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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 , May 04, 2020
28 Copyright @copyright{} 2008-2020, 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 GNAT Studio}, which describes the GNAT Studio
686 Integrated Development Environment.
689 @cite{GNAT Studio Tutorial}, which introduces the
690 main GNAT Studio 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 (GNAT Studio).
901 GNAT Studio 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 GNAT Studio 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_Float_Alignment}, if not zero, is the maximum alignment that the
9456 compiler can choose by default for a 64-bit floating-point type or object.
9458 @code{Double_Scalar_Alignment}, if not zero, is the maximum alignment that the
9459 compiler can choose by default for a 64-bit or larger scalar type or object.
9461 @code{Maximum_Alignment} is the maximum alignment that the compiler can choose
9462 by default for a type or object, which is also the maximum alignment that can
9463 be specified in GNAT. It is computed for GCC backends as @code{BIGGEST_ALIGNMENT
9464 / BITS_PER_UNIT} where GCC macro @code{BIGGEST_ALIGNMENT} is documented as
9465 follows: @cite{Biggest alignment that any data type can require on this machine@comma{} in bits.}
9467 @code{Max_Unaligned_Field} is the maximum size for unaligned bit field, which is
9468 64 for the majority of GCC targets (but can be different on some targets like
9471 @code{Strict_Alignment} is the equivalent of GCC macro @code{STRICT_ALIGNMENT}
9472 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.}
9474 @code{System_Allocator_Alignment} is the guaranteed alignment of data returned
9475 by calls to @code{malloc}.
9477 The format of the input file is as follows. First come the values of
9478 the variables defined above, with one line per value:
9484 where @code{name} is the name of the parameter, spelled out in full,
9485 and cased as in the above list, and @code{value} is an unsigned decimal
9486 integer. Two or more blanks separates the name from the value.
9488 All the variables must be present, in alphabetical order (i.e. the
9489 same order as the list above).
9491 Then there is a blank line to separate the two parts of the file. Then
9492 come the lines showing the floating-point types to be registered, with
9493 one line per registered mode:
9496 name digs float_rep size alignment
9499 where @code{name} is the string name of the type (which can have
9500 single spaces embedded in the name (e.g. long double), @code{digs} is
9501 the number of digits for the floating-point type, @code{float_rep} is
9502 the float representation (I/V/A for IEEE-754-Binary, Vax_Native,
9503 AAMP), @code{size} is the size in bits, @code{alignment} is the
9504 alignment in bits. The name is followed by at least two blanks, fields
9505 are separated by at least one blank, and a LF character immediately
9506 follows the alignment field.
9508 Here is an example of a target parameterization file:
9516 Double_Float_Alignment 0
9517 Double_Scalar_Alignment 0
9522 Long_Double_Size 128
9525 Maximum_Alignment 16
9526 Max_Unaligned_Field 64
9530 System_Allocator_Alignment 16
9536 long double 18 I 80 128
9541 @geindex -gnateu (gcc)
9546 @item @code{-gnateu}
9548 Ignore unrecognized validity, warning, and style switches that
9549 appear after this switch is given. This may be useful when
9550 compiling sources developed on a later version of the compiler
9551 with an earlier version. Of course the earlier version must
9552 support this switch.
9555 @geindex -gnateV (gcc)
9560 @item @code{-gnateV}
9562 Check that all actual parameters of a subprogram call are valid according to
9563 the rules of validity checking (@ref{f6,,Validity Checking}).
9566 @geindex -gnateY (gcc)
9571 @item @code{-gnateY}
9573 Ignore all STYLE_CHECKS pragmas. Full legality checks
9574 are still carried out, but the pragmas have no effect
9575 on what style checks are active. This allows all style
9576 checking options to be controlled from the command line.
9579 @geindex -gnatE (gcc)
9586 Dynamic elaboration checking mode enabled. For further details see
9587 @ref{f,,Elaboration Order Handling in GNAT}.
9590 @geindex -gnatf (gcc)
9597 Full errors. Multiple errors per line, all undefined references, do not
9598 attempt to suppress cascaded errors.
9601 @geindex -gnatF (gcc)
9608 Externals names are folded to all uppercase.
9611 @geindex -gnatg (gcc)
9618 Internal GNAT implementation mode. This should not be used for applications
9619 programs, it is intended only for use by the compiler and its run-time
9620 library. For documentation, see the GNAT sources. Note that @code{-gnatg}
9621 implies @code{-gnatw.ge} and @code{-gnatyg} so that all standard
9622 warnings and all standard style options are turned on. All warnings and style
9623 messages are treated as errors.
9626 @geindex -gnatG[nn] (gcc)
9631 @item @code{-gnatG=nn}
9633 List generated expanded code in source form.
9636 @geindex -gnath (gcc)
9643 Output usage information. The output is written to @code{stdout}.
9646 @geindex -gnatH (gcc)
9653 Legacy elaboration-checking mode enabled. When this switch is in effect,
9654 the pre-18.x access-before-elaboration model becomes the de facto model.
9655 For further details see @ref{f,,Elaboration Order Handling in GNAT}.
9658 @geindex -gnati (gcc)
9663 @item @code{-gnati@emph{c}}
9665 Identifier character set (@code{c} = 1/2/3/4/8/9/p/f/n/w).
9666 For details of the possible selections for @code{c},
9667 see @ref{48,,Character Set Control}.
9670 @geindex -gnatI (gcc)
9677 Ignore representation clauses. When this switch is used,
9678 representation clauses are treated as comments. This is useful
9679 when initially porting code where you want to ignore rep clause
9680 problems, and also for compiling foreign code (particularly
9681 for use with ASIS). The representation clauses that are ignored
9682 are: enumeration_representation_clause, record_representation_clause,
9683 and attribute_definition_clause for the following attributes:
9684 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
9685 Object_Size, Scalar_Storage_Order, Size, Small, Stream_Size,
9686 and Value_Size. Pragma Default_Scalar_Storage_Order is also ignored.
9687 Note that this option should be used only for compiling -- the
9688 code is likely to malfunction at run time.
9691 @geindex -gnatjnn (gcc)
9696 @item @code{-gnatj@emph{nn}}
9698 Reformat error messages to fit on @code{nn} character lines
9701 @geindex -gnatJ (gcc)
9708 Permissive elaboration-checking mode enabled. When this switch is in effect,
9709 the post-18.x access-before-elaboration model ignores potential issues with:
9718 Activations of tasks defined in instances
9724 Calls from within an instance to its enclosing context
9727 Calls through generic formal parameters
9730 Calls to subprograms defined in instances
9736 Indirect calls using 'Access
9745 Synchronous task suspension
9748 and does not emit compile-time diagnostics or run-time checks. For further
9749 details see @ref{f,,Elaboration Order Handling in GNAT}.
9752 @geindex -gnatk (gcc)
9757 @item @code{-gnatk=@emph{n}}
9759 Limit file names to @code{n} (1-999) characters (@code{k} = krunch).
9762 @geindex -gnatl (gcc)
9769 Output full source listing with embedded error messages.
9772 @geindex -gnatL (gcc)
9779 Used in conjunction with -gnatG or -gnatD to intersperse original
9780 source lines (as comment lines with line numbers) in the expanded
9784 @geindex -gnatm (gcc)
9789 @item @code{-gnatm=@emph{n}}
9791 Limit number of detected error or warning messages to @code{n}
9792 where @code{n} is in the range 1..999999. The default setting if
9793 no switch is given is 9999. If the number of warnings reaches this
9794 limit, then a message is output and further warnings are suppressed,
9795 but the compilation is continued. If the number of error messages
9796 reaches this limit, then a message is output and the compilation
9797 is abandoned. The equal sign here is optional. A value of zero
9798 means that no limit applies.
9801 @geindex -gnatn (gcc)
9806 @item @code{-gnatn[12]}
9808 Activate inlining across units for subprograms for which pragma @code{Inline}
9809 is specified. This inlining is performed by the GCC back-end. An optional
9810 digit sets the inlining level: 1 for moderate inlining across units
9811 or 2 for full inlining across units. If no inlining level is specified,
9812 the compiler will pick it based on the optimization level.
9815 @geindex -gnatN (gcc)
9822 Activate front end inlining for subprograms for which
9823 pragma @code{Inline} is specified. This inlining is performed
9824 by the front end and will be visible in the
9825 @code{-gnatG} output.
9827 When using a gcc-based back end (in practice this means using any version
9828 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
9829 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
9830 Historically front end inlining was more extensive than the gcc back end
9831 inlining, but that is no longer the case.
9834 @geindex -gnato0 (gcc)
9839 @item @code{-gnato0}
9841 Suppresses overflow checking. This causes the behavior of the compiler to
9842 match the default for older versions where overflow checking was suppressed
9843 by default. This is equivalent to having
9844 @code{pragma Suppress (Overflow_Check)} in a configuration pragma file.
9847 @geindex -gnato?? (gcc)
9852 @item @code{-gnato??}
9854 Set default mode for handling generation of code to avoid intermediate
9855 arithmetic overflow. Here @code{??} is two digits, a
9856 single digit, or nothing. Each digit is one of the digits @code{1}
9860 @multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
9875 All intermediate overflows checked against base type (@code{STRICT})
9883 Minimize intermediate overflows (@code{MINIMIZED})
9891 Eliminate intermediate overflows (@code{ELIMINATED})
9896 If only one digit appears, then it applies to all
9897 cases; if two digits are given, then the first applies outside
9898 assertions, pre/postconditions, and type invariants, and the second
9899 applies within assertions, pre/postconditions, and type invariants.
9901 If no digits follow the @code{-gnato}, then it is equivalent to
9903 causing all intermediate overflows to be handled in strict
9906 This switch also causes arithmetic overflow checking to be performed
9907 (as though @code{pragma Unsuppress (Overflow_Check)} had been specified).
9909 The default if no option @code{-gnato} is given is that overflow handling
9910 is in @code{STRICT} mode (computations done using the base type), and that
9911 overflow checking is enabled.
9913 Note that division by zero is a separate check that is not
9914 controlled by this switch (divide-by-zero checking is on by default).
9916 See also @ref{f8,,Specifying the Desired Mode}.
9919 @geindex -gnatp (gcc)
9926 Suppress all checks. See @ref{f9,,Run-Time Checks} for details. This switch
9927 has no effect if cancelled by a subsequent @code{-gnat-p} switch.
9930 @geindex -gnat-p (gcc)
9935 @item @code{-gnat-p}
9937 Cancel effect of previous @code{-gnatp} switch.
9940 @geindex -gnatP (gcc)
9947 Enable polling. This is required on some systems (notably Windows NT) to
9948 obtain asynchronous abort and asynchronous transfer of control capability.
9949 See @code{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full
9953 @geindex -gnatq (gcc)
9960 Don't quit. Try semantics, even if parse errors.
9963 @geindex -gnatQ (gcc)
9970 Don't quit. Generate @code{ALI} and tree files even if illegalities.
9971 Note that code generation is still suppressed in the presence of any
9972 errors, so even with @code{-gnatQ} no object file is generated.
9975 @geindex -gnatr (gcc)
9982 Treat pragma Restrictions as Restriction_Warnings.
9985 @geindex -gnatR (gcc)
9990 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
9992 Output representation information for declared types, objects and
9993 subprograms. Note that this switch is not allowed if a previous
9994 @code{-gnatD} switch has been given, since these two switches
9998 @geindex -gnats (gcc)
10003 @item @code{-gnats}
10008 @geindex -gnatS (gcc)
10013 @item @code{-gnatS}
10015 Print package Standard.
10018 @geindex -gnatT (gcc)
10023 @item @code{-gnatT@emph{nnn}}
10025 All compiler tables start at @code{nnn} times usual starting size.
10028 @geindex -gnatu (gcc)
10033 @item @code{-gnatu}
10035 List units for this compilation.
10038 @geindex -gnatU (gcc)
10043 @item @code{-gnatU}
10045 Tag all error messages with the unique string 'error:'
10048 @geindex -gnatv (gcc)
10053 @item @code{-gnatv}
10055 Verbose mode. Full error output with source lines to @code{stdout}.
10058 @geindex -gnatV (gcc)
10063 @item @code{-gnatV}
10065 Control level of validity checking (@ref{f6,,Validity Checking}).
10068 @geindex -gnatw (gcc)
10073 @item @code{-gnatw@emph{xxx}}
10076 @code{xxx} is a string of option letters that denotes
10077 the exact warnings that
10078 are enabled or disabled (@ref{fa,,Warning Message Control}).
10081 @geindex -gnatW (gcc)
10086 @item @code{-gnatW@emph{e}}
10088 Wide character encoding method
10089 (@code{e}=n/h/u/s/e/8).
10092 @geindex -gnatx (gcc)
10097 @item @code{-gnatx}
10099 Suppress generation of cross-reference information.
10102 @geindex -gnatX (gcc)
10107 @item @code{-gnatX}
10109 Enable GNAT implementation extensions and latest Ada version.
10112 @geindex -gnaty (gcc)
10117 @item @code{-gnaty}
10119 Enable built-in style checks (@ref{fb,,Style Checking}).
10122 @geindex -gnatz (gcc)
10127 @item @code{-gnatz@emph{m}}
10129 Distribution stub generation and compilation
10130 (@code{m}=r/c for receiver/caller stubs).
10138 @item @code{-I@emph{dir}}
10142 Direct GNAT to search the @code{dir} directory for source files needed by
10143 the current compilation
10144 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10156 Except for the source file named in the command line, do not look for source
10157 files in the directory containing the source file named in the command line
10158 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10166 @item @code{-o @emph{file}}
10168 This switch is used in @code{gcc} to redirect the generated object file
10169 and its associated ALI file. Beware of this switch with GNAT, because it may
10170 cause the object file and ALI file to have different names which in turn
10171 may confuse the binder and the linker.
10174 @geindex -nostdinc (gcc)
10179 @item @code{-nostdinc}
10181 Inhibit the search of the default location for the GNAT Run Time
10182 Library (RTL) source files.
10185 @geindex -nostdlib (gcc)
10190 @item @code{-nostdlib}
10192 Inhibit the search of the default location for the GNAT Run Time
10193 Library (RTL) ALI files.
10201 @item @code{-O[@emph{n}]}
10203 @code{n} controls the optimization level:
10206 @multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
10221 No optimization, the default setting if no @code{-O} appears
10229 Normal optimization, the default if you specify @code{-O} without an
10230 operand. A good compromise between code quality and compilation
10239 Extensive optimization, may improve execution time, possibly at
10240 the cost of substantially increased compilation time.
10248 Same as @code{-O2}, and also includes inline expansion for small
10249 subprograms in the same unit.
10257 Optimize space usage
10262 See also @ref{fc,,Optimization Levels}.
10265 @geindex -pass-exit-codes (gcc)
10270 @item @code{-pass-exit-codes}
10272 Catch exit codes from the compiler and use the most meaningful as
10276 @geindex --RTS (gcc)
10281 @item @code{--RTS=@emph{rts-path}}
10283 Specifies the default location of the run-time library. Same meaning as the
10284 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
10294 Used in place of @code{-c} to
10295 cause the assembler source file to be
10296 generated, using @code{.s} as the extension,
10297 instead of the object file.
10298 This may be useful if you need to examine the generated assembly code.
10301 @geindex -fverbose-asm (gcc)
10306 @item @code{-fverbose-asm}
10308 Used in conjunction with @code{-S}
10309 to cause the generated assembly code file to be annotated with variable
10310 names, making it significantly easier to follow.
10320 Show commands generated by the @code{gcc} driver. Normally used only for
10321 debugging purposes or if you need to be sure what version of the
10322 compiler you are executing.
10330 @item @code{-V @emph{ver}}
10332 Execute @code{ver} version of the compiler. This is the @code{gcc}
10333 version, not the GNAT version.
10343 Turn off warnings generated by the back end of the compiler. Use of
10344 this switch also causes the default for front end warnings to be set
10345 to suppress (as though @code{-gnatws} had appeared at the start of
10349 @geindex Combining GNAT switches
10351 You may combine a sequence of GNAT switches into a single switch. For
10352 example, the combined switch
10361 is equivalent to specifying the following sequence of switches:
10366 -gnato -gnatf -gnati3
10370 The following restrictions apply to the combination of switches
10377 The switch @code{-gnatc} if combined with other switches must come
10378 first in the string.
10381 The switch @code{-gnats} if combined with other switches must come
10382 first in the string.
10386 @code{-gnatzc} and @code{-gnatzr} may not be combined with any other
10387 switches, and only one of them may appear in the command line.
10390 The switch @code{-gnat-p} may not be combined with any other switch.
10393 Once a 'y' appears in the string (that is a use of the @code{-gnaty}
10394 switch), then all further characters in the switch are interpreted
10395 as style modifiers (see description of @code{-gnaty}).
10398 Once a 'd' appears in the string (that is a use of the @code{-gnatd}
10399 switch), then all further characters in the switch are interpreted
10400 as debug flags (see description of @code{-gnatd}).
10403 Once a 'w' appears in the string (that is a use of the @code{-gnatw}
10404 switch), then all further characters in the switch are interpreted
10405 as warning mode modifiers (see description of @code{-gnatw}).
10408 Once a 'V' appears in the string (that is a use of the @code{-gnatV}
10409 switch), then all further characters in the switch are interpreted
10410 as validity checking options (@ref{f6,,Validity Checking}).
10413 Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in
10414 a combined list of options.
10417 @node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches
10418 @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}
10419 @subsection Output and Error Message Control
10424 The standard default format for error messages is called 'brief format'.
10425 Brief format messages are written to @code{stderr} (the standard error
10426 file) and have the following form:
10429 e.adb:3:04: Incorrect spelling of keyword "function"
10430 e.adb:4:20: ";" should be "is"
10433 The first integer after the file name is the line number in the file,
10434 and the second integer is the column number within the line.
10435 @code{GNAT Studio} can parse the error messages
10436 and point to the referenced character.
10437 The following switches provide control over the error message
10440 @geindex -gnatv (gcc)
10445 @item @code{-gnatv}
10447 The @code{v} stands for verbose.
10448 The effect of this setting is to write long-format error
10449 messages to @code{stdout} (the standard output file.
10450 The same program compiled with the
10451 @code{-gnatv} switch would generate:
10454 3. funcion X (Q : Integer)
10456 >>> Incorrect spelling of keyword "function"
10459 >>> ";" should be "is"
10462 The vertical bar indicates the location of the error, and the @code{>>>}
10463 prefix can be used to search for error messages. When this switch is
10464 used the only source lines output are those with errors.
10467 @geindex -gnatl (gcc)
10472 @item @code{-gnatl}
10474 The @code{l} stands for list.
10475 This switch causes a full listing of
10476 the file to be generated. In the case where a body is
10477 compiled, the corresponding spec is also listed, along
10478 with any subunits. Typical output from compiling a package
10479 body @code{p.adb} might look like:
10484 1. package body p is
10486 3. procedure a is separate;
10497 2. pragma Elaborate_Body
10518 When you specify the @code{-gnatv} or @code{-gnatl} switches and
10519 standard output is redirected, a brief summary is written to
10520 @code{stderr} (standard error) giving the number of error messages and
10521 warning messages generated.
10524 @geindex -gnatl=fname (gcc)
10529 @item @code{-gnatl=@emph{fname}}
10531 This has the same effect as @code{-gnatl} except that the output is
10532 written to a file instead of to standard output. If the given name
10533 @code{fname} does not start with a period, then it is the full name
10534 of the file to be written. If @code{fname} is an extension, it is
10535 appended to the name of the file being compiled. For example, if
10536 file @code{xyz.adb} is compiled with @code{-gnatl=.lst},
10537 then the output is written to file xyz.adb.lst.
10540 @geindex -gnatU (gcc)
10545 @item @code{-gnatU}
10547 This switch forces all error messages to be preceded by the unique
10548 string 'error:'. This means that error messages take a few more
10549 characters in space, but allows easy searching for and identification
10553 @geindex -gnatb (gcc)
10558 @item @code{-gnatb}
10560 The @code{b} stands for brief.
10561 This switch causes GNAT to generate the
10562 brief format error messages to @code{stderr} (the standard error
10563 file) as well as the verbose
10564 format message or full listing (which as usual is written to
10565 @code{stdout} (the standard output file).
10568 @geindex -gnatm (gcc)
10573 @item @code{-gnatm=@emph{n}}
10575 The @code{m} stands for maximum.
10576 @code{n} is a decimal integer in the
10577 range of 1 to 999999 and limits the number of error or warning
10578 messages to be generated. For example, using
10579 @code{-gnatm2} might yield
10582 e.adb:3:04: Incorrect spelling of keyword "function"
10583 e.adb:5:35: missing ".."
10584 fatal error: maximum number of errors detected
10585 compilation abandoned
10588 The default setting if
10589 no switch is given is 9999. If the number of warnings reaches this
10590 limit, then a message is output and further warnings are suppressed,
10591 but the compilation is continued. If the number of error messages
10592 reaches this limit, then a message is output and the compilation
10593 is abandoned. A value of zero means that no limit applies.
10595 Note that the equal sign is optional, so the switches
10596 @code{-gnatm2} and @code{-gnatm=2} are equivalent.
10599 @geindex -gnatf (gcc)
10604 @item @code{-gnatf}
10606 @geindex Error messages
10607 @geindex suppressing
10609 The @code{f} stands for full.
10610 Normally, the compiler suppresses error messages that are likely to be
10611 redundant. This switch causes all error
10612 messages to be generated. In particular, in the case of
10613 references to undefined variables. If a given variable is referenced
10614 several times, the normal format of messages is
10617 e.adb:7:07: "V" is undefined (more references follow)
10620 where the parenthetical comment warns that there are additional
10621 references to the variable @code{V}. Compiling the same program with the
10622 @code{-gnatf} switch yields
10625 e.adb:7:07: "V" is undefined
10626 e.adb:8:07: "V" is undefined
10627 e.adb:8:12: "V" is undefined
10628 e.adb:8:16: "V" is undefined
10629 e.adb:9:07: "V" is undefined
10630 e.adb:9:12: "V" is undefined
10633 The @code{-gnatf} switch also generates additional information for
10634 some error messages. Some examples are:
10640 Details on possibly non-portable unchecked conversion
10643 List possible interpretations for ambiguous calls
10646 Additional details on incorrect parameters
10650 @geindex -gnatjnn (gcc)
10655 @item @code{-gnatjnn}
10657 In normal operation mode (or if @code{-gnatj0} is used), then error messages
10658 with continuation lines are treated as though the continuation lines were
10659 separate messages (and so a warning with two continuation lines counts as
10660 three warnings, and is listed as three separate messages).
10662 If the @code{-gnatjnn} switch is used with a positive value for nn, then
10663 messages are output in a different manner. A message and all its continuation
10664 lines are treated as a unit, and count as only one warning or message in the
10665 statistics totals. Furthermore, the message is reformatted so that no line
10666 is longer than nn characters.
10669 @geindex -gnatq (gcc)
10674 @item @code{-gnatq}
10676 The @code{q} stands for quit (really 'don't quit').
10677 In normal operation mode, the compiler first parses the program and
10678 determines if there are any syntax errors. If there are, appropriate
10679 error messages are generated and compilation is immediately terminated.
10681 GNAT to continue with semantic analysis even if syntax errors have been
10682 found. This may enable the detection of more errors in a single run. On
10683 the other hand, the semantic analyzer is more likely to encounter some
10684 internal fatal error when given a syntactically invalid tree.
10687 @geindex -gnatQ (gcc)
10692 @item @code{-gnatQ}
10694 In normal operation mode, the @code{ALI} file is not generated if any
10695 illegalities are detected in the program. The use of @code{-gnatQ} forces
10696 generation of the @code{ALI} file. This file is marked as being in
10697 error, so it cannot be used for binding purposes, but it does contain
10698 reasonably complete cross-reference information, and thus may be useful
10699 for use by tools (e.g., semantic browsing tools or integrated development
10700 environments) that are driven from the @code{ALI} file. This switch
10701 implies @code{-gnatq}, since the semantic phase must be run to get a
10702 meaningful ALI file.
10704 When @code{-gnatQ} is used and the generated @code{ALI} file is marked as
10705 being in error, @code{gnatmake} will attempt to recompile the source when it
10706 finds such an @code{ALI} file, including with switch @code{-gnatc}.
10708 Note that @code{-gnatQ} has no effect if @code{-gnats} is specified,
10709 since ALI files are never generated if @code{-gnats} is set.
10712 @node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches
10713 @anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{fa}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{ff}
10714 @subsection Warning Message Control
10717 @geindex Warning messages
10719 In addition to error messages, which correspond to illegalities as defined
10720 in the Ada Reference Manual, the compiler detects two kinds of warning
10723 First, the compiler considers some constructs suspicious and generates a
10724 warning message to alert you to a possible error. Second, if the
10725 compiler detects a situation that is sure to raise an exception at
10726 run time, it generates a warning message. The following shows an example
10727 of warning messages:
10730 e.adb:4:24: warning: creation of object may raise Storage_Error
10731 e.adb:10:17: warning: static value out of range
10732 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
10735 GNAT considers a large number of situations as appropriate
10736 for the generation of warning messages. As always, warnings are not
10737 definite indications of errors. For example, if you do an out-of-range
10738 assignment with the deliberate intention of raising a
10739 @code{Constraint_Error} exception, then the warning that may be
10740 issued does not indicate an error. Some of the situations for which GNAT
10741 issues warnings (at least some of the time) are given in the following
10742 list. This list is not complete, and new warnings are often added to
10743 subsequent versions of GNAT. The list is intended to give a general idea
10744 of the kinds of warnings that are generated.
10750 Possible infinitely recursive calls
10753 Out-of-range values being assigned
10756 Possible order of elaboration problems
10759 Size not a multiple of alignment for a record type
10762 Assertions (pragma Assert) that are sure to fail
10768 Address clauses with possibly unaligned values, or where an attempt is
10769 made to overlay a smaller variable with a larger one.
10772 Fixed-point type declarations with a null range
10775 Direct_IO or Sequential_IO instantiated with a type that has access values
10778 Variables that are never assigned a value
10781 Variables that are referenced before being initialized
10784 Task entries with no corresponding @code{accept} statement
10787 Duplicate accepts for the same task entry in a @code{select}
10790 Objects that take too much storage
10793 Unchecked conversion between types of differing sizes
10796 Missing @code{return} statement along some execution path in a function
10799 Incorrect (unrecognized) pragmas
10802 Incorrect external names
10805 Allocation from empty storage pool
10808 Potentially blocking operation in protected type
10811 Suspicious parenthesization of expressions
10814 Mismatching bounds in an aggregate
10817 Attempt to return local value by reference
10820 Premature instantiation of a generic body
10823 Attempt to pack aliased components
10826 Out of bounds array subscripts
10829 Wrong length on string assignment
10832 Violations of style rules if style checking is enabled
10835 Unused @emph{with} clauses
10838 @code{Bit_Order} usage that does not have any effect
10841 @code{Standard.Duration} used to resolve universal fixed expression
10844 Dereference of possibly null value
10847 Declaration that is likely to cause storage error
10850 Internal GNAT unit @emph{with}ed by application unit
10853 Values known to be out of range at compile time
10856 Unreferenced or unmodified variables. Note that a special
10857 exemption applies to variables which contain any of the substrings
10858 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables
10859 are considered likely to be intentionally used in a situation where
10860 otherwise a warning would be given, so warnings of this kind are
10861 always suppressed for such variables.
10864 Address overlays that could clobber memory
10867 Unexpected initialization when address clause present
10870 Bad alignment for address clause
10873 Useless type conversions
10876 Redundant assignment statements and other redundant constructs
10879 Useless exception handlers
10882 Accidental hiding of name by child unit
10885 Access before elaboration detected at compile time
10888 A range in a @code{for} loop that is known to be null or might be null
10891 The following section lists compiler switches that are available
10892 to control the handling of warning messages. It is also possible
10893 to exercise much finer control over what warnings are issued and
10894 suppressed using the GNAT pragma Warnings (see the description
10895 of the pragma in the @cite{GNAT_Reference_manual}).
10897 @geindex -gnatwa (gcc)
10902 @item @code{-gnatwa}
10904 @emph{Activate most optional warnings.}
10906 This switch activates most optional warning messages. See the remaining list
10907 in this section for details on optional warning messages that can be
10908 individually controlled. The warnings that are not turned on by this
10915 @code{-gnatwd} (implicit dereferencing)
10918 @code{-gnatw.d} (tag warnings with -gnatw switch)
10921 @code{-gnatwh} (hiding)
10924 @code{-gnatw.h} (holes in record layouts)
10927 @code{-gnatw.j} (late primitives of tagged types)
10930 @code{-gnatw.k} (redefinition of names in standard)
10933 @code{-gnatwl} (elaboration warnings)
10936 @code{-gnatw.l} (inherited aspects)
10939 @code{-gnatw.n} (atomic synchronization)
10942 @code{-gnatwo} (address clause overlay)
10945 @code{-gnatw.o} (values set by out parameters ignored)
10948 @code{-gnatw.q} (questionable layout of record types)
10951 @code{-gnatw_r} (out-of-order record representation clauses)
10954 @code{-gnatw.s} (overridden size clause)
10957 @code{-gnatwt} (tracking of deleted conditional code)
10960 @code{-gnatw.u} (unordered enumeration)
10963 @code{-gnatw.w} (use of Warnings Off)
10966 @code{-gnatw.y} (reasons for package needing body)
10969 All other optional warnings are turned on.
10972 @geindex -gnatwA (gcc)
10977 @item @code{-gnatwA}
10979 @emph{Suppress all optional errors.}
10981 This switch suppresses all optional warning messages, see remaining list
10982 in this section for details on optional warning messages that can be
10983 individually controlled. Note that unlike switch @code{-gnatws}, the
10984 use of switch @code{-gnatwA} does not suppress warnings that are
10985 normally given unconditionally and cannot be individually controlled
10986 (for example, the warning about a missing exit path in a function).
10987 Also, again unlike switch @code{-gnatws}, warnings suppressed by
10988 the use of switch @code{-gnatwA} can be individually turned back
10989 on. For example the use of switch @code{-gnatwA} followed by
10990 switch @code{-gnatwd} will suppress all optional warnings except
10991 the warnings for implicit dereferencing.
10994 @geindex -gnatw.a (gcc)
10999 @item @code{-gnatw.a}
11001 @emph{Activate warnings on failing assertions.}
11003 @geindex Assert failures
11005 This switch activates warnings for assertions where the compiler can tell at
11006 compile time that the assertion will fail. Note that this warning is given
11007 even if assertions are disabled. The default is that such warnings are
11011 @geindex -gnatw.A (gcc)
11016 @item @code{-gnatw.A}
11018 @emph{Suppress warnings on failing assertions.}
11020 @geindex Assert failures
11022 This switch suppresses warnings for assertions where the compiler can tell at
11023 compile time that the assertion will fail.
11031 @item @code{-gnatw_a}
11033 @emph{Activate warnings on anonymous allocators.}
11035 @geindex Anonymous allocators
11037 This switch activates warnings for allocators of anonymous access types,
11038 which can involve run-time accessibility checks and lead to unexpected
11039 accessibility violations. For more details on the rules involved, see
11048 @item @code{-gnatw_A}
11050 @emph{Supress warnings on anonymous allocators.}
11052 @geindex Anonymous allocators
11054 This switch suppresses warnings for anonymous access type allocators.
11057 @geindex -gnatwb (gcc)
11062 @item @code{-gnatwb}
11064 @emph{Activate warnings on bad fixed values.}
11066 @geindex Bad fixed values
11068 @geindex Fixed-point Small value
11070 @geindex Small value
11072 This switch activates warnings for static fixed-point expressions whose
11073 value is not an exact multiple of Small. Such values are implementation
11074 dependent, since an implementation is free to choose either of the multiples
11075 that surround the value. GNAT always chooses the closer one, but this is not
11076 required behavior, and it is better to specify a value that is an exact
11077 multiple, ensuring predictable execution. The default is that such warnings
11081 @geindex -gnatwB (gcc)
11086 @item @code{-gnatwB}
11088 @emph{Suppress warnings on bad fixed values.}
11090 This switch suppresses warnings for static fixed-point expressions whose
11091 value is not an exact multiple of Small.
11094 @geindex -gnatw.b (gcc)
11099 @item @code{-gnatw.b}
11101 @emph{Activate warnings on biased representation.}
11103 @geindex Biased representation
11105 This switch activates warnings when a size clause, value size clause, component
11106 clause, or component size clause forces the use of biased representation for an
11107 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
11108 to represent 10/11). The default is that such warnings are generated.
11111 @geindex -gnatwB (gcc)
11116 @item @code{-gnatw.B}
11118 @emph{Suppress warnings on biased representation.}
11120 This switch suppresses warnings for representation clauses that force the use
11121 of biased representation.
11124 @geindex -gnatwc (gcc)
11129 @item @code{-gnatwc}
11131 @emph{Activate warnings on conditionals.}
11133 @geindex Conditionals
11136 This switch activates warnings for conditional expressions used in
11137 tests that are known to be True or False at compile time. The default
11138 is that such warnings are not generated.
11139 Note that this warning does
11140 not get issued for the use of boolean variables or constants whose
11141 values are known at compile time, since this is a standard technique
11142 for conditional compilation in Ada, and this would generate too many
11143 false positive warnings.
11145 This warning option also activates a special test for comparisons using
11146 the operators '>=' and' <='.
11147 If the compiler can tell that only the equality condition is possible,
11148 then it will warn that the '>' or '<' part of the test
11149 is useless and that the operator could be replaced by '='.
11150 An example would be comparing a @code{Natural} variable <= 0.
11152 This warning option also generates warnings if
11153 one or both tests is optimized away in a membership test for integer
11154 values if the result can be determined at compile time. Range tests on
11155 enumeration types are not included, since it is common for such tests
11156 to include an end point.
11158 This warning can also be turned on using @code{-gnatwa}.
11161 @geindex -gnatwC (gcc)
11166 @item @code{-gnatwC}
11168 @emph{Suppress warnings on conditionals.}
11170 This switch suppresses warnings for conditional expressions used in
11171 tests that are known to be True or False at compile time.
11174 @geindex -gnatw.c (gcc)
11179 @item @code{-gnatw.c}
11181 @emph{Activate warnings on missing component clauses.}
11183 @geindex Component clause
11186 This switch activates warnings for record components where a record
11187 representation clause is present and has component clauses for the
11188 majority, but not all, of the components. A warning is given for each
11189 component for which no component clause is present.
11192 @geindex -gnatw.C (gcc)
11197 @item @code{-gnatw.C}
11199 @emph{Suppress warnings on missing component clauses.}
11201 This switch suppresses warnings for record components that are
11202 missing a component clause in the situation described above.
11205 @geindex -gnatw_c (gcc)
11210 @item @code{-gnatw_c}
11212 @emph{Activate warnings on unknown condition in Compile_Time_Warning.}
11214 @geindex Compile_Time_Warning
11216 @geindex Compile_Time_Error
11218 This switch activates warnings on a pragma Compile_Time_Warning
11219 or Compile_Time_Error whose condition has a value that is not
11220 known at compile time.
11221 The default is that such warnings are generated.
11224 @geindex -gnatw_C (gcc)
11229 @item @code{-gnatw_C}
11231 @emph{Suppress warnings on unknown condition in Compile_Time_Warning.}
11233 This switch supresses warnings on a pragma Compile_Time_Warning
11234 or Compile_Time_Error whose condition has a value that is not
11235 known at compile time.
11238 @geindex -gnatwd (gcc)
11243 @item @code{-gnatwd}
11245 @emph{Activate warnings on implicit dereferencing.}
11247 If this switch is set, then the use of a prefix of an access type
11248 in an indexed component, slice, or selected component without an
11249 explicit @code{.all} will generate a warning. With this warning
11250 enabled, access checks occur only at points where an explicit
11251 @code{.all} appears in the source code (assuming no warnings are
11252 generated as a result of this switch). The default is that such
11253 warnings are not generated.
11256 @geindex -gnatwD (gcc)
11261 @item @code{-gnatwD}
11263 @emph{Suppress warnings on implicit dereferencing.}
11265 @geindex Implicit dereferencing
11267 @geindex Dereferencing
11270 This switch suppresses warnings for implicit dereferences in
11271 indexed components, slices, and selected components.
11274 @geindex -gnatw.d (gcc)
11279 @item @code{-gnatw.d}
11281 @emph{Activate tagging of warning and info messages.}
11283 If this switch is set, then warning messages are tagged, with one of the
11293 Used to tag warnings controlled by the switch @code{-gnatwx} where x
11298 Used to tag warnings controlled by the switch @code{-gnatw.x} where x
11303 Used to tag elaboration information (info) messages generated when the
11304 static model of elaboration is used and the @code{-gnatel} switch is set.
11307 @emph{[restriction warning]}
11308 Used to tag warning messages for restriction violations, activated by use
11309 of the pragma @code{Restriction_Warnings}.
11312 @emph{[warning-as-error]}
11313 Used to tag warning messages that have been converted to error messages by
11314 use of the pragma Warning_As_Error. Note that such warnings are prefixed by
11315 the string "error: " rather than "warning: ".
11318 @emph{[enabled by default]}
11319 Used to tag all other warnings that are always given by default, unless
11320 warnings are completely suppressed using pragma @emph{Warnings(Off)} or
11321 the switch @code{-gnatws}.
11326 @geindex -gnatw.d (gcc)
11331 @item @code{-gnatw.D}
11333 @emph{Deactivate tagging of warning and info messages messages.}
11335 If this switch is set, then warning messages return to the default
11336 mode in which warnings and info messages are not tagged as described above for
11340 @geindex -gnatwe (gcc)
11343 @geindex treat as error
11348 @item @code{-gnatwe}
11350 @emph{Treat warnings and style checks as errors.}
11352 This switch causes warning messages and style check messages to be
11354 The warning string still appears, but the warning messages are counted
11355 as errors, and prevent the generation of an object file. Note that this
11356 is the only -gnatw switch that affects the handling of style check messages.
11357 Note also that this switch has no effect on info (information) messages, which
11358 are not treated as errors if this switch is present.
11361 @geindex -gnatw.e (gcc)
11366 @item @code{-gnatw.e}
11368 @emph{Activate every optional warning.}
11371 @geindex activate every optional warning
11373 This switch activates all optional warnings, including those which
11374 are not activated by @code{-gnatwa}. The use of this switch is not
11375 recommended for normal use. If you turn this switch on, it is almost
11376 certain that you will get large numbers of useless warnings. The
11377 warnings that are excluded from @code{-gnatwa} are typically highly
11378 specialized warnings that are suitable for use only in code that has
11379 been specifically designed according to specialized coding rules.
11382 @geindex -gnatwE (gcc)
11385 @geindex treat as error
11390 @item @code{-gnatwE}
11392 @emph{Treat all run-time exception warnings as errors.}
11394 This switch causes warning messages regarding errors that will be raised
11395 during run-time execution to be treated as errors.
11398 @geindex -gnatwf (gcc)
11403 @item @code{-gnatwf}
11405 @emph{Activate warnings on unreferenced formals.}
11408 @geindex unreferenced
11410 This switch causes a warning to be generated if a formal parameter
11411 is not referenced in the body of the subprogram. This warning can
11412 also be turned on using @code{-gnatwu}. The
11413 default is that these warnings are not generated.
11416 @geindex -gnatwF (gcc)
11421 @item @code{-gnatwF}
11423 @emph{Suppress warnings on unreferenced formals.}
11425 This switch suppresses warnings for unreferenced formal
11426 parameters. Note that the
11427 combination @code{-gnatwu} followed by @code{-gnatwF} has the
11428 effect of warning on unreferenced entities other than subprogram
11432 @geindex -gnatwg (gcc)
11437 @item @code{-gnatwg}
11439 @emph{Activate warnings on unrecognized pragmas.}
11442 @geindex unrecognized
11444 This switch causes a warning to be generated if an unrecognized
11445 pragma is encountered. Apart from issuing this warning, the
11446 pragma is ignored and has no effect. The default
11447 is that such warnings are issued (satisfying the Ada Reference
11448 Manual requirement that such warnings appear).
11451 @geindex -gnatwG (gcc)
11456 @item @code{-gnatwG}
11458 @emph{Suppress warnings on unrecognized pragmas.}
11460 This switch suppresses warnings for unrecognized pragmas.
11463 @geindex -gnatw.g (gcc)
11468 @item @code{-gnatw.g}
11470 @emph{Warnings used for GNAT sources.}
11472 This switch sets the warning categories that are used by the standard
11473 GNAT style. Currently this is equivalent to
11474 @code{-gnatwAao.q.s.CI.V.X.Z}
11475 but more warnings may be added in the future without advanced notice.
11478 @geindex -gnatwh (gcc)
11483 @item @code{-gnatwh}
11485 @emph{Activate warnings on hiding.}
11487 @geindex Hiding of Declarations
11489 This switch activates warnings on hiding declarations that are considered
11490 potentially confusing. Not all cases of hiding cause warnings; for example an
11491 overriding declaration hides an implicit declaration, which is just normal
11492 code. The default is that warnings on hiding are not generated.
11495 @geindex -gnatwH (gcc)
11500 @item @code{-gnatwH}
11502 @emph{Suppress warnings on hiding.}
11504 This switch suppresses warnings on hiding declarations.
11507 @geindex -gnatw.h (gcc)
11512 @item @code{-gnatw.h}
11514 @emph{Activate warnings on holes/gaps in records.}
11516 @geindex Record Representation (gaps)
11518 This switch activates warnings on component clauses in record
11519 representation clauses that leave holes (gaps) in the record layout.
11520 If this warning option is active, then record representation clauses
11521 should specify a contiguous layout, adding unused fill fields if needed.
11524 @geindex -gnatw.H (gcc)
11529 @item @code{-gnatw.H}
11531 @emph{Suppress warnings on holes/gaps in records.}
11533 This switch suppresses warnings on component clauses in record
11534 representation clauses that leave holes (haps) in the record layout.
11537 @geindex -gnatwi (gcc)
11542 @item @code{-gnatwi}
11544 @emph{Activate warnings on implementation units.}
11546 This switch activates warnings for a @emph{with} of an internal GNAT
11547 implementation unit, defined as any unit from the @code{Ada},
11548 @code{Interfaces}, @code{GNAT},
11550 hierarchies that is not
11551 documented in either the Ada Reference Manual or the GNAT
11552 Programmer's Reference Manual. Such units are intended only
11553 for internal implementation purposes and should not be @emph{with}ed
11554 by user programs. The default is that such warnings are generated
11557 @geindex -gnatwI (gcc)
11562 @item @code{-gnatwI}
11564 @emph{Disable warnings on implementation units.}
11566 This switch disables warnings for a @emph{with} of an internal GNAT
11567 implementation unit.
11570 @geindex -gnatw.i (gcc)
11575 @item @code{-gnatw.i}
11577 @emph{Activate warnings on overlapping actuals.}
11579 This switch enables a warning on statically detectable overlapping actuals in
11580 a subprogram call, when one of the actuals is an in-out parameter, and the
11581 types of the actuals are not by-copy types. This warning is off by default.
11584 @geindex -gnatw.I (gcc)
11589 @item @code{-gnatw.I}
11591 @emph{Disable warnings on overlapping actuals.}
11593 This switch disables warnings on overlapping actuals in a call..
11596 @geindex -gnatwj (gcc)
11601 @item @code{-gnatwj}
11603 @emph{Activate warnings on obsolescent features (Annex J).}
11606 @geindex obsolescent
11608 @geindex Obsolescent features
11610 If this warning option is activated, then warnings are generated for
11611 calls to subprograms marked with @code{pragma Obsolescent} and
11612 for use of features in Annex J of the Ada Reference Manual. In the
11613 case of Annex J, not all features are flagged. In particular use
11614 of the renamed packages (like @code{Text_IO}) and use of package
11615 @code{ASCII} are not flagged, since these are very common and
11616 would generate many annoying positive warnings. The default is that
11617 such warnings are not generated.
11619 In addition to the above cases, warnings are also generated for
11620 GNAT features that have been provided in past versions but which
11621 have been superseded (typically by features in the new Ada standard).
11622 For example, @code{pragma Ravenscar} will be flagged since its
11623 function is replaced by @code{pragma Profile(Ravenscar)}, and
11624 @code{pragma Interface_Name} will be flagged since its function
11625 is replaced by @code{pragma Import}.
11627 Note that this warning option functions differently from the
11628 restriction @code{No_Obsolescent_Features} in two respects.
11629 First, the restriction applies only to annex J features.
11630 Second, the restriction does flag uses of package @code{ASCII}.
11633 @geindex -gnatwJ (gcc)
11638 @item @code{-gnatwJ}
11640 @emph{Suppress warnings on obsolescent features (Annex J).}
11642 This switch disables warnings on use of obsolescent features.
11645 @geindex -gnatw.j (gcc)
11650 @item @code{-gnatw.j}
11652 @emph{Activate warnings on late declarations of tagged type primitives.}
11654 This switch activates warnings on visible primitives added to a
11655 tagged type after deriving a private extension from it.
11658 @geindex -gnatw.J (gcc)
11663 @item @code{-gnatw.J}
11665 @emph{Suppress warnings on late declarations of tagged type primitives.}
11667 This switch suppresses warnings on visible primitives added to a
11668 tagged type after deriving a private extension from it.
11671 @geindex -gnatwk (gcc)
11676 @item @code{-gnatwk}
11678 @emph{Activate warnings on variables that could be constants.}
11680 This switch activates warnings for variables that are initialized but
11681 never modified, and then could be declared constants. The default is that
11682 such warnings are not given.
11685 @geindex -gnatwK (gcc)
11690 @item @code{-gnatwK}
11692 @emph{Suppress warnings on variables that could be constants.}
11694 This switch disables warnings on variables that could be declared constants.
11697 @geindex -gnatw.k (gcc)
11702 @item @code{-gnatw.k}
11704 @emph{Activate warnings on redefinition of names in standard.}
11706 This switch activates warnings for declarations that declare a name that
11707 is defined in package Standard. Such declarations can be confusing,
11708 especially since the names in package Standard continue to be directly
11709 visible, meaning that use visibiliy on such redeclared names does not
11710 work as expected. Names of discriminants and components in records are
11711 not included in this check.
11714 @geindex -gnatwK (gcc)
11719 @item @code{-gnatw.K}
11721 @emph{Suppress warnings on redefinition of names in standard.}
11723 This switch activates warnings for declarations that declare a name that
11724 is defined in package Standard.
11727 @geindex -gnatwl (gcc)
11732 @item @code{-gnatwl}
11734 @emph{Activate warnings for elaboration pragmas.}
11736 @geindex Elaboration
11739 This switch activates warnings for possible elaboration problems,
11740 including suspicious use
11741 of @code{Elaborate} pragmas, when using the static elaboration model, and
11742 possible situations that may raise @code{Program_Error} when using the
11743 dynamic elaboration model.
11744 See the section in this guide on elaboration checking for further details.
11745 The default is that such warnings
11749 @geindex -gnatwL (gcc)
11754 @item @code{-gnatwL}
11756 @emph{Suppress warnings for elaboration pragmas.}
11758 This switch suppresses warnings for possible elaboration problems.
11761 @geindex -gnatw.l (gcc)
11766 @item @code{-gnatw.l}
11768 @emph{List inherited aspects.}
11770 This switch causes the compiler to list inherited invariants,
11771 preconditions, and postconditions from Type_Invariant'Class, Invariant'Class,
11772 Pre'Class, and Post'Class aspects. Also list inherited subtype predicates.
11775 @geindex -gnatw.L (gcc)
11780 @item @code{-gnatw.L}
11782 @emph{Suppress listing of inherited aspects.}
11784 This switch suppresses listing of inherited aspects.
11787 @geindex -gnatwm (gcc)
11792 @item @code{-gnatwm}
11794 @emph{Activate warnings on modified but unreferenced variables.}
11796 This switch activates warnings for variables that are assigned (using
11797 an initialization value or with one or more assignment statements) but
11798 whose value is never read. The warning is suppressed for volatile
11799 variables and also for variables that are renamings of other variables
11800 or for which an address clause is given.
11801 The default is that these warnings are not given.
11804 @geindex -gnatwM (gcc)
11809 @item @code{-gnatwM}
11811 @emph{Disable warnings on modified but unreferenced variables.}
11813 This switch disables warnings for variables that are assigned or
11814 initialized, but never read.
11817 @geindex -gnatw.m (gcc)
11822 @item @code{-gnatw.m}
11824 @emph{Activate warnings on suspicious modulus values.}
11826 This switch activates warnings for modulus values that seem suspicious.
11827 The cases caught are where the size is the same as the modulus (e.g.
11828 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
11829 with no size clause. The guess in both cases is that 2**x was intended
11830 rather than x. In addition expressions of the form 2*x for small x
11831 generate a warning (the almost certainly accurate guess being that
11832 2**x was intended). The default is that these warnings are given.
11835 @geindex -gnatw.M (gcc)
11840 @item @code{-gnatw.M}
11842 @emph{Disable warnings on suspicious modulus values.}
11844 This switch disables warnings for suspicious modulus values.
11847 @geindex -gnatwn (gcc)
11852 @item @code{-gnatwn}
11854 @emph{Set normal warnings mode.}
11856 This switch sets normal warning mode, in which enabled warnings are
11857 issued and treated as warnings rather than errors. This is the default
11858 mode. the switch @code{-gnatwn} can be used to cancel the effect of
11859 an explicit @code{-gnatws} or
11860 @code{-gnatwe}. It also cancels the effect of the
11861 implicit @code{-gnatwe} that is activated by the
11862 use of @code{-gnatg}.
11865 @geindex -gnatw.n (gcc)
11867 @geindex Atomic Synchronization
11873 @item @code{-gnatw.n}
11875 @emph{Activate warnings on atomic synchronization.}
11877 This switch actives warnings when an access to an atomic variable
11878 requires the generation of atomic synchronization code. These
11879 warnings are off by default.
11882 @geindex -gnatw.N (gcc)
11887 @item @code{-gnatw.N}
11889 @emph{Suppress warnings on atomic synchronization.}
11891 @geindex Atomic Synchronization
11894 This switch suppresses warnings when an access to an atomic variable
11895 requires the generation of atomic synchronization code.
11898 @geindex -gnatwo (gcc)
11900 @geindex Address Clauses
11906 @item @code{-gnatwo}
11908 @emph{Activate warnings on address clause overlays.}
11910 This switch activates warnings for possibly unintended initialization
11911 effects of defining address clauses that cause one variable to overlap
11912 another. The default is that such warnings are generated.
11915 @geindex -gnatwO (gcc)
11920 @item @code{-gnatwO}
11922 @emph{Suppress warnings on address clause overlays.}
11924 This switch suppresses warnings on possibly unintended initialization
11925 effects of defining address clauses that cause one variable to overlap
11929 @geindex -gnatw.o (gcc)
11934 @item @code{-gnatw.o}
11936 @emph{Activate warnings on modified but unreferenced out parameters.}
11938 This switch activates warnings for variables that are modified by using
11939 them as actuals for a call to a procedure with an out mode formal, where
11940 the resulting assigned value is never read. It is applicable in the case
11941 where there is more than one out mode formal. If there is only one out
11942 mode formal, the warning is issued by default (controlled by -gnatwu).
11943 The warning is suppressed for volatile
11944 variables and also for variables that are renamings of other variables
11945 or for which an address clause is given.
11946 The default is that these warnings are not given.
11949 @geindex -gnatw.O (gcc)
11954 @item @code{-gnatw.O}
11956 @emph{Disable warnings on modified but unreferenced out parameters.}
11958 This switch suppresses warnings for variables that are modified by using
11959 them as actuals for a call to a procedure with an out mode formal, where
11960 the resulting assigned value is never read.
11963 @geindex -gnatwp (gcc)
11971 @item @code{-gnatwp}
11973 @emph{Activate warnings on ineffective pragma Inlines.}
11975 This switch activates warnings for failure of front end inlining
11976 (activated by @code{-gnatN}) to inline a particular call. There are
11977 many reasons for not being able to inline a call, including most
11978 commonly that the call is too complex to inline. The default is
11979 that such warnings are not given.
11980 Warnings on ineffective inlining by the gcc back-end can be activated
11981 separately, using the gcc switch -Winline.
11984 @geindex -gnatwP (gcc)
11989 @item @code{-gnatwP}
11991 @emph{Suppress warnings on ineffective pragma Inlines.}
11993 This switch suppresses warnings on ineffective pragma Inlines. If the
11994 inlining mechanism cannot inline a call, it will simply ignore the
11998 @geindex -gnatw.p (gcc)
12000 @geindex Parameter order
12006 @item @code{-gnatw.p}
12008 @emph{Activate warnings on parameter ordering.}
12010 This switch activates warnings for cases of suspicious parameter
12011 ordering when the list of arguments are all simple identifiers that
12012 match the names of the formals, but are in a different order. The
12013 warning is suppressed if any use of named parameter notation is used,
12014 so this is the appropriate way to suppress a false positive (and
12015 serves to emphasize that the "misordering" is deliberate). The
12016 default is that such warnings are not given.
12019 @geindex -gnatw.P (gcc)
12024 @item @code{-gnatw.P}
12026 @emph{Suppress warnings on parameter ordering.}
12028 This switch suppresses warnings on cases of suspicious parameter
12032 @geindex -gnatwq (gcc)
12034 @geindex Parentheses
12040 @item @code{-gnatwq}
12042 @emph{Activate warnings on questionable missing parentheses.}
12044 This switch activates warnings for cases where parentheses are not used and
12045 the result is potential ambiguity from a readers point of view. For example
12046 (not a > b) when a and b are modular means ((not a) > b) and very likely the
12047 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
12048 quite likely ((-x) mod 5) was intended. In such situations it seems best to
12049 follow the rule of always parenthesizing to make the association clear, and
12050 this warning switch warns if such parentheses are not present. The default
12051 is that these warnings are given.
12054 @geindex -gnatwQ (gcc)
12059 @item @code{-gnatwQ}
12061 @emph{Suppress warnings on questionable missing parentheses.}
12063 This switch suppresses warnings for cases where the association is not
12064 clear and the use of parentheses is preferred.
12067 @geindex -gnatw.q (gcc)
12075 @item @code{-gnatw.q}
12077 @emph{Activate warnings on questionable layout of record types.}
12079 This switch activates warnings for cases where the default layout of
12080 a record type, that is to say the layout of its components in textual
12081 order of the source code, would very likely cause inefficiencies in
12082 the code generated by the compiler, both in terms of space and speed
12083 during execution. One warning is issued for each problematic component
12084 without representation clause in the nonvariant part and then in each
12085 variant recursively, if any.
12087 The purpose of these warnings is neither to prescribe an optimal layout
12088 nor to force the use of representation clauses, but rather to get rid of
12089 the most blatant inefficiencies in the layout. Therefore, the default
12090 layout is matched against the following synthetic ordered layout and
12091 the deviations are flagged on a component-by-component basis:
12097 first all components or groups of components whose length is fixed
12098 and a multiple of the storage unit,
12101 then the remaining components whose length is fixed and not a multiple
12102 of the storage unit,
12105 then the remaining components whose length doesn't depend on discriminants
12106 (that is to say, with variable but uniform length for all objects),
12109 then all components whose length depends on discriminants,
12112 finally the variant part (if any),
12115 for the nonvariant part and for each variant recursively, if any.
12117 The exact wording of the warning depends on whether the compiler is allowed
12118 to reorder the components in the record type or precluded from doing it by
12119 means of pragma @code{No_Component_Reordering}.
12121 The default is that these warnings are not given.
12124 @geindex -gnatw.Q (gcc)
12129 @item @code{-gnatw.Q}
12131 @emph{Suppress warnings on questionable layout of record types.}
12133 This switch suppresses warnings for cases where the default layout of
12134 a record type would very likely cause inefficiencies.
12137 @geindex -gnatwr (gcc)
12142 @item @code{-gnatwr}
12144 @emph{Activate warnings on redundant constructs.}
12146 This switch activates warnings for redundant constructs. The following
12147 is the current list of constructs regarded as redundant:
12153 Assignment of an item to itself.
12156 Type conversion that converts an expression to its own type.
12159 Use of the attribute @code{Base} where @code{typ'Base} is the same
12163 Use of pragma @code{Pack} when all components are placed by a record
12164 representation clause.
12167 Exception handler containing only a reraise statement (raise with no
12168 operand) which has no effect.
12171 Use of the operator abs on an operand that is known at compile time
12175 Comparison of an object or (unary or binary) operation of boolean type to
12176 an explicit True value.
12179 The default is that warnings for redundant constructs are not given.
12182 @geindex -gnatwR (gcc)
12187 @item @code{-gnatwR}
12189 @emph{Suppress warnings on redundant constructs.}
12191 This switch suppresses warnings for redundant constructs.
12194 @geindex -gnatw.r (gcc)
12199 @item @code{-gnatw.r}
12201 @emph{Activate warnings for object renaming function.}
12203 This switch activates warnings for an object renaming that renames a
12204 function call, which is equivalent to a constant declaration (as
12205 opposed to renaming the function itself). The default is that these
12206 warnings are given.
12209 @geindex -gnatw.R (gcc)
12214 @item @code{-gnatw.R}
12216 @emph{Suppress warnings for object renaming function.}
12218 This switch suppresses warnings for object renaming function.
12221 @geindex -gnatw_r (gcc)
12226 @item @code{-gnatw_r}
12228 @emph{Activate warnings for out-of-order record representation clauses.}
12230 This switch activates warnings for record representation clauses,
12231 if the order of component declarations, component clauses,
12232 and bit-level layout do not all agree.
12233 The default is that these warnings are not given.
12236 @geindex -gnatw_R (gcc)
12241 @item @code{-gnatw_R}
12243 @emph{Suppress warnings for out-of-order record representation clauses.}
12246 @geindex -gnatws (gcc)
12251 @item @code{-gnatws}
12253 @emph{Suppress all warnings.}
12255 This switch completely suppresses the
12256 output of all warning messages from the GNAT front end, including
12257 both warnings that can be controlled by switches described in this
12258 section, and those that are normally given unconditionally. The
12259 effect of this suppress action can only be cancelled by a subsequent
12260 use of the switch @code{-gnatwn}.
12262 Note that switch @code{-gnatws} does not suppress
12263 warnings from the @code{gcc} back end.
12264 To suppress these back end warnings as well, use the switch @code{-w}
12265 in addition to @code{-gnatws}. Also this switch has no effect on the
12266 handling of style check messages.
12269 @geindex -gnatw.s (gcc)
12271 @geindex Record Representation (component sizes)
12276 @item @code{-gnatw.s}
12278 @emph{Activate warnings on overridden size clauses.}
12280 This switch activates warnings on component clauses in record
12281 representation clauses where the length given overrides that
12282 specified by an explicit size clause for the component type. A
12283 warning is similarly given in the array case if a specified
12284 component size overrides an explicit size clause for the array
12288 @geindex -gnatw.S (gcc)
12293 @item @code{-gnatw.S}
12295 @emph{Suppress warnings on overridden size clauses.}
12297 This switch suppresses warnings on component clauses in record
12298 representation clauses that override size clauses, and similar
12299 warnings when an array component size overrides a size clause.
12302 @geindex -gnatwt (gcc)
12304 @geindex Deactivated code
12307 @geindex Deleted code
12313 @item @code{-gnatwt}
12315 @emph{Activate warnings for tracking of deleted conditional code.}
12317 This switch activates warnings for tracking of code in conditionals (IF and
12318 CASE statements) that is detected to be dead code which cannot be executed, and
12319 which is removed by the front end. This warning is off by default. This may be
12320 useful for detecting deactivated code in certified applications.
12323 @geindex -gnatwT (gcc)
12328 @item @code{-gnatwT}
12330 @emph{Suppress warnings for tracking of deleted conditional code.}
12332 This switch suppresses warnings for tracking of deleted conditional code.
12335 @geindex -gnatw.t (gcc)
12340 @item @code{-gnatw.t}
12342 @emph{Activate warnings on suspicious contracts.}
12344 This switch activates warnings on suspicious contracts. This includes
12345 warnings on suspicious postconditions (whether a pragma @code{Postcondition} or a
12346 @code{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect
12347 @code{Contract_Cases}). A function postcondition or contract case is suspicious
12348 when no postcondition or contract case for this function mentions the result
12349 of the function. A procedure postcondition or contract case is suspicious
12350 when it only refers to the pre-state of the procedure, because in that case
12351 it should rather be expressed as a precondition. This switch also controls
12352 warnings on suspicious cases of expressions typically found in contracts like
12353 quantified expressions and uses of Update attribute. The default is that such
12354 warnings are generated.
12357 @geindex -gnatw.T (gcc)
12362 @item @code{-gnatw.T}
12364 @emph{Suppress warnings on suspicious contracts.}
12366 This switch suppresses warnings on suspicious contracts.
12369 @geindex -gnatwu (gcc)
12374 @item @code{-gnatwu}
12376 @emph{Activate warnings on unused entities.}
12378 This switch activates warnings to be generated for entities that
12379 are declared but not referenced, and for units that are @emph{with}ed
12381 referenced. In the case of packages, a warning is also generated if
12382 no entities in the package are referenced. This means that if a with'ed
12383 package is referenced but the only references are in @code{use}
12384 clauses or @code{renames}
12385 declarations, a warning is still generated. A warning is also generated
12386 for a generic package that is @emph{with}ed but never instantiated.
12387 In the case where a package or subprogram body is compiled, and there
12388 is a @emph{with} on the corresponding spec
12389 that is only referenced in the body,
12390 a warning is also generated, noting that the
12391 @emph{with} can be moved to the body. The default is that
12392 such warnings are not generated.
12393 This switch also activates warnings on unreferenced formals
12394 (it includes the effect of @code{-gnatwf}).
12397 @geindex -gnatwU (gcc)
12402 @item @code{-gnatwU}
12404 @emph{Suppress warnings on unused entities.}
12406 This switch suppresses warnings for unused entities and packages.
12407 It also turns off warnings on unreferenced formals (and thus includes
12408 the effect of @code{-gnatwF}).
12411 @geindex -gnatw.u (gcc)
12416 @item @code{-gnatw.u}
12418 @emph{Activate warnings on unordered enumeration types.}
12420 This switch causes enumeration types to be considered as conceptually
12421 unordered, unless an explicit pragma @code{Ordered} is given for the type.
12422 The effect is to generate warnings in clients that use explicit comparisons
12423 or subranges, since these constructs both treat objects of the type as
12424 ordered. (A @emph{client} is defined as a unit that is other than the unit in
12425 which the type is declared, or its body or subunits.) Please refer to
12426 the description of pragma @code{Ordered} in the
12427 @cite{GNAT Reference Manual} for further details.
12428 The default is that such warnings are not generated.
12431 @geindex -gnatw.U (gcc)
12436 @item @code{-gnatw.U}
12438 @emph{Deactivate warnings on unordered enumeration types.}
12440 This switch causes all enumeration types to be considered as ordered, so
12441 that no warnings are given for comparisons or subranges for any type.
12444 @geindex -gnatwv (gcc)
12446 @geindex Unassigned variable warnings
12451 @item @code{-gnatwv}
12453 @emph{Activate warnings on unassigned variables.}
12455 This switch activates warnings for access to variables which
12456 may not be properly initialized. The default is that
12457 such warnings are generated.
12460 @geindex -gnatwV (gcc)
12465 @item @code{-gnatwV}
12467 @emph{Suppress warnings on unassigned variables.}
12469 This switch suppresses warnings for access to variables which
12470 may not be properly initialized.
12471 For variables of a composite type, the warning can also be suppressed in
12472 Ada 2005 by using a default initialization with a box. For example, if
12473 Table is an array of records whose components are only partially uninitialized,
12474 then the following code:
12477 Tab : Table := (others => <>);
12480 will suppress warnings on subsequent statements that access components
12484 @geindex -gnatw.v (gcc)
12486 @geindex bit order warnings
12491 @item @code{-gnatw.v}
12493 @emph{Activate info messages for non-default bit order.}
12495 This switch activates messages (labeled "info", they are not warnings,
12496 just informational messages) about the effects of non-default bit-order
12497 on records to which a component clause is applied. The effect of specifying
12498 non-default bit ordering is a bit subtle (and changed with Ada 2005), so
12499 these messages, which are given by default, are useful in understanding the
12500 exact consequences of using this feature.
12503 @geindex -gnatw.V (gcc)
12508 @item @code{-gnatw.V}
12510 @emph{Suppress info messages for non-default bit order.}
12512 This switch suppresses information messages for the effects of specifying
12513 non-default bit order on record components with component clauses.
12516 @geindex -gnatww (gcc)
12518 @geindex String indexing warnings
12523 @item @code{-gnatww}
12525 @emph{Activate warnings on wrong low bound assumption.}
12527 This switch activates warnings for indexing an unconstrained string parameter
12528 with a literal or S'Length. This is a case where the code is assuming that the
12529 low bound is one, which is in general not true (for example when a slice is
12530 passed). The default is that such warnings are generated.
12533 @geindex -gnatwW (gcc)
12538 @item @code{-gnatwW}
12540 @emph{Suppress warnings on wrong low bound assumption.}
12542 This switch suppresses warnings for indexing an unconstrained string parameter
12543 with a literal or S'Length. Note that this warning can also be suppressed
12544 in a particular case by adding an assertion that the lower bound is 1,
12545 as shown in the following example:
12548 procedure K (S : String) is
12549 pragma Assert (S'First = 1);
12554 @geindex -gnatw.w (gcc)
12556 @geindex Warnings Off control
12561 @item @code{-gnatw.w}
12563 @emph{Activate warnings on Warnings Off pragmas.}
12565 This switch activates warnings for use of @code{pragma Warnings (Off, entity)}
12566 where either the pragma is entirely useless (because it suppresses no
12567 warnings), or it could be replaced by @code{pragma Unreferenced} or
12568 @code{pragma Unmodified}.
12569 Also activates warnings for the case of
12570 Warnings (Off, String), where either there is no matching
12571 Warnings (On, String), or the Warnings (Off) did not suppress any warning.
12572 The default is that these warnings are not given.
12575 @geindex -gnatw.W (gcc)
12580 @item @code{-gnatw.W}
12582 @emph{Suppress warnings on unnecessary Warnings Off pragmas.}
12584 This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}.
12587 @geindex -gnatwx (gcc)
12589 @geindex Export/Import pragma warnings
12594 @item @code{-gnatwx}
12596 @emph{Activate warnings on Export/Import pragmas.}
12598 This switch activates warnings on Export/Import pragmas when
12599 the compiler detects a possible conflict between the Ada and
12600 foreign language calling sequences. For example, the use of
12601 default parameters in a convention C procedure is dubious
12602 because the C compiler cannot supply the proper default, so
12603 a warning is issued. The default is that such warnings are
12607 @geindex -gnatwX (gcc)
12612 @item @code{-gnatwX}
12614 @emph{Suppress warnings on Export/Import pragmas.}
12616 This switch suppresses warnings on Export/Import pragmas.
12617 The sense of this is that you are telling the compiler that
12618 you know what you are doing in writing the pragma, and it
12619 should not complain at you.
12622 @geindex -gnatwm (gcc)
12627 @item @code{-gnatw.x}
12629 @emph{Activate warnings for No_Exception_Propagation mode.}
12631 This switch activates warnings for exception usage when pragma Restrictions
12632 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
12633 explicit exception raises which are not covered by a local handler, and for
12634 exception handlers which do not cover a local raise. The default is that
12635 these warnings are given for units that contain exception handlers.
12637 @item @code{-gnatw.X}
12639 @emph{Disable warnings for No_Exception_Propagation mode.}
12641 This switch disables warnings for exception usage when pragma Restrictions
12642 (No_Exception_Propagation) is in effect.
12645 @geindex -gnatwy (gcc)
12647 @geindex Ada compatibility issues warnings
12652 @item @code{-gnatwy}
12654 @emph{Activate warnings for Ada compatibility issues.}
12656 For the most part, newer versions of Ada are upwards compatible
12657 with older versions. For example, Ada 2005 programs will almost
12658 always work when compiled as Ada 2012.
12659 However there are some exceptions (for example the fact that
12660 @code{some} is now a reserved word in Ada 2012). This
12661 switch activates several warnings to help in identifying
12662 and correcting such incompatibilities. The default is that
12663 these warnings are generated. Note that at one point Ada 2005
12664 was called Ada 0Y, hence the choice of character.
12667 @geindex -gnatwY (gcc)
12669 @geindex Ada compatibility issues warnings
12674 @item @code{-gnatwY}
12676 @emph{Disable warnings for Ada compatibility issues.}
12678 This switch suppresses the warnings intended to help in identifying
12679 incompatibilities between Ada language versions.
12682 @geindex -gnatw.y (gcc)
12684 @geindex Package spec needing body
12689 @item @code{-gnatw.y}
12691 @emph{Activate information messages for why package spec needs body.}
12693 There are a number of cases in which a package spec needs a body.
12694 For example, the use of pragma Elaborate_Body, or the declaration
12695 of a procedure specification requiring a completion. This switch
12696 causes information messages to be output showing why a package
12697 specification requires a body. This can be useful in the case of
12698 a large package specification which is unexpectedly requiring a
12699 body. The default is that such information messages are not output.
12702 @geindex -gnatw.Y (gcc)
12704 @geindex No information messages for why package spec needs body
12709 @item @code{-gnatw.Y}
12711 @emph{Disable information messages for why package spec needs body.}
12713 This switch suppresses the output of information messages showing why
12714 a package specification needs a body.
12717 @geindex -gnatwz (gcc)
12719 @geindex Unchecked_Conversion warnings
12724 @item @code{-gnatwz}
12726 @emph{Activate warnings on unchecked conversions.}
12728 This switch activates warnings for unchecked conversions
12729 where the types are known at compile time to have different
12730 sizes. The default is that such warnings are generated. Warnings are also
12731 generated for subprogram pointers with different conventions.
12734 @geindex -gnatwZ (gcc)
12739 @item @code{-gnatwZ}
12741 @emph{Suppress warnings on unchecked conversions.}
12743 This switch suppresses warnings for unchecked conversions
12744 where the types are known at compile time to have different
12745 sizes or conventions.
12748 @geindex -gnatw.z (gcc)
12750 @geindex Size/Alignment warnings
12755 @item @code{-gnatw.z}
12757 @emph{Activate warnings for size not a multiple of alignment.}
12759 This switch activates warnings for cases of array and record types
12760 with specified @code{Size} and @code{Alignment} attributes where the
12761 size is not a multiple of the alignment, resulting in an object
12762 size that is greater than the specified size. The default
12763 is that such warnings are generated.
12766 @geindex -gnatw.Z (gcc)
12768 @geindex Size/Alignment warnings
12773 @item @code{-gnatw.Z}
12775 @emph{Suppress warnings for size not a multiple of alignment.}
12777 This switch suppresses warnings for cases of array and record types
12778 with specified @code{Size} and @code{Alignment} attributes where the
12779 size is not a multiple of the alignment, resulting in an object
12780 size that is greater than the specified size. The warning can also
12781 be suppressed by giving an explicit @code{Object_Size} value.
12784 @geindex -Wunused (gcc)
12789 @item @code{-Wunused}
12791 The warnings controlled by the @code{-gnatw} switch are generated by
12792 the front end of the compiler. The GCC back end can provide
12793 additional warnings and they are controlled by the @code{-W} switch.
12794 For example, @code{-Wunused} activates back end
12795 warnings for entities that are declared but not referenced.
12798 @geindex -Wuninitialized (gcc)
12803 @item @code{-Wuninitialized}
12805 Similarly, @code{-Wuninitialized} activates
12806 the back end warning for uninitialized variables. This switch must be
12807 used in conjunction with an optimization level greater than zero.
12810 @geindex -Wstack-usage (gcc)
12815 @item @code{-Wstack-usage=@emph{len}}
12817 Warn if the stack usage of a subprogram might be larger than @code{len} bytes.
12818 See @ref{f5,,Static Stack Usage Analysis} for details.
12821 @geindex -Wall (gcc)
12828 This switch enables most warnings from the GCC back end.
12829 The code generator detects a number of warning situations that are missed
12830 by the GNAT front end, and this switch can be used to activate them.
12831 The use of this switch also sets the default front end warning mode to
12832 @code{-gnatwa}, that is, most front end warnings activated as well.
12842 Conversely, this switch suppresses warnings from the GCC back end.
12843 The use of this switch also sets the default front end warning mode to
12844 @code{-gnatws}, that is, front end warnings suppressed as well.
12847 @geindex -Werror (gcc)
12852 @item @code{-Werror}
12854 This switch causes warnings from the GCC back end to be treated as
12855 errors. The warning string still appears, but the warning messages are
12856 counted as errors, and prevent the generation of an object file.
12859 A string of warning parameters can be used in the same parameter. For example:
12865 will turn on all optional warnings except for unrecognized pragma warnings,
12866 and also specify that warnings should be treated as errors.
12868 When no switch @code{-gnatw} is used, this is equivalent to:
13015 @node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches
13016 @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}
13017 @subsection Debugging and Assertion Control
13020 @geindex -gnata (gcc)
13025 @item @code{-gnata}
13031 @geindex Assertions
13033 @geindex Precondition
13035 @geindex Postcondition
13037 @geindex Type invariants
13039 @geindex Subtype predicates
13041 The @code{-gnata} option is equivalent to the following @code{Assertion_Policy} pragma:
13044 pragma Assertion_Policy (Check);
13047 Which is a shorthand for:
13050 pragma Assertion_Policy
13052 Static_Predicate => Check,
13053 Dynamic_Predicate => Check,
13055 Pre'Class => Check,
13057 Post'Class => Check,
13058 Type_Invariant => Check,
13059 Type_Invariant'Class => Check);
13062 The pragmas @code{Assert} and @code{Debug} normally have no effect and
13063 are ignored. This switch, where @code{a} stands for 'assert', causes
13064 pragmas @code{Assert} and @code{Debug} to be activated. This switch also
13065 causes preconditions, postconditions, subtype predicates, and
13066 type invariants to be activated.
13068 The pragmas have the form:
13071 pragma Assert (<Boolean-expression> [, <static-string-expression>])
13072 pragma Debug (<procedure call>)
13073 pragma Type_Invariant (<type-local-name>, <Boolean-expression>)
13074 pragma Predicate (<type-local-name>, <Boolean-expression>)
13075 pragma Precondition (<Boolean-expression>, <string-expression>)
13076 pragma Postcondition (<Boolean-expression>, <string-expression>)
13079 The aspects have the form:
13082 with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate]
13083 => <Boolean-expression>;
13086 The @code{Assert} pragma causes @code{Boolean-expression} to be tested.
13087 If the result is @code{True}, the pragma has no effect (other than
13088 possible side effects from evaluating the expression). If the result is
13089 @code{False}, the exception @code{Assert_Failure} declared in the package
13090 @code{System.Assertions} is raised (passing @code{static-string-expression}, if
13091 present, as the message associated with the exception). If no string
13092 expression is given, the default is a string containing the file name and
13093 line number of the pragma.
13095 The @code{Debug} pragma causes @code{procedure} to be called. Note that
13096 @code{pragma Debug} may appear within a declaration sequence, allowing
13097 debugging procedures to be called between declarations.
13099 For the aspect specification, the @code{Boolean-expression} is evaluated.
13100 If the result is @code{True}, the aspect has no effect. If the result
13101 is @code{False}, the exception @code{Assert_Failure} is raised.
13104 @node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches
13105 @anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{102}
13106 @subsection Validity Checking
13109 @geindex Validity Checking
13111 The Ada Reference Manual defines the concept of invalid values (see
13112 RM 13.9.1). The primary source of invalid values is uninitialized
13113 variables. A scalar variable that is left uninitialized may contain
13114 an invalid value; the concept of invalid does not apply to access or
13117 It is an error to read an invalid value, but the RM does not require
13118 run-time checks to detect such errors, except for some minimal
13119 checking to prevent erroneous execution (i.e. unpredictable
13120 behavior). This corresponds to the @code{-gnatVd} switch below,
13121 which is the default. For example, by default, if the expression of a
13122 case statement is invalid, it will raise Constraint_Error rather than
13123 causing a wild jump, and if an array index on the left-hand side of an
13124 assignment is invalid, it will raise Constraint_Error rather than
13125 overwriting an arbitrary memory location.
13127 The @code{-gnatVa} may be used to enable additional validity checks,
13128 which are not required by the RM. These checks are often very
13129 expensive (which is why the RM does not require them). These checks
13130 are useful in tracking down uninitialized variables, but they are
13131 not usually recommended for production builds, and in particular
13132 we do not recommend using these extra validity checking options in
13133 combination with optimization, since this can confuse the optimizer.
13134 If performance is a consideration, leading to the need to optimize,
13135 then the validity checking options should not be used.
13137 The other @code{-gnatV@emph{x}} switches below allow finer-grained
13138 control; you can enable whichever validity checks you desire. However,
13139 for most debugging purposes, @code{-gnatVa} is sufficient, and the
13140 default @code{-gnatVd} (i.e. standard Ada behavior) is usually
13141 sufficient for non-debugging use.
13143 The @code{-gnatB} switch tells the compiler to assume that all
13144 values are valid (that is, within their declared subtype range)
13145 except in the context of a use of the Valid attribute. This means
13146 the compiler can generate more efficient code, since the range
13147 of values is better known at compile time. However, an uninitialized
13148 variable can cause wild jumps and memory corruption in this mode.
13150 The @code{-gnatV@emph{x}} switch allows control over the validity
13151 checking mode as described below.
13152 The @code{x} argument is a string of letters that
13153 indicate validity checks that are performed or not performed in addition
13154 to the default checks required by Ada as described above.
13156 @geindex -gnatVa (gcc)
13161 @item @code{-gnatVa}
13163 @emph{All validity checks.}
13165 All validity checks are turned on.
13166 That is, @code{-gnatVa} is
13167 equivalent to @code{gnatVcdfimorst}.
13170 @geindex -gnatVc (gcc)
13175 @item @code{-gnatVc}
13177 @emph{Validity checks for copies.}
13179 The right hand side of assignments, and the initializing values of
13180 object declarations are validity checked.
13183 @geindex -gnatVd (gcc)
13188 @item @code{-gnatVd}
13190 @emph{Default (RM) validity checks.}
13192 Some validity checks are done by default following normal Ada semantics
13193 (RM 13.9.1 (9-11)).
13194 A check is done in case statements that the expression is within the range
13195 of the subtype. If it is not, Constraint_Error is raised.
13196 For assignments to array components, a check is done that the expression used
13197 as index is within the range. If it is not, Constraint_Error is raised.
13198 Both these validity checks may be turned off using switch @code{-gnatVD}.
13199 They are turned on by default. If @code{-gnatVD} is specified, a subsequent
13200 switch @code{-gnatVd} will leave the checks turned on.
13201 Switch @code{-gnatVD} should be used only if you are sure that all such
13202 expressions have valid values. If you use this switch and invalid values
13203 are present, then the program is erroneous, and wild jumps or memory
13204 overwriting may occur.
13207 @geindex -gnatVe (gcc)
13212 @item @code{-gnatVe}
13214 @emph{Validity checks for elementary components.}
13216 In the absence of this switch, assignments to record or array components are
13217 not validity checked, even if validity checks for assignments generally
13218 (@code{-gnatVc}) are turned on. In Ada, assignment of composite values do not
13219 require valid data, but assignment of individual components does. So for
13220 example, there is a difference between copying the elements of an array with a
13221 slice assignment, compared to assigning element by element in a loop. This
13222 switch allows you to turn off validity checking for components, even when they
13223 are assigned component by component.
13226 @geindex -gnatVf (gcc)
13231 @item @code{-gnatVf}
13233 @emph{Validity checks for floating-point values.}
13235 In the absence of this switch, validity checking occurs only for discrete
13236 values. If @code{-gnatVf} is specified, then validity checking also applies
13237 for floating-point values, and NaNs and infinities are considered invalid,
13238 as well as out of range values for constrained types. Note that this means
13239 that standard IEEE infinity mode is not allowed. The exact contexts
13240 in which floating-point values are checked depends on the setting of other
13241 options. For example, @code{-gnatVif} or @code{-gnatVfi}
13242 (the order does not matter) specifies that floating-point parameters of mode
13243 @code{in} should be validity checked.
13246 @geindex -gnatVi (gcc)
13251 @item @code{-gnatVi}
13253 @emph{Validity checks for `@w{`}in`@w{`} mode parameters.}
13255 Arguments for parameters of mode @code{in} are validity checked in function
13256 and procedure calls at the point of call.
13259 @geindex -gnatVm (gcc)
13264 @item @code{-gnatVm}
13266 @emph{Validity checks for `@w{`}in out`@w{`} mode parameters.}
13268 Arguments for parameters of mode @code{in out} are validity checked in
13269 procedure calls at the point of call. The @code{'m'} here stands for
13270 modify, since this concerns parameters that can be modified by the call.
13271 Note that there is no specific option to test @code{out} parameters,
13272 but any reference within the subprogram will be tested in the usual
13273 manner, and if an invalid value is copied back, any reference to it
13274 will be subject to validity checking.
13277 @geindex -gnatVn (gcc)
13282 @item @code{-gnatVn}
13284 @emph{No validity checks.}
13286 This switch turns off all validity checking, including the default checking
13287 for case statements and left hand side subscripts. Note that the use of
13288 the switch @code{-gnatp} suppresses all run-time checks, including
13289 validity checks, and thus implies @code{-gnatVn}. When this switch
13290 is used, it cancels any other @code{-gnatV} previously issued.
13293 @geindex -gnatVo (gcc)
13298 @item @code{-gnatVo}
13300 @emph{Validity checks for operator and attribute operands.}
13302 Arguments for predefined operators and attributes are validity checked.
13303 This includes all operators in package @code{Standard},
13304 the shift operators defined as intrinsic in package @code{Interfaces}
13305 and operands for attributes such as @code{Pos}. Checks are also made
13306 on individual component values for composite comparisons, and on the
13307 expressions in type conversions and qualified expressions. Checks are
13308 also made on explicit ranges using @code{..} (e.g., slices, loops etc).
13311 @geindex -gnatVp (gcc)
13316 @item @code{-gnatVp}
13318 @emph{Validity checks for parameters.}
13320 This controls the treatment of parameters within a subprogram (as opposed
13321 to @code{-gnatVi} and @code{-gnatVm} which control validity testing
13322 of parameters on a call. If either of these call options is used, then
13323 normally an assumption is made within a subprogram that the input arguments
13324 have been validity checking at the point of call, and do not need checking
13325 again within a subprogram). If @code{-gnatVp} is set, then this assumption
13326 is not made, and parameters are not assumed to be valid, so their validity
13327 will be checked (or rechecked) within the subprogram.
13330 @geindex -gnatVr (gcc)
13335 @item @code{-gnatVr}
13337 @emph{Validity checks for function returns.}
13339 The expression in @code{return} statements in functions is validity
13343 @geindex -gnatVs (gcc)
13348 @item @code{-gnatVs}
13350 @emph{Validity checks for subscripts.}
13352 All subscripts expressions are checked for validity, whether they appear
13353 on the right side or left side (in default mode only left side subscripts
13354 are validity checked).
13357 @geindex -gnatVt (gcc)
13362 @item @code{-gnatVt}
13364 @emph{Validity checks for tests.}
13366 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
13367 statements are checked, as well as guard expressions in entry calls.
13370 The @code{-gnatV} switch may be followed by a string of letters
13371 to turn on a series of validity checking options.
13372 For example, @code{-gnatVcr}
13373 specifies that in addition to the default validity checking, copies and
13374 function return expressions are to be validity checked.
13375 In order to make it easier to specify the desired combination of effects,
13376 the upper case letters @code{CDFIMORST} may
13377 be used to turn off the corresponding lower case option.
13378 Thus @code{-gnatVaM} turns on all validity checking options except for
13379 checking of @code{in out} parameters.
13381 The specification of additional validity checking generates extra code (and
13382 in the case of @code{-gnatVa} the code expansion can be substantial).
13383 However, these additional checks can be very useful in detecting
13384 uninitialized variables, incorrect use of unchecked conversion, and other
13385 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
13386 is useful in conjunction with the extra validity checking, since this
13387 ensures that wherever possible uninitialized variables have invalid values.
13389 See also the pragma @code{Validity_Checks} which allows modification of
13390 the validity checking mode at the program source level, and also allows for
13391 temporary disabling of validity checks.
13393 @node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches
13394 @anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{103}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{fb}
13395 @subsection Style Checking
13398 @geindex Style checking
13400 @geindex -gnaty (gcc)
13402 The @code{-gnatyx} switch causes the compiler to
13403 enforce specified style rules. A limited set of style rules has been used
13404 in writing the GNAT sources themselves. This switch allows user programs
13405 to activate all or some of these checks. If the source program fails a
13406 specified style check, an appropriate message is given, preceded by
13407 the character sequence '(style)'. This message does not prevent
13408 successful compilation (unless the @code{-gnatwe} switch is used).
13410 Note that this is by no means intended to be a general facility for
13411 checking arbitrary coding standards. It is simply an embedding of the
13412 style rules we have chosen for the GNAT sources. If you are starting
13413 a project which does not have established style standards, you may
13414 find it useful to adopt the entire set of GNAT coding standards, or
13415 some subset of them.
13418 The string @code{x} is a sequence of letters or digits
13419 indicating the particular style
13420 checks to be performed. The following checks are defined:
13422 @geindex -gnaty[0-9] (gcc)
13427 @item @code{-gnaty0}
13429 @emph{Specify indentation level.}
13431 If a digit from 1-9 appears
13432 in the string after @code{-gnaty}
13433 then proper indentation is checked, with the digit indicating the
13434 indentation level required. A value of zero turns off this style check.
13435 The general style of required indentation is as specified by
13436 the examples in the Ada Reference Manual. Full line comments must be
13437 aligned with the @code{--} starting on a column that is a multiple of
13438 the alignment level, or they may be aligned the same way as the following
13439 non-blank line (this is useful when full line comments appear in the middle
13440 of a statement, or they may be aligned with the source line on the previous
13444 @geindex -gnatya (gcc)
13449 @item @code{-gnatya}
13451 @emph{Check attribute casing.}
13453 Attribute names, including the case of keywords such as @code{digits}
13454 used as attributes names, must be written in mixed case, that is, the
13455 initial letter and any letter following an underscore must be uppercase.
13456 All other letters must be lowercase.
13459 @geindex -gnatyA (gcc)
13464 @item @code{-gnatyA}
13466 @emph{Use of array index numbers in array attributes.}
13468 When using the array attributes First, Last, Range,
13469 or Length, the index number must be omitted for one-dimensional arrays
13470 and is required for multi-dimensional arrays.
13473 @geindex -gnatyb (gcc)
13478 @item @code{-gnatyb}
13480 @emph{Blanks not allowed at statement end.}
13482 Trailing blanks are not allowed at the end of statements. The purpose of this
13483 rule, together with h (no horizontal tabs), is to enforce a canonical format
13484 for the use of blanks to separate source tokens.
13487 @geindex -gnatyB (gcc)
13492 @item @code{-gnatyB}
13494 @emph{Check Boolean operators.}
13496 The use of AND/OR operators is not permitted except in the cases of modular
13497 operands, array operands, and simple stand-alone boolean variables or
13498 boolean constants. In all other cases @code{and then}/@cite{or else} are
13502 @geindex -gnatyc (gcc)
13507 @item @code{-gnatyc}
13509 @emph{Check comments, double space.}
13511 Comments must meet the following set of rules:
13517 The @code{--} that starts the column must either start in column one,
13518 or else at least one blank must precede this sequence.
13521 Comments that follow other tokens on a line must have at least one blank
13522 following the @code{--} at the start of the comment.
13525 Full line comments must have at least two blanks following the
13526 @code{--} that starts the comment, with the following exceptions.
13529 A line consisting only of the @code{--} characters, possibly preceded
13530 by blanks is permitted.
13533 A comment starting with @code{--x} where @code{x} is a special character
13535 This allows proper processing of the output from specialized tools
13536 such as @code{gnatprep} (where @code{--!} is used) and in earlier versions of the SPARK
13538 language (where @code{--#} is used). For the purposes of this rule, a
13539 special character is defined as being in one of the ASCII ranges
13540 @code{16#21#...16#2F#} or @code{16#3A#...16#3F#}.
13541 Note that this usage is not permitted
13542 in GNAT implementation units (i.e., when @code{-gnatg} is used).
13545 A line consisting entirely of minus signs, possibly preceded by blanks, is
13546 permitted. This allows the construction of box comments where lines of minus
13547 signs are used to form the top and bottom of the box.
13550 A comment that starts and ends with @code{--} is permitted as long as at
13551 least one blank follows the initial @code{--}. Together with the preceding
13552 rule, this allows the construction of box comments, as shown in the following
13556 ---------------------------
13557 -- This is a box comment --
13558 -- with two text lines. --
13559 ---------------------------
13564 @geindex -gnatyC (gcc)
13569 @item @code{-gnatyC}
13571 @emph{Check comments, single space.}
13573 This is identical to @code{c} except that only one space
13574 is required following the @code{--} of a comment instead of two.
13577 @geindex -gnatyd (gcc)
13582 @item @code{-gnatyd}
13584 @emph{Check no DOS line terminators present.}
13586 All lines must be terminated by a single ASCII.LF
13587 character (in particular the DOS line terminator sequence CR/LF is not
13591 @geindex -gnatyD (gcc)
13596 @item @code{-gnatyD}
13598 @emph{Check declared identifiers in mixed case.}
13600 Declared identifiers must be in mixed case, as in
13601 This_Is_An_Identifier. Use -gnatyr in addition to ensure
13602 that references match declarations.
13605 @geindex -gnatye (gcc)
13610 @item @code{-gnatye}
13612 @emph{Check end/exit labels.}
13614 Optional labels on @code{end} statements ending subprograms and on
13615 @code{exit} statements exiting named loops, are required to be present.
13618 @geindex -gnatyf (gcc)
13623 @item @code{-gnatyf}
13625 @emph{No form feeds or vertical tabs.}
13627 Neither form feeds nor vertical tab characters are permitted
13628 in the source text.
13631 @geindex -gnatyg (gcc)
13636 @item @code{-gnatyg}
13638 @emph{GNAT style mode.}
13640 The set of style check switches is set to match that used by the GNAT sources.
13641 This may be useful when developing code that is eventually intended to be
13642 incorporated into GNAT. Currently this is equivalent to @code{-gnatyydISux})
13643 but additional style switches may be added to this set in the future without
13647 @geindex -gnatyh (gcc)
13652 @item @code{-gnatyh}
13654 @emph{No horizontal tabs.}
13656 Horizontal tab characters are not permitted in the source text.
13657 Together with the b (no blanks at end of line) check, this
13658 enforces a canonical form for the use of blanks to separate
13662 @geindex -gnatyi (gcc)
13667 @item @code{-gnatyi}
13669 @emph{Check if-then layout.}
13671 The keyword @code{then} must appear either on the same
13672 line as corresponding @code{if}, or on a line on its own, lined
13673 up under the @code{if}.
13676 @geindex -gnatyI (gcc)
13681 @item @code{-gnatyI}
13683 @emph{check mode IN keywords.}
13685 Mode @code{in} (the default mode) is not
13686 allowed to be given explicitly. @code{in out} is fine,
13687 but not @code{in} on its own.
13690 @geindex -gnatyk (gcc)
13695 @item @code{-gnatyk}
13697 @emph{Check keyword casing.}
13699 All keywords must be in lower case (with the exception of keywords
13700 such as @code{digits} used as attribute names to which this check
13704 @geindex -gnatyl (gcc)
13709 @item @code{-gnatyl}
13711 @emph{Check layout.}
13713 Layout of statement and declaration constructs must follow the
13714 recommendations in the Ada Reference Manual, as indicated by the
13715 form of the syntax rules. For example an @code{else} keyword must
13716 be lined up with the corresponding @code{if} keyword.
13718 There are two respects in which the style rule enforced by this check
13719 option are more liberal than those in the Ada Reference Manual. First
13720 in the case of record declarations, it is permissible to put the
13721 @code{record} keyword on the same line as the @code{type} keyword, and
13722 then the @code{end} in @code{end record} must line up under @code{type}.
13723 This is also permitted when the type declaration is split on two lines.
13724 For example, any of the following three layouts is acceptable:
13745 Second, in the case of a block statement, a permitted alternative
13746 is to put the block label on the same line as the @code{declare} or
13747 @code{begin} keyword, and then line the @code{end} keyword up under
13748 the block label. For example both the following are permitted:
13765 The same alternative format is allowed for loops. For example, both of
13766 the following are permitted:
13769 Clear : while J < 10 loop
13780 @geindex -gnatyLnnn (gcc)
13785 @item @code{-gnatyL}
13787 @emph{Set maximum nesting level.}
13789 The maximum level of nesting of constructs (including subprograms, loops,
13790 blocks, packages, and conditionals) may not exceed the given value
13791 @emph{nnn}. A value of zero disconnects this style check.
13794 @geindex -gnatym (gcc)
13799 @item @code{-gnatym}
13801 @emph{Check maximum line length.}
13803 The length of source lines must not exceed 79 characters, including
13804 any trailing blanks. The value of 79 allows convenient display on an
13805 80 character wide device or window, allowing for possible special
13806 treatment of 80 character lines. Note that this count is of
13807 characters in the source text. This means that a tab character counts
13808 as one character in this count and a wide character sequence counts as
13809 a single character (however many bytes are needed in the encoding).
13812 @geindex -gnatyMnnn (gcc)
13817 @item @code{-gnatyM}
13819 @emph{Set maximum line length.}
13821 The length of lines must not exceed the
13822 given value @emph{nnn}. The maximum value that can be specified is 32767.
13823 If neither style option for setting the line length is used, then the
13824 default is 255. This also controls the maximum length of lexical elements,
13825 where the only restriction is that they must fit on a single line.
13828 @geindex -gnatyn (gcc)
13833 @item @code{-gnatyn}
13835 @emph{Check casing of entities in Standard.}
13837 Any identifier from Standard must be cased
13838 to match the presentation in the Ada Reference Manual (for example,
13839 @code{Integer} and @code{ASCII.NUL}).
13842 @geindex -gnatyN (gcc)
13847 @item @code{-gnatyN}
13849 @emph{Turn off all style checks.}
13851 All style check options are turned off.
13854 @geindex -gnatyo (gcc)
13859 @item @code{-gnatyo}
13861 @emph{Check order of subprogram bodies.}
13863 All subprogram bodies in a given scope
13864 (e.g., a package body) must be in alphabetical order. The ordering
13865 rule uses normal Ada rules for comparing strings, ignoring casing
13866 of letters, except that if there is a trailing numeric suffix, then
13867 the value of this suffix is used in the ordering (e.g., Junk2 comes
13871 @geindex -gnatyO (gcc)
13876 @item @code{-gnatyO}
13878 @emph{Check that overriding subprograms are explicitly marked as such.}
13880 This applies to all subprograms of a derived type that override a primitive
13881 operation of the type, for both tagged and untagged types. In particular,
13882 the declaration of a primitive operation of a type extension that overrides
13883 an inherited operation must carry an overriding indicator. Another case is
13884 the declaration of a function that overrides a predefined operator (such
13885 as an equality operator).
13888 @geindex -gnatyp (gcc)
13893 @item @code{-gnatyp}
13895 @emph{Check pragma casing.}
13897 Pragma names must be written in mixed case, that is, the
13898 initial letter and any letter following an underscore must be uppercase.
13899 All other letters must be lowercase. An exception is that SPARK_Mode is
13900 allowed as an alternative for Spark_Mode.
13903 @geindex -gnatyr (gcc)
13908 @item @code{-gnatyr}
13910 @emph{Check references.}
13912 All identifier references must be cased in the same way as the
13913 corresponding declaration. No specific casing style is imposed on
13914 identifiers. The only requirement is for consistency of references
13918 @geindex -gnatys (gcc)
13923 @item @code{-gnatys}
13925 @emph{Check separate specs.}
13927 Separate declarations ('specs') are required for subprograms (a
13928 body is not allowed to serve as its own declaration). The only
13929 exception is that parameterless library level procedures are
13930 not required to have a separate declaration. This exception covers
13931 the most frequent form of main program procedures.
13934 @geindex -gnatyS (gcc)
13939 @item @code{-gnatyS}
13941 @emph{Check no statements after then/else.}
13943 No statements are allowed
13944 on the same line as a @code{then} or @code{else} keyword following the
13945 keyword in an @code{if} statement. @code{or else} and @code{and then} are not
13946 affected, and a special exception allows a pragma to appear after @code{else}.
13949 @geindex -gnatyt (gcc)
13954 @item @code{-gnatyt}
13956 @emph{Check token spacing.}
13958 The following token spacing rules are enforced:
13964 The keywords @code{abs} and @code{not} must be followed by a space.
13967 The token @code{=>} must be surrounded by spaces.
13970 The token @code{<>} must be preceded by a space or a left parenthesis.
13973 Binary operators other than @code{**} must be surrounded by spaces.
13974 There is no restriction on the layout of the @code{**} binary operator.
13977 Colon must be surrounded by spaces.
13980 Colon-equal (assignment, initialization) must be surrounded by spaces.
13983 Comma must be the first non-blank character on the line, or be
13984 immediately preceded by a non-blank character, and must be followed
13988 If the token preceding a left parenthesis ends with a letter or digit, then
13989 a space must separate the two tokens.
13992 If the token following a right parenthesis starts with a letter or digit, then
13993 a space must separate the two tokens.
13996 A right parenthesis must either be the first non-blank character on
13997 a line, or it must be preceded by a non-blank character.
14000 A semicolon must not be preceded by a space, and must not be followed by
14001 a non-blank character.
14004 A unary plus or minus may not be followed by a space.
14007 A vertical bar must be surrounded by spaces.
14010 Exactly one blank (and no other white space) must appear between
14011 a @code{not} token and a following @code{in} token.
14014 @geindex -gnatyu (gcc)
14019 @item @code{-gnatyu}
14021 @emph{Check unnecessary blank lines.}
14023 Unnecessary blank lines are not allowed. A blank line is considered
14024 unnecessary if it appears at the end of the file, or if more than
14025 one blank line occurs in sequence.
14028 @geindex -gnatyx (gcc)
14033 @item @code{-gnatyx}
14035 @emph{Check extra parentheses.}
14037 Unnecessary extra level of parentheses (C-style) are not allowed
14038 around conditions in @code{if} statements, @code{while} statements and
14039 @code{exit} statements.
14042 @geindex -gnatyy (gcc)
14047 @item @code{-gnatyy}
14049 @emph{Set all standard style check options.}
14051 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
14052 options enabled with the exception of @code{-gnatyB}, @code{-gnatyd},
14053 @code{-gnatyI}, @code{-gnatyLnnn}, @code{-gnatyo}, @code{-gnatyO},
14054 @code{-gnatyS}, @code{-gnatyu}, and @code{-gnatyx}.
14057 @geindex -gnaty- (gcc)
14062 @item @code{-gnaty-}
14064 @emph{Remove style check options.}
14066 This causes any subsequent options in the string to act as canceling the
14067 corresponding style check option. To cancel maximum nesting level control,
14068 use the @code{L} parameter without any integer value after that, because any
14069 digit following @emph{-} in the parameter string of the @code{-gnaty}
14070 option will be treated as canceling the indentation check. The same is true
14071 for the @code{M} parameter. @code{y} and @code{N} parameters are not
14072 allowed after @emph{-}.
14075 @geindex -gnaty+ (gcc)
14080 @item @code{-gnaty+}
14082 @emph{Enable style check options.}
14084 This causes any subsequent options in the string to enable the corresponding
14085 style check option. That is, it cancels the effect of a previous -,
14089 @c end of switch description (leave this comment to ease automatic parsing for
14093 In the above rules, appearing in column one is always permitted, that is,
14094 counts as meeting either a requirement for a required preceding space,
14095 or as meeting a requirement for no preceding space.
14097 Appearing at the end of a line is also always permitted, that is, counts
14098 as meeting either a requirement for a following space, or as meeting
14099 a requirement for no following space.
14101 If any of these style rules is violated, a message is generated giving
14102 details on the violation. The initial characters of such messages are
14103 always '@cite{(style)}'. Note that these messages are treated as warning
14104 messages, so they normally do not prevent the generation of an object
14105 file. The @code{-gnatwe} switch can be used to treat warning messages,
14106 including style messages, as fatal errors.
14108 The switch @code{-gnaty} on its own (that is not
14109 followed by any letters or digits) is equivalent
14110 to the use of @code{-gnatyy} as described above, that is all
14111 built-in standard style check options are enabled.
14113 The switch @code{-gnatyN} clears any previously set style checks.
14115 @node Run-Time Checks,Using gcc for Syntax Checking,Style Checking,Compiler Switches
14116 @anchor{gnat_ugn/building_executable_programs_with_gnat run-time-checks}@anchor{f9}@anchor{gnat_ugn/building_executable_programs_with_gnat id19}@anchor{104}
14117 @subsection Run-Time Checks
14120 @geindex Division by zero
14122 @geindex Access before elaboration
14125 @geindex division by zero
14128 @geindex access before elaboration
14131 @geindex stack overflow checking
14133 By default, the following checks are suppressed: stack overflow
14134 checks, and checks for access before elaboration on subprogram
14135 calls. All other checks, including overflow checks, range checks and
14136 array bounds checks, are turned on by default. The following @code{gcc}
14137 switches refine this default behavior.
14139 @geindex -gnatp (gcc)
14144 @item @code{-gnatp}
14146 @geindex Suppressing checks
14149 @geindex suppressing
14151 This switch causes the unit to be compiled
14152 as though @code{pragma Suppress (All_checks)}
14153 had been present in the source. Validity checks are also eliminated (in
14154 other words @code{-gnatp} also implies @code{-gnatVn}.
14155 Use this switch to improve the performance
14156 of the code at the expense of safety in the presence of invalid data or
14159 Note that when checks are suppressed, the compiler is allowed, but not
14160 required, to omit the checking code. If the run-time cost of the
14161 checking code is zero or near-zero, the compiler will generate it even
14162 if checks are suppressed. In particular, if the compiler can prove
14163 that a certain check will necessarily fail, it will generate code to
14164 do an unconditional 'raise', even if checks are suppressed. The
14165 compiler warns in this case. Another case in which checks may not be
14166 eliminated is when they are embedded in certain run-time routines such
14167 as math library routines.
14169 Of course, run-time checks are omitted whenever the compiler can prove
14170 that they will not fail, whether or not checks are suppressed.
14172 Note that if you suppress a check that would have failed, program
14173 execution is erroneous, which means the behavior is totally
14174 unpredictable. The program might crash, or print wrong answers, or
14175 do anything else. It might even do exactly what you wanted it to do
14176 (and then it might start failing mysteriously next week or next
14177 year). The compiler will generate code based on the assumption that
14178 the condition being checked is true, which can result in erroneous
14179 execution if that assumption is wrong.
14181 The checks subject to suppression include all the checks defined by the Ada
14182 standard, the additional implementation defined checks @code{Alignment_Check},
14183 @code{Duplicated_Tag_Check}, @code{Predicate_Check}, @code{Container_Checks}, @code{Tampering_Check},
14184 and @code{Validity_Check}, as well as any checks introduced using @code{pragma Check_Name}.
14185 Note that @code{Atomic_Synchronization} is not automatically suppressed by use of this option.
14187 If the code depends on certain checks being active, you can use
14188 pragma @code{Unsuppress} either as a configuration pragma or as
14189 a local pragma to make sure that a specified check is performed
14190 even if @code{gnatp} is specified.
14192 The @code{-gnatp} switch has no effect if a subsequent
14193 @code{-gnat-p} switch appears.
14196 @geindex -gnat-p (gcc)
14198 @geindex Suppressing checks
14201 @geindex suppressing
14208 @item @code{-gnat-p}
14210 This switch cancels the effect of a previous @code{gnatp} switch.
14213 @geindex -gnato?? (gcc)
14215 @geindex Overflow checks
14217 @geindex Overflow mode
14225 @item @code{-gnato??}
14227 This switch controls the mode used for computing intermediate
14228 arithmetic integer operations, and also enables overflow checking.
14229 For a full description of overflow mode and checking control, see
14230 the 'Overflow Check Handling in GNAT' appendix in this
14233 Overflow checks are always enabled by this switch. The argument
14234 controls the mode, using the codes
14239 @item @emph{1 = STRICT}
14241 In STRICT mode, intermediate operations are always done using the
14242 base type, and overflow checking ensures that the result is within
14243 the base type range.
14245 @item @emph{2 = MINIMIZED}
14247 In MINIMIZED mode, overflows in intermediate operations are avoided
14248 where possible by using a larger integer type for the computation
14249 (typically @code{Long_Long_Integer}). Overflow checking ensures that
14250 the result fits in this larger integer type.
14252 @item @emph{3 = ELIMINATED}
14254 In ELIMINATED mode, overflows in intermediate operations are avoided
14255 by using multi-precision arithmetic. In this case, overflow checking
14256 has no effect on intermediate operations (since overflow is impossible).
14259 If two digits are present after @code{-gnato} then the first digit
14260 sets the mode for expressions outside assertions, and the second digit
14261 sets the mode for expressions within assertions. Here assertions is used
14262 in the technical sense (which includes for example precondition and
14263 postcondition expressions).
14265 If one digit is present, the corresponding mode is applicable to both
14266 expressions within and outside assertion expressions.
14268 If no digits are present, the default is to enable overflow checks
14269 and set STRICT mode for both kinds of expressions. This is compatible
14270 with the use of @code{-gnato} in previous versions of GNAT.
14272 @geindex Machine_Overflows
14274 Note that the @code{-gnato??} switch does not affect the code generated
14275 for any floating-point operations; it applies only to integer semantics.
14276 For floating-point, GNAT has the @code{Machine_Overflows}
14277 attribute set to @code{False} and the normal mode of operation is to
14278 generate IEEE NaN and infinite values on overflow or invalid operations
14279 (such as dividing 0.0 by 0.0).
14281 The reason that we distinguish overflow checking from other kinds of
14282 range constraint checking is that a failure of an overflow check, unlike
14283 for example the failure of a range check, can result in an incorrect
14284 value, but cannot cause random memory destruction (like an out of range
14285 subscript), or a wild jump (from an out of range case value). Overflow
14286 checking is also quite expensive in time and space, since in general it
14287 requires the use of double length arithmetic.
14289 Note again that the default is @code{-gnato11} (equivalent to @code{-gnato1}),
14290 so overflow checking is performed in STRICT mode by default.
14293 @geindex -gnatE (gcc)
14295 @geindex Elaboration checks
14298 @geindex elaboration
14303 @item @code{-gnatE}
14305 Enables dynamic checks for access-before-elaboration
14306 on subprogram calls and generic instantiations.
14307 Note that @code{-gnatE} is not necessary for safety, because in the
14308 default mode, GNAT ensures statically that the checks would not fail.
14309 For full details of the effect and use of this switch,
14310 @ref{1c,,Compiling with gcc}.
14313 @geindex -fstack-check (gcc)
14315 @geindex Stack Overflow Checking
14318 @geindex stack overflow checking
14323 @item @code{-fstack-check}
14325 Activates stack overflow checking. For full details of the effect and use of
14326 this switch see @ref{f4,,Stack Overflow Checking}.
14329 @geindex Unsuppress
14331 The setting of these switches only controls the default setting of the
14332 checks. You may modify them using either @code{Suppress} (to remove
14333 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
14334 the program source.
14336 @node Using gcc for Syntax Checking,Using gcc for Semantic Checking,Run-Time Checks,Compiler Switches
14337 @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}
14338 @subsection Using @code{gcc} for Syntax Checking
14341 @geindex -gnats (gcc)
14346 @item @code{-gnats}
14348 The @code{s} stands for 'syntax'.
14350 Run GNAT in syntax checking only mode. For
14351 example, the command
14354 $ gcc -c -gnats x.adb
14357 compiles file @code{x.adb} in syntax-check-only mode. You can check a
14358 series of files in a single command
14359 , and can use wildcards to specify such a group of files.
14360 Note that you must specify the @code{-c} (compile
14361 only) flag in addition to the @code{-gnats} flag.
14363 You may use other switches in conjunction with @code{-gnats}. In
14364 particular, @code{-gnatl} and @code{-gnatv} are useful to control the
14365 format of any generated error messages.
14367 When the source file is empty or contains only empty lines and/or comments,
14368 the output is a warning:
14371 $ gcc -c -gnats -x ada toto.txt
14372 toto.txt:1:01: warning: empty file, contains no compilation units
14376 Otherwise, the output is simply the error messages, if any. No object file or
14377 ALI file is generated by a syntax-only compilation. Also, no units other
14378 than the one specified are accessed. For example, if a unit @code{X}
14379 @emph{with}s a unit @code{Y}, compiling unit @code{X} in syntax
14380 check only mode does not access the source file containing unit
14383 @geindex Multiple units
14384 @geindex syntax checking
14386 Normally, GNAT allows only a single unit in a source file. However, this
14387 restriction does not apply in syntax-check-only mode, and it is possible
14388 to check a file containing multiple compilation units concatenated
14389 together. This is primarily used by the @code{gnatchop} utility
14390 (@ref{36,,Renaming Files with gnatchop}).
14393 @node Using gcc for Semantic Checking,Compiling Different Versions of Ada,Using gcc for Syntax Checking,Compiler Switches
14394 @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}
14395 @subsection Using @code{gcc} for Semantic Checking
14398 @geindex -gnatc (gcc)
14403 @item @code{-gnatc}
14405 The @code{c} stands for 'check'.
14406 Causes the compiler to operate in semantic check mode,
14407 with full checking for all illegalities specified in the
14408 Ada Reference Manual, but without generation of any object code
14409 (no object file is generated).
14411 Because dependent files must be accessed, you must follow the GNAT
14412 semantic restrictions on file structuring to operate in this mode:
14418 The needed source files must be accessible
14419 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
14422 Each file must contain only one compilation unit.
14425 The file name and unit name must match (@ref{52,,File Naming Rules}).
14428 The output consists of error messages as appropriate. No object file is
14429 generated. An @code{ALI} file is generated for use in the context of
14430 cross-reference tools, but this file is marked as not being suitable
14431 for binding (since no object file is generated).
14432 The checking corresponds exactly to the notion of
14433 legality in the Ada Reference Manual.
14435 Any unit can be compiled in semantics-checking-only mode, including
14436 units that would not normally be compiled (subunits,
14437 and specifications where a separate body is present).
14440 @node Compiling Different Versions of Ada,Character Set Control,Using gcc for Semantic Checking,Compiler Switches
14441 @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}
14442 @subsection Compiling Different Versions of Ada
14445 The switches described in this section allow you to explicitly specify
14446 the version of the Ada language that your programs are written in.
14447 The default mode is Ada 2012,
14448 but you can also specify Ada 95, Ada 2005 mode, or
14449 indicate Ada 83 compatibility mode.
14451 @geindex Compatibility with Ada 83
14453 @geindex -gnat83 (gcc)
14456 @geindex Ada 83 tests
14458 @geindex Ada 83 mode
14463 @item @code{-gnat83} (Ada 83 Compatibility Mode)
14465 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
14466 specifies that the program is to be compiled in Ada 83 mode. With
14467 @code{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
14468 semantics where this can be done easily.
14469 It is not possible to guarantee this switch does a perfect
14470 job; some subtle tests, such as are
14471 found in earlier ACVC tests (and that have been removed from the ACATS suite
14472 for Ada 95), might not compile correctly.
14473 Nevertheless, this switch may be useful in some circumstances, for example
14474 where, due to contractual reasons, existing code needs to be maintained
14475 using only Ada 83 features.
14477 With few exceptions (most notably the need to use @code{<>} on
14479 @geindex Generic formal parameters
14480 generic formal parameters,
14481 the use of the new Ada 95 / Ada 2005
14482 reserved words, and the use of packages
14483 with optional bodies), it is not necessary to specify the
14484 @code{-gnat83} switch when compiling Ada 83 programs, because, with rare
14485 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
14486 a correct Ada 83 program is usually also a correct program
14487 in these later versions of the language standard. For further information
14488 please refer to the @emph{Compatibility and Porting Guide} chapter in the
14489 @cite{GNAT Reference Manual}.
14492 @geindex -gnat95 (gcc)
14494 @geindex Ada 95 mode
14499 @item @code{-gnat95} (Ada 95 mode)
14501 This switch directs the compiler to implement the Ada 95 version of the
14503 Since Ada 95 is almost completely upwards
14504 compatible with Ada 83, Ada 83 programs may generally be compiled using
14505 this switch (see the description of the @code{-gnat83} switch for further
14506 information about Ada 83 mode).
14507 If an Ada 2005 program is compiled in Ada 95 mode,
14508 uses of the new Ada 2005 features will cause error
14509 messages or warnings.
14511 This switch also can be used to cancel the effect of a previous
14512 @code{-gnat83}, @code{-gnat05/2005}, or @code{-gnat12/2012}
14513 switch earlier in the command line.
14516 @geindex -gnat05 (gcc)
14518 @geindex -gnat2005 (gcc)
14520 @geindex Ada 2005 mode
14525 @item @code{-gnat05} or @code{-gnat2005} (Ada 2005 mode)
14527 This switch directs the compiler to implement the Ada 2005 version of the
14528 language, as documented in the official Ada standards document.
14529 Since Ada 2005 is almost completely upwards
14530 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
14531 may generally be compiled using this switch (see the description of the
14532 @code{-gnat83} and @code{-gnat95} switches for further
14536 @geindex -gnat12 (gcc)
14538 @geindex -gnat2012 (gcc)
14540 @geindex Ada 2012 mode
14545 @item @code{-gnat12} or @code{-gnat2012} (Ada 2012 mode)
14547 This switch directs the compiler to implement the Ada 2012 version of the
14548 language (also the default).
14549 Since Ada 2012 is almost completely upwards
14550 compatible with Ada 2005 (and thus also with Ada 83, and Ada 95),
14551 Ada 83 and Ada 95 programs
14552 may generally be compiled using this switch (see the description of the
14553 @code{-gnat83}, @code{-gnat95}, and @code{-gnat05/2005} switches
14554 for further information).
14557 @geindex -gnatX (gcc)
14559 @geindex Ada language extensions
14561 @geindex GNAT extensions
14566 @item @code{-gnatX} (Enable GNAT Extensions)
14568 This switch directs the compiler to implement the latest version of the
14569 language (currently Ada 2012) and also to enable certain GNAT implementation
14570 extensions that are not part of any Ada standard. For a full list of these
14571 extensions, see the GNAT reference manual.
14574 @node Character Set Control,File Naming Control,Compiling Different Versions of Ada,Compiler Switches
14575 @anchor{gnat_ugn/building_executable_programs_with_gnat id23}@anchor{10a}@anchor{gnat_ugn/building_executable_programs_with_gnat character-set-control}@anchor{48}
14576 @subsection Character Set Control
14579 @geindex -gnati (gcc)
14584 @item @code{-gnati@emph{c}}
14586 Normally GNAT recognizes the Latin-1 character set in source program
14587 identifiers, as described in the Ada Reference Manual.
14589 GNAT to recognize alternate character sets in identifiers. @code{c} is a
14590 single character indicating the character set, as follows:
14593 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14600 ISO 8859-1 (Latin-1) identifiers
14608 ISO 8859-2 (Latin-2) letters allowed in identifiers
14616 ISO 8859-3 (Latin-3) letters allowed in identifiers
14624 ISO 8859-4 (Latin-4) letters allowed in identifiers
14632 ISO 8859-5 (Cyrillic) letters allowed in identifiers
14640 ISO 8859-15 (Latin-9) letters allowed in identifiers
14648 IBM PC letters (code page 437) allowed in identifiers
14656 IBM PC letters (code page 850) allowed in identifiers
14664 Full upper-half codes allowed in identifiers
14672 No upper-half codes allowed in identifiers
14680 Wide-character codes (that is, codes greater than 255)
14681 allowed in identifiers
14686 See @ref{3e,,Foreign Language Representation} for full details on the
14687 implementation of these character sets.
14690 @geindex -gnatW (gcc)
14695 @item @code{-gnatW@emph{e}}
14697 Specify the method of encoding for wide characters.
14698 @code{e} is one of the following:
14701 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14708 Hex encoding (brackets coding also recognized)
14716 Upper half encoding (brackets encoding also recognized)
14724 Shift/JIS encoding (brackets encoding also recognized)
14732 EUC encoding (brackets encoding also recognized)
14740 UTF-8 encoding (brackets encoding also recognized)
14748 Brackets encoding only (default value)
14753 For full details on these encoding
14754 methods see @ref{4e,,Wide_Character Encodings}.
14755 Note that brackets coding is always accepted, even if one of the other
14756 options is specified, so for example @code{-gnatW8} specifies that both
14757 brackets and UTF-8 encodings will be recognized. The units that are
14758 with'ed directly or indirectly will be scanned using the specified
14759 representation scheme, and so if one of the non-brackets scheme is
14760 used, it must be used consistently throughout the program. However,
14761 since brackets encoding is always recognized, it may be conveniently
14762 used in standard libraries, allowing these libraries to be used with
14763 any of the available coding schemes.
14765 Note that brackets encoding only applies to program text. Within comments,
14766 brackets are considered to be normal graphic characters, and bracket sequences
14767 are never recognized as wide characters.
14769 If no @code{-gnatW?} parameter is present, then the default
14770 representation is normally Brackets encoding only. However, if the
14771 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
14772 byte order mark or BOM for UTF-8), then these three characters are
14773 skipped and the default representation for the file is set to UTF-8.
14775 Note that the wide character representation that is specified (explicitly
14776 or by default) for the main program also acts as the default encoding used
14777 for Wide_Text_IO files if not specifically overridden by a WCEM form
14781 When no @code{-gnatW?} is specified, then characters (other than wide
14782 characters represented using brackets notation) are treated as 8-bit
14783 Latin-1 codes. The codes recognized are the Latin-1 graphic characters,
14784 and ASCII format effectors (CR, LF, HT, VT). Other lower half control
14785 characters in the range 16#00#..16#1F# are not accepted in program text
14786 or in comments. Upper half control characters (16#80#..16#9F#) are rejected
14787 in program text, but allowed and ignored in comments. Note in particular
14788 that the Next Line (NEL) character whose encoding is 16#85# is not recognized
14789 as an end of line in this default mode. If your source program contains
14790 instances of the NEL character used as a line terminator,
14791 you must use UTF-8 encoding for the whole
14792 source program. In default mode, all lines must be ended by a standard
14793 end of line sequence (CR, CR/LF, or LF).
14795 Note that the convention of simply accepting all upper half characters in
14796 comments means that programs that use standard ASCII for program text, but
14797 UTF-8 encoding for comments are accepted in default mode, providing that the
14798 comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator.
14799 This is a common mode for many programs with foreign language comments.
14801 @node File Naming Control,Subprogram Inlining Control,Character Set Control,Compiler Switches
14802 @anchor{gnat_ugn/building_executable_programs_with_gnat file-naming-control}@anchor{10b}@anchor{gnat_ugn/building_executable_programs_with_gnat id24}@anchor{10c}
14803 @subsection File Naming Control
14806 @geindex -gnatk (gcc)
14811 @item @code{-gnatk@emph{n}}
14813 Activates file name 'krunching'. @code{n}, a decimal integer in the range
14814 1-999, indicates the maximum allowable length of a file name (not
14815 including the @code{.ads} or @code{.adb} extension). The default is not
14816 to enable file name krunching.
14818 For the source file naming rules, @ref{52,,File Naming Rules}.
14821 @node Subprogram Inlining Control,Auxiliary Output Control,File Naming Control,Compiler Switches
14822 @anchor{gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control}@anchor{10d}@anchor{gnat_ugn/building_executable_programs_with_gnat id25}@anchor{10e}
14823 @subsection Subprogram Inlining Control
14826 @geindex -gnatn (gcc)
14831 @item @code{-gnatn[12]}
14833 The @code{n} here is intended to suggest the first syllable of the word 'inline'.
14834 GNAT recognizes and processes @code{Inline} pragmas. However, for inlining to
14835 actually occur, optimization must be enabled and, by default, inlining of
14836 subprograms across units is not performed. If you want to additionally
14837 enable inlining of subprograms specified by pragma @code{Inline} across units,
14838 you must also specify this switch.
14840 In the absence of this switch, GNAT does not attempt inlining across units
14841 and does not access the bodies of subprograms for which @code{pragma Inline} is
14842 specified if they are not in the current unit.
14844 You can optionally specify the inlining level: 1 for moderate inlining across
14845 units, which is a good compromise between compilation times and performances
14846 at run time, or 2 for full inlining across units, which may bring about
14847 longer compilation times. If no inlining level is specified, the compiler will
14848 pick it based on the optimization level: 1 for @code{-O1}, @code{-O2} or
14849 @code{-Os} and 2 for @code{-O3}.
14851 If you specify this switch the compiler will access these bodies,
14852 creating an extra source dependency for the resulting object file, and
14853 where possible, the call will be inlined.
14854 For further details on when inlining is possible
14855 see @ref{10f,,Inlining of Subprograms}.
14858 @geindex -gnatN (gcc)
14863 @item @code{-gnatN}
14865 This switch activates front-end inlining which also
14866 generates additional dependencies.
14868 When using a gcc-based back end (in practice this means using any version
14869 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
14870 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
14871 Historically front end inlining was more extensive than the gcc back end
14872 inlining, but that is no longer the case.
14875 @node Auxiliary Output Control,Debugging Control,Subprogram Inlining Control,Compiler Switches
14876 @anchor{gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control}@anchor{110}@anchor{gnat_ugn/building_executable_programs_with_gnat id26}@anchor{111}
14877 @subsection Auxiliary Output Control
14880 @geindex -gnatu (gcc)
14885 @item @code{-gnatu}
14887 Print a list of units required by this compilation on @code{stdout}.
14888 The listing includes all units on which the unit being compiled depends
14889 either directly or indirectly.
14892 @geindex -pass-exit-codes (gcc)
14897 @item @code{-pass-exit-codes}
14899 If this switch is not used, the exit code returned by @code{gcc} when
14900 compiling multiple files indicates whether all source files have
14901 been successfully used to generate object files or not.
14903 When @code{-pass-exit-codes} is used, @code{gcc} exits with an extended
14904 exit status and allows an integrated development environment to better
14905 react to a compilation failure. Those exit status are:
14908 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14915 There was an error in at least one source file.
14923 At least one source file did not generate an object file.
14931 The compiler died unexpectedly (internal error for example).
14939 An object file has been generated for every source file.
14945 @node Debugging Control,Exception Handling Control,Auxiliary Output Control,Compiler Switches
14946 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-control}@anchor{112}@anchor{gnat_ugn/building_executable_programs_with_gnat id27}@anchor{113}
14947 @subsection Debugging Control
14952 @geindex Debugging options
14955 @geindex -gnatd (gcc)
14960 @item @code{-gnatd@emph{x}}
14962 Activate internal debugging switches. @code{x} is a letter or digit, or
14963 string of letters or digits, which specifies the type of debugging
14964 outputs desired. Normally these are used only for internal development
14965 or system debugging purposes. You can find full documentation for these
14966 switches in the body of the @code{Debug} unit in the compiler source
14967 file @code{debug.adb}.
14970 @geindex -gnatG (gcc)
14975 @item @code{-gnatG[=@emph{nn}]}
14977 This switch causes the compiler to generate auxiliary output containing
14978 a pseudo-source listing of the generated expanded code. Like most Ada
14979 compilers, GNAT works by first transforming the high level Ada code into
14980 lower level constructs. For example, tasking operations are transformed
14981 into calls to the tasking run-time routines. A unique capability of GNAT
14982 is to list this expanded code in a form very close to normal Ada source.
14983 This is very useful in understanding the implications of various Ada
14984 usage on the efficiency of the generated code. There are many cases in
14985 Ada (e.g., the use of controlled types), where simple Ada statements can
14986 generate a lot of run-time code. By using @code{-gnatG} you can identify
14987 these cases, and consider whether it may be desirable to modify the coding
14988 approach to improve efficiency.
14990 The optional parameter @code{nn} if present after -gnatG specifies an
14991 alternative maximum line length that overrides the normal default of 72.
14992 This value is in the range 40-999999, values less than 40 being silently
14993 reset to 40. The equal sign is optional.
14995 The format of the output is very similar to standard Ada source, and is
14996 easily understood by an Ada programmer. The following special syntactic
14997 additions correspond to low level features used in the generated code that
14998 do not have any exact analogies in pure Ada source form. The following
14999 is a partial list of these special constructions. See the spec
15000 of package @code{Sprint} in file @code{sprint.ads} for a full list.
15002 @geindex -gnatL (gcc)
15004 If the switch @code{-gnatL} is used in conjunction with
15005 @code{-gnatG}, then the original source lines are interspersed
15006 in the expanded source (as comment lines with the original line number).
15011 @item @code{new @emph{xxx} [storage_pool = @emph{yyy}]}
15013 Shows the storage pool being used for an allocator.
15015 @item @code{at end @emph{procedure-name};}
15017 Shows the finalization (cleanup) procedure for a scope.
15019 @item @code{(if @emph{expr} then @emph{expr} else @emph{expr})}
15021 Conditional expression equivalent to the @code{x?y:z} construction in C.
15023 @item @code{@emph{target}^(@emph{source})}
15025 A conversion with floating-point truncation instead of rounding.
15027 @item @code{@emph{target}?(@emph{source})}
15029 A conversion that bypasses normal Ada semantic checking. In particular
15030 enumeration types and fixed-point types are treated simply as integers.
15032 @item @code{@emph{target}?^(@emph{source})}
15034 Combines the above two cases.
15037 @code{@emph{x} #/ @emph{y}}
15039 @code{@emph{x} #mod @emph{y}}
15041 @code{@emph{x} # @emph{y}}
15046 @item @code{@emph{x} #rem @emph{y}}
15048 A division or multiplication of fixed-point values which are treated as
15049 integers without any kind of scaling.
15051 @item @code{free @emph{expr} [storage_pool = @emph{xxx}]}
15053 Shows the storage pool associated with a @code{free} statement.
15055 @item @code{[subtype or type declaration]}
15057 Used to list an equivalent declaration for an internally generated
15058 type that is referenced elsewhere in the listing.
15060 @item @code{freeze @emph{type-name} [@emph{actions}]}
15062 Shows the point at which @code{type-name} is frozen, with possible
15063 associated actions to be performed at the freeze point.
15065 @item @code{reference @emph{itype}}
15067 Reference (and hence definition) to internal type @code{itype}.
15069 @item @code{@emph{function-name}! (@emph{arg}, @emph{arg}, @emph{arg})}
15071 Intrinsic function call.
15073 @item @code{@emph{label-name} : label}
15075 Declaration of label @code{labelname}.
15077 @item @code{#$ @emph{subprogram-name}}
15079 An implicit call to a run-time support routine
15080 (to meet the requirement of H.3.1(9) in a
15081 convenient manner).
15083 @item @code{@emph{expr} && @emph{expr} && @emph{expr} ... && @emph{expr}}
15085 A multiple concatenation (same effect as @code{expr} & @code{expr} &
15086 @code{expr}, but handled more efficiently).
15088 @item @code{[constraint_error]}
15090 Raise the @code{Constraint_Error} exception.
15092 @item @code{@emph{expression}'reference}
15094 A pointer to the result of evaluating @{expression@}.
15096 @item @code{@emph{target-type}!(@emph{source-expression})}
15098 An unchecked conversion of @code{source-expression} to @code{target-type}.
15100 @item @code{[@emph{numerator}/@emph{denominator}]}
15102 Used to represent internal real literals (that) have no exact
15103 representation in base 2-16 (for example, the result of compile time
15104 evaluation of the expression 1.0/27.0).
15108 @geindex -gnatD (gcc)
15113 @item @code{-gnatD[=nn]}
15115 When used in conjunction with @code{-gnatG}, this switch causes
15116 the expanded source, as described above for
15117 @code{-gnatG} to be written to files with names
15118 @code{xxx.dg}, where @code{xxx} is the normal file name,
15119 instead of to the standard output file. For
15120 example, if the source file name is @code{hello.adb}, then a file
15121 @code{hello.adb.dg} will be written. The debugging
15122 information generated by the @code{gcc} @code{-g} switch
15123 will refer to the generated @code{xxx.dg} file. This allows
15124 you to do source level debugging using the generated code which is
15125 sometimes useful for complex code, for example to find out exactly
15126 which part of a complex construction raised an exception. This switch
15127 also suppresses generation of cross-reference information (see
15128 @code{-gnatx}) since otherwise the cross-reference information
15129 would refer to the @code{.dg} file, which would cause
15130 confusion since this is not the original source file.
15132 Note that @code{-gnatD} actually implies @code{-gnatG}
15133 automatically, so it is not necessary to give both options.
15134 In other words @code{-gnatD} is equivalent to @code{-gnatDG}).
15136 @geindex -gnatL (gcc)
15138 If the switch @code{-gnatL} is used in conjunction with
15139 @code{-gnatDG}, then the original source lines are interspersed
15140 in the expanded source (as comment lines with the original line number).
15142 The optional parameter @code{nn} if present after -gnatD specifies an
15143 alternative maximum line length that overrides the normal default of 72.
15144 This value is in the range 40-999999, values less than 40 being silently
15145 reset to 40. The equal sign is optional.
15148 @geindex -gnatr (gcc)
15150 @geindex pragma Restrictions
15155 @item @code{-gnatr}
15157 This switch causes pragma Restrictions to be treated as Restriction_Warnings
15158 so that violation of restrictions causes warnings rather than illegalities.
15159 This is useful during the development process when new restrictions are added
15160 or investigated. The switch also causes pragma Profile to be treated as
15161 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
15162 restriction warnings rather than restrictions.
15165 @geindex -gnatR (gcc)
15170 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
15172 This switch controls output from the compiler of a listing showing
15173 representation information for declared types, objects and subprograms.
15174 For @code{-gnatR0}, no information is output (equivalent to omitting
15175 the @code{-gnatR} switch). For @code{-gnatR1} (which is the default,
15176 so @code{-gnatR} with no parameter has the same effect), size and
15177 alignment information is listed for declared array and record types.
15179 For @code{-gnatR2}, size and alignment information is listed for all
15180 declared types and objects. The @code{Linker_Section} is also listed for any
15181 entity for which the @code{Linker_Section} is set explicitly or implicitly (the
15182 latter case occurs for objects of a type for which a @code{Linker_Section}
15185 For @code{-gnatR3}, symbolic expressions for values that are computed
15186 at run time for records are included. These symbolic expressions have
15187 a mostly obvious format with #n being used to represent the value of the
15188 n'th discriminant. See source files @code{repinfo.ads/adb} in the
15189 GNAT sources for full details on the format of @code{-gnatR3} output.
15191 For @code{-gnatR4}, information for relevant compiler-generated types
15192 is also listed, i.e. when they are structurally part of other declared
15195 If the switch is followed by an @code{e} (e.g. @code{-gnatR2e}), then
15196 extended representation information for record sub-components of records
15199 If the switch is followed by an @code{m} (e.g. @code{-gnatRm}), then
15200 subprogram conventions and parameter passing mechanisms for all the
15201 subprograms are included.
15203 If the switch is followed by a @code{j} (e.g., @code{-gnatRj}), then
15204 the output is in the JSON data interchange format specified by the
15205 ECMA-404 standard. The semantic description of this JSON output is
15206 available in the specification of the Repinfo unit present in the
15209 If the switch is followed by an @code{s} (e.g., @code{-gnatR3s}), then
15210 the output is to a file with the name @code{file.rep} where @code{file} is
15211 the name of the corresponding source file, except if @code{j} is also
15212 specified, in which case the file name is @code{file.json}.
15214 Note that it is possible for record components to have zero size. In
15215 this case, the component clause uses an obvious extension of permitted
15216 Ada syntax, for example @code{at 0 range 0 .. -1}.
15219 @geindex -gnatS (gcc)
15224 @item @code{-gnatS}
15226 The use of the switch @code{-gnatS} for an
15227 Ada compilation will cause the compiler to output a
15228 representation of package Standard in a form very
15229 close to standard Ada. It is not quite possible to
15230 do this entirely in standard Ada (since new
15231 numeric base types cannot be created in standard
15232 Ada), but the output is easily
15233 readable to any Ada programmer, and is useful to
15234 determine the characteristics of target dependent
15235 types in package Standard.
15238 @geindex -gnatx (gcc)
15243 @item @code{-gnatx}
15245 Normally the compiler generates full cross-referencing information in
15246 the @code{ALI} file. This information is used by a number of tools,
15247 including @code{gnatfind} and @code{gnatxref}. The @code{-gnatx} switch
15248 suppresses this information. This saves some space and may slightly
15249 speed up compilation, but means that these tools cannot be used.
15252 @geindex -fgnat-encodings (gcc)
15257 @item @code{-fgnat-encodings=[all|gdb|minimal]}
15259 This switch controls the balance between GNAT encodings and standard DWARF
15260 emitted in the debug information.
15262 Historically, old debug formats like stabs were not powerful enough to
15263 express some Ada types (for instance, variant records or fixed-point types).
15264 To work around this, GNAT introduced proprietary encodings that embed the
15265 missing information ("GNAT encodings").
15267 Recent versions of the DWARF debug information format are now able to
15268 correctly describe most of these Ada constructs ("standard DWARF"). As
15269 third-party tools started to use this format, GNAT has been enhanced to
15270 generate it. However, most tools (including GDB) are still relying on GNAT
15273 To support all tools, GNAT needs to be versatile about the balance between
15274 generation of GNAT encodings and standard DWARF. This is what
15275 @code{-fgnat-encodings} is about.
15281 @code{=all}: Emit all GNAT encodings, and then emit as much standard DWARF as
15282 possible so it does not conflict with GNAT encodings.
15285 @code{=gdb}: Emit as much standard DWARF as possible as long as the current
15286 GDB handles it. Emit GNAT encodings for the rest.
15289 @code{=minimal}: Emit as much standard DWARF as possible and emit GNAT
15290 encodings for the rest.
15294 @node Exception Handling Control,Units to Sources Mapping Files,Debugging Control,Compiler Switches
15295 @anchor{gnat_ugn/building_executable_programs_with_gnat id28}@anchor{114}@anchor{gnat_ugn/building_executable_programs_with_gnat exception-handling-control}@anchor{115}
15296 @subsection Exception Handling Control
15299 GNAT uses two methods for handling exceptions at run time. The
15300 @code{setjmp/longjmp} method saves the context when entering
15301 a frame with an exception handler. Then when an exception is
15302 raised, the context can be restored immediately, without the
15303 need for tracing stack frames. This method provides very fast
15304 exception propagation, but introduces significant overhead for
15305 the use of exception handlers, even if no exception is raised.
15307 The other approach is called 'zero cost' exception handling.
15308 With this method, the compiler builds static tables to describe
15309 the exception ranges. No dynamic code is required when entering
15310 a frame containing an exception handler. When an exception is
15311 raised, the tables are used to control a back trace of the
15312 subprogram invocation stack to locate the required exception
15313 handler. This method has considerably poorer performance for
15314 the propagation of exceptions, but there is no overhead for
15315 exception handlers if no exception is raised. Note that in this
15316 mode and in the context of mixed Ada and C/C++ programming,
15317 to propagate an exception through a C/C++ code, the C/C++ code
15318 must be compiled with the @code{-funwind-tables} GCC's
15321 The following switches may be used to control which of the
15322 two exception handling methods is used.
15324 @geindex --RTS=sjlj (gnatmake)
15329 @item @code{--RTS=sjlj}
15331 This switch causes the setjmp/longjmp run-time (when available) to be used
15332 for exception handling. If the default
15333 mechanism for the target is zero cost exceptions, then
15334 this switch can be used to modify this default, and must be
15335 used for all units in the partition.
15336 This option is rarely used. One case in which it may be
15337 advantageous is if you have an application where exception
15338 raising is common and the overall performance of the
15339 application is improved by favoring exception propagation.
15342 @geindex --RTS=zcx (gnatmake)
15344 @geindex Zero Cost Exceptions
15349 @item @code{--RTS=zcx}
15351 This switch causes the zero cost approach to be used
15352 for exception handling. If this is the default mechanism for the
15353 target (see below), then this switch is unneeded. If the default
15354 mechanism for the target is setjmp/longjmp exceptions, then
15355 this switch can be used to modify this default, and must be
15356 used for all units in the partition.
15357 This option can only be used if the zero cost approach
15358 is available for the target in use, otherwise it will generate an error.
15361 The same option @code{--RTS} must be used both for @code{gcc}
15362 and @code{gnatbind}. Passing this option to @code{gnatmake}
15363 (@ref{dc,,Switches for gnatmake}) will ensure the required consistency
15364 through the compilation and binding steps.
15366 @node Units to Sources Mapping Files,Code Generation Control,Exception Handling Control,Compiler Switches
15367 @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}
15368 @subsection Units to Sources Mapping Files
15371 @geindex -gnatem (gcc)
15376 @item @code{-gnatem=@emph{path}}
15378 A mapping file is a way to communicate to the compiler two mappings:
15379 from unit names to file names (without any directory information) and from
15380 file names to path names (with full directory information). These mappings
15381 are used by the compiler to short-circuit the path search.
15383 The use of mapping files is not required for correct operation of the
15384 compiler, but mapping files can improve efficiency, particularly when
15385 sources are read over a slow network connection. In normal operation,
15386 you need not be concerned with the format or use of mapping files,
15387 and the @code{-gnatem} switch is not a switch that you would use
15388 explicitly. It is intended primarily for use by automatic tools such as
15389 @code{gnatmake} running under the project file facility. The
15390 description here of the format of mapping files is provided
15391 for completeness and for possible use by other tools.
15393 A mapping file is a sequence of sets of three lines. In each set, the
15394 first line is the unit name, in lower case, with @code{%s} appended
15395 for specs and @code{%b} appended for bodies; the second line is the
15396 file name; and the third line is the path name.
15403 /gnat/project1/sources/main.2.ada
15406 When the switch @code{-gnatem} is specified, the compiler will
15407 create in memory the two mappings from the specified file. If there is
15408 any problem (nonexistent file, truncated file or duplicate entries),
15409 no mapping will be created.
15411 Several @code{-gnatem} switches may be specified; however, only the
15412 last one on the command line will be taken into account.
15414 When using a project file, @code{gnatmake} creates a temporary
15415 mapping file and communicates it to the compiler using this switch.
15418 @node Code Generation Control,,Units to Sources Mapping Files,Compiler Switches
15419 @anchor{gnat_ugn/building_executable_programs_with_gnat code-generation-control}@anchor{117}@anchor{gnat_ugn/building_executable_programs_with_gnat id30}@anchor{118}
15420 @subsection Code Generation Control
15423 The GCC technology provides a wide range of target dependent
15424 @code{-m} switches for controlling
15425 details of code generation with respect to different versions of
15426 architectures. This includes variations in instruction sets (e.g.,
15427 different members of the power pc family), and different requirements
15428 for optimal arrangement of instructions (e.g., different members of
15429 the x86 family). The list of available @code{-m} switches may be
15430 found in the GCC documentation.
15432 Use of these @code{-m} switches may in some cases result in improved
15435 The GNAT technology is tested and qualified without any
15436 @code{-m} switches,
15437 so generally the most reliable approach is to avoid the use of these
15438 switches. However, we generally expect most of these switches to work
15439 successfully with GNAT, and many customers have reported successful
15440 use of these options.
15442 Our general advice is to avoid the use of @code{-m} switches unless
15443 special needs lead to requirements in this area. In particular,
15444 there is no point in using @code{-m} switches to improve performance
15445 unless you actually see a performance improvement.
15447 @node Linker Switches,Binding with gnatbind,Compiler Switches,Building Executable Programs with GNAT
15448 @anchor{gnat_ugn/building_executable_programs_with_gnat linker-switches}@anchor{119}@anchor{gnat_ugn/building_executable_programs_with_gnat id31}@anchor{11a}
15449 @section Linker Switches
15452 Linker switches can be specified after @code{-largs} builder switch.
15454 @geindex -fuse-ld=name
15459 @item @code{-fuse-ld=@emph{name}}
15461 Linker to be used. The default is @code{bfd} for @code{ld.bfd},
15462 the alternative being @code{gold} for @code{ld.gold}. The later is
15463 a more recent and faster linker, but only available on GNU/Linux
15467 @node Binding with gnatbind,Linking with gnatlink,Linker Switches,Building Executable Programs with GNAT
15468 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind}@anchor{1d}@anchor{gnat_ugn/building_executable_programs_with_gnat id32}@anchor{11b}
15469 @section Binding with @code{gnatbind}
15474 This chapter describes the GNAT binder, @code{gnatbind}, which is used
15475 to bind compiled GNAT objects.
15477 The @code{gnatbind} program performs four separate functions:
15483 Checks that a program is consistent, in accordance with the rules in
15484 Chapter 10 of the Ada Reference Manual. In particular, error
15485 messages are generated if a program uses inconsistent versions of a
15489 Checks that an acceptable order of elaboration exists for the program
15490 and issues an error message if it cannot find an order of elaboration
15491 that satisfies the rules in Chapter 10 of the Ada Language Manual.
15494 Generates a main program incorporating the given elaboration order.
15495 This program is a small Ada package (body and spec) that
15496 must be subsequently compiled
15497 using the GNAT compiler. The necessary compilation step is usually
15498 performed automatically by @code{gnatlink}. The two most important
15499 functions of this program
15500 are to call the elaboration routines of units in an appropriate order
15501 and to call the main program.
15504 Determines the set of object files required by the given main program.
15505 This information is output in the forms of comments in the generated program,
15506 to be read by the @code{gnatlink} utility used to link the Ada application.
15510 * Running gnatbind::
15511 * Switches for gnatbind::
15512 * Command-Line Access::
15513 * Search Paths for gnatbind::
15514 * Examples of gnatbind Usage::
15518 @node Running gnatbind,Switches for gnatbind,,Binding with gnatbind
15519 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatbind}@anchor{11c}@anchor{gnat_ugn/building_executable_programs_with_gnat id33}@anchor{11d}
15520 @subsection Running @code{gnatbind}
15523 The form of the @code{gnatbind} command is
15526 $ gnatbind [ switches ] mainprog[.ali] [ switches ]
15529 where @code{mainprog.adb} is the Ada file containing the main program
15530 unit body. @code{gnatbind} constructs an Ada
15531 package in two files whose names are
15532 @code{b~mainprog.ads}, and @code{b~mainprog.adb}.
15533 For example, if given the
15534 parameter @code{hello.ali}, for a main program contained in file
15535 @code{hello.adb}, the binder output files would be @code{b~hello.ads}
15536 and @code{b~hello.adb}.
15538 When doing consistency checking, the binder takes into consideration
15539 any source files it can locate. For example, if the binder determines
15540 that the given main program requires the package @code{Pack}, whose
15542 file is @code{pack.ali} and whose corresponding source spec file is
15543 @code{pack.ads}, it attempts to locate the source file @code{pack.ads}
15544 (using the same search path conventions as previously described for the
15545 @code{gcc} command). If it can locate this source file, it checks that
15547 or source checksums of the source and its references to in @code{ALI} files
15548 match. In other words, any @code{ALI} files that mentions this spec must have
15549 resulted from compiling this version of the source file (or in the case
15550 where the source checksums match, a version close enough that the
15551 difference does not matter).
15553 @geindex Source files
15554 @geindex use by binder
15556 The effect of this consistency checking, which includes source files, is
15557 that the binder ensures that the program is consistent with the latest
15558 version of the source files that can be located at bind time. Editing a
15559 source file without compiling files that depend on the source file cause
15560 error messages to be generated by the binder.
15562 For example, suppose you have a main program @code{hello.adb} and a
15563 package @code{P}, from file @code{p.ads} and you perform the following
15570 Enter @code{gcc -c hello.adb} to compile the main program.
15573 Enter @code{gcc -c p.ads} to compile package @code{P}.
15576 Edit file @code{p.ads}.
15579 Enter @code{gnatbind hello}.
15582 At this point, the file @code{p.ali} contains an out-of-date time stamp
15583 because the file @code{p.ads} has been edited. The attempt at binding
15584 fails, and the binder generates the following error messages:
15587 error: "hello.adb" must be recompiled ("p.ads" has been modified)
15588 error: "p.ads" has been modified and must be recompiled
15591 Now both files must be recompiled as indicated, and then the bind can
15592 succeed, generating a main program. You need not normally be concerned
15593 with the contents of this file, but for reference purposes a sample
15594 binder output file is given in @ref{e,,Example of Binder Output File}.
15596 In most normal usage, the default mode of @code{gnatbind} which is to
15597 generate the main package in Ada, as described in the previous section.
15598 In particular, this means that any Ada programmer can read and understand
15599 the generated main program. It can also be debugged just like any other
15600 Ada code provided the @code{-g} switch is used for
15601 @code{gnatbind} and @code{gnatlink}.
15603 @node Switches for gnatbind,Command-Line Access,Running gnatbind,Binding with gnatbind
15604 @anchor{gnat_ugn/building_executable_programs_with_gnat id34}@anchor{11e}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind}@anchor{11f}
15605 @subsection Switches for @code{gnatbind}
15608 The following switches are available with @code{gnatbind}; details will
15609 be presented in subsequent sections.
15611 @geindex --version (gnatbind)
15616 @item @code{--version}
15618 Display Copyright and version, then exit disregarding all other options.
15621 @geindex --help (gnatbind)
15626 @item @code{--help}
15628 If @code{--version} was not used, display usage, then exit disregarding
15632 @geindex -a (gnatbind)
15639 Indicates that, if supported by the platform, the adainit procedure should
15640 be treated as an initialisation routine by the linker (a constructor). This
15641 is intended to be used by the Project Manager to automatically initialize
15642 shared Stand-Alone Libraries.
15645 @geindex -aO (gnatbind)
15652 Specify directory to be searched for ALI files.
15655 @geindex -aI (gnatbind)
15662 Specify directory to be searched for source file.
15665 @geindex -A (gnatbind)
15670 @item @code{-A[=@emph{filename}]}
15672 Output ALI list (to standard output or to the named file).
15675 @geindex -b (gnatbind)
15682 Generate brief messages to @code{stderr} even if verbose mode set.
15685 @geindex -c (gnatbind)
15692 Check only, no generation of binder output file.
15695 @geindex -dnn[k|m] (gnatbind)
15700 @item @code{-d@emph{nn}[k|m]}
15702 This switch can be used to change the default task stack size value
15703 to a specified size @code{nn}, which is expressed in bytes by default, or
15704 in kilobytes when suffixed with @code{k} or in megabytes when suffixed
15706 In the absence of a @code{[k|m]} suffix, this switch is equivalent,
15707 in effect, to completing all task specs with
15710 pragma Storage_Size (nn);
15713 When they do not already have such a pragma.
15716 @geindex -D (gnatbind)
15721 @item @code{-D@emph{nn}[k|m]}
15723 Set the default secondary stack size to @code{nn}. The suffix indicates whether
15724 the size is in bytes (no suffix), kilobytes (@code{k} suffix) or megabytes
15727 The secondary stack holds objects of unconstrained types that are returned by
15728 functions, for example unconstrained Strings. The size of the secondary stack
15729 can be dynamic or fixed depending on the target.
15731 For most targets, the secondary stack grows on demand and is implemented as
15732 a chain of blocks in the heap. In this case, the default secondary stack size
15733 determines the initial size of the secondary stack for each task and the
15734 smallest amount the secondary stack can grow by.
15736 For Ravenscar, ZFP, and Cert run-times the size of the secondary stack is
15737 fixed. This switch can be used to change the default size of these stacks.
15738 The default secondary stack size can be overridden on a per-task basis if
15739 individual tasks have different secondary stack requirements. This is
15740 achieved through the Secondary_Stack_Size aspect that takes the size of the
15741 secondary stack in bytes.
15744 @geindex -e (gnatbind)
15751 Output complete list of elaboration-order dependencies.
15754 @geindex -Ea (gnatbind)
15761 Store tracebacks in exception occurrences when the target supports it.
15762 The "a" is for "address"; tracebacks will contain hexadecimal addresses,
15763 unless symbolic tracebacks are enabled.
15765 See also the packages @code{GNAT.Traceback} and
15766 @code{GNAT.Traceback.Symbolic} for more information.
15767 Note that on x86 ports, you must not use @code{-fomit-frame-pointer}
15771 @geindex -Es (gnatbind)
15778 Store tracebacks in exception occurrences when the target supports it.
15779 The "s" is for "symbolic"; symbolic tracebacks are enabled.
15782 @geindex -E (gnatbind)
15789 Currently the same as @code{-Ea}.
15792 @geindex -f (gnatbind)
15797 @item @code{-f@emph{elab-order}}
15799 Force elaboration order. For further details see @ref{120,,Elaboration Control}
15800 and @ref{f,,Elaboration Order Handling in GNAT}.
15803 @geindex -F (gnatbind)
15810 Force the checks of elaboration flags. @code{gnatbind} does not normally
15811 generate checks of elaboration flags for the main executable, except when
15812 a Stand-Alone Library is used. However, there are cases when this cannot be
15813 detected by gnatbind. An example is importing an interface of a Stand-Alone
15814 Library through a pragma Import and only specifying through a linker switch
15815 this Stand-Alone Library. This switch is used to guarantee that elaboration
15816 flag checks are generated.
15819 @geindex -h (gnatbind)
15826 Output usage (help) information.
15829 @geindex -H (gnatbind)
15836 Legacy elaboration order model enabled. For further details see
15837 @ref{f,,Elaboration Order Handling in GNAT}.
15840 @geindex -H32 (gnatbind)
15847 Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types).
15848 For further details see @ref{121,,Dynamic Allocation Control}.
15851 @geindex -H64 (gnatbind)
15853 @geindex __gnat_malloc
15860 Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types).
15861 For further details see @ref{121,,Dynamic Allocation Control}.
15863 @geindex -I (gnatbind)
15867 Specify directory to be searched for source and ALI files.
15869 @geindex -I- (gnatbind)
15873 Do not look for sources in the current directory where @code{gnatbind} was
15874 invoked, and do not look for ALI files in the directory containing the
15875 ALI file named in the @code{gnatbind} command line.
15877 @geindex -l (gnatbind)
15881 Output chosen elaboration order.
15883 @geindex -L (gnatbind)
15885 @item @code{-L@emph{xxx}}
15887 Bind the units for library building. In this case the @code{adainit} and
15888 @code{adafinal} procedures (@ref{b4,,Binding with Non-Ada Main Programs})
15889 are renamed to @code{@emph{xxx}init} and
15890 @code{@emph{xxx}final}.
15892 (@ref{15,,GNAT and Libraries}, for more details.)
15894 @geindex -M (gnatbind)
15896 @item @code{-M@emph{xyz}}
15898 Rename generated main program from main to xyz. This option is
15899 supported on cross environments only.
15901 @geindex -m (gnatbind)
15903 @item @code{-m@emph{n}}
15905 Limit number of detected errors or warnings to @code{n}, where @code{n} is
15906 in the range 1..999999. The default value if no switch is
15907 given is 9999. If the number of warnings reaches this limit, then a
15908 message is output and further warnings are suppressed, the bind
15909 continues in this case. If the number of errors reaches this
15910 limit, then a message is output and the bind is abandoned.
15911 A value of zero means that no limit is enforced. The equal
15914 @geindex -minimal (gnatbind)
15916 @item @code{-minimal}
15918 Generate a binder file suitable for space-constrained applications. When
15919 active, binder-generated objects not required for program operation are no
15920 longer generated. @strong{Warning:} this option comes with the following
15927 Starting the program's execution in the debugger will cause it to
15928 stop at the start of the @code{main} function instead of the main subprogram.
15929 This can be worked around by manually inserting a breakpoint on that
15930 subprogram and resuming the program's execution until reaching that breakpoint.
15933 Programs using GNAT.Compiler_Version will not link.
15936 @geindex -n (gnatbind)
15942 @geindex -nostdinc (gnatbind)
15944 @item @code{-nostdinc}
15946 Do not look for sources in the system default directory.
15948 @geindex -nostdlib (gnatbind)
15950 @item @code{-nostdlib}
15952 Do not look for library files in the system default directory.
15954 @geindex --RTS (gnatbind)
15956 @item @code{--RTS=@emph{rts-path}}
15958 Specifies the default location of the run-time library. Same meaning as the
15959 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
15961 @geindex -o (gnatbind)
15963 @item @code{-o @emph{file}}
15965 Name the output file @code{file} (default is @code{b~`xxx}.adb`).
15966 Note that if this option is used, then linking must be done manually,
15967 gnatlink cannot be used.
15969 @geindex -O (gnatbind)
15971 @item @code{-O[=@emph{filename}]}
15973 Output object list (to standard output or to the named file).
15975 @geindex -p (gnatbind)
15979 Pessimistic (worst-case) elaboration order.
15981 @geindex -P (gnatbind)
15985 Generate binder file suitable for CodePeer.
15987 @geindex -R (gnatbind)
15991 Output closure source list, which includes all non-run-time units that are
15992 included in the bind.
15994 @geindex -Ra (gnatbind)
15998 Like @code{-R} but the list includes run-time units.
16000 @geindex -s (gnatbind)
16004 Require all source files to be present.
16006 @geindex -S (gnatbind)
16008 @item @code{-S@emph{xxx}}
16010 Specifies the value to be used when detecting uninitialized scalar
16011 objects with pragma Initialize_Scalars.
16012 The @code{xxx} string specified with the switch is one of:
16018 @code{in} for an invalid value.
16020 If zero is invalid for the discrete type in question,
16021 then the scalar value is set to all zero bits.
16022 For signed discrete types, the largest possible negative value of
16023 the underlying scalar is set (i.e. a one bit followed by all zero bits).
16024 For unsigned discrete types, the underlying scalar value is set to all
16025 one bits. For floating-point types, a NaN value is set
16026 (see body of package System.Scalar_Values for exact values).
16029 @code{lo} for low value.
16031 If zero is invalid for the discrete type in question,
16032 then the scalar value is set to all zero bits.
16033 For signed discrete types, the largest possible negative value of
16034 the underlying scalar is set (i.e. a one bit followed by all zero bits).
16035 For unsigned discrete types, the underlying scalar value is set to all
16036 zero bits. For floating-point, a small value is set
16037 (see body of package System.Scalar_Values for exact values).
16040 @code{hi} for high value.
16042 If zero is invalid for the discrete type in question,
16043 then the scalar value is set to all one bits.
16044 For signed discrete types, the largest possible positive value of
16045 the underlying scalar is set (i.e. a zero bit followed by all one bits).
16046 For unsigned discrete types, the underlying scalar value is set to all
16047 one bits. For floating-point, a large value is set
16048 (see body of package System.Scalar_Values for exact values).
16051 @code{xx} for hex value (two hex digits).
16053 The underlying scalar is set to a value consisting of repeated bytes, whose
16054 value corresponds to the given value. For example if @code{BF} is given,
16055 then a 32-bit scalar value will be set to the bit patterm @code{16#BFBFBFBF#}.
16058 @geindex GNAT_INIT_SCALARS
16060 In addition, you can specify @code{-Sev} to indicate that the value is
16061 to be set at run time. In this case, the program will look for an environment
16062 variable of the form @code{GNAT_INIT_SCALARS=@emph{yy}}, where @code{yy} is one
16063 of @code{in/lo/hi/@emph{xx}} with the same meanings as above.
16064 If no environment variable is found, or if it does not have a valid value,
16065 then the default is @code{in} (invalid values).
16068 @geindex -static (gnatbind)
16073 @item @code{-static}
16075 Link against a static GNAT run-time.
16077 @geindex -shared (gnatbind)
16079 @item @code{-shared}
16081 Link against a shared GNAT run-time when available.
16083 @geindex -t (gnatbind)
16087 Tolerate time stamp and other consistency errors.
16089 @geindex -T (gnatbind)
16091 @item @code{-T@emph{n}}
16093 Set the time slice value to @code{n} milliseconds. If the system supports
16094 the specification of a specific time slice value, then the indicated value
16095 is used. If the system does not support specific time slice values, but
16096 does support some general notion of round-robin scheduling, then any
16097 nonzero value will activate round-robin scheduling.
16099 A value of zero is treated specially. It turns off time
16100 slicing, and in addition, indicates to the tasking run-time that the
16101 semantics should match as closely as possible the Annex D
16102 requirements of the Ada RM, and in particular sets the default
16103 scheduling policy to @code{FIFO_Within_Priorities}.
16105 @geindex -u (gnatbind)
16107 @item @code{-u@emph{n}}
16109 Enable dynamic stack usage, with @code{n} results stored and displayed
16110 at program termination. A result is generated when a task
16111 terminates. Results that can't be stored are displayed on the fly, at
16112 task termination. This option is currently not supported on Itanium
16113 platforms. (See @ref{122,,Dynamic Stack Usage Analysis} for details.)
16115 @geindex -v (gnatbind)
16119 Verbose mode. Write error messages, header, summary output to
16122 @geindex -V (gnatbind)
16124 @item @code{-V@emph{key}=@emph{value}}
16126 Store the given association of @code{key} to @code{value} in the bind environment.
16127 Values stored this way can be retrieved at run time using
16128 @code{GNAT.Bind_Environment}.
16130 @geindex -w (gnatbind)
16132 @item @code{-w@emph{x}}
16134 Warning mode; @code{x} = s/e for suppress/treat as error.
16136 @geindex -Wx (gnatbind)
16138 @item @code{-Wx@emph{e}}
16140 Override default wide character encoding for standard Text_IO files.
16142 @geindex -x (gnatbind)
16146 Exclude source files (check object consistency only).
16148 @geindex -Xnnn (gnatbind)
16150 @item @code{-X@emph{nnn}}
16152 Set default exit status value, normally 0 for POSIX compliance.
16154 @geindex -y (gnatbind)
16158 Enable leap seconds support in @code{Ada.Calendar} and its children.
16160 @geindex -z (gnatbind)
16164 No main subprogram.
16167 You may obtain this listing of switches by running @code{gnatbind} with
16171 * Consistency-Checking Modes::
16172 * Binder Error Message Control::
16173 * Elaboration Control::
16175 * Dynamic Allocation Control::
16176 * Binding with Non-Ada Main Programs::
16177 * Binding Programs with No Main Subprogram::
16181 @node Consistency-Checking Modes,Binder Error Message Control,,Switches for gnatbind
16182 @anchor{gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes}@anchor{123}@anchor{gnat_ugn/building_executable_programs_with_gnat id35}@anchor{124}
16183 @subsubsection Consistency-Checking Modes
16186 As described earlier, by default @code{gnatbind} checks
16187 that object files are consistent with one another and are consistent
16188 with any source files it can locate. The following switches control binder
16193 @geindex -s (gnatbind)
16201 Require source files to be present. In this mode, the binder must be
16202 able to locate all source files that are referenced, in order to check
16203 their consistency. In normal mode, if a source file cannot be located it
16204 is simply ignored. If you specify this switch, a missing source
16207 @geindex -Wx (gnatbind)
16209 @item @code{-Wx@emph{e}}
16211 Override default wide character encoding for standard Text_IO files.
16212 Normally the default wide character encoding method used for standard
16213 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
16214 the main source input (see description of switch
16215 @code{-gnatWx} for the compiler). The
16216 use of this switch for the binder (which has the same set of
16217 possible arguments) overrides this default as specified.
16219 @geindex -x (gnatbind)
16223 Exclude source files. In this mode, the binder only checks that ALI
16224 files are consistent with one another. Source files are not accessed.
16225 The binder runs faster in this mode, and there is still a guarantee that
16226 the resulting program is self-consistent.
16227 If a source file has been edited since it was last compiled, and you
16228 specify this switch, the binder will not detect that the object
16229 file is out of date with respect to the source file. Note that this is the
16230 mode that is automatically used by @code{gnatmake} because in this
16231 case the checking against sources has already been performed by
16232 @code{gnatmake} in the course of compilation (i.e., before binding).
16235 @node Binder Error Message Control,Elaboration Control,Consistency-Checking Modes,Switches for gnatbind
16236 @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}
16237 @subsubsection Binder Error Message Control
16240 The following switches provide control over the generation of error
16241 messages from the binder:
16245 @geindex -v (gnatbind)
16253 Verbose mode. In the normal mode, brief error messages are generated to
16254 @code{stderr}. If this switch is present, a header is written
16255 to @code{stdout} and any error messages are directed to @code{stdout}.
16256 All that is written to @code{stderr} is a brief summary message.
16258 @geindex -b (gnatbind)
16262 Generate brief error messages to @code{stderr} even if verbose mode is
16263 specified. This is relevant only when used with the
16266 @geindex -m (gnatbind)
16268 @item @code{-m@emph{n}}
16270 Limits the number of error messages to @code{n}, a decimal integer in the
16271 range 1-999. The binder terminates immediately if this limit is reached.
16273 @geindex -M (gnatbind)
16275 @item @code{-M@emph{xxx}}
16277 Renames the generated main program from @code{main} to @code{xxx}.
16278 This is useful in the case of some cross-building environments, where
16279 the actual main program is separate from the one generated
16280 by @code{gnatbind}.
16282 @geindex -ws (gnatbind)
16288 Suppress all warning messages.
16290 @geindex -we (gnatbind)
16294 Treat any warning messages as fatal errors.
16296 @geindex -t (gnatbind)
16298 @geindex Time stamp checks
16301 @geindex Binder consistency checks
16303 @geindex Consistency checks
16308 The binder performs a number of consistency checks including:
16314 Check that time stamps of a given source unit are consistent
16317 Check that checksums of a given source unit are consistent
16320 Check that consistent versions of @code{GNAT} were used for compilation
16323 Check consistency of configuration pragmas as required
16326 Normally failure of such checks, in accordance with the consistency
16327 requirements of the Ada Reference Manual, causes error messages to be
16328 generated which abort the binder and prevent the output of a binder
16329 file and subsequent link to obtain an executable.
16331 The @code{-t} switch converts these error messages
16332 into warnings, so that
16333 binding and linking can continue to completion even in the presence of such
16334 errors. The result may be a failed link (due to missing symbols), or a
16335 non-functional executable which has undefined semantics.
16339 This means that @code{-t} should be used only in unusual situations,
16345 @node Elaboration Control,Output Control,Binder Error Message Control,Switches for gnatbind
16346 @anchor{gnat_ugn/building_executable_programs_with_gnat id37}@anchor{127}@anchor{gnat_ugn/building_executable_programs_with_gnat elaboration-control}@anchor{120}
16347 @subsubsection Elaboration Control
16350 The following switches provide additional control over the elaboration
16351 order. For further details see @ref{f,,Elaboration Order Handling in GNAT}.
16353 @geindex -f (gnatbind)
16358 @item @code{-f@emph{elab-order}}
16360 Force elaboration order.
16362 @code{elab-order} should be the name of a "forced elaboration order file", that
16363 is, a text file containing library item names, one per line. A name of the
16364 form "some.unit%s" or "some.unit (spec)" denotes the spec of Some.Unit. A
16365 name of the form "some.unit%b" or "some.unit (body)" denotes the body of
16366 Some.Unit. Each pair of lines is taken to mean that there is an elaboration
16367 dependence of the second line on the first. For example, if the file
16377 then the spec of This will be elaborated before the body of This, and the
16378 body of This will be elaborated before the spec of That, and the spec of That
16379 will be elaborated before the body of That. The first and last of these three
16380 dependences are already required by Ada rules, so this file is really just
16381 forcing the body of This to be elaborated before the spec of That.
16383 The given order must be consistent with Ada rules, or else @code{gnatbind} will
16384 give elaboration cycle errors. For example, if you say x (body) should be
16385 elaborated before x (spec), there will be a cycle, because Ada rules require
16386 x (spec) to be elaborated before x (body); you can't have the spec and body
16387 both elaborated before each other.
16389 If you later add "with That;" to the body of This, there will be a cycle, in
16390 which case you should erase either "this (body)" or "that (spec)" from the
16391 above forced elaboration order file.
16393 Blank lines and Ada-style comments are ignored. Unit names that do not exist
16394 in the program are ignored. Units in the GNAT predefined library are also
16398 @geindex -p (gnatbind)
16405 Pessimistic elaboration order
16407 This switch is only applicable to the pre-20.x legacy elaboration models.
16408 The post-20.x elaboration model uses a more informed approach of ordering
16411 Normally the binder attempts to choose an elaboration order that is likely to
16412 minimize the likelihood of an elaboration order error resulting in raising a
16413 @code{Program_Error} exception. This switch reverses the action of the binder,
16414 and requests that it deliberately choose an order that is likely to maximize
16415 the likelihood of an elaboration error. This is useful in ensuring
16416 portability and avoiding dependence on accidental fortuitous elaboration
16419 Normally it only makes sense to use the @code{-p} switch if dynamic
16420 elaboration checking is used (@code{-gnatE} switch used for compilation).
16421 This is because in the default static elaboration mode, all necessary
16422 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
16423 These implicit pragmas are still respected by the binder in @code{-p}
16424 mode, so a safe elaboration order is assured.
16426 Note that @code{-p} is not intended for production use; it is more for
16427 debugging/experimental use.
16430 @node Output Control,Dynamic Allocation Control,Elaboration Control,Switches for gnatbind
16431 @anchor{gnat_ugn/building_executable_programs_with_gnat output-control}@anchor{128}@anchor{gnat_ugn/building_executable_programs_with_gnat id38}@anchor{129}
16432 @subsubsection Output Control
16435 The following switches allow additional control over the output
16436 generated by the binder.
16440 @geindex -c (gnatbind)
16448 Check only. Do not generate the binder output file. In this mode the
16449 binder performs all error checks but does not generate an output file.
16451 @geindex -e (gnatbind)
16455 Output complete list of elaboration-order dependencies, showing the
16456 reason for each dependency. This output can be rather extensive but may
16457 be useful in diagnosing problems with elaboration order. The output is
16458 written to @code{stdout}.
16460 @geindex -h (gnatbind)
16464 Output usage information. The output is written to @code{stdout}.
16466 @geindex -K (gnatbind)
16470 Output linker options to @code{stdout}. Includes library search paths,
16471 contents of pragmas Ident and Linker_Options, and libraries added
16472 by @code{gnatbind}.
16474 @geindex -l (gnatbind)
16478 Output chosen elaboration order. The output is written to @code{stdout}.
16480 @geindex -O (gnatbind)
16484 Output full names of all the object files that must be linked to provide
16485 the Ada component of the program. The output is written to @code{stdout}.
16486 This list includes the files explicitly supplied and referenced by the user
16487 as well as implicitly referenced run-time unit files. The latter are
16488 omitted if the corresponding units reside in shared libraries. The
16489 directory names for the run-time units depend on the system configuration.
16491 @geindex -o (gnatbind)
16493 @item @code{-o @emph{file}}
16495 Set name of output file to @code{file} instead of the normal
16496 @code{b~`mainprog}.adb` default. Note that @code{file} denote the Ada
16497 binder generated body filename.
16498 Note that if this option is used, then linking must be done manually.
16499 It is not possible to use gnatlink in this case, since it cannot locate
16502 @geindex -r (gnatbind)
16506 Generate list of @code{pragma Restrictions} that could be applied to
16507 the current unit. This is useful for code audit purposes, and also may
16508 be used to improve code generation in some cases.
16511 @node Dynamic Allocation Control,Binding with Non-Ada Main Programs,Output Control,Switches for gnatbind
16512 @anchor{gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control}@anchor{121}@anchor{gnat_ugn/building_executable_programs_with_gnat id39}@anchor{12a}
16513 @subsubsection Dynamic Allocation Control
16516 The heap control switches -- @code{-H32} and @code{-H64} --
16517 determine whether dynamic allocation uses 32-bit or 64-bit memory.
16518 They only affect compiler-generated allocations via @code{__gnat_malloc};
16519 explicit calls to @code{malloc} and related functions from the C
16520 run-time library are unaffected.
16527 Allocate memory on 32-bit heap
16531 Allocate memory on 64-bit heap. This is the default
16532 unless explicitly overridden by a @code{'Size} clause on the access type.
16535 These switches are only effective on VMS platforms.
16537 @node Binding with Non-Ada Main Programs,Binding Programs with No Main Subprogram,Dynamic Allocation Control,Switches for gnatbind
16538 @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}
16539 @subsubsection Binding with Non-Ada Main Programs
16542 The description so far has assumed that the main
16543 program is in Ada, and that the task of the binder is to generate a
16544 corresponding function @code{main} that invokes this Ada main
16545 program. GNAT also supports the building of executable programs where
16546 the main program is not in Ada, but some of the called routines are
16547 written in Ada and compiled using GNAT (@ref{44,,Mixed Language Programming}).
16548 The following switch is used in this situation:
16552 @geindex -n (gnatbind)
16560 No main program. The main program is not in Ada.
16563 In this case, most of the functions of the binder are still required,
16564 but instead of generating a main program, the binder generates a file
16565 containing the following callable routines:
16574 @item @code{adainit}
16576 You must call this routine to initialize the Ada part of the program by
16577 calling the necessary elaboration routines. A call to @code{adainit} is
16578 required before the first call to an Ada subprogram.
16580 Note that it is assumed that the basic execution environment must be setup
16581 to be appropriate for Ada execution at the point where the first Ada
16582 subprogram is called. In particular, if the Ada code will do any
16583 floating-point operations, then the FPU must be setup in an appropriate
16584 manner. For the case of the x86, for example, full precision mode is
16585 required. The procedure GNAT.Float_Control.Reset may be used to ensure
16586 that the FPU is in the right state.
16594 @item @code{adafinal}
16596 You must call this routine to perform any library-level finalization
16597 required by the Ada subprograms. A call to @code{adafinal} is required
16598 after the last call to an Ada subprogram, and before the program
16603 @geindex -n (gnatbind)
16606 @geindex multiple input files
16608 If the @code{-n} switch
16609 is given, more than one ALI file may appear on
16610 the command line for @code{gnatbind}. The normal @code{closure}
16611 calculation is performed for each of the specified units. Calculating
16612 the closure means finding out the set of units involved by tracing
16613 @emph{with} references. The reason it is necessary to be able to
16614 specify more than one ALI file is that a given program may invoke two or
16615 more quite separate groups of Ada units.
16617 The binder takes the name of its output file from the last specified ALI
16618 file, unless overridden by the use of the @code{-o file}.
16620 @geindex -o (gnatbind)
16622 The output is an Ada unit in source form that can be compiled with GNAT.
16623 This compilation occurs automatically as part of the @code{gnatlink}
16626 Currently the GNAT run-time requires a FPU using 80 bits mode
16627 precision. Under targets where this is not the default it is required to
16628 call GNAT.Float_Control.Reset before using floating point numbers (this
16629 include float computation, float input and output) in the Ada code. A
16630 side effect is that this could be the wrong mode for the foreign code
16631 where floating point computation could be broken after this call.
16633 @node Binding Programs with No Main Subprogram,,Binding with Non-Ada Main Programs,Switches for gnatbind
16634 @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}
16635 @subsubsection Binding Programs with No Main Subprogram
16638 It is possible to have an Ada program which does not have a main
16639 subprogram. This program will call the elaboration routines of all the
16640 packages, then the finalization routines.
16642 The following switch is used to bind programs organized in this manner:
16646 @geindex -z (gnatbind)
16654 Normally the binder checks that the unit name given on the command line
16655 corresponds to a suitable main subprogram. When this switch is used,
16656 a list of ALI files can be given, and the execution of the program
16657 consists of elaboration of these units in an appropriate order. Note
16658 that the default wide character encoding method for standard Text_IO
16659 files is always set to Brackets if this switch is set (you can use
16661 @code{-Wx} to override this default).
16664 @node Command-Line Access,Search Paths for gnatbind,Switches for gnatbind,Binding with gnatbind
16665 @anchor{gnat_ugn/building_executable_programs_with_gnat id42}@anchor{12e}@anchor{gnat_ugn/building_executable_programs_with_gnat command-line-access}@anchor{12f}
16666 @subsection Command-Line Access
16669 The package @code{Ada.Command_Line} provides access to the command-line
16670 arguments and program name. In order for this interface to operate
16671 correctly, the two variables
16682 are declared in one of the GNAT library routines. These variables must
16683 be set from the actual @code{argc} and @code{argv} values passed to the
16684 main program. With no @emph{n} present, @code{gnatbind}
16685 generates the C main program to automatically set these variables.
16686 If the @emph{n} switch is used, there is no automatic way to
16687 set these variables. If they are not set, the procedures in
16688 @code{Ada.Command_Line} will not be available, and any attempt to use
16689 them will raise @code{Constraint_Error}. If command line access is
16690 required, your main program must set @code{gnat_argc} and
16691 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
16694 @node Search Paths for gnatbind,Examples of gnatbind Usage,Command-Line Access,Binding with gnatbind
16695 @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}
16696 @subsection Search Paths for @code{gnatbind}
16699 The binder takes the name of an ALI file as its argument and needs to
16700 locate source files as well as other ALI files to verify object consistency.
16702 For source files, it follows exactly the same search rules as @code{gcc}
16703 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). For ALI files the
16704 directories searched are:
16710 The directory containing the ALI file named in the command line, unless
16711 the switch @code{-I-} is specified.
16714 All directories specified by @code{-I}
16715 switches on the @code{gnatbind}
16716 command line, in the order given.
16718 @geindex ADA_PRJ_OBJECTS_FILE
16721 Each of the directories listed in the text file whose name is given
16723 @geindex ADA_PRJ_OBJECTS_FILE
16724 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16725 @code{ADA_PRJ_OBJECTS_FILE} environment variable.
16727 @geindex ADA_PRJ_OBJECTS_FILE
16728 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16729 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat
16730 driver when project files are used. It should not normally be set
16733 @geindex ADA_OBJECTS_PATH
16736 Each of the directories listed in the value of the
16737 @geindex ADA_OBJECTS_PATH
16738 @geindex environment variable; ADA_OBJECTS_PATH
16739 @code{ADA_OBJECTS_PATH} environment variable.
16740 Construct this value
16743 @geindex environment variable; PATH
16744 @code{PATH} environment variable: a list of directory
16745 names separated by colons (semicolons when working with the NT version
16749 The content of the @code{ada_object_path} file which is part of the GNAT
16750 installation tree and is used to store standard libraries such as the
16751 GNAT Run-Time Library (RTL) unless the switch @code{-nostdlib} is
16752 specified. See @ref{87,,Installing a library}
16755 @geindex -I (gnatbind)
16757 @geindex -aI (gnatbind)
16759 @geindex -aO (gnatbind)
16761 In the binder the switch @code{-I}
16762 is used to specify both source and
16763 library file paths. Use @code{-aI}
16764 instead if you want to specify
16765 source paths only, and @code{-aO}
16766 if you want to specify library paths
16767 only. This means that for the binder
16768 @code{-I@emph{dir}} is equivalent to
16769 @code{-aI@emph{dir}}
16770 @code{-aO`@emph{dir}}.
16771 The binder generates the bind file (a C language source file) in the
16772 current working directory.
16778 @geindex Interfaces
16782 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
16783 children make up the GNAT Run-Time Library, together with the package
16784 GNAT and its children, which contain a set of useful additional
16785 library functions provided by GNAT. The sources for these units are
16786 needed by the compiler and are kept together in one directory. The ALI
16787 files and object files generated by compiling the RTL are needed by the
16788 binder and the linker and are kept together in one directory, typically
16789 different from the directory containing the sources. In a normal
16790 installation, you need not specify these directory names when compiling
16791 or binding. Either the environment variables or the built-in defaults
16792 cause these files to be found.
16794 Besides simplifying access to the RTL, a major use of search paths is
16795 in compiling sources from multiple directories. This can make
16796 development environments much more flexible.
16798 @node Examples of gnatbind Usage,,Search Paths for gnatbind,Binding with gnatbind
16799 @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}
16800 @subsection Examples of @code{gnatbind} Usage
16803 Here are some examples of @code{gnatbind} invovations:
16811 The main program @code{Hello} (source program in @code{hello.adb}) is
16812 bound using the standard switch settings. The generated main program is
16813 @code{b~hello.adb}. This is the normal, default use of the binder.
16816 gnatbind hello -o mainprog.adb
16819 The main program @code{Hello} (source program in @code{hello.adb}) is
16820 bound using the standard switch settings. The generated main program is
16821 @code{mainprog.adb} with the associated spec in
16822 @code{mainprog.ads}. Note that you must specify the body here not the
16823 spec. Note that if this option is used, then linking must be done manually,
16824 since gnatlink will not be able to find the generated file.
16827 @node Linking with gnatlink,Using the GNU make Utility,Binding with gnatbind,Building Executable Programs with GNAT
16828 @anchor{gnat_ugn/building_executable_programs_with_gnat id45}@anchor{133}@anchor{gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink}@anchor{1e}
16829 @section Linking with @code{gnatlink}
16834 This chapter discusses @code{gnatlink}, a tool that links
16835 an Ada program and builds an executable file. This utility
16836 invokes the system linker (via the @code{gcc} command)
16837 with a correct list of object files and library references.
16838 @code{gnatlink} automatically determines the list of files and
16839 references for the Ada part of a program. It uses the binder file
16840 generated by the @code{gnatbind} to determine this list.
16843 * Running gnatlink::
16844 * Switches for gnatlink::
16848 @node Running gnatlink,Switches for gnatlink,,Linking with gnatlink
16849 @anchor{gnat_ugn/building_executable_programs_with_gnat id46}@anchor{134}@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatlink}@anchor{135}
16850 @subsection Running @code{gnatlink}
16853 The form of the @code{gnatlink} command is
16856 $ gnatlink [ switches ] mainprog [.ali]
16857 [ non-Ada objects ] [ linker options ]
16860 The arguments of @code{gnatlink} (switches, main @code{ALI} file,
16862 or linker options) may be in any order, provided that no non-Ada object may
16863 be mistaken for a main @code{ALI} file.
16864 Any file name @code{F} without the @code{.ali}
16865 extension will be taken as the main @code{ALI} file if a file exists
16866 whose name is the concatenation of @code{F} and @code{.ali}.
16868 @code{mainprog.ali} references the ALI file of the main program.
16869 The @code{.ali} extension of this file can be omitted. From this
16870 reference, @code{gnatlink} locates the corresponding binder file
16871 @code{b~mainprog.adb} and, using the information in this file along
16872 with the list of non-Ada objects and linker options, constructs a
16873 linker command file to create the executable.
16875 The arguments other than the @code{gnatlink} switches and the main
16876 @code{ALI} file are passed to the linker uninterpreted.
16877 They typically include the names of
16878 object files for units written in other languages than Ada and any library
16879 references required to resolve references in any of these foreign language
16880 units, or in @code{Import} pragmas in any Ada units.
16882 @code{linker options} is an optional list of linker specific
16884 The default linker called by gnatlink is @code{gcc} which in
16885 turn calls the appropriate system linker.
16887 One useful option for the linker is @code{-s}: it reduces the size of the
16888 executable by removing all symbol table and relocation information from the
16891 Standard options for the linker such as @code{-lmy_lib} or
16892 @code{-Ldir} can be added as is.
16893 For options that are not recognized by
16894 @code{gcc} as linker options, use the @code{gcc} switches
16895 @code{-Xlinker} or @code{-Wl,}.
16897 Refer to the GCC documentation for
16900 Here is an example showing how to generate a linker map:
16903 $ gnatlink my_prog -Wl,-Map,MAPFILE
16906 Using @code{linker options} it is possible to set the program stack and
16908 See @ref{136,,Setting Stack Size from gnatlink} and
16909 @ref{137,,Setting Heap Size from gnatlink}.
16911 @code{gnatlink} determines the list of objects required by the Ada
16912 program and prepends them to the list of objects passed to the linker.
16913 @code{gnatlink} also gathers any arguments set by the use of
16914 @code{pragma Linker_Options} and adds them to the list of arguments
16915 presented to the linker.
16917 @node Switches for gnatlink,,Running gnatlink,Linking with gnatlink
16918 @anchor{gnat_ugn/building_executable_programs_with_gnat id47}@anchor{138}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink}@anchor{139}
16919 @subsection Switches for @code{gnatlink}
16922 The following switches are available with the @code{gnatlink} utility:
16924 @geindex --version (gnatlink)
16929 @item @code{--version}
16931 Display Copyright and version, then exit disregarding all other options.
16934 @geindex --help (gnatlink)
16939 @item @code{--help}
16941 If @code{--version} was not used, display usage, then exit disregarding
16945 @geindex Command line length
16947 @geindex -f (gnatlink)
16954 On some targets, the command line length is limited, and @code{gnatlink}
16955 will generate a separate file for the linker if the list of object files
16957 The @code{-f} switch forces this file
16958 to be generated even if
16959 the limit is not exceeded. This is useful in some cases to deal with
16960 special situations where the command line length is exceeded.
16963 @geindex Debugging information
16966 @geindex -g (gnatlink)
16973 The option to include debugging information causes the Ada bind file (in
16974 other words, @code{b~mainprog.adb}) to be compiled with @code{-g}.
16975 In addition, the binder does not delete the @code{b~mainprog.adb},
16976 @code{b~mainprog.o} and @code{b~mainprog.ali} files.
16977 Without @code{-g}, the binder removes these files by default.
16980 @geindex -n (gnatlink)
16987 Do not compile the file generated by the binder. This may be used when
16988 a link is rerun with different options, but there is no need to recompile
16992 @geindex -v (gnatlink)
16999 Verbose mode. Causes additional information to be output, including a full
17000 list of the included object files.
17001 This switch option is most useful when you want
17002 to see what set of object files are being used in the link step.
17005 @geindex -v -v (gnatlink)
17012 Very verbose mode. Requests that the compiler operate in verbose mode when
17013 it compiles the binder file, and that the system linker run in verbose mode.
17016 @geindex -o (gnatlink)
17021 @item @code{-o @emph{exec-name}}
17023 @code{exec-name} specifies an alternate name for the generated
17024 executable program. If this switch is omitted, the executable has the same
17025 name as the main unit. For example, @code{gnatlink try.ali} creates
17026 an executable called @code{try}.
17029 @geindex -B (gnatlink)
17034 @item @code{-B@emph{dir}}
17036 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
17037 from @code{dir} instead of the default location. Only use this switch
17038 when multiple versions of the GNAT compiler are available.
17039 See the @code{Directory Options} section in @cite{The_GNU_Compiler_Collection}
17040 for further details. You would normally use the @code{-b} or
17041 @code{-V} switch instead.
17044 @geindex -M (gnatlink)
17051 When linking an executable, create a map file. The name of the map file
17052 has the same name as the executable with extension ".map".
17055 @geindex -M= (gnatlink)
17060 @item @code{-M=@emph{mapfile}}
17062 When linking an executable, create a map file. The name of the map file is
17066 @geindex --GCC=compiler_name (gnatlink)
17071 @item @code{--GCC=@emph{compiler_name}}
17073 Program used for compiling the binder file. The default is
17074 @code{gcc}. You need to use quotes around @code{compiler_name} if
17075 @code{compiler_name} contains spaces or other separator characters.
17076 As an example @code{--GCC="foo -x -y"} will instruct @code{gnatlink} to
17077 use @code{foo -x -y} as your compiler. Note that switch @code{-c} is always
17078 inserted after your command name. Thus in the above example the compiler
17079 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
17080 A limitation of this syntax is that the name and path name of the executable
17081 itself must not include any embedded spaces. If the compiler executable is
17082 different from the default one (gcc or <prefix>-gcc), then the back-end
17083 switches in the ALI file are not used to compile the binder generated source.
17084 For example, this is the case with @code{--GCC="foo -x -y"}. But the back end
17085 switches will be used for @code{--GCC="gcc -gnatv"}. If several
17086 @code{--GCC=compiler_name} are used, only the last @code{compiler_name}
17087 is taken into account. However, all the additional switches are also taken
17088 into account. Thus,
17089 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
17090 @code{--GCC="bar -x -y -z -t"}.
17093 @geindex --LINK= (gnatlink)
17098 @item @code{--LINK=@emph{name}}
17100 @code{name} is the name of the linker to be invoked. This is especially
17101 useful in mixed language programs since languages such as C++ require
17102 their own linker to be used. When this switch is omitted, the default
17103 name for the linker is @code{gcc}. When this switch is used, the
17104 specified linker is called instead of @code{gcc} with exactly the same
17105 parameters that would have been passed to @code{gcc} so if the desired
17106 linker requires different parameters it is necessary to use a wrapper
17107 script that massages the parameters before invoking the real linker. It
17108 may be useful to control the exact invocation by using the verbose
17112 @node Using the GNU make Utility,,Linking with gnatlink,Building Executable Programs with GNAT
17113 @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}
17114 @section Using the GNU @code{make} Utility
17117 @geindex make (GNU)
17120 This chapter offers some examples of makefiles that solve specific
17121 problems. It does not explain how to write a makefile, nor does it try to replace the
17122 @code{gnatmake} utility (@ref{1b,,Building with gnatmake}).
17124 All the examples in this section are specific to the GNU version of
17125 make. Although @code{make} is a standard utility, and the basic language
17126 is the same, these examples use some advanced features found only in
17130 * Using gnatmake in a Makefile::
17131 * Automatically Creating a List of Directories::
17132 * Generating the Command Line Switches::
17133 * Overcoming Command Line Length Limits::
17137 @node Using gnatmake in a Makefile,Automatically Creating a List of Directories,,Using the GNU make Utility
17138 @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}
17139 @subsection Using gnatmake in a Makefile
17142 @c index makefile (GNU make)
17144 Complex project organizations can be handled in a very powerful way by
17145 using GNU make combined with gnatmake. For instance, here is a Makefile
17146 which allows you to build each subsystem of a big project into a separate
17147 shared library. Such a makefile allows you to significantly reduce the link
17148 time of very big applications while maintaining full coherence at
17149 each step of the build process.
17151 The list of dependencies are handled automatically by
17152 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
17153 the appropriate directories.
17155 Note that you should also read the example on how to automatically
17156 create the list of directories
17157 (@ref{13d,,Automatically Creating a List of Directories})
17158 which might help you in case your project has a lot of subdirectories.
17161 ## This Makefile is intended to be used with the following directory
17163 ## - The sources are split into a series of csc (computer software components)
17164 ## Each of these csc is put in its own directory.
17165 ## Their name are referenced by the directory names.
17166 ## They will be compiled into shared library (although this would also work
17167 ## with static libraries
17168 ## - The main program (and possibly other packages that do not belong to any
17169 ## csc is put in the top level directory (where the Makefile is).
17170 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
17171 ## \\_ second_csc (sources) __ lib (will contain the library)
17173 ## Although this Makefile is build for shared library, it is easy to modify
17174 ## to build partial link objects instead (modify the lines with -shared and
17177 ## With this makefile, you can change any file in the system or add any new
17178 ## file, and everything will be recompiled correctly (only the relevant shared
17179 ## objects will be recompiled, and the main program will be re-linked).
17181 # The list of computer software component for your project. This might be
17182 # generated automatically.
17185 # Name of the main program (no extension)
17188 # If we need to build objects with -fPIC, uncomment the following line
17191 # The following variable should give the directory containing libgnat.so
17192 # You can get this directory through 'gnatls -v'. This is usually the last
17193 # directory in the Object_Path.
17196 # The directories for the libraries
17197 # (This macro expands the list of CSC to the list of shared libraries, you
17198 # could simply use the expanded form:
17199 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
17200 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
17202 $@{MAIN@}: objects $@{LIB_DIR@}
17203 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17204 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17207 # recompile the sources
17208 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17210 # Note: In a future version of GNAT, the following commands will be simplified
17211 # by a new tool, gnatmlib
17213 mkdir -p $@{dir $@@ @}
17214 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17215 cd $@{dir $@@ @} && cp -f ../*.ali .
17217 # The dependencies for the modules
17218 # Note that we have to force the expansion of *.o, since in some cases
17219 # make won't be able to do it itself.
17220 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17221 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17222 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17224 # Make sure all of the shared libraries are in the path before starting the
17227 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17230 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17231 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17232 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17233 $@{RM@} *.o *.ali $@{MAIN@}
17236 @node Automatically Creating a List of Directories,Generating the Command Line Switches,Using gnatmake in a Makefile,Using the GNU make Utility
17237 @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}
17238 @subsection Automatically Creating a List of Directories
17241 In most makefiles, you will have to specify a list of directories, and
17242 store it in a variable. For small projects, it is often easier to
17243 specify each of them by hand, since you then have full control over what
17244 is the proper order for these directories, which ones should be
17247 However, in larger projects, which might involve hundreds of
17248 subdirectories, it might be more convenient to generate this list
17251 The example below presents two methods. The first one, although less
17252 general, gives you more control over the list. It involves wildcard
17253 characters, that are automatically expanded by @code{make}. Its
17254 shortcoming is that you need to explicitly specify some of the
17255 organization of your project, such as for instance the directory tree
17256 depth, whether some directories are found in a separate tree, etc.
17258 The second method is the most general one. It requires an external
17259 program, called @code{find}, which is standard on all Unix systems. All
17260 the directories found under a given root directory will be added to the
17264 # The examples below are based on the following directory hierarchy:
17265 # All the directories can contain any number of files
17266 # ROOT_DIRECTORY -> a -> aa -> aaa
17269 # -> b -> ba -> baa
17272 # This Makefile creates a variable called DIRS, that can be reused any time
17273 # you need this list (see the other examples in this section)
17275 # The root of your project's directory hierarchy
17279 # First method: specify explicitly the list of directories
17280 # This allows you to specify any subset of all the directories you need.
17283 DIRS := a/aa/ a/ab/ b/ba/
17286 # Second method: use wildcards
17287 # Note that the argument(s) to wildcard below should end with a '/'.
17288 # Since wildcards also return file names, we have to filter them out
17289 # to avoid duplicate directory names.
17290 # We thus use make's `@w{`}dir`@w{`} and `@w{`}sort`@w{`} functions.
17291 # It sets DIRs to the following value (note that the directories aaa and baa
17292 # are not given, unless you change the arguments to wildcard).
17293 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17296 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17297 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17300 # Third method: use an external program
17301 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17302 # This is the most complete command: it sets DIRs to the following value:
17303 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17306 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17309 @node Generating the Command Line Switches,Overcoming Command Line Length Limits,Automatically Creating a List of Directories,Using the GNU make Utility
17310 @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}
17311 @subsection Generating the Command Line Switches
17314 Once you have created the list of directories as explained in the
17315 previous section (@ref{13d,,Automatically Creating a List of Directories}),
17316 you can easily generate the command line arguments to pass to gnatmake.
17318 For the sake of completeness, this example assumes that the source path
17319 is not the same as the object path, and that you have two separate lists
17323 # see "Automatically creating a list of directories" to create
17328 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17329 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17332 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17335 @node Overcoming Command Line Length Limits,,Generating the Command Line Switches,Using the GNU make Utility
17336 @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}
17337 @subsection Overcoming Command Line Length Limits
17340 One problem that might be encountered on big projects is that many
17341 operating systems limit the length of the command line. It is thus hard to give
17342 gnatmake the list of source and object directories.
17344 This example shows how you can set up environment variables, which will
17345 make @code{gnatmake} behave exactly as if the directories had been
17346 specified on the command line, but have a much higher length limit (or
17347 even none on most systems).
17349 It assumes that you have created a list of directories in your Makefile,
17350 using one of the methods presented in
17351 @ref{13d,,Automatically Creating a List of Directories}.
17352 For the sake of completeness, we assume that the object
17353 path (where the ALI files are found) is different from the sources patch.
17355 Note a small trick in the Makefile below: for efficiency reasons, we
17356 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17357 expanded immediately by @code{make}. This way we overcome the standard
17358 make behavior which is to expand the variables only when they are
17361 On Windows, if you are using the standard Windows command shell, you must
17362 replace colons with semicolons in the assignments to these variables.
17365 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
17366 # This is the same thing as putting the -I arguments on the command line.
17367 # (the equivalent of using -aI on the command line would be to define
17368 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
17369 # You can of course have different values for these variables.
17371 # Note also that we need to keep the previous values of these variables, since
17372 # they might have been set before running 'make' to specify where the GNAT
17373 # library is installed.
17375 # see "Automatically creating a list of directories" to create these
17381 space:=$@{empty@} $@{empty@}
17382 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17383 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17384 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17385 ADA_OBJECTS_PATH += $@{OBJECT_LIST@}
17386 export ADA_INCLUDE_PATH
17387 export ADA_OBJECTS_PATH
17393 @node GNAT Utility Programs,GNAT and Program Execution,Building Executable Programs with GNAT,Top
17394 @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}
17395 @chapter GNAT Utility Programs
17398 This chapter describes a number of utility programs:
17405 @ref{20,,The File Cleanup Utility gnatclean}
17408 @ref{21,,The GNAT Library Browser gnatls}
17411 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
17414 @ref{23,,The Ada to HTML Converter gnathtml}
17417 Other GNAT utilities are described elsewhere in this manual:
17423 @ref{59,,Handling Arbitrary File Naming Conventions with gnatname}
17426 @ref{63,,File Name Krunching with gnatkr}
17429 @ref{36,,Renaming Files with gnatchop}
17432 @ref{17,,Preprocessing with gnatprep}
17436 * The File Cleanup Utility gnatclean::
17437 * The GNAT Library Browser gnatls::
17438 * The Cross-Referencing Tools gnatxref and gnatfind::
17439 * The Ada to HTML Converter gnathtml::
17443 @node The File Cleanup Utility gnatclean,The GNAT Library Browser gnatls,,GNAT Utility Programs
17444 @anchor{gnat_ugn/gnat_utility_programs id2}@anchor{145}@anchor{gnat_ugn/gnat_utility_programs the-file-cleanup-utility-gnatclean}@anchor{20}
17445 @section The File Cleanup Utility @code{gnatclean}
17448 @geindex File cleanup tool
17452 @code{gnatclean} is a tool that allows the deletion of files produced by the
17453 compiler, binder and linker, including ALI files, object files, tree files,
17454 expanded source files, library files, interface copy source files, binder
17455 generated files and executable files.
17458 * Running gnatclean::
17459 * Switches for gnatclean::
17463 @node Running gnatclean,Switches for gnatclean,,The File Cleanup Utility gnatclean
17464 @anchor{gnat_ugn/gnat_utility_programs running-gnatclean}@anchor{146}@anchor{gnat_ugn/gnat_utility_programs id3}@anchor{147}
17465 @subsection Running @code{gnatclean}
17468 The @code{gnatclean} command has the form:
17473 $ gnatclean switches names
17477 where @code{names} is a list of source file names. Suffixes @code{.ads} and
17478 @code{adb} may be omitted. If a project file is specified using switch
17479 @code{-P}, then @code{names} may be completely omitted.
17481 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
17482 if switch @code{-c} is not specified, by the binder and
17483 the linker. In informative-only mode, specified by switch
17484 @code{-n}, the list of files that would have been deleted in
17485 normal mode is listed, but no file is actually deleted.
17487 @node Switches for gnatclean,,Running gnatclean,The File Cleanup Utility gnatclean
17488 @anchor{gnat_ugn/gnat_utility_programs id4}@anchor{148}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatclean}@anchor{149}
17489 @subsection Switches for @code{gnatclean}
17492 @code{gnatclean} recognizes the following switches:
17494 @geindex --version (gnatclean)
17499 @item @code{--version}
17501 Display copyright and version, then exit disregarding all other options.
17504 @geindex --help (gnatclean)
17509 @item @code{--help}
17511 If @code{--version} was not used, display usage, then exit disregarding
17514 @item @code{--subdirs=@emph{subdir}}
17516 Actual object directory of each project file is the subdirectory subdir of the
17517 object directory specified or defaulted in the project file.
17519 @item @code{--unchecked-shared-lib-imports}
17521 By default, shared library projects are not allowed to import static library
17522 projects. When this switch is used on the command line, this restriction is
17526 @geindex -c (gnatclean)
17533 Only attempt to delete the files produced by the compiler, not those produced
17534 by the binder or the linker. The files that are not to be deleted are library
17535 files, interface copy files, binder generated files and executable files.
17538 @geindex -D (gnatclean)
17543 @item @code{-D @emph{dir}}
17545 Indicate that ALI and object files should normally be found in directory @code{dir}.
17548 @geindex -F (gnatclean)
17555 When using project files, if some errors or warnings are detected during
17556 parsing and verbose mode is not in effect (no use of switch
17557 -v), then error lines start with the full path name of the project
17558 file, rather than its simple file name.
17561 @geindex -h (gnatclean)
17568 Output a message explaining the usage of @code{gnatclean}.
17571 @geindex -n (gnatclean)
17578 Informative-only mode. Do not delete any files. Output the list of the files
17579 that would have been deleted if this switch was not specified.
17582 @geindex -P (gnatclean)
17587 @item @code{-P@emph{project}}
17589 Use project file @code{project}. Only one such switch can be used.
17590 When cleaning a project file, the files produced by the compilation of the
17591 immediate sources or inherited sources of the project files are to be
17592 deleted. This is not depending on the presence or not of executable names
17593 on the command line.
17596 @geindex -q (gnatclean)
17603 Quiet output. If there are no errors, do not output anything, except in
17604 verbose mode (switch -v) or in informative-only mode
17608 @geindex -r (gnatclean)
17615 When a project file is specified (using switch -P),
17616 clean all imported and extended project files, recursively. If this switch
17617 is not specified, only the files related to the main project file are to be
17618 deleted. This switch has no effect if no project file is specified.
17621 @geindex -v (gnatclean)
17631 @geindex -vP (gnatclean)
17636 @item @code{-vP@emph{x}}
17638 Indicates the verbosity of the parsing of GNAT project files.
17639 @ref{de,,Switches Related to Project Files}.
17642 @geindex -X (gnatclean)
17647 @item @code{-X@emph{name}=@emph{value}}
17649 Indicates that external variable @code{name} has the value @code{value}.
17650 The Project Manager will use this value for occurrences of
17651 @code{external(name)} when parsing the project file.
17652 See @ref{de,,Switches Related to Project Files}.
17655 @geindex -aO (gnatclean)
17660 @item @code{-aO@emph{dir}}
17662 When searching for ALI and object files, look in directory @code{dir}.
17665 @geindex -I (gnatclean)
17670 @item @code{-I@emph{dir}}
17672 Equivalent to @code{-aO@emph{dir}}.
17675 @geindex -I- (gnatclean)
17677 @geindex Source files
17678 @geindex suppressing search
17685 Do not look for ALI or object files in the directory
17686 where @code{gnatclean} was invoked.
17689 @node The GNAT Library Browser gnatls,The Cross-Referencing Tools gnatxref and gnatfind,The File Cleanup Utility gnatclean,GNAT Utility Programs
17690 @anchor{gnat_ugn/gnat_utility_programs the-gnat-library-browser-gnatls}@anchor{21}@anchor{gnat_ugn/gnat_utility_programs id5}@anchor{14a}
17691 @section The GNAT Library Browser @code{gnatls}
17694 @geindex Library browser
17698 @code{gnatls} is a tool that outputs information about compiled
17699 units. It gives the relationship between objects, unit names and source
17700 files. It can also be used to check the source dependencies of a unit
17701 as well as various characteristics.
17705 * Switches for gnatls::
17706 * Example of gnatls Usage::
17710 @node Running gnatls,Switches for gnatls,,The GNAT Library Browser gnatls
17711 @anchor{gnat_ugn/gnat_utility_programs id6}@anchor{14b}@anchor{gnat_ugn/gnat_utility_programs running-gnatls}@anchor{14c}
17712 @subsection Running @code{gnatls}
17715 The @code{gnatls} command has the form
17720 $ gnatls switches object_or_ali_file
17724 The main argument is the list of object or @code{ali} files
17725 (see @ref{42,,The Ada Library Information Files})
17726 for which information is requested.
17728 In normal mode, without additional option, @code{gnatls} produces a
17729 four-column listing. Each line represents information for a specific
17730 object. The first column gives the full path of the object, the second
17731 column gives the name of the principal unit in this object, the third
17732 column gives the status of the source and the fourth column gives the
17733 full path of the source representing this unit.
17734 Here is a simple example of use:
17740 ./demo1.o demo1 DIF demo1.adb
17741 ./demo2.o demo2 OK demo2.adb
17742 ./hello.o h1 OK hello.adb
17743 ./instr-child.o instr.child MOK instr-child.adb
17744 ./instr.o instr OK instr.adb
17745 ./tef.o tef DIF tef.adb
17746 ./text_io_example.o text_io_example OK text_io_example.adb
17747 ./tgef.o tgef DIF tgef.adb
17751 The first line can be interpreted as follows: the main unit which is
17753 object file @code{demo1.o} is demo1, whose main source is in
17754 @code{demo1.adb}. Furthermore, the version of the source used for the
17755 compilation of demo1 has been modified (DIF). Each source file has a status
17756 qualifier which can be:
17761 @item @emph{OK (unchanged)}
17763 The version of the source file used for the compilation of the
17764 specified unit corresponds exactly to the actual source file.
17766 @item @emph{MOK (slightly modified)}
17768 The version of the source file used for the compilation of the
17769 specified unit differs from the actual source file but not enough to
17770 require recompilation. If you use gnatmake with the option
17771 @code{-m} (minimal recompilation), a file marked
17772 MOK will not be recompiled.
17774 @item @emph{DIF (modified)}
17776 No version of the source found on the path corresponds to the source
17777 used to build this object.
17779 @item @emph{??? (file not found)}
17781 No source file was found for this unit.
17783 @item @emph{HID (hidden, unchanged version not first on PATH)}
17785 The version of the source that corresponds exactly to the source used
17786 for compilation has been found on the path but it is hidden by another
17787 version of the same source that has been modified.
17790 @node Switches for gnatls,Example of gnatls Usage,Running gnatls,The GNAT Library Browser gnatls
17791 @anchor{gnat_ugn/gnat_utility_programs id7}@anchor{14d}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatls}@anchor{14e}
17792 @subsection Switches for @code{gnatls}
17795 @code{gnatls} recognizes the following switches:
17797 @geindex --version (gnatls)
17802 @item @code{--version}
17804 Display copyright and version, then exit disregarding all other options.
17807 @geindex --help (gnatls)
17812 @item @code{--help}
17814 If @code{--version} was not used, display usage, then exit disregarding
17818 @geindex -a (gnatls)
17825 Consider all units, including those of the predefined Ada library.
17826 Especially useful with @code{-d}.
17829 @geindex -d (gnatls)
17836 List sources from which specified units depend on.
17839 @geindex -h (gnatls)
17846 Output the list of options.
17849 @geindex -o (gnatls)
17856 Only output information about object files.
17859 @geindex -s (gnatls)
17866 Only output information about source files.
17869 @geindex -u (gnatls)
17876 Only output information about compilation units.
17879 @geindex -files (gnatls)
17884 @item @code{-files=@emph{file}}
17886 Take as arguments the files listed in text file @code{file}.
17887 Text file @code{file} may contain empty lines that are ignored.
17888 Each nonempty line should contain the name of an existing file.
17889 Several such switches may be specified simultaneously.
17892 @geindex -aO (gnatls)
17894 @geindex -aI (gnatls)
17896 @geindex -I (gnatls)
17898 @geindex -I- (gnatls)
17903 @item @code{-aO@emph{dir}}, @code{-aI@emph{dir}}, @code{-I@emph{dir}}, @code{-I-}, @code{-nostdinc}
17905 Source path manipulation. Same meaning as the equivalent @code{gnatmake}
17906 flags (@ref{dc,,Switches for gnatmake}).
17909 @geindex -aP (gnatls)
17914 @item @code{-aP@emph{dir}}
17916 Add @code{dir} at the beginning of the project search dir.
17919 @geindex --RTS (gnatls)
17924 @item @code{--RTS=@emph{rts-path}}
17926 Specifies the default location of the runtime library. Same meaning as the
17927 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
17930 @geindex -v (gnatls)
17937 Verbose mode. Output the complete source, object and project paths. Do not use
17938 the default column layout but instead use long format giving as much as
17939 information possible on each requested units, including special
17940 characteristics such as:
17946 @emph{Preelaborable}: The unit is preelaborable in the Ada sense.
17949 @emph{No_Elab_Code}: No elaboration code has been produced by the compiler for this unit.
17952 @emph{Pure}: The unit is pure in the Ada sense.
17955 @emph{Elaborate_Body}: The unit contains a pragma Elaborate_Body.
17958 @emph{Remote_Types}: The unit contains a pragma Remote_Types.
17961 @emph{Shared_Passive}: The unit contains a pragma Shared_Passive.
17964 @emph{Predefined}: This unit is part of the predefined environment and cannot be modified
17968 @emph{Remote_Call_Interface}: The unit contains a pragma Remote_Call_Interface.
17972 @node Example of gnatls Usage,,Switches for gnatls,The GNAT Library Browser gnatls
17973 @anchor{gnat_ugn/gnat_utility_programs id8}@anchor{14f}@anchor{gnat_ugn/gnat_utility_programs example-of-gnatls-usage}@anchor{150}
17974 @subsection Example of @code{gnatls} Usage
17977 Example of using the verbose switch. Note how the source and
17978 object paths are affected by the -I switch.
17983 $ gnatls -v -I.. demo1.o
17985 GNATLS 5.03w (20041123-34)
17986 Copyright 1997-2004 Free Software Foundation, Inc.
17988 Source Search Path:
17989 <Current_Directory>
17991 /home/comar/local/adainclude/
17993 Object Search Path:
17994 <Current_Directory>
17996 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
17998 Project Search Path:
17999 <Current_Directory>
18000 /home/comar/local/lib/gnat/
18005 Kind => subprogram body
18006 Flags => No_Elab_Code
18007 Source => demo1.adb modified
18011 The following is an example of use of the dependency list.
18012 Note the use of the -s switch
18013 which gives a straight list of source files. This can be useful for
18014 building specialized scripts.
18019 $ gnatls -d demo2.o
18020 ./demo2.o demo2 OK demo2.adb
18026 $ gnatls -d -s -a demo1.o
18028 /home/comar/local/adainclude/ada.ads
18029 /home/comar/local/adainclude/a-finali.ads
18030 /home/comar/local/adainclude/a-filico.ads
18031 /home/comar/local/adainclude/a-stream.ads
18032 /home/comar/local/adainclude/a-tags.ads
18035 /home/comar/local/adainclude/gnat.ads
18036 /home/comar/local/adainclude/g-io.ads
18038 /home/comar/local/adainclude/system.ads
18039 /home/comar/local/adainclude/s-exctab.ads
18040 /home/comar/local/adainclude/s-finimp.ads
18041 /home/comar/local/adainclude/s-finroo.ads
18042 /home/comar/local/adainclude/s-secsta.ads
18043 /home/comar/local/adainclude/s-stalib.ads
18044 /home/comar/local/adainclude/s-stoele.ads
18045 /home/comar/local/adainclude/s-stratt.ads
18046 /home/comar/local/adainclude/s-tasoli.ads
18047 /home/comar/local/adainclude/s-unstyp.ads
18048 /home/comar/local/adainclude/unchconv.ads
18052 @node The Cross-Referencing Tools gnatxref and gnatfind,The Ada to HTML Converter gnathtml,The GNAT Library Browser gnatls,GNAT Utility Programs
18053 @anchor{gnat_ugn/gnat_utility_programs the-cross-referencing-tools-gnatxref-and-gnatfind}@anchor{22}@anchor{gnat_ugn/gnat_utility_programs id9}@anchor{151}
18054 @section The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
18061 The compiler generates cross-referencing information (unless
18062 you set the @code{-gnatx} switch), which are saved in the @code{.ali} files.
18063 This information indicates where in the source each entity is declared and
18064 referenced. Note that entities in package Standard are not included, but
18065 entities in all other predefined units are included in the output.
18067 Before using any of these two tools, you need to compile successfully your
18068 application, so that GNAT gets a chance to generate the cross-referencing
18071 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
18072 information to provide the user with the capability to easily locate the
18073 declaration and references to an entity. These tools are quite similar,
18074 the difference being that @code{gnatfind} is intended for locating
18075 definitions and/or references to a specified entity or entities, whereas
18076 @code{gnatxref} is oriented to generating a full report of all
18079 To use these tools, you must not compile your application using the
18080 @code{-gnatx} switch on the @code{gnatmake} command line
18081 (see @ref{1b,,Building with gnatmake}). Otherwise, cross-referencing
18082 information will not be generated.
18085 * gnatxref Switches::
18086 * gnatfind Switches::
18087 * Configuration Files for gnatxref and gnatfind::
18088 * Regular Expressions in gnatfind and gnatxref::
18089 * Examples of gnatxref Usage::
18090 * Examples of gnatfind Usage::
18094 @node gnatxref Switches,gnatfind Switches,,The Cross-Referencing Tools gnatxref and gnatfind
18095 @anchor{gnat_ugn/gnat_utility_programs id10}@anchor{152}@anchor{gnat_ugn/gnat_utility_programs gnatxref-switches}@anchor{153}
18096 @subsection @code{gnatxref} Switches
18099 The command invocation for @code{gnatxref} is:
18104 $ gnatxref [ switches ] sourcefile1 [ sourcefile2 ... ]
18113 @item @code{sourcefile1} [, @code{sourcefile2} ...]
18115 identify the source files for which a report is to be generated. The
18116 @code{with}ed units will be processed too. You must provide at least one file.
18118 These file names are considered to be regular expressions, so for instance
18119 specifying @code{source*.adb} is the same as giving every file in the current
18120 directory whose name starts with @code{source} and whose extension is
18123 You shouldn't specify any directory name, just base names. @code{gnatxref}
18124 and @code{gnatfind} will be able to locate these files by themselves using
18125 the source path. If you specify directories, no result is produced.
18128 The following switches are available for @code{gnatxref}:
18130 @geindex --version (gnatxref)
18135 @item @code{--version}
18137 Display copyright and version, then exit disregarding all other options.
18140 @geindex --help (gnatxref)
18145 @item @code{--help}
18147 If @code{--version} was not used, display usage, then exit disregarding
18151 @geindex -a (gnatxref)
18158 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18159 the read-only files found in the library search path. Otherwise, these files
18160 will be ignored. This option can be used to protect Gnat sources or your own
18161 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18162 much faster, and their output much smaller. Read-only here refers to access
18163 or permissions status in the file system for the current user.
18166 @geindex -aIDIR (gnatxref)
18171 @item @code{-aI@emph{DIR}}
18173 When looking for source files also look in directory DIR. The order in which
18174 source file search is undertaken is the same as for @code{gnatmake}.
18177 @geindex -aODIR (gnatxref)
18182 @item @code{aO@emph{DIR}}
18184 When -searching for library and object files, look in directory
18185 DIR. The order in which library files are searched is the same as for
18189 @geindex -nostdinc (gnatxref)
18194 @item @code{-nostdinc}
18196 Do not look for sources in the system default directory.
18199 @geindex -nostdlib (gnatxref)
18204 @item @code{-nostdlib}
18206 Do not look for library files in the system default directory.
18209 @geindex --ext (gnatxref)
18214 @item @code{--ext=@emph{extension}}
18216 Specify an alternate ali file extension. The default is @code{ali} and other
18217 extensions (e.g. @code{gli} for C/C++ sources) may be specified via this switch.
18218 Note that if this switch overrides the default, only the new extension will
18222 @geindex --RTS (gnatxref)
18227 @item @code{--RTS=@emph{rts-path}}
18229 Specifies the default location of the runtime library. Same meaning as the
18230 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18233 @geindex -d (gnatxref)
18240 If this switch is set @code{gnatxref} will output the parent type
18241 reference for each matching derived types.
18244 @geindex -f (gnatxref)
18251 If this switch is set, the output file names will be preceded by their
18252 directory (if the file was found in the search path). If this switch is
18253 not set, the directory will not be printed.
18256 @geindex -g (gnatxref)
18263 If this switch is set, information is output only for library-level
18264 entities, ignoring local entities. The use of this switch may accelerate
18265 @code{gnatfind} and @code{gnatxref}.
18268 @geindex -IDIR (gnatxref)
18273 @item @code{-I@emph{DIR}}
18275 Equivalent to @code{-aODIR -aIDIR}.
18278 @geindex -pFILE (gnatxref)
18283 @item @code{-p@emph{FILE}}
18285 Specify a configuration file to use to list the source and object directories.
18287 If a file is specified, then the content of the source directory and object
18288 directory lines are added as if they had been specified respectively
18289 by @code{-aI} and @code{-aO}.
18291 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18292 of this configuration file.
18296 Output only unused symbols. This may be really useful if you give your
18297 main compilation unit on the command line, as @code{gnatxref} will then
18298 display every unused entity and 'with'ed package.
18302 Instead of producing the default output, @code{gnatxref} will generate a
18303 @code{tags} file that can be used by vi. For examples how to use this
18304 feature, see @ref{155,,Examples of gnatxref Usage}. The tags file is output
18305 to the standard output, thus you will have to redirect it to a file.
18308 All these switches may be in any order on the command line, and may even
18309 appear after the file names. They need not be separated by spaces, thus
18310 you can say @code{gnatxref -ag} instead of @code{gnatxref -a -g}.
18312 @node gnatfind Switches,Configuration Files for gnatxref and gnatfind,gnatxref Switches,The Cross-Referencing Tools gnatxref and gnatfind
18313 @anchor{gnat_ugn/gnat_utility_programs id11}@anchor{156}@anchor{gnat_ugn/gnat_utility_programs gnatfind-switches}@anchor{157}
18314 @subsection @code{gnatfind} Switches
18317 The command invocation for @code{gnatfind} is:
18322 $ gnatfind [ switches ] pattern[:sourcefile[:line[:column]]]
18327 with the following iterpretation of the command arguments:
18332 @item @emph{pattern}
18334 An entity will be output only if it matches the regular expression found
18335 in @emph{pattern}, see @ref{158,,Regular Expressions in gnatfind and gnatxref}.
18337 Omitting the pattern is equivalent to specifying @code{*}, which
18338 will match any entity. Note that if you do not provide a pattern, you
18339 have to provide both a sourcefile and a line.
18341 Entity names are given in Latin-1, with uppercase/lowercase equivalence
18342 for matching purposes. At the current time there is no support for
18343 8-bit codes other than Latin-1, or for wide characters in identifiers.
18345 @item @emph{sourcefile}
18347 @code{gnatfind} will look for references, bodies or declarations
18348 of symbols referenced in @code{sourcefile}, at line @code{line}
18349 and column @code{column}. See @ref{159,,Examples of gnatfind Usage}
18350 for syntax examples.
18354 A decimal integer identifying the line number containing
18355 the reference to the entity (or entities) to be located.
18357 @item @emph{column}
18359 A decimal integer identifying the exact location on the
18360 line of the first character of the identifier for the
18361 entity reference. Columns are numbered from 1.
18363 @item @emph{file1 file2 ...}
18365 The search will be restricted to these source files. If none are given, then
18366 the search will be conducted for every library file in the search path.
18367 These files must appear only after the pattern or sourcefile.
18369 These file names are considered to be regular expressions, so for instance
18370 specifying @code{source*.adb} is the same as giving every file in the current
18371 directory whose name starts with @code{source} and whose extension is
18374 The location of the spec of the entity will always be displayed, even if it
18375 isn't in one of @code{file1}, @code{file2}, ... The
18376 occurrences of the entity in the separate units of the ones given on the
18377 command line will also be displayed.
18379 Note that if you specify at least one file in this part, @code{gnatfind} may
18380 sometimes not be able to find the body of the subprograms.
18383 At least one of 'sourcefile' or 'pattern' has to be present on
18386 The following switches are available:
18388 @geindex --version (gnatfind)
18393 @item @code{--version}
18395 Display copyright and version, then exit disregarding all other options.
18398 @geindex --help (gnatfind)
18403 @item @code{--help}
18405 If @code{--version} was not used, display usage, then exit disregarding
18409 @geindex -a (gnatfind)
18416 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18417 the read-only files found in the library search path. Otherwise, these files
18418 will be ignored. This option can be used to protect Gnat sources or your own
18419 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18420 much faster, and their output much smaller. Read-only here refers to access
18421 or permission status in the file system for the current user.
18424 @geindex -aIDIR (gnatfind)
18429 @item @code{-aI@emph{DIR}}
18431 When looking for source files also look in directory DIR. The order in which
18432 source file search is undertaken is the same as for @code{gnatmake}.
18435 @geindex -aODIR (gnatfind)
18440 @item @code{-aO@emph{DIR}}
18442 When searching for library and object files, look in directory
18443 DIR. The order in which library files are searched is the same as for
18447 @geindex -nostdinc (gnatfind)
18452 @item @code{-nostdinc}
18454 Do not look for sources in the system default directory.
18457 @geindex -nostdlib (gnatfind)
18462 @item @code{-nostdlib}
18464 Do not look for library files in the system default directory.
18467 @geindex --ext (gnatfind)
18472 @item @code{--ext=@emph{extension}}
18474 Specify an alternate ali file extension. The default is @code{ali} and other
18475 extensions may be specified via this switch. Note that if this switch
18476 overrides the default, only the new extension will be considered.
18479 @geindex --RTS (gnatfind)
18484 @item @code{--RTS=@emph{rts-path}}
18486 Specifies the default location of the runtime library. Same meaning as the
18487 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18490 @geindex -d (gnatfind)
18497 If this switch is set, then @code{gnatfind} will output the parent type
18498 reference for each matching derived types.
18501 @geindex -e (gnatfind)
18508 By default, @code{gnatfind} accept the simple regular expression set for
18509 @code{pattern}. If this switch is set, then the pattern will be
18510 considered as full Unix-style regular expression.
18513 @geindex -f (gnatfind)
18520 If this switch is set, the output file names will be preceded by their
18521 directory (if the file was found in the search path). If this switch is
18522 not set, the directory will not be printed.
18525 @geindex -g (gnatfind)
18532 If this switch is set, information is output only for library-level
18533 entities, ignoring local entities. The use of this switch may accelerate
18534 @code{gnatfind} and @code{gnatxref}.
18537 @geindex -IDIR (gnatfind)
18542 @item @code{-I@emph{DIR}}
18544 Equivalent to @code{-aODIR -aIDIR}.
18547 @geindex -pFILE (gnatfind)
18552 @item @code{-p@emph{FILE}}
18554 Specify a configuration file to use to list the source and object directories.
18556 If a file is specified, then the content of the source directory and object
18557 directory lines are added as if they had been specified respectively
18558 by @code{-aI} and @code{-aO}.
18560 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18561 of this configuration file.
18564 @geindex -r (gnatfind)
18571 By default, @code{gnatfind} will output only the information about the
18572 declaration, body or type completion of the entities. If this switch is
18573 set, the @code{gnatfind} will locate every reference to the entities in
18574 the files specified on the command line (or in every file in the search
18575 path if no file is given on the command line).
18578 @geindex -s (gnatfind)
18585 If this switch is set, then @code{gnatfind} will output the content
18586 of the Ada source file lines were the entity was found.
18589 @geindex -t (gnatfind)
18596 If this switch is set, then @code{gnatfind} will output the type hierarchy for
18597 the specified type. It act like -d option but recursively from parent
18598 type to parent type. When this switch is set it is not possible to
18599 specify more than one file.
18602 All these switches may be in any order on the command line, and may even
18603 appear after the file names. They need not be separated by spaces, thus
18604 you can say @code{gnatxref -ag} instead of
18605 @code{gnatxref -a -g}.
18607 As stated previously, @code{gnatfind} will search in every directory in the
18608 search path. You can force it to look only in the current directory if
18609 you specify @code{*} at the end of the command line.
18611 @node Configuration Files for gnatxref and gnatfind,Regular Expressions in gnatfind and gnatxref,gnatfind Switches,The Cross-Referencing Tools gnatxref and gnatfind
18612 @anchor{gnat_ugn/gnat_utility_programs configuration-files-for-gnatxref-and-gnatfind}@anchor{154}@anchor{gnat_ugn/gnat_utility_programs id12}@anchor{15a}
18613 @subsection Configuration Files for @code{gnatxref} and @code{gnatfind}
18616 Configuration files are used by @code{gnatxref} and @code{gnatfind} to specify
18617 the list of source and object directories to consider. They can be
18618 specified via the @code{-p} switch.
18620 The following lines can be included, in any order in the file:
18629 @item @emph{src_dir=DIR}
18631 [default: @code{"./"}].
18632 Specifies a directory where to look for source files. Multiple @code{src_dir}
18633 lines can be specified and they will be searched in the order they
18641 @item @emph{obj_dir=DIR}
18643 [default: @code{"./"}].
18644 Specifies a directory where to look for object and library files. Multiple
18645 @code{obj_dir} lines can be specified, and they will be searched in the order
18650 Any other line will be silently ignored.
18652 @node Regular Expressions in gnatfind and gnatxref,Examples of gnatxref Usage,Configuration Files for gnatxref and gnatfind,The Cross-Referencing Tools gnatxref and gnatfind
18653 @anchor{gnat_ugn/gnat_utility_programs id13}@anchor{15b}@anchor{gnat_ugn/gnat_utility_programs regular-expressions-in-gnatfind-and-gnatxref}@anchor{158}
18654 @subsection Regular Expressions in @code{gnatfind} and @code{gnatxref}
18657 As specified in the section about @code{gnatfind}, the pattern can be a
18658 regular expression. Two kinds of regular expressions
18668 @item @emph{Globbing pattern}
18670 These are the most common regular expression. They are the same as are
18671 generally used in a Unix shell command line, or in a DOS session.
18673 Here is a more formal grammar:
18677 term ::= elmt -- matches elmt
18678 term ::= elmt elmt -- concatenation (elmt then elmt)
18679 term ::= * -- any string of 0 or more characters
18680 term ::= ? -- matches any character
18681 term ::= [char @{char@}] -- matches any character listed
18682 term ::= [char - char] -- matches any character in range
18690 @item @emph{Full regular expression}
18692 The second set of regular expressions is much more powerful. This is the
18693 type of regular expressions recognized by utilities such as @code{grep}.
18695 The following is the form of a regular expression, expressed in same BNF
18696 style as is found in the Ada Reference Manual:
18699 regexp ::= term @{| term@} -- alternation (term or term ...)
18701 term ::= item @{item@} -- concatenation (item then item)
18703 item ::= elmt -- match elmt
18704 item ::= elmt * -- zero or more elmt's
18705 item ::= elmt + -- one or more elmt's
18706 item ::= elmt ? -- matches elmt or nothing
18708 elmt ::= nschar -- matches given character
18709 elmt ::= [nschar @{nschar@}] -- matches any character listed
18710 elmt ::= [^ nschar @{nschar@}] -- matches any character not listed
18711 elmt ::= [char - char] -- matches chars in given range
18712 elmt ::= \\ char -- matches given character
18713 elmt ::= . -- matches any single character
18714 elmt ::= ( regexp ) -- parens used for grouping
18716 char ::= any character, including special characters
18717 nschar ::= any character except ()[].*+?^
18720 Here are a few examples:
18727 @item @code{abcde|fghi}
18729 will match any of the two strings @code{abcde} and @code{fghi},
18733 will match any string like @code{abd}, @code{abcd}, @code{abccd},
18734 @code{abcccd}, and so on,
18736 @item @code{[a-z]+}
18738 will match any string which has only lowercase characters in it (and at
18739 least one character.
18745 @node Examples of gnatxref Usage,Examples of gnatfind Usage,Regular Expressions in gnatfind and gnatxref,The Cross-Referencing Tools gnatxref and gnatfind
18746 @anchor{gnat_ugn/gnat_utility_programs examples-of-gnatxref-usage}@anchor{155}@anchor{gnat_ugn/gnat_utility_programs id14}@anchor{15c}
18747 @subsection Examples of @code{gnatxref} Usage
18752 * Using gnatxref with vi::
18756 @node General Usage,Using gnatxref with vi,,Examples of gnatxref Usage
18757 @anchor{gnat_ugn/gnat_utility_programs general-usage}@anchor{15d}
18758 @subsubsection General Usage
18761 For the following examples, we will consider the following units:
18769 3: procedure Foo (B : in Integer);
18776 1: package body Main is
18777 2: procedure Foo (B : in Integer) is
18788 2: procedure Print (B : Integer);
18793 The first thing to do is to recompile your application (for instance, in
18794 that case just by doing a @code{gnatmake main}, so that GNAT generates
18795 the cross-referencing information.
18796 You can then issue any of the following commands:
18804 @code{gnatxref main.adb}
18805 @code{gnatxref} generates cross-reference information for main.adb
18806 and every unit 'with'ed by main.adb.
18808 The output would be:
18816 Decl: main.ads 3:20
18817 Body: main.adb 2:20
18818 Ref: main.adb 4:13 5:13 6:19
18821 Ref: main.adb 6:8 7:8
18831 Decl: main.ads 3:15
18832 Body: main.adb 2:15
18835 Body: main.adb 1:14
18838 Ref: main.adb 6:12 7:12
18842 This shows that the entity @code{Main} is declared in main.ads, line 2, column 9,
18843 its body is in main.adb, line 1, column 14 and is not referenced any where.
18845 The entity @code{Print} is declared in @code{bar.ads}, line 2, column 15 and it
18846 is referenced in @code{main.adb}, line 6 column 12 and line 7 column 12.
18849 @code{gnatxref package1.adb package2.ads}
18850 @code{gnatxref} will generates cross-reference information for
18851 @code{package1.adb}, @code{package2.ads} and any other package @code{with}ed by any
18856 @node Using gnatxref with vi,,General Usage,Examples of gnatxref Usage
18857 @anchor{gnat_ugn/gnat_utility_programs using-gnatxref-with-vi}@anchor{15e}
18858 @subsubsection Using @code{gnatxref} with @code{vi}
18861 @code{gnatxref} can generate a tags file output, which can be used
18862 directly from @code{vi}. Note that the standard version of @code{vi}
18863 will not work properly with overloaded symbols. Consider using another
18864 free implementation of @code{vi}, such as @code{vim}.
18869 $ gnatxref -v gnatfind.adb > tags
18873 The following command will generate the tags file for @code{gnatfind} itself
18874 (if the sources are in the search path!):
18879 $ gnatxref -v gnatfind.adb > tags
18883 From @code{vi}, you can then use the command @code{:tag @emph{entity}}
18884 (replacing @code{entity} by whatever you are looking for), and vi will
18885 display a new file with the corresponding declaration of entity.
18887 @node Examples of gnatfind Usage,,Examples of gnatxref Usage,The Cross-Referencing Tools gnatxref and gnatfind
18888 @anchor{gnat_ugn/gnat_utility_programs id15}@anchor{15f}@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatfind-usage}@anchor{159}
18889 @subsection Examples of @code{gnatfind} Usage
18896 @code{gnatfind -f xyz:main.adb}
18897 Find declarations for all entities xyz referenced at least once in
18898 main.adb. The references are search in every library file in the search
18901 The directories will be printed as well (as the @code{-f}
18904 The output will look like:
18909 directory/main.ads:106:14: xyz <= declaration
18910 directory/main.adb:24:10: xyz <= body
18911 directory/foo.ads:45:23: xyz <= declaration
18915 I.e., one of the entities xyz found in main.adb is declared at
18916 line 12 of main.ads (and its body is in main.adb), and another one is
18917 declared at line 45 of foo.ads
18920 @code{gnatfind -fs xyz:main.adb}
18921 This is the same command as the previous one, but @code{gnatfind} will
18922 display the content of the Ada source file lines.
18924 The output will look like:
18927 directory/main.ads:106:14: xyz <= declaration
18929 directory/main.adb:24:10: xyz <= body
18931 directory/foo.ads:45:23: xyz <= declaration
18935 This can make it easier to find exactly the location your are looking
18939 @code{gnatfind -r "*x*":main.ads:123 foo.adb}
18940 Find references to all entities containing an x that are
18941 referenced on line 123 of main.ads.
18942 The references will be searched only in main.ads and foo.adb.
18945 @code{gnatfind main.ads:123}
18946 Find declarations and bodies for all entities that are referenced on
18947 line 123 of main.ads.
18949 This is the same as @code{gnatfind "*":main.adb:123`}
18952 @code{gnatfind mydir/main.adb:123:45}
18953 Find the declaration for the entity referenced at column 45 in
18954 line 123 of file main.adb in directory mydir. Note that it
18955 is usual to omit the identifier name when the column is given,
18956 since the column position identifies a unique reference.
18958 The column has to be the beginning of the identifier, and should not
18959 point to any character in the middle of the identifier.
18962 @node The Ada to HTML Converter gnathtml,,The Cross-Referencing Tools gnatxref and gnatfind,GNAT Utility Programs
18963 @anchor{gnat_ugn/gnat_utility_programs the-ada-to-html-converter-gnathtml}@anchor{23}@anchor{gnat_ugn/gnat_utility_programs id16}@anchor{160}
18964 @section The Ada to HTML Converter @code{gnathtml}
18969 @code{gnathtml} is a Perl script that allows Ada source files to be browsed using
18970 standard Web browsers. For installation information, see @ref{161,,Installing gnathtml}.
18972 Ada reserved keywords are highlighted in a bold font and Ada comments in
18973 a blue font. Unless your program was compiled with the gcc @code{-gnatx}
18974 switch to suppress the generation of cross-referencing information, user
18975 defined variables and types will appear in a different color; you will
18976 be able to click on any identifier and go to its declaration.
18979 * Invoking gnathtml::
18980 * Installing gnathtml::
18984 @node Invoking gnathtml,Installing gnathtml,,The Ada to HTML Converter gnathtml
18985 @anchor{gnat_ugn/gnat_utility_programs invoking-gnathtml}@anchor{162}@anchor{gnat_ugn/gnat_utility_programs id17}@anchor{163}
18986 @subsection Invoking @code{gnathtml}
18989 The command line is as follows:
18994 $ perl gnathtml.pl [ switches ] ada-files
18998 You can specify as many Ada files as you want. @code{gnathtml} will generate
18999 an html file for every ada file, and a global file called @code{index.htm}.
19000 This file is an index of every identifier defined in the files.
19002 The following switches are available:
19004 @geindex -83 (gnathtml)
19011 Only the Ada 83 subset of keywords will be highlighted.
19014 @geindex -cc (gnathtml)
19019 @item @code{cc @emph{color}}
19021 This option allows you to change the color used for comments. The default
19022 value is green. The color argument can be any name accepted by html.
19025 @geindex -d (gnathtml)
19032 If the Ada files depend on some other files (for instance through
19033 @code{with} clauses, the latter files will also be converted to html.
19034 Only the files in the user project will be converted to html, not the files
19035 in the run-time library itself.
19038 @geindex -D (gnathtml)
19045 This command is the same as @code{-d} above, but @code{gnathtml} will
19046 also look for files in the run-time library, and generate html files for them.
19049 @geindex -ext (gnathtml)
19054 @item @code{ext @emph{extension}}
19056 This option allows you to change the extension of the generated HTML files.
19057 If you do not specify an extension, it will default to @code{htm}.
19060 @geindex -f (gnathtml)
19067 By default, gnathtml will generate html links only for global entities
19068 ('with'ed units, global variables and types,...). If you specify
19069 @code{-f} on the command line, then links will be generated for local
19073 @geindex -l (gnathtml)
19078 @item @code{l @emph{number}}
19080 If this switch is provided and @code{number} is not 0, then
19081 @code{gnathtml} will number the html files every @code{number} line.
19084 @geindex -I (gnathtml)
19089 @item @code{I @emph{dir}}
19091 Specify a directory to search for library files (@code{.ALI} files) and
19092 source files. You can provide several -I switches on the command line,
19093 and the directories will be parsed in the order of the command line.
19096 @geindex -o (gnathtml)
19101 @item @code{o @emph{dir}}
19103 Specify the output directory for html files. By default, gnathtml will
19104 saved the generated html files in a subdirectory named @code{html/}.
19107 @geindex -p (gnathtml)
19112 @item @code{p @emph{file}}
19114 If you are using Emacs and the most recent Emacs Ada mode, which provides
19115 a full Integrated Development Environment for compiling, checking,
19116 running and debugging applications, you may use @code{.gpr} files
19117 to give the directories where Emacs can find sources and object files.
19119 Using this switch, you can tell gnathtml to use these files.
19120 This allows you to get an html version of your application, even if it
19121 is spread over multiple directories.
19124 @geindex -sc (gnathtml)
19129 @item @code{sc @emph{color}}
19131 This switch allows you to change the color used for symbol
19133 The default value is red. The color argument can be any name accepted by html.
19136 @geindex -t (gnathtml)
19141 @item @code{t @emph{file}}
19143 This switch provides the name of a file. This file contains a list of
19144 file names to be converted, and the effect is exactly as though they had
19145 appeared explicitly on the command line. This
19146 is the recommended way to work around the command line length limit on some
19150 @node Installing gnathtml,,Invoking gnathtml,The Ada to HTML Converter gnathtml
19151 @anchor{gnat_ugn/gnat_utility_programs installing-gnathtml}@anchor{161}@anchor{gnat_ugn/gnat_utility_programs id18}@anchor{164}
19152 @subsection Installing @code{gnathtml}
19155 @code{Perl} needs to be installed on your machine to run this script.
19156 @code{Perl} is freely available for almost every architecture and
19157 operating system via the Internet.
19159 On Unix systems, you may want to modify the first line of the script
19160 @code{gnathtml}, to explicitly specify where Perl
19161 is located. The syntax of this line is:
19166 #!full_path_name_to_perl
19170 Alternatively, you may run the script using the following command line:
19175 $ perl gnathtml.pl [ switches ] files
19179 @c -- +---------------------------------------------------------------------+
19181 @c -- | The following sections are present only in the PRO and GPL editions |
19183 @c -- +---------------------------------------------------------------------+
19193 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
19195 @node GNAT and Program Execution,Platform-Specific Information,GNAT Utility Programs,Top
19196 @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}
19197 @chapter GNAT and Program Execution
19200 This chapter covers several topics:
19206 @ref{167,,Running and Debugging Ada Programs}
19209 @ref{25,,Profiling}
19212 @ref{168,,Improving Performance}
19215 @ref{169,,Overflow Check Handling in GNAT}
19218 @ref{16a,,Performing Dimensionality Analysis in GNAT}
19221 @ref{16b,,Stack Related Facilities}
19224 @ref{16c,,Memory Management Issues}
19228 * Running and Debugging Ada Programs::
19230 * Improving Performance::
19231 * Overflow Check Handling in GNAT::
19232 * Performing Dimensionality Analysis in GNAT::
19233 * Stack Related Facilities::
19234 * Memory Management Issues::
19238 @node Running and Debugging Ada Programs,Profiling,,GNAT and Program Execution
19239 @anchor{gnat_ugn/gnat_and_program_execution id2}@anchor{167}@anchor{gnat_ugn/gnat_and_program_execution running-and-debugging-ada-programs}@anchor{24}
19240 @section Running and Debugging Ada Programs
19245 This section discusses how to debug Ada programs.
19247 An incorrect Ada program may be handled in three ways by the GNAT compiler:
19253 The illegality may be a violation of the static semantics of Ada. In
19254 that case GNAT diagnoses the constructs in the program that are illegal.
19255 It is then a straightforward matter for the user to modify those parts of
19259 The illegality may be a violation of the dynamic semantics of Ada. In
19260 that case the program compiles and executes, but may generate incorrect
19261 results, or may terminate abnormally with some exception.
19264 When presented with a program that contains convoluted errors, GNAT
19265 itself may terminate abnormally without providing full diagnostics on
19266 the incorrect user program.
19274 * The GNAT Debugger GDB::
19276 * Introduction to GDB Commands::
19277 * Using Ada Expressions::
19278 * Calling User-Defined Subprograms::
19279 * Using the next Command in a Function::
19280 * Stopping When Ada Exceptions Are Raised::
19282 * Debugging Generic Units::
19283 * Remote Debugging with gdbserver::
19284 * GNAT Abnormal Termination or Failure to Terminate::
19285 * Naming Conventions for GNAT Source Files::
19286 * Getting Internal Debugging Information::
19287 * Stack Traceback::
19288 * Pretty-Printers for the GNAT runtime::
19292 @node The GNAT Debugger GDB,Running GDB,,Running and Debugging Ada Programs
19293 @anchor{gnat_ugn/gnat_and_program_execution the-gnat-debugger-gdb}@anchor{16d}@anchor{gnat_ugn/gnat_and_program_execution id3}@anchor{16e}
19294 @subsection The GNAT Debugger GDB
19297 @code{GDB} is a general purpose, platform-independent debugger that
19298 can be used to debug mixed-language programs compiled with @code{gcc},
19299 and in particular is capable of debugging Ada programs compiled with
19300 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
19301 complex Ada data structures.
19303 See @cite{Debugging with GDB},
19304 for full details on the usage of @code{GDB}, including a section on
19305 its usage on programs. This manual should be consulted for full
19306 details. The section that follows is a brief introduction to the
19307 philosophy and use of @code{GDB}.
19309 When GNAT programs are compiled, the compiler optionally writes debugging
19310 information into the generated object file, including information on
19311 line numbers, and on declared types and variables. This information is
19312 separate from the generated code. It makes the object files considerably
19313 larger, but it does not add to the size of the actual executable that
19314 will be loaded into memory, and has no impact on run-time performance. The
19315 generation of debug information is triggered by the use of the
19316 @code{-g} switch in the @code{gcc} or @code{gnatmake} command
19317 used to carry out the compilations. It is important to emphasize that
19318 the use of these options does not change the generated code.
19320 The debugging information is written in standard system formats that
19321 are used by many tools, including debuggers and profilers. The format
19322 of the information is typically designed to describe C types and
19323 semantics, but GNAT implements a translation scheme which allows full
19324 details about Ada types and variables to be encoded into these
19325 standard C formats. Details of this encoding scheme may be found in
19326 the file exp_dbug.ads in the GNAT source distribution. However, the
19327 details of this encoding are, in general, of no interest to a user,
19328 since @code{GDB} automatically performs the necessary decoding.
19330 When a program is bound and linked, the debugging information is
19331 collected from the object files, and stored in the executable image of
19332 the program. Again, this process significantly increases the size of
19333 the generated executable file, but it does not increase the size of
19334 the executable program itself. Furthermore, if this program is run in
19335 the normal manner, it runs exactly as if the debug information were
19336 not present, and takes no more actual memory.
19338 However, if the program is run under control of @code{GDB}, the
19339 debugger is activated. The image of the program is loaded, at which
19340 point it is ready to run. If a run command is given, then the program
19341 will run exactly as it would have if @code{GDB} were not present. This
19342 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
19343 entirely non-intrusive until a breakpoint is encountered. If no
19344 breakpoint is ever hit, the program will run exactly as it would if no
19345 debugger were present. When a breakpoint is hit, @code{GDB} accesses
19346 the debugging information and can respond to user commands to inspect
19347 variables, and more generally to report on the state of execution.
19349 @node Running GDB,Introduction to GDB Commands,The GNAT Debugger GDB,Running and Debugging Ada Programs
19350 @anchor{gnat_ugn/gnat_and_program_execution id4}@anchor{16f}@anchor{gnat_ugn/gnat_and_program_execution running-gdb}@anchor{170}
19351 @subsection Running GDB
19354 This section describes how to initiate the debugger.
19356 The debugger can be launched from a @code{GNAT Studio} menu or
19357 directly from the command line. The description below covers the latter use.
19358 All the commands shown can be used in the @code{GNAT Studio} debug console window,
19359 but there are usually more GUI-based ways to achieve the same effect.
19361 The command to run @code{GDB} is
19370 where @code{program} is the name of the executable file. This
19371 activates the debugger and results in a prompt for debugger commands.
19372 The simplest command is simply @code{run}, which causes the program to run
19373 exactly as if the debugger were not present. The following section
19374 describes some of the additional commands that can be given to @code{GDB}.
19376 @node Introduction to GDB Commands,Using Ada Expressions,Running GDB,Running and Debugging Ada Programs
19377 @anchor{gnat_ugn/gnat_and_program_execution introduction-to-gdb-commands}@anchor{171}@anchor{gnat_ugn/gnat_and_program_execution id5}@anchor{172}
19378 @subsection Introduction to GDB Commands
19381 @code{GDB} contains a large repertoire of commands.
19382 See @cite{Debugging with GDB} for extensive documentation on the use
19383 of these commands, together with examples of their use. Furthermore,
19384 the command @emph{help} invoked from within GDB activates a simple help
19385 facility which summarizes the available commands and their options.
19386 In this section we summarize a few of the most commonly
19387 used commands to give an idea of what @code{GDB} is about. You should create
19388 a simple program with debugging information and experiment with the use of
19389 these @code{GDB} commands on the program as you read through the
19399 @item @code{set args @emph{arguments}}
19401 The @emph{arguments} list above is a list of arguments to be passed to
19402 the program on a subsequent run command, just as though the arguments
19403 had been entered on a normal invocation of the program. The @code{set args}
19404 command is not needed if the program does not require arguments.
19413 The @code{run} command causes execution of the program to start from
19414 the beginning. If the program is already running, that is to say if
19415 you are currently positioned at a breakpoint, then a prompt will ask
19416 for confirmation that you want to abandon the current execution and
19424 @item @code{breakpoint @emph{location}}
19426 The breakpoint command sets a breakpoint, that is to say a point at which
19427 execution will halt and @code{GDB} will await further
19428 commands. @emph{location} is
19429 either a line number within a file, given in the format @code{file:linenumber},
19430 or it is the name of a subprogram. If you request that a breakpoint be set on
19431 a subprogram that is overloaded, a prompt will ask you to specify on which of
19432 those subprograms you want to breakpoint. You can also
19433 specify that all of them should be breakpointed. If the program is run
19434 and execution encounters the breakpoint, then the program
19435 stops and @code{GDB} signals that the breakpoint was encountered by
19436 printing the line of code before which the program is halted.
19443 @item @code{catch exception @emph{name}}
19445 This command causes the program execution to stop whenever exception
19446 @code{name} is raised. If @code{name} is omitted, then the execution is
19447 suspended when any exception is raised.
19454 @item @code{print @emph{expression}}
19456 This will print the value of the given expression. Most simple
19457 Ada expression formats are properly handled by @code{GDB}, so the expression
19458 can contain function calls, variables, operators, and attribute references.
19465 @item @code{continue}
19467 Continues execution following a breakpoint, until the next breakpoint or the
19468 termination of the program.
19477 Executes a single line after a breakpoint. If the next statement
19478 is a subprogram call, execution continues into (the first statement of)
19479 the called subprogram.
19488 Executes a single line. If this line is a subprogram call, executes and
19489 returns from the call.
19498 Lists a few lines around the current source location. In practice, it
19499 is usually more convenient to have a separate edit window open with the
19500 relevant source file displayed. Successive applications of this command
19501 print subsequent lines. The command can be given an argument which is a
19502 line number, in which case it displays a few lines around the specified one.
19509 @item @code{backtrace}
19511 Displays a backtrace of the call chain. This command is typically
19512 used after a breakpoint has occurred, to examine the sequence of calls that
19513 leads to the current breakpoint. The display includes one line for each
19514 activation record (frame) corresponding to an active subprogram.
19523 At a breakpoint, @code{GDB} can display the values of variables local
19524 to the current frame. The command @code{up} can be used to
19525 examine the contents of other active frames, by moving the focus up
19526 the stack, that is to say from callee to caller, one frame at a time.
19535 Moves the focus of @code{GDB} down from the frame currently being
19536 examined to the frame of its callee (the reverse of the previous command),
19543 @item @code{frame @emph{n}}
19545 Inspect the frame with the given number. The value 0 denotes the frame
19546 of the current breakpoint, that is to say the top of the call stack.
19555 Kills the child process in which the program is running under GDB.
19556 This may be useful for several purposes:
19562 It allows you to recompile and relink your program, since on many systems
19563 you cannot regenerate an executable file while it is running in a process.
19566 You can run your program outside the debugger, on systems that do not
19567 permit executing a program outside GDB while breakpoints are set
19571 It allows you to debug a core dump rather than a running process.
19576 The above list is a very short introduction to the commands that
19577 @code{GDB} provides. Important additional capabilities, including conditional
19578 breakpoints, the ability to execute command sequences on a breakpoint,
19579 the ability to debug at the machine instruction level and many other
19580 features are described in detail in @cite{Debugging with GDB}.
19581 Note that most commands can be abbreviated
19582 (for example, c for continue, bt for backtrace).
19584 @node Using Ada Expressions,Calling User-Defined Subprograms,Introduction to GDB Commands,Running and Debugging Ada Programs
19585 @anchor{gnat_ugn/gnat_and_program_execution id6}@anchor{173}@anchor{gnat_ugn/gnat_and_program_execution using-ada-expressions}@anchor{174}
19586 @subsection Using Ada Expressions
19589 @geindex Ada expressions (in gdb)
19591 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
19592 extensions. The philosophy behind the design of this subset is
19600 That @code{GDB} should provide basic literals and access to operations for
19601 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
19602 leaving more sophisticated computations to subprograms written into the
19603 program (which therefore may be called from @code{GDB}).
19606 That type safety and strict adherence to Ada language restrictions
19607 are not particularly relevant in a debugging context.
19610 That brevity is important to the @code{GDB} user.
19614 Thus, for brevity, the debugger acts as if there were
19615 implicit @code{with} and @code{use} clauses in effect for all user-written
19616 packages, thus making it unnecessary to fully qualify most names with
19617 their packages, regardless of context. Where this causes ambiguity,
19618 @code{GDB} asks the user's intent.
19620 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
19622 @node Calling User-Defined Subprograms,Using the next Command in a Function,Using Ada Expressions,Running and Debugging Ada Programs
19623 @anchor{gnat_ugn/gnat_and_program_execution id7}@anchor{175}@anchor{gnat_ugn/gnat_and_program_execution calling-user-defined-subprograms}@anchor{176}
19624 @subsection Calling User-Defined Subprograms
19627 An important capability of @code{GDB} is the ability to call user-defined
19628 subprograms while debugging. This is achieved simply by entering
19629 a subprogram call statement in the form:
19634 call subprogram-name (parameters)
19638 The keyword @code{call} can be omitted in the normal case where the
19639 @code{subprogram-name} does not coincide with any of the predefined
19640 @code{GDB} commands.
19642 The effect is to invoke the given subprogram, passing it the
19643 list of parameters that is supplied. The parameters can be expressions and
19644 can include variables from the program being debugged. The
19645 subprogram must be defined
19646 at the library level within your program, and @code{GDB} will call the
19647 subprogram within the environment of your program execution (which
19648 means that the subprogram is free to access or even modify variables
19649 within your program).
19651 The most important use of this facility is in allowing the inclusion of
19652 debugging routines that are tailored to particular data structures
19653 in your program. Such debugging routines can be written to provide a suitably
19654 high-level description of an abstract type, rather than a low-level dump
19655 of its physical layout. After all, the standard
19656 @code{GDB print} command only knows the physical layout of your
19657 types, not their abstract meaning. Debugging routines can provide information
19658 at the desired semantic level and are thus enormously useful.
19660 For example, when debugging GNAT itself, it is crucial to have access to
19661 the contents of the tree nodes used to represent the program internally.
19662 But tree nodes are represented simply by an integer value (which in turn
19663 is an index into a table of nodes).
19664 Using the @code{print} command on a tree node would simply print this integer
19665 value, which is not very useful. But the PN routine (defined in file
19666 treepr.adb in the GNAT sources) takes a tree node as input, and displays
19667 a useful high level representation of the tree node, which includes the
19668 syntactic category of the node, its position in the source, the integers
19669 that denote descendant nodes and parent node, as well as varied
19670 semantic information. To study this example in more detail, you might want to
19671 look at the body of the PN procedure in the stated file.
19673 Another useful application of this capability is to deal with situations of
19674 complex data which are not handled suitably by GDB. For example, if you specify
19675 Convention Fortran for a multi-dimensional array, GDB does not know that
19676 the ordering of array elements has been switched and will not properly
19677 address the array elements. In such a case, instead of trying to print the
19678 elements directly from GDB, you can write a callable procedure that prints
19679 the elements in the desired format.
19681 @node Using the next Command in a Function,Stopping When Ada Exceptions Are Raised,Calling User-Defined Subprograms,Running and Debugging Ada Programs
19682 @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}
19683 @subsection Using the @emph{next} Command in a Function
19686 When you use the @code{next} command in a function, the current source
19687 location will advance to the next statement as usual. A special case
19688 arises in the case of a @code{return} statement.
19690 Part of the code for a return statement is the 'epilogue' of the function.
19691 This is the code that returns to the caller. There is only one copy of
19692 this epilogue code, and it is typically associated with the last return
19693 statement in the function if there is more than one return. In some
19694 implementations, this epilogue is associated with the first statement
19697 The result is that if you use the @code{next} command from a return
19698 statement that is not the last return statement of the function you
19699 may see a strange apparent jump to the last return statement or to
19700 the start of the function. You should simply ignore this odd jump.
19701 The value returned is always that from the first return statement
19702 that was stepped through.
19704 @node Stopping When Ada Exceptions Are Raised,Ada Tasks,Using the next Command in a Function,Running and Debugging Ada Programs
19705 @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}
19706 @subsection Stopping When Ada Exceptions Are Raised
19709 @geindex Exceptions (in gdb)
19711 You can set catchpoints that stop the program execution when your program
19712 raises selected exceptions.
19721 @item @code{catch exception}
19723 Set a catchpoint that stops execution whenever (any task in the) program
19724 raises any exception.
19731 @item @code{catch exception @emph{name}}
19733 Set a catchpoint that stops execution whenever (any task in the) program
19734 raises the exception @emph{name}.
19741 @item @code{catch exception unhandled}
19743 Set a catchpoint that stops executing whenever (any task in the) program
19744 raises an exception for which there is no handler.
19751 @item @code{info exceptions}, @code{info exceptions @emph{regexp}}
19753 The @code{info exceptions} command permits the user to examine all defined
19754 exceptions within Ada programs. With a regular expression, @emph{regexp}, as
19755 argument, prints out only those exceptions whose name matches @emph{regexp}.
19759 @geindex Tasks (in gdb)
19761 @node Ada Tasks,Debugging Generic Units,Stopping When Ada Exceptions Are Raised,Running and Debugging Ada Programs
19762 @anchor{gnat_ugn/gnat_and_program_execution ada-tasks}@anchor{17b}@anchor{gnat_ugn/gnat_and_program_execution id10}@anchor{17c}
19763 @subsection Ada Tasks
19766 @code{GDB} allows the following task-related commands:
19775 @item @code{info tasks}
19777 This command shows a list of current Ada tasks, as in the following example:
19781 ID TID P-ID Thread Pri State Name
19782 1 8088000 0 807e000 15 Child Activation Wait main_task
19783 2 80a4000 1 80ae000 15 Accept/Select Wait b
19784 3 809a800 1 80a4800 15 Child Activation Wait a
19785 * 4 80ae800 3 80b8000 15 Running c
19788 In this listing, the asterisk before the first task indicates it to be the
19789 currently running task. The first column lists the task ID that is used
19790 to refer to tasks in the following commands.
19794 @geindex Breakpoints and tasks
19800 @code{break`@w{`}*linespec* `@w{`}task} @emph{taskid}, @code{break} @emph{linespec} @code{task} @emph{taskid} @code{if} ...
19804 These commands are like the @code{break ... thread ...}.
19805 @emph{linespec} specifies source lines.
19807 Use the qualifier @code{task @emph{taskid}} with a breakpoint command
19808 to specify that you only want @code{GDB} to stop the program when a
19809 particular Ada task reaches this breakpoint. @emph{taskid} is one of the
19810 numeric task identifiers assigned by @code{GDB}, shown in the first
19811 column of the @code{info tasks} display.
19813 If you do not specify @code{task @emph{taskid}} when you set a
19814 breakpoint, the breakpoint applies to @emph{all} tasks of your
19817 You can use the @code{task} qualifier on conditional breakpoints as
19818 well; in this case, place @code{task @emph{taskid}} before the
19819 breakpoint condition (before the @code{if}).
19823 @geindex Task switching (in gdb)
19829 @code{task @emph{taskno}}
19833 This command allows switching to the task referred by @emph{taskno}. In
19834 particular, this allows browsing of the backtrace of the specified
19835 task. It is advisable to switch back to the original task before
19836 continuing execution otherwise the scheduling of the program may be
19841 For more detailed information on the tasking support,
19842 see @cite{Debugging with GDB}.
19844 @geindex Debugging Generic Units
19848 @node Debugging Generic Units,Remote Debugging with gdbserver,Ada Tasks,Running and Debugging Ada Programs
19849 @anchor{gnat_ugn/gnat_and_program_execution debugging-generic-units}@anchor{17d}@anchor{gnat_ugn/gnat_and_program_execution id11}@anchor{17e}
19850 @subsection Debugging Generic Units
19853 GNAT always uses code expansion for generic instantiation. This means that
19854 each time an instantiation occurs, a complete copy of the original code is
19855 made, with appropriate substitutions of formals by actuals.
19857 It is not possible to refer to the original generic entities in
19858 @code{GDB}, but it is always possible to debug a particular instance of
19859 a generic, by using the appropriate expanded names. For example, if we have
19866 generic package k is
19867 procedure kp (v1 : in out integer);
19871 procedure kp (v1 : in out integer) is
19877 package k1 is new k;
19878 package k2 is new k;
19880 var : integer := 1;
19891 Then to break on a call to procedure kp in the k2 instance, simply
19897 (gdb) break g.k2.kp
19901 When the breakpoint occurs, you can step through the code of the
19902 instance in the normal manner and examine the values of local variables, as for
19905 @geindex Remote Debugging with gdbserver
19907 @node Remote Debugging with gdbserver,GNAT Abnormal Termination or Failure to Terminate,Debugging Generic Units,Running and Debugging Ada Programs
19908 @anchor{gnat_ugn/gnat_and_program_execution remote-debugging-with-gdbserver}@anchor{17f}@anchor{gnat_ugn/gnat_and_program_execution id12}@anchor{180}
19909 @subsection Remote Debugging with gdbserver
19912 On platforms where gdbserver is supported, it is possible to use this tool
19913 to debug your application remotely. This can be useful in situations
19914 where the program needs to be run on a target host that is different
19915 from the host used for development, particularly when the target has
19916 a limited amount of resources (either CPU and/or memory).
19918 To do so, start your program using gdbserver on the target machine.
19919 gdbserver then automatically suspends the execution of your program
19920 at its entry point, waiting for a debugger to connect to it. The
19921 following commands starts an application and tells gdbserver to
19922 wait for a connection with the debugger on localhost port 4444.
19927 $ gdbserver localhost:4444 program
19928 Process program created; pid = 5685
19929 Listening on port 4444
19933 Once gdbserver has started listening, we can tell the debugger to establish
19934 a connection with this gdbserver, and then start the same debugging session
19935 as if the program was being debugged on the same host, directly under
19936 the control of GDB.
19942 (gdb) target remote targethost:4444
19943 Remote debugging using targethost:4444
19944 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
19946 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
19950 Breakpoint 1, foo () at foo.adb:4
19955 It is also possible to use gdbserver to attach to an already running
19956 program, in which case the execution of that program is simply suspended
19957 until the connection between the debugger and gdbserver is established.
19959 For more information on how to use gdbserver, see the @emph{Using the gdbserver Program}
19960 section in @cite{Debugging with GDB}.
19961 GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux.
19963 @geindex Abnormal Termination or Failure to Terminate
19965 @node GNAT Abnormal Termination or Failure to Terminate,Naming Conventions for GNAT Source Files,Remote Debugging with gdbserver,Running and Debugging Ada Programs
19966 @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}
19967 @subsection GNAT Abnormal Termination or Failure to Terminate
19970 When presented with programs that contain serious errors in syntax
19972 GNAT may on rare occasions experience problems in operation, such
19974 segmentation fault or illegal memory access, raising an internal
19975 exception, terminating abnormally, or failing to terminate at all.
19976 In such cases, you can activate
19977 various features of GNAT that can help you pinpoint the construct in your
19978 program that is the likely source of the problem.
19980 The following strategies are presented in increasing order of
19981 difficulty, corresponding to your experience in using GNAT and your
19982 familiarity with compiler internals.
19988 Run @code{gcc} with the @code{-gnatf}. This first
19989 switch causes all errors on a given line to be reported. In its absence,
19990 only the first error on a line is displayed.
19992 The @code{-gnatdO} switch causes errors to be displayed as soon as they
19993 are encountered, rather than after compilation is terminated. If GNAT
19994 terminates prematurely or goes into an infinite loop, the last error
19995 message displayed may help to pinpoint the culprit.
19998 Run @code{gcc} with the @code{-v} (verbose) switch. In this
19999 mode, @code{gcc} produces ongoing information about the progress of the
20000 compilation and provides the name of each procedure as code is
20001 generated. This switch allows you to find which Ada procedure was being
20002 compiled when it encountered a code generation problem.
20005 @geindex -gnatdc switch
20011 Run @code{gcc} with the @code{-gnatdc} switch. This is a GNAT specific
20012 switch that does for the front-end what @code{-v} does
20013 for the back end. The system prints the name of each unit,
20014 either a compilation unit or nested unit, as it is being analyzed.
20017 Finally, you can start
20018 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
20019 front-end of GNAT, and can be run independently (normally it is just
20020 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
20021 would on a C program (but @ref{16d,,The GNAT Debugger GDB} for caveats). The
20022 @code{where} command is the first line of attack; the variable
20023 @code{lineno} (seen by @code{print lineno}), used by the second phase of
20024 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
20025 which the execution stopped, and @code{input_file name} indicates the name of
20029 @node Naming Conventions for GNAT Source Files,Getting Internal Debugging Information,GNAT Abnormal Termination or Failure to Terminate,Running and Debugging Ada Programs
20030 @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}
20031 @subsection Naming Conventions for GNAT Source Files
20034 In order to examine the workings of the GNAT system, the following
20035 brief description of its organization may be helpful:
20041 Files with prefix @code{sc} contain the lexical scanner.
20044 All files prefixed with @code{par} are components of the parser. The
20045 numbers correspond to chapters of the Ada Reference Manual. For example,
20046 parsing of select statements can be found in @code{par-ch9.adb}.
20049 All files prefixed with @code{sem} perform semantic analysis. The
20050 numbers correspond to chapters of the Ada standard. For example, all
20051 issues involving context clauses can be found in @code{sem_ch10.adb}. In
20052 addition, some features of the language require sufficient special processing
20053 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
20054 dynamic dispatching, etc.
20057 All files prefixed with @code{exp} perform normalization and
20058 expansion of the intermediate representation (abstract syntax tree, or AST).
20059 these files use the same numbering scheme as the parser and semantics files.
20060 For example, the construction of record initialization procedures is done in
20061 @code{exp_ch3.adb}.
20064 The files prefixed with @code{bind} implement the binder, which
20065 verifies the consistency of the compilation, determines an order of
20066 elaboration, and generates the bind file.
20069 The files @code{atree.ads} and @code{atree.adb} detail the low-level
20070 data structures used by the front-end.
20073 The files @code{sinfo.ads} and @code{sinfo.adb} detail the structure of
20074 the abstract syntax tree as produced by the parser.
20077 The files @code{einfo.ads} and @code{einfo.adb} detail the attributes of
20078 all entities, computed during semantic analysis.
20081 Library management issues are dealt with in files with prefix
20084 @geindex Annex A (in Ada Reference Manual)
20087 Ada files with the prefix @code{a-} are children of @code{Ada}, as
20088 defined in Annex A.
20090 @geindex Annex B (in Ada reference Manual)
20093 Files with prefix @code{i-} are children of @code{Interfaces}, as
20094 defined in Annex B.
20096 @geindex System (package in Ada Reference Manual)
20099 Files with prefix @code{s-} are children of @code{System}. This includes
20100 both language-defined children and GNAT run-time routines.
20102 @geindex GNAT (package)
20105 Files with prefix @code{g-} are children of @code{GNAT}. These are useful
20106 general-purpose packages, fully documented in their specs. All
20107 the other @code{.c} files are modifications of common @code{gcc} files.
20110 @node Getting Internal Debugging Information,Stack Traceback,Naming Conventions for GNAT Source Files,Running and Debugging Ada Programs
20111 @anchor{gnat_ugn/gnat_and_program_execution id15}@anchor{185}@anchor{gnat_ugn/gnat_and_program_execution getting-internal-debugging-information}@anchor{186}
20112 @subsection Getting Internal Debugging Information
20115 Most compilers have internal debugging switches and modes. GNAT
20116 does also, except GNAT internal debugging switches and modes are not
20117 secret. A summary and full description of all the compiler and binder
20118 debug flags are in the file @code{debug.adb}. You must obtain the
20119 sources of the compiler to see the full detailed effects of these flags.
20121 The switches that print the source of the program (reconstructed from
20122 the internal tree) are of general interest for user programs, as are the
20124 the full internal tree, and the entity table (the symbol table
20125 information). The reconstructed source provides a readable version of the
20126 program after the front-end has completed analysis and expansion,
20127 and is useful when studying the performance of specific constructs.
20128 For example, constraint checks are indicated, complex aggregates
20129 are replaced with loops and assignments, and tasking primitives
20130 are replaced with run-time calls.
20134 @geindex stack traceback
20136 @geindex stack unwinding
20138 @node Stack Traceback,Pretty-Printers for the GNAT runtime,Getting Internal Debugging Information,Running and Debugging Ada Programs
20139 @anchor{gnat_ugn/gnat_and_program_execution stack-traceback}@anchor{187}@anchor{gnat_ugn/gnat_and_program_execution id16}@anchor{188}
20140 @subsection Stack Traceback
20143 Traceback is a mechanism to display the sequence of subprogram calls that
20144 leads to a specified execution point in a program. Often (but not always)
20145 the execution point is an instruction at which an exception has been raised.
20146 This mechanism is also known as @emph{stack unwinding} because it obtains
20147 its information by scanning the run-time stack and recovering the activation
20148 records of all active subprograms. Stack unwinding is one of the most
20149 important tools for program debugging.
20151 The first entry stored in traceback corresponds to the deepest calling level,
20152 that is to say the subprogram currently executing the instruction
20153 from which we want to obtain the traceback.
20155 Note that there is no runtime performance penalty when stack traceback
20156 is enabled, and no exception is raised during program execution.
20159 @geindex non-symbolic
20162 * Non-Symbolic Traceback::
20163 * Symbolic Traceback::
20167 @node Non-Symbolic Traceback,Symbolic Traceback,,Stack Traceback
20168 @anchor{gnat_ugn/gnat_and_program_execution non-symbolic-traceback}@anchor{189}@anchor{gnat_ugn/gnat_and_program_execution id17}@anchor{18a}
20169 @subsubsection Non-Symbolic Traceback
20172 Note: this feature is not supported on all platforms. See
20173 @code{GNAT.Traceback} spec in @code{g-traceb.ads}
20174 for a complete list of supported platforms.
20176 @subsubheading Tracebacks From an Unhandled Exception
20179 A runtime non-symbolic traceback is a list of addresses of call instructions.
20180 To enable this feature you must use the @code{-E}
20181 @code{gnatbind} option. With this option a stack traceback is stored as part
20182 of exception information. You can retrieve this information using the
20183 @code{addr2line} tool.
20185 Here is a simple example:
20194 raise Constraint_Error;
20208 $ gnatmake stb -bargs -E
20211 Execution terminated by unhandled exception
20212 Exception name: CONSTRAINT_ERROR
20214 Call stack traceback locations:
20215 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20219 As we see the traceback lists a sequence of addresses for the unhandled
20220 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
20221 guess that this exception come from procedure P1. To translate these
20222 addresses into the source lines where the calls appear, the
20223 @code{addr2line} tool, described below, is invaluable. The use of this tool
20224 requires the program to be compiled with debug information.
20229 $ gnatmake -g stb -bargs -E
20232 Execution terminated by unhandled exception
20233 Exception name: CONSTRAINT_ERROR
20235 Call stack traceback locations:
20236 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20238 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
20239 0x4011f1 0x77e892a4
20241 00401373 at d:/stb/stb.adb:5
20242 0040138B at d:/stb/stb.adb:10
20243 0040139C at d:/stb/stb.adb:14
20244 00401335 at d:/stb/b~stb.adb:104
20245 004011C4 at /build/.../crt1.c:200
20246 004011F1 at /build/.../crt1.c:222
20247 77E892A4 in ?? at ??:0
20251 The @code{addr2line} tool has several other useful options:
20256 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
20263 to get the function name corresponding to any location
20267 @code{--demangle=gnat}
20271 to use the gnat decoding mode for the function names.
20272 Note that for binutils version 2.9.x the option is
20273 simply @code{--demangle}.
20279 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
20280 0x40139c 0x401335 0x4011c4 0x4011f1
20282 00401373 in stb.p1 at d:/stb/stb.adb:5
20283 0040138B in stb.p2 at d:/stb/stb.adb:10
20284 0040139C in stb at d:/stb/stb.adb:14
20285 00401335 in main at d:/stb/b~stb.adb:104
20286 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
20287 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
20291 From this traceback we can see that the exception was raised in
20292 @code{stb.adb} at line 5, which was reached from a procedure call in
20293 @code{stb.adb} at line 10, and so on. The @code{b~std.adb} is the binder file,
20294 which contains the call to the main program.
20295 @ref{11c,,Running gnatbind}. The remaining entries are assorted runtime routines,
20296 and the output will vary from platform to platform.
20298 It is also possible to use @code{GDB} with these traceback addresses to debug
20299 the program. For example, we can break at a given code location, as reported
20300 in the stack traceback:
20309 Furthermore, this feature is not implemented inside Windows DLL. Only
20310 the non-symbolic traceback is reported in this case.
20315 (gdb) break *0x401373
20316 Breakpoint 1 at 0x401373: file stb.adb, line 5.
20320 It is important to note that the stack traceback addresses
20321 do not change when debug information is included. This is particularly useful
20322 because it makes it possible to release software without debug information (to
20323 minimize object size), get a field report that includes a stack traceback
20324 whenever an internal bug occurs, and then be able to retrieve the sequence
20325 of calls with the same program compiled with debug information.
20327 @subsubheading Tracebacks From Exception Occurrences
20330 Non-symbolic tracebacks are obtained by using the @code{-E} binder argument.
20331 The stack traceback is attached to the exception information string, and can
20332 be retrieved in an exception handler within the Ada program, by means of the
20333 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
20339 with Ada.Exceptions;
20344 use Ada.Exceptions;
20352 Text_IO.Put_Line (Exception_Information (E));
20366 This program will output:
20373 Exception name: CONSTRAINT_ERROR
20374 Message: stb.adb:12
20375 Call stack traceback locations:
20376 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
20380 @subsubheading Tracebacks From Anywhere in a Program
20383 It is also possible to retrieve a stack traceback from anywhere in a
20384 program. For this you need to
20385 use the @code{GNAT.Traceback} API. This package includes a procedure called
20386 @code{Call_Chain} that computes a complete stack traceback, as well as useful
20387 display procedures described below. It is not necessary to use the
20388 @code{-E} @code{gnatbind} option in this case, because the stack traceback mechanism
20389 is invoked explicitly.
20391 In the following example we compute a traceback at a specific location in
20392 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
20393 convert addresses to strings:
20399 with GNAT.Traceback;
20400 with GNAT.Debug_Utilities;
20406 use GNAT.Traceback;
20409 TB : Tracebacks_Array (1 .. 10);
20410 -- We are asking for a maximum of 10 stack frames.
20412 -- Len will receive the actual number of stack frames returned.
20414 Call_Chain (TB, Len);
20416 Text_IO.Put ("In STB.P1 : ");
20418 for K in 1 .. Len loop
20419 Text_IO.Put (Debug_Utilities.Image (TB (K)));
20440 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
20441 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
20445 You can then get further information by invoking the @code{addr2line}
20446 tool as described earlier (note that the hexadecimal addresses
20447 need to be specified in C format, with a leading '0x').
20452 @node Symbolic Traceback,,Non-Symbolic Traceback,Stack Traceback
20453 @anchor{gnat_ugn/gnat_and_program_execution id18}@anchor{18b}@anchor{gnat_ugn/gnat_and_program_execution symbolic-traceback}@anchor{18c}
20454 @subsubsection Symbolic Traceback
20457 A symbolic traceback is a stack traceback in which procedure names are
20458 associated with each code location.
20460 Note that this feature is not supported on all platforms. See
20461 @code{GNAT.Traceback.Symbolic} spec in @code{g-trasym.ads} for a complete
20462 list of currently supported platforms.
20464 Note that the symbolic traceback requires that the program be compiled
20465 with debug information. If it is not compiled with debug information
20466 only the non-symbolic information will be valid.
20468 @subsubheading Tracebacks From Exception Occurrences
20471 Here is an example:
20477 with GNAT.Traceback.Symbolic;
20483 raise Constraint_Error;
20500 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
20505 $ gnatmake -g .\stb -bargs -E
20508 0040149F in stb.p1 at stb.adb:8
20509 004014B7 in stb.p2 at stb.adb:13
20510 004014CF in stb.p3 at stb.adb:18
20511 004015DD in ada.stb at stb.adb:22
20512 00401461 in main at b~stb.adb:168
20513 004011C4 in __mingw_CRTStartup at crt1.c:200
20514 004011F1 in mainCRTStartup at crt1.c:222
20515 77E892A4 in ?? at ??:0
20519 In the above example the @code{.\} syntax in the @code{gnatmake} command
20520 is currently required by @code{addr2line} for files that are in
20521 the current working directory.
20522 Moreover, the exact sequence of linker options may vary from platform
20524 The above @code{-largs} section is for Windows platforms. By contrast,
20525 under Unix there is no need for the @code{-largs} section.
20526 Differences across platforms are due to details of linker implementation.
20528 @subsubheading Tracebacks From Anywhere in a Program
20531 It is possible to get a symbolic stack traceback
20532 from anywhere in a program, just as for non-symbolic tracebacks.
20533 The first step is to obtain a non-symbolic
20534 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
20535 information. Here is an example:
20541 with GNAT.Traceback;
20542 with GNAT.Traceback.Symbolic;
20547 use GNAT.Traceback;
20548 use GNAT.Traceback.Symbolic;
20551 TB : Tracebacks_Array (1 .. 10);
20552 -- We are asking for a maximum of 10 stack frames.
20554 -- Len will receive the actual number of stack frames returned.
20556 Call_Chain (TB, Len);
20557 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
20571 @subsubheading Automatic Symbolic Tracebacks
20574 Symbolic tracebacks may also be enabled by using the -Es switch to gnatbind (as
20575 in @code{gprbuild -g ... -bargs -Es}).
20576 This will cause the Exception_Information to contain a symbolic traceback,
20577 which will also be printed if an unhandled exception terminates the
20580 @node Pretty-Printers for the GNAT runtime,,Stack Traceback,Running and Debugging Ada Programs
20581 @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}
20582 @subsection Pretty-Printers for the GNAT runtime
20585 As discussed in @cite{Calling User-Defined Subprograms}, GDB's
20586 @code{print} command only knows about the physical layout of program data
20587 structures and therefore normally displays only low-level dumps, which
20588 are often hard to understand.
20590 An example of this is when trying to display the contents of an Ada
20591 standard container, such as @code{Ada.Containers.Ordered_Maps.Map}:
20596 with Ada.Containers.Ordered_Maps;
20599 package Int_To_Nat is
20600 new Ada.Containers.Ordered_Maps (Integer, Natural);
20602 Map : Int_To_Nat.Map;
20604 Map.Insert (1, 10);
20605 Map.Insert (2, 20);
20606 Map.Insert (3, 30);
20608 Map.Clear; -- BREAK HERE
20613 When this program is built with debugging information and run under
20614 GDB up to the @code{Map.Clear} statement, trying to print @code{Map} will
20615 yield information that is only relevant to the developers of our standard
20637 Fortunately, GDB has a feature called pretty-printers@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Introduction},
20638 which allows customizing how GDB displays data structures. The GDB
20639 shipped with GNAT embeds such pretty-printers for the most common
20640 containers in the standard library. To enable them, either run the
20641 following command manually under GDB or add it to your @code{.gdbinit} file:
20646 python import gnatdbg; gnatdbg.setup()
20650 Once this is done, GDB's @code{print} command will automatically use
20651 these pretty-printers when appropriate. Using the previous example:
20657 $1 = pp.int_to_nat.map of length 3 = @{
20665 Pretty-printers are invoked each time GDB tries to display a value,
20666 including when displaying the arguments of a called subprogram (in
20667 GDB's @code{backtrace} command) or when printing the value returned by a
20668 function (in GDB's @code{finish} command).
20670 To display a value without involving pretty-printers, @code{print} can be
20671 invoked with its @code{/r} option:
20682 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}
20683 for more information.
20687 @node Profiling,Improving Performance,Running and Debugging Ada Programs,GNAT and Program Execution
20688 @anchor{gnat_ugn/gnat_and_program_execution profiling}@anchor{25}@anchor{gnat_ugn/gnat_and_program_execution id20}@anchor{18f}
20692 This section describes how to use the @code{gprof} profiler tool on Ada programs.
20699 * Profiling an Ada Program with gprof::
20703 @node Profiling an Ada Program with gprof,,,Profiling
20704 @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}
20705 @subsection Profiling an Ada Program with gprof
20708 This section is not meant to be an exhaustive documentation of @code{gprof}.
20709 Full documentation for it can be found in the @cite{GNU Profiler User's Guide}
20710 documentation that is part of this GNAT distribution.
20712 Profiling a program helps determine the parts of a program that are executed
20713 most often, and are therefore the most time-consuming.
20715 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
20716 better handle Ada programs and multitasking.
20717 It is currently supported on the following platforms
20729 In order to profile a program using @code{gprof}, several steps are needed:
20735 Instrument the code, which requires a full recompilation of the project with the
20739 Execute the program under the analysis conditions, i.e. with the desired
20743 Analyze the results using the @code{gprof} tool.
20746 The following sections detail the different steps, and indicate how
20747 to interpret the results.
20750 * Compilation for profiling::
20751 * Program execution::
20753 * Interpretation of profiling results::
20757 @node Compilation for profiling,Program execution,,Profiling an Ada Program with gprof
20758 @anchor{gnat_ugn/gnat_and_program_execution id22}@anchor{192}@anchor{gnat_ugn/gnat_and_program_execution compilation-for-profiling}@anchor{193}
20759 @subsubsection Compilation for profiling
20763 @geindex for profiling
20765 @geindex -pg (gnatlink)
20766 @geindex for profiling
20768 In order to profile a program the first step is to tell the compiler
20769 to generate the necessary profiling information. The compiler switch to be used
20770 is @code{-pg}, which must be added to other compilation switches. This
20771 switch needs to be specified both during compilation and link stages, and can
20772 be specified once when using gnatmake:
20777 $ gnatmake -f -pg -P my_project
20781 Note that only the objects that were compiled with the @code{-pg} switch will
20782 be profiled; if you need to profile your whole project, use the @code{-f}
20783 gnatmake switch to force full recompilation.
20785 @node Program execution,Running gprof,Compilation for profiling,Profiling an Ada Program with gprof
20786 @anchor{gnat_ugn/gnat_and_program_execution program-execution}@anchor{194}@anchor{gnat_ugn/gnat_and_program_execution id23}@anchor{195}
20787 @subsubsection Program execution
20790 Once the program has been compiled for profiling, you can run it as usual.
20792 The only constraint imposed by profiling is that the program must terminate
20793 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
20796 Once the program completes execution, a data file called @code{gmon.out} is
20797 generated in the directory where the program was launched from. If this file
20798 already exists, it will be overwritten.
20800 @node Running gprof,Interpretation of profiling results,Program execution,Profiling an Ada Program with gprof
20801 @anchor{gnat_ugn/gnat_and_program_execution running-gprof}@anchor{196}@anchor{gnat_ugn/gnat_and_program_execution id24}@anchor{197}
20802 @subsubsection Running gprof
20805 The @code{gprof} tool is called as follow:
20810 $ gprof my_prog gmon.out
20823 The complete form of the gprof command line is the following:
20828 $ gprof [switches] [executable [data-file]]
20832 @code{gprof} supports numerous switches. The order of these
20833 switch does not matter. The full list of options can be found in
20834 the GNU Profiler User's Guide documentation that comes with this documentation.
20836 The following is the subset of those switches that is most relevant:
20838 @geindex --demangle (gprof)
20843 @item @code{--demangle[=@emph{style}]}, @code{--no-demangle}
20845 These options control whether symbol names should be demangled when
20846 printing output. The default is to demangle C++ symbols. The
20847 @code{--no-demangle} option may be used to turn off demangling. Different
20848 compilers have different mangling styles. The optional demangling style
20849 argument can be used to choose an appropriate demangling style for your
20850 compiler, in particular Ada symbols generated by GNAT can be demangled using
20851 @code{--demangle=gnat}.
20854 @geindex -e (gprof)
20859 @item @code{-e @emph{function_name}}
20861 The @code{-e @emph{function}} option tells @code{gprof} not to print
20862 information about the function @code{function_name} (and its
20863 children...) in the call graph. The function will still be listed
20864 as a child of any functions that call it, but its index number will be
20865 shown as @code{[not printed]}. More than one @code{-e} option may be
20866 given; only one @code{function_name} may be indicated with each @code{-e}
20870 @geindex -E (gprof)
20875 @item @code{-E @emph{function_name}}
20877 The @code{-E @emph{function}} option works like the @code{-e} option, but
20878 execution time spent in the function (and children who were not called from
20879 anywhere else), will not be used to compute the percentages-of-time for
20880 the call graph. More than one @code{-E} option may be given; only one
20881 @code{function_name} may be indicated with each @code{-E`} option.
20884 @geindex -f (gprof)
20889 @item @code{-f @emph{function_name}}
20891 The @code{-f @emph{function}} option causes @code{gprof} to limit the
20892 call graph to the function @code{function_name} and its children (and
20893 their children...). More than one @code{-f} option may be given;
20894 only one @code{function_name} may be indicated with each @code{-f}
20898 @geindex -F (gprof)
20903 @item @code{-F @emph{function_name}}
20905 The @code{-F @emph{function}} option works like the @code{-f} option, but
20906 only time spent in the function and its children (and their
20907 children...) will be used to determine total-time and
20908 percentages-of-time for the call graph. More than one @code{-F} option
20909 may be given; only one @code{function_name} may be indicated with each
20910 @code{-F} option. The @code{-F} option overrides the @code{-E} option.
20913 @node Interpretation of profiling results,,Running gprof,Profiling an Ada Program with gprof
20914 @anchor{gnat_ugn/gnat_and_program_execution id25}@anchor{198}@anchor{gnat_ugn/gnat_and_program_execution interpretation-of-profiling-results}@anchor{199}
20915 @subsubsection Interpretation of profiling results
20918 The results of the profiling analysis are represented by two arrays: the
20919 'flat profile' and the 'call graph'. Full documentation of those outputs
20920 can be found in the GNU Profiler User's Guide.
20922 The flat profile shows the time spent in each function of the program, and how
20923 many time it has been called. This allows you to locate easily the most
20924 time-consuming functions.
20926 The call graph shows, for each subprogram, the subprograms that call it,
20927 and the subprograms that it calls. It also provides an estimate of the time
20928 spent in each of those callers/called subprograms.
20930 @node Improving Performance,Overflow Check Handling in GNAT,Profiling,GNAT and Program Execution
20931 @anchor{gnat_ugn/gnat_and_program_execution improving-performance}@anchor{26}@anchor{gnat_ugn/gnat_and_program_execution id26}@anchor{168}
20932 @section Improving Performance
20935 @geindex Improving performance
20937 This section presents several topics related to program performance.
20938 It first describes some of the tradeoffs that need to be considered
20939 and some of the techniques for making your program run faster.
20941 It then documents the unused subprogram/data elimination feature,
20942 which can reduce the size of program executables.
20945 * Performance Considerations::
20946 * Text_IO Suggestions::
20947 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
20951 @node Performance Considerations,Text_IO Suggestions,,Improving Performance
20952 @anchor{gnat_ugn/gnat_and_program_execution performance-considerations}@anchor{19a}@anchor{gnat_ugn/gnat_and_program_execution id27}@anchor{19b}
20953 @subsection Performance Considerations
20956 The GNAT system provides a number of options that allow a trade-off
20963 performance of the generated code
20966 speed of compilation
20969 minimization of dependences and recompilation
20972 the degree of run-time checking.
20975 The defaults (if no options are selected) aim at improving the speed
20976 of compilation and minimizing dependences, at the expense of performance
20977 of the generated code:
20986 no inlining of subprogram calls
20989 all run-time checks enabled except overflow and elaboration checks
20992 These options are suitable for most program development purposes. This
20993 section describes how you can modify these choices, and also provides
20994 some guidelines on debugging optimized code.
20997 * Controlling Run-Time Checks::
20998 * Use of Restrictions::
20999 * Optimization Levels::
21000 * Debugging Optimized Code::
21001 * Inlining of Subprograms::
21002 * Floating_Point_Operations::
21003 * Vectorization of loops::
21004 * Other Optimization Switches::
21005 * Optimization and Strict Aliasing::
21006 * Aliased Variables and Optimization::
21007 * Atomic Variables and Optimization::
21008 * Passive Task Optimization::
21012 @node Controlling Run-Time Checks,Use of Restrictions,,Performance Considerations
21013 @anchor{gnat_ugn/gnat_and_program_execution id28}@anchor{19c}@anchor{gnat_ugn/gnat_and_program_execution controlling-run-time-checks}@anchor{19d}
21014 @subsubsection Controlling Run-Time Checks
21017 By default, GNAT generates all run-time checks, except stack overflow
21018 checks, and checks for access before elaboration on subprogram
21019 calls. The latter are not required in default mode, because all
21020 necessary checking is done at compile time.
21022 @geindex -gnatp (gcc)
21024 @geindex -gnato (gcc)
21026 The gnat switch, @code{-gnatp} allows this default to be modified. See
21027 @ref{f9,,Run-Time Checks}.
21029 Our experience is that the default is suitable for most development
21032 Elaboration checks are off by default, and also not needed by default, since
21033 GNAT uses a static elaboration analysis approach that avoids the need for
21034 run-time checking. This manual contains a full chapter discussing the issue
21035 of elaboration checks, and if the default is not satisfactory for your use,
21036 you should read this chapter.
21038 For validity checks, the minimal checks required by the Ada Reference
21039 Manual (for case statements and assignments to array elements) are on
21040 by default. These can be suppressed by use of the @code{-gnatVn} switch.
21041 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
21042 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
21043 it may be reasonable to routinely use @code{-gnatVn}. Validity checks
21044 are also suppressed entirely if @code{-gnatp} is used.
21046 @geindex Overflow checks
21053 @geindex Unsuppress
21055 @geindex pragma Suppress
21057 @geindex pragma Unsuppress
21059 Note that the setting of the switches controls the default setting of
21060 the checks. They may be modified using either @code{pragma Suppress} (to
21061 remove checks) or @code{pragma Unsuppress} (to add back suppressed
21062 checks) in the program source.
21064 @node Use of Restrictions,Optimization Levels,Controlling Run-Time Checks,Performance Considerations
21065 @anchor{gnat_ugn/gnat_and_program_execution id29}@anchor{19e}@anchor{gnat_ugn/gnat_and_program_execution use-of-restrictions}@anchor{19f}
21066 @subsubsection Use of Restrictions
21069 The use of pragma Restrictions allows you to control which features are
21070 permitted in your program. Apart from the obvious point that if you avoid
21071 relatively expensive features like finalization (enforceable by the use
21072 of pragma Restrictions (No_Finalization), the use of this pragma does not
21073 affect the generated code in most cases.
21075 One notable exception to this rule is that the possibility of task abort
21076 results in some distributed overhead, particularly if finalization or
21077 exception handlers are used. The reason is that certain sections of code
21078 have to be marked as non-abortable.
21080 If you use neither the @code{abort} statement, nor asynchronous transfer
21081 of control (@code{select ... then abort}), then this distributed overhead
21082 is removed, which may have a general positive effect in improving
21083 overall performance. Especially code involving frequent use of tasking
21084 constructs and controlled types will show much improved performance.
21085 The relevant restrictions pragmas are
21090 pragma Restrictions (No_Abort_Statements);
21091 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
21095 It is recommended that these restriction pragmas be used if possible. Note
21096 that this also means that you can write code without worrying about the
21097 possibility of an immediate abort at any point.
21099 @node Optimization Levels,Debugging Optimized Code,Use of Restrictions,Performance Considerations
21100 @anchor{gnat_ugn/gnat_and_program_execution id30}@anchor{1a0}@anchor{gnat_ugn/gnat_and_program_execution optimization-levels}@anchor{fc}
21101 @subsubsection Optimization Levels
21106 Without any optimization option,
21107 the compiler's goal is to reduce the cost of
21108 compilation and to make debugging produce the expected results.
21109 Statements are independent: if you stop the program with a breakpoint between
21110 statements, you can then assign a new value to any variable or change
21111 the program counter to any other statement in the subprogram and get exactly
21112 the results you would expect from the source code.
21114 Turning on optimization makes the compiler attempt to improve the
21115 performance and/or code size at the expense of compilation time and
21116 possibly the ability to debug the program.
21118 If you use multiple
21119 -O options, with or without level numbers,
21120 the last such option is the one that is effective.
21122 The default is optimization off. This results in the fastest compile
21123 times, but GNAT makes absolutely no attempt to optimize, and the
21124 generated programs are considerably larger and slower than when
21125 optimization is enabled. You can use the
21126 @code{-O} switch (the permitted forms are @code{-O0}, @code{-O1}
21127 @code{-O2}, @code{-O3}, and @code{-Os})
21128 to @code{gcc} to control the optimization level:
21139 No optimization (the default);
21140 generates unoptimized code but has
21141 the fastest compilation time.
21143 Note that many other compilers do substantial optimization even
21144 if 'no optimization' is specified. With gcc, it is very unusual
21145 to use @code{-O0} for production if execution time is of any concern,
21146 since @code{-O0} means (almost) no optimization. This difference
21147 between gcc and other compilers should be kept in mind when
21148 doing performance comparisons.
21157 Moderate optimization;
21158 optimizes reasonably well but does not
21159 degrade compilation time significantly.
21169 generates highly optimized code and has
21170 the slowest compilation time.
21179 Full optimization as in @code{-O2};
21180 also uses more aggressive automatic inlining of subprograms within a unit
21181 (@ref{10f,,Inlining of Subprograms}) and attempts to vectorize loops.
21190 Optimize space usage (code and data) of resulting program.
21194 Higher optimization levels perform more global transformations on the
21195 program and apply more expensive analysis algorithms in order to generate
21196 faster and more compact code. The price in compilation time, and the
21197 resulting improvement in execution time,
21198 both depend on the particular application and the hardware environment.
21199 You should experiment to find the best level for your application.
21201 Since the precise set of optimizations done at each level will vary from
21202 release to release (and sometime from target to target), it is best to think
21203 of the optimization settings in general terms.
21204 See the @emph{Options That Control Optimization} section in
21205 @cite{Using the GNU Compiler Collection (GCC)}
21207 the @code{-O} settings and a number of @code{-f} options that
21208 individually enable or disable specific optimizations.
21210 Unlike some other compilation systems, @code{gcc} has
21211 been tested extensively at all optimization levels. There are some bugs
21212 which appear only with optimization turned on, but there have also been
21213 bugs which show up only in @emph{unoptimized} code. Selecting a lower
21214 level of optimization does not improve the reliability of the code
21215 generator, which in practice is highly reliable at all optimization
21218 Note regarding the use of @code{-O3}: The use of this optimization level
21219 ought not to be automatically preferred over that of level @code{-O2},
21220 since it often results in larger executables which may run more slowly.
21221 See further discussion of this point in @ref{10f,,Inlining of Subprograms}.
21223 @node Debugging Optimized Code,Inlining of Subprograms,Optimization Levels,Performance Considerations
21224 @anchor{gnat_ugn/gnat_and_program_execution debugging-optimized-code}@anchor{1a1}@anchor{gnat_ugn/gnat_and_program_execution id31}@anchor{1a2}
21225 @subsubsection Debugging Optimized Code
21228 @geindex Debugging optimized code
21230 @geindex Optimization and debugging
21232 Although it is possible to do a reasonable amount of debugging at
21233 nonzero optimization levels,
21234 the higher the level the more likely that
21235 source-level constructs will have been eliminated by optimization.
21236 For example, if a loop is strength-reduced, the loop
21237 control variable may be completely eliminated and thus cannot be
21238 displayed in the debugger.
21239 This can only happen at @code{-O2} or @code{-O3}.
21240 Explicit temporary variables that you code might be eliminated at
21241 level @code{-O1} or higher.
21245 The use of the @code{-g} switch,
21246 which is needed for source-level debugging,
21247 affects the size of the program executable on disk,
21248 and indeed the debugging information can be quite large.
21249 However, it has no effect on the generated code (and thus does not
21250 degrade performance)
21252 Since the compiler generates debugging tables for a compilation unit before
21253 it performs optimizations, the optimizing transformations may invalidate some
21254 of the debugging data. You therefore need to anticipate certain
21255 anomalous situations that may arise while debugging optimized code.
21256 These are the most common cases:
21262 @emph{The 'hopping Program Counter':} Repeated @code{step} or @code{next}
21264 the PC bouncing back and forth in the code. This may result from any of
21265 the following optimizations:
21271 @emph{Common subexpression elimination:} using a single instance of code for a
21272 quantity that the source computes several times. As a result you
21273 may not be able to stop on what looks like a statement.
21276 @emph{Invariant code motion:} moving an expression that does not change within a
21277 loop, to the beginning of the loop.
21280 @emph{Instruction scheduling:} moving instructions so as to
21281 overlap loads and stores (typically) with other code, or in
21282 general to move computations of values closer to their uses. Often
21283 this causes you to pass an assignment statement without the assignment
21284 happening and then later bounce back to the statement when the
21285 value is actually needed. Placing a breakpoint on a line of code
21286 and then stepping over it may, therefore, not always cause all the
21287 expected side-effects.
21291 @emph{The 'big leap':} More commonly known as @emph{cross-jumping}, in which
21292 two identical pieces of code are merged and the program counter suddenly
21293 jumps to a statement that is not supposed to be executed, simply because
21294 it (and the code following) translates to the same thing as the code
21295 that @emph{was} supposed to be executed. This effect is typically seen in
21296 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
21297 a @code{break} in a C @code{switch} statement.
21300 @emph{The 'roving variable':} The symptom is an unexpected value in a variable.
21301 There are various reasons for this effect:
21307 In a subprogram prologue, a parameter may not yet have been moved to its
21311 A variable may be dead, and its register re-used. This is
21312 probably the most common cause.
21315 As mentioned above, the assignment of a value to a variable may
21319 A variable may be eliminated entirely by value propagation or
21320 other means. In this case, GCC may incorrectly generate debugging
21321 information for the variable
21324 In general, when an unexpected value appears for a local variable or parameter
21325 you should first ascertain if that value was actually computed by
21326 your program, as opposed to being incorrectly reported by the debugger.
21328 array elements in an object designated by an access value
21329 are generally less of a problem, once you have ascertained that the access
21331 Typically, this means checking variables in the preceding code and in the
21332 calling subprogram to verify that the value observed is explainable from other
21333 values (one must apply the procedure recursively to those
21334 other values); or re-running the code and stopping a little earlier
21335 (perhaps before the call) and stepping to better see how the variable obtained
21336 the value in question; or continuing to step @emph{from} the point of the
21337 strange value to see if code motion had simply moved the variable's
21341 In light of such anomalies, a recommended technique is to use @code{-O0}
21342 early in the software development cycle, when extensive debugging capabilities
21343 are most needed, and then move to @code{-O1} and later @code{-O2} as
21344 the debugger becomes less critical.
21345 Whether to use the @code{-g} switch in the release version is
21346 a release management issue.
21347 Note that if you use @code{-g} you can then use the @code{strip} program
21348 on the resulting executable,
21349 which removes both debugging information and global symbols.
21351 @node Inlining of Subprograms,Floating_Point_Operations,Debugging Optimized Code,Performance Considerations
21352 @anchor{gnat_ugn/gnat_and_program_execution id32}@anchor{1a3}@anchor{gnat_ugn/gnat_and_program_execution inlining-of-subprograms}@anchor{10f}
21353 @subsubsection Inlining of Subprograms
21356 A call to a subprogram in the current unit is inlined if all the
21357 following conditions are met:
21363 The optimization level is at least @code{-O1}.
21366 The called subprogram is suitable for inlining: It must be small enough
21367 and not contain something that @code{gcc} cannot support in inlined
21370 @geindex pragma Inline
21375 Any one of the following applies: @code{pragma Inline} is applied to the
21376 subprogram; the subprogram is local to the unit and called once from
21377 within it; the subprogram is small and optimization level @code{-O2} is
21378 specified; optimization level @code{-O3} is specified.
21381 Calls to subprograms in @emph{with}ed units are normally not inlined.
21382 To achieve actual inlining (that is, replacement of the call by the code
21383 in the body of the subprogram), the following conditions must all be true:
21389 The optimization level is at least @code{-O1}.
21392 The called subprogram is suitable for inlining: It must be small enough
21393 and not contain something that @code{gcc} cannot support in inlined
21397 There is a @code{pragma Inline} for the subprogram.
21400 The @code{-gnatn} switch is used on the command line.
21403 Even if all these conditions are met, it may not be possible for
21404 the compiler to inline the call, due to the length of the body,
21405 or features in the body that make it impossible for the compiler
21406 to do the inlining.
21408 Note that specifying the @code{-gnatn} switch causes additional
21409 compilation dependencies. Consider the following:
21431 With the default behavior (no @code{-gnatn} switch specified), the
21432 compilation of the @code{Main} procedure depends only on its own source,
21433 @code{main.adb}, and the spec of the package in file @code{r.ads}. This
21434 means that editing the body of @code{R} does not require recompiling
21437 On the other hand, the call @code{R.Q} is not inlined under these
21438 circumstances. If the @code{-gnatn} switch is present when @code{Main}
21439 is compiled, the call will be inlined if the body of @code{Q} is small
21440 enough, but now @code{Main} depends on the body of @code{R} in
21441 @code{r.adb} as well as on the spec. This means that if this body is edited,
21442 the main program must be recompiled. Note that this extra dependency
21443 occurs whether or not the call is in fact inlined by @code{gcc}.
21445 The use of front end inlining with @code{-gnatN} generates similar
21446 additional dependencies.
21448 @geindex -fno-inline (gcc)
21450 Note: The @code{-fno-inline} switch overrides all other conditions and ensures that
21451 no inlining occurs, unless requested with pragma Inline_Always for @code{gcc}
21452 back-ends. The extra dependences resulting from @code{-gnatn} will still be active,
21453 even if this switch is used to suppress the resulting inlining actions.
21455 @geindex -fno-inline-functions (gcc)
21457 Note: The @code{-fno-inline-functions} switch can be used to prevent
21458 automatic inlining of subprograms if @code{-O3} is used.
21460 @geindex -fno-inline-small-functions (gcc)
21462 Note: The @code{-fno-inline-small-functions} switch can be used to prevent
21463 automatic inlining of small subprograms if @code{-O2} is used.
21465 @geindex -fno-inline-functions-called-once (gcc)
21467 Note: The @code{-fno-inline-functions-called-once} switch
21468 can be used to prevent inlining of subprograms local to the unit
21469 and called once from within it if @code{-O1} is used.
21471 Note regarding the use of @code{-O3}: @code{-gnatn} is made up of two
21472 sub-switches @code{-gnatn1} and @code{-gnatn2} that can be directly
21473 specified in lieu of it, @code{-gnatn} being translated into one of them
21474 based on the optimization level. With @code{-O2} or below, @code{-gnatn}
21475 is equivalent to @code{-gnatn1} which activates pragma @code{Inline} with
21476 moderate inlining across modules. With @code{-O3}, @code{-gnatn} is
21477 equivalent to @code{-gnatn2} which activates pragma @code{Inline} with
21478 full inlining across modules. If you have used pragma @code{Inline} in
21479 appropriate cases, then it is usually much better to use @code{-O2}
21480 and @code{-gnatn} and avoid the use of @code{-O3} which has the additional
21481 effect of inlining subprograms you did not think should be inlined. We have
21482 found that the use of @code{-O3} may slow down the compilation and increase
21483 the code size by performing excessive inlining, leading to increased
21484 instruction cache pressure from the increased code size and thus minor
21485 performance improvements. So the bottom line here is that you should not
21486 automatically assume that @code{-O3} is better than @code{-O2}, and
21487 indeed you should use @code{-O3} only if tests show that it actually
21488 improves performance for your program.
21490 @node Floating_Point_Operations,Vectorization of loops,Inlining of Subprograms,Performance Considerations
21491 @anchor{gnat_ugn/gnat_and_program_execution floating-point-operations}@anchor{1a4}@anchor{gnat_ugn/gnat_and_program_execution id33}@anchor{1a5}
21492 @subsubsection Floating_Point_Operations
21495 @geindex Floating-Point Operations
21497 On almost all targets, GNAT maps Float and Long_Float to the 32-bit and
21498 64-bit standard IEEE floating-point representations, and operations will
21499 use standard IEEE arithmetic as provided by the processor. On most, but
21500 not all, architectures, the attribute Machine_Overflows is False for these
21501 types, meaning that the semantics of overflow is implementation-defined.
21502 In the case of GNAT, these semantics correspond to the normal IEEE
21503 treatment of infinities and NaN (not a number) values. For example,
21504 1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By
21505 avoiding explicit overflow checks, the performance is greatly improved
21506 on many targets. However, if required, floating-point overflow can be
21507 enabled by the use of the pragma Check_Float_Overflow.
21509 Another consideration that applies specifically to x86 32-bit
21510 architectures is which form of floating-point arithmetic is used.
21511 By default the operations use the old style x86 floating-point,
21512 which implements an 80-bit extended precision form (on these
21513 architectures the type Long_Long_Float corresponds to that form).
21514 In addition, generation of efficient code in this mode means that
21515 the extended precision form will be used for intermediate results.
21516 This may be helpful in improving the final precision of a complex
21517 expression. However it means that the results obtained on the x86
21518 will be different from those on other architectures, and for some
21519 algorithms, the extra intermediate precision can be detrimental.
21521 In addition to this old-style floating-point, all modern x86 chips
21522 implement an alternative floating-point operation model referred
21523 to as SSE2. In this model there is no extended form, and furthermore
21524 execution performance is significantly enhanced. To force GNAT to use
21525 this more modern form, use both of the switches:
21529 -msse2 -mfpmath=sse
21532 A unit compiled with these switches will automatically use the more
21533 efficient SSE2 instruction set for Float and Long_Float operations.
21534 Note that the ABI has the same form for both floating-point models,
21535 so it is permissible to mix units compiled with and without these
21538 @node Vectorization of loops,Other Optimization Switches,Floating_Point_Operations,Performance Considerations
21539 @anchor{gnat_ugn/gnat_and_program_execution id34}@anchor{1a6}@anchor{gnat_ugn/gnat_and_program_execution vectorization-of-loops}@anchor{1a7}
21540 @subsubsection Vectorization of loops
21543 @geindex Optimization Switches
21545 You can take advantage of the auto-vectorizer present in the @code{gcc}
21546 back end to vectorize loops with GNAT. The corresponding command line switch
21547 is @code{-ftree-vectorize} but, as it is enabled by default at @code{-O3}
21548 and other aggressive optimizations helpful for vectorization also are enabled
21549 by default at this level, using @code{-O3} directly is recommended.
21551 You also need to make sure that the target architecture features a supported
21552 SIMD instruction set. For example, for the x86 architecture, you should at
21553 least specify @code{-msse2} to get significant vectorization (but you don't
21554 need to specify it for x86-64 as it is part of the base 64-bit architecture).
21555 Similarly, for the PowerPC architecture, you should specify @code{-maltivec}.
21557 The preferred loop form for vectorization is the @code{for} iteration scheme.
21558 Loops with a @code{while} iteration scheme can also be vectorized if they are
21559 very simple, but the vectorizer will quickly give up otherwise. With either
21560 iteration scheme, the flow of control must be straight, in particular no
21561 @code{exit} statement may appear in the loop body. The loop may however
21562 contain a single nested loop, if it can be vectorized when considered alone:
21567 A : array (1..4, 1..4) of Long_Float;
21568 S : array (1..4) of Long_Float;
21572 for I in A'Range(1) loop
21573 for J in A'Range(2) loop
21574 S (I) := S (I) + A (I, J);
21581 The vectorizable operations depend on the targeted SIMD instruction set, but
21582 the adding and some of the multiplying operators are generally supported, as
21583 well as the logical operators for modular types. Note that compiling
21584 with @code{-gnatp} might well reveal cases where some checks do thwart
21587 Type conversions may also prevent vectorization if they involve semantics that
21588 are not directly supported by the code generator or the SIMD instruction set.
21589 A typical example is direct conversion from floating-point to integer types.
21590 The solution in this case is to use the following idiom:
21595 Integer (S'Truncation (F))
21599 if @code{S} is the subtype of floating-point object @code{F}.
21601 In most cases, the vectorizable loops are loops that iterate over arrays.
21602 All kinds of array types are supported, i.e. constrained array types with
21608 type Array_Type is array (1 .. 4) of Long_Float;
21612 constrained array types with dynamic bounds:
21617 type Array_Type is array (1 .. Q.N) of Long_Float;
21619 type Array_Type is array (Q.K .. 4) of Long_Float;
21621 type Array_Type is array (Q.K .. Q.N) of Long_Float;
21625 or unconstrained array types:
21630 type Array_Type is array (Positive range <>) of Long_Float;
21634 The quality of the generated code decreases when the dynamic aspect of the
21635 array type increases, the worst code being generated for unconstrained array
21636 types. This is so because, the less information the compiler has about the
21637 bounds of the array, the more fallback code it needs to generate in order to
21638 fix things up at run time.
21640 It is possible to specify that a given loop should be subject to vectorization
21641 preferably to other optimizations by means of pragma @code{Loop_Optimize}:
21646 pragma Loop_Optimize (Vector);
21650 placed immediately within the loop will convey the appropriate hint to the
21651 compiler for this loop.
21653 It is also possible to help the compiler generate better vectorized code
21654 for a given loop by asserting that there are no loop-carried dependencies
21655 in the loop. Consider for example the procedure:
21660 type Arr is array (1 .. 4) of Long_Float;
21662 procedure Add (X, Y : not null access Arr; R : not null access Arr) is
21664 for I in Arr'Range loop
21665 R(I) := X(I) + Y(I);
21671 By default, the compiler cannot unconditionally vectorize the loop because
21672 assigning to a component of the array designated by R in one iteration could
21673 change the value read from the components of the array designated by X or Y
21674 in a later iteration. As a result, the compiler will generate two versions
21675 of the loop in the object code, one vectorized and the other not vectorized,
21676 as well as a test to select the appropriate version at run time. This can
21677 be overcome by another hint:
21682 pragma Loop_Optimize (Ivdep);
21686 placed immediately within the loop will tell the compiler that it can safely
21687 omit the non-vectorized version of the loop as well as the run-time test.
21689 @node Other Optimization Switches,Optimization and Strict Aliasing,Vectorization of loops,Performance Considerations
21690 @anchor{gnat_ugn/gnat_and_program_execution other-optimization-switches}@anchor{1a8}@anchor{gnat_ugn/gnat_and_program_execution id35}@anchor{1a9}
21691 @subsubsection Other Optimization Switches
21694 @geindex Optimization Switches
21696 Since GNAT uses the @code{gcc} back end, all the specialized
21697 @code{gcc} optimization switches are potentially usable. These switches
21698 have not been extensively tested with GNAT but can generally be expected
21699 to work. Examples of switches in this category are @code{-funroll-loops}
21700 and the various target-specific @code{-m} options (in particular, it has
21701 been observed that @code{-march=xxx} can significantly improve performance
21702 on appropriate machines). For full details of these switches, see
21703 the @emph{Submodel Options} section in the @emph{Hardware Models and Configurations}
21704 chapter of @cite{Using the GNU Compiler Collection (GCC)}.
21706 @node Optimization and Strict Aliasing,Aliased Variables and Optimization,Other Optimization Switches,Performance Considerations
21707 @anchor{gnat_ugn/gnat_and_program_execution optimization-and-strict-aliasing}@anchor{f3}@anchor{gnat_ugn/gnat_and_program_execution id36}@anchor{1aa}
21708 @subsubsection Optimization and Strict Aliasing
21713 @geindex Strict Aliasing
21715 @geindex No_Strict_Aliasing
21717 The strong typing capabilities of Ada allow an optimizer to generate
21718 efficient code in situations where other languages would be forced to
21719 make worst case assumptions preventing such optimizations. Consider
21720 the following example:
21726 type Int1 is new Integer;
21727 type Int2 is new Integer;
21728 type Int1A is access Int1;
21729 type Int2A is access Int2;
21736 for J in Data'Range loop
21737 if Data (J) = Int1V.all then
21738 Int2V.all := Int2V.all + 1;
21746 In this example, since the variable @code{Int1V} can only access objects
21747 of type @code{Int1}, and @code{Int2V} can only access objects of type
21748 @code{Int2}, there is no possibility that the assignment to
21749 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
21750 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
21751 for all iterations of the loop and avoid the extra memory reference
21752 required to dereference it each time through the loop.
21754 This kind of optimization, called strict aliasing analysis, is
21755 triggered by specifying an optimization level of @code{-O2} or
21756 higher or @code{-Os} and allows GNAT to generate more efficient code
21757 when access values are involved.
21759 However, although this optimization is always correct in terms of
21760 the formal semantics of the Ada Reference Manual, difficulties can
21761 arise if features like @code{Unchecked_Conversion} are used to break
21762 the typing system. Consider the following complete program example:
21768 type int1 is new integer;
21769 type int2 is new integer;
21770 type a1 is access int1;
21771 type a2 is access int2;
21776 function to_a2 (Input : a1) return a2;
21779 with Unchecked_Conversion;
21781 function to_a2 (Input : a1) return a2 is
21783 new Unchecked_Conversion (a1, a2);
21785 return to_a2u (Input);
21791 with Text_IO; use Text_IO;
21793 v1 : a1 := new int1;
21794 v2 : a2 := to_a2 (v1);
21798 put_line (int1'image (v1.all));
21803 This program prints out 0 in @code{-O0} or @code{-O1}
21804 mode, but it prints out 1 in @code{-O2} mode. That's
21805 because in strict aliasing mode, the compiler can and
21806 does assume that the assignment to @code{v2.all} could not
21807 affect the value of @code{v1.all}, since different types
21810 This behavior is not a case of non-conformance with the standard, since
21811 the Ada RM specifies that an unchecked conversion where the resulting
21812 bit pattern is not a correct value of the target type can result in an
21813 abnormal value and attempting to reference an abnormal value makes the
21814 execution of a program erroneous. That's the case here since the result
21815 does not point to an object of type @code{int2}. This means that the
21816 effect is entirely unpredictable.
21818 However, although that explanation may satisfy a language
21819 lawyer, in practice an applications programmer expects an
21820 unchecked conversion involving pointers to create true
21821 aliases and the behavior of printing 1 seems plain wrong.
21822 In this case, the strict aliasing optimization is unwelcome.
21824 Indeed the compiler recognizes this possibility, and the
21825 unchecked conversion generates a warning:
21830 p2.adb:5:07: warning: possible aliasing problem with type "a2"
21831 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
21832 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
21836 Unfortunately the problem is recognized when compiling the body of
21837 package @code{p2}, but the actual "bad" code is generated while
21838 compiling the body of @code{m} and this latter compilation does not see
21839 the suspicious @code{Unchecked_Conversion}.
21841 As implied by the warning message, there are approaches you can use to
21842 avoid the unwanted strict aliasing optimization in a case like this.
21844 One possibility is to simply avoid the use of @code{-O2}, but
21845 that is a bit drastic, since it throws away a number of useful
21846 optimizations that do not involve strict aliasing assumptions.
21848 A less drastic approach is to compile the program using the
21849 option @code{-fno-strict-aliasing}. Actually it is only the
21850 unit containing the dereferencing of the suspicious pointer
21851 that needs to be compiled. So in this case, if we compile
21852 unit @code{m} with this switch, then we get the expected
21853 value of zero printed. Analyzing which units might need
21854 the switch can be painful, so a more reasonable approach
21855 is to compile the entire program with options @code{-O2}
21856 and @code{-fno-strict-aliasing}. If the performance is
21857 satisfactory with this combination of options, then the
21858 advantage is that the entire issue of possible "wrong"
21859 optimization due to strict aliasing is avoided.
21861 To avoid the use of compiler switches, the configuration
21862 pragma @code{No_Strict_Aliasing} with no parameters may be
21863 used to specify that for all access types, the strict
21864 aliasing optimization should be suppressed.
21866 However, these approaches are still overkill, in that they causes
21867 all manipulations of all access values to be deoptimized. A more
21868 refined approach is to concentrate attention on the specific
21869 access type identified as problematic.
21871 First, if a careful analysis of uses of the pointer shows
21872 that there are no possible problematic references, then
21873 the warning can be suppressed by bracketing the
21874 instantiation of @code{Unchecked_Conversion} to turn
21880 pragma Warnings (Off);
21882 new Unchecked_Conversion (a1, a2);
21883 pragma Warnings (On);
21887 Of course that approach is not appropriate for this particular
21888 example, since indeed there is a problematic reference. In this
21889 case we can take one of two other approaches.
21891 The first possibility is to move the instantiation of unchecked
21892 conversion to the unit in which the type is declared. In
21893 this example, we would move the instantiation of
21894 @code{Unchecked_Conversion} from the body of package
21895 @code{p2} to the spec of package @code{p1}. Now the
21896 warning disappears. That's because any use of the
21897 access type knows there is a suspicious unchecked
21898 conversion, and the strict aliasing optimization
21899 is automatically suppressed for the type.
21901 If it is not practical to move the unchecked conversion to the same unit
21902 in which the destination access type is declared (perhaps because the
21903 source type is not visible in that unit), you may use pragma
21904 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
21905 same declarative sequence as the declaration of the access type:
21910 type a2 is access int2;
21911 pragma No_Strict_Aliasing (a2);
21915 Here again, the compiler now knows that the strict aliasing optimization
21916 should be suppressed for any reference to type @code{a2} and the
21917 expected behavior is obtained.
21919 Finally, note that although the compiler can generate warnings for
21920 simple cases of unchecked conversions, there are tricker and more
21921 indirect ways of creating type incorrect aliases which the compiler
21922 cannot detect. Examples are the use of address overlays and unchecked
21923 conversions involving composite types containing access types as
21924 components. In such cases, no warnings are generated, but there can
21925 still be aliasing problems. One safe coding practice is to forbid the
21926 use of address clauses for type overlaying, and to allow unchecked
21927 conversion only for primitive types. This is not really a significant
21928 restriction since any possible desired effect can be achieved by
21929 unchecked conversion of access values.
21931 The aliasing analysis done in strict aliasing mode can certainly
21932 have significant benefits. We have seen cases of large scale
21933 application code where the time is increased by up to 5% by turning
21934 this optimization off. If you have code that includes significant
21935 usage of unchecked conversion, you might want to just stick with
21936 @code{-O1} and avoid the entire issue. If you get adequate
21937 performance at this level of optimization level, that's probably
21938 the safest approach. If tests show that you really need higher
21939 levels of optimization, then you can experiment with @code{-O2}
21940 and @code{-O2 -fno-strict-aliasing} to see how much effect this
21941 has on size and speed of the code. If you really need to use
21942 @code{-O2} with strict aliasing in effect, then you should
21943 review any uses of unchecked conversion of access types,
21944 particularly if you are getting the warnings described above.
21946 @node Aliased Variables and Optimization,Atomic Variables and Optimization,Optimization and Strict Aliasing,Performance Considerations
21947 @anchor{gnat_ugn/gnat_and_program_execution id37}@anchor{1ab}@anchor{gnat_ugn/gnat_and_program_execution aliased-variables-and-optimization}@anchor{1ac}
21948 @subsubsection Aliased Variables and Optimization
21953 There are scenarios in which programs may
21954 use low level techniques to modify variables
21955 that otherwise might be considered to be unassigned. For example,
21956 a variable can be passed to a procedure by reference, which takes
21957 the address of the parameter and uses the address to modify the
21958 variable's value, even though it is passed as an IN parameter.
21959 Consider the following example:
21965 Max_Length : constant Natural := 16;
21966 type Char_Ptr is access all Character;
21968 procedure Get_String(Buffer: Char_Ptr; Size : Integer);
21969 pragma Import (C, Get_String, "get_string");
21971 Name : aliased String (1 .. Max_Length) := (others => ' ');
21974 function Addr (S : String) return Char_Ptr is
21975 function To_Char_Ptr is
21976 new Ada.Unchecked_Conversion (System.Address, Char_Ptr);
21978 return To_Char_Ptr (S (S'First)'Address);
21982 Temp := Addr (Name);
21983 Get_String (Temp, Max_Length);
21988 where Get_String is a C function that uses the address in Temp to
21989 modify the variable @code{Name}. This code is dubious, and arguably
21990 erroneous, and the compiler would be entitled to assume that
21991 @code{Name} is never modified, and generate code accordingly.
21993 However, in practice, this would cause some existing code that
21994 seems to work with no optimization to start failing at high
21995 levels of optimzization.
21997 What the compiler does for such cases is to assume that marking
21998 a variable as aliased indicates that some "funny business" may
21999 be going on. The optimizer recognizes the aliased keyword and
22000 inhibits optimizations that assume the value cannot be assigned.
22001 This means that the above example will in fact "work" reliably,
22002 that is, it will produce the expected results.
22004 @node Atomic Variables and Optimization,Passive Task Optimization,Aliased Variables and Optimization,Performance Considerations
22005 @anchor{gnat_ugn/gnat_and_program_execution atomic-variables-and-optimization}@anchor{1ad}@anchor{gnat_ugn/gnat_and_program_execution id38}@anchor{1ae}
22006 @subsubsection Atomic Variables and Optimization
22011 There are two considerations with regard to performance when
22012 atomic variables are used.
22014 First, the RM only guarantees that access to atomic variables
22015 be atomic, it has nothing to say about how this is achieved,
22016 though there is a strong implication that this should not be
22017 achieved by explicit locking code. Indeed GNAT will never
22018 generate any locking code for atomic variable access (it will
22019 simply reject any attempt to make a variable or type atomic
22020 if the atomic access cannot be achieved without such locking code).
22022 That being said, it is important to understand that you cannot
22023 assume that the entire variable will always be accessed. Consider
22030 A,B,C,D : Character;
22033 for R'Alignment use 4;
22036 pragma Atomic (RV);
22043 You cannot assume that the reference to @code{RV.B}
22044 will read the entire 32-bit
22045 variable with a single load instruction. It is perfectly legitimate if
22046 the hardware allows it to do a byte read of just the B field. This read
22047 is still atomic, which is all the RM requires. GNAT can and does take
22048 advantage of this, depending on the architecture and optimization level.
22049 Any assumption to the contrary is non-portable and risky. Even if you
22050 examine the assembly language and see a full 32-bit load, this might
22051 change in a future version of the compiler.
22053 If your application requires that all accesses to @code{RV} in this
22054 example be full 32-bit loads, you need to make a copy for the access
22061 RV_Copy : constant R := RV;
22068 Now the reference to RV must read the whole variable.
22069 Actually one can imagine some compiler which figures
22070 out that the whole copy is not required (because only
22071 the B field is actually accessed), but GNAT
22072 certainly won't do that, and we don't know of any
22073 compiler that would not handle this right, and the
22074 above code will in practice work portably across
22075 all architectures (that permit the Atomic declaration).
22077 The second issue with atomic variables has to do with
22078 the possible requirement of generating synchronization
22079 code. For more details on this, consult the sections on
22080 the pragmas Enable/Disable_Atomic_Synchronization in the
22081 GNAT Reference Manual. If performance is critical, and
22082 such synchronization code is not required, it may be
22083 useful to disable it.
22085 @node Passive Task Optimization,,Atomic Variables and Optimization,Performance Considerations
22086 @anchor{gnat_ugn/gnat_and_program_execution passive-task-optimization}@anchor{1af}@anchor{gnat_ugn/gnat_and_program_execution id39}@anchor{1b0}
22087 @subsubsection Passive Task Optimization
22090 @geindex Passive Task
22092 A passive task is one which is sufficiently simple that
22093 in theory a compiler could recognize it an implement it
22094 efficiently without creating a new thread. The original design
22095 of Ada 83 had in mind this kind of passive task optimization, but
22096 only a few Ada 83 compilers attempted it. The problem was that
22097 it was difficult to determine the exact conditions under which
22098 the optimization was possible. The result is a very fragile
22099 optimization where a very minor change in the program can
22100 suddenly silently make a task non-optimizable.
22102 With the revisiting of this issue in Ada 95, there was general
22103 agreement that this approach was fundamentally flawed, and the
22104 notion of protected types was introduced. When using protected
22105 types, the restrictions are well defined, and you KNOW that the
22106 operations will be optimized, and furthermore this optimized
22107 performance is fully portable.
22109 Although it would theoretically be possible for GNAT to attempt to
22110 do this optimization, but it really doesn't make sense in the
22111 context of Ada 95, and none of the Ada 95 compilers implement
22112 this optimization as far as we know. In particular GNAT never
22113 attempts to perform this optimization.
22115 In any new Ada 95 code that is written, you should always
22116 use protected types in place of tasks that might be able to
22117 be optimized in this manner.
22118 Of course this does not help if you have legacy Ada 83 code
22119 that depends on this optimization, but it is unusual to encounter
22120 a case where the performance gains from this optimization
22123 Your program should work correctly without this optimization. If
22124 you have performance problems, then the most practical
22125 approach is to figure out exactly where these performance problems
22126 arise, and update those particular tasks to be protected types. Note
22127 that typically clients of the tasks who call entries, will not have
22128 to be modified, only the task definition itself.
22130 @node Text_IO Suggestions,Reducing Size of Executables with Unused Subprogram/Data Elimination,Performance Considerations,Improving Performance
22131 @anchor{gnat_ugn/gnat_and_program_execution text-io-suggestions}@anchor{1b1}@anchor{gnat_ugn/gnat_and_program_execution id40}@anchor{1b2}
22132 @subsection @code{Text_IO} Suggestions
22135 @geindex Text_IO and performance
22137 The @code{Ada.Text_IO} package has fairly high overheads due in part to
22138 the requirement of maintaining page and line counts. If performance
22139 is critical, a recommendation is to use @code{Stream_IO} instead of
22140 @code{Text_IO} for volume output, since this package has less overhead.
22142 If @code{Text_IO} must be used, note that by default output to the standard
22143 output and standard error files is unbuffered (this provides better
22144 behavior when output statements are used for debugging, or if the
22145 progress of a program is observed by tracking the output, e.g. by
22146 using the Unix @emph{tail -f} command to watch redirected output.
22148 If you are generating large volumes of output with @code{Text_IO} and
22149 performance is an important factor, use a designated file instead
22150 of the standard output file, or change the standard output file to
22151 be buffered using @code{Interfaces.C_Streams.setvbuf}.
22153 @node Reducing Size of Executables with Unused Subprogram/Data Elimination,,Text_IO Suggestions,Improving Performance
22154 @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}
22155 @subsection Reducing Size of Executables with Unused Subprogram/Data Elimination
22158 @geindex Uunused subprogram/data elimination
22160 This section describes how you can eliminate unused subprograms and data from
22161 your executable just by setting options at compilation time.
22164 * About unused subprogram/data elimination::
22165 * Compilation options::
22166 * Example of unused subprogram/data elimination::
22170 @node About unused subprogram/data elimination,Compilation options,,Reducing Size of Executables with Unused Subprogram/Data Elimination
22171 @anchor{gnat_ugn/gnat_and_program_execution id42}@anchor{1b5}@anchor{gnat_ugn/gnat_and_program_execution about-unused-subprogram-data-elimination}@anchor{1b6}
22172 @subsubsection About unused subprogram/data elimination
22175 By default, an executable contains all code and data of its composing objects
22176 (directly linked or coming from statically linked libraries), even data or code
22177 never used by this executable.
22179 This feature will allow you to eliminate such unused code from your
22180 executable, making it smaller (in disk and in memory).
22182 This functionality is available on all Linux platforms except for the IA-64
22183 architecture and on all cross platforms using the ELF binary file format.
22184 In both cases GNU binutils version 2.16 or later are required to enable it.
22186 @node Compilation options,Example of unused subprogram/data elimination,About unused subprogram/data elimination,Reducing Size of Executables with Unused Subprogram/Data Elimination
22187 @anchor{gnat_ugn/gnat_and_program_execution id43}@anchor{1b7}@anchor{gnat_ugn/gnat_and_program_execution compilation-options}@anchor{1b8}
22188 @subsubsection Compilation options
22191 The operation of eliminating the unused code and data from the final executable
22192 is directly performed by the linker.
22194 @geindex -ffunction-sections (gcc)
22196 @geindex -fdata-sections (gcc)
22198 In order to do this, it has to work with objects compiled with the
22200 @code{-ffunction-sections} @code{-fdata-sections}.
22202 These options are usable with C and Ada files.
22203 They will place respectively each
22204 function or data in a separate section in the resulting object file.
22206 Once the objects and static libraries are created with these options, the
22207 linker can perform the dead code elimination. You can do this by setting
22208 the @code{-Wl,--gc-sections} option to gcc command or in the
22209 @code{-largs} section of @code{gnatmake}. This will perform a
22210 garbage collection of code and data never referenced.
22212 If the linker performs a partial link (@code{-r} linker option), then you
22213 will need to provide the entry point using the @code{-e} / @code{--entry}
22216 Note that objects compiled without the @code{-ffunction-sections} and
22217 @code{-fdata-sections} options can still be linked with the executable.
22218 However, no dead code elimination will be performed on those objects (they will
22221 The GNAT static library is now compiled with -ffunction-sections and
22222 -fdata-sections on some platforms. This allows you to eliminate the unused code
22223 and data of the GNAT library from your executable.
22225 @node Example of unused subprogram/data elimination,,Compilation options,Reducing Size of Executables with Unused Subprogram/Data Elimination
22226 @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}
22227 @subsubsection Example of unused subprogram/data elimination
22230 Here is a simple example:
22243 Used_Data : Integer;
22244 Unused_Data : Integer;
22246 procedure Used (Data : Integer);
22247 procedure Unused (Data : Integer);
22250 package body Aux is
22251 procedure Used (Data : Integer) is
22256 procedure Unused (Data : Integer) is
22258 Unused_Data := Data;
22264 @code{Unused} and @code{Unused_Data} are never referenced in this code
22265 excerpt, and hence they may be safely removed from the final executable.
22272 $ nm test | grep used
22273 020015f0 T aux__unused
22274 02005d88 B aux__unused_data
22275 020015cc T aux__used
22276 02005d84 B aux__used_data
22278 $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
22279 -largs -Wl,--gc-sections
22281 $ nm test | grep used
22282 02005350 T aux__used
22283 0201ffe0 B aux__used_data
22287 It can be observed that the procedure @code{Unused} and the object
22288 @code{Unused_Data} are removed by the linker when using the
22289 appropriate options.
22291 @geindex Overflow checks
22293 @geindex Checks (overflow)
22295 @node Overflow Check Handling in GNAT,Performing Dimensionality Analysis in GNAT,Improving Performance,GNAT and Program Execution
22296 @anchor{gnat_ugn/gnat_and_program_execution id45}@anchor{169}@anchor{gnat_ugn/gnat_and_program_execution overflow-check-handling-in-gnat}@anchor{27}
22297 @section Overflow Check Handling in GNAT
22300 This section explains how to control the handling of overflow checks.
22304 * Management of Overflows in GNAT::
22305 * Specifying the Desired Mode::
22306 * Default Settings::
22307 * Implementation Notes::
22311 @node Background,Management of Overflows in GNAT,,Overflow Check Handling in GNAT
22312 @anchor{gnat_ugn/gnat_and_program_execution id46}@anchor{1bb}@anchor{gnat_ugn/gnat_and_program_execution background}@anchor{1bc}
22313 @subsection Background
22316 Overflow checks are checks that the compiler may make to ensure
22317 that intermediate results are not out of range. For example:
22328 If @code{A} has the value @code{Integer'Last}, then the addition may cause
22329 overflow since the result is out of range of the type @code{Integer}.
22330 In this case @code{Constraint_Error} will be raised if checks are
22333 A trickier situation arises in examples like the following:
22344 where @code{A} is @code{Integer'Last} and @code{C} is @code{-1}.
22345 Now the final result of the expression on the right hand side is
22346 @code{Integer'Last} which is in range, but the question arises whether the
22347 intermediate addition of @code{(A + 1)} raises an overflow error.
22349 The (perhaps surprising) answer is that the Ada language
22350 definition does not answer this question. Instead it leaves
22351 it up to the implementation to do one of two things if overflow
22352 checks are enabled.
22358 raise an exception (@code{Constraint_Error}), or
22361 yield the correct mathematical result which is then used in
22362 subsequent operations.
22365 If the compiler chooses the first approach, then the assignment of this
22366 example will indeed raise @code{Constraint_Error} if overflow checking is
22367 enabled, or result in erroneous execution if overflow checks are suppressed.
22369 But if the compiler
22370 chooses the second approach, then it can perform both additions yielding
22371 the correct mathematical result, which is in range, so no exception
22372 will be raised, and the right result is obtained, regardless of whether
22373 overflow checks are suppressed.
22375 Note that in the first example an
22376 exception will be raised in either case, since if the compiler
22377 gives the correct mathematical result for the addition, it will
22378 be out of range of the target type of the assignment, and thus
22379 fails the range check.
22381 This lack of specified behavior in the handling of overflow for
22382 intermediate results is a source of non-portability, and can thus
22383 be problematic when programs are ported. Most typically this arises
22384 in a situation where the original compiler did not raise an exception,
22385 and then the application is moved to a compiler where the check is
22386 performed on the intermediate result and an unexpected exception is
22389 Furthermore, when using Ada 2012's preconditions and other
22390 assertion forms, another issue arises. Consider:
22395 procedure P (A, B : Integer) with
22396 Pre => A + B <= Integer'Last;
22400 One often wants to regard arithmetic in a context like this from
22401 a mathematical point of view. So for example, if the two actual parameters
22402 for a call to @code{P} are both @code{Integer'Last}, then
22403 the precondition should be regarded as False. If we are executing
22404 in a mode with run-time checks enabled for preconditions, then we would
22405 like this precondition to fail, rather than raising an exception
22406 because of the intermediate overflow.
22408 However, the language definition leaves the specification of
22409 whether the above condition fails (raising @code{Assert_Error}) or
22410 causes an intermediate overflow (raising @code{Constraint_Error})
22411 up to the implementation.
22413 The situation is worse in a case such as the following:
22418 procedure Q (A, B, C : Integer) with
22419 Pre => A + B + C <= Integer'Last;
22428 Q (A => Integer'Last, B => 1, C => -1);
22432 From a mathematical point of view the precondition
22433 is True, but at run time we may (but are not guaranteed to) get an
22434 exception raised because of the intermediate overflow (and we really
22435 would prefer this precondition to be considered True at run time).
22437 @node Management of Overflows in GNAT,Specifying the Desired Mode,Background,Overflow Check Handling in GNAT
22438 @anchor{gnat_ugn/gnat_and_program_execution id47}@anchor{1bd}@anchor{gnat_ugn/gnat_and_program_execution management-of-overflows-in-gnat}@anchor{1be}
22439 @subsection Management of Overflows in GNAT
22442 To deal with the portability issue, and with the problem of
22443 mathematical versus run-time interpretation of the expressions in
22444 assertions, GNAT provides comprehensive control over the handling
22445 of intermediate overflow. GNAT can operate in three modes, and
22446 furthemore, permits separate selection of operating modes for
22447 the expressions within assertions (here the term 'assertions'
22448 is used in the technical sense, which includes preconditions and so forth)
22449 and for expressions appearing outside assertions.
22451 The three modes are:
22457 @emph{Use base type for intermediate operations} (@code{STRICT})
22459 In this mode, all intermediate results for predefined arithmetic
22460 operators are computed using the base type, and the result must
22461 be in range of the base type. If this is not the
22462 case then either an exception is raised (if overflow checks are
22463 enabled) or the execution is erroneous (if overflow checks are suppressed).
22464 This is the normal default mode.
22467 @emph{Most intermediate overflows avoided} (@code{MINIMIZED})
22469 In this mode, the compiler attempts to avoid intermediate overflows by
22470 using a larger integer type, typically @code{Long_Long_Integer},
22471 as the type in which arithmetic is
22472 performed for predefined arithmetic operators. This may be slightly more
22474 run time (compared to suppressing intermediate overflow checks), though
22475 the cost is negligible on modern 64-bit machines. For the examples given
22476 earlier, no intermediate overflows would have resulted in exceptions,
22477 since the intermediate results are all in the range of
22478 @code{Long_Long_Integer} (typically 64-bits on nearly all implementations
22479 of GNAT). In addition, if checks are enabled, this reduces the number of
22480 checks that must be made, so this choice may actually result in an
22481 improvement in space and time behavior.
22483 However, there are cases where @code{Long_Long_Integer} is not large
22484 enough, consider the following example:
22489 procedure R (A, B, C, D : Integer) with
22490 Pre => (A**2 * B**2) / (C**2 * D**2) <= 10;
22494 where @code{A} = @code{B} = @code{C} = @code{D} = @code{Integer'Last}.
22495 Now the intermediate results are
22496 out of the range of @code{Long_Long_Integer} even though the final result
22497 is in range and the precondition is True (from a mathematical point
22498 of view). In such a case, operating in this mode, an overflow occurs
22499 for the intermediate computation (which is why this mode
22500 says @emph{most} intermediate overflows are avoided). In this case,
22501 an exception is raised if overflow checks are enabled, and the
22502 execution is erroneous if overflow checks are suppressed.
22505 @emph{All intermediate overflows avoided} (@code{ELIMINATED})
22507 In this mode, the compiler avoids all intermediate overflows
22508 by using arbitrary precision arithmetic as required. In this
22509 mode, the above example with @code{A**2 * B**2} would
22510 not cause intermediate overflow, because the intermediate result
22511 would be evaluated using sufficient precision, and the result
22512 of evaluating the precondition would be True.
22514 This mode has the advantage of avoiding any intermediate
22515 overflows, but at the expense of significant run-time overhead,
22516 including the use of a library (included automatically in this
22517 mode) for multiple-precision arithmetic.
22519 This mode provides cleaner semantics for assertions, since now
22520 the run-time behavior emulates true arithmetic behavior for the
22521 predefined arithmetic operators, meaning that there is never a
22522 conflict between the mathematical view of the assertion, and its
22525 Note that in this mode, the behavior is unaffected by whether or
22526 not overflow checks are suppressed, since overflow does not occur.
22527 It is possible for gigantic intermediate expressions to raise
22528 @code{Storage_Error} as a result of attempting to compute the
22529 results of such expressions (e.g. @code{Integer'Last ** Integer'Last})
22530 but overflow is impossible.
22533 Note that these modes apply only to the evaluation of predefined
22534 arithmetic, membership, and comparison operators for signed integer
22537 For fixed-point arithmetic, checks can be suppressed. But if checks
22539 then fixed-point values are always checked for overflow against the
22540 base type for intermediate expressions (that is such checks always
22541 operate in the equivalent of @code{STRICT} mode).
22543 For floating-point, on nearly all architectures, @code{Machine_Overflows}
22544 is False, and IEEE infinities are generated, so overflow exceptions
22545 are never raised. If you want to avoid infinities, and check that
22546 final results of expressions are in range, then you can declare a
22547 constrained floating-point type, and range checks will be carried
22548 out in the normal manner (with infinite values always failing all
22551 @node Specifying the Desired Mode,Default Settings,Management of Overflows in GNAT,Overflow Check Handling in GNAT
22552 @anchor{gnat_ugn/gnat_and_program_execution specifying-the-desired-mode}@anchor{f8}@anchor{gnat_ugn/gnat_and_program_execution id48}@anchor{1bf}
22553 @subsection Specifying the Desired Mode
22556 @geindex pragma Overflow_Mode
22558 The desired mode of for handling intermediate overflow can be specified using
22559 either the @code{Overflow_Mode} pragma or an equivalent compiler switch.
22560 The pragma has the form
22565 pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]);
22569 where @code{MODE} is one of
22575 @code{STRICT}: intermediate overflows checked (using base type)
22578 @code{MINIMIZED}: minimize intermediate overflows
22581 @code{ELIMINATED}: eliminate intermediate overflows
22584 The case is ignored, so @code{MINIMIZED}, @code{Minimized} and
22585 @code{minimized} all have the same effect.
22587 If only the @code{General} parameter is present, then the given @code{MODE} applies
22588 to expressions both within and outside assertions. If both arguments
22589 are present, then @code{General} applies to expressions outside assertions,
22590 and @code{Assertions} applies to expressions within assertions. For example:
22595 pragma Overflow_Mode
22596 (General => Minimized, Assertions => Eliminated);
22600 specifies that general expressions outside assertions be evaluated
22601 in 'minimize intermediate overflows' mode, and expressions within
22602 assertions be evaluated in 'eliminate intermediate overflows' mode.
22603 This is often a reasonable choice, avoiding excessive overhead
22604 outside assertions, but assuring a high degree of portability
22605 when importing code from another compiler, while incurring
22606 the extra overhead for assertion expressions to ensure that
22607 the behavior at run time matches the expected mathematical
22610 The @code{Overflow_Mode} pragma has the same scoping and placement
22611 rules as pragma @code{Suppress}, so it can occur either as a
22612 configuration pragma, specifying a default for the whole
22613 program, or in a declarative scope, where it applies to the
22614 remaining declarations and statements in that scope.
22616 Note that pragma @code{Overflow_Mode} does not affect whether
22617 overflow checks are enabled or suppressed. It only controls the
22618 method used to compute intermediate values. To control whether
22619 overflow checking is enabled or suppressed, use pragma @code{Suppress}
22620 or @code{Unsuppress} in the usual manner.
22622 @geindex -gnato? (gcc)
22624 @geindex -gnato?? (gcc)
22626 Additionally, a compiler switch @code{-gnato?} or @code{-gnato??}
22627 can be used to control the checking mode default (which can be subsequently
22628 overridden using pragmas).
22630 Here @code{?} is one of the digits @code{1} through @code{3}:
22635 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
22642 use base type for intermediate operations (@code{STRICT})
22650 minimize intermediate overflows (@code{MINIMIZED})
22658 eliminate intermediate overflows (@code{ELIMINATED})
22664 As with the pragma, if only one digit appears then it applies to all
22665 cases; if two digits are given, then the first applies outside
22666 assertions, and the second within assertions. Thus the equivalent
22667 of the example pragma above would be
22670 If no digits follow the @code{-gnato}, then it is equivalent to
22672 causing all intermediate operations to be computed using the base
22673 type (@code{STRICT} mode).
22675 @node Default Settings,Implementation Notes,Specifying the Desired Mode,Overflow Check Handling in GNAT
22676 @anchor{gnat_ugn/gnat_and_program_execution id49}@anchor{1c0}@anchor{gnat_ugn/gnat_and_program_execution default-settings}@anchor{1c1}
22677 @subsection Default Settings
22680 The default mode for overflow checks is
22689 which causes all computations both inside and outside assertions to use
22692 This retains compatibility with previous versions of
22693 GNAT which suppressed overflow checks by default and always
22694 used the base type for computation of intermediate results.
22696 @c Sphinx allows no emphasis within :index: role. As a workaround we
22697 @c point the index to "switch" and use emphasis for "-gnato".
22700 @geindex -gnato (gcc)
22701 switch @code{-gnato} (with no digits following)
22711 which causes overflow checking of all intermediate overflows
22712 both inside and outside assertions against the base type.
22714 The pragma @code{Suppress (Overflow_Check)} disables overflow
22715 checking, but it has no effect on the method used for computing
22716 intermediate results.
22718 The pragma @code{Unsuppress (Overflow_Check)} enables overflow
22719 checking, but it has no effect on the method used for computing
22720 intermediate results.
22722 @node Implementation Notes,,Default Settings,Overflow Check Handling in GNAT
22723 @anchor{gnat_ugn/gnat_and_program_execution implementation-notes}@anchor{1c2}@anchor{gnat_ugn/gnat_and_program_execution id50}@anchor{1c3}
22724 @subsection Implementation Notes
22727 In practice on typical 64-bit machines, the @code{MINIMIZED} mode is
22728 reasonably efficient, and can be generally used. It also helps
22729 to ensure compatibility with code imported from some other
22732 Setting all intermediate overflows checking (@code{CHECKED} mode)
22733 makes sense if you want to
22734 make sure that your code is compatible with any other possible
22735 Ada implementation. This may be useful in ensuring portability
22736 for code that is to be exported to some other compiler than GNAT.
22738 The Ada standard allows the reassociation of expressions at
22739 the same precedence level if no parentheses are present. For
22740 example, @code{A+B+C} parses as though it were @code{(A+B)+C}, but
22741 the compiler can reintepret this as @code{A+(B+C)}, possibly
22742 introducing or eliminating an overflow exception. The GNAT
22743 compiler never takes advantage of this freedom, and the
22744 expression @code{A+B+C} will be evaluated as @code{(A+B)+C}.
22745 If you need the other order, you can write the parentheses
22746 explicitly @code{A+(B+C)} and GNAT will respect this order.
22748 The use of @code{ELIMINATED} mode will cause the compiler to
22749 automatically include an appropriate arbitrary precision
22750 integer arithmetic package. The compiler will make calls
22751 to this package, though only in cases where it cannot be
22752 sure that @code{Long_Long_Integer} is sufficient to guard against
22753 intermediate overflows. This package does not use dynamic
22754 allocation, but it does use the secondary stack, so an
22755 appropriate secondary stack package must be present (this
22756 is always true for standard full Ada, but may require
22757 specific steps for restricted run times such as ZFP).
22759 Although @code{ELIMINATED} mode causes expressions to use arbitrary
22760 precision arithmetic, avoiding overflow, the final result
22761 must be in an appropriate range. This is true even if the
22762 final result is of type @code{[Long_[Long_]]Integer'Base}, which
22763 still has the same bounds as its associated constrained
22766 Currently, the @code{ELIMINATED} mode is only available on target
22767 platforms for which @code{Long_Long_Integer} is 64-bits (nearly all GNAT
22770 @node Performing Dimensionality Analysis in GNAT,Stack Related Facilities,Overflow Check Handling in GNAT,GNAT and Program Execution
22771 @anchor{gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat}@anchor{28}@anchor{gnat_ugn/gnat_and_program_execution id51}@anchor{16a}
22772 @section Performing Dimensionality Analysis in GNAT
22775 @geindex Dimensionality analysis
22777 The GNAT compiler supports dimensionality checking. The user can
22778 specify physical units for objects, and the compiler will verify that uses
22779 of these objects are compatible with their dimensions, in a fashion that is
22780 familiar to engineering practice. The dimensions of algebraic expressions
22781 (including powers with static exponents) are computed from their constituents.
22783 @geindex Dimension_System aspect
22785 @geindex Dimension aspect
22787 This feature depends on Ada 2012 aspect specifications, and is available from
22788 version 7.0.1 of GNAT onwards.
22789 The GNAT-specific aspect @code{Dimension_System}
22790 allows you to define a system of units; the aspect @code{Dimension}
22791 then allows the user to declare dimensioned quantities within a given system.
22792 (These aspects are described in the @emph{Implementation Defined Aspects}
22793 chapter of the @emph{GNAT Reference Manual}).
22795 The major advantage of this model is that it does not require the declaration of
22796 multiple operators for all possible combinations of types: it is only necessary
22797 to use the proper subtypes in object declarations.
22799 @geindex System.Dim.Mks package (GNAT library)
22801 @geindex MKS_Type type
22803 The simplest way to impose dimensionality checking on a computation is to make
22804 use of one of the instantiations of the package @code{System.Dim.Generic_Mks}, which
22805 are part of the GNAT library. This generic package defines a floating-point
22806 type @code{MKS_Type}, for which a sequence of dimension names are specified,
22807 together with their conventional abbreviations. The following should be read
22808 together with the full specification of the package, in file
22809 @code{s-digemk.ads}.
22813 @geindex s-digemk.ads file
22816 type Mks_Type is new Float_Type
22818 Dimension_System => (
22819 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
22820 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
22821 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
22822 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
22823 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"),
22824 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
22825 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
22829 The package then defines a series of subtypes that correspond to these
22830 conventional units. For example:
22835 subtype Length is Mks_Type
22837 Dimension => (Symbol => 'm', Meter => 1, others => 0);
22841 and similarly for @code{Mass}, @code{Time}, @code{Electric_Current},
22842 @code{Thermodynamic_Temperature}, @code{Amount_Of_Substance}, and
22843 @code{Luminous_Intensity} (the standard set of units of the SI system).
22845 The package also defines conventional names for values of each unit, for
22851 m : constant Length := 1.0;
22852 kg : constant Mass := 1.0;
22853 s : constant Time := 1.0;
22854 A : constant Electric_Current := 1.0;
22858 as well as useful multiples of these units:
22863 cm : constant Length := 1.0E-02;
22864 g : constant Mass := 1.0E-03;
22865 min : constant Time := 60.0;
22866 day : constant Time := 60.0 * 24.0 * min;
22871 There are three instantiations of @code{System.Dim.Generic_Mks} defined in the
22878 @code{System.Dim.Float_Mks} based on @code{Float} defined in @code{s-diflmk.ads}.
22881 @code{System.Dim.Long_Mks} based on @code{Long_Float} defined in @code{s-dilomk.ads}.
22884 @code{System.Dim.Mks} based on @code{Long_Long_Float} defined in @code{s-dimmks.ads}.
22887 Using one of these packages, you can then define a derived unit by providing
22888 the aspect that specifies its dimensions within the MKS system, as well as the
22889 string to be used for output of a value of that unit:
22894 subtype Acceleration is Mks_Type
22895 with Dimension => ("m/sec^2",
22902 Here is a complete example of use:
22907 with System.Dim.MKS; use System.Dim.Mks;
22908 with System.Dim.Mks_IO; use System.Dim.Mks_IO;
22909 with Text_IO; use Text_IO;
22910 procedure Free_Fall is
22911 subtype Acceleration is Mks_Type
22912 with Dimension => ("m/sec^2", 1, 0, -2, others => 0);
22913 G : constant acceleration := 9.81 * m / (s ** 2);
22914 T : Time := 10.0*s;
22918 Put ("Gravitational constant: ");
22919 Put (G, Aft => 2, Exp => 0); Put_Line ("");
22920 Distance := 0.5 * G * T ** 2;
22921 Put ("distance travelled in 10 seconds of free fall ");
22922 Put (Distance, Aft => 2, Exp => 0);
22928 Execution of this program yields:
22933 Gravitational constant: 9.81 m/sec^2
22934 distance travelled in 10 seconds of free fall 490.50 m
22938 However, incorrect assignments such as:
22944 Distance := 5.0 * kg;
22948 are rejected with the following diagnoses:
22954 >>> dimensions mismatch in assignment
22955 >>> left-hand side has dimension [L]
22956 >>> right-hand side is dimensionless
22958 Distance := 5.0 * kg:
22959 >>> dimensions mismatch in assignment
22960 >>> left-hand side has dimension [L]
22961 >>> right-hand side has dimension [M]
22965 The dimensions of an expression are properly displayed, even if there is
22966 no explicit subtype for it. If we add to the program:
22971 Put ("Final velocity: ");
22972 Put (G * T, Aft =>2, Exp =>0);
22977 then the output includes:
22982 Final velocity: 98.10 m.s**(-1)
22985 @geindex Dimensionable type
22987 @geindex Dimensioned subtype
22990 The type @code{Mks_Type} is said to be a @emph{dimensionable type} since it has a
22991 @code{Dimension_System} aspect, and the subtypes @code{Length}, @code{Mass}, etc.,
22992 are said to be @emph{dimensioned subtypes} since each one has a @code{Dimension}
22997 @geindex Dimension Vector (for a dimensioned subtype)
22999 @geindex Dimension aspect
23001 @geindex Dimension_System aspect
23004 The @code{Dimension} aspect of a dimensioned subtype @code{S} defines a mapping
23005 from the base type's Unit_Names to integer (or, more generally, rational)
23006 values. This mapping is the @emph{dimension vector} (also referred to as the
23007 @emph{dimensionality}) for that subtype, denoted by @code{DV(S)}, and thus for each
23008 object of that subtype. Intuitively, the value specified for each
23009 @code{Unit_Name} is the exponent associated with that unit; a zero value
23010 means that the unit is not used. For example:
23016 Acc : Acceleration;
23024 Here @code{DV(Acc)} = @code{DV(Acceleration)} =
23025 @code{(Meter=>1, Kilogram=>0, Second=>-2, Ampere=>0, Kelvin=>0, Mole=>0, Candela=>0)}.
23026 Symbolically, we can express this as @code{Meter / Second**2}.
23028 The dimension vector of an arithmetic expression is synthesized from the
23029 dimension vectors of its components, with compile-time dimensionality checks
23030 that help prevent mismatches such as using an @code{Acceleration} where a
23031 @code{Length} is required.
23033 The dimension vector of the result of an arithmetic expression @emph{expr}, or
23034 @code{DV(@emph{expr})}, is defined as follows, assuming conventional
23035 mathematical definitions for the vector operations that are used:
23041 If @emph{expr} is of the type @emph{universal_real}, or is not of a dimensioned subtype,
23042 then @emph{expr} is dimensionless; @code{DV(@emph{expr})} is the empty vector.
23045 @code{DV(@emph{op expr})}, where @emph{op} is a unary operator, is @code{DV(@emph{expr})}
23048 @code{DV(@emph{expr1 op expr2})} where @emph{op} is "+" or "-" is @code{DV(@emph{expr1})}
23049 provided that @code{DV(@emph{expr1})} = @code{DV(@emph{expr2})}.
23050 If this condition is not met then the construct is illegal.
23053 @code{DV(@emph{expr1} * @emph{expr2})} is @code{DV(@emph{expr1})} + @code{DV(@emph{expr2})},
23054 and @code{DV(@emph{expr1} / @emph{expr2})} = @code{DV(@emph{expr1})} - @code{DV(@emph{expr2})}.
23055 In this context if one of the @emph{expr}s is dimensionless then its empty
23056 dimension vector is treated as @code{(others => 0)}.
23059 @code{DV(@emph{expr} ** @emph{power})} is @emph{power} * @code{DV(@emph{expr})},
23060 provided that @emph{power} is a static rational value. If this condition is not
23061 met then the construct is illegal.
23064 Note that, by the above rules, it is illegal to use binary "+" or "-" to
23065 combine a dimensioned and dimensionless value. Thus an expression such as
23066 @code{acc-10.0} is illegal, where @code{acc} is an object of subtype
23067 @code{Acceleration}.
23069 The dimensionality checks for relationals use the same rules as
23070 for "+" and "-", except when comparing to a literal; thus
23088 and is thus illegal, but
23097 is accepted with a warning. Analogously a conditional expression requires the
23098 same dimension vector for each branch (with no exception for literals).
23100 The dimension vector of a type conversion @code{T(@emph{expr})} is defined
23101 as follows, based on the nature of @code{T}:
23107 If @code{T} is a dimensioned subtype then @code{DV(T(@emph{expr}))} is @code{DV(T)}
23108 provided that either @emph{expr} is dimensionless or
23109 @code{DV(T)} = @code{DV(@emph{expr})}. The conversion is illegal
23110 if @emph{expr} is dimensioned and @code{DV(@emph{expr})} /= @code{DV(T)}.
23111 Note that vector equality does not require that the corresponding
23112 Unit_Names be the same.
23114 As a consequence of the above rule, it is possible to convert between
23115 different dimension systems that follow the same international system
23116 of units, with the seven physical components given in the standard order
23117 (length, mass, time, etc.). Thus a length in meters can be converted to
23118 a length in inches (with a suitable conversion factor) but cannot be
23119 converted, for example, to a mass in pounds.
23122 If @code{T} is the base type for @emph{expr} (and the dimensionless root type of
23123 the dimension system), then @code{DV(T(@emph{expr}))} is @code{DV(expr)}.
23124 Thus, if @emph{expr} is of a dimensioned subtype of @code{T}, the conversion may
23125 be regarded as a "view conversion" that preserves dimensionality.
23127 This rule makes it possible to write generic code that can be instantiated
23128 with compatible dimensioned subtypes. The generic unit will contain
23129 conversions that will consequently be present in instantiations, but
23130 conversions to the base type will preserve dimensionality and make it
23131 possible to write generic code that is correct with respect to
23135 Otherwise (i.e., @code{T} is neither a dimensioned subtype nor a dimensionable
23136 base type), @code{DV(T(@emph{expr}))} is the empty vector. Thus a dimensioned
23137 value can be explicitly converted to a non-dimensioned subtype, which
23138 of course then escapes dimensionality analysis.
23141 The dimension vector for a type qualification @code{T'(@emph{expr})} is the same
23142 as for the type conversion @code{T(@emph{expr})}.
23144 An assignment statement
23153 requires @code{DV(Source)} = @code{DV(Target)}, and analogously for parameter
23154 passing (the dimension vector for the actual parameter must be equal to the
23155 dimension vector for the formal parameter).
23157 @node Stack Related Facilities,Memory Management Issues,Performing Dimensionality Analysis in GNAT,GNAT and Program Execution
23158 @anchor{gnat_ugn/gnat_and_program_execution stack-related-facilities}@anchor{29}@anchor{gnat_ugn/gnat_and_program_execution id52}@anchor{16b}
23159 @section Stack Related Facilities
23162 This section describes some useful tools associated with stack
23163 checking and analysis. In
23164 particular, it deals with dynamic and static stack usage measurements.
23167 * Stack Overflow Checking::
23168 * Static Stack Usage Analysis::
23169 * Dynamic Stack Usage Analysis::
23173 @node Stack Overflow Checking,Static Stack Usage Analysis,,Stack Related Facilities
23174 @anchor{gnat_ugn/gnat_and_program_execution id53}@anchor{1c4}@anchor{gnat_ugn/gnat_and_program_execution stack-overflow-checking}@anchor{f4}
23175 @subsection Stack Overflow Checking
23178 @geindex Stack Overflow Checking
23180 @geindex -fstack-check (gcc)
23182 For most operating systems, @code{gcc} does not perform stack overflow
23183 checking by default. This means that if the main environment task or
23184 some other task exceeds the available stack space, then unpredictable
23185 behavior will occur. Most native systems offer some level of protection by
23186 adding a guard page at the end of each task stack. This mechanism is usually
23187 not enough for dealing properly with stack overflow situations because
23188 a large local variable could "jump" above the guard page.
23189 Furthermore, when the
23190 guard page is hit, there may not be any space left on the stack for executing
23191 the exception propagation code. Enabling stack checking avoids
23194 To activate stack checking, compile all units with the @code{gcc} option
23195 @code{-fstack-check}. For example:
23200 $ gcc -c -fstack-check package1.adb
23204 Units compiled with this option will generate extra instructions to check
23205 that any use of the stack (for procedure calls or for declaring local
23206 variables in declare blocks) does not exceed the available stack space.
23207 If the space is exceeded, then a @code{Storage_Error} exception is raised.
23209 For declared tasks, the default stack size is defined by the GNAT runtime,
23210 whose size may be modified at bind time through the @code{-d} bind switch
23211 (@ref{11f,,Switches for gnatbind}). Task specific stack sizes may be set using the
23212 @code{Storage_Size} pragma.
23214 For the environment task, the stack size is determined by the operating system.
23215 Consequently, to modify the size of the environment task please refer to your
23216 operating system documentation.
23218 @node Static Stack Usage Analysis,Dynamic Stack Usage Analysis,Stack Overflow Checking,Stack Related Facilities
23219 @anchor{gnat_ugn/gnat_and_program_execution id54}@anchor{1c5}@anchor{gnat_ugn/gnat_and_program_execution static-stack-usage-analysis}@anchor{f5}
23220 @subsection Static Stack Usage Analysis
23223 @geindex Static Stack Usage Analysis
23225 @geindex -fstack-usage
23227 A unit compiled with @code{-fstack-usage} will generate an extra file
23229 the maximum amount of stack used, on a per-function basis.
23230 The file has the same
23231 basename as the target object file with a @code{.su} extension.
23232 Each line of this file is made up of three fields:
23238 The name of the function.
23244 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
23247 The second field corresponds to the size of the known part of the function
23250 The qualifier @code{static} means that the function frame size
23252 It usually means that all local variables have a static size.
23253 In this case, the second field is a reliable measure of the function stack
23256 The qualifier @code{dynamic} means that the function frame size is not static.
23257 It happens mainly when some local variables have a dynamic size. When this
23258 qualifier appears alone, the second field is not a reliable measure
23259 of the function stack analysis. When it is qualified with @code{bounded}, it
23260 means that the second field is a reliable maximum of the function stack
23263 A unit compiled with @code{-Wstack-usage} will issue a warning for each
23264 subprogram whose stack usage might be larger than the specified amount of
23265 bytes. The wording is in keeping with the qualifier documented above.
23267 @node Dynamic Stack Usage Analysis,,Static Stack Usage Analysis,Stack Related Facilities
23268 @anchor{gnat_ugn/gnat_and_program_execution id55}@anchor{1c6}@anchor{gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis}@anchor{122}
23269 @subsection Dynamic Stack Usage Analysis
23272 It is possible to measure the maximum amount of stack used by a task, by
23273 adding a switch to @code{gnatbind}, as:
23278 $ gnatbind -u0 file
23282 With this option, at each task termination, its stack usage is output on
23284 Note that this switch is not compatible with tools like
23285 Valgrind and DrMemory; they will report errors.
23287 It is not always convenient to output the stack usage when the program
23288 is still running. Hence, it is possible to delay this output until program
23289 termination. for a given number of tasks specified as the argument of the
23290 @code{-u} option. For instance:
23295 $ gnatbind -u100 file
23299 will buffer the stack usage information of the first 100 tasks to terminate and
23300 output this info at program termination. Results are displayed in four
23306 Index | Task Name | Stack Size | Stack Usage
23316 @emph{Index} is a number associated with each task.
23319 @emph{Task Name} is the name of the task analyzed.
23322 @emph{Stack Size} is the maximum size for the stack.
23325 @emph{Stack Usage} is the measure done by the stack analyzer.
23326 In order to prevent overflow, the stack
23327 is not entirely analyzed, and it's not possible to know exactly how
23328 much has actually been used.
23331 By default the environment task stack, the stack that contains the main unit,
23332 is not processed. To enable processing of the environment task stack, the
23333 environment variable GNAT_STACK_LIMIT needs to be set to the maximum size of
23334 the environment task stack. This amount is given in kilobytes. For example:
23339 $ set GNAT_STACK_LIMIT 1600
23343 would specify to the analyzer that the environment task stack has a limit
23344 of 1.6 megabytes. Any stack usage beyond this will be ignored by the analysis.
23346 The package @code{GNAT.Task_Stack_Usage} provides facilities to get
23347 stack-usage reports at run time. See its body for the details.
23349 @node Memory Management Issues,,Stack Related Facilities,GNAT and Program Execution
23350 @anchor{gnat_ugn/gnat_and_program_execution id56}@anchor{16c}@anchor{gnat_ugn/gnat_and_program_execution memory-management-issues}@anchor{2a}
23351 @section Memory Management Issues
23354 This section describes some useful memory pools provided in the GNAT library
23355 and in particular the GNAT Debug Pool facility, which can be used to detect
23356 incorrect uses of access values (including 'dangling references').
23360 * Some Useful Memory Pools::
23361 * The GNAT Debug Pool Facility::
23365 @node Some Useful Memory Pools,The GNAT Debug Pool Facility,,Memory Management Issues
23366 @anchor{gnat_ugn/gnat_and_program_execution id57}@anchor{1c7}@anchor{gnat_ugn/gnat_and_program_execution some-useful-memory-pools}@anchor{1c8}
23367 @subsection Some Useful Memory Pools
23370 @geindex Memory Pool
23375 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
23376 storage pool. Allocations use the standard system call @code{malloc} while
23377 deallocations use the standard system call @code{free}. No reclamation is
23378 performed when the pool goes out of scope. For performance reasons, the
23379 standard default Ada allocators/deallocators do not use any explicit storage
23380 pools but if they did, they could use this storage pool without any change in
23381 behavior. That is why this storage pool is used when the user
23382 manages to make the default implicit allocator explicit as in this example:
23387 type T1 is access Something;
23388 -- no Storage pool is defined for T2
23390 type T2 is access Something_Else;
23391 for T2'Storage_Pool use T1'Storage_Pool;
23392 -- the above is equivalent to
23393 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
23397 The @code{System.Pool_Local} package offers the @code{Unbounded_Reclaim_Pool} storage
23398 pool. The allocation strategy is similar to @code{Pool_Local}
23399 except that the all
23400 storage allocated with this pool is reclaimed when the pool object goes out of
23401 scope. This pool provides a explicit mechanism similar to the implicit one
23402 provided by several Ada 83 compilers for allocations performed through a local
23403 access type and whose purpose was to reclaim memory when exiting the
23404 scope of a given local access. As an example, the following program does not
23405 leak memory even though it does not perform explicit deallocation:
23410 with System.Pool_Local;
23411 procedure Pooloc1 is
23412 procedure Internal is
23413 type A is access Integer;
23414 X : System.Pool_Local.Unbounded_Reclaim_Pool;
23415 for A'Storage_Pool use X;
23418 for I in 1 .. 50 loop
23423 for I in 1 .. 100 loop
23430 The @code{System.Pool_Size} package implements the @code{Stack_Bounded_Pool} used when
23431 @code{Storage_Size} is specified for an access type.
23432 The whole storage for the pool is
23433 allocated at once, usually on the stack at the point where the access type is
23434 elaborated. It is automatically reclaimed when exiting the scope where the
23435 access type is defined. This package is not intended to be used directly by the
23436 user and it is implicitly used for each such declaration:
23441 type T1 is access Something;
23442 for T1'Storage_Size use 10_000;
23446 @node The GNAT Debug Pool Facility,,Some Useful Memory Pools,Memory Management Issues
23447 @anchor{gnat_ugn/gnat_and_program_execution id58}@anchor{1c9}@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility}@anchor{1ca}
23448 @subsection The GNAT Debug Pool Facility
23451 @geindex Debug Pool
23455 @geindex memory corruption
23457 The use of unchecked deallocation and unchecked conversion can easily
23458 lead to incorrect memory references. The problems generated by such
23459 references are usually difficult to tackle because the symptoms can be
23460 very remote from the origin of the problem. In such cases, it is
23461 very helpful to detect the problem as early as possible. This is the
23462 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
23464 In order to use the GNAT specific debugging pool, the user must
23465 associate a debug pool object with each of the access types that may be
23466 related to suspected memory problems. See Ada Reference Manual 13.11.
23471 type Ptr is access Some_Type;
23472 Pool : GNAT.Debug_Pools.Debug_Pool;
23473 for Ptr'Storage_Pool use Pool;
23477 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
23478 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
23479 allow the user to redefine allocation and deallocation strategies. They
23480 also provide a checkpoint for each dereference, through the use of
23481 the primitive operation @code{Dereference} which is implicitly called at
23482 each dereference of an access value.
23484 Once an access type has been associated with a debug pool, operations on
23485 values of the type may raise four distinct exceptions,
23486 which correspond to four potential kinds of memory corruption:
23492 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
23495 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
23498 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
23501 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage}
23504 For types associated with a Debug_Pool, dynamic allocation is performed using
23505 the standard GNAT allocation routine. References to all allocated chunks of
23506 memory are kept in an internal dictionary. Several deallocation strategies are
23507 provided, whereupon the user can choose to release the memory to the system,
23508 keep it allocated for further invalid access checks, or fill it with an easily
23509 recognizable pattern for debug sessions. The memory pattern is the old IBM
23510 hexadecimal convention: @code{16#DEADBEEF#}.
23512 See the documentation in the file g-debpoo.ads for more information on the
23513 various strategies.
23515 Upon each dereference, a check is made that the access value denotes a
23516 properly allocated memory location. Here is a complete example of use of
23517 @code{Debug_Pools}, that includes typical instances of memory corruption:
23522 with Gnat.Io; use Gnat.Io;
23523 with Unchecked_Deallocation;
23524 with Unchecked_Conversion;
23525 with GNAT.Debug_Pools;
23526 with System.Storage_Elements;
23527 with Ada.Exceptions; use Ada.Exceptions;
23528 procedure Debug_Pool_Test is
23530 type T is access Integer;
23531 type U is access all T;
23533 P : GNAT.Debug_Pools.Debug_Pool;
23534 for T'Storage_Pool use P;
23536 procedure Free is new Unchecked_Deallocation (Integer, T);
23537 function UC is new Unchecked_Conversion (U, T);
23540 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
23550 Put_Line (Integer'Image(B.all));
23552 when E : others => Put_Line ("raised: " & Exception_Name (E));
23557 when E : others => Put_Line ("raised: " & Exception_Name (E));
23561 Put_Line (Integer'Image(B.all));
23563 when E : others => Put_Line ("raised: " & Exception_Name (E));
23568 when E : others => Put_Line ("raised: " & Exception_Name (E));
23571 end Debug_Pool_Test;
23575 The debug pool mechanism provides the following precise diagnostics on the
23576 execution of this erroneous program:
23582 Total allocated bytes : 0
23583 Total deallocated bytes : 0
23584 Current Water Mark: 0
23588 Total allocated bytes : 8
23589 Total deallocated bytes : 0
23590 Current Water Mark: 8
23593 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
23594 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
23595 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
23596 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
23598 Total allocated bytes : 8
23599 Total deallocated bytes : 4
23600 Current Water Mark: 4
23606 @c -- Non-breaking space in running text
23607 @c -- E.g. Ada |nbsp| 95
23609 @node Platform-Specific Information,Example of Binder Output File,GNAT and Program Execution,Top
23610 @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}
23611 @chapter Platform-Specific Information
23614 This appendix contains information relating to the implementation
23615 of run-time libraries on various platforms and also covers
23616 topics related to the GNAT implementation on Windows and Mac OS.
23619 * Run-Time Libraries::
23620 * Specifying a Run-Time Library::
23621 * GNU/Linux Topics::
23622 * Microsoft Windows Topics::
23627 @node Run-Time Libraries,Specifying a Run-Time Library,,Platform-Specific Information
23628 @anchor{gnat_ugn/platform_specific_information id2}@anchor{1cd}@anchor{gnat_ugn/platform_specific_information run-time-libraries}@anchor{2b}
23629 @section Run-Time Libraries
23632 @geindex Tasking and threads libraries
23634 @geindex Threads libraries and tasking
23636 @geindex Run-time libraries (platform-specific information)
23638 The GNAT run-time implementation may vary with respect to both the
23639 underlying threads library and the exception-handling scheme.
23640 For threads support, the default run-time will bind to the thread
23641 package of the underlying operating system.
23643 For exception handling, either or both of two models are supplied:
23647 @geindex Zero-Cost Exceptions
23649 @geindex ZCX (Zero-Cost Exceptions)
23656 @strong{Zero-Cost Exceptions} ("ZCX"),
23657 which uses binder-generated tables that
23658 are interrogated at run time to locate a handler.
23660 @geindex setjmp/longjmp Exception Model
23662 @geindex SJLJ (setjmp/longjmp Exception Model)
23665 @strong{setjmp / longjmp} ('SJLJ'),
23666 which uses dynamically-set data to establish
23667 the set of handlers
23670 Most programs should experience a substantial speed improvement by
23671 being compiled with a ZCX run-time.
23672 This is especially true for
23673 tasking applications or applications with many exception handlers.
23674 Note however that the ZCX run-time does not support asynchronous abort
23675 of tasks (@code{abort} and @code{select-then-abort} constructs) and will instead
23676 implement abort by polling points in the runtime. You can also add additional
23677 polling points explicitly if needed in your application via @code{pragma
23680 This section summarizes which combinations of threads and exception support
23681 are supplied on various GNAT platforms.
23684 * Summary of Run-Time Configurations::
23688 @node Summary of Run-Time Configurations,,,Run-Time Libraries
23689 @anchor{gnat_ugn/platform_specific_information summary-of-run-time-configurations}@anchor{1ce}@anchor{gnat_ugn/platform_specific_information id3}@anchor{1cf}
23690 @subsection Summary of Run-Time Configurations
23694 @multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx}
23751 native Win32 threads
23763 native Win32 threads
23788 @node Specifying a Run-Time Library,GNU/Linux Topics,Run-Time Libraries,Platform-Specific Information
23789 @anchor{gnat_ugn/platform_specific_information specifying-a-run-time-library}@anchor{1d0}@anchor{gnat_ugn/platform_specific_information id4}@anchor{1d1}
23790 @section Specifying a Run-Time Library
23793 The @code{adainclude} subdirectory containing the sources of the GNAT
23794 run-time library, and the @code{adalib} subdirectory containing the
23795 @code{ALI} files and the static and/or shared GNAT library, are located
23796 in the gcc target-dependent area:
23801 target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/
23805 As indicated above, on some platforms several run-time libraries are supplied.
23806 These libraries are installed in the target dependent area and
23807 contain a complete source and binary subdirectory. The detailed description
23808 below explains the differences between the different libraries in terms of
23809 their thread support.
23811 The default run-time library (when GNAT is installed) is @emph{rts-native}.
23812 This default run-time is selected by the means of soft links.
23813 For example on x86-linux:
23816 @c -- $(target-dir)
23818 @c -- +--- adainclude----------+
23820 @c -- +--- adalib-----------+ |
23822 @c -- +--- rts-native | |
23824 @c -- | +--- adainclude <---+
23826 @c -- | +--- adalib <----+
23828 @c -- +--- rts-sjlj
23830 @c -- +--- adainclude
23838 _______/ / \ \_________________
23841 ADAINCLUDE ADALIB rts-native rts-sjlj
23846 +-------------> adainclude adalib adainclude adalib
23849 +---------------------+
23851 Run-Time Library Directory Structure
23852 (Upper-case names and dotted/dashed arrows represent soft links)
23855 If the @emph{rts-sjlj} library is to be selected on a permanent basis,
23856 these soft links can be modified with the following commands:
23862 $ rm -f adainclude adalib
23863 $ ln -s rts-sjlj/adainclude adainclude
23864 $ ln -s rts-sjlj/adalib adalib
23868 Alternatively, you can specify @code{rts-sjlj/adainclude} in the file
23869 @code{$target/ada_source_path} and @code{rts-sjlj/adalib} in
23870 @code{$target/ada_object_path}.
23872 @geindex --RTS option
23874 Selecting another run-time library temporarily can be
23875 achieved by using the @code{--RTS} switch, e.g., @code{--RTS=sjlj}
23876 @anchor{gnat_ugn/platform_specific_information choosing-the-scheduling-policy}@anchor{1d2}
23877 @geindex SCHED_FIFO scheduling policy
23879 @geindex SCHED_RR scheduling policy
23881 @geindex SCHED_OTHER scheduling policy
23884 * Choosing the Scheduling Policy::
23888 @node Choosing the Scheduling Policy,,,Specifying a Run-Time Library
23889 @anchor{gnat_ugn/platform_specific_information id5}@anchor{1d3}
23890 @subsection Choosing the Scheduling Policy
23893 When using a POSIX threads implementation, you have a choice of several
23894 scheduling policies: @code{SCHED_FIFO}, @code{SCHED_RR} and @code{SCHED_OTHER}.
23896 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
23897 or @code{SCHED_RR} requires special (e.g., root) privileges.
23899 @geindex pragma Time_Slice
23901 @geindex -T0 option
23903 @geindex pragma Task_Dispatching_Policy
23905 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
23907 you can use one of the following:
23913 @code{pragma Time_Slice (0.0)}
23916 the corresponding binder option @code{-T0}
23919 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
23922 To specify @code{SCHED_RR},
23923 you should use @code{pragma Time_Slice} with a
23924 value greater than 0.0, or else use the corresponding @code{-T}
23927 To make sure a program is running as root, you can put something like
23928 this in a library package body in your application:
23933 function geteuid return Integer;
23934 pragma Import (C, geteuid, "geteuid");
23935 Ignore : constant Boolean :=
23936 (if geteuid = 0 then True else raise Program_Error with "must be root");
23940 It gets the effective user id, and if it's not 0 (i.e. root), it raises
23947 @node GNU/Linux Topics,Microsoft Windows Topics,Specifying a Run-Time Library,Platform-Specific Information
23948 @anchor{gnat_ugn/platform_specific_information id6}@anchor{1d4}@anchor{gnat_ugn/platform_specific_information gnu-linux-topics}@anchor{1d5}
23949 @section GNU/Linux Topics
23952 This section describes topics that are specific to GNU/Linux platforms.
23955 * Required Packages on GNU/Linux::
23959 @node Required Packages on GNU/Linux,,,GNU/Linux Topics
23960 @anchor{gnat_ugn/platform_specific_information id7}@anchor{1d6}@anchor{gnat_ugn/platform_specific_information required-packages-on-gnu-linux}@anchor{1d7}
23961 @subsection Required Packages on GNU/Linux
23964 GNAT requires the C library developer's package to be installed.
23965 The name of of that package depends on your GNU/Linux distribution:
23971 RedHat, SUSE: @code{glibc-devel};
23974 Debian, Ubuntu: @code{libc6-dev} (normally installed by default).
23977 If using the 32-bit version of GNAT on a 64-bit version of GNU/Linux,
23978 you'll need the 32-bit version of the following packages:
23984 RedHat, SUSE: @code{glibc.i686}, @code{glibc-devel.i686}, @code{ncurses-libs.i686}
23987 Debian, Ubuntu: @code{libc6:i386}, @code{libc6-dev:i386}, @code{lib32ncursesw5}
23990 Other GNU/Linux distributions might be choosing a different name
23991 for those packages.
23995 @node Microsoft Windows Topics,Mac OS Topics,GNU/Linux Topics,Platform-Specific Information
23996 @anchor{gnat_ugn/platform_specific_information microsoft-windows-topics}@anchor{2c}@anchor{gnat_ugn/platform_specific_information id8}@anchor{1d8}
23997 @section Microsoft Windows Topics
24000 This section describes topics that are specific to the Microsoft Windows
24005 * Using GNAT on Windows::
24006 * Using a network installation of GNAT::
24007 * CONSOLE and WINDOWS subsystems::
24008 * Temporary Files::
24009 * Disabling Command Line Argument Expansion::
24010 * Windows Socket Timeouts::
24011 * Mixed-Language Programming on Windows::
24012 * Windows Specific Add-Ons::
24016 @node Using GNAT on Windows,Using a network installation of GNAT,,Microsoft Windows Topics
24017 @anchor{gnat_ugn/platform_specific_information using-gnat-on-windows}@anchor{1d9}@anchor{gnat_ugn/platform_specific_information id9}@anchor{1da}
24018 @subsection Using GNAT on Windows
24021 One of the strengths of the GNAT technology is that its tool set
24022 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
24023 @code{gdb} debugger, etc.) is used in the same way regardless of the
24026 On Windows this tool set is complemented by a number of Microsoft-specific
24027 tools that have been provided to facilitate interoperability with Windows
24028 when this is required. With these tools:
24034 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
24038 You can use any Dynamically Linked Library (DLL) in your Ada code (both
24039 relocatable and non-relocatable DLLs are supported).
24042 You can build Ada DLLs for use in other applications. These applications
24043 can be written in a language other than Ada (e.g., C, C++, etc). Again both
24044 relocatable and non-relocatable Ada DLLs are supported.
24047 You can include Windows resources in your Ada application.
24050 You can use or create COM/DCOM objects.
24053 Immediately below are listed all known general GNAT-for-Windows restrictions.
24054 Other restrictions about specific features like Windows Resources and DLLs
24055 are listed in separate sections below.
24061 It is not possible to use @code{GetLastError} and @code{SetLastError}
24062 when tasking, protected records, or exceptions are used. In these
24063 cases, in order to implement Ada semantics, the GNAT run-time system
24064 calls certain Win32 routines that set the last error variable to 0 upon
24065 success. It should be possible to use @code{GetLastError} and
24066 @code{SetLastError} when tasking, protected record, and exception
24067 features are not used, but it is not guaranteed to work.
24070 It is not possible to link against Microsoft C++ libraries except for
24071 import libraries. Interfacing must be done by the mean of DLLs.
24074 It is possible to link against Microsoft C libraries. Yet the preferred
24075 solution is to use C/C++ compiler that comes with GNAT, since it
24076 doesn't require having two different development environments and makes the
24077 inter-language debugging experience smoother.
24080 When the compilation environment is located on FAT32 drives, users may
24081 experience recompilations of the source files that have not changed if
24082 Daylight Saving Time (DST) state has changed since the last time files
24083 were compiled. NTFS drives do not have this problem.
24086 No components of the GNAT toolset use any entries in the Windows
24087 registry. The only entries that can be created are file associations and
24088 PATH settings, provided the user has chosen to create them at installation
24089 time, as well as some minimal book-keeping information needed to correctly
24090 uninstall or integrate different GNAT products.
24093 @node Using a network installation of GNAT,CONSOLE and WINDOWS subsystems,Using GNAT on Windows,Microsoft Windows Topics
24094 @anchor{gnat_ugn/platform_specific_information id10}@anchor{1db}@anchor{gnat_ugn/platform_specific_information using-a-network-installation-of-gnat}@anchor{1dc}
24095 @subsection Using a network installation of GNAT
24098 Make sure the system on which GNAT is installed is accessible from the
24099 current machine, i.e., the install location is shared over the network.
24100 Shared resources are accessed on Windows by means of UNC paths, which
24101 have the format @code{\\\\server\\sharename\\path}
24103 In order to use such a network installation, simply add the UNC path of the
24104 @code{bin} directory of your GNAT installation in front of your PATH. For
24105 example, if GNAT is installed in @code{\GNAT} directory of a share location
24106 called @code{c-drive} on a machine @code{LOKI}, the following command will
24112 $ path \\loki\c-drive\gnat\bin;%path%`
24116 Be aware that every compilation using the network installation results in the
24117 transfer of large amounts of data across the network and will likely cause
24118 serious performance penalty.
24120 @node CONSOLE and WINDOWS subsystems,Temporary Files,Using a network installation of GNAT,Microsoft Windows Topics
24121 @anchor{gnat_ugn/platform_specific_information id11}@anchor{1dd}@anchor{gnat_ugn/platform_specific_information console-and-windows-subsystems}@anchor{1de}
24122 @subsection CONSOLE and WINDOWS subsystems
24125 @geindex CONSOLE Subsystem
24127 @geindex WINDOWS Subsystem
24131 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
24132 (which is the default subsystem) will always create a console when
24133 launching the application. This is not something desirable when the
24134 application has a Windows GUI. To get rid of this console the
24135 application must be using the @code{WINDOWS} subsystem. To do so
24136 the @code{-mwindows} linker option must be specified.
24141 $ gnatmake winprog -largs -mwindows
24145 @node Temporary Files,Disabling Command Line Argument Expansion,CONSOLE and WINDOWS subsystems,Microsoft Windows Topics
24146 @anchor{gnat_ugn/platform_specific_information id12}@anchor{1df}@anchor{gnat_ugn/platform_specific_information temporary-files}@anchor{1e0}
24147 @subsection Temporary Files
24150 @geindex Temporary files
24152 It is possible to control where temporary files gets created by setting
24155 @geindex environment variable; TMP
24156 @code{TMP} environment variable. The file will be created:
24162 Under the directory pointed to by the
24164 @geindex environment variable; TMP
24165 @code{TMP} environment variable if
24166 this directory exists.
24169 Under @code{c:\temp}, if the
24171 @geindex environment variable; TMP
24172 @code{TMP} environment variable is not
24173 set (or not pointing to a directory) and if this directory exists.
24176 Under the current working directory otherwise.
24179 This allows you to determine exactly where the temporary
24180 file will be created. This is particularly useful in networked
24181 environments where you may not have write access to some
24184 @node Disabling Command Line Argument Expansion,Windows Socket Timeouts,Temporary Files,Microsoft Windows Topics
24185 @anchor{gnat_ugn/platform_specific_information disabling-command-line-argument-expansion}@anchor{1e1}
24186 @subsection Disabling Command Line Argument Expansion
24189 @geindex Command Line Argument Expansion
24191 By default, an executable compiled for the Windows platform will do
24192 the following postprocessing on the arguments passed on the command
24199 If the argument contains the characters @code{*} and/or @code{?}, then
24200 file expansion will be attempted. For example, if the current directory
24201 contains @code{a.txt} and @code{b.txt}, then when calling:
24204 $ my_ada_program *.txt
24207 The following arguments will effectively be passed to the main program
24208 (for example when using @code{Ada.Command_Line.Argument}):
24211 Ada.Command_Line.Argument (1) -> "a.txt"
24212 Ada.Command_Line.Argument (2) -> "b.txt"
24216 Filename expansion can be disabled for a given argument by using single
24217 quotes. Thus, calling:
24220 $ my_ada_program '*.txt'
24226 Ada.Command_Line.Argument (1) -> "*.txt"
24230 Note that if the program is launched from a shell such as Cygwin Bash
24231 then quote removal might be performed by the shell.
24233 In some contexts it might be useful to disable this feature (for example if
24234 the program performs its own argument expansion). In order to do this, a C
24235 symbol needs to be defined and set to @code{0}. You can do this by
24236 adding the following code fragment in one of your Ada units:
24239 Do_Argv_Expansion : Integer := 0;
24240 pragma Export (C, Do_Argv_Expansion, "__gnat_do_argv_expansion");
24243 The results of previous examples will be respectively:
24246 Ada.Command_Line.Argument (1) -> "*.txt"
24252 Ada.Command_Line.Argument (1) -> "'*.txt'"
24255 @node Windows Socket Timeouts,Mixed-Language Programming on Windows,Disabling Command Line Argument Expansion,Microsoft Windows Topics
24256 @anchor{gnat_ugn/platform_specific_information windows-socket-timeouts}@anchor{1e2}
24257 @subsection Windows Socket Timeouts
24260 Microsoft Windows desktops older than @code{8.0} and Microsoft Windows Servers
24261 older than @code{2019} set a socket timeout 500 milliseconds longer than the value
24262 set by setsockopt with @code{SO_RCVTIMEO} and @code{SO_SNDTIMEO} options. The GNAT
24263 runtime makes a correction for the difference in the corresponding Windows
24264 versions. For Windows Server starting with version @code{2019}, the user must
24265 provide a manifest file for the GNAT runtime to be able to recognize that
24266 the Windows version does not need the timeout correction. The manifest file
24267 should be located in the same directory as the executable file, and its file
24268 name must match the executable name suffixed by @code{.manifest}. For example,
24269 if the executable name is @code{sock_wto.exe}, then the manifest file name
24270 has to be @code{sock_wto.exe.manifest}. The manifest file must contain at
24271 least the following data:
24274 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
24275 <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
24276 <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
24278 <!-- Windows Vista -->
24279 <supportedOS Id="@{e2011457-1546-43c5-a5fe-008deee3d3f0@}"/>
24281 <supportedOS Id="@{35138b9a-5d96-4fbd-8e2d-a2440225f93a@}"/>
24283 <supportedOS Id="@{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38@}"/>
24284 <!-- Windows 8.1 -->
24285 <supportedOS Id="@{1f676c76-80e1-4239-95bb-83d0f6d0da78@}"/>
24286 <!-- Windows 10 -->
24287 <supportedOS Id="@{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a@}"/>
24293 Without the manifest file, the socket timeout is going to be overcorrected on
24294 these Windows Server versions and the actual time is going to be 500
24295 milliseconds shorter than what was set with GNAT.Sockets.Set_Socket_Option.
24296 Note that on Microsoft Windows versions where correction is necessary, there
24297 is no way to set a socket timeout shorter than 500 ms. If a socket timeout
24298 shorter than 500 ms is needed on these Windows versions, a call to
24299 Check_Selector should be added before any socket read or write operations.
24301 @node Mixed-Language Programming on Windows,Windows Specific Add-Ons,Windows Socket Timeouts,Microsoft Windows Topics
24302 @anchor{gnat_ugn/platform_specific_information id13}@anchor{1e3}@anchor{gnat_ugn/platform_specific_information mixed-language-programming-on-windows}@anchor{1e4}
24303 @subsection Mixed-Language Programming on Windows
24306 Developing pure Ada applications on Windows is no different than on
24307 other GNAT-supported platforms. However, when developing or porting an
24308 application that contains a mix of Ada and C/C++, the choice of your
24309 Windows C/C++ development environment conditions your overall
24310 interoperability strategy.
24312 If you use @code{gcc} or Microsoft C to compile the non-Ada part of
24313 your application, there are no Windows-specific restrictions that
24314 affect the overall interoperability with your Ada code. If you do want
24315 to use the Microsoft tools for your C++ code, you have two choices:
24321 Encapsulate your C++ code in a DLL to be linked with your Ada
24322 application. In this case, use the Microsoft or whatever environment to
24323 build the DLL and use GNAT to build your executable
24324 (@ref{1e5,,Using DLLs with GNAT}).
24327 Or you can encapsulate your Ada code in a DLL to be linked with the
24328 other part of your application. In this case, use GNAT to build the DLL
24329 (@ref{1e6,,Building DLLs with GNAT Project files}) and use the Microsoft
24330 or whatever environment to build your executable.
24333 In addition to the description about C main in
24334 @ref{44,,Mixed Language Programming} section, if the C main uses a
24335 stand-alone library it is required on x86-windows to
24336 setup the SEH context. For this the C main must looks like this:
24342 extern void adainit (void);
24343 extern void adafinal (void);
24344 extern void __gnat_initialize(void*);
24345 extern void call_to_ada (void);
24347 int main (int argc, char *argv[])
24351 /* Initialize the SEH context */
24352 __gnat_initialize (&SEH);
24356 /* Then call Ada services in the stand-alone library */
24365 Note that this is not needed on x86_64-windows where the Windows
24366 native SEH support is used.
24369 * Windows Calling Conventions::
24370 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
24371 * Using DLLs with GNAT::
24372 * Building DLLs with GNAT Project files::
24373 * Building DLLs with GNAT::
24374 * Building DLLs with gnatdll::
24375 * Ada DLLs and Finalization::
24376 * Creating a Spec for Ada DLLs::
24377 * GNAT and Windows Resources::
24378 * Using GNAT DLLs from Microsoft Visual Studio Applications::
24379 * Debugging a DLL::
24380 * Setting Stack Size from gnatlink::
24381 * Setting Heap Size from gnatlink::
24385 @node Windows Calling Conventions,Introduction to Dynamic Link Libraries DLLs,,Mixed-Language Programming on Windows
24386 @anchor{gnat_ugn/platform_specific_information windows-calling-conventions}@anchor{1e7}@anchor{gnat_ugn/platform_specific_information id14}@anchor{1e8}
24387 @subsubsection Windows Calling Conventions
24394 This section pertain only to Win32. On Win64 there is a single native
24395 calling convention. All convention specifiers are ignored on this
24398 When a subprogram @code{F} (caller) calls a subprogram @code{G}
24399 (callee), there are several ways to push @code{G}'s parameters on the
24400 stack and there are several possible scenarios to clean up the stack
24401 upon @code{G}'s return. A calling convention is an agreed upon software
24402 protocol whereby the responsibilities between the caller (@code{F}) and
24403 the callee (@code{G}) are clearly defined. Several calling conventions
24404 are available for Windows:
24410 @code{C} (Microsoft defined)
24413 @code{Stdcall} (Microsoft defined)
24416 @code{Win32} (GNAT specific)
24419 @code{DLL} (GNAT specific)
24423 * C Calling Convention::
24424 * Stdcall Calling Convention::
24425 * Win32 Calling Convention::
24426 * DLL Calling Convention::
24430 @node C Calling Convention,Stdcall Calling Convention,,Windows Calling Conventions
24431 @anchor{gnat_ugn/platform_specific_information c-calling-convention}@anchor{1e9}@anchor{gnat_ugn/platform_specific_information id15}@anchor{1ea}
24432 @subsubsection @code{C} Calling Convention
24435 This is the default calling convention used when interfacing to C/C++
24436 routines compiled with either @code{gcc} or Microsoft Visual C++.
24438 In the @code{C} calling convention subprogram parameters are pushed on the
24439 stack by the caller from right to left. The caller itself is in charge of
24440 cleaning up the stack after the call. In addition, the name of a routine
24441 with @code{C} calling convention is mangled by adding a leading underscore.
24443 The name to use on the Ada side when importing (or exporting) a routine
24444 with @code{C} calling convention is the name of the routine. For
24445 instance the C function:
24450 int get_val (long);
24454 should be imported from Ada as follows:
24459 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24460 pragma Import (C, Get_Val, External_Name => "get_val");
24464 Note that in this particular case the @code{External_Name} parameter could
24465 have been omitted since, when missing, this parameter is taken to be the
24466 name of the Ada entity in lower case. When the @code{Link_Name} parameter
24467 is missing, as in the above example, this parameter is set to be the
24468 @code{External_Name} with a leading underscore.
24470 When importing a variable defined in C, you should always use the @code{C}
24471 calling convention unless the object containing the variable is part of a
24472 DLL (in which case you should use the @code{Stdcall} calling
24473 convention, @ref{1eb,,Stdcall Calling Convention}).
24475 @node Stdcall Calling Convention,Win32 Calling Convention,C Calling Convention,Windows Calling Conventions
24476 @anchor{gnat_ugn/platform_specific_information stdcall-calling-convention}@anchor{1eb}@anchor{gnat_ugn/platform_specific_information id16}@anchor{1ec}
24477 @subsubsection @code{Stdcall} Calling Convention
24480 This convention, which was the calling convention used for Pascal
24481 programs, is used by Microsoft for all the routines in the Win32 API for
24482 efficiency reasons. It must be used to import any routine for which this
24483 convention was specified.
24485 In the @code{Stdcall} calling convention subprogram parameters are pushed
24486 on the stack by the caller from right to left. The callee (and not the
24487 caller) is in charge of cleaning the stack on routine exit. In addition,
24488 the name of a routine with @code{Stdcall} calling convention is mangled by
24489 adding a leading underscore (as for the @code{C} calling convention) and a
24490 trailing @code{@@@emph{nn}}, where @code{nn} is the overall size (in
24491 bytes) of the parameters passed to the routine.
24493 The name to use on the Ada side when importing a C routine with a
24494 @code{Stdcall} calling convention is the name of the C routine. The leading
24495 underscore and trailing @code{@@@emph{nn}} are added automatically by
24496 the compiler. For instance the Win32 function:
24501 APIENTRY int get_val (long);
24505 should be imported from Ada as follows:
24510 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24511 pragma Import (Stdcall, Get_Val);
24512 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
24516 As for the @code{C} calling convention, when the @code{External_Name}
24517 parameter is missing, it is taken to be the name of the Ada entity in lower
24518 case. If instead of writing the above import pragma you write:
24523 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24524 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
24528 then the imported routine is @code{_retrieve_val@@4}. However, if instead
24529 of specifying the @code{External_Name} parameter you specify the
24530 @code{Link_Name} as in the following example:
24535 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24536 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
24540 then the imported routine is @code{retrieve_val}, that is, there is no
24541 decoration at all. No leading underscore and no Stdcall suffix
24542 @code{@@@emph{nn}}.
24544 This is especially important as in some special cases a DLL's entry
24545 point name lacks a trailing @code{@@@emph{nn}} while the exported
24546 name generated for a call has it.
24548 It is also possible to import variables defined in a DLL by using an
24549 import pragma for a variable. As an example, if a DLL contains a
24550 variable defined as:
24559 then, to access this variable from Ada you should write:
24564 My_Var : Interfaces.C.int;
24565 pragma Import (Stdcall, My_Var);
24569 Note that to ease building cross-platform bindings this convention
24570 will be handled as a @code{C} calling convention on non-Windows platforms.
24572 @node Win32 Calling Convention,DLL Calling Convention,Stdcall Calling Convention,Windows Calling Conventions
24573 @anchor{gnat_ugn/platform_specific_information win32-calling-convention}@anchor{1ed}@anchor{gnat_ugn/platform_specific_information id17}@anchor{1ee}
24574 @subsubsection @code{Win32} Calling Convention
24577 This convention, which is GNAT-specific is fully equivalent to the
24578 @code{Stdcall} calling convention described above.
24580 @node DLL Calling Convention,,Win32 Calling Convention,Windows Calling Conventions
24581 @anchor{gnat_ugn/platform_specific_information id18}@anchor{1ef}@anchor{gnat_ugn/platform_specific_information dll-calling-convention}@anchor{1f0}
24582 @subsubsection @code{DLL} Calling Convention
24585 This convention, which is GNAT-specific is fully equivalent to the
24586 @code{Stdcall} calling convention described above.
24588 @node Introduction to Dynamic Link Libraries DLLs,Using DLLs with GNAT,Windows Calling Conventions,Mixed-Language Programming on Windows
24589 @anchor{gnat_ugn/platform_specific_information id19}@anchor{1f1}@anchor{gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls}@anchor{1f2}
24590 @subsubsection Introduction to Dynamic Link Libraries (DLLs)
24595 A Dynamically Linked Library (DLL) is a library that can be shared by
24596 several applications running under Windows. A DLL can contain any number of
24597 routines and variables.
24599 One advantage of DLLs is that you can change and enhance them without
24600 forcing all the applications that depend on them to be relinked or
24601 recompiled. However, you should be aware than all calls to DLL routines are
24602 slower since, as you will understand below, such calls are indirect.
24604 To illustrate the remainder of this section, suppose that an application
24605 wants to use the services of a DLL @code{API.dll}. To use the services
24606 provided by @code{API.dll} you must statically link against the DLL or
24607 an import library which contains a jump table with an entry for each
24608 routine and variable exported by the DLL. In the Microsoft world this
24609 import library is called @code{API.lib}. When using GNAT this import
24610 library is called either @code{libAPI.dll.a}, @code{libapi.dll.a},
24611 @code{libAPI.a} or @code{libapi.a} (names are case insensitive).
24613 After you have linked your application with the DLL or the import library
24614 and you run your application, here is what happens:
24620 Your application is loaded into memory.
24623 The DLL @code{API.dll} is mapped into the address space of your
24624 application. This means that:
24630 The DLL will use the stack of the calling thread.
24633 The DLL will use the virtual address space of the calling process.
24636 The DLL will allocate memory from the virtual address space of the calling
24640 Handles (pointers) can be safely exchanged between routines in the DLL
24641 routines and routines in the application using the DLL.
24645 The entries in the jump table (from the import library @code{libAPI.dll.a}
24646 or @code{API.lib} or automatically created when linking against a DLL)
24647 which is part of your application are initialized with the addresses
24648 of the routines and variables in @code{API.dll}.
24651 If present in @code{API.dll}, routines @code{DllMain} or
24652 @code{DllMainCRTStartup} are invoked. These routines typically contain
24653 the initialization code needed for the well-being of the routines and
24654 variables exported by the DLL.
24657 There is an additional point which is worth mentioning. In the Windows
24658 world there are two kind of DLLs: relocatable and non-relocatable
24659 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
24660 in the target application address space. If the addresses of two
24661 non-relocatable DLLs overlap and these happen to be used by the same
24662 application, a conflict will occur and the application will run
24663 incorrectly. Hence, when possible, it is always preferable to use and
24664 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
24665 supported by GNAT. Note that the @code{-s} linker option (see GNU Linker
24666 User's Guide) removes the debugging symbols from the DLL but the DLL can
24667 still be relocated.
24669 As a side note, an interesting difference between Microsoft DLLs and
24670 Unix shared libraries, is the fact that on most Unix systems all public
24671 routines are exported by default in a Unix shared library, while under
24672 Windows it is possible (but not required) to list exported routines in
24673 a definition file (see @ref{1f3,,The Definition File}).
24675 @node Using DLLs with GNAT,Building DLLs with GNAT Project files,Introduction to Dynamic Link Libraries DLLs,Mixed-Language Programming on Windows
24676 @anchor{gnat_ugn/platform_specific_information id20}@anchor{1f4}@anchor{gnat_ugn/platform_specific_information using-dlls-with-gnat}@anchor{1e5}
24677 @subsubsection Using DLLs with GNAT
24680 To use the services of a DLL, say @code{API.dll}, in your Ada application
24687 The Ada spec for the routines and/or variables you want to access in
24688 @code{API.dll}. If not available this Ada spec must be built from the C/C++
24689 header files provided with the DLL.
24692 The import library (@code{libAPI.dll.a} or @code{API.lib}). As previously
24693 mentioned an import library is a statically linked library containing the
24694 import table which will be filled at load time to point to the actual
24695 @code{API.dll} routines. Sometimes you don't have an import library for the
24696 DLL you want to use. The following sections will explain how to build
24697 one. Note that this is optional.
24700 The actual DLL, @code{API.dll}.
24703 Once you have all the above, to compile an Ada application that uses the
24704 services of @code{API.dll} and whose main subprogram is @code{My_Ada_App},
24705 you simply issue the command
24710 $ gnatmake my_ada_app -largs -lAPI
24714 The argument @code{-largs -lAPI} at the end of the @code{gnatmake} command
24715 tells the GNAT linker to look for an import library. The linker will
24716 look for a library name in this specific order:
24722 @code{libAPI.dll.a}
24740 The first three are the GNU style import libraries. The third is the
24741 Microsoft style import libraries. The last two are the actual DLL names.
24743 Note that if the Ada package spec for @code{API.dll} contains the
24749 pragma Linker_Options ("-lAPI");
24753 you do not have to add @code{-largs -lAPI} at the end of the
24754 @code{gnatmake} command.
24756 If any one of the items above is missing you will have to create it
24757 yourself. The following sections explain how to do so using as an
24758 example a fictitious DLL called @code{API.dll}.
24761 * Creating an Ada Spec for the DLL Services::
24762 * Creating an Import Library::
24766 @node Creating an Ada Spec for the DLL Services,Creating an Import Library,,Using DLLs with GNAT
24767 @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}
24768 @subsubsection Creating an Ada Spec for the DLL Services
24771 A DLL typically comes with a C/C++ header file which provides the
24772 definitions of the routines and variables exported by the DLL. The Ada
24773 equivalent of this header file is a package spec that contains definitions
24774 for the imported entities. If the DLL you intend to use does not come with
24775 an Ada spec you have to generate one such spec yourself. For example if
24776 the header file of @code{API.dll} is a file @code{api.h} containing the
24777 following two definitions:
24787 then the equivalent Ada spec could be:
24792 with Interfaces.C.Strings;
24797 function Get (Str : C.Strings.Chars_Ptr) return C.int;
24800 pragma Import (C, Get);
24801 pragma Import (DLL, Some_Var);
24806 @node Creating an Import Library,,Creating an Ada Spec for the DLL Services,Using DLLs with GNAT
24807 @anchor{gnat_ugn/platform_specific_information id22}@anchor{1f7}@anchor{gnat_ugn/platform_specific_information creating-an-import-library}@anchor{1f8}
24808 @subsubsection Creating an Import Library
24811 @geindex Import library
24813 If a Microsoft-style import library @code{API.lib} or a GNAT-style
24814 import library @code{libAPI.dll.a} or @code{libAPI.a} is available
24815 with @code{API.dll} you can skip this section. You can also skip this
24816 section if @code{API.dll} or @code{libAPI.dll} is built with GNU tools
24817 as in this case it is possible to link directly against the
24818 DLL. Otherwise read on.
24820 @geindex Definition file
24821 @anchor{gnat_ugn/platform_specific_information the-definition-file}@anchor{1f3}
24822 @subsubheading The Definition File
24825 As previously mentioned, and unlike Unix systems, the list of symbols
24826 that are exported from a DLL must be provided explicitly in Windows.
24827 The main goal of a definition file is precisely that: list the symbols
24828 exported by a DLL. A definition file (usually a file with a @code{.def}
24829 suffix) has the following structure:
24834 [LIBRARY `@w{`}name`@w{`}]
24835 [DESCRIPTION `@w{`}string`@w{`}]
24837 `@w{`}symbol1`@w{`}
24838 `@w{`}symbol2`@w{`}
24846 @item @emph{LIBRARY name}
24848 This section, which is optional, gives the name of the DLL.
24850 @item @emph{DESCRIPTION string}
24852 This section, which is optional, gives a description string that will be
24853 embedded in the import library.
24855 @item @emph{EXPORTS}
24857 This section gives the list of exported symbols (procedures, functions or
24858 variables). For instance in the case of @code{API.dll} the @code{EXPORTS}
24859 section of @code{API.def} looks like:
24868 Note that you must specify the correct suffix (@code{@@@emph{nn}})
24869 (see @ref{1e7,,Windows Calling Conventions}) for a Stdcall
24870 calling convention function in the exported symbols list.
24872 There can actually be other sections in a definition file, but these
24873 sections are not relevant to the discussion at hand.
24874 @anchor{gnat_ugn/platform_specific_information create-def-file-automatically}@anchor{1f9}
24875 @subsubheading Creating a Definition File Automatically
24878 You can automatically create the definition file @code{API.def}
24879 (see @ref{1f3,,The Definition File}) from a DLL.
24880 For that use the @code{dlltool} program as follows:
24885 $ dlltool API.dll -z API.def --export-all-symbols
24888 Note that if some routines in the DLL have the @code{Stdcall} convention
24889 (@ref{1e7,,Windows Calling Conventions}) with stripped @code{@@@emph{nn}}
24890 suffix then you'll have to edit @code{api.def} to add it, and specify
24891 @code{-k} to @code{gnatdll} when creating the import library.
24893 Here are some hints to find the right @code{@@@emph{nn}} suffix.
24899 If you have the Microsoft import library (.lib), it is possible to get
24900 the right symbols by using Microsoft @code{dumpbin} tool (see the
24901 corresponding Microsoft documentation for further details).
24904 $ dumpbin /exports api.lib
24908 If you have a message about a missing symbol at link time the compiler
24909 tells you what symbol is expected. You just have to go back to the
24910 definition file and add the right suffix.
24913 @anchor{gnat_ugn/platform_specific_information gnat-style-import-library}@anchor{1fa}
24914 @subsubheading GNAT-Style Import Library
24917 To create a static import library from @code{API.dll} with the GNAT tools
24918 you should create the .def file, then use @code{gnatdll} tool
24919 (see @ref{1fb,,Using gnatdll}) as follows:
24924 $ gnatdll -e API.def -d API.dll
24927 @code{gnatdll} takes as input a definition file @code{API.def} and the
24928 name of the DLL containing the services listed in the definition file
24929 @code{API.dll}. The name of the static import library generated is
24930 computed from the name of the definition file as follows: if the
24931 definition file name is @code{xyz.def}, the import library name will
24932 be @code{libxyz.a}. Note that in the previous example option
24933 @code{-e} could have been removed because the name of the definition
24934 file (before the @code{.def} suffix) is the same as the name of the
24935 DLL (@ref{1fb,,Using gnatdll} for more information about @code{gnatdll}).
24937 @anchor{gnat_ugn/platform_specific_information msvs-style-import-library}@anchor{1fc}
24938 @subsubheading Microsoft-Style Import Library
24941 A Microsoft import library is needed only if you plan to make an
24942 Ada DLL available to applications developed with Microsoft
24943 tools (@ref{1e4,,Mixed-Language Programming on Windows}).
24945 To create a Microsoft-style import library for @code{API.dll} you
24946 should create the .def file, then build the actual import library using
24947 Microsoft's @code{lib} utility:
24952 $ lib -machine:IX86 -def:API.def -out:API.lib
24955 If you use the above command the definition file @code{API.def} must
24956 contain a line giving the name of the DLL:
24962 See the Microsoft documentation for further details about the usage of
24966 @node Building DLLs with GNAT Project files,Building DLLs with GNAT,Using DLLs with GNAT,Mixed-Language Programming on Windows
24967 @anchor{gnat_ugn/platform_specific_information id23}@anchor{1fd}@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files}@anchor{1e6}
24968 @subsubsection Building DLLs with GNAT Project files
24974 There is nothing specific to Windows in the build process.
24975 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
24976 chapter of the @emph{GPRbuild User's Guide}.
24978 Due to a system limitation, it is not possible under Windows to create threads
24979 when inside the @code{DllMain} routine which is used for auto-initialization
24980 of shared libraries, so it is not possible to have library level tasks in SALs.
24982 @node Building DLLs with GNAT,Building DLLs with gnatdll,Building DLLs with GNAT Project files,Mixed-Language Programming on Windows
24983 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat}@anchor{1fe}@anchor{gnat_ugn/platform_specific_information id24}@anchor{1ff}
24984 @subsubsection Building DLLs with GNAT
24990 This section explain how to build DLLs using the GNAT built-in DLL
24991 support. With the following procedure it is straight forward to build
24992 and use DLLs with GNAT.
24998 Building object files.
24999 The first step is to build all objects files that are to be included
25000 into the DLL. This is done by using the standard @code{gnatmake} tool.
25004 To build the DLL you must use the @code{gcc} @code{-shared} and
25005 @code{-shared-libgcc} options. It is quite simple to use this method:
25008 $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ...
25011 It is important to note that in this case all symbols found in the
25012 object files are automatically exported. It is possible to restrict
25013 the set of symbols to export by passing to @code{gcc} a definition
25014 file (see @ref{1f3,,The Definition File}).
25018 $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ...
25021 If you use a definition file you must export the elaboration procedures
25022 for every package that required one. Elaboration procedures are named
25023 using the package name followed by "_E".
25026 Preparing DLL to be used.
25027 For the DLL to be used by client programs the bodies must be hidden
25028 from it and the .ali set with read-only attribute. This is very important
25029 otherwise GNAT will recompile all packages and will not actually use
25030 the code in the DLL. For example:
25034 $ copy *.ads *.ali api.dll apilib
25035 $ attrib +R apilib\\*.ali
25039 At this point it is possible to use the DLL by directly linking
25040 against it. Note that you must use the GNAT shared runtime when using
25041 GNAT shared libraries. This is achieved by using the @code{-shared} binder
25047 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
25051 @node Building DLLs with gnatdll,Ada DLLs and Finalization,Building DLLs with GNAT,Mixed-Language Programming on Windows
25052 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnatdll}@anchor{200}@anchor{gnat_ugn/platform_specific_information id25}@anchor{201}
25053 @subsubsection Building DLLs with gnatdll
25059 Note that it is preferred to use GNAT Project files
25060 (@ref{1e6,,Building DLLs with GNAT Project files}) or the built-in GNAT
25061 DLL support (@ref{1fe,,Building DLLs with GNAT}) or to build DLLs.
25063 This section explains how to build DLLs containing Ada code using
25064 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
25065 remainder of this section.
25067 The steps required to build an Ada DLL that is to be used by Ada as well as
25068 non-Ada applications are as follows:
25074 You need to mark each Ada entity exported by the DLL with a @code{C} or
25075 @code{Stdcall} calling convention to avoid any Ada name mangling for the
25076 entities exported by the DLL
25077 (see @ref{202,,Exporting Ada Entities}). You can
25078 skip this step if you plan to use the Ada DLL only from Ada applications.
25081 Your Ada code must export an initialization routine which calls the routine
25082 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
25083 the Ada code in the DLL (@ref{203,,Ada DLLs and Elaboration}). The initialization
25084 routine exported by the Ada DLL must be invoked by the clients of the DLL
25085 to initialize the DLL.
25088 When useful, the DLL should also export a finalization routine which calls
25089 routine @code{adafinal} generated by @code{gnatbind} to perform the
25090 finalization of the Ada code in the DLL (@ref{204,,Ada DLLs and Finalization}).
25091 The finalization routine exported by the Ada DLL must be invoked by the
25092 clients of the DLL when the DLL services are no further needed.
25095 You must provide a spec for the services exported by the Ada DLL in each
25096 of the programming languages to which you plan to make the DLL available.
25099 You must provide a definition file listing the exported entities
25100 (@ref{1f3,,The Definition File}).
25103 Finally you must use @code{gnatdll} to produce the DLL and the import
25104 library (@ref{1fb,,Using gnatdll}).
25107 Note that a relocatable DLL stripped using the @code{strip}
25108 binutils tool will not be relocatable anymore. To build a DLL without
25109 debug information pass @code{-largs -s} to @code{gnatdll}. This
25110 restriction does not apply to a DLL built using a Library Project.
25111 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
25112 chapter of the @emph{GPRbuild User's Guide}.
25114 @c Limitations_When_Using_Ada_DLLs_from Ada:
25117 * Limitations When Using Ada DLLs from Ada::
25118 * Exporting Ada Entities::
25119 * Ada DLLs and Elaboration::
25123 @node Limitations When Using Ada DLLs from Ada,Exporting Ada Entities,,Building DLLs with gnatdll
25124 @anchor{gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada}@anchor{205}
25125 @subsubsection Limitations When Using Ada DLLs from Ada
25128 When using Ada DLLs from Ada applications there is a limitation users
25129 should be aware of. Because on Windows the GNAT run-time is not in a DLL of
25130 its own, each Ada DLL includes a part of the GNAT run-time. Specifically,
25131 each Ada DLL includes the services of the GNAT run-time that are necessary
25132 to the Ada code inside the DLL. As a result, when an Ada program uses an
25133 Ada DLL there are two independent GNAT run-times: one in the Ada DLL and
25134 one in the main program.
25136 It is therefore not possible to exchange GNAT run-time objects between the
25137 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
25138 handles (e.g., @code{Text_IO.File_Type}), tasks types, protected objects
25141 It is completely safe to exchange plain elementary, array or record types,
25142 Windows object handles, etc.
25144 @node Exporting Ada Entities,Ada DLLs and Elaboration,Limitations When Using Ada DLLs from Ada,Building DLLs with gnatdll
25145 @anchor{gnat_ugn/platform_specific_information exporting-ada-entities}@anchor{202}@anchor{gnat_ugn/platform_specific_information id26}@anchor{206}
25146 @subsubsection Exporting Ada Entities
25149 @geindex Export table
25151 Building a DLL is a way to encapsulate a set of services usable from any
25152 application. As a result, the Ada entities exported by a DLL should be
25153 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
25154 any Ada name mangling. As an example here is an Ada package
25155 @code{API}, spec and body, exporting two procedures, a function, and a
25161 with Interfaces.C; use Interfaces;
25163 Count : C.int := 0;
25164 function Factorial (Val : C.int) return C.int;
25166 procedure Initialize_API;
25167 procedure Finalize_API;
25168 -- Initialization & Finalization routines. More in the next section.
25170 pragma Export (C, Initialize_API);
25171 pragma Export (C, Finalize_API);
25172 pragma Export (C, Count);
25173 pragma Export (C, Factorial);
25178 package body API is
25179 function Factorial (Val : C.int) return C.int is
25182 Count := Count + 1;
25183 for K in 1 .. Val loop
25189 procedure Initialize_API is
25191 pragma Import (C, Adainit);
25194 end Initialize_API;
25196 procedure Finalize_API is
25197 procedure Adafinal;
25198 pragma Import (C, Adafinal);
25206 If the Ada DLL you are building will only be used by Ada applications
25207 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
25208 convention. As an example, the previous package could be written as
25215 Count : Integer := 0;
25216 function Factorial (Val : Integer) return Integer;
25218 procedure Initialize_API;
25219 procedure Finalize_API;
25220 -- Initialization and Finalization routines.
25225 package body API is
25226 function Factorial (Val : Integer) return Integer is
25227 Fact : Integer := 1;
25229 Count := Count + 1;
25230 for K in 1 .. Val loop
25237 -- The remainder of this package body is unchanged.
25242 Note that if you do not export the Ada entities with a @code{C} or
25243 @code{Stdcall} convention you will have to provide the mangled Ada names
25244 in the definition file of the Ada DLL
25245 (@ref{207,,Creating the Definition File}).
25247 @node Ada DLLs and Elaboration,,Exporting Ada Entities,Building DLLs with gnatdll
25248 @anchor{gnat_ugn/platform_specific_information ada-dlls-and-elaboration}@anchor{203}@anchor{gnat_ugn/platform_specific_information id27}@anchor{208}
25249 @subsubsection Ada DLLs and Elaboration
25252 @geindex DLLs and elaboration
25254 The DLL that you are building contains your Ada code as well as all the
25255 routines in the Ada library that are needed by it. The first thing a
25256 user of your DLL must do is elaborate the Ada code
25257 (@ref{f,,Elaboration Order Handling in GNAT}).
25259 To achieve this you must export an initialization routine
25260 (@code{Initialize_API} in the previous example), which must be invoked
25261 before using any of the DLL services. This elaboration routine must call
25262 the Ada elaboration routine @code{adainit} generated by the GNAT binder
25263 (@ref{b4,,Binding with Non-Ada Main Programs}). See the body of
25264 @code{Initialize_Api} for an example. Note that the GNAT binder is
25265 automatically invoked during the DLL build process by the @code{gnatdll}
25266 tool (@ref{1fb,,Using gnatdll}).
25268 When a DLL is loaded, Windows systematically invokes a routine called
25269 @code{DllMain}. It would therefore be possible to call @code{adainit}
25270 directly from @code{DllMain} without having to provide an explicit
25271 initialization routine. Unfortunately, it is not possible to call
25272 @code{adainit} from the @code{DllMain} if your program has library level
25273 tasks because access to the @code{DllMain} entry point is serialized by
25274 the system (that is, only a single thread can execute 'through' it at a
25275 time), which means that the GNAT run-time will deadlock waiting for the
25276 newly created task to complete its initialization.
25278 @node Ada DLLs and Finalization,Creating a Spec for Ada DLLs,Building DLLs with gnatdll,Mixed-Language Programming on Windows
25279 @anchor{gnat_ugn/platform_specific_information id28}@anchor{209}@anchor{gnat_ugn/platform_specific_information ada-dlls-and-finalization}@anchor{204}
25280 @subsubsection Ada DLLs and Finalization
25283 @geindex DLLs and finalization
25285 When the services of an Ada DLL are no longer needed, the client code should
25286 invoke the DLL finalization routine, if available. The DLL finalization
25287 routine is in charge of releasing all resources acquired by the DLL. In the
25288 case of the Ada code contained in the DLL, this is achieved by calling
25289 routine @code{adafinal} generated by the GNAT binder
25290 (@ref{b4,,Binding with Non-Ada Main Programs}).
25291 See the body of @code{Finalize_Api} for an
25292 example. As already pointed out the GNAT binder is automatically invoked
25293 during the DLL build process by the @code{gnatdll} tool
25294 (@ref{1fb,,Using gnatdll}).
25296 @node Creating a Spec for Ada DLLs,GNAT and Windows Resources,Ada DLLs and Finalization,Mixed-Language Programming on Windows
25297 @anchor{gnat_ugn/platform_specific_information id29}@anchor{20a}@anchor{gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls}@anchor{20b}
25298 @subsubsection Creating a Spec for Ada DLLs
25301 To use the services exported by the Ada DLL from another programming
25302 language (e.g., C), you have to translate the specs of the exported Ada
25303 entities in that language. For instance in the case of @code{API.dll},
25304 the corresponding C header file could look like:
25309 extern int *_imp__count;
25310 #define count (*_imp__count)
25311 int factorial (int);
25315 It is important to understand that when building an Ada DLL to be used by
25316 other Ada applications, you need two different specs for the packages
25317 contained in the DLL: one for building the DLL and the other for using
25318 the DLL. This is because the @code{DLL} calling convention is needed to
25319 use a variable defined in a DLL, but when building the DLL, the variable
25320 must have either the @code{Ada} or @code{C} calling convention. As an
25321 example consider a DLL comprising the following package @code{API}:
25327 Count : Integer := 0;
25329 -- Remainder of the package omitted.
25334 After producing a DLL containing package @code{API}, the spec that
25335 must be used to import @code{API.Count} from Ada code outside of the
25343 pragma Import (DLL, Count);
25349 * Creating the Definition File::
25354 @node Creating the Definition File,Using gnatdll,,Creating a Spec for Ada DLLs
25355 @anchor{gnat_ugn/platform_specific_information creating-the-definition-file}@anchor{207}@anchor{gnat_ugn/platform_specific_information id30}@anchor{20c}
25356 @subsubsection Creating the Definition File
25359 The definition file is the last file needed to build the DLL. It lists
25360 the exported symbols. As an example, the definition file for a DLL
25361 containing only package @code{API} (where all the entities are exported
25362 with a @code{C} calling convention) is:
25375 If the @code{C} calling convention is missing from package @code{API},
25376 then the definition file contains the mangled Ada names of the above
25377 entities, which in this case are:
25386 api__initialize_api
25390 @node Using gnatdll,,Creating the Definition File,Creating a Spec for Ada DLLs
25391 @anchor{gnat_ugn/platform_specific_information using-gnatdll}@anchor{1fb}@anchor{gnat_ugn/platform_specific_information id31}@anchor{20d}
25392 @subsubsection Using @code{gnatdll}
25397 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
25398 and non-Ada sources that make up your DLL have been compiled.
25399 @code{gnatdll} is actually in charge of two distinct tasks: build the
25400 static import library for the DLL and the actual DLL. The form of the
25401 @code{gnatdll} command is
25406 $ gnatdll [ switches ] list-of-files [ -largs opts ]
25410 where @code{list-of-files} is a list of ALI and object files. The object
25411 file list must be the exact list of objects corresponding to the non-Ada
25412 sources whose services are to be included in the DLL. The ALI file list
25413 must be the exact list of ALI files for the corresponding Ada sources
25414 whose services are to be included in the DLL. If @code{list-of-files} is
25415 missing, only the static import library is generated.
25417 You may specify any of the following switches to @code{gnatdll}:
25421 @geindex -a (gnatdll)
25427 @item @code{-a[@emph{address}]}
25429 Build a non-relocatable DLL at @code{address}. If @code{address} is not
25430 specified the default address @code{0x11000000} will be used. By default,
25431 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
25432 advise the reader to build relocatable DLL.
25434 @geindex -b (gnatdll)
25436 @item @code{-b @emph{address}}
25438 Set the relocatable DLL base address. By default the address is
25441 @geindex -bargs (gnatdll)
25443 @item @code{-bargs @emph{opts}}
25445 Binder options. Pass @code{opts} to the binder.
25447 @geindex -d (gnatdll)
25449 @item @code{-d @emph{dllfile}}
25451 @code{dllfile} is the name of the DLL. This switch must be present for
25452 @code{gnatdll} to do anything. The name of the generated import library is
25453 obtained algorithmically from @code{dllfile} as shown in the following
25454 example: if @code{dllfile} is @code{xyz.dll}, the import library name is
25455 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
25456 by option @code{-e}) is obtained algorithmically from @code{dllfile}
25457 as shown in the following example:
25458 if @code{dllfile} is @code{xyz.dll}, the definition
25459 file used is @code{xyz.def}.
25461 @geindex -e (gnatdll)
25463 @item @code{-e @emph{deffile}}
25465 @code{deffile} is the name of the definition file.
25467 @geindex -g (gnatdll)
25471 Generate debugging information. This information is stored in the object
25472 file and copied from there to the final DLL file by the linker,
25473 where it can be read by the debugger. You must use the
25474 @code{-g} switch if you plan on using the debugger or the symbolic
25477 @geindex -h (gnatdll)
25481 Help mode. Displays @code{gnatdll} switch usage information.
25483 @geindex -I (gnatdll)
25485 @item @code{-I@emph{dir}}
25487 Direct @code{gnatdll} to search the @code{dir} directory for source and
25488 object files needed to build the DLL.
25489 (@ref{89,,Search Paths and the Run-Time Library (RTL)}).
25491 @geindex -k (gnatdll)
25495 Removes the @code{@@@emph{nn}} suffix from the import library's exported
25496 names, but keeps them for the link names. You must specify this
25497 option if you want to use a @code{Stdcall} function in a DLL for which
25498 the @code{@@@emph{nn}} suffix has been removed. This is the case for most
25499 of the Windows NT DLL for example. This option has no effect when
25500 @code{-n} option is specified.
25502 @geindex -l (gnatdll)
25504 @item @code{-l @emph{file}}
25506 The list of ALI and object files used to build the DLL are listed in
25507 @code{file}, instead of being given in the command line. Each line in
25508 @code{file} contains the name of an ALI or object file.
25510 @geindex -n (gnatdll)
25514 No Import. Do not create the import library.
25516 @geindex -q (gnatdll)
25520 Quiet mode. Do not display unnecessary messages.
25522 @geindex -v (gnatdll)
25526 Verbose mode. Display extra information.
25528 @geindex -largs (gnatdll)
25530 @item @code{-largs @emph{opts}}
25532 Linker options. Pass @code{opts} to the linker.
25535 @subsubheading @code{gnatdll} Example
25538 As an example the command to build a relocatable DLL from @code{api.adb}
25539 once @code{api.adb} has been compiled and @code{api.def} created is
25544 $ gnatdll -d api.dll api.ali
25548 The above command creates two files: @code{libapi.dll.a} (the import
25549 library) and @code{api.dll} (the actual DLL). If you want to create
25550 only the DLL, just type:
25555 $ gnatdll -d api.dll -n api.ali
25559 Alternatively if you want to create just the import library, type:
25564 $ gnatdll -d api.dll
25568 @subsubheading @code{gnatdll} behind the Scenes
25571 This section details the steps involved in creating a DLL. @code{gnatdll}
25572 does these steps for you. Unless you are interested in understanding what
25573 goes on behind the scenes, you should skip this section.
25575 We use the previous example of a DLL containing the Ada package @code{API},
25576 to illustrate the steps necessary to build a DLL. The starting point is a
25577 set of objects that will make up the DLL and the corresponding ALI
25578 files. In the case of this example this means that @code{api.o} and
25579 @code{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
25586 @code{gnatdll} builds the base file (@code{api.base}). A base file gives
25587 the information necessary to generate relocation information for the
25592 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
25595 In addition to the base file, the @code{gnatlink} command generates an
25596 output file @code{api.jnk} which can be discarded. The @code{-mdll} switch
25597 asks @code{gnatlink} to generate the routines @code{DllMain} and
25598 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
25599 is loaded into memory.
25602 @code{gnatdll} uses @code{dlltool} (see @ref{20e,,Using dlltool}) to build the
25603 export table (@code{api.exp}). The export table contains the relocation
25604 information in a form which can be used during the final link to ensure
25605 that the Windows loader is able to place the DLL anywhere in memory.
25608 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25609 --output-exp api.exp
25613 @code{gnatdll} builds the base file using the new export table. Note that
25614 @code{gnatbind} must be called once again since the binder generated file
25615 has been deleted during the previous call to @code{gnatlink}.
25619 $ gnatlink api -o api.jnk api.exp -mdll
25620 -Wl,--base-file,api.base
25624 @code{gnatdll} builds the new export table using the new base file and
25625 generates the DLL import library @code{libAPI.dll.a}.
25628 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25629 --output-exp api.exp --output-lib libAPI.a
25633 Finally @code{gnatdll} builds the relocatable DLL using the final export
25638 $ gnatlink api api.exp -o api.dll -mdll
25641 @anchor{gnat_ugn/platform_specific_information using-dlltool}@anchor{20e}
25642 @subsubheading Using @code{dlltool}
25645 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
25646 DLLs and static import libraries. This section summarizes the most
25647 common @code{dlltool} switches. The form of the @code{dlltool} command
25653 $ dlltool [`switches`]
25657 @code{dlltool} switches include:
25659 @geindex --base-file (dlltool)
25664 @item @code{--base-file @emph{basefile}}
25666 Read the base file @code{basefile} generated by the linker. This switch
25667 is used to create a relocatable DLL.
25670 @geindex --def (dlltool)
25675 @item @code{--def @emph{deffile}}
25677 Read the definition file.
25680 @geindex --dllname (dlltool)
25685 @item @code{--dllname @emph{name}}
25687 Gives the name of the DLL. This switch is used to embed the name of the
25688 DLL in the static import library generated by @code{dlltool} with switch
25689 @code{--output-lib}.
25692 @geindex -k (dlltool)
25699 Kill @code{@@@emph{nn}} from exported names
25700 (@ref{1e7,,Windows Calling Conventions}
25701 for a discussion about @code{Stdcall}-style symbols.
25704 @geindex --help (dlltool)
25709 @item @code{--help}
25711 Prints the @code{dlltool} switches with a concise description.
25714 @geindex --output-exp (dlltool)
25719 @item @code{--output-exp @emph{exportfile}}
25721 Generate an export file @code{exportfile}. The export file contains the
25722 export table (list of symbols in the DLL) and is used to create the DLL.
25725 @geindex --output-lib (dlltool)
25730 @item @code{--output-lib @emph{libfile}}
25732 Generate a static import library @code{libfile}.
25735 @geindex -v (dlltool)
25745 @geindex --as (dlltool)
25750 @item @code{--as @emph{assembler-name}}
25752 Use @code{assembler-name} as the assembler. The default is @code{as}.
25755 @node GNAT and Windows Resources,Using GNAT DLLs from Microsoft Visual Studio Applications,Creating a Spec for Ada DLLs,Mixed-Language Programming on Windows
25756 @anchor{gnat_ugn/platform_specific_information gnat-and-windows-resources}@anchor{20f}@anchor{gnat_ugn/platform_specific_information id32}@anchor{210}
25757 @subsubsection GNAT and Windows Resources
25763 Resources are an easy way to add Windows specific objects to your
25764 application. The objects that can be added as resources include:
25794 version information
25797 For example, a version information resource can be defined as follow and
25798 embedded into an executable or DLL:
25800 A version information resource can be used to embed information into an
25801 executable or a DLL. These information can be viewed using the file properties
25802 from the Windows Explorer. Here is an example of a version information
25809 FILEVERSION 1,0,0,0
25810 PRODUCTVERSION 1,0,0,0
25812 BLOCK "StringFileInfo"
25816 VALUE "CompanyName", "My Company Name"
25817 VALUE "FileDescription", "My application"
25818 VALUE "FileVersion", "1.0"
25819 VALUE "InternalName", "my_app"
25820 VALUE "LegalCopyright", "My Name"
25821 VALUE "OriginalFilename", "my_app.exe"
25822 VALUE "ProductName", "My App"
25823 VALUE "ProductVersion", "1.0"
25827 BLOCK "VarFileInfo"
25829 VALUE "Translation", 0x809, 1252
25835 The value @code{0809} (langID) is for the U.K English language and
25836 @code{04E4} (charsetID), which is equal to @code{1252} decimal, for
25839 This section explains how to build, compile and use resources. Note that this
25840 section does not cover all resource objects, for a complete description see
25841 the corresponding Microsoft documentation.
25844 * Building Resources::
25845 * Compiling Resources::
25846 * Using Resources::
25850 @node Building Resources,Compiling Resources,,GNAT and Windows Resources
25851 @anchor{gnat_ugn/platform_specific_information building-resources}@anchor{211}@anchor{gnat_ugn/platform_specific_information id33}@anchor{212}
25852 @subsubsection Building Resources
25858 A resource file is an ASCII file. By convention resource files have an
25859 @code{.rc} extension.
25860 The easiest way to build a resource file is to use Microsoft tools
25861 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
25862 @code{dlgedit.exe} to build dialogs.
25863 It is always possible to build an @code{.rc} file yourself by writing a
25866 It is not our objective to explain how to write a resource file. A
25867 complete description of the resource script language can be found in the
25868 Microsoft documentation.
25870 @node Compiling Resources,Using Resources,Building Resources,GNAT and Windows Resources
25871 @anchor{gnat_ugn/platform_specific_information compiling-resources}@anchor{213}@anchor{gnat_ugn/platform_specific_information id34}@anchor{214}
25872 @subsubsection Compiling Resources
25882 This section describes how to build a GNAT-compatible (COFF) object file
25883 containing the resources. This is done using the Resource Compiler
25884 @code{windres} as follows:
25889 $ windres -i myres.rc -o myres.o
25893 By default @code{windres} will run @code{gcc} to preprocess the @code{.rc}
25894 file. You can specify an alternate preprocessor (usually named
25895 @code{cpp.exe}) using the @code{windres} @code{--preprocessor}
25896 parameter. A list of all possible options may be obtained by entering
25897 the command @code{windres} @code{--help}.
25899 It is also possible to use the Microsoft resource compiler @code{rc.exe}
25900 to produce a @code{.res} file (binary resource file). See the
25901 corresponding Microsoft documentation for further details. In this case
25902 you need to use @code{windres} to translate the @code{.res} file to a
25903 GNAT-compatible object file as follows:
25908 $ windres -i myres.res -o myres.o
25912 @node Using Resources,,Compiling Resources,GNAT and Windows Resources
25913 @anchor{gnat_ugn/platform_specific_information using-resources}@anchor{215}@anchor{gnat_ugn/platform_specific_information id35}@anchor{216}
25914 @subsubsection Using Resources
25920 To include the resource file in your program just add the
25921 GNAT-compatible object file for the resource(s) to the linker
25922 arguments. With @code{gnatmake} this is done by using the @code{-largs}
25928 $ gnatmake myprog -largs myres.o
25932 @node Using GNAT DLLs from Microsoft Visual Studio Applications,Debugging a DLL,GNAT and Windows Resources,Mixed-Language Programming on Windows
25933 @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}
25934 @subsubsection Using GNAT DLLs from Microsoft Visual Studio Applications
25937 @geindex Microsoft Visual Studio
25938 @geindex use with GNAT DLLs
25940 This section describes a common case of mixed GNAT/Microsoft Visual Studio
25941 application development, where the main program is developed using MSVS, and
25942 is linked with a DLL developed using GNAT. Such a mixed application should
25943 be developed following the general guidelines outlined above; below is the
25944 cookbook-style sequence of steps to follow:
25950 First develop and build the GNAT shared library using a library project
25951 (let's assume the project is @code{mylib.gpr}, producing the library @code{libmylib.dll}):
25957 $ gprbuild -p mylib.gpr
25965 Produce a .def file for the symbols you need to interface with, either by
25966 hand or automatically with possibly some manual adjustments
25967 (see @ref{1f9,,Creating Definition File Automatically}):
25973 $ dlltool libmylib.dll -z libmylib.def --export-all-symbols
25981 Make sure that MSVS command-line tools are accessible on the path.
25984 Create the Microsoft-style import library (see @ref{1fc,,MSVS-Style Import Library}):
25990 $ lib -machine:IX86 -def:libmylib.def -out:libmylib.lib
25994 If you are using a 64-bit toolchain, the above becomes...
25999 $ lib -machine:X64 -def:libmylib.def -out:libmylib.lib
26013 $ cl /O2 /MD main.c libmylib.lib
26021 Before running the executable, make sure you have set the PATH to the DLL,
26022 or copy the DLL into into the directory containing the .exe.
26025 @node Debugging a DLL,Setting Stack Size from gnatlink,Using GNAT DLLs from Microsoft Visual Studio Applications,Mixed-Language Programming on Windows
26026 @anchor{gnat_ugn/platform_specific_information id36}@anchor{219}@anchor{gnat_ugn/platform_specific_information debugging-a-dll}@anchor{21a}
26027 @subsubsection Debugging a DLL
26030 @geindex DLL debugging
26032 Debugging a DLL is similar to debugging a standard program. But
26033 we have to deal with two different executable parts: the DLL and the
26034 program that uses it. We have the following four possibilities:
26040 The program and the DLL are built with GCC/GNAT.
26043 The program is built with foreign tools and the DLL is built with
26047 The program is built with GCC/GNAT and the DLL is built with
26051 In this section we address only cases one and two above.
26052 There is no point in trying to debug
26053 a DLL with GNU/GDB, if there is no GDB-compatible debugging
26054 information in it. To do so you must use a debugger compatible with the
26055 tools suite used to build the DLL.
26058 * Program and DLL Both Built with GCC/GNAT::
26059 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
26063 @node Program and DLL Both Built with GCC/GNAT,Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Debugging a DLL
26064 @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}
26065 @subsubsection Program and DLL Both Built with GCC/GNAT
26068 This is the simplest case. Both the DLL and the program have @code{GDB}
26069 compatible debugging information. It is then possible to break anywhere in
26070 the process. Let's suppose here that the main procedure is named
26071 @code{ada_main} and that in the DLL there is an entry point named
26074 The DLL (@ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) and
26075 program must have been built with the debugging information (see GNAT -g
26076 switch). Here are the step-by-step instructions for debugging it:
26082 Launch @code{GDB} on the main program.
26089 Start the program and stop at the beginning of the main procedure
26095 This step is required to be able to set a breakpoint inside the DLL. As long
26096 as the program is not run, the DLL is not loaded. This has the
26097 consequence that the DLL debugging information is also not loaded, so it is not
26098 possible to set a breakpoint in the DLL.
26101 Set a breakpoint inside the DLL
26104 (gdb) break ada_dll
26109 At this stage a breakpoint is set inside the DLL. From there on
26110 you can use the standard approach to debug the whole program
26111 (@ref{24,,Running and Debugging Ada Programs}).
26113 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Program and DLL Both Built with GCC/GNAT,Debugging a DLL
26114 @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}
26115 @subsubsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
26118 In this case things are slightly more complex because it is not possible to
26119 start the main program and then break at the beginning to load the DLL and the
26120 associated DLL debugging information. It is not possible to break at the
26121 beginning of the program because there is no @code{GDB} debugging information,
26122 and therefore there is no direct way of getting initial control. This
26123 section addresses this issue by describing some methods that can be used
26124 to break somewhere in the DLL to debug it.
26126 First suppose that the main procedure is named @code{main} (this is for
26127 example some C code built with Microsoft Visual C) and that there is a
26128 DLL named @code{test.dll} containing an Ada entry point named
26131 The DLL (see @ref{1f2,,Introduction to Dynamic Link Libraries (DLLs)}) must have
26132 been built with debugging information (see the GNAT @code{-g} option).
26134 @subsubheading Debugging the DLL Directly
26141 Find out the executable starting address
26144 $ objdump --file-header main.exe
26147 The starting address is reported on the last line. For example:
26150 main.exe: file format pei-i386
26151 architecture: i386, flags 0x0000010a:
26152 EXEC_P, HAS_DEBUG, D_PAGED
26153 start address 0x00401010
26157 Launch the debugger on the executable.
26164 Set a breakpoint at the starting address, and launch the program.
26167 $ (gdb) break *0x00401010
26171 The program will stop at the given address.
26174 Set a breakpoint on a DLL subroutine.
26177 (gdb) break ada_dll.adb:45
26180 Or if you want to break using a symbol on the DLL, you need first to
26181 select the Ada language (language used by the DLL).
26184 (gdb) set language ada
26185 (gdb) break ada_dll
26189 Continue the program.
26195 This will run the program until it reaches the breakpoint that has been
26196 set. From that point you can use the standard way to debug a program
26197 as described in (@ref{24,,Running and Debugging Ada Programs}).
26200 It is also possible to debug the DLL by attaching to a running process.
26202 @subsubheading Attaching to a Running Process
26205 @geindex DLL debugging
26206 @geindex attach to process
26208 With @code{GDB} it is always possible to debug a running process by
26209 attaching to it. It is possible to debug a DLL this way. The limitation
26210 of this approach is that the DLL must run long enough to perform the
26211 attach operation. It may be useful for instance to insert a time wasting
26212 loop in the code of the DLL to meet this criterion.
26218 Launch the main program @code{main.exe}.
26225 Use the Windows @emph{Task Manager} to find the process ID. Let's say
26226 that the process PID for @code{main.exe} is 208.
26236 Attach to the running process to be debugged.
26243 Load the process debugging information.
26246 (gdb) symbol-file main.exe
26250 Break somewhere in the DLL.
26253 (gdb) break ada_dll
26257 Continue process execution.
26264 This last step will resume the process execution, and stop at
26265 the breakpoint we have set. From there you can use the standard
26266 approach to debug a program as described in
26267 @ref{24,,Running and Debugging Ada Programs}.
26269 @node Setting Stack Size from gnatlink,Setting Heap Size from gnatlink,Debugging a DLL,Mixed-Language Programming on Windows
26270 @anchor{gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink}@anchor{136}@anchor{gnat_ugn/platform_specific_information id39}@anchor{21f}
26271 @subsubsection Setting Stack Size from @code{gnatlink}
26274 It is possible to specify the program stack size at link time. On modern
26275 versions of Windows, starting with XP, this is mostly useful to set the size of
26276 the main stack (environment task). The other task stacks are set with pragma
26277 Storage_Size or with the @emph{gnatbind -d} command.
26279 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
26280 reserve size of individual tasks, the link-time stack size applies to all
26281 tasks, and pragma Storage_Size has no effect.
26282 In particular, Stack Overflow checks are made against this
26283 link-time specified size.
26285 This setting can be done with @code{gnatlink} using either of the following:
26291 @code{-Xlinker} linker option
26294 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
26297 This sets the stack reserve size to 0x10000 bytes and the stack commit
26298 size to 0x1000 bytes.
26301 @code{-Wl} linker option
26304 $ gnatlink hello -Wl,--stack=0x1000000
26307 This sets the stack reserve size to 0x1000000 bytes. Note that with
26308 @code{-Wl} option it is not possible to set the stack commit size
26309 because the comma is a separator for this option.
26312 @node Setting Heap Size from gnatlink,,Setting Stack Size from gnatlink,Mixed-Language Programming on Windows
26313 @anchor{gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink}@anchor{137}@anchor{gnat_ugn/platform_specific_information id40}@anchor{220}
26314 @subsubsection Setting Heap Size from @code{gnatlink}
26317 Under Windows systems, it is possible to specify the program heap size from
26318 @code{gnatlink} using either of the following:
26324 @code{-Xlinker} linker option
26327 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
26330 This sets the heap reserve size to 0x10000 bytes and the heap commit
26331 size to 0x1000 bytes.
26334 @code{-Wl} linker option
26337 $ gnatlink hello -Wl,--heap=0x1000000
26340 This sets the heap reserve size to 0x1000000 bytes. Note that with
26341 @code{-Wl} option it is not possible to set the heap commit size
26342 because the comma is a separator for this option.
26345 @node Windows Specific Add-Ons,,Mixed-Language Programming on Windows,Microsoft Windows Topics
26346 @anchor{gnat_ugn/platform_specific_information windows-specific-add-ons}@anchor{221}@anchor{gnat_ugn/platform_specific_information win32-specific-addons}@anchor{222}
26347 @subsection Windows Specific Add-Ons
26350 This section describes the Windows specific add-ons.
26358 @node Win32Ada,wPOSIX,,Windows Specific Add-Ons
26359 @anchor{gnat_ugn/platform_specific_information win32ada}@anchor{223}@anchor{gnat_ugn/platform_specific_information id41}@anchor{224}
26360 @subsubsection Win32Ada
26363 Win32Ada is a binding for the Microsoft Win32 API. This binding can be
26364 easily installed from the provided installer. To use the Win32Ada
26365 binding you need to use a project file, and adding a single with_clause
26366 will give you full access to the Win32Ada binding sources and ensure
26367 that the proper libraries are passed to the linker.
26374 for Sources use ...;
26379 To build the application you just need to call gprbuild for the
26380 application's project, here p.gpr:
26389 @node wPOSIX,,Win32Ada,Windows Specific Add-Ons
26390 @anchor{gnat_ugn/platform_specific_information id42}@anchor{225}@anchor{gnat_ugn/platform_specific_information wposix}@anchor{226}
26391 @subsubsection wPOSIX
26394 wPOSIX is a minimal POSIX binding whose goal is to help with building
26395 cross-platforms applications. This binding is not complete though, as
26396 the Win32 API does not provide the necessary support for all POSIX APIs.
26398 To use the wPOSIX binding you need to use a project file, and adding
26399 a single with_clause will give you full access to the wPOSIX binding
26400 sources and ensure that the proper libraries are passed to the linker.
26407 for Sources use ...;
26412 To build the application you just need to call gprbuild for the
26413 application's project, here p.gpr:
26422 @node Mac OS Topics,,Microsoft Windows Topics,Platform-Specific Information
26423 @anchor{gnat_ugn/platform_specific_information mac-os-topics}@anchor{2d}@anchor{gnat_ugn/platform_specific_information id43}@anchor{227}
26424 @section Mac OS Topics
26429 This section describes topics that are specific to Apple's OS X
26433 * Codesigning the Debugger::
26437 @node Codesigning the Debugger,,,Mac OS Topics
26438 @anchor{gnat_ugn/platform_specific_information codesigning-the-debugger}@anchor{228}
26439 @subsection Codesigning the Debugger
26442 The Darwin Kernel requires the debugger to have special permissions
26443 before it is allowed to control other processes. These permissions
26444 are granted by codesigning the GDB executable. Without these
26445 permissions, the debugger will report error messages such as:
26448 Starting program: /x/y/foo
26449 Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
26450 (please check gdb is codesigned - see taskgated(8))
26453 Codesigning requires a certificate. The following procedure explains
26460 Start the Keychain Access application (in
26461 /Applications/Utilities/Keychain Access.app)
26464 Select the Keychain Access -> Certificate Assistant ->
26465 Create a Certificate... menu
26474 Choose a name for the new certificate (this procedure will use
26475 "gdb-cert" as an example)
26478 Set "Identity Type" to "Self Signed Root"
26481 Set "Certificate Type" to "Code Signing"
26484 Activate the "Let me override defaults" option
26488 Click several times on "Continue" until the "Specify a Location
26489 For The Certificate" screen appears, then set "Keychain" to "System"
26492 Click on "Continue" until the certificate is created
26495 Finally, in the view, double-click on the new certificate,
26496 and set "When using this certificate" to "Always Trust"
26499 Exit the Keychain Access application and restart the computer
26500 (this is unfortunately required)
26503 Once a certificate has been created, the debugger can be codesigned
26504 as follow. In a Terminal, run the following command:
26509 $ codesign -f -s "gdb-cert" <gnat_install_prefix>/bin/gdb
26513 where "gdb-cert" should be replaced by the actual certificate
26514 name chosen above, and <gnat_install_prefix> should be replaced by
26515 the location where you installed GNAT. Also, be sure that users are
26516 in the Unix group @code{_developer}.
26518 @node Example of Binder Output File,Elaboration Order Handling in GNAT,Platform-Specific Information,Top
26519 @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}
26520 @chapter Example of Binder Output File
26523 @geindex Binder output (example)
26525 This Appendix displays the source code for the output file
26526 generated by @emph{gnatbind} for a simple 'Hello World' program.
26527 Comments have been added for clarification purposes.
26530 -- The package is called Ada_Main unless this name is actually used
26531 -- as a unit name in the partition, in which case some other unique
26536 package ada_main is
26537 pragma Warnings (Off);
26539 -- The main program saves the parameters (argument count,
26540 -- argument values, environment pointer) in global variables
26541 -- for later access by other units including
26542 -- Ada.Command_Line.
26544 gnat_argc : Integer;
26545 gnat_argv : System.Address;
26546 gnat_envp : System.Address;
26548 -- The actual variables are stored in a library routine. This
26549 -- is useful for some shared library situations, where there
26550 -- are problems if variables are not in the library.
26552 pragma Import (C, gnat_argc);
26553 pragma Import (C, gnat_argv);
26554 pragma Import (C, gnat_envp);
26556 -- The exit status is similarly an external location
26558 gnat_exit_status : Integer;
26559 pragma Import (C, gnat_exit_status);
26561 GNAT_Version : constant String :=
26562 "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL;
26563 pragma Export (C, GNAT_Version, "__gnat_version");
26565 Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL;
26566 pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name");
26568 -- This is the generated adainit routine that performs
26569 -- initialization at the start of execution. In the case
26570 -- where Ada is the main program, this main program makes
26571 -- a call to adainit at program startup.
26574 pragma Export (C, adainit, "adainit");
26576 -- This is the generated adafinal routine that performs
26577 -- finalization at the end of execution. In the case where
26578 -- Ada is the main program, this main program makes a call
26579 -- to adafinal at program termination.
26581 procedure adafinal;
26582 pragma Export (C, adafinal, "adafinal");
26584 -- This routine is called at the start of execution. It is
26585 -- a dummy routine that is used by the debugger to breakpoint
26586 -- at the start of execution.
26588 -- This is the actual generated main program (it would be
26589 -- suppressed if the no main program switch were used). As
26590 -- required by standard system conventions, this program has
26591 -- the external name main.
26595 argv : System.Address;
26596 envp : System.Address)
26598 pragma Export (C, main, "main");
26600 -- The following set of constants give the version
26601 -- identification values for every unit in the bound
26602 -- partition. This identification is computed from all
26603 -- dependent semantic units, and corresponds to the
26604 -- string that would be returned by use of the
26605 -- Body_Version or Version attributes.
26607 -- The following Export pragmas export the version numbers
26608 -- with symbolic names ending in B (for body) or S
26609 -- (for spec) so that they can be located in a link. The
26610 -- information provided here is sufficient to track down
26611 -- the exact versions of units used in a given build.
26613 type Version_32 is mod 2 ** 32;
26614 u00001 : constant Version_32 := 16#8ad6e54a#;
26615 pragma Export (C, u00001, "helloB");
26616 u00002 : constant Version_32 := 16#fbff4c67#;
26617 pragma Export (C, u00002, "system__standard_libraryB");
26618 u00003 : constant Version_32 := 16#1ec6fd90#;
26619 pragma Export (C, u00003, "system__standard_libraryS");
26620 u00004 : constant Version_32 := 16#3ffc8e18#;
26621 pragma Export (C, u00004, "adaS");
26622 u00005 : constant Version_32 := 16#28f088c2#;
26623 pragma Export (C, u00005, "ada__text_ioB");
26624 u00006 : constant Version_32 := 16#f372c8ac#;
26625 pragma Export (C, u00006, "ada__text_ioS");
26626 u00007 : constant Version_32 := 16#2c143749#;
26627 pragma Export (C, u00007, "ada__exceptionsB");
26628 u00008 : constant Version_32 := 16#f4f0cce8#;
26629 pragma Export (C, u00008, "ada__exceptionsS");
26630 u00009 : constant Version_32 := 16#a46739c0#;
26631 pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB");
26632 u00010 : constant Version_32 := 16#3aac8c92#;
26633 pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS");
26634 u00011 : constant Version_32 := 16#1d274481#;
26635 pragma Export (C, u00011, "systemS");
26636 u00012 : constant Version_32 := 16#a207fefe#;
26637 pragma Export (C, u00012, "system__soft_linksB");
26638 u00013 : constant Version_32 := 16#467d9556#;
26639 pragma Export (C, u00013, "system__soft_linksS");
26640 u00014 : constant Version_32 := 16#b01dad17#;
26641 pragma Export (C, u00014, "system__parametersB");
26642 u00015 : constant Version_32 := 16#630d49fe#;
26643 pragma Export (C, u00015, "system__parametersS");
26644 u00016 : constant Version_32 := 16#b19b6653#;
26645 pragma Export (C, u00016, "system__secondary_stackB");
26646 u00017 : constant Version_32 := 16#b6468be8#;
26647 pragma Export (C, u00017, "system__secondary_stackS");
26648 u00018 : constant Version_32 := 16#39a03df9#;
26649 pragma Export (C, u00018, "system__storage_elementsB");
26650 u00019 : constant Version_32 := 16#30e40e85#;
26651 pragma Export (C, u00019, "system__storage_elementsS");
26652 u00020 : constant Version_32 := 16#41837d1e#;
26653 pragma Export (C, u00020, "system__stack_checkingB");
26654 u00021 : constant Version_32 := 16#93982f69#;
26655 pragma Export (C, u00021, "system__stack_checkingS");
26656 u00022 : constant Version_32 := 16#393398c1#;
26657 pragma Export (C, u00022, "system__exception_tableB");
26658 u00023 : constant Version_32 := 16#b33e2294#;
26659 pragma Export (C, u00023, "system__exception_tableS");
26660 u00024 : constant Version_32 := 16#ce4af020#;
26661 pragma Export (C, u00024, "system__exceptionsB");
26662 u00025 : constant Version_32 := 16#75442977#;
26663 pragma Export (C, u00025, "system__exceptionsS");
26664 u00026 : constant Version_32 := 16#37d758f1#;
26665 pragma Export (C, u00026, "system__exceptions__machineS");
26666 u00027 : constant Version_32 := 16#b895431d#;
26667 pragma Export (C, u00027, "system__exceptions_debugB");
26668 u00028 : constant Version_32 := 16#aec55d3f#;
26669 pragma Export (C, u00028, "system__exceptions_debugS");
26670 u00029 : constant Version_32 := 16#570325c8#;
26671 pragma Export (C, u00029, "system__img_intB");
26672 u00030 : constant Version_32 := 16#1ffca443#;
26673 pragma Export (C, u00030, "system__img_intS");
26674 u00031 : constant Version_32 := 16#b98c3e16#;
26675 pragma Export (C, u00031, "system__tracebackB");
26676 u00032 : constant Version_32 := 16#831a9d5a#;
26677 pragma Export (C, u00032, "system__tracebackS");
26678 u00033 : constant Version_32 := 16#9ed49525#;
26679 pragma Export (C, u00033, "system__traceback_entriesB");
26680 u00034 : constant Version_32 := 16#1d7cb2f1#;
26681 pragma Export (C, u00034, "system__traceback_entriesS");
26682 u00035 : constant Version_32 := 16#8c33a517#;
26683 pragma Export (C, u00035, "system__wch_conB");
26684 u00036 : constant Version_32 := 16#065a6653#;
26685 pragma Export (C, u00036, "system__wch_conS");
26686 u00037 : constant Version_32 := 16#9721e840#;
26687 pragma Export (C, u00037, "system__wch_stwB");
26688 u00038 : constant Version_32 := 16#2b4b4a52#;
26689 pragma Export (C, u00038, "system__wch_stwS");
26690 u00039 : constant Version_32 := 16#92b797cb#;
26691 pragma Export (C, u00039, "system__wch_cnvB");
26692 u00040 : constant Version_32 := 16#09eddca0#;
26693 pragma Export (C, u00040, "system__wch_cnvS");
26694 u00041 : constant Version_32 := 16#6033a23f#;
26695 pragma Export (C, u00041, "interfacesS");
26696 u00042 : constant Version_32 := 16#ece6fdb6#;
26697 pragma Export (C, u00042, "system__wch_jisB");
26698 u00043 : constant Version_32 := 16#899dc581#;
26699 pragma Export (C, u00043, "system__wch_jisS");
26700 u00044 : constant Version_32 := 16#10558b11#;
26701 pragma Export (C, u00044, "ada__streamsB");
26702 u00045 : constant Version_32 := 16#2e6701ab#;
26703 pragma Export (C, u00045, "ada__streamsS");
26704 u00046 : constant Version_32 := 16#db5c917c#;
26705 pragma Export (C, u00046, "ada__io_exceptionsS");
26706 u00047 : constant Version_32 := 16#12c8cd7d#;
26707 pragma Export (C, u00047, "ada__tagsB");
26708 u00048 : constant Version_32 := 16#ce72c228#;
26709 pragma Export (C, u00048, "ada__tagsS");
26710 u00049 : constant Version_32 := 16#c3335bfd#;
26711 pragma Export (C, u00049, "system__htableB");
26712 u00050 : constant Version_32 := 16#99e5f76b#;
26713 pragma Export (C, u00050, "system__htableS");
26714 u00051 : constant Version_32 := 16#089f5cd0#;
26715 pragma Export (C, u00051, "system__string_hashB");
26716 u00052 : constant Version_32 := 16#3bbb9c15#;
26717 pragma Export (C, u00052, "system__string_hashS");
26718 u00053 : constant Version_32 := 16#807fe041#;
26719 pragma Export (C, u00053, "system__unsigned_typesS");
26720 u00054 : constant Version_32 := 16#d27be59e#;
26721 pragma Export (C, u00054, "system__val_lluB");
26722 u00055 : constant Version_32 := 16#fa8db733#;
26723 pragma Export (C, u00055, "system__val_lluS");
26724 u00056 : constant Version_32 := 16#27b600b2#;
26725 pragma Export (C, u00056, "system__val_utilB");
26726 u00057 : constant Version_32 := 16#b187f27f#;
26727 pragma Export (C, u00057, "system__val_utilS");
26728 u00058 : constant Version_32 := 16#d1060688#;
26729 pragma Export (C, u00058, "system__case_utilB");
26730 u00059 : constant Version_32 := 16#392e2d56#;
26731 pragma Export (C, u00059, "system__case_utilS");
26732 u00060 : constant Version_32 := 16#84a27f0d#;
26733 pragma Export (C, u00060, "interfaces__c_streamsB");
26734 u00061 : constant Version_32 := 16#8bb5f2c0#;
26735 pragma Export (C, u00061, "interfaces__c_streamsS");
26736 u00062 : constant Version_32 := 16#6db6928f#;
26737 pragma Export (C, u00062, "system__crtlS");
26738 u00063 : constant Version_32 := 16#4e6a342b#;
26739 pragma Export (C, u00063, "system__file_ioB");
26740 u00064 : constant Version_32 := 16#ba56a5e4#;
26741 pragma Export (C, u00064, "system__file_ioS");
26742 u00065 : constant Version_32 := 16#b7ab275c#;
26743 pragma Export (C, u00065, "ada__finalizationB");
26744 u00066 : constant Version_32 := 16#19f764ca#;
26745 pragma Export (C, u00066, "ada__finalizationS");
26746 u00067 : constant Version_32 := 16#95817ed8#;
26747 pragma Export (C, u00067, "system__finalization_rootB");
26748 u00068 : constant Version_32 := 16#52d53711#;
26749 pragma Export (C, u00068, "system__finalization_rootS");
26750 u00069 : constant Version_32 := 16#769e25e6#;
26751 pragma Export (C, u00069, "interfaces__cB");
26752 u00070 : constant Version_32 := 16#4a38bedb#;
26753 pragma Export (C, u00070, "interfaces__cS");
26754 u00071 : constant Version_32 := 16#07e6ee66#;
26755 pragma Export (C, u00071, "system__os_libB");
26756 u00072 : constant Version_32 := 16#d7b69782#;
26757 pragma Export (C, u00072, "system__os_libS");
26758 u00073 : constant Version_32 := 16#1a817b8e#;
26759 pragma Export (C, u00073, "system__stringsB");
26760 u00074 : constant Version_32 := 16#639855e7#;
26761 pragma Export (C, u00074, "system__stringsS");
26762 u00075 : constant Version_32 := 16#e0b8de29#;
26763 pragma Export (C, u00075, "system__file_control_blockS");
26764 u00076 : constant Version_32 := 16#b5b2aca1#;
26765 pragma Export (C, u00076, "system__finalization_mastersB");
26766 u00077 : constant Version_32 := 16#69316dc1#;
26767 pragma Export (C, u00077, "system__finalization_mastersS");
26768 u00078 : constant Version_32 := 16#57a37a42#;
26769 pragma Export (C, u00078, "system__address_imageB");
26770 u00079 : constant Version_32 := 16#bccbd9bb#;
26771 pragma Export (C, u00079, "system__address_imageS");
26772 u00080 : constant Version_32 := 16#7268f812#;
26773 pragma Export (C, u00080, "system__img_boolB");
26774 u00081 : constant Version_32 := 16#e8fe356a#;
26775 pragma Export (C, u00081, "system__img_boolS");
26776 u00082 : constant Version_32 := 16#d7aac20c#;
26777 pragma Export (C, u00082, "system__ioB");
26778 u00083 : constant Version_32 := 16#8365b3ce#;
26779 pragma Export (C, u00083, "system__ioS");
26780 u00084 : constant Version_32 := 16#6d4d969a#;
26781 pragma Export (C, u00084, "system__storage_poolsB");
26782 u00085 : constant Version_32 := 16#e87cc305#;
26783 pragma Export (C, u00085, "system__storage_poolsS");
26784 u00086 : constant Version_32 := 16#e34550ca#;
26785 pragma Export (C, u00086, "system__pool_globalB");
26786 u00087 : constant Version_32 := 16#c88d2d16#;
26787 pragma Export (C, u00087, "system__pool_globalS");
26788 u00088 : constant Version_32 := 16#9d39c675#;
26789 pragma Export (C, u00088, "system__memoryB");
26790 u00089 : constant Version_32 := 16#445a22b5#;
26791 pragma Export (C, u00089, "system__memoryS");
26792 u00090 : constant Version_32 := 16#6a859064#;
26793 pragma Export (C, u00090, "system__storage_pools__subpoolsB");
26794 u00091 : constant Version_32 := 16#e3b008dc#;
26795 pragma Export (C, u00091, "system__storage_pools__subpoolsS");
26796 u00092 : constant Version_32 := 16#63f11652#;
26797 pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB");
26798 u00093 : constant Version_32 := 16#fe2f4b3a#;
26799 pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS");
26801 -- BEGIN ELABORATION ORDER
26805 -- system.case_util%s
26806 -- system.case_util%b
26808 -- system.img_bool%s
26809 -- system.img_bool%b
26810 -- system.img_int%s
26811 -- system.img_int%b
26814 -- system.parameters%s
26815 -- system.parameters%b
26817 -- interfaces.c_streams%s
26818 -- interfaces.c_streams%b
26819 -- system.standard_library%s
26820 -- system.exceptions_debug%s
26821 -- system.exceptions_debug%b
26822 -- system.storage_elements%s
26823 -- system.storage_elements%b
26824 -- system.stack_checking%s
26825 -- system.stack_checking%b
26826 -- system.string_hash%s
26827 -- system.string_hash%b
26829 -- system.strings%s
26830 -- system.strings%b
26832 -- system.traceback_entries%s
26833 -- system.traceback_entries%b
26834 -- ada.exceptions%s
26835 -- system.soft_links%s
26836 -- system.unsigned_types%s
26837 -- system.val_llu%s
26838 -- system.val_util%s
26839 -- system.val_util%b
26840 -- system.val_llu%b
26841 -- system.wch_con%s
26842 -- system.wch_con%b
26843 -- system.wch_cnv%s
26844 -- system.wch_jis%s
26845 -- system.wch_jis%b
26846 -- system.wch_cnv%b
26847 -- system.wch_stw%s
26848 -- system.wch_stw%b
26849 -- ada.exceptions.last_chance_handler%s
26850 -- ada.exceptions.last_chance_handler%b
26851 -- system.address_image%s
26852 -- system.exception_table%s
26853 -- system.exception_table%b
26854 -- ada.io_exceptions%s
26859 -- system.exceptions%s
26860 -- system.exceptions%b
26861 -- system.exceptions.machine%s
26862 -- system.finalization_root%s
26863 -- system.finalization_root%b
26864 -- ada.finalization%s
26865 -- ada.finalization%b
26866 -- system.storage_pools%s
26867 -- system.storage_pools%b
26868 -- system.finalization_masters%s
26869 -- system.storage_pools.subpools%s
26870 -- system.storage_pools.subpools.finalization%s
26871 -- system.storage_pools.subpools.finalization%b
26874 -- system.standard_library%b
26875 -- system.pool_global%s
26876 -- system.pool_global%b
26877 -- system.file_control_block%s
26878 -- system.file_io%s
26879 -- system.secondary_stack%s
26880 -- system.file_io%b
26881 -- system.storage_pools.subpools%b
26882 -- system.finalization_masters%b
26885 -- system.soft_links%b
26887 -- system.secondary_stack%b
26888 -- system.address_image%b
26889 -- system.traceback%s
26890 -- ada.exceptions%b
26891 -- system.traceback%b
26895 -- END ELABORATION ORDER
26902 -- The following source file name pragmas allow the generated file
26903 -- names to be unique for different main programs. They are needed
26904 -- since the package name will always be Ada_Main.
26906 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26907 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26909 pragma Suppress (Overflow_Check);
26910 with Ada.Exceptions;
26912 -- Generated package body for Ada_Main starts here
26914 package body ada_main is
26915 pragma Warnings (Off);
26917 -- These values are reference counter associated to units which have
26918 -- been elaborated. It is also used to avoid elaborating the
26919 -- same unit twice.
26921 E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E");
26922 E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E");
26923 E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E");
26924 E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E");
26925 E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E");
26926 E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E");
26927 E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E");
26928 E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E");
26929 E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E");
26930 E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E");
26931 E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E");
26932 E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E");
26933 E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E");
26934 E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E");
26935 E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E");
26936 E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E");
26937 E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E");
26938 E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E");
26940 Local_Priority_Specific_Dispatching : constant String := "";
26941 Local_Interrupt_States : constant String := "";
26943 Is_Elaborated : Boolean := False;
26945 procedure finalize_library is
26950 pragma Import (Ada, F1, "ada__text_io__finalize_spec");
26958 pragma Import (Ada, F2, "system__file_io__finalize_body");
26965 pragma Import (Ada, F3, "system__file_control_block__finalize_spec");
26973 pragma Import (Ada, F4, "system__pool_global__finalize_spec");
26979 pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec");
26985 pragma Import (Ada, F6, "system__finalization_masters__finalize_spec");
26990 procedure Reraise_Library_Exception_If_Any;
26991 pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any");
26993 Reraise_Library_Exception_If_Any;
26995 end finalize_library;
27001 procedure adainit is
27003 Main_Priority : Integer;
27004 pragma Import (C, Main_Priority, "__gl_main_priority");
27005 Time_Slice_Value : Integer;
27006 pragma Import (C, Time_Slice_Value, "__gl_time_slice_val");
27007 WC_Encoding : Character;
27008 pragma Import (C, WC_Encoding, "__gl_wc_encoding");
27009 Locking_Policy : Character;
27010 pragma Import (C, Locking_Policy, "__gl_locking_policy");
27011 Queuing_Policy : Character;
27012 pragma Import (C, Queuing_Policy, "__gl_queuing_policy");
27013 Task_Dispatching_Policy : Character;
27014 pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy");
27015 Priority_Specific_Dispatching : System.Address;
27016 pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching");
27017 Num_Specific_Dispatching : Integer;
27018 pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching");
27019 Main_CPU : Integer;
27020 pragma Import (C, Main_CPU, "__gl_main_cpu");
27021 Interrupt_States : System.Address;
27022 pragma Import (C, Interrupt_States, "__gl_interrupt_states");
27023 Num_Interrupt_States : Integer;
27024 pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states");
27025 Unreserve_All_Interrupts : Integer;
27026 pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");
27027 Detect_Blocking : Integer;
27028 pragma Import (C, Detect_Blocking, "__gl_detect_blocking");
27029 Default_Stack_Size : Integer;
27030 pragma Import (C, Default_Stack_Size, "__gl_default_stack_size");
27031 Leap_Seconds_Support : Integer;
27032 pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support");
27034 procedure Runtime_Initialize;
27035 pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize");
27037 Finalize_Library_Objects : No_Param_Proc;
27038 pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects");
27040 -- Start of processing for adainit
27044 -- Record various information for this partition. The values
27045 -- are derived by the binder from information stored in the ali
27046 -- files by the compiler.
27048 if Is_Elaborated then
27051 Is_Elaborated := True;
27052 Main_Priority := -1;
27053 Time_Slice_Value := -1;
27054 WC_Encoding := 'b';
27055 Locking_Policy := ' ';
27056 Queuing_Policy := ' ';
27057 Task_Dispatching_Policy := ' ';
27058 Priority_Specific_Dispatching :=
27059 Local_Priority_Specific_Dispatching'Address;
27060 Num_Specific_Dispatching := 0;
27062 Interrupt_States := Local_Interrupt_States'Address;
27063 Num_Interrupt_States := 0;
27064 Unreserve_All_Interrupts := 0;
27065 Detect_Blocking := 0;
27066 Default_Stack_Size := -1;
27067 Leap_Seconds_Support := 0;
27069 Runtime_Initialize;
27071 Finalize_Library_Objects := finalize_library'access;
27073 -- Now we have the elaboration calls for all units in the partition.
27074 -- The Elab_Spec and Elab_Body attributes generate references to the
27075 -- implicit elaboration procedures generated by the compiler for
27076 -- each unit that requires elaboration. Increment a counter of
27077 -- reference for each unit.
27079 System.Soft_Links'Elab_Spec;
27080 System.Exception_Table'Elab_Body;
27082 Ada.Io_Exceptions'Elab_Spec;
27084 Ada.Tags'Elab_Spec;
27085 Ada.Streams'Elab_Spec;
27087 Interfaces.C'Elab_Spec;
27088 System.Exceptions'Elab_Spec;
27090 System.Finalization_Root'Elab_Spec;
27092 Ada.Finalization'Elab_Spec;
27094 System.Storage_Pools'Elab_Spec;
27096 System.Finalization_Masters'Elab_Spec;
27097 System.Storage_Pools.Subpools'Elab_Spec;
27098 System.Pool_Global'Elab_Spec;
27100 System.File_Control_Block'Elab_Spec;
27102 System.File_Io'Elab_Body;
27105 System.Finalization_Masters'Elab_Body;
27108 Ada.Tags'Elab_Body;
27110 System.Soft_Links'Elab_Body;
27112 System.Os_Lib'Elab_Body;
27114 System.Secondary_Stack'Elab_Body;
27116 Ada.Text_Io'Elab_Spec;
27117 Ada.Text_Io'Elab_Body;
27125 procedure adafinal is
27126 procedure s_stalib_adafinal;
27127 pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal");
27129 procedure Runtime_Finalize;
27130 pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize");
27133 if not Is_Elaborated then
27136 Is_Elaborated := False;
27141 -- We get to the main program of the partition by using
27142 -- pragma Import because if we try to with the unit and
27143 -- call it Ada style, then not only do we waste time
27144 -- recompiling it, but also, we don't really know the right
27145 -- switches (e.g.@@: identifier character set) to be used
27148 procedure Ada_Main_Program;
27149 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
27155 -- main is actually a function, as in the ANSI C standard,
27156 -- defined to return the exit status. The three parameters
27157 -- are the argument count, argument values and environment
27162 argv : System.Address;
27163 envp : System.Address)
27166 -- The initialize routine performs low level system
27167 -- initialization using a standard library routine which
27168 -- sets up signal handling and performs any other
27169 -- required setup. The routine can be found in file
27172 procedure initialize;
27173 pragma Import (C, initialize, "__gnat_initialize");
27175 -- The finalize routine performs low level system
27176 -- finalization using a standard library routine. The
27177 -- routine is found in file a-final.c and in the standard
27178 -- distribution is a dummy routine that does nothing, so
27179 -- really this is a hook for special user finalization.
27181 procedure finalize;
27182 pragma Import (C, finalize, "__gnat_finalize");
27184 -- The following is to initialize the SEH exceptions
27186 SEH : aliased array (1 .. 2) of Integer;
27188 Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address;
27189 pragma Volatile (Ensure_Reference);
27191 -- Start of processing for main
27194 -- Save global variables
27200 -- Call low level system initialization
27202 Initialize (SEH'Address);
27204 -- Call our generated Ada initialization routine
27208 -- Now we call the main program of the partition
27212 -- Perform Ada finalization
27216 -- Perform low level system finalization
27220 -- Return the proper exit status
27221 return (gnat_exit_status);
27224 -- This section is entirely comments, so it has no effect on the
27225 -- compilation of the Ada_Main package. It provides the list of
27226 -- object files and linker options, as well as some standard
27227 -- libraries needed for the link. The gnatlink utility parses
27228 -- this b~hello.adb file to read these comment lines to generate
27229 -- the appropriate command line arguments for the call to the
27230 -- system linker. The BEGIN/END lines are used for sentinels for
27231 -- this parsing operation.
27233 -- The exact file names will of course depend on the environment,
27234 -- host/target and location of files on the host system.
27236 -- BEGIN Object file/option list
27239 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27240 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27241 -- END Object file/option list
27246 The Ada code in the above example is exactly what is generated by the
27247 binder. We have added comments to more clearly indicate the function
27248 of each part of the generated @code{Ada_Main} package.
27250 The code is standard Ada in all respects, and can be processed by any
27251 tools that handle Ada. In particular, it is possible to use the debugger
27252 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27253 suppose that for reasons that you do not understand, your program is crashing
27254 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27255 you can place a breakpoint on the call:
27260 Ada.Text_Io'Elab_Body;
27264 and trace the elaboration routine for this package to find out where
27265 the problem might be (more usually of course you would be debugging
27266 elaboration code in your own application).
27268 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
27270 @node Elaboration Order Handling in GNAT,Inline Assembler,Example of Binder Output File,Top
27271 @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}
27272 @chapter Elaboration Order Handling in GNAT
27275 @geindex Order of elaboration
27277 @geindex Elaboration control
27279 This appendix describes the handling of elaboration code in Ada and GNAT, and
27280 discusses how the order of elaboration of program units can be controlled in
27281 GNAT, either automatically or with explicit programming features.
27284 * Elaboration Code::
27285 * Elaboration Order::
27286 * Checking the Elaboration Order::
27287 * Controlling the Elaboration Order in Ada::
27288 * Controlling the Elaboration Order in GNAT::
27289 * Mixing Elaboration Models::
27290 * ABE Diagnostics::
27291 * SPARK Diagnostics::
27292 * Elaboration Circularities::
27293 * Resolving Elaboration Circularities::
27294 * Elaboration-related Compiler Switches::
27295 * Summary of Procedures for Elaboration Control::
27296 * Inspecting the Chosen Elaboration Order::
27300 @node Elaboration Code,Elaboration Order,,Elaboration Order Handling in GNAT
27301 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-code}@anchor{22d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id2}@anchor{22e}
27302 @section Elaboration Code
27305 Ada defines the term @emph{execution} as the process by which a construct achieves
27306 its run-time effect. This process is also referred to as @strong{elaboration} for
27307 declarations and @emph{evaluation} for expressions.
27309 The execution model in Ada allows for certain sections of an Ada program to be
27310 executed prior to execution of the program itself, primarily with the intent of
27311 initializing data. These sections are referred to as @strong{elaboration code}.
27312 Elaboration code is executed as follows:
27318 All partitions of an Ada program are executed in parallel with one another,
27319 possibly in a separate address space, and possibly on a separate computer.
27322 The execution of a partition involves running the environment task for that
27326 The environment task executes all elaboration code (if available) for all
27327 units within that partition. This code is said to be executed at
27328 @strong{elaboration time}.
27331 The environment task executes the Ada program (if available) for that
27335 In addition to the Ada terminology, this appendix defines the following terms:
27343 The act of calling a subprogram, instantiating a generic, or activating a
27349 A construct that is elaborated or invoked by elaboration code is referred to
27350 as an @emph{elaboration scenario} or simply a @strong{scenario}. GNAT recognizes the
27351 following scenarios:
27357 @code{'Access} of entries, operators, and subprograms
27360 Activation of tasks
27363 Calls to entries, operators, and subprograms
27366 Instantiations of generic templates
27372 A construct elaborated by a scenario is referred to as @emph{elaboration target}
27373 or simply @strong{target}. GNAT recognizes the following targets:
27379 For @code{'Access} of entries, operators, and subprograms, the target is the
27380 entry, operator, or subprogram being aliased.
27383 For activation of tasks, the target is the task body
27386 For calls to entries, operators, and subprograms, the target is the entry,
27387 operator, or subprogram being invoked.
27390 For instantiations of generic templates, the target is the generic template
27391 being instantiated.
27395 Elaboration code may appear in two distinct contexts:
27401 @emph{Library level}
27403 A scenario appears at the library level when it is encapsulated by a package
27404 [body] compilation unit, ignoring any other package [body] declarations in
27413 Val : ... := Server.Func;
27418 In the example above, the call to @code{Server.Func} is an elaboration scenario
27419 because it appears at the library level of package @code{Client}. Note that the
27420 declaration of package @code{Nested} is ignored according to the definition
27421 given above. As a result, the call to @code{Server.Func} will be invoked when
27422 the spec of unit @code{Client} is elaborated.
27425 @emph{Package body statements}
27427 A scenario appears within the statement sequence of a package body when it is
27428 bounded by the region starting from the @code{begin} keyword of the package body
27429 and ending at the @code{end} keyword of the package body.
27432 package body Client is
27442 In the example above, the call to @code{Proc} is an elaboration scenario because
27443 it appears within the statement sequence of package body @code{Client}. As a
27444 result, the call to @code{Proc} will be invoked when the body of @code{Client} is
27448 @node Elaboration Order,Checking the Elaboration Order,Elaboration Code,Elaboration Order Handling in GNAT
27449 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order}@anchor{22f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id3}@anchor{230}
27450 @section Elaboration Order
27453 The sequence by which the elaboration code of all units within a partition is
27454 executed is referred to as @strong{elaboration order}.
27456 Within a single unit, elaboration code is executed in sequential order.
27461 package body Client is
27462 Result : ... := Server.Func;
27465 package Inst is new Server.Gen;
27467 Inst.Eval (Result);
27475 In the example above, the elaboration order within package body @code{Client} is
27482 The object declaration of @code{Result} is elaborated.
27488 Function @code{Server.Func} is invoked.
27492 The subprogram body of @code{Proc} is elaborated.
27495 Procedure @code{Proc} is invoked.
27501 Generic unit @code{Server.Gen} is instantiated as @code{Inst}.
27504 Instance @code{Inst} is elaborated.
27507 Procedure @code{Inst.Eval} is invoked.
27511 The elaboration order of all units within a partition depends on the following
27518 @emph{with}ed units
27527 preelaborability of units
27530 presence of elaboration-control pragmas
27533 invocations performed in elaboration code
27536 A program may have several elaboration orders depending on its structure.
27542 function Func (Index : Integer) return Integer;
27547 package body Server is
27548 Results : array (1 .. 5) of Integer := (1, 2, 3, 4, 5);
27550 function Func (Index : Integer) return Integer is
27552 return Results (Index);
27560 Val : constant Integer := Server.Func (3);
27566 procedure Main is begin null; end Main;
27570 The following elaboration order exhibits a fundamental problem referred to as
27571 @emph{access-before-elaboration} or simply @strong{ABE}.
27583 The elaboration of @code{Server}'s spec materializes function @code{Func}, making it
27584 callable. The elaboration of @code{Client}'s spec elaborates the declaration of
27585 @code{Val}. This invokes function @code{Server.Func}, however the body of
27586 @code{Server.Func} has not been elaborated yet because @code{Server}'s body comes
27587 after @code{Client}'s spec in the elaboration order. As a result, the value of
27588 constant @code{Val} is now undefined.
27590 Without any guarantees from the language, an undetected ABE problem may hinder
27591 proper initialization of data, which in turn may lead to undefined behavior at
27592 run time. To prevent such ABE problems, Ada employs dynamic checks in the same
27593 vein as index or null exclusion checks. A failed ABE check raises exception
27594 @code{Program_Error}.
27596 The following elaboration order avoids the ABE problem and the program can be
27597 successfully elaborated.
27609 Ada states that a total elaboration order must exist, but it does not define
27610 what this order is. A compiler is thus tasked with choosing a suitable
27611 elaboration order which satisfies the dependencies imposed by @emph{with} clauses,
27612 unit categorization, elaboration-control pragmas, and invocations performed in
27613 elaboration code. Ideally an order that avoids ABE problems should be chosen,
27614 however a compiler may not always find such an order due to complications with
27615 respect to control and data flow.
27617 @node Checking the Elaboration Order,Controlling the Elaboration Order in Ada,Elaboration Order,Elaboration Order Handling in GNAT
27618 @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}
27619 @section Checking the Elaboration Order
27622 To avoid placing the entire elaboration-order burden on the programmer, Ada
27623 provides three lines of defense:
27629 @emph{Static semantics}
27631 Static semantic rules restrict the possible choice of elaboration order. For
27632 instance, if unit Client @emph{with}s unit Server, then the spec of Server is
27633 always elaborated prior to Client. The same principle applies to child units
27634 - the spec of a parent unit is always elaborated prior to the child unit.
27637 @emph{Dynamic semantics}
27639 Dynamic checks are performed at run time, to ensure that a target is
27640 elaborated prior to a scenario that invokes it, thus avoiding ABE problems.
27641 A failed run-time check raises exception @code{Program_Error}. The following
27642 restrictions apply:
27648 @emph{Restrictions on calls}
27650 An entry, operator, or subprogram can be called from elaboration code only
27651 when the corresponding body has been elaborated.
27654 @emph{Restrictions on instantiations}
27656 A generic unit can be instantiated by elaboration code only when the
27657 corresponding body has been elaborated.
27660 @emph{Restrictions on task activation}
27662 A task can be activated by elaboration code only when the body of the
27663 associated task type has been elaborated.
27666 The restrictions above can be summarized by the following rule:
27668 @emph{If a target has a body, then this body must be elaborated prior to the
27669 scenario that invokes the target.}
27672 @emph{Elaboration control}
27674 Pragmas are provided for the programmer to specify the desired elaboration
27678 @node Controlling the Elaboration Order in Ada,Controlling the Elaboration Order in GNAT,Checking the Elaboration Order,Elaboration Order Handling in GNAT
27679 @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}
27680 @section Controlling the Elaboration Order in Ada
27683 Ada provides several idioms and pragmas to aid the programmer with specifying
27684 the desired elaboration order and avoiding ABE problems altogether.
27690 @emph{Packages without a body}
27692 A library package which does not require a completing body does not suffer
27698 type Element is private;
27699 package Containers is
27700 type Element_Array is array (1 .. 10) of Element;
27705 In the example above, package @code{Pack} does not require a body because it
27706 does not contain any constructs which require completion in a body. As a
27707 result, generic @code{Pack.Containers} can be instantiated without encountering
27711 @geindex pragma Pure
27719 Pragma @code{Pure} places sufficient restrictions on a unit to guarantee that no
27720 scenario within the unit can result in an ABE problem.
27723 @geindex pragma Preelaborate
27729 @emph{pragma Preelaborate}
27731 Pragma @code{Preelaborate} is slightly less restrictive than pragma @code{Pure},
27732 but still strong enough to prevent ABE problems within a unit.
27735 @geindex pragma Elaborate_Body
27741 @emph{pragma Elaborate_Body}
27743 Pragma @code{Elaborate_Body} requires that the body of a unit is elaborated
27744 immediately after its spec. This restriction guarantees that no client
27745 scenario can invoke a server target before the target body has been
27746 elaborated because the spec and body are effectively "glued" together.
27750 pragma Elaborate_Body;
27752 function Func return Integer;
27757 package body Server is
27758 function Func return Integer is
27768 Val : constant Integer := Server.Func;
27772 In the example above, pragma @code{Elaborate_Body} guarantees the following
27781 because the spec of @code{Server} must be elaborated prior to @code{Client} by
27782 virtue of the @emph{with} clause, and in addition the body of @code{Server} must be
27783 elaborated immediately after the spec of @code{Server}.
27785 Removing pragma @code{Elaborate_Body} could result in the following incorrect
27794 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func} has
27795 not been elaborated yet.
27798 The pragmas outlined above allow a server unit to guarantee safe elaboration
27799 use by client units. Thus it is a good rule to mark units as @code{Pure} or
27800 @code{Preelaborate}, and if this is not possible, mark them as @code{Elaborate_Body}.
27802 There are however situations where @code{Pure}, @code{Preelaborate}, and
27803 @code{Elaborate_Body} are not applicable. Ada provides another set of pragmas for
27804 use by client units to help ensure the elaboration safety of server units they
27807 @geindex pragma Elaborate (Unit)
27813 @emph{pragma Elaborate (Unit)}
27815 Pragma @code{Elaborate} can be placed in the context clauses of a unit, after a
27816 @emph{with} clause. It guarantees that both the spec and body of its argument will
27817 be elaborated prior to the unit with the pragma. Note that other unrelated
27818 units may be elaborated in between the spec and the body.
27822 function Func return Integer;
27827 package body Server is
27828 function Func return Integer is
27837 pragma Elaborate (Server);
27839 Val : constant Integer := Server.Func;
27843 In the example above, pragma @code{Elaborate} guarantees the following
27852 Removing pragma @code{Elaborate} could result in the following incorrect
27861 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func}
27862 has not been elaborated yet.
27865 @geindex pragma Elaborate_All (Unit)
27871 @emph{pragma Elaborate_All (Unit)}
27873 Pragma @code{Elaborate_All} is placed in the context clauses of a unit, after
27874 a @emph{with} clause. It guarantees that both the spec and body of its argument
27875 will be elaborated prior to the unit with the pragma, as well as all units
27876 @emph{with}ed by the spec and body of the argument, recursively. Note that other
27877 unrelated units may be elaborated in between the spec and the body.
27881 function Factorial (Val : Natural) return Natural;
27886 package body Math is
27887 function Factorial (Val : Natural) return Natural is
27895 package Computer is
27896 type Operation_Kind is (None, Op_Factorial);
27900 Op : Operation_Kind) return Natural;
27906 package body Computer is
27909 Op : Operation_Kind) return Natural
27911 if Op = Op_Factorial then
27912 return Math.Factorial (Val);
27922 pragma Elaborate_All (Computer);
27924 Val : constant Natural :=
27925 Computer.Compute (123, Computer.Op_Factorial);
27929 In the example above, pragma @code{Elaborate_All} can result in the following
27940 Note that there are several allowable suborders for the specs and bodies of
27941 @code{Math} and @code{Computer}, but the point is that these specs and bodies will
27942 be elaborated prior to @code{Client}.
27944 Removing pragma @code{Elaborate_All} could result in the following incorrect
27955 where @code{Client} invokes @code{Computer.Compute}, which in turn invokes
27956 @code{Math.Factorial}, but the body of @code{Math.Factorial} has not been
27960 All pragmas shown above can be summarized by the following rule:
27962 @emph{If a client unit elaborates a server target directly or indirectly, then if
27963 the server unit requires a body and does not have pragma Pure, Preelaborate,
27964 or Elaborate_Body, then the client unit should have pragma Elaborate or
27965 Elaborate_All for the server unit.}
27967 If the rule outlined above is not followed, then a program may fall in one of
27968 the following states:
27974 @emph{No elaboration order exists}
27976 In this case a compiler must diagnose the situation, and refuse to build an
27977 executable program.
27980 @emph{One or more incorrect elaboration orders exist}
27982 In this case a compiler can build an executable program, but
27983 @code{Program_Error} will be raised when the program is run.
27986 @emph{Several elaboration orders exist, some correct, some incorrect}
27988 In this case the programmer has not controlled the elaboration order. As a
27989 result, a compiler may or may not pick one of the correct orders, and the
27990 program may or may not raise @code{Program_Error} when it is run. This is the
27991 worst possible state because the program may fail on another compiler, or
27992 even another version of the same compiler.
27995 @emph{One or more correct orders exist}
27997 In this case a compiler can build an executable program, and the program is
27998 run successfully. This state may be guaranteed by following the outlined
27999 rules, or may be the result of good program architecture.
28002 Note that one additional advantage of using @code{Elaborate} and @code{Elaborate_All}
28003 is that the program continues to stay in the last state (one or more correct
28004 orders exist) even if maintenance changes the bodies of targets.
28006 @node Controlling the Elaboration Order in GNAT,Mixing Elaboration Models,Controlling the Elaboration Order in Ada,Elaboration Order Handling in GNAT
28007 @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}
28008 @section Controlling the Elaboration Order in GNAT
28011 In addition to Ada semantics and rules synthesized from them, GNAT offers
28012 three elaboration models to aid the programmer with specifying the correct
28013 elaboration order and to diagnose elaboration problems.
28015 @geindex Dynamic elaboration model
28021 @emph{Dynamic elaboration model}
28023 This is the most permissive of the three elaboration models and emulates the
28024 behavior specified by the Ada Reference Manual. When the dynamic model is in
28025 effect, GNAT makes the following assumptions:
28031 All code within all units in a partition is considered to be elaboration
28035 Some of the invocations in elaboration code may not take place at run time
28036 due to conditional execution.
28039 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28040 that invoke internal targets. In addition, GNAT generates run-time checks for
28041 all external targets and for all scenarios that may exhibit ABE problems.
28043 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
28044 preelaborability of units, and elaboration-control pragmas. The dynamic model
28045 attempts to take all invocations in elaboration code into account. If an
28046 invocation leads to a circularity, GNAT ignores the invocation based on the
28047 assumptions stated above. An order obtained using the dynamic model may fail
28048 an ABE check at run time when GNAT ignored an invocation.
28050 The dynamic model is enabled with compiler switch @code{-gnatE}.
28053 @geindex Static elaboration model
28059 @emph{Static elaboration model}
28061 This is the middle ground of the three models. When the static model is in
28062 effect, GNAT makes the following assumptions:
28068 Only code at the library level and in package body statements within all
28069 units in a partition is considered to be elaboration code.
28072 All invocations in elaboration will take place at run time, regardless of
28073 conditional execution.
28076 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28077 that invoke internal targets. In addition, GNAT generates run-time checks for
28078 all external targets and for all scenarios that may exhibit ABE problems.
28080 The elaboration order is obtained by honoring all @emph{with} clauses, purity and
28081 preelaborability of units, presence of elaboration-control pragmas, and all
28082 invocations in elaboration code. An order obtained using the static model is
28083 guaranteed to be ABE problem-free, excluding dispatching calls and
28084 access-to-subprogram types.
28086 The static model is the default model in GNAT.
28089 @geindex SPARK elaboration model
28095 @emph{SPARK elaboration model}
28097 This is the most conservative of the three models and enforces the SPARK
28098 rules of elaboration as defined in the SPARK Reference Manual, section 7.7.
28099 The SPARK model is in effect only when a scenario and a target reside in a
28100 region subject to @code{SPARK_Mode On}, otherwise the dynamic or static model
28103 The SPARK model is enabled with compiler switch @code{-gnatd.v}.
28106 @geindex Legacy elaboration models
28112 @emph{Legacy elaboration models}
28114 In addition to the three elaboration models outlined above, GNAT provides the
28115 following legacy models:
28121 @cite{Legacy elaboration-checking model} available in pre-18.x versions of GNAT.
28122 This model is enabled with compiler switch @code{-gnatH}.
28125 @cite{Legacy elaboration-order model} available in pre-20.x versions of GNAT.
28126 This model is enabled with binder switch @code{-H}.
28130 @geindex Relaxed elaboration mode
28132 The dynamic, legacy, and static models can be relaxed using compiler switch
28133 @code{-gnatJ}, making them more permissive. Note that in this mode, GNAT
28134 may not diagnose certain elaboration issues or install run-time checks.
28136 @node Mixing Elaboration Models,ABE Diagnostics,Controlling the Elaboration Order in GNAT,Elaboration Order Handling in GNAT
28137 @anchor{gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models}@anchor{237}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id7}@anchor{238}
28138 @section Mixing Elaboration Models
28141 It is possible to mix units compiled with a different elaboration model,
28142 however the following rules must be observed:
28148 A client unit compiled with the dynamic model can only @emph{with} a server unit
28149 that meets at least one of the following criteria:
28155 The server unit is compiled with the dynamic model.
28158 The server unit is a GNAT implementation unit from the @code{Ada}, @code{GNAT},
28159 @code{Interfaces}, or @code{System} hierarchies.
28162 The server unit has pragma @code{Pure} or @code{Preelaborate}.
28165 The client unit has an explicit @code{Elaborate_All} pragma for the server
28170 These rules ensure that elaboration checks are not omitted. If the rules are
28171 violated, the binder emits a warning:
28176 warning: "x.ads" has dynamic elaboration checks and with's
28177 warning: "y.ads" which has static elaboration checks
28181 The warnings can be suppressed by binder switch @code{-ws}.
28183 @node ABE Diagnostics,SPARK Diagnostics,Mixing Elaboration Models,Elaboration Order Handling in GNAT
28184 @anchor{gnat_ugn/elaboration_order_handling_in_gnat abe-diagnostics}@anchor{239}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{23a}
28185 @section ABE Diagnostics
28188 GNAT performs extensive diagnostics on a unit-by-unit basis for all scenarios
28189 that invoke internal targets, regardless of whether the dynamic, SPARK, or
28190 static model is in effect.
28192 Note that GNAT emits warnings rather than hard errors whenever it encounters an
28193 elaboration problem. This is because the elaboration model in effect may be too
28194 conservative, or a particular scenario may not be invoked due conditional
28195 execution. The warnings can be suppressed selectively with @code{pragma Warnings
28196 (Off)} or globally with compiler switch @code{-gnatwL}.
28198 A @emph{guaranteed ABE} arises when the body of a target is not elaborated early
28199 enough, and causes @emph{all} scenarios that directly invoke the target to fail.
28204 package body Guaranteed_ABE is
28205 function ABE return Integer;
28207 Val : constant Integer := ABE;
28209 function ABE return Integer is
28213 end Guaranteed_ABE;
28217 In the example above, the elaboration of @code{Guaranteed_ABE}'s body elaborates
28218 the declaration of @code{Val}. This invokes function @code{ABE}, however the body of
28219 @code{ABE} has not been elaborated yet. GNAT emits the following diagnostic:
28224 4. Val : constant Integer := ABE;
28226 >>> warning: cannot call "ABE" before body seen
28227 >>> warning: Program_Error will be raised at run time
28231 A @emph{conditional ABE} arises when the body of a target is not elaborated early
28232 enough, and causes @emph{some} scenarios that directly invoke the target to fail.
28237 1. package body Conditional_ABE is
28238 2. procedure Force_Body is null;
28241 5. with function Func return Integer;
28243 7. Val : constant Integer := Func;
28246 10. function ABE return Integer;
28248 12. function Cause_ABE return Boolean is
28249 13. package Inst is new Gen (ABE);
28254 18. Val : constant Boolean := Cause_ABE;
28256 20. function ABE return Integer is
28261 25. Safe : constant Boolean := Cause_ABE;
28262 26. end Conditional_ABE;
28266 In the example above, the elaboration of package body @code{Conditional_ABE}
28267 elaborates the declaration of @code{Val}. This invokes function @code{Cause_ABE},
28268 which instantiates generic unit @code{Gen} as @code{Inst}. The elaboration of
28269 @code{Inst} invokes function @code{ABE}, however the body of @code{ABE} has not been
28270 elaborated yet. GNAT emits the following diagnostic:
28275 13. package Inst is new Gen (ABE);
28277 >>> warning: in instantiation at line 7
28278 >>> warning: cannot call "ABE" before body seen
28279 >>> warning: Program_Error may be raised at run time
28280 >>> warning: body of unit "Conditional_ABE" elaborated
28281 >>> warning: function "Cause_ABE" called at line 18
28282 >>> warning: function "ABE" called at line 7, instance at line 13
28286 Note that the same ABE problem does not occur with the elaboration of
28287 declaration @code{Safe} because the body of function @code{ABE} has already been
28288 elaborated at that point.
28290 @node SPARK Diagnostics,Elaboration Circularities,ABE Diagnostics,Elaboration Order Handling in GNAT
28291 @anchor{gnat_ugn/elaboration_order_handling_in_gnat spark-diagnostics}@anchor{23b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id9}@anchor{23c}
28292 @section SPARK Diagnostics
28295 GNAT enforces the SPARK rules of elaboration as defined in the SPARK Reference
28296 Manual section 7.7 when compiler switch @code{-gnatd.v} is in effect. Note
28297 that GNAT emits hard errors whenever it encounters a violation of the SPARK
28304 2. package body SPARK_Diagnostics with SPARK_Mode is
28305 3. Val : constant Integer := Server.Func;
28307 >>> call to "Func" during elaboration in SPARK
28308 >>> unit "SPARK_Diagnostics" requires pragma "Elaborate_All" for "Server"
28309 >>> body of unit "SPARK_Model" elaborated
28310 >>> function "Func" called at line 3
28312 4. end SPARK_Diagnostics;
28316 @node Elaboration Circularities,Resolving Elaboration Circularities,SPARK Diagnostics,Elaboration Order Handling in GNAT
28317 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id10}@anchor{23d}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-circularities}@anchor{23e}
28318 @section Elaboration Circularities
28321 An @strong{elaboration circularity} occurs whenever the elaboration of a set of
28322 units enters a deadlocked state, where each unit is waiting for another unit
28323 to be elaborated. This situation may be the result of improper use of @emph{with}
28324 clauses, elaboration-control pragmas, or invocations in elaboration code.
28326 The following example exhibits an elaboration circularity.
28331 with B; pragma Elaborate (B);
28338 procedure Force_Body;
28345 procedure Force_Body is null;
28347 Elab : constant Integer := C.Func;
28353 function Func return Integer;
28360 function Func return Integer is
28368 The binder emits the following diagnostic:
28373 error: Elaboration circularity detected
28377 info: unit "a (spec)" depends on its own elaboration
28381 info: unit "a (spec)" has with clause and pragma Elaborate for unit "b (spec)"
28382 info: unit "b (body)" is in the closure of pragma Elaborate
28383 info: unit "b (body)" invokes a construct of unit "c (body)" at elaboration time
28384 info: unit "c (body)" has with clause for unit "a (spec)"
28388 info: remove pragma Elaborate for unit "b (body)" in unit "a (spec)"
28389 info: use the dynamic elaboration model (compiler switch -gnatE)
28393 The diagnostic consist of the following sections:
28401 This section provides a short explanation describing why the set of units
28402 could not be ordered.
28407 This section enumerates the units comprising the deadlocked set, along with
28408 their interdependencies.
28413 This section enumerates various tactics for eliminating the circularity.
28416 @node Resolving Elaboration Circularities,Elaboration-related Compiler Switches,Elaboration Circularities,Elaboration Order Handling in GNAT
28417 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id11}@anchor{23f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat resolving-elaboration-circularities}@anchor{240}
28418 @section Resolving Elaboration Circularities
28421 The most desirable option from the point of view of long-term maintenance is to
28422 rearrange the program so that the elaboration problems are avoided. One useful
28423 technique is to place the elaboration code into separate child packages.
28424 Another is to move some of the initialization code to explicitly invoked
28425 subprograms, where the program controls the order of initialization explicitly.
28426 Although this is the most desirable option, it may be impractical and involve
28427 too much modification, especially in the case of complex legacy code.
28429 When faced with an elaboration circularity, the programmer should also consider
28430 the tactics given in the suggestions section of the circularity diagnostic.
28431 Depending on the units involved in the circularity, their @emph{with} clauses,
28432 purity, preelaborability, presence of elaboration-control pragmas and
28433 invocations at elaboration time, the binder may suggest one or more of the
28434 following tactics to eliminate the circularity:
28440 Pragma Elaborate elimination
28443 remove pragma Elaborate for unit "..." in unit "..."
28446 This tactic is suggested when the binder has determined that pragma
28453 Prevents a set of units from being elaborated.
28456 The removal of the pragma will not eliminate the semantic effects of the
28457 pragma. In other words, the argument of the pragma will still be elaborated
28458 prior to the unit containing the pragma.
28461 The removal of the pragma will enable the successful ordering of the units.
28464 The programmer should remove the pragma as advised, and rebuild the program.
28467 Pragma Elaborate_All elimination
28470 remove pragma Elaborate_All for unit "..." in unit "..."
28473 This tactic is suggested when the binder has determined that pragma
28474 @code{Elaborate_All}:
28480 Prevents a set of units from being elaborated.
28483 The removal of the pragma will not eliminate the semantic effects of the
28484 pragma. In other words, the argument of the pragma along with its @emph{with}
28485 closure will still be elaborated prior to the unit containing the pragma.
28488 The removal of the pragma will enable the successful ordering of the units.
28491 The programmer should remove the pragma as advised, and rebuild the program.
28494 Pragma Elaborate_All downgrade
28497 change pragma Elaborate_All for unit "..." to Elaborate in unit "..."
28500 This tactic is always suggested with the pragma @code{Elaborate_All} elimination
28501 tactic. It offers a different alernative of guaranteeing that the argument of
28502 the pragma will still be elaborated prior to the unit containing the pragma.
28504 The programmer should update the pragma as advised, and rebuild the program.
28507 Pragma Elaborate_Body elimination
28510 remove pragma Elaborate_Body in unit "..."
28513 This tactic is suggested when the binder has determined that pragma
28514 @code{Elaborate_Body}:
28520 Prevents a set of units from being elaborated.
28523 The removal of the pragma will enable the successful ordering of the units.
28526 Note that the binder cannot determine whether the pragma is required for
28527 other purposes, such as guaranteeing the initialization of a variable
28528 declared in the spec by elaboration code in the body.
28530 The programmer should remove the pragma as advised, and rebuild the program.
28533 Use of pragma Restrictions
28536 use pragma Restrictions (No_Entry_Calls_In_Elaboration_Code)
28539 This tactic is suggested when the binder has determined that a task
28540 activation at elaboration time:
28546 Prevents a set of units from being elaborated.
28549 Note that the binder cannot determine with certainty whether the task will
28550 block at elaboration time.
28552 The programmer should create a configuration file, place the pragma within,
28553 update the general compilation arguments, and rebuild the program.
28556 Use of dynamic elaboration model
28559 use the dynamic elaboration model (compiler switch -gnatE)
28562 This tactic is suggested when the binder has determined that an invocation at
28569 Prevents a set of units from being elaborated.
28572 The use of the dynamic model will enable the successful ordering of the
28576 The programmer has two options:
28582 Determine the units involved in the invocation using the detailed
28583 invocation information, and add compiler switch @code{-gnatE} to the
28584 compilation arguments of selected files only. This approach will yield
28585 safer elaboration orders compared to the other option because it will
28586 minimize the opportunities presented to the dynamic model for ignoring
28590 Add compiler switch @code{-gnatE} to the general compilation arguments.
28594 Use of detailed invocation information
28597 use detailed invocation information (compiler switch -gnatd_F)
28600 This tactic is always suggested with the use of the dynamic model tactic. It
28601 causes the circularity section of the circularity diagnostic to describe the
28602 flow of elaboration code from a unit to a unit, enumerating all such paths in
28605 The programmer should analyze this information to determine which units
28606 should be compiled with the dynamic model.
28609 Forced-dependency elimination
28612 remove the dependency of unit "..." on unit "..." from the argument of switch -f
28615 This tactic is suggested when the binder has determined that a dependency
28616 present in the forced-elaboration-order file indicated by binder switch
28623 Prevents a set of units from being elaborated.
28626 The removal of the dependency will enable the successful ordering of the
28630 The programmer should edit the forced-elaboration-order file, remove the
28631 dependency, and rebind the program.
28634 All forced-dependency elimination
28640 This tactic is suggested in case editing the forced-elaboration-order file is
28643 The programmer should remove binder switch @code{-f} from the binder
28644 arguments, and rebind.
28647 Multiple-circularities diagnostic
28650 diagnose all circularities (binder switch -d_C)
28653 By default, the binder will diagnose only the highest-precedence circularity.
28654 If the program contains multiple circularities, the binder will suggest the
28655 use of binder switch @code{-d_C} in order to obtain the diagnostics of all
28658 The programmer should add binder switch @code{-d_C} to the binder
28659 arguments, and rebind.
28662 If none of the tactics suggested by the binder eliminate the elaboration
28663 circularity, the programmer should consider using one of the legacy elaboration
28664 models, in the following order:
28670 Use the pre-20.x legacy elaboration-order model, with binder switch
28674 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28675 switch @code{-gnatH} and binder switch @code{-H}.
28678 Use the relaxed static-elaboration model, with compiler switches
28679 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28682 Use the relaxed dynamic-elaboration model, with compiler switches
28683 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28687 @node Elaboration-related Compiler Switches,Summary of Procedures for Elaboration Control,Resolving Elaboration Circularities,Elaboration Order Handling in GNAT
28688 @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}
28689 @section Elaboration-related Compiler Switches
28692 GNAT has several switches that affect the elaboration model and consequently
28693 the elaboration order chosen by the binder.
28695 @geindex -gnatE (gnat)
28700 @item @code{-gnatE}
28702 Dynamic elaboration checking mode enabled
28704 When this switch is in effect, GNAT activates the dynamic model.
28707 @geindex -gnatel (gnat)
28712 @item @code{-gnatel}
28714 Turn on info messages on generated Elaborate[_All] pragmas
28716 This switch is only applicable to the pre-20.x legacy elaboration models.
28717 The post-20.x elaboration model no longer relies on implicitly generated
28718 @code{Elaborate} and @code{Elaborate_All} pragmas to order units.
28720 When this switch is in effect, GNAT will emit the following supplementary
28721 information depending on the elaboration model in effect.
28727 @emph{Dynamic model}
28729 GNAT will indicate missing @code{Elaborate} and @code{Elaborate_All} pragmas for
28730 all library-level scenarios within the partition.
28733 @emph{Static model}
28735 GNAT will indicate all scenarios invoked during elaboration. In addition,
28736 it will provide detailed traceback when an implicit @code{Elaborate} or
28737 @code{Elaborate_All} pragma is generated.
28742 GNAT will indicate how an elaboration requirement is met by the context of
28743 a unit. This diagnostic requires compiler switch @code{-gnatd.v}.
28746 1. with Server; pragma Elaborate_All (Server);
28747 2. package Client with SPARK_Mode is
28748 3. Val : constant Integer := Server.Func;
28750 >>> info: call to "Func" during elaboration in SPARK
28751 >>> info: "Elaborate_All" requirement for unit "Server" met by pragma at line 1
28758 @geindex -gnatH (gnat)
28763 @item @code{-gnatH}
28765 Legacy elaboration checking mode enabled
28767 When this switch is in effect, GNAT will utilize the pre-18.x elaboration
28771 @geindex -gnatJ (gnat)
28776 @item @code{-gnatJ}
28778 Relaxed elaboration checking mode enabled
28780 When this switch is in effect, GNAT will not process certain scenarios,
28781 resulting in a more permissive elaboration model. Note that this may
28782 eliminate some diagnostics and run-time checks.
28785 @geindex -gnatw.f (gnat)
28790 @item @code{-gnatw.f}
28792 Turn on warnings for suspicious Subp'Access
28794 When this switch is in effect, GNAT will treat @code{'Access} of an entry,
28795 operator, or subprogram as a potential call to the target and issue warnings:
28798 1. package body Attribute_Call is
28799 2. function Func return Integer;
28800 3. type Func_Ptr is access function return Integer;
28802 5. Ptr : constant Func_Ptr := Func'Access;
28804 >>> warning: "Access" attribute of "Func" before body seen
28805 >>> warning: possible Program_Error on later references
28806 >>> warning: body of unit "Attribute_Call" elaborated
28807 >>> warning: "Access" of "Func" taken at line 5
28810 7. function Func return Integer is
28814 11. end Attribute_Call;
28817 In the example above, the elaboration of declaration @code{Ptr} is assigned
28818 @code{Func'Access} before the body of @code{Func} has been elaborated.
28821 @geindex -gnatwl (gnat)
28826 @item @code{-gnatwl}
28828 Turn on warnings for elaboration problems
28830 When this switch is in effect, GNAT emits diagnostics in the form of warnings
28831 concerning various elaboration problems. The warnings are enabled by default.
28832 The switch is provided in case all warnings are suppressed, but elaboration
28833 warnings are still desired.
28835 @item @code{-gnatwL}
28837 Turn off warnings for elaboration problems
28839 When this switch is in effect, GNAT no longer emits any diagnostics in the
28840 form of warnings. Selective suppression of elaboration problems is possible
28841 using @code{pragma Warnings (Off)}.
28844 1. package body Selective_Suppression is
28845 2. function ABE return Integer;
28847 4. Val_1 : constant Integer := ABE;
28849 >>> warning: cannot call "ABE" before body seen
28850 >>> warning: Program_Error will be raised at run time
28853 6. pragma Warnings (Off);
28854 7. Val_2 : constant Integer := ABE;
28855 8. pragma Warnings (On);
28857 10. function ABE return Integer is
28861 14. end Selective_Suppression;
28864 Note that suppressing elaboration warnings does not eliminate run-time
28865 checks. The example above will still fail at run time with an ABE.
28868 @node Summary of Procedures for Elaboration Control,Inspecting the Chosen Elaboration Order,Elaboration-related Compiler Switches,Elaboration Order Handling in GNAT
28869 @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}
28870 @section Summary of Procedures for Elaboration Control
28873 A programmer should first compile the program with the default options, using
28874 none of the binder or compiler switches. If the binder succeeds in finding an
28875 elaboration order, then apart from possible cases involing dispatching calls
28876 and access-to-subprogram types, the program is free of elaboration errors.
28878 If it is important for the program to be portable to compilers other than GNAT,
28879 then the programmer should use compiler switch @code{-gnatel} and consider
28880 the messages about missing or implicitly created @code{Elaborate} and
28881 @code{Elaborate_All} pragmas.
28883 If the binder reports an elaboration circularity, the programmer has several
28890 Ensure that elaboration warnings are enabled. This will allow the static
28891 model to output trace information of elaboration issues. The trace
28892 information could shed light on previously unforeseen dependencies, as well
28893 as their origins. Elaboration warnings are enabled with compiler switch
28897 Cosider the tactics given in the suggestions section of the circularity
28901 If none of the steps outlined above resolve the circularity, use a more
28902 permissive elaboration model, in the following order:
28908 Use the pre-20.x legacy elaboration-order model, with binder switch
28912 Use both pre-18.x and pre-20.x legacy elaboration models, with compiler
28913 switch @code{-gnatH} and binder switch @code{-H}.
28916 Use the relaxed static elaboration model, with compiler switches
28917 @code{-gnatH} @code{-gnatJ} and binder switch @code{-H}.
28920 Use the relaxed dynamic elaboration model, with compiler switches
28921 @code{-gnatH} @code{-gnatJ} @code{-gnatE} and binder switch
28926 @node Inspecting the Chosen Elaboration Order,,Summary of Procedures for Elaboration Control,Elaboration Order Handling in GNAT
28927 @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}
28928 @section Inspecting the Chosen Elaboration Order
28931 To see the elaboration order chosen by the binder, inspect the contents of file
28932 @cite{b~xxx.adb}. On certain targets, this file appears as @cite{b_xxx.adb}. The
28933 elaboration order appears as a sequence of calls to @code{Elab_Body} and
28934 @code{Elab_Spec}, interspersed with assignments to @cite{Exxx} which indicates that a
28935 particular unit is elaborated. For example:
28940 System.Soft_Links'Elab_Body;
28942 System.Secondary_Stack'Elab_Body;
28944 System.Exception_Table'Elab_Body;
28946 Ada.Io_Exceptions'Elab_Spec;
28948 Ada.Tags'Elab_Spec;
28949 Ada.Streams'Elab_Spec;
28951 Interfaces.C'Elab_Spec;
28953 System.Finalization_Root'Elab_Spec;
28955 System.Os_Lib'Elab_Body;
28957 System.Finalization_Implementation'Elab_Spec;
28958 System.Finalization_Implementation'Elab_Body;
28960 Ada.Finalization'Elab_Spec;
28962 Ada.Finalization.List_Controller'Elab_Spec;
28964 System.File_Control_Block'Elab_Spec;
28966 System.File_Io'Elab_Body;
28968 Ada.Tags'Elab_Body;
28970 Ada.Text_Io'Elab_Spec;
28971 Ada.Text_Io'Elab_Body;
28976 Note also binder switch @code{-l}, which outputs the chosen elaboration
28977 order and provides a more readable form of the above:
28985 system.case_util (spec)
28986 system.case_util (body)
28987 system.concat_2 (spec)
28988 system.concat_2 (body)
28989 system.concat_3 (spec)
28990 system.concat_3 (body)
28991 system.htable (spec)
28992 system.parameters (spec)
28993 system.parameters (body)
28995 interfaces.c_streams (spec)
28996 interfaces.c_streams (body)
28997 system.restrictions (spec)
28998 system.restrictions (body)
28999 system.standard_library (spec)
29000 system.exceptions (spec)
29001 system.exceptions (body)
29002 system.storage_elements (spec)
29003 system.storage_elements (body)
29004 system.secondary_stack (spec)
29005 system.stack_checking (spec)
29006 system.stack_checking (body)
29007 system.string_hash (spec)
29008 system.string_hash (body)
29009 system.htable (body)
29010 system.strings (spec)
29011 system.strings (body)
29012 system.traceback (spec)
29013 system.traceback (body)
29014 system.traceback_entries (spec)
29015 system.traceback_entries (body)
29016 ada.exceptions (spec)
29017 ada.exceptions.last_chance_handler (spec)
29018 system.soft_links (spec)
29019 system.soft_links (body)
29020 ada.exceptions.last_chance_handler (body)
29021 system.secondary_stack (body)
29022 system.exception_table (spec)
29023 system.exception_table (body)
29024 ada.io_exceptions (spec)
29027 interfaces.c (spec)
29028 interfaces.c (body)
29029 system.finalization_root (spec)
29030 system.finalization_root (body)
29031 system.memory (spec)
29032 system.memory (body)
29033 system.standard_library (body)
29034 system.os_lib (spec)
29035 system.os_lib (body)
29036 system.unsigned_types (spec)
29037 system.stream_attributes (spec)
29038 system.stream_attributes (body)
29039 system.finalization_implementation (spec)
29040 system.finalization_implementation (body)
29041 ada.finalization (spec)
29042 ada.finalization (body)
29043 ada.finalization.list_controller (spec)
29044 ada.finalization.list_controller (body)
29045 system.file_control_block (spec)
29046 system.file_io (spec)
29047 system.file_io (body)
29048 system.val_uns (spec)
29049 system.val_util (spec)
29050 system.val_util (body)
29051 system.val_uns (body)
29052 system.wch_con (spec)
29053 system.wch_con (body)
29054 system.wch_cnv (spec)
29055 system.wch_jis (spec)
29056 system.wch_jis (body)
29057 system.wch_cnv (body)
29058 system.wch_stw (spec)
29059 system.wch_stw (body)
29061 ada.exceptions (body)
29069 @node Inline Assembler,GNU Free Documentation License,Elaboration Order Handling in GNAT,Top
29070 @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}
29071 @chapter Inline Assembler
29074 @geindex Inline Assembler
29076 If you need to write low-level software that interacts directly
29077 with the hardware, Ada provides two ways to incorporate assembly
29078 language code into your program. First, you can import and invoke
29079 external routines written in assembly language, an Ada feature fully
29080 supported by GNAT. However, for small sections of code it may be simpler
29081 or more efficient to include assembly language statements directly
29082 in your Ada source program, using the facilities of the implementation-defined
29083 package @code{System.Machine_Code}, which incorporates the gcc
29084 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29085 including the following:
29091 No need to use non-Ada tools
29094 Consistent interface over different targets
29097 Automatic usage of the proper calling conventions
29100 Access to Ada constants and variables
29103 Definition of intrinsic routines
29106 Possibility of inlining a subprogram comprising assembler code
29109 Code optimizer can take Inline Assembler code into account
29112 This appendix presents a series of examples to show you how to use
29113 the Inline Assembler. Although it focuses on the Intel x86,
29114 the general approach applies also to other processors.
29115 It is assumed that you are familiar with Ada
29116 and with assembly language programming.
29119 * Basic Assembler Syntax::
29120 * A Simple Example of Inline Assembler::
29121 * Output Variables in Inline Assembler::
29122 * Input Variables in Inline Assembler::
29123 * Inlining Inline Assembler Code::
29124 * Other Asm Functionality::
29128 @node Basic Assembler Syntax,A Simple Example of Inline Assembler,,Inline Assembler
29129 @anchor{gnat_ugn/inline_assembler id2}@anchor{249}@anchor{gnat_ugn/inline_assembler basic-assembler-syntax}@anchor{24a}
29130 @section Basic Assembler Syntax
29133 The assembler used by GNAT and gcc is based not on the Intel assembly
29134 language, but rather on a language that descends from the AT&T Unix
29135 assembler @code{as} (and which is often referred to as 'AT&T syntax').
29136 The following table summarizes the main features of @code{as} syntax
29137 and points out the differences from the Intel conventions.
29138 See the gcc @code{as} and @code{gas} (an @code{as} macro
29139 pre-processor) documentation for further information.
29143 @emph{Register names}@w{ }
29145 gcc / @code{as}: Prefix with '%'; for example @code{%eax}@w{ }
29146 Intel: No extra punctuation; for example @code{eax}@w{ }
29154 @emph{Immediate operand}@w{ }
29156 gcc / @code{as}: Prefix with '$'; for example @code{$4}@w{ }
29157 Intel: No extra punctuation; for example @code{4}@w{ }
29165 @emph{Address}@w{ }
29167 gcc / @code{as}: Prefix with '$'; for example @code{$loc}@w{ }
29168 Intel: No extra punctuation; for example @code{loc}@w{ }
29176 @emph{Memory contents}@w{ }
29178 gcc / @code{as}: No extra punctuation; for example @code{loc}@w{ }
29179 Intel: Square brackets; for example @code{[loc]}@w{ }
29187 @emph{Register contents}@w{ }
29189 gcc / @code{as}: Parentheses; for example @code{(%eax)}@w{ }
29190 Intel: Square brackets; for example @code{[eax]}@w{ }
29198 @emph{Hexadecimal numbers}@w{ }
29200 gcc / @code{as}: Leading '0x' (C language syntax); for example @code{0xA0}@w{ }
29201 Intel: Trailing 'h'; for example @code{A0h}@w{ }
29209 @emph{Operand size}@w{ }
29211 gcc / @code{as}: Explicit in op code; for example @code{movw} to move a 16-bit word@w{ }
29212 Intel: Implicit, deduced by assembler; for example @code{mov}@w{ }
29220 @emph{Instruction repetition}@w{ }
29222 gcc / @code{as}: Split into two lines; for example@w{ }
29227 Intel: Keep on one line; for example @code{rep stosl}@w{ }
29235 @emph{Order of operands}@w{ }
29237 gcc / @code{as}: Source first; for example @code{movw $4, %eax}@w{ }
29238 Intel: Destination first; for example @code{mov eax, 4}@w{ }
29244 @node A Simple Example of Inline Assembler,Output Variables in Inline Assembler,Basic Assembler Syntax,Inline Assembler
29245 @anchor{gnat_ugn/inline_assembler a-simple-example-of-inline-assembler}@anchor{24b}@anchor{gnat_ugn/inline_assembler id3}@anchor{24c}
29246 @section A Simple Example of Inline Assembler
29249 The following example will generate a single assembly language statement,
29250 @code{nop}, which does nothing. Despite its lack of run-time effect,
29251 the example will be useful in illustrating the basics of
29252 the Inline Assembler facility.
29257 with System.Machine_Code; use System.Machine_Code;
29258 procedure Nothing is
29265 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29266 here it takes one parameter, a @emph{template string} that must be a static
29267 expression and that will form the generated instruction.
29268 @code{Asm} may be regarded as a compile-time procedure that parses
29269 the template string and additional parameters (none here),
29270 from which it generates a sequence of assembly language instructions.
29272 The examples in this chapter will illustrate several of the forms
29273 for invoking @code{Asm}; a complete specification of the syntax
29274 is found in the @code{Machine_Code_Insertions} section of the
29275 @cite{GNAT Reference Manual}.
29277 Under the standard GNAT conventions, the @code{Nothing} procedure
29278 should be in a file named @code{nothing.adb}.
29279 You can build the executable in the usual way:
29288 However, the interesting aspect of this example is not its run-time behavior
29289 but rather the generated assembly code.
29290 To see this output, invoke the compiler as follows:
29295 $ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb
29299 where the options are:
29310 compile only (no bind or link)
29319 generate assembler listing
29326 @item @code{-fomit-frame-pointer}
29328 do not set up separate stack frames
29335 @item @code{-gnatp}
29337 do not add runtime checks
29341 This gives a human-readable assembler version of the code. The resulting
29342 file will have the same name as the Ada source file, but with a @code{.s}
29343 extension. In our example, the file @code{nothing.s} has the following
29349 .file "nothing.adb"
29351 ___gnu_compiled_ada:
29354 .globl __ada_nothing
29366 The assembly code you included is clearly indicated by
29367 the compiler, between the @code{#APP} and @code{#NO_APP}
29368 delimiters. The character before the 'APP' and 'NOAPP'
29369 can differ on different targets. For example, GNU/Linux uses '#APP' while
29370 on NT you will see '/APP'.
29372 If you make a mistake in your assembler code (such as using the
29373 wrong size modifier, or using a wrong operand for the instruction) GNAT
29374 will report this error in a temporary file, which will be deleted when
29375 the compilation is finished. Generating an assembler file will help
29376 in such cases, since you can assemble this file separately using the
29377 @code{as} assembler that comes with gcc.
29379 Assembling the file using the command
29388 will give you error messages whose lines correspond to the assembler
29389 input file, so you can easily find and correct any mistakes you made.
29390 If there are no errors, @code{as} will generate an object file
29391 @code{nothing.out}.
29393 @node Output Variables in Inline Assembler,Input Variables in Inline Assembler,A Simple Example of Inline Assembler,Inline Assembler
29394 @anchor{gnat_ugn/inline_assembler id4}@anchor{24d}@anchor{gnat_ugn/inline_assembler output-variables-in-inline-assembler}@anchor{24e}
29395 @section Output Variables in Inline Assembler
29398 The examples in this section, showing how to access the processor flags,
29399 illustrate how to specify the destination operands for assembly language
29405 with Interfaces; use Interfaces;
29406 with Ada.Text_IO; use Ada.Text_IO;
29407 with System.Machine_Code; use System.Machine_Code;
29408 procedure Get_Flags is
29409 Flags : Unsigned_32;
29412 Asm ("pushfl" & LF & HT & -- push flags on stack
29413 "popl %%eax" & LF & HT & -- load eax with flags
29414 "movl %%eax, %0", -- store flags in variable
29415 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29416 Put_Line ("Flags register:" & Flags'Img);
29421 In order to have a nicely aligned assembly listing, we have separated
29422 multiple assembler statements in the Asm template string with linefeed
29423 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29424 The resulting section of the assembly output file is:
29432 movl %eax, -40(%ebp)
29437 It would have been legal to write the Asm invocation as:
29442 Asm ("pushfl popl %%eax movl %%eax, %0")
29446 but in the generated assembler file, this would come out as:
29452 pushfl popl %eax movl %eax, -40(%ebp)
29457 which is not so convenient for the human reader.
29459 We use Ada comments
29460 at the end of each line to explain what the assembler instructions
29461 actually do. This is a useful convention.
29463 When writing Inline Assembler instructions, you need to precede each register
29464 and variable name with a percent sign. Since the assembler already requires
29465 a percent sign at the beginning of a register name, you need two consecutive
29466 percent signs for such names in the Asm template string, thus @code{%%eax}.
29467 In the generated assembly code, one of the percent signs will be stripped off.
29469 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29470 variables: operands you later define using @code{Input} or @code{Output}
29471 parameters to @code{Asm}.
29472 An output variable is illustrated in
29473 the third statement in the Asm template string:
29482 The intent is to store the contents of the eax register in a variable that can
29483 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29484 necessarily work, since the compiler might optimize by using a register
29485 to hold Flags, and the expansion of the @code{movl} instruction would not be
29486 aware of this optimization. The solution is not to store the result directly
29487 but rather to advise the compiler to choose the correct operand form;
29488 that is the purpose of the @code{%0} output variable.
29490 Information about the output variable is supplied in the @code{Outputs}
29491 parameter to @code{Asm}:
29496 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29500 The output is defined by the @code{Asm_Output} attribute of the target type;
29501 the general format is
29506 Type'Asm_Output (constraint_string, variable_name)
29510 The constraint string directs the compiler how
29511 to store/access the associated variable. In the example
29516 Unsigned_32'Asm_Output ("=m", Flags);
29520 the @code{"m"} (memory) constraint tells the compiler that the variable
29521 @code{Flags} should be stored in a memory variable, thus preventing
29522 the optimizer from keeping it in a register. In contrast,
29527 Unsigned_32'Asm_Output ("=r", Flags);
29531 uses the @code{"r"} (register) constraint, telling the compiler to
29532 store the variable in a register.
29534 If the constraint is preceded by the equal character '=', it tells
29535 the compiler that the variable will be used to store data into it.
29537 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29538 allowing the optimizer to choose whatever it deems best.
29540 There are a fairly large number of constraints, but the ones that are
29541 most useful (for the Intel x86 processor) are the following:
29546 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
29561 global (i.e., can be stored anywhere)
29633 use one of eax, ebx, ecx or edx
29641 use one of eax, ebx, ecx, edx, esi or edi
29647 The full set of constraints is described in the gcc and @code{as}
29648 documentation; note that it is possible to combine certain constraints
29649 in one constraint string.
29651 You specify the association of an output variable with an assembler operand
29652 through the @code{%@emph{n}} notation, where @emph{n} is a non-negative
29658 Asm ("pushfl" & LF & HT & -- push flags on stack
29659 "popl %%eax" & LF & HT & -- load eax with flags
29660 "movl %%eax, %0", -- store flags in variable
29661 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29665 @code{%0} will be replaced in the expanded code by the appropriate operand,
29667 the compiler decided for the @code{Flags} variable.
29669 In general, you may have any number of output variables:
29675 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29678 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29679 of @code{Asm_Output} attributes
29687 Asm ("movl %%eax, %0" & LF & HT &
29688 "movl %%ebx, %1" & LF & HT &
29690 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29691 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29692 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29696 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29697 in the Ada program.
29699 As a variation on the @code{Get_Flags} example, we can use the constraints
29700 string to direct the compiler to store the eax register into the @code{Flags}
29701 variable, instead of including the store instruction explicitly in the
29702 @code{Asm} template string:
29707 with Interfaces; use Interfaces;
29708 with Ada.Text_IO; use Ada.Text_IO;
29709 with System.Machine_Code; use System.Machine_Code;
29710 procedure Get_Flags_2 is
29711 Flags : Unsigned_32;
29714 Asm ("pushfl" & LF & HT & -- push flags on stack
29715 "popl %%eax", -- save flags in eax
29716 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29717 Put_Line ("Flags register:" & Flags'Img);
29722 The @code{"a"} constraint tells the compiler that the @code{Flags}
29723 variable will come from the eax register. Here is the resulting code:
29732 movl %eax,-40(%ebp)
29736 The compiler generated the store of eax into Flags after
29737 expanding the assembler code.
29739 Actually, there was no need to pop the flags into the eax register;
29740 more simply, we could just pop the flags directly into the program variable:
29745 with Interfaces; use Interfaces;
29746 with Ada.Text_IO; use Ada.Text_IO;
29747 with System.Machine_Code; use System.Machine_Code;
29748 procedure Get_Flags_3 is
29749 Flags : Unsigned_32;
29752 Asm ("pushfl" & LF & HT & -- push flags on stack
29753 "pop %0", -- save flags in Flags
29754 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29755 Put_Line ("Flags register:" & Flags'Img);
29760 @node Input Variables in Inline Assembler,Inlining Inline Assembler Code,Output Variables in Inline Assembler,Inline Assembler
29761 @anchor{gnat_ugn/inline_assembler id5}@anchor{24f}@anchor{gnat_ugn/inline_assembler input-variables-in-inline-assembler}@anchor{250}
29762 @section Input Variables in Inline Assembler
29765 The example in this section illustrates how to specify the source operands
29766 for assembly language statements.
29767 The program simply increments its input value by 1:
29772 with Interfaces; use Interfaces;
29773 with Ada.Text_IO; use Ada.Text_IO;
29774 with System.Machine_Code; use System.Machine_Code;
29775 procedure Increment is
29777 function Incr (Value : Unsigned_32) return Unsigned_32 is
29778 Result : Unsigned_32;
29781 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29782 Inputs => Unsigned_32'Asm_Input ("a", Value));
29786 Value : Unsigned_32;
29790 Put_Line ("Value before is" & Value'Img);
29791 Value := Incr (Value);
29792 Put_Line ("Value after is" & Value'Img);
29797 The @code{Outputs} parameter to @code{Asm} specifies
29798 that the result will be in the eax register and that it is to be stored
29799 in the @code{Result} variable.
29801 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29802 but with an @code{Asm_Input} attribute.
29803 The @code{"="} constraint, indicating an output value, is not present.
29805 You can have multiple input variables, in the same way that you can have more
29806 than one output variable.
29808 The parameter count (%0, %1) etc, still starts at the first output statement,
29809 and continues with the input statements.
29811 Just as the @code{Outputs} parameter causes the register to be stored into the
29812 target variable after execution of the assembler statements, so does the
29813 @code{Inputs} parameter cause its variable to be loaded into the register
29814 before execution of the assembler statements.
29816 Thus the effect of the @code{Asm} invocation is:
29822 load the 32-bit value of @code{Value} into eax
29825 execute the @code{incl %eax} instruction
29828 store the contents of eax into the @code{Result} variable
29831 The resulting assembler file (with @code{-O2} optimization) contains:
29836 _increment__incr.1:
29849 @node Inlining Inline Assembler Code,Other Asm Functionality,Input Variables in Inline Assembler,Inline Assembler
29850 @anchor{gnat_ugn/inline_assembler id6}@anchor{251}@anchor{gnat_ugn/inline_assembler inlining-inline-assembler-code}@anchor{252}
29851 @section Inlining Inline Assembler Code
29854 For a short subprogram such as the @code{Incr} function in the previous
29855 section, the overhead of the call and return (creating / deleting the stack
29856 frame) can be significant, compared to the amount of code in the subprogram
29857 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29858 which directs the compiler to expand invocations of the subprogram at the
29859 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29860 Here is the resulting program:
29865 with Interfaces; use Interfaces;
29866 with Ada.Text_IO; use Ada.Text_IO;
29867 with System.Machine_Code; use System.Machine_Code;
29868 procedure Increment_2 is
29870 function Incr (Value : Unsigned_32) return Unsigned_32 is
29871 Result : Unsigned_32;
29874 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29875 Inputs => Unsigned_32'Asm_Input ("a", Value));
29878 pragma Inline (Increment);
29880 Value : Unsigned_32;
29884 Put_Line ("Value before is" & Value'Img);
29885 Value := Increment (Value);
29886 Put_Line ("Value after is" & Value'Img);
29891 Compile the program with both optimization (@code{-O2}) and inlining
29892 (@code{-gnatn}) enabled.
29894 The @code{Incr} function is still compiled as usual, but at the
29895 point in @code{Increment} where our function used to be called:
29901 call _increment__incr.1
29905 the code for the function body directly appears:
29918 thus saving the overhead of stack frame setup and an out-of-line call.
29920 @node Other Asm Functionality,,Inlining Inline Assembler Code,Inline Assembler
29921 @anchor{gnat_ugn/inline_assembler other-asm-functionality}@anchor{253}@anchor{gnat_ugn/inline_assembler id7}@anchor{254}
29922 @section Other @code{Asm} Functionality
29925 This section describes two important parameters to the @code{Asm}
29926 procedure: @code{Clobber}, which identifies register usage;
29927 and @code{Volatile}, which inhibits unwanted optimizations.
29930 * The Clobber Parameter::
29931 * The Volatile Parameter::
29935 @node The Clobber Parameter,The Volatile Parameter,,Other Asm Functionality
29936 @anchor{gnat_ugn/inline_assembler the-clobber-parameter}@anchor{255}@anchor{gnat_ugn/inline_assembler id8}@anchor{256}
29937 @subsection The @code{Clobber} Parameter
29940 One of the dangers of intermixing assembly language and a compiled language
29941 such as Ada is that the compiler needs to be aware of which registers are
29942 being used by the assembly code. In some cases, such as the earlier examples,
29943 the constraint string is sufficient to indicate register usage (e.g.,
29945 the eax register). But more generally, the compiler needs an explicit
29946 identification of the registers that are used by the Inline Assembly
29949 Using a register that the compiler doesn't know about
29950 could be a side effect of an instruction (like @code{mull}
29951 storing its result in both eax and edx).
29952 It can also arise from explicit register usage in your
29953 assembly code; for example:
29958 Asm ("movl %0, %%ebx" & LF & HT &
29960 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29961 Inputs => Unsigned_32'Asm_Input ("g", Var_In));
29965 where the compiler (since it does not analyze the @code{Asm} template string)
29966 does not know you are using the ebx register.
29968 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
29969 to identify the registers that will be used by your assembly code:
29974 Asm ("movl %0, %%ebx" & LF & HT &
29976 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29977 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
29982 The Clobber parameter is a static string expression specifying the
29983 register(s) you are using. Note that register names are @emph{not} prefixed
29984 by a percent sign. Also, if more than one register is used then their names
29985 are separated by commas; e.g., @code{"eax, ebx"}
29987 The @code{Clobber} parameter has several additional uses:
29993 Use 'register' name @code{cc} to indicate that flags might have changed
29996 Use 'register' name @code{memory} if you changed a memory location
29999 @node The Volatile Parameter,,The Clobber Parameter,Other Asm Functionality
30000 @anchor{gnat_ugn/inline_assembler the-volatile-parameter}@anchor{257}@anchor{gnat_ugn/inline_assembler id9}@anchor{258}
30001 @subsection The @code{Volatile} Parameter
30004 @geindex Volatile parameter
30006 Compiler optimizations in the presence of Inline Assembler may sometimes have
30007 unwanted effects. For example, when an @code{Asm} invocation with an input
30008 variable is inside a loop, the compiler might move the loading of the input
30009 variable outside the loop, regarding it as a one-time initialization.
30011 If this effect is not desired, you can disable such optimizations by setting
30012 the @code{Volatile} parameter to @code{True}; for example:
30017 Asm ("movl %0, %%ebx" & LF & HT &
30019 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30020 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30026 By default, @code{Volatile} is set to @code{False} unless there is no
30027 @code{Outputs} parameter.
30029 Although setting @code{Volatile} to @code{True} prevents unwanted
30030 optimizations, it will also disable other optimizations that might be
30031 important for efficiency. In general, you should set @code{Volatile}
30032 to @code{True} only if the compiler's optimizations have created
30035 @node GNU Free Documentation License,Index,Inline Assembler,Top
30036 @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}
30037 @chapter GNU Free Documentation License
30040 Version 1.3, 3 November 2008
30042 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
30043 @indicateurl{http://fsf.org/}
30045 Everyone is permitted to copy and distribute verbatim copies of this
30046 license document, but changing it is not allowed.
30050 The purpose of this License is to make a manual, textbook, or other
30051 functional and useful document "free" in the sense of freedom: to
30052 assure everyone the effective freedom to copy and redistribute it,
30053 with or without modifying it, either commercially or noncommercially.
30054 Secondarily, this License preserves for the author and publisher a way
30055 to get credit for their work, while not being considered responsible
30056 for modifications made by others.
30058 This License is a kind of "copyleft", which means that derivative
30059 works of the document must themselves be free in the same sense. It
30060 complements the GNU General Public License, which is a copyleft
30061 license designed for free software.
30063 We have designed this License in order to use it for manuals for free
30064 software, because free software needs free documentation: a free
30065 program should come with manuals providing the same freedoms that the
30066 software does. But this License is not limited to software manuals;
30067 it can be used for any textual work, regardless of subject matter or
30068 whether it is published as a printed book. We recommend this License
30069 principally for works whose purpose is instruction or reference.
30071 @strong{1. APPLICABILITY AND DEFINITIONS}
30073 This License applies to any manual or other work, in any medium, that
30074 contains a notice placed by the copyright holder saying it can be
30075 distributed under the terms of this License. Such a notice grants a
30076 world-wide, royalty-free license, unlimited in duration, to use that
30077 work under the conditions stated herein. The @strong{Document}, below,
30078 refers to any such manual or work. Any member of the public is a
30079 licensee, and is addressed as "@strong{you}". You accept the license if you
30080 copy, modify or distribute the work in a way requiring permission
30081 under copyright law.
30083 A "@strong{Modified Version}" of the Document means any work containing the
30084 Document or a portion of it, either copied verbatim, or with
30085 modifications and/or translated into another language.
30087 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
30088 the Document that deals exclusively with the relationship of the
30089 publishers or authors of the Document to the Document's overall subject
30090 (or to related matters) and contains nothing that could fall directly
30091 within that overall subject. (Thus, if the Document is in part a
30092 textbook of mathematics, a Secondary Section may not explain any
30093 mathematics.) The relationship could be a matter of historical
30094 connection with the subject or with related matters, or of legal,
30095 commercial, philosophical, ethical or political position regarding
30098 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
30099 are designated, as being those of Invariant Sections, in the notice
30100 that says that the Document is released under this License. If a
30101 section does not fit the above definition of Secondary then it is not
30102 allowed to be designated as Invariant. The Document may contain zero
30103 Invariant Sections. If the Document does not identify any Invariant
30104 Sections then there are none.
30106 The "@strong{Cover Texts}" are certain short passages of text that are listed,
30107 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
30108 the Document is released under this License. A Front-Cover Text may
30109 be at most 5 words, and a Back-Cover Text may be at most 25 words.
30111 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
30112 represented in a format whose specification is available to the
30113 general public, that is suitable for revising the document
30114 straightforwardly with generic text editors or (for images composed of
30115 pixels) generic paint programs or (for drawings) some widely available
30116 drawing editor, and that is suitable for input to text formatters or
30117 for automatic translation to a variety of formats suitable for input
30118 to text formatters. A copy made in an otherwise Transparent file
30119 format whose markup, or absence of markup, has been arranged to thwart
30120 or discourage subsequent modification by readers is not Transparent.
30121 An image format is not Transparent if used for any substantial amount
30122 of text. A copy that is not "Transparent" is called @strong{Opaque}.
30124 Examples of suitable formats for Transparent copies include plain
30125 ASCII without markup, Texinfo input format, LaTeX input format, SGML
30126 or XML using a publicly available DTD, and standard-conforming simple
30127 HTML, PostScript or PDF designed for human modification. Examples of
30128 transparent image formats include PNG, XCF and JPG. Opaque formats
30129 include proprietary formats that can be read and edited only by
30130 proprietary word processors, SGML or XML for which the DTD and/or
30131 processing tools are not generally available, and the
30132 machine-generated HTML, PostScript or PDF produced by some word
30133 processors for output purposes only.
30135 The "@strong{Title Page}" means, for a printed book, the title page itself,
30136 plus such following pages as are needed to hold, legibly, the material
30137 this License requires to appear in the title page. For works in
30138 formats which do not have any title page as such, "Title Page" means
30139 the text near the most prominent appearance of the work's title,
30140 preceding the beginning of the body of the text.
30142 The "@strong{publisher}" means any person or entity that distributes
30143 copies of the Document to the public.
30145 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
30146 title either is precisely XYZ or contains XYZ in parentheses following
30147 text that translates XYZ in another language. (Here XYZ stands for a
30148 specific section name mentioned below, such as "@strong{Acknowledgements}",
30149 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
30150 To "@strong{Preserve the Title}"
30151 of such a section when you modify the Document means that it remains a
30152 section "Entitled XYZ" according to this definition.
30154 The Document may include Warranty Disclaimers next to the notice which
30155 states that this License applies to the Document. These Warranty
30156 Disclaimers are considered to be included by reference in this
30157 License, but only as regards disclaiming warranties: any other
30158 implication that these Warranty Disclaimers may have is void and has
30159 no effect on the meaning of this License.
30161 @strong{2. VERBATIM COPYING}
30163 You may copy and distribute the Document in any medium, either
30164 commercially or noncommercially, provided that this License, the
30165 copyright notices, and the license notice saying this License applies
30166 to the Document are reproduced in all copies, and that you add no other
30167 conditions whatsoever to those of this License. You may not use
30168 technical measures to obstruct or control the reading or further
30169 copying of the copies you make or distribute. However, you may accept
30170 compensation in exchange for copies. If you distribute a large enough
30171 number of copies you must also follow the conditions in section 3.
30173 You may also lend copies, under the same conditions stated above, and
30174 you may publicly display copies.
30176 @strong{3. COPYING IN QUANTITY}
30178 If you publish printed copies (or copies in media that commonly have
30179 printed covers) of the Document, numbering more than 100, and the
30180 Document's license notice requires Cover Texts, you must enclose the
30181 copies in covers that carry, clearly and legibly, all these Cover
30182 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
30183 the back cover. Both covers must also clearly and legibly identify
30184 you as the publisher of these copies. The front cover must present
30185 the full title with all words of the title equally prominent and
30186 visible. You may add other material on the covers in addition.
30187 Copying with changes limited to the covers, as long as they preserve
30188 the title of the Document and satisfy these conditions, can be treated
30189 as verbatim copying in other respects.
30191 If the required texts for either cover are too voluminous to fit
30192 legibly, you should put the first ones listed (as many as fit
30193 reasonably) on the actual cover, and continue the rest onto adjacent
30196 If you publish or distribute Opaque copies of the Document numbering
30197 more than 100, you must either include a machine-readable Transparent
30198 copy along with each Opaque copy, or state in or with each Opaque copy
30199 a computer-network location from which the general network-using
30200 public has access to download using public-standard network protocols
30201 a complete Transparent copy of the Document, free of added material.
30202 If you use the latter option, you must take reasonably prudent steps,
30203 when you begin distribution of Opaque copies in quantity, to ensure
30204 that this Transparent copy will remain thus accessible at the stated
30205 location until at least one year after the last time you distribute an
30206 Opaque copy (directly or through your agents or retailers) of that
30207 edition to the public.
30209 It is requested, but not required, that you contact the authors of the
30210 Document well before redistributing any large number of copies, to give
30211 them a chance to provide you with an updated version of the Document.
30213 @strong{4. MODIFICATIONS}
30215 You may copy and distribute a Modified Version of the Document under
30216 the conditions of sections 2 and 3 above, provided that you release
30217 the Modified Version under precisely this License, with the Modified
30218 Version filling the role of the Document, thus licensing distribution
30219 and modification of the Modified Version to whoever possesses a copy
30220 of it. In addition, you must do these things in the Modified Version:
30226 Use in the Title Page (and on the covers, if any) a title distinct
30227 from that of the Document, and from those of previous versions
30228 (which should, if there were any, be listed in the History section
30229 of the Document). You may use the same title as a previous version
30230 if the original publisher of that version gives permission.
30233 List on the Title Page, as authors, one or more persons or entities
30234 responsible for authorship of the modifications in the Modified
30235 Version, together with at least five of the principal authors of the
30236 Document (all of its principal authors, if it has fewer than five),
30237 unless they release you from this requirement.
30240 State on the Title page the name of the publisher of the
30241 Modified Version, as the publisher.
30244 Preserve all the copyright notices of the Document.
30247 Add an appropriate copyright notice for your modifications
30248 adjacent to the other copyright notices.
30251 Include, immediately after the copyright notices, a license notice
30252 giving the public permission to use the Modified Version under the
30253 terms of this License, in the form shown in the Addendum below.
30256 Preserve in that license notice the full lists of Invariant Sections
30257 and required Cover Texts given in the Document's license notice.
30260 Include an unaltered copy of this License.
30263 Preserve the section Entitled "History", Preserve its Title, and add
30264 to it an item stating at least the title, year, new authors, and
30265 publisher of the Modified Version as given on the Title Page. If
30266 there is no section Entitled "History" in the Document, create one
30267 stating the title, year, authors, and publisher of the Document as
30268 given on its Title Page, then add an item describing the Modified
30269 Version as stated in the previous sentence.
30272 Preserve the network location, if any, given in the Document for
30273 public access to a Transparent copy of the Document, and likewise
30274 the network locations given in the Document for previous versions
30275 it was based on. These may be placed in the "History" section.
30276 You may omit a network location for a work that was published at
30277 least four years before the Document itself, or if the original
30278 publisher of the version it refers to gives permission.
30281 For any section Entitled "Acknowledgements" or "Dedications",
30282 Preserve the Title of the section, and preserve in the section all
30283 the substance and tone of each of the contributor acknowledgements
30284 and/or dedications given therein.
30287 Preserve all the Invariant Sections of the Document,
30288 unaltered in their text and in their titles. Section numbers
30289 or the equivalent are not considered part of the section titles.
30292 Delete any section Entitled "Endorsements". Such a section
30293 may not be included in the Modified Version.
30296 Do not retitle any existing section to be Entitled "Endorsements"
30297 or to conflict in title with any Invariant Section.
30300 Preserve any Warranty Disclaimers.
30303 If the Modified Version includes new front-matter sections or
30304 appendices that qualify as Secondary Sections and contain no material
30305 copied from the Document, you may at your option designate some or all
30306 of these sections as invariant. To do this, add their titles to the
30307 list of Invariant Sections in the Modified Version's license notice.
30308 These titles must be distinct from any other section titles.
30310 You may add a section Entitled "Endorsements", provided it contains
30311 nothing but endorsements of your Modified Version by various
30312 parties---for example, statements of peer review or that the text has
30313 been approved by an organization as the authoritative definition of a
30316 You may add a passage of up to five words as a Front-Cover Text, and a
30317 passage of up to 25 words as a Back-Cover Text, to the end of the list
30318 of Cover Texts in the Modified Version. Only one passage of
30319 Front-Cover Text and one of Back-Cover Text may be added by (or
30320 through arrangements made by) any one entity. If the Document already
30321 includes a cover text for the same cover, previously added by you or
30322 by arrangement made by the same entity you are acting on behalf of,
30323 you may not add another; but you may replace the old one, on explicit
30324 permission from the previous publisher that added the old one.
30326 The author(s) and publisher(s) of the Document do not by this License
30327 give permission to use their names for publicity for or to assert or
30328 imply endorsement of any Modified Version.
30330 @strong{5. COMBINING DOCUMENTS}
30332 You may combine the Document with other documents released under this
30333 License, under the terms defined in section 4 above for modified
30334 versions, provided that you include in the combination all of the
30335 Invariant Sections of all of the original documents, unmodified, and
30336 list them all as Invariant Sections of your combined work in its
30337 license notice, and that you preserve all their Warranty Disclaimers.
30339 The combined work need only contain one copy of this License, and
30340 multiple identical Invariant Sections may be replaced with a single
30341 copy. If there are multiple Invariant Sections with the same name but
30342 different contents, make the title of each such section unique by
30343 adding at the end of it, in parentheses, the name of the original
30344 author or publisher of that section if known, or else a unique number.
30345 Make the same adjustment to the section titles in the list of
30346 Invariant Sections in the license notice of the combined work.
30348 In the combination, you must combine any sections Entitled "History"
30349 in the various original documents, forming one section Entitled
30350 "History"; likewise combine any sections Entitled "Acknowledgements",
30351 and any sections Entitled "Dedications". You must delete all sections
30352 Entitled "Endorsements".
30354 @strong{6. COLLECTIONS OF DOCUMENTS}
30356 You may make a collection consisting of the Document and other documents
30357 released under this License, and replace the individual copies of this
30358 License in the various documents with a single copy that is included in
30359 the collection, provided that you follow the rules of this License for
30360 verbatim copying of each of the documents in all other respects.
30362 You may extract a single document from such a collection, and distribute
30363 it individually under this License, provided you insert a copy of this
30364 License into the extracted document, and follow this License in all
30365 other respects regarding verbatim copying of that document.
30367 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
30369 A compilation of the Document or its derivatives with other separate
30370 and independent documents or works, in or on a volume of a storage or
30371 distribution medium, is called an "aggregate" if the copyright
30372 resulting from the compilation is not used to limit the legal rights
30373 of the compilation's users beyond what the individual works permit.
30374 When the Document is included in an aggregate, this License does not
30375 apply to the other works in the aggregate which are not themselves
30376 derivative works of the Document.
30378 If the Cover Text requirement of section 3 is applicable to these
30379 copies of the Document, then if the Document is less than one half of
30380 the entire aggregate, the Document's Cover Texts may be placed on
30381 covers that bracket the Document within the aggregate, or the
30382 electronic equivalent of covers if the Document is in electronic form.
30383 Otherwise they must appear on printed covers that bracket the whole
30386 @strong{8. TRANSLATION}
30388 Translation is considered a kind of modification, so you may
30389 distribute translations of the Document under the terms of section 4.
30390 Replacing Invariant Sections with translations requires special
30391 permission from their copyright holders, but you may include
30392 translations of some or all Invariant Sections in addition to the
30393 original versions of these Invariant Sections. You may include a
30394 translation of this License, and all the license notices in the
30395 Document, and any Warranty Disclaimers, provided that you also include
30396 the original English version of this License and the original versions
30397 of those notices and disclaimers. In case of a disagreement between
30398 the translation and the original version of this License or a notice
30399 or disclaimer, the original version will prevail.
30401 If a section in the Document is Entitled "Acknowledgements",
30402 "Dedications", or "History", the requirement (section 4) to Preserve
30403 its Title (section 1) will typically require changing the actual
30406 @strong{9. TERMINATION}
30408 You may not copy, modify, sublicense, or distribute the Document
30409 except as expressly provided under this License. Any attempt
30410 otherwise to copy, modify, sublicense, or distribute it is void, and
30411 will automatically terminate your rights under this License.
30413 However, if you cease all violation of this License, then your license
30414 from a particular copyright holder is reinstated (a) provisionally,
30415 unless and until the copyright holder explicitly and finally
30416 terminates your license, and (b) permanently, if the copyright holder
30417 fails to notify you of the violation by some reasonable means prior to
30418 60 days after the cessation.
30420 Moreover, your license from a particular copyright holder is
30421 reinstated permanently if the copyright holder notifies you of the
30422 violation by some reasonable means, this is the first time you have
30423 received notice of violation of this License (for any work) from that
30424 copyright holder, and you cure the violation prior to 30 days after
30425 your receipt of the notice.
30427 Termination of your rights under this section does not terminate the
30428 licenses of parties who have received copies or rights from you under
30429 this License. If your rights have been terminated and not permanently
30430 reinstated, receipt of a copy of some or all of the same material does
30431 not give you any rights to use it.
30433 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
30435 The Free Software Foundation may publish new, revised versions
30436 of the GNU Free Documentation License from time to time. Such new
30437 versions will be similar in spirit to the present version, but may
30438 differ in detail to address new problems or concerns. See
30439 @indicateurl{http://www.gnu.org/copyleft/}.
30441 Each version of the License is given a distinguishing version number.
30442 If the Document specifies that a particular numbered version of this
30443 License "or any later version" applies to it, you have the option of
30444 following the terms and conditions either of that specified version or
30445 of any later version that has been published (not as a draft) by the
30446 Free Software Foundation. If the Document does not specify a version
30447 number of this License, you may choose any version ever published (not
30448 as a draft) by the Free Software Foundation. If the Document
30449 specifies that a proxy can decide which future versions of this
30450 License can be used, that proxy's public statement of acceptance of a
30451 version permanently authorizes you to choose that version for the
30454 @strong{11. RELICENSING}
30456 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30457 World Wide Web server that publishes copyrightable works and also
30458 provides prominent facilities for anybody to edit those works. A
30459 public wiki that anybody can edit is an example of such a server. A
30460 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30461 site means any set of copyrightable works thus published on the MMC
30464 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30465 license published by Creative Commons Corporation, a not-for-profit
30466 corporation with a principal place of business in San Francisco,
30467 California, as well as future copyleft versions of that license
30468 published by that same organization.
30470 "Incorporate" means to publish or republish a Document, in whole or
30471 in part, as part of another Document.
30473 An MMC is "eligible for relicensing" if it is licensed under this
30474 License, and if all works that were first published under this License
30475 somewhere other than this MMC, and subsequently incorporated in whole
30476 or in part into the MMC, (1) had no cover texts or invariant sections,
30477 and (2) were thus incorporated prior to November 1, 2008.
30479 The operator of an MMC Site may republish an MMC contained in the site
30480 under CC-BY-SA on the same site at any time before August 1, 2009,
30481 provided the MMC is eligible for relicensing.
30483 @strong{ADDENDUM: How to use this License for your documents}
30485 To use this License in a document you have written, include a copy of
30486 the License in the document and put the following copyright and
30487 license notices just after the title page:
30491 Copyright © YEAR YOUR NAME.
30492 Permission is granted to copy, distribute and/or modify this document
30493 under the terms of the GNU Free Documentation License, Version 1.3
30494 or any later version published by the Free Software Foundation;
30495 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30496 A copy of the license is included in the section entitled "GNU
30497 Free Documentation License".
30500 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30501 replace the "with ... Texts." line with this:
30505 with the Invariant Sections being LIST THEIR TITLES, with the
30506 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30509 If you have Invariant Sections without Cover Texts, or some other
30510 combination of the three, merge those two alternatives to suit the
30513 If your document contains nontrivial examples of program code, we
30514 recommend releasing these examples in parallel under your choice of
30515 free software license, such as the GNU General Public License,
30516 to permit their use in free software.
30518 @node Index,,GNU Free Documentation License,Top
30525 @anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ }