250 units enters a deadlocked state, where each unit is waiting for another unit
28251 to be elaborated. This situation may be the result of improper use of @emph{with}
28252 clauses, elaboration control pragmas, or invocations in elaboration code.
28254 The following example showcases an elaboration circularity.
28259 with B; pragma Elaborate (B);
28266 procedure Force_Body;
28273 procedure Force_Body is null;
28275 Elab : constant Integer := C.Func;
28281 function Func return Integer;
28288 function Func return Integer is
28296 The binder emits the following diagnostic:
28301 error: Elaboration circularity detected
28305 info: unit "a (spec)" depends on its own elaboration
28309 info: unit "a (spec)" has with clause and pragma Elaborate for unit "b (spec)"
28310 info: unit "b (body)" is in the closure of pragma Elaborate
28311 info: unit "b (body)" invokes a construct of unit "c (body)" at elaboration time
28312 info: unit "c (body)" has with clause for unit "a (spec)"
28316 info: remove pragma Elaborate for unit "b (body)" in unit "a (spec)"
28317 info: use the dynamic elaboration model (compiler switch -gnatE)
28321 The diagnostic consist of the following sections:
28329 This section provides a short explanation describing why the set of units
28330 could not be ordered.
28335 This section enumerates the units comprising the deadlocked set, along with
28336 their interdependencies.
28341 This section enumerates various tactics for eliminating the circularity.
28344 @node Resolving Elaboration Circularities,Elaboration-related Compiler Switches,Elaboration Circularities,Elaboration Order Handling in GNAT
28345 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id11}@anchor{23f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat resolving-elaboration-circularities}@anchor{240}
28346 @section Resolving Elaboration Circularities
28349 The most desirable option from the point of view of long-term maintenance is to
28350 rearrange the program so that the elaboration problems are avoided. One useful
28351 technique is to place the elaboration code into separate child packages.
28352 Another is to move some of the initialization code to explicitly invoked
28353 subprograms, where the program controls the order of initialization explicitly.
28354 Although this is the most desirable option, it may be impractical and involve
28355 too much modification, especially in the case of complex legacy code.
28357 When faced with an elaboration circularity, the programmer should also consider
28358 the tactics given in the suggestions section of the circularity diagnostic.
28359 Depending on the units involved in the circularity, their @emph{with} clauses,
28360 purity, preelaborability, presence of elaboration control pragmas and
28361 invocations at elaboration time, the binder may suggest one or more of the
28362 following tactics to eliminate the circularity:
28368 Pragma Elaborate elimination
28371 remove pragma Elaborate for unit "..." in unit "..."
28374 This tactic is suggested when the binder has determine that pragma
28381 Prevents a set of units from being elaborated.
28384 The removal of the pragma will not eliminate the semantic effects of the
28385 pragma. In other words, the argument of the pragma will still be elaborated
28386 prior to the unit containing the pragma.
28389 The removal of the pragma will enable the successful ordering of the units.
28392 The programmer should remove the pragma as advised, and rebuild the program.
28395 Pragma Elaborate_All elimination
28398 remove pragma Elaborate_All for unit "..." in unit "..."
28401 This tactic is suggested when the binder has determined that pragma
28402 @code{Elaborate_All}
28408 Prevents a set of units from being elaborated.
28411 The removal of the pragma will not eliminate the semantic effects of the
28412 pragma. In other words, the argument of the pragma along with its @emph{with}
28413 closure will still be elaborated prior to the unit containing the pragma.
28416 The removal of the pragma will enable the successful ordering of the units.
28419 The programmer should remove the pragma as advised, and rebuild the program.
28422 Pragma Elaborate_All downgrade
28425 change pragma Elaborate_All for unit "..." to Elaborate in unit "..."
28428 This tactic is always suggested with the pragma @code{Elaborate_All} elimination
28429 tactic. It offers a different alernative of guaranteeing that the argument of
28430 the pragma will still be elaborated prior to the unit containing the pragma.
28432 The programmer should update the pragma as advised, and rebuild the program.
28435 Pragma Elaborate_Body elimination
28438 remove pragma Elaborate_Body in unit "..."
28441 This tactic is suggested when the binder has determined that pragma
28442 @code{Elaborate_Body}
28448 Prevents a set of units from being elaborated.
28451 The removal of the pragma will enable the successful ordering of the units.
28454 Note that the binder cannot determine whether the pragma is required for
28455 other purposes, such as guaranteeing the initialization of a variable
28456 declared in the spec by elaboration code in the body.
28458 The programmer should remove the pragma as advised, and rebuild the program.
28461 Use of pragma Restrictions
28464 use pragma Restrictions (No_Entry_Calls_In_Elaboration_Code)
28467 This tactic is suggested when the binder has determined that a task
28468 activation at elaboration time
28474 Prevents a set of units from being elaborated.
28477 Note that the binder cannot determine with certainty whether the task will
28478 block at elaboration time.
28480 The programmer should create a configuration file, place the pragma within,
28481 update the general compilation arguments, and rebuild the program.
28484 Use of dynamic elaboration model
28487 use the dynamic elaboration model (compiler switch -gnatE)
28490 This tactic is suggested when the binder has determined that an invocation at
28497 Prevents a set of units from being elaborated.
28500 The use of the dynamic model will enable the successful ordering of the
28504 The programmer has two options:
28510 Determine the units involved in the invocation using the detailed
28511 invocation information, and add compiler switch @code{-gnatE} to the
28512 compilation arguments of selected files only. This approach will yield
28513 safer elaboration orders compared to the other option because it will
28514 minimize the opportunities presented to the dynamic model for ignoring
28518 Add compiler switch @code{-gnatE} to the general compilation arguments.
28522 Use of detailed invocation information
28525 use detailed invocation information (compiler switch -gnatd_F)
28528 This tactic is always suggested with the use of the dynamic model tactic. It
28529 causes the circularity section of the circularity diagnostic to describe the
28530 flow of elaboration code from a unit to a unit, enumerating all such paths in
28533 The programmer should analyze this information to determine which units
28534 should be compiled with the dynamic model.
28537 Forced dependency elimination
28540 remove the dependency of unit "..." on unit "..." from the argument of switch -f
28543 This tactic is suggested when the binder has determined that a dependency
28544 present in the forced delboration order file indicated by binder switch
28551 Prevents a set of units from being elaborated.
28554 The removal of the dependency will enable the successful ordering of the
28558 The programmer should edit the forced elaboration order file, remove the
28559 dependency, and rebind the program.
28562 All forced dependency elimination
28568 This tactic is suggested in case editing the forced elaboration order file is
28571 The programmer should remove binder switch @code{-f} from the binder
28572 arguments, and rebind.
28575 Multiple circularities diagnostic
28578 diagnose all circularities (binder switch -d_C)
28581 By default, the binder will diagnose only the highest precedence circularity.
28582 If the program contains multiple circularities, the binder will suggest the
28583 use of binder switch @code{-d_C} in order to obtain the diagnostics of all
28586 The programmer should add binder switch @code{-d_C} to the binder
28587 arguments, and rebind.
28590 If none of the tactics suggested by the binder eliminate the elaboration
28591 circularity, the programmer should consider using one of the legacy elaboration
28592 models, in the following order:
28598 Use the pre-20.x legacy elaboration order model, with binder switch
28602 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28603 switch @code{-gnatH} and binder switch @code{-H}.
28606 Use the relaxed static elaboration model, with compiler switches
28607 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28610 Use the relaxed dynamic elaboration model, with compiler switches
28611 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28615 @node Elaboration-related Compiler Switches,Summary of Procedures for Elaboration Control,Resolving Elaboration Circularities,Elaboration Order Handling in GNAT
28616 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id12}@anchor{241}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-related-compiler-switches}@anchor{242}
28617 @section Elaboration-related Compiler Switches
28620 GNAT has several switches that affect the elaboration model and consequently
28621 the elaboration order chosen by the binder.
28623 @geindex -gnatE (gnat)
28628 @item @code{-gnatE}
28630 Dynamic elaboration checking mode enabled
28632 When this switch is in effect, GNAT activates the dynamic model.
28635 @geindex -gnatel (gnat)
28640 @item @code{-gnatel}
28642 Turn on info messages on generated Elaborate[_All] pragmas
28644 This switch is only applicable to the pre-20.x legacy elaboration models.
28645 The post-20.x elaboration model no longer relies on implicitly generated
28646 @code{Elaborate} and @code{Elaborate_All} pragmas to order units.
28648 When this switch is in effect, GNAT will emit the following supplementary
28649 information depending on the elaboration model in effect.
28655 @emph{Dynamic model}
28657 GNAT will indicate missing @code{Elaborate} and @code{Elaborate_All} pragmas for
28658 all library-level scenarios within the partition.
28661 @emph{Static model}
28663 GNAT will indicate all scenarios invoked during elaboration. In addition,
28664 it will provide detailed traceback when an implicit @code{Elaborate} or
28665 @code{Elaborate_All} pragma is generated.
28670 GNAT will indicate how an elaboration requirement is met by the context of
28671 a unit. This diagnostic requires compiler switch @code{-gnatd.v}.
28674 1. with Server; pragma Elaborate_All (Server);
28675 2. package Client with SPARK_Mode is
28676 3. Val : constant Integer := Server.Func;
28678 >>> info: call to "Func" during elaboration in SPARK
28679 >>> info: "Elaborate_All" requirement for unit "Server" met by pragma at line 1
28686 @geindex -gnatH (gnat)
28691 @item @code{-gnatH}
28693 Legacy elaboration checking mode enabled
28695 When this switch is in effect, GNAT will utilize the pre-18.x elaboration
28699 @geindex -gnatJ (gnat)
28704 @item @code{-gnatJ}
28706 Relaxed elaboration checking mode enabled
28708 When this switch is in effect, GNAT will not process certain scenarios,
28709 resulting in a more permissive elaboration model. Note that this may
28710 eliminate some diagnostics and run-time checks.
28713 @geindex -gnatw.f (gnat)
28718 @item @code{-gnatw.f}
28720 Turn on warnings for suspicious Subp'Access
28722 When this switch is in effect, GNAT will treat @code{'Access} of an entry,
28723 operator, or subprogram as a potential call to the target and issue warnings:
28726 1. package body Attribute_Call is
28727 2. function Func return Integer;
28728 3. type Func_Ptr is access function return Integer;
28730 5. Ptr : constant Func_Ptr := Func'Access;
28732 >>> warning: "Access" attribute of "Func" before body seen
28733 >>> warning: possible Program_Error on later references
28734 >>> warning: body of unit "Attribute_Call" elaborated
28735 >>> warning: "Access" of "Func" taken at line 5
28738 7. function Func return Integer is
28742 11. end Attribute_Call;
28745 In the example above, the elaboration of declaration @code{Ptr} is assigned
28746 @code{Func'Access} before the body of @code{Func} has been elaborated.
28749 @geindex -gnatwl (gnat)
28754 @item @code{-gnatwl}
28756 Turn on warnings for elaboration problems
28758 When this switch is in effect, GNAT emits diagnostics in the form of warnings
28759 concerning various elaboration problems. The warnings are enabled by default.
28760 The switch is provided in case all warnings are suppressed, but elaboration
28761 warnings are still desired.
28763 @item @code{-gnatwL}
28765 Turn off warnings for elaboration problems
28767 When this switch is in effect, GNAT no longer emits any diagnostics in the
28768 form of warnings. Selective suppression of elaboration problems is possible
28769 using @code{pragma Warnings (Off)}.
28772 1. package body Selective_Suppression is
28773 2. function ABE return Integer;
28775 4. Val_1 : constant Integer := ABE;
28777 >>> warning: cannot call "ABE" before body seen
28778 >>> warning: Program_Error will be raised at run time
28781 6. pragma Warnings (Off);
28782 7. Val_2 : constant Integer := ABE;
28783 8. pragma Warnings (On);
28785 10. function ABE return Integer is
28789 14. end Selective_Suppression;
28792 Note that suppressing elaboration warnings does not eliminate run-time
28793 checks. The example above will still fail at run time with an ABE.
28796 @node Summary of Procedures for Elaboration Control,Inspecting the Chosen Elaboration Order,Elaboration-related Compiler Switches,Elaboration Order Handling in GNAT
28797 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id13}@anchor{243}@anchor{gnat_ugn/elaboration_order_handling_in_gnat summary-of-procedures-for-elaboration-control}@anchor{244}
28798 @section Summary of Procedures for Elaboration Control
28801 A programmer should first compile the program with the default options, using
28802 none of the binder or compiler switches. If the binder succeeds in finding an
28803 elaboration order, then apart from possible cases involing dispatching calls
28804 and access-to-subprogram types, the program is free of elaboration errors.
28806 If it is important for the program to be portable to compilers other than GNAT,
28807 then the programmer should use compiler switch @code{-gnatel} and consider
28808 the messages about missing or implicitly created @code{Elaborate} and
28809 @code{Elaborate_All} pragmas.
28811 If the binder reports an elaboration circularity, the programmer has several
28818 Ensure that elaboration warnings are enabled. This will allow the static
28819 model to output trace information of elaboration issues. The trace
28820 information could shed light on previously unforeseen dependencies, as well
28821 as their origins. Elaboration warnings are enabled with compiler switch
28825 Cosider the tactics given in the suggestions section of the circularity
28829 If none of the steps outlined above resolve the circularity, use a more
28830 permissive elaboration model, in the following order:
28836 Use the pre-20.x legacy elaboration order model, with binder switch
28840 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28841 switch @code{-gnatH} and binder switch @code{-H}.
28844 Use the relaxed static elaboration model, with compiler switches
28845 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28848 Use the relaxed dynamic elaboration model, with compiler switches
28849 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28854 @node Inspecting the Chosen Elaboration Order,,Summary of Procedures for Elaboration Control,Elaboration Order Handling in GNAT
28855 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id14}@anchor{245}@anchor{gnat_ugn/elaboration_order_handling_in_gnat inspecting-the-chosen-elaboration-order}@anchor{246}
28856 @section Inspecting the Chosen Elaboration Order
28859 To see the elaboration order chosen by the binder, inspect the contents of file
28860 @cite{b~xxx.adb}. On certain targets, this file appears as @cite{b_xxx.adb}. The
28861 elaboration order appears as a sequence of calls to @code{Elab_Body} and
28862 @code{Elab_Spec}, interspersed with assignments to @cite{Exxx} which indicates that a
28863 particular unit is elaborated. For example:
28868 System.Soft_Links'Elab_Body;
28870 System.Secondary_Stack'Elab_Body;
28872 System.Exception_Table'Elab_Body;
28874 Ada.Io_Exceptions'Elab_Spec;
28876 Ada.Tags'Elab_Spec;
28877 Ada.Streams'Elab_Spec;
28879 Interfaces.C'Elab_Spec;
28881 System.Finalization_Root'Elab_Spec;
28883 System.Os_Lib'Elab_Body;
28885 System.Finalization_Implementation'Elab_Spec;
28886 System.Finalization_Implementation'Elab_Body;
28888 Ada.Finalization'Elab_Spec;
28890 Ada.Finalization.List_Controller'Elab_Spec;
28892 System.File_Control_Block'Elab_Spec;
28894 System.File_Io'Elab_Body;
28896 Ada.Tags'Elab_Body;
28898 Ada.Text_Io'Elab_Spec;
28899 Ada.Text_Io'Elab_Body;
28904 Note also binder switch @code{-l}, which outputs the chosen elaboration
28905 order and provides a more readable form of the above:
28913 system.case_util (spec)
28914 system.case_util (body)
28915 system.concat_2 (spec)
28916 system.concat_2 (body)
28917 system.concat_3 (spec)
28918 system.concat_3 (body)
28919 system.htable (spec)
28920 system.parameters (spec)
28921 system.parameters (body)
28923 interfaces.c_streams (spec)
28924 interfaces.c_streams (body)
28925 system.restrictions (spec)
28926 system.restrictions (body)
28927 system.standard_library (spec)
28928 system.exceptions (spec)
28929 system.exceptions (body)
28930 system.storage_elements (spec)
28931 system.storage_elements (body)
28932 system.secondary_stack (spec)
28933 system.stack_checking (spec)
28934 system.stack_checking (body)
28935 system.string_hash (spec)
28936 system.string_hash (body)
28937 system.htable (body)
28938 system.strings (spec)
28939 system.strings (body)
28940 system.traceback (spec)
28941 system.traceback (body)
28942 system.traceback_entries (spec)
28943 system.traceback_entries (body)
28944 ada.exceptions (spec)
28945 ada.exceptions.last_chance_handler (spec)
28946 system.soft_links (spec)
28947 system.soft_links (body)
28948 ada.exceptions.last_chance_handler (body)
28949 system.secondary_stack (body)
28950 system.exception_table (spec)
28951 system.exception_table (body)
28952 ada.io_exceptions (spec)
28955 interfaces.c (spec)
28956 interfaces.c (body)
28957 system.finalization_root (spec)
28958 system.finalization_root (body)
28959 system.memory (spec)
28960 system.memory (body)
28961 system.standard_library (body)
28962 system.os_lib (spec)
28963 system.os_lib (body)
28964 system.unsigned_types (spec)
28965 system.stream_attributes (spec)
28966 system.stream_attributes (body)
28967 system.finalization_implementation (spec)
28968 system.finalization_implementation (body)
28969 ada.finalization (spec)
28970 ada.finalization (body)
28971 ada.finalization.list_controller (spec)
28972 ada.finalization.list_controller (body)
28973 system.file_control_block (spec)
28974 system.file_io (spec)
28975 system.file_io (body)
28976 system.val_uns (spec)
28977 system.val_util (spec)
28978 system.val_util (body)
28979 system.val_uns (body)
28980 system.wch_con (spec)
28981 system.wch_con (body)
28982 system.wch_cnv (spec)
28983 system.wch_jis (spec)
28984 system.wch_jis (body)
28985 system.wch_cnv (body)
28986 system.wch_stw (spec)
28987 system.wch_stw (body)
28989 ada.exceptions (body)
28997 @node Inline Assembler,GNU Free Documentation License,Elaboration Order Handling in GNAT,Top
28998 @anchor{gnat_ugn/inline_assembler inline-assembler}@anchor{10}@anchor{gnat_ugn/inline_assembler doc}@anchor{247}@anchor{gnat_ugn/inline_assembler id1}@anchor{248}
28999 @chapter Inline Assembler
29002 @geindex Inline Assembler
29004 If you need to write low-level software that interacts directly
29005 with the hardware, Ada provides two ways to incorporate assembly
29006 language code into your program. First, you can import and invoke
29007 external routines written in assembly language, an Ada feature fully
29008 supported by GNAT. However, for small sections of code it may be simpler
29009 or more efficient to include assembly language statements directly
29010 in your Ada source program, using the facilities of the implementation-defined
29011 package @code{System.Machine_Code}, which incorporates the gcc
29012 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29013 including the following:
29019 No need to use non-Ada tools
29022 Consistent interface over different targets
29025 Automatic usage of the proper calling conventions
29028 Access to Ada constants and variables
29031 Definition of intrinsic routines
29034 Possibility of inlining a subprogram comprising assembler code
29037 Code optimizer can take Inline Assembler code into account
29040 This appendix presents a series of examples to show you how to use
29041 the Inline Assembler. Although it focuses on the Intel x86,
29042 the general approach applies also to other processors.
29043 It is assumed that you are familiar with Ada
29044 and with assembly language programming.
29047 * Basic Assembler Syntax::
29048 * A Simple Example of Inline Assembler::
29049 * Output Variables in Inline Assembler::
29050 * Input Variables in Inline Assembler::
29051 * Inlining Inline Assembler Code::
29052 * Other Asm Functionality::
29056 @node Basic Assembler Syntax,A Simple Example of Inline Assembler,,Inline Assembler
29057 @anchor{gnat_ugn/inline_assembler id2}@anchor{249}@anchor{gnat_ugn/inline_assembler basic-assembler-syntax}@anchor{24a}
29058 @section Basic Assembler Syntax
29061 The assembler used by GNAT and gcc is based not on the Intel assembly
29062 language, but rather on a language that descends from the AT&T Unix
29063 assembler @code{as} (and which is often referred to as 'AT&T syntax').
29064 The following table summarizes the main features of @code{as} syntax
29065 and points out the differences from the Intel conventions.
29066 See the gcc @code{as} and @code{gas} (an @code{as} macro
29067 pre-processor) documentation for further information.
29071 @emph{Register names}@w{ }
29073 gcc / @code{as}: Prefix with '%'; for example @code{%eax}@w{ }
29074 Intel: No extra punctuation; for example @code{eax}@w{ }
29082 @emph{Immediate operand}@w{ }
29084 gcc / @code{as}: Prefix with '$'; for example @code{$4}@w{ }
29085 Intel: No extra punctuation; for example @code{4}@w{ }
29093 @emph{Address}@w{ }
29095 gcc / @code{as}: Prefix with '$'; for example @code{$loc}@w{ }
29096 Intel: No extra punctuation; for example @code{loc}@w{ }
29104 @emph{Memory contents}@w{ }
29106 gcc / @code{as}: No extra punctuation; for example @code{loc}@w{ }
29107 Intel: Square brackets; for example @code{[loc]}@w{ }
29115 @emph{Register contents}@w{ }
29117 gcc / @code{as}: Parentheses; for example @code{(%eax)}@w{ }
29118 Intel: Square brackets; for example @code{[eax]}@w{ }
29126 @emph{Hexadecimal numbers}@w{ }
29128 gcc / @code{as}: Leading '0x' (C language syntax); for example @code{0xA0}@w{ }
29129 Intel: Trailing 'h'; for example @code{A0h}@w{ }
29137 @emph{Operand size}@w{ }
29139 gcc / @code{as}: Explicit in op code; for example @code{movw} to move a 16-bit word@w{ }
29140 Intel: Implicit, deduced by assembler; for example @code{mov}@w{ }
29148 @emph{Instruction repetition}@w{ }
29150 gcc / @code{as}: Split into two lines; for example@w{ }
29155 Intel: Keep on one line; for example @code{rep stosl}@w{ }
29163 @emph{Order of operands}@w{ }
29165 gcc / @code{as}: Source first; for example @code{movw $4, %eax}@w{ }
29166 Intel: Destination first; for example @code{mov eax, 4}@w{ }
29172 @node A Simple Example of Inline Assembler,Output Variables in Inline Assembler,Basic Assembler Syntax,Inline Assembler
29173 @anchor{gnat_ugn/inline_assembler a-simple-example-of-inline-assembler}@anchor{24b}@anchor{gnat_ugn/inline_assembler id3}@anchor{24c}
29174 @section A Simple Example of Inline Assembler
29177 The following example will generate a single assembly language statement,
29178 @code{nop}, which does nothing. Despite its lack of run-time effect,
29179 the example will be useful in illustrating the basics of
29180 the Inline Assembler facility.
29185 with System.Machine_Code; use System.Machine_Code;
29186 procedure Nothing is
29193 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29194 here it takes one parameter, a @emph{template string} that must be a static
29195 expression and that will form the generated instruction.
29196 @code{Asm} may be regarded as a compile-time procedure that parses
29197 the template string and additional parameters (none here),
29198 from which it generates a sequence of assembly language instructions.
29200 The examples in this chapter will illustrate several of the forms
29201 for invoking @code{Asm}; a complete specification of the syntax
29202 is found in the @code{Machine_Code_Insertions} section of the
29203 @cite{GNAT Reference Manual}.
29205 Under the standard GNAT conventions, the @code{Nothing} procedure
29206 should be in a file named @code{nothing.adb}.
29207 You can build the executable in the usual way:
29216 However, the interesting aspect of this example is not its run-time behavior
29217 but rather the generated assembly code.
29218 To see this output, invoke the compiler as follows:
29223 $ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb
29227 where the options are:
29238 compile only (no bind or link)
29247 generate assembler listing
29254 @item @code{-fomit-frame-pointer}
29256 do not set up separate stack frames
29263 @item @code{-gnatp}
29265 do not add runtime checks
29269 This gives a human-readable assembler version of the code. The resulting
29270 file will have the same name as the Ada source file, but with a @code{.s}
29271 extension. In our example, the file @code{nothing.s} has the following
29277 .file "nothing.adb"
29279 ___gnu_compiled_ada:
29282 .globl __ada_nothing
29294 The assembly code you included is clearly indicated by
29295 the compiler, between the @code{#APP} and @code{#NO_APP}
29296 delimiters. The character before the 'APP' and 'NOAPP'
29297 can differ on different targets. For example, GNU/Linux uses '#APP' while
29298 on NT you will see '/APP'.
29300 If you make a mistake in your assembler code (such as using the
29301 wrong size modifier, or using a wrong operand for the instruction) GNAT
29302 will report this error in a temporary file, which will be deleted when
29303 the compilation is finished. Generating an assembler file will help
29304 in such cases, since you can assemble this file separately using the
29305 @code{as} assembler that comes with gcc.
29307 Assembling the file using the command
29316 will give you error messages whose lines correspond to the assembler
29317 input file, so you can easily find and correct any mistakes you made.
29318 If there are no errors, @code{as} will generate an object file
29319 @code{nothing.out}.
29321 @node Output Variables in Inline Assembler,Input Variables in Inline Assembler,A Simple Example of Inline Assembler,Inline Assembler
29322 @anchor{gnat_ugn/inline_assembler id4}@anchor{24d}@anchor{gnat_ugn/inline_assembler output-variables-in-inline-assembler}@anchor{24e}
29323 @section Output Variables in Inline Assembler
29326 The examples in this section, showing how to access the processor flags,
29327 illustrate how to specify the destination operands for assembly language
29333 with Interfaces; use Interfaces;
29334 with Ada.Text_IO; use Ada.Text_IO;
29335 with System.Machine_Code; use System.Machine_Code;
29336 procedure Get_Flags is
29337 Flags : Unsigned_32;
29340 Asm ("pushfl" & LF & HT & -- push flags on stack
29341 "popl %%eax" & LF & HT & -- load eax with flags
29342 "movl %%eax, %0", -- store flags in variable
29343 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29344 Put_Line ("Flags register:" & Flags'Img);
29349 In order to have a nicely aligned assembly listing, we have separated
29350 multiple assembler statements in the Asm template string with linefeed
29351 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29352 The resulting section of the assembly output file is:
29360 movl %eax, -40(%ebp)
29365 It would have been legal to write the Asm invocation as:
29370 Asm ("pushfl popl %%eax movl %%eax, %0")
29374 but in the generated assembler file, this would come out as:
29380 pushfl popl %eax movl %eax, -40(%ebp)
29385 which is not so convenient for the human reader.
29387 We use Ada comments
29388 at the end of each line to explain what the assembler instructions
29389 actually do. This is a useful convention.
29391 When writing Inline Assembler instructions, you need to precede each register
29392 and variable name with a percent sign. Since the assembler already requires
29393 a percent sign at the beginning of a register name, you need two consecutive
29394 percent signs for such names in the Asm template string, thus @code{%%eax}.
29395 In the generated assembly code, one of the percent signs will be stripped off.
29397 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29398 variables: operands you later define using @code{Input} or @code{Output}
29399 parameters to @code{Asm}.
29400 An output variable is illustrated in
29401 the third statement in the Asm template string:
29410 The intent is to store the contents of the eax register in a variable that can
29411 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29412 necessarily work, since the compiler might optimize by using a register
29413 to hold Flags, and the expansion of the @code{movl} instruction would not be
29414 aware of this optimization. The solution is not to store the result directly
29415 but rather to advise the compiler to choose the correct operand form;
29416 that is the purpose of the @code{%0} output variable.
29418 Information about the output variable is supplied in the @code{Outputs}
29419 parameter to @code{Asm}:
29424 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29428 The output is defined by the @code{Asm_Output} attribute of the target type;
29429 the general format is
29434 Type'Asm_Output (constraint_string, variable_name)
29438 The constraint string directs the compiler how
29439 to store/access the associated variable. In the example
29444 Unsigned_32'Asm_Output ("=m", Flags);
29448 the @code{"m"} (memory) constraint tells the compiler that the variable
29449 @code{Flags} should be stored in a memory variable, thus preventing
29450 the optimizer from keeping it in a register. In contrast,
29455 Unsigned_32'Asm_Output ("=r", Flags);
29459 uses the @code{"r"} (register) constraint, telling the compiler to
29460 store the variable in a register.
29462 If the constraint is preceded by the equal character '=', it tells
29463 the compiler that the variable will be used to store data into it.
29465 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29466 allowing the optimizer to choose whatever it deems best.
29468 There are a fairly large number of constraints, but the ones that are
29469 most useful (for the Intel x86 processor) are the following:
29474 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
29489 global (i.e., can be stored anywhere)
29561 use one of eax, ebx, ecx or edx
29569 use one of eax, ebx, ecx, edx, esi or edi
29575 The full set of constraints is described in the gcc and @code{as}
29576 documentation; note that it is possible to combine certain constraints
29577 in one constraint string.
29579 You specify the association of an output variable with an assembler operand
29580 through the @code{%@emph{n}} notation, where @emph{n} is a non-negative
29586 Asm ("pushfl" & LF & HT & -- push flags on stack
29587 "popl %%eax" & LF & HT & -- load eax with flags
29588 "movl %%eax, %0", -- store flags in variable
29589 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29593 @code{%0} will be replaced in the expanded code by the appropriate operand,
29595 the compiler decided for the @code{Flags} variable.
29597 In general, you may have any number of output variables:
29603 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29606 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29607 of @code{Asm_Output} attributes
29615 Asm ("movl %%eax, %0" & LF & HT &
29616 "movl %%ebx, %1" & LF & HT &
29618 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29619 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29620 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29624 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29625 in the Ada program.
29627 As a variation on the @code{Get_Flags} example, we can use the constraints
29628 string to direct the compiler to store the eax register into the @code{Flags}
29629 variable, instead of including the store instruction explicitly in the
29630 @code{Asm} template string:
29635 with Interfaces; use Interfaces;
29636 with Ada.Text_IO; use Ada.Text_IO;
29637 with System.Machine_Code; use System.Machine_Code;
29638 procedure Get_Flags_2 is
29639 Flags : Unsigned_32;
29642 Asm ("pushfl" & LF & HT & -- push flags on stack
29643 "popl %%eax", -- save flags in eax
29644 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29645 Put_Line ("Flags register:" & Flags'Img);
29650 The @code{"a"} constraint tells the compiler that the @code{Flags}
29651 variable will come from the eax register. Here is the resulting code:
29660 movl %eax,-40(%ebp)
29664 The compiler generated the store of eax into Flags after
29665 expanding the assembler code.
29667 Actually, there was no need to pop the flags into the eax register;
29668 more simply, we could just pop the flags directly into the program variable:
29673 with Interfaces; use Interfaces;
29674 with Ada.Text_IO; use Ada.Text_IO;
29675 with System.Machine_Code; use System.Machine_Code;
29676 procedure Get_Flags_3 is
29677 Flags : Unsigned_32;
29680 Asm ("pushfl" & LF & HT & -- push flags on stack
29681 "pop %0", -- save flags in Flags
29682 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29683 Put_Line ("Flags register:" & Flags'Img);
29688 @node Input Variables in Inline Assembler,Inlining Inline Assembler Code,Output Variables in Inline Assembler,Inline Assembler
29689 @anchor{gnat_ugn/inline_assembler id5}@anchor{24f}@anchor{gnat_ugn/inline_assembler input-variables-in-inline-assembler}@anchor{250}
29690 @section Input Variables in Inline Assembler
29693 The example in this section illustrates how to specify the source operands
29694 for assembly language statements.
29695 The program simply increments its input value by 1:
29700 with Interfaces; use Interfaces;
29701 with Ada.Text_IO; use Ada.Text_IO;
29702 with System.Machine_Code; use System.Machine_Code;
29703 procedure Increment is
29705 function Incr (Value : Unsigned_32) return Unsigned_32 is
29706 Result : Unsigned_32;
29709 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29710 Inputs => Unsigned_32'Asm_Input ("a", Value));
29714 Value : Unsigned_32;
29718 Put_Line ("Value before is" & Value'Img);
29719 Value := Incr (Value);
29720 Put_Line ("Value after is" & Value'Img);
29725 The @code{Outputs} parameter to @code{Asm} specifies
29726 that the result will be in the eax register and that it is to be stored
29727 in the @code{Result} variable.
29729 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29730 but with an @code{Asm_Input} attribute.
29731 The @code{"="} constraint, indicating an output value, is not present.
29733 You can have multiple input variables, in the same way that you can have more
29734 than one output variable.
29736 The parameter count (%0, %1) etc, still starts at the first output statement,
29737 and continues with the input statements.
29739 Just as the @code{Outputs} parameter causes the register to be stored into the
29740 target variable after execution of the assembler statements, so does the
29741 @code{Inputs} parameter cause its variable to be loaded into the register
29742 before execution of the assembler statements.
29744 Thus the effect of the @code{Asm} invocation is:
29750 load the 32-bit value of @code{Value} into eax
29753 execute the @code{incl %eax} instruction
29756 store the contents of eax into the @code{Result} variable
29759 The resulting assembler file (with @code{-O2} optimization) contains:
29764 _increment__incr.1:
29777 @node Inlining Inline Assembler Code,Other Asm Functionality,Input Variables in Inline Assembler,Inline Assembler
29778 @anchor{gnat_ugn/inline_assembler id6}@anchor{251}@anchor{gnat_ugn/inline_assembler inlining-inline-assembler-code}@anchor{252}
29779 @section Inlining Inline Assembler Code
29782 For a short subprogram such as the @code{Incr} function in the previous
29783 section, the overhead of the call and return (creating / deleting the stack
29784 frame) can be significant, compared to the amount of code in the subprogram
29785 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29786 which directs the compiler to expand invocations of the subprogram at the
29787 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29788 Here is the resulting program:
29793 with Interfaces; use Interfaces;
29794 with Ada.Text_IO; use Ada.Text_IO;
29795 with System.Machine_Code; use System.Machine_Code;
29796 procedure Increment_2 is
29798 function Incr (Value : Unsigned_32) return Unsigned_32 is
29799 Result : Unsigned_32;
29802 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29803 Inputs => Unsigned_32'Asm_Input ("a", Value));
29806 pragma Inline (Increment);
29808 Value : Unsigned_32;
29812 Put_Line ("Value before is" & Value'Img);
29813 Value := Increment (Value);
29814 Put_Line ("Value after is" & Value'Img);
29819 Compile the program with both optimization (@code{-O2}) and inlining
29820 (@code{-gnatn}) enabled.
29822 The @code{Incr} function is still compiled as usual, but at the
29823 point in @code{Increment} where our function used to be called:
29829 call _increment__incr.1
29833 the code for the function body directly appears:
29846 thus saving the overhead of stack frame setup and an out-of-line call.
29848 @node Other Asm Functionality,,Inlining Inline Assembler Code,Inline Assembler
29849 @anchor{gnat_ugn/inline_assembler other-asm-functionality}@anchor{253}@anchor{gnat_ugn/inline_assembler id7}@anchor{254}
29850 @section Other @code{Asm} Functionality
29853 This section describes two important parameters to the @code{Asm}
29854 procedure: @code{Clobber}, which identifies register usage;
29855 and @code{Volatile}, which inhibits unwanted optimizations.
29858 * The Clobber Parameter::
29859 * The Volatile Parameter::
29863 @node The Clobber Parameter,The Volatile Parameter,,Other Asm Functionality
29864 @anchor{gnat_ugn/inline_assembler the-clobber-parameter}@anchor{255}@anchor{gnat_ugn/inline_assembler id8}@anchor{256}
29865 @subsection The @code{Clobber} Parameter
29868 One of the dangers of intermixing assembly language and a compiled language
29869 such as Ada is that the compiler needs to be aware of which registers are
29870 being used by the assembly code. In some cases, such as the earlier examples,
29871 the constraint string is sufficient to indicate register usage (e.g.,
29873 the eax register). But more generally, the compiler needs an explicit
29874 identification of the registers that are used by the Inline Assembly
29877 Using a register that the compiler doesn't know about
29878 could be a side effect of an instruction (like @code{mull}
29879 storing its result in both eax and edx).
29880 It can also arise from explicit register usage in your
29881 assembly code; for example:
29886 Asm ("movl %0, %%ebx" & LF & HT &
29888 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29889 Inputs => Unsigned_32'Asm_Input ("g", Var_In));
29893 where the compiler (since it does not analyze the @code{Asm} template string)
29894 does not know you are using the ebx register.
29896 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29897 to identify the registers that will be used by your assembly code:
29902 Asm ("movl %0, %%ebx" & LF & HT &
29904 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29905 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29910 The Clobber parameter is a static string expression specifying the
29911 register(s) you are using. Note that register names are @emph{not} prefixed
29912 by a percent sign. Also, if more than one register is used then their names
29913 are separated by commas; e.g., @code{"eax, ebx"}
29915 The @code{Clobber} parameter has several additional uses:
29921 Use 'register' name @code{cc} to indicate that flags might have changed
29924 Use 'register' name @code{memory} if you changed a memory location
29927 @node The Volatile Parameter,,The Clobber Parameter,Other Asm Functionality
29928 @anchor{gnat_ugn/inline_assembler the-volatile-parameter}@anchor{257}@anchor{gnat_ugn/inline_assembler id9}@anchor{258}
29929 @subsection The @code{Volatile} Parameter
29932 @geindex Volatile parameter
29934 Compiler optimizations in the presence of Inline Assembler may sometimes have
29935 unwanted effects. For example, when an @code{Asm} invocation with an input
29936 variable is inside a loop, the compiler might move the loading of the input
29937 variable outside the loop, regarding it as a one-time initialization.
29939 If this effect is not desired, you can disable such optimizations by setting
29940 the @code{Volatile} parameter to @code{True}; for example:
29945 Asm ("movl %0, %%ebx" & LF & HT &
29947 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29948 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29954 By default, @code{Volatile} is set to @code{False} unless there is no
29955 @code{Outputs} parameter.
29957 Although setting @code{Volatile} to @code{True} prevents unwanted
29958 optimizations, it will also disable other optimizations that might be
29959 important for efficiency. In general, you should set @code{Volatile}
29960 to @code{True} only if the compiler's optimizations have created
29963 @node GNU Free Documentation License,Index,Inline Assembler,Top
29964 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{259}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{25a}
29965 @chapter GNU Free Documentation License
29968 Version 1.3, 3 November 2008
29970 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
29971 @indicateurl{http://fsf.org/}
29973 Everyone is permitted to copy and distribute verbatim copies of this
29974 license document, but changing it is not allowed.
29978 The purpose of this License is to make a manual, textbook, or other
29979 functional and useful document "free" in the sense of freedom: to
29980 assure everyone the effective freedom to copy and redistribute it,
29981 with or without modifying it, either commercially or noncommercially.
29982 Secondarily, this License preserves for the author and publisher a way
29983 to get credit for their work, while not being considered responsible
29984 for modifications made by others.
29986 This License is a kind of "copyleft", which means that derivative
29987 works of the document must themselves be free in the same sense. It
29988 complements the GNU General Public License, which is a copyleft
29989 license designed for free software.
29991 We have designed this License in order to use it for manuals for free
29992 software, because free software needs free documentation: a free
29993 program should come with manuals providing the same freedoms that the
29994 software does. But this License is not limited to software manuals;
29995 it can be used for any textual work, regardless of subject matter or
29996 whether it is published as a printed book. We recommend this License
29997 principally for works whose purpose is instruction or reference.
29999 @strong{1. APPLICABILITY AND DEFINITIONS}
30001 This License applies to any manual or other work, in any medium, that
30002 contains a notice placed by the copyright holder saying it can be
30003 distributed under the terms of this License. Such a notice grants a
30004 world-wide, royalty-free license, unlimited in duration, to use that
30005 work under the conditions stated herein. The @strong{Document}, below,
30006 refers to any such manual or work. Any member of the public is a
30007 licensee, and is addressed as "@strong{you}". You accept the license if you
30008 copy, modify or distribute the work in a way requiring permission
30009 under copyright law.
30011 A "@strong{Modified Version}" of the Document means any work containing the
30012 Document or a portion of it, either copied verbatim, or with
30013 modifications and/or translated into another language.
30015 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
30016 the Document that deals exclusively with the relationship of the
30017 publishers or authors of the Document to the Document's overall subject
30018 (or to related matters) and contains nothing that could fall directly
30019 within that overall subject. (Thus, if the Document is in part a
30020 textbook of mathematics, a Secondary Section may not explain any
30021 mathematics.) The relationship could be a matter of historical
30022 connection with the subject or with related matters, or of legal,
30023 commercial, philosophical, ethical or political position regarding
30026 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
30027 are designated, as being those of Invariant Sections, in the notice
30028 that says that the Document is released under this License. If a
30029 section does not fit the above definition of Secondary then it is not
30030 allowed to be designated as Invariant. The Document may contain zero
30031 Invariant Sections. If the Document does not identify any Invariant
30032 Sections then there are none.
30034 The "@strong{Cover Texts}" are certain short passages of text that are listed,
30035 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
30036 the Document is released under this License. A Front-Cover Text may
30037 be at most 5 words, and a Back-Cover Text may be at most 25 words.
30039 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
30040 represented in a format whose specification is available to the
30041 general public, that is suitable for revising the document
30042 straightforwardly with generic text editors or (for images composed of
30043 pixels) generic paint programs or (for drawings) some widely available
30044 drawing editor, and that is suitable for input to text formatters or
30045 for automatic translation to a variety of formats suitable for input
30046 to text formatters. A copy made in an otherwise Transparent file
30047 format whose markup, or absence of markup, has been arranged to thwart
30048 or discourage subsequent modification by readers is not Transparent.
30049 An image format is not Transparent if used for any substantial amount
30050 of text. A copy that is not "Transparent" is called @strong{Opaque}.
30052 Examples of suitable formats for Transparent copies include plain
30053 ASCII without markup, Texinfo input format, LaTeX input format, SGML
30054 or XML using a publicly available DTD, and standard-conforming simple
30055 HTML, PostScript or PDF designed for human modification. Examples of
30056 transparent image formats include PNG, XCF and JPG. Opaque formats
30057 include proprietary formats that can be read and edited only by
30058 proprietary word processors, SGML or XML for which the DTD and/or
30059 processing tools are not generally available, and the
30060 machine-generated HTML, PostScript or PDF produced by some word
30061 processors for output purposes only.
30063 The "@strong{Title Page}" means, for a printed book, the title page itself,
30064 plus such following pages as are needed to hold, legibly, the material
30065 this License requires to appear in the title page. For works in
30066 formats which do not have any title page as such, "Title Page" means
30067 the text near the most prominent appearance of the work's title,
30068 preceding the beginning of the body of the text.
30070 The "@strong{publisher}" means any person or entity that distributes
30071 copies of the Document to the public.
30073 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
30074 title either is precisely XYZ or contains XYZ in parentheses following
30075 text that translates XYZ in another language. (Here XYZ stands for a
30076 specific section name mentioned below, such as "@strong{Acknowledgements}",
30077 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
30078 To "@strong{Preserve the Title}"
30079 of such a section when you modify the Document means that it remains a
30080 section "Entitled XYZ" according to this definition.
30082 The Document may include Warranty Disclaimers next to the notice which
30083 states that this License applies to the Document. These Warranty
30084 Disclaimers are considered to be included by reference in this
30085 License, but only as regards disclaiming warranties: any other
30086 implication that these Warranty Disclaimers may have is void and has
30087 no effect on the meaning of this License.
30089 @strong{2. VERBATIM COPYING}
30091 You may copy and distribute the Document in any medium, either
30092 commercially or noncommercially, provided that this License, the
30093 copyright notices, and the license notice saying this License applies
30094 to the Document are reproduced in all copies, and that you add no other
30095 conditions whatsoever to those of this License. You may not use
30096 technical measures to obstruct or control the reading or further
30097 copying of the copies you make or distribute. However, you may accept
30098 compensation in exchange for copies. If you distribute a large enough
30099 number of copies you must also follow the conditions in section 3.
30101 You may also lend copies, under the same conditions stated above, and
30102 you may publicly display copies.
30104 @strong{3. COPYING IN QUANTITY}
30106 If you publish printed copies (or copies in media that commonly have
30107 printed covers) of the Document, numbering more than 100, and the
30108 Document's license notice requires Cover Texts, you must enclose the
30109 copies in covers that carry, clearly and legibly, all these Cover
30110 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
30111 the back cover. Both covers must also clearly and legibly identify
30112 you as the publisher of these copies. The front cover must present
30113 the full title with all words of the title equally prominent and
30114 visible. You may add other material on the covers in addition.
30115 Copying with changes limited to the covers, as long as they preserve
30116 the title of the Document and satisfy these conditions, can be treated
30117 as verbatim copying in other respects.
30119 If the required texts for either cover are too voluminous to fit
30120 legibly, you should put the first ones listed (as many as fit
30121 reasonably) on the actual cover, and continue the rest onto adjacent
30124 If you publish or distribute Opaque copies of the Document numbering
30125 more than 100, you must either include a machine-readable Transparent
30126 copy along with each Opaque copy, or state in or with each Opaque copy
30127 a computer-network location from which the general network-using
30128 public has access to download using public-standard network protocols
30129 a complete Transparent copy of the Document, free of added material.
30130 If you use the latter option, you must take reasonably prudent steps,
30131 when you begin distribution of Opaque copies in quantity, to ensure
30132 that this Transparent copy will remain thus accessible at the stated
30133 location until at least one year after the last time you distribute an
30134 Opaque copy (directly or through your agents or retailers) of that
30135 edition to the public.
30137 It is requested, but not required, that you contact the authors of the
30138 Document well before redistributing any large number of copies, to give
30139 them a chance to provide you with an updated version of the Document.
30141 @strong{4. MODIFICATIONS}
30143 You may copy and distribute a Modified Version of the Document under
30144 the conditions of sections 2 and 3 above, provided that you release
30145 the Modified Version under precisely this License, with the Modified
30146 Version filling the role of the Document, thus licensing distribution
30147 and modification of the Modified Version to whoever possesses a copy
30148 of it. In addition, you must do these things in the Modified Version:
30154 Use in the Title Page (and on the covers, if any) a title distinct
30155 from that of the Document, and from those of previous versions
30156 (which should, if there were any, be listed in the History section
30157 of the Document). You may use the same title as a previous version
30158 if the original publisher of that version gives permission.
30161 List on the Title Page, as authors, one or more persons or entities
30162 responsible for authorship of the modifications in the Modified
30163 Version, together with at least five of the principal authors of the
30164 Document (all of its principal authors, if it has fewer than five),
30165 unless they release you from this requirement.
30168 State on the Title page the name of the publisher of the
30169 Modified Version, as the publisher.
30172 Preserve all the copyright notices of the Document.
30175 Add an appropriate copyright notice for your modifications
30176 adjacent to the other copyright notices.
30179 Include, immediately after the copyright notices, a license notice
30180 giving the public permission to use the Modified Version under the
30181 terms of this License, in the form shown in the Addendum below.
30184 Preserve in that license notice the full lists of Invariant Sections
30185 and required Cover Texts given in the Document's license notice.
30188 Include an unaltered copy of this License.
30191 Preserve the section Entitled "History", Preserve its Title, and add
30192 to it an item stating at least the title, year, new authors, and
30193 publisher of the Modified Version as given on the Title Page. If
30194 there is no section Entitled "History" in the Document, create one
30195 stating the title, year, authors, and publisher of the Document as
30196 given on its Title Page, then add an item describing the Modified
30197 Version as stated in the previous sentence.
30200 Preserve the network location, if any, given in the Document for
30201 public access to a Transparent copy of the Document, and likewise
30202 the network locations given in the Document for previous versions
30203 it was based on. These may be placed in the "History" section.
30204 You may omit a network location for a work that was published at
30205 least four years before the Document itself, or if the original
30206 publisher of the version it refers to gives permission.
30209 For any section Entitled "Acknowledgements" or "Dedications",
30210 Preserve the Title of the section, and preserve in the section all
30211 the substance and tone of each of the contributor acknowledgements
30212 and/or dedications given therein.
30215 Preserve all the Invariant Sections of the Document,
30216 unaltered in their text and in their titles. Section numbers
30217 or the equivalent are not considered part of the section titles.
30220 Delete any section Entitled "Endorsements". Such a section
30221 may not be included in the Modified Version.
30224 Do not retitle any existing section to be Entitled "Endorsements"
30225 or to conflict in title with any Invariant Section.
30228 Preserve any Warranty Disclaimers.
30231 If the Modified Version includes new front-matter sections or
30232 appendices that qualify as Secondary Sections and contain no material
30233 copied from the Document, you may at your option designate some or all
30234 of these sections as invariant. To do this, add their titles to the
30235 list of Invariant Sections in the Modified Version's license notice.
30236 These titles must be distinct from any other section titles.
30238 You may add a section Entitled "Endorsements", provided it contains
30239 nothing but endorsements of your Modified Version by various
30240 parties---for example, statements of peer review or that the text has
30241 been approved by an organization as the authoritative definition of a
30244 You may add a passage of up to five words as a Front-Cover Text, and a
30245 passage of up to 25 words as a Back-Cover Text, to the end of the list
30246 of Cover Texts in the Modified Version. Only one passage of
30247 Front-Cover Text and one of Back-Cover Text may be added by (or
30248 through arrangements made by) any one entity. If the Document already
30249 includes a cover text for the same cover, previously added by you or
30250 by arrangement made by the same entity you are acting on behalf of,
30251 you may not add another; but you may replace the old one, on explicit
30252 permission from the previous publisher that added the old one.
30254 The author(s) and publisher(s) of the Document do not by this License
30255 give permission to use their names for publicity for or to assert or
30256 imply endorsement of any Modified Version.
30258 @strong{5. COMBINING DOCUMENTS}
30260 You may combine the Document with other documents released under this
30261 License, under the terms defined in section 4 above for modified
30262 versions, provided that you include in the combination all of the
30263 Invariant Sections of all of the original documents, unmodified, and
30264 list them all as Invariant Sections of your combined work in its
30265 license notice, and that you preserve all their Warranty Disclaimers.
30267 The combined work need only contain one copy of this License, and
30268 multiple identical Invariant Sections may be replaced with a single
30269 copy. If there are multiple Invariant Sections with the same name but
30270 different contents, make the title of each such section unique by
30271 adding at the end of it, in parentheses, the name of the original
30272 author or publisher of that section if known, or else a unique number.
30273 Make the same adjustment to the section titles in the list of
30274 Invariant Sections in the license notice of the combined work.
30276 In the combination, you must combine any sections Entitled "History"
30277 in the various original documents, forming one section Entitled
30278 "History"; likewise combine any sections Entitled "Acknowledgements",
30279 and any sections Entitled "Dedications". You must delete all sections
30280 Entitled "Endorsements".
30282 @strong{6. COLLECTIONS OF DOCUMENTS}
30284 You may make a collection consisting of the Document and other documents
30285 released under this License, and replace the individual copies of this
30286 License in the various documents with a single copy that is included in
30287 the collection, provided that you follow the rules of this License for
30288 verbatim copying of each of the documents in all other respects.
30290 You may extract a single document from such a collection, and distribute
30291 it individually under this License, provided you insert a copy of this
30292 License into the extracted document, and follow this License in all
30293 other respects regarding verbatim copying of that document.
30295 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
30297 A compilation of the Document or its derivatives with other separate
30298 and independent documents or works, in or on a volume of a storage or
30299 distribution medium, is called an "aggregate" if the copyright
30300 resulting from the compilation is not used to limit the legal rights
30301 of the compilation's users beyond what the individual works permit.
30302 When the Document is included in an aggregate, this License does not
30303 apply to the other works in the aggregate which are not themselves
30304 derivative works of the Document.
30306 If the Cover Text requirement of section 3 is applicable to these
30307 copies of the Document, then if the Document is less than one half of
30308 the entire aggregate, the Document's Cover Texts may be placed on
30309 covers that bracket the Document within the aggregate, or the
30310 electronic equivalent of covers if the Document is in electronic form.
30311 Otherwise they must appear on printed covers that bracket the whole
30314 @strong{8. TRANSLATION}
30316 Translation is considered a kind of modification, so you may
30317 distribute translations of the Document under the terms of section 4.
30318 Replacing Invariant Sections with translations requires special
30319 permission from their copyright holders, but you may include
30320 translations of some or all Invariant Sections in addition to the
30321 original versions of these Invariant Sections. You may include a
30322 translation of this License, and all the license notices in the
30323 Document, and any Warranty Disclaimers, provided that you also include
30324 the original English version of this License and the original versions
30325 of those notices and disclaimers. In case of a disagreement between
30326 the translation and the original version of this License or a notice
30327 or disclaimer, the original version will prevail.
30329 If a section in the Document is Entitled "Acknowledgements",
30330 "Dedications", or "History", the requirement (section 4) to Preserve
30331 its Title (section 1) will typically require changing the actual
30334 @strong{9. TERMINATION}
30336 You may not copy, modify, sublicense, or distribute the Document
30337 except as expressly provided under this License. Any attempt
30338 otherwise to copy, modify, sublicense, or distribute it is void, and
30339 will automatically terminate your rights under this License.
30341 However, if you cease all violation of this License, then your license
30342 from a particular copyright holder is reinstated (a) provisionally,
30343 unless and until the copyright holder explicitly and finally
30344 terminates your license, and (b) permanently, if the copyright holder
30345 fails to notify you of the violation by some reasonable means prior to
30346 60 days after the cessation.
30348 Moreover, your license from a particular copyright holder is
30349 reinstated permanently if the copyright holder notifies you of the
30350 violation by some reasonable means, this is the first time you have
30351 received notice of violation of this License (for any work) from that
30352 copyright holder, and you cure the violation prior to 30 days after
30353 your receipt of the notice.
30355 Termination of your rights under this section does not terminate the
30356 licenses of parties who have received copies or rights from you under
30357 this License. If your rights have been terminated and not permanently
30358 reinstated, receipt of a copy of some or all of the same material does
30359 not give you any rights to use it.
30361 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
30363 The Free Software Foundation may publish new, revised versions
30364 of the GNU Free Documentation License from time to time. Such new
30365 versions will be similar in spirit to the present version, but may
30366 differ in detail to address new problems or concerns. See
30367 @indicateurl{http://www.gnu.org/copyleft/}.
30369 Each version of the License is given a distinguishing version number.
30370 If the Document specifies that a particular numbered version of this
30371 License "or any later version" applies to it, you have the option of
30372 following the terms and conditions either of that specified version or
30373 of any later version that has been published (not as a draft) by the
30374 Free Software Foundation. If the Document does not specify a version
30375 number of this License, you may choose any version ever published (not
30376 as a draft) by the Free Software Foundation. If the Document
30377 specifies that a proxy can decide which future versions of this
30378 License can be used, that proxy's public statement of acceptance of a
30379 version permanently authorizes you to choose that version for the
30382 @strong{11. RELICENSING}
30384 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30385 World Wide Web server that publishes copyrightable works and also
30386 provides prominent facilities for anybody to edit those works. A
30387 public wiki that anybody can edit is an example of such a server. A
30388 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30389 site means any set of copyrightable works thus published on the MMC
30392 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30393 license published by Creative Commons Corporation, a not-for-profit
30394 corporation with a principal place of business in San Francisco,
30395 California, as well as future copyleft versions of that license
30396 published by that same organization.
30398 "Incorporate" means to publish or republish a Document, in whole or
30399 in part, as part of another Document.
30401 An MMC is "eligible for relicensing" if it is licensed under this
30402 License, and if all works that were first published under this License
30403 somewhere other than this MMC, and subsequently incorporated in whole
30404 or in part into the MMC, (1) had no cover texts or invariant sections,
30405 and (2) were thus incorporated prior to November 1, 2008.
30407 The operator of an MMC Site may republish an MMC contained in the site
30408 under CC-BY-SA on the same site at any time before August 1, 2009,
30409 provided the MMC is eligible for relicensing.
30411 @strong{ADDENDUM: How to use this License for your documents}
30413 To use this License in a document you have written, include a copy of
30414 the License in the document and put the following copyright and
30415 license notices just after the title page:
30419 Copyright © YEAR YOUR NAME.
30420 Permission is granted to copy, distribute and/or modify this document
30421 under the terms of the GNU Free Documentation License, Version 1.3
30422 or any later version published by the Free Software Foundation;
30423 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30424 A copy of the license is included in the section entitled "GNU
30425 Free Documentation License".
30428 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30429 replace the "with ... Texts." line with this:
30433 with the Invariant Sections being LIST THEIR TITLES, with the
30434 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30437 If you have Invariant Sections without Cover Texts, or some other
30438 combination of the three, merge those two alternatives to suit the
30441 If your document contains nontrivial examples of program code, we
30442 recommend releasing these examples in parallel under your choice of
30443 free software license, such as the GNU General Public License,
30444 to permit their use in free software.
30446 @node Index,,GNU Free Documentation License,Top
30453 @anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ }